Abstract: A constant pressure valve includes a lock rod, a valve sleeve, a sliding shaft, a biasing unit, and a solenoid unit. The lock rod is formed with a first through hole. The valve sleeve is inserted fixedly into the lock rod, and includes an outer sleeve surface having a shrunk surface portion cooperating with the lock rod to define an annular space in fluid communication with the first through hole. The sliding shaft is movable in the valve sleeve to contact the lock rod, and includes a large-diameter section and a small-diameter section. The constant pressure valve is adapted to maintain a hydraulic device at a preset pressure. The less a difference between the diameters of the large-diameter section and the small-diameter section is, the more the preset pressure can be.

Abstract: A constant pressure valve includes a lock rod, a valve sleeve, a sliding shaft, a biasing unit, and a solenoid unit. The lock rod is formed with a first through hole. The valve sleeve is inserted fixedly into the lock rod, and includes an outer sleeve surface having a shrunk surface portion cooperating with the lock rod to define an annular space in fluid communication with the first through hole. The sliding shaft is movable in the valve sleeve to contact the lock rod, and includes a large-diameter section and a small-diameter section. The constant pressure valve is adapted to maintain a hydraulic device at a preset pressure. The less a difference between the diameters of the large-diameter section and the small-diameter section is, the more the preset pressure can be.