Thermal protection

Abstract

Increased flexibility in setting a temperature for a reversing movement in a cantilevered bimetallic element. A thermal protection device comprises a thermally actuated element 100; this element has a substantially quadrilateral unsupported area 110, a supported area 120 connected to the unsupported area along a longitudinal direction of the unsupported area and to be attached to a stationary body, and a machined section 112, the center point of which is arranged within a triangular area T1 formed by a center point P1 of the unsupported area and the two ends of a boundary 130 between the unsupported area and the supported area.

Description

TECHNICAL FIELD

[0001] The present invention relates to a thermal protection device with a thermally actuated element. STATE OF THE ART

[0002] A bimetallic element is known, which is a thermally actuated element used for thermal protection.

[0003] Patent Document 1 describes a rectangular bimetallic element with a hole portion provided in a central portion. The hole portion serves to position the bimetallic element.

[0004] Patent Document 2 describes a bimetallic element having a reversing portion and a fixed portion. A hole portion for fixing is provided in the fixed portion.

[0005] Patent Document 3 describes a thermal protector in which a heat generating body is formed of a foil-shaped resistor and whose main heat generating portion is arranged near a bimetallic element. LIST OF CITED PRINTED PATENT LITERATURE Patent Document 1: JP 2003-059378 A Patent Document 2: JP H6-119859 A Patent Document 3: JP H11-86703 A SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0006] There is a problem that in a cantilever bimetallic element in which one end portion is fixed in the longitudinal direction, a reversing movement is restricted by the fixing of one end portion and the setting of a temperature at which the bimetallic element performs the reversing movement (especially the activation temperature) is restricted.

[0007] In view of the above circumstances, the present invention aims to increase the flexibility in setting a temperature for a reverse movement in a cantilevered bimetal element. MEANS FOR SOLVING THE PROBLEMS

[0008] According to one embodiment, a thermal protection has a thermally actuated element with the following: a substantially rectangular unfixed area; a fixed area that is connected to the unfixed area along a longitudinal direction of the unfixed area and is to be fixed to a stationary body; and a processed section, the center point of which is arranged within a triangular area formed by a center point of the unfixed area and the two end sections of a boundary section between the unfixed area and the fixed area. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0009] According to the present invention, in a cantilever bimetallic element, the flexibility in setting a temperature for a reversing movement can be increased. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A is a plan view of a bimetallic element according to a first embodiment. Fig. 1B is a cutaway plan view of a thermal protector that protects the Fig. 1A shown bimetallic element. Fig. 1C is a plan view of a bimetallic element according to a modification of the first embodiment. Fig. 2 is a plan view of a bimetallic element according to a second embodiment. Fig. 3 is a plan view of a bimetallic element according to a third embodiment. Fig. 4 is a plan view of a bimetallic element according to a fourth embodiment. Fig. 5A is a top view of a bimetallic element according to a fifth embodiment. Fig. 5B is a sectional view along the line A-A in Fig. 5A. Fig. 6 is a perspective view of a bimetallic element according to a sixth embodiment. EMBODIMENTS OF THE INVENTION

[0010] In the following, the present invention will be described with reference to illustrative embodiments. It should be noted that the present invention is not limited to the embodiments described below. First Embodiment

[0011] Fig. 1A shows a bimetallic element 100, which is a plate-like, thermally actuated element having an essentially rectangular overall shape. Fig. 1B is a cutaway plan view of a thermal protector 900 including the bimetallic element 100. The bimetallic element 100 has an unattached portion 110 and a secured portion 120 that are adjacent to each other in the longitudinal direction. The boundary between the unattached portion 110 and the secured portion 120 is designated by reference numeral 130.

[0012] The unfixed portion 110 is curved so that at least a portion thereof is upwardly convex when the bimetallic element 100 is positioned horizontally at ambient temperature, and its curvature direction is reversed so that the portion becomes downwardly convex when the temperature of the portion reaches a predetermined activation temperature. After the reversal, when the temperature of the unfixed portion 110 reaches a predetermined reset temperature, the inverted portion is reversed again so that it is upwardly convex. A tip portion 111 of the unfixed portion 110 engages with a claw portion 910 formed at an end portion of a movable conductive plate arranged below the bimetallic element 100 in a housing 910 of the thermal protector 900.

[0013] The fixed portion 120 has a greater width than the unfixed portion 110. A hole portion 121 is formed substantially at a center point of the fixed portion 120. This hole portion 121 is engaged with and fixed to a columnar portion 930 formed to extend in the up-down direction in the housing 910.

[0014] As stated above, in the cantilevered bimetallic element 100, the fixed region 120 is fixed and the unfixed region 110 is not fixed. That is, the entire unfixed region 110 of the bimetallic element 100, excluding the fixed region 120, is a reversal region that is reversed when it reaches the activation temperature.

[0015] A center point of the unpaved region 110 is designated by reference symbol P1. The center point P1 is the intersection point of a center line L1 extending in the longitudinal direction of the unpaved region 110 and a center line L2 extending in the transverse direction of the region. A triangular region T1 is formed by the center point P1 and the two end points P2 and P3 of the boundary 130. A circular machined portion (hole portion formed by punching) 112 is provided in the unpaved region 110, and a center point C1 of this circular machined portion 112 is located in the triangular region T1. Specifically, the center point C1 coincides with the intersection point of a line L3 connecting a middle point P4 of the side connecting the center point P1 and the end point P2 and the end point P3, and the center line L1.

[0016] In a cantilevered bimetallic element with a fixed portion and an unfixed portion, the fixation of the fixed portion tends to restrict the reversal movement of the unfixed portion. This tendency is more significant with a higher fixation strength of the fixed portion. As noted by the inventor, the triangular portion designated by reference symbol T1 is related to the restriction of reversal movement.

[0017] Therefore, the above-mentioned circular machined portion is provided in the bimetallic element. This reduces the restrictive effect on the reversing movement that occurs in the above-mentioned triangular region. As a result, the range within which the activation temperature is adjusted can be expanded.

[0018] According to the present embodiment, by partially providing a machined portion such as a hole in a reversing bimetal element, the occurrence of high stress on a side near the fixed area can be prevented, and the resulting stress can be easily relieved. As a result, an even wider temperature range can be achieved. The external shape and material used can be retained as conventional ones.

[0019] Furthermore, the reversal stroke (movement distance) of the tip portion of the unattached area can be increased in a temperature range close to 100°C. Furthermore, a narrow hysteresis can be set in this temperature range and a temperature range below it. In a temperature range above this temperature range, deeper drawing processing than conventional drawing can be performed.

[0020] As a result, a wider activation temperature range than the conventional one can be set, and a narrower hysteresis, or conversely a wider hysteresis, than the conventional one can be set.

[0021] With a temperature switch such as a thermal protector, a wide temperature range can be set.

[0022] The punched portion is not limited to a circular shape, but may be an elliptical or oval shape elongated in the transverse direction, or a polygonal shape (not shown) with rounded corners. Furthermore, its shape may be based on a U-shape or V-shape.

[0023] On the other hand, punching reduces the reversal force because it involves a surface-reducing process. This can be counteracted by increasing the material thickness.

[0024] Furthermore, the reversal force can also be increased by modifying the outer shape within the tolerances. Accordingly, the ratio between the length and width of the outer shape can be changed. Furthermore, a barrel shape, whose longitudinal center section is enlarged outward in the transverse direction, or a polygonal shape, whose width gradually decreases toward the tip section, can also be used.

[0025] Furthermore, if the area of ​​the machined portion provided in conjunction with the above-mentioned triangular region is too wide, it will cause a reduction in the reversing force, preventing the snap action. Accordingly, the area of ​​the machined portion is desirably no more than 15% of the area of ​​the unattached region 110 before punching.

[0026] In areas of the two end sections in the transverse direction of the unpaved area 110 located on the side of the boundary 130, narrowing sections are provided whose dimension decreases in the transverse direction and which are adjacent to the boundary.

[0027] As in Fig. 1C, a bimetallic element 100a may further include a circular machined portion (hole portion) 112a. A center point C1 of the circular machined portion 112a coincides with the intersection point of a line L4 connecting a center point P5 of the side connecting the center point P1 and the end point P3 and the center point P4, and the center line L1. Alternatively, the circular machined portion in question may be provided such that the center point of the circular machined portion lies on the center line L1 and is located between the point C1 ( Fig. 1A) and point C1a ( Fig. 1C). Second embodiment

[0028] Fig. 2 shows a bimetallic element 200 according to the present embodiment. The same elements as in Fig. 1A are denoted by the same reference numerals, and their detailed description will be omitted. In the bimetallic element 200, a machined portion (hole portion) 212 having an oval shape elongated in the same direction as the longitudinal direction of the bimetallic element is provided. A center point of this machined portion 212 is located on the center line L1. The entire machined portion 212 may be located within the triangular region T1, or a part of the machined portion 212 may be located in the fixed region 120.

[0029] Although the activation temperature is set using a similar procedure to the first embodiment, in order to reduce stresses generated by processing in the triangular region, providing the oval-shaped cutout portion as mentioned above reduces the stresses when performing drawing processing and enables processing into a deeper shape. This demonstrates that a wider temperature setting is possible and that the recovery temperature can be set widely because the longitudinal cutout results in greater hysteresis. Third embodiment

[0030] For a bimetal element 300, which is Fig. 3, two machined portions (hole portions) 312 are provided in a row in the transverse direction. The two machined portions are circular, and their centers lie on a line segment connecting point P4 and point P5. Furthermore, the two machined portions are respectively arranged to intersect with the side of the triangular region T1 connecting point P1 and point P2 and the side thereof connecting point P1 and point P3, respectively.

[0031] Compared to the case with only one circular section, the provision of two small circular sections can easily compensate for the influence of further machining and limit a change in hysteresis. Fourth embodiment

[0032] A bimetal element 400, which is Fig. 4, in addition to the Fig. 1C, the bimetallic element 100a has a circular machined portion (hole portion) 412 at a position symmetrical to the machined portion 112a with respect to the center line L2.

[0033] By providing the machined portion 112a whose center is located in the triangular region and the machined portion 412 located outside the triangular region, stress relief with respect to the reversing movement is improved, a warpage shape after the reversing movement is larger, a moving range of the unfixed portion in the reversing movement is increased, a contact movement is large, and a contact pitch (the distance between a movable contact and a fixed contact in the thermal protector) can be set large.

[0034] As the area of ​​the unattached region decreases compared to that before punching, the reversal force decreases. To improve this, the thickness of the bimetallic element can be increased to increase the reversal force. Fifth embodiment

[0035] For a bimetal element 500, which is Fig. 5A and Fig. 5B, a circular machined portion 512 is provided in the triangular region T1. This machined portion 512 is formed not by punching but by drawing, so that it will not be reversed even when the temperature of the bimetallic element reaches the activation temperature. Specifically, while a reversal portion 510a of an unfixed portion 510 of the bimetallic element 500 is curved upwardly with a convex recess, the machined portion (the drawing portion) 512 is curved downwardly with a convex recess.

[0036] As stated above, by performing the drawing processing in such a manner that the curvature directions at the reversal region 510a and the processed portion 512 are directly opposite, there is little restrictive effect on the reversal movement, and similar effects to those of the punching processing are achieved.

[0037] In particular, in the case of identically executed curvature directions with only different curvatures at the reversal region 510a and the machined section 512, the restricting effect on the reversal movement is greater than in the case that the machined section in question does not exist.

[0038] This is because, although the drawing processing for downward convex deformation of the machined portion has the effect of promoting the inversion of the inversion region under recess of 512, the drawing processing for upward convex deformation of the machined portion has the effect of restricting the inversion of the inversion region under recess of 512.

[0039] The more precisely a contour section of the machined portion 512 is defined, the greater the reversal-promoting effect. When the contour section is indefinite, that is, when the reversal region 510a and the machined portion 512 are connected via a curved surface, the edges of the drawn shape are large and the reversal-promoting effect is small. In particular, the drawing depth is not particularly important, and shallow machining is preferable as long as the shape can be maintained. Sixth embodiment

[0040] As in Fig.As shown in Fig. 6, a bimetallic element 600 according to the present embodiment includes an unfixed portion 610 and a fixed portion 6120. Viewed along the transverse direction and the longitudinal direction of the bimetallic element 600, the unfixed portion 610 is upwardly convexly curved so that a predetermined reversal temperature is set for the unfixed portion 610. This curvature is achieved by drawing processing. A vertex PT of this curved shape is located between the center point P1 and a tip portion 611 of the unfixed portion 610. In other words, the vertex PT is eccentric to the side of the tip portion 611 having a large reversal movement. The curvature of the curved shape from the vertex PT to the tip portion 611 is greater than the curvature of the curved shape from the vertex PT to a boundary 630 between the unpaved region 610 and the paved region 120.The triangular region formed by the two end portions of the boundary 630 and the center point P1 thus has a curved shape with a relatively gentle slope. A machined portion (hole portion) 612 is provided in this triangular region.

[0041] The above embodiments relate to the processing of a bimetallic element used for a thermal protector that turns a current on and off by driving a movable plate (or conductive plate) and a movable contact. In a cantilever bimetallic element, the effect of increasing flexibility in setting a temperature for reversal movement is achieved by providing a machined portion (punched portion or drawn portion) at a portion where large stresses occur, which has a reversal movement restricting effect. Specifically, a cantilever bimetallic element can be provided whose activation temperature is set to a relatively high value, which is conventionally difficult to achieve.For example, while the upper limit of the activation temperature is conventionally about 150°C, according to the above embodiments, the upper limit of the activation temperature can be increased to about 200°C.

[0042] Two or more of the above embodiments may be combined as long as no contradiction arises.

[0043] The above embodiments are also applicable to thermally actuated elements other than bimetallic elements, such as shape memory alloys (100°C or below) and trimetals.

[0044] With reference to the embodiments described above, the following additions are disclosed. Supplement 1

[0045] A thermal protector with a thermally actuated element comprising: a substantially rectangular unpaved area; a fixed portion connected to the unfixed portion along a longitudinal direction of the unfixed portion and to be fixed to a stationary body; and a machined portion having a center point located within a triangular area formed by a center point of the unpaved portion and the two end portions of a boundary portion between the unpaved portion and the paved portion. Supplement 2

[0046] The thermal protector according to Supplement 1, wherein the thermally actuated member has a constriction portion adjacent to the boundary at the two end portions of the unfixed area in the transverse direction and whose dimension decreases in the transverse direction, and the machined portion is a hole portion. Supplement 3

[0047] Thermal protection according to Supplement 1, wherein the machined portion has an oval shape which is elongated in the longitudinal direction of the unpaved area. Supplement 4

[0048] Thermal protection according to Supplement 1, where the number of sections processed is two, one of the machined sections is arranged to intersect with one of two sides of the triangular area emanating from the center of the unpaved area, and the other of the machined sections is arranged to overlap with the other of the two sides. Supplement 5

[0049] Thermal protection according to Supplement 1, wherein the thermally actuated element has a further machined portion at a position symmetrical with the machined portion with respect to a line passing through the center of the unpaved area and extending in the transverse direction. Supplement 6

[0050] Thermal protection according to Supplement 1, wherein a section of the unfixed area, excluding the machined section, and the machined section are curved and have different directions of curvature from each other. Supplement 7

[0051] The thermal protector according to Supplement 1, wherein the unpaved portion has a curved shape and an apex of the unpaved portion is disposed between the center of the unpaved portion and a tip portion of the unpaved portion in the longitudinal direction.

[0052] Embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical concept of the present invention. LIST OF REFERENCE SYMBOLS 100, 100a, 200, 300, 400, 500, 600 bimetal element 110 unpaved area 111 peak section 112, 112a, 212, 312, 412, 512, 612 edited section 120 paved area 130 border T1 triangular area QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2003-059378 A

[0005] JP H6-119859 A

[0005] JP H11-86703 A

[0005]

Claims

[1] Thermal protection with a thermally actuated element comprising: a substantially rectangular unpaved area; a fixed portion connected to the unfixed portion along a longitudinal direction of the unfixed portion and fixed to a stationary body; and a machined portion having a center point located within a triangular area formed by a center point of the unpaved portion and the two end portions of a boundary portion between the unpaved portion and the paved portion. [2] Thermal protection according to claim 1, wherein the thermally actuated element has a narrowing portion adjacent to the boundary at the two end portions of the unpaved area in the transverse direction, and a dimension of the narrowing portion in the transverse direction decreases, and the machined section is a hole section. [3] The thermal protector according to claim 1, wherein the machined portion has an oval shape elongated in the longitudinal direction of the unfixed portion. [4] Thermal protection according to claim 1, wherein the number of sections processed is two, one of the machined sections is arranged to intersect with one of two sides of the triangular area emanating from the center of the unpaved area, and the other of the machined sections is arranged to overlap with the other of the two sides. [5] The thermal protector according to claim 1, wherein the thermally actuated member has another machined portion at a position symmetrical with the machined portion with respect to a line passing through the center of the unfixed area and extending in the transverse direction. [6] The thermal protector according to claim 1, wherein a portion of the unfixed area, excluding the machined portion, and the machined portion are curved and have different curvature directions from each other. [7] The thermal protector according to claim 1, wherein the unfixed portion has a curved shape and an apex of the unfixed portion is disposed between the center of the unfixed portion and a tip portion of the unfixed portion in the longitudinal direction.

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