| 摘要 |
PURPOSE:To control a device so that it is automatically operated, by a method wherein, after detection of completion of forward movement of piston for forced- feeding of soil, actuation of a delay motion circuit, and detection of completion of backward movement, a direction switching valve is changed over through motion of the delay motion circuit. CONSTITUTION:By means of a first hydraulic detector 45, completion of forward movement of a piston 30 for forced-feeding of soil is detected. Thereafter, by means of a coil 55 with a timer, a timing motion (a) of a contact 67 and a coil 69, with all of which a first motion delay circuit is formed, after forward movement of the piston 30 is completed, the piston is brought to a stop in the position for a set time. Through the working of a second hydraulic detector 46, completion of backward movement of a piston 19 for pushing an outer cylinder is detected, an electromagnetic valve 42 is switched, and malfunction is prevented from occurring by means of a second delay motion circuit. This prevents the occurrence of a reverse flow due to elasticity of soil, forcibly pushed in a soil forced-feed pipe once, and enables reliable feed of soil to a soil suction port.
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