U.S. patent application number 10/391679 was filed with the patent office on 2004-09-23 for steel spring with dwell for chairs.
This patent application is currently assigned to L & P Property Management Company. Invention is credited to Johnson, LeRoy, McMains, Kevin.
Application Number | 20040183351 10/391679 |
Document ID | / |
Family ID | 32987733 |
Filed Date | 2004-09-23 |
United States Patent
Application |
20040183351 |
Kind Code |
A1 |
Johnson, LeRoy ; et
al. |
September 23, 2004 |
STEEL SPRING WITH DWELL FOR CHAIRS
Abstract
This invention provides a spring assembly for use in a chair
tilt control mechanism. The tilt control mechanism is one that can
recline and return a backrest for a chair. The spring assembly
includes a cylindrical block that has first and second ends and a
central bore. A pair of end caps is located at each of the first
and second ends of the block. Each end cap has a receiving section
that can rotate within the central bore of the block. Each end cap
also has a hole extending through it that provides a coupling point
for the chair backrest. The spring assembly also includes at least
one steel coil spring around the block. The spring has one terminal
end coupled to the tilt control mechanism and the other end coupled
to one of the end caps. The end caps rotate within the block as the
chair backrest is reclined or returned. The force needed to rotate
the end caps is a sum of the spring force provided by the spring
and the frictional relationship between the block and the end
caps.
Inventors: |
Johnson, LeRoy; (Lowell,
MI) ; McMains, Kevin; (Holland, MI) |
Correspondence
Address: |
SHOOK, HARDY & BACON LLP
2555 GRAND BLVD
KANSAS CITY,
MO
64108
US
|
Assignee: |
L & P Property Management
Company
South Gate
CA
|
Family ID: |
32987733 |
Appl. No.: |
10/391679 |
Filed: |
March 19, 2003 |
Current U.S.
Class: |
297/302.3 ;
297/303.3 |
Current CPC
Class: |
A47C 1/03272 20130101;
A47C 1/03274 20180801; A47C 1/03261 20130101; A47C 1/03255
20130101; A47C 1/03266 20130101 |
Class at
Publication: |
297/302.3 ;
297/303.3 |
International
Class: |
A47C 001/032 |
Claims
What is claimed is:
1. A spring assembly for use in a chair tilt control mechanism used
to recline and return a backrest for a chair, the spring assembly
comprising: a cylindrical block having first and second ends and a
central bore; a pair of end caps, one end cap located at each of
the first and second ends of the block, each end cap having a
receiving section rotatingly disposed within the central bore, each
end cap having a hole extending therethrough, the hole providing a
coupling point for the chair backrest; and a steel coil spring
disposed around the block and having terminal ends, one of the
terminal ends being adapted to be coupled to the tilt control
mechanism and the other of the ends being coupled to one of the end
caps, wherein the end caps rotate within the block as the chair
backrest is reclined or returned, and wherein the force needed to
rotate the end caps is a sum of the spring force provided by the
spring and the frictional relationship between the block and the
end caps.
2. The spring assembly of claim 1, wherein the block is made of a
nylon material.
3. The spring assembly of claim 1, wherein the hole in the end caps
is polygonally-shaped.
4. The spring assembly of claim 2, wherein the end caps are made of
a metal material.
5. The spring assembly of claim 1, further comprising an inner
bearing located within the central bore of the block, and having a
hole extending therethrough.
6. The spring assembly of claim 5, wherein the inner bearing is
made of an acetyl material.
7. The spring assembly of claim 1, wherein a pair of the springs
are provided, and wherein each spring has a pair of terminal ends,
one of the terminal ends of each spring being adapted to be coupled
to the tilt control mechanism and the other of the ends of each
spring being coupled to one of the end caps.
8. The spring assembly of claim 7, further comprising a spring
separator section fixedly coupled to the block and extending
radially outwardly therefrom and between the two steel springs,
wherein the spring separator section is adapted to control the
positioning of the springs.
9. The spring assembly of claim 8, further comprising a
polygonally-shaped rod disposed through the end caps, the
polygonally-shaped rod providing the coupling point for the
backrest.
10. The spring assembly of claim 7, wherein the end caps each have
a retaining end that extends outwardly from the receiving section
adjacent the end of the respective first and second ends of the
block, and wherein the retaining ends each have a notch therein for
receipt of one of the ends of the springs, the notches operating to
rotate the ends of the springs as the end caps rotate.
11. A backrest tilt control mechanism for a chair having a base, a
seat and a reclining backrest, the mechanism comprising: a housing
adapted to be coupled to the base; an elongated rod extending
through the housing and rotatingly held therewithin, the rod
adapted to be coupled to the backrest; a pair of spaced apart end
caps coupled within the housing and coupled to the rod, the end
caps rotating as the rod rotates, the end caps each having a cap
section and a receiving section; a cylindrical block having first
and second ends and a central bore, the receiving sections of the
end caps extending into the central bore, the end caps rotating
relative to the block; a pair of springs disposed over the block,
each spring having an inside leg and an outside leg, the inside leg
being coupled to the housing and the outside leg being coupled to
an adjacent cap section of one of the end caps, wherein the
backrest rotates the rod upon recline, and as the rod rotates the
end caps rotate within the block, causing energy to be stored in
the spring as the end cap rotates the outside leg of the spring and
wherein the relative movement of the end caps to the block creates
a desired frictional resistance.
12. The mechanism of claim 11, wherein the end caps are made of a
metal material.
13. The mechanism of claim 11, further comprising a bearing located
within the central bore of the block, the bearing rotating within
the block as the rod rotates.
14. The mechanism of claim 13, wherein the bearing is made of an
acetyl material.
15. The mechanism of claim 11, wherein the springs are made of
steel.
16. The mechanism of claim 15, further comprising an adjustment
member coupled within the housing, wherein the inside legs of the
springs are adjustably secured to the adjustment member so that the
initial energy stored within the springs is adjustable.
17. The mechanism of claim 16, wherein the block is made of a nylon
material.
18. The mechanism of claim 17, further comprising a spring
separator section fixedly coupled to the block and between the two
steel springs, wherein the spring separator section is adapted to
control the positioning of the springs.
19. The mechanism of claim 11, wherein the rod is
polygonally-shaped.
20. A chair having a base, a seat coupled to the base and a
backrest that reclines relative to the seat, comprising: a housing
coupled to the base; an elongated rod extending through the housing
and rotatingly held therewithin, the rod being coupled to the
backrest at its outer ends; a pair of spaced apart end caps coupled
within the housing and coupled to the rod, the end caps rotating as
the rod rotates, the end caps each having a cap section and a
receiving section; a cylindrical block having first and second ends
and a central bore, the receiving sections of the end caps
extending into the central bore, the end caps rotating relative to
the block; a pair of springs disposed over the block, each spring
having an inside leg and an outside leg, the inside leg being
coupled to the housing and the outside leg being coupled to an
adjacent cap section of one of the end caps, wherein the backrest
rotates the rod upon recline, and as the rod rotates the end caps
rotate within the block, causing energy to be stored in the spring
as the end cap rotates the outside leg of the spring and wherein
the relative movement of the end caps to the block creates a
desired frictional resistance.
21. The mechanism of claim 20, wherein the end caps are made of a
metal material.
22. The mechanism of claim 20, further comprising a bearing located
within the central bore of the block, the bearing rotating within
the block as the rod rotates.
23. The mechanism of claim 22, wherein the bearing is made of an
acetyl material.
24. The mechanism of claim 20, wherein the springs are made of
steel.
25. The mechanism of claim 24, further comprising an adjustment
member coupled within the housing, wherein the inside legs of the
springs are adjustably secured to the adjustment member so that the
initial energy stored within the springs is adjustable.
26. The mechanism of claim 25, wherein the block is made of a nylon
material.
27. The mechanism of claim 26, further comprising a spring
separator section fixedly coupled to the block and between the two
steel springs, wherein the spring separator section is adapted to
control the positioning of the springs.
28. The mechanism of claim 20, wherein the rod is
polygonally-shaped.
29. A method of tuning a spring assembly for use in a chair tilt
control mechanism used to recline and return a backrest for a
chair, the spring assembly comprising a cylindrical block having
first and second ends and a central bore; and a pair of end caps,
one end cap located at each of the first and second ends of the
block, each end cap having a receiving section rotatingly disposed
within the central bore, each end cap having a hole extending
therethrough, the hole providing a coupling point for the chair
backrest; wherein the end caps rotate within the block as the chair
backrest is reclined or returned, and wherein the force needed to
rotate the end caps is a sum of the spring force provided by the
spring and the frictional relationship between the block and the
end caps, comprising: determining the desired frictional
relationship between the block and the end caps; and providing the
block and the end caps, the block made of a material that achieves
the desired frictional relationship in combination with the end
cap.
30. The method of claim 29, further comprising adjusting the inner
diameter of the central bore and of the outer diameter of the
receiving section of the end caps.
31. The method of claim 29, further comprising providing a steel
coil spring disposed around the block and having terminal ends, one
of the terminal ends being adapted to be coupled to the tilt
control mechanism and the other of the ends being coupled to one of
the end caps, and adjusting the diameter of the spring's coils.
32. The method of claim 31, further comprising adjusting the number
of coils in the spring.
33. The method of claim 29, further comprising providing a bearing,
wherein the bearing is made of a material that achieves the desired
frictional relationship in combination with the block, and the
bearing is located within the central bore of the block and rotates
within the block as the chair backrest is reclined or returned.
34. The method of claim 33, further comprising adjusting the outer
diameter of the bearing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
TECHNICAL FIELD
[0003] This invention relates generally to chair control
mechanisms, and more particularly to a spring assembly for a chair
tilt control mechanism.
BACKGROUND OF THE INVENTION
[0004] Task chairs or office type chairs have evolved greatly over
the years to improve the support provided to chair occupants and to
provide chairs that better meet the usage needs of modern chair
users. Comfort and promotion of ergonomically healthy sitting are
among factors considered by occupants when choosing a chair. The
development of backrest tilt control mechanisms has enabled chair
occupants to adjust the backrest of a chair to their preferred
positioning.
[0005] The spring assemblies associated with chair tilt control
mechanisms allow occupants to recline the backrest, and also
operate to bias the chair to its upright position when the
reclining force is relieved. The spring assemblies are an important
component in providing comfort to the user. To allow the users to
adjust the chair properly, it is desirable to allow adjustments of
the force needed to recline the chair and the force with which the
chair returns to an upright position.
[0006] It is also desirable that more force be necessary in
reclining the backrest of the chair than when resisting the biasing
force on the backrest that returns it to an upright position. The
difference in these forces is termed "dwell." Dwell is important in
meeting the needs of most chair users. With the dwell properly
balanced, a user can recline the chair to a desired position and
maintain that reclined position with very little effort. Ideally,
the mechanism is adjustable so that the weight of the user's upper
body balances the chair in the reclined position.
[0007] Rubber torsion springs have traditionally been used in the
spring assemblies of tilt control mechanisms to achieve the desired
dwell in the action of the backrest. In use, the rubber springs are
mounted to a rod and energy is stored within the rubber springs as
the backrest is reclined. But rubber springs have a limited life
due to the inherent limitations of the material. For example, the
rubber can break after a long period of use, or the spring
characteristics can shift as the rubber ages. Additionally, even
new rubber springs can vary due to batch differences in the base
rubber material. A mechanism is needed that achieves the desired
dwell in the action of the backrest, without the disadvantages of
rubber springs.
BRIEF SUMMARY OF THE INVENTION
[0008] This invention is directed to a steel spring assembly for
creating dwell when returning the backrest of a chair to an upright
position from a reclined position.
[0009] In one embodiment, the invention provides a spring assembly
for use in a chair tilt control mechanism. The tilt control
mechanism is one that can recline and return a backrest for a
chair. The spring assembly includes a cylindrical block that has
first and second ends and a central bore. A pair of end caps is
located at each of the first and second ends of the block. Each end
cap has a receiving section that can rotate within the central bore
of the block. Each end cap also has a hole extending through it
that provides a coupling point for the chair backrest. The spring
assembly also includes at least one steel coil spring around the
block. Each spring has one terminal end coupled to the tilt control
mechanism and the other end coupled to one of the end caps. The end
caps rotate within the block as the chair backrest is reclined or
returned. The force needed to rotate the end caps is a sum of the
spring force provided by the spring and the frictional relationship
between the block and the end caps.
[0010] In another embodiment the spring assembly further includes a
bearing located within the central bore that can rotate within the
central bore of the block. Each end cap has a truncated receiving
section that can rotate within the central bore of the block. The
bearing and end caps rotate within the block as the chair backrest
is reclined or returned.
[0011] Additional objects, advantages, and novel features of the
invention will be set forth in part in the description which
follows, and in part will become apparent to those skilled in the
art upon examination of the following, or may be learned by
practice of the invention.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0012] In the accompanying drawings which form a part of the
specification and are to be read in conjunction therewith and in
which like reference numerals are used to indicate like parts in
the various views:
[0013] FIG. 1 is a perspective view of a chair;
[0014] FIG. 2 is a view of a tilt control mechanism taken along
line 2-2 of FIG. 1;
[0015] FIG. 3 is a view of the tilt control mechanism similar to
FIG. 2 with portions shown in cross-section to reveal details of
construction;
[0016] FIG. 4 is a partial side view of the tilt control mechanism
with parts broken-away to reveal details of construction;
[0017] FIG. 5 is a partial cross-section taken along line 5-5 of
FIG. 3;
[0018] FIG. 6 is an exploded view of the spring assembly components
of the tilt control mechanism; and
[0019] FIG. 7 is a view of another embodiment of the tilt control
mechanism, similar to FIG. 3, with portions shown in cross-section
to reveal details of construction.
DETAILED DESCRIPTION OF THE INVENTION
[0020] This invention provides a spring assembly for a tilt control
mechanism used on chairs. The spring assembly allows an occupant to
exert a force on the backrest of the chair to recline the backrest.
The spring assembly also biases the chair to an upright position
when the reclining force is relieved. As described below, the
spring assembly also provides dwell in the action of the backrest
without resort to a rubber torsion spring.
[0021] With initial reference to FIG. 1, a chair on which the
mechanism embodying the principles of the invention can be used is
generally indicated by reference numeral 10. Chair 10 is equipped
with a base assembly 12. Base 12 preferably has a number of castors
14 operably supported on the outer ends of a corresponding number
of support legs 16. Support legs 16 converge to a pedestal column
18. Column 18 supports a gas cylinder 20 that allows the height of
the chair to be adjusted by an occupant, as is known to those of
skill in the art. The construction of the base 12 and column 18 is
well known to those of skill in the chair industry.
[0022] With continued reference to FIG. 1, a tilt control mechanism
22 is coupled at one point to gas cylinder 20. Tilt control
mechanism 22 is also coupled to a seat 24 and a chair backrest 26.
Preferably, a pair of armrests 28 is also coupled to tilt control
mechanism 22 or seat 24 or back 26.
[0023] Having briefly described the basic elements of chair 10, a
more detailed description of the various elements of tilt control
mechanism 22 is described below. FIGS. 2, 3, and 4 show various
components of tilt control mechanism 22. Tilt control mechanism 22
has a base housing or chassis 30. Chassis 30 is preferably a
stamped metal piece that provides the overall structure for holding
the various components of the mechanism as described below. Chassis
30 has a pair of spaced-apart sides, each of which has a hole 32.
Hole 32 is used to hold a bearing 34 in place, such as by a
press-fit relationship. Bearing 34 is preferably steel and has a
hole as well. A bushing 36 is located within the hole of bearing
34, as best seen in FIG. 4. The bushing 36 has a polygonal hole
formed therein, the importance of which is described below. As seen
in the figures, the hole is preferably a hexagonal hole. Bushing 36
has an outer diameter that closely matches the diameter of the hole
in the bearing 34, such that the bushing 36 can rotate relative to
the bearing 34. In a preferred embodiment, bushing 36 is made from
a plastic material. The mechanism 22 also includes an elongated rod
38 that is held within the bushings 36. More specifically, the
shape of rod 38 matches the shape of the hole through the bushings
36. In the preferred embodiment, the shape of rod 38 and the shape
of the hole of bushing 36 are hexagonal. Rotation of the rod 38
rotates the bushings 36 within the bearings 34.
[0024] Rod 38 is used to hold and operate a spring assembly 40 and
to attach tilt control mechanism 22 to the frame of chair 10. As
would be understood by those of skill in the art, only the basic
components of the tilt control mechanism 22 that relate to the
spring assembly 40 are shown in the figures. Other components, such
as a height adjustment mechanism or a tilt lock-out mechanism could
be incorporated into mechanism 22, as would be understood by those
of skill in the art. Returning to the spring assembly 40, FIG. 6
most clearly shows the construction, which includes an end cap 42
on each end of the assembly 40. End caps 42 are preferably made of
a metal material, including steel, a sintered metal, a cast metal,
or another material of comparable strength. Each end cap 42 has a
cap section 44 that extends radially beyond a receiving section 46
that extends axially inward from cap section 44. Each end cap 42
also has a spring fulcrum section 47. As best seen in FIG. 4, cap
section 44 has a notch 48 formed in a part thereof, the importance
of which is described more-fully below. A polygonal hole 51 extends
through both cap section 44 and receiving section 46. Hole 51 is
shaped to match the shape of rod 38. In the preferred embodiment
the hole 51 is hexagonal.
[0025] The spring assembly 40 also includes a block 52. Block 52
has a hole 54 that extends axially through the entire length of the
block 52. The hole 54 is used to hold the block 52 on the receiving
section 46 of the end caps. Each receiving section 46 extends into
the hole 54. The hole 54 has an inner diameter that closely matches
the outer diameter of the receiving section 46. Block 52 also has a
pair of raised spring fulcrum sections 56 that are separated by a
radially extending spring separator section 58. As best seen in
FIG. 2, spring separator section 58 is preferably shaped to
separate a pair of coil springs 60.
[0026] In another embodiment best shown in FIG. 7, the spring
assembly 40 further includes a bearing 49 located within hole 54 of
block 52. Bearing 49 is able to rotate within hole 54. In this
embodiment each end cap 42 has a truncated receiving section 45
that extends into the hole 54. A polygonal hole 51 extends through
each end cap 42, including truncated receiving sections 45.
Further, a polygonal hole 53 extends through bearing 49. Polygonal
holes 51 and 53 are shaped to match the shape of rod 38. In this
embodiment, hole 54 is used to hold the block 52 on the bearing 49
and on the truncated receiving sections 45 of the end caps. Hole 54
has an inner diameter that closely matches the outer diameter of
the bearing 49. Preferably, bearing 49 is made of a plastic
material.
[0027] Each coil spring 60 has a longer tail end 62 and a shorter
tail end 64. In-between the tail ends 62 and 64 are a number of
spring coils 66. The short tail 64 has a notch 68 that is located
and shaped to mate with the notch 48 in the end cap 42. As best
seen in FIGS. 2 and 6, springs 60 are held in place on block 52 and
are separated from one another by spring separator section 58.
Longer tail end 62 and shorter tail end 64 pivot upon fulcrum
sections 56 and 47, respectively, allowing coil spring 60 to coil
with minimum restriction. Preferably, springs 60 are made of
steel.
[0028] The tension within springs 60 is preferably adjustable with
a tension adjustment mechanism 70. As best seen in FIG. 5, the long
tails 62 of springs 60 are held within a receiving bracket or nut
72. The receiving bracket or nut 72 is threaded onto a threaded rod
74. Rod 74 terminates at a large bevel gear 76 that mates with a
smaller bevel gear 78. The smaller bevel gear 78 is mounted on the
end of a rod 80 that terminates at a handle 82. By rotating the
handle 82, the user can move the bracket 72 upwardly or downwardly
to adjust the initial tension on springs 60. The tension in springs
60 determines the force necessary to recline the backrest 26 of
chair 10.
[0029] Spring assembly 40 is held in place within tilt control
mechanism 22 by rod 38. More specifically, springs 60 are placed
over the spring fulcrum sections 56 and 47 of block 52 and end caps
42, respectively. The receiving sections 46 or 45 of the end caps
42 are placed in hole 54 of block 52. Rod 38 then slides through
bushing 36, into the hole 51 of end caps 42 and out the other
bushing 36. The outwardly extending ends of rod 38 are then coupled
to backrest 26. As would be understood by those of skill in the
art, many configurations are available for the attachment of the
backrest 26 to the rod 38. The attachment is made such that
reclining the backrest causes rotation of the rod 38.
[0030] As shown in FIG. 3, and as discussed above, receiving
sections 46 of end caps 42 are placed within hole 54 of block 52.
Preferably, block 52 is made from a material that creates a desired
frictional relationship with end caps 42. The desired relationship
creates a frictional force such that dwell is achieved in the
action of spring assembly 40. Again, one such material that may be
used for block 52 is nylon in connection with a metal end cap 42.
It will be understood that any materials that create the desired
frictional relationship and have properties necessary to maintain
the frictional relationship may be chosen for end caps 42 and block
52. One spring 60 is disposed over spring fulcrum sections, 47 and
56, with the notch 68 of short tail 64 located within notch 48 of
the end cap 42. The long tail 62 is held within the receiving
bracket 72.
[0031] In another embodiment as shown in FIG. 7, and as discussed
above, truncated receiving sections 45 and bearing 49 are placed
within hole 54 of block 52. It is preferable that block 52 is made
from a material that creates a desired frictional relationship with
bearing 49. In another embodiment it is preferable that block 52 is
made from a material that creates a desired frictional relationship
with end caps 42 and bearing 49.
[0032] In operation, a user can adjust the energy in springs 60,
which adjusts the force required to recline backrest 26. The
restoring torque exerted by springs 60 against the rotation of rod
38 can be adjusted by changing the position of the long tails 62.
Rotation of the handle 82 causes the receiving bracket 72 to move
linearly along the axis of the rod 74, which in turn moves tails 62
to the desired radial location. Preferably, the gear ratio of the
bevel gears 76, 78 is such that a minimal amount of effort is
required to adjust springs 60 to vary the initial restoring torque
of the springs and, thereby, control the rate at which backrest 26
tilts rearwardly and returns to an upright position.
[0033] When the user reclines, rod 38 rotates. This rotation causes
bushing 36 to rotate within bearing 34 and causes end caps 42 to
rotate relative to block 52. The friction between the end caps 42
and the block 52 adds to the reclining force, such that the force
required to recline the backrest is greater than the return force
of the backrest. In another embodiment the rotation of rod 38
further causes bearing 49 to rotate relative to block 52. In this
embodiment the friction between bearing 49 and block 52 adds to the
reclining force. In another embodiment the friction between both
bearing 49 and end caps 42 with block 52 adds to the reclining
force. The steel spring assembly 40 can achieve roughly the same
reclining force and dwell action as the traditional rubber torsion
springs. The springs 60 are more durable than the rubber springs,
and offer a more consistent spring assembly.
[0034] The action of backrest 26 may be adjusted by altering the
materials and dimensions of the components of spring assembly 40.
As suggested above, different materials may be used for end caps 42
and block 52 to adjust the frictional relationship between these
two components. The desired frictional relationship between end
caps 42 and block 52 may also be altered by adjusting the
dimensions of these elements. For example, the diameter of
receiving section 46 can be altered to provide more or less
clearance from block 52. In addition, the outer diameter of
receiving section 46 (FIG. 3), or the outer diameter of truncated
receiving section 45 and bearing 49 (FIG. 7), along with the inner
diameter of hole 54 of block 52 may be altered to adjust the amount
of force necessary to recline the chair. Springs 60 may also be
adjusted to vary their resistance. The dimensions of springs 60 and
the number of coils 66 may be altered as desired. Such adjustments
are also applicable to the embodiment including bearing 49.
[0035] From the foregoing, it will be seen that this invention is
one well adapted to attain all the ends and objects hereinabove set
forth together with other advantages which are obvious and which
are inherent to the structure. It will be understood that certain
features and subcombinations are of utility and may be employed
without reference to other features and subcombinations. This is
contemplated by and is within the scope of the claims. Since many
possible embodiments may be made of the invention without departing
from the scope thereof, it is to be understood that all matter
herein set forth or shown in the accompanying drawings is to be
interpreted as illustrative and not in a limiting sense.
* * * * *