| 摘要 |
<p>A hand held motor driven electrically powered hammer, comprising an air cushion hammering mechanism in which an air cushion (44) is formed between a piston (38) and a ram (58) and a crank drive arrangement for converting a rotary drive from the motor (2) to a reciprocating drive to the piston (38). An intermediate gear arrangement (14) is provided between the motor (2) and the crank drive arrangement for transmitting rotary drive between the motor and the crank drive arrangement. The crank drive arrangement comprises a con-rod (34), which is made of a plastics material and is designed to break when the air cushion (44) between the piston and the ram deteriorates. In this way the hammer fails by the relatively weak con-rod (34) failing when the air cushion deteriorates due to deterioration of the seals between the piston and the hollow spindle and the ram and the hollow spindle. The failed hammer can be serviced by replacing the con-rod and seals, thereby delaying irreparable failure of the hammer due to repeated impacts between the piston and ram.</p> |
