US Patent 10345183 Screwdriver test bench with improved braking system

A test bench for screwdrivers comprises a hydraulic brake unit (11) provided with a coupling (12) for a screwdriver to be tested and angle and torque measurement transducers (15). The brake unit (11) comprises a disk (40) axially connected to the coupling (12) so as to be rotated by a screwdriver to be tested, and braking plates (42, 43) pushed in a controllable manner with their braking surfaces (44, 45) against the disk (40) by means of a plurality of pistons (46, 47) supplied with fluid by an electrovalve (16). The pistons (46, 47) of the plurality can be selectively activated under the control of the control unit (26) so as to select a maximum braking torque of the brake. The control may be performed by means a PID controller (19) which receives an electrovalve control signal (22) from a control unit (26) so as to follow braking curves depending on the angle of rotation and/or torque measured and has parameters which can be set using different sets of parameters. A method for controlling the bench is also described.