GB2025217A - Spring assemblies for mattresses - Google Patents

Abstract

A spring assembly for a mattress includes a plurality of spiral coil springs (16), arranged in substantially parallel rows, a plurality of cross helicals (22) lacing together adjacent springs in the same row, adjacent coil springs with laced-together terminal convolutions (20) being restricted in their movement relative each other to a maximum angle of deflection. The convolutions (20) of adjacent springs have offset portions (24) with overlying alternating projections (30, 32) which permit a hinging action of the adjacent springs relative to each other about the adjacent offset portions of their terminal convolutions, until the maximum deflection angle between the offsets is reached. Further loading of one spring after this angle is reached results in compression of adjacent springs and greater resistance to loading for a given degree of spring compression, i.e. greater firmness. <IMAGE>

Description

SPECIFICATION Spring assemblies for mattresses This invention relates to spring assemblies and spiral coil springs for mattress innerspring units.

An innerspring unit generally includes a plurality of spiral coil springs arranged in a plurality of substantially parallel rows. The springs of each row are interconnected by lacing each spring to its adjacent springs with cross helicals. Cross helicals are spiral coils of substantially smaller cross-sectional diametes than the coil springs. The cross helicals extend transversely of the rows of the coil springs, in both the upper and lower surfaces of the unit, and lace about the end or terminal convolutions of adjacent coil springs. Terminal convolutions of coil springs generally are closed loops which can be formed with two opposed offset portions. Coil springs that have offsets are arranged in a innerspring unit so that the offsets are adjacent one another in each row and encircled by the cross helicals.

It is desirable to provide an innerspring unit that conforms to the shape of a supported body. Innerspring units containing coil springs with offset portions generally have a greater conformance to a supported body than units having coil springs without such offsets. The spring conformance is attributable, at least in part, to the hinging action between adjacent springs. Conventional spring offsets are U-shaped members and a cross helical encircles the base portions of these U-shaped members. The encircled base portions of adjacent offsets both are disposed within the circumference of the cross helical, substantially parallel to its principal axis.

Although they are disposed in close proximity, an extensive amount of hinging action between them is allowed; the base portions can move past one another. The hinging action permits the coil springs to be compressed somewhat independently of each other, conforming to the shape of a body being supported or other load.

It is also desirable to provide an innerspring unit having a great degree of firmness. Firmness can be defined as the extent of coil spring compression versus the applied load. Firmness of a unit is dependent upon many variables, such as the unit's coil count (number of coils per unit surface area) and the coil stiffness. For a given unit, raising the coil count or substituting coil springs of greater stiffness will dec reuse the extent of spring compression versus the applied load, but will also increase the expense of manufacturing such unit. Another method for increasing the firmness of an innerspring unit, described in U.S. Patent No. 3,653,082, is to crimp or compress the cross helicals about the offsets of coil springs at the longitudinal side borders of the unit.

The crimps frictionally engage the cross helicals to the encircled offsets, restricting the hinging action between the interconnected offsets and therefore between adjacent coil springs. This last method, however, reduces the extent of spring conformation to the shape of a supported body, which is depen dent upon the hinging action.

It is desirable that a mattress innerspring unit be both firm and have a high degree body conformation, without significantly sacrificing one characteristic for the other. It is also desirable to maximize the firmness and the body conformation characteristics of an innerspring unit without adding substantially to the manufacturing expense for such unit. It is also desirable to provide varying degrees of firmness and body conformation to different portions of an innerspring unit, for instance, more firmness to the longitudinal side borders and more body conformation to the center or end portions. It may also be desirable to provide additional firmness at other regions of an innerspring unit, such as the longitudinal mid-region of a very wide mattress.

In accordance with one aspect of the invention, there is provided a spring assembly for an innerspring unit, comprising a plurality of spiral coil springs arranged in a plurality of substantially parallel rows, said coil springs having opposed terminal convolutions forming the upper and lower surfaces of the unit; and a plurality of cross helicals extending transversely of the rows of coil springs, lacing together a plurality of adjacent springs about adjacent portions of their terminal convolutions; wherein at least a pair of said adjacent portions of the terminal convolutions of said coil springs that are laced together by a cross helical are each formed as offsets having a plurality of alternating projections, portions of which are encircled by said cross helical, and wherein said alternating projections of one offset substantially overlie the alternating projections of the second offset of said pair and movement of the offsets of a pair, relative to each other, is substantially restricted to a maximum angle of deflection by said encircling cross helical.

In accordance with another aspect of the invention, there is provided a spiral coil spring comprising a plurality of convolutions ending in two opposed terminal convolutions wherein at least one of said terminal convolutions includes at least one offset portion formed with alternating projections lying in the same plane for restricting the movement of said coil spring to a maximum angle of deflection, relative to an adjacent coil spring, when laced together with an encircling cross helical about said offset.

The spiral coil springs with offset configurations allow hinging action between adjacent coil springs to a predetermined degree and thereafter, upon further loading, transfer a part of the pressure to the surrounding springs, causing a greater resistance to the load, i.e. greater firmness. The spring assembly with at least some of its coil springs having such an offset configuration optimizes both the characteristics of spring conformation and firmness.

In a particular embodiment of the invention des cribed in more detail below, the spiral coil springs each have at least one offset, on at least one of its two terminal convolutions, that has alternating projections forming a sinuous or serpentine configuration. The spring assembly described below includes at least a pair of such coil springs positioned adja cent one another so that the projections of their adj acent offsets are substantially superimposed on one another. The projections preferably extend beyond the circumference of the encircling cross helical.

Such offsets are free to hinge relative to one another until a maximum deflection angle, between the planes of the projections, is reached. This deflection angle is dependent upon the dimensions of the projections and the internal diameter of the encircling cross helical. When this maximum angle is reached, hinging action between the springs is retarded by the cross helical and loading pressure on one of the coil springs will be partially transferred to the other coil spring. This transference of loading pressure results in a lessening of spring compression relative to the amount of load. Greater firmness is therefore provided without sacrificing the desirable amount of a hinging action between springs and therefore the conformation characteristic of the unit.

The coil springs, when laced together by cross helicals, can be considered restricted pairs of coil springs or springs having restricted pairs of adjacent offsets.

The offset projections lie substantially in the same plane as the other portions of the spring's terminal convolution and extend alternately in opposite directions.

Adjacent offsets are configured so as to be substantially superimposed on one another. If pressure is applied to an overlying coil spring of a restricted pair, its inwardly-extending offset projection will be prevented from substantial movement downward by the underlying projection of the other coil spring while its outwardly-extending projection will move in an upward arc until restricted by the encircling cross helical. Thereafter, further loading pressure will be partially transferred to the other coil springs, lessening the extent of compression of the loaded coil spring per amount of load. A similar but opposite action occurs when pressure is applied to a coil spring having an underlying offset.

In a preferred embodiment a terminal convolution of the coil spring is formed with alternating projections on both of its opposed offsets. Moreover, the coil spring may be formed with both of its terminal convolutions so configured.

An innerspring unit incorporating a spring assembly in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which FIGURE 1 is a partially cut-away perspective view of a mattress having the innerspring unit, FIGURE 2 is a fragmentary top plan view of the innerspring unit of Figure 1, FIGURE 3 is an enlarged fragmentary top plan view of the innerspring unit of Figure 1, FIGURE 4 is a cross-sectional side view of the innerspring unit of Figure 1,taken along line 4-4 of Figure 3, FIGURES 5 to 8 are diagrammatic side views of two interconnected coil springs of the innerspring unit of Figure 1, and FIGURE 9 is a top plan view of a preferred spring of the innerspring unit of Figure 1.

Referring to Figure 1, the mattress 10 includes the innerspring unit 12 which is enclosed in a suitable mattress cover 14. The innerspring unit 12 includes a plurality of spiral coil springs 16 which are aligned in a plurality of rows. Each spiral coil 16 is formed of a series of convolutions ending in end orterminal convolutions 20 and is interconnected to adjacent coil springs 16 by cross helicals 22 which lace about the terminal convolutions 20. Each terminal convolution 20 is formed with two opposed offset portions 24 which are encircled by the cross helicals 22. The cross helicals 22 restrict movement of adjacent offset portions 24, relative to one another, to a maximum deflection angle, retarding hinging action between springs 16.Loading pressure on one coil spring 16 will be partially transferred to adjacent coil springs 16, increasing the firmness of the unit 12.

The hinging action allowed between springs 16 before the maximum deflection angle is reached is, however, sufficient for a desirable amount of spring conformation to a supported body.

Referring now to FIGURE 2 also, the spiral coil springs 16 of the innerspring unit 12 are arranged in a plurality of rows that extend longitudinally of the innerspring unit 12. Adjacent coil springs 16 in each row are sufficiently close to one another so that their adjacent offset portions 24 at least partially overlap.

The cross helicals 22 extend transversely of the innerspring unit 12 and lace about the overlapped offset portions 24 of pairs of coil springs 16 in each row, from one longitudinal side of the innerspring unit 12 to the other.

Each coil spring 16 has a terminal convolution 20 at both of its opposite ends and the terminal convolutions 20 of the coil springs 16 form both the upper and lower surfaces of the innerspring unit 12.

The cross helicals 22 lace together the offset portions 24 of the coil springs 16 in both the upper and lower surfaces of the unit 12 in the same manner. For simplicity and clarity, only one of the two terminal convolutions 20 of the coil springs 16 is illustrated and the opposite terminal convolutions 20 can be considered identical.

Referring now to FIGURES 3 and 4 also, the offset portions 24 of the terminal convolutions 20 are formed with alternating projections, designated generally 26, at least some of which extend beyond the circumference of the encircling cross helical 22.

Each terminal convolution 20, including its opposed offset portions 24, lies substantially in a single plane.

Adjacent coil springs 16 are disposed with their adjacent alternating projections 26 at least partially overlapped, and the interconnecting cross helical 22 partially encircles the projections 26. Although other arrangements can be envisioned, each coil spring 16 is preferably positioned so that one of its offset portions 24 overlies the offset portion 24 of the adjacent coil spring 16 and its other offset portion 24 underlies the offset portion 24 of the opposite adjacent coil spring 16.

The alternating projections 26 of the offset portions 24 are preferably formed so as to include a base member 28, a first or inwardly-extending projection 30, and a second or outwardly-extending projection 32. The first and second projections 30,32, therefore, extend in opposite directions relative to one another.If the offset portions 24 are first envisioned as having conventional U-shaped configurations, the alternating-projection configuration deviates from this U-shaped configuration by having the first and second projections 30,32 extend on opposite sides of the base of the hypothetical U-shaped offset The cross helical 22 preferably encircles the overlapped offsets 24so that their base portions 28 lie within its circumference, substantially aligned with the cross helical s principal axis, and portions of both the first and outside of its circum- ference. The effects of such construction will be described in detail below.

The two opposed offsets 24 of a terminal convolution 20 are formed as superimposable mirror images of one another. The right-hand offset portion 24 of a coil spring 1(6 will coincide with the left-hand offset portion 24ofthe adjacent coil springs 16. Adjacent, overlapped offset portions 24 will, therefore, be superimposed on one another.

Referring now to FIGURES 5,16,7, and 3 also, when a coil spring 16 is subjected to loading, i.e. compres- sed, its offset portions 24 will hinge relative to the offset portions 24 of the adjacent springs 16. More specifically, an offset portion 24 that overlies the adjacent offset portion 24 will begin to rotate. Its first or inwardly-extending projection 30 will be substantially prevented from downward movement by the underlying second or outwardly-extending projection 32 of the adjacent offset portion 24. its second projection 32 will be tree to move in an upward arc relative the underlying offset portion 24. Its base member 28 will also move in an upward arc.The planes of these overlapped offset portions 24, which are substantially parallel to one another when the springs 28 are underzero load, will form an angle, the angle of the deflection.

In a similar manner, when the coil spring 16 of an underlying offset portion 24 is compressed, the second or outwardly-extending projection 32 is prevented from movement upward by the first or inwardly-extending projection 30 of the overlying offset portion 24. The underlying offset portion 24, however, rotates relative to the overlying offset portion 24 because its base member 28 and first projection 32 is allowed to move in a downward arc. Again, the planes of the offset portions 24 will move from a relative parallel position to form an angle of deflection.

This movement of one offset portion 24 relative its adjacent offset portion 24 when its coil spring 16 is compressed provides a hinging action between the adjacent springs 16. The hinging action provides a degree of independent spring compression, allowing the innerspring unit 12 generally to conform to the shape of a reclined body. This conformation characteristic of the innerspring unit 12 results in a desirable degree of comfort to a body reclined thereon. If total hinging action was allowed, that is, if the angle of deflection was unrestricted, an innerspring unit would be less firm, for a given coil count and coil stiffness, than the unit 12 of the present invention. The coil springs 16 of the innerspring unit 12 are not allowed a complete hinging action, as described in detail below; the hinging action is allowed only until a predetermined, maximum deflection angle is reached.When a given coil spring 16 is further compressed or loaded, the adjacent coil springs 16 will be compressed along with it. The more coil springs l6thatare placed undercomprns- sion for a given load, the greater the resistance to that load will be; the innerspring unit 12 will have a greater degree of lfirmnness.

The inner diameter of the encimling cross helical 22, relative to the dimensions of the alternating projections 26, defines the maximum angle Sof deflec- tion As described above, eitherthefirstor inwardly-extending projection 30 will rotate in a fdownwardlyssxtending arc, orthe second or outwardly-extending projection will rotate in an upward arc upon compr.ession of its coil spring 16.

The extent (Of movement, relative to the overlying or underlying adjacent offset portion 22, will be restricted bythe encircling cross helical 22. Each of the projections 30,32 have leg portions 34 and tip or peak portions 36. The peak portions 36 lie outside of theencireling cross helical 22 while the leg portions 34 are disposed within its circumference.As the angle of deflection increases upon movement of a given offset24, the leg portions 34 will approach the inner surfaces of the encircling cross helical 22 until they abut, preventing further movement of the offset portion 24 relative its adjacent offset portion 24. The maximum angle of deflection between the offset planes is reached; no substantial movement (of the offset portions 24, relative one another, is possible.

The innerspring unit 12 has the desirable degree of conformation to a reclined body because of the hinging action between adjacent coil springs 16. The innerspring unit 12 also has a greater degree of firmness. A similar unit that does not have offset portions 24 formed with alternating projection 26, for instance a U-shaped offset portion, would be substantially less firm. The optimum firmness is provided without the expense of increasing the coil count of the unit orthe stiffness of the individual coils, and without sacrificing the desired degree of spring conformation to the shape of a supported body.

The preferred angle of deflection is from about 0 to about 15 degrees. The angle chosen would however depend upon the degree of firmness desired and the other variables contributing to the firmness of the unit 12. A preferred coil spring 16, with offset portions that extend 1 to 1-114 inches from end-to-end Ibase line), would have alternating projections 30, 32 extending approximately 114 inch from the base line.

In a preferred embodiment, illustrated in Figure 9, the opposed offset portions of a coil spring 42 can differ from one another. This preferred coil spring 42 has a first and a second offset portion 44,46 with different lengths. The first offset 44 has a first and a second projection 48,50 but substantially no base member. The second offset portion 46 has a first and a second projection 52, 64 and a base member 56.

The second offset portion 46 is about 25% longer than the first offset portion 44.

The configurations of offset portions illustrated and described herein are considered the preferred configurations, although other configurations may be envisioned which would provide the restricted spring hinging action of the present invention.

Moreover, the invention has been described and illustrated for an innerspring unit 12 wherein all of the interconnected, adjacent coil springs 16 have offset portions 24 formed with alternating projec tions 26, in both the upper and lower surfaces of the unit 12. This construction may, however, be provided only in a portion of the unit 12 where a controlled degree of spring conformation and firm ness is desired. The construction of any given innerspring unit 12 may also be varied as to max imum angle of deflection in various portions of the unit 12, so as to provide different degrees of spring conformation and firmness to different portions of the unit 12.

The above described spring assembly is firmer than assemblies having conventional spring offsets and yet has the desired degree of body conform an tion. In the spring assembly spring conformation and firmness characteristics are optimized without substantially increasing the cost of the unit.

Claims (11)

1. Aspring assembly for an innerspring unit, comprising a plurality of spiral coil springs arranged in a plurality of substantially parallel rows, said coil springs having opposed terminal convolutions forming the upper and lower surfaces of the unit; and a plurality of crous helicals extending transversely of the rows of coil springs, lacing together a plurality of adjacent springs about adjacent portions of their terminal convolutions; wherein at least a pair of said adjacent portions of the terminal convolutions of said coil springs that are laced together by a cross helical are each formed as offsets having a plurality of alternating projections, portions of which are encircled by said cross helical and wherein said alternating projections of one offset substantially overlie the alternating projections of the second offset of said pair and movement of the offsets of a pair, relative to each other, is substantially restricted to a maximum angle of deflection by said encircling cross helical.

2. A spring assembly according to claim 1, wherein each offset of a restricted pair of adjacent offsets has a base portion and at least first and second oppositely-extending projections that extend beyond the circumference of the encircling cross helical when said base member is substantially aligned with the principal axis of the encircling cross helical.

3. A spring assembly according to claim 2, wherein the base members and the first and second projections of offsets of a restricted pair overlap each other in substantially contiguous relationship.

4. A spring assembly according to any of claims 1 to 3, further including a plurality of restricted pairs of adjacent offsets in both the upper and lower sur faces of the unit.

5. A spring assembly for a innerspring unit, cons tructed and arranged substantially as herein des cribed with reference to the accompanying draw ings.

6. A spiral coil spring comprising a plurality of convolutions ending in two opposed terminal con volutions wherein at least one of said terminal con volutions includes at least one offset portion formed with alternating projections lying in the same plane for restricting the movement of said coil spring to a maximum angle of deflection, relative to an adjacent coil spring, when laced together with an encircling cross helical about said offset.

7. A spriral coil spring according to claim 6, wherein said offset with alternating projections includes at least a first and a second oppositelyextending projection.

8. A spiral coil spring according to claim 6 or7, wherein at least one of said terminal convolutions includes two opposed offset portions formed with alternating projections.

9. Aspiral coil spring according to claim 8, wherein said opposed offset portions of a terminal convolution have substantially mirror-image configurations.

10. A spiral coil spring according to claim 8 or 9, wherein at least one of said offset portions includes a base member extending perpendicularly from a line bisecting either of the first and second alternately-extending projections.

11. A spiral coil spring constructed and arranged substantially as herein described with reference to the accompanying drawings.