To prevent generation of impact noise at the longest expansion time of a concrete pump by reducing an expansion speed before the longest expansion position of a pump cylinder, in a concrete pump pumping ready-mixed concrete by alternating action of a pair of pump cylinders.
A section before the longest expansion position of a drive cylinder DC2 driving the pump cylinder is detected by a detection means DE2, and operation oil quantity supplied to the drive cylinder DC2 is controlled to be reduced. A projection part 111B provided at the section which is short of the longest expansion position of the drive piston 23 is inserted in a communication oil path 121 of a cylinder barrel 31, and a restriction oil path is formed between the projection part 111B and the communication oil path 121 to limit quantity of working oil circulated to an oil tank T from a working oil chamber of the drive cylinder DC2.
OMURA SHINJIRO
NAKAMURA TAKEYUKI
| JP2007138817A | 2007-06-07 | |||
| JPS5061286U | 1975-06-05 |
Kazuaki Niki
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