GB809188A - Improvements in or relating to centerless grinding machines - Google Patents

Abstract

809,188. Shaft couplings; change-speed control. LIDKOPINGS MEKANISKA VERKSTADS A.B. May 22, 1957 [May 23, 1956], No. 16306/57. Class 80 (2). [Also in Groups XXIII and XXXVII] In a centreless grinding machine, the workpiece 3 is supported, in contact with the regulating wheel 2, by a work rest 4; the grinding wheel 1 is movable towards and away from the regulating wheel, its carriage being moved by a gear on a shaft 20 carrying an arm 19 actuated by the track of a cam 16 driven by a two-speed motor 18. A worm 8 driven by an electric motor meshes with a worm wheel 7 secured to a sleeve 9 freely rotatable on the spindle 5 carrying the regulating wheel. One end of the sleeve 9 is formed as a coupling member 10 having axially extending teeth and carries, by rivets 100, a metal ring 11 insulated from the sleeve by members 110 and having radially inwardly extending teeth; secured to the spindle 5 is a coupling member 12 with radially outwardly extending teeth located between the teeth of members 10, 11. As long as the grinding wheel is not in contact with the workpiece, the latter is driven by the regulating wheel, i.e. part 11 drives part 12; the surfaces 28 on these parts being in contact, a circuit is established, on closure of push-button switch 30, to energize a relay 24 which causes the motor 18 to run at fast speed for rapid approach of the grinding wheel. When the grinding wheel contacts the workpiece, the latter tends to drive the regulating wheel, i.e. the part 12 drives part 10. The relay 24 is thus de-energized and, a switch 22 being closed, a relay 25 is energized causing the motor 18 to run at slow speed for grinding feed. This continues until the grinding is completed and the grinding wheel carriage is returned by the cam to its original position, whereupon a projection 21 on the cam opens the switch 22 and the motor 18 stops. The circuit may be modified so that the return of the grinding wheel carriage is also fast. The push-button switch 30 may be operated manually; when workpieces are automatically fed in sequence to the machine from a magazine a member connected to the magazine closes the switch when the workpiece is in its grinding position. When the relay 25 is energized to give slow grinding feed, a low-torque motor 14, 15 is supplied, the rotor 14 of which is mounted on the spindle 5; as described in Specification 796,280, this provides a torque additional to that exerted upon the regulating wheel by the workpiece and maintains the coupling parts 12, 10 in contact despite unevenness of the workpiece surface. In a modification, the worm 8 is axially displaceable and control is effected by movement of the worm when the torque changes. The two speed mats 18 may be replaced by two motors having the same or different speeds connected to the cam mechanism with different gear ratios; a gearbox with electromagnetically actuated couplings may be used to provide the different speeds.