Abstract:
Improved fan grill/guard construction for fans for supplying air, where the fan has a front grill with an outer ring which wraps around and is dimensionally structured to improve airflow and to diffuse the air over a wide area.

Description:
This application is a continuation-in-part of U.S. patent application Ser. No. 09/828,673 filed Apr. 9, 2001 now U.S. Pat. No. 6,454,537. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an improved fan grill guard construction of the type where the grill has an outer ring, which is dimensionally structured to provide greater airflow and diffusion. 
     2. Description of the Prior Art 
     The typical grill used on the front of oscillating, pedestal or wall mount fans is of round wire, with some fans such as shown in U.S. Pat. No. 6,071,079 having a front grill of molded plastic. There are many advantages in using molded plastic grills, in that plastic does not rust, is inexpensive to mold and does not require welding or painting. In addition, plastic permits easy design variation to achieve a look that is less restrictive in the center, and allows the customer to see the blades. 
     Plastic grills can also be constructed so they do not require additional parts for assembly, such as rings or clips. 
     While the prior art Pat. No. 6,071,079, uses plastic grills, it is designed to provide a focused air pattern, which is not entirely satisfactory if used in an oscillating fan, as it results in an on-off air flow, which is not as desirable as a diffused air flow, which is obtained by the grill construction described herein. 
     SUMMARY OF THE INVENTION 
     It has now been found that an improved fan grill construction can be obtained for a front grill, which has an outer ring which is dimensionally structured so that the air flow is diffused instead of focused, resulting in an improved total air volume (NEMA CFM) over a larger area. 
     The principal object of the invention is to provide front grill construction for a fan that is dimensionally structured to provide increased air volume over a large area. 
     A further object of the invention is to provide fan grill construction that allows tighter spacing to the fan blade periphery to provide a more efficient package with improved safety. 
     A further object of the invention is to provide fan grill construction which adds mass to the outside of the grill to dampen vibration. 
     A further object of the invention is to provide a front grill which is constructed of molded plastic. 
     A further object of the invention is to provide fan grill construction that can be adapted to a variety of types and sizes of fans. 
     Other objects and advantageous features of the invention will be apparent from the description and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The nature and characteristic features of the invention will be more readily understood from the following description taken in connection with the accompanying drawings forming part hereof in which: 
     FIG. 1 is an exploded perspective view of a prior art fan; 
     FIG. 2 is an exploded perspective view of a fan with the new front grill construction of the invention; 
     FIG. 3 is a horizontal sectional view of the assembled prior art fan of FIG. 1; 
     FIG. 4 is a view similar to FIG. 3, but showing the improved fan grill construction of the invention, and 
     FIG. 5 is a graph comparing the performances of the prior art fan grill construction to the improved fan grill construction of the invention, 
     FIG. 6 is a graph of the air velocity profile of prior art fan grills, 
     FIG. 7 is a graph of the air velocity profile for a fan with a plastic rear grill and an improved plastic front grill, and, 
     FIG. 8 is a graph of the air velocity profile of a fan having a different plastic rear grill and the improved plastic front grill. 
    
    
     It should, of course, be understood that the description and drawings herein are merely illustrative and that various modifications and changes can be made in the structures disclosed without departing from the spirit of the invention. 
     Like numerals refer to like parts throughout the several views. 
     The entire disclosure of U.S. patent application Ser. No. 09/828,673 filed Apr. 9, 2001 is incorporated herein by reference as if set forth in full. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     When referring to the preferred embodiment, certain terminology will be utilized for the sake of clarity. Use of such terminology is intended to encompass not only the described embodiment, but also technical equivalents which operate and function in substantially the same way to bring about the same result. 
     Referring now more particularly to FIGS. 1 and 3 of the drawings, a typical prior art fan  10  is illustrated. The fan  10  includes an electric motor housing  11 , which contains an electric motor (not shown) of well known type, which may be connected to a source of electrical power (not shown). The fan motor has an output shaft  12 , with a hub  14  of a blade assembly  15  attached thereto, with three blades  16  being shown. 
     The fan motor housing  11  may be mounted to a yoke (not shown) which may be mounted to a pedestal (not shown) or other well known support structure, which can rest on the floor, on a table or otherwhere as desired. The housing  11  has a rear grill  17  mounted thereto, which is of circular configuration, with a plurality of spaced radial ribs  18 , connected to a plurality of concentric rings  19 , with the radial ribs  18  extending out to a circumferential rim  20  and inwardly to a center ring  21 . A front grill  25  is provided, which has a plurality of spaced radial ribs  26 , which are connected to a plurality of concentric rings  27 . The ribs  26  extend out to an outer rim  28 , which mates with rim  20  of rear grill  17 . 
     The radial ribs  26  also extend inwardly and are connected to a center plate  29 . 
     Both the front and rear grills  25  and  17  are preferably formed of molded plastic. 
     As shown in FIG. 3, the arrows  30  illustrate the airflow through the rear grill  17 , and out the front grill  25  in a focused pattern, which upon oscillation provides the on-off airflow pattern that is not desirable. 
     Referring now more particularly to FIGS. 2 and 4, the improved front grill constuction is therein illustrated, and as part of a fan  50 . 
     The fan  50  includes an electric motor housing  51 , which contains an electric motor (not shown) of well known type, which may be connected to a source of electrical energy (not shown). The fan motor has an output shaft  52 , to which a hub  53  of a blade assembly  54  is attached, with the blade assembly having three blades  55 . 
     The fan motor housing  51  may be mounted to a pedestal (not shown) or other structure as described for fan  10 . 
     The motor housing  51  has a rear grill  57  mounted thereto in conventional manner such as by bolts (not shown). 
     The rear grill  57  has a plurality of concentric rings  58  to which spaced interrupted radial ribs  59  and  60  are connected. The ribs  59  are shorter than ribs  60  and extend out to a rim  62  of grill  57 . The ribs  60  extend out to rim  62  and inwardly to a center ring  63  which is attached to motor housing  51 . 
     A front grill  65  is provided, of circular configuration, with a plurality of concentric rings  66 , which have a plurality of spaced radial ribs  67  and  68  connected thereto, with ribs  67  extending inwardly to a center plate  69 , and outwardly to a ring  70  to be described. 
     The ribs  68  extend outwardly to ring  70 , and inwardly short of plate  69 . 
     The ring  70  preferably includes a curved panel  71 , which extends inwardly to an inclined panel  72 , and outwardly to a rim  73 . The rim  73  mates with rim  62  of grill  57 , with spaced tabs  62 A therearound, which are engaged with slots  74  in rim  73  to retain the grills  57  and  65  together. 
     In FIG. 4, the ring dimensions are indicated by the letters A, B, C and D. The dimension A is the distance from the tip  75  of a blade  55  to the inside diameter of the ring  70 . The dimension B is the depth of ring  70 , or the distance from the rear most portion of rim  73  to the front end of panel  71 . The dimension C is the width of ring  70 . The dimension D is the diameter of the blade assembly  54 . 
     The dimensions A, B, C and D for the fin  50  in the preferred embodiment for a 16 inch fan with blade diameter D=16 inches, are A=0.170 inches, B=1.41 inches and C=0.95 inches. 
     The dimensions A, B, and C for oscillating fans with a typical blade diameter from 10 to 30 inches, with D as an initial dimensional base point, have the dimensions calculated as follows; where the range of A is +/−40% of D as measured from tip  75 , B=0.60 to 4.5 inch, and C=40 to 200% B. 
     It has been found by testing that a 16 inch fan  50  with a front grill  65 , compared to a prior art 16 inch fan  10  with front grill  25 , provides significant improvement. 
     The fan  50  on high speed at 9 feet from the fan provided an air velocity (NEMA CFM) of 5710.00, whereas fan  10  provided an air velocity (NEMA CFM) of 4737.10. 
     Referring to FIG. 5 tests were run on two fans comparing the fans  10  and  50  with measurements at horizontal distances to 34 inches on each side. The results were plotted which shows significantly greater air velocities over distance for fan  50  with the improved front grill construction. 
     Referring to FIGS. 6,  7  and  8  the air velocity profiles for fans having. different front and rear grills were plotted, which shows that the improved front fan grill construction provided a significantly wider air flow pattern than the conventional grills. 
     It will thus be seen that an improved fan grill construction has been provided with which the objects of the invention are achieved.