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 [0001] 1. Field of the Invention [0002] 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. [0003] 2. Description of the Related Art [0004] 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. [0005] More in detail, rotation of the motor arranged in the body of the machine is transferred to a pipe spin...

AI Technical Summary

Benefits of technology

[0009] 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.

[0011] The maximum torque of the motor rotating the shaft is reduced.

[0013] 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.

[0014] Since a drilling operation is performed with lower torque by controlling the maximum torque biting or breaking of the cutting edge is prevented.

[0015] By increasing the number of cutting edges, cutting load per cutting edge is reduced. The breaking of the mounting shaft is thus prevented.

Problems solved by technology

However, the above-described boring machine is subject to biting or breaking of the cutting edge during drilling operation.

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.

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