Abstract:
A venturi-type fan is composed of a wire basket between front and rear flares. The wire basket has a rear portion to which the motor and fan blade assembly is mounted. The rear flare controls the admission of air into the fan to reduce turbulence and allows the flow of air to be accelerated and directed forward in a slowly diffusing column. The openness of the sides of the present fan reduces the noise generally associated with close-sided venturi fans without degrading air movement characteristics

Description:
CROSS REFERENCE TO RELATED PATENTS  
       [0001]     The present application claims priority to U.S. Provisional Application Ser. No. 60/630,113, filed Nov. 22, 2004, incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to fans generally, and to fans used in industrial and commercial settings in particular.  
         [0003]     The purpose of a fan is move air in order to ventilate and cool an area. In industrial and commercial environments, where air conditioning may be impractical, fans are vital to employees&#39; health and comfort.  
         [0004]     There are several types of fans used in commercial and industrial environments. One type includes a fan blade enclosed within a wire frame housing or “cage”, sometimes mounted on a pedestal. The shaft of a motor outside the housing may project into the housing to turn the blades. These fans work fine in smaller quarters. Increasing the speed of the motor and the pitch of the blade allows this type of fan to throw more air, but increases noise. Another type of fan is a venturi fan that has a metal, venturi-shaped housing with a motor and a set of blades mounted therein. The set of blades is rotated by the motor and thus accelerates air through the housing. These fans move a large volume of air and project it over large distances, which fact is especially important in large industrial buildings such as distribution centers, but they are relatively noisy.  
         [0005]     Thus there remains a need for improvements in fans, particularly high volume industrial and commercial fans such as venturi fans.  
       SUMMARY OF THE INVENTION  
       [0006]     According to its major aspects and briefly recited, the present invention is a venturi fan capable of producing a significant, directed flow of air but with significantly reduced noise compared to prior art venturi fans. The present fan has a body comprised of a generally cylindrical wire basket for carrying a motor and fan blade assembly, and a flared intake carried at the rear of the wire basket. Preferably, the front of the basket carries an exit channel, which may also have a flare but is otherwise preferably substantially cylindrical in shape. The rear-flared intake allows for a smooth feed of air into the basket and past the motor and the air-accelerating fan blade assembly. The wire basket, in a preferred embodiment, acts as a conduit for the flow-path air but also admits additional air into the flow path and channels the flow of air produced by the fan while allowing fan noise to dissipate through the sides. The basket also avoids generation of some fan noise and is a safety feature, preventing injury in its role as both the side and rear finger guard.  
         [0007]     An important feature of the present invention is the relatively open sides of the present fan, compared to prior art venturi fans. The relatively open sides contribute significantly and in a number of ways to noise reduction, chiefly by allowing noise to escape, while not significantly degrading the flow of air. Indeed, the openness of the sides increases the amount of air available to the fan.  
         [0008]     Additionally, the combination of the rear flare intake and the wire basket is a significant feature of the present invention. This combination allows the flow of air generated by the fan blade assembly to be created and directed significant distances with little diffusion.  
         [0009]     The use of the wire basket to support the motor and fan blade assembly is yet another important feature of the present invention. This arrangement reduces material, weight and obstructions to air flow while providing a sufficiently sturdy securement for the motor and fan blade assembly.  
         [0010]     These and other features and their advantages will be apparent to those skilled in the art of fan design from a careful reading of the Detailed Description of Preferred Embodiments accompanied by the following drawings. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0011]     In the drawings,  
         [0012]      FIG. 1  is a perspective view of a fan, according to a preferred embodiment of the present invention;  
         [0013]      FIG. 2  is a side view of the fan of  FIG. 1 , according to a preferred embodiment of the present invention;  
         [0014]      FIG. 3  is a front view of the fan of  FIG. 1 ;  
         [0015]      FIG. 4  is a rear view of the Fan of  FIG. 1 ;  
         [0016]      FIG. 5  is a perspective view of the Fan of  FIG. 1  with the front finger guard and fan blade assembly removed to show the mounting of the motor; and  
         [0017]      FIG. 6  is a detailed view of the interior of the fan of  FIG. 2  showing the manner in which the motor is mounted, according to a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     The present invention is an improvement in venturi-style fans. Venturi fans direct a significant quantity of air in a forward direction and are suitable for large buildings such as warehouses. Unfortunately, prior art venturi fans are relatively noisy.  
         [0019]      FIG. 1  illustrates in perspective the present venturi fan  10 . Fan  10  has a housing  12  that is flared on both the front  14  and the rear  16 , and has a front finger guard  18 . Inside housing  12  is a motor  22  and a fan blade assembly  24 .  
         [0020]     Referring now to  FIG. 2 , there is illustrated a side view of venturi fan  10  according to a preferred embodiment of the present invention. Fan  10  is rotationally symmetric so it appears the same from all sides. Unlike prior art venturi fans, venturi fan  10 , shown in  FIGS. 1-6  in its preferred embodiment, has an opening formed in the side wall  28 , preferably a multiplicity of openings such as perforations or an array of slots, but, most preferably, a multiplicity of openings formed by spacing wires  34 , either by constructing a cage or basket  32 , as shown. Basket  32  is illustrated as made from circular wires  34  secured at the desired intervals with cross supports  36 , also made of wire, or, alternatively, by forming a single helical wire secured with cross supports to maintain the desired spacing of each turn of the helical wire. Spacing between adjacent wires is in part dictated by safety requirements imposed by authorities, by the requisite strength required for fan  10 , by the function of fan  10  to serve as an airflow conduit but otherwise fan  10  is preferably open on side  26  to the greatest extent possible.  
         [0021]     Safety requirements relate to the size of the openings between wires  34  that, when properly set, the likelihood that someone will inadvertently stick fingers into the interior of basket  32  in the vicinity of fan blade assembly  40  is minimized. Consequently, the spacing will take into account the age of those likely to come into contact with fan  10  and the proximity of fan blade assembly  24  to basket  32 . Thus, the spacing will be wider if wires  34  are farther from fan blade assembly  24  and narrower closer to fan blade assembly  24 , and can include both spacings in the same basket  32 , as best seen in  FIG. 2 .  
         [0022]     Basket  32  must also be rigid enough to support fan blade assembly  24 , a motor  22  and a rear flare  16 . Rear flare  16  is the solid portion of housing  12 . The term “flare” simply means that the cross sectional area taken at right angles with respect to the direction of air flow increases toward the end of housing  12 , as in the flare of a trumpet. Optionally, front flare  14  is added to fan  10  to give the present fan  10  a symmetric, finished look. Front flare  14  includes an optional front finger guard  18 , best seen in  FIG. 3 . Basket  32  is made to be basket-shaped so that it&#39;s rear portion  50  contiguous with side wall  28  and best seen in  FIG. 5 , acts as a finger guard for the rear of fan  10 .  
         [0023]     Rear flare  16  helps to control the flow of air into fan  10  is because it minimizes turbulence and increases laminar flow. Rear flare  16  is significant from an airflow standpoint; front flare  14  is much less so and is essentially an optional feature of the invention, provided essentially for appearances.  
         [0024]     In addition to acting as a rear finger guard, rear portion  50  provides a surface on which motor  22  can be mounted. Rear portion  50  has a central opening through which motor  22  is partially inserted. Brackets  54 , that run along the side of basket  32  across rear portion  50  and thence into the interior of basket  32  where they form loops  58  and then return, are used to support motor  22 . Threaded posts  60  on the front of motor  22  extend through loops  58 . Nuts  62  are then threaded to posts  60  to secure motor  22  to brackets  54 .  
         [0025]     Motor  42  has a central shaft  68  to which fan blade assembly  40  is attached. Blade assembly may have three or more paddle blades  70 .  
         [0026]     The present fan  10  is much quieter than prior art venturi fans. While not wishing to be bound by theory, it is believed that this result has been achieved by a number of different factors working in combination. First, although fan  10  controls and directs airflow in much the same way as a prior art venturi fan, sound now can disperse over a greater angle because side wall  28  of fan  10  is open and is not channeled with the airflow. Second, in the prior art venturi fan, the tips of its blade assembly normally pass closer to the housing than in the present fan  10  and the turbulence that arises sets up vibrations in the solid housing. Those vibrations are reflected throughout the housing and may resonate. Turbulence is reduced in the present fan  10 . Indeed, the tips of fan blade assembly  24  are farther from wires  34  at least for safety reasons alone, and are no longer as starved for air, as air is admitted freely through side wall  28  between wires  34 . Furthermore, vibrations created by the movement of fan blade assembly  24  in the vicinity of wires  34  are weaker and less easily reflected by wires  34 . The prior art side wall mounted bracket has been removed in favor of mounting motor  22  directly onto rear portion  50 , thus eliminating a structure on the interior of the fan that causes additional turbulence and noise. It is believed that these changes result in less noise and “whiter” noise, that is, noise spread more evenly over the audible frequency spectrum.  
         [0027]     The shapes of the front and rear flares  14 ,  16  may be the same and may be symmetrical with respect to each other, but may alternatively be different if desired for packaging efficiency. For example, rear flare  16  may have a smaller diameter where it fits onto basket  32  than front flare  14  in order that basket  32  may have a slightly frustoconical shape, as shown best in  FIG. 2 , so that it nests better with other baskets  32  in shipping or storing.  
         [0028]     Many modifications and substitutions will be apparent to those skilled in the art of fan manufacture from the foregoing description of the preferred embodiments without departing from the spirit or scope of the present invention. It is intended that the scope of the present invention include all modifications that incorporate its principal design features, and that the scope and limitations of the present invention are to be determined by the appended claims.