U.S. patent application number 10/078520 was filed with the patent office on 2003-04-24 for raisable leg rest.
This patent application is currently assigned to 1239907 Ontario Limited d/b/a Motion Concepts, 1239907 Ontario Limited d/b/a Motion Concepts. Invention is credited to Ciolfe, David, Eakins, Richard, Ma, Son.
Application Number | 20030075967 10/078520 |
Document ID | / |
Family ID | 4170295 |
Filed Date | 2003-04-24 |
United States Patent
Application |
20030075967 |
Kind Code |
A1 |
Ciolfe, David ; et
al. |
April 24, 2003 |
Raisable leg rest
Abstract
A raisable legrest for a wheelchair, the legrest comprising: a
frame, to support a user's lower leg, the frame being attachable to
the wheelchair, the frame being movable between a lowered position
and a raised position about a pivot point when attached to the
wheelchair; and a pivot point position adjustor, located between
the pivot point and the wheelchair, for adjusting the position of
the pivot point in at least a vertical direction; wherein the pivot
point can be positioned by the pivot point position adjustor to be
coaxial with an approximate center of rotation of a knee of the
user.
Inventors: |
Ciolfe, David; (Concord,
CA) ; Ma, Son; (Toronto, CA) ; Eakins,
Richard; (Toronto, CA) |
Correspondence
Address: |
James T. Nenniger
c/o Piasetzki & Nenniger
Suite 2308
120 Adelaide Street West
Toronto
ON
M5H 1T1
CA
|
Assignee: |
1239907 Ontario Limited d/b/a
Motion Concepts
|
Family ID: |
4170295 |
Appl. No.: |
10/078520 |
Filed: |
February 21, 2002 |
Current U.S.
Class: |
297/423.32 |
Current CPC
Class: |
A61G 5/127 20161101;
A61G 5/12 20130101; A61G 5/128 20161101 |
Class at
Publication: |
297/423.32 |
International
Class: |
A47C 007/50 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 19, 2001 |
CA |
2,359,379 |
Claims
We claim:
1. A raisable legrest for a wheelchair, the leg rest comprising:
(a) a frame, to support a user's lower leg, said frame being
attachable to the wheelchair, said frame being movable between a
lowered position and a raised position about a pivot point when
attached to said wheelchair; and (b) a pivot point position
adjustor, located between the pivot point and the wheelchair, for
adjusting the position of the pivot point in at least a vertical
direction; wherein the pivot point can be positioned by the pivot
point position adjustor to be coaxial with an approximate center of
rotation of a knee of the user.
2. The legrest according to claim 1, wherein said pivot point
position adjustor is adjustable in at least a vertical direction by
means of an extendable vertical support element which supports said
pivot point.
3. The legrest according to claim 2, wherein said extendable
vertical support element includes a fastener to hold said
extendable vertical support element at a fixed vertical height.
4. The legrest according to claim 2, wherein said pivot point
position adjustor further includes a holder and one of said
extendable vertical support element or said holder is hollow, and
said extendable vertical support element and said holder fit
together to form a quick release coupling.
5. The legrest according to claim 4, wherein one of said extendable
vertical support element or said holder contains a notch, and the
other of said extendable vertical support element or said holder
contains a pin sized and shaped to engage said notch to form said
quick release coupling.
6. The legrest according to claim 4, wherein said pivot point
position adjustor includes a pivot block, and said extendable
vertical support element engages said holder at one end and said
pivot block at the other end and is adjustably connected
therebetween.
7. The legrest according to claim 6, wherein said extendable
vertical support element includes a vertical element which may be
connected to said pivot block at one of a discrete number of
connection points.
8. The legrest according to claim 7, wherein said connection points
comprise a discrete number of holes on one of said vertical element
or said pivot block, and said pivot block may be connected to said
vertical element by a bolt inserted through one of said holes.
9. The legrest according to claim 2, wherein said extended vertical
support element has a top end and a bottom end, and said pivot
point is located towards said top end.
10. The legrest according to claim 4, wherein said holder is a
hollow cylinder.
11. The legrest according to claim 1, wherein said pivot point
position adjustor is adjustable in at least a vertical direction by
means of a releasable clamp.
12. The legrest according to claim 11, wherein said pivot point
position adjustor further includes a vertical element which
supports said pivot point, and wherein said vertical element is
movable in a vertical direction when said releasable clamp is
released, and said vertical element is set at a fixed vertical
height when said releasable clamp is clamped.
13. The legrest according to claim 1, wherein the pivot point
position adjustor further includes a horizontal adjustor to adjust
the position of the pivot point in a horizontal direction.
14. The legrest according to claim 13, wherein the horizontal
adjustor comprises a horizontal element and a releasable holder to
hold said horizontal element.
15. The legrest according to claim 1, wherein said frame has a
length, said length being adjustable to accommodate the leg of the
user.
16. The legrest according to claim 15, wherein said frame has a
footplate to receive a foot of the user.
17. The legrest according to claim 16, wherein said frame has a top
and a bottom, and said pivot point is located at the top of said
frame and said footplate is located at the bottom of said
frame.
18. The legrest according to claim 17, wherein said lower leg of
said user has a leg-length, the length of the frame can be adjusted
so that the distance between the pivot point and the footplate is
approximately equal to said leg-length, and wherein the frame
remains at said adjusted length as the frame moves between the
lowered and raised position.
19. The legrest according to claim 15, wherein said frame comprises
an upper frame attached to the pivot point and a lower frame
slidably connected to the upper frame.
20. The legrest according to claim 19, wherein one of the upper
frame or the lower frame is hollow, and wherein the other of said
upper frame or lower frame fits into the hollow frame.
21. The legrest according to claim 1, further including a
frame-stop to stop said frame from being movable beyond a
predetermined lowered position.
22. The legrest according to claim 21, wherein said frame-stop has
an adjustable position, and wherein said predetermined lowered
position of said frame can be adjusted by adjusting said position
of said frame-stop.
23. The legrest according to claim 21, wherein said frame-stop is
attachable to at least one of said frame or said pivot point
position adjustor.
24. The legrest according to claim 21, wherein said frame-stop is a
threaded screw.
25. The legrest according to claim 1, further including: (a) a calf
support to further support the user's lower leg, said calf support
being pivotally connected to the frame at a frame pivot point; (b)
an actuator, to apply a force on the calf support, to move said
frame between the lowered position and the raised position; and (c)
a compressible positioning element, positioned between the calf
support and the frame, for permitting the calf support position
relative to said frame to be varied as a moment about said frame
pivot point changes; wherein, as said moment increases about said
frame pivot point, said compressible positioning element
compresses, and said calf pad support moves closer to said frame to
provide support to the lower leg of the user.
26. The legrest according to claim 25, wherein the compressible
positioning element defines a predetermined pivot angle between the
calf support and the frame when the frame is in the lowered
position.
27. The legrest according to claim 25, wherein the calf support
comprises a push plate and a calf pad mounted on the push
plate.
28. The legrest according to claim 27, where the calf pad is
adjustably connected to the push plate.
29. The legrest according to claim 27, wherein the compressible
positioning element is a resilient material and is positioned
between the frame and the push plate of the calf support.
30. The legrest according to claim 27, wherein the compressible
positioning element can be positioned at one of a number of
predetermined locations between the frame and the push plate.
31. The legrest according to claim 29, wherein the compressible
positioning element is rubber.
32. The legrest according to claim 26, further including an
adjustable stop to restrict the pivot range of the calf
support.
33. A raisable legrest for a wheelchair to raise a lower leg of a
user, the legrest comprising: (a) a frame, said frame being
attachable to the wheelchair, said frame being movable between a
lowered position and a raised position about a pivot point when
attached to said wheelchair; (b) a calf support to support the
user's lower leg, said calf support being pivotally connected to
the frame at a frame pivot point; (c) an actuator, to apply a force
on the calf support, to move said frame between the lowered
position and the raised position; and (d) a compressible
positioning element, positioned between the calf support and the
frame, for permitting the calf support position relative to said
frame to be varied as a moment about said frame pivot point
changes; wherein, as said moment increases about said frame pivot
point, said compressible positioning element compresses, and said
calf pad support moves closer to said frame to provide support to
the lower leg of the user.
34. The legrest according to claim 33, wherein the compressible
positioning element defines a predetermined pivot angle between the
calf support and the frame when the frame is in the lowered
position.
35. The legrest according to claim 33, wherein the calf support
comprises a push plate and a calf pad mounted on the push
plate.
36. The legrest according to claim 35, where the calf pad is
adjustably connected to the push plate.
37. The legrest according to claim 35, wherein the compressible
positioning element is a resilient material and is positioned
between the frame and the push plate of the calf support.
38. The legrest according to claim 35, wherein the compressible
positioning element can be positioned at one of a number of
predetermined locations between the frame and the push plate.
39. The legrest according to claim 37, wherein the compressible
positioning element is rubber.
40. The legrest according to claim 33, further including an
adjustable stop to restrict the pivot range of the calf support.
Description
FIELD OF THE INVENTION
[0001] This invention relates to the general field of wheelchairs,
and more particularly to wheelchairs which include leg rests to
support the wheelchair user's legs.
BACKGROUND OF THE INVENTION
[0002] Wheelchairs have been known and used for many years to
assist disabled people in moving about. Wheelchairs generally
include a mobile platform, which includes the base and wheels, a
seat mounted to the base, and legrests to comfortably secure and
support the wheelchair user's legs. Since most wheelchair users are
confined to their chairs for extended periods, wheelchairs are
usually designed to provide a variety of sitting positions. This
enhances user comfort and enables the user to relieve excessive
pressure in any single area, which can cause sores. The need for
variety has given rise to wheelchairs with such features as seats
that tilt or recline, and raisable leg rests. Since individual
wheelchair users vary greatly in size and body type, it is a
challenge to construct a chair that is sufficiently versatile in
providing a range of positions suitable for many people, while
using mechanisms that are safe, reliable, and preferably low
cost.
[0003] Raisable legrests in particular present certain problems.
Legrests are designed to support a user's lower leg and move it
between a lowered position and a raised position. The lower leg
range of motion may be from a vertical (leg bent 90 degrees) to
horizontal (leg straight, parallel to ground). Legrests typically
include a pivoting down tube with a footplate, a calf pad, and an
actuator to move the down tube between selected positions.
Generally the weight of the lower leg will be supported in any
given position by the footplate and the calf pad, with the calf pad
taking on more weight as the legrest is raised.
[0004] A problem with this arrangement is that the user's lower leg
is typically longer than the down tube. As the leg rest is raised
there is an inward pressure created on the user's foot from the
footplate. This will force the user's knee to pop up, lifting the
upper leg off the seat to some extent. The upper leg will therefore
lack support, and there will be localized pressure at the contact
point with the seat. Attempted solutions in the prior art usually
involve providing an extension mechanism to extend or retract the
down tube telescopically in accordance with the raising or lowering
of the legrest. These solutions however are generally complicated,
prone to breakdown, and costly. It is also difficult to provide a
mechanism that works effectively for users of varying size.
[0005] An example of such a structure is shown in U.S. Pat. No.
5,711,580 to Barclay, which uses two down tubes to move the
footplate. The second down tube comprises two link arms connected
at an unsupported, exposed joint 36. Aside from the difficulty of
making such a structure perform as intended, it can be appreciated
that the exposed link arms and joint structure may be easily
damaged in the course of daily use.
[0006] Other problems associated with raisable leg rests concern
the support provided by the calf pad as the legrest is raised. To
begin with, the legrest length problem described above may lead to
the user's leg lifting off the legrest. Another issue arises from
the fact that most users need increasing calf support as the
legrest is raised, but minimal or no support when the legrest is in
the low end of its range. In fact, contact with an unneeded calf
pad can be uncomfortable when the leg rest is in a vertical
position. Calf pad support is related to the distance or spacing
between the calf pad and the down tube. However, most legrests
require the user to select a single predetermined setting for the
calf pad spacing, which then remains fixed over the whole range of
motion. It can be difficult to find a single setting that is both
close enough to provide adequate support while the legrest is being
raised, and at the same time far enough apart to be comfortable
when the legrest is in a substantially lowered position. As a
result, most users are forced to tradeoff a preferred level of
comfort in one position against a lesser level of comfort in
another position.
[0007] A further issue, somewhat related to the above, is that
users may have very different preferences regarding the support
provided by the calf pad relative to the footplate. The wheelchair
using population is as diverse as the general population, and
people will vary greatly in size, weight, leg shape, individual
areas of sensitivity or injury, as well as matters of personal
comfort. For example, a person with heavy calves may be more
comfortable with greater calf support relative to the footplate,
while another may prefer the opposite, perhaps to relieve pressure
from a skin condition at the calf.
[0008] These matters have not been adequately addressed by the
prior art. An attempt to address the issue of user comfort in a
wheelchair legrest is shown in U.S. Pat. No. 3,189,384 to Bliss.
This patent discloses a calf pad mounted to the down tube through
tubular rubber elements. As the legrest rises, the calf pad can
shift into a more comfortable angular postion for the user due to
the resiliency of the rubber. While Bliss may provide a marginal
improvement in comfort, it does not address any of the calf pad
support problems described above.
[0009] Besides reasons of comfort, having a calf pad retract as far
as possible when the legrest is in a fully lowered position is
generally desirable because it shortens the overall length of the
wheelchair, which enhances manoeuvrability. Having a little extra
space behind the calf may allow users to push their feet back,
shortening the effective chair length even further. For some
wheelchair users in cramped or small residential environments, even
a small improvement in this aspect can result in much improved
manoeuvrability and quality of life.
[0010] Yet another problem with raisable legrests is that they are
susceptible to damage from banging into walls, doors, and other
structures, which can occur frequently due to extensive daily use.
The popular powered wheelchairs can reach speeds of 8 m.p.h.,
exacerbating the problem. The problem is most acute with respect to
actuators, since they tend to get easily damaged by sudden shocks
and are costly to replace.
[0011] Unless these and other practical problems associated with
wheelchair legrests are resolved, wheelchair users will continue to
experience discomfort from using legrests that are costly,
ineffective, and unreliable. Such considerations may affect user
behaviour, leading to avoidance of desired leg positions that have
been rendered uncomfortable due to legrest inadequacies. Some users
may also become excessively cautious for fear of an accidental bump
that would incur costly damage to the actuator. For people who are
already compelled to spend the greater part of their lives confined
to a wheelchair, such loss of enjoyment is especially
unfortunate.
SUMMARY OF THE INVENTION
[0012] What is desired is a raisable legrest which overcomes the
problems associated with the current devices used for raising the
legs of wheelchair users.
[0013] Most particularly, the legrest device should allow the user
to raise his or her lower leg over a full range of motion.
Preferably, the lower leg should be raisable from a lowered,
generally vertical position where the lower leg is approximately
perpendicular to the ground to a raised, generally horizontal
position where the lower leg is approximately parallel to the
ground. Throughout the range of motion of the leg the legrest
should comfortably support the lower leg, without applying inward
pressure on the user's foot, which causes the knee to lift, raising
the upper leg off the seat and the lower leg off the legrest. The
legrest should preferably also provide adequate and comfortable
support at the user's calf for any legrest elevation, while at the
same time reducing or eliminating pressure on the calf when the
legrest is in the vertical or down position. There would also be
the added benefit of shortening the length of the chair, or
providing more space behind the calf, for enhanced
manoeuverability. It would be advantageous as well to provide the
user with the means to adjust the legrest to suit his or her
individual needs. In this way, the user would experience an
improved degree of comfort and would thereby be encouraged to use
the legrest without hesitation in accordance with his or her
personal inclination. Preferably the device would be relatively
simple in construction to help keep the cost of the device low and
yet still have a high reliability. Lastly, it would be desirable if
the legrest device were easy to install both on new wheelchairs and
as an easily attached upgrade to existing wheelchairs.
[0014] The raisable legrest device of the present invention
includes a means for adjusting the position of the legrest pivot
point in at least a vertical direction, so that the pivot point can
be positioned close to the axis of rotation of the user's knee.
This allows the legrest down tube to match the length of the user's
lower leg. In this way the legrest down tube is adequate to support
the leg at any raised position, and a telescoping mechanism is not
needed. Calf support is improved by pivotally connecting the calf
support to the down tube, directing the actuator to act on the
pivotable calf pad rather than the down tube, and by installing a
compressible element such as a rubber pad between the calf pad and
down tube. As the legrest is raised, the calf pad accepts an
increasing portion of the leg's weight, causing the rubber pad to
compress and bringing the calf pad closer to the down tube. As the
legrest is lowered, the rubber pad is less compressed, and it acts
to separate the calf pad from the down tube. In this way the
legrest device of the present invention varies support on the calf
as the legrest moves through its full range of motion. A stop on
the down tube protects the actuator from impact when the legrest is
in the down position, and the rubber pad provides similar
protection when the legrest is in a raised position.
[0015] Accordingly, there is provided a raisable legrest for a
wheelchair, the legrest comprising:
[0016] a frame, to support a user's lower leg, said frame being
attachable to the wheelchair, said frame being movable between a
lowered position and a raised position about a pivot point when
attached to said wheelchair; and
[0017] a pivot point position adjustor, located between the pivot
point and the wheelchair, for adjusting the position of the pivot
point in at least a vertical direction;
[0018] wherein the pivot point can be positioned by the pivot point
position adjustor to be coaxial with an approximate center of
rotation of a knee of the user.
[0019] According to another aspect of the invention, there is
further provided:
[0020] a calf support to further support the user's lower leg, said
calf support being pivotally connected to the frame at a frame
pivot point;
[0021] an actuator, to apply a force on the calf support, to move
said frame between the lowered position and the raised position;
and
[0022] a compressible positioning element, positioned between the
calf support and the frame, for permitting the calf support
position relative to said frame to be varied as a moment about said
frame pivot point changes;
[0023] wherein, as said moment increases about said frame pivot
point, said compressible positioning element compresses, and said
calf pad support moves closer to said frame to provide support to
the lower leg of the user.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Reference will now be made, by way of example only, to
preferred embodiments of the invention as illustrated in the
attached figures.
[0025] FIG. 1 is a perspective view of the raised legrest of the
present invention;
[0026] FIG. 2a is a side view of a wheelchair equipped with a
conventional legrest device, with the legrest device in a lowered
position;
[0027] FIG. 2b is a view of the wheelchair of FIG. 2a, with the
legrest device in a raised position;
[0028] FIG. 2c is a side view of a wheelchair equipped with the
legrest device of the present invention, with the legrest device in
a lowered position;
[0029] FIG. 3a is a side view of a wheelchair equipped with the
legrest device of FIG. 1 of the present invention, with the legrest
device in a fully lowered or vertical position;
[0030] FIG. 3b is a view of the wheelchair of FIG. 3a, with the
legrest device in a raised position;
[0031] FIG. 3c is a view of the wheelchair of FIG. 3a, with the
legrest device in a fully raised or horizontal position; and
[0032] FIG. 4 is a schematic view of the legrest device of the
present invention, showing the forces acting on the device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] The raisable legrest apparatus or device of the present
invention is shown in FIG. 1. The apparatus is generally indicated
with reference numeral 10, and broadly comprises a frame or down
tube 12, a pivot point position adjustor 14, a calf support 16, an
actuator 18, and a compressible positioning element 20.
[0034] The present invention 10 attaches to a wheelchair and
provides support for a wheelchair user's lower leg as the leg is
moved between a lowered and a raised position. In FIG. 1 the device
10 is shown attached to a wheelchair frame or seat frame 22 that is
part of a wheelchair (not shown). The seat frame 22 is a generally
preferred point of attachment since it is secure, conveniently
located, and typically constructed of a hollow but high strength
material such as steel.
[0035] As shown in FIG. 1, a horizontal element 24 fits slidably
within the seat frame 22 and is adjustable in a forward and
rearward direction as indicated by arrow 25. Instead of being
constructed as a straight element, the horizontal element 24 can
also be curved outwards to provide a wider space for the user's
leg. Not shown in the figure is a releasable holder which can be
set to hold element 24 in place at a desired horizontal position.
The releasable holder may be, for example, holes in the seat frame
22 and element 24, though which a bolt may be inserted. Thus, upon
initial installation a preferred horizontal position can be
selected to suit the user, and the element 24 can be held or locked
in place by said releasable holder.
[0036] Returning to FIG. 1, a legrest receiver or holder 26 in the
general form of a hollow cylinder is attached towards a forward end
of horizontal element 24. The receiver 26 has two notches 27 cut
out of its upper surface. One notch 27 is visible in FIG. 1, with
the other one positioned on the exact opposite side of the
cylinder.
[0037] A vertical element 28 fits slidably within legrest receiver
26 at right angles to the movement of horizontal element 24 as
indicated by arrow 29. This connection is facilitated by having at
least one of the vertical element 28 or the holder 26 be hollow, so
the other element can slidably fit within the hollow element. The
vertical element 28 has a discrete number of connection points or
holes 31, shown in outline in FIG. 1. There is also a dowel pin 30
built into the vertical element 28. It can be seen that the dowel
pin 30 is sized and shaped to slidably engage the notch 27, so that
vertical element 28 rests on and is connected to legrest receiver
or holder 26. Once inserted, vertical element 28 is prevented from
rotating by the dowel pin 30 in the notch 27.
[0038] A pivot block 32 is adjustably connected towards a top end
of vertical element 28. The pivot block 32 is preferably a solid
block with a hollow section 33 sized and shaped to receive the
vertical element 28, and a carved-out section 34 having a back wall
35 and a pivot pin or pivot point 36.
[0039] It can be seen from FIG. 1 that the pivot block 32 can be
adjustably connected to vertical element 28 by inserting a fastener
or bolt 37 through a hole 38 in the hollow section 33 of the pivot
block 32, and continuing through one of holes 31 in vertical
element 28. It can be appreciated that other means of connection
may also be used as long as the vertical element 28 and pivot block
32 can be adjustably and securely connected. This may include, for
example, a continuous type of connection that allows for more
incremental variations in vertical height.
[0040] It can now be appreciated that the pivot block 32, which
supports pivot point 36, can be raised to a desired vertical height
in a direction along arrow 29 by selecting one of the holes 31 in
the vertical element 28 to insert the bolt 37. Upon bolting, the
vertical element 28 and pivot block 32 will be fixed together, and
so the pivot point 36 will be located at a fixed vertical height.
In this way the pivot point 36 is adjustable in at least a vertical
direction. It is preferred that the range of vertical height
adjustment of pivot point 36 be at least 2 inches. Moreover,
setting the position of horizontal element 24 will set a horizontal
position of pivot point 36.
[0041] The pivot point position adjustor 14 according to the
present invention is located between the pivot point and the
wheelchair and comprehends a means of adjusting the position of the
pivot point 36 in at least a vertical direction. The means of
adjustment may be generally described by an extendable vertical
support element which supports the pivot point.
[0042] For example, in the preferred embodiment of FIG. 1 described
above, the extendable vertical support element may include the
vertical element 28, pivot block 32, and fastener or bolt 37 which
adjust the position of the pivot point 36 in a vertical direction
by means of a rack and pin connection. The fastener or bolt 37
holds the extendable vertical support element at a fixed vertical
height. The extendable vertical support element may alternatively
be considered to be the vertical element 28 and fastener 37 alone,
without the pivot block 32, because elements 28 and 37 are
sufficient to adjust the vertical position of the pivot point 36.
The extendable vertical support element therefore may be said to
engage the holder at one end and the pivot block at the other end,
and is adjustably connected therebetween.
[0043] A feature of this embodiment is that the vertical
adjustability function is separate from the means of attachment to
the wheelchair. As noted, the extendable vertical support element
or vertical element 28 and holder 26 fit together in a dowel pin
and notch arrangement. This arrangement therefore has the advantage
of providing a quick release coupling, since the legrest 10 can be
easily and quickly attached to or removed from the wheelchair by
simply placing the vertical element 28 in the holder 26 or by
lifting it out.
[0044] While the above arrangement is preferred because of the
quick release coupling feature, the present invention comprehends
all mechanically equivalent forms, such as threaded connections,
releasably clampable connections, or the like that permit a
vertical adjustment of the pivot point. For example, in an
alternative embodiment the extendable vertical support element may
be a holder 26 in the form of a releasable clamp and a vertical
element 28 having a pivot point 36. With the clamp released, the
vertical element 28 could be moved in a vertical direction. The
releasable clamp could then be clamped to set the vertical element
28, and with it the pivot point 36, at a fixed vertical height. The
releasable clamp may also include a fastener such as a screw or
bolt to hold the vertical element 28 at a fixed vertical
height.
[0045] It can be appreciated that in this embodiment the pivot
point 36 could be supported by a pivot block fixedly attached to
vertical element 28, or as noted the pivot point 36 could attach
directly to the vertical element 28 and no pivot block is needed.
Thus while the pivot block 32 is a convenient element to use to
attach the pivot point 36, as long as there is an extendable
vertical support element present elsewhere in the pivot point
position adjustor to adjust the height of the pivot point in a
vertical direction, a separate pivot block 32 is not necessary.
However, it can also be appreciated that since the extendable
vertical support element adjusts the position of the pivot point in
a vertical direction, the extendable vertical support element will
preferably have a top end and a bottom end, with the pivot point
being located towards the top end.
[0046] For additional flexibility the pivot point position adjustor
14 may include a horizontal adjustor comprising means to position
the pivot point in a horizontal direction. The horizontal adjustor
may include, for example, the horizontal element 24 and releasable
holder described above.
[0047] The frame or down tube 12 is attachable to the wheelchair
through the pivot point 36. It can be seen in FIG. 1 that the frame
12 is attached to the pivot point 36 at a top of the frame 12.
Accordingly, as the frame 12 pivots or swings about pivot point 36
in a downward direction it can be appreciated that the frame is
movable into a lowered position. Similarly, as the frame 12 pivots
or swings in an upward direction it can be appreciated that the
frame 12 is moveable into a raised position. Therefore the frame 12
is moveable between a lowered and a raised position.
[0048] At a bottom of the frame 12 there is a footplate 42 provided
to serve as a platform for the wheelchair user's foot. The
footplate 42 is generally constructed of metal, plastic, or other
durable material, and through its mounting connection through
footplate fastener 43 the footplate 42 is generally free to pivot,
flex, or flip up with respect to the frame 12.
[0049] The frame 12 is preferably in the form of a tubular metal
element and provides support for the user's lower leg. To perform
this function the frame 12 has a length which is adjustable to
accommodate the user's leg. Accordingly, the frame 12 is preferably
constructed in two parts as an upper frame 39 slidably connected to
a lower frame 40. Upper frame 39 is attached to the pivot point 36
at the top and lower frame 40 is attached at the bottom to
footplate 42. Most conveniently at least one of the frames is
hollow, so that the other frame is slidable within the hollow core.
In FIG. 1 the upper frame 39 is shown as hollow, and lower frame 40
is slidable within the hollow interior of frame 39. The frame 12
may be set to a desired length by placing a bolt (not shown)
through frame extension holes 41 in the upper frame 39 and a
counterpart hole in the lower frame 40. It can be appreciated that
other means of locking the two frames together, such as a
releasable clamp, may also be used.
[0050] The length of the frame 12 may be conveniently measured as
the distance between the pivot point 36 and footplate 42. This
length can be adjusted as described above to be approximately equal
to the leg-length, or length of the user's lower leg. As will be
discussed below, the frame 12 remains at this adjusted length as
the frame 12 moves between the lowered and raised position.
[0051] In the preferred embodiment of the invention shown in FIG. 1
there is also included a frame-stop 44 to stop the frame 12 from
being movable beyond a predetermined lower position. The frame-stop
44 is located towards a top of the frame 12 near the pivot point
36. The frame-stop 44 has an adjustable position and is interposed
between the frame 12 and the back wall 35 of the pivot block 32. As
shown in FIG. 1 frame-stop 44 may be conveniently implemented as a
simple screw threaded into the underside of frame 12. It can be
appreciated however that frame-stop 44 could equally be implemented
as a screw threaded into the back wall 35 of the pivot point
position adjustor. Therefore, frame-stop 44 is attachable to at
least one of the frame 12 or the pivot point position adjustor
14.
[0052] Upon retraction of frame 12 by the actuator or a rearward
force against frame 12, frame-stop 44 contacts the back wall 35 and
stops any further rearward movement of frame 12. The frame-stop
position can be adjusted by threading the screw the desired
distance, since this will affect where the screw hits the back wall
35. This in turn determines the amount of rearward travel of frame
12 and the predetermined lowered position of the frame. In the
event that the frame 12 is forced backward, for example, by the
user banging the legrest 10 against a wall, frame-stop 44 stops the
frame 12 from moving too far backward and damaging actuator 18.
[0053] The calf support 16 further supports the user's lower leg
and is pivotally connected to the frame 12 at a frame pivot point
48. The calf support 16 includes a push plate 45 and a calf pad 56
adjustably connected to the push plate 45 through mounting plate
54. The calf pad 56 is a cushion or pillow type article that
supports the user's calf, and for clarity is shown in outline in
FIG. 1 so that the portion of the push plate 45 hidden by the calf
pad 56 can be more clearly seen. More particularly, it can be seen
in FIG. 1 that the user's lower leg is supported by calf pad 56,
and that push plate 45 pivotally connects with the frame 12 at
frame pivot point 48. A portion of the push plate 45 extends
rearwardly and attaches to the actuator 18 at pivotal connector 52,
which is preferably a quick release type connector.
[0054] Push plate 45 is a fabricated part sized and shaped to
facilitate the interconnection of several elements. It has been
found that a suitable push plate 45 may be constructed as a stamped
metal plate, though it can be appreciated that other forms of the
push plate 45 may also be adequate.
[0055] As shown in FIG. 1, push plate 45 is pivotally connected to
the frame 12 at an adjustable length along the frame 12. There are
a plurality of holes 46 along frame 12 for connecting to the calf
support 16, and a frame pivot point or hole 48 in the push plate.
The pivotal connection may be accomplished by inserting a pin (not
shown) through the selected hole 46 and frame pivot point 48.
[0056] It can be further seen that there are a plurality of
predetermined locations or holes 50 on one of which a compressible
positioning element 20 is positioned. The holes 50 are positioned
so that the compressible positioning element is between the frame
12 and the calf support 16, or in particular the push plate 45 of
calf support 16. In FIG. 1 the holes 50 are shown on a surface of
the push plate 45 but it can be appreciated that they could equally
be on the surface of the frame 12, as long as the compressible
positioning element 20 is between the frame 12 and push plate 45.
In FIG. 1 there are a representative three holes 50, which may be
designated for convenient reference as upper hole 50a, middle hole
50b, and lower hole 50c. The compressible positioning element 20 is
shown inserted in middle hole 50b.
[0057] The compressible positioning element 20 is preferably formed
from a resilient material that can be formed in the shape of a pad
or ball for insertion into a predetermined location or hole 50. The
material preferably maintains some rigidity when in an uncompressed
state and should be sufficiently elastic or resilient to return to
the fully uncompressed state when it is not compressed. It should
also be durable, to withstand repeated compression and
decompression without cracking or loss of elasticity. It has been
found that a compressible positioning element 20 made of rubber
provides adequate results, though it can be appreciated that other
materials such as urethane, a conventional spring, or even an air
or gas spring may also be used. For convenience the compressible
positioning element 20 may be referred to as a rubber pad or rubber
20.
[0058] The push plate also includes a stop 58. In FIG. 1 the stop
58 is shown positioned at the top of the push plate 45 near the
calf support hole 46, and is formed as part of push plate 45 in the
shape of a tab or projecting metal piece, bent back slightly off
the frame 12. In general, the stop 58 is positioned so that as the
portion of the push plate 45 attached to the actuator 18 pivots
away from the frame 12 the stop 58 will contact the frame 12 and
prevent further movement of the push plate 45. In this way the stop
restricts the pivot range of the calf support 16 or in particular,
the push plate 45 of the calf support 16. In the absence of stop 58
the push plate 45 would be able to pivot much farther back, perhaps
as far as 90 degrees away from the frame 12.
[0059] It can be appreciated that the push plate 45 is a convenient
element to pivotally attach the calf pad 56 to the frame 12,
connect to the actuator 18 so the actuator 18 can apply force on
the calf support 16, and allow for the positioning of a
compressible positioning element or rubber 20. While the preferred
embodiment of the push plate 45 is a stamped metal plate that can
be sized and shaped to attach to the frame 12 and make the various
connections shown, it can be appreciated that other means of
connecting the calf pad to the frame, the actuator to the calf pad,
and positioning the rubber 20 may be used. For example, the rubber
20 may be positioned in holes 50 located on the underside or part
of frame 12 rather than on the push plate 45.
[0060] The actuator 18 is preferably an electrically powered
element that moves a shaft within a housing. The actuator 18 is
shown having its shaft attached to the push plate 45 at pivotal
connector 52. The origin of the actuator 18 is whithin the attached
wheelchair and is accordingly not shown in FIG. 1. The actuator 18
represents any element that applies a force on the calf support 16,
or more particularly the push plate 45 and calf pad 56. The
actuator 18 will most commonly be electrically powered,
particularly on powered wheelchairs. However the actuator 18 could
be a manual device, for example, a ratcheted device movable into
successively forward positions by the user or an attendant, or a
hydraulic device.
[0061] The movement of the actuator 18 is generally represented by
arrow 60 and is generally in a forward and backward direction,
where the forward direction applies a force moving the calf pad 56
forward and the reverse direction retracts the calf pad 56. In this
way the actuator 18 moves the calf support 16 and with it the frame
12 between a lowered and a raised position.
[0062] It can be seen that as the actuator 18 moves forward, the
push plate 45 will pivot so that the calf pad 56 moves forward and
the stop 58 moves rearward. The compressible positioning element or
rubber 20 will engage the underside of the frame 12, and cause the
frame 12 and attached footplate 42 to rise. It can be appreciated
that since the rubber 20 is between the push plate 45 and frame 12
it will compress, particularly if the legrest 10 is being used and
it is occupied by a wheelchair user's leg.
[0063] As the actuator 18 retracts the frame 12 will move from a
raised to a lowered position, and eventually to a fully lowered or
down position. Several factors govern the position of the elements
of the legrest 10 of the present invention in the fully lowered
position. First, the frame 12 will stop retracting upon engagement
of the frame-stop 44 with the back wall 35. The frame-stop 44 is
adjustable, and will preferably be adjusted to stop at a
predetermined lowered position that is comfortable for the user.
While this will often be 90 degrees or vertical, some users may
prefer a less vertical setting such as 80 or even 70 degrees from
the horizontal.
[0064] In order to receive the shock protection benefit of the
frame-stop 44 in the fully lowered position, the actuator will
continue to retract past the point where the frame-stop 44 engages.
The amount of further retraction of the actuator again may be
adjusted in advance. Setting the actuator to retract further has
the benefit of pulling the calf pad back a greater distance, so it
will be less likely to contact the user's calf. However, the
actuator has a limited total range of travel. The more it is
allowed to retract to reach the fully lowered position, the less it
will advance when moving forward and raising the frame. In practice
therefore it is often preferable to set the actuator to retract to
just past the point where the frame-stop 44 engages. This ensures
that the frame-stop 44 is engaged, and preserves a maximum degree
of actuator range of motion for forward travel.
[0065] Yet another factor is that the resiliency of the
compressible element or rubber pad 20 will cause the calf support
16, or more particularly the calf pad 56 of calf support 16, to
separate from and form a predetermined pivot angle with the frame
12 when the frame 12 is in the lowered position. Depending on the
setting of the frame-stop 44 and amount of actuator retraction, the
rubber pad 20 may be in an uncompressed state or may still be
compressed. As will be discussed below, the degree of separation or
pivot angle will vary depending on the position of rubber pad 20,
and will be greater the closer the rubber pad 20 is to the frame
pivot point 48.
[0066] Finally, the device 10 is further designed so that the stop
58 on push plate 45 will generally not engage in the ordinary
course of retraction by the actuator to the fully lowered position.
The stop 58 is available to further protect the actuator by
engaging the frame 12 in the event the calf pad 56 receives a
further external mechanical force or push. Preferably stop 58 will
contact the frame 12 without the actuator 18 moving much further,
to better protect the actuator.
[0067] The operation of the raisable legrest 10 can now be
described. Turning to FIG. 2a there is a wheelchair user 62 sitting
on a wheelchair 64. The user 62 has an upper leg 66 supported by a
seat cushion 68 and a lower leg 67 supported by a conventional
legrest device. For clarity, the legrest device shown in FIGS. 2a
and 2b is a representative conventional legrest device of the type
well known in the prior art. It can be seen that this conventional
device also includes an actuator 18, a calf pad 56 and a footplate
42. There is a horizontal element 24 extending from the seat frame
22, and a frame 12 that connects with the element 24 at a
representative fixed pivot point 70.
[0068] In the conventional set-up the horizontal element 24 is used
to extend the seat frame 22 so that it fits the length of the
user's upper leg 66. The user's lower leg 67 is supported by the
legrest, and in particular the frame 12, calf pad 56, and footplate
42. The user has a knee with an effective center of rotation or
knee pivot point 72. In FIG. 2a it can be seen that the
conventional legrest has a radius or length "x" extending from the
pivot point 70 to the footplate 42, that pivots about the pivot
point 70. It can also be seen that the user's lower leg 67 has a
length "y" extending from the effective center of the knee 72 to
the footplate 42. It is clear that in the configuration shown the
length "y" of the user's lower leg 67 is longer than the length "x"
of the legrest frame 12, and that pivot points 70 and 72 are not
co-axial.
[0069] In FIG. 2a the legrest device is shown in a lowered
position, where the legrest is approximately vertical, or
perpendicular to the ground. FIG. 2b shows the legrest in a raised
position as a result of extension of actuator 18. The result of
this configuration associated with the conventional legrest can now
be seen. Due to the difference in length between the conventional
legrest "x" and the user's lower leg "y", and the non-coincident
centers of rotation 70 and 72 respectively, there is insufficient
length in the frame 12 of the legrest to accommodate the user's
lower leg 67. As a result there is an inward pressure on the user's
foot, which forces the knee to pop up off the seat 68. This is
unacceptable as it is uncomfortable and awkward for the user 62. As
well, it forces the weight of the user to be uncomfortably
concentrated at a localized area 74 of the leg 66. As discussed
above, some prior art legrest devices use an extension mechanism
(not shown) to extend the legrest in the direction shown by "z" in
FIG. 2a as the legrest moves from a lowered to an elevated
position. However, such extension mechanism devices are invariably
costly, complicated, and prone to breakdown.
[0070] The wheelchair 64 equipped with the raisable legrest of the
present invention 10 is shown in FIG. 2c. The legrest 10 includes
the additional elements of the vertical element 28, legrest
receiver 26, and pivot block 32 supporting a pivot point 36. The
down tube or frame 12 connects to the pivot block 32 at the pivot
point 36. These elements permit the user to adjust the position of
the pivot point 36 in at least a vertical direction.
[0071] In the operation of the legrest device 10 of the present
invention the user or attendant would adjust the vertical element
28, along with the horizontal position element 24 so that the pivot
point 36 of the legrest device 10 is co-axial with an effective
center of rotation of a knee of the user 72. Further, due to this
arrangement it can be seen in FIG. 2c that the length "x" of the
frame 12 of the legrest device 10 is approximately equal to the
length "y" of the user's lower leg 67. While a complex knee joint
does not have a precise center of rotation like a simple mechanical
pivot, it has been found that being able to position the pivot
point close to the effective center of rotation of the knee
provides increased comfort for users.
[0072] The result of this configuration may be seen in FIG. 3,
which shows the legrest 10 of the present invention in a lowered
vertical position in FIG. 3a, a raised position in FIG. 3b, and at
a fully raised position or approximately a horizontal position, in
FIG. 3c. It can be seen that as a result of the legrest 10 being
co-axial and equal in length to the lower leg 67, raising the
legrest does not produce inward pressure and there is simply no
need for an automatic extension mechanism to dynamically increase
the length of the down tube or frame 12. The user's lower leg 67
remains comfortably supported by the legrest at all times and as
there is no inward pressure the user's knee is not forced up off
the seat 68.
[0073] It can now be appreciated how the legrest device 10 of the
present invention achieves a full range of motion of the user's leg
67. The device 10 of the present invention has the additional
benefit of simplicity since it does not require the extension
mechanism required by the devices of the prior art.
[0074] The operation of the adjustable calf pad feature of the
present invention can now be described. With reference to FIG. 1,
the push plate 45 of calf support 16 may be connected at frame
pivot point 48 with one of the holes 46 on frame 12. Generally, a
particular hole 46 will be selected to optimize the orientation of
actuator 18. It is preferred that actuator 18 be directed close to
the horizontal rather than in an upward direction where it could be
obstructed by other parts of the legrest device 10. Then, the calf
pad 56 may be adjusted in position relative to the push plate 45 by
adjustment of the mounting plate 54. In this way the calf pad 56
may be positioned to line up with the user's calf.
[0075] It can be appreciated that, given the pivot point adjustment
feature of the present invention, it can be expected that the calf
pad 56 will reliably remain behind the user's calf throughout the
full range of motion between the lowered and raised position, as
shown in FIG. 3. Further, shear will not develop between the calf
pad and the calf if the pivot point is properly positioned. This
aspect of the present invention is a significant improvement over
the prior art. Further, it can be appreciated that the adjustable
calf pad feature of the present invention, to be described below,
is enhanced in effectiveness due to the reliable positioning of the
calf pad.
[0076] Returning now to FIGS. 2a and 2b, it may be seen that in the
conventional legrest the calf pad 56 is set to a fixed separation
distance "s1" from the frame 12. While this fixed distance s1 may
be adjustable by the user, once it is set it does not change as the
legrest 10 moves from the lowered to the raised position. It may
also be noted that in this arrangement the actuator 18 can apply
force to either the calf pad 56 or the frame 12. Since the calf pad
and frame are rigidly connected to maintain a fixed spacing, the
frame 12 will be raised the same regardless of whether the actuator
18 connects with the frame 12 or calf pad 56.
[0077] In FIG. 2a the legrest is in a lowered position, close to
vertical, and the calf pad 56 is not needed. In this position it
would be preferable to have a large separation "s" so that the calf
pad 56 does not make contact with the user's calf. However, if s1
is set to a large value then when the legrest is raised, as shown
in FIG. 2b, the user's leg may be somewhat distant and not
naturally be supported by the calf pad. It is possible that the
user's foot may slip slightly out of the footplate 42, to permit
the calf pad 56 to take up some of the weight. The user's leg
however will likely not be comfortably supported when the legrest
is being raised. In practice, users will often choose to make s1
smaller, to get the calf pad support. However in that case there
will be pressure or contact from the calf pad 56 when the legrest
is in the almost fully lowered vertical position of FIG. 2a. Since
no one position of the calf pad 56 or s1 can satisfy the comfort
settings of both lowered and raised positions the result is a
tradeoff which leaves the user dissatisfied in both positions.
[0078] Accordingly, it can be appreciated that while the legrest 10
is rising, it is generally desired to have the calf pad close to
the frame 12, or a small "s", to provide support and take up some
of the weight of the lower leg 67. It is also generally desirable
that when the legrest is in a more lowered position, particularly
when vertical, that the space "s" be larger so that the calf pad
ideally does not exert any pressure on the user's calf. Also as
noted, a larger "s" is desirable to allow for the possibility that
the user's feet may be able to be drawn back and thereby shorten
the effective overall chair length.
[0079] FIG. 3 shows the action of the calf pad 56 of the legrest 10
of the present invention, as the legrest 10 moves from a fully
lowered or vertical position in FIG. 3a to a fully raised or
horizontal position in FIG. 3c. The separation "s" between the calf
pad 56 and the frame 12 in each position is indicated. It can be
seen that the separation "s" starts out relatively large in FIG.
3a, so that the calf pad is either not in contact with the user's
calf, or at least exerting relatively less pressure. In the
intermediate raised position of FIG. 3b it can be seen that the
separation "s" has narrowed, thereby providing more support for the
user's calf. Finally, in the horizontal position of FIG. 3c the
separation "s" has shrunk even further and the calf pad 36 is
directly under the user's lower leg. This profile, by contrast with
the calf pad positioning "s1" shown from the conventional legrest
of FIGS. 2a and 2b, is closer to that desired by most users.
[0080] This may be better understood by noting that in FIG. 3 the
actuator 18 pushes on the push plate 45, which in turn pushes the
calf pad 56. In the fully lowered position of FIG. 3a the actuator
is not active. The rubber 20 presses the push plate 45 and calf pad
56 away from the frame 12 to form the predetermined pivot angle.
When the rubber 20 is in upper hole 50a the separation or
predetermined pivot angle between the calf pad 56 and frame 12 is
largest, for given settings of the frame-stop 44 and actuator 18,
and when in the lower hole 50c the separation is the smallest. In
any event, "s" is relatively large and the calf pad 56 is
relatively far from the user's calf, which is desirable when the
legrest is in the fully lowered position.
[0081] In FIGS. 3b and 3c the actuator is activated and exerts a
force raising the push plate 45 and calf pad 56, as well as the
frame 12. However the weight of the lower leg 67 pushes the frame
12 downwards, which squeezes the rubber 20. This reduces the
separation "s" , bringing the calf pad 56 closer to the frame 12.
The smaller "s" results in better support for the user's calf,
allowing the calf pad 56 to take on more weight than it would under
the conventional arrangement. Again, this resulting smaller "s" is
desirable when the legrest is in a raised position.
[0082] Essentially, the more weight that is placed on the footplate
42, the more compression will occur of the rubber 20, leading the
calf pad 56 to become closer and more able to provide support.
Accordingly, for any position of the rubber 20, the rubber 20
provides a position adjustment through the range of motion of the
calf pad 56 by the actuator 18. Therefore, the legrest 10 of the
present invention is an improvement over the conventional legrest
in that it enables the separation between the calf pad 56 and down
tube 12 to vary over the range of movement of the legrest 10. The
legrests of the prior art have only a fixed separation distance,
forcing the user to trade-off comfort in one position for less
comfort in the other. The present invention 10 transfers weight
from the footplate 42 to the calf as the footplate 42 is elevated.
As well, the user can pre-select the hole 50 in which to place the
rubber 20 to achieve optimum comfort across the range of
movement.
[0083] FIG. 4 provides a more graphical view of the operation of
the present invention. The figure shows the present invention 10
with the legrest in a fully raised position, with a representation
of the various forces at work. The weight of the user's lower leg
67 on the legrest 10 creates a force F1 from the footplate 42, and
a force F2 from the calf pad 56. There is an equal upward
counter-force F3 provided by the actuator 18. In this case the
frame 12 may be viewed as a lever having a distance equal to the
length of frame 12 and acting about the pivot point 36. There will
be a moment produced about the pivot point 36 by the downward force
on the frame 12. This is resisted by an opposite moment created by
the actuator about the frame pivot point 48 equal to the product of
the force F1 and the distance "d". This moment in effect is what
causes the rubber 20 to compress. As the rubber compresses the
separation "s" gets smaller. This however means that the calf pad
will take up more of the weight of the lower leg 67, so F2
increases and F1 decreases, however slightly. The various forces
continue to adjust incrementally until an equilibrium is
reached.
[0084] Thus it can be seen that the compressible positioning
element or rubber pad 20, positioned between the calf support 16
and the frame 12, permits the calf support position relative to the
frame, i.e. the separation "s", to be varied as the moment about
frame pivot point 48 changes. As the moment about frame pivot point
48 increases, the compressible positioning element or rubber pad 20
compresses, and the calf pad 56 support moves closer to the frame
12 to provide support to the lower leg 67 of the user.
[0085] The positioning of the rubber 20 may now be understood. FIG.
1 shows three predetermined locations or holes 50 to receive the
compressible positioning element 20. For illustration purposes the
rubber 20 has been inserted into the middle hole 50b. It can be
appreciated that more than 3 holes could have been used. From the
figure, it can be seen that when the rubber 20 is in the upper hole
50a, the pivot angle of the frame 12 relative to the push plate 45
will be larger and the calf pad 56 will be spaced further from the
down tube 12. This setting accordingly results in more compression
and travel by the calf pad 56. The converse will be true as the
rubber 20 is moved to positions 50b and 50c. For the lower
positions there is less compression, leverage, and travel. The
lowest position is closer to that of the conventional legrest
having a fixed separation s1.
[0086] The advantages of the present invention may be better
understood by considering certain practical issues. Many
wheelchairs have items that act as barriers that prevent the
legrest from reaching a fully lowered or vertical position. For
example, wheelchairs often have a cowling, which is a plastic
covering that covers the top of the wheelchair to enhance the
chair's appearance. The cowling may block the calf pad from
retracting to the fully lowered or vertical position. Other items
that may act as barriers in this way include the battery or battery
cover. However, many users will want to achieve a position as close
to the vertical as possible, to obtain as much of a true sitting
position as possible and to enhance maneuverability. Accordingly,
these users of the present invention will most likely choose to
insert the rubber 20 in the lowest available position. In this way
they will get as close to the vertical position as possible. While
there would be more calf pressure in this setting, this would
probably still be considered preferable by these users since at
least the footrest will be closest to the vertical. While this
setting is closest to conventional legrest it can be appreciated
that the present invention at least offers the user a choice which
would otherwise be unavailable.
[0087] Another type of barrier might be castors that block the
footplate. In this case while the legrest still cannot retract
fully, there may well be nothing blocking the calf pad. Therefore
in this case it would be reasonable to set the rubber 20 at a
higher position. This would force the calf pad back while the
legrest is in the lowest possible position. While the legrest would
not be in a fully lowered vertical position, as before the user at
least has the benefit of choice, and in addition the benefits of
reduced or eliminated calf pressure and the possibility to reduce
the overall chair length and enhance maneuverability.
[0088] In a conventional legrest, where there is a large fixed
separation (s1) the calf pad may well be comfortably off the calf
at a fully lowered legrest position. While this may be desirable to
the user, due to the large separation, as the legrest rises the
calf pad will be unable to receive a large weight transfer and this
may well be uncomfortable to the user. Where the separation (s1) is
small the user will likely have more comfortable calf support as
the legrest rises but uncomfortable calf pad contact when the
legrest is in a fully lowered position.
[0089] Each of the predetermined locations 50a, 50b, and 50c
provide for a separation "s" that is larger in the lowered position
than in the raised position, with the largest separation in the
fully lowered or vertical position, and the smallest separation in
the fully raised or horizontal position of the legrest. The higher
predetermined location such as 50a will have a generally larger
separation throughout the range of motion of the legrest. The user
of the present invention 10 has the opportunity to select the
setting most appropriate to his or her circumstances. This may
include such considerations such as the presence or absence of a
cowling and other aspects of chair configuration, and the user's
personal preferences regarding calf support relative to foot
support, and calf pad contact in the fully lowered position.
[0090] It can now be appreciated how the legrest 10 of the present
invention better transfers weight from the foot to the calf,
resulting in greater comfort for the user.
[0091] Wheelchair users commonly bump into walls, doors, and other
obstacles. Since the legrest is the most forward part of the chair,
it is the part most likely to be struck in a collision. While the
legrest itself is fairly sturdy, it can happen that jarring of the
frame 12 may cause the frame to be pushed back, which in turn could
jolt and damage the actuator. This is a problem for users because
the actuator is an expensive device to replace or repair.
[0092] However, this matter is addressed by the present invention.
The rubber 20 used to affect calf pad separation also acts as a
buffer or bumper to receive unexpected jostling from the front
without causing the actuator to retract.
[0093] Yet another protection against jostling from the front is
provided by the frame-stop 44. If the legrest is jarred from the
front, particularly when in the fully lowered position, the frame
12 will be driven back until the frame-stop 44 engages the back
wall 35. As noted, this is commonly set to occur prior to the
actuator retracting to its bottom position.
[0094] Accordingly, it can now be appreciated how the present
invention is more secure and less fragile than the legrests
otherwise available. It can also be appreciated how the present
invention may be easily manufactured or installed in pre-exising
wheelchairs. All that is required is to secure the device to the
wheelchair at the seat frame 22 or similar location, and connect
the actuator from the wheelchair to the push plate 45.
[0095] It will be appreciated by those skilled in the art that the
foregoing description was in respect of preferred embodiments and
that various alterations and modifications are possible within the
broad scope of the appended claims without departing from the
spirit of the invention. For example, while reference is made to
adjusting the positioning of the compressible element or rubber by
inserting the rubber into one of a plurality of positions, further
variation is possible by threading the rubber into each position.
An even finer adjustment of calf pad positioning may be made
available by adjusting the degree of threading of the rubber into
the selected position of insertion. Further, the stop could also be
made adjustable so that the extent to which the push plate is
allowed to pivot back could be set by the user. Also, further shock
absorbtion may be achieved by adding rubber bushing to the pivot
point 36 and a rubber bumper to the contact point of the frame-stop
44. Various other modifications will be apparent to those skilled
in the art but are not described in any further detail herein.
* * * * *