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Патент USA US2083996

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Patented June 15,1937
2,083,996 '
Tage G. donn, Chicago, Ill., assigner to Breuer
Electric Mfg. Co., Chicago, lll., a corppration
of Illinois
Application February 2, 1935, serial No. 4,616 6 claims.' (cl. 23o-121)
My invention relates to improvements in cen
Figure 3 represents la similar cross section
trifugal> fans and particularly to theshape of
_their blades or varies; and the objects of my
of another- fan, slightly different in. construc- tion, but embodying my invention.>
improvement are: ñrst, to reduce the power re
’ Figure 4 shows another application’Y of my in- A
5 quired for operating a centrifugal fan; second, . vention to a fan of the same general type- as 5
to increase the pressure’ of the fluid it delivers; illustrated in Figure 1. _
and, third; to diminish the noise, characteristic
Figure 5 shows still additional modifications of
oi' high speed fans.
fan blades, _slightly different _in contour but all
I have attained these objects by inventing a
10 new and novel type of blades, the prime feature -
of which is the introduction of the principle of
streamlining, which I have `applied to the rear
in accordance with the-presentdnvention.
Figure 6 illustrates threeei'zamples of my in- l0
vention as applied in multiblade fans.
.Figure 7 is a section on line 1--1 in Figure 6,
showing-however, only one 'of theblades.
always created by rapidly moving bodies, is greatly
Figure 8 shows two kinds -of blades, hereto
fore >conventionally used in the type ofI fans illus- l5
trated in Figures 1 to 5 and without the appli
’When in addition, the pressure sides-as dis
tinguished from the rear sides-of the fan blades -cation of my present inventionrbutV the illustra
are so shaped that the outer, or peripheral, parts tion is included for explanatory purposes.'
of said blades and whereby the suction or drag,
- 15
of them take the form of cams, and as such act
'v As this- invention is 'adaptable 'to all» types of _
20 against the compressed air expelled from the fanV
and surrounding said. fan within the fan cham
centrifugal fans andasI such fans are'designed 20
for many purposes, it‘isnotpossible to show
ber, a most considerable increase can be obtained one embodiment thereof that would be prefer
in the pressure of the air delivered by said fan.
»able in al1 cases, but- Figure 1 clearly illustrates
Further, a centrifugal fan the blades of which » its principal features. 'The fan show_n here con
25 are properly streamlined will operate more quietly
than if said blades were not streamlined, because
of the smoother flow of the air through such a
fan, but the major source >of noise in a high speed
sists of a. central hub i suitable for mounting ona V'25 ‘
drive shaft 2 and a plurality of blades or'vanes
3 held together by a disc or web 4. The direc
tion of the rotation of thefan is indicated by an
fan of this type, is created when the blades pass'4 arrow and the fan is positioned in a common type
30 the cutoff point; that is, lthe point at which the of casing 5, provided with an .outlet s.
so’ '
air is directed from the fan chamber and into ~ ' In operation the air is drawn >into-Aa fan of this
Now, all sounds are type at its center and discharged at its periphery
due to vibrations and if all thej blades in the into the surrounding space of a casing, commonly
fan are of exactly the same shape they' will called fan chamber, from which it is exhausted
g5 cause'. the same kind of vibrations when passing „through an- outlet; and it- is- obvious that: the 35
said 4cutoff point.y This constant repetition _of action of the blades against the air will ‘cause
the same kind of vibrations will have a cumulative .said air to be compressed onthe pressure or
effect and the resultant noise will be of great forward sides of said blades, whilel behind the g
enough volume to be offensive.` However, if the 'blades there», willpbe areas of rareiìed air, caus-40 blades differ in shape (and the diñerence ‘does ing suction, eddies, and drag, provided means 40
not'need to be great) .the vibrations they cause are not incorporated into the'design of the blades
when passing the cutoff, will also diiïer and' to avoid this undesirable condition which is
' there will bev produced a steady stream of varied found wherever there isa moving body, but
' vibrations, which, .because the vibrations vary, i. which is magnified in a fan _as heretofore` con
45 they will not be 'cumulative and therefore not structed because fof the fact that the space be-. 45
increase to a volume that will cause a seriously tween the blades in such a fan becomes greater
objectionable n'oise. Instead, the fan will operate the further they extend from the center, while ’A
the outlet from the same.
with a comparatively subdued humming sound.
at the same time the air between them, as it ~
Several embodiments of the invention are illusà .travels from the center and toward the periph- '
50 trated in the accompanying drawing, in which---> ery, becomes more and more compressed on the 50
Figure 1 is a front viewof a~ fan constructed pressure sides ~of said blades and more and'
in accordance with this invention and positioned more rareñed at their rear sides. (See Figure
in a-conventional fan chamber.
8,- illustrating two types of heretofore commonly
Figure 2 is a vertical cross- section on line
55 2_2 in Figure 1.
used fan blades, 3a „and 3b.); This 'rarefactlon «
of the air, creating a partial vacuum behind re- 55
volving blades 'such as 8a and Ib,__not only causes shape of a cam Il, at its outer end, one form _.
power consuming suction and drag, butit has the ' of which is shown in Figure l (blade I) , will coun-v_v
elIect of permitting some- of the air that is ` press the air _to amuch higher degree than any
r being 'expelled from the pressure sides of the _ other type of blade vwith which I am familiar or
with which I have experimented.
¿_ l
5 blades to re-enter the- fan in the areas of rare
Having now‘described the cardinal featuresv of faction atv the rears of the blades.. 'I‘his backlash
this invention, Iwill briefly [explain those o! its. ~ .
"creates noise, causes some of .the air to be re
'handled by the Ian, preagents a smooth and even
ilow-of theair streams, rand is altogetherpblec
10 tionable.
many possible applications which are illustrated _
' in
VBy'now obs rving the blades I (Figure l) which
_The fan shown in Figures l andi! has already
been described, but asimilar ian will have greater
are designed according to my present invention, it ' eiiiciency if provided'with a front plate or ring ‘l>
readily will be seeuthitt` all .óf the‘above inen A. (see Figure 3). Such a-plateis _used in manyv ¿y ¿_
. tlone'd -objectionable features have been, elim
-15 inated. The front or pressure sides of the blades
-types o_f fans and 'it isftherefore not claimed u a _ _ ‘
part of my`preeent inventiombutit is illustrated _l5
_may be shaped Iin many'desired forms according’ as another type of fan to which this invention isïl '
to the- use for which a fan is intended. as wlllbe
i» _ discussed later, but their rear,:sides are turned _
adaptable. The same plate may also be used in
the ~fans shown in Figures' 4 and 5i! the intended
backward and away from the. front sides of the
use of said fans makesit advisable.
’I‘he blades '_Ic illustrated in Figure 4 are suit- _ 20
would be the areas of rareiiedair; th'e actual
able in- fans intended primarily for suction, where
‘ 20 blades so as to eliminate the spaces that otherwise y
shape _of said rear- sides may be curves, straight
there is such a minor resistance at theexhaust as
lines or a combination ofthe two-l-a‘nd these bacia` ` would bexcaused, for example-by the dustbag o!
' sides, however thusshaped, will hereinafter be re
25 ferred to as being curved. A The frontsides of the
'a household vacuum cleaner. 'I'he front side of
eeen ef seid biedes is convex and turned slightly _ 2s 'backward', but not enough to give said side the _ `
blades are also turned backward 'sro -that said
_ front and _rear sides'join in edges il pointing. characteristics of a cam as in Figure 1.l The rear
v backward in relation tothe fan’s,rotation.„ _Thus side with a concaved surface is also -turnedback
the two streams‘of air'emerging from each side ward and said front and rear sides are united at
their outer ends by a third side ß which prevents 30 _
v 30 of such'a blade will unite without creating suc
tion, eddles, or backlash.. Shortly expressed, I air already expelled into the fan chamber from
have streamlined the rear of the fan blades and re-entering the fan.- The rear end ,of this’pe
obtained the known beneilts _accruing to stream-_ `ripheral side 8 joins the curved back side of the
blade, streamlining said 4sides into an edge Il.
lined bodies.
thus permitting the outflowing stream of air from 85
I 135 _ rrr-mn` what -peint the r'ear sides of the blades
should -start _curving -backwardand away from between theblades to meet and mingle with the
the front sides and how far this' curvature should '_ air already in the fan chamber, without _creating
disturbing currents and eddies.“
reach will depend ontwo main factors; i.‘e., the
speed of the ian. andits intendeduse. As general
40 rules it may be stated: tlrst, that the greater the~
.'speed ofthe fan -blades the morefpronounced
should bethevst'reamlining; second, if a high
pressure is of greater importance than the volume
of- the expelled air,` then the best result is ob»
tained by extending the rear sides ofthe blades
so far backward and toward the front sides of
the following blades that the openings between
said. blades are comparatively small at* the pe
ripheryïof _the fan; while, third, if the’volurne of
the exhausted air is of 4prime importance', the'n'
_ The front sides of the blades shown in Figure 6
are concave. otherwise-with _reference to 'the
present 'invention-they are much like _those
_ shown in Figure 4.
However, blades thus shaped ' ’
will create more noise when v.passing the cutoff l _
(Figure 1) than' blades curved as _shown in Fig
ures if and 4. I have therefore selected this type
to illustrate that feature' of this invention by
vwhich a slight change in the blades’ contour will _
vmaterially reducethe noise of the fan’s operation.
Blade 3d has a sharpdfor'ward edge where the
front side lJoins the peripheral side at It. ‘At 50
re tively‘the
same point in blade 3e _there is a
¿_ the spaces between the tips of the blades should. _
be as large asrpossible, having in mind, however., 1ro ded corner. And bl e 3f is shown with a
sharp -edge 'as in blade 3d, >but it is
that the streamlining aßlways_„_should-be suilicient' ‘similarly
slightly inside the periphery of the fan ' I
te prevent areas of rareiled air-Lbehind the blades. 'disposed
whereby the outer side of the blade becomes s__ßß
'55 ^ A high pressure of the discharged air is'oir-_v
I_la. Any 'number of‘variations or con'ibina-V _
tained by restricting o_uuet s. frias, however, wiu 'canf
tion-of variations oi.'¿ such or similar nature may
cause the fan tooperate againsta` backpressurer' be
introduced in designing the blades of a fan for
with the greatest -load on the blades o_f said fariv at
the purpose ofU decreasing `the noise of operation
Y theirÍouter -ends, where‘the density of .the air is
said fan,I as has already been explained.
50 the greatest,- thus4 vany load will require the f of In
additionto the- fans already discussed. there
greatest amount of power for rotating the fan,
are also centrifugal multiblade i'a'nsof which
_ wheresaid blades -move the fastest. With these simple _type is illustrated somewhat dit_points in mind, Il have, in one embodiment of the . 'ically in Figures 6 and 7. It -is shown with a drive
present invention,'(designed a‘ fan blade which in ’ shaft n en wines-two side ‘putterv lz are mounted. es' _ ,
'65 ~addition »to the’c'entrifugal forcealso utilizes the-
are provided with ports I3 through which
»_ _` principleeof 'the cam-.for developing a _high pres# - the’äir enters the fan., whereuponv it is expelled
' sure.l " The power‘oi' afcam- is'too well known'to
centrifugally,v Many such 'fans have i'lat side
_ -require, discussion. _Against a‘solid object that - plates, as illustrated, while‘said platesïin other
,I0-power is 'theoretically unlimited, but when used vtypes areshaped as~ trimcatedvcohes so that the
- Vagainst a liquid, gas, or air and under conditions
spaceA between' them 'is less _at their _. peripheriœ
_than at-their centers. As innthe'fans previously
_so also-»finv these fans tlievane's may
substances has practicalv limitations. However. -
_ _I as herein discussed-„its power of compressing said .
~the principle 'is the same and. a -fanV` blade -so
ave several shapes.
of which'areillus-
_» .'75 formed merits. pressure .sideterniinetesin the ' __t tedinFlgureajBladeIahasaboncaveps-es- 1I
_ _
sure side, a streamlined rear side. and a periph-4
3. In a centrifugal fan, a plurality of blades
eral side that connectsthe other two. AIn blade
3h thepressure side is straight, the peripheral'side
-each comprising a forward side, a‘rear side and
a' peripheral. side connecting said forward side
' is formed into a _cam Mb, and the rear is stream
to said rear side; the junction point of said pe- ^ lined. 'Blade 3i is very similar to 3g,„except that - rlpheral side with said forward side on one of said
the pressure side is convex.
blades being at a different position relatively to
While I have shown and described several ap-*f . the fan’s periphery than the corresponding point
plications of my invention, other modifications
may be made without departing from its spirit
on the following blade.
10 or the scope of the appended claims. ’ '
. What I claim is:
1. A centrifugal fan with a plurality of blades
'radiating fromv the hub toward the fan’s periph
~ 4. In a centrifugal fan, a plurality of blades
each comprising a forward side, a rear side, and 10
a peripheral side connecting said forward side to
said rear side; the junction points of said pe
ripheral side with said forward `side in one group
ery; the forward surface.. which is presented to I of blades beingat a different position relative to
15 the air, of each of said blades being curved- back- v
wardly relative .to the fan’s rotation and so
' formed that said surface will have the shape and
the fan’s peripherythan‘the corresponding points 15
in another group of blades.
5. In a centrifugal fan, a plurality of blades`
function of a cam; said cam reaching7the fan’s ~each comprising a forward side, a rear side, and
periphery at a point ¿so`close to the forward aperipheral side connecting said forward side
20 surface of the following blade that the peripheral
to lsaid rear side; the junction point of said pe 20
opening lbetween the blades is restricted relatively '
-to the distance between said blades. at a point ripheral side with saidforward side on each- of
A said blades having 4a different shape than the
s'ome distance inside of the fan’s periphery.
2. In .fa centrifugal fan, a plurality. Aof blades corresponding point on eachof the other blades.
radiating from the hub of said fan toward the. ' 6. In a .centrifugal fan, a plurality of blades
fan’s periphery, each of said blades comprising a each comprising a forward side, a rèar side, and _25
.forward side which curves backward relatively to a peripheral side~ connecting said forward side to
» the direction of ~the fan’s rotation, a rearside also
curving backward but at a shallower‘curvature
30 than said -forward side, said forward and rear
_ sides joining in a trailing edge at a point on the
¿said rear side; the junction point of said periph
eral side with said forward side on each of said
blades having a different shape than the -corre 30
sponding point on each of the other blades and
fan’s periphery so close. _to the forward side of a - each of said points beingat a different position
following -blade that the peripheral opening. be
on each of said blades relative to the .fan’s
tween the 'blades is restricted relatively to the
distance between said blades at a point closer to
the hub of said fan.v
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