Valve device using an on-off functioning type electromagnetic actuator

Claim 1

A valve device comprising: a valve seat fixedly disposed in a port section of a fluid passage; a movable valve having a valve steam and which is seated on the valve seat to close the port section; an electromagnetically operated actuator for moving said valve to leave the valve seat thereby opening the port section; a return spring arranged to bias said valve to take the valve seat; and damping means for slowing up the movement of said valve towards the valve seat in opposition to the force of the return spring just before seating of said valve on the valve set so that said valve is gently seated on the valve seat, said damping means comprising: means for defining a chamber; a piston for braking the movement of said valve towards the valve seat just before seating of said valve thereon, said piston having a hole for passing a hydraulic fluid into said chamber and the hydraulic fluid out of said chamber, said hole having a relatively small diameter such that said hole limits the flow of hydraulic fluid passing therethrough, said piston being movable in opposite directions such that said piston increases the volume of said chamber to admit the hydraulic fluid into said chamber through said hole when said valve is moved away from the valve seat and that said piston decreases the volume of said chamber to compress the hydraulic fluid therein when said valve is moved towards the valve seat; said valve stem being constructed and arranged such that just before seating of said valve on the valve seat, said valve stem abuts against said piston so as to bias the same to decrease the volume of said chamber and the movement of said valve towards the valve seat is braked and slowed up by said piston compressing the hydraulic fluid in said chamber due to the action of said valve and forcing out the hydraulic fluid from said chamber through said hole at a limited flow rate.