Patent Publication Number: US-10760590-B2

Title: Flow straightener

Description:
RELATED APPLICATION 
     This application filed under 35 U.S.C. § 371 is a national phase application of International Application Serial Number PCT/EP2016/056278 filed Mar. 22, 2016, which claims priority to European Patent Application No. EP 10 2015 424.1, filed on Mar. 25, 2015, the disclosure of which is entirely incorporated herein by reference. 
     TECHNICAL FIELD 
     The invention relates to a flow rectifier for an axial fan as well as to an axial fan having a flow rectifier. 
     In this context, the term “flow rectifier” refers to a baffle element, whereby this baffle element, which is arranged as a flow rectifier downstream from an axial fan, diverts the air that has been made to flow by the axial fan impeller so as to establish a flow that is as axial and uniform as possible. For this purpose, the flow rectifier has at least one appropriately shaped baffle vane. 
     BACKGROUND ART 
     Fans with large diameters require large flow rectifiers. Such large flow rectifiers, whose parts have diameters of 350 mm, especially of more than 500 mm, are expensive: for cost reasons, these parts are usually made of plastic, for example, by means of injection molding. This calls for injection molding tools that entail high tool costs, especially in the case of large parts. Moreover, production by means of plastic injection molding is quite difficult with such large parts, particularly in view of their thin walls. The parts are basically fragile and problematic when it comes to packaging, storage, transportation and handling. 
     International patent application WO 2014/056657 of the applicant discloses a flow rectifier as well as an axial fan, especially for evaporators in cold-storage rooms. The flow rectifier downstream from the axial fan greatly increases the range of throw of the axial fan, a process in which it converts the swirling outflow of the fan into a uniform axial flow. In this context, the term “range of throw” refers to a distance up to which a limit speed of the air flow is maintained. The flow rectifier is made as a one-piece injection-molded plastic part. Subsequently, it can be detachably mounted as a separate part onto a wall ring or onto a safety grille or support grille of a fan. 
     Depending on the operating point of the fan, it is advantageous in terms of the throughput rate and the efficiency to use flow rectifiers that have a varying number of baffle vanes, whereby the baffle vanes advantageously have different geometries, depending on the operating point of the fan. As a result, the required production run for a specific flow rectifier is smaller than that of the corresponding fan and thus especially too small for a cost-effective production run, since a separate injection mold is needed for each variant of the flow rectifier. 
     The documents European patent application EP 1 408 238 A2, U.S. Pat. Nos. 3,883,264, 6,409,472 B1 and Japanese patent specification JP 2012031750 each disclose a flow rectifier for an axial fan, having a hub and at least one vane, whereby the at least one vane can be operatively connected to the hub so as to be detachable. It is also disclosed that the hub forms a cup with a bottom, an inner circumferential wall and an outer circumferential wall, whereby the hub cup has an opening in the hub bottom. 
     The objective of the invention is to put forward an axial fan with an optional flow rectifier, whereby it should be possible to optimize the geometry of the cost effectively producible flow rectifier for various operating points. 
     This objective is achieved by an axial fan according to the claims. Advantageous embodiments of the axial fan can be gleaned from the claims. 
     DISCLOSURE OF THE INVENTION 
     A flow rectifier according to the invention for an axial fan with a hub and at least one vane is characterized in that the at least one vane can be operatively connected to the hub so as to be detachable. Since the vane and the hub can be connected so as to be detachable, the flow rectifier has a modular structure. Depending on the operating point of the axial fan, more or fewer vanes can be used. Here, the flow rectifier can also have numerous vanes. The vane geometry can also be easily changed. Furthermore, different flow rectifiers are needed for different fan sizes, that is to say, for fans with different impeller diameters. Due to the modular structure, the hub of the flow rectifier can be used for different fan sizes in that various guide vanes are attached to the hub. This increases the production run for the hubs, so that economies of scale result in lower part costs and less capital expenditure. Since the flow rectifier consists of several parts, the size of the individual parts is reduced, leading to lower tool costs and facilitating the injection-molding process. By the same token, packaging, storage, transportation and handling are greatly simplified. 
     It has proven to be advantageous if the hub forms a cup with a bottom, an inner circumferential wall and an outer circumferential wall, whereby the hub cup has an opening in the hub bottom. Particularly when the opening is in the lowest point of the hub cup, water is prevented from accumulating in the hub cup. Moreover, a visual inspection can be made through the opening in order to check, for example, whether the positive connection between the at least one guide vane and the hub was established correctly. 
     It has also proven to be advantageous if the at least one vane can be operatively connected to the hub without the need to use tools. Here, the at least one vane can be operatively connected to the hub positively and/or non-positively. For example, by means of a special geometry on the hub-side end of the at least one vane, the at least one vane can be operatively connected to the hub and to the corresponding counterpart of this geometry on the outer circumference of the hub. This special geometry can advantageously be configured as a dovetail guide. 
     It has proven to be especially advantageous if the operative connection of the at least one vane can be additionally secured onto the hub. For example, the at least one vane can be additionally latched onto the hub. This can be effectuated, for example, in that the vane has a guide with which it can be inserted into the hub. For this purpose, the outer circumference of the hub likewise has corresponding guides. The inside of this guide, i.e. the side facing the center axis of the axial fan, can have a latching hook that faces this side and that can be latched behind a corresponding edge of the hub. In order to increase the flexibility, the guide can have a slit, as a result of which the requisite joining force is minimized. Thanks to the latching, a secure connection is established between the vane and the hub of the flow rectifier. 
     In another advantageous embodiment, on the inside circumferential wall, the hub has a stop facing the center axis, that is to say, the axis of rotation of the impeller. 
     An axial fan according to the invention has an impeller powered by an electric motor, a diffuser, a flow rectifier, a support structure and at least one circumferential ring, whereby the support structure and the at least one circumferential ring are arranged downstream from the impeller, and whereby the flow rectifier can be attached to the at least one circumferential ring. The axial fan can be installed via a wall ring in an appropriate opening in a wall. The support structure then creates the connection between the wall ring and the electric motor, securing the electric motor and thus the impeller in the wall ring. One or more circumferential concentric rings or at least one spiral ring can be attached to the support structure, above which there can be a guard against accidental contact in the form of a safety grille for the impeller and/or for electric parts of the motor. As an alternative, if necessary, the guard against accidental contact, can be in the form of a separate safety device. 
     A flow rectifier increases the peak efficiency of an axial fan in the high pressure range of the characteristic curve of the fan. At low counterpressures and high volume flows, however, the efficiency of a fan having a flow rectifier is lower. The flow rectifier according to the invention can optionally be integrated whenever this is advantageous for the area of application in question. No change needs to be made to the existing parts in order to be able to attach the flow rectifier. 
     Moreover, it has proven to be advantageous if the at least one vane has a connection element in an area facing away from the hub. The flow rectifier can be connected to the support structure and/or to the safety grille via the connection element. Here, the support structure and/or the safety grille contribute to the stability of the flow rectifier. 
     In an especially advantageous embodiment, the flow rectifier can be operatively connected to the at least one circumferential ring without the need to use tools. As a result, the flow rectifier can be very easily installed on the axial fan, if the operating point requires this, and it can be removed again if the flow rectifier is not needed at another operating point. Here, the flow rectifier can be attached to the at least one circumferential ring positively and/or non-positively by means of the connection element. Such an attachment is possible, for example, via an elastic-plastic deformation of the connection element. Here, the connection element is deformed partially elastically, but also partially plastically. 
     In another especially advantageous embodiment, the support structure has a flange ring on its side facing the axis of rotation of the impeller, whereby the flow rectifier can be operatively connected to the flange ring positively and/or non-positively. For example, the flow rectifier can be operatively connected to the flange ring via a latching hook. This connection additionally increases the endurance limit of the flow rectifier. 
     It has also proven to be advantageous for the stop of the hub to cooperate with the flange ring of the support structure and with the latching hook in the installed state in such a way that the axial position of the flow rectifier is fixed. The stop can have a labyrinth-like configuration. As a result, the stop reduces the leakage flow in the connection area. The stop is only interrupted in the area of the latching hooks for production-related reasons. 
     Moreover, it has proven to be particularly advantageous if a gap is formed in the circumferential direction between the diffuser and the at least one vane. As an alternative, the end face of the at least one vane facing in the circumferential direction can also touch the diffuser. 
     Additional advantages, special features and practical refinements of the invention can be gleaned from the subordinate claims and from the presentation below of preferred embodiments making reference to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings show the following: 
         FIG. 1  a flow rectifier according to the invention, in a three-dimensional view, 
         FIG. 2  a section of a flow rectifier according to the invention, in a cross section, 
         FIG. 3  a section of an axial fan according to the invention with an installed flow rectifier, in a cross sectional view, 
         FIG. 4  another section of an axial fan according to the invention, with an installed flow rectifier, in a cross sectional view. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a flow rectifier  20  according to the invention, in a three-dimensional view. The flow rectifier  20  has a hub  5  and a plurality of vanes  4 . The inner circumference of the hub  5  has a circumferential stop  14  as well as latching hooks  12  distributed along the circumference. On their ends facing the center axis  2   a  of the hub, the vanes  4  have guides  4   a  by means of which they are inserted along the outer circumference of the hub  5  into guides  5   e  located there (not visible in this figure). In particular, in this manner, the vanes  4  can be connected to the hub  5  without the need to use tools. Moreover, the vanes  4  each have a connection element  10  in an area on their side facing away from the center axis  2   a  of the hub. 
       FIG. 2  shows a section of a flow rectifier according to the invention, in a cross section. A vane  4  is inserted with its guide  4   a  into the corresponding counterpart of the geometry, namely, the guide  5   e  of the hub  5 . The guides  4   a  and  5   e  are configured as a dovetail guide. The hub  5  has a bottom  5   b , an inner circumferential wall  5   c  and an outer circumferential band  5   d , and it forms a hub cup  5   a . In the hub bottom  5   b , there is an opening  6  through which the water that might accumulate in the bare cup  5   a  can drain. The guide  5   b  is situated in the outer circumferential band  5   d . The guide  4   a  of the vane  4  has a slit  4   b  that is open towards the hub bottom  5   b . This slit  4   b  increases the flexibility of the guide  4   a . The guide  4   a  has a latching hook  9  on its end facing the hub bottom  5   b . When the guide  4   a  of the vane  4  is completely inserted, this latching hook  9  snaps into the guide  5   e  of the hub behind the wall of the guide  5   e , thus securing the vane  4  in the hub  5 . The inner circumferential wall  5   c  has a stop  14  facing the center axis  2   a.    
       FIG. 3  shows a section of an axial fan according to the invention, with an installed flow rectifier  20  in a cross sectional view. The axial fan has an impeller  2  that can be powered by an electric motor, a diffuser  3 , a flow rectifier  20 , a support structure  11   b  and at least one circumferential ring  11   a   1 , whereby the support structure  11   b  and the at least one circumferential ring  11   a   1  are arranged downstream from the impeller as seen in the direction of flow, and whereby the flow rectifier  20  can be attached to the at least one circumferential ring  11   a   1 . The axial fan can be installed via a wall ring  1  in an appropriate opening in a wall. The support structure  11   b  then establishes the connection between the wall ring  1  and the electric motor, securing the electric motor and thus the impeller  2  in the wall ring  1 . One or more circumferential concentric rings  11   a  are attached to the support structure  11   b , above which there can be a guard against accidental contact in the form of a safety grille for the impeller  2  and/or for electric parts of the motor. 
     The flow rectifier  20  can optionally be integrated, that is to say, it can be attached to the axial fan, if this is advantageous for the area of application in question. For a different operating point, however, the flow rectifier  20  can also be easily removed again. In particular, the flow rectifier  20  can be attached and removed again without the need to use tools. No changes need to be made to the existing components in order to be able to attach the flow rectifier  20 . By means of the connection element  10 , the flow rectifier  20  can be attached to the support structure  11   b  via the at least one circumferential ring  11   a   1 . Here, the support structure  11   b  contributes to the stability of the flow rectifier  20 . The flow rectifier  20  can be attached to the at least one circumferential ring  11   a   1  positively or non-positively by means of the connection element  10  in that the fork-like fastening element  10  is slid onto the at least one circumferential ring  11   a   1 . Here, the connection element  10  is deformed partially elastically, but also partially plastically. 
       FIG. 4  shows another section of an axial fan according to the invention, with an installed flow rectifier  20 , in a cross sectional view. 
     The support structure  11   b  has a flange ring  11   c  on its side facing the axis of rotation  2   a  of the impeller  2 , whereby the flow rectifier  20  is operatively connected to the flange ring via a latching hook  12 . This connection additionally increases the endurance limit of the flow rectifier  20 . 
     The hub  5  is pressed onto the support structure  11   b  all the way to the stop  14  of the inner circumferential wall  5   c , whereby the inner circumferential wall  5   c  snaps onto the flange ring  11   c  of the support structure  11   b . As a result, the axial position of the flow rectifier  20  is fixed. The stop  14  has a labyrinth-like configuration, as a result of which the leakage flow in the connection area is reduced. The stop  14  is only interrupted in the area of the latching hooks  12  for production-related reasons. 
     A gap  13  is formed in the circumferential direction between the diffuser  3  and the at least one vane  4 . 
     The embodiments presented here are merely examples of the present invention and thus must not be construed in a limiting fashion. Alternative embodiments taken into consideration by the person skilled in the art are equally encompassed by the scope of protection of the present information. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  wall ring 
           2  impeller 
           2   a  axis of rotation of the impeller, center axis 
           3  diffuser 
           4  vane 
           4   a  guide 
           4   b  slit 
           5  hub 
           5   a  hub cup 
           5   b  hub bottom 
           5   c  inner circumferential wall 
           5   d  outer circumferential wall 
           5   e  guide 
           6  opening 
           7  rotor 
           8  stator 
           9  latching hook 
           10  connection element 
           11   a  ring 
           11   a   1  circumferential ring 
           11   b  support structure 
           11   c  flange ring 
           12  latching hook 
           13  gap 
           14  stop 
           20  flow rectifier