Patent GB-803955-A (GB)
Title: A cutter grinder
IPC: G05B19/04
Filed: 1956-04-26
Abstract: 803,955. Grinding cutters. CINCINNATI MILLING MACHINE CO. April 26, 1956 [May 19, 1955], No. 12832/56. Class 60. [Also in Group XXXVII] A machine for automatically grinding in succession a series of teeth on a helical or other cutter 30 comprises a cutter support 12 movable in relation to a grinding wheel 19, a tooth rest 37 for positioning a tooth of the cutter during grinding, a reversible torque motor 32 for rotating the cutter in one direction so as to maintain a torque thereon during the grinding operation and in the opposite direction to index the cutter, and a flipper tooth rest 45 which restrains the cutter against movement in one direction and is itself moved by the indexing movement of the cutter so that it actuates a switch 1LS for reversing the direction of the torque motor and urging the cutter against the tooth rests. The grinding wheel 19 is mounted on a head 18 carried by a vertically-movable column 14, and the cutter 30 is mounted between a headstock and tailstock on a table 12 movable transversely on a saddle 11 which can be moved to and from the grinding wheel. The table 12 is movable by a feed screw operable by a reversible motor 23 controlled to reverse the direction of traverse of the table at each end of its stroke by limit switches 3LS coacting with dogs 50 on the table, and the headstock carrying the cutter is driven by the reversible torque motor 32. The tooth rest 37 is adjustable vertically on an arm 38 upstanding from the column 14. The flipper tooth rest 45 which serves to maintain the position of the cutter after it has run free of the grinding wheel and tooth rest 37 at the end of a traverse stroke of table 12, consists of two arms adjustable to accommodate cutters of-different helical angles on a shaft 44 in a bracket 42 secured to the head 18 ; the shaft 44 carries an arm 47 which, when the cutter is driven clockwise for indexing, actuates the limit switch 1LS, the cutter then being free of the grinding wheel at one end of its stroke. The motors 23, 32 are arranged in a control circuit including relays, the limit switches, and various hand-settable control switches such as one to determine whether indexing of the cutter is to be effected when the latter is at one or both ends of its traverse, another to set the number of traverse strokes of each tooth in engagement with the grinding wheel, and a torque-setting switch for determining the direction of application of torque of the motor 32 (counterclockwise as shown). With the cutter 30 mounted as shown, the actuation of a push button to start the motor 32 to rotate the cutter counterclockwise is followed by the actuation of a second switch to energize the motor 23 for traverse of the cutter across the grinding wheel in the desired direction. Assuming that the circuit has been set to provide three operative traverse strokes of each tooth, the motor 23 will be controlled by its limit switches to stop and reverse the cutter at the ends of its traverse until, just after the start of its fourth stroke, it is stopped and the torque motor 32 reversed for the indexing of the cutter in clockwise direction. In this indexing movement, the cutter causes the fingers 45 to actuate the limit switch 1LS which, when it is released in the continued movement of the cutter, serves to reverse the drive of the motor 32 and urge one tooth of the cutter against the tooth rest 45 and align the next tooth to be ground with the tooth rest 37 ; a timer is also set at the initial actuation of the switch so that it starts the motor 23 for the first traverse stroke of the next cycle, after a time sufficient for the completion of indexing. A stepping relay in the circuit actuates switch arms at the end of each traverse stroke of the cutter so as to provide a visual indication of how many such strokes have been performed on each tooth, the arms being automatically set back to initial position at the end of the complete operation on the tooth. A jog push button is provided in the circuit for indexing the cutter forward a tooth at a time during setting up of the machine. To.compensate for the fact that in dealing with helical cutters, twisting torque on the cutter will be applied in opposite directions for opposite directions of traverse of the cutter, a switch is initially set so as automatically to insert or take out resistances in the circuit of the motor and therefore provide a constant pressure between the cutter and tooth rest 37 for both directions of traverse. If desired the flipper tooth rest 45 may be mounted on the support 12. Specification 366,462 is referred to.