Patent ID: 7887270

Claim:
An apparatus for cutting an oval hole in the wall of a pipe, said apparatus comprising a baseplate ( 1 ) with elements ( 18 ) for securing a pipe to be cut, a carriage ( 2 ) supported on top of the baseplate ( 1 ) for linear movement along runners ( 3 ), a drive pulley ( 4 ) driven by a power unit ( 7 ) and having an opening ( 8 ) for a tool ( 20 ) and an internal toothed rim ( 9 ) meshing with an external toothed rim ( 19 ) of the tool ( 20 ) for rotating the same, a gear ( 22 ) meshing with a second toothed rim ( 23 ) of the tool ( 20 ) for rotating it slowly, whereby a cutter head ( 24 ) is carried by said slow rotational motion relative to the carriage ( 2 ) along a circular path, the cutter head ( 24 ) rotating at the same time about its own axis driven by the toothed rims ( 9 , 19 ), characterized in that adapted for rotation along with the drive pulley ( 4 ) is a cogged wheel ( 10 ), which through the transmission of a cam lever ( 11 ) is adapted to drive a shaft ( 12 ) whose rotational motion is transmitted on the one hand to drive the gear ( 22 ) and on the other hand to work the carriage ( 2 ) back and forth in relation to the baseplate ( 1 ), a round-trip displacement ( 2 xa ) being equal to a difference between the major axis and the minor axis of a desired ellipse.