阅读说明：本技术 包括摩擦制动器的坠落保护设备 (Fall protection device comprising a friction brake ) 是由 迈克尔·A·布拉斯 基思·G·马特森 于 2018-07-11 设计创作，主要内容包括：一种非机动坠落保护设备,包括卷筒和旋转触发的制动装置,该旋转触发的制动装置包括至少一个棘爪和至少一个棘轮,该至少一个棘轮具有可由所述至少一个棘爪的接合端接合的至少一个齿,其中旋转触发的制动装置包括使用受限的、恒定接触的摩擦制动器,该摩擦制动器包括具有摩擦制动表面的至少一个摩擦材料层和具有接触表面的至少一个可旋转构件,该接触表面与该摩擦材料层的摩擦制动表面接触。(A non-motorized fall protection device comprising a drum and a rotation-triggered braking arrangement comprising at least one pawl and at least one ratchet wheel having at least one tooth engageable by an engagement end of the at least one pawl, wherein the rotation-triggered braking arrangement comprises a limited-use, constant-contact friction brake comprising at least one layer of friction material having a friction braking surface and at least one rotatable member having a contact surface that contacts the friction braking surface of the layer of friction material.)

1. A non-motorized fall protection device comprising:

a spool having a safety line connected to the spool and rotatable relative to a housing of the device; and the combination of (a) and (b),

a rotation-triggered brake device comprising at least one pawl and at least one ratchet wheel having at least one tooth engageable with an engagement end of the at least one pawl,

wherein the rotation-activated braking device comprises a friction brake with limited use, constant contact, comprising at least one friction material layer having a friction braking surface and comprising at least one rotatable member having a contact surface, the contact surface being in contact with the friction braking surface of the friction material layer,

and wherein said rotation-activated braking device and said limited-use, constant-contact friction brake thereof are configured to resist rotation of said rotatable drum in a braking operation having a ratio of peak braking force to average braking force of less than about 1.2.

2. The apparatus of claim 1, wherein the rotation-triggered braking device and the limited-use, constant-contact friction brake thereof are configured to prevent rotation of the rotatable drum in a braking operation in which a ratio of peak braking force to average braking force is less than about 1.1.

3. The apparatus of claim 1, wherein the limited use friction brake is a single use friction brake.

4. The apparatus of claim 1, wherein the safety line comprises at least one shock absorber.

5. The apparatus of claim 1, wherein the safety line does not include a shock absorber.

6. The apparatus of claim 1 wherein the apparatus is a self-retracting lifeline, wherein the safety line includes a proximal end connected to the rotatable drum and a distal end attachable to a harness of a user of the apparatus or to an anchor at a workplace.

7. The apparatus of claim 1, wherein the at least one pawl is biased such that the engagement end of the at least one pawl is urged toward a disengaged position; and wherein said rotation-triggered braking device is configured such that when said rotatable drum rotates beyond a predetermined value, said engagement end of said at least one pawl is urged into an engaged position in which it engages teeth of said ratchet wheel.

8. The apparatus of claim 1, wherein the apparatus comprises at least two pawls each mounted on the rotatable drum, wherein the rotatable member of the friction brake acts as the ratchet of the rotation-triggered braking device, wherein engagement of an engagement end of one of the pawls with a tooth of the ratchet rotates the ratchet relative to the housing of the apparatus, and wherein the at least one layer of friction material is configured to frictionally resist rotation of the ratchet relative to the housing of the apparatus, thereby resisting rotation of the rotatable drum relative to the housing of the apparatus.

9. The apparatus of claim 8, wherein the apparatus comprises first and second friction material layers sandwiching the ratchet, the first and second friction material layers bonded to first and second support plates, respectively, the first and second support plates each keyed to a shaft to prevent rotation of the first and second friction material layers relative to the housing of the apparatus.

10. The apparatus of claim 1, wherein the apparatus is configured such that engagement of the engagement end of the at least one pawl with the teeth of the ratchet stops rotation of the rotatable member relative to the housing of the apparatus, and wherein the layer of friction material is configured to frictionally prevent rotation of the rotatable drum relative to the rotatable member, thereby preventing rotation of the rotatable drum relative to the housing of the apparatus.

11. The device of claim 1, wherein the friction brake comprises a single layer of friction material keyed to the rotatable drum so as to be non-rotatable relative to the drum, wherein the friction brake comprises a single rotatable member that is rotatable relative to the rotatable drum and relative to a housing of the device and that includes at least two pawls mounted to the single rotatable member, and wherein the rotation-triggered braking means comprises a single ratchet that is non-rotatable relative to the housing of the device and that is not the single rotatable member of the friction brake.

12. The apparatus of claim 1, wherein the at least one ratchet wheel is provided as a radially outwardly facing toothed disc or as a radially inwardly facing toothed ring, the ratchet wheel being made of steel.

13. The apparatus of claim 1, wherein the at least one ratchet is a single ratchet provided as an integral feature of the housing of the apparatus or an integral feature of a carrying bracket of the apparatus.

14. The apparatus of claim 1, wherein the friction material layer is a non-abrasive article.

15. The apparatus of claim 1, wherein the rotation-triggered braking device and the limited-use, constant-contact friction brake thereof are configured to resist rotation of the rotatable drum in a braking operation that exhibits a braking force versus time curve, and a local slope of the curve at a peak force of the curve is less than 10 pounds of braking force per millisecond of braking time.

16. The apparatus of claim 1, wherein the rotation-triggered braking device and the limited-use, constant-contact friction brake thereof are configured to prevent rotation of the rotatable drum in a braking operation having a ratio of local initial peak braking force to average braking force of less than about 1.15.

17. A method of operating a fall protection device including a rotation-triggered brake arrangement including a limited-use friction brake, the method comprising:

engaging at least one pawl of said rotation-activated braking device with teeth of a ratchet wheel of said rotation-activated braking device when a safety-line-carrying drum of said apparatus rotates beyond a predetermined value, thereby rotatably moving a rotatable member of said friction brake relative to a layer of friction material of said friction brake;

and the number of the first and second groups,

preventing rotation of the rotatable member of the friction brake relative to the friction material layer of the friction brake by friction between a friction braking surface of the friction material layer and a contact surface of the rotatable member, thereby preventing rotation of the rotatable drum in a braking operation having a ratio of peak braking force to average braking force of less than about 1.2.

18. The method of claim 17, wherein the ratio of peak braking force to average braking force is less than about 1.1.

19. The method of claim 17, wherein the braking operation exhibits a braking force versus time curve, and a local slope of the curve at a peak force of the curve is less than 10 pounds of braking force per millisecond of braking time.

20. The method of claim 17, wherein in the braking operation, a ratio of local initial peak braking force to average braking force is less than about 1.15.

Background

Fall protection devices such as, for example, self-retracting lifelines, are commonly used in applications such as building construction.

Disclosure of Invention

Broadly, disclosed herein is a fall protection device comprising a rotation-activated brake arrangement including a limited-use friction brake comprising a layer of friction material and a rotatable member. These and other aspects will be apparent from the detailed description below. In no event, however, should this broad summary be construed as a limitation on the claimable subject matter, whether such subject matter is presented in the claims of the originally filed application or in the claims of a revised application, or otherwise presented during the prosecution.

Drawings

Figure 1 is a perspective view of an exemplary fall protection device.

Figure 2 is a perspective exploded view of various components of an exemplary fall protection device, including a rotation-activated detent.

Figure 3 is an exploded view in isolation, perspective, of various components of an exemplary fall protection device, including a friction brake of the rotation-activated braking device.

Figure 4 shows force versus time data for a comparative fall protection device.

Figure 5 shows force versus time data for a working embodiment fall protection device.

Like reference symbols in the various drawings indicate like elements. Some elements may be present in the same or equal multiples; in this case, one or more representative elements may be designated by reference numerals only, but it should be understood that such reference numerals apply to all such identical elements. Unless otherwise indicated, all drawings and figures in this document are not to scale and are chosen for the purpose of illustrating different embodiments of the invention. Specifically, unless otherwise indicated, dimensions of various components are described using exemplary terms only, and no relationship between the dimensions of the various components should be inferred from the drawings. Although terms such as "front," "back," "outward," "inward," and "first" and "second" may be used in this disclosure, it should be understood that these terms are used in their relative sense only unless otherwise specified. Terms such as "top," "bottom," "upper," "lower," "below," "above," "horizontal," "vertical," "up," and "down" are to be understood as having their ordinary meaning with respect to the earth.

As used herein, the term "substantially", as a modifier to a property or attribute, unless specifically defined otherwise, means that the property or attribute would be readily identifiable by a person of ordinary skill without requiring a high degree of approximation (e.g., within +/-20% for quantifiable properties). Unless specifically defined otherwise, the term "substantially" means highly approximate (e.g., within +/-10% for quantifiable characteristics). The term "substantially" means highly approximated (e.g., within +/-2% for quantifiable characteristics); it should be understood that the phrase "at least substantially" includes the particular case of an "exact" match. However, even where an "exact" match, or any other characterization is used in terms such as, for example, identical, equal, consistent, uniform, constant, etc., it will be understood that within ordinary tolerances, or within measurement error applicable to the particular situation, rather than requiring an absolutely exact or perfect match. The term "configured to" and similar terms are at least as limiting as the term "adapted to" and require the actual design intent to perform the specified function, not just the physical ability to perform such function. All references herein to numerical parameters (dimensions, ratios, etc.) are understood to be able to be calculated (unless otherwise stated) by using the average of multiple measurements derived from the parameter.

Detailed Description

A fall protection device is disclosed herein, which refers to a device for controllably reducing the speed of a user of the device in the event of a fall of the user. This fall protection device is by definition different from devices used to raise or lower a non-human load such as a crane, winch or the like. By definition, this fall protection device is a non-motorized device. This means that the safety line of the device is not moved by means of an electric motor (i.e. extended or retracted from the housing of the device); in other words, the apparatus is not used as part of a system (e.g., elevator, crane, etc.) that uses one or more motors to raise or lower a load.

In many embodiments, the fall protection device is a self-retracting lifeline (SRL); that is, the deceleration device comprising a housing at least partially houses a reel-wound safety line that can be extended from the housing and retracted into the housing under slight tension during normal movement of a user of the device, and that automatically arrests (i.e., slows to a controlled rate, or stops altogether) the fall of the user when the user falls. This apparatus may include a safety line that may extend out of the lower end of the apparatus, where the apparatus has an upper anchorage end that may be connected, for example, to a safety anchorage point at a workplace. Typically, such devices may include a drum rotatably mounted within a housing therein such that when the line is retracted into the housing, the safety line may be wound around the drum. The apparatus may also include a rotation-triggered brake device. This refers to a device configured to prevent rotation of the drum when the drum rotates beyond a predetermined value (note that the term "value" encompasses velocity, acceleration, or a combination thereof). In some types of fall protection devices, this rotation-triggered brake can bring the drum to a "hard stop" (i.e., near instantaneous stop); in many such cases, the safety line of the device may include a so-called shock absorber (e.g., a tear web or tear strip) to minimize the force experienced by the user when the user stops. In fall protection devices of the type concerned herein, the rotation-triggered braking means comprise a friction brake which, instead of bringing the drum to a "hard stop", stops the drum in a more gradual manner, as described in detail later herein. This minimizes the forces experienced by the user in a fall, for example, without requiring the presence of a shock absorber in the safety line.

An exemplary fall protection device 100 of the self-retracting lifeline type is shown in fig. 1 and 2. This device may comprise a housing 111, for example provided by a first housing part 112 and a second housing part 113, which are assembled and fastened together to form the housing. The housing pieces 112 and 113 may be fastened together, for example, by bolts or by any other suitable fasteners. It should be noted that for ease of presenting the components of primary interest, many of the ancillary components, such as, for example, one or more nuts, bolts, screws, shafts, washers, bushings, precipitates, bearings, etc., are omitted from the figures herein; one of ordinary skill will readily appreciate that any such items may be present according to the functional needs of the apparatus 100. In some embodiments, the housing 111 can be load bearing. In some embodiments, a load bracket 44 or similar component may be present and may provide at least a portion of the load-bearing path of the apparatus.

Within the interior space defined at least in part by the housing 111 is a drum 33 upon which is wound (e.g., helically wound) a length of safety line 229 (the term "line" broadly encompasses any elongated windable load bearing member including, for example, a strap, cable, rope, etc., made of any suitable synthetic or natural polymeric material, metal, etc., or any combination thereof). In the illustrated embodiment, the drum 33 includes a body and a flange 30 that, when engaged to the body, defines a space within which the cord 229 may be received and spirally wound. The proximal end of the cable 229 is directly or indirectly connected to the drum 33 (this connection includes configurations in which the proximal end of the cable 229 is connected to a shaft on which the drum 33 is mounted). In various embodiments, such a spool (e.g., its body and/or flange) may be made of metal (e.g., machined or cast metal), molded plastic, or any other suitable material. In some embodiments, such a spool may be made from a single, unitary piece of material, which may be, for example, a molded polymeric article or a machined or cast metal article. The drum 33 is rotatably connected to the housing 111, for example by being rotatably mounted on a shaft or by being mounted on a shaft that is rotatable relative to the housing. A torsion spring 31 may be provided, for example, externally of the spool 33 (and, in the embodiment shown in fig. 2, separated from the spool 33 by a spacer disc 32) for biasing the spool in a direction to retract the safety line 229 onto the spool unless the biasing force is overcome, for example, by movement of a user.

Rotary-triggered brake device

Within the space defined by the housing is a rotation-activated brake 102, as shown in the exemplary embodiment of FIG. 2. This rotation-activated braking device relies on one or more pawls 20 that are normally co-rotatable with the spool 33. Co-rotation with the drum means that the pawl or pawls are able to rotate with the drum 33, with the pawl(s) moving in an orbital path about the center of orbital motion coincident with the axis of rotation of the drum. In the illustrated embodiment of fig. 2, this arrangement is achieved by mounting two such pawls 20 directly onto the drum 33 so that they rotate with the drum 33. However, it may not be necessary to mount this pawl(s) directly to the spool 33 (e.g., one or more pawls may be mounted to a pawl support plate connected to the spool).

Any such pawl can be biased (in the embodiment shown, this is performed by using a biasing spring 21) such that, in ordinary use of the fall protection device, the engagement end 22 of the pawl is urged to a non-engaged position in which it does not engage any component (e.g., ratchet teeth) that will limit rotation of the spool. This allows the drum to rotate to extend and retract the safety line in response to movement by a user of the fall protection device. In the event that the spool begins to rotate beyond a predetermined value, at least one pawl is urged (against the biasing force of the spring 21) to an engaged position in which an engaging end 22 of the pawl engages the teeth of the ratchet wheel to slow and/or stop rotation of the spool (as described in detail later herein). In many embodiments, one or more pawls may be pivotally mounted to be pivotally movable between a disengaged position and an engaged position (as shown in the design of fig. 2). However, in some embodiments, one or more pawls may be slidably mounted, for example, to be slidably movable between a disengaged position and an engaged position (e.g., as shown in the arrangement disclosed in U.S. patent 8256574.

In the exemplary arrangement shown in fig. 2, each pawl 20 includes a heavy end opposite engaging end 22 such that increased rotational speed moves the heavy end radially outward, thereby urging engaging end 22 radially inward. Such an arrangement may be used with a radially outwardly facing ratchet, such as a ratchet disc of the general type described later herein with reference to fig. 3. In some embodiments, the pawl may be configured such that the engagement end is the end of the pawl that is urged to move radially outward to be engaged; such an arrangement may be used with radially inwardly facing ratchets (e.g., ratchet rings of the general type shown in fig. 4 of the' 574 patent referenced above). In general, one or more detents of any suitable design may be used, made of any material with suitable mechanical strength (e.g., stainless steel); various pawl designs and configurations are described in, for example, U.S. patents 7281620, 8430206, 8430208, and 9488235.

In use of the example fall protection apparatus 100, the upper anchorage end 108 of the apparatus can be connected (e.g., by the connection feature 240) to a safety anchorage point (a fixed point) of a workplace structure (e.g., a truss, a beam, etc.). The distal end of the cord 229 may then be attached (e.g., by a hook 230 or the like) to a harness worn by the worker. As the user moves away from the secure anchorage, the cable 229 extends from within the housing 111; as the user moves toward the fixed anchorage, drum 33 rotates under the bias of torsion spring 31, causing cord 229 to self-retract within housing 111 and wind onto drum 33. During such user activity, pawls 20 are biased by the aforementioned biasing springs 21 such that engaging end 22 of each pawl 20 does not engage the ratchet wheel of the rotation-triggered brake. In the event that the user falls and causes cord 229 to extend rapidly from housing 111, rotation of drum 33 increases above a predetermined value (e.g., a predetermined value of speed) such that engaging end 22 of at least one pawl 20 engages the ratchet wheel, whereby a fall of the worker is prevented as discussed in detail later herein. Various parameters of the rotation-triggered braking device (e.g., weight and shape of the pawl, spring constant of the biasing spring, etc.) may be selected such that engagement of the pawl with the ratchet wheel occurs at a predetermined rotational speed of, for example, the spool.

In many embodiments, centrifugal force caused by the rotational (i.e., orbital) motion of the pawls causes one or more pawls to transition from the disengaged position to the engaged position. However, in some embodiments, this transition may occur at least in part by the pawl while moving along the path of orbital motion, impacting (if the pawl is moving fast enough) an item that physically moves the pawl out of its disengaged position and urges it toward the engaged position. This item may be, for example, a tooth of a ratchet (e.g., a fixed ratchet) positioned at least partially in the orbital path of the moving pawl. A similar effect may be achieved by mounting one or more pawls such that they cannot move rotationally along the orbital path, but are able to pivot (e.g., rock) while remaining in place. An item, such as a rotatable ratchet, may then be positioned such that if the item is rotated at a sufficient speed, a portion of the item may impact a portion of the pawl to physically move the pawl out of the disengaged position and urge (e.g., pivot) the pawl toward the engaged position. This general type of arrangement is disclosed, for example, in U.S. patent 6279682 to Feathers, which is incorporated herein by reference in its entirety. It should be noted that any assembly that utilizes relative rotational movement between at least one pawl and a ratchet wheel to trigger braking (including those disclosed in the '682 patent) falls into the category of the rotationally triggered braking devices disclosed herein (note that an arrangement of the type disclosed in the' 682 patent in which the pawl does not follow an orbital path so as to rotate with the spool) will be an exception to the principle that a rotationally triggered braking device typically includes one or more pawls that are co-rotatable with the spool of the assembly).

Friction brake

A rotation-triggered brake device as disclosed herein will comprise a ratchet wheel comprising at least one tooth engageable by the above-mentioned engagement end of the pawl. This ratchet may be made of any material that exhibits sufficient strength to withstand the forces generated during engagement/braking; in many embodiments, this ratchet can be constructed of stainless steel (e.g., selected from the 300 series (austenitic) class of stainless steels). Various ratchet designs and arrangements are discussed in detail below.

The rotation-activated braking devices disclosed herein will also include friction brakes. By definition, a friction brake will comprise at least one layer of friction material and at least one rotatable member, wherein the friction braking surface of the layer of friction material is in contact with the contact surface of the rotatable member (typically during normal use of the fall protection device). By rotatable member is meant a term (e.g., disk, ring, rotor, etc.) configured such that when sufficient differential torque is applied to the friction material layer and rotatable member due to the engagement of the pawl with the ratchet wheel of the rotationally triggered brake device, the member and the friction material layer can be set into rotational motion relative to one another. In many embodiments, the friction braking surface of the layer of friction braking material and the contact surface of the rotatable member are pressed together to provide sufficient static friction that there is no relative movement between the two surfaces when the user moves around the workplace in the ordinary use of the device. However, when the pawl engages the ratchet wheel of the rotation-triggered brake device, sufficient differential torque is generated to overcome the static friction force so that relative movement of the two surfaces (and thus relative movement of the rotatable member and the layer of friction material) can occur. The rotatable member and the friction material layer are configured such that the relative rotation of the friction material layer and the rotatable member will be slowed and/or stopped by friction between a friction braking surface of the friction material layer and a contact surface of the rotatable member. This slowing of the relative rotation will help slow (e.g. stop) the rotation of the drum with the safety line.

In some exemplary embodiments, the rotation-activated braking device 102 may include a friction brake 103 of the general type disclosed in the isolated exploded view of fig. 3. This friction brake 103 comprises a ratchet wheel 47 (in this case, a radially outward toothed disc) comprising at least one tooth 147 engageable by the above-mentioned engagement end 22 of the pawl 20. In an exemplary design, the ratchet 47 is mounted on a keyed (e.g., flat) shaft 39 that passes through complementary keyed openings in the housing member 112 and the load band 44, as shown in FIG. 3. Although the shaft 39 is therefore not rotatable relative to the housing of the device, the ratchet 47 is rotatable relative to the shaft 39 and thus relative to the housing of the device. The ratchet 47 is sandwiched between the first friction material layer 146 and the second friction material layer 148. Each friction material layer is bonded to and supported by a support plate 145 and 150 (e.g., made of a metal such as stainless steel) that is keyed to shaft 39 such that each friction material layer cannot rotate relative to shaft 39. The first friction material layer 146 includes a first friction braking surface 144 in contact with the first contact surface 142 of the ratchet 47; the second friction material layer 148 includes a second friction braking surface 149 that contacts the second contact surface 143 of the ratchet 147. In the assembly of the friction brake 103, a lock nut 151 is threaded onto the threaded end portion of the key engagement shaft 39 (e.g., by using a torque wrench) to a selected degree to exert a desired amount of pressure on the friction brake. This causes the first and second friction braking surfaces 144 and 149 of the first and second friction material layers 146 and 148 to be pressed against the contact surfaces 142 and 142 of the ratchet 47 with a force selected to apply a desired amount of frictional resistance to movement to provide a desired braking power. For example, the force may be selected such that a user's fall will be arrested for a suitably short time and/or over a suitably short fall distance, while not subjecting the user to adverse forces resulting from the braking action.

It should be understood that the particular design shown in FIG. 3 is merely one example of a friction brake and ratchet arrangement; many other configurations are possible. For example, FIG. 3 depicts a ratchet comprising two contact surfaces and sandwiched between two layers of friction material. In other embodiments, the ratchet wheel of the friction brake may include only a single contact surface that may be in contact with only a single layer of friction material. Further, the ratchet may be radially inwardly facing rather than radially outwardly facing, as shown in FIG. 3. A friction brake comprising a ratchet wheel in the form of a radially inwardly facing ring gear and only a single contact surface in contact with the friction braking surface of a single layer of friction material is described in fig. 4 of us patent 8430206 to Griffiths, which is incorporated herein by reference in its entirety.

In some embodiments, the ratchet of the rotation-triggered brake device may conveniently serve as the rotatable member of the friction brake of the brake device. It should be understood that the rotary activated brake devices and friction brakes described above in connection with fig. 2-3 belong to this general category. In many such designs, the ratchet is able to rotate relative to the housing of the device, but typically remains stationary during normal use of the device. That is, as the user moves around the workplace, the drum may rotate (relatively slowly) relative to the housing to extend and retract the safety line. However, is not affected by any rotational forces, and the ratchet, which is keyed to one or more friction material layers of the shaft as described above, frictionally constrains the one or more friction material layers from rotating relative to the housing. In the event that the spool begins to rotate rapidly (e.g., due to a fall), the engagement end of the pawl (e.g., the spool-mounted pawl) engages the teeth of the ratchet wheel and overcomes this frictional constraint and causes the ratchet wheel to rotate relative to the layer(s) of friction material and thus relative to the housing of the device. Friction between the friction braking surface of the friction material and the contact surface of the ratchet then slows or stops rotation of the ratchet relative to the device housing, thereby slowing or stopping rotation of the rotatable drum relative to the device housing. A product available under the trade name ULTRA-LOK from 3M Fall Protection, RedWing, MN, red wing, minnesota provides an example of a Fall Protection device comprising a rotation-triggered detent device with friction brakes arranged in this way.

In other embodiments, the rotatable member of the friction brake of the rotation-triggered braking device may not necessarily act as a ratchet of the braking device. Rather, in some cases, the ratchet of the rotation-triggered braking device and the rotatable member of the friction brake of the rotation-triggered braking device may be separate items. In one exemplary arrangement of this general type, the rotatable member of the friction brake may take the form of, for example, a plate, disc, etc., on which one or more pawls of the braking device are mounted, with a contact surface of the rotatable member in contact with the friction braking surface of the friction material layer. The friction material layer is mounted on a support plate keyed to the safety line receiving drum of the device such that the friction material layer cannot rotate relative to the drum. In some such embodiments, the ratchet of the brake device may be non-rotatable relative to the housing of the apparatus (e.g., the ratchet may be provided as an integral feature of the housing, e.g., molded directly into a housing piece of the apparatus). Thus, the engagement of the engaging end of the pawl with the teeth of the ratchet wheel will cause the rotatable member on which the pawl is mounted to immediately stop rotating, while the differential torque between the rotatable member and the layer of friction material allows the layer of friction material and thus the drum to continue to rotate briefly. The friction between the contact surface of the rotatable member and the friction braking surface of the friction material layer slows or stops the rotation of the friction material layer, thereby slowing or stopping the rotation of the drum itself.

An example of this general type of Fall Protection product is provided by the product available under the trade name REBEL from 3M Fall Protection, Red Wing, MN, Red Wing, where the rotation-triggered detent comprises a rotatable member and a ratchet that is a separate item. The REBEL product family also provides examples of friction brakes that use a single layer of friction material rather than two layers with an interposed rotatable member. It should be understood that many variations of the above-described exemplary arrangements may be employed. For example, there may be multiple layers of friction material and/or multiple rotatable members if desired.

In some embodiments, the ratchet can be provided, for example, as an integral (e.g., molded, cast, or machined) feature of the device housing, rather than, for example, as a toothed disc or ring that is separately prepared and inserted into the housing of the fall protection device. The REBEL product family described above provides examples of this type of ratchet. Another possible variation of the ratchet design is presented in us patent 9488235, in which the ratchet takes the form of a single tooth ("stop member") provided as an integral component of a bracket (e.g., a load bearing bracket) of the fall protection apparatus. It should be apparent that the device described in the' 235 patent is a device in which a rotation-triggered braking device reaches a "hard" (near instantaneous) stop for the spool when the pawl is brought into engagement with the stop member; that is, the' 235 rotation-triggered braking device does not include a friction brake. Instead, a shock absorber is provided in the safety line of the device. Thus, the' 235 patent does not include a friction brake and is used herein only to illustrate the variations allowable in ratchet designs. Any suitable ratchet design, including any of the ratchet designs and arrangements described herein, may be used in the rotation-triggered brake devices disclosed herein.

As is apparent from the above discussion, the ratchet wheel of the rotation-triggered detent can be any component (e.g., a toothed disc or ring, or a portion of a fall protection bracket or housing) that presents at least one tooth that can be engaged by the engagement end of the pawl to initiate a detent operation of the rotation-triggered detent. It should be emphasized that the term "ratchet" is used for convenience of description; use of this term does not require that the ratchet and pawl(s) must be arranged, for example, such that relative rotation of these components is permitted in one direction, but excludes relative rotation in the opposite direction. (however, the ratchet and pawl(s) may be arranged so as to provide such functionality if desired.) it should also be emphasized that the arrangements and functionality disclosed herein may be used in any design of rotation-triggered brake device.

A friction brake as disclosed herein includes at least one friction material layer including at least one friction braking surface configured to contact a contact surface of a rotatable member of the friction brake. In some embodiments, the friction material layer may be disposed on (e.g., laminated or bonded to) the support plate, as described herein. In other embodiments, the friction material layer may be "free-standing" rather than bonded to the backing plate. In some embodiments, a layer of friction material (e.g., a separate layer) and a rotatable member (e.g., a ratchet wheel) may be sandwiched between, for example, a backing plate and a pressure plate, which may enhance the uniformity with which the friction braking surface of the layer of friction material and the contact surface of the rotatable member of the friction brake are pressed together. An arrangement of this general type is described in us patent 8430206.

Brake with limited use

By definition, the rotation-activated braking means of a fall protection device as disclosed herein, in particular the friction brakes thereof, are items of limited use. By limited use, it is meant that the braking device and friction brake are not activated during normal use of the fall protection apparatus (e.g., when a user of the device is performing a workplace operation and/or moving around a workplace). Instead, the braking device and its friction brake are only activated at the beginning of the fall. Thus, by definition, the friction brakes disclosed herein are distinct from friction brakes of a mobile vehicle, centrifugal brakes or clutches of a motor machine, or the like.

In various embodiments, the limited use friction brake may be activated no more than ten, five, or two times during the life of the fall protection device. In some embodiments, this friction brake will be a single use item that is not triggered more than once. That is, in common use of many such fall protection devices, the rotation-activated brake device and its friction brakes will remain in a ready state, but will rarely be activated. Further, in the event of a fall (e.g., such that a "shock indicator" of the device is activated or triggered), it is common for the fall protection device to be taken out of service (e.g., shipped back to the manufacturer) for inspection, refurbishment, and/or refurbishment as needed (as discussed in, for example, U.S. patent 7744063). Thus, in the relatively rare case where the friction brake of the fall protection device is triggered, the friction material of the friction brake will typically be replaced prior to any subsequent use of the device.

One of ordinary skill will appreciate that the readiness of a device such as a rotation-activated brake of a self-retracting lifeline is typically checked in the field, for example, by quickly pulling on the safety line to engage the pawl(s) with the ratchet to confirm that the rotation-activated brake can be "locked" as desired. However, because the force applied in such locking tests is much lower than that encountered when actually preventing a user from falling, such locking tests typically do not cause any significant movement of the contact surface of the rotatable member (e.g., ratchet wheel) of the friction brake relative to the friction braking surface of the friction material layer (and such tests typically do not have a significant abrasive effect or wear any portion of the friction material layer). In such a case, such a lock-up test is not considered to be "use" or "triggering" of the friction brake in the context considered herein.

It is clear from the above discussion that the friction brakes of fall protection devices are used in a very different way than most friction brakes used, for example, in mobile vehicles, machinery such as clutches, differentials, torque converters, etc. The latter application typically involves the triggering of a very high number (e.g. thousands) of friction brakes during its service life. Thus, manufacturers and users of such friction brakes consider ensuring that the friction material does not exhibit excessive wear, ensuring that it does not excessively wear the surfaces it contacts (e.g., the surfaces of a vehicle brake disc, rotor, or brake drum), and that the performance of the friction material remains relatively constant even when the friction material is mostly worn away upon repeated use. In contrast, the friction material of the friction brake of the fall protection device can exhibit the same friction braking surface during most or all of the usable service life of the device as when the friction brake was initially installed in the device. Thus, in many embodiments, the friction material layer of the fall protection device will be a non-abrasive item and thus distinguished from, for example, a vehicle brake pad or the like.

Constant contact brake

In many embodiments, the friction brake of the rotation-triggered braking device of the fall protection apparatus as disclosed herein is a constant contact brake. This means that the friction braking surface of the friction material layer remains in direct close contact with the contact surface of the rotatable member during use operation of the fall protection device. This also means that during normal use of the device there is no relative movement (sliding) between the two surfaces unless a fall of the user occurs. This constant contact brake is different from, for example, a brake or clutch of a vehicle or a motor machine, in that relative movement/slip between a friction braking surface and a contact surface occurs frequently and repeatedly during ordinary operation of the vehicle or machine. In particular, a constant contact brake may be contrasted with a friction brake that takes a significant portion of the time to retract the friction material layer from the contact surface such that a gap exists between the friction braking surface and the contact surface of the friction material layer.

It will be appreciated that since the friction brake of a fall protection device, such as for example a self-retracting lifeline, is rarely activated and typically resists a fall of a user for a fraction of a second (for example, within about 0.2-0.3 seconds), the friction material is less likely to encounter problems such as the need to minimize noise generation during operation or the need to ensure that performance does not deteriorate during extended periods of continuous use or during rapid continuous multiple uses. Furthermore, such friction materials are less likely to be affected by problems with performance in the presence of large amounts of water or lubricating oil, or problems with the speed at which the friction material wears the contact surfaces of the rotatable members of the friction brake. This is in stark contrast to problems arising in the use of friction materials, for example in vehicle brake pads, in clutches and transmissions for automotive machines, etc. Such considerations may explain why friction materials have not been vigorously developed and optimized in recent years for particular areas of friction brakes of fall protection devices.

The above discussion has presented that in various fall protection devices, friction brakes are used to gradually and gently resist a user's fall to some extent, rather than stopping the user abruptly. This can advantageously minimize the forces encountered during the process of arresting a fall. A continuing need in the fall protection industry is that many rotation-activated brake devices of fall protection apparatuses do not provide a uniform braking force during braking operations. In contrast, braking forces generally vary greatly over the duration of a braking operation, and in particular may exhibit peak braking forces of relatively short duration that are significantly higher than the braking forces present during other portions of the braking operation. Since very high braking forces (even in the case of short durations) can be undesirable, it is often necessary to configure the friction brakes of a rotation-triggered brake device such that the average braking force over the duration of the braking operation is lower than originally desired in order to ensure that the peak braking force remains below a specified level.

The operation of the invention shows that in many cases the peak braking force occurring during the friction braking operation of the rotation-triggered braking means of the fall protection arrangement is the initial braking force generated at the initial triggering of the rotation-triggered braking means. Such behavior is recorded in fig. 4, which is a comparative fall test showing a typical braking force versus time curve for a fall arrest by a self-retracting lifeline having a friction brake that uses a friction material representative of friction materials commonly used in the industry. It is clear that the initial braking force appears to be significantly higher than the average braking force (F)_a658 pounds force) of the sample _p926 pounds of force).

Ratio of peak brake force to average brake force

As shown by the force versus time curve presented in the working embodiment drop test of fig. 5, the inventive drop protection devices disclosed herein exhibit a significantly reduced tendency to peak braking force upon initial activation of a rotationally activated brake arrangement, which is significantly higher than the braking force applied during the remainder of the braking operation. In fact, fig. 5 shows that although a small local initial peak may occur, the local peak force may actually be lower than the force present during most of the remaining braking operations. This working example exhibited an absolute peak force F of 721 pounds_p(which actually occurs at the end of the braking operation rather than at the beginning of braking) and an average force F of 651 pounds_a. Thus, the ratio of peak force to average force for this working example was about 1.1, while the ratio of peak force to average force for the above comparative example was about 1.4. In various embodiments, the friction brakes disclosed herein may exhibit a ratio of peak force to average force of less than about 1.3, 1.2, 1.15, 1.1, 1.05, or 1.02.

In some embodiments, the performance of a friction brake may be characterized by the local slope of the force curve at the peak force that occurs during a braking operation. For purposes of such characterization, a time period of 4 milliseconds (starting from the time of the peak force and advancing in time) may be used or until a significant local minimum force is encountered. For example, for the comparative example of FIG. 4, this local slope would be (926-)/4, which corresponds to a change in braking force of approximately 70 pounds-force per millisecond of braking time. For the working embodiment of FIG. 5, this local slope would be (721- & gt 720)/4 or about 0.2 pound-force per millisecond of brake time. It will therefore be appreciated that even where a local peak in the force curve may occur at the initial triggering of the brake (as shown in figure 5), the maximum force may occur later, for example in a relatively flat portion of the force curve, allowing the total braking force to be maximised relative to the maximum force present. In various embodiments, the friction brakes disclosed herein may exhibit a local slope of the force curve at a peak force of less than about 40, 20, 10, 4, 2, 1, 0.5, 0.3, 0.2, or 0.1 pound-force change per millisecond of braking time.

In some embodiments, the performance of the friction brake may be characterized by the ratio of the braking force at the local initial force peak (if present) to the average braking force. For the working embodiment of fig. 5, the local initial force peak was significant and exhibited a force of 680 pounds. Thus, this ratio would be 680/658, or about 1.0. (since the local initial peak force is the same as the absolute peak force (926 pounds) in the comparative example of FIG. 4, the ratio would be 926/658, or about 1.4, for this example). Thus, in various embodiments, the friction brakes disclosed herein may exhibit a ratio of local initial peak force to average force of less than about 1.3, 1.25, 1.15, 1.10, 1.05, 1.0, or 0.95.

It will be appreciated that providing a braking operation that does not exhibit an initial peak force significantly higher than the force generated during the remainder of the braking operation (regardless of the particular quantitative manner in which the performance of the friction brakes of the rotation-triggered braking arrangement of the fall protection device is characterized) can allow a higher average braking force to be achieved without causing the peak braking force to exceed a desired value. This may advantageously enhance the braking efficiency of the rotation-triggered braking device and may provide, for example, that the desired braking may be achieved in a shorter duration and/or a shorter fall distance. That is, a more efficient braking action may be achieved while at the same time being smoother, and in particular not subjecting the user to a relatively large initial peak force upon first activation of the rotation-activated braking device. In various embodiments, the fall protection devices disclosed herein will exhibit peak brake forces of less than 1500 pounds, 1200 pounds, or 900 pounds.

The above discussion shows that, in at least some instances, peak braking force issues that significantly exceed the overall average braking force during a braking operation may be caused by the presence of an initial braking force that greatly exceeds the subsequent braking force. This may be due, at least in part, to the difference between the static and dynamic frictional behavior of the materials used in the friction brake. This may also be caused at least in part by inertial effects that occur upon initial activation of the rotation-activated brake. With the guidance provided by these findings, the performance of a rotation-triggered arresting device in a fall protection arrangement can be enhanced.

It has now been recognized that it is useful to minimize the frictional interaction between the frictional braking surfaces of the friction material layer and the contact surfaces of the rotatable member under non-moving (static) conditions, relative to the frictional interaction between these surfaces under moving (dynamic) conditions. In other words, minimizing static frictional interaction between these surfaces, as compared to dynamic frictional interaction between these surfaces, can minimize the force generated when the two surfaces begin to move relative to each other, as compared to the force that occurs on the rest of the braking operation. This may allow an advantageously high average braking force to be used during a braking operation while still remaining below the desired peak braking force.

The reduction in peak force encountered in a braking operation may be achieved, for example, by configuring the contact surface of the rotatable member of the friction brake to combine with the friction braking surface of the friction material layer to preferentially reduce the braking force present at the initial engagement of the brake as compared to the braking force present during the remainder of the braking operation. (alternatively, this may be considered as preferentially increasing the braking force present during the remainder of the braking operation over the initial braking force). In some embodiments, this may be accomplished, at least in part, by increasing the frictional force present under dynamic (moving) conditions relative to the frictional force present under static (non-moving) conditions. Conventional parameters such as dynamic and static coefficients of friction may provide guidance for such behavior. However, one of ordinary skill will appreciate that such parameters rely on a simple tribology model (often referred to as a "coulomb" model or a "standard" friction model) that does not take into account the various factors that will be discussed later herein. Thus, it should be understood that while various methods of measuring the coefficient of friction can be used to screen potentially useful materials, the most suitable way to determine whether a friction material will provide enhanced braking performance in a friction brake of a fall protection device is to install the material in the fall protection device and subject the device to the fall test disclosed herein.

However, various test equipment and procedures for measuring the coefficient of friction may be used to screen potentially useful materials. For example, the coefficient of friction test may be performed using a RHEOMETER, such as that available under the trade designation ARES-G2RHEOMETER from TA Instruments, united states of newcastle, tera (TA Instruments, New Castle, delaware (usa)), equipped with a Tribo RHEOMETER attachment. (unless otherwise indicated, all values of static and dynamic coefficients of friction mentioned herein will be derived from such rheometer tests.) for such tests, a layer of friction material may be mounted on the support plate for ease of handling. Using this rheometer, the friction braking surface of a friction material sample is brought into contact with the contact surface of a sample of a rotatable member having a specified force, after which the samples are moved relative to each other at a specified speed. (convenient test conditions may provide testing at room temperature at a nominal normal force of 20N and a nominal slip speed of 4 m/s.) the friction material and/or rotatable member material may be sized and shaped as needed to conform to the test equipment, noting that the effect of any such manipulation may be minimal, as the results will typically be calculated as a ratio of the static coefficient of friction to the dynamic coefficient of friction obtained using the same sample format and geometry.

Screening of potentially useful materials may also be performed by using a so-called Nano-indentation testing apparatus, for example, a product available under the trade name Nano-introducer G200 from Keysight Technologies, inc. In such tests, a probe tip (e.g., having a relatively large diameter, such as 1mm, and a material selected to represent a contact surface of a rotatable member of a friction brake, such as stainless steel) is contacted with a surface of a test specimen with a specified force, followed by moving the probe tip and the test specimen relative to each other at a desired speed. Screening of potentially useful materials may also be performed by using a sliding, weight-slide apparatus and process of the general type disclosed in ASTM test method D1894-14. The friction characteristics of vehicle brake pads are typically evaluated by using an inertia dynamometer or a CHASE apparatus; this apparatus can be used to screen potentially suitable materials if desired. In any such test, sufficient iterations may be performed to obtain statistically significant results. However, (as discussed above, the friction material layer is not typically a wear item), in order to provide a test method most similar to actual use conditions, a single sample should not be subjected to repeated tests that wear away a significant portion of the friction material layer.

Thus, in some embodiments, the frictional behavior of the friction braking surface of the friction material layer and the contact surface of the rotatable member may be evaluated by measuring the static coefficient of friction between the friction braking surface of the friction material layer and the contact surface of the rotatable member, and by measuring the dynamic coefficient of friction between the two surfaces. In some embodiments, the static coefficient of friction of the two surfaces may be about equal to or less than the dynamic coefficient of friction of the surfaces. In this case, "about equal to" means that the ratio of the static coefficient of friction of the surfaces to the dynamic coefficient of friction of the surfaces does not exceed 1.09; in some embodiments, the ratio is less than 1.04 or 1.01 microns.

In the operation of the present invention, it should be understood that when the friction brake is first activated, the inertial effects due to the rapid movement of the pawl(s), spool, and/or any portion of the safety line wound on the spool may also contribute to the peak forces that occur when the rotation-activated braking device is first activated. In this case, in some embodiments, it is advantageous to provide that the static coefficient of friction of the two surfaces is less than the dynamic coefficient of friction of the two surfaces. Thus, in various embodiments, the ratio of the static coefficient of friction to the dynamic coefficient of friction of the two surfaces may be less than 1.00, 0.99, 0.97, 0.95, 0.92, 0.90, 0.85, or 0.80.

In some embodiments, the composition of at least the contact surface of the rotatable member of the rotation-triggered braking device may be selected to promote increased friction under dynamic conditions as compared to friction under static conditions. However, in some embodiments (e.g., if the rotatable member is a ratchet of a friction brake), the options available for the rotatable member may be limited depending on, for example, strength requirements. Thus, in many embodiments, the rotatable member may be made of, for example, a metal such as stainless steel (e.g., 300 series steel), brass, bronze, and the like. Within any such limitations imposed by such requirements, the composition of the rotatable member may be varied to facilitate the effects disclosed herein. Furthermore, the contact surface of the rotatable member may be coated, treated, etc., for example, to advantageously promote increased friction under dynamic conditions.

Composition of friction material

The composition of the friction material layer may be selected to promote increased friction under dynamic conditions as compared to friction under static conditions. The skilled artisan can select from any suitable friction material, according to the guidance provided herein. The friction material layer may take any suitable physical form and geometry. Thus, in some embodiments, the friction material layer may be, for example, a monolithic material layer (e.g., a ring or disc). However, in some convenient embodiments, the friction material may be a composite material having a first (matrix) phase and having a second phase comprising one or more additives. In some embodiments, the first phase comprises an organic polymeric binder; for example a crosslinked organic polymeric binder such as, for example, a cured epoxy resin, a phenol-formaldehyde resin or a urethane resin. In many convenient embodiments, this binder may take the form of a liquid or latex (to which one or more additives are added) that is crosslinked and/or cured to form a first phase; however, in some embodiments, the binder may include, for example, at least some particles that are melted or otherwise agglomerated, and may be crosslinked or cured, if desired. In particular embodiments, the first phase may comprise a fibrous web (e.g., a nonwoven web) impregnated with a binder. In various embodiments, the first phase (e.g., binder) may comprise at least about 5, about 10, 15, 20, 30, 40, 50, 60, 70, or 80 weight percent of the total friction material. In further embodiments, the first phase (e.g., binder) may comprise up to about 85 wt.%, about 75 wt.%, 65 wt.%, 55 wt.%, 45 wt.%, 35 wt.%, 25 wt.%, 18 wt.%, 13 wt.%, or 8 wt.% of the total friction material.

In some embodiments, the additive(s) of the second phase may comprise one or more particulate materials, which term is used broadly and includes any material that is present, for example, in the form of particles, granules, powder, fibers, and the like. Such particulate materials may have any shape, size, or aspect ratio, and may exist as discrete entities, or may exist in such amounts, sizes, and/or forms so as to occupy an at least semi-continuous second phase. In various embodiments, any such particulate material may have an average particle size of at least 0.1 micron, 0.5 micron, 1.0 micron, 5.0 microns, 10 microns, 20 microns, 50 microns, or 100 microns. In further embodiments, any such particulate material may have an average particle size of up to about 1000 microns, 500 microns, 400 microns, 300 microns, 200 microns, 120 microns, 80 microns, or 40 microns. (if a plurality of particulate materials having different compositions are included, the particle size of each type of material may be evaluated separately; in the case of a fiber additive, the length of the fiber may be used as the particle size.)

The additives may be selected from, for example, filler materials (e.g., particles and/or fibers), abrasives (e.g., particles), structural (e.g., reinforcing) materials, and any of a variety of performance additives sometimes added to, for example, vehicle brake pads. Some such materials may be used only as, for example, relatively inexpensive space fillers, while other materials may impart particular characteristics (e.g., they may be abrasive in nature, or may be used to enhance the structural integrity of the friction material). It is to be understood that the boundaries between such functional categories may not be definite boundaries, and that many such additives may serve multiple functions. (it is also noteworthy that many materials have historically been included in friction materials, such as vehicle brake pads, to impart properties that are of little or no concern in this patent application (e.g., wear resistance and uniformity of performance over extended periods of use.)

Specific additives that may be included in the friction material, for example, particulate additives, may include, for example, inorganic particles such as, for example, mineral fillers, quartz, barium sulfate, calcium hydroxide, calcium carbonate, alumina, talc, clays, diatomaceous earth, mica, molybdenum disulfide, potassium titanate, metal sulfides, ceramic microspheres, and/or inorganic fibers such as glass fibers or mineral wool. Other ingredients that may be included are carbon-based or carbonaceous materials such as, for example, carbon black, graphite, coal dust, ground or particulate (e.g., recycled) rubber, ground nut shells such as, for example, cashew shell, carbon fiber, particulate or fibrous aramid fibers, particulate or fibrous aramid, and the like. Other potential constituents include metallic materials such as, for example, iron or steel powder and particulate copper. In some embodiments, a liquid or semi-liquid material (e.g., oil, wax, or putty) may comprise any desired ingredients, for example, as a lubricant, stabilizer, or for any other function. (particular liquids found to be useful in, for example, vehicle brake pads include, for example, cashew nut shell liquids, linseed oils, etc., noting that in some cases some such additives may be cross-linkable to form part of the first phase of the above-described compositions.) any such additives may, for example, be mixed into a curable resin (e.g., an epoxy resin and/or a phenol-formaldehyde resin) to form a mixture, which may then be reacted (cured) to form a composite. In some embodiments, one or more additional polymers or resins (whether curable; e.g., curable or non-curable silicone resins) may be included.

Various components and additives that may be included in the friction material are described, for example, in U.S. patent 6630416 to Lam, U.S. patent 7441635 to Rosenlocher, and U.S. patent application publication 2014/0124310 to Chiddick, all of which are incorporated herein by reference in their entirety for this purpose. Some of these sources may provide useful guidance to the ordinarily skilled artisan regarding the effect of various ingredients and compositions on the behavior of the friction material. However, it should be emphasized that such documents are primarily concerned with controlling the friction material composition to address issues (e.g., minimizing noise generated during braking, or maximizing the ability to quickly dissipate heat and/or resist performance degradation when exposed to high temperatures for extended periods of time), which would not be considered relevant to the use of friction materials in fall protection devices. In particular, such documents do not guide the average technician in controlling the friction material composition to reduce the initial force peak at the time of the rotation-triggered detent engagement of the fall protection apparatus relative to the braking force on the remainder of the braking operation.

The findings presented herein show that modifications that increase the frictional interaction between the surface of the friction material and the contact surface of the rotatable member during a later portion of a braking operation (i.e., after an initial start of the braking operation) can advantageously enhance the braking performance of the fall protection apparatus. While in some cases this enhancement may be manifested by an increase in the ratio of static to dynamic coefficients of friction as measured by one of the test methods described above, it should be understood that such methods may provide an incomplete or surface view of the tribological phenomena that actually occur during a friction braking operation of the fall protection device. That is, the method of providing the coefficient of friction is based on a simplified friction model as previously indicated herein, and may not take into account that, for example, dynamic frictional interactions may vary with the magnitude of shear forces between surfaces and/or with the duration of shear forces. Furthermore, the dynamic frictional interaction may vary with a variable (e.g., local temperature) that itself varies with the magnitude and/or duration of the shear force.

It is therefore not necessary to capture the increase in braking performance of the friction brake of the rotation-triggered braking device of the fall protection with a conventionally measured friction coefficient. For example, the working example data of FIG. 5 shows that the braking force appears to increase during most of the remainder of the braking operation after a slight oscillation at the start of braking. This indicates that tribological phenomena may occur that are not well represented (e.g. by a single constant dynamic friction coefficient); also, the enhanced braking behavior observed based solely on the ratio of the measured static coefficient of friction to the measured dynamic coefficient of friction may not be interpretable or predictable.

In various embodiments, the friction material layer of a friction brake may include one or more additives for providing enhanced braking performance, for example, by facilitating increased dynamic frictional interaction of the friction braking surface of the friction material layer with the contact surface of the rotatable member during a later stage of a friction braking operation. For example, in some embodiments, this additive may be a particulate (granular) material that exhibits a characteristic known as swellability; i.e. a material whose volume increases when exposed to shear forces. When exposed on the friction braking surface of the friction material and when subjected to shear friction forces on the contact surface of the rotatable member, the particulate additive of this material may tend to expand (e.g., swell) outwardly against the contact surface of the rotatable member in a manner that increases the frictional interaction between the surface of the particulate additive and the contact surface of the rotatable member. Therefore, such a phenomenon may cause the friction braking force to increase during the latter stage of the friction braking operation. In some embodiments, one or more particulate additives may be used that provide increased frictional interaction of the frictional braking surface of the friction material with the contact surface of the rotatable member due to, for example, softening of the particulate additives during a braking operation. Such softening may be due, for example, to a slight local heating effect of the frictional interaction (which may be local and transient enough to make routine measurements difficult), and may, for example, allow the surface of the particulate additive to more thoroughly wet against the contact surface of the rotatable member, thereby increasing the frictional interaction.

Exemplary particulate additives that may have a beneficial effect due to one or more of the above mechanisms may include, for example, organic polymeric elastomer particles, such as, for example, rubber particles (whether in the form of granules, powders, etc., and whether made from natural rubber or from any of the available synthetic rubbers and elastomers). In various embodiments, such elastomeric particles may be thermoplastic or may be crosslinked to any desired degree, and may have other compositions and/or processing parameters selected to advantageously control properties such as modulus, elasticity or viscoelastic properties, viscosity, softening point, melting point, glass transition temperature (if present), and the like.

Other methods may also be used, for example, instead of or in combination with any of the above methods. For example, the friction material layer may include an additive that is a non-newtonian, shear thickening fluid. This fluid may be added directly to the binder used to prepare the friction material; alternatively, it may, for example, be adsorbed into particles of a porous material (e.g., foam) dispersed into the binder such that at least some of the particles and fluid therein are present at the friction braking surface of the resulting layer of friction material. In other methods, the first (matrix) phase of the friction material layer may be partially or completely formulated with a binder that itself provides shear thickening behavior. For example, such a binder may include shear rate dependent physical crosslinks (e.g., for certain boric acids including poly (siloxane) and poly (vinyl alcohol) materials). Any of the above methods can be used in combination, if desired, in order to enhance the braking performance of the fall protection apparatus.

As described above, the above-described effects relate to a phenomenon (for example, shear variance and/or time variance of dynamic friction interaction) that is not necessarily captured or displayed in the conventional friction coefficient obtained by the above-described test method. Such effects may have been previously overlooked and/or unexpected, for example in view of the very short time frame of operation of such friction brakes, in the fact that such effects may be effectively used in friction brakes of fall protection devices.

Any of the above materials and ingredients may be used in any combination as desired. As noted, in some embodiments, the resulting friction material may be a composite material, such as a multiphase material. In some embodiments, the resulting friction material may exhibit a porosity of at least 0.1%, 0.2%, 0.5%, 1.0%, 2.0%, 5.0%, or 10.0%. In other embodiments, the resulting friction material may exhibit a porosity of less than 8%, 4%, 1.5%, 0.45%, 0.25%, 0.15%, or 0.05%. In some embodiments, the friction material may include a ceramic material (e.g., it may include silicon carbide as a particle additive or as a sintering binder). In other embodiments, the friction material may comprise less than 20%, 10%, 5%, 2%, 1%, 0.5%, or 0.1% by weight of the ceramic material. In some particular embodiments, the friction material may comprise less than 20%, 10%, 5%, 2%, 1%, 0.5%, or 0.1% by weight of a metal (in elemental or alloy form). In some embodiments, the friction material is not a ceramic material or a sintered material.

As noted, in some embodiments, the friction material may be provided as a layer of friction material having one major surface exposed to provide a friction braking surface and the other opposing major surface bonded to the support plate. This support plate can enhance the mechanical integrity and strength of the friction material layer and/or can allow the friction material layer to be, for example, positioned and retained at a particular location within the housing of the fall protection device (e.g., onto a shaft or drum of the device). In other embodiments, the friction material layer may be independent as described above. In some embodiments, the exposed friction braking surface of the friction material layer may be, for example, ground, polished, etc., e.g., to control the smoothness of the surface.

Since friction brakes are limited items of use that may wear little or no friction material during ordinary use of the fall protection device, in some embodiments, the layer of friction material may be relatively thin, for example, compared to a vehicle brake pad. In various embodiments, the friction material layer may exhibit a thickness equal to or less than 5.0mm, 4.0mm, 3.0mm, 2.5mm, 2.0mm, 1.5mm, or 1.0 mm. In some embodiments, the friction material layer may include a multi-layer structure having a base layer (e.g., containing only a binder, or containing a binder and a filler, and which may itself be disposed on a metal support plate), and a relatively thin outermost layer that provides the friction braking surface of the friction material layer and includes, for example, a binder and various additives as needed to facilitate the effects disclosed herein.

The absolute value of the coefficient of friction of the friction material can be set to any desired range as long as the effects disclosed herein are allowed, if necessary. In various embodiments, the static coefficient of friction of the friction braking surface of the friction material when combined with the contact surface of the rotatable member may be at least about 0.1, 0.2, 0.3, 0.4, 0.5, or 0.6; in further embodiments, it may be up to about 0.85, 0.65, 0.55, 0.45, 0.35, or 0.25. In various embodiments, the friction braking surface of the friction material may have a dynamic coefficient of friction of at least about 0.15, 0.25, 0.35, 0.45, 0.55, or 0.65; in further embodiments, it may be up to about 0.9, 0.7, 0.6, 0.5, 0.4, or 0.2.

Fall protection product

The arrangement disclosed herein can be advantageously used with any fall protection device; in particular, for use in self-retracting lifelines. Fall protection devices such as, for example, self-retracting lifelines, which can advantageously utilize the arrangements disclosed herein, are described in U.S. patents 8181744, 8256574, 8430206, 8430207, 8511434 and 9488235 and U.S. published patent application 2016/0096048, in addition to the documents previously cited herein.

In some embodiments, the fall protection device is a self-retracting lifeline that meets the requirements of ANSI Z359.14-2014. In general, the arrangements disclosed herein may be used in any fall protection device where it is desirable to resist a user falling while minimizing peak braking force relative to average braking force. In some embodiments, the arrangements disclosed herein can be used in fall protection products, which can be used as a descender (e.g., can allow self rescue capability) or rope adjuster in at least some modes of operation. For example, the fall protection device can include both a full arrest (stop) mode and a descent mode, e.g., as described in U.S. published patent application 2010/0226748.

In various embodiments, the fall protection device is used with or as part of any suitable fall protection system, such as, for example, a horizontal lifeline or retractable horizontal lifeline, a positioning lanyard, a shock absorbing lanyard, a rope adjuster or rope grab, a vertical safety system (such as, for example, a flexible cable, a rigid rail, a climbing assistance or fixed ladder safety system), an enclosed space rescue system, or a lift system. In some embodiments, a Fall Protection device as disclosed herein can include a housing configured such that the interior of the device is at least partially SEALED, such as the product line available under the trade name (SEALED-black) from 3M Fall Protection, for example, for use in harsh or marine environments. In some cases, the fall protection apparatus disclosed herein may be applicable to so-called "leading edge" workplace environments. It should also be noted that the discussion herein is primarily directed to devices (e.g., self-retracting lifelines) that include a housing that is mounted, for example, to a high altitude anchor and that includes a safety line having a distal end that is attachable to a harness of a user. It will be appreciated that the arrangements disclosed herein may also be used, for example, with a "personal" self-retracting lifeline that includes a housing that is mountable to a harness of a user and includes a safety line having a distal end that is attachable, for example, to a high altitude anchor. Such devices are exemplified by the product family available from 3M Fall Protection (3M Fall Protection) under the trade name talen.

It should be understood that any such fall protection device can include or be used with a variety of ancillary items not described in detail herein. Such items may include, but are not limited to, one or more of lanyards, shock absorbers, tear strips, harnesses, straps, bands, liners, tool holsters or pouches, impact indicators, hook loops, D-rings, anchor connectors, and the like. Many such devices, products and components are described in detail, for example, in the 3M DBI-sal full-range catalog (fall 2016). Although in many embodiments, it may not be necessary due to the presence of a friction brake, in some embodiments, the safety line of the device may include a shock absorber of the type previously described herein. In other embodiments, such shock absorbers will not be present. It should be understood that a "non-motorized" fall protection device as previously defined and described herein can also include such items as one or more electrically powered sensors, monitors, communication units, actuators, and the like.

List of exemplary embodiments