US3046054A - Height adjusting cam lock - Google Patents

Description

July 24, 1962 Filed D60. 7, 1960 fie- 9.

S. A. ERICSON ET AL HEIGHT ADJUSTING CAM LOCK 2 Sheets-Sheet l Wm-a 95 /1. 14/ PA/PEOTT 5. ,4. fF/C'SO/V 4 TI'OF/VEJ/ July 24, 19 2 s. A. ERICSON ET AL 3,046,054

HEIGHT ADJUSTING CAM LQCK Filed Dec. '7, 1960 2 Sheets-Sheet 2 INYENTOEE H W PAP/P077 5'. A. fE/CJ'O/V United States Patent aseaesa HEIGHT ADJUSTING CAM LGCK Sidney Albert Ericson, Bridgeport, and Henry Wheeler Parrott, Shelton, Conan, assignors to The Bassick Company, Bridgeport, Conn, a corporation of Connecticut Filed Dec. 7, 1969, er. No. 74,312 9 Claims. Cl. 27353) This invention relates to chairs of the so-called posture type such as oflice of typewriter chairs, and more par ticularly to an improved height adjustment arrangement for the chair back.

While the invention is particularly useful with a chair of the tilting back type, it may be incorporated in chairs of other types, for instance, a chair of the type in which the back is normally rigidly supported.

There are various known types of adjusting means for adjusting the vertical height of a chair back for posturetype chairs. The locking arrangements associated with such adjustments have included devices which provide a positive type lock between the back support member and a relatively stationary bottom support member. In addition, frictional enga ing means have been employed using moving cams or the like to supply the force required to frictionally engage the inner fitting members. However, even where cam operated locking means have been employed, such means are complicated and have included a relatively large number of parts. In addition, it has been necessary to produce the parts with close tolerances to insure positive action of the cam locking means for every desired height. Even with such relatively complex structure, the permanency of this type of lock to maintain the desired back height was never fully insured.

It is therefore the object of the present invention to provide an improved height adjusting cam lock for an adjustable chair back.

It is a further object of this invention to provide an improved height adjusting cam lock for an adjustable chair :back wherein the tightness of fit between a guide and a hinge may be adjusted to insure a positive lock regardless of the position to which the chair back has been adjusted.

It is another object of this invention to provide an improved adjusting cam lock for an adjustable chair back wherein the chair back will remain reliably locked at the desired adjusted position.

It is a further object of this invention to provide an improved height adjusting cam lock for a chair back in which the adjusting means will be positioned out of the way of the user or occupant of the chair after the height adjustment has been made.

It is a further object of this invention to provide an improved height adjusting cam lock for a chair back wherein the over-all construction of the lock is greatly simplified, allowing the locking device to be constructed in minimum time, at greatly reduced cost.

Other objects of this invention will be pointed out in the following detailed description and claims and illustrated in the accompanying drawings which disclose by way of example the principle of this invention and the best mode which has been contemplated of applying that principle.

In the drawings:

FIGURE 1 is a side elevational view of a posture-type chair including the improved cam lock of the present invention;

FIGURE 2 is a side elevational view of a portion of the chair shown in FIGURE 1, partially in section, showing in detail the height adjusting cam lock;

FIGURE 3 is a bottom plan view of the adjusting lock means shown in FIGURE 2;

FIGURE 4 is a perspective view of the hand Wheel body assembly utilized in this invention;

FIGURE 5 is a perspective view of the embossed tilting hinge used in this invention;

FIGURE 6 is a perspective view of the embossed back plate guide used in this invention;

FIGURE 7 is a side elevational view of the cam locking lever;

FIGURE 8 is a front elevational view of the cam locking lever shown in FIGURE 7;

FIGURE 9 is a side elevational view of the cam lever bolt used in the embodiment shown in FIGURES 1 to 3;

FIGURE 10 is a side elevational view of the cam lever washer;

FIGURE 11 is a side view, partially in section, illustrating the height adjustment locking means of this invention.

In general, the apparatus of this invention includes an embossed tilting hinge or bracket member which is pivotally fixed to the spider horn assembly of a posturetype chair. A U-shaped, embossed back plate guide or height adjusting memi er is positioned adjacent the relatively fixed tilting hinge in an inner fitting relationship, such that the back plate guide may move vertically with respect to the tilting hinge.

A rounded flange or track portion of the back plate guide rides within the embossed or guide track portion of the guide plate. In this respect, the two side portions of the U-shaped embossed back plate guide form resilient fingers which are adapted to engage the outer surfaces of the side portions of the embossed tilting hinge. A cam lever bolt extends through suitable apertures formed within the embossed tilting hinge and parallel slots formed longitudinally of the side members of the embossed back plate guide such that the back plate guide moves relative to the laterally extending cam lever bolt. At one end of the cam lever bolt, on the exterior surface of the embossed back plate guide, there is provided a pivoted locking lever having an inwardly directed cam sunface which is adapted to engage an intermediate cam lever washer. The opposite end of the cam lever bolt. is threaded, and a suitable nut is provided on this end of the cam lever bolt. The normal resiliency of the embossed back plate guide finger on either side of the tilting hinge is insufficient to keep the back plate guide positioned vertically with respect to the tilting hinge. However, when the cam locking lever is pivoted such that it lies parallel to the side of the tilting hinge, the cam surface of the cam locking lever snaps into contact with the cam lever washer with suflicient force to compress the fingers of the back plate guide against the embossed portion of the tilting hinge to lock the track portion within the track guide. The support member will then remain fixed in its vertical position with respect to the chair seat support means. The nut on the other end of the cam lever bolt may be axially adjusted to vary the frictional locking force provided by the pivotable cam locking lever.

Referring now to the drawings, there is shown in FIG- URE 1 a chair of the general type disclosed in the W. F. Hill Patent 2,321,385, having a supporting pedestal or base ill and a chair seat 12 which is vertically adjusted with respect to the pedestal or base by means of spider horn assembly 14. The chair shown in this particular embodiment is of the so-called posture type such as an oflice or typewriter chair and includes a chair back 16 which is pivotally mounted relative fixed seat 12 by means of a chair back pivot support assembly 20 having a tension spring 38. The chair further includes a chair back height adjustment assembly 24.

Eefore directing attention to the details of the chair back height adjustment assembly 24, brief reference may be had to FIGURE 2 which shows, in detail, a portion of the chair seat pivot support assembly 20. Associated with the spider horn assembly 14 is a generally cylindrical member 26 which is used as an adjusting means for adice justing the height of the chair seat with respect to the pedestal or base 10. Immediately above the cylinder 26 is located a spider horn 23 which is rigidly coupled to the screw post (not shown). The spider horn 28 includes a pair of side members 30, FIGURE 3, which form parallel supporting means for the various seat and back members. A pair of longitudinally extending spider arms 32 are rigidly attached to the bottom surface of seat 12 by means of rivets or screws 33. The spider arms 32 are fixedly mounted upon the parallel side members 30 of spider horn 28 by bolts 3%.

A hand wheel body assembly 56, FIGURE 4, formed of sheet metal, is bent into a somewhat inverted U-shape as indicated in FIGURE 4 and is adapted to be pivotally mounted upon spider horn 28 by means of a laterally extending bolt 37. In order to resiliently bias the chair back with respect to chair base 12 or support means 10, there is provided a tension spring 33, FIGURE 2, which is positioned upon a tension spring mounting T- bolt 40, with one end of the bolt adapted to pass through a recess 42 formed Within an upturned flange portion 44 of the hand wheel body assembly 36 as indicated in FIG- URE 4. As such, one end of tension spring 33 contacts the front surface of the flange portion 44 while the other end of the tension spring 38 engages the front of the inner surface of hand wheel 46. Conventional means (not shown) are provided whereby rotation of hand wheel 46 will vary the spring bias of spring 38 to allow the chair back 16 to pivot with respect to the base 10 under an amount of force which is determined, and adjusted at the will of the occupant.

In addition to the means for allowing the chair back 16 to tilt with respect to the pedestal or base, there is also provided conventional means for adjusting the angle of the chair back 16 with respect to the axis of the spider horn assembly 14. These means include an embossed tilting hinge or bracket support member 48 (FIG- URE 5) which is pivotally mounted on the rear of the hand wheel body assembly 36 by means of a third laterally extending bolt 56. The embossed tilting hinge 48 is of generally U-shape and includes a rear, vertically extending base portion 52 and a pair of side arm portions 54 which are directed forwardly, parallel to the sides of hand wheel body assembly 36. The bolt 5%) is adapted to extend through apertures 56 formed within the hand wheel body or" assembly 36 and apertures 58 which are formed within the arms of embossed tilting hinge 48. A laterally extending hinge spacer 66 is rigidly coupled to the front edges of the two side arm portions 54 of the embossed tilting hinge 4% for the purpose a of providing rigidity to this portion of the structure. In addition, the hinge spacer 66 includes an aperture 62 as the center thereof.

Suitable means such as the back tilt adjusting hand wheel assembly 64 is provided to move the chair back in an are about the laterally extending bolt St) in order to change the angle of inclination of the chair back with respect to the vertical axis of the spider horn assembly. Included is a hand wheel 66 which is rigidly coupled to a threaded shaft 68. The threaded shaft is rotatably 'coupled at one end to a downwardly projecting rigid member 70 which is fixedly attached to the hand wheel body assembly 36. In order to adjustably couple the shaft with respect to the pivoted embossed tilting hinge 48, there is further provided a generally U-shaped sheet metal back tilting nut 72 which is positioned over the hinge spacer 60 so that the arms of the nut '72 are posi tioned on either side thereof, as shown in FEGURE 2. The shaft 68 is positioned within apertures formed within the U-shaped back tilting nut 72, and an anti-wabble spring 74 is positioned along the inner surface of one of the arms of the U-shaped back tilting nut 72 and the surface of the hinge spacer 60 to keep the distance between the U-shaped back tilting nut 72 and the hinge spacer 6t} relatively constant regardless of adjustment of hand wheel 66. Briefly, the angle between the chair back 16 and the vertical axis of the chair is varied simply by rotating hand wheel 66 to pivot the embossed tilting hinge 4% around the laterally extending through-bolt St The occupant of the chair, however, will tend to tilt the back of the chair in a counterclockwise direction around pivot point 37 and the amount of such movement will be dependent solely upon the force exerted by the occupant to compress spring 33.

The present invention is directed to an improved cam lock for locking the embossed back plate guide or height adjustment member against the embossed tilting hinge or bracket support member, to provide vertical height adjustment for the chair back. The embossed back plate guide 76, FIGURE 6, is also formed of sheet metal or the like and is of generally U-shape configuration. The guide member 76 includes a relatively flat rear portion 78 and a pair of somewhat flexible arm portions 8t} which are adapted to be positioned adjacent to the outer surface of the side wall 554 of the embossed tilting hinge 58. in order to provide a suitable frictional contact surface between the embossed tilting hinge 48 and the embossed back pla e guide 76, the ends of each of the arm portions of the back plate guide are embossed or rolled such that they have inwardly directed track portions 82. Likewise, the side walls of the embossed tilting hinge 48 also have inwardly directed channels or guide tracks 84 formed along a vertical line intermediate of their ends such that the rounded track portions 32 of the back plate guide 7r: may readily contact the surface of the tilting hinge at this point.

While the dimensions of the back plate guide and the tiitirtg hinge are such that the arm portions 8% of the back piate guide member and the sides 54 of the embossed tilting hinge normally lie adiacent to each other, especially at the points where the rounded track portions 82 engage the guide track portions 84-, there is insufficient frictional engagement between these two members to keep the two members in relatively fixed engagement under the weight of the chair back 16 and its associated supported members. it is, therefore, necessary to include means for providing sufficient frictional force to securely lock the embossed back plateguide against the embossed tilting edge. To insure that the two members will be relatively immovable in a horizontal direction, While allowing free movement in a vertical direction, there is further provided a cam lever bolt 86 to couple the two members together. As such, apertures 83 are formed within the side portions 54 of the embossed tilting hinge 48 intermediate the top and bottom edges thereof to receive the cam iever bolt as. The embossed back plate guide 76 is further provided with a pair of vertical, aligned, elongated slots 93 which are positioned along a line which runs through the axis of the aperture 88 formed within the side arms 54 of the embossed tilting hinge 48. The cam lever bolt as is also positioned within the elongated slots 99 formed within the back plate guide 76. The back plate guide 76 is relatively free to move in a vertical direction with respect to the relatively stationary embossed tilting hinge 4-8, but this movement is limited by the length of the slot 9! A relatively simple, inexpensive, and quite effective arrangement is provided for delivering sufiicient lateral force to the sides of the fingers or arm portions 80 of the embossed back plate guide 76 to frictionally engage the back plate guide 76 in any adjusted position with the embossed tilting hinge 48. A cam locking lever 92, FIGURE 7, is pivotally mounted at one end of the cam lever bolt 86 by means of a pin 94 which extends at right angles to the axis of the bolt, through aligned apertures 96 formed within the two spaced parallel side portions d8 of the cam locking lever. As such, the cam locking lever 92 rotates in a plane defined by the axis of bolt 86 and the lever itself. The cam locking lever 92 is formed of sheet metal in a conventional manner to provide a single flat;

tened hand contact surface portion 100 which is generally at right angles to the pair of spaced side mounting portions 98.

The side portions 98 present generally arcuate cam surfaces 101 of substantial uniform radius. Flat cam surfaces 102 interrupt the arcuate cam surfaces 101 at transition points 103 and extend generally toward the hand contact portion 100. The apertures 96 are offset from the center of the arcuate cam surfaces 101 on the side opposite the center from the fiat cam surfaces 102, but are generally aligned with the center in a direction perpendicular to surfaces 102. The surfaces 101 and 102 are adapted to engage a washer 104 which is positioned on bolt 86 between the back guide member and the lever. The cam lever bolt 86 is threaded at 106 and has a mating nut 108 and an interposed washer 110.

Consequently, lever 92 upon being rotated from a position aligned with bolt 86 to a position generally at right angles to the bolt displaces washer 104 axially of the bolt toward washer 110. When the lever approaches the position at an angle approximately 90 from the axis of the bolt, the engagement of the washer 104 with the cam surface 101 passes the transition point 103 to the flat cam surfaces 102. The lever is thus locked in the latter position against the washer. This relative displacement of the washers toward each other squeezes the side portions 80 of the back guide plate 76 against the side portions 54 of the bracket support member 48 and frictionally locks them together.

The purpose of providing a threaded connection at 106 is to allow the axial distance between washers 104 and 110 to be varied. This will create a varying frictional force between the track portions 82 and the channel portions 84 sufiicient to maintain the chair back secured regardless of loads to which it is subjected. In addition, such an arrangement will always allow the lock to provide the required tightness regardless of variation on dimensions of the parts making up the locking arrangement. Thus the need for close tolerances between the individual parts has been virtually eliminated. Furthermore, since bolt 86 engages the flexible arm portions 80 of the guide member 76 symmetrically of the track portions 82 and 84, positive frictional engagement between the portions 82 and 84- is ensured while providing minimum strain on the flexible arm portions 80.

In the embodiment shown, the chair back 16 is rigidly coupled to a vertically positioned chair support member 112 by any conventional means. As seen in FIGURES 2 and 3, the bottom of the chair back support member 112 is also rigidly coupled to the rear portion 78 of the U-shaped embossed back plate guide 76 by means of a pair of rivets 114.

Normally, there would be a tendency for the cam look ing lever 92 to rotate a complete 360 since the cylindrical lever bolt 86 is free to move or rotate within the apertures 8S and the elongated slots 90 of the U-shaped back plate guide 76. In addition to providing a relatively simplified cam locking arrangement, it is also desirable to provide a lever which is conventiently positioned such that the occupant may easily adjust the position of the chair back with respect to the chair seat. It is also desirable to provide a lever which will be located in close proximity to the rest of the supporting structure when the chair back is locked securely in the adjusted position. The present invention fulfills both these needs in that the apparatus is relatively simple, permanent locking is secured and the means for providing the locking function will not in any way interfere with the occupant of the chair. In addition, by use of a rather unique arrangement, the locking lever will always remain in one position when the locking action has been initiated.

The cam locking bolt 86 has an enlarged rectangular end portion v116 which when assembled is received be tween the side portions 98 of lever 92. Aperature 117 is provided to receive pin 94. Another enlarged rectangular portion 118 of substantially the same size as portion 116 is adjacent the enlarged portion 116. The two portions are rotated relatively until the opposite corners are aligned, or because of the relative proportions, at an angle ap proximately 30. Washer 104 has a rectangular opening 120 which fits over the enlarged portion 116 but which abuts the rotated corners of the portion 118. When the unit is assembled, washer 104 is thus free to slide on the portion 116 between the rectangular portion 118 and the cam surfaces 101 and 102 of lever 92. The enlarged portion 118 of the bolt is adapted to fit within one of the elongated slots as the bolt is inserted within the assembly. By proper alignment of the portion 116 within the slot 90, the cam locking lever 92 is positioned at an angle of approximately 60 with respect to the longitudinal axis of slot 90, with its outer end directed toward the front of the chair seat. This position ensures that the cam locking lever 92 will always remain at this angle with respect to the vertical axis of the chair with which it is employed. Proper assemblied relationship can be further ensured by making only one of the apertures 88 suficiently large to receive the enlarged portion 118.

In operation, the operator may easily grasp the outer or contact surface of the cam locking lever 92 and rotate it approximately 90 until the cam surfaces 102 snap into position and fully contact the cam lever washer 104, exerting suficient force to lock the U-shaped embossed back plate guide 76 permanently against the tilting hinge 48. The cam locking lever will then be in the position shown in FIGURES 2 and 3.

While the present invention is advantageously employed as a locking means for adjusting the height of a chair back with respect to a chair seat, the improved height adjusting cam lock may be employed as means to permanently lock other relatively moving parts of a posture chair or the like. For instance, such a locking means may be employed in connection with the tilting hinge at the point where the tilting hinge is pivotally connected to the spider arms. It is therefore entended that the present invention not be limited tothe particular chair back height adjusting arrangement as shown in the preferred embodiment, since the invention is broadly applicable to cam locking arrangements for other adjustable elements of a posturetype chair or the like.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to the preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims:

What is claimed is:

1. In a chair having a seat portion and a back portion, an arrangement for effecting adjustment of the back portion with respect to the seat portion, comprising a support member associated with the seat portion including spaced side portions, a U-shaped back guide plate member associated with the back portion including resilient spaced arm portions positionable over and normally spaced from the support member side portions and movable with respect thereto, said arm and side portions having aligned apertures therein elongated in a generally common direction, a bolt member extending through the aligned apertures and projecting outwardly past the arm portions, stop means at one end of the bolt member adjacent one of the arm portions, and a lever pivotally connected to the bolt at the opposite end thereof to r0- tate about a pivot axis transverse to the longitudinal axis of the bolt, said lever having a camming surface extending generally in a direction parallel to the pivot axis and disposed adjacent the other of the arm portions, said camming surface being operable upon rotation of the lever to a first position to move the arm portions toward aoaasea 'each other for frictionally locking the back portion relative the seat portion and being operable upon rotation of the lever to a second position to release the arm portions for effecting adjustment of said back portion.

2. In a chair having a seat portion and a back portion, an arrangement for effecting adjustment of the back portion with respect to the seat portion, comprising a support member associated with the seat portion including spaced side portions having generally aligned tracks, a U-shaped back guide plate member associated with the back portion including resilient spaced arm portions positionable over and normally spaced from the support member side portions and movable with respect thereto, said arm portions having tracks matable with but normally spaced from the first mentioned tracks and movable only in the direction of the tracks, said arm and side portions having aligned apertures therein disposed symmetrically of the tracks and elongated in the direction of the tracks, a bolt member extending through the aligned apertures and projecting outwardly past the arm portions so that the support member and guide plate member can only move relatively to the limits of the elongated apertures, stop means at one end of the bolt member adjacent one of the arm portions, and a lever pivotally connected to the bolt at the opposite end thereof and having a camming surface adjacent the other of the arm portions, said camming surface being operable upon rotion of the lever to a first position to move the arm portions toward each other for frictionally locking the tracks to secure the back portion relative the seat portion and being operable upon rotation of the lever to a second position to release the arm portions for effecting adjustment of said back portion.

3. In a chair having a seat portion and a back portion, an arrangement for eifecting adjustment of the back portion with respect to the seat portion, comprising a support member associated with the seat portion and including spaced side portions, a U-shaped back guide plate member associated with the back portion including resilient spaced arm portions positionable over and normally spaced from the support member side portions and movable with respect thereto, said arm portions having tracks matable with but normally spaced from the first mentioned tracks and movable only vertically with respect thereto, said arm and side portions having aligned apertures therein elongated in the direction of adjustment, a bolt member extending through the aligned apertures and having its opposite ends project outwardly past the arm portions, stop means at one end of the bolt member adjacent one of the arm portions, and a lever pivotally connected to the bolt at the opposite end thereof and having a camming surface extending generally in a direction transverse to the longitudinal axis of the lever and adjacent the other of the arm portions, said camming surface being operable upon rotation of the lever to a first position to move the arm portions toward each other for frictionally locking the back portion relative the seat portion and being operable upon rotation of the lever to a second position to release the arm portions for effecting adjustment of said back portion.

4. An improved chair back height adjusting arrangement including a chair back, a chair seat support, a generally U-shaped chair back supporting bracket member carried by said support including a guide track positioned on the outer surface of the arm portion of said U-shaped bracket member, a generally U-shaped height adjusting member connected to said chair back and including track means formed on the arm portions of said U-shaped height adjusting member, said track means slidably engaging the guide track of said bracket member, aligned apertures formed within said bracket member adjacent said guide track, aligned elongated slots formed within said height adjusting member, the axis of said apertures and said slots lying within the same plane when said bracket member'and said height adjusting member are in assembled relation, a bolt member extending through said aligned slots and said aligned apertures and allowing only limited vertical relative movement between said assembled members, stopmeans positioned at one end of said bolt member adjacent the outer surface of said height adjusting member, a fiat, longitudinally extending cam locking lever pivotally mounted on the other end of said shaft member and adapted to rotate in a plane defined by the longitudinal axes of the shaft and said locking lever, said locking lever including a camming surface extending transverse to said plane for exerting a camming force between the arms of said bracket member and said height adjusting member such that the camrning force is a minimum when said lever extends along a line passing through the axis of said bolt and a maximum when said lever is positioned at right angles thereto, said locking lever being adapted to exert sufiicient force against said height adjusting memher to cause said track means to frictionally engage said guide track whereby said chair back is locked in the adjusted position.

5. Apparatus as claimed in claim 4 further including means positioned upon said bolt member at the point where said shaft member extends through one of said aligned elongated slots and adjacent said cam lever pivot point such that said shaft is prevented from rotation within said apertures and said slots.

6. Apparatus as claimed in claim 5 wherein said means for preventing said shaft from rotating within said apertures comprises a generally rectangular portion formed on one end of said shaft adjacent said pivot point of said cam locking lever, said portion being positioned within one of said elongated slots when said apparatus is in said assembled relation, such that two opposing sides of said portion are contacting the sides of said slot and said cam locking lever being positioned adjacent the side of said height adjusting member with the free end of said lever being directed downwardly and inwardly toward the seat support means at an angle of approximately 60 with respect to said vertical elongated slot, when said cam locking lever is in the locking position.

7. An improved chair back height adjusting arrangement including a chair back, a chair seat support, a chair back supporting bracket member carried by said seat support including aligned apertures and a guide track extending in a generally vertical direction, a height adjusting member connected to said chair back and including aligned elongated slots and a portion'having track means slidably engaging the guide track of said bracket member, said slots extending generally parallel to said track means, the axis of said apertures and said slots lying within the same plane when said bracket member and said height adjusting member are in assembled relation, a bolt member extending through said aligned slots and said aligned apertures and allowing limited vertical relative movement between said assembled bracket member and height adjusting member, stop means positioned on one end of said bolt member adjacent the outer surface of said height adjusting member, a cam locking lever pivotally mounted on the other end of said bolt member and adapted to rotate in a plane defined by the longitudinal axes of the bolt member and said locking lever, said locking lever including a camming surface such that the camming force is a minimum when said lever extends along a line passing through the axis of said bolt member and a maximum when said lever is positioned at right angles thereto, said cam locking lever being adapted to exert sufficient force against said height adjusting member to cause said track means to frictionally engage said guide track whereby said chair back is locked in the adjusted position.

8. Apparatus as claimed in claim 4 wherein said stop means comprises an axially threaded nut mounted on said shaft operable to vary the force against the height adjusting member, thereby varying the locking frictional engagement.

9. An improved chair back adjusting arrangement including a chair back, a chair seat support, a chair back supporting bracket member carried by said seat support, an adjusting member connected to said chair back and slidably engaging the bracket member, means for holding said adjusting member and said bracket member in engagement while allowing limited movement between said members in the direction of adjustment, means for pivotally supporting a generally fiat cam locking lever adjacent the outer surface of said adjusting member wherein said cam locking lever rotates about a pivot axis transverse to the longitudinal axis of said locking lever, said cam locking lever including a camming surface extending generally in a direction parallel to said pivot axis and disposed such References Cited in the file of this patent UNITED STATES PATENTS 2,249,828 Herold July 22, 1941 2,321,385 Herold June 8, 1943 2,374,350 Herold Apr. 24, 1945

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