REDUCED ACTUATION TIME THERMAL RELAY SYSTEM

• US 3,858,141 A
• Filed: 12/03/1973
• Issued: 12/31/1974
• Est. Priority Date: 12/03/1973
• Status: Expired due to Term

• Current Assignee: Robert P. Lackey
• Original Assignee: Robert P. Lackey
• Inventors: Lackey, Robert P.
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Bell, Fred E.
• Application Number:
  US05/420,997
• Time in Patent Office: 393 Days
• Field of Search: 337/99,123,124,128,136,139,140 219/492
• US Class Current: 337/140
• CPC Class Codes: H01H 61/0107 making use of shape memory materials

Abstract

A reduced actuation time thermal relay system for controlling energization of a load by a power supply. The system comprises a thermal relay having a resistive control element and a pair of mating contacts movable between closed circuit and open circuit positions in response to the temperature of the control element rising above a predetermined level and falling substantially therebelow. The system also includes means for electrically energizing the resistive control element initially to apply a first voltage thereby to cause rapid heating of the element and thereafter to apply a second and reduced voltage to the element, the reduced voltage being of sufficient magnitude to prevent the temperature of the element from falling substantially below the predetermined level whereby the actuation time of the thermal relay is substantially reduced without damaging the resistive control element.

Claims

1. A reduced actuation time thermal relay system for controlling energization of a load by a power supply, said system comprising:

a thermal relay having a resistive control element and a pair of mating contacts movable between closed circuit and open circuit positions in response to the temperature of said control element rising above a predetermined level and falling substantially therebelow; and

means for electrically energizing said resistive control element initially to apply a first voltage thereby to cause rapid heating of the element and thereafter to apply a second and reduced voltage to said element, said reduced voltage being of sufficient magnitude to prevent the temperature of said element from falling substantially below said predetermined level whereby the actuation time of said thermal relay is substantially reduced without damaging said resistive control element.

2. A relay system as set forth in claim 1 wherein said resistive control element comprises a wire of a martensitic memory alloy.

3. A relay system as set forth in claim 2 in which the energizing means includes means for reducing tbe first voltage in response to initial movement of the contacts from one position to the other.

4. A relay system as set forth in claim 3 wherein the voltage reducing means includes means for preventing application of said second and reduced voltage to said control element until after initial movement of said contacts and means for terminating application of said first voltage to said control element after initial movement of said contacts.

5. A relay system as set forth in claim 4 in which said means for preventing application of the reduced voltage comprises a diode.

6. A relay system as set forth in claim 4 wherein said terminating means includes another contact of said relay adapted to be disengaged after initial movement of the said pair of contacts.

7. A relay system as set forth in claim 4 in which said energizing means further includes means for energizing said control element in response to the presence of a control signal and for deenergizing the control element when said control signal is absent.

8. A relay system as set forth in claim 7 wherein the means responsive to the control signal includes a transistor having its collector-emitter circuit serially connected with said control element across said first voltage and the control signal is applied to the base thereof.

9. A relay system as set forth in claim 2 in which the energization means includes means for reducing the first voltage in response to completion of contact movement from one position to the other.

10. A relay system as set forth in claim 9 wherein the voltage reduction means comprises means for simultaneously terminating application of the first voltage to the control element and applying said second voltage thereto upon completion of contact movement.

11. A relay system as set forth in claim 10 wherein said means terminating application of said first voltage comprises first and second diodes.

12. A relay system as set forth in claim 9 in which said energizing means further includes means for energizing said control element in response to the presence of a control signal and for deenergizing the control element in the absence thereof.

13. A relay system as set forth in claim 12 wherein the means responsive to the control signal incLudes a transistor having its collector-emitter circuit serially connected with said control element and the control signal is applied to the base thereof.

14. In a thermal relay system for controlling energization of a load by a power supply, said system including a thermal relay having a resistive control element and a pair of mating contacts movable between closed circuit and open circuit positions in response to the temperature of said control element rising above a predetermined level and falling substantially therebelow;

the improvement comprising means for electrically energizing said resistive control element initially to apply a first voltage thereby to cause rapid heating of the element and thereafter to apply a second and reduced voltage to said element, said reduced voltage being of sufficient magnitude to prevent the temperature of said element from falling substantially below said predetermined level whereby the actuation time of said thermal relay is substantially reduced without damaging said resistive control element.