WO2006119209A2

WO2006119209A2 - Chair with recline control mechanism, recline limit control and back tilt mechanism

Info

Publication number: WO2006119209A2
Application number: PCT/US2006/016665
Authority: WO
Inventors: Jay R. Machael; Marcus C. Koepke; John Koch; Aaron Michael Ickes
Original assignee: Hni Technologies Inc.
Priority date: 2005-05-02
Filing date: 2006-05-02
Publication date: 2006-11-09
Also published as: US20060284461A1; WO2006119209A3

Abstract

A chair (10) having a recline control mechanism (154), a limit control apparatus (270) and a tilt mechanism (50). The recline control mechanism (154) operates to adjust resistance to rotation of a back assembly (12) of the chair and includes an actuator lever (182) having a lock structure (224) attached to a movable spring assembly (152). Moving the spring assembly (152) toward and away from a rotation axis (142) for the back assembly (12) adjusts the resistance. The limit control apparatus (270) selectively limits the extent of rotation of the back assembly (12) from about zero degrees to about 3.5 degrees to about seven degrees by using abutment surfaces (306,308,310). The tilt mechanism (50) provides an independent and stable yet passive tilt capability to a backrest of the back assembly (12) by using a pair of brackets (378,322) , two pairs of links (325,328,330,332) and two pairs of rods (336,338,340,342).

Description

CHAIR WITH RECLINE CONTROL MECHANISM, RECLINE LIMIT CONTROL AND BACK TILT MECHANISM

BACKGROUND OF THE INVENTION Field of the Invention

[0001] The present invention relates to a chair with a reclining back assembly and, more particularly, to a chair that includes a more efficient mechanism for adjusting resistance to the recline of a chair back assembly, a simple apparatus for limiting the angle of recline and a tilt mechanism that results in a more comfortable passive tilt adjustment of a chair back in various chair recline positions.

Description of the Related Art

[0002] Reclinable office chairs are ubiquitous and appear in many different styles and designs and with many different functions. Most, if not all, include some mechanism to resist a reclining back. See for example, U.S. Patent No. 6,053,574 which includes movable springs. Some chairs also include adjustable stops to control the angle of recline. See for example, U.S. Patent Nos. 6,616,231 and 6,193,314. Still other chairs include tiltable backs. See for example, U.S. Patent Nos. 1,756,825 and 3,938,858 and Reissue 36,335. Adjustable office chairs are sometimes complicated to operate or are overly complex in structure and are often expensive, unreliable or difficult to use.

BRIEF SUMMARY OF THE INVENTION

[0003] The difficulties encountered with previous devices have been over come by the present invention. What is described here is a chair with a reclining back including a seat assembly, a back assembly, a pivot forming structure defining an axis of rotation for allowing the back assembly to rotate relative to the seat assembly and a biasing structure for resisting the rotation of the back assembly, the biasing structure being spaced from the axis of rotation and also being movable forwardly and rearwardly relative to the axis of rotation with specific structural elements as a way of controlling resistance to the rotation of the back assembly. The invention here also includes a limit control apparatus having specific structure including a first structure having a step configuration, a second structure including an abutment surface for engaging the first structure and an actuator for moving either the first or second structures. The present invention further includes a tilt mechanism for the back of the back assembly including a first bracket, a second bracket, a first pair of links, a second pair of links, a first rod and a second rod so as to allow the second bracket which is connected to the chair back to pivot in a plane generally perpendicularly to the axes of the rods so as to provide a stable but passive adjustment of the chair back as the back assembly reclines.

[0004] A complete understanding of the present invention and other objects, advantages and features thereof will be gained from a consideration of the present specification which provides a written description of the invention, and of the manner and process of making and using the invention, set forth in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same in compliance with Title 35 U.S.C. section 112 (first paragraph). Furthermore, the following description of a preferred embodiment of the invention read in conjunction with the accompanying drawing provided herein represent an example of the invention in compliance with Title 35 U.S.C. section 112 (first paragraph), but the invention itself is defined in the Claims section attached hereto.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING [0005] FIGURE 1 is a rear isometric view of the inventive office chair described herein.

[0006] FIGURE 2 is a sectional elevation view of the chair shown in FIG. 1 in an upright position. [0007] FIGURE 3 is a sectional elevation view similar to that shown in FIG. 2 but with the chair in a folly reclined position.

[0008] FIGURE 4 is a front isometric view of controls and frame members of the chair shown in FIG. 1.

[0009] FIGURE 5 is an enlarged top plan view of a box for the controls of the chair shown in FIG. 1.

[0010] FIGURE 6 is an isometric view of the box shown in FIG. 5 and including a bracket for attachment of the box to a support column.

[0011] FIGURE 7 is an isometric view of an upper mount of the chair shown in FIG. 1.

[0012] FIGURE 8 is an exploded isometric of the elements shown in FIG. 4 but with the absence of some elements.

[0013] FIGURE 9 is an isometric view of a plastic slide plate.

[0014] FIGURE 10 is an isometric view of the controls of the chair of FIG. 1 showing a spring assembly absent a helical spring and a top cap.

[0015] FIGURE 11 is an isometric view of an actuator lever for vertical adjustment of the chair shown in FIG. 1.

[0016] FIGURE 12 is an isometric view of the top cap for the spring assembly of the chair shown in FIG. 1.

[0017] FIGURE 13 is an isometric view of the helical spring used in the spring assembly. [0018] FIGURE 14 is a downward looking isometric view of a spring guide for the spring assembly.

[0019] FIGURE 15 is an upward looking isometric view of the spring guide shown in FIG. 14.

[0020] FIGURE 16 is an isometric view of a spring carrier of the spring assembly.

[0021] FIGURE 17 is an isometric view of a recline control mechanism for moving the spring assembly.

[0022] FIGURE 18 is an isometric view of an actuator lever of the recline control mechanism.

[0023] FIGURE 19 is a downward looking isometric view of a crank of the recline control mechanism.

[0024] FIGURE 20 is a bottom view of the crank shown in FIG. 19.

[0025] FIGURE 21 is a partial sectional view illustrating a lock structure in a locked position.

[0026] FIGURE 22 is a view similar to FIG. 21 illustrating the lock structure being unlocked.

[0027] FIGURE 23 is a view similar to FIGS. 21 and 22 illustrating the lock structure in an unlocked position.

[0028] FIGURE 24 is a view similar to FIGS. 21-23 illustrating the lock structure in an unlocked and moving position. [0029] FIGURE 25 is an isometric view of the recline control mechanism and the spring assembly in a position close to a recline rotation axis.

[0030] FIGURE 26 is a view similar to FIG. 25 with the recline control mechanism and the spring assembly in a position further from the rotation axis than is shown in FIG. 25.

[0031] FIGURE 27 is a view similar to FIGS. 25 and 26 illustrating the recline control mechanism and the spring assembly in a position furthest from the rotation axis.

[0032] FIGURE 28 is a rear isometric view of the controls shown in FIGS. 4 and 8 and illustrating a limit control apparatus.

[0033] FIGURE 29 is an isometric view of a brace of the limit control apparatus.

[0034] FIGURE 30 is an isometric view of an actuator lever of the limit control apparatus.

[0035] FIGURE 31 is an isometric view of an abutment structure of the limit control apparatus.

[0036] FIGURE 32 is an isometric view of a slide block of the limit control apparatus.

[0037] FIGURE 33 is a diagrammatic elevation view of the actuator lever, the abutment structure, and the slide block of the limit control apparatus.

[0038] FIGURE 34 is an exploded isometric view of a tilt mechanism for the chair shown in FIG. 1.

[0039] FIGURE 35 is an isometric view of the tilt mechanism in an assembled condition.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION [0040] While the present invention is open to various modifications and alternative constructions, the preferred embodiment illustrating the best mode contemplated by the inventors of carrying out their invention is shown in the various figures of the drawing and will be described herein in detail, pursuant to Title 35 U.S.C. section 112 (first paragraph). It is understood, however, that there is no intention to limit the invention to the particular embodiment, form or example which is disclosed herein. To the contrary, the intention is to cover all modifications, equivalent structures and methods, and alternative constructions falling within the spirit and scope of the invention as expressed in the appended Claims section attached hereto, pursuant to Title 35 U.S.C. section 112 (second paragraph).

[0041] Referring now to FIGS. 1-3, there is illustrated a chair 10 having a back assembly 12, a seat assembly 14, a set of controls 16, a pair of arms 18, 20, a support column 22, a base 24, and a set of casters 26, 28, 30, 32, 34.

[0042] The illustrated chair 10 is of an office type which swivels, adjusts vertically, glides easily on a floor or carpet pad and includes reclining and tilt back features. The reclining and tilt back features are shown by comparing FIGS. 2 and 3 where in FIG. 2 the chair 10 is illustrated in a full upright position and in FIG. 3 the chair 10 is illustrated in a full recline position. The back assembly 12 goes from an angle of about 86 degrees from a reference vertical line 36 at full upright to about 79 degrees at full recline, although other angles may be used. The backrest 38 of the back assembly also reclines in a movement from about 10 degrees to about 24 degrees. It is noted that the backrest 38 is independently able to tilt a maximum of about 7.2 degrees while undergoing a recline with the back assembly, although other angles may be employed. It is further noted that the reclining and the tilt back features may also be used on non-office chairs, for example, chairs used in conference centers, theaters or lecture halls where there may be no horizontal movement because the chairs are fixed to a floor or a platform. The reclining and tilt back features may also be used independently of each other. For example, a chair may have the reclining feature but not the tilt back and vice versa.

[0043] The backrest 38 may include a support panel 42 and a back cushion 44, the frame 40 may include a pair of parallel tubular frame members 46, 48, and the back assembly 12 may include a tilt mechanism 50 connecting the support panel 42 and the frame members 46, 48. The seat assembly 14 may include a seat pan 52 and a seat cushion 54. It is noted that the back assembly may include only a panel of flexible and/or resilient material such that a cushion is not needed. The same may be true of the seat assembly where only a seat panel of flexible and/or resilient material is used.

[0044] The base 24 may include five arms 60, 62, 64, 66, 68 and a hub 70, and the base rigidly supports the column 22 in the hub 70. The support column may include a gas cylinder for allowing vertical adjustment of the seat and back assemblies.

[0045] The set of controls 16 are located in and about a lower mount box 74, FIGS. 4, 5 and 6. The box 74 may include a pair of side walls 76, 78 having lever openings 80, 82, 84, a front wall 86, a rear wall 88 and a bottom wall 90. The box may also include a pair of horizontally extending flanges 92, 94 with fastener receiving openings 96, 98, 100, 102 for fasteners (not shown) to connect the box 74 to the seat pan 52. The bottom wall 90 may include a series of lock holes 103 extending over an arc of about 30 degrees measured from a fastener receiving hole 104 located near the lever opening 80. Another fastener receiving hole 106 may be placed near the lever opening 84. A longitudinally directed slot 108 is formed in the center portion of the bottom wall 90 and a column receiving opening 110 is formed toward the rear of the bottom wall. Rigidly affixed to the bottom wall is a bracket 112 to which the support column 22 may be connected. The side walls 76, 78 also include two horizontally aligned pivot openings 120, 122. [0046] Pivotally mounted to the box 74 may be a U-shaped upper mount plate 126, FIGS. 4 and 7. The upper mount plate 126 includes a top wall 128, two side walls 130, 132 and a rear wall 133, FIG. 8. The top wall includes a longitudinally directed slot 134 and the side walls include two horizontally aligned pivot openings 136, 138. As shown in FIGS. 4 and 8, the pair of frame members 46, 48 are attached to the plate 126 by any suitable technique such as by welding. A pivot rod 140 may be inserted into the aligned openings 120, 122 of the box 74 and the aligned openings 136, 138 of the plate 126. This arrangement, a pivot forming structure, allows the back assembly 12 to recline relative to the remainder of the chair, and in particular, relative to the seat assembly 14, the support column 22 and the base 24 as is typical of an office chair.

[0047] The pivot forming structure of the control box 74, the plate 126 and the pivot rod 140 creates an axis of rotation 142, FIGS. 2 and 3, that is coincident with the longitudinal axis of the pivot rod 140. This pivot axis is located forward of the support column 22. As seen in FIGS. 2 and 3, the axis of rotation 142 is under the forward portion of the seat assembly 14. In one embodiment the rotation axis 142 is about 6.125 inches forward of a vertically aligned longitudinal axis 144, FIGS. 2 and 3 of the column 22.

[0048] Located within the box 74 may be a low friction plastic slide plate 150, FIGS. 8 and 9, a slidable spring assembly 152, FIGS. 2, 3, 8 and 10, a recline control mechanism 154, FIGS. 8 and 10, for moving the spring assembly forward toward the rotation axis 142 and rearward away from the rotation axis. The slide plate 150 includes a longitudinal slot 160 extending forwardly and rearwardly which is parallel to and aligned with the slot 108 of the box 74 and the slot 134 of the plate 126. The slide plate 150 may also include an opening 165 to receive the bracket 112, a first fastener pass-through hole 164 that aligns with the hole 104 of the box 74, a second fastener pass-through hole 166 that aligns with the hole 106 of the box 74, a series of detent recesses 168, two upstanding flanges 170, 172, a lateral slot 174 along the rear portion of the slide plate and a cut-out 176 to expose the lock holes 103. It should be noted that the lock holes may be formed in the slide plate and thus the cut-out may be obviated.

[0049] Extending from lever opening 82, FIG. 5, of the box 74 may be an actuator lever 180, FIGS. 4, 8 and 10, for adjusting the vertical height of the seat and back assemblies. Extending from the lever opening 80 is an actuator lever 182, part of the recline control mechanism 154 for controlling resistance to rotational movement of the back assembly during recline, and extending from the lever opening 84 is an actuator lever 184 for limiting the degree of rotation of the back assembly.

[0050] The actuator lever 180 may include a handle portion 190, FIG. 11, a fulcrum portion 192 and a bearing portion 194. The fulcrum portion includes a hole 196 for receiving a pin 197, FIG. 18, that pivotally mounts the actuator lever 180 to the flanges 170, 172 of the slide plate 150. The bearing portion 194 operates the air cylinder in the usual fashion known by those skilled in the art.

[0051] The spring assembly 152 is a biasing structure and may include a spring carrier 200, FIGS. 8, 10 and 16, having a tab portion 202 with a pin receiving opening 204 and a slot 205, a spring guide 206, FIGS. 8, 10, 14 and 15 with a post portion 208, a cup portion 210 and a runner portion 212, a top cap 214, FIGS. 8 and 12, with a central opening 216, and a helical spring 218, FIG. 13. The helical spring 218 is mounted around the post portion 208 and is supported by the cup 210. The post portion 208 extends through the central opening 216 of the top cap 214. The runner portion 212 of the spring guide 206 extends through the slot 205 of the spring carrier 200. The runner portion 212 extends into the longitudinal slot 160 of the slide plate 150 and is guided and limited by the slot 160. The upper end of the post portion 208 extends out of the central opening 216 of the top cap 214 and into the slot 134 of the plate 126. The spring may be made of flattened steel wire, 3 inches in length with a spring constant of 375 pounds per inch of deflection. It is to be noted that other types of energy devices may be used instead of the helical spring, such as a rubber spring or an air spring.

[0052] The recline control mechanism 154 has a "lost motion" feature and may include the actuator of lever 182 having a handle portion 220, FIGS. 17-20 attached to a link portion 222. Also included is a crank 224 mounted above the actuator lever 182. The link portion 222 has a crank pin 226, a spring pin 228, two lock ball openings 230, 232, a bridge wall 234 between the lock ball openings, a tab cutout 236 and a fastener opening 238.

[0053] The crank 224 may include a fastener receiving opening 240, FIGS. 19 and 20 to allow the crank to pivot independently of the handle portion 220 and the link portion 222. The crank also includes a tab recess 242 with a fastener receiving opening 244, a crank pin slot 246, a U-shaped groove 248 and a ball cage flange 250 with a ball receiving slot 252. The recline control mechanism 154 also includes a lock ball 254 and a wire spring 256, FIGS 8, 10 and 17. The lock ball 254, the ball cage flange 250, the bridge wall 234 and the openings 230, 232 form a lock structure. The wire spring 256 fits into the groove 248 and includes two legs 257, 258, FIG. 8, that are pre-loaded to engage the spring pin 228 so that movement of the spring pin 228 flexes one or the other of the legs 257, 258 to create a return biasing force acting on the crank 224 and thereby the lock ball 254. A shoulder bolt 259, FIG. 10, extends through the openings 238, 240 in the link portion 222 and the crank 224 pivotally connecting these elements to the box 74 by threading into the hole 104. Another bolt 260, FIG. 10, extends through the opening 204 in the carrier 206 and the opening 244 in the tab recess 242 of the crank 224 to pivotally connect the carrier 200 and the crank 224. [0054] In operation, the actuator lever 182 is able to rotate a short distance, about 3-4 degrees about the bolt 259 in a first step so as to remove any restraint on the lock ball 254 exerted by the bridge wall 234. As shown in sequence in FIGS. 21-24, the bridge wall 234 depresses the lock ball 254 in one of the lock holes 103 of the box 74 to lock the recline control mechanism 154 and the spring assembly 152. As the actuator lever 182 is rotated, the bridge wall 234 moves away from the lock ball 254 so that the lock ball is located under either the opening 230 or the opening 232. After the bridge wall 234 rotates out of the way, the lock ball 254 is able to be moved from one of the lock holes 103 in the bottom wall 90 of the box 74 to another lock hole. As rotation of the actuator lever continues, the crank pin 226 of the link portion 222 engages one or the other ends 261, 262 of the wall surrounding the crank slot 246. The crank 224 then moves causing the spring assembly 152 to move along the slot 160 of the slide plate 150. Motion is transmitted to the spring assembly 152 through the carrier 200 which is connected to the crank 224 by the shoulder bolt 260. The wire spring 256 ensures that after movement of the spring assembly, the actuator lever 182 will be biased back to a locking position where the bridge wall 234 again bears downwardly on the lock ball 254 so as to drop it into one of the lock holes 103 in the bottom wall 90 of the box 74.

[0055] The purpose of the spring assembly 152 is to resist rotation of the back assembly 12 about the rotation axis 142. The further the spring assembly is from the rotation axis, the greater is the moment arm and the higher is the resistance to the reclining back assembly. By moving the spring assembly closer to the rotation axis, the moment arm is decreased and recline of the back assembly is more easily accomplished. This arrangement for altering the tension applied to the back assembly is simple, robust, reliable and very easy to use. The control may be accessed from the side of the chair instead of from under the chair and operation merely requires a lever to be pivoted with an attendant mechanical advantage instead of a knob to be rotated. This feature also provides a user easy feedback to easily judge the current tension or resisting force and then to alter the force, if desired. Also, moving the lever forward to decrease tension and rearward to increase tension may be displayed graphically on the handle portion 220 which is easily seen by a chair user. This compares favorably to an under chair knob without any indication of the correct direction of rotation and with the great difficulty in determining the comfort level of the recline once an adjustment is made.

[0056] The user determines his/her comfort level by moving the lever forward or rearward while attempting to recline. When the amount of resistance force is found to be suitable, the user releases the handle portion 220 of the actuator lever 182. The wire spring 256 returns the actuator lever to an at-rest position where the bridge wall 234 is positioned over the lock ball 254 causing the lock ball to be depressed into one of the six lock openings' 103. This locks the crank 224, and the actuator lever 182, and thereby the spring assembly 152, into position relative to the rotation axis 142. The distance of the spring assembly from the pivot axis defines the amount of resistance that the spring assembly offers to oppose the rotation of the back assembly 12. Movement of the actuator lever 182 and the spring assembly 152 is shown in FIGS. 25, 26 and 27. Total linear movement of the spring assembly may amount to about 0.75 inches.

[0057] The lock structure may take any of a number of forms. For example, a lock structure may be formed by a detent arrangement like that used with the actuator lever 184 as explained below in relation to the detent recesses 168 in the slide plate 150. Or, a lock structure may be formed of high friction material or friction increasing surface textures. The rotation or recline force applied by a chair user is somewhat oblique thereby creating a force component acting in the direction of the rotation axis 142. The greater the recline angle, the greater will be the force component. The lock structure must be sufficient to resist the force component and any one of various mechanisms may prove satisfactory.

[0058] It is also noted that the amount of force needed to compress the spring 218 is a function of the distance between it and the rotation axis 142. In addition, the further the distance from the rotation axis, the greater must be the deflection or compression of the spring to reach a desired recline. This greater compression distance adds a component to the total force resisting recline of the back assembly.

[0059] The chair 10 may also include a limit control apparatus 270, FIGS. 4, 8, 10 and 28- 33, for determining the extent of allowable recline or to prevent any recline at all. There may be three limits or stops which a chair user may select for limiting the amount of rotation of the back assembly from zero degrees, no recline, for tasking, to about 3.5 degrees for tasking or conferencing to about 7 degrees, full recline, for conferencing or lounging.

[0060] The limit control apparatus 270 may include an actuator structure or lever 184 with a handle portion 274 and a link portion 276, a slide block 278, a brace 280 and a stepped abutment structure 282. The link portion 276 has a first end portion 284 with a fastener receiving opening 286 connected to the handle portion 274, and a second end portion 288 with a slot 290. The fastener receiving opening accommodates a shoulder bolt 292, FIG. 10, to connect the actuator structure 272 to the box 74 through hole 106 and to establish a pivot axis 294. The link portion 276 also includes a small foot 295 to engage the detent recesses 168 in the slide plate 150 to ensure the proper location and retention. The slide block 278 has a base portion 296, a pin 298, an upstanding projection 300 and a rail 302. The rail 302 rides in the lateral slot 174 of the slide plate 150, FIGS. 8 and 10. The pin 298 is received by the slot 290 of the link portion 276 for transforming rotational motion of the handle portion 274 to linear motion of the slide block 278. The brace 280 is affixed to the frame members 46, 48 of the back assembly 12 and the stepped abutment structure 282 is connected to the brace 280.

[0061] The upstanding projection 300 of the slide block 278 may include an abutment surface 304, and the abutment structure 282 includes three complementing abutment surfaces 306, 308, 310, each abutment surface of the abutment structure being at a different elevation from the other two surfaces. The abutment surfaces are generally horizontal when the chair is in an upright position, however, because of the recline of the back assembly, the shorter abutments topped by the surfaces 308, 310 are slanted at about 3.5 and 7 degrees, respectively so that contact is made along generally the entire surfaces. It is noted that the abutment structure 282 may be mounted on the box and the slide block 278 may be mounted on the back assembly 12, if found desirable.

[0062] In operation, the limit control apparatus 270 functions by pivoting the handle portion 274 through a maximum arc of about 21 degrees about the pivot axis 294. Rotation of the handle portion is translated to linear motion of the slide block 278 and moving the slide block allows selective placement of the upstanding projection 300 opposite one of three abutment surfaces 306, 308, 310 of the abutment structure 282. Because the abutment structure is affixed to the back assembly 12, rotation of the back assembly is selectively limited. When the abutment surface 306 of the abutment structure 282 is aligned with the abutment surface 304 of the upstanding projection 300, the back assembly will not be able to recline. When the abutment surface 308 is aligned with the upstanding projection 300, the back assembly will be able to be reclined about 3.5 degrees. When the abutment surface 310 is aligned with the upstanding projection 300, the back assembly will be able to be reclined fully, about 7 degrees. The limit control apparatus is very easy to operate, is very reliable and is robust. [0063] The tilt mechanism 50 is based on a four bar mechanism, and may include a first or frame bracket 322, a second or backrest bracket 324, a first or upper pair of links 326, 328, a second or lower pair of links 330, 332, a first or upper pair of structures, such as rods 334, 336, and a second or lower pair of structures, such as rods 338, 340. The tilt frame bracket 322 is secured to the frame members 44, 46 in any convenient fashion. The backrest bracket 324 is connected to the support panel 42 and allows the back to pivot in a plane generally perpendicular to longitudinal axes 342, 344, 346, 348 of the rods in reaction to the movement of a chair user's back.

[0064] The frame bracket 322 includes a first or upper pair of holes 350, 352 and a second or lower pair of holes 354, 356. The front upper rod 336 is pivotally connected to the frame bracket through the upper holes 350, 352 such that the pivot axis 344 of the rod 336 does not translate. The front lower rod 340 which is pivotally connected to the frame bracket through the lower holes 354, 356, such that the pivot axis 348 of the rod 340 is also restrained from translating. The frame bracket 322 may also include a first or upper pair of cutouts in the form of curved slots 358, 360 and a second or lower pair of cutouts in the form of slots 362, 364.

[0065] The back bracket 324 includes a first or upper pair of holes 366, 368, a second or lower pair of holes 370, 372, a first or upper pair of cutouts 374, 376 and a second or lower pair of cutouts 378, 380. Each link 326, 328, 330, 332 includes a first or front end portion 390, 392, 394, 396 and a second or rear end portion 398, 400, 402, 404.

[0066] The front end portions 390, 392 of the upper links 326, 328 may include rod openings 410, 412 which receive the front upper rod 336. The rear end portions 398, 400 of the upper links 326, 328 includes rod openings 414, 416 which receive the rear upper rod 334. The front lower rod 340 is received by openings 418, 420 in the front end portions 394, 396 of the lower links 330, 332 and the rear lower rod 338 is received by openings 422, 424 in the rear end portions 402, 404 of the lower links 330, 332.

[0067] The upper rear pivot axis 342 is allowed to travel within the arc generally defined by the pair of upper curved slots 358, 360 in the upper portion of the frame bracket 322. The lower rear pivot axis 346 is allowed to travel along an arc generally defined by the pair of curved lower slots 362, 364 in the frame bracket 322. The upper front rod 336 moves in the cutouts 374, 376 of the backrest bracket 324 and the lower front rod 340 moves in the cutouts 378, 380 of the backrest bracket 324. The upper links 326, 328 are able to pivot about the pivot axis 344 and the lower links 330, 332 are able to pivot about the pivot axis 348. The pivot axes 344, 348 allow the upper pair of links 326, 328 to rotate about 40 degrees downwardly until limited by the ends of the upper slots 358, 360, and the lower pair of links 330, 332 also rotate about 40 degrees downwardly. At rest, the ends of the lower slots 362, 364 limit rotation of the backrest bracket 324. These rotations combine to allow the backrest bracket 324 to pivot about 7 to 8 degrees in a plane generally perpendicular to the pivot axes 342, 344, 346, 348. This creates a stable, wobble-free platform for the backrest 38.

[0068] The effect of the two-dimensional movement of the backrest bracket 324 is that the chair back follows and supports the back of the chair user with little shear so that there is little or no "shirt pull" of the garment being worn by the chair user even when the user fully reclines the back assembly. This rotational adjustment feature of the back is very stable, passive and functions with chair users of various sizes.

[0069] The above specification describes in detail a preferred embodiment of the present invention. Other examples, embodiments, modifications and variations will, under both the literal claim language and the doctrine of equivalents, come within the scope of the invention defined by the appended claims. For example, different lever, link and mechanism designs are considered equivalent structures and will also come within the literal language of the claims. The same applies to the dimensions and physical characteristics mentioned as well as the amount of recline and tilt. Still other alternatives will also be equivalent as will many new technologies. There is no desire or intention here to limit in any way the application of the doctrine of equivalents nor to limit or restrict the scope of the invention.

Claims

1. A chair with a reclining back comprising: a seat assembly; a back assembly including a frame member connected to said seat assembly; a pivot forming structure defining an axis of rotation for allowing said back assembly to rotate relative to said seat assembly; a biasing structure for resisting the rotation of said back assembly, said biasing structure. being spaced from said axis of rotation of said back assembly and being movable forwardly toward said axis of rotation and rearwardly away from said axis of rotation for controlling resistance to rotation of said back assembly; a lock structure connected to said biasing structure for locking said biasing structure in a selected position; and an actuator structure connected to said biasing structure and to said lock structure for selectively locking and unlocking said lock structure and for moving said biasing structure.

2. The chair of claim 1 wherein: said biasing structure includes a spring.

3. The chair of claim 1 including: a limit control apparatus connected to said back assembly and to said pivot forming structure for limiting recline of said back assembly.

4. The chair of claim 3 wherein: said limit control apparatus includes a first structure having a stepped configuration with a plurality of abutment surfaces, each of said abutment surfaces being disposed in a generally horizontal attitude, said first structure being connected to either a chair lower mount or to the reclining back assembly; a second structure including an abutment surface for selectively engaging said abutment surfaces of said first structure, said abutment surface of said second structure being disposed in a generally horizontal attitude; and an actuator structure being connected either to said first structure or to said second structure for controlling engagement of said first and said second structures.

5. The chair of claim 1 wherein: said back assembly includes a tilt mechanism for maintaining said back assembly in contact with a chair user during recline of said back assembly.

6. The chair of claim 5 wherein: said tilt mechanism includes a first bracket affixed to a frame member that is part of said back assembly, said first bracket having a first pair of holes and a second pair of holes; a second bracket pivotally mounted to said first bracket and affixed to a back of said back assembly, said second bracket having a first pair of holes and a second pair of holes; a first pair of links, each link of said first pair of links having first and second end portions; a second pair of links, each link of said second pair of links having first and second end portions; a first structure for pivotally connecting said first bracket through said first pair of holes and said first end portions of said first pair of links; a second structure for pivotally connecting said second bracket through said first pair of holes and said second end portions of said first pair of links; a third structure for pivotally connecting said first bracket through said second pair of holes and said first end portions of said second pair of links; and a fourth structure for pivotally connecting said second bracket through said second pair of holes and said second end portions of said second pair of links.

7. The chair of claim 6 wherein: said first structure includes a first rod; said second structure includes a second rod; said third structure include a third rod; and said fourth structure includes a fourth rod.

8. A limit control apparatus for a reclining back assembly of a chair comprising: a first structure having a stepped configuration with a plurality of abutment surfaces, each of said abutment surfaces being disposed in a generally horizontal attitude, said first structure being connected to either a chair lower mount or to the reclining back assembly; a second structure including an abutment surface for selectively engaging said abutment surfaces of said first structure, said abutment surface of said second structure being disposed in a generally horizontal attitude; and an actuator structure being connected either to said first structure or to said second structure for controlling engagement of said first and said second structures.

9. The apparatus of claim 8 wherein: said actuator structure is rotatable about a generally vertical axis; and said second structure slides linearly in response to movement of said actuator structure.

10. The apparatus of claim 9 wherein: said actuator structure includes a handle and a link, said link having a first end portion pivotally connected to said handle and a second end portion having a slot for pivotal engagement with said second structure.

11. The apparatus of claim 8 wherein: said second structure is mounted to a chair lower mount and said first structure is mounted to the back assembly.

12. The apparatus of claim 8 wherein: said second structure includes a projection forming said abutment surface, a slidable base for mounting said projection and a post connected to said base and to said actuator structure.

13. A tilt mechanism for a chair back comprising: a first bracket adapted to be affixed to a chair frame member that supports the chair back, said first bracket having a first pair of holes and a second pair of holes; a second bracket pivotally movably mounted to said first bracket adapted to be affixed to the chair back, said second bracket having a first pair of holes and a second pair of holes; a first pair of links, each link of said first pair of links having first and second end portions; a second pair of links, each link of said second pair of links having first and second end portions; a first structure for pivotally connecting said first bracket through said first pair of holes and said first end portions of first pair of links; a second structure for pivotally connecting said second bracket through said first pair of holes and said second end portions of said first pair of links; a third structure for pivotally connecting said first bracket through said second pair of holes and said first end portion of said second pair of links; and a fourth structure for pivotally connecting said second bracket through said second pair of holes and said second end portions of said second pair of links.

14. The tilt mechanism of claim 13 wherein: said first structure includes a first rod; said second structure includes a second rod; said third structure includes a third rod; and said fourth structure includes a fourth rod.

15. The tilt mechanism of claim 14 wherein: said second bracket is restricted to move in a two-dimensional plane generally perpendicular to longitudinal axes of said first, said second, said third and said fourth rods.