Abstract:
The present invention provides for a drop-in seat unit as well as a method of manufacturing the drop-in seat unit that does not require the worker to affix one end of the spring to a frame rail and stretch the spring from one of the frame rails to the other frame rail. The ends of the spring are affixed to the frame rails while the springs are in an un-stretched state. Once the plurality of springs is attached to the two frame rails, the rails are mechanically pulled away from each other, thus creating a larger open area between the frame rails and thus extending the springs. Once the rails are properly positioned in this extended state, support members are positioned between the two frame rails and one end of each support member is affixed to each frame rail, traversing the space or gap between the two frame rails. The support members fix the distance between the two frame rails. Once the springs are attached to the two frame rails and the support members are affixed to the two frame rails, the completed drop-in seat unit or seat box assembly is unclamped and released from the manufacturing apparatus and is ready for shipment or use in further construction of the sofa or chair.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 11/704,162 filed Feb. 8, 2007, now U.S. Pat. No. 7,438,362, issued Oct. 21, 2008, which claims the benefit of U.S. Provisional Patent Application No. 60/771,849, filed Feb. 8, 2006, the disclosure of which are hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of furniture and furniture manufacture. In particular, the invention concerns the manufacture of drop-in seat units for use in the construction of sofas, couches, chairs and the like. 
     BACKGROUND OF THE INVENTION 
     Furniture such as sofas, couches, upholstered chairs and the like generally comprise a horizontal frame of metal or wood that delineates the base or seating area of the article, an upright section attached to the frame which supports the back, and two arm rests located on either end of the furniture article, to support the arms of a seated person. Cushions are generally positioned over the seating area and the upright section of the sofa or chair, to provide for padded and comfortable support for the seat and back of a person sitting on the sofa or chair. 
     Generally, the seat assembly of a sofa or chair includes a metal or wood seat box with a plurality of sinuous wires or springs, or coiled springs, extending across the frame, to provide support and flexibility for the seating area of the sofa or chair. Cushions or some other type of padding is placed upon the seating area to provide for a comfortable seat. The springs that extend across the frame of the seating area provide some “give” or flex to the seating area, such that the seating area can conform somewhat to the person seated on the sofa or chair. 
     The metal seat box of a sofa or chair generally includes four rails, with at least one pair of opposite rails containing a plurality of clips or hooks upon which the spring ends are attached. Generally, a spring end is affixed to a first rail of the drop-in seat box, the spring is extended, traversing the space between the first rail and the second rail which are parallel to one another, and the other spring end is affixed to the second (opposite) rail of the drop-in seat box. The spring ends are affixed to the drop-in seat box rails by way of a staple, hook or clip device. The extended springs are in a state of tension, as are the staples, clips or hooks holding the springs to the metal drop-in seat box. 
     Further, support devices or “seat stretchers” may be extended between the rails of the seat box assembly upon which the springs are affixed. Generally, the support devices are welded to the rails. 
     The above process of manufacturing the seat box for a sofa or chair is time-consuming since a number of parts must be assembled to construct the seat box, and construction may require certain expertise in assembly. Further, the handling and manufacture of the seat box as described can cause physical strain to the employees manufacturing the seat box. 
     SUMMARY OF THE INVENTION 
     According to the present disclosure, the structure and techniques for manufacturing a sofa or chair drop-in seat box are disclosed. The techniques and manufacturing processes utilized in manufacturing these sofa and/or chair drop-in seat units provide for the reduction of worker strain in the manufacturing process and increase output of drop-in seat units. 
     The present invention provides for a novel spring hook as well as a method of manufacturing the drop-in seat unit that does not require the worker to affix one end of the spring to a frame rail and stretch the spring from one of the frame rails to the other frame rail. The ends of the spring are affixed to the frame rails while the springs are in an unstretched state. Once the plurality of springs is attached to the two frame rails, the rails are mechanically pulled away from each other, thus created a larger open area between the frame rails and thus extending the springs. Once the rails are properly positioned in this extended state, support members are positioned between the two frame rails and one end of each support member is affixed to each frame rail, traversing the space or gap between the two frame rails. The support members fix the distance between the two frame rails. Once the springs are attached to the two frame rails and the support members are affixed to the two frame rails, the completed drop-in seat unit or seat box assembly is unclamped and released from the manufacturing apparatus and is ready for shipment or use in further construction of the sofa or chair. 
     The drop-in seat unit described above does not require any welding and uses few component parts. Further, the frame rails do not require end pieces on the frame rail ends. The support members that join the two frame rails can be displaced from the ends of the rails and provide support where desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a completed drop-in seat unit. 
         FIG. 2  is an perspective and exploded view of a partially completed drop-in seat unit. 
         FIG. 2A  is a close-up perspective view of a frame rail with hooks attached. 
         FIG. 2B  is a close-up perspective view of a hook affixed to a frame rail. 
         FIG. 2C  is a close-up perspective view of the interior side of a frame rail with a hook in place, showing the hook attachment. 
         FIG. 3  is a side view of a hook. 
         FIG. 4  is a side view of a hook affixed to a frame rail. 
         FIG. 5  is a perspective view of a hook affixed to a frame rail. 
         FIG. 6  is a top view of sinusoidal springs affixed to the two frame rails through the hook. 
         FIG. 7  is a top view of hooks affixed to a frame rail. 
         FIG. 8  is a side view of hooks affixed to a frame rail. 
         FIG. 9  is a side view of a support member affixed to a frame rail. 
         FIG. 10  is a step diagram showing the basic structure fixing steps in the drop-in seat unit assembly production process. 
         FIG. 11  is a side view of a support member. 
         FIG. 12  is a top perspective view of the packaged stacked pre-assembled frame rails. 
         FIG. 12A  is a close-up perspective view of the stacked pre-assembled frame rails, showing the offset hooks. 
         FIG. 13  is a side view of the packed stacked support members. 
         FIG. 13A  is a top plan view of the stacked support members. 
         FIG. 13B  is a close-up view of the stacked support members. 
         FIG. 14  is a side view of an embodiment of the frame rails in the assembly production process. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the invention is provided using a sofa drop-in seat unit as one example or embodiment, however other embodiments, for example, a chair seat box, are contemplated. The invention may be embodied in different forms and should not be construed as limited to the embodiments provided herein. 
     Referring to  FIG. 1 , there is provided a completed sofa drop-in seat unit or seat box assembly  10 . The drop-in seat unit  10  comprises frame rails  11 ,  12 , hooks  14 , springs  40 , and support members  50 . In one embodiment, the frame rails  11 ,  12  are generally L-shaped with one frame rail leg  30  positioned perpendicularly to the second frame rail leg  32 , as noted in  FIG. 2A . Additional frame rail configurations and hook attachments are contemplated. Frame rail leg  32  further includes apertures  34  adapted to receive one end of the hook  14 . Hook body segment  15  of the hook  14  lies along the surface of frame rail leg  30 . 
       FIG. 3  provides further detail of the shape of the hook  14 . One end of the hook  14  is curved, curving back upon itself to form the receiving slot  13  for the end of spring  40 . The hook body segment  15  of the hook  14  then bends at approximately 90 degrees (90°), forming a vertical segment  17  of the hook, perpendicular to hook body segment  15 . The vertical hook segment  17  bends again at approximately 90 degrees (90°) in a horizontal direction, parallel and opposite to hook body segment  15 , forming hook end segment  19 . Hook body segment  15  and hook end segment  19  are generally parallel to one another. 
       FIG. 4  demonstrates the position of hook  14  as it is affixed to a frame rail  11 ,  12 . The hook body segment  15  is disposed adjacent frame rail leg  30 , in a horizontal position, such that the hook receiving slot  13  is oriented upward, positioned to receive a spring end  42 ,  44 . The hook vertical segment  17  is disposed adjacent frame rail leg  32 . Hook end segment  19  extends through an aperture  34  in the frame rail leg  32 , and bends towards frame rail leg  30 , on the interior of the frame rail  11 ,  12 . Bending hook segment  19  towards frame rail leg  30  secures hook  14  in place and to the frame rail  11 ,  12 . Hence, the hooks  14  can be affixed to the frame rails  11 ,  12  in a pre-assembly operation and can be shipped to a furniture manufacturer without loss of hooks  14  from the frame rail  11 ,  12  or damage to the hooks  14 . As shown in  FIG. 5 , hook  14  is affixed to frame rail  11  (affixed identically to frame rail  12 ) by inserting hook end segment  19  through aperture  34 , and then bending hook end segment  19  towards frame rail leg  30 . A plurality of hooks  14  are affixed to the two frame rails  11 ,  12  such that when the two frame rails  11 ,  12  are aligned in parallel to each other, the hooks  14  on first frame rail  11  are also aligned in parallel to the hooks  14  affixed to the second frame rail  12 . 
       FIG. 6  shows a plurality of sinusoidal springs  40  that are extended between the two frame rails  11 ,  12 . Other shaped springs may also be used and are within the scope of the invention. Sinusoidal spring  40  contains two spring ends  42 ,  44 . The spring ends  42 ,  44 , are affixed to hooks  14  that have been affixed to the frame rails  11 ,  12 . The frame rails  11 ,  12  are oriented in parallel to one another, such that the hooks  14  affixed to the first frame rail  11  are oriented in parallel to the hooks  14  affixed to the second frame rail  12 . Sinusoidal spring end  42  is disposed in receiving slot  13  of hook  14 , wherein hook  14  is affixed to first frame rail  11 , and sinusoidal spring end  44  is disposed in receiving slot  13  of hook  14 , wherein hook  14  is affixed to second frame rail  12 . The position of the attached sinusoidal springs  40  relative to the rail frames  11 ,  12  is shown in  FIGS. 1 and 6 . 
     In addition to the plurality of sinusoidal springs  40  extended between the first frame rail  11  and the second frame rail  12 , there is a plurality of support members  50  also extended between the first frame rail  11  and the second frame rail  12 . The support members  50  are generally arcuate, and are positioned among the sinusoidal springs  40  that are affixed to the frame rails  11 ,  12 . Alternatively, the support members  50  may be other-shaped, such as straight shaped, instead of arcuate. Further, alternatively, the support members  50  may be positioned at the ends of the frame rails  11 ,  12 , extending between the first frame rail  11  and the second frame rail  12 . In another embodiment, support members  50  may be positioned at the ends of the frame rails  11 ,  12 , and other support members  50  may be positioned among the sinusoidal springs  40  that are affixed to the frame rails  11 ,  12 . The arcuate shape of the support members  50  provides strength to the drop-in seat unit and the seat. The support members  50  can be of various shaped tubing, but preferably are comprised of square tubing.  FIG. 1  shows one embodiment of the frame rails  11 ,  12 , with the sinusoidal springs  40  and the arcuate support members  50  affixed to the frame rails  11 ,  12 . 
     The frame rails  11 ,  12  have a plurality of apertures  52  in frame rail leg  30 , wherein the apertures  52  are adapted to receive a bolt  58 , or other mechanical attachment device, such as a screw, pin, nail, or the like. The arcuate support member  50  has an aperture  54 ,  56  disposed at each end  53 ,  55  of the arcuate support member  50 . The aperture  54 ,  56  is also adapted to receive a bolt  58 . The arcuate support member  50  extends between the frame rails  11 ,  12 , connecting the first frame rail  11  to the second frame rail  12 . As shown in  FIG. 9 , the support member end  53  is positioned such that the top surface  51  of the support member end  53  abuts frame rail surface  31 , in the interior of the L-shape of the first frame rail  11 . The aperture  52  in the first frame rail  11  is aligned with the aperture  54  in the support member  50  and the bolt  58  is inserted through both apertures  52 ,  54  and secured. Bolt  58  can be a self-tapping bolt. 
     Similarly, the support member end  55  is positioned such that the top surface  51  of the support member end  55  abuts frame rail surface  31 , in the interior of the L-shape of the second frame rail  12 . The aperture  52  in the second frame rail  12  is aligned with the aperture  56  in the support member  50  and the bolt  58  is inserted through both apertures  52 ,  56  and secured. The completed drop-in seat unit comprises the frame rails  11 ,  12 ; the hooks  14 ; the sinusoidal springs  40 , and the support members  50  which are affixed to the frame rails  11 ,  12  by way of bolts  58 . 
     Method of Assembly 
     The drop-in seat unit is assembled in a series of steps. The hooks  14  are affixed to the frame rails  11 ,  12  by placing the hook body segment  15  along the frame rail leg  30  and inserting the hook end segment  19  through an aperture  34  in the frame rail leg  32 , and bending the hook end segment  19  towards frame surface  31 , on the interior of the frame rail  11 ,  12 . A plurality of hooks  14  is affixed to first frame rail  11  and a plurality of hooks is affixed to second frame rail  12  in this manner. As shown in  FIG. 10 , the frame rails  11 ,  12  are positioned in an apparatus  70  wherein the first frame rail  11  is clamped  72  in one section of the apparatus  70  and the second frame rail  12  is clamped  72  in another section of the apparatus  70 . The blocks representing the frame rails  11 ,  12 , of  FIG. 10  are representative of the frame rails; L-shaped frame rails or frame rails of another shape.  FIG. 14  depicts L-shaped rails  11 ,  12  clamped  72  in apparatus  70 . The frame rails  11 ,  12  are clamped in parallel position to each other with a distance D 1  between the frame rails  11 ,  12 . The frame rails  11 ,  12  are positioned in the apparatus such that the hooks  14  are positioned on the top surface of the frame rails  11 ,  12 . 
     Once the frame rails  11 ,  12  are each clamped  72  in place, a plurality of sinusoidal springs  40  are affixed to the frame rails  11 ,  12 . A first end  42  of a sinusoidal spring  40  is inserted in receiving slot  13  of hook  14  on one of the frame rails, e.g. first frame rail  11 . Then a similar action is repeated with the other end of the sinusoidal spring  40  in the other frame rail, e.g. frame rail  12 . A second end  44  of the sinusoidal spring  40  is inserted in the receiving slot  13  of the hook  14  on the second frame rail  12 . Hence, one end  42  of sinusoidal spring  40  is affixed to the first frame rail  11  and the other end  44  of the sinusoidal spring  40  is affixed to the second frame rail  12 , thereby connecting the two frame rails. 
     After the plurality of sinusoidal springs  40  is attached to the two frame rails  11 ,  12  and tapped in place, the apparatus  70  is adjusted to increase the distance D (D 2 ) between the first frame rail  11  and the second frame rail  12 . Hence, the distance D 2  is greater than the distance D 1 . The increase in distance between the frame rails  11 ,  12  causes tension to be added to the sinusoidal springs  40  and for the sinusoidal springs  40  to elongate. When the frame rails  11 ,  12  are moved to a predetermined separation distance D 2 , then the arcuate support members  50  are added to the drop-in seat unit  10 . 
     A plurality of arcuate support members  50  is affixed between the first frame rail  11  and the second frame rail  12 , bridging the gap between the frame rails  11 ,  12 . The top surface  51  of support end  53  is disposed adjacent first frame rail  11  surface  31 , such that top surface  51  of support end  53  abuts first frame rail  11  surface  31 . The aperture  54  in support end  53  is aligned with aperture  52  in first frame rail  11 , and a bolt  58 , preferably a self-tapping bolt  58 , is inserted into the aligned apertures  52 ,  54  and fixed. Further, the other end of the support member  50 , support end  55 , is disposed adjacent second frame rail  12  surface  31 , such that top surface  51  of support end  55  abuts second frame rail  12  surface  31 . The aperture  56  in support end  55  is aligned with aperture  52  in second frame rail  12 , and a bolt  58 , preferably a self-tapping bolt  58 , is inserted into the aligned apertures  52 ,  56  and fixed. In each instance, the support end  53 ,  55  is positioned in the interior of the L formed by the two surfaces of the frame rail  11 ,  12 . It is understood that the position of the support member is reversible, such that support end  53  can be affixed to second frame rail  12  and support end  55  can be affixed to first frame rail  11 . 
     Once the arcuate support members  55  are affixed to the frame rails  11 ,  12 , then the apparatus is adjusted such that the clamping devices  72  holding the frame rails  11 ,  12  in place are released, and the frame rails  11 ,  12  are no longer gripped in the apparatus. The completed drop-in seat unit (seat box assembly) is removed from the apparatus and the cycle can begin again with the placement of a first frame rail  11  and a second frame rail  12  in the apparatus  70  and clamping  72  of the frame rails  11 ,  12  in place. 
     The method described above allows a worker to construct the drop-in seat unit  10  without the worker having to stretch the sinusoidal springs  40  to be able to attach the sinusoidal springs  40  to the frame rails  11 ,  12  after the frame rails  11 ,  12  are properly spaced apart. Instead, the apparatus  70  provides the force to separate the frame rails  11 ,  12  to the appropriate spacing (D 2 ) after the sinusoidal springs  40  have been attached to the frame rails  11 ,  12 . Further, no welding is required in the manufacture of the drop-in seat unit. 
     Pre-assembled frame rails may be easily nested for stacking, storage or shipping, as shown in  FIG. 12 . The pre-assembled frame rails  11 ,  12  include the hooks  14  already affixed to the frame rails  11 ,  12 . The hooks  14  can be affixed to the frame rails  11 ,  12  by the manufacturer of the frame rails  11 ,  12 , a job shop or some other party. The pre-assembled frame rails  11 ,  12  are stacked for shipping as shown in  FIG. 12 . The pre-assembled frame rails  11 ,  12  are stacked offset to allow for the hooks  14 , which are fixed to the frame rails  11 ,  12 .  FIG. 12A  demonstrates the offset position of the hooks  14 , which are fixed to the frame rails  11 ,  12 .  FIG. 12A  demonstrates not interfere with one another and allow for compact nesting of the pre-assembled frame rails  11 ,  12 . The hooks  14  are affixed to the frame rails  11 ,  12 , as described above, such that the hooks  14  are “locked” to the frame rails  11 ,  12 . With the hooks  14  locked onto the frame rails  11 ,  12 , the pre-assembled frame rails  11 ,  12  can be stacked and transported without the loss of hooks  14  and without a need to use resources to replace missing hooks  14 . 
     The pre-assembled frame rails  11 ,  12  can be stacked in various heights and widths, however a preferred configuration is described below. The number of pre-assembled frame rails in the stacks can be varied and still fall within the scope and spirit of the patent. The pre-assembled frame rails  11 ,  12  are stacked in three tiers, wherein each tier contains 25 pre-assembled frame rails across the width (W) and 12 pre-assembled frame rails  11 ,  12  in height (H). A dunnage board  62  is placed under the first tier  61 , and the first tier  61  of pre-assembled frame rails  11 ,  12  is stacked on the dunnage board  62 . A second dunnage board  62  is placed on the first tier  61  of pre-assembled frame rails  11 ,  12 . A second tier  63  of pre-assembled frame rails  11 ,  12  is placed on the dunnage board  62 , in the same configuration as the first tier  61  of pre-assembled frame rails  11 ,  12 . Another dunnage board  62  is placed on top of the second tier  63  of the pre-assembled frame rails  11 ,  12 . A third tier  65  of pre-assembled frame rails  11 ,  12  is placed on top of the third dunnage board  62 . The third tier  65  of pre-assembled frame rails  11 ,  12  is configured similarly to the first and second tiers of pre-assembled frame rails  11 ,  12 . A fourth dunnage board  62  is placed on top of the third tier  65  of pre-assembled frame rails  11 ,  12 , and forms the top of the frame rail unit  60 . 
     The dunnage board  62  that is utilized in packing the pre-assembled frame rails  11 ,  12  is made from MDF, plywood, OSB material and the like. Further, the dunnage board  62  must be at least 16 mm thick or thicker. The frame rail unit  60  is banded in between the tiers as shown in  FIG. 12 . Banding the frame rail unit  60  in-between the dunnage boards  62  assists in preventing the pre-assembled frame rails  11 ,  12  from shifting during transport. Further, the configuration of the bands  64  is conducive to banding a tier, stacking another tier, and banding together those tiers, and so on. The bands  64  are made from corrugated tie sheets and the like. Further, the entire frame rail unit  60  is banded with bands  64  extending around the top and the bottom dunnage boards  62 . Prior to shipping, the entire frame rail unit  60  is stretch wrapped. The configuration of the frame rail unit  60  provides a compact method of transporting the pre-assembled frame rails  11 ,  12  such that there is minimal damage to the pre-assembled frame rails  11 ,  12  and the hooks  14  are not displaced due to stacking and remain affixed during transport. Further, the configuration of the frame rail unit  60  also allows for stacking of frame rail units  60  for transport. 
     The support members  50  can also be compactly stacked for transport. The number of support members in the stacks can be varied and still fall within the scope and spirit of the patent, however, a preferred configuration is provided below. The support members  50  can be arranged horizontally and stacked on top of each other in vertical stacks of 65 support members, with two such stacks of support members  50  positioned end to end.  FIG. 13A  shows the position of the two stacks of 65 support members each. An additional 20 support members  50  are stacked and oriented vertically to the side of the two stacks of 65 support members  50 .  FIG. 13A  shows the orientation of the two stacks of 65 support members  50  and the one stack of 20 support members  50  to each other. 
       FIG. 13B  provides a close-up of the orientation of the support members  50  in the packed configuration. The two stacks of 65 support members  50  are oriented horizontally, along with the stack of 20 support members  50 . Three such groupings are stacked one on too of the other on a bottom dunnage board  82 . A dunnage board  82  is placed on top of this arrangement of 450 support members (3 layers of 130; 3 layers of 20). Then another 450 support members  50  are arranged in the same configuration on top of the dunnage board  82 . A dunnage board  82  is placed on top of this layer of support members  50 , and the support member unit  80  is banded.  FIG. 13  shows the orientation of the support member  50  in the packed configuration, with the dunnage boards  82  and bands  84  in place. 
     The dunnage boards  82  used are made from material such as MDF, plywood OSB material and the like. The dunnage board  82  is preferably 16 mm thick or thicker. The bands  84  are preferably corrugated tie sheets. Once the support member unit  80  is compiled, preferably 6 layers of 150 support members  50 , and banded, the entire support member unit  80  is stretch wrapped for transport. The use of the dunnage board  82  provides a number of benefits, including protecting the support members  50 , keeping the support members  50  from shifting during transport, and being able to stack the support member units  80 . 
     The embodiments above are intended to be illustrative and not limiting. Additional embodiments are within the claims. Although the present invention has been described with reference to particular embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.