Patent ID: 6171075
Filing Date: 2001-01-09
Classification: F04B

Abstract:
A method for controlling a thick matter pump,said pump comprising:a material feed tank;first and second conveying cylinders (1, 1'), each in fluid communication with a material feed tank and each including a conveying piston (7, 7') for pumping thick matter through the respective conveying cylinder,hydraulic drive cylinders (5, 5'), each of which having a drive piston (8, 8') connected via a piston rod (9, 9') to a conveying piston (7, 7'), each drive cylinder coupled at one end to a respective port of a hydraulic reversing pump (6) and coupled at the other end to each other by way of an oscillating oil line (12) thereby forming a closed hydraulic circuit, the reversing pump driving a respective drive piston through a compression stroke by pumping pressurized fluid to the respective drive cylinder, anda hydraulically operable pipe shunt (3) disposed within the material feed container and adapted to be alternately coupled to the conveying cylinders to receive the thick matter being pumped from the respective conveying cylinder to which it is coupled, and being coupled to a conveying line (4) to direct the flow of thick matter from each conveying cylinder into the conveying line (4), andsaid method comprising:actuating the pipe shunt to be decoupled from the first conveying cylinder and coupled to the second conveying cylinder when the drive piston of the first conveying cylinder reaches the end of its compression stroke,reversing the direction of fluid flow through the reversing pump (6) to initiate the compression stroke of the second drive cylinder, including closing off the oscillating oil line (12) at least momentarily during the reversing the direction of fluid flow through the reversing pump (6) and reopening the oscillating oil line (12) at a time between shortly before and after the pipe shunt has been switched,when the drive piston of the second conveying cylinder reaches the end of its compression stroke, actuating the pipe shunt to be decoupled from the second conveying cylinder and coupled to the first conveying cylinder,reversing the direction of fluid flow through the reversing pump (6) to initiate the compression stroke of the first drive cylinder, including closing off the oscillating oil line (12) at least momentarily during the reversing the direction of fluid flow through the reversing pump (6) and reopening the oscillating oil line (12) at a time between shortly before and after the pipe shunt has been switched,wherein pressure oil is taken off directly from hydraulic lines (11, 11') in order to effect the switching of the pipe shunt (3).