US3536416A - Squirrel-cage rotor for fluid moving devices - Google Patents

Description

Oct. 27, 1970 D. 2. GLUCKSMAN 5 3 SQUIRREL-CAGE ROTOR FOR FLUID MOVING DEVICES I Filed May 14, 1968 v 4 Sheets-Sheet 1 INVENTOR.

Oct. 27, '1970 o. z. GLUCKSMAN SQUIRREL-CAGE ROTOR FOR FLUID MOVING DEVICES I Filed May 14, 1968 4 sheezs-slijjt '2 och 1970 X I73. 2. GLUCKSMAN I 3,536,416

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032m g F United States Patent O 3,536,416 SQUIRREL-CA-GE ROTOR FOR FLUID MOVING DEVICES Dov Z. Glucksman, 26 Chease Ave., West Newton, Mass. 02165 Filed May 14, 1968, Ser. No. 729,031 Int. Cl. B21k 3/04; F0411 29/26 U.S. Cl. 416178 8 Claims ABSTRACT OF THE DISCLOSURE Squirrel-cage rotors for fluid moving devices, and more particularly centrifugal fans and transverse flow fans include tapered blades of a plastic material having lateral surfaces which are eccentric cylindrical surfaces having radii of different length. Such squirrel-cage rotors miniinize the formation of eddies and can be fabricated with a minimum of cost by a novel assembly process using plastic blade-forming extrusions.

BACKGROUND OF INVENTION Squirrel-cage rotors for fluid-moving devices of a plastic material may either be fabricated, or molded as single integral units. Squirrel cage rotors designed for the latter method are relatively inflexible and, therefore, squirrel-cage rotors designed for production by the former method are preferable wherever flexibility of design, is a factor of prime importance. This invention is concerned with a squirrel-cage rotor fabricated from plastic extrusions. The geometry of the extrusions is such as to resultin a relatively small exit velocity which, in turn, is conducive to a streamlined flow pattern minimizing the formation of eddies therein. The way in which the ex- .trusions are assembled results in increased dimensional stability and reduced cost of fabrication.

Squirrel-cage rotors are used in connection with two types of fluid moving devices, namely centrifugal blowers and transverse flow blowers. In the former air, or another gaseous medium, is drawn into the cavity of the rotor,

or impeller, in an axial direction, and then passes through the rotating cascade of blades into a scroll-shaped housing having an opening from which the air or other gaseous ,medium is discharged. In the latter air, or another gaseous medium, is drawn by the rotor, or impeller, into a spe- 7 provided on both ends with tabs, or equivalent fastening projections. These tabs, or equivalent fastening projections, are used to secure both ends of the blades to end members designed to receive the tabs, or equivalent fastening projections, which are generally crimped to establish a firm connection between the blades and the end .members. The latter are generally disc-shaped, or ringshaped. The cost of manually assembling such a rotor tend to be excessive. semiautomatic assembly lines designed to cut production cost are of limited value on account of their complexity, and high prime cost.

Squirrel-cage rotors, or impellers, may also be formed of strips of metal such as steel, for instance, or aluminum, fed into a press or punch which forms consecutive blades out of the center portion of the stripof metal, leaving See" both lateral portions of the strip of metal unpunched to form lateral supports for the blades. Such blade-forming strips are then afiixed with the lateral sides thereof to disc-shaped end members. In squirrel-cage rotors fabricated in this fashion there are serious limitations in regard to the width of the blades, and in regard to the curvature, or angles, thereof. Such rotors, or impellers, therefore cannot perform as well as rotors, or impellers, which are assembled of individually formed blades.

As mentioned above, the squirrel-cage rotors, or impellers, of plastic material molded in one piece are a relatively inflexible design. Such squirrel-cage rotors, or impellers, are subject to additional limitations. Owing to mechanical strength and material flow considerations, blades of squirrel-cage rotors molded in one piece must be thicker than the blades of a comparable rotor, or impeller, having blades of metal. This results in a relatively lower performance of rotors, or impellers, which are molded in one piece. Since a plastic rotor, or impeller, molded in one piece has to be designed in such a way that the mold can be opened after completion of the molding process, the end of the blades cannot be bridged, or mechanically interconnected by an annular end member, unless the annular end member is external to the outer diameter of the blades. Such an annular end member is generally the weakest point of a squirrel-cage rotor, or impeller, that is molded in one piece.

SUMMARY OF INVENTION A squirrel-cage rotor for fluid-moving devices includes a plurality of tapered blades of a plastic material, particularly a synthetic resin. The aforementioned plurality of blades define fluid passageways having open ends close to the axis of the rotor and having open ends remote from the axis of the rotor. The surface elements of said plurality of blades adjacent said open ends close to the axis of the rotor are oriented substantially radially. The surface elements of said plurality of blades adjacent said open ends remote from the axis of the rotor are oriented substantially tangentially. Each of said plurality of blades has a pair of lateral substantially cylindrical fluid-passageway-defining surfaces. These cylindrical surfaces have radii of different length, and are eccentric. The fluid passageways defined by said plurality of blades have at least the same and preferably a larger, cross-sectional area at the open ends thereof remote from the axis of the rotor than at the open ends thereof close to the axis of said rotor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a transverse cross section through a portion of a squirrel-cage rotor embodying the present invention;

FIG. 2 is a transverse cross section through a portion of a prior art squirrel-cage rotor having blades of con stant thickness rather than tapered blades;

FIG. 3 is an exploded view of the constituent parts of a squirrel-cage rotor embodying the present invention;

FIG. 4 is a transverse cross section through a portion of a squirrel-cage rotor fabricated by assembling the parts shown in FIG. 3;

FIG. 5 is a section along VV of FIG. 4;

FIG. 6 is in part an elevation and in part a longitudinal section of another squirrel-cage rotor embodying the present invention;

FIG. 7 is a diagrammatic representation of a double inlet centrifugal blower including a squirrel-cage rotor embodying the present invention;

FIG. 8 is a diagrammatic representation of a transverse flow blower and including a squirrel-cage rotor embodying the present invention.

3 DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION This invention is based on Eulers equation for turbo machines Ap denotes the total theoretical pressure obtainable in a turbo machine;

the density of the medium;

g--the gravitational constant;

c the absolute velocity of the gaseous medium at the tip of the blades;

c the absolute velocity of the gaseous medium at the base of the blades;

u the linear speed of the rotor at the tip of the blades;

u the linear speed of the rotor at the base of the blades;

w the velocity of the gaseous medium relative to the blades at the bases thereof; and

-w -the velocity of the gaseous medium relative to the blades at the tips thereof.

It is apparent from the above equation that Ap increases as the difference between the absolute velocities of the gaseous medium at the tips of the blades and at the bases of the blades increases. It is further apparent from the above equation that Ap increases if the flow of the gaseous medium relative to the blades is decelerated from the bases of the blades to the tips thereof. This invention is predicated on the last-mentioned fact.

The squirrel-cage rotor shown in FIG. 1 includes a plurality of tapered blades 1 of a plastic material, such as a synthetic resin. Tapered blades 1 define fluid passageways 2 therebetween. Each pair of contiguous blades defines one fluid passageway 2 having a pair of open ends. The surface elements of blades 1 adjacent the open ends of passageways 2 close to the axis (not shown) of the rotor are oriented substantially radially. Hence angle a enclosed between the median plane of blades 1 and the cylindrical surface defined by the bases of blades 1 is about 90 deg. The surface elements of blades 1 situ ated adjacent the open ends of passageways 2 remote 'from they axis of the rotor are oriented substantially tangentially. Hence angle 6 enclosed between the median plane of blades 1 and the cylindrical surface c defined by the tips of blades 1 is an acute angle much smaller than 90 deg. Each blade 1 has a pair of fluid-passagedefining substantially cylindrical surfaces In and 1b. Surfaces 1a, 1b have radii of different length, and are eccentric. To be more specific, the radius of surfaces In is considerably larger than the radius of surfaces 1b. Each fluid passageway 2 has at least the same, and preferably a larger, cross-sectional area at the downstream end thereof adjacent the tips of blades 1 than at the upstream end thereof adjacent the bases of blades 1. Preferably, the cross-sectional area of passageways 2 increases in the direction of the flow of fluid indicated by arrows R, or in the direction from the radially inner cylindrical surface 0 to the radially outer cylindrical surface c The increase in cross-sectional area may be up to 10%, but should not be larger than 10%. The curvature of blades 1 should be 70 to 120 degrees.

Blades 1 are formed of plastic extrusions which are preferably tubular, i.e., define at least one internal passage extending in a direction longitudinally of the axis of the squirrel-cage rotor. As shown in FIG. 1, each blade 1 defines two such passages 1c, 1d. The tubular configuration of blades 1 tends to establish a favorable mechanicalstrength-to-weight ratio. As shown in FIG. 1, the passages 1c adjacent the bases of blades 1 are circular in cross-section and the passages 1d adjacent the tips of blades 1 are tear-drop-shaped in cross-section. The bases of blades 1 are formed by cylindrical surfaces having a 4 much smaller radius than fluid-passage-defining cylin drical surfaces 1a and 1b. e

The structure of FIG. 1 is conducive to low exit velocities, and to a streamlined flow pattern, minimizing eddies.

The prior art structure illustrated in FIG. 2 includes nontapered blades 1' having substantially the same radius of curvature as those shown in FIG. 1. In FIG. 2 the velocity of the gaseous medium is increased as the same flows through fluid passageways 2. This acceleration is followed by an abrupt deceleration at the downstream ends of passageways 2', resulting in the formation of eddies, and resulting noise and relative inefficiency.

Referring now to FIG. 3, this figure shows a plurality of blades 1 having the same geometrical configuration as described more in detail in connection with FIG. 1. FIG. 3 further shows a pair of substantially disc-shaped end members 3 and 4. End member 3 defines a hub 3a for receiving a shaft 5 which may be keyed to hub 3a by means of key clip 6. End member 3 includes an outer rim portion 3b and an intermediate plate portion 30 arranged between rim portion 3b and hub 3a. A plurality of radially extending reinforcement ribs 3d tie the plate portion 30 to hub 3a. Rim portion 3b is provided with pins 3e intended to engage the passages or cavities defined inside of tubular blades 1. Both end members 3 and 4 are of a thermoplastic material, and provided with so-called energy directors for ultrasonic welding which are circular and wedge-shaped in cross section. Reference character 3f has been applied to indicate the energy directors on end member 3 and reference character 4] has been applied to indicate the energy directors on end member 4. End member 4 is further provided with axially inwardly extending pins 4e intended to engage the passages 10 in tubular blades 1. Pins 3e and 4e are tapered in order to allow for simple location in passages 1c. The taper also provides for an interference fit with passages 10 so that these two elements will fuse together when ultrasonic vibrations are applied to members 3 and 4. Pins 32, 4e may also be cemented by an adhesive to tubular passages 10.

FIG. 4 shows the annular configuration of energy directors 39 on end member 3. The energy directors 4] on end member 4 have the same shape. When fused, energy directors 3 4f melt due to the heat generated by the friction caused by the ultrasonic vibrations, and thus firmly secure blades 1 to end members 3 and 4. The pins 3e, 4e of end members 3, 4 engage passages 10 of blades 1 when the parts shown in FIG. 3 are assembled as shown in FIG. 5. When end members 3, 4 and blade 1 are assembled to form a squirrel-cage rotor, end members 3, 4 support all tubular blades 1 on both ends thereof.

Referring now to FIG. 6, the double inlet squirrel-cage rotor shown therein includes a system of tubular blades 1 each defining a radially inner longitudinal passage 10 and a radially outer longitudinal passage 1d. The system of tubular blades 1 is the same as shown in FIGS. 1-5, and described in connection with these figures. The structure of FIG. 6 differs from that of FIGS. 3-5 in regard to the shape of the end members 3' and 4'. End members 3', 4' are identical and each includes a peripheral portion 312', 4b and a radially and axially inner portion 3g and 4g. A system of spiders 3h ties peripheral portion 3b to portion 3g, and a system of spiders 4h ties peripheral portion 4b to portion 4g. Portions 3g and 4g of end members 3, 4' are annular and a tubular hub member 3a extends through portions 3g, 4g of end members 3', 4'. The right end (as seen in FIG. 6) of hub member 3a is provided with a flange 3a" abutting against the right end surface of part 4g. Hub members 3a is made of a thermoplast and thermally staked at the left end thereof, as indicated at 3a'. 'Pins 3e integral with end member 3' project into the left ends of passages 10 defined by blades 1. In a like fashion, end member 4' is secured to the right ends of tubular blades 1. End members 3', 4' are secured simultaneously by ultrasonic welds to each of tubular blades 1, as explained more in detail in connection with FIGS. 3-5.

Referring now to FIG. 7, the structure shown therein is a rotor including tubular blades 1 and disc-shaped end members 3" and 4" supporting tubular blades 1 at the ends thereof. The rotor shown in FIG. 7 differs from the rotors which have been described above by the provision of a support 5 for tubular blades 1 arranged between end members 3", 4". Support 5 has a hub 5:: for receiving a shaft. In FIG. 7 an electric motor 6 for driving rotor 1-34"-5 and a housing 7 for housing rotor 13"-4"'5 have been indicated in dash-and-dot lines. The directions of fluid flow have been indicated by arrow S.

The rotor for a transverse flow blower shown in FIG. 8 has a considerable length. The ends of blades 1 are supported by end members 3", 4" and three additional blade supports 5', 5", 5" are arranged between end members 3", 4". In FIG. 8 an electric motor 6' for driving rotor 13"-5-5"5'-4" and a housing 7' for housing the same have been indicated by dash-and-dot lines. The direction of fluid flow has been indicated by arrows S.

I claim as my invention:

1. A squirrel-cage rotor for fluid-moving devices having a plurality of tapered blades of a plastic material, particularly of a synthetic resin, said plurality of blades defining fluid passageways having open ends close to the axis of said rotor and open ends remote from the axis of said rotor, the surface elements of said plurality of blades adjacent said open ends close to the axis of said rotor being oriented substantially radially and the surface elements of said plurality of blades adjacent said open ends remote from the axis of said rotor being oriented substantially tangentially, each of said plurality of blades having a pair of lateral substantially cylindrical fluid-passageway-defining surfaces, said surfaces having radii of different length and being eccentric, and said blades defining fiuid passageways each having an up to 10% larger cross-sectional area at the open ends thereof remote from the axis of said rotor than at the open end thereof close to the axis of said rotor.

2. A squirrel-cage rotor as specified in claim 1 wherein the blade curvature of each of said plurality of blades is between 70 degrees and 120 degrees.

3. A squirrel-cage rotor as specified in claim 1 wherein each of said plurality of blades defines at least one internal passage extending in a direction longitudinally of the axis of said rotor and wherein said plurality of :blades are arranged between a pair of end members at least one of said pair of end members having axially extending projections at the axially inner surface thereof each registering with said internal passage of one of said plurality of blades and each of said projections engaging an internal passage in one of said plurality of blades to firmly position said one of said plurality of blades relative to said one of said pair of end members.

4. A squirrel-cage rotor as specified in claim 1 wherein each of said plurality of blades is attached at each of the ends thereof to one of a pair of end members, each of said pair of end members including an axially outer portion having a relatively large diameter, an axially inner portion having a relatively small diameter and a system of slanting spiders integrating said axially outer portion and said axially inner portion of each of said pair of end members, said squirrel-cage rotor further including a tubular hub member projecting transversely through said axially inner portion of each of said pair of end members.

5. A squirrel-cage rotor for fluid-moving devices having a plurality of tubular blades of a plastic material, particularly a synthetic resin, each of said plurality of blades defining at least one internal passage extending in a direction logitudinally of the axis of said rotor from one end of each of said plurality of blades to the other end of each of said plurality of blades, said plurality of blades being arranged between and afiixed to a pair of substantially circular end members having an outer periphery substantially in registry with the radially outer edges of said plurality of blades, each of said pair of end members having on the axially inner surface thereof a plurality of axially extending projections each arranged in registry with one internal passage of one of said plurality of blades, and each of said plurality of said projections engaging an internal passage in one of said plurality of blades to firmly position said one of said plurality of blades relative to said pair of end members.

6. A squirrel-cage rotor for fluid-moving devices having a plurality of tapered blades of a plastic material, particularly of synthetic resin, said plurality of blades defining fluid-passageways having open ends close to the axis of said rotor and open ends remote from the axis of said rotor and at least the same cross-sectional area at said open ends remote from said axis of said rotor as at said open ends close to said axis of said rotor, the surface elements of said plurality of blades adjacent said open ends close to said axis of said rotor being oriented substantially radially and the surface elements of said plurality of blades adjacent said open ends remote from said axis of said rotor being oriented substantially tangentially, each of said plurality of blades having a pair of lateral substantially cylindrical fluid-passageway-defining surfaces, said surfaces having radii of different length and being eccentric, each of said plurality of blades being tubular and defining at least one internal passage extending in a direction longitudinally of the axis of said rotor, and said plurality of blades being arranged between a pair of end members having registering projections at the axially inner end surfaces thereof, and each of said projections engaging an internal passage in one of said plurality of blades to firmly position said one of said plurality of blades relative to said pair of end members.

7. A squirrel-cage rotor as specified in claim 6 wherein said plurality of blades are supported between the ends thereof by intermediate support means arranged between said pair of end members.

-8. A squirrel-cage rotor for fluid-moving devices having a plurality of tapered blades of a plastic material, particularly of synthetic resin, said plurality of blades defining fluid-passageways having open ends close to the axis of said rotor and open ends remote from the axis of said rotor and at least the same cross-sectional area at said open ends remote from said axis of said rotor as at said open ends close to said axis of said rotor, the surface elements of said plurality of blades adjacent the open ends close to the axis of said rotor being oriented substantially radially and the surface elements of said plurality of blades adjacent said open ends remote from said axis of said rotor being oriented substantially tangentially, each of said plurality of blades having a pair of lateral substantially cylindrical fiuid-passageway-defining surfaces, said surfaces having radii of different length and being eccentric, each of said plurality of blades being attached at each of the ends thereof to one of a pair of end members including an axially outer portion having a relatively large diameter, an axially inner portion having a relatively small diameter and a system of slanting spiders integrating said axially outer portion and said axially inner portion of each of said pair of end members, said squirrel-cage rotor further including a tubular hub member projecting transversely through said axially inner portion of each of said pair of end members.

References Cited UNITED STATES PATENTS 2,111,136 3/1938 Bauer 230134 1,447,916 3/ 1923 Watkins 230 -l34.45 1,906,180 4/1933 iRees 230l34.45 2,652,190 9/1953 Meltzer et a1. 230134.45

(Other references on following page) .7 8 UNITED STATES-PATENTS 1 720,856 12/ 1954 Great Britain. 2 991 004 7 19 1 D t 2 0 134 848,131 9/1960 Great Britain. 3,136,035 6/1964 22 954,369 4/1964 Great Britain. 3,140,042 7/1964 Fujii 230-134.45 y 3,226,085 12/1965 Bachl 230 134 4s 5 HENRY RADUAZO Pnmary Examiner 2,400,649 5/1946 Larsen. US Cl X R FOREIGN PATENTS 3,253 1878 Great Britain.

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