US3708155A

US3708155A - Cooling tower fan blade assembly having yieldable,expendable tip

Info

Publication number: US3708155A
Application number: US00088020A
Authority: US
Inventors: J Holmberg; E Allgeyer
Original assignee: Marley Co LLC
Current assignee: MC ACQUISITION Corp
Priority date: 1970-11-09
Filing date: 1970-11-09
Publication date: 1973-01-02
Anticipated expiration: 1990-01-02

Abstract

A yieldable and expendable blade tip for use on the outer end of each of the blades of a cooling tower fan mounted within a fan cylinder. The tips each comprise a deformable body, preferably constructed of a synthetic resin material or the like, adapted to be mounted over the end of the blade, and releasably secured thereto by means of a binding strap and a series of fasteners extending into a respective blade. Fastener clearing slots are provided in the tip body to permit the latter to be shifted in or out longitudinally of the blade as required so that the tip may be positioned in close proximity to the inner surface of the fan cylinder. The blade tips prevent significant damage to the blades as well as the fan cylinder in case the latter is displaced by unexpectedly strong wind to an extent to permit engagement of the inner surface of the fan cylinder with the blade tips.

Description

United States Patent [191 Holmberg et al.

[ 1 Jan. 2, 1973 [54] COOLING TOWER FAN BLADE ASSEMBLY HAVING YIELDABLE, EXPENDABLE TIP [75] Inventors: Joyce D. Holmberg, Overland Park, Kans; Earl R. Allgeyer, Raytown, Mo.

[73] Assignee: The Marley Company, Kansas City,

[22] Filed: Nov. 9, 1970 [21] Appl. No.: 88,020

[56] References Cited UNITED STATES PATENTS 2,299,920 10/1942 Moore ..26l/D1G. 11 3,544,231 1 12/1970 Zerlauth.. ..415/174 3,079,128 2/1963 Burge ..415/174 885,032 4/1908 De Ferranti ..415/172 930,907 8/1909 Westinghouse "415/174 3,199,836 8/1965 Moyer ..415/174 2,447,957 8/1948 Moore ..415/174 Primary Examiner-Tim R. Miles Assistant Examiner-Steven H. Markowitz Attorney-Schmidt, Johnson, Hovey & Williams [5 7 ABSTRACT A yieldable and expendable blade tip for use on the outer end of each of the blades of a cooling tower fan mounted within a fan cylinder. The tips each comprise a deformable body, preferably constructed of a synthetic resin material or the like, adapted to be mounted over the end of the blade, and releasably secured thereto by means of a binding strap and a series of fasteners extending into a respective blade. Fastener clearing slots are provided in the tip body to permit the latter to be shifted in or out longitudinally of the blade as required so that the tip may be positioned in close proximity to the inner surface of the fan cylinder. The blade tips prevent significant damage to the blades as well as the fan cylinder in case the latter is displaced by unexpectedly strong wind to an extent to permit engagement of the inner surface of the fan cylinder with the blade tips.

16 Claims, 8 Drawing Figures PATENTEDJM ems 3.708.155

' sum 1 or 2 //v VEN 75025..

flTTORNEYS.

[Joyce 0. Ha/mbe/g COOLING TOWER FAN BLADE ASSEMBLY HAVING YIELDABLE, EXPENDABLE TIP This invention relates to water cooling towers and particularly to improved fan structure therefor wherein deformable, synthetic resin tips are provided on the fan blades so that in the event of engagement of the tips with the fan cylinder normally surrounding the fan blades, the tips deform as required to prevent complete destruction of the cylinder or the blades themselves.

Induced draft water cooling towers are conventionally provided with a fan cylinder surrounding each of the draft fans. These cylinders normally have a venturi type constriction at a point adjacent to and in direct alignment with the plane of rotation of the fan. The inner surface of the cylinder is of smooth configuration and aerodynamically designed with streamlined tapering of the inner cylinder wall leading up to and away from the point of maximum constriction.

The streamlining of the inner surface of the cylinder wall is desirable in order to decrease friction and air drag and the venturi constriction is provided to assure maximum air flow through the tower as well as maximum exhaust air speed out of the tower. Maximum hot air exhaust velocity is required to prevent cycling of the hot air expelled back through the cool air inlet of the tower which would lower the cooling efficiency of the tower.

The fans for large capacity cooling towers often are 28 feet in diameter or more to move sufficient air to effectively cool the extremely large quantities of water handled by these towers. Manifestly, blades for fans of this diameter must be of sufficient strength to not only withstand cantilever mounting thereof but also resist significant deflection during operation. Large cast metal or glass fiber reinforced synthetic resin members of relatively high weight have been found to be the most satisfactory materials for constructing such fan blades.

The provision of a venturi type fan cylinder for a cooling tower and the advantages derived therefrom is of common knowledge to those skilled in the cooling tower field. In this connection, it is known that the fan blades must be positioned extremely close to the inner surfaces of the cylinder wall in order to take full advantage of the inherent properties of the venturi,

Problems arise, however, when high winds or other factors cause the fan cylinder to bend or flex. The bending or deforming of the fan cylinder can permit the fan blades to strike the inner surface of a cylinder wall and thus cause severe damage to the cylinder wall, fan blades, transmission, and supporting structure. This damage is not only expensive to repair but valuable operational time is lost as well. Even if the damage is slight with only a portion of a fan blade being damaged, the repair or replacement of the blade still amounts to a significantly large loss of operational time. In addition, the amount of work output required to repair or replace the blade coupled with the cost thereof makes it desirable to take precautionary steps against engagement of the blades with the fan cylinder. It can be appreciated in this respect that the usual practice of shortening the blades is not a really satisfactory solution to the problem since the effective volume of air capable of being moved by the fan and the effectiveness of the venturi would both be diminished.

Therefore, it is desirable to have a blade tip which will, upon striking the inner surface of a cylinder wall, cause as little damage as possible to the cylinder wall and other related fan assembly parts and which is also capable of being quickly and easily replaced with as little operational time lost as possible. Accordingly, it is the primary object of this invention to provide a yielda ble fan blade tip for a cooling tower fan located within a fan cylinder which will substantially eliminate cylinder wall scoring and other types of damage to fan assembly parts resulting from cylinder wall deflection or other conditions which cause the fan blade to strike the inner surface of the cylinder wall.

It is another important object of this invention to provide such a fan blade tip which will permit the blade to be positioned as closely as possible to the cylinder wall in order to assure mostefficient utilization of the fan and the venturi as well.

It is still another important object of this invention to provide such a fan blade tip which may be quickly and conveniently installed on and removed from the blade body when necessary for replacement or repair purposes.

A further important object of the invention is to provide a deflectable fan blade tip of the characteristics described which especially lends itself to fabrication from a synthetic resin by conventional extrusion or injection molding techniques thereby making it possible to produce the tips at a reasonable unit cost and to reproduce the same as needed without additional tooling costs.

Still other important objects of the invention will be made clear or become apparent to those skilled in the art from the drawings, and the description of a preferred embodiment of the invention as set forth hereinafter.

In the drawings:

FIG. 1 is a fragmentary elevational view of a cooling tower having a fan assembly equipped with a cupshaped blade tip of preferred construction and embodying the principles of our invention, parts of the tower being partially broken away and shown in vertical cross section to reveal details of construction;

FIG. 2 is an enlarged perspective view of the blade tip of FIG. 1 shown removably mounted in place on the outer portion of a typical fan blade;

FIG. 3 is an enlarged, fragmentary, end elevational view of the outer extremity of the blade tip as shown in FIG. 4 is an enlarged, fragmentary, plan view, of the blade tip as illustrated in FIG. 3 with portions of the blade tip broken away to reveal details of construction;

FIG. 5 is an end elevational view of a modified form of the invention comprising a tubular blade tip adapted to be constructed by extrusion techniques;

FIG. 6 is a plan view of the blade tip illustrated in FIG. 8 is a plan view of the blade tip shown in FIG. 7 and illustrating the modified tip mounted in place on a fan blade with certain parts thereof also being broken away and in section.

. The induced draft, crossflow water cooling tower illustrated in FIG. 1 is generally designated by the numeral 10. Cooling tower 10 conventionally includes a fan assembly 12 mounted in the upper framework thereof above divider 28 separating opposed fill assemblies 26 one from the other. Hot water distribution basins 27 overlie respective fill assemblies and deliver hot water thereto for eventual delivery to cold water basin 30 underlying the casing 32 of the tower after cooling of the water by evaporation of a part thereof. Fan assembly 12 is made up of a gear unit 18 operably driven through shaft 20 by electric motor 22 coupled thereto and joined to the series of radially extending blades 14 for rotating the latter in a horizontal plane at a present speed. Each of the blades 14 is provided with a removable, expendable tip 16 on the outer end thereof proximal to the smooth inner surface 240 of fan cylinder 24 located in surrounding relationship to fan assembly 12.

In the preferred form of the invention detailed in FIGS. 24, each of the blade tips 16 is constructed of yieldable synthetic resin material and molded to present a hollow cup-shaped body configured to partially telescope over the outer end of the blade 14. Tips 16 are each secured to a corresponding blade 14 by an elongated binding strap 34 and fasteners 36. The outer, elongated, longitudinally curved, transversely straight end wall 38 of each blade tip 16 is adapted to lie alongside the inner surface of the fan cylinder wall 24 and is provided with a series of water drain holes 40 to prevent accumulation of water in the interior of the blade tip 16. The blade tips 16 have a series of spaced slots 42 provided therein around the open end 46 of each blade tip 16 remote from end wall 38.

Referring to FIG. 1, illustrating the relative relationship between the various components of the cooling tower, it is to be seen that the fan assembly 12 is mounted within the fan cylinder 24 with the plane of rotation of the blades 14 in substantial alignment with the plane of maximum venturi restriction through the points on the inner surface of the cylinder wall indicated by the numerals 44. The fact that the outer end extremity 38 of the blade tip 16 can be easily positioned in close proximity to the inner surface of the cylinder wall 24 is readily apparent. It also can be appreciated that any deflection or deformation of the fan cylinder 24 by wind currents or otherwise will cause the tip 16 to come'in contact with the inner surface of the cylinder wall 24. However, because the blade tip 16 is constructed of yieldable synthetic resin material or the like, the blade tip 16 will bend or shred when striking the cylinder wall 24 thereby allowing the cylinder wall 24 to escape any scoring or structural damage. The bending and shredding of the blade tip 16 also prevents damage to the gear unit 18 or drive shaft 20 by eliminating the shock of the blade tip 16 striking the cylinder wall and the momentary binding of the blade tip 16 on the cylinder wall 24 which would normally be transmitted through the drive line of the fan assembly if a conventional blade and blade tip were used. The only damage which can occur then, resulting from the blade tip 16 striking the inner cylinder wall 24 is tothe blade tip 16 itself; however, since the blade tip 16 may be removed and discarded, a new blade tip 16 may readily be mounted on the blade 14 in place of the damaged member.

The blade tip 16 of preferred construction as shown in FIGS. 2-4 is constructed generally in the form of a flattened cup with elongated sidewalls defining an opening 46 at the end thereof remote from the end wall 38. This construction is desirable for two reasons. First, it provides a convenient method of mounting the blade tip 16 on the blade 14 by slipping the blade tip 16 over the terminal end 48 of the blade 14 and along a portion of the latter with the terminal end 48 being complementally received within the open extremity 46 of blade tip 16 and partially within the interior of the latter. Secondly, the hollow construction of blade tip 16 reduces the rigidity thereof thus lessening the possibility of cylinder wall damage upon engagement of the tip member with the inner surface of the fan cylinder. The potential problem presented within member 16 of moisture accumulating within the hollow chamber 50 is solved by the provision of drain holes 40 through the end wall 38 allowing entrapped moisture to escape therethrough.

The blade tip 16 is also provided with an external configuration similar to that of blade 14 in order to maintain the aerodynamic properties of blade 14 throughout the entire length of the blade 14 and tip 16. It should be noted that the end wall 38 of the blade tip 16 is longitudinally arcuate in the direction of rotation of blade 14 to permit disposition of the blade tip 16 in close proximity to the inner surface of the cylinder wall 24. The end wall 38 is curved across the width thereof as can be observed in FIG. 4 but is straight or flat in a transverse direction between the top and bottom surfaces thereof in order to allow a greater amount of surface area of end wall 38 to be disposed in close proximity to the inner. surface of the cylinder 24, thereby providing increased volumetric efficiency and venturi utilization.

In use, the blade tip 16 is mounted on the blade 14in the manner previously described by slipping the blade tip 16 over a portion of the blade 14 with the terminal end 48 of the blade 14 being received within the open extremity 46 of the blade tip 16. Binding strap 34 is then positioned around the blade tip 16 in an overlying relationship thereto, as illustrated in FIG. 4. The fasteners 36 are inserted through openings (not shown) provided in the binding strap 34 and aligned, elongated slots 42 in the blade tip 16, and are finally received within threaded holes 52 provided in the blade 14 adjacent the terminal end 46. The blade tip 16 may now be adjusted inward and outward in relation to the blade 14 by virtue of elongated slots 42 for proper positioning of the blade tip 16 relative to the inner surface of the cylinder wall 24.

After the blade tip has been positioned properly relative to the cylinder wall 24, the fasteners 36 are tightened down to secure the blade tip 16 to the blade 14. When it is necessary to remove the blade tip 16 for replacement purposes the fasteners 36 and binding strap 34 may readily be removed and the blade tip 16 then slipped off of the end 46 of the blade 14.

An alternate blade tip broadly designated 116 is shown in FIGS. 5 and 6 of the drawings. Tip 116 comprising a tubular sleeve 116a is of uniform cross-sectional configuration permitting extrusion thereof from synthetic resin material. It is tobe noted though that the cross-sectional shape of tip 1 16 is the same as tip 16 and the internal passageway 116b therethrough is of a size to accommodate blade 14 so that the tubular sleeve may be complementally fitted over the outer end of the blade and elongated slots 142 in sleeve 116a functionin the manner as slots 42 for adjustment of tip 116 longitudinally of blade 14 as desired while fasteners 136 and strap 134 serve in a fashion similar to

components

34 and 36 to releasably secure tip 116 to blade 14.

Blocks 152 between and secured to the opposed major inner surfaces of sleeve 116a reinforce the end margins of the tip body and assure that the tip retains its shape during rotation of the fan blade on which the tip 1 16 is mounted. Water cannot collect in the interior passage 1l6b of sleeve 116a because spacers 152 do not block the outer open end of the tip body.

Another alternate blade tip 216 illustrated in FIGS. 7 and 8 is adapted to be injection molded from synthetic resin material and includes a solid main body portion 216a conforming to the configuration of tip 16 and the outer shape of blade 14 and has a cup-shaped cavity 216!) molded in one end thereof for complementally receiving the outer end of blade 14 in telescopic relationship thereto. Elongated openings 242 in body portion 216a aligned with cavity 216k permit adjustment of the disposition of tip 216 relative to blade 14 longitudinally of the latter as previously described with reference to tip 16 and 116 while fasteners and a strap (not shown) the same as

fasteners

34 and 134 as well as a strap equivalent to

straps

34 and 134 are also provided for releasably afiixing tip 216 to blade 14. j

A series of individual, outwardly projecting fingers 2160 are integral with body 216a and are of shape to also conform with the adjacent cross-sectional shape of body portion 216a with adjacent fingers being provided with mutually cooperable tongue and groove surfaces 216d and 216a intermediate opposed major faces of the tip which serve to interconnect proximal fingers 216a but'do not interfere with relative longitudinal shifting thereof as illustrated in FIG. 8. I

Thus, upon engagement of fingers 2160 with the inner fan of the fan' cylinder, the fingers deflect as shown and do not tear up the cylinder wall as would be a yieldable, expendable tip member carried byeach of the blades at the outermost extremity thereof adjacent the inner surface of said cylinder and interposed between the latter and a respective blade,

said tip members having opposed, curved sidewalls of generally complemental shape to said sidewalls of a corresponding blade and provided with leading and trailing edges which terminate in proximal relationship to adjacent edges of a respective blade, j j j means releasably securing each tip member to a corresponding blade to permit replacement-thereof as required without the necessity of replacing the en tire blade.

2. The invention of claim 1, wherein each of said tip members is provided with spaced sidewalls and an end wall defining a cavity for complementally receiving the terminal end of a respective blade.

3. The invention of claim 2, "wherein each of the blades is telescopically received within a corresponding tip member with the outer end of each blade disposed in spaced relationship from the end wall of the respective tip member.

4. The invention of claim 3, wherein the outermost end of each tip member remote from the blade on which it is mounted being longitudinally arcuate in the direction of rotation thereof to permit disposition of the tip member in close proximity to the inner surface of the fan cylinder.

5. The invention of claim 2, wherein is provided a binding strap in at least partial circumscribing relationship to each tip member andoverlying the extremity of the blade telescoped into the cavity thereof, and said releasably securing means comprises a series of fasteners extending through the strap and said tip member into the blade. 1

6. The invention of claim 5, wherein each of said tip members is provided with an elongated slot therein receiving a respective fastener, said slots being of greatest length in a direction extending longitudinally of the blade to permit selective adjustmentof the tip the case with a solid fan blade tip. Unless the tip 216 engages the cylinder wall with an unusually great degree of force, the fingers 216a can simply be returned to their normal linear configuration and thus making it unnecessary to replace 216. Oftentimes, this is accomplished automatically, during rotation of the fan due to the centrifugal force on tip 216.

Having thus described the invention, what isclaimed as new and desired to be secured by Letters Patent is:

1. In a water cooling tower having a fan assembly provided with a series of radially extending blades, and a fan cylinder in surrounding relationship to said assembly, the outermost end extremity of each blade proximal to the fan cylinder being provided with transversely curved and opposed sidewalls, the combination therewith of:

member toward and away from the inner surface of the fan cylinder.

7. The invention of claim 3, wherein said end wall of each tip member is provided with at least one opening therein to prevent accumulation of water in the cavity of a respective tip member.

8. The invention of claim 1;,wherein each of'said tip members comprises a cup-shaped element having rela tively thin, readily deformable walls fabricated of synthetic resin material. t

9. The invention of claim 1, wherein the transversely arcuate sidewalls of each tip are configured to complementally engage opposed sides of a corresponding blade. 1

10. The invention of claim 9, wherein the outermost end extremity of each blade proximal to the fan cylinder has curved edges connecting respective opposed extremities of said sidewalls and thetip member mounted thereon has opposed arcuate edge walls connecting respective opposed tip member sidewalls configured to complementally engage opposed edges of the blade;said outermost end of each tip member remote from the blade in which it is mounted being transversely straight in a direction perpendicular to the direction of rotation thereof to allow a greater amount of surface area of said outermost end to be disposed in close proximity to the inner surface of the fan cylinder.

11. The invention of claim 1, wherein each of said tip members comprises a tubular sleeve having walls presenting a central passage therethrough of a configuration to complementally receive the outer end of a fan blade therein for telescopic mounting of the sleeve on the blade, and spacer means within the outer open end sleeve being of uniform thickness to permit extrusion of the sleeve.

1;. The invention of claim 1, wherein each of said tip members is provided with a body portion provided with means thereon for mounting the body portion of the outer end of a corresponding blade, and a series of deflectable fingers joined to the body portion and extending outwardly therefrom in a direction toward the fan cylinder when the tip member is mounted on a corresponding blade.

14. The invention of claim 13, wherein said fingers are parallel, disposed in side-by-side, interengaging relationship and are integral with said body portion.

15. The invention of claim 14, wherein adjacent fingers are provided with mutually cooperable, slidably interlocked tongue and groove portions which prevent movement of the fingers away from each other but do not interfere with relative longitudinal movement of the fingers in the event of engagement of the fingers with said fan cylinder.

16. The invention of claim 14, wherein the outer configuration of the body portion and said fingers is substantially complemental to the cross-sectional shape of the blade and said body portion is provided with a cavity in the extremity thereof remote from said blade for complementally receiving the outer end thereof.

Claims

1. In a water cooling tower having a fan assembly provided with a series of radially extending blades, and a fan cylinder in surrounding relationship to said assembly, the outermost end extremity of each blade proximal to the fan cylinder being provided with transversely curved and opposed sidewalls, the combination therewith of: a yieldable, expendable tip member carried by each of the blades at the outermost extremity thereof adjacent the inner surface of said cylinder and interposed between the latter and a respective blade, said tip members having opposed, curved sidewalls of generally complemental shape to said sidewalls of a corresponding blade and provided with leading and trailing edges which terminate in proximal relationship to adjacent edges of a respective blade, means releasably securing each tip member to a corresponding blade to permit replacement-thereof as required without the necessity of replacing the entire blade.

3. The invention of claim 2, wherein each of the blades is telescopically received within a corresponding tip member with the outer end of each blade disposed in spaced relationship from the end wall of the respective tip member.

5. The invention of claim 2, wherein is provided a binding strap in at least partial circumscribing relationship to each tip member and overlying the extremity of the blade telescoped into the cavity thereof, and said releAsably securing means comprises a series of fasteners extending through the strap and said tip member into the blade.

6. The invention of claim 5, wherein each of said tip members is provided with an elongated slot therein receiving a respective fastener, said slots being of greatest length in a direction extending longitudinally of the blade to permit selective adjustment of the tip member toward and away from the inner surface of the fan cylinder.

8. The invention of claim 1, wherein each of said tip members comprises a cup-shaped element having relatively thin, readily deformable walls fabricated of synthetic resin material.

9. The invention of claim 1, wherein the transversely arcuate sidewalls of each tip are configured to complementally engage opposed sides of a corresponding blade.

10. The invention of claim 9, wherein the outermost end extremity of each blade proximal to the fan cylinder has curved edges connecting respective opposed extremities of said sidewalls and the tip member mounted thereon has opposed arcuate edge walls connecting respective opposed tip member sidewalls configured to complementally engage opposed edges of the blade; said outermost end of each tip member remote from the blade in which it is mounted being transversely straight in a direction perpendicular to the direction of rotation thereof to allow a greater amount of surface area of said outermost end to be disposed in close proximity to the inner surface of the fan cylinder.

11. The invention of claim 1, wherein each of said tip members comprises a tubular sleeve having walls presenting a central passage therethrough of a configuration to complementally receive the outer end of a fan blade therein for telescopic mounting of the sleeve on the blade, and spacer means within the outer open end of the sleeve for supporting the outer extremities of the walls thereof remote from the blade, said spacer means being in only partial blocking relationship to the outer end of the sleeve to prevent accumulation of water in said passage.

12. The invention of claim 11, wherein the outer cross-sectional configuration of said sleeve transversely thereof is of the same shape as said blade in a transverse direction at the area thereof adapted to be telescopically received in the passage, said walls of the sleeve being of uniform thickness to permit extrusion of the sleeve.

13. The invention of claim 1, wherein each of said tip members is provided with a body portion provided with means thereon for mounting the body portion of the outer end of a corresponding blade, and a series of deflectable fingers joined to the body portion and extending outwardly therefrom in a direction toward the fan cylinder when the tip member is mounted on a corresponding blade.