Push switch

Abstract

The utility model discloses a push switch, which comprises a key cap, a conductive pressing block, a guide frame, a shell and a rubber column, and is characterized in that one end of the guide frame is connected with the key cap, and the other end of the guide frame is arranged corresponding to the conductive pressing block; the shell is arranged on the outer side of the guide frame in a sleeving mode, and the guide frame is axially connected into the shell in a sliding mode. The rubber column is positioned in the guide frame and is arranged between the guide frame and the shell; a blocking arm is arranged at the position, corresponding to the rubber column, of the shell, the blocking arm is arranged at the top end of the rubber column in a suspended mode, and when the pressing switch is reset, the top end of the rubber column makes contact with the blocking arm. The push switch provided by the utility model eliminates collision noise when the switch is reset, and has a better mute effect.

Description

Technical Field

[0001] The utility model relates to the technical field of switches, in particular to a push switch. Background Art

[0002] With the increasing demand of vehicle manufacturers for the operating quality of switches, the demand for silent vehicle switches is also becoming more and more extensive.

[0003] For common current vehicle switches, the pressing feel is realized by a rubber pad between the switch and the printed circuit board. However, during the switch rebound process, the contact between the guiding part and the housing lacks buffering, resulting in plastic collision noises during the switch pressing operation, which is difficult to meet the silent demand of vehicle manufacturers for improving the operating quality of switches. Summary of the Utility Model

[0004] In view of this, the utility model provides a push switch, which eliminates the collision noise during switch reset and has a better silent effect.

[0005] To achieve the above object, the utility model provides the following technical solutions:

[0006] A push switch, comprising:

[0007] A key cap;

[0008] A voltage-conducting block;

[0009] A guiding frame, one end of the guiding frame is connected to the key cap, and the other end is correspondingly arranged with the voltage-conducting block;

[0010] A housing, sleeved outside the guiding frame, and the guiding frame is axially slidably connected in the housing;

[0011] A rubber column, located inside the guiding frame and arranged between the guiding frame and the housing; a blocking arm is arranged at a position of the housing corresponding to the rubber column, the blocking arm is suspended at the top end of the rubber column, and when the push switch resets, the top end of the rubber column contacts the blocking arm.

[0012] Optionally, an installation groove with an open top end is arranged on the guiding frame, the rubber column is connected in the installation groove, and the height of the rubber column is greater than the groove depth of the installation groove.

[0013] Optionally, a limiting convex rib is arranged on the side surface of the guiding frame, the limiting convex rib is slidably connected to a limiting groove on the inner side surface of the housing, and the limiting groove extends along the height direction of the housing.

[0014] Optionally, it further includes a base, the shell is connected to the base, the conductive voltage block is located in the base, and a driving structure for pressing the conductive voltage block is provided on the outer side of the guide frame near the base;

[0015] The driving structure includes a connecting arm and a driving pressure plate connected together, one end of the connecting arm is fixedly arranged on the side of the guide frame, and the other end is fixedly connected to the driving pressure plate, and the driving pressure plate is arranged corresponding to the conductive voltage block.

[0016] Optionally, a clearance opening groove is provided on the shell, the opening of the clearance opening groove is provided at the bottom end of the shell, and the clearance opening groove is slidably mounted on the connecting arm.

[0017] Optionally, the guide frame is provided with a first cavity with openings at both ends, and the base is provided with a second cavity with openings at both ends, the size of the second cavity is larger than the size of the guide frame, and when the push switch is pressed, the guide frame slides in the second cavity;

[0018] A first connecting block is disposed on the side wall of the first cavity, and the first connecting block is connected to a first connecting plate on the button cap.

[0019] Optionally, a second connection block is disposed on the outer surface of the shell, a second connection plate is disposed on the base at a position corresponding to the second connection block, and the second connection block is clamped with the second connection plate.

[0020] Optionally, a limiting column is provided on the outer surface of the shell, a limiting hole is provided on the base at a position corresponding to the limiting column, and the limiting column is inserted into the limiting hole;

[0021] There are two limit columns, which are arranged at both ends of the shell. The limit hole includes a limit circular hole and a limit elliptical hole. One limit column is arranged corresponding to the limit circular hole, and the other limit column is arranged corresponding to the limit elliptical hole. The long axis of the limit elliptical hole is arranged along the line connecting the hole centers of the limit circular hole and the limit elliptical hole.

[0022] Optionally, the conductive voltage block includes a rubber pad and conductive particles, the conductive particles are arranged on the bottom surface of the rubber pad, and one end of the rubber pad provided with the conductive particles is inserted into a connecting through hole on the base;

[0023] A limiting skirt is arranged on the rubber pad, the diameter of the limiting skirt is larger than the diameter of the connecting through hole, and the rubber pad is mounted on the connecting through hole through the limiting skirt.

[0024] Optionally, a limiting block is provided on the outer surface of the guiding frame, and a supporting platform is provided at a position corresponding to the limiting block on the inner side surface of the housing. The bottom surface of the limiting block is correspondingly arranged with the upper surface of the supporting platform. When the pressing switch is at the lower stop position, the bottom surface of the limiting block is in contact with the upper surface of the supporting platform.

[0025] As can be seen from the above technical solution, for the pressing switch provided by the present utility model, by providing a rubber column at one end of the guiding frame close to the key cap and providing a blocking arm on the housing, when the guiding frame returns to the upper stop position during the reset of the pressing switch, the top end of the rubber column is in contact with the blocking arm, so as to realize the limiting of the guiding frame. The flexible limiting during the return of the guiding frame is realized by the contact between the rubber column and the housing. Compared with the hard guiding frame in the prior art directly colliding with the hard housing for limiting, the contact between the rubber column and the housing in the present utility model is the contact between a flexible structure and a hard structure, realizing flexible contact limiting, thereby eliminating noise. The flexible structure rubber column can buffer the collision between the guiding frame and the housing during the rebound, meeting the silent requirement. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is an exploded structural schematic diagram of the pressing switch provided by the embodiment of the present utility model;

[0028] Figure 2 It is an assembled structural schematic diagram of the pressing switch provided by the embodiment of the present utility model;

[0029] Figure 3 It is a sectional structural schematic diagram of the pressing switch after being pressed provided by the embodiment of the present utility model;

[0030] Figure 4 It is a sectional structural schematic diagram of the pressing switch after being reset provided by the embodiment of the present utility model;

[0031] Figure 5 It is a structural schematic diagram of the guiding frame provided by the embodiment of the present utility model from one angle;

[0032] Figure 6 It is a structural schematic diagram of the guiding frame provided by the embodiment of the present utility model from another angle;

[0033] Figure 7 It is a structural schematic diagram of the guiding frame provided by the embodiment of the present utility model from yet another angle;

[0034] Figure 8 A schematic diagram of the structure of a housing provided in an embodiment of the utility model;

[0035] Figure 9 A schematic diagram of the assembly structure of the guide frame and the rubber column provided in an embodiment of the utility model;

[0036] Figure 10 for Figure 9 A schematic diagram of the assembly structure in and the assembly structure of the shell;

[0037] Figure 11 A schematic diagram of the structure of a base provided in an embodiment of the utility model;

[0038] Figure 12 A schematic diagram of the assembly structure of the base and the conductive voltage block provided in an embodiment of the utility model;

[0039] Figure 13 for Figure 9 A schematic diagram showing the positions of the two after the assembly structure in the figure is assembled on the base;

[0040] Figure 14 A schematic diagram of the assembly structure of the base and the shell provided in an embodiment of the utility model;

[0041] Figure 15 A schematic diagram of the assembly structure of the base, the housing, the guide frame and the rubber column provided in an embodiment of the utility model;

[0042] Figure 16 A schematic diagram of the structure of a button cap provided in an embodiment of the utility model.

[0043] in:

[0044] 1. Button caps,

[0045] 101. a first connecting plate, 102. a first connecting hole,

[0046] 2. Shell,

[0047] 201, third cavity, 202, blocking arm, 203, second connecting block, 204, opening slot for making way, 205, limiting column, 206, convex rib plate, 207, limiting slot, 208, supporting platform,

[0048] 3. Rubber column,

[0049] 4. Guide frame,

[0050] 401, mounting groove, 402, limiting ridge, 403, first connecting block, 404, supporting plate, 405, connecting arm, 406, driving plate, 407, limiting block, 408, first cavity,

[0051] 5. Conductive voltage block

[0052] 501. Limit skirt

[0053] 6. Base

[0054] 601. Seat body, 602. Connecting through hole, 603. Second connecting plate, 604. Second cavity, 605. Limit elliptical hole, 606. Limit round hole, 607. Second connecting card hole Detailed implementation manners

[0055] The utility model discloses a push switch, which eliminates the collision noise during switch reset and has better mute effect

[0056] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments in the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model

[0057] Referring to Figures 1 to 16 , the push switch of the present utility model includes a guide frame 4 and a housing 2 that are slidably connected. One end of the guide frame 4 is connected to the key cap 1, and the other end is correspondingly arranged with the conductive voltage block 5. The housing 2 is sleeved outside the guide frame 4, and the guide frame 4 is axially slidably connected inside the housing 2. A rubber column 3 is arranged at one end of the guide frame 4 close to the key cap 1. The rubber column 3 is located inside the guide frame 4 and is arranged between the guide frame 4 and the housing 2. A blocking arm 202 is arranged at a position of the housing 2 corresponding to the rubber column 3. The blocking arm 202 is suspended at the top of the rubber column 3. When the push switch is reset, the top of the rubber column 3 contacts the blocking arm 202

[0058] Among them, the housing 2 is fixedly connected to the base 6. The guide frame 4 slides axially under the drive of the key cap 1 to realize the opening and closing of the switch. When the guide frame 4 is pressed, the conductive voltage block 5 is pressed down to make the electrical conduction. The blocking arm 202 provides the upper stop position of the switch

[0059] The push switch of the present utility model is provided with a rubber column 3 at one end of the guide frame 4 close to the key cap 1, and a blocking arm 202 is provided on the housing 2. When the guide frame 4 of the push switch returns to the upper limit position during reset, the top of the rubber column 3 contacts the blocking arm 202 to realize the limit of the guide frame 4. When the guide frame 4 returns to its position, the flexible limit is realized through the contact between the rubber column 3 and the housing 2. Compared with the hard guide frame 4 in the prior art directly colliding with the housing 2 for limiting, the contact between the rubber column 3 and the housing 2 in the present utility model is the contact between a flexible structure and a hard structure, realizing flexible contact limiting, thereby eliminating noise. The flexible structure rubber column 3 can buffer the collision between the guide frame 4 and the housing 2 during rebound, meeting the silent requirement.

[0060] To facilitate the installation of the rubber column 3, an installation groove 401 with an open top is provided on the guide frame 4, and the rubber column 3 is connected in the installation groove 401. Preferably, the rubber column 3 is directly inserted into the installation groove 401, as Figure 9 shown. It can be understood that the height of the rubber column 3 is greater than the groove depth of the installation groove 401, so that the top of the rubber column 3 extends out of the installation groove 401, enabling the top of the rubber column 3 to contact the blocking arm 202 of the housing 2. The cross-section of the rubber column 3 is circular, square or rectangular. A support plate 404 is provided on the housing 2, and the support plate 404 is arranged on both sides of the installation groove 401. The height of the support plate 404 is greater than the height of the rubber column 3 after installation, and the top of the support plate 404 contacts the bottom surface of the key cap 1, facilitating the direct transfer of force to the guide frame 4 when the key cap 1 is pressed.

[0061] To ensure the stability of the guide frame 4 during the pressing process, a limiting rib 402 is provided on the side surface of the guide frame 4, and the limiting rib 402 is slidably connected to the limiting groove 207 on the inner side surface of the housing 2. To avoid interfering with the sliding of the guide frame 4, the limiting groove 207 extends along the height direction of the housing 2 and extends to the bottom of the housing 2. To ensure the structural strength of the limiting groove 207 and at the same time reduce the wall thickness of the housing 2, a ribbed plate 206 is provided at the position of the housing 2 for setting the limiting groove 207. The ribbed plate 206 is arranged on the outer surface of the housing 2, and its setting position corresponds to the limiting groove 207, and the width is greater than the groove width of the limiting groove 207, thereby providing the structural requirements for the setting of the limiting groove 207.

[0062] Specifically, the conductive voltage block 5 is connected to the base 6, and a driving structure for pressing the conductive voltage block 5 is provided on the outer side of the guide frame 4 near the base 6. The driving structure includes a connecting arm 405 and a driving pressure plate 406 connected together, one end of the connecting arm 405 is fixedly provided on the side of the guide frame 4, and the other end is fixedly connected to the driving pressure plate 406, and the driving pressure plate 406 is provided corresponding to the conductive voltage block 5. When the guide frame 4 slides downward, the driving pressure plate 406 presses the conductive voltage block 5. In order to improve the structural stability, two connecting arms 405 are provided corresponding to each driving pressure plate 406, and the two connecting arms 405 are symmetrically provided on both sides of the driving pressure plate 406. Among them, two of the driving structures are provided on the guide frame 4, and the two driving structures are provided on two opposite sides of the guide frame 4.

[0063] In order to facilitate the casing 2 to be mounted on the guide frame 4, the casing 2 is provided with a clearance opening slot 204 for the connecting arm 405 to pass through. Figure 8 As shown, the opening of the clearance opening slot 204 is set at the bottom end of the housing 2, so that the housing 2 is mounted on the guide frame 4 from the top of the guide frame 4 downward, and the clearance opening slot 204 is slidably mounted on the connecting arm 405. In one embodiment, two driving pressure plates 406 are provided, and four connecting arms 405 are provided. Figures 5 to 7 Correspondingly, four opening slots 204 are provided, such as Figure 8 The structure after the guide frame 4 and the housing 2 are sleeved is shown in FIG. Figure 10 .

[0064] Since the switch backlight needs to be provided by the light source element on the printed circuit board in the upper assembly, the guide frame 4 is configured as a hollow structure to ensure that the backlight is transmitted to the key cap 1. Specifically, a first cavity 408 with openings at both ends is provided on the guide frame 4, and a second cavity 604 with openings at both ends is provided on the base 6, so that the backlight is easily transmitted to the key cap 1 through the base 6 and the guide frame 4. In order to prevent the base 6 from affecting the sliding of the guide frame 4, the size of the second cavity 604 is larger than the outer size of the guide frame 4. When the push switch is pressed, the guide frame 4 slides in the second cavity 604. It can be understood that a third cavity 201 with openings at both ends is provided on the shell 2, so that the guide frame 4 can be sleeved in the shell 2. In order to facilitate the connection between the key cap 1 and the guide frame 4, the side wall of the first cavity 408 of the guide frame 4 is provided with a first connecting block 403, such as Figure 5 and Figure 6 As shown, two first connection blocks 403 are provided, and the two first connection blocks 403 are symmetrically arranged on two opposite side walls of the first cavity 408. Correspondingly, a first connection plate 101 is arranged on the surface of the key cap 1 close to the guide frame 4, as shown in FIG. Figure 16 As shown, the first connecting plate 101 is provided with a first connecting hole 102 , and the first connecting block 403 is correspondingly engaged with the first connecting hole 102 .

[0065] To facilitate the connection between the housing 2 and the base 6, a second connection block 203 is provided on the outer surface of the housing 2. At a position corresponding to the second connection block 203 on the base 6, a second connection plate 603 is provided. A second connection hole 607 is provided on the second connection plate 603, and the second connection block 203 is snapped into the second connection hole 607. In one embodiment, four second connection blocks 203 are provided. Correspondingly, four second connection holes 607 are provided, as Figure 8 shown.

[0066] To facilitate installation and positioning, a limit post 205 is provided on the outer surface of the housing 2. At a position corresponding to the limit post 205 on the seat body 601 of the base 6, a limit hole is provided, and the limit post 205 is inserted into the limit hole. Among them, two limit posts 205 are provided, and the two limit posts 205 are respectively arranged at both ends of the housing 2. As Figure 8 shown, the limit post 205 is connected to the outside of the convex rib plate 206. To adapt to the dimensional error of the structure, the limit hole includes a limit round hole 606 and a limit oval hole 605. One limit post 205 is correspondingly arranged with the limit round hole 606, and the other limit post 205 is correspondingly arranged with the limit oval hole 605. The long axis of the limit oval hole 605 is arranged along the connection line of the centers of the limit round hole 606 and the limit oval hole 605.

[0067] Specifically, the voltage-conducting block 5 includes a rubber pad and conductive particles. The rubber pad is the main structure of the voltage-conducting block 5, so as to provide a feel for the switch and be electrically connected to the printed circuit board. The conductive particles are arranged on the bottom surface of the rubber pad, and one end of the rubber pad provided with the conductive particles passes through the connection through hole 602 on the base 6 and contacts the PCB. To facilitate the support and limitation of the voltage-conducting block 5, a limit skirt 501 is provided on the rubber pad. The diameter of the limit skirt 501 is larger than the diameter of the connection through hole 602, and the rubber pad is erected on the connection through hole 602 through the limit skirt 501. The limit skirt 501 is also made of rubber material to provide elastic support.

[0068] To limit the sliding down position of the push switch, a limit block 407 is provided on the outer surface of the guide frame 4, as Figure 5 shown. At a position corresponding to the limit block 407 on the inner side surface of the housing 2, a support platform 208 is provided, as Figure 14 shown, that is, a support platform 208 is provided on the side wall of the third cavity 201. The bottom surface of the limit block 407 is correspondingly arranged with the upper surface of the support platform 208. When the push switch is in the lower limit position, the bottom surface of the limit block 407 contacts the upper surface of the support platform 208 to limit the downward position of the guide frame 4.

[0069] When the push switch of the present utility model is installed, first, the rubber column 3 is inserted into the installation groove 401 of the guide frame 4, seeFigure 9 as shown. Then, the housing 2 and the guide frame 4 are pre-assembled, referring to Figure 10 as shown. Next, the voltage-conducting block 5 is installed at the connection through-hole 602 of the base 6, referring to Figure 12 as shown. Then, the pre-assembled housing assembly is placed into the base 6. The housing 2 and the base 6 are snap-fitted and fixed through the second connection block 203 and the second connection hole 607. At this time, the voltage-conducting block 5 and the guide frame 4 form a limit in the switch pressing direction, as Figure 15 as shown. Finally, the button cap 1 is installed. The button cap 1 is snap-fitted onto the first connection block of the guide frame 4 through the first connection hole 102. When the switch is pressed, the guide frame 4 presses the voltage-conducting block 5, and the conductive particles contact the PCB to complete electrical conduction. When the switch is released, the guide frame 4 rebounds, and the rubber column 3 on the guide frame 4 contacts the housing 2, serving as the upper stop position of the switch. When rebounding after release, since the contact between the rubber column 3 and the housing 2 is a soft contact, noise can be eliminated to achieve silence.

[0070] In the description of this solution, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "vertical", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to this solution.

[0071] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this solution, the meaning of "a plurality" is two or more, unless otherwise specifically defined.

[0072] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts among the various embodiments can be referred to each other.

[0073] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A push switch, characterized in that: include: Button cap (1); Conductive voltage block (5); A guide frame (4), one end of the guide frame (4) is connected to the button cap (1), and the other end is arranged corresponding to the conductive voltage block (5); A shell (2) is sleeved on the outer side of the guide frame (4), and the guide frame (4) is axially slidably connected in the shell (2); The rubber column (3) is located in the guide frame (4) and is arranged between the guide frame (4) and the shell (2); a blocking arm (202) is arranged at a position of the shell (2) corresponding to the rubber column (3); the blocking arm (202) is suspended at the top end of the rubber column (3); when the switch is pressed to reset, the top end of the rubber column (3) contacts the blocking arm (202).

2. The push switch according to claim 1, characterized in that: The guide frame (4) is provided with a mounting groove (401) with an open top, the rubber column (3) is connected in the mounting groove (401), and the height of the rubber column (3) is greater than the groove depth of the mounting groove (401).

3. The push switch according to claim 1, characterized in that: A limiting ridge (402) is provided on the side of the guide frame (4), and the limiting ridge (402) is slidably connected to a limiting groove (207) on the inner side of the shell (2), and the limiting groove (207) is extended along the height direction of the shell (2).

4. The push switch according to any one of claims 1 to 3, characterized in that: It also comprises a base (6), the shell (2) is connected to the base (6), the conductive voltage block (5) is located inside the base (6), and a driving structure for pressing the conductive voltage block (5) is provided at a position outside the guide frame (4) close to the base (6); The driving structure comprises a connecting arm (405) and a driving pressure plate (406) connected together, one end of the connecting arm (405) is fixedly arranged on the side of the guide frame (4), and the other end is fixedly connected to the driving pressure plate (406), and the driving pressure plate (406) is arranged corresponding to the conductive voltage block (5).

5. The push switch according to claim 4, characterized in that: The shell (2) is provided with a clearance opening slot (204), the opening of the clearance opening slot (204) is provided at the bottom end of the shell (2), and the clearance opening slot (204) is slidably mounted on the connecting arm (405).

6. The push switch according to claim 4, characterized in that: The guide frame (4) is provided with a first cavity (408) with openings at both ends, and the base (6) is provided with a second cavity (604) with openings at both ends, the size of the second cavity (604) is larger than the size of the guide frame (4), and when the push switch is pressed, the guide frame (4) slides in the second cavity (604); A first connecting block (403) is provided on the side wall of the first cavity (408), and the first connecting block (403) is connected to the first connecting plate (101) on the button cap (1).

7. The push switch according to claim 4, characterized in that: A second connection block (203) is provided on the outer surface of the shell (2), a second connection plate (603) is provided on the base (6) at a position corresponding to the second connection block (203), and the second connection block (203) is snap-connected with the second connection plate (603).

8. The push switch according to claim 4, characterized in that: A limiting column (205) is provided on the outer surface of the housing (2), a limiting hole is provided on the base (6) at a position corresponding to the limiting column (205), and the limiting column (205) is inserted into the limiting hole; Two limiting posts (205) are provided, and the two limiting posts (205) are respectively provided at the two ends of the shell (2); the limiting hole comprises a limiting circular hole (606) and a limiting elliptical hole (605); one limiting post (205) is provided corresponding to the limiting circular hole (606), and the other limiting post (205) is provided corresponding to the limiting elliptical hole (605); the major axis of the limiting elliptical hole (605) is provided along a line connecting the hole centers of the limiting circular hole (606) and the limiting elliptical hole (605).

9. The push switch according to claim 4, characterized in that: The conductive voltage block (5) comprises a rubber pad and conductive particles, wherein the conductive particles are arranged on the bottom surface of the rubber pad, and one end of the rubber pad provided with the conductive particles is inserted into a connecting through hole (602) on the base (6); A limiting skirt (501) is provided on the rubber pad, the diameter of the limiting skirt (501) is greater than the diameter of the connecting through hole (602), and the rubber pad is mounted on the connecting through hole (602) via the limiting skirt (501).

10. The push switch according to claim 1, characterized in that: A limit block (407) is arranged on the outer surface of the guide frame (4), a support platform (208) is arranged on the inner side surface of the shell (2) at a position corresponding to the limit block (407), the bottom surface of the limit block (407) is arranged corresponding to the upper surface of the support platform (208), and when the push switch is located at the lower stop position, the bottom surface of the limit block (407) contacts the upper surface of the support platform (208).

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