Patent Publication Number: US-6668406-B2

Title: Spring units

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to spring units and more particularly to spring units for beds, divan beds, mattresses, and other upholstery units. Such beds etc will be hereinafter referred to as ‘sprung units’. 
     2. Description of the Related Art 
     Sprung units are conventionally made in differing degrees of hardness, this usually being achieved by varying the number of springs per unit area—generally known as ‘the spring count’—of the sprung unit, or by changing the gauge of the wire from which the springs are made. Such variation in the manufacturing procedure, i.e. the incorporation of differing numbers of springs or changing the wire gauge, complicates the manufacturing procedure and consequently increases the manufacturing costs. 
     It has previously been proposed to incorporate a second spring within a first spring so as to form a double spring unit whereby the springs are compressed in stages so as to lessen the shock on the sprung unit when a person sits or lays upon the sprung unit, Examples of such spring units are shown and described in U.S. Pat. Nos. 1,192,510 (Fischmann), 3,031,690 (Ramsey), and 2,631,840 (Bugenhagen). However, in such previous proposals, the second spring has been connected, either directly or indirectly, to said first spring such that the second spring has not been freely movable within said first spring, which places restrictions on the sprung unit in use. 
     SUMMARY OF THE INVENTION 
     The present invention therefore seeks to provide an improved form of spring unit which will obviate the disadvantages of known spring units. 
     According to the present invention there is provided a spring unit for incorporation into a bed, divan bed, mattress, or other upholstery unit comprising a first spring and a second spring located within said first spring, said second spring having no connection to said first spring so as to be freely movable within said first spring. 
     Preferably, the length of said second spring will be less than that of said first spring. 
     In an embodiment of the invention, the first spring may be a pocketted spring, and in an alternative embodiment of the invention the second spring may be a pocketted spring. In yet a further alternative embodiment, each of said first and second springs may be pocketted springs. 
     The pocket of the or each pocketted spring may be composed of a woven material such as calico which is sewn in order to form the pocket(s). Alternatively, the pocket(s) may be composed of synthetic material which is sewn or sonic or heat welded in order to form the pocket(s). Where both springs are pocketted springs, both pockets may be composed of a woven material or both may be composed of synthetic material, or the pockets may be formed one of each material, the pocket of woven material preferably being around said first spring. 
     According to another aspect of the present invention there is provided a sprung unit incorporating a plurality of spring units, each of said spring units comprising a first spring and a second spring located within said first spring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order that the invention may be more readily understood, embodiments of the invention will now be described, by way of example only, reference being made to the accompanying drawings, wherein: 
     FIG. 1 is a view of a spring unit according to a first embodiment of the invention; 
     FIG. 2 is a view of a spring unit according to a second embodiment of the invention; 
     FIG. 3 is a view of a spring unit according to a third embodiment of the invention; 
     FIG. 4 is a view of a further embodiment of a spring unit according to the invention; and 
     FIG. 5 is a view of a sprung unit, partly cut away, to show the incorporation of a plurality of spring units. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings and firstly to FIG. 1, there is shown a spring unit which is indicated generally by reference numeral  2  and which comprises a first, outer spring  4  and a second unconnected, inner spring  6 . As will be seen, the length of the inner spring is less than the length of the outer spring  4 , and the pitch of the spring  6  is less than that of the spring  4 . 
     The inner spring  6 , captive within the outer spring  4 , is movable longitudinally within the outer spring  4  between the end  4 A and the other end  4 B of the spring  4 . 
     Referring now to FIG. 2, it will be seen that the outer spring  4  and the inner spring  6  are located within a single pocket  8 —so as to form a pocketted spring A—in engagement with the outer spring  4 . The pocket is formed by longitudinal lines of retention  10  and  12  and by lateral lines of retention  14  and  16 . 
     The pocket  8  may be composed of a woven material such as calico, in which case the lines of retention will be formed by sewing. Alternatively, the pocket  8  may be composed of a synthetic material, in which case the lines of retention may be formed either by sewing or by means of sonic or heat welding. 
     As with the spring unit of FIG. 1, the inner spring  6  is movable within the pocket  8  of the outer spring  4 , as shown in FIG.  2 . 
     FIG. 3 illustrates a spring unit  2  in which the inner spring  6  is located within a pocket  20 —so as to form a pocketted spring B—which is composed of either a woven material such as calico, in which case the pocket will be secured in position around the spring  6  by sewing, or alternatively of synthetic material, in which case the pocket  20  will be secured in position around the spring  6  either by sewing or by sonic or heat welding. The pocketted spring B, formed by the pocket  20  and the spring  6 , is as in the embodiment of FIGS. 1 and 2, movable longitudinally between the end  4 A and the end  4 B of the outer spring  4 . 
     Referring now to FIG. 4, there is illustrated a ‘composite’ pocketted spring unit which is a combination of the spring units of FIGS. 2 and 3. Thus the spring unit of FIG. 4 comprises an outer pocketted spring A and an inner pocketted spring B, and for ease of identification, the reference numerals of FIGS. 2 and 3 have been applied to FIG.  4 . The inner pocketted spring B is movable longitudinally within the outer pocketted spring A from one end  4 A to the other end  4 B of the outer pocketted spring A. 
     The pockets of the pocketted springs A and B may both be composed of a woven material such as calico, or both may may be composed of a synthetic material, or there may be one of each, in which case it is preferred that the pocket of pocketted spring A is composed of the woven material. 
     In use, and referring to now to FIG. 5, which illustrates part of sprung unit  22 , it will be seen that the unit incorporates a plurality—two are indicated—of the spring units as shown in FIG. 4, i.e. the composite pocketted spring unit. The spring units  2  are located between upper and lower layers of padding  24  and  26  and side walls  28  and  30 , the spring units being held in position in conventional manner. 
     The sprung unit  22  may be formed wholly of spring units in accordance with the invention, or alternatively a plurality of spring units in accordance with the invention may be used in conjunction with or in combination with a plurality of conventional pocketted springs, or indeed with other suitable types of conventional and known springs. 
     Thus the invention provides a spring unit  2  and a sprung unit  22  which incorporates a plurality of said spring units  2  wherein, in use of the sprung unit  22 , the outer spring  4  will be partially compressed first followed by compression together of the outer spring  4  and the inner spring  6 , the amount of compression of the spring(s) being dependent upon the weight of the user. 
     Thus there is provided a sprung unit, i.e. a bed, divan bed, mattress or other upholstery unit, whose degree of hardness is variable—depending upon the amount of compression of the springs of the sprung unit—and therefore it will not be necessary to manufacture ‘hard’ sprung units and ‘soft’ sprung units by varying the ‘spring count’ of the unit, such ‘spring count’ automatically being adjusted and established by the user of the sprung unit. 
     Finally, it will be appreciated that whilst parallel springs and spring units have been described and illustrated, the invention is equally applicable to barrel shaped and other shaped springs and spring units.