Note: Descriptions are shown in the official language in which they were submitted.
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216P 1 CA
The present invention relates to wheelchairs and, more particularly, to
wheelchairs provided
with anti-tipping devices for preventing the wheelchairs from tipping over
rearwardly.
A conventional wheelchair comprises a seat on a frame, a pair of side wheels
supporting the
frame and, forwardly from the side wheels, a pair of front castors.
la
Various anti-tipping devices have, in the past, been proposed for
counteracting the problem
that, when the chair is required to move forwardly over an obstruction, for
example over a
curb of a sidewalk, the front castors must be raised by a certain amount,
which inevitably tilts
the wheelchair backward by a corresponding amount, and there is therefore a
risk that the
15 rearward tilting of the wheelchair and its occupant may cause their joint
centre of gravity to
be displaced rearwardly to such an extent that the wheelchair and its occupant
fall
backwardly.
For example, in United States Patent No. 3,848,883, issued November 19, 1974,
to Stephen
20 J. Breacain, there is disclosed an anti-tip apparatus for a wheelchair
which includes a main
tube extending laterally and rearwardly from the rear frame upright of a
wheelchair, with
extension tubes slidably received in the main tubes and spring-biased to a
retracted position.
The extended ends of the extension tubes are joined by a transverse support
tube, and a wheel
or coaster is provided at the end of each extension tube. A manually
releasible spring detent
25 latch on each main tube holds the apparatus in the extended position,
allowing the wheelchair
occupant safely to tip the chair back onto the extended wheel or coaster to
negotiate steps
and curbs and to retract the apparatus when maneuvering in close quarters.
However, the
latch is located behind the wheelchair seat, in a position in which the latch
is not accessible
to the occupant of the seat. There is no mechanism which can be operated by
the occupant,
3() while seated in the seat, for extending and retracting the wheel or
coaster.
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United States Patent No. 3,580,591, issued May 25, 1971, to H. Franklin Coffey
et al., shows
another type of wheelchair anti-tipping device which, again, is located behind
the wheelchair
seat in a position inaccessible by the occupant of the seat and which also has
no mechanism
for extending and retracting the anti-tipping device.
United Patent No. 3,573,877, issued April b, 1971, to Burton H. Locke, teaches
a wheelchair
with a curb-climbing structure comprising a lifting means to be actuated by
the occupant of
the chair to raise the rear of the chair to a curb level after the front
portion of the chair is
placed on the curb.
It is, however, an obj ect of the present invention to provide an anti-tipping
device intended
for use in circumstances other than when the chair is moved over an
obstruction, e.g. for use
when the chair is negotiating a hill or is being used in a sport, the anti-
tipping device being
retractable when the chair is moved over a curb or other obstruction.
According to the present invention, there is provided a wheelchair with an
anti-tipping device
which includes a ground engagement member mounted for movement to and fro
between a
rearwardly extended operative position and a forwardly retracted inoperative
position, and
a horizontally extensible and retractable displacement device, operable in
response to
actuation of an actuating member accessible to a person seated on the seat, to
displace the
ground engagement member between these two positions.
Thus, the occupant of the wheelchair, while remaining seated in the
wheelchair, can access
and actuate the actuating member to displace the ground engagement member
rearwardly
from the frame into the operative position when there is a risk that the
wheelchair may tip
rearwardly. This operative position is preferably spaced above the ground.
When the anti-
tipping device is not required to be operational, the ground engagement member
can be
retracted forwardly relative to the frame and, preferably, into a position in
which the
displacement device and the ground engagement member are accommodated entirely
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beneath the frame and, therefore, do not form any rearward proj ection or
obstruction from
the frame.
In a preferred embodiment of the invention, the displacement device comprises
a four-link
linkage which can be collapsed, by use of the actuating member, to draw the
ground
engagement member into its inoperative position and which can also be
extended, by
operation of the actuating member, so as to deploy the ground engagement
member into its
operative position.
The present invention will be more readily understood from the following
description of a
preferred embodiment thereof given, by way of example, with reference to the
accompanying
drawings, in which:-
Figures 1 and 2 show views in side elevation of a wheelchair embodying the
present
invention with a pair of anti-tipping devices in a retracted inoperative
positions and in an
extended operative positions, respectively;
Figure 3 shows a view in rear elevation o:P the wheelchair of Figures 1 and 2;
Figure 4 shows a view of the wheelchair of Figures 1 to 3 with the anti-
tipping devices in
operation;
Figure 5 shows an exploded view, in perspective, of the components of one of
the anti-
tipping devices of Figures 1 to 3;
Figure 6 shows a view taken in vertical cross-section through a connection
between one of
the anti-tipping devices and a frame of the wheelchair of Figures 1 to 3;
Figures 7, 8 and 9 show side views of one of the anti-tipping devices in three
different
conditions;
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Figure 10 shows a view in perspective of parts of one of the anti-tipping
devices;
Figures 11, 12 and 13 show some of the parts of Figure 9 in successive stages
of a latching
operation; and
Figure 14 shows a view in side elevation of a modification of the wheelchair
and anti-tipping
device shown in Figures 1 and 2.
In Figures l and 2, there is shown a wheelchair indicated generally by
reference numeral 10,
which comprises a seat indicated generally by reference numeral 12, a frame
indicated
generally by reference numeral 14, a pair of side wheels 16, of which only one
is shown, on
opposite sides of the flame 14 and, at the front and opposite sides of the
frame 14, a pair of
front castors 18, of which only one is shown. Beneath the frame 14, and at
opposite sides
of the frame 14, there are suspended a pair of anti-tipping devices, as
indicated generally by
reference numeral 20, one of which is shown in Figures 1, 2 and 4 and both of
which are
shown in Figure 3.
In Figure 1, the anti-tipping device 20 is shown in a forwardly retracted
inoperative
condition, in which the anti-tipping device 20 is substantially entirely
located beneath the
seat 12 and the frame 14 and therefore does not form any rearward proj ection
which would
obstruct a person behind the wheelchair 10, for example a person pushing the
wheelchair 10.
In Figure 2, however, the anti-tipping device 20 is illustrated deployed in a
rearwardly
extended operative condition, and in Figure 4 the wheelchair is tilted
backwardly by an
amount limited by engagement of the deployed anti-tipping device with the
ground.
The components of the anti-tipping device are shown in greater detail in
Figure 5.
As shown in Figure 5, a pair of ground engagement members in the form of
wheels 22 are
rotatably secured at the rear or free end of a support comprising ax arm 24,
which is an
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extension of a link 26. The link is part of an extensible and retractable
displacement device
which is indicated generally by reference numeral 28 and which comprises a
first link 30, in
the form of a tube secured as described below to the underside of the
wheelchair frame 14,
the link 26 constituting a second link of the linkage, and third and fourth
links 32 and 34
S (Figures 7 through 9).
The third link 32 is formed by two parallel bars 36 and 38 (Figure 5) which
are pivotally
connected at their opposite ends, by means of pivots 40 and 42, to the first
link and to a tube
forming the second link 26 and its extension arm 24.
The fourth link 34 is formed by a pair of bars 44 and 46 (Figure 5), of which
the bar 46 forms
one arm of a double-armed lever, the other arm of which is indicated by
reference numeral
48. The bars 44 and 46 are connected by pivots 47 and 49 to the first link 30
and the second
link 26. The free end of the arm 48 is connected to one end of a tension
spring 50, the
opposite end of which is connected to the pivot 40 connecting the first and
third links.
One end of a fifth link 52 is connected by a pivot 54 to the mid-points of the
bars 44 and 46.
The second link 26, at its end opposite from the arm 24, is extended by an end
portion 56
beyond the pivot 49, and the end portion 56 is formed with a catch 58 (see
Figure 10) for
the purpose described in greater detail below.
The opposite end of the fifth link 52 is connected by a pivot 68 to one end of
an arm 60 of
a double-armed lever indicated generally by reference numeral 62, the other
arm 64 of which
serves as an actuating member or hand grip by means of which the occupant of
the chair 10
can operate the anti-tipping device 20. The double-armed lever 62 is connected
by a pivot
66 to one end of the first link 30.
Figure 6 shows a connection between the link 30 and a tube 63 which forms part
of the frame
14 of the wheelchair 10. As shown in Figure 6, a nut 65 and a bolt 67 extend
through the
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link 30 and the tube 63, and also through a washer 69 which is interposed
between and
shaped to conform to the link 30 and the tube 63. This connection is one of a
pair of similar
connections between the link 30 and the tube 63, in the present embodiment of
the invention.
In an alternative embodiment of the invention shown in Figure 14, the tube 63
acts as the
first link of the linkage, the link 30 being omitted.
The operation of this anti-tipping device will be apparent from consideration
of Figures 7
through 9.
Figure 7 shows the linkage in a collapsed condition, in which the arm 24 and
the wheels 22
are retracted under the action of the tension spring 50 into their retracted
or inoperative
positions, in which they are located substantially entirely beneath the frame
14 of the
wheelchair 10 as shown in Figure 1.
By gripping the arm 64 of the lever 62, and by rotating the lever 62 in an
anti-clockwise
direction, as viewed in Figures 7 through 9, the linkage can be erected from
its collapsed
condition, as shown in Figure 7, and thus rearwardly extended, through an
intermediate
condition, shown in Figure 8, to an extended condition, shown in Figure 9, in
which the arm
24 and the wheels 22 are located in their rearwardly extended operative
position as shown
in Figure 2.
Between the collapsed condition of Figure 7 and the intermediate condition of
Figure 8, the
spring 50 acts in tension so as to urge the linkage back into its collapsed
condition shown in
Figure 7. As, however, the linkage passes through the intermediate condition
of Figure 8,
and the line of action of the spring 50 thus passes below the pivot, the
spring 50 tends to
rotate the double-armed lever 62 in an anti-clockwise direction and, thus,
tends to urge the
linkage from its intermediate condition shown in Figure 8 into its rearwardly
extended or
deployed condition, shown in Figure 9.
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In the extended condition shown in Figure 9, the second link 26 is
longitudinally aligned
with fourth link 34, i.e. the bars 44 and 46, and is releasibly retained in
this position by
means of a latch mechanism indicated generally by reference numeral 70 in
Figures 10
through 13.
More particularly, the bars 44 and 46 forming the fourth link 34 are each
formed with a
longitudinally extending slot 72, and the pivot pin 54 is slidable to and fro
along these slots
72. As the second link 26 moves into alignment with the fourth link 34, the
catch 58 engages
the pivot pin 54 and displaces it along the slots 72 as illustrated in Figure
12, until the tip of
the catch 58 passes the pivot pin 54, whereupon the pivot pin 54 falls, under
gravity, into
engagement with the catch 58 as shown in Figure 13. If required, a spring (not
shown) may
be added to urge the pivot pin 54 into engagement with the catch 58.
When the occupant of the wheelchair 1 fl subsequently wishes to retract the
anti-tipping
mechanism 20, he or she pivots the double-armed lever 62 in a clockwise
direction from the
position shown in Figure 9. This causes the fifth link 52 to move the pivot
pin 54 along the
slots 72 so as to release the catch 58 from engagement with the pivot pin 54.
The links 26
and 34 can then pivot relative to one another from the positions shown in
Figure 13 to those
shown in Figure 11, and the linkage can then be retracted through the
intermediate condition
shown in Figure 8 to the collapsed condition shown in Figure 7.
As will be apparent to those skilled in the art, various modifications may be
made in the
above-described embodiment within the scope of the appended claims.
