Thermal fuse using thermosensitive material
In the present invention, a physical and chemical property of thermosensitive material is noted in selecting and using thermosensitive material to provide a noble and improved thermal fuse using thermosensitive material. To achieve this object, the present thermal fuse includes: a thermosensitive material formed of thermoplastic resin fusing at a prescribed temperature; a cylindrical enclosure accommodating the thermosensitive material; a first lead member attached at one opening of the enclosure, forming a first electrode; a second lead member attached at the other opening of the enclosure, forming a second electrode; a movable conductive member accommodated in the enclosure and engaged with the thermosensitive material; and a spring member accommodated in the enclosure, and pressed against and thus acting on the movable conductive member. When the thermosensitive material fuses at an operating temperature an electrical circuit between the first and second electrodes is switched.
1. A thermal fuse comprising:
a thermosensitive member comprising a polyolefin material fusing at a prescribed temperature, and an anti-oxidant or an anti-aging agent;
a cylindrical enclosure accommodating said thermosensitive member;
a first lead member attached at a first opening of said enclosure, forming a first electrode;
a second lead member attached at a second opening of said enclosure, forming a second electrode;
a movable conductive member accommodated in said enclosure and engaged with said thermosensitive member; and
a spring member accommodated in said enclosure and pressed against said movable conductive member to act on said movable conductive member,
said thermosensitive member fusing at an operating temperature to switch an electrical circuit located between said first and second electrodes.
2. The thermal fuse of claim 1 , wherein said thermosensitive member further comprises alumina or silica.
3. The thermal fuse of claim 1 , wherein said anti-oxidant or said anti-aging agent is 2,6-di-tert-butyl-p-cresol.
4. The thermal fuse of claim 1 , wherein said cylindrical enclosure is a cylindrical metallic casing having an end with said second opening receiving an insulated bushing, said first lead member is crimped, fixed to and thus electrically and mechanically coupled with said first opening of said metallic casing and also has said first electrode formed at an internal wall surface of said casing, said second lead member penetrates said bushing and is insulatively attached at said second opening of said metallic casing and has an end thereof forming said second electrode, said movable conductive member is a movable contact that is movable as desired between said first and second electrodes, and said spring member is a compression spring member engaged with said movable contact.
5. The thermal fuse of claim 4 , wherein said compression spring member comprises a strong compression spring and a weak compression spring and wherein when said thermosensitive member is not fused, said strong compression spring acts against a resilience of said weak compression spring to allow said movable contact to abut against said second electrode.
6. The thermal fuse of claim 5 , wherein said strong compression spring is arranged between said thermosensitive member and said movable contact and when said thermosensitive member fuses, a force of said weak compression spring moves said movable contact to interrupt a circuit.
7. The thermal fuse of claim 5 , wherein said strong compression spring is arranged as compressed by said thermosensitive member, and when said thermosensitive member fuses, said strong compression spring acts against a force of said weak compression spring to move said movable contact to allow said electrical circuit to conduct.
8. The thermal fuse of claim 1 , wherein said cylindrical enclosure is a cylindrical metallic casing having an end with said second opening sealed by an insulated bushing, said first lead member is crimped, fixed to and thus electrically and mechanically coupled with said first opening of said metallic casing and also forms said first electrode at an internal wall surface of said casing, said second lead member penetrates said bushing and is insulatively attached at said second opening of said metallic casing and at an end thereof forms said second electrode, said movable conductive member and said spring member are two flat plates in a form of tongues extending lengthwise and having conductance and resilience arranged between said first and second electrodes, said two flat plates sandwich said thermosensitive member to achieve contact with said internal wall surface of said metallic casing and when said thermosensitive member fuses, a spacing between said flat plates is reduced to achieve a non-contact condition.
9. The thermal fuse of claim 1 , wherein said cylindrical enclosure is a cylindrical, insulated tube, said first and second lead members are fixed to said first and second openings of said tube, respectively and also form said first and second electrodes, respectively, at an internal wall surface of said tube, said movable conductive member is a conductor that is movable from a conducting position of said first and second electrodes to an interrupt position of said first and second electrodes, said spring member is arranged at one end of said tube, and via an insulator said conductor is pressed against said thermosensitive member.