| 摘要 |
An impulsive unit (12) for a jack hammer (10) or rock drill (80, Figs 2 and 3) is adapted to be powered by water, and comprises a piston (34) slidable within a cylinder (32), and carrying a striker portion (35) thereon. At least a portion of the piston and/or cylinder is coated with ceramic. The ceramic is most suitably an aluminium oxide-titanium dioxide composite, which enables the clearance between the internal diameter of the cylinder and the external diameter of the piston to be reduced to between 8 and 10 micro-metres. |
