Rotating chair arm structure

April 18, 1961

F. W. BECHTOLD

2,980,170

ROTATING CHAIR ARM STRUCTURE

Filed Jan. 29, 1960

Sheets-Sheet 1

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ATTOEME.XS

April 18, 1961

F. W. BECHTOLD

ROTATING CHAIR ARM STRUCTURE

2,980,170

Filed Jan. 29, 1960

Sheets-Sheet 2

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ΑΤΤΟΕ.Κ1ΕΥ«»

April 18, 1961

F. W. BECHTOLD

2,980,170

ROTATING CHAIR ARM STRUCTURE

Filed Jan. 29, 1960

Sheets-Sheet 3

<img file="US2980170A_D0003.tif" />

ATTOiaMEY-S

2,980,170

Patented Apr. 18, 1961

United States Patent Office

2,980,170

ROTATING CHAIR ARM STRUCTURE

Friedrich W. Bechtold, West New Brighton, N.Y., assignor to The S. S. White Dental Manufacturing Company, Philadelphia, Pa., a corporation of Pennsylvania

Filed Jan. 29, 1960, Ser. No. 5,466

Claims. (Cl. 155—198)

This invention relates to adjustable arms for chairs, for example the chairs employed by dentists for seating patients, and is particularly concerned with pivoting and locking structures therefor.

Such employment of arms which can be moved apart is in itself known. In the present invention, the arm can be smoothly formed and blended smoothly with «. the chair frame, and is competent of rocking through a large angle of motion and accurate and sturdy locking at any desired position.

An object of the present invention is the provision of a * chair assembly with an adjustable arm structure located concentrically with the axis of motion, and having a control means positioned on a relatively fixed part of the chair assembly.

Another object is the provision of such an assembly in which the arm is easily removable with pivotal and locking structures for inspection, repair and replacement.

Another object is the provision of such an assembly in which interengaging parts are provided on the relatively fixed structure and on the movable arm, the parts being movable along the axis for locking the arm, and with a control means accessible on the relatively fixed structure for moving the said interengaging parts axially.

With these and other objects in view, as will appear in the course of the following description and claims, an illustrative embodiment of the invention is shown in the accompanying drawings, in which:

Fig. 1 is a side view of a chair assembly including two of the movable arms;

Fig. 2 is a front view, indicating adjusted positions of the arms;

Fig. 3 is an axial section on an enlarged scale, taken substantially on the line 3—3 of Fig. 2;

Fig. 4 is a radial section, substantially on line 4—4 I of Fig. 3, at a larger scale;

Fig. 5 is a fragmentary section, on a greatly enlarged scale, substantially on line 5—5 of Fig. 4;

Fig. 6 is a radial section, substantially on line 6—6 of Fig. 3, at a larger scale;

Fig. 7 is a radial section, substantially on line 7—7 of Fig. 3, at a larger scale;

Fig. 8 is a radial section, substantially on line 8—8 of Fig. 3, at a larger scale.

In these drawings, the illustrated chair is for dentist’s use; and has a base 10 for mounting on a floor, with a telescoping column 11 rising therefrom and having at the top a seat structure 13 with a foot rest 15. A tilting back 16 is pivoted relative to the seat structure 13 for adjustment to and locking in various positions by devices not further shown, and which may be of forms known in the art: and a head rest 18.

The seat structure 13 includes lateral portions 20 which are hollow with a bore 23, as shown in Fig. 3; and may be formed as castings around a sleeve 24 which provides the bore. The arm rests proper 21 are connected with a portion 22 extending radially from the axis of the bore 23 in the respective fixed portion 20.

A pivot shaft 25 is closely received in the inner end 23α of the bore 23 at its reduced cylindrical portion 26, and has opposed flats 27 on a larger portion and within the outer part of the bore 23. The end of the larger 5 portion extends into the arm portion 22 and has a longitudinal slot 28 which is broadened at the bottom to provide walls 29 which converge from the lower side toward the upper in Fig. 6. A wedge block 30 fits these walls, and screws 31 in the arm portion 22 can be 10 rotated to force the block 30 into the shaft slot 28 and against the walls 29 for forcing the parts of the shaft radially into tight holding engagement with the inner wall surfaces 31 of the arm portion 22.

A first plurality of friction washers 35, Figs. 3 and 16 8, each have circular outer edges so that they can be moved into the bore 23, and have chordal inner edges 36 for close engagement upon the flats 27, whereby these washers are caused to rotate with the shaft 25. A second plurality of friction washers 40, Figs. 3 and 7, have ²⁰ projections 41 at their outer edges, for engaging in the spline grooves 42 inside the lateral portion 20, and are circular at their inner edges for a sliding and rotating fit on the larger portion of the shaft 25. The washers 35, 40 are arranged alternately on the shaft 25, with ²⁵ friction washers 44 interposed between them, these intermediate friction washers having circular inner and outer edges.

A collar assembly 45 is secured to the shaft 25 by a diametrical pin 46 so that it is fixed against axial ³θ or rotative movement relative thereto. The washer assembly abuts against the collar assembly 45, with a washer 35 in contact therewith. A ram ring 47 fits over the larger portion of the shaft 25 and can be pressed axially along the shaft; with abutment against the end ³⁵ washer 40 of the washer assembly. A ball race 48 abuts against the ring 47, and has its opposite face grooved to receive the balls 49 carried in an annular retainer 50. An annular locking cam 51 is slidable along the reduced portion 26 of the shaft and has de⁴⁰ pressions 52, Figs. 4 and 5, in one face, equal in number to the number of balls 49 and cooperative therewith to press these balls and therewith the ram ring 47 toward the washer assembly upon rotation of cam 51 in one direction. A second retainer 53 has balls 54 therein, for like cooperation with a set of depressions' 52 in the ⁴⁵ other face of the cam 51. These balls '54 engage in a groove in the face of the ball race 56. An actuating rod 66 is threaded into the cam 51 and extends through a slot 61 in the respective lateral portion 20 for access, so that upon moving the rod 60 along the slot, the ^υ cam 51 is rotated about the shaft axis. The rod 60 may have a T-shaped outer end for easy operation.

The washer assembly, ram ring, retainers, cam and ball races can be assembled upon the shaft 25, and then introduced into the bore 22 in the respective portion 20, rotating each washer 40 as necessary to aline its projections 41 with the spline grooves in the portion 20. When fully introduced, the free end of the reduced portion 26 of the shaft is rotatably received in a bearing 63 at the bottom of the bore 22 and with the ball race 56 ^υ in abutment with a wall surface 64 around the bearing 63.

An externally threaded clamp ring 65 can rotate about the larger portion of the shaft 25 and be engaged with threads inside the bore 22 at the outer end thereof. This ⁰ ring is rotated to advance it into the bore 22 until the assembly is completed, with partial rotation of the shaft 25 if necessary to assure that the balls 50, 54 are seated in respective depressions 52. The actuating rod 60 is introduced through its slot and threaded into the cam 51; ¹ and moved to locking position, that is, the position at which the ram 47 has been moved to greatest separation

2,980,170 from the ball race 56. The ring 65 is then rotated until a desired torque, e.g. 100 foot-pounds, is required to rotate the shaft 25 in the extension 20 and is held by a screw 66. The movable arm assembly 21, 22, with the locking wedge 3® held loosely by the screws 31 is then slid over the protruding end of the shaft 25; and the screws 31 rotated to tighten the shaft within the portion 22. The movable arm is now held in this position. The portion 22 may be reduced to a smaller diameter 68 at its end, to fit inside the bore 23; and a sealing and decorative ring 69 may be included between the parts.

It is preferred, Fig. 5, to form each depression 52 with a deeper end 70 ending at a wall 71 which prevents further relative travel of the respective ball 49 or 54; a rising slope surface 72 having a minor dip 73 adjacent the shallower end of the depression 52; and an end wall 74 for limiting the ball motion. With such arrangement, with each ball at the deepest part of 7® of its depression, there is no end thrust upon the washer assembly, and the arm 21 is free to move; as the cam 51 moves and the ball travels relatively to the right in Fig. 5, end thrust develops. At proper adjustment, the inherent elasticity of parts permits the ball to come to the position 75, in the dip 73 while exerting its part of the endwise thrust; and therewith is held against accidental return toward the deeper part 70 of the depression.

If the arm position is to be changed, the actuating rod 60 is moved along its slot, so that the cam 51 is rotated, and the deeper parts of depression 52 are presented to the balls 50, 54 and therewith the axial clamping effort upon the ram ring 47 is reduced. The arm can now be rocked to a desired position. The actuating rod 60 is moved back, so that the cam 51 now presents the shallower parts of its depressions 52 to the balls, and an axial clamping force is exerted upon the ram ring 47, and therewith the washer assembly is pressed tightly together, with frictional resistance to relative rotation of the pluralities of washers 35, 40 being present between each two adjacent washers, and the total frictional effort being effective to prevent movement of the chair arm.

As the cam 51 rotates, the balls 50, 54 roll along the surfaces of the depressions 52 and likewise travel along the surfaces of ball races 48, 56 so that small effort upon the actuator rod 69 is required to attain a strong locking.

The parts may be removed for inspection and repair by loosening the screws 31 and removing the arm assembly 21, 22; and then backing out of the clamp ring 65 until free of the threaded part of the bore in extension 20. The actuating rod 60 is removed. The shaft 25, 26 and the locking parts can then be withdrawn.

The illustrative embodiment is not restrictive; and the invention can be employed in many ways within the scope of the appended claims.