US2750322A - Gasket and method of making same - Google Patents

Description

June 12, 1956 e. B. COOKE ET AL 2,750,322

GASKET AND METHOD OF MAKING SAME Filed March 20, 1951 INVENTORSJ Gales ,3. Coalfe, William flflarmer wa mu, l d/{y Maw ATTORNEKY.

United States Patent GASKET AND METHOD or MAKING SAME Giles B. Cooke and William C. Rainer, Baltimore, Md.,

assignors to Crown Cork 8; Seal Company, End, Baltimore, Md., a corporation of New York Application March 20, 1951, Serial N 0. 216,488

11 Claims. (Cl. 154-439) This invention relates to gaskets particularly useful in connection with the filling valves of bottle-filling machines.

Usually leather gaskets have been employed which are impregnated with wax to make them firm and hard and provide a good wearing surface. The leather gaskets frequently have been provided with a separate thin coextensive rubber gasket in order to effect a seal at the bottom of the filling valve. This combination has several objectional features. For instance, the leather gaskets are hard and it has often been necessary to install the gaskets in the beverage machine at night in order to allow the wax-encrusted leather to absorb sufficient moisture "to soften the gasket and form an eflicient seal. In absorbing moisture the leather swells into the ports of the valve arm, producing raised portions which abrade when the beverage machine is operated, and a very high pressure is, therefore, necessary for breaking or opening the valve in the morning, after the beverage machine has been shut down. Further, it has been increasingly difficult to secure a uniformly high quality of leather for the leather gasket.

We have discovered that a one-piece gasket, rather than the provision of a combination of separate leather and rubber layers solves many of the problems incident to the use of such a combination and gives more uniformly satisfactory service.

The present invention consists of a one-piece gasket having an upper portion, the top surface of which is reasonably hard so as to withstand abrasion and, at the same time, the gasket possesses appreciable flexibility. This upper, relatively hard surface of the gasket is very smooth,

whereby the moving arm of the filling valve may move freely. In this manner, abrasion is kept at a minimum and the need for high pressures to break or start the filling valve after a period of shut-down is avoided.

The bottom portion of this one-piece gasket is relatively soft in order to effect a perfect seal, and when placed in the filling valve readily conforms to any irregularities of the valve seat, whereby to give a watertight seal immediately.

In the preparation of a one-piece gasket of this type, we use rubber compositions employing rubbery polymeric compounds with which may optionally be included some natural rubber. These formulations are compounded on conventional rubber compounding equipment and after calendering, the layers of the respective compounds are placed in a mold with the composition which provides the hard upper layer at the top and with the softer composition providing the lower layer at the bottom. The two layers are press-cured and the finished gasket has a thickness of approximately 75 of an inch. By reason of this method, the two layers are integrally bonded by vulcanization into a highly suitable unitary gasket. In some cases, an intermediate layer of a rubbery composition is pro- 2,750,322 Patented June 12, 1956 vided which is softer than the top layer but less soft than the bottom layer and when the three superposed layers are cured, this intermediate layer acts as the binding means for the upper and lower layers. During the curing process, the several adjacent layers, under heat and pressure, flow into each other and the single unit has a gradation of properties from top to bottom.

Essentially, the gasket of this invention consists of two or more layers of a rubbery composition containing 1) a plastic, e. g., polystyrene, wax, e. g., ceresin, (2) synthetic rubber, such as GRS, Buna N, Buna S, Geon Resin No. 121, i. e., vinyl chloride polymer, natural rubber, with conventional fillers, anti-oxidants, accelerators and stabilizers, and a vulcanizing agent. Buna N rubber is butadiene-acrylonitrile copolymer; Buna S rubber is butadiene-styrene copolymer; and GRS rubber is the same as Buna S rubber. A substantial amount of wax is employed which slowly exudes or blooms to the surface of the gasket and provides a lubricant for the valve arm which is in constant motion forward and backward when the beverage filling machine is in operation. The Wax also increases the water resistance of the gasket and lowers the elasticity of the rubber. For instance, it is preferable that the rubber in the bottom portion of the gasket have a lower elasticity, for example, under 30 by the Shore Durometer.

Referring to the drawings:

Figure l is a top View of the gasket;

Figure 2 is an edge view of a gasket having three portions, namely, an upper, relatively hard portion, an intermediate, relatively softer portion, and a bottom portion of greater softness than the intermediate portion;

Figure 3 is a sectional view of the gasket shown in Figure 2;

Figure 4 is an edge view of a gasket having two portions; and I Figure 5 is an edge view of a gasket having four portions, the gaskets of Figures 1 to 5 having gradually decreasing properties of relative hardness and softness, from the hard upper surface to the softer lower surface.

In all cases, the hard upper portion of the gasket is either equal to or of greater thickness than the soft lower portion.

Referring to Figure l, the unitary gasket is indicated as a whole at 10 and has the usual holes and ports which are indicated generally by the numeral 11.

Referring to Figures 2 and 3, the upper, hard portion is indicated at 12, the intermediate, less hard and bonding portion is indicated at 13, and the softest portion is indicated at 14.

Referring to Figure 4, the upper, hard portion is indicated at 15 and the lower, softer portion at 16.

In Figure 5 the unitary gasket comprises four portions having gradually decreasing properties of hardness and softness from the top portion 17 through the intermediate portions 18 and 19, to the lower portion 20.

In the case of a three-composition gasket, as shown in Figures 2 and 3, the intermediate or bonding portion 13 is relatively thicker and the exposed portions 12 and 14 are of equal thickness. In the case of the two-composition gasket of Figure 4, the lower or softer portion 16 is preferably of less thickness than the upper or harder portion 15.

The gasket of Figure 5 may have the portions of equal thickness or of varying thickness.

It vis preferable that the lower or softer portion, 14, 16 or 20, as the case may be, shall be of substantial thickness, but the thickness of the various portions may be varied, as required by the particular beverage ma chine.

EXAMPLE I (Figures 2 and 3) The top, or hard portion, has the following composition:

Top portioncalendered 0.055"

Parts GRS 150.0 Neozone D 1.5 Marbon S (polystyrene) 150.0 Zinc oxide 7.5 Philblack O 18.0 Dixie clay 210.0 Talc 150.0 Wax (ceresin) 60.0 Tetrone A u 7.2 Sulfur 12.0

The intermediate part which serves to bond strongly the top and bottom portions and also gives strength and flexibility to the finished gasket has the following composition:

Intermediate portioncalendered 0.100"

Parts GRS 150.0 Neozone D 1.5 Marbon S (polystyrene) 30.0 Zinc oxide 7.5 Philblack O 18.0 Dixie clay 210.0 Talc 150.0 Wax (ceresin) 60.0 Tetrone A 7.2 Sulfur 12.0

The bottom part which forms a perfect seal over the valve seat has the following composition:

Bottom portion-calendered 0.055

Parts GRS 150.0 Neozone D 1.5 Pigment 2.0 Zinc oxide 7.5 Dixie clay 210.0 Talc 150.0 Wax (ceresin) 60.0 Tetrone A 3.6 Sulfur 6.0

These formulations are compounded on the conventional rubber compounding equipment. After calendering, the several compounds are placed in order with the softest at the bottom and the hardest on top in a mold and press-cured at about 325 F., 1000 pounds pressure for thirty minutes. The finished gasket has a thickness of approximately 7 EXAMPLE II (Figure 4) Clay 209.7 Talc 150.0 Wax (ceresin) 60.0 Sulfur 6.0 Tetrone A 3.6

The top layer is calendered 0.155 inch thick and the bottom layer 0.055 inch thick. The two are press-cured at 1000 pounds pressure in a mold at 280 F. for twentyfive minutes.

EXAMPLE 111 (Figure 4) Top portion Parts Buna S rubber 127.5 Natural rubber 22.5 Antioxidant (phenylbetanaphthylamine) 1.5 Polystyrene f 60.0 Zinc oxide 7.5 Red oxide 18.0 Clay 210.0 Talc 150.0 Wax (ceresin) 36.0 Wax (carnauba) 24.0 Sulfur 15.0 Tetrone A 7.2

Bottom portion Parts Buna S rubber 150.0 Antioxidant 1.5 Zinc oxide 7.5 Red oxide 18.0 Clay 209.7 Talc 150.0 Wax (ceresin) 60.0 Sulfur 6.0 Tetrone A 3.6

The upper portion is calendered 0.150 inch thick and the lower portion 0.055 inch thick. They are presscured together for twenty-five minutes at 315 F. at 1000 pounds pressure.

EXAMPLE lV (Figure 4) Top portion Parts Geon resin #121 (vinyl chloride polymer) 150.0

Bottom portion Same as for Examples 11 and 111.

The top portion is calendered to 0.150 inch and the bottom portion to 0.055 inch. They are press-cured at 1000 pounds pressure into a single unit at 280 F. for twenty-five minutes.

EXAMPLE V (Figure 4) Top portion Parts Geon resin #121 (vinyl chloride polymer) n n 200.0 Buna N rubber 70.0 Stabilizer for Geon resin 1.0 Wax (ceresin) 1.0

Bottom portion Parts Geon resin #121 100.0 Buna N rubber 100.0 Stabilizer for Geon 0.5 Wax (ceresin) 1.0

The top and bottom portions are each calendered 0.100 inch thick and press-cured at 1000 pounds pressure into a single unit at 280 F. for twenty-five minutes.

EXAMPLE VI (Figure 4) Top portion Parts Geon resin #121 (vinyl chloride polymer) 150.0 Buna N rubber 70.0 Stabilizer for Geon resin 1.5 Stearic acid 3.0 Zinc oxide 4.0 Wax (ceresin) 1.0 Tetrone A 9.3 Thionex 1.9

Bottom portion Parts Buna N rubber 150.0

Zinc oxide 7.5 Red oxide 18.0

Clay 209.7 Talc 150.0 Wax (ceresin) 60.0 Sulfur 6.0 Tetrone A 3.6

The top portion is calendered 0.150 inch thick and the bottom portion is calendered to 0.055 inch. The two are press-cured at 280 F. for twenty-five minutes under 1000 pounds pressure.

EXAMPLE VII (Figures 2 and 3) T op portion Parts Buna S rubber 15.0.0 Antioxidant 1.5 Polystyrene 100.0 Zinc oxide 7.5 Red Oride 18.0 Clay 210.0 Talc 150.0 Wax (ceresin) 60.0 Sulfur 12.0 Tetrone A 7.2

Intermediate portion Parts Buna S rubber 150.0 Antioxidant 1.5 Polystyrene 30.0 Zinc oxide 7.5 Red oxide 18.0 Clay 210.0 Talc 150.0 Wax (ceresin) 60.0 Sulfur 12.0 Tetrone A 7.2

Bottom portion Parts Buna S rubber 150.0 Antioxidant 1.5 Zinc oxide 7.5 Red oxide 18.0 Clay 209.7 Talc 150.0 Wax (ceresin) 60.0 Sulfur 9.0 Tetrone A 5.4

In manufacturing this gasket the top and bottom portions are-calendered .050 inch thick and the middle portion is calendered .100 inch. The three portions are placed in a mold and press-cured at 325 F. for thirty minutes at 1000 pounds pressure.

(Figure 5 Second portion Same as top portion of Example VII.

Third portion Same as middle portion of Example VII.

Bottom portion Same as bottom portion of Example VI.

The three upper portions are calendered to 0.047 inch and the bottom portion to 0.059 inch. The four portions are placed in a mold and press-cured at 325 F. for thirty minutes.

During the curing process the several compounds, under heat and pressure, flow into each other. The cured finished product is a single unit having a gradation of properties from top to bottom.

Referring to Example I, for instance, we have found that in preparing the top portion 12 of the gasket, preferably a weight of GRS rubber equal to that of the polystyrene plastic is desirable. The rubber is cured and in the vulcanized state gives dimensional stability and retards cold flow in the finished gasket. The wax which is included in substantial amount blooms to the surface in the cured product and serves as a lubricant. In the intermediate part 13 the quantity of polystyrene plastic has been reduced in order to lower the hardness and to increase flexibility in the finished gasket. The bottom portion which is primarily a soft cushion for tight sealing, contains no polystyrene plastic. In the finished gasket the top has a Shore A hardness of approximately 90, while the softer bottom has a hardness of approximately 70.

In the manufacture of the gasket, when the product is cured and removed from the hot mold, it is advantaneous to place the gasket immediately in cold water. This sudden chilling of the gasket causes a quick crystallization of the wax which produces very fine particles in contrast to large crystals which develop during slow cooling. This rapid cooling also produces a surface of close texture rather than an open or porous surface.

Example II shows the use of a mixture of Buna N and Buna S rubbers with a vinyl resin. The rubber is cured in this gasket.

Example III consists of a mixture of Buna S and natural rubbers with polystyrene resin. The rubber is cured in this gasket.

Example IV is similar to Example II with respect to Buna N and Buna S rubbers, which are cured, and vinyl resin. However, the required hardness is obtained by omitting the talc and part of the clay and adding Vanadiset resin. This resin also increases the anti-frictional quality of the top surface.

Example V consists of a hard vinyl resin plasticized with uncured Buna N rubber for the top and a soft vinyl compound in which uncured Buna N rubber functions as a plasticizer for the bottom.

Example VI may have the same top portion as Example V, but the bottom portion consists of a cured Buna N rubber compound as described.

Example VII consists of three portions, the top of which contains less polystyrene than given in Example I. The bottom portion contains more sulfur and accelerator namely Tetrone A which is an accelerator having the composition dipentamethylene thiuram tetrasulfide than the bottom portion of Example I.

Example VIII consists of four portions, the top having a high percentage of polystyrene. This type of gasket is suitable for a stainless steel valve arm, while Example VII is more suitable for a nickel-silver valve arm.

The above formulas, Examples I to VIII all give a gasket with a hard, smooth top portion and a comparatively soft bottom portion. In general, the top has a Shore hardness (A) or 88 to 100 and the bottom a Shore hardness (A) of from 65 to 80. It will be appreciated that different metals demand some variation in hardness. For example, a nickel-silver valve arm may function satisfactorily when the top hardness of the gasket is 92 while a stainless steel valve arm may require a gasket having a hardness of 98 on the top surface.

Neozone D is phenyl-beta-naphthylamine, Philblack O is a high abrasion furnace carbon black, Tetrone A is dipentamethylenethiuram tetrasulfide and Thionex is tetramethylthiuram monosulfide.

These above compositions are prepared in a polished mold, and immediately upon removal the hot panels are immersed and cooled in water, as described, or in mineral lubrication oil. A mineral oil of grade S. A. E. 30 is satisfactory.

After the panels have cooled to room temperature they are removed from the water or oil and allowed to drain. The oil treatment softens the bottom portion and enables it to effect a better seal. The oil is slightly absorbed on the top surface and permits the easy, free movement of the valve arm.

As explained, the layers 12 to are prepared separately and calendered to a predetermined thickness. The superposed layers are placed in the mold and during the curing, the plastic is softened and flows and the layers blend together. The vulcanized product has a relatively hard layer on one surface of the gasket and a relatively softer, conformable layer on the other surface of the gasket. After the unitary structure produced in the mold is cured, gaskets, as illustrated in the drawings, are stamped from the composite unitary structure. The layers are cured in the molds at a temperature of about 280 F. and a pressure of about 1000 lbs. for from about to minutes.

Essentially, the gasket of this invention consists of two or more layers of varied compositions consisting of a plastic for example, polystyrene, polyvinyl chloride; synthetic rubber, for example, butadiene-styrene copolymer, butadiene-acrylonitrile copolymer or combinations thereof; with conventional fillers, antioxidants, stabilizers. accelerators, for example, dipentamethylene thiuram tetrasulfide and/ or tetramethyl thiuram monosulfide; vulcanizing agents, for example, free sulphur or combined sulphur (sulphur containing compounds), and lubricant, for example, ceresin wax. A substantial amount of wax, for example, 8% and up to 11.5% is employed in most instances which slowly but constantly exudes or blooms to the surface of the gasket and thus provides continuous lubrication for the valve arm which is in constant motion forward and backward when the beverage filling valve is in operation. The wax also lowers the elasticity of the rubber or plastic-rubber composition. For instance, it is preferable that the rubber or plastic-rubber have a relatively low elasticity, for example under 30.

We claim:

1. A gasket provided with a passage and having a relatively hard upper portion and a lower relatively softer portion, said portions each including essentially a rubbery polymeric compound, wax in a minor portion of the total composition and filler and being vulcanized together, the upper surface being smooth and abrasion resistant and the lower surface being soft and comformable.

2. A gasket provided with a passage and having a relatively hard upper portion and a lower relatively softer portion, said portions each including essentially a rubbery polymeric compound, wax in a minor portion of the total composition and filler and being vulcanized together, and a plastic, the amount of plastic being greater in the upper portion than in the lower portion, the upper surface being smooth and abrasion resistant and the lower surface being soft and conformable.

3. A gasket according, to claim 1 wherein the rubbery polymeric compound is selected from the group consisting of butadiene-acrylonitrile copolymer and butadienestyrene copolymer.

4. A gasket according to claim 2 wherein the plastic is present in one of the portions in amount about equal to that of the rubbery compound.

5. A gasket according to claim 2 wherein the plastic is polystyrene and is present in the upper portion only.

6. A gasket according to claim 2 wherein the plastic is vinyl chloride polymer.

7. A gasket according to claim 1 also containing natural rubber.

8. A gasket according to claim 2 wherein the rubber is selected from the group consisting of butadiene-acrylonitrile copolymer and butadiene-styrene copolymer and the plastic is polystyrene and is present in the upper portion only.

9. A gasket according to claim 2 wherein the rubber is selected from the group consisting of butadiene-acrylonitrile copolymer and butadiene-styrene copolymer and the plastic is vinyl chloride polymer.

10. A gasket according to claim 2 wherein the rubber is a mixture of a rubber selected from the group consisting of butadiene-acrylonitrile copolymer and butadienestyrene copolymer and natural rubber and the plastic is polystyrene and is present in the upper portion only.

11. The method of making a gasket provided with a passage and which comprises preparing layers each including essentially a rubbery polymeric compound, wax in a minor portion of the total composition and filler, and a plastic, the amount of plastic being greater in the upper portion than in the lower portion, superposing said layers in a mold with one of said layers which will produce a relatively hard composition upon vulcanization forming one surface, and another of said layers which upon vulcanization will produce a relatively softer conformable composition forming the other surface, curing said layers in the mold at a temperature of between about 280 F. and about 325 F. and a pressure of about 1000 pounds for from about twenty-five to thirty minutes, to thereby vulcanize the layers together into a unitary structure, removing the structure from the mold and immediately cooling the same, and forming a passage through the unitary structure.

References Cited in the file of this patent UNITED STATES PATENTS 1,367,231 Boyer Feb. 1, 1921 1,884,266 Russell Oct. 25, 1932 2,167,716 Harkins Aug. 1, 1939 2,201,576 Dempsey May 21, 1940 2,278,802 Sarbach Apr. 7, 1942 2,467,322 Lightbown et al Apr. 12, 1949 2,498,653 Daly Feb. 28, 1950 2,560,195 Smith et al. July 10, 1951 FOREIGN PATENTS 463,211 Canada Feb. 14, 1950

Claims (2)

1. A GASKET PROVIDED WITH A PASSAGE AND HAVING A RELATIVELY HARD UPPER PORTION AND A LOWER RELATIVELY SOFTER PORTION, SAID PORTIONS EACH INCLUDING ESSENTIALLY A RUBBERY POLYMERIC COMPOUND, WAX IN MINOR PORTION OF THE TOTAL COMPOSITION AND FILLER AND BEING VULCANIZED TOGETHER, THE UPPER SURFACE BEING SMOOTH AND ABRASION RESISTANT AND THE LOWER SURFACE BEING SOFT AND COMFORABLE.

11. THE METHOD OF MAKING A GASKET PROVIDED WITH A PASSAGE AND WHICH COMPRISES PREPARING LAYERS EACH INCLUDING ESSENTIALLY A RUBBERY POLYMERIC COMPOUND, WAX IN A MINOR PORTION OF THE TOTAL COMPOSITION AND FILLER, AND A PLASTIC, THE AMOUNT OF PLASTIC BEING GREATER IN THE UPPER PORTION THAN IN THE LOWER PORTION, SUPERPOSING SAID LAYERS IN A MOLD WITH ONE OF SAID LAYERS WHICH WILL PRODUCE A RELATIVELY HARD COMPOSITION UPON VULCANIZATION FORMING ONE SURFACE, AND ANOTHER OF SAID LAYERS WHICH UPON VULCANIZATION WILL PRODUCE A RELATIVELY SOFTER CONFORMABLE COMPOSITION FORMING THE OTHER SURFACE, CURING SAID LAYERS IN THE MOLD AT A TEMPERATURE OF BETWEEN ABOUT 280* F. AND ABOUT 325* F. AND A PRESSURE OF ABOUT 1000 POUNDS FOR FROM ABOUT TWENTY-FIVE TO THIRTY MINUTES, TO THEREBY VULCANIZE THE LAYERS TOGETHER INTO A UNITARY STRUCTURE, REMOVING THE STRUCTURE FROM THE MOLD AND IMMEDIATELY COOLING THE SAME, AND FORMING A PASSAGE THROUGH THE UNITARY STRUCTURE.

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