AU754258B2 - Integrated fan assembly with variable pitch blades - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Applicant(s): HORTON, INC Actual Inventor(s): Chris Nelson, Dave Hennessy, Dave Hein and Bradford Palmer Address for Service: PATENT ATTORNEY SERVICES 26 Ellingworth Parade Box Hill Victoria 3128 Australia Title: INTEGRATED FAN ASSEMBLY WITH VARIABLE PITCH BLADES The following statement is a full description of this invention, including the best method of performing it known to me/us:- INTEGRATED FAN ASSEMBLY WITH VARIABLE PITCH BLADES BACKGROUND OF THE INVENTION The present invention pertains to cooling systems and, more particularly, to a fan assembly incorporating blades which may be adjusted to vary the pitch thereof in order to alter the air flow characteristics of the fan assembly. The invention is also directed to an improved blade unit for use in such a fan assembly, as well as a method of constructing the fan assembly.

Providing a fan assembly including a plurality of circumferentially spaced blades for developing a flow of air for cooling purposes is well known. Such fan assemblies are widely used in numerous fields, such as for cooling heat generating devices. For example, in the automotive art, fan assemblies are commonly used for engine cooling purposes. More specifically, a fan assembly is generally attached to a block of the internal combustion engine and is driven by the engine through a sheave and belt drive arrangement. The fan assembly mainly delivers a flow of air across a radiator and is incorporated as part of an 15 overall, thermostatically controlled engine cooling system.

Since the fan assembly is driven by the engine, the rotating speed of the fan blades tracks the rpm's of the engine. However, the drive to the fan assembly typically incorporates a clutching mechanism such that the fan assembly either assumes an off condition, wherein no air flow is generated by the fan assembly, or an on condition, wherein the fan assembly is 20 driven at a maximum rate established by the prevailing engine speed. With such an arrangement, a considerable initial load is placed on the drive system, particularly the belts, when the clutching mechanism is activated while the engine is running at a high rate of speed. Another problem associated with such typical engine cooling arrangements is that** speed. Another problem associated with such typical engine cooling arrangements is that there is no control over the amount of power the fan assembly will use. Instead, the horsepower draw from the engine is always locked into a predetermined power versus fan speed relationship, power draw is cubic in relation to the rotating speed of the fan, while accounting for air density and temperature factors. This is particularly disadvantageous when cooling needs are low, but the fan assembly is still activated at a high speed. Furthermore, engaging the fan assembly can be a major source of noise, especially at low engine rpm's.

For instance, when the engine is idling, noise generated by the engagement of the fan can be quite disturbing, with the majority of the noise being produced by the engagement of the frictional elements of the clutching mechanism.

Mainly due to the problems outlined above, variable speed fan assemblies, such as those incorporating viscous and eddy current-type fan clutches, and variable pitch fan assemblies have been developed. In general, variable speed fan assemblies are advantageous as the operating speed of the fan blades can be better correlated to the degree of cooling required.

15 Of course, even variable speed fan assemblies still only provide a set air flow rate at o any given fan operating speed. In addition, viscous drives cannot generally provide a fully "off' condition or a "maximum" air flow condition since they are continuously slipping.

Here, variable pitch fan assemblies can be advantageously used since the pitch of the blades can be adjusted according to prevailing cooling requirements such that a reduced power 20 draw from the engine can be achieved. Furthermore, variable pitch fan assemblies can be S.initially engaged in a smooth and quiet manner, even at low engine speeds, and can readily assume both off and full on conditions.

Although variable pitch fan assemblies can be adjusted to establish further enhanced air flow characteristics, problems exist in current designs, particularly regarding the ease of maintenance. For example, due to the connections needed to alter the pitch of the blades during use, the blades cannot be readily detached from the remainder of the fan assembly.

In addition, the blades of prior art variable pitch fan assemblies have stems rotatably supported in outer housing openings only, typically through bearings that are connected to the stems. This arrangement can result in considerable force being exerted on concentrated portions of the housing, particularly during times of high speed operation. Furthermore, given that considerable force can act on the fan blades which tend to draw the blades radially outward, loosening and even separation of the blade stem from the bearings and housing can Occur.

Based on the above, there exists a need for a fan assembly which is designed to exhibit superior maintenance characteristics.

SUMMARY OF THE INVENTION 15 The present invention alleviates at least some deficiencies and problems related to fan Sassemblies by providing an improved fan assembly particularly applicable for use in cooling internal combustion engines.

In accordance with the invention, there is provided a fan assembly adapted to be readily removably attached, as a unit, to a drive unit, including: a housing including first and 20 second interconnected housing sections, with the first and second housing sections having inner wall portions which are spaced so as to define an internal housing chamber, with at least one of the first and second housing sections including a plurality of circumferentially spaced openings formed in a peripheral portion thereof; a plurality of first fasteners interconnecting the first and second housing sections at first, circumferentially spaced locations; a plurality of blade units, with each of the blade units including a support stem being mounted in a respective one of the openings; and a plurality of second fasteners for removably attaching the housing to the drive unit, with access to the plurality of first fasteners being adapted to be blocked by the drive unit such that disassembly of the first and second housing sections is only permitted upon detaching the housing from the drive unit.

Preferably the plurality of first fasteners extend through the second housing section and into the first housing section, with the second housing section being adapted to abut the drive unit, and the plurality of second fasteners extend through each of the first and second housing sections for connecting the housing to the drive unit.

The fan assembly may be adapted to be attached to the drive unit including a sheave, with a portion of the sheave covering the plurality of first fasteners when the fan assembly is attached to the drive unit.

The support stem of each of the blade units is preferably rotatably mounted in a 15 respective one of the openings and the fan assembly further includes, in combination: an actuator member movably mounted within the internal housing chamber, with the actuator member being interconnected with the support stem of each of the blade units such that movement of the actuator member relative to the housing causes the blade units to rotate relative to the housing to vary a pitch of the blade units, thereby altering the air flow 20 characteristics of the fan assembly. In this preferred embodiment, the actuator member may be constituted by a piston and the fan assembly further includes, in combination: a passage formed in the housing for introducing a fluid medium therein for shifting of the piston and a flexible diaphragm positioned within the housing, between the piston and the passage.

The fan assembly may further include, in combination: a hub member extending from the housing at a position spaced radially from the openings, with the hub member including circumferentially spaced pockets, and wherein each support stem includes a cylindrical journal portion rotatably mounted in a respective one of the openings; a post portion which extends from the journal portion, with the post portion including a terminal end portion adapted to be rotatably mounted in a respective one of the pockets such that each blade unit is supported at two, radially spaced locations for rotation relative to the housing to vary a pitch of the blade units, thereby altering the air flow characteristics of the fan assembly; and a flange portion interposed between the journal portion and the post portion, with the flange portion being sized larger than the opening within which the journal portion is rotatably mounted, with the support stem being formed as an integral member such that the journal, flange and post portions constitute a single unit. In this embodiment, each blade unit may ifurther include, in combination: a bushing sleeve interposed between the journal portion and the opening and a thrust bearing arranged between the flange portion and the housing, with 15 each blade unit being integrated into a single, replaceable unit with the support stem receiving the thrust bearing and bushing sleeve and a base of a fan blade being moulded to *the support stem to integrally retain the thrust bearing and bushing sleeve between the flange portion and the fan blade.

The fan assembly may be adjusted during operation to alter air flow characteristics 20 thereof, and may further include, in combination: a sensing system including a first sensor element attached to the actuator member so as to both rotate in unison with the actuator member about a first axis and to shift in unison with the actuator member along the first axis and a second sensor element fixed to the drive unit, with the second sensor element being adapted to sense both a rate of rotation of the first sensor element about the first axis and a degree of shifting of the first sensor element in order to develop signals indicative of a rotating speed and axial position of the actuator member which, in turn, correspond to a rotating speed and pitch of the blade units.

It is thus an object of the present invention to provide a fan assembly formed from multiple, interconnected housing sections which support various components such that an integrated unit is provided to facilitate its attachment to a drive unit, as well as its removal therefrom for ease of maintenance.

Additional features and advantages of the fan assembly of the present invention and its method of assembly will become more readily apparent from the following detailed description of the preferred embodiment thereof when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a partial cross-sectional front view of the fan assembly of the present 15 invention particularly illustrating mounting features of the blade units.

0FIG. 2 is a cross-sectional view of the fan assembly according to section line 2--2 of FIG. I and illustrating the mounting of the fan assembly to a drive device with an actuator member shown in one extreme operating position in the top half of the figure and in another o extreme operating position in the lower half.

20 FIG. 3 is a cross-sectional view of the fan assembly according to section line 3--3 of FIG. 1.

FIG. 4 is a partial cross-sectional view of the fan assembly generally taken along section line 4--4 of FIG. 3. section line 4--4 of FIG. 3.

At this point, it should be noted that all of these figures are drawn for ease of explanation of the basic teachings of the present invention only; the extension of the figures with respect to the number, position, relationship, and dimensions of the parts to form the preferred embodiment will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific force, weight, strength and similar requirements will likewise be within the skill of the art after the following teachings of the present invention have been read and understood.

Furthermore, when the terms "first", "second", "inner", "outer", "radially", "axially", "circumferentially" and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the invention.

DETAILED DESCRIPTION The preferred embodiment of a fan assembly according to the preferred teachings of 15 the present invention is shown in the drawings and generally designated 10. In its most preferred form, fan assembly 10 is particularly adapted for use in connection with cooling an *internal combustion engine of a vehicle, but other applications for fan assembly 10 of the invention will become readily apparent. Therefore, in the preferred application of the invent .55.55 on, fan assembly 10 is shown attached to a drive unit 12 that includes a heave 14 rotatably 20 mounted through a pair of bearing units 16 and 18 to a stub shaft 20 of a journal bracket 22 (see FIG. Journal bracket 22 also include a flange portion 24 that is formed integral with S. stub shaft 20 and which is provided with a plurality of holes 26 for use in fixedly securing journal bracket 22 to an engine block or the like (not shown).

More specifically, bearing units 16 and 18 are press-fit to sheave 14 and sub shaft and are axially separated by a spacer ring 32. The inner races (not separately labelled) of bearing units 16 and 18 are axially maintained on stub shaft 20 by means of a washer 34 and a nut 36 that is threaded onto a terminal end portion of stub shaft 20. Outer race (also not separately labelled) of bearing units 16 and 18 are press-fit against sheave 14 an d are retained in a desired axial position by their engagement with sheave 14 and the presence of a retainer ring 38.

Sheave 14 is formed with an outer grooved surface section 40 that is adapted to receive a drive belt that is driven by the internal combustion engine. With this arrangement, sheave 14 is constantly driven during running of the engine. Although various arrangements could be incorporated to vary the relative rotational speeds (drive ratio) between the engine and the sheave, such as by simply altering the relative size of the sheave from the drive shaft, in the preferred embodiment, sheave 14 is preferably driven at a 1:1 ratio with the engine. For reasons which will become evident below, sheave 14 also includes a generally frustoconical annular drive ring 42 having a terminal axial surface 44.

:00 As shown in this figure, stub shaft 20 is formed with an internal bore 46 within which is positioned a fluid supply coupling 48. In general, fluid supply coupling 48 takes the form of a cartridge that is known in the art and therefore will not be detailed here. However, it should be noted that fluid supply coupling 48 includes an internal passage 50 that is adapted 20 to receive a supply of pressurized fluid delivered through an inlet passage 52 formed in Sjournal bracket 22.

Stub shaft 2 has attached thereto a plate 54 by means of fasteners 56. Plate 54 carries at least one sensor 58 which, in the preferred embodiment, is adapted to sense at least one of a blade pitch and an operating speed of fan assembly 10 in the preferred form as will be Sfurther detailed below. At this point, although not shown in FIG. 2, it should be recognized that sensor 58 is adapted to be electrically interconnected with a control unit by means of a plurality of wires that are fed to sensor 58 through an axial groove 60 formed in stub shaft As best shown in FIGS. 2 and 3, fan assembly 10 includes a housing 68 formed from first and second housing sections 70 and 72 which are adapted to be interconnected at spaced peripheral locations by means of a plurality of first threaded fasteners 74 (see FIG.

In the preferred embodiment, fasteners 74 extend entirely through second housing section 72 and are threaded to first housing section 70 while head portions of fasteners 74 are received in countersunk through holes 76 formed in second housing section 72. Fan assembly 10 is adapted to be attached to sheave 14 by means of a second set of threaded fasteners 78. More specifically, first and second housing sections 70 and 72 are formed with a plurality of aligned through holes 80 which are spaced between countersunk through holes 1 5 76 and receive fasteners 78 for connecting fan assembly 10 to annular drive ring 42 with axial surface 44 of annular drive ring 42 covering the heads of fasteners 74. With this .arrangement, access to fasteners 74 is only permitted following detachment of fan assembly 10 from sheave 14.

Housing sections 70 and 72 have spaced inner wall portions (not labelled) that define 20 therebetween an internal housing chamber 82. Second housing section 72 is formed with a central opening 84 that leads into internal housing chamber 82. A cover member 86 extends across central opening 84 and is secured to second housing section 72 by various, **circumferentially spaced fasteners 88. Cover member 86 is provided with a central aperture circumferentially spaced fasteners 88. Cover member 86 is provided with a central aperture within which is threadably secured a coupling 92 having a fluid passage 94. When fan assembly 10 is secured to sheave 14, fluid passage 94 is aligned with internal passage 50 of fluid supply coupling 48 such that pressurized fluid delivered to inlet passage 52 can flow into internal housing chamber 82 through fluid supply coupling 48 and coupling 92. A flexible diaphragm 96 is positioned within internal housing chamber 82 adjacent cover member 86, with diaphragm 96 having an annular peripheral portion sealingly interposed between second housing section 72 and cover member 86. With this arrangement, the flow of pressurized fluid into internal housing chamber 82 will act upon diaphragm 96 to deflect the same as will be more fully discussed below.

Attached to first housing section 70, within internal housing chamber 82, is a hub member 106. In the preferred embodiment, hub member 106 is formed separate from first housing section 70 and is secured thereto by means of a recessed bolt 108. Hub member 106 has an outer, preferably cylindrical surface which is adapted to guidingly receive an actuator member 112. In the preferred embodiment, actuator member 112 is constituted by a piston S 15 having an end plate portion 114 formed with a cavity 116 opposite hub member 106 and an outwardly extending plate portion 118. Outwardly extending plate portion 118 is provided o. with various spaced bores 120 (see FIGS. 1, 2 and 4) which are adapted to receive springs 122 for biasing actuator member 112 towards cover member 86. Springs 122 are maintained in a desired alignment by extending about studs 124 which project into internal housing chamber 82 from first housing section Actuator member 112 is preferably multi-faceted as best shown in FIG. 1 and each face thereof is formed with a peripheral slot 128 that leads to a radially extending groove o 130. Each radially extending groove 130 is aligned with a respective recessed pocket 132 formed in hub member 106 (see FIGS. I and Received within an aligned radial groove 130 and recessed pocket 132 is an elongated post portion 138 of a blade unit 140.

Elongated post portion 138 actually forms part of an integrally formed support stem 142 of blade unit 140. Support stem 142 also includes an enlarged flange portion 144, a raised diametric portion 146, a journal portion 148 and an extension portion 150 (see FIG.

Support stem 142 is preferably integrally formed of metal, however, other materials could be readily employed. In any event, support stem 142 is formed of a homogeneous material throughout without separation lines, breaks or the like for superior structural integrity. For instance, support stem 142 can be formed by casting as a single element in a single mold cavity or by machining from a single block of material such that no fasteners, welds or other connections exist that could break or vibrate loose.

Each blade unit 140 further includes a fan blade 152 having a base 154 that is mounted upon extension element 150. In the preferred embodiment, fan blade 152 is formed of plastic and is molded upon extension element 150. Prior to molding of fan blade 152, a thrust bearing 156 (FIG. 3) is positioned upon enlarged flange portion 144 and about raised diametric portion 146. In addition, a bushing sleeve 158 is mounted about journal portion *148 and engages thrust bearing 156. Therefore, once thrust bearing 156 and bushing sleeve S. 158 are mounted upon support stem 142 and fan blade 152 is molded upon extension element 150, the entire blade unit 140 defines an integral unit.

20 Blade units 140 are adapted to be mounted in circumferentially spaced openings 162 formed in housing 68. Although the specific number of blade units 140 can vary in accordance with the invention, an equal number of diametrically opposed blade units 140 are preferably provided for dynamic balancing purposes. In the preferred embodiment, each opening 162 is actually formned upon mating of first and second housing sections 70 and 72 as best shown in FIG. 3. Therefore, each housing section 70 and 72 defines an arcuate portion of a respective opening 162. As clearly shown in this figure, each blade unit 140 is mounted with bushing sleeve 158 clamped between first and second housing sections 70 and 72 while post portion 138 extends through radial groove 130 and into a respective recessed pocket 132. With this construction, each blade unit 140 is rotatably supported by both hub member 106 and housing 68 at opening 162 through bushing sleeve 158. By providing these radially spaced support locations, forces acting upon blade units 14 during operation of fan assembly 10 can be effectively distributed, with the mounting of post portion 138 in pocket 132 and bushing sleeve 158 in opening 162 aiding in distributing bending forces and with flange portion 144 reacting radial forces through a portion of bushing sleeve 158 and thrust bearing 156. Although hub member 106 can be formed from various materials, bearing bronze is preferably utilized such that hub member 106 itself acts as a bearing to minimize the number of necessary parts.

The enlarged flange portion 144 of each support stem 142 is formed with a hole (not labelled) that is eccentric or offset from a longitudinal rotational axis defined by post portion 138 and journal portion 148. Each hole has secured therein a pin 166 which projects into a corresponding slot 128 formed in actuator member 112. Of course, it should be realised that pin 166 could also be integrally formed with flange portion 144. In addition, a bushing (not 20 shown), preferably formed of a lubrication impregnated polymer, could be placed over pin 166 and received in a respective slot 128. In any event, linear shifting of actuator member 112 within internal housing chamber 82 by the introduction of pressurized fluid through fluid passage 94 causes rotation of each blade unit 140 about the longitudinal axis defined by both post portion 138 and journal portion 148 through the interengagement between actuator member 112 and pin 166. More specifically, as best shown in FIG. 4, since pin 166 is positioned within slot 128 which extends perpendicular to the movement of actuator member 112 and parallel to but spaced from a longitudinal axis defined by post portion 138, linear movement of actuator member 112 will cause the pins 166 to rotate about the longitudinal axis of post portion 138 to cause rotation of blade units 140. This rotation of blade unit 140 effectively adjusts the pitch of fan blade 152, thereby altering the air flow characteristics of fan assembly 10. Of course, this shifting of actuator member 112 away from cover member 86 (see lower half of FIG. 2) is performed against the biasing force developed by springs 122, as the biasing force tends to place fan blades 152 in a maximum flow position. The extension of actuator member 112 is limited in the preferred embodiment shown by abutment with terminal ends of studs 124.

With reference to FIG. 2, second housing section 72 and cover member 86 are formed with aligned apertures (not labelled) through which is adapted to extend a respective shaft 177. One end of each shaft 177 is fixed for movement with actuator member 112 relative to housing 68, such as through a threaded connection, and a second end of shaft 177 is preferably provided with a magnet 180. Magnet 180 operates in conjunction with sensor 58 to signal at least one of the pitch of fan blades 152 and the rotational speed thereof. More specifically, sensor 58 functions to sense the presence and strength of the magnetic field generated by magnet 180. As the distance between magnet 180 and sensor 58 directly correlates with the pitch of the fan blades 152 and the timing between passes of the magnet 180 by sensor 58 reflects the operating speed of fan assembly 10, this simple sensing S oi arrangement can provide multiple signals to a control unit for use in regulating the flow of pressurized fluid into internal housing chamber 82.

In accordance with the invention, fan assembly 10 is constructed by initially attaching each shaft 177 (actually one or more can be provided) to actuator member 112. Then, while holding hub member 106 within cavity 116 of actuator member 112, one blade unit 140 is positioned such that pin 166 extends into slot 128 and the terminal end of post portion 138 is placed within a respective pocket 130. Of course, as indicated above, blade unit 140 is constituted by an integrated assembly with support stem 142 being integrally formed with extension element 150, journal portion 148, raised diametric portion 146, enlarged flange 144 and post portion 138, thrust bearing 156 and bushing sleeve 158 being mounted upon support stem 142 and base 154 of fan blade 152 being molded about extension element 150.

Once one blade unit 140 has been connected to actuator 112 and hub member 106, hub member 106 can be released and the remaining blade units 140 can be connected in the same manner. After all of the blade units 140 have been properly inserted, each of the blade units 140, actuator member 112 and hub member 106 are simultaneously positioned within second housing section 72, while aligning each shaft 177 with a respective aperture formed in second housing section 72. At this point, it should be noted that cover member 86, diaphragm 96 and fasteners 88 are not yet attached to second housing section 72. After positioning springs 122 in bores 120 of actuator member 112, first housing section 70 is 20 mated with first housing section 72, with studs 124 being received within springs 122 and each of the mating surfaces of first and second housing sections 70 and 72 collectively defining openings 162 which clamp upon bushing sleeve 158. The mating of first and second housing sections 70 and 72 require springs 122 to be compressed such that there *.o exists a tendency for the housing 68 to come apart. While holding the first and second housing sections 70 and 72 together, fasteners 74 are positioned in through holes 76 and secured within first housing section 70. Next, fastener 108 is tightened through a central bore (not labelled) formed in actuator member 112 (see FIG. Thereafter, diaphragm 96 and cover member 86 are secured by means of fasteners 88. Finally, coupling 92 is installed.

As clearly shown in FIG. 3, at least a portion of bushing sleeve 158 and enlarged flange portion 144 for each blade unit 140 have associated diameters which are larger than the corresponding opening 162. Therefore, support stem 142 cannot pass through opening 162, without the occurrence of major structural damage. With this arrangement, radial loads developed during operation of fan assembly 10 are transmitted to housing 68 through enlarged flange portion 144, thrust bearing 156 and part of bushing sleeve 158 (see FIG. 3).

In addition, given that enlarged flange portion 144 is formed integral with post portion 138 and the remainder of support stem 142, flange portion 144 cannot be undesirably shifted relative to post portion 138, thus preventing support stem 142 from escaping from housing 68, as is known in prior art devices having separate flange portions, when large radial forces are developed during operation of fan assembly 10. Finally, fasteners 88 are used to secure .cover member 86 to second housing section 72 with diaphragm 96 positioned therebetween.

*0.

This step can be performed with coupling 92 pre-attached to cover member 86 or coupling 92 can be subsequently secured in position.

20 As fan assembly 10 is particularly adapted for use in cooling an internal combustion engine, the preferred construction of drive unit 12 enables assembly thereof by initially press-fitting bearing units 16 and 18 into sheave 14 and attaching retaining ring 38. At least one wire lead is positioned in groove 60 for sensor 58. Stub shaft 20 of journal bracket 22 is S ot then pressed into bearing units 16 and 18 and secured by means of washer 34 and nut 36.

Fluid supply coupling 48 is inserted into bore 46 and captured by a retaining ring (shown in FIG. 2 but not separately labelled). Plate 54 with sensor 58 is then attached to journal bracket 22 by fasteners 56.

As indicated above, journal bracket 22 is adapted to be secured to a block portion of the engine at holes 26 of flange portion 24. A drive belt from the engine is then placed around sheave 14 and properly tensioned. Housing 68 of fan assembly 10 can then be readily attached to sheave 14 by means of fasteners 78 for concurrent rotary movement.

Since housing 68 is not attached to sheave 14 until after a drive belt is placed about sheave 14, belt installation is simplified. Again, upon securing housing 68 to sheave 14, axial surface 44 of annular drive ring 42 covers fasteners 74. This arrangement advantageously assures that housing 68 cannot be disassembled without first disconnecting housing 68 from drive unit 12. This is important since, as indicated above, springs 122 are compressed upon assembly of housing 68 such that inadvertent removal of fasteners 76 could not only cause the entire fan assembly 10 to come apart, but serious injuries could be caused to those nearby. However, since fasteners 74 are covered by annular drive ring 42, fasteners 74 cannot be inadvertently removed. Of course, fan assembly 10 can be readily removed from sheave 14 for repair and maintenance purposes with fasteners 78 being readily visible and accessible for this purpose. If a blade unit 140 is in need of repair, housing 68 can simply be detached from sheave 14, without having to remove journal bracket 22 from the engine chassis, opened and a new blade unit 140 can be substituted for the damaged unit. Since the various components of each blade unit 140 are integrated into a single unit, replacement is simple and efficient.

oS Now that the basic teachings of the fan assembly according to the preferred embodiment of the present invention has been set forth, other variations will be obvious to the persons skilled in the art. For example, although the pitch of fan blades 152 are adjusted through the use of a fluid pressure driven actuation system, various actuation systems, including mechanical, electrical, hydraulic and pneumatic systems, could be employed.

Therefore, actuator member 112 can take various forms other than a piston while still accomplishing the desired function described above. In addition, the mounting of actuator member 112 can be modified to even induce reverse flow by simply expanding its permissible degree of travel. It should also be realised that fan blades 152 can assume various shapes, such as providing a twist to increase the efficiency of the airfoil without compromising the articulation of thile blade which provides for infinitely variable cooling capacities between a zero capacity to a maximum value based on engine/fan speed.

Furthermore, the sensing arrangement is not intended to be limited to the specific embodiment described. Rather, various types of known speed and position sensors could be employed, including other types of capacitive-type sensors. In addition, it should be realised "that the sensing arrangement of the invention could be utilized in other rotational control we apparatus as well, such as clutches. Finally, various materials could be used to form the components of fan assembly 10, including various metals and plastics. Particularly advantageous is the formation of first and second housing sections 70 and 72, as well as 20 actuator member 112, of plastic to reduce weight and cost factors.

Thus the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof and the embodiment described herein which should be considered in all respects illustrative and not restrictive. The scope S S of the invention is to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalence of the claims are intended to be embraced therein.

*o*19 *o o ~q

Claims (9)

1. A fan assembly adapted to be readily removably attached, as a unit, to a drive unit, including: a housing including first and second interconnected housing sections, with the first and second housing sections having inner wall portions which are spaced so as to define an internal housing chamber, with at least one of the first and second housing sections including a plurality of circumferentially spaced openings formed in a peripheral portion thereof; a plurality of first fasteners interconnecting the first and second housing sections at first, circumferentially spaced locations; a plurality of blade units, with each of the blade units including a support stem being mounted in a respective one of the openings; and a plurality of second fasteners for removably attaching the housing to the drive unit, with access to the plurality of first fasteners being adapted to be blocked by the drive unit such that disassembly of the first and second housing sections is only permitted upon detaching the housing from the drive unit.

2. The fan assembly of claim 1, wherein the plurality of first fasteners extend through the second housing section and into the first housing section, with the second housing section being adapted to abut the drive unit, and the plurality of second fasteners extend through :'.ieach of the first and second housing sections for connecting the housing to the drive unit.

3. The fan assembly of claim I or 2, wherein the fan assembly is adapted to be attached to the drive unit including a sheave, with a portion of the sheave covering the plurality of first fasteners when the fan assembly is attached to the drive unit.

4. The fan assembly of any preceding claim, wherein the support stem of each of the "".blade units is rotatably mounted in a respective one of the openings and the fan assembly further includes, in combination: an actuator member movably mounted within the internal housing chamber, with the actuator member being interconnected with the support stem of each of the blade units such that movement of the actuator member relative to the housing causes the blade units to rotate relative to the housing to vary a pitch of the blade units, thereby altering the air flow characteristics of the fan assembly.

5. The fan assembly of claim 4, wherein the actuator member is constituted by a piston and the fan assembly further includes, in combination: a passage formed in the housing for introducing a fluid medium therein for shifting of the piston and a flexible diaphragm positioned within the housing, between the piston and the passage.

6. The fan assembly of any preceding claim, further including, in combination: a hub member extending from the housing at a position spaced radially from the openings, with the hub member including circumferentially spaced pockets, and wherein each support stem includes a cylindrical journal portion rotatably mounted in a respective one of the openings; a post portion which extends from the journal portion, with the post portion including a terminal end portion adapted to be rotatably mounted in a respective one of the pockets such that each blade unit is supported at two, radially spaced locations for rotation relative to the housing to vary a pitch of the blade units, thereby altering the air flow characteristics of the fan assembly; and a flange portion interposed between the journal portion and the post portion, with the flange portion being sized larger than the opening within which the journal portion is rotatably mounted, with the support stem being formed as an integral member 20 such that the journal, flange and post portions constitute a single unit.

7. The fan assembly of claim 6, wherein each blade unit further includes, in combination: a bushing sleeve interposed between the journal portion and the opening and a o. thrust bearing arranged between the flange portion and the housing, with each blade unit being integrated into a single, replaceable unit with the support stem receiving the thrust bearing and bushing sleeve and a base of a fan blade being moulded to the support stem to integrally retain the thrust bearing and bushing sleeve between the flange portion and the fan blade.

8. The tfan assembly of claim 4 or 5 which may be adjusted during operation to alter air flow characteristics thereof, further including, in combination: a sensing system including a first sensor element attached to the actuator member so as to both rotate in unison with the actuator member about a first axis and to shift in unison with the actuator member along the first axis and a second sensor element fixed to the drive unit, with the second sensor element being adapted to sense both a rate of rotation of the first sensor element about the first axis and a degree of shifting of the first sensor element in order to develop signals indicative of a rotating speed and axial position of the actuator member which, in turn, correspond to a rotating speed and pitch of the blade units.

9. A fan assembly as claimed in claim 1 and substantially as herein before described with particular reference to the accompanying drawings. Dated this 20th day of November 2001 PATENT ATTORNEY SERVICES 0e 0 Attorneys for *ORON INC HORTON, INC 0e