Patent ID: 8113803

Claim:
A lubricating system ( 2 ) for lubricating a drive ( 3 ) powering a helicopter rotor, said lubricating system ( 2 ) comprising: a lubricating pump ( 1 ); a tank ( 4 ) of lubricating fluid; and a casing ( 9 ) housing a lubricated member of said drive ( 3 ); said lubricating pump ( 1 ) comprising: a first stage ( 5 ) comprising an intake ( 6 ) hydraulically connected to said tank ( 4 ) and a delivery outlet ( 7 ) hydraulically connected to a number of nozzles ( 8 ) for feeding said lubricating fluid into said casing ( 9 ) and onto said lubricated member, said first stage ( 5 ) compressing, in use, said lubricating fluid from said tank ( 4 ) to a pressure to supply to said lubricated member housed within said casing ( 9 ); and a second stage ( 10 ) comprising an inlet ( 11 ) hydraulically connected to an opening ( 12 ) defined by said casing ( 9 ) and an outlet ( 13 ) hydraulically connected to said tank ( 4 ), said second stage ( 10 ) feeding said lubricating fluid in said casing ( 9 ) back into said tank ( 4 ); said second stage ( 10 ) being a Roots type comprising a first rotor ( 31 ) and a second rotor ( 32 ) rotating, in use, in opposite directions to feed said lubricating fluid from said inlet ( 11 ) to said outlet ( 13 ); said first rotor ( 31 ) and said second rotor ( 32 ) both being operated by said first stage ( 5 ); said first rotor ( 31 ) comprising a number of first lobes ( 33 ) and said second rotor ( 32 ) comprising a number of second lobes ( 34 ) such that said first and second lobes ( 33 , 34 ) having conjugate profiles in constant contact with one another; said first stage ( 5 ) comprising a third rotor ( 35 ) and fourth rotor ( 36 ) connected functionally to said first and second rotors ( 31 , 32 ), respectively; one of said third and fourth rotors ( 35 , 36 ) being powered and rotating, in use, the other one of said third and fourth rotors ( 35 , 36 ); said lubricating pump ( 1 ) further comprising: a first shaft ( 37 ) fitted with and connecting said first and third rotors ( 31 , 35 ); a second shaft ( 39 ) fitted with said second and fourth rotors ( 32 , 36 ); and a housing ( 20 ) housing said first and second stages ( 5 , 10 ); said housing ( 20 ) comprising: a first end body ( 21 ) and a second end body ( 22 ) defining respective axial ends of said housing ( 20 ); a first plate ( 23 ) and a second plate ( 25 ) interposed axially between said first and second end bodies ( 21 , 22 ) and separating said first and second end bodies ( 21 , 22 ) in a fluid tight manner; said first end body ( 21 ) having a first cavity facing said first plate ( 23 ) and housing said first and second rotors ( 31 , 32 ); said second end body ( 22 ) having a second cavity facing said second plate ( 25 ) and housing said third and fourth rotors ( 35 , 36 ).