Heat motor operated load regulating switch assembly

• US 5,847,636 A
• Filed: 02/07/1997
• Issued: 12/08/1998
• Est. Priority Date: 02/07/1997
• Status: Expired due to Term

• Current Assignee: Robertshaw US Holding Corp.
• Original Assignee: Ranco Incorporated of Delaware (Schneider Electric SE)
• Inventors: Sehlhorst, Scott B.
• Primary Examiner(s): Phillips, Michael W.
• Assistant Examiner(s): Vortman, Anatoly
• Application Number:
  US08/797,531
• Time in Patent Office: 669 Days
• Field of Search: 337/37, 337/38, 337/39, 337/41, 337/51, 337/52, 337/53, 337/83, 337/93, 337/94, 337/82, 337/57, 337/106, 337/103, 337/105, 337/107, 337/101, 337/104, 337/113, 337/333, 337/337, 337/324, 337/348, 337/377, 337/380, 337/342, 337/394, 219/511
• US Class Current: 337/303
• CPC Class Codes: H01H 37/14 by anticipatory electric heater
• CPC Class Codes: H01H 37/18 by varying bias on the thermal element due to a separate spring
• CPC Class Codes: H01H 37/32 Thermally-sensitive members
• CPC Class Codes: H01H 61/013 Heating arrangements for operating relays
• CPC Class Codes: H01H 61/063 making use of a bimetallic element
• CPC Class Codes: H01H 89/04 Combination of a thermally actuated switch with a manually operated switch
• CPC Class Codes: H05B 1/0213 using bimetallic elements

Abstract

A user adjustable switching controller for duty cycle regulating flow of current to an electrical load such as a resistance heater, particularly for cooking appliances. A load current switch, when closed by a user operated cam also energizes a heat motor which includes a resistive strip attached to one active leg of a U-shaped bi-metal member. The load current switch snap spring is attached to the heated leg of the bi-metal. The other leg of the U-shaped bi-metal is anchored to one of the load connecting stationary terminals and serves to provide ambient temperature compensation. User rotation of the cam deflects a bias spring which acts on the portion of the bi-metal attached to the load switch snap spring to effect closing of the load current switch and energization of the heat motor. Heating of the bi-metal causes warpage which overcomes the bias spring to open the load switch and shut off the heat motor. Cooling of the bi-metal allows the load current switch to re-close repeating the cycle. User adjustment of the cam varies the bias on the snap spring and thus the re-open point of the switch with respect to the cycle, thereby varying the ratio of "on" to "off" time of the load current.

Claims

1. A controller for duty cycling or regulating first and second electrical loads comprising:

(a) a housing structure;

(b) a switching structure associated with said housing structure and including a moveable switch member, operable upon movement to effect snap-action making and breaking of a first set of electrical contacts;

(c) a cam means operable upon user movement thereof to effect said movement of said switch member for said first set;

(d) a heat motor operative upon connection to a source of power to effect cycling of said movement of said switch member for said first set when said cam means has effected said member movement for making said first set of contacts, wherein said first set of electrical contacts is connected with said heat motor means and a first electric load and wherein a second set of contacts is also connected with said first electrical load and said power source;

(e) a third set of contacts series connected with a second electrical load and said second set of contacts; and

,

(f) said second and third sets of contacts are operated by said cam means.

2. The assembly defined in claim 1, wherein said switching structure includes an operator member having U-shaped configuration with an end of one leg of said U-shape anchored to said housing structure with said operator member extending in cantilever therefrom with a second leg of said U-shape operatively connected to said moveable switch member.

3. The assembly defined in claim 1, wherein said moveable member includes an integrally formed blade spring loaded in longitudinal compression for effecting said snap-action.

4. The assembly defined in claim 1, wherein said moveable member includes an integrally formed blade spring operative upon said movement to undergo over-center movement for effecting said snap-action;

and, said heat motor is operative upon energization to cause said over-center movement for effecting breaking of said first set of contacts.

5. The controller defined in claim 1, further comprising a fourth set of contacts series connected between an auxiliary load and a power supply, said fourth set of contacts being actuated by said cam means.

6. The controller defined in claim 1, wherein said first set of contacts includes a snap-acting blade spring member;

and, said cam means is operative to contact said second end of said U-shaped operator member for effecting cam actuation of said first set of contacts.

7. A heat motor operated regulating switch assembly comprising:

(a) a base member having a projection extending therefrom;

(b) a bi-metal member having a U-shaped configuration and having an end of a first leg of said U-shape attached to said base member and extending in cantilever therefrom;

(c) a heater attached to said bi-metal member and operable upon electrical energization to effect warping of said bi-metal;

(d) a moveable contact member having a blade spring integrally formed therewith and extending from a first end thereof toward a second end distal said first end, said contact member having said second end registered on said base projection and having said blade spring having first portions connected to a second end of said bi-metal distal said bi-metal first end, said bi-metal having second portions connected intermediate the ends of said contact member, wherein said blade spring is placed in compression;

and, upon over-center movement thereof said blade spring effects a snap-action movement of said contact member wherein said first end of said contact member includes structure which functions as a moveable electrical contact; and

,

(e) a stationary contact disposed adjacent said moveable contact structure wherein, upon energization of said heater, said bi-metal moves said blade spring over-center and effects snap-actuation of said contact member in one direction, and upon de-energization of said heater, said bi-metal cools and effects snap-actuation of said contact member in a direction opposite said one direction.

8. The switch assembly defined in claim 7, wherein said heater comprises resistive material disposed on the surface of said bi-metal member with said resistive material electrically connected to said blade spring.

9. The switch assembly defined in claim 7, wherein said bi-metal has a flat plate configuration with a flange portion thereof at right angles thereto with said flange portion attached to said blade spring.

10. The switch assembly defined in claim 7, wherein said contact blade member has an elongated channel shaped configuration with said spring formed integrally int eh web of said channel configuration.

11. The switch assembly defined in claim 7, wherein said blade spring is attached to said bi-metal member by weldment.

12. The switch assembly defined in claim 7, wherein said bi-metal member is attached to said base by weldment.

13. The switch assembly defined in claim 7, wherein said moveable contact structure has a noble metal contact attached thereto.

14. The switch assembly defined in claim 7, wherein said moveable contact is electrically series connected with said heater.

15. The switch assembly defined in claim 7, wherein said spring has an end thereof contacting said heater for electrically connecting said moveable contact member therewith.

16. The switch assembly defined in claim 7, wherein said blade spring has a L-shaped configuration with an end portion of said L-shape connected to said bi-metal member.

17. The switch assembly defined in claim 7, further comprising an ambient temperature compensator attached to said bi-metal member.

18. The switch assembly defined in claim 7, wherein said bi-metal member includes an active portion heated by said heater and an ambient temperature compensation portion not heated by said heater.

19. The switch assembly defined in claim 7, wherein said bi-metal member has one leg of said U-shape forming an active leg with said heater attached thereto and with the other leg of said U-shape being unheated and comprising an ambient temperature compensating element.

20. An electrical load cycling switch assembly comprising:

(a) a housing structure having first and second line power connecting terminals and first, second and third load connecting terminals thereon;

(b) a user operated cam mounted for rotation on said housing structure;

(c) a first switch assembly including a spring member and a moveable contact member mounted on said housing, with a portion thereof comprising said first load connecting terminal (H1), said first switch operative for making and breaking a circuit with said first line power connecting terminal (L1);

(d) a cam follower operable upon user rotation of said cam for effecting a variable bias on said first switch assembly spring member;

(e) a second switch associated with said housing and having one side connected to said second load connection terminal (L2) and a moveable member operative to contact said cam for user actuation thereof in response to user rotation of said cam, wherein said second switch a second side connected to one side of a third switch, said third switch having the other side thereof connected to said second load connecting terminal (H2), wherein said variable bias is operative actuate said switch to the closed condition; and

, said first switch includes a bi-metal actuator including a heat motor energized upon closing of said first switch for effecting warping of said bi-metal member and opening of said first switch causing said heat motor to be de-energized;

whereupon said bi-metal member cools effecting redosing of said first switch.

21. The switch assembly defined in claim 20 said second and third switches have one side thereof formed on a common member.