Wheel chair abstract
In a foldable wheel chair supporting frames for a back, a seat,
a pair of back wheels and a pair of front wheels are mutually pivotally
connected by means of pivot assemblies positioned at the seat-back
junction and comprising a blocking mechanism which is deactuated
for releasing the pivotal connection between the supporting frames
by turning the seat in a direction of a predetermined reduction
of the angular separation between the seat and the back. Each pivot
assembly may comprise a pivot pin secured to one supporting frame,
and pivot cams secured to the other supporting frames together with
an interlocking cam positioned between two of said pivot cams.
Wheel chair claims
What is claimed is:
1. A foldable wheel chair, comprising a back and a seat of a formstable,
non-flexible material, two wheel pairs, at least three individual
supporting frames for said back, said seat and said wheel pairs
and two identical pivot assemblies positioned opposite each other
at the back-seat junction for pivotally connecting said supporting
frames relative to each other around pivot axes extending in parallel
relationship to a shaft for one of said wheel pairs, and including
a blocking mechanism for interlocking engagement of the seat and
back supporting frames with the supporting frame or frames for said
wheel pairs in the normal operative state of the chair, said blocking
mechanism including means for releasing said interlocking engagement
only in response to a pivotal movement of said seat supporting frame
to a predetermined reduction of the angular separation of said seat
and back supporting frames, and to allow combined pivotal movement
of said seat and back supporting frames relative to the supporting
frame or frames for said wheel pairs in a direction opposite to
the preceding pivotal release movement of said seat supporting frame,
parts of said pivot assemblies connected with said seat supporting
frame being rigidly connected with each other to syncronize the
pivotal movements of the two pivot assemblies.
2. A wheel chair as claimed in claim 1, wherein said predetermined
reduction amounts to at least half the angular separation of said
seat and said back in the normal operative state of the chair.
3. A wheel chair as claimed in claim 1, wherein each pivot assembly
comprises a pivot pin extending parallel to said wheel shaft and
connected with said back supporting frame, a first pivot cam journalled
pivotally on said pivot pin and connected with said seat supporting
frame and a second pivot cam arranged for pivotal movement relative
to said pivot pin and said first pivot cam around a pivot axis displaced
in parallel relationship to said pivot pin, said second pivot cam
being connected with a wheel supporting frame, said blocking mechanism
comprising in each pivot assembly an interlocking cam journalled
pivotally on said pivot pin between said first and said second pivot
cams in such an operative engagement with said cams that in the
angular position of said first pivot cam corresponding to the normal
operative state of the chair, it prevents said cam from pivotal
movement opposite the release direction, on one hand, and is influenced
by said first pivot cam, on the other hand, to prevent relative
pivotal movement of said pivot pin and said second pivot cam, whereas
in response to pivotal movement of said first pivot cam in the direction
of release, it is carried along to release the interlocking engagement
between said pivot pin and said second pivot cam.
4. A wheel chair as claimed in claim 3, comprising four supporting
frames, wherein separate supporting frames for a pair of back wheels
and a pair of front wheels are connected with said second pivot
cam and a third pivot cam, respectively, said third pivot cam being
pivotally journalled on said pivot pin on the opposite side of said
interlocking cam relative to said second pivot cam, said second
pivot cam being constructed to prevent rotary movement of said pivot
pin in its blocked condition.
5. A wheel chair as claimed in claim 3, wherein said interlocking
cam is in engagement with said first pivot cam by means of a pin
secured in one of said cams and being guided in a circular guideway
formed in the other of said cams concentrically with the axis of
said pivot pin and having a circumferential length corresponding
to the predetermined pivotal movement of said seat supporting frame
to release the blocking mechanism, said interlocking cam being in
engagement with said second pivot cam by means of a pin secured
in one of said cams and a hook-shaped circumferential cut-out in
the other of said cams.
6. A wheel chair as claimed in claim 3, wherein a hook-shaped circumferential
cut-out is formed in said second pivot cam to match a portion of
said pivot pin of a non-circular cross-section.
7. A wheel chair as claimed in claim 4, wherein said second pivot
cam is journalled on a further pivot pin connected with said third
pivot cam and displaced relative to said pivot pin.
Wheel chair description
The invention relates to a foldable wheel chair of the kind having
a back and a seat of a formstable, non-flexible material and two
wheel pairs which are individually secured relative to at least
three supporting frames pivotally connected with each other with
pivot axes extending in parallel relationship to a shaft for one
of said wheel pairs by means of only two identical pivot assemblies
positioned opposite each other at the back-seat junction and including
a blocking mechanism which interlocks the seat supporting frame
relative to the wheel supporting frame or frames in the normal operative
state of the chair, but may be released to disengage said interlocking
engagement by pivotal movement of the seat supporting frame in a
direction towards the back supporting frame.
BACKGROUND OF THE INVENTION
In known foldable wheel chairs available on the market the seat
and back are usually manufactured from a flexible strong textile
material such as canvas, so that the chair is folded around the
vertical symmetry plane parallel to the wheels. In such chairs,
it is often a disadvantage to the user that the flexible material
of the seat and the back does not provide sufficient support. Moreover,
even in its folded condition such a chair will normally occupy much
space in the vertical direction, since the back may normally not
be folded relative to the wheels.
Such a relatively great demand of space is also a disadvantage
of a known chair disclosed in Danish Design Application No. 914/1977
which has been published in the Danish Design Journal (Registreringstidende
for Monstre) of 15th Feb. 1978. Contrary to most wheel chairs, this
known chair is provided with quite small wheels and has in the same
manner as ordinary folding chairs a support structure, the mutually
pivotally connected parts of which may be pivoted around a pivot
axis parallel to the wheel shafts whereby a possibility is provided
to use a seat and a back of a formstable, non-flexible material.
Another wheel chair for retarded persons, which chair is foldable
by pivotal movement of mutually pivotally connected supporting parts
around axes parallel to a wheel shaft, has been disclosed in Danish
Design Application No. 394/1977, which has been published in the
Danish Design Journal of 1st Dec. 1977. The supporting parts for
the seat comprise in this case several mutually pivotally connected
link rods which complicate the manufacture and make it more expensive
and, furthermore, make folding of the chair and rearrangement of
it from a folded condition to the normal operative state more difficult.
From Swedish published patent specification No. 373,325, a foldable
baby carriage is known, in which a front wheel supporting frame
is pivotally connected with a back wheel supporting frame around
an axis parallel to the the wheel axes, whereas the back wheel supporting
frame is pivotally connected around an axis displaced in parallel
relationship thereto with a U-shaped frame structure forming a handle
and being provided in the lower free end in each side with a bent
interlocking part engaging a locking bushing on the side pieces
of the front wheel supporting frame. The engagement of said interlocking
part and said locking bushing, which must be easily movable relative
to each other, is released by slightly lifting the handle frame
to open the triangular link which in the raised position of the
carriage constitute the blocking mechanism, whereby the back wheel
supporting frame is allowed to turn against the front wheel supporting
frame followed by pivotal movement of the two wheel supporting frames
up towards the handle frame. In addition to the fact that the release
movement is associated with a considerable risk of unintended folding
of the carriage due to the very simple blocking mechanism, the construction
requires at least the back to be of a flexible material which due
to the reasons mentioned in the foregoing would lead to considerable
disadvantages when used in a wheel chair.
In U.S. Pat. No. 3,450,432, a usual folding chair not provided
with wheels is disclosed, said chair having a seat and a back of
a formstable, non-flexible material. In this case, a limited number
of pivotally connected supporting parts, a small demand of space
in a folded condition and a simple operation when folding and re-raising
the chair, have been obtained in that the seat, the back, a front
leg supporting structure and a back leg supporting structure are
mutually pivotally connected only by means of two identical pivot
assemblies positioned opposite each other at the seatback junction
and including a blocking mechanism which is releasable by upwards
turning of the seat towards the back. In this known construction,
the back is only secured in the normal operative state of the chair
relative to the seat by engagement between two opposed shoulder
parts on flange portions connected with the seat and the back, respectively,
whereby the back is only prevented from turning in a direction to
increase the angular separation of the seat and back, whereas it
is free to turn in the opposite direction, and no blocking is present
between the back and the leg support structures. Thereby, also this
construction suffers from a considerable risk of unintendedly folding
when a person sitting in the chair leans back heavy enough to turn
the seat upwardly beyond a position, in which the pivotal movement
of the seat results in folding of the leg support structures. Furthermore,
in spite of the intended simplification, reraising of the chair
is difficult in that the back must be turned 180.degree. and the
seat 270.degree. from the folded condition. Moreover, the two pivot
assemblies are not safely synchronized, so that already at a modest
heavy or robust manipulation there will be a risk of distortion
of the pivot assemblies. Finally, due to the above mentioned movability
of the back in the normal operative state, a chiar constructed in
this manner will not be suitable for use as a wheel chair.
SUMMARY OF THE INVENTION
Taking as a starting point a simple structural design of a wheel
chair according to the same main principles as disclosed in the
above mentioned U.S. Patent for an ordinary folding chair, it is
the object of the invention to provide a foldable wheel chair offering
an improved security against unintended folding, a simplified operation
when reraising the chair from a folded condition and an improved
security against overloading of the pivot assemblies as a result
of heavy manipulation.
According to the invention, a wheel chair is provided, comprising
a back and a seat of a formstable, non-flexible material, two wheel
pairs, at least three individual supporting frames for said back,
said seat and said wheel pairs and two indentical pivot assemblies
positioned opposite each other at the back-seat junction for pivotally
connecting said supporting frames relative to each other around
pivot axes extending in parallel relationship to a shaft for one
of said wheel pairs, and including a blocking mechanism for interlocking
engagement of the seat and back supporting frames with the supporting
frame or frames for said wheel pairs in the normal operative state
of the chair, said blocking mechanism including means for releasing
said interlocking engagement only in response to a pivotal movement
of said seat supporting frame to a predetermined reduction of the
angular separation of said seat and back supporting frames, whereby
to allow combined pivotal movement of said seat and back supporting
frames relative to the supporting frame or frames for said wheel
pairs in a direction opposite to the preceding pivotal release movement
of said seat supporting frame, parts of said pivot assemblies connected
with said seat supporting frame being rigidly connected with each
other to syncronize the pivotal movements of the two pivot assemblies.
In the same manner as in the folding chair disclosed in the above
mentioned U.S. Patent, the release of the blocking of the pivot
assemblies existing in the operative state takes place by turning
the seat upwardly towards the back, but contrary to the known construction,
a considerable positive reduction of the angular separation of the
seat and back will be a condition for the release in the wheel chair
according to the invention. Moreover, since the pivotal movement
of the seat and back towards the wheels during folding of the chair
takes place in the opposite direction relative to the preceding
release movement of the seat, a simpler operation is obtained both
when folding and reraising the chair. Finally, the rigid interconnection
of the parts of the pivot assemblies connected with the supporting
frame, viz. the seat supporting frame, by the initial movement of
which the complete release is actuated, results in a safe synchronization
of the two pivot assemblies and improved safety against overloading
thereof.
Structurally simple pivot assemblies may be obtained in that each
pivot assembly comprises a pivot pin extending parallel to said
wheel shaft and connected with said back supporting frame, a first
pivot cam journalled pivotally on said pin and connected with said
seat supporting frame and a second pivot cam arranged for pivotal
movement relative to said pivot pin and said first pivot cam around
a pivot axis displaced in parallel relationship to said pivot pin,
said second pivot cam being connected with a wheel supporting frame,
said blocking mechanism comprising in each pivot assembly an interlocking
cam journalled pivotally on said pivot pin between said first and
said second pivot cams in such an operative engagement with said
cams that in the angular position of said first pivot cam corresponding
to the normal operative state of the chair, it prevents said cam
from pivotal movement opposite the release direction, on one hand,
and is influenced by said first pivot cam, on the other hand, to
prevent relative pivotal movement of said pivot pin and said second
pivot cam, whereas in response to pivotal movement of said first
pivot cam in the direction of release, it is carried along to release
the interlocking engagement between said pivot pin and said second
pivot cam.
Such a pivot assembly comprises only relatively few parts, viz.
in addition to a pivot pin and said pivot cam connected individually
with the mutually pivotal supporting frames, a single interlocking
cam.
If the wheel pairs are connected to the same supporting frame,
the chair according to the invention may be designed with only three
supporting frames. However, a smaller demand of space may be obtained
by using four supporting frames. To achieve this, a preferred embodiment
of the wheel chair using pivot assemblies as described in the foregoing
is designed so that separate supporting frames for a pair of back
wheels and a pair of front wheels are connected with said second
cam and a third pivot cam, respectively, said third pivot cam being
pivotally journalled on said pivot pin on the opposite side of said
interlocking cam relative to said second pivot cam, said second
pivot cam being constructed to prevent rotary movement of said pivot
pin in its blocked condition. Thereby, the front wheels and back
wheels of the chair may be brought as close to each other as possible
in the folded condition.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the invention will be explained in further detail
by means of an embodiment thereof and with reference to the accompanying
drawings, in which
FIGS. 1 to 3 show a wheel chair according to the invention in a
side view and a front view in normal operative state and in a folded
condition, respectively;
FIG. 4 shows a pivot assembly in the wheel chair shown in FIGS.
1 to 3; and
FIGS. 5 to 9 illustrate the positions of the individual elements
of the pivot assembly in different functional states.
DETAILED DESCRIPTION
In the embodiment shown, a wheel chair according to the invention
comprises a back 1 and a seat 2, each of which is preferably made
from a formstable, non-flexible material, said back and seat being
secured to a back supporting frame 3 and a seat supporting frame
4, respectively. In a manner known per se, a head back support 5
as well as an operating handle 6 and two armrests 7 and 8 are connected
with the back supporting frame 3. The handle 3 and the armrests
7 and 8 are pivotally connected with the back supporting frame 3,
so that when folding the chair, they can be pivoted to be substantially
coplanar with the back 1, whereas in the operative state illustrated,
they are secured against pivotal movement.
The wheel chair has two back wheels 9 and 10 arranged on a rigid
shaft 11 forming part of a back wheel supporting frame 12, with
which a braking device 13 acting on the back wheels 9 and 10 to
block said wheels is pivotally connected in a manner known per se.
As shown, the back wheels 9 and 10 are preferably of a size so that
they may relatively easily pass smaller obstacles.
Furthermore, the wheel chair has two smaller controlable front
wheels 14 and 15, each of which is designed as a twin-wheel in the
embodiment shown, and is rotatably connected with a side piece of
a front wheel supporting frame 16, with the front end of which side
pieces there is pivotally connected two telescopically displaceable
connecting rods 17 and 18 for a feet support 19, as well as two
handles 20 and 21 to be used together with the operation handle
6 when the chair is to be lifted by two persons.
In the embodiment shown, the supporting frames 3, 4, 12 and 16
are made from relatively rigid pipe profiles which, when the back
wheel shaft 11 is considered part of the back wheel supporting frame
12 and the feet support 19 with the telescopically displaceable
connecting rods 17 and 18, are considered part of the front wheel
supporting frame 16, is of a substantially U-shaped configuration,
in which the free ends of the legs are bent inwardly.
In accordance with the invention, the supporting frames 3, 4, 12
and 16 in the embodiment shown are pivotally connected with each
other by means of two pivot assemblies 22 and 23 positioned opposite
each other at the back-seat junction of the chair, with which pivot
assemblies the free ends of each of the U-shaped supporting frames
are connected in the manner more clearly shown in FIG. 3. The two
pivot assemblies 22 and 23, the detailed construction of which will
be explained in the following, are mutually connected by a pipe
piece 24 serving for synchronization of the movements of the pivot
assemblies, on one hand, and as carrying handles in the folded condition
of the chair shown in FIG. 3, on the other hand.
Due to this construction of the chair, in which the pivotal connections
between the supporting frames 3, 4, 12 and 16 are solely locallised
to the back-seat junction of the chair, it is obtained, as apparent
from FIG. 3, that the chair will occupy as small a space as possible
in a folded condition and, in the embodiment shown, will in addition
be in a stable balance in an upstanding folded condition, since
the upper edge of the back supporting frame 3 and the front wheels
14 and 15 are substantially equally spaced from the pivot assemblies
22 and 23.
As shown in FIG. 4, each of the pivot assemblies 22 and 23 comprises
in the embodiment shown a pivot pin 25 secured in one free end of
the pipe profile of the back supporting frame 3, a first pivot cam
26 welded to one free end of the pipe profile of the seat supporting
frame 4 and pivotally journalled on the pivot pin 25, a second pivot
cam 27 welded to one free end of the pipe profile of the back wheel
supporting frame 12, an interlocking cam 28 journalled pivotally
on the pivot pin 25 between the pivot cams 26 and 27 and a third
pivot cam 29 welded to one free end of the pipe profile of the front
wheel supporting frame 16.
As most clearly apparent from FIGS. 5 to 9, each of the pivot cams
26 and 29 and the interlocking cam 28 is formed with cylindrical
bores 30, 31 and 32, respectively, adapted to the pivot pin 25 so
as to allow rotation of said cams around the axis of the pivot pin.
In contradistinction thereto, the pivot cam 27 is arranged for pivotal
movement around an axis displaced in parallel relationship to the
pivot pin 25, said axis being defined by a pin 33 rigidly connected
with the pivot cam 29 and fitting into a cylindrical bore 34 in
the pivot cam 27. Furthermore, the pivot cam 27 is formed with a
circumferential, hook-shaped cut-out 35 matching an engaging in
the normal operative state of the chair shown in FIGS. 1 and 2,
a part 36 of the pivot pin 25 having a non-rotational symmetrical
cross-section provided, for example, by means of diametrically opposed
cut-outs having an axial length corresponding to the thickness of
the pivot cam 27. Moreover, in the normal operative state of the
chair, a pin 37 rigidly connected with the pivot cam 27 engages
a circumferential hook-shaped cut-out 38 in the interlocking cam
32. Finally, a pin 39 rigidly connected with the interlocking cam
32 engages in a non-removable manner a circular guide way 40 formed
in the side of the first pivot cam 26 facing the interlocking cam
28 coaxially with the bore 30.
FIG. 5 illustrates the positions assumed by the pivot cams 26,
27 and 29 and the interlocking cam 28 relative to each other and
the pivot pin 25 in the normal operative state of the chair shown
in FIGS. 1 and 2, in which the angular separation of the seat 2
and the back 1 is approximately 90.degree.. Since the seat supporting
frame 4, as shown in FIG. 4, is secured to a protruding arm 41 on
the pivot cam 26, the weight of the seat 2 with or without a person
sitting thereon will keep the hook-shaped cut-out 35 on the second
pivot cam 27 in firm engagement with the part 36 of the pivot pin
25 having a non-rotational symmetrical cross-section due to the
engagement of the guide way 40 and the pin 39 connected with the
interlocking cam 28, on one hand, and the engagement of the cut-out
38 of the interlocking cam 28 and the pin 37 of the second pivot
cam 27. Due to the engagement of the pin 39 with the guide way 40,
pivotal movement of the seat connected with the pivot cam 26 in
a downwards direction will, thereby, be prevented. Due to the engagement
of the pin 37 and the hook-shaped cut-out 38 of the interlocking
cam 28 and the engagement of the hook-shaped cut-out 35 of the pivot
cam 27 and the part 36 of the pivot pin 25 having a non-rotational
symmetrical cross-section, the back wheel supporting frame 12 connected
with the pivot cam 27 will, furthermore, be effectively locked and,
simultaneously, the pivot pin 25 will be blocked due to the latter
engagement against rotation relative to the pivot cams 26, 27 and
29. Moreover, due to the locking of the pivot cam 27, the pivot
cam 29 will be prevented from turning relative to any of the other
parts.
Thereby, for each pivot assembly, a locking mechanism is obtained
which secures an effective mutual interlocking engagement of the
relatively pivotal supporting frames in the normal operative state
of the chair.
As illustrated in FIGS. 6 and 7, this blocking mechanism is released
in accordance with the invention by pivotal movement of the pivot
cam 26 around the pivot pin 25 corresponding to pivotal movement
of the seat 2 towards the back 1. In the position shown in FIG.
6, the pivot cam 26 has been turned to an extent, by which the pin
39 connected with the interlocking cam 28 will now be encircled
by the opposite end of the guide way 40 relative to the position
shown in FIG. 5. However, in this position, the pin 37 connected
with the pivot cam 27 will still be in engagement with the hook-shaped
cut-out 38 in the interlocking cam 28, so that the back wheel supporting
frame 12, the front wheel supporting frame 16 and the back supporting
frame 3 will still be secured relative to each other. However, by
continuous pivotal movement of the seat 2 upwardly towards the back
1, the engagement between the pin 37 and the hook-shaped cut-out
38 will be released, such as shown in FIG. 7, and since the pivot
cam 27 is pivotally movable around a pivot axis displaced in parallel
relationship to the pivot pin 25, as defined by the pin 33, the
pivot cam 27 may now be turned in the same direction as the pivot
cam 26 and the interlocking cam 28 carried along by the pivotal
movement of the latter, corresponding to a pivotal movement of the
back wheel supporting frame 12 towards the front wheel supporting
frame 16, the side pieces of which have such a lateral separation
that the back wheels 9 and 10 may pass outside said side pieces.
Subsequent to this pivotal movement of the pivot cam 27, the parts
25 to 29 assume mutual positions, as shown in FIG. 8. By the pivotal
movement of the pivot cam 27, the engagement between the hook-shaped
cut-out 35 and the part 36 of the pivot pin 25 having a non-rotational
symmetrical cross-section is released, and the pivot pin 25 may
now be turned relative to the cams 26, 28 and 29, such as shown
in FIG. 9, corresponding to folding of the back 1 and the seat 2
which has been turned upwardly against the back in a downwards direction
towards the folded wheel supporting frames 12 and 16.
Thus, it will be apparent that folding of the chair from the operative
state shown in FIGS. 1 and 2 requires pivotal movement of the seat
2 upwardly towwards the back 1 to a predetermined reduction of the
angular separation of the seat 2 and the back 1, before the blocking
mechanism of pivot assemblies 22 and 23 may be released. For reasons
of security, the prescribed reduction of the angular separation
should preferably amount to about half the angular separation of
the back 1 and the seat 2 in the operative state, i.e. about 45.degree.,
such as apparent from FIGS. 5 to 9. By continued pivotal movement
of the seat 2 beyond this prescribed reduction of the angular separation,
the back wheel supporting frame may be pivoted towards the front
wheel supporting frame, and after this the seat and the back may
be folded over the two wheel supporting frames. Thereby, a possibility
for another simple folding of the chair is obtained, since after
actuation of the braking device 13 to block the back wheels 9 and
10, only a pivotal movement of the seat 2 upwardly towards the back
1 and a slightly backwardly directed pressure on the back and the
seat will be required, whereby the complete chair will be folded.
Before this operation, the head back support 5 is displaced downwardly
so as to be positioned within the back 1, and the operating handle
6 serving as a pushing device, and the arm rests 7 and 8 are pivoted
to a co-planar position relative to the back 1, in addition to which
the telescopic connecting rods 17 and 18 ae pressed and pivoted
towards the front wheel supporting frame 16. When, subsequently,
the chair is to be reraised from the folded condition shown in FIG.
3 to the normal operative state shown in FIGS. 1 and 2, it is laid
down from the upright position shown in FIG. 3, so that the wheels
rest on the support, whereafter the back 1 and the seat 2 are pivoted
outwardly to the angular position shown in FIG. 1 relative to the
front wheel supporting frame 16, and the back wheel supporting frame
12 is turned into place to lock the back supporting frame 3 by engagement
between the pivot cam 27 and the pivot pin 25. Thereafter, the back
wheel supporting frame 12 is locked by downwards pivotal movement
of the seat 2 to the operative state, after which the auxiliary
means 5, 6, 7 and 8 as well as 17, 18 and 19 may be brought into
place. Thus, operation of the chair is very simple, since no operations
to secure separate interlocking means positioned at different places
relative to the supporting frames are required.
The invention is not limited to the embodiment of the wheel chair
shown in the drawings, since the feature essential to the invention
that the supporting frames are mutually connected by means of pivot
assemblies of the seat-back junction associated with a blocking
mechanism which is deactuated by turning the seat upwardly towards
the back may also be used in a chair having only three main supporting
frames for the back, the seat and both wheel pairs, respectively.
If a pivot assembly as illustrated in FIGS. 4 to 9 is used in such
an embodiment, the pivot cam 29 may be dispensed with, whereby the
pin 33 defining the pivot axis for the pivot cam 27 displaced in
parallel relationship to the pivot pin 25 may instead be firmly
connected with the wheel supporting frame. However, in such an embodiment,
the chair will occupy a little more space in a folded condition
than shown in FIG. 3. Similarly, the design of the individual parts
of the pivot assembly shown in FIGS. 4 to 9 represents only a practically
suitable embodiment which can be modified without difficulties.
|