How concrete pump works?

A concrete pump which comprises an elongated hollow housing in which a valve element reciprocates. The valve element includes a pair of transversely extending tubes and a pair of concrete guiding chambers. The valve element moves between two positions. In the first position a first guide chamber is opposite a first pump cylinder and guides concrete from an upright conduit associated with the first pump cylinder into the first pump cylinder and a first tube is opposite a second pump cylinder and guides concrete from the second pump cylinder into a discharge line associated with the second pump cylinder. At the second position a second guide chamber is opposite the second pump cylinder and guides concrete from an upright conduit associated with the second pump cylinder into the second pump cylinder and the second tube is opposite the first pump cylinder and guides concrete from the first pump cylinder into the discharge line associated with the first pump cylinder.