A conversion socket

Abstract

The application discloses a conversion socket, which comprises a shell and an inner shell arranged in the shell, and the inner shell is fixed with the shell through a locking structure to realize screw-free assembly. In order to solve the problem that the traditional buckle type structure is firm in assembly but difficult to disassemble and maintain, a gap is reserved between the peripheral wall of the inner shell and the cavity wall of the shell to form an unlocking channel which is open to the port, the unlocking channel forms an insertion port at the port for inserting a sheet-shaped unlocking sheet, and the buckle in the locking structure is located in the unlocking channel, and the side of the buckle facing the insertion port is provided with a guide slope, so that after the unlocking sheet is inserted from the insertion port, the unlocking sheet can push the buckle away from the clamping part along the guide slope, thereby releasing the fixation of the inner shell and the shell without damaging the shell. The structure not only ensures the reliability of the buckle locking in normal use, but also provides a simple path for disassembly and maintenance through the cooperation of the unlocking channel and the guide slope.

Description

Technical Field

[0001] This invention relates to the field of power connector technology, and more particularly to a conversion socket. Background Technology

[0002] Adapter sockets are used to convert between different plug types, providing safe power to electrical appliances. With the trend towards miniaturization and high integration in products, adapter sockets need to balance ease of assembly with structural robustness in their structural design. In existing technologies, to simplify assembly and reduce product costs, adapter sockets typically use a snap-fit ​​structure instead of screws. However, snap-fit ​​structures are often designed to be quite tight to meet drop test requirements, making disassembly and repair during product development and production extremely difficult and prone to damage to the outer casing or internal structure. Furthermore, existing safety doors in similar products often use a linear movement structure along the plug insertion direction. When opening, the safety door needs to move downwards and occupies a large vertical space, limiting the miniaturization design of the product. Simultaneously, the existing contact method between the spring contacts and plug pins is prone to increased contact resistance and excessive temperature rise after long-term use, and the circuit board fixing method is also prone to damage due to improper force after repeated insertion and removal. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention provides a conversion socket that is securely assembled, easy to disassemble and maintain, and conducive to miniaturization.

[0004] The technical solution adopted by this invention to solve its technical problem is: A conversion socket includes a housing and an inner shell inserted into the housing. The housing has a receiving cavity and a port communicating with the receiving cavity, the receiving cavity being surrounded by a cavity wall. The inner shell includes a panel and a peripheral wall extending from the periphery of the panel. After the inner shell is inserted into the receiving cavity, a gap is left between the peripheral wall and the cavity wall, the gap forming an unlocking channel opening towards the port. The unlocking channel forms an insertion port at the port for inserting a piece-shaped unlocking piece. The inner shell and the housing are fixed by a locking structure, the locking structure including a latch and a locking part that engage with each other. One of the latch and the locking part is located on the peripheral wall, and the other is located on the cavity wall, and the latch is located within the unlocking channel. The latch has a guide slope on the side facing the insertion port, such that an unlocking piece inserted into the unlocking channel from the insertion port can push against the latch and the locking part along the guide slope to disengage the latch and release the fixation between the inner shell and the housing.

[0005] Furthermore, the buckle is provided on the cavity wall and protrudes towards the peripheral wall, and the engaging part is a buckle hole opened in the peripheral wall; the side of the buckle facing away from the insertion port forms a locking surface, and the locking surface abuts against the hole wall of the buckle hole to lock the inner shell and the outer shell.

[0006] Furthermore, the guide slope extends obliquely from the cavity wall toward the peripheral wall, so that the unlocking piece inserted through the insertion port is supported by the edge of the port and deflects along the guide slope toward the peripheral wall to assume an oblique posture.

[0007] Furthermore, the peripheral wall has an end edge away from the panel, and along the insertion direction of the unlocking piece from the insertion port into the unlocking channel, the end edge is located downstream of the buckle; the unlocking piece, in an inclined posture, can press against the end edge after passing the end edge, generating an axial component force on the inner shell toward the outside of the port, so as to push the inner shell out of the receiving cavity.

[0008] Furthermore, the locking structure is in multiple sets, and the multiple sets of locking structures are distributed circumferentially along the peripheral wall; when the unlocking piece is inserted into each of the multiple sets of locking structures, each buckle disengages from the corresponding engaging part, and the axial force at each location works together to cause the inner shell to pop out of the receiving cavity.

[0009] Furthermore, the panel is embedded in the port and flush with the edge of the port, and the seam between the periphery of the panel and the edge of the port forms the insertion port.

[0010] Furthermore, the height of the buckle protruding towards the peripheral wall is greater than the thickness of the peripheral wall at the buckle hole, so that the buckle passes through the buckle hole and remains engaged with the hole wall.

[0011] Furthermore, it also includes a circuit board assembly housed within the inner shell, the inner shell having a support post that presses against the circuit board assembly; it also includes a safety door fastener that is fixed to the inner shell by heat fusion; the circuit board assembly includes a spring contact for plug pins to be inserted, the safety door fastener having a first protrusion that presses against the spring contact to fix the circuit board assembly; the safety door fastener also has a second protrusion that supports and limits the spring contact.

[0012] Furthermore, the spring has an opening angle, and after the plug pins are inserted, they are parallel and attached to each other with the contact surface of the spring.

[0013] Furthermore, the inner shell is provided with two safety door shafts, a spring shaft, and safety door limiting ribs; it also includes two safety doors and V-shaped springs. The two safety doors are respectively pivotally mounted on the corresponding safety door shafts through mounting holes. The V-shaped springs are mounted on the spring shafts and their two ends are respectively fixed in the spring grooves of the two safety doors to drive the two safety doors to remain closed. The surface of the safety door where the plug pins abut is a beveled surface. When the plug pins are inserted, the two safety doors rotate in opposite directions around the corresponding safety door shafts to open.

[0014] The beneficial effects of this invention are: This invention provides a conversion socket, comprising a housing and an inner housing housed within the housing. The inner housing and the housing are fixed together by a locking structure, achieving screwless assembly. To address the problem of traditional snap-fit ​​structures being securely assembled but difficult to disassemble and maintain, this invention provides a gap between the peripheral wall of the inner housing and the cavity wall of the housing to form an unlocking channel opening towards the port. The unlocking channel forms an insertion port at the port for inserting a plate-shaped unlocking piece. The snap-fit ​​in the locking structure is located within this unlocking channel, and a guide slope is provided on the side of the snap-fit ​​facing the insertion port. This allows the unlocking piece, after being inserted into the insertion port, to push against the snap-fit ​​and disengage from the locking part along the guide slope, thereby releasing the inner housing from the outer housing without damaging the housing. This structure ensures the reliability of the snap-fit ​​locking during normal use and provides a simple path for disassembly and maintenance through the cooperation of the unlocking channel and the guide slope. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0016] Figure 1 This is a three-dimensional structural schematic diagram of the present invention; Figure 2 This is a cross-sectional structural diagram of the present invention; Figure 3 yes Figure 2 Enlarged view of point A in the middle; Figure 4 This is a schematic diagram of the disassembled structure of the present invention; Figure 5 This is a schematic diagram of the inner shell and safety door of the present invention; Figure 6 This is a structural schematic diagram of the safety door fixing component of the present invention; Figure 7 This is a schematic diagram of the safety door structure of the present invention; Figure 8 This is a schematic diagram of the spring sheet of the present invention.

[0017] in, 1. Outer shell; 11. Cavity wall; 12. Receiving cavity; 13. Port; 2. Inner shell; 21. Panel; 22. Peripheral wall; 221. End edge; 222. Support column; 23. Safety door hinge; 24. Spring hinge; 25. Safety door limiting rib; 3. Safety door; 31. Spring groove; 32. Mounting hole; 4. V-shaped spring; 5. Gap; 51. Unlocking channel; 52. Insertion port; 6. Locking structure; 61. Buckle; 611. Guide slope; 612. Locking surface; 62. Engaging part; 7. Circuit board assembly; 71. Spring piece; 8. Safety door fixing component; 81. First boss; 82. Second boss. Detailed Implementation

[0018] The following will clearly and completely describe the concept, specific structure, and technical effects of the present invention in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Furthermore, all connections / linkages involved in the patent do not simply refer to direct contact between components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this invention can be combined interactively without contradicting each other.

[0019] Reference Figure 1 The present invention provides a conversion socket, which has a square structure with four sides and is mainly composed of an outer shell 1 and an inner shell 2 installed inside the outer shell 1 to form a basic frame.

[0020] Reference Figures 2-4 The outer shell 1 has a receiving cavity 12 and a port 13 communicating with the receiving cavity 12. The receiving cavity 12 is surrounded by a cavity wall 11, and the port 13 is arranged facing upward. The inner shell 2 is inserted into the receiving cavity 12 from the top of the outer shell 1 through the port 13. The inner shell 2 includes a panel 21 and a peripheral wall 22 integrally extending from the periphery of the panel 21. The panel 21 forms the top surface of the inner shell 2, and the peripheral wall 22 extends downward from the edge of the panel 21 to form an enclosing structure for accommodating and protecting the internal electronic components.

[0021] Reference Figure 3After the inner shell 2 is inserted into the receiving cavity 12, the panel 21 is embedded in the port 13 and flush with the edge of the port 13, making the top of the entire adapter a complete flat surface, resulting in a clean appearance and effectively preventing dust from entering the receiving cavity 12. A tiny seam is formed between the periphery of the panel 21 and the edge of the port 13, which constitutes the insertion port 52 for inserting the disc-shaped unlocking piece. Because the panel 21 is flush with the edge, this seam is extremely small under normal use, providing a sealing and dustproof effect, while also preserving an insertion channel for the unlocking piece for subsequent disassembly and maintenance. During disassembly, the unlocking piece can be smoothly inserted through this seam without causing irreversible damage to the inner shell 2 or the outer shell 1.

[0022] Continue to refer to Figure 3 After the inner shell 2 is inserted into the receiving cavity 12, a gap 5 is left between the peripheral wall 22 and the cavity wall 11. This gap 5 extends along the space between the peripheral wall 22 and the cavity wall 11, forming an unlocking channel 51 that opens toward the port 13. The unlocking channel 51 forms the aforementioned insertion port 52 at the port 13, allowing the sheet-like unlocking piece to be inserted downwards from the insertion port 52 along the unlocking channel 51.

[0023] Reference Figures 2-4 The inner shell 2 and the outer shell 1 are fixed together by a locking structure 6. The locking structure 6 includes a snap-fit ​​snap 61 and a locking part 62 that engage with each other. The snap-fit ​​snap 61 is located on the cavity wall 11 and protrudes towards the peripheral wall 22, and the locking part 62 is a locking hole formed in the peripheral wall 22. The snap-fit ​​snap 61 is located within the unlocking channel 51, that is, the snap-fit ​​snap 61 is located in the gap 5 space between the peripheral wall 22 and the cavity wall 11. The side of the snap-fit ​​snap 61 facing away from the insertion port 52 forms a locking surface 612, which abuts against the hole wall of the locking hole, thereby firmly locking the inner shell 2 and the outer shell 1, so that even if the adapter socket is dropped from a height of 1 meter under normal use, the inner shell 2 will not come out of the outer shell 1.

[0024] The height of the buckle 61 protruding toward the peripheral wall 22 is greater than the thickness of the peripheral wall 22 at the locking hole. After the buckle 61 passes through the locking hole, its end extends beyond the inner surface of the peripheral wall 22, maintaining a sufficient engagement with the hole wall to ensure that the locking structure 6 will not accidentally disengage during drop impacts or daily use.

[0025] Reference Figure 3The latch 61 has a guide slope 611 on the side facing the insertion port 52, which extends obliquely from the cavity wall 11 toward the peripheral wall 22. When the unlocking piece is inserted into the unlocking channel 51 from the insertion port 52, as it slides downward along the guide slope 611, it will deflect along the guide slope 611 toward the peripheral wall 22 with the edge of the port 13 as a support point, thus adopting an oblique posture. Since the plastic material used in the outer shell 1 is harder than that of the inner shell 2, the outer shell 1 has higher strength. Therefore, when the unlocking piece deflects with the edge of the outer shell 1 as a rigid support, the force generated mainly acts on the peripheral wall 22 of the inner shell 2, causing the peripheral wall 22 to undergo elastic deformation inward, thereby forcing the latch hole to disengage from the latch 61.

[0026] Reference Figure 4 , Figure 5 The peripheral wall 22 has an end edge 221 away from the panel 21. Along the insertion direction of the unlocking piece from the insertion port 52 into the unlocking channel 51, the end edge 221 is located downstream of the latch 61, that is, the end edge 221 is below the latch 61. When the unlocking piece, in an inclined position, passes the position of the latch 61 and continues to be inserted downward, after passing the end edge 221 of the peripheral wall 22, the inclined position of the unlocking piece allows it to press against the end edge 221, generating an axial component force on the inner shell 2 toward the outside of the port 13, that is, an upward pushing force, thereby pushing the inner shell 2 upward out of the receiving cavity 12.

[0027] In this embodiment, the adapter socket has a square structure with four sides. Multiple sets of locking structures 6 are distributed circumferentially along the peripheral wall 22. At least one set of locking structures 6 is provided on each side, preferably two or three sets per side. The multiple sets of locking structures 6 on opposite sides are positioned close to each other to facilitate the insertion of the unlocking piece for engagement.

[0028] The specific disassembly process is as follows: When the inner shell 2 needs to be disassembled, prepare four piece-shaped unlocking tabs. First, insert the first unlocking tab into the unlocking channel 51 corresponding to the first side from the seam between the periphery of the panel 21 and the edge of the port 13, to a depth of about 3 mm, until it reaches the position of the latch 61. Then, insert one unlocking tab into each of the other three sides in turn, also inserting it about 3 mm. At this time, all four unlocking tabs have reached their respective latch 61 positions. Next, push each unlocking tab downwards by about 7 mm in turn. The unlocking tabs deflect along the guide slope 611 and go beyond the position of the latch 61, so that each latch 61 disengages from its corresponding locking hole. When the last unlocking tab is inserted to a depth of 7 mm, all locking structures 6 are unlocked. The axial component force generated by each unlocking tab on the end edge 221 of the inner shell 2 works together, and the inner shell 2 automatically pops out of the receiving cavity 12 under the push of this combined force.

[0029] The advantages of this structure are: it allows for a secure fixation between the inner shell 2 and the outer shell 1 without the use of screws; assembly is simple and quick; the structure is robust and reliable, and it can withstand a drop test from a height of 1 meter; furthermore, when maintenance is required, the inner shell 2 can be easily and quickly removed using only four unlocking tabs, without the need for special tools, and the disassembly process does not damage the shell, allowing for repeated disassembly and assembly. The steeply angled guide ramp 611 design facilitates the smooth insertion of the inner shell 2 during assembly and also allows the unlocking tabs to easily push open the latches 61 during disassembly.

[0030] In some embodiments, the outer casing 1 has a button hole for mounting a button to control the on / off state of the internal circuitry of the adapter. Beside the button hole, the outer casing 1 has two positioning ribs arranged parallel to each other, forming a positioning groove between them. Additionally, on both sides of the button hole, the outer casing 1 also has positioning holes for inserting positioning pins.

[0031] The button has one long leg and two positioning posts. The long leg extends from one end of the button and has a certain length, capable of providing restoring force after elastic deformation. The two positioning posts are connected to the button body through side arms extending from both sides of the button body. The side arms extend outward from the left and right sides of the button body, with a positioning post at each end.

[0032] During assembly, the longer leg is first placed into the groove between the two positioning ribs. The longer leg is held and positioned by the two positioning ribs, thus determining the initial position and orientation of the button. Then, the entire button is pressed into the button hole of the outer casing 1. At this time, the positioning pins at the ends of the two side arms are inserted into the corresponding positioning holes, realizing the positioning and limiting of the button in the left and right directions.

[0033] When the button is pressed, it moves inward, triggering a switching element on the internal circuit board. Upon release, the long leg and the side arms on both sides generate an elastic restoring force, driving the button back to its initial position. Because the long leg is held and constrained by two positioning ribs, and the positioning pins at the ends of the side arms are constrained by positioning holes, the button maintains a stable movement trajectory throughout its movement, without any deviation or jamming.

[0034] The advantages of this button structure are: the assembly process requires no screws or additional fasteners and can be completed with just one press-in operation, which is simple and quick; the long legs and the two side arms form a three-point support and recovery structure, which has good elasticity and even force distribution, and the button feels smooth and does not stick; the entire button structure is compact and does not take up extra space inside the housing.

[0035] In some embodiments, refer to Figure 5 , Figure 7The inner shell 2 is provided with two safety door hinges 23, one spring hinge 24, and two safety door limiting ribs 25. The two safety door hinges 23 are symmetrically arranged, and the spring hinge 24 is located between the two safety door hinges 23. The two safety doors 3 are respectively fitted onto the corresponding safety door hinges 23 through their respective mounting holes 32, forming a pivotal connection that can rotate around the safety door hinges 23.

[0036] Reference Figure 7 A V-shaped spring 4 is mounted on a spring shaft 24. Both ends of the V-shaped spring 4 extend into and are fixed within the spring grooves 31 on the two safety doors 3. The spring force keeps the two safety doors 3 biased towards the closing direction, meaning that when no external force is applied, the two safety doors 3 are in the closed state, covering the neutral and live wire holes of the socket to prevent the insertion of foreign objects and the risk of electric shock. Safety door limiting ribs 25 restrict the closing position of the safety doors 3, keeping them in a predetermined position when closed.

[0037] The two safety doors 3 form a scissor-type safety door structure. The surface of the safety door 3 where the plug prongs contact is an inclined plane. When the ground prong (the longer prong) of the plug is inserted first, it simultaneously contacts the inclined surfaces of both safety doors 3 and applies a downward force. Due to the guiding effect of the inclined planes, this downward force is decomposed into components that cause the two safety doors 3 to rotate in opposite directions around their respective safety door axes 23. The two safety doors 3 open simultaneously to both sides like the two blades of scissors. At this time, the neutral and live wire holes of the socket are exposed, allowing the neutral and live wire prongs of the plug to enter smoothly. After the plug is unplugged, the restoring force of the V-shaped spring 4 drives the two safety doors 3 to close again.

[0038] The beneficial effect of this scissor-type safety door 3 structure is that the way the safety door 3 rotates around its axis makes its movement trajectory a plane rotation, which does not require space to move downwards. Compared with the traditional solution of the safety door 3 moving downwards, it greatly reduces the space required in the thickness direction of the product, which is conducive to the miniaturization design of the product.

[0039] In some embodiments, the inner housing 2 houses a circuit board assembly 7, which includes a neutral wire pin, a live wire pin, and a spring contact 71 for plug pins to be inserted onto the circuit board. The inner housing 2 is provided with a support post 222, which protrudes from the inner wall surface of the inner housing 2. When the circuit board assembly 7 is placed into the inner housing 2, the end of the support post 222 presses against the surface of the circuit board assembly 7, providing initial positioning and clamping for the circuit board.

[0040] The safety door fastener 8 is fixed to the inner shell 2 by heat fusion. Specifically, the inner shell 2 is provided with heat fusion pillars, and the safety door fastener 8 is provided with corresponding holes. During assembly, after the safety door fastener 8 is placed in place, the heat fusion process is used to melt the heat fusion pillars to form an unremovable connection with the safety door fastener 8.

[0041] The safety door fixing component 8 is provided with a first protrusion 81, which is positioned above the spring tab 71. When the safety door fixing component 8 is fixed in place, the first protrusion 81 presses against the spring tab 71, thereby indirectly fixing the circuit board assembly 7 by fixing the spring tab 71. In this fixing method, the force is applied to the spring tab 71 rather than directly to the circuit board body, which disperses and buffers the stress on the circuit board, preventing damage such as cracks or solder joint detachment caused by stress concentration during 30,000 repeated plugging and unplugging of the plug.

[0042] The safety door fixing component 8 is also provided with a second protrusion 82, which is located on the side of the spring piece 71 and serves to support and limit the spring piece 71. The second protrusion 82 limits the maximum deformation of the spring piece 71 when the plug pins are inserted, preventing the spring piece 71 from losing its elasticity due to excessive opening and plastic deformation, thereby increasing the structural strength and service life of the spring piece 71.

[0043] Reference Figure 8 The spring contact 71 has an opening angle of 3 degrees. When no plug pins are inserted, the two contact surfaces of the spring contact 71 are at a slight opening angle of 3 degrees. When plug pins are inserted into the spring contact 71, the thickness of the pins causes the two contact surfaces of the spring contact 71 to be stretched open to a state parallel and in contact with the pin surface. At this time, the contact surface and the pin are in surface contact rather than line contact or point contact, maximizing the contact area and thus minimizing contact resistance. This reduces the heat generated by contact resistance when a large current passes through, effectively controlling the temperature rise.

[0044] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A converter socket, comprising a housing and an inner housing inserted into the housing, characterized in that: The outer shell has a receiving cavity and a port communicating with the receiving cavity, the receiving cavity being surrounded by a cavity wall; the inner shell includes a panel and a peripheral wall extending from the periphery of the panel; after the inner shell is inserted into the receiving cavity, a gap is left between the peripheral wall and the cavity wall, the gap forming an unlocking channel opening towards the port, the unlocking channel forming an insertion port at the port for inserting a piece-shaped unlocking piece; the inner shell and the outer shell are fixed by a locking structure, the locking structure including a buckle and a locking part that engage with each other, one of the buckle and the locking part being located on the peripheral wall and the other on the cavity wall, and the buckle being located within the unlocking channel; the buckle has a guide slope on the side facing the insertion port, so that the unlocking piece inserted into the unlocking channel from the insertion port can push the buckle and the locking part along the guide slope to disengage from the engagement, thereby releasing the fixation between the inner shell and the outer shell.

2. The adapter socket according to claim 1, characterized in that: The buckle is provided on the cavity wall and protrudes towards the peripheral wall, and the engaging part is a buckle hole opened in the peripheral wall; the side of the buckle facing away from the insertion port forms a locking surface, and the locking surface abuts against the hole wall of the buckle hole to lock the inner shell and the outer shell.

3. The adapter socket according to claim 2, characterized in that: The guide slope extends obliquely from the cavity wall toward the peripheral wall, so that the unlocking piece inserted through the insertion port is supported by the edge of the port and deflects along the guide slope toward the peripheral wall to assume an oblique posture.

4. The adapter socket according to claim 3, characterized in that: The peripheral wall has an end edge away from the panel, and along the insertion direction of the unlocking piece into the unlocking channel from the insertion port, the end edge is located downstream of the buckle; The unlocking piece, which is tilted, can press against the end edge after passing the end edge, generating an axial force on the inner shell toward the outside of the port, so as to push the inner shell out of the receiving cavity.

5. The adapter socket according to claim 4, characterized in that: The locking structure consists of multiple sets, which are distributed circumferentially along the peripheral wall. When an unlocking piece is inserted into each of the multiple sets of locking structures, each latch disengages from its corresponding engaging part, and the axial forces at each location work together to cause the inner shell to pop out of the receiving cavity.

6. The adapter socket according to any one of claims 1-5, characterized in that: The panel is embedded in the port and flush with the edge of the port, and the seam between the periphery of the panel and the edge of the port forms the insertion port.

7. The adapter socket according to claim 2, characterized in that: The height of the buckle protruding toward the peripheral wall is greater than the thickness of the peripheral wall at the buckle hole, so that the buckle passes through the buckle hole and remains engaged with the hole wall.

8. The adapter socket according to claim 1, characterized in that: It also includes a circuit board assembly housed in the inner shell, the inner shell having a support post that presses against the circuit board assembly; It also includes a safety door fastener, which is fixed to the inner shell by heat fusion; the circuit board assembly includes a spring piece for plug pins to be inserted, and the safety door fastener is provided with a first boss, which presses against the spring piece to fix the circuit board assembly. The safety door fixing component is also provided with a second protrusion, which supports and limits the spring piece.

9. The adapter socket according to claim 8, characterized in that: The spring has an opening angle, and after the plug pins are inserted, they are parallel and fit together with the contact surface of the spring.

10. The adapter socket according to claim 1, characterized in that: The inner shell is provided with two safety door shafts, one spring shaft, and safety door limiting ribs; it also includes two safety doors and V-shaped springs. The two safety doors are respectively pivotally mounted on the corresponding safety door shafts through mounting holes. The V-shaped springs are mounted on the spring shaft and their two ends are respectively fixed in the spring grooves of the two safety doors to drive the two safety doors to remain closed. The surface of the safety door for the plug pins to contact is a bevel. When the plug pins are inserted, the two safety doors rotate in opposite directions around the corresponding safety door shafts to open.

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