Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a sheet metal fan
assembly of the type particularly a~apted for use with the
cooling system of an internal combustion engine mounted in
an automotive vehicle. A typical example of the utility
of the fan assembly of this invention is between the
radiator and the engine of an automotive vehicle. The fan
draws air from ambience through the radiator thereby to
assist in cooling the liquid which has transferred heat
from the interior o~ the engine to the radiator. Such
fans are well known, exist in a wide variety of forms and
have enjoyed the attention of numerous workers in this art.
One common form of such a fan construction is
defined by a sheet metal hub or spider having arms pro-
~ jecting radially outwardly. Each arm carries an associat-
¦~15 ed blade which may be attached as by welding, riveting, or
the like. Either the blade or the attaching arm or both
may be twi~sted so æs to vary the pitch of the fan. The
spider hub is attached to a pulley or other rotary member
whlch is powered by the engine. Examples of such prior
~20 ~ ~ art~ sheet metal fan constructions are given by the follow- :
~` ~ ing patents: U.S. 295,449, issued to S~ith; 1,041,913 issued
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to Tyson; 1,117,103, issued to Steinbach; 1,255,346, issued
to Sparks; 1,404,298, issued to Jacobs; 1,597,175, issued to -~
Boening; 1,868,528, issued to Gardner; 2,681,708, issued `
to Mix; 2,906,349, issued to Hans; 3,147,811, issued to
Klonoski; 3,147,958, issued to ~tiffler; 3,827,8~2,
issued to Pope; British Patent Noi ~17,232; German Patent
No. 762,625; alld British Patent No. 908,586. It will be
understood that~these patents do not necessarily define
~30 all of the prior art.
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There is provided a sheet metal fan assembly
adapted to be placed between an internal combustion engine
. and its radiator with a limited spacing being allotted
: therebetween for the blades of the fan assembly, said ~ :
~ 5 fan assembly comprising a sheet metal hub having a
;~ plurality of radially projecting arms and a sheet metal
: fan blade attached to and projecting radially from each
arm; each blade being of generally rectangular configura~
tion in plane and of a substantially constant width and
having the major portion of its length, exclusive of a
tip portion $hereof, curved into a part-cylindrical shape
., centered about an axis parallel to the longitudinal axis
, of that blade, each blade being twisted out of the plane :~-
'~ of said hub whereby the opposite sides of each said major
portion of a blade projects a width in a direction parallel :
. to the axis of rotation which is less than said allotted
j space between an engine and a radiator and said tip has a
;~ forward bend relative to said blade major portion with the --
forward bend of said tip being such that the leading edge
;.i 20 o~ said tip o~ each blade extends the projected width ~- .
of said blade in that region to the full extent of said .
1 allotted space between an engine and a radiator. - ~:
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IN THE DRAWIMGS:
Figure 1 is a plan view of a typical sheet metal
fan blade construction according to the practice of this
invention.
Figure 2 is a view taken along section 2-2 of
Figure 1. , . :
:~ Figure 3 is an enlarged view of a typical fan . ` .
, 30 blade and spider arm of Figure 1.
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Figure 4 is a sectioll taken along section line
4-4 of Fig. 3.
Figure 5 is a section taken along section line
5-5 of ~ig. 3.
~igure 6 is a radial section taken along section
line 6-6 of Fig. 3.
Referring now to the drawings, the numeral 10
denotes generally the sheet metal fan assembly of this
invention and is defined by a sheet metal hub 12 having a
plurality of angularly spaced arms 14. The hub 12 is
sometimes referred to as a spider and the arms as spider
~, arms. The numeral 16 denotes a typical fan blade accord-
ing to this construction, the radially outermost portion
18 of the blade being curved away from the remainder of
j 15 the blade. Each blade is in the general form of a part-
~ cyllnder surface, with the bent portion 18 extending along;'! the entire width of the blade and away from the general
plane of the blade. The numeral 20 d~enotes one leg of a
reinforcing channel (rib) while the numeral 22 denotes a
similar channel. The two channels 20 and 22 are of
' ~ ; generally U-shaped and merge with each other and with the ~;
radial rib 30 in the channel portion 24, forming a branch-
,1 .ed rib configuration of generally Y-shape. The rib 30
extends from the radially innermost portion of` each blade
16 and intersects the radially innermost portion o~ the
, :: :
1 closed loop. Both the reinforcing channel 20, 22, 24 and
~ ~ the reinforcing rib 30 bulge outwardly from the forward
s ~ side of the blade, both the reinforcing rib 30 and the
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, ~ reinforcing channel be1ng of the same depth.
The numeral 32 denotes rivets employed to fasten
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~` each blade 16 to its associated spider arm 14. One of the
rivets is inside of the branched reinforcing channel.,. ~ :
while the other two are outside of it, one lying on one
side of the reinforcing rib 30 and the other on the other
.` 5 side of the reinforcing rib 30.
The spider or hub 12 is provided wi.th a side
wall 40 joining the inner portion 41 with the marginal ~ .
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flange 46. As will be seen from Figures 3 and 4, each arm
, 14 presents a forwardly facing mounting pad surface 45 - .
.; 10 which is displaced radially outwardly from the hub 12 and
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.. ' is of generally triangular shape. This mounting pad sur~
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face is flat and is twisted from the plane of the marginal .
~`~I - flange 46 but merges smoothly therewith as indicated at .-
i 46'. The inner end of each blade similarly is provided -
~ . . .
I 15 with a flat, generally triangular area 4~ whose rear face .:
'~ is securely affixed against the mounting pad surface 45.
j Each arm 14 is provided with a channel or trough .:
44 which interrupts the wall 40 as shown iD Figure 3 and
1~ thereby merges smoothly with the forward surface of the
-~I 20 inner portion 41 of the hub, extending radially therefrom
:¦ into the mounting pad surface 45 to terminate short of the
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j't~ area of the outermost rivet, as.shown in broken lines in
i Figure 2. The trough or channel 44 bulges rearwardly from
-3 the arm 14 and defines the radially~extending reinforcing ~.
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.~ 25 rib 44'. The two ribs 44' and 30 are registered to form a ..
-, tube-like reinforcing structure as is illustrated in
I Figures 5 and 6.
, The surface of the fan blade 16 in the region
; of the rivets 32 is flat, as is the surface of the arm 14,
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~ 30 except for the reinforcing rib 30 and the reinforcing rib : .
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44'. The radially outermost portion of the spider 12
terminates in a flange denoted by the numeral 46. As may
be observed particularly from Fig. 2, the spider arms 14
are twisted relative to the plane of the spider hub 12 to
define the pitch of the blades.
The reader will note that an imaginary line
drawn from the outermost rivet 32 inside the reinforcing
channel to either of the other two rivets intersects
orthogonally the channel portion 24.
A typical sheet metal fan blade failure occurs
under the action of the first mode of resonance of the
spider arm. Bending will typically ocGur about the attach~
, ment points defined by rivets 32. In the presen~ con-
struction, bending of fan blade 16 (see Fig. 3) about an
~ imaginary axis from the inner rivet '32 to either of the
two outer rivets 32 will be at right angles to the rein-
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forcing channel portion 24 and accordingly the blade 16 of
this inven~ion will be better able to resist failure be~
cause of this geometrical relationship. The reader will
also observe that one of the strongest structural shapes
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l~ is a triangle and is the general relationship of the
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,~ reinforcing ribs 20, 22, 24~ That is to say, one of the
~ sides 20, 22, 24 is not easily distorted while leaving the
-i other two sides free from distortion. The reader will
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also observe that the rib 30 at the radially innermost
portion of each fan blade 16 gives continuity and radial
stiffness relative to the spider hub 12, the rib 44' and
the rib 30 opposing each other to yield such continuity.
It will be observed particularly from Fig. 2 of the draw-
ings that the hub 12 is in the general form of a dish.
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This results in a i`orward offset and permits center pierc-
ing or rearward offset of the blade with a minimal dimen-
sion required be~ween the mounting surface and the rear of
the assembly, A typical fan blade assembly fashioned in
accordance with this invention employs a reinf'orcing
channel 20, 22, 24 and reinforcing rib 30 of approximately
5/16 inch width at approximately 0.30 inches de,ep, Typi-
cal prior art reinforcing channels in ribs have employed
depths of the order of 0.120 inches. This relatively high -
ratio between the depth of the channels or ribs and their
width permits the use of thinner metal for the fan blades.
Another advantage displayed by this construction
is the greater radial air flow causecl by the tip of each `' '' '
blade being beDt towards the suction side of the fan ,
l~ 15 assembly.
Another advantage displayed by this construction ,
,~ is the greater radial air flow caused by the tip of each
blade being bent towards the suction side of the fan
assembly, i.e., towards the radiator. As noted, greater
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`,~ 20 radlal air ~low improves the cooling efficiency of a fan
assembly.
~ In Fig. 2, the bend of each tip is toward the
,~ right, the tlps extending beyond the projected width of
~,, the fan assembl~. The projected width of a fan assembly
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;~ 25 is its width as viewed at right angles to the axis of ro- ,
'~ tation of the fan assembly. The numeral 19 designates " ,
! the extension of the blade tips beyond the projected width ,
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of the remainder of the fan, the latter denoted as P.~.
The fan blade tips thus define the widest part of the pro- :
~, 30 jected width of the fan assembly. ~
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The rear face of the inner portlon 41 of the hub
serves to mount the fan assembly to a member (not shown)
driven by the engine. Often, the space T between the
radiator and the engine block, represented respectively by
the lines ~ and B in Fig. 2, is quite restricted and the
space allotted for the fan assembly correspondingly has
little depth. Because the engine block is close to and
j immediately behind the fan blades, the air exhausted by
the fan tends to impinge directly upon the engine block.
This not only restricts the flow of air but also causes
; the ~an to consume needless power. Consequently, fan
blades of this type utilize forwardl~ bent tip portions in
order to induce a radial, outward discharge flow of alr
and thus decrease the mass flow of air impinging against
lS the engine block. In customary practice, the forwardly
bent fan blade tips are cut away generally along a line
such as that indicated at 48 in Fig. 2 and the twist of
the blade is adjusted so that the projected width o-~ the
blade is equal to the distance W. FLowever, by making most
of the blades of the smaller projected width P.W. as
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herein, and having the leading edge portion 49 of each ~ -
blade tip present the maximum projected width, a lower
consumption of fan power results while still obtaining the il
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requisite flow of air through the radiator.
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