Screw rotor for a screw type vacuum pump

Abstract

A screw rotor is for a screw type vacuum pump, preferably for a screw type vacuum pump having a pumping capacity less than 50 m 3 /h. The rotor has a rotor shaft, a rotor core which rests on the rotor shaft, and a rotor cover which rests on the rotor core and at least partially encloses the rotor core. The rotor core is made of a material having a thermal conductivity greater than 100 W/m·K, preferably a thermal conductivity greater than 200 W/m·K. A screw type vacuum pump has correspondingly designed rotors.

1 . A screw rotor for a screw type vacuum pump, the screw rotor comprising:
 a rotor shaft, a rotor core which rests on the rotor shaft, and a rotor cover which rests on the rotor core and at least partially encloses the rotor core,   wherein the rotor core is made of a material having a thermal conductivity greater than 100 W/m·K.   
     
     
         2 . The rotor according to  claim 1 , wherein
 the rotor shaft is made of a material having a thermal conductivity greater than 100 W/m·K.   
     
     
         3 . The rotor according to  claim 2 , wherein
 the rotor shaft and the rotor core are designed as one piece.   
     
     
         4 . The rotor according to  claim 1 , wherein
 the rotor core extends into the screw threads of the rotor.   
     
     
         5 . The rotor according to  claim 4 , wherein
 the rotor core extends into the screw threads of the rotor only in an area of the rotor which during operation faces an outlet of a pump chamber.   
     
     
         6 . The rotor according to  claim 1 , wherein
 the rotor cover is made of a material which has a low thermal conductivity compared to the thermal conductivity of the rotor core and of the rotor shaft.   
     
     
         7 . The rotor according to  claim 6 , wherein
 the rotor cover is made of plastic.   
     
     
         8 . The rotor according to  claim 7 , wherein
 at least one of the rotor core, parts thereof, and the rotor shaft is made of copper, aluminum, or alloys of these materials.   
     
     
         9 . The rotor according to  claim 1 , wherein
 the rotor is configured for a one-sided bearing at only one end of the rotor shaft.   
     
     
         10 . The rotor according to  claim 9 , wherein
 in an area of the end of the rotor facing away from the one end used for the bearing, the rotor shaft has a reduced cross section, a recess, or is missing completely, and a volume that is missing compared to an otherwise complete outer dimension of the rotor, is filled by the rotor cover.   
     
     
         11 . The rotor according to  claim 1 , wherein
 a heat transfer means for delivering heat to the ambient atmosphere is situated on the rotor shaft at a distance from the rotor core.   
     
     
         12 . A rotor according to  claim 1 , wherein the rotor core is made of a material having a thermal conductivity greater than 200 W/m×K. 
     
     
         13 . A rotor according to  claim 4 , wherein the rotor core, at a location where the rotor core extends into the screw threads of the rotor, has a reduced thickness. 
     
     
         14 . The rotor according to  claim 13 , wherein the rotor cover has a thickness of 0.1 mm to 10 mm in the location where the rotor core extends into the screw threads of the rotor. 
     
     
         15 . The rotor according to  claim 6 , wherein the rotor cover is made of a material which has a thermal conductivity less than 5 W/m. 
     
     
         16 . The rotor according to  claim 7 , wherein the plastic is thermoplastic. 
     
     
         17 . The rotor according to  claim 7 , wherein the plastic is a chemically resistant plastic selected from the group consisting of PPS, PEEK, and fluoroplastic. 
     
     
         18 . The rotor according to  claim 7 , wherein the plastic is reinforced with a filler selected from the group consisting of carbon fibers and glass fibers. 
     
     
         19 . The rotor according to  claim 1 , wherein the screw type vacuum pump has a pumping capacity less than 50 m 3 /h. 
     
     
         20 . A screw type vacuum pump comprising:
 a screw pump stator with at least one inlet and one outlet, and   two helical rotors which rotate in mutual contactless engagement with one another in a fittingly shaped pump chamber of the screw pump stator, and thus convey a gaseous medium from the inlet to the outlet,   wherein the rotors each comprises:   a rotor shaft, a rotor core which rests on the rotor shaft, and a rotor cover which rests on the rotor core and at least partially encloses the rotor core,   wherein the rotor core is made of a material having a thermal conductivity greater than 100 W/m·K.   
     
     
         21 . The screw type vacuum pump according to  claim 20 , wherein
 the outlet of the pump chamber is situated at an end of the pump chamber facing the supported ends of the rotors.   
     
     
         22 . The screw type vacuum pump according to  claim 20 , comprising
 a dual-shaft synchronous drive for driving the rotors.   
     
     
         23 . The screw type vacuum pump according to  claim 20 , wherein the screw type vacuum pump has a pumping capacity less than 50 m 3 /h.