Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
RECONFIGURABLE TILT WHEELCHAIR
FIELD OF THE INVENTION
This invention relates to wheelchairs. More particularly, the invention
relates to a
modular wheelchair assembly that is configurable to different tilt
configurations
and to features thereof.
BACKGROUND OF THE INVENTION
The designs of most wheelchairs are optimized to accommodate a particular
level of disability. Persons with low disability tend to use wheelchairs that
have
no seat tilt or a fixed seat tilt and a footrest assembly that easily
accommodates
self-propulsion using the occupant's feet.
Persons with moderate disability may prefer a wheelchair that allows for
optional
self-propulsion but that can be tilted to offer a range of seating angles.
Tilting the
zo seat provides pressure relief to the occupant, reduces discomfort
associated with
sitting for long periods of time, and provides passive correction for
deformities.
The ability to self propel using the feet may be preserved despite various
tilt
angles by providing the axis of rotation near the front of the seat such that
the
distance from the knees to the ground remains relatively constant. A
disadvantage of such a configuration is the force required in order to move
the
weight of the occupant about the axis of rotation. This is sometimes
compensated for by a pneumatic assist mechanism extending between the base
of the chair and the seat frame as described in commonly owned United States
Patent No. 6,447,064.
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High disability individuals typically require a wheelchair with deeper tilt
angles to
improve trunk stability and head control. Some such wheelchairs also use
mechanical actuators to accommodate the significant force sometimes required
to move the weight of the occupant through deep tilt angles. It is also known
in
the prior art to minimize the effort required to tilt the occupant by
providing a pivot
point as close as possible to his center of gravity. United States Patent No.
7,007,965 provides an example of such a system.
io While various tilt configurations may be suited to particular types or
levels of
disability, many individuals suffer from disabilities that progress over time.
Over
the course of such a disability, the occupant may graduate through 3-4
different
types of wheelchairs, each having different attributes. For example, a no-tilt
or
fixed tilt wheelchair may be used at the early onset of disability, a self-
propellable
tilting wheelchair can be used when the disability becomes moderate, and a
deep
tilt wheelchair can be used in the later stages of disability.
The present invention addresses the need for a reconfigurable modular
wheelchair that is capable of being selectively configured in a fixed tilt
configuration, a dynamic tilt-in-space configuration with the axis of rotation
near
the occupant's knees, or a dynamic tilt-in-space configuration with the axis
of
rotation near the occupant's center of gravity, as required to accommodate the
evolving needs of the occupant.
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SUMMARY OF THE INVENTION
The wheelchair according to the invention comprises a base frame, a seat
frame,
and interchangeable interface components adapted to assemble the base frame
and seat frame to one another according to either a fixed tilt configuration,
a
dynamic tilt-in-space configuration with the axis of rotation near the front
of the
seat, or a dynamic tilt-in-space configuration with the axis of rotation near
the
center of gravity of the occupant.
In a first configuration, the wheelchair comprises a base frame assembly
pivotally
connected to a seat frame assembly about cooperating pivot elements at a pivot
point located near the knees of the occupant. A support assembly extends
between a base crossbar assembly and a seat crossbar assembly. The support
assembly comprises a bracket removably attached to one of such crossbar
assemblies, and an interface element attached between the brace and the other
one of such crossbar assemblies. The interface element includes a plurality of
attachment points arrayed to share a constant radius in relation to the pivot
point.
The selection of the attachment point allows the base frame and the seat frame
assemblies to be assembled at a variety of fixed tilt angles to thereby
provide
adjustable static positioning for the user requiring minimal support and
correction.
In a second configuration, the wheelchair again provides a pivot point near
the
knees of the occupant through cooperating pivot elements on the base frame and
seat frame assemblies. A support assembly extending between the base
crossbar assembly and the seat crossbar assembly comprises a bracket and a
bias mechanism such as a gas strut to enable the occupant to be lifted from a
low tilt angle more easily than would be the case without the mechanism. In
one
aspect, the pneumatic mechanism includes a bell crank arrangement to convert
the longitudinal force from the gas strut to an upward force to lift the seat
frame
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and modulate the degree of resistance provided at different tilt angles as the
centre of gravity of the occupant moves forward or rearward and to translate.
In a third configuration, the chair may be tilted about an axis that
approximately
coincides with the centre of gravity of the occupant. The tilting is provided
by
suspending the seat frame from an axis of rotation supported on the base
frame.
This configuration has the advantage of making it very easy to tilt the
wheelchair
and obviates the need for pneumatic mechanisms or actuators.
The invention is also directed to a drive wheel system wherein the wheel lock
assembly and the anti-tip assembly are connected to the axle mounting plate
such that the change of drive wheel position on the base frame does not
require
consequent adjustment of the lock and anti-tip assemblies.
In yet a further aspect, the invention is directed to a telescoping crossbar
assembly comprising an outer sleeve having a base with a non-straight cross-
section, a hollow inner shaft having a base with a cross-section conforming to
said non-straight cross-section, and a pair of aligned fastener holes in said
outer
sleeve, one of said fastener holes having a larger diameter than the other.
In yet a further aspect, the invention is directed to a mounting assembly for
securing fasteners to an elongated hollow member such as a side tube of a
wheelchair. The hollow member has a plurality of fastener apertures extending
longitudinally along the hollow member. An elongated insertion member is
adapted to be longitudinally inserted and retained in the hollow member. A
plurality of nuts are retained in several seats provided along the length of
the
insertion member such that when it is inserted and retained in the hollow
member
with the nuts aligned to the fastener apertures, fasteners inserted into the
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apertures will engage the nuts and be retained without the need to traverse
the
opposing wall of the hollow member.
In a further aspect, the wheelchair has a seat frame assembly comprising
opposed seat rails and at least one seat crossbar assembly extending between
them. A base frame assembly comprises opposed base rails and at least one
base crossbar assembly extending between the base rails. A forward portion of
the seat frame assembly and a forward portion of the base frame assembly is
adapted to receive opposed removable pivot assemblies to pivot the seat frame
io assembly in relation to the base frame assembly. The seat and base crossbar
assemblies are adapted to removably receive a support assembly extending
between them. A forward portion of each of the seat rails is adapted to
selectively attach a pivot member thereto and a rearward portion of each of
the
base rails is adapted to receive a removable pivot arm thereon enabling
reconfiguration of the wheelchair between a pivot point near the user's knees
and
a center of gravity pivot point.
In another aspect, a fixed tilt wheelchair comprises a seat frame assembly and
a
base frame assembly. A first pivot element is removably attached to a forward
portion of the seat frame assembly. A second pivot element is removably
attached to a forward portion of the base frame assembly and the first and
second removable pivot elements, when installed, cooperate to define a pivot
point between them. A removable support assembly is connected between the
seat frame assembly and the base frame assembly, the support assembly being
configurable to define any one of a plurality of predetermined relative pivot
angles between the seat frame and base frame assemblies.
Another aspect of the invention relates to a mounting assembly for an
elongated
hollow member. An elongated hollow member has a plurality of fastener
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apertures extending transversely of the hollow member. An elongated insertion
member is adapted to be longitudinally inserted and retained in the elongated
hollow member, the insertion member having a plurality of seats for retaining
nuts therein. A plurality of nuts are seated in the seats and the insertion
member
is inserted into the hollow member to align said nuts with the fastener
apertures.
In another aspect a dynamically tiltable wheelchair comprises a seat frame
assembly, a base frame assembly, a first pivot element removably attached to a
forward portion of the seat frame assembly and a second pivot element
removably attached to a forward portion of the base frame assembly. The first
and second removable pivot elements, when installed, cooperate to define a
pivot point between them, said first and second pivot elements being
operatively
secured to one another. A removable support assembly is connected between
the seat frame assembly and the base frame assembly, the support assembly
comprising bias means between the seat frame assembly and the base frame
assembly.
In another aspect the bias means comprises an extendible element one end of
which is pivotally secured to a bell crank, and said bell crank is retained in
operative relationship to said base frame assembly.
In another aspect, a dynamically tiltable wheelchair comprises a seat frame
assembly having opposed seat rails and a base frame assembly having opposed
base rails. A pivot arm is removably secured to a rearward portion of each of
the
base rails, said pivot arm extending upwards above said seat frame assembly. A
hanger member is removably secured to a rearward portion of each of the seat
rails and extends upwardly. The pivot arm and the hanger member cooperate to
define a pivot point near the expected center of gravity of a wheelchair
occupant
for pivoting the seat frame assembly in relation to the base frame assembly.
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In a method according to the invention, the wheelchair may be reconfigured
from
a fixed tilt configuration to a dynamically tiltable configuration. By
removing from
the fixed tilt configuration an element that renders a removable support
assembly
configurable to any one of a plurality of predetermined relative pivot angles
between the seat frame and the base frame. A biasing mechanism is also
installed that provides a mechanical advantage in tilting the seat frame in
relation
to the base frame.
In another method according to the invention, the wheelchair is reconfigurable
from a first dynamically tiltable configuration where the pivot axis is near
the front
of the wheelchair to a second dynamically tiltable configuration where the
tilt axis
is near the expected center of gravity of an occupant. The first dynamically
tiltable configuration comprises a seat frame, a base frame, a removable
forward
pivot assembly pivotally attaching the forward portion of the seat frame to
the
forward portion of the base frame and a removable support assembly connected
between the seat frame and the base frame, the support assembly comprising a
biasing mechanism that provides a mechanical advantage in tilting the seat
frame in relation to the base frame. The reconfiguration is accomplished by
disengaging the forward pivot assembly and installing a center of gravity
pivot
assembly comprising a pivot point near the expected center of gravity of a
seated
occupant.
In another aspect, the invention comprises a kit for a reconfigurable
wheelchair
system comprising a seat frame assembly, a base frame assembly and a
plurality of alternative support assemblies for supporting the seat frame
assembly
on the base frame assembly.
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In an aspect of the invention relating to the crossbar assembly, there is
provided
a telescoping crossbar assembly for rigidly extending between structural
elements at selectable degrees of extension comprising a hollow outer tube, an
inner tube slidably receivable in the outer tube, the inner tube and the outer
tube
having generally corresponding cross-sectional shapes. A plurality of
fasteners
extend through the outer tube and the inner tube, each of the fasteners having
a
body portion and a head portion larger than the body portion, and wherein the
head portion bears on the inner tube through an aperture in the outer tube.
In yet another aspect, the invention is a drive wheel assembly for a
wheelchair
comprising a mounting element adapted to be adjustably secured to a
component of a base frame in one of a plurality of alternative positions. A
wheel
mountable on the mounting element and an elongated member having a wheel
lock assembly mounted thereon is attached to the mounting element.
Adjustment of the mounting element in relation to the base frame maintains the
position of the wheel lock assembly in relation to the wheel without requiring
separate adjustment thereof.
In a further aspect of the invention, there is provided a crossbar mounting
system
zo for the crossbar between opposed rails. The crossbar has a substantially
hollow
tube having opposed apertures therein and the rail has at least one aperture
extending therethrough. An insert is adapted to be inserted through said
opposed apertures, said insert having at least one aperture adapted to receive
a
fastener extending through said aperture and said rail for securing said
crossbar
to the rail.
In one of its aspects, the invention is a wheelchair having a base frame
assembly
comprising opposed base rails and at least one base crossbar assembly
extending between the base rails. Each of the base rails comprises a
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longitudinal recess in a rearward portion of the base rail and a plurality of
spaced
apertures along the longitudinal recess extending transversely of the base
rail.
In a more particular aspect, the base crossbar assembly includes an aperture
for
receiving a fastener for removable attachment of a brace assembly thereto.
In a different particular aspect, the longitudinal recess is adapted to
receive a
plurality of caps. In a more particular aspect, the longitudinal recess
comprises
at least one groove into which the caps may be inserted.
In a different particular aspect, the apertures are adapted to receive one or
more
fasteners.
In another different particular aspect, the wheelchair further comprises a
drive
wheel assembly, and the drive wheel assembly is mountable on the base frame
assembly.
In another different particular aspect, the wheelchair of claim 1 further
comprises
an axle plate that is mountable on the frame assembly.
In another aspect, the invention is a dynamically tiltable wheelchair
comprising a
seat frame assembly comprising opposed seat rails and at least one seat
crossbar assembly extending between the seat rails. A base frame assembly
comprises opposed base rails and at least one base crossbar assembly
extending between the base rails. A forward portion of the seat frame assembly
and a forward portion of the base frame assembly are adapted to receive
opposed removable pivot assemblies extending between the seat frame
assembly and the base frame assembly for pivoting of the seat frame assembly
in relation to the base frame assembly about a pivot defined by the pivot
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assembly. The seat and base crossbar assemblies are adapted to removably
receive a support assembly extending between them. Each of the opposed base
rails comprises a longitudinal recess in a rearward portion of the base rail
and a
plurality of spaced apertures along the longitudinal recess.
In a more particular aspect, the wheelchair further comprises a pivot element
removably mounted on the base frame assembly, and a lock assembly pivotally
attached to the pivot element at one end,
The foregoing was intended as a broad summary only and of only some of the
aspects of the invention. It was not intended to define the limits or
requirements
of the invention. Other aspects of the invention will be appreciated by
reference
to the detailed description of the preferred embodiment and to the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The preferred embodiment of the invention will be described by reference to
the
drawings thereof in which:
Fig. 1 is a front perspective view of the IF configuration of the wheelchair
of the
preferred embodiment;
Fig. 2a is a side elevation of the TF configuration at a neutral (horizontal)
tilt
angle;
Fig. 2b is a side elevation of the IF configuration at a different tilt angle
than in
Fig. 2a;
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Fig. 3 is a bottom rear perspective view of the TF configuration;
Fig. 4 is a front perspective view of the 120 configuration;
Fig. 5a is a side elevation of the T20 configuration at a neutral (horizontal)
tilt
angle;
Fig. 5b is a side elevation of the T20 configuration at a different tilt angle
than in
Fig. 5a;
Fig. 6 is a front perspective view of the 150 configuration;
Fig. 7a is a side elevation of the 150 configuration at a neutral (horizontal)
tilt
angle;
Fig. 7b is a side elevation of the T50 configuration at a different tilt angle
than in
Fig. 7a;
Fig. 8 is a perspective view of the base frame, seat frame, support and pivot
assemblies of the TF configuration;
Fig. 8a is a perspective view of the base frame assembly of the TF
configuration,
with the interface mount secured to the rear base crossbar assembly;
Fig. 9 is a perspective view of the base frame, seat frame, support and pivot
assemblies of the T20 configuration;
Fig. 9a is a partially sectioned side view of the support assembly of the 120
configuration;
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Fig. 10 is a perspective view of the base frame, seat frame, support and pivot
assemblies of the T50 configuration;
Fig. 10a is a top perspective view of the base frame assembly of the T50
configuration, including the pivot arms mounted thereon;
Fig. 10b is a partially sectioned, top perspective view of the support (lock)
assembly for the T50 configuration;
Fig. 11 is a perspective view of a pivot support;
Fig. 12 is a side elevation of a pivot support;
Fig. 13 is a perspective view of a bracket used in the 120 and 150
configurations;
Fig. 14 is an exploded view showing the crossbar assembly and the mounting of
the crossbar on a rail;
Fig. 15 is a bottom perspective view of the seat frame, pivot and support
assemblies for the T50 configuration, using transit tie-down brackets;
Fig. 16 is an exploded view of the pivot assembly in relation to the base and
seat
frame assemblies in the 150 configuration;
Fig. 17 is a cross-sectional view of the crossbar assembly according to the
preferred embodiment;
Fig.18 is a partially sectioned view of the inner tube of the crossbar
assembly;
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Fig. 19 is a perspective view of a transit tie-down bracket;
Fig. 20 is side and end elevations of the transit tie-down bracket;
Fig. 21 is a side elevation of a rear crossbar mount;
Fig. 22 is a partially exploded view of rear base rail mounting system;
Fig. 23 is an exploded view of the rear (drive) wheel mounting assembly;
Fig. 24 is a partially sectioned view of the rear wheel mounting assembly;
Fig. 25 is a partially sectioned view of the rear wheel mounting assembly,
including the wheel lock assembly;
Fig. 26 is an exploded view of back cane mounting assembly for the IF and T20
configuration; and,
zo Fig. 27 is a side elevation of a pivot hanger bracket.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figs. 1, 2a, 2b and 3 illustrate the preferred embodiment of the fixed tilt
configuration of the wheelchair according to the invention, which in this
disclosure will be referred to as the "TF" configuration. In TF configuration,
the
wheelchair is set at one of several possible angles of tilt about a pivot axis
10
near the knees of the occupant. Figs. 2a and 2b illustrate two alternative
fixed tilt
angles for the TF configuration.
Figs. 4, 5a and 5b illustrate the preferred embodiment of the dynamic tilt-in-
space
configuration of the wheelchair, in which the axis of rotation 12 is provided
near
the front of the seat frame assembly 14. The preferred embodiment of this
configuration is designed to ensure that the front of the occupant's knees
move
upward only a very small amount as the chair undergoes a full range of tilt of
up
to 20 degrees. In this disclosure, this configuration will be referred to as
the
"T20" configuration. Figs. 5a and 5b illustrate two different degrees of tilt
for the
T20 configuration.
Figs. 6, 7a and 7b illustrate the preferred embodiment of the dynamic tilt-in-
space
configuration of the wheelchair, in which the axis of rotation 16 is provided
near
the center of gravity of the occupant. The preferred embodiment of this
configuration is designed for tilt angles of up to 50 degrees. In this
disclosure,
that configuration will be referred to as the "150" configuration. Figs 7a and
7b
illustrate two different degrees of tilt for the 150 configuration
Each of the TF, T20 and T50 configurations is built around a set of sub-
assemblies that is common to each of the configurations, and that are adapted
to
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receive interchangeable components to modify the wheelchair to the desired
configuration.
The principal sub-assemblies that are modified to effect a change in the
configuration of the wheelchair are the support assemblies for providing load-
bearing support between the base frame assembly and the seat frame assembly
(or to lock the seat frame against pivoting), and the pivot assemblies that
provide
a pivot connection between the base frame assembly to the seat frame assembly.
Figs. 8, 9 and 10 illustrate the base frame and seat frame assemblies for the
IF,
120 and T50 configurations respectively, including their associated support
and
pivot assemblies.
TF Configuration
Referring to Fig. 8, a seat frame consists of an assembly 18 comprising a left
and
right seat rails 20, 22 joined by front and rear seat crossbar assemblies 24,
26. A
base frame consists of an assembly 28 comprising left and right base rails 30,
32
joined by front and rear base crossbar assemblies 34, 36. In the IF
configuration, seat frame assembly 18 is set in pivoted relation to the base
frame
assembly 28 about opposed pivot points (only pivot point 38 is visible in Fig.
8)
located near the front of the left and right seat rails 20, 22. The pivot
points are
located between 1 5/8 and 6 5/8 inches from the forward edge of a seat pan
that
is secured, as intended, to the seat crossbar assemblies 24, 26. The pivot
assembly in the IF configuration generally comprises two pivot elements that
cooperate to define pivot point 38 between them: pivot supports 40 and pivot
hanger brackets 42.
The support assembly 44 for the TF configuration is attached between the front
and rear seat crossbar assemblies 24, 26 and the rear base crossbar assembly
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36. Support assembly 44 comprises brace bracket 46 and an interface mount
element 48. Different degrees of relative tilt between the seat frame and base
frame are achieved by connecting the lower end of brace bracket 46 to one of
several attachment points 50 on interface mount 48 that is in turn removably
attached to the inner tube 52 of the rear base crossbar assembly 36. The
attachment points comprise apertures 50 arrayed at different angular positions
along an arc of constant radius in relation to the pivot points 38. Inner tube
52 of
the rear base crossbar assembly 36 includes a centrally located aperture 54 to
receive a removable fastener 56 for attachment of the interface mount 48
thereto.
A better view of the interface mount 48 is provided in Fig. 8a.
Referring to the pivot assembly, the pivot support 40 is illustrated in detail
in Figs.
11 and 12. Pivot support 40 consists of a seating block one surface 58 of
which
is shaped to conform to the inside of a seat rail, and further including a
downwardly extending tab 60 having a pivot pin hole 62 therethrough to receive
a
pivot pin. Seating block 40 includes two spaced apertures 64, 66 for receiving
fasteners that are used to secure the front seat crossbar assembly 24 to the
rail
as will be discussed in more detail below.
Referring to Figs. 8 and 27, the pivot hanger bracket 42 similarly includes a
pivot
pin hole to receive a pivot pin at pivot point 38. Pivot hanger bracket 42
also has
a base 72 through which extend two apertures for receiving fasteners 74, 76
used to attach the lower end of the bracket to the front base crossbar
assembly
34. The pivot hanger bracket 42 is preferably provided with an oblong aperture
78 in the body thereof so as to be used as a transit tie-down bracket for
optional
use in securing the wheelchair to tie-down stations in vehicles. Referring to
Fig.
9, the pivot hanger bracket 42 has a portion thereof that is shaped to mate
with a
shoulder provided in a partial sleeve 80 that is welded to the front portion
of each
rail.
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T20 Configuration
Fig. 9 illustrates the base frame, seat frame, support and pivot assemblies
for the
T20 configuration. As in the case of the TF configuration, the seat frame
assembly 18 and the base frame assembly 28 are connected at pivot points 38
by means of pivot supports 40 mounted to the left and right seat rails 20, 22
and
pivot hanger brackets 42 mounted to the left and right base rails 30, 32. The
pivot supports and pivot hanger brackets of the TF and T20 configurations are
identical.
The 120 configuration uses a different support assembly than does the TF
configuration. Referring to Figs. 9 and 9A, the 120 support assembly 106
comprises a bracket 108 attached to the front and rear seat crossbar
assemblies
and to the rear base crossbar assembly by means of a bell crank 110 pivotally
mounted to the inner tube 52 of the rear base crossbar assembly. The bell
crank
serves to modulate the degree of resistance provided at different tilt angles
and
to accommodate the change in spatial relationship between the bracket and the
base frame as the seat frame is tilted.
Referring to Fig. 9, 9a and 13, bracket 108 has spaced shoulders 114, 116. The
front 118 of the bracket includes a bridge 120 extending between the shoulders
114, 116. Bridge 118 has a fastener aperture for attachment of one end of a
gas
strut 120 that is mounted between the shoulders of the bracket. One end of gas
strut 120 is secured to bridge 118 by means of a shoulder bolt while the other
end is attached to another shoulder bolt 122 extending through the medial
portion of the bell crank 110. A trigger 124 is provided to control the gas
strut.
Because the gas strut is connected to the center of the bell crank, a pivoting
of
the base frame 84 in relation to the seat frame 82 will also cause a
translation of
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the lower end of the bell crank in relation to the vertical plane. Such
translation is
accommodated by connecting the lower end of the bell crank to a slide 126
mounted on a guide tang 128 that is attached to the inner tube 112 of the rear
base crossbar assembly by means of a fastener threaded through a suitable
aperture in the inner tube 112.
T50 Confiquration
Fig. 10 illustrates the base frame, seat frame, support (lock) and pivot
io assemblies for the T50 configuration. In the T50 configuration, the forward
pivot
point that was a feature of the TF and T20 configurations is not present and
the
pivot hanger brackets are not used. The pivot supports on the seat rails may
be
replaced by transit tie-down brackets 132 (see Fig. 15) according to whether
the
wheelchair is intended to be attachable to tie-downs on public and private
transit
vehicles. The transit tie-down brackets also double as crossbar mounting
elements. The pivot hanger brackets that would normally be seated in partial
sleeve 80 on the base rails are replaced by filler blocks 134.
Referring to Figs. 10 and 10A, the pivot assembly for the T50 configuration
comprises a pivot arm 136 extending up from each of left and right base rails
30,
32 to a height 142 above the seat pan. In the preferred embodiment, apart from
being secured to the rails, each pivot arm is also braced by attachment to the
rear base crossbar assembly 144. The seat frame assembly is supported about
pivot pins 146 at the upper end of the pivot arms by means of opposed pivot
hanger plates 148 that are attached to the left and right seat rails 20, 22
and that
are pivotally suspended from the pivot pins 146.
The pivot arm 136 comprises a base 154 having a surface 157 conforming to the
rear of the base rail (see Fig. 10). Apertures 156 are provided in the base
154 to
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enable the base to be secured by fasteners to selected apertures 158 in a
longitudinal recess 160 formed in the rear portion of the base rails.
Vertically
spaced apertures 162 are adapted to secure the pivot arm 136 to the rear base
crossbar assembly 144. In the preferred embodiment, the pivot arm 136
extends generally upward to a forwardly extending elbow 164 to avoid
interfering
with the hardware used to secure the seat frame, then upwards to the pivot
point
146.
Pivot pin 146 extends through the pivot arm 136 and through the pivot aperture
of the pivot hanger plate 148.
The height of the pivot point 146 is selected by reference to the expected
center
of gravity of the occupant, as calculated using publicly available anatomical
data.
In the preferred embodiment, the height of this point is about 6.75 inches
(171.4mm) above the seat pan. Such height has been selected by accounting
for a typical seat cushion of about 2" in thickness and an anatomically
typical
occupant.
The precise location in the horizontal plane of the center of gravity of a
occupant
tends to vary more than does its location in the vertical plane. The invention
accommodates such variation by providing means to adjust the horizontal
position of the back rest and of the seat pan in the fore and aft directions.
This
allows the occupant or installer to optimize the coincidence of the pivot
point 146
with the center of gravity of the occupant. A matrix of apertures 166 (see
Fig. 6)
is provided along the edge of the seat pan 168 allowing the seat pan to be
located at different fore and aft positions in relation to the seat frame
assembly.
The pivot arm 136 is also adapted to be set at various fore and aft positions
on
the base rails, for example to change the wheel base load distribution and to
clear interference of the front rigging and front casters.
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Referring to Fig. 16, the pivot hanger plate 148 has a broad base 170 that
tapers
to a pivot aperture 172 in the top of the plate forming a generally triangular
shape
that can also serve as a guard to prevent the occupant's clothing from coming
into contact with the rear wheel. The base 170 of the pivot hanger plate
includes
a bottom portion 174 that conforms to the top surface of the rail 20, and a
downwardly extending flange 178 shaped to abut the outside of the rail. The
flange 178 includes a plurality of apertures 180 the rearmost five of which
are
used to receive fasteners for releasably securing the back cane mounting to
the
pivot hanger plate 148 and the rail 20. Two of the apertures are to receive
fasteners extending through the hanger plate 148, the rail 20, the transit tie-
down
bracket 184 (for tansit-ready chairs only) and a threaded insert 186 (see Fig.
14)
extending laterally through the sleeve tube 188 of the rear crossbar assembly.
A
tab 190 extends downward from the center of the flange and is securable to the
transit tie-down bracket by means of a fastener.
A plurality of cane mounting apertures are provided at the rear of the pivot
hanger plate including three sets of apertures 192 arranged in diverging arcs.
The apertures are used to mount a back cane at various angles and positions in
relation to both the rail 20 and the pivot hanger plate 148.
Referring again to Fig. 10, the support assembly for the T50 configuration
comprises the same bracket 108 as in the 120 configuration, as well as an
extendible lock rod 193 attached between the rear ends 194 of the shoulders of
the bracket. The rear end of the lock rod is pivotally attached to a rod mount
196
attached to the inner tube 52 of the base crossbar assembly. A trigger 200 is
provided to selectively lock the rod against retraction or extension to
prevent
rocking of the seat frame about the pivot points.
20
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Crossbar assemblies
In order to provide adjustability in the width of the wheelchair, each of the
seat
and base crossbar assemblies are telescope assemblies in which an inner tube
52 is received within opposed sleeve tubes 188 as may appreciated by reference
to Figs. 14, 17 and 18. The inner and sleeve tubes have generally
corresponding
cross-sectional shapes and dimensions to facilitate the telescoping function.
Inner tube 52 is hollow save for a series of ribs 189 extending along the
central
longitudinal axis of the tube. A series of apertures 204 adapted to receive
fasteners 206 are located between the ribs. The ribs provide rigidity against
deformation when the inner and sleeve tubes are brought into engagement with
one another by means of head screws 206 extending through selected ones of
the apertures 208 and corresponding apertures in the sleeve tube.
A feature of the invention is the means by which the crossbar assemblies may
be
secured in a given telescoped position with a high degree of rigidity. Rather
than
the head of a fastener bearing on one side of the sleeve tube and a nut
bearing
on its opposite side, the invention provides apertures 208 in the top wall 210
of
the sleeve tube 188 that are larger than the opposed aligned apertures in the
bottom wall (not visible) of the sleeve tube. Apertures 208 are sufficiently
large
that the head of the fastener bears directly on the top wall 212 of the inner
tube
52. This allows the inner tube 52 to bear against the inner bottom surface 214
of
the sleeve tube thereby providing a great deal of friction against relative
displacement.
In addition, the inner tube shape and dimensions are selected to accommodate a
small degree of elastic deformation of the inner tube to further lock the
inner tube
against the sleeve tube when the positioning fasteners are tightened. In the
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preferred embodiment, this is accomplished by providing non-flat mating bottom
walls 216, 218 of the inner and sleeve tubes respectively such that any
deformation of the inner tube will result in several points and angles of
contact
between them. In the preferred embodiment such non-flat portions comprises
opposed, spaced protuberances 220, 222.
In order to accommodate the elastic deformation of the inner tube, a small
dimensional gap 224 or tolerance is provided between the inner and sleeve tube
contact surfaces. It will be appreciated that the extent of the gap is
selected
according to the elastic range of the inner tube but it should not be so large
as to
allow plastic deformation to occur. The telescoping joint mechanism ensures
that
the joint stays tight even with continuous variations in loading (fatigue).
Plastic
deformation of the inner tube would compromise the joint integrity and allow
the
joint to become loose over time.
Crossbar Mounting
Referring to Fig. 14, each seat crossbar assembly is secured to each rail by a
mounting element 130 that interfaces between the rail 226 and the sleeve tube
188 of the crossbar assembly and by fasteners 228 that extend through the rail
and the mounting element 130 to engage an insert 186 seated laterally through
the sleeve tube.
The front seat crossbar mounting elements for all configurations are the pivot
supports 40 (see also Fig. 8). One side of each mounting element conforms
(Fig.
12) to the inside of a rail 226, and the opposite side is shaped to engage the
outer end of the sleeve tube 188. Two apertures 230 are provided in the
mounting element and are spaced to correspond to the spacing of two mounting
holes 232 in the rail so that fasteners 228 may be received through the rail
and
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through the mounting element. The fasteners engage insert 186 that extends
laterally through the hollow inside of the sleeve tube.
The mounting elements for the rear seat crossbar assemblies for all
configurations consist of either a simple mounting element 130 as in Fig. 14
or a
transit tie-down bracket 132, best illustrated in Figs. 19 and 20 that conform
on
one side to the inside of the rail and are configured on the other side to
engage
the end of the crossbar assembly.
In the case of the base crossbar assemblies, securement to the rails is by
means
of components that conform to a part of the rail and that include a shaped
surface to receive and secure the end of the crossbar assembly by means of
fasteners. In the case of the TF and T20 configurations, the front base
crossbar
assembly abuts partial sleeve 80 and the rear base crossbar assembly abuts
rear crossbar mount 81. Rear crossbar mount 81 is shaped to conform to the
outside and top of the rear portion of the rail, including recess 160 as seen
in Fig.
21. Rear crossbar mount 81 also has a flat surface 83 for receiving and
securing
the end of the crossbar assembly. The rear base crossbar assembly is oriented
such that its transverse breadth lies in the vertical plane. This allows
attachment
of the interface mount 48 (Fig. 8), the slider assembly 126, 128 (Fig. 9) or
the
Mechlok rod mount 196 (Fig. 10), as the case may be, to be attached to the
inner
tube by a fastener through an aperture traversing the width of the inner tube.
Referring to Fig. 10, in the case of the T50 configuration, the front base
crossbar
assembly is seated against a shaped surface in a partial sleeve-like forward
crossbar mount 80 that conforms to part of the front of the base rail and that
has
a shaped surface adapted to receive and secure the end of the crossbar
assembly. The rear base crossbar assembly of the T50 configuration is located
in
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a shaped surface provided on the inside of the base of the pivot arm 136 and
is
secured by two screws 162.
Base Rail Mounting System
Referring to Fig. 22, the invention provides adjustability of the wheel base
as well
as the location of the pivot point in the horizontal plane for the T50
configuration
by a longitudinal recess 160 journaled in the rear portion of each base rail.
A
plurality of aligned apertures 234 along the interior of the recess receive
fasteners 236 that are used to secure the rear (drive) wheel axle mounting
plate
238, crossbar mounts or the base of the pivot arms as the case may be. The
relative front to back position of those components can be adjusted by
selecting
the appropriate apertures. The edges of the channel include grooves 240
adapted to receive clip-on masking caps 242 (see for example Fig. 5a) to
provide
an aesthetic cover for those portions of the channel that are not otherwise
covered by one of the foregoing components.
A mounting assembly is provided for securing the fasteners within the hollow
interior of the rail. An elongated rod 244 is adapted to be longitudinally
inserted
and retained in the hollow rail 32. A plurality of nuts 246 are retained in
several
spaced seats 248 provided along the length of the rod such that when it is
inserted and retained in the rail with the nuts aligned to the fastener
apertures
234, fasteners 236 inserted into the apertures will engage the nuts and be
retained without the need to traverse the opposing wall of the rail. This
arrangement also avoids potential problems that might arise from securing the
fasteners directly to the rail itself. As the rail and the fasteners may be of
different materials, the potential for reaction between them is reduced by the
invention.
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The forward ends of the rails terminate in a caster clamp for retaining a
standard
caster assembly. The forward ends of the seat rails terminate in a front
rigging
hanger with an insertion tube adapted to telescope a selected depth into the
front
end of the rail and a vertically oriented sleeve adapted to receive a standard
footrest assembly.
Drive/Wheel Assembly
The rear (drive) wheel assembly is illustrated in Figs. 23, 24 and 25. The
wheel
assembly includes an axle mounting plate 250 secured to the base rail 30 and
means to mount each of the wheel, the wheel lock assembly and the anti-tip
assembly directly onto the axle mount. This allows the position of the wheel
on
the frame to be adjusted by changing the location of the axle mounting plate,
rather than needing to separately adjust an anti-tip assembly 254, an axle
mounting plate and a wheel lock assembly 256.
The axle mounting plate 250 has a base 258 with an inner dimension
corresponding to the outer shape of the rail including the recess, and an
extension 260 having a plurality of aligned vertical positioning apertures 262
for
receiving a rear wheel axle receiver 264 in any one of several vertical
positions.
The axle mounting plate 250 is secured to the rail by fasteners 266 extending
through apertures in the base of the axle mounting plate and through apertures
provided in the recess 160 (see Fig. 22).
The axle receiver 264 is inserted through a selected one of the vertically
aligned
apertures 262 according to the preferred ground clearance for the base frame
of
the wheelchair. A wheel lock tube 268 is secured between the rear wheel 270
and the axle mounting plate 250 by means of a mounting piece 272 that is
adapted to provide a secure mating seat 274 for the side of the axle mount. A
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clearance aperture 276 through the mounting piece 272 provides a passageway
for the axle receiver. The end of the axle receiver is threaded so as to
receive a
nut 278 used to tighten the wheel lock tube (through the mounting piece) to
the
axle mount. The axle 280 is inserted through the nut and the mounting piece
272
and into the hollow interior of axle receiver 264. The end of axle 280
includes
retainers 282 that project out of the end of axle receiver to hold the axle
therein.
Retainers 282 are biased and may be manually depressed to allow the axle to be
disengaged from the axle receiver. Upon doing so, removal of the nut is all
that
.1 o is required in order to remove the axle receiver 264 and mounting piece
272 so
as to be able to reposition the axle receiver into a different vertical
positioning
aperture 262.
The invention provides a simple means of repositioning the height of the rear
wheel 270 in relation to the base frame with a minimum of tools and effort. In
addition, since the anti-tip assembly 254 and the wheel lock assembly 256 are
both mounted on the wheel lock tube 268 which in turn is mounted to the axle
mounting plate, it is possible to adjust the horizontal position of the rear
wheel on
the base rail by repositioning the axle mount without the need to separately
readjust the anti-tip assembly or the wheel lock assembly.
Back Cane Mounting
A back cane assembly illustrated in Fig. 26. The assembly is adapted to be
mounted in various angular and fore and aft positions by providing a back
plate
286 having plurality of suitable apertures to accommodate different
orientations
and positions of the cane 290. Back plate 286 is secured to the inside of the
seat
rail 18 by means of two fasteners 296 on the inside of the back cane. A number
of fore and aft positions can be selected using a plurality of apertures 298
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provided on the rail. The cane is then secured to the back plate by a pivot
fastener 300 and by a second fastener 302 inserted through one of several
apertures 288 provided in an arc about the pivot fastener 300, thereby
enabling
the cane to be mounted at different angles in relation to the rail.
In the TF and T20 configurations, a second back plate 302 is provided on the
outside of the rail and all fasteners extend through both the inside and
outside
back plates as shown in Fig. 26. In the case of the T50 configuration, the
outside
back plate 302 is omitted but the pivot hanger plate 148 (see Fig. 16) is
provided
with corresponding apertures and fulfills the same function as the outside
back
plate does in the TF and T20 configurations.
Converting from TF to T20 or 150
Reconfiguring a wheelchair from the IF fixed tilt configuration to a
dynamically
tiltable configuration (i.e. to either the 120 or the T50) is generally
accomplished
as follows.
The TF configuration comprises a support assembly (brace bracket 46 and
interface mount element 48, Fig. 3) connected between the seat frame assembly
18 and the base frame assembly 28 (Fig. 2B). The interface mount element 48 is
configurable by the selection of different attachment points 50 (Fig. 8A) to
define
any one of a plurality of predetermined relative pivot angles between the seat
frame and the base frame. When converting from the TF to the 120
configuration, the interface mount element 48 is first removed by removing
fasteners 56 and 57 (see Fig. 8). A bias mechanism is then installed to
provide a
mechanical advantage in tilting the seat frame in relation to the base frame,
thereby providing a dynamically tiltable wheelchair. In the case of the T20,
the
bias mechanism is the assembly consisting of gas strut 120, bell crank 110 and
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slide 126 as seen in Fig. 9. One end of gas strut 120 is secured to bell crank
110.
The other end of the gas strut is secured to the seat frame, or more
particularly to
a bracket 108 that is associated with the seat frame. Bell crank 110 is
secured
(through slide 126 and guide tang 128) to the same attachment point that
received fastener 56 in the TF configuration. In the case of the T50 the bias
mechanism is a linear locking device.
Converting from T20 to 150
The conversion from the T20 to the T50 configuration involves both a change of
the pivot assembly and of the support assembly.
In the T20, the pivot assembly consists of cooperating pivot elements, namely
pivot supports 40 and pivot hanger brackets 42, each of which is removably
attached to the chair by the same fasteners 68, 70 or fasteners 74,76 that
were
used in the TF configuration (see Fig. 8). In converting to a T50
configuration,
the pivot assembly of the T20 is removed by disengaging fasteners 68, 70, 74
and 76. A new centre of gravity pivot assembly is installed by mounting pivot
arms 136 on the base rails and mounting pivot hanger plates 148 to the seat
rails,
and pivotally connecting the pivot arms to the hanger plates by pivot pins
146, all
as seen in Fig. 10. The pivot arm is secured to the base rails by inserting
fasteners in apertures that extend to the pivot arm and into the base rails.
The
hanger plates are mounted by securing fasteners to the plate and into
apertures
in the seat rails. As seen in Fig. 6, if desired, a transit tie down bracket
132 can
be installed where the pivot hanger brackets would normally be attached in the
T20 configuration.
The preferred embodiment of the invention has been described in some detail.
However, those skilled in the art will appreciate that the scope of the claims
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should not be limited by the preferred embodiments set forth in the examples,
but
should be given the broadest interpretation consistent with the description as
a
whole, and that modifications to the constructional details of the embodiment
may be practiced within the scope of the claims that follow. The following
claims
are further to be considered part of the disclosure herein.
29
