Modular backrest system for a wheelchair

A modular backrest system for a wheelchair is removably attached to backrest posts of the wheelchair. The backrest system includes a back support that provides a surface against which the back of a wheelchair user rests, and a support chassis mounted to the back support for supporting the back support at a desired incline with respect to the posts, and at a desired seat depth with respect to the seat. An attachment assembly is further included that is operably connected to the support chassis at two locations and to the posts to allow the support chassis and back support to be readily removed from or attached to the chair. The particular back support employed in conjunction with the support chassis is based upon the support needs of the wheelchair user. One embodiment of the back support includes a backing plate, and a cushion or insert attached to a forwardly presented face of the backing plate against which the back of the individual rests when sitting on the seat. Another embodiment of the back support includes a plurality of pads adjustably attached to support tubes extending upwardly from the support chassis. Each pad is attached to at least one of the support tubes at a desired location by an elbow joint that permits forward and rearward movement and side-to-side movement of the pad. Each pad is attached to the elbow joint by a ball and socket joint that permits rotational movement of the pad with respect to the second member.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
Not Applicable. 
BACKGROUND OF THE INVENTION 
This invention relates to seating, and in particular to a modular backrest 
system for wheelchairs. 
In general, a wheelchair includes a seat and backrest that are supported by 
and extend between a pair of side frames, and a pair of wheels attached to 
the side frames. Backrest posts extend upwardly from the rear end of each 
frame, and turn rearwardly way from the backrest to form handles that 
allow a third party to push or move the wheelchair. Collapsible struts are 
positioned between the frames to maintain the frames in a parallel, spaced 
apart orientation when the chair is occupied by a user. When the struts 
are collapsed, the frames move inwardly together to allow for easy 
transportation or storage of the wheelchair. Typically, the seat and 
backrest are constructed from flexible material that easily folds when the 
wheelchair is collapsed. 
However, the flexible material of the seat and backrest does not provide 
optimum support or comfort for the occupant. Contoured universal backrests 
have been developed to provide improved support for individuals requiring 
special support, such as those having spinal deformities or muscular 
atrophy, but these backrests are difficult to adjust to accommodate 
specific needs and proportions of individual users. Furthermore, the 
universal backrests are not adjustable for wheelchairs having various 
widths, and are not readily removable from the wheelchair frame. Special 
contoured backrests also exist to provide tailored support for a 
particular user, but such backrests are expensive and cannot be easily 
adjusted after they are manufactured. For example, molded backrests 
generally requires at least three stages of fitting: first, the shape and 
dimensions of the user are obtained; second, a mold is produced based on 
these dimension; and third, the mold is fit and refined for the particular 
user. Such custom mold techniques are expensive, labor intensive and time 
consuming, often taking from two to four months for delivery. Furthermore, 
the molds must be remade or replaced if the initial fit is incorrect, or 
if the person's condition or dimensions (height or width) change, or if 
the backrest no longer properly supports the user. Additionally, such 
backrests can be heavy and difficult to transport, with full molded 
systems often weighing up to 25 lbs. 
Therefore, it is desirable to develop a backrest system that provides 
improved support and comfort for wheelchair users. Such a system should be 
adjustable and expandable to accommodate the unique posture, proportions 
and support requirements of each individual user. Furthermore, this system 
should be easy to assemble by a trained technician, and be movable into a 
multitude of positions, if desired. The system should be adjustable in 
width to accommodate any of various widths of the wheelchair, and should 
be able to accommodate wheelchair backrest posts having different 
diameters. Moreover, the system should be lightweight and easily mounted 
to and disengaged from the wheelchair to allow for transportation and 
storage of the chair. 
BRIEF SUMMARY OF THE INVENTION 
Accordingly, one object of the present invention is to provide a new and 
improved backrest system that is detachably mounted to backrest posts 
extending upwardly from the side frames of a wheelchair. 
Another object of this invention is to provide an improved wheelchair 
backrest system that enhances the support and posture of a user by 
providing adjustable support that is specifically tailored to the needs of 
the user. 
Still another object of this invention is to provide an improved wheelchair 
backrest system that is easily mounted to and removed from the wheelchair, 
so that the wheelchair can be collapsed into a compact configuration for 
transportation or storage. 
Another object of this invention is to provide an improved wheelchair 
backrest system that is adjustable in width so that the backrest can be 
attached to wheelchairs having differing distances between the backrest 
posts. 
Another object of this invention is to provide an improved wheelchair 
backrest system that can be mounted to backrest posts having different 
diameters or peripheries. 
Yet another object of this invention is to provide an improved wheelchair 
backrest system that is lightweight, waterproof, durable, and easily 
adjusted to accommodate a particular disabled individual based upon his or 
her size and support needs. 
Another object of this invention is to provide an improved wheelchair 
backrest system that includes a support chassis that is adapted to 
accommodate one or more back supports. 
Another object of this invention is to provide an improved wheelchair 
backrest system having a back support that includes a preshaped shell with 
a support cushion or insert secured thereto that allows for height 
adjustments to the back support based upon the size of the user. 
Another object of this invention is to provide an improved wheelchair 
backrest system having a back support that includes a set of adjustable 
pads that provide a low resolution displaceable surface to support the 
user, where the number of pads employed is based upon the degree of 
support required for the particular user. 
Another object of this invention is to provide an improved ball and socket 
joint and an improved elbow joint that allow for precise positioning of 
the adjustable pads. 
Another object of this invention is to provide an improved backrest system 
with adjustable pads that are designed to provide a high degree of 
postural support and stability, and can accommodate a wide range of spinal 
curvatures, including upright, kyphotic and scoliotic curvatures of the 
spine. 
Another object of this invention is to provide an improved backrest system 
with adjustable pads that enhance management of muscle "tone" in back 
through intimate contact surface. 
Another object of this invention is to provide an improved backrest system 
that can accommodate both changes in growth and condition of an 
individual. 
Another object of this invention is to provide an improved backrest system 
that is reusable for multiple patient applications. 
Yet another object of this invention is to provide an improved backrest 
system that can be easily and rapidly fitted for an individual. 
Another object of this invention is to provide an improved backrest system 
that is cost-effective based on its ability to readjust and grow to meet 
changing needs of a patient. 
Still another object of this invention is to provide an improved wheelchair 
backrest system that includes a detachable headrest. 
Another object of this invention is to provide an improved wheelchair 
backrest system that can be expanded to include detachable lateral pads 
and hip pads. 
These and other objects will become apparent to those skilled in the art in 
light of the following disclosure and accompanying drawings. 
In accordance with the invention, generally stated, a backrest system for a 
chair for seating an individual is provided. The chair has a seat and 
upright posts extending upwardly from the rear of the seat in a spaced 
apart, substantially parallel manner. The backrest system includes 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. The system also includes a support chassis mounted 
to the back support for supporting the back support at a desired incline 
with respect to the posts, and at a desired seat depth with respect to the 
seat. An attachment assembly is further included that is operably 
connected to the support chassis at two locations and to the posts to 
allow the support chassis and back support to be readily removed from or 
attached to the chair. More specifically, the backrest system is designed 
to fit a broad range of wheelchair models, and utilizes quick release 
assemblies that allow for the backrest system to be easily attached to or 
removed from a wheelchair with only two points of fixation. 
The backrest system can be designed so that the support chassis further 
includes a pair of side plates with one side plate being disposed between 
each post and the back support. The support chassis also includes a pair 
of mounting posts extending inwardly from each side plate, and a pair of 
horizontal tubes that are removably secured to the mounting posts such 
that the tubes extend transversely across the back support. Use of the 
mounting posts and horizontal tubes allow for the support chassis to be 
adjusted in width to accommodate individuals having a wide range of trunk 
girths. In the preferred embodiment, the support chassis width is 
adjustable from 12 to 20 inches. This allows the backrest system to be 
easily adjusted as the individuals dimensions and support needs change 
over time, without enormous costs, time and effort associated with 
refitting conventional backrest. 
Each side plate also has a substantially horizontal slot formed therein 
which permits forward and rearward movement of the back support with 
respect to the posts to allow for said back support to be positioned at 
the desired seat depth. In the preferred embodiment, the slot allows for 
up to 10 inches of seat depth adjustment. 
At least one opening is formed in each side plate to reduce the weight of 
the back rest system. One such opening on each side plate also is adapted 
to accommodate an attachment assembly for a lateral pad. 
The 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 the back support with respect to the posts to allow said back 
support to be positioned at the desired incline. In the preferred 
embodiment, the swivel clamps allow for up to 60 degrees of angular 
movement of the backrest. 
The particular back support employed in conjunction with the support 
chassis is based upon the support needs of the wheelchair user. One 
embodiment of the back support includes a backing plate, and a cushion or 
insert attached to a forwardly presented face of the backing plate against 
which the back of the individual rests when sitting on the seat. In this 
configuration, the backing plate is mounted to the tubes by inserting a 
plurality of threaded bolts through a plurality of openings formed in the 
tubes and through a plurality of openings formed in the backing plate at a 
location corresponding to the openings in said tubes. The bolts then are 
secured in place by a plurality of nuts. 
Another embodiment of the back support includes a plurality of pads 
adjustably attached to a pair of spaced apart vertical support tubes 
extending upwardly from the support chassis at desired locations along the 
support tubes. 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. The elbow joint includes a first member 
having one end securely clamped to the support tube, and a second member 
attached at one end to the pad and at an opposite end to the first member 
so that the first member rotates freely with respect to the second member. 
Each pad is attached to the second member of the elbow joint by a ball and 
socket joint that permits angular movement of the pad with respect to the 
second member. It will be appreciated that the elbow joint and ball and 
socket joint of the present invention each can be used in other devices 
and applications. 
The backrest system also can be expanded to include a headrest assembly, 
lateral pad assemblies and hip pad assemblies, if desired, depending upon 
the support needs of the user. 
The backrest system of the present invention is designed in view of the 
underlying biomechanical nature of the spine to achieve postural stability 
for individuals having varying degrees of support needs. The system easily 
can be modified and expanded as the individual's support needs change over 
time. The provision of independent support pads at each crucial level of 
the spine ensures maximum support at each level. The pad assembly provides 
a displaceable surface that fits and contours the body in both passive and 
dynamic modes. The pads follow the contours of the spine and distribute 
pressure to produce a stable and balanced posture by direct support to key 
areas of the spinal column, and provide significantly greater support and 
stability than conventional planar back systems that are currently 
available. The adjustability and expandability of the backrest system and 
pad assembly allows the system to be used over extended periods of time, 
or even the life of a person, and to be upgraded, maintained or changed as 
the person's dimensions and support needs change.

Corresponding reference characters indicate corresponding parts throughout 
the several views of the drawings. 
DETAILED DESCRIPTION OF THE INVENTION 
The following detailed description illustrates the invention by way of 
example and not by way of limitation. The heading contained herein are 
solely for convenience when reading the detailed description of the 
invention, and do not constitute a part hereof. This description will 
clearly enable one skilled in the art to make and use the invention, and 
describes several embodiments, adaptations, variations, alternatives and 
uses of the invention, including what we presently believe is the best 
mode of carrying out the invention. 
Referring now to the drawings, and in particular FIG. 1, a wheelchair is 
shown, referred to generally by reference number 10, that includes a pair 
of side frames 12, each having a spindle 14 on which a large wheel 16 
rotates. Fitted to the front of each side frame 12 is a smaller 
caster-type wheel 18. The side frames 12 are maintained in a substantially 
parallel relationship at a fixed distance apart by a pair of collapsible 
struts 20. The struts 20 fold so that the sides of the frames can be moved 
together to allow the wheelchair to assume a more compact configuration 
for transport or storage. The side frames 12 include horizontal members 22 
that support a seat 24 extending between them. A backrest post 26 extends 
upwardly from the rear of each side frame 12. The upper ends of the 
backrest posts 26 extend rearwardly to form a pair of handles 28 that are 
used to push or maneuver the wheelchair. 
Modular Backrest System 
The wheelchair 10 further includes a modular backrest system 30 that is 
attached to the backrest posts 26 as shown in FIGS. 1-3, 6 and 7. While 
the posts 26 shown in these drawings have a substantially round 
circumference, it will appreciated that the present invention can be 
easily adapted for use in conjunction with posts 26 having other 
peripheries such as, for example, an elliptical, rectangular or D-shaped 
perimeter. The backrest system 30 includes a support chassis 32 to which a 
back support assembly 34 is attached. As set forth in greater detail 
below, the back support assembly 34 preferably is either a single pad 180 
(e.g., FIGS. 1 and 16), or a set of pads 298 (e.g., FIG. 17). The back 
support assembly 34 supports and positions a user's back when sitting in 
the wheelchair 10. As will be discussed below, the support chassis 32 can 
be attached to a broad range of wheelchairs with different configurations. 
The backrest system preferably is assembled and fitted for a particular 
patient by an orthotist, therapist, seating technician (RTS) or other 
similarly qualified prescriber. As will be appreciated, the above 
description of the wheelchair 10 sets forth a conventional configuration 
for wheelchair side frames, wheels, struts, seat and backrest posts 26, 
and is provided for illustrative purposes only. The present invention 
resides in the modular backrest system 30. 
I. Frame Clamp Attachment Assembly 
The support chassis 32 is attached to the backrest posts 26 via a frame 
clamp attachment assembly 42 (FIGS. 2 and 3) that includes two points of 
attachment to the wheelchair 10, as opposed to the customary four point 
attachment scheme employed by other backrests such as that set forth in 
U.S. Pat. No. 5,364,162, issued Nov. 15, 1994 to Bar et al. and assigned 
to the same assignee of the present invention. 
A. Bands and Adapters 
More specifically, the attachment assembly 42 includes a pair of adjustable 
bands 44 that are positioned around the backrest posts 26 at a desired 
location. By moving the bands 44 upwardly or downwardly along the 
wheelchair backrest posts 26, the height of the back support assembly 34 
can be varied. The band 44 (FIGS. 4 and 6) has a substantially elliptical 
shape with a center opening 46 that permits insertion of the wheelchair 
backrest post 26 therethrough and a pair of inwardly extending flanges 48. 
As will be appreciated, the bands 44 are adapted to be used in conjunction 
with a wide variety of wheelchair designs, and are designed to accommodate 
a variety of features, such as removable arm rest supports, and hinged 
back siding seat braces. In the preferred embodiment shown in FIG. 4, the 
band 44 is sized to receive wheelchair backrest posts 26 having diameters 
ranging from 0.75 to 1.2 inches. 
The band 44 is secured to the backrest post 26 as shown in FIGS. 2, 3, 6 
and 7. The attachment assembly 42 also includes a pair of wedges 50 
inserted inside the band 44 to assist in positioning the band 44 on the 
backrest post 26. The dimensions of the wedges 50 are based upon the 
diameter of the backrest post 26. An adapter 52 having an opening 53 
extending axially therethrough also is disposed inside the band 44 as 
shown in FIGS. 6 and 7. The adapter 52 has a longitudinal slot opening 58 
(FIG. 6) formed therein that is aligned with the opening 53 and is adapted 
to receive the flanges 48 of the band 44. As discussed below in greater 
detail, the adapter 52 is used to support a quick release mounting post 70 
(FIGS. 7-9) that secures the support chassis 32 to the attachment assembly 
42. The band 44, wedges 50 and adapter 52 are held in position along the 
backrest post 26 by a fastening device such as a threaded bolt 54 as shown 
in FIGS. 2 and 3 that is inserted through openings 55 formed in the band 
and openings 57 formed in the wedges 50 and locked in place by a nut 56. 
To further assist in securing the adapter 52 to the band 44, aligned 
openings 59 and 59a are formed in the adapter 52 adjacent to the slot 58. 
Openings 60, 61, and 62 are formed in the band 44 and its flanges 48, 
respectively, to permit insertion of a fastening device such as a threaded 
bolt 63 through the opening 60 in the band 44, into and through the 
opening 59 in the adapter 52, through flange 48 openings 61 and 62, and 
then into the remaining portion of the opening 59a in the adapter 52, 
which opening 59a is threaded. This configuration of the adapter 52 and 
band 44 prevents accidental movement or dislocation of the adapter 52 with 
respect to the band 44 (see, FIGS. 4, 6 and 7). 
B. Quick Release Assemblies 
The attachment assembly 42 also includes a pair of quick release assemblies 
68 that releasably secure the support chassis 32 to the attachment 
assembly 42. As will be discussed in detail hereinafter, the quick release 
assemblies are attached on each side of the support assembly 42. FIGS. 7, 
8 and 9 show the connection between the quick release assemblies 68 and 
the attachment assembly 42. 
Each quick release device 68 includes a mounting post 70 having a body 
portion 71 with an opening 72 extending axially therethrough and a tapered 
or angled lower end 73. A lever 74 is secured to the upper end of the body 
portion 71 via a cam mechanism 75 and a threaded stud 76 or pin that 
extends downwardly from the cam mechanism 75 into the opening 72 in the 
mounting post 70. For example, in one embodiment of the present invention, 
the quick release device 68 is a quick release bicycle seat post binder 
sold by Kalloy, a Chinese company, as model number ST5221, where the 
Kalloy binder is modified for the present invention to provide the lever 
74, cam mechanism 75 and stud 76 by bending the lever of the Kalloy binder 
at an angle of approximately 90.degree., and extending the length of the 
stud 76 as shown in FIGS. 8 and 9. As shown in FIGS. 2 and 3 and discussed 
below, the mounting posts 70 are removably secured inside openings 96 
(FIG. 10) associated with the support chassis 32. The mounting post 70 
also includes a small tapered barrel 84 that is secured to the lower end 
73 of the body portion 71 by the stud 76. The barrel 84 and body portion 
71 are sized to be slidably received in the opening 53 extending axially 
through the adapter 52. In the preferred embodiment, a washer 86 is 
attached at a desired location along the body portion 71 of the mounting 
post 70 to provide a visual indication as to when the mounting post 70 and 
barrel 84 are properly positioned inside the adapter 52. When the mounting 
post 70 and barrel 84 are properly inserted, the washer 86 is disposed 
inside a recess 87 formed in an upper end 88 of the adapter 52. As shown 
in FIGS. 6 and 7, the upper end 88 of the adapter 52 preferably includes a 
shoulder 88A that is adapted to rest on an upper edge 89 of the band 44 
upon assembly to prevent downward movement of the upper end 88 of the 
adapter 52 into the passage 46 of the band 44. Similarly, a lower end 90 
of the adapter 52 preferably includes a shoulder 90A adapted to rest 
against a lower edge 91 of the band 44 upon assembly to prevent upward 
movement of the lower end of the adapter 52 into the passage 46 of the 
band 44. 
The barrel 84 is moved axially upwardly (or inwardly) and downwardly (or 
outwardly) by the stud 76 and cam mechanism 75 based upon the position of 
the lever 74. When the lever is raised into a unlocked position (FIG. 8), 
the body portion 71 and barrel 84 move freely inside the opening 53 of the 
adapter 52. When the lever 74 is pressed downwardly into a locked position 
as indicated by the arrow "A" in FIG. 9, the barrel 84 is moved upwardly 
by the stud 76 and slides radially outwardly against the tapered surface 
73 of the body portion 71 (arrow "B") so that the tapered ends of the body 
portion 71 and barrel 84 are wedged inside the opening 53 into engagement 
with the inner surface of the adapter 52. In this locked position, the 
mounting post 70 and barrel 84 are securely retained inside the adapter 52 
so as to prevent lateral or axial movement of the mounting post 70 (FIG. 
9). 
Thus, the quick release devices 68 allow for the chassis 32 and associated 
back support 34 to be easily removed from and assembled to the wheelchair 
10. More specifically, to attach the backrest 30 to the attachment 
assembly 42, the levers 74 are moved into the unlocked position, and the 
mounting posts 70 are inserted into the openings 53 of the adapters 52. 
When the mounting posts 70 are properly positioned in the adapters 52 
(e.g., the washer 86 is disposed inside the recess 87 of the adapter 52), 
the levers 74 are moved into the locked position so that the support 
chassis 32 is anchored to the wheelchair 10. To remove the backrest 30 
from the wheelchair 10, the levers 74 are moved into the unlocked 
position, and the mounting posts 70 and barrels 84 of the two quick 
release devices 68 are removed from the adapters 52. 
II. Swivel Clamps 
As shown in FIGS. 2 and 3, the body portion 71 of each mounting post 70 
associated with the quick release devices 68 is secured to a swivel clamp 
92 associated with the support chassis 32 by a retaining clamp 93. The 
swivel clamp 92 and retaining clamp 93 have corresponding concave notches 
94, 95, respectively, formed therein that combine to define an opening 96 
sized to receive the mounting post 70 therein (FIG. 10). A pair of screws 
97 are inserted into openings 98 in the retaining clamp 93 and 
corresponding openings 106 in each swivel clamp 92 to hold the mounting 
post 70 in position at a desired location or height. Each swivel clamp 92 
has a pair of slots 108 (FIG. 10) formed therein that allow for rotational 
or angular movement of the support chassis 32 and back support 34 with 
respect to the wheelchair 10. In the preferred embodiment, the slots 108 
allow for 30.degree. of rearward recline and 30.degree. of forward tilt 
(for a 60.degree. total angular displacement) of the backrest 30 relative 
to a vertical line of the wheelchair backrest posts 26. The swivel clamp 
92 is secured in a desired position by screws 110 that are inserted 
through washers 111 and the slots 108, and then tightened against the 
outwardly presented face of the swivel clamp 92 to prevent rotational 
movement of the swivel clamp 92. As discussed below, the screws 110 are 
tightened into threaded bushings 112 associated with a swivel mounting 
plate 114. 
III. Support Chassis 
A. Side Plates 
Each swivel clamp 92 is secured to a side plate 122 associated with the 
support chassis 32 by the swivel mounting plate 114 ant the two bushings 
112 formed therein. Each side plate 122 has formed therein at least one 
opening 128 to provide necessary weight reducing functions for the 
backrest system 30. As discussed below, at least one such opening 128A on 
each side plate is adapted to accommodate a mounting assembly 502 for a 
lateral pad 500 (FIG. 35). 
The side plate 122 shown in FIGS. 1-3 and 11 preferably is employed for 
wheelchair users requiring more extensive back support, and preferably has 
six openings 128, including openings 128A for the lateral pad assemblies. 
FIG. 11A illustrates an alternative configuration for the side plates, 
showing a smaller side plate 123 that includes two opening 128A to provide 
weight reducing functions and allow for mounting of the mounting assembly 
502 associated with the lateral pads 500. This smaller version of the side 
plates shown in FIG. 11A is used, for example, in back support systems 34 
for children or "active" wheelchair users who do not require extensive 
back support. However, it will be appreciated that the larger side plates 
122 shown in FIG. 11 permit sufficient adjustment of the backrest system 
30 to accommodate a child or "active" wheel user, if desired. 
Each side plate 122 includes a horizontal slot 130 extending substantially 
the entire width of the side plate 122. A stud 116 extends outwardly from 
the swivel clamp 92 as shown in FIGS. 3 and 10, and is sized to be 
slidably received within the slot 130 of the side plate 122. To adjust the 
seat depth of the wheelchair 10, the swivel clamp 92 and stud 116 are 
slidably moved forwardly and rearwardly within the slot 130 of the side 
plate 122 to a desired position. The stud 116 also is inserted through an 
opening 118 formed in the swivel mounting plate 114. In the preferred 
embodiment of side plate 122, the slot 130 is approximately 4.5 inches in 
length to allow for up to 2.5 inches of depth adjustment of the seat 24. 
After the swivel clamp 92 is rotated to the desired angle with respect to 
the backrest posts 26, the screws 110 are inserted through the swivel 
clamp slots 108 and the side plate slot 130 into the aligned threaded 
mounting plate bushings 112, and tightened to thereby clamp the side plate 
122 between the mounting plate 114 and the swivel clamp 42 and secure the 
swivel clamp 92 to the support chassis 32. As shown in FIGS. 2 and 3, each 
side plate 122 has a cavity 131 formed in its inwardly presented face that 
is sized to accommodate the swivel mounting plate when it is attached to 
the swivel clamp 92 at any location within the slot 130. Thus, the swivel 
clamp 92 and mounting plate 114 allow for forward and rearward angular 
movement of the backrest 30 by rotating the backrest 30 in the slots 108, 
as well as adjustment of seat 24 depth by moving the swivel clamp 92 to a 
desired position in the side plate slot 130. This adjustability of the 
backrest system 30 allows for the wheelchair 10 to be sized to accommodate 
dimensions ranging from a small child to a large adult. 
B. Horizontal Tubes and Mounting Posts 
In the preferred embodiment shown in FIGS. 2 and 3, the support chassis 32 
further includes two hollow cylindrical horizontal tubes 132 extending 
transversely across the rear of the back support assembly 34. A pair of 
mounting posts 133 extend inwardly from each side plate 122, and are 
adapted for engagement within the horizontal tubes 132. The mounting posts 
132 are similar to the quick release mounting posts 70 in that each 
mounting post 132 has a body portion 134 with a tapered or angled end 135 
(FIG. 11) and a tapered barrel 136 that is secured to the body portion 134 
at the tapered end 135. The barrel 136 is secured to the body portion 134 
by a threaded bolt or screw 137 that extends through an axially extending 
opening (not shown) formed in the body portion 134 into the barrel 136. A 
seat (not shown) is formed inside the opening of the body portion 134 
against which a head of the bolt 137 rests when the barrel 136 is in an 
unlocked position (discussed below). The seat extends radially inwardly 
from an inner surface of the body portion 134, and includes an opening 
extending axially therethrough that is sized to accommodate the screw 137 
therein. The barrel 136 is moved axially inwardly and outwardly with 
respect to the body portion 134 by the screw 137. 
More specifically, a hex ball driver (not shown) is inserted through an 
opening 138 (FIG. 11) formed in the side plate 122, and into the opening 
formed in the body portion 134 into engagement with the head of the screw 
137. As discussed above with respect to mounting post 70 (FIGS. 8 and 9), 
when the screw 137 is tightened by a technician operating the hex ball 
driver, the barrel 136 is moved inwardly into abutment with the tapered 
surface 135 of the body portion 134 and displaced radially outwardly so 
that edges of the tapered end 135 of the body portion 134 and the tapered 
barrel 136 are wedged against the inner surface of the tube. In this 
locked position, the posts 133 are securely retained inside the tubes 132 
to prevent lateral movement of the tube 132 with respect to the posts 133. 
To disassemble or adjust the width of the support chassis, the screws are 
loosened so that the barrel 136 moves axially outwardly away from the 
tapered surface 135 of the body portion 134 so that the edges of the body 
portion 134 and barrel 136 no longer engage the inner surface of the tube 
132. In this unlocked position, the mounting posts 133 move freely inside 
the tubes 132. 
In the preferred embodiment, a technician or therapist that is fitting the 
backrest assembly for a particular user can increase the width of the 
support chassis 32 by approximately two inches beyond the length of the 
horizontal tubes 132 by varying the extent to which the posts 133 are 
inserted into the tubes 132. In the preferred embodiment, the width of the 
support chassis 32 can be varied from 12 to 20 inches depending upon the 
length of the particular horizontal tubes 132 employed and the extent to 
which the mounting posts 133 are inserted into the tubes 132. The bands 44 
can be rotated about the backrest posts 26 so that the adapters 52 are 
moved toward or away from the support chassis 32. 
To accommodate support chassis 32 of differing widths, in the preferred 
embodiment, the band 44 can be rotated about the wheelchair post 26 to 
accommodate variations in width of the support chassis 32 of up to 
approximately two inches. 
IV. Vertical Back Support Tubes and Tube Clamp Assemblies 
The backrest system 30 also includes a pair of vertically extending hollow, 
cylindrical back support tubes 148 which each have an opening 149 that 
extends axially therethrough. The vertical tubes 148 are attached to the 
horizontal tubes 132 by tube clamp assemblies 150. 
Each tube clamp assembly 150 includes a first clamp 152 and a second clamp 
154 (FIGS. 2, 3 and 12) that is integrally formed with the first clamp 
152. The first clamp 152 has a first opening 153 extending therethrough 
that is sized to accommodate either a horizontal tubes 132 or a vertical 
back support tube 148, and a slot 155 extending radially outwardly from 
the opening 153 to an outer surface 156 of the first clamp 152. Similarly, 
the second clamp 154 has a second opening 157 extending therethrough that 
is sized to accommodate either a horizontal tube 132 or a vertical back 
support tube 148, and a slot 158 extending radially outwardly from the 
opening 157 to an outer surface 159 of the second clamp 154. When the 
first clamp 152 is secured to a vertical tube 148, the second clamp 154 is 
secured to a horizontal tube 132. When the first clamp 152 is secured to a 
horizontal tube 132, the second clamp 154 is secured to a vertical tube 
148. The center axis of the first opening 153 is offset by approximately 
90.degree. with respect to the center axis of the second opening 157, so 
that the vertical support tubes 148 are oriented in a substantially 
perpendicular relationship with respect to the horizontal tubes 132. 
The tube clamp 150 also includes a third opening 160 that extends through 
the first and second clamps 152, 154 and through the slots 155, 158 as 
shown in FIGS. 3 and 12. A screw 162 is inserted through the third opening 
160 and a nut 164 is attached to the screw 162 to retain the screw 162 in 
the opening 160. A counterbore 166 is formed in the tube clamp 150 to 
accommodate the nut 164 during tightening of the screw 162. When the 
support chassis 32 is positioned at a desired height on the back support 
tubes 148, the screws 162 are tightened, forcing slots 155, 158 to close. 
This forces the first clamp 152 to securely engage the horizontal support 
chassis tube 132 and the second clamp 154 to securely engage the vertical 
back support tube 148. The clamps 152, 154 prevent rotational and 
longitudinal displacement of the tubes 132, 148 when the clamps 152, 154 
are locked in place by the screw 162 and nut 164. 
Thus, the vertical back support tubes 148 are secured at a desired location 
or height inside the openings 157 of the tube clamp assemblies 150 as 
shown in FIG. 2 upon assembly of the backrest system 30. The tube clamps 
150 provide sufficient clamping force to securely hold the support tubes 
148 in position. Furthermore, the fastening screws 162 can be loosened to 
allow the height or positioning of the tubes 148 to be adjusted with 
respect to the horizontal tubes 132, if required. The position of the 
vertical support tubes 148 also can be adjusted inwardly or outwardly 
along the horizontal tubes 132 by mounting the tube clamps 150 at any 
location along the horizontal tubes 132. Thus, the height and width of the 
backrest 30 can be varied in these manners as well to accommodate 
different types of back supports 34 and different sizes of users. 
Moreover, as discussed below and shown in FIG. 34, if the vertical tubes 
148 are not of a sufficient length for a particular application, an 
extension tube assembly 463 can be mounted to either an upper end 170 or a 
lower end 172 of the vertical tubes 148, or both ends 170 and 172, if 
desired (FIG. 19). 
V. Back Supports 
As will be apparent to those skilled in the art, numerous types of back 
supports 34 can be secured to the vertical support tubes 148 of the 
present invention. The modular backrest system 30 of the present invention 
is designed to be highly adaptable, and satisfies users having a broad 
range of disabilities. In the preferred embodiment, one of two types of 
back supports 34 is employed, depending upon the support needs of the 
particular wheelchair user. As discussed hereinafter, wheelchairs 10 used 
to transport individuals who do not require extensive positioning and back 
support (e.g., the elderly) are provided with a back support 180 (FIGS. 
13-16) having a rigid backing plate or shell 182, and an insert 184 
attached to the backing plate 182. In this configuration, the height of 
the back support 180 can be varied, based upon the support needs of the 
user (see FIGS. 13 and 16, and discussion hereinafter). When more 
extensive support and positioning are required (e.g., for paraplegics or 
quadriplegics), an adjustable pad assembly 300 (FIGS. 17-33) set forth 
hereinafter is attached to the support tubes 148 (instead of the backing 
plate 182 and insert 184) to provide a low resolution displaceable back 
support surface 298. The number of pads 300 used in this configuration is 
based upon the degree of support required for the particular user. 
A. Single Pad 
Turning now to the first embodiment of the back support 180 shown in FIGS. 
1, and 13-16, the backing plate 182 and insert 184 configuration is a 
simpler system for a prescriber or technician to fit to the particular 
user than the pad assembly 300. The backing plate 182 is constructed from 
a generally rigid polymer material such as ABS plastic, and is molded to 
include a plurality of predefined surface levels or tiers that allow for 
varying the height of the back support by manually trimming or cutting the 
shell to a desired size. Alternatively, multiple backing plates of varying 
sizes can be constructed and fitted with inserts, and an appropriate back 
support is selected from this group based upon the support needs of a 
particular wheelchair user. In the preferred embodiment of FIGS. 14 and 
15, five predefined tiers 185, 186, 187, 188, 189 are shown, with a 
plurality of "cut lines" 190, 191, 192 indicating the locations where the 
prescriber or technician can cut the shell 182 to fit to adjust the height 
for the particular end user. Thus, the cut lines 190, 191, 192 provide a 
cutting guide to reduce the shell 182 size to appropriate dimensions while 
ensuring that correct proportions are maintained for the back support 180. 
As shown in FIG. 13, the shell 182 has a short member 194 and a tall 
member 196 located on either side of a pair of notches 198 that extend 
inwardly and transversely across the shell 182. The tall member includes 
tiers 185, 186 and 187, and has a greater overall height or length than 
the short member which includes tiers 188 and 189. The notches 198 are 
sized to receive the tubes 132 when the shell 182 is attached to the 
support chassis 32 so that the rearwardly presented surfaces of the tubes 
132 are flush with the rearwardly presented face of the shell 182. The 
shell 182 also includes a four recesses 199 extending inwardly from 
notches 198 that are adapted to accommodate the tube clamps 150 when the 
shell is attached to the support chassis 32 (FIGS. 13 and 15). In the 
embodiment of the shell 182 shown in FIG. 15, openings 197 can be formed 
in the notches of the shell 182 that are sized to accommodate screws or 
bolts 202 to fasten the shell 182 to the horizontal tubes 132. Based upon 
the height and support needs of the user, the orientation of the back 
support 180 can be varied such that either the short member 194 (tiers 188 
and 189) or the tall member 196 (tiers 185, 186, 187) of the backing plate 
182 extends upwardly from the support chassis 32. 
FIG. 13 shows the backing plate 182 mounted to the support chassis 32, with 
the tubes 132 positioned inside the notches 198. The support chassis 32 
provides structural integrity and incorporates additional adjustable 
features as discussed above. The backing plate 182 is attached to the 
tubes 132 of the support chassis 32 by a fastening mechanism such as, for 
example, nuts (not shown) and bolts 202, or the backing plate 182 can be 
molded to fasten or snap around at least a portion of the tubes 132. The 
support tubes 148 of the backrest 30 are positioned between the backing 
plate 182 and insert 184, and extend outwardly through openings 203 formed 
in a surface 204 extending between tiers 186 and 187 of the back support 
180. As discussed hereinafter, the back support 180 also can be expanded 
to include a headrest assembly 315 (FIG. 33) that is mounted to the 
support tubes 148 and lateral pads 500 that are mounted to the side plates 
122 to provide additional support for the user. 
The insert 184 against which the user rests his or her back is secured to 
the forwardly presented face of the backing plate 182. In the preferred 
embodiment, a fastening mechanism 174 such as VELCRO.RTM. hook and loop 
fasteners is used to removably secure the insert 184 to the backing plate 
182. The insert 184 can be constructed from a single piece of foam, a 
plurality of air cells or can be a composite of a cellular cushion 
including a plurality of air cells disposed in a center portion of the 
cushion with foam provided on either side of the air cells. A suitable air 
cell cushion is the type manufactured and sold by ROHO, Inc. of 
Belleville, Ill., and set forth in U.S. Pat. Nos. 4,541,136, issued Sep. 
17, 1985 and 5,369,828 issued Dec. 6, 1994. When a foam cushion is 
employed, the insert preferably has a self-skinned foam barrier as the 
forwardly presented surface of the insert that prevents moisture or fluids 
from entering the cushion. A removable, washable fabric cover 175 (FIG. 
15A) preferably is positioned over the insert 184 and at least a portion 
of the associated backing plate 182. In FIG. 15A, the cover 175 wraps 
around the entire back support 180, and is held in position by a fastening 
mechanism 176 such as VELCRO.RTM. hook and loop fasteners. Alternatively, 
an elastic band can be attached to the outer edge of the cover so that the 
cover can be slipped over the insert 184 and a portion of the shell 182, 
and held in place by the elastic band. 
FIG. 16 illustrates the form of the back support 180 that can be used when 
the minimal amount of support is required for an "active" wheelchair user. 
In this configuration, the backing plate 182 is cut along cut lines 191 
and 192 so that only tiers 187 and 188 are employed. The insert 184 is 
adapted to fit within this reduced shell size. Alternatively, instead of 
cutting down the shell shown in FIGS. 13-15, this "active user" form of 
the back support 180 can be constructed as a solid molded shell 182 that 
includes only tiers 187 and 188. Support tubes 148 are not provided in 
this configuration since the active user requiring this minimal back 
support should not require a headrest assembly 315, hip pads 672 or 
lateral pads 500, 800. 
In the preferred embodiment of back support 180, the backing plate is 
constructed from a single sheet of a substantially rigid polymer material, 
such as ABS plastic, and attached to the chassis 32 after the chassis 
width is established. However, in an alternative construction shown in 
FIG. 16A, the backing plate 182 is divided into two parts 208, 210 along 
its vertical center line to allow for limited width adjustment of the 
shell 182 to accommodate different trunk girths associated with various 
end users. In this configuration, the width of the shell 182 can be 
increased up to a maximum width (e.g., four inches), if desired, by 
providing horizontal tubes 132 of a desired length and properly 
positioning the tubes in the mounting posts to widen the support chassis 
32 to the desired width. A middle section 209, preferably between 4 to 5 
inches in width, is disposed between the two parts 208, 210, and extends 
between upper and lower ends of the backing plate 182. The middle section 
209 acts as a filler to occupy the space between the first and second 
parts 208, 210 when the shell is expanded in width by moving each part 
208, 210 outwardly. The shell 182 can be preformed for various heights, 
with the width of the shell 182 preferably being adjustable up to two 
inches for each height. 
B. Adjustable Pad Assembly 
FIGS. 17 to 33 show a second embodiment of the back support for the 
backrest system 30, referred to generally by reference numeral 298. In 
this configuration, the back support 298 includes a plurality of pads 300 
that are adjustably mounted to the vertical support tubes 148 (or to 
separate mounting assemblies as discussed hereinafter) to provide a low 
resolution displaceable surface against which the user rests his or her 
back. As discussed hereinafter, the pads 300 can be manipulated inwardly 
and outwardly, tilted downwardly and upwardly, rotated and selectively 
positioned at desired heights along the support tubes 148 to conform the 
back support surface to the user's back and provide improved support. The 
number of pads 300 employed in the back support 298 is dependent upon the 
degree of support required for a particular wheelchair user, and the size 
of the user. As discussed below, pads 300 easily can be added to or 
removed from the support tubes 148 by the prescriber so that the backrest 
system 30 can be assembled to satisfy individual needs of the user. Pads 
300 can be attached to the support tubes 148 symmetrically or 
asymmetrically based upon the individual needs (e.g., when the user has 
scoliosis). 
In one embodiment of the present invention that is shown schematically in 
FIG. 18, the pad assembly 300 is designed to provide adjustable support 
for up to five regions of the user's spinal column, if necessary. These 
five regions or tiers of support include: (1) the sacral region, (2) the 
lower thoracic/lumbar region, (3) mid-thoracic region, (4) the 
upper-thoracic region, and (5) the head. The back support 298 can be 
assembled to provide one or more pads 300 to support the user's spinal 
column in each of these five regions. 
The pad assembly 300 generally is referred to as including up to five tiers 
of support for the above regions of the user's spinal column. These tiers 
include a first tier 301 for supporting the sacral region and stabilizing 
the pelvis, a second tier 302 for supporting the lumbar region, a third 
tier 303 for supporting the mid-thoracic region, a fourth tier 304 for 
supporting the upper-thoracic region, and a fifth tier 305 for supporting 
the head. As shown in FIG. 18, each of the first, third and fourth tiers 
301, 303, 304 preferably includes a substantially oval-shaped single trunk 
pad, 311, 313, 314, respectively. Up to two wing pads 316 can be added to 
any of these oval pads 311, 313, 314, if desired to provide additional 
support. The second tier 302 includes two thoracic pads or dual trunk pads 
312a, 312b, and the fifth tier 305 includes a substantially oval shaped 
headrest pad 315 that has different dimensions than those of pads 311, 
313, 314 to provide improved support for the head as discussed 
hereinafter. Wing pads 316 preferably are not employed in conjunction with 
the dual trunk pads 312a, 312b or headrest pad 315. However, wing pads or 
similarly configured temporal lobe pads (not shown) can be attached to the 
headrest pad 315, if desired. As previously noted, FIG. 18 schematically 
illustrates the layout of the pads 311, 312a, 312b, 313, 314, and 315, and 
the wing pads 316 associated with each tier 301, 302, 303, 304 and 305 of 
support. FIGS. 40A and 40B further illustrate this orientation of the pads 
300 with respect to a wheelchair occupant. It will be appreciated that the 
foregoing arrangement of dual trunk pads and single trunk pads that is set 
forth as the preferred embodiment is only one of numerous possible pad 300 
arrangements. At any tier of support, either a single trunk pad or dual 
trunk pads can be employed, if desired, to provide optimum support for the 
particular wheelchair user. The dual trunk pads allow for more precise pad 
placement because they are moveable within six degrees or planes of 
freedom and allow for greater contouring and support for individuals 
having severe curvature of the spine. Wing pads 316 can be added to any 
single trunk pad to provide additional support. 
For illustrative purposes only, the following description assumes that the 
"typical" user requiring improved support associated with the pad assembly 
300 requires a "standard" configuration of the back support 298 that 
includes the pads 311, 312a, 312b, 313 associated with the first, second 
and third tiers 301, 302, 303 (see FIGS. 22A-D). However, it will be 
appreciated that the number of pads 300 can be varied to provide 
additional support based upon the individual needs of the user. The back 
support 298 can be assembled with one or more tiers of pads 300, each of 
which is specifically tailored to provide a desired degree of support for 
the user's spinal column. Pads 314, 315 associated with the fourth and/or 
fifth tier 304, 305 can be added, if necessary. Furthermore, pads can be 
removed from the standard configuration, if such pads are not necessary to 
provide support to the user. For example, an "active" wheelchair user, 
such as a paraplegic, may require only minimal trunk support. In this 
situation, the back support for an active user may employ the first and 
second tiers 301, 302 of pads 311, 312a, 312b, or may use the first and 
third tiers 301, 303 of pads 311, 313. In contrast, a high level lesion 
(e.g., quadriplegic) may require first, second, third and fourth tiers 
301, 302, 303, 304 of pads 311, 312a, 312b, 313, 314. In another example, 
some disabilities are progressive, such as Duchenne Muscular Dystrophies, 
and require progressive support from the age of eight years on as the 
user's ability to maintain an upright posture diminishes to a point of 
complete collapse by late teenage years. This backrest system 30 allows 
the degree of support to be uniquely tailored to present needs of the 
user, and expanded at a later time by adding additional pads 300 if 
additional support is needed. Moreover, as stated above, single trunk pads 
or dual trunk pads can be used to provide support for any region of the 
user's spinal column. Thus, the pad assembly 300 allows for the backrest 
system 30 to be uniquely tailored for each individual's support needs by 
providing the ability to accommodate anyone from an active user who 
requires only minimal trunk support to a severely disabled person who 
requires a fully supportive system that is capable of addressing complex 
seating requirements. 
1. Pad Construction 
As shown in FIG. 20, each pad of the pad assembly 300 includes a backing 
plate or shell 320a, 320b or 320c (referred to collectively as backing 
plate 320) and a cushion or insert 322 that is attached to the backing 
plate 320 and against which the user rests his or her back. The backing 
plate for the single trunk pads is referred to by reference number 320a. 
The backing plate for the dual trunk pads is referred to by reference 
number 320b, and reference number 320c refers to the backing plate for the 
headrest pad. The cushion 322 attached to each backing plate 320 may be a 
simple foam located over the forwardly presented face of the backing plate 
320 (FIG. 18A). Alternatively, the cushion can be glued to the backing 
plate 320. The foam cushion preferably has a self-skinned foam barrier as 
the forwardly presented surface of the cushion to prevent moisture or 
fluids from entering the cushion 322. In the preferred embodiment, a 
fastening mechanism 319 such as VELCRO.RTM. hook and loop fasteners is 
used to removably secure the cushion to the backing plate 320 (FIG. 18A). 
Alternatively, the insert 322 can be glued to the backing plate 320. A 
removable, washable fabric cover 321 (FIG. 18A) preferably is positioned 
over each cushion and at least a portion of the associated backing plate. 
In FIG. 18A, the cover 321 wraps around the entire pad, and is held in 
position by a fastening mechanism 323 such as VELCRO.RTM. hook and loop 
fasteners. 
The backing plate 320 preferably is formed from a sheet of generally rigid 
polymer material such as ABS plastic. The back plate 320a of the single 
trunk pads 311, 313, 314 associated with the first, third and fourth tiers 
generally includes a substantially flat member 324 and two forwardly 
angled flanges 325 extending from opposite sides of the flat member 324 at 
an obtuse angle, as shown in FIGS. 19, 20, 21A-21C and 27. The flat member 
324 has a rearwardly extending rib 326 formed therein that improves the 
structural integrity of the backing plate 320a to prevent flexing and 
bending of the flat member 324 (FIG. 26). Each flange 325 has a rearwardly 
extending housing 327 formed therein that is adapted to receive a socket 
base 376 (FIGS. 24A or 24B) associated with a ball and socket joint 342 
(discussed hereinafter). As discussed more fully below, a socket base 376A 
is shown in FIG. 24A for the single trunk pad that has a hexagon shape and 
allows for attachment of wing pads 316 thereto. 
The backing plates 320b for the dual trunk pads 312a, 312b associated with 
the second region have substantially elliptical shapes as shown in FIG. 
19. As shown in FIG. 19, each of the backing plates 320b for pads 312a and 
312b also has a rearwardly extending housing 328 formed therein that is 
adapted to receive a socket base 376B associated with the ball and socket 
joint 342 (discussed hereinafter), and a rib 329 extending rearwardly from 
the housing 328 to improve structural integrity of the backing plate 320b. 
The socket base 376B has a round configuration for the dual trunk pad 
assemblies (see FIG. 24B). As will be appreciated in view of the 
discussion below, the hexagon-shaped socket bases 376A are not needed on 
the dual trunk pads because wing pads 316 preferably are not attached to 
the dual trunk pads. The hexagon socket base 376A of the single trunk pads 
and the round socket base 376B of the dual trunk pads are referred to 
collectively as socket base 376. As set forth below and shown in the 
drawings, the ball and socket joints 342, along with elbow joints 338, 
allow for precise positioning of each pad of the pad assembly 300 based 
upon the support needs of the particular user. 
The headrest pad 315 (FIG. 28) includes a backing plate 320c that has a 
flat member 330 that is sized to accommodate the user's head, and a pair 
of flanges 332 extending forwardly from opposite ends of the flat member 
330 at a lesser obtuse angle than that of flanges 325. The flat member 330 
has a rearwardly extending rib 334 formed therein that improves the 
structural integrity of the backing plate 320c to prevent flexing and 
bending of the flat member 330. Each flange 332 has a rearwardly extending 
housing 336 formed therein that is adapted to receive a triangular socket 
base 376A associated with a ball and socket joint 342 (discussed 
hereinafter). As discussed above and below, the triangular socket base 
376A allows for attachment of wing pads 316 thereto. 
The backrest system that employs the pad assembly 300 also is designed to 
be lightweight to allow for easy disassembly and transportation of the 
wheelchair. In the preferred embodiment, the backrest system weighs 
approximately three pounds (3 lbs.) when two single trunk pads are 
employed at the first and third tiers for active wheelchair users. The 
"standard" three tier 301, 302, 303 assembly employing pads 311, 312a, 
312b and 313 weighs approximately five and a half pounds (5.5 lbs.). When 
pads are used at all five tiers to provide support, the backrest assembly 
weighs approximately ten pounds (10 lbs.). If hip pads and lateral pads 
are attached to the backrest assembly, the entire assembly weighs 
approximately twelve pounds (12 lbs.). It will be appreciated that the 
weight of such an assembly is considerably less than fully supportive 
molded systems currently available to the public. 
2. Elbow Joints and Ball and Socket Joints 
Each single trunk pad such as those pads 311, 313, 314 associated with the 
first, third and fourth tiers 301, 303, 304, and the headrest pad 315 of 
the fifth tier 305 preferably are mounted to the support tubes 148 (or 
separate mounting assemblies as discussed below for pads 314 and 315) by 
two elbow joints 338 (see FIGS. 20 and 23A-B). More specifically, one end 
of the elbow joint 338 is securely clamped around the support tube 148 
(FIG. 20) at a desired height by a first clamp 340 that has an opening 360 
formed therein which is adapted to receive the support tube 148. Another 
end of the elbow joint 338 is attached to the rearwardly presented face of 
the flanges 325 of the backing plate 320 by a ball and socket joint 342. 
Pads 312a, 312b of the second tier 302 are similarly attached to the 
support tubes 148 by one elbow joint 338, with one end of the elbow joint 
338 being clamped around the support tube by clamp 340 and another end of 
the elbow joint 338 being attached to the rearwardly presented face of the 
backing plate 320 by the ball and socket joint 342 as shown in FIG. 20. 
The elbow joint 338 and ball and socket joint 342 allow each pad to be 
independently adjustable with at least five degrees of freedom, thereby 
providing a highly displaceable back support surface. The six planes of 
movement in which the pads can move relate to the three body planes of an 
individual in which body movement occurs, namely, the sagittal plane, the 
frontal (coronal) plane and the transverse (horizontal) plane. These 
planes are perpendicularly oriented with respect to each other, in a 
similar fashion as the conventional three dimensional x, y and z planes, 
and intersect at the center of gravity of the body. As will be appreciated 
by those skilled in the art, the sagittal plane refers to any vertical 
plan that passes through the body parallel to the sagittal suture (median 
plane) which passes through the midline of the body so as to divide the 
body into equal right and left portions along the Sagittal Sinus. The 
frontal (coronal) plane refers to a vertical plane passing through the hip 
joints and the erect trunk dividing the body into anterior and posterior 
halves, and is parallel to the Coronal Suture of the skull. The transverse 
(horizontal) plane divides the body into superior and inferior portions, 
and extends horizontally from one side of the body to the other. Within 
these planes, the six degrees of movement include up and down in the 
frontal plane; side to side in the transverse plane; forward and back in 
the sagittal plane; tilt in the transverse plane; tilt in the frontal 
plane; and tilt in the sagittal plane. 
The six degrees of freedom also can be illustrated in terms of the 
conventional three dimensional x, y and z planes. With respect to a 
horizontal x-axis, side-to-side movement along the x axis and rotational 
movement about the x-axis are permitted. With respect to the vertical 
y-axis that is perpendicular to the x axis, up and down movement along the 
y axis and rotational movement about the y axis are permitted. With 
respect to the z axis that intersects the x and y axes at right angles, 
forward and rearward movement along the z axis and rotational movement 
about the z axis are permitted. 
More specifically, when one elbow joint 338 and one ball and socket joint 
342 are used to attach a dual trunk pad to one support tube 148 (e.g., for 
pad 312a or 312b), the dual trunk pad can be adjusted in every direction, 
or within six degrees or planes of freedom (FIGS. 19 and 26). When two 
elbow joints 338 and two ball and socket joints 342 are used to attached 
the single trunk pads and headrest pad 315 to the support tubes 148, these 
pads can be adjusted within five degrees or planes of freedom (i.e., side 
to side in the transverse plane; forward and back in the sagittal plane; 
tilt in the transverse plane; tilt in the frontal plane; and tilt in the 
sagittal plane). To obtain the sixth degree of movement for the single 
trunk pads (i.e., limited rotational or up/down movement in the frontal 
plane), first members 344 of the elbow joints 338 can be displaced with 
respect to each other on the support tubes. In this configuration, the 
first member 344 of one elbow joint 338 is clamped to one vertical tube 
148 at a higher location than the other first member 344 of the second 
elbow joint 338 associated with the single trunk pad. Since the dual trunk 
pads employ only one elbow joint, these pads have a larger range of 
movement than the single trunk pads with respect to the ball and socket 
joint 342. 
With respect to the single trunk pads and dual trunk pads, each first 
member can be moved upwardly and downwardly along the vertical tube to a 
desired height, and can be rotated forwardly or rearwardly about the 
vertical tube to move the pad toward or away from the user. The first 
member and second member also can be rotated with respect to each other at 
the elbow joint. For the single trunk pads, the first member can be 
displaced with respect to each other at different heights along the 
vertical tubes, if desired, to obtain limited rotational movement in the 
frontal plane. The single trunk pad can be rotated within five degrees of 
freedom around the ball and socket joint. If the elbow joint is locked so 
that the second member does not rotate with respect to the first member 
and the ball remains unlocked in the socket, the single trunk pad can tilt 
within limited degrees of movement in the sagittal plane. 
FIGS. 22A to 22D show possible pad arrangements and orientations that can 
be employed to support the back of individuals having varying degrees of 
spinal curvature (e.g., natural lordosis, kyphosis or scoliosis). The pad 
311 associated with the first tier helps stabilize and support the sacrum 
by controlling pelvic tilt in an anterior-posterior direction. As 
discussed below, hip pads 672 can be added in this region to provide 
lateral stability as well. The orientation of pad 311 is easily adjusted 
to meet different needs such as the kyphotic position or rotation 
(scoliosis). Pad 311 can be moved within six degrees of freedom so that it 
is able to be properly positioned for any individual, regardless of the 
extent of asymmetry present for a particular person. 
The third tier pad 313 is positioned over the lower ribs and thoracic spine 
to assist in stabilizing the trunk. Pad 313 sets the angle of the spine 
with respect to the pelvis. If the spine is flexible, it also affects the 
lumbar curve because the relationship between the anterior pelvic tilt 
(set by pad 311) and the lower thoracic spine initiates lordosis of the 
lumbar spine (see FIGS. 22A-D). It is possible to sit in a stable posture 
with only pads 311 and 313 attached to the vertical support tubes 148 
provided the lower trunk of the individual has sufficient muscle tone to 
prevent it from collapsing. The curvature of the backing plate and insert 
for pad 313 provide sufficient lateral support to help stabilize this 
area. Without any lateral support in this area, the spine otherwise would 
have a tendency to rotate and shift laterally, thus initiating spinal 
curves and an unstable posture. 
The dual trunk pads 312a and 312b are used for the second tier to provide 
lumbar trunk support. The dual trunk pads are preferred in this region to 
provide improved lumbar support and lateral stability to the spine in this 
very flexible area of the spine. Thus, these pads 312a and 312b can be 
used to add lumbar support, or lateral support, or both. The pads 312a and 
312b can be rotated around the trunk to provide some uplift for the rib 
cage. In this manner, the pads 312a, 312b help support the rib box and 
prevent it from collapsing forward onto the pelvis. This can help the 
respiratory function of the seated individual as well as that person's 
posture. 
Thus, the pads 311, 312a, 312b, 313 associated with the first, second and 
third tiers are used to stabilize the lower trunk. For individuals who 
have tone in their upper trunks and tolerate a relatively upright posture, 
these pads 311, 312a, 312b, 313 generally provide sufficient trunk support 
for complete stability. If deformities exist, the pads 311, 312a, 312b, 
313 can be positioned to help stabilize the deformity, as illustrated in 
FIGS. 22A-D. 
More specifically, for the kyphotic sitter (FIG. 22C), the dual pads 312a, 
312b can be used to accommodate the hump and apply lateral stability to 
the trunk. The split or opening between the pads 312a, 312b also is useful 
for relieving pressure over the apex of the curve which can be 
particularly prominent over the spinous processes with this type of 
deformity. 
When scoliosis exists (FIG. 22D), the dual pad assembly 312a, 312b at the 
second tier can be rotated so that the pads provide asymmetric support and 
fit around the hump of the rib cage on the convex side of the curve and 
under the concavity of the lower rib cage on the other side to provide 
essential support around this region. This helps to prevent the collapse 
of the lower ribs on the concave side of the curve onto the top of the 
iliac crest on the same side. 
In either case of kyphosis or scoliosis, the dual trunk pads can be used at 
any tier and positioned at any location along the vertical support tubes 
148, instead of using a single trunk pad. If severe spinal curvature is 
present, the use of dual pads at other regions or tiers further increases 
the ability to contour the backrest system to asymmetric curves of the 
body so that severe deformities can be accommodated and supported. 
a. Elbow Joints 
Each elbow joint 338 includes a first member 344 that is operably attached 
to a second member 346 by a swivel attachment device 348 so that the first 
member 344 rotates freely with respect to the second member 346 around the 
swivel attachment device 348. In one embodiment of the present invention, 
the attachment device 348 includes a swivel 350 having an opening 351 
formed therein that is adapted to accommodate one end 352 of the second 
member that is opposite the ball and socket joint 342, as shown in FIGS. 
20, 23A and 23B. As discussed below, in this configuration, the swivel 
350, first member 344 and second member 346 of the elbow joint 338 
preferably are constructed from a strong engineering plastic material or a 
polycarbonate material. The swivel 350 includes a post 353 that extends 
downwardly through an opening 354 formed in a second clamp 355 associated 
with the first member 344. As shown in FIG. 23A and 23B, the first and 
second clamps 340, 355 are disposed at opposite ends of the first member 
344. The post 353 is held in the opening 354 in the second clamp 355 by a 
retaining ring 356 that is securely retained inside a radially inwardly 
extending notch 349 formed around the periphery of the lower end of the 
post 350. The retaining ring 356 allows the first member 344 to rotate 
freely around the post 350. The elbow joints 338 permit side-to-side 
movement and forward and rearward movement of each flange of the pads 311, 
313, 314, and 315 and of pads 312a and 312b. Thus, the elbow joints 338 
allow for adjustability of the back support 298 in depth, width and 
height. By adjusting the pads 300 via the elbow joints 338, the back 
support 298 can be adjusted to asymmetrical positions if required so that 
scoliotic and kyphotic spinal curves can be accommodated by the backrest 
system 30. Various orientations of the pads 300 with respect to the 
support chassis 32 and tubes 148 are shown in FIGS. 21A, 21B and 21C. 
The first member 344 preferably has a cylindrical opening 358 extending 
axially therethrough that is sized to receive a threaded bolt 362 that is 
used as a locking mechanism to prevent movement of the first member with 
respect to the support tube 148 and the post 350 of the second member 346. 
The bolt 362 preferably is held in place by a lock nut 396 as shown in 
FIGS. 23B, 19 and 27. The opening 358 extends between two recesses 397 
formed in the clamps. The recesses 397 are adapted to accommodate the lock 
nut, and to prevent rotation of the lock nut as the bolt 362 is tightened. 
For example, when the periphery of the lock nut is a hex nut having a 
hexagonal periphery, the recess is sized as shown in FIGS. 23B, 19 and 27 
to accommodate the nut therein and prevent rotation of the nut as the bolt 
is tightened. 
As shown in FIGS. 23A and 23B, a slot 361 extends outwardly through the 
first member 344 from the openings 360 and 354 in the clamps 340 and 355. 
As hereinbefore discussed, the support tube 148 is inserted through the 
opening 360 in the clamp 340 and moved upwardly or downwardly along the 
tubes 148 to a desired location. 
In the preferred embodiment, the first and second members 344, 346 are 
constructed from a lightweight and durable plastic material, and the 
horizontal tubes 132 and vertical tubes 148 are constructed from a metal 
material. The horizontal tubes 148 preferably have a glass bead blast 
finish on their outer surfaces. This rough finish has microscopic 
perturbations on the surface topology of the tube 148 so that the clamp 
340 fits snugly around the tube 148, and the rough surface opposes 
vertical movement of the clamp 340 after the therapist positions the first 
member 344 at the desired height along the tube 148. Therefore, the 
therapist does not have to worry about the first member 344 sliding 
downwardly along the tube 148 when he or she releases the first member. 
If the tubes 148 have a smooth polished finish, an O-ring 357 preferably is 
disposed in a recess 359 formed in the bottom end of clamp 340 (FIG. 23D). 
The O-ring 357 is positioned around the tube 148 to retard downward 
movement of the elbow joint when the clamp 340 is unlocked. The O-ring 357 
also is used in heavy duty applications such as those set forth below with 
respect to FIG. 23C for individuals weighing over 200 pounds, or 
individuals having a high degree of spacicity, or when the back support 34 
is over 18 inches in width. In such applications, the first members 344 of 
elbow joints and the swivel attachment assembly 348 preferably are 
constructed from a metal material such as aluminum that is heavier than 
the plastic elbow joints, and the O-rings are used to retard downward 
movement the aluminum elbow joints 338. 
To evaluate the requirements and fit of the backrest system for a 
particular individual, the technician preferably uses a backrest system 
assessment kit to determine how the backrest system should be tailored for 
the particular support needs of the individual by evaluating factors such 
as the number of pads needed, whether dual trunk, single trunk, lateral, 
hip and headrest pads are needed, the preferred arrangement of pads for 
that individual, and the desired width of the support chassis so that 
vertical tubes of a proper length can be ordered. The backrest systems 30 
associated with such an assessment kit preferably includes hex head screws 
362 and knobs 363 and/or handles 365, instead of socket head screws 362 
and lock nuts 396 that preferably are used for long term patient use. The 
knobs 363 and handles 365 allow the elbow joints 338 and ball and socket 
joints 342 (discussed below) to be easily locked and unlocked, and for the 
pads to be easily manipulated into a desired position so that the 
prescriber can readily access the viability of the pad arrangement. FIG. 
26 shows one arrangement of knobs 363 and handles 365 that allows for 
quick and easy manipulation and positioning of the pads 300. 
As discussed above, the handles 365 and knobs 363 preferably are not used 
on the backrest system that is fitted by the technician for a particular 
patient for long term use so that the patient or caregiver cannot easily 
adjust the pads and tamper with the pad arrangement established by the 
technician. For backrest systems 30 fitted for a particular patient, bolts 
362 preferably are socket head screws that are held in place by lock nuts 
396. However, such knobs 363 and handles 365 can be used on the backrest 
system, if desired. For example, certain disabilities may require pad 
adjustment throughout the day so that use of the knobs 363 and/or handles 
365 is preferred. Such disabilities include underlying neurological 
diseases that cause the individual's back to weaken as the day progresses 
such that the individual needs to recline more to rest against the back 
support 34 during the course of a day to alleviate weight borne by the 
individual's spine. Using knobs 363 and handles 365 on the pads 314, 315 
of the fourth and fifth tiers 304, 305 allow for easy adjustment of the 
pads during the day. Children with mobile deformities also may need to 
have knobs 363 and handles 365 on the backrest system 30 to allow for the 
pads 300 to be progressively adjusted to counter deformities and try to 
straighten out curvatures of the spine. 
When the clamp 340 is positioned at the desired location, and the first 
member 344 is properly positioned with respect to the second member 346, 
the threaded bolt 362 is tightly secured inside the opening 358 to force 
slots 361 into a closed position. As the slots 361 close, clamping force 
exerted by the clamp 340 on the support tube 148 increases to prevent 
movement of the first member 344 with respect to the support tube 148. 
Similarly, clamping force is exerted by the clamp 355 on the post 350 as 
the bolt 362 is tightened, preventing rotation of the first member 344 
with respect to the second member 346. It will be appreciated that other 
locking mechanisms can be used instead of the bolt 362 to lock the elbow 
joint 338 to the support tubes 148 or to prevent movement of the first 
member 344 with respect to the second member 346. 
In another embodiment of the present invention, the swivel attachment 
device 348 and locking mechanism are configured as shown in FIG. 23C. In 
this embodiment, the swivel attachment device 348 includes a post 390 that 
is integrally formed with and extends downwardly from one end 352 of the 
second member 346 that is opposite the ball and socket joint 342. The post 
390 also includes a tab 391 extending outwardly therefrom that has a 
clearance hole or opening 392 extending therethrough. The second clamp 355 
and slot 361 shown in FIG. 23B on the first member 344 are replaced by a 
locking mechanism that includes a substantially semi-circular flange 393 
that extends outwardly from the first member 344 as shown in FIG. 23C. The 
flange 393 includes a plurality of tapped holes 394 extending 
therethrough. When the pad is positioned in the desired location, the 
opening 392 in the tab 391 is aligned with one of the openings 394 in the 
flange 393 that is in nearest proximity to the tab 391 opening 392. A 
fastening device such as a screw 395 is inserted through the clearance 
hole 392 in the tab 391 into the aligned tapped hole 394 in the flange 393 
to lock the orientation of the pad 300 in the desired position and prevent 
movement of the first member 344 with respect to the second member 346. 
This locking assembly of FIG. 23C preferably is used in heavy duty 
applications such as, for example, for individuals weighing in excess of 
200 pounds, or individuals who experience a high degree of spacicity, or 
when the back support 34 is over 18 inches in width. In this construction, 
the first member 344 and the swivel attachment assembly 348 of the elbow 
joints preferably are constructed from a lightweight, strong metal 
material such as aluminum to provide additional strength and durability. 
It will be appreciated that other swivel attachment devices and locking 
mechanisms can be used to prevent movement of the elbow joint 338 and pad 
300 when the pad 300 is moved into a desired position by a technician. 
b. Ball and Socket Joints 
The other end of the second member 346 opposite the post 350 or 390 is 
attached to a ball 366 that is disposed in a socket 367 associated with 
the ball and socket joint 342. The ball and socket joint 342 permits 
rotary movement of a pad in every direction through movement of the socket 
367 about the ball 366. Allowing for rotation of the socket 367 about the 
ball 366 enables the pad to be precisely positioned to provide optimum 
support for the wheelchair user. 
The ball 366 preferably includes two sections, namely, a first section 371 
and a second section 372. In the preferred embodiment (FIGS. 22 and 
23A-B), the second section 372 of the ball 366 is permanently attached to 
the second member 346, and constructed as a single molded part. The first 
portion of the ball 366 is attached to the second portion 372 by a screw 
or threaded bolt 368 that extends through an opening or throughbore 370 
formed in the second member 346 and an axially aligned threaded opening 
374 extending through the second section 372 (FIG. 23B) into engagement 
with the first section 371. The bolt 368 moves the first portion 371 of 
the ball 366 horizontally with respect to the second ball section 372. In 
other words, as the bolt 368 is screwed into the throughbore 370 and 
opening in the second section 372, the first portion 371 moves outwardly 
away from the second section 372. As the bolt 368 is loosened or screwed 
outwardly from the throughbore 370 and second portion 372, the first 
portion 371 moves inwardly toward the second portion 372 until the first 
section 371 abuts the second portion 372. Thus, the split construction of 
the ball 366 allows for the ball 366 to be tightened in the socket 367. 
The ball and socket joint 342 of the present invention differs 
significantly from conventional ball and socket joints in which the socket 
is tightened around the ball. Additionally, in conventional ball and 
socket joints, the ball typically rotates in a stationary socket. It will 
be appreciated that the elbow joint and ball and socket joint of the 
present invention each can be used in other devices and applications. 
More specifically, the threaded bolt 368 is disposed in either an extended 
or retracted position within the second member 346 by screwing or twisting 
the bolt 368 into or out of the opening 370 in the second member 346. 
Thus, when a portion of the threaded bolt 368 is tightened or screwed into 
the opening 370 into the extended position, the first section 371 of the 
ball 366 is moved outwardly from the second section 372 into a locked 
position as shown in FIG. 25B. When a portion of the threaded bolt 366 is 
loosened or screwed out of the opening 370 in the second member 346, the 
first section 371 of the ball 366 moves inwardly toward the second section 
372 into an unlocked position to permit rotation of the socket 367 about 
the ball 366 (FIG. 25A). In other words, when the ball 366 is in the 
unlocked position (FIG. 25), the socket 367 rotates freely about the ball 
366 to permit angular or rotational movement of the associated pad. When 
the pad is moved into a desired position and orientation, the threaded 
bolt 368 is screwed into the opening 370 into the extended position, and 
the first section 371 of the ball 366 is moved into the locked position 
against the socket 367 to prevent further angular movement of the pad via 
that ball and socket joint 342 (FIG. 25B). Therefore, the ball and socket 
joints 342 allow for precise positioning of the pads 300 against the 
user's back by providing for rotational and angular adjustment of the pads 
300 to fit the curvature of the user's spinal column which often has 
compounded curves owing to deformities that can exist with certain 
disabilities, especially when other neurological complications are 
present. 
The socket 367 in which the ball 366 is positioned includes a base 376 
having a cavity 378 formed therein that is sized to receive a portion of 
the ball 366, and a C-shaped bracket 380 that is secured to the rearwardly 
presented face of the backing plate 320 of the pad as shown in FIGS. 24A, 
24B, 25A and 25B. As previously discussed, the base 376 is positioned 
inside each housing 327, 328 and 336 associated with the backing plate 320 
of the pads 300 between the backing plate 320 and the cushion 322. The 
backing plate 320 of each pad has an opening 381 (FIGS. 25A, 25B) formed 
in each housing 327, 328, 336 that is adapted to be aligned with the 
cavity 378 formed in the base 376 when the base is positioned inside the 
housing 327, 328, 336 (FIG. 26). When the opening 381 and cavity 378 are 
aligned, a portion of the ball 366 is positioned inside the opening 381 
and cavity 378. The bracket 380 then is positioned on the rearwardly 
presented face of the housing 327, 328, 336 associated with the backing 
plate 320 around a portion of the ball as shown in FIGS. 19 and 20. The 
base is secured to the C-shaped bracket 380 and backing plate 320 by 
fastening devices such as screws 382 that are inserted through aligned 
openings bracket 380, backing plate 320 and base 376A or B. 
To adjust each pad of the back support assembly 298 from the rear of the 
wheelchair 10, the threaded bolts 362 of the elbow joints 338 and the 
threaded bolts 368 associated with the ball and socket joints 342 are 
loosened or unlocked or moved into a retracted position. As previously 
discussed with respect to bolts 362, knobs 363 or handles 365 can be 
attached to bolts 368 to assist the prescriber in tightening or loosening 
the bolts 368 to manipulate the pads 300. When the bolts 368 and 362 are 
loosened, the ball 366 rotates freely inside the socket 367 and the first 
member 344 rotates freely with respect to the second member 346. When each 
pad is properly positioned against the user's back, the bolts 368 and 362 
are tightened by the prescriber. This adjustment process is repeated for 
each pad employed in the backrest system 30. 
As discussed above, the second member 346 of the elbow joint 338 and the 
second section 372 of the ball 366 are molded together as a single unitary 
structure. In the preferred embodiment, the first member 344 and swivel 
attachment assembly 348 are constructed from a lightweight strong metal 
such as aluminum for heavy duty applications (e.g., patients over 200 
pounds, having a high degree of spacicity). In all other applications, the 
first member 344 and swivel attachment assemblies 348 preferably are 
constructed from a strong engineering plastic material such as RYTON.RTM., 
sold by Phillips Petroleum Co., Bartlesville, Okla., or a polycarbonate 
material such as LEXAN.RTM., sold by General Electric Company, Pittsfield, 
Mass. 
In all applications, the second member 346 and second section 372 of the 
ball 366 preferably are constructed from a strong engineering plastic 
material such as RYTON.RTM., sold by Phillips Petroleum Co., Bartlesville, 
Okla., or a polycarbonate material such as LEXAN.RTM., sold by General 
Electric Company, Pittsfield, Mass. In this configuration, the base 376 of 
the socket 367 also is constructed preferably from a strong plastic 
material such as RYTON.RTM.. However, the first portion 371 of the ball 
366 preferably is constructed from a more ductile, resilient, durable and 
high-strength material such as nylon or other similar synthetic polymer. 
The nylon material is capable of withstanding forces exerted on the first 
portion 371 without cracking when the ball 366 is in the locked position. 
The nylon material also is preferred since the nylon first portion 371 
deforms in the base 376 of the socket 367 when the first portion 371 is 
subjected to loading forces in the locked position. Since the first 
portion 371 is constructed from a softer material than the base 376 in the 
preferred embodiment, the cavity 378 of the base 376 does not deform or 
degrade, and the locking feature of the ball and socket joint 342 remains 
operational over time. 
In the preferred embodiment, the C-ring bracket 380 of the socket 367 is 
constructed from a lightweight, strong metal such as aluminum. Since the 
second section 372 of the ball 366 and second member 346 are constructed 
from an engineering plastic material such as RYTON or a polycarbonate 
material such as LEXAN, the plastic or polycarbonate material of the 
second section 372 of the ball 366 is softer than the aluminum C-ring 
bracket 380 so that the inner edge 383 of the bracket 380 cuts into the 
plastic or polycarbonate second portion 372 of the ball 366 when the first 
section 371 of the ball 366 is in the locked position. Thus, in these 
configurations, the C-ring bracket 380 prevents rotation of the ball 366 
in the socket 367 when the ball 366 is in the locked position. 
Alternatively, the C-ring bracket 380 can be constructed from a strong 
engineering plastic material such as RYTON.RTM. or a polycarbonate 
material such as LEXAN.RTM.. When the engineering plastic material or 
polycarbonate material is used to construct the C-ring bracket 380 and the 
second section 372 of the ball 366, the inner edge 383 of the bracket 380 
can be machined to provide a sharp edge and/or molded to form a rough 
surface that frictionally engages or grips the second portion 372 of the 
ball 366 to prevent movement of the ball 366 when the first section 371 is 
in the locked position. 
C. Wing Pads 
It will be appreciated that the number and size of pads 300 attached to the 
support tubes 148 by the elbow joints 338 and ball and socket joints 342 
can be varied depending upon the support needs and anthropometric 
dimensions of the user. Furthermore, one or two wing pads 316 can be added 
to any of the pads 311, 313, 314, 315 associated with the first, third, 
fourth or fifth tiers 301, 303, 304, 305 of support. As shown in FIGS. 30 
and 31, each wing pad 316 includes a backing plate 400 and a cushion or 
insert 402 attached to the forwardly presented face of the backing plate 
400. The user rests against the cushion 402. The backing plate 400 
preferably is constructed from a substantially rigid polymer such as ABS 
plastic, and the cushion 402 preferably is constructed from a foam 
material. Each wing pad 316 includes a pair of L-shaped support posts 406 
with each support post 406 having a first member 408 and a second member 
410 extending perpendicularly from the first member 408 as shown in FIG. 
30. The first members 408 are attached or welded to a retaining plate 412 
that is attached or riveted to the rearwardly presented face of the 
backing plate 400 of the wing pad 316. As discussed below, the second 
members 410 of the support posts 406 extend perpendicularly from the first 
members 408 in a substantially parallel fashion through openings in the 
backing plate 320 and the hexagon-shaped socket base 376A of the socket 
assembly 367 as shown in FIG. 31. 
As shown in FIGS. 19, 20, 27, 28, 31 and 33, each housing 327 of the single 
trunk pads 311, 313, 314 and housing 336 of headrest pad 315 has four 
openings 413 formed therein through which the second members 410 extend 
when the wing pads 316 are used. These openings 413 are aligned with two 
passages 415 formed in the hexagon-shaped socket base 376A (see FIGS. 
24A-B). The second member 410 of each support 406 is inserted through one 
opening 413 in the backing plate 320, through the aligned passage 415, and 
then through the second opening 413 in the backing plate 320 to attach the 
wing pad to the pad. The passage 415 is sized to slidably receive the 
second members therein to attach the wing pads to the pads. Each socket 
376A also includes two slots 414 that extend upwardly and downwardly from 
the passage 415 as shown in FIGS. 24A, and 25A-B. Thus, each slot 414 
effectively splits portions 416 and 417 of the base 376A into two sections 
416a and 416b, and 417a and 417b, respectively. 
When the second members 410 are positioned in the passages 415, a screw 418 
is inserted into an opening 419 formed in portions 416 and 417, which, in 
turn, clamps together sections 416a and 416b and sections 417a and 417b to 
securely retain the second members 410 in the passages 415. This 
configuration allows the wing pads 416 to be easily attached to and 
removed from the pads, if desired. The wing pads 416 extend the width of 
the back support 298, and provide additional support for the user. 
D. Fourth Tier Mounting Assembly 
The height of the backrest system can be extended to include support for 
the upper trunk by adding the pad 314 associated with the fourth tier 304. 
For individuals who can sit in an upright position and have weak or absent 
muscle control, the upper trunk pad 314 may be required. Often the 
backrest system 30 is reclined rearwardly with respect to the backrest 
posts 26 when the fourth tier pad 314 is used. If poor head control 
exists, then a headrest assembly 434 and headrest pad 315 (discussed 
below) also can be included in the backrest system 30 to stabilize the 
head which sits on top of the cervical spine. 
In the preferred embodiment, only the pads 311, 312a, 312b, and 313 of the 
first, second and third tiers 301, 302 and 303, respectively are mounted 
directly onto the support tubes 148 via the clamps 340 of the elbow joints 
338. The pad 314 of the fourth tier 304 preferably is mounted (via the 
elbow joints 338 and ball and socket joints 342) to a fourth tier mounting 
assembly 422, which, in turn, is removably secured to the support tubes 
148. Alternatively, the support tubes 148 can be cut to a sufficient 
length to allow for the fourth tier pad 314 to be mounted thereto via the 
elbow joints 338. The fourth tier mounting assembly 422 is a split tube 
assembly as shown in FIG. 27, and includes a pair of vertical, 
spaced-apart tubes 424 having an upper end 426 and a lower end 428, and a 
horizontal mounting tube 425 extending inwardly from each vertical tube. 
The horizontal mounting tubes 425 are adapted for engagement with a 
substantially cylindrical, hollow support tube 427 that extends 
horizontally between the vertical tubes 424. More specifically, each 
mounting post 425 preferably is substantially cylindrical hollow tube 
having an outer diameter that slightly less than an inner diameter of the 
support tube so that the support tube can be slid over the mounting tubes 
upon assembly of the fourth tier mounting assembly 422. The mounting tubes 
425 and support tube 427 allow for width adjustment of the fourth tier 
mounting assembly 422 so that the mounting assembly 422 can be adapted for 
mounting on back support systems 34 of varying widths. The mounting tubes 
425 allow for the width of the mounting assembly 422 to be increased by 
approximately two inches beyond the length of the horizontal support tube 
427 in the preferred embodiment. 
As shown in FIGS. 17 and 18, the clamps 340 of the elbow joints 338 
associated with the fourth tier pad 314 are attached in the vicinity of 
the upper ends 426 of the vertical tubes 424. As shown in FIG. 27, the 
lower ends 428 of the tubes 424 are sized to be matingly received by the 
upper ends 170 of the support tubes 148, and attached to the support tubes 
148 via mounting posts 453. In the preferred embodiment, the mounting 
posts 453 operate in a similar fashion as set forth above with respect to 
mounting posts 70. More specifically, an opening 452 extends axially 
through the vertical tubes 424, and the lower end 428 of each vertical 
tube 424 has a body portion 454 integrally formed with and extending 
downwardly therefrom. The body portion 454 has a lower tapered or angled 
end 455 substantially tapered or angled surface. A small tapered barrel 
431 is attached to the lower tapered end 455 of the body portion 454 by a 
stud 432 that extends from inside the opening 452 in the tube 424 through 
an opening 433 formed in the body portion 454 into engagement with the 
barrel 431. The body portion 454 and barrel 431 are sized to be slidably 
received inside the support tubes 148. A radially outwardly extending seat 
456 is formed at the intersection of the vertical tube 424 and the body 
portion 454 that prevents downward movement or insertion of the tube 424 
into the tube 148. The barrel 431 is moved axially upwardly and downwardly 
by the stud 432 when the stud 432 is tightened or loosened by the 
prescriber. When the stud 432 is loosened, the barrel 431 and body portion 
454 move freely inside the support tube 148. When the stud 432 is 
tightened, the barrel 431 is moved upwardly by the stud 432 and slides 
radially outwardly against the tapered surface 455 of the body portion 454 
so that the tapered ends of the body portion 454 and the barrel 431 are 
wedged into engagement with the inner surface of the support tube 148. In 
this locked position, the body portion 454 and barrels 431 are securely 
retained inside the support tubes 148 so as to prevent axial movement of 
the mounting assembly 422. As discussed hereinafter, the headrest pad 315 
can be attached to the upper end 426 of the fourth tier vertical tubes 424 
via a headrest mounting assembly 434, if desired. If no headrest pad 315 
is used, plugs (not shown) can be inserted into the upper ends 426 of the 
vertical tubes 424. Likewise, if no fourth tier pad 314 or head rest pad 
315 is employed, plugs (not shown) can be inserted into the upper ends of 
the support tubes 148. 
E. Extension Tubes 
The height of the back support 34 can be increased by adding one or more 
extension tubes 463 to each vertical support tube 148 and the vertical 
tubes 424 of the fourth tier mounting assembly 442, as needed. As shown in 
FIG. 34, each extension tube includes a body portion 465 having an axially 
extending opening 467 formed therein and a tapered or angled end 468, and 
a tapered barrel 470 attached to the tapered end 468 of the body portion 
465 by a screw or threaded bolt 471. A counterbore seat 472 is formed 
inside the opening 467 of the body portion 465 against which a head of the 
bolt 471 rests when the barrel 470 is in the unlocked position (discussed 
below). The seat extends radially inwardly from an inner surface of the 
body portion 465, and includes an opening extending axially therethrough 
that is sized to accommodate the bolt 471 therein so that the head of the 
bolt rest in the counterbore. This arrangement of the bolt 471 in the seat 
472 provides resistance when tightening the bolt, and allows the 
prescriber to easily locate and access the bolt 471. The seat 472 has a 
configuration similar to the seat discussed above for mounting posts 133 
associated with side plates 122. The screw 471 extends through the opening 
in the seat 472 downwardly into the opening 467 of the body portion 465, 
and then into the barrel 470, to attach the barrel 470 to the body portion 
465. 
The extension tube 463 preferably is approximately three to four inches 
long. The tapered barrel 470 and angled end 468 of the body portion 465 
are adapted to be inserted into the upper end 170, 426 of one or more of 
the vertical tubes 148, 424 associated with the support tubes 148 or 
fourth tier mounting assembly 422, respectively, or the lower end 172 of 
the vertical support tubes 148. The extension tube 463 is secured to the 
vertical tubes 148 and/or 424 by tightening the screw 471 in a similar 
manner as set forth above for the mounting posts 70 or 453. More 
specifically, as the screw 471 is tightened by a hex ball driver, the 
barrel 470 is moved inwardly toward the tapered end 468 of the body 
portion 465 such that an edge of the tapered end 468 and an edge of the 
tapered barrel 470 engage an inner surface of the tube in which the 
extension tube 463 is inserted, thereby locking the extension tube 463 in 
a fixed location with respect to the vertical tube and preventing rotation 
of the vertical and extension tubes. 
An upper end 473 of the extension tube 463 also is adapted to accommodate 
one of the tapered barrels 431 associated with the fourth tier mounting 
assembly 422. As shown in FIG. 34, a circumferentially extending seat 475 
is formed in the body portion 465 that prevents further inward movement of 
the body portion 465 into the vertical tube on which the extension tube 
463 is mounted. When a pair of extension tubes 463 are mounted on 
corresponding ends of the vertical tubes 148 and/or 424, the height of the 
back support 31 is increased by approximately two to three inches in the 
preferred embodiment. The extension tubes 463 permit the length or height 
of the back support system 34 to be increased as needed, e.g., as the 
user's height, dimensions or support needs change over time. 
F. Headrest Mounting Assembly 
If poor head control exists, then the headrest pad 315 (discussed below) 
can be included in the backrest system 30 to stabilize the head. As will 
be appreciated in view of the following disclosure, the headrest pad 315 
and headrest mounting assembly 434 allow for a wide range of movement so 
that the headrest pad can be positioned to accommodate individuals having 
spinal deformities. 
In the preferred embodiment shown in FIGS. 17, 28 and 33, the fifth tier 
pad 315 is attached to either the support tubes 148, fourth tier mounting 
assembly 422, or extension tubes 463 via a headrest mounting assembly 434 
(FIG. 28) and elbow joints 338 and ball and socket joints 342. When the 
headrest pad 315 is used, determinations as to whether the fourth tier pad 
314 and mounting assembly 422, the extension tubes, and/or the headrest 
mounting assembly 434 are employed, are based upon the height and support 
requirements of the specific wheelchair user. In the preferred embodiment, 
a pair of elbow joints 338 and a pair of ball and socket joints 342 are 
employed to attach the headrest pad 315 to the mounting assembly 434. The 
headrest assembly 434 and pad 322 also can be attached directly to the 
support tubes 148 when the first embodiment of the back support 180 is 
used. 
The headrest mounting assembly 434 is shown in FIG. 28, and includes an 
upper section 435 and a lower section 436 with the upper section 435 being 
rotatably attached to the lower section 436 to allow for proper 
positioning of the headrest pad 315. The upper section 435 includes three 
integrally formed mounting posts, namely, a first post 437, a second post 
438 and a third post 439. The clamps 340 of the elbow joints 338 that are 
associated with the headrest pad 315 are secured to first posts 437 at a 
desired height or location. The second post 438 extends between the first 
post 437 and the third post 439, as shown. Lower ends 440 of the third 
posts 439 are adapted to be matingly received by upper ends 441 of 
vertical tubes 442 associated with the lower section 436 such that the 
third post 439 can rotate freely about a common longitudinal axis 
associated with the third post 439 and vertical tubes 442. As discussed 
below, the third posts 439 are locked in place at a desired position when 
the headrest mounting assembly is attached to the vertical tubes 148, 
extension tubes 463 or fourth tier mounting assembly 422 and when the 
elbow joints 338 are locked in place. 
The lower section 436 preferably is a split tube assembly that includes a 
pair of spaced apart, vertical tubes 442 and a horizontal tube 444 
extending between the vertical tubes 442. The horizontal tube 444 
preferably is a hollow, cylindrical tube having an opening 444a extending 
axially therethrough. The lower ends 440 of the third posts 439 associated 
with each upper section 435 are positioned inside the upper ends 441 of 
the vertical tubes 442. Each vertical tube 442 includes a horizontally 
extending mounting post 480 projecting outwardly therefrom as shown in 
FIG. 28. The mounting posts 480 operate in a similar fashion as mounting 
posts 453 and those shown in FIG. 27. The mounting posts 480 are adapted 
for engagement with the horizontal tube 444 to support the horizontal tube 
444 between the vertical tubes 442. More specifically, the mounting posts 
453 are sized to disposed inside the opening 444a of the tube 444. The 
horizontal tube 444 provides torsional stiffness and rigidity for the 
headrest assembly 434 when it is not attached to the back support 298. 
Each mounting post 453 includes a body portion 484 with a tapered or 
angled end 484, and a tapered barrel 486 that is secured to the tapered 
end 487 of the body portion 484 by a screw or threaded bolt 487. The screw 
extends through an axially extending opening 489 formed in the body 
portion 482 into engagement with the barrel 486. In the preferred 
embodiment, a seat (not shown) is formed inside the opening 467 of the 
body portion 465 against which a head of the bolt 471 rests when the 
barrel 470 is in the unlocked position (discussed below). The seat extends 
radially inwardly from an inner surface of the body portion 484, and 
includes an opening extending axially therethrough that is sized to 
accommodate the bolt 487 therein. The seat has a configuration similar to 
the seat 472 discussed above for extension tube 463 and shown in FIG. 34. 
The screw 487 extends through the opening in the seat downwardly into the 
opening 489 of the body portion 484, and then into the barrel 486, to 
attach the barrel 486 to the body portion 484. 
The screw 487 is tightened or loosened to move the barrel 486 axially 
inwardly or outwardly by a hex ball driver that is inserted through an 
opening 490 formed in the vertical tube 442 into the opening 489 in the 
body portion 482 to access the screw head. As the screw 487 is tightened, 
the barrel 486 is moved into abutment with the tapered end 484 of the body 
portion 482 and along the tapered surface 484 of the body portion 482 so 
that an edge of the barrel 486 and an edge of the tapered end 484 of the 
body portion 482 engage an inner surface of the horizontal tube 444, 
thereby preventing movement of the horizontal and vertical tubes 442, 444. 
As discussed above with respect to the fourth tier mounting assembly 422, 
the mounting posts 480 and horizontal tube 444 allow for width adjustment 
of the headrest mounting assembly 434 in the preferred embodiment up to 
approximately two inches beyond the length of the horizontal tube 444, if 
desired. 
As shown in FIG. 28, each vertical tube 442 also has a vertically oriented 
mounting post 445 at its lower end that is adapted to be matingly received 
by the upper ends of either the support tubes 148, the upper ends 426 of 
the vertical tubes 424 of the fourth tier mounting assembly 422, or the 
upper ends of extension tubes 463. Each mounting post 445 includes a body 
portion 445A having a tapered or angled lower end 445B and a tapered 
barrel 445C that is attached to the lower end 445B of the body portion 
445A by a stud 446. A shoulder or seat 447 is formed at the intersection 
of the vertical tube 442 and an upper end of the body portion 445A of the 
mounting post 445 that prevents downward movement of the vertical tube 442 
into tubes 148, 424 or 463. An opening 449 extends axially through the 
body portion 445A of the mounting post 445, the vertical tube 442 and 
third posts 439 of the headrest assembly. After the horizontal tube 444 is 
secured to mounting posts 480, the stud 446 is inserted through the 
opening 449 in the third post 439, the vertical tube 442 and body portion 
445A, and into engagement with the barrel 445C. 
Operation of barrel 445C, stud 446 and tapered end 445B in this mounting 
assembly 434 is similar to that discussed above with respect to mounting 
posts 453 and 480. The mounting posts 445 are sized to be slidably 
received inside tubes 148, 424 or 463. The barrel 445C is moved axially 
upwardly and downwardly by the stud 446 when the stud 446 is tightened or 
loosened by the prescriber. When the stud 446 is loosened, the barrel 445C 
and body portion 445A move freely inside the tube 148, 424 or 463. When 
the stud 446 is tightened, the barrel 445C is moved upwardly by the stud 
446 against the tapered surface of the lower end 445B of the mounting post 
445 so that the tapered ends of the body portion 445A and the barrel 445C 
are wedged into engagement with the inner surface of the tube 148, 424 or 
463. In this locked position, the mounting posts 445 are securely retained 
inside the tubes 148, 424 or 463 so as to prevent axial movement of the 
mounting assembly 434. Moreover, compressive forces exerted on the 
vertical tube 442 and third posts 439 when the stud 446 is tightened 
provide rotational resistance for the third posts 439 with respect to the 
vertical tubes 442. The third post 439 is further locked in place when the 
elbow joints and ball and socket joints (discussed below) are locked in a 
desired position. 
In one embodiment of the present invention, a knob 448 is attached to the 
end of the stud 446 opposite barrel 445C to assist the prescriber in 
tightening and loosening the stud 446. The knob 448 extends outwardly from 
the upper end of the third post 439. The stud 446 is tightened or loosened 
when the prescriber turns the knob 448. In another embodiment of the 
present invention, a quick release assembly 476 (see, e.g., FIG. 29), that 
is similar to the quick release assembly 68 (see FIGS. 8 and 9), is 
employed to move the barrel 445C axially upwardly and downwardly so that 
the headrest assembly 434 can be easily removed from or attached to the 
back support assembly. In this configuration, a lever 477 is secured to 
the upper end of the third post 439 via a cam mechanism (not shown) and 
the stud 446. The barrel 445C is moved axially upwardly and downwardly by 
the stud 446 and cam mechanism based upon the position of the lever 477. 
That is, when the lever 477 is raised into a unlocked position (see, e.g., 
FIG. 8 ), the body portion 445A and barrel 445C move freely inside the 
opening of the tube 148, 424 or 463. When the lever is pressed downwardly 
into a locked position (see, e.g., FIG. 9), the barrel 445C is moved 
upwardly by the stud 446 against the tapered surface 445B of the body 
portion 445A so that the tapered ends of the body portion 445A and barrel 
445C are wedged inside the opening into engagement with the inner surface 
of the tube 148, 424 or 463. Thus, the knob 448 or quick release devices 
allow for the headrest mounting assembly 434 to be easily removed from and 
assembled to the wheelchair 10. 
An alternative embodiment of a lower section 436' is shown in FIG. 28A. 
This lower section 436' is a split tube assembly similar to that 
associated with the fourth tier mounting assembly. More specifically, the 
lower section 436 includes two hollow cylindrical mounting tubes 480' that 
extend horizontally and inwardly from the vertical posts 442, instead of 
mounting posts 480 as shown in FIG. 28. The mounting tubes 480' are 
adapted to be received inside the opening 444a associated with the hollow 
horizontal tube 444. A pair of tube clamps 450 preferably are mounted on 
the horizontal tube 450. Each clamp 450 includes an opening through which 
the horizontal tube 444 is inserted, and a slot 450a extending radially 
outwardly from the opening through the clamp 450. When the horizontal tube 
444 is positioned on the mounting tubes 480', the tube clamps 450 are 
tightened by a bolt 451A and nut 451B so that the slot is forced into a 
closed position and clamping forces are exerted on the horizontal tube 444 
and mounting tubes 480' to prevent dislocation of the horizontal tube 444. 
The fifth tier mounting assembly 434 also can be adapted to accommodate a 
wide variety of conventional headrest assemblies, if desired, instead of 
employing the elbow joints 338, ball and socket joints 342 and fifth tier 
headrest pad 315 associated with the present invention. In this 
configuration, an adapter 491 (see FIGS. 29 and 29A) is mounted onto the 
first posts 437 of the upper section 435 associated with the mounting 
assembly 434 via a swivel attachment assembly 495. The adapter 491 
includes a support member 492 that extends between two end portions 493a 
and 493b, with each end portion 493a, 493b having an opening 494a, 494b, 
respectively, extending therethrough that is adapted to accommodate a 
swivel 495 therein. Each swivel 495 includes a head portion 495a that 
extends outwardly from the openings 494a, 494b, a body portion 495b that 
is positioned inside the openings 494a, 494b, and a radially inwardly 
extending notch 495c formed at a lower end opposite the head portion 495a 
that is adapted to accommodate a retaining ring 496 therein. The retaining 
ring 496 is used to attached the swivel 495 to a swivel arm 497 that 
extends between the first post 437 of the upper section 435 and the 
adapter 491. The swivels 495 and retaining rings 496 allow the swivel arm 
497 to rotate about the body portions 495b to properly position the 
adapter 491 at a desired location. 
The swivel arm 497 includes a clamp 497a, 497b at each end, with each clamp 
497a, 497b having a vertically extending opening 497c, 497d, respectively 
formed therethrough. Each of the clamps 497a, 497b further includes a slot 
497e, 497f, respectively that extends radially outwardly through the 
clamps from the openings 497c, 497d. A cylindrical opening (not shown) 
extends through the swivel arm 497 and passes through the slots 497e, 
497f. The cylindrical opening is sized to receive a threaded bolt 498 that 
is used as a locking mechanism to prevent movement of the swivel arm 497 
with respect to the swivel 495 and adapter 491 and with respect to the 
first post 437. The bolt 498 preferably is held in place by a lock nut 
(not shown). Two recesses 499a are formed in the clamps 497a, 497b at ends 
of opening that are adapted to accommodate the lock nut, and to prevent 
rotation of the lock nut as the bolt 498 is tightened. Alternatively, 
knobs 363 or handles 365 can be used instead of the lock nut to allow for 
easy manipulation and positioning of the adapter. 
When the adapter 491 is positioned at the desired location, and the swivel 
arm 497 is properly positioned with respect to the first post 437, the 
bolt 498 is tightened inside the opening to force slots 497e, 497f into a 
closed position. As the slots 497e, 497f close, clamping forces exerted by 
the clamps 497a, 497b on the first post 437 and swivel body 495b increase 
to prevent movement of the swivel arm 497. 
The conventional headrest then is mounted to the adapter in the vicinity of 
flange 491a. It will be appreciated that flange 491a is shown for 
illustrative purposes only, and can be modified to accommodate numerous 
attachment or mounting assemblies associated with various conventional 
headrests. For example, the flange 491a shown in FIGS. 29 and 29A allows 
for mounting of head support systems such as the Spectrum Series head 
support systems sold by Whitmyer Biomechanix, Inc., Tallahassee, Fla. 
VI. Lateral Pads 
The backrest system also can be expanded to include lateral pads 500 and/or 
800 to provide additional support, regardless of the type of back support 
34 employed. As set forth below, lateral pads 500 can be mounted to the 
side plates 400 (FIGS. 35 and 36), and lateral pads 800 can be mounted to 
the vertical support tubes 148 (FIG. 32). 
A. Lateral Pads 500 
One lateral pad 500 can be mounted to each side plate 122 via a lateral pad 
mounting assembly 502 as shown in FIGS. 35 and 36. The lateral pads 500 
have a backing plate 504 and a cushion or insert 506 attached to the 
forwardly presented face of the backing plate 504. The backing plate 504 
can be substantially flat or curved, depending upon the region of the body 
to be supported. FIG. 35 shows a rear perspective view of the lateral pad 
500 having a curved construction. The backing plate 304 includes a 
rearwardly extending housing 505 that is adapted to accommodate the socket 
367 associated with a ball and socket joint 342. The housing 505 and 
opening (not shown) formed in the housing that is aligned with the cavity 
378 in the base 376B of the socket 367 are oriented to allow for rotation 
of the lateral pad 500 and socket 367 about the ball 366 to obtain proper 
positioning of the lateral pad 500 against the wheelchair user and ensure 
proper operation of the ball and socket joint. 
The backing plate 504 preferably is constructed from a substantially rigid 
polymer material such as ABS plastic, and the insert 506 can be 
constructed from a foam material. The housing 505 preferably includes 
support members 508 that are formed in the backing plate 504, and extend 
laterally across the backing plate 504 from the ball and socket joint to 
provide improved structural integrity for the lateral pads 500 (FIG. 36). 
A washable fabric cover 507 preferably is disposed around the pad 500 and 
held in place by a fastening mechanism such as Velcro hook and loop 
fasteners 509. 
Each lateral pad mounting assembly 502 includes a first disc 510 and a 
second disc 512 that are positioned inside the opening 128A on the side 
plate 122. More specifically, the first disc 510 includes a recess 514 
extending inwardly from its outwardly presented face 515 that is adapted 
to accommodate a support arm 516, a substantially semi-circular protrusion 
518 extending outwardly from an inwardly presented surface 520 of the disc 
510, and an opening 522 extending through a center axis of the disc 510. 
The second disc 512 has a similar construction as the first disc 510, with 
a recess 524 extending inwardly from its outwardly presented face 525 that 
is adapted to accommodate a reinforcement brace 526, a substantially 
semi-circular protrusion 528 extending outwardly from an inwardly 
presented surface 530 of the disc 512, and an opening (not shown) 
extending through a center axis of the disc 512. Upon assembly of the 
mounting assembly, the protrusions 518, 528 are disposed inside the 
opening 128A in the side plate 122 so as to define a substantially 
circular member that rotates freely inside the opening 128A. When the 
recesses 514, 524 for the support arm 516 and reinforcement brace 526, 
respectively, are positioned at a desired orientation, a threaded screw 
534 is inserted through one of a plurality of threaded openings 536 formed 
in the support arm 516, through the openings formed in the discs 510, 512, 
and then through one of a plurality of tapped openings 538 formed in the 
reinforcement brace 526. The protrusion 528 of the second disc 512 has a 
notch 542 formed therein that is aligned with a corresponding notch (not 
shown) in protrusion 518 of the first disc 510 when properly positioned 
inside the opening 128A of the side plate 122 to allow for passage of the 
screw 534 therethrough. 
The openings 538 in the reinforcement brace 526 are formed at locations 
corresponding to the openings 536 in the support arm 516. The openings 438 
and 536 are aligned upon assembly of the mounting assembly 502. Two or 
more screws or threaded studs 545 preferably are inserted through the 
aligned openings 536, 538 to further strengthen the support arm 516. 
Spacers 547 having openings 549 extending therethrough preferably are 
positioned between the support arm 516 and the reinforcement brace 526 
before the threaded studs 545 are inserted, so that each stud 545 passes 
through the opening 536 in the support arm 516, through the opening 549 in 
the spacer 547 and then through the opening 538 in the reinforcement brace 
526. 
The mounting assembly 502 preferably also includes a circular cap 553 (FIG. 
36) having a substantially similar diameter as the discs 510, 512 and an 
opening 555 extending through the cap 553 at its center axis. The cap 553 
is attached to the outwardly presented surface of the support arm 516 by 
the screw 534 to provide an aesthetically appealing finish to the mounting 
assembly 502. In the preferred embodiment, the support arm 516 has a 
greater thickness than the reinforcement brace 526. In this embodiment, 
the support arm 516 extends outwardly from the recess 514 of first disc 
510, while the reinforcement brace 526 is flush with the outer surface 525 
of the second disc 510 when the brace 526 is in recess 524. Thus, the cap 
553 preferably includes a recess 554 adapted to accommodate the portion of 
the support arm 516 that extends outwardly from the recess 514 of the 
first disc 510. 
The extent to which the pad 500 projects forwardly from the side plate 122 
can be varied by sliding the support arm 516 in the recess 524 to a 
desired position, aligning the opening 522 in the disc 510 with the 
nearest opening 536 in the support arm 516, and then positioning the 
reinforcement arm 526 in the recess 524 of the second disc 512 so that the 
corresponding opening 538 in the reinforcement brace 526 is aligned with 
the opening 536 in the support arm 516 and the openings in the discs 510, 
512. The angular orientation of the support arm 516 also can be varied by 
rotating the support arm 516 while disposed in the recess 514 so as to 
also rotate the discs 510, 512 within the opening 128A of the side plate 
122. When the desired orientation of the pad 500 is obtained by the 
prescriber, the screw 534 is inserted into these aligned openings. 
A forwardly extending end 559 of the support arm 516 has a clamp 561 
disposed at its end. The forwardly extending end can be angled slightly 
inwardly as shown in FIG. 36, or the support arm 516 can be substantially 
straight, depending upon the support needs of the wheelchair user. The 
clamp 561 has an opening 563 extending therethrough, with a slot 565 
extending radially outwardly from the opening 563. The clamp 561 also has 
a second opening (not shown) that extends through the slot 565, and is 
adapted to accommodate a screw or threaded stud 567 therein. A swivel 
assembly 569 extends through the opening 563 in the clamp 561, and is 
secured at a desired orientation by tightening the screw 567 in the second 
opening so as to force the slot 565 into a closed position. 
The preferred embodiment of the swivel assembly 569 is shown in FIG. 37. 
This construction of the swivel 569 allows for the lateral pad 500 to be 
pivoted outwardly away from the individual seated in the wheelchair 10 
without loosening the clamp 561 or removing or readjusting the support arm 
516. Thus, the lateral pads 500 can be easily moved way from the 
individual when necessary (e.g., for physical therapy or to remove the 
individual from the wheelchair 10) without disassembling the mounting 
assembly 502. In the preferred embodiment shown in FIG. 37, the swivel 569 
includes a swivel pivot 571, a swivel base 573 having a post 575 
integrally formed with and extending downwardly therefrom, a pair of dowel 
pins 577 that are inserted through openings 579 in the base 573 and 
securely retained in openings 581 formed in the swivel pivot 571, a thread 
rod 583 that is inserted through an opening 585 formed in the swivel base 
573 and post 575 into an opening 587 formed in the swivel pivot 571, a 
tension spring 589 disposed around the thread rod 583, and a swivel 
retainer 591 having an opening 593 extending therethrough that is adapted 
to be securely positioned around a lower end 595 of the thread rod 583. 
Upon assembly of the mounting assembly 502 , the swivel pivot 571 and 
swivel base 573 extend upwardly from the clamp 561, and the swivel post 
575, spring and swivel retainer 591 are disposed inside the opening 563 of 
the clamp 561. The spring 589 normally biases the swivel 569 into a locked 
position such that the dowel pins 577 are disposed inside the openings 579 
in the swivel base 573 and the pad 500 cannot rotate about the swivel 569 
(see FIG. 37A). To pivot the lateral pad 500 away from the wheelchair 
occupant, the swivel pivot 571 is manually pulled upwardly so that the 
dowel pins 577 are removed from the openings 579 in the swivel base 573. 
While the swivel pivot 571 is being pulled upwardly so that the dowel pins 
577 are removed from the base 573, the swivel pivot 571 is rotated so that 
the dowel pins 577 are no longer aligned with the openings 579 in the 
swivel base 573. When the pads 500 are pivoted away from the wheelchair 
user and the pivot 571 is rotated sufficiently to prevent the dowel pins 
577 from entering the base 573 openings 579, the pivot 571 can be released 
by the person rotating the pads 500 so that the swivel 569 is in an 
unlocked position with the dowel pins 577 resting on an upper surface 579 
of the base (see FIG. 37B). To return the pad 500 to its desired location 
in the locked position when the occupant is returned to the wheelchair 10, 
the swivel pivot 571 can be pulled upwardly and rotated back to the locked 
position with the dowel pins 577 in the openings 579 of the base 573, or 
the pad 500 simply can be pushed inwardly toward the occupant until the 
dowel pins 577 slide back into the openings 579 in the swivel base 573. 
The swivel pivot 571 also has an opening 605 extending radially 
therethrough that is adapted to accommodate a threaded stud or screw 607. 
In the preferred embodiment, a socket head screw is employed as screw 607. 
The threaded stud 607 secures one end 608 of an attachment arm 609 to the 
swivel pivot 571. The opposite end 611 of the attachment arm 609 is 
attached to a ball 613 associated with a ball and socket joint 615. The 
ball 613 is disposed inside a socket 617 formed in the backing plate 504 
of the lateral pad. More specifically, the backing plate 504 has a socket 
base (not shown) formed therein that includes a cavity (not shown) adapted 
to receive at least a portion of the ball 613. The socket base of the 
lateral pad assembly preferably has a round configuration similar to that 
of socket base 376B since no wing pads preferably are attached to the 
lateral pads 500. The ball and socket joint 615 and swivel assembly 569 
permit adjustment of each lateral pad 500 within six degrees of freedom. 
The ball 613 has a similar construction to that set forth above for ball 
366. That is, the ball 613 includes a second section that is attached to 
or integrally formed with the attachment arm 609, and a first section that 
is attached to the second section by the threaded stud or screw 607 that 
extends through an opening (not shown) formed in the attachment arm 609 
and through a threaded opening (not shown) formed in the second section. 
As discussed above with respect to second member 346 and the second section 
372 of ball 366, the attachment arm 609 and the second section of the ball 
613 preferably are molded together as a single unitary structure, and 
preferably are constructed from a strong engineering plastic material such 
as RYTON.RTM., sold by Phillips Petroleum Co., Bartlesville, Okla., or a 
polycarbonate material such as LEXAN.RTM., sold by General Electric 
Company, Pittsfield, Mass. In this configuration, the base of the socket 
617 also is constructed preferably from a strong plastic material such as 
RYTON.RTM.. However, the first portion of the ball 613 preferably is 
constructed from a more ductile, resilient, durable and high-strength 
material such as nylon or other similar synthetic polymer. The nylon 
material is capable of withstanding forces exerted on the first section 
without cracking when the ball 613 is in the locked position. The nylon 
material also is preferred since the nylon first section deforms in the 
base of the socket 617 when the first section is subjected to loading 
forces in the locked position. Since the first section is constructed from 
a softer material than the base in the preferred embodiment, the cavity of 
the base does not deform or degrade, and the locking feature of the ball 
and socket joint 615 remains operational over time. The socket 617 also 
includes a C-ring bracket 619 that is mounted to the socket base. The 
bracket 619 preferably is constructed from a lightweight, strong metal 
such as aluminum. Alternatively, the C-ring bracket 380 can be constructed 
from a strong engineering plastic material such as RYTON.RTM. or a 
polycarbonate material such as LEXAN.RTM. with an inner edge that is 
molded to have a rough surface. As discussed above with respect to ball 
and socket joints 342, the inner edge of the C-ring bracket 619 grips or 
frictionally engages the ball 613 when the screw is in the extended or 
locked position to assist in preventing rotation of the ball 613. 
The threaded stud 607 is disposed in an extended position or retracted 
position within the attachment arm 609 and second section 619 by screwing 
or twisting the screw 607 into or out of the opening in the attachment arm 
609. Thus, when a portion of the threaded screw 607 is tightened or 
screwed into the opening of the attachment arm 609 into the extended 
position, the first section (not shown) of the ball 613 is moved radially 
outwardly from the second section 619 into a locked position (compare to 
FIG. 25B for ball 366). When a portion of the threaded screw 607 is 
loosened or screwed out of the opening in the attachment arm 609, the 
first section of the ball 613 moves radially inwardly toward the first 
section into an unlocked position such that the ball rotates freely inside 
the socket to permit angular or rotational movement of the lateral pad 
(compare to FIG. 25A for ball 366). When the lateral pad 500 is moved into 
a desired position and orientation, the threaded screw 607 is screwed into 
the extended position, and the first section of the ball 613 is moved into 
the locked position against the socket 617 to prevent further angular 
movement of the pad 500 via that ball and socket joint 615. 
Therefore, the ball and socket joint 615 and swivel assembly 569 allow for 
precise positioning of the lateral pads 500 against the user by providing 
for rotational and angular adjustment of the lateral pads 500. To adjust 
the lateral pads 500 from the rear or side of the wheelchair 10, the 
threaded bolts 567 of the clamps 561 and the threaded screw 607 associated 
with the ball and socket joints 615 are loosened or unlocked or moved into 
a retracted position to allow for unrestricted movement of the pads 500 to 
a desired location and orientation. As previously discussed with respect 
to bolts 362 and 368, knobs 363 or handles 365 can be attached to studs 
567 and/or 607 to assist the prescriber in tightening or loosening the 
studs 567, 607 and manipulating the lateral pads 500. When the studs 567 
and 607 are loosened, the ball 613 rotates freely inside the socket 617 
and the attachment arm 609 rotates freely with respect to the support arm 
516. When each pad is properly positioned against the user's back, the 
studs 567 and 607 are tightened by the prescriber. 
B. Lateral Pads 800 
The backrest system 30 also can be expanded to include one or more lateral 
pads 800 that are mounted at any location along the support tubes 148, 
vertical tubes 424 of the fourth tier mounting assembly and/or vertical 
tubes 442 of the headrest mounting assembly 434. Lateral pads 800 can be 
used in addition to lateral pads 500, or instead of lateral pads 500, 
depending upon the support needs of the wheelchair user. FIG. 32 
illustrates a partially exploded view of the preferred embodiment of one 
lateral pad 800. The lateral pads 800 have a backing plate 802 and a 
cushion or insert 803 attached to the forwardly presented face of the 
backing plate 802. The backing plate 802 preferably is constructed from a 
substantially rigid polymer material such as ABS plastic, and the cushion 
can be constructed from a foam material. Support members 804 are formed in 
the backing plate 802, and extend diagonally across the backing plate 802 
to provide improved structural integrity for the pads 800. 
The lateral pads 800 are attached to the support tubes 148 at a desired 
location via an elbow joint 812 and the ball and socket joint 810 in a 
similar manner as discussed before with respect to elbow joint 338 and 
ball and socket joint 342. A ball 811 of the ball and socket joint 810 
preferably is identical to ball 366 of ball and socket joint 342. However, 
for the lateral pad 800 assembly, the ball and socket joint 810 includes a 
socket 807 having a socket base 808 with a cavity 809 formed therein, an 
upper socket portion 814 that is mounted to the base 808 and has an 
opening formed therein to accommodate a portion of the ball 811 therein, 
and a C-shaped bracket 816 that is mounted to the upper bracket section 
814 as shown in FIG. 32. As discussed above with respect to ball 366, the 
ball 811 includes two sections, namely a first section 813 and a second 
section 815, and is attached to a second member 818 of the elbow joint 812 
by a stud 819, in an identical manner as discussed above with respect to 
the second member 346 and bolt 368 of elbow joint 338. The operation of 
the ball 811 is identical to that of ball 366, and is not repeated herein 
for ball 811. 
The second member 818 also has a post 828 that extends outwardly therefrom 
in a similar manner as discussed above with respect to post 350. The post 
828 is inserted through an opening 836 of a clamp 830 associated with a 
first member 832 of the elbow joint 812 by a retaining ring 834, in a 
similar manner as discussed above with respect to post 350, retaining ring 
356 and clamp 355 of elbow joint 338. Thus, the first member 832 can 
rotate freely about the post 828. The clamp 830 further includes a slot 
838 which extends from the opening 836 through the clamp 830, and an 
opening (not shown) that extends through the clamp and perpendicularly 
intersects the slot 838. The opening is adapted to receive a screw 840 
therein (see FIG. 32). When the first member 832 is positioned in a 
desired orientation with respect to the second member 818, the screw 840 
is inserted into the opening and tightened to close the slot 838. When 
this occurs, the clamp 830 exerts clamping forces on the post 828 to 
prevent rotation of the first member 832 with respect to the second member 
818. 
The first member 832 of the elbow joint 812 also includes a U-shaped 
attachment mechanism 852 that extends outwardly from the clamp 830 as 
shown in FIG. 32, and a sleeve 854 having an opening 856 formed therein 
that is adapted to slidably receive the attachment mechanism 852. The 
attachment mechanism 852 can be moved inwardly and outwardly within the 
opening 856 to adjust the length of the first member 832. This allows the 
lateral pad to be precisely located at various points along the user's 
torso to provide additional support. When the desired length of the first 
member 832 is obtained, a screw 858 is inserted through an opening 860 
formed in the sleeve 854, and tightened by the prescriber to prevent 
further movement of the attachment mechanism 852 in the opening 856. 
The first member 832 is attached to the support tube 148 or tubes 424 or 
442 by a locking mechanism such as clamp 862 shown in FIG. 32. The clamp 
862 includes two U-shaped sections 864 and 866 that are secured together 
to define an opening therebetween through which is inserted the support 
tube 148. When the sections 864, 866 are positioned at a desired height 
along the support tube 148, the two sections 864, 866 are secured together 
around the tube 148 by a pair of screws 868 that are inserted through 
openings 870, 872 formed in the sections 864, 866, respectively. Thus, the 
lateral pad can be easily removed from or attached to the support tube 148 
via the clamp 862. 
In view of the foregoing, it will be apparent that either lateral pads 800 
or lateral pads 500, or both, can be used to apply pressure to the 
exoskeletal structure (ribs) of the user to provide improved lateral 
support of the spine. Furthermore, the lateral pads 800 can be positioned 
along the support tubes 148 such that the pads 800 are displaced with 
respect to each other (i.e., asymmetric positioning). Similarly, the 
mounting assembly 502 for lateral pads 500 can be rotated in the openings 
128A of the side plates 122 so that the pads 500 are displaced with 
respect to each other to provide asymmetric positioning. This allows 
curvatures of the spine that are mild to moderate in nature to be 
supported properly by the backrest system 30. By attaching a pair of hip 
pads 672 (discussed below) to the support tubes 148 of the backrest system 
30 in conjunction with the lateral pads 800 and/or 500, a three point 
force system is applied to the user's spine to provide corrective forces 
for "C" curves. 
VII. Hip Pad Assembly 
A hip pad assembly 670 (FIGS. 38 and 39) also can be used to provide 
additional support for the user, regardless of the type of back support 
employed (e.g., the insert 184 and shell 182 configuration, or the pad 
assembly 300). As discussed above, the pad 311 associated with the first 
tier helps stabilize and support the sacrum by controlling pelvic tilt in 
an anterior-posterior direction (see FIGS. 22A-D). Hip pads 672 can be 
added in this region to provide lateral stability as well. The hip pad 
assembly 670 includes one or two hip pads 672 that provide additional 
support by positioning the hip pads 672 over the greater trochanter so 
that the hip pads 672 apply a small amount of pressure to the user's hip 
region to encourage mid-line positioning of the pelvis (FIGS. 40A and 
40B). As discussed herein, the hip pads 672 and lateral pads 500 can be 
used to provide the three point force system to control or correct mild to 
moderate scoliotic spinal curves. 
Each hip pad 672 generally has a backing plate 673 and a cushion or insert 
674 attached to the upwardly or inwardly presented face of the backing 
plate 672. The backing plate 672 preferably is constructed from a 
substantially rigid polymer such as ABS plastic, and includes a housing 
675 extending rearwardly therefrom that is adapted to accommodate a round 
socket 376B for a ball and socket joint 740 (discussed below). The insert 
674 can be constructed from a single piece of foam, a plurality of air 
cells, or can be a composite of a cellular cushion including a plurality 
of air cells disposed in a center portion of the cushion with foam 
provided on either side of the air cells. A suitable air cell cushion is 
the type manufactured and sold by ROHO, Inc. of Belleville, Ill., and set 
forth in U.S. Pat. Nos. 4,541,136 issued Sep. 17, 1985, and 5,369,828 
issued Dec. 6, 1994. 
The hip pad assembly 670 is attached to the lower end 172 of the support 
tubes 148 by a pair of extension tubes 463. As discussed above, each 
extension tube 463 has a body portion 465 with a tapered or angled end 468 
and a tapered barrel 470 that is attached to the body portion 465 at the 
tapered end 468 by a screw 471 (not shown in FIGS. 38, 39). The tapered 
barrel 470 is inserted in the opening 149 of the support tube 148, and 
then the screw is tightened to force the barrel 470 into abutment with the 
tapered end 468 of the body portion 465 until edges of the tapered barrel 
470 and the tapered end 468 engage an inner surface of the support tube 
148, thereby locking the assembly 670 in place. 
In the preferred embodiment, the extension tubes 463 that support the hip 
pad assembly 670 are modified to also include a tubular arm 676 extending 
outwardly from the body portion 465 in a substantially perpendicular 
fashion as shown in FIG. 38. When the extension tubes 463 are attached to 
the support tubes 148, the arms 676 are oriented to extend inwardly to 
allow for a cylindrical tube 678 having an opening 680 extending axially 
therethrough to be inserted around the arms 676. The arms 676 support the 
tube 678 in a generally horizontal fashion across the rear of the back 
support assembly 34. The arms 676 and tube 678 improve the structural 
integrity of the hip pad assembly 670. 
Each hip pad 672 is attached to the body portion 465 of the extension tube 
463 via a pair of elbow joints, namely a first elbow joint 682 and a 
second elbow joint 684, and a ball and socket joint 686. The elbow joints 
682, 684 and ball and socket joints 686 operate in a similar manner to 
those set forth above for dual trunk pads 312a and 312b, allowing for the 
hip pads 672 to be adjusted within six degrees of freedom. The socket base 
(not shown) of the ball and socket joint 686 preferably has a round 
configuration that is similar to base 376B since no wing pads are attached 
to the hip pads 672. Using two elbow joints 682, 684 to attach the hip 
pads 672 to the extension tubes 463 allows for a greater range of forward, 
rearward and lateral pad movement than if only one elbow joint was used. 
The first elbow joint 682 includes a first member 688 (similar to the 
first member 344 of elbow joint 338) that has a first clamp 690 at one end 
and a second clamp 692 at the opposite end. The body portion 465 of the 
extension tube 463 is inserted through an opening 693) formed in the first 
clamp 690, and then the clamp 690 is tightened to secure the first member 
688 to the extension tube 463. The clamp 690 preferably has a slot 696 
extending radially outwardly from the opening in the first clamp 690 that 
is at least partially closed when the clamp 690 is tightened around the 
extension tube 463. The clamp 690 is tightened by a locking mechanism such 
as threaded bolt 700 that is inserted through an opening 694 formed in the 
first member 688 that extends through the slot 696 and held in place by a 
lock nut 701 in a similar fashion as discussed above with respect to the 
first member 344 of elbow joint 338. 
The first member 688 is operably attached to a second member 702 by a 
swivel attachment assembly 704 that allows the first member 688 to rotate 
freely with respect to the second member 702 about the attachment device 
704. In the embodiment shown in FIG. 39, the swivel attachment device 704 
includes a post 706 that is integrally formed with and extends upwardly 
from one end of the second member 702 through an opening 708 formed in a 
second clamp 692 associated with the first member 688. The second clamp 
692 includes a slot 714 extending radially outwardly from the opening 708. 
The opening 694 extending the length of the first member 688 in which the 
bolt 700 is disposed also extends through the slot 714 so that as the bolt 
700 is tightened, slot 714 closes and clamp 692 exerts clamping force on 
the post 706. As discussed above with respect to attachment device 348, 
the post 706 is held in the opening 708 by a retaining ring 712 that is 
received in an inwardly extending notch 707 formed around the periphery of 
the upper end of the post 706 so that the first member 688 rotates freely 
around the post 706. When the pad 672 is arranged at a desired position, 
the threaded bolt 700 is tightened to force slots 696 and 714 to close, 
thereby preventing movement of the first clamp 690 with respect to the 
extension tube 463, and the second clamp 692 with respect to post 706. 
The second member 702 also is connected to a swivel attachment assembly 716 
associated with the second elbow joint 684. With respect to the second 
elbow joint 684, more specifically, the second member 702 includes a clamp 
718 having an opening 720 extending therethrough and a slot 722 extending 
radially outwardly from the opening 720 that is formed at an end of the 
second member 702 that is opposite the post 706. The second member 702 is 
operably attached to a third member 724 associated with the second elbow 
joint 684 by an attachment assembly 716 that allows second member 702 to 
rotate freely with respect to the third member 724. The swivel attachment 
assembly 716 is similar to the attachment assembly 704 of the first elbow 
joint 682 in the embodiment shown in FIG. 39. More specifically, the 
attachment assembly 716 includes a post 726 that is integrally formed with 
and extends downwardly from one end of the second member 702 through the 
opening 720 formed in the clamp 718 associated with the second member 702. 
The post 726 is held in the opening 720 by a retaining ring 728 that is 
received in an inwardly extending notch 727 formed around the periphery of 
the lower end of the post 726 so that the second member 702 rotates freely 
around the post 726. The clamp 718 is tightened by a locking mechanism 
such as threaded bolt 730 that inserted through an opening 732 formed in 
the second member 702 that extends through the slot 722 and held in place 
by a lock nut 731 in a similar fashion as discussed above with respect to 
the clamps 690, 692 of the first member 688 (FIG. 39). 
It will be appreciated that the posts 706, 726, clamps 692, 718, and 
retaining rings 712, 728 of the swivel attachment assemblies 704, 716, 
respectively, and the associated locking mechanisms are set forth for 
illustrative purposes. Other swivel assemblies and locking mechanisms can 
be used to prevent rotational movement of members of the elbow joints 
(e.g., see FIG. 23C). 
The end of the third member 724 that is opposite post 726 is attached to a 
ball 734 that is disposed inside a socket 376B (not shown) associated with 
the ball and socket joint 740. A c-ring bracket 737 is attached to the 
socket and housing of the backing plate by bolts 738 in a similar manner 
as discussed above for c-ring 380 and bolts 382. The ball and socket joint 
740 permit rotary movement of the pads 672 in every direction through 
movement of the ball 734 in the socket. In one embodiment, the ball 734 is 
attached to the third member 724 by a screw or threaded bolt (not shown) 
that is inserted through an opening formed in the third member 724 in a 
similar manner as set forth above for ball and socket joint 342. In the 
preferred embodiment, the ball 734 includes two sections (not shown) that 
operate in an identical manner as sections 371 and 372 to allow for 
movement of the ball 734 in the socket 736 when the bolt is in a retracted 
position (i.e., the ball 734 is in an unlocked position), and prevent 
movement of the ball 734 in the socket 736 when the bolt is in an extended 
section (i.e., the ball 734 is in the locked position). As discussed above 
with respect to ball 366, the second section of the ball 734 preferably is 
integrally formed with the third member 724, and the first section is 
secured to the second section by the bolt. 
VIII. Back Cover 
The backrest system 30 also can include a back cover 750 that is removably 
secured to back support 34 as shown in FIG. 33 to provide an improved 
aesthetic view from the rear of the wheelchair 10 by covering the support 
chassis 32 and at least a portion of the back support 34. When the pad 
assembly 300 is employed, the back cover 750 preferably hides from view 
the support chassis 32, elbow joints 338 and ball and socket joints 342 
associated with at least pads 311, 312a, 312b, 313 associated with the 
first, second and third tiers 301, 302, 303. In the preferred embodiment, 
the back cover 750 is constructed from a washable fabric material, and 
held in position by a fastening mechanism such as VELCRO.RTM. hook and 
loop fasteners 752 attached to an inner surface of the back cover 750 and 
the back support 34. Alternatively, the fastening mechanism can include an 
elastic band that is attached to an outer edge of the back cover material 
so that the cover can be slipped over the back support and held in place 
by the elastic band. 
In view of the above, it will be seen that the several objects and 
advantages of the present invention have been achieved and other 
advantageous results have been obtained. 
The foregoing description is set forth only for illustrative purposes only 
and is not meant to be limiting. As various changes could be made in the 
above constructions without departing from the scope of the invention, it 
is intended that all matter contained in the above description or shown in 
the accompanying drawings shall be interpreted as illustrative and not in 
a limiting sense. Numerous variations, within the scope of the appended 
claims will be apparent to those skilled in the art in light of the 
foregoing description and accompanying drawings.