| 摘要 |
A pump (10) including a power rotor (12) and an idler rotor (14a, 14b), the rotors (14a, 14b) each being provided with a generally helical screw thread (20, 20', 26a, 26a',26b, 26b') and being mounted for rotation in a housing (12, 14a, 14b) such that the screw threads (20, 20', 26a, 26a',26b, 26b') of the rotors (12, 14a, 14b) mesh and rotation of one rotor (12, 14a, 14b) causes rotation of the other rotor (12, 14a, 14b), the power rotor (12) being connected to a driving means operation of which causes rotation of the power rotor (12), wherein the pitch of the threads (20, 20', 26a, 26a',26b, 26b') is less than 1.6 times the outer diameter of the power rotor (ODP), the depth of the threads (TD) is less than or equal to 0.2 times the outer diameter of the power rotor (ODP), and the root diameter of the idler rotor (RDI) is less than 0.31 times the outer diameter of the power rotor (ODP).
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