Adjustable armrest

An adjustable armrest for a chair includes a housing having a cavity defined by a wall and a latch member slideably mounted in the cavity. The latch member includes a wedge shaped portion having a first and second surface forming a oblique angle between them. One of the first and second surfaces engages the wall of the housing at least when the latch is in the engaged position.

BACKGROUND OF THE INVENTION

The present invention relates generally to tiltable chairs, and in particular, to a synchrotilt chair having an adjustable seat, backrest and armrests.

Chairs of the type typically used in offices and the like are usually configured to allow tilting of the seat and backrest as a unit, or to permit tilting of the backrest relative to the seat. In chairs having a backrest pivotally attached to a seat in a conventional manner, the movement of the backrest relative to the seat can create shear forces which act on the legs and back of the user, and which can also create an uncomfortable pulling of the user's shirt, commonly called “shirtpull.”

To enhance the user's comfort and to promote ergonomically healthy seating, synchro-tilt chairs provide for the seat and backrest to tilt simultaneously, but at different rates, preferably with the back tilting at a greater rate than the seat. Normally, synchro-tilt chairs employ compression and/or tension springs, torsion springs and/or torsion bars to bias the seat and back upwardly and to counterbalance the rearward tilting of the user. Chairs using these types of springs can have various limitations associated with the type of spring used therein.

For example, the proper placement of compression springs and/or torsion springs within the chair can often require a large or bulky housing with associated aesthetic limitations. Moreover, the ride, or resistive force experienced by the user, may be unsatisfactory because spring rates associated with compression springs are not linear and tend to increase as the spring bottoms out. In addition, the cost of manufacturing the chair, due to the placement of the springs and the introduction of additional load bearing elements, can be increased. This problem can be exacerbated when two or more springs are used in the chair. Moreover, synchrotilt chairs typically provide for the spring to act on one of the seat or back support, and for the force to then be transferred to the other through a pivotal attachment, which can require additional load carrying capabilities.

Furthermore, inconsistencies in the performance of compression and torsion springs, and the longevity thereof, can often be traced to the inherent properties of steel, which is typically used to make such springs. For example, steel is subjected to the problem of “creep” and various inconsistencies introduced during the manufacture of the steel and the subsequent heat-treating processes. Moreover, because of the requisite size of the springs, the mechanisms used to adjust the amount of initial resistive compression can be difficult to activate, and can be progressively more difficult to adjust as higher settings are reached.

Chairs employing torsion bars may experience similar limitations. For example, the length and diameter of the bar is dictated by the range of movement and force output desired, and the desire to avoid overstressing the spring. Often, relatively heavy and highly stressed bars of great length are required to provide the control necessary to adequately support a user. Thus, the shape and associated aesthetics of the chair are dictated by the size of the spring. In addition, the chair must be provided with load-bearing elements at the ends of the bar and at the point of adjustment. Moreover, as with compression and torsion springs, activation or adjustment mechanisms used to achieve a desired initial pretorque setting can be difficult to manipulate, and can become increasingly so as higher settings are reached.

Leaf springs can also be used to support the user in the chair. However, leaf springs are typically clamped at one or more ends of the spring, usually by passing a bolt or like fastener through the spring. This is especially true when the leaf spring is configured as a cantilever similar to a diving board. Holes in the spring can introduce stress risers, however, and clamping one or more ends, as opposed to having them simply supported, introduces indeterminate moments and resultant stresses in the spring which may not be evenly distributed. Moreover, the resistive force of many leaf springs, including cantilevered springs, is often adjusted by varying the prestress of the spring through bending. As with the other springs described above, such an adjustment mechanism can be difficult to activate, and becomes progressively more so as higher settings are reached.

It is also desirable to provide a chair that can be adjusted to accommodate the various needs and sizes of the user. In particular, it is desirable to provide a chair having an adjustable backrest, adjustable armrests, and an adjustable seat depth.

The typical approach to adjustably supporting a backrest is to provide a single, centered spline, which can be located internally or externally to the backrest cushion, or like support. Typically, such a spline is linear so as to allow for adjustment of the backrest. However, it is often desirable to provide contours in the backrest of the chair so as to conform to the shape of the user's back. When the spline is located inside the backrest, the assembly is necessarily thick to accommodate the spline and desired contour. In addition, the backrest must itself be structural, and securely attached to the spline with tight tolerances, to provide lateral support for the user on the outer edges of the backrest and to avoid a feeling of sloppiness. Moreover, if armrests are desired, they must typically be positioned on separate supports projecting from the seat or from beneath the chair, since the spline centered backrest is usually structurally unable to support the large loads imparted on the armrests by a user along the sides of the backrest. When adjustable, such armrest supports often house complex and expensive to manufacture height adjustment mechanisms.

Furthermore, synchrotilt chairs typically provide pivot axes and links along the sides of the chair. Mechanically, there is an advantage to give the driven links input (occupant) and output forces (e.g., springs) as great a relative “stance” as possible. As a result, the use of a centered spline can result in a control that feels less “lively” when the occupant is not centered. Additionally, centered spline chairs often provide an adjustment mechanism adjacent the spline at the center of the back, which can be difficult to access, especially by a seated occupant when the backrest is in a lowermost position.

SUMMARY OF THE INVENTION

Briefly stated, the invention is directed to an improved synchrotilt chair having an improved tilt control mechanism and an adjustable backrest, armrests and seat.

In one aspect of the invention, the chair includes a housing, a back support pivotally connected to the housing about a first horizontal axis and a seat support pivotally connected the housing about a second horizontal axis. A leaf spring includes a first end engaging a forward portion of the housing and a second end biasing the seat support and the back support in an upward direction. A fulcrum member is moveably supported in the housing and engages the leaf spring between its first and second end. In operation, the fulcrum member can be easily moved longitudinally within the housing so as to vary the length of the leaf spring lever arm and thereby vary the amount of resistive force supporting the user.

In a preferred embodiment, the seat support is also slideably connected to the housing about the second horizontal axis and is pivotally connected to the back support about a third horizontal axis.

In another aspect of the invention, a seat having a seat pan is adjustably mounted on the seat support. In operation, the seat can be moved in a longitudinal direction to adjust the depth of the seat relative to the backrest and thereafter releasably locked to the seat support.

In yet another aspect of the invention, a tilt limiter is provided to limit the rearward tilting of the chair. The tilt limiter includes a cam member pivotally mounted in the housing and having a plurality of teeth which engage a rack, or plurality of laterally oriented grooves, formed in the seat support. In operation, the cam member can be pivoted to limit the rearward tilting of the user.

In another aspect of the invention, a selector member is connected to the tilt limiter. The selector member includes indicia that indicates the setting of the tilt limiter so as to apprise the user of the maximum rearward tilt position of the seat, or chair, even when the seat or chair is in a tilt position other than the maximum rearward tilt position. In a preferred embodiment, the selector member comprises a handle connected to the cam member. The handle preferably has an substantially flat elongated portion forming the indicia such that the angular orientation of the substantially flat elongated portion indicates the setting of the tilt limiter, and the corresponding maximum rearward tilt position of the seat and chair.

In another aspect of the invention, the back support includes a pair of uprights extending upwardly along opposite sides of the chair. Each upright includes a first and second bar mounted thereto in a parallel and spaced apart relationship with the other. A backrest is slideably mounted on the first bar members and an armrest is slideably mounted to each of the second bar members. Preferably, the uprights are located externally of the backrest and are connected with a cross member so as to form a one-piece back support.

In a preferred embodiment, an engagement member is mounted to a bracket member which is mounted on the first bar member. The engagement member is adapted to engage a rack located on the upright to thereby releasably secure the backrest to the uprights. The armrest preferably includes a locking device which is adapted to engage the second bar member and thereby releasably secure the armrest to the upright.

The present invention provides significant advantages over other synchrotilt chairs, and chairs having adjustable backrests and armrests. For example, in the most preferred embodiment, an improved tilt control mechanism is provided which can be manufactured in a compact and aesthetically pleasing housing. In particular, the leaf spring, or preferably a pair thereof, extends longitudinally within the housing, which can be made in a compact and aesthetically pleasing form with little or no depth due to the nature of the spring. The width of the housing also need not be dictated by length of the spring. The resistive force of the leaf springs is easily and simply adjusted by moving the fulcrum member longitudinally within the housing. Consequently, the springs are not prestressed at differing levels, and the adjustment member can be easily manipulated without progressive difficulty. The leaf spring also provides a relatively uniform spring rate throughout the tilting range of the chair.

The leaf springs also are preferably made of composite material, which is more resistant to creep. The leaf spring preferably supports a shaft pivotally connecting the seat support and back support. In this way, the leaf spring biases both members upwardly together, rather than acting on one member with the force then transmitted to the other member through a pivotal attachment. As such, the number of load bearing elements are reduced and simplified.

The three bar slide mechanism also provides several advantages. For example, the linkage provides for a synchrotilt chair wherein the back tilts at a greater rate than the seat, but avoids the use of a fourth bar, which can add to the complexity and manufacturing costs of the chair. Indeed, the overall design is greatly simplified by forming “bars” out of the housing, seat support and back support. Additionally, the use of a slide member allows for the assembly to be made in a more compact and aesthetically pleasing form.

The unique back support also provides many advantages. For example, by providing a one-piece back support, a simplified and aesthetically pleasing structure is provided, which also performs the combined tasks of forming one of the bars of the linkage assembly, providing a support for the backrest and providing a support for the armrests. Additionally, the exoskeletal nature of the back support framing a cushion gives the user a strong visual of support, security and durability. Moreover, by providing uprights along the sides of the chair, the backrest is not required to be structural in nature, and the loads imparted by a user against the side of the backrest can be transmitted directly through the forwardly extending arms of the back support to the housing and spring member so as to provide a more “lively” control for the user. Moreover, since the backrest is supported on both sides, looser tolerances can be accommodated during the assembly of the backrest without sacrificing any tightness in the feel of the backrest.

The uprights can also be used to also support the armrests, which thereby avoids the need for separate supports and complex mechanisms. In this regard, the bar members, which are mounted to the uprights, provide a simple but sturdy support for the backrest and armrests.

The present invention, together with further objects and advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The terms “longitudinal” and “lateral” as used herein are intended to indicate the direction of the chair from front to back and from side to side, respectively. Similarly, the terms “front”, “side”, “back”, “forwardly”, “rearwardly”, “upwardly” and “downwardly” as used herein are intended to indicate the various directions and portions of the chair as normally understood when viewed from the perspective of a user sitting in the chair.

Referring to the drawings,FIG. 1shows a preferred embodiment of the chair having tilt control housing10, seat support20, seat cushion22, back support30, backrest32and seat pan24. A pneumatically adjustable support column12is mounted to a rear portion of the housing at opening14as shown inFIGS. 4 and 6. A top portion of the column12having an actuation button extends into the housing. As shown inFIGS. 19-21, a pivot member34having a forwardly extending arm36engaging a stop40and a rearwardly extending arm38adapted to engage the actuation button is mounted to a pivot rod42by engagement of a key member within a key hole. The pivot rod is rotatably mounted to housing10at lug member166. A handle44is mounted to the end of the pivot rod42. In operation, the handle44is rotated so as to rotate the rearwardly extending arm38of the pivot member and thereby engage the actuation button, which in turn allows the support column to extend in response to a gas spring contained therein, or to collapse in response to the weight of the user being applied to the seat.

Referring toFIG. 1, a base16, preferably a five arm base with casters, is mounted to the bottom of the support column12in a conventional manner. One of skill in the art would understand that other support columns and bases can be used to support the housing, including fixed height support columns and non-rolling bases.

As shown inFIGS. 3 and 4, the back support30includes a pair of support arms50, extending forwardly along opposite sides of the chair. Each of the support arms50terminates in a first lug portion52having a horizontal opening54. Referring toFIG. 19, the housing10includes a boss60extending outwardly from each sidewall62of the housing in a perpendicular relationship therewith. The lug portions52are pivotally mounted to the bosses60on opposite sides of the housing with a pair of hollow pivot rods56, which are inserted through an opening64extending through each boss and which defines a first horizontal pivot axis. The pivot rod42for actuating the gas spring extends through and is rotatably mounted in the hollow pivot rod56.

As shown inFIGS. 3 and 30, each support arm also includes a second lug portion58positioned rearwardly of said first lug portion52. The second lug portions58are pivotally connected to the seat support with a pivot rod66, which define a third horizontal pivot axis, as shown inFIGS. 3 and 4.

Referring toFIG. 4, pivot rod68extends outwardly from each sidewall62of the housing and defines a second horizontal axis. The seat support20is pivotally and slideably connected to the housing at the second horizontal pivot axis by inserting the pivot rods through slots30formed in opposite sidewalls67of the seat support as shown in FIG.3A. Alternatively, the pivot rods68are disposed in slotted channels72formed in each of the sidewalls as shown in FIG.9. Or, in yet another alternative embodiment, shown inFIG. 9A, pivot rod74extends inwardly from the seat support sidewall to engage a slot76formed in the sidewall of the housing. In a preferred embodiment, the second horizontal pivot axis68is positioned forwardly of the first horizontal pivot axis56, which is positioned forwardly of the third horizontal pivot axis66.

In operation, the housing10, seat support20and back support30form a three-bar linkage with a slide. Because the second pivot axis is positioned forwardly of the first pivot axis which is positioned forwardly of the third pivot axis, the back support30tilts rearwardly at a greater rate and angle than does the seat support20. Preferably, the back to seat inclination is at a ratio of about 2;1. The three-bar linkage provides a simple and compact mechanism which avoids the use of additional links. Additionally, by forming the linkage assembly from the seat support, back support and housing, complex and expensive links and load bearing parts are avoided. When combined with a pair of leaf springs80, the resultant chair can be designed in a compact and aesthetically pleasing form. It should be understood that the three-bar linkage could be formed by pivotally connecting the seat support and back support to the housing and by pivotally and slideably connecting the seat support to the back support, or by pivotally connecting the seat support to the housing and to the back support and then pivotally and slideably connecting the back support to the housing.

Although the above-described three-bar mechanism is preferred, it should be understood that the leaf springs can also be incorporated into synchro-tilt chairs using linkage mechanisms such as four-bar linkages and the like. With a four-bar linkage, links can be provided to pivotally connect the seat support and/or back support to the housing and/or to each other about various horizontal axes.

As best shown inFIGS. 6-9,19and27-29, a fulcrum member90is moveably installed in the housing10beneath the pair of leaf springs80. The fulcrum member90is preferably formed from a single piece of hard, durable material having a relatively low coefficient of friction, such as DELRIN or CELCON Acetal, so as to allow the fulcrum member to slide relatively easily along a bottom surface of the housing, even when heavily loaded by the spring. It should be understood, however, that other materials such as steel would also work. Similarly, the bottom surface can be lined with a material having a low coefficient of friction, such as TEFLON. Referring toFIGS. 24 and 25, the fulcrum member90includes a bottom surface92and a pair of support pads94formed on a top of the fulcrum member. Preferably, the support pads94on each side of the fulcrum member are separated by a groove96which reduces the surface area in contact with the spring80and the attendant friction forces which act on the spring.

The fulcrum member90also includes end portions98which are tapered outwardly and downwardly from the support pads94, and a lug portion100formed at a bottom center portion of the member. Alternatively, as shown inFIG. 24A, the end portions include a small lip portion760. The lug portion100includes a longitudinally oriented hole102. In one embodiment, at least a portion of the hole is threaded. Alternatively, a threaded fitting can be inserted into the bore provided in the lug portion, or a entirely separate bracket having a threaded opening can be mounted to a bottom of the fulcrum member.

As shown inFIGS. 5-9and19, the fulcrum member90is disposed laterally within the housing10such that the bottom surface92of the fulcrum member slideably engages a pair of longitudinally oriented landings107formed along opposite sides of the bottom of the housing. The end portions98of the fulcrum member90abut the inner surface of the side walls62of the housing and act as guides for the fulcrum member as it is moved longitudinally within the housing. Referring toFIG. 9, the lug portion100is disposed within a channel104longitudinally formed in the housing below and between the landings102. The lug portion100also acts as a guide within the channel104so as to maintain the alignment of the fulcrum member within the housing as it moves longitudinally along its path.

In an alternative embodiment, shown inFIG. 26, the fulcrum member106includes a shaft108and a carriage110disposed on the shaft. A pair of rollers112are rotatably mounted on the shaft108so as to be in alignment with the pair of leaf springs80. Two pairs of support rollers114are rotatably mounted on the shaft on opposite sides of each of the rollers112in alignment with landings116formed on a bottom surface of the housing. In operation, the fulcrum member can be rolled longitudinally within the housing on rollers114, as rollers112engage leaf springs80. A clip118, or like retainer, is installed on each end of the shaft to capture and retain the rollers and carriage on the shaft. Preferably, the shaft, rollers and carriage are made of steel.

As illustrated inFIGS. 5,6and16-18, an adjustment member120, preferably a threaded shaft, is inserted through an opening122in a front wall124of the housing and is rotatably secured thereto. A knob126is mounted on an end of the adjustment member120externally of the housing for access by the user. An opposite end of the shaft is rotatably supported by a stop member40extending upwardly from the bottom surface of the housing. It should be understood, however, that the end of the shaft need not be supported at all as the fulcrum member is guided by the housing. The shaft threadably engages the opening in the lug portion100of the fulcrum member, or an opening in the carriage110.

It should also be understood that the fulcrum member can be fixed within the housing at a specific location, such that the resistive force of the chair can not be adjusted.

As shown inFIG. 19, the front wall124of the housing includes laterally oriented slotted openings126formed along opposite sides of the front wall124of the housing. Cross members130are defined by and formed over the openings. The pair of leaf springs80are installed in the chair by inserting an end82of each spring through one of the openings128such that a top surface86of the spring engages the cross member130. Alternatively, as shown inFIGS. 27-29, a horizontal rod88can be installed laterally in a forward portion of the housing so as to engage the top surface86of the forward end82of the spring. In one embodiment, a forward edge of the spring abuts the front wall of the housing so as to maintain the longitudinal position of the spring within the housing. Alternatively, as shown inFIG. 7, a protuberance132extends downwardly from the cross member130and engages a hole134or detent formed in a forward portion of the spring so as to maintain the longitudinal position of the spring.

The leaf springs80are constrained laterally within the housing by the sides of the slotted opening at the front of the housing and by the sides of a pair of openings500, or notches, formed in a rear vertical wall of the seat support as shown inFIGS. 13 and 19. The leaf spring80extends rearwardly within the housing10such that a bottom surface87engages the pad members94of the fulcrum member90. An end84of the spring is inserted beneath pivot rod66as shown inFIGS. 5 and 19such that top surface86engages pivot rod66. Although each spring is shown as a single leaf, it should also be understood that multi-leaf springs could also be employed. The leaf springs are preferably made of a composite material, such as a fiberglass and epoxy matrix, although it should be understood that other resilient materials such as steel would also work. The composite material can be a fibrous composite, a laminated composite or a particulate composite. A suitable composite spring is commercially available from Gordon Plastics, Inc. of Montrose, Colo. under the specification designation of GP68-UD Unidirectional Fiber Reinforced Bar Stock, and sold under the tradename POWER-TUFF. The fiberglass/epoxy matrix bar preferably is unidirectional with a glass content of about 68% and a laminate density of 0.068 lbs./in.3. The bar preferably has a flexstrength of about 135,000 psi, a flex modulus of about 5,000,000 psi, and an ultimate strain of about 2.4%. The use of a composite material bar can help eliminate the problems associated with creep.

In operation, the end84of the leaf spring biases pivot rod66, and the pivotally connected back support30and seat support20, in an upward direction so as to thereby support a user sitting in the chair. Since the leaf spring80acts on the pivot rod66, rather than on just one of the back support30or seat support20, the supports20,30are not required to transmit the biasing force to the other of the supports20,30, and can therefore be made less robust and at less cost. Rather, the bending loads are carried by the pivot rod66. Obviously it should be understood, however, that the leaf spring could directly engage either the back support or seat support so that the upwardly biasing force is transmitted to the other thereof through the pivotal attachment. The opposite end82of the spring engages the cross member130or rod88mounted in the housing, while the middle of the spring is supported by the fulcrum member90. In this way, the spring80acts as a simply supported beam with a load imparted intermediate the supported ends82,84thereof. To adjust the force applied to the pivot rod, the user simply rotates the knob126which causes the adjustment member120, or shaft, to rotate and thereby threadably engage the fulcrum member so as to move it in a linear, longitudinal direction within the housing.

As the fulcrum member90is moved rearwardly in the housing10, the distance between the point of support and the pivot rod is decreased as shown inFIG. 29, so as to correspondingly increase the force applied by the end84of the spring. Conversely, as shown inFIG. 28, the fulcrum member90can be moved forwardly in the housing10to decrease the amount of resistive force applied to the seat support and back support by increasing the beam length, or the distance between the fulcrum90and the pivot rod66. Since the leaf spring80is simply supported at each end, rather being clamped to the housing, the pivot rod or both, bending moments are not introduced at the ends of the spring. When clamped, the properties of the spring, and the amount of the clamping, can effect the loading and associated stresses. Moreover, by providing a simply supported spring, tolerances can be relaxed and the curvature of the spring is allowed to undulate as the beam length changes.

Because the leaf springs80are disposed in the housing10in a side-by-side arrangement, and are preferably formed as flat bars, the housing can be made more compact at lower cost in an aesthetically pleasing way. This advantage is even more apparent when the leaf spring arrangement is combined with the three bar mechanism. Moreover, the resistive force of the spring can be adjusted easily and simply by slideably moving the fulcrum90within the housing10. Since the resistive force is determined by the beam length, rather than by prestressing the spring, the adjustment does not require a progressively larger actuation force as is typically associated with torsion springs and bars and compression springs.

Now turning toFIGS. 11-14, a rack136is shown as being formed on a top of the seat support. The rack136consists of a plurality of outwardly facing notches138formed along one side of the seat support. The seat support also includes outwardly facing channels140that run longitudinally along the top surface of the seat support as shown inFIGS. 13 and 14.

A rack142is also formed on a bottom surface of the seat support. The rack142is formed along a concave portion of the bottom surface of the seat support and includes a plurality of laterally extending grooves144.

As shown inFIGS. 8 and 23, inwardly facing longitudinal channels26extend downwardly from the seat pan24and are aligned to communicate with and engage the outwardly facing channels140on the seat support. The seat pan24is slideably mounted to the seat support by slideably engaging the cooperating channels. In addition, a pair of longitudinally aligned pins506, or similar protuberances, extend upwardly from the housing and are received in a pair of slots508, or channels, formed in the seat pan. The pins prevent the seat pan from moving laterally with respect to the housing such that the lateral tolerances between the intermitting channels26,140can be maintained rather loosely. Preferably, a seat cushion22is attached to the seat pan24. The travel of the seat pan along a longitudinal path from front to back can be limited either by the travel of the pin within the slots, or by engagement of various stop members extending from one or both of the seat support and seat pan.

As shown inFIGS. 30 and 31, a bracket member146is mounted to a bottom of the seat pan with a plurality of fasteners engaging holes in the seat pan. A lever148having a handle and an inwardly extending nose portion150is slideably mounted to the bracket member. The nose portion150is shaped to releasably engage the notches138of rack136. In operation, the user pulls the lever148outwardly to disengage the nose portion150from the rack136and thereafter slides the seat cushion and seat pan24forwardly or rearwardly with respect to the seat support20until a desired seat depth position is reached. The lever148is then pushed inwardly so that the nose portion150engages one of the notches in the rack136. The lever148can also be spring mounted so as to be biased toward the rack and into the engaged position. The seat cushion is attached to the seat pan.

Alternatively, as shown inFIGS. 9 and 31A, the nose portion510includes a notch512that is shaped to engage one of the ribs514forming the rack.

As shown inFIGS. 58-62, an information card910providing indicia for using the various chair mechanisms can be slidably mounted to the bracket146. Preferably, the card and bracket are provided with travel limiting members to prevent the card from being removed from the chair where it can be then be lost.

Referring toFIGS. 16-18, a tilt limiter152is shown as pivotally mounted to the housing on an axle156. In one embodiment, the tilt limiter includes a cam member154having a substantially semi-circular shape with a convex upper surface shaped to communicate with and to engage the concave rack142of the seat support. The cam member is preferably one piece and is made from a single piece of high impact plastic, although it should be understood that other materials such as steel and other combinations of parts would also work. In the one piece embodiment, the axle is in-molded with the cam member. A bracket182is mounted over the axle to capture it between the bracket and the housing. A plurality of fine, laterally oriented teeth158are formed along the outer convex surface of the cam member. Teeth158engage the rack142formed on the bottom of the seat support to limit the rearward tilting of the seat support and chair.

In an alternative embodiment, shown inFIGS. 19-21, a plurality of larger stepped teeth159, or engagement surfaces, are arranged around the periphery of the cam member155. As shown inFIGS. 12A and 57, the seat support includes a plurality of longitudinally extending ribs950and a laterally extending rib952intersecting ribs950. The cam member155can be rotated such that one of the plurality of teeth159engages the ribs950,952to limit the rearward tilting of the seat support and chair.

Referring toFIGS. 16-21, a pivot rod160extends through and is rotatably mounted within the hollow pivot rod56connecting the back support30and the seat support20opposite pivot rod42. A handle800is secured to one end of the pivot rod160and can be used to pivot the rod about a substantially horizontal axis. An opposite end of the pivot rod160is mounted to a pivot member162and is rotatably supported by lug member164. A forwardly extending arm168of the pivot member162is pivotally connected to a connecting member170, preferably formed from a piece of wire, which extends rearwardly to engage the cam member154,155. In operation, the handle800and pivot rod160are rotated to pivot the pivot member162and attached connecting member170, which in turn rotates the cam member about axle156to the desired tilt position. As the user tilts rearwardly, the seat support20pivots and slides about the third pivot axis68until the rack142is brought into engagement with the teeth158on the cam member154, or until the ribs950,952engage the teeth159of cam member155, wherein the seat support is prevented from tilting further rearwardly. Since, as shown inFIGS. 16 and 21, the cam member154,155is pivotally attached to the housing along an axis off-center from the center of the approximately shaped arc formed by the convex surface of the cam member, the user can pivot the cam member about the off-center axis such that different sets of teeth158engage the rack142at various positions, or such that a different stepped tooth159engages the ribs950,952, wherein the seat support is engaged at varying desired tilt positions. For example, as shown inFIGS. 58-62, the tilt limiter, including the cam member, can be moved to a plurality of settings or positions so as to limit the rearward tilting of the seat to a plurality of maximum rearward tilt positions, including, but not limited to, a forward tilt position, an upright tilt position, various intermediate tilt positions and a reclined tilt position,

As shown inFIGS. 58-62, the handle800(also shown in FIG.21), functions as a selector member for selecting the position of the tilt limiter. In particular, the selector member is rotated so as to rotate pivot rod160, which in turn pivots the pivot member162and the connected cam member154,155so as to vary the tilt position thereof. The selector member includes indicia910for indicating the setting or position of the tilt limiter. In particular, as shown in the preferred embodiment ofFIGS. 58-62, the selector member includes an intergrally formed substantially elongated flat portion910that extends laterally outward from and radially across the face of the selector member. The flat portion910has upper and lower concave surfaces and is grippable by a user for rotating the handle, pivot member and connected cam member. As shown inFIGS. 58-62, the angular orientation of the indicia910, or flat portion, provides the user with an indication of the setting or position of the tilt limiter.

For example, as shown inFIG. 58, a forward portion912of the indicia is angled downwardly, with a rear portion914angled upwardly, such that the angular orientation of the indicia substantially mirrors the relative position of the seat, the rearward tilting of which is being limited to a forward maximum rearward tilt position. As such, the selector member with its indicia provides the user with an indication that the tilt limiter is set at the forward tilt position such that the seat cannot be tilted rearwardly past the forward tilt position. As explained below, a forward bias device is actuated to permit the chair to be tilted into the forward bias position. The forward bias device, when used in combination with the tilt limiter positioned in the forward tilt position, allows the user to lock the seat and chair in the forward bias position such that it cannot be tilted rearwardly. It should be understood, however, that the forward bias device can be actuated without the tilt limiter being positioned in the forward tilt position.

Referring toFIG. 59, the indicia910is in a substantially horizontal position, which corresponds to the tilt limiter being in an upright or normal tilt position or setting. Again, the selector member with its indicia provides the user with an indication of the tilt limiter setting and informs the user that the seat cannot be tilted rearwardly past the upright tilt position. Although the seat is shown in the maximum rearward tilt position for this setting, which corresponds to the normal or upright tilt position, it should be understood that the user can tilt the seat forwardly, if permitted by a proper setting of the forward bias device, without affecting the position of the selector member or its indicia. Therefore, the user is apprised of the maximum available tilt position even when the seat is not located in that position.

Referring toFIGS. 60 and 61, the forward portion912of the indicia is now angled slightly upward with the rear portion914angled slightly downward so as to again mirror the maximum rearward tilt positions of the seat, which are shown as intermediate tilt positions. Again, the selector member with its indicia provides the user with an indication of the tilt limiter setting and informs the user that the seat cannot be tilted rearwardly past one of the intermediate tilt positions. As explained above, the selector member with its indicia performs this notice function even when the seat is located at some tilt position other than the maximum rearward tilt position.

Referring toFIG. 62, the indicia910provides the user with an indication of the tilt limiter setting and informs the user that the seat can be tilted rearwardly to its maximum reclined position.

The selector member with its indicia910provides a simple but ideal way to select the tilt position of the tilt limiter, and the corresponding maximum rearward tilt position of the seat, while simultaneously providing the user with an indication of the current maximum rearward tilt position of the seat. The user is informed of the maximum rearward tilt position of the seat even when the seat is in a tilt position other than the maximum rearward tilt position. For example, the selector member and tilt limiter can be set to the reclined position such that the indicia informs the user of that setting as shown in FIG.62. The selector with the indicia will remain in this position even as the user tilts forwardly to any of a forward, upright or intermediate position so as to continue to inform the user that he or she can tilt rearwardly to the reclined position.

Although the selector member has been shown as a handle, or knob, with the indicia providing a grippable portion of the handle, it should be understood that that selector member can be configured as any number of members including for example, but not limited to, a lever, dial, arm or gear. In addition, it should be understood that the indicia can take many forms other than the integrally formed and laterally extending raised portion described above. For example, the indicia can be comprised of various numerical or alphanumeric characters, words or color codes applied to or formed on a selector member or similar member Similarly, the selector member can be provided with any number of markings, including, but not limited to scales, grids and arrows, such that angular rotation thereof will provide the user with an indication of the corresponding position of the tilt limiter. The indicia, including any markings or etchings, can also comprise raised portions, indentations or applied materials, such as paint, or adhesive labels.

Although the preferred embodiment of the selector member with its grippable indicia has been shown as comprising the handle used to actuate the tilt limiter, it should be understood that the selector member can be separate from the handle, or similar actuator. In such an embodiment, the selector member is linked or connected to the tilt limiter or actuator so as to provide an indication of the tilt limiter setting.

As shown inFIGS. 16-19, a forward bias device172is rotatably mounted to the seat support20with a pair of C-shaped catches502and includes a rod174and a pair of cam members176. The housing includes two pairs of notches178,180shaped to receive the cam members along a top of each of the sidewalls62of the housing. In operation, as the user tilts rearwardly in the chair, as shown inFIGS. 16 and 17, the rod174is rotated such that the cam members176are pivoted forwardly so as to be substantially parallel with the seat support. As the user returns the seat to the upright position, the cam members are received in the upper notches178, which define the forward bias position of the chair. Alternatively, the user can rotate the rod174such that the cam members176angle downwardly from the seat support and are received in the lower notches180, which define the normal seating position of the chair.

Alternatively, a forward bias spacer can be mounted in the catches502as shown inFIGS. 6A and 15. The forward bias spacer includes an axle600connected to a laterally extending spacer member604, or flange, with an arm602. A rear portion of the arm extends rearwardly of the axle to act as a stop606such that the forward bias spacer cannot rotate about the axis of the axle. The spacer member604is positioned between the front wall of the housing and the bottom or the seat support and maintains the seat in the upright normal seating position. The forward bias spacer replaces the forward bias device when it is not desirable to have a chair that can be biased into the forward bias or tilt position.

Now referring toFIGS. 32-39, the back support30includes a pair of uprights200extending upwardly from the support arms50. A lower cross member202connects the support arms and an upper cross member204connects the upper portions of the uprights. Preferably, the back support30is one piece and is formed from a single piece of material. As shown inFIGS. 1 and 3, the back support is exoskeletal in nature and provides the user with a strong visual of support, security and durability.

Each upright200is preferably formed as a channel212as shown inFIGS. 32,35and36. Cover members640are snap fitted onto lower portions of the back support to cover the lower portion of the channel. For example, in one embodiment, a rib extends from the channel and a corresponding rib extends from the cover so as to be aligned with the rib of the backsupport. The ribs are connected with S-shaped clips.

A rack206, consisting of a plurality of laterally oriented notches208, is formed along an inner portion of the base portion210of the channel. As shown inFIGS. 1,2and36, a bar member220preferably configured as a cylindrical rod, is installed in each channel212in an overlying relationship with the rack206by mounting opposite ends of the bar to the base portion210of the channel.

In a preferred embodiment, the upper end222of the bar member is received in a groove226while the lower end224is bolted to a lug228formed in the channel. Bar member230, preferably having a flat rectangular cross-section, is mounted to the upright in a spaced apart and parallel relationship with bar member220by attaching opposite ends232,234of the bar member to lug portions236,238formed in the channel212.

As shown inFIGS. 36 and 39, opposite ends of bracket240are slideably mounted on each bar member220. As shown inFIG. 1, a backrest32, preferably including a cushion and an internal pan (not shown) is attached to the brackets240. The backrest32, and brackets, slide along the bar members220and are releasably secured to the uprights of the back support with a locking device.

In a preferred embodiment, shown inFIG. 36, the bracket includes an upper vertically oriented slot242on each side of the bracket and a lower slot244extending inwardly from the edge of the bracket and then downwardly along a vertical path. A pawl member246is disposed within the bracket and is pivotally mounted within the upper slot242with a pair of guide members248. A lower portion of the pawl member includes an engagement portion250adapted to engage the rack206and a pair of guide members252engaging the lower slot244. A spring254is disposed within the bracket so as to bias the pawl246and engagement member250toward the rack206. Preferably, either the pawl or the notches of the rack are tapered with a flat horizontal surface so as to allow the pawl to pass over the notches without engagement when traveling in the upward direction.

In operation, the backrest32is raised to a desired position where the engagement member250of the pawl246engages one of the notches in the rack. As the backrest is raised to its uppermost position, the guide members252engage a ramped guide rail256formed in the back support channel212. The guide rail256forces the lower guide members252forwardly in the slot244against the force of the spring254and then downwardly in the slot244as the upper guide members248are also moved downwardly within the slot242so as to lock the pawl member in a disengaged position away from the rack. The user can lower the backrest to a lowermost position wherein a stop member258engages the guide members252to move the pawl246upwardly within the slots244,242until the spring254biases the pawl forwardly into engagement with the rack, wherein the backrest can again be raised to the desired position. In this way a simple device is provided for adjusting the backrest without a multiplicity of moving parts and levers.

In an alternative embodiment, the pawl is simply pivotally connected to the bracket, without the additional slots that allow for vertical travel. The pawl is biased into engagement with the rack by the spring disposed between the bracket and the pawl. A paddle, similar to the one shown inFIG. 44, extends inwardly from the pawl so as to be exposed to the user adjacent the upright. The paddle can be actuated by the user in opposition to the spring so as to disengage the pawl wherein the backrest can be raised or lowered to the desired position.

A similar device is shown inFIGS. 44-45. Since this embodiment of the backrest support structure is similar to previously described embodiments, similar parts appearing inFIGS. 44 and 45are represented by the same reference numbers. As shown in the alternative embodiment ofFIGS. 44 and 45, a lever260including a handle262, or paddle, and a nose portion264is pivotally attached to a bracket266. The handle262extends laterally inward from the upright200and is exposed to the user adjacent the upright. The nose portion264engages one of the notches of the rack. A spring268biases the handle262and lever rearwardly to maintain operable engagement between the nose portion264and the rack. To adjust the height of the backrest32, the user pivots the handles and lever forwardly to disengage the nose portion from the rack and thereafter slides the backrest to the desired position. In a preferred embodiment, the lever is biased against the neck with a spring. The lever is then released so that the nose portion engages the rack once again. Preferably, the nose portion and cooperating notches in the rack are tapered upwardly such that the backrest can be moved upwardly without moving the handle and lever. For upward adjustment, the user simply lifts the backrest such that the nose portion rides over the notches until the desired height is reached.

In yet another alternative embodiment shown inFIGS. 53-55, the upright includes a longitudinal groove270. A rack272is formed in the upright adjacent to and in parallel relationship with the groove. A spline member274has a base portion276and a tongue member278extending rearwardly from the base portion and terminating in a hook portion280. The tongue member278if inserted in the groove270such that the hook portion280engages an inner track282opening into and communicating with the groove. Once the tongue and hook member are engaged in the groove and track, a plate member284is inserted and snapped into place between the tongue278and a surface of the groove so as to securely mount the spline274to the upright in a sliding relationship. A latch member286is installed in a recess288formed in the base portion276and includes a inwardly extending lever290accessible to the user adjacent the upright. A nose portion292of the latch member engages the notches in the rack. A spring294is installed between the latch member and the backrest, which is mounted on the base portion, to bias the nose portion into engagement with the rack. The latch member286is retained in the recess of the base portion by the back portion and spring. In operation, the backrest can be adjusted as described above. In this embodiment, the armrests are shown as being fixedly attached to the housing, but it should be understood that they can be made height adjustable as explained below.

Since the backrest is supported on opposite sides of the chair, it does not need to be structural in nature, and can be made at less expense and with more tolerance at the interface of the backrest and uprights. Moreover, the load imparted by a user against the side of the backrest can be transmitted directly through the forwardly extending arms of the back support to the housing and spring member so as to provide better support for the user. Additionally, the lever for releasably locking the backrest is preferably located adjacent the uprights at the side of the chair, and is therefore easily accessed by the user.

In addition, the backrest32covers the channel212bin the upright so as to conceal the bar members220,230, the backrest bracket240and the armrest base portion302having the locking device disposed therein. In this way, the chair is provided with an exoskeleton backrest support, but with the sliding and locking parts concealed from the user so as to provide an aesthetically pleasing appearance.

Another feature of the improved chair is the adjustable armrest300shown inFIG. 37, which is slideably mounted on bar member230. Each armrest300includes a base portion302and an arm portion304extending forwardly from the base portion. Preferably, pads306are installed on an intermediate support307which are then mounted on an upper surface of the arm portion. A cavity308is formed internally in the base portion. An upper and lower opening communicate with the cavity and are shaped to receive bar member230. A locking device310, including a latch member312, is disposed in the cavity and releasably engages a rack314consisting of a plurality of notches formed in a front surface316of the bar member. Preferably, as shown inFIG. 40A, the cavity308has front wall318which forms an oblique angle with the front surface316of the bar member which passes through the cavity. Likewise, the latch member312is configured as a wedge-shaped member having opposite surfaces322,324forming an oblique angle with each other. The latch member also includes a protuberance320, or tooth, extending rearwardly from the rear surface322.

In an alternative embodiment shown inFIG. 37A and 40, a cap700, preferably metal, is mounted to the top of the base portion with a fastener702. The base portion includes a raised boss701on which the cap is disposed. The cap has an opening704shaped to receive the bar member. The cap member is preferably formed with a slightly smaller opening than the upper opening in the base portion so that the metal cap member absorbs the loading from the arm. The boss701and the fastener702then transmit the load into the base portion of the armrest.

By providing uprights along opposite sides of the chair, the armrests can be conveniently attached to the uprights, rather than being supported by separate supports extending from the base or housing of the chair. In this way, the armrests can be firmly attached in a simple way at less cost.

In operation, the wedge-shaped latch member312is disposed in the cavity such that the rear surface322abuts the front surface316of the bar member and such that the protuberance320is received within one of the notches of the rack. The front oblique surface324abuts the front wall of the cavity318. The latch member includes a downwardly extending trigger member820having an outwardly extending flange member338. The wedge shaped latch member biases or wedges the base portion against the rear surface326of the bar member so as to tightly secure the armrest to the upright and thereby provide a firm support for the user's arm. A guide member328is mounted within the cavity in the base portion and engages a bottom surface330of the cavity. A spring332is inserted between the guide member328and the wedge-shaped latch member312to bias the latch member upwardly against the armrest and against the bar member.

As shown inFIG. 37, a lever member334is pivotally mounted to the bottom of the armrest and includes an end336operably engaging an outwardly extending flange338of the latch member312. Alternatively, as shown inFIG. 37A, a U-shaped clip810is disposed over the lever and engages the armrest to secure the lever in the armrest such that it pivots about a fulcrum in the armrest. The lever member preferably includes a cantilevered spring portion337that engages a surface in the arm to bias outwardly a button portion340of the lever that is exposed to the user.

To adjust the armrest, the user pushes end340of the lever member so as to pivot the opposite end336while simultaneously lifting the armrest. In this way, the end336of the lever acts on the flange338of the latch member to pull it down against the force of the spring332. As the arm is moved relative to the latch member, the latch member slides along the front wall318of the base portion such that the protuberance, or tooth, disengages from the rack in the bar member. When the latch member is disengaged, the user can move the armrest to the desired position. The user can thereafter release the lever and armrest to reengage the bar member by engaging the rack with the protuberance or tooth. As with the backrest, the armrest can be moved upwardly without actuating the lever, since the upward movement naturally allows the latch member to disengage from the bar as it slides downwardly within the cavity.

As shown inFIG. 43, an alternative embodiment of the locking device includes a wedge shaped latch member344disposed in the cavity, but without a protuberance or corresponding rack on the bar member, although it should be understood that such aspects could be incorporated into the device. Parts similar to those described above are represented by the same reference number for the sake of simplicity. A spring332is disposed in the cavity308between a bottom wall330of the cavity and a bottom surface342of the latch member. A lever346extends upwardly from the wedge shaped member through the upper opening in the base section so to be exposed to the user. In operation, the user pushes the lever downwardly against the force of the spring while lifting the armrest to thereby relieve the frictional forces acting between the armrest, latch member and bar member. The armrest can then be moved to the desired position where the lever is then released, the spring acting on the latch member to force it once again into frictional engagement between the armrest and bar member. In such an embodiment, the armrest is provided with infinite adjustment capability.

In yet another alternative embodiment shown inFIG. 46, a rack348is formed along a rear surface of the bar member and the base portion includes a integrally formed nose portion350shaped to be received within the rack. As with the backrest, the nose portion350and rack348are preferably tapered in an upward direction. A spring352and button354are installed in a top portion of the base and engage a front surface of the bar member. Alternatively, it should be understood that a leaf spring could be substituted for the spring and button. In operation, the user simply lifts up on the arm portion of the armrest in opposition to the force of the spring so as to disengage the nose portion. The armrest is then moved to the desired position and released such that the nose portion engages a notch in the rack.

Referring now toFIGS. 47-49, various embodiments of a locking device are shown as having a rack356formed in the base portion of the upright, again with upwardly tapered notches. The armrest includes either a nose portion358integrally formed in the base portion,FIG. 48, a first pin360attached to the base portion and engaging the rack and a second pin362trapped in a track364formed between the bar and the upright channel,FIG. 49, or a latch member366having a nose portion368,FIG. 47, which engages the rack. The device ofFIG. 48also includes a button370and spring372to bias the armrest into engagement. Again, it should be understood that a leaf spring could also work in place of the button and spring. The device ofFIG. 47includes a button374having a wedge shaped surface376that engages a cooperating wedge shaped surface378on the latch member366. The button is actuated to force the latch member forwardly against the force of a spring as the wedge shaped surfaces slide over each other and thereby disengages the nose portion from the rack. A similar device is shown inFIG. 56, but with the rack located on the bar member.

In yet another alternative embodiment shown inFIG. 50, a pivot member380is pivotally mounted to the base portion of the armrest. The pivot member includes a nose portion382shaped to engage a rack384located on the bar member. A cable386is connected to the pivot member. In operation, the user actuates the cable to pivot the pivot member into and out of engagement with the rack. Alternatively, the pivot member can be directly actuated, or pivoted, by hand without a cable. It is preferable to apply the lifting force to the armrest adjacent or proximate the bar member so as to reduce the binding force between the base portion and the bar member. When applying the lifting force at the forward portion of the arm distal of the bar member, low friction bearing surfaces applied to one or more of the armrest and/or bar member can facilitate the adjustment operation.

In yet another embodiment shown inFIG. 52, the armrest includes a pair of pins which ride in a slot394formed in the upright. The upper pin390engages a rack388formed in the upright. In operation, the armrest is lifted upwardly to disengage the upper pin. The armrest is then moved to the desired position where it is released so that the upper pin once again engages the rack.

In yet another embodiment shown inFIG. 51, a laterally extending pin396is mounted to the upright. The base portion of the armrest includes a pivot member398having a rack400formed in a rear surface thereof. The pivot member398is pivoted forwardly against the biasing force of a spring402mounted in the base portion to release the rack from the pin after which the armrest can be moved to the desired position. The pivot member is then released such that the spring462biases the pivot member398and rack into engagement with the pin.

Although a number of alternative embodiments of the locking mechanism for the armrest have been shown and described, it should be understood by one of skill in the art that various combinations of racks, wedges, levers and/or springs not specifically described herein would also work.

Although the present invention has been described with reference to preferred embodiments, those skilled in the ant will recognize that changes may be