Abstract:
In order to provide a ventilator hub ( 1 ) having means ( 2, 3 ) for connecting to a ventilator spindle and an essentially cylindrical fastening section ( 4 ) having radial adapters ( 6 ) for a number of ventilator blades, whereby the fastening section ( 4 ) has an inner casing surface ( 5 ) that ensures fastening of the ventilator blades with sufficient tensile strength, even at high temperatures, such as they can occur in tunnel fires, without thereby having an undesirably high mass, it is proposed to provide the ventilator hub with an essentially annular, closed reinforcement element ( 7 ) having means ( 10 ) for fastening the ventilator blades with high tensile strength, that is designed essentially separate from the fastening section ( 4 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the National Phase Application under 35 USC §371 of International Application No. PCT/EP2010/002222, filed Apr. 9, 2010, which claims priority to German Patent Application 10 2009 017 307.2, filed Apr. 11, 2009. 
     
    
     BACKGROUND 
       [0002]    A. Technical Field 
         [0003]    The present invention relates to a ventilator hub, with means for connecting a ventilator spindle and a substantially cylindrical fastening section with radial adapters for a number of ventilator blades, whereby the fastening section has an inner casing surface. 
         [0004]    The invention likewise relates to a reinforcement element for use with a ventilator hub having means for fastening a number of ventilator blades with high tensile strength. 
         [0005]    Finally, the invention relates to a method for the production of a ventilator with a ventilator hub according to one of claims  7  to  11 . 
         [0006]    B. Background of the Invention 
         [0007]    Ventilators for underground railways or tunnels and/or closed vehicle buildings such as, for example, underground garages, must work very reliably for very long useful lives at various load conditions and environmental conditions. The installation of ventilators in underground railroads or tunnels or underground garages is typically configured for an operating life of several years or decades. In particular, when ventilators are used as smoke removing ventilators in subways or tunnels by metro or tunnel operators, demands are made on the operability of the ventilator at high temperatures, as they occur, in particular, in cases of fire. Some of the demands are specified by law. 
         [0008]    On the other hand, as is generally customary, there is a desire to produce ventilators as cost-effective and material-saving as possible. In general, the basic structure of a ventilator consists of a ventilator hub, to which a number of ventilator blades are attached radially. The ventilator blades are fastened by using fastening means such as, for example, pins. 
         [0009]    Given the background of the general demands made on ventilators described above, various ventilator blades are known. To keep the mass low, ventilator hubs are known that consist of solid aluminum or an aluminum alloy. However, their limited usability at temperatures above 300° C., makes ventilator hubs made of aluminum disadvantageous. Because the tensile strength of aluminum decreases substantially at the cited temperatures, so that the aluminum slowly begins to flow. Even specialized aluminum alloys are not able to significantly improve this shortcoming. As a consequence of this disadvantageous property of aluminum, ventilator blades can detach from a ventilator hub made of aluminum at high temperatures such can as they occur, for example, in fires. 
         [0010]    Because of this shortcoming of ventilator hubs made of aluminum, high volume smoke removing ventilators, i.e. at high speed and/or with large blade lengths of related art use ventilator hubs made of solid steel. But, ventilator hubs made of steel have the disadvantage of having a very large mass. 
       SUMMARY OF THE INVENTION 
       [0011]    It is therefore the objective of the present invention to provide a ventilator hub of the type cited at the beginning that ensures a fastening of ventilator blades with sufficient tensile strength even at high temperatures such as they can occur in the case of tunnel fires, without thereby having an undesirably large mass. 
         [0012]    The invention is likewise based on the objective to provide a reinforcement element for use with a ventilator hub of the type cited at the beginning, with the help of which the disadvantages of prior art that were mentioned can be avoided. 
         [0013]    Finally, the present invention is based on the objective to provide a method for producing a ventilator with a ventilator hub according to one of claims  7  to  11 . 
         [0014]    According to the invention, this type of problem of the ventilator hub described at the beginning is solved thereby, that a substantially annular, closed reinforcement element with means for fastening the ventilator blades with high tensile strength is provided that is essentially separate from the fastening section. Thus, it is provided within the scope of the invention, to add a reinforcement element to the ventilator hub in the form of an additional component. 
         [0015]    Thereby that according to the invention, the reinforcement element is substantially annular, the reinforcement element can absorb radial forces and keep them completely away from the axial fan wheel hub that is made of aluminum, for example. In the case of balanced ventilators, the reinforcement element does not exert any force on the ventilator hub. 
         [0016]    The tensile strength of the unit that is subject to heat, which consists of ventilator hub and reinforcement element, is thereby determined exclusively by the material of the reinforcement element. In this way, an optimized work material can be selected advantageously for the purpose of fastening the ventilator blades at the ventilator with high tensile strength. At the same time, and independent of that, an optimized material can be selected for the actual ventilator hub. In particular, the reinforcement element can be advantageously selected from a material with high tensile strength when subjected to heat and good long-time behavior at high temperatures. According to the invention, at the same time, an especially light material can be selected for the ventilator hub, without thereby influencing the tensile strength of the ventilator overall when it is subjected to heat. 
         [0017]    In [an] advantageous design of the invention it is provided that the reinforcement element has at least two segments that can be welded together. The production of a ventilator hub, which is provided with the reinforcement element according to the invention, is particularly simple based on this technique. In particular, it is possible to retrofit an axial fan wheel hub of the conventional type with a reinforcement element according to the invention, in order to improve the tensile strength when subjected to heat. 
         [0018]    In [a] further advantageous design of the invention it is provided that the number of segments corresponds to half of the number of ventilator blades that are to be attached. For example, in the case of a four-blade fan wheel, i.e. a fan wheel with a total of four ventilator blades, two segments can be provided. In a six-blade fan wheel, three segments can be provided. In an eight-blade fan wheel, four segments can be provided correspondingly. 
         [0019]    The fastening of the reinforcement element according to the invention at a ventilator hub is improved even further if in the design of the invention, the reinforcement element has an at least substantially flat section, the surface normal of which—when used as intended—can be oriented in the radial direction of a ventilator hub. 
         [0020]    In [the] preferred design of the reinforcement element according to the invention, the number of the flat sections corresponds to twice the number of the ventilator blades that are to be attached. Thus, according to this design of the invention, in a four-blade fan wheel, eight flat sections are present. Because of the symmetry that is to be generally demanded of rotating structures, a cross section surface of the substantially annular reinforcement element results, that corresponds to an n-corner. In corresponding manner, a six-blade fan wheel would have twelve flat sections, an eight-blade fan wheel sixteen flat sections, and a twelve-blade fan wheel would have twenty four flat sections. 
         [0021]    In another advantageous design of the reinforcement element according to the invention, it is essentially made of steel. The tensile strength when subjected to heat and the long-time behavior of steel are excellent, even at temperatures above, for example, 300° C. In particular, the tensile strength when subjected to heat is substantially better at the cited temperatures than that of aluminum. 
         [0022]    The problem on which the invention is based is likewise solved by a ventilator hub with means for connection with a ventilator spindle and/or a hub core and an essentially cylindrical fastening section with radial adapters for a number of ventilator blades, whereby the fastening section has an inner casing surface, which is provided with an essentially annular, closed reinforcement element with means for fastening the ventilator blades with high tensile strength that is designed substantially separate from the fastening section. The substantially annular fastening section can advantageously be made of a material with more tensile strength than the ventilator hub otherwise. The fastening section can, for example, have the form of a bent steel brace. In the simplest case, the means for fastening the ventilator blades with tensile strength can be bores with or without a thread. 
         [0023]    The ventilator hub according to the invention is improved further when the reinforcement element is located essentially along the inner casing surface of the fastening section. The interior space of the ventilator hub is, as a rule, free of structural parts. Therefore, the reinforcement element according to the invention can be advantageously retrofitted approximately in the form of a bent steel brace, without requiring design adaptations of the fan wheel hub. Moreover, in the event of imbalances of the ventilator, the cylindrical fastening section of the hub can additionally absorb radial forces, if necessary, in order to retain the reinforcement element in position. 
         [0024]    A particularly firm retention that is also suitable for absorbing axial forces between the reinforcement element and the ventilator hub results in the refinement of the ventilator hub according to the invention, if the inner casing surface—in a section around a least one radial adapter—has an essentially flat section, the surface normal of which is essentially oriented in the radial direction of the ventilator hub. The flat sections can, for example, be produced by milling. 
         [0025]    It is especially favorable, if within the scope of the invention, the ventilator hub is essentially made of aluminum. Aluminum is the preferred material for an axial fan wheel hub, because of weight. According to the invention, a ventilator hub made of aluminum can, in spite of the unfavorable properties of aluminum with respect to tensile strength when subjected to heat, have, in connection with a reinforcement element according to the invention, the required tensile strength when subjected to heat. Because the reinforcement element can, within the scope of the invention, simultaneously be made of steel. 
         [0026]    In particular, in [an] advantageous embodiment of the ventilator hub according to the invention, the reinforcement element is designed according to one of claims  1  to  6 . 
         [0027]    The objective of the method on which the present invention is based is solved by a method for producing a ventilator with a ventilator hub according to one of claims  7  to  11 , in which 
         [0000]    a. first, each segment of the reinforcement element of the inner casing surface of the fastening section of the ventilator hub is brought closer in such a way that the means for fastening with high tensile strength with the radial adapters of the cylindrical fastening section, are aligned in radial and axial direction;
 
b. subsequently, threaded bolts of the ventilator blades that are to be fastened are inserted into the radial adapter of the cylindrical fastening section and into the means for fastening with high tensile strength;
 
c. subsequently, each segment of the reinforcement element is screwed together with the cylindrical fastening section of the ventilator hub by using the threaded pin of the ventilator blade that is to be fastened respectively;
 
d. finally, the segments of the reinforcement element that are screwed together with the cylindrical fastening section of the ventilator hub are welded together to form a continuous, substantially annular, closed reinforcement element.
 
         [0028]    The method according to the invention makes subsequent retrofitting of conventional axial fan wheel hubs made of aluminum, or other hubs for ventilators with a reinforcement element according to the invention possible. As the result of the annular form of the steel element being created only upon welding the individual segments of the reinforcement element after fastening the individual segments to the hub—under certain circumstances—a problematic adaptation of a one-part reinforcement element is avoided, during which, for example, a ventilator hub made of aluminum, could perhaps be damaged by scratches. Moreover, by using the production process according to the invention, an optimal contact of the reinforcements that consists of individual segments with the inner casing surface of the ventilator hub element is achievable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The invention is described by way of an example in a preferred embodiment by referring to a drawing, whereby additional advantageous details can be learned from the figures in the drawing. 
           [0030]    Functionally equal parts are labeled with the same reference number. 
           [0031]    In detail, the figures of the drawing show: 
           [0032]      FIG. 1  illustrates an axial fan wheel hub made of aluminum as component of an embodiment of the invention. 
           [0033]      FIGS. 2(   a ) and  2 ( b ) illustrate a radial cross section through a steel reinforcement brace according to various embodiments in the invention, and a radial cross section through the axial fan wheel hub according to  FIG. 1 , to which the reinforcement brace according to the invention according to part (a) can be added, whereby the cross section extends along line II-II in  FIG. 1 ; 
           [0034]      FIG. 3  illustrates an axial top view onto various designs of the reinforcement element according to the invention as per  FIG. 2(   a ) in schematic illustration. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]      FIG. 1  shows an axial fan wheel hub  1  in perspective view. Axial fan wheel hub  1  essentially corresponds to a hub according to prior art. It has a central bore  2  for connecting—if necessary by using a hub core that is not shown—with a ventilator spindle that is not shown. Around central bore  2 , fastening bores  3  are situated on a circular line for establishing a flange connection with the hub core—not shown—for fastening with a ventilator spindle that is not shown. 
         [0036]    Beyond that, axial fan wheel hub  1  has a cylindrical fastening section  4 . Fastening section  4  has an inner casing surface  5 . In cylindrical fastening section  4 , radial adapter bores  6  are present at equal angular distance. In the schematic illustration according to  FIG. 1 , not all adapter bores  6  that are actually required for load-free operation of a ventilator are shown. 
         [0037]    Adapter bores  6  serve to accommodate ventilator blades that are not shown with the aid of blade pins that are attached to the ends of the ventilator blades. In prior art, fastening of the ventilator blades is accomplished by inserting the blade pins into the radial adapter bores  6  in cylindrical fastening section  4  of axial fan wheel hub  1 , and subsequently screwing together the ventilator pin having a thread with the aid of a screw nut located at inner casing surface  5 . A tapered casing section  11  is attached to cylindrical fastening section  4  having radial adapter bores  6 . To the extent axial fan wheel hub  1  is made of aluminum, this arrangement has, however, insufficient tensile strength at temperatures as they can occur in tunnel fires, i.e. at 300° C. to 400° C. 
         [0038]    With the help of  FIG. 2  it is illustrated how, within the scope of the invention, the problem of insufficient tensile strength when an axial fan wheel hub  1  made of aluminum is subjected to heat, is solved. Part (a) of  FIG. 2  shows a reinforcement brace  7  according to the invention in a radial cross section corresponding to cross sectional direction II-II from  FIG. 1 . 
         [0039]    At bending lines  8 , the reinforcement brace  7  is bent respectively at the same angle a (compare  FIG. 3 ). In the perspective view according to  FIG. 2(   a ), the curve is to be understood as extending from the plane of projection. Between bending lines  8 , reinforcement brace  7  respectively extends in the form of a flat, unbent section  9 . Unbent sections  9  have, according to this embodiment, respectively the same length and width. Each third flat section  9  has a bore  10 . According to a different embodiment of the invention, which is described in the following with the help of  FIG. 3(   a ′), longer sections  9  are located respectively adjacent to shorter sections  9 ′. 
         [0040]    Furthermore, it can also be seen in Figure (a) that reinforcement brace  7  consists of segments  7   a,    7   b.  Segments  7   a,    7   b  are connected with each other along welding seam  12 . Welding seam  12  is simultaneously a bending line within the meaning of bending lines  8 . 
         [0041]    In the same cross section perspective as that of part (a) of  FIG. 2 ,  FIG. 2(   b ) shows an axial fan wheel hub  1 , which is essentially constructed like axial fan wheel hub  1  that is shown in perspective in  FIG. 1 . In  FIG. 2(   b ), however, the specific design of the inner casing surface  5  can also be seen. In inner casing surface  5 , flat surfaces  13  are located aligned in axial direction to each other. Flat surfaces  13  have approximately the same dimensions in a direction that is perpendicular to the axial direction, as the flat sections  9  of reinforcement brace  7 . 
         [0042]    Various designs of reinforcement brace  7  are shown in an axial lateral view in  FIG. 3 . Thereby,  FIG. 3(   a ) shows a reinforcement brace  7  for use in an axial fan wheel hub  1  for a four-blade fan wheel, i.e. a fan wheel with a total of four ventilator blades. Reinforcement brace  7  is constructed from two segments  7   a,    7   b.  Segments  7   a,    7   b  are connected or can be connected along welding seams  12 . 
         [0043]      FIG. 3  ( a ′) shows an alternative embodiment of the reinforcement brace according to the invention as per  FIG. 3(   a ). Congruent with the reinforcement brace according to  FIG. 3(   a ), the reinforcement brace shown in  FIG. 3(   a ′) is provided for use in an axial fan wheel hub  1  for a fan wheel with a total of four ventilator blades. Differing from the embodiment according to  FIG. 3(   a ), unbent sections  9  have, however, pair wise different lengths in radial direction. As can be seen in  FIG. 3(   a ′), adjacent, unbent sections  9  or  9 ′ have different length in radial direction. However, radially diametrically opposed sections  9 ,  9 ′ respectively have the same radial lengths. In this design, the longer sections  9  do not touch the ventilator hub. 
         [0044]    In  FIG. 3(   b ), an embodiment of reinforcement brace  7  according to the invention is shown for a six-blade fan wheel. Reinforcement brace  7  according to  FIG. 3(   b ) consists of three segments, which are or which can be connected with each other at welding seams  12 . 
         [0045]      FIG. 3(   c ) shows an embodiment of reinforcement brace  7  according to the invention for an eight-blade fan wheel, which consists of four segments  7   a,    7   b,    7   c,    7   d.  Finally,  FIG. 3   d ) shows an embodiment of reinforcement brace  7  according to the invention that is suitable for a twelve-blade fan wheel, and is likewise constructed from four segments. The structure of the embodiment according to  FIG. 3(   c ) and ( d ) otherwise corresponds to the embodiments according to Figures (a) and (b). 
         [0046]    In order to provide an axial fan wheel hub according to  FIG. 1  or  FIG. 2(   b ) with a reinforcement brace  7  according to the invention, first each segment  7   a,    7   b,  . . . , is screwed in at the inner casing surface  5  of axial fan wheel hub  1 . To do so, the blade pin of the ventilator blades that are to be fastened is inserted through the radial adapter bore  6  into cylindrical fastening section  4  of radial fan wheel hub  1 , and subsequently inserted through aperture  10  that has been aligned with adapter bore  6 , into reinforcement brace  7 . Thereby, the flat sections  9  of reinforcement brace  7  engage with the cutouts  13  in inner casing surface  5  of fastening section  4  of hub  1 . 
         [0047]    The unit consisting of the segment of reinforcement brace  7  and axial fan wheel hub  1  is then screwed together with the help of a counter nut in the customary way. After each of the segments  7   a,    7   b,  . . . of reinforcement brace  7  has been screwed into inner casing surface  5  of cylindrical fastening section  4  of axial fan wheel hub  1  in the way described, the individual segments  7   a,    7   b  of reinforcement brace  7  are welded together along welding seams  12  in the interior of axial fan wheel hub  1 . 
         [0048]    In this way, an axial fan wheel hub  1  according to the invention is obtained, which is for one light in weight, and for another, even at higher temperatures, such as they can occur perhaps in fires in underground railways or tunnels, has sufficient tensile strength. According to the invention, this is achieved by making the reinforcement brace, in particular, out of a construction steel such as, for example, S235JR, and axial hub  1  out of aluminum or an aluminum alloy.