Method and device for perforating a pipe wall

A method for perforating a wall of a pipe with a punch, the punch comprising a body (1), a cutting punch (2) and a three-part die (3, 5, 8) including an upper die part (3), a lower die part (5) and a wedge (8) between the upper and lower die parts (3, 5), the method comprising the following steps:

• positioning the pipe in a punching position such that the die (3, 5, 8) is inside the pipe,
• expanding the die (3, 5, 8) in a direction of movement of the cutting punch by moving the wedge (8) in a first direction of transfer towards a free end of the die to thereby increase a distance between the upper and lower die parts (3, 5) and form an expanded die (3, 5, 8),
• perforating the wall of the pipe with the cutting punch (2) to thereby form a perforation including rims while supporting the wall with the expanded die (3, 5, 8) during punching, whereupon the piece punched off from the pipe falls into a hole (16) in the upper die part (3),
• contracting the die (3, 5, 8) by moving the wedge (8) in a second direction of transfer opposite to the first direction of transfer and away from the free end of the die,
• removing the perforated pipe from the punching position, and
• positioning the perforated pipe in a position for finishing the rims of the perforation,
• wherein the die (3, 5, 8) is supported by a support bushing (14) attached to the body (1),
• wherein the die (3, 5, 8) is kept out of contact with an inner surface of the pipe proximate to the die during the positioning of the pipe in the punching position, and the die (3, 5, 8) is brought into contact with the inner surface of the pipe during the expansion such that the upper die part is rotated upwards and the lower die part is rotated downwards as a result of the wedge being moved in the first direction of transfer,
• wherein after perforating the wall, the wedge (8) is moved by a first transfer distance in the second direction of transfer, which contracts the die by allowing the upper and lower die parts (3, 5) to rotate in an articulated manner towards each other,
• wherein when the perforated pipe is removed from the punching position, the lower part (5) of the die and the wedge (8) are then moved together by a second transfer distance in the said second direction of transfer thus exposing a base of the hole (16) in the upper die part, whereupon the piece punched off from the pipe falls out through the base of the hole (16), and
• wherein upon moving the lower die part (5) and the wedge (8) the second transfer distance in the second direction of transfer, the lower die part (5) is rotated upwards or supported in an upwards rotated position by supporting the lower die part of the die on the support bushing (14) by means of a notch (15) on a lower surface of the lower die part.