Note: Descriptions are shown in the official language in which they were submitted.
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Title: MOTORIZED CHAIR BASE
FIELD OF THE INVENTION
This invention relates to a motorized base for a
transportation device, such as a wheelchair, a stretcher, or the like.
BACKGROUND OF THE INVENTION
Traditionally, powered wheelchairs have two drive wheels
at the rear and two castor wheels at the front. These chairs drive like a
car in that they pivot about the rear of the chair. Accordingly, such
motorized wheelchairs are generally adapted for movement either
along a straight line or along a steered curved arc, somewhat in the
same manner as an automobile. They require a significant turning
radius and, as with a car, many manoeuvres must be executed
backwards. Further, these chairs tend to lose traction on downward
slopes since the rear drive wheels tend to become unloaded.
If it is desired to realign the wheelchair, for movement
from one fixed position in an entirely new direction, it is typically
necessary to go through complex turning manoeuvres, somewhat
similar to the three point turn utilized on occasion in operating an
automobile. The manoeuvres require a significant amount of space
and many tight spaces must be approached backwards in a manner
similar to a car reversing into a parking spot. These complex
manoeuvres are sometimes difficult for disabled persons to carry out.
There are some powered chairs where the powered drive
wheels are at the front. However, these chairs also require a large
turning radius and tend to lose traction when going uphill.
In addition, existing motorized wheelchairs frequently
have difficulty in traversing uneven flooring or terrain or when
travelling along an incline, such as a wheelchair ramp, and may lose
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traction and/or they may become unstable to the point where they can
tip over.
Due to these problems, wheelchairs have been designed
with the drive wheels positioned towards the centre of the chair (i.e.
between the front castor wheels and the rear castor wheels). Generally,
these chairs, which are known as midwheel drive chairs, operate with
only four of the six wheels in contact with the ground. The drive
wheels are positioned either in front of or behind the centre of gravity
with the chair balanced on either the front or the rear castor wheels. In
order to prevent the chair from tipping over on slopes, or during
acceleration or deceleration, an additional pair of wheels in front of or
behind the drive wheels to act as anti-tippers. These anti-tipping
wheels are positioned a short distance above the ground.
These midwheel drive chairs are garnering a reputation as
being unstable as, in operation, the chairs lurch a lot as the chair tips
onto its anti-tipping wheels. Further, they do not achieve optimal
manoeuvrability as the drive wheels are not positioned under the
centre of the chair (i.e. at the centre of gravity). Further, as the anti-
tipping wheels are generally not castor wheels, they are dragged along
the ground during some manoeuvres.
In United States Patent Number 5,445,233 (Fernie et al), the
applicant disclosed a novel midwheel design for a motorized
wheelchair. This wheelchair utilized a pair of drive wheels which were
centrally mounted beneath the seat of the chair and four free running
stabilizing wheels which were positioned at each of the four corners of
the base of the chair. In order to stabilize the chair so as to travel over
uneven surfaces, the drive wheels were rotatable mounted on a shaft at
a fixed position beneath the seat of the chair. The free running wheels
were mounted on a collar so as to be vertically movably mounted on
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the shaft. The free running wheels were urged into contact with the
ground via a spring mounted around the shaft. Accordingly, for
example, if the wheelchair of Fernie et al were travelling in a forward
direction and encountered uneven terrain, the front wheels could
pivot upwardly or downwardly about the shaft while ensuring that the
drive wheels remained in contact with the ground. The spring would
continually urge the free running wheels into engagement with the
ground to stabilize the wheelchair and thereby prevent the wheelchair
from tipping over.
One disadvantage with this approach was that the free
running wheels would rock forward to backward and/or side to side as
a person sat down or stood up from the wheelchair. This produced a
sensation that the wheelchair was unstable and would cause concern to
a disabled person. This was undesirable as midwheel drive chairs are
garnering a reputation as being unstable.
In order to enable the occupant of the chair to reach objects
positioned on a low shelf or on the ground, the chair included a shaft
having two telescoping sleeves. One of the sleeves was connected to
the seat of the chair and the other was connected to the drive wheels. A
motor was used to extend or retract one of the telescoping sleeves thus
raising or lowering the seat of the chair. While this design achieved the
goal of allowing a person to reach low lying objects, it has several
disadvantages. First, it necessitated the use of complex gearing and a
the incorporation of a further motor into the design of the wheelchair.
This constituted additional parts which were subject to wear and tear
and potential failure. Further, the parts substantially added to the cost
of the wheelchair thereby restricting the ability of some disabled people
to acquire the wheelchair.
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SUMMARY OF THE PRESENT INVENTION
In accordance with this invention, there is provided a base
for receiving a seat comprising:
(a) a longitudinally extending chassis having a front end, a
rear end, a central portion positioned therebetween and
opposed sides extending longitudinally between the front
and rear ends;
(b) at least one drive wheel mounted below the central
portion;
(c) a plurality of rotatably mounted wheels positioned
around the chassis and mounted at a fixed distance below
the chassis; and
(d) a biasing member associated with the at least one drive
wheel to bias the at least one drive wheel to engage the
surface on which the base is situated and reduce the weight
supported by the rotatably mounted wheels whereby the
rotatably mounted wheels support sufficient weight of the
base and the unoccupied seat to define a stable platform.
In accordance with another embodiment of this invention,
there is provided a motorized chair comprising:
(a) a longitudinally extending chassis having a front end, a
rear end, a central portion positioned therebetween,
opposed sides extending longitudinally between the front
and rear ends and a seat mounted thereon;
(b) at least one drive wheel mounted below the central
portion;
(c) a plurality of rotatably mounted wheels positioned
around the chassis, the plurality of rotatably mounted
wheels including a pair of forward wheels; and,
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(d) a biasing member to maintain contact between the at
least one drive wheel and the surface on which the base is
situated and, when a person of average weight is seated in
the seat, the forward pair of rotatably mounted wheels
support up to 25% of the weight of the occupied chair.
In one embodiment, the at least one drive wheel
comprises two drive wheels, each of which is driven by a motor. The at
least one drive wheel preferably supports a major proportion of the
weight of the base and the unoccupied seat. The at least one drive
wheel may support at least 75% of the weight of the base and the
unoccupied seat, preferably more than 85%, more preferably more than
90% and, most preferably, about 95%.
In another embodiment, when a person is seated in a seat
affixed to the base, the rotatably mounted wheels support a major
proportion of the weight of the person. preferably, the weight of the
person is evenly divided between each of the rotatably mounted
wheels.
In another embodiment, the rotatably mounted wheels
include a pair of forward wheels and, when a person of average weight
is seated in a seat affixed to the base, the forward pair of rotatably
mounted wheels support up to 25% of the weight of the occupied seat.
In accordance with another embodiment of this invention,
there is provided a base for receiving a seat comprising:
(a) a longitudinally extending chassis having a front end, a
rear end, a central portion positioned therebetween and
opposed sides extending longitudinally between the front
and rear ends;
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(b) at least one drive wheel mounted on the central
portion to engage the surface on which the base is
positioned;
(c) a plurality of rotatably mounted wheels positioned
around the chassis and mounted below the chassis to
engage the surface on which the base is positioned; and,
(d) a forward compartment positioned adjacent the front
end for receiving at least one battery and a rearward
compartment positioned adjacent the rear end for
receiving at least one battery.
The base may further comprise batteries positioned in the
forward and rearward compartments with the weight of the batteries
being essentially evenly divided between the forward and rearward
compartments.
One advantage of the instant design is that it provides a
stable low profile base for a chair, stretcher or the like. Accordingly,
even though the base may be used in the construction of a midwheel
drive chair, the base is stable not only when a user is entering or exiting
the chair, but also while the chair is in operation over a variety of
terrain. Further, the base maintains good stability and traction when
travelling up or down a ramp. This is particularly important when
traversing uneven terrain (such as a bumpy road), or going up or down
an incline (such as a ramp into a house or a building, particularly
where it is necessary to turn either to the left or to the right while
proceeding up the ramp).
Further, given the low height of vans, it is particularly
suitable for a person who has the ability to drive a motor vehicle as the
wheelchair may easily enter, travel through and exit a van which has
been adapted for a handicapped person.
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More importantly, even with its low profile, the
motorized chair base is particularly adapted to provide sufficient power
to the drive wheels. The battery compartments which are positioned
fore and aft are sufficiently large to receive four sealed lead acid type UI
batteries (12V, approximately 35Ahr). The batteries may be wired to
deliver approximately 70 Ahr of energy at 24V. This is substantially
more than the battery power which is typically provided to wheelchairs
which are currently on the market namely 50Ahr at 24V or less.
BRIEF DESCRIPTION OF THE DRAWING
These and other advantages of the instant invention will
be more fully and particularly understood in connection with the
following description of a preferred embodiment of the invention in
which:
Figure 1 is a perspective view of the motorized chair base
according to the instant invention;
Figure 2 is a side view of the motorized chair base of
Figure 1;
Figure 3 is a perspective view of the motorized chair base
of Figure 1 with the top panels removed;
Figure 4 is a cross-section along the line 4 - 4 of Figure 1;
Figure 5 is a perspective view of the tractor for the
motorized base shown in Figure 4; and,
Figure 6 is a cross-section along the line 6 - 6 of Figure 4.
DESCRIPTION OF PREFERRED EMBODIMENT
As shown in Figure 1, motorized base chair 10 comprises a
chassis 12, drive wheels 14 and free running wheels 16.
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Chassis 12 has a front end 20, a rear end 22, a first opposed
side 24 extending between front and rear ends 20 and 22, a second
opposed side 26 extending between front and rear ends 20 and 22, a top
28 and a bottom 30 (see Figure 4).
Base 10 may be used in the manufacture of a motorized
transport device, such as a wheelchair or to support a stretcher or
trolley to support a load. The following description is based on the use
of base 10 for a wheelchair; however, it will be appreciated that base 10
may be modified to receive thereon the superstructure of a stretcher or
other transportation device. Accordingly, a seat (not shown) may be
affixed to top surface 28 by any means known in the art. Preferably, the
seat which is affixed to the chair is a seat for a wheelchair so that, when
assembled, the unit comprises a wheelchair. Motorized chair base 10 is
particularly adapted for use in the industry as it may easily be adapted
to receive any existing wheelchair seat or the like. Front end 20 is
defined by the direction which a person faces when seated in the chair
which is affixed to the wheelchair.
Chassis 12 may be made from any particular construction
which will provide the requisite strength to support a person when
seated in a seat or chair affixed to motorized base chair 10. For example,
chassis 12 may be manufactured from a series of sheet metal parts
which may be manufactured by, for example, a stamping process or the
like. These sheet metal parts may be assembled by any means known in
the art to form chassis 12. Alternately, it will be appreciated that chassis
12 may be manufactured from high strength materials such as high
strength plastics, carbon reinforced composite materials and other
similar materials which are known in the industry. Accordingly, a
variety of manufacturing techniques may be utilized to manufacture
and assemble chassis 12. The preferred techniques utilize a thin wall
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construction so as to maximize the internal space of chassis 12 to
receive the various components discussed below.
In the preferred embodiment, a plurality of rotatably
mounted wheels 16 are positioned around the chassis and mounted at
a fixed distance below the chassis. Free running wheel 16 are positioned
so as to provide a stable base for chassis 12 when a person is entering or
exiting the wheelchair. A free running wheel is preferably provided
adjacent each corner of base 10.
Free running wheels 16 may be fixed to chassis 12 by
means of brackets 32. A pair of brackets 32 are preferably positioned on
each opposed side 24, 26 and spaced apart so as to be adjacent front and
rear ends 20, 22. Bracket 32 has a vertically extending central portion 34
which is positioned between upper and lower arms 36 and 38 and is
affixed to one of the sides 24, 26 by any means known in the art, such as
by screws, rivets, welding or the like. Spacer 46 is affixed to arms 36 and
38 and is counterbored at each end to receive a bearing at each end.
Free running wheels 16 are rotatably mounted on axle 40.
Axle 40 is mounted in U shaped bracket 42. Shaft 44 is affixed to U
shaped bracket 42 and has a shoulder (not shown) to abuts against the
lower race of the bottom bearing. In order to rotatably mount wheel 16
on bracket 32, vertically extending shaft 44 extends upwardly from U
shaped bracket 32 through an opening provided in lower arm 38,
through spacer 46 and through an opening provided in upper arm 36.
Shaft 44 may be lockingly held in position by any means known in the
art such as a set screw, a set washer or shaft 44 may have a threaded end
to receive a nut, or the like. Accordingly, each wheel 16 may
independently rotate and follow along a path set by drive wheels 14.
It will be appreciated that more than four wheels 16 may be
freely rotatably mounted to chassis 12. Further, it will be appreciated
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that each of the four wheels 16 may be positioned internal of the
perimeter of chassis 12. For example, a recess (not shown) may be
provided in bottom 30 for rotatably receiving shaft 44 or a bracket 32. It
will be appreciated that any means known in the art may be used to
rotatably mount wheels 16 to chassis 12.
As shown in Figure 1, top 28 comprises centre top panel 50,
front top panel 52 and rear top panel 54. It will be appreciated that top
28 may comprise only a single panel. Further, the top panel or panels
may be secured to chassis 12 by any means known in the art. For
example, as shown in Figure 1, top centre panel 50 is secured in
position by means of a plurality of screws 56.
In Figure 3, top centre panel 50 and front and rear top
panels 52 and 54 have been removed showing the internal
configuration of chassis 12. Chassis 12 has forward compartment 60,
central compartment 62 and rearward compartment 64 (see also Figure
4). These compartments define sufficient storage space for the
electronic motor controls for base 10 as well as the batteries to power
the motor for base 10. For example, in the preferred embodiment, two
batteries 66 may be positioned in forward compartment 60 and two
battery 66 may be positioned in rearward compartment 64.
One advantage of the instant design is that each
compartment 60 and 64 is sufficiently large to accommodate two
currently available batteries which will providing ample power to the
motor for the drive wheels. It will be appreciated that the size and
configuration of the battery which is received in the compartment 60
and 64 may vary depending upon those available in the marketplace
and the power which is to be delivered to the motor drive of wheels 14.
It will be appreciated that as battery technology improves, an increase
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number of smaller batteries capable of delivering even more power
may be positioned in compartment 60 and 64.
It will be appreciated that each battery 66 is relatively
heavy. For example, a battery 66 may weigh in the order of 25 pounds.
Accordingly, each of forward compartments 60 and rearward
compartment 64 may provide a storage space for 50 pounds of battery.
Thus, the weight of the batteries may be equally divided between the
front end 20 of base 10 and rear end 22 of base 10.
Tractor 70, which is shown in Figure 5, is mounted in base
10 as shown in Figure 4. Accordingly, the drive wheels 14 are
positioned centrally on base 10 between front and rear ends 20 and 22
and effectively immediately below the person when seated in the chair
affixed to base 10.
In the preferred embodiment, tractor 70 has an upper
housing 72 comprising upper plate 74 and lower plate 76. Upper plate
74 may be secured to lower plate 76 by any means known in the art
such as screws 78 (see Figure 3). Upper housing 72 is used to secure
tractor 70 in central compartment 62. Accordingly, central
compartment 62 may be provided with two transversely extending
support members 80 onto which upper housing 72 may be secured by
any means known in the art, such as screws.
The support shaft for drive wheels 14 extends downwardly
from upper housing 72. Drive wheels 14 are mounted below housing
72 and biased so as to maintain their engagement with the ground
upon which base 10 is positioned. In the preferred embodiment,
wheels 14 are mounted on a telescoping shaft which is biased, such as
by a spring, to engaging the ground. It will be appreciated that other
suspension means for biasing wheels 14 into the ground engaging
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position shown in Figure 4 may be utilized, including, eg., biased struts
or suspension arms.
Drive wheels 14 are biased so as to receive a substantial
portion of the weight of an occupied chair when it is mounted onto
base 10. For example, the weight of base 10, including batteries, the
motor drive for wheels 14 and a chair mounted on base 10 may be in
the order of about 100 kilograms. A substantial portion of this weight
is supported by drive wheels 14. In the preferred embodiment, drive
wheels 14 may support 75% of this weight, preferably more than 85% of
this weight, more preferably than 90% of this weight, and most
preferably, about 95% of this weight. It will thus be seen that free
running wheels 16 do not support very much weight of an unoccupied
chair but are in engagement with the ground. When a person is seated
in the chair, due to the biasing member, the weight of the person will
be distributed, preferably evenly, amongst free running wheels 16. Due
to compression of the free running wheels, some this weight may be
supported by drive wheels 14. However, the amount of the weight of
the person which is supported by drive wheels 14 may be minimal (eg.
in the order of 5% to 10% or less). Any of this weight which is
supported by the drive wheels would be beneficial as it would increase
the traction between drive wells 14 and the ground.
A typical adult male may weigh in the order of 100 kg.
Accordingly, excluding mechanical losses, free running wheels 16 will
essentially support all of this weight while drive wheels 14 are
supporting essentially the entire weight of the unoccupied chair (also
about 100 kilograms). If the weight of the person is evenly distributed
amongst the four free running wheels 16, then the forward pair of free
running wheels 16 and the rearward pair of free running wheels 16
will each support approximately 50 kg. while the centre drive wheel
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will support approximately 100 kg. Thus, about 25% of the weight of
the loaded wheelchair will be supported by each of the forward and
rearward pairs of free running wheels 16 and 50% of the weight of the
loaded wheelchair will be supported by drive wheels 14.
This configuration has particular advantages. First, the
weight which is supported by drive wheels 14 ensure that they stay in
contact with the ground. As the surface which the base traverses varies
in height, the biasing member will allow drive wheels to retract
upwardly or extend downwardly so as to follow the profile of the
ground. Thus the dynamic stability of the chair is improved, even
when in motion, since about half or more of the weight of a loaded
wheelchair is supported by centrally positioned drive wheels 14. This
provides substantial advantages, including increased traction by drive
wheels 14, when a wheelchair incorporating base 10 travels up or down
an inclined plane, such as a ramp for a handicapped person.
Further, in a typical wheelchair, approximately 40% to 60%
of the weight of a loaded wheelchair is supported by the front pair of
wheels. With the design of the instant invention, only about 25% of
the weight of a loaded wheelchair is supported by the front pair of
wheels (or less if the individual is lighter, such as an adult female who
may weigh 50 to 60 kg.). Thus, despite the fact that the forward pair of
free running wheels 16 are fixed in position relative to bottom 30 of
base 10, this allows the forward pair of free running wheels 16 to move
upwardly so as to roll over bumps and low curbs, such as those at the
beginning of a ramp. The decreased amount of weight being supported
by wheels 16 compared to a the same wheels on a typical wheelchair
allows a wheelchair incorporating base 10 to more easily pass over an
uneven terrain.
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A further advantage is that, if the terrain is soft such as
grass, it is less likely that forward wheels 16 will plough into the
ground resulting in the wheel chair becoming stuck.
In the preferred embodiment, a central shaft mount 82 is
positioned below upper housing 72 (see Figures 4 - 6) for providing a
support member for receiving the members which permit the
telescoping vertical motion of drive wheels 14. Centrally positioned
within central shaft mount 82 is mount 86 for receiving spline bushing
84. Spline bushing 84 has a cental opening for receiving spline shaft 88.
The splines of bushing 84 are positioned so as to mate with splines
provided in shaft 88 so as to permit shaft 88 to move upwardly or
downwardly with respect to upper housing 72. In this manner, it will
be appreciated that shaft 88 is non-rotatably mounted in central shaft
mount 82. It will be apparent to those skilled in the art that other
mechanisms may be used to non-rotatably mount shaft 88 with respect
to mount 82. It will also be appreciated that in some embodiments, it
may be desirable to include a mechanism to permit shaft 88 to rotate
with respect to upper housing 72, such as is described in Fernie et al.
which is incorporated here and by reference.
Spring 90 is centrally positioned within spline shaft 88 so
as to bias drive wheels 14 to the ground engaging position. As shown
in Figure 4, spring 90 is positioned in hollow core 92 of spline shaft 88
and extends from bottom 94 of hollow core 92 upwardly so as to engage
the bottom surface of upper plate 74. This maintains tension in spring
90 and forces drive wheels 14 downwardly. It will be appreciated that if
spring 90 exerts too great a tensile force, drive wheels 14 will extend
downwardly below the plane defined by free running wheels 16 and
accordingly free running wheels 16 will not define a stable platform for
base 10. Accordingly, spring 90 exerts a sufficient tensile strength so
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that drive wheel 14 and free running wheel 16 engage the ground
while base 10 is stationary and, preferably, with only a minimal
amount of weight being supported by free running wheels 16.
Drive wheels 14 may be driven by any motor known in the
art. Referring to Figure 4, bottom 30 of chassis 12 has a recessed central
portion 100 so as to define a cavity 102 positioned below recess portion
100 within which the motor drive for drive wheel 14 may be received.
It will be appreciated that by extending opposed sides 24, 26, all or a
portion of the motor drive for wheels 14 may be included within
chassis 12.
Referring to Figure 5, spline shaft 88 is mounted on lower
shaft support 104. Preferably, each of drive wheels 14 is connected to
the motor so that they may independently rotate clockwise or counter
clockwise. Therefore, a motor 106 is preferably provided for each drive
wheel 14. Each motor 106 may be drivingly connected to a transfer case
108 which has an associated axle 110. Drive wheel 14 is non-rotatably
mounted on axle 110 so as to rotate with axle 110. Motors 106 may be
angled upwardly from the horizontal so as to be recessed in cavity 102.
Further, by angling motors 106 upwardly, the likelihood that motors
106 may be damaged by contact with the ground or surface debris is
reduced.
In order to permit both drive wheels to remain in contact
with the ground over various terrain, the drive wheels 14 are
preferably mounted to pivot in a plane transverse to the direction of
travel of base 10. As shown in Figure 5, shaft support 104 may be
pivotally mounted about shaft 88 by means of pivot 112. Thus, as base
10 travels over uneven terrain, one drive wheel 14 may move
upwardly while the other may move downwardly without any, or any
significant amount of, traction.
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It will be appreciated by those skilled in the art that varying
numbers of drive wheels 14 may be provided. Further, the two drive
wheels may be operated by a single motor 106, if desired, such that they
will always both rotate in the same direction. Further, base 10 may be
adapted for use with non-motorized drive wheels. In such an
embodiment, wheels 14 may be the regular drive wheels used on a
manually operated wheel chair. In such a case, no battery or motor for
the drive wheels is required. However, this design still provides a
stable base with mid wheel drive for improved manoeuvrability.
