A multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install

Abstract

The present invention discloses a multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install. In order to solve the problem that the functional modules of the prior art intelligent terminal are fixed in the terminal cabinet, which is inconvenient to disassemble and install; the present invention includes a shell and a terminal row, and the terminal row is arranged at one end of the shell; a functional module placement area is provided on the shell; a plurality of modular power supply ports and modular signal transmission ports are arranged in the functional module placement area; a power supply interface and a signal interface adapted to the modular power supply port and the modular signal transmission port are arranged on the side where the functional module of the terminal contacts the functional module placement area; each modular signal transmission port is electrically connected in sequence inside the shell according to the logical relationship of the corresponding functional module. This scheme adopts modular functional modules and interfaces, which is convenient for disassembly and installation.

Description

Technical Field

[0001] The present invention relates to the field of intelligent terminals, and in particular to a multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install. Background Art

[0002] Domestic distribution network automation uses DTU screens for online monitoring and protection of 10kV ring network cabinets. For European transformers or box transformers, online monitoring and protection are not performed, and faults cannot be located. The DTU screen can cover the high-voltage side of European transformers or box transformers, but the DTU screen processes the DTU core unit, power module, communication module, operation button, terminal block and other electrical accessories through the panel group method, which is large in size (generally 1300*600*400mm), large installation space, complex construction and large investment. Traditional DTU screens must be connected to zero-sequence PT and CT, and the transient zero-sequence power method is generally used for single-phase grounding judgment. In addition, each functional module is fixed, which is inconvenient to disassemble and install.

[0003] For example, in a patent document published in China, "An Intelligent Distributed DTU Power Distribution Terminal and Control Method", with the announcement number CN111342555A, the measurement and control module realizes the monitoring of the switch; the communication module is used to realize the communication of the user's control information with the single-chip microcomputer through the USB interface; the fault location module can realize the location collection of all fault information in the line within the unit; the busbar protection module realizes the tripping operation when the busbar is abnormally locked. The functional modules of this solution are fixed in the terminal cabinet, which is inconvenient to disassemble and install, and inconvenient to replace after a fault. Summary of the invention

[0004] The present invention mainly solves the problem that the functional modules of the prior art intelligent terminal are fixed in the terminal cabinet and are inconvenient to disassemble and install; it provides a multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install, adopts modular functional modules and interfaces, and is convenient for disassembly and installation.

[0005] The above technical problems of the present invention are mainly solved by the following technical solutions:

[0006] A multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install, comprising a shell and a terminal block, wherein the terminal block is arranged at one end of the shell; a functional module placement area is provided on the shell; a plurality of modular power supply ports and modular signal transmission ports are arranged in the functional module placement area; a power supply interface and a signal interface adapted to the modular power supply port and the modular signal transmission port are arranged on the side where the functional module of the terminal contacts the functional module placement area; and each modular signal transmission port is electrically connected in sequence inside the shell according to the logical relationship of the corresponding functional module.

[0007] Different modular functional modules are placed in the functional module placement area. The functional modules receive power and signals through modular power supply ports and modular signal transmission ports. Full-duplex signal transmission is adopted, and the signal transmission ports are connected inside the shell to complete the signal transmission of each functional module. The modular power supply ports and modular signal transmission ports are adjusted in the functional module placement area according to the power interface and signal interface positions of different modules to adapt to functional modules with different signals. When a module fails, only the functional module needs to be taken out, which is convenient for installation and disassembly, and easy for maintenance.

[0008] Preferably, the functional modules include an acquisition module, a calculation module and a communication module; each functional module is provided with a plurality of functional chips; the power interface and the signal interface are electrically connected to each functional chip inside through a bus. The acquisition module acquires various signals input from the terminal block, processes and calculates them through the calculation module, makes judgments, and transmits the results and decisions to the display module through the communication module or performs remote control.

[0009] Preferably, the functional module placement area includes a plurality of fixedly installed module placement frames; each module placement frame corresponds to a functional module; slide rails are respectively arranged along the four sides of the module placement frame, and two parallel mounting rods are respectively arranged along the horizontal and vertical directions of the module placement frame; the two ends of the mounting rods are respectively clamped in the slide rails of the module placement frame; the modular power supply port and the modular signal transmission port are respectively clamped between the horizontal mounting rod and the vertical mounting rod. By translating the movement of the mounting rod and the movement of the modular power supply port and the modular signal transmission port on the mounting rod, the modular power supply port and the modular signal transmission port can move freely in the module placement frame to adapt to functional modules of different models.

[0010] Preferably, one side of the functional module placement area is connected to a protective cover via a hinge; the other side of the functional module placement area is adsorbed to the protective cover via a magnet; when the protective cover is closed, it is tightly attached to the functional module, protecting the functional module, limiting the position of the functional module, and making it easy to open and install and remove the functional module.

[0011] Preferably, the area formed by the two transverse mounting rods and the two longitudinal mounting rods is the positioning area, and a fixing component is provided at the position corresponding to the functional module and the positioning area, and the fixing component is respectively engaged with the transverse mounting rod and the longitudinal rod. The power interface and the signal interface of the functional module can determine the position of a fixing component, and the functional module and the module placement frame are limited by the fixing component.

[0012] Preferably, the fixing assembly includes a button, a button channel, an arc-shaped spring piece, a spring, a clamping rod and a telescopic channel; the telescopic channel is vertically connected to the button channel, and the button is arranged in the button channel; the arc-shaped protrusion in the middle of the arc-shaped spring piece is against the bottom of the button, one end of the spring is connected to the arc-shaped recess in the middle of the arc-shaped spring piece, and the other end of the spring is connected to the side wall of the telescopic channel; the clamping rod is arranged in the telescopic channel, one end of the clamping rod is fixedly connected to one end of the arc-shaped spring piece, and the other end of the clamping rod is provided with a clamping interface for matching the mounting rod.

[0013] When the protective cover is closed, the protective cover presses the button, which causes the arc-shaped spring sheet to deform and extend to both ends, pushing the clamping rod outward, so that the clamping interface of the clamping rod is clamped with the mounting rod under the action of force. Similarly, when the protective cover is opened, the button is pushed up under the elastic force of the spring and the arc-shaped spring sheet, and the distance between the two ends of the arc-shaped spring sheet is reduced, pulling the clamping rod back into the telescopic channel, and the clamping interface of the clamping rod is pulled out under the action of the arc-shaped spring sheet force, thereby canceling the lock.

[0014] Preferably, an electromagnetic strip is arranged above the frame of the module placement frame, and a permanent magnet is arranged at the lower side of the functional module; a normally closed switch for controlling the on and off of the electromagnetic strip is arranged on the side of the functional module placement area where the magnet is arranged; when the protective cover is closed, the normally closed switch is disconnected, and the electromagnetic strip is non-magnetic; when the protective cover is opened, the normally closed switch is closed, and the electromagnetic strip is magnetic. When the protective cover is opened, the functional module is adsorbed on the module placement frame by magnetic force to ensure that the installation position does not move and the connection is stable; when the protective cover is closed, the position of the functional module is limited by the protective cover and the fixing component.

[0015] Preferably, the functional module placement area is provided with a bus interface and a bus channel for displacement of the bus interface on the side, and the bus interface is electrically connected to the terminal block; the bottom of the bus interface is in contact with the cam, and the acquisition module is provided with an interface connection channel adapted to the bus interface on the side, and the acquisition interface is provided in the interface connection channel, and the first return spring is provided on both sides of the acquisition interface, and one end of the first return spring is against the bus interface. The bus interface is pushed out by the rotation of the cam, so as to be connected to the acquisition interface, and when not in use, it is stored on the side to reduce space occupation.

[0016] Preferably, the side of the functional module placement area is extended with a limited slot, the side of the acquisition module is provided with an adaptive convex strip, and the side of the bus interface is provided with a convex strip; when the bus interface is connected to the acquisition interface, the convex strip on the bus interface is flush with the convex strip on the acquisition module, limiting the position of the acquisition module and ensuring a firm connection between the bus interface and the acquisition interface.

[0017] Preferably, the cam shaft is provided with a threaded column, the inner wall of the cam shaft is provided with an adapting thread, a key cap is installed at one end of the threaded column, and a second return spring is provided between the key cap and the cam side wall. By pressing the threaded column, the cam rotates, ejects the bus interface, and is returned to its original position by the second return spring.

[0018] The beneficial effects of the present invention are:

[0019] 1. The modular power supply port and the modular signal transmission port are adjusted in the functional module placement area according to the power interface and signal interface positions of different modules to adapt to functional modules with different signals; when a module fails, only the functional module needs to be taken out, which is convenient for installation and disassembly and maintenance.

[0020] 2. By translating the installation rod and moving the modular power supply port and the modular signal transmission port on the installation rod, the modular power supply port and the modular signal transmission port can be freely moved in the module placement frame to adapt to functional modules of different models.

[0021] 3. The protective cover protects the functional module, limits the functional module, and is easy to open, making it convenient for installation and removal of the functional module.

[0022] 4. By designing the electromagnetic strips on the frame of the fixed components and the module placement frame, the functional module can be limited when the protective cover is opened or closed. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the multi-mode intelligent high-voltage integrated terminal of the present invention.

[0024] Figure 2 It is a structural schematic diagram of a module placement frame of the present invention.

[0025] Figure 3 It is a schematic structural diagram of the fixing assembly of the present invention.

[0026] Figure 4 It is a schematic diagram of the installation structure of the acquisition module of the present invention.

[0027] Figure 5 It is a cross-sectional view of the cam of the present invention.

[0028] In the figure, 1. shell, 2. terminal block, 3. functional module placement area, 4. acquisition module, 5. calculation module, 6. communication module, 7. bus interface, 8. display screen, 9. indicator light, 10. button, 11. module placement frame, 12. mounting rod, 121. horizontal mounting rod, 122. longitudinal mounting rod, 13. modular power supply port, 14. modular signal transmission port, 15. electromagnetic strip, 16. button channel, 17. telescopic channel, 18. button, 19. arc spring, 20. spring, 21. clamping rod, 22. cam, 23. limit slide groove, 24. convex strip, 25. acquisition interface, 26. first reset spring, 27. threaded column, 28. second reset spring. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0030] Example:

[0031] The embodiment of the present invention is a multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install, such as Figure 1 As shown, it includes a housing 1, a terminal block 2, a functional module placement area 3, a display screen 8, an indicator light 9 and a button.

[0032] The terminal row 2 is arranged at the lower part of the housing 1 , a functional module placement area 3 is provided in the middle of the housing 1 , a display screen 8 is provided at the upper left corner of the housing 1 , and an indicator light 9 and a button 10 are provided on one side of the display screen 8 .

[0033] The functional modules of the terminal are placed in the functional module placement area 3. In this embodiment, the functional modules include a collection module 4, a calculation module 5 and a communication module 6. Several functional chips are respectively arranged inside each functional module.

[0034] Several modular power supply ports 13 and modular signal transmission ports 14 are arranged in the functional module placement area 3. The side of the functional module of the terminal in contact with the functional module placement area is provided with a power interface and a signal interface adapted to the modular power supply port 13 and the modular signal transmission port 14, and the power interface and the signal interface are electrically connected to each internal functional chip through a bus.

[0035] Each modular signal transmission port is electrically connected in sequence inside the housing according to the logical relationship of the corresponding functional module. In this embodiment, the signal transmission adopts the form of full-duplex, and the logical relationship of the functional modules is the acquisition module 4, the calculation module 5 and the communication module 6. The acquisition module 4 collects the signal connected to the terminal block 2, transmits it to the functional chip in the calculation module 5, performs calculation judgment respectively, and sends the obtained judgment result and decision result to the communication module 6. The communication module 6 displays the calculation result through the display screen 8 or the indicator light 9, and the communication module 6 controls the remote device through remote signaling.

[0036] In this embodiment, the functional modules include remote control, telemetry, telesignaling, power failure protection, time synchronization, historical record reporting, fault detection, telemetry over-limit detection, communication, line short circuit alarm, line grounding alarm, two-stage overcurrent protection, zero-sequence overcurrent protection, acceleration after closing, excitation inrush current lockout, non-interrupting current lockout and signal reset functions.

[0037] One side of the functional module placement area 3 is connected to a protective cover by a hinge, and the other side of the functional module placement 3 is adsorbed to the protective cover by a magnet; when the protective cover is closed, it is tightly attached to the functional module. The protective cover protects the functional module, limits the functional module, and is easy to open, so as to facilitate the installation and removal of the functional module.

[0038] The functional module placement area 3 includes a plurality of fixedly installed module placement frames 11, each of which corresponds to a functional module. In this embodiment, the module placement frames 11 include a computing module placement frame and a communication module placement frame.

[0039] like Figure 2 As shown, slide rails are respectively arranged along the four sides of the module placement frame 11, and two parallel mounting rods 12 are respectively arranged along the horizontal and vertical directions of the module placement frame 11. The two ends of the mounting rod 12 are respectively clamped in the slide rails of the module placement frame 11, and the two ends of the modular power supply port 13 and the modular signal transmission port 14 are respectively clamped between the horizontal mounting rod 121 and the vertical mounting rod 122.

[0040] By translating the movement of the mounting rod and the movement of the modular power supply port and the modular signal transmission port on the mounting rod, the modular power supply port and the modular signal transmission port can be freely moved in the module placement frame to adapt to functional modules of different models.

[0041] An electromagnetic strip 15 is arranged above the frame of the module placement frame 11, and a permanent magnet is arranged at the lower part of the side of the functional module; a normally closed switch for controlling the on and off of the electromagnetic strip 15 is arranged on the side of the functional module placement area 3 where the magnet is arranged; when the protective cover is closed, the normally closed switch is disconnected and the electromagnetic strip is non-magnetic; when the protective cover is opened, the normally closed switch is closed and the electromagnetic strip is magnetic.

[0042] When the protective cover is opened, the functional module is adsorbed on the module placement frame 11 by magnetic force to ensure that the installation position does not move and the connection is stable; when the protective cover is closed, the position of the functional module is limited by the protective cover and the fixing components.

[0043] The area formed by the two transverse mounting rods 121 and the two longitudinal mounting rods 122 is a positioning area. A fixing component is arranged at a position corresponding to the functional module and the positioning area. The fixing component is respectively clamped with the transverse mounting rod 121 and the longitudinal mounting rod 122.

[0044] The power interface and signal interface of the functional module can determine the position of a fixed component, and the functional module and the module placement frame are limited by the fixed component.

[0045] like Figure 3 As shown, the fixing assembly includes a button 18 , a button channel 16 , an arc-shaped spring sheet 19 , a spring 20 , a clamping rod 21 and a telescopic channel 17 .

[0046] The telescopic channel 17 is vertically connected to the key channel 16, and the key 18 is arranged in the key channel; the arc-shaped protrusion in the middle of the arc-shaped spring piece 19 is against the bottom of the key 18, one end of the spring 20 is connected to the arc-shaped depression in the middle of the arc-shaped spring piece 18, and the other end of the spring 20 is connected to the side wall of the telescopic channel 17.

[0047] The clamping rod 21 is disposed in the telescopic channel 17, one end of the clamping rod 17 is fixedly connected to one end of the arc-shaped spring sheet 19, and the other end of the clamping rod 21 is provided with a clamping interface adapted to the mounting rod 12. In this embodiment, the clamping interface 21 is a C-shaped clamping interface 21.

[0048] When the protective cover is closed, the protective cover presses the button 18 on the surface of the functional module, which causes the arc-shaped spring sheet 19 to deform and extend to both ends, pushing the clamping rod 21 outward, so that the clamping interface of the clamping rod 21 is clamped with the installation rod 12 under the action of force.

[0049] Similarly, when the protective cover is opened, under the elastic force of the spring 20 and the arc-shaped spring piece 19, the button 18 is pushed up, the distance between the two ends of the arc-shaped spring piece 19 is reduced, and the clamping rod 21 is pulled back into the telescopic channel. Under the action of the force of the arc-shaped spring piece 19, the clamping interface of the clamping rod 21 is deformed and disengaged, thereby canceling the clamping connection with the mounting rod 12.

[0050] A bus interface 7 is provided on the side of the functional module placement area 3, and the bus interface 7 is electrically connected to the terminal block 2. The acquisition module 4 is directly connected to the bus interface 7. Figure 4 As shown, a bus interface 7 and a bus channel for displacement of the bus interface 7 are provided on the side of the functional module placement area 3; the bottom of the bus interface 7 is in contact with the cam 22, and an interface connection channel adapted to the bus interface 7 is provided on the side of the acquisition module 4, and an acquisition interface 25 is provided in the interface connection channel, and first return springs 26 are respectively provided on both sides of the acquisition interface 25, one end of the first return spring 26 is against the bus interface 7, and the other end of the first return spring 25 is fixed to the upper wall of the interface connection channel.

[0051] A limited slot 23 is extended from the side of the functional module placement area 3, a convex strip 24 adapted to the limited slot 23 is provided on the side of the acquisition module 4, and a convex strip is provided on the side of the bus interface 7; when the bus interface 7 is connected to the acquisition interface 25, the convex strip on the bus interface 7 is flush with the convex strip on the acquisition module 4. The position of the acquisition module is limited to ensure that the bus interface and the acquisition interface are firmly connected.

[0052] like Figure 5 As shown, a threaded column 27 is provided at the rotating shaft of the cam 22, and an adapting thread is provided on the inner side wall of the rotating shaft of the cam 22. A key cap is installed at one end of the threaded column 27, and a second return spring 28 is provided between the key cap and the side wall of the cam. One end of the second return spring 28 is fixedly connected to the key cap, and the other end of the second return spring abuts against the cam. By pressing the threaded column 27, the cam 22 rotates and pushes out the bus interface 7, and is reset by the second return spring 28 after being released.

[0053] In this embodiment, when installing the acquisition module 4, align the interface connection channel of the acquisition module 4 with the bus channel, press the threaded column 27, rotate the cam 22 to push out the bus interface 7, and the bus interface 7 compresses the first return spring 26 and completes the connection with the acquisition interface 25. Move the acquisition module 4 to the left, and the convex strip 24 on the acquisition module 4 and the convex strip 22 on the bus interface 7 are snapped into the limiting slide groove 23.

[0054] When the acquisition module 4 is disassembled, it is moved to the right. When the bus interface 7 is moved above the bus channel, the elastic force of the first return spring 26 pushes the bus interface 7 back into the bus channel.

[0055] When installing other functional modules, it is only necessary to move and adjust the positions of the corresponding modular power supply ports 13 and modular signal transmission ports 14 according to the positions of the different power interfaces and signal interfaces of the functional modules, and connect the signal interface first. In this embodiment, the modular power supply port 13 adopts magnetic adsorption power supply, which is convenient for power supply connection.

[0056] The protective cover is opened during installation, and the functional module is adsorbed on the module placement frame 11; after installation, the protective cover is closed, and the protective cover presses the button 18 on the functional module, and the functional module is clamped on the installation rod 12 through the fixing component.

[0057] In the disassembly mode, the protective cover is opened, and the function module is disengaged from the mounting rod 12 due to the arc-shaped spring piece and the spring force in the fixing assembly. The function module to be disassembled only needs to be picked up and the signal interface is unplugged.

[0058] In the solution of this embodiment, the modular power supply port and the modular signal transmission port are adjusted in the position of the functional module placement area according to the positions of the power interfaces and signal interfaces of different modules to adapt to functional modules with different signals; when a module fails, only the functional module needs to be removed, which is convenient for installation and disassembly, and easy for maintenance.

[0059] It should be understood that the embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the appended claims of the application.

Claims

1. A multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install, comprising a housing (1) and a terminal block (2), wherein the terminal block is arranged at one end of the housing; characterized in that: The shell is provided with a functional module placement area (3); the functional module placement area is provided with a plurality of modular power supply ports (13) and modular signal transmission ports (14); a power interface and a signal interface adapted to the modular power supply port and the modular signal transmission port are provided on the side of the functional module of the terminal in contact with the functional module placement area; each modular signal transmission port is electrically connected in sequence inside the shell according to the logical relationship of the corresponding functional module; the functional module placement area includes a plurality of fixedly installed module placement frames, two parallel mounting rods are respectively provided along the horizontal and vertical directions of the module placement frames, and the fixed components are respectively engaged with the horizontal mounting rod and the vertical mounting rod, and the fixed components include a key, a key channel, an arc-shaped spring sheet, a spring, a clamping rod and a telescopic channel; the telescopic channel is vertically connected to the key channel; the arc-shaped protrusion in the middle of the arc-shaped spring sheet abuts against the bottom of the key, one end of the spring is connected to the arc-shaped recess in the middle of the arc-shaped spring sheet, and the other end is connected to the side wall of the telescopic channel; one end of the clamping rod is fixedly connected to one end of the arc-shaped spring sheet, and the other end of the clamping rod is provided with a clamping interface adapted to the mounting rod.

2. The multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install according to claim 1 is characterized in that: The functional modules include a collection module (4), a calculation module (5) and a communication module (6); a plurality of functional chips are arranged inside each functional module; and a power supply interface and a signal interface are electrically connected to each functional chip inside via a bus.

3. A multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install according to claim 1 or 2, characterized in that: The module placement frame is respectively provided with a corresponding functional module; slide rails are respectively arranged along the four sides of the module placement frame, and the two ends of the mounting rod are respectively clamped in the slide rails of the module placement frame; the modular power supply port (13) and the modular signal transmission port (14) are respectively clamped between the transverse mounting rod (121) and the longitudinal mounting rod (122).

4. The multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install according to claim 3 is characterized in that: One side of the functional module placement area (3) is connected to a protective cover via a hinge; the other side of the functional module placement area is adsorbed to the protective cover via a magnet; and the protective cover is tightly attached to the functional module when closed.

5. The multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install according to claim 4 is characterized in that: The area formed by the two transverse mounting rods (121) and the two longitudinal mounting rods (122) is a positioning area, and a fixing component is arranged at a position corresponding to the functional module and the positioning area.

6. The multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install according to claim 4, characterized in that: An electromagnetic strip (15) is arranged above the frame of the module placement frame (11), and a permanent magnet is arranged at the lower part of the side of the functional module; a normally closed switch for controlling the on and off of the electromagnetic strip is arranged on the side of the functional module placement area (3) where the magnet is arranged; when the protective cover is closed, the normally closed switch is disconnected and the electromagnetic strip is non-magnetic; when the protective cover is opened, the normally closed switch is closed and the electromagnetic strip is magnetic.

7. The multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install according to claim 2 is characterized in that: The functional module placement area (3) is provided with a bus interface (7) and a bus channel for displacement of the bus interface on the side, and the bus interface is electrically connected to the terminal block (2); the bottom of the bus interface is in contact with the cam (22); the acquisition module (4) is provided with an interface connection channel adapted to the bus interface (7) on the side, and a acquisition interface (25) is provided in the interface connection channel; first return springs (26) are respectively provided on both sides of the acquisition interface, and one end of the first return spring abuts against the bus interface.

8. The multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install according to claim 7, characterized in that: The functional module placement area (3) is provided with a limit slot (23) extending from the side thereof, the acquisition module (4) is provided with a matching convex strip (24) on the side thereof, and the bus interface (7) is provided with a convex strip on the side thereof; when the bus interface is connected to the acquisition interface, the convex strip on the bus interface is flush with the convex strip on the acquisition module.

9. The multi-mode intelligent high-voltage integrated terminal that is easy to disassemble and install according to claim 7, characterized in that: A threaded column (27) is arranged at the rotating shaft of the cam (22), an adaptable thread is arranged on the inner side wall of the rotating shaft of the cam, a key cap is installed at one end of the threaded column, and a second return spring (28) is arranged between the key cap and the side wall of the cam.

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