GB2048746A

GB2048746A - Pipe-cutting Apparatus

Info

Publication number: GB2048746A
Application number: GB8013214A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-05-14
Filing date: 1980-04-22
Publication date: 1980-12-17
Also published as: DE3018580A1; FR2456584A1; JPS55150911A; SE414463B

Abstract

A pipe-cutting apparatus comprises a plurality of circular cutting elements (17) mounted on a chain (10-12) which is capable of being placed around the pipe (13) to be cut and which has side links (14, 15) pivotally mounted on pins (16) on which the circular cutting elements, flanked by the side links, are mounted for rotation for cutting engagement with the pipe; a tensioning device (19) for connecting together the ends of the length of chain (10-12) and for tightening the chain around the pipe (13); and means (28, 29) connected to the tensioning device for causing the chain to move backwards and forwards peripherally of the pipe to ensure that the cutting elements (17) cut into the pipe uniformly around the circumference thereof, the chain (10-12) is divided into at least two parts, the mutually adjacent ends of which are joined together at (30, 31) by means of a respective further tensioning device (32), to tighten the chain around the pipe. <IMAGE>

Description

SPECIFICATION An Arrangement in Pipe Cutting Apparatus The present invention relates to an arrangement in pipe-cutting apparatus of the kind comprising a number of circular cutting elements mounted on a chain of the roller-type which is capable of being placed around the pipe to be cut and which has side links pivotally mounted on pins on which the circular cutting elements, flanked by the side links, are mounted for rotation for cutting engagement with the pipe: a tensioning device for connecting together the ends of the length of chain utilized in effecting a cutting operation and for tightening the chain around the pipe; and means connected to the tensioning device for causing the chain to move backwards and forwards peripherally of the pipe.

A pipe cutting apparatus of the previously described kind is known, for example, from the Swedish Patent Specification No. 343 226 and the corresponding U.S. Patent Specification No. 3 763 559. The cutting chain is tightened by means of the tensioning device during a pipe cutting operation as the cutting elements cut into the pipe. This known kind of pipe cutting apparatus is normally very effective and trouble-free. One problem is encountered, however, with such an apparatus when cutting pipes which are of large diameters, for example diameter of about 400 mm and thereabove, and which are made of a tough material, for example nodular iron.This problem is manifested by the fact that when cutting pipes whose diameter is of the aforementioned magnitude and which are made of such tough material, the cutting elements tend to cut rapidly only in the vicinity of the tensioning device, while cutting of the remainder of the pipe wall takes an unproportionally long time.

The object of the invention is to provide an apparatus whereby said problem is at least substantially eliminated.

To this end it is proposed in accordance with the invention that in a pipe cutting apparatus of the kind described in the introduction the cutting chain is divided into at least two sections, the mutually adjacent ends of which are joined together at each dividing location by a respective further tensioning device. Because, with this arrangement, the cutting chain is also tightened around the pipe during a pipe cutting operation by means of the further tensioning device or devices, the cutting elements are pressed against the pipe in a more uniform fashion, wherewith all the cutting elements cut into the pipe more evenly so as to enable pipes having large diameters and comprising tough material to be cut rapidly and effectively.

Preferably, the cutting chain is divided at two locations so as to comprise three sections of substantially equal length, which are joined together by a respective one of two further tensioning devices. In this way it is possible to position the cutting apparatus around a pipe with substantial uniform distribution of the tensioning devices around the periphery of said pipe, while practically totally eliminating the problem to be solved by the invention, in a manner such that no additional space, or only a small additional space is required beneath the pipe for accommodating the further tensioning devices. This is of particular advantage when cutting pipes which are laid in trenches, because firstly there is normally no free space beneath the pipes, and secondly it is difficult to create therebeneath the necessary space.

The invention will now be described with reference to an exemplary embodiment thereof illustrated in the accompanying drawing, further characterizing features of the invention and advantages afforded thereby also being made apparent.

Figure 1 is a partial side view of a pipe cutting apparatus according to the invention.

Figure 2 is a side view of part of a cutting chain and a device for shortening said chain.

Figure 3 is a view seen in the direction of arrows Ill-Ill in Figure 2.

Illustrated in the drawing is a cutting chain 10--12 placed around a pipe 13 to be cut. The cutting chain is of the roller kind having side links 14, 1 5 pivotally connected together by pins 16 having rotatably mounted thereon cutting elements 17 which are intended for cutting engagement with the pipe and which are flanked by the side links. Arranged between the side links 14, 1 5 are support rollers 1 8. The purpose of the support rollers 18 is to limit the depth to which the cutting elements 17 cut into the pipe 13, and to prevent the chain 10-12 fastening in the pipe 13 or to prevent any of the side links 14, 15 rubbing against the pipe on those occasions when the cutting elements penetrate the pipe locally.

The reference 19 generally identifies a tensioning device for tightening the cutting chain 10-1 2 around the pipe 13. The tensioning device comprises two arms 20, 21 which are pivotally connected together by means of a pin 22 at the end remote from the pipe 13. The arms 20, 21 exhibit mutually co-operating guide surfaces, of which one is shown at 23, and which ensure that when pivoting about the pin 22 the arms move along a plane extending at right angles to said pin.

The arm 20 is pivotally connected at the end thereof remote from the pin 22 to one end of the cutting chain 10-12 by means of a pin 24 which passes through said end part of the arm 20 and the two side links 14 of the last chain link at said one end of the chain. The other arm 21 of the tensioning device 19 is releasably connectable at its end remote from the pin 22 to the other end of the length of cutting chain 10-12 utilized for the cutting operation.For the purpose of tightening the cutting chain around the pipe 13, there is provided an externally threaded spindle 25 which is pivotally mounted on the arm 20 and which extends through a hole or a slot in the arm 21 and carries at one end a nut 26 which is arranged to co-operate with the side of the arm 21 remote from the arm 20 as an abutment surface and to be tightened during the pipe cutting operation, in proportion to the depth to which the cutting elements 17 cut into the pipe.

The tensioning device 19 is connected in a readily releasable manner to the outer end of the piston rod 28 of a preferably pneumatic linear piston engine by means of a pin 27 extending parallel with the axis of the pipe 13. The cylinder housing of the piston engine is only partially illustrated and is referenced 29. The cylinder housing 29 is carried by the pipe 13 by means of an attachment arrangement not shown and which may, to advantage, be of the type illustrated and described in the U.S. Patent Specification No. 3 763 559.

The cutting chain is divided at 30 and 31 so as to comprise three separate sections 10, 11 and 12 respectively, the mutually adjacent ends of said chain sections being joined together at each dividing location 30 and 31 respectively by a further tensioning device generally shown at 32.

As will be seen from the drawing, each tensioning device 32 comprises two pairs of arms 33, 34 which are pivotally mounted at one end on a shaft or pin 35. At the other end one pair of arms 33 is pivotally mounted on a pin 16 located nearest to the dividing location 30 or 31 on one chain section, while the other pair of arms 34 is pivotally mounted on a pin 16 located nearest the same dividing location on the other chain section.

For the purpose of tightening the chain by means of the tensioning devices 32, each of said tensioning devices is provided with a threaded bolt 37 journalled in the two arms 34 at 36 and passing freely displaceable through a square bush 39 journalled in the two arms 33 at 38. A nut 40 is screwed onto the bolt 37 and is arranged to be tightened, with the side of the bush 39 remote from the arms 34 acting as an abutment surface, in substantially the same manner as the nut 26 is tightened during a cutting operation, proportionally to the extent to which the cutting elements have entered the pipe.

By forcing the cutting chain 10, 11, 12 against the pipe 13 with the aid of a plurality of tensioning devices 1 9, 32, the resultant penetration of the cutting elements 1 7 into the pipe wall during a cutting operation is made considerably more uniform, thereby avoiding premature, local penetration of the cutting elements of the pipe with subsequent disadvantages.

Although in the illustrated embodiment only two further tensioning devices 32 are provided in addition to the tensioning device 19 normally found, it will be understood that the number of additional tensioning devices 32 can be one or can be more than two. Although the provision of a single additional tensioning device 32, located substantially diametrically opposite the tensioning device 19, will provide, to a large extent, the advantages sought for by means of the invention, a relatively large space is required beneath the pipe 13, which can be a disadvantage in many cases. Further, it has been found that the use of more than two further tensioning devices 32, in addition to the tensioning device 19 normally provided, is seldom necessary.Thus, the embodiment having two further tensioning devices 32 is preferred, the tensioning devices 1 9, 32 being distributed substantially uniformly around the periphery of the pipe 13, and the pipecutting apparatus suitably being mounted in the illustrated manner, so only a small free space is required beneath the pipe 13. The optimal result is obtained when angles between the tensioning devices, calculated in a counter clockwise direction from the tensioning device 19, are about 1 300, 1100 and 1200 respectively.

Figures 2 and 3 illustrate a device which can be used for shortening the cutting chain. without greatly changing the angles between the tensioning devices. To this end there is used coupling elements 41 which have substantially the same form as the links 14, 1 5 and which can be removably placed on the ends of the pins 1 6 projecting laterally outwardly from the outer links 15. In the embodiment of Figure 2 and 3, a chain section has been shortened by approximately the length of one link, by positioning two adjacent links at an angle such that the distance between the pins 1 6 at the ends of the angled links corresponds to the distance between the holes in the coupling elements 41, whereafter a coupling element 41 is placed on the pins 16 from each side of the chain.

The invention is not restricted to the aforedescribed and illustrated embodiment, but can be modified within the scope of the following

Claims

claims. Claims

1. An arrangement in pipe-cutting apparatus of the kind comprising a plurality of circular cutting elements (17) mounted on a cutting chain (10 1 2) of the roller-type which is capable of being placed around the pipe (13) to be cut and which has side links pivotally mounted on pins on which the circular cutting elements, flanked by the side links, are mounted for rotation for cutting engagement with the pipe; a tensioning device (19) for connecting together the ends of the length of chain (10--12) utilized in effecting a cutting operation and for tightening the chain around the pipe (13); and means (28,29) connected to the tensioning device for causing the chain to move backwards and forwards periphery of the pipe, characterized in that the chain (10--12) is divided into at least two sections, the mutually adjacent ends of which are joined together at each dividing location (30. 31) by means of a respective further tensioning device (32).

2. An arrangement according to claim 1, characterized in that the cutting chain (10--12) is divided at two locations (30, 31) so as to comprise three sections (10, 11, 12) of substantially equal length, said sections being joined together by a respective one of two further tensioning devices (32).