US2873908A

US2873908A - Fan arrangement for domestic appliances

Info

Publication number: US2873908A
Application number: US489483A
Authority: US
Inventors: James H Powers
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1955-02-21
Filing date: 1955-02-21
Publication date: 1959-02-17
Anticipated expiration: 1976-02-17

Description

Feb. 17, 1959 J. H.

POWERS

2, 73

FAN ARRANGEMENT FOR DOMESTIC APPLIANCES Filed Feb. 21, 1955 I 3 Sheets-Sheet 1 IN V EN TOR.

d AM ES H POWERS H S ATTORN EY Feb. 17, 1959 J. H. POWERS FAN ARRANGEMENT FOR DOMESTIC APPLIANCES Filed Feb. 21, 1955 3 Sheets-Sheet 2 m m 0 O O STAT C PRESSU E o w. o M. M.

sTAT C DQESSUQE CFM INVEN TOR.

JAMES H. POWERS HIS ATTORNEY Feb. 17, 1959 J. H. POWERS. 2,873,908

FAN ARRANGEMENT FOR DOMESTIC APPLIANCES JAMES H. POWERS M HIS ATTORNEY United States Patent FAN ARRANGEMENT FOR DOMESTIC APPLIANCES James H. Powers, Anchorage, Ky., assignor to General Electric Company, a corporation of New York Application February 21, 1955, Serial No. 489,483

2 Claims. (Cl. 230-119) My invention relates to fan arrangements, and more particularly to such arrangements for moving air through an element which resists the flow of air, and to domestic appliances using such fan arrangements.

Air moving means such as propeller fans or blowers are provided in various types of domestic appliances in order to create a flow of air therethrough. For example, room air conditioners, dehumidifiers, and air purifying or filtering appliances all include fans or blowers for setting up a flow of air over their air treating means. In a room air conditioner one fan or blower is utilized to send a stream of room air through a filter and over a refrigerant evaporator, and a second fan or blower is used to force a stream of outside air over a refrigerant condenser. In a dehumidifier a fan or blower is utilized to send a stream of room air over an evaporator, and in an air purifying appliance one of these air moving means is used to force a flow of air through a filter or purifying element.

Which of them, a propeller fan or a blower, is used in any particular appliance depends upon the application.

The conventional axial flow propeller fan delivers a large volume of air through a air treating means when no appreciable static pressure is required in order to create the flow, that is, when it is operating substantially as a free air fan. But if the air treating means offers any substantial resistance to air flow, the propeller fan is not suitable because the fiow from the fan drops oif considerably as the resistance increases, and in fact if the air treating means presentsa great enough resistance to flow, the fan may not send any air through it at all. This is because, in the operation of a propeller fan approximately 75% of the air moved is thrown forwardly from the tips of the blades, the remaining 25% being thrust forwardly from the central area of the fan. In other words the center of the fan is weak; and as a result, if a sufficient resistance is encountered in the output forward flow, the air takes the path of least resistance and flows back through the center of the fan to the rear intake side thereof, from which area it again is thrust forwardly by the tips of the blades. In this way, a local recirculation of the air occurs in a closed path right through the center of the fan. Due to this return and recirculation the fan is unable to build sufficient pressure to force the air through the resistance.

A centrifugal blower on the other hand creates a comparatively large static pressure so that it can force air through air treating means of relatively high resistance. But in operation, the blower packs air against the air treating means or other resistance by centrifugal pressure, and in doing so creates a vortex within the center of the blower wheel; this vortex limits the volume of flow by causing the air to tend to thin out in the center of the wheel with the result that the output flow is restricted. This phenomenon is commonly known as shock loss. Thus, while a blower may be used to deliver a given volume of air through a resistance, a comparatively large, powerful and expensive one is required.

Because of these characteristics, a propeller fan is Patented Feb. 17, 1959 ordinarily used where a large volume of air is to be delivered and no great pressure is required whereas the blower is used when the need for pressure is the overriding factor. In the above-mentioned domestic appliances it is ordinarily the air treating means which presents the major portion of the resistance to air flow, and it is thus the requirements of the air treating means which have determined which fan will be used, a propellertype fan or a blower-type fan. Whenever possible, it has been customary to use a propeller fan since such fans are less expensive than blowers and occupy less space. But in certain instances, for example when the air flow is to pass through high resistance mechanical or electrostatic filters or through relatively thick heat exchangers, it has been necessary to use blowers despite their greater cost and space requirement. Thus blowers are often employed both in air purifying appliances and in room air conditioners in order to obtain the desired flow. The resulting appliances and conditioners have therefore, of course, been more expensive and bulkier than if fans could have been used.

Accordingly, it is an object of my invention to provide a new and improved fan arrangement by which an axial flow propeller fan is enabled to pass an air stream through high resistance air treating elements.

It is another object of my invention to provide a new and improved fan arrangement having materially different and improved pressure and volume characteristics than those obtained from conventional free air axial flow propeller fans.

A further object of my invention is to provide a new and improved fan arrangement which enables an axial flow propeller fan to produce higher pressures than heretofore possible with such fans and also to maintain substantial flow .at such higher pressures.

Still another object of my invention is to provide a fan arrangement of the above type having new and improved means for shaping and accelerating the output flow.

My invention also has as its object the provision of a new and improved air purifying appliance utilizing an axial flow propeller fan for creating the air flow therethrough.

In carrying out my invention I provide a fan arrangement utilizing a generally axial flow fan having a plurality of air propelling blades. In this arrangement the intake opening to the fan is defined by an annular shroud, and the shroud is so mounted that it surrounds at least the rear portion of the fan. By my invention the arrangement further includes means for efiecting a pressure rise in the output flow from the fan. These means comprise a panel positioned directly in front of the output side of the fan for diverting radially the output flow therefrom, and a chamber surrounding the forward portion of the fan and the shroud and containing a body of free air for collecting therein the radial flow effected by the panel. This chamber has side walls spaced substantially equidistant from the fan; and as the output flow of the fan passes into the chamber, a pressure rise is etfected in the flow. As I understand it, this pressure. rise is due both to centrifugal forces set up as a result of the radial outward and circular movement of the flow, and to a free stream diffusion process occurring as the flow passes through the area between the panel and the shroud. Because of its change to the radial direction, the flow is directed away from the center of the fan and prevented from return and re-circulation therethrough. After it has increased in pressure, the flow is then discharged from the chamber by means of an outlet opening leading therefrom outwardly of the periphery of the blades and the shroud, By reason of the pressure rise so effected in the output flow, this arrangement enables the axial flow fan to maintain flow through high resistance air treating means or to be used in other applications where a relatively high pressure is required.

The novel features which I believe to be characteristic of my invention are set forth with particularityin the appended claims. My invention itself, however, both as to its organization and method of operation may be best understood by reference to the following description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a vertical sectional view of an improved air purifying appliance incorporating a preferred embodiment of my new and improved fan arrangement as a part thereof;

Fig. 2 is a vertical sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a graph showing the performance characteristics of the fan arrangement of Fig. l for different spacings between the fan and the front panel;

Fig. 4 is a graph showing the performance characteristics of the fan arrangement of Fig. 1 for different spacings between the fan and the sides of the collecting chamber;

Fig. 5 is a schematic view in vertical section of an improved air purifier incorporating an alternate embodiment of my fan arrangement;

Fig. 6 is a schematic view in vertical section of an air purifier including another embodiment of my new and improved fan arrangement;

Fig. 7 is a schematic view in vertical section of an air purifier including still another embodiment of my fan arrangement;

Fig. 8 is a front view of the air purifier of Fig. 7;

Fig. 9 is a fragmentary schematic view in vertical section of an air purifier embodying an additional feature of my invention, this purifier including novel means for accelerating and shaping the output flow from the purifier;

and

Fig. 10 is a fragmentary top view of the air purifier of Fig. 9.

Referring now to Figs. 1 and 2, I have shown therein an air purifying or filtering appliance 1 which incorporates a preferred embodiment of my new and improved fan arrangement. The purifier 1 includes ahousing 2 to which an air inlet opening is provided by a grill 3 at the rear thereof. This grill extends completely across the back of the appliance from top to bottom and from side to side and, as shown, is designed with inclined the dust particles or other materials are given a negative charge as they pass the side 6 of the filter. Then as the air stream carries them to side 5 of the filter these particles or other materials are attracted by the high potential side 5 and held on the elements thereof. In other words, the high potential side of the filter acts to pull the particles out of the air and thereby filter it. Further, the filter 4 includes porous or gauze-like sheets of material which are positioned between the electrically charged sides 5 and 6 and which also help to filter the air. The gauze-like sheets of material act as simple mechanical filters to catch and retain dust or other passageway so that it is impossible for a child to stick his fingers or other articles through its passageways. It should be understood, however, that any suitable grill may be used and that a grill with inclined passageways,

- such as is illustrated, is not necessary to the operation of my invention.

Within the housing 2 and directly in front of the grill 3 thereis positioned a filter element 4. Like the grill 3 the filter element 4 extends completely across the housing 2 and thus any air flowing through the grill 3 and into .the housing 2 must necessarily pass through the filter element 4. This filter element 4 is of the electrostatic type and includes a high potential side 5 and a negative or grounded side 6. The high potential side 5 is energized by means of a spring-biased contact 7 which is connected to a high voltage source or power pack 8. The power pack includes a step-up transformer and a rectifier, and the appliance is provided with a cord (not shown) so that the power pack may be energized from any con ventional household electrical outlet. The opposite or negative side 6 of the filter is likewise engaged by a spring contact, and this contact 9 is connected directly to the housing 2 so that the negative side 6 is always grounded.

The negative side 6 of the filter 4 lies adjacent to the extraneous materials in the air entering the purifier 1,

particles.

In order that the filter element 4 may be removed from the housing for cleaning purposes or to be replaced, it is mounted on a separate housing section 10 which is releasably attached to the rest of the housing. The housing section 10 may be attached to the bottom wall of the housing by any suitable means as for example by clips, and when these clips or other means are released, the housing section 10 and the filter 4 may be pulled completely out of the housing. Suitable safety means (not' shown) are provided so that Whenever the filter is taken out of the housing the supply circuit to the power pack. 8 is broken and it isde-energized. Further, on chance that there may be some charge remaining in the power pack even though the supply circuit is broken, the contact 7 is so arranged that it automatically rotates downwardly and comes into contact with the housing 2 as the filter is removed. This effectively grounds the power pack and insures that there is no stray voltage remaining to injure anyone.

To create a fiow of air through the filter element 4 I have mounted within the housing 1a preferred embodiment of my new and improved fan arrangement. This fan arrangement utilizes a generally axial fiow, propeller fan 11. The fan 11 includes a plurality of blades 12, and is driven by an electric motor 13 through a shaft 14. Both the fan 11 and the motor 13 are supported by means of mounting brackets 15 which are attached to the casing of the motor 13 at their one end and to the bottom plate 16 of the housing 2 at their other ends. It will be understood however that any suitable means may be utilized to mount the motor and the fan within the housing.

To define an intake opening to the fan 11 there is provided an annular shroud or ring 17. This shroud extends forwardly from the rear or intake side of the fan sothat it surrounds at least a portion of the periphery of the blades. Specifically in my preferred embodiment it extends forwardly so that it surrounds two-thirds of the fan from rear to front, that is, two-thirds of the projected thickness of the fan blades measured from the rear. Only the front one-third of the fan extends outwardly beyond the front edge 18 of the shroud. I have found that the best results are produced by arranging the shroud in this manner so that it surrounds the rear twothirds of the fan with the forward one-third of the fan extending outwardly from it.

As is better shown in Fig. 2 the annular shroud 17 at its rear edge'is attached to or is formed integrally with a panel or wall 19. This panel 19 extends outwardly from the rear edge of the shroud to all sides of the housing 2, and it completely isolates the space within the housing behind the fan from the space within the housing in front of the fan. Due to the panel 19 the only way air can pass from the space behind the fan to the space in front of the fan is through the fan itself. In my preferred embodiment the lower and middle portions of the panel 19 extend outwardly in generally the same plane as the rear of the fan, that is, the plane containing the rear edges of the blades, to the bottom wall 16 of the housing and to the side walls 20 and 21 of the housing. However, the portion of panel 19 above centrifugal effect.

the shroud is slanted rearwardly toward the filter 4 as it extends upwardly to the top wall 22 of the housing.

In my novel fan arrangement, now to be described, the fan 11 is so arranged that it is effective to produce a greater pressure than is normally obtainable from axial free air flow fans. More exactly, the fan 11 is so arranged that it produces a greater pressure than it itself could produce if utilized in the customary arrangements for axial air flow fans. This higher pressure is needed in order to pull the air through the filter element 4 which presents a relatively high resistance to the flow of air particularly when clogged up after use.

In the embodiment of Figs. 1 and 2, my novel fan arrangement includes a panel or planar baffle 23 which is positioned directly in front of the output side of the fan so that the axially moving output stream of the fan flows directly into it. Preferably, this panel 23 comprises the front wall of the air purifier housing 2. The panel 23 serves to divert radially outward the axial output flow of the fan, or in other words it changes the direction of the output flow of the fan as soon as it leaves the fan. In addition to the panel 23 my fan arrangement also includes a chamber which contains a body of free air for collecting the radial flow effected by the panel. This collecting chamber in accordance with my invention extends around or surrounds at least the forward portions of the fan 11 and its shroud 17. For example, in the embodiment of Figs. 1 and 2 a chamber 24 surrounding the fan 11 and the shroud 17 is defined by the front wall or panel 23, the shroud 17 itself, the panel 19 extending outwardly from the shroud, the side walls 20 and 21 of the housing and the bottom wall 16 of the housing. Actually, the chamber 24 so defined by these walls, surrounds more than just the forward portions of the fan and the shroud; it in fact surrounds substantially all of the shroud and the fan and thereby provides a body of free air all around them. However, as mentioned above, the chamber may surround only the forward or output portions of the fan and the shroud and my increased pressure and volume effect now to be explained will still be produced. But for best results the chamber should use the fan shroud as the rear wall thereof so that the full depth of shroud is included in the chamber. I have found that the combination of apanel positioned directly in front of an axial flow fan, and a chamber surrounding at least the forward portions of the fan and its shroud for collecting the radial flow effected by the panel, is effective to cause a pressure rise in the output flow from the fan. In other words, the conversion of the axial output flow to radial flow by the panel 23 and the collection of .this radial flow by the body of free air contained in the chamber 24 causes a pressure rise in the flow itself. As-I understand this novel pressure rise, it occurs because my fan arrangement in effect converts the axial flow fan into a mixed flow compressor by adding 3. Normally an axial flow fan, such as the fan 11, when operating as a free air fan, adds energy to the air by increasing its kinetic energy with only a'very small rise in pressure. However, by restricting the axial output flow with a plate or panel, such as the panel 23, the output air is made more to flow out radially. As a result, a centrifugal force field is created in the fan output flow and a pressure rise is experienced due to the centrifugal forces on adjacent air molecules in the centrifugal force field. In addition to this effect, a pressure rise also occurs in the region of the annular peripheral area lying between the forward end 18 of the shroud and the panel 23. In other words an additional pressure rise occurs at the area of the radial discharge between the shroud and the panel. This pressure rise results from a free stream diffusion process which is simply a conversion of some of the radial velocity head leaving the blades into a pressure head by virtue of a decrease in the velocity of the moving air. Moreover, because of the change in the direction of flow directly in front of the 6 fan, the increased pressure is not lost through leakage at the center of the fan. The flow being directed radially away from the fan is prevented from returning and recirculating through its' center. Thus .there is no substantial leakage flow to diminish and/or limit the pressure otherwise produced by the fan.

To explain the pressure rise in somewhat simpler language it may also be descn'fbed as follows: One pressure rise is effected by the decrease in velocity of the axial air flow from the fan as it is converted to radial flow by the interference of the panel; and a second pressure rise is effected by the decrease in velocity of the radial flow as its centrifugal forces are resisted by the adjacent free air in the exhaust or collecting chamber. Further, because the flow is directed away from the center of the fan, there is effectively no leakage therethrough to diminish and/or limit the pressure. But whatever the explanation may be, I have found by actual tests that a material pressure rise is effected in the output flow of the fan by my novel fan arrangement.

It will be noted incidentally that the bottom corners of the chamber formed by the plane, parallel side walls 20 and 21 and the bottom wall 16 are right-angle or square corners. These square corners provide a damping action on any whirling circulation which may tend .to occur in the body of free air contained in the chamber 24; and I have found that better results from the standpoint of pressure increase and air flow are obtained from my fan arrangement when such damping of the 'body of free air is employed. When the body of air within the chamber 24 is held relatively still, higher pressures are produced than when the body of free air is able'to cin culate freely. It will be understood though that my invention is not limited to a chamber with square corners since chambers with rounded corners and a more freely circulating body of air may be used although with not quite so good results. Whatever the chamber configuration, sound deadening material may be placed on'the walls to reduce noise without materially affecting the pressure and volume characteristics obtained.

After a pressure rise has been effected in the output flow from the fan by means of my new and improved arrangement, the flow is then discharged outwardly from the chamber. In order to provide means for this dis charge flow, an outlet opening is defined in the chamber 24 outwardly of the periphery of the blades 12 of the fan. Specifically in the embodiment of Figs. 1 and 2 the outlet opening comprises an aperture 25 in the top wall 22 of the housing. This aperture or opening 2 5 is covered with a perforate grill 25a for safety purposes. Although the output flow from the fan flows radially in all directions along the panel 23 into the chamber 24, the flow eventually works its way around and goes out through the opening 25. In fact, the outlet opening would not have to be in the topwall of the chamber, rather it could be in any wall thereof, outwardly of the periphery of the fan blades, and the flow would still find its way to it. My increased pressure effect would be obtained just as in the embodiment of Figs. 1 and 2 provided that the opening were positioned outwardly of the periphery of the blades. It will be noted that in the embodiment of Figs. 1 and 2, because of the inclination of the wall 19, the chamber 24 widens out from front to rear just be low the outlet opening 25. This widening of the chamber however is not necessary to this embodiment and could be eliminated if desired.

In the embodiment shown in Figs. 1 and 2 the fan 11 is of course pulling" air through a filter mounted on the downstream side of the fan rather than forcing air through a filter mounted on the upstream side of the fan. In order to pull through the filter, the fan 11 creates a partial vacuum in the portion of the housing lying on the downstream side of the filter but on the upstream side of the fan. In other words it creates a partial vacuum in the portion of the housing generally indicated at 26.

This partial vacuum in the space 26 then allows the normal atmospheric pressure to force air through the filter 4 into that space. The amount of flow through the filter of course depends upon the magnitude of the partial vacuum created by the fan.

My new and improved fan arrangement enables the fan 11 to create a higher vacuum in the space 26 than would have been heretofore possible with an axial fan. The fan 11 during its operation pulls the air out of the space 26 and throws it outwardly toward the panel 23. As explained above, a pressure rise then occurs in the air flow as it moves into the chamber 24. By the time the flow is absorbed by the free air in the chamber 24 it has risen to a pressure slightly higher than atmospheric. Because of this slightly higher pressure the air then moves outwardly through the openings 25 into the surrounding atmosphere. Since the pressure of the output flow is only slightly more than atmospheric at the opening 25 and can rise no higher, and since a large pressure rise occurs between the output of the fan and the opening 25, this means that the pressure immediately in front of the fan is much lower than atmospheric. Further, since a small rise is experienced as the air passes through the fan itself, the pressure in the chamber 26 is even lower. The increased pressure effect resulting from my novel arrangement is added to the normal pressure effect of the fan to cause a lowering of the pressure in the chamber 26 to a point much below that which would be possible with the fan mounted in the conventional manner to operate in free air. As a result the fan 11 is enabled to maintain a satisfactory flow through the filter 4 even when it clogs up with use.

In order to explain more fully the results which may be obtained by the use of my new and improved fan arrangement, I have shown in Figs. 3 and 4 a set of performance curves showing variations in air delivered in cubic feet per minute (C. F. M.) with variations in static pressure in inches of mercury for a ten inch, 23 pitch, axial fiow propeller type fan mounted as shown in Figs. 1 and 2, each curve being for a different spacing between the fan and the front panel 23 or between the fan and the side walls of the collecting chamber. For the purpose of comparison, Figs. 3 and 4 also include a curve showing the performance of the fan when mounted in the conventional manner to operate as a free air fan without any obstruction to the free flow of air discharged from it. The fan employed to obtain the data from which these curves were plotted is of a standard propeller type and was driven by a 1/50 horsepower motor at approximately 1550 revolutions per minute.

Referring to Fig. 3 the curve 27 indicates the normal results which are produced by this ten inch fan when it is operated as a free air fan in the customary manner to discharge freely straight out into the atmosphere. It will be noted that the maximum pressure which may be produced with the fan operating in this conventional manner is approximately 0.22 inch of mercury measured immediately in front of the fan, and at this pressure the flow from the fan is practically negligible. The

curves

28, 29, and 30, however, indicate the results which are obtained when my new and improved fan arrangement is used. As these curves show, my fan arrangement enables the fan to produce much higher pressures, for example over 0.5 inches of mercury, and to maintain substantial flow at these higher presures.

The

curves

28, 29 and 30 were plotted from data obtained by using a fan arrangement in which the side walls 20 and 21 of the collecting chamber 24 were fixed and positioned 4 inches from the periphery of the fan, and the bottom wall 16 also fixed, was positioned 2 inches from the fan periphery; but the fan and the shroud were .moved together as a unit relative to the diverting plate or panel 23 so as to vary the distance therebetween. The positions of the fan and the shroud relative to each other were, however, kept the same. For the curve 28 the dis tance between the forward end 18 of the panel and the shroud was 1% inches, for the curve 29 the distance was 2 /2 inches, and for the curve 30 the distance was 5 inches. The fan, of course, protruded forwardly from the edge 18 the same distance for all three curves, i. e. one-third of the fan extended forwardly of the edge 18.

a It will be noted that the curve 29 is superior from the standpoint of air delivered to the curve 28 at all points. In other words, no matter what the static pressure is picked out, the fan is handling more air when operating on the curve 29 then when operating on the curve 28. The 2 /2 inch spacing thus gives better results than the 1% inch spacing. Also, comparing the curve 29 with the curve 30, it will be noted that for the lower pressures more air is handled when the distance between the forward end of the shroud and the panel is 5 inches. However, for the greater pressures, in other words, for pressures above .425 inch of mercury, the curve 29 is superior; that is, the fan handles more air when the distance between the front end of the shroud and the panel is only 2 /2 inches. Since the purpose of my fan arrangement is to maintain flow even when rather high pressures are required, as when the air treating means such as the filter 4 clog up, I therefore consider the curve 29 to be the superior performance curve of the three curves illustrated. 7

It is also to be noted that when the distance between the forward edge of the shroud and the panel is 2 /2 inches, which distance gives the best results for a ten inch fan, the annular peripheral area between the panel and the forward edge of the shroud for a ten inch fan is approximately equal to the area of the'intake opening to the fan defined by the shroud. The minimum diameter of the shroud is about 10%; inches fora ten inch-fan, and it thus defines an intake opening of approximately 78.5 square inches. With a 2% inch spacing between the panel and the front of the shroud, the annular peripheral area therebetween is also approximately equal to that figure. Moreover, this relationship of the most desirable results being obtained when the intake area equals the peripheral discharge area tends to hold true as the size of the fan is changed. Specifically, I have tested various fans, eight inches in diameter and larger, and have found that the best performance is obtained from all of these fans when the intake area to the fan defined by the shroud is approximately equal to the annular peripheral area between the front edge of the shroud and the panel. Also, this relationship holds true regardless of the pitch of the blades. Even though changing the pitch changes the results obtained, the best results still occur when the area of the intake opening equals the area of the peripheral discharge opening.

Returning to the ten inch fan of the curves (Fig. 3), as the distance between the panel and the shroud increases beyond 5 inches the performance of the fan steadily moves away from my improved pressure and volume effect and toward the normal performance characteristics of a ten inch fan. In other words, the performance steadily moves from the more or less inclined high pressure characteristic of curve 30 toward the relatively level, normal, low pressure characteristic defined by curve 27. This same sort of change also tends to occur for other sizes of fans. Thus ordinarily for good results from my fan arrangement, the annular peripheral area between the shroud and the front panel should not be more than 200% of the intake area to the fan. Conversely, for good results, I would not decrease the aforesaid peripheral area between the front of the shroud and the panel to less than 50% of the intake area to the fan. Below that point there tends to be choking or retarding of the flow so that although it is still possible to produce considerable pressure, nonetheless the flow rate is materially decreased. Of course, it is possible to obtain my increased pressure effect when the distance between the shroud and the panel is beyond these limits. But ordinarily to obtain desirable results the annular peripheral area between the front of the shroud and the panel should be from 50% to 200% of the intake area to the fan defined by the shroud.

Referring now to Fig. 4 I have shown therein the effects which are obtained when the distance between the sides 20 and 21 is varied. As in Fig. 3 the curve 27 is included to show the normal performance of the fan when my novel fan arrangement is not used, in other words, when the fan is blowing freely and directly out into the room without a radially diverting panel and collecting chamber. The remaining curves 31, 32, 33 and 34 in Fig. 4 show different performance characteristics which are obtained from the fan 11 for different distances between the sides 20 and 21 of the chamber. As mentioned above, these curves are made with a ten inch fan driven by a ,3 horsepower motor as approximately 1550 revolutions per minute. To take the curves, the bottom wall 16 was spaced 2 inches from the fan periphery, and the fan and the shroud were fixedly positioned so that the forward edge 18 of the shroud was spaced 2 /2 inches from the panel 23. The curve 31 shows the performance of the fan when the sides of the chamber are spaced 12 inches apart, the curve 32 when the sides are spaced 14 inches apart, the curve 33 when the sides are spaced 16 inches apart, and the curve 34 when the sides are spaced 18 inches apart. The curve 34 taken on the 18 inch spacing is the best curve i. e. for any given pressure the fan maintains the greatest flow when operating on it. All of the curves are however obviously superior in pressure to the normal curve 27.

When the sides are spaced beyond 18 inches for this size fan, the fan performance thereupon begins to steadily approach the normal performance curve 27. Some, and eventually all, of the desirable effects of my arrangement are lost as the distance between the sides is increased beyond 18 inches. When the sides are spaced 18 inches apart, the distance between the periphery of the blades and the sides of the chamber is approximately 4 inches or less than 50% of the diameter of the ten inch fan. In other words, with the ten inch fan the best results are obtained when the sides of the chamber are spaced a distance from the periphery of the fan which is less than 50% of the diameter of the fan. Further, I have found from many tests made of fans eight inches in diameter and larger, that this relationship holds true with fans of various size, within wide limits. It will be understood, of course, that my novel fan arrangement can be used with the chamber sides spaced beyond this 50% limit, but the desirability of the performance obtained ordinarily decreases as the sides are moved beyond it. Also there is a limit on the minimum spacing of the side walls from the periphery of the fan for good results. I have found the allowable minimum spacing is about of the diameter of the fan. If the side walls are brought closer to fan periphery than that, my increased pressure and volume effect is progressively lost.

It will be noted that the side walls 20 and 21 are spaced equidistant from the sides of the fan. I have found that substantially equidistant spacing is necessary for the effective operation of my new and improved fan arrangement, and that the best results are obtained if the inner surfaces of the side walls are parallel. If one side is spaced from the periphery of the fan a distance substantially greater than the other side, a portion of my increased pressure and volume effect is lost. In fact if the difference in spacing is great enough, the entire increased pressure and volume is lost. When the sides are not spaced substantially equidistant, the air is able to escape on the side spaced further from the fan without any considerable interference and thereby there is no decrease in velocity and rise in pressure.

Further, the spacing of the bottom wall 16 is also important to the operation of my fan arrangement. For

best results its spacing from the periphery of the fan should be equal to that of the sides of the chamber; and in any case it should be spaced from the fan periphery a distance not greater than 50% of the diameter of the fan. A greater spacing than that results in the increased pressure and volume effect being decreased, and if the spacing is made large enough, the effect is entirely lost. In taking the curves shown in Figs. 3 and 4 the bottom wall was of course spaced nearer to the fan than were the side walls but this was done only to decrease the size of the apparatus and some of my increase pressure and volume effect was lost as a result. In this particular application, however, the advantage of space saving outweighed the slight decrease in performance. Like the sidewalls the bottom wall should not be spaced closer to the periphery of the fan than 10% of the diameter of the fan.

Referring now to Fig. 5 I have shown therein a second embodiment of my new and improved fan arrangement. This fan arrangement is mounted within an air purifier or filtering appliance 40. The air purifier 40 includes an outer housing or casing 41 to which an inlet opening is defined at the rear thereof. A filtering element 42 is positioned in front of this opening so that any air flowing into the unit passes through the filter and is filtered thereby. This filter may be either of the electrostatic or the mechanical type or may be a combination of both. After flowing into the filter 42 the intake air enters a chamber 43 positioned behind a fan. 44.

The fan 44 is of the conventional axial flow propeller type and is incorporated in an alternate embodiment of my new and improved fan arrangement. As shown, the fan 44 is driven by means of an electric motor 45 and the mounting for the fan and the motor is provided by suitable mounting brackets 46 which are attached to the casing 41. The intake opening to the fan is formed by means of a scroll 47 which surrounds at least the rear portion of the blades and preferably two-thirds thereof from rear to front; and this scroll 47 is either attached to or formed integrally with the wall 48 which serves as the front wall of the chamber 43 behind the fan. In accordance with my invention, the output flow from the fan is blown directly against a panel 49 which comprises the front wall of the housing 41. The panel 49 is positioned directly in front. of the fan and it diverts the output flow radially outward into a chamber 50 defined by the panel itself,the side walls of the housing (not shown), the scroll'47, the wall 48, and the bottom wall 50a of the housing. This chamber 50 contains a body of free air in which the flow is then collected, and it preferably includes right angleor square bottom corners to damp any whirling circulation therein.

Due to the action set up by the panel 49 and the chamber 50 a pressure rise is effected in the output of the fan 44 in the same manner as was effected for the fan 11 of the embodiment of Figs. 1 and 2. After experiencing this pressure rise the output flow of the fan is then discharged through -an outlet 51 in the top wall of the chamber. This opening 51 may be covered by any suitable means, as for example by a perforate grill, to pre: vent anyone from sticking his hand or dropping objects down into the fan.

. The foregoing structure is essentially the same as shown in Figs; 1 and 2, but in the embodiment ofFig. 5 I have provided additional means which reduce the noise of the fan and which also tend to improve the performance characteristics somewhat. These additional means comprise a member 52 which is mounted on the shaft 53 of the fan between the fan and the panel 49. This member 52, which preferably comprises a circular disk, rotates at the same speed as the fan and helps the wall 49 in diverting the axial flow from the fan radially outward. The disk 52 in effect reduces friction by allowing the air leaving the fan to slip off radially from a moving member rather than being diverted by a stationary member.

As mentioned above, this not only decreases noise but also improves the performance characteristics of the fan arrangement somewhat. This disk may be made of any suitable material as, for example, aluminum. Although the size of the disk may be varied I have found that the preferable size is approximately four-fifths that of the fan. Thus, if a ten inch fan is used, the disk for best results should be approximately eight inches in diameter.

It will be understood that the fan arrangement of Fig. operates to pull air through its filter in the same manner as does the fan arrangement of Fig. 1. In other words, the fan arrangement of Fig. 5 creates a vacuum in the chamber 43 behind the filter so that atmospheric pressure forces air through the filter, and then it raises the air to a pressure somewhat above atmospheric in the chamber 50 so that the airfiows outwardly into the room.

Referring now to Fig. 6, I have shown therein another embodiment of my invention. This embodiment comprises an air purifying or filtering appliance 60 which incorporates a still different modification of my new and improved fan arrangement. This air filtering appliance 60 includes a housing 61 to which an inlet opening 62 is formed in one wall thereof. Communicating directly with this inlet opening is a shroud 63 which defines an intake opening to an axial flow propeller fan 64. The shroud 63 is so designed that it surrounds at least the rear or intake portion of the fan 64, and in my preferred arrangement it surrounds approximately two-thirds of the fan from its intake to its outlet side. The fan 64 itself is driven from a suitable electric motor 65 by means of a shaft '66. The mounting for both the fan and the motor is accomplished by means of a plurality of brackets 67 which are secured tothe casing of the motor and to the housing 61.

In accordance with my invention the fan 64 is so arranged that a pressure rise is effected in the output flow thereof. This pressure rise in the output flow enables the fan 64 to force the air taken in through the shroud 63 out through a filter element 68 which is positioned over the outlet opening from the housing 61. Specifically, the outlet opening and the filter element extend completely across the top area of the housing 61.

In order to effect a pressure rise between the fan 64 and the filter element 68 a panel 69 is positioned directly in front of the output side of the fan. The panel 69 diverts the axial output flow of the fan radially outward in all directions. This radial output flow is then collected in a chamber 70 which surrounds the fan 64 and the scroll 63. The chamber 70, which is defined by the panel 69, the bottom plate 71 of the housing, the scroll 63, an extension 71a of the panel 69, and the side walls of the housing (not shown), contains abody of free air and this free air slows down and collects the radial output fiow as it moves outwardly into the chamber. As a result a pressure rise occurs in the output flow in the same manner as described With respect to the embodiment of Figs. 1 and 2. After so increasing in pressure the air then passes outwardly through the filtering element 68.

To improve further the results obtained from the fan arrangement, a rotating disk 72 is mounted on the same shaft as the fan 64 between the fan and the panel 69. This disk 72 materially reduces the friction as the air is diverted from the axial direction to a radial flow and thereby both reduces noise and improvesthe performance characteristics. The size of the disk may be varied, but preferably its diameter should be four-fifths that of the fan.

In this embodiment of my invention, the new and improved fan arrangement operates to create a high pressure behind the filter rather than to create a partial vacuum between the filter and the intake of the fan. Here the fan takes in atmospheric air and then through my improved fan arrangement, a high pressure is created as the fiow moves radially outward into the chamber 70. This high pressure in turn forces the .air out through the filter 68 and enables a substantial flow to'bemaintained even upon some clogging of the filter. It will be understood that the filter 68 can be either an electrostatic filter or a mechanical filter or a combination of both. Itwill also be noted that the space 73 directly behind the filter 68 is made considerably Wider than the other portions of the collecting chamber 70. This permits the use of a filter of large area. The other portions of the chamber 70, of course, communicate directly with this space 73. As in the previously described embodiments, the bottom corners of the collecting chamber are preferably formed as right-angle or square corners thereby to damp any whirling flow in the. chamber.

Referring now to Figs. 7 and 81 have shown therein still another embodiment of my invention. This embodiment comprises an air purifying appliance which in corporates another modification of my new and improved fan arrangement. The appliance 80 includes a housing 81 to which an inlet opening is defined at the rear end thereof. A filter element 82 is positioned over this opening so that any air flowing through the opening must pass therethrough; and in order to set up a flow of air through the opening and the filter, an axial fiow propeller fan 83 is mounted within the housing 81. The fan 83 is driven by a motor 84 by means of a shaft 85, and both fan 83 and the motor 84 are mounted by means of a plurality of bracket members 86 which are firmly attached to the casing of the motor and to the housing 81. The intake opening to the fan 83 is defined by means of a shroud 87 which communicates with thejspace88 lying between the filter element 82 and the fan. The shroud 87, which is an annular member, surroundsat least the rear portion of the fan in order to form the intake opening and preferably it extends forwardly a distance along the periphery of the fan. For best results I have found that it should extend for two-thirds of the distance from therear to the front of the fan.

In order that the fan 83 may create the desired flow of air through the filter 82, I have provided means which together with the fan comprise another modification of my new and improved fan arrangement. This means includes a panel 89 which is positioned directly in front of the fan 83, and a collecting chamber 90 which surrounds the fan and the shroud 87. In this arrangement, the axial output fiow from the fan flows directly against the panel or plate 89 and is diverted radially thereby. The radial flow then moves outwardly into the chamber 90 surroundingthe scroll 87 and the fan and is slowed down and collected in a body of free air lying in this chamber. The chamber 90 includes the panel 89 as the front wall thereof and the scroll 87 as a portion of the rear wall thereof. The side walls (not shown) of the housing form the sides of the chamber 90, and the top and bottom walls of the chamber are formed by

wall members

91 and 92 which are attached to or formed integrally with the scroll. The corners of the chamber are preferably formed as right-angle or square corners to damp any whirling flow in the chamber.

For the reasons discussed with respect to the embodiment of Figs. 1 and 2 the output flow from the fan 83 increases in pressure as it is diverted radially outward and collected in the chamber 90. In this embodiment the increased pressure airis however discharged from the collecting chamber in adifferent manner than it was from the collecting chamber ofFigs. l and 2. Specifically in Figs. 7 and 8 the'discharge opening from the chamber 90 comprises a continuous aperture 93 which extends around the plate 89. The discharge flow thus leaves the chamber 90 flowing in essentially the same axial direction as it was before being diverted radially by the plate 89. The plate 89 is of sufiicient size though that an increased pressure efiect is created in the flow before it reaches the discharge opening. The inner sides ofthe aperture 93, i. e., the outer edges of the plate 89, are spaced outwardly from the periphery of the fan 83 and the scroll 87 so that the air is both diverted radially and slowed down and collected in a body of free'air before it reaches the aperture 93. These two actions, as in the other embodiments, cause an increase in pressure in the flow between the fan and the discharge opening.

In the embodiment of Figs. 7 and 8, the fan arrangement creates a fiow through the filter 82 by creating a partial vacuum in the space 88 behind the filter. Atmospheric pressure thus forces air through the filter. The air then passes through the fan 83 and is raised in pressure as it flows outwardly radially outward into the chamber 90. After rising to a pressure somewhat above atmospheric the air is finally discharged outwardly through the opening 93 into the room.

Although I have not shown performance curves for the embodiments of Figs. -8 it will be understood that they produce results equivalent to or better than the results shown in Figs. 3 and 4 for the embodiment of Figs. 1 and 2. In fact, as mentioned above, the inclusion of a rotating disk between the fan and the radially diverting panel, as shown in Figs. 5 and 6, both reduces noise and improves the output characteristics of the fan arrangement somewhat. The rotating disk can also be included in the embodiment of Figs. 7 and 8 and in fact, if desired, the panel 89 could be replaced by a rotating disk or somewhat larger diameter than the fan 83. In the latter case the disk in effect becomes a wall of the collecting chamber. Thus when I state that the chamber includes the panel placed in front of the fan, it will be understood that the panel may be fixed to it, or the panel may be rotatingwith respect to it. Further, although in the various illustrated embodiments I have shown the discharge opening from the collecting chamber as leading either through the top or the front of the chamber, my invention is not limited to embodiments wherein the opening is in such walls. Rather the opening from the collecting chamber could be in the bottom of the chamber or if suitable passageways are pro vided the opening could lead therefrom back through the same wall in which the inlet to the fan is taken. Of course, with this latter arrangement suitable bathe means would have to be provided between the inlet and the outlet in order to separate the intake and discharge fiows.

It should be noted incidentally that the same dimensional relationships mentioned with regard to the embodiment of Figs. 1 and 2 also apply to the embodiments of Figs. 58. For the best operation the spacing of the flow diverting panel from the forward edge of the shroud, and the spacing of the side walls and the bottom wall of the collecting chamber from the periphery of the fan should be generally the same in Figs. 58 as in Figs. 1 and 2. In these embodiments also, the pcripheral discharge area between the forward end of the shroud and the panel should preferably be from 50% to 200% of the intake area to the fan defined by the shroud; and the side walls and the bottom Wall of the collecting member should preferably be spaced from the periphery of the fan a distance less than 50% but greater than of the diameter of the fan. Further,,the spacing of the side walls from the fan should be the same, e. g. they should be equidistant therefrom, and preferably the spacing of the bottom of the chamber from the fan should also be the same as that of the side walls. Moreover, in Figs. 7 and 8 the same spacing is preferably used for the top of the chamber also.

Referring now to Figs. 9 and 10 I have shown therein still another modification of my improved fan arrangement. This embodiment includes a casing 101 to which an inlet opening is defined at the rear thereof. A mechanical or electrostatic filter (not shown) may be positioned in front of this inlet so that any air passing through the casing 101 is filtered or purified.

In order to set up a flow of air through the casing 101 there is mounted therein a generally axial fiow propeller 102. This fan is mounted in the same manner as the fan of the embodiment ofFigs. 1 and 2 and is driven by a suitable electrical motor (not shown). The intake opening to the fan 102 is defined by means of an annular shroud 103 which communicates with the space 104 lying behind the fan. The shroud 103 surrounds at least the rear portion of the fan in order to form the intake opening and preferably it extends forwardly a distance along the periphery of the fan. As in the previously discussed embodiments the best results are obtained when it extends forwardly for two-thirds of the distance from the rear to the'frorit of the fan.

In accordance with my invention the output from the fan 102 flows directly against a panel or plate 105 positioned in front of the fan, and is diverted radially by this plate. The radial flow then moves outward into a chamber 106 surrounding the scroll and the fan and is slowed down and collected in a body of free air lying in this chamber. The chamber 106 includes the panel 105 as the front wall thereof and the scroll 103 as a portion of the rear wall thereof. The side walls and bottom walls of the chamber are not shown but it will be understood that the chamber is similar to the chamber shown in the embodiment of Figs. 1 and 2. Like the chamber of that embodiment, it preferably includes square or right-angle corners at its bottom.

For the reasons described at length with regard to the other embodiments, the output flow from the fan 102 increases in'pressure as it is diverted outwardly and collected in the chamber 106. In this embodiment, however, a somewhat different means is provided for discharging the air from the chamber. In this embodiment the outlet opening from the chamber is comprised of 'a plurality of slots 107 which are defined in a cover member 108 mounted at the top of the chamber 106. The number and size of the slots 107 are such that the discharge from the chamber1106 is somewhat restricted, and as a result a pressure is built up within the chamber 106. Further, the slots 107 are so shaped narrowing from their inlet sides to their outlet sides that they form or act as nozzles. Acting as nozzles the slots 107 are effective to increase the velocity of the air as it is discharged therethrough; and along with this increase in velocity a cooling of the air also occurs. Due to the pressure-volume change effected by the slots the temperature of the air decreases as it is accelerated. The higher the acceleration of the air, the cooler the air becomes. The provision of the slots 107 thus results in a rapidly moving cool stream of air being discharged from the casing 101.

The cover 108 and the slots 107 are so arrange-d that the air is discharged in an upward direction toward the ceiling of the room in which the casing or appliance 101 is positioned. Moreover, the slots are so arranged that the discharge air is confined or shaped to a narrow stream of relatively small proportions until it reaches the upper level of the room. At this upper level the high velocity air is then slowed down by the resistance of the free air in the room. After slowing down, the air spreads out and because of its coolness settles gently in a downward direction. By this method the air is introduced into the room without the annoyance of an air stream blowing directly onto any person within the room. This embodiment of my fan arrangement is thus efiective to produce a particularly pleasing result, since it discharges a cool stream of air which due to its velocity and direction of discharge circulates throughout the room but yet does not blow directly on the user. Additionally, if this fan arrangement is placed in a window so that it draws in outside air through its intake, it is effective to produce a higher degree of cooling than can be obtained from a conventional fan placed in a window. The effect produced by the slots 107 results in a cooler stream of air being introduced into the room.

It will be understood that the same dimensional relationship discussed with respect to Figs. 1 and 2 also applies to this embodiment of my fan arrangement. Here again, for best results the peripheral discharge area between the forward end of the shroud and the panel should preferably be from fifty percent to two hundred percent of the intake area to the fan defined by the shroud; and the side walls and the bottom wall of the collecting chamber should preferably be spaced from the periphery of the fan a distance not less than 50% but more than of the diameter of the fan. Further, the side walls should bespaced equidistant from the fan and, preferably the same spacing should also be used for the bottom wall. Also, a rotating disk may be mounted between the fan 102 and the panel 105 in order to reduce noise and improve the output characteristics of the fan arrangement somewhat.

It will be noted that in this embodiment, as in the embodiment of Figs. 1 and 2, the collecting chamber widens out from front to rear just below the outlet. Such a widening was, of course, not necessary in the embodiment of Figs. 1 and 2, but here it is desirable in order that a sufiicient number of slots 107 may. be provided to handle the flow and maintainv the desired characteristics therein.

. While in accordance with the patent statutes I have described. what at present are consideredto be the preferred embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications maybe made therein and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

I claim:

1. A fan arrangement comprising a generally axial flow fan having a plurality of blades, an annular shroud forming an intake opening to said fan and surrounding only the upstream portion of said fan, and means for effecting a pressure rise in the output flow from said fan, said means including a planar baifie positioned substantially at right angles to the axis of said fan in front of the output side of said fan for diverting radially the axial flow therefrom, the annular peripheral area between said panel and the forward edge of said shroud being from 50% to 200% of the area of said intake opening to said fan defined by said shroud, a rectangular shaped chamber surrounding at least the forward portions of said fan and said shroud and containing a body of free air-for collecting therein the radial flow effected by said planar bafHe, said rectangular shaped chamber having three side walls spaced substantially equidistant from 16 said fan and enclosing the periphery of said fan around at least three sides thereof, and means defining an air outlet opening in the fourth side Wall of said chamber outwardly of the periphery of said blades.

2. A fan arrangement comprising a generally axial flow fan having a plurality of blades, an annular shroud forming an intake opening to said fan and surrounding only the upstream portion of said fan, and means for effecting a pressure rise in the output flow from said fan, said means includinga planar baffle positioned substantially at right angles to the axis of said fan in front of the output side of said fan for diverting radially the axial output flow therefrom, the annular peripheral area between said planar baffle and the forward edge of said shroud being from 50% to 200% of the area of said intake opening to said fan defined by said shroud, a rectangular shaped chamber surrounding at least the forward portions of said fan and said shroud and containing a body of free air for collecting therein the radial flow effected by said planar bafile, said rectangular shaped chamber including said shroud as a portion of the walls thereof and having side walls spaced from the periphery of said fan a distance less than 50% of the diameter of said fan and enclosing the periphery of said fan around at least three sides thereof, said chamber having generally square corners at the enclosed end thereof for damping circulating fiow within said chamber, .and means defining an air outlet opening from said chamber at the end thereof opposite from said end with square corners.-

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