US2876946A

US2876946A - Centrifugal blower

Info

Publication number: US2876946A
Application number: US433654A
Authority: US
Inventors: Hornschuch Hanns
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Co
Priority date: 1954-06-01
Filing date: 1954-06-01
Publication date: 1959-03-10
Anticipated expiration: 1976-03-10

Description

March 10, 1959 H. HORNSCHUCH 2,876,946

. CENTRIFUGAL BLOWER Filed June 1, 1954 7 r so g j v 2 ss 82 83 64 7| 20 2s I83 I 74 2 38 4O 4 I 4 60 92 98 7 45L '46 4 5 42 as 7s I INVENTOR HANNS HORNSCHUCH HIS ATTORNEY United States CENTRIFUGAL BLOWER Harms Hornschuch, Easton, Pa., assignor to Ingersoll- Rand Company, New York, N. Y., a corporation of 'New Jersey Application June 1, 1954, Serial No. 433,654

6 Claims. (Cl. 230-127) This invention relates to blowers, and more particu* larly to a casing for high pressure centrifugal blowers. An object of the invention is to provide an improved construction for a high pressure centrifugal blower casing which minimizes and balances deformation of the casing, thereby eliminating misalignment of the rotative parts of the blower with respect to the driving motor.

. Other objects will be apparent from the following description of the accompanying drawings, which illustrate a preferred embodiment of the invention in which similar reference numerals refer to similar parts.

Fig. 1 is'a side elevation of a motor driven centrifugal blower having a casing constructed in accordance with the practice of the invention,

Fig. 2 is a cross section taken along the line 2-2 of Fig. 1 looking in the direction of the arrows, and

Fig. 3 is a cross section taken along the line 3-3 of Fig. 2 looking in thedirection of-the arrows;

Referring to Fig. 1 of the drawings, the invention is shown as applied to a centrifugal blower 20 driven by an electric motor 22 through a coupling 24- for compressing a fluid, such as gas, which enters a casing 26 under pressure through an inlet nozzle" 28 at one end of the casing and is discharged at increased pressure through a discharge nozzle 30 on the side of the casing.

Referring in greater detail to the construction of the blower, the casing 26 has a demountably attached bearing housing 32, fastened thereto:by bolts 34 to support a shaft 36, which is rotatable in

bearings

38 and 40, at the inner' and outer ends, respectively, of the bearing housing 32. On the inner end of the shaft 36 is fixedly mounted a centrifugal type impeller 42 by means of a nut 44, a beveled washer 46 and a key 48. The impeller 42, which is of the closed type, receives the gas axially at the eye 50 and discharges it radially through passages 52 formed by blades 54 and front and rear end walls 56 and 58, respectively.

On the outer end of the shaft 36 is fixedly mounted the coupling 24 for transmitting power from a motor shaft 60 to the shaft 36 and the impeller 42. Suitable packing means 62 is provided in the bearing housing 32 for preventing leakage of gas along the shaft 36 to the atmosphere.

In accordance with the practice of the invention, the casing 26, comprises a relatively thick-walled generally circular-shaped outer portion 64 coaxial with the shaft 36 and including the integrally connected inlet nozzle 28 and the laterally extending discharge nozzle 38 which, with the exception of the inlet nozzle, are internally subjected to the gas discharge pressure. The outer casing portion 64, by reason of its thick wall, is adapted to resist the discharge pressure. Likewise, by means of its generally circular shape and coaxial relation with the shaft it is adapted to balance the small amount of strain produced by said pressure and thereby prevent localized deformation.

Contained within the outer walled portion 64 of the casing 26 and integral therewith is a relatively thin-walled 2,876,946 Patented Mar. 10, 1959 volute-shaped inner casing portion 66 which defines a discharge chamber 68 positioned about the impeller in radial communicative relation with the passages 52, thereby constituting the working part of the casing 26. Two

chambers

70 and 71 in the outer walled portion 64 surround the inner casing portion 66 at the motor end and the nozzle end of the blower, respectively. Communication between the discharge chamber 68 and the discharge nozzle 30 is afforded by a passage 80 in the casing 26.

For the purpose of bracing the inner casing portion 66, a radially disposed Wall 82 is cast integral with the inner casing portion and the outer casing portion 64. Holes 83 are formed in the wall 82 for providing com munication between the

chambers

70 and 71.

The inner section of the inner casing portion 66 on the motor side comprises a hub 72 encircling a cylindrical portion 74 on the inner end of the bearing housing 32 with suflicient clearance to form an annular restricted passage 76 for connecting the

chambers

68 and 70. Thus, gas under discharge pressure is permitted on both sides of the inner casing portion 66 such that the pressure is substantially equalized, thereby preventing the occurrence of any strain in said inner casing portion.

A truncated-cone-shaped duct 84 having radially disposed internal ribs conveys the gas from the inlet nozzle 28 to the impeller and is connected to an internal circular flange 86 on the inner casing portion 66 on the inlet side of the impeller. The inlet end of the duct 84 has a short cylindrical surface 88 on its periphery for slidable engagement with a correspondingly shaped surface 96 in the nozzle 28. The surface 88 has a groove 92 containing packing 94 to provide a seal for the joint thus formed.

On the inner end of the duct 84 is an external annular flange 96 which seats against the outer side of the flange 86 to form a fluid tight joint. Seating against the inner side of the flange 86 is a wearing ring 98 encircling the eye 50 of the impeller 42 in sliding engagement to prevent leakage of discharge gas into the impeller eye. The flanges 86 and 96 and the wearing ring 98 are clamped together by bolts 100, which pass through the ring 98 and the flange 86 and threadedly engage the flange 96.

In operation, gas under pressure in the neighborhood of 780 pounds per square inch is drawn into the blower 20 through the inlet nozzle 28 and the duct 84 to the eye 50 of the impeller 42. There it is picked up by the impeller blades 54 which impel it radially at increased pressure in the neighborhood of 800 pounds per square inch through the passages 52 into the discharge chamber 68 within the volute-shaped inner casing portion 66 and thence out through the passage and the discharge nozzle 38. Simultaneously, some of the discharge gas leaving the impeller passages 52 continues through the passage '76 into the chamber 70 and thence through the holes 83 into the chamber 71, thereby equalizing the pressure in the

chambers

68, 70 and 71.

It will be seen that the inner casing portion 66, being subjected to the discharge pressure of the gas both internally and externally, is always in balance and, therefore, cannot transfer any strain to the integrally connected outer casing portion 64. Likewise, the generally circularshaped outer casing portion with its thick wall and in tegrally connected inner casing portion serving as a rib therefor, is adapted to resist the internal discharge pressure, prevent radial deformation and minimize and balance any axial strain imposed thereby. In addition, the duct 84 being subjected internally to the inlet pressure and externally to the discharge pressure is also suited by reason of its shape and internal ribs 75 to eliminate any unequal deformation therein, and by virtue of its slidable engagement with the nozzle 28 cannot transmit any axial strain of the outer casing portion 64 to the inner casing portion 66. Moreover, "the-passage 76 is of sufficient width to preventcontact of the hearinghousingfilwith the inner casing portion 66,,thereby eliminating the possibility of any transmission of strain thereto.

Thus,:a blower casinglisprovided which precludes-unevendeformation ,thereof and; accordingly maintains the aXialalignment-of the rotatingparts, thereby eliminating vibration and=preventing excessive bearing wear.

It willbeunderstood, that the preferred embodiment shownin the drawings as applied to a blower with end suction is only. one form ofthe invention. The invention -.could conceivably also take the form of acasing for a blowerwith side-suction, wherein the inlet and discharge-nozzles would belocatedon opposite sides of the casingiin thesame or parallel planes. Inbothcases, the chambers :between the inner and-outer casing portions mightbetin:communicationewith the inlet nozzle and blocked oil from the discharge chamberwithin the inner casing portion. :Any strain occurringin the inner casing portion-resulting. from the existence of a pressure differential thereacrosswould then not be transmitted to the outer casing:.portion because of the relatively small area of contact between the two portions.

Therefore, a rugged and effective construction is provided whereby the objects hereinbefore referred to are accomplished.

I claim:

1. A centrifugal blower comprising an inner casing of volute form, a shaft extending into the volute casing, a rotor onthe shaft in the volute casing, an outer casing enveloping the inner casing and forming integrally therewith a pressure chamber surrounding the volute casing and meansto equalize the innerand outer pressures on all parts of the volute casing,-said outer casing having a wall ofsubstantially uniform section throughout and beinglsubstantialiyin the form of a figure of revolution about the axis of said shaft.

2. A- centrifugal blower comprising an inner casing of volute form, a shaft extending into the volute casing, a rotor on theshaft in the volute casing, an outer casing enveloping the increasing and forming integrally therewith a pressure chamber surrounding the volute casing, means to equalize pressures within and outside at all parts of the volute casing, said outer casing having a wall of uniform section throughout and being substantially in the form of a figure ofrevolution about the axis of said shaft, a nozzle formed axially in the outer casing, an inlet aperture in said volute casing and a duct attached to one of saidcasings and having a fluid tight slidsaid .nozzle into thevolute. easing.

3. A centrifugal blower comprising an inner casing of volute form, a shaft extending into the volute casing, a rotor on the shaft in the volute casing, an outer casing enveloping the inner casing and forming integrally therewith a pressure chamber surrounding the volute casing and means to equalize the pressures within and without the volute casing at. allpartsthereof; said outer casing having awall of substantially uniform section throughout andbeingsubstantially. in th v form of avfiguretof -reyolution about the axis of said shaft, saidvolute .casing -.-and said outer casing being formed integrally with each other.

4. A- centrifugal blower comprising-a shaft, :2. centrifugal impeller on the shaft to develop fluid pressure, a volute casing for the impeller, afl'uid tight external casing having an inlet nozzle and having a connection to the volute casing only at the central periphery thereof and forming the -1sole,-support-of:2the vvo1ute,-.--,said1:outer casing envelopingr -said .volute;;casing .whereby taxi. .ex-. pansion. and contraction .ofthe .side wallsnfs'aid outer casing is entirely independent-of.said.volute.-.casing,,z,a bearing housing for the. shaft mounted-.011 the outencasing. and extending. into thevolute-casing: to fQl'fllvil'B- stricted passage-to the interior. of the outercasing; and free tomove with respect to the volutecasing; andtaduct positioned at the eye of said impeller-rand slidablyasso-v ciating said nvolute casing and; said. inlet nozzle.

5. A centrifugal blower. as set forth in claim.4 in which saidconnection is integral with both said'casings.

16. A centrifugal blower as set forth-in claim 4 inwhich said restricted passage providesmeansfor equalizing the fiuid pressure on the inner and outer wallsof said volute casing.

References. Cited lathe -file;of this patent UNITED STATES PATENTS