WO2008127028A1

WO2008127028A1 - Apparatus for blocking overheat by using shape memory alloy

Info

Publication number: WO2008127028A1
Application number: PCT/KR2008/002046
Authority: WO
Inventors: Hwan-Kook Jung
Original assignee: Hwan-Kook Jung
Priority date: 2007-04-12
Filing date: 2008-04-11
Publication date: 2008-10-23

Abstract

An apparatus for preventing overheating in appliances and electric heat devices includes a shape memory alloy linear actuator linearly contracting by a predetermined deformation amount at a predetermined operating temperature, and a bias spring elastically moving in order to return a contact to its original position after the shape memory alloy linear actuator contracts. The apparatus can be semi-permanently used against overheating or overcurrent to reduce costs through repeated use thereof, is eco-friendly because it does not exhaust noxious gases even in a fire, and enhances product reliability through full range temperature inspection.

Description

APPARATUS FOR BLOCKING OVERHEAT BY USING SHAPE

MEMORY ALLOY

Technical Field

[1] The present invention relates to an apparatus for preventing overheating, and more particularly, to an apparatus for preventing overheating using a shape memory alloy. Background Art

[2] In general, an electric/electronic product carries the risk of accidents due to overheating and overcurrent. In order to prevent accidents, there is employed a disposable fuse, which is filled with a specific material that is melted by heat at a predetermined temperature, or a bimetal switch which uses two types of metal plates having different thermal expansion coefficients. Recently, a repeatedly usable fuse made of a specific polymer is used.

[3] The disposable fuse is cheap, but is not reusable, and the bimetal switch provides only a function of contact, and therefore has a large temperature deviation and requires, for example, a separate limiting device. Furthermore, the polymer fuse can be repeatedly used, but has poor material stability due to the use of chemical material, and has a slower response time, tending to cause an emergency situation, in which not even a moment's delay is admissible. Moreover, the polymer fuse has a problem of producing pollutants. Disclosure of Invention Technical Problem

[4] The present invention has been designed to solve the above mentioned problems with the prior art, and therefore the present invention is directed to an apparatus for preventing overheating using a shape memory alloy, which can be permanently used to protect against overheating and overcurrent.

[5] The present invention is also directed to an apparatus for preventing overheating using a shape memory alloy, which has excellent reliability against overheating and overcurrent.

[6] Furthermore, the present invention is also directed to an apparatus for preventing overheating using a shape memory alloy, which is eco-friendly. Technical Solution

[7] According to an aspect of the present invention, there is provided an apparatus for preventing overheating in appliances and electric heat devices. The apparatus includes a shape memory alloy linear actuator linearly contracting by a predetermined deformation amount at a predetermined operating temperature; and a bias spring elastically moving in order to return a contact to its original position after the shape memory alloy linear actuator contracts.

[8] The shape memory alloy linear actuator may be collinearly aligned with the bias spring.

[9] According to another aspect of the present invention, there is provided an apparatus for preventing overheating in appliances and electric heat devices. The apparatus includes a shape memory alloy linear actuator linearly contracting by a predetermined deformation amount at a predetermined operating temperature; a bias spring elastically moving in order to return a contact to its original position after the shape memory alloy linear actuator contracts; and a pivoting rod having a first end connected to one end of the shape memory alloy linear actuator and a second end connected to an end of the bias spring, the pivoting rod pivoting around a hinge.

[10] The shape memory alloy linear actuator may be arranged parallel to the bias spring.

Advantageous Effects

[11] According to the invention as mentioned above, the apparatus for preventing overheating using a shape memory alloy can be semi-permanently used to protect against overheating or overcurrent to reduce costs through repeated use thereof, is eco- friendly because it does not emit noxious gases even when incinerated, and enhances product reliability through full-range temperature inspection.

[12] Also, according to the invention, since the shape memory alloy is processed in a straight shape and has a constant deformation amount such that the shape memory alloy can operate by changing the inside structure thereof depending on the temperature, a particular shape thereof (e.g., a spring, a wire or plate which has a deformed portion, for example, by bending in order to cause a force in a non-straight state) is not required. Therefore, since each of the products manufactured as mentioned above can be repeatedly operated at a predetermined temperature, full range temperature inspection thereof can be performed to thus enhance product reliability.

[13] Furthermore, according to the invention, in manufacturing the shape memory alloy linear actuator, a continuously produced wire can be cut, and the cut wire can be used directly as the shape memory alloy linear actuator to allow mass production and enhance productivity.

Brief Description of the Drawings

[14] FIG. 1 is a view showing an operating process of an I-type overheating-preventing apparatus using a shape memory alloy according to a first embodiment of the invention;

[15] FIG. 2 is a view showing an operating process of an M-type overheating-preventing apparatus using a shape memory alloy according to a second embodiment of the invention; and

[16] FIG. 3 is a view showing an operating process of an alternative embodiment of the I- type overheating-preventing apparatus using a shape memory alloy according to the first embodiment of the invention.

[17] <Major Reference Numerals of Drawings>

[18] 110: shape memory alloy linear actuator

[19] 120: metal holder

[20] 122: shape memory alloy fixed terminal

[21] 130: bias spring 132: contact

[22] 140: lead wire 150: insulation case

[23] 210: shape memory alloy linear actuator

[24] 220: bias spring 230: pivoting rod

[25] 232: contact 234: hinge

[26] 240: lead wire 250: insulation case

Mode for the Invention

[27] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the attached drawings. In the following description, well- known constitutions and functions will not be described in detail when such unne cessary detail would obscure the invention.

[28] First Embodiment

[29] FIG. 1 is a view showing an operating process of an I-type overheating-preventing apparatus using a shape memory alloy according to a first embodiment of the invention.

[30] Referring to FIG. 1, FIG. l(a) shows the relaxed state of a shape memory alloy linear actuator 110, and FIG. l(b) shows the contracted state of the shape memory alloy linear actuator 110. The I-type overheating-preventing apparatus according to the invention includes the shape memory alloy linear actuator 110, adapted to linearly contract by a predetermined deformation amount at a predetermined operating temperature. The I-type overheating-preventing apparatus also includes two metal holders 110, a bias spring 130, a lead wire 140 and an insulation case 150. Each of the metal holders 110 has a shape memory alloy fixed terminal 122, which is connected to a corresponding end of the shape memory alloy linear actuator 110. The bias spring 130 is disposed between the two metal holders 120 and is adapted to elastically move in order to allow the metal holders 120 to touch a contact 132 again after the shape memory alloy linear actuator 110 contracts. The lead wire 140 is connected to the metal holders 120 and the contact 132, thereby forming a circuit. The insulation case 150 houses the shape memory alloy linear actuator 110, the metal holders 120, the bias spring 130, etc. Herein, the shape memory alloy linear actuator 110 and the bias spring 130 may be collinearly aligned, and the shape memory alloy linear actuator 110 may be disposed inside the bias spring 130.

[31] Furthermore, in the I-type overheating-preventing apparatus according to the invention, the shape memory alloy linear actuator 110, the metal holders 120 and the contact 132 may be electrically connected with each other to form a circuit.

[32] Describing the operation of the I-type overheating-preventing apparatus according to the invention, the shape memory alloy linear actuator 110 is in a relaxed state at room temperature, as shown in FIG. l(a). When the temperature rises due to the overheating of an object, particularly, above a predetermined temperature or in the occurrence of a fire, the shape memory alloy linear actuator 110 can contract by a deformation amount as shown in FIG. l(b) due to the change in the inside structure thereof. Therefore, the shape memory alloy linear actuator 110 can overcome the elastic force of the bias spring 130 to thus disconnect the metal holders 120 from the contact 132, so that the circuit can be cut off.

[33] Second Embodiment

[34] FIG. 2 is a view showing an operating process of an M-type overheating-preventing apparatus using a shape memory alloy according to a second embodiment of the invention.

[35] Referring to FIG. 2, FIG. 2(a) shows the relaxed state of a shape memory alloy linear actuator 210, and FIG. 2(b) shows the contracted state of the shape memory alloy linear actuator 210. The M-type overheating-preventing apparatus according to the invention includes the shape memory alloy linear actuator 210 connected to one end of a pivoting rod 230 and adapted to linearly contract by a predetermined deformation amount at a predetermined operating temperature. The M-type overheating-preventing apparatus also includes a bias spring 230, which is connected to the other end of the pivoting rod 230 and is adapted to elastically move in order to allow the one end of the pivoting rod to touch a contact 232 again after the shape memory alloy linear actuator 210 contracts. The pivoting rod 230 is adapted to pivot around a hinge 234 by contracting/relaxing movements of the shape memory alloy linear actuator 210 and the elastic movement of the bias spring 220. The M-type overheating-preventing apparatus also includes lead wires 240, each of which is connected to each of the shape memory alloy linear actuator 210 and the contact 232, thereby forming a circuit, and an insulation case 250, which houses the shape memory alloy linear actuator 210, the bias spring 220, etc. Herein, the shape memory alloy linear actuator 210 and the bias spring 210 may be arranged parallel to each other.

[36] Describing the operation of the M-type overheating-preventing apparatus according to the invention, as shown in FIG. 2(a), the shape memory alloy linear actuator 210 is in a relaxed state at room temperature, and one end of the pivoting rod 230 remains in contact with the contact 232 due to the elastic force of the bias spring 220. Then, when the temperature increases due to the overheating of an object to be heated, particularly, above a predetermined temperature or in the occurrence of a fire, the shape memory alloy linear actuator 210 can be contracted by the deformation amount thereof by changing the inside structure thereof as shown in FIG. 2(b). As a result, the shape memory alloy linear actuator 210 can overcome the elastic force of the bias spring 220 such that the pivoting rod 220 can be disconnected from the contact 232 and the circuit can be opened. In this case, the pivoting rod 230, to which the one end of the linear actuator 210 is secured, may be made of an electrically conductive material (e.g., a metal rod) or an electrically insulating material. When the pivoting rod 230 is made of an electrically insulating material, the end of the linear actuator 210 may have an extended structure to thus be connected through the pivoting rod 230 to the opposite lead wire 240. Furthermore, a portion of the pivoting rod 230, to which the linear actuator 210 is secured, may be made of an electrically conductive material, and the remaining portion thereof (i.e., the portion to which the bias spring 220 is connected) may be made of an electrically insulating material. When the pivoting rod 230 is made of an electrically conductive material or only the remaining portion thereof connected to the linear actuator 210 is made of an electrically conductive material, the linear actuator 210 and the bias spring 220 may remain in a state of being electrically insulated from each other. Even if the linear actuator 210 is broken due to overheating or overcurrent, the insulation between the linear actuator 210 and the bias spring 220 may prevent the bias spring 220 and the pivoting rod 230 from forming an electrical path, thereby effectively protecting the circuit.

[37] Meanwhile, when the overheating-preventing apparatus according to the invention is broken, the I-type overheating-preventing apparatus has to be disassembled into the shape memory alloy linear actuator 110, the metal holders 120 and the bias spring 130 in order to repair a broken part. In the case of the M-type overheating-preventing apparatus, a broken part can be easily detected and repaired since the shape memory alloy linear actuator 210 and the bias spring 130 are separated from each other.

[38] Third Embodiment

[39] FIG. 3 is a view showing the operating process of an alternative embodiment of the I- type overheating-preventing apparatus using a shape memory alloy according to the first embodiment of the invention.

[40] Referring to FIG. 3, FIG. 3 (a) shows the relaxed state of the shape memory alloy linear actuator 110. The I-type overheating-preventing apparatus according to this embodiment is similar to the first embodiment. Specifically, the overheating- preventing apparatus according to this embodiment includes the shape memory alloy linear actuator 110 adapted to linearly contract by a predetermined deformation amount at a predetermined operating temperature. The overheating-preventing apparatus also includes a bias spring 130, a lead wire 140 and an insulation case 150. The bias spring 130 is adapted to elastically move in order to allow metal holders 120 to touch a contact 132 again after the shape memory alloy linear actuator 110 contracts. The lead wire 140 is connected to the metal holders 120 and the contact 132, thereby forming a circuit. The insulation case 150 houses the shape memory alloy linear actuator 110, the metal holders 120, the bias spring 130, etc. Herein, the shape memory alloy linear actuator 110 and the bias spring 130 may be collinearly aligned, and the shape memory alloy linear actuator 110 may be disposed inside the bias spring 130.

[41] However, this alternative embodiment is different from the first embodiment in that at least one of two metal holders 120, each of which has a shape memory alloy fixed terminal 122 connected to a corresponding end of the shape memory alloy linear actuator 110, is made of a non-conductive material. More specifically, at least one of the metal holders 120 of the first embodiment is constructed as a non-conductive holder 120a. Also, one end of the linear actuator 110, which is secured to the non- conductive holder 120a, is disposed on the distal end of the non-conductive holder 120a via a fixed terminal 122a. Therefore, the bias spring 130 and the linear actuator 110, which are secured to the non-conductive holder 120a, can be electrically insulated.

[42] The circuit in the first embodiment, which consists of the external lead wire 140, the metal holder 120, the linear actuator 110, the metal holder 120 and the external lead wire 140, can be opened when the linear actuator 110 contracts at a predetermined temperature. At this time, when the temperature continuously increases, the linear actuator 110 can lose the property of a shape memory alloy, and in serious cases can break. Then, the bias spring 130 can return back such that electrical current can flow again through a circuit constituted by the metal holder 120, the bias spring 130 and the metal holder 120. Conversely, according to this embodiment, even when the linear actuator 110 has lost the property of the shape memory alloy, such that the bias spring 130 can return back, the electrical insulation by the non-conductive holder 120a can prevent electrical current from flowing. Therefore, due to the linear actuator 110, the overheating-preventing apparatus according to this embodiment can be repeatedly used within a predetermined temperature range, and can protect the circuit even when overheating or overcurrent occurs. FIG. 3(b) shows how to prevent electrical conduction when the linear actuator 110 is broken.

[43] The shape memory alloy materials used in both of the I-type and M-type overheating-preventing apparatuses of the invention may be Ni-Ti alloys, and the bias springs 130 and 220 may be made of materials having constant elastic force. As a result, the bias spring 130 and 220 can disconnect the contacts 132 and 232 due to the contraction of the shape memory alloy linear actuators 110 and 210 at a predetermined temperature, and then cause the contacts 132 and 232 to be connected again when force exerted by the shape memory alloy linear actuators 110 and 210 is reduced with temperature decrease. Furthermore, the insulation cases 150 and 250 may be made of a non-conductive material, such as glass, which can withstand higher temperatures and does not generate noxious material.

[44] The shape memory alloy linear actuators 110 and 210 according to the invention may be constituted by a wire 0.01 mm or more in diameter, and the shape memory alloy linear actuators 110 and 210 may contract in a range exceeding 0% and not exceeding 10% of the length of the shape memory alloy linear actuators 110 and 210. As a result, the shape memory alloy linear actuators 110 and 210 can withstand the elastic force of the bias springs 130 and 220 in a normal state, but can be appropriately deformed to overcome the elastic force of the bias springs 130 and 220 when an appliance or an electrical heating device is overheated.

[45] Furthermore, the shape memory alloy linear actuators 110 and 210 according to the invention may use shape memory alloy material having an operating temperature of more than 5O⁰C and less than 12O⁰C. If the shape memory alloy linear actuators 110 and 210 have an operating temperature of 5O⁰C or less, the shape memory alloy linear actuators 110 and 210 tend to operate due to hot weather, for example, in summer or in the event of a slight temperature increase. Conversely, if the shape memory alloy linear actuators 110 and 210 have an operating temperature of 12O⁰C or more, there is a risk of a fire occurring due to the overheating of an appliance and an electrical heating device since the operating temperature of the shape memory alloy linear actuators 110 and 210 is excessively high.

[46] According to the invention, since the shape memory alloy is processed to have a straight shape and has a constant deformation amount such that the shape memory alloy can be operated by changing the inside structure thereof to correspond to a temperature, a particular shape thereof (e.g., a spring, a wire or plate which has a deformed portion, for example, by bending in order to cause a force in a non-linear state) is not required. Therefore, since each of products manufactured as mentioned above can repeatedly operate at a predetermined temperature, full range inspection thereof can be performed to thus enhance product reliability, and a continuously produced wire can be cut and the cut wire can be used directly as the shape memory alloy linear actuators 110 and 210 to allow mass production and enhance productivity.

[47] As set forth above, it is to be appreciated that those skilled in the art can make substitutions, change or modify the embodiments into various forms without departing from the scope and spirit of the present invention. Accordingly, the foregoing embodiments should be regarded as illustrative rather than limiting. The scope of the present invention is not defined by the detailed description set forth above but by the accompanying claims of the invention. It should also be understood that all alterations or modifications derived from the definitions and scope of the claims and their equivalents fall within the scope of the invention.

Claims

[1] An apparatus for preventing overheating in appliances and electric heat devices, comprising: a shape memory alloy linear actuator linearly contracting by a predetermined deformation amount at a predetermined operating temperature; and a bias spring elastically moving in order to return a contact to an original position after the shape memory alloy linear actuator contracts.

[2] The apparatus according to claim 1, wherein the shape memory alloy linear actuator is collinearly aligned with the bias spring.

[3] The apparatus according to claim 1, further comprising two holders, each of which is secured to a corresponding end of the shape memory alloy linear actuator and a corresponding end of the bias spring.

[4] The apparatus according to claim 3, wherein at least one of the two holders is a non-conductive holder, and the corresponding end of the shape memory alloy linear actuator is disposed on an distal end of the non-conductive holder in order to be connected to an external lead wire, wherein the shape memory alloy linear actuator and the bias spring are electrically insulated from each other by the non- conductive holder.

[5] An apparatus for preventing overheating in appliances and electric heat devices, comprising: a shape memory alloy linear actuator linearly contracting by a predetermined deformation amount at a predetermined operating temperature; a bias spring elastically moving in order to return a contact to an original position after the shape memory alloy linear actuator contracts; and a pivoting rod having a first end connected to an end of the shape memory alloy linear actuator and a second end connected to an end of the bias spring, the pivoting rod pivoting around a hinge.

[6] The apparatus according to claim 5, wherein the shape memory alloy linear actuator is arranged parallel to the bias spring.

[7] The apparatus according to claim 5, wherein at least a portion of the pivoting rod is made of electrically insulating material, and the end of the shape memory alloy linear actuator is electrically connected to an external lead wire via the pivoting rod, wherein the shape memory alloy linear actuator and the bias spring are electrically insulated from each other by the pivoting rod.

[8] The apparatus according to any one of claims 1 through 7, wherein the shape memory alloy linear actuator comprises Ni and Ti.

[9] The apparatus according to any one of claims 1 through 7, wherein the shape memory alloy linear actuator comprises a wire having a diameter of 0.01 mm or more.

[10] The apparatus according to any one of claims 1 through 7, wherein the deformation amount of the shape memory alloy linear actuator contracts in a range exceeding 0% and not exceeding 10% of a length of the shape memory alloy linear actuator.

[11] The apparatus according to any one of claims 1 through 7, wherein the shape memory alloy linear actuator is shape memory alloy material having an operating temperature higher than 5O⁰C and lower than 12O⁰C.