Note: Descriptions are shown in the official language in which they were submitted.
CA 02574803 2007-01-22
CHAIR CONTROL
BACKGROUND
[0001] This invention relates to a chair control and to a spring tensioner
for a chair
control.
[0002] A chair control may have a main frame, a seat bracket, and a back
bracket. The
main frame may be configured for mounting on a seat post and may support the
seat
bracket. A chair seat may be attached to the seat bracket and a chair back
rest may be
attached to the back bracket. The back bracket may be hinged to the seat
bracket, and a
main spring may act between the main frame and the back bracket in order to
bias the back
bracket toward a rest position. In a typical configuration, the main spring is
a helical spring
housed in a cylindrical, downwardly projecting, stub of the main frame. A hand
wheel
extends below the cylindrical stub. When a chair occupant leans back in the
chair, the back
bracket will pivot against the urging of the main spring so that the back rest
tilts backwards.
Rotation of the handwheel in one direction compresses the spring in order to
increase the
urging force applied by the spring. Thus, the occupant can set the force with
which the
main spring resists tilting of the backrest by turning the handwheel.
[0003] This invention seeks to provide an improved mechanism.
SUMMARY OF INVENTION
[0004] A chair control has a threaded element with a thread extending along
an axis. A
retainer limits axial freedom of the threaded element and a user control
rotates the threaded
element. A spring backstop is threaded to the threaded element and a spring
with a
projection has this projection stopped against the spring backstop.
[0005] In another aspect of the invention, a spring tensioner for a chair
control
mechanism has a hand crank, a worm gear rotated by the hand crank, a pinion
and captive
bolt rotated by the worm gear, a retainer limiting axial freedom of the bolt,
and a spring
backstop threaded to the bolt.
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CA 02574803 2015-03-06
05171-167
10005a1 In an aspect, there is provided a chair control, comprising: a
main frame; a
back bracket pivoted to said main frame; an axially constrained rotatable
threaded element
extending upwardly from said main frame; a rotatable user tension control
projecting laterally
from a side of said main frame; gear means connecting said user tension
control to said
threaded element such that rotation of said user control rotates said threaded
element; a spring
backstop threaded to said threaded element; and a torsion spring having a
first end stopped
against said spring backstop and a second opposite end stopped against said
back bracket.
[0005b] In another aspect, there is provided a spring tension chair control
mechanism,
comprising: a main frame; a back bracket pivoted to said main frame; a torsion
spring having
a first end backstopped by said back bracket; a hand crank disposed at a side
of said main
frame; a worm gear rotated by said hand crank; a pinion and captive bolt
rotated by said worm
gear; a spring backstop threaded to said bolt backstopping a second, opposite,
end of said
torsion spring.
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CA 02574803 2007-01-22
[0006] Other features and advantages of the invention will become apparent
from the
following description in conjunction with the drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0007] In the figures which illustrate an example embodiment of the
invention,
[0008] FIG. 1 is a top perspective view of a chair control made in
accordance with this
invention,
[0009] FIG. 2 is a top perspective view with the seat bracket removed,
[0010] FIG. 3 is a top perspective view with the seat bracket and back
bracket removed,
[0011] FIG. 4 is an exploded view of a portion of the chair control,
[0012] FIG. 5 is a cross-sectional view along the lines V-V of FIG. 3,
[0013] FIG. 6 is a partially exploded view of a portion of the chair
control,
[0014] FIG. 7 is a perspective view of a portion of the chair control,
[0015] FIG. 8 is top perspective view of a portion of the chair control,
and
[0016] FIGS. 9A and 9B are side views of a portion of the chair control
showing
operation of this portion of the chair control.
DETAILED DESCRIPTION
[0017] Turning to FIGS. 1 and 2, a chair control 10 has a main frame 12, a
seat bracket
14, and a back bracket 16. The seat bracket 14 may be mounted to the main
frame by pins
18 and may have flanges 20 with bores 22 by way of which a chair seat may be
affixed to
the seat bracket.
[0018] The back bracket 16 may be pivotably joined to the main frame by shaft
26. A
number of user controls may extend from the main frame, namely a spring
tension hand
crank 30, a gas control paddle 32, and a backrest tilt lock control 34. As is
apparent, the
paddle 32 may extend from a cylindrical sleeve 36 which is supported for
rotation on an
arm 38 extending from the hand crank. The hand crank itself may have a
depending finger
40 terminating in a rotatable tip 42 which may be grasped by a user.
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[0019] Turning to FIGS. 3 to 5, a main spring 50 may have two helically wound
sections 46a, 46b which each terminate at an inner end in a projection: tangs
52a and 52b.
The tangs project from one side of the helically wound sections. Each
helically wound
section may terminate at its opposite, outer, end in another projection: arms
48a and 48b,
which are joined by a bar 54. The arms project from an opposite side of the
helically wound
sections.
[0020] The main spring 50 may be supported in main frame 12 by an annular
shaft 56
which extends through the central axis of the helically wound sections of the
spring. The
annular shaft is carried on shaft 26 (FIG. 2) and the ends of shaft 26 extend
through
openings 58 in the main frame (and openings in the back bracket).
[0021] The bar 54 of the spring abuts the underneath of the back bracket 16
(FIG. 2).
The two tangs 52a, 52b abut the underneath of a wear plate 62 associated with
a threaded
spring backstop 60. The spring backstop 60 is threaded to a bolt 66. The
threaded shaft of
the bolt passes through a retainer plate 70. Bolts 74 extend through the main
frame 12, a
block 76, and the retainer plate. Nuts 75 are screwed to the bolts 74 to fix
the retainer plate
70 to the block 76, and to fix both the retainer plate and the block within
the main frame. A
thrust bearing 72 may be used to reduce friction between the head of the bolt
66 and the
retainer plate 70 when the bolt 66 is turned. The thread of the shaft of bolt
66 may have
about five turns per inch. This may be achieved by, for example, utilising a
triple start
thread that has sixteen turns per inch.
[0022] A cavity in block 76 is configured to house a pinion 78 and a worm gear
80 so
that these gears are held in meshing relation. The pinion 78 may have a
hexagonal central
bore into which the hexagonal head of bolt 66 is received such that the pinion
and bolt have
a common central axis and the bolt is constrained to turn with the pinion. The
shaft 38
extending from hand crank 30 is joined to the worm gear 80 such that turning
the crank
turns the worm gear. In this regard, the end of shaft 38 may be hexagonal and
fit in a
hexagonal opening in the end of the worm gear, as seen in FIG. 6.
[0023] Turning
to FIG. 6 along with FIGS. 3 and 5, block 76 may have an extension 84
to which a gas control lever 86 is mounted by pivots 88. A control end 90 of
the lever may
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abut a gas control finger 92 of a gas cylinder 94. A controlled end 96 of the
lever may have
a slot 98 which receives a boss 102 extending from the cylindrical sleeve 36
of the paddle
32.
[0024] Turning to FIGS. 7 and 8, a resilient arm 106 depends from the
opposite side of
block 76. The resilient arm 106 has lands 108, 110 on either side of a
protuberance 112.
The back rest tilt lock control 34 may be rotationally mounted to a shaft 114
which extends
through an opening in main frame 12 and is joined to a cam finger 118. The cam
finger
may abut arm 106 and deflect it from its rest position. The cam finger may
have a
cylindrical receptor 120 which receives a boss (not shown) extending from the
back rest tilt
lock control 34 through a slot 122 in the main frame. The cam finger may also
have a
projection 124 with a bore through which a stiff wire 126 extends. Springs
128, 130 may
extend over the stiff wire 126 on either side of the projection. Each spring
may be
sandwiched between the projection and a respective enlargement 132, 134 (FIG.
9A) on the
stiff wire.
[0025] An dog 136 may be pivotably joined to a plate 138 proximate one side of
the
plate 138. Wire 126 may be joined via the dog 136 to the plate 138. The plate
may be
pivoted to the main frame, proximate the other side of the plate, by a pivot
140. A locking
tongue 142 may extend from plate 138 and be received within one of an array of
locking
receptors in a rack (not shown) extending from the back bracket 16 (FIG. 3).
As seen in
FIGS. 9A and 9B, the cam finger 118 has two stable positions, one on either
side of the
protuberance 112.
[0026] In operation, a user may rotate hand crank 30 to turn worm gear 80.
This, in
turn, rotates pinion 78 and its captive bolt 66. The bolt is constrained from
moving axially
upwardly by retainer plate 70. Consequently, when the bolt is rotated in one
direction,
threaded spring backstop 60 is drawn toward the retainer plate. This moves the
tangs 52a,
52b of the springs downwardly thereby increasing the pressure that the bar 54
of the spring
exerts on back bracket 16. This increases the force with which the main spring
50 resists
backward tilting of any backrest attached to the back bracket. Conversely, if
the bolt is
rotated in the opposite direction, the spring backstop 60 moves away from the
retainer plate
70. This allows the tangs 52a, 52b of the spring to move upwardly thereby
decreasing the
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pressure that the bar 54 of the spring exerts on back bracket 16 and reducing
the resistance
to backward tilting of the backrest. By providing a thread for bolt 66 that
effectively has a
low number of turns per inch (e.g., a triple start thread), the user may make
a substantial
adjustment in the spring tension with a relatively small adjustment to hand
crank 30. This
therefore makes adjustment of the spring tension quicker and less tiring for
the user.
[0027] The user may lock the backrest at different tilt angles by rotating
the backrest tilt
lock control 34 so that cam finger 118 moves from an unlocking position shown
in FIG.
9A, over protuberance 112, to a locking position shown in FIG. 9B. Resilient
arm 106
deflects to allow this movement. In the locking position, spring 128 is
compressed, thereby
urging wire 126 in a locking direction L. This, through dog 136, urges the
plate 138 to
rotate in the locking direction. In consequence, if the locking tongue 142 is
registered with
one of the array of locking receptors in the rack (not shown) extending from
the back
bracket 16, the tongue will enter the registered receptor and the back bracket
will be locked
in position. If, however, the tongue is not registered with any receptor, then
the tongue will
simply be pushed against the rack and pop into a receptor whenever the angle
of the back
bracket changes so as to register any receptor with the tongue.
[0028] To unlock the backrest, the user may rotate the backrest tilt lock
control 34 so
that cam finger 118 moves back to the unlocking position shown in FIG. 9A.
This
compresses spring 130 which urges wire 126 in a direction opposite locking
direction L.
The pressure exerted by the main spring 50 may create a binding force between
the tongue
and the side of the receptor receiving the tongue. This may prevent the tongue
from
popping out of the receptor until a user may adjusts their weight in the chair
to relieve this
binding force.
[0029] The user may push paddle 32 in order to cause boss 102 extending
from the
sleeve 36 joined to the paddle to tilt the control end 90 of lever 86 against
the gas control
finger. By depressing the gas control finger in this way, the height of the
chair may be
adjusted.
[0030] From FIG. I it will be apparent that the three user controls 30, 32,
34 may
project from the sides of the chair control 10. This has the advantage that a
chair occupant
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never need reach between their legs to make a chair adjustment. Further, with
the gas
control paddle 32 having a sleeve 36 co-axially mounted to the arm 38
extending from the
hand crank 30, these two controls may conveniently be placed in close
proximity. For
aesthetics, the chair control may be designed as shown in FIG. 1 with the
chair back lock
arm 34 co-axial with the hand crank arm 38.
[0031] Many
modifications are possible. For example, pinion 78 and worm gear 80
could be replaced by two bevel gears. Also the spur and worm gears could be
reversed so
that the bolt 66 is captured by the worm gear. Indeed, if the thread of bolt
66 were provided
with a sufficiently large pitch, in place of the gears and hand crank, a lever
could be
connected directly to the bolt extending at roughly a right angle to the bolt.
In this instance,
the lever could be rotated to directly rotate the bolt and move the spring
backstop. With all
of these options, the chair control retains the advantage that an occupant
never need reach
between their legs to make a chair adjustment. In another embodiment, it would
be possible
to omit the gears and have the hand crank connected directly to the end of the
bolt so that
the crank projects downwardly from the chair control. This is not preferred,
however, as the
chair control would lose its advantage of never requiring an occupant to reach
between their
legs to make a chair adjustment.
[0032] While in
the illustrated embodiment, the head of the bolt 66 is captured by a
hexagonal bore in the pinion, optionally, the bolt, or any threaded shaft,
could be affixed to
the pinion in any suitable fashion. In another embodiment, the bolt 66 could
be replaced by
a nut captured by, or affixed to, the pinion. In this case, the spring
backstop could support a
threaded shaft which extends downwardly into threaded engagement with the nut.
[0033] Other
modifications will be apparent to those skilled in the art and, therefore, the
invention is defined in the claims.
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