Patent GB-936787-A (GB)
Title: Tracer control circuit for machine tools
IPC: B23Q35/18
Filed: 1962-04-03
Abstract: 936,787. Copying lathes. S. R. CUDNOHUFSKY. April 3, 1962 [Dec. 14, 1961], No. 12697/62. Class 83 (3). [Also in Group XXIX] In an hydraulically operated tracer circuit for a machine tool, movement of the cutting tool 32 is effected by piston and cylinder assemblies, 28, 26 and 22, 18 attached to the carriage 20 and tool slide 16, for longitudinal and transverse movement respectively, the control of this movement being effected by a tracer valve 10 to which a stylus 12 is attached, the stylus following the contour of a template 14. The movement of the stylus on the template contour is transmitted through the circuit to produce the same movement of the cutting tool 32. High and low pressure pumps 34 and 36 respectively form the pressure source, and control of the directional flow of hydraulic fluid is effected by a solenoid operated pilot valve 40 comprising a pilot component 42 and main component 44. The valve 40 is connected by line 46 to the low pressure pump 34 and the high pressure pump is connected via line 62 to the tracer valve 10 which is operated by the stylus. In the inoperative or idling position fluid from the high pressure pump 36 is supplied to the tracer valve 10 via line 62, the tracer valve is adjusted to provide sufficient back pressure in the line 62 to produce the withdrawal of the piston 22 in the cylinder 18 together with the stylus and maintain the stylus in the withdrawn position whilst permitting the fluid to return via line 66 through valve 44 to sump 68. To move the stylus towards the template, valve 40 operates to permit fluid from the low pressure pump 34 to enter the head end of the cylinder 18 via lines 46, 78 and 72, this pressure being above the back pressure from the high pressure side of circuit and in the same position valve 40 maintains the high pressure fluid return via line 66 to sump 68. When the stylus engages the template a restriction in the tracer valve increases the back pressure in the high pressure line 62 to equal the low pressure side of the system and thus arrests the forward movement of the stylus. This condition in the system remains static provided there is no change in the transverse position of the stylus during its longitudinal movement. To effect longitudinal movement of the stylus and slide along the corresponding template contour solenoid valve 74 is operated to permit fluid from the low pressure pump 34 to the rod end of the cylinder 26 via line 102 whilst maintaining the low pressure to the head end of cylinder 18 through by-pass line 122 and fluid flow to the sump 68 through flow control valve 110. Similarly, the head end of longitudinal feed cylinder 26 is connected to the draw line 92 by line 94, check valve 100 and control valve 90. The rate of longitudinal movement produced is determined entirely by the setting of the flow control valve 90. The combination of both transverse and longitudinal movement of the slide 16 and carriage 20 are produced by oblique or inclined movement of the stylus on such a particular contour of the template 14. The angle of inclination of the contour on the template determines the setting of valve 82 which controls the fluid between the high and low pressure sides of the system in relation to the cylinders 18 and 26 in conjunction with flow control valves 86, 90, 98 and 110. In another embodiment, the flow control valves 86, 90 and 110 are replaced by a flow integrator valve 150 which is in the form of a spring-biased spool 156, reciprocably located in bore 154 in housing 152. The position of the spool in relation to the fluid inlet and discharge ports 158, 160, 162 is determined by the direction of movement of the stylus, whereby interconnection between particular flow passages within the valve maintains the flow circuit as previously described.