US 1620875 A
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March 15, G- G, CURRIE A FAN WHEEL Filed March 7, 1921 2Sheets-Sheet 'L i .i w )l 02/ Curre MneJJ: Q
v 1,620 875 March 15, 1927. G. G. CURRIE g FAN WHEEL Filed March '7. 1921 2 Sheets-Sheet 2 :l-'i317 lwenfor faz/ Currie Patented Mar. l15, 1927.
GAIL G. CURBIE, 0F LOS ANGELES, CALIFORNIA.
application med March 7, v1921. serial No. 450,289.
This invention relates to exhaust fan wheels for moving large volumes of nonliquid fluids.
An object of the invention is to increase the efficiency of fans of that character.
Fans of this character are driven by belt drive or directconnected motors and for the purpose of this description, it will be shown as' constructed to be direct -driven by an electric motor. The fan may be positioned in any manner desiredv and which is best adapted for the service required; and lts axis. of revolution may extend in any directlon.
Certain terminology relating to the fan yis thereforel somewhat arbitrary in the present specification and claims, and, to avoid confusion, certain directions relative to the vfan and the translation of motion are termed as follows:
Onward signifies the direction in which` the current of air is driven b y the fan; front signies the surface the air leaves 1n its onward course; back and backward 1ndicates the opposite offront and onward;4
forward refers to the direction the blades of the fan move relative to the edges, surfaces or parts of the blades that out the air; rearward and rearwardly signi'fy the opposite direction of forward; center and inner rel fers to the portion of the fan adjacent the hub; and outer, the direction and locus away from the hub.
This invention is broadlyI new', basic and pioneer in that'the fan wheel comprises fan blades having dentated forward edges and having front facesv formed with loops or cavities, the front ioors of which slo e from the dentations onwardly,'forming yetween Y said dentations a channel at the back of the blade so that air pressure on the back of the blade will be supplied to the back of both of the loo s from the adjacent edges of the loops.; an I have found by experiment that. the most etl'ective place at which to locate said channel, is about a, half to two-thirds of the way from the rim to the hub of the wheel. `By `this construction,l the tendency to vacuum produced by each revolving blade will be supplied more readily and directly, and the resistance to revolution Aof the wheel is thereby decreased.
By this construction, the wheel is pro-v vided with an inner and an outer circle orV set of outwardly and onwardly diminishing loops having floors that slope onward from the air cutting edge, and onward in the dij rection of air propulsion, the tloorsotl ther the blade, and to drive it forward at agreater initial velocity than would be given if the floor was at a less angle than the floors of the outer set of cavities.
By this novel construction and arrangement, the'volume of air driven onward at the central part of the wheel is increased, and, a greater volume of air will be driven onward by a predetermined amount ot' power than with former fan wheels.
The inner loops of greater pitch ser've to offset the decrease in peripheral velocity at. the shorter radius, thus moving onward a greater amount of air with a minimum expenditure of horsepower. 4
In common practice the blades mayor may not extend to the hub of the wheel.
An. object of this invention is to make provision whereby the tendency of the fan y 4 lades to create a vacuum behind the blades will be offset by a full supply of air under atmospheric pressure to the back of the blades in the most efiicient manner; and this I accomplish by providing an abrupt rearward oli'set or detent Yin the front edge of the blade near the inner end thereof and producing a loop extending from said oilset to the rear edge of the blade so that the bottom of the loop operates as an air propelling element arranged at a more abrupt angle than the outer portions of the blades thus to increase the volume-and velocity of the air moved onward bythe blades near thel center of the wheel.
The angle of the rear face of theblade; at i the junction of the offset. vwith the main body of the blade forms a backA channel to receive atmospheric air and to distribute it over the back of the blade on both sides ot'- said channel extending from the forward to eliminating any retardation of the motor by reasons of vacuum atthe back of the blades. The inventlon includes the combination with the outer curved pockets of the fanpick up air at a peripheral speed lower than that of the rim of the wheel. t,
Other objects, advantages and features ofinvention may appear from the accompanying drawing, the subjoined detail description and the appended claims.
The accompanying drawing illustrates the invention.
Figure 1 is a fragmental section on line indicated at x1, Figs. 2 and 3, showing the fan attached toa. motor.
Fig. 2 is a reduced rear view of the fan detached from the motor and support.
Fig. 3 is a front view of the fan shown in Fig. 2. y
Figs. 4, 5 and 6 are sect-ions on the respective lines m4, m5, and ai, Fig. 3, looking in the direction of the arrows, respectively.
Fig. 7 is a view of a blank `from which `one of the direct blades may be bent up.
Fig. 8 is a detached View of a blade formed by bending up the blank showir in Fig. 7.
The fan A is mounted in a suitable frame near the hub and form an outer detent a and an air impelling surface b sloping to the plane of the rim 8, and the contour of the back c and also the forward cutting edge l of each blade is broken by the loop e; the cutting edge f of which is located so far from the rear edge that the pitch of the loop e from its cutting edge f to the rear edge g is at a greater angle to the plane of rotation than is the floor of the outer loop and there is a channel 11 at the back of the blade between the loops. The bottom 13 of the loop e extends or slopes backward and onward so as to produce a current of air in the onward direction; that is, away from the motorin parallelism with the axis of rotation, and increases the volume of the onwardly propelled current of air. I have provided the direct blades of my fan with looped dentate forward edges, the loops constituting depressed portions a, d, e and f, the loops e, f having side walls 11 and 12 and bottoms 13 sloping from their front retracted edges d, and f rearwardly with relation to the direction in which the wheel rotates and onward in the diiection of the current of air, the loops or dentations f, thus forming supplementary air impelling faces at a greater angle to the plane of rotation, than the main bodies 9 of the blades.
By v.this construction the fan blades are adaptedvto cause a considerable increase in the volume and velocity of the current of free air amounting to -about 25%, more or less.
The parts 14 act as braces to the blades 9, and increase the rigidity of their attachment tothe spokes. By this construction and arrangement, a channel 15 is provi-ded on the back of the blades at the meeting edges of the loops; and as the fan wheel rotates, the forward points `of the dentated edges of the blades cut the air before the edge of the back channel 15 so that air is allowed to flow to the inner portion of the back face of the outer loop and on the outer portion of the back face of the inner loop, thus allowing air pressure to be applied over the back of the blades from an intermediate point, .thus relieving the vacuum more completely than has heretofore been the case in fan wheels.
In practical operation the fan wheel is rotated in the direction indicated by the large curved arrows in Figs. 2 and 3. The direct blades with ltheir outer and inner loops aand f drive the air onward with marked increase over blades not having the inner pockets.
In the drawings the outer loops are shownas extending about two-thirds of the way from the rim toward the hub and the channels 15 between the loops a and f extends from the forward eedges of the blades to rearward edges respectively. It is thus seen that I have not only succeeded in increasing the volume of air impelled by the wheel, buthave also delivered the vacuum at the back of the wheel, thus taking a measure of strain ofi" of the shaft.
1. A fan wheel comprising fan blades the rear edges of which are in a common plane and the forward edges and front fans of which blades are formed with dentations; the forward faces of said blades being respectively formed with outer and. inner loops and there heilig channels at the backs of the blades between the dentations and loops.
2. A fan Wheel comprising a rim, a hub, and radial spokes between the hub and rim; and alsol comprising fan blades, the rear edges of which are fixed to the spokes respectively, and the forward edgesof which blades are formed with dentations; the forward faces of said blades being respectively formed in loops sloping onward respectively from the dentations to the plane of the spokes and rim.
3. A fan lwheel comprising a rim, a hub, and radial spokes between the hub and rim; and also comprising fan blades, the rear edges of which are fixed to the spokes respectively, and the forward edges of which blades are formed with major and minor dentations; the forward faces of said blades being respectively formed in major and minor loops sloping onward respectively from the major and minor dentations to the plane of the spokes and rim.
4. A fan wheel comprising a rim, a hub, and radial spokes between the hub and rim; and also comprising fan blades, the rear edges of which are fixed to the spokes respectively, and the forward edges of which blades are formed with dentations; the forward faces of said blades being respectively l'orined in loops sloping onward respectively from the deutated edges to the spokes and to the plane of the rim; said lnajor dentations and loops occupying approximately two-thirds of the space between the rim and hub of the wheel.
A fan wheel coinprising'a rim, av hub, and radial spokes between the hub and rim; and also comprising fan blades, the rear edges of which are fixed to the spokes respectively,` and the forward edges of which blades are formed with dentations; the for ward faces of said blades being respectively formed in loops sloping onward respectively from the dentated edges to the spokes and to the plane of the rim, said major dentations and loops occupying approximately two-thirds of the space between the rim and hub of the wheel; and the pit-ch of the floors of the loops being greater than that of the lioors of the major loops.
(i. A fan wheel provided with sheet metal blades, the front edges of which are bowed rearwardly for a distance from the rim and then returned approximately to the plane produced from the rim and there pro vided with a rearward offset to pick up the air near the hub of the wheel; the rear edge of the blade beingy practically straight and in the said plane of the rim ofthe blade.
7. A fan wheel comprising a rim, a hub, and radial spokes between the hub and rim; and also comprising fan blades, the rear edges of which are fixed to the spokes respectively, and the forward edges of which blades are formed with major and minor rearwarddentations; the forward faces of saidblades being respectively formed with major and minor cavities extending'respectively from the major and minor dentations to the plane of theI spokes and rim, saidniajor dentations and c'oncavities` extending approximately two-thirds of the distance from rim to hub of the wheel.
8. A revolving fan` wheel in w-hich the front edgesv of the blades are offset near the axis of revolution.
9. A fan wheel comprisingy fan blades y Garn G. CURRIE.