US3297239A

US3297239A - Cooling system for shafts and the like

Info

Publication number: US3297239A
Application number: US451899A
Authority: US
Inventors: Ellis W Bullock
Original assignee: Fly Ash Arrestor Corp
Current assignee: Fly Ash Arrestor Corp
Priority date: 1965-04-29
Filing date: 1965-04-29
Publication date: 1967-01-10
Anticipated expiration: 1984-01-10

Description

1967 E. w. BULLOCK COOLING SYSTEM FOR SHAFTS AND THE LIKE Filed April 29, 1965 INVENTOR. E/Z ZS M Bil/lack %447 4/M A f/omgys United States Patent 3,297,239 COOLING SYSTEM FOR SHAFTS AND THE LIKE Ellis W. Bullock, Birmingham, Ala., assignor to The Fly Ash Arrestor Corporation, a corporation of Alabama Filed Apr. 29, 1965, Ser. No. 451,899 Claims. (230128) system of the character designated which reduces linear shaft expansion to a minimum thus permitting improved coupling clearances, which results in improved performance with reduced maintenance and longer coupling life.

A further object of my invention is to provide a cooling system of the character designated which eliminates the necessity of providing a turning gear to keep the assembly from being in a static condition when the assembly is stopped under temperatures high above ambient.

A further object of my invention is to provide a cooling system of the character designated which shall be simple of construction, economical of manufacture and one which includes improved means for circulating cooling air around the shaft and hub of a fan or blower handling hot gases, which shall be effective to cool the shaft and hub without unnecessarily diluting and cooling the gases being handled.

Heretofore in the art to which my invention relates, various means have been devised for cooling the shaft of a blower or fan handling hot gases. It has been proposed to introduce cooling air between a shaft and a sleeve by drawing all of the cooling air in through passageways at the end of the sleeve. Also, the use of various liquids, such as water, oil and the like have been proposed for cooling the shaft of a blower handling hot gases. Such methods of cooling shafts have proved to be entirely unsatisfactory due to the difliculties encountered in handling the various liquids.

To overcome the above and other difficulties, I provide means for cooling the shaft of a centrifugal blower by providing a sleeve which surrounds the blower shaft whereby air is induced through the space between the sleeve and the shaft by the partial vacuum created by the centrifugal blower. Instead of providing an air inlet at the outer end of the sleeve for introducing all of the cooling air, I provide an air blower which is in communication with the outer end of the sleeve whereby cooling air is forced between the sleeve and the shaft upon an increase in pressure within the intake side of the centrifugal blower, such as would occur when the centrifugal blower is stopped. That is, the cooling air is drawn through the blower into the space between the shaft and the sleeve so long as there is a negative pressure between the sleeve and the shaft. Also, I provide means for deenergizing the cooling air blower when the temperature of the gas being conveyed through the centrifugal blower decreases to a predetermined point. One end of the sleeve surrounding the shaft communicates with a conical member which flares outwardly toward the impeller whereby the cooling air passes adjacent the impeller hub and then it is drawn outwardly by the impeller.

Apparatus embodying features of my invention is illustrated in the accompanying drawing, forming a part of this application, in which:

FIG. 1 is an elevational view partly in section, showing a conventional centrifugal blower having my invention incorporated therein;

' like.

ICC

FIG. 2 is an enlarged, elevational view, partly in section, showing one side of the apparatus shown in FIG. 1; and

FIG. 3 is a fragmental, sectional view taken generally along the line 33 of FIG. 1.

Referring now to the drawing for a better understanding of my invention, I show a centrifugal blower having a casing 10 with two

inlet chambers

11 and 12 at each side thereof. The centrifugal blower is provided with an outlet 13 and an impeller housing 14. The

inlet chambers

11 and 12 communicate with the impeller housing by conical members 16 which are tapered inwardly toward the impeller housing, as shown. Extending through the

inlet chambers

11 and 12 and the impeller housing 14 is a shaft 17 which is mounted in suitable bearings 18 which, in turn, are supported on pedestals 19, as shown. Mounted within the impeller housing 14 is an impeller having blades 21 supported by a central plate 22 and hub members 23 mounted on the shaft 17.

The apparatus described hereinabove is conventional for blowers which handle hot gases from furnaces and the My improved apparatus embodies the means for cooling the shaft 17 and the hub 23 to overcome expansion and balance problems encountered with high temperature conditions.

Surrounding the shaft 17 at each side of the plate 22 is a cooling sleeve 24. As shown in FIG. 2, each sleeve 24 surrounds the shaft 17 with a relatively close clearance and extends from a point adjacent the outer side of its associated inlet chamber to a point adjacent the hub 23. The outer end of each sleeve 24 is secured to the outer wall of the

inlet chambers

11 and 12 by suitable means, such as bolts 26.

Communicating With each sleeve 24 adjacent the outer end thereof is one end of a conduit 27. The other end of the conduit 27 is connected to the discharge side of an air blower indicated generally at 28. Where the centrifugal blower is employed to convey gases at extremely high temperatures, the cooling sleeve 24 and the conduit 27 are surrounded by a suitable insulating material indicated generally at 29 in order to keep the cooling air requirement at a minimum,

The inner end of each sleeve 24 is connected to a cone-shaped member 31 which flares outwardly toward the plate 22, as shown in FIG. 2, The cone-shaped members 31 may be formed integrally with the sleeves 24 or may be secured thereto by suitable means. Each cone member 31 is spaced from the plate 22, as shown in FIG. 2, to provide an air passageway 32 therebetween.

Mounted at each side of the plate 22 inwardly of the impeller blades 21 is an annular row of cooling air vanes 33 which serve as radiation fins and also as small fan blades that assist in producing the necessary flow of cooling air between the sleeve 24 and the shaft 17. The cone members 31 are also surrounded by the insulation material 29, as shown.

The intermediate portion of each sleeve 24 is supported by radially extending bars 34 which are connected at their outer ends to the conical members 16 of the centrifugal blower. The inner ends of the bar 34 may be connected to an annular member '36 which surrounds the insulation material 29 carried by the sleeves 24. Each annular member 36 is adapted for sliding movement relative to the insulation material 29 to permit expansion and contraction of the sleeve 24 in response to changes in temperatures.

Mounted within each

intake chamber

11 and 12 is the sensing element of a pressure switch 37 which is operatively connected to the cooling air blower 28 by :a line 38. The pressure switch 37 is designed to energize the cooling air blower when the pressure Within the

intake chambers

11 and 12 is reduced to a predetermined amount, such as occurs when the centrifugal blower is stopped. Also mounted within, each

intake chamber

11 and 12 is the sensing element of a thermal switch 39 which is operatively connected to the blower 28 by a line 41. The pressure switch 37 and the thermal switch 39 are connected to each other in series whereby they are both in circuit with the cooling air blower 28 by the

lines

38 and 41.

From the foregoing description, the operation of my improved cooling system for shafts and the like will be readily understood. When the centrifugal fan unit is Operating in a manner to create a negative inlet pressure and a slight positive discharge pressure, the negative pressure produced by the impeller blades 21 in addition to the negative pressure produced by the venturi effect resulting from gas flow over the cooling sleeve cone and in addition to the fan effect of the cooling air vanes 33 causes an air flow through the space defined between the sleeve 24 and the shaft 17. The cooling air is thus drawn inwardly through the cooling air blower 28 whereupon it passes through conduit 27 into sleeve 24 whereupon it flows in the direction of the arrows shown in FIG. 2 and is finally discharged through the passageways 32 defined between the conical members 31 and the plate 22. As the air passes between the sleeve 24 and the shaft 17, the shaft 17 is cooled. Also, the passage of the air adjacent the hub 23 cools the hub prior to discharge of the air into the impeller housing. So long as the centrifugal blower is operating with a negative intake pressure and a slight positive discharge pressure, it is not necessary for the cooling air blower 28 to be operating while the centrifugal fan unit is running. In actual practice, I find that suflicient fiow of outside air is induced through the blower 28, conduit 27 and sleeve 24 to maintain the temperature of the shaft 17 and the hub 23 below 125 F; even though the temperature of the gases being conveyed by the centrifugal blower is in excess of 1000 F.

When the centrifugal blower unit stops for any reason, the pressure switch 37 energizes the cooling air blower 28 which supplies sufiicient air through the cooling sleeve 24 to maintain the temperature of the shaft and the hub below the 125 F. maximum temperature. When the internal temperature of the

intake chambers

11 and 12 reaches a point that is F. above outside temperature, the thermal switch 39 deenergizes the air cooling blower 28. That is, when the temperature of the gases being conveyed by the centrifugal blower unit are lowered sufi'iciently to bring about a reduced internal temperature within the

intake chambers

11 and 12 which is 10 F. above outside temperature, the thermal switch 39 is moved to open position to thereby deenergize the cooling air blower 28.

When the centrifugal blower unit is operating with positive pressure on the blower discharge, no cooling air is drawn inwardly between the sleeve 24 and the shaft 17. However, since the pressure switch 37 energizes the cooling air blower 28 when there ceases to be a negative pressure within the

intake chambers

11 and 12, the cooling air blowers 28 would be energized to thus supply sufiicient cooling air to maintain the shaft 17 and the hub 23 at the desired, reduced temperature. Since the thermal switch 39 is connected in series with the pressure switch 37, the cooling air blower 28 is not energized until the fan reaches its full speed whereby the internal temperature of the

intake chambers

11 and 12 would be greater than 10 above the outside temperature. Also, while operating the centrifugal blower under positive pressures, the pressure switch 37 would cause the cooling air blower 28 to continue operation after shut-down until the internal temperature of the

intake chambers

11 and 12 reached a point that is 10 above outside temperature.

The shaft 17 for the centrifugal blower is subject to deflection due to a concentrated weight from the impeller in addition to a deflection due to a uniform loading of its own weight. These deflections determine the critical speed or frequency of the shaft. When the centrifugal blower unit is operating the deflections result in rapidly changing stress reversals that have no effect on the balance of the assembly in a properly designed and balanced unit. However, if the unit is stopped under high temperatures above ambient temperature and allowed to cool to ambient temperature in a static condition, there occurs stress concentrations that cause a temporary shaft distortion. This results in suflicient eccentricity of motion to cause a serious imbalance of the assembly. With small, high speed units having small deflections, the vibration from distortion is not of sufiicient amplitude to cause a safety problem. The unbalanced condition will disappear within twenty to third minutes of operation under a stabilized temperature condition. With large units, on the other hand, the starting vibration will exceed reasonable safe limits and in order to prevent the stress concentrations that cause a serious imbalance condition, it is necessary to provide a turning gear to keep the assembly from being in a static condition while the assembly is allowed to cool to ambient temperature. It will thus be seen that maintaining the shaft and hub at low temperatures minimizes excessive stress concentrations and on a properly designed unit eliminates the necessity for a turning gear. Also, maintaining the shaft and hub cool at all times prevents serious imbalance from thermal shock resulting from a quick, high temperature rise on a cold assembly.

From the foregoing, it will be seen that I have devised an improved cooling system for shafts and the like. By maintaining the shaft and hub cool at all times I not only eliminate serious imbalance conditions but eliminate all problems of the impeller and hub becoming loose on the shaft. Also, I reduce linear shaft expansion to a minimum thus permitting better coupling clearances which result in improved performance with reduced maintenance and longer coupling life.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

1. In a centrifugal blower having a lateral inlet chamber, an outlet, an impeller and a rotatable impeller shaft extending through the inlet chamber, means for cooling the impeller shaft comprising:

(a) a sleeve surrounding and in closely spaced relation to the shaft with one end of the sleeve extending to a point adjacent the Outer side of the inlet chamber and the other end thereof terminating adjacent the impeller to define a passageway between said sleeve and said shaft for the passage of cooling air,

(b an air blower communicating with said sleeve adacent said one end thereof and disposed to supply cooling air to said sleeve, and

(c? means to energize and deenergize said air blower 111 response to predetermined variations in temperature or pressure within the centrifugal blower,

2. In apparatus as defined in claim 1 in which an in. sulatron materlal surrounds the sleeve to reduce the cooling an requirements where the centrifugal blower is emp yed to convey gases at extremely high temperatures.

3. In apparatus as defined in claim 1 in whi h id other end of the sleeve flares outwardly within the i peller.

4. In apparatus as defined in claim 1 in which a conduit communicates said air blower with said one end of the sleeve.

5. In apparatus as defined in claim 4 in which the conduit extends through the inlet chamber and is surrounded by an insulating material.

6. In a centrifugal blower embodying a lateral inlet chamber, an outlet, and impeller blades carried by a plate which is secured to a hub mounted on a shaft extending through the inlet chamber, means for cooling the shaft comprising:

(a) a sleeve surrounding and in closely spaced relation to the shaft with one end of the sleeve extend- 1 ing to a point adjacent the outer side of the inlet chamber and the other end thereof terminating in spaced relation to the hub to define a passageway between said sleeve and said shaft for the passage of cooling air,

(b) a conical member communicating with said other end of the sleeve and flaring outwardly toward and in spaced relation to said plate to define a passageway therebetween for exhausting cooling air which is conveyed through said sleeve and said conical member,

(c) an air blower communicating with said sleeve adjacent said one end thereof and disposed to supply cooling air to said sleeve, and

((1) means to energize and deenergize said air blower in response to predetermined variations in temperature or pressure within the centrifugal blower.

7. In apparatus as defined in claim 6 in which the conical member is formed integrally with said sleeve.

8. In apparatus as defined in claim 6 in which the conical member is surrounded by an insulating material.

9. In apparatus as defined in claim 6 in which angularly spaced vanes are carried by said plate inwardly of said impeller blades in position to provide radiation fins and draw cooling air outwardly of said conical member.

10. In apparatus as defined in claim 6 in which the sleeve is supported intermediate its ends by radially extending bars which are connected at their outer ends to portions of the centrifugal blower.

11. In a centrifugal blower having a lateral inlet chamber, an outlet, an impeller and a rotatable impeller shaft extending through the inlet chamber, means for cooling the impeller shaft comprising:

(a) a sleeve surrounding and in closely spaced relation to the shaft with one end of the sleeve extending to a point adjacent the outer side of the inlet chamber and the other end thereof terminating adjacent the impeller to define a passageway between said sleeve and said shaft for the passage of cooling a1r,

(b) an air blower communicating with said sleeve adjacent said one end thereof and disposed to supply cooling air to said sleeve, and

(c) means to energize said air blower upon an increase in pressure within the centrifugal blower above a predetermined amount and upon an increase in internal temperature of the centrifugal 5 blower above a predetermined amount to force cooling air through said sleeve.

12. In a centrifugal blower having a lateral inlet chamber, an outlet, an impeller and a rotatable impeller shaft extending through the inlet chamber, means for cooling the impeller shaft comprising:

(c) a pressure switch having a sensing element within the centrifugal blower and operatively connected to said air blower to energize said air blower when the pressure at the receiving side of the centrifugal blower increases to a predetermined amount, and

(d) a thermal switch having a sensing element within gas being conveyed by the centrifugal blower.

References Cited by the Examiner UNITED STATES PATENTS 100,238 2/1870 Sturtevant 230209 2,755,989 7/1956 COWfil'd 230-128 FOREIGN PATENTS 149,509 11/1931 Switzerland.

MARK NEWMAN, Primary Examiner.

F. RADUAZO, Assistant Examiner.

Claims

1. IN A CENTRIFUGAL BLOWER HAVING A LATERAL INLET CHAMBER, AN OUTLET, AN IMPELLER AND A ROTATABLE IMPELLER SHAFT EXTENDING THROUGH THE INLET CHAMBER, MEANS FOR COOLING THE IMPELLER SHAFT COMPRISING: (A) A SLEEVE SURROUNDING AND IN CLOSELY SPACED RELATION TO THE SHAFT WITH ONE END OF THE SLEEVE EXTENDING TO A POINT ADJACENT THE OUTER SIDE OF THE INLET CHAMBER AND THE OTHER END THEREOF TERMINATING ADJACENT THE IMPELLER TO DEFINE A PASSAGEWAY BETWEEN SAID SLEEVE AND SAID SHAFT FOR THE PASSAGE OF COOLING AIR, (B) AN AIR BLOWER COMMUNICATING WITH SAID SLEEVE ADJACENT SAID ONE END THEREOF AND DISPOSED TO SUPPLY COOLING AIR TO SAID SLEEVE, AND (C) MEANS TO ENERGIZE AND DEENERGIZE SAID AIR BLOWER IN RESPONSE TO PREDETERMINED VARIATIONS IN TEMPERATURE OR PRESSURE WITHIN THE CENTRIFUGAL BLOWER.