United States Patent 3689946

A box-spring type seat construction formed of an upper frame, a lower frame and interconnecting coil springs, with a horizontally elongated fabric strip having wire stiffened upper and lower edges secured to the upper and lower frames respectively at the forward edge of the seat construction, with the strip vertically extending between the frames for limiting the expansion of the springs. The strip is formed of fine strands of linearly oriented polypropylene felted into a randomly oriented non-woven, smooth sheet for roughly equal stretch resistance and equal tension absorption in all of its planar directions.

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International Classes:
A47C27/00; A47C27/04; (IPC1-7): A47C23/02
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Primary Examiner:
Gay, Bobby R.
Assistant Examiner:
Moore, Garry
Having fully described an operative embodiment of this invention, I now claim

1. In a box-spring type seat construction formed of a pair of roughly flat and horizontally arranged springy wire-like frames, one located above the other in vertical alignment therewith, and with generally vertically arranged coil springs secured between and interconnecting the two frames for resilient movement of the frames towards and away from each other, and with a cushioning pad arranged upon the upper frame, and upholstery material covering the pad and the side edges of the seat construction and spanning the spaces between the edges of the two frames, to define a seat having a front and side edges and an upper seating surface, the improvement comprising:

2. A construction as defined in claim 1, and at least the surface of the strip adjacent the upholstery fabric being coated with a film of a smooth, slippery plastic material.

3. A seat edge spacer for fastening between the edges of upper and lower frames of a coil-spring, box-spring type construction for limiting the separation of the frames due to the tendency of the springs to expand, said strip comprising:


Box-spring type sheet constructions, which are used for automobile type seats as well as for certain types of furniture seats, generally consist of an upper wire frame spaced above a lower wire frame, with the two frames interconnected by numerous vertially arranged coil springs. Seat padding is placed upon the upper frame and thereafter, upholstery fabric is arranged upon the upper surface of the padding as well as around the edges of the seat construction.

Usually, the coil springs are under slight compression when the seat is unoccupied. When a weight is applied to a seat, as for example, by a user sitting upon the seat, the spring is compressed and the upper wire frame, with its padding and upholstery fabric is moved downwardly towards the lower frame. Upon release of the weight, the springs expand or rebound and have a tendency to overexpand thus applying a tension force upon the upholstery fabrics around the edges of the seat, particularly at the forward edge of the seat.

The repeated buckling of the upholstery fabric, particularly around the forward edge of the seat, with the repeated tension applied thereto, causes this material to pucker, tend to crack if it is a plastic material, and tends to tear this material.

Hence, various types of limiting means have been applied to such seat constructions to reduce the tension load upon the upholstery fabric and to restrict the expansion of the springs. One such type has been a strip of burlap material arranged around the front of the seat frame, between the upper and lower frames and secured thereto for buckling when the seat is compressed and for straightening and absorbing the tension forces caused by the expanding springs when the seat is unweighted.

Such type of seat edge spacer, formed of a heavy, rough burlap material as has been used in the past, has numerous disadvantages, such as a tendency to stretch, particularly when moist or wet, thus permitting tension to be applied to the upholstery fabric at the forward edge of the seat. In addition, it tends to rub against or drag against the upholstery fabric, increasing puckering or creasing thereof.

Thus, the invention herein relates to an improved seat edge spacer strip which eliminates or reduces the disadvantages of prior devices of this character, and which more effectively serves to absorb the tension forces of the expanding spring to better protect the upholstery fabric.


The invention herein relates to a seat edge spacer in the form of an elongated strip secured between the forward edges of the upper and lower seat frames, and being formed of a thin, flexible sheet made of fine strands of linearly oriented polypropylene which are felted into a non-woven randomly oriented sheet. The horizontal edges of the strip are turned over into hems into which wires are inserted for stiffening and reinforcing the upper and lower edges of the strip. Such strip is characterized by being smooth and relatively slippery surfaced, to reduce frictional drag and interlocking with the upholstery fabric adjacent thereto. In addition, the strip construction substantially equally resists stretching and substantially equally absorbs tension in all of its planar directions and is substantially free of stretch, even when wet.

These and other objects and advantages of this invention will become apparent upon reading the following description, of which the attached drawings form a part.


FIG. 1 is a perspective view of the box-spring type of seat construction with the seat edge spacer secured thereto.

FIG. 2 is a fragmentary, prospective view, showing the seat edge spacer, per se.

FIG. 3 is an enlarged fragmentary perspective view of a portion of the spacer.

FIG. 4 is an enlarged, cross-sectional view of the forward edge of the overall seat construction.

FIG. 5 is a partial or fragmentary view, showing the forward edge of the seat when compressed under weight.


Fig. 1 illustrates a conventional box-type spring 10 which generally is formed of an upper wire frame 11, spaced above and aligned with a lower wire frame 12, with each of the frames having flat, springy metal cross-strips 13 and 14 against which the upper and lower edges of vertically arranged coil springs 15 are abutted. The wire frames 11 and 12 are each generally arranged in the horizontal plane, although actually they are at somewhat of an angle to the horizontal to form the general seat configuration as is found in conventional automobile constructions.

The upper frame is covered with a resilient padding 16 and upholstery fabric 17 is placed upon the upper seating surface and around the forward, side and rear edges of the spring frame construction, with the upholstery fabric secured to the bottom of the construction in some conventional manner.

In this construction, when a user sits upon the seat, the springs 15 are compressed and the wire frame 11 bends resiliently so that the seat conforms to the contour of his body. This causes bending, puckering or buckling of the upholstery fabric. Usually, the coil springs 15 are pre-compressed slightly when the seat is in its non-used position. Thus, upon release of the weight from the seat, the coil springs tend to overexpand or over rebound, thus tending to separate the upper and lower frames beyond their normal designed spacing. This put a considerable tension load upon the upholstery fabric, particularly at the forward edge and the side edges, near the forward edge of the seat. Repeated buckling of the upholstery edge fabric, with the repeated tension applied, as the seat is used, ultimately will cause the fabric to tear, in addition to previously causing puckering and also cracking where the fabric is of a plastic type material as is commonly used.

To preserve the spacing of the frames and to limit overexpansion of the springs, as well as to absorb the tension of the springs and resist the application of tension forces to the upholstery fabric, the spacer strip 20 is applied between the upper and lower frame at the forward edge of the seat. As illustrated in Fig. 1, the spacer strip is an elongated strip of a predetermined width which fits between the forward edges of the two frames at the forward edge of the seat and along the forward portion of the side edges.

The strip is formed of fine strand, linearly oriented polypropylene, which is felted into a randomly oriented, non-woven fabric. As an example, the fabric may be approximately 13 mils in thickness, and 3 1/2 oz. per square yard in weight.

The strip fabric is generally smooth and slippery. However, the smoothness and slipperiness of the fabric can be increased even further by applying a thin, continuous coating of a polyethylene film 21 upon its opposite surfaces. In effect, this serves as a lubricant for the surfaces.

The upper and lower edges 23 of the strip are doubled over to form hemmed tunnels 24 into which a continuous springy wire 25 is inserted. Preferably, the wire is wrapped with a kraft paper covering 26. The hem may be formed by stitches 27 which preferably are formed by heat welding, utilizing sonic type heat welding equipment. Alternatively, it can be stitched with thread in the conventional manner.

The strip is assembled to the frames by arranging it in the space between the upper and lower frames and then passing conventional hog rings 28 around the adjacent frame portions and wire 25 portions to thus mechanically secure the strip to the frames. As illustrated in Fig. 4, the strip is closely adjacent to the upholstery fabric at the forward edge 30 of the seat. Hence, when a weight, schematically illustrated by the arrow 31 in Fig. 5, is applied to the upper surface of the seat, the springs are compressed, the upper frame moves downwardly, and the upholstery fabric at the forward, side edges and covers of the seat, along with the strip, tend to buckle and intermesh. The smoothness and slipperiness of the strip reduces the tendency of the upholstery fabric to drag or pucker at this point.

Thereafter, when the weight 31 is removed, the springs pop up or expand and the tension in the vertical direction, as well as various sidewise or angular directions, due to the straightening of the upper wire frame 11, is absorbed by the spacer 20 with the upholstery fabric being substantially free of such tension forces. Thus, the upholstery fabric is protected against tearing or wear.

The strip material is substantially non-stretchable in all of its planar directions. In addition, it is substantially equal in all of its planar directions in its capacity to absorb tension. Thus, at all times it protects against tension load, vertical as well as angular, from being transferred to the upholstery fabric at the edges of the seat. The strip fabric does not absorb nor is it affected by moisture, so that even when wet, its operation is unchanged.

In addition, in certain types of constructions, the seat edge spacer is arranged closely adjacent to the springs near the forward and side edges of the seat. Thus, even if the spacer buckles into the gaps between the coils of the springs, its slipperiness prevents it from being pinched or pulled by the coils.

The spacer may be extended around the sides to the rear of the spring 10, and even around the rear, where necessary.