CA1216561A

CA1216561A - Vibration isolating seal for mounting fans and blowers

Info

Publication number: CA1216561A
Application number: CA000412850A
Authority: CA
Inventors: Dale W. Schubert; Richard S. Gureghian
Original assignee: Barry Wright Corp
Current assignee: Hutchinson Aerospace and Industry Inc
Priority date: 1981-10-08
Filing date: 1982-10-05
Publication date: 1987-01-13
Also published as: FR2514431B1; NL8203897A; GB2107787A; CH662623A5; IT1150389B; JPS5872700A; DE3237017A1; BR8205891A; IT8249213A0; DE3237017C2; IL66917A0; JPS635600B2; GB2107787B; FR2514431A1

Abstract

ABSTRACT OF THE DISCLOSURE

A vibration isolating and sealing device for mounting a fan having a propeller rotatably secured within a housing, said device comprising an outer, substantially square frame; an inner substantially square frame; a generally "S" shaped flexural membrane disposed between and connecting said inner to said outer frame; said membrane being made of elastomer, and wherein the inner frame has a central bore configured to channel air to the propeller of the fan.

Description

'~ ~f' S~

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 .

~ . ...

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~

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.

.
. .

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-.'~

L

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, :, 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, .
: -7-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, : ~ , ' .

~
.
, . ~ ~

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_ ' .

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 rj~

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 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 .. . . . . . . . . . . . . _._ __ .. ___ . .. -- . _ .. ._ _ _ , _ 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 .

.. ..... , .. _ _ .. _ .. _ _ _ _ . . . .... _ . .. . . .... . .. , " _ , . _ _ 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 .

Claims

CLAIMS:

1. A vibration isolating and sealing device for mounting a fan having a propeller rotatably secured within a 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 said first and second frames to vibrationally isolate there-between; said second frame defining therein a central opening equal to or larger than the maximum diameter of the fan propeller, and being adapted and configured to channel air to the propeller of the fan; and said housing being securable to and supportable by one of the frames and the other frame being securable to a support surface.

2. The device of claim 1 wherein the second frame is secured to the fan housing.

3. The device of claim 1 wherein the second frame is integral with the fan housing.

4. The device of claim 1 wherein the first and second frames are each of a generally square shape.

5. A device comprising a housing including a cage portion, and a mounting portion axially connected to said cage portion, a fan including a propeller having a plurality of radially extending blades rotatably mounted on a hub fixedly secured to the cage housing, and wherein the mounting portion includes:

.

(a) an outer, substantially rigid frame having four elongate elements of substantially equal length, each one orthogonally connected at each of its ends to an end of another of the elements so as to form a generally square shape, (b) an inner, substantially rigid frame having four elongate elements of substantially equal length, each one orthogonally connected at each of its ends to an end of another of the elements so as to form a generally square shape, and defining therein an opening having a cross-sectional size not less than the diameter defined by the propeller blades, (c) a flexural elastomeric element of generally continuous square shape bonded to said inner frame and said outer frame and vibrationally isolating one from the other, (d) first means for fixedly securing said cage portion to said outer frame, (e) second means for fixedly securing said inner frame to a substantially flat mounting surface, (f) said first and second securing means being configured and adapted to substantially prevent air passage between the cage and the inner frame and between the outer frame and the flat surface while the fan is in operation, and (g) whereby the housing is both a vibration isolator and seal.

6. A mounting device for use with a muffin fan comprising a housing including a cage and a fan including a propeller having a plurality of radially-extending blades rotatably mounted on a hub and disposed within the cage, said mounting device including:
(a) an outer, substantially rigid frame, said outer frame including first mounting means;
(b) an inner, substantially rigid frame, said inner frame including second mounting means;
(c) a flexural membrane of generally continuous shape disposed and bonded between said inner frame and said outer frame and being the only structural connection there-between;
(d) wherein said cage is fastened to said inner frame by use of said second mounting means; and said outer frame is fastened to a surface on which the muffin fan is to be mounted by use of said first mounting means;
(e) whereby said connection between said cage and said mounting device and between said mounting device and said surface is such as to substantially prevent air passage there-through when the muffin fan is inoperation; and (f) whereby said mounting device is both a vibration isolator and seal, and supports the static and dynamic loads of the muffin fan while providing a path break for structure borne noise and vibration.

7. The device of claim 6 wherein the cage portion and the mounting portion are integrally constructed.

8. The device of claim 6 further comprising an inner frame, and an outer frame and wherein the elastomeric element is bonded to and connects the inner and outer frame and is coaxial therewith.

9. The device of claim 7 wherein the mounting means extends through at least one bore provided in the flat surface.