西德维尔特(Wirth)公司发明了一种顺序迈步式天井钻机,由直径不等的上下两级扩孔乃盘和连接于其间的液压缸组成。液压缸以水为传动介质,可使上下刀盘作轴向移动,但不能产生相对转动。作业时,扩孔器刀盘上的中心拉杆与导孔内的钻杆连接,获得来自钻机的扭矩和轴拉力,每一循环由两级顺序扩孔组成。第一级扩孔:液压缸全部伸出,钻机通过钻杆驱动,扩孔器旋转和向上推进,上刀盘接触岩 Wirth Company invented a step-by-step progressive boring machine consisting of two non-expanding upper and lower countersinking plates and a hydraulic cylinder connected in between. Hydraulic cylinder to water as the transmission medium, can make the upper and lower cutter for axial movement, but can not produce relative rotation. During operation, the center tie rod on the reamer head is connected to the drill rod in the pilot hole to obtain the torque and shaft pull from the drill. Each cycle consists of a two-stage sequence reaming. The first level of reaming: all the hydraulic cylinders are extended, drilling rig driven by the drill, reamer rotating and pushing up, on the cutter contact rock