Patent Publication Number: US-6213718-B1

Title: Air circulation fan with removable shroud

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally directed to a fan. Particularly, the present invention is directed to an air circulation fan having a shroud for enhancing fan performance. 
     2. Description of the Related Art 
     Electric fans for circulating air are widely used in commercial and industrial environments. For example, air circulation fans are commonly located at each work station in factories, such as automobile plants. In the past, operation of air circulation fans has generated a considerable amount of noise. The primary source of noise during the operation of such fans is the interaction of the tip region of each blade with moving air generated by operation of the fan. Reduction in noise levels caused by the operation of an air circulation fan is therefore desired, particularly in those environments in which a large number of such fans are utilized. 
     Air circulation fans have previously not been used in agricultural settings for a variety of reasons. Most notably, in agricultural settings, such as poultry barns, it is desirable to use fans which can disperse unclean air at high flow rates. Conventional air circulation fans, which utilize traditional front and rear fan guard members in the form of a grille, do not produce these desired results, and have thus been unsatisfactory for use in a poultry barn. Accordingly, box-type fans, which have a closed structure and a venturi surrounding the periphery of the fan propeller, have been widely used in agricultural settings. Box-type fans operating under adverse static pressures can produce a flow of air having a cfm valve. A distinct disadvantage, however, is that the inlet flow field pattern is purely axial which results in stagnant flow regions in areas upstream and adjacent to the fan itself. The need exists for a fan which enhances air circulation without significantly increasing the cost of the fan and noise levels as well as the complexity of its manufacture. Additionally, the need exists for an air circulator fan which is useful in an agricultural setting, such as a poultry barn. The present invention meets these needs while overcoming the drawbacks of the prior art. 
     SUMMARY OF THE INVENTION 
     An air circulation fan has front and rear fan guard members. Each front and rear fan guard member has a plurality of spaced apart ribs extending radially outward from a generally central location. A conventional grill is secured over the ribs to form a concave dish-shaped member. An outer peripheral rim is secured along the outer periphery of each guard member to an outer end portion of each radially extending rib. 
     Each fan guard member preferably defines a central opening. The central opening in the front fan guard member accepts a name plate, while the central opening in the rear fan guard member is preferably slightly larger than the opening in the front fan guard member, and receives a portion of an electrical motor. The motor is secured by fasteners to the rear fan guard member, and any conventional propeller or blade arrangement is attached to the electrical motor. 
     A plurality of selected ribs of the ribs on the front fan guard member are each bent at an outer end to form a hook. Each hook overlaps and partially surrounds the outer peripheral rim of the rear fan guard member, thereby securing two fan guard members together. When the front fan guard member is secured to the rear fan guard member, the radially extending ribs of the respective guard members are offset from each other, to prevent the radially extending ribs of the rear fan guard member from interfering with the hook portions. It will be understood that hook members could, alternatively, or additionally, be formed on outer ends of selected ribs on the rear fan guard member. 
     In accordance with the principles of the invention, a removable shroud is positioned about an outer peripheral portion of the front fan guard member. The shroud forms an annular ring having a central, air discharge opening. 
     In one embodiment, the removable shroud is formed of an integral piece of stretchable material, such as an elastomeric material. In such an embodiment, the removable shroud forms an elastomeric band which releasably engages about an outer peripheral portion of the front fan guard member. Particularly, the shroud is stretched, and thus expands, to place it into engagement with the front fan guard member. The stretchable shroud thus securely adapts to the contour of the outer peripheral portion of the front fan guard member. 
     In an alternate embodiment, the removable shroud is formed of a plurality of identical shroud portions. Each shroud portion has at least one clip for clipping to the front fan guard member. In each embodiment, the central opening of the shroud preferably has a diameter which is slightly less than the diameter of an imaginary circle caused by a line of rotary movement of the outer tips of the blades of the propeller. 
     In operation of the fan, with the removable shroud secured to the outer peripheral portion of the front fan guard member, the noise generated by the fan is greatly reduced when compared to operation of the fan with the shroud removed. Additionally, inclusion of the shroud on the fan allows the air circulator to operate under a static pressure differential. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects and features of the invention noted above are explained in more detail with reference to the drawings, in which like reference numerals denote like elements, and in which: 
     FIG. 1 is a front view of an air circulation fan having a removable shroud in accordance with a first embodiment of the present invention; 
     FIG. 2 is a right side view of the air circulation fan having a removable shroud in accordance with the first embodiment of the present invention; 
     FIG. 3 is an enlarged cross-sectional view illustrating the air circulation fan having a removable shroud in accordance with the first embodiment of the invention; 
     FIG. 4 is a fragmentary view taken along line  4 — 4  of FIG. 3; 
     FIG. 5 is an enlarged, fragmentary, cross-sectional view illustrating an air circulation fan having a removable shroud in accordance with a second embodiment of the present invention; 
     FIG. 6 is an enlarged, fragmentary, cross-sectional view illustrating an alternate shape of the invention; 
     FIG. 7 is a front view of the air circulation fan having a different blade assembly; and 
     FIG. 8 is a partial side view of the fan illustrated in FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIGS. 1 and 2, an air circulation fan of the present invention is denoted generally by reference numeral  10 . As shown, air circulation fan  10  has a front fan guard member  12  and a rear fan guard member  14 , each of which is preferably formed of metal. Each fan guard member  12 ,  14 , forms a concave disc and has a plurality of respective ribs  16 ,  18 . As illustrated, the guard is oversized, but could be any conventional size. Ribs  16 ,  18  extend radially outward from a generally central location, to an outer periphery of the respective guard members  12 ,  14 . Each guard member  12 ,  14  has a grill, or screen, as denoted generally by the reference numeral  20 ,  22 . The grills  20 ,  22  are preferably formed by spiraling a wire rod member in the manner illustrated, although the grills  20 ,  22  could be formed in other conventional manners, such as with concentric rings. The formation of grills  20 ,  22  will be readily understood by those with skill in the art. Grills  20 ,  22  are secured to respective ribs  16 ,  18  in any conventional manner, such as by welding. Each guard member  12 ,  14  has an outer peripheral rim  24 ,  26  secured to outer portions of associated ribs  16 ,  18 . 
     Front fan guard member  12  defines a central opening. Particularly, front fan guard member  12  defines a central opening adapted to receive a cover, or insert  28 , such as a conventional name or logo-bearing plate. Rear guard member  14  has a central aperture (not shown) for receiving an output portion  30  of an electric motor having a rotary output. The motor is preferably a one-half horsepower motor, and has a housing  31 . Rear guard member  14  is secured to motor housing  31  by fasteners in any conventional manner. 
     A propeller, denoted generally by reference numeral  34 , is secured to the output portion  30  of the motor and particularly a shaft  33  thereof, in any conventional fashion. Propeller  34  includes a conventional central hub  36  having a plurality of outwardly extending wings  38  and fan blades  40 . The fan blades  40  are connected by fasteners, such as rivets  42 , to respective wings  38 . The described structure and arrangement of conventional fan guards, fan motors, and propellers will be readily appreciated by those with skill in the art, as will the attachment of the rear guard member  14  to the fan motor. 
     In the embodiment of the present invention illustrated in FIGS. 1-2, fan blades  40  are generally rectangular in shape, and are preferably of a type manufactured by Revcor, Inc., and known as a G-Series blade. Such blades are commonly used on air circulation fans. 
     With particular reference to FIGS. 2 and 3, each of a plurality of selected ribs  16   a  of front ribs  16  is bent at an outer end to form a hook, as designated by hooks  44 . As illustrated, hooks  44  overlap and partially surround outer peripheral rim  26  of rear guard member  14 . Hooks  44  serve to releasably secure front guard member  12  to rear guard member  14 . As illustrated by FIG. 3, the position of ribs  16  on front guard member  12 , and particularly those selected ribs  16   a  having a hook  44  at an outer end thereof, are offset from (e.g., not in alignment with) the ribs  18  of rear fan guard member  14 . As will be readily appreciated, the offset arrangement of the ribs  16 ,  18  prevents ribs  18  on rear guard member  14  from interfering with hooks  44  on front guard member  12 . It will be appreciated that hooks  44  could alternatively, or additionally, be located on rear guard member  14  for engaging with front guard member  12 . In any such embodiment, hooks  44  at the periphery of the fan guard  10  permit guard members  12 ,  14  to be secured together. 
     Referring to FIGS. 1-4, and in accordance with a first embodiment of the present invention, air circulation fan  10  has a removable shroud  50  engaged about an outer peripheral portion of front fan guard member  12 . In the embodiment illustrated in FIGS. 1-4, removable shroud  50  is formed of four separate, and identically formed shroud portions  50   a ,  50   b ,  50   c , and  50   d . Each removable shroud portion  50   a-   50   d  is preferably formed of rigid, or semi-rigid (e.g., partially flexible) plastic. It will be understood and appreciated that shroud  50  could be formed of a single piece of plastic material, or could be made from two halves, three thirds, etc. The removable shroud  50  forms an annular ring having a central, air discharge opening. As illustrated in FIGS. 1 and 3, the diameter of the central, air discharge opening, defined by the inner most edge  52  of removable shroud  50 , is slightly less than the diameter of an imaginary circle defined by the outermost tips of blades  40  when rotating. 
     Each shroud portion  50   a-   50   d  has a front face  54  and a rear face  56 . Each shroud portion may include a layer of sound absorbing material, such as foam, applied to rear face  56 . The front face  54  of removable shroud  50  provides a surface for placement of indicia, such as logos and trademarks, instructions, warnings, etc. A plurality of clips  58  are connected to, and extend outwardly from, rear face  56  of each shroud portion  50   a-   50   d . As illustrated in FIGS. 3 and 4, each clip  58  is positioned on rear face  56  of its respective shroud portion  50   a-   50   d  so as to receive one of the ribs  16  on front fan guard  12 . In this way, each shroud portion  50   a-   50   d  is releasably secured to front fan guard member  12 . Particularly, as illustrated in FIG. 4, each clip  58  has a pair of outwardly extending, curved portions  60 ,  62  defining a channel  64  and an internal cavity. As will be appreciated, placement of each removable shroud portion  50   a-   50   d  onto front fan guard member  12  requires clipping of the clips onto ribs  16  by placing the shroud in a position so that the clips engage ribs  16  at a mouth portion thereof. As the shroud is forced onto the front fan guard member, the outwardly extending, curved portions  60 ,  62  bow outwardly to permit the respective rib  16  to pass through the channel  64 . Once the shroud  50  is completely secured to front fan guard member  12 , each rib  16  is snugly received and grasped by the various clips  58 . 
     As illustrated in FIG. 3, the front fan guard member  12  is disc shaped with a flat face portion  66 . Front fan guard member  12  has an outer peripheral portion having a convex portion  68 . In accordance with an aspect of the invention, removable shroud  50  is constructed to closely engage with an outer peripheral portion  51  of the front fan guard member  12 . Accordingly, each shroud portion  50   a-   50   d  itself has a concave portion  70  for overlying the convex portion of the outer peripheral portion of the fan guard member  12 . Similarly, front fan guard member  12  has a generally frustoconical section  72 , and the removable shroud  50  also has a frustoconical section  74  for overlying the frustoconical section  72  of the front fan guard member  12 . The shroud  50  has an outer edge  76  which terminates just beyond the outer peripheral rim  24  of front fan guard member  12 . 
     With reference to FIG. 5, an alternate embodiment of the invention is shown and described. The air circulation fan of the embodiment of the invention illustrated in FIG. 5 has the same components as the air circulation fan of the first embodiment of the invention set forth above, with the exception that the shroud is constructed differently. In the embodiment illustrated in FIG. 5, removable shroud  150  is formed of one integral piece of stretchable material. Particularly, removable shroud  150  is formed from a flexible elastomeric band. For example, removable shroud  150  may be formed of a material that has sound absorbing characteristics, such as foam or rubber, or a combination thereof. 
     Removable shroud  150  as illustrated in FIG. 5 conforms to the configuration of front fan guard member  12 . Removable shroud  150  as illustrated in FIG. 5 is dimensioned so that placement of the shroud  150  on front fan guard member  12  is accomplished by stretching the shroud  150  and releasing it into the position illustrated. The overall dimensions and location of removable shroud  150  illustrated in FIG. 5 are similar to that discussed above with reference to removable shroud  50 . 
     With reference to FIG. 6, an air circulation fan having a shroud, in accordance with the principles of the present invention, is illustrated wherein the fan has a right circular shape. As illustrated, removable shroud  250  corresponds in shape to the front fan guard member  252 , illustrated in FIG.  6 . Particularly, removable shroud  250  has a portion  254  which extends inwardly over the face of the front fan guard member from an outer peripheral corner  256  thereof. Removable shroud  250  further has a side portion  257  extending from the corner  256  to a rear of the front fan guard member. As illustrated, portions  254 ,  257  extend at a right angle with respect to each other. 
     The shroud  250  defines a central air discharge opening and, as in previously described embodiments, the diameter of the air discharge opening is slightly less than the diameter of an imaginary circle defined by the blade tips when propeller  34  is rotating. In the embodiment illustrated, clips  258 , located on shroud  250 , serve to releasably secure shroud  250  to front fan guard member  252 . 
     In use, an air circulation fan of the present invention is positioned at a desired location. As discussed above, conventional air circulator fans are often utilized in overhead fans in industrial manufacturing environments. In many such environments, such as in an automobile plant, hundreds or even thousands of fans are located above individual work stations. In such embodiments, the noise generated by the conventional fans is bothersome. Utilization of the air circulation fan of the present invention, having a removable shroud positioned about an outer peripheral portion of the front fan guard member, significantly reduces noise associated with the fan. In this regard, the tip region of each blade is a primary source of noise in conventional air circulation fans. By incorporating a removable shroud with the fan, the tip region of each blade is prohibited from significantly interacting with the downstream region of the air flow domain produced by the fan, thus reducing the noise generated by the fan. Moreover, tests have shown that the velocity, pressure and throw width of air produced by the fan of the present invention, with the shroud in place, is greater than these characteristics produced by the fan with the shroud removed. 
     With reference now to FIGS. 7 and 8, an alternate embodiment of the present invention is illustrated and described. In the embodiment of FIGS. 7 and 8, the air circulator fan components, including the shroud, are generally the same as those illustrated and described in conjunction with the foregoing embodiments of the invention, with one notable exception. In the embodiments of FIGS. 7 and 8, fan blades  340  are of a type conventionally utilized on box-type poultry fans. These blades are much larger and heavier than the conventional rectangular shaped blades illustrated above in conjunction with FIGS. 1-6. More specifically, each fan blade  340  has a leading edge  342  and a trailing edge  344 . Each fan blade  340  has an outer edge  346 , and an inner edge  348 . Each fan blade  340  is fastened to a corresponding wing  338  of a central hub  336 , as illustrated. Attachment of each blade  340  to its corresponding wing  338  is made utilizing fasteners  343 . 
     Particularly, each blade  340  is preferably of a type such as manufactured by Revcor as part No. 5-02767. Each blade  340  has a cut-away notch portion  350  at an inner, leading edge thereof. Furthermore, each blade  340  has a flared portion  352  at an inner, trailing portion thereof with such blades, the centerline at the inlet region of the fan  10  is not void of a velocity profile. Such blades are particularly useful for stirring air and cooling the fan motor. The presence of a shroud of the present invention permits these blades  340  to be utilized, because the shroud causes the air to sufficiently cool the one-half horsepower motor to permit use of these blades  340 . 
     From the foregoing it will be seen that this invention is one well adapted to attain all ends and objects hereinabove set forth together with the other advantages which are obvious and which are inherent to the structure. 
     It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. 
     Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative, and not in a limiting sense.