Electro mechanical device

A solenoid is an electro mechanical device that converts electrical power into mechanical force and motion.

Directional spool valves may be either direct or pilot operated. Whether a valve is direct or pilot operated, primarily depends on the required operating force and hence the size of the valve.

Actuating or shifting the valve either spool, poppet or rotary is operated manually, electro-hydraulically, mechanically, hydraulically, pneumatically and electrically.

Electrical operation

This type of operation is the most common due to the automatic process required in the industry. The advantage of this is that the valves can be operated remotely by means of an electrical signal.

DCV spools is move into two or three positions, and the valves are 2/2, 3/2, 4/2 or 4/3 type.

Electro mechanical device trigger the spool

To shift the spool a valve actuator is use. Solenoid actuator operates many directional valves nowadays. A solenoid works by creating a magnetic field around a wire coil when an electric current is pass through it. Practically the magnetic field moves the metal armature into a desire position. When the current is off the magnetic field is no longer exist. The spool can then be return to its neutral position by a spring or by energizing a second solenoid at the opposite side of the valve spool.

For a 4/3 valve with open center illustrate below, when neither of the coils is energize, the spool will be keep in the center position by the spring fitted on either side.