Modular backrest system for a wheelchair

Claims

What is claimed is:

1. A ball and socket joint comprising:

a substantially spherical ball including a first section and a second section having a threaded opening extending therethrough, said first and second sections having spherical outer surface areas terminating in juxtaposed planar base surfaces defined by a cutting plane, said planar base surfaces having diameters corresponding to a diameter of a small circle of the ball;

a socket having a cavity formed therein that is sized to receive a portion of said ball, said socket including a base having said cavity formed therein, and a bracket secured to said base when said ball is positioned inside said cavity, said bracket having an inner edge positioned around a portion of said ball;

a threaded stud secured to said first section of said ball and extending through said opening in said second section outwardly from said socket, said stud being movable within said opening inwardly to an extended position and outwardly to a retracted position, said stud moving said first section of said ball into abutment with said second section when said stud is in the retracted position to permit said ball to rotate freely in said socket, said stud moving the planar base surface of said first section of said ball outwardly away and spaced from the planar base surface of said second section and the outer surface area of the first segment into engagement with the cavity of said socket when said stud is in the extended position to prevent rotation of said ball in said socket, said inner edge of said bracket engaging said ball when said stud is in the extended position to prevent rotation of said ball in said cavity.

2. A backrest system for a chair for seating an individual, said chair having a seat and upright posts extending upwardly from the rear of the seat in a spaced apart, substantially parallel manner, said backrest system comprising:

a back support adapted to be positioned generally between the posts to provide a surface against which the back of an individual rests when the individual sits on the chair seat;

a support chassis mounted to said back support for supporting said back support at a desired incline with respect to the posts, and at a desired seat depth with respect to the seat; said support chassis including a pair of side plates with one side plate being adapted to be disposed between each post and said back support, and at least one horizontal tube attached to and extending transversely between said side plates across said back support; and

an attachment assembly operably connected to said support chassis and connectable to the posts to allow said support chassis and back support to be readily removed from or attached to the chair.

3. The backrest system as set forth in claim 2, wherein each of said side plates has a substantially horizontal slot formed therein which permits forward and rearward movement of said back support with respect to said posts to allow for said back support to be positioned at the desired seat depth.

4. The backrest system as set forth in claim 3, wherein said support chassis further includes a pair of swivel clamps with each swivel clamp having a pair of slots formed therein that permit angular movement of said back support with respect to said posts to allow said back support to be positioned at the desired incline.

5. The backrest system as set forth in claim 4, wherein said support chassis further includes fastening mechanisms that are inserted into said slots of said swivel clamp and said slots of said side plates to prevent further movement of said back support when said back support is positioned at the desired seat depth and the desired incline.

6. The backrest system as set forth in claim 2, wherein said attachment assembly further includes a pair of bands with one band being adapted to be positioned around each of said posts at a desired height, a pair of adapters having axially extending openings formed therein with one adapter being adapted to be positioned opposite to said post inside each band, and at least one wedging mechanism adapted to be positioned inside each band between said post and said adapter to force said band to remain in place along said post.

7. The backrest system as set forth in claim 6, wherein said attachment assembly further includes a pair of mounting devices attached to said support chassis for releasably securing said support chassis to said chair via said adapters, each mounting device including a mounting post attached to and extending outwardly from said support chassis, a barrel disposed at an outermost end of each mounting post, and a lever disposed at an opposite end of each mounting post, said lever having a locked position and an unlocked position, and being operably connected to said barrel, said openings in said adapters being sized to slidably receive one of said mounting posts and barrels therein when said lever is in the unlocked position, said barrel being moved into secure engagement with said adapter when said mounting post and barrel are positioned inside said opening and said lever is actuated into the locked position, thereby preventing removal of said mounting post and barrel from said opening.

8. The backrest system as set forth in claim 2, wherein said back support includes a backing plate and an insert attached to a forwardly presented face of said backing plate against which the back of the individual rests when sitting on the seat.

9. The backrest system as set forth in claim 8, wherein said backing plate is mounted to said horizontal tube by inserting at least one threaded bolt through an opening formed in said horizontal tube and through an aligned opening formed in said backing plate, said bolt being secured by a nut that is attached thereto.

10. The backrest system as set forth in claim 2, wherein said horizontal tube includes an opening extending axially therethrough, and is attached to each side plate by a mounting post that extends transversely and inwardly therefrom, said mounting post being adapted to be received in said opening of said horizontal tube.

11. The backrest system as set forth in claim 10 wherein each of said mounting posts includes a locking assembly for selectively securing said mounting posts to said horizontal tube.

12. The backrest system as set forth in claim 11 wherein said locking assembly includes a body portion with a tapered end and a tapered barrel that is secured to said body portion at said tapered end, said barrel being secured to said body portion by a threaded bolt that extends through an axially extending opening formed in said body portion into said barrel, said barrel being moved axially inwardly and outwardly with respect to said body portion by said bolt, said barrel being moved inwardly into abutment with said tapered end of said body portion and displaced radially outwardly so that edges of said tapered end of said body portion and said tapered barrel are wedged against an inner surface of said horizontal tube when said bolt is tightened to securely retain said mounting posts inside said horizontal tubes, said barrel being moved axially outwardly away from said tapered end of said body portion when said bolt is loosened so that edges of said tapered end of said body portion and barrel do not engage said inner surface of said tube and said mounting posts move freely inside said horizontal tubes.

13. The backrest system as set forth in claim 11, wherein each of said horizontal tubes is attached to vertical tubes by a pair of tube clamp assemblies that retain said horizontal tubes and said vertical tubes in a substantially perpendicular relationship and prevent rotational and longitudinal movement of said tubes.

14. The backrest system as set forth in claim 2, wherein two horizontal tubes are attached to and extend between said side plates in a substantially parallel manner, and further including a pair of vertically extending support tubes that are attached to and extend perpendicularly from said horizontal tubes in a substantially parallel fashion.

15. The backrest system as set forth in claim 14, wherein said back support includes a plurality of pads adjustably attached to said support tubes at desired locations along the support tubes based upon support needs of the individual.

16. The backrest system as set forth in claim 15, wherein each pad is attached to at least one of the support tubes by an elbow joint that permits forward and rearward movement and side-to-side movement of the pad, said elbow joint including a first member having one end securely clamped to said support tube, and a second member attached at one end to said pad and at an opposite end to another end of said first member so that said first member rotates freely with respect to said second member.

17. The backrest system as set forth in claim 16, wherein each pad is attached to the second member of said elbow joint by a ball and socket joint that permits rotary movement of the pad with respect to the second member.

18. A backrest system for a chair for seating an individual, said chair having a seat and upright posts extending upwardly from the rear of the seat in a spaced apart, substantially parallel manner, said backrest system comprising:

a back support adapted to be removably positioned between said posts to support a back of an individual sitting on the chair seat;

a support chassis adapted to be disposed between said posts and mounted to said back support for supporting said back support at a desired incline with respect to said posts; and

a two-point attachment assembly connectable to each of said posts at a desired location along each post for releasably securing said support chassis to said posts.

19. The backrest system as set forth in claim 18, wherein said attachment assembly is adjustably connectable to said posts at a desired location based upon the height of the individual.

20. The backrest system as set forth in claim 18, wherein said support chassis is movable forwardly and rearwardly with respect to said posts to allow for positioning of said back support at a desired seat depth with respect to said seat, said support chassis allowing for the seat depth and the incline of said back support to be adjusted independently.

21. The backrest system as set forth in claim 20, wherein said support chassis further includes a pair of side plates disposed on opposite sides of said back support, said side plates being adapted to be disposed between said back support and said posts, each side plate having a horizontally extending slot formed therein to permit forward and rearward movement of said back support to adjust the seat depth.

22. The backrest system as set forth in claim 18 wherein said back support includes a substantially rigid backing plate and an insert attached to a forwardly presented face of said backing plate against which the back of the individual rests when sitting in the chair; said backing plate being supported by said support chassis at the desired incline.

23. The backrest system as set forth in claim 18 further including a pair of support tubes attached to said support chassis and extending vertically therefrom in a substantially parallel, spaced apart manner.

24. The backrest system as set forth in claim 23 wherein said back support includes a plurality of pads mounted to said support tubes at desired locations based upon support needs and proportions of the individual.

25. The backrest system as set forth in claim 24 wherein each of said pads is adjustable inwardly, outwardly and laterally with respect to said support tubes and at forward and rearward inclines with respect to said support tubes to provide a support surface for the individual sitting on the seat based upon that individual's dimensions and support needs.

26. A backrest system for a chair for seating an individual, said chair having a seat and upright posts extending upwardly from the rear of the seat in a spaced apart, substantially parallel manner, said backrest system comprising:

a back support adapted to be removably positioned between said posts to support a back of an individual sitting on the chair seat;

a support chassis adapted to be disposed between said posts and mounted to said back support for supporting said back support at a desired in