SEAL PART STRUCTURE OF PRESSURE SWITCH

PROBLEM TO BE SOLVED: To prevent deformation of a ring-shaped sealing member to seal a pressure switch in its gap between a diaphragm and a joint confronting it. SOLUTION: A square ring 23 is installed in minor diameteric part 21b of a joint 21, whose major diameteric part 21a is put externally on a switch box 3 in its peripheral surface portion nearer the open end face 3c, and a thin wall part 21g is folded and caulked along a protruded part 3d on the switch box 3 so that the joint 21 is attached externally fast to the box 3, and a diaphragm 19 is held pinchedly by the open and face 3c of the switch box 3 and the square ring 23, wherein a groove 3g is formed in the protrusion 3d, and the gap S3 between the square ring 23 and the minor diameteric part 21b of the joint 21 and/or the gap S5 between the protrusion 3d and the thin wall part 21g of the joint 21 is/are put in communication with the outside of the box 3 through a gap S7 formed between the thin wall part 21g and that part of protrusion 3d where the groove 3g is provided.