US3395761A - Fan - Google Patents

Description

g- 6, 1968 w. HOLZER 3,395,761

FAN

Filed June 20, 1966 INVENVTORI \A/Am-ER HOLZER Attorney United States Patent 3,395,761 FAN Walter Holzer, Drosteweg 19, Meershurg (Bodensee), Germany Filed June 20, 1966, Ser. No. 558,924 Claims priority, application Germany, June 24, 1965,

Claims. (CL, 170-160.5)

ABSTRACT OF THE DISCLOSURE The present invention concerns a fan for moving an adjustable quantity of air, comprising a drive of variable speed and fan blades.

The invention aims to provide a simple, cheaply produced fan in which the amount of air moved can be made uniform although the rotary speeds of the drive may fluctuate widely. It is particularly important that overload ing of the drive should be prevented.

Known fans have rigid or quasi rigid blades provided with obliquely positioned or helically designed fins at a predetermined angle of attack. Although such arrangements have proved successful at uniform driving speed it is often disadvantageous to use them with drives where the speed varies. In cooling systems for internal combustion engines, for example, it is frequently undesirable for the cold air blower to move particularly large quantities of air just when the engine is running rapidly. As the amount of air moved has at least a quadratic dependence on the speed of the rigid bladed fan, such blower systems are not particularly suitable for drives where the speeds fluctate widely. Many different regulating means have been proposed for this reason, but they are generally very expensive and often highly complex and therefore liable to trouble.

The problem of the invention is to avoid these disadvantages and to provide an apparatus which is simple in construction and economic to produce, with which the fluctation in the amount of air being moved can be kept within predetermined limits, notwithstanding wide variations in thte speed of the drive, and with which overloading of the drive may be prevented.

According to the invention the problem is solved by a fan for moving adjustable quantities of air, comprising a drive of variable speed and fan blades, in which the fan blades have fins, the effective mean angle of attack of the fins to the direction of air flow being variable by the air flow itself in dependence on the rotary speed.

This feature of the invention makes it unnecessary to provide special means for varying the effective mean angle of attack of the fan blades or fins. It is sufficient to provide the blades with fins, the effective mean angle of attack of which can be adjusted by the actual air flow so that as the speed and the air resistance increase at least the outer parts of the fins will seek a new angle of attack. Since this is a withdrawing movement provoked by the air flow itself, according to the principle of energy conservation and the least constraint a reduction in the amount of air moved must result. Thus as the speed increases the amount of air moved no longer increases quadratically or more than quadratically, so the load on the drive is correspondingly decreased. The amount of air moving is also made uniform, which is a great advantage for many applications.

In an important embodiment of the invention the fan blades have a rigid component which is connected to the drive and on which the fins are mounted for resilient yielding movement.

With the fins attached in this way the fan blades can be of simple and light construction. Their regulating function is fully maintained. To assist this function it may be desirable to give the rigid component and/ or the fins a special sectional shape, for example a taper increasing towards the outside. The rigid component will then always constitute the front part of the blade in a rotary direction.

The invention further provides for the rigid component to be in the form of a shaft with the fins pivotally mounted thereon.

In this case the fin as a whole may be set in the respective withdrawal position under the influence of the air resistance which fluctuates widely with speed. It is quite possible to provide detents and/ or restoring springs. The curve of the fan may be further influenced by adjustably variable bearing friction.

In a further embodiment of the invention the rigid component is in the form of one or more spokes with the fins attached thereto.-

Here no moveable bearing is required and the resilient withdrawing movement is restricted to resilient yielding of the outer and central portions of the fin. Regulating means of this type should be provided particularly in cases where the driving speed only fluctates slightly or where wide fluctations in the movement of air are permissible.

An important feature of the invention is that the fins are detachable.

Such an arrangement provides several advantages.

The detachability of the fins not only facilitates servlcmg but makes it possible for different fins with a different regulating curve to be fitted rapidly. Larger or smaller fins may also be fitted as required. If they are individually detachable and one or a few of the fins becomes damage it is not necessary to change all the blades.

In an important embodiment of the invention a holder for the fins is non rotatably attached to the drive shaft and at least the outer portions of the fins are held thereto either detachably or so that they engage in a position of rest. This is a simple way of enabling restoring and/or holding forces to come into action. The starting position of the fins, i.e. their effective mean angle of attack in the rest position, can thereby be defined.

There are various possible ways of doing this. One is for the fins to be resiliently connected to the holder.

This provides an opportunity of continuously adjusting the fin under the influence of the air resistance prevalent at the time. As far as the practical construction is concerned, any type of spring may be used.

Another possibility is for one or more magnets to be attached to the holder.

Such magnets may serve to fix the fins of the blade in their position of rest, the fins either being magnetic themselves or carrying magnets of suitable polarity. Whereas permanent magnets are generally appropriate for mounting on the fins, the magnets on the holders may advantageously be electro-magnets, in which case special regulating effects become possible because of the dependency of the magnetization on current.

In respect of construction it is important for the holder to be in the form of one or more arms.

The number of arms provided should preferably be equal to the number of fins or blades. This has the advantage that, by suitably arranging the arms, some fins can be given a different position of rest from the others. Naturally every single fin may have a different rest position.

A further embodiment provides that the arms should be connected by a ring or a covering cap of streamlined shape.

In this way the holders may have a favorable construction from the point of view of flow technique and will thereby contribute little themselves to the air resistance of the fan. At the same time the ring or cap can advantageously by employed as a fastening element.

In a further feature of the invention which is extremely important from the point of view of economic manufacture, the fan blades are integral with the rigid component.

This greatly simplifies the manufacture and assembly of the blades. It also makes it easier to handle the parts during servicing.

In a very advantageous embodiment of the invention the fan blades are in the form of a unit which is fitted onto the drive shaft with a socket connection.

The embodiment is particularly suitable for cases Where whole fan blades often have to be interchanged. For boltin fans this measure greatly simplifies after-sales service.

The invention also provides for the fins to be made of or clad with plastics.

This construction is very advantageous not only as a means of simplifying manufacture but also in order to reduce weight or to increase safety from accidents. Plastic fins or fan blades of this type may be produced by the usual modern methods, for example by injection molding.

Examples of this invention will now be explained by reference to the drawings. Like the description, these disclose further advantages and features of the invention and in them:

FIG. 1 is a plan view of the blade of a fan according to the invention;

FIG. 2 is a side view of the blade in FIG. 1;

FIG. 3 is a side view of the fins on a blade in various positions;

FIG. 4 shows a pivotable mount for the fins with magnetic holding means;

FIG. 5 shows a pivotable mount for the fins with spring restoration; and

FIG. 6 shows a detachable fin.

As illustrated in the drawings, the fan according to the invention comprises a blade with fins 1 which may, for example, be attached to a hub 3 on the shaft 2 of a drive. The rotary direction is shown at 10.

FIG. 2 shows show the fins 1, instead of being mounted perpendicularly to the rotary axis of the hub 3, are mounted at a predetermined angle on the hub in known manner. The fins 1 are designed so that as the speed increases and the air resistance rises at least their outer portions will yield resiliently back away from the direction of air flow, so that although the fan may be revolving at high speed the quantity of air conveyed thereby will not increase to inadmissible proportions.

If the fins are attached to rigid spokes 4 the effective mean angle of attack may be varied by making the fins 1 narrow and flexible, i.e. liable to yield back as a result of their inherent resilience. FIG. 3 shows such a construction, and here the fin 1 moves into dotted-line position 1a as the speed increases.

In the FIG. 4 embodiment the hub 3 has spokes 4 on which the fins 1 are pivotally mounted. A holder 6 provided with a magnet 5 is also non rotatably attached to the hub 3. The magnet 5 serves to hold the fin 1 in its rest position, but the forces arising as the speed increases are sufficient at a given speed to release the fin 1 abruptly and move it into dotted-line position 1a. This effect may be exploited to turn off the fan, yet it enables the amount of air being conveyed to be reduced at will down to idle running, depending on the position of a limit stop, even without the drive being turned off. For the sake of simplicity in construction permanent magnets will generally be used, although electro-magnets may also be employed and the fact that their magnetization is dependent on current gives a further opportunity of influencing the adjustment curve.

FIG. 5 illustrates a further embodiment of the invention. Here the fin 1 is fixed by a spring 7 to the holder 6, which is in the form of an arm. A pivotal mount on the spokes 4 is again provided for the fin 1. As the rotary speed of the blade fluctuates the fin 1 Will continuously adjust its angle of attack to the air flow. By selecting the spring curve it is an easy matter to set up various resistances to such movement and thus to ensure that the desired quantities of air are displaced;

It is important to note that it is quite unnecessary for the holder 56 to be aranged in front of the blade in the direction 11 of air flow. It is perfectly possible for it to be mounted on the drive side, for example on the shaft 2. In this case compression springs may be used to hold the fins 1 in their position of rest. If small magnets are mounted on the fins such attachment must also be obtained with magnets 5 of opposite polarity fixed to the arm or holder 6. Conversely, force to assist movement out of the position of rest may be applied by magnets 5 of the same polarity and/or Without opposed magnets on the fins 1 or else by tension springs 7. This produces a throttling action on the amount of air being displaced, starting at relatively low speeds.

FIG. 6 shows a further embodiment in which a fan blade in the form of a profiled resiliently bending fin 1 is detachably fixed to the spoke 4. The attachment may be secured, for example, by a split pin 8.

By combining several features of the invention, such as the resiliently bending fins, the pivotal mount, the magnetic hold and the restoring springs, any desired regulating curves may be obtained, possibly even for protection against overloading.

In designing the fan blades one will obviously proceed according to the usual aerodynamic principles. To avoid undesirable resonances it may be advisable or necessary to provide the fins with suitable stiffeners such as reinforcing ribs or a special profile. The material of the fins may, for example, be spring steel, although plastics, rubber, etc. may also be used. Manufacture can be made particularly economic by constructing the fan blades in one piece for attachment to the shaft 2 with a socket connection. For reasons of cost the injection molding method is generally preferred.

The invention may be applied to all cases where overloading of the fan drive on a rapid increase in speed is prevented by resiliently yielding fan blades or parts thereof.

Although the above description refers to axial fans the principle of the invention may be applied without any restriction to tangential ones.

I claim:

1. A fan which provides a controllable feed output comprising a drive shaft, said drive shaft being adapted to be driven at variable speeds, a plurality of fins rotatably mounted on said drive shaft, a plurality of holders mounted on said drive shaft, an individual holder being provided for each fin, restraining means interlinking each of said fins with said holder associated therewith, said restraining means causing said fins to be restrained in a position of rest when said shaft is at rest, whereby when said shaft is driven at variable speeds, said fins are caused to rotate, so as to permit the effective mean angle of attack of the fins to be varied by varied loads of air fiow, said holders being adjustable in relationship to said fins, whereby the air flow of the fan can be varied for a given speed.

2. The fan of claim 1 wherein said restraining means comprises springs connected between said holders and said fins, wherein adjustment of said holders varies the restraining force between said holders and said fins.

3. The fan of claim 2 wherein said springs are connected in tension between said fins and said holders.

4. The fan of claim 2 wherein said springs are connected in compression between said fins and said holders.

5. The fan of claim 1 wherein said fins are comprised at least partially of magnetic material, and wherein said restraining means comprises magnets mounted on said holders.

6. The fan of claim 5 wherein said magnets are permanent magnets.

7. The fan of claim 5 wherein said magnets are electromagnets.

8. The fan of claim 1 wherein at least a portion of said holders is comprised of magnetic material, and wherein said restraining means comprises magnets mounted on said fins.

9. The fan of claim 8 wherein said magnets are permanent magnets.

10. The fan of claim 8 wherein said magnets are electro-magnets.

References Cited UNITED STATES PATENTS 2/1936 Paton 1031 15 10/1938 Smith 103-415 3/1939 Bouvy et a1. 103115 5/1946 Roche 103-115 10/1951 Rosenkraus et al. 103115 8/1941 Larsh 103--115 12/1931 Crowhurst 230114 FOREIGN PATENTS 5 1948 France. 1/1923 Great Britain. 10/ 1940 Great Britain.

9/ 1925 Austria. 2/ 1953 Germany. 11/1931 France. 12/ 1947 Great Britain.

HENRY F. RADUAZO, Primary Examiner.

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