BACKGROUND OF THE INVENTION

This invention generally relates to mattress foundations. Mattress foundations generally comprise a frame, a plurality of slats disposed across the frame and secured at their respective ends to the frame, a plurality of springs supported by the slats, and a wire grid supported above the slats by the springs. The grid comprises a plurality of long and cross wires arranged in a grid pattern and surrounded by a border wire. The foundation is encased in a fabric material.

In the pas ^* c, one commonly used method of attaching the long and cress wires to the border wire has been to wrap the ends of the long and cross wires around the border wire. As the diameter of the long or cross wires increases beyond certain tolerable size, the wrapped wires tend to form unsightly protrusions that can be seen through the outer fabric material that covers the mattress foundation. Further, such protru¬ sions tend to cause localized wear of the outer cover¬ ing fabric, such that the aesthetic appearance is ^' further diminished and the useful life of the assembly including the fabric material is shortened. These drawbacks are amplified when heavy gauge wire is desired for the purpose of obtaining a firm grid. A

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further drawback of the prior art wrapping methods is that the border wire is not firmly located by the wrap¬ ped around end portions of the long and cross wires. This can put additional stress on the edges of the grid and can also contribute to a shortened life span of the covering material.

Another problem of traditional foundation assemblies relates to the main springs. Foundation assemblies are tested for durability by the repeated application of a heavy load thereto. It has been found that some prior art main springs do not perform well in such tests.

Still further problems of some traditional foundation assemblies relate to the metal slats. Some foundations have arched slats which flex and therefore reduce the overall firmness of the foundation.

Another problem relating to metal slats is that their outer edges are sharp and prone to cause injury to foundation builders. Thus, there presently exists the need for an improved foundation which can accommodate large diameter long or cross wires without suffering from above-stated disadvantages when these wires are wrapped around the border wire. There is also a need for a highly durable main spring which can be firmly attached to the grid and an improved metal slat that will improve the firm¬ ness of the foundation. The present invention provides an improved foundation which satisfied these needs.

SUMMARY OF THE INVENTION This invention is directed to improved mat¬ tress foundations.

In accordance with one aspect of the present invention, an improvement to a grid is provided. The improvement comprises a flattened, preferably coined,

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end surface defined at the ends of wires wrapped around the border wire. The flattened end surface defines a radius of curvature, disposed between the unaltered round section of the wire and a substantially flat sec- tion of the wire, that is preferably substantially equal to that of the border wire such that the border wire is securely seated therein. The flattening or coining of the wrapped around end facilitates location of the wires during processing, provides a tighter and more secure connection, and reduces the undesirable protrusion created by the wrapping.

In accordance with a second aspect of the present invention, highly durable main springs are pro¬ vided for a mattress foundation. Each main spring co - prises an upper, substantially horizontal load-bearing section. This upper section defines first and second spaced, substantially parallel outer bars. A middle bar having first and second ends is disposed between and substantially parallel to the first and second outer bars. A first transverse bar connects the first end of the middle bar to a first end of the first outer bar, and a second transverse bar connects the second end of the middle bar to a first end of the second outer bar. Two substantially vertical bars extend downwardly from second ends of the respective first and second outer bars. Two substantially horizontal, spaced, and substantially parallel lower horizontal bars depend in a substantially perpendicular direction from a respective one of the vertical bars. These lower horizontal bars are substantially vertically aligned with the respective outer bars, and extend in a substantially parallel relationship thereto. Two down¬ wardly sloping angle bars each depend from an opposite end of a respective one of the lower horizontal bars. Each form an angle of from 41° to about 50° , and

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preferably from 41° to about 44° _. from a horizontal reference plane intersecting therewith. Two substan¬ tially horizontally disposed mounting feet, each de¬ fining an approximate U-shape oriented in opposite directions from one another, depend from a respective one of the downwardly sloping angle bars.

In accordance with a further aspect of the present invention, flat horizontal metal slats and a central beam beneath the centers of the slats are pro- vided to assure firmness of the foundation.

In accordance with still another aspect of the present invention, each metal slat is provided with slanted side edges to prevent injuries to foundation builders. In accordance with still another aspect of the present invention, a plurality of clips are used to attach each spring to the grid. The clips fit on either side of the cross wires to prevent sliding of the spring along the long wire. The clips therefore stabilize the foundation and improve its durability.

The aspects of the present invention can be used either separately or in combination to produce improved foundation units.

The invention together with objects and attendant advantages, will be best understood by the following detailed description, read together with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a plan view of the improved foundation of the preferred embodiment of the present invention.

FIGURE 2a shows a cross-sectional view of the improved foundation taken along line 2a - 2a of FIG. 1.

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FIGURE 2b is a cross-sectional view of the improved foundation taken along line 2b - 2b of FIG. 1.

FIGURE 3a is a perspective view of a corner spring of the improved foundation unit of FIG. 1. FIGURE 3b is a side elevational view, in par¬ tial cross-section, of the corner spring taken along line 3b - 3b of FIG. 3a.

FIGURE 4 is a plan view of a cross wire hav¬ ing a coined end before it is wrapped around the border wire of the foundation of FIG. 1.

FIGURE 5 is a side elevational view in par¬ tial cross-section of the coined end of the cross wire of FIG. 4 when wrapped around the border wire.

FIGURE 6 is a plan view of the wires shown in FIG. 5.

FIGURE 7 is a side elevational view, in par¬ tial cross-section, of cross wire wrapped around the border wire in a conventional manner.

FIGURE 3 shows a plan view of the wires shown in FIG. 7.

FIGURE 9 is a perspective view of the main spring and metal slat of FIG. 1.

FIGURE 10 is a side elevational view taken along line 10-10 of FIG. 9. FIGURE 11 is a side elevational view in par¬ tial cross-section taken along line 11-11 of FIG. 10.

FIGURE 11a is a view similar to that of FIG. 11, but showing a spring at the border of the foundation of FIG. 1. FIGURE 12 is a bottom view of the main spring and slats of the foundation of FIG. 12.

FIGURE 13 is a diagrammatic view of the main spring of a preferred embodiment of the present inven¬ tion. FIGURE 14 is a diagrammatic view of the main spring of the prior art.

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DETAILED DESCRIPTION OF THE PRESENT INVENTION

Turning now to the drawings, FIGURES 1 through 3 show a foundation incorporating the aspects of the present invention. The foundation 1 comprises a frame 2, and a plurality of slats 3 extending in a transverse direction across the frame 2. A support beam 4 extends in a longitudinal direction, beneath the slats 3, adding structural support to the foundation unit 1 and making the foundation firm. A plurality of main springs 5, mounted on the slats 3, supports a grid 6. The grid 6 comprises a plurality of long wires 7, extending in a longitudinal direction, and a plurality of cross wires 8, extending transversely thereto. The grid 6 has a border wire 9 at its perimeter. A fabric outer cover- ing 10 envelopes the foundation 1.

The first aspect of the invention is directed to the attachment of the cress wires 8 to the border wire 9. This aspect is best understood with reference to FIGURES 4 through 3. According to this aspect of the invention, ends II of the cross wires 8 are flatten¬ ed, preferably coined, and then wrapped around the bor- der wire 9 to form protrusions 13 that are relatively thin and flat when compared to the protrusions that would result from wrapping the cross wires 8 without flattening them first. The radius of curvature defined between the coined and the unaltered round sections of the cross wires 3 is preferably substantially equal to that of the border wire 9, such that the border wire 9 is securely seated in the recesses formed in the cross wires 8. The attachment of the border wire in this fashion produces a grid 6 with significant advantages over the prior art. Although only the thicker cross wires a in the foundation depicted in the FIGURES have flattened or coined ends, it should be understood tha _t the invention is equally applicable to the use of the flattened or coined ends of long wires 7 as desired.

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One advantage of this improved grid of the invention is that it reduces wear at portions 12 of the outer covering 10 which overlie the protrusions 13. Since the cross wires 8 are coined or flattened at these protrusions 13, pressure or tension between the outer covering 10 and the protrusions 13 is spread over a greater surface area than would be the case if the cross wires 8 were wrapped without this improvement. Without the improvement of the present invention, all the pressure or tension from stretching the outer covering 10 at each protrusion 13 would be focused on a much smaller area, corresponding to a point on the cir¬ cumference of the wrapped wire against which the cover¬ ing 10 is pressed. A corroiary advantage resulting from this improvement is that the distance between the border wire 9 and the outermost portion 14 of the pro¬ trusions 13 is less than it would be if the ends 11 of the cross wires 8 had not been coined before being wrapped. This feature also reduces tension on the portions 12 o . the covering 10 that overlie the protru¬ sions 13. Thus, both the flattened shape and the de¬ creased thickness of the protrusions 13 contribute to the advantage of reducing wear on the outer covering 10. A further advantage is that foundations 1 with less noticeable protrusions are aesthetically more pleasing. A uniform, substantially smooth border gives the foundation a higher quality appearance than a border with Obvious protrusions. Of course, another factor contributing to greater aesthetic appeal is that the outer fabric will not wear out as quickly when this improvement is incorporated into the grid.

Another advantage is that it is easier to wrap the thinner ends 11 than the full thickness of the cross wire 3 around the border wire 9, and more uniform results are obtained.

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A still further advantage is that the transi¬ tion from the thicker portions to the thinner ends 11 of the cross wires 8 provides a recess which firmly seats and ensures correct positioning of the border wire 9.

Another aspect of the present invention re¬ lates to improved main springs 5. The main springs 5 of the present invention are best understood with re¬ ference to FIGURES 9 through 14. Each main spring com- prises an upper, substantially horizontal load-bearing section 20. This upper section 20 includes a middle bar 21 for attaching the spring 5 to the grid 6. From opposite ends of the middle bar 21 the upper section 20 defines two transverse bars 22. The upper section 20 also defines two spaced, substantially parallel outer bars 23 which are connected to the transverse bars 22 and are disposed in a substantially parallel relation¬ ship to the middle bar 21. Two substantially vertical bars 24 depend downwardly from the outer bars 23, each vertical bar 24 depending from an opposite end of a respective one of the outer bars 23. Two substantially parallel lower horizontal bars 25 depend in a substan¬ tially perpendicular direction from a respective one of the vertical bars 24. These lower horizontal bars 25 are substantially vertically aligned with the outer bars 23, and extend in a substantially parallel rela¬ tionship thereto. Two downwardly sloping angle bars 26 each depend from- an opposite end of a respective one of the lower horizontal bars 25. Each form an angle of from 41° to about 50°, and preferably from 41° to about 44°, from a horizontal reference plane intersecting therewith. Two substantially horizontally disposed mounting feet 27, each defining an approximate U-shape oriented in opposite directions from one another, de- pend from a respective one of the downwardly sloping anσie bars 25.

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It has been found that the angle between the respective angle bars 25 and the mounting feet 27 is critical in providing durability for the spring 5. Surprisingly, when clearance between the lower horizon- tal bars 25 and the mounting feet 27 is increased over that provided by the prior art by providing an angle of from 41° to about 50°, and preferably ^* from 41° to about 44°, between the mounting feet 27 and the angle bars 26, the durability of the spring 5 increases dramati- cally.

In accordance with another aspect of the pre¬ sent invention, which will be understood by reference to FIGURES 9 and 13, the metal slat 3 is provided with a substantially flat top surface 30 and is supported by a central beam 4. Since the metal slats are essential¬ ly flat and are supported at their center, they do not flex when load is applied to the springs. This results in a firmer foundation.

Still another aspect of the invention is that the metal slat 3 is provided with slanted edges 32.

This structure has the advantages of providing the slat 3 with additional strength, and of providing safety for foundation workers by concealing the sharp side edge JO. A further aspect of the invention illustrated in FIGURE 9, is that two clips 29 are used to attach each main spring 5 to the grid 6. The two clips 29, placed on either side of an intersection 15 of the long wire 7 and the cross wire 3, between said intersection 15 and respective ones of the transverse bars 22, sub-- stantially immobilize the main spring 8 against any sliding along the long wire 7. This arrangement sig¬ nificantly contributes to the overall stability of the foundation and improves its durability.

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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment will now be discus¬ sed in detail. However, it should be understood that although improvements of the present invention are used in combination in the preferred embodiment, they may also be used separately from one another.

As seen in FIGURE 1, the foundation 1 gener¬ ally comprises the grid 6, supported by the plurality of main springs 5, in turn supported by the plurality of metal slats 3. The metal slats 3 are supported by the frame 2 and the wooden support rail 4. The frame 2 is disposed at the perimeter of the foundation 1, and is substantially vertically aligned with the border wire 9 of the wire grid 6. The support rail 4 extends centrally and longitudinally across the foundation 1, substantially in a common plane with the frame 2. Pre¬ ferably, the frame 2 and the support beam 4 are both constructed from wood. A fabric material forms the outer covering 10 which encases the foundation 1. This material is preferably damask, with a layer of cotton padding underneath.

As seen in FIGURES 1 through 3, the grid 5 generally comprises the plurality of- long wires 7 and cross wires 8, forming a grid pattern with the border wire 9 disposed at the perimeter thereof. It is pre¬ ferred that the cross wires 8 are thicker than the cross wires 7 so that grid durability is improved. In the presently preferred embodiment, the long wires 7 are 12-gauge wires, the cross wires 8 are 9-gauge wires and the border wire 9 is β^-gauge spring wire.

The ends 11 of the cross wires 8 are coined by mechanical means such a press brake. The ends 11 of the cross wires 8 of the preferred embodiment are coin¬ ed to a thickness of from about .90 to about .100 inches, and preferably about .095 inches. The coined

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ends 11 are then wrapped around the border wire by con¬ ventional mechanical wrappers. The radius of curvature defined between the coined and the round sections of the cross wire is substantially equal to that of the border wire, such that the border wire is securely seated in the recesses formed in the cross wire. The radius of curvature is in the range of about .150 to about .160 inches, and preferably about .155 inches. The long wires 7 and the cross wires 8 are welded at their intersections 15, but are not welded at the border wire 9. Welding is not necessary here because the transition from thinner to thicker wire provides a well defined recess 16 and stop 17 that co¬ operate to firmly and securely seat the border wire 9 in the cross _. wires 8. The long wires 7 and cross wires 8 are preferably made from bright basic steel wire and border wire 9 are preferably made from spring steel wire.

As seen in FIGURES 9 through 14, the main springs 5 generally comprise the substantially horizon¬ tally disposed upper section 20 which includes the middle bar 21, the transverse bars 22 and the outer bars 23. The middle bar has a first end 41 and a second end 42. The transverse bars 22 are connected to the respective first end 41 and second end 42 of the middle bar 21, and are also connected to a first end 43 of the respective outer bars 23. Substantially verti¬ cal bars 24 depend downwardly from a second end 44 of each of the outer bars 23. Lower horizontal bars 25 depend from the vertical bars 24 in a substantially perpendicular relationship thereto and in a substan¬ tially parallel relationship to the outer bars 23. From an opposite end of each of the lower horizontal bars 25 depends an angle bar 26, and from each of the angle bars 26 depends a mounting foot 27. The mounting

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feet 27 each define a U-shape in opposing orientations, disposed in a plane substantially parallel to the plane including the upper section 20, and the mounting feet 27 are substantially vertically aligned with the upper section 20. An offset portion 28 is defined by each of the mounting feet 27.

The angle between each mounting foot 27 and each angle bar 26 is in the range of from 41° to about 50°, and is preferably from 41° to about 44°. This angle is critical for obtaining a high level of dur¬ ability of the main spring 5.

The main springs 5 are attached at the middle bar 21 to the grid 6 by two conventional clips 29, one such clip 29 disposed on each side of the intersection 15 of the long wires 7 and the cross wires 8, between said intersection 15 and the transverse bars 22. This arrangement substantially prevents the main springs 5 from becoming displaced relative to the grid 5. If desired, the clips can be formed to substantially occupy the entire region between the intersection 15 and the respective transverse bars 22.

The attachment of the main springs 5 to the metal slats 3 is accomplished by inserting the mounting feet 27 in the elongated slots 31 of the metal slats 3. The offset portion 28 of each mounting foot 27 holds the main springs 5 securely in the slots 31 such that motion of the main springs 5 in the slots 31 is sub¬ stantially prevented.

Preferably, the main springs 5 are made from 8-%-gauge steel wire. The height of the unloaded main springs 5 is from 5.25 to 5.35 inches, the width thereof is from about 2.50 to 2.80 inches and the length thereof is from about 5.90 to 6.10 inches. Pre¬ ferably, the attachment bars 21 are about 1.65 inches long. There are 8 to 10 rows and 3 columns of main

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springs 5 in a twin bed foundation; 8 to 10 rows and 4 to 5 columns in a single bed foundation; 9 to 11 rows and 5 to 6 columns in a queen bed foundation; and 9 to 11 rows and 3 columns in an extra long twin bed founda- ticn.

As seen in FIGURES 9 through 12, the metal slats 3 generally comprise the top surface 30, which is substantially flat and horizontally disposed; the pair of spaced side walls 33, depending from the top surface 30 and disposed in a substantially perpendicular rela¬ tionship thereto; and the slanted portions 34 depending upwardly from each of the side walls 33 and extending outwardly therefrom.

The metal slats 3 are also provided with small openings 37 at their ends 38 and center 39 for stapling the slats 3 to the frame 2 and support rail 4.

The metal slats 3 are preferably made from 50K psi minimum flat strip steel. For a twin founda¬ tion they have dimensions of about .98 to 1.02 inches high by about 34.76 inches to about 34.38 inches long by about 1.50 to about .06 inches wide. The corre¬ sponding dimensions for a single foundation are abcut .98 to about 1.02 inches high by about 49_.32 to abcut 49.94 inches long by about 1.44 to about 1.56 inches wide, for a queen foundation are about .98 to about

1.02 inches high by about 56.32 to about 56.94 inches long by about 1.44 to about 1.55 inches wide and for an extra long twin foundation are about .98 to about 1.02 inches high ^' by about 34.76 to about 34.88 inches long by about 1.44 to about 1.56 inches wide.

Of course, the dimensions and details of con¬ struction are set forth in this specification only by way of example and not by way of limitation. A wide range of changes and modifications can be made to the preferred embodiment described above without departing

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from the scope of this invention. It is therefore in¬ tended that the following claims, including all equiva¬ lents, define the scope of this invention.