Axial flow fan wheel

Claim 1

An axial flow fan wheel comprising a drive shaft, a hub secured on said drive shaft, a hub ring rigidly connected with said hub, adjustable vanes journaled with radial axis on said hub ring, a hydraulic adjustment system for the adjustment of said vanes during the rotation of said wheel, said adjustment system comprising an adjustment member displaceable in the axial direction relative to said hub ring and connected with said hub ring for the rotation thereof together with said wheel, a first hydraulic-working member and a second hydraulic-working member, one of said first working member and said second working member being a working cylinder the other of said first and second working members being a working piston displaceably disposed relative to said working cylinder within same, said first hydraulic-working member being rigidly connected with said drive shaft, said working piston having different effective areas on its two opposite sides and a communicating channel interconnecting said opposite sides for equilibrating the pressure on said opposite sides, saiD second hydraulic-working member being rigidly connected with said adjustment member, an adjustment cylinder disposed coaxially with said second hydraulic working member rigidly connected therewith, an adjustment piston displaceably disposed in the adjustment cylinder, a rotor seal casing mounted displaceably but unrotatably relative to said adjustment cylinder and rotatably but nondisplaceably supported on an extension of said adjustment piston, said rotor seal casing being provided with connecting branches leading to separate areas inside said rotor seal casing, said areas being fluid sealed against each other, a fluid inlet channel and a fluid outlet channel being provided in said adjustment piston and said extension thereof, extending from one and the other said areas respectively, said inlet channel communicating with the space of said working cylinder at that of said sides of said working piston having the smaller area, said outlet channel communicating with the space at the other side of said working piston through adjustable throttling means, said means being constituted by said adjustment piston and said adjustment cylinder, one of said connecting branches being connected with means for the supply of hydraulic fluid at a constant pressure to said inlet channel, said communicating channel in said working piston having a flow resistance of such value relative to the flow resistance of said throttling means that in a state of equilibrium the proportion of the pressure drop over said throttling means to the total pressure equals the proportion of said different effective areas on both sides of said working piston.