Miniature circuit breakers

Abstract

A small circuit breaker, wherein an operating mechanism and a static contact are provided in a shell, wherein the operating structure includes a contact support, wherein the contact support is provided with a moving contact cooperating with the static contact, wherein a shielding member for shielding the arc between the moving contact and the static contact is provided in the shell; wherein the shielding member is provided with a rotating end, a limiting end and a shielding end; wherein the rotating end is rotatably connected to the shell, wherein the limiting end is provided with a slide groove for controlling the relative position of the shielding member and the moving contact, wherein the moving contact extends into the slide groove through a protruding contact portion to drive the shielding member to rotate relative to the moving contact around the rotating end; when opening the switch, the shielding end rotates between the moving contact and the static contact, and when closing the switch, the shielding end rotates out between the moving contact and the static contact. During the opening and closing process, the shielding member is driven by the moving contact under the action of the slide groove and rotates relative to the moving contact around the rotating end, wherein the structure is simple and compact, and the rotation space occupied is small.

Description

Technical Field

[0001] The invention relates to low-voltage electrical appliances, in particular to a small circuit breaker. Background Art

[0002] There is a critical current or a small current that needs to be disconnected in the DC power system. Since DC does not have the characteristic of zero current like AC, the arc is not easy to extinguish. The opening distance between the contacts of the existing small circuit breaker is between 5mm and 5.5mm. When the circuit breaker disconnects the critical current or the small current, the arc cannot be elongated. The arc continues to burn, is difficult to extinguish, and the burning time is long, which is not conducive to the normal use of the circuit breaker. Some existing circuit breakers are equipped with shielding parts for shielding moving contacts and static contacts, but their structure is relatively complex, and the coordination of various parts is relatively cumbersome. A certain space is required in the circuit breaker, which is not conducive to the production and processing of the circuit breaker. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a small circuit breaker with simple structure and high reliability.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A small circuit breaker, wherein an operating mechanism and a static contact are arranged in a housing, the operating structure comprises a contact support, the contact support is provided with a moving contact matched with the static contact, a shielding member for shielding an arc between the moving contact and the static contact is arranged in the housing; the shielding member is provided with a rotating end, a limiting end and a shielding end; the rotating end is rotatably connected to the housing, the limiting end is provided with a slide groove for controlling the relative position of the shielding member and the moving contact, the moving contact extends into the slide groove through a protruding contact portion to drive the shielding member to rotate relative to the moving contact around the rotating end;

[0006] When the switch is opened, the shielding end moves into the gap between the moving contact and the stationary contact.

[0007] When the circuit breaker is closed, the shielding end rotates out of the gap between the moving contact and the stationary contact.

[0008] Furthermore, the slide groove is divided into a first groove section and a second groove section. The part away from the rotating end is the first groove section, and the part close to the rotating end is the second groove section. The connection between the first groove section and the second groove section forms an angle with the opening facing the shielding end, and the angle is an obtuse angle. When the switch is opened, the contact part slides from the first groove section into the second groove section so that the shielding end rotates counterclockwise between the moving contact and the static contact; when the switch is closed, the contact part slides from the second groove section into the first groove section so that the shielding end rotates clockwise out from between the moving contact and the static contact.

[0009] Furthermore, the angle between the first groove section and the second groove section is 140° to 160°.

[0010] Furthermore, the angle at which the shielding member rotates due to the sliding fit between the contact portion and the first section of the groove is smaller than the angle at which the shielding member rotates due to the sliding fit between the contact portion and the second section of the groove.

[0011] Furthermore, when the contact portion and the first section groove are in sliding cooperation, the rotation angle of the shielding member is 8° to 12°, and when the contact portion and the second section groove are in sliding cooperation, the rotation angle of the shielding member is 40° to 50°.

[0012] Furthermore, the average rate of change of the shielding member's rotation angle relative to the moving contact when the contact portion slides with the first slot is smaller than the average rate of change of the shielding member's rotation angle relative to the moving contact when the contact portion slides with the second slot;

[0013] When the contact portion is slidably matched with the first section of the groove, the average rate of change of the rotation angle of the shielding member relative to the moving contact is in the range of 1 to 3;

[0014] When the contact portion is slidably matched with the second section groove, the average rate of change of the rotation angle of the shielding member relative to the moving contact is in the range of 3 to 7.

[0015] Furthermore, when the contact portion slides with the first slot, the average rate of change of the shielding member's rotation angle relative to the moving contact is 1.7, and when the contact portion slides with the second slot, the average rate of change of the shielding member's rotation angle relative to the moving contact is 4.6.

[0016] Furthermore, the contact portion is protrudingly arranged on the side wall of the contact support and is integrally formed with the contact support, and the movable contact is provided with a connecting hole for the contact portion to pass through, and the contact portion passes through the connecting hole and extends into the slide groove of the shielding member.

[0017] Furthermore, the contact portion is protrudingly arranged on the side wall of the moving contact and is integrally formed with the moving contact.

[0018] Furthermore, the shielding end is provided with an arc-shaped shielding baffle, the area of ​​the shielding baffle is larger than and can completely cover the contact surface between the moving contact and the static contact.

[0019] Furthermore, the shielding member is located on either side of the moving contact close to the shell, the rotating end of the shielding member is rotatably supported on the shell, and a section of arc track is provided on the shell close to the shielding end; a plurality of legs are provided on the edge of the shielding member close to one side of the shell, and the legs are located between the shielding end and the limit end and slide along the arc track; a shielding baffle is provided at the shielding end, and the extension direction of the shielding baffle is opposite to the extension direction of the legs.

[0020] Furthermore, the shielding member is triangular in shape as a whole, the rotating end is located at the first end angle of the triangle, the shielding end is located at the second end angle of the triangle, the sliding groove of the limiting end is arranged between the shielding end and the third end angle of the triangle, the rotating end is provided with a rotating shaft protruding to one side and integrally formed with the shielding member, the shielding end is provided with an arc-shaped shielding baffle protruding to the other side, and a support leg protruding to one side is provided between the third end angle of the shielding member and the shielding end, and the extension direction of the shielding baffle is opposite to the extension direction of the rotating shaft and the support leg.

[0021] The miniature circuit breaker of the present invention is provided with a shielding member between the moving contact and the stationary contact for shielding the arc between the two. When opening, the shielding member moves into the space between the moving contact and the stationary contact, forcing the arc between the moving contact and the stationary contact to be elongated, and causing the arc to burn and cool along the surface of the shielding member, effectively reducing the burning time of the arc and causing the arc to extinguish more quickly; when closing, the shielding member moves out from between the moving contact and the stationary contact, thus not affecting the normal operation of the circuit breaker. During the opening and closing process, the shielding member is driven by the moving contact under the action of the slide slot and rotates relative to the moving contact around the rotating end. The structure is simple and compact, and the rotation space occupied is small.

[0022] In addition, the shielding part of the present invention is driven by a passive contact through a slide slot, and the slide slot is divided into two parts. By controlling the rotation angle of the shielding part in each part of the slide slot and the average change rate of the rotation angle relative to the moving contact, the shielding end of the shielding part is turned into or out of the gap between the moving contact and the static contact. The structure is simple and is conducive to production and processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of a miniature circuit breaker of the present invention;

[0024] Figure 2 It is a structural schematic diagram of the miniature circuit breaker of the present invention when it is closed;

[0025] Figure 3 It is a structural schematic diagram of the miniature circuit breaker of the present invention when it is opened;

[0026] Figure 4 It is a connection diagram of the contact support, the moving contact and the shielding member of the miniature circuit breaker of the present invention;

[0027] Figure 5 It is a schematic diagram of the structure of the contact support of the miniature circuit breaker of the present invention;

[0028] Figure 6 It is a structural schematic diagram of a moving contact of a miniature circuit breaker of the present invention;

[0029] Figure 7 It is a structural schematic diagram of a shielding member of a miniature circuit breaker of the present invention;

[0030] Figure 8It is a schematic structural diagram of a shielding member of a miniature circuit breaker of the present invention close to a housing side;

[0031] Fig. 9 It is a schematic structural diagram of a shielding member of a miniature circuit breaker of the present invention away from a side of the housing;

[0032] Fig.10 is a curve diagram showing the relationship between the moving contact rotation angle and the shield rotation angle of the miniature circuit breaker of the present invention;

[0033] Fig.11 The diagram is a proportional relationship diagram between the rotation angle change of the moving contact and the rotation angle change of the shielding member of the miniature circuit breaker of the present invention. DETAILED DESCRIPTION

[0034] The following is combined with Figures 1 to 9 The following embodiments are provided to further illustrate the specific implementation of the miniature circuit breaker of the present invention. The miniature circuit breaker of the present invention is not limited to the description of the following embodiments.

[0035] A small circuit breaker, wherein an operating mechanism and a static contact 3 are arranged in a shell, the operating structure comprises a contact support 2, the contact support 2 is provided with a moving contact 4 cooperating with the static contact 3, a shielding member 5 for shielding an arc between the moving contact 4 and the static contact 3 is arranged in the shell; the shielding member 5 is provided with a rotating end 5a, a limiting end 5b and a shielding end 5c; the rotating end 5a is rotatably connected to the shell, the limiting end 5b is provided with a slide groove for controlling the relative position of the shielding member 5 and the moving contact 4, the moving contact 4 extends into the slide groove through a protruding contact portion 7 to drive the shielding member 5 to rotate relative to the moving contact 4 around the rotating end 5a; when opening, the shielding end 5c rotates into the gap between the moving contact 4 and the static contact 3, and when closing, the shielding end 5c rotates out of the gap between the moving contact 4 and the static contact 3.

[0036] The miniature circuit breaker of the present invention is provided with a shielding member 5 between the moving contact 4 and the stationary contact 3 for shielding the arc therebetween. When opening the circuit, the shielding member 5 moves in between the moving contact 4 and the stationary contact 3, forcing the arc therebetween to be elongated, and causing the arc to burn and cool along the surface of the shielding member 5, effectively reducing the burning time of the arc and causing the arc to extinguish more quickly. When closing the circuit, the shielding member 5 moves out between the moving contact 4 and the stationary contact 3, thus not affecting the normal operation of the circuit breaker. During the opening and closing process, the shielding member 5 is driven by the moving contact 4 under the action of the slide slot and rotates around the rotating end 5a relative to the moving contact 4. The structure is simple and compact, and the rotation space occupied is small.

[0037] like Figure 1-3As shown, the miniature circuit breaker includes a shell consisting of a base 1 and a cover body, an operating mechanism and a static contact 3 are arranged in the shell, the operating structure includes a contact support 2, the contact support 2 is provided with a moving contact 4 matched with the static contact 3, a shielding member 5 for shielding the arc between the moving contact 4 and the static contact 3 is arranged in the shell; the shielding member 5 is provided with a rotating end 5a, a limiting end 5b and a shielding end 5c; the rotating end 5a is rotatably connected to the shell, and the limiting end 5b is provided with a slide groove for controlling the relative position of the shielding member 5 and the moving contact 4, the moving contact 4 extends into the slide groove through the protruding contact portion 7 to drive the shielding member 5 to rotate relative to the moving contact 4 around the rotating end 5a; when opening, the shielding end 5c is rotated between the moving contact 4 and the static contact 3, and when closing, the shielding end 5c is rotated out between the moving contact 4 and the static contact 3 in the opposite direction of the rotation direction.

[0038] The protruding contact portion 7 can be integrally formed with the side wall of the moving contact 4. From the perspective of the connection stability of the shielding member 5, it can also be as follows Figure 4-6 As shown, the contact portion 7 is arranged on the side wall of the contact support 2. The contact portion 7 arranged on the contact support 2 is preferably formed integrally with the contact support 2. The portion of the moving contact 4 corresponding to the contact portion 7 is provided with a connecting hole 41 for the contact portion 7 to pass through. The contact portion 7 passes through the connecting hole 41 and extends into the slide groove of the shielding member 5 to drive the shielding member 5 to rotate around the shielding end 5c relative to the moving contact 4.

[0039] like Figure 6 As shown, the moving contact 4 includes a first connecting arm 42, a second connecting arm 45, a contact portion 43 and an arc-starting portion 44 which are connected in sequence. The first connecting arm 42 and the second connecting arm 45 are L-shaped and cooperate with the contact support limiter. The side of the contact portion 43 protrudes toward the side of the first connecting arm 42 and is provided with a moving contact which cooperates with the static contact 3. The first connecting arm 42, the second connecting arm 45 and the contact portion 43 are U-shaped to form an avoidance gap 46 for avoiding the shielding member 5. The contact portion 43 is provided with a connecting hole 41 for the contact portion 7 to pass through. The arc-starting portion 44 is arranged on the side of the contact portion 43 away from the second connecting arm 45 and extends in a direction away from the moving contact.

[0040] like Figure 4 , 7As shown in , 8 and 9, in order to make the shielding end 5c accurately rotate in and out between the moving contact 4 and the stationary contact 3, the shielding component 5 needs to set the shielding end 5c and the rotating end 5a higher than the limit end 5b during installation. The sliding groove is divided into two parts, the part close to the shielding end 5c is used as the first section groove 61, and the part close to the rotating end 5a is used as the second section groove 62. An angle A with an opening facing the shielding end 5c is formed at the connection between the first section groove 61 and the second section groove 62. This angle A is preferably an obtuse angle to ensure that when the switch is opened, the contact part 7 slides from the first section groove 61 into the second section groove 62 to make the shielding end 5c rotate counterclockwise between the moving contact 4 and the stationary contact 3; when the switch is closed, the contact part 7 slides from the second section groove 62 into the first section groove 61 to make the shielding end 5c rotate clockwise between the moving contact 4 and the stationary contact 3. The angle A between the first section groove 61 and the second section groove 62 is preferably 140° to 160°, preferably 150°.

[0041] In order to further ensure that the shielding member 5 rotates around the rotating end relative to the moving contact 4, it is preferably designed that the contact portion 7 and the first section groove 61 slide together to make the shielding member 5 rotate at a smaller angle than the contact portion 7 and the second section groove 62 slide together to make the shielding member 5 rotate at. This design method can make the structure design in the circuit breaker compact, which is conducive to saving space. Specifically, under the cooperation of the contact portion 7 and the first section groove 61, the rotation angle of the shielding member 5 is 8° to 12°, preferably 10°, and under the cooperation of the contact portion 7 and the second section groove 62, the rotation angle of the shielding member 5 is 40° to 50°, preferably 46°; at the same time, for the shielding end 5c Accurately and quickly rotate in and out between the moving contact 4 and the static contact 3, effectively shielding the arc, the average rate of change of the rotation angle of the shielding part 5 relative to the moving contact 4 when the contact part 7 slides with the first section slot 61 should be less than the average rate of change of the rotation angle of the shielding part 5 relative to the moving contact 4 when the contact part 7 slides with the second section slot 62. When the contact part 7 slides with the first section slot 61, the average rate of change of the rotation angle of the shielding part 5 relative to the moving contact 4 ranges from 1 to 3, specifically 1.7; when the contact part 7 slides with the second section slot 62, the average rate of change of the rotation angle of the shielding part 5 relative to the moving contact 4 ranges from 3 to 7, specifically 4.6. This method of accurately controlling the shielding end 5c to rotate in and out between the moving contact 4 and the static contact 3 only through the slide groove has a simple structure and is conducive to production and processing.

[0042] In order to achieve a better arc extinguishing effect, the shielding end 5c of the shielding member 5 is provided with an arc-shaped shielding baffle 51. The area of ​​the shielding baffle 51 is larger than the contact surface between the moving contact 4 and the static contact 3 and can completely cover the contact surface of the two. The arc between the moving contact 4 and the static contact 3 can burn and cool on the shielding baffle 51, effectively shortening the arc burning time.

[0043] like Figure 3 , 4As shown in FIG. 8 , the shielding member 5 can be arranged on any side of the moving contact 4 close to the housing. The shielding member 5 is arranged on the side of the moving contact 4 close to the housing. The rotating end 5a of the shielding member 5 is rotatably supported on the housing. A section of arc track 11 is arranged on the housing close to the shielding end 5c (see FIG. Figure 3 ); the shielding member 5 is provided with a plurality of legs 52 at an edge close to one side of the shell, the legs 52 are located between the shielding end 5c and the limit end 5b and slide along the arc track 11; the shielding end 5c is provided with a shielding baffle 51, and the extending direction of the shielding baffle 51 is opposite to the extending direction of the legs 52, Figure 1-3 As shown, the shielding member 5 is arranged on the side of the moving contact 4 close to the base 1, and the rotating end 5a of the shielding member 5 is rotatably supported on the base 1, and a section of arc track 11 is provided on the base 1; at least one leg 52 is provided on the edge of the side of the shielding member 5 facing the base 1, and the leg 52 is located between the shielding end 5c and the limit end 5b, and the leg 52 can slide along the arc track 11. The track structure of the arc track 11 shown in the figure is a convex structure with a smooth surface. Of course, a groove matching the leg 52 can also be provided on the convex structure (not shown in the figure); a shielding baffle 51 is provided on the side of the shielding end 5c away from the base 1, and the area of ​​the shielding baffle 51 is larger than and can completely cover the contact surface between the moving contact 4 and the static contact 3.

[0044] The rotating end 5a of the shielding member 5 is connected to the housing by a pin, and the rotating end 5a is provided with a rotating shaft 53 integrally formed with the shielding member 5, and the housing is provided with an axial hole 8 matched with the rotating shaft 53. Of course, the axial hole 8 can also be provided at the rotating end 5a and a shaft matched with the axial hole 8 can be provided on the housing. The shielding member 5 can be provided with convex ribs to reduce friction.

[0045] Specifically, Figure 7-8 As shown, the shielding member 5 is approximately triangular in shape as a whole, the rotating end 5a is located at the first end angle of the triangle, the shielding end 5c is located at the second end angle of the triangle, the slide groove of the limiting end 5b is arranged between the shielding end 5c and the third end angle of the triangle, the rotating end 5a is provided with a rotating shaft 53 which is protruding to one side and is integrally formed with the shielding member 5, the shielding end 5c is provided with an arc-shaped shielding baffle 51 which is protruding to the other side, and a support leg 52 which is protruding to one side is provided between the third end angle of the shielding member 5 and the shielding end 5c, and the extension direction of the shielding baffle 51 is opposite to the extension direction of the rotating shaft 53 and the support leg 52.

[0046] The relationship curve between the rotation angle of the moving contact 4 and the rotation angle of the shielding member 5 is shown in FIG. Fig.10 , wherein: segment AB represents that the contact portion 7 is located in the first segment groove 61, and segment BC represents that the contact portion 7 is located in the second segment groove 62;

[0047] The proportional relationship between the rotation angle change of the moving contact 4 and the rotation angle change of the shielding member 5 is shown in Fig.11, wherein: segment AB represents that the contact portion 7 is located in the first segment groove 61, and segment BC represents that the contact portion 7 is located in the second segment groove 62;

[0048] The comparison of arcing time during opening of the circuit breaker of the present invention and the circuit breaker without the shielding member 5 is shown in the following table:

[0049]

[0050] It can be seen from the above table that the arcing time of the circuit breaker of the present invention is significantly shorter than that of the circuit breaker without the shielding member 5 .

[0051] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A miniature circuit breaker, wherein an operating mechanism and a stationary contact (3) are arranged in a housing, wherein the operating mechanism comprises a contact support (2), wherein the contact support (2) is provided with a moving contact (4) cooperating with the stationary contact (3), wherein: A shielding member (5) for shielding an arc between a moving contact (4) and a stationary contact (3) is provided in the housing; the shielding member (5) is provided with a rotating end (5a), a limiting end (5b) and a shielding end (5c); the rotating end (5a) is rotatably connected to the housing, and the limiting end (5b) is provided with a slide groove for controlling the relative position of the shielding member (5) and the moving contact (4); the moving contact (4) extends into the slide groove through a protruding contact portion (7) to drive the shielding member (5) to rotate around the rotating end (5a) relative to the moving contact (4); When the switch is opened, the shielding end (5c) moves between the moving contact (4) and the stationary contact (3). When the switch is closed, the shielding end (5c) moves out from between the moving contact (4) and the stationary contact (3). The slide groove comprises a first groove section (61) and a second groove section (62). The portion away from the rotating end (5a) is the first groove section (61), and the portion close to the rotating end (5a) is the second groove section (62). The connection between the first groove section (61) and the second groove section (62) forms an angle (A) with the opening facing the shielding end (5c). When the switch is opened, the contact portion (7) slides from the first groove section (61) into the second groove section (62) so that the shielding end (5c) is rotated between the moving contact (4) and the stationary contact (3); when the switch is closed, the contact portion (7) slides from the second groove section (62) into the first groove section (61) so that the shielding end (5c) is rotated in the opposite direction out of between the moving contact (4) and the stationary contact (3).

2. The miniature circuit breaker according to claim 1, characterized in that: The angle (A) is an obtuse angle; when the switch is opened, the shielding end (5c) rotates counterclockwise into between the moving contact (4) and the stationary contact (3); when the switch is closed, the shielding end (5c) rotates clockwise out from between the moving contact (4) and the stationary contact (3).

3. The miniature circuit breaker according to claim 2, characterized in that: The angle (A) is 140° to 160°.

4. The miniature circuit breaker according to claim 2, characterized in that: The angle at which the shielding member (5) rotates due to the sliding fit between the contact portion (7) and the first slot (61) is smaller than the angle at which the shielding member (5) rotates due to the sliding fit between the contact portion (7) and the second slot (62).

5. The miniature circuit breaker according to claim 4, characterized in that: When the contact portion (7) and the first slot (61) are in sliding cooperation, the shielding member (5) has a rotation angle of 8° to 12°, and when the contact portion (7) and the second slot (62) are in sliding cooperation, the shielding member (5) has a rotation angle of 40° to 50°.

6. The miniature circuit breaker according to claim 2, characterized in that: The average rate of change of the rotation angle of the shielding member (5) relative to the moving contact (4) when the contact portion (7) and the first slot (61) are in sliding engagement is smaller than the average rate of change of the rotation angle of the shielding member (5) relative to the moving contact (4) when the contact portion (7) and the second slot (62) are in sliding engagement; When the contact portion (7) and the first section groove (61) are slidably matched, the average rate of change of the rotation angle of the shielding member (5) relative to the moving contact (4) is in the range of 1 to 3; When the contact portion (7) and the second section groove (62) are slidably matched, the average rate of change of the rotation angle of the shielding member (5) relative to the moving contact (4) is in the range of 3 to 7.

7. The miniature circuit breaker according to claim 6, characterized in that: When the contact portion (7) and the first section slot (61) are slidably matched, the average rate of change of the rotation angle of the shielding member (5) relative to the moving contact (4) is 1.7; when the contact portion (7) and the second section slot (62) are slidably matched, the average rate of change of the rotation angle of the shielding member (5) relative to the moving contact (4) is 4.

6.

8. The miniature circuit breaker according to claim 1, characterized in that: The contact portion (7) is protrudingly arranged on the side wall of the contact support (2) and is integrally formed with the contact support (2); the movable contact (4) is provided with a connecting hole (41) for the contact portion (7) to pass through; the contact portion (7) passes through the connecting hole (41) and extends into the slide groove of the shielding member (5).

9. The miniature circuit breaker according to claim 1, characterized in that: The contact portion (7) is protrudingly arranged on the side wall of the moving contact (4) and is integrally formed with the moving contact (4).

10. The miniature circuit breaker according to claim 1, characterized in that: The shielding end (5c) is provided with an arc-shaped shielding baffle (51), and the area of ​​the shielding baffle (51) is larger than and can completely cover the contact surface between the moving contact (4) and the stationary contact (3).

11. The miniature circuit breaker according to claim 1, characterized in that: The shielding member (5) is located on any side of the moving contact (4) close to the shell, the rotating end (5a) of the shielding member (5) is rotatably supported on the shell, and a section of arc track (11) is provided on the shell close to the shielding end (5c); a support leg (52) is provided on the edge of the shielding member (5) close to the shell, and the support leg (52) is located between the shielding end (5c) and the limit end (5b) and slides along the arc track (11); the shielding end (5c) is provided with a shielding baffle (51), and the extension direction of the shielding baffle (51) is opposite to the extension direction of the support leg (52).

12. The miniature circuit breaker according to claim 1, characterized in that: The shielding member (5) is in the shape of a triangle as a whole, the rotating end (5a) is located at a first end angle of the triangle, the shielding end (5c) is located at a second end angle of the triangle, the sliding groove of the limiting end (5b) is arranged between the shielding end (5c) and the third end angle of the triangle, the rotating end (5a) is provided with a rotating shaft (53) which is protruding to one side and is integrally formed with the shielding member (5), the shielding end (5c) is provided with an arc-shaped shielding baffle (51) which is protruding to the other side, and a supporting leg (52) which is protruding to one side is provided between the third end angle of the shielding member (5) and the shielding end (5c), and the extending direction of the shielding baffle (51) is opposite to the extending direction of the rotating shaft (53) and the supporting leg (52).

Images