Patent GB-480888-A (GB)
Title: Improvements in and relating to machines for grinding crank pins
IPC: B24B5/42
Filed: 1936-10-19
Abstract: 480,888. Grinding crankshafts. NORTON CO. Oct. 19, 1936, No. 28440. Convention date, Oct.< >18, 1935. [Class 60] In a crankpin grinding machine, the crankshaft is mounted on a longitudinally movable table and is driven at both ends, the pins being ground by means of a grinding-wheel mounted on a transversely movable slide, and a steady rest for the work being provided. The table is movable by hydraulic means at different speeds to position a crankpin for grinding and the wheel may be fed to the work by manual means or hydraulic means ; the workholders also are operated hydraulically and the steady rest is raised and lowered by hydraulic means. Devices also are provided for " jogging " the work table to position the work, and for adjusting the wheel to " split the spark " durring grinding, and interlocking means are provided to avoid incorrect sequence of the operations of the machine, whilst the main movements of the machine are controlled by two valves actuated by a single handle. The machine comprises a base 30 supporting a grinding-wheel 32 on a slide 31 and a work table 40 movable on ways 41, 42 and having two work-heads 45, 46, supporting workholders 47, 48. Work clamping and rotating. The work-holders 47, 48 have clamping jaws actuated by a toggle 49 moved by rods 50, 55 respectively, the rods being urged by springs 51, 56 to cause the work to be gripped at its ends. The heads are carried by spindles 52, 57 driven by chains from a driven shaft 62, and the jaws are opened, to release the work, by pistons 71, 76 secured to the rods 55, 50 and moving in cylinders 70, 75. Wheel feed. The wheel slide 31 is movable by a screw 81 rotated, through gearing 84 . . . 93, by a hand wheel 94, and in order to obtain a rapid movement of the wheel towards and from the work, the screw is connected by a rod 98 to a piston 99 movable in a cylinder 100. In order to slow down the approaching and receding movements of the wheel to grind the opposed crank-cheeks, the rod 98 is slidable through a dashpot piston 101 moving in a cylinder 102 provided with a needle valve 105, the piston being engaged at a predetermined point by an adjustable nut 103 on the rod 98. The table 40 is moved longitudinally by means of a rod 112 connected to a piston 111 movable in a cylinder 110. Steady rest and splash guard. The crankpin 120 is engaged, during grinding, by a steady rest shoe 119 adjustable on a frame 115, to maintain contact with the work, by a nut 121, the frame 115 being slidable vertically on a way 118 by a piston 123 movable in a cylinder 122 so as to raise the rest to operative position or lower it, for insertion, &c. of the work. A splash guard is provided comprising a part 135 pivoted at 136 to the frame 115 and riding on a part 137 pivoted at 138, so that when the frame 115 is lowered the guards 135, 137. assume the positions 135a, 137a shown in dotted lines. Work table jogging. In order accurately to position the work table 40 manually after it is moved rapidly by the fluid pressure means, a rack 145 is formed on the table and is engaged by a gear 146, which is rotated through gears 148, 149 by an internal gear 162 movable by a lever 155 and movable axially into and out of operative position by gearing 158, 159 actuated by transverse movement of the lever 155. Hydraulic control. The movements of the parts of the machine are controlled by two valves 175, 230 fed with fluid from a reservoir 190 by a pump 191 and the valves are so arranged that the movements are interlocked, so as to prevent traverse of the table during wheel feed, and wheel feed during table traverse, and also to prevent unclamping of the work during feed of the wheel or traverse of the table. The valve 175, which comprises a stem 176 and a hollow piston member with pistons 178..] 185, Fig. 22, is movable axially so that in the various positions it causes rapid travel of the table to the right or the left, slow movement of the table under control of throttle valves 212, 226 in the exhaust, and stopping of the table when a crankpin has reached the grinding position : the valve 230, which has pistons 233-236 thereon, is mounted above the valve 175 and in the inoperative position, shown in Fig. 22, fluid passes to the cylinders 100, 110 and 122 to hold the work clamps open, the grinding- wheel withdrawn, and the steady rest down. The valve is then moved so that the work clamps may be closed by their springs to hold the shaft to be ground, the wheel and steady rest being inoperative, after which the valve is moved so that the wheel advances, with the steady rest still down, to grind off rough spots ; the valve is then further moved so that the steady rest rises for finish grinding. Single control lever. The valves 175, 230 are moved by a single lever 270, Figs. 4 to 6, pivoted at 272 to a yoke pivoted at 273 on an axis at right-angles to the pivot 272 so that, by movement towards and from the base 30 about the pivot 272, the valve is moved by a yoke 277 on the lever and a rod 275 secured to the valve stem, and by movement parallel to the base, about the pivot 273, the valve 174 is moved through operation of a bell-crank lever 282. Movements of the lever are limited by means of a cross-shaped slot 289 in a bracket 288, which serves to prevent movements of the lever other than required by the interlocking described above ; the various positions of the lever are indicated at 270a . . . . 270k in Fig. 6. Work table locating. The work table 40 is located in any one of a plurality of predetermined positions for grinding successive crankpins by means of spaced notches 291 in a bar 290 secured to the table and engaged by a plunger 292 slidable in a bracket 294 by a spring 295 engaging a lever 297 linked at 299 to the plunger. The control lever 270 carries a pin 304 which, when the ]ever is in position for rapid traverse of the table, holds the plunger withdrawn, but when in position for slow traverse releases the plunger to allow it to snap into the desired notch when this arrives at the grinding position. Spark splitting. In order to " split the spark," or equalize the side grinding during the grinding of the crankpin cheeks, the wheel 32 and its spindle are movable axially in the bearings 304, 305, Fig. 19, by an arm pivoted at one end and engaging, by pins 311, 312, a collar 306 axially fixed on the spindle, the other end of the arm being engaged by a pin 314 moved by a screw 317, which engages a nut 318 rotated, through bevel gearing 320, 321, and gearing 323.. 329 by a lever 331. Work stop control. In order to stop the work holders 47, 48 in a predetermined position for loading &c., a cam 335 carried by the valve stem 232 of valve 230, engages, when the lever 270 is moved after a crankpin has been ground, a roller 336 to open a switch 337, thereby de-energizing a solenoid 338, Figs. 16 and 18, and allowing a spring 339 to press a roller 341 on the periphery of a cam 344 mounted to rotate with the spindle 57 and thereby, when the roller rides into a depression 357 in the cam, opening a switch 355 which opens the circuit of the power field of the work rotating motor, this motor having a power field and a reverse field ; a switch 353 also is caused to close to operate the reverse field switch 352 thereby reversing the field and rapidly stopping the motor. A safety switch 365 is provided to open if current fails and the work rotation may be " jogged " by manipulation of switches 362, 363, whilst a two way switch 364 renders the automatic control of the work rotation operative or renders manual control operative. Table jogging interlock. In order to prevent operation of the lever 155 to jog the work table during power traverse thereof, a bar 374 is provided which is slidable behind the slidable gear 162 so that except when a cut-out part 380 of the bar is opposite the gear, when the control lever 270 is in central, or neutral position, the gear cannot be slid into operative position. The bar 374 is moved longitudinally by a lever 370 pivoted at 371 and having a pin 372 engaging a slot in the control lever 270. In order to prevent traverse of the table 40 sufficient to bring the work holders 47, 48 into engagement with the wheel 32, the table 40 carries safety dogs 384, 38'5 which, in the end positions of the table 40, engage pins 382, 383 on the bar 374, and, by movement of the bar, rock the lever 370, thereby rocking the control lever 270 to neutral position. In order to prevent the wheel slide 31 from moving too far to the rear, a limit switch 391 is provided, which is opened by a screw 393 on the slide in the rearmost position thereof, thereby opening the circuit of a motor 395 driving the pump 191. Specifications 351,522, 471,287, and 473,094 are referred to.