Note: Descriptions are shown in the official language in which they were submitted.
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~IE~L HUB LATCH MEC11ANISM FOR POWER WHEELCHAIRS
Field of The Invention
This invention relates generally to wheelchairs and
more particularly to a wheel hu~ latch mechanism for power type
wheelchairs for freeing the wheels from the drive mechanism so
that a patient in the chair can be moved around easily in those
9i tu~ltioll'', "here power iS not used.
Background of the Invention
Power wheelchairs generally include storage batterles
with electric motors for drlving the rear axle of the wheelchair
which in turn ls connected to the rear wheel hub. A common axis
may be providcd for these rear wheels or each rear wheel may be
independently driven by appropriate motor means.
In many situations, it i9 often desirable to move ths
wheelchair with a patient in the chalr only a ~hort dlstance or
maneuver it into a more convenient posltlon for a partlcular
activity. In some instances, the patient may be asleep ln the
chalr and there is normally no need to use the power mechanlsm.
In fact, under such condltions where the patient is not consclous,
it would be awkward for a nurse or doctor to try to operate the
power portion of the chair.
Because the motor is connected to the rear wheels to drive
the same, ~ny movement of the wheelchair without the benefit of
the motors is difficult because of the drag resulting from the
drive connection to the wheels.
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Brief Description of the Present Invention
~ith the foregoing in mind, the present invention contem-
plates a unique wheel hub latch mechanism for power type wheel-
S chairs wherein the mobility of the power chair is vastly improved
when electric power is not being used.
More particularly, ln accord with the present invention,
there is provided a wheel hub latch mechanism comprised of a
specially designed wheel hub, Bearing means are provided secured
to tlle axle and 80 designed as to mount the newly designed wheel
hub for free rotation about the bearing means so a~ to be independent
of the power drive system for the rear axle of the wileel. A
manually operablc latch means, ln turn, i8 provided for locking
the wheel hub to the bearing means for rotation with the bearing
means whenever it is dcsired to operate the wheelchair by the
power driven rear axle. When it i~ desired to permit rotation of
the rear wheels independently of the drive mechanism; that is,
provide for "free wheeling", it is only necessary to manually
manipulate the latch means to unlock the wheel hub from the bearing
means
The latch means and other components are so designed that
no special tools are reguired and the engagement and disengagement
of the wheel with the power transmission can easily be csrried out
by a nurse or other attendant.
Brief_Description of the Drawings
A better understanding of this invention will be had by
referring to the accompanying drawings in which:
FIGURE 1 is a perspective view of a typical power wheelchair
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incorporating the wheel hub latch mechanism of this invention;
FIG~E 2 is an enlarged exploded perspective view of the
basic components making up the wheel hub latch of FIGURE 1
and,
FIGURE 3 is a greatly enlarged cross sectlon of the various
components of FIGURE 2 ln assembled relationship wherein certain
ones of the components are shown in full lines.
Detailed Descri tion of the Preferred Embodiment
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Referring Eirst to FIGURE 1, there i8 shown a typlcal power
wheelchair 10 incorporating sultable storage batteries and a
drive motor a11 schematically indicated by the block 11 carried on
the wheelchair 10 under ehe seat. Motors for each of the wheels
will transmlt torque to the wheels through a rear axle such as
indlcAted flt 12 by way of the wheel hub.
Because of the foregoing described connection, it ls
difficult for an attendant to roll around the wheelchair when the
electrical power is not to be used because of the drive connection
between the 00tor and the wheels. As mentioned heretofore, in
accord with the present invention, this problem is overcome by
providing a latch mechanlsm which will, ln effect, dlsengage the
rear wheel from the drive mechanism so that it ls free wheellng.
This hub latch mechanlsm takes the form of a modified
designed hub shown at 13 in FIGURE 1 supporting a wheel 14 and
arranged to be disengaged from the axle 12 by a latch means. A
part of this latch means in the form of a pin head 15 is shown
in FIGURE 1 on the exterior or outside portion of the hub 13 and
is arranged to be pulled outwardly in the direction of the arrow
to effect the desired dlsengagement, all as will become clearer
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as the description proceeds.
Referring now to FIGURE 2, the hub latch mechanism in-
cludes, in addition to the modified hub 13, a bearing member
16 comprised of a tubular portion 17 for surrounding an end
5 portion of the axle 12 normally secured to a conventional wheel
hub. In addition, the bearing member 16 includes an integrally
formed flange portion 18 extending radially outwardly from the
inner end of the tubular portion 17. This flange includes ad-
jacent to its outer periphery at least one hole 19 passing there-
through ln a direction parallel to the axis of the tubular portion
17 and at a given radial distance therefrom. This axis is indicated
at A-A and corresponds to the axis of the axle 12 when the
components are assembled. The given radial distance is indicated
by the letter R in FIGUR~ 2.
Appropriate means in the form of a key 20 and corresponding
groove 21 in the axle 12 and inside of the tubular portion 17 of
the bearing member are provided for locking the bearing member to
the axle for power rotation therewith.
The hub 13 itself is journalled on the outer surface of
the tubular portion 17 of the bearing member 16, this tubular
portion comprising a special plastic material which provides a
journal bearing for the hub permitting free rotation of the hub
13 on the tubular portion 17 even though the tubular portion and
flange are locked to the axle 12.
The hub 13 and bearing member 16 are axially held captive
on the axle 12 by retaining ring 22 and front retainer cup 23.
Nut 24 threads to the end of the axle 12 to secure the retainer
cup 23 in place.
The actual latching of the hub 13 to the bearing member 16
so as to be power driven by rotation of the axle 12 is accomplished
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by providing a bore 25 in the hub 13 running parallel to the
axis A-A and at the same radLal distance ~ from this axis as
is the hole 19 in the besring member flange 18. A pin shank
26 extending from the latch head 15 described ln conjunction
5 with FIGURE 1 is receivable in the bore 25 and in the hole 19
when in its maximum lnward posltlon to thereby lock the hub 13
to the flange 18.
In the partlcular embodlment lllustrated ln FIGU~E 2,
the flange 18 includes a serles of addltlonal holes 27 at the
10 same rsdlnl distance R from the axls A-A as the hole 19 and
e~ually clrcumferentlally spaced ~uccesslvely relatlve to the
hole 19. By provldlng addltlonal holes 27, the pin shank 26
can be recelved ln any one of the holes to effect an lmmediate
locklng of the hub 13 to the flange. Thus, as the hub rotates
lS relatlve to the flnnge, the bore 25 wlll come lnto successlve
reglstration with the various holes 27 and the pln shank as
stated can be recelved in any one of these holes.
All of the foregoing will become clearer by now referrlng
to the a3sembled vlew of FIGURE 3. In FIGURE 3, the same numerals
20 used in FIGURES 1 and 2 designate the correspondlng parts.
As shown the nut 24 18 secured to the end of the axle 12
to retain the cup 23 ln place 80 that the bearlng element 16
and thus the hub 13 18 held captlve axlally to the axle 12,
The pln shank 26, ln turn, ls illustrated in FIGURE 3
25 in lts maximum lnward posltion wherein its end is recelved wlthln
the hole 19 shown ln regl3tratlon wlth the bore 25. In this
solid llne position of the pin shank 26 and head 15, the hub 13
is locked for rotatlon wlth the bearing element 16 and thus wlth
the axle 12 because of the keying of the bearing element to the
30 axle.
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When the latch me~ns ln the form of the pin shank 26 and
head 15 is retracted to the right to the dotted line posltion 15'
the end of the pin shank 26 is free of the hole L9 but still
within the bore 25. As a consequence, the hub is now free to
rotate about the tubular portion 17, the exterior of this portion
constituting a journalling or bearing surface for the hub.
In order that the latch ls held in one position or the
other, there is preferably provided a spring indlcated at 28 in
FIGURE 3 biasing the pin shank 26 towards the flange 18. When-
ever one of the holes in the flange 18 is in registration with
the bore 25, the pin shank 26 will thus automatically pass into
the hole and lock the hub to the flange.
In order to hold the pin in its retracted positlon to
provide ~or free wheeling, the entrance opening to the bore 25
lS on the outer side of the hub 13 may be assymmetric as by providing
a small slot 29. The head 15 itself also includes an assymmetric
portion such as a small rib 30 arranged to register with the
assymmetric portion 29 in the entrance opening when the pin head
is in a first rotated position.
With the foregoing arrangement, retractlon of the head
free of the entrance opening and rotation thereof will then
position the rib 30 out of registration with the slot 29 and
thus the head will be held in the dotted line position indicated
at 15' in FIGURE 3 to thereby hold the pin shank 26 free of
the hole 19 in the flange 18.
The foregoing operation can be easily carried out manually
by a nurse or attendant whenever it is desired to free the
wheel on the hub 13 from the power drive mechanism connected to
the axle 12.
As alresdy described, by providing the spring 28, once the
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head 15 of the latch i9 rotated so as to brlng the rib 30 into
registration with the slot 29 in the entrance opening of the
bore so that the pin can move to the left as illustrated in
FIGURE 3, the shank will automatically pop into the next hole
coming into registration with the bore 19 as the flange is power
rotated r.elative to the wheel. ~opping in of the pin shank is
assured by the provision of the spring 28, Once the pin is
received in one of the holes in the flange, the desired locking
is effected and the wheel is thu~ in engagement for driving
by the motor on the wheelchair,
The foregoing hub latch arrangement has advantages in
that by making the given rudial distance R of the hole and bore
from the axi~ of the tubular portion 17; that is, the axls A-A
of the axle 12, greater than twice the diameter D of the axle,
an increased driving torque is provided for the hub over that
provided by a direct connection of the axle to the hub thereby
lessening strain on the latch hub mechanism when transferring
power from the axle to the hub, By reducing such strain, the
life of the latch mechanism i9 substantially increased.
It will be understood that if the opposite wheel for the
power wheelchair shown in FIGURE 1 is driven by a motor, a
similar modified hub structure with a latch means can be provided
identical to that described herein so that both power drlven
wheels can be disengaged.
From all of the foregoing, it will now be evident that
the present invention has provided a valuable and unique wheel
hub latch mechanism for power driven wheelchairs which permits
the power wheels to be essentially disengaged from the drive
structure for easy free wheeling whereby an attendant can very
easily maneuver the wheelchair without electrlc power should
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such be desired. Further, it will be evident from the foregoing
description that the latch itself can be easily manually
manipulated without requiring any special tools.
Various changes falling within the scope and spirit of
S this invention will occur to those skilled in the art. The
whcel hub latch mechanism is therefore not to be thought of as
limited to the specific embodiment set forth merely for illustra-
tive purposes.
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