Positive displacement gear pump

Abstract

A positive displacement pump ( 1 ) comprises a casing with a central body ( 2 ) and two closing lids ( 20 ), said central body ( 2 ) being provided with two cylindrical communicating chambers ( 22, 23 ), one suction pipe (I) and one discharge pipe (O), and two rotors ( 3, 4 ) revolvingly mounted in said chambers ( 22, 23 ) of the central body and supported by shafts ( 5, 6 ) revolvingly mounted in said closing lids ( 20 ). The two rotors comprise: a male rotor ( 3 ) comprising only protuberances ( 30 ), not cavities, and a female rotor ( 4 ) comprising only cavities ( 40 ), not teeth or protuberances.

1 . A positive displacement pump comprising:
 a casing comprising a central body and two closing lids, said central body being provided with two communicating cylindrical chambers, one suction pipe and one discharge pipe, and   two rotors revolvingly mounted in said chambers of the central body and supported by corresponding shafts revolvingly mounted in said closing lids,   characterized in that said two rotors comprise:   a male rotor having an outer surface that comprises protuberances said outer surface being substantially free of cavities, and   a female rotor having an outer surface that comprises cavities said outer surface being substantially free of protuberances and teeth,   wherein the protuberances of the male rotor are engaged in the cavities of the female rotor without contact between the two rotors.   
     
     
         2 . The pump of  claim 1 , wherein said male rotor comprises a cylindrical body and a plurality of protuberances that protrude radially from the cylindrical body and said female rotor comprises a cylindrical body and a plurality of cavities that extend radially inside the cylindrical body. 
     
     
         3 . The pump of  claim 2 , wherein
 each protuberance of the male rotor cross-sectionally comprises two involute-shaped sides converging into a rounded head, the two sides of each protuberance being symmetrical with respect to a radial axis of symmetry passing through the head of the protuberance, and   each cavity cross-sectionally comprises two involute-shaped sides joined into a bottom surface with concave shape, wherein the profiles of the two sides of the cavity are asymmetrical with respect to a radial straight line passing through the bottom of the cavity, the involute-shaped profile of the inlet side having a higher curvature than the involute-shaped profile of the outlet side of the cavity.   
     
     
         4 . The pump of  claim 3 , wherein the male and female rotors are centered in the chambers of the central body in such manner to leave a tolerance space of between 0.05 mm, and 0.02 mm, between the following parts:
 between the heads of the protuberances of the male rotor and the internal surface of the cylindrical chamber of the central body,   between the heads of the protuberances of the male rotor and the bottom surface of the cavities of the female rotor,   between the external surface of the cylindrical body of the female rotor and the internal surface of the cylindrical chamber of the central body of the casing,   between the external surface of the cylindrical body of the female   rotor and the external surface of the cylindrical body of the male rotor.   
     
     
         5 . The pump of  claim 1 , wherein the male rotor comprises two diametrally opposite protuberances and the female rotor comprises two diametrally opposite cavities. 
     
     
         6 . The pump of  claim 1 , wherein the protuberances of the male rotor are provided with heads and the head diameter of the male rotor is identical to the diameter of the cylindrical body of the female rotor. 
     
     
         7 . The pump of  claim 2 , wherein the diameter of the cylindrical body of the male rotor is identical to the diameter of the cylindrical body of the female rotor. 
     
     
         8 . The pump ( 1 ) of  claim 1 , wherein the male rotor comprises a cylindrical body provided with seats and said protuberances consist in sectors comprising a base that is engaged in the seat of the cylindrical body of the rotor. 
     
     
         9 . The pump of  claim 1 , further comprising two external gears comprising toothed wheels keyed onto the shafts of the rotors outside said casing. 
     
     
         10 . The pump of  claim 1 , also further comprising:
 two plate-shaped seal gaskets disposed between said central body and said lids and   a plurality of springs disposed between said lids and seal gaskets in such manner to stress the seal gaskets against the planar sides of the rotors.   
     
     
         11 . The pump of  claim 10 , wherein said seal gaskets and said rotors are coated with an anti-friction self-lubricating material. 
     
     
         12 . The pump of  claim 3 , wherein the male rotor comprises two diametrally opposite protuberances and the female rotor comprises two diametrally opposite cavities. 
     
     
         13 . The pump of  claim 3 , wherein the protuberances of the male rotor are provided with heads and the head diameter of the male rotor is identical to the diameter of the cylindrical body of the female rotor. 
     
     
         14 . The pump of  claim 3 , wherein the diameter of the cylindrical body of the male rotor is identical to the diameter of the cylindrical body of the female rotor. 
     
     
         15 . The pump of  claim 3 , wherein the male rotor comprises a cylindrical body provided with seats and said protuberances consist in sectors comprising a base that is engaged in the seat of the cylindrical body of the rotor. 
     
     
         16 . The pump of  claim 3 , further comprising:
 two plate-shaped seal gaskets disposed between said central body and said lids; and   a plurality of springs disposed between said lids and seal gaskets in such manner to stress the seal gaskets against the planar sides of the rotors.   
     
     
         17 . The pump of  claim 16 , wherein said seal gaskets and said rotors are coated with an anti-friction self-lubricating material. 
     
     
         18 . The pump of  claim 6 , wherein the male rotor comprises a cylindrical body provided with seats and said protuberances consist in sectors comprising a base that is engaged in the seat of the cylindrical body of the rotor. 
     
     
         19 . The pump of  claim 6 , further comprising:
 two plate-shaped seal gaskets disposed between said central body and said lids; and   a plurality of springs disposed between said lids and seal gaskets in such manner to stress the seal gaskets against the planar sides of the rotors.   
     
     
         20 . The pump of  claim 19 , wherein said seal gaskets and said rotors are coated with an anti-friction self-lubricating material.