| 摘要 |
595,601. Making electric contacts. WESTERN ELECTRIC CO., Inc. July 20, 1944, No. 13950. Convention date, March 16, 1943. [Class 83 (ii)] [Also in Groups XXXVI and XL] The end of a fine wire for use as an electrical contact member, e.g. in detectors or rectifiers for ultra high frequency radio &c., is given a desired form, e.g. by grinding, is electrolytically etched, and is then pressed against the member it is to remain in contact with, and preferably tapped, to flatten the point into a contact engaging area. A tungsten wire 0.005 inches in diameter, preferably gold plated, is given a conical end, 75-degrees apex angle by rotating it in contact with a high speed grinding wheel. The other end of the wire is then soldered to a holder 3 of brass or other conductor and the wire bent a number of times to give it resilience. A number of these holders 3 are mounted on a strip 4 and arranged with the ground points of the wires immersed in 25 per cent potassium hydroxide solution in a dish 5, Fig. 7. The dish is levelled by means of a tripod table 7 with adjusting screws 8, 9, 10 and the height of the solution 6 is regulated by altering the pressure in a flask 13, connected to the dish by a syphon, by means of a two-way valve 11, an air pump in the form of a rubber bulb 12, and an exhaust pipe 22. The dish 5 contains a cathode 15 and a potential difference of 0.80 volts, as registered by the meter 18 is applied for two seconds to etch the points to a spherical form, e.g. with a radius of 0.0003 inches. This etched form is then polished by applying 2 volts for 0.2 seconds twice. These times and voltages are obtained by use of the switch 16 and rheostat 14. The level of the electrolyte is then lowered, the strip 4 with its holders 3 is removed and the wires are washed and dried. A holder 3 is inserted in a plug 25, Fig. 8, which is screwed into a ceramic cylinder 23, the base of which is closed by a screw plug 24 carrying a wafer 27 of crystalline silicon. The holder is adjusted to exert enough force on the wire point to flatten it to a small finite area and is so secured by set screws 29. The device is then tapped so as to produce a flattened area of about 0.0003 inches in diameter. In modifications, the wire is ground or otherwise formed to a wedge, Fig. 11 or 13, instead of to a cone and then treated as described. |
