| 摘要 |
PURPOSE:To prevent breakage of a hammer, by a method wherein, when, during hammering of a pile, a weight or a cap is lowered excessively in relative relation to a casing, a weight driving device is brought to a stop. CONSTITUTION:When a pile 9 is driven to a too low depth and a cap 7 is lowered, as shown by a virtual line 7', relatively to a casing 1, an approach switch 10, located to an under cover 4, detects such lowering. When a signal is generated from the approach switch 10, a weight driving device is brought to a stop. This, when the driving distance of the pile 9 per one driving time is brought to a limit, enables stopping of the weight driving device, resulting in the possibility to prevent breakage of a hydraulic hammer.
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