Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a sheet ~.etal fan
assembly of the type particularly adapted for use with the
cooling system of an internal combustion engine mounted in
an automotive vehicle. A typical example of the utility
o-f 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 of 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 bIade t~hich may be attached as by ~elding, riveting, or
the like. Either the blade or the attaching arm or both
ma~ be twisted so as to vary the pitch of the fan. The
spider hub is attached to a pulley or other rotary member
which 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,~13 issued
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 Eans, 3,147,811, issued to
Klonoski; 3,147,958, issued to ~ti~ler; 3,8~7,842,
issued to Pope; British Patent No. 417,232; German Patent
No. 762,625; and British Patent No. 908,586. It will be
understood that these patents do not necessarily define
all of the pri.or art.
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According to the practice o~ this invention,
a fan assembly is constructed wherein each blade is bent
outwardly from the plane of rotation of the fan assembly
so as to assist in outward radial flow. Such radial out-
ward flow reduces the exhaust space required directly
behind the fan. The fan assembly o~ this invention em-
ploys reinforcing rib elements in relatively thin steel
blades. The ribs add strength to the blade and thereby
permit metal of lesser thic~ness and weight. Further
the fan assembly includes a sheet metal hub having a
plurality of radially extending spider arms each provided
with a sheet metal fan blade, the improvement comprising,
a radially extending rib on each arm thereof and extending
outwardly from the surface of the arm, each blade pro-
vided at its radially inner portion with a rib extending
radially along the blade and projecting outwardly from
; the surface of the blade, each blade being rigidly attached
to an associated spider arm with the said rib on the blade
and the said rib on the spider arm being in registered
2~ relationship, the tip of each blade being curved away from
the remainder of the blade, thereb~ to induce radially
outward flow of air, the tips defining the widest part
of the projected width of the fan assembly.
IN THE DRAWINGS:
Figure 1 is a plan view o~ 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
blade and spider arm of Figure 1.
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Fig-ure 4 is a section taken along section ~ine
4-4 of Fig. 3.
Figure 5 is a section taken alollg section line
5-5 o~ ~`ig. 3.
Figure 6 is a radial section taken along section
line 6-6 of Fig. 3.
Referrin~ 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 o~ 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
` 15 the bladeO Each blade is in the general form of a part-
cylinder surface, with the bent portion 18 e~tending along
~he entire width of the blade and away ~rom the general
pla~ne of the blade. The numer~l 2~ denotes 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, ~orming a branch-
ed rib configuration of generally Y-shape. The rib 30
extends from the radially innermost portion of each blade
16 and interseets the radially innermost portion of the
closed loop. Both the reinforcing ch~nnel 20, 22, 24 and
the reinforcing rib 30 bulge outwardly flola the for~ard
side of the blade, both the reinforcing ril~ 30 and the
reinfGrcing channel being of the same depth.
The numer~l 32 denotes rivets employed to fasten
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each bladc 16 to its associated spider arm 14. One of the
rivets is inside of the branched reinforcing charnel,
while the other t~o ar~ outside of it, one lying on one
side of the reinforcing rib 30 and the other on the o~her
side of the reinforcing rib 30.
The spider or hub 12 is provided with a side
wall 40 joilling the inner portion 41 with the maxginal
flange 46. As will be seen from Figures 3 and 4, each arm
14 presents a forwardly facing mounting pad surface 45
which is displaced radially outwardly from the hub 12 and
is of generally triangular shape. This mounting pad sur-
face is flat and is twisted from the plane of the marginal
flange 46 but merges smoothly therewith as indicated at
46'. The inner end of each blade similarly is provided
with a flat, generally triangular area 47 whose rear face
is secure'ly affixed against the mounting pad surface 45.
Each arm 14 is provided with a channel or trough
44 which interrupts the wall 40 as show~ in Figure 3 and
t'hereby merges smoothly with the forward surface of the
inner portion 41 of the hub, extending radially there-From
into the mounting pad surface 45 to terminate short of the
area of the outermost rivet, as sho~n in brvken lines in
Figure 2. The trough or channel 44 bulges reartl~ardly :from
the arm 14 and defines the radially extending reinlnrcing
rib 44'. The two ribs 44' and 30 are registered to :~orm a
tube-like reinforcing structure as is ill.ustrated in
Figures 5 and 6.
The surface of the fan hlade 16 in the reginn
of the rivets 32 is ~'lat, as is the surface of the arm 14,
except for the reinforcing rib 30 and the reill~orcing rib
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44'. The radially outermost portion of the spider 12
~ terminates in a flange denoted by the nllmeral 4ff. 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 occur about the attach
ment points defined by rivets 32. In the present 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-
forcing channel portion 24 and accordingly the blade 16 of
this invention will be better able -to resist failure he- ;
cause of this geometrical rela$ionship. The reader will
~0 also observe that one of the strongest structural shape~s
is a triangle and is the general relationship o~ the
reinforcing ribs 20, 22, 24. That is to say, one of the
sides 20, 22, 24 is not easily distorted while leaving the
other two sides free from di~tortion. The reader will
also observe that the rib 30 at the radiall~ innermost
por-tion of each fan blade 16 gives con~inuity and radial
stiffness relaJcive ~o the spider hub 3~ tbe rlb 44' arld
the rib 30 opposin~ each other to yielcl sueh COntlllUj.ty.
It will be observed partic~llarly fror,l 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 forward offset all~ permits c:enter pierc-
ing or rearward offset of the blade with a minimal dimen--
sion required between the mounting surf'ace and the rear of
the assembly. A typical fall blade assembly fashioned in
accordance with this invention employs a rein~orcing
channel 20, 22~ 24 and reinforcing rib 30 of approximately
5/16 inch width at approximately 0.30 inches deep. l'ypi-
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 hlades.
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.
Another advantage displayed by this construction
is the greater ra~ial air flow caused by the tip of each
blade being bent towards the suction side o~ the fan
assembly, i.e., towards the radiator. As noted, greater
radial air flo~r improves the cooling efficiency of a fan
assembly~
In Fig. 2 J the bend of each tip is toward the
right, the tips extending beyond the projected width of
the f'an assembly. The projected width of a fan assembly
i~ i~s width as viewed at right angles to the axis of ro-
tation of the fan assembly. The nunleral 19 designates
the extension of the blade tips be~oncl the projected width
of the r~mainder of the fan, the latter denoted as P.~.
The fan blade tips thus define the widest: part of the pro-
jected width of the fan assclllbly.
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The rear face of the inner portion 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 R 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 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 fan to consume needless power. Consequently,
fan blades of this type utilize forwardly bent tip por-
tions in order to induce a radial, outward dischaxge flow
of air and thus decrease the mass flow of air impinging
against the engine block. In customary practice, the
orwardly 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 of the blade is e~ual to the distance W. ~Iowever,
by allowing the bent tip to protrude forward (towards
the radiator) as shown in Fig. 2, such that the projected
width at the tip is given by the distance "W", a lower
consumption of fan power results while still obtaining
the re~uisite flow of air through the radiator.
