PURPOSE: To shorten the pressure accumulation time length of the accumulator in a hydraulic circuit for a hydraulic crane, by causing the communication between the accumulator and a bottom-side chamber of a cylinder and the communication between the bottom-side chamber thereof and a rod-side chamber thereof when the load body is lowered.
CONSTITUTION: When a load body 12 is kept stopped at the lowered end, a controller 25 detects that the load body 12 is located at the lowered end, by a signal inputted via a signal line 34 from a lowered end limit switch 32. It starts causing a pressure accumulation in an accumulator 1 by driving an electric motor 3 and a hydraulic pump 2, and opening solenoid valves 20 to 22. When the controller 25 detects that the pressure in the accumulator 1 has become high enough to cause the load body 12 to rise, by a signal inputted via a signal line 27 from a pressure switch 24, it stops the rotation of the electric motor 3 and closes the solenoid valves 20 to 22. When, thereafter, a rise switch 29 is operated, the load body 12 rises.
KANAI TAKASHI
OCHIAI MASAMI
OSHINA MORIO
SONODA MITSUO
KATO HIDEYO
KUBOTA TAKAYUKI
TSURIGA YASUTAKA
