Patent GB-679816-A (GB)
Title: Improvements in capacitors and methods and apparatus for making the same
IPC: H01G4/10
Filed: 1948-02-27
Abstract: 679,816. Condensers. DEPARTMENT OF COMMERCE, DIRECTOR OF THE OFFICE OF TECHNICAL SERVICES OF. Feb. 27, 1948 [July 28, 1944], No. 5998/48. Class 37. In a method of manufacturing a blank for a stacked type condenser, in which a thin sheet 51 of vitreous enamel dielectric has a thin plate 69 of metallic conducting material 65 sprayed on at least one side of it, the plate 69 coats the central part and one peripheral part only of the sheet 51 and extends beyond the peripheral part, to form a tab 79. The term " vitreous enamel " includes glass. The enamel sheet 51 is supported on a stainless steel conveyer 53, having been, e.g. sprayed thereon. The material 65, e.g. silver powder in a liquid vehicle, is sprayed through paddle-shaped holes 57 in a shield 55, knives 72 serving the sheet 51 with its metal coatings 69 to form blanks 73 which are fired in an oven, and then stacked automatically with the tabs 79 of alternate blanks facing in opposite directions. The stack is then fused in a die to form a structure 97, Fig. 4, a predetermined number of which are stacked with intervening dielectric sheets 103 for stiffening to form a condenser assembly. U-shaped clips 99, with rods 101 which penetrate the tabs 79 on the condenser structure 97, serve as terminals, wires 105 being, e.g. soldered to the rod 101, or lead wires may be soldered directly to the tabs 79, the clips 99 and rods 101 being dispensed with. The assembly is then placed in a second die containing liquid vitreous enamel which completely surrounds the assembly and firing takes place to form the finished condenser which is hermetically sealed in an enamel envelope. If desired, the enamel envelope may be formed by spraying or dipping. Several modifications are described. The enamel sheet 51 with its coatings 69 may be fired before cutting, or the sheet 51 may be cut before being sprayed with silver, Fig. 7 (not shown), and in any modification enamel may be sprayed on the metal coatings 69 to form enamel coatings on both sides thereof. Finally the order of the operations may be altered. The enamel may be sprayed onto a suitable base, the silver sprayed thereon, the whole partially dried, cut, stacked and fired, the step of fusing being dispensed with. The Specification as open to inspection under Sect. 91, comprises also the method of manufacturing blanks for stacked type condensers in which enamel 147, Fig. 8 (Cancelled), is sprayed on metal foil 135. A long narrow ribbon of foil 129 is cut into pairs of paddleshaped portions 135 which are sprayed through a shield 141 with enamel 147, the ends of metal tabs 145 being left uncoated. Each pair of blanks is passed through a firing oven, severed, stacked and completed as in the previously described method. In a modification the foil is cut into a number of paddled-shaped blanks arranged on a conveyer, the tabs facing the same way, and the usual sequence of operations carried out. In a further modification the cutout metal blanks are suspended by their tabs and dipped in a vat of enamel after which they are passed through a firing oven. This subjectmatter does not appear in the Specification as accepted. The Specification as open to inspection under Sect. 91, comprises also the subjectmatter of Specification 679,907.