Patent Application
20170345602
The present invention relates to a temperature-sensitive pellet type thermal fuse, and more particularly, to a temperature-sensitive pellet type thermal fuse in which when a periphery temperature or a circuit temperature rises to a predetermined level or higher, a temperature-sensitive pellet inside a cabinet is melted so that a moving terminal elastically supported by a spring and a lead wire are attached to or detached from each other, thereby allowing a circuit to be turned on or off.
A thermal fuse is a component detecting an abnormal overheat of an apparatus and promptly shutting off a circuit of the apparatus, and is used in various fields such as automotive parts of a vehicle, various home appliances, portable electronic communication devices, office equipments, vehicle-loaded automotive parts, AC adapters, chargers, motors and batteries.
The thermal fuse employs, as a temperature-sensitive material, a pellet type molded with an organic material which is generally melted at a predetermined fuse activation temperature. The thermal fuse has been known by the disclosure in multiple documents including the following patent documents.
(Patent document 1) KR10-1202434 B1
(Patent document 2) U.S. Pat. No. 5,530,417 B1
In the case of a conventional thermal fuse disclosed in the patent document 1, when a support unit is melted in an activation temperature range, a moving terminal selectively conducting a first contact connected to a first lead wire and a first contact (an inner wall of a metal case) connected to a second lead wire is moved in a direction separating the contacts by force of a spring pressing and holding the support unit to electrically short-circuit the first and second contacts, so that a circuit is switched off.
However, in the conventional thermal fuse, the moving terminal instantly short-circuits the first and second contacts at a moment when a second spring force acting in a direction separating the moving terminal from the second contact becomes greater than a first spring force acting in a direction making the moving terminal contact the first contact, i.e. a moment when the support unit being melted is decreased to a predetermined height, so the conventional thermal fuse has a structure in which a switch operation is sensitive to the change in the height of the support unit.
Accordingly, since the structure is such that a cut-off operation is sensitive to a minute difference between acting forces of the two springs or a tiny reduction of the temperature-sensitive pellet, there has been a limitation that a malfunction of shutting off the circuit happens when an unintended shrinkage deformation occurs in the temperature-sensitive pellet in a lower temperature range less than the predetermined activation temperature range. Since the conventional thermal fuse having the structure sensitively reacts against periphery temperature changes, there has been a limitation in that operation of the conventional thermal fuse is unstable.
Besides, since the conventional thermal fuse has the structure in which one end of the moving terminal in an outer perimeter direction thereof contacts the inner wall surface of the metal case in a line contact state, there has been a limitation in that, when the force of the spring elastically supporting the moving terminal is not evenly applied to the moving terminal, the moving terminal is deflected in any one direction to be caught by the inner wall of the case and causing malfunction by being unable to perform a slide movement.
Accordingly, the present invention is directed to a temperature-sensitive pellet type thermal fuse that substantially obviates one or more problems due to limitations and disadvantages of the related art, the temperature-sensitive pellet type thermal fuse having high operation reliability and accurately operating in a predetermined temperature range without malfunction owing to stable contact or separation performance between contacts.
Embodiments of the present invention provide a temperature-sensitive pellet type thermal fuse including: a cylindrical metal case; a first lead fixedly installed on one end of the case to be insulated from the case by an insulating bushing; a second lead electrically connected to the other end of the case; a temperature-sensitive pellet installed inside the case and having a height varied while being melted at a predetermined temperature or higher; and a moving terminal, one end of which is elastically supported by a first spring to the temperature-sensitive pellet, and a moving terminal electrically separating the first lead and the second lead from each other in accordance with height decrease of the temperature-sensitive pellet, wherein the temperature-sensitive pellet type thermal fuse further includes: an activating member moving in a height decrease direction of the temperature-sensitive pellet by an elastic repulsive force of a second spring acting toward the temperature-sensitive pellet when the temperature-sensitive pellet is melted and thereby is reduced in height, and actuating the moving terminal, from a time point when the temperature-sensitive pellet is reduced in height to a predetermined height, such that a first moving contact of the moving terminal is separated from a first fixed contact of the first lead.
In one aspect of the present invention, the thermal fuse according to an embodiment of the present invention may include a fixed terminal plate provided inside the case and under the insulating bushing and contacting the case so as to be electrically connected to each other, and having a hole perforated coaxially with a through-hole of the insulating bushing, wherein the moving terminal may be slidingly guided into the hole of the fixed terminal plate, and an inner wall of the hole may serve as a second fixed contact electrically connecting the first fixed contact of the first lead and the case at the second lead side while slidingly contacting an outer circumferential surface of the moving terminal until the temperature-sensitive pellet arrives at an activation height at which a switch is turned off.
In one aspect of the present invention, the moving terminal may have a head part provided on a lower end of a body and expanded at a relatively greater diameter than the diameter of the body, the first spring may be compressedly installed between a lower surface of the head part of the moving terminal and an upper surface of a base plate placed on an upper surface of the temperature-sensitive pellet, the activating member may have a through hole defined in an upper end sidewall thereof such that the body of the moving terminal passes therethrough, a lower surface of the upper end sidewall may contact an upper surface of the head part of the moving terminal when the height change amount of the temperature-sensitive pellet arrives at a predetermined level, and the activating member may move the moving terminal when the temperature-sensitive pellet is excessively melted beyond the predetermined level specified as the height change amount of the temperature-sensitive pellet.
In one aspect of the present invention, the base plate may have a hole such that, when the temperature-sensitive pellet is melted, a melted portion of the temperature-sensitive pellet is introduced in the inside of the activating member.
In one aspect of the present invention, the case may have a stepped portion formed at a border between an upper region having a relatively greater inner diameter and a lower region having a relatively less inner diameter, the fixed terminal plate may be placed on and fixed by the stepped portion of the case, and the insulating bushing may be placed on and fixed by an upper surface of the fixed terminal plate.
Additional advantages and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Hereinafter, a temperature-sensitive pellet type thermal fuse according to embodiments of the present invention will be described in detail with reference to accompanying drawings.
As shown in
In the lower region of the case 11, a temperature-sensitive pellet 12, a base plate 13, a first spring 17, a moving terminal 16, an activating member 15 and a second spring 18 are insertedly installed in a sequential manner from the floor 11c side of the case 11, and in the upper region of the case 11, a fixed terminal plate 19 and an insulating bushing 20 are insertedly provided in a sequential manner.
The fixed terminal plate 19 is preferably provided in a disc type made of metal. The fixed terminal plate 19 is placed on and fixed by the stepped portion while contacting an inner wall surface of the case 11 along a perimeter of a side surface so as to be electrically connected to the case 11. The fixed terminal plate 19 has a hole 19a such that the moving terminal 16 moves in a central axis direction while slidingly contacting the hole 19a. Thus, the fixed terminal plate 19 is electrically connected to the case 11 by contacting the inner wall surface of the case 11 and/or the stepped portion, and is also electrically connected to the moving terminal 16 slidingly contacting the hole 19a, and at the same time, the fixed terminal plate 19 also serves a role to guide the moving terminal 16, so that the moving terminal 16 moves while slidingly contacting an inner wall of the hole 19a.
The temperature-sensitive pellet 12 is made by compressing and molding a non-conductive organic material in a pellet shape. The temperature-sensitive pellet 12 has an initial height H0, and is installed to be loaded on the floor 11c inside the cabinet 11, and as illustrated in
A first lead 1 passes through a through-hole 21 of the insulating bushing 20, such that one end of which extends to the outside of the case 11 while a surface of the other end provides a first fixed contact 1a inside the through-hole 21. On the floor 11c of the case 11, a second lead 2 is electrically connected to the case 11 while facing the first lead 1. An opened upper side of the insulating bushing 20 is sealed with a sealing material 3.
The moving terminal 16 has, on one end, a first moving contact 16b contacting a first fixed contact 1a of the first lead 1 and, on the other end, a head part 16c expanded at a relatively greater diameter than the diameter of a body 16a. As illustrated in
The base plate 13 is disposed between the first spring and the temperature-sensitive pellet 12 so as to stably support one end of the first spring 17 even in the case that the temperature-sensitive pellet 12 is deformed by molten deformation or damage. The base plate 13 has a hole 13a such that a melted portion 12a may escape therethrough when the temperature-sensitive pellet 12 is deformed by being melted.
The thermal fuse according to an embodiment of the present invention has the activating member 15 configured to separate a first moving contact 16b of the moving terminal 16 from the first fixed contact 1a of the first lead 1 such that a switch performs an off operation when the temperature-sensitive pellet 12 is melted, in accordance with the rise of the periphery temperature, and is reduced in height from the initial height H0 to a predetermined height H2 or less at which the switch performs an off operation.
The activating member 15 is provided in a cylindrical shape having an opened lower end, an upper end having an upper end sidewall 15c, and a spring support step 15b on an outer surface of the lower end. The activating member 15 is placed on and supported by the base plate 13 and receiving the moving terminal 16 and the first spring 17 in an internal space thereof, wherein the body 16a of the moving terminal 16 passes through a through-hole 15a of the upper end sidewall 15c to extend towards the first lead 1, and the head part 16c is elastically supported by the first spring 17 in the internal space of the activating member 15. The second spring 18 having a relatively greater modulus of elasticity than the first spring 17 is elastically installed on the outside of the activating member 15 to elastically deflect the activating member 15 towards the temperature-sensitive pellet 12 in response to a height decrease due to melting of the temperature-sensitive pellet 12.
As illustrated in
As described above, when the moving terminal 16 moves in the same direction as a sliding movement direction of the activating member 15 by interlocking with a sliding movement of the activating member 15, the moving terminal 16 is guided by the body 16a slidingly contacting an inner wall of the hole 19a of the fixed terminal plate 19, so it is possible to prevent a phenomenon in which the moving terminal 16 is tilted and caught by an inner wall of the case to cause a malfunction.
Hereinafter, an operating mechanism of the thermal fuse according to an embodiment of the present invention will be described with reference to the accompanying drawings.
Normal State: Switched on State (
As illustrated in
From the state exhibited in
Switched Off State (
The temperature-sensitive pellet 12 is continuously melted as the periphery temperature rises, and is continuously reduced in height, and accordingly, the activating member 15 also moves towards the floor 11c of the case 11. However, after a time point (G=0) when the lower surface 15d of the upper-end sidewall 15c of the activating member 15 contacts the upper surface 16d of the head part 16c of the moving terminal 16, the activating member 15 moves the moving terminal 16 towards the temperature-sensitive pellet 12 by the force of the second spring 18, which is greater than the force of the first spring 17, to separate the first moving contact 16b from the first fixed contact 1a of the first lead, and thus a switch off operation is performed.
While the activating member 15 moves the moving terminal 16 for the switch off operation, the body 16a of the moving terminal 16 is linearly guided while sliding into the hole 19a of the fixed terminal plate 19, thus the moving terminal 16 performs a linear movement without shaking, and thus it is possible to prevent an inoperability or malfunction in that the moving terminal 16 is deflected in any one direction and caught by the inner wall of the case due to an uneven force of the spring which gives a moving force when the moving terminal 16 moves for the switch off operation.
According to the configuration set forth herein, when the moving terminal moves in accordance with melting of the temperature-sensitive pellet, the moving terminal is guided along the inner wall surface of the hole of the fixed terminal plate, and a separation of the moving terminal from the fixed contact is stably performed, so the switch operation is accurately performed within the predetermined temperature range without malfunction.
Also, the switching operation is performed only when the temperature-sensitive pellet is melted and deformed by a predetermined amount by rise of the periphery temperature without being directly affected by deformation of the temperature-sensitive pellet caused by unexpected factors such as external vibration or impact, thereby ensuring high operation reliability.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2016-0063954 | May 2016 | KR | national |
