Boring machine

Abstract

In a boring machine, rotation of a motor is transferred to a pipe spindle and a shaft, a cutting edge feeding mechanism arranged side by side with the pipe spindle moves the shaft toward a workpiece and a cutting edge attached to an end of the shaft drills a hole in the workpiece. The cutting edge feeding mechanism slidably but non-rotatably supports a chain holder around an outer circumference of the pipe spindle. A sprocket wrapped around by a chain is rotated by a handle to move the shaft. The radius of rotation of the handle is reduced to slowly move the shaft. The maximum torque of the motor rotating the shaft is controlled. The number of cutting edges falls within a range from six to eight.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to improvements in boring machines for drilling holes for branch line on one of a main line of water pipe and a gas pipe for branch line.

2. Description of the Related Art

In a conventional method of attaching a branch line to one of a water-pipe main line and a gas-pipe main line, a saddle corporation stop is typically fixed onto the main line, and a hole is drilled on the pipe with a boring machine mounted on the saddle corporation stop. A variety of boring machines has been proposed. For example, Japanese Unexamined Patent Application Publication No. 2002-66819 discloses one boring machine. In the disclosed boring machine, a cutting edge feeding mechanism using a chain is employed, and a cutting edge rotated by a motor is raised and lowered by handle operation.

More in detail, rotation of the motor arranged in the body of the machine is transferred to a pipe spindle, and then to a shaft arranged within the pipe spindle. With the cutting edge secured to the shaft being moved toward a workpiece (main line pipe), the boring machine drills a hole. The cutting edge feeding mechanism including a chain is arranged side by side with the pipe spindle. The cutting edge feeding mechanism moves the shaft arranged in the pipe spindle toward the workpiece while the cutting edge drills a hole in the workpiece. A holder of the chain is slidably but non-rotatably supported on the outer circumference of the pipe spindle. The chain is secured to the holder with both ends. Sprockets wrapped around by the chain are rotated by a handle. The shaft is thus moved by the holder.

However, the above-described boring machine is subject to biting or breaking of the cutting edge during drilling operation. Such troubles are likely to occur as below. When the handle is operated to lower the shaft having the cutting edge attached thereto, the handle and the shaft are directly linked to each other by the chain. In response to the operation, the shaft is suddenly lowered, thereby being put into contact with the workpiece (main pipe) with strong force. This causes the lack of the cutting force and thus results in the cutting edge to bite into the workpiece and to be lodged there, or the cutting edge may be even broken.

Even if the handle operation is performed carefully, the cutting edge can be locked or broken down when the torque of the cutting edge becomes too high due to high torque of the motor.

The cutting edge of the known boring machine is secured to the end of the shaft using a mounting shaft, and the number of cutting edges is typically four with this type of machine. Load acting on each cutting edge becomes large enough to break the mounting shaft.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a boring machine free from troubles caused by operations of a handle and a motor.

In accordance with a boring machine of the present invention, rotation of a motor arranged in a body of the machine is transferred to a pipe spindle, and then to a shaft arranged within the pipe spindle. A cutting edge feeding mechanism is arranged side by side with the pipe spindle. The shaft in the pipe spindle is moved toward a workpiece by the cutting edge feeding mechanism. A cutting edge is mounted on a tip of an end of the shaft. A chain holder is supported slidably but non-rotatably on the outer circumference of the pipe spindle. A chain is fixed to the chain holder with both ends thereof anchored to the chain holder. A sprocket wrapped around by the chain is rotated by a handle. The shaft is thus moved by the chain holder. The radius of rotation of the handle of the cutting edge feeding mechanism is set to be reduced so that the shaft is slowly moved.

The maximum torque of the motor rotating the shaft is reduced.

The number of cutting edges falls within a range of six to eight.

The shaft moves slowly because the radius of rotation of the handle is reduced for moving the shaft in the cutting edge feeding mechanism. As described above, the shaft moves slowly because the radius of rotation of the handle is reduced for moving the shaft in the cutting edge feeding mechanism, thus a large torque is not applied to the cutting edge, and the cutting edge is free from biting or breaking.

Since a drilling operation is performed with lower torque by controlling the maximum torque biting or breaking of the cutting edge is prevented.

By increasing the number of cutting edges, cutting load per cutting edge is reduced. The breaking of the mounting shaft is thus prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a boring machine of one embodiment of the present invention with a portion thereof of broken away;

FIG. 2 is a front view of the boring machine with a portion thereof of broken away; and

FIG. 3 is a partial side view of the boring machine attached onto a saddle corporation stop.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Boring machines of the preferred embodiments of the present invention are described below with reference to the drawings. FIG. 1 is a side view of the boring machine of one embodiment of the present invention with a portion thereof of broken away, FIG. 2 is a front view of the boring machine with a portion thereof of broken away, and FIG. 3 is a partial side view of the boring machine attached onto a saddle corporation stop.

Referring to FIGS. 1 through 3, there are shown a boring machine 1, a pipe spindle 2 rotatably supported within the boring machine 1, and a shaft 3 vertically slidably supported within the pipe spindle 2. A cutting edge 4 for cutting a water pipe is mounted to an end of the shaft 3 with a mounting shaft. A cutting edge feeding mechanism 5, employing a chain, vertically moves the shaft 3 through the pipe spindle 2. A motor 6 rotates the pipe spindle 2 and the shaft 3 via a reduction gear train 8 in a gear box 7. A saddle bracket 9 is fixed on the lower end of the body of the boring machine 1. The lower end of the shaft 3 is rotatably supported at the lower end thereof on a needle bearing 10 in the saddle bracket 9. A saddle fixing nut 11, loosely fitted over the saddle bracket 9, is used to fix the boring machine onto a saddle corporation stop (S) secured to a water main pipe (H).

A shaft guide 12 is fixed to the shaft 3 by a C-clip 13. Two ends of the shaft guide 12 are received in longitudinal grooves 2a vertically formed in the pipe spindle 2. Pin guides 14 are attached to the ends of the shaft guide 12 and are slidably supported on the outer circumference of the pipe spindle 2. The pin guides 14 are also connected to respective ends of a pin 15 that penetrates through the top portion of the pipe spindle 2. Pin covers 16 are arranged on the outer circumference of the pin guides 14, and ball bearings 17 are press fitted to the upper and lower portion of the pin guides 14. A chain holder 18 is slidably supported on the outer circumference of the pipe spindle 2, and covers the pin guides 14, the pin covers 16, and the ball bearings 17. The chain holder 18 is fixed by a C-clip 19.

The shaft 3 is housed in the pipe spindle 2, and the longitudinal grooves 2a are symmetrically arranged in the pipe spindle 2 with respect to the center axis of the pipe spindle 2. The shaft guide 12 and the pin 15 are received in the longitudinal grooves 2a in a manner such that the shaft guide 12 and the pin 15 are vertically slidable but not rotatable around. The lower end of the shaft 3 is slidably supported on a bushing 20 within the pipe spindle 2. The pipe spindle 2 is rotatably supported on the upper end portion thereof on a needle bearing 21 and a thrust bearing 22 on a main body cover 1a. The pipe spindle 2 is rotatably supported at the lower end portion thereof on a ball bearing 23 to the gear box 7 mounted on the lower portion of the boring machine 1.

The cutting edge feeding mechanism 5 as a chain driving mechanism is arranged side by side in a standing condition. A chain 5a has both ends thereof anchored to the chain holder 18 to be endless, and is wrapped around a pair of sprockets 24 and 25 respectively arranged on the upper and lower portions of the boring machine 1. As shown in FIG. 2, the upper sprocket 24 is secured to a sprocket shaft 26. A gear 27 is also secured to the sprocket shaft 26 with a predetermined space allowed to the upper sprocket 25. A handle shaft 28 is rotatably supported on the boring machine 1. A gear 29 formed on the handle shaft 28 is in meshing arrangement with the gear 27 of the sprocket shaft 26. A handle 30 is mounted onto the handle shaft 28. In the known art, the handle 30 has a length of about 130 mm, but in this embodiment of the present invention, the handle 30 has a length of about 100 mm to reduce the radius of rotation of the handle. A brake mechanism 34 including a spring 31, a brake 32, a brake disk 33, etc. is built into the handle shaft 28. The lower sprocket 25 is rotatably supported on a bushing 36 in a sprocket shaft 35 secured to the boring machine 1.

As shown in FIG. 1, a first gear 37 is attached to the lower portion of the pipe spindle 2. The first gear 37 is in meshing arrangement with an output shaft 38 of the motor 6 via the reduction gear train 8 in the gear box 7. With the rotary drive of the motor 6 rotating, the pipe spindle 2 rotates at a reduced speed. The motor 6 is a compact type and outputs a low torque in comparison with the known art with the maximum torque thereof limited.

A reverse rotation prevention belt 39 functions as reverse rotation prevention means of the boring machine. A hook 40 of the reverse rotation prevention belt 39 is anchored at an eye nut 41 connected to the end of a bolt of the saddle corporation stop. The reverse rotation prevention belt 39 thus allows tension to work in a direction opposite to the direction of slackness of the boring machine 1.

A drilling operation of the boring machine 1 thus constructed is described below. The saddle corporation stop (S) is fastened to the main line water pipe (H). The boring machine 1 is then mounted on the saddle corporation stop (S) using the saddle fixing nut 11. The reverse rotation prevention belt 39 is anchored at the eye nut 41. When the motor 6 is switched on, the first gear 37 is driven by the motor 6 via the reduction gear train 8, and furthermore the pipe spindle 2 is rotated. With this rotation of the pipe spindle 2 causes the shaft 3 to be also rotated, and the cutting edge 4 attached to the shaft 3 is also rotated.

When the handle 30 is turned in this state, the gear 29 formed on the handle shaft 28 is also rotated as well as the gear 27 in meshing engagement with the gear 29. The rotation of the sprocket shaft 26 thereby causes the sprocket 24 to rotate. And thus, this rotation causes the chain 5a wrapped around the sprockets 24 and 25 to turn. When the chain 5a turns, the chain holder 18 attached to the chain 5a slides downward along the rotating pipe spindle 2. The pin guides 14 and the shaft guide 12 housed in the chain holder 18 also slide downward along the longitudinal grooves 2a of the pipe spindle 2. The shaft 3 having the shaft guide 12 thereon moves downward while rotating at the same time. The cutting edge 4 attached to the bottom end of the shaft 3 then drills a hole in the main line water pipe (H). When the hole is completely drilled, pressure of running water in the water pipe acts on the end surface of the shaft 3, thereby pushing the shaft 3 upward. Since the handle shaft 28 includes the brake mechanism 34, the cutting edge 4 is free from being pushed upward. The handle 30 is not reverse rotated.

During the hole drilling, the shaft 3 having the cutting edge 4 attached thereto is lowered by operating the handle 30. The radius of rotation of the handle in the known boring machine is large. Depending on the manner of operation, a high torque occurs, causing the shaft to suddenly be lowered. The cutting edge is put into contact with the main line water pipe with strong force. The cutting edge may bite into the workpiece or may be broken. In accordance with the present embodiment, the radius of rotation of the handle is reduced by shorten the length of the handle, and the shaft 3 is slowly lowered with low torque. The possibility of edge biting and edge breaking is thus reduced.

With the compact motor used, the maximum torque is set to be modest. With low torque, hole drilling is performed. The biting of the cutting edge into the workpiece with high torque is thus prevented. The entire boring machine is thus reduced in scale.

In contrast to the known boring machine employing four cutting edges, the boring machine of the embodiment of the present embodiment employs six to eight cutting edges. Cutting load per cutting edge is thus reduced. The possibility of breaking of the cutting edge mounting shaft is also reduced.

Claims

1. A boring machine comprising: a machine body; a pipe spindle freely rotatably supported within the machine body; a shaft vertically slidably supported through the pipe spindle; a cutting edge supported at one tip of the shaft with a cutting edge mounting shaft; a cutting edge feeding mechanism for vertically moving the shaft through the pipe spindle, the cutting edge feeding mechanism including a chain; a motor for rotating the pipe spindle and the shaft; and a saddle bracket arranged on a lower end of the machine body.

2. The boring machine according to claim 1, wherein the pipe spindle is rotatably supported at a top end thereof on a needle bearing and a thrust bearing at a machine body cover of an upper portion of the machine body, and rotatably supported at a bottom end thereof on a ball bearing in a gear box secured to a lower portion of the machine body, wherein the pipe spindle comprises a pair of grooves vertically extending in symmetry with respect to the center axis of the pipe spindle and houses the shaft therewithin.

3. The boring machine according to claim 1, wherein the shaft comprises: a shaft guide received in the grooves of the pipe spindle, the shaft guide including pin guides respectively on two ends thereof, the pin guides slidably engaged with an outer circumference of the pipe spindle, and fixing the ends of a pin penetrating through a top portion of the shaft; a pin cover arranged on an outer circumference of each of the pin guides; and a chain holder housing the pin guides and the pin covers and being slidably supported on the outer circumference of the pipe spindle, wherein the shaft is slidably supported at a lower end thereof within the pipe spindle.

4. The boring machine according to claim 1, wherein the cutting edge feeding mechanism comprises: a chain holder arranged side by side in a standing condition with the pipe spindle and slidably but non-rotatably supported on an outer circumference of the pipe spindle; a chain having two ends thereof anchored to the chain holder; a sprocket wrapped around by the chain; and a handle for rotating the sprocket, wherein rotation of the handle causes the sprocket to rotate, thereby moving the chain holder and the shaft.

5. The boring machine according to claim 4, wherein the cutting edge feeding mechanism comprises: the chain holder; the chain having two ends thereof anchored to the chain holder; a pair of upper and lower sprockets arranged to be wrapped around by the chain; a sprocket shaft supporting the upper sprocket; a handle shaft linked with the sprocket shaft via a gear; a handle secured to the handle shaft; a brake assembly housed in the handle shaft; and a sprocket shaft supporting the lower sprocket.

6. The boring machine according to claim 5, wherein a radius of rotation of the handle is reduced so that the shaft slowly moves.

7. The boring machine according to claim 1, wherein the motor comprises a supporting shaft which is engaged, via a gear train in a gear box, with a first gear fixed to the pipe spindle, wherein the pipe spindle and the shaft are rotated at a reduced speed by the motor.

8. The boring machine according to claim 7, wherein the shaft is rotated at a lower torque with the maximum torque of the motor controlled.

9. (canceled)

10. The boring machine according to claim 1, wherein the number of cutting edges to be mounted on the shaft falls within a range from six to eight.

11. A boring machine comprising: a machine body; a pipe spindle freely rotatably supported within the machine body, wherein the pipe spindle is rotatably supported at a top end thereof on a needle bearing and a thrust bearing at a machine body cover of an upper portion of the machine body, and rotatably supported at a bottom end thereof on a ball bearing in a gear box secured to a lower portion of the machine body, wherein the pipe spindle includes a pair of grooves vertically extending in symmetry with respect to a center axis of the pipe spindle; a shaft vertically slidably supported through the pipe spindle, the shaft including a shaft guide received in the grooves of the pipe spindle, the shaft guide including pin guides respectively on two ends thereof, the pin guides slidably engaged with an outer circumference of the pipe spindle, and fixing the ends of a pin penetrating through a top portion of the shaft, a pin cover arranged on an outer circumference of each of the pin guides, and a chain holder housing the pin guides and the pin covers and being slidably supported on the outer circumference of the pipe spindle, wherein the shaft is slidably supported at a lower end thereof within the pipe spindle; a cutting edge supported at one tip of the shaft with a cutting edge mounting shaft; a cutting edge feeding mechanism for vertically moving the shaft through the pipe spindle, the cutting edge feeding mechanism including a chain holder arranged side by side in a standing condition with the pipe spindle and slidably but non-rotatably supported on an outer circumference of the pipe spindle, a chain having two ends thereof anchored to the chain holder, a sprocket wrapped around by the chain, and a handle for rotating the sprocket, wherein rotation of the handle causes the sprocket to rotate, thereby moving the chain holder and the shaft; a motor for rotating the pipe spindle and the shaft, wherein the motor includes a supporting shaft which is engaged, via a gear train in a gear box, with a first gear fixed to the pipe spindle, wherein the pipe spindle and the shaft are rotated at a reduced speed by the motor; and a saddle bracket arranged on a lower end of the machine body.