A method for perforating a pipe wall with a punch comprising a body, a cutting punch and a three-part die with an upper die part, a lower die part and a wedge between the die parts, the method comprising the following stages:

- moving the pipe in its longitudinal direction to a punching position where the die is inside the pipe,

- expanding the die in the direction of movement of the cutting punch by moving the wedge in a first direction of transfer towards the end of the die,

- perforating the wall of the pipe with a cutting punch while supporting the wall with an expanded die during punching, whereupon the piece punched off from the pipe falls into a hole in the upper die part,

- contracting of the die by moving the wedge in a second direction of transfer opposite to the first direction of transfer,

- moving the perforated pipe away from the punching position in its longitudinal direction and

- moving the pipe to a position for finishing the rims of the hole.

A device for perforating a pipe wall, the device comprising a body, a cutting punch arranged to reciprocate with respect to the body and having the shape and size of the desired hole, an elongated die supported on the body by means of a support bushing and having a free end, the die comprising an upper die part with a hole corresponding to the shape and size of the cutting punch, and a lower die part as well as a wedge between the die parts, which can be reciprocated by a first power unit to expand and contract the die.

From the patent publication US 6128991 is known a method and device for perforating a pipe with a rectangular cross-section by punching. By means of the moving die part of a two-part die, the pipe is positioned on the centre line with respect to the cutting punch part by expanding the die in the lateral direction against the side walls of the pipe.

From the publication JPH 11244957 A is also known a method and device for perforating a pipe with a rectangular cross-section by punching. In it, a three-part die is expanded in the direction of movement of the cutting punch against the inner sur- faces of the pipe by moving the middle die part, the wedge surfaces on the lower surface of which cooperate with the wedge surfaces on the upper surface of the lowest die part. The topmost die part is attached to the body and the lowest die part is supported by a pivoted shaft on the base of the topmost die part. Below the die, the lower surface of the pipe is supported on the body for receiving the punching force of the cutting punch. The reciprocating movements of the middle die part serve the expansion of the die and the distance of travel is limited to the operating area of the wedge surfaces. The piece punched off from the pipe first falls against the inner surface of the pipe and may scratch the inner surface of the pipe when the pipe is pulled out. In addition, the die parts drag along the inner surface of the pipe when the pipe is pushed into the punching position and pulled out of it. This may also scratch the inner surface of the pipe.

When a cylinder, or collar, branching from the pipe wall is made in the pipe by stretching the wall material of the pipe, on the wall must first be made a suitable pilot hole from the rims of which the desired cylinder or collar can be stretched. The hole must be of such quality that its rim withstands stretching (so-called collaring) to form the desired collar.

The quickest known way of making holes in relatively thin walls is by punching. However, punching does not produce sufficiently high quality for stretching a branching cylinder or collar. When stretched, the material rips on the rim of a hole made by punching.

Another known way of making a high-quality hole for collaring purposes is to machine the hole by milling. From the point of view of production, milling is a slow way of making a hole of the desired shape because it requires chipping a large amount of material.

In the present invention, these two known perforating methods are combined by first making a pilot hole by punching and then finishing the pilot hole by milling. For this purpose, in the present invention has been developed a quick and efficient method and device for making a hole by piercing, or punching. The object of the present invention is to provide a method and device for efficiently producing a pilot hole which meets collaring requirements as an initial process stage of a collaring process. The method and device according to the invention must be applicable especially for perforating round pipes without deforming, scratching or otherwise damaging the pipe.

This object is achieved by the method according to the accompanying claim 1. The object is also achieved by means of the device according to claim 4. The dependent claims disclose preferred embodiments of the invention.

An embodiment of the invention is described in the following with reference to the accompanying drawings in which:

Figure 1 shows a top view of the perforating device according to the invention,

Figure 2 shows a section of Fig. 1 along line II-II,

Figure 3 shows a side view of the device according to Figs. 1 and 2,

Figure 4 shows a diagonal top view of the same device,

Figure 5 shows a diagonal top view of the wedge,

Figures 6A and 6B show the upper die part diagonally from above and below, and

Figures 7A and 7B show the lower die part diagonally from below and above.

The device comprises a body 1 and a cutting punch 2 which is arranged to reciprocate with respect to the body and the cutting punch blade of which has the shape and size of the desired hole. An elongated die 3, 5, 8 is supported on a support bushing 14 attached to the body 1, from which support bushing the die 3, 5, 8 projects. The die 3, 5, 8 has a free end from the direction of which the pipe to be perforated can be pushed around the die. The die 3, 5, 8 comprises an upper die part 3 with a hole 16 corresponding to the shape and size of the cutting punch, and a lower die part 5 as well as a wedge 8 between the die parts, which can be reciprocated in the longitudinal direction of the die by a first power unit 9 to expand and contract the die.

The pipe to be perforated is moved in its longitudinal direction to the punching position such that the three-part die 3, 5, 8 is pushed inside the pipe. The upper die part 3, which is the die part on the cutting punch 2 side, is attached to the support bushing 14 by means of a swivel joint 4 which allows the turning movement of the upper die part 3 in the direction of movement of the cutting punch 2 within the limits allowed by the support bushing 14 and the wedge 8. Due to this articulated support, the cutting punch side of the upper die part 3 is positioned inside the inner surface of the moving pipe at the pipe pushing stage without touching the inner surface of the pipe.

As can be seen in Figs. 6A and 6B, the upper die part 3 comprises an arm 3a with a hole 4a. The swivel joint 4 consists of a cotter bolt which penetrates the hole 4a. This means that the die part 3 can be easily replaced by another with a similar arm 3a but with an actual die part 3 adapted in size to the desired pipe diameter and hole size.

The lower die part 5 is attached to a carriage 10 moved by a second power unit 12 by means of a swivel joint 6 which allows the turning movement of the lower die part 5 in the direction of movement of the cutting punch 2 within the limits allowed by the support bushing 14 and the wedge 8.

As can be seen from Figs. 7A and 7B, the lower die part 5 comprises an arm 5a which has a hole 6a. The swivel joint 6 consists of a cotter bolt which penetrates the hole 6a. The die 6 can thus easily be replaced by another with a similar arm 6a but with an actual die part 5 adapted in size to the desired pipe diameter and hole size.

As shown in Fig. 5, the wedge 8 has wedge surfaces 8a, 8b on both sides which turn both die parts 3, 5 away from each other in an articulated manner to expand the die when the first power unit 9 moves the wedge 8 towards the free end of the die 3, 5, 8. The wedge 8 comprises an arm 18 with a hole 7b penetrated by the cotter bolt 7a with which the moving part 7 (such as the piston rod 7 of a piston type cylinder device) of the power unit 9 is attached to the wedge 8 arm 8a. In this case also the wedge 8 can easily be replaced in connection with the replacement of the dies 3 and 5. The support bushing 14 does not need to be replaced when the size and shape of the arms 3a, 5a and 18 of the die parts and the wedge remain constant.

The first power unit 9 is adapted to move the wedge 8 by a first transfer distance in the contracting direction. The second power unit 12 is adapted to move the lower die part 5 and the wedge 8 together by a second transfer distance, which is an extension of the first transfer distance. Due to the second transfer distance, the base of the hole 16 of the upper die part 3 opens and the piece punched off falls. Before this, the die had been contracted and the pipe had been removed from around the die and thus the fallen piece did not scratch the inner surface of the pipe.

Arrow 17 marks a power unit, such as a spring which turns the lower die part 5 upwards with respect to the swivel axis formed by the swivel joint 6 as the wedge 8 is moved backwards, that is, in the direction of contraction. Thus, the lower die part does not drag along the inner surface of the pipe either when the perforated pipe is pulled away from the punching position. The upper die part 3 turns downwards due to gravity when the die part contracts.

On the lower surface of the lower die part 5 is a threshold 15 which is adapted to rest against the support bushing 14 at the beginning of the said second transfer distance and to turn the lower die part 5 upwards or to support the lower die part 5 in the already upwards turned position to which the spring 17 has turned the die part 5.

The first power unit 9 is preferably a piston type cylinder device, the cylinder of which is attached to a carriage 10 and the piston rod 7 is attached with a cotter bolt 7a to the wedge 8. The piston rod 7 and the cotter bolt 7a are able to move through the carriage 10 opening. The second power unit 12 is preferably also a piston type cylinder device, the cylinder of which is attached to the body 1 and the piston rod is attached to the carriage 10. In the embodiment shown, on the lower surface of the upper die part 3 is a wedge surface which slopes downwards towards the free end of the die, whereupon the upper die part 3 thickens towards its end. The upper surface of the lower die part 5 slopes upwards, whereupon the lower die part 5 thickens towards its free end. The wedge angle of the wedge surfaces of the die parts 3, 5 is the same as the wedge angle of the wedge surfaces of the wedge 8. This provides as large as possible wearing surfaces and a solid die.

The direction of movement of the carriage 10 and correspondingly the direction of movement of the wedge 8 and the lower die part 5 is the same as the direction of movement of the pipe and the axial direction. The wedge 8 is on the centre line of the die and causes the symmetrical expansion of the die 3, 5, 8 in the direction of movement of the cutting punch when the power unit 9 moves the wedge 8 towards the free end of the die.

The cutting punch 2 is used to punch a hole in the pipe wall, which is supported by an expanded die 3, 5, 8 during punching. The piece punched off from the pipe falls into the hole 16 of the upper die part 3. The piece must not fall inside the pipe and drag along the inner surface of the pipe or follow the pipe when the perforated pipe moves to the next working stage. The perforated pipe is moved in its longitudinal direction away from the punching position and the pipe is moved to the hole rim finishing position in which the rim of the hole cut by the cutting punch is finished (by chipping) with a rotating blade, the movement of which follows the shape of the punched hole. The shape of the hole is more or less oval when the hole is made in the wall of a round pipe for making a branch collar. In this case, also the curvature of the cross-section of the upper and lower surface of the die 3, 5, 8 corresponds to the curvature of the inner surface of the round pipe. The width of the die is slightly smaller than the cross-section of the pipe.

Before punching the hole, the die 3, 5, 8 is expanded in the direction of movement of the cutting punch 2 by means of the wedge surfaces 8a, 8b of the wedge 8 by moving the wedge 8 in the first direction of transfer (towards the free end of the die) with respect to the die parts 3 and 5. During the transfer movement of the wedge 8 and the expansion of the die 3, 5, 8 , the die 3, 5, 8 is supported in the support bushing 14 from which the die 3, 5, 8 extends outside the support bushing 14. At the end of the transfer movement of the wedge the wedge surfaces 8a and 8b expand the die by turning the upper part and lower part of the die into contact with the inner surface of the pipe. During punching, the punching force is transmitted by means of the die 3, 5, 8 to the support structures (not shown) on the other side of the pipe without flattening the pipe.

After punching, the wedge 8 is moved by a first transfer distance in the second direction of transfer, which contracts the die by allowing the die parts 3, 5 to turn in an articulated manner towards each other. The die is no longer pressed against the pipe wall and the die parts 3 and 5 detach from contact with the inner wall of the pipe when the upper die part turns downwards and the spring 17 turns the lower die part 5 upwards. The die is then no longer in contact with the inner surface of the pipe when the pipe is pulled away from the punching position. The threshold 15 on the lower surface of the lower die part 5 is adapted to rest against the support bushing 14 and to keep the lower die part 5 turned upwards when the lower die part 5 and the wedge 8 are moved by a said second transfer distance. The base of the hole 16 then opens and the piece punched off from the pipe falls.

After this, the lower part 5 of the die and the wedge 8 are returned by means of the power unit 12 and the carriage 10 by the said second transfer distance towards the free end of the die, whereupon the device is ready to receive the next pipe to be perforated. The hole 16 is of the same size with the cutting punch and the hole to be made in the pipe over a certain distance and after that the hole 16 expands conically downwards, that is, in the direction of the working movement of the cutting punch 2, towards the wedge 8 and the lower die part 5.

The said first transfer distance is preferably shorter than the second transfer distance. The carriage 10 is supported by means of linear bearings 11 on a body (not shown) external to the device, to which the body 1 of the device is also attached by means of a body flange la.