Patent GB-1060408-A (GB)
Title: Improvements in and relating to grinding machines
Inventor: BALSIGER HAROLD EDWARD
IPC: B24B5/42
Filed: 1964-06-02
Abstract: 1,060,408. Grinding crankshafts. LANDIS TOOL CO. June 2, 1964,: No. 22692/64. Heading B3D. A machine for grinding axially spaced portions of a workpiece W, such as a crank-shaft, having axially spaced portions having variable degrees of stiffness both from portion to portion and from one angular position to another within an individual portion, comprises a work support 12 on a bed 10, a headstock 15 and footstock 16 on the support for rotatably supporting the workpiece, a support 31 movable towards and away from the work support and having one or more grinding wheels 30, means for moving the wheel support to effect a preliminary grinding on one or more of the portions which assume an elliptical cross-section because of the variable stiffness, means to retract the wheel support when it has reached a predetermined position, a work rest 100 which has means for advancing it into engagement with the one or more portions while the wheel support is retracted to support the workpiece for rotation about its true axis, and means for advancing the grinding wheel to reduce the major diameter of the portion until the portion has a uniform diameter coaxial with the headstock and tailstock. The wheel support 31 may be manually advanced and retracted by a hand wheel 40 on a shaft 41 having a worm 42 meshing with a worm-wheel 43 on a second shaft 44 having a worm and wheel connection 45 with a feed screw 46. The forward end of the screw slides in the bed and its foremost position is determined by a stop 47. The rear end of the screw is formed as a piston 50 slidable in a cylinder 51 for effecting a rapid feed of the wheel support, the piston having a rod 52 connected to a dashpot piston 56. The shaft 41 can be rotated to provide a fast feed by a piston-and-cylinder 72, 73 connected to a rack 71 engaging a pinion on the shaft which also has a ring 60 having cams A, B, C, D for operating limit switches controlling relays and solenoids in an electro-hydraulic circuit of the machine. The work rest 100 is moved by a spring-urged wedge member 112 which is movable to an inoperative position by fluid pressure acting on a piston 114 in a cylinder 111. In operation, the crank-shaft is mounted between the headstock and footstock with the centre main bearing in alignment with the grinding wheel, the footstock operating a limit switch to permit the motor 20 driving the headstock to be started. The feed of the wheel support is initiated by movement of a lever 85 which operates a limit switch 3LS controlling a solenoid-operated valve 90 and direct fluid through a throttle valve 91 and check valve 92 to the head end of cylinder 73 when a pilot valve 80 has been shifted by fluid pressure from a port 93 of the rapid feed cylinder. The pilot valve 80 is operated by an infeed relay and directs fluid through an infeed valve 81 and check valve to the head end of the rapid feed cylinder to advance piston 50 and the wheel support at a rapid speed until the dashpot 54 is picked up to reduce the speed while the side walls of the bearing are ground. The advance continues until the screw 46 engages the stop 47 and port 93 is uncovered to permit flow to the valve 81 and cylinder 73 to advance piston 72 and rotate shaft 41 so that the wheel support advances at a fast speed for a rough grinding operation until the cam A actuates limit switch 17LS which moves solenoidoperated valve 90 so that fluid flow to cylinder 73 passes through throttle valve 96 to slow down the speed of advance of the wheel support. The slower speed of advance continues until cam C actuates limit switch 18LS to stop the feed and start a timer defining a round-out period after which a relay operates a reset solenoid-operated valve 83 to direct fluid to the opposite end of cylinder 73 to return the piston 72 and wheel support to the position at which the fast feed started. Up to this stage the work rest 100 has been inoperative and the workpiece has the elliptic shape shown in Fig. 5 because of the variable stiffness and is oversize on its minor diameter. After a period determined by a timer, a solenoid 5 is deenergized to move a valve 110 to its central position which reduces the pressure in cylinder 111 from a value at which the spring 115 has been compressed, to a lower value to permit the spring to advance the work rest which engages and deflects the workpiece, the work rest being spaced from the centre of rotation a distance equal to the radius of a finished workpiece. Thereafter valve 90 is moved to direct fluid to cylinder 73 for a fast feed of the wheel support to a point at which the grinding wheel is slightly more than the length of the major diameter from the work rest and limit switch 8LS is actuated, valve 90 then being operated again to reduce the speed of advance so that the grinding gradually reduces the major diameter, as shown in Fig. 8, to the length of the minor diameter, the workpiece then being round but still oversize. During this second advance, cams A and B engage limit switches 17LS and 18LS again but these are not operative and grinding continues until cam B actuates limit switch 6LS which may act to start a precision fine feed or stop the grinding at the desired final diameter by directing fluid to the return ends of cylinders 50 and 73 to return the wheel support through the rapid and fast feed distances. The valve 110 is also shifted to the right so that the cylinder 111 is connected to exhaust to permit the full pressure of the spring 115 to maintain the work rest 100 in its operative position engaging the wcrkpiece. By operation of a lever 135 fluid pressure is supplied to a cylinder 144 to traverse carriage 11 so as to place an end bearing in alignment with the grinding wheel and rapid feed of the wheel support is again effected until the grinding wheel reaches the side walls of the bearing and a cam 140 on the wheel supports actuates a limit switch 16LS to move solenoid-operated valve 130 and block fluid flow from the dashpot 54, the flow being controlled by a throttle valve 130 to reduce the rate of feed for grinding the side walls which continues until the stop 47 is engaged. Fluid is then supplied to cylinder 73 for effecting a fast feed which is continued until limit switch 6LS is again actuated to initiate a precision fine feed or retract the wheel support and work rest so that the workpiece may be removed from the machine.