U.S. patent application number 09/746180 was filed with the patent office on 2001-05-10 for tilt control for chair.
This patent application is currently assigned to Haworth, Inc.. Invention is credited to Clark, John, Dral, Joel, Nelson, Patrick, Roark, Troy, Roslund, Richard N. JR., Simpson, Steve, Wilkerson, Larry Allen.
Application Number | 20010000939 09/746180 |
Document ID | / |
Family ID | 26688519 |
Filed Date | 2001-05-10 |
United States Patent
Application |
20010000939 |
Kind Code |
A1 |
Roslund, Richard N. JR. ; et
al. |
May 10, 2001 |
Tilt control for chair
Abstract
A tilt control mechanism for an office chair includes a spring
arrangement which permits forward and rearward tilting of the chair
while also urging the chair to a normal upright position. The
spring arrangement includes front and rear springs which act in
combination such that the upward acting forces acting on the chair
can be varied during use. The forces being applied by the front
spring are adjusted by a side-actuated tension adjustment mechanism
which incorporates a wedge block for adjusting the spring forces.
Further, the rear springs provide a variable spring force such that
the spring force is maximized when in the normal position but is
decreased substantially once the chair is fully reclined. This
reduction in spring force allows a user to maintain the chair in
the fully reclined position with significantly less force than was
required to tilt the chair rearwardly while a sufficient spring
force continues to be applied by the front spring to urge the chair
to the normal position.
Inventors: |
Roslund, Richard N. JR.;
(Jenison, MI) ; Nelson, Patrick; (Holland, MI)
; Wilkerson, Larry Allen; (Comstock Park, MI) ;
Roark, Troy; (West Olive, MI) ; Dral, Joel;
(Lula, GA) ; Simpson, Steve; (Holland, MI)
; Clark, John; (Holland, MI) |
Correspondence
Address: |
Flynn, Thiel, Boutell & Tanis, P.C.
2026 Rambling Road
Kalamazoo
MI
49008-1699
US
|
Assignee: |
Haworth, Inc.
|
Family ID: |
26688519 |
Appl. No.: |
09/746180 |
Filed: |
December 21, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09746180 |
Dec 21, 2000 |
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09434431 |
Nov 4, 1999 |
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09434431 |
Nov 4, 1999 |
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09016371 |
Jan 30, 1998 |
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6015187 |
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09016371 |
Jan 30, 1998 |
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08846618 |
Apr 30, 1997 |
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5909924 |
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Current U.S.
Class: |
297/303.3 ;
297/300.4; 297/303.4 |
Current CPC
Class: |
A47C 1/03272 20130101;
A47C 1/03266 20130101; A47C 1/03255 20130101 |
Class at
Publication: |
297/303.3 ;
297/303.4; 297/300.4 |
International
Class: |
A47C 001/038 |
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. In a chair having a base, a seat assembly, a back assembly and a
tilt control mechanism which is supported on said base and effects
rearward tilting of said seat and back assemblies in response to a
user, said tilt control mechanism including a fixed body supported
on said base and a pivot member which pivots downwardly relative to
said fixed body about a sidewardly extending horizontal pivot axis
in response to said rearward tilting of said seat and back
assemblies, said tilt control mechanism further including a spring
having a first leg portion acting on said fixed body and a second
leg portion acting on said pivot member, said second leg portion
being resiliently deflectable relative to said first leg portion so
as to act against but permit pivoting of said pivot member about
said pivot axis and bias said pivot member to counteract said
rearward titling of said seat and back assemblies, the improvement
comprising an adjustment mechanism for adjusting a deflection of
said first leg portion relative to said second leg portion, said
adjustment mechanism including a tension adjustment handle which is
movable sidewardly relative to said fixed body, and a wedge which
is slidable toward and away from said spring in an axial direction
transverse to the movement of said adjustment handle, said
adjustment mechanism further including connector means for
transferring said sideward movement of said adjustment rod into
said axial movement of said wedge to move one of said first and
second leg portions vertically to vary the spring force being
applied by said spring on said pivot member.
2. A chair according to claim 1, wherein said connector means
comprise an elongate track which projects upwardly from said fixed
body and is oriented at an angle relative to said pivot axis, said
wedge including an elongate channel which opens from a bottom
surface thereof and slidably receives said track therein, said
wedge being slidable along said track so as to have both a forward
component of motion and a sideward component of motion.
3. A chair according to claim 2, wherein said adjustment rod is
threadingly engaged with said fixed body such that rotation of said
adjustment rod effects sideward movement thereof, said rod acting
against a side surface of said wedge and being movable toward said
wedge so as to effect said angled sliding of said wedge along said
track toward said spring.
4. A chair according to claim 3, wherein said wedge includes an
inclined surface facing toward said spring, said one of said first
and second leg portions being slidable axially along said inclined
surface as said wedge is moved axially to effect vertical movement
of said one of said first and second leg portions.
5. A chair according to claim 1, wherein said first leg portion
acts downwardly on a bottom surface of said fixed body, and said
second leg portion acts upwardly on said pivot member.
6. A chair according to claim 1, wherein a plate is positioned
between an inclined surface of said wedge and said one of said
first and second leg portions being moved by said wedge, said plate
including mounting means for mounting said plate on said fixed body
so as to be movable vertically by said wedge to effect a
corresponding vertical movement of said one of said first and
second leg portions, said mounting means limiting sideward movement
of said plate to thereby prevent sideward movement of said one of
said first and second leg portions in response to said sideward
component of motion of said wedge.
7. In a chair having a base, a seat assembly, a back assembly and a
tilt control mechanism which is supported on said base and effects
rearward tilting of said seat and back assemblies in response to a
user, said tilt control mechanism including a fixed body supported
on said base and a pivot member which pivots downwardly relative to
said fixed body about a sidewardly extending horizontal first pivot
axis in response to said rearward tilting of said seat and back
assemblies, said tilt control mechanism further including a spring
having a first leg portion acting on said fixed body and a second
leg portion acting on said pivot member, said second leg portion
being resiliently deflectable relative to said first leg portion so
as to act against but permit pivoting of said pivot member about
said first pivot axis and bias said pivot member to counteract said
rearward titling of said seat and back assemblies, the improvement
comprising adjustment means for adjusting an effective spring rate
of said spring, said adjustment means comprising an arcuate bearing
surface supported on said fixed body, an end of said first leg
portion acting downwardly on a top surface portion of the arcuate
bearing surface so as to act with a vertical force component
thereon, said spring being movable downwardly with said pivot
member such that said first leg portion is deflected upwardly to
increase a spring force acting on the pivot member, said first leg
portion being inclined so as to act axially and downwardly on a
side of said bearing surface such that said spring force includes
horizontal and vertical force components.
8. A chair according to claim 7 wherein said arcuate bearing
surface is supported on a rearward end of said fixed body, said
spring being movable downwardly so that said first leg portion
extends axially and upwardly toward said arcuate bearing surface
into contact with said side thereof.
9. A chair according to claim 7, wherein said tilt control
mechanism includes a back support member which has a forward end
pivotally connected to said fixed body and a rearward end which
supports said back assembly, a rearward end of said pivot member
being pivotally connected to said back support member rearwardly of
said second pivot axis such that said back support member moves
downwardly in combination with said pivot member, said spring being
supported on said back support member so as to move vertically
therewith.
10. A chair according to claim 7, which includes a second spring
having a first leg portion acting on said fixed body and a second
leg portion acting on said pivot member, said second leg portion
being resiliently deflectable relative to said first leg portion so
as to act against but permit pivoting of said pivot member about
said first pivot axis and bias said pivot member to counteract said
rearward tilting of said seat and back assemblies, said second
spring providing a substantially continuous spring force which acts
on said pivot member during pivoting thereof.
11. A chair according to claim 10, which includes adjustment means
for adjusting said spring force being provided by said second
spring.
12. A chair according to claim 11, wherein said adjustment means
comprises a wedge which is slidable in an axial direction toward
and away from one of said first and second leg portions of said
second spring, and actuation means for moving said wedge in said
axial direction toward said spring to deflect one of said first and
second leg portions thereof relative to the other of said first and
second leg portions to adjust the spring force provided
thereby.
13. A chair comprising: a seat assembly for supporting a seat of a
user; a back assembly for supporting a back of a user; a base; and
a tilt control mechanism which is supported on said base and
effects rearward tilting of said seat and back assemblies in
response to a user, said tilt control mechanism including a fixed
body supported on said base, a back support member which projects
rearwardly away from said fixed body and includes a forward end
pivotally connected to said fixed body such that said back support
member pivots vertically about a first horizontal pivot axis, and a
top plate overlying said fixed body which includes a front portion
which is pivotally connected to said fixed body so as to pivot
vertically about a second horizontal pivot axis and a rear portion
which is connected to said back support member such that said top
plate and said back support member pivot vertically together in
response to said rearward tilting of said seat and back assemblies,
said seat assembly being supported on said top plate and said back
assembly being supported on said back support member, said tilt
control mechanism further including a front spring and a rear
spring biasing said top plate upwardly, said front spring having a
first leg acting on said fixed body and a second leg acting
upwardly on said top plate, said first and second legs of said
front spring being resiliently deflectable relative to each other
such that said second leg acts against but permits pivoting of said
top plate about said second pivot axis and biases said top plate to
counteract said rearward tilting of said seat and back assemblies,
said second spring being supported on said back support member so
as to move vertically therewith and including a lower leg acting
downwardly on a rear portion of said fixed body and an upper leg
acting upwardly on said top plate, said first and second legs of
said second spring being resiliently deflectable relative to each
other so as to act against but permit pivoting of said pivot member
about said first pivot axis and bias said pivot member to
counteract said rearward tilting of said seat and back assemblies,
said rear portion of said fixed body including an upward facing
arcuate bearing surface which supports an end of said lower leg of
said rear spring thereon, said lower leg extending forwardly so as
to act on a top surface portion of the bearing surface to act with
a vertical force component, said lower leg extending upwardly from
said second spring as said second spring is moved vertically
downwards by said back support member such that said lower leg acts
on a side of said bearing surface with both horizontal and vertical
force components.
14. A chair according to claim 13, wherein said tilt control
mechanism includes adjustment means for adjusting said spring force
provided by said front spring, said spring force being applied by
said front spring acting substantially continuously during downward
pivoting of said top plate.
15. A chair according to claim 14, wherein one of said first and
second spring legs of said front spring are deflected vertically by
said adjustment means so as to increase and decrease said spring
force.
16. A chair according to claim 13, wherein a plastic spacer is
provided between said upper leg of said rear spring and a downward
facing surface of said top plate so as to limit friction
therebetween.
17. A chair according to claim 16, wherein said front and rear
springs are coil springs, said rear spring being supported on said
back support member by a cylindrical body inserted in a hollow
interior of said rear spring, said elastic member being formed
integrally with said cylindrical body and projecting forwardly
therefrom.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
1. This application is a continuation-in-part application of
copending U.S. patent application Ser. No. 08/846 618, filed Apr.
30, 1997.
FIELD OF THE INVENTION
2. This invention relates to an office chair and in particular, to
an office chair which includes seat and back assemblies which are
tiltable forwardly and rearwardly relative to a chair base.
BACKGROUND OF THE INVENTION
3. Office chairs have been developed where seat and back assemblies
thereof are tiltable forwardly and rearwardly. One type of office
chair is commonly referred to as a "synchro-tilt" type chair
wherein the back assembly tilts synchronously with respect to the
seat assembly but at a greater rate. As a result, the back assembly
tilts relative to the seat assembly as the latter tilts relative to
a chair base on which the seat and back are supported. Such
synchronous tilting is provided by a tilt control mechanism which
mounts to the chair base and joins the back assembly to the seat
assembly. Numerous control mechanisms have been developed which
effect such tilting.
4. More particularly, these tilt control mechanisms typically
include a spring arrangement contained therein which resists the
rearward tilting of the seat and back. Preferably, the spring
arrangements cooperate with a spring adjustment mechanism so as to
adjust the load of the spring which resists the rearward tilting.
Thus, the amount of force necessary to tilt the seat rearwardly can
be manually adjusted to suit each user.
5. Typically these spring adjustment mechanisms include handles
which project out of the tilt control mechanism housing and are
rotatable so as to vary the spring load. While a large number of
these adjustment mechanisms use adjustment knobs which project
downwardly through the bottom of a control housing, providing the
adjustment knobs on the side of the tilt control mechanism is
easier to operate since a user need not reach down below the
seat.
6. Examples of tilt control mechanisms having side tension
adjustment mechanisms are disclosed in U.S. Pat. Nos. 4,865,384,
4,889,384, 5,106,157, 5,192,114 and 5,385,388.
7. Accordingly, it is an object of the invention to provide an
improved tilt control mechanism for an office-type chair which
preferably is a synchro-tilt control. It is a further object that
the tilt control mechanism include a side-actuated tension
adjustment mechanism which acts upon a spring arrangement to vary
the spring force tending to urge the seat assembly to a normal
forward position. To optimize the space required for the tilt
control mechanism, it is a further object that the control
mechanism have a low-profile design wherein a combination of front
and rear springs is provided. In view thereof, it is an object of
the invention that the tension adjustment mechanism act on either
the forward or rearward springs. A still further object is to
provide a tilt control mechanism wherein the spring arrangement
urges the seat forwardly but provides for a drop-off or dwell in
the spring load being applied once the seat reaches a rearward
position such that the seat can be readily maintained in the
rearward position with less force than was required to move the
seat to the rearward position.
8. In view of the foregoing, the invention relates to a tilt
control mechanism for a chair which provides for synchronous
tilting of the seat and back assemblies. Preferably the tilt
control mechanism is supported on a chair base while the seat
assembly and back assembly are joined together by the tilt control
mechanism. The tilt control mechanism disclosed herein permits both
rearward tilting of the seat relative to the chair base while also
permitting a corresponding rearward tilting of the back assembly
relative to the seat. The tilting of the back assembly is at a
different and preferably greater rate than the rearward tilting of
the seat which is commonly referred to as "synchro-tilt". The tilt
control mechanism also permits forward tilting of the seat relative
to the base to further optimize the comfort of a user.
9. More particularly, the tilt control mechanism includes a
box-like control housing which is rigidly secured to the base. The
control housing opens upwardly to define a hollow interior and
contains the internal components of the tilt control mechanism.
10. To effect rearward tilting, the control mechanism includes a
seat back support member which is hinged to the control housing by
a center pivot rod, screws or the like. The back support member
extends rearwardly therefrom to support the back assembly. In
particular, the center pivot rod defines a first horizontal pivot
axis so as to permit vertical swinging of the back support member
about this horizontal pivot axis. The back support member forms a
lower generally horizontal leg of an L-shaped back upright which
supports the back assembly thereon. Thus, the back assembly tilts
rearwardly in response to a corresponding swinging movement of the
back support member.
11. The control mechanism further includes a horizontally enlarged
top plate which has a front edge portion pivotally secured to the
control housing by a front pivot rod, and a rear edge portion
slidably secured to the back support member by a rear pivot rod,
screws or other suitable fasteners. In particular, the rear edge
portion of the top plate includes horizontally elongate slots which
are formed through the side walls thereof and slidably receive the
opposite ends of the rear pivot rod therethrough. Unlike the center
and front pivot rods which only provide for pivoting movement, the
opposite ends of the rear pivot rod project from the back support
member and are movable forwardly and rearwardly along the slots
formed in the top plate. Preferably, the opposite ends of the rear
pivot rod includes bearings or rollers that roll along the slots so
as to reduce friction. Thus, while the control housing remains
stationary, the top plate and back support member pivot downwardly
together but at different rates during rearward tilting of the
chair. While this movement is in a downward direction, the rearward
tilting of the seat and back occurs. Similarly, upward pivoting of
the top plate and back support member effects a forward tilting of
the seat and back.
12. To normally maintain the back assembly in an upright position,
the control mechanism includes a front coil spring supported on the
front pivot rod, and a pair of rear coil springs supported on the
rear pivot rod. These coil springs include lower legs which act
downwardly on the stationary control housing and upper legs which
act upwardly on the pivotable top plate. The front and rear coil
springs thereby urge the top plate as well as the back support
member upwardly relative to the stationary control housing. The
springs, however, permit rearward tilting of the top plate and the
back support member.
13. The tension being applied by the coil springs is adjusted by a
tension adjustment mechanism. The tension adjustment mechanism
includes a wedge block which preferably seats underneath the lower
legs of the front springs, and a side-actuatable adjustment rod
which is movable laterally into and out of the control housing to
move the wedge block forwardly. To transform the lateral movement
of the rod into the forward movement of the wedge block, the wedge
includes an angled groove on a bottom surface thereof which is
seated on an elongate track that projects upwardly from the control
housing. The track extends at an angle toward the front of the
control housing, and the wedge slidably seats on the track such
that the wedge block is slidable therealong at an angle relative to
the coil springs. Thus, upon sideward movement of the adjustment
rod, the wedge block is moved both sidewardly and forwardly as it
travels along the angled track wherein the forward movement of the
block tends to urge the lower spring legs upwardly and increase the
spring force being applied thereby.
14. To minimize the effects of the sideward movement of the wedge
block on the spring legs, an intermediate plate is disposed between
an inclined front surface of the wedge block and a lower surface of
the spring legs. By providing the intermediate plate, the sideward
movement of the wedge block does not tend to urge the spring legs
sidewardly as would otherwise occur if the wedge block acted
directly on the spring legs. This tension adjustment mechanism
thereby permits ready adjustment of the force provided by the front
coil springs.
15. A further aspect of the chair is provided by the rear springs
wherein the lower legs of the springs act upon the control housing,
and in particular, act upon an arcuate bearing surface that is
supported on a rear edge of the control housing. When the top plate
is in the normal horizontal position, the lower spring legs tend to
act directly downwardly onto the bearing surface which maximizes
the spring forces acting upwardly on the top plate. However, as the
top plate and back support member pivot downwardly during rearward
tilting of the chair, the rear springs also swing downwardly below
the height of the control housing which thereby deflects the lower
spring legs. In particular, the lower spring legs deflect from a
generally horizontal orientation to a steeply inclined position
such that the lower spring legs act more on a side of the arcuate
bearing surface instead of the top thereof. Since a substantial
portion of the force applied by the lower spring leg now acts
forwardly instead of downwardly, the upward acting forces provided
by the rear springs are significantly reduced so as to define a
dwell for a user. Accordingly, once the chair is tilted rearwardly
to its rearward position, a significant reduction in the forces
applied by the rear springs occurs which makes it easier for a user
to maintain the chair in the rearward position.
16. 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
17. FIG. 1 is a front perspective view of an office chair of the
invention.
18. FIG. 2 is a side elevational view of the chair.
19. FIG. 3 is a rear elevational view of the chair.
20. FIG. 4 is an isometric view of a seat support structure.
21. FIG. 5 is a partial perspective view of a tilt control
mechanism and an upright assembly supported thereby.
22. FIG. 6 is a partial front elevational view of the chair.
23. FIG. 7 is a partial side elevational view of the tilt control
mechanism illustrated in a forwardly tilted position.
24. FIG. 8 is a partial side elevational view of the tilt control
mechanism illustrated in a normal generally horizontal
position.
25. FIG. 9 is a partial side elevational view of the tilt control
mechanism illustrated in a rearwardly tilted position.
26. FIG. 10 is an exploded view of the tilt control mechanism.
27. FIG. 11 is a top plan view of the tilt control mechanism with a
top plate removed.
28. FIG. 12 is a partial side elevational view in cross section
illustrating the tilt control mechanism as viewed in the direction
of arrows 12-12 in FIG. 14.
29. FIG. 13 is a partial side elevational view in partial cross
section illustrating the tilt control mechanism as viewed in the
direction of arrows 13-13 in FIG. 14.
30. FIG. 14 is a top plan view of the tilt control mechanism.
31. FIG. 15 is an enlarged top plan view of a tension adjustment
mechanism.
32. FIG. 16 is an enlarged top plan view of the tension adjustment
mechanism in a withdrawn position.
33. FIG. 17 is an enlarged partial side elevational view in cross
section illustrating the tension adjustment mechanism of FIG.
16.
34. FIG. 18 is an enlarged partial side elevational view in cross
section illustrating a rear spring in the rearwardly tilted
position.
35. FIG. 19 is an enlarged partial side elevational view in cross
section illustrating a rearward tilt lock in a locked position.
36. FIG. 20 is an enlarged partial side elevational view in cross
section illustrating a rear spring of a second embodiment of the
invention in the rearwardly tilted position.
37. FIG. 21 is a front perspective view of a further embodiment of
the tilt control mechanism of the invention.
38. FIG. 22 is a partial top plan view of the control housing.
39. FIG. 23 is an enlarged top plan view of a tension adjustment
mechanism.
40. FIG. 24 is a partial front cross sectional view of a pneumatic
actuator mechanism.
41. FIG. 25 is a partial front cross sectional view of the
pneumatic actuator mechanism after being actuated.
42. FIG. 26A a top plan view of a seat assembly of the
invention.
43. FIG. 26B is a cross sectional view of a cable adjustment
assembly as viewed in the direction of arrows 26B-26B of FIG.
26A.
44. FIG. 26C is a partial top plan view in cross section of the
cable adjustment assembly of FIG. 26B.
45. FIG. 27 is an exploded perspective view of the seat
assembly.
46. FIG. 28 is a partial side elevational view in cross section of
an actuator handle.
47. FIG. 29 is a partial top plan view of the actuator handle in
cross section.
48. FIG. 30 is a partial top plan view of the tilt control
mechanism.
49. FIG. 31 is a front cross sectional view of the mounting for the
front tilt lock plate as viewed in the direction of arrows 31-31 of
FIG. 30.
50. FIG. 32 is a right side elevational view in cross section of
the rear lock actuator mechanism.
51. 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 arrangement and designated parts thereof. Said
terminology will include the words specifically mentioned,
derivatives thereof, and words of similar import.
DETAILED DESCRIPTION
52. Referring to FIGS. 1-3, the invention relates to an office-type
chair 10 which includes a seat assembly 11 and back assembly 12
which are pivotally supported on a chair base or pedestal 13 to
support a user thereon. To increase the comfort of the user, the
seat assembly 11 is tiltable forwardly and rearwardly in the
direction of arrow A (FIG. 2) by a tilt control mechanism 14 while
the back assembly 12 thereof is tiltable laterally from side to
side, i.e. in the leftward and rightward directions as indicated by
reference arrow B (FIG. 3) by a back torsion mechanism 15.
53. Generally with respect to the main components of the chair 10,
the base 13 is adapted to be supported on a floor and the seat
assembly 11 is mounted to the base 13 by the tilt control mechanism
14. The tilt control mechanism 14 thereby permits rearward tilting
of the seat assembly 11 relative to the base 14. To improve the
comfort of a user, the tilt control mechanism 14 uses a
double-spring arrangement which is adjustable as described in more
detail hereinafter to urge the chair 10 to a normal upright
position.
54. Further, the back torsion mechanism 15 rigidly joins the back
assembly 12 to the seat assembly 11 such that the back assembly 12
pivots rearwardly in response to rearward tilting of the seat
assembly 11. At the same time, the back torsion mechanism 15 also
defines a forwardly extending horizontal pivot axis whereby the
back assembly 12 can be pivoted to the left and right sides. The
back torsion mechanism 15 is disclosed in U.S. patent application
Ser. No. 08/846,614, entitled CHAIR BACK WITH SIDE TORSIONAL
MOVEMENT, filed Apr. 30, 1997. The disclosure of this latter
application, in its entirety, is incorporated herein by reference.
This combination of forward-rearward tilting and torsional movement
thereby provides three-dimensional chair movement to increase the
comfort of a user.
55. More particularly with respect to the chair 10 and the tilt
control mechanism 14, the chair pedestal 13 includes a central hub
16 and a plurality of pedestal legs 17 which project radially
outwardly therefrom. The ends of the pedestal legs 17 include
casters 18 which are of conventional construction and support the
chair 10 on a floor.
56. Further, the hub 16 supports a vertically elongate spindle 19
which is movable vertically so as to permit adjustment of the
height of the chair 10. The spindle 19 is a rigid upright tube
wherein the upper end of the spindle 19 supports a bottom of the
seat assembly 11 thereon. The spindle 19 also is formed with a
pneumatic cylinder therein of conventional construction which tends
to move the upright 19 upwardly relative to the hub 16 to raise and
lower the chair height. A normally closed control valve 20 (FIG.
10) is formed at the upper end of the upright 19 which can be
opened to permit adjustment of the height of the seat assembly
11.
57. The seat assembly 11 is supported on the upper end of the
spindle 19 by the tilt control mechanism 14 which provides for
forward and rearward tilting of the chair 10. To support the seat
of a user, the seat assembly 11 further includes a cushion assembly
22 which is supported on the tilt control mechanism 14.
58. The cushion assembly 22 includes a seat support frame 25 (FIGS.
1-4) which mounts to the tilt control mechanism 14. In particular,
the seat support frame 25 is supported on the tilt control
mechanism 14 by a rectangular center mounting structure 26 which
includes a downwardly depending peripheral side wall 27 that is
adapted to be fitted over the top of the tilt control mechanism 14.
The center mounting structure 26 thereafter is secured to the top
of the control mechanism 14 by suitable fasteners.
59. The seat support frame 25 further includes four support arms 28
which project sidewardly away from the left and right sides of the
center mounting structure 26 and extend generally upwardly to
support a ring-like rim 29 a predetermined distance above the
control mechanism 14. The ring-like rim 29 has a generally annular
shape and is open in the central region above the center mounting
structure 26. The peripheral rim 29 is adapted to support a
horizontally enlarged plastic inner shell (not illustrated) which
overlies the open area of the peripheral rim 29 and includes a
resiliently flexible membrane in the central region thereof to
provide support to a cushion 30 which is attached thereto. The seat
and back assemblies 11 and 12 are disclosed in U.S. patent
application Ser. No. 08/846 616, entitled MEMBRANE CHAIR, filed
Apr. 30, 1997. (Atty Ref: Haworth Case 215). The disclosure of this
latter application, in its entirety, is incorporated herein by
reference.
60. The back assembly 12 also supports a pair of chair arms 31
which project sidewardly and upwardly from a hub 32 on the lower
end of the back assembly 12. The hub 32 is connected to the tilt
control mechanism 14 by the back torsion mechanism 15.
61. Generally with respect to the tilt control mechanism 14, these
types of mechanisms are used to mount a seat assembly to a chair
base and permit rearward tilting of the chair relative to the base.
The particular tilt control mechanism 14 (FIGS. 5-7) disclosed
herein permits both rearward tilting of the seat 11 relative to the
pedestal 13 about a first horizontal pivot axis P1 while also
permitting a corresponding rearward tilting of the back assembly 12
relative to the seat about a second horizontal pivot axis P2.
Preferably the tilting of the back assembly 12 is at a different
and preferably greater rate than the rearward tilting of the seat
assembly 11 in the direction of arrow A which arrangement is
commonly referred to as a "synchro-tilt" mechanism. The tilt
control mechanism 21 also permits forward tilting of the seat 11
relative to the base 13 to further optimize the comfort of a
user.
62. The tilt control mechanism 14 includes a box-like control
housing 34 which is rigidly secured to the base 13 and opens
upwardly to define a hollow interior. The hollow interior is
adapted to contain the internal components of the tilt control
mechanism 14 as described in more detail hereinafter. Generally,
the interior of the control housing 34 includes a pedestal mounting
bracket 35 proximate the rear edge thereof which mounts the control
housing 34 to the upper end of the spindle 19. Preferably, the
pedestal mounting bracket 35 also permits swivelling of the chair
10 about a vertical axis.
63. The control mechanism 14 effectively defines a linkage which
causes the synchronous tilting of the seat and back assemblies 11
and 12. In particular, the control mechanism 14 includes a seat
back support member 36 which is hinged to the control housing 34 by
a center or intermediate pivot rod 37. The center pivot rod 37
defines the second horizontal pivot axis P2 and extends sidewardly
so as to permit vertical swinging of the back support member 36.
Alternatively, screws or other suitable fasteners could be used in
place of the rod 37.
64. The control mechanism 14 further includes a top plate 39 which
has a front edge pivotally secured to the front of the control
housing 34 by a front pivot rod 40, and a rear edge portion
slidably secured to the back support member 36 by a rear pivot rod
41. The front and rear pivot rods 40 and 41 also are oriented
horizontally and extend sidewardly, and the front pivot rod 40
defines the first pivot axis P1 about which the top plate 39
pivots. While the control housing 34 remains stationary during use,
the top plate 39 and back support member 36 are joined one with the
other so as to pivot downwardly together during rearward tilting of
the chair 10.
65. To urge the top plate 39 upwardly and maintain the seat and
back assemblies 11 and 12 in the normal position illustrated in
FIGS. 1-3, the control mechanism 14 also includes a front coil
spring 42 which is supported on the front pivot rod 40, and a pair
of rear coil springs 43 which are supported on the rear pivot rod
41. The front coil spring 42 acts downwardly on the control housing
34 and acts upwardly on the top plate 39 so as to resist downward
pivoting of the top plate 39. The rear coil springs 43 similarly
urge the top plate 39 upwardly so as to assist the front spring 42.
The front and rear coil springs 42 and 43 thereby combine to urge
the top plate 39 upwardly and tend to maintain the back assembly 12
in the vertically upright position as will be discussed in more
detail hereinafter.
66. The tilt control mechanism 14 also generally includes a tension
adjustment mechanism 46 which is actuatable from the side of the
control housing 34 by the adjustment knob 47 that projects
therefrom. The upward force acting on the top plate 39 thereby can
be adjusted so as to make it easier or harder to tilt the seat and
back assemblies 11 and 12.
67. More particularly, with respect to the components of the tilt
control mechanism 14, the control housing 34 (FIGS. 10-13) is
formed with a bottom wall 51, front wall 52, opposite side walls 53
and a rear wall 54. The front wall 52, side walls 53 and rear wall
54 extend upwardly from the bottom wall 51 so as to define the
upward-opening hollow interior thereof.
68. To support the control housing 34 on the spindle 19, the bottom
wall 51 includes an aperture 56 near the rearward end thereof which
receives the upper end of the spindle 19 therethrough. The mounting
bracket 35 is mounted to the bottom wall 51 to further support the
spindle 19. The mounting bracket 35 has a generally U-shape defined
by downwardly extending legs 57 which are welded to the housing
bottom 51, and a top wall 58 which overlies the aperture 56 formed
in the bottom wall 51. The top wall 58 includes a further aperture
59 which is coaxially aligned with the aperture 56 such that the
upper end of the spindle 19 is fixedly secured to the mounting
bracket 35 by any suitable fastening method such as by welding or a
friction fit.
69. Referring to FIGS. 10, 11 and 13, the aperture 59 also provides
access to the pneumatic control valve 20 of the spindle 19. To
actuate the pneumatic cylinder within the spindle 19, the vertical
legs 57 of the mounting bracket 35 include openings 61 on the
opposite sides thereof. An actuation bracket or lever 62 is
provided which has a hooked end 63 which engages one of the
openings 61 such that the lever 62 extends over the aperture 59 and
is movable upwardly and downwardly. The opposite end of the lever
62 includes a downward leg which moves vertically. While the
remaining components for actuating the lever 62 have been omitted
from FIG. 10 for the sake of clarity and are not required for an
understanding of the invention disclosed herein, the lever 62 is
adapted to open the control valve 20 in response to downward
pivoting of the lever 62 which thereby permits adjustment of the
seat height.
70. To join the top plate 39 and back support member 36 to the
control housing 34 as generally described above, the opposite side
walls 53 of the control housing 34 include front apertures 66 and
rear apertures 67. The front apertures 66 receive the front pivot
rod 40 for connecting the top plate 39 thereto, while the rear
apertures 67 receive the center pivot rod 37 for connecting the
back support member 36 thereto. The left side wall 53 further
includes a middle aperture 68 for the adjustment knob 47.
71. To support the back assembly 12 on the control housing 34, the
back support member 36 includes an upward-opening rearward end
section 71 to which the back assembly 12 is connected by the back
torsion mechanism 15. In particular, the back assembly 12 includes
a rigid vertical upright 69 and the back torsion mechanism 15
rigidly connects the lower end of the upright 69 to the back
support member 36. As a result, the upright 69 moves in combination
with the back support member 36 while the back torsion mechanism 15
permits sideward tilting of the upright 69 and in particular,
sideward tilting of the back assembly 12 which is supported by the
upright 69.
72. The back support member 36 also includes a pair of pivot arms
72 which project forwardly from the rearward end section 71 and are
pivotally secured to the side walls 53 of the control housing 34 by
the intermediate pivot rod 37. The pivot arms 71 include coaxially
aligned apertures 73 at the forward ends thereof which are
supported on the center pivot rod 37.
73. More particularly, the center pivot rod 37 extends sidewardly
or laterally through the aligned apertures 67 and 73 formed in the
side walls 53 and pivot arms 72 respectively. As a result, the
center pivot rod 37 defines the second horizontal pivot axis P2
such that the back support member 36 moves vertically or pivots in
the direction of reference arrows C (FIG. 5).
74. To connect the top plate 39 to the back support member 36, the
rearward end section 71 also includes coaxially aligned apertures
74 formed through the side walls thereof. The apertures 74 receive
the rear pivot rod 41 therethrough to connect the top plate 39 and
back support member 36 together as described in more detail
hereinafter.
75. The top plate 39 (FIGS. 10 and 14) includes a horizontal top
wall 76 and downwardly extending side walls 77 so as to seat over
the control housing 34 and a portion of the back support member 36.
The side walls 77 also include a pair of coaxially aligned front
apertures 78 which receive the front pivot rod 40 therethrough. As
a result, the front section of the side walls 77 is secured to the
housing 34 by the front pivot rod 40 which permits vertical
pivoting of the top plate 39 generally in the direction of
reference arrow D (FIG. 5) about the pivot axis P1. This vertical
pivoting of the top plate 39 permits corresponding tilting of the
seat assembly 11 which is connected thereto.
76. The rear section of the side walls 77 also includes
horizontally elongate slots 79 through which the opposite ends of
the rear pivot rod 41 project. Thus, unlike the center and front
pivot rods 37 and 40 respectively which only permit pivoting
movement, the rear pivot rod 41 is slidable along the slots 79
generally in the direction of reference arrow E. In particular, the
slots 79 permit both rotational and translational movement of the
rear pivot rod 41.
77. Once the control housing 34, back support member 36 and top
plate 39 are pinned together by the center, front and rear pivot
rods 37, 40 and 41 as described above, vertical pivoting of the top
plate 39 about axis P1 causes a corresponding vertical pivoting of
the back support member 36 about axis P2. This vertical pivoting of
the back support member 36 thereby results in the forward and
rearward tilting of the back assembly 12 which projects upwardly
therefrom.
78. During use, as seen in FIGS. 7-9, the top plate 39 is pivotable
by a user between a forwardly inclined position (FIG. 7) and a
rearwardly declined or tilted position (FIG. 9). In the forwardmost
position, the rear pivot rod 41 slides forwardly to a front end of
the slots 79. In this forward position, the top plate 39 is
inclined at an angle of approximately 3.degree. relative to a
horizontal plane while the back upright 69 is tilted forwardly of a
vertical plane at an angle of 10.degree.. Since the rear pivot rod
41 is able to slide along the length of the slot 79, the top plate
39 can be rearwardly pivoted to a normal seating position
illustrated in FIG. 8. In this normal position, the rear pivot rod
41 is disposed generally at the midpoint of the elongate slot 79
wherein the top plate 39 preferably is reclined at an angle of
approximately 2.degree. relative to the horizontal plane and the
upright 69 is tilted rearwardly of the vertical plane at an angle
of 0.degree.. Upon further rearward pivoting of the top plate 39,
the rear pivot rod 41 moves to the rearward end of the slot 79. In
this rearward position, the top plate 39 preferably is reclined at
an angle of approximately -12.degree. relative to the horizontal
plane while the upright 69 is at 20.degree..
79. As can be seen, the back assembly 12 pivots rearwardly as the
top plate 39 pivots. However, the back support member 36 and
accordingly, the back assembly 12 which is connected to this back
support member 36 tilts rearwardly at a greater rate than the top
plate 39. This tilting of the top plate 39 and back support member
36 at different rates is commonly referred to as synchronous
tilting or in other words, the tilt control mechanism 14 is
referred to as a "synchro-tilt" mechanism. Preferably, the tilt
differential between the top plate 39 and back support member 36 is
approximately a two-to-one ratio wherein as the top plate 39 tilts
rearwardly or downwardly 5.degree., the back upright 69 pivots
rearwardly approximately 10.degree..
80. The top wall 76 (FIGS. 10 and 14) also includes a pair of
angled slots 81 near the front edge thereof which are adapted to
support a front tilt lock plate 82 as will be described in more
detail hereinafter. The angled slots 81 preferably have one end
which is enlarged similar to a keyhole shape for engagement with
the front tilt lock plate 82.
81. In the middle region of the top wall 76, three sidewardly
elongate slots 84 are formed which pivotally receive a rear tilt
lock plate 85 as also will be discussed in more detail hereinafter.
Still further, a rectangular central opening 86 is formed
rearwardly of the slots 84 and is located directly above the
spindle mounting bracket 35 in the control housing interior.
Preferably, the periphery of the opening 86 is defined by an
upturned lip 87 which provides additional rigidity to the top wall
76. On the right side of this opening 86, a further opening 88 is
formed through the top wall 76 so as to permit an actuator
mechanism (not illustrated) to extend therethrough for actuating
the rear tilt lock plate 85. Further, the rear edge of the top wall
76 includes an inclined flange 89 which projects upwardly and
rearwardly therefrom and at least partially overlies the rear coil
springs 43.
82. Referring to FIGS. 11 and 12, the tilt control mechanism 14
further includes a spring arrangement within the hollow interior of
the control housing 34 which acts upwardly on the top plate 39 so
as to normally urge the back assembly 12 and seat assembly 11 to
the forward position (FIG. 7). This spring arrangement, however,
permits rearward tilting of the seat and back assemblies 11 and 12
in response to movement by a user.
83. This spring arrangement preferably includes the aforementioned
front spring 42 and the rear springs 43. Both the front and rear
springs 42 and 43 act upwardly on the top plate 39.
84. More particularly, the front spring 42 preferably is formed
from a single length of a coil spring material. Accordingly, the
front spring 42 includes lower legs 91 which are defined by the
opposite ends of the coil spring material, a plurality of adjacent
spring coils 92 and a bridging section 93 which extends sidewardly
between the opposite end coils 92 to define an upper leg 94 of the
spring 42.
85. To support the front spring 42 in the control housing 34, the
front pivot rod 40 extends coaxially through the center of the
spring coils 92 and includes a hollow cylindrical plastic spacer 96
(FIG. 15) which supports the spring coils 92 thereon. The coils 92
fit closely about the outer circumference of the spacer 96, and the
lower and upper spring legs 91 and 94 preferably extend rearwardly
away from the housing front wall 52.
86. The upper spring leg 94 thereby acts upwardly on the bottom
surface of the top plate 39, while the lower spring legs 91 act
downwardly toward the housing bottom wall 51. While the front
spring 42 is resiliently flexible and permits downward pivoting of
the top plate 39, the spring 42 applies an upward acting spring
force to return the top plate 39 to the forward position.
87. To adjust the tension in the front coil spring 42, the side
tension adjustment mechanism 46 (FIGS. 10, 12 and 15) is provided
within the control housing 34 and preferably acts on the lower legs
91 to adjust the spring force applied against the top plate 39.
88. Generally, the tension adjustment mechanism 46 includes a
plastic wedge block 101 which is movable forwardly and rearwardly
so as to raise and lower the lower legs 91 and increase and
decrease the spring tension respectively. The tension adjustment
mechanism 46 includes a steel guide plate 102 that defines an
upturned angled track 103 on which the wedge block 101 is slidably
engaged. The wedge block 101 slides forwardly along the track plate
102 in response to sideward pushing by the tension adjustment knob
47. In particular, the adjustment knob serves to drive an elongate
shaft 104 sidewardly against the wedge block 101 wherein the wedge
block 101 slides at an angle along the angled track 103 so as to
move both sidewardly and forwardly underneath the lower legs 91. By
suitable movement of the adjustment shaft 104, the wedge block 101
is moved forwardly or rearwardly to adjust the position of the
lower legs 91.
89. More particularly, the track plate 102 includes a planar bottom
section 106 which is welded onto the bottom wall 51 of the control
housing 34 such that the track 103 remains stationary. The plate
102 also includes an upstanding support flange 107 which has an
aperture 108 for receiving the adjustment shaft 104. To support the
flange 107, a brace 109 (FIGS. 10, 13 and 15) extends sidewardly
from the flange 107 and is welded to the housing side wall 53.
Further, the track plate 102 includes an adjustment nut 111 (FIG.
15) which is welded on the inner side of the support flange 107 and
is threadingly engaged with the adjustment shaft 104. As a result,
the adjustment shaft 104 is laterally movable into and out of the
control housing 34.
90. To slidably guide the wedge 101, the track 103 is formed along
one edge of the bottom section 106, and extends upwardly therefrom.
The track 103 preferably is formed at an angle of approximately
45.degree. relative to the axis of the front pivot rod 40.
91. With respect to the adjustment shaft 104, the distal end
thereof includes a threaded portion 112 as well as a convex drive
knob 113 at the end thereof. The threaded portion 112 is engaged
with the adjustment nut 111 such that rotation thereof causes the
shaft 104 to be moved laterally toward and away from the wedge 101.
Preferably the threaded engagement of the adjustment shaft 104 and
the stationary nut 111 is through "acme" type threads which make it
easier for a user to rotate the adjustment knob 67.
92. The drive knob 113 abuts against the side of the wedge block
101 to push the wedge 101 sidewardly as the shaft 104 is advanced
into the control housing 34 as described in more detail
hereinafter. Since the wedge 101 also moves forwardly as it moves
along the track 103, the drive knob 113 is convex to reduce its
contact area with the wedge 101 and reduce friction therebetween
during forward movement of the wedge 101.
93. To move the wedge block 101, the bottom surface of the wedge
block 101 includes a channel 116 which preferably is formed at an
angle in the range of 35.degree.-55.degree. and preferably at
approximately a 45.degree. angle. The angle of the channel 116
corresponds to the angle of the track 103. The channel 116 is
adapted to receive the track 103 therein so that the wedge 101 is
freely slidable therealong in response to the sideward movement of
the adjustment shaft 104.
94. Preferably, the wedge block 101 is formed of an acetal or other
suitable plastic or low-friction material which freely permits
sliding of the wedge block 101. To further decrease friction, the
wedge block 101 is formed with additional shallow channels (not
illustrated) on the bottom surface thereof which are parallel to
the deep channel 116 and thereby reduce the overall surface area on
the bottom of the wedge block 101 which is in contact with the
track plate 102.
95. Accordingly, in response to rotation of the adjustment shaft
104, the shaft 104 is advanced or moved sidewardly as generally
illustrated in FIGS. 15 and 16 so as to apply a sideward driving
force on the side surface of the wedge block 101. However, since
the wedge block 101 is slidably engaged with the guide track 103,
the wedge 101 thereby moves at an angle along the track 103 between
a withdrawn position (FIGS. 12 and 16) and an inserted position
(FIGS. 15 and 17). This movement along the track 103 has both a
sideward component of motion as well as a forward component of
motion. It is the forward component of motion that serves to drive
lower spring legs 91 upwardly as seen in FIG. 17.
96. The wedge block 101 preferably has an inclined surface 117 on
the front face thereof which is inclined at an angle in the range
of 30.degree.-50.degree. and preferably at an angle of
approximately 40.degree. relative to the bottom surface of the
wedge 101 and serves to raise and lower the lower spring leg 91.
The angle of the inclined surface 117 can be varied although it is
selected so as to permit free sliding of the wedge block 101
underneath the spring legs 91 while at the same time, being
sufficiently steep such that the downward force of the spring legs
91 tends to urge the wedge block 101 rearwardly. Thus, when the
adjustment shaft 104 is backed out of the control housing 34 (FIG.
16), the wedge block 101 is pressed rearwardly by the lower spring
legs 91 to slide back up the track 103. Accordingly, the drive knob
113 of the shaft 104 need only abut against the side of the wedge
block 101 and a positive connection is not required therebetween.
As the wedge block 101 is driven sidewardly and forwardly, the side
surface of the wedge 101 slides freely along the drive knob 113 in
the forward direction.
97. Preferably, the tension adjustment mechanism 46 also includes
an intermediate support plate 119 which is provided between the
inclined surface 117 of the wedge 101 and the bottom of the lower
spring legs 91. The support plate 119 (FIG. 10) includes a central
section 120 (FIGS. 10 and 15) which is placed between the wedge 101
and the lower spring legs 91.
98. To mount the support plate 119 in position, the central section
120 is formed with upturned flanges 121 on the opposite sides
thereof. The flanges 120 include apertures 122 which are adapted to
receive the front pivot rod 40 therethrough such that the support
plate 119 is movable upwardly and downwardly about the front pivot
rod 40. The support plate 119 also includes an inclined flange 123
along the rearward free edge thereof. To avoid interference with
the upstanding track 103, the plate 119 is notched on the right
side thereof.
99. When the plate 119 is supported on the pivot rod 40, the plate
119 supports the lower spring legs 91 on an upper surface thereof.
During operation, the inclined surface 117 of the wedge 101 slides
underneath the support plate 119 to drive the plate 119 as well as
the lower spring legs 91 upwardly.
100. The support plate 121 thereby serves several functions in that
the inclined flange 123 provides an inclined surface 123 which
slides up the wedge 101 to provide for smooth sliding of the wedge
101. The inclined flange 123 also prevents the direct contact of
sharp edges, such as the ends of the lower legs 91, with the
inclined wedge surface 117 which might otherwise gouge the inclined
surface 117. Further, the support plate 119 distributes the forces
being applied by the lower spring legs 91 over the central plate
section 120 which avoids localized forces that might be applied
directly to the inclined wedge surface 117 by the lower spring legs
91.
101. Also, the support plate 119 isolates the spring legs 91 from
the sideward motion of the wedge 101. In particular, the side
flanges 121 not only serve to mount the support plate 119 on the
rod 40, but they also abut against the side walls 53 of the control
housing 34 as seen in FIG. 15 so as to limit sideward movement
thereof. Otherwise if the wedge 101 directly contacted the spring
legs 91, the wedge block 101 would tend to urge the lower legs 91
not only upwardly but also sidewardly due to friction which could
lead to undesirable distortion of the front spring 42.
102. As can be seen, the tension being applied by the front spring
42 is adjusted by manual rotation of the adjustment knob 47 and
selective driving of the adjustment shaft 104 into and out of the
control housing 34.
103. While the tension adjustment mechanism 46 acts on the lower
spring legs 91 of the front spring 42, the skilled artisan will
also appreciate that the tension adjustment mechanism 42 could be
used to press the upper spring leg 94 downwardly to adjust the
spring force. Further, the skilled artisan will appreciate that the
tension adjustment mechanism 42 is usable on other types and
arrangements of springs to adjust the spring forces being applied
by the spring.
104. With respect to the rear springs 43, the springs 43 act in
combination with the front spring 42 to urge the top plate 39
upwardly. Generally, each of the rear springs 42 includes an upper
leg 126 which acts upwardly on the top plate 39, and a lower leg
127 which acts downwardly on the rear wall 54 of the control
housing 34.
105. More particularly, the rear coil springs 43 are supported on
the rear pivot rod 41 in substantially coaxial relation therewith
by inner plastic spacers 128. The inner plastic spacers 128 are
substantially cylindrical and have a bore therethrough so as to
receive the rear pivot rod 41. Thus, as the back support member 36
pivots downwardly, some rotational movement of the rear springs 43
relative to the rear pivot rod 41 is permitted.
106. To bias the top plate 39 upwardly, the lower legs 127 of the
springs 43 extend forwardly into the control housing 34 and act
downwardly upon the rear housing wall 54. Preferably, the rear
springs 43 are formed as mirror images of each other such that the
lower legs 127 thereof are both spaced inwardly of the housing side
walls 53. The lower legs 127 are supported on the rear wall 54 by a
semi-cylindrical steel support pin 129 which is welded thereto.
Preferably, the support pin 129 has a semi-circular shape and
includes two peripheral grooves 130 near the opposite ends thereof
which positively retain the lower spring legs 127 therein. The
peripheral grooves 130 define arcuate bearing surfaces 131 on which
the lower spring legs 127 act.
107. Referring to FIGS. 15 and 16, the lower spring legs 127 extend
generally forwardly and horizontally when the top plate 39 is in
forward tilted or in the normal position illustrated in FIGS. 8 and
9. In either position, the lower spring legs 127 act downwardly
onto the top of the arcuate bearing surface 131. As a result,
substantially all of the spring forces of the rear coil springs 43
act upwardly on the top plate 39 since the lower legs 127 act in an
opposite direction downwardly.
108. However, upon rearward tilting of the top plate 39 and back
support member 36, the rear springs 43 which are joined to the back
support member 36 move downwardly therewith such that the angle of
the lower spring legs 127 changes significantly. In particular, as
seen in FIG. 18, the lower spring legs 127 are steeply inclined so
as to act generally on the side surfaces of the arcuate bearing
surface 131 instead of the top thereof. While the force of the
lower spring legs 127 acting on the arcuate bearing surface 131
preferably has a vertical component which acts downwardly on the
support pin 129, most of the spring forces act sidewardly or
forwardly on the pin 129 with a horizontal force component. Thus,
the magnitude of the forces acting upwardly on the top plate 39 is
significantly less than would otherwise occur if the lower legs 127
acted solely with a vertical force component. This is desirable
since the rear springs 43 still serve to urge the chair to its
normal position. Further, the upward acting force on the chair is
reduced when the seat and back assemblies 11 and 12 are pivoted
rearwardly to the rear position illustrated in FIGS. 9 and 18 since
the lower legs 127 also act with the horizontal force component.
Thus, a user can tilt the chair to the rearwardly reclined position
(FIG. 9) with significantly less tilting force than would otherwise
be required to tilt the chair rearwardly. This reduction in force
further optimizes the comfort of a user.
109. With respect to the upper spring legs 126, these legs 126
preferably extend below the top plate 39 so as to act upwardly.
However, since some sliding or displacement of these upper spring
legs 126 along the lower surface of the top plate 39 occurs during
rearward tilting of the chair, an intermediate plastic bearing
plate 134 is preferably provided to reduce the friction generated
between the top plate 39 and the upper spring legs 126.
110. Preferably, the bearing plate 134 is formed as an extension of
the plastic spacers 128. In particular, the bearing plate 134 is
cantilevered from an outer end of the plastic spacers 128 and
projects forwardly and below the top plate 39 so as to be in
contact with the inclined flange 89. Preferably, the free end of
the bearing plate 134 also includes a rounded rib 135 projecting
upwardly therefrom which contacts the bottom of the top plate 39.
The rib 135 is preferred since it reduces the amount of surface
area of the bearing plate 134 which is in contact with the top
plate 39.
111. As a result of the spring arrangement disclosed herein, the
upward acting forces on the top plate 39 can be varied during use.
In particular, the forces being applied by the front spring 42 are
continuous during use but can be adjusted by the tension adjustment
mechanism 46. The rear springs 43, however, which assist the front
spring 42 not only provide a spring force which acts upwardly on
the top plate 39, but also serve to vary the overall spring force
acting on the top plate 39. In particular, the spring force
provided by the rear springs 43 is reduced when the top plate 39 is
raised to its forwardmost position since the deflection of the rear
springs 43 is reduced. However, as the back support member 36 tilts
downwardly, the lower legs 127 are significantly inclined. As a
result, while the actual forces applied by the rear springs 43
increase, the forces applied by the lower legs 127 act with both
the horizontal and vertical force components such that the vertical
force urging the top plate 39 upwardly is less than would otherwise
occur. The arrangement of the rear springs 43 and the support pin
129 serves to reduce the effective spring rate of the rear springs
43 as the chair is reclined. This reduction in spring force allows
a user to maintain the chair 10 in the fully reclined position with
significantly less force than was required to tilt the chair
rearwardly.
112. By separating the forces being applied to the top plate 39
through the use of both the front spring 42 and the rear springs
43, the overall height or profile of the tilt control mechanism 14
is reduced.
113. With the foregoing structure, the seat and back assemblies 11
and 12 tilt both forwardly and rearwardly. However, it is also
desirable to be able to lock out either the forward tilting or the
backward tilting or both. Thus, the tilt control mechanism 14 also
includes a front locking arrangement and a rear locking
arrangement.
114. The front locking arrangement includes the aforementioned
front tilt lock block 82 (FIGS. 10 and 13) which is slidably
engaged with the top plate 39.
115. In particular, the front block 82 includes upstanding pins 139
which are inserted from below into the wide end of the slots 81
formed at the front of the top plate 39. The pins 139 have a
reduced diameter section which allows for sliding of the pins 139
along the reduced diameter portion of the slots 81. By sliding the
front block 82 along the slots 81, the front block 82 is movable
forwardly and rearwardly relative to the front housing wall 52. The
forward and rearward movement of the front tilt lock plate 82 is
effected by a front actuation mechanism (not illustrated) which is
activated by rotation of a front locking knob 140 (FIGS. 1-4). The
front locking knob 140 serves to rotate an elongate rod 138 (FIG.
4) which is supported by one of the arms 28 of the seat support
frame 25. The inner end of this rod 138 includes a leg which pivots
upon rotation of the front locking knob 140 and abuts against a
lever (not illustrated) mounted on the control housing 34 that
pivots about a vertical pivot axis. The lever (not illustrated)
thereby acts against the rightward pin 139 of the front tilt lock
plate 82 which is formed with a cylindrical bearing surface 141 so
as to be movable forwardly and rearwardly along the angled slots
81. Thus, upon clockwise and counter-clockwise rotation of the
front locking knob 140, the front tilt lock block 82 can be moved
forwardly and rearwardly.
116. Referring to FIG. 11, the front tilt lock block 82 includes a
thin portion 142 along the front edge thereof, and a thick portion
143 along a rear edge thereof. Locking out of forward tilting is
accomplished by moving the thicker portion 143 of this front tilt
lock block 82 into the space formed between the upper edge of the
front wall 52 and a bottom surface of the top plate 39.
117. In particular, when the thin portion 142 is disposed in the
gap formed between the housing front wall 52 and the top plate 39
as seen in FIG. 12, the top plate 39 is able to pivot forwardly
about the front pivot axis P1 to the forwardly tilted position
illustrated in FIG. 9. Upon rearward tilting of the top plate 39,
however, the front edge thereof pivots upwardly away from the top
edge of the housing front wall 52.
118. Thus, to lock out the forward tilting, the front tilt lock
block 82 can be moved forwardly into this space such that the thick
portion 143 is positioned between the housing front wall 52 and the
top plate 39. This thick portion 143 thereby prevents forward
tilting of the top plate 39 past the normal horizontal chair
position illustrated in FIG. 8. Upon rearward movement of the front
tilt lock plate 82 out of this space, forward tilting can then be
resumed. However, even though forward tilting is locked out,
rearward tilting is still permitted.
119. To also lock out the rearward tilting of the chair 10, the
aforementioned rear tilt lock plate 85 is provided as seen in FIGS.
10 and 12. The rear tilt lock plate 85 includes rearwardly
extending flanges 146 along the top edge thereof which are adapted
to be slid from below into the corresponding slots 84 (FIG. 14)
formed in the top plate 39. The rear tilt lock plate 85 thus is
pivotally connected to the top plate 39 so as to be movable
forwardly to the forwardmost position illustrated in FIG. 12 and
rearwardly into an interfering relation with the mounting bracket
35 located in the control housing 34.
120. More particularly, when the rear tilt lock plate 85 is
disposed in the forwardmost position illustrated in phantom outline
in FIG. 17, rearward tilting of the seat and back assemblies 11 and
12 is permitted. However, the rear tilt lock plate 85 can be
rearwardly swung into an interfering relation with the mounting
bracket 35 to lock out rearward tilting when the chair is either in
the forwardmost position (FIG. 9), or the normal horizontal
position (FIG. 8).
121. To lock the chair in the forward tilted position (FIGS. 9 and
10), the bottom edge of the rear tilt lock plate 85 includes a
central tab 147 which projects downwardly therefrom. This tab is
adapted to be slidably received into a corresponding notch 148
formed in the front edge of the mounting bracket 35. When the
central tab 147 seats in this notch 148 as seen in FIG. 17, the
lower edge of the rear tilt lock plate 85 is seated on the top
surface of the mounting bracket 35. The rear tilt lock plate 85
thereby acts as a brace which extends upwardly from the mounting
bracket to the bottom surface of the top plate 39 which prevents
rearward tilting of the top plate 39.
122. The rear tilt lock plate 85 also is usable to lock out
rearward tilting of the chair 10 from the normal horizontal
position while still permitting forward tilting thereof. In
particular, the rear tilt lock plate 85 also includes a pair of
tabs 149 (FIGS. 10 and 19) which project rearwardly and downwardly
from the plate 85. To lock out rearward tilting, the rear tilt lock
plate 85 is tilted rearwardly until the lower edge thereof abuts
against the front edge of the mounting bracket 35. When the rear
tilt lock plate 85 is in this position, the rearwardly projecting
tabs 149 are disposed directly above the front edge of the mounting
bracket 35 and act as a stop upon rearward tilting of the top plate
39. While forward tilting is permitted, rearward tilting of the top
plate 39 causes the tabs 149 to move downwardly until they contact
the top surface of the mounting bracket 35 and thereby limit or
stop further rearward tilting.
123. The forward and rearward swinging of the rear tilt lock plate
85 is provided by a rear tilt lock actuation mechanism (not
illustrated). The rear tilt lock actuation mechanism is controlled
by a rear locking knob 151 (FIGS. 1-3) which is rotated clockwise
and counter-clockwise to rotate an elongate rod 152 which is
mounted on the rear support arm 28 of the seat support frame 25.
This rod 152 causes movement of the lock plate 85.
124. In view of the foregoing, the tilt control mechanism 14 is
tiltable both forwardly and rearwardly. Further, this forward and
rearward tilting can be locked out by a user.
125. In a further embodiment illustrated in FIG. 20, the plastic
spacers 128 may be eliminated while the upper spring legs 126 are
received in a downward opening pocket 156. The pocket 156 is formed
in the top plate 39 and slidably receives the upper spring legs 126
therein. The pocket 156 therefore guides the spring leg 126 during
movement of the back support member 36.
126. Alternatively, the pocket 156 also can be formed as a separate
bracket which is fastened to the top surface of the top plate 39.
In particular, the pocket 156 can be formed as a downward-opening
U-shaped bracket which is bolted onto the top plate 39 and traps
the upper spring leg 126 therein. In this arrangement, the inclined
flange 123 is eliminated and the spring legs 126 extend over the
top of the top plate 39.
127. Referring to FIGS. 21-32, an improved tilt control mechanism
14-1 is illustrated. The tilt control mechanism 14-1 operates
substantially the same as the tilt control mechanism 14 for
rearward tilting of the chair and the following discussion
therefore is directed to the improvements in the tilt control
mechanism 14-1. Since both of the tilt control mechanisms 14 and
14-1 include common components which operate substantially the same
or serve the same function, these common components in the tilt
control mechanism 14-1 are identified by the same reference
numerals previously defined herein, although designated with "-1"
at the end thereof.
128. As seen in FIG. 21, the tilt control mechanism 14-1 includes a
control housing 34-1, a seat back support member 36-1 and a top
plate 39-1 which are supported on the spindle 19-1 and are
pivotally connected together by pivot pins, such as the front pivot
rod 40-1, to permit rearward tilting of the chair. Front and rear
spring arrangements are positioned in the control housing 34-1 to
urge the chair forwardly to its upright position. These components
interact and function in substantially the same manner as the
equivalent components in the tilt control mechanism 14 described
previously and thus, a more detailed discussion of these components
is not believed necessary.
129. One difference, however, in the tilt control mechanism 14-1 is
that the above-described dwell provided by the rear spring
arrangement preferably is minimized. To minimize the dwell, the
control housing 34-1, top plate 39-1 and support member 36-1 are
formed such that the top plate 39-1 contacts the control housing
34-1 prior to a let off in the rear spring load.
130. With respect to the other primary differences in the tilt
control mechanism 14-1, this mechanism includes an improved tension
adjustment mechanism 46-1, pneumatic adjustment mechanism 170, rear
lock actuator mechanism 171 and front lock actuator mechanism
172.
131. With respect to the tension adjustment mechanism 46-1 as seen
in FIGS. 21-23, this mechanism functions substantially the same as
the mechanism 46 in that it wedges the spring legs of the front
spring upwardly to adjust the spring force provided thereby. In
operation, the tension adjustment mechanism 46-1 converts sideward
movement of an adjustment shaft 104-1 into forward movement of a
wedge block 101-1 so as to raise and lower the lower spring
legs.
132. More particularly, the tension adjustment mechanism 46-1
includes a steel guide plate 102-1 (FIG. 23) which has a bottom
section 106-1 that is mounted on the floor or bottom of the control
housing 34-1. The guide plate 102-1 includes an upstanding guide
flange 103-1 that extends at an angle of approximately 20-25
degrees and preferably 22.5 degrees relative to the
forward-rearward axis of the control housing 34-1. The plate 102-1
further includes an upstanding support flange 107-1 which is
threadingly engaged with a threaded section 112-1 of the shaft
104-1 so as to effect axial or sideward movement of the shaft 104-1
during manual rotation thereof.
133. The wedge block 101-1 is modified from the block 101 in that
the block 101-1 is tapered on its opposite sides 175 and 176 so as
to be generally V-shaped when viewed from above. The side surface
175 is at an angle corresponding to the angle of the guide flange
103-1 and slidably abuts against the opposing face of the guide
flange 103-1 so that the block 101-1 slides generally in the
forward-rearward direction. The opposite side surface 176 also is
tapered at an angle of approximately 45 degrees so as to permit
driving of the block 101-1 forwardly.
134. The wedge block 101-1 includes an inclined surface 117-1 on
the front thereof which is inclined at approximately a 35 degree
angle relative to the bottom thereof and slides under the pivoting
plate 119-1 as described previously.
135. Further, an intermediate wedge block 177 is positioned between
the adjustment shaft 104-1 and the block 101-1. The intermediate
wedge block 177 includes an inclined front surface 178 upon which
the steel plate 119-1 can rest. The inclined surface 178 is at an
angle of approximately 35 degrees so as to be substantially flush
with the inclined surface 117-1 when in the position illustrated in
FIG. 23.
136. The wedge block 177 also includes a side surface 179 which is
at an angle corresponding to the angle of the opposing side surface
176 and slidably abuts against the side surface 176. To prevent
rearward movement of the intermediate wedge block 177, the guide
plate 102-1 includes an upstanding flange 180 at the rear edge
thereof which abuts against the rear surface of the wedge block
177. Thus, upon sideward movement of the intermediate wedge block
177 toward the guide flange 103-1, the wedge block 101-1 is pressed
or squeezed therebetween to effect forward movement of the wedge
block 101-1.
137. The wedge block 177 also includes a vertical tab 183
projecting therefrom which limits forward movement of the rear
locking plate 85-1.
138. To drive the intermediate wedge block 177 sidewardly, the
opposite side surface 181 includes a concave pocket 182 (FIGS. 21
and 23) in which the tip end of the shaft 104-1 is received. The
tip end of the shaft 104-1 also has a reduced diameter and includes
a washer 185 thereon which abuts against the side surface 181 and
prevents the shaft 104-1 from gouging the wedge block 177. Still
further, a pin 186 projects radially from the threaded section
112-1 to prevent a user from unscrewing the shaft 104-1 from the
threaded flange 107-1.
139. Further, to prevent bending of the shaft 104-1, a cylindrical
support tube 188 projects out of the control housing 34-1 and
slidably receives the shaft 104-1 therethrough. A sleeve 189 is
also inserted into the support tube 188 so that the shaft 104-1 is
supported along the length thereof.
140. With this improved tension adjustment mechanism 46-1, the
shaft 104-1 is manually rotated to drive the intermediate wedge
block 177 sidewardly which squeezes the wedge block 101-1
forwardly. The intermediate wedge block 177 therefore eliminates
sliding of the shaft 104-1 along the block 177 which otherwise
could cause wear.
141. Referring to FIGS. 21, 22, 24 and 25, the tilt control
mechanism 14-1 also includes the improved pneumatic actuator 170
for raising and lowering the height of the seat assembly. The
pneumatic actuator 170 is preferred since it effects vertical
movement of the pneumatic valve 20-1 through a horizontal pivoting
movement of the actuator lever 62-1, which is particularly
advantageous in a tilt control having a lower profile or vertical
height. Further, the pneumatic actuator 170, while actuated in a
forward-direction in the tilt control mechanism 14-1, can be
actuated in any horizontal direction if desired.
142. More particularly, a pneumatic pressure cylinder 191 is
mounted in the spindle 19 and includes a cylinder shaft 192 at the
lower end thereof. The pressure cylinder 191 is connected between
the chair base and the control housing 34-1 so as to act
therebetween and raise the seat assembly. The valve 20-1 (FIGS. 21
and 24) of the pressure cylinder 191 is located at the top thereof
and includes a valve button 193 which can be depressed to open the
valve 20-1 and permit adjustment of the seat height. The button 193
is vertically movable and includes an arcuate button surface
194.
143. The upper end of the pressure cylinder 191 is enclosed by a
shroud 196 which is fixed in position or sandwiched between the
pressure cylinder 191 on the lower side thereof and the pedestal
mounting bracket 35-1 (FIG. 21) on the upper side thereof. The
shroud 196 includes an increased diameter chamber 197 which seats
over the button 193, and a passage 198 which extends vertically
through the upper wall thereof.
144. To depress the button 193, a pin 200 is positioned in the
chamber. In particular, the pin 200 includes a circular head 201 on
the lower end thereof which has an annular rim 202 projecting
downwardly into contact with the button surface 194. The upper
surface of the circular head 201 contacts the top wall of the
shroud 196.
145. The pin 200 also includes a vertically elongate shaft 203
extending upwardly from the head 201. The shaft 203 extends
vertically through the passage 198 of the shroud 196 and out of the
pedestal mounting bracket 35-1. As seen in FIG. 25, the pin 200 is
able to be pivoted in any sideward direction, and when pivoted, one
side of the head 201 contacts the shroud 196 so as to define a
pivot point. The side of the head 201 opposite the pivot point then
swings downwardly against the button 193 to depress the button 193
and actuate the valve 20-1 for adjusting the chair height.
146. Since the bottom 193, shroud 196, passage 198, head 201 and
shaft 203 are circular when viewed from above, the pin 200 can
actuate the button 193 when the pin 200 is tilted in any sideward
or horizontal direction. Thus, while the pin 200, as described
herein, is tilted forwardly during use, the pin 200 can also be
actuated in any other direction including rearwardly and sidewardly
without modifying the arrangement of the pin 200 and shroud
196.
147. To actuate the pin 200, the actuator lever 62-1 is connected
to the top of the pedestal mounting bracket 35-1 and is pivotable
forwardly. More particularly, one end of the lever 62-1 is
pivotally connected to the bracket 35-1 by a pivot screw 206 (FIGS.
21 and 22). An intermediate section of the lever 62-1 includes an
opening 207 through which the pin shaft 203 is received, and the
free end thereof includes a cable bracket 208.
148. As seen in FIG. 22, a coaxial cable 209 is connected to the
cable bracket 208 so as to pull or pivot the free end of the lever
62-1 forwardly. When the lever 62-1 is pulled forwardly, the pin
200 is tilted as seen in FIG. 25 for adjusting the chair
height.
149. To secure the cable 209 to the lever 62-1, an interior cable
210 of the coaxial cable 209 connects to the cable bracket 208 so
as to move therewith while the cable sheath 211 is connected to a
stationary U-shaped bracket 212 on the control housing 34-1.
150. The opposite end of the cable 209 connects to the seat support
frame 25-1 as seen in FIG. 26. The interior cable 210 also is
connected to a manual actuator mechanism 214 which mounts to the
seat support frame 25-1 as seen in FIG. 27 by fasteners.
151. Referring to FIGS. 26A, 26B and 26C, the cable 209 is adjusted
by an adjustment assembly 221 on the support frame 25-1. The
adjustment assembly 221 includes a bracket 222 overlying the cable
209 proximate the actuator mechanism 214, and a pair of screws 223
threadedly engaged with the frame 25-1. Further, the cable 209
includes a threaded collar 209a which includes threads 209b that
cooperate with corresponding threads or grooves on the bracket 222.
The collar 209a can be repositioned farther into or out of the
bracket 222 to adjust the end position of the cable 209 to permit
fine adjustment of the cable 209 and accommodate variations in the
length of the cable 209. For example, the collar 209a can be
longitudinally toward the bracket 22 for a longer cable 209.
152. With this arrangement, the pneumatic actuator mechanism 170 is
readily usable to raise and lower the seat height, while at the
same time being readily modifiable to permit the actuator pin 200
to be tilted from any sideward direction.
153. Referring to FIGS. 21, 26A and 27, the tilt control mechanism
14-1 further includes the rear lock actuator mechanism 171 and the
front lock actuator mechanism 172 which generally mount to the top
plate 39-1 as seen in FIG. 30. Before discussing the specific
construction of these lock mechanisms 171 and 172, the following
discussion relates to the front and rear actuator handles 227 and
226 for the lock mechanisms 171 and 172 respectively which are
movable between two positions for actuating these lock
mechanisms.
154. In particular, the actuator handles 226 and 227 respectively
include front and rear locking knobs 140-1 and 151-1 which are
connected to the outer ends of front and rear rods 138-1 and 152-1.
The actuator handles 226 and 227 are substantially identical except
that the front rod 138-1 is longer than the rear rod 152-1. Each of
these rods is bent at the inner free end thereof to define a radial
projection 228 having a predetermined length to engage with the
interior components of the front and rear lock mechanisms 172 and
171 as will be described herein. The length of the radial
projection 228 can also be varied where necessary.
155. To mount the actuator handles 226 and 227 to the chair, the
left side support arms 28-1 of the seat support frame 25-1 have
horizontally elongate channels 230 that permit the rods 138-1 and
152-1 to pass therethrough. In particular, each support arm 28-1
includes an outer wall 231 at an outer end thereof which has an
aperture 232 therethrough. The aperture 232 rotatably supports the
outer end of the respective rod 138-1 or 152-1 therein.
156. The center mounting structure 26-1 of the support frame 25-1
also includes U-shaped support brackets 233 which extend upwardly
therefrom and rotatably support the inner ends of the respective
rod 138-1 or 152-1. With this arrangement, the rods are supported
on the support frame 25-1.
157. To connect the rods 138-1 and 152-1 to the respective lock
mechanisms 172 and 171, a T-shaped vertical passage or port 234 is
provided immediately adjacent to the inner support brackets 233. As
seen in FIGS. 28 and 29, the radial projections 228 project
downwardly through the ports 234 into engagement with the internal
components of the lock mechanisms 172 and 171 respectively.
158. To define two engagement positions (as seen in solid outline
and phantom outline in FIG. 29), for example, locked and unlocked
positions for the actuator handles 226 and 227, each port 234
includes a generally V-shaped ramp 236 on the inner edge thereof.
Each side 237 and 238 of the ramp 236 defines a position for the
actuator handles 226 and 227. Thus, upon rotation of the handles
226 and 227, the respective radial projection 228 slides up and
over the apex of the ramp 236 between engaged and disengaged
positions. Preferably, the apex of the V-shaped ramp 236 is rounded
to minimize wear during sliding of the radial projection 228.
159. To permit this sliding over the ramp 236, each rod 138-1 and
152-1 is axially or longitudinally movable relative to the support
frame 25-1. However, each handle 226 and 227 also includes biasing
means 241 which resists this axial movement and tends to bias the
rods axially toward the engaged or disengaged positions on the
opposite sides of the apex.
160. As seen in FIGS. 27-29, the biasing means 241 comprises a pair
of annular collars 242 slidably positioned on the rods, and a coil
spring 243 disposed between the collars 242. Each rod includes a
pair of pinched projections 244 near the radial projections 228 and
the innermost collar abuts against these projections 244. The outer
collar 242, however, is unrestrained on the rod 138-1 or 152-1.
161. When the rods 138-1 and 152-1 are mounted in position, the
spring 243 is in compression and the collars 242 act in opposite
axial directions against the support bracket 233 and the
projections 244. The support bracket 233 also includes a rim or lip
233a which defines a sidewardly opening seat for the collar 242.
The rim 233a prevents the collar from move sidewardly or vertically
relative to the bracket 233 to prevent the collar 242 from sliding
off the bracket 233.
162. The rod, however, is axially movable relative to the support
bracket 233 so that the radial projection 228 can slide up and over
the ramp 236 but is normally biased to one of the operative
positions. With this arrangement, the actuator handles 226 and 227
can be snapped or moved between one of the two positions by
rotation of the knobs 140-1 and 151-1.
163. More specifically with respect to the rear lock mechanism 171
as seen in FIGS. 21, 30 and 32, this mechanism includes the rear
lock plate 85-1 which functions substantially the same as the lock
plate 85 previously described herein. However, the lock plate 85-1
is mounted to the top plate 39-1 in an improved manner.
164. The lock plate includes three tabs 251 on the upper edge
thereof which project vertically through the corresponding slots
81-1 formed in the top plate 39-1. Two of the tabs 251 include
bores 252 extending horizontally therethrough.
165. The tabs 251 also project vertically through corresponding
slots 253 in a plastic isolator 254 (FIGS. 21, 30, 32) which lays
on top of the top plate 39-1. The isolator 254 is formed so as to
permit pins 255 to be inserted sidewardly through the exposed bores
252 of the tabs 251 and into a corresponding bore in the isolator
254. The isolator 254 also includes resilient plastic fingers 256
which snap over the end of each pin 255 after insertion to prevent
the pins 255 from being dislodged.
166. The pins 255 thereby secure the lock plate 85-1 to the
isolator 254. The pins 255 are dimensioned smaller than the bores
252 in the tabs 251 so that forward and rearward rocking of the
lock plate 85-1 can occur. Since the isolator 254 is plastic, metal
to metal contact is minimized which results in a quieter, smoother
acting mechanism.
167. To actuate the lock plate 85-1, the lock plate 85-1 includes a
slot 258 (FIGS. 21 and 32) through which a rod 259 extends. Two
separate springs 260 and two washers 261 are provided on the
opposite sides of the lock plate 85-1 and a drive block 262 is
connected to the rod 259 at one end thereof. The springs 260 are
retained on the rod 259 by a retainer 263.
168. As seen in FIG. 30, the drive block 262 is slidably supported
on the top of the top plate 39-1. The drive block 262 also includes
a recess 264 on the top thereof which receives the above-described
radial projection 228 of the rear actuator handle 227. Thus,
movement of the handle 227 between the engaged and disengaged
positions moves the drive block 262 forwardly and rearwardly which
causes one or the other of the springs 260 to bias the lock plate
85-1 forwardly or rearwardly.
169. Due to the spring connection, if the lock plate 85-1 is
temporarily bound or prevented from pivoting, the springs 260
permit the actuator handle 227 to move completely to one of its
engagement positions, and the lock plate 85-1 would eventually
shift to its locked or unlocked position once any interference has
been removed such as by normal forward or rearward tilting of the
chair by the occupant.
170. In the front lock actuator mechanism 172, a similar
arrangement is used in that a slidable drive block 270 is provided
which includes a top recess 270a connected to the front actuator
handle 226 for forward and rearward movement of the drive block
270. The drive block 270 moves a rod 271 extending forwardly
therefrom, and a pair of springs 272 are slid and retained on the
rod 271.
171. As described previously and as seen in more detail in FIGS.
30-31, the front tilt-lock plate 82-1 includes two projections 273
which project upwardly therefrom and extend through corresponding
key-shaped slots 81-1 in the top plate 39-1. These projections 273
have a circular, large-diameter section 274 but are still slidable
forwardly and rearwardly along the narrow portions of the
key-shaped slots 81-1.
172. To move the tilt-lock plate 82-1, a plastic carrier 276 is
connected to these projections 273 on the top of the top plate
39-1. In particular, the projections 273 have an oval section 277
projecting upwardly from the large-diameter section 274 which snaps
into corresponding openings 278 in the carrier 276 so that the
carrier 276 and the lock plate 82-1 move together.
173. The carrier 276 further includes a downwardly depending rear
wall 277 which is formed with a horizontal aperture for the rod
271. The springs 272 act on the opposite side surfaces 278 and 279
of the rear wall 277 and push the carrier 276 forwardly or
rearwardly.
174. The connection of the springs 272 to the carrier 276
preferably has sufficient clearance and play so as to permit the
carrier 276 and tilt-lock plate 82-1 to rotate or twist relative
thereto as indicated by the arrow in FIG. 30. Preferably, the slots
81-1 and projections 273 also have additional clearance so as to
permit this twisting. As a result, if the tilt-lock plate 82-1
binds or catches on one end thereof, the plate 82-1 can still twist
so as to permit a portion of the plate 82-1 to be moved to its
locked or unlocked position. Upon the removal of the interference
such as by normal movement of the chair, the carrier 276 would
self-center or realign itself.
175. As discussed herein, the tilt control mechanism 14-1 operates
substantially the same as the tilt control mechanism 14 but
includes additional improvements therein.
176. Although particular preferred embodiments of the invention
have 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.
* * * * *