Abstract: A method for manufacturing a piston device, comprises the following steps. Processing a first raw material to form a piston with a top surface and a bottom surface. Processing a second raw material to have the diameter of said second raw material slightly larger than the diameter of said piston. Cutting the second raw material into a plural cylinders. Mounting the annular component on the top surface or the bottom surface through the convex portion. The durability and the life cycle of the piston device can be extended by mounting the annular component onto the piston.

Abstract: An automatic adjustment apparatus comprises a pulley having a spindle hole, an one-way bearing disposed in the spindle hole, a two-way bearing disposed in the spindle hole and located at a side of the one-way bearing, a sleeve and at least one constraint component. The sleeve is disposed in the one-way bearing and the two-way bearing, and a constraint portion is concaved at a side of the sleeve. The constraint component is mounted on the constraint portion for constraining the displacement of the pulley moving at the axial direction of the sleeve. Therefore, the pulley can glide at the sleeve so as to prevent inclination of the installing position of a belt at the pulley which results in rapid abrasion in belt and bad driving safety.

Abstract: An oil seal for preventing oil leakage and adapted to fit a shaft comprises an annular casing, a first seal component, a second seal component, a first seal lip and a second seal lip. The annular casing has a hole provided for the shaft passing through the annular casing. The first seal component is mounted on the annular casing. The second seal component is mounted on the annular casing and used for preventing a lubricating oil leaking from the first seal component. The first seal lip is disposed on the first side of the annular casing and used for preventing the lubricating oil leaking from the first side of the annular casing. The second seal lip is disposed on second side the annular casing, the second side is opposite to the first side, and the second seal lip used for preventing the dust from entering the oil seal.

Abstract: A piston device and its manufacturing method are disclosed. The piston device comprises a piston body having at least one annular groove on the side wall of the piston body, and at least one piston ring made of flexible material and mounted in the annular groove. The outer diameter of the piston ring mounted on in the annular groove is larger than the diameter of the piston body, so that the piston ring contacts with the inner wall but the piston body has no contact with the inner wall while the piston device moves reciprocally at the axial direction of the cylinder.

Abstract: The present invention discloses a piston device which is disposed in a cylinder. The cylinder has a chamber including a bore and an inner wall. The piston device comprises a piston body and at least an annular ring. The piston body has a top side and a bottom side, the diameter of the piston body is smaller than the bore, and either one of the top side or the bottom side has a convex portion. The annular ring is clamped to the top side or the bottom side by engaging said convex portion, and the annular ring has a diameter slightly larger than the diameter of the piston body. While said piston therein moves reciprocally at which the axial direction of the cylinder, the annular ring slides against the inner wall but the piston body has no contact with said inner wall.