Abstract:
A grill for an air conditioning unit has one or more grill members wrapped with wire so as to present a varying topographical surface to the flow of air over the grill members. The resulting grill member profile that is presented to the air flow reduces vortex shedding noise that would otherwise occur without the wire wrapping. Various wire wrappings are disclosed which produce the desired effect of reducing the vortex shedding noise.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to the flow of air through the grill of an air conditioning unit and in particular to reducing the noise level produced by such air flow. 
     Air conditioning units, including heat pump units, typically include grill structure which prevents entry of foreign objects into the unit while allowing the free flow of air. The flow of air is into the unit if it is the condensing unit or section of an air conditioning system. The flow of air is out of the unit if it is an evaporating unit. 
     A fan normally defines the flow of air into or out of the unit. Today&#39;s fans are capable of producing a high flow of air through the grill. This may result in unacceptable noise levels as the air flows through the grill structure. It would be preferable to have a grill structure which would lower these unacceptable noise levels. 
     SUMMARY OF THE INVENTION 
     A grill for an air conditioning unit is provided which reduces the level of noise produced by the flow of air through the grill. The grill may be of any shape necessary to accommodate the particular unit in which it is installed. The grill preferably has one or more grill members wrapped with wire so as to present a varying topographical surface to the flow of air over the grill member. The wire wrapping may be formed in various ways including twisted strands of wire thereafter wrapped around the one or more grill members. The wire may also be a single piece of wire having spaced protrusions so as to disrupt the flow of air when wrapped around one or more grill members. Another embodiment is a round wire that is flattened at various intervals so as to present a discontinuous shaped wire wrapped around one or more grill members. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages of the present invention will be apparent from the following description in conjunction with the accompanying drawings, in which: 
     FIG. 1 illustrates an air conditioning unit with a grill mounted therein; 
     FIG. 2 illustrates an internal fan and heat exchanger configuration within the air conditioning unit of FIG. 1; 
     FIG. 3 illustrates a particular wire wrapping of grill members so as to thereby reduce the noise produced by air flow through the grill; 
     FIG. 4 is an alternative wire wrapping of a member of the grill of FIG. 3; 
     FIG. 5 is yet another alternative wire wrapping of a grill member; 
     FIG. 6 is yet another alternative wire wrapping of a grill member; and 
     FIG. 7 illustrates a wire wrapping of a differently shaped grill than that shown in FIGS.  1 - 6 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment described herein refers to a rectangular shaped grill within a rectangular shaped air conditioning unit. It is to be understood however that this invention has like applicability to differently shaped grills in differently shaped air conditioning units including the typical circular shaped grill for the outdoor condensing unit of an air conditioning system or the outdoor evaporator unit of an air heat pump system. 
     Referring to FIG. 1, an air conditioning unit  10  includes a grill  12  positioned therein. As noted above, the shape of the grill and the shape of the air conditioning unit should not be a limiting feature of the invention. 
     Referring to FIG. 2, the air conditioning unit  10  is broken away so as to show a fan  14  drawing air through the grill  12  and hence over a heat exchanger  16 . It is to be appreciated that the fan could also move the air in the opposite direction in various types of air conditioning units. The fan  14  produces a significantly high flow of air through the grill  12  so as to require a noise level reduction. 
     Referring now to FIG. 3, a portion of the grill  12  is shown in further detail. In particular, two horizontal grill members  18  and  20  intersected by a series of vertical grill members are shown. The horizontal grill members  18  and  20  are each wrapped with single pieces of wire  22  and  24 . The wrapping of the grill members by the single pieces of wire is such as to produce a significant variation in the grill member profile to the incoming air flow. This variation in the grill member profile reduces the vortex shedding noise that would otherwise be produced by the airflow through the grill  12 . It is to be appreciated that the number of wire wrappings per lineal measurement along the lengths of the grill members will vary per application depending on the particular level of air flow produced by the fan  14 . The resulting grill member profile to the flow of air should produce various out of phase levels of noise which tend to cancel each other at the particular level of air flow. 
     Referring now to FIG. 4, an alternative wire wrapping of the grill member  18  is illustrated. In particular, the wire  22  is replaced by a twisted pair wire  26  which causes an even further variation in the grill member profile to the incoming air flow through the grill  12 . It is to be appreciated that the twisted pair wire wrapping  26  produces a more profound variation in grill member profile to the incoming air than that of the single wire wrapping of FIG.  3 . The twisted wire  26  is preferably twisted at least once during each successive wrapping of the member  18  by the twisted wire  26 . The number of wire wrappings of the twisted pair wire per lineal measurement along the lengths of the grill members will vary per application depending on the particular level of air flow produced by the fan  14 . 
     Referring now to FIG. 5, yet another form of wire wrapping of the horizontal member  18  is illustrated. In particular, a wire  28  includes spaced protrusions such as  30 - 1  through  30 - 3 . The spaced protrusions define a variation in grill member profile to the airflow. The spacing of the protrusions  30 - 1  to  30 - 3  may either be uniform or variable. The number of wire wrappings of the wire  28  per lineal measurement along the length of the grill members will vary per application depending on the particular level of air flow produced by the fan  14 . 
     Referring now to FIG. 6, a still further wire wrapping around the horizontal grill member  18  is illustrated. The wire wrapping is preferably formed by flattening various portions of an otherwise circular wire so as to produce flattened sections  34 - 1 ,  34 - 2 ,  34 - 3  between otherwise normally shaped wire sections  36 - 1 ,  36 - 2 ,  36 - 3 . The spacing of the flattened sections  34 - 1 ,  34 - 2 ,  34 - 3  between otherwise normally shaped wire sections  36 - 1 ,  36 - 2 ,  36 - 3  may either be uniform or variable. The discontinuities produced by this type of wire wrapping again results in a varying grill member profile to the air flow produced by the fan  14 . The number of wire wrappings of the alternately flattened wire per lineal measurement along the length of a grill member can again be chosen as to produce the desired break up of the vortex shedding noise otherwise produced by the particular fan moving air over the particular grill. 
     Referring now to FIG. 7, a wire wrapping of circular grill members of a circular grill is shown. The particular wire wrapping  38  around each circular grill member is preferably the same as the twisted pair wire shown in FIG.  4 . It is to be appreciated that the twisted pair wire wrapping of the circular grill members could be replaced with any of the disclosed wire wrappings of FIGS. 3,  5 ,  6 , or any other wire wrapping that would produce the desired break up of the vortex shedding noise otherwise produced by the particular fan moving air over the circular grill. 
     It is to be appreciated from the above that various embodiments of the invention have been described. Alterations, modifications and improvements thereto can be made within the scope of the invention. For example, many different wire wrappings other than the twisted wire or the other two embodiments of the wire wrapping may be used to wrap the grill member so as to produce the disruptive grill member profile to the flow of air. Accordingly, the forgoing description is by way of example only and the invention is to be limited by the following claims and equivalents thereto.