Successive hole boring machine and lost strike preventing device for successive hole boring machine

摘要

A plurality of rods each having a bit at a front end are disposed in parallel to one another so that adjacent bits are displaced to some extent forward and backward, and a striking device operatively connected to each of the rods includes a striking block. The striking block includes a single cylinder block having a plurality of cylinder tubes, and a striking piston is slidably fitted into each of the cylinder tubes. The striking block further includes a change-over valve for changing over between a forward movement and a backward movement of each striking piston. A rear end of each rod is connected through an adapter to a shank rod which is connected to the striking device. In the striking device, a spring is provided between a bearing holder which holds the shank rod rotatably and the adapter to push the rod in a forward direction. When the bit is not reached the rock, the rod is pushed forward by the spring to hold the shank rod at a position before the striking point.