Whisper quiet electromagnetic fluid pump

In combination with an electromagnetic fluid pump having a magnetically susceptible piston disposed in a non-magnetic piston guide, an inlet port provided at an opposite end of said piston guide and an outlet port provided at the other end of said piston guide, a solenoid coil circumscribing said piston guide, a detection coil magnetically coupled to said solenoid coil, an oscillator responsive to the signal induced in said detection coil by said solenoid coil to periodically energize said solenoid coil to produce a magnetic field displacing said piston to a first position adjacent to said inlet port, resilient means for displacing said piston to a second position adjacent to said outlet port, and valve means for providing unidirectional flow of fluid from said inlet port through said outlet port as said piston travels from said first position towards said second position, an improvement comprising:

• an annular rubber bumper disposed between said outlet port and said opposite end of said piston guide;
• and
• a semi-rigid annular plastic washer disposed between said annular rubber bumper and said piston, said semi-rigid annular plastic washer applying a uniform compressive force on said annular rubber bumper as said piston approaches said second position whereby any hammering noise associated with the impact of said semi-rigid annular plastic washer by said piston as said means for reciprocating said piston moves said piston from said first position to said second position is absorbed by said resilient annular bumper.

An electromagnetic fluid pump comprising:

• a housing having an inlet port, an outlet port, and a cylindrically shaped piston guide disposed between said inlet port and said outlet port;
• a piston disposed in said cylindrically shaped piston guide, said piston being reciprocal between a first position adjacent said outlet port and a second position adjacent said inlet port;
• a solenoid coil operative to generate a magnetic field displacing said piston from said first position to said second position;
• a detection coil magnetically linked to said solenoid coil to generate a control signal;
• blocking oscillator means for periodically energizing said solenoid coil to generate said magnetic field in response to said control signal;
• resilient means for displacing said piston from said second position to said first position;
• valve means for providing a uniform fluid flow through said electromagnetic fluid pump in response to the reciprocation of said piston in said cylindrically shaped piston guide, said valve means being mounted to said piston;
• a resilient annular rubber bumper disposed in said housing adjacent to said outlet port;
• and
• a semi-rigid annular plastic washer disposed in said housing between said resilient annular rubber bumper and said piston, said semi-rigid annular plastic washer being displaced by said piston as said piston approaches said second position and applying a uniform compressive force on said resilient annular rubber bumper to noiselessly terminate the displacement of said piston at said second position whereby any hammering noise associated with the impact of said semi-rigid annular plastic washer by said piston as said piston moves from said first position to said second position is absorbed by said resilient annular rubber bumper.