Control system for superhigh pressure generation circuit

Claim 1

A control system for a superhigh pressure generation circuit, comprising: a pressure setting unit which produces an electric signal representing a preselected pressure; an electrohydraulic servo valve for controlling an amount of fluid supply from a hydraulic fluid source in response to an output signal of the pressure setting unit; a boost cylinder having a primary cylinder, a secondary cylinder integral with the primary cylinder and a stepped piston including a first piston portion and a second piston portion, said boost cylinder being constructed to generate a high fluid pressure in the secondary cylinder in response to fluid admitted into the primary cylinder from the servo valve in accordance with the ratio in effective sectional area between the first and second piston portions; an amplifier valve receiving a controlled flow of fluid from the servo valve as a pilot flow and delivering a larger flow rate of fluid from the fluid source in proportion to the pilot flow, the primary cylinder of the boost cylinder being supplied with a controlled fluid flow from the amplifier valve; a high pressure supply line into which the generated high pressure is introduced, a pressure sensor sensitive to the fluid pressure in said high pressure supply line, said pressure sensor being constructed to feed the sensed pressure back to the servo valve; a high pressure relief valve disposed in a line which branches off the high pressure supply line into hydraulic connection with a reservoir, said high pressure relief valve being opened in response to an output signal of the sequence circuit when the fluid pressure in the high pressure supply line is elevated to an unusual level; a shut-off valve disposed in said high pressure line, a suction line for supplying a fluid supply to said secondary cylinder, a suction valve in said supply line, and a sequence circuit which, when the piston in the boost cylinder reaches an end of a forward or inward stroke thereof, closes the shut-off valve disposed in the high pressure supply line and so switches the fluid pressure in the primary cylinder as to return the piston back to an initial position thereof, said sequence circuit also opening said suction valve in said supply line after said shut-off valve is closed to admit fluid supply to said secondary cylinder as said piston returns back to said initial position.