A photographing device for a masonry drill bit test failure apparatus

Abstract

The utility model belongs to the technical field of detection equipment, concretely relates to a photographing device for mason drill bit test failure equipment, the utility model provides a photographing device for mason drill bit test failure equipment, aims at solving the problem that dust is easy to attach on the industrial camera in the mason drill bit detection equipment in prior art. A photographing device for mason drill bit test failure equipment, including frame, be provided with the dustproof box of closed on the frame, still be provided with the positioning assembly of positioning drill bit and the support assembly of supporting drill bit on the frame, be provided with the image taking assembly of shooting drill bit in the dustproof box, still be provided with transparent plate on the dustproof box, the utility model passes through setting dustproof box of closed, effectively prevents dust from attaching on the industrial camera lens. Because dust is one of the important factors of influencing camera shooting definition, the lens clean can guarantee the drill bit image quality of shooting higher, thereby makes the result of subsequent software analysis more accurate, greatly improves the detection precision.

Description

Technical Field

[0001] This utility model belongs to the field of testing equipment technology, specifically relating to a photographic device for testing the failure of a stone drilling bit. Background Technology

[0002] Stone drill bits need to be tested during use or before leaving the factory. During the testing process, an industrial camera is generally used to take an image of the head, i.e. the cutting edge, of the drill bit, and then the image is analyzed by the corresponding software to determine whether the stone drill bit has failed or is damaged.

[0003] Existing inspection equipment typically includes a main body and an industrial camera fixed to it. The drill bit is mounted on the main body via a positioning assembly. V-blocks are generally installed on the main body; different drill bit sizes are paired with different sized V-blocks. These V-blocks support the drill bit at a specific height, ensuring it is coaxial with the axes of one or more industrial cameras. During inspection, the industrial camera captures an image of the drill bit, which is then analyzed. However, existing industrial cameras are exposed to the elements, making them susceptible to dust accumulation on the lenses, resulting in lower inspection accuracy. Utility Model Content

[0004] This invention provides a photographic device for testing failures of stone drilling bits, aiming to solve the problem of dust easily adhering to industrial cameras in existing stone drilling bit testing equipment.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0006] A photographic device for testing the failure of a stonemason drill bit includes a frame, a closed dustproof box on the frame, a positioning component for positioning the drill bit and a support component for supporting the drill bit on the frame, the positioning component being located between the dustproof box and the support component, an image-capturing component for photographing the drill bit inside the dustproof box, and a transparent plate on the dustproof box, through which the image-capturing component photographs the drill bit on the support component;

[0007] The imaging assembly includes a top imaging industrial camera and a side imaging industrial camera. The axis of the top imaging industrial camera is coaxial with the axis of the drill bit on the support assembly. The side imaging industrial camera is mounted on the frame via a bracket. A focusing assembly is provided between the side imaging industrial camera and the bracket. There are at least three side imaging industrial cameras, which are evenly arranged around the circumference of the top imaging industrial camera. Each side imaging industrial camera corresponds to a focusing assembly, and the focusing assembly drives the side imaging industrial camera to move in a direction closer to or further away from the drill bit.

[0008] A further improved solution: The imaging component further includes a light source, the light emitted by the light source illuminating the drill bit on the support component.

[0009] Based on the above technical solution, the light emitted by the light source directly illuminates the drill bit on the support assembly, providing sufficient and uniform illumination. During the shooting process, sufficient light enables the surface features of the drill bit to be presented more clearly, reducing problems such as image blurring and shadows caused by insufficient or uneven lighting, thereby improving the quality of the captured image and allowing subsequent software analysis to more accurately identify the details and features of the drill bit.

[0010] A further improved solution: The light source is a ring-shaped light emitter, and the light emitted by the ring-shaped light emitter surrounds the drill bit on the support assembly. The light source is mounted on the dustproof box.

[0011] Based on the above technical solution: the light emitted by the ring-shaped emitter surrounds the drill bit on the support assembly. This design allows for uniform illumination of the drill bit from all sides, avoiding the shadows and uneven reflections that occur when light shines from only one direction. This ensures that all parts of the drill bit receive sufficient and consistent illumination, resulting in clearer details in the captured images, improved image quality, and a reliable basis for subsequent accurate analysis of whether the drill bit has failed or is damaged.

[0012] A further improved solution: A support frame is provided on the frame, and the top-mounted industrial camera is mounted on the frame via the support frame.

[0013] Based on the above technical solution, the support frame provides a stable mounting base for the top-mounted industrial camera. During the inspection process, the industrial camera needs to maintain a fixed position and orientation to ensure that its axis is coaxial with the axis of the drill bit on the support assembly during each shot. The robust structure of the support frame effectively prevents the camera from shifting or shaking due to equipment vibration, external collisions, or other factors, thereby ensuring the stability and consistency of the captured images and improving inspection accuracy.

[0014] A further improved solution: The support frame is fixed to the machine frame with bolts, and the top-mounted industrial camera is fixed to the support frame with bolts.

[0015] Based on the above technical solution: Bolt connection is a common and reliable mechanical connection method. The support frame is fixed to the machine frame with bolts, capable of withstanding significant external forces. During the operation of the inspection equipment, even in the event of vibration or impact, the connection between the support frame and the machine frame remains secure, preventing easy loosening or separation, thus providing stable foundation support for the top-mounted industrial camera. Similarly, the top-mounted industrial camera, fixed to the support frame with bolts, ensures that the camera's position remains fixed during shooting, preventing shaking due to equipment operation, thereby guaranteeing the clarity and accuracy of the captured images and improving inspection precision.

[0016] A further improved solution: The side-viewing industrial camera includes a front end with a lens and a rear end opposite to the lens, wherein the distance between the front end and the positioning component is less than the distance between the rear end and the positioning component.

[0017] Based on the above technical solution: the side-viewing industrial camera is positioned at an angle to capture images of the drill bit, with the front end closer to the positioning component and the rear end farther away. This allows the camera lens to better capture detailed features of the drill bit's side, especially key areas near the positioning component, such as the cutting edge. Simultaneously, this angled setup expands the camera's field of view, enabling the acquisition of more comprehensive image information of the drill bit's side, avoiding blind spots caused by poor shooting angles, and improving the overall comprehensiveness of the inspection.

[0018] A further improved solution: the angle between the side-viewing industrial camera and the vertical plane is 15 degrees, the side-viewing industrial camera is mounted on the bracket via the focusing assembly, the cross-sectional shape of the bracket is a regular hexagon, and there are three side-viewing industrial cameras.

[0019] Based on the above technical solution: the side-viewing industrial camera is angled at 15 degrees to the vertical plane; this specific angle is carefully designed. For inspection objects like drill bits, the 15-degree tilt angle allows the camera to capture images of the drill bit's side from a more suitable perspective. It clearly presents key features of the drill bit's side, such as the wear condition of the cutting edge and the shape of the helical grooves, while avoiding image distortion or incomplete capture of critical areas due to excessively large or small angles. This provides high-quality image data for subsequent accurate analysis of whether the drill bit has failed or is damaged.

[0020] A further improved solution: The focusing assembly includes a fixed base fixed to the bracket and a sliding base slidably connected to the fixed base. The side-viewing industrial camera is fixed to the sliding base. A lead screw is rotatably connected to the fixed base. The sliding base is provided with a screw hole that mates with the lead screw. The fixed base is also provided with a guide rail. The sliding base is provided with a groove that mates with the guide rail. The fixed base is also provided with a first motor that drives the lead screw.

[0021] Based on the above technical solution: the focusing assembly is securely mounted on the bracket via a fixed base, providing a stable foundation for the entire focusing structure. The sliding base is slidably connected to the fixed base, and the side-image industrial camera is fixed on the sliding base. This design allows the camera to move along the fixed base. The lead screw on the fixed base engages with the screw hole on the sliding base. When the first motor drives the lead screw to rotate, due to the threaded transmission relationship between the screw hole and the lead screw, the sliding base will move linearly along the axis of the lead screw. Simultaneously, the guide rail on the fixed base engages with the sliding groove on the sliding base, guiding and limiting the direction of movement of the sliding base, ensuring that the sliding base can only move smoothly along the direction of the guide rail without deviation or wobbling. Through this precise mechanical transmission and guiding structure, the operator can very accurately control the position of the side-image industrial camera, thereby achieving precise focusing and ensuring clear and sharp images.

[0022] A further improved solution: The positioning component includes a positioning plate, and the positioning component also includes a driver for driving the positioning plate. The positioning plate is slidably connected to the frame along the diameter direction of the drill bit on the support component. The positioning plate includes a positioning station that contacts the drill bit to position the axial position of the drill bit and a clearance station that is offset from the drill bit to prevent the positioning plate from interfering with the image acquisition component. The driver drives the positioning plate to move between the positioning station and the clearance station. The driver includes a lead screw rotatably connected to the frame. A mounting base is slidably connected to the frame. The positioning plate is disposed on the mounting base. The mounting base is provided with a threaded hole that mates with the lead screw. A second motor that drives the lead screw is also disposed on the frame. A track is disposed on the frame. A guide groove that mates with the track is disposed on the mounting base.

[0023] Based on the above technical solution: Under the action of the driver, the positioning plate in the positioning assembly can slide along the diameter direction of the drill bit on the support assembly on the frame. When the positioning plate is in the positioning position, it contacts the drill bit, which can accurately determine the axial position of the drill bit. This is crucial for subsequent inspection work, because only when the axial position of the drill bit is accurate can the imaging components such as the side-mounted industrial camera acquire images that accurately reflect the state of the drill bit, ensuring that the inspection results can truly reflect whether the drill bit has failed or is damaged, and providing a reliable basis for the quality assessment of the drill bit.

[0024] A further improved solution: The support component includes a pad fixed to the frame, a V-shaped block provided on the pad, the V-shaped block being inserted into the pad, a plug provided on the V-shaped block, and a slot provided on the pad to cooperate with the plug. The V-shaped block and the plug are an integral structure.

[0025] Based on the above technical solution: the support assembly uses pads fixed to the frame as the basic support structure, providing a stable foundation for the entire support system. The V-blocks on the pads are key components that directly contact the drill bit. The unique V-groove design of the V-blocks can well adapt to the cylindrical shape of the drill bit. When the drill bit is placed on the V-block, the two inclined surfaces of the V-groove can constrain and support the drill bit from two directions, ensuring a relatively stable position for the drill bit in both the axial and radial directions. This reduces the shaking and displacement of the drill bit during the inspection process, providing stable conditions for subsequent positioning and imaging operations, and ensuring the accuracy of the inspection results.

[0026] The beneficial effects of this utility model are as follows:

[0027] This invention effectively prevents dust from adhering to the lens of an industrial camera by using a sealed dustproof box. Since dust is a significant factor affecting the clarity of camera images, a clean lens ensures higher quality drill bit images, leading to more accurate software analysis and significantly improved detection precision.

[0028] The imaging assembly includes a top imaging industrial camera and at least three side imaging industrial cameras evenly arranged along its circumference. The top camera is coaxial with the drill bit axis, enabling precise imaging of the top of the drill bit; the side cameras capture images of the drill bit's sides from different angles, comprehensively acquiring image information from all parts of the drill bit, avoiding blind spots, and more accurately determining whether the drill bit has failed or is damaged.

[0029] A focusing assembly is installed between the side-viewing industrial camera and the support, and the focusing assembly corresponds one-to-one with the side camera, which can drive the side camera to move in a direction closer to or further away from the drill bit. This design allows the side camera to be focused according to actual inspection needs to obtain the clearest image, enhancing the equipment's adaptability to different drill bit sizes. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For users of ordinary skills in the art, other related drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of a photographic device for testing the failure of a stone drilling bit, according to this utility model.

[0032] Figure 2 This is a front view of the internal structure of a photographic device for testing the failure of a stone drilling bit, according to this utility model.

[0033] Figure 3 This is a schematic diagram of the internal structure of a photographic device for testing the failure of a stone drilling bit, according to this utility model.

[0034] Explanation of the labels in the diagram:

[0035] 1-Dustproof box; 2-Positioning assembly; 3-Support assembly; 4-Transparent plate; 5-Top imaging industrial camera; 6-Side imaging industrial camera; 7-Focusing assembly; 8-Light source; 9-Support frame; 10-Bracket; 11-Fixed seat; 12-Sliding seat; 13-Positioning plate; 14-Driver; 15-Padded block; 16-V-block. Detailed Implementation

[0036] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present utility model and are not intended to limit the present utility model. All other embodiments obtained by users of the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0037] refer to Figures 1 to 3 A photographic device for testing the failure of a stonemason drill bit includes a frame, a closed dustproof box 1 on the frame, a positioning component 2 for positioning the drill bit and a support component 3 for supporting the drill bit on the frame, the positioning component 2 being located between the dustproof box 1 and the support component 3, an image-capturing component for photographing the drill bit inside the dustproof box 1, and a transparent plate 4 on the dustproof box 1, through which the image-capturing component photographs the drill bit on the support component 3;

[0038] The imaging assembly includes a top imaging industrial camera 5 and a side imaging industrial camera 6. The axis of the top imaging industrial camera 5 is coaxial with the axis of the drill bit on the support assembly 3. The side imaging industrial camera 6 is mounted on the frame via a bracket 10. A focusing assembly 7 is provided between the side imaging industrial camera 6 and the bracket 10. There are at least three side imaging industrial cameras 6, which are evenly arranged around the circumference of the top imaging industrial camera 5. Each side imaging industrial camera 6 corresponds to a focusing assembly 7, and the focusing assembly 7 drives the side imaging industrial camera 6 to move in a direction closer to or further away from the drill bit.

[0039] Specifically, the imaging component also includes a light source 8, which emits light that illuminates the drill bit on the support component 3. The light source 8 is a ring-shaped emitter, and the light emitted by the ring-shaped emitter surrounds the drill bit on the support component 3. The light source 8 is mounted on the dustproof box 1. Mounting the ring-shaped emitter on the dustproof box 1 makes full use of the space within the dustproof box 1, without occupying excessive space on the frame, making the entire inspection equipment structure more compact. At the same time, this layout facilitates unified management and maintenance of the light source 8. When the light source 8 malfunctions or needs adjustment, operators can more easily perform related operations on the dustproof box 1, improving the maintainability of the equipment. Because the ring-shaped emitter is positioned around the drill bit, regardless of the drill bit's size, as long as it is placed on the support component 3, the ring-shaped emitter can evenly illuminate it from all sides. This characteristic allows the inspection equipment to adapt to the inspection needs of stonemasonry drill bits of different sizes and shapes, expanding the equipment's application range and improving its versatility.

[0040] The frame is equipped with a support frame 9, and the top-viewing industrial camera 5 is mounted on the frame via the support frame 9. The support frame 9 is fixed to the frame with bolts, and the top-viewing industrial camera is fixed to the support frame 9 with bolts. The side-viewing industrial camera 6 includes a front end with a lens and a rear end opposite to the lens. The distance between the front end and the positioning component 2 is less than the distance between the rear end and the positioning component 2. The side-viewing industrial camera 6 forms an angle of 15 degrees with the vertical plane. The side-viewing industrial camera 6 is mounted on the bracket 10 via the focusing component 7. The bracket 10 has a regular hexagonal cross-section, and there are three side-viewing industrial cameras 6. The focusing assembly 7 includes a fixed base 11 fixed to the bracket 10 and a sliding base 12 slidably connected to the fixed base 11. The side-image industrial camera 6 is fixed to the sliding base 12. A lead screw is rotatably connected to the fixed base 11. The sliding base 12 has a screw hole that mates with the lead screw. The fixed base 11 also has a guide rail, and the sliding base 12 has a groove that mates with the guide rail. A first motor that drives the lead screw is also mounted on the fixed base 11. The lead screw drive features high transmission accuracy and smooth movement. Driven by the first motor, the lead screw can rotate evenly, causing the sliding base 12 to move smoothly without sudden jumps or jamming. The cooperation of the guide rail and the groove further enhances the stability of the sliding base 12's movement and reduces movement irregularities caused by friction or external interference. This stable and reliable focusing process ensures that the side-image industrial camera 6 can accurately adjust to the appropriate focal length in different detection scenarios, guaranteeing high-quality image capture. The primary motor enables automated control of the focusing process. Operators simply send commands to the primary motor via the control system, and the motor drives the lead screw to rotate according to a preset program, thereby focusing the sliding seat 12 and the side-mounted industrial camera 6. Compared to manual focusing, automated focusing is more convenient and efficient, significantly reducing focusing time and improving inspection efficiency. Especially when multiple drill bits need to be inspected continuously, the automated focusing function can quickly and accurately adjust the camera to the appropriate focal length, reducing errors and labor intensity associated with manual operation.

[0041] Wherein: the positioning component 2 includes a positioning plate 13, and the positioning component 2 also includes a driver 14 for driving the positioning plate 13. The positioning plate 13 is slidably connected to the frame along the diameter direction of the drill bit on the support component 3. The positioning plate 13 includes a positioning station that contacts the drill bit to position the axial position of the drill bit and a clearance station that is offset from the drill bit to prevent the positioning plate 13 from interfering with the image acquisition component. The driver 14 drives the positioning plate 13 to move between the positioning station and the clearance station. The driver 14 includes a lead screw rotatably connected to the frame. A mounting base is slidably connected to the frame. The positioning plate 13 is disposed on the mounting base. The mounting base is provided with a threaded hole that mates with the lead screw. A second motor that drives the lead screw is also disposed on the frame. A track is disposed on the frame. A guide groove that mates with the track is disposed on the mounting base. The support component 3 includes a pad 15 fixed to the frame, a V-shaped block 16 disposed on the pad 15, the V-shaped block 16 being inserted into the pad 15, and an insert block disposed on the V-shaped block 16. The pad 15 has a slot that mates with the insert block, and the V-shaped block 16 and the insert block are an integral structure. Because the V-groove of the V-shaped block 16 has a precise geometric shape and size, when the drill bit is placed in the V-groove, the drill bit's axis can be automatically positioned at the center of the V-groove, achieving precise drill bit positioning. This positioning method does not require complex positioning devices or cumbersome adjustment processes; relying on the geometric characteristics of the V-groove, the drill bit can be quickly and accurately positioned in the appropriate location. This provides a good foundation for the subsequent positioning component 2 to position the drill bit's axial position and for the imaging component to acquire images of the drill bit, helping to improve the detection accuracy and reliability of the entire detection system. The positioning plate 13 is equipped with a clearance station. When positioning is not required or the imaging component is performing an image acquisition operation, the driver 14 drives the positioning plate 13 to move to the clearance station, thus displacing it from the drill bit. This prevents the positioning plate 13 from obstructing the drill bit or interfering with the imaging component's shooting angle, ensuring that the imaging component can clearly capture all parts of the drill bit, obtain complete and accurate image information, and improve the comprehensiveness and accuracy of the inspection.

[0042] The working principle of this embodiment:

[0043] The stonemason drill bit to be inspected is placed on the support component 3 on the frame, and the drill bit is positioned using the positioning component 2, providing a basis for accurate subsequent imaging and inspection.

[0044] Because the frame is equipped with a sealed dustproof box 1, the image acquisition components (including the top-viewing industrial camera 5 and the side-viewing industrial camera 6) are located inside the dustproof box 1. During shooting, light passes through the transparent plate 4 on the dustproof box 1, allowing the image acquisition components to clearly capture the image of the drill bit on the support assembly 3. The dustproof box 1 serves to isolate dust and ensure that the camera lens is not affected by dust.

[0045] The top-viewing industrial camera 5, with its axis coaxial with the drill bit axis, can directly capture images of the top of the drill bit. The side-viewing industrial camera 6 is mounted on the frame via a bracket 10. During the inspection process, according to the specifications of the drill bit and the inspection requirements, the focusing assembly 7 drives the side-viewing industrial camera 6 to move in a direction closer to or further away from the drill bit, adjusting the focus so that each side camera can capture a clear image of the drill bit's side.

[0046] After acquiring images of the top and sides of the drill bit, the image acquisition component transmits these images to the corresponding software for analysis. The software performs feature extraction and comparison operations on the images to determine whether the drill bit has failed or is damaged, and provides the detection results.

[0047] This utility model is not limited to the above-mentioned optional embodiments. Under the premise of non-contradiction, the various solutions can be combined arbitrarily. Anyone can derive other forms of products under the guidance of this utility model. However, no matter what changes are made in their shape or structure, all technical solutions that fall within the scope of the claims of this utility model are within the protection scope of this utility model.

Claims

1. A photographic device for testing the failure of a stonemason's drill bit, characterized in that: The device includes a frame, on which a closed dustproof box is installed. The frame also includes a positioning component for positioning the drill bit and a support component for supporting the drill bit. The positioning component is located between the dustproof box and the support component. Inside the dustproof box, an image-capturing component for capturing images of the drill bit is installed. A transparent plate is also installed on the dustproof box. The image-capturing component captures images of the drill bit on the support component through the transparent plate. The imaging assembly includes a top imaging industrial camera and a side imaging industrial camera. The axis of the top imaging industrial camera is coaxial with the axis of the drill bit on the support assembly. The side imaging industrial camera is mounted on the frame via a bracket. A focusing assembly is provided between the side imaging industrial camera and the bracket. There are at least three side imaging industrial cameras, which are evenly arranged around the circumference of the top imaging industrial camera. Each side imaging industrial camera corresponds to a focusing assembly, and the focusing assembly drives the side imaging industrial camera to move in a direction closer to or further away from the drill bit.

2. The photographic device for testing failure of a stonemason's drill bit according to claim 1, characterized in that: The imaging assembly also includes a light source, the light emitted by which illuminates the drill bit on the support assembly.

3. The photographic device for testing failure of a stonemason's drill bit according to claim 2, characterized in that: The light source is a ring-shaped light emitter, and the light emitted by the ring-shaped light emitter surrounds the drill bit on the support assembly. The light source is mounted on the dustproof box.

4. The photographic device for testing failure of a stonemason's drill bit according to claim 1, characterized in that: A support frame is provided on the frame, and the top-viewing industrial camera is mounted on the frame via the support frame.

5. The photographic device for testing failure of a stonemason's drill bit according to claim 4, characterized in that: The support frame is fixed to the machine frame by bolts, and the top-mounted industrial camera is fixed to the support frame by bolts.

6. The photographic device for testing failure of a stonemason's drill bit according to claim 1, characterized in that: The side-view industrial camera includes a front end with a lens and a rear end opposite the lens, wherein the distance between the front end and the positioning component is less than the distance between the rear end and the positioning component.

7. The photographic device for testing failure of a stonemason's drill bit according to claim 6, characterized in that: The side-viewing industrial camera has an angle of 15 degrees with the vertical plane. The side-viewing industrial camera is mounted on the bracket via the focusing assembly. The bracket has a regular hexagonal cross-sectional shape. There are three side-viewing industrial cameras.

8. The photographic device for testing failure of a stonemason's drill bit according to claim 7, characterized in that: The focusing assembly includes a fixed base fixed to the bracket and a sliding base slidably connected to the fixed base. The side-viewing industrial camera is fixed to the sliding base. A lead screw is rotatably connected to the fixed base. The sliding base is provided with a screw hole that mates with the lead screw. The fixed base is also provided with a guide rail. The sliding base is provided with a groove that mates with the guide rail. The fixed base is also provided with a first motor that drives the lead screw.

9. The photographic device for testing failure of a stonemason's drill bit according to claim 1, characterized in that: The positioning assembly includes a positioning plate and a driver for driving the positioning plate. The positioning plate is slidably connected to the frame along the diameter direction of the drill bit on the support assembly. The positioning plate includes a positioning station that contacts the drill bit to position the axial position of the drill bit and a clearance station that is offset from the drill bit to prevent the positioning plate from interfering with the image acquisition assembly. The driver drives the positioning plate to move between the positioning station and the clearance station. The driver includes a lead screw rotatably connected to the frame. A mounting base is slidably connected to the frame. The positioning plate is disposed on the mounting base. The mounting base is provided with a threaded hole that mates with the lead screw. A second motor that drives the lead screw is also disposed on the frame. A track is disposed on the frame. A guide groove that mates with the track is disposed on the mounting base.

10. The photographic device for testing failure of a stonemason's drill bit according to claim 1, characterized in that: The support assembly includes a pad fixed to the frame, a V-shaped block provided on the pad, the V-shaped block being inserted into the pad, a plug provided on the V-shaped block, and a slot provided on the pad to mate with the plug. The V-shaped block and the plug are an integral structure.

Images