GB475840A - High vacuum pumps - Google Patents

Abstract

475,840. High-vacuum pumps. GAEDE, W. Dec. 21, 1936, No. 35042. Convention date, Dec. 21, 1935. [Classes 8 (i) and 71] [Also in Group XXVI] A high - vacuum pump has a working chamber separated from the suction passage, to which additional air or gas is supplied so that the vapour drawn from the space being evacuated is prevented from or hindered in its condensation. Fig. 1 shows a piston pump drawing from a source 8 through a chamber 6 in which a slide valve 7 controls communication with the ends of the pump cylinder. The pump delivers to a chamber 71 formed in the slide valve, to which extra gas is supplied through a regulable valved passage 11, the mixed gases passing off by an outlet 9. Fig. 2 shows a rotary sliding-vane pump in which the gas inlet 26 is automatically controlled by a diaphragm 23 subject to the vacuum in the inlet so that gas is admitted increasingly during the later stages of evacuation. Fig. 8 shows a rotary hinged-abutment pump with manually controlled gas inlet 123, immersed in an oil bath. Sufficient gas is admitted to prevent condensation of the vapour in the bubbles formed by the discharged gas. The surface of the liquid may be kept free of water vapour by a draught of air blown across it. Two-stage pumps may be employed, one stage being a diffusion pump. Fig. 10 shows a molecular pump in which a cylinder 56 rotates in a cylindrical casing formed with helical grooves through which the rotation draws the gas from an inlet passage 58 ; extra gas is supplied to the ends of the casing through a throttled passage 64 ; the mixed gases and vapour, including oil vapours from the bearings, are drawn off through a delivery passage 63 by a second vacuum pump. Specification 385,192, [Group XXVI], is referred to.