Screwer test bench with bidirectional control
Within a test bench for screwdrivers, comprising a braking unit ( 11 ) with a brake ( 14 ) equipped with a fitting ( 12 ) for a screwdriver to be tested and transducers ( 15 ) for the measurement of angle and torque, a method for controlling the brake ( 14 ) comprises a step wherein movement along a torque/angle curve ( 17 ) is controlled in a bidirectional manner, in the sense that the brake is controlled according to a curve whose torque values are based on the angle during both decremental progression of the angle and incremental progression of the angle. The method can also comprise a step consisting of setting a starting Cstart torque value other than zero and following the torque/angle curve ( 17 ) from the said Cstart value during a screwdriver test.
1. A control method for a test bench for screwdrivers, comprising a braking unit with a brake equipped with a fitting for a screwdriver to be tested and transducers for measurement of angle and torque, the brake being instructed by a control unit to follow, during a screwdriver test, a torque/angle curve, and the method comprising the step of controlling movement along the torque/angle curve in a bidirectional manner such that the brake is controlled to apply a torque value to the fitting according to the torque/angle curve with torque values being a function of angle values measured by the transducers during both decremental progression of the angle and incremental progression of the angle.
2. The method according to claim 1 , wherein the progression of the curve is followed up to the torque/angle value set as a start of a plastic behaviour of the screw simulated by the test bench with the torque/angle curve.
3. The method according to claim 1 , comprising the steps of:
setting a starting Cstart torque value other than zero and following the torque/angle curve from the said Cstart value.
4. The method according to claim 3 , comprising the steps of:
storing—in a memory of the test bench—one or more torque/angle curves or values or points which are representative of such curves, for generation of the curves, with such curves starting from a torque value of zero and an angle value of zero,
selecting the curve to test a screwdriver,
shifting the curve in order to start from a Cstart torque value with a zero angle value, and
controlling the brake according to the shifted curve.
5. A test bench for screwdrivers comprising a braking unit with a brake equipped with a fitting for a screwdriver to be tested and transducers for measurement of angle and torque and a control unit controlling the brake, the control unit being adapted to control the brake according to at least one torque/angle curve in a bidirectional manner as a function of the angle measured by the transducers during both decremental progression of the angle and incremental progression of the angle.
6. The test bench according to claim 5 , further comprising a selection unit for selection of a braking curve from a plurality of braking curves, the selection unit comprising a memory containing one or more torque/angle curves or values or points which are representative of such curves for the generation of the curves, and a processing unit for the calculation of a selected braking curve, connected to the control unit for the control of the brake according to the selected braking curve.
7. The bench according to claim 5 , wherein the brake is hydraulically operated brake connected to a source of pressurised fluid via an electrically powered proportional valve controlled by the control unit.