Abstract:
Disclosed is a chair containing a flexible back support frame mechanism that includes an improved spring assembly designed to allow reclining movement of a back support frame relative to a seat assembly. The spring can assembly of the present invention is, preferably, carried by a rear cross support member thereby eliminating the need for cumbersome elongated springs and their attendant support members. Further, the spring can assembly of the present invention allows the compression member to be readily and easily changed, thus providing the ability to easily adjust the flex tension of the back support member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates generally to the field of seating and chairs including moveable and stackable seating. More specifically, this invention relates to stackable chairs having a flexible back support with an improved spring assembly. 
     2. Description of the Related Art 
     Prior chairs having a flexible backrest frame have provided frame members with spring members connected internal of seat tube members for control of movement of the backrest frame of the chair. A typical flexible backrest is illustrated in U.S. Pat. No. 5,039,163, issued to Tolleson, which discloses a chair including depending leg members and a hollow support frame having members with open ends terminating beneath the seat assembly of the chair. The chair includes a pair of hollow backrest frame members having open frame ends extending beneath the seat assembly for alignment with respective open ends of the support frame members. Each open end of the respective frame members includes at least one flexible spring member inserted therein. Prior configurations of spring members allow insertion of opposed spring member ends into opposed and aligned open frame ends, with each spring member being aligned with the frame ends and extended to fill any gap between the respective back frame members and support frame members. Therefore, replacement of the spring member required full disassembly of the chair frame and removal of each inserted spring member end. In order to prevent each spring element from excessive flexing during reclining movements of the chair backrest, the spring member ends have been typically enclosed by pairs of U-shaped brackets of metal that limit the range of angular movement of each enclosed spring member, thereby limiting the reclining movements of the chair backrest. Additional pairs of spring members and U-shaped brackets have been required to be added for rigorous use. The additional pairs of spring members are typically positioned parallel to each first set of spring members with associated enclosure by U-shaped brackets of greater width or depth, thereby requiring an increased width or depth of the support frame members to accommodate the additional spring members and brackets. 
     Another example of a prior art chair having a flexible backrest frame is illustrated in U.S. Pat. No. 6,896,327, issued to Barile, which discloses a stackable chair with a seat assembly and flexible back support having a seat spring system attached there between. The seat assembly includes seat sides having spaced apart rear portions. The back support includes lower ends curved forwardly and disposed in registry with and separated by right and left gaps from respective seat side rear portions. Right and left spring members are disposed inwardly adjacent to bridge each gap. Each spring member includes forward ends connected to respective right and left front support members extended inbound from respective seat sides, and includes rear ends connected to opposed ends of a frame rear cross-member. The spring members allow limited reclining movement of the back frame. A limit to excessive forward movement of the back support is provided by pairs of fixation plates positioned in aligned and abutting relationship on upper surfaces of each respective forward and rear ends of each spring member. 
     The prior art leaf springs are securely fastened to the frame of the chair making replacement of the spring difficult and labor intensive. What is missing from the art is a stackable chair with a flexible back support frame employing a spring assembly attached directly to the rear cross support member of the seat assembly that allows for easily replacing the spring, or compression, member allowing for ease of adjustment of flex tension, thus eliminating elongated, or leaf, spring members and their attendant support members. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides an improved spring assembly for a chair frame for a stackable chair having a flexible back member. While described herein in terms of a stackable chair, it will be appreciated that the present invention has utility with non-stackable chairs as well. The chair frame comprises a seat support portion for supporting a chair seat, and a pair of leg assemblies oppositely disposed on either side of the seat support portion. Each leg assembly includes a front leg and a rear leg, and an upper support member. Each leg assembly also includes a stacking bar extending between the front leg and the rear leg, the stacking bar being disposed below, and being selectively spaced from the upper support member. The stacking bar of each leg assembly has a lower surface configured to closely engage at least a portion of the upper surface of the upper support member of another chair frame of the present invention to facilitate the stacking of the chair frame on such other chair frame. 
     The back support frame includes frame lower ends curved forwardly and positioned in registry with and spaced apart by a gap separation from the rear portions of the seat assembly. Right and left spring can assemblies are carried by the rear cross support member. This improved spring can assembly dispenses with the need for the prior art elongated springs and their attendant support components that were previously required. 
     During reclining movement of the back support frame, the back support frame member compresses the compression member downwardly to a compressed position. When reclining pressure is released from the back support frame member, the spring member biases the back support frame member to a non-reclined position, thereby returning the back support to a substantially upright position when not reclined by a seat occupant. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and additional features of the invention will become more clearly understood from the following detailed description of the invention read together with the drawings in which: 
         FIG. 1  illustrates a perspective view of a chair constructed in accordance with the present invention. 
         FIGS. 2A and 2B  illustrate a partial rear elevation view of the chair illustrated in  FIG. 1 . 
         FIG. 3  illustrates an exploded view of the plunger, compression member, and plunger of the present invention. In  FIGS. 3A and 3B , the compression member is illustrated as a helical coil spring. In  FIG. 3C , the compression member is illustrated as a crest-to-crest wave spring. 
         FIGS. 4A and 4B  illustrates the hinge member of the present invention;  FIG. 4A  is an assembled perspective view; while  FIG. 4B  is an exploded perspective view. 
         FIG. 5  is a partial perspective view of the chair illustrated in  FIG. 1 . 
         FIGS. 6A, 6B and 6C  are partial elevation views showing the interaction of the back frame member and the spring assembly during assembly of the chair and during reclining of the back frame member. 
         FIG. 7  is a side elevation view of the chair illustrated in  FIG. 1  showing a seat cushion. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A chair frame for a stackable chair incorporating various features of the present invention is illustrated generally at  10  in  FIGS. 1-7 . While the chair frames  10 , constructed in accordance with the present invention may be stacked, one upon another, to facilitate the storage of a plurality of chairs, it will be appreciated that the present invention is not limited to stackable chairs but rather could be utilized with non-stacking chairs or other seating structures, such as benches, that include a back support frame. 
     The chair frame  10  includes a seat support portion  15  which in the preferred illustrated embodiment defines a generally U-shaped frame portion  20  and a rear cross support member  25  which extends across, and is secured at its opposite ends to, the right and left leg assemblies  35 ,  40 . The seat support portion  15  is used to support the seat portion of a chair utilizing the frame  10 , such as the seat cushion  30 . 
     The right and left leg assemblies  35  and  40  are disposed on opposite sides of, and attached to, the seat support portion  15 . Each of the leg assemblies  35  and  40  includes a front leg  45  and a rear leg  50 . The leg assemblies  35  and  40  also include an upper support member  55  which is disposed between the upper ends of the front leg  45  and the rear leg  50 . As will be understood by those skilled in the art, the upper support members  55  serve to support another chair utilizing a chair frame  10  which is stacked above. In the preferred embodiment, the support members  55  extend between, and serve to support, the associated leg members  45  and  50 . Each of the leg assemblies  35  and  40  are also provided with a stacking bar  60  which extends between the front leg  45  and the rear leg  50 , and which is selectively spaced below the upper support member  55 . 
     In the preferred embodiment the chair frame  10  also includes a back support frame member  65  for supporting a seat back member (not shown), which can be a cushion or a rigid member for supporting the back of an occupant of the chair. The back support frame member  65  includes an upper portion  70  joined at opposed ends to right and left frame side members  75  and  80  which are spaced apart by a sufficient width to accept a seat back member (not shown). Each frame side member  75  and  80  extends downwardly and is bent forwardly to form respective frame lower ends  75 ′,  80 ′ that extend forwardly to a generally horizontal orientation in aligned registry with and spaced apart from the seat member rear portions  90  and  95 . In order to facilitate the preferred hinged attachment of the frame lower ends  75 ′, and  80 ′ with the seat member rear portions  90  and  95 , a gap is preferably provided there between. 
     As best illustrated in  FIGS. 4A and 4B , the chair frame  10  includes hinge assembly  100  defined by cooperating hinge members  105  and  110  for connecting the lower ends  75 ′ and  80 ′ of the back support frame member  65  to the rear portions  90  and  95  of the seat assembly  15  respectively. In the preferred embodiment, each hinge member  105  and  110  includes at least one knuckle  115  which are connected hingedly by a pin  120 . In one embodiment, hinge member  105  defines a tenon which is releasably received by the tubular end of either of the lower ends  75 ′ and  80 ′, in mortise and tenon manner. Similarly, hinge member  110  defines a tenon which is releasably received by the tubular end of the rear portions  90  and  95  of the seat assembly  15 . Whereas the figures, specifically  FIGS. 4A and 4B  depict a tenon and mortise configuration for the knuckles  115  of the hinge members  105  and  110 , it will be appreciated by those skilled in the art, that the hinge members  105  could include a plurality of knuckles for receiving hinge pin  120 . It will be appreciated that the present invention does not intend to limit the number or configuration of the knuckles of hinge assembly  100 . Rather, it should be appreciated that, regardless of the configuration and number of knuckles of the hinge assembly  100 , hinge assembly  100  is configured so as to provide pivotal motion of the lower ends  75 ′ and  80 ′ with respect to rear portions  90  and  95 . Further, while one type of hinge member has been shown, those skilled in the art will appreciate that various types of hinge members could be utilized. Further, it will be recognized that frame lower ends  75 ′ and  80 ′ could be pivotally secured to a portion of the chair frame in a manner that allows for pivotal motion of the back frame support  65  and maintains the substantial horizontal plane alignment with the seat member rear portions  90  and  95  when the back fram support  65  is in the non-reclined position. 
     In order to provide a back support frame  65  that repetitively reclines and rebounds to a generally vertical position relative to the seat assembly  15 , the rear cross support member  25  includes distal ends  125  which are secured to the rear legs  50 . A recess  130  is provided at each distal end  125 . Further, at least one compression member  140  is carried by at least one distal end  125 . In the preferred embodiment, a cylindrical can member  135  is carried by recess  130 . The compression member  140  is received within the can member  135 . Further, a plunger member  145  is received within the can member  135  and engages the compression member  140  such that the compression member biases the plunger  145  upward when the plunger  145  engages and compresses compression member  140 . In this regard, the can  135  is positioned such that the lower surface of each lower end  75 ′ and  80 ′ of the back support frame member  65  engages the plunger  145 . As a reclining force is applied to the back support frame member  65  by an occupant of the chair  10 , the lower ends  75 ′ and  80 ′ compress the plunger  145  against the biasing force of the compression member  140 . The can member  135  serves as a stop to limit the extent of reclining motion for the back support frame member. The fully reclined position is illustrated in  FIG. 6C . 
     The compression member  140  of the improved spring can assembly biases the back frame support member  65  to return to the non-reclined position shown in  FIG. 6B , after the reclining force is released. Whereas in one embodiment, illustrated in  FIGS. 3A and 3B , compression member  140  is defined by a helical coil spring, it will be appreciated that other compression members could be utilized. For instance, as illustrated in  FIG. 3C , compression member  140 ′ could be defined by a crest-to-crest wave spring. Those skilled in the art will recognize that other known compression members could be utilized for biasing the plunger  145  upward upon release of the reclining pressure applied to the back support frame member  65 . In the preferred embodiment, the range of compression of the plunger member  145  and compression member  140  is limited to approximately ⅜″. Further, while the can member  135  is illustrated as being a separate component carried by recess  130 , it will be appreciated that the can member  135  and the recess  130  could be integrally formed. 
     In one embodiment, as the chair  10  is being assembled, it will be appreciated that the frame members will be fully assembled prior to the attachment of either the seat cushion  30  or the supporting seat back member (not shown) are attached. With the back frame support member  65  tilted forward, as illustrated in  FIG. 6A , compression member  140  and plunger member  145  are inserted within can  135 . The back frame support member  65  is then returned to a neutral, i.e. non-reclined position. The seat cushion  30  is then secured to the seat support  15 . The back portion of the seat cushion  30  extends over the frame lower ends  75 ′ and  80 ′. In this position, the frame lower ends  75 ′ and  80 ′ will engage the lower surface of the seat cushion  30  if the back frame support member is flexed substantially forward, thereby retaining compression member  140  and plunger  145  within the can member  135 . It will be appreciated by those skilled in the art that the spring can assembly of the present invention allows the compression member to be readily and easily changed, thus providing the ability to easily adjust the flex tension of the back support member. 
     While the present invention has been illustrated by description of some embodiments, and while the illustrative embodiments have been described in detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant&#39;s general inventive concept.