Patent GB-1502981-A (GB)
Title: Electro-erosion machining
IPC: B23Q1/54
Filed: 1975-02-04
Abstract: 1502981 Electroerosion CAREL FOUCHE LANGUEPIN 4 Feb 1975 [13 Feb 1974] 4796/75 Heading B3V A circular movement of adjustable radius, in planes perpendicular to the feed direction of an electrode of an electro-erosion machine, is imposed between the electrode support 3 and a workpiece support (not shown) by at least two mechanisms D1, D2 shown in Fig. 1, each comprising a frame 4-6 rigidly secured to the machining head A which causes electrode feed 1, if the electrode support is the one moved, and an eccentric axle 16a rotatably mounted in a bearing 23 in the electrode support 3 so as to form with the support a crank-rod assembly. The crank arm length, i.e. the degree of eccentricity of the axle, of both or all mechanisms is the same, the axle of at least one of them is motion-driven and all the axles being synchronously operable, each mechanism having electromagnetic control means responsive to a common signal to vary the crank arm length and thus the radius of orbital movement without having to stop the machine. In the mechanism D1 shown in Figs. 2 and 3, a drum 10 keyed to and eccentrically disposed on a shaft 9 driven by a motor 7a houses an electromagnetic device 42-44 which when energized causes a guide 15 and slide block 16, Fig. 3 to rotate with the shaft. The slide block, which is urged by springs 34 against the drum, is integral with the axle 16a so that, during machining, the eccentricity of the drum 10 relative to the shape 9 imparts, via the axle 16a, a circular, orbital movement to the electrode support 3 which is located between bearings 28, 29 and 30 in fixed member 5 and 31. A lower electromagnet device 17-19 is separated from the slide block by an antimagnetic plate 21 so that on de-energization of the magnetic device 42-44 and energization of the lower device 17-19, the guide 15 and slide block 16 are held against rotation with the shaft 9, the drum, acting as a cam, causing the slide block to reciprocate within the guide. The variation in the relative angular disposition of the block and the drum caused by this relative rotation varies the eccentricity of the axle 16a relative to the shaft 9 and thus the crank arm length. An alternative form of cam face on the drum may comprise two symmetrical portions of an archimedean spiral (41a), Fig. 6 (not shown). The windings 42 of the upper magnetic device are continuously supplied by de-energization of a reversing relay 37. For a rotation of the shaft 9 at 1 r.p.m., push buttons 39 1-3  are provided for supplying current to the relay respectively for <SP>1</SP>/ 10  sec., for 1 second and continuously. Since the variation in crank arm length required would always be an increase, the initial orientation of the slide block relative to the drum is chosen to permit this. A thin antimagnetic plate may be imposed between the upper magnetic device 42-44 and the slide block and guide so that the slide block and guide can slide relative to the electromagnets when an exceptionally strong force is applied thereto, as for example when the axes of both shafts 9 and both axles 16a are inaligmnent. Thus accurate adjustment of the distance between the axis of the shaft 9 and the axle 16a of only one mechanism need be carried out, the other automatically following when the axes are aligned as described.