GB654128A - Improvements in electrically heated vessels - Google Patents

Abstract

654,128. Heating vessels by electric resistances. DUNLOP RUBBER CO., Ltd., POWELL, E. F. Sept. 17, 1948, No. 24395. [Class 39(iii)] Vessels for heating liquids, e.g. kettles or saucepans are heated by an electrically conductive resinous coating on their inner or outer surfaces. The coating is a dispersion of graphite or carbon black in a synthetic resin e.g. a silicone resin. Each end of a conductive band on the outside of a glass flask may be sprayed with metal e.g. zinc or may be silver-plated to form terminals on which springy brass strips are pressed. A protective coating of insulating resin is then applied over the heating surface, which has a resistance of 5-50,000 ohms per sq. cm. If the vessel surface is metallic, an insulating resinous coating is first applied, and the vessel may form an earthed terminal for the heater. An aqueous solution of colloidal graphite may be incorporated in a resin solution, which is applied as a coating and when heated forms a water-insoluble resin. Immersion heaters are formed by filling long tubes with the conductive solution, emptying the tubes and leaving a coating the tubes being finally sealed. Among the resins used are polyvinyl, phenol, glyptol, copal and coumarine resins; ethyl cellulose and cellulose acetate may be used.