US2231062A - Centrifugal blower - Google Patents

Description

Feb. 11, 1941. A EVANS 2,231,062

CENTRIFUGAL BLOWER Filed Jan. 7, 1939 INVENTOR ADDISON W. EVANS ATTORNEY Patented Feb. 11, 1941 CENTRIFUGAL BLOWER Addison W. Evans, Torrington, Conn, assignor to The Torrington Manufacturing 00., Torrington, Conn, a corporation of Connecticut Application January 7, 1939, Serial No. 249,714

10 Claims.

This invention relates to improvements in centrifugal blowers, and particularly to an improved rotor, fan or blower wheel assembly, together with improvements in methods ofmaking same.

Centrifugal blower wheels have usually heretofore been constructed of a plurality of separate vane or blade-forming elements, each provided at its ends with a flange or the like through which the blades are riveted, welded or other- 10 wise secured to the shaft mounting elements, which, if at the end of the wheel, are often known as end rings. The principal prevailing objection to this form of blade is found in that the labor and the equipment required for the separate securement of the individual blades of a rotor of this type to the shaft mounting elements, entail a substantial expense.

Several attempts have heretofore been made in the art to form blower wheels or rotors by constructing the rim or body of the wheel of a single continuous strip of sheet metal or the like, this strip being punched or slitted longitudinally, i. e., in the direction of the axis of the Wheel, and the metal between the slits being formed and shaped to provide the blades. It is to this type of construction that the present invention pertains, and in the improvement of which is found its principal objective. As is understood, the blower wheels of the type last referred to, and which have heretofore appeared in the art, were characterized by a high proportion of metal spoilage and rejects because of the tendency, when forming up the individual blades, and under stress or operation, for the lines of fracture therebetween and defining the blades to extend endwise therebeyond. This difliculty may be partly overcome by using metal of heavier gauge, but thus entailing added expense and needlessly increasing the weight of the wheel. The present invention has 40 as a further important object, an avoidance of the difiiculty last above discussed, without increasing the Weight of the wheel.

Still other objects of the invention include an improved manner of securement of the shaft mounting elements to a blower body of sheet metal type, so as to obviate or minimize the number of rivets or the extent of welding or the like, usually resorted to for the assembly securement of these parts.

Yet another object of the invention is attained in an arrangement enabling the use of sheet metal of a lighter gauge in the construction of blower wheels of substantial length, this expedient consisting, in the disclosed example, of an intermediate external tension element embracing the blades, and so located as to resist deflection thereof under the influenec of centrifugal stresses.

The foregoing and numerous other objects will appear from the following detailed description, 5 considered in connection with the accompanying drawing, in which:

Fig. 1 is an isometric view showing a blower wheel constructed in accordance with the present invention; Fig. 2 is an enlarged fragmentary plan view of a peripheral end portion of the blower shown by Fig. 1; Fig. 3 is an enlarged fragmentary showing of a plurality of the blades and tension element, as viewed over a small area centrally of the outer surface of the rotor or wheel; Fig. 4 is a section along the plane indicated by line. l--l of Fig. 3; Fig. 5 is a fragmentary end view of a peripheral portion of the rotor showing certain details of construction, and

Fig. 6 is a section of a portion of the end ring and adjacent body or rim structure, as viewed along line 6-6 of Fig. 5.

Referring now by characters of reference to the drawing, and first to Fig. 1, the assembly shown by way of example is a double inlet blower wheel of reasonably large diameter, the inlets to which are at the ends. The blower shown is not provided with a center plate or other intermediate shaft mounting element, although obviously such an element may be utilized when desired, for certain types of service.

The shaft mounting elements or end rings are indicated at It) and II, and each of these consists preferably of a one-piece punched annulus of sheet metal characterized by radial arms or spokes l2, of which three are shown, serving to connect the peripheral portion l3, to the central disk or spider portion [4, the latter being optionally provided with openings l5 for the reception of stud bolts, cap screws or other holding elements engaging a shaft collar (not shown). The rigidity of the spokes I2 is considerably augmented by pressed-in ribs or the like I 6. The original diameter of each of the formed end rings, is somewhat greater than the intended finished diameter of the wheel, and to this end the annu lar peripheral flange l3 of each end ring extends somewhat beyond the periphery of the rim as it appears in Fig. 1; this extra material at the margin of the ring is resorted to as an assembly expedient, by crimping to the rim or body of the wheel, as is hereinafter more fully pointed out.

Referring now more particularly to the rim or body of the wheel, it is a. preference. that, for lightness and reduction of cost of assembly in production, this element be formed of a single strip of sheet metal, although obviously more than one may be employed if desired. This strip, shown in finished form by Figs. 1, 2 and 3 particularly, is either originally supplied with, or is cut to provide substantially even parallel margins thereon so that the strip is of fairly uniform width throughout its length, and in case as is preferred, a single element be used to form the periphery of the blower wheel, this length is of course the same as or somewhat greater than the circumference of the finished wheel.

Considering in a preferred order the steps involved in the method of forming up the body, the strip indicated generally at 20 in its finished form, is subjected to a first operation of gauging and perforating somewhat inwardly of the opposite lateral margins of the strip, a plurality of evenly spaced rounded apertures 2|. In the case of a double inlet wheel of the type disclosed, in which each end is provided with a mounting ring or the like, as well as in a single inlet wheel, the opposite margins of the strip 20 will be perforated at corresponding points so as to provide a double row of the openings 2| in such manner that the openings are in pairs opposite each other on a line at a distinct angle, in many cases a right angle to the margins or length of the strip. The openings 2| may be produced easily and at a low cost by known and available punch press or other known equipment, which need not here be described in detail since it constitutes of itself no part of the present invention.

The ensuing step in forming the body strip consists in slitting, punching ofotherwise cutting the strip along a series of evenly spaced parallel lines connecting the openings 2| above described. It is a preference that, as the strip is so apertured these lines, although straight for the greater part of their length, be curved somewhat at their ends, as best appears. in Fig. 2, these curved portions of the adjacent blade lines being indicated respectively at 23 and 24.

Either simultaneously with the slitting or punching operation or following it, the portions intervening the transverse slits, the rectilinear.

parts of which are indicated at 25 in the finished body, are bent out of the plane of the strip, each to the same extent and shape, so as to provide the requisite blade form and angle.

Another operation which, as will be understood, may be conducted concurrently with either or both of those aforesaid, consists in bending up a marginal portion of the strip 20 so as to form thereon one or more flanges 26 (Fig. 6), each such flange being preferably at a right angle to the body of the strip and in assembly being disposed radially, preferably .outwardly, of theflnished rotor body. A still further operation which may be conducted concurrently with or subsequently to any of those aforesaid, consists in providing by any suitable or known equipment, a plurality of substantially evenly spaced and radially extending notches 21, these recesses extending inwardly to a slight extent from the outermost periphery of the flange 26. The strip from which the body is formed, may be now considered ready for assembly to the end ring or rings, being now pierced between blades, with the blades shaped, the peripheral flange or flanges 26 formed thereon, and they in turn being peripherally notched to facilitate assumption by the body of the required cylindrical form.

The circumferential blade strip is now passed through a suitable shaping agency, for example, a roll coiler, to bring it to the desired cylindrical form, the radius of curvature to be imparted as by the roll coiler, being determined by the length of strip, and more particularly by the diameter of completed wheel orrotor. Incident to the caller operation on the body-forming strip, there is applied thereto, preferably midway between the ends of the blades 30, a tension band or the like which is of a length approximating the circumference of the finished wheel. A suitable form of this element is indicated at 3| as consisting of a wire of round section, preferably of a metal conforming somewhat to that of the body of the rotor, for example, a drawn steel wire. It will be understood that the application of the band 3| at the time of coiling the body strip, results in its serving a distinct purpose in the method outlined, in that the band prevents any tendency of the strip throughout subsequent steps, to reassume its rectilinear form. As will hereinafter appear, the band or wire 3i further serves an important structural purpose in the finished assembly, as a restraining or confining element, being essentially a tension member. The ends of the wire are welded together to form a smooth joint, being preferably butt welded as at 32 so as to obviate any substantial overlap.

It is a preference, incident to forming the slits 25 as by punching in order to define the blades of the wheel, that alternate slits 25 in the strip 20 be provided with notches or depressions best shown at 33 (Fig. 3), the resulting recesses serving as seats for the tension band or wire 3|, and conforming substantially thereto in curvature or other shaping. This arrangement serves as will appear, to enable locating the band or wire 3| substantially within the peripheral confines of the body proper, and the interfitting relation of the tension band 3| and the blades, serves in operation or handling of the fan, to obviate any tendency of the band to slip in either direction axially of the rotor or otherwise to become displaced. If desired, the band 3| may be even more rigidly positioned by spot welding it to some or all of the blades, as indicated at 3IA (Fig. 3).

It is preferred that the length of the strip 20 be such that its ends will meet smoothly, without overlap, and the strip ends welded internally to the and ring or rings. However, if desired, the bladed por'tion of the strip 20 may be provided with an extension beyond one or both of the terminal blades of .the strip, and when coiled into cylindrical form, the extended areas are.

overlapped between the end blades of the strip, and lap welded internally of the rotor body, for example along a zone or line as indicated at 3| (Fig. 1).

There now remains to be described, the assembly of the finished cylindrical body rim to the one or more shaft-mounting rings which may, for example, consist of the end rings constituted by elements l2, l3, l4, etc. The assembly of the rings and body consists, through suitable jigs or holding agencies, in locating the ring portions of the rim l3 including portions 35 and 36, are folded over the flange 26 m that the part 35 overlies the flange, the part 36 then being doubled over the finished rim l3 and brought parallel thereto with the efiect of firmly gripping or embracing the flange 26 between the elements l3 and 36.

It may be noted that the end ring (2, for example, is initially or later so formed as to pro- 'vlde an offset 31 resulting in a. shoulder 40 constituting a seat or rest for the margin of the strip or rim. It is a further preference that the original diameter of the ring l2 be such that, having regard for the gauge of the body and hence the flange 26, when the portions 35 and 36 are crimped into assembly as shown by Fig. 6, the end margin of the downturned flange 36 abuts the portion of the strip 20 just inwardly of the flange. The ofiset 31 also offers the advantage of providing a seat for the reception, between the ring and edge of strip ill, of welding metal as indicated at H. A line of welding in this zone may not be necessary in the smaller sizes of wheels, but when desired for strengthening in the larger sizes, may be utilized as suggested by Fig, 6.

It is a preference, as before noted, that the line of openings 2!, defining the ends of the blades, be located somewhat inwardly of the margin of the strip forming the bladed portion of the body, so that in the finished rotor or wheel, there remains at each end an appreciable cylindrical portion 42. This arrangement tends to obviate any likelihood of fracture of the metal beyond the openings 2|, incident to any vibration of the finished wheel, or due to stresses in forming up the bladed strip.

It is to be noted that in the assembly described, there is a distinct coaction and cooperative relation between the crimped end-ring assembly and the intermediate tension ring, with the stripformed body, in that each of the holding and assembly expedients provides a continuous zone of securement, in distinction from the spaced points of anchorage provided by the more usual riveted construction. The presently described arrangement enables the use of a. lighter gauge of metal, or conversely stated, produces a. more rigid wheel, utilizing any given gauge of metal. The characteristic of rigidity'is an important feature, since the rotor of the disclosed example cannot, without resulting in adverse air efiects, be internally braced after the manner of many stationary cylindrical structures.

Although the example disclosed has been described throughout as a welded structure, it is to be noted that soldering, brazing, or in some cases riveting may be employed within the scope of some of the aspects of the invention, and that a number of changes may be made in the several elements and their assembly as well as in the steps involved in the described method of producing the article, all without departing from the full intended scope and spirit of the invention as defined by the claims hereunto appended.

I claim:

1. A rotor for a centrifugal blower, including a rim or body formed of a continuous strip of sheet metal provided with slits and formed between the slits to provide a. plurality of blades, and provided with a continuous margin adjacent the ends of the blades, said marginal portion being bent radially beyond the cylindrical plane of the adjacent strip, and provided with a plurality of radially extending notches, and a shaftmounting ring of sheet metal including a periphcral portion folded into crimped assembled relation to the rim or body and embracing and covering the notched areas of said marginal portion.

2. An open end centrifugal blower wheel or fan, including a one-piece bladed body or rim provided with a notched, radially extending flange lying substantially in the plane of the end of the wheel, a one-piece end ring of sheet metal having a rim portion of greater diameter than that of the body of the wheel, and a doubled portion on the rim of the ring, which engages opposite sides of said flange and overlies the notched portion thereof for securement oi the end ring to the body of the wheel.

3. A centrifugal blower wheel of double end type, including a body or rim element of cylindrical form, constructed of a strip of sheet metal characterized by slits of axial trend and provided with rounded apertures at the ends of the slits, and inwardly of the lateral margins of the strip, the metal portions intervening the slits and apertures being shaped and bent inwardly of the cylindrical plane of the body to form blades of the desired form and angle, a radially extending flange formed on each of the body beyond the blade-forming portions thereof, the flanges being radially and peripherally slotted, a shaft mounting ring at each end of the body, each such ring including an annular offset providing a shoulder or seat for the body strip, a peripheral portion outwardly of the shoulder, folded and crimped into embracing engagement with the flange and overlying the notched portion thereof for assembly of the ring to the body, a tension band embracing the body on a bladed portion thereof substantially between the shaft mounting rings, a plurality of the blades being provided with recesses conforming to and partially embracing the tension band and enacting therewith to prevent axial displacement of the band along the blades.

4. In a rotor for a centrifugal blower, a rotor rim or body formed of a strip of sheet metal curved to cylindrical form, and provided with incisions of a generally axial trend, the metal between which is shaped and inclined to form, a plurality of blades, at least one margin of the blade or body being provided with an out-turned radial flange, the flange being provided with a plurality of indents or interrupted areas extending depthwise of the flange substantially throughout its full width or depth, and an end ring formed of sheet metal and having a peripheral portion bent over said flange in embracing relation thereto for the purpose of covering said indents, embracing the flange and serving to secure the end ring to the rim or body of the rotor.

5. A centrifugal blower wheel of double end type, including a body or rim element of cylindrical form, constructed of a strip of sheet metal characterized by slits of axial trend and provided with roimded apertures at the ends of the slits, and inwardly of the lateral margins of the strip, the metal portions intervening the slits and providing a shoulder or seat for the body strip,

a peripheral portion outwardly of the shoulder.

'folded and crimped into embracing engagement with the flange and overlying the notched portion thereof for assembly of the ring to the body.

6. A centrifugal blower wheel of double open end type, including a body element of cylindrical form, constructed of a. strip of sheet metal characterized by slits of axial trend terminating inwardly of the lateral margins of the strip, the

metal portions intervening the slits being shaped and bent inwardly of the cylindrical plane of the body to form blades of the desired form and angle, a' radially extending flange formed on each of the body margins beyond the bladeforming portions thereof, the flanges being radially slotted, a shaft mounting ring at each end of the body, each said ring including antannular oifset providing a shoulder or seat for the body strip, and a peripheral portion outwardly of the shoulder, secured in engagement with the flange and overlying the notched portions thereof.

7. A centrifugal blower wheel of double open end type including a body or rim element of cylindrical form, constructed of a single strip of sheet metal characterized by slots of axial trend terminating inwardly of the lateral margins of the strip, the portions intervening the slits being shaped and bent inwardly of the cylindrical plane of the body to form blades of the desired form and angle, an out-turned radially extending flange formed on each of the opposite margins of the body beyond the blade-forming portions thereof, the flanges being indented or interrupted substantially over their full width, and radially or depthwise thereof, a shaft mounting ring at each end of the body, each such ring being formed to provide an annular offset constituting a shoulder or seat for the body strip and extended outwardly of the strip and into embracing engagement with the flange so as to overlie and grip the interrupted or indented portions of the flange for holding the ring in assembly with 1 the body.

8. An open end centrifugal blower wheel or fan, including a one-piece body provided with blades, and including a notched, radially extending flange lying substantially in the plane of the end of the wheel, a one-piece end ring of sheet metal having a rim portion of greater diameter than that of the body of the wheel, and a doubled portion on the rim of the ring which engages opposite sides of said flange and overlies the notched portion thereof for securement of the end ring to the body of the wheel, one of the elements of said doubled portion lying in a plane normal to the axis of the wheel and having an annular edge portion snugly abutting and endwise overlying the adjacent lateral margin of the body, in a manner directly to resist any tendency of outward movement of the body, under centrifugal stresses.

9. An open end centrifugal blower wheel or fan, including a one-piece body provided with blades, and including a notched, radially extending flange lying substantially in the plane of the end of the wheel, a one-piece end ring of sheet metal having a rim portion of greater diameter than that of the body of the wheel, a doubled portion on the rim. of the ring, which engages opposite sides of said flange and overlies the notched portion thereof for securement of the end ring to the body of the wheel, one of the elements of the doubled portion on the rim, lying in a plane normal to the axis of the wheel and having an annular edge portion snugly abutting and directly overlying the adjacent lateral margin of the body, in a manner directly to resist any tendency of outward movement of the body under centrifugal stresses, and means securing the body to the end ring, along a substantially continuous zone of junction of the body and end ring, interiorly of the body.

10. A centrifugal blower wheel or fan including a one-piece body formed to provide blades thereon, and further provided with a notched radially extending flange lying substantially in the plane of the end of the wheel, a one-piece end ring of sheet metal having a rim portion of greater diameter than that of the body, the outer portion of the ring being bent axially outwardly to provide an annular offset constituting a seat on which the body of the wheel rests, the rim of the ring outwardly of said seat including a doubled portion which engages opposite sides of said notched flange and overlies the notched portion thereof for securement of the end ring to the body of the wheel, said doubled portion terminating just over, and coacting with said annular seat, to embrace the margin of the body between said doubled portion and seat.

ADDISON W. EVANS.

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