WO2002028339A2

WO2002028339A2 - Seat back

Info

Publication number: WO2002028339A2
Application number: PCT/US2001/030448
Authority: WO
Inventors: Bryan J. Griffiths; James L. Christofferson; Sharon L. Pratt
Original assignee: Sunrise Medical HHG Inc
Current assignee: Sunrise Medical HHG Inc
Priority date: 2000-10-02
Filing date: 2001-09-28
Publication date: 2002-04-11
Anticipated expiration: 2003-04-02
Also published as: AU2001294877A1; WO2002028339A3

Abstract

A seat back includes a shell, a targeting member mounted to a lower portion of the shell, and a coupling member mounted to an upper portion of the shell. The targeting member is adapted to be positioned substantially colinear to the wheelchair occupant's posterior superior illiac spine. The coupling member mounted is adjustable independently of said targeting member to adjust the orientation of the shell without affecting the position of the lower portion of the shell.

Description

SEAT BACK

BACKGROUND OF THE INVENTION This invention relates in general to chairs and more particularly, to seats for wheelchairs. Most particularly, the invention relates to wheelchair seat backs that are movable and flexible to accommodate an increased load capacity.

The anatomy and biomechanics of the human spine with normal neuromuscular function could be described as having an anterior curve in the lumbar area, a posterior curve in the thoracic area, and an anterior curve in the cervical area. When a person is in a seated position, large muscle groups, for example, the abdominal muscles and the spinal extensors, work hard in harmony to hold the body in a state of balance. The pelvis provides a support foundation, upon which the spine and the head are balanced.

When a person is in a seated position, the pelvis needs to be neutral or in a slightly anterior position in order for the spine and head to be in their most stable and therefore functional position. Three conditions affect the needs of the pelvis when a person is seated in a conventional seat.

First, the pelvis encounters posterior tilt or rocks backwards. When the pelvis rocks backwards, the spinal curves change. For example, the thoracic spine curvature increases, or becomes kyphotic, and the lumbar spine flattens or loses its anterior curve. This is not a desirable position for safety, function or skin protection.

Therefore, it is desirable to block the posterior pelvis so as to prevent posterior rocking of the pelvis, which will happen if the pelvis is unsupported due to the effects of gravity and fatigue of the major muscle groups.

Second, the back tends to flatten. The thoracic spine has a natural posterior curve. A flat back does not support a functional posture. Moreover, it causes fatigue. To prevent the muscles from having to work too hard and ultimately fatiguing, the spine needs to be supported accordingly. Third, the gluteal mass or soft tissue tends to spread in a posterior curve below a hinge point of the seat. When unaccommodated by back support, this causes the person to slide forward in the seat and consequently lose posterior pelvic contact with the seat, which further causes undesirable posterior pelvic tilt. What is needed is a back support that will solve the above identified problems by blocking the posterior pelvis at the level of an anatomic hinge point in the persons spine with a back support hinge that lines up with the anatomic hinge, extending posteriorly above the hinge point to accommodate the natural curvature and biomechanics of the spine, and flaring posteriorly beneath the hinge point to accommodate the curvature of the gluteal mass or soft tissue.

SUMMARY OF THE INVENTION The present invention is directed towards a back support that blocks the posterior pelvis while accommodating the natural curvature and biomechanics of the spine and curvature of the gluteal mass or soft tissue. The back support is comprised of a biangular seat back that includes a shell, a targeting member mounted to a lower portion of the shell, and a coupling member mounted to an upper portion of the shell. The targeting member is adapted to be positioned substantially colinear to the wheelchair occupant's posterior superior illiac spine. The coupling member mounted is adjustable independently of said targeting member to adjust the orientation of the shell without affecting the position of the lower portion of the shell.

Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an exploded perspective view of a wheelchair seat back. Fig. 2 is a front elevational view of the seat back shown in Fig. 1. Fig. 3 is a side elevational view of the seat back shown in Figs. 1 and 2. Fig. 4 is a perspective view of an alternative upper mounting bracket. Fig. 5 is a perspective view of the seat back attached to wheelchair seat back tubes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, there is illustrated in Figs. 1-3 a wheelchair seat back 10. The seat back 10 comprises an upper shell 12 and a lower shell 14. The upper and lower shells 12, 14 are pivotally connected together by a hinge 16. The hinge 16 is preferably adapted to be disposed at lower mounting points on wheelchair seat back tubes T (shown in Fig. 5). The lower mounting points are adapted to be positioned adjacent the posterior superior illiac spine (PSIS) of a person or user seated in the wheelchair against the seat back 10. The hinge 16 of the seat back 10, the PSIS of a user, and the lower mounting point all roughly line up to allow the user's pelvis to be oriented separately from the rest of the seat back 10. The upper and lower shells 12, 14 are adapted to be adjusted to fit the user's needs.

In accordance with a preferred embodiment of the invention, upper mounting brackets 18 are attached to upper opposing side portions of the upper shell 12. Lower mounting brackets 20 are attached to lower opposing side portions of the upper shell 12. The upper and lower mounting brackets 18, 20 are preferably laterally adjustable to accommodate wheelchairs of varying width. In a preferred embodiment of the invention, the lateral supports 22 are adjustable an aggregate amount of three inches to accommodate standard width wheelchairs. The adjustment of the lateral supports 22 may also render the seat back 10 suitable for use with wheelchairs that are dimensioned according to English and metric standards. Each upper mounting bracket 18 is comprised of a mounting block 24 that is adapted to be attached to the upper shell 12. A rack 26 is attached to each mounting block 24. An upper coupling member, such as the pin 25 shown, is supported by each rack 26. The racks 26 are preferably adjustable relative to the mounting blocks 24. In the preferred embodiment of the invention, the racks 26 are adjustable by discrete amounts.

Adjustment of the racks 26 may be accomplished in any suitable manner. For example, each rack 26 may be provided with a slot 28 for receiving one or more fasteners 30, such as the button-head cap screws shown. The fasteners 30 may be threadably engageable with threaded apertures (not shown) in the lateral ends of the mounting blocks 24 to secure the racks 26 to the mounting blocks 24. The racks 26 may be provided with a series of discretely spaced reliefs 32, which are adapted to receive the heads of the fasteners 30. The position of each rack 26 may be adjusted as desired by tightening the fasteners 30 so that the fastener heads tightly engage corresponding reliefs 32.

An alternative upper mounting bracket 18' is shown in Fig. 4. This upper mounting bracket 18' includes a rack 26' having a plurality of discretely spaced reliefs 32' that cooperate with one or more mating elements 33 supported by a mounting block 24'. The mating elements 33 are adapted to selectively engage desired reliefs 32' to orient the racks 26' in a desired position relative to the mounting blocks 24' of the upper mounting bracket 18'. This permits the seat back 10 to be oriented as desired. The orientation may be changed by engaging the mating elements 33 with other reliefs 32'. The rack 26' is secured to the mounting block 24' with fasteners 30. Upon securing the rack 26' to the mounting block 24', the mating elements 33 are secured into engagement with corresponding reliefs 32'.

Similar to the upper mounting brackets 18, the lower mounting brackets 20 are each comprised of a mounting block 34 that is adapted to be secured to the upper shell 12. A rack 36 is adapted to be attached to each mounting block 34. A lower coupling member, such as the pin 38 shown, is supported by each rack 36. In the preferred embodiment of the invention, the lower mounting brackets 20 are dimensioned and configured to support the pins 38 in a position that is substantially colinear to that of the PSIS of the user. Hence, the pins 38 function to position a lower portion of the upper shell 12 adjacent the PSIS of the user. In this way, the pin 38 functions as a locating or targeting member.

A plurality of vertically spaced, laterally extending slots 40, 42 may be provided in the upper shell 12. Similar slots 44 may be provided in the lower shell 14. Certain slots 40, 42 may permit lateral adjustment of the upper and lower mounting brackets 18, 20. These slots 40, 42 may also permit vertical adjustment of the upper and lower mounting brackets 18, 20. This may be accomplished with fasteners (not shown), similar to the button-head cap screws described above. The fasteners may be inserted through the mounting blocks 24, 34 and selective slots 40, 42 and then threadably engaged with threaded apertures in a mounting plate 46. The mounting blocks 24, 34 and plate 46 may be displaced laterally by loosening the fasteners.

Lateral supports 22 may be secured to the upper and/or lower shells 12, 14. The lateral supports 22 function to provide extra support for the upper trunk or torso of the user and thus, provide added stability. Lateral supports 22 of varying shape and dimension may be employed.

Slots 40, 42, 44 in the upper and lower shells 12, 14 permit lateral adjustment of the lateral supports 22. For example, lateral adjustment of the lateral supports 22 may be required for users having a wide pelvis and a relatively narrow upper torso. Such users are commonly referred to as having a "pear-shaped" physique. To ensure that the lateral supports 22 provide support where needed, the lateral supports may also be adjusted vertically. This may be accomplished via the use of fasteners, such as the button-head cap screws described above. The fasteners may be inserted through selective slots 40, 42, 44 and threaded into apertures in the lateral supports 22. The fasteners may be loosened to laterally adjust the lateral supports 22 and retightened once the lateral supports 22 are in a desired position.

The hinge 16 permits the lower shell 14 to be adjusted relative to the upper shell 12. The hinge 16 is adapted to be secured in a non-pivotal or fixed position to maintain the lower shell 14 in a substantially fixed position. This may be accomplished in any suitable manner. For example, the hinge 16 may include two members. An upper member may include a mounting plate 48 and a single hinge plate 50 integral with the mounting plate 48. A lower member may include a mounting plate 52 and a pair of laterally spaced hinge plates 54 integral with the mounting plate 52. The mounting plates 48, 52 are adapted to be secured to corresponding shells 12, 14. The single hinge plate 50 is adapted to be inserted and secured between the laterally spaced hinge plates 54. A fastener is adapted to be loosed to permit the single hinge plate 50 to pivot to allow the angular relationship between the upper and lower shells 12, 14 to be adjusted. Once a desired angular relationship is achieved, the fastener may be tightened to prevent the lower shell 14 from moving relative to the upper shell 12.

The upper shell 12 is preferably dish shaped in construction, meaning that the overall contour of the upper shell 12 is preferably concave. The concave contour is a consideration when determining the dimension of the racks 26 of the lower mounting brackets 20 and the location of the pins 38 relative to the PSIS of the user.

A central region of the upper shell 12 may be provided with a concave relief 56. The relief 56 is adapted to receive the spine of the user. Moreover, the relief 56 increases the structural integrity of the upper shell 12. The lower shell 14 may have a shape complementary to the upper shell 12.

That is to say, the lower shell 14 may likewise be dish shaped and provided with a concave relief 58. The complementary shape would be aesthetically pleasing. Central cutaways, generally indicated at 60, may be provided in the upper and lower shells 12, 14. A lower portion of the upper shell 12 and an upper portion of the lower shell 14 are preferably provided with cutaways 60. The cutaways 60 are provided to reduce the risk of the upper and lower shells 12, 14, or the adjacent concave relief 56, 58 thereof, contacting with one another throughout the hinged movement of the lower shell 14.

The lateral supports 22 may be covered with a foam cushion material and a cover. The cushion material and cover may be formed in a unitary construction, as shown at 62. The cushion material protects the user against the harsh lateral support structure and increases the level of comfort of the user.

The hinges 16 and the opening defined by the cutaways 60 are preferably covered with pelvic blocks 64. The pelvic blocks 64 aid to ensure that the user is properly and comfortably positioned adjacent the seat back 10. The pelvic blocks 64 are preferably formed from a substantially rigid foam material as opposed to a soft foam material. The rigid foam material is preferred because the rigid foam material holds its shape to provide continued support for the pelvis of the user. In a preferred embodiment of the invention, the pelvic blocks 64 are identical in shape and size to permit the same pelvic blocks 64 to be used to cover the hinges 16 and the opening defined by the cutaways 60. The same.pelvic blocks 64 may also be used to cover the hinges 16 and the openings of seat backs of various widths. The use of the same pelvic blocks 64 reduces the need for an expansive inventory.

The lateral supports 22, the pelvic blocks 64, and the seat back 10 are preferably covered with a foam overlay (not shown). The foam overlay is preferably a soft, comfortable foam overlay. A three-quarter inch foam overlay would be suitable for carrying out the invention.

In operation, the pins 25, 38 are adapted to be received by channels 66, 68 supported by upper and lower mounting members, generally indicated at 70, 72. The mounting members 70, 72 are coupled to the wheelchair seat back tubes T. This may be accomplished with straps or tube clamps, such as the clamps 74, 76 shown. The seat back tubes T are adapted to be supported by the wheelchair base frame (not shown). The mounting members 70, 72 are adjustable in a substantially vertical direction along the seat back tubes T. The lower mounting members 72 are adjustable to align the pins 38 with the PSIS of the user. The upper mounting members 70 are provided with levers 78 that may be actuated to prevent the pins 25 of the upper mounting brackets 18 from inadvertently escaping from their respective channels 66. The shells 12, 14 are preferably formed from a flexible material. Hence, the shells 12, 14 flex when supporting a load. That is to say, the weight of the user causes the shells 12, 14 to flex which, in turn, causes lateral displacement of the pins 25, 38. For at least this reason, the pins 25, 38 are preferably free to move in the channels 66, 68 in lateral directions.

The seat back 10 is adapted to be set up as follows. First, the lateral supports 22 and pelvic blocks 64, if desired, are attached to the upper and/or lower shells 12, 14. The lateral supports 22 are attached to the shells 12, 14 at desired elevations by securing the lateral supports 22 relative to select vertically spaced slots 40, 44. The lateral supports 22 may be adjusted laterally in the slots 40, 44 as desired prior to tightening fasteners that secure the lateral supports 22 to the shells 12, 14. Once the lateral supports 22 are adjusted to a desired vertical and lateral position, the fasteners may be tightened. With the lateral supports 22 secured in place, the lateral supports 22 may be covered with foam cushion and a covering 62. Finally, the upper and lower shells 12, 14, the covered lateral supports 22, and the pelvic blocks 64 may be covered with a cushion overlay. Next, a wheelchair occupant or user is seated on a wheelchair seat or seat cushion (not shown) and his or her pelvis is adjusted to a desired position. With the pelvis in the desired position, the lower mounting members 72 are clamped to the wheelchair seat back tubes T at points proximate the PSIS of the user. The pins 38 of the lower mounting brackets 20 are inserted in the channels 68 supported by the lower mounting members 72. The lower mounting members 72 may be adjusted vertically to bring the pins 38 into colinear alignment with the PSIS of the user. Following the adjustment of the lower mounting members 72, the upper mounting members 70 may be adjusted relative to the seat back tubes T to receive the pins 25 of the upper mounting brackets 18 in their corresponding channels 66 and then clamped to the seat back tubes T. Subsequently, the racks 26 of the upper mounting brackets 18 are adjusted to orient the upper shell 12 at a desired angle. The angle of the upper shell 12 is generally adjusted to the user's comfort. Moreover, a typical user's line of sight may often be directed downward. This may result from the user's spine being fused in a position that tips the upper torso forward or because of extraneous tissue on the scapula. The angle of the upper shell 12 may be tilted backward to adjust the user's line of sight. Once the angle of the upper shell 12 is adjusted as desired, the angle of the lower shell 14 may be adjusted out of contact with the gluteal mass or extraneous tissue of the user. This is accomplished by loosing the hinge fasteners, pivoting the lower shell 14 relative to the upper shell 12 to achieve a desired angular relationship between the upper and lower shells 12, 14, and then retightening the hinge fasteners to secure the hinge 16 and lower shell 14 in a substantially fixed position.

The lower shell 14 functions to aid in supporting the pelvic blocks 64 and foam overlay. In addition, the lower shell 14 functions as a flap to cover the gluteal mass or extraneous tissue of the user. For at least this reason, it is preferable that the lower end of the lower shell 14 be even with or slightly below the seat or seat cushion to insure that the extraneous tissue is covered.

The present invention places the pins 38 of the lower mounting brackets 20 in colinear relationship with the user's PSIS. Moreover, the present invention places the hinges 16 in a proximate colinear relationship with the pins 38 of the lower mounting brackets 20 and the user's PSIS. In addition, the present invention permits the upper and lower mounting brackets 18, 20 to be secured independently of one another. This permits the lower mounting brackets 20 to be secured in place first, with its pins 38 in a colinear relationship with the user's PSIS. The upper mounting brackets 18 may subsequently be adjusted independently of the lower mounting brackets 20 to position the upper shell 12 as desired without affecting the position of the lower mounting brackets 20.

The seat back 10 is preferably formed form a durable, lightweight material and most particularly, a resilient or slightly flexible material. The seat back 10 is preferably adapted to be disengaged relative to the wheelchair seat back tubes T by first displacing the levers 78 and then, tilting the upper shell 12 back and lifting the seat back 10 all in one motion. The seat back 10 is adapted to be transported with relative ease simply by carrying the seat back 10 by its handle opening 80. In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.

Claims

CLAIMS What is claimed is:

1. A seat back for a wheelchair, said seat back comprising: an upper shell, a targeting member mounted to a lower portion of said shell and adapted to be positioned substantially colinear to the posterior superior illiac spine of a wheelchair occupant; and a coupling member mounted to an upper portion of said shell, said coupling member being adjustable independently of said targeting member to adjust the orientation of said shell without affecting the position of said lower portion of said shell.

2. The seat back according to claim 1, wherein said targeting and coupling members are pins.

3. The seat back according to claim 1, further including a lower shell pivotally connected to said upper shell, said lower shell being adapted to be secured in a substantially fixed position.

4. The seat back according to claim 3, wherein said lower shell is pivotally connected to said upper shell by a hinge positioned proximate the PSIS of the wheelchair occupant.

5. The seat back according to claim 3, wherein each said shell has a concave contour.

6. The seat back according to claim 5, wherein a central region of each said shell is provided with a concave relief that is adapted to receive the spine of the wheelchair occupant.

7. A seat back for a wheelchair, said seat back comprising: an upper shell; a lower shell pivotally connected to said upper shell by a hinge that is adapted to be secured in a substantially fixed position; a lower pin mounted to a lower portion of said upper shell and adapted to engage a lower mounting member coupled to the wheelchair at a position substantially colinear to the wheelchair occupant's posterior superior illiac spine; and an upper pin mounted to an upper portion of said upper shell and adapted to be adjustable relative to an upper mounting member coupled to the wheelchair independently of said lower pin to adjust the orientation of said upper shell without affecting the position of said lower pin.

8. The seat back according to claim 7, wherein said lower pin is mounted to the wheelchair by a lower mounting bracket attached to said lower portion of said upper shell and said upper pin is mounted to the wheelchair by an upper mounting bracket attached to said upper portion of said upper shell.

9. The seat back according to claim 8, wherein each said mounting bracket is comprised of a mounting block that is adapted to be attached to said upper shell and a pin rack attached to said mounting block, said pins being fixed to said pin racks, said pin rack of said upper mounting bracket being adjustable relative to said mounting block.

10. The seat back according to claim 7, wherein said shells have a concave contour.

11. The seat back according to claim 10, wherein a central region of each said shell is provided with a concave relief that is adapted to receive the wheelchair occupant's spine.

12. The seat back according to claim 11, further including cutaway portions in said shells to reduce the risk of said shells contacting one another throughout movement of said shells.

13. A wheelchair comprising: a base frame; a seat supported by said base frame; seat back tubes supported towards a rear end of said seat; a seat back comprising an upper shell and a lower shell pivotally connected to said upper shell by a hinge that is adapted to be secured in a substantially fixed position; lower mounting brackets coupling lower opposing side portions of said upper shell to said seat back tubes at positions substantially colinear to a wheelchair occupant's posterior superior illiac spine; and upper mounting brackets coupling upper opposing side portions of said upper shell to said seat back tubes, said upper mounting brackets being adjustable relative to said seat back tubes to adjust the orientation of said upper shell without affecting the colinear relationship established by said lower mounting brackets.

14. The wheelchair according to claim 13, wherein each said mounting bracket is comprised of a mounting block that is adapted to be attached to said upper shell, a pin rack attached to said mounting block, and a pin fixed to said pin rack, said pin rack of each said upper mounting bracket being adjustable relative to said upper mounting block.

15. The wheelchair according to claim 14, wherein said pins are adapted to be received by channels supported by upper and lower mounting members coupled to said seat back tubes.

16. The wheelchair according to claim 13, wherein said shells have a concave contour.

17. The wheelchair according to claim 16, wherein a central region of each said shell is provided with a concave relief that is adapted to receive the wheelchair occupant's spine.

18. The wheelchair according to claim 13, wherein said seat back is adapted to support one or more lateral supports and one or more pelvic blocks.

19. The wheelchair according to claim 13, wherein said lateral supports, said pelvic blocks, and said seat back are covered with a foam overlay.

20. A method for securing a seat back to a wheelchair, said method comprising the steps of: providing a seat back having upper and lower shells; mounting a lower portion of the upper shell to seat back tubes at points proximate the PSIS of the occupant; adjusting an upper portion of the upper shell independent of the lower portion to orient the upper shell at a desired angle without affecting the position of the lower portion of the upper shell. adjusting the angle of the lower shell relative to the upper shell.