Transient resistant transistorized blocking oscillator for switching inductive loads

Claim 2

A reciprocating electromagnetic device powered by an electrical source comprising: a reciprocating means; a transistor having an emitter, a base and a collector; a solenoid having first and second terminals connected by its first terminal to the emitter and by its second terminal to the electrical source, and magnetically linked to the reciprocating means, said transistor controlling the current flow from the electrical source through the solenoid; biasing means, including a detection coil means magnetically linked to the solenoid and connected between the emitter and base circuit means of the transistor, responsive to increasing and decreasing solenoid current for respectively biasing the transistor toward saturation and cutoff; and means of controllably dissipating energy released by the solenoid during collapse of its magnetic field; said means comprising a serially connected combination of a resistor and a rectifier interconnecting the base of the transistor with the second terminal of the solenoid, the rectifier biased to pass electrical current from the base of the transistor to the second terminal of the solenoid, said means operative to cause the initial stages of collapse of the solenoid field to generate current which prevents transistor cutoff for a brief interval.

Claim 3

A device as described in claim 1, additionally comprising control means for limiting the initial transistor cutoff bias thereby controlling transistor cutoff, so that a reverse voltage induced in the solenoid by its collapsing magnetic field is limited by controlling the rate of collapse.

Claim 4

A device as described in claim 1, wherein the biasing means comprises: a coil magnetically linked to the solenoid by the reciprocating means and connected to the emitter and base; and a first resistor connected to the base and the collector.

Claim 5

A device as described in claim 3, wherein the biasing means additionally comprises a resistor in series with the coil.

Claim 6

A device as described in claim 2, wherein the control means comprises a resistor connected between the base and the biasing means.

Claim 7

A dEvice as described in claim 3, additionally comprising a second resistor interposed between the base and a connection between the coil and the first resistor.

Claim 8

A device as described in claim 6, additionally comprising a third resistor interposed between the coil and the first and second resistors.

Claim 9

A device as described in claim 7, wherein the energy dissipating means comprises: a fourth resistor; and a rectifier connected in series with the fourth resistor, said series connected in shunt relationship with the solenoid and coil so that energy released by the solenoid during collapse of its magnetic field is controllably dissipated.

Claim 10

A device as described in claim 1, additionally comprising a rectifier having a cathode connected to the emitter and an anode connected to the base to limit reverse base to emitter voltage.

Claim 11

A device as described in claim 9, additionally including a capacitor between the emitter and collector.

Claim 12

A device as described in claim 1, additionally comprising: a resistor connected between the energy-dissipating means and the solenoid; and a rectifier having a cathode connected to a connection between that last-mentioned resistor and the energy dissipating means and an anode connected to the emitter.

Claim 13

A device as described in claim 1, wherein the reciprocating means is a plunger in a fluid pump.

Claim 14

A device as described in claim 12, additionally comprising: a hollow guide means positioned coaxially within the solenoid and having a fluid inlet and a fluid outlet, the plunger being slideably disposed in said guide member for reciprocal movement; and a check valve means for allowing fluid flow in one direction only that being from the fluid inlet to the fluid outlet.

Claim 15

A device as described in claim 1, additionally comprising: a rectifier having a cathode connected to the solenoid and an anode connected to the energy-dissipating means; and a resistor connected between the anode of the last-mentioned diode and the emitter of the transistor.

Claim 16

A circuit for actuating a movable member, connectable to a source of energy comprising: main inductive means having a first terminal and a second terminal, adapted when energized by the source to cause movement of the movable member; transistor means, having a base electrode, a collector electrode and an emitter electrode, connected by said emitter electrode to said first terminal of said inductive means and adapted to control current flow therethrough; first resistive means interconnecting said base electrode and the source of energy; direction means connected in series relationship with said main inductive means and interconnecting said emitter electrode and said first resistive means; said first resistive means responsive to the current in said main inductive means reaching the saturation level operative to cause said transistor means to become less conductive, whereby current flow through said main inductive means tends to decrease; and means, including serially connected second resistive means and diode means interconnecting said first resistive means and said second terminal, cooperative with said first resistive means and said detection means to maintain, for a brief period of time, a reduced level of conduction in said transistor means whereby a large portion of the energy stored in said main inductive means is dissipated through said transistor means and to thereafter drive said transistor means to cutoff.

Claim 17

A circuit for actuating a movable member, connectable to a source of energy comprising: main inductive means having a first terminal and a second terminal, adapted when energized by the source to cause movement of the movable member; transistor means, having a base electrode, a collector electrode and an emitter electrode, connected by said emitter electrode to said first terminal of said inductive means and adapted to control current flow therethrough; first resistive means interconnecting said base electrode and the source of energy; direction means connected in series relationship with said main inductive means and interconnecting said emitter electrode and said first resistive means; said first resistive means responsive to the current in said main inductive means reaching the saturation level operative to cause said transistor means to become less conductive, whereby current flow through said main inductive means tends to decrease; and means, including serially connected second resistive means and diode means interconnecting said first resistive means and said second terminal, cooperative with said first resistive means and said detection means to maintain, for a brief period of time, a reduced level of conduction in said transistor means whereby a large portion of the energy stored in said main inductive means is dissipated through said transistor means and to thereafter drive said transistor means to cutoff.

Claim 18

The circuit as claimed in claim 15 wherein said diode is arranged, and said main inductive means and detection means are coils and are magnetically linked so that said diode is blocked when current flow through said main inductive means is increased and to be conductive when current flow through said main inductive means is decreasing.