PURPOSE: To enable the reduction of overall piston length and obtain a ball joint type piston device of sturdy construction and less expensive wherein an oil basin can be easily formed, by caulking a connection between the piston and the ball at a part other than the end of piston periphery.
CONSTITUTION: An escape 13a as contacting a spherical surface and used as an oil basin is provided inside of the caulking position of piston spherical part 11. In this spherical part 11 is inserted a ball 6 and oil is sealed. And one part 5a other than the end of the periphery of a piston 5 is made to form a plurality of caulking connections a all around said piston 5 or exceeding three positions. The positional relation of the piston 5 and the ball 6 is such that a contact position between the piston spherical part 11 and the ball 6 is so taken as to keep an angle θ at 20 degrees or more between a line C connecting the center of gravity b of the ball to a part of the piston spherical part 11, and another line d in parallel with piston top and passing said center of gravity b.
YAMAGUCHI YOJI
KAWAKAMI KOICHI
AKAZAWA KIYOSHI
TAKAGI HIROSHI
OSANO MOTOHIKO
TAKAHASHI AKIO
ISHIZAKI YOSHIKIMI
HIGASHIFUJI DENKI KK
TAKAKO SEIKI KK