US2537805A

US2537805A - Blower

Info

Publication number: US2537805A
Application number: US635454A
Authority: US
Inventors: Carl E Wiken
Original assignee: Lau Blower Co
Current assignee: Lau Blower Co
Priority date: 1945-12-17
Filing date: 1945-12-17
Publication date: 1951-01-09
Anticipated expiration: 1968-01-09

Description

Jan. 9, 1951 c. E. WILKEN 2,537,805

BLQWER Filed Dec. 17, 1945 4 Sheets-Sheet 1 0 '0 27 INVENTOR I TqI-EI CMeaZ/JIL J 7W 6%! TTORNEYJ C. E. WILKEN Jan. 9, 1951 BLOWER 4 Sheets-Sheet 2 Filed Dec. 1'7, 1945' INVENTOR ATTORNEY c. E. WlLKEN BLOWER Jan. 9, 1951 Filed Dec. 17, 1945 4 Sheets-Sheet s INVENTOR BY (Lida/$4M mmullew ATTORNEY C. E. WlLKE-N Jan. 9, 1951 BLOWER 4 Sheets-Sheet 4 Filed Dec. 17, 1945 INVENTOR (Me 6. m BY 2 ATTORNEYS Patented Jan, 9, 1951 BLOWER Carl E. Wilken, New Lebanon, Ohio, assignor to The Lau Blower Company, Dayton, Ohio, a corporation of Ohio Application December 17, 1945, Serial No. 635,454

This invention relates to multiblade centrifugal fans of the type commonly known as blowers andto rotors or blower wheels therefor.

It is the principal object of the invention to provide an improved blower wheel which is simple and economical in construction, which can be made at less expense than wheels heretofore available, which has individual blades shaped to develop the most desirable performance and air delivery, and which is of high strength and rigidity and capable of operating with freedom from objectionable vibration and noise at high speeds.

It is a further object to provide a blower wheel having a plurality of separately formed blades which are held in operative position without the use of welded or riveted joints and which has good balance and concentricity as initially formed and in operation.

It is a further object to provide a blower wheel made up of separate blades which are assembled and securely held in proper operative position without the use of any heating operation making possible the use of blades which have been galvanized or otherwise surface treated, and further enabling the use of non-- metallic blade materials where desired.

It is also an object to provide a spun end ring construction for such blower wheels which securely locks the blades in operative relation in the wheel requiring no welding, riveting, or the like and providing great strength, stiffness, and concentricity.

It is a further object to provide a blower Wheel which has a maximum effective length of the blades with only a relatively small space required at the ends for blade retention.

It is also an object to provide a blower wheel of the double inlet type having a center disk against which the blades are drawn and compressed under the action of the end rings providing a pre-stressed condition in the blades.

It is also an object to provide a method of forming such a blower wheel including the spinning of an end ring into locking position to retain the blades in assembled relation, the spinning operation being accomplished quickly and easily and tending to promote concentricity and proper balance of the wheel.

It is also an object to provide a novel method of making the wheel in motion providing for developing inherent concentricity and precision.

Other objects and advantages will be apparent from the following description, the accompanying drawings and the appended claims.

15 Claims. (01. 230-134) V In the drawings:

Figs. 1, 2 and 3 are respectively a side elevation, a plan, and a partial perspective of an individual blade for a blower wheel constructed in accordance with the present invention;

Figs. 4, 5 and. 6 show three sequential steps in the assembly of the blades and the end rings in the spinning operation;

Fig. 7 is a section through the blade on the line 'i-'i of Fig. 6;

Fig. 8 is a broken section through the end flange and the end ring of the blade on the line 88 of Fig. 6;

Fig. 9 is a-transverse section on the line 99 of Fig. 6;

Fig. 10 is a side elevational view of the fixture used for holding the blades in proper position during the spinning operation;

Fig. 11 is a section view on the line |l--ll of Fig. 10;

Fig. 12 is a View of the assembled wheel of the double inlet type with portions broken away indicating the pre-stressed condition of the blades;

Fig. 13 is a partial end elevational view on the larger scale of the finished wheel with a portion of the end flange broken away;

Fig. 14 is a perspective view of the finished wheel of the double inlet type;

Figs. 15 and 16 are sectional view on an enlarged scale of a different form of end ring and lock for the end flange;

Fig. 17 is a sectional view showing the application of the invention to a wheel of the single inlet type; and i Fig. 18 is a vertical sectional view through the wheel in its assembled operative position in a housing constructed to develop high overall output and efiiciency.

Blower wheels may be constructed from an integral sheet of material by stampin the bladesfrom the sheet in the form of louvers, or they wheel may be assembled from a group of individual and separately formed blades which are then secured in proper operative relation. If

the wheel is made from a continuous or integral sheet, the limitations inherent in this construc-.

tion make it impracticable to use the most advantageous form of blade, i. e., as to depth, angle, and spacing from adjacent blades, to develop the maximum output from the blower. In accordance with the present invention, a construction incorporating separate blades is utilized making it possible to form the blades in the shape found most desirable for developing maximum performance, and without the inherent limitations arising from the use of an integral sheet. Thus for example by using separate blades they may have a relatively large depth of face and may be spaced close together making it possible to obtain substantially improved performance.

In addition the present invention provides a construction which avoids the necessity for separately mounting and fastening the individual blades in place, and avoids the use of riveting or welding operations which require a substantial amount of skilled workmanship in order to produce an acceptable finished blower wheel. In the present construction the blades are assembled rapidly and without individual manual handling for securing the blades in place, the securing of the blades in assembled position being eifected without the use of riveting, welding, or similar operation requiring the use of heat. As a result, it is entirely practicable with the presentinvention to utilize blades which have been galvanized or otherwise coated or treated for rust prevention, the securing oi the blades in proper assembled relation in the absence of a step involving heat resulting in the maintenance of the protective or rust proof coating substantially unimpaired while at the same time avoiding the deforming stresses which accompany such heating steps. It is even possible to make use of blades of non-metallic material, such for example as plastic or the like, which may be easily assembled in the same manner.

The blower wheel as so produced not only secures the blades in assembled position but accomplishes the assembly in a manner which tends to assure accurate concentricity of the entire wheel about the axis on which the wheel will rotate in use. The assembly is effected by spinning an end ring in position over outwardly extending end flanges formed on the blades, and with the spinning of the rings in position, a bending stress is developed in the blades which tends to draw them uniformly into accurate and concentric position, the wheel being rotated in the operation about the axis on which it will rotate in use. This has been found to contribute quite substantially to obtaining the proper balance of the wheel, making it a relatively simple matter to'eifect the-final balancing of the finished wheel. If balancing weights are required, they are relatively small and thus balance obtained at one speed is much more nearly correct at higher speeds than is the case where through manufacturing variations it is necessary to add weights of considerable size, establishing a localized mass which may create unbalanced forces and tend to cause vibration when rotated under operating speeds.

The end ring may be suitably made of material of high tensile strength and thus contributes substantially to the strength of the assembly, providing a materially stronger wheel which can be operated reliably, without danger of vibra tion, noise, or mechanical failure, at speeds niaterially above the normal operating speed. Also the end ring provides a smooth and. continuous outer periphery afiording protection to the blades themselves but may be made quite narrow in its inward extent, leaving the major portion of the inner ends of the blades uncovered, thus further contributing to improved performance of the wheel in use.

The invention likewise provides for the support of the blades from the drive memberin such 4 manner that the drive takes place directly to each blade, thus establishing balanced mechanical forces and loadings, and avoiding the transmission of concentrated or unbalanced stresses through the structure where the support is provided at only a relatively few points.

Referring now to the drawings which illustrate apreferred embodiment of the invention, a typical blade construction is shown inFigs-l, 2 and 3 where the blade is shown as having a curved working face It which is arcuately shaped in a uniform manner over the major portion of the length of the blade. At either end the wall of the blade is turned over at approximately right angles as shown at l2 forming a laterally extending wall on the convex side of the blade. Beyond the wall it, the material of the blade is flanged as shown at 13, this flange being bent upwardly at right angles to the longitudinally extending blade surface, the flange thus projecting radially outwardly of and overhanging the working face of the blade. As shown the flange is-tangent to one side of the working face-mat approximately the point Id, and the end wallli is thus of varying width of face as clearly :appears in Fig. 3. Also the outer periphery of the flange l3 may be either flat 0r arcuate as shown at l5 about a radius corresponding to the radius of the blower wheel.

The blades are preferably notched at their inner central portions as indicated at [6, and the blades are all die stamped and formed from a single continuous sheet of material. With such construction a corresponding notch'is formed on the opposite side of the blade, but this latter notch is of no particular value so far as the operation of the device is concerned.

The blades are assembled in' parallelrelation about the circumference of a center disk member shown at 20. The disk has notches 2| spaced around its outer peripheryin corresponding number and angular relationship .to the individual blades. The disk may convenientlybeformedlby stamping and pressing a pair of sheet metal plates with a centrally ofiset portion shown at 22 forming lateral extensions on which hub members 23 are secured. This provides-a support'for receiving the shaft of the wheel, suitablefastening means such as set screws 24 providing for securing the-wheel to the s'haftinproper working relation.

In the assembly of the blades they are loosely fitted into place each with its inwardly extending notch l6 engaged in the corresponding notch 2i of the center disk. End rings indicated generally at 25 are suitablypositionedat either end of the blades, providing for receiving the outwardly extending blade flanges f3 therein asthe blades are progressively stacked in place. This operation is performed quite readily with the blades being introduced into proper position within the end rings and in engagement with the notched center disk, as the center disk is slowly rotated on the shaft. As will be evident from Fig. 4, the end ring 25 is provided with an offset shoulder portion 26 and an inwardly projecting flange portion 2? which is'adapted to interfit with the projection formed by theoverhanging end flange 13. The projectionson-the ends of the blades thus are received within the end rings and supported loosely-on the shoulders 26 with the flanges l3 extending radially'outwardly. The number of blades andthe'peripheral extent of their end flanges :is preferably such that they are not in contact with each other but some clearance therebetween is provided.

The assembly and proper spacing of the blades is facilitated by the use of the fixture arrangement shown in Figs. and 11. As there shown, the blades II! are placed in a fixture comprising a notched retaining disk 30 which is bolted as shown at 31 in proper spaced relation with respect to an adjustable end plate 32 keyed as shown at'33 to a shaft 34. An adjustable nut 35 provides for the setting of the end plate in predetermined axial relationship with respect to a fixed plate 33 at the opposite end of the shaft and also rotatable therewith. Each end plate has a shoulder 3? formed thereon on which the shouldered part 26 of the end ring is adapted to be received, the flange 23 of the end ring being open as shown. Disk is provided with a series of tapered notches :10 around its periphery which lead through a restricted neck portion 41 into a series of inner drilled apertures 42, a pair of bowed spring members d3 being arranged on each side of the notch in position to yieldably and frictionally engage the surface of each blade as it is inserted radially into the notch. It will be clear from Fig. 11 that the outer periphery of the disk 35] is substantially less than that of the end plates and it can thus be withdrawn axially of the blades without disturbing their assembled relation.

In the assembly of a wheel in accordance with the present invention, a center disk 2%! is first located on the shaft 34 at a central position thereon, and the continuous end rings 25 are positioned in the shoulders 3'! of the oppositely facing plates 32 and 3B. The shaft 34 is then revolved slowly while the individual blades it] are assembled using the notches 48 of the disk 30 as a guide for receiving the blades and temporarily holding them in proper assembled relation with their center notches engaged in the corresponding notches of the center disk 28. The blade flanges is are received in the end rings at opposite ends in the relationship illustrated in Fig. 4. If desir d a similar disk 38 may be positioned adjacent the fixed plate 36, although it has been found that a single such plate will function satisfactorily. The blades are easily slipped into oosition between the springs 43 with their bottom edge seating in the respective apertures 42 and the stacking continues in tbismanner until a complete set of blades is assembled.

When the blades are properly assembled, the adjustable end plate 32 is moved axially of the shaft by the tightening of nuttE to compress the two end plates toward each other and thus assure the proper axial alignment of all individual blades and at the same time bringing the respective end rings into tight relation therewith and with the shoulders 26 engagingunder the overhanging blade end flanges.

The fixture is then rotated, which may be conveniently accomplished by placing the shaft 34 in a lathe and suitably driving the fixed plate 36 in the usual way. A spinning tool indicated diagrammatically at 45 is then brought into work ng relation with the two end rings 25 to effect the spinning of the rings into final gripping and locking relation with the end flanges of the plates.

operation is completed, the spinning tool moves radially inwardly and the material of the portion 23 of the end ring is drawn forcibly into contact with the series of, blade flanges l3, causing a firm and secure interlocking action which serves the desirable purpose of retaining the blades in proper position in use. downwardly against the outer peripheries of the end flanges, the extent of the actual contact therewith depending upon Whether the end flanges are flat or conform to the circular shape. This operation also tightens the outer portion of ring 25, drawing the shoulder 26 forcibly up against the overhanging projection at the base of end flanges I3.

' As shown in Fig. 6, the length of the portion 28 of the end ring is preferably such that it is longer than the height of flange i3 and thus in finished position a lip 5f! is formed on the inner portion of the ring, bearing against the outer surface of the blades and extending axially .of the blades toward the ring on the opposite end.

As shown in Figs. 7, 8 and 9, the width of the peripheral extent of flanges i3 is so limited that small clearances or gaps 55 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 thus available, a desirable interlocking action is secured. The gaps should be present at least at the outer peripheries of the flanges l3 and may continue radially inwardly so that as shown in Fig. 8 adjacent blades are actually separated from each other at all points.

This locking action is provided in the following manner. v It is found that the spinning operation may be made to deve.op substantial forces in the material of the end ring tending to draw or work the metal into the gaps provided between the end flanges of the blades. This results in forming small projections which extend into the gaps 55 and interlock each blade to hold it securely in position in the end rings. Thematerial of the end ring 25 is drawn tightly aroundthe outer peripheral surface E5 of the end flanges and in part into the gaps between those flanges, the pressure being such as to cause the material to be drawn or to flow somewhat into the gaps as indicated at 56, thus forming a series of inward projections between each pair of adjacent blades. These projections on the outer periphery of the end ring in conjunction with the gripping action afforded by the U-shaped section of the end ring engaging opposite sides of the flanges serve to firmly retain the blades in assembled reation against relative movement or vibration and provide a strong and a highly advantageous device. Further, the spinning operation may be made to so work the metal forming the vertical face of wall 28, that it tends to flow into the gaps 55 between the sides of the fianges [3 as shown by projections 58. While the outer surface 59 of this portion of the end ring may retain a substantially smooth appearance because of the action of the spinning tool, the presence of such interlocking inward projections 58 extending into the gaps between adjacent flanges provides a furtherlocking action of all of the blades. in proper operative I will be understood that it is not essential that all of these groups of locking projections be formed,

The endring is drawn absence but one or more urine-interlocking actionsmay be utilized as desired.

Since this spinning operation is carried out while the assembly is being rotated'about the actual axisofmotation "of the finished wheel, the spinning action itself promotes desired concentricity, and tends to develop a greater stress upon any blade or portion thereof which tends to project radially outwardly from the others with the result that the finished-wheel following the spinning operation is found to require very little additional balance. This not only simplifies the manufacturing process, but provides for better operating conditions without the use of large weights.

Preferably the 'spinning'operation is so .carried out that a definite confining stress is'developed in the end rings to how the blades inwardly against the center disk 26. This is illustrated in Fig. 12 in a somewhat exaggerated way, the blades l shown as being drawn together at their opposite ends so that the ends are pulled radially inwardly from the dottedaline positions illustrating the normal positionwhich such blades would occupy. This bending action is easily accomplished by the proper application of pressure to the end rings inthe'spinning operation, and is further desirable since it provides for secure locking interengagement between the central notches of the bladesand the center disk assembly 20. It will be noted by examination of Fig. .12 that the bowing of the blades takes place in two planes, i. e., in the-vertical plane as shown by the blades illustrated at the top and bottom of the wheel and also in the horizontal plane by the blades asshown in elevation at-thecenter of the wheel. Each blade thus has a double .or complex bowed relation subjecting the blade to a torsional deformation, the bow preferably being against the directionin which the wheel will rotate in use.

Following the spinning operation the fixture is removed from the lathe or other rotating support and nut 35 is removed, providing for the withdrawal of end plate 32 which likewise effects withdrawal ofthe disk'30 from its contact with the inner edges of the "bladeawithout however disturbing the blades'in their'n'ow completely assembled relation. Thefinished wheel may then be removed from the shaft andthe fixturereused for the formation of another wheel.

A wheel constructed in accordance with the present invention'h'as been foundto have a high degree of -mechanical strength. "This is made possible by the fiangedconstru'ct-ion at the end of the blade and the similarly flanged and shouldered construction of the end ring which engages the blade flanges. As will be evident, the shoulder 26 and the lip 50 of the-end ring both extend at right angles to the remaining portions of the end ring and in such manner as to add substantially to its strength .and stiifmess. The finished ring is spun :into the noonstruction shown and providesa firm :and sturdy construction, securely fixing the 'bladesdn .iproper relation, and preventing vibration, noise, or failure at speeds even several times the .normal speed. As will be evident, the end ring is relatively narrow and preferably is so confined that it :leaves the major portions of the .ends of the blades free and unobstructed. Thus while :the end ring provides a continuous flange around the outer circumference of the wheel, forming a support for the wheel which tends to prevent damage-tothe edges of the-blades themselvespthe radially inner portions of the blades are left substantially uncovered at'the ends, contributing'to substantially improved performance of the wheel. As is clearly shown in Fig. '7, for example, the innermost extent of the portion 21 of the end ring is such that the major part of the working surrace=of the blade is left free at its-end. This has been found advantageous from the standpoint of providing betterperformance and output characteristics, the structure at the same time assuring adequate strength and'rigidity.

As shownin Fig. 13 the maximum diameter of the center disk portions 28 is less than the inner diameter of the annular end ring members, and for convenience and economy of manufactureit is desiredto form the center disk structure from the stamping cut from the metal sheet in'the forming of the end ring, thereby providing for substantially eliminating waste material in the operation.

It willbe evident from the above disclosure that the entire assembly of the wheel is accomplished without the use of riveting, welding or other operations involving the use of heat. The wheel is therefore not subjected to strains resulting from wide temperature changes, does not have the lack of uniformity encountered in the making of individual welded or riveted joints, and assures both greater strength, and concentricity. It is evident therefore that the-blades may be made of galvanized material or otherwise treated to prevent rust or chemical action, the spinning of the end rings to retain thenblades in position being anoperation which does not adversel affect such treated surfaces. As-above stated, it is also possible to form the blades from molded plasticor other non metallic materials having the necessary strength.

Different constructions of end ring securing meansmay-beusedand an alternate construction is shown by way of example in Figs. 15 and 16 which are sectional views on an enlarged scale showing two steps in the formation of such modi fied construction. As shown the blade 64 has an end flange E55 which is generally similar to'the endflange l3 described above, the blade end in this case being shown curved as indicated at 66, since the flat ended blade form previously described is not required in all cases. The ring'fil is provided which is received over and engages the radially outer peripheries of the flanges 65. The radially inner end of thering is shown at 68 being offset to be received under the overhanging projection of the end flange of the blade and terminating in bent portion 59 which is spaced from-the curved end of the blade as shown. After the end ring is positioned over the end flanges of the blades shown in Fig. 15, the portion 6'? is turned or spun downwardly to overlap the series of end flanges and the overlapped parts then folded'down fiat upon themselves into the shape shown in Fig. 16. This is conveniently done-by a'spinningoperation similar to thatdescribed above, and such operation may also .develop the interfitting projecting portions inthe gaps between the blades, in the manner already described. When the parts are folded fiat'upon themselves, a completely effective lock is thus provided assuring the tight retention of the blades in the end ring firmly and in whatever spaced relation is desired.

While the above-description refers to double inlet wheels, it will be evident that it is also applioable'to single inlet wheels. Ancxampleof 7 this latter construction is shown in Fig. 17 in which the end ring Til at the open end of the wheel is substantially similar in construction and its manner of formation to the construction described above. At the closed end, a plate 72 is centrally apertured to receive the bearing '53, the plate having suitable offset portions as shown at 14 and i to provide added stiffness. The outer periphery of the plate i2 is formed as shown at I6 in the same manner as the end ring construction, and is spun into securing relation with the end flange ii on blades E3 in a manner similar to that already described.

Referring to Fig. 18, a blower is shown inoor porating a blower Wheel of the present construction in a housing comprising a casing 83 which is provided with a fiange Bl on its base and having a spiral air delivery chamber 32, the wheel being centered axially between the opposite ends of the casing. For most satisfactory blower operation it has been determined that the diameter Dof the wheel measured to the outer periphery of the blades should approximately equal the axial length of the blades. Further as will be evident from the arrangement shown in the drawing the inlet for either end should be formed by curved inlet members 84, 85, the radius R of which has a relation to the diameter of the wheel for best operating results. Thus it will be seen that the inlet opening is approximately the same as the inner diameter of the blades, and is relatively closed spaced thereto. For best operating results the casing itself should have a definite spacing axially beyond the ends of the blower, i. e., the dimension marked A On the drawing having a definite relationship to the diameter of the wheel. Very satisfactory results have been secured where the dimension A is approximately 12 to 14% of the diameter of the wheel while the radius R of the inlet ring is approximately 9 to of the diameter of the wheel.

It will also be noted that the housing is shown as comprising a plurality of arms 81, preferably three in number, for supportin the bearings 88 in which the blower shaft 89 is journaled, the arrangement of such arms being desirable as not adversely affecting the air supply to and the output of the blower. Suitable resilient members are provided in such supporting arms for resilientl-y mounting the .blower shaft.

The above invention thus provides a simple and highly satisfactory blower wheel construction embodying new and desirable features of construction which provide for developing superior performance and output while at the same time furnishing a maximum of strength and stiffness in the finished wheel. The formation of the wheel is very simple, and takes place rapidly and without individual handling of th separate blades, not only saving in the time required for individual blade attachments but further materially saving in the finishing-time required to accomplish proper balancing of the blade. 'Reference is made to copending application. Serial No. 784,335, filed November 6, 1947, as a division of the present application. v H

While the forms of apparatus and process herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus and process, 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:

l. A centrifugal blower wheel comprising a plurality of separate blades, each said blade having a flange at the end thereof extending radially of said wheel, said blades being arranged around the periphery of said wheel with gaps between adjacent flanges, and a continuous retaining ring secured in position over said flanges and indented in interlocking relation into the gaps between adjacent said blades for holding the blades in operative position with said flanges spaced from each other to form said wheel.

2. A centrifugal blower wheel comprising a plurality of separate blades, each said blade having a flange thereon extending radially'of said wheel, said blades being arranged around the periphery of said wheel with gaps between adjacent flanges, and a retaining ring having portions thereof indented in interlocking relation to the gaps between said flanges for holding said blades in assembled relation to form said wheel.

3. A centrifugal blower wheel comprisingv a plurality of separate blades each having a flange thereon extending radially outwardly of the wheel in a direction substantially normal to the axis of the wheel with radially extending gaps 1 between adjacent flanges, and a single continuous retaining ring overlying said flanges and having radially extending portions interfitting into said gaps to retain said blades in assembled position.

4. A centrifugal blower wheel comprising a plurality of separate blades each having a flange at the end thereof extending radially outwardly in a plane substantially normal to the axis of' the wheel with gaps between adjacent flanges, and a continuous ring substantially U-shaped in cross-section overlying and enclosing said flanges on opposite sides'thereof to retain said blades in operative position forming said wheel, the axially outer surface of said ring being substantially smooth and the axially inner portion thereof being indented into the gaps betwee said flanges.

5. A centrifugal blower wheel comprising a plurality of separate blades circumferentially arranged to form a wheel, each said blade having a flange formed thereon at its opposite ends extending radially outwardly thereof, said blades being spaced fromeach other around the periphery of said wheel by small gaps, and a retaining ring received over and enclosing said flanges, the 1 material of said ring extending into said gaps between adjacent said blades to'provide an interlocking construction for retaining said blades in assembled working relation with each other.

' 6. A centrifugal blower wheel comprising a plurality of separate blades 'circumferentially arranged to form a wheel, each said blade having a flange formed thereon at its end extending radially outwardly thereof, said blades being spaced from each other around the periphery of said wheel by small gaps, and a retaining ring spun in position over said flanges and hav ing portions thereof interlocking into said gaps.

between adjacent said blades to provide for securely retaining said blades in assembled position.

'7. A centrifugal blower wheel comprising a plurality of separate blades circumferentially arranged to form a wheel, each said blade having a' flange formed thereon at its end extending radially outwardly thereof, said blades being spaced from each other around the periphery of said wheel by small gaps, and a retaining ring spun in position over said flanges and forming a lip extending axially inwardly of said wheel from the, portions enclosing said. flanges.

8. A centrifugal blower wheel comprising a plurality of separate blades oircumferentially arranged to form a. wheel, each said bladehaving a. flangev formed thereon at its. opposite ends extending radially outwardly thereof, said blades being spaced from. each other around the periphery of said wheel by small gaps, and, a retaining ring spunin position over said flanges and having portions thereof extending from the outer periphery, of the ring into the gaps between. adjacent flanges. to,v lock, said blades. in place.

9. A. centrifugal; blowerv wheel comprising a plurality of separate blades circumferentially arranged to ,form a, wheel, each said blade having a flange formed thereon at its opposite ends extending radiall'y outwardly thereof, said'blades being spaced from each otheraround theperiplh e y otsaid. wheel by smallgaps, andiaretaining ring receivedover said flangeswith the axially inner. wall thereof spun, in position over said flanges and ininterlocking engagement into said gaps to firmly secure said blades in assembled relation.

10. A centrifugal blower wheel comprising a plurality of separate blades circumferentially arranged to form a wheel, each. said blade having a flange formed thereon at its opposite ends extendingradially outwardly thereof, said blades being spaced "from. each other. around the periphcry of said wheel by small gaps, and a; retaining ringreceived'over saidflanges with the axially inner wall thereof spun in position over said flanges" and into contact with the body ofsaid blades; saidinner wall having portions thereof extending into said. gaps between adiacent flanges to lock saidblades in place.

11. The method of forming ablower wheel from a; group, of .separatelyformed blades, having outwardly extending end flanges thereon which comprises assembling said blades into the, form of a wheel, temporarily supporting said blades with portions of their adjacentend' flanges spaced fromeach other, spinning an end ring intopositionover said end flanges to cause projections thereon-to extend into the spaces between said adjacent end flanges to lock theblades in-proper operative relation; and thereafter withdrawing thetemporary support to leave the finished wheel with the blades in completely assembled relation.

12. A centrifugal blowerwheel comprising a plurality: of separately formed blades: arranged aroundthe periphery of the wheel each'having a I flange; atthe endthereof' located radiallyoutwardly of; the formed-,suri'ace of:the-blade and extendingradially outwardly with respect tozsaid formed surface; each saidblade-havinga turned.

over: wall extending laterally-- from the convexside, thereof; and a continuous retaining ring: secured in gripping position over the flanges of said blades for holding said bladesin position to form saidwheel, said ring havingaqflat portion ex tending generally-radially of the wheel and overlying said turned: over wall portions of said blades over arelatively narrow extent thereof leaving the major portion of the inner ends of said blades uncovered providing for improved performance of the wheel in use.

13. A centrifugal blower wheel comprising a plurality of separately formed blades arranged around the periphery of the wheel, a supporting disk engaging the inner portions of said blades intermediate the ends thereof, the inner diameter of the outer ends of said blades in the finished Wheel being less than the inner diameter of said blades at said disk, and end rings engaging the ends of said blades outwardly of said. disk retain ing the ends of said blades inwardly at said lesser diameter causing the bowing of said blades with a maintained stress condition therein.

14. A centrifugalv blower wheel comprising a plurality of separately formedv blades arranged around. the periphery of the wheel, each said blade having endflanges extending radially out.- wardly of said wheel, a supporting disk having a peripheral portion interengaging with the inner portions of said blades intermediate the. ends thereof, the inner diameter of the outer endsof said blades in the finished wheel being less than the inner diameter of said blades. at said disk,

and end rings engaging the end flanges of said. blades retaining the ends of said blades radially inwardly at said lesser diameter causing the bowing of said blades witha maintained stress condition therein.

1,5. A centrifugal blower wheel comprising a plurality of separate blades circumferentially arranged to form a wheel, v each said blade havinga flange at. its opposite end overhanging the working. face of the blade and extending radially outwardly of the Wheel, and an annular ring closely engaging said flanges and having a lip on its. axially inner portion adapted to be received i reinforcing engagement with the outer edges of the working, surfaces of said blades.

CARL E; WILKEN;

REFERENCES CITED The following references are of recordinthe file of this patent:

UNITED STATES PATENTS Number Name Date 568,885 Steward ,Oct. 6; 1896 801,303 Davidson Oct. 10, 1905 1,567,446 McClure "Dec.- 29, 1925 1,724,509 Nelson Aug. 13; 1929 1,812,151 Jacocks June 30, 1931 2,053,254 Fair'child a, Sept; 8, 1936' 2143.335. Toler Jan. 10, 1939 2,155,264 Freed Apr; 18; 1939 2,157,441 Sullivan May 9, 1939 2,181,592 Sullivan Nov; 28,1939 2,195,869 Rathburn Apr. 2, 1940' 2,231,062 Evans ,Feb. 11, 1941 2,240 238 Baker Apr. 29, 1941 2,272,695 Evans Feb. 10, 1942 2,297 ,049 Cotton et a1. Sept. 29, 1942 2,315,407 Evans Mar;30,'1943 2,392,113 Anderson Jan. 1,1946 2,431,648 Mayne Nov; 25, 1947 Certificate of Correction Patent No. 2,537,805 January 9, 1951 CARL E. NILKEN It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 9, line 31, for closed read closely; column 10, line 18, for to read into; column 11, line 53, after the Word formed insert curved and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 17th day of April, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.