CYCLE HAMMER FOR DRILLING HARD ROCK GROUND

PROBLEM TO BE SOLVED: To provide a cycle hammer housing a plurality of air hammers, in which a drilling bit of each of the air hammers can be uniformly abraded on its entire peripheral surface, while occurrence of action deficiencies caused by flow of small pieces such as a packing material, a small stone or the like into the air hammer can be controlled. SOLUTION: A hex plate 1 has an unnecessary-object-inflow-protection net 3 arranged on its lower surface and can be detachably mounted in an airtight state on an upper case 4 partitioning a high-pressure air chamber S4. The hex plate 1 can also retain the drilling bit 16 of the respective air hammer AH to a drive sub 15 rotatably in a vertically slidable manner, while generating rotation action R2 on each of the drilling bits 16 along with the drilling action by the rotation R1 of the cycle hammer CH and leveling out the abrasion of a drilling head 16F, so as to improve the operation rate of the drilling bit 16. COPYRIGHT: (C)2011,JPO&INPIT