Information
-
Patent Grant
-
6682252
-
Patent Number
6,682,252
-
Date Filed
Friday, March 1, 200222 years ago
-
Date Issued
Tuesday, January 27, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Price Heneveld Cooper DeWitt & Litton LLP
-
CPC
-
US Classifications
Field of Search
US
- 403 83
- 403 98
- 403 146
- 403 99
- 403 84
- 403 97
- 403 101
- 403 96
- 403 3221
- 297 374
-
International Classifications
-
Abstract
A joint is provided that automatically pre-tensions itself during assembly. The joint includes first and second structural members, such as a back upright and a pivot link in a chair. A torsion spring bushing and a pair of threaded anchors pivotally connect the first structural member to the second structural member. The anchor and back upright include mating angled surfaces that inter-engage and rotate the torsion spring bushing during assembly in a manner that pre-tensions the spring bushing while engaging the anchors in a direction parallel an axis of rotation defined by the joint.
Description
BACKGROUND
The present invention relates to energy joints biased with a torsion spring, such as are sometimes used for biasing the back of an office chair to an upright position. However, the present invention is not believed to be limited to office chairs, nor to furniture. Instead, it is contemplated that the present torsional energy joint is useful in many different applications, particularly high-volume assembly situations, where it is desirable to provide a torsional joint with pre-tension.
Chairs often have reclineable backs for increased comfort. The reclineable backs are typically biased toward an upright position in a manner that both supports a person's upper torso when leaning rearwardly, yet that also permits a comfortable recline that feels secure during the reclining motion. Many different types and styles of biasing mechanisms are known in the art. However, improvements are desired to overcome various problems. For example, many such biasing mechanisms include undesirably expensive components and/or “too many” components. Further, the size of the components and/or the complexity of the assembly can lead to warranty problems and/or unacceptably increase the cost of repair (i.e. “in factory” repairs as well as “in service” repairs in the field).
Another desired improvement is in the area of assembly. Many assemblies require multiple and complex fixtures for holding components together during assembly. The fixturing is often made considerably more complex where the biasing mechanism must be given a pre-tension and then held together until the assembly is sufficient to hold the biasing mechanism in its pre-tensioned state. It is noted that pre-tension is required, for example, to provide an initial level of support to a seated user's upper torso before recline begins. The pre-tension forces can be considerable, particularly where the chair is adjustable for large or heavy persons, and where the torque arm on the biasing spring is small compared to the torque of the back upright that a seated user leans against. This results in a fixture that must be capable of applying considerable forces, yet that must do so safely and quickly.
In office chairs and public seating, the above problems are sometimes exacerbated by the appearance requirements of these products, because the products must provide optimal aesthetics in order to result in a sale. In modern times, many product designs have tended to include sleek and thin profiles, and hidden or minimally-sized functional components. This complicates and makes more difficult the design of long-lasting durable biasing mechanisms that are replaceable and repairable.
Accordingly, an apparatus is desired solving the aforementioned problems and having the aforementioned advantages.
SUMMARY OF THE PRESENT INVENTION
In one aspect of the present invention, a jointed apparatus includes first and second structural members, a torsion spring adapted to pivotally support and rotationally bias the first structural member relative to the second structural member about a joint, an anchor for holding the first and second structural members together, and a pre-tensioning device that torsionally tensions the torsion spring as the first and second structural members, the torsion spring, and the anchor member are assembled together.
In another aspect of the present invention, a seating unit includes first and second elongated structural members pivoted together and defining a joint. A bushing is provided that includes a first section attached to the first structural member, a second section, and a torsion spring connecting the first and second sections. A pre-tensioning device engages the second section and the second structural member. The pre-tensioning device has angled surfaces that inter-engage to rotate the second section during assembly to pre-tension the torsion spring during assembly.
In another aspect of the present invention, a method comprises steps of attaching first and second structural members and a torsion spring together with an anchor to form a joint. The step includes torsionally pre-tensioning the torsion spring simultaneously and increasingly as the anchor is tightened in a direction parallel an axis of rotation defined by the joint and the joint is assembled together.
These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1
is a perspective view of a chair including a joint embodying the present invention;
FIG. 2
is an exploded perspective view of the joint circled as area II in
FIG. 1
;
FIG. 3
is a cross sectional view of the joint circled in
FIG. 1
, the cross section being taken parallel an axis of rotation of the joint;
FIG. 4
is an exploded view of
FIG. 3
;
FIG. 5
is a side view of the joint circled in
FIG. 1
;
FIG. 6
is an enlarged side view of a bottom section of the back upright shown in
FIG. 5
, the bottom section forming a part of the joint;
FIG. 7
is a cross sectional view of the joint circled as area II in
FIG. 1
, the cross section being taken perpendicular to the axis of rotation of the joint;
FIG. 8
is a view similar to
FIG. 7
but with the joint in a rotated/reclined position where the chair back is fully reclined;
FIG. 9
is a fragmentary view of the circled area IX in
FIG. 6
, with the spline fingers on the anchors being added and shown in dashed lines, the spline fingers being shown as 16° off from the receiving spline grooves; the keyways and channels of the link, the spring bushing, and the back upright engaging to initially orient the anchors relative to the back upright, but the illustrated arrangement being before the anchors are axially tightened to cause the spline fingers to engage the angled surfaces to rotate and pre-tension the spring bushing; and
FIG. 10
is a view similar to
FIG. 9
, but with the anchors tightened axially to about 50% of their final depth, such that the spline fingers have engaged the angled surfaces and are rotated in direction “A” about 50% toward their final destination in the spline grooves.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
A joint
20
(
FIG. 1
) is provided that automatically pre-tensions itself during assembly. The joint
20
includes first and second structural members
21
and
22
, such as the illustrated back upright (
21
) and the pivot link (
22
) in the chair
10
. A torsion spring bushing
24
(
FIG. 2
) and a pair of mating anchors
25
and
26
pivotally connect the first structural member
21
to the second structural member
22
, as described below. In the illustrated arrangement, the anchors
25
and
26
and back upright
21
include mating surfaces that inter-engage and rotate the torsion spring bushing
24
during assembly in a manner that pre-tensions the torsion spring bushing
24
while the anchors
25
and
26
are drawn together in a direction parallel an axis of rotation
29
defined by the joint
20
. The spring bushing
24
further supports the upright
21
with increasing torque during recline of the upright
21
, which provides a comfortable counterbalancing support to a seated user during recline.
Chair
10
(
FIG. 1
) includes a four-legged base frame
11
, a seat
12
, a back assembly
13
, and two links
22
. The four-legged frame
11
includes a pair of seat-supporting standards
14
located generally at a mid-point of the seat and on opposing sides of the seat
12
. Back assembly
12
includes a torso-supporting panel
15
, and a pair of uprights
21
secured to opposing sides and hanging downwardly. The seat
12
is pivoted to a top of the standards
14
at a middle-of-seat pivot axis
16
, and is pivoted to the back uprights
21
at rear-of-seat pivot axis
17
. Each link
22
is pivoted to the associated back upright
21
at upper link pivot axis
29
and is pivoted to the base frame
11
at lower link pivot axis
19
. By this arrangement, a four bar linkage is constructed that supports the seat and back for synchronous movement upon recline of the back by a seated user. Due to the vertical orientation of the links
22
in their “at rest” position and due to the middle-location of the middle-of-seat pivot axis (which is close to a center of gravity for a seated user), the torsion spring bushings
24
do not need to be excessively strong nor large in order to provide sufficient torque for a comfortable recline by a seated user.
It is contemplated that, even though a particular joint
20
illustrated, any of the joints of the four-bar linkage in the chair
10
could be similarly constructed, using the present inventive principles. Further, it is contemplated that the present joint arrangement can be used on any seating unit where a pre-tensioned torsional spring arrangement is desired, such as pedestal chairs, or stadium or auditorium seating, or in any chair or bench seating where a bias is desired, any transportation seating (e.g. buses, airplanes, boats, and other vehicles), and the like. Also, it is contemplated that the present joint arrangement can be used in a wide variety of non-seating applications, such as for control levers, handles, and the like where it is desirable to bias a member to a home position with pre-tension, e.g. to prevent accidental movement.
As noted above, in the illustrated arrangement, the first and second structural members comprise the back upright
21
and the pivot link
22
in the chair
10
. The chair
10
is sufficiently described above (and below) for an understanding of the present invention, but for the reader's benefit it is noted that a chair like chair
10
is disclosed in more detail in application Ser. No. 09/578,568, file May 25, 2000, entitled Synchrotilt Chair, the entire contents of which are incorporated herein by reference. It is specifically noted that a joint
20
can be incorporated into one of the joints in the single-post pedestal base chair disclosed in application '568, such as in the link that is most similar to the four-legged chair shown in the application '568.
The illustrated back upright
21
(
FIG. 2
) comprises a hollow polymeric component molded by gas-assist injection-molding techniques. The back upright
21
includes an elongated body
30
with opposing longitudinally-extending parallel flanges
31
and
32
extend from its lower end. The flanges
31
and
32
include aligned holes
33
and
34
, and further each include an outer surface
35
and an inner surface
36
. The outer surfaces
35
each include a recess
37
for receiving a washer-like head
63
on the outer ends of the anchor members
25
and
26
. At a bottom of each of the recesses
37
is an annular flange
38
that defines a plurality of radially-positioned splines or grooves
39
that extend longitudinally through the holes
33
(and
34
). There are illustrated ten such grooves
39
(see FIG.
6
), but more or less can be used depending upon the functional requirements and stresses generated by the particular spring bushing
24
being used.
The link
22
(
FIG. 2
) also comprises a molded polymeric component. The link
22
is shaped like a dog-bone, and has an upper end
40
with a transverse hole
41
and a lower end
42
. The hole
41
has a pair of channel-like keyways
43
that extend along the longitudinal axis
29
of the hole
41
. A ridge
45
is located on an outside top surface
46
of the upper end
40
, and extends parallel the keyways
43
. The ridge
45
is located and shaped to engage the mating lip
47
on the lower end of body
30
to limit rotation of the link
22
relative to the body
30
. When the torsion spring bushing
24
is pre-tensioned, the stop formed by features
45
/
47
limits rotation of the components
21
and
22
to maintain the pre-tension (see FIG.
7
). A second ridge
47
′ is located on the components
21
to limit arcuate rotation of the components
21
and
22
in a second opposite direction (FIG.
8
), such as to limit recline. The stop
45
/
47
holds the upright
21
in its upright or home position, and the stop
45
/
47
′ limits travel of the upright
21
in its rearmost reclined position.
Between each of the grooves
39
(
FIG. 6
) is an inwardly-extending radial section of material or finger
50
. Each of the sections
50
includes an exterior angled surface
51
that is angled relative the axial direction
29
. The angled surfaces
51
form ramps that engage mating features or spline ridges
61
(
FIGS. 2 and 10
) on the anchors
25
and
26
to twist (i.e. rotate) and thus pre-tension the torsion spring bushing
24
during assembly, as discussed below.
The torsion spring bushing
24
(
FIG. 2
) includes an outer ring member
55
, an inner ring member
56
, and a rubber spring member
57
bonded between the two ring members
55
and
56
. The outer ring member
55
is a stamped metal component and includes oppositely-facing outwardly-extending ridge keys
58
formed to interlock with the channel keyways
43
in the upper end
40
of the link
22
. The keys
58
and keyways
43
are shaped to slide linearly together for assembly in a direction parallel to the axis of rotation
29
. When interconnected, they interlockingly engage to prevent undesired rotation. The inner ring member
56
is a machined component (although it could also be stamped or otherwise formed), and includes oppositely-facing inwardly-extending ridge keys
59
formed to interlock with the channel keyways
60
formed in the anchors
25
and
26
, as described below.
The anchors
25
and
26
are powdered metal components. The anchors
25
and
26
each have a tubular shank
62
with the channel keyways
60
formed on an outside surface for engaging ridge keys
43
in the torsion spring bushing
24
. They also each include L-shaped spline ridges
61
extending from the trailing end of the shank
62
and onto the heads
63
that mate with grooves
39
. The shanks
62
of the anchors
25
(and
26
) are hollow and include end surfaces that abut each other upon complete and full assembly. The washer-like heads
63
fit mateably into the recesses
37
upon complete and full assembly. The anchor
25
includes a screw
64
that threadably engages a threaded hole
65
in the other anchor
26
. The screw
64
is run in during assembly, and draws the anchors
25
and
26
together, causing the spline ridges
61
to operably engage the angled surfaces
51
for pre-tensioning the spring
57
.
More specifically, during assembly, as the anchors
25
and
26
are brought together along the axis direction
29
by screw
64
, the ridges
61
engage the angled surfaces
51
(see
FIG. 9
) and then force the anchors
25
(and
26
) to rotate a predetermined number of degrees about the axis
29
relative to the link
22
(see
FIG. 10
) where the anchors are inserted 50% of the way. When fully assembled, the L-shaped spline ridges
61
fit into mating L-shaped pockets
66
that align with the grooves
39
. This rotation creates the pre-tension in the rubber spring member
57
, since the outer ring member
55
is held in a stationary position by stop
45
/
47
and the inner ring member
56
is forced to rotate by action of the anchors
25
and
26
. The amount of force to accomplish the assembly and provide the desired pre-tension in the rubber spring member
57
is affected by a number of different factors. For example, the following are some of the factors that affect the step of assembly and affect the design of components: the amount of the desired rotation for pre-tensioning the spring
57
, the angle of inclination of the angled surfaces
51
along with the number and length of the angled surfaces
51
, the size and physical “geometry” of the joint design (such as the maximum distance of draw or length of screw that can be used), the strength and lubricity of all components, the functional requirements of the assembly (such as the gross torsional force required by the chair design), and similar factors. The illustrated arrangement rotates the spring
57
about 16 degrees during assembly, and the angled surfaces extend arcuately at an angle of about 45° to the axis
29
.
Testing has shown that the joint
20
can be made to be assembled without use of a separate fixture or clamp assist when assembling the joint
20
and pre-tensioning the spring
57
. For example, in the illustrated arrangement, when the rotation of the screw
64
is in the same direction as the pre-tensioning direction for the spring
57
, it has been found that the threads in the anchors
25
and
26
and the angled surfaces and related components of the illustrated arrangement will provide sufficient draw or “pulling force” and structure necessary for full and complete assembly. However, on the opposite side, where the rotation of the screw
64
is in an opposite direction of the pre-tensioning direction for the spring
57
, the illustrated arrangement requires an assist to help clamp and draw the anchors
25
and
26
together and to rotate the anchors
25
and
26
for full and complete assembly.
It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.
Claims
- 1. A jointed apparatus comprising:first and second structural members; a torsion spring adapted to pivotally support and rotationally bias the first structural member relative to the second structural member about a joint; an anchor for holding the first and second structural members together; and a pre-tensioning device that automatically rotates during assembly and thus torsionally tensions the torsion spring as the first and second structural members, the torsion spring and the anchor member are assembled together in a coaxial direction.
- 2. The jointed apparatus defined in claim 1, wherein the pre-tensioning device includes features integrally formed on one or more of the first structural member, the second structural member, the anchor, and the pre-tensioning device.
- 3. The jointed apparatus defined in claim 2, wherein at least one of the features is integrally formed on the anchor.
- 4. The jointed apparatus defined in claim 3, wherein the anchor comprises two mating pieces that telescope together in a direction parallel an axis of rotation defined by the joint.
- 5. The jointed apparatus defined in claim 4, wherein the at least one feature includes angled surfaces forming ramps that axially engage in a manner causing rotation of a portion of the torsion spring as the two mating pieces are assembled together.
- 6. The jointed apparatus defined in claim 5, including a stop on at least one of the first and second structural members, and wherein the torsion spring is pre-tensioned against the stop by action of the angled surfaces during assembly.
- 7. The jointed apparatus defined in claim 1, wherein the anchor comprises two mating pieces that telescope together in a direction parallel an axis of rotation defined by the joint.
- 8. A jointed apparatus comprising:first and second structural members; a torsion spring adapted to pivotally support and rotationally bias the first structural member relative to the second structural member about a joint; an anchor for holding the first and second structural members together; and a pre-tensioning device that torsionally tensions the torsion spring as the first and second structural members, the torsion spring and the anchor member are assembled together, wherein the pre-tensioning device includes angled surfaces and mating surface on the anchor and on at least one of the structural members, the angled surfaces forming ramps that engage the mating surfaces to thus angularly rotate the torsion spring relative to the first and second structural members during coaxial assembly of the anchor to the structural members.
- 9. A jointed apparatus comprising:first and second structural members; a torsion spring adapted to pivotally support and rotationally bias the first structural member relative to the second structural member about a joint; an anchor for holding the first and second structural members together; and a pre-tensioning device that torsionally tensions the torsion spring as the first and second structural members, the torsion spring and the anchor member are assembled together, wherein the torsion spring has an inner member keyed to the first structural member, an outer member keyed to one of the second structural member and the anchor, and an elastomeric member located between the inner and outer members.
- 10. The jointed apparatus defined in claim 9, wherein the elastomeric member comprises rubber.
- 11. The jointed apparatus defined in claim 9, wherein the outer member includes a first key engaging the anchor member, and the anchor member includes a second key engaging the second structural member.
- 12. The jointed apparatus defined in claim 1, wherein the first and second structural members are first and second pivotally-connected components of a seating unit.
- 13. The jointed apparatus defined in claim 12, wherein the seating unit includes a back having an upright frame member, and one of the first and second structural members comprises the upright frame member.
- 14. The jointed apparatus defined in claim 12, wherein the seating unit comprises a chair having a seat, a base, a back upright, and at least one pivot link connected to each other at multiple joints to define a four-bar linkage for supporting the back upright for movement between reclined and upright positions, one of the multiple joints being the first-mentioned joint.
- 15. A jointed apparatus comprising:first and second elongated structural members pivoted together and defining a joint; a bushing including a first section attached to the first structural member, a second section, and a torsion spring connecting the first and second sections; and a pre-tensioning device engaging the second section and the second structural member, the pre-tensioning device having angled surfaces forming ramps on at least one of the pre-tensioning device and the structural members that inter-engage mating surfaces on another of the pre-tensioning device and the structural members to automatically rotate the second section during assembly to pre-tension the torsion spring during coaxial assembly.
- 16. The jointed apparatus defined in claim 15, wherein the pre-tensioning device includes at least one anchor member interconnecting the first and second structural members.
- 17. The jointed apparatus defined in claim 16, wherein the at least one anchor member includes first and second anchor members that engage in a direction parallel an axis of rotation defined by the joint.
- 18. The jointed apparatus defined in claim 16, wherein the at least one anchor member includes angled surfaces that engage mating surfaces on one or more of the first structural member, the second structural member, and the bushing.
- 19. The jointed apparatus defined in claim 1, wherein the first and second structural members form components of a seating unit.
- 20. The jointed apparatus defined in claim 19, wherein at least one of the first and second structural members forms a leg of a chair.
- 21. The jointed apparatus defined in claim 15, wherein the first and second elongated structural members form components of a support structure for a seating unit.
US Referenced Citations (7)