GB701630A - Gang apparatus for tightening a plurality of threaded fastening elements - Google Patents

Abstract

701,630. Screwing-up bolts &c. STEVENS, D. July 8, 1952 [July 17, 1951], No. 17212/52. Class 83 (3). [Also in Groups XXIV and XXIX] In a machine for simultaneously screwing-up several screwed fastening elements, such as nuts 10, the nuts are tightened in two or more stages, the initial stage tightening the nuts to a predetermined torque and the succeeding stage or stages re-tightening them to the same torque or a higher torque to ensure a uniform degree of tightness. Any nut that may have initially tightened earlier than the others and been relieved of its share of holding force when the other nuts tighten is thus brought back to full tightness during the later stage or stages. The torque-limiting means may be controlled electro-magnetically or by fluid pressure. The wrenches 14 are driven separately by electric or other motors 66 and are yieldably mounted by springs 68 in standards 15 on a sliding table 16 which is fed forward by a pneumatic piston 70 and retracted by another piston 74 or by a return spring 72 on the first piston. The work W is mounted on a conveyer 11 and, through a switch 127, initiates the supply of current to a timer-motor 115 which drives a cam shaft 116 under the control of a ratchet switch 123 operated by solenoids 128, 136 having leaf-spring plungers 132, 138. As shown in Fig. 1, the torque-limiting clutch 40, Fig. 3, in each wrench is controlled by air-pressure supplied to the sealed casing 18 of the wrench and acting behind a piston 47 formed on a sliding member 33 which is engageable by inclined teeth with the hollow driving spindle 42 and is connected by balls 35 and splines to a secondary clutch member 27. The clutch member 27 has teeth 26 which engage teeth 25 on a socket spindle 22 when the latter is pressed rearwardly on contact with a nut 10. In operation, when the work W closes the switch 27, the solenoid 128 rotates the switch 123 to energize the timer motor and rotate the cam shaft 116 to operate the valves 86, 92, 97, 100 (see Group XXIX) which, when open, supply air to the operating units and, when closed, vent the air to atmosphere. A cam c first opens the valve 86 so that air from a lowpressure accumulator 81 is supplied behind the piston 47 in each wrench thus engaging each torque-limiting clutch 40. At the same time or a little later, a cam a opens the valve 97 so that the piston 70 advances the table 16 to engage the sockets and nuts and shift the spindles 22 inwardly so that the secondary clutch teeth 25, 26 engage. The nuts are then tightened until the horizontal component of force on the inclined teeth of each clutch 40 forces the member 33 outwards against the pressure on the piston 47 and allows the air to escape through the hollow spindle 42. Balls 53 in the member 27 are then forced out behind bevelled surfaces 60 on the member 33 by the bevelled ends 55 of a spring- loaded sleeve 56, and latch the clutch 40 in the disengaged position. The cam c then allows the valve 86 to close and a cam e opens the valve 100, supplying pressure to the piston 74 and retracting the table 16 against the action of the other piston 70 sufficiently for the teeth 25, 26 to be disengaged, the latch means 53, 55 released and the piston 47 moved back by a spring 62 to seat on the spindle 42. As the cam shaft continues to rotate, a cam d and valve 92 cause air from a high-pressure accumulator 82 to be supplied to the clutch piston 47 and, following venting of the line for the retracting piston 74, the pressure on piston 70 again advances the table 16 so that the nuts are again tightened to a greater degree. Finally, the cam a allows the valve 97 to close and vent the line to the piston 70 so that the spring 72 retracts the table 16, a cam b vents the header line 80 to the wrenches and a cam f momentarily closes a switch 119 so that the solenoid 136 rotates the ratchet switch to a position in which the circuit to the timermotor is broken. The pressure in both accumulators may be adjusted to the same value. In a modification, the machine and the wrenches are similar to those described above but the piston 47 is replaced by an electromagnet that attracts the sliding member 33 in order to engage the torque-limiting clutch 40 and a pair of cams, replacing the cams b, c and d, control switches for supplying current at a low or high voltage, or separately at the same voltage, to the electromagnet through collector rings on the driving spindle 42. In a modified wrench, the socket spindle 22a, Fig. 13, has teeth 181 engageable with teeth 180 on a torsion tube 179 having a forward disc 178 carrying fulcrum pins 177 for a pair of bell-crank pawls 176 that are spring- loaded to engage projections 174 on the driving shaft 171 and form the torque-limiting clutch. A drum 202, which does not transmit torque, surrounds the tube 179 and has a pair of spring- loaded contacts 197, 198 that are engaged by adjustable opposed contacts on a bar 191 in the disc 178 when the tube 179 twists relatively to the drum under load. Both pairs of opposed contacts are connected through collector rings 209, 215, 218, to a current supply at the same voltage but one pair of contacts has a closer spacing than the other pair and is operative at a lower load (and lesser amount of twist of the rod 179), to give the initial tightening to the nuts. The pawls 176 are normally locked in engagement with the projections 174 by a spring- loaded disc 182 which engages forward surfaces 190 on the pawls, as shown in Fig. 13, but, when the contacts 197 or 198 are closed, an electromagnet 187 is energized and is attracted towards the disc 178 so that, through pins 188, it pushes back the locking disc 182 and allows the pawls 176 to disengage. A spring-loaded latching sleeve 227 on a rod 224 connected to the socket spindle 22a then moves rearwardly to engage the surfaces 231 of the pawls and hold them disengaged until the secondary clutch teeth 180, 181 are next disengaged. A single cam, replacing the cams b, c and d, Fig. 1, may control a switch rendering the closer-spaced pair of contacts inoperative after the initial tightening of the nuts at the lower torque, or, if it is desired to retighten them at the same torque, the cam may hold the switch closed for sufficient time for a second application of the wrenches to the nuts or, alternatively, both pairs of contacts may have the same spacing. Portable machines.-A modified version adapted to be slung from a cable is also described and comprises wrenches of the type shown in Fig. 3 arranged round and geared to the shaft of a single driving motor. The wrenches are enclosed in a sealed casing to which air at low or high pressure can be supplied under the control of a two-way valve.