CN108734255B

CN108734255B - Anti-breaking U disk

Info

Publication number: CN108734255B
Application number: CN201810421751.9A
Authority: CN
Inventors: 张利峰
Original assignee: Jinling Institute of Technology
Current assignee: Jinling Institute of Technology
Priority date: 2018-05-04
Filing date: 2018-05-04
Publication date: 2021-02-26
Anticipated expiration: 2038-05-04
Also published as: CN108734255A

Abstract

The invention discloses a breakage-proof USB flash disk, which comprises a USB plug and a shell, wherein the USB plug is fixedly connected with the shell and comprises a front-end plug and a rear-end socket, and the rear-end socket is fixedly connected with the shell; the front end plug is fixedly connected with a boss, and the rear end socket is provided with a cavity for the boss to be inserted; the side surface of the boss is provided with a pattern drawing angle, and the boss is gradually reduced towards the direction far away from the front-end plug; the inner wall of the concave cavity is provided with a die drawing angle matched with the die drawing angle of the side surface of the boss; an anti-disengaging structure is arranged between the front-end plug and the rear-end socket, and after the boss is inserted into the cavity, the anti-disengaging structure can prevent the front-end plug and the rear-end socket from being separated from each other; a communicating structure is arranged between the boss and the cavity, and after the boss is inserted into the cavity, the front-end plug and the rear-end socket are electrically connected through the communicating structure. The front end plug and the rear end socket can be separated from each other after the acting force generated by the collision of the shell reaches a certain value, so that the connecting part of the shell and the USB plug is prevented from being bent or broken.

Description

Anti-breaking U disk

Technical Field

The invention relates to the technical field of mobile storage, in particular to a folding loss prevention USB flash disk.

Background

The USB flash disk is a miniature high-capacity mobile storage product using a USB interface and without a physical driver, and can be connected with a computer through the USB interface.

Generally, the USB flash disk includes a USB plug, a PCB board, and a housing, wherein a main control core is integrated on the PCB board. The PCB is positioned in the shell and fixedly connected with the USB plug, the USB plug is used for being inserted into a USB socket on the computer, and after the USB plug is inserted into the USB socket, the computer can read data information stored in the machine core and can write the data information into the machine core. Because the USB plug is fixedly connected with the PCB, when the USB flash disk is collided by the outside, the connection part of the USB plug and the machine core is easy to bend and even break, and when the USB flash disk is seriously bent or broken, the USB flash disk is damaged and cannot be used any more.

Disclosure of Invention

The invention aims to provide a breakage-proof USB flash disk, which is used for solving the problem that the existing USB flash disk inserted into a computer is easy to break after being collided.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the utility model provides a prevent losing USB flash disk, includes USB plug and casing, USB plug and casing looks fixed connection, and the USB plug includes front end plug and rear end socket, and rear end socket and casing looks fixed connection, the detachable fixed connection of front end plug and rear end socket.

Through the technical scheme, when the USB socket connector works, the front-end plug is connected with the USB socket on a computer in an inserting mode, the rear-end socket is located outside the USB socket, when the shell is collided in a lateral mode, the shell is acted by lateral acting force, when the acting force reaches a certain force, the front-end plug and the rear-end socket are separated from each other, the USB plug can be prevented from being bent and deformed or the connection position of the USB plug and the shell is prevented from being broken, the front-end plug and the rear-end socket can be well restored after being spliced again, and the USB socket connector can be used normally.

The invention is further configured to:

the front end plug is fixedly connected with a boss, and the rear end socket is provided with a cavity for the boss to be inserted;

the side surface of the boss is provided with a pattern drawing angle, and the boss is gradually reduced towards the direction far away from the front-end plug;

the inner wall of the concave cavity is provided with a die drawing angle matched with the die drawing angle of the side surface of the boss;

an anti-disengaging structure is arranged between the front-end plug and the rear-end socket, and after the boss is inserted into the cavity, the anti-disengaging structure can prevent the front-end plug and the rear-end socket from being separated from each other;

a communicating structure is arranged between the boss and the cavity, and after the boss is inserted into the cavity, the front-end plug and the rear-end socket are electrically connected through the communicating structure.

Through the technical scheme, after the boss and the cavity are mutually inserted, the relative movement between the front-end plug and the rear-end socket along the direction vertical to the direction in which the boss is inserted into the cavity can be limited, the anti-disengaging structure can prevent the front-end plug and the rear-end socket from being relatively far away along the direction parallel to the direction in which the boss is inserted into the cavity, so that the boss and the cavity are stably inserted, the front-end plug and the rear-end socket are stably spliced, and the circuit between the front-end plug and the rear-end socket can be mutually communicated through the communicating structure; because the side face of the boss is provided with the die drawing angle, after the shell is subjected to lateral acting force, a contact point between one side edge of the front-end plug and the rear-end socket, which is spliced with each other, and the side edge of the front-end plug and the side edge of the rear-end socket, which is opposite to the stressed surface of the shell, forms a fulcrum, the front-end plug and the rear-end socket rotate around the fulcrum, and the die drawing angle can prevent the boss from interfering with the inner wall of the cavity in the process that the boss rotates around.

The invention is further configured to:

the anti-falling structure is an adsorption anti-falling structure which comprises a front end magnet and a rear end magnet;

the front end magnet is fixedly connected to one end, close to the rear end socket, of the front end plug, and the rear end magnet is fixedly connected to one end, close to the front end plug, of the rear end socket;

after the boss is inserted into the concave cavity, the front end magnet and the rear end magnet are attached to each other.

Through the technical scheme, the front end magnet and the rear end magnet are mutually adsorbed, so that the front end plug and the rear end socket can be stably connected, and the boss and the cavity can be stably inserted and connected; when the separation acting force generated by the external acting force on the shell along the direction that the boss is inserted into the cavity is larger than the adsorption acting force between the front end magnet and the rear end magnet, the front end plug and the rear end socket are separated from each other to achieve the effect of automatic separation; the damage to the USB plug caused by the separation process is extremely small, and the operation of the recombination process after separation is simple and convenient.

The invention is further configured to:

the anti-falling structure is an adhesion anti-falling part which is a gel layer, and the gel layer is bonded and fixed between the front end plug and the rear end socket.

The invention is further configured to: the anti-disengaging structure is joint anti-disengaging structure, and joint anti-disengaging structure includes fixed connection and is in pothook on the rear end socket and set up the draw-in groove in order to supply the pothook joint on the front end plug, the pothook has elasticity.

The invention is further configured to: the anti-falling structure is an elastic tensioning anti-falling part which is an extension spring; the two ends of the extension spring are respectively fixedly connected with the front end plug and the rear end socket.

The invention is further configured to: the cross section of the boss is oval.

The invention is further configured to: one end of the front end plug, which is close to the rear end socket, is fixedly connected with a convex strip, the side surface of the convex strip is provided with a pattern drawing angle, and the convex strip is gradually reduced towards the direction far away from the front end plug; the rear end socket is provided with a groove for the insertion of the convex strip near one end of the front end plug, and the side wall of the groove is provided with a pattern drawing angle matched with the pattern drawing angle of the side surface of the convex strip.

The invention is further configured to: the communicating structure comprises a contact fixedly connected to the boss and a movable contact telescopically connected to the inner wall of the cavity, and the movable contact is abutted to the contact after the boss is inserted into the cavity.

The invention is further configured to: prevent losing the USB flash disk still includes the PCB board, the PCB board with USB plug looks fixed connection, the PCB board is located inside the casing, the inside buffer spring that is equipped with of casing, the buffer spring both ends respectively with PCB board and casing looks fixed connection.

The invention has the following advantages:

1. the USB plug is detachably connected, when the shell is collided, the USB plug can be separated into two parts by lateral bending acting force, the front end plug is left in the USB socket of the computer, the rear end socket is separated along with the shell so as to avoid the bending or breaking phenomenon between the USB plug and the shell, and after separation, the USB plug can be recombined and restored to be intact through the lug boss and the concave cavity;

2. the cross section of the boss is oval, the boss can be smoothly rotated around the rotation center to be pulled out of the concave cavity after the lateral surface of the shell is subjected to acting forces in different directions, and the rotation of the front-end plug and the rear-end socket around the central axis of the boss can be limited.

Drawings

FIG. 1 is a schematic view of the present invention;

fig. 2 is a schematic view showing a relative positional relationship between the front end plug and the housing in embodiment 1;

FIG. 3 is a schematic view showing the structure of the cover body in embodiment 1;

fig. 4 is a schematic view showing a connection relationship between the rear socket and the PCB in embodiment 1;

fig. 5 is a schematic view showing a structure of a front end plug in embodiment 1;

fig. 6 is a schematic view showing a rear end socket structure in embodiment 1;

fig. 7 is a schematic view showing a front end magnet structure in embodiment 1;

fig. 8 is a schematic view showing a fitting relationship between the front plug and the rear socket in embodiment 1;

fig. 9 is a schematic view showing a state in which the front plug and the rear jack are separated from each other after the body casing is subjected to an external force in embodiment 1;

FIG. 10 is a schematic view showing the relationship between the boss height, the boss rotation center and the boss side draft angle in example 1;

FIG. 11 is a schematic view showing a connection relationship between a front-end wire and a rear-end wire in embodiment 1;

fig. 12 is a schematic view showing a structure of the connector in embodiment 1;

FIG. 13 is an enlarged view of a portion of FIG. 11 at D;

FIG. 14 is a schematic view showing a structure of a damper spring in embodiment 1;

FIG. 15 is a schematic view showing the structure of a gel layer in example 2;

FIG. 16 is a schematic view showing a snap fit retaining structure in embodiment 3;

fig. 17 is a schematic view showing the structure of the extension spring in embodiment 4.

Reference numerals

1. A housing;

2. a cover body;

3. a USB plug;

31. a front end plug; 311. a boss; 312. a front end fixing groove; 313. a front end magnet; 314. a convex strip; 315. connecting sheets; 316. a front end lead; 317. a card slot; 318. a contact;

32. a rear end socket; 321. a concave cavity; 322. a rear end fixing groove; 323. a rear end magnet; 324. a groove; 325. a connector; 3251. a barrel; 32511. necking; 3252. a movable contact; 32521. a flange; 3253. a connecting spring; 326. a rear end lead; 327. a hook;

33. a gel layer;

34. an extension spring;

35. an accommodating cavity;

4. a PCB board; 41. a buffer spring.

Detailed Description

The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Example 1

A breakage-proof USB flash disk is shown in figure 1 and comprises a shell 1 and a cover body 2, a USB plug 3 is fixedly connected to one end of the shell 1 in combination with figure 2, and the USB plug is connected with the cover body 2 in an inserted mode in combination with figure 3.

As shown in fig. 4, a PCB 4 is disposed inside the housing 1, the PCB 4 is used for integrated circuits and other electrical components, and the PCB 4 is fixedly connected to the USB plug 3. After the USB plug 3 is inserted into a USB socket of a computer, data stored in the USB flash disk can be read or written into the USB flash disk.

The USB plug 3 is detachable and includes a front plug 31 and a rear socket 32, and the front plug 31 is used for being plugged into a USB socket on a computer. The rear socket 32 is adapted to receive the front plug 31, so that the front plug 31 is connected to the PCB 4.

As shown in fig. 5, a boss 311 is fixedly connected to an end of the front plug 31 close to the rear socket 32, the boss 311 has a draft angle, and a smaller end of the boss 311 faces a direction away from the front plug 31. Referring to fig. 6, a cavity 321 for the insertion of the boss 311 is formed at one end of the rear socket 32 close to the front plug 31, a draft angle of the cavity 321 is the same as a draft angle of the boss 311, and after the boss 311 is inserted into the cavity 321, an outer wall of the boss 311 can be tightly abutted to the cavity 321, so that the front plug 31 and the rear socket 32 can be limited to move relatively along a direction perpendicular to a longitudinal axis of the boss 311. The boss 311 is oval in cross-section and limits relative rotation between the front plug 31 and the rear socket 32.

As shown in fig. 7, a front end fixing groove 312 is formed at one end of the front end plug 31 close to the rear end socket 32, and a front end magnet 313 is fixedly connected in the front end fixing groove 312; referring to fig. 6, a rear end fixing groove 322 is formed in one end of the rear end socket 32 close to the front end plug 31, a rear end magnet 323 is fixedly connected in the rear end fixing groove 322, and after the boss 311 is inserted into the cavity 321, the front end magnet 313 and the rear end magnet 323 can attract each other to form an adsorption anti-disengaging structure, so that the front end plug 31 and the rear end plug can be stably engaged, and relative movement between the front end plug 31 and the rear end socket 32 in a direction away from each other is limited.

As shown in fig. 5, a protruding strip 314 is fixedly connected to an end of the front plug 31 close to the rear socket 32, and referring to fig. 6, a groove 324 is formed in an end of the rear socket 32 close to the front plug 31, and after the boss 311 is inserted into the cavity 321, the protruding strip 314 is inserted into the groove 324, so that the connection strength and the connection stability of the front plug 31 and the rear socket 32 along the direction perpendicular to the central axis of the boss 311 can be further enhanced. The protruding strips 314 are arc-shaped, the protruding strips 314 are bent towards the direction away from the boss 311, and the protruding strips 314 are provided with a pair and are respectively symmetrically distributed on two sides of the boss 311. The protruding strip 314 has a draft angle, and the smaller end of the boss 311 faces away from the front plug 31. The groove 324 is complementary to the protrusion 314, i.e. it is also arc-shaped and has a draft angle, after the protrusion 314 is inserted into the groove 324, the outer wall of the protrusion 314 can tightly abut against the inner wall of the groove 324.

As shown in fig. 8, when the front plug 31 is inserted into the USB socket of the computer, and the housing 1 is subjected to an impact force in a lateral direction (as shown in fig. 8, the direction indicated by the arrow denoted by f is the force receiving direction of the housing 1), the rear socket 32 and the front plug 31 tend to separate from each other, and when the impact force reaches a certain strength, the separating force between the rear socket 32 and the front plug 31 is greater than the attractive force between the front magnet 313 and the rear magnet 323, and the housing 1 deflects in the force receiving direction, and the rotation center is the surface where the front plug 31 and the rear socket 32 are spliced and is located on the side away from the force receiving surface of the housing 1, and since the boss 311, the cavity 321, the rib 314, and the groove 324 have draft angles, the boss 311 does not interfere with the inner wall of the cavity 321, and the strip does not interfere with the inner wall of the groove 324.

The value of the force when the front plug 31 and the rear socket 32 are separated from each other by the applied force is called a bending force threshold, that is, when the force generated by the impact exceeds the bending force threshold, the front plug 31 and the rear socket 32 are automatically separated from each other without bending or breaking, and the boss 311 can be restored to be intact after being reinserted into the cavity 321.

Since the cross section of the boss 311 is oval, the front plug 31 and the rear socket 32 can be smoothly separated from each other when the housing 1 is impacted from different directions of the side surface of the housing 1 and the acting force generated by the impact exceeds the bending force threshold.

Referring to fig. 10, AB in fig. 10 indicates the draft edge of the boss 311 or the cavity 321, AC indicates the height of the boss 311, denoted by h, O indicates the rotation center of the boss 311, a indicates the point at which the end face of the boss 311 is farthest from the rotation center, AO indicates the distance at which the end face of the boss 311 is farthest from the rotation center, denoted by s, and θ indicates the draft angle. If the angle OAB is less than 90 degrees, interference will occur, with AB being the limit when perpendicular to AO. Therefore, taking AB perpendicular AO as an example, and angle AOB is also θ, the relationship between the draft angle, the height of the boss 311, and the position of the center of rotation of the boss 311 is: h ═ s × sin (θ). After the angle theta and the distance s are determined, h is less than or equal to s sin (theta), after the height h and the distance s are determined, theta is greater than or equal to arcsin (h/s), and after the height h and the angle theta are determined, s is greater than or equal to h/s sin (theta).

As shown in fig. 11, a connecting piece 315 is fixedly connected inside the front plug 31, one end of the connecting piece 315 close to the rear socket 32 is connected with a front lead 316, the front lead 316 is embedded inside a boss 311, and in combination with fig. 7, one end face of the boss 311 close to the rear socket 32 is fixedly connected with a contact 318, and the contact 318 is connected with a lead. Referring to fig. 6, a connector 325 is fixedly connected to an end surface of the cavity 321 away from the front plug 31 (i.e., a bottom surface of the cavity 321), a rear wire 326 is connected to an end of the connector 325 away from the front plug 31, and the rear wire 326 is embedded in the rear socket 32 and connected to the circuit on the PCB board 4 after passing through the rear socket 32.

As shown in fig. 12, the connector 325 includes a cylinder 3251, a movable contact 3252 and a connection spring 3253, and in connection with fig. 11, the cylinder 3251 is fixedly connected to the rear socket 32 and connected to the rear wire 326; the movable contact 3252 is slidably connected with the inner wall of the cylinder 3251, and two ends of the connecting spring 3253 are respectively in compression abutment with the movable contact 3252 and the inner wall of the cylinder 3251; a reduced port 32511 is integrally formed at one end of the cylinder 3251 close to the boss 311, a flange 32521 is integrally connected at one end of the movable contact 3252 close to the connecting spring 3253, and after the movable contact 3252 moves in the axial direction (the direction in which the connecting spring 3253 extends and retracts) in the direction away from the connecting spring 3253, the flange 32521 can be abutted against the reduced port 32511 to limit the sliding out of the cylinder 3251. After the boss 311 is inserted into the cavity 321, the movable contact 3252 abuts against the contact 318, so that the front end wire 316 and the rear end wire 326 can be electrically connected to each other.

As shown in fig. 13, when the contact 318 abuts against the movable contact 3252, the movable contact 3252 presses the connection spring 3253, the connection spring 3253 is compressed, and the elastic force of the connection spring 3253 keeps the movable contact 3252 and the contact 318 constantly connected stably. When the distance between the end surface of the boss 311 and the bottom surface of the cavity 321 is increased, the movable contact 3252 can still keep the movable contact 3252 connected to the contact 318 within the stroke of the connection spring 3253 recovering its shape.

The movable contact 3252 is made of copper, so that it can prevent oxidation and maintain good contact with the contact 318, and can prevent attraction between the front magnet 313 and the rear magnet 323, and is not limited to copper, as long as it is not iron, cobalt, or nickel and is a conductor.

As shown in fig. 14, a buffer spring 41 is disposed on one side surface of the PCB 4, and two ends of the buffer spring 41 are respectively and fixedly connected to the surface of the PCB 4 and the inner wall of the housing 1. When the housing 1 is collided by the outside, the buffer spring 41 can absorb a part of the vibration energy, convert the kinetic energy into elastic potential energy, reduce the kinetic energy transmitted to the PCB 4, and buffer the PCB 4.

Example 2

A breaking-proof usb disk, which is different from that of embodiment 1, as shown in fig. 15, an adhesion-proof member is disposed between a front plug 31 and a rear socket 32, the adhesion-proof member is a gel layer 33, the gel layer 33 can adhere the front plug 31 and the rear socket 32 to each other, and a boss 311 is restricted from being pulled out of a cavity 321 in a direction away from the cavity 321. When the external force f applied to the housing 1 exceeds the threshold of the bending force, the gel layer 33 can be torn, the front plug 31 and the rear socket 32 can be separated from each other, and after the boss 311 is inserted into the cavity 321, the front plug 31 and the rear socket 32 can be bonded together again through the gel layer 33.

Example 3

A breaking-proof usb disk, which is different from that in embodiment 1, as shown in fig. 16, a clamping anti-releasing structure is disposed between the front plug 31 and the rear socket 32, the clamping anti-releasing structure includes a hook 327 fixedly connected to the rear socket 32 and a slot 317 opened on the front plug 31, after the boss 311 is inserted into the cavity 321, the hook 327 can be snapped into the slot 317 to limit the front plug 31 to move in a direction away from the rear socket 32. The hook 327 has a certain elasticity, when the external force f applied to the housing 1 exceeds the threshold of the bending force, the hook 327 can be elastically deformed and separated from the slot 317, the front plug 31 and the rear socket 32 can be separated from each other, and after the boss 311 is inserted into the cavity 321, the hook 327 can be re-locked into the slot 317.

Example 4

An anti-breaking U disk is different from that of embodiment 1 in that, as shown in fig. 17, an elastic tensioning anti-releasing piece is arranged between a front end plug 31 and a rear end socket 32, the elastic tensioning anti-releasing piece is an extension spring 34, an accommodating cavity 35 is arranged between the front end plug 31 and the rear end socket 32, the extension spring 34 is located inside the accommodating cavity 35, two ends of the extension spring 34 are fixedly connected with the front end plug 31 and the rear end socket 32 respectively, and the extension spring 34 is always in a stretched state, so that the front end plug 31 and the rear end socket 32 can be stably spliced. When the external force f applied to the housing 1 exceeds the bending force threshold, the extension spring 34 is extended, the front plug 31 and the rear socket 32 are separated from each other, and when the external force f is removed, the front plug 31 and the rear socket 32 can automatically move toward each other under the elastic force of the extension spring 34, and the boss 311 is automatically inserted into the cavity 321.

Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims

1. The utility model provides a prevent losing USB flash disk, includes USB plug (3) and casing (1), USB plug (3) and casing (1) looks fixed connection, characterized by: the USB plug (3) comprises a front end plug (31) and a rear end socket (32), the rear end socket (32) is fixedly connected with the shell (1), and the front end plug (31) is detachably and fixedly connected with the rear end socket (32);

the front end plug (31) is fixedly connected with a boss (311), and the rear end socket (32) is provided with a concave cavity (321) for the boss (311) to be inserted;

the side surface of the boss (311) is provided with a drawing angle, and the boss (311) is gradually reduced towards the direction far away from the front end plug (31);

the inner wall of the concave cavity (321) is provided with a die drawing angle matched with the die drawing angle of the side surface of the boss (311);

an anti-disengaging structure is arranged between the front end plug (31) and the rear end socket (32), and after the boss (311) is inserted into the cavity (321), the anti-disengaging structure can prevent the front end plug (31) and the rear end socket (32) from being separated from each other;

a communication structure is arranged between the boss (311) and the cavity (321), and after the boss (311) is inserted into the cavity (321), the front-end plug (31) and the rear-end socket (32) are electrically connected through the communication structure;

prevent losing USB flash disk still includes PCB board (4), PCB board (4) with USB plug (3) looks fixed connection, PCB board (4) are located inside casing (1), inside buffer spring (41) that is equipped with of casing (1), buffer spring (41) both ends respectively with PCB board (4) and casing (1) looks fixed connection.

2. The anti-breaking U disk as claimed in claim 1, wherein:

the anti-falling structure is an adsorption anti-falling structure which comprises a front end magnet (313) and a rear end magnet (323);

the front end magnet (313) is fixedly connected to one end, close to the rear end socket (32), of the front end plug (31), and the rear end magnet (323) is fixedly connected to one end, close to the front end plug (31), of the rear end socket (32);

after the boss (311) is inserted into the concave cavity (321), the front end magnet (313) and the rear end magnet (323) are attached to each other.

3. The anti-breaking U disk as claimed in claim 1, wherein:

the anti-disengaging structure is an adhesion anti-disengaging piece, the adhesion anti-disengaging piece is a gel layer (33), and the gel layer (33) is bonded and fixed between the front-end plug (31) and the rear-end socket (32).

4. The anti-breaking U disk as claimed in claim 1, wherein: the anti-disengaging structure is joint anti-disengaging structure, and joint anti-disengaging structure includes fixed connection pothook (327) on rear end socket (32) and seting up in draw-in groove (317) of front end plug (31) for pothook (327) joint, pothook (327) have elasticity.

5. The anti-breaking U disk as claimed in claim 1, wherein: the anti-falling structure is an elastic tensioning anti-falling part which is an extension spring (34); the two ends of the extension spring are respectively fixedly connected with the front end plug (31) and the rear end socket (32).

6. The anti-breaking U disk as claimed in claim 1, wherein: the cross section of the boss (311) is elliptical.

7. The anti-breaking U disk as claimed in claim 1, wherein: one end of the front end plug (31) close to the rear end socket (32) is fixedly connected with a convex strip (314), the side surface of the convex strip (314) is provided with a drawing angle, and the convex strip (314) is gradually reduced towards the direction far away from the front end plug (31); one end of the rear socket (32) close to the front plug (31) is provided with a groove (324) for the insertion of the convex strip (314), and the side wall of the groove (324) is provided with a pattern drawing angle matched with the pattern drawing angle of the side surface of the convex strip (314).

8. The anti-breaking U disk as claimed in claim 1, wherein: the communication structure comprises a contact (318) fixedly connected to the boss (311) and a movable contact (3252) telescopically connected to the inner wall of the cavity (321), and after the boss (311) is inserted into the cavity (321), the movable contact (3252) is abutted to the contact (318).