Abstract:
A mattress includes a chamber defined by upper and lower panels and a peripheral border all constructed from synthetic polymeric/copolymeric plastic material and housing therein a spring unit. The spring unit includes a plurality of springs having upper ends connected to a peripheral border rod. The spring unit is devoid of a peripheral border rod at lower ends of the springs. Upper edges of the spring unit can be deformably gripped by the upper panel, the peripheral border and/or both to prevent “swimming pool” effect.

Description:
BACKGROUND OF THE INVENTION 
     Conventional mattresses are constructed in many different ways to provide uniform or varied firmness along their lengths, such as conventional coil spring mattresses or synthetic foam mattresses. Other mattresses include housings made of synthetic polymeric/copolymeric plastic material generally formed by upper and lower layers or panels and a peripheral border therebetween. In one type of mattress one or more synthetic plastic material panels are housed within the chamber of the mattress housing. In another type mattress a spring unit or a series of springs or inflatable units or conventional natural fibers are similarly housed within the chamber of such mattress housings. A further mattress includes both one or more panels of synthetic plastic material and coil springs housed within a chamber of a mattress housing. 
     All such mattresses are said to have a variety of different advantages, and typical of mattresses defined by a synthetic plastic material mattress housing defining a chamber in which are housed one or more layers of polymeric/copolymeric plastic material, including foam, are McEvoy, U.S. Pat. No. 4,405,681 issued on Sep. 20, 1983; Dahle, U.S. Pat. No. 2,836,228 issued on Jun. 15, 1956; Lück, U.S. Pat. No. 5,107,559 issued on Apr. 28, 1992; Talbert et al., U.S. Pat. No. 4,086,675 issued on May 2, 1978 and May, U.S. Pat. No. 5,701,623 issued on Dec. 30, 1997. Such mattresses are said to advantageously provide desired support, differential hardnesses, extremely high resistance to compression, resilience to return from a compressed condition substantially to the original uncompressed form, differential firmness, edge firmness and softer centers, etc. 
     Much the same advantages are claimed for mattresses in which a spring unit or individual spring coils are housed within a chamber of a synthetic plastic material mattress housing with or without synthetic plastic panels also being housed within the chamber. Typical of the latter mattresses can be found in Zocco, U.S. Pat. No. 5,065,485 issued on Nov. 19, 1991; Pollock, U.S. Pat. No. 3,210,781 issued on Oct. 12, 1965; Schenker, U.S. Pat. No. 2,469,084 issued on May 3, 1949; Kraft, U.S. Pat. No. 5,136,740 issued on Aug. 11, 1992 and Hutchinson et al., U.S. Pat. No. 5,105,488 issued on Apr. 21, 1992. Though the latter type mattresses exhibit numerous advantages, a major disadvantage is the “swimming pool” effect of the coil spring unit and the synthetic polymeric/copolymeric synthetic plastic material housing. Heretofore such spring units continuously floated or shifted within the associated chamber of the plastic mattress housing (“swimming pool” effect) which created excessive wear and increased the return rate of such mattresses which quickly deteriorated over a short period of time as the inner surfaces or walls defining the mattress housing deteriorated under continuous rubbing and grinding of the spring unit as it continuously shifted when in use. Normally such coil spring units are defined by a number of coils and upper and lower heavier peripherally extending border rods which are attached to the coils by clips. When such coil spring units are loosely dropped into and are housed loosely within the chamber of an associated plastic mattress the clips and the upper and lower border rods rub and grind away at the inner surfaces or walls of the peripheral border and/or the upper and/or lower panels of the plastic mattress housing. 
     Such conventional mattresses utilizing spring units formed by both upper and lower relatively rigid peripheral border rods clipped to upper and lower coil loops of coils are also extremely rigid and are not susceptible to bending either transversely or longitudinally, as is oft times desired when mattresses are transported, removed, installed, flipped, etc. Such rigidity in conventional coil spring/foam housing mattresses also creates a transition area between the upper border rod and the spaced peripheral border of the mattress housing which creates an undesired peripheral gap and/or lump between the two which is noticeable when a person sits upon an edge of the mattress. 
     SUMMARY OF THE INVENTION 
     The invention herein provides a mattress formed of synthetic polymeric/copolymeric plastic material, preferably foam plastic, which forms a mattress housing defined by a lower foam panel, an upper foam panel and a peripheral foam border formed of one, two or more pieces of material collectively defining a spring unit chamber. A spring unit of the mattress of this invention includes a plurality of coil springs having upper and lower loops to the upper loops of which is connected by clips a peripheral border rod. The coil spring unit includes only one peripheral border rod and the latter is located only at the upper side of the coil spring unit. The overall length and width of the border rod is exactly equal to, slightly larger than or somewhat larger than the corresponding dimensions of the inner walls or surfaces of the peripheral border of the housing. Accordingly, with the bottom panel adhesively bonded to the peripheral border, the coil spring unit is dropped-in a chamber of the mattress housing from above with the lower coil loop of each coil spring resting upon an innermost surface of the lower panel. The border rod must be forced down into the chamber and if the peripheral dimensions thereof correspond substantially identically to the peripheral dimensions of the housing border, the upper border rod and its clips are in frictional locking relatively immobilized relationship to the inner wall or surface of the peripheral border of the housing. However, the dimensions of the inner walls or surfaces of the border are preferably foreshortened ¼-½ inch relative to the same dimensions of the upper border rod which during assembly causes the synthetic foam plastic material along an innermost upper edge of the border to compress and essentially lockingly grip the peripheral border rod along the upper edge of the plastic material border when the coil spring unit is fully seated within the mattress chamber. The latter locking avoids the “swimming pool” effect earlier described while the absence of any further peripheral border rods and particularly a lower peripheral border rod permits the mattress to be bent as earlier described. 
     Instead of oversizing the length and width of the upper peripheral border rod relative to the respective length and width of the mattress chamber dimensions, the height of the coil spring unit can be ¼-½ inch higher than the distance between the inner opposing surfaces of the upper and lower panels which would be the same as the height of the mattress border as defined between upper and lower surfaces thereof. After the lower panel has been adhesively bonded to the mattress border and the coil spring unit has been placed therein, the upper peripheral border rod would project the ¼-½ inch above the upper surfaces of the mattress border. However, as the upper panel is placed atop the coil spring unit and is pushed downwardly, the upper peripheral border rod and its clips embed into the inner surface of the upper panel creating a peripherally extending downwardly opening locking channel which prevents the “swimming pool” effect after the mattress has been completed by adhesively uniting the upper panel to the upper surface of the mattress peripheral border. 
     In further keeping with the present invention, the overall peripheral size and height of the coil spring unit can be ¼-½ inch greater than the corresponding dimensions of the chamber of the mattress housing. When finally assembled, the upper peripheral border rod will lock both with the upper interior surface of the housing border and the inner surface of the upper panel in respectively peripherally extending inwardly opening and downwardly opening locking grooves or channels. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a novel mattress constructed in accordance with this invention, and illustrates upper and lower panels and a polygonal border constructed from synthetic plastic material defining a chamber in which is housed a spring unit including only a single upper peripheral border rod united by clips to upper loops of a plurality of coil springs. 
         FIG. 2  is a fragmentary exploded perspective view of the mattress of  FIG. 1 , and illustrates details of the coil spring unit including upper and lower bonnell lacings uniting upper and lower loops of coil springs from head end to foot end of the mattress to prevent roll together. 
         FIG. 3  is a fragmentary vertical cross-sectional view taken through the assembled mattress and illustrates the upper and lower panels adhesively bonded to the housing border and the upper peripheral border rod locked in an inwardly opening peripheral extending groove of the housing border formed during the force-fit assembly of the coil spring unit into the mattress housing chamber. 
         FIG. 4  is a fragmentary enlarged cross-sectional view of the encircled portion of  FIG. 3 , and more clearly illustrates the manner in which the upper peripherally extending border rod and one of the clips is locked in the locking channel formed by deformation of the mattress housing border during assembly. 
         FIG. 5  is an enlarged fragmentary view of another mattress taken in the same area as that of  FIG. 4 , but illustrates the manner in which the upper peripheral border rod is locked in a downwardly opening peripherally extending channel of the upper panel of the mattress housing caused by the compression of the plastic material during assembly. 
         FIG. 6  is an enlarged fragmentary cross-sectional view of another mattress taken through the same area as  FIG. 4 , and illustrates the manner in which both the peripheral border and the upper panel are deformed or distorted during assembly to form a locking channel in each for locking the upper peripheral border rod and its clips therein. 
     
    
    
     DETAILED DESCRIPTION 
     A novel mattress constructed in accordance with this invention is illustrated in  FIGS. 1 through 3  of the drawings and is generally designated by the reference numeral  10 . 
     The mattress  10  is defined by a synthetic foam plastic mattress housing  11  and a coil spring unit  12  ( FIG. 3 ). 
     The mattress housing  11  is defined by a substantially rectangular or polygonal lower or bottom panel  13  having an innermost surface or wall  14 , and an upper substantially polygonal or rectangular panel  15  having an innermost surface or wall  16  and a border  17  having an inner peripheral surface or wall  18 . The border  17  can be a single molded component or can be a single piece of material bent at three corners and glued at a fourth corner or can be made of a plurality of individual border members, such as three of four border members illustrated in  FIG. 1  and individually identified by reference numerals  21 ,  22  and  23 . The border  17  includes an upper surface  24  and a lower surface  25  which defines a border height Bh. The inner peripheral surface or wall  18  of the border  17  also defines an inner border width Bw and an inner border length Bl ( FIGS. 1  and  2 ). The dimensions Bh, Bw and BI define the overall dimensions of a chamber  30  in which is housed the coil spring unit  12 . 
     The coil spring unit  12  includes a plurality of identical bonnell coils or coil springs each being designated by the reference numeral  40  and each having respective upper and lower opposite loop portions  41 ,  42  positioned respectively adjacent the inner surfaces  16 ,  14  of the respective upper and lower panels  15 ,  13  in the completely assembled mattress  10 , as is shown in  FIG. 3 . A selected plurality or all of the upper loop portions  41  are connected to each other by conventional metallic clips  43  as are the lower loop portions  42  by similar conventional metallic clips  44 . A relatively rigid metallic peripheral border rod  50  is located in exterior surrounding relationship to the upper loop portions  41  of the peripherally outermost coil springs  40 . The metallic clips  43  connect the peripheral border rod  50  to the upper loop portions  41  of the coil springs  40  extending along the long sides of the border  17  but need not necessarily be united to the uppermost loops in the row adjacent each of the short sides or width of the border  17 , as is readily apparent from  FIG. 2  of the drawings. However, the clips  43  can also be used to connect the peripheral border rod  50  to the upper loop portions  41  of the coil springs  40  in the row of coil springs most adjacent the short sides (head and foot ends) of the mattress. However, head end to foot end bonnell lacings are “laced” longitudinally to connect the upper loop portions  41  and the lower loop portions  42  of all longitudinally extending rows of coil springs  40  with the upper and lower lacings being respectively identified by reference characters  56  and  57  in  FIG. 2  of the drawings. The springs  40  are also preferably spaced closer together toward the middle of the mattress  10  than at the head and foot ends to provide better support where a supine body needs it most. A plastic netting or mesh  60  encases all of the coil springs  40  and the peripheral border rod  50 . 
     The coil spring unit  12  has a height Sh ( FIG. 2 ), a length Sl and a width Sw. The dimensions Sh, Sl and Sw of the coil spring unit  12  correspond to the respective dimensions Bh, Bl and Bw of the chamber  30 . In accordance with this invention, one or more relative dimensions Sh, Sl and/or Sw define at a minimum a frictional fit relationship, more preferably a force-fit relationship, and still more preferably an oversize fit of between ¼-½ inch relative to the corresponding dimensions Bh, Bl and/or Bw. In this manner at least one dimension, length, width or height of the coil spring unit  12  is greater than at least one dimension, length, width or height of the chamber  30  which assures that the coil spring unit  12  is virtually immovably interlocked within the chamber  30 . More specifically, in keeping with the mattress  10  thus far described, both the spring unit length SI and the spring unit width Sw which are measurements of the respective length and width of the peripheral border rod  50  are ¼-½ inch greater in size than the respective dimensions BI and Bw defining the interior length and width of the chamber  30  of the mattress housing  10 . Therefore, as the spring unit  12  is lowered into the chamber  30 , after the surfaces  14 ,  25  of the respective lower panel  13  and border  17  have been adhesively bonded to each other, the peripheral border rod  50  and the clips thereof contact the upper surface  24  of the border  17  because of the oversized peripheral dimension of the upper border rod  50  as compared to the peripheral dimension of the inner surface  18  of the border  17 . As the spring unit  12  is forced downwardly into the chamber  30  the upper edge of the inner peripheral surface  18  becomes distorted and, in a preferred embodiment of the invention in which the border  17  is constructed from foam material, the foam is crushed to form interlocking means  70  ( FIG. 4 ) in the form of an inwardly opening peripherally extending channel  70  which immobilizes the coil spring unit  12  within the chamber  30 . The lower interior surface  16  of the upper panel  15  is then bonded to the upper peripheral surface  24  of the border  17 . As is most evident from  FIG. 3 , the lower loop portions  42  are unconstrained relative to the inner peripheral surface  18  of the border  17  because of the absence thereat of a peripheral border rod corresponding to the upper peripheral border rod  50 . Thus the interlocking means  70  assures the “swimming pool” effect is eliminated while at the same time providing a mattress  10  of superior characteristics which can be bent considerably about its length or width, again because of the absence of any peripheral border rods beyond the border rod  50 . 
     In further accordance with the present invention, a mattress  10 ′ is illustrated in  FIG. 5  which is identical in construction to the mattress  10  except the dimensions Bl, Sl and Bw, Sw are substantially the same but the height Sh of the coil spring unit  12  as measured from the top of the peripheral border rod  50  and the lowest loop portions  42  of the coil springs  40  is ¼-½ inch greater than the distance or height Bh ( FIG. 3 ) of the chamber or compartment  30 . Thus, peripheral locking means  70 ′ is formed in the inner surface  16  of the upper panel  15  when the latter is forced downwardly upon the coil spring unit  12 ′. In this case the locking or interlocking means  70 ′ is effected between only the upper panel  15 ′ and the spring unit  12 ′ whereas the border  17 ′ includes its normal undeformed inner peripheral surface  18 ′. 
     A mattress  10 ″ of  FIG. 6  includes interlocking means  70 ″ which is defined by both of the interlocking means  70 ,  70 ′ of respective  FIGS. 4 and 5  heretofore described. In other words, the locking or interlocking means  70 ″ is achieved by dimensioning all three dimensions Sh, Sl and Sw of the coil spring unit  12  greater than the respective dimensions Bh, Bl and Bw of the chamber  30 . The locking or interlocking means  70 ″ is thereby effected between the coil spring unit  12 ″ and both the inner surface  16 ″ of the upper panel  15 ″ and the inner peripheral surface  18 ″ of the border  17 ″.