US 2354653 A
Description (OCR text may contain errors)
w. H. ALLEN 2,354,653
IMPELLER Filed June 11. 1940 2 Sheets-Sheet 1 Inventor-z Wayne H. Allen,
His Att or-ne Aw I, 1944. w. H. ALLEN 2,354,653
IMPELLER Filed June 11, 1940 2 Sheets-Sheet 2 Inventor: Wayne H. Allen,
Wa ye. Awwlm his Attorney Patented Aug. 1, 1944 IMPELLER Wayne H. Allen, Lynn, Mass., assignor to General ,Electric Company, a corporation of New York Application June 11, 1940, Serial No. 339,911
The present invention relates to impellers such as are used in centrifugal blowers for impelling and compressing air and like gaseous mediums. Such impellers usually are in the form of a disk with a plurality of blades secured thereto or in-' tegrally formed therewith. The blades may be in radial direction but preferably they are inclined to the radial direction.
The object of my invention is to provide an improved construction and method of making impellers whereby high pressure rise for a given impeller diameter and speed and high efficiency in operation are attained and the manufacturing cost reduced.
For a consideration of what I believe to be novel and my invention, attention is directed to the following description and the claims appended thereto in connection with the accompanying drawings.
In the drawings Fig. 1 illustrates a perspective view of an impeller embodying my invention; Fig. 2 shows to a smaller scale than Fig. l a blank from which the impeller is made; Figs. 3, 4, 5 and 6 illustrate the impeller in several stages and positions during the manufacturing process, together with tools used in the manufacture; Fig. 4 is a front view of the arrangement shown in Fig. 3; Fig. 7 shows a special cutter used in the machining of the impeller; Fig. 8 shows a top view of a modification of an impeller partly broken away, and Fig. 9 shows a blower embodying my invention.
The impeller as shown in Fig. 1 comprises a disk Ill with a plurality of blades ll integrally formed with the disk. The outer edge of the disk It may be sawtoothed as disclosed in U. S. Patent No. 2,042,550, issued June 2, 1936, to S. R. Pufier, and assigned to the same assignee as the present application. The central portion of the impeller has a bore I! for connection to, a shaft, not shown. Each blade has an inner portion l3, an outer portion 14 of a width smaller than that of the inner portion IS. The impeller is intended for rotation in clockwise direction when viewed in the position shown in Fig. 1. The blades are inclined forward in the direction of rotation with regard to the corresponding radii or tangents tion. During operation, air or other medium to be impelled is forced into the channels formed between adjacent impeller blades and thrown outward by the action of the impeller. As the inlet portions of impeller blades form a smooth, continuous surface with the other portions of the blades, no abrupt change in the direction of fluid passing through the impeller passages is caused by the impeller blades but instead the path of the fluid is gradually changed from axial to radial direction thus assuring smooth operation. The direction of the flow at the exit or periphery of the blades depends upon the diameter and the speed of the impeller as well as on the degree of inclination from the radial direction of the blades.
Themethod of making an impeller according to my invention comprises as a first step the machining of a body, preferably from forged metal, for example, as shown in Fig. 2. The body constitutes essentially a disk 20 with an outer portion 2 I, an intermediate portion 22, and an inner or hub portion 23. These portions are concentric and the intermediate portion 22 is slightly thicker than the inner portion 23 and considerably thicker than the outer portion 2|. The intermediate portion 22 blends gradually into the adjacent plane surface of the outer portion 2i. The inner portion 23 forms the aforementioned axial bore or opening l2.
The second step during the manufacturing process according to my invention is the formation of the impeller blades on the disk or body 20. These blades are formed by a milling operation. To this end, as shown in Figs. 3 and 4, the body 20 is eccentrically secured to a rotatable faceplate 25 of a milling machine by means of a bolt 26. The center of rotation of the face plate 25 is spaced from the center of the body 20 by a distance designated by 21 in Fig. 4. The milling and cutting of the blades is accomplished by a milling or cutting tool 28 securely held in fixed position on a tool holder 29.
The cutting tool specially devised for this purpose, as best shown in Fig. '7, comprises two spherically shaped, concentrically spaced cutting elements 3!) and 3| having outer rortions or edges forming cutting teeth 32 and 33 respectively. Each element 30, 3| in the present example is of substantially uniform thickness and forms a segment of a sphere. These spherical cutting elements are held in spaced relation by spacing means, such as a spacer 36 between them, and secured to a stem 35 by means including a bolt 35. Relative rotational movement of the two cutting elements 30, 3| about the stem 35 is prevented by a key 31 located in aligned keyways in the elements 30, 3 l the spacer 34 and the stem 35 respectively. The spherical cutter, as shown in Fig. 4, is positioned so that the spherical center of the concentric cutting elements 30, 3| is located on the axis of rotation of the face plate 25. In addition, the spherical center of the spherical cutter, in the present instance, is located vertically at a point below the upper surface of the body 20, preferably near the lower surface thereof, as shown in Fig. 4.
The spacing of the two spherical cutting elements 30, 3|, that is, the w dth of the spacer 34 is equal to the thickness of the impeller blades. With the spherical cutter and the body 20 adjacent on the milling machine, as shown in Figs. 3 and 4, the cutting of the blades may be accomplished by successively turning the face plate in clockwise direction, when viewed in Fig. 3, predetermined distances or angles and intermittently, that is, intermediate successive turning operations of the face plate 25, adjusting the body 2 I. During a single cutting operation the surfaces of an individual blade are completely formed except for the root portion of such blade. The cutting operation is terminated shortly before the cutters reach the central portion 23 (Fig. 2) of the body. In Fig. 3 the arrangement is shown in a position in which the body is moved from the cutter, that is, after the formation of two cutting grooves 38 forming a blade 39 between them. Fig. shows the cutter in engagement with the body. The body may be moved into the cutter by clockwise turning of the face plate 25 (Fig. 3) in which case the blade 39 just cut would enter the space formed between the cutting elements 30, 31. This relation is indicated by dash-dotted extensions 40 of the grooves 38. Thus. during a single cutting operation two concentric grooves are formed. The surfaces of these grooves are indicated by four radii 4 Fig. 3. The two grooves form an impeller blade 42 between them. The upper portion of the blade 42 and adjacent parts are cut away and shaded to bring out more clearly the concentric relationship of the grooves and the blades. The terms spherically shaped" and "spherical are used herein in their broader sense, meaning that the elements referred to form part of spheres or have surfaces forming part of spherical surfaces.
After a blade is cut, the face plate is turned counterclockwise. Fig. 4, that is, the body 20 is removed from the cutter and thereupon the bolt 26 is loosened and the body 2'1 is m-- tated and adjusted for the cutting of another blade. To facilitate adjustment and positioning of the body member on the face pla e m mbe". one of these members is indexed and the other s provided with a mark. In the present instance the face plate 25 has a radial mark 43. Fi 4, and the body 20 on its outer cylindrical surface has sixteen uniformly spaced indexing marks 44, the number being equal to the number of blades to be formed. Thus, upon t e completion of a blade the body 20 is rotated about ts center until the next indexing mark of the body registers with the mark 43 on the face plate.
The four radii 45 indicate the surfaces of another two concentric, spherically shamed grooves forming another blade 46 between them.
Thus, with the milling operation as described above, consecutive pairs of grooves are formed defining blades between each pair of grooves. This operation does not remove all of the material between adjacent blades. Wedge-shaped portions 41 of material are formed between consecutive pairs of grooves, that is, between adjacent 1 blades. These wedge-shaped portions of material are removed in a subsequent cutting operation, as illustrated in Fig. 6. The removal or sweeping of these wedge-shaped portions is effected by a spherical cutter 48 similar to the cutter of Fig. '7 except that it comprises only a single, spherical cutting element. The cutter 48 also serves to complete the root portion of the blades, that is, to remove material between adjacent blades adjacent the central portion 23. During manufacture. the blank 20 is gradually fed into the cutter 48. At the same time the blank is oscillated through an are bounded by adjacent blades whereby the wedge-shaped piece is gradually and completely removed. This process is known as sweeping. Upon complete removal or sweeping of the wedge-shaped portions 41 the body which now constitutes an impeller may be subject to a final machining and polishing operation to smoothen the edges of the blades. The step of removing the wedge-shaped portions 41 may be at least partly eliminated if the blank from which the impeller is made is originally formed with grooves by a forg ng die.
The impeller of Fig. 8 comprises a metal disk 50 with an outer saw-toothed edge 5| to form openings for the lateral discharge of impeller medium as more fully disclosed in the aforementioned Patent No. 2,042,550. A plurality of spherically shaped blades or vanes 52 are integrally formed with the disk. The pitch of the blades 52 is smaller than that of the corresponding blades II in Fig. 1 and the spherical centers of the blades are locatedso that adjacent blades, more particularly the inner portions thereof, overlap each other in the top view of Fig. 8. The end faces of the blades are machined to form sharp entrance edges 53.
The centrifugal type blower or compressor shown in Fig. 9 comprises a casing 55 formin an impeller chamber in which an impeller 56 is located. The impeller is driven by a shaft 51. The casing also forms a diffuser chamber 58 accommodating a diffuser having a plurality of diffuser vanes 55. The diffuser chamber 58 surrounds the outlet portion of the impeller and is in turn surrounded by a discharge scroll 60. During operation the medium to be compressed is forced into the inlet of the impeller and on its path through the passages formed by the impeller the medium is impelled and compressed. A part of the velocity energy of the medium discharged by the impeller is converted into pressure energy by the diffuser 58 on its passage into the discharge scroll 60.
Having described the method according to my invention, together with the apparatus for carryin out the method, I wish to have it understood that the apparatus and method are only illustrative and that changes may be made in both the apparatus and the method without departing from the spirit of my invention and the scope of the appended claims.
What I claim as new and desire to secure by Letters Patent of the United States, is:
1. Impeller for centrifugal compressor comprising a disk and a plurality of circumferentially spaced blades integrally formed with the front'of the disk, each blade having inner and outer surfaces concave-shaped when viewed from the back of the disk and forming parts of concentric spheres.
and forming parts 01' con- 3. Impeller for centrifugal compressors com prising a disk and a plurality of circumferentlally spaced blades integrally formed with the iront oi the disk, each blade having inner and Outer surfaces concave-shaped when viewed from the back of the disk and forming parts oi con- WAYNE H. LLEN.