Note: Descriptions are shown in the official language in which they were submitted.
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E~ACKGROt~ND OFF Involution
PHYLA OF THE; INVENTION
This invention relates lo, an ail for the disabled,
for example to a fo1dii~q backrest of a wheelchair.
inscription OF THY: PROP ART
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Folding wheelchairs are commonly carried from
place to place in motor cars, so that a patient may
become mobile at his destination.
It is conventional for substantially the whole, or
an upper part of, the backrest of a folding wheelchair to
hinge down rearwardly to decrease the overall height of
the wheelchair for easy accommodation of the wheelchair
in a back. seat or a boot of a motor car.
For example it is known from British Patent
Specification 1175684 for two side frames of a folding
wheelchair to include two rear upper and two rear
vertical lower side tubes, with a strip of canvas or like
material extending between the two upper tubes as a rest
for the patient's back. The two upper tubes are
connected by rear hinge, to the respective lower tubes so
that they can be turned down rearwardly from raised
conditions in whictl their lower ends extend vertically
upwards prom the lower tubes and their remainders extend
almost vertically upwards but slightly rearwardly. The
two upper tubes are releasable held in their raised
positions by respective latching pins which are
spring-biassed into positions in which they project as
sliding fits out of the lower ends of reinforcing bushes
fixed in the lower ends of the upper tubes into the upper
ends of reinforcing bushes fixed in the upper ends of the
lower tubes. The upper ends of the pins are bent over to
project laterally out of slots along the upper tubes and
are externally provided with respective knobs whereby an
attendant can raise the pins out of the lower tubes
against the action of the springs to allow the two upper
tubes to be hinged down rearwardly.
This latching arrangement is based upon linearly
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sliding parts and in practice is prone to jamming.
Unfortunately, the looser the fit between the sliding
part in to latched, raised position of the bookrack,
and thus the less prong to jamming, the greater the
degree of tree movement between the sliding part and
thus the greater the amount of rattling during use of the
wheelchair.
United States Patent Specification 4,164,354
discloses similar latching mechanisms in a folding
wheelchair except that, instead of the latching
mechanisms being at about seat level, they are at about
arm rest level.
British Patent Specification 1203431 discloses a
latching mechanism for a linkage comprised of first and
second rectangular strips to the first of which is
riveted a triangular plate at an ape of which the
second strip is pivotal mounted. On the second strip
is also pivotal mounted a latching device consisting of
two triangular plates fixed together by two post. The
nearer end or the first strip extends between the two
plates end between the two posts in the latched
condition, and the latching device it urged into that
position by a torsion sprint acting between the device
and the second strip. One of the two plates has an edge
zone bent over the outer edge of the second strip to form
a latch-releasing flange or pressing by a user to move
the outer post from the path of the nearer end of the
first strip
This mechanism is unsuitable for use in relation
to a wheelchair backrest in that the elongate members of
the linkage are not end-to-end in their latched
condition, and thus the canvas material of the backrest
could not be both smooth in that condition and well
attached to the elongate members Moreover, the patient
would be liable to catch, or even hurt, himself on the
projecting nearer end of the foremost one of the members
Another disadvantage of the mechanism is that the
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latching device calm perform a significant amount of free
movement relative to the first strip in the latched
condition, iron a siqrll,ican~ rattle problem.
SUMMARY OWE THE INVENTION
According to the present invention, there is
provided a folding aid lot- the disabled, including first
and secorld aid parts which in a latched condition are
disposed end-to-end, hinge means interconnecting said aid
parts such that said parts are turntable relative to each
other about an axis of said hinge means between the
latched condition and a folded condition, latching means
tunably mounted on the first aid part so as to be
manually turntable relative thereto, and detent means
mounted on the second aid part so as to be releasable
engage able by said latching means so as to retain said
aid parts in said latched condition, said latching means
being biassed towards its condition in which it
releasable engages said detent means.
Owing to the invention, a folding aid in which the
aid parts are disposed end-to-end in their latched
condition employs a turning latching action, so reducing
the likelihood of jamming of the latching mechanism.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be clearly
understood and readily carried into effect, reference
will now be made, by way of example, to the accompanying
drawings, in which:-
Figure 1 shows a fragmentary side elevation of folding backrest of a wheelchair, the backrest being in a
raised condition, and
Figure 2 is a view Seymour to Figure I but
showing the backrest in a lowered condition.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings, the wheelchair includes
a folding frame 1 which itself includes two rear,
vertical members 2 (of which only one it seen). A back 3
of flexible sheet material comprises a vertical, lower
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part 3 attached at respective vertical edge zones thereof
to the rear owe the respective members 2, a set (not
shown) of simile:- mclterial ~einq attached to respective
ilorizontal members (not: sown) o- thy frame l. Thy back
3 also includes an upper part 311 which, in the raised
condition ox the backrest, is slightly inclined
rearwardly fryer the vertical. the par, 3'' is attached
at its two upwardly extending edge zones to respective
bent tubes a (of which only one is seen) which are each
provided with a handle 5 for grasping by an attendant.
The back 3 has a cut-out 3''' at each lateral side to
receive a latching mechanism which will now be described.
The inner end of each tube 4 has welded to its
respective lateral sides vertical t parallel plates 6 each
of a roughly triangular form these plates 6 embracing
the upper end of the adjacent member 2 and being
pivotal connected thereto by a horizontal pivot pin 7
extending transversely ox the wheelchair. These two pins
7 art co-axial with each other. Extending horizontally
between the plate I; 01 each pair is 2 pin 8 on which is
pivotal mounted a vertical, substantially vectorial
plate 9 to which is fixed a laterally outwardly
projecting pin lo torsion spring if urges the plate 9
anticloc1cwise~ in the drawings. From the rear side of
each member 2 projects a pair of vertical, parallel lugs
12 welded to the member 2 and interconnected by a
horizontal pin 13.
The curved, outer peripheral edge surface 14 of
the plate 9 is not truly concentric with the axis of the
pin 8, which is the axis of turning of the plate 90
Either the surface 14 is a true arc of a cylinder but
slightly eccentric relative to the axis of the pin 8, or
the surface 14 varies slightly from being a true arc, but
in either case such that its radius from its axis of
turning increases gradually and slightly clockwise in the
drawings .
In use, an attendant can grasp the handles 5 and
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turn the parts 3'' and 4 about the pivot pins 7 to Bryan
the backrest into either the raised condition shown in
Figure 1 or hi lowered condition shown in Figure I. In
thy rules condition, the par. 3'' is inclined slyly
rearwardly from the vertical, so providing a more
comfortable seating arrangement for the occupant than if
it were truly vertical. Moreover, in that condition,
each plate 9 extends downwardly between the upper parts
of the lugs I of its associated pair and bears with an
upper substantially linear surface portion 15 thereof
against the member 2 and, under the action of the spring
11, with a substantially linear portion of its surface 14
against the pin 13, so that the items 3'' and 4 are
prevented from being rotated downwards about the pivot
pin 7 by the plate 9 abutting downwardly against its
associated pin 13. The portion 15 is part of and located
part-way around an arcuate external peripheral surface of
the plate 9 co-axial with the pin 8. From the raised
condition, and in order to bring the backrest to its
lowered condition, the atterldant uses a finger to swintJ
each pin 10 rearward to swing the plate 9 beyond
abutment with the pin 13, against the action of the
spring 11, end then lowers the items 3'' and 4 about the
pivot pins 7 into the lowered condition shown in Figure
2, in which the plate 9 bears against the member 2 and
the pin 10 abuts the adjacent plate 6. If the space into
which the wheelchair is to be loaded is very restricted,
the items 3'' and 4 can be further lowered if the plates
9 are kept swung to near to the tubes 4. To return the
items 3'' and 4 to their raised condition, the handles 5
are simply lifted to turn the items 3'' and 4 about the
pins 7 and to cause the plates 9 to ride upwards over the
rear sides of the pins 13 until they commingle latch
behind those pins 13, as in Figure 1. Such gemming
effect obtained by the gradually increasing radius of the
surface 14 from its axis of turning has the advantage of
giving rigid locating of the tube 4 relative to the
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member 2 in the condition of Figure 1., and thereby
eliminating clearance without requiring precision
marlu~acture and thereby also allowing wear of the plate 9
or thy pyre, 13 during use to be taken up. Moreover,
reliance upon the portion 15 abutting the member 2 to
define the raised pOsitioll of the tube 4 avoids reliance
upon mutual abuttinc1 of the adjacent ends of the tube 4
and the member 2 to define such raised position, thereby
avoiding the need for precision manufacture in the region
o those ends-
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