| 摘要 |
<p>PURPOSE:To reduce the number of pipings within a rotary joint running to an upper rotary table, by a method wherein a regulation cylinder for regulating tension of a track shoe is communicated with a counterbalance valve in a line for a hydraulic motor for running through a switching valve. CONSTITUTION:A hydraulic motor 9 for running is attached to a lower running body, and a counterbalance valve 8 is installed in the oil pressure piping of the motor for running. Further, a regulation cylinder 16 for regulating tension of a track shoe, communicated with the counterbalance valve 8, is provided. A switching valve 23, on the pressure receiving part of which the pressure of the regulation cylinder 16 is exerted directly, is provided, and the switching valve 23 is disposed so that is shuts off a line through which an oil pressure piping for running and a counterbalance valve 15 are intercoupled. When a pressure in a pressure receiving chamber 24 is increased to a value exceeding a given pressure, the switching valve 23 is changed over, oil is drained from the pressure receiving part of the counterbalance valve 15 through the switching valve 23, and the counterbalance valve 15 is brought to a neutral state. This enables simplification of a rotary joint.</p> |
