US3241742A

US3241742A - Fan

Info

Publication number: US3241742A
Application number: US427429A
Authority: US
Inventors: Laing Nikolaus
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-03-11
Filing date: 1965-01-22
Publication date: 1966-03-22
Anticipated expiration: 1983-03-22
Also published as: DE1403552A1; US3258195A; US3327934A; GB983901A

Description

N. LAING March 22, 1966 FAN 4 Sheets-Sheet 1 Filed Jan. 22, 1965 INVENTOR 9 flM W 43 a? ATTORNEYS Ni koluus Lain Hil /2 h? N. LAING March 22, 1966 FAN 4 Sheets-Sheet 2 Filed Jan. 22, 1965 FIGS.

INVENTOR Nikolaus Laing BYXQWMFZM W47, 7 MM fiToRNEYs March 22, 1966 Filed Jan. 22, 1965 N. LAlNG FAN J f n g I n 4 Sheets-Sheet 5 INVENTOR Niko uus Laing BY M, u /a, 1% X ATTORNEYS N. LAING March 22, 1966 FAN 4. Sheets-Sheet 4.

Filed Jan. 22, 1965 FIG. 10.

INVENTOR United States Patent 3,241,742 FAN Nikolaus Laing, Hofener Weg 35, Aldingen, near Stuttgart, Germany Filed Jan. 22, 1965, Ser. No. 427,429 Claims priority, application Germany, Mar. 11, 1960, L 35,582 20 Claims. (Cl. 230-117) This application is a continuation-in-part of my copending application No. 95,405 filed March 13, 1961 now abandoned.

This invention relates to fans and more particularly to cross-flow fans, i.e. fans of the kind comprising one or more cylindrical bladed rotors and guide means cooperating therewith whereby on rotor rotation to induce a flow of air from an inlet side of the rotor through the path of the rotating blades thereof to the interior of the rotor and thence again through the path of the rotating blades to an outlet side of the rotor, the general direction of the flow being transverse to the rotor axis.

It is believed that cross-flow fans were invented at the end of the last century, and it has been stated that such fans were used for a time for colliery ventilation, and later replaced by centrifugal fans. Since that time various types of cross-flow fans have been proposed. All these cross-flow fans, so far as can be judged from the literature, are of large capacity and suited only for industrial use or the like: also, they depend for their operation on the maintenance of close tolerances between the rotor and the guide means. British Patent No. 876,611 (of which I am co-inventor) discloses a new principle of cross-flow fan design, especially suited to small sizes such as for domestic use, and in which the guide means are wholly external of the rotor and may with advantage be well spaced therefrom. The disclosures of British Patent No. 876,611 accordingly provide the basis for the design of a technically effective and readily mass-produced domestic fan.

One important form of domestic fan is the smallcapacity compact and readily portable fan called herein table fan which may be placed on a table or the like near the user, and produce a stream of air directed at him, eg for cooling purposes in summer. Hitherto small axial fans have been used for this purpose. Such fans can be produced very cheaply. The cross-flow fan as disclosed in British Patent No. 876,611 has certain characteristics which would give it advantages over the axial fan, in application to table fans: thus, a satisfactory volume of air may be moved at relatively low peripheral blade speed, so that noise can be reduced, and the emergent jet of air is smoother and of greater penetrating power than that of an axial fan, which is full of random eddies. However, the configuration of the cross-flow fan does not immediately adapt itself to a table fan: in any case whatever configuration is adopted it must be at least as convenient to use as the well known axial fan and comparable in cost of manufacture, otherwise it cannot be expected to enjoy great commercial success. A main object of the invention is to provide a table fan of the cross-flow type having the advantages just mentioned of convenience in use and ease of manufacture.

With this main object in view, the invention provides a cross-flow fan having a flat base adapted to stand on a table, a support upstanding from the base and rigid therewith, a motor casing mounted on the support, a motor in the casing having a substantially horizontal shaft, a bladed cylindrical rotor overhung-mounted on one end of the motor shaft and projecting beyond the casing and said support, and a flow guide unit also supported on and projecting beyond said support, the flow guide unit present- Patented Mar. 22, 1966 ice ing guide surfaces opposite the rotor which co-operate therewith on rotor rotation to induce a flow of air from one side of the rotor through the path of the rotating blades thereof to the interior of the rotor and thence again through the path of the rotating blades to another side of the rotor.

In a preferred form of the invention, the support terminates on a mounting ring the axis of which extends substantially parallel to the plane of the base; the motor casing is supported on the mounting ring and overhung in one direction therefrom, while the rotor and guide unit are overhung in the other direction clear of the casing and mounting ring.

The fan unit configuration described is convenient to use and simple and effective to manufacture. Thus in one non-adjustable form the base, support, motor casing and the major part of the guide unit may be a single integral plastics moulding, the motor with rotor attached being simply push-fitted into the casing therefor. In another preferred form of the invention, the guide unit is angularly movable about the axis of the motor and rotor.

Other features of the invention have to do with features permitting ready disassembly of the motor and rotor for cleaning of the latter.

Further features of the invention will appear from the following detailed description of various embodiments thereof.

In the drawings, in which:

FIGURES 1 and 2 are respectively a transverse and an axial section of a room fan unit;

FIGURES 3a, 3b and 3c are scrap axial sections showing three different ways in which a rotor and shaft such as shown in FIGURES 1 and 2 can be detachably assembled together;

FIGURE 4 is an axial section of a second room fan unit;

FIGURE 4a is a perspective view of part of the FIG- URE 4 unit;

FIGURES 5, 6 and 7 are diagrams illustrative of different ways in which a rotor such as shown in FIGURE 4 can be assembled with a driving motor therefor;

FIGURE 8 is an axial section of a rotor together with means upon which it is to be secured, the rotor being shown separate from these means;

FIGURE 8a is a partial axial section of a rotor showing means for closing the non-driven end thereof, these means being shown separate from the rotor;

FIGURES 9 and 10 are respectively an axial and a transverse section of a further form of room fan unit, and

FIGURE 11 is an end elevation of the unit of FIG- URES 9 and 10 showing a minor variation upon this unit.

Where axial and transverse sections correspond the section plane of the transverse section is shown on the axial section with the figure number of the transverse section in Roman numerals.

Referring to the drawings, the room fan unit shown in FIGURES 1 and 2 comprises a base 1, supported upon legs 2 a housing 3 wherein is located a motor. The motor is of conventional type and not shown and the housing is indicated simply as a block having an upper wall 3a of substantial thickness. The motor has a horizontal spindle and the two end portions of the spindle designated 4, 4', extend symmetrically from the housing at either end thereof. Each end portion 4, 4' of the spindle is formed with a

flange

5, 5 spaced from its end, which end is formed as a threaded stub 6, 6'. A pair of similar cylindrical bladed rotors 7, 7' are mounted on the end portions 4, 4 of the spindle. Each rotor comprises

end discs

10, 11 supporting between them a series of blades 12, and the end disc 11 has a tapped axial hole enabling it to be screwed upon the corresponding 3 threaded stub 6, 6' until it comes flat against the flange 5,

The fan unit further comprises a guide unit 3 having two similar sections 13a, 13b, each section co-operating with one of the rotors 7, 7'. The guide unit sections 13a, 13b are connected by an integral central portion 130 which overlies the housing 3 and is secured thereto by a milled-headed screw 14 working in a tapped hole in the wall 3a of the housing.

Each guide unit section 13a, 13b provides a pair of approximately crescent-

shaped end walls

15, 16 respectively coplanar with the

rotor end discs

10, 11 and joined by guide walls 17, 18. As seen in FIGURE 1 the guide wall 17 is short and converges with the periphery of the rotor 7 in the direction of rotor rotation indicated by the arrow 20 in FIGURE 1. The line 18a of nearest approach of the guide wall 18 to the rotor 7 lies approximately diametrally opposite the line 17a of nearest approach of the guide wall 17. At both lines 17a and 18a the respective guide walls 17, 18 are spaced from the rotor substantially more than a working clearance, preferably about half the radial blade depth, or possibly more. The wall 18 extends away from the rotor 7 with a steady increase in radius of curvature going from the line 18a. Guide walls 17 and 18 terminate remote from the rotor in lines 17b, 1812 which define the outlet from the unit, for the rotor 7. The plane joining the

lines

17b, 18b is oblique to the direction of flow through the outlet.

The blades 12 of the rotor 7 will be seen to be concave facing the direction of rotation and to have their outer edges leading their inner edges.

In operation of the unit a cylindrical vortex having a core shown by the flow lines V is formed adjacent the guide wall 17: the vortex core intersects the blades and lies parallel and eccentric to the axis of the rotor. Air is induced to flow through the rotor as shown by the flow lines F. The principles upon which the fan unit of FIG- URES 1 and 2 operates are set forth in detail in the British patent specification 876,611 which should be referred to.

The flow machine of FIGURES 1 and 2 can readily be disassembled for cleaning without the use of tools by simply unscrewing the rotors 7, 7 from their threaded stubs 6, 6' and removing the guide unit 13 after unscrewing the milled-headed screw 14. The rotors 7, 7' and guide unit 13 can conveniently be moulded of plastics material.

Three further ways of detachably securing a rotor to a driving shaft, in an arrangement such as that of FIG-

URES

1 and 2, are shown in FIGURES 3a, 3b and 30. In FIGURE 3a, a circular retainer plate 30 of greater diameter than the rotor 7 is formed on the end of the shaft portion in place of the flange 5 of FIGURE 2. The adjacent end disc 11' of the rotor 7 differs from the end disc 11 of FIGURE 2 in carrying a threaded projecting boss 31 co-operating with female threads 32 formed axially of the retainer plate 30. The plate 30 and rotor 9 can readily be grasped in the hands when it is desired to separate them: this arrangement is therefore particularly suitable where the construction of FIGURES 1 and 2 is modified to present only one rotor.

FIGURES 3b and 3c show rotors 7 detachable by snap action. In FIGURE 3b the shaft end portion 4 is shown terminating beyond the flange 5 in a cylindrical boss 33 formed with a transverse bore 33a locating a pair of balls 34 urged outwardly by a helical compression spring 35 acting between them, the balls being prevented from flying out of the bore by lips 33b formed at its mouth. The rotor end disc 11" is formed with a bore 11a receiving the boss 33 in a close fit, and a groove 11b opening out of the bore. The balls 34 are received in the groove 11b; the rotor can readily be assembled and disassembled simply by exerting a pronounced axial force thereon. Drive from the shaft 4 to the rotor 7 is effected by friction, bearing in mind that only low torques are involved. Alternatively co-operating flats may be formed on the boss 33 and end disc 11", or a projection on the flange 5 may engage a recess in the end disc.

Parts of the FIGURE 3c construction similar to that of FIGURE 3b are given the same reference numerals and will not need further description. Instead of the transverse bore 33a of FIGURE 3b, the boss 33 of FIG- URE 30 has a peripheral groove 36 locating a toroidally wound resilient strip 37. Once again assembly and disassembly is effected by pronounced axial force such as can readily be applied manually without the aid of tools.

The fan unit of FIGURES 4 and 4a comprises a base 40, a supporting post 41 upstanding from the base and mounting a motor housing 42 in the form of a cylinder with a closed end, and guide means designated generally 43 which extends to one end of the motor housing. The parts so far mentioned are all moulded integrally from plastics material by means of a four-part mould, one part of which is stationary and the other parts of which move in three directions at right angles to one another when it is required to release a completed article from the mould, the article finally being stripped from the stationary part. After moulding, a strip of plastics material 44 is secured across the guide means 43 e.g. by adhesive; thereafter the parts appear as shown in FIGURE 4a.

A motor 45 is push-fitted into the housing 42 and retained therein by friction. The motor has a shaft 46 mounting a magnetic disc 47 in line with the opening in the housing 42, this disc having a central conical centering projection 48. A rotor designated generally 49 and having

end discs

50, 51 supporting blades 52 between them is mounted on the magnetic disc 47, the end disc 51 for this purpose being made of magnetic material and having a recess 52 co-operating with the centering projection 48.

The rotor 49, apart from the end disc 51, resembles the rotor 7 in FIGURES 1 and 2. The guide means 43 provides

end walls

53, 54 similar to the

end walls

15, 16 of FIGURES 1 and 2, and a guide wall 55 similar to the guide wall 18 of those figures. The strip 44 corresponds in function to the guide wall 17 of FIGURES 1 and 2. The flow conditions in the FIGURE 4 fan unit are therefore exactly similar to those illustrated in FIGURE 1, and will require no further description.

The

discs

47 and 51 can be magnetized in various ways: as shown in FIGURE 5 annular zones can be formed, the zones, going radially, alternating in polarity. Alternatively, as shown in FIGURE 6 the zones can be sectorshaped. In the FIGURE 7 arrangement the disc designated generally 47 is formed as a magnetized block 70 of cylindrical shape associated with a magnetic disc 71 having an axially directed peripheral flange 72; the rotor disc 51 is ferromagnetic, and magnetic circuits are set up in radial planes the flux wherein tends to hold the disc 51 up to the disc 47.

To disassemble the fan unit illustrated it suffices to exert an axial pull on the rotor 49 to overcome the magnetic forces set up between the

discs

47 and 51; the rotor can then be washed if desired and the interior of the guide means 43 becomes accessible for cleaning. The motor 45 can be removed by exerting pressure on the end 75 of the shaft 46 opposite the disc 47; this end 75 of the shaft projects into a small hole 76 in the end wall of the motor housing 42. Once the motor 45 is out of the housing 42, the unit consisting of base 40, post 41, housing 42 and guide means 43 can be washed.

A further method of detachably securing a rotor to a shaft is shown in FIGURE 8. The rotor, designated generally 80, is made of resilient plastics material and comprises blades 81 extending between a disc 82 at one end and a ring 83 at the other. The ring 83 has its inner periphery bevelled slightly. The shaft 84 mounts a disc 85 of resilient plastics material the periphery of which is also slightly bevelled, and the disc 85 carries a steppedback flange 86 that extends radially. The means diameter of the inner periphery of the ring 83 is the same as the means diameter of the disc 85, but because of their being bevelled their opposing edges 83a, 85a interfere. On account of the resiliency of the plastics these edges 83a, 85a can be forced past each other with a snap action and will thereafter interengage to hold the ring 83 tight against the flange 86.

.FIGURE 8a shows a similar arrangement for an end closure disc at the non-driven end of the rotor. Parts similar to those of FIGURE 8 are given the same reference numerals as used in that figure but distinguished by a prime; these parts will therefore need no further description.

FIGURES 9 and 10 show a room fan unit comprising a base 90, a post 91 upstanding from the base, and a support ring 92 carried by the post. An axial flange 93 rigid and coaxial with the ring 92 carries a series of resilient projections 93a over which frictionally engages a motor housing 94 in the form of a cylinder with one end closed. The support ring 92 supports a motor 95 within the housing the shaft of which extends through the ring and carries a rotor 96 that comprises a pair of end discs and blades supported thereby, these discs and blades resembling those of the rotor 7 of FIGURES 1 and 2 and being designated by'the

same reference numerals

10, 11, 12 respectively. Unlike the rotor 7, however, the rotor 96 includes a set of short blades 97 secured to the side of the end disc 11 opposite the blades and forming an auxiliary rotor of the axial-in, radial-out type. As will have been appreciated the projections 93a space the housing 94- from the flange 93 and permit entry of air to the interior of the housing: the auxiliary rotor formed by the blades 97 ejects air from the housing 94 and sets up a circulation as indicated by the arrows 98.

A one-piece guide unit 99 co-operates with the rotor 96 and differs from one of the guide unit sections 13a, 13b of FIGURE 1 only in the method of its support: the parts of the unit 99 are therefore given the same reference numerals as those of FIGURES l and 2 and will need no further description. The guide unit 99 and rotor 96 co-operate to induce flow as described with reference to FIGURES 1 and 2. The unit 99 is simply rested on a radial flange 100 forming an extension of the ring 92 and held in place by interengagement with that extension, as by means of lugs 99a formed integrally with the guide unit end wall 16, the flange 100 being gripped between this end wall and the lugs. The guide unit 99 is angularly movable about the axis of the motor 95 and rotor 96 and retained in adjusted position by friction between the end wall 16 and lugs 99:: on the one hand and the flange 100 on the other. Other means of releasably attaching the unit 99 to the support ring 92 may be devised by those skilled in the art.

The various parts of this fan unit, with of course the exception of the motor 95, can conveniently be made from sheet metal; the motor casing 94, guide unit 99 and base 90 could alternatively be made with advantage in plastics. To disassemble the fan unit it is merely necessary to lift off the guide unit 99 and pull off the motor housing 92 against the friction applied therto by the projections 93a. The rotor 96 is also readily detachable as described above.

FIGURE 11 shows a modification of the fan unit of FIGURES 9 and 10 wherein the end wall 16 of the guide unit 99 overlies the end disc 10 instead of being coplanar therewith.

I claim:

1. A portable domestic fan having a flat base adapted to stand on a table, a support upstanding from the base and rigid therewith, a motor casing mounted on the support, a motor in the casing having a substantially horizontal shaft, a bladed cylindrical rotor overhung-mounted on one end of the motor shaft and projecting beyond the casing and said support, and a one-piece flow guide unit also supported on and projecting beyond said support,

the flow guide unit presenting guide surfaces opposite the rotor which co-operate therewith on rotor rotation to induce a flow of air from one side of the rotor through the path of the rotating blades thereof to the interior of the rotor and thence again through the path of the rotating blades to another side of the rotor.

2. A fan as claimed in claim 1, wherein the motor casing is centrally disposed with respect to the base and carries two similar rotors one on each end of the motor shaft and two guide units are provided which project to either side of the motor casing for co-operation with the respective rotors.

3. A fan as claimed in claim 2, wherein the guide units are interconnected by a central connecting portion overlying the motor casing and detachably connected thereto.

4. A fan as claimed in claim 1, wherein the rotor has its blades supported between a pair of imperforate end discs.

5. A fan as claimed in claim 4, wherein the motor shaft has a flange adjacent the rotor, the rotor is connected to the motor shaft by a screw connection with one rotor end disc, the end disc when fully screwed to the shaft abutting the flange thereon.

6. A fan as claimed in claim 5, wherein the flange has at least the same diameter as the rotor end disc whereby both may be grasped manually.

7. A fan as claimed in claim 4, wherein the motor shaft has a boss carrying outwardly urged locating elements releasably received in one rotor end disc.

8. A fan as claimed in claim 4, wherein the motor shaft has a flange adjacent the rotor which contacts one rotor end disc, the flange and end disc having co-operating magnetic means holding the end disc releasably to the flange.

9. A portable domestic fan having a flat base adapted to stand on a table, a support upstanding from the base and rigid therewith, a motor casing mounted on the support and overhung in one direction therefrom, a motor in the casing having a substantially horizontal shaft, a bladed cylindrical rotor mounted on one end of the rotor shaft and overhung thereon in the other direction beyond the casing and said support, and a flow guide unit also supported on and overhung beyond said support in said other direction, the flow guide unit presenting guide surfaces opposite the rotor which co-operate therewith on rotor rotation to induce a flow of air from one side of the rotor through the path of the rotating blades thereof to the interior of the rotor and thence again through the path of the rotating blades to another side of the rotor.

10. A fan as claimed in claim 9, wherein the base, motor casing and the major part of said guide unit are a single plastics moulding.

11. A fan as claimed in claim 9, wherein the rotor has its blades supported between a pair of imperforate end discs.

12. A fan as claimed in claim 11, wherein the guide unit comprises a pair of end walls interconnected by a side wall extending the length of the rotor, the end walls forming endwise extending guide surfaces for air leaving the rotor, the end wall remote from the motor being coplanar with the corresponding rotor end disc and defining an arcuate edge overlying an arc thereof in closely spaced relation.

13. A fan as claimed in claim 9, wherein the guide unit comprises a pair of end walls located at either end of the rotor and a pair of side walls interconnecting said end walls and defining an outlet from the rotor.

14. A fan as claimed in claim 13, wherein the guide unit is supported by the end wall adjacent the motor casing.

15. A fan as claimed in claim 9, wherein the rotor includes an end disc adjacent the motor, a series of main blades supported on the end disc, said main blades being arranged in a ring centred on said axis and extending parallel thereto and away from the motor, a series of auxiliary blades also supported on the end disc and extending towards the motor, said casing having a peripheral inlet opening and a central outlet opening facing said auxiliary blades and said auxiliary blades in operation setting up by centrifugal fan operation a cooling air current flowing between said openings which current is independent of the air flow through the main rotor blades.

16. A portable domestic fan having a fiat base adapted to stand on a table, a support upstanding from the base and rigid therewith and terminating in a mounting ring the axis of which extends substantially parallel to the plane of the base, a motor casing supported on the mounting ring and overhung in one direction therefrom, a motor in the casing having a substantially horizontal shaft coaxial with the mounting ring, a bladed cylindrical rotor mounted on one end of the motor shaft and overhung thereon in the other direction clear of the casing and said mounting ring, and a flow guide unit also supported on and overhung clear of said mounting ring in said other direction, the flow guide unit presenting guide surfaces opposite the rotor which co-operate therewith on rotor rotation to induce a flow of air from one side of the rotor through the path of the rotating blades thereof to the, interior of the rotor and thence again through the path of the rotating blades to another side of the rotor.

17. A fan as claimed in claim 16, wherein the flow guide unit is rotatable with respect to the mounting ring to vary the direction of air flow out from the rotor.

18. A fan as claimed in claim 16, wherein the rotor comprises a pair of end discs and a series of blades arranged in a ring about the axis and supported onthe end discs and the How guide unit comprises a pair of end walls at either end of the rotor, a pair of side walls interconnecting the end walls and providing the aforesaid guide surfaces, the side walls and end walls defining an outlet for flow from the rotor, and the end wall remote from the motor is coplanar with the corresponding end disc and defines an arcuate edge closely overlying an arc of the end disc.

19. A fan unit comprising a plate-like base, a support upstanding from the base and rigid therewith, said support terminating in a mounting ring the plane of which extends at right angles to the plane of the base, an electric motor supported on the mounting ringvin overhung relation thereto and on one side thereof, the motor having a shaft aligned on the axis of the mounting ring, a casing around the motor, a cylindrical bladed rotor supported coaxially on the motor shaft in overhung relation to the motor and on the opposite side of the mounting ring to said motor, and guide, means supported on the mounting ring in overhung relation thereto and extending the length of the rotor, said guide means co-operating with the rotor to guide air twice through the blades of the rotor in a direction transverse to the rotor axis, on operation of the motor, said rotor including an end disc adjacent the motor, a series of main blades supported on the end disc, said main blades being arranged in a ring centred on said axis and extending parallel thereto and away from the motor, a series of auxiliary blades also supported on the end disc and extending towards the motor, said mounting ring, motor and easing defining a first opening to the interior of the casing at the ring end thereof and adjacent the blades, said casing having also a second opening, and said auxiliary blades in operation setting up a cooling air current flowing between said openings which current is independent of the air flow through the main rotor blades.

20. A fan unit comprising a plate-like base, a support upstanding from the base and rigid therewith, said support terminating in a mounting ring the plane of which extends at right angles to the plane of the base, an electric motor supported on the mounting ring in overhung relation thereto and on one side thereof, the motor having a shaft aligned on the axis of the mounting ring, a casing around the motor, a cylindrical bladed rotor supported coaxially on the motor shaft in overhung relation to the motor and on the opposite side of the mounting ring to said motor, and guide means supported on the mounting ring in overhung relation thereto and extending the length of the rotor, said guide means co-operating with the rotor to guide air twice through the blades of the rotor in a direction transverse to the rotor axis, on operation of the motor, said rotor including a pair of end discs, a series of blades supported between the end discs, said blades being arranged in a ring about the axis of the motor shaft and extending parallel thereto, said guide means including parallel end walls and guide walls extending between and rigid with the end walls, the end wall remote from the mounting ring closely overlying an arc of the corresponding rotor end disc and being radially aligned therewith.

References Cited by the Examiner UNITED STATES PATENTS 1,366,519 1/1921 Carmean et al. 2301l7 1,950,768 3/1934 Anderson 230 2,768,316 10/1956 Neiss 64-30 2,814,432 11/1957 Eiserman 2301 17 2,881,602 4/1959 Baker et a1. 64-29 FOREIGN PATENTS 559,024 1/1958 Belgium.

ROBERT M. WALKER, Primary Examiner.

Claims

1. A PORTABLE DOMESTIC FAN HAVING A FLAT BASE ADAPTED TO STAND ON A TABLE, A SUPPORT UPSTANDING FROM THE BASE AND RIGID THEREWITH, A MOTOR CASING MOUNTED ON THE SUPPORT, A MOTOR IN THE CASING HAVING A SUBSTANTIALLY HORIZONTAL SHAFT, A BLADED CYLINDRICAL ROTOR OVERHUNG-MOUNTED ON ONE END OF THE MOTOR SHAFT AND PROJECTING BEYOND THE CASING AND SAID SUPPORT, AND A ONE-PIECE FLOW GUIDE UNIT ALSO SUPPORTED ON AND PROJECTING BEYOND SAID SUPPORT, THE FLOW GUIDE UNIT PRESENTING GUIDE SURFACES OPPOSITE THE ROTOR WHICH CO-OPERATE THEREWITH ON ROTOR ROTATION TO INDUCE A FLOW OF AIR FROM ONE SIDE OF THE ROTOR THROUGH THE PATH OF THE ROTATING BLADES THEREOF TO THE INTERIOR OF THE ROTOR AND THENCE AGAIN THROUGH THE PATH OF THE ROTATING BLADES TO ANOTHER SIDE OF THE ROTOR.