Abstract: A three-passage valve comprising (1) a body with a main passage (10) and two secondary passages (12,13), each of the secondary passages being fitted with a respective closure member (2,3) and the valve as a whole being provided with a single, common actuator unit (6) to operate the closure members in such a manner that the valve can occupy any one of three positions: a first position in which the main passage is in communication with a first one of the secondary passages while the other secondary passage is closed; a second, or intermediate, position in which both of the secondary passages are closed; and a third position in which said first passage is closed while the main passage is in communication with said other secondary passage.

Abstract: A two stage pumping unit for evacuating tubes, and in particular television ubes. A primary mechanical pump is air-cooled and is connected in series with an oil diffusion pump. The inlet for the stem of a tube to be evacuated has a sealing ring and between the sealing ring and the diffusion pump there is a baffle. Between the two pumps there is an oil condensation device and an oil trap. The trap, the condensation device, the oil diffusion pump, the baffle and the sealing ring are arranged for cooling by forced air.

Abstract: A steam flow vacuum pump has a grooved cylindrical pump body surrounded by a housing having a radius slightly greater than the pump body and a high-power ventilator pulsating the air in the housing. The housing is provided with vents on the opposite side to the ventilator. The swirling flow of the air causes a great cooling of the pump body.