| 摘要 |
An apparatus to feed a constant flow of concrete comprises two hydraulic cylinder-piston units (2, 3), acting alternately so as to operate two corresponding pistons (22, 23) feeding the concrete to a concrete delivery pipe (17) through a commutating valve (6), and a proportioning device to feed the additives having to be added to the concrete. The device proportioning the additives consists of a pump (5), which is operated by a hydraulic motor (4) driven by a hydraulic circuit derived from the main hydraulic circuit operating said cylinder-piston units (2, 3). Said derived hydraulic circuit consists of a circuit which connects said hydraulic motor (4) to the exhaust chambers of the cylinders of said cylinder-piston units (2, 3) through a valve system (20) apt to "rectify" the hydraulic flow.
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