US2838228A - Automatically adjustable centrifugal fan - Google Patents

Description

June 10, 1958 c. M. BREMNER AUTOMTICALLY ADJUSTABLE CENTRIF'UGAL FAN Filed Aug. 9, 195e 2 Sheets-Sheet 1 (NUEKTOQ.

C. M. BREMNER AUTOMATICALLY ADJUSTABLE CENTRIFUGAL. FAN

Filed Aug. 9, 1956 2 Sheets-Sheet 2 inited States Patent AUTOMATICALLY ADJUSTABLE CENTRIFUGAL FAN Claude M. Bremner, Cranbrook, British Columbia, Canada, assignor to ivi. C. Marcotte, Hudson Bay, Saskatchewan, Canada Application August 9, 1356, Serial No. 603,051

il Claims. (Cl. 230--114) My invention relates tol new and useful improvemeiits in fans, particularly fans adapted to be used in agricul tural machinery, such as threshing machines and combines, in which the fan directs Ia stream of air through various screens and the like in order to lseparate chaff from grain, the principal object and essence of my invenautomatically increases the volume of air when the speed thereof decreases and vice versa, thus enabling a larger volume of air to be sent through the machine when, for example, it strikes a relatively heavy stand of grainwhich slows `down the machine. Alternatively, when the machine strikes a relatively light stand of grain, the tendency is for the machine to speed up, which normally would increase the volume of air put out by the fan. However, with this device the volume of air automatically decreases under these conditions, thus enabling much more efficient separation to take place undera variety of conditions.

A still further object of my invention is to provide a device of the character herewithin described which requires only .one setting, such settings being made by the operator while the `machine is running and without any danger attendent thereto. i f

A still further object of my invention is `to provide a device of the character herewithin ydescribed which 'eliminates'the necessity for shutters and flaps and other `such means normally associated with fans of this nature for controlling the volume of air ldisplaced thereby.

Yet another object Aof my invention is to provide a device of the character herewithin described which is relatively simple in construction, economical in manufacture, and otherwise well suited to the -purpose for which it is designed.

With the foregoing objects in view. and such vother o'bjects `and advantages as will vbecome apparent to those skilled in the art to which this invention relates as this specification proceeds, my invention consists essentially in the arrangement and construction of parts all as hereinafter more particularly described, reference being `had to the accompanying .drawings in which:y

Figure l is a side sectional elevation 'of my device taken substantially along the li-nes -1-1 of Figmre 2.

Figure 2 is a sectional elevation at right angles to Figure ltaken along `thelines 2-2of Figure 1.

Figure 3 is an enlarged partially sectioned of the trunnion gear and cam per se.

In the drawings likeV characters of reference indicate corresponding parts in the Idiiferent Ifigures. t

Proceeding now to describe my invention Vin detail, it will be seen upon reference to the accompanying drawings that l'hayeillustrated a fan unit'collec'tively"desigelevation nated 1 mounted upon a drive shaft 2, which is journalled for rotation within bearings 3, it being understood that these bearings are supported by conventional structure, and that the fan unit i is normally surrounded by duct work also conventional in character in order to direct the air to where it is required.

The fan unit l comprises a spider collectively designated 4, which includes asupporting hub 5 secured to shaft 2 by means of set screws 6. A web 7 extends outwardly from the shoulder 5 and carries an annular casing component 8, the purpose of which will hereinafter be described.

The casing S is vmade in two halves, 8 and S', joined together centrally by means of lugs 9l and bolts 10, and -it will be noticed that the half 8' of the casing includes enclosing flanges 11. Bearing apertures 12 are formed symmetrically around the perimeter of the casing land supports for partial rotation spindles or shafts 13, the ends l@ of which extend beyond the sides of the casing.

Substantially rectangular planar fan blades 15 are providedwith securing brackets i6 which terminate in bosses i7, said bosses engaging over the aforementioned ends i4 of the shaft i3 and are secured thereto by means of set screws 1S.

Within the enclosure i9 formed by the casing 8 is situated what l define as trunnion means takingthe form of a gear journalled for independent rotation upon shaft 2 by means of roller or ball bearings 2l. Means collectively designated 22 extend between this trunnion gear 20 and the fan blade shaft 14 for rotating said shaft within limits and in this embodiment these means take the form of sector gears 23.V Y

Each .of these sector gears 23 is provided with a hub 24' by which it is secured to the shaft 13 medially along the length thereof and within an annular recess 25 formed when the halves S and 8' of the spider casing are secured together. The perimetrical portions 26 of the sector gears are provided with teeth 27 engageablc with the teeth 28 of the aforementioned trunnion gear 20.

From a perusal'of the foregoing it will be appreciated that movement of the trunnio-n gear rotatively will cause corresponding angular movement of the fan blade 15 due to the engagement of the trunnion gear with the sector gears and it is to be appreciated that this movement is equal toall fan blades situated upon the unit.

One face 29 o-f the trunnion gear 20 is provided with .a pair of inclined cams 3b as clearly shown in Figure 3 and these cams are engageable byl means collectively desig. nated 3l adapted to be shifted endwise upon shaft 2. The means 31 consist of a cylindrical housing 32 surrounding shaft 2 and being splined thereto for limited endwise movement, reference character 33 indicating the splines upon the shaft 2. It will be appreciated that the inner bore of the housing 32 is also vsplined to lengage splines 33 thus permitting the housing to be revolved by shaft 2 but also permitting endwise movement thereupon.

Adjacent the end 34 of the housing I have provided -a plurality of rollers 35 journalled for rotation by means of bolts 36, it being seen that the plane of rotation of these rollers is parallel to the longitudinal axis of shaft 2. it will also be observed that the perimeters of these rollers are adapted to engage the aforementioned cam upon the trunnion gear 2d.

It will therefore also be seen that endwise' movement of the housing 3l will cause the rollers 35 to bea-r against the cam 30 thus causing rotation of the trunnion gear and hence ro-tation of the sector gears which will alter the angle of inclination of the fan blades l5 and'that also the reverse action will be true.

Means collectively designated 3S are provided to .control this rotative movement of the trunnion gear 26 and take the form of an open-ended cylinder 39 mounted externally of the spider casing 4. A rod 40 is freely slidable through this cylinder 39 but endwise movement of the rod in a leftward direction with reference to Figure l is restricted by means of apin 41 passing through the shaft and engaging within the end 42 of the cylinder 39.

The end 43 of the rod is screw-threaded and passes through a ring 44 which freely encircles an annular groove 45 formed upon the end 46 of the aforementioned housing 32. This groove'is made by providing a shoulder upon the housing and encircling the outer end of the shoulder with sleeve 47 held in position by means of set screws 48.

The aforementioned end 43 of rod 40 is held in the desired position by means of clamped nuts 49 one upon each side of the ring 44 and these clamp nuts together with the screw-threaded end 43 of the rod constitute a primary adjustment for the device as will hereinafter be described.

Within cylinder 39 is a relatively heavy duty coil spring 50 reacting between pin 41 on the rod and an adjusting nut l screw-threadably engageable within the other end 52 of the cylinder so that tightening thc adjusting nut 51 inwardly increases the tension on the spring S0 reacting upon the rod 40.

In operation, the initial setting of the rod 40 is made by means of the aforementioned locking nut 49 so that for example the pressure of spring 50 forces the rod 40 leftwardly with reference to Figure l thus rotating the trunnion gear 20 so that the fan blades are in the position shown in Figure 2.

The fan, which is adapted to rotate in the direction of arrow 3 displaces a given volume of wind for a given speed of rotation and the adjusting nut 51 should be adjusted so that the pressure generated by the air against the blades causes them to incline towards the position shown in phantom in Figure 1.

Assuming that the desired volume of air is produced for a given speed of rotation with the fan blade approximately half way between Vthe position shown in phantom and the position shown in full line, it will be appreciated that as long as the speed of rotation is maintained, a constant volume of air will be produced.

However if a relatively heavy stand of grain is encountered, the machine will perforce slow down due to the loading of the threshing cylinders and the like. This causes a slowing down in the speed of rotation of the fan thereby decreasing the air pressure upon the surfaces of the blades. Assuming that pin 41 has moved inward in 39 from its limiting position shown in Fig. l, these circumstances permit spring 50 to force rod 40 leftwardly slightly with reference to Figure l thus causing the rollers 35 to turn the trunnion gear 20 in a direction to move the blades towards the position shown in full line in Figure 2, thus increasing the volume of air displaced by the blades and bringing it back to the original volume of air being displaced prior to the slowing down of the machine.

Conversely if a relatively light stand of grain is encountered, the machine will tend to speed up thus increasing the air pressure upon the surfaces of the blades which will cause them to move towards the direction shown in phantom in Figure 2. This will rotate the trunnion gear and the cams against rollers 35 and force the rollers together with housing 31 rightwardly with respect to Figure l and against pressure of spring 59. It will be appreciated that the design of the blades and the upper and lower limits of the speed of rotation thereof should be such that the aerodynamic air pressure effect is always greater than the inherent centrifugal effect in order that the said aero-dynamic effect can control the angular relationship of the blade thus maintaining the constant air volume desired.

In both of the foregoing examples, it will be appreciated that the trunnion gear 20 although freely rotatable upon shaft 2, is not capable of endwise movement due to 4 the provision of a thrust race 54 between the hub of the trunnion gear and the hub 5 of the spider.

From the foregoing it will be appreciated that a constant volume of air can be maintained within limits irrespective of the speed of rotation of the fan unit.

Since various modifications can be made in my invention as hereinabove described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained'in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

What I claim as my invention is:

l. A fan adapted to automatically maintain a given volume of air within limits, comprising in combination a drive shaft journalled for rotation between bearing, a spider casing secured to said drive shaft and rotatable therewith, a set of fan blades, shafts for each of said fan blades mounted around the perimeter of said spider casing for limited rotative movement relative thereto, trunnion means journalled for rotation upon said shaft, means cooperating between said trunnion means and said fan blade shafts whereby relative movement of said tunnion means provides relative movement to said fan blades, means on said shaft mounted for limited endwise movement thereon engaging said trunnion means and adapted to rotate said trunnion means within limits, and adjustment means externally of said spider casing adapted to pleselect said limits of rotation on said trunnion means, said means cooperating between said trunnion means and said fan blade shaft including a segment gear secured to each of said fan blade shafts adjacent the apex of said segment gear, said trunnion means taking the form of a gear for bearing rotation on said shaft, said gears on said fan blade shalt engaging said trunnion gear.

2. The device according to claim l in which said gears on said fan blade shaft take the form of segment gears secured to each of said fan blade shafts adjacent the apex of said segment gears.

3. The device according to claim l in which said means on said shaft mounted for limited endwise movement thereon includes a carrier surrounding said shaft, and being in splined relationship therewith for said endwise movement, rollers journalled for rotation around one end of said carrier in a plane parallel to the longitudinal axis of said shaft, and cam faces on one side of said trunnion means engageable by said rollers.

4. The device according to claim l in which said ad justment means includes an annular groove within said means adapted to rotate said trunnion means, an endshifting ring freely mounted within said groove, a rod extending from said ring, a guide cylinder for said rod, and spring means reacting between said rod and said cylinder, and an adjusting nut within one end of said cylinder for adjusting the tension of said spring.

5. The device according to claim 3 in which said adjustment means includes an annular groove within said means adapted to rotate said trunnion means, an end-shifting ring freely mounted within said groove, a rod extending from said ring, a guide cylinder for said rod, and spring means reacting between said rod and said cylinder, and an adjusting nut within one end of said cylinder for adjusting the tension of said spring.

6. The device according to claim 2 in which said means on said shaft mounted for limited endwise movement thereon includes a carrier surrounding said shaft, and being in splined relationship therewith for said endwise movement, rollersjournalled for rotation around one end of said carrier in a vplane parallel to the longitudinal axis of said shaft, and cam faces on one side of said trunnion means engageable by said rollers.

.7. The device according to claim 2 in which said adjustment means includes an annular groove within said means adapted to rotate said trunnion means, and endshifting ring freely-mounted within said groove, a rod extending from said ring, a guide cylinder for said rod, and spring means reacting between said rod and said cylinder, and an adjusting nut within one end of said cylinder for adjusting the tension of said spring.

8. The device according to claim 6 in which said adjustment means includes an annular groove within said means adapted to rotate said trunnion means, an endshifting ring freely mounted within said groove, a rod extending from said ring, a guide cylinder for said rod, and spring means reacting between said rod and said cylinder, and an adjusting nut within one end of said cylinder for adjusting the tension of said spring.

References Cited in the le of this patent UNITED STATES PATENTS Moran Dec. 4,

Strite Feb. 14,

Wagner Aug. 19,

Scofield Sept. 5,

Mader Aug. 21,

FOREIGN PATENTS Germany Nov. 7,

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