Bernhard Steiner, Rudolf Scheidl, Gudrun Hametner,
"Development of an ultra fast emergency stop valve"
: Proceedings of the 18th International Conference on Hydraulics and Pneumatics, Vol. 1, Seite(n) 214-223, 2003, ISBN: 80-02-01567-3
Development of an ultra fast emergency stop valve
Sprache des Titels:
Proceedings of the 18th International Conference on Hydraulics and Pneumatics
The paper describes the conceptual design, simulation, and experimental results of a 2/2-way-poppet-valve with an integrated pilot valve and an additional metering edge in the cartridge element. The principal requirements for the valve are: High flow rate and a response time less than 2 ms.
The basic idea is to use a 2/2-way-cartridge-valve for the main stage and a closely integrated pilot valve, in order to reduce the hydraulic capacitance. Standard 2/2-way-cartridge-valves have a very high nominal flow rate, but they are too slow. The pilot valve is a normally open 2/2-way-seat-valve with a solenoid actuation. The nominal flow rate of the pilot valve is very small, due to the short stroke of the solenoid. The actuation force of the solenoid will be controlled by a pulse width modulated voltage signal. This technology allows to switch off the current of the solenoid very quickly.
In this combination the cartridge valve and the pilot valve do not meet the required response dynamics. Therefore, an additional positive feedback metering edge was integrated in the poppet of the cartridge element. The flow rate of this edge is very high. If the poppet opens, the positive feedback edge opens as well and the oil from the back side of the cartridge valve deflates very quickly. As a result of the fast pressure reduction at its back side the poppet opens in a very short time.
The emergency stop valve is used to immediately release the pressure of a hydraulic cylinder. It is directly mounted on the top of this cylinder and the outlet port is directly connected to a low pressure reservoir. The advantage of this design is the minimised hydraulic inductivity, a prerequisite for the intended fast pressure release.
This valve provides much faster response than conventional cartridge valves at the cost of an increased leakage at the positive feedback metering edge.
Keywords: 2/2-way-poppet-valve, integrated pilot valve, positive feedback metering edge