Box spring grid and method of manufacture

#Conventional box springs for supporting mattresses are comprised of a lower wooden support frame and an upper wire mesh support grid which is secured to a steel frame. Between the upper grid and the lower wood frame there are disposed a plurality of springs which are generally helical or cylindrical coil springs. To insure that the axis of each of the springs remains vertical, each spring must be secured to both the upper grid and to the lower wood frame.

#The prior art discloses a number of grid constructions which include means for securing the top or bottom coil of a spring to the grid. For example, U.S. Pat. No. 867,952 discloses a construction wherein the longitudinal grid wires are provided with ears or wings and the end coil of a spring is stretched around the ears. To insure that the coils of the spring remain stationary, so called tie rods are employed and are secured to the end coil of the spring by clips. One of the disadvantages of such a construction is the necessity of supplying such clips. Thus, from the point of view of the box spring manufacturer, the clips are another item of inventory and are another item which the spring assembler must have available and must mount on the product. As a result, both manufacturing and material costs are increased.

#U.S. Pat. No. 3,199,122 discloses a construction which employs so called links to hold the springs on a grid. While such a construction probably functions adequately to hold the springs in place, several disadvantages attend the use and assembly of this construction. For example, when the support grid and the springs are assembled, each of the links must be essentially woven between the end coil of a spring and the wire mesh which comprises the support grid. Thus, assembly time and costs are increased and it is necessary for the assembler to have available not only a quantity of coil springs and a pair of grids but, additionally, a quantity of links. Further, after the assembly is completed and the mattress is used, the nature of the construction is such as to permit relative movement between the links and the end coils of the springs whereby noise may be generated.

#FIG. 1 is a plan view of a box spring support grid embodying the instant invention and showing a illustrative arrangement of coil springs.

#FIGS. 2-4 are fragmentary views of portions of the assembly shown in FIG. 1 taken on lines 2--2, 3--3 and 4--4 of FIG. 1.

#FIG. 5 is a plan view of a box spring support grid embodying another form of this invention and showing an array of spring coils.

#Referring to FIG. 1, wire mesh grid 10 is comprised of a plurality of spaced apart, orthogonally disposed wires. More particularly, the wire mesh grid 10 is comprised of a plurality of longitudinally disposed warp wires 12 and a plurality of transversely disposed fill wires 14. Additionally, the grid 10 of FIG. 1 includes a plurality of support wires 16 which are disposed parallel to the warp wires 12. All the longitudinally disposed wires of the grid are secured, preferably by welding, to the orthogonally disposed fill wires 14 at intersections, for example the intersections 18.

#Between each pair of fill wires 14, an ear 20 is formed in each longitudinally disposed wire. Thus, it will be seen that a plurality of ears 20 are formed in each of the longitudinally disposed warp wires 12, a different one of said ears being disposed between each pair of adjacent fill wires 14. Similarly, each individual support wire 16 includes an ear 21 formed therein between the fill wires 14 adjacent to it. FIG. 2 is a fragmentary side view of a support wire 16 showing an ear 21 formed therein.

#Also shown in FIG. 1 is the end coil 24 of a plurality of coil springs. As may be seen, each end coil 24 has been expanded so as to have been snapped over opposing pairs of ears 20 whereby opposite sides of each end coil are engaged by a respective ear. Additionally, intermediate each ear one end of a support wire 16 has been reversely bent, as at 26, so as to engage and grip an end coil 24. In order to insure an adequate engagement between the reversely bent end portions of the support wires and the end coils of the springs, each of the rectangles or openings formed by a pair of fill wires and a pair of warp wires is dimensioned such that the distance between any pair of fill wires is not less than the inner diameter of the end coil of the spring to be attached thereto. In this manner, it is insured that each of the reversely bent end portions of a support wire 26 positively contact and engage the end coil of a spring. Also, it is preferable that the transverse dimension of each opening or rectangle be less than the inner diameter of the end coil which will be secured therein. However, this latter limitation regarding the transverse dimension of each rectangle or opening contemplates that a spring coil will be expanded, and the grid wires contracted, when a spring is mounted on the grid. Thus, with this preferred construction, the end coil of each spring may be slightly elongated when it is mounted on the support grid 10.