Method of Constructing Box Springs or the Like

The present invention relates to spring assemblies for furniture, such as mattress box springs for example, and to methods for manufacture thereof.

In coil spring assemblies previously proposed, particularly mattress box spring assemblies of the type which include generally conical coil springs, one end of each of a plurality of spaced springs is fixedly attached to a rigid support such as a frame and the opposing spring ends are attached to each other by wires which form a relatively coarse mesh to hold the springs in spaced relation to each other and to prevent individual spring from toppling or collapsing in the lateral direction. Techniques for attaching the wire mesh to the springs, such as by means of a plurality of clips separate from or integral with the mesh wires as in Ciampa et al U.S. Pat. No. 3,577,574, or by interweaving of the mesh wires with the spring ends as in Ciampa et al U.S. Pat. No. 3,270,354, have proven to be relatively expensive as compared with the cost of the resulting spring assemblies as a whole. Moreover, the resulting assemblies are not completely satisfactory from the standpoints of comfort and durability.

Accordingly, objects of the present invention are to provide a spring assembly for furniture or the like which is easy and economical to assemble, and which is comfortable, quiet and durable in operation; to provide an economical method for manufacturing furniture spring assemblies; and, in particular, to provide an economical mattress box spring and a method for manufacture thereof.

The invention, together with additional objects, features and advantages thereof, will be best understood from the following description when read in conjunction with the accompanying drawings in which:

FIG. 1 is a fragmentary, partially sectioned perspective view of a presently preferred embodiment of the invention as applied to mattress box springs;

FIG. 2 is a sectional view taken along the line 2--2 in FIG. 1; and

FIG. 3 is an enlarged view of a portion of FIG. 2 encircled by the line 3--3.

Referring to the drawings, a mattress box spring 10 which embodies the principles of the invention comprises a frame 12 having a plurality of parallel wooden slats 14 nailed or otherwise affixed to a frame base 16 with a spacer element 18 or the like disposed therebetween. The number of and spacing between slats 14 depend upon the desired size and grade of mattress 10, as is conventional and well known in the art. A plurality of generally conical coil springs 20 are disposed in a rectilinear array of parallel rows and columns on frame 12, each spring 20 being rigidly affixed to a slat 14 by the staples 22 at the spring base or end coil 24 of lesser diameter. As best seen in FIG. 2, the diameter of spring base coil 24 is increased or flared as compared with the generally tapering diameter of the spring as a whole to facilitate attachment of staples 22. The spring upper end coils 26 of greater diameter lie in a substantially common plane. Only a corner segment of box spring 10 is shown in the drawings, it being understood that the construction hereinabove and hereinafter described is repeated as required to form a box spring of desired size.

In accordance with one important aspect of the invention, the diameter d (FIG. 2) of each upper end coil 26, which coincides with the maximum diameter of conical spring 20, is of a dimension which is at least equal to, and preferably is greater than the overall spring heighth. In one presently preferred embodiment of the invention as applied to a mattress box spring construction which is illustrated to scale in the drawings, the spring heighth is approximately equal to four inches and the maximum spring diameter d is approximately equal to six inches or fifty percent more than the spring height. This may be contrasted with typical prior art box spring constructions in which the above-noted height and diameter dimensions are reversed. In cooperation with the shorter and wider springs provided herein, it is presently preferred to fabricate springs 20 of relatively thick wire stock, as on the order of ten gauge wire (0.135 inch diameter) or larger. The resulting springs are relatively stiff in the axial direction thereby to provide comfortable support, and at the same time inherently resist bending or toppling in the lateral direction when loaded. Spacers 18 compensate for the reduced height of springs 20 so that mattress 10 may possess standard overall outside dimensions.

A planar mesh 28 of woven spring wire or the like is bent at its generally rectangular periphery 29 around a border wire 30 and overlies springs 20 in the common plane of spring end coils 26 with border wire 30 being disposed above the periphery of frame 12. In accordance with another important feature of the invention, spring end coils 26 are unattached or free-floating with respect to mesh 28 and with respect to each other, i.e., are not positively connected to mesh 28 in any way. Because the shorter and wider configuration of springs 20 discussed hereinabove inherently resists lateral toppling, spring ends 26 need not be coupled to each other to maintain the desired spaced relationship therebetween as in the prior art, thereby eliminating a time-consuming and expensive step in the construction of mattress 10. The openings in mesh 28 are preferably substantially less than the diameter of spring end coil 26, the one inch grid of mesh 28 illustrated in the drawings being preferred. This relatively fine mesh not only eliminates support "holes" between the spring ends thereby to increase comfort and support, but also helps distribute the mattress load among the springs. Because of the present trend toward stiff box springs for enhanced sacral support, relatively thick wire for mesh 28, as on the order of fifteen gauge wire (0.072 inch), is preferred.

In accordance with a further feature of the invention, mesh 28 is coated as by dipping or brushing with a thin skin or layer 40 of resilient elastomeric material. One preferred material for brush-application to mesh 28 is a latex rubber marketed by Firestone Tire & Latex Co. of Akron, Ohio under the name HARTEX 102. Resilient skin 40 provides enhanced frictional contact between mesh 28 and spring end coils 26 so as to cooperate with the spring construction previously described to resist lateral toppling without providing positive attachment of the mesh and springs. Additionally, skin 40 deadens or eliminates rattling due to make-and-break contact between the mesh and springs during use. A skin thickness of up to 1/32 inch is contemplated, with 1/64 inch or less being preferred to minimize cost of material and achieve the desired thickness in a minimum of dipping operations--preferably one.

A mattress cover and pad 32 overlies mesh 28 and has a periphery 34 which drapes over border wire 30 and is fastened by tacks 36 to frame base 16. Preferably cover 32 is taut, i.e., in tension, and springs 20 are slightly compressed in the assembled condition of the mattress such that cover 32 holds mesh 28 and border wire 30 firmly in position with respect to springs 20. The relatively fine mesh 28 possesses the additional advantage of helping to prevent cover 32 from becoming snagged or torn by the upper ends of springs 20. In the assembly of mattress 10, springs 20 are fastened to a preassembled frame 12 as described. Cover 32 and a suitable pad (not shown) is placed on a work bench or the like, and the preassembled and precoated combination of mesh 28 and border wire 30 is located thereover. The assembled combination of frame 12 and springs 20 is then inverted and placed on mesh 28, and cover 32 is fastened to frame 12 as hereinabove described.

From the foregoing description it will be appreciated that the spring construction and method of assembly provided by the present invention produces a firm and comfortable mattress while significantly reducing the fabrication cost thereof. Although the invention has been described in connection with one specific embodiment thereof, many modifications and variations are contemplated. For example, spacer 18 may be removed from the mattress embodiment illustrated in the drawings to yield a relatively thin box spring which may be used in bunk beds, for example, and yet which retains all of the comfort and support characteristics of a box spring of standard size. Springs 20 need not be provided in a rectilinear row and column array; indeed, the present invention is uniquely adaptable for use with other spring array configurations since the mesh is not fastened to the springs. Thus one size of mesh 28 may be used on all mattresses of similar peripheral size regardless of desired mattress height or grade, an advantage which significantly reduces inventory problems. The mattress illustrated in the drawings embodies generally conical coil springs 20 which are presently preferred in the art for reasons of comfort and support. However, the present invention is equally applicable to and useful with other spring types, such as coiled helical springs of uniform diameter. In accordance with the invention, the diameter of the helical springs in the modification so proposed will be at least equal to and preferably greater than the corresponding spring height to provide firm support in the axial direction and yet inherently resist toppling or bending in the lateral direction, and the upper ends of the springs will be unattached or free-floating with respect to mesh 28 and to each other.

It will also be appreciated that those features of the invention embodied in latex coating on mesh 28 are useful with other than conical springs. Indeed, it is felt that a coating of latex may provide sufficient frictional engagement between the mesh and springs as spring end coils 26 "sink" into coating 29 to prevent toppling and thereby eliminate the requirement for clips and the like coupling mesh 28 to springs of conventional configuration. Although a dip- or brush-applied coating is preferred as described, the resilient material may also take the form of a thin sheet disposed between the mesh and springs. It will also be apparent that the entirety of each spring 20 may be precoated, or that only the upper end coils 26 may be brush-coated in situ, for example. These latter techniques are not preferred.

Although the invention has been described in connection with a mattress box spring, it will be appreciated that the invention is not limited thereto and is equally applicable to other furniture coil spring assemblies, such as in sofas or chairs for example. Indeed, the invention is intended to embrace the foregoing and all other alternatives and modifications as fall within the spirit and broad scope of the appended claims.