US2338705A - Cap - Google Patents

Description

1944. cosTA ETAL ,33

CAP

' Filed NOV. 7, 1941 3 Jc'omz, 3,

Edward Y I cl'qr 09,33,072.

Patented Jan. 11, 1944 Md., assignors to Crown Cork & Seal Company, Inc., Baltimore, Md., a corporation of New York Application November 7,1941, Serial No. 418,248

2 Claims.

The present invention relates to container closures, and particularly closures of the crown type which include a metal shell having a crimped or corrugated skirt and a cushion sealing liner or disc' assembled within the shell. The closure or cap is applied to a container such as a standard crown beverage bottle by drawing the crimped skirt into locking engagement with a shoulder on the container lip whereby the liner is tightly compressed thereon to seal the contents against leakage past the lip surface. This crowning pressure frequently reaches as high as 900 pounds and it is necessary for the cushion liner to have a high degree of permanent resiliency under this pressure so as to constantly flow and fill any inequalities in the lip surface and maincork granules held together by a binder such as lue or synthetic resin, the cork being largely predominant and the 'binder'being present substantially only in an amount to hold the cork granules together. Such cork liners or discs are generally cut so as to have a total thickness of about 0.1 inch and under crown sealing compression are reduced to a thickness of the order of 0.017 inch. Notwithstanding such high degree of sealing compression, the cork composition disc maintains its permanent resiliency and scaling properties as evidenced by the tightness of the seal and further by its rapid expansion or return when the compression is released after long periods of time. In addition, the cork composition liner does not shrink to any appreciable'extent, and withstands high internal pressures of 120 pounds or more such as are created by carbonated beverages, e. g., beer, so that a leakproof seal is continuously maintained and the contents ar prevented from seeping or exhausting between the liner and the lip surface Of the container. It can be appreciated from the foregoing why crown caps including a cork sealing liner have been preferred. However, at, th present time, due'to remote sources of supply and to national defense needs, sufiicient cork to meet the requirements of the closure industry is no longer assured.

To improve this situation, experiments have been conducted with newsboard, "wood-pulpboard, straw board, "sulphit board, press board and vulcanized fiber board, all of which are commercially available and have been adequate in th case of screw or lug caps where a high sealing compression comparable to that occasioned by crown scaling is not encountered. These inexpensive board materials and many others notwithstanding they have been faced with foil, paper or resistant coatings have not made satisfactory crown caps for sealing. pressure beverages and liquid." because the sealing liner lacks the required permanent resiliency under high sealing compression, tends to shrink objectionably and is not resistant to leakage under internal pressures produced by carbonated beverages.

We have discovered that a crown cap having a cushion liner of paper board is equally as suitable as a cap provided with a cork cushion liner, provided the liner .hasincorporated therein in addition to board pulp, raw chemically untreated, i. e., uncooked, fibers such as cotton fibers, in amount effective to produce relatively permanent or continuing resiliency under high sealins compression. It is preferred that the board .pulp to which is added the raw fibers be mostly mechanical pulp, i. e., contain littl or no cooked fibers. These latter apparently so deaden the liner that it remain substantially set under compression and is not as readily improved by theinclusion of the untreated fibers as those pulps which contain no treated fibers or a small proportion of the same. Uncooked non-ligneous fibers are preferred as the resiliency imparting agent for all types of board pulps.

The primary object of the invention is to provide a closure cap of the crown type having a cushion liner made of paper board which will possess the required permanent resiliency under high sealing compression to form a leakproof' when subjected to crowning pressures, the thick ness is reduced to substantially 0.017 inch to 0.028 inch and under crown sealing compression, the liners exhibit substantially the same continuing resiliency, resistance to internal pressures and lack of shrinkage, as well as sharp rebound on release of pressure which characterize composition cork liners under the same conditions.

An equally important object of the invention is to provide a closure cap of the crown type having a cushion liner which can be made by high speed production methods and at a cost comparable to the use of cork composition.

In the accompanying drawing, we haveillustrated a crown cap for a standard crown beverage bottle and it is to be understood that other types of closure caps are similarly improved by use of the present invention.

Referring to the drawing:

Figure 1 is an elevation of the inside of a crown cap showing the cushion liner assembled therein;

and

Figure 2 is a section on theline 2-2 of Figure 1.

The cap shown in Figure 1 includes a metal shell l having a skirt H, as shown in Figure 2, and formed with crimps or corrugations I2. In the case of a standard crown beverage bottle, such caps are usually described as standard 26 mm. crown which means that the diameter taken from the inside perpendicular wall of the skirt l I is 26.7818 mm: or 1.0545 inches. The invention is equally satisfactory with other types of crowns of both larger and smaller diameters. The cushion liner is in the form of a circular disc l3 and is assembled in the shell and secured thereto in any suitable manner.

In Figure 2, the cushion liner is shown having its uncompressed or original total thickness. The

- exposed surface of the cushion liner I3 has adhered thereto a' spot facing I4 of paper, foil or in the form of a suitable coating of resistant material such as vinyl resin or chlorinated rubber. This facing l4,'in some cases, extends over the entire exposed surface of the liner so as to give overall coverage.

In preparing the material from which the liners are formed, a suitable paper pulp is employed, preferably mechanical pulp or one containing mostly untreated fibers as explained above. merous board pulps are, of course, available from which a boardhaving improved sealing qualities can be made by the inclusion therein of an effective amount of uncooked fibers, such as cotton fibers, to impart the desired compressibility and resiliency. For example, a mechanical pulp such as that prepared from seasoned ground wood is highly satisfactory although not available at the present time in required quantities. .Likewise,

Waste news'containing mostly uncooked fibers and about 15% of sulphite pulp, forms a very suitable board, although not now obtainable in commercially useful amounts. Ground wood made from green wood and having included about 15% sulphite pulp is the most suitable pulp avail able under current circumstances since it can.

be obtained in sufficient amount and at a commercially acceptable price. These respective pulps make satisfactory boards forcushion liners ticularly compatability with the raw, live, un-

cooked fibers which are added in effective amount to make the board permanently resilient.

With a pulp of the character just described, there is mixed raw, uncooked fibers in amount to produce in the finished board, compressibility and rebound of the order of the characteristic continuing resilience of composition cork. That is, crown liners cut out from the board will exhibit relatively permanent or continuing resiliency under high crown Sealing compression and form a reliable leakproof seal between the-crown cap shell and the lip of a container for an indefinite period.

Experiments were made using sulphite pulp, sulphate '(kraft) pulp, soda pulp, straw pulp, rag pulp, and cotton linters pulp as the resiliency imparting agent; but .in each case, the resulting board did not possess sealing qualities of the order of composition cork when used for crown cushion liners. On the other hand, raw, untreated fibers, preferably vegetable fibers and non.- li'gneo'us fibers, such as cotton floss, cotton linters, and ginned cotton, were'found to be satisfactory and enhanced the resilience and strength of the cushion liner material so that it was substantially as satisfactory under high crown sealing compression as composition cork. While we have referred to cotton fibers as the resiliency imparting agent, it will be appreciated that other fibers are equally suitable, such as flax, ramie,

nection with the use of 25% cotton floss, 63.75%

green ground wood and 11.25% sulphite pulp. The invention is equally operative with the other pulps and fibers referred to and We do not wish to be limited to the specific proportions in the example just recited. With respect to the 'relative percentage of pulp and raw fibers resiliency-imparting, the compressibility and rebound, i. e., resiliency, increases as the amount of cotton fiber, which in the present example is cotton floss,

is increased from 15% to 25%. At about 25%, the maximum resilience appears to be obtained. With further additions of such raw fibers the resilience tends to decrease, and when the product contains 63% of raw fibers, the compressibility and rebound is about the same as that of the pulp without the fiber addition. It will be seen that the proportions of raw fibers to pulp are critical to assure maximum resiliency for an unlimited or indefinite period of time. In some cases, the pulps will have a compressibility and rebound characteristic so that less than 25% of live fiber may be included to give a satisfactory result, and in other cases there are pulps which are so lacking in the compressibilit and rebound factor that somewhat more than 25% may be necessary to bring the final material to the required permanent resiliency.

In preparing the pulp mixture for the paper making operation, the cotton fibers are first speed of hydration. For example, cotton linters,

since they are short fibers, need not be given a preliminary beating as is done in the case of cotton floss. When the beaten stock is fed to the paper machine, the pulp dilution should be controlled so that the dried board product will have the desired thickness, density and resilience. The two factors of hydration of the pulp and dilution are critical to the end that when the cushion liner is subjected to high sealing compression, it will exhibit permanent resilience, and not become dead or so lose its compressibility and rebound characteristic as to produce .leakers. At this tween 0.031" and 0.056".

point, it should be understood that liners made in accordance with this invention may be stored for long periods before and after assembly in caps and as pointed out, will hold a seal indefinitely.

-The stock -is fabricated on acylinder paper making machine preferablyhaving six cylinders although satisfactory boards may be made using as little as three or as many as seven or more cylinders. Stock dilution is generally increased when a greater number of cylinders are used and correspondingly decreased when a fewer number ofcylinders is employed.

The board produced on the cylinder machine is dried by the usual drying means which finish the materialawith a moisture content of between 2/z% and 8%. We prefer to calender the product lightly to render the surfaces smooth and suitable to receive the facing H, the reduction in thickness due to calendering being controlled so that it is not more than substantially 15% and is preferably held at about 10%.

The board material may have adhered to one or both surfaces thereof a facing ll of one or;

two sides coated varnish paper, metal foil, such as aluminum foil, or a resistant material, such as vinyl resin or chlorinated rubber, and the discs are then punchedirom such laminated product. The discs are assembled in the caps with the facings exposed to the contents. In lieu of punching out such laminated cushion liners, the

liners may be punched from the board and subsequently provided with a spot or overall facing of one of the materials above mentioned. Also,-a coating may be suitably sprayed on the surfaces of the board and the discsthen punched out.

For example, a coating composed of a mixture of latex, casein, and inorganic filler, may be cylinder machine roduct.

vthe severe pressures entailed in the crowning operation and the crown sealing compression, the residual thickness will be between 0.017" and 0.028". and at the same time, the cushion liner will retain its resilient properties for an indefinite period of time, as is characteristic of the usual cork composition liner. By the present invention, a product is obtained which, under the most severe sealing pressures, has a residual thickness within the range of that characteristic of the customary cork disc, and like the cork disc at this residual thickness has sufficient compressibility and rebound to afford a permanent leakproof seal. Products made in accordance with this invention, after drying or after drying and light calendering, and before facing, preferably have an original or total thickness of be- The original or total thickness is critical only to the extent that under the high pressures above mentioned incident to the-crowning operation and the crown sealingcompreSsio'n, the cushion liner will be reduced to a residual thickness described which is of the order of that to, which cork composition is reduced under similar conditions, and at the same time retain the continuing resilience and other sealing qualities characteristic of the customary cork disc.

The term crowning pressure is intended to denote the pressure exerted by the crowning apparatus in looking the crimped skirt of a crowned cap upon the locking shoulder of a container such.

this. pressure is in the neighborhood of 900 pounds and constitutes a high sealing pressure, l. e., the crowning pressure is substantially the same as the continuing sealing pressure.

The term resiliency is intended to cover the properties of high compressibility and quick rebound when the compressing force is released, which properties are possessed substantially alike by the liner disc described herein and the heretofore used cork composition disc. these properties, the cushion liner at all times closes any openings or fills any inequalities between tainer.

-We claim:

1. A crown cap having a the cap and the sealing lip of the concushion liner of paper board, said board comprising ligneous untreated mechanical paper fibers in major amount, and in lesser amount, raw chemically untreated nonligneous vegetable fibers, said cushion liner having a thickness of substantially .031" to .056" and said untreated non-ligneous fibers being present in amount to impart to the liner a resiliency of the order of cork composition cap liners. v I

2. A crown cap having a'cushion liner of paper board, said board comprising ligneousuntreated mechanical paper fibers in major amount, and in lesser amount, raw chemically untreated nonligneous vegetable fibers, said cushion liner having a thickness of substantially .031" to .056" and said untreated non-ligneous fibers being present in amount of substantially 15 to 25%. EDWARD'J. COSTA.

VICTOR A. RYAN.

It is a critical requirement of discs produced Because of

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