Ventilating arrangement for steam flow vacuum pump

In a steam flow vacuum pump cooling means for cooling the pump by an air flow comprising a cylindrical pump body provided with grooves on at least a portion of the outer surface thereof, a cylindrical housing coaxially mounted on said pump body to enclose at least the portion thereof containing said grooves, said cylindrical housing having a radius which is only slightly larger than the radius of said pump body, and ventilator means connected to an intake opening in said cylindrical housing for supplying an air flow to said housing, said housing also including a plurality of vent holes to permit escape of said air flow, characterized in that said pump includes a cross-head communicating with the interior of said pump body and having, towards its end disposed outside the pump body, a plurality of grooves around which the air leaving said vent holes flows, and characterized in that the air leaving said vent holes is directed towards the grooves of the cross-head by means of a secondary housing surrounding the grooved end of the cross-head and fixed to the housing surrounding the pump body and provided with an air discharge hole on the opposite side to the vent holes.