US3111343A

US3111343A - Chair adjustment mechanism

Info

Publication number: US3111343A
Application number: US109535A
Authority: US
Inventors: Maxwell E Pearson
Original assignee: Knoll Associates Inc
Current assignee: Knoll Associates Inc
Priority date: 1961-05-12
Filing date: 1961-05-12
Publication date: 1963-11-19
Anticipated expiration: 1980-11-19

Description

Nov. 19, 1963 r M. E. PEARSON 3,111,343

CHAIR ADJUSTMENT MECHANISM 5 Sheets-Sheet 1 'FIGJ. FICLE.

Filed May 12. 1961 FIG.3.

no a: IOQ, av 22 3b [IO 25: I I I 9 30. 25b as 3 a e. 34 23b 23 INVENTOR. MAXWELL E. PEARS ON.

Nov. 19, 1963 M. E. PEARSON 3,111,343

CHAIR ADJUSTMENT MECHANISM Filed May 12, 1961 v s Sheets-Sheet 2 mmvrox MAXWELL E. PEARSON ymncw Nov. 19, 1963 Filed May 12, 1961 XVII M. E. PEARSON 3,111,343

CHAIR ADJUSTMENT MECHANISM 5 Sheets-Sheet 3 INVENTOR. MAXWELL E. PEARSON "lion; )4 M Nov. 19, 1963 M. E. PEARSON 3,111,343

CHAIR ADJUSTMENT MECHANISM Filed May 12, 1961 5 Sheets-Sheet 4 FIG.8.

III n. nlLfllIL 1| 1| 1 INVENTOR.

MAXWELL E. PEARSON 1" B7 rm/Mn Nov. 19, 1963 Filed May 12, 1961 FIG. I2.

FIG. l5.

M. E. PEARSON CHAIR ADJUSTMENT MECHANISM 5 Sheets-Sheet 5 I NVENTOR. MAXWELL E, PEARSON "254a D VQZW ATTOKA/f) United States Patent 3,111,343 Cl im ADEUrlTh/EENT IVEQHANEM Maxwell E. Pearson, Baily, ?a., assign'or to Knoli Associates, The, New York, N.Y., a corporation of New York Filed May 12, 1%1, Ser. No. 109,535 18 (Ilaims. (Cl. 297306) This invention relates to chairs, and is particularly concerned with chairs which are useful in business offices, for example secretarial chairs.

Typical secretarial chairs of the prior art are provided with a back adjustable with respect to the seat. In many chairs, the angular relationship of the back with respect to the seat may be adjusted and the height of the back with respect to the seat may be separately adjusted. Many such chairs have a tiltable back, spring loaded to a forward position, so that the user of the chair may lean back against a yielding spring. It is common to provide means for adjusting the tension of such a spring.

The various adjustments for the back angle, back height, and spring tension commonly include parts having complex surfaces, such as screw threads or knurled surfaces. Those parts must necessarily be accessible for changing the adjustments to suit the requirements of particular users of the chair. This accessibility has commonly been secured by placing the adjustable parts where they are readily visible. The parts in question are usually unsightly, and their complex surfaces provide many small areas which are subject to deposit of dust and dirt, making them even more unsightly.

An object of the present invention is to provide an improved chair seat construction.

Another object of the invention is to provide a chair having a seat and a back, and improved means for ad justing the angular relationship between the back and the seat.

Another object is to provide, in a chair of the type described, improved means for adjusting the height of the back relative to the seat.

Another object is to provide in a chair having a yielda'ole back, improved means for controlling the spring tension which biases the back toward its normal angular position with respect to the seat.

It is a further object of the present invention to provide a chair of the type described in which all the adjustments are made by mechanisms which are for the most p rt concealed. A further object is to provide those parts of the adjusting mechanism which are not concealed with simple, smoothly contoured surfaces.

The foregoing and other objects of the invention are attained in the chair described herein, which is adapted for mounting on a base with a central swivel spindle. On the top of the spindle is mounted a cast aluminum shell, generally concave as viewed from the top and open at the top.

A pivot means including a torsion spring is mounted transversely of the shell and completely inside it. This pivot means includes inner and outer concentric metal sleeves and a rubber member between and bonded to both sleeves and serving as a torsion spring. A torque arm is fixed to the outer sleeve and projects rearwardly from it. A lever arm is journaled on the outer sleeve and also projects rearwardly from it through an aperture provided in the shell and beyond the rear edge of the seat. The lever arm is provided with a pivotally mounted rearward extension. The arm and the extension have interengageable gear segments. When the gear segments are engaged, the angular position of the rear extension is fixed. Engagement and disengagement of the gear segments is accomplished by rotating the pivot pin, which has an eccentric engaging the extension.

The rear section of the lever arm is apertured to receive an upright which carries the back structure.

A wedge member is insertable into the aperture through an opening provided in the rear extension of the lever arm. The wedge is operable either to lock the upright against vertical movement or to release it for adjustment of the back h ight.

The eccentric for releasing the back angle adjustment is operated by a knob fixed on one end of the pivot pin for the rear extension of the lever arm. Another knob threaded on the opposite end of the pivot pin is operable both to lock the back angle adjustment and the locking Wedge for the height adjustment.

Other objects and advantages of the invention will become apparent from a consideration of the following specification and claims, taken together with the accompanying drawings.

In the drawings:

FIG. 1 is a side elevational view of a chair embodying the invention;

PEG. 2 is a plan view taken on the 1 with the seat removed;

FIG. 3 is a view partly in elevation and partly in section on the line iii-i i of H6. 2, showing the back angle adjustment mechanism and the spring tension adustment;

4 is a view, partly in perspective and partly in section on the line i k-V of PEG. 2, showing the seat attaching clips;

FIG. 4A is a cross-sectional view showing one of the retainers for the seat attaching clips;

ELL? 5 is a plan view of the seat supporting shell with the seat removed;

PEG. 6 is a crosssection view of the shell shown in 5, taken on the ins. VlVI of FIG. 5, and with certain parts removed;

FIG. 7 is a perspective View showing the shell of FIG. 5 with angle plates mounted thereon to serve as supports for the back supportin lever arm pivot;

Fit 8 is a view partly in plan and partly in section on the Viii-/lli of FIG. 9 of the front section of the lev arm with all other parts removed;

FIG. 9 is an elevational view of one half of the lever arm of FIG. 8, taken on the line 1XlX of FIG. 8;

FIG. 10 is a perspective view of a connecting pin shown in dotted lines in FIG. 8;

mi 1G. 10A is a cross-sectional view of the pin of FIG.

FIG. 11 is a cross-section view taken on the line Xi-Xl of PEG. 9;

FIG. 12 is a cross-sectional view taken on the line iilXil of FIG. 1;

FIG. 13 is an eievational view of the rearward section of the lever arm taken on the line X HXHI of FIG. 12;

PEG. 14 is a sectional view, taken through the pivot axis of the is er arm, looking upward;

i6. 15 is a fragmentary view showing stop structures which limit rotation of a control knob;

FIG. 16 is a fragmentary front elevational view, showing the general contour of the seat and seat supporting shell;

PEG. i7 is a fragmentary sectional view, taken on the line XViiXVil of PEG. 14, illustrating a detail;

FIG. 18 is a plan View of one of the plates for mounting the lever arm pivot; and

FIG. 19 is an elevational view of the plate of FIG. 18.

PEG. 1 illustrates a chair including a base 1 in which is journaled a vertical spindle 2. A shell 3 is supported on the top of the spindle 2 and in turn supports a seat cushion 4. A lever arm 24 extends rearwardly from the line 11-1! of FIG.

shell 3, and has a rearward extension 25 which supports an upright 6 which carries the back '7 of the chair.

The base 1 and the spindle 2 form no part of the present invention, and are shown only generally in the drawings. The base 1 and spindle 2 may be provided with a suitable height adjustment mechanism (not shown). Spindle 2 is enclosed within a dust shield 5.

The shell 3 is shown in detail in FIGS. 5 and 6. The shell 3 has a concave upper surface, and is open at the top. Two reinforcing ribs 3 extend from the front rim of the shell to the back rim. Two other reinforcing ribs 9 extend from one side rim of the shell to the other.

Ribs

8 and 9 and the rim of the shell provide a smoothly contoured surface for supporting a base plate ltl (FIGS. 3 and 4) on which is mounted the seat cushion 4.

The shell 3 may be of cast aluminum or other suitable material. The seat plate It may be of a reinforced plastic material which is somewhat flexible, for example, Masonite.

The shell 3 is provided near its lowest portion with a hub 3a (HG. 6) having a central aperture 3b adapted to receive the upper end of the spindle 2.

The seat plate 1b is apertured to receive a plurality of spring clips 11 (HG. 4), each having an end Illa which extends below the seat plate 1%) and projects horizontally, so as to be generally parallel with the seat plate it In the shell 3, adjacent the ribs 9 are a plurality of bosses 12, each provided in its upper surface with two spaced apertures 12a for receiving a leg of a U-shaped spring retainer 13. The central portion of the retainer 13 extends above the upper surface of the rib 9.

Near the rear edge of the shell 3, along its centerline, there is provided an upwardly extending projection 3c (FIG. 3) which is adapted to be received in an opening a formed in the seat plate 16.

The seat, including the cushion 4 and the plate It may be assembled on the shell 3 by sliding the seat forwardly along the top of the shell so that the clip ends Ila slide between the central portions of the U-shaped retainer 13 and the tops of the bosses 12. The projection 3c and the aperture 163a are so placed that when the edge of the seat is aligned with the edge of the rim, the projection 30 snaps into the aperture lilo. During the horizontal movement of the seat, the plate it) must be suiticiently flexible to bend and accommodate the movement of the seat plate 10 past the projection 36.

The rim of the shell 3 is protected by a rubber ring 14 (FIG. 3) having a generally U-shaped cross-section. This rim may be formed as a rubber extrusion, which is cut in lengths somewhat shorter than the perimeter of the shell. The ends of each length are then vulcanized together to form a ring and the ring is stretched over the shell rim. The rubber ring 14- provides a smooth and resilient surface which may receive impacts from adjacent objects without being marred or damaged.

On either side of the hub 3a, the shell 3 is provided with a pair of bosses 15 (FIG. 5) in which are formed screw holes 15a. Another pair of bosses 16 are provided in the shell 3 at localities spaced to the rear and to the side from the bosses 15. The bosses 16 are also provided with screw holes 16a. A pair of angle plates 17 (see FIGS. 7, 14, 18 and 19) are supported on the

bosses

15 and 16 and are held in place by 5 rows extending through the plates and into the bosses. The angle plates 17 are provided with downwardly depending portions 17a which are adapted to receive the ends of a bolt 18 (see FIG. 14). The bolt 18 is provided at one end with a head which abuts the outside of one of the angle plates 17. The opposite end of the boltlS is threaded to receive a nut l Mounted on the bolt 13 between the plates 17 is a torsion spring including an inner sleeve 20', and an outer sleeve 21, separated by a rubber torsion spring member 22 which is bonded to both the inner sleeve 2d and the outer sleeve 21. The term rubber is used herein as a generic term including natural rubber and any of the synthetic rubbers which have equivalent or superior stretching properties. in the plates 17, adjacent the apertures which receive the bolt 18, there are provided inwardly projecting indentations 17b (FIG. 17), which engage correspondingly formed grooves in the ends of the inner sleeve 2t). The indentations 17b and the grooves serve as keys to lock the inner sleeve 2%) against rotation with respect to the plates 17.

On the outer surface of the outer sleeve 21, at its middle portion, there is fixed a torque arm 23. The torque arm 2-3 may be fixed to the sleeve 21 by a plastic bonding agent or other suitable means. The arm 23 projects rearwardiy from the sleeve 21 and is provided at its rear end with an aperture 23:: for receiving a screw 235, whose slotted screw head is at the lower end of the screw.

The lever arm 24-, best seen in FIGS. 8 to 11, is pivotally mounted (see FIG. 14-) on the outer sleeve 21, and its rearward extension 25, best seen in FIGS. 3 and 12, is pivotally mounted (see P10. 12) on a pivot pin 26 journaled on the rear end of the lever arm 2 The lever arm 24 is built up from two

parts

24a, 24b of generally channel shaped cross-section (see FIGS. 8 and 11). Near their centers, the two parts 24a, 2452 are provided with two holes 27 (FIG. 9), each adapted to receive a V-notched pin 28. Each V-notched pin 28 (FIG. 10) is made with a slightly larger diameter than the holes 27 and is driven into one of the holes, thereby compressing its V-shaped notch, which extends the full length of the pin. After two pins are inserted in one of the parts 2%, 24b, the other of the two parts is then assembled on the pins by simply forcing it on, and the compression of the V-shaped notches in the pins holds the pins and the two

parts

24a and 24b tightly together.

Each of the

parts

24a, 24b has a projection 24c adapted to be received in a corresponding recess 24d on the other one of the two parts. The interlocking projection 24c and recess 24d cooperate to prevent relative motion between the

parts

24a, 24b.

The complete lever arm 24, as seen in FIG. 8, is bifurcated at its front end to provide two hubs 29, which are journaled for rotation on the outer sleeve 21, which serves as a pivot means for the lever arm. Each of the hubs 29 carries two projections 3t 31 (FIG. 9), which cooperate with the seat plate ill and the shell 3 respectively to limit the rotation of the lever arm 24.

The lever arm 24 extends rearwardly through an aperture 302 in the shell 3, best seen in FIG. 6.

The rear end of the lever arm 24 is also bifurcated to provide two hubs 32, which are apertured to receive the pivot pin 26 (see FIGS. 8 and 12).

The two

parts

24a, 24b are placed together with the flanges of their channel shaped cross-sections abutting, as shown in FIG. 11. On the under side of the abutting upper flanges, there is attached, as by welding, a wear plate 33 against which the screw 23b abuts (see PEG. 3). The lower flanges of the

parts

24a and 24b opposite the wear plate 33 are apertured to provide an access opening 34- through which the screw 2 may be reached to adjust the spring tension which is biasing the torque arm 23 clockwise as viewed in FIG. 3, and thus biasing the front section 24 of the lever arm clockwise to hold the projections 3% and 31 against the shell 3.

The rear extension 25 of the lever arm includes a forwardly projecting portion 35 (FIGS. 12 and 13) provided at its front end with a gear segment 35a adapted to engage a gear segment 36 (see FIG. 9) formed on the front section 24 of the lever arm.

The rear extension 25 of the lever arm also comprises a hub 25a which is journaled on an eccentric portion 26a (FIG. 12) of the pivot pin 26. To the rear of the pivot pin 26, the rear extension 25 includes a portion 25b. Extending generally vertically through the portion 25b is an aperture 250 of generally wedge-shaped horizontal cross-section, as best seen in FIG. 12. The upright 6 which carries the back 7 extends through the aperture 25c, and similarly has a generally wedge-shaped crosssection, as seen in FIG. 12. The aperture 250 is slightly longer from front to back than the upright 6 and is slightly wider at its widest or front end. A washer 37 is received in a recess on one side of the arm extension 25 and is provided with a tongue 37a having a tapered tip which projects through an opening in the arm extension 25 and into the aperture which receives the upright 6.

The pivot pin 26 is provided on one end with an enlargement 26b which serves as a knob for rotating the pin 2 5. Another knob 38 is fixed on a screw 39 which is threaded into an internally threaded hole extending along the axis of the pin 26 at the end opposite the knob 2617.

When the knob 38 is rotated and tightened against the washer 37, then the tongue 37a is forced into the aperture 25c and drives the upright 6 toward the narrow end of the wedge-shaped aperture, thereby wedging the upright 6 against vertical movement. The parts are shown in this tightened position in FIG. 12. At the same time, the knob 26 and the knob 38 compressively engage the hubs 32 of the lever arm 24, so that the pin 26 is held against rotation.

When it is desired to change the angular position or the height of the back, the knob 38 is loosened, thereby allowing the tongue 37:: to slip out of the aperture 250. '1'" he upright 6 can then be moved up or down to set the back 7 at the required new position. While the nut 38 is loosened, the knob 26b may be rotated to move the eccentric from the position shown in FIG. 12 to a position which moves the lever arm extension 25 rearwardly and disengages the gear segment 35a from the gear segmeat 36. As soon as the gear segments are disengaged, the arm extension 25 may be rotated on the eccentric 26a to any new angular position desired within the range (best shown in FIG. 13) permitted by the top and bottom flanges of the

lever arm sections

24a and 24b. After the back is positioned in its desired angular relationship with respect to the seat, the knob 26b may again be rotated one-half turn to bring the

gear segments

35a and 36 into engagement, thereby fixing the new angular position. The

lever arm sections

24 and 25 may then be locked against relative movement by tightening the knob 38, which also drives the tongue 37a into the aperture 250 and locks the upright 6 against vertical movement.

The knob 2o!) carries two inwardly projecting stops that, 4% on the rim of the knob. T'hese stops 49a, 49b cooperate with a fixed stop 41 carried by the 'arm 24a (see FIG. 9). When the knob 26 is in the angular position shown in FIG. 15, the eccentric 26a has moved the rear arm section 25 to the forwardmost point of its travel, so that the ear segments 35a and '36 are fully engaged. A person changing the back angle adjustment on the chair will tend to move the knob 26b as far as it will go, he ever, thereby carrying the stop dfia past the position shown in FIG. 15 until it abuts against the fixed stop 41. This carries the eccentric 26:: past the point of maximum inward movement of the arm 25 and sepwates the gear segments 35:: and 35 slightly. This slight separation serves as a safety lock, so that the angular position will not change due to vibration of the chair. In order for the gear segments to be released from this look, the knob 26b must be rotated in a direction such that the initial movement of the arm 25 will tend to tighten the gear segments 35:: and 35 more close y together. When it is desired to change the back angle adjustment, the knob 26b is rotated one half turn, until the stop 4% strikes the fixed stop 51. At that position of the eccentric 26a, the

gear segments

35a and 36 are disengaged, and the rear arm extension 25 is free to rotate on the eccentric 26a.

l Vhile I have shown and described a preferred embodiment of my invention, other modifications thereof will readily occur to those skilled in the art and I therefore intend my invention to be limited only by the appended claims.

I claim:

1. A chair, comprising a seat, a frame supporting said seat, a back, an upright supporting said back, a first arm supported on said frame and extending rearwardly therefrom, a second arm supporting said upright, :pivot means supporting the second arm on the rear end of the first arm, said arms having parts interengageable in different angular positions of the second arm relative to the first arm, and means for shifting said second arm from a for ward position in which said parts are interengaged to prevent angular movement of the second arm on said pivot means to a reanward position in which said parts are disengaged and said second arm is angularly movable on the pivot means to change the angular relationship between the back and the seat.

2. A chair as defined in claim 1, in which said interenga eable parts are gear segments.

3. A chair as defined in claim 1, in which said pivot means comprises a pin having a first cylindrical portion journaled in said first arm, and a second cylindrical portion eccentric with respect to said first cylindrical portion and journaled in said second arm, and said means for shifting said second arm comprises a knob for rotating said pin in said first arm between first and second angularly spaced positions corresponding respectively to the forward and rearward positions of the second arm, and means operable to lock said pin in said first position.

4. A chair as defined in claim 3, including stop means to limit the rotation of the pin to one-half revolution, said first angularly spaced position of the pin corresponding to the center of said one half revolution.

5. A chair as defined in claim 1, in which: said first arm is bifurcated at its rearward end to provide two horizontally spaced members; said second arm is located between said spaced members; and said pivot means comprises a pin leaving two spaced, aligned cylindrical portions journaled in said spaced members and a third cylindrical portion eccentric with respect to said two portions and journaled in said second arm.

6. A chair as defined in claim 5, in which said means for shifting said second arm comprises a first knob fixed on one end of said pin for rotating said pin in said first arm between first and second angularly spaced positions corresponding in which the eccentric portion of the pin is effective to establish the second arm respectively in its fonward and rearward positions, and a second knob threaded on the other end of said pin and rotatable to clamp the two members between the knobs and thereby to lock the pin in its first angular position.

7. A chair, comprising a seat, a frame supporting said seat, a back, an uprigirt supporting said back, said upright having a generally wedge-shaped cross-section, an arm supported on the seat frame and extending rearwardly therefrom, said arm having a vertically extending aperture adjacent its rearward end, said aperture having a cross-section similar to that of the upright but wider at its widest end and slightly longer, said upright being received in said aperture, a wedge member insertable in said widest end to drive the upright toward the narrow end of the aperture and thereby to wedge the upright against vertical movement, and means for moving the wedge member between its inserted position and a retracted position wherein it allows free vertical movement of the back and upright.

8. A chair, comprising a seat, a frame supporting said seat, a back, an upright supporting said back; means for varying the angular relationship of the back relative to the seat, including a first armsupported on said frame and extending rearwardly therefrom, a second arm supporting said upright, pivot means supporting the second arm on the rear end of the first am, said arms having parts interengageable in different angular positions of the second arm relative to the first arm, and means for shifting said second am from a forward position in which said parts are interengaged to prevent angular movement of the second arm on said pivot means to a rearward position in which said parts are disengaged and said second arm is :angularly movable on the pivot means to change the angular relationship between the back and th seat; means for varying the height of the back relative to the seat, including a portion of said upright having a generally wedge-shaped cross-section, a portion of said second arm having a vertically extending aperture adjacent its rearward end, said aperture having a cross-section similar to that of the upright but wider at its widest end and slightly longer, said upright portion being received in said aperture, a wedge member insertable in said widest end to drive the upright toward the narrow end of the aperture and thereby to wedge the upright against ventical movement, and means for moving the wedge member between its inserted position and a retracted position wherein it allows free vertical movement of the back and upright; and means operated concurrently with movement of the wedge member to its inserted position to lock said second arm in its forward position, the eby fixing the height and angular relationship of the back relative to the seat.

9. A chair as defined in claim 8, in which said pivot means comprises a :pin extending through said first and second arms, said means to lock said second arn comprises a nut threaded on said pin; said wedge member moving means comprises a washer encircling said pin; and said wedge member comprises a tongue projecting from said washer toward said widest end of the aperture, said tongue being moved by tightening of the nut into said aperture to wedge the upright against vertical move ment, said pin being locked against angular movement by tightening the nut against the adjacent one of said arms.

10. A chair, comprising a base, a shell open at the top and having in its under surface a recess for receiving the upper portion of the base, a seat, means for attaching the seat to the shell to close the open top thereof, pivot means extending transversely of the shell including concentric inner and outer sleeves and a rubber torsion spring member between and bonded to said sleeves, a torque arm fixed to the outer sleeve and projecting outwardly therefrom, means connecting the inner sleeve to the frame -including key means to prevent relative rotation of the inner sleeve and frame, a first supporting arm journaled on the outer sleeve and extending therefrom rearwardly through an apenture in the shell, a screw threaded into the outer end of the torque arm and abutting said supporting arirn, stop means to limit the rotation of the back supporting arm with respect to the frame, said screw being adjustable to vary the force of the torsion spring member tending to hold the supporting arm against said stop means, a back for the chair, an upright supporting the back; and means for varying the angular relationship between the seat and the back including said supporting arm, a second supporting arm carrying said upright, second pivot means mounting the second a m on the rear end of the first arm, said arms having parts interengageable in diiferent angular positions of the second arm relative to the first arm, and means for shifting said second arm from a forward position in which said parts are interengaged .to prevent angular movement of the second arm on said pivot means to a rearward position in which said parts are disengaged and said second arm is angularly movable on the pivot means to change the angular relationship between the back and the seat.

11. A chair, comprising a base, a shell open at the top and having in its under surface a recess for receiving the upper portion of the base, a seat, means for attaching the seat to the shell to close the open top thereof, pivot means extending transversely of the shell including concentric inner and outer sleeves and a rubber torsion spring member between and bonded to said sleeves, a torque anm fixed to the outer sleeve and projecting rearwardly therefrom, means connecting the inner sleeve to the frame including key means to prevent relative rotation of the inner sleeve and frame, a first supporting arm journaled on the outer sleeve and extending therefrom rearwardly through apenture in the shell, a screw threaded into the outer end. of the torque arm and abuttingsaid supporting arm, stop means to limit the rotation of the back supporting arm with respect to the frame, said screw being adjustable to vary the force of the torsion spring member tending to hold the supporting against said stop means, a b k for the chair, an upright supporting the back; means for varying the angular relationship between the seat and the back including said supporting arm, a second supporting arm carrying said upright, second pivot means mounting the second arm on the rear end of the first arm, said arms having parts interengageable in different angular positions of be second arm relative to the first arm, and means for shifting said second arm from a forward position in which said parts are in-terengaged to prevent angular movement of the second arm on said pivot means to a rearward position in which said parts a e disengaged and said second arm is angularly movable on the pivot means to change the angular relationship between the back and the seat; means for varying the height of the back relative to the seat, including a portion of said second arm having a vertically extending aperture adjacent its rearward end, said aperture having a cross-section similar to that of the upright but wider at its widest end and slightly longer, said upright portion being received in said aperture, a wedge member insertable in said widest end to drive the upright toward the narrow end of the aperture and thereby to wedge the upright against vertical movement, and means for moving the wedge member between its inserted position and a retracted position wherein it allows free vertical movement of the back and upright; and means operated concurrently with movement of the wedge member to its inserted position to lock said second arm in its forward position, thereby fixing the height and angular relationship of the back relative to the seat.

12. A chair comprising a base, a frame supported on said base, torsion spring means including concentric inner and outer sleeves and a rubber torsion spring member between and bonded to said sleeves, a torque arm fixed to one of the sleeves and projecting outwardly therefrom, means connecting the other sleeve to the frame including key means to prevent relative rotation of said other sleeve and the frame, a back, an arm supporting the back and journaled on said one sleeve, a screw threaded into the outer end of the torque arm and abutting said back supporting arm, and stop means to limit the rotation of the back supporting arm with respect to the frame, said screw being adjustable to vary the force of the torsion spring member tending to hold the back supporting arrn against said stop means.

13. A chair as defined in claim 12, in which said one sleeve is the outer sleeve and said other sleeve is the inner sleeve; said back supporting arm is bifurcated at its forward end to provide two horizontally spaced members journaled on said outer sleeve on opposite sides of said torque arm, said back supporting arm including a first web connecting the upper parts of said members, overlying said torque arm and abutting said screw, and a second web connecting the lower parts of the members and extending under the torque arm and the screw, said second web being apertured to provide access to the head of the screw for adjusting the force of the torsion spring means.

14. A chair, comprising a base, a frame supported on the base, a seat, means for attaching the seat to the frame, pivot means extending transversely of the frame including concentric inner and outer sleeves and a rubber torsion spring member between and bonded to said sleeves, a torque arm fixed to the middle of the outer sleeve and projecting reanwardly therefrom, means connecting the inner sleeve to the frame including key means to prevent relative rotation of the inner sleeve and frame, a first supporting arm bifurcated to provide two horizontally spaced members journaled on the outer sleeve on opposite sides of the torque arm, said supporting arm extending rearwardly from said members through an aperture in the frame, a screw threaded into the outer end of the torque arm and abutting said supporting arm, stop means to limit the rotation of the back supporting arm with respect to the frame, said screw being adjustable to vary the force of the torsion spring member tending to hold the supporting arm against said stop means, a back for the chair, an upright supporting the back; means for varying the angular relationship between the seat and the back including said supporting arm, said supporting arm being bifurcated at its rearward end to provide spaced fingers, a second supporting arm carrying said upright, second pivot means mounting the second arm between the fingers on the rear end of the first arm, said arms having parts interengageable in difierent angular positions of the second arm relative to the first arm, and means for shifting said second arm from a forward position in which said parts are interengaged to prevent angular movement of the second arm on said pivot means to a rearward position in which said parts are disengaged and said second arm is angularly movable on the pivot means to change the angular relationship between the back and the seat.

15. A chair as defined in claim 14, including means for varying the height of the back relative to the seat, said height varying means including a portion of said second arm having a vertically extending aperture adjacent its rearward end, said aperture having a crosssection similar to that of the upright but wider at its widest end and slightly longer, said upright portion being received in said aperture, a wedge member insertable in said widest end to drive the upright toward the narrow end of the aperture and thereby to wedge the upright against vertical movement, and means for moving the wedge member between its inserted position and a retracted position wherein it allows free vertical movement of the back and upright; and means operated concurrently with movement of the wedge member to its inserted position to lock said second arm in its forward position,

thereby fixing the height and angular relationship of the back relative to the seat.

16. A chair, comprising a base, a shell open at the top and having in its under surface a recess for receiving the upper portion of the base, a seat mounted on and covering the top of the shell, pivot means extending transversely of the shell, means in the shell for mounting said pivot means, an arm pivotally supported on said pivot means and extending therefrom rearwardly through an aperture in the shell, a back for the chair, and means for supporting the back on the rear end of the arm.

17. A chair as defined in claim 16, in which said pivot means includes concentric inner and outer sleeves and a rubber torsion spring member between and bonded to said sleeves, a torque arm fixed to the outer sleeve and projecting outwardly therefrom, means connecting the inner sleeve to the shell, including key means to prevent relative rotation of the inner sleeve and shell, said arm being journaled on the outer sleeve, a screw threaded into the outer end of the torque arm and abutting said back supporting arm, and stop means to limit the rotation of the back supporting arm with respect to the frame, said screw being adjustable to vary the force of the torsion spring member tending to hold the back supporting arm against said stop means.

18. A chair as defined in claim 16, in which said mounting means comprises a pair of angle plates, each angle plate having a horizontal portion and a downward- 1y depending vertical portion, abutment means in the shell projecting upwardly therefrom and supporting said angle plates, and means fastening the angle plates to the abutment means, said vertical portions of the angle plates being apertured to receive the ends of the pivot means.

References Cited in the file of this patent UNITED STATES PATENTS 2,310,476 Todd Feb. 9, 1943 2,437,940 Cramer Mar. 16, 1948 2,584,614 Rasmussen Feb. 5, 1952 2,664,305 Hobart Dec. 29, 1953

Claims

1. A CHAIR, COMPRISING A SEAT, A FRAME SUPPORTING SAID SEAT, A BACK, AN UPRIGHT SUPPORTING SAID BACK, A FIRST ARM SUPPORTED ON SAID FRAME AND EXTENDING REARWARDLY THEREFROM, A SECOND ARM SUPPORTING SAID UPRIGHT, PIVOT MEANS SUPPORTING THE SECOND ARM ON THE REAR END OF THE FIRST ARM, SAID ARMS HAVING PARTS INTERENGAGEABLE IN DIFFERENT ANGULAR POSITIONS OF THE SECOND ARM RELATIVE TO THE FIRST ARM, AND MEANS FOR SHIFTING SAID SECOND ARM FROM A FOR-