High friction can separator pad

Details High friction can separator pad High friction can separator pad

1998-11-23

2001-01-16

Robinson, Ellis (Department: 1772)

Stock material or miscellaneous articles

Structurally defined web or sheet

Including components having same physical characteristic in...

C428S141000, C428S156000, C428S219000, C428S340000, C428S516000, C428S523000, C211S059400, C442S104000

Reexamination Certificate

active

06174593

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to sheets or pads, and more particularly to sheets or pads for separating vertically stacked groups of containers.
BACKGROUND OF THE INVENTION
The canning or bottling of beverages typically requires that empty beverage containers be shipped from a container manufacturer to the beverage manufacturer where they are filled using an automated filling machine. In the case of canned soft drinks and beer, the empty cans are ordinarily sent to the beverage manufacturer in large quantities, and are typically stacked on pallets for shipment. To facilitate shipment to the beverage manufacturer, it is common for layers of equal-height cans to be tightly packed on a pallet, with each layer of cans being covered with a separator sheet which provides a surface for a next layer of cans to be placed. This process is repeated until the desired number of cans is stacked on the pallet. The stack of cans is then covered with a top frame, which can be made of plastic, wood, or other materials, and the pallet of stacked cans is secured for shipment. When using separator sheets of this type, a typical pallet may contain as many as about 20 layers having 400 cans per layer, or 8000 cans.
The separator pads must be designed to allow uncomplicated palletizing and depalletizing of the cans while simultaneously preventing cans from slipping out from the stack and falling off the pallet. Furthermore, the material used must be suitable in terms of sanitation, flavor-producing agents, and durability. Separator pads have previously been made from a chipboard material containing cellulose materials and a binder. Because the cellulose-based material is porous, insects and moisture could enter the sheet and cause contamination. Additionally, the chipboard sheets were sometimes found to emit an undesired flavor into the unfilled cans which, once filled, ultimately changed the flavor of the product. The chipboard sheets were also easily damaged, thus limiting their useful life.
A reusable composite polymer-based sheet has since been designed to overcome the disadvantages associated with the chipboard separator sheets. Such a sheet is disclosed in U.S. Pat. No. 5,080,960, the disclosure of which is hereby incorporated by reference. The sheet described in that patent comprises a central core of high basis weight, nonwoven, spunbonded fabric which is coated with a polymer layer that is finely roughened during processing resulting in a sheet with a matte finish. To overcome several disadvantages of the prior art, including the chipboard sheets, the sheet was designed to be flexible yet shape retaining, tear-resistant, and otherwise durable. In addition, the sheet was designed to expedite the palletizing and depalletizing of the cans, allowing the cans to easily slide on and off the pallets, facilitating palletizing operations.
However, it has been found that as the can weight is decreased in order to lower costs, cans occasionally fall off during palletizing, shipment, depalletizing, and other times when the cans are moved.
SUMMARY OF THE INVENTION
The present invention provides a separator sheet which overcomes the limitations and disadvantages of the conventional chipboard and more recent composite polymer-based separator sheets. Like the prior composite polymer-based sheets, the separator sheet of the present invention is shape-retaining, tear-resistant, non-porous, and non-toxic. However, in accordance with the present invention, the separator sheet disclosed herein has a high friction surface which prevents the fallout of cans that may occur during shipment. In particular, the separator sheet has a gloss finish in lieu of the matte finish of the prior matte finish composite polymer-based sheet. The gloss finish has higher static and kinetic coefficients of friction than the previous matte-finish separator sheets, and thus is significantly more effective in preventing can movement and fallout. Although the static and kinetic coefficients of friction are significantly higher, the kinetic coefficient of friction produced by the gloss finish does not impede the sliding of the cans during loading and unloading, thus facilitating successful palletizing and depalletizing of the cans.
The separator sheet of the present invention comprises a flexible sheet which is coated on both sides with a polymer layer having a smooth finish, resulting in a static coefficient of friction that is at least 0.35, measured in accordance with ASTM test method D1894-93. To ensure proper can retention, both sides of the separator sheet should have the threshold static coefficient of friction of at least 0.35. A static coefficient of friction of at least 0.35 provides the necessary friction to discourage can movement, and specifically can fallout, during transport. The unique surface characteristics of the separator sheet of the present invention may alternatively be defined by a standard surface gloss measurement. Sheets having the desired frictional properties also possess a surface gloss of at least 20, as determined in accordance with ASTM Test Method D-523 (60 degree gloss measurement). Both surfaces of the sheet should desirably have this minimum surface gloss value.
The core layer preferably consists of a high basis weight, nonwoven spunbonded fabric similar to that used in the aforementioned matte-finish sheet. The high friction surface is then imparted by applying a polymer layer to the core layer and forming a smooth gloss surface on the polymer layer, e.g. with a chill roll having a polished finish. The gloss finish gives the surface of the sheet higher static and kinetic coefficients of friction than the rougher matte-finish sheet. By having a gloss surface, more surface area of the sheet contacts the cans, thus increasing the friction therebetween. With a matte-finish sheet, the rough, grainy surface decreases the surface area which contacts the cans, thus reducing the relative friction between the sheet and the cans.
While the gloss and matte finish sheets cost more than chipboard sheets, they have been found to last significantly longer making them a more cost effective design.


REFERENCES:
patent: 3666604 (1972-05-01), Coffet
patent: 4262051 (1981-04-01), Welz et al.
patent: 4507348 (1985-03-01), Nagata et al.
patent: 4748070 (1988-05-01), Beehler
patent: 4961983 (1990-10-01), Smorada et al.
patent: 5080960 (1992-01-01), Smorada
Brochure entitledTYPAR Separator Sheets-Innovative Packaging for the Food and Beverage Industry, Reemay, Inc. of Old Hickory, Tennessee, TS-91001, 1991.

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