US 3211364 A
Description (OCR text may contain errors)
Oct. 12, 1965 Filed Oct. 30, 1963 FlG-6 FIG -7 Q R-Bo FIG 43 79 W. H. WENTLING ETAL /JBY JOSEPH c. GANTNER BLOWER WHEEL 5 Sheets-Sheet 2 FIG-12 6O\67 63 66 INVENTORS WILLIAM H. WENTLING 8 ATTORNEYS ,1965 w. H. WENTLING ETAL 3,21
BLOWER WHEEL Filed Oct. 30, 1963 3 Sheets-Sheet 3 Pg; -14 I6 88 8O FIG-19 FIG-2O FIG-23 125 FIG-24 I35 5 mo INVENTORS 80a. WILLIAM H.WENTL|NG a BY JOSEPH C.GANTNER ATTORNEYS M M M United States Patent 3,211,364 BLOWER WHEEL William H. Wentling, Dayton, and Joseph C. Gantner, Kettering, Ohio, assignors to The Lau Blower Company, Dayton, Ohio, a corporation of Ohio Filed Oct. 30, 1963, Ser. No. 320,062 7 Claims. (Cl. 230-134) The invention relates generally to air moving devices, and particularly to the improved construction of blower wheels.
A large percentage of the single inlet centrifugal blower wheels used today are fabricated from sheet metal by forming a plurality of individual blades having end flanges thereon, and then spinning an end ring and back plate over these flanges to lock the blades in the desired spaced relationship. Another popular construction utilizes a louvered blade sheet which is rolled into a tube and has an end ring and back plate suitably secured to the opposite ends thereof. The same methods are also used to construct double inlet blower wheels by securing an end ring to each end of the blades and securing a center disk intermediate the end rings.
The primary advantages of blower wheels of this type are their relatively low cost and light weight, and the ease with which the complex blade shapes required for eflicient operation are formed. However, they suffer from a serious disadvantage in that they are susceptible to failure when subjected to the centrifugal forces present when they are rotated at high speed, or when subjected to vibration, e.g., as produced when the blower wheel is driven by an internal combustion engine. In order to construct a blower wheel which will withstand these forces and vibrations, it is necessary to weld the blades to the end ring and back plate or center disk, to form an integral blower wheel. Such a structure is dilflcult and expensive to manufacture, and it is necessarily relatively heavy since the components must be of heavier metal stock in order to permit brazing or welding.
Accordingly, it is an important object of this invention to provide improved blower wheels of the single or double inlet type which are not subject to failure as a result of the vibrations or centrifugal forces present during high performance operation thereof.
Another object of this invention is to provide a blower wheel of the aforesaid type which is light in weight and capable of being inexpensively manufactured at high speed, and further to provide a process for producing this improved blower wheel by using present machinery and equipment without major modifications, thus reducing the cost of producing the blower wheel.
A further object of the invention is to provide an improved process for producing an integral blower wheel of single or double inlet type which has the advantages of substantially all the fabricated blower wheels known today and which can be utilized at speeds and vibration rates substantially above those of present day blower wheels.
Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.
In the drawings- FIG. 1 is a schematic illustration of the steps involved in the process of the invention;
FIG. 2 is a perspective view of a typical single inlet blower wheel in accordance with the invention;
FIG. 3 is a perspective view of one end of a blade used in the blower wheel shown in FIG. 2;
FIG. 4 is a cross-sectional view through a portion of the blower wheel shown in FIG. 2 subsequent to fabrication by conventional methods;
FIG. 5 is a sectional view similar to FIG. 4 and illustrating the blower wheel after the completion of the process;
FIG. 6 is a sectional view through the back plate after the fabrication step;
FIG. 7 is a sectional view similar to FIG. 6 after the process has been completed;
FIG. 8 is a sectional view taken along the line ,88 of FIG. 4;
FIG. 9 is a sectional view similar to FIG. 8 taken along the line 99 of FIG. 5;
FIG. 10 is a sectional view taken essentially along the line 1010 of FIG. 4;
FIG. 11 is a View similar to FIG. 10 taken along the line 11--11 of FIG. 5;
FIG. 12 is a sectional view through the center disk arrangement of another embodiment of the invention prior to the completion of the process;
FIG. 13 is a sectional view showing the blade arrangements of the double inlet wheel shown in FIG. 12. after the completion of the process;
FIG. 14 is a sectional view of another embodiment of a double inlet blower wheel;
FIG. 15 is a perspective view of a blade used in the blower wheel shown in FIG. 14;
FIG. 16 is a sectional view taken essentially along the line 1616 of FIG. 14;
FIG. 17 is a sectional view taken along the line 1717 of FIG. 16;
FIG. 18 is a sectional view similar to FIG. 17 but after the process has been completed;
FIGS. 19 and 20 are sectional views taken along the line 19-19 of FIG. 17 showing this structure before and after the brazing step, respectively;
FIGS. 21 and 22 are sectional views taken along the line 2121 of FIG. 16 showing this structure before and after the brazing step, respectively;
FIG. 23 is a fragmentary sectional view showing another embodiment of the center disk structure; and
FIG. 24 is a sectional view similar to FIG. 23 but after the brazing step.
Referring to the drawings, which illustrate preferred embodiments of the invention, FIG. 1 shows schematically the process of the invention as it is employed to produce an integral blower wheel 10 of the single inlet type. The first step includes the production of the end ring 11 and back plate 12 from relatively thin sheet metal stock 13, such as steel, which has been coated on both sides with a thin layer of copper or similar metal having a melting point substantially lower than that of the sheet metal.
The individual blades 15 having the flanges 16 on the opposite ends thereof are formed from an uncoated strip of sheet metal stock 18, and then the blades 15, end ring 11 and back plate 12 are formed into the blower wheel 10 by spinning, or otherwise deforming, the outer peripheries of the end ring and back plate over the flanges 16 of the blades 15. Suitable apparatus for securing these components together is described and claimed in the copending US. application of Wentling et al., Serial No. 215,988, filed August 9, 1962 and assigned to the assignee of this invention.
Subsequently the reinforcing disk which is also copper coated is secured in contact with the back plate 12 by deforming the flange 23 on the hub 22, as shown in FIG. 6, to lock the back plate 12 and disk 20 between the shoul der 24 of hub 22 shown in FIG. 1 and the. deformed flange 23 on FIG. 6. The fabricated blower wheel 10 is then placed in a furnace F or otherwise subjected to a temperature slightly above the melting point of the copper for the brazing step which causes the copper to melt 3 and flow into the space between the adjacent surfaces of the end ring 11, the back plate 12 and the blades 15.
Capillary action causes this molten metal to flow into small corners and voids, and between surfaces which are tightly in contact to fill substantially completely the spaces between adjacent surfaces. When the heat is removed and the blower wheel allowed to cool slowly, the copper solidifies causing the end ring 11 and back plate 12 to be integrally fused at opposite ends of the individual blades 15, so that a rigid and very strong blower wheel is formed. Similarly, the reinforcing disk and hub 22 are integrally fused to the back plate.
Although the process has been initially described in connection with a single inlet blower wheel having a particular construction, it is not so restricted and may be utilized to produce other types of single inlet wheels, as well as double inlet blower wheels of many dilferent types, as will be described hereinafter.
The proper thickness coating on the end rings, back plates and center disks is important since an inadequate thickness will result in inferior fusing action, whereas excessive copper will puddle into large masses thus complicating the balancing of the blower wheel. Preferred results have been obtained by using copper in a thickness of .0005", and a coating within approximately the range of .0003" to .001" which will create a satisfactory integral connection between the components of the blower wheel.
Referring now to the specific construction of a single inlet blower wheel as shown in FIGS. 211, FIG. 3 illustrates the blade 15 having identical flanges 16 projecting longitudinally from each end thereof adjacent the leading edge 25 of the blade surface 26 for use in securing the blades 15 to the end ring 11 and back plate 12. Each of the flanges 16 includes a tapered section 30 having an axially extending shoulder 31 at its outer end, and from the outer edge thereof the upturned flange 33 projects in a plane parallel to the leading edge 25 of the blade under consideration. Th edge 34 of each upturned flange 33 also lies radially inwardly of the blower wheel from the leading blade edges 25 so that the outer diameter of the end ring 11 and back plate 12 will be substantially equal to the outer diameter of the blower wheel at the blades.
The end ring 11 and back plate 12, as seen in FIG. 4, have identical outer peripheral constructions which include a groove 35 for receiving the flanges 16 of each blade 15. The grooves 35 are defined by an inner support wall 36 which supports the lower surface of the shoulder 31, a radial side wall 40 which engages the outermost side wall of the flanges 33, and the upper deformable wall 42 which has been spun over the inner side of the flanges 33 and into engagement with the top surface of the shoulder 31. The side edge 43 of the blade surface 26 is compressed against the radially inwardly extending lip 44 during the spinning operation, and thus the end ring 11 and back plate 12 rigidly lock the blades 15 in position against movement in any direction. The blower wheel 10 is fabricated substantially in accordance with the teaching of the copending US. application of Wentling et al. Serial No. 270,582, filed April 4, 1963, now Patent No. 3,165,258, and assigned to the assignee of this invention.
During the heating or brazing step, the copper coating on the end ring 11 and back plate 12 is melted and flows into small spaces and between adjacent surfaces to fuse the blower wheel together, as shown in FIGS. 5, 7, 9 and 11. Upon cooling, solid beads are formed in the area where the flanges 16 and the end ring 11 and back plate 12 were secured together. Similarly the side edges 43 of the blade surface 26 become fused to the adjacent portion 44 of the end ring 11 and back plate 12, as shown in FIG. 5. The relieved corners 52 on the blade flanges 16 may create small voids 53 in thebeads 50 (FIGS. 9
and 11) but otherwise these beads are a substantially solid integral mass of metal.
The hub 22 and the coated reinforcing disk 20 are also fused to the back plate 12 to form an integral hub structure, as shown in FIG. 7, and the circumferential groove 54 in the back plate 12 cooperates with the reinforcing disk 20 to create a tubular reinforcing rib 55 which resists angular and twisting forces on the back plate 12. Moreover, the hub 22 also becomes integrally secured to the back plate 12 and the reinforcing disk 20 for providing additional resistance to vibration without a significant increase in weight.
Another embodiment of the invention is shown in FIGS. 12 and 13, and includes a double inlet blower wheel 60 formed by interconnecting, prior to the brazing step, two single inlet blower wheels 15a and 15b, of the type described above, with their copper coated back plates 12a and 12b clamped together by the hub 61. The blower wheel 15a and 15b are substantially identical except that one is designed for clockwise rotation and the other for counterclockwise rotation, so that when they are placed with their back plates in contact, they require rotation in the same angular direction.
To assemble the wheel 60, the hub 61 is first inserted through a central aperture in each of the back plates 12a and 12b, and then the flange 62 on one end thereof is deformed to clamp the back plates 12a and 12b between this flange and the shoulder 63 of the hub 61. In this position, the side walls 65 of the outer peripheral flanges 66 and 67, and the intermediate walls 68 between the slanted shoulders 70 and the reinforcing beads 72, are in intimate contact.
The brazing and subsequent cooling operations form a double inlet blower wheel having a single integral center disk 76 (FIG. 13) with the hub 61 integral therewith. The radially inner and outer reinforcing ribs 77 and 78 which are formed in the center disk 76 are tubular in cross-section and extend circumferentially of the hub 61 and thus add rigidity and strength to the blower wheel 75 for resisting the compound forces which would cause failure of conventionally fabricated blower wheels. The peripheral flanges 66 and 67 of the back plates 12a and 12b become fused into a solid bead 79 which adds further strength to the blower wheel 60. Each of the single inlet blower wheels 15a and 15b which form the double inlet blower wheel 60 also has the structural features shown in FIG. 5, such as the solid bead 50 around each inlet.
Referring now to FIGS. 14-22, which illustrate another embodiment of a double inlet blower wheel 80, a typical blade construction is shown in FIG. 15 where the blade 81 has a curved working face 82 which is arcuately shaped in a uniform manner over the major portion of the length of the blade. Each end of the blade face 82 of the blade 81 is turned over at approximately right angles thus forming a laterally extending side wall 84 of the convex side of the blade. Beyond the walls 84, the support walls 85 are formed and extend perpendicularly to the side walls 84, and the flanges 86 are bent upwardly at right angles to the support wall 85 so that the flange 86 projects radially outwardly of and overhangs the working face 82 of the blade 81.
The copper coated end rings 88 are suitably spun onto the opposite ends of the blades 81 in much the same manner as described above in connection with the embodiment shown in FIG. 2. As will be evident from FIG. 14, the end rings 88 are provided with offset shoulders 91 and inwardly projecting flange portions 92 which are adapted'to interfit with the support wall 85 and the overhanging end flange 86. The projections on the ends of the blades thus are received within the end rings and supported loosely on the shoulders 91 with the flanges 86 extending radially outwardly. The number of blades and the peripheral extent of their end flanges are preferably such that they are separated by a small clearance which is used to lock the blades securely in position, as will be explained.
As shown in FIG. 17, the length of the portion 91 of the end ring 88 is longer than the height of flange 86, and thus in finished position, a lip 93 is formed on the inner portion of the ring. This lip bears against the outer surface of the blades 81 and extends axially of the blades toward the end ring on the opposite end of the blower wheel. As shown in FIGS. 16, 19 and 21, the width of the peripheral extent of flanges 86 is so limited that small clearance or gaps 95 are provided between adjacent blades. The actual dimensions of these gaps need not be large, but it is found that where even a limited space is provided, a desirable interlocking action is secured. The gaps should be present at least at the outer peripheries of the flanges 86 and may continue radially inwardly so that, as shown in FIG. 19, adjacent blades are actually separated from each other at all points.
This locking action is accomplished during the spinning operation when substantial forces are developed in the material of the copper coated end rings 88 tending to force the metal into the gaps 95 provided between the end flanges 86 of the blades 81. This results in forming small projections 96 which extend into the gaps 95 and interlock each blade to hold it securely in position in the end rings.
The projections 96 on the outer periphery of the end rings 88 in conjunction with the gripping action afforded by the end rings engaging opposite sides of the flanges 86 serve to retain the blades 81 firmly in assembled relation. Further, during the spinning operation, the metal tends to flow into the gaps 95 between the sides of the flanges 86 to form projections 100 (FIG. 21) providing a further locking action of all of the blades in proper operative relation.
The spinning of the lip 93 may also develop projecting portions 103 which extend into the gaps (FIG. 16) between adjacent blades, thus further contributing to the desired locking action. It will be understood that it is not essential that all of these groups of locking projections be formed, but one or more of the interlocking actions may be utilized as desired.
The blower wheel of FIG. 14 incorporates a supporting center disk structure which includes a pair of disk members 105 and 106 of copper coated sheet metal, and both of these disks are shown as carrying hubs 107 for mounting the blower wheel on a drive shaft for rotation. The disks 105 and 106 are of lesser outer diameter than the inner diameter of end rings 88 to provide for assembly of the disks within the blower wheel after the end rings are in place.
The disks 105 and 106 are secured in mechanically coupled relation with intermediate portions of all of the blades 81 by interfitting parts which are located entirely within the projected inner diameters of the end rings 88, and which therefore can be readily assembled and interconnected after the cage portion of the wheel is otherwise complete. As shown in FIG. 15, each blade 81 is provided with a small hole 108- located approximately midway between its ends and adjacent its innermost edge 110 which lies radially innermost in the finished wheel. The hole 108 is thus spaced radially outwardly of the blade 81 from the edges 110 by a small marginal portion 111 which may conveniently be of the same minimum radial diameter of the hole 108.
Referring to FIG. l6,'the disks 105 and 106 are provided initially with a plurality of openings 113 extending through the outer peripheral portion thereof and equal in number to the blades 81. Satisfactory results have been obtained when each of these openings is of the same dimension as the holes 108 in the blades and located in similarly spaced relation with the outer periphery of the disk. Each opening 113 is also connected with the outer 6 periphery of the disks and 106 by a radially extending slot 114.
Prior to assembly of the disks 105 and 106 within the blower wheel, the tongue portions are deformed axially outwardly of the disks by an amount sufficient to widen the slots 114 until their width is sufficiently greater than the thickness of each blade 81 to permit ready movement of a blade therethrough. The tongue portions 115 of the two disks 105 and 106 are formed away from the hub portions of the disks so that when the disks are thus assembled with the tongue portions thereon aligned and facing each other, these tongue portions will abut each other and thus hold the adjacent disk portions in axially spaced relation. The two disks 105 and 106 are inserted in this relation in the wheel by sliding the blades through the aligned pairs of widened slots 114 until each of the double pairs of tongue portions 115 are in line with one of the holes 108 through the adjacent blade 81.
The two disks 105 and 106 are then pressed together until the tongue portions 115 are returned to their orig inal positions in coplanar relation with the adjacent portions of the disks, and until the peripheral portions of the two disks are substantially in face to face contact. As shown in FIG. 16, this action forces the tongue members 115 to enter into the holes 108 in the blades 81 from opposite sides thereof in overlapping relation with the marginal portions 111 of the blades. The result of these manufacturing operations is to establish firm locking of each blade 81 to the supporting center structure so that the intermediate portions of all of the blades 81 are thus secured in fixed radial relation with the axis of the wheel. This particular center disk structure is similar to that disclosed in US. Patent No. 2,852,182, issued September 16, 1958.
Subsequent to the fabrication of the blower wheel 80, it is subjected to the heat during the brazing step thus causing the copper coating on the two end rings 88 and the center disks 105 and 106 to melt and flow into the space between adjacent surfaces of the blower wheel components. When the blower wheel is allowed to cool, this copper solidifies forming a rigid blower capable of high speed operation. Specifically, as shown in FIG. 18, the end rings 88 and the blades 81 become fused into substantially solid beads and thus the blade flanges 86, the walls 84 and 85, and end rings 88 are integrally connected. The gaps or spaces 95 may result in small voids 95a (FIGS. 20 and 22) which lessen the weight of the blower wheel and do not detract from the rigidity thereof.
The center disks 105 and 106 become integrally fused together to form a solid outer portion 122 (FIG. 18), and the tongues 115 become similarly rigidly connected to the blades 81 so that the resulting product is a rigid integral blower having substantially all of the advantages of both fabricated and welded blower wheels. In a manner similar to that described above, the hubs 118 become fused to the disks 105 and 106.
FIGS. 23 and 24 illustrate another embodiment of the center disk structure which can be used in the double inlet blower wheel, shown in FIG. 14. To accommodate this center disk structure, each of the blades 81a is provided with a dovetail slot 125 in the trailing edge 110 thereof for receiving the outer peripheral portions 126 of each of the copper coated disks 127 and 128. The portions 126 are forced into the slots 125 by loosely placing the disks 127 and 128 in the blower wheel with the peripheries of the disks in the slots 125 and then flattening the beads 130 thus radially expanding the disks causing the peripheral portions 126 thereof to be forced tightly into the slots 125 in engagement with the blades 81a. In practice, this causes the blades 81a to be bowed slightly thus insuring that the disks are positioned securely in the blower wheel. Fabrication of the center disk structure mentioned above is substantially in accordance with that 7 disclosed in the U.S. Patent to Mertz, No. 3,080,105, issued March 5, 1963.
After the blower wheel 80a has been fabricated and the center disks 127 and 128 are securely in position, the blower wheel 80a is placed in an oven or otherwise subjected to temperature sufficient to melt the copper coatings. This causes the end ring structure to be fused into rigid beads 120, substantially as described above, and the center disks 127 and 128 to be fused to each other to the center portion of the blades as shown in FIG. 24.
The intermediate portions 133 and 134 of the center disks 127 and 128 are fused into a solid wall 135, and the beads 130 form an enclosed tubular channel 137 which contributes substantially to the rigidity and strength of the finished blower wheel. Moreover, the outer peripheral portions 126 of the disks 133 and 134 are fused adjacent the edge portions of the dovetail slots 125 in the blade 81a thus integrally securing the disks and the blades. This rigid connection factor provides additional strength when the blades are subjected to centrifugal forces since it clearly offers additional resistance to outward radial movement of the blades as caused by centrifugal force.
While the invention has ben described as using a copper coated steel end ring, back plate, or center disk, it should be understood that the material utilized can vary widely within the scope of the invention. The important feature is that the coating must flow at temperatures below those that will cause the base metal to melt or become unduly distorted by warpage. Thus silver solder is 0 one example of a metal which could be used in lieu of copper, and aluminum could be used rather than steel for the metal blades, end rings, back plates and center disks. Moreover, it is possible to coat the blades with the brazing metal, in lieu of or in addition to, the end ring, back plate or center disks. The invention also contemplates the use of resins in place of the coating, e.g., resins which will flow in response to being heated.
The manner in which the coatings can be raised to a temperature sufficient to cause flow thereof can also vary widely within the scope of the invention. This can be accomplished by use of an oven, by induction brazing, or by direct application of a torch to raise the temperature. Preferred results have been obtained from using an oven since this allows each of the separate components of the blower wheel to be heated to the same temperature at the same rates thereby reducing Warpage. When copper is coated on cold rolled steel, the wheel is preferably heated to approximately 2060 F. for one-half hour in an atmosphere of ExO gas, which contains approximately 40% hydrogen to hold corrosion to a minimum. The wheel is subsequently reduced to a temperature of 120 F. gradually over a period of one hour. After it is straightened and balanced as required, it is painted and packed for shipment or storage.
While the methods and forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.
What is claimed is:
1. An integral blower wheel of the character described made substantially entirely of sheet metal parts comprising, a plurality of separately formed parallel sheet metal blades circumferentially arranged to form a wheel having a predetermined diameter, each said blade having a smooth pumping blade surface with radially outwardly extending flange portions at each end thereof, sheet metal ring means at each end of each said blade encompassing and supporting said flange portions to lock said flange portions and said ring means against relative movement in any direction, said ring means having weld material means disposed between the entire area of encompassing contact between said flange portions and said ring means and providing a continuous annular ring of weld material securely locking said separating flange portions together and to said ring means, said ring means having an outer diameter substantially equal to or greater than said predetermined diameter to provide rigid supports at the opposite ends of said sheet metal blades, a relatively thin radial inner flange on each of said ring means which is integrally connected to at least part of the end portion of said sheet metal blades, and hub means integrally secured to at least one of said ring means to support the blower wheel for rotation.
2. An integral blower wheel as defined in claim 1 wherein one of said end ring means defines an inlet to said blower wheel and the other of said ring means is a back plate which has said hub means secured thereto thus forming a single inlet blower wheel.
3. An integral blower wheel as defined in claim 1 wherein one of said annular means is a sheet metal back plate, said hub means being connected integrally to said back plate, an annular groove in said back plate surrounding said hub, a reinforcing disk integrally secured to said back plate over said groove to create a hollow reinforcing rib in said back plate to add rigidity to said back plate.
4. An integral double inlet blower wheel of the character described made substantially entirely of sheet metal parts comprising, a plurality of separately formed parallel sheet metal blades circumferentially arranged to form a wheel having a predetermined diameter, each said blade having a smooth pumping blade surface with radially outwardly extending flange portions at each end thereof, sheet metal ring means at each end of each said blade encompassing and supporting said flange portions to lock said flange portions and said ring means against relative movement in any direction, said ring means having weld material means disposed between the entire area of encompassing contact between said flange portions and said ring means and providing a continuous annular ring of weld material securely locking said separate flange portions together and to said ring means, said ring means having an outer diameter substantially equal to or greater than said predetermined diameter to provide rigid supports at the opposite ends of said sheet metal blades, a relatively thin radial inner flange on each of said ring means which is integrally connected to at least part of the end portion of said sheet metal blades, a center disk assembly secured centrally with the cage formed by said blades and having an outer portion thereof which extends into cutout portions of said blades, said outer portion being integrally connected to the adjacent portions of said blades, and hub means secured to said center disk assembly to support the blower wheel for rotation.
5. A blower wheel as defined in claim 4 wherein at least one circumferentially hollow reinforcing rib is provided in said center disk assembly adjacent said outer portion to add rigidity to the blower wheel.
6. A double inlet blower wheel of the character described made substantially entirely of sheet metal parts comprising, a pair of single inlet blower wheels each including a plurality of separately formed parallel sheet metal blades circumferentially arranged to form a wheel having a predetermined diameter, each said blade having a smooth pumping blade surface with radially outwardly extending flange portions at each end thereof, a sheet metal end ring at one end of said blades and a back plate at the opposite end of said blades, each said end ring and back plate encompassing and supporting said flange portions of the adjacent said blades to lock said flange portions against relative movement in any direction, said end rings and back plates having weld material means disposed between the entire area of encompassing contact between said flange portions and providing a continuous annular ring of weld material securely locking said separate flange portions together and to said end rings and back plates, said back plates being substantially smooth so that they can be placed adjacent and in contact with each other means integrally securing the contacting areas of said back plates together to form the double inlet blower wheel, and hub means secured to at least one of said back plates to support the blower wheel for rotation.
7. A double inlet blower wheel as defined in claim 6 wherein complementary grooves are provided in said back plates to create hollow reinforcing ribs when said back plates are secured together.
References Cited by the Examiner UNITED STATES PATENTS 1,951,122 3/34 Balze 29-470.5 2,071,583 2/37 Schutt 29-470.5 2,231,062 2/41 Evans 234-134 2,272,695 2/ 42 Evans 234-134 2,537,805 1/51 Wilken 230-134 2,592,851 4/52 Beranek 230-134 Wilken 230-134 Garratt 29-470.5 Burrowes 230-134 King et al. 29156.8 Wilken 230-134 Hathaway 230-134 Kreuchen 29-470.5 Newton et al 230-1345 Merz 230-1345 Glasson 29-156.8 Murray 29470.5 Hathaway 29156.8 Wentling et a1 230-1345 15 DONLEY J. STOCKING, Primary Examiner.
HENRY F. RADUAZO, Examiner.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 0 3, 211,364 October 12, 1965 William H. Wentling t 1, It is hereby certified that error a ppears in the above numbered pat ent requiring correction and that the said Letters Patent should read as corrected below.
Column 8, line 5, for "separating" line 75, after "other" read separate insert a comma; column 10, line 12, for "9/61" read 9/64 Signed and sealed this 14th day of June 1966.
ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents