THERMALLY RESPONSIVE SWITCH

• US 20090315666A1
• Filed: 08/08/2007
• Published: 12/24/2009
• Est. Priority Date: 08/10/2006
• Status: Active Grant

• Current Assignee: Ubukata Industries Co., Ltd.
• Original Assignee: Ubukata Industries Co., Ltd.
• Inventors: Urano, Mitsuhiro, Ueda, Yoshihisa, Sato, Shigemi, Koike, Takeo
• Granted Patent: US 8,902,038 B2
• Time in Patent Office: Days
• US Class Current: 337/298
• CPC Class Codes: H01H 1/02372 containing as major components one or more oxides of the following elements only: Cd, Sn, Zn, In, Bi, Sb or Te
• CPC Class Codes: H01H 2050/025 containing inert or dielectric gasses, e.g. SF6, for arc prevention or arc extinction
• CPC Class Codes: H01H 37/5427 encapsulated in sealed miniaturised housing

Abstract

A thermally responsive switch includes a hermetic container (2) including a metal housing (3) and a header plate (4), at least one conductive terminal pin (10A, 10B) hermetically fixed in the through hole (4A, 4B), a fixed contact (8) fixed to the terminal pin (10A, 10B) in the container (2), a thermally responsive plate (6) having one end connected and fixed to an inner surface of the container (2) and reversing a direction of curvature at a predetermined temperature, and at least one movable contact (7) secured to the other end of the thermally responsive plate (6). Each of the fixed contact (8) and the movable contact (7) includes a silver-cadmium oxide system contact, and the container (2) is filled with a gas containing helium ranging from 50% to 95% so that an internal pressure of the container (2) ranges from 0.38 to 0.68 atm. at room temperature.

Claims

1. A thermally responsive switch which is used to cut off AC current flowing through a compressor motor, the thermally responsive switch comprising:

a hermetically sealed container (2) including a metal housing (3) and a header plate (4) hermetically secured to an open end of the housing (3);

at least one conductive terminal pin (10A, 10B) inserted through a through hole (4A, 4B) formed through the header plate (4) and hermetically fixed in the through hole (4A, 4B) by an electrically insulating filler (9);

a fixed contact (8) fixed to the terminal pin (10A, 10B) in the container (2);

a thermally responsive plate (6) having one of two ends conductively connected and fixed to an inner surface of the container (2) and formed into a dish shape by drawing so as to reverse a direction of curvature at a predetermined temperature;

at least one movable contact (7) secured to the other end of the thermally responsive plate (6) and constituting at least one pair of switching contacts together with the fixed contact (8),

wherein each of the fixed contact (8) and the movable contact (7) comprises a silver-cadmium oxide system contact, and the container (2) is filled with a gas containing helium ranging from 50% to 95% so that an internal pressure of the container (2) ranges from 0.38 atmosphere to 0.68 atmosphere at room temperature.

2. The thermally responsive switch according to claim 1, wherein the container (2) is filled with the gas so that the internal pressure of the container (2) ranges from 0.45 atmosphere to 0.6 atmosphere at room temperature.

3. The thermally responsive switch according to claim 1, wherein the movable contact (7) and the fixed contact (8) have an intercontact distance therebetween in an open state, the intercontact distance being set at or above 0.4 mm so that the thermally responsive plate (6) abuts against the inner surface of the container (2) during a contact opening operation and so that a subsequent operation of the thermally responsive plate (6) is limited during a curvature direction reversing operation.

4. The thermally responsive switch according to claim 2, wherein the movable contact (7) and the fixed contact (8) have an intercontact distance therebetween in an open state, the intercontact distance being set at or above 0.4 mm so that the thermally responsive plate (6) abuts against the inner surface of the container (2) during a contact opening operation and so that a subsequent operation of the thermally responsive plate (6) is limited during a curvature direction reversing operation.

5. The thermally responsive switch according to claim 1, wherein each of the fixed contact (8) and the movable contact (7) is formed into a disc shape having a diameter ranging from 3 mm to 5 mm.

6. The thermally responsive switch according to claim 2, wherein each of the fixed contact (8) and the movable contact (7) is formed into a disc shape having a diameter ranging from 3 mm to 5 mm.

7. The thermally responsive switch according to claim 3, wherein each of the fixed contact (8) and the movable contact (7) is formed into a disc shape having a diameter ranging from 3 mm to 5 mm.

8. The thermally responsive switch according to claim 4, wherein each of the fixed contact (8) and the movable contact (7) is formed into a disc shape having a diameter ranging from 3 mm to 5 mm.

9. The thermally responsive switch according to claim 5, wherein at least one of the fixed contact (8) and the movable contact (7) has a convexly curved surface.

10. The thermally responsive switch according to claim 6, wherein at least one of the fixed contact (8) and the movable contact (7) has a convexly curved surface.

11. The thermally responsive switch according to claim 7, wherein at least one of the fixed contact (8) and the movable contact (7) has a convexly curved surface.

12. The thermally responsive switch according to claim 8, wherein at least one of the fixed contact (8) and the movable contact (7) has a convexly curved surface.