Abstract:
A fan arrangement comprises a fan ( 10 ) having a fan housing ( 30 ) within which is arranged a blower wheel ( 18 ) which, in operation, moves air from an intake side of the fan ( 10 ) to a delivery side. Arranged radially outside the fan housing ( 30 ) is a surrounding mounting frame ( 34 ) that serves to support the fan housing ( 30 ). A membrane ( 32 ), made of an elastic material, elastically connects the fan housing ( 30 ) and mounting frame ( 34 ) to one another and is formed with through holes or apertures ( 33 ) that, in the event of a closure of the output or delivery side of the fan arrangement ( 40 ), enable a return flow, from the delivery side to the intake side of the fan arrangement ( 40 ), of air moved by the blower wheel ( 18 ).

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to an improved vibration-damping fan arrangement, and to a method of making the fan arrangement. 
     BACKGROUND 
     In numerous applications, for example ventilation of a vehicle seat or of equipment units, the vibrations produced by a fan are perceived as obtrusive. Such vibrations result from the normal operation of the fan and from changes in load and rotation speed. These vibrations tend to be transferred from the fan to the entire apparatus in which the fan is located. 
     DE 196 43 760 C1 and corresponding U.S. Pat. No. 6,050,890, BAYER+/DAIMLER/CHRYSLER disclose a fan arrangement in which a fan is suspended within flexible belts. This solution has the disadvantage that the belts are complex and laborious to manufacture, and to thread/assemble, after their manufacture. 
     SUMMARY OF THE INVENTION 
     It is therefore the object of the invention to provide a novel fan arrangement and a method of manufacturing the same. 
     According to the invention, this object is achieved by arranging a fan housing radially within a surrounding mounting frame, and interconnecting the housing and frame by an elastomeric membrane formed with apertures. As a result of the membrane, the vibrations produced by the fan are effectively decoupled from the mounting frame; and a reverse flow of air from the delivery side to the intake side is possible if the fan arrangement is closed off on its delivery side. 
     Another advantageous feature of the invention is the method of making the membrane, namely by placing a mold radially between the fan housing and mounting frame, and injection-molding the elastomeric interconnecting membrane. With such a method, a membrane can be quickly, reliably, and economically manufactured from an elastomeric material. It is also advantageous to make the fan housing and mounting frame from a hard plastic by injection molding. 
     Further details and advantageous refinements of the invention are evident from the exemplary embodiments, in no way to be understood as limitations of the invention, that are described below and depicted in the drawings. 
    
    
     
       BRIEF FIGURE DESCRIPTION 
         FIG. 1  is a plan view of a first exemplary embodiment of a fan arrangement according to the present invention, viewed in the direction of arrow I of  FIG. 2 ; 
         FIG. 2  is an enlarged sectioned depiction viewed along line II—II of  FIG. 1 ; 
         FIG. 3  shows a second exemplary embodiment of a fan arrangement according to the present invention, in a sectioned depiction analogous to  FIG. 2 ; 
         FIG. 4  is a section through a third exemplary embodiment of a fan arrangement according to the present invention having an undulating membrane, in a depiction analogous to  FIGS. 2 and 3 ; 
         FIG. 5  is a section through a fourth exemplary embodiment of a fan arrangement according to the present invention having an adhesively mounted membrane; 
         FIG. 6  is a plan view of a fifth exemplary embodiment of a fan arrangement according to the present invention having a membrane that is formed with oval elongated apertures; 
         FIG. 7  is a plan view of a sixth exemplary embodiment of a fan arrangement according to the present invention having a membrane with angular elongated apertures; 
         FIG. 8  schematically shows an upper injection mold and a lower injection mold for manufacturing a fan housing and a mounting frame; and 
         FIG. 9  schematically shows an apparatus having an upper mold part and a lower mold part for manufacturing a membrane. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a plan view of a first exemplary embodiment of a fan arrangement  40  according to the present invention having a fan  10 , viewed in a direction indicated by arrow I of  FIG. 2 . 
       FIG. 2  is a side view of fan arrangement  40 , viewed in section along line II—II of  FIG. 1 . 
     Fan  10  has an electric motor  12  comprising a stator arrangement  14  and a rotor  16 , also fan blades  18 , struts  28 , a motor retention flange  29  (see  FIG. 3 ), and a fan housing  30  comprising a lateral projection  31 . The rotation axis of the fan is labeled  50  in  FIG. 2 . 
     Fan arrangement  40  has a membrane or diaphragm  32  comprising a plurality of apertures (through holes)  33 , as well as a mounting frame  34  comprising a projection  35 , a mounting frame holder  36 , and a mounting opening  38 . 
     Stator  14  is connected via struts  28  to fan housing  30 , and drives rotor  16 . Motion is thereby imparted to fan blades  18 , and an air stream flows through region  20  between fan housing  30  and stator  14 . An axial fan  12  is depicted, but the invention is similarly suitable, for example, for diagonal or centrifugal fans. 
     Fan housing  30  is connected via the circumferential annular membrane  32  to mounting frame  34 , which in this exemplary embodiment comprises two mounting frame holders  36 . Mounting openings  38  in mounting frame holders  36  serve for the mounting of mounting frame  34  and thus also of fan  10 , for example by means of screws (not shown). 
     Membrane  32  thus connects fan  10  to mounting frame  34 . For reliable connection, it encompasses both a projection  31  on fan housing  30  and a projection  35  on mounting frame  34 . Projections  31 ,  35  can also be dovetail-shaped. In this exemplary embodiment, projections  31 ,  35  extend around the entire circumference of the fan, i.e. 360°. Fan housing  30  and mounting frame  34  are thus connected, in elastically resilient fashion, to one another over the entire or substantially the entire circumference, both on the fan housing side and on the mounting frame side. 
     Fan housing  30  and mounting frame  34 , as well as projections  31 ,  35  formed integrally with them in this exemplary embodiment, are preferably manufactured from plastic or metal; and membrane  32  is preferably made of an elastomer. 
     Mode of Operation 
     Fan housing  30 , and thus also fan  10 , are retained both axially and radially by membrane  32  in the desired position relative to mounting frame  34 , and thus constitute fan arrangement  40 . 
     The connection is not rigid, but rather elastic and capable of vibrating or oscillating. Whereas rigid connections would transfer vibrations of fan  10  to the mounting frame largely undamped, membrane  32 , being made of an elastomer, results in a desirably greater damping in terms of the transfer of vibrations from fan  10  to mounting frame  34 . 
     A membrane  32  is capable of vibrating because it is relatively thin. As is evident from  FIG. 2 , the membrane has in edge regions  32 ′, at which it is mounted on fan housing  30  and mounting frame  34 , a thickness suitable for reliable connecting. At center  32 ″, on the other hand, it is thin, so that fan  10  can move with respect to mounting frame  34 . 
     The damping resulting from membrane  32  depends on the frequency to be transferred and on the membrane properties, i.e. in particular the material and shape of the membrane. 
     Each fan  10  produces vibrations in individually characteristic frequency ranges. 
     It is therefore advantageous to influence the membrane properties in such a way that, especially in the characteristic frequency ranges, membrane  32  exhibits good damping and thus also good decoupling. From the modification possibilities below, an optimum for the respective fan type is ascertained empirically. 
     A suitable plastic, in particular an elastomer whose hardness can be varied, is preferably used as the material from which the membrane is manufactured. One measure of hardness is the so-called Shore hardness. A combination of different materials is also possible. 
     In addition, in order to influence the membrane properties, the basic shape of the membrane is adapted, openings are configured in the membrane, and the thickness of the membrane is varied. Further exemplary embodiments, in some cases also representing combinations of these possible variations are presented below. 
       FIG. 3  is a partially sectioned side view of a second exemplary embodiment of a fan arrangement  40  according to the invention, in a section corresponding to  FIG. 1 . 
     Membrane  32  is U-shaped in cross section in this exemplary embodiment, and the fan can therefore generate vibrations with larger vibration amplitudes. This is advantageous in particular for damping low-frequency vibrations. 
     Membrane  32  comprises one or more openings or apertures  33  at bulge  32 ′″. The vibration properties of membrane  32  are influenced by the absence of material (and therefore of mass) at this point. 
     Opening  33  furthermore has the advantage that, in applications in which the delivery side is closed off (for example, when a driver is sitting on a vehicle seat and all the outlet openings are covered), a so-called pneumatic short-circuit is prevented because air can flow back to the intake side through opening  33 . As a result, fan  10  can continue to operate in a preferred working range. This aspect will preferably also be considered when selecting the exact configuration of openings  33 . 
       FIG. 4  is a partially sectioned side view of a third exemplary embodiment of a fan arrangement  40  according to the present invention, in a section corresponding to  FIG. 1 . 
     In this exemplary embodiment, membrane  32  of fan arrangement  40  is formed in an undulating or approximately sinusoidal shape, and has several bulges  32 ′″. Because of the greater length of membrane  32 , fan  10  can perform larger movements or excursion in both the axial and radial directions. 
     In this exemplary embodiment, as in  FIG. 3 , it is also possible to create openings in membrane  32  in order to influence the damping properties. 
       FIG. 5  is a partially sectioned side view of a fourth exemplary embodiment of a fan arrangement  40  according to the present invention, in a section corresponding to  FIG. 1 . 
     Here a membrane  32  is adhesively connected to fan housing  30  and to mounting frame  34 . In other words, no projections  31 ,  35  are present with which membrane  32  is positively connected. The material of membrane  32  must be suitable for such a connection, for example by entering into a chemical bond with the surfaces of the material of fan housing  30  and mounting frame  34 . 
     Peripheral regions  32 ′ of membrane  32  are made thicker in order to produce a larger surface area for connection. 
       FIG. 6  is a plan view of a fifth exemplary embodiment of a fan arrangement  40  according to the present invention. 
     Fan housing  30  and mounting frame  34  are connected via a membrane  32  that is equipped over the entire circumference with elongated holes  33 ′ which have rounded ends  37 ′, If a U-shaped or undulating membrane is used for diaphragm  32 , holes  33 ′ are then preferably located at an axially highest or lowest point (see  FIG. 3 ). 
     In this exemplary embodiment, projections  31 ′ and  35 ′ are interrupted at regular intervals. If positive connection at the projections is not sufficient for secure retention of membrane  32 , the latter is preferably additionally adhesively secured, at least at the locations without projections  31 ′,  35 ′. 
       FIG. 7  is a plan view of a sixth exemplary embodiment of a fan arrangement  40  according to the present invention. 
     Fan housing  30  and mounting frame  34  are connected via a membrane  32  that is equipped with angular elongated holes  33 ″ which have substantially rectangular ends  37 ″. 
     Many variations, modifications, and especially combinations are, of course, possible in the context of the present invention. In addition to round, oval, and rectangular shapes, holes  33  might also have triangular, polygonal, square, or other shapes. Good vibratory behavior in membrane  32  can be achieved for the particular motor type by selecting the shape and number of holes  33 . 
     Projections  31  on fan housing  30  and projections  35  on mounting frame  34  can be differently configured, the shape of the projections can be varied, and the possible interruption of projections  31  and  35  around the circumference can be varied. 
     In order additionally to minimize vibration transfer, mounting frame  34  can likewise be mounted elastically on a component to be cooled. 
     Alternatively, a second membrane offset axially with respect to first membrane  32  can be provided in addition to the one membrane  32 . This guarantees secure retention of fan  10  even when the forces occurring are large. 
     Method of Making 
       FIG. 8  schematically shows an upper injection mold half  60  and a lower injection mold half  62 , and  FIG. 9  schematically shows a holding apparatus  70 , an upper mold part  72 , and a lower mold part  74 . Upper mold parts  60  and  72  each have conduits  80  and  82 , respectively, through which the material to be processed is fed. 
     A so-called 2-K technique, in which two plastics are processed, is used to manufacture holding apparatus  40 . In this, fan housing  30  (optionally with struts  28  and motor retention flange  29 ) and mounting frame  34  are produced, for example using the injection-molding method, from a hard plastic by injection through conduits  80 , and held in the correct position relative to one another (see  FIG. 8 ). 
     The shape of membrane  32  is defined by way of two complementary mold parts  72 ,  74  protruding in from both axial sides as shown in  FIG. 9 , and membrane  32  is produced by injecting a soft elastomer. Fan  10  is then pressed into flange  29 . 
     No threading-in or other laborious procedures are necessary here, and a positive connection to projections  31 ,  35  is immediately created. 
     Various changes and modifications are possible within the scope of the invention. Therefore, the invention is not limited to the specific embodiments shown and described, but rather is defined by the following claims.