Thermal overload relay

Abstract

To provide a thermal overload relay that can be automatically assembled by simplifying assembly.SOLUTION: A push shifter 14 and a pull shifter 15 are provided, which are displaced by engaging with a plurality of bimetals 13U, 13V, 13W from one side and the other side in a displacement direction. The push shifter has an elongated hole formed in the displacement direction, and the pull shifter also has an elongated hole formed in the displacement direction. Projections 45a1, 45b1, 45a2, 45b2 protruding from an end face of a partition wall of a case 12 are formed with shifter fall-off prevention portions 48b, 49b that prevent the push shifter and the pull shifter from falling off when the shifter fall-off prevention portions are fitted into the elongated holes of the push shifter and the pull shifter and moved in the displacement direction.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a thermal overload relay. [Background technology]

[0002] When an overcurrent continues to flow, a thermal overload relay trips by bending the bimetal due to heat, and protects the main circuit from overload by shutting off the electromagnetic contactor or molded case circuit breaker. As shown in Patent Document 1, when the bimetal of a thermal overload relay is heated and bent, it pushes the shifter to activate the reversing mechanism and enters a tripped state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-107023 Summary of the Invention [Problem to be solved by the invention]

[0004] Thermal overload relays are available in 2E (two-element) type, which protect the main circuit from overload and phase loss. Inside the case 12, there are arranged a three-phase bimetal (U, V, W), a push shifter, a pull shifter, a lever, a reversing mechanism, etc. The assembly of this 2E type thermal overload relay involves assembling the push shifter, pull shifter, and lever together, then engaging the push shifter and pull shifter with the free ends of the bimetal, and engaging the lever with the compensating bimetal of the reversing mechanism. However, the assembly procedure for the push shifter, pull shifter, and lever is complicated, and it is difficult to align the push shifter and pull shifter with the free ends of the bimetal, and to align the lever with the compensating bimetal.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal overload relay that can be assembled automatically by simplifying the assembly process. [Means for solving the problem]

[0006] In order to achieve the above object, one embodiment of the present invention provides a thermal overload relay comprising a plurality of partitions provided inside a case, a plurality of bimetals arranged between the partitions and bending when heated, a shifter attached to cover the ends of the plurality of partitions and displaced when pushed by the bimetal when the bimetal bends, a lever that rotates when pushed by the displacement of the shifter, and a reversing mechanism that reverses the contacts when pushed by the rotation of the lever, and is provided with a plurality of elongated holes extending longitudinally in the displacement direction of the shifter, a plurality of protrusions protruding from the end faces of the plurality of partitions and into which the elongated holes are slidably fitted to guide the displacement of the shifter, and a shifter fall-off prevention portion that prevents the shifter from falling off from the partitions by moving the shifter in the displacement direction, with the elongated holes fitted into the plurality of protrusions. [Effects of the Invention]

[0007] According to the thermal overload relay of the present invention, by providing a shifter fall-off prevention portion that prevents the shifter from falling off the case, assembly can be simplified and automated. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a thermal overload relay of a first embodiment according to the present invention with a cover removed. [Figure 2] FIG. 1 is a perspective view showing a thermal overload relay. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. 2 is a diagram illustrating a configuration of a differential lever. [Figure 7] FIG. 2 is a diagram showing the positions of a push shifter, a pull shifter, and a differential lever. [Figure 8]FIG. 8 is a cross-sectional view taken along the arrow BB in FIG. 7. [Figure 9] FIG. 10 is a diagram showing the state in which the pull shifter is attached to the case. [Figure 10] FIG. 10 is a diagram showing the state in which the push shifter is attached to the case. [Figure 11] FIG. 10 is a diagram showing a state in which the differential lever is attached to the case. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the drawings are schematic and may differ from the actual product. Furthermore, the following embodiments exemplify devices and methods for embodying the technical concept of the present invention, and are not intended to limit the configuration to that described below. In other words, the technical concept of the present invention can be modified in various ways within the technical scope described in the claims. In the following description, for convenience, three mutually orthogonal directions will be referred to as the vertical direction, the width direction, and the depth direction.

[0010] FIG. 1 is a diagram showing a thermal overload relay 11 according to a first embodiment of the present invention. The thermal overload relay 11 is a three-element 2E (two-element) type device that provides overload and phase loss protection. 1 and 2, the thermal overload relay 11 has, inside a case 12, U, V, and W three-phase bimetal elements 13U, 13V, and 13W, a push shifter 14, a pull shifter 15, a differential lever 16, a reversing mechanism 24, and a reset rod 25. Here, the differential lever 16 is referred to as a lever in this invention.

[0011] The three-phase bimetals 13U, 13V, and 13W extend in the depth direction and are formed as plates aligned in the vertical and depth directions, with the front end in the depth direction being a fixed end and the back end being a free end. Each of the bimetals 13U, 13V, and 13W has its front end connected to a main terminal and its back end joined to one end of a heater 26. The heater 26 is wound around each of the bimetals 13U, 13V, and 13W, and its other end joined to a connection terminal 27 on the front side in the depth direction.

[0012] The push shifter 14 and the pull shifter 15 are supported by the case 12 so that they are flush with each other in the thickness direction. When an overload condition occurs, the three-phase bimetals 13U, 13V, and 13W bend, displacing the push shifter 14 to the other side in the width direction, and along with the displacement of the push shifter 14, the pull shifter 15 and the differential lever 16 are displaced. When a phase loss occurs, the unbent bimetal of the phase where the loss occurred restricts the displacement of the pull shifter 15, so that the push shifter 14 displaces in the same way as when an overload condition occurs.

[0013] The reversing mechanism 24 is a mechanism that reverses the contacts when an overload is detected, i.e., closes the a-contact and opens the b-contact, and includes a compensating bimetal 31, a release lever 32, a tension spring 33, a movable plate 34, a leaf spring 35, and an interlocking plate 36. The reversing mechanism 24 is not a major component of the embodiment, so only an outline will be given. The compensating bimetal 31 extends in the depth direction and is formed in the shape of a flat plate along the depth direction and the vertical direction, with the front side in the depth direction fixed to the release lever 32 and the back side in the depth direction being the free end which engages with the lever 16. The release lever 32 extends in the depth direction and is formed in the shape of a plate along the depth direction and the vertical direction, and is rotatably supported by a support shaft along the vertical direction, with the rear side in the depth direction in contact with the tension spring 33. The tension spring 33 pulls the movable plate 34 toward the rear side in the depth direction.

[0014] The movable plate 34 is flat and extends in the depth and vertical directions, with the front side of the movable plate 34 being movable in the width direction, with the rear side in the depth direction as a fulcrum. The upright position of the movable plate 34 is its dead center, and when a force acts on one or the other side in the width direction, the movable plate 34 tilts to one or the other side in the width direction due to the tension of the tension spring 33. Under normal conditions, the movable plate 34 tilts to one side in the width direction, but when an overload occurs, the movable plate 34 is pushed to the other side in the width direction by the release lever 32 via the compensating bimetal 31. The rear side in the depth direction of the movable plate 34 is connected to one of the auxiliary terminals, and a movable contact is formed on the front side in the depth direction.

[0015] The leaf spring 35 is a flat plate extending in the depth direction and aligned in the depth and vertical directions, with the rear side in the depth direction connected to the other auxiliary terminal and a fixed contact formed on the front side in the depth direction facing the movable plate 34. Under normal conditions, the movable contact of the movable plate 34 is separated from the fixed contact of the leaf spring 35, but when an overload condition occurs, the movable plate 34 tilts to the other side in the width direction, causing the movable contact of the movable plate 34 to come into contact with the fixed contact of the leaf spring 35. The fixed contact and the movable contact constitute an a-contact, and the trip state is achieved when the a-contact is closed.

[0016] Interlocking plate 36 is formed in the shape of a plate extending in the width and depth directions, is rotatably supported by a vertical support shaft, and its rear side in the depth direction engages with movable plate 34. Interlocking plate 36 rotates in conjunction with movable plate 34, thereby opening and closing the contacts on the back side of interlocking plate 36 (not shown in the figure). That is, under normal circumstances, the movable contact is in contact with the fixed contact, but when an overload condition occurs, interlocking plate 36 rotates, causing the movable contact to separate from the fixed contact. These fixed contact and movable contact constitute a b-contact, and a trip condition is achieved when the b-contact opens.

[0017] The reset rod 25 is an operating element for recovering from a tripped state. It is formed in a generally cylindrical shape with its axis extending in the depth direction, and is disposed on the other side of the case 12 in the vertical direction and the other side of the width direction. The reset rod 25 is supported by the case 12 so as to be displaceable in the depth direction and rotatable about its axis, and is further biased toward the front side in the depth direction by a leaf spring 35 extending in the vertical direction. The reset rod 25 has an initial position, a manual reset position, and an automatic reset position. The initial position is a position where the front side in the depth direction protrudes beyond the case 12. The manual reset position is a position where the reset rod 25 is simply pushed toward the rear side in the depth direction from the initial position. The automatic reset position is a position where the reset rod 25 is pushed toward the rear side in the depth direction from the initial position and rotated approximately 90 degrees clockwise as viewed from the front side in the depth direction, thereby maintaining its position in the depth direction.

[0018] As shown in FIG. 2, the case 12 has partition walls 41 to 43 and a girder plate 44 formed inside the case 12. Here, the girder plate 44 is described as a wall portion of the case. On the other vertical side of the partition walls 41 to 43, multiple protrusions 45a1, 45b1 are formed lined up along the width direction. The protrusions 45a1 formed on the partition walls 41, 43 protrude in a columnar shape. The protrusion 45b1 formed on the partition wall 42 is formed with a column portion 48a protruding from the partition wall 42 and a head portion 48b protruding from the tip of the column portion 48a to the other vertical side. A plurality of protrusions 45a2, 45b2 are also formed lined up in the width direction on one vertical side of the partition walls 41 to 43. The protrusions 45a2 formed on the partition walls 41, 43 protrude in a columnar shape. The protrusion 45b2 formed on the partition wall 42 includes a pillar portion 49a protruding from the partition wall 42 and a head portion 49b protruding from the tip of the pillar portion 49a to the other side in the vertical direction.

[0019] As shown in FIG. 3, the push shifter 14 has a slot 51 formed on one widthwise side to receive the protrusion 45a1 of the partition wall 41, and a slot 52 formed on the other widthwise side to receive the protrusions 45b1 of the partition wall 42 and the protrusions 45a1 of the partition wall 43. The width of the slot 52 on one widthwise side is larger than the vertical dimension of the head 48b of the protrusion 45b1, and the width of the slot 52 on the other widthwise side is smaller than the vertical dimension of the head 48b of the protrusion 45b1 and larger than the vertical dimension of the column 48a of the protrusion 45b1. One widthwise side of the slot 52 corresponds to the mounting hole described in the present invention. The push shifter 81 also has engagement pieces 53-55 formed on one vertical side.

[0020] The pull shifter 15 is a substantially rectangular insulator with its long sides extending widthwise and its short sides extending vertically. As shown in FIG. 4 , the pull shifter 15 has a slot 85 formed on one widthwise side, into which the protrusion 45a2 of the partition wall 41 fits, a slot 86 formed on the other widthwise side, into which the protrusion 45b2 of the partition wall 43 fits, and a slot 87 formed on one vertical side between the slots 85 and 86. The width of the slot 87 on the other widthwise side is larger than the vertical dimension of the head 49a of the protrusion 45b2, and the width of the slot 87 on one widthwise side is smaller than the vertical dimension of the head 49a of the protrusion 45b2 and larger than the vertical dimension of the cylindrically protruding portion of the protrusion 45b2. The other widthwise side of the slot 87 corresponds to the mounting hole described in the present invention. In addition, the pull shifter 82 has engagement pieces 88 to 90 formed on the other vertical side, and an engagement groove 91 that opens on the other vertical side and extends to one side is formed on the other widthwise side of the pull shifter 82.

[0021] FIG. 5 is a perspective view showing the differential lever 16, FIG. 6(a) is a view of the differential lever 16 as seen from the other side in the width direction, and FIG. 6(b) is a cross section taken along line AA in (a). The differential lever 16 has a pair of opposing plates 92, 93 formed on one side in the vertical direction. The pair of opposing plates 92, 93 are formed as flat plates extending in the vertical and width directions, face each other while being spaced apart in the depth direction, and are connected by a cylindrical support shaft 94 extending in the depth direction. The distance between the pair of opposing plates 92, 93 is slightly greater than the thickness of the girder plate 44 of the case 12, and the diameter of the support shaft 94 is slightly smaller than the groove width of the engagement groove 91 of the pull shifter 82. The other side in the vertical direction of the differential lever 16 has an end surface 95 formed as a flat surface extending in the vertical and depth directions and facing one side in the width direction. The other side in the vertical direction of the differential lever 16 has an end surface 96 formed as a curved surface extending in the depth direction and convex toward the other side in the width direction.

[0022] 7, the push shifter 14 is disposed so as to be displaceable in the width direction by fitting the elongated hole 51 onto the protrusion 45a1 of the partition wall 41 of the case 12, and the elongated hole 52 onto the protrusions 45b1 of the partition wall 42 and the protrusions 45a1 of the partition wall 43. When the protrusion 45b1 of the partition wall 42 is located on one side of the elongated hole 52 in the width direction, the hole width is set to allow the head 48b to pass through, making it possible to remove the push shifter 14. When the protrusion 45b1 of the partition wall 42 is located on the other side of the elongated hole 52 in the width direction, the head 48b of the protrusion 45b1 acts as a retainer, making it impossible to remove the push shifter 14. In addition, the engagement piece 53 of the push shifter 14 engages with the free end of the U-phase bimetal 13U from the other side in the width direction, and the engagement piece 54 engages with the free end of the V-phase bimetal 13V from the other side in the width direction. The engaging piece 55 engages with the free end of the W-phase bimetal 13W from the other side in the width direction, and the differential lever 16 engages with a tip 56 facing the other side in the width direction.

[0023] 7, the pull shifter 15 is disposed so as to be displaceable in the width direction by fitting the elongated hole 85 with the partition wall 41 and the protrusion 45a2 of the case 12, the elongated hole 86 with the protrusion 45a2 of the partition wall 43, and the elongated hole 87 with the protrusion b2 of the partition wall 42. When the protrusion 45b2 of the partition wall 42 is on the other side of the width direction of the elongated hole 58, the hole width is set to allow the head 49b to pass through, making it possible to remove the pull shifter 82. When the protrusion 45b2 of the partition wall 42 is on one side of the width direction of the elongated hole 58, the head 49b of the protrusion 45b2 acts as a retainer, making it impossible to remove the pull shifter 15. Additionally, engagement piece 88 of pull shifter 15 engages with the free end of U-phase bimetal 13U from one widthwise side, engagement piece 89 engages with the free end of V-phase bimetal 13V from one widthwise side, and engagement piece 90 engages with the free end of W-phase bimetal 13W from one widthwise side.

[0024] 7 and 8, the differential lever 16 is supported on the case 12 so as to be rotatable about a support shaft 94, with a pair of opposing plates 92, 93 sandwiching the girder plate 44 of the case 12 and the support shaft 94 fitting into the engagement groove 91. An end face 95 of the differential lever 16 facing one widthwise side engages with the tip 56 of the engagement piece 55 of the push shifter 14. An end face 96 of the differential lever 16 facing the other widthwise side engages with the free end of the compensating bimetal 31 of the reversing mechanism 24.

[0025] When the thermal overload relay 11 of the first embodiment enters an overload state, the three-phase bimetals 13U, 13V, and 13W bend, causing the push shifter 14 and the pull shifter 15 to displace to the other side in the width direction. As the push shifter 14 and the pull shifter 15 displace to the other side in the width direction, the end face 95 of the differential lever 16 is pressed by the tip of the engagement piece 55, causing the differential lever 16 to rotate counterclockwise around the support shaft 93 as the center of rotation. As a result, the free end side of the compensating bimetal 31 displaces to the other side in the width direction, causing the reversing mechanism 24 to enter a trip state in which the a-contact is closed and the b-contact is opened.

[0026] Next, we will explain what happens when a phase loss occurs in one of the three-phase bimetals 13U, 13V, and 13W. For example, if the U-phase bimetal 13U is lost, the bimetal 13U is not heated as much as the other bimetals 13V and 13W, resulting in a lower temperature. Therefore, no bending displacement occurs, or even if bending displacement does occur, it is smaller than the other bimetals 13V and 13W. As the bending displacement of the three-phase bimetals 13U, 13V, and 13W varies from phase to phase, the push shifter 14 displaces toward the compensating bimetal 31 by the amount of the bimetal 13V or 13W with the largest bending displacement, while the pull shifter 15 displaces only the amount of the bimetal 13U with the smallest bending displacement, resulting in a difference in the amount of displacement between the push shifter 14 and the pull shifter 15. When this differential occurs, the counterclockwise rotation of the differential lever 16 around the support shaft 94 becomes larger than in an overload state. This rotation of the differential lever 16 causes the displacement of the differential lever 16 to be greater than the displacement of the push shifter 14. As a result, if an open phase occurs, the trip state occurs earlier than when an overload current flows.

[0027] Next, the assembly of the push shifter 14, pull shifter 15 and differential lever 16 that constitute the thermal overload relay 80 of the first embodiment will be described. First, the assembly of the pull shifter 15 will be described with reference to FIG. 9. The pull shifter 82 is moved from the rear to the front in the depth direction toward the side where the protrusions 45a2 and 45b2 of the partition walls 41 to 43 are provided. Then, the protrusion 45a2 is fitted into the elongated holes 85 and 86 of the pull shifter 15, and the head 49b of the protrusion 45b2 is fitted into the other side in the width direction (the mounting hole) of the elongated hole 87. Next, the pull shifter 15 is slid toward the other side in the width direction (the direction of arrow S1 shown in FIG. 9). At this time, the engagement pieces 88 to 90 engage with the free ends of the three-phase bimetals 13U, 13V, and 13W from one side in the width direction, completing the alignment of the pull shifter 15. When the alignment of the pull shifter 15 is completed, the protrusion 45b2 moves to one side of the elongated hole 87 in the width direction, and the head 49b of the protrusion 45b2 is prevented from coming off from one side of the elongated hole 87 in the width direction, and the pull shifter 15 is assembled to the case 12 in a state where it is prevented from falling off to the back side in the depth direction.

[0028] Next, the assembly of the push shifter 14 will be described with reference to FIG. 10. The push shifter 14 is moved from the rear to the front in the depth direction toward the side where the protrusions 45a1 and 45b1 of the partition walls 41 to 43 are provided. Then, the protrusion 45a1 is fitted into the elongated hole 51 of the push shifter 14, and the head 48b of the protrusion 45b1 is fitted into one side in the width direction (the mounting hole) of the elongated hole 52. Next, the push shifter 14 is slid toward one side in the width direction (the direction of arrow S2 shown in FIG. 10). At this time, the engagement pieces 53 to 55 engage with the free ends of the three-phase bimetals 21U, 21V, and 21W from the other side in the width direction, completing the alignment of the push shifter 81. When the alignment of the push shifter 14 is completed, the protrusion 45b1 moves to the other side of the elongated hole 52 in the width direction, and the head 48b of the protrusion 45b1 is prevented from coming off from the other side of the elongated hole 52, and the push shifter 14 is assembled to the case 12 in a state where it is prevented from falling off to the back side in the depth direction.

[0029] Next, the assembly of the differential lever 16 will be described with reference to Figures 18 and 11. The differential lever 16 is moved to one side in the vertical direction (the direction of arrow S3 shown in Figure 11) until the pair of opposing plates 92, 93 abuts against the engagement groove 91 of the pull shifter 15 and the girder plate 44. As a result, the differential lever 16 is positioned with the pair of opposing plates 92, 93 sandwiching the girder plate 44, as shown in Figure 8, and is assembled to the case 12 in a state where it is prevented from falling off to the far side in the depth direction. In the above-described assembly procedure for the push shifter 14, pull shifter 15, and differential lever 16, the pull shifter 15 is first assembled to the case 12, followed by the push shifter 14. However, it is also possible to assemble the push shifter 14 and then the pull shifter 15 to the case 12.

[0030] Next, the main operation of the thermal overload relay 11 of the first embodiment will be described. The push shifter 14 moves from the back side to the front side in the depth direction to fit the protrusion 45a1 into the elongated hole 51, and then fits the head 48b of the protrusion 45b1 into one side (mounting hole) in the width direction of the elongated hole 52, and then slides toward one side in the width direction. As a result, the engagement pieces 53 to 55 of the push shifter 14 engage with the free ends of the three-phase bimetals 13U, 13V, and 3W, completing the alignment. After this alignment is completed, the head 48b of the protrusion 45b1 functions as a retainer to prevent the push shifter 14 from falling out of the other side of the elongated hole 52, and the push shifter 14 is assembled to the case 12 in a state where it is prevented from falling out.

[0031] Furthermore, the pull shifter 15 moves from the rear side to the front side in the depth direction, fitting the protrusion 45a2 into the elongated holes 85 and 86, and fitting the head 49b of the protrusion 45b2 into the other widthwise side (mounting hole) of the elongated hole 87, and then slides toward the other widthwise side. As a result, the engagement pieces 88-90 of the push shifter 14 engage with the free ends of the three-phase bimetals 13U, 13V, and 13W, completing the alignment. After this alignment is completed, the head 49b of the protrusion 45b2 functions as a retainer to prevent the pull shifter 15 from falling out from one widthwise side of the elongated hole 87, and the pull shifter 15 is assembled to the case 12 in a state where it is prevented from falling out.

[0032] Furthermore, by moving the differential lever 16 to one side in the vertical direction, the support shaft 94 fits into the engaging groove 91 of the pull shifter 82, the end face 95 facing one side in the width direction engages with the tip 56 of the engaging piece 55 of the push shifter 14, and the end face 96 facing the other side in the width direction engages with the compensating bimetal 31 of the reversing mechanism 24, completing the alignment. After completing this alignment, the differential lever 16 is assembled to the case 12 with the pair of opposing plates 92, 93 sandwiching the girder plate 44 of the case 12 to prevent it from falling off. Therefore, each of the push shifter 14, pull shifter 15 and differential lever 16 can be slid and assembled individually into the case 12, which simplifies the assembly procedure.

[0033] Furthermore, the push shifter 14, pull shifter 15 and differential lever 16 can be assembled by moving them in the depth direction, vertical direction and width direction which are perpendicular to the three-dimensional directions, so automatic assembly by a robot hand can be achieved. Furthermore, even when the semi-finished thermal overload relay 11 is transported on the line, the push shifter 14, pull shifter 15 and differential lever 16 can be reliably prevented from falling off the case 12, thereby improving production efficiency.

[0034] Although the present invention has been described above with reference to a limited number of embodiments, the scope of the invention is not limited thereto, and modifications of the embodiments based on the above disclosure will be obvious to those skilled in the art. [Explanation of symbols]

[0035] 11 Thermal overload relay 12 cases 13U, 13V, 13W Bimetal 14 Push Shifter 15 pull shifter 16 Differential lever 24 Reversal mechanism 25 Reset Stick 26 Heater 27 Connection terminal 31 Compensating Bimetal 32 Release lever 33 Tension spring 34 Movable plate 35 Leaf spring 36 Interlocking plate 41~43 Bulkhead 44 digit board 45a1,45b1 Protrusion 48a Pillar 48b Head 45a2,45b2 Protrusion 49a Pillar 49b Head 51 slotted hole 52 slot 53~55 Engagement piece 85~87 slotted hole 88~90 Engagement piece 91 Engagement groove 92,93 opposing plates 94 Spindle 95,96 End face

Claims

1. A plurality of partitions provided inside the case; a plurality of bimetals disposed between the plurality of partition walls and bending when heated; a shifter attached to cover the ends of the plurality of partition walls and pushed by the bimetal to be displaced when the bimetal is bent; a lever that rotates when pushed by the displacement of the shifter; a reversing mechanism that is pushed by the rotation of the lever to reverse the contacts, a plurality of elongated holes formed so as to extend longitudinally in the displacement direction of the shifter; a plurality of protrusions that protrude from end surfaces of the plurality of partition walls and into which the plurality of elongated holes are slidably fitted, and that guide the displacement of the shifter; a shifter fall-off prevention portion that prevents the shifter from falling off from the partition by moving the shifter, whose multiple long holes are engaged with the multiple protrusions, in a displacement direction.

2. The shifter dropout prevention portion is a head portion formed at a tip of a predetermined one of the plurality of protrusions and protruding in a direction perpendicular to the displacement direction within the same plane; an attachment hole formed at an end of the elongated hole that engages with the predetermined protrusion and through which the head can pass; 2. A thermal overload relay according to claim 1, characterized in that the head functions as a retainer for the protrusion from the elongated hole by moving the shifter, which has passed the head through the mounting hole, in the displacement direction.

3. 3. A thermal overload relay according to claim 1, wherein the lever is provided with a lever fall-off prevention portion that engages with a wall portion of the case to prevent the lever from falling off when the lever engages with the shifter from a direction perpendicular to the displacement direction in the same plane.

4. 4. A thermal overload relay according to claim 3, wherein said lever dropout prevention portion is a pair of opposing plates formed on said lever which sandwich the wall portion of said case.

5. the shifters are push shifters and pull shifters that are displaced by engaging with the plurality of bimetals from one side and the other side in the displacement direction, 3. A thermal overload relay according to claim 1, wherein the push shifter and the pull shifter are each provided with a shifter dropout prevention portion.

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