| 摘要 |
<p>PURPOSE: To reduce a shock in switching operation of both hydraulic cylinders by extending an contracting a succeeding hydraulic cylinder after a preceding hydraulic cylinder reaches the stroke end in control of a boom extending and contacting hydraulic cylinder for sequentially operating a plurality of hydraulic cylinders. CONSTITUTION: When an extending and contracting boom provided with a plurality of extending and contracting hydraulic cylinders, and to be used for a crane is contracted from the full extending state, a preceding hydraulic cylinder 1 is contracted. When a full contraction detecting means 32 detects that the hydraulic cylinder 1 reaches the stroke end, a selector valve 4 is switched by a valve control means 36. Therefore, the boom contracting operation is performed by a succeeding hydraulic cylinder 2 in place of the preceding hydraulic cylinder 1, and the boom is finally contracted to the full contracting state. On the other hand, when the boom is extending from the full contracting state, the selector valve 4 is switched in response to the output of a full extension detecting means 33.</p> |
