Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: OFFICE CHAIR
FIELD OF THE INVENTION
This invention relates to office chairs. In particular, this invention
relates to chairs that can be used in work place environments, such as
offices,
by people with physical impairments wherein mobility is required to access
material or equipment at various locations and various heights.
BACKGROUND
Office chairs are known in the art. Typically, an office chair has a
wheeled base or a slide base. The seat of the chair is mounted on a
telescopic gas cylinder to permit the height of the seat to be adjusted. Such
chairs are not adapted for use by people with physical impairment to their
legs
since such a person may not be able to easily stand up and walk across an
office to work at a different !ocation or to obtain material required for
their
work.
Wheel chairs are also known in the art. A variety of designs are
known. In order for a wheel chair to provide a stable platform for a person
when sifting down in the wheel chair or standing up from a wheel chair, wheel
chairs typically have a!arge foot print. This makes them undesirable in many
work place environments.
U.S. Patent No. 3,953,054 (Udden et al.) discloses a hand
operated wheel-chair having a pair of main wheels rigidly connected to the
frame-work of the chair, at least one of which is either motor or hand
operated, two forwardly positioned castor wheels, and two rearwardly
positioned support wheels. The castor wheels and the support wheels are
mounted in different planes above the ground surface so that either the castor
wheels or the support wheels are in contact with the ground surface at any
one time. Therefore, the chair may rock forwards or rearwardly as the vertical
through the center of gravity is moved from one side to the other side of the
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main wheels. The wheel chair also comprises a seat that is mounted on a
central column. A jack is provided for adjusting the height of the seat.
One disadvantage of the wheel chair of Udden et al is that it
does not provide a stable seat as it may rock forwards and rearwardly. This
disadvantage is exacerbated when the seat is raised. In particular, when the
seat is raised, the centre of gravity of the chair and the occupant is raised.
As
the chair can rock forwardly and rearwardly about the main wheels, the raised
centre of gravity increases the likelihood the chair could tip over, thereby
posing an increased safety risk. In addition, the wheel chair of Udden et al
has a footrest that extends forwards of the forward caster wheels, thereby
increasing the size of the footprint of the chair and limiting its mobility in
an
office environment.
SUMMARY OF THE INVENTION
In accordance with the instant invention, an office chair is
provided with position adjustability features typically associated with office
chairs, and mobility features typically associated with wheel chairs, all in a
single seating apparatus. The office chair provides increased mobility in an
office environment and permits an employer to hire a disabled person without
having to purchase a desk designed for use with a wheel chair, and other
custom or disabled-specific office equipment, such as file cabinets wherein
all
the shelves are positioned such that a person can reach to pick up files while
seated at the normal seat height of a wheelchair. Accordingly, the employer is
more able to treat a disabled employee as a non-disabled employee and
move the disabled employee to different positions in an office with fewer
concerns. The disabled person can more easily be integrated in an office
having disabled and non-disabled employees, reducing barriers to
employment and improving morale and self-esteem of disabled persons.
An occupant may use this single seating apparatus to travel
between one or more workstations in an office which may be on different
levels requiring the occupant to travel up or down a ramp, or between home
and office, for example, and use the same seating apparatus to comfortably
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position himself or herself when working at any particular workstation for an
extended period of time. In particular, the chair preferably has a seat,
backrest
and, optionally arms, that may be any of those known in the office chair art
so
that an occupant may be seated comfortably for a normal work shift. This can
avoid or reduce the need for providing multiple chairs at respective locations
for a particular person, storing and/or transporting chairs, and making
difficult
(and often dangerous) transfers between chairs.
In accordance with one aspect of the instant invention, there is
provided an office chair comprising:
(a) a base comprising:
a pair of centrally positioned, laterally spaced apart drive
wheels, the drive wheels having a radius and a top portion;
at least one forward support wheel mounted at a fixed height;
at least one rearward support wheel pivotally mounted to the
office chair about a horizontal axis; and,
(b) a height adjustable seat mounted to the base and having a
front end.
In order to render an office accessible to a disabled person,
ramps are typically provided. One advantage of this embodiment of the
invention is that the front and rear support wheels are in contact with the
floor
so as to enhance the stability of the chair. However, as the rearward support
wheels are pivotally mounted, then these wheels may deflect upwardly or
downwardly as the chair is moved up or down a ramp thus permitting the drive
wheels of the chair to remain in contact with the floor (and function as drive
wheels) even when the office chair is moved up a ramp.
In one embodiment, the office chair further comprises a seat
height adjustment motor drivingly connected to the seat. Preferably, the
office
chair further comprises a battery connected to the motor. The motor may be
controlled by a switch or button that may be provided on the arm of the chair,
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if the chair is provided with arms. Alternately, the switch or button is
preferably
positioned at a location that the occupant can reach while seated in the
chair,
such as underneath the seat.
In another embodiment, the height of the seat is adjustable from
a position below the top portion of the drive wheels to a position above the
top
portion of the drive wheels. This enhances the ability of a disabled person to
access material at different heights while seated in the chair. For example,
by
raising the seat, an occupant may be able to reach a shelf that is above
shoulder height when seated in a standard wheelchair. Preferably, the drive
wheels are provided with brakes. The brakes may be engaged prior to the
seat being raised so as to reach an object of an upper shelf.
In another embodiment, the seat is non-rotatably mounted to the
base.
In another embodiment, the forward support wheels and the
rearward support wheels are rotatably mounted to the base. Preferably, the
forward support wheels and the rearward support wheels comprise casters.
An advantage of this embodiment is that the ability of the office chair to
rotate
about a central point is enhanced.
In another embodiment, the forward support wheels and the
rearward support wheels are mounted on arms and the arms are non-
rotatably mounted with respect to the drive wheels.
In another embodiment, the forward support wheels and the
rearward support wheels are laterally positioned between the drive wheels.
In another embodiment, the forward support wheels and the
rearward support wheels extend forwardly less than the radius of the drive
wheels. An advantage of this embodiment is that the footprint of the office
chair is further reduced.
In another embodiment, the drive wheels are sized to be
manually operated by a person when seated in the office chair. For example,
the diameter of the drive wheels may be the same as those used in
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wheelchairs and is preferably about two feet. An advantage of this
embodiment is that the occupant may themselves propel the chair as if it were
a wheel chair.
In another embodiment, the office chair has a pair of forward
support wheels and rearward support wheels and the forward support wheels
and the drive wheels are positioned to define an open area in front of the
seat
whereby a person's feet can touch the surface on which the office chair is
situated while seated in the chair and move the office chair with their feet.
An
advantage of this embodiment is that the occupant may trippel the office
chair,
i.e. move the office chair with their feet. An occupant may become tired if
they
have to continually move the office chair by manually rotating the drive
wheels. By configuring the chair to permit the occupant to also move the chair
with their feet, the user may, from time to time, rest their arms. Further,
the
occupant may be able to move the chair while holding a file or other work
material in their hands.
In another embodiment, the office chair further comprises a
footrest that is mounted at a position rearward of the front end of the seat.
An
advantage of this embodiment is that the occupant may be able to rest their
feet above the ground, in a more ergonomic position, without increasing the
footprint of the chair and decreasing the mobility of the chair. Preferably,
the
footrest is pivotally mounted between a generally horizontal in use position
and a generally vertical storage position.
In another embodiment, the office chair further comprises a seat
back wherein the inclination of the seat back with respect to the vertical is
adjustable. It will be appreciated that alternately, or in addition, the
inclination
of the seat may be adjustable and the chair may have arms which may be
adjustable.
In another embodiment, the office chair further comprises a
drive motor drivingly connected to the drive wheels. Thus, the occupant may
be able to move the chair by using a joy stick or other control mechanism
known in the art.
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It will be appreciated that the various embodiments may be
combined in various combinations and sub-combinations to provide different
preferred embodiments of this invention. For example, in accordance with
another embodiment of the instant invention, there is also provided an office
chair comprising:
(a) a base comprising:
a pair of centrally positioned, spaced apart drive wheels;
at least one forward support wheel;
at least one rearward support wheel;
(b) a height adjustable seat mounted to the base and
having a front end; and,
(c) a seat height adjustment motor drivingly connected to the
seat.
In accordance with another embodiment of the instant invention,
there is also provided an office chair comprising:
(a) a base comprising:
a pair of centrally positioned, spaced apart drive wheels;
forward support wheels;
rearward support wheels; and,
(b) a height adjustable seat mounted to the base and having a
front end;
wherein the office chair is configured to define an open area in
front of the seat whereby a person's feet can touch the surface on which the
office chair is situated while seated in the chair and move the office chair
with
their feet.
Other aspects and features of the Applicant's teaching will
become apparent, to those ordinarily skilled in the art, upon review of the
following description of the specific examples of the specification.
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BRIEF DESCRIPTION OF THE DRAWINGS
The drawings included herewith are for illustrating various
examples of articles, methods, and apparatuses of the present specification
and are not intended to limit the scope of what is taught in any way. In the
drawings:
Figure 1 is a perspective view of an office chair embodying one
or more aspects of the applicant's teaching;
Figure 2 is a left side view of the chair of Figure 1, with the seat
portion in a lowered position;
Figure 3 is a right side view of the chair of Figure 1, with the seat
portion in a raised position;
Figure 4 is a left side view of the chair of Figure 1, with the seat
portion in a raised position and showing additional and/or optional features
thereof in greater detail;
Figure 5 is a perspective exploded view of the chair of Figure 1;
Figure 6 is a bottom plan view of part of the base portion of
Figure 5;
Figure 7 is a cross sectional view of part of the structure of
Figure 5, taken along the line 7-7 of Figure 6;
Figure 8 is an enlarged view of a portion of the structure shown
in Figure 7;
Figure 9A is an exploded perspective view of the structure of
Figure 8;
Figure 9B is a non-exploded partial cut-away view of the
structure of Figure 9A; and
Figure 10 is a front elevation view of the chair of Figure 1.
DETAILED DESCRIPTION
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Various apparatuses or processes will be described below to
provide an example of an embodiment of each claimed invention. No
embodiment described below limits any claimed invention and any claimed
invention may cover processes or apparatuses that are not described below.
The claimed inventions are not limited to apparatuses or processes having all
of the features of any one apparatus or process described below or to
features common to multiple or all of the apparatuses described below. It is
possible that an apparatus or process described below is not an embodiment
of any claimed invention. The applicants, inventors or owners reserve all
rights that they may have in any invention disclosed in an apparatus or
process described below that is not claimed in this document, for example the
right to claim such an invention in a continuing application and do not intend
to abandon, disclaim or dedicate to the public any such invention by its
disclosure in this document.
An office chair 110 in accordance with the applicant's teaching is
shown in Figure 1. The office chair 110 includes a base 112 and a seat
assembly 114 supported by the base 112. The chair 110 generally defines a
longitudinal axis 116 extending front to back of the chair 110, and a
transverse (or lateral) axis 118 extending generally normal to the
longitudinal
axis 116, between left and right sides of the chair.
Referring also to Figures 2 and 3, the chair 110 has a plurality of
support wheels secured thereto for supporting the chair 110 on a surface 119.
The support wheels include at least one front support wheel 120 and at least
one rear support wheel 122. Preferably, as shown, the support wheels
include a pair of laterally spaced apart front support wheels 120, and a pair
of
laterally spaced apart rear support wheels 122. The front and rear support
wheels 120, 122 rotate about respective front and rear wheel horizontal axes
121, 123 adjacent respective longitudinally spaced apart front and rear ends
of the chair 110. Individual left and right elements of pairs of elements are
denoted with "L" and "R" suffixes appended to the respective reference
character.
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The chair 110 preferably comprises a pair of laterally spaced
apart drive wheels 124 rotatable about a horizontal drive wheel axis 125 and
positioned lohgitudinally intermediate the front and rear support wheels 120,
122, and preferably with the axis 125 in line with the seat support column
202.
The drive wheels 124 (including left and right drive wheels 124L, 124R) are
adapted to facilitate movement of the chair 110 with an occupant therein
across' the surface 119, which can comprise, for example, a floor in an
office.
The drive wheels 124 can also facilitate moving the chair 110 over
considerably longer distances, and can generally provide an occupant with a
similar level of mobility to that afforded by a conventional wheelchair. The
drive wheels 124 may be rotated manually by an occupant of the seat 110, or
may be powered or power-assisted to effect rotation of the drive wheels 124,
thereby moving the chair 110 over the surface 119. The base 112 is
preferably designed to result in the drive wheels 124 contacting the surface
119, even when the chair 110 moves across or straddles a transition in
elevation of the surface 119, as further discussed hereinafter.
The drive wheels 124 may be any drive wheels known in the
wheel chair art. Preferably, drive wheels 124 are sized so as to be manually
rotated by an occupant of the chair 110. Accordingly, drive wheels 124 may
comprise a ground-contacting tire portion 126 and a hand rim portion 128
(Figure 1) adjacent the tire portion 126 and adapted to be grasped by the
hand of an occupant for moving the chair 110 with respect to the surface 119
on which the chair 110 is situated. The front support wheels, rear support
wheels, and drive wheels 120, 122, 124 each have a corresponding front,
rear, and drive wheel radius 130, 132, 134 (Figure 3). The drive wheel radius
134 is, in the example illustrated, generally equal to the radius of the tire
portion 126 (i.e. the tire portion radius 136). The hand rim 128 may have a
hand rim radius 138 that is less than the tire portion 136 radius 136. In the
embodiment iilustrated, the front support wheel radius 130 is about 75mm, the
rear support wheel radius 132 is generally equal to the front support wheel
radius 130, and the drive wheel radius 134 is about 300mm.
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When moving the chair 110 across an office or over longer
distances, the surface 119 may be uneven over portions thereof, presenting
height inconsistencies (or transitions in elevation) such as, for example,
inclines or relatively small steps in height associated with a change in
flooring
elevation. In accordance with one preferred embodiment, front support
wheels, rear support wheels, and drive wheels are configured such that drive
wheels 124 remain in engagement with the surface 119 when traveling over
such height inconsistencies so that control and propulsion of the chair 110
over the surface 119 is not impeded. Accordingly, preferably at least one of
the front and rear pair of wheels 120, 122 are adjustably mounted to the base
112 so that the respective axis 121, 123 about which the at least one pair of
wheels 120, 122 rotate can move between vertically raised and lowered
positions, and/or between a vertically neutral, raised and lowered positions,
relative to the drive wheel axis 125. More preferably, only one of the front
and
rear pair of wheels 120, 122 is adjustably mounted to the base 112 and, most
preferably, the rear pair of wheels 122 are adjustably mounted to the base
112. The adjustable mounting is preferably a pivot mount.
When all wheels are in contact with a surface at the same
elevation, i.e., front, rear, and drive wheels 120, 122, and 124 have
respective
lowermost portions 140, 142, and 144 that are coplanar, then the chair 110 is
positioned on a flat, planar portion of the surface 119 (Figure 4). This
position
may be defined as a neutral position. Upon encountering a height
inconsistency in the surface 119, e.g., an occupant commences to propel the
chair 110 up a ramp or down a ramp, the front and rear wheels 120, 122
would, if their respective axes 121, 123 were fixed relative to the drive
wheel
axis 125, lift the lowermost portion of the drive wheels 124 up and away from
the surface 119 at a point of transition between elevations thereof.
Accordingly, in accordance with a preferred embodiment of this invention, to
facilitate maintaining engagement of the drive wheels 124 with the floor when
encountering height inconsistencies in an uneven surface, at least one of the
front or rear wheel axes 121, 123 is movable to lengthen or shorten the
distance between the seat and the axes which move, thus permitting all
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wheels to remain in contact with the surface 119 and avoiding any lifting of
the
drive wheels 124 when crossing a transition in elevation of the surface 119.
In the preferred embodiment that is illustrated, the pair of
rearward support wheels 122 are pivotally mounted to the base 112 of the
chair 110. The rear support wheels 122 are movable between a neutral
position 146 (shown in solid line in Figure 4), in which the lowermost
surfaces
140, 144, 142 of the front, drive, and rear wheels 120, 124, 122,
respectively,
are generally coplanar, to a raised position 148 (shown in phantom in Figure
4), in which the lowermost surfaces 142 of the rear support wheels 122 are
vertically raised relative to a plane defined by the lowermost surfaces 140
and
144 of the front support wheels 120 and drive wheels 124, respectively. In
other words, when in the raised position 148, if the chair 110 were on a
horizontal surface, the rear wheel axis 123 is raised relative to the drive
wheel
axis 125, to shorten a vertical spacing between axis 123 and the seat. The
vertical travel of the rear wheel axis 123 between the raised and neutral
positions may be about 15-50mm or more, and preferably is about 20-30mm.
When moving from the lower end of a ramp to a level surface therebelow, the
front wheels, upon contact with the lower level surface, will exert a force on
the chair 110 urging the chair to pivot rearwards about the drive wheel axis
125. This puts the rear wheels 122 under a compressive force, bearing
against the ramp, which moves the rear wheels 122 from the neutral position
146 to the raised position 148.
The rear support wheels 122 may, in some embodiments, also
be movable between the neutral position 146 and a lowered position (not
shown). In the lowered position, the lowermost surfaces 142 of the rear
support wheels are positioned vertically below a plane defined by the
lowermost surfaces 140 and 144 of the front support and drive wheels 120,
124, respectively (i.e., further from the seat). When moving from a level
surface down an upper portion of a ramp, the rear wheels 122 would be lifted
clear of the level surface prior to engagement with ramp if the wheels 122 are
biased to the neutral position. If the wheels 122 are biased to the lowered
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position, the rear support wheels 122 will move downwards relative the drive
wheel axis 125 and towards the surface 119, to maintain engagement
therewith.
Further details of a preferred base 112 and the adjustable
mounting of the rear support wheels 122 to the base 112 can be seen with
reference to Figure 5. In the example illustrated, the base 112 comprises a
frame 150 having a front frame sub-assembly 152 and a rear frame sub-
assembly 154. The front frame sub-assembly 152 includes a central hub 156,
from which laterally opposing left and right drive wheel arms 158L, 158R
(generically referred to as drive wheel arms 158) extend. In the example
illustrated, the drive wheel arms 158 extend generally along the transverse
axis 118.
The preferred front frame subassembly 152 further includes left
and right front support wheel arms 160L, 160R extending from the central hub
156, longitudinally towards the front end of the chair 110 and in a laterally
diverging manner. The central hub 156, drive wheel arms 158, and the front
support wheel arms 160 may be of, for example, but not limited to, cast
aluminum alloy construction, or a combination of cast and welded
construction, or plastic which can provide the front frame subassembly as a
unitary, relatively rigid member.
The preferred rear frame subassembly 154 includes left and
right rear support wheel arms 162L, 162R to which the rear support wheels
122 may be secured by any means known in the art. The rear frame
subassembly 154 is, in the example, illustrated, pivotally secured to the
central hub 156 of the frame 150. The rear frame subassembly 154 may
include a central web 164 from which the rear support wheel arms 162 extend
longitudinally rearward in a diverging manner.
Referring now also to Figures 6, 7, and 8, the web 164 is, in the
example illustrated, coupled to the central hub 156 by a pivot joint 166
defining a generally horizontal pivot axis 168 about which the rear frame sub-
assembly 156 can pivot relative to the front frame subassembly 152. As seen
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in Figure 9A, the pivot joint 166 may include a horizontal bore 169 provided
in
the web 164 for receiving a pivot pin 170 therethrough. The central hub 156
is, in the example illustrated, provided with opposing left and right vertical
flanges 172L, 172R, each flange 172 having an aperture 174 therein for
securing the pivot pin 170 to the front frame subassembly 152. The pivot pin
170, and hence the pivot axis 168, is in the illustrated embodiment positioned
along the longitudinal direction proximate the drive wheel axis 125. The
longitudinal spacing between the pivot axis 168 and the drive wheel axis 125
defines a pivot axis offset 175 (Fig. 6). The pivot axis offset 175 is
preferably
less than the longitudinal spacing between the drive wheel axis 125 and the
front support wheels 120, and less than the longitudinal spacing between the
drive wheel axis 125 and the rear wheels 122. In the embodiment illustrated,
the pivot axis 168 is longitudinally rearward of the drive wheel axis 125, by
an
axis offset 175 in a range of about 5 to 25mm.
In use, the rear frame assembly 154, including the rear support
wheel arms 162 and rear support wheels 122, can pivot about the pivot pin
170, effecting movement of the rear support wheels 122 between the neutral
and vertically raised positions 146, 148, and in some embodiments, between
the neutral position 146 and a vertically lowered position. The greatest
bending load on the frame 150 when the chair 110 crosses a transition in
elevation in the surface 119 will generally be at or near a longitudinally
midway point between the front and rear wheels 120, 122, near the seat
supporting column 202 and the drive wheel axis 125. Positioning the pivot
axis 168 near the drive wheel axis 125 can therefore position the pivot axis
where highest bending (or torque) loads are exerted on the frame 150, thus
facilitating pivoting of the rear frame subassembly 154 about the pivot axis
168. The chair 110 provides a single pivot joint 166 about which both of the
rear wheels 122L, 122R pivot simultaneously in tandem, which can improve
lateral stability of the chair 110 when the rear wheels 122 move between, for
example, the neutral and raised positions, since each of the laterally spaced
apart rear wheels 122L, 122R will be at the same elevation, thus reducing the
risk of side-to-side rocking of the chair 110.
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As best seen in Figures 9A and 9B, the pivot joint 166 may
include stop elements to limit the pivoting of the rear frame subassembly 154
about the pivot axis 169 between an upward-most pivot angle and a
downward-most pivot angle. In some preferred embodiments, the web 164 of
the rear frame subassembly 154 may be provided with a front stop surface
176 extending vertically above the bore 169 and that engages a rear face 177
of the,'central hub 156 when the rear frame subassembly is in the upward-
most pivot position. The web 164 may alternatively or additionally be
provided with a horizontal stop surface 178 extending horizontally forward of
the bore 169 and that engages an underside surface 179 of the central hub
156 when the rear subassembly 154 is in the downward-most pivot position.
The stop elements 176-179 can prevent unwanted over-rotation of the rear
frame subassembly 154, which could compromise safety of the chair 110.
Limiting the range of pivotability of the rear frame subassembly 154 can also
protect the pivot joint 166 and optional biasing mechanism 180 against
damage.
In embodiments where the wheels, such as the rear support
wheels 122, are adjustably mounted, the frame 150 is preferably provided
with a biasing member for biasing the wheels to a biased position. The biased
position may correspond to the neutral position 146 (i.e., a position in which
all wheels are coplanar) or a lowered position (i.e., the wheels are biased
downwardly to a position below the plane defined by the wheels being
coplanar).
The biasing member may be a resilient member (e.g.
elastomeric) or a spring or any other means known in the art. The pivoting
wheels may be pivotally mounted to chair 110 by any means known in the art.
For example, an adjustable biasing mechanism 180 may be used for biasing
the rear support wheels 122 to a biased position, and for adjusting the
position of the rear support wheels 122 relative to the drive wheels 124 when
in the biased position. In the embodiment illustrated, the adjustable biasing
mechanism 180 biases the rear wheels 122 to the neutral position 146. The
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mechanism 180 preferably includes a resiliently compressible biasing member
182 secured to the central hub 156, and an abutment member 184 secured to
the rear frame subassembly 154, the abutment member 184 presenting an
abutment surface 186 for engagement with the biasing member 182.
The mechanism 180 may include, as in the example illustrated,
an adjustment rod 188 (Fig. 8) secured to the web 164 of the rear frame
subassembly 154 and directed towards the central hub 156 of the front frame
subassembly 152. The biasing member 182 may comprise an annular
bushing of a resiliently compressible elastomeric material disposed about the
adjustment rod 188. The central hub 156 may have an aperture 187 in a rear
wall thereof (Fig. 9A and 9B) for receiving a forward portion of the rod 188
and/or biasing member 182 therethrough. The abutment member 184 may be
adjustably secured to the adjustment rod 188, and the biasing member 182
may have opposing longitudinal ends compressively engaged by the
abutment member 184 at one end, and an upright 202 fixed to the central hub
156 at the other end.
The mechanism 180 is, in the example illustrated, disposed
vertically above the pivot axis 168. The biasing member 182 bears against
the abutment surface 186, urging the abutment surface 186 (and thus the rear
frame subassembly 154) away from the central hub 156 of the front frame
subassembly 152. This exerts a rotational force on the rear frame
subassembly 154 about the pivot axis 168, urging the rear frame
subassembly 154 to pivot in a clockwise direction when viewed from the left
side, and thus urging the rear support wheels 122 downward, to the neutral
position 146.
The longitudinal position of the abutment surface 186 relative to
the rear frame subassembly 154 may be adjusted, for example by turning the
abutment member 184 along a threaded portion of the rod 188, causing a
corresponding adjustment in the rotational orientation of the rear frame
subassembly 154 about the pivot axis 168, and hence an adjustment in the
vertical position of the rear wheel axis 123 with respect to the drive wheel
axis
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125 when the rear support wheels 122 are in the neutral position 146. It will
be appreciated that any biasing member, such as those that use springs,
elastomeric members or the like, may be used.
Other optional features that are preferably included in chair 110
are described with reference to Figure 4. First, it is preferred that chair
110
includes one or' more of a seat pan 190, a backrest 192, and a left and right
armrest 194L, 194R, and more preferably at least a seat pan 190 and a
backrest 192. Secondly, the seat assembly 114 is preferably adjustable
between raised and lowered positions 195 (Figure 3) and 197 (Figure 2),
respectively. Preferably, as shown in the example illustrated, when in the
lowered position 197, the seat pan 190 is at an elevation below that of an
uppermost or top portion 196 of the drive wheels 124, and the armrests 194
are positioned above the top portion 196 of the drive wheels 124. In this way,
the lowered position 197 can facilitate safe and comfortable travel of the
chair
110 across the surface 119, by providing a relatively low center of gravity
for
the occupant relative to the base 112, and by providing comfortable access to
the hand rims 128 of the drive wheels 124. This position can facilitate an
occupant reaching for an object on a lower shelf of a bookshelf or a lower
filing drawer.
When in the raised position 195 (Figures 3 and 4), in the
example illustrated, the seat pan 190 is preferably positioned above the top
portion 196 of the drive wheels 124. This can facilitate positioning an
occupant at a variety of heights for working at a desk, counter, or
workstation.
When in the raised position 195, the occupant can have a relatively high
center of gravity relative to the base 112, and it may be desirable to avoid
movement of the chair 110 across the surface 119 when the seat assembly
114 is in the raised position 195. This position can facilitate an occupant
reaching for an object on an upper shelf of a bookshelf or an upper filing
drawer.
The chair 110 may be provided with a brake element (not
shown) to prevent rotation of the drive wheeis 124 about the drive wheel axis
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125. Any brake means known in the wheel chair art may be used. The brake
element is preferably configured so that it may be activated when the chair
110 is in the raised position to improve safety of the chair 110.
Any seat height adjustment mechanism known in the art may be
used. A preferred example is shown in Figure 4. As exemplified therein,
extendible/retractable lifting mechanism 200 is positioned generally between
the seat assembly 114 the base 112 to facilitate raising and lowering of the
seat assembly 114. The lifting mechanism 200 includes, in the example
illustrated, a tubular housing 202 secured to the central hub 156 of the frame
150. An extendible member 204 has a lower portion 206 telescopically
coupled to the tubular housing 202, and an upper end 207 connected to the
seat pan 190. The lifting mechanism 200 thus provides a telescoping column
supporting the seat assembly 114 above the base 112.
The lifting mechanism 200 may be provided with anti-rotate
means, to prevent rotation of the seat assembly 114 relative to the base 112.
This advantageously facilitates the proper alignment of the seat pan 190 (and
optional arm rests 194) in a prefixed position between the drive wheels 124
when the seat assembly 114 is in (or near) the lowered position. In one
preferred embodiment, the anti-rotate means is provided at least in part by
the
shape of the uprights 202, 204 of the lifting mechanism 200, which are
shaped to prevent member 204 from rotating with respect to member 202 and
more preferably are generally rectangular in cross-section. The rectangular
shape of the extendible member 204 within the corresponding rectangularly
shaped tubular housing 202 provides for non-rotation of the extendible
member 204 relative to the tubular housing 202. Similarly, the tubular
housing 202 is preferably securely fixed to the central hub 156 of the frame
150 and is received within a corresponding rectangular upright aperture 209
provided therein (Fig. 6), so that the tubular housing 202 is non-rotatably
secured to the base 112. The seat pan 190 is preferably non-rotatably
secured to the upper end 207 of the extendible member 204. Accordingly, the
illustrated embodiment provides non-rotatable mounting of the seat assembly
CA 02539236 2006-03-10
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114 to the base 112. Any other means to prevent the rotation of the seat
relative to the base 112 may be used. For example, the telescoping column
may be circular in cross section with a clamp fixedly mounted to the upper
and lower telescoping elements and a guide member extending from one
clamp and being slidable received in the other clamp.
Referring again to Figure 5, to facilitate raising and lowering of
the seat assembly 114, the lifting mechanism 200 may include an actuating
device 208 driven by a power source 210 to affect displacement of the
extendible member 204 within the tubular housing 202. The actuating device
208 preferably includes a height adjustment motor 212 drivingly connected to
the seat assembly 114. It will be appreciated that the motor that is used and
the method of coupling the motor to the lifting mechanism 200 may be any
known in the arts and may vary depending upon the type of lifting mechanism
200 that is used. Preferably, the chair 110 is provided with a battery 214
connected to the motor 212 to provide power thereto. A switch (e.g. a rocker
switch) 216 that may be used to control the motor 212 may be mounted for
convenient access by an occupant, for example, in or near one of the optional
arm rests 194. The actuating device 208 and lifting mechanism 200 can
facilitate raising and lowering the seat assembly 114 with the full weight of
an
occupant therein, so that the need for standing up when raising or lowering
the seat assembly 114 is avoided. It will be appreciated that the battery
required to power a height adjustment motor may be substantially smaller
than that required to power the drive wheels of a wheel chair due to the
reduced power required to actuate movement and the fact that fewer
actuations may occur in a given day. The battery may be removable mounted
so that it is removed for recharging. Alternately, or in addition, the battery
may
be rechargeable in situ (i.e. the user may plug a recharger into the battery
when installed in the chair 110).
The seat assembly 114 may be provided with any additional
features known in the office chair arts. For example, the chair 110 may be
adjustable to comfortably position an occupant therein. For example, the
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backrest 192 may be adjustable, both in terms of height and incline relative
to
the seat pan 190. The optional armrests 194 may also be adjustable in terms
of height, lateral distance from the seat pan 190 and incline relative to the
seat pan 190. The seat and the backrest may be padded as a standard office
chair.
The front and rear support wheels 120, 122 are preferably
mounted to swivel about a vertical axis and are more preferably casters 220.
As exemplified in Figure 4, casters 220 may rotate 360 about respective
vertical axes 222. Using casters 220 for the front and rear support wheels
120, 122 improves the overall maneuverability of the chair 110, and can help
to compensate for any non-rotatability of the seat assembly 114 relative to
the
base 112. By rotating each of the drive wheels 124 in opposite directions, the
chair 110 can generally pivot in place about a fixed vertical axis.
To facilitate maneuverability of the chair 110 and access in tight
spaces, the left and right front wheels 120L, 120R and left and right rear
wheels 122L, 122R may be spaced apart laterally by a respective front wheel
spacing 226 and rear wheel spacing 228 (Figure 10). Each of the front and
rear wheel spacings 226, 228 are preferably narrower than the lateral spacing
between the left and right drive wheels 124L, 124R (defining a drive wheel
spacing 230), so that the front and rear support wheels 120, 122 are
positioned inside of the drive wheels 124, and thus does not define a
footprint
that is wider than the drive wheels 124.
As seen in Figure 4, in the longitudinal direction, the front
support wheels 120 may extend beyond a front-most portion 232 of the drive
wheels 124 (i.e. the arm support for the wheel may be longer than the radius
of the drive wheel if the arm supports are co-mounted with the drive wheels).
In an alternate embodiment, the front wheel horizontal axis 121 may be no
further forward than the front-most portion 232 of the drive wheels 124. In
other examples, the front wheel axis 121 can be set rearward of the front-
most portion 232 of the drive wheels 124 by an amount generally equal to or
greater than the front wheel radius 130, so that the entirety of the front
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support wheels 120 are generally longitudinally rearward of the front-most
portion 232 of the drive wheels 124. The front wheel horizontal axis 121 of
the front support wheels 120 may be spaced rearwardly away from the front-
most portion 232 by a rearward offset that can be 1 to 150 mm, and
preferably75 to 100 mm. Similarly, in some embodiments the rear support
wheels 122 may be spaced longitudinally away from the drive wheel axis 125
so that the rear support wheels 122 do not extend past a rear-most portion of
the drive wheels 124, or in other words, do not extend rearward from the drive
wheel axis 125 by an amount greater than the drive wheel radius 134.
Shortening the wheel base (i.e. the longitudinal spacing between the front and
rear support wheels 120, 122) of the chair 110 may also help to ensure that
the drive wheels 124 remain engaged with the surface 119 when crossing a
height inconsistency, since the shorter the wheelbase, the more closely the
chair 110 is able to follow the contour of the surface 119.
To further facilitate maneuverability of the chair 110, the chair
110 is preferably adapted to be propelled by engagement of an occupant's
feet with the surface 119 on which the chair 110 is situated. Such a method
of propelling the chair is generally known as "trippeling" the chair.
Accordingly
the chair 110 is preferably configured to define an open area 238 (Figures 1
and 4) generally vertically below the front end of the seat pan 190, and
laterally between the forward portions of the drive wheels 124. In this
embodiment, front support wheels 120 are preferably laterally positioned
adjacent a respective drive wheel 124. In the example illustrated, the lateral
front wheel spacing 226 is greater than the rear wheel spacing 228 to
facilitate
providing the open, clear area 238 for an occupant's feet to engage the
surface 119 (see also Figure 6).
Furthermore, the chair 110 may be provided with a footrest
assembly 240. Preferably, the footrest assembly 240 is configured to be
moved between a deployed position 241 (shown in solid line in Figure 4) for
supporting an occupant's feet, and a stowed position 243 (shown in phantom
in Figure 4) to provide the open area 238 provided between the front support
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wheels 120. The footrest assembly 240 may be mounted by any means
known in the art, such as a bracket 242 extending vertically downward from
the seat pan '190, and a foot supporting portion 244 attached to the bracket
242.
It is preferred that the footrest assembly 240 is mounted so that,
when in the stowed position, the footrest assembly 240 does not interfere with
the use of open area 238 to trippel the chair 110. The footrest assembly 240
may be mounted under the seat pan 190 to avoid intrusion in front of, and/or
between, the front support wheels 120. The bracket 242, in the example
illustrated, extends from a position rearward of the front end of the seat pan
190, and extends only partway down from the seat pan 190 towards the
surface 119 on which the chair 110 is situated. The bracket 242 is provided
with a horizontal pivot joint 246 at a lower end 248 thereof to which the foot
supporting portion 244 is pivotally secured. The foot supporting portion 244
may be generally vertically oriented, and in abutment with the bracket 242
when in the stowed position 243, and may be pivoted forward to, e.g., about
45 degrees below the horizontal when in the deployed position 241. In this
configuration, the pivot joint 246 is spaced relatively far rearward and at a
relatively high elevation, thus helping to provide the open area 238 for
propulsion of the chair 110 by the engagement of an occupant's feet with the
surface 119 (i.e. for trippeling the chair).
While the above description provides examples of one or more
processes or apparatuses, it will be appreciated that other processes or
apparatuses may be within the scope of the accompanying claims.
