1. Field of the Invention
The field of the present invention relates to reinforced bedding foundations and, in particular, to structural frames which provide reinforcement to increase the resistance to deflection under load of either resilient or non-resilient foundations for mattresses.
2. Description of Related Art
In the bedding industry, foundations for mattresses may be of resilient or non-resilient construction. Generally, resilient foundations are of a type referred to as "box-spring" constructions wherein structural frames are employed with assemblies of wire springs supported on the structural frames and with padded upper surfaces applied over the springs. Normally, this entire construction is encased within a pre-sewn ticking that is stapled or otherwise tacked to the underside of the structural frame around its periphery. Usually, a dust cover formed from a light plastic film or like material is applied to the underside of the structural frame. Examples of such constructions are disclosed in U.S. Pat. No. 4,339,573, issued to Baright and in U.S. Pat. No. 4,519,107, issued to Dillon et al, both of which are assigned to the common assignee herein, the disclosures of which are expressly incorporated herein by reference.
In conventional non-resilient foundations, the springs of the resilient constructions are absent and the mattresses rest on support assemblies such as wire or plastic loops, nets or screens, wooden or plastic blocks and the like which are attached to and extend from the structural frames. Padded upper surfaces are applied over the support assemblies and, normally, this entire construction is encased within a pre-sewn ticking that is stapled or otherwise tacked to the underside of the structural frame around its periphery with a dust cover applied to the underside of the structural frame.
Traditionally, both resilient and non-resilient foundations have been produced utilizing unreinforced wooden structural frames consisting of perimeter frames of flat lumber that have side rails and end rails nailed together at the frame corners and numerous cross slats spanning the frame, with or without a center rail. Such constructions were found to be adequate in strength to carry normal loads with only peripheral support. However, such frames have been found to exhibit substantial deflection under load and may, in time, develop a degree of permanent deflection. This permanent deflection interferes with the foundation's intended function of providing a planar support surface for the mattress.
A sagging foundation is indicated by the sagging or tilting of the mattress it carries which interferes with the essential function of the mattress, i.e., to uniformly support an outstretched body despite the uneven distribution of the body's weight. In addition, the foundation may exhibit a permanent sag, which is reflected in the mattress as a depression that is considered unsightly and unattractive.
To remedy these shortcomings, the inventions embodied in U.S. Pat. Nos. 4,399,573 and 4,519,107 are proposed wherein longitudinally extending support beams are secured to the upper surface of the cross slats of the structural frame of a foundation. For example, in U.S. Pat. No. 4,399,573, L-shaped frame stiffening braces or beams are secured to the upper surface of the cross slats of a structural frame and these frame stiffening beams extend longitudinally substantially the entire length from a head end to a foot end of the frame. These longitudinal beams are positioned so that they do not interfere with the resilient deflection in the foundation, and do not alter the smooth outline of either the upholstered top surface or the undersurface of a box-spring.
In the construction of U.S. Pat. No. 4,519,107, hollow cylindrical stop members are disclosed for limiting the amount that springs in a resilient foundation can be compressed. In that patent, it is disclosed that supporting L-shaped braces or beams may also be employed. The L-shaped braces or beams disclosed for use in that constructions are of the same type as those disclosed in U.S. Pat. No. 4,399,573 which extend longitudinally substantially the entire length of the frame from head to foot and may be accompanied by other beams or braces which likewise extend longitudinally but for a shorter distance.
However, despite the advances made possible by the inventions embodied in U.S. Pat. Nos. 4,399,573 and 4,519,107, it has been found that foundations which make use of longitudinally extending braces or beams nevertheless exhibit a certain level of deflection when normal loads are encountered. In time (i.e., after extended use), these foundations may also suffer permanent sagging that interferes with the essential function of the mattress and may result in the mattress having an unsightly sagging appearance.
Also, foundations constructed utilizing longitudinally extending support braces or beams require the use of significant amounts of materials in fabrication and, particularly, when the braces or beams extend substantially from head to foot of the structural frame as is disclosed in both of U.S. Pat. Nos. 4,399,573 and 4,519,107. Thus, these constructions clearly utilize more material than would be desirable and, thereby, result in both added cost and weight of the foundations. In addition, it has been found that structural frames for use in bedding foundations employing longitudinally extending reinforcing braces or beams have a tendency to exhibit tensile failure at joints when fasteners such as nails, staples and like fasteners are employed to interconnect frame members since the fasteners are not in shear with the load applied thereto when the braces or beams are longitudinally oriented.