Improvements in or relating to torque control mechanism

摘要

913,367. Clutch control. BLISS CO., E. W. Sept. 22, 1959 [Sept. 22, 1958], No. 32241/59. Class 80 (2). A fluid-pressure actuated friction clutch for a crank-driven power press in which the torque transmitted to the press crank-shaft produces the rated tonnage for positions relatively high in the stroke and in which the torque is thereafter progressively diminished so as to continue to produce, but not exceed, the rated tonnage, is provided with control means for relieving the clutch engaging pressure in order to reduce the torque transmitted, the control means ensuring that the rate of relief is constant despite possible wear of the friction linings of the clutch. Driven clutch-plates 16, 24 rotating with a crank-shaft 30 are engaged with a plate 26 fast with a driving flywheel 28 by air pressure on a piston 34 and are disengaged, with consequent engagement of a brake 12, by springs. To engage the clutch, solenoid-actuated pilot valves 42, 52 are actuated so that a valve chamber 56 is opened to exhaust through the pilot valve 52 and a chamber 46 is supplied with air from a pressure tank 36 through a line 74 and valve 42. Tank 36 also supplies air through a line 62 to unseat an inlet valve piston 58 from a seat 64 so that air is supplied through a line 66 to engage the clutch. Pressure in chamber 46 seats an outlet valve piston 48 on a seat 79 to close an exhaust line 60. To reduce the engaging pressure the solenoids of both pilot valves are de-energized so that pressure is supplied to chamber 56 to seat the inlet valve piston 58, and chamber 46 is opened to exhaust through a restriction 78. The pressure in chamber 46 falls at a controlled rate and piston 48 moves to give a throttled exhaust from the clutch cylinder, the pressure drop in the clutch cylinder being a function of the drop in the chamber 46 and hence independent of wear of the plates and consequent changes in the effective volume of the clutch cylinder. An electric control circuit including switches actuated by cams on a cam-shaft geared to the crankshaft is described for automatic control of the press through a complete cycle.