Pumping unit for television tubes

In a two stage pumping unit for evacuating tubes terminating in a stem, said unit comprising a frame, an air-cooled mechanical vacuum pump supported by said frame, an oil diffusion pump, a discharge pipe connecting said mechanical vacuum pump and said oil diffusion pump in series with said mechanical vacuum pump acting as a first stage pump and said oil diffusion pump acting as a second stage pump, a suction pipe connected to said diffusion pump and having an inlet for receiving the stem of said tube to be evacuated, said oil diffusion pump including a pump body, a seal surrounding the inlet and an oil vapor baffle carried by said suction pipe and disposed between the inlet and the pump body, a main housing for enclosing said diffusion pump body, said discharge pipe having a portion extending parallel to and to the side of said oil diffusion pump, the improvement comprising:

• said unit having forced draft generator means for drawing air from a relatively cool region of said frame, and forcing a cooling draft through said first housing across said parallel portion of said discharge pipe extending parallel to said oil vapor baffle, and across said baffle and said suction pipe in the vicinity of the seal surrounding the inlet.