Information
-
Patent Grant
-
6793284
-
Patent Number
6,793,284
-
Date Filed
Wednesday, March 19, 200321 years ago
-
Date Issued
Tuesday, September 21, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Cuomo; Peter M.
- Harris; Stephanie
Agents
-
CPC
-
US Classifications
Field of Search
US
- 297 3033
- 297 3013
- 297 292
- 297 296
- 297 297
- 297 3011
- 297 3014
- 297 3031
- 297 3034
- 297 3001
- 297 3003
- 297 3004
- 297 3021
- 297 3023
- 297 3024
- 297 408
- 267 155
- 267 131
-
International Classifications
-
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 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 forced 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.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
TECHNICAL FIELD
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
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 modem 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.
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.
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.
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
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.
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.
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.
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
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:
FIG. 1
is a perspective view of a chair;
FIG. 2
is a view of a tilt control mechanism taken along line
2
—
2
of
FIG. 1
;
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;
FIG. 4
is a partial side view of the tilt control mechanism with parts broken-away to reveal details of construction;
FIG. 5
is a partial cross-section taken along line
5
—
5
of
FIG. 3
;
FIG. 6
is an exploded view of the spring assembly components of the tilt control mechanism; and
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
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.
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.
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
.
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
.
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 lockout 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.
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
.
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.
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.
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
.
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
.
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
.
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
.
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.
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.
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
.
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.
Claims
- 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 then 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.
US Referenced Citations (18)