Patent ID: 6186043
Filing Date: 2001-02-13
Classification: F15B

Abstract:
A hydraulic cylinder comprising:a cylindrical tube having an inside wall;a piston having a rod attached thereto is slidably received in the cylindrical tube and defines a piston side and a rod side of the hydraulic cylinder, the piston is provided with first and second circumferential seals that engage the inside wall of the cylindrical tube and prevent the longitudinal flow of fluid between the piston and the inside wall of the tube, the piston is also provided with a bore having a first passage that is provided with a passage orifice which is in fluid communication with one of the piston side and the rod side of the hydraulic cylinder wherein the bore extends radially inward from the inside wall of the cylindrical tube and the first passage extends longitudinally from the bore, the piston is provided with a longitudinally extending cavity adjacent to the inside wall of the tube, the longitudinally extending cavity communicates with the bore which extends radially inward from the cavity, the bore is provided with a second passage that is parallel to the first passage and extends longitudinally between the bore and one of the piston side and the rod side of the hydraulic cylinder;a piston side end cap for sealing the piston side of the hydraulic cylinder;a rod side end cap through which the rod passes for sealing the rod side of the hydraulic cylinder;a port for exhausting fluid from the tube, the port being in fluid communication with first and second metering orifices formed in the cylindrical tube longitudinally spaced from one another, wherein movement of the piston in the tube causes the first circumferential seal to cover the first metering orifice in the cylindrical tube preventing the passage of fluid through the first metering orifice while the second metering orifice remains open, further movement of the piston allows the first circumferential seal to reopen the first metering orifice and subsequently closes the second metering orifice preventing the flow of fluid through the second metering orifice, fluid can then pass through the passage orifice into the now open first metering orifice.