Automatic control circuit for an electrically powered hydraulic pump

In a vehicle having an engine, hydraulic control means actuated by hydraulic fluid under pressure, a main hydraulic pump driven by said engine to provide hydraulic fluid under pressure for actuating said control means, and an auxiliary hydraulic pump driven by an electric motor to provide hydraulic fluid under pressure for actuating said control means;

• an electrical control circuit for said electric motor comprising:
• a. a source of electrical power;
• b. a first solenoid operated relay having normally open contacts connected in series with said electric motor across said source of electrical power;
• c. a second solenoid operated relay having normally open contacts connected in series with the solenoid of said first solenoid operated relay across said source of electrical power;
• d. a third solenoid operated relay having normally open contacts;
• e. first switch means having normally closed contacts adapted to be automatically opened by a given fluid flow from said main hydraulic pump;
• f. second switch means having normally open contacts adapted to be automatically closed after said engine is in normal operation;
• and
• g. third switch means having normally closed contacts adapted to be manually opened;
• said normally closed contacts of said first switch means and the solenoid of said second solenoid operated relay being electrically connected in series with each other and with said normally open contacts of said second switch means across said source of electrical power, the solenoid of said third solenoid operated relay being electrically connected across said series connected normally closed contacts of said first switch means and solenoid of said second solenoid operated relay, said normally open contacts of said third solenoid operated relay being electrically connected in parallel with said normally open contacts of said second switch means, and said contacts of said third switch means being interposed between at least said solenoid of said third solenoid operated relay and said source of electrical power.