GB1469658A - Disc grinding machines - Google Patents

Abstract

1469658 Grinding LITTON INDUSTRIES Inc 28 May 1974 [31 May 1973] 23694/74 Heading B3D A grinding machine comprises means for rotating a pair of coaxial abrasive discs 10, means 25 for mounting a workpiece W, such as a Wankel engine cylinder, for rotational displacement on a work paddle 20, means 28 for displacing the work paddle from a first retracted position whereat the workpiece is remote from the discs 10 to a second advanced position whereat the workpiece is located in the grinding zone intermediate the discs, means for rotating the workpiece in a first direction and a second direction when the workpiece is located in the grinding zone, and means for periodically reversing the direction of rotation of the workpiece. The discs 10 preferably have axially extending bores and are mounted on respective slides 12 displaceable for infeed by mechanisms 16. The work paddle 20 is reciprocatable along a rail 22 which extends through bridge plates 30 by a fluid motor 28. The workpiece W is mounted on a carrier 24 having a plate 26 to which the workpiece is secured and which is secured to an annular member 25, the periphery of which has a row of sprocket teeth 32 disposed between track surfaces 33. The carrier is rotatably supported in the paddle by rollers 40, 50 which are mounted between spaced plates 34 of the paddle on pins 42 and engage the track surfaces 33. Sprocket teeth 32 are formed on the periphery of the carrier 24 and the rollers 50 are formed with grooves (52, Fig. 4, not shown) to provide clearance for the teeth and the rollers 40 are formed with larger grooves 44 to provide clearance for the teeth and a chain 36 which is driven by an hydraulic motor 38 and runs around the rollers 40 engaging the sprocket teeth 32 between the rollers. The hydraulic motor 38 is included in a circuit having solenoid-operated valves controlling the fluid flow to the motor so that the carrier 24 is rotatable in one direction or the other at fast and slow speeds. On depressing a pair of start buttons, the paddle 20 is advanced by the motor 28 along the rail 22 at a fast rate from the load position, shown in Fig. 1, to a position at which the workpiece lies midway between the inner and outer peripheries of the abrasive discs and a trip switch LSI is actuated to cause the motor 38 to rotate the carrier 24 at a grind speed in a first direction. The paddle is then further advanced and retracted repetitively at the fast speed between positions in which the workpiece overlaps the inner and outer peripheries of the discs under the control of limit switches LS2, LS3 until the workpiece has been ground to size whereupon the paddle is retracted at the fast speed to a position at which a limit switch LS4 causes a slow retraction and the movement is stopped by actuation of a limit switch LS5 for unloading the workpiece and loading a new workpiece. During the grinding of the next workpiece the supply to the motor 38 is reversed so that the carrier 24 rotates in the second or opposite direction, i.e. the rotation of the carrier is reversed for each cycle. The rotation of the carrier at the load-unload position is stopped at a predetermined position to facilitate automatic loading and unloading by inductive proximity switches PS1, PS2 which sense the sprocket teeth 32. At least one of the teeth is cut off at the pitch line and timers are incorporated in the circuit of the switches, the switches actuating the timers each time a full tooth is sensed, and the timers timing out when cut-off teeth pass the switches. When the timer of the first actuated switch times out, the supply to the motor 38 is reduced to cause slow rotation of the carrier until the timer associated with the second switch times out and the carrier is stopped. When the direction of rotation of the carrier is reversed for the next grinding cycle, the operation of the switches is reversed.