US3255469A - Pneumatic cushion - Google Patents

Description

June 14, 1966 y R. H. BLECKER ETAL 3,255,469

PNEUMATIC CUSHION Filed Feb. 25. 1964 I ISIN IN IN ISIN IDE IN IN IR.

INVENTORS RAYMOND H. BLECKER ROBERT C. COSTELLO MUNZER MAKANSI BY www ATTORNEY United States Patent O 3,255,469 PNEUMAIIC CUSHION Raymond H. Bleeker, Homewood, and Robert C: Costello, Flossmoor, Ill., and Munzer Makansi, Wilmlngton, Del.; said Makansi assgnor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Feb; 25, 1964, Ser. No. 347,298 4 Ciaims. (Cl. 5-351) T-his linvention relates to the structure of upholstered articles, such as seat cushions, mattresses, box springs and the like, and more particularly to such .articles comprised of a particular spring insulator pad.

In the fabrication of lupholstered articles .it is irequently desirable to employ a spring insulator pad. Such a pad is interposed ybetween an underlying spring structure and an overlying layer of relatively soft padding material for purposes of protecting the padding material from damage by the spring structure through abrading, scuffing or cutting, as well as for -supporting the padding 1n the interspaces between elements ci the spring structure.

`Conventional types lof spring insulator pads include elted sisal sheets, burlap or similar woven fabrics, and films of various ilexible plastic materials. The latter generally require tensile reinforcement from suitably elastic laments which are adhered to their surface. -Even apart lfrom the increased manufacturing costs which are encountered in the provision `ot-such reinforcement, the resultant pads also tend to curl up so as to make it diicult to fasten yto the spring units. The customarily used sisal pads display the variable properties associated with natural tiber products and `are subject to the variable cost patterns associated with imported materials. These observations pertain also to the woven burlap sheets, which have the `further Vdeiiciency of 'contributing little to the resiliency of the overall structure.

This invention provides upholstered articles having a spring insulator .pad material of constant predetermined physical properties, which is not subject to the difficulties sometimes experienced With natural fibre materials, and which contributes significantly to the overall resiliency of the article. The pads employed in accordance with the invention also have the advantage of 'being readily stored and handled and be-ing easily secured to the underlying spring structure. Further advantages o'f the articles of this invention will be .apparent from the remainder of the :specification and claims.

The improved spring insulator pad as employed in accordance with this invention comprises Ia pneumatic integral foam sheet of a synthetic polymeric material comprised of predominantly closed cells, the sheet extending over substantially the entire upper surface o'f the spring structure of the upholstered article, and the sheet having a multitude 'of lsmall spacedaapa-rt perforations extending from tone surface thereof through the thickness of the sheet to the opp-osite surface thereof.

A typical embodiment of the invention 'will nofw be described with reference to the drawings wherein:

FIGURE l is a tragmentary perspective view, partially broken away, showing a mattress, and

FIGURE 2 is an enlarged fragmentary sectional View taken along line II-II of FIGURE l.

ice

yFIGURE 3 is la 'fragmentary perspective view, partially broken away, of a spring insulator pad of crosslapped structure.

The upholstered article, in this case a mattress 10, includes an underlying spring structure comprising a series of generally parallel upstanding coil springs 16, spring insulator pads I14 covering `both sides of the spring structure, .and padding material 13, all enclosed by a lfabric 12 or other covering. A myriad of spaced apart perforations 1'5 are provided in the sheet 14.

In lFIGURES a spring insulator pad structure C17 is shown comprising two crosslapped foam sheets 18 and 20. ,These may be laminated together lby an adhesive, not shown. Perforations 115 extend fully through the thickness of the pad 17. Arrows at the edges of the sheets show the direction of sheet tor-mation and orientation.

It will tbe apparent that the nature of the spring structure is not material to the invention so long as it is resiliently distortable under force of a general magnitude imposed by the weight of a person resting thereon. Thus zig-Zag wire spring elements or other types of springs can also be used. Similarly the overlying surface padding material may comprise any of a number of materials, for example cotton wadding, iiberlill batting, urethane or foam rubber pads, or other materials customarily used in the art.

The cellular sheets employed as spring insulator pads in accordance with the .present invention require certain essential :characteristics and properties.` A number of commercially available foam materials 1as well as others less well known nevertheless possess such features and hence can 'be satisfactorily' utilized. A particularly essential characteristic of a suitable foam is that it have a major proportion, by number, of closed cells since open cells do not ordinarily afford adequate properties with respect to pneumaticity. By pneumaticity in this sense is meant that air or `other gas -is effectively contined within the cel-ls so that in conjunction 'with the resiliency provided by the cell walls, it can substantially contribute to the load bearing ability of the pad. For practical purposes mere visual lor microscopic examination will often readily reveal whether or not a particular cellular structure predom-inates in closed or open cells. The closed-cell content of a yieldable foam sample may be determined by the gas displacement Vmethod of Remington and Pariser, Rubber World, May 1958, p. 26d, modiiied yby operating at as `low a pres-sure differential as possible to minimize volume changes of the yieldalble closed cells.

A further essential characteristic of the `tfoams to be employed in the structures of this invention is that they lbe yieldable, i.e. resilient such that substantial deformation occurs upon application of mechanical pressure. By substantial deformation is meant that the cellular structure is yieldable such that its volume can be compressed by Iat least about 10% under a load ot 10 lbs. per square inch sustained for a period of l second with recovery of at least about 50% of its original volume on release of lthe load. Foams which do not compress to that extent are generally too rigid and hence do not afford a suilcient degree of resiliency.

The wall portions of the cellular sheets are composed of a synthetic, high molecular weight thermoplastic polymer. The polymers may be selected from a wide variety of organic addition and condensation polymers, provided, of course, that in the form of a ycellular structure they possess the described essential characteristics. Typical of such polymers are the polyolens such as polyethylenes, linear or branched, polypropylene, polyamides such as nylon 6 or polyesters such as polyethylene terephthalate, halohydrocarbon polymers such as polychlorotriuoroethylene, etc. The manufacture of cellular materials in sheet form from such polymers is well known in the art as illustrated by U.S. Patents 2,948,665, 2,945,261 and 2,256,483. A preferred class of cellular structures is that prepared from crystalline organic synthetic polymers, since excellent strength and pneumaticity properties are afforded therewith.

Cellular sheets of the above description tend to possess a high tensile strength and toughness. These properties are important for spring insulator pad duty; that is, the pad must withstand repeated flexing in the thickness direction as well as considerable stresses in the transverse directions. By virtue of the predominance of individual closed cells, the cellular sheet itself has a pneumatic character and contributes significantly to the overall resiliency of the structure. Low density cellular sheets having thin Walled cells provide for ecient use of the polymer while maximizing the strength of the sheet.

The total thickness of the cellular sheet may range from about ls" to 2" or even thicker. The higher thicknesses are preferred where the apertures of the associated spring unit are large, i.e. increased thickness giving rise to greater stiffness and improved ability to bridge across the larger apertures and prevent capping of the surface padding. The integral insulator pad may be either a single foam sheet or a laminate of individual pneumatic foam sheets in various configurations, such as crosslaminated sheets. The foam insulator pads may, of course, be laminated to lm, paper, fabric, and other surfacing layers, where desired.

As an essential feature of the invention, the foam spring insulator pads must be perforated in order to minimize the drumming problem which tends to occur when a flat sheet of appreciable area extends across the surface of a spring unit. These perforations apparently either break up the undesirable vibration patterns otherwise set up in the unperforated sheets, or permit a freerfiow of air through the sheet, or in some other manner minimize the drumming sound generated when the assembled cushioning unit is rapidly loaded or unloaded. The shape, size and distribution of the perforations appear to be relatively uncritical. Nevertheless the perforations should be -small compared with the dimensions of the individual elements in the underlying spring unit, i.e. so that portions of the spring structure do not become lodged Within the pad holes. The perforations can have a Variety of cross-sections, e.g. be round, rectangular, oval, or triangular, although the area of each cross-section should preferably range upwards from 0.0004 square inch. In a preferred embodiment, the holes have a cross sectional area of 0.005 to .500 square inch. The perforations may be prepared by punching, cutting, slitting and laterally stretching, melting or any other technique known in the art. One suitable pattern consists of approximately 1A" diameter holes perforated in a square pattern on 11/2 centers.

Polypropylene is the preferred polymer from which these foam spring insulator pads are prepared, although foam sheets with the required physical properties may also be prepared from various other synthetic polymers. The preference for polypropylene in the present invention resides in a favorable combination of low cost of polymer, excellent tensile properties of the product, adequate retention of pneumaticity, and generally pleasing aesthetics.

The spring insulator pads of this invention may readily be incorporated in upholstered articles in any of a number of ways. For example, a pad which is co-extensive with the surface of the spring unit may be fastened thereto at intervals along the edge of the spring unit by conventional techniques using hog rings, staples, tie straps, or by stitching. If the pad is somewhat larger in area than the surface of the spring unit, the resilience and vcompliance of these foam pads permit the over-hang to be folded over and fastened along the sides of the spring unit. Such construction provides additional protection for the upholstery and padding from the edges of the spring unit. Again, due to the desirable tendency of these foam pads to lie flat during assembly, it is possible simply to place the insulator pad on the surface of the spring unit with no special fastening at all, and depend on the subsequently applied over-lying surface padding and fabric cover to maintain the insulator pad in place. Furthermore, since they may be perforated without danger of runs or slits developing, these foam insulator pads may also be employed in so-called tufted constructions where the assembly is fastened together by buttons on opposite surfaces of the upholsteredarticle tied together with cords passing through the body of the unit (and hence also through the insulator pad).

The following specific example further illustrates the present invention.

Example A highly pneumatic closed cell polypropylene foam sheet is prepared at a thickness of approximately 0.030- 0.050" with a sheet density of approximately 1.25 lbs./ft.3. The sheet is cut into lengths of 7.5 and 5.5 respectively. Eight layers of these cut lengths are then laminated together, in crosslapped orientation, using a rubber-based adhesive diluted with chloroform to 2 weight percent solids. The resulting structure is an eight-layer laminated sheet approximtaely 7.5 long x 5.5 wide x 0.33 thick, weighing 580 g. and possessing balanced properties in length and width dimensions. The resulting pad is compressed to W16" thickness and simultaneously embossed with an S-mesh wire screen pattern by placing it in a flat press at 70 C. and 70 p.s.i.g. for five minutes between two S-mesh wire screens using 3/16 thick shims (spacers) at the end of the two sides of the platens to control thickness at 3/16. The embossed pad is then perforated with approximately ls to 3716 diameter tapered holes melted in the sheet in a -square pattern on 1" centers. The pad is then trimmed to produce a mattress spring insulator pad long x 57 wide x 0.19 thick at a density of 2.0 lbs./ft.3.

Spring insulator pads prepared in the above manner are next aixed to opposite sides of a coil spring construction unit. The mattress fabrication procedure is then completed by conventional methods Well known in the art.

Even apart from other advantages, the weight saving of up to l0 lbs. per mattress resulting from the use of the low density spring insulator pads is considered to have a great advantage not only in freight costs, but also in handling the mattress in the plant during manufacturing and also at home where the mattress is used.

What is claimed is:

1. In an upholstered article having an underlying spring structure which is resiliently distortable .under force of a general magnitude imposed by the weight of a person resting thereon, an overlying layer of padding material, and an interposed pad supporting said padding material and protecting same from damage by said spring structure; the improvement wherein said interposed pad comprises a pneumatic integral foam sheet of a synthetic polymeric material comprised of predominately closed cells, said sheet extending over substantially the entire upper surface of the spring structure, and said sheet having a multitude of small spaced apart perforatons extend- References Cited by the Examiner ing -from one surface thereof through the thickness of Y UNITED STATES PATENTS the sheet to the opposite surface thereof.

3,080,579 3/1963 Gordon 5--354 cross sectional area of 0.005 to 0.500 square inch.

4. The article of claim 1 wherein said foam sheet comprises a crosslapped structure of at least two individual 10 FRANK B' SHERRY Primary Exammer' layers. C. A. NUNBERG, Assistant Examiner.

Claims (1)

1. IN AN UPHOLSTERED ARTICLE HAVING AN UNDERLYING SPRING STRUCTURE WHICH IS RESILIENTLY DISTORTABLE UNDER FORCE OF A GENERAL MAGNITUDE IMPOSED BY THE WEIGHT OF A PERSON RESTING THEREON, AN OVELYING LAYER OF PADDING MATERIAL, AND AN INTERPOSED PAD SUPPORTING SAID PADDING MATERIAL AND PROTECTING SAME FROM DAMAGE BY SAID SPRING STRUCTURE; THE IMPROVEMENT WHEREIN SAID INTERPOSED PAD COMPRISES A PNEUMATIC INTEGRAL FOAM SHEET OF A SYNTHETIC POLYMERIC MATERIAL COMPRISED OF PREDOMINATELY CLOSED

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