GB808002A - Improvements relating to electrical engraving machines - Google Patents

Abstract

808,002. Engraving. HILL, J. W. Sept. 24, 1957 [June 26, 1956], No. 19700/56. Class 100(2) Apparatus for use with an electrical engraving machine for enabling engraving to be done in the direction of curvature of curved surfaces comprises a carriage slidably mounted for movement in a straight line and adapted to be interconnected with the electrode to follow its movement along this or a parallel line, a rotatable workholding mounting on the carriage, and means for rotating the work in accordance with the movement of the electrode, in such a way that the circumferential displacement of a point on the curved work surface initially in contact with the electrode is equal to the simultaneous linear displacement of the electrodes. A nut 45, Fig. 5, and bolt 43 clamp together arms 41, Figs. 1 and 5 (a square part of the bolt engaging in a slot 42 between the arms), a base 44 and the work-table 36 of the electrical engraving machine described in Specification 759,074. Secured to the arms 41 is a plate 11 on which is slidable by balls whose travel is limited by pegs 39 a carriage 10, comprising a block 16 and apron portions 14 carrying rods 15 supporting a block 17, which rests on the arms 41 by means of balls 12<1>, and is secured to the rods 15 by bolts 40. The blocks 16, 17 have co-axial roller races 18, 19 respectively, the former carrying a centre 20 to engage one end of the work W to be engraved, and the latter carrying a hollow conical member 21 to support the other end of the work. The block 16 supports on rods 23 a plate 22 having a slot 30 to engage a bush 25 round a spigot 26 carrying the electrode 27 projecting from the engraving unit 28 of the machine, the electrode and plate 22 being free to move relatively at right-angles to the direction of movement of the carriage but constrained to move together in the direction of said movement. A part 34 of the carriage slidably supports plungers 50 carrying a bridge piece 33 rotatably supporting a friction wheel 31 which is in contact with the plate 11 and is urged against the work W by springs 35. When the carriage is moved by the electrode, the wheel 31 rotates the work so that its surface moves under the electrode by an amount equal and opposite to the component of movement of the electrode in the direction of carriage movement, for engraving the direction of curvature. For engraving along the work the arms 41 and the assembly carried thereby are mounted at right-angles to the position of Figs. 1 and 5 by means of the bolt 43, and the carriage is secured if desired on the plate 11 by a bolt 49, and the arms 41 being secured with the bolt 43 in that position along the slot 42 which correctly positions the work relatively to the electrode. The wheel 31 has a facing of fibre, or may be rigid and urged by resilient means against the surface it is to engage. The wheel may be replaced by an inextensible friction driving tape, band or wire anchored to the base at one end, passed round the work and anchored to the base by a tension spring at the other end.