Perforator

Abstract

To provide a piercing machine which can prevent a spindle from decentering when a lower surface of a pipe is pierced.SOLUTION: In a piercing machine 1 of the invention, when a knob 7 is rotated, a compression spring 25 causes a plunger tip 23a to protrude in an inner direction relative to an inner peripheral surface 2c of an underbody 2b and the plunger tip 23a contacts with a movement stop part 10. The action restricts the movement stop part 10 from moving. Thus, the movement stop part 10 is prevented from falling due to its self-weight when a lower surface of a pipe P is pierced.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a drilling machine for drilling pipes.

Background Art

[0002] Conventionally, a drilling machine is known that generates a plurality of rotation driving forces that are driven independently of each other, and outputs the rotation driving forces generated by each of the plurality of motors on the same axis (for example, Patent Document 1). Such a drilling machine is formed with a first screw portion having a predetermined pitch centered on the axis, and a first member that rotates around the axis based on the rotation driving force output from the motor, and a second screw portion that engages with the first screw portion. A second member that rotates around the axis based on the rotation driving force output from another motor, and controls the motor according to the positional relationship between the pipe and the cutting tool. Based on these relative rotational movements and the pitch of the screw, the feed pitch is determined each time the cutting tool makes one rotation. Thereby, while suppressing the increase in the size of the apparatus, the rotational speed and the feed speed of the cutting tool can be controlled respectively.

[0003] Further, in the drilling machine disclosed in Patent Document 1, a movement restraining portion is provided on the outer periphery of the spindle. By providing this movement restraining portion, it is possible to prevent the core deflection of the spindle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventional drilling machines, including the drilling machine disclosed in Patent Document 1, are generally used for branch work on pipes supported on the ground or underground. Here, when drilling the lower surface of a pipe using the drilling machine disclosed in Patent Document 1, there was a problem that the movement restraint portion would fall due to its own weight, and it was impossible to prevent the core deflection of the spindle.

[0006] In view of such problems, an object of the present invention is to provide a drilling machine capable of preventing the core deflection of a spindle when drilling the lower surface of a pipe.

Means for Solving the Problems

[0007] In order to solve such problems, a drilling machine according to the present invention is a drilling machine capable of drilling the lower surface of a pipe, A body having a top body and an underbody, a spindle to which a cutter is attached, inside the underbody, attached to the outer periphery of the spindle, the a movement restraint portion for preventing the core deflection of the spindle, and a movement restraint stopper for preventing the movement restraint portion from falling due to its own weight when drilling the lower surface of the pipe, and is characterized by including falling movement the above. , the movement stopper is displaceable between a lock position where the falling movement of the movement restricting portion is restricted and a free position where the falling movement of the movement restricting portion is not restricted, and further includes an operation portion for switching the position of the movement stopper between the lock position and the free position This is the feature.

[0008] Further, in the drilling machine according to the present invention, the movement restraint stopper is displaceable between a lock position where the movement of the movement restraint portion is restricted and a free position where the movement of the movement restraint portion is not restricted, and further includes an operation portion for switching the position of the movement restraint stopper between the lock position and the free position. This is the feature.

[0009] Further, in the drilling machine according to the present invention, the movement restraint stopper includes a plunger that abuts on the movement restraint portion at the lock position, and a biasing member that biases the plunger when the operation portion is operated. This is the feature.

[0010] Also, in the drilling machine according to the present invention, the movement stop stopper includes a rod that presses the movement stop portion, a nut attached to the rod, and a male screw into which the nut is tightened. By pushing in the rod and tightening the nut onto the male screw, it is characterized in that the movement stop portion is prevented from falling by its own weight.

Effects of the Invention

[0011] According to the present invention, it is possible to provide a drilling machine capable of preventing the core deviation of the spindle when drilling the lower surface of a pipe.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Modes for Carrying Out the Invention

[0013] (First Embodiment) Hereinafter, the first embodiment of the present invention will be specifically described with reference to the drawings.

[0014] (External view of the drilling machine 1) First, with reference to FIG. 1, the external view of the drilling machine 1 will be described.

[0015] The drilling machine 1 includes a cylindrical body 2 having a length in the vertical direction, and a spindle 3 to which a cutter 17 described later is attached. Here, the body 2 is composed of a top body 2a and a hollow underbody 2b provided below the top body 2a. Further, the spindle 3 includes a head 3a, a hexagonal portion 3b, a tip portion 3c, and a tip groove portion 3d.

[0016] The drilling machine 1 also includes a feed handle 4 that can rotate in the release direction and the drilling direction, a purge port coupler 5 for checking the airtight performance of the drilling machine 1 by applying pressure, a lock position where the movement of a movement stop stopper 15 described later is restricted, and a knob 7 that switches between a free position where the movement of the movement stop stopper 15 described later is not restricted.

[0017] (Cross-sectional view of the drilling machine 1) Next, with reference to FIG. 2, the partial cross-sectional view of the drilling machine 1 will be described.

[0018] As shown in FIG. 2(A), the drilling machine 1 is provided with a power switch 8 for switching ON / OFF of the power supply of the drilling machine 1 and a power plug 9. Inside the underbody 2b and on the outer periphery of the spindle 3, a movement stop portion 10 is provided. Here, the outer peripheral surface of the movement stop portion 10 is in contact with the inner peripheral surface 2c of the underbody 2b.

[0019] As shown in Fig. 2(B), the movement stopper 10 includes a movement stop ring 11 that prevents the spindle 3 from wobbling during drilling, a ball plunger 12 incorporated in the inner diameter of the movement stop ring 11, an O-ring 13 that elastically cushions the impact when the movement stopper 10 and the inner peripheral surface 2c of the underbody 2b collide when the spindle 3 is pulled up, and a dust seal 14 made of an elastic body (e.g., urethane rubber). Further, the drilling machine 1 includes a movement stop stopper 15 that prevents the movement stopper 10 from falling due to its own weight. The dust seal 14 includes a storage recess 14a for storing chips generated when the pipe P described later is drilled, and a convex portion 14b that abuts against the inner peripheral surface 2c of the underbody 2b.

[0020] Also, as shown in Fig. 2(B), the movement stopper 10 includes a vent hole 29 that is a passage for discharging the gas inside the drilling machine 1 to the outside of the drilling machine 1 and taking in the air outside the drilling machine 1 into the inside of the drilling machine 1, and a mesh portion 30 for preventing chips described later from entering the inside of the drilling machine 1 from the vent hole 29.

[0021] (Movement stop stopper 15) Next, the movement stop stopper 15 will be described with reference to Figs. 3 to 4. Fig. 3 is an external perspective view of the movement stop stopper 15, and Fig. 4 is a cross-sectional view of the movement stop stopper 15.

[0022] As shown in Fig. 3, the movement stop stopper 15 is connected to the knob 7 and includes a casing 20. The casing 20 is provided with a first display portion 21 and a second display portion 22. Characters indicating the lock position are displayed on the first display portion 21, and characters indicating the free position are displayed on the second display portion 22.

[0023] Further, a positioning line 7a is engraved on the knob 7. When the knob 7 is rotated and the positioning line 7a faces in the free direction (the direction of arrow α), the movement stopper 15 is in the free position. On the other hand, when the knob 7 is rotated and the positioning line 7a faces in the lock direction (the direction of arrow β), the movement stopper 15 is in the lock position.

[0024] Here, a screw hole H is drilled in the movement stopper 15. Then, by inserting and screwing a screw (not shown) into the screw hole H, the movement stopper 15 is attached to the underbody 2b.

[0025] As shown in FIG. 4, the movement stopper 15 includes a plunger 23 that abuts against the movement stop portion 10, a plunger holder 24 that holds the plunger 23, a compression spring 25 that compresses the plunger 23, and an airtight member 26 that blocks the entry of fluid (e.g., gas). Further, parallel pins 27 are attached to the outer periphery of the plunger 23, and the casing 20 is provided with a contact wall 28 that contacts the parallel pins 27.

[0026] FIG. 4(A) is a cross-sectional view when the movement stopper 15 is in the free position. At this time, the compression spring 25 is in a compressed state, and the tip 23a of the plunger is located outside the inner peripheral surface 2c of the underbody 2b. At this time, the parallel pins 27 are not in contact with the contact wall 28. As a result, the tip 23a of the plunger is not in contact with the movement stop portion 10, so the movement of the movement stop portion 10 is allowed.

[0027] FIG. 4(B) is a cross-sectional view when the movement stopper 15 is in the locked position. Specifically, when the knob 7 is rotated in the state of FIG. 4(A) and the positioning line 7a is displaced from the free direction to the locking direction, the compression spring 25 is displaced from the compressed state to the uncompressed state, and the parallel pin 27 moves until it contacts the contact wall 28, and the plunger tip 23a protrudes inward from the inner peripheral surface 2c of the underbody 2b. As a result, the plunger tip 23a contacts the movement stopper 10, and the movement of the movement stopper 10 is restricted. Therefore, when drilling the lower surface of the pipe P described later, the movement stopper 10 is prevented from falling by its own weight.

[0028] (Procedure for Preparation of Drilling of Drilling Machine 1) Next, with reference to FIG. 5, the procedure for preparing for drilling of the drilling machine 1 will be described.

[0029] First, as shown in FIG. 5(A), the center drill 18 is inserted into the cutter 17 for attachment, and the cutter 17 with the center drill 18 attached is attached to the tip 3c of the spindle 3.

[0030] Next, as shown in FIG. 5(B), after confirming that the movement stopper 15 is in the free position by checking the position of the knob 7, the clutch (not shown) installed in the drilling machine 1 is released. Then, the spindle 3 is pulled up to the uppermost position in the direction of arrow A, and the cutter 17 is housed inside the inner peripheral surface 2c of the underbody 2b.

[0031] Next, as shown in FIG. 5(C), the spindle stopper 16 is inserted, and after confirming that the spindle 3 and the movement stopper ring 11 have been surely pulled up to the uppermost position, the drilling machine 1 is attached to the pipe P described later.

[0032] Next, as shown in FIG. 5(D), while maintaining the feed handle 4 in the release direction, the hexagonal portion 3b of the spindle 3 is aligned and pushed in the direction of arrow B, and at the same time, the tip groove portion 3d of the spindle 3 and the ball plunger 12 are fitted together, so that the movement stop ring 11 is pushed out to the foremost surface of the underbody 2b, and the movement stop stopper 15 is set from the free position to the lock position by rotating the knob 7. At this time, it is advisable to check the airtightness of the punching machine 1 from the purge port coupler 5.

[0033] Here, the reason for pushing out the movement stop ring 11 to the foremost surface of the underbody 2b is that it is better for the movement stop portion 10 to be close to the punching target from the viewpoint of preventing the core deviation of the spindle 3, so as to maintain the movement stop portion 10 at this position during punching.

[0034] Next, as shown in FIG. 5(E), rotate the feed handle 4 in the punching direction and confirm that the spindle 3 interlocks. Then, rotate the feed handle 4 in the punching direction to lower the center drill 18 to the pipe surface of the pipe P described later.

[0035] (Punching procedure of the punching machine 1) Next, the punching procedure of the punching machine 1 will be described with reference to FIG. 6.

[0036] First, as shown in FIG. 6(A), with the power plug 9 inserted into an outlet (not shown), operate the power switch 8 to turn it ON.

[0037] Next, as shown in FIG. 6(B), place the center drill 18 against the lower surface of the pipe P and punch by rotating the feed handle 4 in the punching direction. At this time, since the movement stop stopper 15 is in the lock position, the movement stop portion 10 is prevented from falling by its own weight.

[0038] Next, as shown in FIG. 6(C), when the punching using the punching machine 1 is completed, operate the power switch 8 to turn it OFF and remove the power plug 9 to complete the punching operation.

[0039] (Removal procedure of the cutter 17) Next, with reference to FIG. 7, the removal procedure of the cutter 17 will be described.

[0040] First, as shown in FIG. 7(A), by rotating the knob 7, the movement lock stopper 15 is moved from the locked position to the free position. As a result, the movement restriction of the movement stop portion 10 in the direction of the tip portion 3c is released. Then, the feed handle 4 is rotated in the release direction to pull up the spindle 3, and the closing confirmation cover 19 is fitted to the spindle 3. At this time, a purge operation for purging the gas between the purge port coupler 5 and the drilling machine 1 may be performed.

[0041] Next, as shown in FIG. 7(B), the drilling machine 1 is removed from the pipe using a predetermined jig. Then, the cutter 17, the center drill 18, and a section of the pipe P are removed using a predetermined jig. After that, it is advisable to remove and clean the chips such as the drilling machine 1 and the movement lock ring 11.

[0042] (Second Embodiment) The second embodiment of the present invention will be specifically described with reference to the drawings using FIGS. 8 to 11. In the second embodiment, the description of the same points as in the first embodiment may be omitted.

[0043] (External View of the Large Drilling Machine 40 in the Second Embodiment) First, with reference to FIG. 8, the external view of the large drilling machine 40 in the second embodiment will be described.

[0044] The large drilling machine 40 has a larger size compared to the drilling machine 1 in the first embodiment, but is common in that it drills the pipe P. Further, the large drilling machine 40 includes a feed clutch 31 that is displaced between a set state and a released state, a rotation clutch knob 32 that is operated when automatically feeding and automatically retracting the spindle 3, and a stop stopper 33 that is displaced between an open state and a closed state. Note that the large drilling machine 40 in the second embodiment differs in that the hexagonal portion 3b of the spindle 3 in the first embodiment is an octagonal portion 3e, the shape of the tip portion 3c of the spindle 3 is different, and the tip groove portion 3d is a rounded portion 3f.

[0045] Here, the feed clutch 31 includes a cam cap 31a that is operated when moving the half nut fixing ring 31b, a half nut fixing ring 31b that meshes with the octagonal portion 3e, and a half nut base 31c provided below the half nut fixing ring 31b. The feed clutch 31 has a half nut (not shown) and a feed clutch spring (not shown) installed inside. Specifically, the half nut is installed inside the half nut fixing ring 31b and the half nut base 31c, and the feed clutch spring is installed inside the half nut base 31c. This half nut is interlocked with the half nut fixing ring 31b by the feed clutch spring. Also, the anti-rotation stopper 33 includes a rod 33a that presses an anti-rotation portion 34 described later, a nut 33b attached to the rod 33a, and a male screw 33c into which the nut 33b is tightened.

[0046] (Set state and release state of the feed clutch 31) Next, with reference to FIG. 9, the set state and release state of the feed clutch 31 will be described.

[0047] FIG. 9(A) shows the feed clutch 31 in the set state. In the set state, the half nut fixing ring 31b is in contact with the half nut base 31c. Here, when the cam cap 31a is rotated with the half nut fixing ring 31b pulled, the half nut fixing ring 31b separates from the half nut base 31c and changes from the set state to the release state. In the release state, since the half nut and the octagonal portion 3e of the spindle 3 do not mesh, the spindle 3 can be moved in the vertical direction.

[0048] Figure 9(B) shows the release clutch 31 in the released state. In the released state, the half nut fixing ring 31b is not in contact with the half nut base 31c. Here, when the cam cap 31a is rotated, the half nut fixing ring 31b moves toward the half nut base 31c by a spring (not shown), so that the half nut fixing ring 31b comes into contact with the half nut base 31c and changes from the released state to the set state. In the set state, the feed clutch spring biases the half nut in the inner direction of the feed clutch 31. As a result, the half nut meshes with the octagonal portion 3e of the spindle 3, enabling drilling by the automatic feed of the spindle 3.

[0049] (Open and closed states of the vibration stopper 33 in the second embodiment) Next, with reference to FIG. 10, the open and closed states of the vibration stopper 33 in the second embodiment will be described.

[0050] As shown in FIG. 10, the drilling machine 1 in the second embodiment includes a vibration prevention portion 34 that prevents the core deflection of the spindle 3 during the drilling operation. The vibration prevention portion 34 has the same configuration as the moving vibration prevention portion 10 in the first embodiment, and the outer peripheral surface of the vibration prevention portion 34 is in contact with the inner peripheral surface 2c of the underbody 2b.

[0051] Figure 10(A) shows the vibration stopper 33 in the open state. When the vibration stopper 33 is in the open state, since the vibration stopper 33 does not press the rear surface of the vibration prevention portion 34, the movement of the vibration prevention portion 34 is not restricted. Therefore, the open state corresponds to the free position in the first embodiment.

[0052] Here, when the spindle 3 is pushed in while the locking stopper 33 is in the open state, the locking portion 34 is pushed out to the foremost position with the rounded portion 3f of the spindle 3 and the ball plunger 12 being in a fitted state. Then, the rod 33a is pushed in to tighten the nut 33b onto the male screw 33c. As a result, the moving space of the locking portion 34 disappears, and the locking stopper 33 changes from the open state to the closed state. Further, when the spindle 3 is pushed in further, the ball plunger 12 moves deeper, and the large cutter 41 housed within the inner peripheral surface 2c of the underbody 2b comes out of the inner peripheral surface 2c of the underbody 2b.

[0053] FIG. 10(B) shows the locking stopper 33 in the closed state. When the locking stopper 33 is in the closed state, since the locking stopper 33 presses the rear surface of the locking portion 34, the movement of the locking portion 34 is restricted. Therefore, the closed state corresponds to the lock position in the first embodiment.

[0054] Also, in the closed state, since the rear surface of the locking portion 34 is pressed by the locking stopper 33, the locking portion 34 does not fall due to its own weight when drilling the lower surface of the pipe P.

[0055] (Procedure for Preparation of Drilling of the Large Drilling Machine 40 in the Second Embodiment) Next, with reference to FIG. 11, the procedure for preparation of drilling of the large drilling machine 40 in the second embodiment will be described.

[0056] First, as shown in FIG. 11(A), a large drill 42 used in the large drilling machine 40 is inserted into a large cutter 41 used in the large drilling machine 40 for attachment, and the large cutter 41 with the large drill 42 attached is attached to the tip portion 3c of the spindle 3.

[0057] Next, as shown in FIG. 11(B), pull up the spindle 3 to the uppermost position in the direction of arrow A, insert the spindle stopper 16, and confirm that the spindle 3 has been pulled up to the uppermost position. At this time, the large cutter 41 is housed within the inner peripheral surface 2c of the underbody 2b. Then, after confirming that the anti-rotation stopper 33 is in the open state and the feed clutch 31 is in the released state, attach the drilling machine 1 to the pipe P.

[0058] Next, as shown in FIG. 11(C), remove the spindle stopper 16 and rotate the rotation clutch knob 32.

[0059] Next, as shown in FIG. 11(D), while pushing the spindle 3 in the direction of arrow B, simultaneously change the anti-rotation stopper 33 from the open state to the closed state. As a result, the anti-rotation portion 34 is pushed out to the foremost surface of the underbody 2b.

[0060] Next, as shown in FIG. 11(E), further push the spindle 3 in the direction of arrow B and set the feed clutch 31.

[0061] (Other Embodiments) In the following, other embodiments will be described.

[0062] In the above-described first embodiment, the movement anti-rotation stopper 15 is configured such that the movement of the anti-rotation portion 10 in the direction of the tip portion 3c is restricted by the plunger tip 23a coming into contact with the anti-rotation portion 10, but it is not limited thereto. For example, a recess may be provided on the outer periphery of the anti-rotation portion 10, and the movement of the anti-rotation portion 10 in the direction of the tip portion 3c may be restricted by inserting the plunger tip 23a into this recess.

[0063] In the first embodiment described above, the plunger 23 is configured such that when the knob 7 is rotated, the tip 23a of the plunger protrudes in the direction of the inner peripheral surface 2c of the underbody 2b. However, the present invention is not limited to this. For example, the tip 23a of the plunger may protrude in the direction of the inner peripheral surface 2c of the underbody 2b by pressing a button.

[0064] In the first embodiment described above, the movement restricting stopper 15 is illustrated as a single unit for explanation. However, the present invention is not limited to this. For example, a plurality of movement restricting stoppers 15 may be provided. Similarly, a plurality of stopping stoppers 33 in the second embodiment may be provided. By providing a plurality of movement restricting stoppers 15 and stopping stoppers 33, the core deviation of the spindle 3 can be further prevented.

[0065] As described above, when the knob 7 of the drilling machine 1 according to the present invention is rotated, the tip 23a of the plunger protrudes in the inner direction from the inner peripheral surface 2c of the underbody 2b by the compression spring 25, and the tip 23a of the plunger comes into contact with the movement restricting portion 10. As a result, since the movement of the movement restricting portion 10 is restricted, when drilling the lower surface of the pipe P, the movement restricting portion 10 is prevented from falling due to its own weight, so that it is possible to provide a drilling machine 1 capable of preventing the core deviation of the spindle 3.

[0066] (First Invention) The first invention is a drilling machine capable of drilling the lower surface of a pipe (for example, pipe P), comprising a spindle (for example, spindle 3) to which a cutter (for example, cutter 17) is attached, a movement restricting portion (for example, movement restricting portion 10, stopping portion 34) for preventing core deviation of the spindle, and a movement restricting stopper (for example, movement restricting stopper 15, stopping stopper 33) for preventing the movement restricting portion from falling due to its own weight when drilling the lower surface of the pipe.

[0067] (Second Invention) The second invention is the drilling machine according to the first invention, characterized in that the movement stopper is displaceable between a lock position for locking the movement stop portion and a free position for not locking the movement stop portion, and further includes an operation portion (for example, knob 7, nut 33b) for switching the position of the movement stopper between the lock position and the free position.

[0068] (Third Invention) The third invention is the drilling machine according to the second invention, characterized in that the movement stopper includes a plunger (for example, plunger 23) that abuts against the movement stop portion in the lock position, and a biasing member (for example, compression spring 25) that biases the plunger when the operation portion is operated.

[0069] (Fourth Invention) The fourth invention is the drilling machine according to the second invention, characterized in that the movement stopper includes a rod (for example, rod 33a) that presses the movement stop portion, a nut (for example, nut 33b) attached to the rod, and a male screw (for example, male screw 33c) into which the nut is tightened, and preventing the movement stop portion from falling by its own weight by pushing the rod and tightening the nut onto the male screw.

[0070] Note that the matters shown in the above embodiments and modifications are merely examples, and can be appropriately changed without departing from the scope of the present invention.

Explanation of Reference Numerals

[0071] 1 Drilling machine 2 Body 2a Top body 2b Under body 2c Inner peripheral surface 3 Spindle 3a Head 3b Hexagonal portion 3c Tip portion 3d Tip groove portion 3e Octagonal portion 3f Rounded portion 4 Feed Handle 5 Purge Port Coupler 7 Knob 7a Positioning Line 8 Power Switch 9 Power Plug 10 Movement Stopper 11 Movement Stopper Ring 12 Ball Plunger 13 O - Ring 14 Dust Seal 14a Storage Recess 14b Protrusion 15 Movement Stopper 16 Spindle Stopper 17 Cutter 18 Center Drill 19 Closing Confirmation Cover 20 Casing 21 First Display Unit 22 Second Display Unit 23 Plunger 23a Plunger Tip 24 Plunger Holder 25 Compression Spring 26 Airtight Member 27 Parallel Pin 28 Contact Wall 29 Vent Hole 30 Mesh Part 31 Feed Clutch 31a Cam Cap 31b Half - Nut Fixing Ring 31c Half - Nut Base 32 Rotation Clutch Knob 33 Stopper 33a Rod 33b Nut 33c Male Screw 34 Stopper 40 Large Drilling Machine 41 Large Cutter 42 Large Drill H Screw Hole P Pipe

Claims

1. A drilling machine capable of drilling through the lower surface of a pipe, a body having a top body and an under body, a spindle to which a cutter is attached, a movement damping portion that is inside the under body, attached to the outer periphery of the spindle, and prevents core deflection of the spindle, a movement damping stopper that prevents the movement damping portion from falling by its own weight when drilling through the lower surface of the pipe, comprising, the movement damping stopper, is displaceable between a lock position where the downward movement of the movement damping portion is restricted and a free position where the downward movement of the movement damping portion is not restricted, and further comprises an operating portion for switching the position of the movement damping stopper between the lock position and the free position. The drilling machine is characterized by this.

2. The movement damping stopper, a plunger that abuts against the movement damping portion in the lock position, a biasing member that biases the plunger when the operating portion is operated, and is characterized by comprising the above. The drilling machine according to claim 1.

3. The movement damping stopper, a rod that presses the movement damping portion, a nut attached to the rod, a male screw into which the nut is tightened, and is characterized by comprising the above, and by pushing in the rod and tightening the nut onto the male screw to prevent the movement damping portion from falling by its own weight. The drilling machine according to claim 1.

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