US3911511A

US3911511A - Spring assembly

Info

Publication number: US3911511A
Application number: US528018A
Authority: US
Inventors: Larry Higgins; Henry Zapletal
Original assignee: Leggett and Platt Inc
Current assignee: Leggett and Platt Inc
Priority date: 1974-11-29
Filing date: 1974-11-29
Publication date: 1975-10-14
Anticipated expiration: 1992-10-14
Also published as: DK421875A; ZA755014B

Abstract

A spring assembly for mattresses, innersprings, and the like. The assembly comprises rows of coils, each row comprising a continuous length of wire formed into a plurality of like-handed coils interconnected by Z-shaped wire segments alternately disposed at the top and bottom of the coils. Adjacent rows of coils are of the same hand or twist and are coupled by a helical wire wound through overlapping Z-shaped wire segments.

Description

[4 1 Oct. 14, 1975 United States Patent [1 1 t al.

Higgins e SPRING ASSEMBLY Thomas, Jr. 5/351 [75] Inventors: Larry Higgins; Henry Zapletal, both of Carthage, Mo.

Primary Examiner-Casmir A. Nunberg Assigneei Legge & Plan, Incorporated, Attorney, Agent, or FirmWood, Herron & Evans Carthage, Mo.

ABSTRACT [22] Filed: Nov. 29, 1974 A spring assembly for mattresses, innersprings, and the like. The assembly comprises rows of coils, each row comprising a continuous length of wire formed into a plurality of like-handed coils interconnected by Z-shaped wire segments alternately disposed at the top and bottom of the coils. Adjacent rows of coils are of the same hand or twist and are coupled by a helical wire wound through overlapping Z-shaped wire segments.

1.0 l 5O5 3 3 /52 52... C 6 040,5 5 5 SN6 34 0 C5 7 "4 M M 8 1 H m m 8 "m s. l 0 2a 1 C 0. .l D. h A UmF 1]] l 21 2 555 .I [ll [56] References Cited UNITED STATES PATENTS 3,462,774 8/1969 5/260 13 Claims, 7 Drawing Figures US. Patent Oct. 14, 1975 Sheet 1 of4 3,911,511

US. Patent Oct. 14, 1975 Sheet 2 of 4 3,911,511

US. Patent Oct. 14, 1975 Sheet 3 of 4 3,911,511

m 1- I E US. Patent 0a. 14 1975 Sheet4 SPRING ASSEMBLY The present invention relates to spring assemblies of the type commonly used in the construction of innersprings, mattresses, upholstered furniture, and the like. More particularly, the present invention relates to a mattress spring core assembly in which each of the rows of coils is formed from a single continuous length of wire.

The prior art is replete with spring assemblies useful for mattresses, innersprings, and the like. While these are of various configurations, most of them employ rows of coils interconnected at the top and bottom by wire lacings. Such prior art spring assemblies, varied though they are in exact configuration, all are subject to some shortcomings. Primary among these shortcomings is the large amount of wire employed to make up the coil, as well as the complexity of the lacing schemes employed for the interconnection of the coils. Many of the configurations are subject to the requirement that they be hand assembled and consequently they are excessively expensive to manufacture.

Another typical problem in the manufacture of mattresses or innersprings is that of optimizing comfort by utilizing coil assemblies which are relatively firm yet resilient, with a minimum of lateral deflection, or socalled water bed effect. Optimally, when a person is lying on a mattress, the coils beneath him give sufficiently to accommodate the contour of the body but not so much so that proper orthopedic support of the body is lost. Moreover, the coils to either side of the person should be deflected by a minimal amount and help to carry the weight on the primary loaded spring coils. Then, too, the mattress or innerspring should be quiet, i.e., free from noise caused by scraping or slapping of adjacent coils or interconnections when deflected by the weight of a person sitting or reclining on the spring assembly.

One approach to overcoming the problems and shortcomings set forth hereinabove is disclosed in U.S. Pat. No. 3,657,749 in which rows of coils are formed from a continuous length of wire interconnected by Z- shaped connecting segments. The opposite rows of coils are of opposite hands, i.e., of alternately right hand and left hand twist, and the rows are interconnected by a zigzag connector wire. The primary advantage of the spring assembly disclosed in this patent is that it facilitates machine construction of the springs without any manual assistance and it substantially reduces the quantity of wire required to obtain a given degree of firmness.

While the spring core assembly disclosed in U.S. Pat. No. 3,657,749 has the advantages set forth hereinabove, it also suffers from several shortcomings. Specifically, that assembly has been found to be very noisy in that it allows wires to snap over each other and to come into contact with other wires during compression and relaxation of the individual spring coils. Additionally, there is a problem of the invididual coils shifting laterally in the course of compressing with the result that the complete assembly has the feel of a water bed, i.e., it allows the top surface to move laterally as well as to deflect in the course of compression.

Another problem or shortcoming encountered with the spring assembly disclosed in U.S. Pat. No. 3,657,749 is that it is possible when a corner is deflected severely as mattresses often are in the course of placing a fitted sheet over the mattress, for the coils to become overlapped and locked in that overlapped condition. When that overlapping occurs the mattress either has a hole or unsupported area in it, or it is maintained in a deflected or bent condition.

The shortcomings of U.S. Pat. No. 3,657,749 have been overcome by this invention without sacrificing the advantages of their construction. According to the practice of this invention, a row of coils are all made of a single continuous strand of wire and all of the rows are of the same hand or twist. These rows are placed in juxtaposition with the Z-shaped interconnecting segments of adjacent rows in overlapping relation and the overlapping sections of the Z-shaped segments are laced or secured together by a helical wire connector.

This construction has numerous advantages over that of the above identified patent while it still retains the advantages of the spring assembly of U.S. Pat. No. 3,657,749. Specifically, it maintains the advantages of being capable of being manufactured and assembled without any hand labor and it maintains the advantage of being capable of being manufactured of lightweight, inexpensive wire so that material cost is substantially reduced. Additionally, though, it overcomes the shortcomings of the mattress assembly disclosed in the above identified patent by eliminating the noise and the lateral shifting problem. It also is so constructed that it is impossible for the individual coils to become overlapped and interlocked.

Another advantage of the spring core assembly of this invention is that it is easily adaptable to the manufacture of varying size mattresses because the length may be varied without varying the width and vice versa. In the mattress core assemblies of the above identified patent, the variation in one dimension, i.e., length, required a corresponding change in the other direction, i.e., width. With the construction of this invention, either may be varied without affecting the other.

These and other advantages of this invention will be more readily apparent from the following description of the drawings, in which:

FIG. 1 is a perspective view of a corner of an innerspring embodying the invention of this application.

FIG. 2 is a top plan view of the innerspring of FIG. 1.

FIG. 3 is an end elevational view taken on line 33 of FIG. 2.

FIG. 4 is an end elevational view taken on line 4-4 of FIG. 2.

FIG. 5 is a diagrammatic plan view in which each coil pair in each row is designated by block lines constituting continuations of the Z-shaped coil interconnection segments.

FIG. 6 is a top plan view of a second embodiment of the invention of this application.

FIG. 7 is a diagrammatic plan view of the embodiment of FIG. 6 in which each coil pair in each row is designated by block lines constituting continuations of the Z-shaped coil interconnection segments.

Referring now to the drawings and particularly to FIGS. 1 and 2, there is shown an innerspring unit 20 utilizing a spring assembly made in accordance with the invention of this application. The upper surface 21 of innerspring 20 has a generally rectangular periphery 22 which may be enclosed by a border wire (not shown). Similarly, the lower surface 23 of innerspring 20 has a rectangular periphery which also may be enclosed by a border wire (not shown).

Innerspring includes a plurality of

rows

24, 25, 26 of coils, all of the same twist, as, for example, all right handed twist or all left handed twist. As best illustrated in FIGS. 1 and 2, each

row

24, 25, and 26 of coils is formed from a continuous length of wire. The wire is wound to form a plurality of spaced coil pairs 27 interconnected by substantially Z-shaped wire segments 28,

18 disposed sequentially first in the plane of upper in-' nerspring surface 21 and then within the plane of lower innerspring surface 23.

As best illustrated in FIG. 2, each coil pair 27 comprises a first right handed coil 27a offset from a second right handed coil 27b, having the same number of turns as coil 27a. As seen in FIG. 5, the axes of coils 27a lie within a plane 29 which is parallel to, but spaced apart from, a second plane within which lie the axes of offset coils 27b. It will be appreciated from FIG. 2 that the axes of adjacent coils 27a and adjacent coils 27b are equidistant, the axes being generally perpendicular to.

the upper and

lower surfaces

21 and 23 of innersrping unit 20.

While each of the

coils

27a and 27b is illustrated as having approximately two full turns or revolutions, this number is not critical. Thus, a greater or lesser number of convolutions may be used, depending upon the tensile strength of the wire and the manner in which the coils are formed so as to provide a spring force appropriate to the particular application.

As will be appreciated from the following description, the coil interconnection technique utilized in innerspring mattress 20 prevents adjacent coils from binding when compressed even though they are not of hourglass configuration. Thus, a variety of shapes may be employed such as hourglass or potbellied, but the cylindrical shape illustrated is perferred.

Each

row

24, 25, and 26 is configured identical to each adjacent row and each coil within each

row

24, 25, 26 is identical to every other coil and of the same twist or hand.

In the preferred embodiment of the invention, the spacing between axes of adjacent coils within row 24 is the same as between axes spacing of adjacent coils and

rows

25 and 26. Further, should a coil pair in row 24 be interconnected in the plane of upper innerspring surface 21, the adjacent coil pair in row 25 is interconnected in the same plane of upper innerspring surface 21. This is best illustrated in FIGS. 1 and 2 where in row 24, typical

adjacent coils

27a, 27b are interconnected by Z-shaped wire segment 28 lying within upper innerspring surface 21. The adjacent coil pair 32 in row 25,

coils

31a and 31b, are interconnected by a Z- shaped wire segment 32 lying in the same plane of the upper innerspring surface 21 and Z-shaped wire segment 33 lying in the same plane of the lower surface 23. This pattern is repeated throughout the innerspring unit 20. The result is Z-shaped segments in the plane of the upper surface 21 are aligned in columnar fashion and similarly the Z-shaped segments in the plane of the lower surface 23 are also aligned in columnar fashion in vertical planes which are located midway between the vertical plane of the Z-shaped segments in the plane of the upper surface 2]. Otherwise expressed, the Z- shaped segments which interconnect the pairs of coils are aligned both in rows and in columns in the planes of the upper and

lower surfaces

21 and 23.

In order to connect the adjacent rows of coils, the Z- shaped segments which interconnect adjacent pairs of coils within each row are positioned so that they overlap the Z-shaped segments of the adjacent row of coils.

These overlapped portions or sections of the Z-shaped segments are then tied together by helical wire connectors. A first set of helical wire connectors, herein designated 34, is disposed within the plane of upper innerspring surface 21 so as to join together overlapped portions 35 of upper Z-shaped interconnection segments 28, 32. Similarly, a second set of helical wire connectors, herein designated 36, lie within the plane of lower innerspring surface 23 and serve to join together overlapped portions 37 of lower Z-shaped interconnection segments 18 and 33. As evident in the plan view of FIG. 2, the length of each helical wire is the same as the length of the rows, and the

helical wires

34, 36 extend parallel to the rows.

The assembly of the helical wires to the row of continuous coils may be easily accomplished on a completely automatic assembly machine. In such a machine, the adjacent rows of coils are positioned so that the

sections

35 and 37 of the adjacent Z-shaped segments are positioned in overlapping relationship and a helical wire is then rotated or screwed onto the overlapping portions of the Z-shaped segments. After completion of the threading of the helical coil onto the Z-' shaped segments, the helical coil is cut to length so that the now-connected adjacent rows of coils may be indexed forwardly and another pair of upper and lower helical wires threaded over the next row of coils. This process is repeated for the desired length of the mattress, after which the spring assembly is removed from the machine.

Referring now to FIG. 2, it will be seen that the diameters of the

helical wires

34 and 36 are approximately one-fourth the radius of the overlapped

portions

35 and 37 of the Z-shaped segments. This relationship of having the radius of the Z-shaped segments over which the helical wire is threaded approximately eight timesthe radius of the helical wire has the effect of permitting two rotations of the helical wire to pass through and lock adjacent overlapped segments together. So locked or interconnected, the adjacent coils are free to pivot relative to each other but are locked against relative longitudinal or lateral movement. In other words, this relatively small diameter helical coil when used to lock the overlapped large radiused sections of the segments together, permits only relative pivotal movement between the adjacent interconnected coils.

Referring now to FIG. 5, each block 50 represents the outline of a typical upper Z-shaped interconnection segment 28 in coil row 24. Similarly, each block 52 represents the outline of a typical upper Z-shaped interconnection segment 32 in coil row 25. Each blOCk represents the outline of typical lower Z-shaped interconnection segment 18 in coil row 24 and each block 61 represents the outline of a typical lower Z-shaped interconnection segment 33 in coil row 25. As is apparent from the diagram in FIG. 5, the

blocks

50, 52, and 60, 61 represent load supporting units; Each of these

units

50, 52 and 60, 61 are overlapped so that the effect of the construction of coil assembly is one of .a very densely packed innerspring assembly with a very high count of coils. This construction enables a very small gage wire to be utilized in the innerspring. It is a particularly advantageous structure for use in a foamed in spring mattress such as the spring mattress disclosed in US. Pat. No. 3,660,876.

Referring to FIG. 6, there is illustrated a second embodiment of the invention of this application. This construction is illustrated diagrammatically in top plan view in FIG. 7.

In general, the spring assembly of FIGS. 6 and 7 is identical to the spring assembly of FIGS. 1-5, except that the rows of coils are positioned within the interconnecting Z-shaped segments so that the vertical axes of all of the coils of a single row are located in the same vertical plane 130, rather than being alternately staggered in two different planes as in the embodiment in FIGS. 1-5. The Z-shaped segments, rather than extending outwardly from one side only of each coil extend outwardly beyond both sides of each coil so that this construction has the same advantages of the embodiment of FIGS. 1-5 in that it minimizes or eliminates any tendency of the coils to overlap or contact adjacent convolutions of the same coil. Specifically, referring to FIG. 5, it will be seen that in this embodiment each row of

coils

124, 125, 126 is formed from a continuous length of wire and each wire is wound to form a plurality of spaced coil pairs 127 interconnected by substantially Z-shaped wire segments 128 disposed in the plane of upper innerspring surface 121. The substantially Z- shaped wire segments 118 interconnect adjacent coil pairs 127 within the plane of lower innerspring surface 123.

In this embodiment each coil pair 127 comprises a first right handed coil 127a offset from asecond right hand coil 127b having'the same number of turns as coil 127a. In this embodiment though the axes of coils 127a lie within the same plane 130 within which lie the axes of coils 12712. In this embodiment as in the embodiment of FIGS 1-5, each

row

124, 125, 126 is configured identically to each adjacent row and each coil within each row is of the same twist or hand.

In this embodiment, the corners of the interconnecting Z-shaped segments are both located outwardly from the circumference of the coils 127a and 127b within each pair of coils in both the planes of the upper and lower surfaces of the mattress. This outward spacing of the Z-shaped segments facilitates interconnection of the overlapped portions of Z-shaped segments by the helical springs 134. p

The primary advantage of both embodiments of the spring assembly described herein is that they both utilize continuous springs which extend for the length of each row of coils and because of this continuous row construction, the assembly may be easily machine manufactured and assembled. This construction also has the advantage of eliminating the knots conventionally formed in each coil. Additionally, this construction has the advantage of facilitating the manufacture of a very firm mattress or innerspring unit from a very thin gage wire and a gage which is much thinner than any which has heretofore been acceptable for manufacture of innerspring units. Additionally, the invention of this application eliminates side sway of water bed effect. It also eliminates noise problems encountered when adjacent coils move relative to each other or snap past each other in the course of flexure of the unit assembly.

While we have described only two embodiments of 6 from the spirit of our invention. Therefore, we do not intend to be limited except by the scope of the following appended claims.

Having described our invention, we claim:

l.'A spring assembly comprising,

a plurality of rows of coils, each of said rows of coils being formed from a continuous length of wire, segments of wire interconnecting adjacent coils in each of said rows, said segments each being substantially Z-shaped and disposed alternately in first and second planes generally perpendicular to the axis of said coils at the ends thereof, portions of said Z-shaped segments extending beyond the periphery of said coils, said Z-shaped interconnecting segments each generally defining a rectangle of width greater than the maximum diameter of said coils, adjacent coils within each of said rows being situated at diagonally opposite corners of said rectangles, the axes of coils in each of said rows thereby being disposed alternately in two offset parallel planes,

sections of each of said Z-shaped interconnecting segments of each row being overlapped relative to Z-shaped interconnecting segments of adjacent rows,

helical spring means extending parallel to said rows for the length of said rows, said helical spring means being wound through said overlapped sections of said Z-shaped interconnecting segments so as to secure said rows of coils in an assembled relation, and

said overlapped sections of said Z-shaped interconnecting segments being radiused, the radii of said overlapping sections being substantially greater than the radius of said helical wire so that said helical wire permits relative pivotal movement between said overlapped sections of said Z-shaped interconnecting segments of said rows but precludes all other relative movement.

2. The spring assembly as defined in claim 1 wherein the coils within each row are like-handed and the coils in adjacent rows are also like-handed.

3. The spring assembly of claim 1 in which said radius of said overlapped sections of said Z-shaped interconnecting segments is approximately eight times the radiusof said helical wire.

4. A spring assembly comprising a plurality of rows of coils, each of said rows being formed from a single continuous piece of wire and each of said rows containing a plurality of coils interconnected by Z-shaped interconnecting segments, alternate ones of said Z-shaped interconnecting segments being disposed in the planes of the upper and lower surfaces of said spring assembly, the axes of alternate ones of said coils in one of said rows being disposed in a first plane perpendicular to the upper and lower surfaces of said spring assembly, the axes of the other coils in said row being substantially parallel and disposed in a second plane parallel to, but displaced from said first plane,

sections of each of said Z-shaped interconnecting segments of each row being overlapped relative to Z-shaped interconnecting segments of an adjacent row,

said overlapped sections of said Z-shaped interconnecting segments being radiused, the radii of said overlapping sections being substantially greater than the radius of said helical wire so that said helical wire permits relative pivotal movement between said overlapped sections of said Z-shaped' interconnecting segments of said rows but precludes all other relative movement.

5. The spring assembly of claim 4 in which said overlapped sections of said Z-shaped interconnecting segments are radiused, the radii of said overlapping sections being substantially greater than the radius of said helical wire so that said helical wire permits relative pivotal movement between said overlapped sections of said Z-shaped interconnecting segments of said rows but precludes all other relative movement.

6. The spring assembly of claim 4 in which said radius of said overlapped sections of said Z-shaped interconnecting segments is approximately eight times the radius of said helical wire.

7. A spring assembly comprising,

a plurality of rows of coils, each of said rows of coils being formed from a continuous length of wire, segments of wire interconnecting adjacent coils in each of said rows, said segments each being substantially Z-shaped and disposed alternately in first and second planes generally perpendicular to the axis of said coils at the ends thereof, portions of said Z-shaped segments extending beyond the periphery of said coils,

helical spring means extending parallel to said rows for the length of said rows, said helical spring 10. The spring assembly of claim 7 in which said ra-,

dius of said overlapped sections of said Z-shaped interconnecting segments is approximately eight times the.

radius of said helical wire.

11. A spring assembly comprising a plurality of rows of coils, each of said rows being formed from a single continuous piece of wire and each of said rows containing a plurality of coils interconnected by Z-shaped interconnecting segments, alternate ones of said Z-shaped intercon-.

necting segments being disposed in the planes of the upper and lower surfaces of said spring assembly, the axes of said coils being disposed perpendicular to the upper and lower surfaces of said spring assembly,

said overlapped sections of said Z-shaped interconnecting segments being radiused, the radii of said overlapping sections being substantially greater than the radius of said helical wire so that said helical wire permits relative pivotal movement be-,

tween said overlapped sections of said Z-shaped interconnecting segments of said rows but precludes all other relative movement.

12. The spring assembly as defined in claim 11 wherein the coils within each row are like-handed and the coils in adjacent rows are also like-handed. I

13. The spring assembly of claim 11 in which said radius of said overlapped sections of said Z-shaped interconnecting segments is approximately eight times the radius of said helical wire.

Claims

1. A spring assembly comprising, a plurality of rows of coils, each of said rows of coils being formed from a continuous length of wire, segments of wire interconnecting adjacent coils in each of said rows, said segments each being substantially Z-shaped and disposed alternately in first and second planes generally perpendicular to the axis of said coils at the ends thereof, portions of said Z-shaped segments extending beyond the periphery of said coils, said Z-shaped interconnecting segments each generally defining a rectangle of width greater than the maximum diameter of said coils, adjacent coils within each of said rows being situated at diagonally opposite corners of said rectangles, the axes of coils in each of said rows thereby being disposed alternately in two offset parallel planes, sections of each of said Z-shaped interconnecting segments of each row being overlapped relative to Z-shaped interconnecting segments of adjacent rows, helical spring means extending parallel to said rows for the length of said rows, said helical spring means being wound through said overlapped sections of said Z-shaped interconnecting segments so as to secure said rows of coils in an assembled relation, and said overlapped sections of said Z-shaped interconnecting segments being radiused, the radii of said overlapping sectionS being substantially greater than the radius of said helical wire so that said helical wire permits relative pivotal movement between said overlapped sections of said Z-shaped interconnecting segments of said rows but precludes all other relative movement.

3. The spring assembly of claim 1 in which said radius of said overlapped sections of said Z-shaped interconnecting segments is approximately eight times the radius of said helical wire.

4. A spring assembly comprising a plurality of rows of coils, each of said rows being formed from a single continuous piece of wire and each of said rows containing a plurality of coils interconnected by Z-shaped interconnecting segments, alternate ones of said Z-shaped interconnecting segments being disposed in the planes of the upper and lower surfaces of said spring assembly, the axes of alternate ones of said coils in one of said rows being disposed in a first plane perpendicular to the upper and lower surfaces of said spring assembly, the axes of the other coils in said row being substantially parallel and disposed in a second plane parallel to, but displaced from said first plane, sections of each of said Z-shaped interconnecting segments of each row being overlapped relative to Z-shaped interconnecting segments of an adjacent row, helical spring means extending parallel to said rows for the length of said rows, said helical spring means being wound through said overlapped sections of said Z-shaped interconnecting segments so as to secure said rows of coils in an assembled relation, and said overlapped sections of said Z-shaped interconnecting segments being radiused, the radii of said overlapping sections being substantially greater than the radius of said helical wire so that said helical wire permits relative pivotal movement between said overlapped sections of said Z-shaped interconnecting segments of said rows but precludes all other relative movement.

7. A spring assembly comprising, a plurality of rows of coils, each of said rows of coils being formed from a continuous length of wire, segments of wire interconnecting adjacent coils in each of said rows, said segments each being substantially Z-shaped and disposed alternately in first and second planes generally perpendicular to the axis of said coils at the ends thereof, portions of said Z-shaped segments extending beyond the periphery of said coils, sections of each of said Z-shaped interconnecting segments of each row being overlapped relative to Z-shaped interconnecting segments of adjacent rows, helical spring means extending parallel to said rows for the length of said rows, said helical spring means being wound through said overlapped sections of said Z-shaped interconnecting segments so as to secure said rows of coils in an assembled relation, and said overlapped sections of said Z-shaped interconnecting segments being radiused, the radii of said overlapping sections being substantially greater than the radius of said helical wire so that said helical wire permits relative pivotal movement between said overlapped sections of said Z-shaped interconnecting segments of said rows but precludes all other relative movement.

8. The spring assembly of claim 7 in which said Z-shaped interconnecting segments each generally define a rectangle of width greater than the maximum diameter of said coils, the coils within each row being like-handed and the coils in adjacent rows also being like-handed.

9. The spring assembly as defined in claim 7 wherein the coils within each row are like-handed and the coils in adjacent rows are also like-handed.

10. The spring assembly of claim 7 in which said radius of said overlapped sections of said Z-shaped interconnecting segments is approximately eight times the radius of said helical wire.

11. A spring assembly comprising a plurality of rows of coils, each of said rows being formed from a single continuous piece of wire and each of said rows containing a plurality of coils interconnected by Z-shaped interconnecting segments, alternate ones of said Z-shaped interconnecting segments being disposed in the planes of the upper and lower surfaces of said spring assembly, the axes of said coils being disposed perpendicular to the upper and lower surfaces of said spring assembly, sections of each of said Z-shaped interconnecting segments of each row being overlapped relative to Z-shaped interconnecting segments of an adjacent row, helical spring means extending parallel to said rows for the length of said rows, said helical spring means being wound through said overlapped sections of said Z-shaped interconnecting segments so as to secure said rows of coils in an assembled relation, and said overlapped sections of said Z-shaped interconnecting segments being radiused, the radii of said overlapping sections being substantially greater than the radius of said helical wire so that said helical wire permits relative pivotal movement between said overlapped sections of said Z-shaped interconnecting segments of said rows but precludes all other relative movement.

12. The spring assembly as defined in claim 11 wherein the coils within each row are like-handed and the coils in adjacent rows are also like-handed.