Cooled screw vacuum pump

A cooled screw vacuum pump, having a suction side and a pressure side, comprising a housing that defines a pumping chamber and two rotating systems, each rotating system comprising:

• a screw rotor,
• a shaft connected at one end to the screw rotor and extending out of the pumping chamber,
• at least two mutually spaced bearings on each shaft supporting the screw rotors in a cantilevered fashion in the pumping chamber, all bearings being on the same side of the rotor, and
• a cavity defined in each rotor, open on the bearing side, within which cavity there is respectively located a cooling fluid which cools the rotor internally,
• each rotor including a suction-side threaded segment and a pressure-side threaded segment with different thread profiles, the depth of the thread profile of the pressure-side segment being small than the depth of the thread profile of the suction-side segment.

A cooled screw vacuum pump having a suction side and a pressure side, the vacuum pump further including:

• a housing and two rotating systems, each rotating system including a screw rotor, a shaft, and mutually spaced bearings on each shaft supporting the rotors;
• each rotor defining a cavity open on a bearing side, within which cavity there is respectively:
• a cooling element located in the cavity which cools the rotor internally;
• a first helical pumping chamber defined in the housing;
• a second helical pumping chamber with a reduced cross section relative to the first pumping chamber extending from the first pumping chamber to an outlet passage;
• a bore extending from the outlet passage to an end of the first pumping chamber adjacent the second pumping chamber;
• and
• a non-return valve mounted to the bore to limit flow to a direction from the first pumping chamber to the outlet.

An evacuation apparatus comprising:

• a housing having an inlet port and an outlet port;
• a pump section arranged in said housing and having a suction side and an exhaust side, the pump section including interengaging rotors, each of the rotors having at least one threaded portion, the threaded portions, together with said housing, defining a gas-transporting space, each rotor further including a cooling cavity defined in and opening only to an exhaust-side portion of the rotor;
• a means for circulating a cooling fluid flow through each cavity to cool the rotors internally;
• a rotating shaft connected to the exhaust-side portion of each rotor;
• bearings supporting the rotating shafts in a cantilever fashion, the bearings being axially spaced apart from the threaded portions, all on the same side of the rotor, and fliaidically isolated from the cooling fluid flow circulating through the cooling cavity;
• and
• at least one motor for rotating the interengaging rotors.

A cooled screw vacuum pump, having a suction side and a pressure side, the pump comprising a housing and two rotating systems, each rotating system comprising:

• a rotor with a thread, the threads of the rotors and the inside of the housing acting together, when the rotors are rotating, to transport a gas from the suction side to the pressure side;
• a hollow shaft supporting the rotor;
• mutually spaced bearings on the shaft, all bearings being situated at the pressure side of the rotor;
• each rotor being provided with a cavity open only to the pressure side,
• the bearing closest to the rotor being located outside the cavity,
• a cooling pipe extending axially through the hollow shaft forming a first channel in fluid connection with the cavity in the rotor;
• and,
• the cooling pipe and the hollow shaft forming a second channel surrounding the cooling pipe and in fluid connection with the cavity in the rotor.

A fluid cooled screw vacuum pump comprising:

• a housing defining a pumping chamber and a coolant chamber which are fluidically isolated from each other, the housing defining a suction inlet into the pumping chamber and a pressure outlet from the pumping chamber;
• and
• a pair of rotating systems each including:
• at least two bearings mounted to the housing in the coolant chamber;
• a shaft rotatably mounted in the bearings with one end extending cantilevered into the pumping chamber;
• a threaded screw rotor connected to the one end of the shaft, the screw rotor being supported only by the shaft in a cantilevered fashion in the pumping chamber, the screw rotors of the pair of rotating systems intermeshing to pump gas from the suction inlet to the pressure outlet;
• and
• a cavity defined in the shaft and the screw rotor in fluid communication with coolant chamber through which cavity coolant fluid is passed to cool the screw rotor internally.

A cooled screw vacuum pump, having a suction side and a pressure side, comprising a housing and two rotating systems, each rotating system comprising:

• a rotor with a thread, the threads of the rotors and the inside of the housing acting together, when the rotors are rotating, to transport a gas from the suction side to the pressure side, the rotor being segmented and including a suction-side segment and a pressure-side segment joined to the suction-side segment;
• a hollow shaft supporting the rotor;
• mutually spaced bearings on the shaft, all bearings being situated at the pressure side of the rotor;
• each pressure-side segment being provided with a cavity adjacent the suction-side segment and open to the pressure side;
• the bearing closest to the rotor being located on the pressure side outside the cavity;
• a cooling agent, contacting an inner surface of the cavity directly;
• a cooling pipe extending axially through a central opening of the hollow shaft, the inner surface of the cooling pipe forming a first channel in fluid connection with the cavity in the rotor,
• the central opening of the hollow shaft and the pipe forming a second channel surrounding the pipe, being annular and in fluid connection with the cavity in the rotor.

A cooled screw vacuum pump, having a suction side and a pressure side, comprising a housing and two rotating systems, each rotating system comprising:

• a rotor with a thread, the threads of the rotors and the inside of the housing acting together, when the rotors are rotating, to transport a gas from the suction side to the pressure side;
• a hollow shaft supporting the rotor;
• mutually spaced bearings on the shaft, all bearings being situated at the pressure side of the rotor;
• each rotor being provided with a cavity open to the pressure side;
• the bearing disposed closest to the rotor being located outside the cavity;
• a cooling pipe extending axially through the hollow shaft, an inner surface of the cooling pipe forming a first channel in fluid connection with the cavity for supplying a cooling agent to an inner surface of the cavity directly in the rotor;
• and a central opening of the shaft and the pipe forming a second, annular channel surrounding the pipe, in fluid connection with the cavity in the rotor, and,
• a first set of channels through a wall of the housing adjacent the rotors through which the cooling agent flows.