GB2231924A - A hub for adjustable or variable pitch axial and propeller fans - Google Patents

Abstract

The hub, formed from sheet material, has recesses 2, 5 in back plate 1 and clamp plate 4 to receive fan wing roots 3. A sleeve, needle, ball or roller bearing may be interposed between roots 3 and plates 1, 4 to enable pitch adjustment during operation. A flange 8 on each root engages slots 7, 10 in the plates. The hub may be made in any desired size and with any desired number of wing root recesses, enabling the production of a fan with optimum performance and characteristics. The size of the recesses may be altered to suit different wing roots, and the hub may be made in any desired shape. <IMAGE>

Description

HUB FOR AXIAL FLOW FANS The present invention is an improved impellor hub for use with fans of the axial and propellor type.

Axial and propellor fans are used in a wide range of applications and for a wide range of different duties. It follows, therefore, that the performance of any given fan may be varied according to its intended use. In conventional axial or propellor fans, the duty of a fan of given size and speed is varied by adjusting the number of wings, or blades (hereinafter the"wings") and by adjustment of these wings relative to a suitable datum, such as the fan axis or the plane of the fan hub. This is normally achieved by clamping the bottom end of each wing (hereinafter the "root") between two halves of a cast or moulded hub once the pitch angle has been set. An alternative method is to pass the root, which may be threaded, through the flange of a cast or fabricated hub and to fasten it by nuts and/or setscrews.

All such hub designs involve the use of castings or mouldings or expensive fabrications, the size (diameter) of which should, ideally be made proportional to each diameter of fan e.g. in a ratio of one third or one half the fan diameter and so on. Since the cost of tooling and production of such hubs is high, in practice, one hub may serve a number of diameters, with consequent deviations in performance.

Alternatively, only a limited number of fan sizes, but with their correct hub/diameter ratios, may be made. A further feature of such hubs is that both the number and size of wing recesses is fixed and thus imposes a further limitation on the fan design.

It is an objective of the present invention to provide a novel form of hub which may be readily adapted to the production of the exact size size required by any given fan, whilst providing the potential to choose the exact number of wings and the correct pitch angle for any given duty, using relatively simple production methods, at the same time allowing variation of wing root size if the design requires it.

The hub according to this present invention comprises a metal plate (the "back plate") cut from a sheet of the appropriate thickness and having a plurality of radial directed apertures, or recesses, around its periphery, each recess being designed to receive the root of a wing, such root being similar in shape to the said recess, and a second part aligned with the first part (hereinafter the "clamp plate") with similar recesses to accomodate wing roots. The two plates are mechanically fastened to each other, clamping the wing roots betwen them.

At the lower end of each recess in both back plate and clamp plate there is cut a slot through which passes a projection or flange located at the lower end of each root. This projection or flange engages upon the lower end of the metal forming the recess thus preventing the wing being thrown out radially under centrifugal forces. The number of recesses will not be less than two but can thereafter be any number necessary to suit the specific requirements of a particular fan. In all cases, the shape of the wing roots and the recesses are such that the wing may be turn3d to the correct angle before the back plate and the clamp plate are finally fastened together. The recesses may be symmetrically or asymmetrically spaced, the latter to improve the acoustic performance of the fan by avoiding pure tones or beat notes, provided that the mechanical balance is maintained.The preferred shape of the back plate and clamp plate would be either circular or polygonal, but any other shape, e.g.oval may be used. Polygonal shapes have the advantage of simplicity of manufacture by simple tools.Where polygonal back plates are used, the single clamp plate may be replaced by a plurality of discreet clamps, one for each recess.

It is a feature of this invention that the recesses are pressed into back and clamp plates and that by changing tools the recesses may be varied in size to accomodate different sized roots.

In a further development of this invention, the roots may be provided with sleeve, ball, roller or needle bearings as required, the recesses being of the requisite size to embrace the outer surfaces of the bearings, the roots being connected by linkages to a suitable operating device which will allow the pitch angle of the wings to be continually adjusted whilst the fan is rotating, permitting the fan to meet a varying duty, as, say, in an industrial process or in a variable volume air conditioning scheme.

In this present invention, the hub may be completed by fixing a proprietary metal boss to the centre of the back plate, bored to take different sizes of taper lock or similar bushes, thus providing a simple and flexible method of fixing the hub to drive shafts of different diameters, or the backplate may be left plain, for fixing to the face of a wheel, pulley or the rotor of an external rotor motor.

The invention will now be further described, with reference to the following drawings: Fig 1: Is an elevation of part of a circular hub, showing one embod iment of the hub according to the present invention, with a single, circular clamp plate.

Fig 2: Is a vertical cross section of the part-hub shown in Fig 1.

Fig 3: Is a horizontal cross section of the part-hub shown in Fig 1.

Fig 4: Is an elevation of part of a polygonal hub, illustrating individual clamp plates for each wing root.

In Fig 1, the back plate,l, of the circular hub as illustrated is provided with a number of radial recesses,2, of which only one is visible.

The wing root,3, will be a close fit within the recess. A clamp plate,4, similar inconstruction to the back plate and similarly provided with recesses,5, is placed over the wing roots and the fastening bolts or screws,6, inserted and partially tightened. The wing pitch angle is set to the required degree and the bolts or screws tightened.

Should any subsequent adjustment of the pitch angle be required, the bolts may be slackened and the wings turned as required. The back plate is provided with a slot at the lower end of each recess,7, through which protrudes the root flange,8, or other projection, this flange engaging upon the lower edge of the recess. The clamp plate may be varied in width to to meet different stresses imposed by different fan duties, but wide plates are provide with slots,l0, the root flange engaging on the bottom end of the recess,ll. Where the hub is polygonal Fig 4, here illustrated as a hexagon, the single clamp plate shown for the circular hub in Fig 1 is replaced by a plurality of clamp plates, either wide,12, for highly stressed hubs or narrow,13, for low duties.

Claims (7)

1. We claim: 1. A hub for adjustable or variable pitch axial or propellor fans made from sheet metal or other materials in two or more parts forming a back plate with matching clamp plate or plates, into each of which is pressed a suitably shaped recess or recesses to house fan wing root members, the latter, after setting at the required pitch angle, being clamped between the back and clamp plates.
2. 2. A hub as claimed in Claim 1, into which any desired number of wing root recesses may be formed.
3. 3. A hub as claimed in Claim 1 and Claim 2 in which radial movement of the wing root member is restrained by a projection or projections at its lower end engaging upon the wing root recesses in the back and clamp plates.
4. 4. A hub as claimed in Claim 1, Claim 2 and Claim 3 which may be made in any desired size to match the requirements of a specific fan.
5. 5. A hub as claimed in Claim 1, Claim 2, Claim 3 and Claim 4 which may be made in any desired shape to suit a particular fan.
6. 6. A hub as claimed in Claim 1, Claim 2, and Claim 3 in which the fan wing root recesses may be varied in size to suit the requirements of different wing roots.
7. 7. A hub as claimed in Claim 1, Claim 2, Claim 3, Claim 4, Claim 5 and Claim 6 in which sleeve, needle, ball or roller bearings may be interposed betwen the fan wing root and the back and clamp plate(s), permitting the fan wing, when provided with a suitable operating mechanism, to be continuasly adjusted as to its pitch angle whilst the fan impellor is rotating.