Hot galvanizing pickling sealing device
Through the design of the closed pickling device and shaking mechanism, the problems of acidic substance volatility and incomplete pickling caused by incomplete sealing of the pickling container are solved, and the effect of stable concentration of the pickling liquid and sufficient pickling on the surface of the metal parts is achieved.
Patent Information
- Application Number
- CN202422596686.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-28
- Publication Date
- 2025-08-22
- Estimated Expiration
- 2034-10-28
AI Technical Summary
The existing pickling containers are usually not completely closed, resulting in the volatilization of acidic substances in the pickling liquid and the concentration decreases. The metal parts are not completely pickling when they are stationary in the acid liquid, and the effect is not good.
The closed pickling device is adopted, and the metal parts are placed in the pickling tank through the lifting mechanism, and the metal parts are repeatedly shaken in the acid liquid by using the shaking mechanism. Combined with the sealing design, the acidic substances are prevented from evaporating, and the concentration of the pickling liquid is stable.
The enclosure of the pickling process is achieved, the acidic substances are prevented from evaporating, the concentration of the pickling liquid remains unchanged, and the pickling effect on the surface of the metal parts is improved through the shaking mechanism to ensure complete pickling.
Smart Images

Figure CN223255441U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of hot-dip galvanizing and pickling, in particular to a hot-dip galvanizing and pickling sealing device. Background Art
[0002] Hot-dip galvanizing involves reacting molten metal with an iron substrate to create an alloy layer, thereby bonding the substrate and the coating. Hot-dip galvanizing involves first pickling the steel parts to remove iron oxide from the surface. After pickling, the parts are then cleaned in an aqueous solution of ammonium chloride or zinc chloride, or a mixed aqueous solution of ammonium chloride and zinc chloride, before being placed in a hot-dip coating tank. Hot-dip galvanizing offers advantages such as uniform coating, strong adhesion, and a long service life. However, existing technologies present the following problems:
[0003] The existing containers used for pickling are mainly pickling tanks. During the pickling and use process, since the pickling tanks are usually not fully enclosed, some acidic substances in the pickling liquid are prone to volatilization, resulting in a decrease in the pickling concentration. Secondly, since the metal parts are in a static state in the acid solution, the pickling device does not completely pickle the surface of the metal parts, resulting in poor pickling effect of the device. Utility Model Content
[0004] The utility model provides a metal part pickling sealing device to solve the problems existing in the above background technology.
[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:
[0006] A metal pickling and closing device includes a cleaning table, wherein the top of the cleaning table is fixedly connected to columns near the four corners, the tops of the four columns are fixedly connected to a top plate, the top of the top plate is provided with a lifting mechanism, the top of the cleaning table is fixedly connected to a pickling tank, the bottom of the outer wall of the lifting mechanism passes through the interior of the pickling tank, and the bottom of the cleaning table is provided with a shaking mechanism.
[0007] The further improvement of the technical solution of the present utility model is that: the lifting mechanism includes a hydraulic telescopic cylinder, a mounting plate, a pickling assembly, two fixed cylinders, two support rods, two positioning plates, two bolts and two nuts, the bottom of the hydraulic telescopic cylinder is fixedly connected to the middle side of the top of the top plate, the output end of the hydraulic telescopic cylinder passes through the bottom of the top plate and is fixedly connected to the middle side of the top of the mounting plate. The outer diameter of the mounting plate is equal to the inner diameter of the pickling tank, the bottom of the outer wall of the two fixed cylinders passes through the left and right sides of the bottom of the top plate and are fixedly connected thereto, the outer walls of the two support rods are respectively slidably connected to the inside of the two fixed cylinders, the bottoms of the two support rods are respectively fixedly connected to the left and right sides of the top of the mounting plate, the tops of the two positioning plates are respectively fixedly connected to the front and rear sides of the bottom of the mounting plate, the opposite surfaces of the two positioning plates are provided with slide grooves, and the left and right sides of the top of the mounting plate are respectively provided with connecting holes that pass through up and down.
[0008] A further improvement of the technical solution of the present utility model is that: the pickling assembly includes a pickling basket, two plug-in plates, and two connecting plates, one end of the two plug-in plates are respectively fixedly connected to the tops of the front and rear ends of the pickling basket, one end of the two connecting plates are respectively fixedly connected to the tops of the left and right ends of the pickling basket, and the middle part of the two connecting plates is provided with a vertically penetrating socket, and the two plug-in plates and the two connecting plates are arranged on the same horizontal plane.
[0009] A further improvement of the technical solution of the present invention is that the outer walls of the two plug plates are respectively plugged into the inner parts of the two slide grooves, the top of the outer wall of the bolt passes through the insertion hole and the connecting hole to the top of the top plate, and the inside of the nut is threadedly connected to the upper side of the outer wall of the bolt.
[0010] A further improvement of the technical solution of the present utility model is that: a positioning frame is fixedly connected to the upper side of the inner wall of the pickling tank, a sealing strip is fixedly connected to the upper surface of the positioning frame, a liquid inlet pipe is fixedly connected to the left end of the sealing strip near the lower side of the sealing strip, a flange is fixedly connected to the outer wall of the liquid inlet pipe, a drain pipe is fixedly connected to the bottom of the left end of the pickling tank, and a drain valve is provided on the outside of the drain pipe.
[0011] A further improvement of the technical solution of the present utility model is that the top of the positioning frame is overlapped with the lower surface of the mounting plate through a sealing strip, and the interior of the pickling tank is sleeved with the exterior of the pickling assembly.
[0012] The further improvement of the technical solution of the present utility model is that the shaking mechanism includes a base, two vertical plates, a driving motor, a disc, two sliding rods, two moving blocks, four return springs and a push plate, the bottoms of the two vertical plates are respectively fixedly connected to the front and rear sides of the top of the base, the bottom of the driving motor is fixedly connected to the top middle side of the base near the front vertical plate, the output end of the driving motor is connected to the bottom side of the disc, the front and rear ends of the two sliding rods are respectively fixedly connected to the left and right sides of the opposite surfaces of the two vertical plates, the outer walls of the two sliding rods respectively pass through the front and rear ends of the middle of the two moving blocks and are slidably connected therebetween, the inner parts of the two return springs are respectively sleeved on the outer walls of the front and rear sides of the slide rod close to the moving block, the rear end of the push plate is fixedly connected to the front middle side of the washing table, and the front surface of the push plate overlaps the outer wall of the disc.
[0013] A further improvement of the technical solution of the present utility model is that the tops of the two moving blocks are respectively fixedly connected to the left and right sides of the bottom of the washing table, the ends of the two front and rear return springs that are away from each other are overlapped with the opposite surfaces of the two vertical plates, and the adjacent ends of the two front and rear return springs are respectively overlapped with the front and rear ends of the moving block.
[0014] Due to the adoption of the above technical solution, the present invention has achieved the following technical advancements compared to the prior art:
[0015] 1. The utility model provides a metal pickling sealing device, which adopts the cooperation between a cleaning table, a column, a top plate, a lifting mechanism and a pickling tank. The metal part to be pickled is placed in the pickling assembly in the lifting mechanism, and then the pickling assembly is fixed to the bottom of the mounting plate by sliding magnetic attraction. Then, the pickling assembly is placed into the pickling tank through the mounting plate by operating the hydraulic telescopic cylinder. At the same time, the mounting plate and the pickling tank are sealed to prevent some acidic substances in the pickling solution from volatilizing. This solves the problem that the existing container for pickling is mainly the pickling tank. During the pickling and use process, since the pickling tank is usually not fully closed, some acidic substances in the pickling solution are prone to volatilization, resulting in a decrease in the pickling concentration. The utility model achieves the beneficial effect of pickling the metal parts in a closed manner, avoiding the volatilization of some acidic substances in the pickling solution, and ensuring that the pickling concentration remains unchanged.
[0016] 2. The utility model provides a metal pickling closing device, which adopts the cooperation between the cleaning table and the shaking mechanism. During the pickling process, by operating the shaking mechanism, the pickling device is driven by the cleaning table to move back and forth repeatedly and continuously, so that the pickling liquid in the pickling tank drives the metal parts to shake, and the surface of the metal parts is fully pickled. This solves the problem that the pickling device does not fully pickle the surface of the metal parts due to the metal parts being in a static state in the acid solution, resulting in poor pickling effect of the device. It achieves the beneficial effect of fully pickling the surface of the metal parts and improving the pickling effect of the device. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 This is a schematic diagram of the three-dimensional structure of the hot-dip galvanizing and pickling sealing device of the utility model;
[0018] Figure 2 This is a schematic diagram of the three-dimensional structure of the lifting mechanism of the utility model;
[0019] Figure 3 This is a schematic diagram of the three-dimensional structure of the pickling component of the present utility model;
[0020] Figure 4 This is a schematic diagram of the three-dimensional structure of the pickling tank of the utility model;
[0021] Figure 5 It is a schematic diagram of the three-dimensional structure of the shaking mechanism of the present utility model.
[0022] In the figure: 1. Cleaning table; 2. Column; 3. Top plate; 4. Lifting mechanism; 41. Hydraulic telescopic cylinder; 42. Mounting plate; 420. Connecting hole; 43. Pickling assembly; 431. Pickling basket; 432. Insert plate; 433. Connecting plate; 434. Insert hole; 44. Fixing cylinder; 45. Support rod; 46. Positioning plate; 460. Slide groove; 47. Bolt; 48. Nut; 5. Pickling tank; 51. Positioning frame; 52. Sealing strip; 53. Liquid inlet pipe; 54. Flange; 55. Drain pipe; 56. Drain valve; 6. Rocking mechanism; 61. Base; 62. Vertical plate; 63. Drive motor; 64. Disc; 65. Slide rod; 66. Moving block; 67. Return spring; 68. Push plate. DETAILED DESCRIPTION
[0023] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods:
[0024] like Figure 1As shown, the utility model provides a hot-dip galvanizing pickling enclosed device, comprising a cleaning table 1, wherein columns 2 are fixedly connected to the top of the cleaning table 1 near the four corners, a top plate 3 is fixedly connected to the top of the four columns 2, a lifting mechanism 4 is provided on the top of the top plate 3, a pickling tank 5 is fixedly connected to the top of the cleaning table 1, the bottom of the outer wall of the lifting mechanism 4 passes through the interior of the pickling tank 5, and a shaking mechanism 6 is provided on the bottom of the cleaning table 1;
[0025] A cleaning table 1, a column 2, a top plate 3, a lifting mechanism 4, a pickling tank 5 and a shaking mechanism 6 are provided. By operating the lifting mechanism 4, the metal parts are lifted and inserted into the pickling tank 5 for closed pickling. During the pickling process, the pickling device is repeatedly and continuously displaced back and forth by operating the shaking mechanism 6 to improve the pickling effect of the device.
[0026] like Figure 2 As shown, the utility model provides a technical solution for a hot-dip galvanizing pickling closing device: the lifting mechanism 4 includes a hydraulic telescopic cylinder 41, a mounting plate 42, a pickling assembly 43, two fixed cylinders 44, two support rods 45, two positioning plates 46, two bolts 47 and two nuts 48. The bottom of the hydraulic telescopic cylinder 41 is fixedly connected to the middle side of the top of the top plate 3, the output end of the hydraulic telescopic cylinder 41 passes through the bottom of the top plate 3 and is fixedly connected to the middle side of the top of the mounting plate 42. The outer diameter of the mounting plate 42 is equal to the inner diameter of the pickling tank 5. The outer wall bottoms of the two fixed cylinders 44 pass through the left and right sides of the bottom of the top plate 3 and are fixedly connected therebetween. The outer walls of the two support rods 45 are respectively connected to the inner walls of the two fixed cylinders 44. The support rod 45 is connected in a sliding manner and slides along the inside of the fixed cylinder 44, thereby improving the lifting stability when the hydraulic telescopic cylinder 41 performs the lifting operation on the pickling assembly 43. The bottoms of the two support rods 45 are fixedly connected to the left and right sides of the top of the mounting plate 42, and the tops of the two positioning plates 46 are fixedly connected to the front and back sides of the bottom of the mounting plate 42. The opposite surfaces of the two positioning plates 46 are provided with sliding grooves 460. The positioning plates 46 are connected on both sides of the bottom of the mounting plate 42. When the pickling assembly 43 is installed on the bottom of the mounting plate 42, it does not affect the connection between the mounting plate 42 and the pickling tank 5. The left and right sides of the top of the mounting plate 42 are respectively provided with connecting holes 420 that pass through from top to bottom.
[0027] like Figure 3As shown, the utility model provides a technical solution for a hot-dip galvanizing pickling closure device: the pickling assembly 43 includes a pickling basket 431, two plug-in plates 432, and two connecting plates 433. One end of the two plug-in plates 432 is fixedly connected to the top of the front and rear ends of the pickling basket 431, and one end of the two connecting plates 433 is fixedly connected to the top of the left and right ends of the pickling basket 431. The middle part of the two connecting plates 433 is provided with a vertically penetrating socket 434. The two plug-in plates 432 and the two connecting plates 433 are arranged in the same water tank. On the plane, the outer walls of the two insert plates 432 are respectively plugged into the interior of the two slide grooves 460, and the pickling basket 431 is inserted from the slide groove 460 through the insert plates 432 on both sides, so that the pickling basket 431 is installed on the lower surface of the mounting plate 42. The top of the outer wall of the bolt 47 passes through the insertion hole 434 and the connecting hole 420 to the top of the top plate 3, and the inside of the nut 48 is threadedly connected to the upper side of the outer wall of the bolt 47. By using the bolt 47 and the nut 48, the pickling basket 431 is fixed to the bottom of the mounting plate 42.
[0028] like Figure 4 As shown, the utility model provides a technical solution for a hot-dip galvanizing pickling closing device: a positioning frame 51 is fixedly connected to the upper side of the inner wall of the pickling tank 5, a sealing strip 52 is fixedly connected to the upper surface of the positioning frame 51, a liquid inlet pipe 53 is fixedly connected to the left end of the sealing strip 52 near the lower side of the sealing strip 52, a flange 54 is fixedly connected to the outer wall of the liquid inlet pipe 53, a drain pipe 55 is fixedly connected to the bottom of the left end of the pickling tank 5, a drain valve 56 is provided on the outside of the drain pipe 55, the top of the positioning frame 51 is overlapped with the lower surface of the mounting plate 42 through the sealing strip 52, and the sealing strip 52 is provided on the positioning frame 51 to increase the sealing performance of the press fit between the positioning frame 51 and the mounting plate 42, and the interior of the pickling tank 5 is socketed with the exterior of the pickling assembly 43.
[0029] like Figure 5As shown, the utility model provides a technical solution for a hot-dip galvanizing pickling closing device: the shaking mechanism 6 includes a base 61, two vertical plates 62, a driving motor 63, a disc 64, two slide bars 65, two moving blocks 66, four return springs 67 and a push plate 68. The bottoms of the two vertical plates 62 are respectively fixedly connected to the front and rear sides of the top of the base 61, the bottom of the driving motor 63 is fixedly connected to the top middle side of the base 61 near the front vertical plate 62, the output end of the driving motor 63 is connected to the bottom side of the disc 64, and the output shaft of the driving motor 63 drives the disc 64 to rotate, so that the disc 64 is pushed to the cleaning table 1 through the push plate 68. The front and rear ends of the two slide bars 65 are respectively fixedly connected to the left and right sides of the opposite surfaces of the two vertical plates 62, and the outer walls of the two slide bars 65 are respectively fixedly connected to the left and right sides of the opposite surfaces of the two vertical plates 62. The front and rear ends of the two moving blocks 66 are respectively connected to each other in a sliding manner. The interiors of the two return springs 67 are respectively sleeved on the outer walls of the front and rear sides of the slide rod 65 close to the moving block 66. When the cleaning table 1 is pushed backward, the moving block 66 drives the cleaning table 1 to slide backward along the slide rod 65. When the force disappears, the cleaning table 1 is driven to reset and move by the elasticity of the return spring 67. The rear end of the push plate 68 is fixedly connected to the middle side of the front end of the cleaning table 1, and the front surface of the push plate 68 overlaps the outer wall of the disc 64. The tops of the two moving blocks 66 are respectively fixedly connected to the left and right sides of the bottom of the cleaning table 1. The ends of the front and rear return springs 67 that are away from each other are overlapped with the opposite surfaces of the two vertical plates 62, and the adjacent ends of the front and rear return springs 67 are respectively overlapped with the front and rear ends of the moving block 66.
[0030] The following is a detailed description of the working principle of this hot-dip galvanizing pickling sealing device.
[0031] like Figure 1-5As shown, when pickling hot-dip galvanized metal parts, first, the device is connected to the power supply, and the storage barrel filled with pickling liquid is connected to the flange at one end of the liquid inlet pipe 53 on the pickling tank 5 through the flange on the water pump input end, so that the water pump injects the pickling liquid into the pickling tank 5 through the liquid inlet pipe 53. Then, the metal parts to be pickled are uniformly placed in the pickling basket 431, and then the plugs 432 on both sides of the pickling basket 431 are inserted into the slide grooves 460 in the positioning plate 46, so that the plug holes 434 are aligned with the connecting holes 420. Then, use the bolt 47 to pass through the insertion hole 434 from the inside of the communicating hole 420 from top to bottom, and then use the nut 48 to screw the outer part of the bolt 47 to fix it on the top plate 3, so that the pickling basket 431 is installed and fixed on the lower surface of the mounting plate 42. After the installation is completed, start the hydraulic telescopic cylinder 41, and the output end of the hydraulic telescopic cylinder 41 drives the mounting plate 42 to move downward, so that the support rods 45 on both sides slide downward along the fixing cylinder 44, and the outer part of the pickling basket 431 is inserted into the interior of the pickling tank 5 through the positioning frame 51, and The sealing strip 52 on the positioning frame 51 is pressed and fitted with the lower surface of the mounting plate 42 to seal the opening of the pickling tank 5, so that the pickling liquid can immerse the metal parts in the pickling basket 431, thereby preventing some acidic substances in the pickling liquid from volatilizing and ensuring that the concentration of the pickling liquid remains unchanged. During the pickling process, the drive motor 63 is started, and the output shaft of the drive motor 63 drives the disc 64 to rotate. During the rotation process, the disc 64 pushes the push plate 68, and the elasticity of the return spring 67 is utilized to drive the cleaning The moving block 66 at the bottom of the washing table 1 is repeatedly and continuously displaced back and forth along the surface of the slide rod 65, so that the pickling liquid in the pickling tank 5 drives the metal parts to shake, thereby fully pickling the surface of the metal parts and improving the pickling effect. After the pickling is completed, the pickling assembly 43 is driven upward out of the interior of the pickling tank 5 by starting the hydraulic telescopic cylinder 41, and then the nuts 48 on both sides of the top plate 3 are unscrewed from the bolts 47 respectively, the bolts 47 are removed, and then the pickling basket 431 is taken out from the lower surface of the mounting plate 42.
[0032] The specific types and structures of the hydraulic telescopic cylinder 41, drive motor 63, and drain valve 56 used are all existing products, and the specific circuit connection structure and control relationship between the hydraulic telescopic cylinder 41 and the drive motor 63 are all existing technologies, so no further details will be given here.
[0033] The above generally describes the present invention in detail. However, it is obvious to those skilled in the art that modifications or improvements may be made to the present invention. Therefore, modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.
Claims
1. A hot dip galvanizing pickling closure device, comprising a cleaning station (1), characterized in that: The top of the cleaning table (1) is fixedly connected to columns (2) near the four corners, the tops of the four columns (2) are fixedly connected to a top plate (3), the top of the top plate (3) is provided with a lifting mechanism (4), the top of the cleaning table (1) is fixedly connected to a pickling tank (5), the bottom of the outer wall of the lifting mechanism (4) passes through the interior of the pickling tank (5), and the bottom of the cleaning table (1) is provided with a shaking mechanism (6).
2. A hot dip galvanizing pickling sealing device according to claim 1, characterized in that: The lifting mechanism (4) includes a hydraulic telescopic cylinder (41), a mounting plate (42), a pickling assembly (43), two fixing cylinders (44), two support rods (45), two positioning plates (46), two bolts (47) and two nuts (48). The bottom of the hydraulic telescopic cylinder (41) is fixedly connected to the middle side of the top of the top plate (3). The output end of the hydraulic telescopic cylinder (41) passes through the bottom of the top plate (3) and is fixedly connected to the middle side of the top of the mounting plate (42). The outer diameter of the mounting plate (42) is equal to the inner diameter of the pickling tank (5). The two fixing cylinders (44) The bottom of the outer wall of the two support rods (45) passes through the left and right sides of the bottom of the top plate (3) and is fixedly connected therebetween. The outer walls of the two support rods (45) are respectively slidably connected to the inside of the two fixed cylinders (44). The bottoms of the two support rods (45) are respectively fixedly connected to the left and right sides of the top of the mounting plate (42). The tops of the two positioning plates (46) are respectively fixedly connected to the front and back sides of the bottom of the mounting plate (42). The opposite surfaces of the two positioning plates (46) are provided with sliding grooves (460). The left and right sides of the top of the mounting plate (42) are respectively provided with connecting holes (420) that pass through from top to bottom.
3. A hot dip galvanizing pickling sealing device according to claim 2, characterized in that: The pickling assembly (43) comprises a pickling basket (431), two inserting plates (432), and two connecting plates (433). One end of the two inserting plates (432) is fixedly connected to the tops of the front and rear ends of the pickling basket (431), and one end of the two connecting plates (433) is fixedly connected to the tops of the left and right ends of the pickling basket (431). The middle parts of the two connecting plates (433) are each provided with an inserting hole (434) that passes through from top to bottom. The two inserting plates (432) and the two connecting plates (433) are arranged on the same horizontal plane.
4. A hot dip galvanizing pickling sealing device according to claim 3, characterized in that: The outer walls of the two inserting plates (432) are respectively plugged into the interior of the two sliding grooves (460), the top of the outer wall of the bolt (47) passes through the insertion hole (434) and the connecting hole (420) to the top of the top plate (3), and the interior of the nut (48) is threadedly connected to the upper side of the outer wall of the bolt (47).
5. The hot-dip galvanizing and pickling sealing device according to claim 1, characterized in that: A positioning frame (51) is fixedly connected to the upper side of the inner wall of the pickling tank (5), a sealing strip (52) is fixedly connected to the upper surface of the positioning frame (51), a liquid inlet pipe (53) is fixedly connected to the left end of the sealing strip (52) near the lower side of the sealing strip (52), a flange (54) is fixedly connected to the outer wall of the liquid inlet pipe (53), a drain pipe (55) is fixedly connected to the bottom of the left end of the pickling tank (5), and a drain valve (56) is provided on the outside of the drain pipe (55).
6. A hot dip galvanizing pickling sealing device according to claim 5, characterized in that: The top of the positioning frame (51) is overlapped with the lower surface of the mounting plate (42) through a sealing strip (52), and the interior of the pickling tank (5) is sleeved with the exterior of the pickling assembly (43).
7. The hot-dip galvanizing pickling sealing device according to claim 1, characterized in that: The shaking mechanism (6) comprises a base (61), two vertical plates (62), a driving motor (63), a disc (64), two slide bars (65), two moving blocks (66), four return springs (67) and a push plate (68). The bottoms of the two vertical plates (62) are respectively fixedly connected to the front and rear sides of the top of the base (61). The bottom of the driving motor (63) is fixedly connected to the middle side of the top of the base (61) near the front vertical plate (62). The output end of the driving motor (63) is connected to the bottom of the disc (64). On one side, the front and rear ends of the two slide bars (65) are respectively fixedly connected to the left and right sides of the opposite surfaces of the two vertical plates (62), the outer walls of the two slide bars (65) respectively pass through the front and rear ends of the middle parts of the two moving blocks (66) and are slidably connected therebetween, the interiors of the two return springs (67) are respectively sleeved on the outer walls of the front and rear sides of the slide bars (65) close to the moving blocks (66), the rear end of the push plate (68) is fixedly connected to the middle side of the front end of the washing table (1), and the front surface of the push plate (68) overlaps the outer wall of the disc (64).
8. The hot-dip galvanizing and pickling sealing device according to claim 7, characterized in that: The tops of the two moving blocks (66) are respectively fixedly connected to the left and right sides of the bottom of the washing table (1); the ends of the two front and rear return springs (67) that are away from each other are overlapped with the opposite surfaces of the two vertical plates (62); and the adjacent ends of the two front and rear return springs (67) are respectively overlapped with the front and rear ends of the moving block (66).