Patent Application
20100207716
(a) Field of the Invention
The present invention relates to an overcurrent protection structure and a method and an apparatus for making the same, and more particularly to an overcurrent protection structure, which can ensure that the overcurrent protection structure would blow at high temperature when reaching a specific current or a specific temperature and the protection effect against excess current, and a method and an apparatus for making the same.
(b) Description of the Prior Art
A fuse is designed to protect electric circuits or electrical equipments in an electric circuit from the damage on sophisticated electronic instruments caused by an instantaneous excess current or an excess voltage. Therefore, the fuse is a necessary electronic component. A conventional fuse unit has a coil or a fuse material, and the fuse material is sealed in a tube made of hard glass, ceramic or other insulating materials. The insulating tube is filled therein with an inert gas or an arc resistant packing material. The both ends of the tube are electric conductors respectively, and the current can flow through the fuse by the connection of the electric conductors to the soldering joints on a circuit board. When an instantaneous current exceeds the predetermined current rating, the fuse material will blow at high temperature due to the heat induced by the instantaneous excess current so as to break the circuit. Thus, the excess current would stop flowing into the circuit to protect the electric circuits and electrical equipments from damage. When a fuse unit of such structures is used at a larger current (240 A) or at a high voltage (2250 V), the instantaneously generated energy would result in the high heat of the fuse blowout such that the surrounding media will expand rapidly and burst the tube. In the meantime, the arcs will occur so that it is easy to burn out the peripheral electronic components and damage expensive system equipments.
Therefore, the conventional structures of fuse unit and their manufacturing method mostly emphasize the suppression of arcs, such as U.S. Pat. No. 6,507,264, U.S. Pat. No. 5,572,181, U.S. Pat. No. 5,923,239, U.S. Pat. No. 6,507,265, U.S. Pat. No. 5,812,046, U.S. Pat. No. 5,596,306, and the like but their processes are relatively complicated. Accordingly, TW Patent 200727319 proposed an overcurrent protection element, as illustrated in
However, in reality, when the fuse body 11 is electrically energized and generates heat, a part of the heat will dissipate through the heat conduction of the fuse coating 12 due to the contact of the fuse body 11 with the fuse coating 12 so that when a set excess current flows through the fuse body 11, the fuse body 11 cannot reach a specific current or a specific temperature and blow at high temperature. As a result, it is unable to achieve the circuit protection effect against excess current such that the electronic circuits of electrical devices would be damaged or burned out.
The primary objective of the present invention is to provide an overcurrent protection structure, which can ensure that the overcurrent protection structure would blow at high temperature when reaching a specific current or a specific temperature and the protection effect against excess current, and a method and an apparatus for making the same.
To achieve the above objective, the overcurrent protection structure according to the present invention mainly comprises a fusible fuse structure unit disposed in a coating, and the both ends of the fusible fuse structure unit extend outwardly beyond the coating and form a first electrode and a second electrode. In the manufacturing process, a gas-assisted injection molding process enables at least one space for accommodating gas disposed between the fusible fuse structure unit and the coating such that the heat generated by the electrically energized the fusible fuse structure unit will not dissipate through the heat conduction of the coating in order to ensure that it will blow at high temperature when reaching a specific current or a specific temperature and the circuit protection effect against excess current.
The present invention is related to an overcurrent protection structure and a method and an apparatus for making the same. As illustrated in
The coating 21 can be an arc resistant material, which can be a thermoplastic material or a thermosetting material. Wherein the thermoplastic material includes (a) crystalline polymeric material: polyethylene, polypropylene, polytetrafluoroethylene, nylon 12, nylon 6, nylon 66, nylon 6T, nylon 9T, polybutylene terephthalate, polyethylene terephthalate, polyoxymethylene, PEEK, liquid crystal polymers, ethylene copolymers, polyethersulfone, polyphenylene sulfone; (b) amorphous polymeric material: acrylonitrile-butadiene-styrene terpolymer, polystyrene, polycarbonate, polysulfonate, polydiethyl ether sulfonate, polystyrene oxide, phenoxy resin, polyamide, polyether amide, polyether amide/silicon block copolymer, polycarboxylate, propylene resin, polymethacrylate, styrene/propylene-trichloroethylene, poly(4-methylpent-1-ene), styrene block copolymer. And the thermosetting material can be epoxy resin, phenolic resin, unsaturated polyester resin, urea resin, melamine resin, polyimide resin and silicone resin, and the like. Furthermore, the above thermoplastic material or thermosetting material filled with a hydrated inorganic material can also be used as the arc resistant material, and the hydrated inorganic material is, for example, aluminum hydroxide trihydrate or magnesium hydroxide dihydrate. It is understood that the coating 21 can also be formed with an inner layer 211 and an outer layer 212, as illustrated in
In the overcurrent protection structure 2 according to the present invention, the coating 21, which encapsulates the fusible fuse structure unit 22, is formed by means of an arc resistant material and a gas-assisted injection molding process, and the space 25 between the fusible fuse structure unit 22 and the coating 21 is simultaneously formed. Accordingly, when the overcurrent protection structure is in a condition of excess current, the coating 21 can absorb the heat generated by the blowout of the fusible fuse structure unit 22 and suppress the occurrence of arcs. The fusible fuse structure unit 22 can make no contact with the coating 21 directly by the space 25 such that the heat from the fusible fuse structure unit 22 will not dissipate through the heat conduction of the coating 21 in order to ensure that the fusible fuse structure unit 22 will blow at high temperature due to a specific current or a specific temperature, thereby achieving the circuit protection effect against excess current. Besides, the outside of the fusible fuse structure unit 22 can be further coated with a thermal insulating material 26 with arc resistance, as illustrated in
The manufacturing apparatus for an overcurrent protection structure according to the present invention at least comprises a stamping unit, a soldering unit, a gas-assisted injection molding unit, a cutting unit and a transporting unit located between each unit as described above, whereby the steps are performed as follows:
Step A: providing a lead frame;
Step B: performing a stamping process by using the stamping unit 31 to form a plurality of supporting units 41 and a connection unit 42 for connecting each supporting unit 41 on the lead frame 4, as illustrated in
Step C: disposing the fusible fuse structure units 22 between the supporting units 41, as illustrated in
Step D: performing a gas-assisted injection molding process by using the gas-assisted injection molding unit to mold the coatings 21 which encapsulate the fusible fuse structure units 22 and a part of the supporting units 41 by using injection, as illustrated in
Step E: performing a cutting process, as illustrated in
Moreover, in step D, the gas-assisted injection molding process is combined with a coinjection system, that is, the gas-assisted injection molding unit at least comprises a coinjection molding machine, a gas-assisted injection apparatus, a gas generator and an air compressor. The coinjection molding machine contains the arc resistant material and ordinary material such that the molded coating 21 is formed with the inner layer 211 and the outer layer 212, as illustrated in
It should be noted that the present invention when compared to the prior art provides the following advantages:
1. The coating according to the present invention is made of an arc resistant material, and said coating can absorb the heat generated by the blowout of the fusible fuse structure unit and suppress the occurrence of an arc.
2. The arc resistant material according to the present invention can be a thermoplastic material or a thermosetting material filled with magnesium hydroxide dihydrate. The coating will release water of crystallization until its temperature reaches 340° C. so that it is more suitable for the current lead-free solder system with the melting point of the lead-free solder being about 210-230° C., and the thermal endurance and the arc resistance of that containing magnesium hydroxide dihydrate are better.
3. At least one space for accommodating gas is disposed between the fusible fuse structure unit and the coating to make the fusible fuse structure unit in no contact with the coating directly such that the heat generated by the electrically energized the fusible fuse structure unit will not dissipate through the heat conduction of the coating in order to ensure that it will blow at high temperature when reaching a specific current or a specific temperature, thereby ensuring the circuit protection effect.
The technical contents and features of the present invention are disclosed above. However, anyone who familiars with the technique could possibly make change or modify the details in accordance with the present invention without departing from the technological ideas and spirit of the invention. Therefore, the protection scope of the present invention shall not be limited to what embodiment discloses, and should include various modification and changes that are made without departing from the technological ideas and spirit of the present invention, and should be covered by the claims mentioned below.
