Fan Drive Assembly

Abstract

A fan drive assembly specifically designed for cooling towers. The fan drive assembly includes: A fan means, having a plurality of blades associated therewith; a motor means for driving the fan means, positioned below the fan means within the stream of air flow; and a single reduction parallel shaft gear reducer means mounted immediately below the fan means for connecting the fan means to the motor means.

Description

BACKGROUND OF THE INVENTION

This invention relates to a fan drive assembly specifically designed for cooling towers.

Conventional cooling tower installations, of the types applicable to the present invention are illustrated and described in U. S. Pat. No. 3,468,521, assigned to the same assignee as the instant invention. Air flow, induced by a cooling tower fan assembly, enters a contact chamber through a set of louvers adjacent an air inlet, and is drawn through the contact chamber to cool falling and splashing water droplets and water films (on tower filling) by intimate contact with the air before exiting through an air outlet. Cooling is brought about by heat and mass transfer: by evaporation and sensible heat transfer from the water droplets and films.

More specifically, the invention pertains to an improved cooling tower fan drive assembly for discharging air from the air inlet through the contact chamber to the air outlet. Conventional cooling tower fan drive assemblies have heretofore included a fan assembly driven by an electric motor, mounted outside the air stream. Mounted below the fan assembly was a right angle double reduction speed reducer which was connected to a floating drive shaft and flexible coupling assembly driven by the motor. Intermediate pillow blocks have been required in towers with fans of 22' diameter or greater. Maintaining proper shaft alignment, of the above-described drive assembly, has long been a problem in the cooling tower industry. The present invention provides a novel fan drive assembly, specifically designed for cooling tower operation, that is easily assembled and maintained in an optimum performance condition.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a fan drive assembly specifically designed for cooling towers which eliminates the need for a long drive shaft and two coupling assemblies, and thus facilitates shaft alignment.

Another object is to provide a fan drive assembly for use in a cooling tower wherein the motor and the gear reducer are both closely coupled to the fan assembly within the stream of air flow.

A further object is to provide a fan drive assembly for use in a cooling tower which includes a single reduction parallel shaft gear reducer unit closely coupled directly below the fan assembly.

A still further object is to provide a fan drive assembly for use in a cooling tower which includes a single reduction parallel shaft gear reducer unit utilizing double helical or herringbone gears to reduce shaft end thrust and to permit the use of cylindrical roller bearings.

Another object is to provide a fan drive assembly for use in a cooling tower which includes a gear reducer unit which permits adding, in tandem, a second input shaft connected to a lower speed motor such that a two speed system results.

To attain these and other objectives, the fan drive assembly of the present invention provides a parellel shaft single reduction gear reducer unit and an electrical motor closely coupled to the fan assembly within the stream of air flow. The gear reducer unit includes a housing containing a vertical input shaft and a vertical output shaft each journalled for rotation about a vertical axis. The input shaft is connected to the motor output shaft and has a double helical or herringbone pinion gear attached thereto. The output shaft is connected to the fan assembly hub and has a large diameter double helical or herringbone gear attched thereto, positioned so as to mesh with and be driven by the pinion gear. The housing permits the addition of a second vertical input shaft, having a double helical or herringbone pinion gear attached thereto, to mesh with the large diameter output shaft gear. The second input shaft is connected to a second motor, of lower speed than the first motor, to permit two speed operation.

BRIEF DESCRIPTION OF THE DRAWING

Other objects and features of the present invention will become apparent to those skilled in the art as the disclosure is made in the following description of preferred embodiments of the invention, as illustrated in the accompanying sheets of drawings, in which:

FIG. 1 is a vertical section taken through a representative crossflow cooling tower embodying the fan drive assembly of the present invention;

FIG. 2 is a vertical section of a gear reducer in accordance with the present invention; and

FIG. 3 is a vertical section of a portion of the gear reducer, as shown in FIG. 2, after conversion for two speed operation.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, a representative crossflow cooling tower 10 is shown as having a housing 11 incorporating a top 12 defining a water distributing pan 13. Liquid such as water to be cooled is pumped at 14 into the pan, from which the liquid drains via suitable outlets 15. After descending through contact chamber 16, which contains fill or packing (not shown), the liquid is collected in basin 18 for removal at 19. A fan 20, rotated in stack 21 by fan drive assembly 22, draws air laterally through the tower for upward discharge via stack 21. The air drawn in through inlet opening 23, having inlet louvers 24 associated therewith passes successively through contact chamber 16 and drift eliminator louvers 25, and leaves the tower through air outlet 26 and stack 21, as indicated by arrows 125.

Referring to FIGS. 1 and 2, the fan drive assembly 22 of the present invention includes a fan blade 20, a motor 30, and a gear reducer 40. As seen in FIG. 1, motor 30 and gear reducer 40 are mounted directly below fan 20 within the stream of air flow. Fan 20 is preferably of the type disclosed in U. S. Pat. applicant, Ser. No. 21,009, assigned to the same assignee as the present invention. Fan drive assembly 22 is mounted on equipment support 27 which is in turn mounted to the tower framing (not shown) in a suitable manner.

Referring to FIG. 2, gear reducer 40, forming an important part of the present invention, includes a reducer housing 41 containing a central cavity 42 and a pair of outer cavities 43 and 44 formed therein. Vertical output shaft 45, centrally positioned within cavity 42, is journalled for rotation about a substantially vertical axis. The lower end of shaft 45 is supported by a conventional lower tapered roller bearing assembly 46, fitted in a circular bearing-supporting opening in the bottom of cavity 42. Shaft 45 extends through opening 47 in the top of cavity 42 and is supported by an upper tapered roller bearing assembly 48 fitted in cavity 42 adjacent opening 47. An oil seal assembly 49 is positioned above bearing 48 to prevent lubricating oil from leaving housing 41 and to prevent dust from contacting roller bearing 48. A dust shield 85 is provided above helical seal assembly 49. A large diameter driven double helical or herringbone gear 50, secured to shaft 45 between bearings 46 and 48, is positioned in cavity 42, such that its outer periphery extends into cavities 43 and 44. The lower portion of central cavity 42 forms an oil sump 51 which is filled with oil to a level indicated by line 52.

Vertical input shaft 60, positioned within cavity 43, is journalled for rotation about a substantially vertical axis. The upper end of shaft 60 is received by an upper cylindrical roller bearing assembly 61 positioned in a cylindrical opening in the top portion of cavity 43. Shaft 60 extends through opening 62 in the bottom of cavity 43 and is supported by a lower cylindrical bearing assembly 63 fitted in cavity 43 adjacent opening 62. Input oil seal assembly 64 is provided to engage shaft 60 below bearing assembly 73. A double helical or herringbone pinion gear 65, secured to shaft 60 between bearings 61 and 63, is positioned in a meshing relationship to gear 50. Gears 50 and 65 are preferably double helical or herringbone gears to reduce the end thrust on shaft 60 and thus permit the use of cylindrical support bearing assemblies 61 and 63.

A pump housing 75, positioned atop of housing 41 adjacent bearings 61, contains a conventional oil pumping means 76 positioned therein. Pump 76 pumps oil from sump 51 through a tube (not shown) into chamber 77. A portion of the oil in chamber 77 is forced through passageway 78 to lubricate bearings 61 and 63 and gears 50 and 65. The remaining oil from chamber 77 is forced through passageway 79, conduit 80, and passageways 81 and 82 into opening 47 to lubricate bearing assembly 48. The oil drains into sump 51 from which it is continuously recycled.

The hub portion of fan blade 20 is secured to the upper portion of output shaft 45 in a suitable manner. The output shaft 70, of motor 30, is secured to one side of flexible coupling 72 and the bottom of shaft 60 is secured to the other side of coupling 72. In the operation of gear reducer 40, motor output shaft 70 rotates shaft 60 and pinion gear 65 attached thereto. Pinion gear 65 meshes with gear 50 and thus imparts rotational movement to gear 50 and to shaft 45 attached thereto. Fan blade 20, being secured to shaft 45 is caused to rotate and draws air through the tower as aforedescribed.

Reducer housing 41 includes a second outer cavity 44 which permits gear reducer 40 to be converted to two speed operation, without the use of a single two speed motor. To convert reducer 40 for two speed operations, openings 90 and 91 are bored respectively out of housIng 41, as seen in FIG. 3. A second vertical input shaft 92 is positioned within cavity 44 and journalled for rotation about a substantially vertical axis. The upper end of shaft 92 is received by an upper cylindrical roller bearing assembly 93 supported within opening 90. Shaft 92 extends through opening 91 and is supported by a lower cylindrical bearing assembly 94 supported within opening 91. Input oil seal assembly 95 is provided to engage shaft 92 below bearing assembly 94 supported within opening 91. Input oil seal assembly 95 is provided to engage shaft 92 below bearing assembly 94. A second double helical pinion gear 96, secured to shaft 92 between bearings 93 and 94, is positioned in a meshing relationship to gear 50. The lower end of shaft 92 is secured to one side of a flexible coupling 97 and the output shaft 102 of a second electrical motor 98 is secured to the other side of coupling 97. A plate 99, secured to housing 41, is provided to close off opening 90. Oil conduit 100, in communication at one end with oil chamber 77 and at the other end with a nozzle 101 passing through plate 99, supplies lubrication oil to bearings 93 and 94 and gears 50 and 96. Motors 30 and 98 are rated at different output speeds to permit two speed operation of fan drive assembly 22. For example, motor 30 may be rated at 100 h.p. and 1,800 rpm and motor 98 rated at 25 h.p. and 900 rpm.

The ability to selectively operate fan drive assembly 22 at different speeds permits optimum utilization of the tower under varying operating conditions.

Although illustrated and disclosed in conjunction with a crossflow cooling tower the fan drive assembly of the present invention is equally applicable to a counterflOw cooling tower. Various modifications are contemplated and may obviously be resorted to by those skilled in the art without departing from the spirit and scope of the invention, as hereinafter defined by the appended claims, as only preferred embodiments thereof have been disclosed.

Claims

What is claimed:

1. In a cooling tower having a contact chamber and an air inlet and outlet, wherein air is displaced to flow in cooling relation with dropping particulate liquid with said contact chamber, the improvement in a fan drive assembly for discharging air from said air inlet through the contact chamber to said air outlet, comprising:

a. a fan means, having a plurality of substantially horizontal blades associated therewith, positioned adjacent said air outlet;

b. motor means for driving said fan means positioned below said fan means within the stream of air flow; and

c. a single reduction parallel shaft gear reducer means mounted immediately below said fan means for connecting said fan means to said motor means, said gear reducer meanS comprising a housing having a central cavity and an outer cavity formed therein, said outer cavity having a substantially vertical input shaft journalled therein for rotation about a substantially vertical axis, said input shaft being connected to said motor means and having a helical pinion gear attached thereto, said central cavity having a substantially vertical output shaft journalled therein for rotation about a substantially vertical axis, said output shaft being connected to said fan means and having a large diameter helical gear attached thereto positioned so as to mesh with and be driven by said pinion gear.

2. The invention of claim 1 wherein said pinion gear and said large diameter gear are double helical gears so as to eliminate end thrust on said input and output shafts and thus permit the use of cylindrical roller bearings to support said input shaft within said housing.

3. The invention of claim 1 wherein said pinion gear and said large diameter gear are herring-bone gears so as to eliminate end thrust on said input and output shafts and thus permit the use of cylindrical roller bearings to support said input shaft within said housing.

4. The invention of claim 1 wherein said housing includes a second outer cavity formed therein for selectively receiving a second substantially vertical input shaft journalled for rotation about a substantially vertical axis, said second input shaft, having a second helical pinion gear attached thereto to mesh with and drive said large diameter gear, said second input shaft being positioned to be connected to a second motor means.