US2516647A - Method of making closure elements - Google Patents

Description

July 25, 1950 l. F. ROGERS ETAL 2,515,647

METHOD OF MAKING CLSURE ELEMENTS Filed May 13, 1946 SECOND DEPOSIT ANNULUS lo THIRD DEPOSIT \l=m* I VULCANIZE PUNCH 8| FORM ATTORNEYS Patented July 25, 1950 METHOD F MAKING CLOSURE ELEMENTS Louis F. Rogers and Michael S. Ebert, Wilmington, Del., assignors to Continental Can Company, Inc., New York, N. Y., a corporation of New York Application May 13, 1946, Serial No. 669,450

Claims.

In the preparation of container closure elements such as ends and crown seals, it has been the practice to employ an elastic liner for sealing the element to the container. For example, crown seals have been made with cork cushion liners with or without a central spot of aluminum foil, or with cushioning and sealing liners of natural rubber or like composition which was preformed and then inserted or was deposited in the formed crown shell as a fluid and then dried in place; wherewith the practice was rst to' punch and form a metal sheet into crown shells and then by subsequent operations adheslvely apply the liners into the shells. Another proposal has been to print a, metal sheet with disks or rings of thermo-adhesive substance and then punch and form the shells in the cold, then heat to adhesiveness, and then apply the liners.

According to the present invention, closure elements are prepared by printing the blank with a material which itself provides cushioning and sealing, in individually thin deposits which are 2 being baked in theusual fashion. 'Ihe sheet is then subjected to a succession of further applying operations at its other face, employing a composition of the following formulation:

2) a thin illm l2 of this fluid material over an area of the blank which in size and shape corresponds to the inner end surface of the crown shell to be formed, covering this area entirely.

In practice, each sheet of metal (Figure 6) prosuccessively made until the desired total thickness is'obtained, and thereafter punching and forming the closure elements with the cushion seal already present on the blank.

In the accompanying drawing;

Figure 1 is a sectional view, on a greatly enlarged scale, of a metal sheet having a lithographed coating on its lower face;

Figure 2 is a corresponding view, showing the vides materials for several hundred blank crown shells and accordingly simultaneous application is made for these individual crown shells, locating each circle of deposit on the inner face but in alignment with the lithographed identifying printing of a first cushion deposit on such a sheet;

Figure 3 is a corresponding view showing the printing of a. second deposit;

Figure 4 is a corresponding view showing the sheet with three successive deposits thereon;

Figure 5 is a view, on the same scale, through a crown seal made in accordance with this invention;

Figure 6 is a perspective view on a smaller scale, showing part of a large sheet having a multiplicity of deposited areas thereon;

Figure '7 is a flow diagram, indicating the steps of a preferred method of operation.

In this illustrative practice of the invention, a flat blank sheet I0 (Figure l) of metal, such as tin plate, is printed at the side which is later to provide the exposed surface of the cap, with the usual identifying and surfacing matter in the usual ways, these lithographed coatings Il then matter which has been placed on the outer face. A preferred manner of applying is by use of a silk screen printing stencil with impermeable portions Il, wherewith the circular deposits l2, at points of the sheet corresponding to the location of the permeable screen portions I5 in the stencil. are produced by the delivery through untreated parts of the screen in the usual manner of silk screen printing. The sheet is then dried, wherewith the localized deposits I2 provide adhesive films having a thickness of about eight oncthousandths of an inch. The sheet is then subjected to further applying operations, in which the successive stencils with impermeable portions I6, il and annular permeable portions I8 deliver annular deposits 20, 2| along the outer periphery of the initialv circular deposit, with a radial dimension corresponding to the dimension of the lip of the container which is to be closed by the crown seal. Each successive application is dried before the next is applied, so that an annular structure is built up: these applications illustratively have individual thicknesses about eight one-thousandths of an inch after drying. The same composition as above is employed. The

total thickness of the three layers of deposit (Figure 4) being the ilrst or circular deposit l2 and two subsequent annular deposits 20, 2|, is about twenty-five thousandths of an inch. The deposit should be cured before punching the crown seals therefrom. The curing or vulcanizing operation may be performed successively upon each of the layers as deposited in succession to the drying operation; or the curing can be effected upon a number of layers, or even upon all layers, at a-single vulcanizing operation. It is presently preferred (diagram with legends Figure 7) to dry each layer individually before applying the next, and to employ the vulcanizing heat only after the total deposit has been effected. The curing can be accomplished by passing the printed sheets through an oven, e. g. on a moving conveyor, wherewith to heat them to a temperature of 240 degrees F. for thirty minutes, wherewith the material becomes vulcanized and fixed in its properties. Other time-temperature conditions can be used, as known in the art: care being taken to avoid employing excessive heating with mixtures which may be harmed thereby, as for example when very light colors are being printed, the temperature of exposure should be not over 260 degrees F. to prevent color-darkening.

When the last deposit has been completed and cured, the sheet is fed in the usual manner into a blanking and forming press, which has its die recesses and punches aligned with the locations of the identifying matter at the outer face for the crown shell and the above deposits at the inner face, and crown shells are now stamped and formed (note legend in Figure 7) to provide them the usual crimped skirts. The above composition adheres to the metal, and the output from the punch press is a bulk group of the formed crown shells (Figure each having a multiple coating of the aforesaid material and structure at its interior, along with the residual scrap of the sheet.

These crown shells (Figure 3) have the usual body la and crimped skirt IDD, with the eX- ternal lithographed matter Il and the internal circular deposit I2 upon which are the two successive annularv deposits 20, 2l located ready to engage the lip of a bottle, can, etc. They are now ready for application to bottles, cans, etc. by the usual sealing or crimping devices.

The artificial rubber employed in the above illustrative practice was the material available on the market under the name GR-S and is so called in lSpecications for Government Synthetic Rubbers issued by Reconstruction Finance Corporation, Oillce of Rubber Reserve, and effective January 1, 1947. The material is a copolymer of butadiene and styrene to which approximately 1.25% of a standard rubber antioxidant has been added during manufacture: of the hydrocarbon present, approximately 23.5% by weight is derived from styrene.

Other types of butadiene-styrene copolymer rubber, natural rubber, butyl rubber and mixtures of natural and synthetic rubbers, may be employed, provided that the same is capable of forming a homogeneous and essentially compatible mixture with the paraffin and is capable upon the said vulcanization of producing a mass of elastically yielding characteristic.

The vulcanizing agent employed can be of the type commercially used with rubber compositions: in general, the accelerators employed in the vulcanization of rubber dolls and toys are usable, as

they have been devised te avoid the later presence The paraffin, employed in the above example,

was a refined parafn wax having a melting point of 133 to 135 F. It is preferred to have a paraiiin wax with a limited range of melting point: such materials are available in commerce from various sources, with trade specifications setting the range of melting point at 2 or 3 degrees F. In the above example, the parailin wax employed at a specific gravity (solid at 60 F.) of 0.889 and (at 140 F. corrected to 60 F.) of 0.782; S. U. viscosity at 210 F. of 37/38; and was a refined crystalline type parailin as distinguished from microcrystalline type. The quantity of paramn can be varied from 10 to 40 parts, with corresponding variations of the behavior of the material. It is presently preferred to use a higher proportion of paraffin in making crown seals for soft drinks, and a lower proportion in making crown seals for beer. The parailln operates to restrict moisture vapor penetration, to restrict blocking, and to decrease any later leaching of materials from the composition by the action of some products which may be present in the container closed by the seal. The melting point of the paramn wax may be higher or lower, but it is presently preferred to have the melting point above normal atmospheric temperature conditions, and below the temperature at which the container may later be heated for pasteurization or processing. When large proportions of wax are used, and a relatively sharp temperature transition is desired, it is preferred to employ paraffin waxes of the stated conventional type in distinction from microcrystalline waxes which appear to have less compatibiltywith buna and natural rubbers than the conventional grades of paraiiin wax, and in distinction from petrolatum waxes which have a relatively wide temperature range of softening; as these materials do not behave so desirably as conventional paraffin waxes during the manufacture and use of the crown seals.

The titanium oxide and clay are llers and also pigments. In the above example, the clay and the titanium oxide were commercially available products widely used as inert llers and pigments: other specific clays and forms of titanium oxide have been employed and are employable. With the indicated proportions of these i'lllers 'and pigments, the resulting rubber film was substantially white in color. The ratio of fillers to one another may be varied in accordance with the color desired, and their total amount may be between about 200 parts and about 400 parts per parts of rubber base. These substances are illustrative of the general class of inert earthly fillers, and the various ochres, clays, barytes, etc. can be employed. The filler should be in finely divided condition, and preferably is dense as distinguished from uify or spongy.

The composition can be blended on a rubber mill with means, such as an internal cold water now, for keeping the rolls cool. The Buna rubber is Amilled with cold rolls for approximately ve minutes and then the zinc oxide and sulphur are added. When they have been incorporated in about five minutes time, the parailin wax is added in the melted form: it is combined in about fifteen minutes. When this-combination has been effected, the pigments are added and combined. The vulcanizing agent is preferably added just before the rubber mass is to be coated or printed. Accordingly, the material can be made up in the absence of vulcanizing agent and diluent and stored for a considerable period without particular care. When it is to be used, the composition can be again rolled for incorporating the vulcanizing agent and then thinned with the diluent, or the stock mixture can be worked up with the diluent and the vulcanlzing agent then incorporated, dependent upon the conditions for use.

The xylol is illustrative of diluent or fluidifying material, and its proportion may vary from 500 to 1000 parts. dependent upon the consistency of the printing which provides a deposit of uniform thickness without excessive flowing during the drying operation. It is preferred to bring the composition to liquid form by employing about 500 parts of the diluent xylol, and then introduce further diluent as necessary to bring the composition to proper viscosity for the printing operation. Other thinners can be employed, such as toluol or in general the volatile viscosityreducing agents employed with rubbers: a true solvent action is not required as the function is to produce a mixture which will flow at the desired rate during printing.

In the above example, a thickness of individual deposit of about eight one-thousandths of an inch was set out. This thickness can be varied as desired, with a maximum thickness of about twelve one-thousandths of an inch. In practice, a dry thickness of fifteen one-thousandths of an inch total was produced by three coatings of the rubber compound, employing toluol as a thinner, representing three successive printings of five one-thousandths of an inch each with intervening drying operations.

The above illustration of practice describes a procedure of making a crown seal of the normal or standard size and shape, with manufacture from a blank having a diameter of one and onehalf inch, with an annular deposit having a thickness of twenty-five one-thousandths of an inch, and a central or web thickness of eight onethousandths of an inch. It has been found that, by employing the successional coatings, with forming and punching of shells and final vulcanization, satisfactory seals can be made with crown shells having a shorter skirt, and with employment of liner thicknesses of about fifteen one-thousandths of an inch. By comparison, it may be remarked that when cork composition is employed, the liner thickness is about 90 to 110 thousandths of an inch, which is compressed to about 30 thousandths of an inch as an incident of applying and crimping the crown seal.

In making a crown shell of the short skirt type, the printing operation may be conducted on the basis of blank diameters of 11% inch, thus representing a saving of about 9% of the metal. Three deposits of composition, providing a total thickness of fifteen one-thousandths of an inch for the annular portion was employed, with a central web of five one-thousandths of an inch. These seals held excellently on standard bottle mouths and withstood the usual specifications with respect to internal pressure held with carbonated beverages. The thickness of a satisfactory sealing cushion is related to the total skirt depth; and the skirt edge should not be brought into interfering contact with the bottle neck during the operation of closing by crimping methods with the rolls having printing areas f terials are prepared usually in mixture with filler and pigment such as clay and titanium oxide, thinnedto suitable viscosity by an appropriate volatile agent such as xylol or toluol and then employed in the printing operation. Successive deposits, of limited thicknesses as set out above, are employed with drying oi the diluent after each application, until a total thickness is built up to provide adequate yield for conforming to the irregularities at the container mouth to be sealed, these thicknesses being substantially those set out above for the rubber-parailin mixtures. These deposits may be hardened individually, or as a group, by heating to the temperature at which curing by vulcanization, condensation or polymerization occurs, wherewith the product loses its original characteristic of being swollen or dissolved by the solvents, and of swelling by water.

The invention has been described above in illustrative practices. It will be understood that these are to indicate presently preferred conditions, and that the invention may be practiced in many ways within the scope of the appended claims.

We claim:

1. The method of making a crown closure, which comprises printing upon a sheet metal blank a succession of deposits of uid material upon a predetermined area thereof corresponding to the internal end wall area of a crown shell, at least one of said deposits extending over the entire end wall area and at least one other of said deposits being restricted to the annular region at which the lip of the container engages the crown closure, said individual fluid material deposits comprising a volatile fluidlfying substance and an elastically yieldable adherent material, the deposits being limited to produce after drying a maximum thickness per deposit of 0.012 inch and a maximum thickness ofthe total deposits of about 0.025 inch, drying olf said volatile medium after each deposit and before the next deposit, and then forming the blank at parts radially outside the area into a container-engageable projecting flange with the deposits inside the same.

2. The methodA of making a crown closure, which comprises printing upon a sheet metal blank a succession of deposits of iiuid material upon a predetermined area thereof corresponding to the internal end wall area of a crown shell, at least one of said deposits extending over the entire end wall area and at least one other of said deposits being restricted to the annular region at which the lip of the container engages the crown closure, said individual iiuid material deposits comprising a volatile ii-uidifying substance and an elastically yieldable adherent material having a vulcanizable base and a. vulcanizing agent, the deposits being limited to produce after drying va maximum thickness per deposit of 0.012 inch and a maximum thickness of the total deposits of about 0.025 inch, drying 011 said volatile medium after each deposit and before the next deposit, then heating the blank to effect vulcanization of said material, and then forming the blank at parts radially outside the area into a container-engageable projecting nange with the deposits inside the same.

3. The method of making a crown closure, which comprises printing upon a sheet metal blank a succession of deposits of fluid material upon a predetermined area thereof correspond ing to the internal end wall area, of a crown shell, at least the rst of said deposits extending over the entire end wall area and at least the last of said deposits being restricted to the annular region at which the lip of the container engages the crown closure, said individual iluid material deposits comprising a volatile fiuidifying substance and an elastically yieldable adherent material, the deposits being limited to produce after drying a thickness per deposit of about 0.005 to 0.008 inch and a maximum thickness of total deposits of 0.015 to 0.025 inch, drying off said volatile medium after each deposit and before the next deposit, and then forming the blank at parts radially outside the area into a containerengageable projecting flange with the deposits inside the same.

4. The method of making a crown closure, which comprises printing upon a sheet metal blank a succession of deposits of iiuid material upon a predetermined area thereof corresponding to the internal end wall area of a crown shell, at least the iirst of said deposits extending over the entire end wall area and at least two subsequent deposits being restricted to the annular region at which the lip of the container engages the crown closure, said individual Huid material deposits comprising a volatile iiuidifying substance and an elastically yieldable adherent material, the deposits being limited to produce after drying a maximum thickness per deposit of 0.012 inch and a maximum thickness of total deposits of about 0.025 inch, drying oil said volatile niedium after each deposit and before the next de- 8 posit, and then forming the blank at parts radially outside the area into a container-engageable projecting nange with the deposits inside-the same.

5. The method of making a crown closure, which comprises printing upon a sheet metal blank at each of a. plurality of spaced predetermined regions on one side thereof a succession of deposits of iluid material, each said predetermined region including the internal end wall area of a crown shell, at least one of said deposits extending over the entire end wall area at each region and at least one other of said deposits being restricted to the annular part of each said region at which the lip of the container engages the crown closure, said individual fluid material deposits comprising a volatile iluidifying substance and an elastically yieldable adherent material having a vulcanizable base and a vulcanizing agent, the deposits being limited to produce after drying a maximum thickness per deposit of 0.012 inch and a *maximum* thickness of total deposits of about 0.025 inch, drying on said volatile medium after each deposit and before the next deposit, then heating the blank after the inal deposit of said material thereon to effect vulcanization-of said material, and then forming each said region of the blank at parts radially outside the corresponding said area, into a container-engageable projecting flange with the corresponding deposits inside the same.

LOUIS F. ROGERS. MICHAEL S. EBERT.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,734,347 Bond Nov. 5, 1929 1,832,321 Owens Nov. 1'?, 1931 1,901,682 Warth Mar. 14, 1933 2,114,309 McGowan et al. Apr. 19, 1938

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