Patent GB-1364196-A (GB)
Title: Method and apparatus for advancing workpieces to be ground by dou ble disc grinding machines
IPC: B24B7/17
Filed: 1972-08-03
Abstract: 1364196 Grinding LITTON INDUSTRIES Inc 3 Aug 1972 [20 Sept 1971] 36384/72 Heading B3D A method of grinding a workpiece by means of a double-disc grinding machine comprises using a workpiece carrier 21 which, during a first phase of a grinding operation, advances the workpiece from a peripheral entrance location 27 to a position inwardly of the periphery of the abrasive discs, and which, during a second phase of the operation, moves the workpiece towards a peripheral exit location 28, the speed of advance of the workpiece being decreased during the first phase of the operation. In apparatus for carrying out the method, the machine has a pair of grinding heads 11L, 11R which are slidable towards and away from one another on a base 12 and have spindles 13L, 13R supporting grinding discs 14L, 14R for rotation about horizontal axes which may be aligned or spaced apart. A workpiece carrier assembly 17 is secured by a hinge pin bracket 19 to the base 12 and has a horizontal spindle 22 which is rotatable by a motor 29 and is secured to the workpiece carrier 21. As described, the carrier 21 has three workpiece-holding stations 23A, 23B, 23C for receiving workpieces and carrying them so that only one workpiece at a  time is between the discs. The workpieces are  loaded by a pneumatic device 56 from a shoot 55 one at a time into the apertures forming the stations 23A, 23B, 23C and are carried clockwise as seen in Fig. 2 to the entry location 27. As the workpiece is carried between the discs towards the area 48 near the axis of the discs, the speed of the carrier is reduced so that a substantially constant grinding rate is achieved. From the area 48, the speed of the carrier is increased to carry the workpiece to the exit location 28 and thence to an unloader 59 which has a magnetic workpiece engaging part which withdraws the workpiece from the carrier and deposits it on an unload shoot 62. The reduction in speed of the carrier during the first phase of grinding each workpiece and the increase at the beginning of the second phase occurs three times, as there are three workpiece-holding stations, for each rotation of the carrier 21. The variation of the speed is controlled by control of the motor 29 rotating the carrier. The spindle 22 of the carrier is connected to a geared pulley 30 engaged by a positive drive belt 32 to a pulley 31 on a shaft 33 having a segment gear 39 formed with an arc (40, Fig, 4, not shown) of teeth for engaging a gear 42 on a shaft 43 of a potentiometer 44 controlling the motor 29. A spring 50 returns the gear 42 and potentiometer to their initial position after each displacement by the teeth 40 so that after reduction in speed of the carrier during each first phase of the grinding cycle, the speed is rapidly increased at the beginning of each second phase. Coolant is supplied between the discs through nozzles 71, 72. The speed control of the carrier may be effected by a solid state transducer, a variable speed hydraulic motor may he used, or a stepping motor actuated by pulses supplied by an encoder, logic circuit and rate multiplier. In other embodiments, the workpiece carrier is in the form of an oscillating arm or a reciprocatory fixture.