DETAILED DESCRIPTION OF PREFERRED AND ALTERNATE EMBODIMENTS

[0014] With reference to the Figures, there is shown a high profile innerspring coil, indicated at 10 , with an overall finished end-to-end length or height dimension in an approximate range of six and three quarters to seven and one half inches (or the approximate range of 170-190 mm). The coil 10 is made of helical formed wire, for example 12-16 gauge, in the form of a helical body 13 , with contiguous end convolutions 16 at opposite ends of the coil body. In this particular embodiment there are three convolutions or turns which make up the body of the coil, including the intermediate body convolutions 14 a and 14 b , and a center convolution 12 . Alternate embodiments of the coil of the invention may be constructed with different configurations, such as different numbers of convolutions or turns, and different shapes to the coil ends, as further described. In this particular embodiment of a five turn helical coil, the center convolution 12 has the smallest diameter, and the diameters of the adjoining intermediate body convolutions 14 a and 14 b being larger by a defined degree, and the diameters of the end convolutions 16 being largest. The intermediate body convolutions 14 a and 14 b are stabilized by the larger end convolutions 16 , and compress within the diameter of the end convolutions 16 as the coil is compressed on-axis.

[0015] FIGS. 1 and 2 illustrate the coil 10 in a raw form as produced by conventional coiler wire forming equipment, with the end convolutions 16 in generally circular form as shown in FIG. 2 . For the coil 10 in the raw form may be subsequently formed with the end convolutions as shown in FIG. 4 , or in any other form, and with the other coil parameters as described herein. The raw coil should have a preferred total coil height in the approximate range of 8½ inches to 9½ inches. This is an important parameter which can be set and measured in the course of manufacturing high profile coils in accordance with the invention to ensure a desired finished height in the range of 6¾ inches to 7½ inches.

[0016] In accordance with the design principles of the invention in providing a high profile coil which is readily balable in a conventional baling process, the coil dimension measured from an outermost edge of one convolution to the adjacent convolution is referred to herein as “pitch” and designated “A”, “B” and “C” in FIG. 1 . “A” represents the pitch of the center convolution 12 . “B” represents the pitch of the intermediate convolutions 14 . “C” represents the pitch of the end convolutions 16 . The center convolution has an outer diameter (O.D.), measured laterally from an outer tangent of the center convolution to the opposing turn, represented by “x”, and an intermediate convolution O.D. represented by “y”. For coil with a coil height/length of approximately 7 inches (178 mm), preferably the center convolution O.D. “x” is in a range of 50 mm to 53 mm. In accordance with the design principles of the invention, the intermediate convolution O.D. “y” must be at least 1 mm larger than the center convolution O.D. “x”. These dimension are critical to the performance and behavior of the coil, particularly under compression and under the high compression of baling. The behavior of the coil under compression is ideally “on-axis”, meaning that the coil compresses along the axis of the helical coil body with little or no lateral distortion. On-axis compression is critical to maintain alignment of the coils in a matrix, as in an innerspring assembly and particularly in large innerspring assemblies as used in mattress construction and to avoid any contact with adjacent coils which produces a clicking sound as the coils/innerspring are loaded and unloaded. As used herein, the term “balable” refers to the characteristic of a coil, or innerspring assembly made with such coils, which compresses and decompresses on-axis, particularly under the compressive load of an innerspring baling machine used, for example, in mattress manufacturing.

[0017] For dimensional stability in a high profile balable coil, a finished coil 10 made in accordance with the design principles of the invention should have the following dimensional ranges. The center convolution 12 should have a pitch dimension in the range of 54-58 mm, and an O.D. in the range of 51-55 mm. The intermediate convolutions 14 should have a pitch in the range of 53-60 mm, and an O.D. in the range of 52-55 mm. The end convolutions 16 should have a pitch in the range of 25-35 mm, and an outer diameter (O.D.) in the range of 59-65 mm. The high profile coil of the invention preferably has a total uncompressed height in the range of 6¾ inches to 7½ inches.

[0018] The following dimensions are also representative of desired dimensional ranges of the pitch and O.D. measurements of the high profile coil of the invention in its various states of manufacture prior to heat treatment and prior to initial compression (setting), and after heat treatment but prior to initial compression (setting), and in the finished state. 1

[0019] After the coil 10 has been heat treated, but prior to initial compression or “set”, the coil should have the following dimensions. The end convolutions 16 should have a pitch dimension in the range of 25-35 mm, and an O.D. in the range of 59-65 mm. The intermediate body convolutions 14 should have a pitch in the range of 59-66 mm, and an O.D. in the range of 52-55 mm. The center convolution 12 should have a pitch in the range of 58-63 mm, and an O.D. in the range of 50-55 mm.

[0020] After the coil 10 has been heat treated and compressed, the coil should have the following dimensions. The end convolutions 16 should have a pitch in the range of 25-35 mm, and an O.D. in the range of 59-65 mm. The intermediate body convolutions 14 should have a pitch in the range of 53-60 mm, and an O.D. in the range of 52-55 mm. The center convolution 12 should have a pitch in the range of 54-58 mm, and an O.D. in the range of 51-55 mm.

[0021] If the O.D.s of any of the described convolutions is greater than the described ranges, the coils 10 will not compress on-axis in a baling operation, i.e., in an innerspring baling machine, and may touch together at laterally tangential points when under a load in an innerspring assembly. If the described O.D.s of the convolutions are below these ranges, the coils will not be dimensionally stable, particularly under the compressive load of baling, and will spin-out of the coil body out of alignment with the end convolutions, i.e., not compress on-axis. Also, if the described pitches between the convolutions is larger than the described ranges, the coils 10 will not be dimensionally stable, particularly under baling compression. And if the pitch between the convolutions is smaller than the described ranges, the coil 10 will resist baling and spin-out by lateral deflection of the body convolutions relative to the end convolutions.

[0022] As shown in FIG. 5 , one example of how coil springs 10 may be interconnected in an innerspring assembly is by lacing end convolutions 16 together with cross helical wires 18 . Other examples include the use of fabric or other encapsulation to arrange coils in a parallel axis array, or use of other types of fastening devices to hold an array of coils in a matrix arrangement with axes of the coils generally parallel. In the illustrated example, the cross helical lacing wires 18 extend transversely between the rows of coils 10 , in this case along the end convolutions 16 at opposing ends of the coils, to form an innerspring with a thickness equal to the axial length of the coils. Although shown laced together in a particular radial orientation, it is understood that one or more of the coils may be rotated relative to other coils in the innerspring assembly.

[0023] The compressive force required to compress coil 10 , having an overall height or length in the range of six and three quarters to seven and one half inches without disrupting the baling process, is 1.55 to 1.95 pounds per inch, as measured by a Carlson type spring tester. As known in the art, a Carlson tester provides a standardized spring rate test which measures the amount of force required to compress a coil one inch beyond compression to twenty percent of unloaded height or length. Based on this measurement, the compression force required to bale a coil 10 is determined. It has been discovered by the inventors that a coil 10 having the described dimensions, if compressible in the Carlson tester within the range of 1.55 to 1.95 pounds per inch, will when assembled in an innerspring, bale substantially on-axis in a baling machine, without interference with adjacent coils. The baling referred to includes bulk baling of at least several innersprings stacked together, separated by a sheet of material such as heavy paper, and compressed in the baler in bulk, as is common practice in the industry. The coils 10 are designed to compress on-axis under the baling pressure required to simultaneously bale multiple innersprings.

[0024] As shown in FIG. 2 , the end convolutions 16 of the coil 10 can be formed generally circular, terminating the coil in a generally planar form which serves as the supporting end structure of the coil for attachment to adjacent coils and for the overlying application of padding and upholstery. Other configurations of the end convolutions are executable within the design principles of the high profile coil of the invention.

[0025] FIGS. 3 and 4 illustrate an alternate embodiment of the invention wherein the coil 10 has a uniquely configured end convolution 16 for the described high profile coil. As shown in FIGS. 3 and 4 , the end convolution 16 is formed with a first offset 24 which extends from the intermediate body convolution 14 a or 14 b through a connecting segment 20 which extends at an angle between the intermediate convolution and the end convolution. The connecting segment 20 can be included in one or both ends of the coil. The length of the connecting segment 20 may be adjusted to alter the spring characteristics of the coil without altering the on-axis compression performance of the coil in an innerspring. The first offset segment 24 is connected at one end to a second offset segment 26 which is generally orthogonal to and laterally disposed relative to the first offset segment 24 . The second offset segment 26 is connected at a second end to a third offset segment 28 , which is generally orthogonal to the second offset segment and generally opposed to the first offset segment, and which terminates the coil at terminus 29 . The connecting segment 20 is adjustable in length to vary the compression and firmness of the coil 10 . In addition to serving as support members at the ends of the coil, the first and third offset segments 24 , 28 also serve as inter-coil connection members which are laced together with adjacent coils in an innerspring assembly, as shown in FIG. 5 . Although not circular in form, the end convolution 16 formed with the offsets is considered to have a diameter or outer diameter as measured from an offset across the end of the coil. In the circular form shown in FIG. 2 , the outer diameter of the end convolution is measured across the end of the coil.

[0026] The principles of the invention are applicable to other types of wire-form coils or springs, which may vary in design and dimension. The form of the end convolutions of the coils of the invention are not critical to the linear behavior of the coils under full compression. Also, the orderly compression and decompression of the coils of the invention, or innersprings constructed with the coils of the invention, is applicable not only to the process of baling innersprings as an intermediate handling step in product production, but also advantageous in the end use of the coils or innersprings, such as full compression of a seating or bedding structure which may occur in a folding or storage operation.