Time delayed shut-down circuit for recirculation pump

• US 3,963,375 A
• Filed: 03/12/1974
• Issued: 06/15/1976
• Est. Priority Date: 03/12/1974
• Status: Expired due to Term

• Current Assignee: George C. Curtis
• Original Assignee: George C. Curtis
• Inventors: Curtis, George C.
• Primary Examiner(s): Freeh, William L.
• Assistant Examiner(s): La Pointe, G. P.
• Application Number:
  US05/450,300
• Time in Patent Office: 826 Days
• Field of Search: 417/12, 417/38, 417/44, 318/484
• US Class Current: 417/12
• CPC Class Codes: F04B 49/022 by means of pressure
• CPC Class Codes: F04B 49/06 Control using electricity regulating by means of floats actuating electric switches F04B49/04
• CPC Class Codes: H01H 7/00 Devices for introducing a predetermined time delay between the initiation of the switching operation and the opening or closing of the contacts time or time-programme switches H01H43/00

Abstract

A circuit is provided for shutting off the motor of an intermittently activated, electrically powered fluid recirculation pump to prevent the pump motor from burning out its windings or bearings. A power control relay is energized to activate the pump motor for a predetermined period of time, allowing the pump to reach steady state flow condition, after which a time delay relay opens and current flows to the power control relay through a pressure switch. The pressure switch opens to shut-off the recirculation pump motor whenever the pump discharge pressure falls below a predetermined minimum.

Claims

1. A circuit for controlling the application of electrical power to a pump motor, comprising

a plurality of electrical conductors adapted to be connected to an electrical pump motor for applying electrical power thereto,

a first relay having a pair of cooperating contacts in at least one of said conductors for controlling the flow of current therethrough,

a second relay having a coil connected between two of said conductors, said second relay thereby being actuated upon the application of an electrical potential between said two conductors,

one end of the coil of said first relay being connected to a first of said two conductors and the other end thereof being connected to a first fixed contact of said second relay, said other end of said coil of said first relay also being connected to a second fixed contact of said second relay through a pressure-sensitive switch adapted to sense the output pressure of a pump driven by such motor, said pressure-sensitive switch being adapted to open and interrupt the connection between said first relay coil and said second fixed contact of said second relay for sensed pressures less than a predetermined minimum, and

a movable contact on said second relay connected to a second of said two conductors and contacting said first fixed contact when said second relay is first actuated, said second relay being adapted to return to a de-energized condition upon the expiration of a predetermined period of time, moving said movable contact into contact with said second fixed contact,

whereby energization of an associated pump motor is assured for a predetermined period of time irrespective of the output pressure of the associated pump, after which period of time the pump motor will be de-energized when such output pressure drops below a predetermined level.