Bulletproof mechanism of automatic test jig

Abstract

The utility model provides a bulletproof mechanism of an automatic test jig, which comprises a base, a driving device, a pressing device and a test fixture, a bottom plate is arranged above the base, a lower bottom plate is arranged above the bottom plate, the test fixture is arranged above the lower bottom plate, the driving device is connected with the pressing device, the pressing device comprises a fixing plate, a pressing driving cylinder and a pressing plate, and the fixing plate is connected with the pressing driving cylinder. The pressing-down driving air cylinder is connected with the fixing plate and used for fixing the pressing-down driving air cylinder, the driving end of the pressing-down driving air cylinder is connected with the pressing-down plate and drives the pressing-down plate to move up and down, bulletproof mechanisms are arranged on the left side and the right side of the upper end of the fixing plate, and each bulletproof mechanism comprises a clamping column, a clamping piece and a kidney-shaped hole formed in the bottom plate and matched with the clamping column. When the driving mechanism drives the fixing plate to press downwards, the clamping columns penetrate through the kidney-shaped holes to be connected with the clamping pieces in a clamped mode so as to prevent the situation that when the pressing-down driving air cylinder works in a pressing-down mode, due to overlarge pressure, the fixing plate rebounds upwards, and accurate detection cannot be conducted.

Description

Technical Field

[0001] The utility model relates to the technical field of testing jigs, in particular to an anti-bounce mechanism of an automated testing jig. Background Art

[0002] With the rapid development of information technology and the expansion of electronic product production, test fixtures are essential for functional testing of PCB boards. As the test content and parameter complexity of PCB boards increase, the original test operation method requires more testers, which has low labor efficiency, low output, inconsistent operation, and the test quality cannot be standardized.

[0003] The existing patent announcement number: CN 217443497 U discloses a pneumatic test fixture, which relates to the field of electronic tag testing technology, including: a base and a cover plate, the base and the cover plate are connected by gas springs arranged on both sides of the base, and a column is arranged at the top of the base between the gas springs, and the cover plate is movably connected to the column through a rotating shaft; a workpiece carrier is movably arranged at the top of the base, a test probe is arranged at the bottom of the workpiece carrier, and a mutually symmetrical hook support is arranged on one side of the workpiece carrier; a plurality of linear bearings are arranged at the top of the cover plate, one end of the linear bearing extends to the bottom of the cover plate and is connected to a bearing needle plate, the top of the bearing needle plate is connected to a cylinder arranged at the top of the cover plate, and a test probe is arranged at the bottom of the bearing needle plate. Beneficial effects: It has the advantages of reducing manual operation time, improving test efficiency and accuracy, and at the same time increasing the production capacity of each test section, and is conducive to reducing production costs and improving corporate benefits.

[0004] However, in the prior art, when the test workpiece is placed on the workpiece carrier, the cover plate and the base are locked by manually pressing the hand lever of the cover plate in cooperation with the column and the support plate and the hook support, and the bearing needle plate of the cylinder under the action of the linear bearing cooperates with the test probe and the test probe at the bottom of the bearing needle plate to fit the test workpiece respectively. Since the prior art does not have an anti-bounce mechanism, when the cylinder presses down the bearing needle plate, the cover plate will bounce upwards under the reaction force, and cannot be accurately detected, affecting the detection efficiency. Utility Model Content

[0005] Therefore, in order to solve the above problems, the utility model proposes an anti-bounce mechanism for an automated test fixture, comprising a base 10, a driving device 20, a pressing device 30, a test fixture 40, a bottom plate 50 is provided above the base 10, a lower bottom plate 60 is provided above the bottom plate 50, the test fixture 40 is placed above the lower bottom plate 60, the driving device 20 is connected to the pressing device 30, the pressing device 30 comprises a fixed plate 301, a pressing driving cylinder 302 and a lower pressing plate 303, the pressing driving cylinder 302 is connected to the fixed plate 301, and is used to fix the pressing driving cylinder 302, the driving end of the pressing driving cylinder 302 is connected to the lower pressing plate 303, and drives the lower pressing plate 303 to move up and down, and the upper end of the fixed plate 301 is provided with a bottom plate 50 on both sides. There is an anti-bounce mechanism 70, which includes a clamping column 701, a clamping piece 702, and a waist-shaped hole 80 matching the clamping column 701 is provided on the bottom plate 50. When the driving mechanism drives the fixed plate 301 to press down, the clamping column 701 passes through the waist-shaped hole 80 and is clamped with the clamping piece 702, which is used to prevent the fixed plate 301 from rebounding upward due to excessive pressure when the downward driving cylinder 302 is pressed down, and cannot be accurately detected. Since the anti-bounce mechanism is set up, when the driving mechanism drives the fixed plate 301 to press down, the clamping column 701 passes through the waist-shaped hole 80 and is clamped with the clamping piece 702. When the downward driving cylinder 302 is pressed down, the fixed plate 301 cannot rebound upward, thereby improving the detection efficiency and achieving accurate detection.

[0006] An anti-bounce mechanism for an automated test fixture, comprising a base 10, a driving device 20, a pressing device 30, a test fixture 40, a bottom plate 50 is provided above the base 10, a lower bottom plate 60 is provided above the bottom plate 50, the test fixture 40 is placed above the lower bottom plate 60, the driving device 20 is connected to the pressing device 30, the pressing device 30 comprises a fixing plate 301, a pressing driving cylinder 302 and a pressing plate 303, the pressing driving cylinder 302 is connected to the fixing plate 301, and is used to fix the pressing driving cylinder 302, the driving cylinder 302 of the pressing driving cylinder 302 The moving end is connected to the lower pressure plate 303, driving the lower pressure plate 303 to move up and down. Anti-bounce mechanisms 70 are provided on the left and right sides of the upper end of the fixed plate 301. The anti-bounce mechanism 70 includes a clamping column 701, a clamping piece 702, and a waist-shaped hole 80 matching the clamping column 701 is provided on the bottom plate 50. When the driving mechanism drives the fixed plate 301 to press down, the clamping column 701 passes through the waist-shaped hole 80 and is clamped with the clamping piece 702, so as to prevent the fixed plate 301 from rebounding upward due to excessive pressure when the downward driving cylinder 302 is working downward, and cannot be accurately detected.

[0007] Furthermore, one end of the clamping column 701 is connected to the fixing plate 301, and the other end of the clamping column 701 is clamped to the clamping member 702. The top of the clamping column 701 is a buckle 90, and the diameter of the clamping column 701 at one end close to the buckle 90 is smaller than the diameter of the clamping column 701 at the other end.

[0008] Furthermore, a clamping platform 100 is provided at one end close to the buckle 90 , and the diameter of the clamping platform 100 is larger than the cross-section of the waist-shaped hole 80 , so as to prevent the clamping column 701 from moving downward too much and play a limiting role.

[0009] Furthermore, the buckle 90 is a hemispherical buckle for easy guidance.

[0010] Furthermore, the clamping member 702 is connected to the lower surface of the base plate 50, and the clamping member 702 includes a pushing cylinder 7021 and a cylinder clamping member 7022. The cylinder clamping member 7022 is connected to the driving end of the pushing cylinder 7021. When the driving device 20 drives the fixed plate 301 to be pressed down, the clamping column 701 passes through the waist-shaped hole 80, and the pushing cylinder 7021 drives the cylinder clamping member 7022 to be clamped with the buckle 90, so that when the downward driving cylinder 302 is pressed down, the fixed plate 301 cannot rebound upward.

[0011] Furthermore, the diameter of the slot of the cylinder fastener 7022 is smaller than the diameter of the clamping column 701 at one end close to the fastener 90. When the fixing plate 301 is reset, the cylinder fastener 7022 and the fastener 90 can be quickly disengaged due to the action of the pushing cylinder 7021.

[0012] Furthermore, the driving device 20 includes a driving motor 201, a hexagonal shaft 202, a synchronous belt 203 and a synchronous wheel 204, the driving end of the driving motor 201 is connected to the synchronous wheel 204 through the synchronous belt 203, the hexagonal shaft 202 passes through the synchronous wheel 204 and both ends of the hexagonal shaft 202 are provided with a rotating shaft 110 and a rotating shaft seat 120, the rotating shaft 110 is connected to the pressing device 30, and the rotating shaft seat 120 is connected to the bottom plate 50. When the pressing device 30 is pressed down, the driving motor 201 drives the synchronous wheel 204 to rotate through the synchronous belt 203, so that the pressing device 30 is closed downward, and after the pressing stroke is completed, the driving motor 201 drives the pressing device 30 to reset upward.

[0013] Furthermore, linear bearings 130 are provided at the corners of the upper surface of the fixing plate 301 , and a sliding guide rod 140 is provided in the linear bearing 130 , and the bottom end of the sliding guide rod 140 is connected to the lower pressing plate 303 . The sliding guide rod 140 is slidably connected to the linear bearing 130 .

[0014] Furthermore, a spring 150 is sleeved on the upper end of the sliding guide rod 140, which is used to keep the lower pressure plate 303 pressed down in parallel under the action of the sliding guide rod 140 when the downward pressure driving cylinder 302 presses down the lower pressure plate 303, and when the downward pressure driving cylinder 302 drives the lower pressure plate 303 to rise, the lower pressure plate 303 is subjected to the same force under the action of the spring 150, and the lower pressure plate 303 is kept rising in parallel.

[0015] Furthermore, a spring stopper 160 is provided at the top of the sliding guide rod 140 to prevent the spring 150 from falling off the sliding guide rod 140 .

[0016] Beneficial effects of the utility model: The utility model proposes an anti-bounce mechanism for an automated test fixture, comprising a base 10, a driving device 20, a pressing device 30, a test fixture 40, a bottom plate 50 is provided above the base 10, a lower bottom plate 60 is provided above the bottom plate 50, the test fixture 40 is placed above the lower bottom plate 60, the driving device 20 is connected to the pressing device 30, the pressing device 30 comprises a fixed plate 301, a pressing driving cylinder 302 and a lower pressing plate 303, the pressing driving cylinder 302 is connected to the fixed plate 301, and is used to fix the pressing driving cylinder 302, the driving end of the pressing driving cylinder 302 is connected to the lower pressing plate 303, and drives the lower pressing plate 303 to move up and down, and the upper end of the fixed plate 301 is provided with a cylinder 301 on both sides. The anti-bounce mechanism 70 includes a clamping column 701, a clamping piece 702, and a waist-shaped hole 80 matching the clamping column 701 is provided on the bottom plate 50. When the driving mechanism drives the fixed plate 301 to be pressed downward, the clamping column 701 passes through the waist-shaped hole 80 and is clamped with the clamping piece 702 to prevent the fixed plate 301 from rebounding upward due to excessive pressure when the downward driving cylinder 302 is pressed downward, and cannot be accurately detected. Since the anti-bounce mechanism is provided, when the driving mechanism drives the fixed plate 301 to be pressed downward, the clamping column 701 passes through the waist-shaped hole 80 and is clamped with the clamping piece 702. When the downward driving cylinder 302 is pressed downward, the fixed plate 301 cannot rebound upward, thereby improving the detection efficiency and achieving accurate detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The utility model is an open state of the overall structural schematic diagram of the anti-bounce mechanism of the automatic testing jig.

[0018] Figure 2 The utility model is a closed state of the overall structural schematic diagram of the anti-bounce mechanism of the automatic testing jig.

[0019] Figure 3 The utility model is a partial structural schematic diagram of an anti-bounce mechanism of an automated testing jig.

[0020] Figure 4 The utility model is a partial structural schematic diagram of an anti-bounce mechanism of an automated testing jig.

[0021] Description of main component symbols:

[0022] Base 10, driving device 20, motor 201, hexagonal shaft 202, synchronous belt 203, synchronous wheel 204, pressing device 30, fixing plate 301, pressing driving cylinder 302, lower pressing plate 303, test fixture 40, bottom plate 50, lower bottom plate 60, anti-bounce mechanism 70, clamping column 701, clamping part 702, pushing cylinder 7021, cylinder clamping part 7022, waist-shaped hole 80, buckle 90, clamping table 100, rotating shaft part 110, rotating shaft seat 120, linear bearing 130, sliding guide rod 140, spring 150, spring baffle 160.

[0023] The following specific implementation manner will further illustrate the present utility model in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0024] The following examples are described to assist the understanding of the present application, and the examples are not and should not be interpreted in any way as limiting the scope of protection of the present application.

[0025] In the following description, those skilled in the art will recognize that throughout this discussion, components may be described as separate functional units (which may include sub-units), but those skilled in the art will recognize that various components or portions thereof may be divided into separate components or may be integrated together (including within a single system or component).

[0026] At the same time, the connections between components or systems are not intended to be limited to direct connections, rather, the data between these components may be modified, reformatted, or otherwise changed by intermediate components. In addition, additional or fewer connections may be used. It should also be noted that the terms "coupled," "connected," or "input" should be understood to include direct connections, indirect connections through one or more intermediate devices, and wireless connections. Embodiment 1:

[0027] like Figure 1 As shown, it is the open state of the overall structural schematic diagram of the anti-bounce mechanism of an automated testing jig of the utility model; Figure 2 As shown, it is a closed state of the overall structural schematic diagram of the anti-bounce mechanism of an automated testing jig of the utility model; Figure 3FIG. 1 is a partial structural schematic diagram of an anti-bounce mechanism of an automated testing jig of the utility model;

[0028] like Figure 4 The figure is a partial structural schematic diagram of an anti-bounce mechanism of an automated testing jig according to the present invention.

[0029] An anti-bounce mechanism for an automated test fixture, comprising a base 10, a driving device 20, a pressing device 30, a test fixture 40, a bottom plate 50 is provided above the base 10, a lower bottom plate 60 is provided above the bottom plate 50, the test fixture 40 is placed above the lower bottom plate 60, the driving device 20 is connected to the pressing device 30, the pressing device 30 comprises a fixing plate 301, a pressing driving cylinder 302 and a pressing plate 303, the pressing driving cylinder 302 is connected to the fixing plate 301, and is used to fix the pressing driving cylinder 302, the driving cylinder 302 of the pressing driving cylinder 302 The moving end is connected to the lower pressure plate 303, driving the lower pressure plate 303 to move up and down. Anti-bounce mechanisms 70 are provided on the left and right sides of the upper end of the fixed plate 301. The anti-bounce mechanism 70 includes a clamping column 701, a clamping piece 702, and a waist-shaped hole 80 matching the clamping column 701 is provided on the bottom plate 50. When the driving mechanism drives the fixed plate 301 to press down, the clamping column 701 passes through the waist-shaped hole 80 and is clamped with the clamping piece 702, so as to prevent the fixed plate 301 from rebounding upward due to excessive pressure when the downward driving cylinder 302 is working downward, and cannot be accurately detected.

[0030] One end of the clamping column 701 is connected to the fixing plate 301, and the other end of the clamping column 701 is clamped with the clamping member 702. The top of the clamping column 701 is a buckle 90, and the diameter of the clamping column 701 at one end close to the buckle 90 is smaller than the diameter of the clamping column 701 at the other end.

[0031] A clamping platform 100 is provided at one end close to the buckle 90 . The diameter of the clamping platform 100 is larger than the cross section of the waist-shaped hole 80 , and is used to prevent the clamping column 701 from moving downward too much, thereby playing a limiting role.

[0032] The buckle 90 is a hemispherical buckle for easy guidance.

[0033] The clamping member 702 is connected to the lower surface of the base plate 50, and the clamping member 702 includes a pushing cylinder 7021 and a cylinder clamping member 7022. The cylinder clamping member 7022 is connected to the driving end of the pushing cylinder 7021. When the driving device 20 drives the fixed plate 301 to be pressed down, the clamping column 701 passes through the waist-shaped hole 80, and the pushing cylinder 7021 drives the cylinder clamping member 7022 to be clamped with the buckle 90, so that when the downward driving cylinder 302 is pressed down, the fixed plate 301 cannot rebound upward.

[0034] The diameter of the slot of the cylinder fastener 7022 is smaller than the diameter of the clamping column 701 at one end close to the fastener 90. When the fixing plate 301 is reset, the cylinder fastener 7022 and the fastener 90 can be quickly disengaged due to the action of the pushing cylinder 7021.

[0035] The driving device 20 includes a driving motor 201, a hexagonal shaft 202, a synchronous belt 203 and a synchronous wheel 204. The driving end of the driving motor 201 is connected to the synchronous wheel 204 through the synchronous belt 203. The hexagonal shaft 202 passes through the synchronous wheel 204 and both ends of the hexagonal shaft 202 are provided with a rotating shaft 110 and a rotating shaft seat 120. The rotating shaft 110 is connected to the pressing device 30, and the rotating shaft seat 120 is connected to the bottom plate 50. When the pressing device 30 is pressed down, the driving motor 201 drives the synchronous wheel 204 to rotate through the synchronous belt 203, so that the pressing device 30 is closed downward. After the pressing stroke is completed, the driving motor 201 drives the pressing device 30 to reset upward.

[0036] Linear bearings 130 are provided at the corners of the upper surface of the fixing plate 301 , and a sliding guide rod 140 is provided in the linear bearing 130 , and the bottom end of the sliding guide rod 140 is connected to the lower pressing plate 303 . The sliding guide rod 140 is slidably connected to the linear bearing 130 .

[0037] A spring 150 is sleeved on the upper end of the sliding guide rod 140, which is used to keep the lower pressure plate 303 pressed down in parallel under the action of the sliding guide rod 140 when the downward pressure driving cylinder 302 presses down the lower pressure plate 303, and when the downward pressure driving cylinder 302 drives the lower pressure plate 303 to rise, the lower pressure plate 303 is subjected to the same force under the action of the spring 150, and the lower pressure plate 303 is kept rising in parallel.

[0038] A spring stopper 160 is disposed at the top of the sliding guide rod 140 to prevent the spring 150 from falling off the sliding guide rod 140 .

[0039] Beneficial effects of the utility model: The utility model proposes an anti-bounce mechanism for an automated test fixture, comprising a base 10, a driving device 20, a pressing device 30, a test fixture 40, a bottom plate 50 is provided above the base 10, a lower bottom plate 60 is provided above the bottom plate 50, the test fixture 40 is placed above the lower bottom plate 60, the driving device 20 is connected to the pressing device 30, the pressing device 30 comprises a fixed plate 301, a pressing driving cylinder 302 and a lower pressing plate 303, the pressing driving cylinder 302 is connected to the fixed plate 301, and is used to fix the pressing driving cylinder 302, the driving end of the pressing driving cylinder 302 is connected to the lower pressing plate 303, and drives the lower pressing plate 303 to move up and down, and the upper end of the fixed plate 301 is provided with a cylinder 301 on both sides. The anti-bounce mechanism 70 includes a clamping column 701, a clamping piece 702, and a waist-shaped hole 80 matching the clamping column 701 is provided on the bottom plate 50. When the driving mechanism drives the fixed plate 301 to be pressed downward, the clamping column 701 passes through the waist-shaped hole 80 and is clamped with the clamping piece 702 to prevent the fixed plate 301 from rebounding upward due to excessive pressure when the downward driving cylinder 302 is pressed downward, and cannot be accurately detected. Since the anti-bounce mechanism is provided, when the driving mechanism drives the fixed plate 301 to be pressed downward, the clamping column 701 passes through the waist-shaped hole 80 and is clamped with the clamping piece 702. When the downward driving cylinder 302 is pressed downward, the fixed plate 301 cannot rebound upward, thereby improving the detection efficiency and achieving accurate detection.

[0040] The above-mentioned embodiments only express several implementation methods of the utility model, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.

Claims

1. An anti-bounce mechanism for an automated test fixture, comprising a base (10), a driving device (20), a pressing device (30), and a test fixture (40); a bottom plate (50) is provided above the base (10); a lower bottom plate (60) is provided above the bottom plate (50); the test fixture (40) is placed above the lower bottom plate (60); the driving device (20) is connected to the pressing device (30); the pressing device (30) comprises a fixed plate (301), a pressing drive cylinder (302), and a lower pressing plate (303); the pressing drive cylinder (302) is connected to the fixed plate (301) for fixing the pressing drive cylinder (302); a driving end of the pressing drive cylinder (302) is connected to the lower pressing plate (303) to drive the lower pressing plate (303) to move up and down; and the characteristics are as follows: The left and right sides of the upper end of the fixed plate (301) are provided with an anti-bounce mechanism (70), the anti-bounce mechanism (70) comprising a clamping column (701), a clamping piece (702), and a waist-shaped hole (80) matching the clamping column (701) is provided on the bottom plate (50). When the driving mechanism drives the fixed plate (301) to be pressed downward, the clamping column (701) passes through the waist-shaped hole (80) and is clamped with the clamping piece (702), so as to prevent the fixed plate (301) from rebounding upwards and failing to be accurately detected due to excessive pressure when the downward driving cylinder (302) is working downward.

2. The anti-bounce mechanism of the automated testing jig according to claim 1, characterized in that: One end of the clamping column (701) is connected to the fixing plate (301), and the other end of the clamping column (701) is clamped to the clamping member (702); the top end of the clamping column (701) is a buckle (90), and the diameter of the clamping column (701) at one end close to the buckle (90) is smaller than the diameter of the clamping column (701) at the other end.

3. The anti-bounce mechanism of the automated testing jig according to claim 2, characterized in that: A clamping platform (100) is provided at one end close to the buckle (90); the diameter of the clamping platform (100) is larger than the cross section of the waist-shaped hole (80) and is used to prevent the clamping column (701) from moving downward too much, thereby playing a limiting role.

4. The anti-bounce mechanism of the automated testing jig according to claim 3, characterized in that: The buckle (90) is a hemispherical buckle, which is convenient for guiding.

5. The anti-bounce mechanism of the automated testing jig according to claim 2, characterized in that: The clamping member (702) is connected to the lower surface of the base plate (50), and the clamping member (702) comprises a pushing cylinder (7021) and a cylinder clamping member (7022). The cylinder clamping member (7022) is connected to the driving end of the pushing cylinder (7021). When the driving device (20) drives the fixing plate (301) to be pressed downward, the clamping column (701) passes through the waist-shaped hole (80), and the pushing cylinder (7021) drives the cylinder clamping member (7022) to be clamped with the buckle (90), so that when the downward driving cylinder (302) is pressed downward, the fixing plate (301) cannot rebound upward.

6. The anti-bounce mechanism of the automated testing jig according to claim 5, characterized in that: The diameter of the clamping groove of the cylinder clamping piece (7022) is smaller than the diameter of the clamping column (701) at one end close to the clamping piece (90), and when the fixing plate (301) is reset, the cylinder clamping piece (7022) and the clamping piece (90) can be quickly disengaged due to the action of the pushing cylinder (7021).

7. The anti-bounce mechanism of the automated testing jig according to claim 1, characterized in that: The driving device (20) comprises a driving motor (201), a hexagonal shaft (202), a synchronous belt (203) and a synchronous wheel (204); the driving end of the driving motor (201) is connected to the synchronous wheel (204) via the synchronous belt (203); the hexagonal shaft (202) passes through the synchronous wheel (204); and both ends of the hexagonal shaft (202) are provided with a rotating shaft member (110) and a rotating shaft seat (120); the rotating shaft member (110) is connected to the pressing device (30); and the rotating shaft seat (120) is connected to the bottom plate (50); when the pressing device (30) is pressed downward, the driving motor (201) drives the synchronous wheel (204) to rotate via the synchronous belt (203), so that the pressing device (30) is closed downward; after the pressing stroke is completed, the driving motor (201) drives the pressing device (30) to reset upward.

8. The anti-bounce mechanism of the automated testing jig according to claim 1, characterized in that: Linear bearings (130) are provided at the four corners of the upper surface of the fixed plate (301), a sliding guide rod (140) is provided inside the linear bearing (130), the bottom end of the sliding guide rod (140) is connected to the lower pressing plate (303), and the sliding guide rod (140) is slidably connected to the linear bearing (130).

9. The anti-bounce mechanism of the automated testing jig according to claim 8, characterized in that: The upper end of the sliding guide rod (140) is sleeved with a spring (150) for keeping the lower pressing plate (303) pressed down in parallel under the action of the sliding guide rod (140) when the downward pressing driving cylinder (302) presses down the lower pressing plate (303); and when the downward pressing driving cylinder (302) drives the lower pressing plate (303) to rise, the lower pressing plate (303) is subjected to the same force under the action of the spring (150), while keeping the lower pressing plate (303) rising in parallel.

10. The anti-bounce mechanism of the automated testing jig according to claim 9, characterized in that: A spring stopper (160) is provided at the top end of the sliding guide rod (140) for preventing the spring (150) from falling off the sliding guide rod (140).

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