Protective device

• US 10,483,061 B2
• Filed: 07/01/2014
• Issued: 11/19/2019
• Est. Priority Date: 07/02/2013
• Status: Active Grant

• Current Assignee: Littelfuse Japan G.K. (Littelfuse Incorporated)
• Original Assignee: Littelfuse Japan G.K. (Littelfuse Incorporated)
• Inventors: Yokota, Takayuki, Iwai, Masaaki, Takegawa, Hirotsugu, Ikawa, Naotaka
• Primary Examiner(s): Nguyen, Danny
• Application Number:
  US14/901,987
• Publication Number:
  US 20180040443A1
• Time in Patent Office: 1,967 Days
• Field of Search: 361 13, 361103, 361106, 361 937- 939
• CPC Class Codes: H01C 7/02 having positive temperature coefficient ceramics C04B
• CPC Class Codes: H01H 2235/01 Spiral spring
• CPC Class Codes: H01H 37/34 Means for transmitting heat thereto, e.g. capsule remote from contact member
• CPC Class Codes: H01H 37/60 Means for producing snap action inherent in bimetallic element H01H37/54; caused by a magnet H01H37/66
• CPC Class Codes: H01H 37/761 with a fusible element forming part of the switched circuit H01H37/767 takes precedence
• CPC Class Codes: H01H 61/02 wherein the thermally-sensitive member is heated indirectly, e.g. resistively, inductively
• CPC Class Codes: H01H 85/0241 Structural association of a fuse and another component or apparatus switches with built-in fuses H01H9/10, spark-gap arresters H01H85/44, transformers and inductances H01F27/402, capacitors H01G2/14, lamps H01K1/66, semiconductors H01L23/5256 or H01L23/62
• CPC Class Codes: H01H 85/46 Circuit arrangements not adapted to a particular application of the protective device
• CPC Class Codes: H02H 3/085 making use of a thermal sensor, e.g. thermistor, heated by the excess current also responsive to the temperature of the protected device H02H5/041, thermal images H02H6/00

Abstract

A protection device including: (i) a protection component having a first thermal fuse and a resistive body, the resistive body being supplied with a current in an abnormal state to generate heat, the heat activating the first thermal fuse to cut off the current; (ii) a PTC component; and (iii) a second thermal fuse, the second thermal fuse being electrically connected in series to the PTC component, the first thermal fuse of the protection component being electrically connected in parallel to the PTC component and to the second thermal fuse, and the protection component being activated in the abnormal state so that the PTC component trips to generate heat, the heat blowing the second thermal fuse.

Claims

1. A protection device comprising:

(i) a protection component comprising a first thermal fuse and a resistive body wherein in an abnormal state the resistive body is supplied with a current to generate heat, and by the heat the first thermal fuse activates to cut off the current;

(ii) a PTC component; and

(iii) a second thermal fuse,

wherein the second thermal fuse is electrically connected to the PTC component in series,

the first thermal fuse of the protection component is electrically connected to the PTC component and to the second thermal fuse in parallel, and

by activating the protection component in the abnormal state, the PTC component trips to generate heat, and the heat fuses the second thermal fuse;

wherein an activating time of the PTC component is longer than an insulation time of a fuse element of the first thermal fuse.

2. The protection device according to claim 1, wherein the protection component is a fusing resistor.

3. The protection device according to claim 2, wherein

the fusing resistor has a pair of lead fixed electrodes, a guide shaft is juxtaposed to the lead fixed electrodes, wherein

a movable electrode is disposed such that it bridges the lead fixed electrodes while being inserted into the guide shaft,

a tip of each of the lead fixed electrodes and the movable electrode are joined with a low-melting-point alloy, and the guide shaft and the movable electrode is joined with a low-melting-point alloy,

a compression spring is provided which applies a force to the movable electrode in a direction away from the lead fixed electrodes, and

when the low-melting-point alloy is melted, the compression spring presses the movable electrode so that the movable electrode separates from the lead fixed electrodes.

4. The protection device according to claim 3, wherein

in the fusing resistor, one lead conductor of a resistor having lead conductors fitted to both ends of the resistive body is used as the guide shaft,

a coil spring is used as the compression spring,

the coil spring is inserted in the one lead conductor between the resistive body and the movable electrode, and

a circuit applying a current to a resistor for generating a heat is connected between the one lead conductor of the resistor and either one of the two lead fixed electrodes.

5. The protection device according to claim 1, wherein the PTC component is a polymer PTC component.

6. The protection device according to claim 1, wherein a resistance value of the PTC component at a use temperature is equal to or less than a rated voltage of the protection component/abnormal current.

7. The protection device according to claim 5, wherein a resistance value of the PTC component at a temperature lower 10°

C. than a softening point of a polymer material of the polymer PTC component is equal to or less than a rated voltage of the protection component/abnormal current.

8. The protection device according to claim 1, wherein an activating time of the PTC component is 3 milliseconds or more.

9. The protection device according to claim 1, further comprising one or more PTC components electrically connected to the PTC component in parallel and electrically connected to the second thermal fuse in series.

10. The protection device according to claim 1, wherein an activation temperature of the second thermal fuse is lower than a trip temperature of the PTC component.

11. The protection device according to claim 1, wherein a fusing time of the second thermal fuse at an abnormal current is longer than a tripping time of the PTC component.

12. The protection device according to claim 1, wherein the second thermal fuse has a withstand voltage equal to or more than an abnormal voltage at a leak current when the PTC component is in its tripping state.