US 3173343 A
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Ma n-1e, 1965' P. J. A. BERRY 3,173,343
DEVICE FOR CONTROLLING THE VARIATION IN PITCH OF A FAN Filed July 29. 1963 Myth me 840/. (11/1. zs/v 41v TOI/YE 35?? Y 0% L mrw Arr-y.
United States Patent M 4 Claims. c1. 92-151 The present invention relates to a device for controlling the variation in pitch of a fan while running, in which the orientation of the blades of the fan is adjustable by axial displacement, controlled by a fluid jack, of a so-called bell member rotating in unison with the fan. The control jack may be of the pneumatic or hydraulic fluid type.
In known devices of this kind, when the device is mechanical, there are experienced play in the transmission and flexibility of the supports between the bell and the servo-motor, generally located on the exterior, resulting in a hystresis effect detrimental to the accuracy of the control, or when the device is pneumatic, the presence of a rotary joint for the supply of fluid to the jack is a source of undesirable leakage.
The present invention has for its object a device of the kind referred to above which is free from the drawbacks mentioned, and in which the jack is fixed angularly and is axially supported on the shaft so as to eliminate all external reaction and to avoid the use of a rotating joint.
More particularly, in accordance with the invention, both the bell and the jack are mounted on the shaft of the fan, the said bell being slidably mounted along the said shaft while the jack is angularly fixed, having its two constituent parts, of which one is a cylinder and the other a piston, coupled respectively to the said shaft and to the said bell by two axially-rigid couplings which are free for rotation.
The particular features and advantages of the invention will furthermore become apparent from the description which follows below of one form of embodiment chosen by way of example, reference being made to the accompanying drawing, of which the single figure is a view in longitudinal section of a helicoidal fan provided with a device according to the invention.
In the form of embodiment shown, a helicoidal fan comprises a shaft 19 which is suitably supported by bearings, one of which is shown diagrammatically at 9. To the right of these bearings, that is to say in an overhung position, a wheel 11 with orientatable blades 12 is mounted on the shaft 10. The blades 12 are disposed in an annular passage 13 formed between two fixed concentric Walls 14 and 15. There is shown at 16 a distributor ring arranged in the passage 13 on the upstream side of the blades 12.
Each blade 12 is provided with a tail 17 which is pivotally mounted in a guide 18 carried by the wheel 11. The axis of the guide 18 is perpendicular to the axis of the shaft 10. The various tails 17 are coupled by cranks 19 and connecting rods 20 to a so-called bell member 21, rotating in unison with the wheel 11 and adapted to move axially along the axis of the shaft Ill under the control of a pneumatic or hydraulic fluid jack 22.
The bell 21 and the jack 22 are mounted on the end of the shaft 10, to the right of the wheel 11. The bell 21 is mounted slidably along the shaft 16, while the jack 22 is angularly fixed. The jack 22 comprises a cylindrical member 23 and piston means 24. In the example shown, the jack 22 is of the double-acting type and comprises two chambers 25 and 26. The chambers 25 and 26 are defined by the cylinder member 23, a fixed partition 27 3,173,343 Patented Mar. 16, 1965 of this cylinder and two pistons 28 and 29 respectively of the piston means 24.
The cylinder 23 is connected to the shaft 10 by a coupling which is axially fixed relative to shaft 10 and free for rotation. This coupling comprises a thrust and roller bearing 30 and a device consisting of a sleeve 31. The piston means 24 with its two pistons 28 and 29 is connected to the bell 21 by a coupling which is axially fixed relative to bell 21 and free for rotation. This coupling comprises a thrust and roller bearing 32 and a device comprising radial arms 33, rods 34 parallel to the axis, and a casing 35. The cylinder and piston means are angularly fixed. The bearing 30 is located axially between the jack 22 and the bearing 32. The rods 34 surround the sleeve 31 and the bearing 30.
The chambers 25 and 26 are respectively connected to fixed conduits 36 and 37 which are coupled to .a distribu tor 38, with which coordinate a fluid pressure conduit 39 and a conduit 40 connected to atmosphere or to a tank. The distributor 38 has a control comprising a modulated fluid follow-up device for ensuring the accuracy of the jack 22 with a connection to the casing 35 by means of a light rod system 41 with means for taking-up play by a spring or other appropriate means.
In order to modify during running the pitch of the fan, that is to say the orientation of the blades 12, the fluid under pressure is directed by the distributor 38 into the chamber 25, for example, whereas the chamber 26 is connected to the atmosphere. This has the effect of pushing the system 3344-35, and in consequence the bell 21, towards the left. Through the intermediary of the connecting rods 20 and the cranks 19, the blades 12 all pivot by the same amount in the same direction. The operation is similar but in the reverse direction, when the fluid under pressure is directed to the chamber 26.
It will be appreciated that with the arrangement according to the invention, all reaction on an external support is eliminated. Any possible movement of the shaft 10 in its bearings does not cause any modification of the angular setting of the blades 12, irrespective of the direction of thrust. In addition, as the jack 22 is angularly fixed, no rotating joint is necessary and there is no risk of leakage.
The fan in accordance with the invention can therefore be utilized with special advantage in applications in which the operation is continuous and where the working must be very precise. This is particularly the case for the fans in electric power stations, the inspection and maintenance of which can only be carried out at long intervals.
The invention is of course not limited to the form of construction described and shown, but includes all its alternative forms. For example, the arrangement can be applied not only in the case of a fan 10 having its wheel 11 overhung, but also when the wheel 11 is mounted between two bearings. In this latter case, and when the axial reactions so permit, the sleeve 31 may be used as a bearing.
What I claim is:
1. A control device for varying the pitch of the blades of a fan during operation, comprising a fan shaft, a member rotatable with the shaft and axially shiftable along the shaft to vary the pitch setting of the blades, fluid motor means having at least a cylinder and a piston, first thrust and roller bearing means mounting the motor means on the shaft and fixing one of said cylinder and piston against axial movement relative to the shaft, means securing the motor means against rotation with the shaft, second thrust and roller bearing means fixing the other of said cylinder and piston against axial movement relative to said member, said motor means and said first and second bearing means being coaxial, said first bearing means being disa posed between said second bearing means and said motor means.
2. A control device as claimed in claim 1, and means extending between and interconnecting said second bear.- ing means and said other of said cylinder and piston and surrounding said first bearing means.
3. A control device as claimed in claim 2, said interconnecting means comprising a plurality of rods parallel to the axis of the shaft.
4. A control device for varying the pitch of the blades of a fan during operation, comprising a fan shaft, a member rotatable with the shaft and axially shiftable along the shaft to vary the pitch setting of the blades, fluid motor means having cylinder means comprising a pair of coaxial cylinders and piston means comprising a pair of coaxial pistons one disposed in each cylinder, means interconnecting said cylinders in unitary assembly, means interconnecting said pistons in unitary assembly for conjoint movement of the cylinder means and the piston means relative to each other, first thrust and roller bearing means mounting the motor means on the shaft and fixing one of said cylinder means and piston means against axial movement relative to the shaft, means securing the motor means against rotation with the shaft, second thrust and roller bearing means fixing the other of said cylinder means and piston means against axial movement relative to said member, and means for selectively directing fluid under pressure to one of said cylinders and while exhausting fluid from the other of said cylinders and for directing fluid under pressure to said other of said cylinders while exhausting fluid from said one cylinder.
References Cited by the Examiner UNITED STATES PATENTS 1,327,381 1/20 Furber 123-41 1,875,598 9/32 Heath 170-16024 2,231,292 2/41 Neugebauer 123-41 2,316,940 4/43 Dewey et a1. 123-41 2,377,386 6/45 Stalker 170-16032 2,472,728 6/49 Sanders 123-41 2,902,938 9/59 Ebert 230-114 FOREIGN PATENTS 942,363 9/48 France.
RICHARD B. WILKINSON, Primary Examiner.