US3300123A - Vane for an axial ventilator and method for producing the same - Google Patents

Description

Jan. 24, 1967 EYH LD ET AL 3,300,123

VANE FOR AN AXIAL VENTILATOR AND METHOD FOR PRODUCING THE SAME Filed May 24, 1965 United States Patent 3,300,123 VANE FOR AN AXIAL VENTILATOR AND METHOD FOR PRODUCING THE SAME Helmut Freyholdt and Alfred Aebischer, Stafa, Zurich, Switzerland, assignors to Ventilator A.-G., Stafa, Switzerland Filed May 24, 1965, Ser. No. 458,341 Claims priority, application Switzerland, May 29, 1964, 7,012/ 64 Claims. (Cl. 230-434) The present invention has reference to an improved sheet metal blade or vane for axial blowers and to a new and improved method for the production of such vane.

Although the use of sheet metal vanes is known for wall ventilators and also for tubular axial blowers, in such instance there was only used sheet iron or steel with relatively thick walls in order to enable welding of the vane to the steel hub of the ventilator. Even though a considerable reduction of the weight of the vanes and thus the weight of the impeller provides important advantages it has been found that thin wall sheet steel causes great difiiculties during welding to the steel hub of the impeller and, furthermore, has the tendency to distort. Likewise, the use of aluminium sheet for this purpose has not proven to be satisfactory since with the welding of aluminium a week location appears at the welding seam.

Accordingly, it is a primary object of the present invention to provide an improved construction of vane or blade for axial blowers or the like operating at relatively high pressures and high rotational speeds which enables the use of thin wall sheets, particularly aluminium sheets.

A further important object of this invention has reference to an improved method of manufacturing vanes for use with axial ventilators and the like.

Another specific object of this invention concerns itself with the construction of an improved blade or vane for fluid-flow machinery, such as axial ventilators, which is relatively easy and inexpensive to manufacture, provides good operating efiiciency, is simple to mount to the hub of the impeller, even can b repositioned after mounting.

The vane or blade designed according to the teachings of the present invention generally comprises a folded sheet strip and exhibits a vane portion and a flexed, slightly arched i.e. slightly convexed base portion. It is to be understood that the inventive blade can be used for practically all ventilators, for instance wall ventilators.

The method of the invention for the manufacture of a sheet metal vane is generally characterized by the features that a sheet metal strip is cut substantially trapezoidal and stamped or otherwise formed into a twisted vane, at the wide end of the vane there is formed a base portion which is flexed at approximately right-angles to the vane proper. This base portion is then formed so as to possess a slightly arched configuration, i.e. is slightly convex, and the fold edge between vane portion and base portion defines the transition from a substantially cylindrical surface into a partial sphere or spherical shell.

By virtue of the inventive vane or blade construction it is possible to dispense with welding of the vane to the impeller hub, and, for example, to use a screw connection. Consequently, it is possible to use thin wall sheet metal e.g. aluminium as material for forming the inventive vanes.

Use of a screw connection enables adjustment and subsequently re-positioning of the inlet or approach angle of the blade. Due to this possibility there is effectively overcome a major disadvantage of previous sheet metal vanes, namely impossibility of subsequently accommodating their approach angle to momentarily encountered operating conditions. This possibility of re-positioning is subordinate for so-called profiled vanes since in con- "ice trast with sheet vanes deviations of the output from the rated value does not bring about important disadvantages for a large efliciency range. Previously, a sheet metal vane or blade was only practically as aerodynamically efficient as a profiled vane in the so-called optimum point. However, the present invention renders it possible to provide a new and improved sheet vane possessing all of the advantages of the profiled vane and the sheet vane and still further advantages, and at the same time does not possess all essential disadvantages of both these type vanes.

Other features, objects and advantages of the invention will become apparent by reference to the following detailed description and drawing in which:

FIGURE 1 is a perspective view of an impeller designed according to the teachings of the present invention wherein one vane has been removed to facilitate illustration of details of the impeller hub; and

FIGURE 2 is a perspective view of a new and improved impeller vane designed according to the invention.

Describing now the drawing, by referring to FIGURE 1 it will be seen that the individual sheet or sheet metal vanes 1 are screw-connected or threaded for instance with a spherical-shaped impeller hub 2. Each inventive impeller vane 1 is composed of a thin-walled, bent sheet strip and possesses a twisted vane portion 3 and an arched e.g. slightly convex, flexed base portion 4 appropriately accommodated to the outer surface 2a of the impeller hub 2. It will be further observed that this base portion 4 exhibits a centering hole 5 arranged at the axis SS passing through the center of gravity of the vane portion 3. A pivot bolt 15 or equivalent structure, conveniently shown in phantom lines in FIGURE 2, is receivable in the centering 'hole 5 and engages with a centering hole 8 (FIGURE 1) provided at the impeller hub 2. Base portion 4 also is seen to possess two further apertures or holes 6 and 7. In addition to a centering hole 8 provided at the impeller hub 2 at the location of attachment of each vane 1 there is further provided two arcuate- shaped slots 9, 10, typically kidney-shaped, through each of which there piercingly extends a respective connecting screw 11 and 12 passing through the holes 6 and 7 respectively of the base portion 4. To complete the connection non-illustrated nuts are threaded at the inner surface of the impeller hub 2 to the screws 11 and 12.

Since the pressed or stamped hollow substantially spherical-shaped base portion 4 of each vane 1 exhibits an internal radius corresponding to the outer'radius of the impeller hub 2, the vane 1, specifically its base por- 7 tion 4 snugly bears against the hub 2 in any given position. Such also permits adjustment of the angular position of the vane 1 about its prescribed axis of rotation, and with the aid of the slots 8 and 9 and the screws 11 and 12 respectively the desired position at the hub 2 is fixed. As previously mentioned each vane 1 is provided with a pivot pin 15 arranged in the centering hole 5 and extending out of the base portion 4 for engagement with a centering hole 8 of the hub 2, to thereby permit turning of the relevant vane 1 about its center of gravity axis SS.

The previously described vane construction permits the use of thin sheet and the use of aluminium as the material for the vanes due to dispensing with a welding operation and by utilizing a screw-connection. As a result, there is provided a considerable saving in weight in contrast ment of the vanes.

Furthermore, the use of aluminium sheet enables production of impellers which are corrosion resistant, and the vanes need not be provided with a costly protective layer safeguarding against corrosion as was previously the case. Moreover, the use of a simple screw connection in place of cumbersome welding of the vanes brings about considerable saving in costs and the time for mounting, so that no skilled labor is required.

Due ot the relatively light weight of the inventive vane relatively small centrifugal forces appear at the impeller, so that the impeller hub can likewise be constructed of lighter weight than was previously the case. Hence, the overall construction including shaft, bearings, housing and foundation can be made lighter, thereby bringing about a further saving in cost.

Moreover, by using thin-walled sheets there are obtained considerably thinner discharge edges at the vanes, so that reduced tunbulence at such location results in better efficiencies and less noise than previously. It need not be particularly stressed that both these factors play an important role in ventilators. There is still further mentioned that the invention provides an improvement of fiow conditions at the inlet edge of the vane due to the use of thin-walled sheets.

The inventive vane is considerably lighter than the known profiled vanes either cast or machined as solid bodies. This is likewise true for vanes formed of plastic, wood or other non-metallic materials.

A further advantage of the inventive sheet metal vane in comparison with known profiled vanes is the smoothness of its surface. While with known profiled vanes it is only possible to obtain a smooth surface by a subsequent costly treatment, for instance by polishing, the inventive vane makes it possible to even obtain a mirrorsmooth surface by proper selection of the vane sheet metal, and, thus, there can be obtained a vane with better efiiciency without additional processing.

In addition to a surface treatment the cast vanes constructed as profiled solid bodies require an extensive aftertreatment, among other things threading has to be cut for the attachment bolts, the vane edges at the inside and outside have to be exactly faced, and the axis of rotation has to be determined. In contradistinction, the inventive vane does not require any after-treating steps, resulting in a considerable saving in cost.

A further disadvantage of the cast profiled vanes not present with the inventive vane is the irregularity in the vane weight which unfavorably affects balancing, so that mounting of the impeller requires a great deal of time and effort. Due to the uniformity in weight of the inventive sheet vane mounting at the impeller is considerably simplified.

Since the inventive vane has its axis of rotation coinciding with the center of gravity axis turning of the vane does not result in any shifting of the center of gravity. This provides a considerable advantage since changing of the vane angle is possible without requiring subsequent balancing. With most of the cast, profiled vanes generally used in ventilators the axis of the attachment bolts does not coincide with the center of gravity axis of the vane, so that upon rotating the vane there is produced a new imbalance. Since balancing of the impeller usually entails returning it to the manufacturer-not possible in many casesthere is generally foregone any re-adjust- Thus, the possibility of accommodating the vane angle to momentarily encountered operating conditions becomes illusory and these profiled vanes are practically used as rigidly mounted vanes.

It is further mentioned that with certain special vane construction for axial ventilators or turbines it is known to have the axis of rotation coincide with the axis of the center of gravity, whereby however, it must be underscored that in so doing certain technical difiiculties and considerable increase in cost is associated therewith. Rotating the vane about its center of gravity axis is possible 4. in the present instance without increased costs due to the inventive construction incorporating a lateral base portion against which bear externally of the rotational axis of the vane the attachment screws. With the exception of certain very expensive casting processes there are no casting processes for profiled vanes which result in such a uni formly cast vane that the theoretical center of gravity axis coincides with the actual center of gravity axis. On the other hand, the inventive light-weight sheet metal vane for the first time renders it possible to bring into coincidence, in the most simple manner, the rotational axis and the center of gravity axis.

Furthermore, by referring to FIGURE 1 it will be recognized that it is possible without any considerable further cost to provide an angle adjustment scale 16 at the base portion 4 of the vane 1 which cooperates with a, marking 17 located at the impeller hub 2 in order to facilitate adjustment of the angle of attack of the vane 1. Consequently, the flexed base portion 4 not only permits turning of the vane 1 with constant position of its center of gravity, rather also very simple and exact adjustment of its position.

The good hearing or contact of the base portion 4 of the inventive vane 1 with the impeller hub 2 further provides tight sealing, this not being previously possible with rotatable profiled vanes without difiiculty. Air-tight sealing between vane 1 and impeller hub 2 provides higher efficiency and reduced air noise.

It is further mentioned that the hollow partial sphereshaped or arched base portion 4 constructed as an integral Component of the vane 1 strengthens this vane at the zone most subjected to load. The fold edge or line 18 of the base portion 4 to a certain extent provides the transition of one partial sphere into a second partial sphere, so that even with relatively thin sheets there is imparted to this edge a particularly high strength and stiffness, Due to this substantially convex or spherical-shaped configuration of the base portion 4 of the vane 1 tensile and bending loads can be transmitted up to both connecting screws 11, 12 without deformation of base portion 4. Since the strongly curved base portions 4 are fixedly screwed to the region of the impeller hub 2 most subjected to load and serve as reinforcement of the hub it is possible to use a light-weight impeller construction.

It is important for ventilator impellers to maintain a uniform impeller gap between the tips of the vanes and the ventilator housing in order that the efficiency is not impaired. Therefore, the spacing of all blade or vane tips from the axis of the impeller must be held within very narrow limits. In prior art impellers having heavy profiled vanes, the tips of the vanes were milled after the vanes were mounted upon the impeller hub. This expensive operation, for instance milling or grinding of the vane tips, up to the present was avoided with rigid sheet metal vanes, firstly, because such was associated with difficulties, and secondly, because the opinion prevailed that sheet metal vanes at any rate were cheap alternatives having poor efficiency.

Since the inventive vane construction should at least be equally eflicient in all respects to all previous. constructions, a uniform impeller gap can be obtained if from the start all vanes are formed somewhat short, whereby during mounting the vanes can be brought to the desired external diameter of the impeller by using underlays or supports formed of thin foils or sheets. This renders it possible to satisfactorily avoid subsequent working of the vane tips.

In order to ensure against any displacement of the rotational axis during turning of the vane, particularly with impellers rotating at high speeds, each base portion 4 of the vane 1 can be provided with the previously considered pin 15 engaging in an associated guide hole 8 provided at the impeller hub 2, such pin serving as pivot shaft or axis for the vane.

To simplify cutting of the sheet metal vane from a strip of sheet and to make the punching or stamp-ing tools necessary for such work cheaper, the present invention contemplates cutting a sheet metal strip into trapezoidal shape. Moreover, according to the invention, this sheet metal strip is pressed or otherwise formed into a twisted vane and at its wide end there is flexed at approximately right angles to the twisted vane portion the base portion 4. The latter is formed so as to be slightly convex, whereby the fold line or edge 18 between vane portion 3 and base portion 4 forms the transition of a substantially cylindrical generated surface int-o a substantially partial sphere. As a result, aerodynamic design of the sheet metal vanes is such that both lengthwise edges of the cut vane are linear.

Although in most instances it would be desirable to provide the impeller with tan inflow hood to increase the efficiency, this expedient has previously been dispensed with since such hood must be separately manufactured and subsequently connected with the ventilator housing. These additional costs could not be readily justified.

However, since the impeller hub 2 of the inventive axial ventilator can be manufactured of sheet metal it is possible to construct this impeller hub 2 in such a manner that its forward portion 2b is eflective as an inflow hood, so that without any considerable increased cost there is obtained a combined impeller hub and inflow hood 2, 212 respectively.

With previously known impellers the impeller hub is generally broken off into a sharp edge at the outflow side so that formation of turbulence and noise could not be prevented at this location. Furthermore, with such known constructions it was not possible to reverse the flow direction with respect to the impeller hub since the subsequent application of an inflow hood at the original outflow side was not possible due to a lack of space.

On the other hand, with the inventive ventilator it is possible to aerodynamically configure the impeller hub 2 at both sides. Since there is likewise formed a bent-over collar, generally designated by reference character 2c, at the outflow side of the hub 2 there is not only obtained an aerodynamically favor-able impeller construction usable in both flow directions, rather also an additional stiffening of such hub.

It is still further to be mentioned that the hollow spherical-shaped impeller hub 2 permits simple application of the balancing weights from one side both in the forward and also rea-r balancing planes, so that the impeller does not have to be removed from the balancing machine, as was previously the case, in order to be able to apply the balancing weights to the side facing the machine. To this end, the impeller hub could be provided with a marking edge for the forward balancing plane. Furthermore, the hollow spherical-shaped hub 2 enables adhesive application of the balancing weights 1'9; previously such always had to be either screwed or welded. Adhesive application of the weights 19 which is both simpler and cheaper is possible with the inventive construction of impeller hub 2 because no danger exists that with possible failure of the adhesive material the weights can be propelled away during the balancing operation itself or after. wards. In contrast with previous impeller hub shapes the 6 hollow spherical-shaped hub always retains the balancing weights within its region.

While there is shown and described present preferred embodiment of the invention it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practised within the scope of the following claims.

What is claimed is:

1. In combination, an axial flow impeller having an annular hub with an outer spherical shaped surface portion, a plurality of vane means mounted on the spherical shaped hub portion, each vane means comprising a folded sheet metal strip incorporating a vane portion and a base portion, said base portion having a substantially spherical shaped surface corresponding to that of said spherical shaped surface portion, means adjustably securing the base portion of said vanes to the spherical shaped surface portion, said means comprising a central centering means and a pair of clamp fasteners engaging slots in the spherical shaped hub surface portion whereby said vane means on the release of the securing means may be pivoted about the central centering means.

2. The combination defined in claim 1, wherein the inner opposed surface of said annular hub is also spherical shaped; and including balancing weights cemented to said inner opposed surface.

3. The combination defined in claim 1, wherein said centering means is a pivot pin on said base portion and an opening in said spherical shaped surface portion for accepting said pin.

4. The combination defined in claim 1 wherein each base portion is provided with a scale for adjusting the angular position of said vane means at the impeller hub, said spherical shaped surface portion being provided with a respective surface marking cooperating with said scale of the associated vane means.

5. The combination defined in claim 1 wherein said impeller hub is provided with an inflow hood in front of said plurality of vane means and an outflow collar behind said plurality of vane means.

References Cited by the Examiner UNITED STATES PATENTS 525,928 9/1894 Thompson 230134 984,812 2/1911 Hearst 230134 1,476,137 12/1923 Bilan 230- 1,603,076 10/1926 Hanson 29-156.8 2,915,238 12/1959 Szydlowski 230134 2,985,952 5/1961 Nutter et a1 29l56.8 3,085,632 4/1963 Schwegler -l67 3,201,857 8/1965 Klonoski 29156.8

FOREIGN PATENTS 1,121,516 5/1956 France.

949,899 9/1956 Germany.

167,581 2/ 1921 Great Britain.

631,231 10/ 1949 Great Britain.

702,312 1/1954 Great Britain.

DONLEY J. STOCKING, Primary Examiner.

HENRY F. RADUAZO, Examiner,

Claims (1)

1. IN COMBINATION, AN AXIAL FLOW IMPELLER HAVING AN ANNULAR HUB WITH AN OUTER SPHERICAL SHAPED SURFACE PORTION, A PLURALITY OF VANE MEANS MOUNTED ON THE SPHERICAL SHAPED HUB PORTION, EACH VANE MEANS COMPRISING A FOLDED SHEET METAL STRIP INCORPORATING A VANE PORTION AND A BASE PORTION, SAID BASE PORTION HAVING A SUBSTANTIALLY SPHERICAL SHAPED SURFACE CORRESPONDING TO THAT OF SAID SPHERICAL SHAPED SURFACE PORTION, MEANS ADJUSTABLY SECURING THE BASE PORTION OF SAID VANES TO THE SPHERICAL SHAPED SURFACE PORTION, SAID MEANS COMPRISING A CENTRAL CENTERING MEANS AND A PAIR OF CLAMP FASTENERS ENGAGING SLOTS IN THE SPHERICAL SHAPED HUB SURFACE PORTION WHEREBY SAID VANE MEANS ON THE RELEASE OF THE SECURING MEANS MAY BE PIVOTED ABOUT THE CENTRAL CENTERING MEANS.

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