The present invention relates to a thermal fuse, and more specifically to an organic temperature-sensing thermal fuse which is capable of resisting large surge current.
An over-current protecting has been widely used in manufacturing home appliance and industrial equipment because excessive heating induced by electricity can result into fire. Except for the over-temperature protecting, an over-temperature protection is also needed.
Currently, existing non-resettable thermal fuse used can be sorted into two categories. One category of the thermal fuse uses alloy with low melting point as temperature sensing component. The other category of the thermal fuse uses pressed organic material as a temperature sensing body. A metal elastic clamp contacts with a lead wire electrode through the joining force coming from a compressed compression spring and the temperature sensing body, thus forming a single contact point conductive structure. When the temperature of the environment reaches a pre-set temperature, the temperature sensing body melts. A thin compression spring forces the metal elastic clamp separate from the lead wire electrode, thus cutting off the electric connection. The single contact point conductive structure between the elastic clamp and lead wire electrode has the drawback of high contacting resistance. This conductive structure cannot withstand high current. When surge current flows through the device, a resistance welding would occur and thus disabling the protecting function of the thermal fuse.
The present invention overcomes the drawback of existing technology and provides an organic temperature sensing thermal fuse, comprising an insulating cylindrical tube, a first metal cap and a second metal tube to form a temperature sensing chamber. The temperature sensing chamber axially arranges a plurality of components in the following sequence: an organic temperature sensing body; a conductive bridge; an insulating supporting pillar a spring compressed by the insulating supporting pillar; when the organic temperature sensing body melts after heating, the spring pushes the conductive bridge towards the organic temperature sensing body. The conductive bridge thus achieves or cuts off the electric connection between the first metal cap and the second metal tube.
The conductive bridge has multiple contacting points with the metal tube, thus forming a structure which equivalently has multiple parallel branches. This structure lowers the contacting resistance, decreasing the heating power when a surge current flows through this device. The value of working current and the ability to withstand current shock are thus increased.
The present invention discloses a thermal fuse having dual metal elastic clamps, which comprise: an insulating cylindrical tube with an axially through hole; a first metal cap, wherein one end of the first metal cap is axially fixed on one end of the through hole, the other end of the first metal cap is connected with a first conducting wire extending outward; a second metal tube, wherein one end of the second metal tube is axially fixed on the other end of the through hole, the other end of the second metal tube is connected with a second conducting wire extending outward.
The first metal cap, the second metal tube and the inner side wall of the middle part of the through hole form a temperature sensing chamber. The temperature sensing chamber axially arranges a plurality of components in the following sequence from the first metal cap to the second metal tube: an organic temperature sensing body capable of melting when heated, a conductive bridge, an insulating supporting pillar and a compressed spring. The conductive bridge further axially arranges a plurality of components in the following sequence from the first metal cap to the second metal tube: a metal pad, a first metal elastic clamp, a connecting pillar and a second metal elastic clamp.
The first metal elastic clamp and the second metal elastic clamp comprise a circular base board and a plurality of arc-shaped extending parts bending toward the same side of the circular base board. The plurality of arc-shaped extending parts are glidingly connected with the inner wall of the temperature sensing chamber. The second metal tube, the second metal elastic clamp, the connecting pillar, the first elastic clamp and the first metal cap are electrically connected with each other.
The above invention can be modified as the following:
In one preferred embodiment, one end of the second conductive wire has a flat heading. The flat heading is located on the inner part of the second metal tube and rivets the lip-like edges of the second metal tube. The flat heading is electrically connected with the second metal tube.
In one preferred embodiment, the clamps of the first elastic clamp and the second elastic clamp bent towards the second metal tube.
In one preferred embodiment, the first metal elastic clamp and the second metal elastic clamp relative to the first metal cap and the second metal tube are in normally closed condition. The first metal elastic clamp is electrically connected with the first metal cap when the organic temperature sensing body is in rigid and melting position. The second metal elastic clamp is electrically connected with the second metal tube when the organic temperature sensing body is in rigid condition and electrically insulated with the second metal tube when the organic temperature sensing body is in melting position.
In another preferred embodiment, the first metal elastic clamp and the second metal elastic clamp relative to the first metal cap and the second metal tube are in normally open condition. A distance between the first metal elastic clamp and the second metal elastic clamp is greater than a distance between the first metal cap and the second metal tube. The first metal elastic clamp is electrically insulated with the first metal cap when the organic temperature sensing body is in rigid condition, while the first metal elastic clamp is electrically connected with the first metal cap when the organic temperature sensing body is in melting condition. The second elastic clamp is electrically connected with the second metal tube when the organic temperature sensing body is in rigid or melting conditions.
In one preferred embodiment, a contact surface between the second metal elastic clamp and the connecting pillar is a flat surface. A contact surface between the first metal elastic clamp and the connecting pillar is also as flat surface. The two flat contact surfaces are both perpendicular to the axis of the insulating cylindrical tube.
In one preferred embodiment, a heater is located on the outer wall of the insulating cylindrical tube, the heater can be heated up when powered on.
In one specific embodiment, the heater is metal resistance wire which has pins extending outwardly. Based on this specific embodiment, two pins are respectively located on two ends of the insulating cylindrical tube and electrically connected with the first metal cap and the second metal tube correspondingly.
In one preferred embodiment, the inner wall of the temperature sensing chamber is a smooth surface.
Beneficial effects of this invention are as following:
Firstly, the first metal elastic clamp, the second metal elastic clamp and the connecting pillar form a conductive bridge. This conductive bridge is a movable conductive component. Clamps from the two metal elastic clamps cooperate with the inner wall of the temperature sensing chamber from the side wall. The clamps slide flexibly in the temperature sensing chamber and have multiple contacting points with the first metal cap and the second metal tube. This results in a low contacting resistance and can withstand large current, thus increasing the reliability.
Secondly, the movable structure of the metal elastic clamp can form a normally closed and open embodiment.
Thirdly, the simple structure of the thermal fuse can cooperate with other heating components, thus achieving a function of initiative cut-off.
A detailed description of the invention is described with the drawings. The invention of an organic temperature-sensing thermal fuse with multiple contacting points is not limited to these embodiments illustrated below, but conforms to a broadest scope consistent with the principle and novel features disclosed herein.
Referring to
Insulating cylindrical tube 101 provides support for the overall structure and can be made of ceramic or engineering plastics. A first metal cap 102A and a second metal tube 102B are respectively embedded into two sides of insulating cylindrical tube 10. A first conductive wire 103A and the bottom of the first metal cap 102A are electrically connected with each other through riveting. The heading of the second conductive wire 103B is a flat heading 103B-1 and is inserted into the flaring step of the lip-like edges of the second metal tube 102B. The lip-like edge of the second metal tube 102B is screwed tightly and thus forms a conductive connection with the second conductive wire 103B. Conductive wires 103A and 103B respectively extend outwardly from two ends along the axis. A temperature sensing chamber is located between the first metal cap and the second metal tube. The temperature sensing chamber axially arranges a plurality of components in the following sequence from the first conductive wire 103A to the second conductive wire 103B through the second metal tube 102B; an organic temperature sensing body 201; a metal pad 202: a first metal elastic clamp 301; a connecting pillar 303; a second metal elastic clamp 302; an insulating supporting pillar 402 and a compressed spring 401.
Referring to
When all the components are assembled together, the lip-like edge 102B-1 of the second metal tube 102B is screwed tightly and forms the overall structure of the thermal fuse. When assembling, an epoxy resin type blinder can be coated on the out peripheral of the first metal cap 102A and the second metal tube 102B in order to secure the insulating cylindrical tube 101, the first metal cap 102A and the second metal tube 102B. Then, the first metal cap 102A and the second metal tube 102B are pushed into the insulating cylindrical tube 101. The lip-like edges of the second metal tube 102B is also coated with an epoxy resin type blinder in order to form a closed chamber between the first metal cap 102A and the second metal tube 102B. Thus, a high-temperature stability of the organic temperature sensing body 201 can be improved.
The organic temperature sensing body 201 melts from solid to liquid and loses holding force when outside temperature exceeds the melting point of the organic temperature sensing body 201. The compressed spring 401 pushes the insulating support column 402 and the conductive bridge 300 move towards the first conductive wire 103A. The electric circuit will be cut of when the second metal elastic clamp 302 separates from the second metal tube 102B and reaches the middle part of the insulating cylindrical tube 101. Thus, a function of over-temperature protection can be achieved.
When the rated current is set at AC with a value of 15 A, the organic temperature-sensing thermal fuse having dual metal elastic clamps can withstand a peak value of 10 KA when a surge current with a value of 8*20 μS flows. A current welding can be avoided. Thus the thermal fuse will never lose the over-temperature protection due to the invalidation of becoming a permanent conductive thermal fuse. Existing thermal fuse uses one conductive to directly contact the organic temperature-sensing thermal fuse having single metal elastic clamp. When a 8*20 μS current flows through the existing thermal fuse and the current value exceeds 3 KA, a current welding occurs. The existing thermal fuse thus becomes a permanent conductive thermal fuse and loses the function of over-temperature protection.
The conductive bridge 300, the first metal cap 102A and the second metal tube 102B form a normally closed structure. The normally closed structure exists when the organic temperature sensing body is in rigid condition and the first metal elastic clamp 301, the second metal elastic clamp 302 are respectively connected with the first metal cap 102A and the second metal tube 102.
Similarly, the thermal fuse can be a normally open structure referring to
Referring to
Conductive bridge 300 comprises a conductive pillar 310, two rows of petal shaped wings 314 and 315. The petal shaped wings are formed by cleaving a copper cylinder radially and extend outwardly to form an integrative structure. The two rows of petal shaped wings 314 and 315 are respectively and electrically connected with the first metal cap 102A and the second metal tube 102B.
Likewise, the second embodiment can be processed with a normally open structure as the first embodiment.
Referring to
If the input power source for the heater is the main circuit, the metal ring can be directly set on the first metal cap 102A. Metal resistance wire, metal film or carbon film resistance passes through the surface of the insulating cylindrical tube 101 and extends to metal ring 502B. thus pin 501A can be reduced.
Referring to
Referring to
Elastic convex reeds are obtained from curving the metal piece. Grid slots 104A is arranged radically. Cylindrical conductive pin 105 is installed inside flexible arc-shaped structure 104B. A linear and multiple contact points along the axis between the arc-shaped surface of elastic convex reeds and the cylinder surface of cylindrical conductive pin 105 are achieved due to an elastic deformation of convex reeds.
Cylindrical conductive pin 105 is used as an active connective point for first convex reed 104 and second convex reed 104. The length of the temperature sensing body 103 exceeds the distance when cylinder conductive pin 105 slides off second convex reed 107. When temperature sensing body 103 heats up due to abnormal rising of outside temperature, temperature sensing body 103 is in melting position. The compressed spring 108 releases an elastic force and pushes cylinder conductive pin 105 away from second convex reed 107. This results in an one-time electric cut-off between first metal cap 102 and second metal cap 109 without recovery.
Referring to
Beneficial effects of this invention are as following:
Using an integrated structure or constructing a conductive bridge formed by a first metal elastic clamp, a second metal elastic clamp and a connecting pillar.
Temperature sensing body melts when the outside temperature is abnormal; this conductive bridge is a movable conductive component. Clamps from the two elastic clamps cooperate with the inner wall of the temperature sensing chamber from the side wall. The clamps slide flexibly in the temperature sensing chamber and have multiple contact points with the first metal cap and the second metal tube. This results in as lower contacting resistance and can withstand a large current, thus increasing the reliability.
While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method and examples herein. The invention should therefore not be limited to the above described embodiments, but by all embodiments and methods within the scope and spirit of the invention.
Number | Date | Country | Kind |
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201310108845.8 | Mar 2013 | CN | national |
Filing Document | Filing Date | Country | Kind |
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PCT/CN2014/074277 | 3/28/2014 | WO | 00 |