Abstract:
A spring and grid sub-assembly for use in furniture and box spring assemblies in which spring modules are attached to the wire grid through an attachment system in which the springs are in both an over-under relationship and a side-to-side interwoven relationship with the cross wires through plastic deformation of the cross wires whereby the springs can not be removed from the wire grid without plastic deformation of either the grid or spring modules. The resultant sub-assembly can be easily transported from a sub-assembler to a final assembler without risk of the springs being displaced or removed from the wire grid. Furthermore, spring clips are not needed for attaching the spring modules to the grid.

Description:
BACKGROUND AND SUMMARY 
     This invention relates generally to grid and spring subassemblies for bedding and furniture foundations for mattresses and seat cushions. Foundations for mattresses, typically referred to as box spring assemblies, conventionally consist of a support frame, a wire grid positioned above the support frame, and springs supporting the grid on the frame for yieldable movement under load toward the frame. 
     The metal components of a box spring assembly include the springs and the grid and in some cases the support frame. In this invention, the springs and grid are assembled into a subassembly which is supplied to the bedding or furniture manufacturer for final assembly and ultimate sale. In the case of box spring assemblies, various sizes and grades are made by the manufacturer and this requires the maintenance by the furniture manufacturer of a large inventory of metal component subassemblies. It is necessary that the spring subassemblies be assembled in such a manner that the springs will not become detached from the grid or move out of the proper position on the grid during transport and handling. One way of assuring that the springs stay attached to the grid is to use clips to attach the springs to the grid. However, the use of clips, of which several are needed for a box spring assembly, dramatically increases the number of components needed in the metal subassembly. In addition, certain types of loading applied directly to a cross wire can cause the clips to open and the springs to loosen from the grid. 
     Box spring assemblies have been developed in which the springs and the wire grid are interfit with one another in an &#34;over and under&#34; relationship with the grid to attach the spring to the grid. However, until the lower ends of the springs are attached to the support frame, it is possible to move the springs out of the desired position on the grid by inadvertent contact with the springs. It is also possible to inadvertently remove the springs from the grid. Such detachment or movement creates difficulties when the spring and grid subassembly is attached to the support frame due to misposition or loss of the springs. Examples of interfitting spring and grid subassemblies are shown in U.S. Pat. Nos. 4,339,834; 4,921,228 and 4,932,535. 
     It is an object of the present invention to provide a grid and spring subassembly in which the springs are secured to the grid without spring clips but in a manner which assures retention of the springs on the grid at all times. 
     Because spring and grid subassemblies must be transported from the subassembler to the final furniture assembler, it is beneficial if the subassemblies are stackable. Examples of stackable subassemblies are shown in co-pending patent applications Ser. No. 07/628,086 filed Dec. 17, 1990 entitled NESTABLE SPRING ASSEMBLIES FOR BEDDING AND FURNITURE and Ser. No. 07/656,585 filed Feb. 19, 1991 entitled STACKABLE SPRING ASSEMBLIES WITH FORMED WIRE SPRING MODULES. Both of these applications are commonly assigned with the present application and are hereby incorporated by reference. 
     According to the present invention, the grid cross wires are formed with periodic vertical offsets. The upper ends of the springs include attaching portions that are configured with at least one pair of segments in each spring transverse to the cross wire. These transverse segments are connected by a return bent portion so as to enable the spring attaching portion to be interfit with the cross wire at the vertical offset with one transverse segment overlying the vertically offset of the cross wire and the other transverse segment underlying the cross wire adjacent the vertical offset. 
     The cross wire is seated in the return bent portion between the two transverse segments. This interfitting engagement is accomplished by moving the spring attaching portion horizontally into engagement with the cross wire. In the engaged position, a longitudinal segment of the spring attaching portion extends parallel to the vertical offset of the cross wire but is vertically above the offset and horizontally to one side of the offset, opposite from the return bent portion. 
     After engagement, the vertical offset is plastically deformed vertically to a position along side a longitudinal segment of the spring attaching portion to entrap the longitudinal segment on the opposite side of the cross wire from the return bent portion of the spring attaching portion. This prevents withdrawal of the spring attaching portion from engagement with the cross wire in a direction normal to the cross wire while the over-under engagement relationship of the spring attaching portion to the cross wire prohibits movement in all other directions. 
     The plastic deformation of the cross wire offset results in a permanent attachment of the spring to the cross wire. The spring can only be detached from the cross wire by permanent deformation of the cross wire. 
     Preferably, the springs are configured in a V-shape to enable a plurality of grid and spring subassemblies to be stacked one upon the other with the lower portion of the spring being inserted into the rectangular pockets formed between cross wires in the grid stacked below. 
     Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary perspective view of the spring and grid sub-assembly of this invention mounted to a support frame; 
     FIG. 2 is a fragmentary perspective view of the attaching portions of a spring and the grid during assembly; 
     FIG. 3 is a fragmentary plan view of a spring and the wire grid assembled; 
     FIG. 4 is a fragmentary elevational view of the structure shown in FIG. 3; and 
     FIG. 5 is a fragmentary elevational view of a nested stack of three spring and grid sub-assemblies according to this invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the drawing, the spring and grid sub-assembly of this invention, indicated generally at 10, is illustrated in FIG. 1 mounted on a supporting frame 12. Only a portion of the subassembly is illustrated but it is of generally rectangular shape. The subassembly 10 consists of a wire grid 14, also of rectangular shape, a plurality of main spring modules 16 and corner spring modules 17 which are attached to the wire grid 14. When the spring modules 16 are mounted on the frame 12, they act to support the grid 14 at a predetermined elevation above the frame 12 and in general alignment therewith. 
     The frame 12 consists of a pair of end rails 18, a pair of side rails 20, and a plurality of cross rails 22. The frame 12 is conventional so only one of each of the rails is illustrated in FIG. 1. The wire grid 14 consists of a rectangular border wire 24 and a plurality of cross wires 26 which are arranged in a criss-cross fashion and are supported on the border wire 24. In the illustrated embodiment of the grid 14, the cross wires 26 are illustrated as having return bent portions forming loops 28 at their ends which are bent around the border wire in order to support the cross wires on the border wire 24. 
     The spring modules 16 are identical and are each formed of a single piece of conventional spring wire folded, in the preferred embodiment of this invention, to be generally V-shaped. Each of the spring modules 16 includes a body 30 formed of spring wire which is generally upright and has a support torsion bar 32 at its lower end or apex attached to the frame 12 by staples 60. A pair of straight upwardly diverging columns 34 extend upwardly from opposite ends of the bar 32 and are formed integral at their upper ends 36 with oppositely extending generally parallel torsion bars 38. The torsion bars 38 are formed integral with generally horizontal connecting bars 40 which terminate in upwardly diverging support arms 42. 
     At the upper end of the body 30, the spring module 16 is formed with a pair of horizontally spaced apart attaching portions 44 which are integral with the support arms 42. The attaching portions 44 and the cross wires 26 are configured so that they can be interlocked to provide a clipless attachment of the spring modules 16 to the grid 14. The spring modules 16 are connected to the grid 14 so that up and down movement of the grid 14 in response to bedding loads results in corresponding substantially vertical compression and expansion of the spring modules 16 in reaction to the loads. 
     Each attaching portion 44 includes, adjacent to the upright support arm 42, a pair of transverse segments 46 and 48 which extend generally transverse to the cross wire 26 to which the spring module is attached. The two transverse segments 46 and 48 are connected by a return bent segment 50 which is characterized as being generally parallel to the cross wire 26. A longitudinal segment 52 of the attaching portion 44 extends parallel to the cross wire 26 from one end of transverse segment 48. At the opposite end of the longitudinal segment 52, the wire is bent to form another pair of transverse segments 46A and 48A joined by a return bent segment 50A. The transverse segments 46A and 48A and return bent segment 50A are mirror images of the transverse segments 46 and 48 and return bent segment 50. The entire attaching portion 44, consisting of the longitudinal segment 52, the transverse segments and the return bent segments, lies in a common horizontal plane. 
     The cross wires 26 are formed with vertical offsets 54, at the locations of spring attachment. Each offset 54 has a pair of first offset segments 56 which are aligned with one another and a second center offset segment 58 therebetween. The offset 54 is joined to the main portion of the cross wire 26 by risers 62. The main portion of the cross wire, the risers 62 and vertical offset 54 are in a common vertical plane. 
     The spring modules are attached to the grid by spreading the two spring attachment portions 44 away from one another to the position shown in FIG. 2 in which the spring attaching portions are separated by more than the distance between the two cross wires 26 to which the spring module is attached. Once the grid is positioned in alignment with the spring attaching portions, the spring attaching portions are allowed to return toward their normal positions whereby the spring attaching portions move toward one another into engagement with the cross wires. 
     The attaching portions move horizontally in the direction of the arrows shown in FIG. 2 which is generally parallel to the lengths of the transverse segments. The spring attaching portions engage the cross wires in an interfitting relationship in which the transverse segments 46 and 46A underlie the cross wire while the transverse segments 48 and 48A overlie the first offset segments 56 of the cross wire with the risers 62 being seated in the bent return segment 50 of the spring attaching portions 44. 
     In this interfitting position, the pairs of transverse segments 46 and 48 and 46A and 48A engage opposite vertical sides of the cross wire 26 and opposite horizontal sides of the risers 62 in the longitudinal direction of the cross wire. The spring module 16 is restrained from moving horizontally along the length of the cross wire 26 and vertically due to the over-under relationship of the transverse segments with the cross wire. 
     The transverse segments 48 and 48A are of a length transverse to the cross wire 26 approximately equal to the diameter of the cross wire 26 such that when the attaching portion is engaged with the cross wire, the longitudinal segment 52 of the attaching portion is positioned on the opposite horizontal side of the cross wire 26 from the return bent segment 50. This relationship is shown in the plan view of FIG. 3. 
     To interlock the spring module with the cross wire so that the spring module is restrained in all directions, the vertical offset portion 54 is deflected upward by application of a vertical load to the second offset segment 58. The second offset segment 58 is curved. During upward deflection, the radius of curvature of segment 58 is increased as the offset segments 56 are deflected upward, using spring sections 48 and 48A as a fulcrum point so that the spacing between the two risers 62 remains the same. 
     The vertical offset 54 is plastically deformed beyond its elastic limit so as to remain in the deflected position adjacent to the longitudinal segment 52 of the spring attaching portion 44. In this position, the offset portion serves as a mechanical lock to prevent horizontal displacement of the spring attaching portion from the cross wire. the spring module can not be removed from the grid without subsequent plastic deformation of the cross wire or the spring attaching portion. The spring will thus remain attached to the wire grid during handling and transport of the spring and grid sub-assembly from one location to another. 
     Each of the spring attaching portions 44 is independent of the other, they are not in a working association with one another. The attaching portions will function if the support bar 32 were separated to form two springs. The spring module 16 functions as two springs in combination. The use of two attaching portions for each spring module does prevent rotation of the spring module about the cross wire which could occur if the spring module had only one attaching portion. 
     The corner spring modules 17 are similar to the main spring modules 16 but differ in terms of their attachment to the grid 14. Like numerals are used on the corner spring modules 17 to indicate like parts on the main spring modules 16. At their upper ends, the support arms 42 in the corner spring modules are formed with attaching bars 66 instead of the attaching portions 44. The attaching bars 66 in each corner spring module 17 are generally perpendicular to each other and extend generally toward each other. This configuration of the attaching bars 66 enables them to be positioned in a side-by-side relation with the border wire 24 at a corner 67 of the border wire, as shown in FIG. 1. Conventional spring clips 68 are utilized to clamp the attaching bars 52 to the side-by-side portions of the border wire 24 and assure a stable positioning of the corner spring module 17 at a corner of the border wire. 
     From the above description, it is seen that a spring and grid sub-assembly 10 is formed by assembling a plurality of main spring modules 16 with the wire grid 14, the exact number of spring modules 16 to be used being dependent entirely on the assembler. Large numbers of identical assemblies 10 can be arranged in vertical stacks, as shown in FIG. 5. Nested bundles of sub-assemblies 10 can be palletized and stacked to whatever height and configuration is best suited to the particular transportation mode that is being utilized . 
     While the V-shape configuration of the spring modules is preferred because it facilitates stacking of the spring and grid sub-assemblies, the configuration of the attaching portions 44 and cross wires 26 of the present invention can be used with spring modules in which the body 30 of the modules is different from the spring modules 16 illustrated and described. 
     The greatest utility in the spring attaching system is in situations where the subassembly 10 must be transported from the place of subassembly to the place of completion of the assembly with the support frame 12. The attachment system of this invention provides a clipless attachment of the spring modules to the wire grid with assurance that the spring modules will remain in place. 
     It is to be understood that the invention is not limited to the exact construction illustrated and described above, but that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.