Device for testing compressive strength of recycled concrete sample

Abstract

The invention relates to the technical field of concrete detection, in particular to a recycled concrete sample compressive strength testing device which is arranged to conveniently clamp and fix the center of a recycled concrete sample, so that the testing result of the recycled concrete sample is ensured. Comprising a workbench, a fixing frame, a strength testing device, a fine adjustment device and a clamp assembly, the fixing frame is installed at the top end of the workbench, the strength testing device is installed at the top of the fixing frame, and the fine adjustment device is installed at the top end of the workbench; the clamp assembly comprises a placing table, two first two-way screws, two clamping plates, four first sliding blocks, two second two-way screws, four clamping plates, four second sliding blocks, two belt wheels, a belt, a motor and a mounting frame, the placing table is connected with the fine adjustment device in a matched mode, and the four first sliding blocks are mounted on the front sides and the rear sides of the bottom ends of the two clamping plates correspondingly; the motor is mounted at the inner end of the mounting frame which is mounted on the right rear side of the bottom end of the placement table.

Description

Technical Field

[0001] The invention relates to the technical field of concrete detection, in particular to a device for testing the compressive strength of recycled concrete samples. Background Art

[0002] Recycled concrete is a new concrete material made from construction waste (such as old concrete blocks) as aggregate. This practice not only helps to reduce construction waste, but also saves natural resources and has significant environmental benefits. The preparation and testing of recycled concrete samples are key steps in studying its performance and application.

[0003] The compressive strength test of recycled concrete specimens is one of the important links in evaluating the performance of recycled concrete. The compressive strength test is usually carried out using a special testing device to ensure the accuracy and repeatability of the test results. However, the existing testing device may cause the specimen to be placed off-center, resulting in eccentricity during loading, which affects the test results. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a recycled concrete sample compressive strength testing device which facilitates the center clamping and fixing of the recycled concrete sample by setting up this device, thereby ensuring the test results.

[0005] A regenerated concrete sample compressive strength testing device of the present invention comprises a workbench, a fixed frame, a strength testing device, a fine-tuning device and a clamp assembly, wherein the fixed frame is mounted on the top of the workbench, the strength testing device is mounted on the top of the fixed frame, the fine-tuning device is mounted on the top of the workbench, and the clamp assembly is mounted on the fine-tuning device, the clamp assembly comprises a placing table, two groups of first bidirectional screws, two groups of clamping plates, four groups of first sliding blocks, two groups of second bidirectional screws, four groups of clamping plates, four groups of second sliding blocks, two groups of pulleys, belts, a motor and a mounting frame, the placing table is cooperatively connected with the fine-tuning device, the front and rear sides of the top of the placing table are both provided with slide grooves, the two groups of first bidirectional screws are rotatably mounted in the two groups of slide grooves of the placing table, the four groups of first sliding blocks are respectively mounted on the front and rear sides of the bottom ends of the two groups of clamping plates, and the four groups of first sliding blocks are in the two groups of slide grooves of the placing table Sliding, the four groups of first sliders are all connected with threaded holes, the four groups of first sliders are threadedly connected with the two groups of first bidirectional screws, the inner ends of the two groups of clamping plates are provided with sliding grooves, the two groups of second bidirectional screws are rotatably installed in the sliding grooves of the two groups of clamping plates, the two groups of small motors are respectively installed at the rear ends of the two groups of clamping plates, the output ends of the two groups of small motors respectively pass through the rear ends of the two groups of clamping plates and are connected with the rear ends of the two groups of second bidirectional screws, the four groups of second sliders slide in the sliding grooves of the two groups of second bidirectional screws, the four groups of second sliders are respectively installed at the outer ends of the four groups of clamping plates, the four groups of clamping plates are slidably connected with the inner ends of the two groups of clamping plates, the two groups of pulleys are respectively installed on the right parts of the two groups of first bidirectional screws, the two groups of pulleys are synchronously driven by belts, the motor is connected to the right end of the first bidirectional screw on the rear side, the motor is installed at the inner end of the mounting frame, and the mounting frame is installed on the right rear side of the bottom end of the placement table.

[0006] Preferably, the fine-tuning device includes a vertical plate, a first screw, a handwheel and an adjusting device. The vertical plate is installed on the front side of the top of the workbench, the first screw is rotatably installed in the middle of the front end of the placement table, a threaded hole is provided in the middle of the vertical plate, the first screw is threadedly connected to the vertical plate, the handwheel is installed at the front end of the first screw, the adjusting device is installed on the top of the workbench, and the adjusting device is cooperatively connected to the placement table.

[0007] Preferably, the adjusting device includes six groups of fixed seats, a second screw, a turning handle, a handle, two groups of fixed rods, five groups of fixed blocks and a connecting device. The six groups of fixed seats are respectively installed on the left and right sides of the top of the workbench, the second screw is rotatably installed on the two middle groups of fixed seats, the turning handle is installed on the right end of the second screw, and the handle is rotatably installed on the lower side of the right end of the turning handle. The two groups of fixed rods are respectively installed on the two front groups of fixed seats and the two rear groups of fixed seats. The five groups of fixed blocks are connected to the placement table through the connecting device. A threaded hole is provided in the middle of the middle fixed block, and the middle fixed block is threadedly connected to the second screw. The four outer groups of fixed blocks are all connected with sliding holes, and the four groups of fixed blocks are respectively slidably connected to the two groups of fixed rods.

[0008] Preferably, the connecting device is configured as five groups of third sliders, which are respectively installed on the top of five groups of fixed blocks, two groups of auxiliary rollers are rotatably arranged on the top of each group of third sliders, and slide grooves are arranged on the left, right and middle parts of the bottom end of the placing table, and the five groups of fixed blocks slide respectively in the three groups of slide grooves of the placing table.

[0009] Preferably, a mounting groove is provided in the middle of the top of the placing table, the transmitter is installed in the mounting groove of the placing table, a mounting groove is provided in the middle of the bottom of the strength testing device, the receiver is installed in the mounting groove of the strength testing device, and the positions of the transmitter and the receiver correspond.

[0010] Preferably, it also includes a reminder, which is installed on the left front side of the top of the workbench and is electrically connected to the receiver.

[0011] Preferably, it also includes two groups of guide rods, which are respectively installed on the left and right sides of the front end of the placement table. The left and right parts of the vertical plate are both connected and provided with sliding holes, and the two groups of guide rods slide in the two groups of sliding holes of the vertical plate.

[0012] Preferably, a rubber pad is provided at the inner end of the clamping plate.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: the recycled concrete sample is placed in the middle of the top of the placing table, and the motor is turned on, so that the motor drives the first bidirectional screw on the rear side to rotate, and the first bidirectional screw on the rear side drives the first bidirectional screw on the front side to rotate through two sets of pulleys and belts, and the two sets of first bidirectional screws are threadedly connected with the four sets of first sliders, and the four sets of first sliders drive the two sets of clamping plates to move inward synchronously, and the two sets of clamping plates perform transverse center clamping on the recycled concrete sample, and then the two sets of small motors are turned on, and the two sets of small motors drive the two sets of second bidirectional screws to rotate, and the two sets of second bidirectional screws are threadedly connected with the four sets of second sliders, and the four sets of second sliders drive the four sets of clamping plates to move inward, and the four sets of clamping plates perform longitudinal center clamping on the recycled concrete sample, and by setting this equipment, it is convenient to perform center clamping and fixing of the recycled concrete sample, thereby ensuring its test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 yes Figure 1 Schematic diagram of the local decomposition structure; Figure 3 yes Figure 1 A is a schematic diagram of the enlarged structure of the middle part; Figure 4 yes Figure 1 A schematic diagram of the enlarged structure of B; Markings in the attached drawings: 1. workbench; 2. fixed frame; 3. strength testing device; 4. placing table; 5. first bidirectional screw; 6. clamping plate; 7. first slider; 8. second bidirectional screw; 9. clamping plate; 10. second slider; 11. vertical plate; 12. first screw; 13. hand wheel; 14. fixed seat; 15. second screw; 16. turning handle; 17. handle; 18. fixing rod; 19. fixing block; 20. third slider; 21. auxiliary roller; 22. prompter; 23. guide rod; 24. pulley; 25. belt; 26. motor; 27. mounting frame. DETAILED DESCRIPTION

[0015] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0016] like Figures 1 to 4 As shown, a regenerated concrete sample compressive strength testing device of the present invention comprises a workbench 1, a fixing frame 2, a strength testing device 3, a fine-tuning device and a fixture assembly, the fixing frame 2 is mounted on the top of the workbench 1, the strength testing device 3 is mounted on the top of the fixing frame 2, the fine-tuning device is mounted on the top of the workbench 1, and the fixture assembly is mounted on the fine-tuning device, the fixture assembly comprises a placing table 4, two groups of first bidirectional screws 5, two groups of clamping plates 6, four groups of first sliders 7, two groups of second bidirectional screws 8, four groups of clamping plates 9, four groups of second sliders 10, two groups of pulleys 24, belts 25, motors 26 and mounting frames 27, the placing table 4 is cooperatively connected with the fine-tuning device, the front and rear sides of the top of the placing table 4 are both provided with slide grooves, the two groups of first bidirectional screws 5 are rotatably mounted in the two groups of slide grooves of the placing table 4, the four groups of first sliders 7 are respectively mounted on the front and rear sides of the bottom ends of the two groups of clamping plates 6, and the four groups of first sliders 7 are in the two groups of slide grooves of the placing table 4 The four first sliders 7 are connected with threaded holes, the four first sliders 7 are threadedly connected with the two first bidirectional screws 5, the inner ends of the two clamping plates 6 are provided with sliding grooves, the two second bidirectional screws 8 are rotatably installed in the sliding grooves of the two clamping plates 6, the two small motors are respectively installed at the rear ends of the two clamping plates 6, the output ends of the two small motors pass through the rear ends of the two clamping plates 6 and are connected with the rear ends of the two second bidirectional screws 8, the four second sliders 10 slide in the sliding grooves of the two second bidirectional screws 8, the four second sliders 10 are respectively installed at the outer ends of the four clamping plates 9, the four clamping plates 9 are slidably connected with the inner ends of the two clamping plates 6, the two pulleys 24 are respectively installed at the right parts of the two first bidirectional screws 5, the two pulleys 24 are synchronously driven by the belts 25, the motor 26 is connected with the right end of the rear first bidirectional screw 5, the motor 26 is installed at the inner end of the mounting frame 27, and the mounting frame 27 is installed at the right rear side of the bottom end of the placing table 4; The recycled concrete sample is placed in the middle of the top of the placing table 4, and the motor 26 is turned on. The motor 26 drives the first bidirectional screw 5 on the rear side to rotate, and the first bidirectional screw 5 on the rear side drives the first bidirectional screw 5 on the front side to rotate through two sets of pulleys 24 and belts 25. The two sets of first bidirectional screws 5 are threadedly connected with the four sets of first sliders 7, and the four sets of first sliders 7 drive the two sets of clamping plates 6 to move inward synchronously, and the two sets of clamping plates 6 perform transverse center clamping on the recycled concrete sample, and then the two sets of small motors are turned on. The two sets of small motors drive the two sets of second bidirectional screws 8 to rotate, and the two sets of second bidirectional screws 8 are threadedly connected with the four sets of second sliders 10, and the four sets of second sliders 10 drive the four sets of clamping plates 9 to move inward, and the four sets of clamping plates 9 perform longitudinal center clamping on the recycled concrete sample. By setting up this equipment, it is convenient to perform center clamping and fixing of the recycled concrete sample, thereby ensuring its test results.

[0017] As a preferred embodiment of the above, the fine-tuning device includes a vertical plate 11, a first screw 12, a hand wheel 13 and an adjusting device. The vertical plate 11 is installed on the front side of the top of the workbench 1, the first screw 12 is rotatably installed in the middle of the front end of the placement table 4, a threaded hole is provided in the middle of the vertical plate 11, the first screw 12 is threadedly connected to the vertical plate 11, the hand wheel 13 is installed at the front end of the first screw 12, the adjusting device is installed on the top of the workbench 1, and the adjusting device is connected with the placement table 4; By setting the vertical plate 11, the first screw rod 12, the hand wheel 13 and the adjustment device, the first screw rod 12 is rotated by the hand wheel 13, and the first screw rod 12 is threadedly connected with the vertical plate 11, and the vertical plate 11 drives the placement table 4 to move longitudinally, so as to perform longitudinal fine adjustment on the placement table 4 as a whole.

[0018] As a preferred embodiment of the above, the adjusting device includes six groups of fixed seats 14, a second screw 15, a turning handle 16, a handle 17, two groups of fixed rods 18, five groups of fixed blocks 19 and a connecting device. The six groups of fixed seats 14 are respectively installed on the left and right sides of the top of the workbench 1, the second screw 15 is rotatably installed on the two middle groups of fixed seats 14, the turning handle 16 is installed on the right end of the second screw 15, and the handle 17 is rotatably installed on the lower side of the right end of the turning handle 16. The two groups of fixed rods 18 are respectively installed on the two front groups of fixed seats 14 and the two rear groups of fixed seats 14. The five groups of fixed blocks 19 are connected to the placement table 4 through the connecting device. A threaded hole is provided in the middle of the middle fixed block 19, and the middle fixed block 19 is threadedly connected to the second screw 15. The four outer groups of fixed blocks 19 are all connected with sliding holes, and the four groups of fixed blocks 19 are respectively slidably connected to the two groups of fixed rods 18; By arranging a fixed seat 14, a second screw rod 15, a turning handle 16, a handle bar 17, a fixed rod 18, a fixed block 19 and a connecting device, the turning handle 16 is driven to rotate by the handle bar 17, and the turning handle 16 drives the second screw rod 15 to rotate, the second screw rod 15 is threadedly connected to the middle fixed block 19, and the middle fixed block 19 drives the placement table 4 to move horizontally through the connecting device, and the four outer groups of fixed blocks 19 are slidably connected to the two groups of fixed rods 18, so as to perform a lateral fine adjustment on the placement table 4.

[0019] As a preferred embodiment of the above, the connecting device is configured as five groups of third sliders 20, which are respectively mounted on the top of five groups of fixed blocks 19, and two groups of auxiliary rollers 21 are rotatably arranged on the top of each group of third sliders 20, and slide grooves are arranged on the left, right and middle of the bottom of the placement table 4, and the five groups of fixed blocks 19 slide in the three groups of slide grooves of the placement table 4 respectively; By setting the third slider 20 and the auxiliary roller 21, when the placing table 4 is fine-tuned longitudinally, the placing table 4 slides on the five groups of fixed blocks 19, and when the placing table 4 is fine-tuned transversely, the five groups of fixed blocks 19 drive the placing table 4 to be fine-tuned transversely through the five groups of third sliders 20, so as to facilitate the transverse and longitudinal fine-tuning of the placing table 4.

[0020] As a preferred embodiment of the above embodiment, a mounting groove is provided in the middle of the top of the placing table 4, the transmitter is installed in the mounting groove of the placing table 4, a mounting groove is provided in the middle of the bottom of the strength testing device 3, the receiver is installed in the mounting groove of the strength testing device 3, and the transmitter and the receiver are located in corresponding positions; By turning on the transmitter, if the positions of the transmitter and the receiver correspond, it means that the placement table 4 is consistent with the center of the strength testing device 3. If the receiver cannot receive the signal from the transmitter, it means that the placement table 4 needs to be fine-tuned to facilitate calibration of the placement table 4.

[0021] As a preferred embodiment of the above embodiment, it further includes a prompter 22, which is installed on the left front side of the top of the workbench 1, and the prompter 22 is electrically connected to the receiver; By setting the reminder 22 , when the receiver receives the signal from the transmitter, it will give a reminder through the reminder 22 . At this time, the placement table 4 is in the center position, which is convenient for the staff to calibrate the placement table 4 .

[0022] As a preferred embodiment of the above embodiment, two sets of guide rods 23 are further included, and the two sets of guide rods 23 are respectively installed on the left and right sides of the front end of the placement table 4, and the left and right parts of the vertical plate 11 are both connected to each other and provided with sliding holes, and the two sets of guide rods 23 slide in the two sets of sliding holes of the vertical plate 11; By providing the guide rods 23 , when the placement table 4 is finely adjusted longitudinally, the two groups of guide rods 23 slide on the vertical plate 11 , thereby improving the stability of the placement table 4 .

[0023] As a preferred embodiment of the above, a rubber pad is provided at the inner end of the clamping plate 9; The friction between the clamping plate 9 and the recycled concrete sample can be increased, thereby improving the stability of clamping the recycled concrete sample.

[0024] A device for testing the compressive strength of recycled concrete samples of the present invention, when working, firstly, the recycled concrete sample is placed in the middle of the top of the placing table 4, and the motor 26 is turned on, and the motor 26 drives the first bidirectional screw 5 on the rear side to rotate, and the first bidirectional screw 5 on the rear side drives the first bidirectional screw 5 on the front side to rotate through two sets of pulleys 24 and belts 25, and the two sets of first bidirectional screws 5 are threadedly connected with the four sets of first sliders 7, and the four sets of first sliders 7 drive the two sets of clamping plates 6 to move inward synchronously, and the two sets of clamping plates 6 clamp the recycled concrete sample laterally in the center, and then turn on the two sets of small motors, and the two sets of small motors drive the two sets of second bidirectional screws 8 to rotate, and the two sets of second bidirectional screws 8 are threadedly connected with the four sets of second sliders 10, and the four The second slider 10 drives the four groups of clamps 9 to move inward, and the four groups of clamps 9 clamp the recycled concrete sample in the longitudinal center. The placement table 4 needs to be calibrated after being used for a period of time. The first screw 12 is rotated by the hand wheel 13, and the first screw 12 is threadedly connected to the vertical plate 11. The vertical plate 11 drives the placement table 4 to perform longitudinal fine-tuning. The placement table 4 slides on the five groups of fixed blocks 19, and the handle 17 drives the turning handle 16 to rotate. The turning handle 16 drives the second screw 15 to rotate. The second screw 15 is threadedly connected to the middle fixed block 19. The third slider 20 on the five groups of fixed blocks 19 drives the placement table 4 to fine-tune horizontally. The four outer groups of fixed blocks 19 are slidably connected to the two groups of fixed rods 18, so that the placement table 4 can be calibrated.

[0025] The installation method, connection method or setting method of the recycled concrete sample compressive strength testing device of the present invention are all common mechanical methods, and can be implemented as long as they can achieve their beneficial effects; the indicator 22 and motor 26 of the recycled concrete sample compressive strength testing device of the present invention are purchased on the market, and technicians in the industry only need to install and operate them according to the accompanying instruction manual.

[0026] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A device for testing the compressive strength of recycled concrete samples, characterized in that: The invention comprises a workbench (1), a fixing frame (2), a strength testing device (3), a fine-tuning device and a fixture assembly, wherein the fixing frame (2) is mounted on the top of the workbench (1), the strength testing device (3) is mounted on the top of the fixing frame (2), the fine-tuning device is mounted on the top of the workbench (1), and the fixture assembly is mounted on the fine-tuning device. The fixture assembly comprises a placing table (4), two sets of first bidirectional screws (5), two sets of clamping plates (6), four sets of first slide blocks (7), two sets of second bidirectional screws (8), four sets of clamping plates (9), and four sets of The second slider (10), two groups of pulleys (24), belts (25), a motor (26) and a mounting frame (27), the placement table (4) is connected with the fine-tuning device, the front side and the rear side of the top of the placement table (4) are provided with slide grooves, the two groups of first bidirectional screw rods (5) are rotatably mounted in the two groups of slide grooves of the placement table (4), the four groups of first sliders (7) are respectively mounted on the front side and the rear side of the bottom end of the two groups of clamping plates (6), the four groups of first sliders (7) slide in the two groups of slide grooves of the placement table (4), and the four groups of first sliders ( 7) are connected with threaded holes, the four sets of first sliders (7) are threadedly connected with the two sets of first bidirectional screws (5), the inner ends of the two sets of clamping plates (6) are provided with sliding grooves, the two sets of second bidirectional screws (8) are rotatably installed in the sliding grooves of the two sets of clamping plates (6), the two sets of small motors are respectively installed at the rear ends of the two sets of clamping plates (6), the output ends of the two sets of small motors respectively pass through the rear ends of the two sets of clamping plates (6) and are connected to the rear ends of the two sets of second bidirectional screws (8), the four sets of second sliders (10) are connected to the two sets of second bidirectional screws (8) ), four sets of second slide blocks (10) are respectively mounted on the outer ends of four sets of clamping plates (9), the four sets of clamping plates (9) are slidably connected to the inner ends of the two sets of clamping plates (6), two sets of pulleys (24) are respectively mounted on the right parts of the two sets of first bidirectional screw rods (5), the two sets of pulleys (24) are synchronously driven by belts (25), the motor (26) is connected to the right end of the rear first bidirectional screw rod (5), the motor (26) is mounted on the inner end of the mounting frame (27), and the mounting frame (27) is mounted on the right rear side of the bottom end of the placement table (4).

2. A recycled concrete sample compressive strength testing device as claimed in claim 1, characterized in that: The fine-tuning device comprises a vertical plate (11), a first screw rod (12), a hand wheel (13) and an adjusting device, wherein the vertical plate (11) is mounted on the front side of the top end of the workbench (1), the first screw rod (12) is rotatably mounted on the middle part of the front end of the placement table (4), a threaded hole is arranged in the middle part of the vertical plate (11), the first screw rod (12) is threadedly connected to the vertical plate (11), the hand wheel (13) is mounted on the front end of the first screw rod (12), the adjusting device is mounted on the top end of the workbench (1), and the adjusting device is cooperatively connected to the placement table (4).

3. A recycled concrete sample compressive strength testing device as claimed in claim 2, characterized in that: The adjusting device comprises six sets of fixed seats (14), a second screw rod (15), a rotating handle (16), a handle (17), two sets of fixed rods (18), five sets of fixed blocks (19) and a connecting device. The six sets of fixed seats (14) are respectively mounted on the left and right sides of the top of the workbench (1), the second screw rod (15) is rotatably mounted on the two sets of fixed seats (14) in the middle, the rotating handle (16) is mounted on the right end of the second screw rod (15), and the handle (17) is rotatably mounted below the right end of the rotating handle (16). The two groups of fixing rods (18) are respectively mounted on the two groups of fixing seats (14) on the front side and the two groups of fixing seats (14) on the rear side. The five groups of fixing blocks (19) are connected to the placement table (4) through a connecting device. A threaded hole is provided in the middle of the middle fixing block (19). The middle fixing block (19) is threadedly connected to the second screw rod (15). The four groups of fixing blocks (19) on the outer sides are all connected to sliding holes. The four groups of fixing blocks (19) are respectively slidably connected to the two groups of fixing rods (18).

4. A recycled concrete sample compressive strength testing device as claimed in claim 3, characterized in that: The connecting device is configured as five groups of third sliders (20), the five groups of third sliders (20) are respectively mounted on the top of the five groups of fixed blocks (19), two groups of auxiliary rollers (21) are rotatably arranged on the top of each group of third sliders (20), and slide grooves are arranged on the left side, the right side and the middle of the bottom of the placement table (4), and the five groups of fixed blocks (19) slide in the three groups of slide grooves of the placement table (4) respectively.

5. A recycled concrete sample compressive strength testing device as claimed in claim 4, characterized in that: The placement platform (4) is provided with a mounting groove in the middle of the top end, the transmitter is mounted in the mounting groove of the placement platform (4), the strength testing device (3) is provided with a mounting groove in the middle of the bottom end, the receiver is mounted in the mounting groove of the strength testing device (3), and the transmitter and the receiver are positioned correspondingly.

6. A recycled concrete sample compressive strength testing device as claimed in claim 5, characterized in that: It also includes a prompter (22), which is installed on the left front side of the top of the workbench (1), and the prompter (22) is electrically connected to the receiver.

7. A recycled concrete sample compressive strength testing device as claimed in claim 6, characterized in that: It also includes two groups of guide rods (23), which are respectively installed on the left and right sides of the front end of the placement table (4). The left and right parts of the vertical plate (11) are both connected and provided with sliding holes, and the two groups of guide rods (23) slide in the two groups of sliding holes of the vertical plate (11).

8. A recycled concrete sample compressive strength testing device as claimed in claim 7, characterized in that: A rubber pad is provided at the inner end of the clamping plate (9).

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