Patent GB-1224359-A (GB)
Title: Method and apparatus for friction welding
IPC: B23K20/12
Filed: 1968-05-03
Abstract: 1,224,359. Welding by pressure. NORTH AMERICAN ROCKWELL CORP. 3 May, 1968 [30 June, 1967], No. 21212/68. Heading B3R. In friction welding two metal workpieces, one workpiece is rotated relatively to the other, one workpiece is moved towards the other, the initial speed of movement is reduced to decelerate the moving workpiece to avoid rebounding on initial contact, the engagement pressure is abruptly increased to a first thrust level and then gradually increased to a second and higher thrust level to render the metal fusible and then abruptly increasing the pressure to a third thrust level, the pressure being released after the rotation has stopped. In friction welding three workpieces end to end the central workpiece 12, e.g. an axle housing centre section is held stationary in a cradle 14 on a machine base by adjustable jaws 15, 16 and 18, 19 and work.- piece 11, 13, e.g. wheel bearing end spindles are mounted upon similar hydrostatic bearing carriers 22, 23 respectively at opposite ends of the workpiece 12. The jaws 15, 16 are driven by an hydraulic piston and cylinder device and the jaws 18, 19 are driven by rotary hydraulic motors. The carrier 22 comprises an annular frame 51 having side members slidable on rails 52, 53 on the machine base, hydraulic cylinders 53, 54 being fixed to the base with their piston rods 56, 57 secured to the side members to effect movement of the carrier along the machine base. Shaft 58 extends slidably with a splined connection through an axially stationary pulley 61, the pulley being driven by belts 63, 64 from a drive motor 67 having clutch and braking devices 68, 69 and the shaft being operatively connected to the workpiece 13 in the carrier. The carrier 23 is similarly mounted to slide along the machine base with a similar drive shaft connection. A housing T, Fig. 3, is fitted within the frame 51 of carrier 22 and a frustoconical nose portion 75 is secured to the housing, the housing having a large recess 77 with front and rear spaced cylindrical surfaces 78, 79. Within the recess 77 is secured a core section 83 having, cylindrical surfaces 85, 86 mating with and sealed to surfaces 78, 79 so that an annular chamber 89 is formed within the housing. The driven shaft 58 is connected to the end of a drive sleeve 92 splined to a hollow arbor 95 having a surface 97 within a bore 98 in the core 83, a radially enlarged flange 99 adjacent a flat face 100 of the core 83 and a front section 101 within the nose portion 75. A piston 107 is slidable within the arbor 95, a spring 112 urging the piston to the right in Fig. 3, the piston rod 114 of the piston carrying a coupling 118 with a series of duct elements 121 to grip the workpiece 11. Heated oil under pressure is supplied through passage 153 to flow through calibrated orifices 157 into a series of circumferentially spaced cavities 154 between the arbor and the nose portion 75 to support the arbor front section 101 on the oil as a hydrostatic journal bearing. Oil is also supplied through passage 161 to the chamber 89 to be supplied to a series of spaced cavities 163 between the arbor and the core 83, to support the arbor rear section on the oil as a second hydrostatic journal bearing. Oil from the chamber 89 also flows into the arbor to force, when the oil pressure is increased, the piston 107 to the left to clamp the workpiece. Oil is also supplied by a passage 181 to the space between the rear face of the arbor flange 99 and the front face 100 of the core 83 to flow to a low pressure passage 162, the oil providing a first hydrostatic thrust bearing. Oil from the front of the piston 107 flows through radial passages 191 in the flange to a groove 194 to form a second hydrostatic bearing. The carrier 23 has similar hydrostatic journal and thrust bearings. In operation the centre workpiece is clamped to the machine base by the jaws 15, 16 and 18, 19 and the end workpieces 11, 13 are inserted loosely into the chucks in the carriers 22, 23, with oil flowing in the hydrostatic bearing circuit. A cycle start switch is pressed and pressure in the bearing circuit builds up so that clamping of the workpieces 11, 13 is effected. A first and a second timer are simultaneously energized as a result of the pressure build up and the brakes on the drives for the shafts 38, 58 are released. The first timer causes energization of clutch devices on the drive devices to start rotation of the end workpieces 11, 13 and the second timer delays forward advancement of the carriers until the desired rotational speed of the workpieces 11, 13 is obtained. When the second timer times out, oil is delivered to the cylinders 32, 33, 54, 55 to accelerate the carriers towards the centre workpiece and as the carriers advance they trip switches which cause the hydraulic and electric circuits to decelerate the carriers so that the workpieces 11, 13 gently abut the centre workpiece 12. A third timer times the deceleration period and when it times out fourth and fifth timers are energized. The fourth timer causes the circuits to increase the oil flow rate to the cylinders 32, 33, 54, 55 to abruptly push the outer workpieces 11, 13 against the centre workpiece in about three seconds. The engagement pressure is then gradually built up and the fourth timer allows sufficient heat to be generated to bring the workpiece surfaces to a fusible condition. The first timer times out to stop the rotation of the workpieces 11, 13 and just after this the fourth timer times out to cause -an abrupt increase in the oil pressure in the cylinders 32, 33, 54, 55 to produce a final weld pressure. This pressure is held until the fifth timer times out to cause unclamping of the workpieces and return of the carriers. The workpieces 11, 13 may be braked or allowed to coast to a stop and the final weld pressure may be applied before the rotation is stopped.