Chair mechanism

Abstract

A chair (100, 300) is equipped with a dual-mode tilt and collapsing mechanism (110, 306), and / or a release mechanism (134) for reconfiguring the chair between a ready-to-use configuration and a collapsible configuration, and / or a leg extension and retraction mechanism (120, 316) for extending and retracting legs (130, 314) of the chair in response to moving a chair seat (132, 302) into and out of a collapsed position. Optionally the chair may be equipped with all three mechanisms, which provides for simplified conversion or reconfiguring of the chair between the ready-to-use configuration and the collapsed configuration that occupies substantially less floor space and less vertical space. Seating comfort of the chair is enhanced by the dual-mode tilt and collapsing mechanism (110, 306) in the ready-to-use configuration, which permits limited rearward tilting of the seat (132, 302) and seatback (150, 320) as a user shifts their weight on the seat.

Description

PCT APPLICATION EUD01 FP-102(PCT) CHAIR MECHANISM FIELD

[0001] The present invention relates to seating furniture and, more particularly, to chairs with seats that are movable relative to other chair components.BACKGROUND

[0002] Chairs that are used for work tasks, such as at a desk or table, frequently have seats that are pivotable to a limited extent in a forward and backward pitching movement. This is typically a pivoting movement about a horizontal lateral axis, and often resisted by one or more resilient members such as coil or leaf springs, an air spring, or gas charged strut. This allows a seated person to recline the seat to a limited degree while they are seated, adjusting their position for comfort as desired. Often a backrest or seatback is coupled to the seat, and pivots with the seat either in a rigid manner (i.e., the relative angle of the seatback to the seat remains substantially fixed as they pivot together), or with some limited pivoting of the seatback relative to the seat permitted to a limited degree, such as to allow a person to recline the seatback to a greater degree than the seat, as both seat and seatback are reclined. For example, a seatback coupling or coupling mechanism may permit the seatback to pivot at a different rate than the seat pivots, and tensioners or pre-load adjusters may be provided to accommodate users of different sizes or weights. Thus, a chair with seat that is pivotable to a limited degree, relative to the support below (e.g., legs or a pedestal), can provide more comfort options to a person who may wish to shift their weight forward or backward on the seat, achieving different seat angles depending on how the seat is being loaded by the seated person.SUMMARY

[0003] A task chair utilizes a dual-mode mechanism to allow limited tilting or pivoting movement of a seat while the chair is in use, and which also allows a far greater degree of pivoting movement of the seat while the chair is unloaded and not in use. By allowing more pivoting movement than would be useful for a person seated at the chair, the dual-mode mechanism allows for significantly more compact storage of the chair, whose horizontal "footprint" can be made considerably smaller, and the vertical height lowered, for when the chair is not in use. Bymoving the seat from the compact storage configuration to the in-use configuration and then loading the seat and seatback by sitting upon the chair, the dual-mode mechanism is operable in an in-use mode that permits only limited tilting movement when a person is seated thereon. When the seat and seatback are unloaded, the dual-mode mechanism operates in a collapsible mode in which it is able to pivot the seat further back while the seatback drops downwardly. Optionally, a manual release mechanism allows a user to cause the dual-mode mechanism to fully collapse so that the seat is pivoted rearwardly to a near-vertical orientation and the seatback also drops to a lower position. The seatback may maintain a substantially continuous orientation as it drops downwardly, and as the seat pivots rearwardly relative to the seatback so that the seat and seatback lie in close proximity with one another in the fully collapsed position. Optionally, a leg retraction and extension mechanism is engaged by a seat-coupled actuator near the end of the seat's travel in the collapsing direction, which automatically retracts support legs in order to further reduce the horizontal footprint of the chair for compact storage. The leg retraction and extension mechanism is also capable of automatically extending the support legs for use during initial pivoting movement of the seat out of the collapsed configuration and toward the ready-for- use configuration. Optionally, leg extension and retraction forces are applied by manually forcing the chair to move along a ground surface while wheels or feet of the movable legs frictionally engage the ground surface.

[0004] In one form, a chair seat support includes four links coupled together at four pivots to form a four-bar linkage. A first link is pivotable coupled to a second link, and at least a portion of the first link is able to translate relative to the second link. One of the links is coupled to a seat, which is rearwardly tiltable to a limited degree as the first link translates.

[0005] In one aspect, the first link is a resilient flexible member.

[0006] Optionally, there is a compressible biasing member at one of the pivots associated with the first link, where the biasing member resists translation of the first link relative to the second link.

[0007] In another aspect, the chair seat support includes an upper link having forward and rearward pivots, a rear link having upper and lower pivots, a lower link having forward and rearward pivots, a forward link having upper and lower pivots, and a guide that permits the forward pivot of the lower link to translate a limited distance forwardly and rearwardly. The various links are pivotably coupled together, with the upper pivot of the rear link is pivotably coupled to therearward pivot of the upper link, the rearward pivot of the lower link pivotably coupled to the lower pivot of the rear link, the forward link is configured for coupling to a chair support leg or post, the lower pivot of the forward link is pivotably coupled to the forward pivot of the lower link, and the upper pivot of the forward link is pivotably coupled to the forward pivot of the upper link. The guide is defined at any one of the pivots, such as at the forward link and the lower link at the location where the forward pivot of the lower link is pivotably coupled to the lower pivot of the forward link. The forward pivot of the lower link can translate a limited distance forwardly and rearwardly relative to the forward link as the upper link pivots about the forward pivot of the upper link and the upper pivot of the forward link. When the upper link is coupled to a lower portion of a seat, the seat is tiltable rearwardly to limited degree as the forward pivot of the lower link translates the limited distance forwardly and rearwardly relative to the forward link.

[0008] In a further aspect, the lower link is the first link, and the forward link is the second link.

[0009] In yet another aspect, there is a guide defined at the forward link or the lower link at the location where the forward pivot of the lower link is pivotably coupled to the lower pivot of the forward link. The guide permits the forward pivot of the lower link to translate a limited distance forwardly and rearwardly relative to the forward link as the upper link pivots about the forward pivot of the upper link and the upper pivot of the forward link. Optionally, the guide is in the form of an elongate channel formed in the forward link.

[0010] In a still further aspect, a biasing member is provided to bias the forward pivot of the lower link and thereby bias the seat to pivot forwardly.

[0011] In another aspect, the forward pivot of the lower link compresses the biasing member in response to tilting the seat rearwardly.

[0012] In yet another aspect, a seatback is coupled to the rear link, and the seat pivots into closer proximity to the seatback during the rearward tilting of the seat in response to a downward force acting on the seatback.

[0013] Optionally, the chair seat support is combined with a seatpost extending downwardly from the base, a leg mechanism coupled to the seatpost below the seat base, a plurality of chair legs coupled to the seatpost, and a plunger coupled to a rear portion of the seat. The plunger ismovable with the seat into engagement with the leg mechanism, which is configured to retract at least one of the chair legs in response to the engagement by the plunger.

[0014] In one aspect, the leg mechanism is operable to extend at least one of the plurality of chair legs in response to movement of the plunger while the plunger is engaged with the leg mechanism. The leg mechanism may further be operable to secure the plunger at the leg mechanism when the plurality of chair legs are retracted. Optionally, the leg mechanism is further operable to release the plunger only once the plurality of chair legs are extended.

[0015] In another form, a chair leg mechanism includes a base, a leg actuator, a pair of movable chair legs, and a retainer mechanism. The leg actuator has forward and rearward end portions, and is movable in forward and rearward directions relative to the base. The movable chair legs having proximal end portions that are pivotably coupled to the base and coupled to the forward end portion of the leg actuator. The retainer mechanism is at the rearward end portion of the leg actuator, and is configured to (i) receive and capture a movable seat-coupled actuator, (ii) move with the leg actuator in the forward direction in response to the leg actuator being pushed by the seat-coupled actuator, and (iii) release the seat-coupled actuator after the leg actuator has moved fully in the rearward direction in response to the leg actuator being pulled by the seat-coupled actuator. The movable chair legs are retractable in the rearward direction in response to the leg actuator moving in the forward direction, and the chair legs are extendable in the forward direction in response to the leg actuator moving in the rearward direction.

[0016] In one aspect, the retainer mechanism is a receiver-carriage movably engaged with the leg actuator and with a guide that is formed in a portion of the base. The receiver-carriage is configured to follow the guide while capturing the seat-coupled actuator as the leg actuator moves in the first and second directions, respectively. Optionally, the guide is L-shaped or arcuate in shape.

[0017] In another aspect, the receiver-carriage defines an opening for selectively receiving the seat- coupled actuator, and at least one lockable pawl configured to receive and releasably retain the seat-coupled actuator.

[0018] Optionally, the chair leg mechanism is incorporated into a chair having a seatpost, a seat pivotably coupled to the seatpost, where the seat-coupled actuator is coupled to the seat, and afixed chair leg coupled to the base. The base is coupled to a lower portion of the seatpost, and the movable chair leg is pivotable with respect to the fixed chair leg.

[0019] In yet another form, a chair seat support includes a seat, a seatpost below the seat, an upper link coupled to the seat and having forward and rearward pivots, a rear link having upper and lower pivots, in which the upper pivot of the rear link is pivotably coupled to the rearward pivot of the upper link, a seatback coupled to the rear link, a lower link having forward and rearward pivots, wherein the rearward pivot of the lower link is pivotably coupled to the lower pivot of the rear link, and a forward link coupled to the seatpost and having upper and lower pivots, the forward link configured for coupling to a chair support leg or post. The lower pivot of the forward link is pivotably coupled to the forward pivot of the lower link, and the upper pivot of the forward link is pivotably coupled to the forward pivot of the upper link. The seat is tiltable rearwardly from an in-use orientation to an upright orientation, and to pivot into closer proximity to the seatback in the upright orientation.

[0020] The combination of mechanisms allows for simple operation and reconfiguration of the chair between the ready-to-use configuration with a more comfortable ride provided by limited seat tilt in response to shifting weight, and a compact storage configuration that requires substantially less floor space and less vertical space than when in the ready-to-use configuration. Numerous features of the chair contribute to user comfort while seated, optionally including proportional movements permitted by the dual-mode mechanism that may permit the seatback to tilt at a different rate than the seat (e.g., two degrees of seatback tilt for every one degree of seat tilt), spring rate of the seatback support structure, pivotable connection of seatback to its support structure, spring rate of one or more springs in the dual-mode mechanism, and a soft forward-tilt bump-stop. Optional locking devices prevent the chair from inadvertently moving toward the collapsed storage configuration when in the ready-to-use configuration, and prevent the chair from inadvertently moving toward the ready-to-use configuration when in the collapsed storage configuration.

[0021] These and other objects, advantages, purposes and features of the present invention will become apparent upon review of the following specification in conjunction with the drawings.BRIEF DESCRIPTIONS OF THE DRAWINGS

[0022] FIG. 1 is a perspective view of a task chair having a dual-mode ride mechanism with collapsible seat and retractable legs;

[0023] FIG. 2 is a right side elevation view of the seat and seatback portion of the task chair, with portions removed to provide a clearer view of the dual-mode ride mechanism shown in a sitting mode with fully forward seat tilt and initial sitting load applied;

[0024] FIG. 2A is an enlarged and partially transparent view of a forward portion of the dual-mode ride mechanism at region 2A of FIG. 2;

[0025] FIG. 3 is another right side elevation view of the seat and seatback portion of the task chair of FIG. 2, shown in a partially tilted-back position of the seat with additional or rearward-shifted sitting load applied;

[0026] FIG. 3A is an enlarged and partially transparent view of a forward portion of the dual-mode ride mechanism at region 3 A of FIG. 3;

[0027] FIG. 4 is another right side elevation view of the seat and seatback portion of the task chair of FIG. 3, shown in a further tilted-back position of the seat with additional or rearward-shifted sitting load applied;

[0028] FIG. 4A is an enlarged and partially transparent view of a forward portion of the dual-mode ride mechanism at region 4A of FIG. 4;

[0029] FIG. 5 is a front-right perspective view of a rear portion of a lower seat structure and lower portion of seatback bracket, with seat omitted to show underlying seat structures;;

[0030] FIG. 5 A is an enlarged cut-away view of a rear region along the line designated VA-VA of the lower seat structure of FIG. 5 ;

[0031] FIG. 5B is a side elevation view of the cut-away rear region of FIG. 5A;

[0032] FIG. 5C is another front-right perspective view of a rear portion of a lower seat structure and lower portion of seatback bracket of FIG. 5, with addition of locking plates for fixing the orientation of a rear link to which the seatback bracket is mounted;

[0033] FIG. 5D is enlarged view of the seat structure and seatback bracket of FIG. 5C, with foreground portion of the seat structure omitted to show the underlying mechanism;

[0034] FIG. 5E is a side elevation view of the rear link and one of the locking plates of FIG. 5D;

[0035] FIG. 6 is another right side elevation view of the seat and seatback portion of the task chair of FIG. 1 , shown in an unloaded collapsible mode, shown in an initial in-transit configuration, with portions removed to provide a clearer view of the dual-mode ride mechanism;

[0036] FIG. 6A is an enlarged and partially transparent view of a forward portion of the dual-mode ride mechanism at region 6A of FIG. 6;

[0037] FIG. 7 is another right side elevation view of the seat and seatback bracket of the task chair of FIG. 6, shown in a fully collapsed position;

[0038] FIG. 7A is an enlarged and partially transparent view of a forward portion of the dual-mode ride mechanism at region 7 A of FIG. 7;

[0039] FIG. 8 is another right side elevation view of the seat and seatback bracket of the task chair of FIG. 1 , shown in an unloaded collapsible mode, and with a hand-release lever at initial application of a releasing force;

[0040] FIG. 8 A is an enlarged view of a release mechanism at region 8 A of FIG. 8;

[0041] FIG. 9 is another right side elevation view of the seat and seatback bracket of the task chair of FIG. 8, shown with the seat and seatback in the same position as FIG. 8, with the hand-release lever pulled out to a release position by the releasing force;

[0042] FIG. 9 A is an enlarged view of a release mechanism at region 9 A of FIG. 9;

[0043] FIG. 10 is another right side elevation view of the seat and seatback bracket of the task chair of FIG. 8, shown with the seat tilted back further than in FIGS. 8 and 9;

[0044] FIG. 10A is an enlarged view of a release mechanism at region 10A of FIG. 10;

[0045] FIG. 11 is another right side elevation view of the seat and seatback bracket of the task chair of FIG. 8, shown with the seat and seatback tilted back further than in FIG. 10, with the handrelease lever returning to a locking position due to spring load;

[0046] FIG. 11 A is an enlarged view of a release mechanism at region 11 A of FIG. 11 ;

[0047] FIG. 12 is another right side elevation view of the seat and seatback bracket of the task chair of FIG. 8, shown with the seat and seatback in the same position as in FIG. 11, with the handrelease lever returned to the locking position due to spring load;

[0048] FIG. 12A is an enlarged view of a release mechanism at region 12A of FIG. 12;

[0049] FIGS. 13A-13F are a series of sectional right side elevation views of the task chair of FIG. 1, depicting sequential steps of releasing and moving the seat and seatback from an initial configuration in the unloaded collapsible mode with legs extended, to final collapsed configuration with legs retracted;

[0050] FIGS. 14A-14F are a series of top plan views of the leg retraction and extension mechanism at sequential positions during the corresponding sequential steps of FIGS. 13A-13F;

[0051] FIGS. 15A-15D are a series of top plan views of a lower portion of the leg retraction and extension mechanism at sequential positions of leg extension;

[0052] FIGS. 16A and 16C are enlarged sectional right side elevation views of the leg retraction and extension mechanism corresponding to the positions of FIGS. 15 A and 15C, respectively;

[0053] FIG. 17 is a left side sectional elevation view of another task chair having a dual-mode ride mechanism with collapsible seat and retractable legs, taken through a vertical plane that is offset laterally from a central longitudinal plane, and shown in a use configuration;

[0054] FIG. 18A is a left side sectional elevation view of the task chair of FIG. 17, taken through the central longitudinal plane;

[0055] FIG. 18B is another left side sectional elevation view of the task chair of FIG. 17, taken through the central longitudinal plane, and shown in a storage configuration;

[0056] FIG. 19A is an enlarged view of the region designated XIXA in FIG. 18A;

[0057] FIG. 19B is an enlarged view of the region designated XIXB in FIG. 18B;

[0058] FIG. 20A is a top sectional elevation view of the leg mechanism of the task chair of FIG. 17;

[0059] FIG. 20B is another top sectional elevation view of the leg mechanism of the task chair of FIG.17, taken through a higher horizontal plane than that of FIG. 20A, and shown in the storage configuration;

[0060] FIG. 21 A is a top elevation view of the leg mechanism of the task chair of FIG. 17;

[0061] FIG. 21B is a top elevation view of the leg mechanism of the task chair of FIG. 17, shown in the storage configuration;

[0062] FIG. 22A is a side sectional elevation of the seating and tilt mechanism portions of the task chair of FIG. 17;

[0063] FIG. 22B is another side sectional elevation of the seating and tilt mechanism portions of the task chair of FIG. 17, shown in a rearward-tilted configuration;

[0064] FIG. 23A is an enlarged view of the tilt mechanism in the region designated XXIIIA in FIG.22A;

[0065] FIG. 23B is an enlarged view of the tilt mechanism in the region designated XXIIIB in FIG.22B;

[0066] FIG. 24 is another left side sectional elevation view of the task chair of FIG. 18A, shown in the rearward-tilt configuration;

[0067] FIG. 25 is an enlarged view of the tilt mechanism and leg mechanism in the region designated XXV in FIG. 24;

[0068] FIG. 26 is an exploded front-left perspective view of the tilt mechanism of the task chair of FIG.17;

[0069] FIG. 27 is an exploded front-left perspective view of the tilt mechanism and legs of the task chair of FIG. 17;

[0070] FIG. 28 is an enlarged view of the leg mechanism components in the region designated XXVIII in FIG. 27;

[0071] FIG. 29A is an enlarged view of the leg mechanism components in the region designated XXIXA in FIG. 20A;

[0072] FIG. 29B is an enlarged view of the leg mechanism components in the region designated XXIXB,C in FIG. 20B; and

[0073] FIG. 29C is another enlarged view of the leg mechanism components in the region designated XXIXB,C in FIG. 20B, taken from an elevated perspective that is moved forward from the elevated perspective of FIGS. 20B and 29B.DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0074] Referring now to the drawings and the illustrative embodiments depicted therein, a task chair 100 is equipped with a seat support in the form of a dual-mode tilt and collapsing mechanism 110, and a leg retraction and extension mechanism 120 (FIG. 1). In FIGS. 1 and 13A-15D, chair 100 is shown fitted with both the dual-mode tilt and collapsing mechanism 110 and the leg retraction and extension mechanism 120, although it is envisioned that these mechanisms may be implemented separately. In the illustrated embodiment the tilt and collapsing mechanism 110 cooperates with the leg retraction and extension mechanism 120 so that a plurality of movable legs 130 will extend and retract in response to pivoting movement of a seat 132 of the chair 100. In this way, chair 100 can be readily converted from a compact storage configuration (FIG. 13F) to a ready-for-use configuration (FIG. 13A) or an in-use configuration (FIGS. 2-4). The chair 100 can secure itself in the storage configuration by a user, after releasing any release or latch (if provided), simply allowing the seat 132 to pivot back and a seatback 150 to move down under gravity (or by an applied force) to the storage configuration, and the chair 100 can be returned to the ready-for-use configuration by the user optionally actuating a release mechanism 134 (FIGS.1, and 8-13F), and pivoting the seat 132 forward and moving the seatback 150 up to the ready- for-use configuration, while the legs 130 move automatically and are secured in the retracted and extended positions, respectively, in response to the user pivoting the seat 132 back to the storage configuration and later pivoting the seat forward to the ready-for-use configuration. Optionally the legs 130 may be extended or retracted by a user pushing or pulling on the chair to move it along a ground surface, while wheels or feet associated with the legs 130 frictionally engage the ground surface to impart an extension or retraction force to the legs as the chair is pushed or pulled along the ground surface. With the chair in the ready-for-use configuration, the user can sit and shift their weight upon the seat 132 and seatback 150, which causes the tilt and collapsing mechanism 110 to operate in a seating mode that permits only limited rearward tilting of the seat 132 and seatback 150, such as shown in FIG. 4. This arrangement allows the chair 100 to maintain the in-use configuration when a user is seated, and allows the chair to assume the compact storage configuration when a user is not seated, optionally with the chair locking itselfin one or both configurations to reduce the risk of misuse or instability while in use, while also providing more comfortable seating than chairs with seats that are rigidly mounted and cannot be tilted in response to the user shifting their weight.

[0075] Dual-mode tilt and collapsing mechanism 110 is coupled to a lower structure 136 of the seat 132, and is further coupled an upper portion 138a of a seatpost 138. Dual-mode tilt and collapsing mechanism 110 is operable in a seating mode (FIGS. 2-4) that permits only limited rearward tilting of the seat 132 and seatback 150 when loaded with a user's weight, and is operable in a collapsing mode (FIGS. 6-12) when not loaded with a user's weight. Referring to FIGS. 2-4, the dual-mode tilt and collapsing mechanism 110 includes an upper link 140 having a forward pivot 140f and a rearward pivot 140r, a rear link 142 having an upper pivot 142u and a lower pivot 1421, a lower link 144 having a forward pivot 144f and a rearward pivot 144r, and a forward link 146 having an upper pivot 146u and a lower pivot 1461. The seat's lower structure 136 is pivotably coupled to forward link 146 in the form of a support structure that receives or is coupled to the upper portion 138a of a seatpost 138, such that lower structure 136 and seat 132 pivot rearwardly about the upper link's forward pivot 140f, which is also the forward link's upper pivot 146u. When viewed from the side, such as shown in FIGS. 2-7, pivots 140f, 146u are located reward of the center of seat 132 and lower structure 136. Thus, a sitting load applied to seat 132 and centered at (i.e., center of gravity located at) the seat's fore / aft center will tend to pivot the seat forwardly, whereas only a sitting load centered aft of pivots 140f, 146u, and / or with sufficient load applied to seatback 150, will pivot the seat 132 rearwardly. When a user is seated at a typical location and posture along seat 132, the pivots 140f, 146u, which are coincident with the pivot or tilt axis of seat 132, are located in close proximity to the user's center of loading along the seat 132. The pivots 140f, 146u may be located further back toward the rear of seat 132 than is typical for chairs with tilt mechanisms. Links 140, 142, 144, 146 are coupled together to form a four-bar linkage, with the rear link's upper pivot 142u being pivotably coupled to the upper link's rearward pivot 140r, the lower link's rearward pivot 144r pivotably coupled to the rear link's lower pivot 1421, the forward link's lower pivot 146f pivotably coupled to the lower link's forward pivot 144f, and the forward link's upper pivot 146u pivotably coupled to the upper link's forward pivot 140f.

[0076] In the illustrated embodiment, forward link 146 is a bracket that is also pivotably coupled to the lower structure 136 of seat 132 at the forward link's upper pivot 146u, and is further coupled tothe upper portion 138a of seatpost 138. Rear link 142 is pivotably coupled to the lower structure 136 of seat 132 at the rear link's upper pivot 142u. Also coupled to rear link 142 is a seatback bracket 148 that supports the seatback 150 to provide a backrest for a user sitting upon seat 132, and a seat-coupled actuator or actuator key 152 (FIGS. 1 and 13A-16C) that serves to actuate the leg retraction and extension mechanism 120, as will be described in more detail below.

[0077] Load applied to seatback 150 by a seated user will apply load to seatback bracket 148, which may be made from spring steel or other suitably strong and resilient material, which in turn applies a load to rear link 142, in the counterclockwise direction as viewed from the right side in FIGS. 2-7. With this arrangement, a person seated with their load (center of gravity) located forward of pivots 140f, 146u, and no load or comparatively little load applied rearwardly to seatback 150, will cause the seat 132 to tilt forwardly, while a person seated with their load rearward of pivots 140f, 146u and / or with sufficiently high applied rearwardly to seatback 150, will cause the seat 132 to tilt rearwardly. The four-bar linkage of links 140, 142, 144, 146 is thus affected by loads applied to seatback 150, which act upon rearward link 142 in a direction that urges its lower pivot 1421 toward the upper link's forward pivot 140f, and prevents the four-bar linkage from operating in the collapsible mode while a person is seated.

[0078] To provide limited rearward tilting of the seat 132 when dual-mode tilt and collapsing mechanism 110 is in the seating mode, lower link 144 is permitted to translate forwardly along its longitudinal axis during rearward tilting of the seat 132 while the seat is loaded, as can be seen by viewing FIGS. 2, 3, and 4 in sequence. To control the translation movement of lower link 144, its forward pivot 144f is mounted in an elongate slot 153 that acts as a guide, as best shown in FIGS. 2A-4A, 6A, and 7A. As can be seen in the figures, the elongate slot 153 is sloped downwardly from back to front, and is generally in-line with lower link 144 when mechanism 110 is in the seating mode, although it will be appreciated that the slot may have a different angle and need not be sloped downwardly or aligned with lower link 144 in the seating mode. Moreover, an angle-adjustable slot and / or a non-linear slot may be provided in order to change the angle of force transmission during movement, thus changing the resistive force imparted to seat 132 and seatback 150 at different positions of mechanism 110. Optionally, an additional linkage may be provided in order to change the spring force transmission angle during compression of spring 154 to provide a variable support rate. When a user is seated upon seat 132 and leans back or shifts their weight rearwardly, seat 132 is able to tilt rearwardly about theforward pivot 140f of upper link 140 because lower link 144 is able to translate forwardly relative to forward link 146 with forward pivot 144f moving in slot 153. Forward translation of lower link 144 is resisted by a biasing member in the form of at least one coil spring 154 that is positioned forwardly of forward pivot 144f in slot 153. Other types of biasing members are envisioned, such as a compressible rubber or rubber-like material, a leaf spring arrangement, gas- charged strut, or powered actuator.

[0079] Coil spring 154 imparts a resistive rearward force to forward pivot 144f, which in turn causes seat 132 to tilt or pivot forwardly when unloaded or when the user shifts their weight forward on the seat 132 (FIGS. 2-4 and 2A-4A). The spring rate of coil spring 154 therefore affects the amount of force required to tilt the seat 132 rearwardly, which affects the feel of the seat's rearward tilting motion and overall "ride" to a person seated at and shifting their weight upon seat 132 and seatback 150. It is also envisioned that multiple springs may be used simultaneously to provide a variable spring rate during compression, or that a single spring having different spring rates in different sections may similarly be used to give the desired resistance to rearward tilting of seat 132 at different degrees of tilt. Optionally, a forward end of spring 154 may be supported by a movable pad that can be moved forwardly or rearwardly, such as by rotating a threaded screw that is accessible at a front of the bracket that forms forward link 146, in order to set a desired level of preload on spring 154. Similarly, the length of slot 153 will affect the limited degree of forward and rearward tilt of seat 132 when mechanism 110 is in the seating mode with the user's weight applied to the seat 132. Although the illustrated embodiment includes lower link 144 that is substantially rigid but able to translate linearly by a short distance owing to compression of the spring 154 in the slot, it is envisioned that a compressible or flexible lower link may be substituted for those components in order to provide a similar function of resisting (but allowing a limited degree of) rearward tilt of seat 132. When seat 132 is unloaded, and during all travel movements of the seat 132 and seatback 150 in the collapsible mode of FIGS. 6-7A, spring 154 is at its minimum compression state (i.e., at a desired preload) or substantially unloaded and therefore fully expanded.

[0080] The arrangement of the four-bar linkage also allows the seatback 150 to tilt rearwardly under load at a different rate than the corresponding rearward tilt of the seat 132. This is accomplished by changing the angle of rear link 142 relative to upper link 140, which can entail sliding the lower link's forward pivot 144f forwardly in slot 153 and compressing spring 154. Flexibility ofseatback bracket 148 and the elastomeric seatback mount 159 also allows for additional rearward pivoting of seatback 150 in response to load on the seatback 150 by a seated user. For example, seatback 150 may pivot rearwardly under load at different rate compared to rearward pivoting movement of seat 132 while a user is seated with their weight centered sufficiently rearwardly, thus providing a ratio of seatback angle relative to the seat angle which adapts to the user, including their size, weight, seating position, and posture. It should be appreciated that, except for flexing, the seatback 150 pivots only with rear link 142, while the flexing of seatback bracket 148 and elastomeric seatback mount 159 may provide a majority of the movement of seatback 150 relative to seat 132. However, it will be appreciated that seated users may affect the position of seatback 150 relative to seat 132 differently based on their size, position, and posture, due to flexibility of seatback bracket 148 and the ability of rear link 142 to pivot by at least a limited amount when the seat 132 and seatback 150 are tilted rearwardly.

[0081] It will further be appreciated that the mechanism 110 is self-adapting to provide greater resistance to rearward tilt for heavier users, and lesser resistance to rearward tilt for lighter users, so that lighter users may achieve the same or similar degrees of rearward tilt as heavier users seated in the same chair with no adjustments required. Heavier users will usually direct higher load into the spring 153 through the seat 132, seatback 150, and mechanism 110, thus compressing the spring 153 to a higher degree than would a lighter user whose weight is centered at the same location. It should be appreciated, however, that this will not always be the case, such as when a heavier user is leaning forward and / or seated at a forward location along the seat 132. Because the spring 153 is typically more compressed by a heavier user, the spring 153 is providing greater resistance to pivoting movement of rear link 142, seatback bracket 148, and seatback 150, which provides more support and more resistance to rearward pivoting for the heavier user through the seatback 150. When the same chair 100 is occupied by a lighter user, the spring 153 is typically less compressed and therefore provides less resistance to pivoting movement of rear link 142, seatback bracket 148, and seatback 150, which provides less resistance to rearward pivoting for the lighter user through the seatback 150. As a result, a lighter user is able to achieve the same or similar levels of rearward tilt for the seatback 150 as they shift their weight back, as compared to a heavier user who must apply higher forces to achieve the same degree of rearward tilt for the seatback 150. As a result, the dual-mode tilt and collapsing mechanism 110 of chair 100 adapts to provide similar comfort levels for users ofdifferent weights, allowing the different users to achieve similar levels of tilt, and therefore similar levels of comfort, without need for adjusting any spring pre-load or adjusting any tensioners. However, as discussed above, the spring rate(s) of one or more springs 154 in slot 153 may be selected to provide a desired level of resistance, and / or a pre-load device may be installed to compress the spring(s) 154 to a desired level of compression when the seat 132 is unloaded.

[0082] Mechanism 110 is also passively adaptive to a user's posture in a way that minimizes or relieves pressure. As a user of any size alters their posture to place more weight forward on the seat 132, the seat will tilt forward to a greater degree to provide a complimentary support angle of seat 132 with optimized contact area. Optionally, a soft resilient bumper or pad 156 (FIG. 4) may be positioned forwardly of pivots 140f, 146u, between forward link 146 and seat structure 136, and arranged so as to be compressible between forward link 146 and seat structure 136 as the user shifts their weight forward. Bumper or pad 156 provides a gradual increase in resistance that leads to a natural and gentle forward rocking sensation to the user as they lean or shift forwardly along seat 132. To do this, bumper or pad 156 may have a varying cross section so that initial resistance to compression is relatively low and increases non-linearly with further compression. Bumper or pad 156 may be engaged even when the user's center of load remains behind the pivots 140f, 146u. As the user changes posture to place more weight rearward on the seat 132, the seat tilts rearward to follow the user and continue to provide adaptive support. As the user shifts and leans backwards (FIG. 4), the user's back increasingly loads the seatback 150 rearwards. The rear link 142 rotates rearward (counterclockwise as viewed from the right) while doing little to further load the spring 154 in the slot 153 because rear link 142 is already nearly in-line with lower link 144. The high mechanical advantage of the rear link 142 rotating and moving the lower link 144 allows a low to moderate user load on the seatback 150 to operate the four-bar mechanism 110 even when the spring force is high.

[0083] After some initial pivoting motion of rear link 142 in this manner during rearward tilt of seat 132, a portion of rear link 142 may contact an optional bumper-stop 157 that is attached to upper link 140 as shown in FIG. 4 (and with a close variation shown in FIGS. 5-5E), so that rear link 142 is not pivotable further relative to upper link 140 during additional rearward tilting of seat 132, and thus the upper link 140 and rear link 142 pivot together as a unit during this phase of movement. Bumper-stop 157 may be a substantially rigid point of contact (e.g., metal-to-metal)or may incorporate an elastomeric material for additional compliance, which may affect the loading of spring 154 during rearward tilting of seat 132 under load. At this point the four-bar linkage 110 is no longer operating as a four-bar linkage because rear link 142 is no longer pivotable relative to bottom link 144. Instead, because spring 154 may still be compressed further in slot 153, once rear link 142 contacts optional bumper-strop 157, further loading the seatback 150 and rear portion of seat 132 causes the four-bar linkage to operate as a spring- loaded slider crank mechanism. At the same time, seatback bracket 148 flexes and continues to act as a leaf spring between the rear link 142 and the seatback 150. An elastomeric seatback mount 159 is coupled between seatback 150 and an upper portion of seatback bracket 148, and allows seatback 150 to pivot about a lateral axis (pitch) and a vertical axis (yaw). Another optional form of compliance may be provided with elastomeric couplings between a seating surface and underlying seat structure. Optionally, a locking plate 161 (FIG. 4B) may be provided to secure the relative positions of rearward pivot 140r, lower pivot 1421; and bumperstrop 157.

[0084] It will be appreciated that the two modes of the dual-mode tilt and collapsing mechanism 110 may be engaged without any user sitting in the chair. With a person seated, a bias force downward on the front of the seat 132 (FIG. 2) holds the upper link 140 in position as a person starts to recline. The user's subsequent reclining motion then causes the rear link 142 to rotate counterclockwise (as viewed in FIGS. 2-4, for example) about rearward pivot 140r. As described above, that rotating motion of rear link 142 is stopped when it contacts bumper-stop 157, when provided. Once the rear link 142 is bottomed against the bumper-stop 157 on upper link 140, any increase in rearward bias on the seat back 150 applies a force to the upper link 140 and rear link 142 in a counterclockwise direction about forward pivot 140f of upper link 140, and that urges lower link 144 forwardly. Once this force is sufficiently high, spring 154 will begin to compress from its preload state. This allows compliance for the rear link 142 to rotate counterclockwise, resisted by the spring force, and permitting upper link 140 to rotate counterclockwise about forward pivot 140f. If upper link 140 is equipped with the optional bumper-stop 157 as described above with respect to FIGS. 4-5B, then rear link 142 and upper link 140 will be rotating counterclockwise together, without pivoting relative to one another. At the same time, if the rearward force applied to seatback 150 is increasing, then the seatback bracket 148 is also flexing to allow relative motion between the seatback 150 and the seat 132and legs 130, 182. Conversely, if there is no forward biased force on the seat 132, any rearward motion (or gravity) causes the four-bar linkage of dual-mode tilt and collapsing mechanism 110 to perform like a parallelogram four-bar mechanism, and collapse to the storage configuration. During this movement the stiffness and preload of the spring 154 causes the lower link's forward pivot 144f to remain in a fixed rearward position in slot 153.

[0085] Although the illustrated embodiment depicts the lower link 144 being capable of forward translation along a downward slope defined by slot 153, it will be appreciated that other mechanisms may achieve a similar "ride" effect of limited tilting of the seat 132 and seatback 150 under load of a seated user. For example, placing a slot with spring at any of the other three pivot joints may accomplish substantially the same effect. It is further envisioned that any one or more of the links in the four-bar mechanism may be made compressible or flexible so that the distance between its two end pivots can be varied due to seating loads. For example, if the illustrated embodiment of FIGS. 2-4 were changed by rigidly mounting the lower link's forward pivot 144f to the forward link 146 without permitting translation, and instead lower link 144 were made as a resilient member that could bow outwardly under load and return to an un-bowed or less-bowed shape when not loaded, or if lower link 144 was instead formed as a spring-loaded piston-cylinder arrangement or similar extendable member, the same overall "ride" effect could be achieved.

[0086] Release mechanism 134 is provided to selectively maintain the seat 132 and seatback 150 in the collapsed or compact storage configuration (FIGS. 7, 12, and 13F) until the user is ready to use the chair 100, as well as to maintain the seat 132 and seatback 150 in the ready-for-use configuration (FIGS. 1, 6, 8, 13A) until the user is ready to stow the chair 100 in its storage configuration. Release mechanism 134 limits the rearward tilt of the seat 132 and the upper link 140 until an external releasing force Fr is applied to a release handle 160 (FIGS. 8 and 9A). Releasing force Fr allows the dual-mode tilt and collapsing mechanism 110 to be moved into the collapsible mode by tilting the seat 132 back from the ready-for-use configuration after pulling a grasping portion 160a of the release handle 160 to a releasing position as shown in FIGS. 9 and 9 A. This action moves a pawl or follower 162 out of engagement with a first curved outer surface portion 164a of the forward link 144, the first curved outer surface portion 164a being a circular segment spaced outwardly from the forward pivot 144f of the lower link 144.

[0087] Follower 162 is positioned between the grasping portion 160a and a release handle pivot 166 (FIGS. 10-12A and 13A-13F), so that pulling the grasping portion 160a forward and up causes follower 162 to lift away from the first curved surface portion 164a. Release handle 160 has a rear extension arm 160b that projects rearwardly from release handle pivot 166, opposite the grasping portion 160a, and that compresses a biasing member in the form of a release handle spring 168 (FIGS. 11-12A) when the grasping portion 160a is pulled. Release handle spring 168 thus urges follower 162 radially inwardly toward the forward pivot 144f of the lower link 144 when external releasing force Fr is not applied.

[0088] As shown in FIGS. 8 and 8A, when seat 132 is in the ready-for-use configuration and before follower 162 is lifted away from the first curved surface portion 164a, follower 162 is resting against both the first curved surface portion 164a and a radial projection or tooth 170. Radial projection 170 prevents further rearward tilt of seat 132 from the ready-for-use configuration, and thus prevents dual-mode tilt and collapsing mechanism 110 from entering the collapsing mode. When the collapsing mode is desired, the user grips the grasping portion 160a of release handle 160 and pulls forward and up to move follower 162 above (i.e., radially outwardly of) the radial projection 170 (FIGS. 9 and 9A) and then the seat 132 may be further tilted rearwardly (FIGS. 10 and 10 A) so that follower 162 passes over (radially outwardly of) the first projection 170 (FIGS. 10 and 10A).

[0089] Once the seat 132 has tilted all the way rearwardly to reach the compact storage configuration, follower 162 will have passed circumferentially beyond the radial projection 170 (FIGS. 11 and 11A). This allows the release handle spring 168 to force the follower 162 radially inwardly into engagement with a second curved surface portion 164b of the lower link 144 as shown in FIGS.12 and 12A, where the second curved surface portion 164b is located on an opposite side of radial projection 170 from the first curved surface portion 164a. With follower 162 in this location along second curved surface portion 164b at radial projection 170, dual-mode tilt and collapsing mechanism 110 is maintained in the collapsing mode and release mechanism 134 prevents seat 132 and seatback 150 from being moved out of the compact storage configuration of FIG. 12.

[0090] To return chair 100 to the ready-for-use configuration from the compact storage configuration, the user lifts once again on the release handle grasping portion 160a to lift the follower 162 awayfrom second curved surface portion 164b and over the radial projection 170 (compare FIG. 11 to FIG. 12). The user may then begin to tilt the seat 132 and seatback 150 forwardly, its movement being guided by the dual-mode tilt and collapsing mechanism 110 (which remains in the collapsing mode during this initial movement), so that follower 162 traverses over radial projection 170 in the direction of first curved surface portion 164a (compare FIG. 10 to FIG. 11). Once the seat 132 and seatback 150 are pivoted sufficiently forwardly to reach the ready-for-use configuration, the four-bar linkage of dual-mode tilt and collapsing mechanism 110 is once again in the ready-for-use configuration and follower 162 has passed fully beyond radial projection 170 to again overlie the first curved surface portion 164a (FIGS. 9 and 9A). The release handle grasping portion 160a is then released and the release handle spring 168 urges follower 162 radially inwardly back into engagement with the first curved surface portion 164a and the radial projection 170, as shown in FIGS. 8 and 8A. Follower 162 allows additional forward tilting movement of seat 132 and seatback 150 during use, in which case follower 162 slides along first curved surface portion 164a in the direction away from radial projection 170. With follower 162 in this region (along first curved surface portion 164a), the release mechanism 134 prevents seat 132 and seatback 150 from being tilted rearwardly and out of the ready-for-use configuration of FIG. 8, such that dual-mode tilt and collapsing mechanism 110 remains in the ready-for-use configuration and is operable or usable in the manner described above with reference to FIGS. 2- 4. It will be appreciated that FIGS. 13A-13F also illustrated the operation of release mechanism 134 in conjunction with the operation of leg retraction and extension mechanism 120, which will be described below.

[0091] Optionally, instead of (or in addition to) the pivotable release handle 160 directly at the release mechanism 134, a remote release 158 (FIG. 7) may be placed elsewhere on the chair. A release handle 158a may be placed along the seatback 150 and used to pull the seatback 150 (in the collapsed configuration of FIG. 7) rearwardly and upwardly while squeezing a release lever 158b in order to move a cable that is coupled to the follower 162. By lifting the follower 162 using release lever 158, the seatback 150 and rear of the seat 132 are free to be lifted up toward the ready-for-use configuration, which can also cause the movable legs 130 to extend or deploy as described below, so that a smooth and continuous one-grasp motion can be used to reconfigure the chair 100 from the fully collapsed configuration to the ready-for-use configuration.Similarly, when chair 100 is in the ready-for-use configuration the release handle 158a andrelease lever 158b may be grasped and the seatback 150 lowered to cause the seat 132 to tilt fully rearwardly under force of gravity owing to the center-of-gravity of seat 132 and setback 150 relative to forward pivot 140f of upper link 140, while a forward pushing force on remote release 158 or seatback 150 can also cause the movable legs 130 to collapse or retract and lock because of the seat-coupled actuator or actuator key 152, as described below, and / or because of the movable legs 130 engaging another structure such as described in commonly-owned U.S. patent application, Ser. No. 18 / 634,058, filed Apr. 12, 2024, which corresponds to U.S. Pub. No.2024 / 0251951, as well as in commonly-owned International patent application, Ser. No.PCT / IB2022 / 059828 (Pub. No. WO 2023 / 062583), both of which are hereby incorporated herein by reference in their entireties. As described above, frictional engagement of feet or wheels 186 with a floor or ground surface (where wheels 186 may have high-friction bearings) may facilitate extension and retraction of legs 130 while a user is pulling and pushing the chair 100. This allows a user to reconfigure the chair 100 to the collapsed and ready-for-use configurations while standing behind or adjacent the chair, with little or no bending required to reach the remote release compared to release handle 160 below seat structure 136. Optionally, friction dampers or other dampening mechanism may be provided to slow the drop of seatback 150 and the rear portion of seat 132 under force of gravity.

[0092] The dual-mode tilt and collapsing mechanism 110 is configured so that when it is in the collapsible mode (FIGS. 6, 7, 10-12, and 13B-13F), the lower link's rearward pivot 144r is movable downwardly relative to the lower link's forward pivot 144f during the rearward tilting of the seat. This can be observed by comparing FIG. 7 to FIG. 6, and by observing FIGS. 8-12 in sequence. When the dual-mode tilt and collapsing mechanism 110 is in the ready-for-use configuration and is actively in use, the lower link's rearward pivot 144r does not move downwardly relative to the lower link's forward pivot 144f as the lower link 144 translates forwardly during the rearward tilting of the seat 132. This can be observed by comparing FIGS.2-4 in reverse order.

[0093] Leg retraction and extension mechanism 120 provides four functions when used in combination with the release mechanism 134 described above. First, the mechanism 120 is operable to secure the chair's movable legs 130 in the retracted position of FIGS. 13F, 14F, and 15D when seat 132 is pivoted fully back to the compact storage configuration where it is locked by the release mechanism 134. This prevents movable legs 130 from inadvertently extending while the chair isfully collapsed. Second, the mechanism 120 is operable to secure the chair's movable legs 130 in the extended position of FIGS. 13A, 14A, and 15A when seat 132 is in the ready-for-use configuration or in an in-use position of FIGS. 2-4. This prevents movable legs 130 from inadvertently retracting and reducing stability of the chair 100 when a user is seated. Third, the mechanism 120 is operable to actuate the movable legs 130 from the retracted position to the extended position during final rearward pivoting movement of seat 132 to the compact storage configuration. This allows a single actuation movement by the user, namely, grasping release handle 160 and tilting the seat 132 back, to also cause the legs 130 to retract. Fourth, the mechanism 120 is operable to actuate the movable legs 130 from the extended position to the retracted position during initial forward pivoting movement of seat 132 out of the compact storage configuration toward the ready-for-use configuration. This allows a single actuation movement by the user, namely, grasping release handle 160 and tilting the seat 132 forward, to also cause the legs 130 to extend. If leg retraction and extension mechanism 120 were installed on a chair not equipped with the release mechanism 134 or similar locking functionality, the leg retraction and extension mechanism 120 would still be capable of providing the leg-extension and leg-retraction functions.

[0094] As will be best understood with reference to FIGS. 13A-15D, leg retraction and extension mechanism 120 includes a base structure 180 that supports or includes a pair of non -pi voting legs 182, that pivotably supports the movable legs 130, that supports the seatpost 138, and that supports a movable leg actuator plate 184 as well as additional structures (described below) that are associated with leg actuator plate 184, and that selectively receives a forward-extending portions of the seat-coupled actuator or actuator key 152. Leg retraction and extension mechanism 120 provides the four functions described above by receiving the actuator key 152 (compare FIGS. 13B and 14B to FIGS. 13A and 14A, and see also FIGS. 15A and 16A), locking itself to the actuator key 152 (FIGS. 13C, 14C, 15B, 15C, and 16C), being pushed (for leg retraction) by the actuator key 152 (FIGS. 13B-13E, 14B-14E, and 15B-15D viewed in numerical sequence), being pulled (for leg extension) by the actuator key 152 (FIGS. 13B-13E, 14B-14E, and 15B-15D viewed in reverse numerical sequence), and by unlocking itself from and releasing the actuator key 152 (FIGS. 15A and 15B viewed in reverse numerical sequence).

[0095] The interior space defined by base structure 180 is sufficiently tall to accommodate some vertical movement of actuator key 152 during actuation of leg retraction and extension mechanism 120(compare FIG. 16C to FIG. 16A, and view FIGS. 13B to 13E in sequence). However, it will be appreciated that seatpost 138 may be vertically raisable and lowerable to permit raising and lowering of seat 132 and seatback 150 for comfort during use and for compact stowage. Because actuator key 152 is coupled to a lower rear portion of the lower seat structure 136, when seatpost 138 is vertically raisable and lowerable it may be necessary for the user to lower the upper portion 138a of seatpost 138 so that lower seat structure 136 (as well as seat 132 and seatback 150) are in their fully lowered and most vertically compact position before tilting seat 132 fully back, so that actuator key 152 will properly align with the interior space defined by base structure 180 and properly engage with structures associated with leg actuator plate 184. For a similar reason, it may be desirable to prevent seat 132 from rotating about the longitudinal axis of seatpost 138, relative to leg retraction and extension mechanism 120, or to use a seatpost that has a return-to-center feature, so that actuator key 152 will always be circumferentially aligned with leg retraction and extension mechanism 120. In such an arrangement, rotation of seat 132 about the vertical axis may still be permitted by caster wheels 186 at the distal end of each chair leg 130, 182.

[0096] The initial engagement of actuator key 152 with leg actuator plate 184 and its associated structures is shown in FIGS. 13A, 13B, 14A, 14B, 15A, and 15B. Prior to actuator key 152 being initially received by leg actuator plate 184, the leg actuator plate 184 is set fully rearwardly as shown in FIGS. 13 A, 14 A, 15 A, and 16 A. In the illustrated embodiment, the leg actuator plate 184 defines an elongate central opening 188 for receiving the seatpost 138, the central opening having a discorectangular shape with half-circular forward and rearward portions sized and shaped to receive the forward and rearward surfaces of seatpost 138. When leg actuator plate 184 is set fully rearwardly and it is not engaged by actuator key 152, a pair of upward- extending top posts 190 are received in lateral-extending regions 192a of respective L-shaped guides or channels 192 that are formed in a cover plate 193 as shown in FIG. 15A. Optionally, a spring or other resilient member is held in compression between the top posts 190 to ensure that the top posts 190 do not move laterally inboard along the L-shaped channels' lateral regions 192a, toward longitudinal-extending regions 192b, except when engaged by the actuator key 152 as described below. Top posts 190 are the uppermost portions of respective lock / release members 194 that extend rearwardly from lower end portions of the top posts 190 and have main key-engaging portions 196 fitted with downward-extending bottom posts 198, as best shown inFIGS. 16A and 16C. Bottom posts 198 may be received in their own respective L- shaped channels 200 (FIG. 16C) that have shapes corresponding to L-shaped channels 192 so that lock / release members 194 maintain their upright orientations during their lateral and longitudinal movements that will be described below.

[0097] The longitudinal movements of leg actuator plate 184 are mechanically tied to the longitudinal movements of lock / release members 194 such that when top posts 190 are received in the respective lateral-extending regions 192a of L-shaped channels 192 (and bottom posts 198 may be simultaneously received in respective later-extending regions of L-shaped channels 200), lock / release members 194 and leg actuator plate 184 are prevented from sliding in the forward direction. This locks the movable legs 130 in the extended configuration because the pivoting movements of legs 130 are dictated by forward and rearward movement of leg actuator plate 184, which defines two lateral slots 199 at opposite sides of its forward region, such as shown in FIGS. 14A-14F. The lateral slots 199 receive respective upwardly-extending pins or posts 201 that are attached to proximal ends of the respective movable legs 130, near where those legs are pivotably mounted to base structure 180 at respective pivot-mounts 203. By viewing FIGS. 14A-14F in sequence, it can be seen that forward movement of leg actuator plate 184 pushes forwardly on the upwardly-extending posts 201 at lateral slots 199, causing the corresponding legs 130 to pivot rearwardly toward their fully retracted position of FIGS. 13F and 14F.

[0098] As can be seen in the top views of FIGS. 14A-14F and 15A-15C, the main key-engaging portions 196 of lock / release members 194 are sized and shaped to fit into respective diagonal slots 202 of actuator key 152. As best shown in FIGS. 15A and 15B, diagonal slots 202 are defined between a central T-shaped projection 204 and a pair of side wings 206 at the forward end portion of actuator key 152. Main key-engaging portions 196 of lock / release members 194 have respective inward-extending lobes that are size and shaped to fit behind the lateral extending portions of the actuator key's central T-shaped projection 204. When top posts 190 are set outboard in the lateral-extending regions 192a of the L-shaped channels 192, the lateral distance between the inboard surfaces of the key-engaging portions' lobes is approximately equal to the maximum width of the actuator key's T-shaped projection 204. As seat 132 is pivoted back and down to move actuator key 152 down and forwardly into engagement with the leg retraction and extension mechanism 120, the actuator key's T-shaped projection 204 passes between the lobes of the lock / release members' main key-engaging portions 196, as shown inFIG. 15 A. This initial engagement does not affect the leg retraction and extension mechanism 120, but is the precursor to initial movement of the main key-engaging portions 196 of the lock / release members 194.

[0099] Referring to FIGS. 14B and 15B, forward movement of actuator key 152 causes the lock / release members' main key-engaging portions 196 to fully enter the diagonal slots 202 of actuator key 152. During this movement, the outboard surfaces of main key-engaging portions 196 engage and slide along inboard diagonal surfaces of the actuator key's side wings 206, which urges both key-engaging portions 196 laterally inboard toward one another and causes the top posts 190 to slide laterally inboard along lateral-extending regions 192a of respective L-shaped channels 192 (FIG. 15B). Once top posts 190 have been moved fully laterally inboard, key engaging portions 196 have bottomed-out in the diagonal slots 202 and the actuator key 152, lock / release members 194, and leg actuator plate 184 are now free to move longitudinally forward together with top posts 190 now traversing the longitudinal-extending regions 192b of the respective L-shaped channels 192 (FIGS. 14B and 15C). The longitudinal forward movement of leg actuator plate 184 begins causing movable legs 130 to pivot back toward their retracted positions as described above. Because the lobes of key-engaging portions 196 are held laterally inboard while top posts 190 are located in the L-shaped channels' longitudinal extending regions 192b, the central T- shaped projection 204 is captured by the key-engaging portions 196 and cannot be released. Thus, if the seat 132 were tilted forward to draw actuator key 152 rearwardly while top posts are traversing the longitudinal extending regions 192b of L-shaped channels 192, the central T- shaped projection 204 would pull the leg actuator plate 184 rearwardly and cause the movable legs 130 to begin pivoting forwardly toward their fully-extended positions.

[0100] Assuming that seat 132 is tilted fully rearwardly to its fully collapsed configuration, actuator key 152 will be pushed fully forwardly into leg retraction and extension mechanism 120, causing top posts 190 to reach the forward ends of the longitudinal extending regions 192b of L-shaped channels 192 as shown in FIG. 15D. This corresponds to the movable legs 130 reaching their fully retracted positions of FIGS. 13E, 13F, 14E, 14F. In the illustrated embodiment, the leg retraction and extension mechanism 120 does not lock the leg actuator plate 184 in its forward- most position, and therefore the mechanism 120 also does not lock the movable legs 130 in their retracted positions. Instead, this locking function is provided by the release mechanism 134 asdescribed above. However, it is envisioned that the locking function may be provided by a modified version of mechanism 120.

[0101] If the user is not lifting the grasping portion 160a of release mechanism 134 as leg actuator plate 184 reaches its forward- most position and movable legs 130 reach their fully retracted positions, the follower 162 will automatically drop into engagement with the second curved surface portion 164b of the lower link 144 as shown in FIGS. 12 and 12A. This locks actuator key 152 in its forward-most position and prevents leg actuator plate 184 from moving rearwardly out of its forward-most position and prevents movable legs 130 from moving forwardly out of their fully retracted positions, until grasping portions 160a is again lifted to clear the follower 162 over the radial projection 170 as described above.

[0102] Once actuator key 152, lock / release members 194, leg actuator plate 184, and movable legs 130 are freed to move rearwardly by release mechanism 134, the user may tilt the seat 132 forwardly to draw actuator key 152 rearwardly. Leg actuator plate 184 remains secured to T-shaped projection 204 of actuator key 152 by key-engaging portions 196 of the lock / release members 194 as top posts 190 are drawn rearwardly along longitudinal extending regions 192b of L- shaped channels 192, so that movable legs 130 are moved forwardly toward their fully extended positions by upwardly-extending posts 201 at lateral slots 199 of leg actuator plate. Once top posts 190 reach the rear ends of the L- shaped slots' longitudinal extending regions 192b, the posts 190 are again free to move laterally outboard in the lateral extending slot regions 192a. This allows the key-engaging portions 196 to be urged laterally outboard away from one another as the T-shaped projection 204 is drawn rearwardly and its sloped surfaces push the lobes of keyengaging portions 196 laterally outboard, causing top posts 190 to move laterally outboard once again to their positions of FIG. 15A. At this point the T-shaped projection 204 has been released by key-engaging portions 196, which at this point been mostly withdrawn from the diagonal slots 202 of actuator key 152, and the key-engaging portion 196 (and, thus, the entire actuator key 152) is now free to move further rearwardly and upwardly as seat 132 is returned to the ready- for-use configuration, leaving leg retraction and extension mechanism 120 with lock / release members 194 locked in their laterally outboard positions, leg actuator plate 184 locked in its rearward-most position, and movable legs 130 are locked in their fully extended positions so that chair 100 is ready for use.

[0103] Referring now to FIGS. 17-29C, another collapsible task chair 300 provides substantially the same functionality as task chair 100 described above, but utilizing somewhat different mechanisms to achieve it. The foregoing descriptions will focus primarily on significant differences between task chair 300 and task chair 100, with other (less significant) differences being readily apparent based on study and comparison of the drawings and descriptions such that repetition of descriptions can be largely avoided.

[0104] Task chair 300 includes a seat 302 resting on a seat frame 304 whose positioning is supported and controlled by a tilt mechanism 306, which in turn is supported by a seatpost 308 and a leg assembly 310 including two fixed rear legs 312 and two selectively pivotable front legs 314 controlled by a leg mechanism 316 and a D-ring plunger or actuator 318 coupled to the seat frame 304 (FIGS. 17-18B). A seatback 320 is mounted to the seat frame 304 by a resilient coupler 322 and a seatback bracket 324 having an integral upper handle 326. Task chair 300 is configured so that a person may be supported upon seat 302, and may optionally lean back to apply significant rearward force to seatback 320, causing seat 302 and seatback 320 to tilt rearwardly to varying degrees, with the degree of tilt by seat 302 limited in part by springs 328 of tilt mechanism 306, and in part by an internal stop bumper 330, such as shown in FIGS. 22 A- 26. During tilting movement while a person is seated, D-ring plunger 318 remains clear of any structures of the leg mechanism 316 and front legs front legs 314 remain fixed in their extended positions, such as shown in FIG. 24.

[0105] On the other hand, when a person is not seated in the task chair 300, then owing to the center of gravity of the combination seat 302, seat frame 304, seatback 320, and seatback bracket 324 being located behind a tilt pivot shaft 332, the seat 302 and seatback 320 assume a partially- collapsed or mostly-collapsed configuration in between the in-use configuration of FIGS. 17 and 18 A, and the fully-collapsed configuration of FIG. 18B. At this stage the front legs 314 remain fixed in their extended positions, and the front legs 314 still cannot be moved to their retracted positions. However, in the partially-collapsed configuration, a user may grasp handle 326 of seatback bracket 324 and push down and / or forwardly on the handle 326 to force the seat 302 and seatback 320 toward the fully-collapsed configuration of FIG. 18B, with the D-ring plunger 318 engaging a receiver-carriage 334 of the leg mechanism 316. This motion and engagement by the D-ring plunger 318 has the dual purpose of both unlocking the front legs 314 and urging the front legs 314 to retract to their stowed positions of FIG. 18B. At the same time, frontwheels 336 of the respective front legs 314 will exhibit some rearwardly-directed rolling resistance along the floor surface upon which task chair 300 is resting, owing to the forward component of the manual forces applied to the handle 326 during the collapsing motion. The rearwardly-directed rolling resistance applies an additional retraction force to front legs 314, which aids in fully retracting the front legs 314 and simultaneously fully-seating the D-ring plunger 318 in the receiver-carriage 334, where the D-ring plunger 318 is securely retained so that the task chair 300 maintains the fully-collapsed configuration, in which the chair 300 is unsuitable for sitting (FIG. 18B).

[0106] To return the task chair 300 to the in-use configuration of FIGS. 17 and 18A, the user grasps the handle 326 and begins pulling in an upward and rearward direction. This upward-rearward pulling force is imparted to the D-ring plunger 318, causing the plunger 318 to pull upwardly and rearwardly on the receiver-carriage 334, which does not release the D-ring plunger 318 until the receiver-carriage 334 reaches the rearward extent of its travel, which coincides with the front legs 314 again being fully extended. Thus, the seat 302 and seatback 320 cannot assume a sitting configuration until after D-ring plunger has been released by the receiver-carriage 334, which can only occur once the front legs 314 are fully extended. As a result, the chair 300 can only be sat upon when the front legs 314 are fully extended. Assisting with the return of the front legs 314 to the fully-extended configuration is the rolling resistance of the front wheels 336 along the floor surface, which imparts a forwardly-directed rolling resistance for an additional extension force to front legs, which aids in fully extending the front legs 314 and simultaneously moving the receiver-carriage 334 to its fully rearward-extended position so that it can release the D-ring plunger 318 in response to further upward-rearward pulling force applied to the handle 326 by the user. Front wheels 336 may incorporate friction bushings or bearings to increase the rolling resistance of the wheels and thus aid in the movements described above.

[0107] It will be appreciated that the required motions come naturally to a user grasping the handle 326 and causing the chair 300 to assume either its fully-collapsed configuration of FIG. 18B, or its fully-deployed in-use configuration of FIGS. 17 and 18 A. A single grasp and movement by the user is all that is needed to secure the chair in its fully-collapsed configuration, or to release it from the fully-collapsed configuration to assume the in-use configuration, with no need for release buttons or triggers, no separate latching movements, and no need for multi-stage manipulations of chair components. The mechanisms that achieve these movements andreconfiguring of task chair 300 in response to simple forces applied by a user will be described in more detail below.

[0108] Leg mechanism 316 operates by selectively capturing and retaining D-ring plunger or actuator 334 in a vertical slot 338 of receiver-carriage 334, using a pair of lockable pivoting pawls 340, as best shown in FIGS. 29A-29C, which are spring-biased toward an open configuration by a tension spring 342 (shown in FIG. 29C) when they are not secured in their closed positions. Receiver-carriage 334 is formed by an upper carriage portion 334a and a lower carriage portion 334b (FIG. 28), which are secured together to enclose pawls 340 and spring 342. A pair of rails 344 are coupled to a base 364 from which rear legs 312 emanate, and serve to guide movement of the receiver-carriage 334, and link those movements to the front legs 314 by a pair of leg links 346. Rearward end portions 346a of leg links 346 couple to forward attachment points 345 at opposite sides of the receiver-carriage 334, while forward end portions 346b of leg links 346 couple to respective ears 348 (FIGS. 19A, 19B, 20A and 20B) that are attached to proximal ends of the respective movable front legs 314, which are mounted on spindles 347 fitted with bearings 349.

[0109] Each pawl 340 includes an open jaw 350 that intersects the vertical slot 338 in either a receiving orientation (FIG. 29 A) in which the D-ring plunger 318 is free to enter or exit both jaws 350, or a latching orientation in which the D-ring plunger 318 is captured by the jaws 350 (FIG. 29B). During this movement of pawls 340, a pair of pins 352 that extend downwardly from respective ears 354, traverse respective arcuate slots 356 that are formed in a lower region of the lower carriage portion 334b. Tension spring 342 is coupled to upper ends of the pins 352, and biases the pawls 340 toward their open configuration of FIG. 29A. When pawls 340 have been biased closed (FIGS. 29B and 29C) by the downward and forward force being applied to D-ring plunger 318 via handle 326, the lower ends of pins 352 are moved outboard in the arcuate slots 356 so that the pins' lower ends are moved outboard of a central ridge formed along an arcuate upper surface 360 of a wedge block 362 that is mounted to the base 364 from which rear legs 312 emanate (FIGS. 18A-19B and 28). Once the lower ends of pins 352 have moved outboard of the central ridge along the arcuate upper surface 360 of wedge block 362, receiver-carriage 334 is free to move forward and downward relative to the base 364 and wedge block 362 in response to additional force being applied to handle 326, as well as in response to any rolling resistance applied to front legs 314 by front wheels 336. When receiver-carriage 334 is freed to move inthis manner by the positioning of pawls with D-ring plunger 318 captured as shown in FIGS.29C and 29D, D-ring plunger 318 is captured by the pawls 340, which cannot release the D-ring plunger 318 when pins 352 are disposed on opposite sides of the central ridge of the an arcuate upper surface 360 of a wedge block 362, which is at all times when receiver-carriage 334 is moved forward and downward from its fully rearward and upward position of FIGS. 18A and 19 A, which is only the case when front legs 314 are fully extended due to their interconnection with the receiver-carriage 334 via leg links 346 and the rails 344 for receiver-carriage 334. Optionally, instead of a central ridge formed along the arcuate upper surface 360 of wedge block 362, the upper surface 360 may define generally L-shaped channels in a similar manner as L- shaped guides or channels 192 that are formed in a cover plate 193 of leg retraction and extension mechanism 120, described above with reference to FIGS. 15A-15C.

[0110] The receiver-carriage's rails 344 capture respective pairs of roller bushings 366a, 366b that mount to respective attachment points 368a, 368b along the sides of the receiver-carriage 334. Roller bushings 366 roll along respective downwardly-facing tracks 370a, 370b that are formed along an interior (lower) surface of a top cover 372, during movement of the receiver-carriage 344. Roller bushings 366a, 366b are captured against tracks 370a, 370b by respective channels 374a, 374b formed along inboard surfaces of the rails 344 (FIG. 28). Tracks 370a, 370b are set at different angles to impart an arcuate motion to receiver-carriage 334 as it moves between its upward / rearward position in which front legs 314 are extended (FIGS. 18 A, 19 A, and 20A) and its downward / forward position in which front legs 314 are retracted and D-ring plunger 318 is captured by pawls 340 (FIGS. 18B, 19B, and 20B). This motion by receiver-carriage 334 generally follows the arcuate path followed by D-ring plunger 318 as it pivots with the rear end of seat 302 and bottom of seatback bracket 324 about tilt pivot shaft 332 and a collapsing pivot 390 described below. By substantially matching the arcuate motion of receiver-carriage 334 to that of the rear of seat 302 and D-ring plunger 318, a user grasping handle 326 feels a relatively smooth motion of the handle as the seat 302 drops and the D-ring plunger 318 engages the carriage 334 and then pushes the carriage along its matching arcuate path. This configuration also reduces friction and noise as the chair transitions from its in-use configuration to its stowed configuration, and vice versa.

[0111] In addition to wedge block 362 ensuring that D-ring plunger 318 remains captured by pawl 340 at all times that front legs 314 are not fully extended, so that seat 302 cannot be used for sitting,wedge block 362 can optionally be adjusted forward and rearward a limited distance along base 364 to account for stacking tolerances in the leg mechanism 316, minimizing any free play of front legs 314 when they are fully extended, and helping to limit any noise emanating from the leg mechanism 316 during operation. The wedge-like shape of wedge block 362 allows for the wedge block to be moved forwardly along base 364 to reduce undesired play in the leg mechanism 316, and to be moved rearwardly along base 364 to reduce any undesired amount of tightness in the leg mechanism 316.

[0112] Leg mechanism 316 therefore provides for smooth low-force transitions between the in-use configuration with front legs 314 deployed and seat 302 and seatback 320 ready for use, and the stowed or collapsed configuration with front legs 314 retracted and seat 302 and seatback 320 secured in the collapsed and unusable configuration. The transition between each configuration is readily accomplished by a single smooth motion of a user grasping handle 326 and lifting while pulling back to deploy the front legs 314 and release the D-ring plunger 318 so that the seat 302 and seatback 320 can be used, or by grasping handle 326 and pushing downwardly and forwardly to lock the D-ring plunger in the receiver-carriage 334 to secure the seat 302 and seatback 320 in their collapsed configuration, and retracting the front legs 314 for storage.

[0113] Tilt mechanism 306 incorporates a four-bar arrangement with the ability to operate in a tilt function with translating link when a person is seated, and that permits a collapse function when a person is not seated. A raise and lower function is also provided within the tilt mechanism. As best shown in FIGS. 19A and 19B where symbolic lines are provided to clarify the "links" described below (symbolic lines for links also appear in FIGS. 18A and 18B), four-bar arrangement includes an upper link 380 formed by seat frame 304 and extending between collapsing pivot shaft 332 and an upper-rear pivot 382 where seatback bracket 324 is attached; a rear link 384 extending from the upper-rear pivot 382 to a lower-rear pivot 386, both pivots 382, 386 having seatback bracket 324 attached; a lower link 388 extending through tilt mechanism 306 from the lower-rear pivot 386 to a front-lower pivot 390 that is translatable during tilt operations and also defines a collapse axis; and a forward link 392 defined between the front- lower pivot 390 (collapse axis) and the tilting pivot shaft 332 (tilt axis). Springs 328, which are internal to a tilt housing 393, are received between rear spring cups 394 and forward spring caps 396, the springs 328 being held in compression between a forward end portion 388a of the lower link 388 and associated collapse shaft 398 (which defines front-lower pivot 390 at a forward endof lower 388), and a front end plate 400 of tilt housing 393. A rubber stop pad 402 may be placed along the interior surface of front end plate 400 to provide a soft-stop for a front surface of the forward end portion 388a of lower link 388, in the event that lower link 388 slides forward so far (due to large back-leaning forces applied to seat 302 and setback 320) as to fully compress springs 328, as shown in FIG. 25.

[0114] Springs 328 may be initially installed into tilt housing 393 under little or no load, and then a preload imparted to them by installation of a pair of wedge blocks 404 that fit behind rear spring cups 394 and press forwardly on the rear spring cups 394 as the wedge blocks 404 are tightened down into tilt housing 393. Collapse shaft 398 is inserted through forward openings of lower link 388 that define collapsing pivot (front-lower pivot) 390, and the rear spring cups 394 are slid over the respective outboard end portions of collapse shaft 398 and held in place with C-clips 406. Wedge blocks 404 may push forwardly directly on collapse shaft 398 to urge the shaft 398, lower link 388, rear spring cups 394, and the rear ends of springs 328 forwardly to preload the springs 328. A pair of metal plates 408 are installed over the wedge blocks 404 to provide structural rigidity. A central region of collapse shaft 396 (at front-lower pivot 390) is received by a pair of slots 410 formed in upper regions of a pair of slot-bushings 412, which are secured to a lower region of tilt housing 393. Slots 410 guide the fore-aft sliding movement of shaft 396 and the front-lower pivot 390 it defines (along with forward end portion 388a of lower link 388) while a person is seated and leaning back to cause lower link 388 to translate forwardly and compress springs 328.

[0115] Tilt pivot shaft 332 is secured to upper surfaces of the metal plates 408 by a pair of capture blocks 414 that are accommodated by an upper-rear region 416a of a tilt housing cap 416. Stop bumper 330 is secured to an underside of tilt housing cap 416 at a central portion of the upperrear region 416a, and provides a compliant stop surface for an upper surface 388b of the lower link 388 when a person is seated and the seatback 320 is upright (FIG. 18A). It will be appreciated that in FIGS. 18A and 19A a lower end of the stop bumper 330 appears to overlap or intersect a middle region of lower link 388, but in practice the lower end of stop bumper 330 will press against the upper surface 388b and will be compressed upwardly against the underside of tilt housing cap 416 in this configuration.

[0116] Provision is also made in tilt mechanism 306 for a vertical raising and lowering function via telescopic extension and retraction of seatpost 308. In the illustrated embodiment, seatpost 308 is a standard item having a lower gas-charged cylinder 308a with integral damper, which can extend (raise) a piston associated with an upper seatpost 308b to which tilt mechanism 306 is attached, and which has a spring-loaded valve-release button 308c at its upper end that allows for raising the upper seatpost 308b when no person is seated, and lowering the upper seatpost 308b when a person is seated. The seatpost's valve -release button 308c can be depressed by a finger 418 of a pivotable lever 420 when the lever 420 is actuated by a height adjustment lever 422 that can be manually raised by a person seated at the chair 300. Pivotable lever 420 is pivotally coupled to the tilt housing 393 by a capture block 424, with a lower plunger 422a of heightadjustment lever 422 coupled to a lower region of pivotable lever 420 and exiting a right-hand side of the tilt housing 393.

[0117] To ensure that the chair 300 is fully compact for storage, including minimum vertical height, D- ring plunger 318 is insertable into the vertical slot 338 of receiver-carriage 334 when seat 320 is fully or nearly-fully lowered, which means that the upper end and piston of seatpost 308 is fully or nearly fully compressed (lowered). Therefore, prior to configuring chair 300 for compact storage, a seated person will raise height-adjustment lever 422 to fully lower the upper seatpost 308b before they stand. Because it is not desirable to raise upper seatpost 308b, seat 302, and seatback 320 when chair 300 is configured for storage, lower link 388 provides a lockout feature by engaging the pivotable lever's finger 418 (see FIG. 19B) and thus blocking the pivotable lever 420 from being moved by the height-adjustment lever 422 when the seat 302 and seatback 320 are at or near their collapsed configuration of FIGS. 18B and 19B.

[0118] Much as with the four-bar tilt and collapse mechanism of task chair 100, tilt mechanism 306 allows for raising and lowering the seatpost 308 for comfort during use, provides spring-resisted rearward lean or tilt function by allowing the lower link 388 of a four-bar mechanism to translate forwardly in response to downward and rearward forces applied to the rear of seat 302 and the seatback 320 by a seated person, and when a person is not seated, the lower link 388 is urged to its rearward-most position by springs 328 so that the four-bar mechanism can provide a collapsing function whereby the seat 320 tips rearwardly and into closer proximity to the seatback 320 and seatback bracket 324 (FIG. 18B), which may maintain the same or similar upright orientation as when the seat 320 and seatback 320 are positioned for sitting (FIG. 18A).One or more dampers may be installed at tilt pivot shaft 332 and / or collapse shaft 398 so that when a person stands up from chair 300, the gravitational loads at the rear of seat 302 (including the weight of the rear portion of seat 302, the rear portion of seat frame 304, the seatback 320, and the seatback bracket 324) will cause the seat 302, seatback 320, seatback bracket 324, and D-ring plunger 318 to lower in a slow and controlled manner. At this stage, and assuming seatpost 308 has been fully lowered, the D-ring plunger 318 may be positioned just outside or just inside the vertical slot 338 of receiver-carriage 334.

[0119] To facilitate alignment of D-ring plunger 318 with vertical slot 338, seatpost 308 may have a self-aligning feature that allows for limited rotation of the upper seatpost 308b relative to the lower seatpost cylinder 308a about its longitudinal (vertical) axis, and a spring-biased centering force that aligns the D-ring plunger 318 with the vertical slot 338 of receiver-carriage 334 when a person is not applying a rotational load to seat 302 relative to chair legs 312, 314. Additional forces manually applied to handle 326 will then be sufficient to fully insert the D-ring plunger 318 into the vertical slot 338 where it will be captured by pawls 340 and cause the receivercarriage 334 to move forwardly, which in turn causes front legs 314 to pivot rearwardly, as does any rolling resistance imparted to front legs 314 by front wheels 336, as described above.

[0120] Accordingly, the collapsible chair utilizes a dual-mode seat mechanism that allows limited tilting or pivoting movement of a seat while the chair is in use, and which also allows the seat and seatback portions of the chair to be pivoted to near- vertical orientations for compact storage. A leg extension and retraction mechanism can extend and retract at least some of the chair's legs in response to movement of the chair's seat near its travel limit in the collapsed configuration, providing for an even more compact storage configuration of the chair. The chair, in its collapsed configuration, may be sufficiently compact to fit underneath the work surface of a standard-height desk or table. The leg mechanism's ability to capture a plunger attached to the seat when the seat is in a stowage orientation helps to ensure that the chair's seat cannot be inadvertently moved into an orientation in which it can be sat upon, without the chair legs first being fully deployed. The various mechanisms allows simplified operation of the chair while also providing a comfortable ride that includes limited seat tilt in response to the user shifting their weight on the seat and optionally leaning back against a seatback. The mechanisms accommodate different postures that are assumed by users, offers desirable levels and evenness of support in those different postures, is well-balanced to allow users to shift between differentpostures with little resistance, and is able to adapt to different body sizes and weights without requiring manual adjustments.

[0121] Changes and modifications in the specifically described embodiments may be carried out without departing from the principles of the present invention, which is intended to be limited only by the scope of the appended claims as interpreted according to the principles of patent law including the doctrine of equivalents.

Claims

CLAIMS1. A chair seat support and tilt mechanism comprising:a base;a seat coupled to said base; andfour links for coupling said seat so said base, said four links coupled together at four pivots to form a four-bar linkage;wherein a first of said links is pivotably coupled to a second of said links, and at least a portion of said first link is translatable relative to a second of said links in response to tilting movement of said seat relative to said base; andwherein when one of said links comprises a portion of said seat, and another of said links comprises a portion of said base.

2. The chair seat support and tilt mechanism of claim 1 , wherein said first link comprises a resilient flexible member.

3. The chair seat support and tilt mechanism of claim 1, wherein said four links and said four pivots comprise:an upper link having forward and rearward pivots, said upper link comprising said portion of said seat;a rear link having upper and lower pivots, wherein said upper pivot of said rear link is pivotably coupled to said rearward pivot of said upper link;a lower link having forward and rearward pivots, wherein said rearward pivot of said lower link is pivotably coupled to said lower pivot of said rear link, and said lower link comprising said portion of said base; anda forward link having upper and lower pivots, said forward link configured for coupling to said portion of said base, wherein said lower pivot of said forward link is pivotably coupled to said forward pivot of said lower link, and said upper pivot of said forward link is pivotably coupled to said forward pivot of said upper link.

4. The chair seat support and tilt mechanism of claim 1 , further comprising a compressible biasing member at one of said pivots associated with said first link, where said biasing member resists translation of said first link relative to said second link.

5. The chair seat support and tilt mechanism of claim 3, wherein said lower link comprises said first link, and said forward link comprises said second link.

6. The chair seat support and tilt mechanism of claim 3, further comprising a guide defined at one of said forward link and said lower link at the location where said forward pivot of said lower link is pivotably coupled to said lower pivot of said forward link, wherein said guide permits said forward pivot of said lower link to translate a limited distance forwardly and rearwardly relative to said forward link as said upper link pivots about said forward pivot of said upper link and said upper pivot of said forward link.

7. The chair seat support and tilt mechanism of claim 6, wherein said guide comprises an elongate channel formed in said forward link.

8. The chair seat support and tilt mechanism of claim 7, further comprising a biasing member configured to bias said forward pivot of said lower link and thereby bias said seat to pivot forwardly.

9. The chair seat support and tilt mechanism of claim 4, wherein said forward pivot of said lower link compresses said biasing member in response to tilting said seat rearwardly.

10. The chair seat support and tilt mechanism of claim 3, further comprising a seatback coupled to said rear link, wherein said seat pivots into closer proximity to said seatback during the rearward tilting of said seat in response to a downward force acting on said seatback.

11. The chair seat support and tilt mechanism of claim 1, further comprising:a seatpost extending downwardly from said base;a leg mechanism coupled to said seatpost below said seat base;a plurality of chair legs coupled to said seatpost; anda plunger coupled to a rear portion of said seat;wherein said plunger is movable with said seat into engagement with said leg mechanism, which is configured to retract at least one of said chair legs in response to the engagement by said plunger.

12. The chair seat support and tilt mechanism of claim 11, wherein said leg mechanism is configured to extend at least one of said plurality of chair legs in response to movement of said plunger while said plunger is engaged with said leg mechanism.

13. The chair seat support and tilt mechanism of claim 12, wherein said leg mechanism is configured to secure said plunger at said leg mechanism when said plurality of chair legs are retracted.

14. The chair seat support and tilt mechanism of claim 13, wherein said leg mechanism is configured to release said plunger only once said plurality of chair legs are extended.

15. A chair leg mechanism comprising:a base;a leg actuator having first and second end portions, wherein said leg actuator is movable in first and second directions relative to said base;a movable chair leg having a proximal end portion pivotably coupled to said base and coupled to said first end portion of said leg actuator; anda retainer mechanism at said second end portion of said leg actuator, wherein said retainer mechanism is configured to:receive a movable seat-coupled actuator;capture the seat-coupled actuator as said leg actuator moves in the first direction in response to said leg actuator being pushed by the seat-coupled actuator; and release the seat-coupled actuator as or after said leg actuator moves in the second direction in response to said leg actuator being pulled by the seat-coupled actuator; wherein said movable chair leg is retractable in the second direction in response to said leg actuator moving in the first direction, and said movable chair leg is extendable in the first direction in response to said leg actuator moving in the second direction.

16. The chair leg mechanism of claim 15, wherein said retainer mechanism comprises a receiver-carriage movably engaged with said leg actuator and with a guide that is formed in a portion of said base, wherein said receiver-carriage is configured to follow said guide while capturing the seat-coupled actuator as said leg actuator moves in the first and second directions, respectively.

17. The chair leg mechanism of claim 16, wherein said guide is L-shaped or arcuate in shape.

18. The chair leg mechanism of claim 15, wherein said leg actuator comprises a receivercarriage defining an opening for selectively receiving said seat-coupled actuator, and at least one lockable pawl configured to receive and releasably retain said seat-coupled actuator.

19. A chair comprising said chair leg mechanism of claim 15, wherein said chair comprises:a seatpost;a seat pivotably coupled to said seatpost, wherein said seat-coupled actuator is coupled to said seat; anda fixed chair leg coupled to said base;wherein said base is coupled to a lower portion of said seatpost; andwherein said movable chair leg is pivotable with respect to said fixed chair leg.

20. A chair seat support comprising:a seat;a seatpost below said seat;an upper link coupled to said seat and having forward and rearward pivots; a rear link having upper and lower pivots, wherein said upper pivot of said rear link is pivotably coupled to said rearward pivot of said upper link;a seatback coupled to said rear link;a lower link having forward and rearward pivots, wherein said rearward pivot of said lower link is pivotably coupled to said lower pivot of said rear link; anda forward link coupled to said seatpost and having upper and lower pivots, said forward link configured for coupling to a chair support leg or post, wherein said lower pivot of said forward link is pivotably coupled to said forward pivot of said lower link, and said upper pivot of said forward link is pivotably coupled to said forward pivot of said upper link;wherein said seat is tiltable rearwardly from an in-use orientation to an upright orientation, and to pivot into closer proximity to said seatback in the upright orientation.

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