Patent Abstract:
A chair having a synchronously moving seat bottom and seat back includes a frame having a seat bottom support portion and a seatback support portion and a seat assembly having a seat bottom and a seat back interconnected by a flexible intermediate portion. The seat bottom is slidably mounted to side support members in the bottom frame providing forward and aft movement of the seat bottom. The seat back is pivotably engaged to the seat back support portion of the frame. The flexible intermediate portion provides for cooperative movement of the seat bottom and seat back between an upright seating position and a reclined position. Preferably, the seat assembly is a one piece molded plastic shell having a flexible intermediate portion interconnecting the seat bottom and seat back. In one embodiment of the invention, the chair can be provided with legs to enable stacking of the chairs.

Full Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of seating and in particular to a chair in which the seat and seat back move in concert to provide a reclining position for the user. 
     BACKGROUND OF THE INVENTION 
     There is an ever-present need for economical and temporary seating space that is typically satisfied by the provision of low cost stackable chairs. The use of low to moderate cost stacking chairs is well known in the art. However, such chairs are designed not with comfort or ergonomics in mind, but rather to provide a large quantity of temporary seats for occasional use, which can ordinarily be stored and take up minimal storage space. 
     Recent years have brought a growing interest in the development of such chairs based on ergonomic designs intended to promote a sitting posture with a maximum of comfort. One aspect of comfort is the ability to adjust the back of the chair to suit the user. Unfortunately, most stacking chairs do not provide any adjustment capabilities and the ones that do merely provide limited flexibility in the seat back portion with little ergonomic benefit. On the other hand, home and office chairs have been produced in a variety of ergonomic designs that have mechanisms for moving the backs of the chairs into a reclining position. 
     Chairs featuring the ability to adjust for certain preferences of the user relating to seat height, reclining range, and the like are also well known in the art. These features are accompanied by complexity of manufacture and require the use of expensive and complicated mechanisms that are cumbersome or awkward to adjust and may be subject to malfunction. Such chairs are not suitable for stacking nor use for temporary seating. 
     In the prior art, U.S. Pat. No. 5,944,382 to Ambasz features a chair providing movement of both the seat and seat back. The Ambasz chair features a slideable seat and also a moveable seat back. There is a separate lumbar section between the seat bottom and the seat back making a three-part seat assembly. The seat bottom has a pair of sockets that fit over seat supporting portions of the seat frame to allow the seat bottom to slide forward and aft. The seat back slides up and down and also tilts to the rear to recline. The seat back is mounted on an articulated linkage that includes springs between the seat back and the upper portion of the linkage to bias the seat back in the upward position. Bellows members connect the seat bottom and the lumbar section and the seat back together. The Ambasz design typifies the complexity and expense of most ergonomic chair designs. Moreover, the Ambasz chair does not lend itself to stacking for storage. 
     One attempt to marry ergonomics with economics is shown in U.S. Pat. No. RE36,335 to Perry, which discloses a chair having a flexible frame to achieve partial reclining of the seat back. The seat back interconnects the ends of a continuous chair frame with one end projecting upward from the rear legs to the seat back and the other projecting upward from the rear of the seat to the seat back. This two-point connection to the seat back along with curved frame members through the seat back allows limited pivoting of the seat back and also limits pivoting of the seat back. The chair is stackable but of limited comfort, lacking the natural feel provided in a chair having coordinated movement between the seat and seat back. 
     A need has remained for a chair combining the benefits ergonomic design in a low cost and stackable chair. 
     SUMMARY OF THE INVENTION 
     Briefly describing one aspect of the invention, a chair featuring a movable seat bottom and seat back is provided. The seat bottom and seat back move in concert between an upright position and a reclined position. The chair includes a frame having a seat bottom support portion and a seat back support portion. In one embodiment, the seat bottom support portion includes a pair of side support members on which the seat bottom is slidably supported. The seat back support portion includes a transverse member to which the seat back is pivotably connected. In one aspect of the invention, this pivotable connection can be accomplished by a plurality of hooks that are preferably molded into the seat back. 
     The seat bottom and seat back are connected to each other in a manner that allows the seat bottom to slide forward and the seat back to recline in response to the natural forward movement of the seated user&#39;s pelvis along with pressure on the seat back from the user. With this feature, the pivotable connection of the seat back to the support frame allows the frame to act as a fulcrum. Specifically, as force is applied to an upper portion of the seat back, the back pivots about the frame, thereby exerting a force on the seat bottom, causing the bottom to slide along the seat bottom support. 
     In a preferred embodiment, the seat bottom and seat back are most preferably a one-piece molded plastic shell having a resilient intermediate portion interconnecting the seat bottom and seat back. The intermediate portion operates primarily as a deformable and resilient hinge. Secondarily, the resilient intermediate portion can act as a force transmitting element that translates the pivoting movement of the seat back into a fore and aft force on the seat bottom. The natural characteristics of the plastic shell causes it to rebound to the original position without the use of any mechanical devices as the user brings herself back to the non-reclined position or rises out of the chair. 
     In certain features, the resilient intermediate portion forms a slack region that exhibits a first curvature when the seat is in an original, non-reclined orientation. When the user reclines, the seat back pivots, the seat bottom slides, and the intermediate slack region deforms to a different second curvature. The resilient intermediate region is configured to allow the user to easily recline the seat by leaning back against the pivotable seat back, while the seat back maintains support for the user&#39;s back at any angle of recline. 
     The invention further contemplates the use of rail members and slide blocks to effect sliding of the seat bottom. In one preferred aspect, the upper portions of multiple slide blocks are integral with the underside of the seat bottom. Lower portions of the slide blocks can be combined to form a channel slidably surrounding a corresponding one of the rail members. Stops can be provided at opposite ends of the rail members to limit the fore and aft movement of the seat bottom relative to the seat frame. 
     In one embodiment of the invention, the chair is provided with legs configured to facilitate stacking, while still retaining the pivoting seat back and sliding seat bottom features. In an alternative embodiment, the chair can be provided with a castered pedestal base for ease of movement. Similarly, the chair can be provided with or without arms. In certain armchair versions, the arms project from the back frame at a slight outward angle and with a slight curvature to provide a comfortable seating experience for the user. 
     Accordingly, it is one object of the invention to provide an ergonomic chair of relatively simple construction, without mechanical springs or lever devices, and at a reasonable cost. Another object is achieved by features of the invention that allow a user to easily recline the chair while the seat back maintains support for the user&#39;s back. 
     Another object of the invention is to provide a chair with a one-piece molded shell that can be not only reclined, but also easily stacked when not in use. These and other objects, advantages and features are accomplished according to the devices and assemblies, and methods of the present invention. 
    
    
     DESCRIPTION OF THE FIGURES 
     FIG. 1 is a front perspective view of a chair according to one embodiment of the present invention. 
     FIG. 2 is a side perspective view of a chair frame for use with the embodiment of the inventive chair depicted in FIG.  1 . 
     FIG. 3 is a top elevational view of the chair frame shown in FIG.  2 . 
     FIG. 4 is a back elevational view of two chairs according to the present invention depicted in a stacked arrangement for storage. 
     FIG. 5 is a side elevational view of the chair shown in FIG.  1 . 
     FIG. 6 is a rear elevational view of the chair shown in FIG.  1 . 
     FIG. 7 is a side elevational view of a chair according to an alternative embodiment of the present invention. 
     FIG. 8 is a rear elevational view of the chair shown in FIG.  6 . 
     FIG. 9 is a bottom perspective view of a chair, such as the chair depicted in FIG. 1, showing the attachment of the seat bottom to the bottom frame according to one aspect of the invention. 
     FIG. 10 is an exploded view of a slide block assembly according to one embodiment of the invention for use in the attachment depicted in FIG.  8 . 
     FIG. 11 is a front perspective view of an armchair according to one embodiment of the present invention. 
     FIG. 12 is a top perspective view of the chair shown in FIG.  11 . 
     FIG. 13 is a front perspective view of a chair including armrests and a castered pedestal base according to another embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. The invention includes any alterations and further modifications in the illustrated devices and described methods and further applications of the principles of the invention that would normally occur to one skilled in the art to which the invention relates. 
     The present invention provides a chair with a synchronously moving seat and seat back. The seat slides forward as the seat back tilts rearward to provide a reclined seating position in response to the natural forward movement of the seated user&#39;s pelvis along with the user leaning against the seat back. The resilience of the seat allows it to return to an upright seating position when the pressure on the seat back is removed. 
     Referring to the drawings, a chair  10  in accordance with one embodiment of the invention is illustrated in FIG.  1 . The chair  10  includes a seat assembly  11  and a frame  12 . Frame  12 , which is preferably of a metal construction such as steel, is shown in detail in FIGS. 2-3. Frame  12  includes a seat bottom support member or portion  20 , and a seat back support member or portion  16 . Seat bottom support  20  includes front and rear transverse members  22 A and  22 B respectively, and a pair of frame rails or side support members  24 . Preferably, side support members  24  are the primary elements supporting the seat bottom  32  when the seat assembly  11  is mounted on the frame  12 . Preferably, the elements of the frame  12  are of tubular construction, most particularly the frame rails or side support members  24 . 
     Seat back support portion  16  includes a pair of upright support members  17 , and a transverse support element  18  that interconnects the upper ends  19 A,  19 B of the upright support members  17 . Transverse support element  18  is preferably positioned at approximately the center of the seat back when the seat assembly  11  is in place on the frame  12 . As shown more clearly in FIG. 3, transverse support element  18  has a center portion  18 A that is displaced rearwardly from the upright support elements  17  in this embodiment. Right and left end sections,  18 B and  18 C extend at an angle α forward and also slightly upward from center section  18 A to connect to the upright support elements  17  and to maintain contact with shell hook members described herein. End sections  18 B and  18 C also angle forward to accommodate a curvature or concavity of the seat back  34 . 
     In one embodiment of the invention, as depicted in FIGS. 2 and 3, the chair is supported by front legs  13  and rear legs  15 . Preferably, front legs  13  project slightly forward and outwardly from seat bottom support portion  20 , while rear legs  15  project slightly outward and rearwardly from seat back support portion  16 . In this particular embodiment, each rear leg  15  is connected to the corresponding front leg  13  with a ground-engaging component or floor member  14  in a sled configuration. In this embodiment, each floor member  14  is integral with the corresponding rear member  15  and is welded at a weld point  14 A to the corresponding front leg  13 . 
     These features provide stability to the chair while in use and also allow the chair to be stacked when not in use. In one embodiment, the configuration of the legs  13  and  15  allows the chair  10  to be stacked with other similar chairs to facilitate storage, as depicted in FIG.  4 . In this embodiment, the seat assembly  11 , and particularly the seat bottom  32  has a width, and the legs  13  and  15  are flared outwardly to a width greater than the width of the seat bottom to allow the chairs to be stacked. 
     For certain features of the invention, the configurations of the legs  12 ,  13  and floor member  14  are not critical and any suitable design is contemplated. Other suitable configurations include, but are not limited to, four-leg, cantilever and caster-based styles. 
     Returning now to FIG. 1, seat assembly  11  includes a seat bottom  32  and a seat back  34 . In accordance with beneficial features of the invention, seat bottom  32  is slidably engaged to frame rails  24 , while seat back  34  is pivotably supported by the transverse support element  18 . Most preferably, the seat back  34  is supported at the center section  18 A of transverse support element  18  with a plurality of connectors. The seat back  34  is positioned relative to the transverse support element  18  so that an upper portion  34 A of the seat back is situated above the support element. In this way, the user can apply pressure or force against the upper portion  34 A to recline the chair  10 , with the support element  18  acting as a fulcrum. 
     FIG. 3 shows a preferred angular configuration of transverse support member  18 . This geometry accommodates a concave curvature in the seat back  34 , which provides comfort for the user throughout the entire range of movement of the chair. In particular, the center section  18 A is supported by left and right sections  18 B and  18 C. FIGS. 3,  5  and  6  show the upward projection of the right and left sections  18 B and  18 C of transverse support element  18 . 
     In a preferred embodiment, the seat back  34  is pivotably supported on the support element  18  by way of a number of connectors  42  that engage the support element. In a preferred embodiment, these connectors are hooks  42 A and  42 B attached to the seat back  34  as shown in FIGS. 5 and 6. Most preferably, hooks  42 A and  42 B also are formed with stiffening ribs  42 C to add stiffness to seat back  34 . Stiffening ribs  42 C also blend hooks  42 A and  42 B into seat back  34  for a more aesthetic effect to the rear side of seat back  34 . 
     Center section  18 A of transverse support element  18  is a pivot axis or fulcrum about which seat back  34  can pivot or rotate to and from a reclined seating position. The hooks or connectors  42  attaching seat back  34  to the transverse support element  18  are preferably of two types. Referring to FIG. 6, hooks  42 A engage the center section  18 A with a snap-fit to limit the motion of seat back  34  to that of rotation relative to this section of transverse support element  18 . The snap-fit hooks  42 A thus help retain the seat back  32 , and ultimately the entire seat assembly  11 , engaged to the chair frame  12 . The second type of hooks, hooks  42 B supported on the angled portions  18 B and  18 C of the transverse support element  18  preferably do not clamp or snap-fit to the transverse support element  18 . Most preferably, hooks  42 B are provided with clearance to move relative to transverse support element  18  as seat back  34  rotates. 
     In accordance with certain features of the present invention, any suitable connector  42  is contemplated so long as the transverse element  18  is freely rotatable to ensure smooth movement of the chair. For instance, in an alternative embodiment, hooks  42 A could be replaced by mounting pad  40  mounted on seat back  34 ′, as depicted in FIGS. 7 and 8. The mounting pad  40  defines a recess  37  configured for snap-fits onto center section  18 A. Mounting pad  40  is preferably integral with seat back  34 ′ and can be used either alone or in combination with hooks  42 B on sections  18 B and  18 C of transverse support element  18 . 
     Referring again to FIGS. 5 and 6, seat back  34  can include a lip  35  that wraps around the upper ends  19 A,  19 B of upright support members  17  to prevent any lateral movement of the seat back relative to the frame. In addition, the peripheral lip  35  adds stiffness to the seat back  34 , particularly when the seat assembly  11  is in the form of a molded shell. 
     Seat assembly  14  preferably includes a resilient intermediate portion  46  which provides hinge movement, as shown most clearly in FIGS. 1,  5  and  7 . Intermediate portion  46  interconnects seat bottom  32  and seat back  34  and links relative movement between seat bottom  32  and seat back  34 . In a preferred embodiment, intermediate portion  46  includes an upper region  47  connected to the bottom portion  34 B of seat back  34 , and a slack region  48  connected to seat bottom  32 . Upper region  47  preferably exhibits a curvature that provides lumbar support to the user in both reclined and upright seating positions. Slack region  48 , also referred to as a rebound section, exhibits a slight rearwardly curved projection that provides slack in the seat material. This slack is taken up as the seat bottom  32  slides forward on the rails  24 , without being lifted from the seat frame  20 . Referring specifically to FIG. 5, the intermediate portion  46  is resiliently deformable and exhibits a first curvature in an original position of the slack region  48 . As the seat is reclined, the intermediate portion deforms to a different second curvature, as the slack portion is slightly flattened out. 
     As shown most clearly in FIG. 6, intermediate portion  46  preferably has a nominal width W 2  that is less than the width W 1  of seat back  34 . This reduced width is most advantageous when the seat back  34  has a concave curvature to provide adequate clearance for a person sitting in the chair. Of course, the relationship between the two widths is not critical, and W 2  may equal or exceed W 1 . 
     Preferably, seat assembly  14  will be composed of a resilient material at intermediate portion  46 . Most preferably, seat assembly  14  is a one-piece shell made from a resilient material, such as polypropylene or other similar materials. However, it is important that the intermediate portion be able to withstand repeated flexing or deformation as the seat is reclined and then returned to its upright position. Most preferably, the intermediate portion  46  is not only resilient, but also sufficiently stiff to transmit force, generated by the pivoting movement of the seat back  34  to the seat bottom  32 . This transmitted force can assist the sliding movement of the seat bottom along the frame  12  and assist the return of the seat bottom to its original non-reclined position. 
     Seat assembly  11  preferably includes at least one slide block  38  connecting seat bottom  32  to frame rails  24 , as shown in FIGS. 5,  9  and  10 . One version of slide block  38  is shown in detail in FIG.  10 . Slide block  38  has an upper portion  52  connected to a lower surface  32 A of seat bottom  32  (FIG. 9) and a lower portion  54 . Suitable fasteners such as screws  57  connect these two portions  52 ,  54  via threaded holes. In this particular embodiment, lower portion  54  can define a pair of through-holes  54 A for inserting screws  57  to engage corresponding holes (not shown) in upper portion  52 . The corresponding holes can be, for example, threaded or self-threading. 
     Each portion  52 ,  54  of the slide block  38  defines a channel  58  or upper and lower portions of a bore configured to receive a frame rail member  24 . In a preferred embodiment, each half of the slide block  52 ,  54  also includes a self-lubricating bushing  56  inserted into channels  58 . The shape of bushings  56  correspond to that of channels  58 . Bushings  56  provide bearing surfaces  60  to reduce friction as the seat bottom  32  slides along the side support members  24 . In one particular embodiment, tabs  55  projecting from bushings  56  are receivable in corresponding slots  59  in the slide block upper and lower portions  52 ,  54  to lock the bushings  56  in position. Tabs  55  are preferably positioned to form an angle of less than about 90°, with a most preferred angle of about 45°. Bushings  56  are preferably made of a material such as polyamide resin, which is preferably harder than the material of the chair seat assembly  11  or the slide block  38  bodies. 
     In a preferred embodiment, the upper portion  52  of the slide block  38  can be made integral with the lower surface  32 A of seat bottom  32 . In this embodiment, the side support members or rail members  24  are parallel to each other and extend forward and aft in the direction of motion of seat bottom  32 . Also, in a preferred embodiment of the invention, two such slide blocks are used on each side support member. It is contemplated that a suitable number of slide blocks will be used as required for the smooth operation and stability of the chair. 
     Referring now to FIGS. 2 and 9, each side support member or rail  24  preferably includes a pair of stops  26 A,  26 B for limiting the travel of the seat assembly  11 . Front stops  26 A limit forward travel, while rear stops  26 B limit rearward movement and help define the original non-reclined position of the seat bottom  32 . In this particular embodiment, front stops  26 A are provided on a bottom surface of the frame rails  24 , away from the underside of the seat bottom. On the other hand, back stops  26 B project from the top surface of the rails  24 , adjacent or facing the underside of the seat bottom. It has been determined through testing that the chairs of this invention, with the stops configured in this manner, can have a greater resistance to damage from impact when the chair is dropped. However, stops can be provided on any suitable surface of the frame rails  24 . Alternatively, front and rear transverse members  22 A and  22 B can perform this limiting function. 
     Referring again to FIG. 9, seat bottom  32  also preferably includes reinforcement or stiffening ribs  39 . Ribs  39  can be molded into seat bottom  32  to add strength to the front portion of seat bottom  32 , particularly when the seat is reclined. In the preferred embodiment, the seat bottom is configured so that a portion is cantilevered over the support frame  12 . The ribs  32  project into this cantilevered portion, adding stiffness and allowing the amount of front overhang of seat bottom  32  relative to front transverse member  22 A to be increased. Moreover, the ribs  32  extend inboard of the seat bottom for sliding support on the frame  12 , and most particularly the front transverse member  22 A. 
     Numerous variations of the invention are contemplated. For instance, the frame rail or side support members  24  can be non-parallel, in which case a channel would be provided in the seat bottom to allow for lateral movement of the slide blocks in response to the divergence of the side support members. Alternatively, the slide block could be modified to include a slot wide enough to accommodate the divergence of the side support members. 
     In another version of the invention, the side support members could comprise a slotted structure configured to receive a pin attached to the underside of the seat bottom. The slots in the side support members can then act as a channel within which the pin travels as the seat slides back and forth. The length of the channels could determine the extent of motion provided to the seat bottom. Here again, if the side members are not parallel to each other, the seat bottom could include a transverse slot for each pin to allow lateral movement of the pin relative to the seat bottom to accommodate the lateral motion introduced by the non-parallel side support members. 
     Referring again to FIG. 5, in use, the seat back  34  reclines as the seat bottom  32  extends in response to a user leaning back against seat back  34  and the natural forward movement of the user&#39;s pelvis. The extension of seat bottom  32  and the rotation of seat back  34  causes deformation of the intermediate portion  46  from its original configuration, thereby placing this portion in tension. This tension in intermediate portion  46  causes the seat to return to its upright position when unoccupied or when the user of the chair removes pressure from the seat back  34 . The resilience of the seat  11  causes it to rebound to the original position without the use of any mechanical devices. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It should be understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. For example, arms  64  can be provided to produce an armchair as in FIGS. 11 and 12. As shown in FIG. 12, arms  64  preferably flare slightly outward and exhibit a slight inward curvature to provide a more natural and more comfortable seating position. In addition, these features more comfortably accommodate the larger user and allow for the free movement from side to side. In yet another version of the invention, the seat bottom frame can be mounted on a pedestal base  66  as in FIG. 13, which includes castors  68  for ease in moving the chair. 
     This invention presents an aesthetically pleasing ergonomic chair of simplified design. The simplified design allows the chair to be produced at a reasonable cost. The stackable feature allows the chair to be stored within a minimum of space when not in use. It should be noted however, that the user does not have to change his position relative to the seat bottom of the chair in order to move the chair from an upright to a recline position. The user need only relax and lean back against the seat back. Thus the seating position can be changed without undue ruffling and disturbance of clothing. This provides a further benefit in embodiments in which the chair is upholstered because the movement of the user in the chair does not cause wear on the upholstery. One of the most important features of this invention is that the chair remains comfortable to the user even after long periods of time due to its ability to respond when the user changes seating position. The user merely sits back, and the chair knows what to do.

Technology Classification (CPC): 0