GB1172309A - Method for the Tightening of Screw Connections - Google Patents

Abstract

1,172,309. Nut-runners. PRESSLUFTWERKZEUG-UND MASCHINENBAU " PREMAG" G.m.b.H. 15 March, 1967 [16 March, 1966], No. 12165/67. Heading B3N. Fasteners are tightened by pneumatic nut runners 8 to a precise final tightening torque by first providing a torque whose value is below the final torque, interrupting the tightening during a required time period, and then tightening to the desired torque, during which time the tightening is interrupted for a desired time period. In operation, a manually operated valve 2 is opened and low pressure air flows through a circuit including a distributer 15 and a pressure reducing valve 18, to place a valve 4 in a first position wherein low pressure air flows through a line 6. A valve is also opened in a line 13, and air flows through valves 12, 9, to open an on/off valve 7. Low pressure air is supplied from line 6 to nut runners 8, the fasteners are tightened to a value below the final torque, and the nut runners stop. Back pressure builds up in line 6 until a valve 14 opens, and air is fed through this valve from distributer 15 to open a valve 16. Air at a higher pressure is fed to valve 4 through valves 17, 16 and 19, and simultaneously to a distributer 11, and thence to valve 12 which closes and interrupts the air flow to valve 7, which also closes and prevents air feed to runners 8. Air is also fed from distributer 11 to a normally closed valve 10, which is associated with means for providing a time delay, so that the valve is closed during this time and thereafter opens, and allows air to flow to valve 7, which opens and the runners 8 are driven at the increased torque. This supply of increased torque is interrupted intermittently for given intervals of time by control means associated with valve 10. A preselected number of interruptions may be counted, and valve 2 or valve 7 may be closed automatically.