Patent GB-795655-A (GB)
Title: Improvements relating to apparatus for cutting or relieving sheet metal by electrolytic etching
IPC: C25F7/00
Filed: 1954-07-30
Abstract: 795,655. Electrolytic etching. STEVENS, R. J. July 18, 1955 [July 30, 1954; July 30, 1954], Nos. 22262/54 and 22263/63. Class 41. An electrolytic etching unit for cutting or etching sheet metal W through a mask m, e.g. a resist or a stencil, separating the work W from an electrolyte, comprises contact finger elements 2 for connecting the work W as anode, and a surface or surfaces 4 on the side of the work W remote from the elements 2 adapted in conjunction with the elements 2 yieldingly to nip the work W. The work W is removably secured at 35, 36 to the transparent bottom 4 of an open-topped box 3 which pivots about a shaft 5 into and out of a bath 1 for insertion and removal of the work W. The elements 2 are fixed to brackets 42, Fig. 4, which are adjustable along longitudinal bars 24 which are laterally adjustable along transverse rods at each end of the unit by tubular spacers 28 on the rods. The rods in turn are carried by lugs 27 on a frame 22 which pivots about 29 under the action of a piston device 33 and a connecting linkage to bring the elements 2 into and out of contact with the work W, final upward movement of the bar 24 compressing a rubber cushion 44 to force a rubber ring 39 on the element 2 into sealing engagement with the work, a hole 46 being provided in the resist m for the tip 40, which may be silver or silver alloy or may be plated therewith, of a rod 37 forming the element 2. During etching, clamps 36 are released, the work being held by the elements 2 against the bottom 4, and the box 3 is held firmly by fingers on a shaft 17 which are rotated anti-clockwise in Fig. 3 to contact the ends of channels 19 which connect the box 3 rigidly to the shaft 5. The work may have a backing resist b and a cathode C is suitably supported, e.g. on the frame 22. Air may be pumped at 52a into the bath to facilitate escape of gas. In a modification, the cushion 44 may be replaced by two pairs of inflatable tubes, one pair above and one below the bar 24, running longitudinally thereof, final sealing movement of the rod 37 being ensured by inflating the top pair and deflating the. bottom. In this case, a stencil, which supports the cathode, may replace the resist m and be supported by the contact elements. If desired, some or all of the elements 2 may act as pressers only, current being delivered to the work through fixed contact fingers passing through the bottom m, the backing b having suitable holes. Further, the frame 22 may be lifted and lowered by a solenoid-operated device instead of by the device 33. In another modification, Fig. 15, the work W is clamped by a rigid plate 55 carried by the contact element 59, 60 against a soft rubber backing 54, a semi-rigid plate 58 intervening. Holes 56 in the plate 55 allow electrolyte access to the work through apertures 57, 46 of suitable contour, e.g. annular, in the plate 58 and resist m, the apertures 46, 57 having bridge pieces. Holes 46a in the resist b allow the rubber 54 to enter the cut in the work as it is made. A hole in the resist m for the element rod 60 is not shown. In this modification, the backing b may be omitted, and the resist m replaced by a rigid stencil. In further modifications, the work W in strip form is led through the etching unit by an endless belt conveyer having a stationary guide track which incorporates magnets, or the work strip, suitably masked, is led under an endless belt as above, and is mechanically held there against by two narrow endless belts, both the conveyers being as described in conjunction with the multi-station apparatus which is described in Specification 795,656. The electric connections may include a circuit for testing each contact element separately.