US3901962A

US3901962A - Method of making expanded polystyrene partition structure

Info

Publication number: US3901962A
Application number: US440256A
Authority: US
Inventors: Louis G Kuchuris; Stanley Gembicki
Original assignee: Cutting Equipment Leasing Inc
Current assignee: Cutting Equipment Leasing Inc
Priority date: 1972-05-18
Filing date: 1974-02-06
Publication date: 1975-08-26
Anticipated expiration: 1992-08-26

Abstract

A partition structure for shipping or storage containers having a plurality of interfitting partition strips with interlocking slots and with the partition strips being formed of expanded polystyrene. In one form thereof, the planar faces of a partition strip have a relatively low density because of said surfaces being formed by saw cut from a block of expanded polystyrene, while the entire peripheral edge of the partition strip, including the interlocking slots, are formed by hot wire cutting to have a higher density on the surface thereof to provide greater physical strength for the partition strip.

Description

United States Patent H9} Kuchuris et al.

[ METHOD OF MAKING EXPANDED POLYSTYRENE PARTITION STRUCTURE [75] Inventors: Louis C. Kuchuris, Chicago; Stanley Gembicki, Des Plaines. both of Ill (73] Assignee: Cutting Equipment Leasing, Inc.,

Chicago, Ill.

[22] Filed: Feb. 6, I974 [2| Applt No.: 440,256

Related U.S. Application Data [62] Division of Ser No. 254,749, May 18. I972, Pat. No,

[ 1 Aug. 26, 1975 OTHER PUBLICATIONS Cutting and Fabrication," Technical Manual Dylite Expandable Polystyrene. Bulletin C9273 Chapter 3h, December I, 1962.

Primary ExumincrRoy Lake Assistant Examinerlames F. Coan Attorney, Agent. or FirmWegner, Stellman, McCord Wiles & Wood [57] ABSTRACT A partition structure for shipping or storage containers having a plurality of interfitting partition strips with interlocking slots and with the partition strips being formed of expanded polystyrene. In one form thereof. the planar faces of a partition strip have a rel atively low density because of said surfaces being formed by saw cut from a block of expanded polystyrene, while the entire peripheral edge of the partition strip. including the interlocking slots. are formed by hot wire cutting to have a higher density on the surface thereof to provide greater physical strength for the partition strip.

5 Claims. 5 Drawing Figures METHOD OF MAKING EXPANDED POLYSTYRENE PARTITION STRUCTURE This is a division, of application Ser. No. 254,749 tiled May I8, 1972 now US. letters Pat. No. 3.837.560.

BACKGROUND OF THE INVENTION This invention pertains to partition structure and. more particularly, to partition strips formed of expanded polystyrene.

Partition structures for shipping and storage containers, as generally known prior to this invention, are formed from corrugated paper material. Such structures are relatively expensive considering the cost of raw materials and labor in manufacture. Apart from the cost thereof, a less than satisfactory partition structure results because the paper material has many properties which are undesirable in the shipping and storing of material. The paper is subject to mold, staining, combustion, water damage and, once subject to crushing forces. does not have any memory to return to its origi nal shape.

SUMMARY With the partition structure and partition strips disclosed herein and formed of expanded polystyrene, the partition is a relatively inert structure which is not subject to water damage, mold, staining and is practically noncombustible and a vapor barrier. Additionally, the cost of the raw material and labor, in forming the partition strips, is less than that of conventional corrugated paper partition structure, adding to the advantages thereof. The resulting partition structure is relatively lightweight and provides the desired cushioning contact and structural strength for a shipping container without substantial addition to the shipping weight of the container.

In addition to the novelty of the partition strip formed of expanded polystyrene, it is possible to provide a one-piece laminate, in effect, with the planar faces of the partition strip being formed by sawcutting of the strip from a block of expanded polystyrene to have the faces with the same low density as that of the basic block from which they are formed, while the entire peripheral edge, including the interlocking slots formed in a partition strip, are subject to hot wire formation to provide melting of the surface of the partition strip along the entire edge. This melting provides a relatively high density layer along the surface of the partition strip edge to provide added structuralstrength and also forms a tension surface to provide a prestressed beam effect for the partition strip. The hot wire forming of the interlocking slots, due to the melt ing of the surface polystyrene, also provides strength to the interlocking slots.

Additionally disclosed herein is a novel method of forming the partition strips wherein a block of expanded polystyrene has its top, bottom and sides and a plurality of interlocking slots shaped by hot wire cutting to form the higher density surface layer followed by saw cuts of successive partition strips along a line transverse to the length of the block to have the exposed planar faces of the partition strip of unmodified low density expanded polystyrene for cushioning contact with a product.

In view of the foregoing, a general object of this invention is to provide a new and improved partition structure wherein interlocking partition strips are formed of expanded polystyrene.

Another object of the invention is to provide a partition strip for interlocking relation with other such strips to form a partition structure usable in shipping or storage containers comprising a generally planar integral body of expanded polystyrene with the planar faces of said body having relatively low density for cushioning contact with the product and the edge of the strip having a higher density for adding structural strength to the strip.

Still another object of the invention is to provide a partition structure for shipping and storage containers having a plurality of interfitting partition strips with interlocking slots wherein the partition strips are formed of a molded plastic material and with the partition strip having generally planar faces with relatively low density for cushioning contact with the product and the peripheral edge of the strip having a higher density for added structural strength.

A further object of the invention is to provide a method of forming a partition strip and a partition strip resulting from said method wherein successive partition strips are sawed from a block of expanded polystyrene to have the planar faces thereof of the same density as the basic block of material and with the slots formed in the partition strip and the entire edge of the strip being preformed prior to sawing by hot wire cutting applied to the block with resulting melting of expanded polystyrene at the surfaces contacted by the hot wire to form a higher density surface layer in the partition strip.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a tool usable in forming the interlocking slots in a block of expanded polystyrene prior to formation of an individual partition strip;

FIG. 2 is a perspective view showing the saw'cutting of a partition strip from a block of expanded polystyrene;

FIG. 3 is a perspective view of a formed partition strip;

. FIG..4 is a perspective view of a partition structure showing a plurality of interlocked partition strips; and

FIG. 5 is a fragmentary, enlarged view of a part of a partition strip showing the different density between the major part of the body of the partition strip and the edge thereof, with the latter being formed by hot wire cutting.

DESCRIPTION OF THE PREFERRED METHOD AND EMBODIMENT In describing the method, reference may be made to FIGS. 1 and 2 wherein a block I0 of expanded polysty rene is shown. This block has a length extending from left to right as viewed in FIGS. 1 and 2, with a top II and a bottom (not shown) and with a front side 12 and a rear side (not shown). One end is indicated at 15. This block 10 has a height and width equal to the height and length, respectively, of a partition strip indicated generally at 20 in FIG. 3.

The top 11, bottom and front side 12 and rear side of the block I0 are formed by hot wire cutting prior to the step of the method illustrated in FIG. I. As shown in FIG. I, a tool, which is illustrative only, is provided for hot wire forming of a plurality of

slots

21, 22, and

23 in the partition strip 20. A plurality of hot wires 24, 25 and 26 are, as known in the art, electrically heated and suitably mounted in a vertically-movable frame, indicated generally at 30, whereby they may be lowered into the block 10 to a desired depth to form the interlocking slots 21-23 by melting of the expanded polystyrene. Following formation of the interlocking slots along the entire length of the block 10, the block 10 is then moved relative to a saw-cut device, such as a band saw, indicated generally at 40, having a travelling blade 41, to cut successive partition strips 20 of the desired thickness from the block 10. This is accomplished by relative movement between the block and the blade along a line transverse to the length of the block, with successive repositioning of the block and blade relative to each other for a succeeding cut. After the step performed as shown in FIG. 2, the partition strip 20 is then complete and is as shown in FIG. 3. A series of partition strips 200 are then positioned in spaced, parallel relation with their interlocking slots faced upwardly and are interfitted with an inverted series of parallel spaced partition strips 20b to form the partition structure illustrated in FIG. 4.

With the method as described herein, the entire peripheral edge of the partition strip 20 including a bottom edge 50, the front and rear edges 51 and 52, respectively, and the top edge 53 including the entire surface of the interlocking slots 21-23 are initially formed by hot wire cutting which results in melting of the expanded polystyrene. This melting results in a relatively high density surface layer, as illustrated at 60 in FIG. 5, while the major part of the partition strip is of a low density and the same as that of the basic block 10 of expanded polystyrene and as indicated at 6| in FIG. 5. This results in the formation of a tension surface for the partition strip about the entire edge thereof having a higher density for structural strength and, in effect, providing a prestressed beam effect for the partition strip, and with resultant strengthening of the bottom of the interlocking slots.

The generally planar partition strip 20 has a pair of opposed planar faces, with one face 70 shown in FIG. 3 and with each of these faces being formed by the sawcut step of the method illustrated in FIG. 2. The saw cut results in the formation of the partition strip from the block without creating any dust and without any modification of the density of the planar surface whereby the density is the same as that of the basic block and is of a relatively low value. This results in soft" surfaces for the partition strips which can be in cushioning contact with a product in a shipping or storage container and when the partition strips are assembled into the partition grid structure illustrated in FIG. 4.

The partition strips of expanded polystyrene are capable of meeting many different packaging requirements. The basic block can be selected to have a density in the range of 1 pound per cubic foot, or less, up to a density of 4 to 5 pounds per cubic foot. This results in planar faces for the partition strip which are relatively soft but which still have a memory to return to the initial shape after compression The surface layer density along the peripheral edge of the partition strip and in the slots 21-23 of the strip can then be controlled by the hot wire cutting process, with density variation being controlled by the temperature of the wire, the diameter of the wire. and the speed of travel of the wire relative to the block 10 in the formation of the slots as well as the initial shaping of the block 10. Additionally, the size of the slots 21-23 of the partition strip 20 can also be varied by control of the temperature, diameter, and speed of travel of the wires 2426, shown in FIG. I.

With the structure and process disclosed herein, it will be seen that partition strips are provided of relatively low-cost basic material and minimal production cost wherein the partition strip, in effect, is an integral laminate with a high density peripheral edge surface to provide for handling strength and resistance to crushing of the partition strip, while the planar faces thereof are of low density to provide maximum cushioning effeet in contact with products.

Examination of a partition strip made by the process disclosed herein shows that the planar faces thereof have a relatively smooth, soft surface, while the peripheral edge around the entire partition strip, including the interlocking slots, has a rougher and harder surface.

As an example, partition strips of expanded polystyrene have been found to perform satisfactorily wherein the density of the basic block 10 is approximately onehalf pound per cubic foot and with the peripheral edge of the strip being formed by hot wire cutting to have a surface layer with a density of approximately 4t) pounds per cubic foot. These values are not limiting, but are only given as an example of one particular strip made by the process disclosed herein.

We claim:

I. A method of forming a partition strip of expanded polystyrene comprising the steps of: shaping a block of polystyrene to a width and height equal to the desired length and height ofa partition strip by hot wire cutting along the top, bottom and sides of the block; forming a series of spaced slots extending lengthwise of the block by hot wire forming to a depth sufficient to provide for subsequent interlocking with other strips; and sawing said block along a line transverse to the length thereof in successive cuts to form individual partition strips with relative soft planar faces for contact with a product while the entire exposed edge of the strip including said slots and the bottom thereof has a higher surface density resulting from the hot wire cutting to provide added physical strength to the partition strip.

2. A method of forming a partition strip of expanded polystyrene comprising the steps of: forming a series of spaced slots by hot wire cutting in a block of expanded polystyrene to a depth sufficient to provide interlocking slots for assembly with other partition strips, sawing a partition strip from said block, and subjecting the entire edges of said partition strip to a hot wire to form a higher density surface along said edges.

3. The method of claim 2 in which the step of subjecting the entire edges of said partition strip to a hot wire to form a higher density surface along said edges includcs the step of shaping the block to a width and height equal to the desired length and height of the partition strip by hot wire cutting along the top, bottom and sides of the block.

4. The method of claim 2 in which the step of sawing a partition strip from said block is successively repeated to form a plurality of partition strips, and said edges of the partition strip are subjected to a hot wire prior to sawing the strip from the block.

5. The method of claim 2 in which the hot wire cutting results in a density increase in the polystyrene adjathe wire at a selected temperature and moving the wire into the block at u selected speed corresponding to the desired density.

Claims

1. A METHOD OF FORMING A PARTITION STRIP OF EXPANDED POLYSTYRENE COMPRISING THE STEPS OF: SHAPING A BLOCK OF POLYSTYRENE TO A WIDTH AND HEIGHT EQUAL TO THE DESIRED LENGTH AND HEIGHT OF A PARTITION STRIP BY HOT WIRE CUTTING ALONG THE TOP, BOTTOM AND SIDES OF THE BLOCK, FORMING A SERIES OF SPACED SLOTS EXTENDING LENGTHWISE OF THE BLOCK BY HOT WIRE FORMING TO A DEPTH SUFFICIENT TO PROVIDE FOR SUBSEQUENT INTERLOCKING WITH OTHER STRIPS, AND SAWING SAID BLOCK ALONG A LINE TRANSVERSE TO THE LENGTH THEREOF IN SUCCESSIVE CUTS TO FORM INDIVIDUAL PARTITION STRIPS WITH RELATIVE SOFT PLANAR FACES FOR CONTACT WITH A PRODUCT WHILE THE ENTIRE EXPOSED EDGE OF THE STRIP INCLUDING SAID SLOTS AND THE BOTTOM THEREOF HAS A HIGHER SURFACE DENSITY RESULTING FROM THE HOT WIRE CUTTING TO PROVIDE ADDED PHYSICAL STRENGTH TO HE PARTITION STRIP.

3. The method of claim 2 in which the step of subjecting the entire edges of said partition strip to a hot wire to form a higher density surface along said edges includes the step of shaping the block to a width and height equal to the desired length and height of the partition strip by hot wire cutting along the top, bottom and sides of the block.

5. The method of claim 2 in which the hot wire cutting results in a density increase in the polystyrene adjacent the cut, and the precise change in density varies with the temperature of the wire, the diameter of the wire, and the speed of travel of the wire relative to the block, and said step of forming a series of spaced slots by hot wire cutting includes the steps of maintaining the wire at a selected temperature and moving the wire into the block at a selected speed corresponding to the desired density.