阅读说明：本技术 可调节的人体工学椅子 (Adjustable ergonomic chair ) 是由 P.J.拜尔 K.R.弗利特 T.A.贝林加 于 2020-01-03 设计创作，主要内容包括：一种办公型椅子包括：底座；从底座向上延伸的高度可调节的轴架；包括后座部部分和前座部部分的座部组件；以及将轴架连接到座部组件的连杆系统。连杆系统适于使座部组件在用作工作椅的降低的位置和用作升高的座位支承的升高的位置之间枢转。靠背布置可从座部组件延伸。在降低的位置,前座部部分和后座部部分两者均大体上水平定向。在升高的位置,后座部部分可略微向前倾斜,并且相比于在降低的位置,其定位得更高,并且前座部部分可相对于后座部部分以向下的角度延伸。(An office-type chair comprising: a base; a height adjustable pedestal extending upwardly from the base; a seat assembly including a rear seat portion and a front seat portion; and a linkage system connecting the pedestal to the seat assembly. The linkage system is adapted to pivot the seat assembly between a lowered position for use as a work chair and a raised position for use as a raised seat support. The backrest arrangement may extend from the seat assembly. In the lowered position, both the front seat portion and the rear seat portion are oriented substantially horizontally. In the raised position, the rear seat portion may be slightly inclined forwardly and positioned higher than in the lowered position, and the front seat portion may extend at a downward angle relative to the rear seat portion.)

1. An office-type chair comprising:

a base;

a height adjustable pedestal extending upwardly from the base;

a seat assembly including a rear seat portion and a front seat portion;

a linkage system connecting the shaft bracket to the seat assembly, wherein the linkage system is adapted to pivot the seat assembly between a first, generally horizontal position for use as a work chair and a second, more upwardly and forwardly angled position for use as a raised seat support, and

a backrest arrangement including a recline mechanism and a backrest support extending upwardly from the seat assembly to support a user's back in the first and second positions, wherein the recline mechanism is connected to the rear portion of the seat assembly and the backrest support rotates relative to the recline mechanism.

2. The chair according to claim 1, wherein said base includes a plurality of support arms having non-locking casters.

3. The chair according to claim 1, wherein the linkage system includes a support arm that articulates in a continuous path of motion between a first, in-position and a second, more elevated, position.

4. A chair according to claim 3, characterized in that it comprises a bridge between said front seat portion and said rear seat portion, said bridge being formed by a staggered arrangement of finger-like projections slidable with respect to each other.

5. The chair according to claim 4, wherein said bridge between said front seat portion and said rear seat portion is located a distance of approximately 6 inches forward of the ischial tuberosities of the occupant.

6. A chair according to claim 3, wherein in the first position of the seat assembly, both the front seat portion and the rear seat portion are oriented substantially horizontally such that they are in line with each other with a rearward inclination of approximately 3.5 degrees.

7. The chair according to claim 3, wherein in said second position said rear seat portion is angled forwardly approximately 5 degrees.

8. A chair according to claim 3, wherein in the second position the front seat portion is at an angle of approximately 40 degrees relative to the rear seat portion.

9. The chair according to claim 3, wherein at least a portion of said rear seat portion is approximately 5 inches higher in said second position than in said first position.

10. A chair according to claim 3 wherein the rear seat portion includes a concave portion forming an ischial tuberosity recess, and wherein in the second position the ischial tuberosity recess is generally vertically in line with the centre of the height adjustable pedestal.

11. The chair according to claim 3, wherein said linkage system support arms include at least one rear support arm connected to said rear seat portion and at least one front support arm connected to said front seat portion, said support arms each having an upper end that moves in an arcuate motion between a first position and a second position.

12. An office-type chair comprising:

a base;

a height adjustable pedestal extending upwardly from the base;

a seat assembly supported on the pedestal, the seat assembly including a front seat surface and a rear seat surface, the front seat surface being pivotably connected to the rear seat surface; and

a linkage assembly supporting the seat assembly, the linkage assembly comprising: a rear portion connected to the rear seat portion, a front portion connected to the front seat portion, and an auxiliary portion, the linkage assembly being movable between a lowered position and a raised position, wherein in the lowered position the front seat surface and the rear seat surface are substantially aligned in a seat plane, and wherein in the raised position the rear seat portion is raised above its position in the lowered position and the front seat surface is angularly pivoted relative to the rear seat portion, the front seat surface extending at a downward angle relative to the rear seat portion to reduce stress on a user's thighs, wherein the user can actuate the auxiliary portion to assist in moving the seat assembly to the raised position.

13. The chair according to claim 12, wherein in the second position, the rear seat portion is angled forward approximately 5 degrees.

14. The chair according to claim 14, wherein in said second position, said front seat portion is at an angle of approximately 40 degrees relative to said rear seat portion.

15. The chair of claim 13, wherein the chair includes a back support that extends at a back angle relative to the seat assembly, and wherein movement of the seat assembly from the lowered position neither increases nor decreases the back angle.

16. The chair according to claim 13, wherein the angle of said rear seat portion from said lowered position to said raised position varies between about 8-10 degrees.

17. An office-type chair comprising:

a base;

a height adjustable pedestal extending upwardly from the base;

a seat assembly supported on the pedestal, the seat assembly comprising a front seat surface and a rear seat surface, the front seat surface being pivotably connected to the rear seat surface, wherein the seat assembly is movable between a lowered position and a raised position, wherein in the lowered position the front seat surface and the rear seat surface are substantially aligned in a seat plane, and wherein in the raised position the rear seat portion is raised above its position in the lowered position and the front seat surface pivots at a downward angle relative to the rear seat portion; and

a backrest arrangement connected to the rear seat surface, the backrest arrangement including a backrest support extending upwardly from the seat assembly and a recliner mechanism, the backrest arrangement moving with the rear seat surface between the lowered position and the raised position, the backrest support pivoting about the recliner mechanism relative to the rear seat surface.

18. The chair according to claim 17, wherein the change in angle of the rear seat portion from the lowered position to the raised position is between about 8-10 degrees and the change in angle of the front seat portion relative to the rear seat portion is about 40 degrees, thereby promoting a neutral posture of the user such that the angle of the user's thighs to torso is between about 121 and 135 degrees and the user's Posterior Superior Iliac Spine (PSIS) is positioned higher than the user's Anterior Superior Iliac Spine (ASIS).

19. A chair according to claim 18, characterized in that it comprises a bridge between said front seat portion and said rear seat portion, said bridge being formed by a staggered arrangement of finger-like projections slidable with respect to each other.

20. The chair according to claim 19, wherein the bridge between the front seat portion and the rear seat portion is located a distance of approximately 6 inches forward of the ischial tuberosities of the occupant.

Technical Field

The present invention relates to chairs, and more particularly to a chair configured to provide ergonomic sitting support in an elevated ergonomic position and adjustment between a standard upright posture and an elevated ergonomic position.

Background

Various designs for office chairs have been developed to provide ergonomic improvements for individuals who spend a significant amount of work time at the desk. In general, office chairs are designed to support an individual in an upright sitting position and are capable of reclining (recine) the seat back or adjusting the angle of the seat pan horizontally forward (referred to as "forward tilt"), or otherwise adjusting the angle of the seat pan according to individual preference. Most office chairs also include height adjustment for moving the seat portion of the chair up and down to accommodate individuals of different heights and sizes and/or the height of the tables used.

Stools, high-level stools and chairs, and other chairs, having a wide range of height adjustability have been used to enable users to work in either a sitting or standing position. Stools, bench-tops and chairs offer individuals the option of elevated seating when using a height adjustable table, but they also have a number of disadvantages (buffer from). First, stools and highchairs have stability problems in the elevated position, often requiring complex caster locking mechanisms, heavy bases and limited tilting. Second, stools have ergonomic problems, such as the individual needing to rest their feet on a foot ring for support, which results in an angle between the thigh and lower leg of less than 90 degrees and can restrict blood flow.

Noting the drawbacks of stools and elevated stools and chairs, the staff is left with the following options: fully seated or standing beside their work surface. Both of these postures are classified as "static" postures, in which the muscles are tight but not moving (as opposed to dynamic postures in which the muscles are tight and move with them). Static working posture is known to produce fatigue, for example, because the blood supply to muscles is reduced when the muscles exert a force in a stationary posture.

In contrast to static postures, dynamic postures (including movement while in a sitting position or between postures) promote proper blood flow and ensure proper maintenance of various healthy biological functions. Movement helps blood circulation through the muscles. Additionally, movement is ergonomically beneficial to the spine because spinal motion over time changes the load on the spine, thereby providing spinal nutrition (nutrition). Loading and unloading the spinal column allows fluid to be infused into and out of the disc by osmosis, thus improving nutritional support to the disc. Undermovement (such as from a static posture) will eventually cause muscle fatigue in the lower vertebrae, which may lead to discomfort.

The facilitation of a "neutral" sitting position may also reduce stress and moderate stress on the body to provide a comfortable working experience for an extended period of time. Each body joint has a neutral posture which is related to its alignment with respect to the rest of the body, in which case the musculoskeletal stresses of the joint are minimized and its strength is maximized. Minimizing stress to the joints increases the comfort of the body in this position. However, any change of the joints from their neutral posture reduces the strength of the body part, sometimes significantly, and may reduce the comfort of the body in the new posture.

Specifically, for the spine, neutral posture means that all three regions (cervical, thoracic and lumbar) are aligned. That is, the shape of the spine is based on the orientation of the pelvis. The neutral position of the pelvis may allow for ideal alignment of the pelvis and spine (specifically the lower back or lumbar region). As the orientation of the pelvis changes, the curvature of the lumbar spine also changes. Thus, when the pelvis is rotated backwards to allow an individual to sit in a traditional fixed 90 to 100 degree upright position, the natural lordotic curvature of the spine is flattened and may exhibit a reverse spinal curvature known as kyphosis. If the person's hip is restricted in flexion, they can also compensate by further bending the lumbar spine. When the lumbar spine is in this kyphotic state, it may compress the lumbar intervertebral discs unevenly (and may even cause the lumbar intervertebral discs to protrude posteriorly), and this subsequent spinal compression may cause both back pain and leg pain.

When seated with the spine in its neutral posture, generally, for individuals within the normal BMI range, the person's center of mass is directly above the ischial tuberosities. In a conventional upright sitting position, the seat cushion supports approximately 70-75% of the occupant's weight. This can result in pressure levels at the thigh-hip junction exceeding 2.25 psi with sitting, causing capillary inclusions (inclusions). Prolonged sitting postures can cause limited blood perfusion and often lead to irritation or the desire to transfer weight intermittently. If the pelvis is rotated forward, the weight of the person is transferred forward, causing more of their weight to be supported by the legs.

Early studies showed that the generally neutral position of the lumbar spine, where muscle relaxation of balance occurs, is an angle between the trunk and thighs of between about 121 and 135 degrees. Most current chairs are designed to support an occupant in an upright position (thighs at an angle of approximately 98-100 degrees to the torso). In addition, these chairs also provide some additional back tilt, increasing the thigh to torso angle to 120 degrees, but only in a more reclined position. While this tilting action induces movement of the riders by increasing the angle of the thighs to the torso, which is considered beneficial to the human body, it is done by pulling the riders off their tables and does not easily facilitate a continuous workflow. Some studies have also shown that in an inclined position, the weight of the abdomen can also cause the curvature of the lumbar spine to decrease (flatten), even though one would expect the angle of the torso and thighs to open up in effect increasing the lumbar curvature.

Referring now to fig. 14, the alignment of the pelvis relative to the spine is also important. When the person is in a neutral position, the Posterior Superior Iliac Spine (PSIS)104 is positioned slightly above the Anterior Superior Iliac Spine (ASIS) 106. In a standing position, known as the neutral position (despite the disadvantage of having all weight on the user's legs and feet), there is an average downward tilt angle of the pelvis (also known as the pelvic angle 108) which is about 9.9 degrees as measured in the sagittal (as shown, horizontal) plane 110. As the pelvis rotates backwards as it moves to the sitting position, the relationship between PSIS and ASIS changes, with ASIS becoming inline (in linewith) with it, or possibly even higher than PSIS.

In summary, studies have shown that an increase in dynamic posture, and an increase in the amount of time a user spends in a more neutral posture, can help reduce the stress on the user's musculoskeletal, resulting in less fatigue and a more ergonomic user experience. A more neutral posture is experienced when the thigh-to-torso angle is between about 121 and 135 degrees and the pelvis angle is such that the Posterior Superior Iliac Spine (PSIS) is positioned higher than the Anterior Superior Iliac Spine (ASIS), but not so high that the pelvis is no longer considered to be in a neutral posture. Manufacturers with an understanding of proper ergonomics will continue to develop seating styles that support and maximize these healthy and ergonomic postures.

Disclosure of Invention

The present invention provides an office-type chair that provides adjustment between a standard upright position and an ergonomically elevated position. Furthermore, it also facilitates activity and dynamic movement in the transition from one gesture to another.

In one embodiment, a chair includes a base, a height adjustable pedestal extending upwardly from the base, a seat assembly including a rear seat portion and a front seat portion, and a linkage system connecting the pedestal to the seat assembly. The linkage system is adapted to pivot the seat assembly between a first, generally horizontal position for use as a work chair and a second, more upwardly and forwardly angled position for use as a raised seat support. The chair may additionally include a work chair back arrangement including a recline mechanism and a back support extending upwardly from the seat assembly to support a user's back in the first and second positions, wherein the recline mechanism is connected to a rear portion of the seat assembly and the back support rotates relative to the recline mechanism.

In one embodiment, in the lowered position of the seat assembly, both the front seat portion and the rear seat portion are oriented substantially horizontally such that they are in line with each other. When the chair is in the raised position, the rear seat portion may be slightly inclined forwardly and positioned higher than in the lowered position, and the front seat portion may extend at a downward angle relative to the rear seat portion. In this raised position, the forward tilt of the rear seat portion promotes forward rotation of the user's pelvis, and the combination of the forward tilt of the rear seat portion and the downward angle of the front seat portion reduces stress on the user's thighs and promotes the thigh-torso angle to open to a neutral posture.

The rear seat portion of the chair may include a concave portion that forms the ischial tuberosity recess and functions to retain and support the user even when the rear seat portion is tilted slightly forward. In the raised position, the ischial tuberosity recesses are generally vertically in line with the center of the height adjustable pedestal to provide stability for a user seated on the rear seat portion. The chair may further comprise a bridge between the front seat portion and the rear seat portion, the bridge being formed by a staggered arrangement of relatively slidable finger-like projections. The bridge may be located a distance of approximately 6 inches forward of the ischial tuberosities of the occupant.

In one embodiment, the base includes a plurality of support arms with non-locking casters. In some cases, these casters may include features that prevent accidental repositioning of an unoccupied chair when the chair is articulated between the lowered and raised postural positions. As discussed in more detail below, the arrangement of the seat assembly in the raised ergonomic position provides adequate support for the user, with the user's feet supported on the ground, and the locking caster is unnecessary to use. Moving the seat to the raised position may require the user to stand on the chair in a dynamic position with natural pivoting at the ankle joint and the caster need not move significantly.

These and other objects, advantages and features of the invention will be more fully understood and appreciated by reference to the description of the current embodiment and the drawings.

Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in various other embodiments and of being practiced or of being carried out in various alternative ways not explicitly disclosed herein. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including" and "comprising" and variations thereof is meant to encompass the items listed thereafter and equivalents thereof, as well as additional items and equivalents thereof. In addition, descriptions that can be used for various embodiments are enumerated. The use of enumeration should not be understood as limiting the invention to any particular order or number of components unless explicitly stated otherwise. The use of enumeration also should not be understood as excluding from the scope of the present invention any additional steps or elements that may be combined or incorporated into the enumerated steps or elements.

Drawings

Fig. 1 is a front perspective view of a chair according to one embodiment of the present invention.

FIG. 2 is a front perspective view of the chair in a raised ergonomic position.

Figure 3 is a side view of a chair according to one embodiment.

Figure 4 is a side view of the chair in a raised ergonomic position.

Figure 5 is a front view of a chair according to one embodiment.

Figure 6 is a front view of the chair in a raised ergonomic position.

Figure 7 is a rear perspective view of a chair according to one embodiment.

FIG. 8 is a rear perspective view of the chair in the raised ergonomic position.

Figure 9 is a rear view of a chair according to one embodiment.

Figure 10 is a rear view of the chair in the raised ergonomic position.

Figure 11 is a front perspective view of a chair with the seat upholstery removed, according to one embodiment.

FIG. 12 is a front perspective view of the chair with the chair in the raised ergonomic position.

Figure 13 is a side view of a chair according to one embodiment with the back support shown in an upright position and an inclined position.

Fig. 14 is a schematic side view of the lumbar spine and pelvis of a user.

Detailed Description

Referring to the drawings, an office-type chair according to one embodiment of the present invention is shown and generally designated 10. The chair 10 includes a base 12, an axle bracket 14 extending upwardly from the base 12, a seat assembly 16 supported on the axle bracket 14, and a backrest 18 extending upwardly from the seat assembly 16. The linkage 20 operatively connects the seat assembly 16 to the pedestal 14 or base 12 and enables the seat assembly 16 to move from a lowered, generally horizontal position to a raised, ergonomic position, which will be described in greater detail below.

The base 12 forms a ground engaging surface for the office chair 10. In one embodiment, the base 12 includes a cylindrical hub 22 and a series of five support arms 24 extending radially outward from the hub 22 (although other types and different numbers of support members are possible). The support arms 24 may each include a caster 26, and in one embodiment, the caster 26 may be a non-locking caster 26. The non-locking caster may include standard non-locking casters and the following: limiting the speed or amount of rolling and may help prevent accidental repositioning or rolling off of the chair 10, for example, when a user is seated in the chair in a lowered or raised position. In another embodiment, not shown, the casters 26 may be selectively lockable such that a user may lock the casters to prevent the casters from rolling and, thus, prevent the chair 10 from moving along the floor.

An axle bracket 14 extends upwardly from the base 12. In the illustrated embodiment, the pedestal 14 includes a lower portion 28 and an upper portion 30 secured to the lower portion 28. The lower portion 28 is generally cylindrical and is sized to fit within the hub 22 of the base 12. The hub 22 may include a generally conventional height adjustment mechanism that may be actuated by a user to raise and lower the pedestal 14, and thus the height of the seat assembly 16 relative to the ground, by sliding the lower portion 28 of the pedestal 14 within the hub 22. In one embodiment, the activation lever 27 is connected to the height adjustment mechanism such that a user can activate the height adjustment mechanism by pulling the lever 27. The lower portion 28 is also rotatable within the hub 22 to enable rotational rotation of the seat assembly 16. In the illustrated embodiment, the upper portion 30 of the axle bracket 14 is secured to the lower portion 28, but extends at an angle from an upper end 32 of the lower portion 28. More particularly, in the illustrated embodiment, the upper portion 30 extends upwardly at an angle of approximately 30 degrees relative to the generally vertical lower portion 28, and the upper portion 30 extends forwardly toward the front edge of the seat assembly, as described in more detail below. Thus, the upper portion 30 functions as a support for the seat assembly 16 and the linkage 20. In the illustrated embodiment, the upper portion 30 is Y-shaped, extending from a narrow first end 31 and widening toward a second end 33, the second end 33 forming a yoke (yolk) having a first arm 35 and a second arm 37.

The seat assembly 16 is supported above the pedestal 14 and is movable between a lowered, generally horizontal position, as shown in FIG. 3, and a raised, ergonomic position, as shown in FIG. 4. In one embodiment, the seat assembly 16 includes a front portion 34 and a rear portion 36. The seat assembly 16 includes a cushion backer 35 extending continuously over both the front 34 and the rear 36. Upholstery 35 on front portion 34 includes an upper surface 38 and upholstery 35 on back portion 36 includes an upper surface 40. The front and rear portions 34, 36 are pivotable relative to each other, and as shown in the embodiment, the front portion 34 is pivotable downward relative to the rear portion 36. As described in more detail below, when the seat assembly 16 is lifted to the upper raised position shown in fig. 2, 4, 6, 8, 20, and 12, the front portion 34 pivots downward relative to the rear portion. In a lowered position, such as shown in fig. 1, 3, 5, 7, 9, and 11, the upper surface 38 of the front portion 34 and the upper surface 40 of the rear portion 36 are substantially aligned on the same plane. As shown in FIG. 3, this plane may be slightly rearwardly inclined relative to horizontal, such as about 3.5 degrees rearwardly inclined relative to horizontal, such that the rear edge 42 of the rear portion 36 is slightly lower than the front edge 44 of the front portion 36. In another embodiment, the angle of inclination of the seat assembly may be different, such as a rearward angle of inclination slightly greater or less than 3.5 degrees, or even truly horizontal or slightly forward inclined.

Referring now to fig. 2, 4, 6, 8 and 10, when the seat assembly 16 is in the ergonomically raised position, both portions of the seat assembly 16 can be raised from their lowered positions and the front portion 34 is tilted downward relative to the rear portion 36. In one embodiment, the rear portion 36 is raised from its lowered position by a dimension of between about 4 inches and 8 inches, and in a more particular embodiment, the rear portion is raised from its lowered position by about 5 inches and is generally aligned above the lower portion 28 of the pedestal 14. In addition, the rear portion 36 is inclined forwardly relative to its lowered position. In one embodiment, the rear portion of the seat undergoes a change in tilt angle of about 8.5 degrees as the rear portion of the seat moves from the lowered position to the raised position. In one embodiment, when the seat assembly is in the raised position, the rear portion 36 is tilted forward approximately 5 degrees relative to horizontal such that the rear portion 36 experiences a change in tilt angle of approximately 8.5 degrees from the lowered position (where the rear portion is tilted slightly backward approximately 3.5 degrees) to the raised position (where the rear portion is tilted forward approximately 5 degrees).

The movement of the front portion 34 is different from the movement of the rear portion 36 when moved to the raised position in a manner predetermined to promote a neutral posture. In one embodiment, when the seat assembly 16 is moved to the raised position, movement of the front portion 34 causes it to pivot generally about an axis 48 extending laterally through the front edge 44 of the front portion 34. The forward rear edge 50 is lifted from its lowered position. Thus, in the raised position, the front portion 34 is angled downwardly relative to the rear portion 36. In one embodiment, this angle between the front and rear portions 34, 36 is set at about 40 degrees, such that the front portion 34 is dropped (drop off) relative to the rear portion 36 to relieve stress on the user's thighs and promote an ergonomic posture by enabling the user's thigh-torso angle to open.

Referring now to fig. 11-12, the seat assembly 16 is shown with the cushion upholstery removed, exposing the seat pan 52. In the illustrated embodiment, the seat pan 52 is designed to be used with the chair 10 in both the lowered position and the raised position. The seat pan 52 includes a forward portion 54 associated with the forward portion 34 of the seat assembly and an aft portion 56 associated with the aft portion 36 of the seat assembly 16. As noted above, the front portion 54 is configured to pivot or flex relative to the rear portion 56 to enable the front portion 34 of the seat assembly 16 to pivot relative to the rear portion 36. In one embodiment, the forward and rearward portions 54, 56 of the seat pan pivot about the lateral axis 58 between the forward and rearward portions 54, 56 (and likewise, the forward and rearward portions 34, 36 of the seat assembly 16 also pivot about the lateral axis 58 generally aligned with the pivot point 92). The position of the lateral pivot axis 58 may be selected to facilitate bending of the seat assembly 16 at a desired location, such as a desired distance between the user's thighs and the ischial tuberosities. In one embodiment, the lateral axis 58 is located approximately six inches forward of the recess 60 such that the lateral pivot axis 58 is located approximately 6 inches forward of the user's ischial tuberosities, resulting in a comfortable experience for most users.

As shown in fig. 11 and 12, at least a portion of the rear portion 56 of the seat pan may be concave, forming a depression or "recess" 60 for receiving the ischial tuberosities of the user. In one embodiment, the recess 60 may be provided with a series of slots 62 extending through the seat plate 52 to provide increased flexibility to the seat plate 52 in the area of the recess 60. In another embodiment, also shown in fig. 11 and 12, the seat pan 52 includes a series of slots 53 in the front portion 54 of the seat pan 52, the slots 53 increasing the flexibility of the seat pan at the location of the slots and thus acting to relieve stress on the back of the user's thighs. The size and location of these slots 53 may be predetermined to relieve stress at desired locations. In the illustrated embodiment, slots 53 include a center group 55, a left side group 57, and a right side group 59.

While various methods may be used to create the pivoting or bending of the seat pan 52, the illustrated embodiment shows one such method that enables bending while reducing stress on the user. As shown in fig. 11 and 12, in this embodiment, forward portion 54 and rearward portion 56 of seat pan 52 cooperate to form a bridge 64 therebetween. In particular, the rear edge 66 of the front portion 54 includes a series of spaced apart flexible fingers 68 extending outwardly therefrom. Similarly, the front edge 70 of the rear portion 56 includes a single series of spaced apart flexible fingers 72. The fingers 68, 72 interlock with each other, with the fingers 68 extending into the gaps between the fingers 72 and below the leading edge 70 of the rear portion, and with the fingers 72 extending into the gaps between the fingers 68 and below the trailing edge 66 of the front portion 54. As shown in FIG. 12, when the seat assembly 16 is moved to the raised position, each finger 68, 72 flexes and slides relative to the opposing adjacent finger 68, 72, thereby providing a smooth rounded surface to the bridge 64 at this position of the lateral axle 58. In one embodiment, bridge 64 includes hinges 74 at lateral edges 76, 78 of seat pan 52 that interconnect forward portion 54 and aft portion 56 of seat pan 52. The characteristics of the bridge, such as the amount of curvature of the bridge 64 and the degree of flexibility of the bridge 64, may be controlled by varying the characteristics of the fingers 68, 72.

The chair 10 includes a mechanism for coupling the pedestal 14 (or in another embodiment, the base 12) to the seat assembly 16 to enable the seat assembly 16 to move between a lowered position and a raised ergonomic position. In the illustrated embodiment, the mechanism is a linkage mechanism 20 connected between the axle bracket 14 and the seat assembly 16. As shown, the link mechanism 20 includes a pair of first link arms 80, a pair of second link arms 82, and an auxiliary device 83. The first pair of link arms 80 and the second pair of link arms 82 together form a four-bar link. A first pair of link arms 80 extend from a central portion of the upper shaft mount 30 to the rear edge 42 of the rear portion 36 of the base assembly 16. The forward end 84 of the link arm 80 pivots relative to the pedestal 14 and the rearward end 86 of the link arm 80 pivots relative to the seat assembly 16. The second pair of link arms 82 extend between the front edge 33 of the upper pedestal 30 and the front edge 44 of the front portion 34. The second link arms 82 each include: a front end 90 pivotally connected to the axle bracket 14 (and aligned with the pivot axle 48) and a rear end 92 pivotally connected to the seat assembly 16. In the illustrated embodiment, these second link arms 82 are integral with the side faces 76, 78 of the seat plate 52, but they may alternatively be separate from the seat assembly 16. In one embodiment, the second link arm 82 is shorter than the first link arm 80. The arms 80, 82 are collectively pivotable between a first position, in which they are generally horizontal, and a second position, in which they are angled upwardly. During pivoting of the link arms, the rearward ends 86, 92 of the link arms move in a continuous arcuate motion that drives the seat assembly 16 from the lower position to the raised ergonomic position. The length and position of the link arms 80, 82 are predetermined so that the seat assembly is provided with the desired positioning in both positions. For reference, fig. 3 and 4 schematically illustrate (with crosshairs) the positions of the front end 90 of the link arm 82, the rear end 92 of the link arm 82, the front end 84 of the link arm 80, and the rear end 86 of the link arm 80. These four crosshair positions form the pivot point for the four bar linkage 20. Thus, one embodiment of the relative movement of the pivot points 86 and 92 between the two chair position positions can be seen in fig. 3 and 4.

The assist device 83 is mounted between a portion of the chair 10 and the seat assembly 16 and is actuatable to assist in moving the link arms 80, 82 and the seat assembly 16 to the ergonomic position. In one embodiment, the auxiliary device 83 is a gas assist cylinder 94 mounted between the upper axle bracket 30 and the front portion 34 of the seat assembly 16. The cylinder 94 includes a piston 95 that can be actuated to extend and drive the seat assembly 16 to a raised position. An activation rod 96 is connected to the cylinder 94 and can be pulled by a user to actuate the piston 95. In one embodiment, the assistance device 83 is provided with sufficient force to move the unoccupied chair 10 from the lowered position to the raised position, but insufficient force to move the occupied chair 10. As a result, the user must change from a static posture to a dynamic posture when the chair 10 is activated to move it to the elevated position. In alternative embodiments, the auxiliary device 83 may be a hydraulic cylinder, an electric drive, or another mechanism for assisting the movement of the seat assembly 16.

Referring now to FIG. 13, the backrest 18 extends upwardly from the seat assembly 16. As shown, the backrest 18 is connected to a rear edge 42 of the rear portion 36 of the seat assembly 16. As a result, the backrest 18 moves with the rear portion 36 as the rear portion moves between the lowered position and the raised ergonomic position. In one embodiment, the backrest 18 includes a tilting mechanism and is tiltable from an upright position shown in broken lines to a reclined position shown in solid lines as shown in FIG. 13. The user may operate the tilt mechanism at both the lowered position and the raised position of the seat assembly.

Figures 3 and 4 show a schematic form of an occupant 99 seated in the chair 10 to illustrate the occupant's posture and the change in the occupant's posture between the lowered position of the chair 10 shown in figure 3 and the raised ergonomic position of the chair 10 shown in figure 4. The position of the seat assembly 16 in the raised ergonomic position is predetermined to place the occupant or user 99 in a neutral position. In particular, the forward inclination of the upper surface 40 of the rear portion 36 and the angle between the upper surface 38 of the front portion 34 of the seat assembly 16 and the upper surface 40 of the rear portion 36 are predetermined to promote a neutral posture. The relative angles and positions of the front and rear portions 34, 36 promote a neutral posture of the occupant 99. Figures 3 and 4 show a vertical reference line 98 at the center of the body taken along the lateral midline of the torso using the center of the shoulder joint as a reference. Also shown is the midline of the thigh 100, which is aligned with the lateral midline of the femur, using the center of the knee joint as a reference. The angle 102 between these two lines is the thigh-torso angle and, as noted above, is an important measure of neutral posture. As shown in FIG. 3, in the lowered position of the chair 10 (typical of a standard work chair), the thigh-to-torso angle 102 is approximately between 90-100 degrees. As shown in fig. 4, when the chair 10 has been moved to the elevated ergonomic position, the thigh-to-torso angle 102 increases to approximately 128 degrees within an acceptable range of neutral postures, and thus provides the user with associated advantages. This is generally due to the combination of the forward inclination of the upper surface 40 of the rear portion 36 and the downward angle of the seat assembly front portion 34 relative to the rear portion 36. The forward tilt of the posterior portion 36 acts to rotate the pelvis forward so that the user's Posterior Superior Iliac Spine (PSIS) is higher than the user's Anterior Superior Iliac Spine (ASIS). The downward angle of the seat assembly front 34 acts to relieve stress on the user's thigh and enables the thigh-torso angle 102 to expand. Importantly, the raised ergonomic position promotes a neutral posture without pulling the user away from the work surface. In addition, the upper surface 40 of the rear seat assembly 36 and the ischial recesses 60 support the majority of the weight of the user even with the chair 10 in the raised position, thereby relieving stress and fatigue from standing. Finally, in the raised ergonomic position, the rear portion 36 of the seat assembly 16 is generally aligned above the pedestal lower portion 28, aligning the user's center of gravity above the center of the base, and maintaining the chair stable in the raised position.

Operation of the chair 10 according to one embodiment includes one or more of the following steps: (a) rolling the chair 10 to a desired position using the casters 26 (in an office environment, the desired position will generally be adjacent a work surface); (b) sitting on the chair 10 with the chair in the lowered position, wherein the upper surface 38 of the front portion 34 and the upper surface 40 of the rear portion 36 of the seat assembly 16 are substantially aligned to form a flat seating surface; (c) adjusting the height of the seat assembly 16 to a desired position by pulling the lever 27 to actuate the height adjustment mechanism; (d) when the user stands slightly to enable the chair to move to the raised ergonomic position, the user is moved from the static position to the dynamic position by pulling the activation lever 96 to activate the auxiliary cylinder 94 to move the seat assembly 16 from the lowered position to the raised ergonomic position. When in the raised ergonomic position, the user may release the lever 96 to lock the seat assembly 16 in the raised position so that the user may sit on the upper surface 40 of the rear portion 36 of the seat assembly 16. In one embodiment, the seat assembly 16 is only locked in the lowered position and the predetermined raised ergonomic position to facilitate the neutral position of the raised ergonomic position and to prevent the user from positioning the chair in a less ergonomic position. However, in alternative embodiments, the chair 10 may be configured such that a user may release the level (level) to also lock the chair 10 in any position between the lowered position and the raised position.

The above description is that of the current embodiment of the invention. Various modifications and changes may be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. This disclosure is presented for illustrative purposes and should not be construed as an exhaustive description of all embodiments of the invention or to limit the scope of the claims to the particular elements shown or described in connection with these embodiments. For example, and without limitation, any individual element(s) of the described invention may be replaced by alternative elements providing substantially similar functionality or otherwise providing appropriate operation. For example, this includes alternative elements that are currently known, such as those that may be currently known to those of skill in the art, and that may be developed in the future, such as those that may be recognized as alternatives by those of skill in the art at the time of development. Further, the disclosed embodiments include a number of features that are consistently described and that can cooperatively provide a range of benefits. The present invention is not limited to those embodiments that include all of these features or that provide all of the stated benefits, except to the extent explicitly stated in the issued claims. Features of various embodiments may be used in conjunction with features from other embodiments. Directional terms such as "vertical," "horizontal," "top," "bottom," "front," "back," "upper," "lower," "inner," "inward," "outer," "outward," "forward," and "rearward" are used to aid in the description of the invention based on the orientation of the embodiments shown in the drawings. The use of directional terms should not be construed to limit the invention to any particular orientation(s). For example, any reference to a claimed element in the singular using the articles "a," "an," "the," or "said" is not to be construed as limiting the element to the singular.