| 摘要 |
685,259. Metal oxide resistors; temperaturevariable resistors. WESTERN ELECTRIC CO., Inc. Dec. 20, 1950 [Dec. 23, 1949], No. 31021/50. Class 37. The thermistor shown in Fig. 1 comprises a metal oxide plate or flake resistance element 11 which is the end product of a series of manufacturing operations as follows: (a) mixing metallic oxide particles of the order of 10<SP>-6</SP> cm. diameter with coarser metallic oxide particles, for example of the order of 10<SP>-4</SP> cm. diameter, and with a long-chain polymer temporary binder and a solvent for the latter; (b) spreading the mixture as a deposit or layer on an optical flat or other smooth surface and permitting the solvent to evaporate; (c) removing the dried deposit from the optical flat, for example by soaking with water; (d) drying this product and afterwards cutting into flakes of the required size; (e) firing these green or uncured flakes to remove the binder and yield sintered flakes of which 11 is exemplary. A first manufacturer may be responsible to stage (d) inclusive, i.e. batch production of uncured resistor flakes, and a second manufacturer receive supplies of the flakes and carry out stage (e). In the embodiment described stages (a) and (d) are given with respect to the following details. Stage (a) comprises milling 6 grams of a mixture of nickel and manganese oxide particles of from one to one-half micron diameter with 6 grams of polyvinyl butyral as the temporary binder and 12 c.c. of solvent until the oxide particles are reduced to about one hundredth the original size and then adding 7 grams of two micron diameter particles of the same oxide mixture and further milling this totality mixture. The first milling takes six hours and produces a gel mixture and the second milling proceeds for one hour and achieves uniform suspension of the larger diameter particles throughout the gel. In stage (d) the polyvinyl butyral binder is driven off by depolymerization by gradually raising the temperature to 400‹ C. The sintering process in stage (d) according to one instruction involves raising the temperature according to a curve, Fig. 4 (not shown), up to from 1000‹ to 1300‹ C. in an interval of about an hour and then gradually cooling to a soak temperature of about 860‹ C. and holding at this temperature for 16 hours and followed by cooling in the furnace employed. In modifications to the sintering procedure the temperature may be dropped from the peak temperature without a low temperature soak or a lower peak temperature may be employed with a soak of from 16 to 64 hours at the peak temperature. Suitable binders include isobutyl methacrylate and cellulose acetate butyrate as well as polyvinyl butyral. As additions or alternatives to manganese and nickel oxides there may be employed cobalt, copper, iron, zinc and uranium oxides. Specification 638,436 is referred to. |
