| 摘要 |
<p>PCT No. PCT/GB96/01389 Sec. 371 Date Mar. 13, 1998 Sec. 102(e) Date Mar. 13, 1998 PCT Filed Jun. 10, 1996 PCT Pub. No. WO96/41694 PCT Pub. Date Dec. 27, 1996Apparatus for cutting a hole through a plastic liner in a gas or other main comprises a body forming module of a train of modules adapted to travel through the main. The body has a radially movable platform carrying a cutter. The platform has four cams engaging four cams pivotally mounted on tie-bars. Advancing movement of the platform pushes the cams outwardly causing support legs to move outwardly and to cause four slave legs carried by the support legs to engage the plastic liner. Further advancing movement of the platform causes the cutter to engage the liner and also holds the support legs in their advanced position as noses on the cams traverse the faces of the cams.</p> |
