US2316608A

US2316608A - Centrifugal fan

Info

Publication number: US2316608A
Application number: US301416A
Authority: US
Inventors: Kenton D Mcmahan
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1939-10-26
Filing date: 1939-10-26
Publication date: 1943-04-13
Anticipated expiration: 1960-04-13

Description

April 13, 1943. K. DQMcMAHAN CENTRIFUGAL FAN Filed Oct. 26, 1939 Fig. I.

Kenton D 51 han, b JV 5. 2

Invent or V c me 'ing the air.

Patented Apr. 13, 1943 CENTRIFUGAL FAN Kenton D. McMahan, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application October 26, 1939, Serial No. 301,416

(or. 23o 117 5 Claims.

The-present invention relates to centrifugal fans and similar devices having rotatable parts which must be accurately aligned with a cooperating part or device,

The object of my invention is to provide an improved construction and arrangement for resiliently supporting and aligning a rotatable device and in particular for resiliently supporting and aligning centrifugal fan impellers with respect to the fan casings. For a consideration of what I believe novel and my invention, attention is directed to the following description and the claims appended thereto. In the accompanying drawing, Fig. 1 is a sectional elevation of a centrifugal fan embodying my invention; Fig. 2 is a fragmentary perspective view of one of the resilient supporting rings; Fig. 3 is an enlarged sectional view of the resilient support; and Fig. 4 is a diagrammatic view illustrating the use of the fan.

Referring to the drawing, there is shown a centrifugal fan having a scroll casing I provided with an inlet orifice ring 2 connected to a duct 3, and a discharge outlet 4 connected to a duct 5. The fan casing is supported on a base 6 having a pedestal 1 at the front bolted to thefan casing and having a pedestal 8 at the rear provided at its upper end with a cylindrical housing 9 for an electric motor l0. At the ends of the housing 9 are circular end frames II and I2 which are clamped to the ends of the housing 9 by through-bolts I3 extending through clearance openings (not shown) in the motor. The end frame II forms part of the rear wall of the fan casing. By turning the fan casing with respectto the pedestal 'l and the end frame II, the angular position of the discharge outlet 4 may be changed to conform with the position of the duct 5. Within the fan casing is a bladed centrifugal fan impeller l4 having a hub l5 flxed to the motor shaft I6. 7 covered by a cap l1 fixed to the impeller hub. The front ends ill of the fan blades project within the inlet orifice 2 and serve as scoops for directing air from the inlet to the discharge edges IQ of the fan blades. A shroud ring 20 secured to the blades at the front ends assists in direct- Leakage of air between the fan blades and the inlet opening is prevented by a flange 2| on the shroud ring which has a running clearance with a flange 22 at the inner end of the casing inlet 2. Leakage at the back of the fan The end of the motor shaft is is prevented by a cylindrical flange 26 on the im- I peller hub l5 and projecting within a flange 21 on the end frame member II. The flanges 26 and 21 are closely spaced and cooperate to provide a seal. For best operation of the centrifugal fan it is desirable that the clearance between the flanges 2| and 22 and between the

flanges

28 and 27 be a minimum.

The motor and impeller are resiliently supported by resilient rings 28 of rubber or similar material arranged within circular openings in the end frames II and I2 and surrounding hubs'29 at each end of the motor. The outer surfaces 30 of the rubber rings are of slightly smaller diameter than the concave inner surfaces 3| of the openings in the end frames II and I2. The rubber rings 28 may therefore be easily inserted in the openings in the end frames. The rubber rings are clamped to the motor hubs 29 by clamping rings 32 secured to the motor hubs by bolts 33 extending through axial grooves 34 in the inner surfaces of the rub-ber rings. Thebolts cooperate with the grooves to non-rotatably key the rubber rings to the motor hubs. Before the bolts 33 are tightened, the rubber rings fit loosely between the concave surfaces 3| on the end frames II and I2 and between the opposed radial surfaces 35 and 36 respectively on the motor hubs and on the clamping rings and concentric with the surfaces 3|. When the bolts 33 are tightened, the rubber rings are compressed axially and the rubber flows or is squeezed radially, being forced outward into tight engagement with the concave surfaces 3| and being forced laterally into tight engagement with the surfaces of '35 and 36on the motor hub and clamping ring.

Due to the grooves 31a in the inner surface of the rubber rings and also to the fact that the pressure of the clamping rings is mainly on the inner part of the rubber rings, the rubber rings are squeezed mainly outward so that pressure is not exerted on the bolts 33 in an amount great enough to prevent turning of the bolts. From one aspect, the rubber rings are subjected to an eccentric squeezing. When the rubber rings are squeezed between the clamping rings, the rubber rings are non-rotatably secured by friction to the concave surfaces 3i and to'the radial surfaces 35 and 36. The axial grooves 34 are therefore unnecessary in so far as the securing of the rubber rings to the motor hubs is concerned. I Since the rubber rings are fixed both to the motorhubs 29 and to the end frames II and I2, the rings provide a torsionally resilient support for'the motor and impeller spaced apart along and surrounding the axis of the motor which decreases the noise and vibration transmitted from the motor and impeller.

Since the weight of the motor and impeller is carried by the lower half of the rubber rings, the compression of the rubber rings will vary with the position in which the fan is mounted. For example, if the'fan is mountedon the floor, as shown in full lines in Fig. 4, the weight of the motor and impeller will be carried by the lower half of the rubber rings. pended from the ceiling, as shown in dotted lines in Fig. 4, the weight will now be carried by that If the motor is suspart of the rubber rings which was the upper half when the fan was mounted on the floor. The compression of the rubber rings under the weight of the motor and impeller causes the axis of the impeller to be shifted with respect to the fan casing. This obviously changes, the running clearance between the impeller and casing and makes necessary either the provision of larger clearance, resulting in less efficient operation, or the use of expensive constructions for re-aligning the impeller with the casing. Alignment of the impeller with the casing is also necessary to take care of variations in the casing dimensions which are likely to be large if the casing is made of sheet metal. The variations in casing dimensions may be due to manufacture or to distortion of the casing during use.

In the present construction the alignment of the impeller with the casing is effected by varying the compression of the rubber rings between the clamping rings 32 and the motor hubs 29. The function of the clamping rings in aligning the impeller is illustrated in Fig. 3. At the lower half of Fig. 3 the bolts 33 are tighter than at the upper half, and accordingly the rubber rings are squeezed radially outward to a greater extent at the lower half. If no load were carried by the rubber rings, the distance A would therefore be greater than the distance B and the center of the motor shaft and impeller would be above the center of the fan casing. When the support is arranged so that the load is carried on thelower half of the rubber rings, the rubber deflects so that the distance A becomes equal to the distance B and, in other words, brings the center of the motor and impeller into coincidence with the center of the fan casing. By tightening or loosenv ing the bolts 33 around the circumference of the clamping rings-32 it is therefore possible to align the motor and impeller with respect to the fan casing.

In carrying out the alignment operation, the impeller I4 is removed from the motor hub and the bolts 33 in the clamping ring 32 at the end frame II are adjusted so that; the motor shaft I 6 is centrally located with respect to the casing flange 21. The impeller I4 is then mounted on the motor shaft and the bolts in the clamping ring at the end frame H! are adjusted to provide the proper clearance between the flanges 2| and 22. When this operation is completed the impeller is accurately aligned with respect to the fan casing for the position in which the fan is to be mounted. If the fan is moved to another position the alignment operation will have to be repeated since the load distribution on the rubber rings is changed by the new location.

The above-described construction provides an efficient resilient mounting which has the further'advantage of facilitating alignment of the impeller with its casing. Although the invention has been described as applied to a centrifugal fan it is applicable to other uses where a device mounted on a shaft is to be resiliently supported and aligned with a cooperating part.

the motor for yielding movement relative to the casing comprising rings of rubber-like material between said surfaces, and means for compressing the rings axially to squeeze the rings radially into engagement with said surfaces, said compressing means being adjustable to vary the compression of the rings around the circumference thereof to displace the motor axis radially and thereby align the impeller with its casing.

2. In combination, a motor, an impeller mounted thereon, a support, a casing for the impeller with which the impeller has a running clearance, a resilient mounting for supporting the motor for yielding movement relative to the casing comprising members of rubber-like material spaced along and surrounding the motor axis, inner and outer'surfaces on the motor and support engageable by the inner and outer surfaces of said members, and means for compressing said members axially to squeeze the members radially into engagement with said surfaces, said compressing means adjustable to vary the compression of said members around the motor axis to displace the motor axis radially and thereby align the impeller with its casing.

3. In combination, a motor, an impeller mounted thereon, a support, a casing for the impeller with which the impeller has a running clearance, a resilient mounting for sup porting the motor for yielding movement relative to the casing including a ring of rubberlike material surrounding the motor axis, concentric inner and outer surfaces on the motor and support, and clamping means for compressing said rubber ring axially to squeeze the rubber ring radially into engagement with said surfaces, the pressure of said clamping means being adjustable around the motor axis whereby the amount of radial squeezing of the rubber ring is adjustable to shift the motor axis radially and align the impeller with its casing.

4. In combination, a structure having a shaft journaled therein, a support, said structure and said support comprising members movable relative to each other transverse to the axis of the shaft, a resilient mounting for said structure ineluding a ring of rubber-like material surrounding the axis of the shaft and having inner and outer surfaces, one of said surfaces having a circumferential groove therein and the other of said surfaces engaging one of said members, clamping means secured to the other of said members and engaging the ends of the ring for compressing the ring axially adjacent saidgroove whereby said other'surface of the ring is squeezed radially into engagement with said one member.

5. In combination, a structure having a shaft journaled therein, a support, a part with which What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a motor, an impeller mounted thereon, a support, a casing for the impeller with which the impeller has a running clearance, inner and outer surfaces on the motor and support spaced apart along and surrounding the motor axis, a resilient mounting for supporting the shaft is to be aligned, said structure and said support comprising members movable relativeto each other transverse to the axis of the shaft, a resilient mounting for supporting the structure for-yielding movement relative to said part comprising rubber-like material surrounding the axis of the shaft and having inner and outer surfaces engaging said members, and means for compressing said rubber-like material axially to squeeze it radially and thereby shift the axis of said shaft relative to said support, said compressing means being adjustable around the axis of the shaft to vary the amount of radial squeezing whereby the shaft may be aligned with said part.

KENTON D. McMAI-IAN.