U.S. patent application number 10/274425 was filed with the patent office on 2003-07-17 for tension control mechanism for a chair.
Invention is credited to Thole, Doug.
Application Number | 20030132653 10/274425 |
Document ID | / |
Family ID | 26956797 |
Filed Date | 2003-07-17 |
United States Patent
Application |
20030132653 |
Kind Code |
A1 |
Thole, Doug |
July 17, 2003 |
Tension control mechanism for a chair
Abstract
The chair includes seat and back assemblies interconnected in a
four-bar linkage. The chair further includes a tension mechanism
comprising a coil spring projecting forwardly from a base and an
adjustment linkage which is connected to said coil spring and to a
front link of said four-bar linkage. A back linkage end of said
adjustment linkage being axially movable along an axis of said coil
spring and a front linkage end being vertically movable along said
front link to adjust displacement of said adjustment linkage during
rearward pivoting of said front link.
Inventors: |
Thole, Doug; (Grand Rapids,
MI) |
Correspondence
Address: |
FLYNN, THIEL, BOUTELL & TANIS, P.C.
2026 RAMBLING ROAD
KALAMAZOO
MI
49008
US
|
Family ID: |
26956797 |
Appl. No.: |
10/274425 |
Filed: |
October 18, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60330180 |
Oct 18, 2001 |
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Current U.S.
Class: |
297/300.2 |
Current CPC
Class: |
A47C 1/03274 20180801;
A47C 1/03272 20130101; A47C 1/03266 20130101; A47C 1/03255
20130101 |
Class at
Publication: |
297/300.2 |
International
Class: |
A47C 001/024 |
Claims
What is claimed is:
1. A chair having a seat assembly and a back assembly which are
interconnected in a four-bar linkage arrangement, the chair
including a base wherein the four-bar linkage arrangement includes
a base link fixed to the base and a front link pivotally
interconnected to the base link and the seat assembly so as to
pivot rearwardly upon tilting of said seat and back assemblies,
said tension control mechanism including a spring arrangement
comprising a coil spring affixed to the base link and an adjustment
linkage having a back linkage end connected to a front end of said
coil spring and a front linkage end connected to said front link,
said back linkage end being slidable axially along the longitudinal
axis of said spring and said front linkage end being slidable
vertically along said front link wherein the vertical position of
said front linkage end on said front link defines the axial
displacement of said back end of said adjustment linkage during
rearward pivoting of said front link.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/330,180, filed Oct. 18, 2001.
FIELD OF THE INVENTION
[0002] The invention relates to an office chair having a tilt
control with an improved tension mechanism.
BACKGROUND OF THE INVENTION
[0003] Conventional office chairs frequently have a tiltable seat
assembly which tilts downwardly during rearward tilting of a back
assembly. Such chairs include a tilt control mechanism which
controls tilting of the seat and back assemblies and includes a
tension arrangement which normally biases the chair to an upright
position. Such tension mechanisms also include an adjustment
mechanism for adjusting the return force generated thereby.
[0004] The invention relates to an improved tension control
mechanism for adjusting the return force generated by a coil
spring. The seat and back assemblies in this chair are functionally
and structurally interconnected together in a four-bar linkage
arrangement wherein the tension control mechanism includes an
adjustment linkage connected between the coil spring and a front
link of the four-bar linkage. An actuator adjusts a front end of
the adjustment linkage vertically along the front link to vary the
operating characteristics thereof and thereby adjusts the return
force.
[0005] Other objects and purposes of the invention, and variations
thereof, will be apparent upon reading the following specification
and inspecting the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1A is a perspective view of a chair having a tilt
control connecting a seat-back assembly to a pedestal.
[0007] FIG. 1B is a side elevational view of the chair in a normal
upright position.
[0008] FIG. 1C is a side elevational view of the chair in a
rearwardly tilted position.
[0009] FIG. 2 is an enlarged perspective view of the tilt control
and an adjustable tension mechanism thereof.
[0010] FIG. 3 is an exploded view of the tilt control.
[0011] FIG. 4 is a side elevational view of the tilt control
illustrating the tension mechanism adjusted to a first tension
position.
[0012] FIG. 5 is a side elevational view of the tilt control
illustrating the tension mechanism in a second tension
position.
[0013] FIG. 6 is a side elevational view illustrating the tension
mechanism in the first position when the chair is tilted.
[0014] FIG. 7 is a side elevational view illustrating the tension
mechanism in the second tension position when the chair is
tilted.
[0015] FIG. 8 is a perspective view of a front link of the chair
and the actuator mechanism for adjusting the tension mechanism.
[0016] FIG. 9 is a front elevational view of the front link.
[0017] FIG. 10 is a perspective view of a slidable block for the
actuator mechanism.
[0018] FIG. 11 is a side elevational view in cross-section of the
actuator mechanism.
[0019] FIG. 12 is a front diagrammatic view of the actuator
mechanism.
[0020] FIG. 13 is a top cross-sectional view of the actuator
mechanism.
[0021] Certain terminology will be used in the following
description for convenience in reference only, and will not be
limiting. For example, the words "upwardly", "downwardly",
"rightwardly" and "leftwardly" will refer to directions in the
drawings to which reference is made. The words "inwardly" and
"outwardly" will refer to directions toward and away from,
respectively, the geometric center of the system and designated
parts thereof. Said terminology will include the words specifically
mentioned, derivatives thereof, and words of similar import.
DETAILED DESCRIPTION
[0022] Referring to FIGS. 1A and 1B, a chair 10 is illustrated
having a seat-back arrangement comprising a seat unit 12 supported
on a pedestal or base 14 and a back unit 16 pivotally connected to
the pedestal 14.
[0023] Generally, the office chair 10 includes the pedestal 14
having legs 19 radiating outwardly from a lower end of a vertical
post 20. The outer ends of the legs 19 include conventional casters
which support the office chair 10 on a floor or other similar
surface.
[0024] The upper end of the pedestal post 20 rigidly supports the
seat unit 12 thereon by a tilt control 23. The pedestal post 20
also includes a pneumatic cylinder 22 (FIG. 1B) which permits
raising and lowering of the seat unit 12. In particular, the tilt
control 23 includes a structural seat frame 24 and a horizontally
enlarged suspension seat assembly 25 which seat assembly 25
overlies and is supported on the seat frame 24.
[0025] Referring to FIGS. 1B and 1C, the tilt control 23 generally
includes a rigid control body 26 which is rigidly connected to the
pedestal post 20 and is cantilevered outwardly therefrom to define
an arm, and an L-shaped upright 27 which has separate lower ends 53
that are pivotally connected to the body 26. The upper end of the
upright 27 supports the back unit 16 thereon. The back unit 16
includes a vertically enlarged suspension back assembly 28 that has
a suspension fabric which supports the body of the chair occupant
and a back frame 29 on which the back assembly 28 is connected.
[0026] The base 14 further includes a front link 30 which is
pivotally connected at its lower end to the control body 26
forwardly of the upright 27 so as to pivot about pivot axis 30A.
The seat frame 23 is pivotally connected to the upper end of the
front link 30 at an upper pivot axis 30B and also to the upright 27
to thereby define a four-bar linkage which governs simultaneous
tilting of the seat unit 12 and the back unit 16.
[0027] For tilting, the tilt control 26 includes a tension
mechanism 32 to resist tilting. As a result, rearward tilting of
the back unit 16 causes a corresponding downward tilting of the
seat unit 12 about the front link 30. A pair of support arms 31
also are connected to opposite sides of the seat frame 23 and move
therewith.
[0028] Referring to the tilt control 23 of FIGS. 2-4, the control
body includes a bottom wall 40 and side walls 41 and 42 which
extend rearwardly and are joined together by a common back wall 43.
A stepped strengthening plate 44 is welded into the back end of the
control body 26 and includes a mounting collar 45 which is rigidly
attached to the bottom wall 42 and plate 44. The upper end of the
pneumatic cylinder 22 is received in the collar 45 wherein the
actuator button 46 for the cylinder 22 is accessible vertically
therefrom. As such, the control body 26 is rigidly connected to the
pedestal 14 and projects forwardly in cantilevered relation away
from the upper end of the cylinder 22.
[0029] The strengthening plate 44 also includes an inclined front
wall 47 having a mounting bore 48 angling downwardly therethrough.
A rigid, rod-like support post 49 is rigidly fitted into the
mounting bore 48 and welded in place. The post 49 angles upwardly
at an angle of approximately 33.5 degrees relative to the bottom
body wall 40.
[0030] The side walls 41 and 42 further include pivot openings 50.
The pivot openings 50 are generally circular except that they
include flat bottom edges 51. The pivot openings 50 define the
locations at which the lower ends 53 of the upright 27 are
pivotally connected to the control body 26. The lower sections 53
of the upright 27 in particular are pivotally connected to and
cooperate with the control body 26 through the tension mechanism
32. As a result, the tension mechanism 32 resists rearward tilting
of the upright 27 and generates a resilient restoring force which
biases the upright 27 to the non-tilted position of FIG. 1A.
[0031] As described herein, the tension mechanism 32 provides a
primary spring load or force which is nonadjustable, as well as an
additional adjustable spring load to allow the overall restoring
force to be adjusted to accommodate the unique characteristics of
the different users who use the chair 10.
[0032] As for the fixed-load spring arrangement, this arrangement
includes a torsional spring arrangement comprising a pair of coil
springs 55 having free upper spring legs 56 and respective lower
spring legs 57. The lower spring legs 57 are joined together by a
transverse spring section 58.
[0033] To support the springs 55, a pivot shaft 60 is provided
which extends horizontally between the openings 50. The shaft 60
has a hexagonal cross-sectional shape or other non-circular
geometric shape and includes cylindrical bushings 61 at the
opposite ends thereof. The outermost ends of the cylindrical
bushings each include a reduced-diameter end section 62 which fits
into the opening 50 while the innermost portions of the bushing 61
are disposed in the control body 26 within the hollow interiors of
the coil springs 55. The coil springs 55 thereby are supported on
the pivot shaft 60 by the bushings 61.
[0034] The pivot shaft 60 also includes washers 63 which are
located on the outside of the control body side walls 41 and 42.
The outer ends 64 of the shaft 60 project out of the control body
26 and are fixedly connected to the lower ends 53 of the uprights
27 so as to be connected thereto by a connector 65. As such,
rearward pivoting of the uprights 27 causes the pivot shaft 60 to
rotate in the clockwise direction of reference arrow 66 (FIG.
3).
[0035] When the springs 55 are mounted in place, the lower spring
legs 57 abut against the control body bottom wall 40 and act
downwardly thereon. The upper spring legs 56 project rearwardly and
are connected to the shaft 60 by a connector body 70. The connector
body 70 has a bore extending sidewardly therethrough which has a
hexagonal shape that corresponds to the shape of the shaft 60 and
therefore is keyed so as to rotate in unison with the shaft 60. The
connector body 70 includes yoke-like arms 71 which respectively
engage the upper spring legs 56. Therefore, upon rearward tilting
of the upright 27 as generally indicated in FIG. 6, the yokes 71
rotate with the shaft 60 which causes downward deflection of the
spring legs 56. This generates a torsional spring force or load
which acts in the opposite direction on the yoke 71 to resist
tilting of the upright 27 and restore the chair 10 to the fully
upright position.
[0036] To lock out rearward tilting, the connector body 70 also
includes a rearwardly projecting arm 72, and a lock-out block 73 is
provided generally below the arm 72. The block 73 includes an
upward facing stop surface 74. The block 73 is slidable sidewardly
by a suitable drive mechanism so that when located in a first
position, the stop surface 74 is clear of the arm 72 to permit
rotational movement of the arm 72. However, to lock out rearward
tilting, the block 73 may be moved sidewardly to an interference
position wherein the arm 72 contacts the stop surface 74 to prevent
rotation of the shaft 60 and lock out tilting.
[0037] The spring force generated by the springs 55 is not
adjustable and is selected so as to provide the primary restoring
force on the upright 27.
[0038] To adjust the chair 10 to accommodate different users,
however, an additional adjustable spring 80 is provided which also
generates a restoring force which resists tilting of the chair.
This restoring force, however, may be adjusted as described
hereinafter.
[0039] The spring 80 is mounted to the control body 26 and
cooperates with an adjustment linkage 81 to apply a biasing force
directly to the front seat link 30. More particularly, the spring
80 is mounted on the support post 49 of the control body 26. The
support post 49 receives a lower bushing 83 formed of any suitable
material such as plastic. The lower end 84 of the spring 80 is
fitted onto the bushing 83 so as to be centered thereby and abuts
against the face of the inclined wall 47.
[0040] An additional slide bushing 85 is provided on the outermost
end 86 of the post 49. The slide bushing 85 includes a narrow
cylindrical portion 87 having a bore 88 formed therethrough. The
post 49 is received through the bore 88 wherein the narrow portion
87 is fitted within the interior of the coil spring 80. The bushing
85 includes an annular rim 90 projecting outwardly therefrom which
abuts against the outer end of the spring 80. The flange 90 further
includes a pair of connector flanges 91 which project forwardly
therefrom.
[0041] An adjustment link 95 is pivotally connected to the bushing
85 and the front link 30 to transfer the axial spring force of the
spring 80 to the front link 30. In particular, the adjustment link
95 includes a pair of pivot pins 96 which are pivotally connected
to the respective flanges 91 of the bushing 85 and define a
horizontal pivot axis thereat. The front end 97 of the adjustment
link 95 also includes a pair of pivot pins 98 which are pivotally
connected to a slidable block or bushing 99 and define a horizontal
pivot axis. This slide block 99 is received within a vertical
channel 100 formed in the front link 30 and is vertically slidable
therein to adjust the radial distance between the front link end 97
and the pivot axis 30A.
[0042] Referring to FIG. 4, the slide block 99 may be positioned
radially close to the pivot axis 30A or may be vertically slid
along the link 30 to a remote position illustrated in FIG. 5
wherein the front link end 97 is radially close to the pivot axis
30B. By the connection of the adjustment link 95 to the front link
30 and the bushing 85, pivoting or angular movement of the front
link 30 can be used to displace the link 95 and compress the spring
80 wherein the spring 80 serves to resist pivoting of the front
link 30.
[0043] For example, when the slide block 99 is located near the
outer end of the front link 30 near the pivot axis 30B as seen in
FIG. 5, and when the chair is in its upright position, the spring
80 is compressed only a relatively low amount. However, as seen in
FIG. 7, rearward tilting of the chair causes the front link 30 to
pivot rearwardly about the axis 30A which causes the link 95 to be
driven rearwardly and downwardly along an angular path centered
about the pivot axis 30A. This causes a corresponding movement of
the bushing 85 along the post 49 so as to compress the spring 80.
The amount of compression is generally indicated by reference
distance 100 which depicts the linear displacement of the bushing
85 from the initial start position 101 to the final position
102.
[0044] Since the bushing 85 is slidable along the post 49, the
bushing 85 is constrained to a linear movement along the post 49.
In accord therewith, compression of the spring 80 is constrained to
an axial compression. The pivot connections between the opposite
ends of the adjustment link 95 and the front link 30 and bushing 85
serves to translate the angular motion of the front link end 97
into a linear motion of the back link end 103.
[0045] Since the front link end 97 is located at its closest
position to the pivot axis 30B in FIG. 7 and as such is most
distant from the center axis 30A, the angular displacement of the
front link end 97 is at its maximum and in accord therewith, the
linear displacement of the back link end 103 is also at its
maximum. As such, when the link 95 is in the position illustrated
in FIGS. 5 and 7, the total spring load between the spring 55 and
the spring 80 is at its maximum. To reduce this overall spring
force, the front link end 97 is selectively adjusted downwardly
towards the pivot axis 30A as seen in FIGS. 4 and 6 which serves to
reduce the total amount of compression of the spring 80 during
rearward tilting of the chair.
[0046] More particularly referring to FIGS. 4 and 6, the front link
end 97 may be positioned at its closest location adjacent to the
pivot axis 30A which significantly reduces the angular displacement
of the front link end 97 during tilting of the chair. This thereby
minimizes the linear or axial displacement of the bushing 85. For
example, the initial upright position of FIG. 4 is identified by
reference line 110 in FIG. 6. During rearward tilting of the chair,
the front link 30 pivots rearwardly which causes the front link end
97 to also pivot rearwardly since the front link end 97 is spaced
radially from axis 30A. This causes the back link end 103 to be
displaced although this displacement is limited to linear
displacement by the sliding engagement or cooperation of the
bushing 85 with the post 49. As such, the bushing 85 is displaced a
relatively small amount to the position illustrated by reference
line 111 wherein the overall displacement 112 is significantly less
than the total displacement of the spring 80 as indicated by
reference line 100. As such, the majority of the tilt resistance is
provided solely by the springs 55 while only a minimal amount of
additional tilt resistance is provided by the spring 80. The link
95 when in the position of FIG. 6 defines the lowest spring load
for the tension mechanism.
[0047] It will be understood that the front link end 97 may be
positioned at any intermediate position between the upper limit of
travel of FIG. 5 and the lower limit of travel of FIG. 4 to set the
amount of compression of the spring 80 to a magnitude which is
between the minimum compression 112 and the maximum compression
100. By varying the magnitude of the linear compression of the
spring 80, the overall tilt resistance is selectively adjusted to
accommodate the unique characteristics of the user.
[0048] As an additional matter, the geometry of the front link 30,
adjustment link 95 and the bushing 85 is selected so as to increase
the pre-tension of the spring 80 when the link 95 is in its upper
limit of travel. More particularly, when the link 95 is in its
lower position of travel (FIG. 4), it is closest to the end of the
post 49. This position is also indicated by reference line 114 in
FIG. 5. When the front link end 97 is moved to its upper limit of
travel (FIG. 5), the bushing 85 is moved downwardly to the position
101 whereby the spring 80 is compressed by the amount indicated by
reference line 115. Thus, the preload on the spring 80 is increased
due to displacement of the bushing 85 by the distance 115. This
preload is governed by the geometric relationship of the components
and may also be modified, for example, by increasing the angle of
the fixed post 49 relative to the control body bottom wall 40
during manufacturing of the control body 26.
[0049] Referring now to FIGS. 8-13, the front link 30 is configured
to slidably support the slide block 99 and includes an actuator
mechanism 120 for selectively moving the slide block 99.
[0050] More particularly, the front link 30 is configured generally
as a box formed by a pair of mating U-shaped plates 121 and 122.
The plates 121 and 122 define a hollow interior 123. When mated
together, the opposite end walls 124 and 125 of the front link 30
include upper openings or apertures 126 and lower openings or
apertures 127. The upper openings 126 are pivotally connected to
the seat frame 24 by pivot pins 133 to define the pivot axis 30B.
Additionally, the lower apertures 127 are pivotally connected to
the control body side walls 41 and 42 by pivot pins 134 to thereby
define the pivot axis 30A.
[0051] A generally U-shaped channel member 130 is fitted vertically
within the hollow interior 123 and includes flanges. 131 which are
rigidly fixed to the opposing surface of the front plate 122. The
channel member 130 thereby defines the vertical slot 100 which is
open on its upper and lower ends.
[0052] To provide access to the slide block 99, the front plate 122
includes a vertically elongate slot 135. Additionally, the back
wall 136 of the channel 130 also includes a vertically elongate
slot 137 as seen in FIG. 13.
[0053] Referring to the slide block 99 of FIG. 10, the slide block
99 includes a generally triangular recess 140 having an opening 141
which opens through the front face 142 of the slide block 99. The
recess 140 also includes bores 143 which open through the opposite
side walls 144 of the block 99. The recess 140 and bores 143 are
adapted to pivotally connect to the front link end 97 as described
in further detail herein.
[0054] The block 99 also includes a guide projection 146 which
projects from the back face 147 of the block 99. The guide
projection 146 includes inclined guide surfaces 148 which are
formed parallel to each other.
[0055] As referenced previously, the block 99 is confined within
the channel 130 so as to be movable vertically as indicated by
reference arrows 150 in FIGS. 11 and 12. The front channel 140 is
in registry with the slot 135 formed in the front plate 122.
Accordingly, the front link end 97 is inserted into the recess 140
through the aligned slots 135 and 140 and then is pivotally
connected to the slide block 99 by engagement of a horizontal pivot
pin through the pivot bores 143. As such, the front link end 97
moves vertically with the slide block 99 as generally indicated in
phantom outline in FIG. 11.
[0056] In addition, the guide projection 146 projects rearwardly
through the slot 137 formed in the channel member 130. The guide
projection 146 is constrained to only be movable vertically and
this is provided to effect vertical movement of the block 99 as
described hereinafter.
[0057] More particularly, a generally L-shaped guide plate 160 is
also slidably received within the interior 123 of the front link
130. The drive plate 160 includes an end flange 161 which is
oriented generally parallel and faces towards the end face 124 of
the link 30. The drive plate 160 is slidable horizontally within
the hollow interior 123 as indicated by reference arrow 162 in FIG.
8. The plate 160 also includes an inclined slot 163 which slidably
receives the guide projection 146 therein as seen in FIG. 12. When
moving the drive plate 160 horizontally sidewardly, the guide
projection 146 can only move within the slot 163 but since the
guide projection 146 is also constrained within the vertical slot
137, the projection 146 can only move vertically. Therefore, the
horizontal movement of the plate 160 effects a corresponding
vertical movement of the guide projection 146 as indicated by
reference arrow 150.
[0058] To manually move the plate 160, an actuator handle 170 is
drivingly connected to the plate 160. In particular, the actuator
handle 170 includes an inner end 171 which is fixedly connected to
the end flange 161. The actuator handle 170 includes an externally
threaded plastic sleeve 172 which includes helical threads 173
thereon. The threaded sleeve 172 is threadedly engaged with a
spiral stamped plate 174 that is affixed to the end 124 of the
front link 30. Therefore, rotation of the actuator handle 170 as
indicated by reference arrow 175 causes an axial displacement of
the handle 170 as indicated by reference arrow 176. This therefore
causes horizontal displacement of the drive plate 160 which in turn
causes the block 99 to move vertically. A suitable knob 177 is
provided at the end of the actuator handle 170 as indicated in FIG.
9.
[0059] Therefore, rotation of the actuator handle 170 allows the
slide block 99 to be raised or lowered vertically to any desired
position. This causes the vertical position of the front end 97 of
the adjustment link 95 to be adjusted. By adjusting the relative
radial distance between the front link end 97 and the pivot axis
30A, the spring output of the spring 80 may be adjusted.
[0060] Although a particular preferred embodiment of the invention
has been disclosed in detail for illustrative purposes, it will be
recognized that variations or modifications of the disclosed
apparatus, including the rearrangement of parts, lie within the
scope of the present invention.
* * * * *