GB1322475A - Air locks for use in electrical high tension apparatus - Google Patents

Abstract

1322475 Discharge tubes MAX-PLANCK-GES ZUR FORDERUNG DER WISSENSCHAFTEN EV 11 Feb 1972 [26 Feb 1971] 6415/72 Heading H1D An air-lock, to permit access to a discharge tube 1, 2 mounted within an evacuated or gasfilled housing 5, 6 without substantial loss of the vacuum or gas filling, is located within the housing in a rest position, Fig. 7, during operation of the tube, and is movable into a sealing position, Fig. 2, to provide a sealed channel between opposed closable openings 4 and 7 in the walls of the tube and the housing, the movement being in a plane at right angles to the axis of the air-lock, and extension means being provided to operate when the air-lock reaches its sealing position, to cause it to extend axially to form a gas-tight seal between sealing surfaces of the housing and the tube. The air-lock is formed by an extensible metal bellows 9 having at its ends sealing flanges 10 and 11 which are provided with projections 18a and 19a, and are coupled to toggle levers 20a which are pivoted on a carriage which, by means of crank 29, may be moved along guide rails from the rest position of Fig. 1 to the sealing position of Fig. 2. Towards the end of the movement, the projections 18a and 19a encounter fixed surfaces 32 and 33 which retain the air-lock in a position aligned with the openings 4 and 7, while continued movement of the carriage, to a position determined by a projection 23a on the carriage, causes the toggle levers to pivot and thrust the sealing flanges against mating sealing surfaces. The sealing flanges are each provided with a threaded ring, to permit adjustment of their distance apart in the sealing position, and the interior space of the air-lock is normally filled with a removable filler plug 30, to reduce the loss of gas filling from the housing during operation of the lock. Reference is made to movement of the air-lock in a circular rather than a rectilinear path, and in a modified arrangement (Fig. 5, not shown) telescopic tubes rather than extensible bellows are employed. As described, the air-lock is employed for replacing the cathode 3 of an electron microscope;