24 swivel joint 34 permits rotation of drum 12 while a vacuum is being maintained in the drum vacuum door 24 may be positioned on hinges not shown or may simply be a removable member that can be stored at another site during the loading and cooling processes of this drum referring to fig2 the same tumble mixer 10 is illustrated but in this instance with a vent door 36 positioned at the entry and discharge end section 26 vent door 36 includes a vent 38 which is connected to a flexible conduit not shown that will vent the gaseous contents of rotatable drum 12 to the atmosphere preferably the vent system vents the cryogenic gases used in cooling to be described to the outside of the building which contains the tumble mixer vent door 36 as described in u s pat no 5 104 232 does not rotate with drum 12 but rather remains stationary while positioned on hinges 40 it can also be completely removable it is pointed out that vacuum door 24 does rotate with the drum and the rotation is taken up by the swivel 34 so that conduit 30 does not rotate with the drum having described the essential points of previous tumble mixers it is appropriate to point out at this stage that in the present devices entry and discharge of material is performed through entry and discharge end section 26 generally speaking this is performed by either a loading.