Note: Descriptions are shown in the official language in which they were submitted.
WHEELCHAIRS
The present invention relates to hand-propelled wheelchairs.
More particularly the present invention relates to improved
wheelchairs enabling the variance of the center of gravity of the user
and the seat of the wheelchair with reference to the axis of the drive
wheels.
In the last decade many patents have issued which propose various
ways to change or alter the overall center of gravity of the
whee~chair for different purposes.
Thus, e.g. U.S. Patent ~,310,167 describes and claims a variable
position center of gravity wheelchair comprising an articulated
chassis having a subframe to which is mounted a pair of main wheels
and a rear caster wheel, and a sea~ frame assembly carrying a seat and
a front caster wheel and connected to the subframe for movement
relative thereto between a first position with the seat positioned
over the main wheels and a second position forwardly of the main
wheels to facilitate curb climbing; said main wheels and front and
rear caster wheels being arranged in a diamond pattern whereby lateral
drift of the wheelchair is minimized while traversing sloping
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surfaces; and resiliently yieldable means connected between the
subframe and seat frame assembly to minimize the tendency for the
front caster wheel to lift off the ground when the main wheels are
strongly propelled, and to provide shock absorption when traversing
rough ground.
As stated in said Patent the principal object thereof was the
design of a wheelchair which can traverse sloping surfaces without
experiencing side drift and yet which may be easily manipulated to
climb curbs and the li.ke and which may traverse rough ground without
undue discomfort to the user.
A still further object of said patent was to provide a movable
center of gravity wheelchair in which the seat and thus the center of
gravity is located essentially over the main wheels during normal use
but in which means is provided for easily shifting the seat and center
of gravity forwardly to remove weight from the main wheels to
facilitate curb climbing.
The disadvantage of said arrangement is that it is limited to
articulated movement of a subframe comprising the seat and front
caster wheel from a first position to a second position for curb
climbing.
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In a series of Patents by J.P. Minnebraker there is described a
different type of wheelchair construction enabling the use of the same
wheelchair for normal riding conditions and in sports activities.
Thus, as described in U.S. Patents 4,351,540 and 4,477,098 and in
Reissued Patent 32,242 wheelchair constructions have remained
unchanged, except for relatively minor features for a substantial
period of time. While wheelchairs have existed for many years, they
generally were constructed of a main frame, front and rear wheels,
side rails or so-called "arm rests" and foot support members. However,
there was no means for creating or manufacturing a wheelchair of
different sizes, at a relatively low cost, from standard sized
components, in order to accommodate different size users.
Prior art wheelchair manufacturers constructed several different
sized wheelchairs and used different sized components for each of the
differently sized wheelchairs. In the case of a tall individual, the
main frame had to be larger, the seat located in a different position,
and a foot support member extended further from the seat, than in the
case of a wheelchair for a smaller individual. In addition, for the
larger sized wheelchair, the seat may have to be located at a higher
elevation in order to permlt the user to engage rims on the wheels for
propelling the wheelchair in an easy and convenient manner.
., .. ... ~. .. . .
Notwithstanding, heretofore there has not been any wheelchair
which is designed for anything except normal transport. In other
words, wheelchairs heretofore constructed were not designed to permit
any form of athletic activity, and particularly, for fast-moving
sports activities. This was primarily due to the fact -that the prior
art wheelchairs were all of a box-like construction with the seat, and
hence, the center of gravity, located at a fixed and at a substantial
distance above the ground. Consequently, the prior art wheelchairs
were not designed for any fast movement, and if one attempted to
propel any of the prior art wheelchairs at any significant speed, or
attempted to turn a corner quickly,the wheelchair might well tip over,
causing injury to the user.
In recent years, it has been found to be highly beneficial for
paraplegics and others required to use wheelchairs on a relatively
permanent basis to engage in various forms of athletic activities,
including wheelchair racing, tennis and the like. However, the
wheelchair construction heretofore did not lend themselves to such
form of activities.
In the wheelchairs described in each of said Patents and
especially in U.S. Reissued Patent 32,242 there is described and
claimed an apparatus for selectively positioning the rear wheels of a
wheelchair having a frame means to selectively alter the center of
gravity thereof, said apparatus comprising:
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a. a ~irst pair of connected and spaced apart plates provided
for attachment to one side of said frame means and a second pair of
connected and spaced apart plates provided for attachment to an
opposite side of said frame means.
b. a plurality of axle receiving openings on each of said pairs
of spaced apart plates and the openings in the plates of each pair
being aligned so as to be capable of receiving a rear wheel axle in
each of said axle receiving openings,
c. a separate rear wheel axle capable of extending outwardly
from the rear wheel axle openings on each of said pairs of plates,
d. flange means on at least one of the plates of each of said
pairs for fastener attachment to a frame means of said wheelchair such
that the pairs of plates can be attached to the frame means in any of
a plurality of selected locations to accommodate the size and intended
use of a user.
e. quick release means associated with said rear wheel axle to
enable quick release and replacement of rear wheels on said rear wheel
axle, such that said axle can be easily removed from one location and
replaced in another axle receiving location on said plates so that the
response and center of gravity and wheel base on said frame can be
easily and quickly altered.
Thus, Minnebraker's approach to providing a multifunctional
wheelchair which would be used for normal indoor and outdoor use as
well as for sports activities was based on providing the frame with a
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plurality of axle receiving openings so that the center of gravity of
the wheelchair could be altered by disassembling the wheelchair and
repositioning the wheels relative to the frame.
In U.S. Patent 4,405,142 there is described and claimed a similar
arrrangement of a quick breakdown wheelchair assembly comprising a
pair of side frames wherein each of said side frames includes a wheel
bracket for detachably mounting a wheel, said wheel bracket having a
plurality of axle mounting bores.
While this approach has been adopted on wheelchairs marketed
today, it has many disadvantages as discussed fully in U.S. Patent
4,852,89~ which points out that with the growing participation of
wheelchairs in sports, greatly increased demands have been placed upon
the balance and as well the general maneuverability of a wheelchair.
In this regard decisive meaning has been attached to the maneuvering
speed of the so-called sportschairs, in particular with the basketball
wheelchairs.
Modification of the center of gravity of a chair raises or
lowers the maneuvering speed of these chairs. However, on the one hand
it should not be forgotten that each modification of the center of
gravity naturally changes and affects the stability and/or tipping
possibilities nf tAe device with increasing degree.
. .
- 7 - 7) I~ 7 ~36~ f-.~
Further, it is generally recognlzed that the more a person moves
the axles for the two load bearing rear wheels rearwardly, that is,
displacement in the direction opposite from the two front wheels of
the wheelchair, the more stabilization is gained for the wheelchair as
such. On the other hand, wieh such adjustment the front part of the
wheelchair becomes heavier and heavier - as is apparent from its own
weight - and with this, naturally, comes decreased maneuverability.
Besides the individual possibilities of shifting the center of
gravity, there is also the need to take into consideration for today's
state of the art the various adjusting possibilities for the angle of
the seat, the angle of the backrest in regard to the seat surface as
well as the adjustment possibility of the camber of ~he rear wheels in
order to shift the height of the center of gravity.
For adjusting the center of gravity in relation to the seat
surface one can make use of essentially two adjustment criteria in the
st~tte of the art (see for example, Sports and Spokes, The Magazine for
Wheelchair Sports and Recreation, March-April 1986, Vol. 11, No. 6,
"Adjustability in Lightweight Wheelchairs"). For structural solutions
to the shifting of the center of gravity below the seat surface of a
t~heelchair one utilizes a rearrangement of the two large drive wheels
of the wheelchair. These two drive wheels are for the most part
repositionable bAck and forth along their axes in longitudinal guides
of the so-called axial support plates. By this means, the wheels
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themselves can be adjusted in a direction closer to or further from
the smaller front wheels.
For angular adjustment of the seat back of the wheelchair with
response to the seat surface, the so-called l'positioning angle" has
been primarily employed in the prior art. By this means the seat back
is adjusted for each application and then is fixedly locked in the
adjustment position by means of this positioning angle.
In addition, in the prior art the two front wheels are not
directly connected with the frame bars of the seat surface, but
instead they are pivotally connected to this frame so that they work
as carrying bars which extend parallel to the seat surface frame bars.
In this regard, they are also angularly adjustable as is illustrated
for example on page 15 of the publication mentioned immediately
above.
It has also been established in the prior art to be a serious
disadvantage firstly that precise adjustment of the three interrelated
adjustment parameters with respect to one another, these being the
position of the axles of the rear wheels, the position of the vertical
axles of the front wheels and the angle between the seat surface and
the back rest, is achieved only with great difficulty. For this the
two rear wheels in certain constructions are always individually
adjustable, that is 9 the axles of each individual wheel are separately
. ..
9 ~ ~ ~ ~ 3 ~ .~
and distinctly adiusted. It is therefore not difficult to demonstrate
how easily a small change in the setting of one wheel axis can affect
the other two wheel axes. Now this however, leads to a skewing of the
actual wheel axis relative to the seat surface of the wheelchair, and
with it a disadvantageous modification of the balance and also - quite
substantially - the tracking of the wheelchair. Still more severely
dominant, however, is the shifting which thereby occurs such that the
fixing means of one wheel becomes dissociated from the other wheel and
introduces the possibility of a completely unexpected shifting of one
wheel axis with respect to the opposing wheel axis.
Furthermore, tools are required to effect a positional change, so
in practice the position chosen is usually retairled without change.
To overcome the above problem U.S. Patent 4,852,899 suggests that
by adjusting two telescoping-type interengaging shiftable parts for
each of two frame bars of a support frame of a lightweight wheelchair,
the sitting position of the same can be adjusted with respect to the
seat surface and with it the adjustment of the center of gravity can
be dynamically adjusted with respect to the user.
Thus said patent provides a lightweight wheelchair adjustable for
a specific balance, comprising a seat arranged on two frame bars
characterized in that the frame bars at the seat level have at least
two parts telescopically adjustable relative to one another and
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adjustably connecting the back rest with the support frame to
selectively shift the position of the back rest relative to the seat.
It is not possible to effect a positional change while the user
occupies the seat of the wheelchair.
This arrangement has the disadvantage that the center of gravity
is shifted by forcing the use} to sit further back or further forward
in the seat as a function of the positioning of the backrest which is
a source of discomfort to the user.
In U.S. Patent 4,489,955 there is also cognizance of the
disadvantage of providing a wheel bracket having a plurality of axle
mounting bores for repositioning of the wheels relative to the frame
to adjust and vary the center of gravity and thus said patent suggests
yet another approach to this problem.
Thus said patent inter alia describes and claims a wheelchair
comprising a base frame comprising a pair of side plates and a web
extending between said side plates; a plurality of wheels including
two drive wheels and at least one other wheel; means for propelling
said drive wheels, said means consisting of hand engagable rim means
associated with said drive wheels; means fo} mounting said wheels to
said base frame, but so that the wheelbase thereof is substantially
fixed; chair support means; and means for mounting said chair support
~7~3
means to said frame so that the position of said chair support means
with respect to said frame and with respect to said drive wheels is
adjustable, so that the center of gravity of said wheelchair is
adjustable by adjusting the portion of said chair support means with
respect to said frame, and without adjustment of the position of said
drive wheels with respect to said frame, said means comprising: a pair
of inner and outer flanges of said chair means for receipt of each of
said frame side plates; means defining elongated openings in said web
adjacent each of said side plates; and fastener means extending
through said elongated openings into operative association with said
chair support means.
As will be realized said patent also has the same disadvantage as
the means suggested by Minnebraker in that the center of gravity for
any specific use must be prechosen and fixed before the user mounts
the chair thereby increasing the dependency of the user on others and
failing to provide dynamic versatility.
With this state of art in mind, there is now provided according
to the present invention a hand-propelled wheelchair comprising a
frame element to which is mounted a pair of large drive wheels and a
pair of front caster wheels, said wheelchair further comprising a seat
unit having a b~se and a back, said seat unit being slidably mounted
on said frame in such a manner as to be manually slidable and
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arrestable in a plurality of desired positions along said frame
element by the user while seated in the seat of the wheelchair to vary
the center of gravity of the user and the seat unit with reference to
the axis of the drive wheels without disassembly of the drive wheels,
the frame element or the seat unit from each other.
In a first preferred embodiment of the present invention said
base and back are hingedly attached to each other, said base and back
being arrestable in at least one position defining an angle of greater
than 100 therebetween to provide a wheelchair with a reclining
backrest.
As will be reali~ed the present invention provides for the first
time a versatile multifunctional wheelchair having a multiplicity of
possible positions of altered center of gravity effected by the user
himself while comfortably sitting in the seat of the wheelchair.
Thus e.g., even in a simplified version of a wheelchair according
to the present invention, used in a geriatric ward, the user when
wishing to recline can simply move the center of gravity of himself
and the seat unit forward with reference to the axis of the drive
wheels so that upon reclining the wheelchair does not tip over
backwards.
13 ~ ~ 4 ~ r7
For the more active user of the proposed wheelchair, the
advantages are much more numerous. Thus as is known, on normal
sidewalks there exists a slight incline towards the gutter of about 2
to 3 degrees for drainage purposes. A person riding in a wheelchair on
such a sidewalk perpendicular to the direction of incline finds that
the wheelchair drifts in the direction of incline and this inter alia,
because the center of gravity of the wheelchair is normally positioned
forward of the contact point between the drivewheels and the ground.
Traveling along such sidewalks in such a manner is uncomfortable
since the user must use one hand to propel one of the drive wheels,
while the other hand is used to brake the second drive wheel to
counter the tendency to drift in the direction of the incline.
In the wheelchair according to the present invention, this
problem can be ameliorated by simply sliding the seat backwards along
the frame to an arrested position of minimal distance between the
center of gravity and the axis of the drive wheels.
Similarly, moving the seat forward in relation to the frame moves
the center of gravity forward and provides greater stability for the
wheelchair in climbing curbs or steep slopes.
'J ~ ~ ~ f-3
Conversely moving the seat backwards in relation to the frame,
moves the center of gravity backward and gives greater stability when
the wheelchair is going down an incline slope.
As indicated hereinbefore, the manueverability of a wheelchair is
principally determined by the relationship between the center of
gravity and the axis of the drive wheels. When the center of gravity
is closer to the axis of the drive wheels, the effect on the casters
is less and the wheelchair has greater maneuverability. Therefore,
moving the center of gravity backwards adapts the wheelchair for
greater maneuverability for sports and activities such as basketball
and tennis.
Another problem solved by the present wheelchair is that of
change in the center of gravity as a result of a change in the weight
load in the chair. Thus, e.g., when the user of the chair takes a
child on his lap or is carrying packages, the center of gravity of the
chair is shifted from the optimum which existed before. With the chair
of the present invention, the user simply slides the seat in relation
to the frame to find the best position which restores said optimum.
In the preferred embodiments of the present invention said frame
element is rigid having a first frame bar defining a first axis to
which said drive wheels are attached.
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Since in these embodiments the seat unit is foldable onto the
frame rather than the frame itself being foldable the seat can be
orthopedically contoured for maximum comfort and support.
In an especially preferred embodiment of the present invention
said seat unit is attached to said frame via a linkage arrangement for
varying the vertical distance between said seat base and said frame.
As will be described with reference to the figures hereinafter,
this feature provides even greater versatility for wheelchairs
according to the present invention. Thus, in preferred embodiments
ssid seat base is hingedly attached to at least one linkage arm which
arm is in turn hingedly attached to a mounting member slidingly
mounted on said frame.
Preferably said hinges include integral inden~ and/or guide and
stop means which fully define and delimit predetermined angular
positions of said linkage arm with respect to said base and said frame
element and said hinges are designed so as to restrict the freedom of
movement of said linkage arm to only one plane.
The above features enable the user to choose and control by
himself his position relative the ground and the axis of the wheels
thus providing ver3atility and independence heretofore not available
with prior art wheelchairs.
~
- 16 -
In U.S. Patent 3,953,05~ there is described and claimed awheelchair which includes means for adjusting the height of the seat,
however, this patent describes adjustment means which are to be preset
before the user sits in the wheelchair and not adjustment means to be
operated by the user while sitting as the need for adjustment arises.
Thus this patent in effect teaches an adjustable office chair
provided on a wheelchair chassis.
The wheelchair of the present invention can be used in
conjunction with an electric drive attachment of the type described,
e.g., in Israel specification 91588 corresponding to U.S.S.N.
07/575,222 filed 30.8.90 and the teachings of which are incorporated
herein by reference.
Similarly the wheelchair can be used in conjunction with an
electrically powered hydraulic or mechanical or pneumatic jack as
described hereinafter.
Employing the above features it is possible to even adapt the
proposed wheelchair to function as stand-up wheelchair, e.g., by
providing an arrangement wherein said linkage arm is hingedly attached
to a front surface of said base and said linkage arrangement is
arrestable in at least one position defining an angle greater than 90
between the bottom surface of said base and said linkage arm thereby
- 17 - ~J ~
enabling the positioning of said base in an orientation approaching
perpendicular with the ground for adaptation of said wheelchair for
use as a stand-up wheelchair.
The invention will now be described in connection with certain
preferred embodiments with reference to the following illustra~ive
figures so that it may be more fully understood.
~ ith specific reference now to the figures in detail, it is
stressed that the particulars shown are by way of example and for
purposes of illustrative discussion of the preferred embodiments of
the present invention only and are presented in the cause of providing
what is believed to be the most useful and readily understood
description of the principles and conceptual aspects of the invention.
In this regard, no attempt is made to show structural details of the
invention in more detail than is necessary for a fundamental
understanding of the invention, the description taken with the
drawings making apparent to those skilled in the art how the several
forms of the invention may be embodied in practice.
In the drawings:
Fig. 1 shows a perspective view of a preferred embodiment of the
~heelchair according to the invention;
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Fig. 2 is a side view of the same embodiment;
Fig. 3 is a side view of the same embodiment after disassembly of
the drive wheels and folding for transport or storage;
Fig. 4 is a plan view of the frame element;
Fig. 5 is a side view of the same embodiment but adjusted to
provide a high seating position;
Figs, 6A and 6B are cross-sectional views of a preferred
embodiment of the mounting member;
Fig. 7 is a side elevation of the linkage arm and a preferred
embodiment of its hinges;
Fig, 8 is a side view of an embodiment of the wheelchair adapted
for use of a standing user;
Fig. 9 is a side view of a further embodiment provided with
auxiliary wheels;
Fig. 10 is a side view of yet a further embodiment of the
wheelchair provided with an electric drive attachment; and
Fig. 11 is a side view of the embodiment of Fig. 2 but adapted
for use of a reclining person.
Fig. 12 is a side view of an embodiment wherein the seat is
mounted on horizontal sliding rails; and
Figs. 13A and 13B show details of these rails.
There is seen in Figs. 1 and 2 a wheelchair provided with a frame
element 10 to which is mounted a pair of large drive wheels 12 and a
pair of front caster wheels 14. A seat unit 16 having a base 18 and a
- 19 - ~ 3
back 20 supports also a pair of footrests 21, and is slidably mounted
on the frame element 10, being manually slidable and arrestable in a
plurality of desired positions along the frame element 10 by the user
while seated in the seat unit 16 to vary the center of gravity of the
user and the seat unit with reference to the first axis 22 of the
drive wheels 12 without disassembly of any parts of the wheelchair.
The base 18 and the back 20 are both upholstered rigid bodies,
thus providing the user with a comfortable seating posture for the
extended time periods that the user is likely to remain seated.
Furthermore, the base 18 and the back are hingedly attached to each
other by the hinge 24, and are arrestable in various positions, at
least one position defining an angle of greater than 100 therebetween
to provide a wheelchair with reclining backrest as will be described
with reference to Fig. 11.
For further improvement of the sitting posture the seat unit 16
is orthopedically contoured.
Armrests 26 are attached to back 20 by means of hinges 28, these
too being arrestable at various angular positions.
Fig. 3 shows the same embodiment after disassembly, for purposes
of transport or storage, of the drive wheels 12. The frame element 10
is hingedly interconnected by a plurality of hinges 30, 32 having axes
- 20 ~ 2 ~
extending perpendicular to a vertical central plane of symmetry of the
wheelchair. The drive wheels 12, which are not shown in this figure,
as they have been disassembled, are demountably attached to the first
axis 22 of the frame element 10. The back 20 is seen folded onto the
base 18 which in turn is seen folded onto the frame element 10 to form
the compact lightweight array shown.
The dimensions of the folded wheelchair may be reduced further
than that shown in Fig. 3 by also disassembling the caster wheels 14.
Here it should be noted that the convenient demountability of the
drive wheels 12 from the first axis 22 is of further utility for
passage in very narrow pathways such as are found, for example, in
passenger aircraft. In such circumstances the auxiliary wheels 68
which will be described with reference to Fig. 9 are used, the drive
wheels 12 having been disassembled.
Fig. 4 shows the frame element 10 which is rigid, having a first
frame bar defining a first axis 22 to which drive wheels 12 are
attachable. Therefore the wheelchair of the present invention,
unlike most~ known wheelchairs, remains rigid in both horizontal
dlrections. folding is achieved in the vertical direction, as has been
explained with reference to Fig. 3. The caster wheels 14 are
revolvably suppor~ed in bearings 34. The mounting member 36 will be
described with reference to Fig. 6.
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There is seen in Fig. 5 the same embodiment as in Fig. 2 but is
shown here adjusted to provide a high seating position such as might
be required by a tall user. The extra height shown is ob~ained by
locking the linkage arm 38 in a vertical position. Conversely it is of
course possible to lock the linkage arm 38 in a horizontal or near
horizontal position to obtain a very low seating position to suit the
requirement of a very short user. The desired position of the center
of gravity of the seat unit 16 with user can still be maintained at a
desired location by moving the mounting member 36 as will be
explained.
Figs. 6A and 6B show a preferred embodiment of the mounting
member 36, which is provided with means for frictional engagement to
the frame element 10. Means are provided for selectively clamping and
unclamping the mounting member to the frame element 10.
In the preferred embodiment shown, these means are provided in
the form of a coil spring 40 assembled around and frictionally
en8aging and clamping a horizontal member 42 of the frame element 10,
one extremity 44 of the coil spring 40 being attached to the mounting
member 36 and the re~aining spring extremity 46 being a~tached to a
tensioning device such as a cable 48, which when tensioned b~ the user
by means of a handgrip 50 shown in Fig. 5, slightly unwinds and
expands the coii spring 40 and thereby releases the frictional
engagement between the coil spring 40 and the horizontal member 42.
- 22 - ~ 3
When tension is released bg the user, the coil spring diameter
revert~ to a smaller dimension, thereby causing re-engagement of the
coil spring 40 and the horizontal member 42. It wlll be noted that
this form of frictional clamping can be repeated many times wlthout
marring the ~mooth outer surface of the horizontal member 42. A linear
motion ball bearing 52 is shown supporting the mounting member 36 on
the horizontal member 42. In an alternative embodiment (not ~hown) a
pair of low-cost sleeve bearing3 are used inside a mounting block of
increased length.
The function of the described mounting member 36 is to support
the linkage arm 38 as will be explained.
It will be realised that while not shown A plurality of linkage
arms 38 forming a multiplicity of functional parallelagrams for
greater support can also be provided.
It will be noted that movement of the mounting member 36 to a
different position along the horizontal member 42 will cause a
corresponding change in the position of the center of gravity of the
seat unit 16 and user relative to the first axis 22. The following
table summarizes the various positions of the center of gravity and
the corresponding advantages obtained.
~fl~
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TABLE
POSITION OF CENTER OF GRAVITY ADVANTAGE GAINED
Adjacent the axis 22 of Least power consumption.
the drive wheels 12
Adjacent the axis 22 of Best for movement on side
the drive wheels 12 sloping surface.
Adjacent the axis 22 of Least effort for "wheelie"
the drive wheels 12 maneuver.
Adjacent the axis 22 of Easiest maneuverability.
the drive wheels 12
Halfway between the 2 wheels Least overturn danger on
level,
Near caster wheels 14 Easy backward stair climbing
with helper.
Near caster wheels 14 Least overturn danger on
upward slope.
Near caster wheels 14 Easiest dismounting from
wheelchair.
Adjacent the axis 22 of Safe traverse of downward
the drive wheels 12 slope.
Behind drive wheels 12 To raise caster wheels from
ground balance retained by
control of drive wheels.
Adjust as required Carry extra load or child.
Near drive wheels but unlocked Easy dynamic curb climbing.
Fig. 7 shows the linkage arm 38 and a preferred embodiment of its
hinges 30, 32. The seat base 18 is hingedly attached to at least one
linkage arm 38, which arm is in turn hingedly attached to the mounting
member 36 which is slidingly mounted on the frame element 10. Both
hinges 30, 32 are configured to restrict the freedom of movement of
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the linkage arm 38 to only one vertical plane. In the embodiment shown
a fixed pin 54 is provided at each hinge center and a removable pin 56
is provided which is insertable in any of a plurality of apertures 58,
so that the hinges 30, 32 include integral indent and/or guide and
stop means which fully define and delimit predetermined angular
positions o~ the linkage arm 38 with respect to the seat base 18 and
~he frame element 10.
As has been explained, a change in the linkage arm angle changes
the height of the seat unit 16.
There is seen in Fig. 8 an embodiment of ~he wheelchair adapted
to suit a standing user, or for use of a sitting or reclining user who
wishes to assume a standing position but is unable to do so without
help.
The linkage arm 38 is hingedly attached to the seat base 18 and
is arrestable in at least one position defining an angle greater than
90 between the bottom surface of the seat base 18 and the linkage arm
38. Thereby the positioning of the seat base 18 in an orientation
approaching perpendicular with the ground is achieved, for adaptation
of the wheelchair for use as a stand-up wheelchair.
In the pre erred embodiment shown an electrically powered
hydraulic, pneumatic or mechanical jack 60 is provided for selectively
~ ~ 7
- 25 -
positioning the seat base 18 in an orientation approaching
perpendicular to the ground. Obviously the remcvable pin 56 is
previously removed from the upper hinge 30 to allow the jack 60 to
carry out its function. A secondary linkage 62 is provided to change
the an~le between the base 18 and the back 20 as shown.
Also provided in this embodiment are adjustable-height footrests
64, which are adjustable to essume a locked position at a height
suitable for normal use or extended to contact the ground when the
seat base 18 is oriented in a near-vertical position. A preferred
method of operating the adjustable height footrests 64 is by means of
a second jack 66.
Fig. 9 shows a further embodiment provided with a pair of
auxiliary wheels 68. These are positioned to the rear of the drive
wheels 12 at a height above ground level such that the auxiliary
wheels 68 contact the ground when the front caster wheels 14 are
raised from the ground for a purpose such as going up a curb step 70.
Preferably means are provided to allow the horizontal distance by
which the auxiliary wheels 68 are behind the first axis 22 of the
drive wheels to be varied.
In the preferred embodiment shown the auxiliary wheels 68 are
suspended from an arm 72 attached to the mounting member, whereby the
horizontal position of the auxiliary wheels 68 may be conveniently
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varied by the user whi]e remaining seated by moving the seat unit 16
horizontally forward or backward relative to the frame elemen-t 10. The
auxiliary wheels 68 thus prevent the wheelchair from overturning when
moving the seat unit 16 backwards relative to the frame element 10
while traveling on side sloping surfaces or carrying out a "wheelie"
maneuver. However, undesirable contact between the auxiliary wheel3 68
and the road surface can be avoided by the user moving the auxiliary
wheels forward nearer the first axis 22 when their assistance is not
required.
It has previously been noted that the auxiliary wheels 68 can
support the wheelchair when the drive wheels 12 have been removed for
some purpose such as traverse of a narrow passage.
Fig. 10 shows yet a further embodiment of the wheelchair provided
with an electric drive attachment 74. Such attachments are well known
and require no description. An extension 76 of the frame element is
added to provide a mounting member for the attachment 74. The weight
of the attachment 74 is compensated for by moving the seat unit 16
further forward than in previous embodiments.
Fig. 11 shows again the embodiment which has been previously
described with reference to Fig. 2 but is here shown as adjusted for
use by a reclining person. This has been achieved by lowering the
inclination of the back 20 by use of the hinge 24, and by raising the
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footrests 21 to a horiæontal position. Such adjustment would be of
utility to allow a user to sleep in the wheelchair and for hospitals
for moving unconscious patients.
Fig. 12 shows the seat unit 16 mounted on horizontal sliding
rails 78, 80. A~ least one rail is provided; the embodiment shown is
provided with a pair of parallel rails. The rails 78 are fixedly
attached to the base 18, and are shaped to be guided by the rails 80
engaging the rails 78 and free to slide axially therealong. The
linkage arm 38 is attached to and supports the rail 80 via the hinge
30, whereby in conjunction with the hinge 32 the wheelchair may be
collapsed when required as shown in Fig. 3. The hinge 32 is fixedly
attached to the frame element 10. As in previous embodiments, the
height of the seat unit 16 may be altered by changing the angle of the
linkage arm 38 as has been explained with reference to Fig. 7.
Figs. 13A and 13B show details of the rails 78, 80. One edge of
the rail 80 is provided with a series of apertures 82, any one of
which may be engaged by a pin 84 connected by a short shaft 86 to the
handgrip 50. Thereby the user, while remaining seated, may slide the
seat unit 16 forward or backward to any desired position while
temporarily releasing the pin 84 from engagement with the apertures
82.
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2 ~ 3
It will be evident to those skilled in the art that the invention
is not limited to the details of the foregoing illustrative
embodiments and that the present invention may be embodied in other
specific forms without departing from the spirit or essential
attributes thereof. The present embodiments are therefore to be
considered in all respects as illustrative and not restrictive, the
scope of the invention being indicated by the appended claims rather
than by the foregoing description, and all changes which come within
the meaning and range of equivalency of the claims are therefore
intended to be embraced therein.
