阅读说明：本技术 滚珠螺杆密封件 (Ball screw seal ) 是由 M·索默菲尔德 于 2020-08-21 设计创作，主要内容包括：一种滚珠螺杆组件(2)包含：螺帽(4),该螺帽(4)具有形成于径向内表面(10)上且限定轴线(X)的第一螺旋沟槽；螺杆(6),该螺杆(6)沿该轴线(X)设置且位于该螺帽(4)内,该螺杆(6)包含形成于径向外表面(12)上且与该第一螺旋沟槽相对以便形成螺旋滚道的第二螺旋沟槽；及复数个滚珠,该复数个滚珠设置在该螺旋滚道中。环形密封件(18)径向设置在该螺帽(4)与该螺杆(6)之间,该密封件(18)包含弹性主体(26)；及层(32),该层(32)由PTFE形成且径向设置在该弹性主体(26)与该螺杆(6)之间且经构造来接触该螺杆(6)之该径向外表面(12)。环形刮刀(22)轴向设置成邻近于该密封件(18),该刮刀(22)经构造来在一个轴向端部处接收流体且在第二轴向端部处排出流体。(A ball screw assembly (2) comprising: a nut (4), the nut (4) having a first helical groove formed on a radially inner surface (10) and defining an axis (X); a screw (6), the screw (6) being arranged along the axis (X) and being located inside the nut (4), the screw (6) comprising a second helical groove formed on the radially outer surface (12) and opposite to the first helical groove so as to form a helical raceway; and a plurality of balls disposed in the spiral raceway. An annular seal (18) is radially disposed between the nut (4) and the screw (6), the seal (18) comprising an elastomeric body (26); and a layer (32), the layer (32) being formed of PTFE and being disposed radially between the elastic body (26) and the screw (6) and being configured to contact the radially outer surface (12) of the screw (6). An annular scraper (22) is axially disposed adjacent to the seal (18), the scraper (22) being configured to receive fluid at one axial end and to discharge fluid at a second axial end.)

1. A ball screw assembly (2), comprising:

a nut (4), the nut (4) having a first helical groove formed on a radially inner surface (10) and defining an axis (X);

a screw (6), the screw (6) being arranged along the axis (X) and being located inside the nut (4), the screw (6) comprising a second helical groove formed on the radially outer surface (12) and opposite to the first helical groove so as to form a helical raceway;

a plurality of balls disposed in the spiral raceway;

an annular seal (18), the annular seal (18) being disposed radially between the nut (4) and the screw (6), the seal (18) comprising:

an elastic body (26); and

a layer (32), the layer (32) being formed of PTFE and being disposed radially between the elastic body (26) and the screw (6) and being configured to contact the radially outer surface (12) of the screw (6); and

an annular scraper (22), the annular scraper (22) axially disposed adjacent to the seal (18), the scraper (22) configured to receive fluid at one axial end and to discharge fluid at a second axial end.

2. The ball screw assembly (2) of claim 1, wherein the resilient body (26) is formed of a resilient and/or compliant material.

3. The ball screw assembly (2) of claim 1 or 2, further comprising a housing (34), the housing (34) being positioned between the resilient body (26) and the nut (4), wherein the housing (34) is formed of a different material than the resilient body (26).

4. The ball screw assembly (2) of claim 3, wherein the housing (34) is formed of stainless steel.

5. The ball screw assembly (2) of any preceding claim, wherein the seal (18) further comprises a lip (38), the lip (38) directly contacting the screw (6) at the second helical groove.

6. The ball screw assembly (2) of claim 5, wherein the lip (38) abuts the resilient body (26).

7. A ball screw assembly (2) as claimed in claim 5 or 6, wherein the lip (38) contacts the helical groove along less than half the axial pitch of the groove.

8. A ball screw assembly (2) as claimed in claim 5, 6 or 7, wherein the lip (38) contacts the helical groove along less than one third of the axial pitch of the groove.

9. The ball screw assembly (2) of any preceding claim, wherein the scraper (22) comprises a plurality of slots (25), the plurality of slots (25) being angled relative to the axis X and configured to lift and guide fluid out of the second helical groove (12).

10. The ball screw assembly (2) of claim 9, wherein the slots (25) form a generally helical shape.

11. The ball screw assembly (2) of any preceding claim, wherein the nut (4) further comprises one or more passages (36), the one or more passages (36) having an opening at the radially inner surface (10), the scraper (22) being arranged adjacent to the opening and configured such that fluid guided by the slots (25) from the second helical groove (12) enters the one or more passages (36) for discharge from the ball screw assembly (2).

12. An actuator for an aircraft engine thrust reverser comprising a ball screw assembly (2) according to any preceding claim.

13. An aircraft engine comprising a thrust reverser comprising the actuator of claim 12.

14. A seal assembly (16) for a ball screw assembly, the seal assembly (16) comprising:

an annular seal (18), the seal (18) comprising:

an elastic body (26);

a layer (32), the layer (32) being formed of PTFE and being disposed on one side of the elastic body (26); and

a housing (34), the housing (34) being disposed on opposite sides of the resilient body (26), wherein the housing (34) is formed of a different material than the resilient body (26); and optionally

An annular scraper (22), the annular scraper (22) axially disposed adjacent to the seal (18), the scraper (22) configured to receive fluid at one axial end and to discharge fluid at a second axial end.

15. A method of manufacturing a seal assembly (16) according to claim 14, the method comprising:

molding the layer (32) over the elastomeric body (26);

press fitting the resilient body into the housing (34); and optionally

The scraper (22) is provided and positioned adjacent to the resilient body (26) and/or the housing (34).

Technical Field

The present disclosure relates generally to ball screw assemblies and, more particularly, to aspects and embodiments of seals for ball screw assemblies. The seal is configured to move with the nut of the ball screw assembly and is configured to limit leakage of lubricant from the ball screw while the nut is moving in use, while limiting ingress of water into the ball screw.

Background

The ball screw assembly is used to convert rotational input into axial displacement with minimal friction loss. The ball screw assembly may include an actuator and may be used in various applications, including aircraft and aircraft engines.

Ball screw actuators are typically lubricated to facilitate relative movement between ball screw assemblies including a screw capable of rotating about an axis, a nut that moves axially relative to the screw, and ball bearings located between the nut and a working surface (e.g., a helical groove) of the screw. Most of the lubricant is located in the space between the nut and the screw to facilitate ball bearing movement. In use, lubricant will leak from this space and must be reapplied to the space in order to maintain an acceptable amount of lubricant. Therefore, it is desirable to seal the ball screw in the following manner: attempting to prevent leakage of lubricant from this space. This helps to maximize the time period between re-application of lubricant. Sealing is also desirable to limit the ingress of water or other contaminants from the exterior of the ball screw, which could impair the function of the ball screw by interfering with the lubricant.

This may be a particular concern for ball screw assemblies used in conjunction with aircraft, such as for flight control surfaces or thrust reverser actuation systems ("TRAS". A. for example, TRAS will be deployed upon landing, and in so doing, will expose the actuators of the ball screw assembly to a significant amount of moisture.

It is difficult to achieve an effective seal for a ball screw actuator. Seals that successfully limit lubricant leakage and water ingress typically create too much friction between the screw and nut, binding the actuator and preventing it from functioning properly. For example, seals made primarily of relatively rigid materials and powered by spring members must be designed with large clearances with the screw and nut in order to avoid frictional binding. Such voids result in an ineffective seal.

Accordingly, it is desirable to limit lubricant leakage from and water ingress into the ball screw, while also limiting the frictional forces between the various components of the ball screw.

Disclosure of Invention

According to a first aspect of the present disclosure, there is provided a ball screw assembly comprising: a nut having a first helical groove formed on a radially inner surface and defining an axis; a screw disposed along the axis and within the nut, the screw including a second helical groove formed on a radially outer surface opposite the first helical groove to form a helical raceway; a plurality of balls disposed in the spiral raceway. An annular seal is disposed radially between the nut and the screw, the seal comprising an elastomeric body (which may be referred to as a body made of a resilient and/or compliant material); and a layer formed of PTFE and disposed radially between the elastomeric body and the screw and configured to contact the radially outer surface of the screw. An annular scraper is disposed axially adjacent to the seal, the scraper being configured to receive fluid at one axial end and to discharge fluid at a second axial end.

In one embodiment, the resilient body is formed of a resilient and/or compliant material.

In a further embodiment according to any of the preceding embodiments, the ball screw assembly further comprises a housing positioned between the elastomeric body and the nut, wherein the housing is formed from a different material than the elastomeric body.

In a further embodiment according to any of the preceding embodiments, the housing is formed of stainless steel.

In a further embodiment according to any of the preceding embodiments, the seal further comprises a lip directly contacting the screw at the second helical groove.

In a further embodiment according to any of the preceding embodiments, the lip abuts the resilient body.

In a further embodiment according to any of the preceding embodiments, the lip contacts the helical groove along less than half of an axial pitch of the groove.

In a further embodiment according to any of the preceding embodiments, the lip contacts the helical groove along less than one third of the axial pitch of the groove.

In a further embodiment according to any of the preceding embodiments, the scraper comprises a plurality of slots angled with respect to the axis and configured to lift and direct fluid out of the second helical groove.

In a further embodiment according to any of the preceding embodiments, the slots form a substantially helical shape.

In a further embodiment according to any of the preceding embodiments, the nut further comprises one or more passages having an opening at the radially inner surface, the scraper being disposed adjacent to the opening and configured such that fluid directed from the second helical groove by the slots enters the one or more passages for discharge from the ball screw assembly.

According to a further aspect of the present invention there is provided an actuator for an aircraft engine thrust reverser comprising a ball screw assembly according to any one of the preceding embodiments.

According to a further aspect of the invention, an aircraft engine is provided comprising a thrust reverser according to the preceding embodiment.

According to a further aspect of the present invention, a seal assembly for a ball screw assembly is provided, the seal assembly comprising an annular seal, the seal comprising a resilient body; a layer formed of PTFE and disposed on one side of the elastic body; and a housing disposed on an opposite side of the resilient body, wherein the housing is formed of a different material than the resilient body. The seal assembly optionally further includes an annular scraper axially disposed adjacent to the seal, the scraper configured to receive fluid at one axial end and to discharge fluid at a second axial end.

According to a further aspect of the present invention, there is provided a method of manufacturing the seal assembly of the previous embodiment, the method comprising: molding the layer over the elastomeric body; press fitting the resilient body into the housing; and providing the scraper and positioning the scraper adjacent to the resilient body and/or the housing (e.g., against the resilient body and/or the housing without any additional components therebetween).

Drawings

FIG. 1 illustrates a partial cross-sectional view of a ball screw assembly according to one embodiment.

Fig. 2 shows a partial sectional view along line a-a of fig. 1.

Detailed Description

Various embodiments of a ball screw assembly, which may form a portion of an actuator, will be described herein. The actuators may be used in aircraft, such as actuators for flight control surfaces or thrust reverser actuation systems. Aspects of the present disclosure include an aircraft including an actuator and/or ball screw assembly that may be configured to actuate a flight control surface or thrust reverser actuation system. However, the present disclosure in its broadest aspect relates to a seal assembly for a ball screw which is itself advantageous and independently claimable.

As will be described in greater detail below, the seal assembly is configured to move with the nut of the ball screw, and is particularly suitable for use with flight control surfaces or thrust reverser actuation systems ("TRAS"), as the disclosed seal assembly may help limit lubricant leakage from the ball screw while limiting water ingress into the ball screw as the nut moves in use.

FIG. 1 schematically illustrates a partial cross-sectional view of a ball screw assembly 2 according to one embodiment. The ball screw assembly 2 includes a nut 4, a screw 6, and a plurality of balls (e.g., ball bearings; not shown). The nut 4 includes a helical groove (not shown) formed on a radially inner surface 10 thereof and the screw 6 includes a corresponding opposing helical groove 12 formed on a radially outer surface 14 thereof. The screw 6 is arranged within the nut 4 and, as is typical, balls are seated between the screw 6 and the nut 4 in respective helical grooves. The screw 6 is rotatable within the nut 4, which causes the screw 6 and the nut 4 to move relative to each other along the shared axis X.

The screw 4, nut 6 and balls are lubricated to facilitate this movement. The ball screw assembly 2 may use any suitable lubricant known in the art, in particular an oil lubricant or a grease lubricant.

The ball screw assembly 2 comprises an outboard end positioned towards the intended direction of actuation and closest to the external environment; and an inboard end positioned away from an intended actuation direction and furthest from an external environment.

The ball screw assembly 2 includes a seal assembly 16 disposed between the nut 4 and the screw 6. The sealing assembly 16 is arranged at a section of the nut 4 not comprising a helical groove and instead forms a recessed portion 5 with a corresponding space 7 between the radially inner surface 10 of the nut 4 and the radially outer surface 14 of the screw 6. The recessed portion 5 and the corresponding space 7 are shaped to receive a sealing component 16.

The seal assembly 16 includes an inboard end 17 and an outboard end 19, the outboard end 19 being proximate the outboard end of the ball screw assembly. The seal assembly 16 includes a seal 18, the seal 18 being located at an outboard end of the ball screw assembly 2.

The seal 18 is annular and extends circumferentially at least one full turn (360 °) around the screw 6. The seal 18 includes a resilient and/or compliant body 26. In one embodiment, the elastomeric body 26 comprises an elastomer. The body 26 includes a first base section 28, which first base section 28 may be generally rectangular in cross-section and is partially disposed in the gap 7. The body 26 also comprises a second section 30, the second section 30 being adjacent to the first section 28 and being disposed in the helical groove 12 of the screw 6 and being shaped to fit within the helical groove 12. The second section 30 may follow the same contour as the helical groove 12 of the screw 6, e.g. the second section 30 may be substantially semi-cylindrical.

The seal 18 further includes a cap or layer 32, the cap or layer 32 being disposed between the body 26 and the helical groove 12 and being configurable to prevent contact between at least the second section 30 of the body 26 and the helical groove 12 of the screw 6. A layer 32 separates the body 26 from the screw 6, wherein the layer may extend completely over the second section 30 and at least partially over the first section 28. The layer 32 may extend at least over the second section 30 of the body 26. Layer 32 may be formed of a material having a lower coefficient of friction (and/or more rigid) than the elastomeric material of body 26 so as to create less friction when in contact with screw 6. In one embodiment, the coefficient of friction of the material of body 26 may be at least half of the coefficient of friction of the material of layer 32. The material of the body 26 may comprise polytetrafluoroethylene ("PTFE").

The elastomeric material of the body 26 biases the layer 32 in a direction towards the screw 6 so as to energize the layer 32 into contact with the screw 6. The seal 18 thus provides a sealing contact between the nut 4 and the screw 6, in contrast to the direct contact achieved by the body 26 and the screw 6. Layer 32 reduces the coefficient of friction between the screw 6 and the seal 18 compared to body 26 alone, while allowing the use of highly elastic (but high friction) elastomeric materials for body 26. Thus, the combination of the elastomeric body 26 and the layer 32 provides effective sealing contact while avoiding binding of the ball screw assembly due to friction. Layer 32 also limits damage and wear to body 26. The combination of the resilient or compliant body 26 and the layer 32 means that large voids (mentioned in the background section above) can be substantially eliminated and the layer 32 is able to contact a larger surface area of the screw 6 in use.

In various embodiments, the seal further comprises a housing 34, which housing 34 may be disposed between the body 26 and the nut 4 at the recessed portion 5. The housing 34 may cover the radially outer side of the first section 28 so that the body 26 does not contact the nut 4. The elastomeric material of the sealing body 26 may be biased between the shell 34 and the layer 32 such that the elastomeric body 26 energizes the shell 34 to bring it into contact with the nut 4. The housing 34 helps to protect the housing 26 from damage and wear that may occur due to direct contact with the nut 4. To provide sufficient protection, the housing 34 may be formed from a material such as stainless steel. In various embodiments, body 26 is press fit into housing 34.

Even where an effective seal is provided, a certain amount of water may still enter the ball screw assembly, especially when environmental conditions are particularly adverse and large amounts of water accumulate near the seal. It is therefore desirable to prevent water from accumulating at the outboard end of the seal in order to reduce the water repellency requirements of the seal.

As described above, the seal assembly 16 includes a scraper 22 located outside of the seal. The scraper 22 is arranged between the screw 6 and the nut 4 and may be located in the space 7 formed by the recessed portion 5 of the nut (e.g. with the seal 18). The scraper 22 is directly adjacent to the seal 18 and may contact the seal 18, e.g., the scraper 22 may contact the housing 34. The scraper 22 may be a generally cylindrical component disposed about the axis X. The scraper 22 includes one or more slots 25 (shown schematically in fig. 1), the one or more slots 25 extending from an outboard end to an inboard end of the scraper 22 and being angled relative to the axis X such that an inboard end 27 of the slot 25 is radially outward of an outboard end 29 of the slot 25. In one embodiment, the scraper may contain a plurality of slots 25, such as at least 2, 3, 4, or 5 slots 25.

Fig. 2 shows a cross-sectional view through the blade 22 along the line a-a. As indicated, the slot 25 may extend at least partially around the circumference of the blade 22 as the slot 25 travels from its outboard end 29 to the inboard end 27. In this way, the slot 25 follows a substantially helical path as it moves axially from its outer end 29 to its inner end 27. The spiral path expands radially along the axial length of the blade 22 as the slot 25 also travels radially outward from its outer end 29 to its inner end 27.

Referring to both fig. 1 and 2, the one or more slots each receive or collect water at their outboard ends 29 as the screw 6 rotates relative to the scraper 22. The water travels through the slot pushed by the relative rotation of the screw 6 and the shape of the slot 22 before reaching the inboard end 27 and being discharged radially outwardly from the scraper 22. The nut 4 may include a passageway 36, the passageway 36 having an inlet formed through the radially inner wall 8 of the recessed portion 5 to allow for the removal of drained water from the ball screw assembly 2. Although only one passage 36 is shown, it should be understood that there may be multiple passages 36 formed in the nut 4. The scraper 22 may be arranged such that the slot inner end 27 intermittently aligns with one or more of the passages 36 during rotation. The water that has traveled to the inboard end 27 may then be discharged from the scraper 22 into the passage 36, and subsequently transported through the passage 36 and out of the ball screw assembly 2.

Thus, the scraper 22 removes water from the ball screw assembly 2 before the water reaches the seal 18, thereby improving the performance of the seal assembly 16. This is particularly useful when retracting the ball screw, as water can be removed before contacting the seal 18 and potentially entering the ball screw and undesirably interacting with the balls of the ball screw. As the screw 6 rotates, the slots 25 may be configured to lift and direct water out of the helical groove 12 of the screw 6 and toward one or more passageways 36.

In some embodiments, the body 26 of the seal 18 includes a third section or lip 38. The third section 38 is axially adjacent to and abuts the first section 28 and is formed of the same material. The third section 38 is located at the outer side of the seal 18 and may be axially located between the first section 28 and the scraper 22. The third section 38 forms a lip which extends around the layer 32 and past (the radially inner part of) the layer 32 so as to directly contact a relatively small part of the helical groove 12 of the screw 6 (i.e. relative to the larger contact area between the layer 32 and the screw). The lip 38 may contact the helical groove 12 along less than half of the axial pitch or extent of the groove 12 (e.g., less than one-third of the axial pitch of the groove). The third section 38 may extend axially less than about 15%, 10%, or even 5% of the axial length of the elastomer 26.

Although the scraper 22 acts to remove most of the water 22, some of the water may not be drained. The third section or lip 38 of the body 26 acts as a wiper on the screw 6 to wipe off water that was not initially removed by the scraper 22, and also provides additional sealing to the screw 6. The friction between the elastomeric material of the third section 38 and the screw 6 provides for efficient removal of residual water from the screw 6, while the limited contact of the third section 38 along the axial pitch of the helical groove 12 minimizes the contact area and consequent friction to prevent substantial binding of the ball screw assembly 2. Although the lip 38 is not necessary for the broadest aspects of the present disclosure, the lip 38 is considered to be the best balance between sealing and friction when combined with the seal 18 and scraper 22. That is, the gap between the seal 18 and the screw 6 may still be substantially eliminated (to provide improved sealing and low friction, as discussed above), while still providing a small direct contact area between the resilient or compliant material of the body 26 to further substantially reduce water ingress.

As described above, the ball screw assembly 2 may be used in actuators in aerospace applications, such as in linear actuators for aircraft engine thrust reversers. Thrust reverser actuators need to operate reliably while having low mass and low maintenance intervals. Additionally, components in aerospace applications are susceptible to adverse environmental conditions, which result in water ingress, and the presently disclosed technology is optimized to reduce this water ingress while maintaining low friction and improved sealing, as discussed above.

It is to be understood that the above description is a non-limiting example of the present disclosure. Changes and modifications may be made without departing from the scope of the present disclosure as defined in the following claims.