GB545290A - Improvements in dry cells and method of making the same - Google Patents

Abstract

545,290. Centrifugal machines. BURGESS BATTERY CO. Oct. 25, 1940, No. 15720. Convention date, Nov. 9, 1939. [Class 23] [Also in Groups XXXVI and III] The metal electrode (e.g. the zinc can) of a dry cell is coated with "separating material" (e.g. ungelatinized starch) by a centrifugal or spinning operation. The can may comprise two layers 11 of zinc separated by vinyl acetate resin 12 as in Specification 531,379, [Group XXXVI], the end caps 13 of zinc being crimped to form a liquid tight joint with the layers 11, the bottom of the can being filled with wax or pitch 14. A liquid suspension of ungelatinized starch (which may contain an electrolyte such as ammonium or zinc chloride, sodium diohromate, or mercuric chloride) is placed in a can which is put on a rotating platform 30, Fig. 3, so that the suspension spreads over the can and the starch separates from the liquid leaving a moist layer of starch on the can excess liquid passing into a receptacle 31. Glue or other adhesive may be added to suspension, and moisture removed from the starch layer 15 by a current of warm air or by a heating coil 32. A layer of insulating material 16 is then placed in the can, the depolarizing material 20 incorporating the electrolyte added before or after compacting, and the carbon rod 17 forced through the depolarizing mass, sheet 16, and wax 14 as shown in Fig. 2. The upper end of the zinc can is bent over a washer 23 and the whole sealed at 27. The layer of starch is gelatinized by absorbing electrolyte and gradually swells, thereby reducing the contact resistance between the zinc can and the depolarizer. If no gelatinizing agent is present in the original electrolyte, the gelatinizing of the starch does not take place until zinc chloride is formed when the cell is used, or, in the case of an inert all, until the electrolyte is added. The layer of starch is thicker near the base of the can than at the top. Magnesium, iron, and other electrodes for dry cells may be similarly coated with starch or with other cereals or with clays, powdered silica, &c. To augment the metal content of the electrode, with powdered zinc or other metal may be incorporated in the starch suspension, the zinc being projected against the electrode surface during the spinning operation and held in position by the starch layer.