BACKGROUND OF THE INVENTION Pocketed springs for use in upholstery have been known for many years, dating at least from early in the twentieth century. Assemblies of such springs as cores for mattresses or cushions are known in the industry as"Marshall"constructions or units, for the man believed to have originated the concept. See U. S.

Patent 685,160 of 1901.

Machinery developed for the commercial manufacture of such units inserted axially compressed springs between the plies of a strip of sheeting folded in half longitudinally, and then seamed the folded strip along its edges, and transversely between the springs, to form pockets each enclosing a single spring. After re-expansion, the springs were turned in their pockets, resulting in a continuous strip of axially parallel springs with the marginal flaps of the edge seams of the fabric strip located at the same one end of all of the springs. The sewn seam version is typified by U. S.

Patent No. 1,813,993 to John F. Gail, and the welded seam version of thermally weldable pocket sheeting by my prior U. S. Patent 4,489,977.

When strips of such springs are assembled by the usual methods in rows in which the springs are axially parallel, the seamed edges of the fabric are found on the same face of the assembly, which some experts have concluded contributes an undesirably different feel to opposite sides of a mattress embodying such an assembly, due to the presence of the upstanding seam margins of the fabric strip on the outside of the

closing seam of the fabric. While the validity of that proposition may smack of the fairy tale of the princess and the pea, it has sufficiently engaged the interest of bedding manufacturers to promote the development of pocketed springs in strips in which the closure of the longitudinally folded fabric strip occurs along one side of the strip of pocketed springs rather than at the ends thereof. One example is provided by my U. S. Patents 4,854,023 and 4,986,518, to which subsequent improve- ments are suggested by U. S. Patents 5,613, 287, St. Clair et al., and 5,749,133, Mauldin et al.

The reality, however, is that that approach, for whatever reason, failed to supplant the widely used spring-end closure seam that remains standard today.

BRIEF DESCRIPTION OF THE INVENTION Taking a different approach to a side-seam closure for pocketed springs, I have developed a manu- facturing method and apparatus which utilizes known methodology to the extent of inserting compressed springs between the plies of a longitudinally folded strip and making a longitudinal seam adjacent to the fabric edges, but withholding the transverse, pocket- defining seams until after the springs have expanded.

In this arrangement, disclosed in my co. pending application for patent, Serial No. 09/334,910, filed June 17,1999, the expansion of the spring transfers the closing seam from the end of the spring to approximately mid-height thereof where the seam margins are folded over and incorporated into the transverse seams on one side of the fabric strip when the pocket-defining cross seams are made between the springs. With the seam margins in that position, not only is the possibility of differential face"feel"of a mattress eliminated, but the fabric margins outwardly of the closing seam, secured in folded-down contact with the outside of the

fabric wall of the pocket, form a two-ply fabric belt along one side of the strip which facilitates and reinforces the connections of adjacent strips of springs to one another, whether in two-row modules or in more extensive assemblies of strip multiples.

The belted pocketed spring strip per se and its assemblies are the subject of this invention. The method and apparatus for manufacture of the strip are the subject of my co-pending U. S. patent application Serial No. 09/334,910, filed June 17,1999.

DESCRIPTION OF THE DRAWINGS This invention is hereinafter described in reference to the following drawings, in which: FIGURE 1 is a cross-section of a single pocketed spring of a strip thereof in accordance with the invention, taken transversely of such a strip with springs in line, as on the line 1-1 of FIG. 3; FIGURE 2 is a fragmentary enlargement of FIG. 1 to illustrate the two-ply belt formed by the folded margins of the strip outwardly of the closing seam; FIGURE 3 is a perspective view, looking slightly downward, of a four-spring fragment of a two-row pocketed spring module in accordance with the invention; FIGURE 4 is a fragmentary top (or bottom) view of a two-row pocketed spring module; FIGURE 5 is an elevational view of the same; FIGURE 6 is a plan view of the interior of a mattress construction illustrating one manner of using the inherently stable two-row module in a polyfoam box; and FIGURE 7 is a plan view of another of a pocketed spring assembly, either of two-row modules in touching contact within a polyfoam border, or of a

unitary, multiple row assembly joined as single-row increments.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT AND UTILIZATION Referring initially to FIGS. 1 to 3, the latter shows the connection of two two-spring segments of two connected rows 10 and 12 of pocketed springs 13, positioned one row behind the other. The four springs shown in FIG. 3 correspond to either end group of four springs of FIG. 4, indicated by the bracket 3 of FIG. 4, severed from the adjoining springs of their respective rows. Furthermore, the two springs of the front-row 10 of FIG. 3 have been displaced sidewardly from their normal, unstressed four-spring cluster. by bending them outwardly to illustrate more clearly the pocket-defining cross-seam 14, the two springs 12 of the rear row being crammed together in the process.

Focusing upon the front row 10 of springs in FIG. 3, the marginal flaps 16 of the two plies of the folded strip of fabric 18 outwardly of the longitudinal seam 20 which formed the plies into a tube or sleeve, are folded downwardly from the seam 20, and incorporated into the cross-seams 14 of the fabric sleeve which defined the successive pockets about the individual springs. When made by the method and with the apparatus of my co-pending application Serial No. 09/334,910, the cross-seams 14 are made after the springs, compressed for insertion between the fabric plies before the longi- tudinal seam is made, have been permitted to expand within the fabric sleeve.

The fabric flaps 16 outwardly of the closing seam 20 thus become a two-ply belt 22 of the pocket fabric running along each row or strip of pocketed springs approximately midway between the ends of the springs.

Further in accordance with the invention, the belt 22 becomes the location at which two adjacent rows of such pocketed springs are attached to one another at midheight of the two rows 10 and 12, preferably by a single tack 24, whether by tack stitch, staple, or adhesive, but preferably by a tack or button weld in pocket material of thermoplastic fiber such as the Duon material of Phillips Fibers, or a material having a sufficient thermoplastic content for effective thermal welding by ultrasonic means. In FIG. 3, the tack weld 24 is made in the shape of a stylized letter"S".

In FIGS. 3,4, and 5, the belts 22 of the pocketed springs are placed on the outsides of the two back-to-back spring rows 10 and 12, but it will be understood that two-row modules may also be made in the same fashion with the belts of the two rows in touching contact, i. e., with the belt concealed within the two-row module, or, indeed, with the belt of each row on the same one side of each row, as when multiple rows are successively united in single row increments. In each instance, the connection 24, whether by stitch, etc., or by weld, unites eight layers of the pocket fabric in an extremely strong and durable joint.

The two-row module 26 (FIG. 4) is preferred for its versatility as a unit of mattress core assembly and for its relative ease of manufacture. It is very stable, whether stood on either face, and will not tip o : topple, or turn over when in service as part of a mattress core. It is easily grasped in one hand by the assembler, and lends itself well to the creation of mattress cores which vary in firmness by zones from head to foot of the mattress for the better support of the human body in repose.

The two-row module has the further advantage of relative ease of manufacture, particularly when the pocket sheeting-is thermally weldable, using equipment

that is fairly simple and need not represent heavy capital investment.

Multiple-row modules or units in excess of two rows can, of course, be made readily on equipment such as that of my earlier U. S. Patent 4,401,501, issued August 30,1983, but such equipment is more capital intensive than the simpler apparatus envisioned for inserting an ultrasonic probe and opposing probe-anvil between the springs of two rows of pocketed coils advancing side by side through a welding station to be joined at the hip, so to speak, by a tack or spot weld through the belts of the rows.

Assembled mattress cores using the belted pocketed springs of the invention are depicted in FIGS. 6 and 7.

In FIG. 6, I illustrate a form of assembly in which two-row modules 26 are placed transversely of the mattress within a surrounding border frame 28 of "polyfoam" (e. g., foamed polyurethane), on a base sheet 30 of the foamed material, with the two-row modules in touching contact. In the illustrated case, the belts of the spring strips are on the outside of the two-row module, as indicated by double-lines where the modules contact each other. The mattress core is completed by a covering sheet 32 of the foamed material secured by adhesive to the polyfoam border frame to facilitate further handling of the assembled core during manu- facture, e. g., for application of a ticking cover, and, where desired, for tufting.

The construction of pocketed spring assemblies from modules of two rows can have other advantages as well, for example, a head-to-foot orientation of mattress-length modules for the sake of mattress halves of different firmness, to suit the different preferences of husband and wife. The more likely application is expected to be transverse orientation of modules of

mattress-width length, to facilitate the provision of variable firmness to accommodate the weight distribution of the human body in repose.

FIG. 7 may be taken to illustrate an integral multiple-row assembly constructed one row at a time, with the inter-row connections of consecutive rows displaced sidewardly by one spring from row to row, as illustrated by the crossed diagonals 34. It is equally adaptable to the zonal firmness variations attributed to mattress assemblies of two-row modules, and may be boxed in polyfoam as depicted for the modular assembly of FIG. 6.

For the convenient severance of the pocketed spring strips into individual rows or two-row modules, the interpocket cross seam 14 is preferably made in two rows of individual spot welds spaced adequately between the rows for a severance cut without either sacrificing a spring or compromising the adjacent pockets. See FIG. 3.

A significant aspect of the invention wholly apart from its successful elimination of the differ- ential"feel"of opposite sides of a pocketed coil mattress, is the outer belt of the strip of pocketed springs which greatly enhances the strength to the inter-row connections, whether made by spot welding through both belts to merge eight layers of the pocket material in a fusion of exceptional strength, or by other forms of attachement which unite the two belts.

The features of the invention believed new and patentable are set forth in the following claims.