Abstract: There is provided a seal apparatus for sealing against a rod, comprising a double seal including a rod seal and an O-ring which serves as a back-up ring for the rod seal. The double seal is provided in an annular groove formed on an inner circumferential surface of a rod guide which guides a sliding motion of the rod. An annular partition wall extends from the rod guide so that a force applied to the rod seal from the O-ring is shared between the rod seal and the partition wall. An annular protrusion is formed on a front end surface of the partition wall, so that when the rod seal is pressed with a large force toward the low-pressure side, the protrusion bites into a stepped surface of the rod seal and a front end surface of the rod seal is brought into contact with a low-pressure-side seal-bearing surface of the rod guide. The force applied to the rod seal is distributed to two sites.

Abstract: A cylinder apparatus including a piston slidably fitted in a cylinder having a hydraulic fluid sealed therein. A piston rod is connected at one end thereof to the piston. The other end portion of the piston rod extends as far as the outside of the cylinder through a seal block fitted to an open end portion of the cylinder. The seal block retains a double seal including a rod seal that is in sliding contact with the piston rod and an O-ring that resiliently biases the rod seal toward the piston rod. The seal block is provided with a projection extending between the O-ring and the rod seal to bear a part of biasing force applied to the rod seal from the O-ring. The projection is provided at a side of the O-ring and rod seal which is remote from the piston.

Abstract: A hydraulic shock absorber has a case that includes an oil chamber, a cylinder and a reservoir chamber inside the case. A piston connected to a piston rod is fitted into the cylinder. A pump rod is fitted into a pump tube located inside the piston rod for forming a pump chamber. The pump chamber is communicated with an oil chamber through an oil passage and with a cylinder upper chamber through another oil passage. The motion of the pump rod caused by extension and retraction of the piston rod allows oil to flow from the oil chamber to the pump chamber and then to the cylinder upper chamber for extending the piston rod. When a vehicle height is increased to a normal height, cut-outs formed in the pump rod serve to communicate the pump chamber with the cylinder upper chamber for stopping the extension of the piston rod. When it becomes higher than the normal height, an orifice passage serves to relieve oil of the cylinder upper chamber to the oil chamber for lowering the vehicle height.

Abstract: A hydraulically adjustable suspension apparatus for an automobile has a proportional type of solenoid operated valve assembly for controlling the pressure or flow rate of a pressurized fluid introduced into a cylinder tube through a fluid passage. The fluid passage is formed in a piston rod so as to communicate a cylinder tube with a hydraulic control circuit. The solenoid operated valve assembly is integrally attached to either the piston rod or the cylinder tube outside of the cylinder tube.

Abstract: A vehicle height control system has oil under pressure generated by a pump, the oil being charged into and discharged from a cylinder that is provided for each wheel through a charge-discharge valve. This action effects vehicle height control. The control system includes a gas spring that has two gas chambers and is connected to the cylinder. A pilot-controlled directional control valve has a pilot chamber and is provided on the gas spring so as to selectively communicate and cut off from each other the gas chambers. The directional control valve is drivable in response to charging and discharging of oil under pressure through a pilot line which is connected at one end thereof to the pilot chamber of the directional control valve and at the other end thereof to a passage connecting the charge-discharge valve and the pump.

Abstract: A compact vehicle height control system is capable of changing the spring constant of gas springs to thereby control the vehicle attitude stabilizing characteristics so as to provide a comfortable vehicle ride. Pilot-controlled directional control valves are interposed in passages that connect first and second gas springs in parallel. When the pilot-controlled directional control valves are opened, the first and second gas springs are communicated with respective cylinders in parallel, whereas, when the directional control valves are closed, only the first gas springs are communicated with the cylinders, thereby changing the spring constant. The pilot-controlled directional control valves are hydraulically operable, thereby eliminating solenoid operated valves.