SPRING ASSEMBLY

Abstract

A method of assembling a spring inside of a tube includes providing a coil spring and a tube having a first retaining structure at a first end of the tube. The method includes positioning a rod in the tube. The spring is positioned in the tube, and a second retaining structure is attached to the rod with the spring positioned between the first and second retaining structures. A force is applied to the spring, and the second retaining structure is fixed at a position wherein the spring provides a desired preload.

Claims

1. An energy mechanism, comprising: a spring generating a spring force upon deformation of the spring; an enclosure housing at least a portion of the spring therein; an actuator having a first portion disposed inside the enclosure and operably engaging the spring, and a second portion extending out of the enclosure to transmit a spring force outside the enclosure, the actuator being movable in a first direction from an initial position wherein the spring is deformed an initial amount and generates an initial spring force acting on the actuator, to a second position wherein the spring is deformed a second amount and generates a second spring force that is greater than the initial spring force; a stop that prevents movement of the actuator in a second direction that is opposite the first direction when the actuator is in the initial position; and wherein the spring is supported in a partially stressed condition within the enclosure after being prestressed to deform the spring to the initial amount of deformation to generate the initial spring force, such that an applied force acting on the actuator must be at least as great as a predetermined initial force to shift the actuator in the first direction from its initial position.

2. The energy mechanism of claim 1, wherein: the stop comprises a fitting disposed at an end of the housing.

3. The energy mechanism of claim 2, wherein: the enclosure defines first and second opposite ends; the second portion of the actuator extends out of the first end of the enclosure; and the fitting is disposed at the second end of the enclosure.

4. The energy mechanism of claim 3, wherein: the fitting includes an inner portion that is disposed inside the enclosure; the enclosure defines an axis that extends through the first and second opposite ends of the enclosure; and the second end of the enclosure comprises a flange that extends inwardly in a direction that is transverse to the axis; the flange engaging the inner portion of the fitting and retaining the inner portion of the fitting inside the enclosure.

5. The energy mechanism of claim 4, wherein: the flange is non-movably fixed with respect to the enclosure.

6. The energy mechanism of claim 5, wherein: the housing includes a sidewall extending parallel to the axis, and wherein the flange is integrally formed with the sidewall.

7. The energy mechanism of claim 6, wherein: the enclosure comprises a tubular member having generally cylindrical inner and outer surfaces.

8. The energy mechanism of claim 1, wherein: the enclosure comprises a tubular member having first and second opposite ends, the first end being at least partially closed by a spring-engaging structure; and the actuator includes an elongated rod having a spring-engaging flange at an inner end of the actuator, and wherein the spring is disposed between the spring-engaging structure and the spring-engaging flange.

9. The energy mechanism of claim 1, wherein: the initial spring force is fixed such that the initial spring force cannot be adjusted.

10. An energy mechanism, comprising: a spring; an enclosure housing the spring; an actuator movable in a first direction from an initial position to at least one displaced position, the actuator extending to the coil spring to transmit a spring force outside of the enclosure; and the spring being supported in a preselected preloaded state within the enclosure after being preloaded to a predetermined spring force, such that an initial spring force required to move the actuator from the initial position correlates to the predetermined force amount, and wherein the initial spring force is fixed such that the initial spring force cannot be adjusted.

11. The energy mechanism of claim 10, wherein: the enclosure includes a stop that prevents movement of the actuator in a second direction that is opposite the first direction when the actuator is in the initial position.

12. The energy mechanism of claim 10, wherein: a portion of the enclosure is deformed to retain the spring in the preselected preload state.

13. The energy mechanism of claim 12, wherein: the spring is retained at the initial position unless a force exceeding the initial spring force is applied to the actuator.

14. The energy mechanism of claim 10, wherein: the enclosure is deformed to form a stop such that the actuator cannot move in a direction opposite the first direction when the actuator is in the initial position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is an isometric view of a chair including one or more spring assemblies according to the present invention;

[0008] FIG. 2 is a side elevational view of the chair of FIG. 1;

[0009] FIG. 3 is a schematic view of the linkage and springs of the chair of FIG. 1;

[0010] FIG. 4 is a partially fragmentary isometric view of a spring assembly according to the present invention;

[0011] FIG. 5 is a side elevational view of a spring assembly according to the present invention;

[0012] FIG. 5A is an exploded cross sectional view of the pin and retainer of FIG. 5;

[0013] FIG. 6 is an exploded isometric view of a spring assembly according to the present invention;

[0014] FIG. 7 is a cross-sectional view of a machine utilized to assemble the spring assembly according to the present invention;

[0015] FIG. 8 is a partially fragmentary view of a spring subassembly according to the present invention;

[0016] FIG. 9 is a partially fragmentary view of a spring assembly according to the present invention; and

[0017] FIG. 10 is a cross-sectional view of a spring assembly according to the present invention.

DETAILED DESCRIPTION

[0018] For purposes of description herein, the terms upper, lower, right, left, rear, front, vertical, horizontal, and derivatives thereof shall relate to the invention as oriented in FIG. 1. However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

[0019] A chair 1 includes a back 2, a seat 3, armrests 4 and a base 5 with castors 6. With further reference to FIGS. 2 and 4, chair 1 includes a four bar linkage comprising a base link 12 that is fixed to the chair base 5, a seat link 14, a control link 16, and a lower link 18. The links 12-16 are interconnected by first, second, third, and fourth pivots 21, 22, 23, and 24, respectively. A spring assembly 30 generates tension forces F1 and F2 acting on points 31 and 32 to thereby bias the four bar linkage 10 into an upright position as shown in FIGS. 2 and 3. It will be understood that the spring and method of the present invention is not limited to coil springs, and also is not limited to spring assemblies generating a tension force.

[0020] With further reference to FIGS. 4-6 and FIGS. 9-10 spring assembly 30 includes a coil spring 34, an actuator or rod 36 having an opening 52 at end 54, a housing or enclosure 38, and an end plug or fitting 40. The spring assembly 30 also includes washers, 42A, 42B and bushings 44A, 44B. A pin 46 extends through an opening 50 in end plug or fitting 40, and a retainer 48 retains the pin 46 in the opening 50. Retainer 48 may comprise a C clip that is received in an annular grove, or it may comprise other suitable retaining devices to retain pin 46 in opening 50 of end plug 40. With reference to FIG. 5A, in a preferred embodiment, pin 46 includes a cylindrical portion 46A having a raised ring-like protrusion or ridge 46B and a slot 46C. Retainer 48 includes an annular ridge 48A that snaps over ridge 46B such that retainer 48 is retained on pin 46. Pin 46 and/or retainer 48 may comprise steel or other suitable material.

[0021] When assembled, pin 46 and opening 52 at end 54 of rod 36 are utilized to transmit forces through the spring assembly 30. When spring assembly 30 is assembled, end flanges 56 and 58 of housing 38 retain the spring 34 in a prestressed, compressed condition. As discussed in more detail below, the flange 58 is formed during assembly while measuring a force applied to rod 36 and end plug or fitting 40, such that the spring 34 has a predefined preload. Thus, the magnitude of tension forces F1 and F2 applied to rod 36 and end plug 40, respectively, must exceed a specified preload force amount before the rod 36 and end fitting 40 will move relative to one another from the initial position shown in FIG. 5. If tension forces F1 and F2 exceed the predefined preload force, coil spring 34 will compress further, resulting in movement of rod 36 in the direction of the arrow A (5) relative to end plug or fitting 40. The spring assembly 30 of the present invention can be assembled in a way that ensures that the actual tension forces F1 and F2 required to cause movement of rod 36 relative to fitting 40 fall within a predefined acceptable range.

[0022] With reference to FIG. 8, housing 38 is initially formed to include an inwardly-extending flange 56A at first end 62A of housing 38. Circular edge 66 at second end 62B of housing 38 is not initially formed to include a flange. During assembly, a first washer 42A is initially positioned in the inner space 60 of housing 38 in position against flange 56A at a first end 62A of housing 38, and a first bushing 44A and rod 36 are positioned as shown in FIG. 8. Rod 36 initially includes a reduced diameter end portion 64 that receives second washer 42B. A coil spring 34 is then positioned in housing 38, and a second bushing 44B and second washer 42B are then positioned in the interior space 60 with second washer 42B disposed on reduced diameter end portion 64 of rod 36. The edge 66 of housing 38 is initially not formed to include a flange, such that washers 42A and 42B, and bushings 44A and 44B can be inserted into interior space 60 of housing 38.

[0023] End 64 of rod 36 is then deformed utilizing a known radial riveting process or other suitable process to create an enlarged end portion 65 which securely retains the washer 42B on end 68 of rod 36. Enlarged end portion 65 is shown in dashed lines in FIG. 8, and in solid lines in FIG. 9. This forms a subassembly 30A as shown in FIG. 8.

[0024] Subassembly 30A is then positioned in a fixture 70 (FIG. 7). Fixture 70 includes first and second pins 72 and 74, respectively, that are received in openings 50 and 52, respectively of spring subassembly 30A. An end plug or fitting 40 is positioned in second end 62B of housing 38. Pins 72 and 74 may be inserted utilizing pneumatic or hydraulic cylinders (not shown). Upper pin 72 fixes the plug 40 relative to upper plate 90 of fixture 70, and lower pin 74 fixes the rod 36 relative to a vertically adjustable cylinder 84. Cylinder 84 can be driven upwardly by threaded force adjustment device 86 by rotating a hand wheel 88. A load cell 82 is utilized to measure the force generated by coil spring 34 on pin 74 due to upward movement of cylinder 84. Although a threaded adjustment device 86 and hand wheel 88 are shown in the fixture 70, the force adjustment device utilized to compress coil spring 34 may comprise a hydraulic cylinder, an electrically-powered actuator, or other suitable powered device.

[0025] Once a predetermined or predefined force is generated as measured by load cell 82, a forming tool 92 is shifted downwardly into position adjacent second end 62B of housing 38 utilizing a hydraulic cylinder 80 or other suitable powered actuator. The forming tool 92 then forms edge 66 (FIG. 8) into flanges 56B (FIG. 9) to retain plug 40 at a position wherein the coil spring 32 is preloaded at the desired level. This process thereby sets the preload force at a desired, predefined level or to a predefined range that includes acceptable tolerance variations. The final spring assembly 30 (FIGS. 9 and 10) is then removed from fixture 70.

[0026] Referring again to FIG. 1, chair assembly 1 includes two spring assemblies 30. Because the spring assemblies 30 are consistent with respect to the preload or initial force required to initially extend the spring assemblies 30, a plurality of chairs 1 can be manufactured and the springs 30 do not need to be adjusted at the time of assembly of the chair 1. Furthermore, each chair 1 assembled will have substantially the same tilt characteristics with respect to the amount of force required to tilt the chair back.