Patent Publication Number: US-2011065374-A1

Title: Grille Cover and Contaminant Level Indicator

Description:
FIELD OF THE INVENTION 
     The present invention relates to improvements in the field of return air grilles for air conditioning systems or the like. 
     BACKGROUND OF THE INVENTION 
     It is known that return air ducts for air conditioning systems are typically covered by coarse mesh grilles aimed at providing minimal disturbance to air flow but preventing the passage of larger objects into the duct. In dirty environments where air entrained dust and other materials exist in reasonably high levels, the mesh covering the return air duct can become covered in this material to an extent where it can block or at least partially block the return air flow into the duct system leading to the air conditioning system. This commonly occurs in restaurant, cafe and other similar environments where cooking occurs but it can also occur in other environments. When the contaminant build up on the return air grille cover is sufficiently great, it is normal for the grille to be removed, cleaned of the contaminant material and returned to the operating position. This periodic cleaning of the grille is a quite expensive process. The objective of the present invention is to provide an arrangement usable with a return air grille or the like that will simplify the cleaning of same when necessary. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention, there is provided a disposable cover for an air flow grille of the type permitting air flow through a plurality of air flow openings in a predefined array of said openings, each said air flow opening having a forward inlet aperture and a passage wall extending from said forward opening to a discharge aperture on a downstream side of said air flow grille, said disposable cover being made from a thin walled mouldable plastics material having passage means corresponding to the predefined array of said openings in said air grille and being engageable therein during use of the disposable cover, said disposable cover, in use, covering at least forward facing regions of said air flow grille and at least a portion of each of the passage walls extending towards the discharge aperture on the downstream side of said air flow grille. 
     Preferably, the disposable cover may cover, in use, all of each of the passage walls. In a further possible arrangement, the disposable cover may extend, in use, beyond the downstream side of the air flow grille. 
     In a preferred arrangement, the air flow openings in the air flow grille may be square or rectangular and said disposable cover includes a plurality of thin walled tubular passage portions corresponding in position and shape to the square or rectangular air flow openings in the air flow grille, each of the tubular passage portions being open in a forward side and a rear side of the disposable cover. Conveniently a thin walled peripheral flange region surrounds the thin walled tubular passage portions. Preferably also a continuous flange region surrounds each of said tubular passage portions connecting said tubular passage portions to adjacent said tubular passage portions on said forward side. 
     By providing a disposable cover member of the above described type, it is possible, in use, to operationally install the cover member in any desired air flow grille and if and when it may become choked with contaminant materials it can simply be stripped from the air flow grille and replaced with a clean new disposable cover member. Thus cleaning of the air flow grille is simply and conveniently avoided with the costs of such disposable cover members being a very small percentage of the costs associated with cleaning such grilles. 
     In accordance with a second aspect of this invention, there is provided a method of making a disposable cover adapted, in use, to cover surface regions of an air flow grille, said method including the steps of: 
     moulding a thin sheet of plastics material in a mould representing an array of air flow openings in a predetermined air flow grille to form a discrete array of extended bubble formations corresponding to said array of air flow openings in the air flow grille; and 
     removing end regions of said extended bubble formations to produce a plurality of adjacent thin walled passage portions extending from a forward side to a rear side of said thin sheet of plastics material. Conveniently, the moulding step may be a vacuum moulding process, preferably including heating the plastics material sheet being formed. 
     Conveniently the step of removing the end regions of the extended bubble formations may occur either within the mould or after the disposable cover member has been removed from the mould. In the latter case, the length of the thin walled passage portions formed thereby might be made selectably variable. Preferably the mould may have an array of square or rectangular moulding cavities corresponding to the array of air flow openings in the predetermined air flow grille. 
     In a preferred arrangement an air flow sensor device might be employed with an air flow grille including a cover member installed in said air flow grille, the air flow sensor being adapted to sense when air flow levels drop to a level indicative that contaminant build up has occurred sufficient to suggest that the cover member and contaminant covering should be removed and replaced with a replacement cover member. In accordance with this proposal, the present invention also includes an air flow sensor usable with an air flow grille, to sense air flow through said grille below a predetermined volume rate, said sensor being mountable, in use, on a downstream side of said air flow grille and includes a flow passage to receive air flow through said grille, said sensor further including a first member subject to air flow through said air flow passage connected to an indicator member normally held within the air flow grille or an upstream side of the airflow grille, said indicator member being movable to an upstream side of the air flow grille when said first member receives air flow from said air flow passage below said predetermined volume rate. In this manner, once the indicator member moves to the upstream side of the air flow grille, this will indicate contamination levels are likely to be blocking the air flow grille and then the protective cover member with the blocking contaminants can be removed and replaced. 
     Several preferred embodiments of the present invention are described hereafter with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial section view of a mould or sheet of plastics material to be formed in the mould to produce a cover member; 
         FIG. 2  is a view similar to  FIG. 1  after a first step of the moulding process; 
         FIG. 3  shows a view similar to  FIG. 2  after a further step in the manufacturing process has been carried out; 
         FIG. 4  is a view similar to the previous drawings showing the formed cover member removed from the mould; 
         FIG. 5  is a partial upper perspective view of the cover member shown in  FIG. 4 ; and 
         FIG. 6  shows diagrammatically a sensor device for sensing air flow through an air flow grille with an installed cover member as depicted in earlier drawings. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings,  FIG. 1  shows a mould  10  with an array of mould cavities  11 . The cross-sectional shape of the mould cavities  11  (into the paper) is square as is conventional for return air grilles in air conditioning systems. The cross-sectional shape could be rectangular or potentially other shapes consistent with the air flow grille that the cover member is intended to be used with. The physical array of the mould cavities is identical to the air flow passages in the air flow grille that the cover member is intended to be used with.  FIG. 1  also shows a sheet of heat formable plastics material  12  positioned above the mould  10 . As shown in  FIG. 2 , the sheet  12  is vacuum moulded into the mould cavities  11  to form a plurality of extended bubble formations  13  each connected to one another by a continuous flange material  14 . The extended bubble formations  13  may extend beneath the mould  10  such that their end regions  15  might be removed by any suitable technique such as milling or cutting ( FIG. 3 ). This step might be performed while the cover member  12  is retained within the mould  10  or it may be stripped from the mould  10  and performed as a separate operation elsewhere. In either case a cover member  12  as shown in  FIGS. 4 and 5  may be produced consisting of tubular passage portions  16  open at the top and the bottom and having a cross-sectional shape identical to that of the mould cavities  11  and thereby the air flow openings in the desired air flow grille. Conveniently a flat peripheral flange (not shown in the drawings) may be provided around the array of tubular passage portions  16 . In practice the cover member will have a size and configuration to completely cover the upstream side  18  of an air flow grille  17  ( FIG. 6 ) with the tubular passage portions  16  fitting into and being engaged with the air flow openings  19  in the grille  17 . It is believed that friction between the tubular passage portions  16  and the passage walls  20  of the air flow openings  19  will be sufficient to operationally hold the cover member  12  in position. If this may not be the case, then separate fastener or adherence means might be employed between the cover member  12  and the grille  17 . If such means is used, then they would still need to be releasable as, once used, the cover member would need to be removable once contaminants have accumulated therein to an undesirable stage. 
       FIG. 6  also illustrates diagrammatically, a sensor device  21  for sensing air flow rates through the air flow grille  17  and installed cover member  12 . The sensor device  21  includes a tubular flow passage  22  which may include fastener means (not shown) of any suitable type to connect the tubular flow passage  22  to the downstream face  26  of the grille  17 . The device  21  includes a slide indicator  23  having an upper disc member  24  secured thereto that receives air flow through the passage  22  to push the disc member  24  upwardly (as illustrated). In this configuration, air flow through the grille  17  is not obstructed by contaminant build up. Once air flow drops to a predetermined level as a result of contaminants building up on the cover member  12 , the disc member  24  will no longer hold its illustrated position and the slide indicator  23  will drop downwardly. The free lower end  25  of the slide indicator  23  will eventually project upstream of the grille  17  to indicate that the grille has been blocked sufficiently to require removal and replacement of the cover member  12 . 
     While the drawings illustrate the presently preferred embodiments, many modifications or changes to the illustrated features might also be employed. In relation to the sensor device the disc member  24  might be added to with weights or decreased in size by having portions removable to thereby adjust the sensor for particular applications. While the drawings illustrate the cover member  12  covers the upstream side of the grille  17  and all parts thereof to the downstream face of the grille  17 , in some cases the cover member might have thicker or thinner dimensions. Other possible variations will be apparent to those skilled in the art.