Mattress Spring Unit Construction

Abstract

An improved mattress inner spring unit having a plurality of coil springs arranged in rows with each coil spring being comprised of a series of convolutions. Each coil spring terminates in end convolutions which have offset portions formed thereon. The coil springs are arranged in the inner spring unit so that the offset portions extend into overlapping relation with adjacent offset portions. Such an arrangement allows the coil springs to be secured together by spirally rotating a helical coil across each of the rows so as to interlace the offset portions. The helical coils are thus positioned in both the upper and lower surfaces of the inner spring unit. When all adjacent offset portions have been interlaced with the helical coils, the end portions of each helical coil are compressed around the overlapped offset portions of the outermost row of coil springs.

Description

This invention relates to improvements in mattress inner spring units and, more particularly, to the cross helical coil structure for mattress inner spring units.

For the most part, the mattress inner spring units are formed of a plurality of interconnected coil springs arranged in side by side relation in a plurality of parallel rows between upper and lower border wires which are connected to the external coil springs, usually by means of helical wires, to provide the coil spring assembly. It has been the practice to interconnect the coil springs with a plurality of parallel helical coils extending transversely across each of the rows in both the upper and lower surfaces of the unit. The coil springs are interconnected by rotating each helical coil spirally about its major axis until it is extended across each of the rows interlacing overlapping portions of the adjacent coil springs. However, once the helical coils are in position they have a tendency to "spin-out". (Helical "spin-out" is a commonly used term in the bedding field referring to the helical coil unwinding from the inner spring unit.) To eliminate this action, it has been the practice to give each end of the helical coil a reverse twist, which is the doubling back of the end portion of the coil on itself, thus creating obstructions that prevent the helical coil from unwinding from the inner spring unit.

It has also been the prior practice to strengthen the interconnected coil springs by "crimping", which comprises reducing the diameters of the interlaced portions of the helical coils to approximately the same cross-sectional area as the overlapping portions of the coil springs, as shown for example in U.S. Pat. No. 2,111,026. However, the prior art practice of crimping at every point where the coil springs overlap greatly inhibits the action of the coils and thus, reduces resiliency.

It is therefore an object of the present invention to provide a mattress inner spring unit which contains helical coils where the diameter of each helical coil is reduced at only the overlapping portions of the outermost rows of coil springs so as to eliminate helical spin-out and stiffen the sides, but not the head and foot, of the inner spring unit.

It is another object to provide an inner spring unit of this type that allows full action and resiliency of all inner coil springs.

It is a further object to provide an inner spring unit of this type that maintains better body conformity.

The foregoing and other objects are realized in accord with the invention by providing a generally rectangular mattress inner spring unit comprising a plurality of coil springs arranged in rows so that adjacent portions of each coil spring overlap. The coil springs are tied together by spirally rotating helical coils across each of the rows to interlace the overlapping portions of the coil springs in both the upper and lower surfaces of the inner spring unit. The end portions of each helical coil are compressed at the overlapped portions of the outermost row of coil springs. The compression reduces the diameter of the helical coil to approximately the same cross-sectional area as the overlapped portions so that the overlapped portions are held in a non-hinging position. The outermost row of coil springs are thus stiffened and helical spin-out is eliminated.

FIG. 1 is a fragmentary plan view of an inner spring unit embodying the features of this invention;

FIG. 2 is a fragmentary plan view of the inner spring unit of FIG. 1 taken along line 2--2 of FIG. 1.

Referring now to the drawings, and more particularly to FIG. 1, there is illustrated a mattress inner spring unit embodying the features of the present invention and indicated generally by reference numeral 4. The inner spring unit 4 includes a plurality of coil springs 6 arranged in rows with each coil spring 6 being comprised of a series of convolutions. Each coil spring 6 terminates in end convolutions 9 which have opposed offset portions 8 formed thereon. The coil springs 6 are positioned so that the offset portions 8 extend into overlapping relation with adjacent offset portions 8. Such an arrangement allows the coil springs 6 to be secured together by spirally rotating a helical coil 10 across each of the rows so as to interlace the offset portions 8. The helical coils 10 are thus positioned in both the upper and lower surfaces of the inner spring unit 4. When all adjacent offset portions 8 have been interlaced with the helical coils 10, end portions 12 of each helical coil 10 are compressed around the overlapping offset portions 8 of the outermost row of coil springs 6. The compression of the end portions 12 reduces the coil diameter to approximately the same cross-sectional area as the offset portions 8 so that the offset portions 8 are frictionally engaged.

Considering now the mattress inner spring unit 4 in more detail, and referring to FIGS. 1 and 2, the inner spring unit 4 includes a plurality of coil springs 6 arranged in side by side relation in a plurality of parallel rows. Each coil spring 6 is preferably tapered from its ends toward the middle so that intermediate convolutions will be of smaller diameter than end convolutions 9. Only one end convolution 9 is indicated in the drawing as the other end convolution is identical with it. Each end convolution 9 is formed to be generally circular in shape with the exception of two offset portions 8. The offset portions 8 are preferably U-shaped and are formed so as to be directly opposite each other on each convolution 9. When the coil springs 6 are properly positioned in the inner spring unit 4 so as to be in rows, the offset portions 8 extend to overlap adjacent offset portions 8. The coil springs 6 can thus be secured together by spirally rotating helical coils 10 across each of the rows in a conventional manner so as to interlace the overlapping offset portion 8. The helical coils 10 are of relatively small diameter in comparison to the end convolutions 9 but are sufficiently large to be interlaced with the offset portions 8, thus holding the coil springs 6 together in both the upper and lower surfaces of the inner spring unit 4.

Each end portion of the helical coils 10, designated by reference numeral 12, is compressed by any suitable means, such as a pair of dies, so that the offset portions 8, on the outermost coil springs 6, are held against relative hinging movement. The compression of the helical coils 10 at their ends 12, as shown in FIG. 2 of the drawings, reduces the diameter of this portion of the helical coil 10 so that it is approximately the same cross-sectional area as the overlapping offset portions 8. This deformation of the helical coil 10 eliminates the tendency of the helical coil 10 to spin out of the inner spring unit 4, and arrests the hinging action of the overlapping offsets 8 by frictionally engaging them. In this manner, the outermost rows of coil springs 6 are stiffened while the inner rows of coil springs 6 are allowed full hinging action to provide for better body conformity and more resiliency.

It will be understood that changes may be made in the details of construction, arrangement and operation without departing from the spirit of the invention, especially as defined in the following claims.

Claims

I claim:

1. In a generally rectangular mattress inner spring unit, a spring structure comprising:

a. a plurality of coil springs arranged in side by side relation in a plurality of parallel rows defining upper and lower surfaces of said unit;

b. offset portions formed on each end of said springs extending so as to overlap adjacent offset portions;

c. helical coils extending across each of said rows in said upper and lower surfaces and coiling about said overlapping offset portions so that adjacent springs are interconnected, each of said helical coils being deformed only on the end portions, said deformed end portions frictionally engaging offset portions located on the outermost rows of coil springs so that said offset portions are held in a non-hinging position; and

d. said deformed end portions being compressed so as to distort the diameter of said helical coil.

2. In the generally rectangular mattress inner spring unit of claim 1 wherein said offsets are U-shaped.

3. In a generally rectangular mattress inner spring unit, a spring structure comprising:

a. a plurality of coil springs arranged in side by side relation in a plurality of parallel rows defining upper and lower surfaces of said unit;

b. U-shaped offset portions formed on each end of said springs extending so as to overlap adjacent U-shaped offset portions;

c. helical coils extending across each of said rows in said upper and lower surfaces and coiling about said overlapping U-shaped offset portions so that adjacent springs are interconnected, each of said helical coils being deformed only on the end portions; and

d. said deformed end portions being compressed so as to distort the diameter of said helical coil and said deformed end portions frictionally engaging offset portions located on the outermost rows of said coil springs so that said offset portions are held in a non-hinging position.