Preloaded spring assembly

Details Preloaded spring assembly Preloaded spring assembly

1999-03-04

2001-02-13

Oberleitner, Robert J. (Department: 3613)

Spring devices

Spring panel

With means to vary preliminary tension of spring

C005S261000

Reexamination Certificate

active

06186483

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to spring assemblies for use in furniture and bedding products; more particularly to furniture and bedding spring products in which the springs are preloaded prior to assembly.
DESCRIPTION OF THE PRIOR ART
Furniture and bedding products typically comprise a plurality of helical coil springs arranged in transversely extending rows and longitudinally extending columns of springs. The coil springs are generally secured in an assembled relationship by means of wire or steel connectors or helical lacing wires or by the upper and lower end turns of the coil springs being secured to a grid and/or wooden base. The coil springs are often of identical height in order to ensure a uniform “feel” across the entire width of the product. The height of these springs is often such that the product has a “soft feel” to it when one sits or lays on the product. This “soft feel” is caused by the load on the end turns of the coil springs causing the coil springs to compress a relatively large distance per unit load until the spring reaches a certain compression point at which point the amount of load necessary to compress the coil spring a further unit of distance is greatly increased. Until this compression point is reached, a lesser load is needed to initially compress the spring the first or initial unit of distance. The effect of this unequal reaction to the same load is that the user experiences a sinking feeling when initially laying or sitting on the spring assembly. This sinking effect is uncomfortable and disconcerting to the user of the product and may cause the user to think the product is not functioning correctly.
One method which has been used to eliminate this increasing resistance to compression of the springs or initial softness of the springs is to preload or precompress the coil springs before they are joined together into an assembly. Each individual coil spring is preloaded or partially compressed until the coil spring reaches the point at which this initial softness is eliminated. One method of preloading a coil spring before placing it in the assembly has been to place the individual coil spring inside a pocket of fabric material which encases the entire coil spring. Coil springs enveloped in fabric are called pocketed coil springs and are the subject of numerous patents, for example, U.S. Pat. Nos. 1,455,847 and 3,082,438.
Another method of preloading individual coil springs is to tie the coil springs to each other and downwardly in what is traditionally called an 8-way hand tie. Using this method, an operator manually compresses each coil spring the desired amount before tying
8
points of the end turns of each coil spring to another coil spring or to the frame of the spring assembly. Twine or rope is used to tie one side of a furniture frame to a number of different springs using knots and then to the other side of the frame. The springs are compressed to the proper level by a skilled artisan before being tied down to the frame. However, this method of preloading coil springs with all springs compressed to the same degree is very difficult to achieve with the result that only craftsmen who have repeated the procedure many times are able to achieve the requisite degree of precision and skill necessary to assemble an acceptable product. This skill requirement therefore necessarily increases cost and decreases productivity. Other difficulties encountered assembling a precompressed spring unit with a traditional 8-way hand tie are: 1) if fabric is used as the base, the fabric is subject to stretching or ripping; 2) the twine or rope may stretch over time causing the amount of compression of the coil springs to decrease over time; and 3) trying to establish a crown effect in the middle part of the spring assembly in which the coil springs are compressed less than at the edges of the assembly is difficult. Few artisans are skilled enough to practice this art.
One patent which discloses a coil spring assembly made of precompressed coil springs is U.S. Pat. No. 2,048,637. In this patent, two endless strips of fabric are wrapped around opposite sides of each coil spring in order to precompress the coil spring before the coil springs are assembled together. Helical lacing wire is wrapped through the endless strips of fabric in order to connect adjacent rows of coil springs together. A spring assembly made of preloaded coil springs as disclosed in this patent is excessively expensive and time consuming to manufacture, primarily because two endless strips of fabric are required to be wrapped around each coil spring.
Therefore, it has been an objective of the present invention to provide a preloaded spring assembly which is less costly and less labor intensive to produce than heretofore known preloaded spring assemblies.
Another objective of the present invention has been to construct a preloaded spring assembly without the use of traditional 8-way hand tying.
A further objective of the present invention has been to provide a preloaded spring assembly without the use of pocketed coil springs.
Another objective of the present invention has been to provide a spring assembly in which rows and columns of preloaded coil springs may be easily interconnected.
SUMMARY OF THE INVENTION
The invention which accomplishes these objectives comprises a bedding or furniture spring product comprising a spring assembly comprising a plurality of coil springs preferably arranged in linear columns and rows. Each of the coil springs is compressed or preloaded by an endless strip or loop of fabric which encircles the exterior of each of the coil springs in the bedding or furniture spring product. Each of the coil springs has an upper end turn, a lower end turn and a central spiral portion between the end turns. The endless strip of fabric passes across and above the top end turn of each coil spring, along the exterior sides of the central spiral portion of the coil spring and across the bottom below the lower end turn of the coil spring. Typically, the endless strip of fabric does not contact the central spiral portion of the coil spring but does contact the upper and lower end turns of the coil spring. The strip of fabric is of a width sufficient to hold the coil spring in a compressed condition without ripping or tearing but is of a width less than the diameter of the end turns of the coil spring. Consequently, a portion of the upper and lower end turns is exposed and not covered by the strip of fabric. These uncovered portions are aligned with one another so that a helical lacing wire or other attaching means or device may attach adjacent springs by encircling the uncovered portions of the end turns of the coil springs without penetrating or tearing the strip of fabric.
In order to prevent the strip of material from sliding off the compressed coil spring and causing the coil spring to decompress into a relaxed condition, the strip of fabric is preferably made of a knitted, woven, non-woven or other fabric material having non-slip properties such as those imparted by a coating of foamed polyvinyl chloride (PVC). Alternatively, the strip of fabric may be made of any fabric material sprayed or coated on the interior surface thereof with a non-slip material such as PVC so that when the fabric encircles the coil spring, the non-slip surface on the inside of the strip contacts the end turns of the coil spring and prevents the strip from sliding off the coil spring. Yet another alternative for preventing the strip of fabric from sliding off of the compressed coil spring is to coat the end turns of the coil springs with a non-slip material such as polyvinyl chloride (PVC).
A coil spring assembly used for furniture or bedding made in accordance with this invention may have the preloaded springs interconnected by helical lacing wires or metal clips or may have the springs interconnected to wire grids. In the later case, a wire grid in the top plane of the assembly generally comprises a border wire and a plurality of crossing wires connected at the ends to the b

Affiliated with

Also associated with

Rating

Preloaded spring assembly does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Preloaded spring assembly, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Preloaded spring assembly will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2600467