Process and device for feeding concrete or other thick materials

A method comprising:

• feeding thick materials from a container into a feeding pipe via two feeding cylinders which are alternately connectable by a switching device to said container or to said feeding pipe, with feeding pistons of said feeding cylinders alternately performing a suction stroke and a pressure stroke, wherein the average piston speed V.sub.3 during the suction stroke is at least temporarily greater than during the pressure stroke, wherein, during a switching period t.sub.u of said switching device, the two feeding cylinders are substantially separated from said container at least temporarily and are short-circuited together to form a joint connection with said feeding pipe, wherein, during the switching period t.sub.u, one of said feeding pistons is still finishing its pressure stroke and the other of said feeding pistons begins its pressure stroke, wherein said one feeding piston only performs its suction stroke when the short-circuit is substantially cancelled again the feeder cylinder associated with said one feeding piston is connected to said container, wherein said short-circuit is established by a single switching device which, during short circuiting, separates said two feeding cylinders from said container, wherein said one feeding piston begins its pressure stroke during a time interval .DELTA.t of the switching period t.sub.u while said other feeding piston has not yet finished its pressure stroke, and wherein, during time interval .DELTA.t, both feeding pistons move at substantially half the average speed V.sub.1 of the remaining pressure stroke.

An apparatus for feeding thick materials, comprising:

• (1) at least two feeding cylinders which each have a feeding piston that alternately performs a suction stroke and a pressure stroke;
• (2) a switching device which alternately connects said feeding cylinders to a container or to a feeding pipe, said switching device comprising a pivot pipe which is pivotable with an inlet opening thereof alignable with mouth openings of said feeding cylinders, wherein said inlet opening and surrounding closing regions of said pivot pipe are designed such that, during a switching operation, said feeding cylinders are substantially short-circuited together with said feeding pipe but are substantially separated from said container;
• and (3) a separate cylinder/piston unit which drives each of said feeding pistons and which includes a cylinder, and wherein a selectively switchable line of a first pump is connectable to or separable from a first chamber of each cylinder at a piston rod side thereof, and further comprising a second pump which supplies pressurized fluid to a pressure chamber of each of said cylinders located at a front side of the associated piston, wherein said second pump is connectable, via a switchable line, either individually or jointly to said pressure chambers of said cylinders, and wherein the first chambers of said cylinders are jointly connectable to a pressurized-fluid return device.

An apparatus for feeding thick materials, comprising:

• (1) at least two feeding cylinders which each have a feeding piston that alternately performs a suction stroke and a pressure stroke;
• (2) a switching device which alternately connects said feeding cylinders to a container or to a feeding pipe, said switching device comprising a pivot pipe which is pivotable with an inlet opening thereof alienable with mouth openings of said feeding cylinders, wherein said inlet opening and surrounding closing regions of said pivot pipe are designed such that, during a switching operation, said feeding cylinders are substantially short-circuited together with said feeding pipe but are substantially separated from said container;
• and (3) a separate cylinder/piston unit which drives each of said feeding pistons, wherein a selectively switchable line of a first pump is connectable, via a respective adjustable flow divider, jointly to a pressure chamber of each cylinder located at a front side of the associated piston and to another chamber of each cylinder located at a piston rod side of said piston, or is separable therefrom, and further comprising a second pump that supplies pressurized fluid to the pressure chambers and that is connectable, via a switchable line, either individually or jointly to said pressure chambers, wherein lines of said flow dividers which lead to said pressure chambers are respectively connectable jointly with said pressure chambers, or can be blocked together, and wherein said flow dividers are jointly connectable to a pressurized-fluid return device when said flow dividers are separated from said first pump.