Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02528570 2005-11-30
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WHEELCHAIR AND ONE-PIECE MOLDED BRAKING SUPPORT WHEEL
THEREFOR
This invention relates generally to wheelchairs for the handicapped, and
more particularly to a one-piece molded wheel support wheel formed as a unit
for
supporting and braking the wheelchair.
Manually propelled wheelchairs having two smaller castered front wheels
and two larger rear wheels are well known. These assistive devices are
utilized by
users which are physically impaired individuals unable to walk or who find
walking
difficult and are typically propelled by the user. Such wheelchairs require
periodic
1 o immobilization and stabilization thereof as determined by the user or
attendant and
are therefore equipped with a hand-actuated brake assembly (typically one per
each braking support wheel) attached to a frame member of the wheelchair frame
assembly adjacent the wheelchair seat allowing the user or attendant to
selectively
move a hand operated lever of the brake assembly to engage or disengage a
Z5 friction braking member in the form of a bar or plate which presses against
the
outer periphery of each corresponding tire of the braking support wheels of
the
wheelchair.
However, due to wheel wear, moisture, dirt, oil and other wheel periphery
surface modifying debris or contaminants, the limited pressure exerted by the
2 o friction member thereagainst will vary greatly and thus correspondingly
affect the
degree of braking friction for immobilization of the wheelchair. Should the
frictional
force between the outer periphery of the rear wheel and the friction member be
compromised and reduced, unexpected movement of the wheelchair may be
experienced.
25 A more efficient brake mechanism has been incorporated into battery
powered motorized three-wheeled scooters which provide motorized personal
transportation for a seated user. These motorized scooters typically include
spaced apart coaxially mounted rear wheels, one or both of which serve as a
driving wheel connected to the battery powered motor mounted on the scooter
3 o carriage and a steerable front wheel which includes a wheel housing
supporting a
single front wheel and a brake mechanism having a tightenable brake band and
drum arrangement. However the steerable front wheel of such power scooters is
typically supported between spaced downwardly extending ears or plates of the
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wheel housing such that the entire wheel and brake mechanism are held on an
elongated mounting shaft connected between the lower ears of the wheel housing
itself.
The present invention replaces the conventional support wheel and
corresponding wheel perimeter brake engaging members with a one-piece molded
braking and support wheel which includes a molded-in brake drum wheel operably
receiving a brake assembly. Substantially greater consistent braking and
immobilization are achieved by providing a brake and support wheel mold formed
more efficiently as a unit of wheelchairs and which is substantially less
impervious
Zo to conditions of tire wear, moisture, dirt, oil and other debris which
would typically
collect on the outer perimeter surface of the wheel tire.
This invention is directed to a molded braking and support wheel assembly
for a multi-wheeled wheelchair for a handicapped person. The wheel assembly
includes a braking support wheel molded as a single unit of plastic or plastic-
like
i5 material and having a tire receiving rim, a wheel bearing and brake
assembly
receiving hub, and spaced wheel spokes substantially radiaily extending
between
the hub and rim. A ring-shaped metal brake drum is molded as a unit into the
hub,
the brake drum having a plastic-interlocking outer surface and a generally
cylindrical inner braking friction surface. The plastic-interlocking outer
surface is
2 o molded into said hub as a single unit with the support wheel to secure the
brake
drum from relative movement in the hub. The brake drum defines a generally
cylindrical cavity for operatively receiving a brake assembly, the hub
including a
wheel bearing cavity coaxial with said brake drum for receiving a wheel
bearing
positioned therein.
25 it is therefore an object of this invention to provide a wheelchair for an
ambulatory-impaired user which includes a substantially more reliable brake
mechanism for selective immobilization of the wheelchair.
Still another object of this invention is to provide an improved wheel brake
mechanism for wheelchairs which is uniquely incorporated into a new one-piece
3 o molded brake and support wheel having a molded-in rigid metal brake drum
which
is ready to receive the brake assembly.
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Yet another object of this invention is to reduce the amount of rear wheel
tire tread wear caused by current brake lever engagement thereagainst to brake
a
wheelchair.
Still another object of this invention is to provided more consistent braking
s function of the brake assemblies of a wheelchair along with substantially
less brake
wear and significantly less adjustment thereof.
In accordance with these and other objects which will become apparent
hereinafter, the instant invention will now be described with reference to the
accompanying drawings.
1 o Figure 1 is a perspective view of a typical wheelchair showing the
improved
braking support wheel therewith.
Figure 2 is a perspective view of another wheelchair showing the improved
braking support wheel therewith.
Figure 2A is a perspective view of another invention embodiment in the form
15 of a folding 3-wheeled rollator including the improved wheel braking
mechanism of
the present invention.
Figure 3 is a perspective view of one embodiment of a brake actuator
assembly ready for clamping engagement to either of the frame assemblies of
Figures 1 and 2.
2 o Figure 4 is a perspective view of the brake assembly and including the
brake drum for clarity.
Figure 5 is an exploded perspective view of Figure 4.
Figure 6 is a perspective view of a smaller embodiment of the braking wheel
and braking assembly connected together.
2 s Figure 7 is a side elevation view of the braking support wheel of Figure
6.
Figure 8 is a section view in the direction of arrows A-A in Figure 7.
Figure 9 is an enlarged view of the central hub area of Figure 8, also
showing the brake assembly and wheel bearings installed therein.
Figure 10 is an enlarged side elevation view of the central hub area showing
3 o an alternate embodiment of the brake drum.
Referring now to the drawings, a partially exploded view of one embodiment
of a wheelchair of the present shown generally at numeral 10 in Figure 1. This
embodiment 10 includes a larger rear braking and support wheel assembly shown
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generally at numeral 12 forming the larger-in-diameter spaced rear wheels 14
of
this wheelchair assembly 10 and conventional front casters 62 supporting the
front
portion of the frame assembly 60. The frame assembly 60 includes spaced
upright
frame members 64 and spaced horizontal frame members 66 as shown.
The hub 16 of each molded one-piece braking support wheel 14 operably
receives a brake assembly 30 which, for the purpose of clarity, is shown
installed
into the brake drum 18, the brake drum 18 being permanently molded into the
hub
16 as a unit with the braking support wheel 14 as will be described herebelow.
A
brake actuator assembly 68 is clampingly engaged onto the spaced horizontal
1 o frame members 66 in a conventional manner. A flexible brake cable 70
interconnects the brake actuator assembly 68 and the brake mechanism 30 as
will
be described more fully herebelow. The molded braking support wheel 14
includes
an outer tire-receiving rim 28 which supportively receives a tire T in a
conventional
manner.
Referring now to Figure 2, an alternate embodiment of the wheelchair frame
assembly 60' is there shown at 10'. The wheelchair frame assembly 60' includes
spaced horizontal frame members 66' upright frame members 64' having
rearwardly, upwardly extending portions thereof which receive hand grips 48
and
brake actuator levers 50. The brake actuator levers 50 are operably connected
by
2 o flexible brake cable 70' to the brake assembly 30. Each smaller braking
support
wheel assembly 12' includes a smaller-in-diameter braking support wheel 14'
supporting a tire T' of a generally smaller diameter than that shown in Figure
1.
The hub configuration 16' includes a molded-in brake drum 18 supporting the
brake assembly 30 as previously described.
2s In Figure 3, details of the brake actuator assembly 68 include an elongated
brake support shaft and clamp 74 which serves to clampingly engage the brake
actuator assembly 68 to the upper horizontal seat frame member 66 shown in
Figure 1. Brake finks 76 and 78 pivotally connected together as shown respond
to
pivotal movement of the brake handle 80 in the direction of the arrows to
actuate
3 o the brake cable 70.
In Figures 4 and 5, the opposite end of cable 70 is attached to an adjuster
support flange 56 of the support arm 44 of a brake support plate 32 of the
brake
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assembly 30. A threaded adjuster 46 receives the end of the outer sleeve of
the
brake cable 70, while the core wire 58 extends to be clampingly engaged by a
core
wire clamp 82 to adjacent the distal end of a pivotally movable motion
transfer arm
40. The brake assembly 30 further includes a debris flange 54 mounted against
s the inner surface of the brake support plate 32. The opposing brake friction
shoes
34 are mounted against the debris flange 54 in pivotal position about a brake
shoe
support shaft 38 through a common aligned pivotal aperture 24 in a proximal
opposingly positioned end of each brake friction shoe 34.
The motion transfer arm 40 is operably engaged with a brake cam 42 which
1 o rotates consonant with pivotal movement of the motion transfer arm 40 as
effected
by in and out movement of the core wire 58 in the direction of the arrow. This
brake cam 42 includes opposing flats which are held biasingly by a wire spring
(not
shown) against brake shoe actuator surfaces 36 of the opposing spaced ends of
each of the brake friction shoes 34. Thus, as the brake cam 42 is rotated, the
brake shoes 34 are pivotally spread apart to act against the inner cylindrical
drum
friction surface 20 of the brake drum 18. Referring additionally to Figure 6,
a
hexagonal brake plate anti-rotation aperture 52 is operably engaged with a
mating
surface of either an upright frame member 64 or a hexagonal surface formed
onto
a wheel mounting shaft (not shown) to resist the rotational torque exerted
against
2 o the brake support plate 32 during braking operation.
Referring now to Figures 7, 8 and 9, a most important aspect of the
invention is there shown. In Figures 7 and 8, the injection-molded plastic or
plastic-
like braking support wheel 14" is formed as a unit of injection-molded plastic
or
plastic-like materials. This braking support wheel 14", as does the braking
support
2~ wheels 14 and 14' which is identical except with respect to outside
diameter of the
rim 28, 28' and 28", includes radially extending evenly spaced wheel spokes 84
which tie the hub 16" and rim 28" together structurally. Lightening wheel
spoke
webs 92 form lightening apertures shown to both enhance strength while
maintaining a low total weight of the braking support wheel 14".
3 o Molded into and as a part of the hub 16" is the rigid metal brake drum or
band 18 formed typically of steel for strength and wear resistance. However,
other
metallic materials are equally suitable for this purpose. The brake drum 18
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includes annular grooved plastic-interlocking outer surface 22 of sufficient
width so
that the plastic material fully engages into this grooved outer surface 22
during the
mold-forming of the braking support wheel 14". This grooved outer surface 22
insures that there is no movement between the brake drum 18 and the hub 16"
during operation of the wheelchair, including the braking thereof as
previously
described.
The hub 16" includes concentrically and coaxially formed inner and outer
wheel bearing cavities 116 and 118 which, as seen in Figure 9, forcibly
receive the
inner and outer wheel bearings 96 and 98, respectively. These wheel bearings
96
1o and 98 are press fit and held spaced apart for added strength by an
inwardly
extending molded bearing spacer 88 forming the bearing gap 86. The hub 16"
also includes an assembly clearance or access cavity 106 so that a
conventional
socket wrench may be utilized to install and remove the wheel support shaft S
by
its head H (shown in Figure 10 in phantom).
15 To add strength to the hub 16", hub ribs 26 are provided which are evenly
spaced and radially extending and which substantially stiffen the entire hub
16"
while maintaining a minimum weight of molded plastic material to accomplish
the
necessary task of supporting the inner and outer wheel bearings 96 and 98 and
brake drum 18 as previously described.
2 o Referring particularly to Figure 9, details of the brake mechanism 30 are
there shown in section view positioned within the brake drum 18 with the brake
friction shoes 34 bearing against the drum friction surface 20 to effect
braking as
previously described. An elongated main support tube 100 having an elongated
longitudinal main support shaft bore 102 is positioned centrally within the
brake
25 assembly 30 with an enlarged end portion 104 forming a brake plate spacer
between the inner bearing 96 against end surtace 120 and support tube shoulder
108 against the brake support plate 32. With the wheel mounting shaft S
slidably
engaged through the inner bores of bearings 86 and 86 and the main support
shaft
bore 102, securement of this arrangement into a suitable aperture or receiver
3 o formed through the upright frame member 64 (shown in phantom), of frame
assembly 60 is effected.
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Still referring to Figure 9, an alternate means for preventing rotation of the
brake support plate 32' is in the form of anti-rotation tabs 112 and 114
formed
integrally with the brake support plate 32'. These tabs 112 and 114 are angled
and
spaced apart so as to engage against the outer surface of the upright frame
s member 64 as shown. Preferably, two spaced upper and lower anti-rotation tab
sets 112 and 114 are provided so that a set of four such tabs, two on either
side of
frame member 64, provide positive anti-rotation alignment of the brake support
plate 32 and the entire brake assembly 30.
Referring lastly to Figure 10, an alternate embodiment of the brake drum 18'
z o is there shown. Molded into the hub 16' of the braking support wheel (not
shown
for simplicity) during the plastic injection mold forming thereof. This brake
drum 18'
includes the cylindrical drum friction surface 20' which operably engages
against
the outer surfaces of the brake friction shoes 34 as previously described.
However, the outer surface of the brake drum 18' includes spaced apart
transverse
15 hub engaging grooves 94 which are better suited for resisting the torsional
forces
generated during braking operation of the wheelchair assembly. in this hub
embodiment 16", the bearing gap 86 and brake drum support hub 90 are similar
to
those previously described in Figures 7, 8 and 10.
While the instant invention has been shown and described herein in what
2 o are conceived to be the most practical and preferred embodiments, it is
recognized
that departures may be made therefrom within the scope of the invention, which
is
therefore not to be limited to the details disclosed herein, but is to be
afforded the
full scope of the claims so s to embrace any and all equivalent apparatus and
articles.
