Safe-to-operate hydraulic drive

A method of operating a drive system including at least one cylinder with at least one cylinder chamber and one second cylinder chamber separated from the same, which are connected to one another via a connecting line to form a fluid-filled hydraulic circuit with a hydraulic drive arranged therein, and the connecting line has at least one parallel system, between the hydraulic drive and one of the two cylinder chambers, of at least one first sub-connection with at least one first stop valve and a second sub-connection with a baffle arranged therein, wherein the connecting line, including the first sub-connection and excluding the second sub-connection, has a first flow resistance and the second sub-connection, has a second flow resistance determined by the baffle arranged therein, which is greater than the first flow resistance for the fluid, the method comprising the following steps:

• opening at least the first stop valve for a normal mode of the drive system;
• conveying the fluid by means of the hydraulic drive in normal mode from one cylinder chamber, via at least the first sub-connection, into the other cylinder chamber in order to move a piston rod of the cylinder;
• closing the first stop valve in order to operate the drive system in a safe mode, wherein a maximum permissible speed of the piston rod is not exceeded in the safe mode, even where an external force acts on the drive system in the direction of movement of the piston rod, by having selected a suitably high second flow resistance;
• and
• conveying the fluid by means of the hydraulic drive in safe mode from one cylinder chamber, via the second sub-connection, into the other cylinder chamber in order to move the piston rod of the cylinder.

A hydraulic drive system for moving a piston rod of at least one cylinder, the drive system comprising at least a first cylinder chamber and a second cylinder chamber separated from the same, which are connected to one another via a connecting line to form a fluid-filled hydraulic circuit, and a hydraulic drive for conveying the fluid from one cylinder chamber, via the connecting line, into the other cylinder chamber, is arranged in connecting line, wherein the connecting line has at least one parallel system of at least one first sub-connection with at least one first stop valve- and a second sub-connection with a baffle arranged therein, between the hydraulic drive-and one of the two cylinder chambers, wherein the connecting line, excluding the second sub-connection, has a first flow resistance and the second sub-connection has a second flow resistance due to the baffle arranged therein, which is greater than the first flow resistance for the fluid, wherein the drive system is provided with at least one open first stop valve in normal mode and with a closed first stop valve in safe mode for conveying the fluid, and a suitably high second flow resistance has been selected such that a maximum permissible speed for the piston rod is not exceeded in safe mode, even where an external force acts on the drive system in the direction of movement of the piston rod, wherein the first stop valve can be operated electronically and the drive system includes a drive control for actuating the hydraulic drive for moving the piston rod and for electronic switching of at least the first stop valve for at least normal and safe mode, and wherein the drive control incorporates a safety logic circuit, which is provided in order at least to switch over at least the first stop valve from normal mode to safe mode, in response to the safety signals received.

A hydraulic drive system for moving a piston rod of at least one cylinder, the drive system comprising at least a first cylinder chamber and a second cylinder chamber separated from the same, which are connected to one another via a connecting line to form a fluid-filled hydraulic circuit, and a hydraulic drive for conveying the fluid from one cylinder chamber, via the connecting line, into the other cylinder chamber, is arranged in connecting line, wherein the connecting line has at least one parallel system of at least one first sub-connection with at least one first stop valve- and a second sub-connection with a baffle arranged therein, between the hydraulic drive-and one of the two cylinder chambers, wherein the connecting line, excluding the second sub-connection, has a first flow resistance and the second sub-connection has a second flow resistance due to the baffle arranged therein, which is greater than the first flow resistance for the fluid, wherein the drive system is provided with at least one open first stop valve in normal mode and with a closed first stop valve in safe mode for conveying the fluid, and a suitably high second flow resistance has been selected such that a maximum permissible speed for the piston rod is not exceeded in safe mode, even where an external force acts on the drive system in the direction of movement of the piston rod, wherein the first stop valve can be operated electronically and the drive system includes a drive control for actuating the hydraulic drive for moving the piston rod and for electronic switching of at least the first stop valve for at least normal and safe mode, and wherein a second stop valve is arranged in the connecting line outside of the first sub-connection in order to enable safe shutdown of the drive system.