US2903182A - Fan equipment - Google Patents

Description

S. H. DOWNS FAN EQUIPMENT Sept. 8, 1959 Filed Oct. 17, 1957 2 Sheets-Sheet 1 Sept. 8, 1959 s. H.l DowNs 2,903,182

FAN EQUIPMENT Filed Oct. 17, 1957 l 2 Sheets-Shee 2 United States Patent Oilice Patented Sept. 8, 1959 FAN EQUIPMENT Sewell H. Downs, Kalamazoo, Mich., assignor to Clarage Fan Company, Kalamazoo, Mich., a corporation of Michigan Application Getober 17, 1957, Serial No. 690,726

4 Claims. (Cl. 23o-130) This invention relates in general to a multi-stage blower and, more particularly, to a type thereof having a pair of inlet boxes which are disposed between, and communicate respectively with, a pair of spaced single inlet blower housings, each of which contains a blower wheel mounted upon the same shaft structure.

A recognized need has long existed for air handling equipment capable of moving relatively large volumes of air -at relatively high outlet pressures, without sacricing eciency and at a reasonable cost. Present conventional blower runits are incapable of producing the desired pressures -without exceeding permissible tip speeds and/ or sound levels. As a result of this, centrifugal compressors are being used more frequently, particularly in multiple stages, to provide the higher pressures which are demanded. However, such compressors are presently made from carefully machined parts which are relatively costly to purchase originally and, also, are costlyto maintain, particularly in heavy duty operations where replacements are often needed. Furthermore, the volume produced by such compressors is relatively small by comparison with the cost of the installation.

It has previously been recognized that, if two or more centrifugal blower units could be staged in an efficient manner, it would be possible to produce substantially larger pressures than are presently available with a single blower unit, while at the same time maintaining the lower cost and the higher volumes of centrifugal blowers, by comparison with compressors. It is also recognized that, if the air moving from one stage to another has rotational components around the blower wheel axis as it enters the blower unit of the higher stage, there will be a correspending reduction in capacity. In one form of multiple blower installation, two or more conventional, otherwise independent, blower -units are serially interconnected by the ducts connecting the outlet of one to the inlet of another. Where, for example, two blower |units are so arranged, the space requirements are at least double, as compared with a single unit, and the costs are very materially increased. Even though the increased cost may be acceptable, the increased space requirements are `frequently unacceptable.

Another type of multiple blower installation comprises a double width, double inlet, blower unit having inlet boxes on the opposite sides thereof. A divider plate encircles the double width wheel substantially co-planar with the center plate thereof, thereby dividing the double unit into two single units. However, this arrangement necessitates the use of a very large and heavy shaft and correspondingly heavy bearing structures. More specifically, the shaft must be large and strong, both because of its long span and because the blower Wheel is mounted at the center of such span. Furthermore, because of the necessarily large diameter of the shaft at its center, the wheel hub must be correspondingly large and heavy. The oversized hub not only further `aggravates the shaft size problem, but also produces a reduction in the performance of the blower wheel. Thus, not much is gained by using such a structure, except for saving some space by eliminating two of the four bearing assemblies, which would lbe required by simply providing two separate units. There is no saving in cost because of the increase in cost of the oversized shaft, the oversized hub structure for the blower wheel and the oversized bearing structures required to support the oversized shaft. Furthermore, the resultant structure is relatively heavy and dicult to install, particularly where large units are required.

Another problem, which is characteristic of the double width assembly, arises when the two sides of the assembly are interconnected. As stated above, the double width blower housing is divided by a central wall which, at least in eiect, produces two single width blower units. In order to stage these two units, the outlet Ifrom one blower unit must be connected by a diuct to the inlet box of the lother unit, which necessitates that the connecting duct pass around the other blower unit. Often, particularly in large installations, it is desirable, if not essential, that both blower units discharge in the same direction. Thus, the interconnecting duct must either block the outlet of the blower crossed over or it is necessary to make this crossover through a very tort-uous path, which not only adds to the cost of the installation, but also often introduces rotational components in the air flow which materially reduce the capacity of the unit and may even prevent its use.

Accordingly, a primary object of this invention has been the provision of a multi-stage blower Structure capable of producing -a relatively high total pressure with a minimum of loss in capacity and/or eiliciency, with a minimum of increase in cost of fabrication and operation, and with an absolute minimum of space required for the installation.

A further object of this invention has been the provision of a two-stage blower construction wherein the operational and performance advantages of single blower units are retained, wherein the space required for the connections between, as well las with, the two blower units is held to an absolute minimum while the construction remains capable of variation in installation arrangements, and wherein the weight of the blower wheels is supported upon the shaft substantially adjacent to the shaft supporting bearings, thereby minimizing the size of the shaft required to support the wheels.

Other objects and purposes of this invention will become apparent to persons familiar with this type of equipment upon reading the following specioation and examining the accompanying drawings, in which:

Figure 1 is a side elevational View of a two-stage blower assembly characterizing the invention.

Figure 2 is atop plan view of said two-stage blower assembly.

Figure 3 is a sectional View taken along the line III-III of Figure 2.

Figure 4 is` a side View of a modied struct-ure.

For the purpose of convenience in description, the terms upperj lower and derivatives thereof will have reference to the two-stage blower assembly in its normal position of operation, as shown in Figures l and 3. The terms innen outer, and yderivatives thereof will have reference to the geometric center of the blower assembly and parts thereof.

General description ln order to meet the objects and purposes of this invention, including those set forth above, there has been provided a two-stage blower assembly comprised of a pair of single width, single inlet, blower housings spaced from blower housings so that they communicate with the inlet openings in their respective housings. A shaft, which extends through said blower housings and said inlet boxes coaxially with. said inlet' openings, ,is supportednear-ts opposite/ends upon-'a 'pair of bearing' assemblies'located onthe remotesidessof'said. blower housings. A pair of single'width,l single inlet, blower wheels 'are mounted upon said-shaftwithin -theirrespectivey housings and, therefore, adjacent, respectively, to the bearing assemblies. The outlet of one blowerhousing-.and theinlet ofthe inlet box associated with the other'blower housing preferably open in substantially the-same direction and 'are interconnected` byf-aV U-shaped-.d-uct. Thus, the airand pressure produced i by l the fone fan f unit are: transferred i to. the inlet oftheother fan unit for steppingup such pressure.

VDetailed construction As shown particularly in Figures land 3, the two-stage blower assembly is comprised of two single width, singleinlet, blower housings 11 and 12 and two adjacent inlet'boxes 13 and 14, which are disposed between, and are associated respectively with, saidV housings 1l and l2, said'housings and inlct-boxes-being fabricated primarily from sheet-form materials, as 'shown in Figure 3.V The mutual side walls 16.and 17 between the corresponding blower housings and inlet-boxes are provided with coaxial' inlet' cones i8 and'l9. The blower housings and inlet-boxes are all connectedtogether. and said inlet boxes havev a-common intermediate-wall 2l. A shaft 22 extends completely through both inlet boxes and both blower housingscoaxially. with the inlet cones 1 randy 19. An appropriate shaft seal 20l (Figure 3). may be provided inl the wall. 23 around theshaft 22 for sealing purposes.' Said shaft is rotatably supported nearits opposite'ends by means of the bearings -23 and 24,- which maybe sub-v stantially conventional in construction and which are blower housing il, inlet box'. 21.3 and wheel Sal-comprise a iirst blower unit 34 in the blowerassemblyl0, whereas the-blower housing l2, inlet box 14 and wheel 32 comprise a second blower unit- 35 .in said blower. assembly l0.

The common wall 2l between the inlet boxes 13 and 14 is, in this particular embodiment; sloped with respect' to the axis of the shaft 22,. and the inlet openings 37 and 38 in the inlet boxes 13 and 14,. respectively, enter opposite sides, such as,.for. example, the bottom` and the top, of the assembly 19, where said common wall 2] is at the maximum divcrgency with respect to the particular inlet box. This arrangement materially reduces the spacerequired by said inlet boxes between the blower housings and thereby permits the use of a. smaller shaft 22-than would otherwise be permissible.

In this particular embodiment, the inlet opening 37 `is in the bottom of the inlet box 13 and the inlet opening'38 is in the top of the inlet box 14, and bothblower housings l1. and 12 have upwardly,dischargingoutlets 40 and 4i, respectively. The discharge directions ofthe two blower housings ll and l2 may vary with respect to each other. However, because the two wheels 3i. and 32 are always rotating in the same direction, the rotational directions of their discharge will always be the same, that is, they will both have either a clockwise or a counterclockwise direction of discharge. The direction of discharge from the outlet 4) of the rst blower unit 34 will be substantially the same, hence on the same side of the assembly 10, as the direction of entry of the inlet opening 38 of the inlet box 14 associated with the second blower unit 35. Thus, the outlet 40 can be easily connected to the inlet opening 38 by means of a U-shaped connector duct 42. In this particular embodiment, said duct 42 has an expanding cross-section because the area of said outlet 40 is smaller than the area of said inlet 38. However, the area of said outlet 40 may be the same as, or larger than, the area of said inlet 38.

Operationv The operation of the two-stage blower assembly 10 commences with air being drawn through the inlet opening 37 (Figure 3) in the inlet box i3 and thence passing through the inlet conel'where it enters the inlet of the blower wheel 31 and is driven thereby through the outlet 40 in the blower housing 11. The air leaving the outlet 40 is conveyed to the inlet opening38 by the expanding connector. duct'42 which, inthis embodiment, reduces the air'velocity, thereby increasing the eciency of the rstbloWer'unit' 34. Such air, having thus reached the inlet' box 14 of the ,second blower unit r35', is drawn thereby'through the* inlet cone 19'where the blower wheel 32 discharges such air'through'the outlet opening 41 into any convenient, conventional, duct'system, not shown. It; has been found'th'at', by use of' the two-stage blower assemblylt'substantially as disclosed, air departing from the outlet-'40 in' the rst stageblower unit 34 at a given pressure-andvolume'will depart 'from' the-outlet 4l in the second stage-blower uniti35 'with its pressure approximately doubled.` It has also 'been found that, by having the V'outlet 40 and -inlet opening 38 face in substantially the-same direction; the air moving through the connector duet'42 enters the inlet cone 19 without rotational components about the shaft 22, which components can materiallyreduce-the'performance of the second blower unit 35. This is'due tothe fact 'that the Velocity component offthe air flow from the outlet 4i) to the inlet cone i9 is in ai direction substantially parallel with al plane including the axis of said `shaft`1and parallel with the direction of discharge from: said outlet 405v The fact that .the-wheels 31-and 32 are-disposed very close tothe bearings 23 and 24, respectively, makes it possible touseashaft 22 which is considerably smaller int maximum diameter and, therefore, in weight than the shaft wouldhave to be if the blower wheels were mounted, accordingftoxpresent'teachings, at or near the center thereof. Accordingly, the bearings 23 and 24, as well as theirsupport pedestals 216'y and 27, may also be substantially smaller than would otherwise be required if said wheels weremounted at the center of the shaft. Because'the'blower wheels 31 and 32am-mounted adjacent to the ends of the shaft, where the shaft has its smallest diameter; th'efwheelahubs 33 may also be of a minimum size and Weight.' This not only-permits the use of a shaft 22y havingV a' minimum'. size andi weight, but also results in aof-'interference'with the airflow through the fanwh'eels:andythereforethe b'est performance available.

In order to meet' specific installation requirements, the outlet 40 of the first blower unit 34 may face in a difierent direction, such' as sidewardly, lthan the outlet opening 41'in the second.' blower unit 35i However, the outlet 40 and inlet: opening willl normally face in substantially the-samedirectionto'eliminate undesirable rotational components in the air flow.' Further, where other factors, such Yas ease of fabrication,'. are more important than the maximum saving in:.cost= and 'space requirements, the commonwall 21 may'be substantially perpendicular to the axis ofi-the shaft422, Athereby requiring an increase in the space occupied/by the. inlet ' boxes 13 and 14. Such a condition may occur where it is'desirable to have the inlet opening 37 *atanV angleof 90, instead of 180 as shown, tothe inlet opening-38. However, the most desirable arrangement: includes a sloping common wall 21.

Figure 4- illustrates a multiple blower assembly 50, comprised'of centrifugal blowers S1, 52 and 53 and inlet boxes 55, 56 and 57. The blowers 51 and 52 and the inlet boxes 55 and 56 may be arranged in substantially the same manner as that set forth hereinabove with respect to the assembly of Figure 1. However, the outlet of blower 52 is connected by the duct 58 to the inlet box 57 associated with the blower 53, thereby producing the three-stage blower assembly 50. The blower wheels (not shown) within the blowers 51, 52 and 53 may be supported upon a single shaft 59, which is supported upon the bearings 61 and 62.

Although particular, preferred embodiments of the invention have been disclosed hereinabove for illustrative purpose, it will be understood that variations or modifications of such disclosure, which lie within the scope of the appended claims, are fully contemplated.

I claim:

l. A multi-stage, centrifugal blower assembly for moving a gas, comprising: first and second, single inlet and single outlet, centrifugal blower housings spaced from each other and having axially aligned inlet openings on the opposing sides thereof; a pair of inlet cones secured respectively to said housings concentric with and adjacent to said inlet openings therein; rst and second adjacent inlet boxes disposed between, and communicating respectively with, the inlet openings in said housings, said inlet boxes having single inlet openings facing in substantially opposite directions, the inlet opening of the second inlet box facing in substantially the same direction as the outlet opening of the first blower housing, said housings and inlet boxes being fabricated primarily from relatively thin materials, whereby the combined length of said housings and inlet boxes, axially of said inlet cones, is held -to a minimum; a shaft extending through said blower housings and said inlet boxes coaxially with said cones; bearing means adjacent to the remote, outer sides of said housings and rotatably supporting said shaft, said bearings providing the sole support of said shaft therebetween; a pair of centrifugal blower wheels supported entirely upon said shaft and rotatable therewith within said blower housings, each wheel being disposed between and adjacent to, but spaced from, one of said bearing means and the adjacent one of said cones; and a substantially U-shaped connecting duct extending between the outlet opening of said rst blower housing and the inlet opening of said second inlet box.

2. 'Ihe structure of claim 1 wherein said inlet boxes have a common, intermediate and relatively thin, substantially planar wall which diverges with respect to the opposing wall of each box toward the inlet opening in each box, said common wall having a central opening through which said shaft is freely received; wherein the axis of curvature of said connecting duct is substantially perpendicular to the axis of said shaft, whereby air enters said second blower housing substantially without rotational components about said axis of said shaft; and wherein said U-shaped connector duct has a greater cross-sectional area at its outlet end, adjacent to the inlet opening of said second inlet box, than it does at its inlet end, adjacent to the outlet opening of said rst blower housing.

3. A two-stage, centrifugal blower assembly for moving air, comprising: first and second single inlet and single outlet, centrifugal lblower housings spaced from each other and having coaxial inlet openings on the opposing sides thereof; a pair of inlet cones secured respectively to said housings adjacent to and concentric with the inlet openings thereof, said cones extending into said housings; rst and second adjacent inlet boxes disposed between, and communicating respectively with, the inlet openings in said housings, each inlet box having a single inlet opening disposed in the periphery thereof, the inlet openings of said boxes facing in substantially opposite directions and the inlet opening of said second box facing in substantially the same direction as the outlet opening of the rst blower housing, the walls of said housings and inlet boxes being fabricated primarily from sheet-form materials, whereby the combined length of said housings and inlet boxes, axially of said inlet cones, is held to a minimum, said inlet cones extending into said inlet boxes and said housings; a shaft extending through said blower housings and said inlet boxes coaxially with said cones; bearing means adjacent to the remote, outer sides of said housings rotatably supporting said shaft near the ends thereof, said bearings being located at a minimum distance from each other and providing the sole support for said shaft; a pair of centrifugal blower impellers secured to and supported entirely by said shaft for rotation respectively within said blower housings, said impellers being adjacent respectively to said bearing means, and each impeller having an inlet rim concentric with, adjacent to and spaced from one of said cones; and a substantially U-shaped connecting duct extending between the inlet opening of said second box and the outlet opening of said rst blower housing.

4. A multi-stage, centrifugal fan assembly for moving a gas, comprising: first and second, single inlet and single outlet, centrifugal fan housings spaced from each other and having axially aligned inlet openings on the opposing sides thereof; a pair of annular structures secured respectively to said housings concentric with and adjacent to said inlet openings therein; first and second adjacent inlet boxes disposed between, and communicating respectively with, the inlet openings in said housings, said inlet boxes having single inlet openings facing substantially radially from the axis of the inlet openings of said housings in directions displaced circumferentially from each other at an angle in excess of degrees around said axis of the inlet openings of said housings, the inlet opening of the second inlet box facing in substantially the same direction as the outlet opening of the lirst fan housing, said housings and inlet boxes being fabricated primarily from relatively thin materials, whereby the combined length of said housings and inlet boxes, axially of said annular structures, is held to a minimum; a shaft extending through said fan housings and said inlet boxes coaxially with said annular structures; bearing means adjacent lto the remote, outer sides of said housings and rotatably supporting said shaft, said bearings providing the sole support of said shaft therebetween; a pair of centrifugal fan wheels supported entirely upon said shaft and rotatable therewith within said fan housings, each wheel being disposed between and adjacent to, but spaced from, one of said bearing means and the adjacent one of said annular structures; and a substantially U-shaped connecting duct extending between the outlet opening of said first fan housing and the inlet opening of said second inlet box.

References Cited in the le of this patent UNITED STATES PATENTS 1,408,291 Haentjens Feb. 28, 1922 1,536,573 Drysdale et al May 5, 1925 2,331,299 Blom Oct. 12, 1943 2,368,962 Blom Feb. 6, 1945 2,407,987 Landberg Sept. 24, 1946 FOREIGN PATENTS 316,807 Great Britain Aug. 8, 1929 376,149 Germany May 24, 1923

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