Constant volume seal-free reciprocating pump

Claim 1

An electromagnetic reciprocating pump for handling biomedical fluids, gases, mixtures of gases and fluids and the like under sterile conditions free of contamination, said pump comprising a vertically oriented hollow elongate cylinder having a check valve at the lower extremity thereof, a tubular elongate piston slidably positioned in said cylinder for vertical movement therein, a magnetic component fixedly attached to said piston for movement therewith, a solenoid coil surrounding the outside of said cylinder in close proximity thereto for producing an external magnetic field, said solenoid coil being positioned immediately above the magnetic component attached to said piston to cause upward movement of said piston by attracting the magnetic component attached thereto, valve means located in said piston for controlling the flow of fluids through said pump in response to cyclic applications of the magnetic field thereto, and a power supply for alternately energizing and deenergizing the solenoid coil producing the external magnetic field including a serially connected transformer and full wave rectifier, a Zener diode connected across said rectifier, a timer operating in the astable mode powered by said power supply, and a relay controlled by the output of said timer for momentarily connecting said power supply to the solenoid coil, such that said piston is caused to move upward in response to magnetic attraction of said magnetic component by the external magnetic field and to move downward under the influence of gravity when the magnetic field is deenergized.