Adjustable seat back assembly for a wheelchair

An adjustable seat back assembly for a wheelchair of the type having a frame with an upwardly extending rear frame portion and an adjustable angle seat support which includes a pivotable front end and a rear end which is secured to said rear frame portion at any of a plurality of different positions. A seat back support is mounted to pivot on the seat support from adjacent its rear end. A link connects the seat support to a slider on the rear frame portion to maintain the position of the slider relative to the seat back support pivot as the seat angle is adjusted. A releasable seat back angle adjuster secures the seat back support to the slider at any of a plurality of positions. When the seat back angle adjuster is released, the seat back support may be folded down towards said seat support.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
Not Applicable. 
BACKGROUND OF THE INVENTION 
Adjustable wheelchairs are frequently used by persons requiring wheelchairs 
who are involved in action sports such as basketball, tennis and other 
sports. As taught, for example, in U.S. Pat. No. 5,509,893, various 
settings of a wheelchair may be made adjustable, including the wheel 
location relative to the center of gravity, the wheel camber, and the seat 
angle. 
The seat, for example, may be mounted to top rails or supports on side 
frames for the wheelchair. The top rail on each side frame is pivoted from 
near the front of the frame over an arc on a back frame member for seat 
angle adjustment. Quick release pins may be provided to secure the top 
rails to the back frame member at any of a plurality of discrete locations 
to provide a number of discrete seat angles. The lower end of seat back 
supports are hinged to each top rail. The back supports also are each 
connected to a slider which slides on the back frame member as the seat 
angle is adjusted. Consequently, the seat back moves up and down with the 
back of the seat as the seat angle is adjusted. The seat back angle will 
remain substantially constant as the seat angle is adjusted. There has 
been no provision for easily changing the angle of the seat back to 
accommodate the needs of a user or to permit the seat back supports to be 
easily folded down for storage or transport without the use of tools. 
BRIEF SUMMARY OF THE INVENTION 
The present invention is directed to an adjustable back for a wheelchair 
which allows easy adjustment of the seat back angle to accommodate the 
comfort and the needs of the wheelchair user. Seat back supports are 
pivotally mounted to left and right side frame top members at their lower 
ends for positioning at different angular orientations. The angular 
orientation of the seat back support can be changed by the user while 
sitting in the wheelchair by simply pulling on a lanyard to disengage 
release pins from a sliding bracket on a rear frame member. When the pins 
are disengaged, the seat back is free to be pivoted forwardly or 
rearwardly according to the desires or needs of the user. When the seat 
back is in a desired position, the lanyard is released and the pins 
reengage the bracket to lock the seat back at the set angle. The seat back 
position may be easily changed several times a day if desired. This not 
only helps to ensure user comfort but also helps to change pressure 
points, to help reduce incidence of pressure sores. Further, when the 
wheelchair is used for basketball, tennis or other sports, the seat back 
may be quickly set to a desired angle while playing the sport and reset to 
a different angle after the sport is completed. 
Accordingly, it is an object of the invention to provide an easily adjusted 
seat back for a wheelchair. 
Other objects and advantages of the invention will become apparent from the 
following detailed description of the invention and the accompanying 
drawings.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 of the drawings illustrates a wheelchair 10 incorporating an 
adjustable seat back assembly 11 according to the invention and FIG. 2 
shows details of a frame assembly 12 for the wheelchair 10. As best shown 
in FIG. 2, the frame assembly 12 includes two side frames 13 connected 
together by a plurality of lateral supports 14. Each side frame 13 
includes a lower frame portion 15, each of which has a rear end 16 and a 
front end 17. A rear frame portion 18 extends upwardly from the rear end 
17 of the lower frame portion 15 and a front frame portion 19 extends 
upwardly from the front end 16 of the lower frame portion 15. An upper end 
20 of the front frame portion 19 and an area 21 of the rear frame portion 
18 are coupled by a top rail or seat portion 22. The seat portion 22 is 
pivotally mounted to an upper end of the front frame portion 19 at a pivot 
23 and is adjustably mounted to one of several positions defined by holes 
24 in the rear frame portion area 21. The seat portion 22 is secured to a 
selected one of the holes 24 by a quick release pin 25. An adjustable seat 
back support 26 is mounted to a rear end of each seat portion 22 and to 
each rear frame portion 18. A conventional seat (not shown) is mounted to 
the seat portions 22 on each side frame 13 and a conventional backrest 
(not shown) is mounted to the seat back supports 26. For simplicity of 
illustration, the seat and backrest are not shown. 
Drive wheels 27 and casters wheels 28 are mounted on each lower frame 
member 15. Details for preferred mountings for the drive wheels 27 and 
caster wheels 28 are shown in U.S. Pat. No. 5,590,893, the disclosure of 
which is incorporated herein. 
FIGS. 3-7 show an adjuster assembly 32 according to one embodiment of the 
invention by which the angle of the seat back support 26 can be adjusted 
by the user while sitting in the wheelchair 10 without the use of tools. 
Each back support 26 is mounted to a seat portion 16 of the frame assembly 
12 by a hinge or pivot 33 on a bracket 31 so that the seat back supports 
26 can pivot forward and backwards on pivot pins 33. To maintain the seat 
back supports 26 in a desired orientation and to permit the seat back 
supports 26 to be folded down, an angle adjustment arm 34 is secured by a 
bracket 35 to each seat back support 26. A bolt 36 and a nut 37 secure 
each bracket 35 to a seat back support 26. While the position of the 
bracket 35 along the seat back support 26 could be adjusted or changed, in 
practice it is generally secured in one position. Alternately, some type 
of quick release fastener may be used for securing the bracket 35. 
The arm 34 has a number of intersecting, parallel bores 38 having 
countersunk ends 39. The bores 38 are sized for receipt of a tapered end 
40 on a release pin 41. The release pin 41 is biased toward engagement 
with a selected bore 38 by a compression spring 42. The compression spring 
42 is mounted over the release pin 41 and is captured between the end of a 
countersunk opening (not shown) formed in an adjustment arm receiver plate 
43 and a shoulder 44 adjacent the end 40 of the release pin 41. An outer 
end 45 of the release pin 41 is threaded for being secured to a knob 46 to 
which a lanyard 47 is secured. Pulling on the lanyard 47, which can be 
accomplished by many wheelchair users while seated in the wheelchair, 
pulls on the knob 46 so as to compress the spring 42 to disengage the 
release pin 41 from a bore 38. 
The adjustment arm 34 is captured between double tapered faces 50 in an 
adjustment arm receiver body 51. In one preferred embodiment, the body 51 
is a one piece integral extension of a slider body 52. The receiver body 
51 combines with the receiver plate 43 to form an adjustment receiver with 
the two parts secured together by cap screws 53. 
The slider body 52 includes a central bore 54 which houses an anti-scratch 
liner 55. An outer surface 56 of the liner 55 is adhered to the wall of 
the bore 54 using a suitable adhesive. The liner 55 is relatively soft and 
snugly positions the slider body 52 about the rear frame portion 18. The 
liner 55 may be, for example, a length of looped fabric material, such as 
material sold under the trademark Velcro.RTM.. 
FIG. 4 illustrates the seat portion 22 at its topmost position, that is, 
with about 1 inch (2.5 centimeters) drop front to back and the seat back 
support 26 is generally vertical. To change the orientation of the seat 
back support 26 rearwardly about 6.5.degree. to the position of FIG. 5, 
the lanyard 47 is grasped and pulled upwardly. This pulls on the knobs 46 
for each adjuster assembly 32, withdrawing the tapered ends 40 of the 
release pins 41 from an opening 57 in the adjustment arm receiver body 51 
and at least partly from the bore 38 to permit the seat back support 26 to 
be rotated rearwardly. As the seat back support 26 is rotated, different 
bores 38 become aligned with the release pin 41. When the desires seat 
back position is achieved, the lanyard 47 is released and the springs 42 
move the tapered end 40 of each release pin 41 to engage an adjustment arm 
bore 38 and to reseat within the opening 57. Thus, the seat back supports 
26 are locked in the new position. 
FIG. 6 shows the seat back support 26 at the opposite extreme, that is, 
angled about 12.degree. forward from a vertical axis as opposed to the 
6.5.degree. backward lean from a vertical axis of FIG. 5. This is achieved 
in the same way, that is, by pulling the lanyard 47 and pulling the seat 
back support 28 in the desired direction. As can be seen by comparing the 
positions of the slider body 52 in FIGS. 5 and 6, the pivotal movement of 
the seat back support 26 is accommodated by the movement of the slider 
body 52 along the rear frame portion 19. Once the release pin 41 fully 
engages a bore 38, a rigid triangle is created between the pivot pin 33, 
the bolt 36 and the release pin 41. Thus, it is not necessary to lock 
the-slider body 52 to the rear frame portion 18 to maintain the seat back 
support 26 in a desired position. 
The adjuster assembly 32 is shown with the adjustment arm 34 extending from 
the seat back support 26. If desired, the adjustment arm 34 could extend 
from the rear frame portion 18. Also, regardless of whether the adjustment 
arm 34 extends from the seat back support 26 or from the rear frame 
portion 18, the slider body 52 and the adjustment arm mounting bracket 35 
can be reversed so that the slider body 52 slides over the seat back 
support 26 and the adjustment arm mounting bracket 35 is fixed to the rear 
frame portion 18. 
Also, the use of the lanyard 47 provides a simple and inexpensive means for 
disengaging the release pins 41 to permit the seat back supports 26 to be 
rotated forward or rearward. If desired, other types of actuators can be 
provided in lieu of the lanyard 47. Further, the seat back support 26 can 
be spring biased in a forward direction, for example, by a torsion spring 
at the pivot pin 33. This will allow the user, while seated in the 
wheelchair 10, to sit at a desired position while pulling the lanyard 47. 
The seat back will then move to abut the user's back. When the lanyard 47 
is then released, the seat back will be locked in the set position. 
FIG. 7 illustrated the complete removal of the angle adjustment arm 34 from 
the adjustment arm receiver body 51 to permit the seat back support 26 to 
be folded down to a generally horizontal position adjacent the seat 
portion 22. The seat back is typically folded down for storage or during 
transport. The double tapered faces 50 aid in guiding the angle adjustment 
arm 34 into the adjustment arm receiver body 51. The receiver body 51 is 
made with the double tapered faces 50 on each side so that a single part, 
in this case the slider body 52 and the receiver body 51, can be used on 
the seat back support 26 on either side of the wheelchair. Optionally, a 
sliding key arrangement (not shown) can be provided between the rear frame 
portion 18 and the slider body 52 to prevent rotation of the slider body 
on the rear frame portion 18, while permitting the slider body 52 to slide 
in an axial direction. This will facilitate alignment of the angle 
adjustment arm 34 with the adjustment arm receiver body 51 when the seat 
back is returned from the folded down position to an upright position. 
FIG. 8 shows a fragmentary portion of a seat back angle adjuster assembly 
60 according to a modified embodiment of the invention. The wheelchair 
wheel 27, the rear frame portion 18, the seat portion 22, the seat back 
support 26, the seat back support bracket 31 and the pivot pin 33 remain 
the same as in FIGS. 4-7. For each side of the wheelchair, the seat back 
angle adjuster assembly 60 includes a modified slider 61 which slides up 
and down in an axial direction along the rear frame portion 18. A link 62 
connects the slider 61 to the seat support 22 and preferably to the pivot 
pin 33 on the seat support 22. A rivet, screw or pin 63 connects the link 
62 to the slider 61. The link 62 maintains the relative spacing between 
the seat back pivot pin 33 and the slider 61 as the angle of the seat 
portion 22 is adjusted. Also, the link 62 prevents the slider 61 from 
rotating on the rear frame portion 18. 
A bracket 64 is secured to the seat back support 26 with the bolt 36. An 
angle adjustment arm 65 extends from the bracket 64. The arm 65 releasably 
engages the slider 61 for positioning the seat back support 26 at a 
selected angle relative to the seat portion 22 and for permitting the seat 
back support 26 to be folded down to adjacent the seat portion 22 for 
transportation or storage. A free end 66 of the arm 65 is secured to a 
desired position 67 on the slider 61. The different positions 67 may be 
defined, for example, by holes in the slider 61 which are engaged by a 
quick release pin 68 on the arm 65. Although only three positions 67 are 
shown in FIG. 8, it will be appreciated that any desired number of 
positions 67 may be provided and that they may be located to provide 
desired seat back angles. Since the seat back support 26 rotates about the 
pivot pin 33, the positions are located on a circle at a fixed radius from 
the pivot pin 33 so that the quick release pin 68 will always align with 
each of the positions 67 as the seat back angle is adjusted. A lanyard 
(not shown) may be provided for operating the release pins 68 to 
facilitate seat back angle adjustment by a user while seated in the 
wheelchair. 
FIG. 8 shows the arm 65 disengaged from the slider 61 as the seat back 
support 26 is pivoted or folded down towards the seat portion 22. It will 
be seen that the position of the slider 61 is maintained relative to the 
pivot pin 33 by the link 62 and that the slider 61 is prevented from 
rotating on the rear frame portion 18. Consequently, when the seat back 
supports 26 are returned to their upright position, the quick release pin 
66 on each arm 65 will align with the positions 67 on the slider 61. 
In the embodiment shown in FIGS. 3-7, the quick release pin 41 is shown 
mounted on the adjuster assembly 32 for engaging the arm 34, while in the 
embodiment shown in FIGS. 8-9 the quick release pin 66 is mounted on the 
is on the arm 65 for engaging the slider 61. It will be appreciated that 
the quick release pin may be located either on the arm secured to the seat 
back support 28 or on the slider which slides on the rear frame portion. 
Further, it will be appreciated that a link 62 may be used for positioning 
the adjuster assembly 32 of FIGS. 3-7 relative to the pivot pin 33. The 
link 62 will assure that each arm 39 will automatically align with the 
passage between the tapered faces 50 and the receiver plate 43 when the 
seat back supports are returned from a folded down position to an upright 
position. 
It will be appreciated that various modifications and changes may be made 
to the above described preferred embodiment of without departing from the 
scope of the following claims. Although the link 62 is shown attached to 
the pivot 33, it will be appreciated that it may be attached to another 
location on the seat support 22 so as to maintain a constant spacing from 
the pivot 33 as the angle of the seat support 22 is adjusted.