BACKGROUND OF THE INVENTION This type of fans is known, for example, US Patent N 4,553,075 with the priority of 4 August 1983, published on 12 November 1985, Int. Cl. H02K 29/02 and US Patent N 4,459,087 with the priority of 2 June 1982, published on 10 July 1984, Int. Cl. F04B 35/04.

The US Patent N 4,553,075 includes an annular permanent magnet magnetized in segments about its circumference. Each segment is oppositely radially magnetized with respect to its adjacent segments. Fan blades located within the annular magnet. A coil comprising two electrically independent bifilar wound windings, connected to be oppositely energized, and an electromagnet structure defining two pole pieces reside outside the permanent magnet annulus.

A Hall effect device alternately energizes the separate coil windings in response to passage of the segments of the rotor magnet to alternately produce opposite magnetic fields in the pole pieces.

The US Patent N 4,459,087 includes a fan unit for cooling an internal combustion engine comprising a fan impeller associated with a coaxial channel for guiding the air traveling through said impeller and an electric driving motor of DC type. The channel is fixed to the ends of the blades of the impeller and rotates with the impeller and itself constitutes the rotor of the electric motor whose stator coaxially surrounds at least a part of the channel. The stator is rigid with a fixed shaft around which the impeller rotates.

The fan units disclosed in both of these prior patents suffer from the disadvantage of requiring large mass ring member that encircles the blades edges in order to establish the N-S radially oriented magnetic segments that cooperate with the stator electromagnetic fields to generate torque and motion. These members prevent miniaturization of the fan design, require a large mass ring member or expensive magnetic materials which increases manufacturing cost and power consumption during operation and generally lowers the efficiency of the fan.

DISCLOSURE OF THE INVENTION According to the principles of the present invention a unit of fan blades rotating round an axis is mounted on a fan housing. The fan blades unit contains at least two blades magnetized in radial direction. The blades rotation is provided by the interaction of the blades magnetic field with the electromagnetic field created by a pulse electromagnetic field unit.

Thus the structure of an annulus large mass magnetic ring as found in the prior art can be eliminated or reduced because in accordance with the principles of the present invention its function has been transferred to the fan blades themselves.

Alternatively, the mass of a magnetic ring can be reduced significantly because the mass contributes to the magnetic function of the impeller. The efficiency of the fan is enhanced by making the outer edge of the blade wider than its inner edge, which tends to alleviate the contradiction between the two blade functions-to move air and-to produce torque. In this case the large mass (i. e. magnetic ring) is reduced or eliminated from or at the outer edges or periphery of the blades.

In particular applications of the invention the construction of the fan has the following special features.

The fan blades unit contains an axial member fixed rigidly relative to the housing and a hub mounted on the axial member with the possibility to rotate. The unit blades are mounted to the hub.

If the hub is executed from non-magnetized material, each blade is a separate magnet. If the hub is executed from magnetized material, then each adjacent pair of blades is magnetically joined through the hub so that they form a U-shaped or V-shaped magnet with N-S field in the air gap formed by the magnetized blades which interact with the electromagnetic field created by the pulse electromagnetic unit.

In one exemplary embodiment of the fan the fan blades unit contains at least four blades. Each blade has N-S or S-N radial orientation of magnetic field which is opposite to the orientation of the adjacent blade. Each inner side of the blade is mounted to a hub.

In alternative exemplary embodiment the fan blades unit consists of the first and the second subunits wherein all blades of the first subunit are magnetized in the same radial N-S direction. All blades of the second subunit are magnetizes in the opposite-S-N direction. Each subunit has an equal number of blades. The first and the second subunits are fixed to each other and are mounted about the same rotating axis with the blades of one equally annularly

spaced from or between the blades of the other subimpeller to form blade portions with alternating N-S orientation.

The blades of the impeller subunit can have ring segments on the edges having annular shape. When the fan blades subunits are assembled they form a continuous ring. Each ring segment has the same magnetic orientation as the blade. The ring combined from the segments is a source of electromagnetic field and at the same time is an air flow cowling preventing air leakage.

The pulse electromagnetic field unit includes at least two electromagnetic coil units connected to the control circuit and oriented at an angle of 180 degrees to each other radially along the line passing through the fan blades axis. In this case the fan blades unit contains at least four blades with alternating N-S and S-N magnetic orientation.

The pulse electromagnetic unit includes also a pair of sensors mounted with the possibility of interaction with the magnetic field of the blades. The sensors are connected with the control circuit meant for stators energizing. In particular sensors are Hall effect sensors.

In the another embodiment the pulse electromagnetic field unit includes at least two stators each containing a U-shaped ferromagnetic core. The core is formed by a pair of spaced legs usually located radially circumferentially, mounted on the housing and connected by the ring segment. On a part of each said core the coil is wound connected to the control circuit.

Such core configuration increases the stator coil magnetic field flux density in the radial direction and maximize the drive torque generated by the interaction of stator coil and blade magnetic field. This, in turn, increases the power output of the rotor drive motor and the fluid flow volume generated by rotation of the blades for a given electrical voltage applied to the stator coil windings.

The fan housing includes a magnetically permeable shroud surrounding the blades in this case at least two stators are mounted on the outer side of the shroud. The shroud can be made of plastic or stainless steel.

Various advantages result from a fan design according to the principles of the present invention, for example, such as reduction of manufacturing cost, increase of fan blades airflow, increase of airflow per unit power consumed, losses reduction, sufficient reduction of fan dimensions while achieving low power consumption and high airflow specifications.

The advantage of the improved rotor motor drive using exterior stator coils and magnetized fan blades is that the airflow does not pass through, past or over the electrical components of the motor and control.

The invention provides as well such construction of the fan motor drive housing which isolates the airflow from any contact with the electrical components to render the fan suitable for use in explosive or contaminated atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an end view of the fan.

Fig. 2 is a side section elevation view taken along line 2-2 of Fig. 1.

Fig. 3 is a front elevation of a fan blades subunit of Fig. 1.

Fig. 4 is a front elevation of another fan blade subunit of Fig. 1.

Fig. 5 is similar to Fig. 1 and shows an end view of the second alternative fan embodiment.

Fig. 6 is similar to Fig. 2, a side section elevation taken along line 6-6 of Fig. 5.

Fig. 7 is a partial enlarged section showing the detail marked"E"of Fig. 6.

Fig. 8 is similar to Fig. 3 for the fan of Fig. 5.

Fig. 9 is similar to Fig. 4 for the fan of Fig. 5.

Fig. 10 is an electric control circuit of pulse electromagnetic field unit for embodiments of Fig. 1.

Fig. 11 is an end view of the third alternative fan embodiment, similar to Fig. 1.

Fig. 12 is similar to Fig. 2 for the fan of Fig. 11.

Fig. 13 is an end view of the fourth alternative fan embodiment, similar to Fig. 1.

Fig. 14A-14D are end views of the embodiment shown on Fig. 1 in different rotated conditions of the fan blades with a diagrammatic depiction of the energizing conditions of two stator coils.

Fig. 15 is another electrical control circuit of pulse electromagnetic field unit for the embodiment of Fig. 11.

Fig. 16 is an end view and a section of one of the possible fan embodiments.

Fig. 17 is a sectional view of a centrifugal fan in accordance with the present invention and a section taken along line A-A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT One of the fan embodiments in accordance with the principles of the present invention is shown in Fig. 1-4 and includes a housing 20, fan blades unit 21, pulse electromagnetic unit 22 mounted on the housing 20.

The housing 20 includes a plate or frame 23 preferably supporting a cylindrical ring, cowling or shroud 24 that confines and directs the airflow indicated by the arrows in Fig. 2. The frame 23 includes struts 25 spaced sufficiently to enable at least maximum rated intake air to pass through in response to the fan blades unit 21 operation, described below. The frame 23 and struts 25 also mounts and supports the axis or shaft 26 of the fan blades unit 21.

In this embodiment the fan blades unit 21 includes two subunits 27 and 28 each having four blades 29 magnetized in radial direction.

Each blade 29 is executed from suitable material that can function as a permanent magnet with a sufficient mechanical strength to function as will be described below. Examples of such materials include ferromagnetic impregnated plastics and ferrous materials (such as steel, iron or ferrous alloys) that have been permanently magnetized. When processing the materials into the fan blades 29 in accordance with the present invention, if desired, the magnetic materials can be evenly distributed in radial direction or alternatively can be concentrated towards the radial outer edge of each blade 29 as long as the magnetic properties of each blade 29 are substantially the same. Concentration gradients or uniformity of magnetic materials in circumferential direction throughout each blade 29 can also be selected to yield the greatest interaction between the blade magnetic field and the pole shoe field given the particular shape of the fan blade 29 and the shoe.

All blades 29, for example, four blades 29 in Fig. 3 can be magnetized simultaneously as a single unit after the assembly of the blade 29 on a hub 30 or blades 29 can be magnetized prior to assembly on the hub 30 (as desired). The same applies to all other, for example, four blades 29 in Fig. 4. It is preferred that the dimensions of each blade 29 for the fans shown in Fig. 1-4 expand in radial direction for enhancing the torque and air efficiency of the fan blades unit of the system Each blade of the subunit 27 is, for example, permanently magnetized with S-N orientation of outer-inner bearing edges and each blade of the subunit 28 has an opposite S-N orientation as seen in Fig. 3 and 4. The blades 29 of the subunit 27 are mounted in the hub 30

that rotates with low friction on shaft 26. The blades 29 of the subunit 28 are mounted in the hub 31 that mounts by any suitable means in fixed relation to the hub 30.

Bushings 30 and 31 interlock for the creation of the fan blades unit that revolves about the shaft 26. As seen from Fig. 3 the blades 29 of the subunit 27 are equally spaced in annular direction and alternate in S-N orientation. In this example all blades 29 are substantially equal in dimensions, mass, magnetic orientation and magnetic parameters and it is preferred that the gap between the outer edges of blades 29, pole shoe 32 and shroud 24 be as small as possible for maximum torque to be generated with a given power consumption and airflow.

Bushings 30 and 31 can be executed from any suitable non-magnetic materials such as copper, aluminum or non-ferrous alloy, or standard hard plastic normally used in such types of devices.

It should be understood that bushings 30 and 31 can be executed as a single unitary piece, if desired, with all blades 29 mounted on them In this case blades 29 are preferably magnetizes individually and prior to mounting in their respective bushing although magnetization following bushing mounting is possible. Further, although eight blades and four electromagnets are shown, other suitable combinations may be selected depending on desired operation parameters and applications.

The pulse electromagnetic unit 22 includes electromagnetic coil units 33 having predetermined number of coils turns around iron core 34 that forms an electromagnetic pole shoe 32 having elongated arcular shape in annular direction. The shroud 24 is preferably made of plastic or stainless steel. As seen from Fig. 1 this embodiment includes four electromagnetic coil units 33 mounted to frame 23 preferably at its corners.

Another embodiment of the present invention is shown in Fig. 5-9 wherein like reference numerals refer to like elements of Fig. 1-4. The fan includes a housing 20 that has an annular lip 35 spanning the periphery of the air flow opening. The lip 35 includes an annular channel or groove 36 opening to the rear or upstream to the airflow direction. Subunits 27 and 28 are mounted to their outer ring segments 37 and 38 of the blades 29 edges shaped to form a continuous ring when subunits 27,28 are assembled. As seen from Fig. 7 the forward (downstream) edge 39 of ring segments 37 and 38 projects into and rides within groove 36 during rotation of the fan blade unit.

The ring channel 36 and the edge 39 are dimensioned to substantially prevent air leakage and turbulence within the space outward of the blades 29 edges and within the housing 20, that would during operation lower the fan efficiency and axial downstream air pressure.

However, the edge 39 should not touch the groove 36 walls and should avoid friction or drag development during operation. Segments 37 and 38 can be made of the same magnetic material as the blades and be molded as a part of the blade in the blade molding process. Accordingly, in this arrangement elements 37 and 38 would have the same N-S orientation as the blade to which they are connected. Ferrite density can be greater, equal or less than the ferrite density of the associated blade if magnetized plastics are used. Segments 37 and 38 can have low mass compared to magnetic blades and serve as an airflow cowling that also blocks air leakage by riding in the lip 36 of the housing.

Magnetic blades 29 can be mounted in the hub 31 made of material that is a good conductor of magnetic fields. Accordingly, each pair of blades 29 is magnetically joined through the hub 31 to form U-shaped or V-shaped magnet that interacts with the respective field of electromagnetic coil units 33. The hub 31 can be mounted on or secured to plastic or other suitable material bushing 30 that rotates on the shaft 26.

The hub 31 can be made of ferromagnetic impregnated plastic such as polyamide, ferrite material, ferrous materials or any suitable alternative.

One of the examples of a control circuit for controlling fan operation is shown in Fig. 10. Controlling of fan operation with the help of this circuit is performed as follows.

Power and timing are supplied to the circuit through a positive regulator 40 to maintain a predetermined voltage, for example 12 volts, though motor drive coils can operate at a higher supply voltage levels, for example, 35 volts. This regulated voltage is filtered by a capacitor 41 to reduce transient noise generated by the Hall effect IC 42. The IC 42 has two outputs which change states high and low based on north and south poles crossing of blades 29 face of the fan blade unit 21. The states are latched or maintained until the opposite magnetic pole is applied across its face. These outputs are held at a high state by resistors 43 and 44 through which the current flows until the IC 42 pulls them to a low state. The outputs are used through resistors 45 and 46 to turn on the power enhancement MOS-FETS 47 and 48.

Resistors 45 and 46 limit the current to the gate of MOS-FETS. The MOS-FETS respond to the gate voltage to switch high consumption current to

the corresponding coil of the electromagnetic coil unit 33. Diodes 49 and 50 protect MOS- FETS from damaging peak reverse voltages generated in coils of electromagnetic coil unit 33 when de-energized. Coils 51 and 52 respectively in this embodiment are a part of two electromagnetic coil units 33 located in two opposite corners of the pulse electromagnetic field unit 22, such as A and C in Fig. 1 and 5. All coils preferably have equal number of turns. Coils 53 and 54 respectively are a part of electromagnetic coil units 33 located in two other opposite corners of the pulse electromagnetic field unit 22, such as B and D in Fig. 1 and 5. For convenience the corners of the pulse electromagnetic field unit are labeled A, B, C and D.

Accordingly, when coil voltage across coils A and C is positive, the coil voltage across coils C and D is negative. And when coil voltage across coils A and C is negative, positive voltage appears across coils B and D respectively. In response, the A and C pole shoes will be annularly magnetized with N-S orientation when B and D pole shoes are annularly magnetized S-N. The magnetic fields from the shoes interact with the magnetic fields of each blade. The predetermined timed reversal of the plus/minus output of the IC 42 creates an annular pull- push effect (torque) between the electromagnetic coil unit fields and magnetized blades 29.

This action causes continuous blades rotation under predetermined speed, power and air flow conditions.

The next embodiment of the fan construction is shown in Fig. 11-12. The housing 20 consists of mounting flanges 55 made as a single piece with the cylindrical shroud 24 of the housing 20. The pulse electromagnetic field unit 22 includes two stators 33 located at two corners of flanges 55 and consisting of U-shaped core 56 with windings of the electromagnetic coils of the stator 33 around the segment 57 connecting two legs 58. Each leg 58 extends in an approximately radial direction with respect to the fan blades unit 21.

The fan blades 29 are preferably made of permanently magnetized plastic of a known material or have pieces of ferromagnetic material which can be magnetized. The magnetized plastic material avoids the build up of static electricity which could otherwise occur to prevent any resultant sparking due to a discharge of such static.

The housing 20 portions are made of non-ferromagnetic material such as suitable plastic which is nonetheless freely permeable by magnetic flux.

A stainless steel shroud 24 also produces very good performance of the fan.

The control circuit diagram for this fan embodiment is shown in Fig. 15. In the considered circuit the same operation principle is used as in the control circuit in Fig. 10. The differences are in the fact that commercially available IC 42 with Hall effect sensors 59A and 59B are used that do not need external elements. Integrated circuits HAL508UA by Microns can be used as such sensors.

Each IC 42 is oriented so as to be triggered upon the movement of the blade leading edge to a precise trigger point 60A, 60B respectively. In the preferred embodiment the IC 42 in one circuit is oriented so as to triggered upon the movement of a blade leading edge to a precise trigger point of Hall sensor 60A, and the IC 42 in another circuit is oriented so as to be triggered upon the movement of a blade leading edge to a precise trigger point 60B.

Each sensor 59A, 59B acts as a switch and is triggered by the presence of a particular blade polarity, each sensor sensing the opposite polarity with respect to another. In the preferred embodiment 59A is triggered by the presence of the north pole, and 59B is triggered by the presence of the south pole. Together unipolar sensors 59 operate as a dual output bipolar sensor.

The blades 29 (see Fig. 14A-14D) are spaced apart at a particular distance so that when the leading blade edge 29A or 29B reaches the trigger point 60A, the next trailing blade 29B or 29A is centered between the legs 58 of the stator coil 33A. When the leading blade edge 29A or 29B reaches the trigger point 60A the leading blade 29A or 29B is centered on the stator 33B. Thus, only one blade 29A, 29B at a time can trigger sensors 59 in each IC 42.

The respective trigger points 60A, B are oriented towards blades 29 so that the respective stator coil 33A, B that have the blade 29 located between legs 58 will be energized on startup.

When the leading edge of the blade 29A registers with the trigger point 60A the stator 33A is energized so as to produce the polarity shown in Fig. 14A. Another stator coil 33B is energized in the same way.

The distinctive feature of this circuit is application of optical coupler 61 having several channels connecting the IC 42 with power amplifiers 62. The power amplifiers 62 operate for respective stator coil 33.

Implementation of power FETS of power amplifier 62 causes the trailing blade 29B to be rotated counterclockwise by setting up repulsion-attraction. This rotation causes the sensor 59B to turn off) at a point determined by the blade width and pitch angle), but the fan blades unit 21 will continue to coast by inertia to the position shown in Fig. 14B.

At this point the blade 29B moves into registry with the second trigger point 60B. This causes the sensor 59A in the second circuit to be activated which in turn causes the stator coils 33B to be energized in the corresponding circuit so as to establish the magnetic polarity shown in Fig. 14B. This sets up repulsion-attraction of the blade 29B centered between the stator 33B legs to urge the fan blades unit 21 to continue its counterclockwise rotation.

After stator 33B is de-energized by the movement of the blade 29B past the trigger point 60B, the fan blades unit 21 coasts by inertia to the position shown in Fig. 14C where a trailing blade 29B moves into registry at the trigger point 60A of the sensor 59 in the first circuit causing the stator 33A to re-energize, but with the opposite polarity as shown. The fan blades unit 21 is again urged to rotate counterclockwise and coasts by inertia to the position shown in Fig. 14B after the stator 33A is de-energized.

This brings the trigger point 60B of the sensor 59 in the second circuit to registry with the blade 29A causing 59B to be activated, and the stator 33B power circuit to re-energize.

The entire cycle described by four stages repeats over and over causing continuous counterclockwise rotation of the fan blade unit 21.

This arrangement locates the electrical components out of the path of the gas flow.

Accordingly conduits 62,63 (Fig. 12) can be sealed to the shroud in order the fan can be used in hazardous environments.

Fig. 13 shows an arrangement with four pulse electromagnetic field units utilizing two additional units 22C, 22D.

It should be mentioned that the fan in accordance with the principles of the present invention has many applications in different environments. The example is given in Fig. 16, the fan blades unit is executed in the form of a centrifugal fan and is a part of a leaf blower. The cowling/channels about the fan blades direct the air flow to the exit. Additional tubes (not shown) can be inserted to extend the exhaust location in the standard manner. Fig. 17 shows the location of the U-shaped core on the fan housing 20.

INDUSTRIAL APPLICABILITY The physical design of the fan and the shape of its blades can take a wide variety of forms depending on particular applications. For example, the present invention can be applied to axial flow fans, centrifugal fans, large, small and micro-fans.

The advantages of the present invention will become apparent when using in small fans, for example, in electronic equipment, personal computers, fan trays and various electronic instrumentation.