Swivel Construction For A Chair

Abstract

An improved chair swivel includes a housing tube which may be attached to the chair legs. Within the tube is a stationary cam and a movable cam. The movable cam is attached to a spindle that engages the chair seat. The movable cam is biased into engagement with the stationary cam and has a normal rest position. Upon rotation of the chair seat, the movable cam is driven from the normal rest position by the spindle. Release of the force on the chair seat permits the seat to return to its normal rest position.

Description

BACKGROUND OF THE INVENTION

In a principal aspect, the present invention relates to an improved chair swivel construction and, more particularly, to a swivel construction that is self-centering.

Swivel chair mechanisms and self-centering swivel chair mechanisms have been heretofore known. Such mechanisms permit the seat of a chair to be rotated relative to the legs. Upon removal of the force required to effect the rotation, the seat will return to its normal rest or centered position.

Preferably, a mechanism which will accomplish this result is compact, easy to install, easy to service and inexpensive to manufacture. Another characteristic desired in such mechanisms is reliability. It is with these objectives in mind that the present invention was conceived.

SUMMARY OF THE INVENTION

In a principal aspect, the present invention comprises the combination of a chair including a leg portion and a separate seat and an improved mounting and swivel mechanism for attaching the seat to the leg portion. The swivel includes a cylindrical housing with a stationary cam fixed in the lower end of the housing. A movable cam is biased against the stationary cam so that the cam surfaces of the movable and stationary cam are engaged. The movable cam rotates with a spindle that is attached to the chair seat. The biased cams tend to drive the seat to a centered or rest position.

It is thus an object of the present invention to provide an improved chair swivel and mounting mechanism.

It is a further object of the present invention to provide a chair swivel mechanism utilizing a minimum number of parts wherein the swivel housing is shaped to cooperate with a stationary cam to hold that cam in a substantially fixed position within the housing.

It is a further object of the present invention to provide a chair swivel mechanism having a pair of complementary cams which serve to center or return the chair seat to a predetermined desired position whenever a turning force is released from the swivel.

Another object of the present invention is to provide a spring operated chair swivel mechanism having a memory characteristic.

These and other objects, advantages and features of the present invention will be set forth in greater detail in the description which follows.

BRIEF DESCRIPTION OF THE DRAWING

In the detailed description which follows, reference will be made to the drawing comprised of the following figures:

FIG. 1 is a cross-sectional view of the improved swivel and chair combination of the present invention;

FIG. 2 is a cross-sectional view taken along the line 2--2 in FIG. 1;

FIG. 3 is a cross-sectional view of a swivel mechanism taken along the line 3--3 in FIG. 1;

FIG. 4 is a cross-sectional view of the swivel mechanism taken along the line 4--4 in FIG. 1;

FIG. 5 is a cross-sectional view of the swivel mechanism taken along the line 5--5 in FIG. 1;

FIG. 6 is a cross-sectional view taken along line 6--6 in FIG. 1;

FIG. 7 is a plan view of the complementary cams utilized in the chair swivel mechanism of the present invention; and

FIG. 8 is a front plan view of the stationary cam utilized in the swivel mechanism of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The combination of the invention will be described principally by reference to FIG. 1, although the other figures should be viewed, particularly during the discussion of the shapes of non-cylindrical portions of the device. FIG. 1 discloses a cross-sectional view of a swivel 16 incorporated with a chair seat 10 and chair legs 18. The chair seat 10 is attached by bracket arms 12 to a center, cylindrical mounting tube 14. The tube 14 receives a shaft 68 extending from the swivel 16. The opposite end of the swivel 16 is fixed to legs 18. The attachment of the swivel 16 to the legs 18 is discussed in greater detail below.

The swivel 16 includes a generally cylindrical tube 20 having a longitudinal axis 22. The lower end of the tube 20 includes a tapered section 24 and terminates with a narrowed polygonally shaped end 26. FIG. 3 illustrates the cross-sectional shape of the end 26. The opposite end of the tube 20 terminates with an outwardly extending flange 28. A groove 30 adapted to receive a retaining ring 32 is provided near the upper end of the tube 20.

Positioned within the tube 20 is a stationary cam 34, preferably made from a plastic material such as Celcon. The cam 34 is generally cylindrical. However, cam 34 includes at its lower end a complementary tapered section 36 which cooperates with tapered section 24 of tube 20 to prevent movement of the cam 34 along the longitudinal axis 22 through the lower end of the tube 20. The cam 34 also includes a lower polygonal cross section portion 38 which is complementary with the end 26 of tube 20. In this manner, the cam 34 is maintained in a non-rotative position in tube 20. The cam 34 also includes a projecting end stud 40 which is further illustrated in the cross-sectional view of FIG. 2. The stud 40 cooperates with a retaining ring 42 in a manner to be described below.

A spindle 44 which is generally cylindrical and concentrically positioned on axis 22 is mounted with its lower end 46 in a pocket 48 defined in cam 34. The pocket 48 has a circular cross section as illustrated in FIG. 4. The lower end 46 of spindle 44 has double or opposite side flats for cooperation with a movable cam 50. Thus, movable cam 50 as illustrated in FIG. 5 includes a center opening 52 having a pair of flats so that cam 50 and spindle 44 rotate coincidentally. Cam 50 is also preferably made from a plastic such as Celcon plastic.

The cams 34 and 50 include complementary cam surfaces 54 and 56 respectively. The particular shape and function of these surfaces will be set forth in greater detail below during discussion of FIGS. 7 and 8.

The movable cam 50 is maintained in constant contact with the stationary cam 34 by means of a spring 60. Spring 60 is maintained against the upper surface of cam 50 by means of an E ring 62 which is maintained in a groove 64 of spindle 44. The E ring 62 bears against an upper bearing 66 for spindle 44. The upper bearing 66 is, in turn, maintained in position by the retainer ring 32 in the groove 30. Note that the bearing 66 serves to maintain the alignment of the spindle 44.

An outer extension or shaft 68 of the spindle 44 projects into cooperation with the tube 14 in the manner previously described. Preferably, the shaft 68 is tapered. Typically, the taper would be a No. 3 Morse taper, a taper configuration well known to those skilled in the art.

FIGS. 7 and 8 illustrate the configuration of cam surfaces 54 and 56 of cams 34 and 50. The stationary cam 34 includes a continuous circumferential surface 54 having a substantially horizontal lower surface land 70 and continuously ascending surface portions 72 and 74 on either side of the lower land 70. At a point 180.degree. from the lower land 70 is a substantially horizontal planar land or crest 76.

The complementary upper or movable cam 50 includes a lower horizontal engagement crest 78 which cooperates with the total surface 54. For example, crest 78 engages the lower land 70 when the swivel is in the rest position. Since the cam 50 is continuously biased by spring 60, the surface crest 78 will always tend to seek the lower land 70. This is true regardless of the position of the crest 78 on the surface 54 since the surfaces 72 and 74 are continuously ascending with no detent positions.

Referring again to FIG. 1, the swivel of the present invention may be mounted in a chair leg tube 82 by using an adapter cap 84 which is attached to the cylindrical tube 20 and engages against flange 28. Thus, if the leg tube 82 has, for example, a polygonal cross section, the cap 84 may act as a transition piece to attach the swivel 16 to the tube 82.

The cap 84 includes a downwardly extending flange 86 which may be welded or otherwise press fitted onto the tube 82. Preferably, a retainer ring 42 is included and attached to the stud 40 to hold the swivel 16 within the tube 82 and also to assist in centering the swivel 16 within the tube 82. An alternative construction or means for attaching the swivel 16 to a chair leg tube 82 provides for a smaller tube 82 and welding the flange 28 to such a smaller tube.

In use, the spindle 44 and attached cam 50 rotate coincidentally with the seat 10. The tube 20 and stationary cam 34 move in unison with the legs 18 and associated leg tube 82. Thus, due to the compression force of the spring 60, the seat 10 will normally be in a rest or a neutral position determined by the relationship of the land 78 of cam 50 and lower land 70 of stationary cam 34.

However, seat 10 may be rotated manually or otherwise. This will cause the movable cam 50 to rotate. Thus, the land 78 of cam surface 56 will follow the cam surface 54 and will remain in position to return the seat 10 to its rest or neutral position upon release of the rotative force that causes the spindle 44 to turn. The swivel 16 thus has a memory characteristic. When not in use, the chair is effectively biased to a neutral position. After turning, the seat will return to its neutral or normal unused position.

The invention which has been described is, therefore, to be limited only by the following claims and their equivalents.

Claims

What is claimed is:

1. In combination with a chair of the type including a leg portion and a separate seat, an improved mounting and swivel mechanism for attaching the seat to the leg portion, said swivel comprising in combination:

a hollow generally cylindrical tube with a longitudinal swivel axis, said tube having a lower end which is of decreasing diameter and at least in part polygonally shaped;

a stationary cam member in said tube, said cam including a tapered, polygonal portion cooperative with the lower end of the tube to hold the cam in a substantially non-rotatable and downwardly non-translatable position, said stationary cam including an upwardly facing cam surface with a central pocket;

a spindle fitted in said pocket and extending upward along the longitudinal axis from said tube, said spindle mounted for free rotation in said cam pocket, said spindle including a projecting shaft for engaging a mounting plate for the seat;

a movable cam mounted on the spindle in the tube for rotative movement with said spindle, said cam being translatable on the spindle and including an active cam surface engaging the stationary cam surface; and

spring means in said tube for biasing the movable cam against the stationary cam including means for retaining the spring in said tube, said cam surface of said stationary cam being a continuous closed loop path including a lower centered position and an upper active position diametrically opposite the lower position, said positions being connected by continuously ascending cam paths whereby the tube is connected to the leg portion and the spindle to the seat, the seat being normally maintained in a fixed orientation relative to the leg portion as determined by the lower cam position, movable to any other orientation by rotation of the seat and spindle and returnable to the lower position by the force of the biased spring on the cams.

2. The combination of claim 1 wherein said spindle is tapered and engages a cylindrical tube attached to the seat.

3. The combination of claim 1 including a cap having a downwardly depending flange attached to outside of the tube, said cap being engageable with a chair leg tube.

4. The combination of claim 1 including a retainer spring attached to the lower end of the swivel for engaging a chair leg tube.

5. The combination of claim 1 including a spindle bearing in said tube adjacent the end of the spring opposite the movable cam, said retaining means cooperative to mount said bearing and simultaneously maintain said spring within said tube.