US3746605A

US3746605A - Cushioning material

Info

Publication number: US3746605A
Application number: US00170179A
Authority: US
Inventors: B Dillon; R Long
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1971-08-09
Filing date: 1971-08-09
Publication date: 1973-07-17
Anticipated expiration: 1990-07-17

Abstract

Cushioning material having a layer of material formed into a plurality of closely spaced cellular protrusions extending from one side, is provided with an imperforate backing sheet on open sides of the cellular protrusions. An air permeable sheet is interposed between the layer having the cellular protrusions and the backing sheet, to provide restrictive air passages between adjacent cells, while also providing for spaced areas of connection between the layer having the cellular protrusions and the backing sheet.

Description

United States Patent 1191 Dillon et a1.

CUSHIONING MATERIAL Inventors: Brian D. Dillon; Robert L. Long,

both of Kingsport, Tenn.

[73] Assignee: Eastman Kodak Company,

Rochester, NY. Filed: Aug. 9, 1971 Appl. No.: 170,179

[52] U.S. Cl ..161/122,156/145,156/210, 156/290,161/89,l61/113,161/127,

Int. Cl 1332b 3/12 Field of Search 161/116, 118, 122, 161/125, 126, 127,130,131, 69,112,151, 113, 89,146,148;156/145,198, 210, 209, 219, 309,290

[5 6] References Cited UNITED STATES PATENTS l/l958 Beck 161/127 X 8/1969 Young et al. 161/69 X 9/1958 Chavannes 161/127 X Lli'l ll ivl 1451 July 17, 1973 3,008,214 Foster et al l6l/l27 X 3,048,514 8/1962 Bentele et a1 .1 156/145 3,294,387 12/1966 Chav'annes 161/127 X 3,423,263 l/1969 Pannone l6l/l27 X 3,589,972 6/1971 Greig et al. 161/122 X FOREIGN PATENTS OR APPLICATIONS 625,657 7/1949 Great Britain [61/127 Primary Examiner-William A. Powell Attorney-Cecil D. Quillen, Jr. and John F. Stevens [57] ABSTRACT Cushioning material having a layer of material formed into a plurality of closely spaced cellular protrusions extending from one side, is provided with an imperforate backing sheet on open sides of the cellular protrusions. An air permeable sheet is interposed between the layer having the cellular protrusions and the backing sheet, to provide restrictive air passages between adjacent cells, while also providing for spaced areas of connection between the layer having the cellular protrusions and the backing sheet.

6 Claims, 7 Drawing Figures PATENIEU JUL 1 SHEET 1 [IF 3' BRIAN D. DILLON ROBERT L. LONG I M A NVE TO ATTORNEY PATENIEU mm mm sum 2 or 3 BRIAN D. DILLON ROBERT L L [M15 f T ATTORNEY PATENIEUM'TW 3.746.605

SHEEIBBFS BRIAN D DILLON ROBERT L. LONG INV TORS ATTORNEY CUSHIONING MATERHAL This invention relates to cellular cushioning material having superior qualities of shock absorbency and ability to withstand sustained loads.

There are a number of characteristics which cushioning material should have in order to meet the present high standards for packaging. Cushioning material used in packaging should not create litter so as to cause clean-up problems, such as those encountered with shredded paper, excelsior and the like. Further, cushioning material should be impervious to water, moderately bulky, resistant to rot, mildew, insects and other destructive forces. The single most important characteristic of the cushioning material, however, is that it be able to protect a packaged article from impact forces which would nonnally damage the article. In addition to withstanding such impact forces, it should have the ability to substantially recover its original shape, enabling it to absorb further impacts. Cushioning materials used in such fields as carpet backing, etc., have similar requirements.

Synthetic thermoplastic materials have a number of attributes which make them ideally suited for many cushioning applications. Among these attributes are their resistance to rot, insect damage, mildew, imperviousness to moisture and ease with which articles may be wrapped therein. Sheets of thermoplastic material are sometimes fabricated into shapes which will give the desired impact resistance. For example, it has been suggested that a sheet of thermoplastic material be formed into dimples and a second sheet laminated thereto to seal air in the dimples to form bubbles. The air bubbles, in this instance, are relied on to give the desired impact resistance. While such a sheet is resistant to damage from moisture, mildew, insects and the like, its impact resistance depends on bubbles of air. If the air bubbles rupture, the impact resistance of the sheet is completely destroyed.

U. S. Pat. No. 3,231,454 discloses cushioning material formed of either one or a plurality of sheets of resilient material, at least one sheet of which is so constructed that uniform static and dynamic cushioning may be effected both by the compressive columnar loading of hollow, columnar-shaped projections formed therein and by the pneumatic shock absorbing effect of air trapped within these projections, the latter being provided with vent openings through which the air may pass when a sudden or shock load is applied thereto, whereby fragile or highly finished articles encased thereby will be cushioned and protected or insulated from physical shock, whether disposed within a container or not. In this cushioning material, the vent openings act as restricting orifices to limit the flow of air from the projections, thereby acting as shock absorbers. The present invention differs from this type of cushioning material in that, instead of the pneumatic cushioning property being confined to only the cells which are acted upon by a load, pneumatic resistance to deformation is distributed over many cells as air pressure in the cells thereof will tend to equalize. The present invention also differs from this prior art in that, instead of air being lost from the cells when a load is applied, it is merely displaced under pressure, and is available to urge the cellular protrusions back to their original shape when the load is eased or removed.

In accordance with the present invention, cushioning material is provided which comprises a sheet having both structural and pneumatic properties which contribute to its effective cushioning ability. At least one of the components of the cushioning material is a thermoplastic sheet having a multiplicity of closely spaced, cellular protrusions extending from one side thereof. The cellular protrusions are defined by substantially vertical sidewalls with respect to the plane of the sheet and terminate in thin membranes at their outwardly projecting ends. The cellular protrusions are spaced at their bases by land areas which, in conjunction with sidewalls of adjacent cells, form interconnected, hollow beams throughout the sheet. When formed into the shape of a hollow beam, even flexible materials have increased resistance to bending and crushing. Further, the beam design enables the material to regain its original shape after being deformed. The fact that the beams are all interconnected so as to form a grid aids in providing additional strength and crush resistance. Also, the material itself and the number of protrusions per unit area contribute significantly to the shock absorbency and resilience of the material. The cellular sheet is preferably of a molded thermoplastic material such as polyethylene, polypropylene, polyvinyl acetate, polyvinylidene chloride or the like, with low-density polyethylene being preferred.

The sheet having the cellular protrusions is provided with an impervious backing sheet overlying the land areas and connected thereto by means of a sheet interposed between the land areas and the backing sheet. The sheet interposed between the land areas and backing sheet is air-permeable. The layer of material interposed between the cellular sheet and the backing sheet will be hereinafter referred to as the permeable sheet or layer.

The backing sheet may be of any suitable material which is substantially resistant to the flow of air therethrough, such as a thermoplastic material, foil, paper or the like. Preferably, however, the backing sheet is of a material which is heat sealable to the land areas of the cellular sheet. The permeable sheet may be of any material which will provide separation at least at spaced locations between the land areas of the cellular sheet and the backing sheet, and provide connection between the cellular sheet and the backing sheet such that upon the application of pressure on a cellular protrusion, or group of cellular protrusions, air will flow between the land area and backing sheet into adjacent cellular protrusions. In this manner, air is permitted to pass slowly, and against a back pressure, from cell to cell to absorb forces applied against the cells over an area much greater than the area of the cells which are contacted by the force, thereby resisting rupture which sometimes occurs in sealed cells, and causing a large portion of the material to absorb the force.

The presence of dyes, pigments, antioxidants and the like which are commonly used in thermoplastic materials, does not adversely affect the cushioning properties of the material.

Accordingly, it is an object of this invention to provide a flexible, crush resistant, protective cushioning material.

It is another object of this invention to provide a cushioning material in which the cushioning characteristics are derived from both the structural design of the material and a pneumatic resistance to impact and sustained loads.

With reference to the accompanying drawings wherein like numerals designate like parts and wherein:

FIG. 1 is an elevational view in section illustrating cushioning material according to this invention;

FIG. 2 is a partial plan view, with layers of components partially removed, of the cushioning material according to this invention;

FIG. 3 is an elevational view in section, similar to FIG. 1, illustrating other embodiments of the invention;

FIG. 4 is an elevational view in section, similar to FIG. 1, illustrating another embodiment of the invention; and

FIGS. 5, 6 and 7 are elevational views in section, il lustrating the cushioning material before, during and after loading.

Referring to the drawings, the reference numeral 10 denotes sheet material having a multiplicity of imperforate cellular protrusions 12 and an interconnected grid of land areas 14 between adjacent cells. The land areas 14 form the base of an inverted U or channel-shaped structure which extends throughout the material, and side walls 16 of cellular protrusions 12 form the sides of this structure.

Cellular protrusions 12 extend from one side of the sheet material and are defined by walls 16 which are integral with andextend from the land areas 14. The walls 16 extend for a substantial distance in a direction generally perpendicular to the land areas 14. The walls 16 around each cell are preferably hexagonal as illustrated in FIG. 2. The walls around the cells taper from a substantial thickness at the base of the land area to a relatively thin, somewhat expandable membrane 20 at the top thereof. The decrease in thickness from the base of the land area 14 to the thin, imperforate membrane 20 promotes a gradual increase in cushioning effect as a load is applied in a direction normal to land areas by allowing the side walls to begin bending at their thinner sections adjacent the membrane, and as more load is applied, bending progresses to the thicker sections. Thus, this cushioning material provides efficient cushioning over a wide range of loadings. Light loads are adequately cushioned by the action of the thinner sections, and as loads are increased, the resistance to bending of the thicker sections is encountered. Adjacent side walls 16 cooperate in their bending to complement each other in their cushioning effect. This structure is highly resistant to deformation, and when deformed, has great ability to regain its original shape. This is true over loadings for extended periods of time, and over repeated loadings, allowing the sheet to be reusable as a cushioning material.

Preferably, the area of the sheet material occupied by the cellular protrusions 12 is at least 75 percent of the total area of the sheet material and the spacing of the protrusions is substantially the same throughout the sheet. Also, the efficiency of the molded sheet as a cushioning material is dependent upon the number of cellular protrusions per unit of area. Generally, it is desirable to have at least I50 cells per square foot, and preferably more than 500.

The cellular material described above, according to this invention, is provided with a backing sheet 24 and interposed between the land areas 14 of sheet 10 and the backing sheet 24 is a permeable layer of material which maintains separation, at least at spaced points,

I between the land areas and the backing sheet. The permeable layer is illustrated in FIGS. 1 and 2 as a woven material 26, such as a fabric. This permeable layer allows the use of a uniform, continuous backing sheet 24, such as plastic film, and yet prevents complete lamination of this layer to the cellular material which would seal air in the cells. It is often desirable to avoid sealed cells in this type of cellular cushioning material because the application of pressure may cause the thin membrane sections of the cells to rupture, thereby propagating tear, decreasing structural integrity and thus the cushioning ability of the material.

The permeable layer 26 may in some instances be of any suitable material such as to permit connection between the cellular sheet 10 and the backing sheet 24 only at spaced, random locations 28, i.e., at voids in the permeable sheet, where the backing sheet 24 is allowed to contact the land areas. The permeable sheet should be of such a configuration that the contact pattern occurs at least once and perhaps several times along the land areas between each adjacent cell. This configuration allows air in the cells to pass from one cell to another and prevents cell rupture under pressure. The permeable sheet 26 is of such a configuration as to sup port and maintain the backing sheet 24 spaced from the land areas at certain points, to thereby form small air passages 30 between cells. The air passages 30 may be very tiny, and their function is to permit air to pass from one cell to the next, as a load is applied to withstand the impact but still be resistant to rupture. Also, the permeable layer may maintain the backing sheet in spaced relation to the land areas and be the intennediate layer of a laminate. A loose, fibrous sheet 40 would be an example, as illustrated in FIG. 3. In FIG. 4, there is illustrated an embodiment of this invention in which the backing sheet is in the form of a cellular sheet similar to or even the same as cellular sheet 10, separated by air permeable layer of material 40.

The cushioning material may be produced by an inline operation, by passing both the backing sheet and the permeable sheet, if used, simultaneously under a pressure roll, to thereby force these sheets tightly against the cellular material while it is still molten, or semi-molten, thus causing only spaced, random connections between the backing sheet and the land areas.

Structural rigidity is aided by the backing sheet 24 which inhibits distortion of the land areas 14 under load. Furthermore, the backing sheet 24 is substantially airtight, so that as a load is applied to the cushioning material, the air from the cells under load will be forced to adjacent cells rather than through the backing sheet. Thus, some back pressure is exerted against the flow of air from cell to cell by the air pressure'and by the small passages between adjacent cells.

FIGS. 5, 6 and 7 are progressive-sequence views illustrating the cushioning material according to this invention before, during and after loading. In FIG. 6, there is illustrated an article 60 which has been placed on the cushioning material, and which represents an article which is desired to be protected from shock which might occur during shipment. It can readily be seen that

cells

66, 68 and 70 have been compressed, and have displaced air to

adjacent cells

62, 64, 72 and 74. The arrows indicate direction of movement of the air. In FIG. 6, the membranes 20 of

cells

62, 64, 72 and 74 have fully expanded. After the article 60 is removed, as illustrated in FIG. 7, some of the compressed air in

cells

62, 64, 72 and 74 returns to

cells

66, 68 and 70 as the air pressure equalizes, as shown by the arrows.

It will thus be seen from the foregoing description that an extremely efficient cushioning material is provided which resists impact and provides cushioning EXAMPLE Polyethylene having a density of 0.917 is vacuum formed into a multi-cellular form of the general shape illustrated in the drawings. Cell dimensions are substantially as follows:

distance from one wall measured across the cell to the opposite wall 9 mm.

wall thickness (adjacent the land areas) 0.8 mm.

depth of cells 9 mm. The polyethylene is molded such that the cells occupy a surface area of at least about 75 percent of the total surface. A sheet of porous tissue paper is placed over the land areas, and over the open sides of the cells. A fiat backing sheet of about 1 mil. thickness is placed over the tissue paper and either the cellular sheet or the backing sheet is softened, or maintained semi-molten until pressure is applied to press the cellular sheet land areas into contact with the backing sheet. The joining or connection between the land areas and backing.

sheet will be at randomly spaced intervals, permitting passage of air between adjacent cells, but still structurally rigid.

The invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

We claim:

1. Cushioning material comprising a first layer of thermoplastic material having a network of interconnected land areas extending throughout the layer and a multiplicity of cellular protrusions having open bases integral with said land areas, a backing sheet overlying said first layer and connected to the land areas of the first layer, and a permeable sheet interposed between the land areas of said first layer and said backing sheet fonning air passages between adjacent cellular protrusions in said first layer.

2. Cushioning material according to claim 1 in which the walls of said cellular protrusions extend for a substantial distance away from said land areas in a direction substantially perpendicular thereto and taper to a relatively thin membrane at their extremities.

3. Cushioning material according to claim 1 in which the bases of said cellular protrusions are substantially hexagonal.

4. Cushioning material according to claim 1 in which said means include a permeable sheet having voids therein interposed between the land areas of said first layer and said backing sheet, thereby allowing connection over only a portion of the area between said land areas and said backing sheet.

5. Cushioning material according to claim 1 in which the connection between the land areas and said backing sheet is by means of heat seal.

6. Cushioning sheet material according to claim 1 in which said first layer and said backing sheet are substantially impenneable to air.

Claims

2. Cushioning material according to claim 1 in which the walls of said cellular protrusions extend for a substantial distance away from said land areas in a direction substantially perpendicular thereto and taper to a relatively thin membrane at their extremities.
3. Cushioning material according to claim 1 in which the bases of said cellular protrusions are substantially hexagonal.
4. Cushioning material according to claim 1 in which said means include a permeable sheet having voids therein interposed between the land areas of said first layer and said backing sheet, thereby allowing connection over only a portion of the area between said land areas and said backing sheet.
5. Cushioning material according to claim 1 in which the connection between the land areas and said backing sheet is by means of heat seal.
6. Cushioning sheet material according to claim 1 in which said first layer and said backing sheet are substantially impermeable to air.