Fluid reaction surfaces (i.e. – impellers) – Specific working member mount – Adjustable
Patent
1990-10-16
1992-07-07
Look, Edward K.
Fluid reaction surfaces (i.e., impellers)
Specific working member mount
Adjustable
416219A, F01D 700
Patent
active
051278014
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an impeller for an axial flow fan having vanes each of which is adjustably mounted each of which is mounted and connected with a vane pitch control device arranged internally in the impeller for simultaneous adjustment of all the vanes during operation for simultaneous adjustment of all the vanes during operation.
In conventional axial flow fans the impeller comprises usually an impeller ring in which the vanes are suspended in rigid connection with a hub section, and the impeller ring and the hub section have mostly been constructed as a casted unit which complicates and increases the cost of the manufacture, especially in the case of large and relatively high speed impellers which under operation must be able to take up a considerable amount of dynamic load due to the centrifugal force, the adjustment forces etc.
With a view of simplifying and reducing the cost of manufacture, especially of very large impellers, a construction is known from Danish patent no. 149694 in which the vanes are suspended in a supporting ring connected with front and back plates through welded joints with the particular ability of having a certain resiliency in the radial direction so that the forces are mainly taken up by the supporting ring itself. Although this construction entails various advantages, it is subjected to limitations with respect to loading just as a result of the resilient welded joints, and it is especially less suitable for use in fans with variable speed where a change of the number of revolutions produces big momentary loads on the impeller.
It is an object of the invention to provide an impeller of the type mentioned which remedies these problems and moreover has the advantage of being composed of relatively uncomplicated individual parts connected in such a way that they can take up a very considerable amount of load and changes of load which make the impeller suitable for use in high speed fans with variable number of revolutions, and in addition it is made possible with regard to the tolerances in the impeller to individually adjust the vanes in order to obtain an optimal adaption of the play between the vane edges and the surrounding casing.
This is achieved according to the invention in that the vanes are suspended in a rigid supporting ring which is centered and kept in position by means of mainly radial supporting plates one of which forms a connection to a hub section journalled on a drive shaft, said supporting plates having circumferential collar parts engaging recesses on opposite sides of the supporting ring and being furthermore connected with the supporting ring by means of parallel connecting bolts and being connected with each other by distance members parallel to the axes and forming slide guides for said vane pitch control device designed as an axially movable control disc, the vanes being suspended in said supporting ring so as to be individually adjustable in their axial direction.
In the impeller according to the invention the supporting ring and the supporting plates are preferably designed as forged pieces. The engagement between the supporting ring and the supporting plates provides an accurate centering of the supporting ring and at the same time the connecting bolts offer the possibility of obtaining an easy access to the interior of the impeller for inspection of the vane suspension bearings and the control means.
In a preferred embodiment each vane is fixed in a predetermined angular position on one end of a short vane shaft extending through a bore provided in the supporting ring and forming at the inner side of the supporting ring a bearing casing for a vane suspension bearing which is kept in position in the bearing casing by means of a nut screwed onto said vane shaft and forming a bottom of the bearing casing, a vane balancing device and a control arm connected with said control disc being formed as an integral unit which is removably retained in the axial direction and in a predetermined angular position on the other end of said vane shaft, said
REFERENCES:
patent: 2566696 (1951-09-01), Cushman
patent: 4573874 (1986-03-01), Andersen et al.
patent: 4579510 (1986-04-01), Dalsgaard
patent: 4844647 (1989-07-01), Johansen
Lee Michael S.
Look Edward K.
Novenco A/S
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