Patent GB-484777-A (GB)
Title: Improvements in or relating to the manufacture of vitreous layers
IPC: H01B3/10
Filed: 1937-09-23
Abstract: 484,777. Coating articles with glass or enamel. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. Sept. 23, 1937, No. 25822. Convention date, Sept. 26, 1936. [Class 56] [Also in Group XXXVI] A vitreous layer on a substratum is made by transforming the material for the said layer into a suspension, applying the material so suspended to the substratum by electrophoresis, the substratum acting as an electrode, and heating, if desired in a non-oxidizing atmosphere, to obtain a coherent layer in a vitreous state. The substratum may consist of a metal wire or band, or a resistance of high operating temperature consisting of a semiconductor or of carbon or an electrical heating element. The heating may be interrupted as soon as the applied layer adheres sufficiently, whereupon the insulated material is shaped to the desired form, and the heating is resumed. The starting material may consist of a powdered glass or a mixture of glasses, or a mixture of two or more substances jointly capable of forming a glass or an enamel on heating, or of a powdered mixture of glass and a substance which does not flow during heating, and does not react with the glass. The invention may be used in the production of insulated coils and resistances, and of condensers. In examples : (1) a glass containing silica, litharge and alumina is crushed, ground in a ball mill, treated with dilute hydrochloric acid, washed, dried, and suspended in acetone ; a copper wire, raised to a potential of 100 volts, is passed through the stirred suspension, and then through a tube furnace in an atmosphere of carbon dioxide. The wire may be wound into any desired shape and again heated ; (2) a short copper wire or tube is placed in the suspension of example 1, surrounded by a nickel cylinder which acts as negative electrode, and raised to 50 volts ; it is then heated to 780‹ C. in carbon dioxide by winding the product with a thin metal wire, a condenser may be obtained ; (3) a suspension of a black enamel comprising litharge, silica, boron trioxide, and smaller amounts of chromic oxide, aluminium oxide, cuprous oxide, zinc oxide and cobalt oxide in methanol is used to coat a copper wire at a negative potential of 50 volts, followed by heating to 500‹ C. ; (4) a hard glass comprising silica, aluminium oxide, boron trioxide, calcium oxide, magnesia, barium oxide, alkali and antimony is ground, suspended in acetone, and used to coat a resistance rod, formed by sintering together clay and silicon, at a positive voltage of 70, followed by heating in an atmosphere of carbon dioxide, or of nitrogen and hydrogen at 1000‹ C. ; (5) a suspension as used in (4) is mixed with a suspension of boric acid in acetone and used as in (4) ; (6) the glass used in (1) is ground, suspended in water and used to coat a copper wire at a positive voltage of 10 volts, followed by heating at 780‹ C. in carbon dioxide ; (7) a hard glass containing silica, alumina, boron trioxide, calcium oxide, magnesia and potassium oxide is ground, suspended in methanol, and used as in (4) to coat a resistance rod ; (8) the process of (1) is repeated but using a glass comprising silica, magnesia, calcium oxide, potassium and sodium oxides and a nickel iron wire ; (9) a nickel-iron band is coated, using the process of example 2 ; (10) quartz is ground, added to one of the suspensions described in (1) or (2), and the resulting suspension used to coat a copper wire. Specification 444,723, [Group XXXVI], is referred to.