US 3185595 A
Description (OCR text may contain errors)
May 25, 1965 R. l.. scHENK, JR
REINFoRcED CELL cLosuRE Original Filed Aug. 4. 1960 INVENTOR.
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3,185,595 REBNFORCED CELL CLOSU Raymond L. Schenk, lr., Minneapolis, Minn., assignor to i Union Carbide Corporation, a corporation of New York Continuation of application Ser. No. 47,408, Aug. 4, 1960. This application Apr. 24, 1963, Ser. No. 275,378
4 Claims. (Cl. 136-133) This application is a continuation of my application Serial No. 47,408, filed August 4, 1960, now abandoned, for Reinforced Cell Closure.
This invention relates to a cell closure for cylindrical galvanic cells and more particularly to a closure for cells which are 11A inches in diameter or greater.
United States patent application Serial No. 774,931, led November 19, 1958, in the name of R. Carmichael et al. and now U.S. Patent No. 3,069,489 discloses an excellent closure for cylindrical alkaline galvanic cells which is extremely resistant to caustic creepage. The disclosed cell closure comprises an annular gasket of a hard, di-electric, plastic-like material which is resistant to cold iiow and a metallic container cover, the gasket being interposed between the cell container wall and the edge of the cell cover in supporting relation with the cell cover. The actual sealing is effected by radially compressingvthemgasket between the container and the cell cover under a high radial force. After the compressive force is removed from the container, the gasket will exert a radial compressive force outwardly against the container Which is substantially equivalent to, but not greater than, the yield strength of the metal of which the container is made.
The term cold flow as used herein and in the appended claims refers to the gradual deformation of a material that occurs when that material is subjected to a constant load at room temperature. Materials which deform very little or only when large forces are applied and which do not continue to deform or creep when the force is applied for a considerable length of time are said to have good cold flow characteristics.
In the above cell closure, the tensile strength of the metal container, the cold flow characteristics of the plastic gasket and the resiliency of the metal cover are factors which affect the success of the closure. The radial seal is accomplished by the balance of the internal resilience of the cover exerting a pressure on the compressed plastic gasket and the metal container resisting this internal force. During the actual radial sealing of the cell by a sizing die of smaller diameter than the container, the metal cover springs or bows, the plastic compresses and flows, and the container yields, growing in length and reducing in diameter.
The ability of the container to maintain this new diameter by resisting the internal forces after the sizing operation is all important if the closure is to be eiective in preventing caustic creepage. The ability of the metal container to resist such deforming is dependent upon the modulus of elasticity of the metal of the container. It is known that the yield or permanent set increases in direct proportion to an increase in the diameter of the container when the wall thickness remains the same.
It' may thus be appreciated that an increase in the diameter of the container will reduce the total elastic resistance of the container, keeping a constant wall thickness, and that the greater the total area, the higher the pressure employed must be in sealing the container, and accordingly, some difficulties may be encountered in sealing large diameter cells with the above disclosed cell closure.
The principal object of the invention is to provide radially sealed galvanic cells of relatively large diameters.
A concurrent object of the invention is to provide means whereby radially sealed relatively large diameter cylindrical containers may resist deforming under the pressure p exerted by the compressed plastic gasket and the stress energy stored in the cover.
The objects of the invention are accomplished by a cylindrical galvanic cell wherein the cell closure comprises an annular gasket having a depending flange and which is made of a hard di-electric material which is resistant to cold iiow, interposed and radially sealed between the container wall and a metal cover, the rim of which is offset from the horizontal; the top of the outside of the container being provided with a metal reinforcement ring.
The invention will be more readily understood by reference to the accompanying drawing wherein:
vFIGURE l is a front sectional view of a cylindrical galvanic cell employing the cell closure of the invention prior to being radially compressed; and
FIG. 2 is a view of the cell of FIG. l after it has been radially sealed.
In the practice of the invention, the seal gasket must be made of a material which will not be attacked by the corrosive electrolyte ofthe cell and which has good dielectric properties as well, the gasket serving to insulate the positiveiy and negatively charged parts of the cell. Of course, the material must be one generally characterized by its high compressive and shear strength and one capable of withstanding large stresses without a tendency to cold low.
Nylon, a polymer of hexamethylene diammonium adipate, is a hard plastic composition that has been found to be a suitable material for use in practice of the invention. A nylon plastic sold under the trademark Zytel is the preferred material.
Referring now to the drawing, the cell closure of the invention comprises an annular hard nylon gasket 10, provided with a tapered depending flange 12 and a second ange 14 which isolates the oppositely charged parts of the cell; the gasket 10 being interposed and radially sealed between a metal cell container 16 and a metal cover 18 in such a manner that the depending flange 12 is within the cell container 16 and the second flange 14 is outside the cell container 16. In addition, a metal reinforcing ring 20, provided with an inward facing ange 22 and a dependent flange 24, is provided around the top of the container wall 16.
The cover 18 is provided with an integral terminal boss 26 which acts to impart resiliency to the cover 13. The cover 13 accordingly acts as a spring and exerts a backup pressure on the nylon gasket 10 after radial sealing and insures the continuance of a good seal. This quality of resiliency is especially important when the cell is subjected to changes in temperature, and expansion or contraction of the container 16 and reinforcement ring 26 result. ln cells in which the contraction or expansion is significant, changes in diameter are compensated for by the spring-like action of the cover 18. To further insure this spring-like action of the cover 18, the rim 2S of the cover 18 is offset at an angle A which is between 5 and 10 and preferably 7 from the horizontal. By forming the cover 18 in this manner, the contents of the cell, i.e., the negative electrode 30, the separator 32 and the positive electrode 34, support the cover 18 and prevent it from buckling when the radial pressure is applied during the sealing operation.
The actual radial sealing of the cell, as shown in FIG. 2, may be accomplished in a number of ways, a typical way being by pushing or forcing an assembled cell through a sizing die so that the ring 20 is reduced in diameter to the diameter of the unreinforced portion of the container 16 thereby causing a maximum radial seal compressive force to be exerted against the container 16. The deformation of the metal container 16 by the sizing operation is permanent for any spring back of the container 16 after passing through the sizing die is prevented by the reinforcement ring 20.
1. For sealing a galvanic cell which includes a cylindrical cupped metallic container containing an electrolyte, enclosing means comprising an annular hard plastic gasket which is resistant to cold ilow interposed between said container and a resiliently secured metallic cell cover; said gasket having a depending flange extending down inside of said container and a second iiange extending external of said container between said container and said cover; said cover being provided with an integral central terminal boss projecting upwardly and the rim of said cover being spaced radially outwardly from said boss and ottset upwardly from the horizontal at an angle of between and 10; and an external metal reinforcement ring encircling said container at its top, having a depending ange in direct contact with the outer periphery thereof and an inwardly facing ange adjacent said second ange on said gasket; said gasket being in a state of radial compression between said container and said cover and exerting a radial force substantially equivalent to but not greater than the yield strength of the metal of which said container and ring are made.
2. The enclosing means of claim 1 wherein said gasket is maderof hard nylon and said rim of said cover is oiset an angle of 7 from the horizontal.
3. A sealed galvanic cell comprising a cylindrical cupped metallic container having as internal elements therein a positive electrode, a negative electrode,` a'separator therebetween and an electrolyte, said cell being sealed at the open end of said cupped container by a closure which comprises an annular hard plastic gasket which is resistant to cold ow interposed between said container and a horizontally disposed resilient metallic cell cover of smaller diameter than said container; said gasket having a depending flange extending down inside of said container and a second flange extending axially external of said container which separates said container and said cover; said cover being supported by said internal cell elements and being provided with an integral central terminal boss which projects upwardly and the rim of said cover being offset upwardly from the horizontal at an angle of between 5 and 10; and an external metal reinforcement ring encircling said container at its top, having a depending ange in direct contact with the outer periphery thereof, and an inwardly facing flange in contact with said second ange on said gasket; said gasket being in a state of radial compression between said container and said cover rim and exerting a radial force substantially equivalent to, but not greater than, the yield strength of the metal of which said ring is made.
4. The sealed galvanic cell of claim 3 wherein said gasket is made of hard nylon, and said rim of said cover is offset an angle of approximately 7 from the horizontal.
References Cited by the Examiner UNITED STATES PATENTS Gelardin 136-133 JOHN H. MACK, Primary Examiner.