Cutting – Processes – Cutting wall of hollow work
Patent
1986-07-25
1988-05-17
Kazenske, E. R.
Cutting
Processes
Cutting wall of hollow work
83180, 83182, 83186, 83189, 83188, B26D 300, B23D 2114
Patent
active
047442778
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of cutting pipe lengths as well as to a device for carrying out said method.
To date, piping has been cut to pipe lengths practically exclusively by sawing or by grinding. Another possibility is autogenous cutting.
All said methods have one common drawback, which is that a substantial loss of material is unavoidable and that the cutting speed is rather slow. Furthermore, the quality of the cutting area is very low especially if a slightly higher cutting speed is selected, so that a subsequent working of said area cannot be avoided if said area has to have little roughness.
Furthermore, it is known from Soviet Inventions Illustrated Section P 54 Week D 29 of Aug. 26, 1981, page 25, to cut piping to lengths by shearing. For said purpose, use is made in most cases of cutters or blades which grip around the pipe to be cut, with the one cutter or blade in most cases being supported eccentrically relative to the other cutter or blade. In this connection, it is known also to support the pipes from the inside by a divisible mandrel whose line of division is disposed on the plane of the abutting cutters. The drawback of said method is the low quality of the cutting areas with respect to surface roughness and dimensional stability of the cutting area. Therefore, using said cutting method leads in most cases to damage because material is torn out within the zone of the trailing cutting edge.
The objective of the invention is to propose a method of cutting pipe lengths that permits a high cutting speed and avoids loss of material and assures smooth and clean cutting areas.
According to the invention, said objective is accomplished by subjecting the wall of the pipe to be cut within the zone of the intended cutting plane to pressure at both sides of said cutting plane both from the inside and outside and also in the axial direction of the pipe, and by initiating a relative motion between the pipe and the length of pipe to be separated therefrom, while maintaining the pressure.
By said measures, the pipe to be cut is kept under a high compressive stress on all sides. In this way, it is avoided that shearing cracks are produced while the pipe is moving relative to the length of pipe to be cut, which motion causes said length of pipe to be sheared off. Said cutting by shearing in the spatial state of stress causes the material to substantially flow or slide along the shearing area, which assures a high measure of accuracy of the area and high surface quality.
In said connection, it is particularly favorable if the pressure applied to the wall of the pipe in the radial direction and in the axial direction stresses the material by at least 70%, preferably 100% of its yield limit. If such a state of stress is maintained during the cutting step, the material practically simply flows or slides along the cutting area, which results in very smooth cutting areas.
Another objective of the invention is to propose a device for carrying out the method according to the invention. Said device for carrying out the method of the invention is based on a device with closed cutters or blades surrounding the pipe, and a stop means, at least one cutter or blade being rotatable relative to the second cutter around an axis of rotation which is spaced from the center point of its penetration in the cutting plane. The cutters or blades rest against each other in a plane and a mandrel is guided in the holding device of the one cutter or blade, said mandrel being axially displaceable relative to the cutters by means of a drive, preferably a cylinder-and-piston arrangement, the cross section of said mandrel and the inside cross section of the pipe to be cut producing a forced fit. The mandrel is divided and the plane of division of its two abutting parts is disposed in the pushed-in state in the cutting plane of the two cutters or blades.
Such a device is described, for example in the above-cited publication "Soviet Inventions Illustrated". Said device is provided with a divisible mandrel for effecting an expansion
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Kazenske E. R.
Kelman Kurt
Smith Scott A.
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