Note: Descriptions are shown in the official language in which they were submitted.
CA 02233928 1998-04-03
1
FLEXIBLE CONTOUR WHEELCHAIR BACKREST
BACKGROUND OF THE INVENTION
1. Field of the invention:
The present invention relates to a flexible backrest, in
particular but not exclusively a wheelchair backrest, having a contour that
can be easily adjusted to the morphology and anthropometry of a user's
back.
2. Brief description of the prior art:
Manual wheelchairs usually come with conventional
sling backrests. Originally, this type of backrest was designed to enable
easy folding of the wheelchair. However, some studies have
demonstrated that prolonged use thereof may negatively affect user's
posture, comfort, function and health (Zollars, J. & Axelson, P. (1993)
"The back support shaping system: an altemafive for persons using
wheelchairs with sling upholstery'; Proceedings of the 16t" Annual
RESNA Conference, Las Vegas, RESNA Press, 274-276; Harms, M.
( 1990) "Effects of v~heelchair design on posture and comfort of users';
Physiotherapy, 76, 5, 266-271; Bergen, A. & Presperin, J. (1990),
"Positioning for functions: wheelchairs and other assistive technologies';
CA 02233928 1998-04-03
2
Valhalla Rehabilitation Publications Ltd; and Zacharkow, D. (1984),
"Wheelchair posture and pressure sores", Springfield, Illinois) . In fact,
they may cause the spine to curve into a kyphotic geometry and produce
a posterior tilting of the pelvis, which can lead to back and neck pain, and
even to long-term deformities of the spine and pelvis. Moreover,
conventional sling backrests do not provide sufficient lateral trunk support
to prevent, manage or correct trunk alignment problems.
Considering these problems, the development of special
seating for people with disabilities become important. The technology in
seating has rapidly evolved around cushions or combination of rigid
interfaces and cushions with great results. There is a general consensus
that, from a posture standpoint, they offer some of the best solutions
(Valiquette, C. & Audet, J. (1992) "Pushing the limits of the sling concept.'
the contoured sling backrest", Canadian seating and mobility conference,
Toronto). Unfortunately, the use of cushions deprives many wheelchair
users of the advantages of the sling backrests such as foldability, light
weight, low cost and simplicity (Valiquette, C. & Audet J. (1992),
"Pushing the limits of the sling concept: the contoured sling backrest",
Canadian seating and mobility conference, Toronto; and Zollars J. &
Axelson P. (1993), "The back support shaping system: an alfemative for
person using wheelchairs with sling upholstery", Proceedings of the 16t"
Annual RESNA Conference, Las Vegas: RESNA Press, 274-276).
In this way, adjustable-tension back upholstery was
introduced on the market to preserve the sling backrests characteristics
while improving the user's posture and comfort. Adjustable-tension back
upholstery are foldable and can accommodate lumbar lordosis or
CA 02233928 1998-04-03
3
kyphosis by the use of adjustable straps. In spite of the improvement,
they often give poor lateral trunk support and some adjustments are still
missing to maintain neutral pelvic position and lumbar lordosis. Given this
context, the conception of a new backrest for wheelchair is worthwhile.
OBJECTS OF THE INVENTION
An object of the present invention is therefore to provide
a flexible contour backrest, in particular but not exclusively a wheelchair
backrest, which overcomes the above mentioned drawbacks of the prior
art.
Another object of the present invention is to provide a
flexible contour backrest, in particular but not exclusively a wheelchair
backrest, having a contour that can be easily adjusted to fit a plurality of
users' back contours in view of ( a) suitably supporting the back of these
users and ( b) improving lateral trunk support.
SUMMARY OF THE INVENTION
More specifically, in accordance with the present
invention, there is provided a flexible contour backrest comprising two
side posts, and a flexible backrest body extending between the two side
posts. The flexible backrest body comprises a plurality of transversally
CA 02233928 1998-04-03
4
extending and vertically spaced apart flexible straps each interconnecting
the two side posts and each having an adjustable length, and a plurality
of substantially stiff stays intersecting at least one of the flexible straps.
In operation, the contour of the backrest body can be adjusted to the
contour of a user's back by adjusting the length of the straps and the
shape of the stays.
Also in accordance with the present invention, in a
flexible contour backrest comprising two side posts, and a flexible
backrest body extending between the two side posts and including two
opposite sides attached to the two side posts, respectively, the
improvement comprises an elongated curved front face of each side post
for receiving the two opposite sides of the flexible backrest body,
respectively. This elongated curved front face of each side post has a
forwardly bulging section for inducing a depth dimension to the flexible
backrest body to fit the posterior lateral contour of a user's back and
thereby providing lateral support to the user's trunk.
The present invention further relates to a flexible contour
backrest comprising two side posts each comprising an elongated curved
front face, and a flexible backrest body extending between the elongated
curved front faces of the two side posts. The flexible backrest body
comprises ( a) a plurality of transversally extending and vertically spaced
apart flexible straps each interconnecting the two side posts with
elongated curved front faces, and each having an adjustable length, and
( b) a plurality of substantially stiff stays intersecting at least one of the
flexible straps.
CA 02233928 1998-04-03
In accordance with preferred embodiments:
- the substantially stiff stays are malleable to facilitate adjustment of
their
shape;
5 - the plurality of transversally extending and vertically spaced apart
flexible straps comprises an upper strap, a lower strap, and an
intermediate strap situated between the upper and lower strap, and the
flexible contour backrest further comprises means for adjusting a vertical
position of the intermediate strap on the two side posts;
- the transversally extending and vertically spaced apart flexible straps
are generally perpendicular to the two side posts, and the substantially
stiff stays are generally perpendicular to these straps;
- the flexible backrest body comprises elongated pockets for receiving the
substantially stiff stays;
- the two side posts are mounted on a chair frame, and the flexible
contour backrest further comprises mechanical means for adjusting the
vertical position of the two side posts on the chair frame; and
- the flexible contour backrest comprises mechanical means for varying
the distance between the forwardly bulging sections of the elongated
curved front faces of the two side posts, in order to adapt the distance
between said forwardly bulging sections to the width of the user's trunk.
In accordance with a first alternative embodiment:
CA 02233928 1998-04-03
6
- the two side posts each comprise an elongated member defining a two-
dimensional or three-dimensional curve and having a substantially
straight lower end mounted to a chair frame, this substantially straight
lower end having a longitudinal geometrical axis;
- the mechanical means comprises means for rotating the substantially
straight lower end of the curved elongated member on the chair frame
about the longitudinal geometrical axis, and means for locking the
substantially straight lower end of the curved elongated member on the
chair frame in a plurality of different angular positions about the
longitudinal geometrical axis; and
- the mechanical means further comprises means for axially moving the
substantially straight lower end of the curved elongated member about
the chair frame and means for locking the substantially straight lower end
of the curved elongated member on the chair frame in a plurality of
different axial positions.
In accordance with a second alternative embodiment:
- the two side posts each comprise an elongated member, and a contour
member mounted on the elongated member to define the elongated
curved front face of the side post;
- the mechanical means comprises means for rotating the contour
member about the elongated member, and means for locking the contour
member in a plurality of different angular positions about the elongated
member; and
CA 02233928 1998-04-03
7
- the mechanical means further comprises means for moving the contour
member longitudinally on the elongated member, and means for locking
the contour member in a plurality of different positions along the
elongated member.
In operation, the shape of the flexible contour backrest
according to the invention can be adjusted to the morphology and
anthropometry of the posterior lateral contour of the user's back by
adjusting:
- the length of the upper, lower and intermediate straps;
- the shape of the stays;
- the vertical position of the intermediate strap and
eventually the vertical position of the upper and lower straps on the two
side posts;
- the angular position of the substantially straight lower
end of the curved elongated member on the chair frame about the
longitudinal geometrical axis;
- the axial position of the substantially straight lower end
of the curved elongated member about the chair frame;
- the angular position of the contour members about the
elongated members; andlor
- the position of the contour members along the
elongated members.
The objects, advantages and other features of the
present invention will become more apparent upon reading of the
following non restrictive description of a preferred embodiment thereof,
CA 02233928 1998-04-03
given by way of example only with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the appended drawings:
Figure 1, which is labelled as "prior art", is a side
elevational view of a conventional wheelchair;
Figure 2 is a front, perspective view, partially cut away,
of a first embodiment of the flexible contour backrest according to the
invention;
Figure 3 is an elevational, cross sectional view of a
mechanism for rotating the substantially straight lower ends of side posts
of the flexible contour backrest of Figure 2 about their longitudinal
geometrical axis;
Figure 4 is a side elevational view of the side posts of
the first embodiment of the flexible contour backrest according to the
invention;
Figure 5 is a rear elevational view of a flexible contour
backrest body of the first embodiment of the flexible contour backrest
according to the invention;
CA 02233928 1998-04-03
9
Figure 6 is a side elevational view of the side posts of
a second embodiment of the flexible contour backrest according to the
invention;
Figure 7 is a cross sectional view of a contour member
of the side post of Figure 6, taken along line 7-7 of Figure 6;
Figure 8 is a cross sectional plan view of a mechanism
for adjusting the angular position of the contour member of Figure 7,
taken along line 8-8 of Figure 6; and
Figure 9 is a rear perspective view of a flexible backrest
body of the second embodiment of the flexible contour backrest according
to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Although the preferred embodiments of the flexible
contour backrest according to the present invention will be described
hereinafter with reference to the backrest of a wheelchair, it should be
kept in mind that the present invention also applies to the backrest of
other types of chairs, or to the backrest of any other apparatuses.
Figure 1 illustrates an example of conventional
wheelchair 2 comprising on both sides thereof a generally vertical, one-
piece rear tubular post such as 1. The upper portions of the rear tubular
CA 02233928 1998-04-03
posts such as 1 which receive side posts (often referred to as "back post"
in the literature) such as 3 of the backrest 4. The side posts such as 3
can be either vertical or slightly inclined rearwardly as shown in Figure 1.
The upper end of the side posts such as 3 are bent rearwardly to form
conventional wheelchair handles such as 5.
5
Conventional wheelchairs are well known to those of
ordinary skill in the art and, accordingly, do not need to be further
described in the present specification.
10 In accordance with a first preferred embodiment of the
present invention, the side posts of the flexible contour backrest are made
of curvilinear and rotatable tubular members.
More specifically, as illustrated in Figure 2, the vertical
rear tubular posts of a wheelchair comprises upper and lower sections.
The upper sections of the generally vertical rear tubular posts form the
side posts 6 and 16, respectively, on both sides of the flexible contour
backrest 20. Each side post 6, 16 is formed of an elongate curvilinear
and rotatable tubular member having a substantially straight lower end 7,
17 rotatably mounted in the upper end 8, 18 of the lower section 9, 19 of
the generally vertical rear tubular post of the wheelchair.
A preferred embodiment of the mechanism for rotatably
mounting the substantially straight lower end 7,17 of the side post 6, 16
in the upper end 8, 18 of the lower portion 9, 19 of the generally vertical
rear tubular post is illustrated in Figure 3. The lower tubular end 7, 17 is
first mounted, for example press-fit in a tubular upper section 22 of a
CA 02233928 1998-04-03
11
cylindrical member 21. The lower portion 23 of the cylindrical member 21
has an outer cylindrical surface 24 formed with an annular groove 25.
The cross section of the annular groove 25 is shown in Figure 3.
The upper end 8, 18 is provided with a series of radial
square holes 26, 27 and 28. Each square hole 26, 27 or 28 is capable of
receiving a block 29 having a toothed face that snugly fits into the annular
groove 25. As an example, Figure 3 shows the block 29 inserted in the
radial hole 27 and having its toothed face snugly fitted into the annular
groove 25. A collar 31 is tightened on the upper end 8, 18 over the block
29 to complete the assembly.
Those of ordinary skill in the art will appreciate that the
toothed face of block 29 snugly fitting into the annular groove 25 will
enable, when the collar 31 is untightened, to rotate the substantially
straight lower end 7, 17 of the side post 6, 16 about the longitudinal,
geometrical axis of this substantially straight lower end 7, 17. The
toothed face of the block 29 snugly fitting into the annular groove 25 will
also prevent axial movement of the substantially straight lower end 7, 17
in the upper end 8, 18 of the lower section 9, 19. When tightened the
collar 31 will prevent both rotation of the substantially straight lower end
7, 17 about its longitudinal geometrical axis and axial movement of the
substantially straight lower end 7, 17 in the upper end 8, 18.
Referring back to Figure 2 of the appended drawings,
the substantially straight lower end 7, 17 of the side post 6, 16 is
generally straight and parallel to the lower post section 9, 19. The side
post 6, 16 is then successively bent forwardly and rearwardly to produce
CA 02233928 1998-04-03
12
a forwardly bulging section 32, 33. Finally, the upper free end of the side
post 6, 16 is bent rearwardly to form a handle 34, 35. A preferred non
limitative embodiment of the side posts 6 and 16 is given in Figure 4, in
which the dimensions, lengths, radius of curvature, etc., are given in
inches. The external diameter of the tubular members forming the side
posts 6 and 16 is 314 inch.
Although Figure 4 presents a preferred embodiment in
which the side posts are formed with a two-dimensional curve, it is within
the scope of the present invention to provide side posts presenting a
three-dimensional curve.
The above described rotation of the substantially straight
lower end 7, 17 about its longitudinal geometrical axis will enable
adjustment of the angular position of the forwardly bulging section 32, 33
in relation to the requirements of the morphology and anthropometry of
a user's back, in particular in relation to the width of the user's trunk.
The flexible contour backrest comprises, as illustrated
in Figure 2, a flexible backrest body 45 extending between the two side
posts 6 and 16. This flexible backrest body 45 comprises an upper strap
36 extending between the upper ends of the side posts 6 and 16. The
flexible backrest body 45 further comprises an intermediate strap 37 and
a lower strap 38. The lower strap 38 extends between the substantially
straight lower ends 7 and 17 of the side posts 6 and 16. Regarding the
intermediate strap 37, it extends, in the preferred embodiment illustrated
in Figure 2, between the forwardly bulging sections 32 and 33 of the side
posts 6 and 16.
CA 02233928 1998-04-03
13
The flexible backrest body 45 further comprises a layer
of foam 38' covered by an envelope of nylon fabric 39. In a preferred
embodiment, the central region of the layer of foam is'h inch thick. The
lateral regions of the layer of foam is 1 inch thick to prevent any
discomfort caused to the user's trunk by the side posts. As can be seen
in Figure 2, the front layer of nylon fabric forms the front face 40 of the
backrest body 45. The rear face 41 of the backrest body 45 is illustrated
in Figure 5.
Referring now to Figure 5 of the appended drawings, the
nylon fabric comprises on the rear face 41 a series of five upper slits 42',
42, 43, 44 and 44' in the nylon fabric on the back of the flexible backrest
body 45. A first end of the upper strap 36 is sewed inside the flexible
backrest body 45. A second end of the upper strap 36 exits the flexible
backrest body 45 through slit 42, and is then passed around the upper
end of the side post 6, below the handle 34, to form a loop 46. Post 6 is
provided with a strap holding element (similar to elements 130 and 132
of Figure 9) to prevent the loop 46 from sliding downwardly on that side
post 6, and thereby hold the flexible backrest body 45 in stable vertical
position on that side post 6.
The second end of the upper strap 36 successively
enters slit 42' and exits slit 44'. The strap 36 is then passed around side
post 16 below handle 35, and then successively enters slit 44 and exits
slit 43. Finally, a Velcro (trademark) fastener provided on the second end
of the strap 36 is attached to a complementary Velcro (trademark)
fastener 47 fixed on the rear face 41 of the backrest body 45. Again, post
16 is provided with a strap holding element (similar to elements 130 and
CA 02233928 1998-04-03
14
132 of Figure 9) to prevent the upper strap 36 from sliding downwardly on
that side post 16, and thereby hold the backrest body 45 in stable vertical
position on the side post 16.
As also illustrated in Figure 5 of the appended
drawings, the flexible backrest body 45 comprises on the rear face 41 a
series of five lower slits 48", 48, 49, 50 and 50' made in the nylon fabric
on the back of the flexible backrest body 45. A first end of the lower strap
38 is sewed inside the flexible backrest body 45. A second end of the
lower strap 38 exits the flexible backrest body 45 through slit 48, and is
then passed around the lower end 7 of the side post 6 to form a loop (not
shown). The second end of the lower strap 38 successively enters slit 48'
and exits slit 50'. The strap 38 is then passed around the lower end 17
of the side post 16, and successively enters slit 50 and exits slit 49.
Finally, a Velcro (trademark) fastener provided on the second end of the
strap 38 is attached to a complementary Velcro (trademark) fastener 51
fixed on the rear face 41 of the backrest body 45.
Regarding intermediate strap 37, it is passed around
both the forwardly bulging sections 32 and 33 of the side posts 6 and 16,
and is also passed through loops 52 and 53. For example, the loops 52
and 53 are made of nylon fabric and comprise respective Velcro
(trademark) fasteners (not shown) for attaching the loops 52 and 53 to
respective, spaced apart vertical Velcro (trademark) strips 200 and 201
mounted, for example sewed to the rear face 41. Accordingly, the loops
52 and 53 are adjustable vertically to retain the strap 37 at the desired
vertical position on the side posts 6 and 16 within the range delimited by
the strips 200 and 201.
CA 02233928 2003-06-17
It is also within the scope of the present invention to
provide for vertical adjustment of the upper 36 and lower 38 straps.
A set of elongated, vertical pockets 54-57 are formed in
5 the nylon fabric of the rear face 41 to receive respective malleable,
substantially stiff metallic stays 58-61 (Figure 2). In the illustrated
example,
four pockets and stays are provided; it is however within the scope of the
present invention to provide a smaller or larger number of pockets and stays
in accordance with the requirements. Also, the stays can be in the form of
10 rectangular plates, elongated bars, rods, or other particular shapes, etc.
For
example, the stays may be made of aluminium or other metals or materials,
including metal alloys or plastics.
Still referring to Figure 5, the flexible backrest body 45
15 comprises:
- a lower flap 63 padded with a %2 inch thick layer of
foam and comprising a Velcro (trademark) fastener 64 for fixation at different
possible positions under the seat 66 (Figure 2) of the wheelchair. The flap 63
is attached under the seat to establish a contact between the user's sacral
seat region and the lower portion of the backrest;
- a left flap 69 shown in part in Figure 5 and made of
nylon fabric, to be folded over and fixed to the rear face 41 of the backrest
body 45 by means of Velcro (trademark) fasteners mounted, for example
sewed on the rear face 41 and the inner face of the flap 69 (only VeIcroT""
fastener 68 being shown in Figure 5); and
CA 02233928 2003-06-17
16
- a right flap 67 shown in part in Figure 5 and made of
nylon fabric, to be folded over and fixed to the outer face of the left flap
69 by
means of Velcro (trademark) fasteners (not shown) fixed on the outer face of
the left flap 69 and on the inner face of the right flap 67.
The flaps 67 and 69 ensure both fixation of the layer of foam 38' and nylon
fabric envelope 39, and covering and finishing of the rear face 41 of the
backrest body 45.
The idea of curving the side posts 6 and 16 originates
from the need to induce a depth dimension to the flexible backrest body 45 in
order to fit the posterior lateral contour of the user's back and thereby
provide
lateral support to the user's trunk. More specifically, the side posts 6 and
16
define respective elongated curved front faces from which the flexible
backrest body 45 is suspended and adjusted to the posterior lateral contour of
the user's back.
Conventionally, the side posts of wheelchairs are straight
and serve two main purposes: they support the backrest and enable an
assistant to push the wheelchair by means of the handles. By curving
(bulging) the side posts 6 and 16 as explained in the foregoing description,
the additional purpose of providing lateral support for the user's trunk is
implemented. However, curving the side posts 6 and 16 alone is not sufficient
to achieve adequate lateral trunk support: it is also essential that the width
between the posts 6 and 16 corresponds to the width of the user's trunk. The
side posts 6 and 16 of the flexible contour wheelchair backrest are rotatable
about their lower end longitudinal geometrical axis whereby the distance
separating the forwardly bulgin
CA 02233928 1998-04-03
17
sections 32 and 33 can be reduced or increased to accommodate the
width of the user's trunk. As indicated in the foregoing description, the
lateral trunk region of the backrest body 45 is padded with a thicker layer
of foam (1 inch) so that the side posts 6 and 16 are not felt against the
user's trunk to thereby enable the user to seat comfortably.
By adjusting ( a) the angular and vertical positions of the
side posts 6 and 16 by means of the mechanism of Figure 3, ( b) the
length of the upper strap 36, the intermediate strap 37 and the lower strap
38, ( c) the vertical position of the intermediate strap 37, and ( d) the
shape of the stays 58-61, the flexible contour wheelchair backrest is
capable of adapting to a great number of users' back contour.
The idea of using stays that can be easily bent into
shape originates from the need to reproduce different back shapes on the
sagittal plane (from normal geometry to mild kyphosis or light scoliosis).
In an advantageous embodiment, each stay is made of aluminum and
has a height of 12 inches and a width of 518 inch. Their stiffness depends
on their thickness; a thickness of 1116 inch is normally sufficient for stays
to support back curves on the sagittal plane and they remain easy to
manipulate. This thickness can be modified if different stiffness is
needed. Height and width of the stays can be also modified for better
accommodation.
Since back curves are not given enough support with
stays alone, the additional support is provided by the three adjustable
upper 36, intermediate 37 and lower 38 straps. The combination of stays
and straps and curved side posts allows for better adjustment of the
CA 02233928 1998-04-03
18
shape of the flexible contour backrest body to fit the posterior and
posterior lateral shape of the user's back. Furthermore, by increasing the
contact surface the stays enable even distribution of pressure through the
flexible contour backrest.
Figures 6-9 illustrate a second preferred embodiment
100 of the flexible contour backrest according to the invention. Referring
to Figure 6, the flexible contour backrest 100 uses the either vertical or
slightly rearwardly inclined side posts 101 and 102 (hereinafter referred
to as tubular members 101 and 102) of conventional wheelchairs (Figures
6, 8 and 9). The upper end of the tubular members 101 and 102 are
usually bent rearwardly to form conventional wheelchair handles 118 and
119.
In accordance with the second preferred embodiment
of the present invention, a contour member 103 having a suitable profile
(a possible profile being shown in Figure 6) is mounted to each tubular
member 101 and 102 through a pair of specially designed fasteners 104
and 105 to form side posts 204 and 205 with respective elongated curved
front faces. As illustrated in Figure 8, each fastener 104, 105 comprises
a split sleeve member 106 tightened on the tubular member 101, 102 by
means of a screw 107 interconnecting two end ears 108 and 109 of the
split sleeve member 106. As also shown in Figure 8, one 108 of the two
end ears comprises a flat bar extension 110.
The contour member 103 comprises an inner rigid core
plate 111 (Figures 7 and 8) of, for example, aluminium material. Other
materials can be used to fabricate the inner rigid core plate 111. A layer
CA 02233928 1998-04-03
19
of padding foam material 112 (Figure 7) is applied to each face of the
inner rigid core plate for the user's comfort. As illustrated in Figure 8, the
rigid plate 111 is fixed to the flat bar extensions 110 of the two fasteners
104 and 105 by means of rivets, nut-and-screw assemblies, etc. (see 113
and 114).
Therefore, by loosening the screws 107 and therefore
the split sleeve members 106 of the two fasteners 104 and 105, the split
sleeve members 106 and accordingly the contour member 103 can be
raised or lowered on the tubular member 101, 102 (see arrows 115 in
Figure 6). In the same manner, the split sleeve members 106 and
accordingly the contour member 103 can be rotated about the tubular
member 101, 102 (see arrows 116 in Figure 8). Therefore, the position
of the contour member 103 can be adjusted as required to adapt the
morphology and anthropometry of the user's back as well as to
accommodate the width of the user's trunk.
An advantage of the embodiment of Figures 6-9 is that
it requires no modification of the existing side posts (tubular members 101
and 102) of conventional wheelchairs.
The flexible contour backrest 100 further comprises a
flexible backrest body 124 extending between the two side posts 204 and
205.
Referring to Figure 9, the backrest body 124 comprises
a layer of foam (not shown) covered by an envelope of nylon fabric. In a
preferred embodiment, the layer of foam is 1 inch thick. Figure 9 shows
CA 02233928 1998-04-03
the rear layer of nylon fabric forming a rear face 125 of the flexible
backrest body 124.
The flexible backrest body 124 further comprises an
upper strap 117 extending between the upper ends of the side posts 204
5 and 205 with respective elongated curved front faces, below the handles
118 and 119. The flexible backrest body 124 further comprises an
intermediate strap 120 and a lower strap 121. The lower strap 121
extends between the lower ends 122 and 123 of the side posts 204 and
205 with respective elongated curved front faces. Regarding the
10 intermediate strap 120, it extends between the central forwardly bulging
sections of the contour members 103 of the two side posts 204 and 205.
Still referring to Figure 9, the nylon fabric comprises on
the rear face 125 a series of five upper slits, including slits 126, 127 and
15 128, made in the nylon fabric on the back of the flexible backrest body
124. A first end of the upper strap 117 is sewed inside the flexible
backrest body 124. A second end of the upper strap 117 exits the flexible
backrest body 124 through slit 128, and is then passed around the upper
end of the tubular member 102, below the handle 119, to form a loop 129.
20 Tubular member 102 is provided with a strap holding element 130 to
prevent the loop 129 from sliding downwardly on that tubular member
102, and thereby hold the flexible backrest body 124 in stable vertical
position on the side post 204.
The second end of the upper strap 117 successively
enters the upper slit (not shown) situated farther to the right, and exits the
upper slit (not shown) situated farther to the left. The upper strap 117 is
CA 02233928 1998-04-03
21
then passed around the upper end of tubular member 101, and then
successively enters slit 126 and exits slit 127. Finally, a Velcro
(trademark) fastener provided on the second end of the strap 117 is
attached to a complementary Velcro (trademark) fastener 131 fixed on
the rear face 125 of the backrest body 124. Again, tubular member 101
is provided with a strap holding element 132 to prevent the upper strap
117 from sliding downwardly on that tubular member 101, and thereby
hold the backrest body 124 in stable vertical position on the side post
205.
As also illustrated in Figure 9 of the appended
drawings, the flexible backrest body 124 comprises on the rear face 125
a series of five lower slits including slits 133, 134 and 135 made in the
nylon fabric on the back of the flexible backrest body 124. A first end of
the lower strap 121 is sewed inside the flexible backrest body 124. A
second end of the lower strap 121 exits the flexible backrest body 124
through slit 135, and is then passed around the lower end 123 of the
tubular member 102 to form a loop 136. The second end of the lower
strap 121 successively enters the lower slit (not shown) situated farther
to the right, and exits the lower slit (not shown) situated farther to the
left.
The strap 121 is then passed around the lower end 122 of the tubular
member 101, and successively enters slit 133 and exits slit 134. Finally,
a Velcro (trademark) fastener provided on the second end of the strap
121 is attached to a complementary Velcro (trademark) fastener 137 fixed
on the rear face 125 of the backrest body 124.
Regarding intermediate strap 120, it forms a loop
comprising two ends sections 139 and 140 respectively inserted in slots
i
CA 02233928 2003-06-17
22
such as 138 of the contour members 103 of the two side posts 204 and 205.
To complete the loop, the two end sections 139 and 140 are attached
together by means of complementary Velcro (trademark) fasteners. The
intermediate strap 120 passes through loops 141 and 142. For example, the
loops 141 and 142 are made of nylon fabric and comprise respective Velcro
(trademark) fasteners (not shown) for attaching the loops 141 and 142 to
respective, spaced apart vertical Velcro (trademark) strips 143 and 144
mounted, for example sewed to the rear face 125. Accordingly, the loops 141
and 142 are adjustable vertically to retain the intermediate strap 120 at the
desired vertical position within the range delimited by the strips 143 and 144
and the length of the slots 138.
Two elongated, vertical and laterally adjacent pockets
145 and 146 are formed in the nylon fabric of the rear face 125 to receive,
respective stays 147 and 148. In the illustrated example, finro pockets and
stays are provided; it is however within the scope of the present invention to
provide a smaller or larger number of pockets and stays in accordance with
the requirements of an intended application. Also, the stays can be in the
form
of rectangular plates, elongated bars, rods, or other shapes, etc. They can be
made of metallic material such as aluminum and any other metal or material,
including metal alloys and plastics.
Still referring to Figure 9, the flexible backrest body 124
comprises:
-a lower flap 149 padded with a 1 inch thick layer of foam
and comprising a Velcro (trademark) fastener (not shown) for
CA 02233928 2003-06-17
23
fixation at different possible positions under the seat 66 (Figure 2). The
flap
149 is attached under the seat to establish a contact between the user's
sacral seat region and the lower portion of the backrest;
- a left flap 151 made of nylon fabric, to be folded over
and fixed to the rear face 125 of the backrest body 124 by means of Velcro
(trademark) fasteners (not shown) fixed on both the rear face 125 and the
inner face of flap 151; and
- a right flap 150 made of nylon fabric, to be folded over
and fixed to the outer face of the left flap 151 by means of Velcro
(trademark)
fasteners (not shown) fixed on the outer face of the left flap 151 and on the
inner face of the flap 150.
The flaps 150 and 151 ensure both fixation of the layer of foam and nylon
fabric envelope to the two side posts 204 and 205, and covering and finishing
of the rear face 125 of the backrest body 124.
The idea of providing the tubular members 101 and 102
with contour members 103 originates from the need to induce a depth
dimension to the flexible backrest body 124 in order to fit the posterior
lateral
contour of the user's back and thereby provide lateral support to the user's
trunk. More specifically, the contour members 103 define respective
elongated curved front face from which the flexible backrest body 124 is
suspended and adjusted to the posterior and posterior lateral contour of the
user's back.
CA 02233928 1998-04-03
24
Conventionally, the side posts of wheelchairs are
straight and serve two main purposes: they support the backrest and
enable an assistant to push the wheelchair by means of the handles. By
providing the contour members 103 as explained in the foregoing
description, the additional purpose of providing support for the user's
trunk is implemented. However, providing the contour members 103
alone is not sufFcient to achieve adequate lateral trunk support; it is also
essential that the width between the contour members 103 corresponds
to the width of the user's trunk. Since the two contour members 103 are
rotatable about the tubular members 101 and 102, respectively, the
distance separating the fonwardly bulging sections of the contour
members 103 can be reduced or increased to accommodate the width of
the user's trunk. Since the contour members 103 and the flexible
backrest body 124 are padded with foam material, they are not felt
against the user's back to thereby allow the user to seat comfortably.
By adjusting ( a) the angular and vertical positions of the
contour members 103 (see arrows 115 of Figure 6 and arrows 116 of
Figure 8), ( b) the length of the upper strap 117, intermediate strap 120
and lower strap 121, ( c) the vertical position of the intermediate strap
120, and ( d) the shape of the stays 147 and 148, the flexible contour
wheelchair backrest is capable of adapting to a great number of user's
back shapes.
The idea of using stays that can be easily bent into
shape originates from the need to reproduce different back shapes on the
sagittal plane (from normal geometry to mild kyphosis or light scoliosis).
In an advantageous embodiment, each stay has a height of 12 inches
CA 02233928 1998-04-03
and a width of 4 inches. Their stiffness depends on their thickness; a
thickness of 1116 inch is normally sufficient for stays to support back
curves on the sagittal plane and they remain easy to manipulate. This
thickness can be modified if different stiffness is needed.
5 Since back curves are not given enough support with
stays alone, the additional support is provided by the three adjustable
upper strap 117, intermediate strap 120 and lower strap 121. The
combination of stays and straps, and contour members allows for better
adjustment of the shape of the flexible contour backrest body to fit the
10 posterior and posterior lateral shape of the user's back. Furthermore, by
increasing the contact surface the stays distribute evenly the pressure
through the flexible contour wheelchair backrest.
Although substantially stiff and malleable stays 58, 59,
15 60, 61, 147 and 148 have been described in the foregoing description,
these stays can also be pre-formed elements.
It should also be mentioned that the flexible contour
backrest according to the present invention is sufficiently flexible to cause
20 no interference upon folding of a wheelchair.
Moreover, the flexible contour backrest according to the
invention can be modified to enable adjustment of the divergence and
convergence of the side posts with elongated curved front faces.
Finally, the substantially straight lower ends 7, 17 may
remain rotatable on the upper ends 8, 18, or the contour members 103
CA 02233928 1998-04-03
26
may remain rotatable on the tubular member 101 and 102 to enable
automatic adjustment of the width between the forwardly bulging sections
32 and 33 or the contour members 103 to the width of the user's trunk
when the user sits in the wheel chair.
Although the present invention has been described
hereinabove by way of preferred embodiments thereof, these
embodiments can be modified at will, within the scope of the appended
claims, without departing from the spirit and nature of the subject
invention.
