Patent GB-863253-A (GB)
Title: A method of and a device for controlling the infeed mechanism in a machine tool
IPC: B24B5/35
Filed: 1959-11-12
Abstract: 863,253. Pneumatic gauging apparatus. CINCINNATI MILLING MACHINE CO. Nov. 12, 1959 [March 30, 1959], No. 38379/59. Class 106 (2). [Also in Group XXIII] A method of controlling the infeed mechanism in a machine tool in which a workpiece is carried in a cradle-like support of predetermined size during the operation thereon comprises the steps of measuring the amount the workpiece settles in the support during the operation, measuring the amount the workpiece settles in the support as a result of spread of the support from said predetermined size only, and actuating the infeed mechanism when predetermined differences in these amounts occur. A centreless grinding machine, Figs. 1, 3 and 4, comprises a grinding wheel 11, a regulating wheel 12 and a workpiece supporting blade 15. The base 15a of the blade is clamped by screw 21 in mounting block 16. The upper portion 15b of the blade has a face 20 sloping downwardly toward its regulating wheel and aligned with the grinding wheel so as to support the workpiece portion being ground; other faces, such as 20a, support other workpiece portions, such as the flange 17a, not being ground. A member 70 is connected to side face 15c of the upper portion 15b by bolts 71 engaged with a shoulder in slot 72 of member 70, the slot 72 permitting vertical adjustment of the member 70. This adjustment is effected by rotation of a screw 74 having a pointed end engaging the rounded end of a depending portion 721 of the member 70. A plate 75 on the upper surface of member 70 has an orifice 75a therein communicating with a first air discharge passage 76 in member 70, the orifice 75a registering with the workpiece 17 and sensing the settling of the workpiece in the cradle (formed by the blade 15 and regulating wheel 12) due to reduction in size of the workpiece by grinding and/or to spreading of the cradle (owing to deflection of blade 15 or wear of regulating wheel 12). A prutruding portion 77 of member 70 has an orifice 77a therein communicating with a second air discharge passage 78 in member 70, the orifice 77a registering with the regulating wheel 12 and sensing spreading of the cradle. The pneumatic circuit, Fig. 5, comprises a source 80 of air under pressure, pressure-regulating valve 83, 84, pressure gauges 85, 86 and adjustable restrictor valves 89, 90. Valve 89 is connected to orifice 75a and also, through a reversing relay 94, to the chamber 97a of a differential meter switch 97; the reversing relay transforms a pressure increase at its input to an equal decrease at its output. Valve 90 is connected to orifice 77a and also to chamber 97b within a bellows in the meter switch 97. A gauge 97c, mechanically actuated by the bellows, indicates the pressure difference between chambers 97a, 97b. Switches 99a, 99b and 100a, 100b are similarly actuated in response to predetermined pressure differences in the chambers. Pressure gauge 92a measures the pressure in the line leading to orifice 77a. In a modification, Fig. 6, the pneumatic circuit comprises a source 180 of air under pressure, a regulator valve 183, a pressure'gauge 185 and an adjustable restrictor valve 189. The latter is connected to the orifices 175a, 177a, to a pressure gauge 197c and to pressure switches 199a, 199b and 200a, 200b. On depression of a start push button, the regulating wheel 12 and blade 15 are moved, as a unit, rapidly towards the grinding wheel 11. Actuation of a limit switch changes the movement to a fast feed rate. When the workpiece reaches a predetermined size, the gauging arrangement effects closure of switch 99a, 99b (Fig. 5) or 199a, 199b (Fig. 6) changing the movement to a slow feed rate. When the workpiece reaches the desired size, the gauging arrangement effects closure of switch 100a, 100b (Fig. 5) or 200a, 200b (Fig. 6) to retract the regulating wheel and blade. The movements are effected hydraulically, as in Specification 850,049.