Abstract:
A four legged or sled chair having a reclinable seat comprising a frame structure, a seat mounted within the frame structure for pivoting about a transverse torsion bar(s) axis, and elastic stops defining said seat position of maximum rearward pivoting and the position of maximum forward pivoting in relation thereto.

Description:
DESCRIPTION OF THE PRIOR ART 
     Chairs of the abstract description are unknown, but torsion bar chair controls for office-type chairs are common. When utilizing a torsion bar in an office-type chair, the elongated axis of the bar is usually located above the chair post, within a mechanism that also contains the seat rotation stops and the seat initial resiliency controls. Typical office chairs having a torsion bar mechanism are described in U.S. Pat. Nos. 3,136,580; 3,240,528 and 3,224,807. The only four legged chair known to the applicant that has a torsion bar, is disclosed in U.S. Pat. No. 4,938,532. In this chair the torsion bar, its bearings and a non-adjustable seat stop are mounted on an aluminum extrusion bar that is welded to the chair frame. Here the torsion bar is used to provide a flexible back support, only. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to four legged and sled chairs of the type used in conference halls and restaurants. Said chairs always have a fixed seat; usually they don&#39;t have arm rests and are of a stackable type. 
     In this invention, the seat is supported and guided by a transverse torsion bar(s) so as to enable it to pivot, tilt or recline with respect to the chair frame, thereby enabling the user to rotate the seat position from upright (maximum forward) seating to a fully reclining (maximum rearward) seating, and vice versa. Thus, giving a pleasing sense of freedom and comfort to the occupant. The torsion bar(s), anchored to the chair frame and to the bottom seat board, provides the resilient torque that bias the seat to its upright position. Means attached to said bottom seat board engage travel limiting means placed in the side frame that would define the maximum forward and rearward rotation of said seat. 
     In the present state-of-the-art, only chairs having a vertical post with the ubiquitous spider base offers reclinable seating, all others have fixed seating —or at most— a tiltable back board. But those spider based chairs —though very comfortable— are too unsightly, expensive and/or cumbersome to move and to store-away, to be used in high density seating areas like restaurants, bingo parlors, auditoriums, etc. 
     In view of the shortcomings mentioned above, it is the principal object of the present invention to introduce a chair having a reclinable seat mounted on a four legged frame, or a sled frame, whereby said frame could be made of plastic, metal and/or wood. Yet, another object of the invention is to provide an inexpensive reclinable chair having enhanced aesthetics and comfort. A further object of the invention is to provide a simplified method of manufacturing and assembling such chairs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a perspective view of a four legged reclinable chair having a tubular frame according to the present invention; 
     FIG. 2 is a schematic side elevation view of the chair shown in FIG. 1 with the seat in the upright position; 
     FIG. 3 is a schematic side elevation view of the chair shown in FIG. 1, with the seat in a fully reclined position; 
     FIG. 4 is an exploded partial perspective view of the bottom board of FIG. 1; 
     FIG. 5 is a sectional view of FIG. 4 taken along line C—C; 
     FIG. 6 is a schematic sectional view of FIG. 5, taken along line B—B; 
     FIG. 7 is a schematic sectional view of FIG. 5, taken along line A—A, showing the torsion bar control mechanism; 
     FIG. 8 is an exploded perspective view of the chair shown in FIG. 1; 
     FIG. 9 is a schematic sectional view of the seat of FIG. 4, taken along line C—C, showing another embodiment of the invention; 
     FIG. 10 is a perspective view of a wooden sled framed reclinable four legged chair according to the present invention; 
     FIG. 11 is a schematic side elevation view of the chair shown in FIG. 10 with the seat in the upright position; 
     FIG. 12 is a partial view of FIG. 11 taken along line G—G; 
     FIG. 13 is a partial view of FIG. 11 taken along line F—F; 
     FIG. 14 is a partial view of FIG. 10 taken along line D—D; 
     FIG. 15 is a sectional view illustrating the stop mechanism taken along line E—E of FIG. 2, and 
     FIG. 16 is partial sectional view of FIG. 3 taken along line H—H showing the fastening of the side frame to the cross-rail. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now in detail to the embodiments of the chair shown in FIG. 1 which comprises a supporting metal frame incorporating two similar square tubular side frames  10 , each tubular element bent to provide a substantially horizontal member and substantially vertical leg members. A front cross-rail  11 , and a rear cross-rail  15  connect both side frames in a spaced apart relationship. 
     The seat comprises an upholstered bottom board  12  and an upholstered back board  14  which are connected to each other at an obtuse angle by a flat spring  13 . The seat pivot as a unit in response to a backward leaning movement of the chair occupant. The upholstery consist of contoured foam blocks that are glued to the bottom and back boards and are subsequently covered by a cloth, that in turn, is stapled to the wooden boards. It will be understood that the hardware is symmetrically disposed on both side of the chair; hence, the hardware on one side only will be described. 
     In the exploded perspective view of the bottom board  12 , as shown in FIG. 4, the fabric covering the foam  16  is not shown, and the foam  16  that is placed in top of the wooden —or plastic— bottom board  17  have been vertically displaced for clarity. Shown in broken outline are the two tubes  23  through which passes the square section torsion bar  18 .  21  is the elastic seat stop in the form of a block of material made of rubber, or covered with rubber, having an opening  26  facing the side frame, and a fastener  24  that connect it to the board  17 . 
     In FIG. 5, the ends of the torsion bar  18  are securely engaged to inserts  25  that are placed inside the horizontal members of the side frames  10 , while at a point intermediate within the bar ends an anchor  20  will transmit the torsion to the board  17 , to which said anchor is engaged. Here,  23  are a pair of hardened steel cylindrical bushings placed and fastened into a kerf that runs across the board  17 . Though the bushings  23  are shown placed underneath the board  17 , they could as well be placed on top of the board, or within the board thickness, without changing their function. The two bushings  23  engage the torsion bar  18  to the bottom board  17  while allowing rotation thereof, hence, the seat is basically being supported and positioned from —and— by the torsion bar  18  ends; only with the seat in the upright position do the bracket  31  absorb some of the chair occupant weight. It is worth noting that once an initial torque is applied, the friction of the torque bar against the frame inserts  25 , the bearings  23  and the anchor  20 , are enough to eliminate any side motions of the bars and/or the seat relative to the frame. 
     The hardened steel tube  23  is shown here as a full length tubular bushing for the square bar  18 , that is hardened and tempered. Innumerable tests has proven that such an arrangement have a long service life expectancy if the bar flats are placed horizontally, as shown in FIG. 6, and if the square bar edges were previously dulled. For the type of chairs described in this invention, the seat rotation between the upright and the fully reclined positions is about 10°, thus, the rotation of the square bar inside the tubes varies from almost zero at the point of insertion into the anchor  20 , to about 10° at the outer edges of the seat. Taking in account the small forces involved, the large hardened bearing surfaces in play, the lubricants and the infrequent and relatively small rotation between the torsion bar and the tube, wear and friction proved to be insignificant. 
     In FIG. 7, the referral number  20  belongs to a rotatable anchor that is an aluminum extrusion having a complementary square opening to allow the tight passage of said rod  18  throughout. The rotatable anchor  20  is located in the opening  30 , a cut out in the center of the wooden board  17 . The chair assembly procedure is to insert the rod  18  through the pivotably anchor  20  and once the whole chair is assembled, to rotate the anchor  20  clockwise by means of the adjusting screw  27 , whereby, the seat and the rods get locked in the desired position, thus, setting the initial resiliency of the seat.  28  is a thrust plate underneath the board to absorb the screw thrust and, rotary joint  29  is a cylinder nested in the anchor that transmits the screw thrust to the anchor regardless of its relative position with the board. 
     As it was mentioned above, the ends of bar  18  penetrates inside the horizontal members of the side frames  10 , but since the side frames  10  are made of thin wall tubes, no firm anchoring of the torsion bar is possible. To provide a reliable anchoring, a solid metal insert  25 , as shown in FIG. 4, FIG.  5  and FIG. 9, was securely placed inside the tube element prior of bending the frames  10 . A subsequent machining operation produces a square cavity that would keep the end of the torsion bar  18  firmly in place, plus distributing the torsion moment over a larger area of the tube. In operation, the torsion bar  18  —while supporting the seated person weight— will twist if said person reclines the seat backward; thus, while the ends of bar  18  anchored in the side frames  10  remains immovable, in a nonrotatable relation with said frame, the middle point of the rod, nonrotatable engaged to the adjustable anchor  20  rotates (twist), with the bottom board  17 . We now have a seat that will pivot around a virtual axis P—P passing through the center of the torsion bar  18  as shown in FIG. 4, plus a resilient force given by said torsion bar that, in the absence of other forces, would bias the seat toward its maximum forward pivoting position, as shown in the illustration of FIG.  2 . In this embodiment, the torsion bar  18  are usually made of a square cross-section medium carbon steel SAE 1045 because of this alloy elastic characteristics though in other possible embodiments other cross-sections including laminated bars, torsion bar ends configurations, alloys or materials could be used without departing from the inventive principle. 
     FIG. 9 shows one of such other possible embodiment, whereby, the torsion bars are two co-axial cylindrical rods  44 , each having its contiguous end machined down to a square key  45 , while its outside key is the 90 degree bent end  46 . As in a key and keyhole lock arrangement, complementary recessed shapes on the rotatable anchor  20  and inserts  25  provides a firm ‘keyhole’ anchoring to the bar&#39;s keys  45  and  46 , respectively. 
     In other possible embodiments, the torsion bar cross-section and/or its keys could assume the shape of any geometric figure, plus the ends of a bar could be bent without departing from the original concept of providing complementary attaching means to a keyed torsion bar ends. It is obvious by now that in this invention the torsion bar(s) and the seat rotation control means could be contained —and concealed— within the upholstered bottom board, thereby producing an esthetically neat and pleasant looking chair. 
     In the present manufacturing state-of-the-art, an upholstered bottom seat board is attached to an already assembled chair frame, but this would be hard to do in the present invention where the bottom board has torsion bar ends and seat control means protruding from its sides. Instead, in the present invention the chair frame is assembled ‘around’ the bottom seat board. 
     In FIG. 8 (an exploded perspective view of the chair of FIG.  1 ), we see how the frame is assembled ‘around’ the seat board, very securely, fast and inexpensively by using screws that will remain hidden. Because concealing the fastening means is so aesthetically fundamental to a good industrial design, it became one of the main purposes of the present invention. 
     Moreover, since many of these type of chairs have anodized aluminum frames, it is cheaper to bend, machine, and screw together individual frame components made from long aluminum bars that come already anodized from the mill, than bend, machine and weld together —the same components— that would then have to be carefully anodized and handled as an assembled frame. The manufacturing savings could be substantial, hence, a less expensive chair is possible. 
     In FIG. 8, the upholstered bottom board seat shows the seat stop bracket  31  and a short length of the square torsion bar  18  protruding from the seat side. Meanwhile, all of the screws  40  needed to assembly the frame  10  legs to the cross-rails  11  and  15  have already been placed into their legs clearance holes  48 , and kept in place by jigs and/or fixtures not shown in the illustration. 
     Finshing the assembly becomes very simple now, we just have to place the loose end of bar  18  into the square hole of insert  32  at the same time that we place the seat stop bracket  31  into the corresponding opening  26 . Thereafter, with a suitable tool bit  47  —as shown in phantom lines in FIG.  16 — passing through the tool bit access holes  19  we fasten the screws  40  into the corresponding threaded holes  49  existent at the end of the aluminum extruded cross rails  11  and  15 . Holes  48  and holes  19  are aligned on opposite walls of the frame legs. Finally, the initial pivoting resilient torque is set by rotating the anchor  20  of FIG. 7, hence, slightly twisting the torsion bar  18 . This is accomplished by rotating clockwise the adjusting screw  27 , urging the seat to its upright position. 
     FIG. 10 is still another embodiment of the present invention in the form of a sled chair having a wooden frame. Here each side frame comprises two identical vertical legs  37  attached to two substantially horizontal members  40 . A front cross-rail  38 , and a rear cross-rail  39  connect both side frames. The seating comprises an upholstered bottom board  16  and an upholstered back board  51  which are connected together to each other at an obtuse angle by a flat spring  52 . It will be understood that the hardware is symmetrically disposed on both side of the chair, hence, the hardware on one side only will be described. In FIG. 12 the two co-axial round torsion bars  50  have bent ends and are engaged to the upper horizontal members  40  by means of metal inserts  42  placed into the wood; said metal inserts have corresponding rectangular holes that will nest the bent ends of said torsion bars. A plurality of bushings  56  attached to the board  54  support and guide the two bars  50 , as shown. Here,  55  is the rotatable anchor,  58  is its adjusting screw and,  59  is a thrust plate disposed underneath the board to distribute the screw thrust over a larger area of said board. 
     In FIG.  13  and in FIG. 14 a seat stop bracket  41 , affixed to the underneath of the board  54  by means of fasteners  43 , would limit the angle of rotation of said board, that by extension limits the seat travel between its upright and its fully reclined positions. Here, the ends of the bracket  41  extend into cavities  44  that have been machined into the upper horizontal members  40 .  45  and  46  are the upper and the lower elastic stops, respectively, for said seat stop bracket  41 ; said elastic seat stops, made of rubber, are glued to the top and bottom of cavities  44  to elastically limit the travel of said bar, and by extension, the rotation of the chair&#39;s seat. 
     In FIG. 14,  50  is the torsion bar showing its key (the bent end) placed inside insert  42 . The two extreme pivoting positions of the upholstered board  16  are shown in phantom lines, and  52  is the flat spring connecting the bottom board  16  to the back board  51  (not shown). 
     FIG. 15 is another embodiment of the present invention, whereby, the means to limit the rotation of a chair seat are hidden from view by locating them within the upholstered bottom board. Here  10  is the horizontal member of the tubular side frame; the seat stop bracket  31  is attached by fastener  33  to the solid insert  25  that is press fitted inside said tubular side frame.  21  is the elastic seat stop and  24  (shown in dotted lines) is the fastener that attach it to the board  17 .  27  is a small metallic shield plate welded to the stop bracket  31  to avoid access to pinch points inside the opening  26 . FIG. 15 being a cross-sectional view of the chair of FIG. 2, shows the seat in the upright position. In this position the seat stop bracket  31  stops the elastic seat stop  21  from traveling further down; with the seat in the fully reclined position the stop bracket would be stopped by the lower surface  36  of the block opening  26 .