| 摘要 |
<p>A two-way pressure-control valve has a housing formed with an axially extending bore adjacent whose front end opens a front port and adjacent whose rear end opens a rear port. A valve body is slidable in the bore between the rear port and the front end and a piston is slidable in the bore between the rear end and the rear port. Thus the valve body can slide across the front port and block fluid flow between the ports via the bore, and the valve body and the piston define a front compartment, a middle compartment always connected to the rear port and connectable to the front port when the valve body is moved forwardly, and a rear compartment. A passage is formed in the housing for connecting the front port to the rear compartment so that the pressure in the middle and rear ports is always effective across the piston. In addition the valve body is formed with an axially through-going small-diameter orifice that allows pressurization of the front compartment to the same pressure as the middle compartment. The front compartment is connected to the front port via a pilot valve that opens when a predetermined pressure differential is exceeded. Finally a spring biases the valve body rearwardly into a position blocking the front port. Such a valve opens whenever the pressure in either of the ports exceeds the pressure in the other port by a predetermined pressure differential.</p> |
