Today in 1981, US Patent 4255457 A was issued, an invention of George J. Collias, assigned to the Kepros-Ganes Company, for his “Method and Apparatus for Preventing Buckle of Beer Cans During Pasteurization.” Here’s the Abstract:

A method is described for preventing buckling of beer-can tops and bottoms during pasteurization of the beer. Prior to the pasteurization, an anti-buckle ring is mated with each beer can such that the ring captures the base portion of the can’s bottom. The ring permits the bottom’s panel to bulge outwardly while preventing radial displacement of the bottom’s base area and, hence, buckling of the can bottom, when the heat applied during pasteurization causes the internal pressure of the can to increase. To prevent buckle of the beer can’s top, another anti-buckle ring may be mated with the top of the can such that the latter ring captures the double-seam area on the top of the can to prevent radial displacement at key points of the top. After pasteurization, both rings are automatically removed from the can for use with another can.