Abstract: A cup seal includes a base portion disposed on a cylinder bore opening portion side of a seal groove, an inner circumferential lip portion extended from an inner circumferential side of the base portion toward a cylinder bore bottom portion and having an inner circumferential surface slidably abutting against an outer circumferential surface of a piston (plunger), and an outer circumferential lip portion extended from an outer circumferential side of the base portion toward the cylinder bore bottom portion and having an outer circumferential surface abutting against a seal groove bottom surface. The cup seal also includes an abutment surface and contact pressure adjustment surface.

Abstract: A cup seal 21 includes a base portion 21a disposed on a cylinder bore opening portion side of a seal groove, and an inner lip portion 21b extended from an inner circumferential side of the base portion toward a cylinder bore bottom portion and having an inner circumferential surface slidably abutting against an outer circumferential surface of a piston. In a state where the cup seal 21 is fitted into the seal groove and a plunger 19 is inserted into a cylinder bore 12, an abutting force maximum portion 21m where an abutting force against the plunger 19 becomes maximum within an inner circumferential surface of the cup seal 21 is provided on an end portion on the cylinder bore opening portion side of an inner circumferential surface part of the base portion 21a.

Abstract: A cup seal 21 includes a base portion 21a disposed on a cylinder bore opening portion side of a seal groove, an inner circumferential lip portion 21b extended from an inner circumferential side of the base portion toward a cylinder bore bottom portion and having an inner circumferential surface slidably abutting against an outer circumferential surface of a piston (plunger), and an outer circumferential lip portion 21c extended from an outer circumferential side of the base portion toward the cylinder bore bottom portion and having an outer circumferential surface abutting against a seal groove bottom surface.

Abstract: A cup seal 21 includes a base portion 21a, an inner circumferential lip 21b slidingly contactable with a plunger 19 and an outer circumferential lip 21c contactable with the bottom surface 26a of the seal groove 26. Further, on the cup seal 21, there are provided elastic projections 21d projecting from the outer circumferential side leading end of the inner circumferential lip 21b toward the cylinder hole bottom portion. The length of the cup seal 21 from the base end face 21e to the leading end portions 21f is set longer than axial length of the seal groove 26. When the cup seal 21 is fitted into the seal groove 26, force is imparted on the inner circumferential lip 21b toward the cylinder hole inner circumferential direction to energize the inner circumferential lip 21b toward the piston all the time.

Abstract: A cup seal 21 includes a base portion 21a disposed on a cylinder bore opening portion side of a seal groove, and an inner lip portion 21b extended from an inner circumferential side of the base portion toward a cylinder bore bottom portion and having an inner circumferential surface slidably abutting against an outer circumferential surface of a piston. In a state where the cup seal 21 is fitted into the seal groove and a plunger 19 is inserted into a cylinder bore 12, an abutting force maximum portion 21m where an abutting force against the plunger 19 becomes maximum within an inner circumferential surface of the cup seal 21 is provided on an end portion on the cylinder bore opening portion side of an inner circumferential surface part of the base portion 21a.

Abstract: A cup seal 21 includes a base portion 21a disposed on a cylinder bore opening portion side of a seal groove, an inner circumferential lip portion 21b extended from an inner circumferential side of the base portion toward a cylinder bore bottom portion and having an inner circumferential surface slidably abutting against an outer circumferential surface of a piston (plunger), and an outer circumferential lip portion 21c extended from an outer circumferential side of the base portion toward the cylinder bore bottom portion and having an outer circumferential surface abutting against a seal groove bottom surface.

Abstract: A cup seal 21 includes a base portion 21a, an inner circumferential lip 21b slidingly contactable with a plunger 19 and an outer circumferential lip 21c contactable with the bottom surface 26a of the seal groove 26. Further, on the cup seal 21, there are provided elastic projections 21d projecting from the outer circumferential side leading end of the inner circumferential lip 21b toward the cylinder hole bottom portion. The length of the cup seal 21 from the base end face 21e to the leading end portions 21f is set longer than axial length of the seal groove 26. When the cup seal 21 is fitted into the seal groove 26, force is imparted on the inner circumferential lip 21b toward the cylinder hole inner circumferential direction to energize the inner circumferential lip 21b toward the piston all the time.

Abstract: A reed switch unit 44 for detecting a liquid level in a reservoir 30 of a master cylinder which comprises a reed switch 11 including a contact part 14 which is sealingly contained in a glass tube 16, and lead portions 18, 18 which axially extend from opposite ends of the glass tube 16, and a unit body 45 provided with terminals 50 for respectively supporting the lead portions 18, 18 so as to be electrically connectable thereby to fix the reed switch 11. The lead portions 18 and the terminals 50 are connected with each other by means of a resistance welding. Accordingly, it is possible to provide a reed switch unit which is improved in quality as well as enhanced in productivity, by mounting a reed switch on a unit body without conducing soldering.