Positioning tool for drilling of boom tail of cargo boom

Abstract

The utility model provides a positioning tool for drilling a boom tail of a cargo boom. The positioning tool comprises a bottom plate, a clamping device and a positioning plate, the clamping device and the positioning plate are arranged on the bottom plate corresponding to the two ends of the arm tail respectively, the clamping device comprises a clamping frame, a baffle and a jacking assembly, the clamping frame is oppositely arranged at one end of the bottom plate, the baffle and the jacking assembly are correspondingly arranged on the clamping frame, and one end of the arm tail can be clamped through cooperation of the baffle and the jacking assembly. The baffle can abut against the corresponding outer end face of the arm tail, the positioning plate is correspondingly arranged at the other end of the bottom plate, and a positioning hole is formed in the position, corresponding to the mounting hole, of the positioning plate. According to the positioning tool, a stable foundation is provided through the bottom plate, it is ensured that the positioning tool is firmly clamped on the arm tail through the combined action of the clamping frame, the baffle and the jacking assembly, the accurate position of the other end of the arm tail is ensured through the positioning holes in the positioning plate, follow-up drilling operation is facilitated, and the efficiency and precision of drilling operation are improved.

Description

Technical Field

[0001] The utility model relates to the field of cranes, in particular to a positioning tool for drilling holes at the tail of a crane boom. Background Art

[0002] A crane is a multi-action lifting machine that can lift and transport heavy objects vertically and horizontally within a certain range. It is also called an overhead crane, overhead crane, or crane. Some lifting equipment has an intermittent working characteristic, that is, the corresponding mechanisms for taking materials, moving, and unloading are working alternately in a working cycle. Cranes are becoming more and more widely used in the market. The boom tail is an important structural component of the crane boom, usually made of multiple plate-like parts fixed by riveting and / or welding (such as Figure 1 Assemble it on the boom through the mounting holes.

[0003] Prior art CN202210628320.6 A crane boom tail processing device and processing method thereof, comprising: a top outer ring assembly, a bottom outer ring assembly, a plurality of connecting plates and a plurality of positioning plates, the top outer ring assembly is installed above the bottom outer ring assembly through a plurality of connecting plates, the inner contours of the top outer ring assembly and the bottom outer ring assembly are both in line with the outer contour of the crane boom tail, and are used to position the boom tail to be processed; the bottoms of the plurality of positioning plates are installed on the bottom outer ring assembly, through holes are provided on the top outer ring assembly corresponding to the positions of the positioning plates, the tops of the plurality of positioning plates pass through the corresponding through holes and extend upward, and the plurality of positioning plates are close to the side of the boom tail and abut against the outer contour of the boom tail to be processed; although this solution can improve the processing efficiency and processing accuracy of the crane boom tail, the following problems still exist:

[0004] 1. During the drilling process at the end of the boom, the operator relies on on-site measurement, marking, and then drilling. This method is not only time-consuming, but also prone to human errors, resulting in inaccurate hole positions, affecting subsequent assembly quality and work efficiency.

[0005] 2. During the drilling process, due to the thickness and hardness of the arm tail, if the fixation is not stable enough, it may cause slight displacement or deformation of the arm tail during drilling, thus affecting the accuracy of the hole position. The influence of this unstable factor is particularly obvious during high-speed drilling.

[0006] 3. The existing drilling positioning device is relatively complicated to operate and requires specially trained operators to master it. This means higher training costs and longer learning cycles for enterprises. At the same time, the complex operating process will also affect production efficiency. Utility Model Content

[0007] In view of this, the purpose of the present invention is to provide a positioning tool for drilling holes at the tail of a crane arm, which provides a stable foundation through a base plate, and the clamping device and the positioning plate are respectively located at the two ends of the tail of the arm. The clamping frame, baffle and tightening assembly work together to ensure that one end of the tail of the arm is firmly clamped, reducing the error caused by the movement of the tail of the arm, and the positioning hole on the positioning plate ensures the precise position of the other end of the tail of the arm, which facilitates subsequent drilling operations and improves the efficiency and accuracy of the drilling operation.

[0008] The technical solution adopted by the utility model to solve its technical problems is:

[0009] Provided is a positioning tool for drilling holes at the tail of a crane boom, comprising: a base plate, a clamping device and a positioning plate;

[0010] The clamping device and the positioning plate are respectively arranged on the base plate corresponding to the two ends of the arm tail. The clamping device includes a clamping frame, a baffle and a tightening assembly. The clamping frame is arranged at one end of the base plate. The baffle and the tightening assembly are correspondingly arranged on the clamping frame, and can clamp one end of the arm tail through the cooperation of the baffle and the tightening assembly, and the baffle can abut against the corresponding outer end surface of the arm tail. The positioning plate is correspondingly arranged at the other end of the base plate, and a positioning hole is provided on it at the position corresponding to the mounting hole.

[0011] It should be noted that this solution provides a stable foundation through the base plate, and the clamping device and the positioning plate are respectively located at the two ends of the arm tail. The clamping frame, baffle and tightening assembly work together to ensure that one end of the arm tail is firmly clamped, and the positioning hole on the positioning plate ensures the precise position of the other end of the arm tail, which is convenient for subsequent drilling operations. The clamping frame and the base plate can be made of high-strength materials to give them sufficient rigidity and stability to ensure that the tooling of the arm tail can be stable during the drilling process, and its height and width are set corresponding to the size of the arm tail; the baffle is installed on one side of the clamping frame for close contact with the front end surface of the arm tail to provide lateral limitation, which can prevent the positioning plate at the other end of the base plate from moving sideways when drilling the arm tail; the tightening assembly can adjust the tightening force according to the specific size of the arm tail to ensure the clamping effect while avoiding damage to the arm tail. The contact surface of the tightening assembly can be made of anti-slip material to increase friction and improve the reliability of clamping.

[0012] Preferably, the tightening assembly includes a fixing plate and a tightening screw. The fixing plate is arranged on the clamping frame and is arranged parallel to the baffle. A screw hole is correspondingly provided on the fixing plate, and the tightening screw is arranged in the screw hole.

[0013] It's important to note that the jacking screw rotates within the screw hole on the mounting plate. By rotating the jacking screw, you can adjust its extension, thereby adjusting the pressure on the boom tail. This design not only accommodates boom tails of varying thicknesses but also ensures uniform pressure, preventing displacement or deformation of the boom tail during drilling.

[0014] Preferably, one end of the tightening screw rod close to the inner side surface of the arm tail is in contact with a pad, and the pad is movably arranged on the fixed plate through a connecting rod.

[0015] It should be noted that by having the pad in direct contact with the end of the arm, it is possible to avoid the tightening screw pressing directly on the end of the arm, causing scratches or other damage. Compared with directly using the tightening screw, the pad increases the contact area with the end of the arm, making the pressure distribution more uniform, which helps to improve the stability and safety of clamping and reduce the risk of deformation caused by local stress concentration.

[0016] Preferably, a buffer pad is provided on the surface of the backing plate and the baffle close to the arm tail.

[0017] It should be noted that buffer pads can effectively reduce scratches, indentations, and other damage that may occur when metal parts (such as backing plates and baffles) come into direct contact with the boom tail, especially for boom tail parts that require high surface finishes. Buffer pads are typically made of rubber, plastic, or other high-friction materials, significantly increasing friction with the boom tail surface, thereby improving clamping stability. Furthermore, during the drilling process, especially at high speeds, the boom tail may be subject to certain shocks and vibrations. Buffer pads absorb these shocks and vibrations, reducing damage to the boom tail and tooling, and improving overall stability and safety.

[0018] Preferably, the base plate and the positioning plate are integrally formed.

[0019] It should be noted that the one-piece molding of the base plate and the positioning plate can significantly improve the structural strength and rigidity of the entire tooling, ensuring that no deformation or displacement occurs during the clamping and drilling process; the one-piece molded base plate and positioning plate can ensure that the relative position and size of the two are more precise during the manufacturing process, reduce positioning deviations caused by connection errors, and also reduce connectors and assembly steps, reducing assembly time and labor costs.

[0020] Preferably, the base plate is detachably connected to the positioning plate, the positioning plate is fixedly provided with a locking screw, and the base plate is correspondingly provided with an adjustment hole, and the positioning plate is fixed to the base plate through the cooperation of the adjustment hole and the locking screw.

[0021] It should be noted that the position of the positioning plate can be accurately adjusted through the cooperation of the adjustment hole and the locking screw to ensure the hole position accuracy and consistency of each drilling. If the positioning plate needs to be fine-tuned, the locking screw can be loosened, the position of the positioning plate can be adjusted and then re-fixed. The operation is simple and quick. Through the detachable connection, positioning plates of different specifications can be quickly replaced to adapt to arm tails of different models and sizes. It not only improves the versatility and flexibility of the tooling, but also simplifies the maintenance and replacement process, improves the convenience and safety of operation, and only needs to prepare positioning plates of different specifications, instead of preparing a whole set of tooling for each model of arm tail, which reduces inventory costs.

[0022] Preferably, the adjustment hole on the base plate is a waist-shaped hole arranged along its axial direction, and the positioning plate is adjustably fixed to the base plate through the cooperation between the locking screw and the waist-shaped hole.

[0023] It should be noted that the waist-shaped hole is set along the axial direction, allowing the positioning plate to move axially within a certain range, thereby adapting to arm tails with different lengths or position requirements, and improving the flexibility of the tooling; the operator can easily install and remove the positioning plate quickly through the cooperation of the locking screw and the waist-shaped hole, reducing assembly time and difficulty.

[0024] Preferably, a scale bar is correspondingly provided on the bottom plate on one side of the waist-shaped hole.

[0025] It should be noted that the scale bar provides a clear reference mark. The operator can use the scale bar to accurately adjust the position of the positioning plate to ensure the accuracy and consistency of the hole position each time it is drilled. The scale bar allows the operator to intuitively see the adjustment position of the positioning plate, facilitating quick alignment and adjustment, reducing operation time and difficulty.

[0026] Beneficial effects of the utility model:

[0027] The utility model provides a positioning tool for drilling holes at the tail of a crane boom, which significantly improves the efficiency and accuracy of drilling operations through the ingenious design of the base plate, clamping device and positioning plate; the clamping device includes a clamping frame, a baffle and a tightening assembly to ensure that one end of the boom tail is firmly clamped, reducing the error caused by the movement of the boom tail; the positioning holes on the positioning plate and the scale bar on the base plate ensure the precise position of the other end of the boom tail, improving the accuracy and consistency of the hole position; the base plate and the positioning plate are detachably connected, and the positioning plate can be quickly adjusted and replaced through the cooperation of the locking screw and the waist-shaped hole to adapt to boom tails of different models and sizes, thereby improving the work efficiency. The versatility and flexibility of the tooling; the design of the buffer pad and the pad reduces the direct contact between the metal parts and the arm tail, prevents scratches and deformation, and improves the stability and safety of clamping; the overall structure is made of high-strength materials to ensure the rigidity and stability of the tooling and extend its service life; in addition, the design simplifies the operation process, reduces assembly time and difficulty, improves production efficiency and safety, and reduces maintenance costs; in summary, the utility model not only improves the accuracy and efficiency of drilling operations, but also has high versatility, flexibility and safety, and is very suitable for use in large-scale, high-efficiency processing environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the arm tail of the utility model.

[0029] Figure 2 This is a three-dimensional schematic diagram of a positioning tool for drilling holes at the tail of a crane boom according to Example 1 of the utility model.

[0030] Figure 3 This is a diagram showing the usage status of a positioning tool for drilling holes at the tail of a crane boom according to Example 1 of the utility model.

[0031] Figure 4 This is a schematic diagram of the three-dimensional structure of the clamping device of Example 1 of the present utility model.

[0032] Figure 5 This is a three-dimensional schematic diagram of a positioning tool for drilling holes at the tail of a crane boom according to Example 2 of the utility model.

[0033] Figure 6 This is a diagram showing the usage status of a positioning tool for drilling holes at the tail of a crane boom according to Example 3 of the utility model.

[0034] In the figure: 1. Base plate; 11. Adjustment hole; 2. Clamping device; 21. Clamping frame; 22. Baffle; 23. Tightening assembly; 231. Fixing plate; 232. Tightening screw; 3. Positioning plate; 31. Positioning hole; 32. Locking screw; 4. Pad; 41. Connecting rod; 5. Scale bar.

[0035] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but rather to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] Example 1

[0038] like Figure 1-Figure 4 As shown, a positioning tool for drilling a hole at the end of a boom, comprising: a base plate 1, a clamping device 2 and a positioning plate 3;

[0039] The clamping device 2 and the positioning plate 3 are respectively arranged on the base plate 1 at the two ends of the arm tail. The clamping device 2 includes a clamping frame 21, a baffle 22 and a tightening assembly 23. The clamping frame 21 is arranged at one end of the base plate 1. The baffle 22 and the tightening assembly 23 are correspondingly arranged on the clamping frame 21, and can clamp one end of the arm tail through the cooperation of the baffle 22 and the tightening assembly 23, and the baffle 22 can abut against the corresponding outer end surface of the arm tail. The positioning plate 3 is correspondingly arranged at the other end of the base plate 1, and a positioning hole 31 is provided on it at the position corresponding to the mounting hole.

[0040] The jacking assembly 23 includes a fixing plate 231 and a jacking screw 232. The fixing plate 231 is arranged on the clamping frame 21 and is arranged parallel to the baffle 22. The fixing plate 231 has corresponding screw holes, and the jacking screw 232 is arranged in the screw holes.

[0041] The bottom plate 1 and the positioning plate 3 are integrally formed.

[0042] The working principle and use method of a positioning tool for drilling a hole at the end of a boom of this embodiment:

[0043] The present embodiment provides a positioning tool for drilling holes at the tail of a crane arm, which is in close contact with the front end surface of the tail of the arm through the baffle 22 to provide lateral limitation to prevent the tail of the arm from moving laterally during the drilling process; the tightening screw 232 is rotated to extend and abut against the inner side surface of the tail of the arm, and pressure is applied to the tail of the arm through the tightening component 23 to ensure that one end of the tail of the arm is firmly clamped; the positioning hole 31 on the positioning plate 3 corresponds to the position on the tail of the arm where a hole needs to be drilled, ensuring the precise position of the other end of the tail of the arm; the positioning plate 3 and the base plate 1 are integrally formed to ensure the accuracy of the relative position and size of the two; the positioning hole 31 on the positioning plate 3 corresponds to the position on the tail of the arm where a hole needs to be drilled, ensuring the precise position of the other end of the tail of the arm; through the positioning hole 31, the operator can quickly align the drilling position to ensure the accuracy and consistency of the hole position of each drilling.

[0044] When in use, fix the arm tail on the workbench to ensure that its position is stable; check whether the various components of the positioning tooling are intact and ensure that all components are working normally, place the positioning tooling on the arm tail so that the base plate 1 is located in the space in the middle of the arm tail, the clamping device 2 at one end is clamped on the arm tail, and the positioning plate 3 at the other end is in contact with its upper surface; adjust the position of the positioning tooling so that the baffle 22 at one end is in close contact with the front end face of the arm tail; rotate the tightening screw 232 so that it extends and abuts against the inner side face of the arm tail; continue to rotate the tightening screw 232 until the positioning tooling is firmly clamped to ensure that no displacement occurs during the drilling process; then use the drilling equipment to drill the arm tail according to the position of the positioning hole 31; after the drilling is completed, loosen the tightening screw 232 and remove the positioning tooling; check the quality of the drilling to ensure that the hole position is accurate.

[0045] Example 2

[0046] like Figure 5 and Figure 6 As shown, a positioning tool for drilling a hole at the end of a boom of this embodiment includes: a base plate 1, a clamping device 2 and a positioning plate 3;

[0047] The clamping device 2 and the positioning plate 3 are respectively arranged on the base plate 1 at the two ends of the arm tail. The clamping device 2 includes a clamping frame 21, a baffle 22 and a tightening assembly 23. The clamping frame 21 is arranged at one end of the base plate 1. The baffle 22 and the tightening assembly 23 are correspondingly arranged on the clamping frame 21, and can clamp one end of the arm tail through the cooperation of the baffle 22 and the tightening assembly 23, and the baffle 22 can abut against the corresponding outer end surface of the arm tail. The positioning plate 3 is correspondingly arranged at the other end of the base plate 1, and a positioning hole 31 is provided on it at the position corresponding to the mounting hole.

[0048] The jacking assembly 23 includes a fixing plate 231 and a jacking screw 232. The fixing plate 231 is arranged on the clamping frame 21 and is arranged parallel to the baffle 22. The fixing plate 231 has corresponding screw holes, and the jacking screw 232 is arranged in the screw holes.

[0049] One end of the tightening screw 232 close to the inner side of the arm tail is in contact with a pad 4 , and the pad 4 is movably arranged on the fixed plate 231 via a connecting rod 41 .

[0050] Buffer pads are provided on the surfaces of the backing plate 4 and the baffle 22 close to the arm tail.

[0051] The base plate 1 is detachably connected to the positioning plate 3 , and the positioning plate 3 is fixedly provided with a locking screw 32 . An adjustment hole 11 is correspondingly provided on the base plate 1 , and the positioning plate 3 is fixed to the base plate 1 through the cooperation between the adjustment hole 11 and the locking screw 32 .

[0052] The adjustment hole 11 on the base plate 1 is a waist-shaped hole arranged along its axial direction. The positioning plate 3 is adjustably fixed to the base plate 1 through the cooperation between the locking screw 32 and the waist-shaped hole.

[0053] A scale bar 5 is correspondingly provided on the bottom plate 1 on one side of the waist-shaped hole.

[0054] The working principle and use method of a positioning tool for drilling a hole at the end of a boom of this embodiment:

[0055] This embodiment provides a positioning tool for drilling holes in the tail of a crane arm. The positioning plate 3 and the base plate 1 are connected in a detachable manner, which enables the positioning tool to quickly replace positioning plates 3 of different specifications according to different operating requirements to adapt to different models and sizes of boom tails. Such a design not only improves the versatility and flexibility of the positioning tooling, but also simplifies the maintenance and replacement process, and reduces the company's inventory costs; the pad 4 is movably set on the fixed plate 231 through the connecting rod 41, which not only increases the contact area between the tightening screw 232 and the inner side of the arm tail, reduces local pressure, and avoids damage to the arm tail surface during the clamping process, but also the mobility of the pad 4 can adapt to the shape changes of different parts of the arm tail, thereby improving the clamping effect; a buffer pad is set on the contact surface of the pad 4 and the baffle 22 with the arm tail. The buffer pad is usually made of soft materials such as rubber, which can protect the surface of the arm tail during the clamping process, prevent scratches or indentations caused by hard contact, and at the same time improve the uniform distribution of the clamping force and enhance the clamping effect; the waist-shaped hole cooperates with the locking screw 32 to allow the positioning plate 3 to adjust its position within a certain range, thereby more accurately matching the drilling positions of different arm tails. A scale bar 5 is provided on the bottom plate 1 on one side of the waist-shaped hole, which is convenient for the operator to intuitively read the position information of the positioning plate 3, ensuring that the position of the positioning plate 3 is accurate each time it is installed, thereby improving work efficiency and drilling accuracy.

[0056] When using, first check whether all parts of the positioning tool are intact and ensure that all parts can work normally, especially check whether the tightening screw 232, the pad 4, the buffer pad and other parts are damaged or worn, and replace them if necessary; and according to the specific size of the boom tail to be processed and the drilling requirements, select a suitable positioning plate 3 and install it on the bottom plate 1. If the position of the positioning plate 3 needs to be adjusted, it can be fine-tuned through the locking screw 32 and the waist-shaped hole on the bottom plate 1 to ensure that the positioning hole 31 on the positioning plate 3 accurately corresponds to the position where the hole needs to be drilled on the boom tail; then place the positioning tool On the tail of the arm, the base plate 1 is located in the space in the middle of the tail of the arm, the clamping device 2 at one end is aligned with one end of the tail of the arm to clamp it, and the positioning plate 3 at the other end is fitted with the upper surface of the other end of the tail of the arm; then the tightening screw 232 is rotated, and the pad 4 will move as the tightening screw 232 extends, ensuring good contact with the inner side of the tail of the arm. At the same time, the buffer pad can protect the surface of the tail of the arm from damage until the positioning tool is firmly clamped on the tail of the arm; finally, use the drilling equipment to align the drill bit with the positioning hole 31 on the positioning plate 3 to drill. After the drilling is completed, loosen the tightening screw 232 and take out the positioning tool.

[0057] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is intended only to illustrate the technical solution of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

[0058] In the description of the present invention, it should be understood that the terms "upper", "lower", "upper end", "lower end", "upper surface", "lower surface", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0059] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," and "disposed" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

Claims

1. A positioning tool for drilling holes at the tail of a crane boom, comprising: A base plate (1), a clamping device (2) and a positioning plate (3); characterized in that: The clamping device (2) and the positioning plate (3) are respectively arranged on the base plate (1) at the two ends of the arm tail. The clamping device (2) includes a clamping frame (21), a baffle (22) and a tightening assembly (23). The clamping frame (21) is arranged at one end of the base plate (1). The baffle (22) and the tightening assembly (23) are correspondingly arranged on the clamping frame (21). The baffle (22) and the tightening assembly (23) can clamp one end of the arm tail through the cooperation of the baffle (22) and the tightening assembly (23). The baffle (22) can abut against the outer end surface corresponding to the arm tail. The positioning plate (3) is correspondingly arranged at the other end of the base plate (1), and a positioning hole (31) is provided on it at a position corresponding to the mounting hole.

2. A positioning tool for drilling a hole at the end of a boom as claimed in claim 1, characterized in that: The tightening assembly (23) comprises a fixing plate (231) and a tightening screw (232). The fixing plate (231) is arranged on the clamping frame (21) and is arranged parallel to the baffle (22). A screw hole is correspondingly provided on the fixing plate, and the tightening screw (232) is arranged in the screw hole.

3. A positioning tool for drilling a hole at the end of a boom as claimed in claim 2, characterized in that: One end of the tightening screw (232) close to the inner side surface of the arm tail is in contact with a pad (4), and the pad (4) is movably arranged on the fixed plate (231) via a connecting rod (41).

4. A positioning tool for drilling a hole at the end of a boom as claimed in claim 3, characterized in that: Buffer pads are provided on the surfaces of the pad (4) and the baffle (22) close to the arm tail.

5. The positioning tool for drilling a hole at the end of a boom according to claim 1, characterized in that: The bottom plate (1) and the positioning plate (3) are integrally formed.

6. The positioning tool for drilling a hole at the end of a boom according to claim 1, characterized in that: The base plate (1) is detachably connected to the positioning plate (3); a locking screw (32) is fixedly provided on the positioning plate (3); an adjustment hole (11) is correspondingly provided on the base plate (1); and the positioning plate (3) is fixed to the base plate (1) through the cooperation between the adjustment hole (11) and the locking screw (32).

7. A positioning tool for drilling a hole at the end of a boom as claimed in claim 6, characterized in that: The adjustment hole (11) on the base plate (1) is a waist-shaped hole arranged along its axial direction, and the positioning plate (3) is adjustably fixed to the base plate (1) through the cooperation of the locking screw (32) and the waist-shaped hole.

8. The positioning tool for drilling a hole at the end of a boom according to claim 7, characterized in that: A scale bar (5) is correspondingly provided on the bottom plate (1) on one side of the waist-shaped hole.

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