Patent GB-789298-A (GB)
Title: Control equipment for copying machine tools
IPC: B23Q35/08
Filed: 1954-12-31
Abstract: 789,298. Copy-turning. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET. Dec. 31, 1954 [Jan. 2, 1954], No. 37759/54. Class 83 (3). [Also in Groups XXIX, XXXV and XXXVIII] Control equipment for a copying-machinetool, in which' the movement of the tool 2 is influenced by a feeler 14 coupled thereto and moving along a pattern 3 to reproduce the desired workpiece 1, comprises electro-hydraulic control means for controlling the tool in at least one of its directions of movement, which means contains at least two cascaded members 42, 8 with integral action. The stylus 4 of the feeler actuates, via a damping-device 11, a member 13 to vary inductances 15a, 15b in an A.C. bridge including secondary winding 16 of transformer 17 fed from an A.C. source 18. Movement of member 13 from its central position causes a voltage to occur across terminals 19 connected across the bridge, which voltage is amplified and passed through transformer 22 to rectifying bridges 25a, 25b which are connected through resistances 26a, 26b to secondary windings 27, 28 of transformer 17, and also to outputterminals 29 and a central-terminal of the secondary winding 23 of transformer 22. The D.C. voltage at terminals 29 is applied to a coil 34 actuating a valve-closure-member 37 controlling the flow of liquid from line 40 to reservoir 47 via line 41. Liquid is drawn from the reservoir by pump 48, and supplied through line 49 to valve 46 and to annular space 43a beneath piston 43, and through the restriction 44 to the space above the piston, which is connected to line 40. Thus, when valve 37 is moved to restrict or increase the outflow from line 40, piston 43 moves down or up, respectively, and carries with it valve 46, whereby liquid is supplied to the spaces beneath or above, respectively, a fixed piston 54 in a movable cylinder 8 which moves the tool 2 towards or away from the work 1. Cylinder 8 is connected to the feeler-housing 14 supporting the inductances 15a, 15b, by a link 56 which may be constituted by a slide 7 supporting the tool and feeler, and slidable on guides disposed at 45 degrees to the feed-direction of the tool along the work. Disposed in one of the leads from terminals 29 to coil 34 is a differentiating-link 30 comprising a resistance 32 and a capacitor 31, the link functioning to supply a reverse signal when the voltage at terminals 29 commences to fall, thereby to stop movement of valve 37 without hunting. Damping-device 11 consists of a cylinder 57 and piston 59 loaded by springs 62, 64 and damped by a liquid. Spring 62 abuts a disc 61 engageable with shoulders 63 in the cylinder, and is only effective to load the piston when picked up by collar 60 on the piston-rod which constitutes the feeler 4. Cylinder 57 is connected to housing 14 by springs 58. For small movements the device acts as a rigid connection between the feeler 4 and member 13. For large movements the device prevents the tool from being applied too rapidly to the work. The arrangement of two cascaded members enables the slide 7 carrying the tool and feeler to move at a constant speed, with the feeler touching the work and the member 13 in central position, e.g. in producing an inclined surface. Further cascaded members can be added if constant acceleration &c. is required.