Patent GB-1444638-A (GB)
Title: Machine tools
IPC: B23Q16/02
Filed: 1973-10-19
Abstract: 1444638 Welding by pressure PRODUCTION TECHNOLOGY Inc 19 Oct 1973 [25 Oct 1972] 48938/73 Heading B3R A machine tool having a chuck 12 rotatable by an hydraulic motor 22 includes an indexing apparatus for locating the chuck in a selected angular position, the apparatus comprising control means for varying the fluid pressure imposed on the motor to control the speed of the motor, a first signalling device coupled with the control means to commence operation of the motor at a first speed, a second signalling device for sensing a first angular position of the chuck and thereupon causing the motor to operate at a second, lower, speed and a third signalling device for sensing a second angular position of the chuck to cause a valve to close a fluid outlet from the motor whereby the motor is braked to stop the chuck in said selected position. In an embodiment a friction welding machine includes a tailstock 14 movable along the machine frame and carrying a chuck 13 secured against rotation and an axially foxed but rotatably mounted chuck 12. The chuck 12 is mounted on a shaft 17 carrying an inertial weight 24 and driven through gearing 26 by the hydraulic motor 22 driven in turn by an hydraulic pump 21 rotated by an electric motor. Pressure fluid is supplied from the pump 21 via a main valve 27 operable by a pilot valve 28 controlled by a solenoid J. A small pump 31 is connected to the motor 22 by a valve 32 controlled by a solenoid V and when fluid from the pump 31 is supplied to the motor 22 fluid returning via orifice 36 and possibly by orifice 34 through the valve 32, a valve 33 controlled by a solenoid 7 blocking the orifice 34 or placing it in parallel with the orifice 36. A valve 56 controlled by a solenoid P may place the pump 31 in communication with a brake valve 57. A limit switch 37 is operable by an element 38 on the tailstock 14 to initiate operation of the motor 22 by the pump 31 and a pneumatic circuit 41 controls stopping of the pump 31, the circuit 41 including an air pump 42 is connected to two nozzles 51, 52 by a valve 44 controlled by a solenoid A, the nozzles being on the same radii of a plate 46 secured to the shaft 17 as a pair of elongated circumferentially spaced apertures in the plate 46 and the nozzles being connected to pressure responsive switches 53, 54. In operation two workpieces WP1 and WP2 are friction welded in the machine and after welding, the chuck 12 is opened and the welded workpieces are retracted in the tailstock for removal. Switch 37 is operated by the tailstock as it is retracted to energize the solenoids P.V.Y and A, the solenoids V and Y shifting the valves 32, 33 to allow fluid from the pump 31 to rotate the chuck at 60 r.p.m. with return fluid from the motor passing through both orifices 34, 36. The solenoid A shifts valve 44 to allow air to exit from nozzles 51, 52 and when the nozzle 51 aligns with the aperture 47 the switch 53 de-energizes solenoid Y to block the orifice 34 and the speed of the chuck is reduced to 20 r.p.m. As the nozzle 52 aligns with aperture 48 the switch 54 de-energizes solenoid V to close valve 32. The inertia of the motor 22 &c. causes the motor to act as a pump to produce pressure in the brake valve 57, thus stopping the motor 22 immediately. A new component may be automatically placed in the chuck 12. A similar device but including a light sensing control circuit instead of the pneumatic circuit 41 is described.