Improvements in or relating to vacuum impregnation apparatus, and methods of operating such apparatus
713,532. Vacuum impregnation. VOGT, A. April 11, 1951 [April 11, 1950], No. 8409/51. Class 140. In a method, of operating vacuum impregnation apparatus in which the impregnation medium is spread out on the outer surface of an impregna-. tion chamber in a layer thin compared with the width of the chamber, and is held. in this way in a reserve chamber, the medium, melted if necessary, is then brought into the chamber under the action of a vacuum produced therein and any excess medium unused in the impregnation is then conveyed back to the reserve chamber by a..vacuum applied thereto. As shown in Fig. 1, the apparatus comprises an impregnation tank 10 within an outer reservoir tank :11, the whole being closed in a vacuum-tight manner and each being connected to a vacuum pump 27 and each having a conduit (23; 20 respectively) leading from the bottom to valves 21, 24. Heating elements 14, 15.with heat insulator 16 between are provided, respectively . surrounding the inner tank 10 and near the partition wall 12 forming the inner limit of a reservoir chamber 13 bounded externally by the tank wall 11. On placing the inner tank 10 serving as impregnation chamber 10a under vacuum and unlocking valve 21 melted impregnation medium in the chamber 13 moves through conduit 20 and discharges into the impregnation chamber 10a, the valve 21 opening to permit such flow. If the valve 21 was unlocked and the chamber 13 was under vacuum, a flow of impregnation medium would not be permitted by valve 21 in the reverse direction since the higher pressure in chamber 10a would maintain the valve closed. If the reservoir chamber 13 is placed under vacuum and the valve 24 is unlocked, impregnating medium flows through the conduit 23 back again into the reserve chamber 13, the valve being such that it may only open when the pressure conditions are such as to move the medium back to the chamber 13. In a modification as shown in Fig. 3 the connecting conduit 30 is disposed at the bottom of the inner tank 10 so that it only has the form of a conduit leading from the chamber 13 to the chamber 10a.The valve plate 31 operates together with the upper end of the conduit 30 located in the tank 10 so that the conduit may be closed. A bolt 32 connected to the plate 31 is mounted for - longitudinal displacement in a bushing 33. located at the bottom of the outer tank 12 and is pivotally connected to a lever 34. A compression spring 35 holds the valve 31, 32 closed at all times unless the lever 34 is operated normally by depressing a foot pedal 36 on the lever 34. According to a modification (not shown) an additional chamber surrounds the reserve chamber (having if necessary heating means between them), and may contain purification devices, e.g. filters for the medium, wherein the movement of the latter through the purification chamber may take place according to changes of the medium in the impregnating chamber which preferably is connected by tubular conduits to the reserve chamber.