BENDER DRIVING DEVICE

WIPO Patent Application WO/2012/096338

A1

A bender driving device provided with: a drive cylinder (11) which moves one table (2) in a reciprocating manner; an electrically-driven device (13) which has a motor (14) and a ball screw rod (16) connected to the motor and in which the ball screw rod (16) moves in a reciprocating manner by means of the motor (14) being driven; a first control cylinder (21) which is connected to the ball screw rod (16); a second control cylinder (22) which is connected to the first control cylinder (21); and a control valve (23) which is disposed between the first control cylinder (21) and the drive cylinder and between the second control cylinder (22) and the drive cylinder, and which switches between connecting and disconnecting the first control cylinder (21) with the drive cylinder (11) and between connecting and disconnecting the second control cylinder (22) with the drive cylinder (11). The diameter (d1) of the cylinder chamber (25) of the first control cylinder (21), the diameter (d2) of the cylinder chamber (35) of the second control cylinder (22), and the diameter (d3) of the cylinder chamber (45) of the drive cylinder (11) fulfill the following relationship: d1