TWM643972U - Ultra-thin balanced keypad - Google Patents

Abstract

Provided is an ultra-thin balanced keypad for triggering electronic components on a PCB board to generate signal signals. The keypad includes a keycap, a base plate, and a linkage member set between the keycap and the base plate. The linkage member includes a linkage wing and a trigger wing that are mutually pivoted and extended with pivot arms on both sides thereof. The end of the pivot arm of the linkage wings and the end of the pivot arm of the trigger wings are pivoted to each other, and each of the pivot arms is provided with a limit structure. The base plate is also provided with a bracket member for limiting the position of the linkage member in cooperation with the limit structure. A stilted pivot point against the base plate is formed on the position of each pivot arm near the end towards the base plate. With the trigger wings and the linkage wings mutually pivoted, the structures such as the limit cover are reduced, the upward and downward movement is further reduced while ensuring a stable press balance, and the positioning of the linkage members is stable. Therefore, the keypad structure can be more material-saving and thinner.

Description

Slim Balanced Buttons

The invention relates to a switch device, in particular to an ultra-thin balanced key.

The input device is a device that points to the computer to input data and information, and is a bridge for the computer to communicate with the user or other devices, such as a keyboard. The keyboard is composed of several key switches.

Existing electronic devices are becoming more and more miniaturized, and the requirements for thinner and lighter keyboards are also getting higher and higher. Take the notebook computer as an example. Now the weight of the notebook computer is only about 1kg, the thickness of the whole machine is only about 13mm, and the key stroke of the switch button is only about 1.5mm. In order to meet the thin and light design of electronic equipment, one of the biggest obstacles affecting the thickness is the keyboard. The thickness of the keyboard, and the core issue that affects the thickness of the keyboard is the height (thickness) of the key switch. How to make the key switch ultra-thin without affecting the balance and stability when pressing, so as to ensure that the user can press the key cap at different positions. Accurate and stable generation of switching signals is a technical problem in this field. In the prior art, in order to realize the balanced and stable pressing of ultra-thin key switches, scissors feet with a small key stroke are basically used to achieve this. However, the mechanism principle of the scissors feet itself limits the ability to further make it thinner.

In addition, in the prior art, in order to achieve longer key switch life, dustproof and waterproof and other technical effects, a large number of photoelectric switches are used to replace traditional metal contacts, contacts and other switches. A photoelectric switch is a switch that changes the amount of light received by the light-receiving element from the light-emitting element through a grating to form a switch signal.

Chinese patent application number CN202111067452.8 patent titled "ultra-thin balanced pressing photoelectric button structure" discloses a button structure that can effectively reduce the pressing distance, but in this structure, a limit cover plate is used to fix the torsion spring, and correspondingly Increased production cost, still not streamlined enough, this creation aims at this problem, proposes a kind of new key structure.

In view of the above problems, the invention aims to provide an ultra-thin balanced key that saves materials and is pressed stably.

In order to achieve this technical purpose, the proposal of this creation is: an ultra-thin balanced key, which is used to trigger the electronic components arranged on the PCB board to generate signals, including the keycap, the bottom plate and the linkage member arranged between the keycap and the bottom plate,

The linkage component includes a linkage wing and a trigger wing which are pivotally connected to each other, pivot arms are extended on both sides of the linkage wing and the trigger wing, and the ends of the pivot arm of the linkage wing are pivotally connected to the ends of the pivot arm of the trigger wing , each pivot arm is equipped with a position-limiting structure; the bottom plate is also equipped with a bracket component that cooperates with the position-limiting structure to limit the linkage components;

A rocking fulcrum abutting against the base plate is formed on one side of each pivot arm adjacent to the end towards the base plate;

The linkage member also includes a return tension spring, one end of which is connected to the linkage wing, and the other end is connected to the trigger wing;

The keycap is fastened on the upper part of the linkage wing and the trigger wing, and the trigger wing is provided with a trigger structure for generating signals by trigger electronic components.

As a preference, the outer end of one of the pivoting arms of the linkage wing has a central positioning post, the inner side has a pivot shaft, and the end of the other pivoting arm of the linkage wing has only a pivot hole; the trigger wing The outer end of one of the pivotal arms has a central positioning column, the inner side has a pivotal shaft, and the end of the other pivotal arm of the trigger wing has only a pivotal hole; the linkage wing and the trigger wing pass through the respective pivotal shaft Coupling with the pivot hole of the other party forms a pivot connection; the support member is provided with a central positioning groove relative to the central positioning columns of the linkage wing and the trigger wing, and the center positioning column is limited in three directions: left, right and downward .

As a preference, each pivot arm has a limit post on the outer side adjacent to the end; the support member is equipped with a limit hole relative to the limit post on each pivot arm, and the position limit post is upward. The direction is limited.

Preferably, the maximum diameter of the limiting protrusion is smaller than the left and right width of the limiting hole, and the bottom of the limiting protrusion facing the bottom plate is configured as a ramp structure.

As a preference, the bottom plate corresponding to the central positioning groove is provided with an avoidance groove that allows the end of the pivoting arm to go down, and the two sides of the central positioning groove are located at the avoidance groove. An arc that can limit the downward movement of the central positioning column support frame.

As a preference, hooks are provided on the arms of both ends of the reset extension spring, connecting holes for connecting the hooks are arranged on the linkage wing and the trigger wing, and the arms of the arms at both ends of the reset extension spring are respectively fixed on the connection hole.

Preferably, the electronic component is a light pair tube assembly composed of a light-emitting element and a photosensitive element that is electrically connected to a patch and arranged on a PCB, and the trigger structure is a grating plate configured between the pivot arms on both sides of the trigger wing , when the keycap is pressed, the grating plate of the trigger wing moves downward to change the light path between the light emitting element and the photosensitive element.

Preferably, the grating plate is a light-shielding plate, and the light-emitting element and the photosensitive element are located on both sides of the light-shielding plate.

Preferably, the grating plate is a reflective plate, and the light-emitting element and the photosensitive element are located on the same side of the reflective plate.

Preferably, a space-avoiding column is provided at the bottom of the grating plate, and space-avoiding holes corresponding to the space-avoiding column are opened on the bottom plate.

Preferably, the electronic component is a patch that is electrically connected to a Hall sensor arranged on the PCB, and the trigger structure is a magnetic piece configured between the pivot arms on both sides of the trigger wing. When the keycap is pressed, the trigger wing The downward movement of the magnetic piece changes the magnetic flux received by the Hall sensor.

Preferably, the keycap is provided with a pivot cavity for pivoting the trigger wing and the top end of the linkage wing, and the two ends of the trigger wing and the linkage wing protrude from a pivot column corresponding to the pivot cavity, and the trigger wing and the linkage The top ends of the wings are limited to the pivot cavity on the keycap by the pivot post.

Preferably, the key also includes a sound-generating mechanism for producing a knocking sound when the key is pressed.

Preferably, the sounding mechanism includes a sounding torsion spring installed on the pivoting arm of the linkage wing, the sounding torsion spring has a fixed arm and a sounding arm; the linkage wing is provided with a sounding power storage part corresponding to the sounding arm , the bottom of the keycap is provided with a sounding pressure block corresponding to the sounding arm structure, the sounding force storage part has a slanting block part and an impacted part located on the slanting block part, and the sounding arm abuts on the slanting block part; when the key is pressed When the cap is on, the sounding pressure block applies pressure to the sounding arm to accumulate force downwards. When the keycap is pressed to a certain stroke, the sounding arm slides away from the sounding pressure block under the action of the inclined block and resets upwards to strike the affected part to send out a percussion. sound, when the keycap is released to make the sound pressing block go up to leave the sound arm, the sound arm resets.

As a preference, the pivot arm for installing the sounding torsion spring has a torsion spring fixing column and a fixed arm limit block, the sounding torsion spring is sleeved on the torsion spring fixing column, and the fixing arm of the sounding torsion spring abuts against the Fixed arm limit block.

The beneficial effect of this creation is: the trigger wing and the linkage wing pivotally connected to each other are adopted, together with the tension spring and other structures, the structure of the limit cover plate is reduced, and the up and down movement stroke is further reduced on the premise of ensuring the balance and stability of the pressing. The positioning and coordination between them are stable, so that the key structure can be more material-saving and thinner; in addition, the key also has the function of outputting photoelectric signals and the function of pressing and sounding, providing users with a flat pressing feel, easy assembly and disassembly, suitable for industrial quantities Produce.

The creation will be described in further detail below in conjunction with the drawings and specific embodiments. In order to describe the technical solution clearly and completely, the following embodiments are selected for illustration; the following embodiments are part of the embodiments of this creation; based on this creation, other embodiments obtained without creative work are all The scope of protection of this creation.

In the following embodiments, it should be noted that the orientations or positional relationships of the terms "upper", "lower", "left", "right", "inner", "outer", and "top/bottom" are all based on the The orientation or positional relationship shown in the formula is only for the convenience of clearly describing this embodiment, and does not indicate or imply that the device or element referred to must have a specific orientation, so it should not be construed as a limitation on this creation. Meanwhile, "first" and "second" in the embodiments are only used for distinguishing and describing purposes, and do not mean to indicate or imply relative importance.

The specific embodiment of this creation is an ultra-thin balanced key, which is used to trigger the electronic components arranged on the PCB board 9 to generate signals, including a keycap 1, a bottom plate 2 and a linkage member arranged between the keycap 1 and the bottom plate 2, The PCB board 9 is arranged on the bottom plate 2 and is designed according to the components on the bottom plate 2 and the corresponding openings of the slots. The linkage component enables the keycap 1 to move downward synchronously when pressing any position of the keycap 1. The linkage component includes the linkage wings 3 and The trigger wing 4, the two sides of the linkage wing 3 and the trigger wing 4 are all extended with pivot arms 5, and the ends of the linkage wings 3 pivot arms 5 and the trigger wings 4 pivot arms 5 are pivotally connected to each other, and each pivot arm 5 is equipped with a limit structure; the bottom plate 2 is also equipped with a bracket member 6 that cooperates with the limit structure to limit the linkage components;

Linkage component also comprises reset extension spring 7, and one end of this reset extension spring 7 connects linkage wing 3, and the other end connects trigger wing 4, is provided with hook 71 on the two ends force arms of reset extension spring 7, linkage wing 3 and trigger wing 4 Connecting holes 56 for connecting hooks 71 are arranged on the top, and the force arms at both ends of the return tension spring 7 are respectively connected to the connecting holes 56 through the hooks 71 . The key cap 1 is fastened on the upper part of the linkage wing 3 and the trigger wing 4. When no external force is applied, the return tension spring 7 is in a contracted state, and the linkage wing 3 and the trigger wing 4 are pulled up. When the keycap 1 is pressed, the linkage The wing 3 and the trigger wing 4 are synchronously downward, and the reset extension spring 7 is stretched until the reset extension spring 7 shrinks and resets after letting go.

The position adjacent to the end of each pivot arm 5 is formed with a rocking fulcrum 51 abutting on the bottom plate 2 on the side facing the bottom plate 2. When the keycap 1 is pressed, the linkage wing 3 and the trigger wing 4 swing around the pivot arm 5 The moving fulcrum 51 descends, and the end of the pivot arm 5 rises but is limited on the support member 6 due to the limiting structure. When the keycap 1 is released, the return tension spring 7 shrinks and pulls the linkage wing 3 and the trigger wing 4 upward. .

The position-limiting structure of the key pivot arm 5 includes a central positioning column 52 and a position-limiting protrusion 55. Specifically, the outer side of one of the pivotal arms 5 of the linkage wing 3 has a central positioning column 52, and the inner side has a pivot joint. There is only a pivot hole 54 at the end of the other pivot arm 5 of the linkage wing 3; there is a central positioning column 52 on the outside of the end of one of the pivot arms 5 of the trigger wing 4, and a pivot shaft 53 on the inside. There is only a pivot hole 54 at the end of the other pivot arm 5 of the trigger wing 4 ; the linkage wing 3 and the trigger wing 4 are coupled to each other's pivot hole 54 through their respective pivot shafts 53 to form a pivot relationship. When installing, the support member 6 is provided with a center positioning groove 61 relative to the center positioning column 52 of the linkage wing 3 and the trigger wing 4, and the center positioning column 52 is limited in three directions, left, right, and downward. There is an avoidance groove 64 corresponding to the end of the pivot arm 5 provided on the top, and the center positioning groove 61 can prevent the end of the pivot arm 5 from shifting left and right. The space-avoiding groove 64 descending at the end, the two sides of the center positioning groove 61 are located at the position of the space-avoiding groove 64, and an arc-shaped support frame 63 capable of restricting the downward movement of the center positioning column 52 is constructed, so that the center positioning column 52 falls to the arc-shaped support frame At 63, the end of the pivot arm 5 falls on the escaping groove 64 correspondingly, and the arc support frame 63 can limit the position to the bottom of the center positioning column 52, preventing the 5 ends of the pivoting arm from sliding downward, and the evacuating groove 64 is pivotally connected. The end of the arm 5 plays a role of avoiding the air, preventing the end of the pivoting arm 5 from hitting the bottom plate 2 .

Limiting post 55 is positioned at the outside of each pivoting arm 5 adjacent to the end, and relative to the limiting post 55 on each pivoting arm 5 on the support member 6, a limiting hole 62 is arranged, and the limiting hole 62 is arranged on the limiting post 55. The upward direction is limited so that when the pivoting arm 5 swings upward around the rocking fulcrum 51 , the limiting protrusion on the pivoting arm 5 is always limited in the limiting hole 62 . Preferably, the bottom of the limiting post 55 toward the bottom plate 2 is configured as a ramp structure, so that it can rotate more smoothly in the limiting hole 62. After the linkage wing 3 and the triggering wing 4 are connected by the pivot arm 5, Since the maximum diameter of the limiting post 55 is smaller than the left and right width of the limiting hole 62 , the limiting post 55 can be directly aligned with the limiting hole 62 for insertion and locking.

The button of this creation can be configured as a photoelectric button capable of outputting photoelectric signals. The electronic components of the button are patch electrical connections and are arranged on the light-to-tube assembly 8 composed of light-emitting elements and photosensitive elements on the PCB board 9. The trigger structure is structured. The grating plate between the pivoting arms 5 on both sides of the trigger wing 4, when the keycap 1 is pressed, the grating plate of the trigger wing 4 moves downward to change the light path between the light-emitting element and the photosensitive element, thereby outputting a photoelectric signal.

The grating plate of the photoelectric button is preferably a light-shielding plate 41, and the light-emitting element and the photosensitive element are positioned at both sides of the light-shielding plate 41, and a light path is formed between the light-emitting element and the photosensitive element, and the light-shielding plate 41 changes the distance between the light-emitting element and the light-sensitive element downward. light path.

The grating plate of the photoelectric button is preferably a reflector, and the light-emitting element and the photosensitive element are located on the same side of the reflector. When the reflector goes down, the light emitted by the light-emitting element is reflected by the reflector to the photosensitive element to form a light path.

In order to make the grating plate contact the PCB board 9 , a space-avoiding post 42 is provided at the bottom of the grating plate, and a space-avoiding hole 21 corresponding to the space-avoiding post 42 is provided on the bottom plate 2 .

The button of this invention can be configured as an electromagnetic button capable of outputting electromagnetic signals. The electronic component is a patch electrically connected to the Hall sensor arranged on the PCB board 9. The trigger structure is configured between the pivoting arms 5 on both sides of the trigger wing 4. When the keycap 1 is pressed, the magnetic part of the trigger wing 4 moves downward to change the magnetic flux received by the Hall sensor.

In order to prevent the keycap 1 from shaking horizontally, the keycap 1 is provided with a pivot cavity 12 for pivoting the top ends of the trigger wing 4 and the linkage wing 3 . Column, the top ends of the trigger wing 4 and the linkage wing 3 are limited to the pivot cavity 12 on the keycap 1 by the pivot column, the pivot cavity 12 can prevent the linkage wing 3 and the trigger wing 4 from moving up due to reset The keycap 1 that becomes smaller causes shaking from side to side due to the movable gap.

This key can be used as a mute or sounding key. When used as a sounding key, the key also includes a sounding mechanism for making a knocking sound when the key is pressed. The sounding mechanism includes a sounding torsion spring 31 installed on the pivot arm of the linkage wing 3 The sounding torsion spring 31 has a fixed arm 311 and a sounding arm 312; the linkage wing 3 is provided with a sounding arm 312 corresponding to the sounding arm 312, and the bottom of the keycap 1 is provided with a sounding pressure block 11 corresponding to the sounding arm 312. The force part 32 has an inclined block part 321 and an impacted part 322 located on the inclined block part 321, and the sounding arm 312 abuts against the inclined block part 321; when the keycap 1 is pressed, the sounding pressure block 11 applies pressure to the sounding arm 312 Make it downward to store force, when the keycap 1 is pressed to a certain stroke, the sounding arm 312 slides away from the sounding pressure block 11 under the action of the slanting block 321 and resets upwards and hits the affected part 322 to make a knocking sound. When the keycap is released 1. When the sounding pressure block 11 moves up to leave the sounding arm 312, the sounding arm 312 is reset.

Specifically, the sounding torsion spring 31 is fixed on the pivot arm 5 through the torsion spring fixing column 34 and the fixed arm stopper 33, the sounding torsion spring 31 is sleeved on the torsion spring fixing column 34, the fixing of the sounding torsion spring 31 The arm 311 abuts against the fixed arm limit block 33 .

When installing this button, the PCB board 9 is assembled on the base plate 2, and electronic components are pasted on the PCB board 9. 55 is pressed into the limit hole 62, and the pivot arm 5 is positioned using the central positioning column 52, and then the sounding torsion spring 31 and the reset tension spring 7 are installed, and finally the tops of the linkage wing 3 and the trigger wing 4 are fastened to the keycap 1 .

The above is only a preferred embodiment of this creation, and is not intended to limit this creation. Any minor modifications, equivalent replacements and improvements made to the above embodiments based on the technical essence of this creation should be included in this creation. within the scope of protection of the program.

1: Keycap 11: Sound pressing block 12: pivot cavity 2: Bottom plate 21: Avoid holes 3: linkage wing 31: sounding torsion spring 311: fixed arm 312: sounding arm 32:Voice storage department 321: oblique block 322: Attacked Department 33: Fixed arm limit block 34: torsion spring fixed column 4: trigger wing 41: Visor 42: Empty column 5: pivot arm 51: Rocking fulcrum 52: Center positioning column 53: Pivot shaft 54: Pivot hole 55: limit boss 56: Connection hole 6: Bracket components 61: Center positioning slot 62: limit hole 63: arc support frame 64: Avoid slot 7: Return tension spring 71: hook 8: Light-to-tube assembly 9: PCB board

Figure 1 is an exploded view of this creation; Fig. 2 is the structural representation of the connecting seat in this creation; Fig. 3 is the structural representation of the keycap in this creation; Fig. 4 is the schematic diagram of the structure of the linkage wing in this creation; Fig. 5 is a structural schematic diagram of the trigger wing in this creation; Figure 6 is a reference diagram of the unpressed state of the linkage wing and the trigger wing in this creation; Figure 7 is a reference diagram of the pressing state of the linkage wing and the trigger wing in this creation; Figure 8 is a schematic diagram of the assembly structure of the bracket component and the linkage component in this creation; Fig. 9 is a schematic diagram of the bottom structure of the trigger wing in this invention.

1: Keycap

2: Bottom plate

3: linkage wing

31: sounding torsion spring

311: fixed arm

312: sounding arm

4: trigger wing

5: pivot arm

6: Bracket components

7: Return tension spring

71: hook

8: Light-to-tube assembly

9: PCB board

Claims (15)

An ultra-thin balanced key, used to trigger an electronic component arranged on a PCB board to generate a signal, the ultra-thin balanced key includes a key cap, a bottom plate and a linkage member arranged between the key cap and the bottom plate, The linkage component includes a linkage wing and a trigger wing which are pivotally connected to each other. A pivot arm extends from both sides of the linkage wing and the trigger wing. are pivotally connected to each other, and each of the pivot arms is provided with a position-limiting structure; the bottom plate is also provided with a bracket component that cooperates with the position-limiting structure to limit the position of the linkage member; A rocking fulcrum abutting against the base plate is formed at a position adjacent to the end of each pivot arm facing the base plate; The linkage member also includes a return tension spring, one end of which is connected to the linkage wing, and the other end is connected to the trigger wing; The keycap is fastened on the upper part of the linkage wing and the trigger wing, and a trigger structure for triggering the electronic component to generate a signal is configured on the trigger wing. The ultra-thin balance key according to claim 1, wherein the outer end of one of the pivoting arms of the linkage wing has a central positioning post, and the inner side has a pivot shaft, and the other pivot arm of the linkage wing There is only one pivot hole at the end; the outer end of one of the pivot arms of the trigger wing has a central positioning column, and the inner side has a pivot shaft, and the other end of the pivot arm of the trigger wing has only a pivot hole; The linkage wing and the trigger wing are coupled to each other's pivot hole through their respective pivot shafts to form a pivot connection; the support member is provided with a central positioning column relative to the linkage wing and the trigger wing. The positioning groove is used to limit the left, right and downward directions of the central positioning column. The ultra-thin balance key according to claim 2, wherein each of the pivoting arms has a limiting protrusion on the outside near the end; the bracket member is opposite to the limiting protrusion on each of the pivoting arms. The structure is provided with a limit hole, and the upward direction of the limit protrusion is limited. The ultra-thin balance button according to claim 3, wherein the maximum diameter of the limiting post is smaller than the left and right width of the limiting hole, and the bottom of the limiting post towards the side of the bottom plate is configured as a ramp structure. The ultra-thin balance button as described in claim 3, wherein the bottom plate corresponding to the central positioning groove is provided with a space-avoiding groove that allows the end of the pivoting arm to go down, and the two sides of the center positioning groove are located in the space-saving groove An arc-shaped support frame capable of restricting the downward movement of the central positioning column is constructed at the position. The ultra-thin balance button as described in claim 1, wherein a hook is provided on the arms at both ends of the return extension spring, and a connection hole for connecting the hook is provided on the linkage wing and the trigger wing, and the return extension spring The two ends of the moment arms are respectively fixed on the connecting holes by the hooks. The ultra-thin balanced button as described in claim 3, wherein the electronic component is a patch electrically connected to a light-to-tube assembly composed of a light-emitting component and a photosensitive component on the PCB, and the trigger structure is configured on the A grating plate between two sides of the trigger wing and the pivot arm, when the keycap is pressed, the grating plate of the trigger wing moves downward to change the light path between the light emitting element and the photosensitive element. The ultra-thin balanced key according to claim 7, wherein the grating plate is a light-shielding plate, and the light-emitting element and the photosensitive element are located on both sides of the light-shielding plate. The ultra-thin balanced key according to claim 7, wherein the grating plate is a reflective plate, and the light-emitting element and the photosensitive element are located on the same side of the reflective plate. The ultra-thin balanced button according to claim 7, wherein a space-avoiding post is provided at the bottom of the grating plate, and a space-avoiding hole corresponding to the space-avoiding post is opened on the bottom plate. The ultra-thin balanced button as described in claim 3, wherein the electronic component is a patch electrically connected to a Hall sensor arranged on the PCB, and the trigger structure is constructed between the pivot arms on both sides of the trigger wing When the keycap is pressed, the magnetic part of the trigger wing moves downward to change a magnetic flux received by the Hall sensor. The ultra-thin balance key according to claim 3, wherein the keycap is provided with a pivot cavity for pivotally connecting the trigger wing and the top end of the linkage wing, and the two ends of the trigger wing and the linkage wing protrude correspondingly A pivotal connection post of the pivotal connection cavity, the top ends of the trigger wing and the linkage wing are limited to the pivotal connection cavity on the keycap by the pivotal connection post. The ultra-thin balanced key according to any one of claims 1 to 12, wherein the ultra-thin balanced key further includes a sound-generating mechanism for producing a knocking sound when the ultra-thin balanced key is pressed. The ultra-thin balanced key according to claim 13, wherein the sounding mechanism includes a sounding torsion spring mounted on the pivot arm of the linkage wing, the sounding torsion spring has a fixed arm and a sounding arm; the linkage wing Corresponding to the sounding arm structure is provided with a sounding force storage part, the bottom of the keycap is provided with a sounding pressure block corresponding to the sounding arm structure, the sounding force storage part has a slanted block part and an impacted part located on the slanted block part, The sounding arm abuts against the slanting block; when the keycap is pressed, the sounding pressure block exerts pressure on the sounding arm to store force downward, and when the keycap is pressed to a certain stroke, the sounding arm The action of the inclined block slides away from the sounding pressure block and resets upwards to hit the struck part to make a knocking sound. When the keycap is released and the sounding pressure block moves up to leave the sounding arm, the sounding arm resets. The ultra-thin balance key according to claim 14, wherein the pivot arm on which the sounding torsion spring is installed has a torsion spring fixing post and a fixed arm limit block, and the sounding torsion spring is sleeved on the torsion spring fixing post , the fixed arm of the sounding torsion spring abuts against the fixed arm limit block.