Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FIELD OF INVENTION
This invention relates to fans and in
particular to a multi-bladed propeller type ~an
adjustable to reverse the flow of air or other ~luids or
gases in which the fan operates.
BACRGROUND OF TH~ INVENTION
There are numerous fan installations in
industry where the fan is required to move air in one
direction and then, after a period of time, to move the
air in the opposite direction. It is also desirable that
a fan be adjusted to move a smaller amount of air without
changing the speed of the fan. For example, on the
engine of a tracked type of tractor such as a bulldozer
or the like it is desirable to have the fan in a neutral
or zero pitch position when the engine of the vehicle is
being warmed up. When the equipment is being used in the
summer, however, it is preferred to have air blown
through the radiator and away from the operator but just
the reverse is desired in the colder winter months when
it is preferred to have the warm air of the radiator
blown towards the operator.
A further example is when such equipment
is used industry and dirty conditions resulting in
radiators being partially plugged or blocked with debris
from the environment. It is desirable at such times that
the fan be reversed in order to blow out the dust, dirt
or other materials from the interstices of the radiator
core.
Systems presently available require that
the en~ine fan be stopped so that the blades can be
manually adjusted one at a time to set the required
pitch, by the operator.
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Another example is in the mining industry
where, in a mine shaft, fans are used to move air down a
shaft and then, after a time, the motors are reversed and
the air is exhaust~d from the mine. These are large
diameter fans and require large motors of substantial
horsepower The stopping, starting and reversing of these
motors i5 time consuming and expensive.
In large agricultural operations it is
required to keep the air in buildings at a constant
temperature during changing outside air temperature
levels. A variable speed reversing fan which is
temperature controlled is expensive when compared to a
constant speed fan with variable pitch blades.
There are fans on the market which are
reversible but they do not move air in both directions
with equal efficiency. There are also some designs which
disclose adjustable blades but they are limited in the
number of blades and have inherent friction and
lubrication problems associated with the inner components
of the fan assemblies. Such fans have never come into
production due to these problems. There is also th~
problem of the physical size associated with the
available adjustable blade fans which prohibits their use
in many vehicular applications. For example, one
existing fan has fan blades that include an airfoil
configuration similar to an airplane wing so that the fan
blades have differential blade surfaces on either side of
the blade. Hence, the fan does not provide equal fore
and aft thrust.
Another fan uses an airscrew shape, in
which the fan blade is twisted along its length.
However, this fan blade needs a relatively large amount
of space in which to turn to be orientable from forward
to rearward operation.
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SUMM~RY OF THE INVEN~ION
The present invention overcomes many of
the above mentioned problems associated with conventional
S fan assemblies. The present invention allows an engine
or electric motor to continue running in one direction
while the blade pitch can be reversed yradually to
completely change the direction of the air flow. In the
example of the large agricultural operations mentioned
above, the present invention provides a constant speed,
variable pitch fan controlled by a temperature sensing
system.
According to a broad aspect, the invention
relates to a fan assembly incorporating a plurality of
variable pitch blades adjustable during operation of said
assembly to alter volume and direction of air flow
induced by said assembly, comprising:
a main, non-rotatable shaft;
a second shaft coaxially located within the
main shaft for limited axial fore and aft movement within
the main shaft;
a main hub mounted for rotation on the main
shaft;
a blade hub secured to the main hub for
rotation therewith;
drive means attached to one of the main hub and
the blade hub for driving the fan assembly;
a plurality of fan blades each having a blade
shaft mounted for rotation in the blade hub;
each fan blade being straight and having a
neutral airfoil shape in cross-section extending along
the fan blade;
each blade shaft having an interior end
3S extending into the blade hub, and having a crank arm
secured to the interior end;
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means for axially moving th~ secondary shaft
within the main shaft;
a spider rotatahly mounted on the secondary
shaft, the spider including a plurality of bearings, one
5bearin~ corresponding to each blade shaft; and
the crank arm of each blade shaft being mounted
for rotation within the bearing corresponding to that
blade shaft.
loFurther summary of the invention may be found
in the claims.
BRIEF l) SCRIPTION OF THE DRAWINGS
15The invention is illustrated by way of
example in the accompanying drawings in which:
Figure 1 is a frontal view of a six bladed
version of the present invention;
Figure 2 is a side elevation in cross-
section of the fan assembly according to the present
invention showing the relative position of the internal
parts of the assembly with the blades of the assembly in
25a forward pitch position;
Figure 3 is a view similar to figure 2 but
shows the relative position of the internal parts of the
assembly with the blades in a reverse pitch position;
Figure 4 is a schematic view, partly in
cross-section, illustrating the lubrication system of the
invention;
35Figure 5 is a cross-section of a typical
neutral airfoil shape of the blade of the fan assembly;
6 ~ r b ~
and
Figure 6 shows the fan assembly of figure
2 with an alternative drive means..
DET_ ~ED DE8CRIPTION OF THE PREFERRED EMBODIMBNT~
The fan assembly is driven by any suitable
means such as an electric motor, gasoline or diesel
engine, lay shaft or the like, and such power means to
the fan is not illustrated.
Different numbers of blades may be used
in the configuration to be described, and the preferred
shape of airfoil blade is shown in figure 5. Figure 5 is
a 45~ scaled down version of an actual cross-section of
airfoil blade. It may be made of aluminum, but is
preferably made from an injected nylon- fibreglass-resin
compound known as ZITEL, available from Dupont Canada
Inc. of Ontario, Canada. ZITEL is a trade-mark of
Dupont. The inventor has found that variation from the
cross-sectional shape shown in figure 5 results in
reduced thrust.
Referring to figures 1 and 2, the fan
assembly indicated generally at 10 externally discloses
a plurality of blades 12 mounted in an assembly housing
14 rotatably mounted on a main shaft 16. Housing 14
comprises a blade hub 18 having a front cover 20 and
sealed thereto by means of an oil ring seal 22. A main
hub 24 and pulley 26 are secured to the blade hub 18 by
means of a series of circumferentially positioned bolts
28. Pulley 26 together with the power means and belts
(not shown) constitute the drive means for the fan
assembly of figure 2. An alternative but eguivalent
drive means is shown in figure 6, described below.
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As clearly seen in figures 2 and 3, the
main hub 24 is rotatably mounted to the main shaft 16 by
means of a pair of spaced bearing races 30 which include
a suitable oil seal 32 ad~acent to one race and the other
race securing the main hub 24 in place by means of a
locknut 34 and washer 36. As illustrated main hub 24
includes an inner peripheral shoulder 38 of reduced
diameter which lies between the two bearing races 30 and
is thereby axially located on the main shaft 16.
Pulley 26 is shown as a separate component
from main hub 24 and this is the preferred arrangement
although a unit structure of these two components is
feasible.
The means for reversing the pitch of the
fan blades 12 includes a secondary shaft 40 which is
interconnected to blade reversing means illustrated
generally at 42 and located within the cavity 44 of the
fan assembly.
Secondary shaft 40, like main shaft 16, is
a non-rotating element of the assembly and is
concentrically located within the main shaft 16 and
mounted for reciprocating, axial movement with respect to
the main shaft from the back position shown on figure 2
to the forward position shown on figure 3. Shaft 40 is
slidably positioned in shaft 16 by way of suitable
bushings 46 and that portion of shaft 40 that lies
outside the rotatable assembly 10 is provided with a slot
or like opening 48 which receives an actuating pin or
crank 50 mounted on a shaft 52 which in turn is located
on a bracket or mounting plate 54 which is used to secure
the assembly to a desired location on the vehicle. The
crank 50 is located between the mounting plate 54 and the
main hub 24. The placing of the crank 50 in this
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location allows for a more compact fan assembly which may
be retrofitted to any of various equipment.
It will be appreciated that the means for
S actuating the crank or pin 50 to reciprocate the
secondary shaft ~0 within the main shaft 16 can be a
manual operation, or a hydraulic or electric operation
possibly governed by temperature sensing means.
The end of the secondary shaft 40 remote
from the crank 50 has a portion 56 of reduced diameter on
which a pair of bearing races 58 are located and which
support a spider 60 mounted for rotation thereon.
As shown in figures 2 and 3, each fan
blade 12 has a shaft 62 the upper end of which 64 is
secured to the fan blade while the lower end of the shaft
62 is located in a cylindrical aperture 66 in the hub 18
by means of a bushing 68. An oil seal 69 mounts the
outer end of the end of the shaft 62 in the bushing 68
and the inner end of the shaft 62 is supported by a
bearing 70 located in a raceway 72 at the inner end of
aperture 66.
A bellcrank 74 interconnects the inner end
of each blade shaft 62 to the spider 60 and this is
accomplished by means of an offset crank pin 76 mounted
in an arm 78 by means of a tapered locking pin 80 secured
in place by a suitable nut and washer combination 82 and
84 which secure the crank arm 78 to the inner end of the
blade shaft 62.
The crank pin 76 includes an inner end 86
which is located in the spider 60 by means of spherical
bearings 88, one for each crank pin 76. The inner ends
86 of the crank pin 76 are snugly fit within the
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spherical bearings 88. For compactness, it is preferable
that the spherical bearings are located in the spider 60
offset from the location of the bearing races 58.
Placing the spherical bearings 88 radially adjacent the
bearing races 58 requires the spider 60 to be made
thicker, and consequently the fan assembly to be radially
less compact.
As shown by the cross~section of the blade
12, in figure 5, its configuration provides an equal
surface to the air whether it is oriented for forward or
rearward attack against the air as shown between figures
2 and 3. As shown in figure 1, each fan blade is
straight, that is, it is not twisted, and thus provides
an equal surface to the air no matter whether oriented
for rearward or forward attack. Thus, it is important
that both sides of the fan blade have the same airfoil
shape~ In the model shown, the fan blades are 6.6 inches
from leading edge to trailing edge and provide a peak
power at about a 42 pitch, with the velocity of the tip
of the blade being about 4500 to 4600 feet per minute.
In particular, making the leading edge 104
of the fan blade 12 more pointed has been found to reduce
the thrust. Hence, the important characteristics of the
shape of blade are believed to be the blunted, almost
rounded, leading edge 104, and the more sharply tapered
trailing edge 106. The actual coordinates of the blade
shape in cross-section, with the centre of the leading
edge 108 at (0.0) are listed in Table 1.
Figure 2 shows the crank pin 50 being so
located in the slot 48 o~ secondary shaft 40 that the
shaft 40 is located at its innermost position in the main
shaft 16 and a peripheral ~lange 41 on the shaft 40
engages the terminal end 17 of main shaft 16 to limit the
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innermost movement of one shaft within the other.
Actuating the crank pin 50 to vary the
pitch of the fan blades results in the change of location
of the elements shown in figure 3. It will be observed
that the secondary shaft 40 has moved to the left in
figure 3 by virtue of the crank pin 50 operating in the
slot 48 of the sha~t and, in so doing, the spider 60,
operating on the crank pins 76 of the bellcranks 74
rotate the blade shafts 62 and therefore the fan blades
12 to their illustrated position, a reverse pitch
compared to that of figure 2.
The secondary shaft 40 also incorporates
lS the lubrication system of the present invention.
It will be noted from figures 2 and 3 that
an oil ring seal 23 is located between the mating
surfaces of the main hub 24 and blade hub 18 as well as
between the cover 20 and the blade hub 18. These oil
ring seals, together with the oil seal 32 provide a
sealed cavity 44 in which oil can be distributed and
circulated. To this end, secondary shaft 40 includes a
plurality of oil galleries 90 adapted to direct oil to
the bushings and bearings of the assembly. The galleries
90 ara interconnected to the central gallery 92 which in
turn is interconnected to a feed pipe 94 and is in
communication therewith through a short gallery 96. As
seen in figure 4 as well as in figures 2 and 3, the lower
end of the feed pipe has a pickup end 98 which sits in a
trough 100 that provides a reservoir for lubricating oil,
the level thereof shown being that when the assembly i5
running.
When the fan assembly is being rotated,
centrifugal force throws the lubricating oil into the.
o
trough 100 and the pickup end 9~ of the feed pipe 9~
receives the oil under the pressure induced by the
rotation of the assembly, that pressure worXing through
the galleries 96, 92 and 90 to lubricate the bearing
races and bushings between the stationary and rotatable
parts of the assembly. The lubricant works through the
bearings and splashes onto the remainder of the moving
parts before being again directed to the reservoir
portion of the cavity.
Referring to figure 6, there is shown an
alternative form of drive means including drive shaft
102 attached to or forming part of cover 20, which in
turn is secured to blade hub 18. The drive shaft 102 may
be used to drive the fan assembly by direct connection to
a power source, such as an electric motor, or equivalent
motor, not shown. For that purpose, drive shaft 102 may
be connected by any of various known means to the motor
shaft (such as a spline on the shaft). In this
embodiment, the pulley 26 is redundant, and may be
omitted. The power source itself may be connected to the
same structure to which the mounting plate 54 is
attached.
While the present invention has been
described in connection with a specific embodiment
thereof and in a speci~ic use, various modifications of
the invention will occur to those skilled in the art
without departing from the spirit and scope of the
invention as set forth in the attached claims.
The terms and expressions which have been
employed in this specification are used as terms of
description and not of limitation and there is no
intention in the use of such terms and expressions to
exclude any equivalents of the features shown and
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described or portions thereof. It is recognized that
various modif ications are possible within the scope of
the invention as claimed.
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T A B L E
NO. COORDINATE NO. COORDINATE .
~05, . 02~ ) 26 (2. 99 2. . 5-9~
2 . .01 0,.039 ) 27 (3 1 89 .579")
.. _ .,-~ ., ... . ~,
3020,.066 ) ~ (3.386,.558")
! 4_ 030,.088 ) 29 (3 5~;~i"537
i S (.o39,-1 07 ) 30 (3.780 .51 3")
6 _( . 059, .1 41 " ) - 31 (3. 9 76 . 49 O" )
`:7 `( 791 '1 68"~ 32 (4.1 73 .460 )
8 (.1 1 8.. Z1 8") ` 33 ~4.-3-7-0,.433 ')
9 ~.197,.290 ) 34 (4.567,.406')
_10(~276,.344 ') 35 (4. /'64,.376")
11 (-354,.384 ) 36 (4.961,.349
12 (.433~.415") 37 (5.157, .317 ')
13 (.591.... 464") 38 (5.3541.288")
1 4 _(.748t.499 1~ 39 (5 551 ~-258 2
(~. 906,. 529 ') 40 (5.709, .233"~
16 ~1 .063~.55i ") - 41 15.866.. 206'r)
17 (1.220, .569"~ 42 ~6.024,.178~')
18 (1.417,.581")~ 43 (6.181,.148 )
19 (1.6141 593 ) 44 ~6.339, 114')
20 _ 1 .81 1 .. 600") 45 (6.41 7,~096")
21 _ 2.008,.610 ) 46 (6.496,.077
22 (2.20S.615" 47 (6.575,.054 )
23 (2.~02 .61 2" _ 48 (~6.65--4-.-030")
2~ ~98L'61 0 _ 49 ~6.666,0 )
25 (2.795,.610") I ~ENTER FOR
= -- 0.025" RAD!US
