Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to fans and blowers, and
more particularly to a vibration-isolatiny and sealing
device for mounting same to, for example, metallic
cabinets and enclosures housing operating electronic
devices.
As is well known to one in the art, electrical
components and de~ices, by their operation, generate
heat and are, by their nature, susceptible to damaye by
the elevated temperatures. Frequently, specific devices
are provided with heat sinks, such as heat-conductive
finsj to remove the unwanted hea-t from the device by
radiation, conduction and convection to t~le environment.
Space limitations and the drive towards miniatur-
ization have resulted in smaller space allowances for
electronic components used in, for example, data
processing equipment and peripherals, especially desk
top units. The electronic equipment is ty~ically
packayed in a cabinet or enclosure which pro~ec~s thc
devices but frequently provides minimal room within for
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convection cooliny. To provide air circulation the
cabinets are provided with fans which are, all too il
often, fastened directly to the cabinets, an arrange-
ment known as "hard mountiny". The fans are ~cnerally
known as "muffin fans" and typically com~rise a ~ro-
peller rotatably mounted within a frame on a hub
containing the prime mover. In the four corners of the
frame are disposed hcles for receiving bolts whicl
secure the fan to a panel of the cabinet.
Hard-mounting can result in the vibrational
excitation of the cabinet at the one-per-revolution and
blade-pass fre~uencies, and their respective harmonics,
of the ~an during operation as well as the power line
frequency and its harmonics. This structure-borne
lS com~onent of noise can be most unaesirable for particular
locations, such as when the electronic cabinets are
within an office, and especially when several such fans
are oyerating.
To reduce the structure~borne noise, various
mounting arrangements have been sugyested. One such
scheme involves the use of cylindrical isolators, onc
dis~osed axially about each bolt between tlle fan and
the cabinet ~anel. Unfortunately, without redesign of
the cabinet, this mounting arran~ement results in a ga~
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between the fan and the panel. The gay provides a
secondary path for air pushed or drawn by the fan and
thus would reduce the effectiveness of the ~an in
dissipatiny heat from within the cabinet. ~urther, in
arrangements in which fans blow air, often filtered,
into the cabinet to maintain positive pressure, such a
gap would hinder pressure build-up.
To fill the gap an annular foam insert has been
used as a seal to channel the moviny air and prevent
its escape through the gap. This.arrangement can be
cumbersome and expensive, both in manufacture, repair
and assembly.
~ nother disadvantage with the prior art just
described is its profile. Since the fans are fre~uently
mounted within the cabinet, minimal space consum~tion
is desirable. The profile or stand-off height ~measured
from the cabinet panel on which the fan is mounted to
the opposite side of the fan) should preferably be as
small as possible. With the cylindrical isolators
disposed about each bolt, the fan may haYe a most
undesirable profile.
~ ccordinyly an object of the present invention is
to provide a vibration~lsolating and mounting arranye-
men~ for fans and blowers.
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Another objec~ of the ~resent inv~ntion is to
provide a seal dis~osable between a device such as a
an or blower and a surface on which the device is
mounted.
A further object of ~he invention i5 to provide a
vibration-isolatiny and sealing means for mounting
fans, blowers and the like and preventing the trans-
mission of structure-borne noise.
~ still further object of the invention is to
provide a vibration~isolating and sealing means having
a reduced profile or .~and-off height.
Yet anothex object of the present invention is to
~rovide a Yibration-isolating and sealing means which
is of simple design and can be economically manufac-
tured and assembled.
These and the other objects are met
; in the present invention in which is provided
a vibration isolating and sealing device for
mounting a fan having a propeller rotatably secured within a
: 20 housing, said device comprising: a first, substantially rigid
frame; a second, substantially rigid frame; the frames sub-
stantially lying one in the other, means for structurally inter-
connecting said first and second frames, said means containing
a flexural elastomeric membrane disposed and bonded between
: 25 said first and second frames to vibrationally isolate there-
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between; said second frame defininy therein a central opening
equal to or larger than the maximum di.ameter of the fan
propeller, and being adapted and configured to channel air to
the propeller of the fan; and said housing being securable ~o and
supportable by one of the frames and the other fr~ne being
securable to a support surface~ In one emxxlDent of the invention the
vibration~isolating ~eal i5 made inteqrally with the
housing of the fan. The mount, or mount and housing
unit, can be manufactured, for exam~le, by the ~rocess
10 described in the United States Patent No. 4,385,025
issued May 24th~ 1983 and conunonly assigned,
The invention is illustrated by way of example in
the accompanying drawings wherein:
~ig. 1 i5 a perspective view o a fan includiny a
~an housing incorporatiny a vibration-isolating seal
made in accordance with thc pres nt invcn~lon;
Fiy. 2 is a top ~lan view of a vibra~ion-isola~iny
and sealing mount constructed in aecordance with an
eln~odi;nent of the invention;
B
Fiy. 3 is a side vlew in elevation of the vibration-
isolating and sealing mount shown in Fig 2;
- Fig. 4 is a bottom ~lan view of the vibration-
isolating and sealiny mount shown in Fig. 2;
Fig. 5 is a sectional view taken along line V - V
of Fig. 2; and
Fig. 6 is a sectional view tahen along line VI -
VI of Fig. 4.
Referring to Fig. 1, a fan 10 is shown as comprising
a housing 12, a hub 14 fixedly connected to the housing
by ribs 16, and a propeller 18, a term used in its
broadest sense to include impellers, comprising an
annular portion 20, and a plurality of circumferentially-
spaced blades 22 radiating from and connected to tlle
annular portion t said annular portion being ro-tatably
mounted on said hub. In the version of the fan 10
shown,. hub 14 includes therein a prime mover (not
shown~ such as a small electrical motor ellcLtJize~l
throuyh leads 24. The fan housin~ 12 inclu~es a first
flange element 25, a second flanye element 28 i~
spaced parallel relation to the first flange element,
:,
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and a cylindrical bocly 30 therebetween. 'l'l~e flange
elements 26 and 28 have central openings 27 and 29,
resuectively. The cylindrical body 30 has a central
circular o~ellinc3 32 extending axially theretllrough and
in axial alignment with and of a diameter ay~roxi.mately
equal to the openinys 27 and 29. O~eniny 32 is further
sized so as to have an axial extent greater than that
of the blades 22 and a diameter sufficient to permit
the unemcumbered rotation of the ~ropeller 18. Pref-
erably the diameter of the opening 32 is minimized and
yet is sufficient to permit a clearance fit of the yro-
peller 18 therein. Thus the opening 32 effectively
channels air pushed or drawn by the propeller 180 The
annular portion 20, for example, is disposed concent-
ricaLly about the hub 14 over a portion of its axial
extent, and the ribs 16 are peri~herally-s~aced and
connected to the remaining axial extent of the hub
~roximate its planar end 34 closest to the first Elange
element 26.
Preferably the flange elements 26 and 2~ are of a
square geometry, extending radially beyond thc body 30
at their corners, desiynated 40 and 42 res~cctivcl.y.
~ach of the corners 40 and corners 42 carl ~e providecl
with one of the axially-directed holes 44 ancl 46,
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respecti~e]y size~ to accommodate therethrouyh bolts 45.
The outer diameter of the body 30 is equal to the
length of a side of the square-sha~ed flan(~e elements.
Thus the overall size of the housing 12 as just dcs-
cribed is minimized.
Also illustrated in Fig. l is a device 50, made in
accordance with the invention, which acts as a vibration-
isolating seal, shroud and mount. ~s shown, the
housing 12 is fastened to the device 50 by bolts 45.
In lieu of this arrangemen~ other means for fas-tening,
such as adhesi~e or tongue-and-slot are within the
purview of the invention. Or, for example, the housinc3
càn be integrally formed with the device 50. This
shall be more fully described following the detailed
description of device 50 below.
Figures 2, 3, 4 and 5 illustrate the device 50,
which comprises an outer, substantially s~uare frame
52; an inner, substantially square frame 54 dis~osed
coaxially and radially within the outer frame; and a
generally "S" shaped flexural membrane 56 disposed
between and connectiny said inner to said outer frame,
and for exam~le, structurally bonded thercbetweell. 'l`he
shape of the membrane 56 provides im~rovcd bond s~rcng~h
to the ou-ter and inner frames 52 and 54, respectively,
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by increasing bond area. Further, the sha~e is dictated
by o~erational reyuirements, namely, the shown confiyura--
tion achieves approximately e~ual translational and
coaxial stiffness and lower radial stiffness tnan a
flat element would and thereby provides stable low-
stiffness support of the fan lO (Fiy. l). For example,
the membrane 56 is made of elastomer and said inner and
outer frall1es 52 and 54 are made of a su~stantially
rigid o~ non-~xtensible material, for example, metal,
polymer (pl~stic), an elas~omer material more rigid
(higher shear and young's moduli) than said membrane
material or a polymer metal com~osite. The membrane 56
both supports -the 9 tatic and dynamic loads and provides
a path-brea~ for structure-borne noise and vibration.
The term "elastomer" is used herein in its broader
meaning to include various elastic substances which are
rubber or rubber-like. The term, for example, embraces
polymers which are cross linked to become rubber-like
and are thermoset~vulcanized, as well as thermoplastic
copolymer compounded materials. The flexural membrane,
for example, has a static shear modulus in the ran~s~ o
100 ~OUIldS ~cr s~uare inch and a Youn~'s modulus Lor
compression in the ran~e of threc times the shear
- modulus; hence the ma~nitude of posion's ratio is 0.5.
_g_
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In effect the membrane 56 can be termed "yisco-elastic",
i.e., it has a broad yield ran~e on its assoclateci
stress/strain curve and a "memory" so that it returns
to its original shape after ren~oval of applied ~orces.
Its viscous nature provides its inherent hysteretic
properties which result in dynamic enerc3y loss or -
vibrational dam~incj. The inner and ou-ter frames 52
and 54 respectively, should be made substantially riyid
though sufficiently deformable to achievc "sealill~J"
between the outer frame 52 and a support surface
(not shown~ and the inner frame 54 and the fan 10
(Fig. 1) despite surface irregularities.
The outer frame 52, as shown in Fig. 2, com~rises
four elonc~ate elemen~s 60, 61, 62, 63 of ec-~ual lenyth,
lS each one connected orthogonally at its ends to another
of the elements so as to forrn a sc~uare. Pre~erably
the elements 60, 61, 62, 63 are molded inteyrally. The
corners 64, 65., 66 and 67 between abutting ends of the
elements 60-63, respectively, are each provided with
bulbous projections 68, 69, 70, 71, respectively,
extencdiny radially outward. ~xially directed holes 72,
73, 74, 75 extencl throuyh the projectiolls G8-71,
rcs~)ectivcly, ancl arc size~cl ancl spacccl ~o rocc~jvc bolts
ox screws ~not shown~ therethrough, which fasten the
devlce 50 to a support surface, for exam~le, a panel o
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an electrical equipment cabinet (not shown). A strenyth- ¦
ening fla-t 80 is disposed about the periphery o~ the
outer frame 52. The cross~sectlonal shal~c of elements 60-
63 can be gleaned from Fig. 6 which is a re~)resentative
example. This figure is a sectional view taken along
line VI - VI of Fig. 4 which is the bottom plan view.
The element 62 is shown in cross-section as havinc3 a
planar bottom surface 82 with two or1;hogonally depcn-
ding side walls 90 and 91. A surface 92 of element 62
is not planar and does not extend axially to surface 84
except for a short transition piece 94 which connects
the elemen-t 6~ to the strengthening rib 80 which is
disposed ~erpendicular thereto. The surface 92 is
curvaceous, having a generally "S" shaped silhouette
for reasons hereinafter provided.
The inner frame 54, as shown in Fiy. 2 and 4
comprises four integrally-molded elongate elements 100,
101, 102, 103 of equal lenyth, each one connected
orthogonally at its ends to another of the elements so
as -to form a square. Corners 105, 106, 107, 108
betwecn abutting ends oE elcments 100~103 arc cacll
provided with holes 110, 111, 11~, 113 and crescellt
flats 115, 116, 117, 118, respectively. Iloles llU-113
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are sized and spaeed to receive thercthro-lcJh bolts 45
whieh fasten the fan 10 to the deviee 50. For example,
the holes 110-113 ean be threaded so as to reeeive the
bolts 45 in threaded engac;ement. ~s a re~resentative
exam~le, ereseent flat 118, corner 108 an(:l hale 113 are
shown in Fig. 5. The eross-seetional shape of elenients
100~103 ean be gleanecl :~rom Fig. 6. The element 101 is
shown in eross-section as having a planar surface 119
substan-tially coplanar with surface 82, two de~ending
side walls 120 and 122, and a surfaee 123 substantially
eoplanar with surfaee 82. The overall cross-sectional
configuration is boot-like, with -the radial extent or
thiekness of planar surfaee 123 being less than that of
surfaee 119~ Side wall 120 is disposed E~erpendicularly
to both surfaees 123 and 119. Side wall 122 has a
portion 125 whieh is parallel to side wall 120 and
proximate to surface 119, and an arcuate port:ion 127
disposed between the portion 125 and surfaee 123.
Returning to Fiy. 4, the ereseent flats 115-118
20 are planar elements having an axial extcnt l~ss than
the elements 100-103, and a raclial extcnt [rom t:llc
eorners ].05-108 inward a distance sufficient to proviclc
a substantially eireular openiny 120 (all:~eit with
flattened sides 121, 122, 123, 124 though such are not
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y~
necessary). The diameter of the circular o~ening 120
should be a~proximately e~ual to tlle ~iameter of
o~ening 32 in cylindrical body 30 of the Ean housing 12
(Fig. l). Thus the openinys 120, 27, 29 and 32 (Fiys. l
S and 4) act as cylindrical yuides or shrouds which
direct the air flow to or away from the pro~eller L~
(Fig. 1). Tl~is effective]y reduces turbulent air flow
and the resultant noise, and loss of efficiency of the
fan lO (Fiy. 1) associated with turbulent flow. The
invention can be practiced with a variety of commer-
cially available fans and blowers. The a~ial thickness
and width of the membrane 56 (Fiy. 5) and the shear and
Youny's moduli of elasticity characteriziny -the elastomer
from which it is made can be selected and desiyned in
manufacture so that the device 50 (Fig. 1) can sup~ort
the required weiyht while achieviny the clesired vi~ra-
tional isolation at the particular band-pass frequencies.
The following is an example of performance and desiyn
for a typical application of the invention. A muffin
fan o$ three inch diameter having seven blades and a
weight of 0.86 lbs. may opcrate at speeds of 3,000 I~PM
(50 IIZ). The device 50 constructed in accordance witll -
the invention can be.4.6 inches s~uare an~ 0.~7 incllcs
.
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thick, with a natural frequency of 18 hertz, peak
transmissibillty of six to ei~ht and an isolation
efficiency (analyticly deterrnined) of approxiinately 736
at 50 Elert~ disturbance and ap~roxilnately 99~ at 350 llz
disturbance.
Thouyh the housing 12 and mount 50 are shown in
Fig. l as separately formed elements joined by bolts 45,
it should be understood that the invention also con-
templates their manufacture as an integral, one-piece
unit, and thus not require bolts 45. Such a vibration
isolating and sealiny housiny would effect economies in
manufacture and assembly.
It will be apparent that the invention herein
described is susceptible of being practiced otherwise
than is herein illustrated. For example, the device 50
can be ~rovided with two or more openings 120 so as to
serve as a vibration isolating and sealing mount for
two or more fans simultaneously. ~s a furtller exaMple,
the deYice 50 can be reconfigured into a circular or
. . .
triangular form instead of the syuare as illustrated,
f tlle al~plica tiOll permi ts .
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