Abstract:
Contamination of an automatic faucet with bacteria,  e - coli  and other harmful materials is avoided by coating inlet screens of such faucets with silver. Contact of the silver coating with water borne contaminants within the faucet removes most harmful contaminants in the water. A screen structure particularly suited for insertion in the water inlet of automatic faucets is disclosed.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Field of Invention  
         [0002]     This invention provides protection against latent contamination of automatic faucets with water borne contaminants, like bacteria,  e - coli.  This protection is provided by coating water inlet screens or other particulate removal means with silver. Particulate removal means are generally placed in automatic faucet water inlets to remove particulate matter that would otherwise interfere with the operation of such faucets by clogging small water passages used therein. These particulate removal means, however, are a breeding ground for contaminants that are trapped on such means and the particulate matter trapped thereon. Applicants have found that coating such screens with silver has yielded unexpected benefits by reducing the potential for contamination of the water emanating from such faucets.  
         [0003]     2. Prior Art  
         [0004]     While silver has been used in some applications to reduce water borne bacteria contamination, no one has used silver on screens or particulate removal means of automatic faucets to reduce such contamination.  
         [0005]     U.S. Pat. No. 6,082,407 assigned to Speakman Company describes one example of a faucet that would benefit from this invention. This faucet contains a screen in the inlet of the solenoid (see Col. 3, lines 24-27 and FIG. 1( a ) of U.S. Pat. No. 6,082,407). But that screen is subject to biological contamination from the water supply or from other sources. For example, in a situation where flood waters reach inlets to water treatment plants, biological contamination in the flood waters can be carried by the water supply and collect on the inlet screen of a faucet. Such contaminants are often difficult to dislodge from the inlet screen, even with backflushing or use of astringents such as chlorine. Applicants have found that these problems may be overcome with use of a silver coating on the inlet screen.  
         [0006]     Examples of prior uses of silver in water borne applications are described below.  
         [0007]     U.S. Pat. No. 6,306,350 issued to ITT Manufacturing Enterprises, Inc. describes a water quality sampling apparatus for extracting biological or chemical analytes from contaminated waterways (col. 1, lines 6-9). The water sample passes through a series of successively finer filter membranes. Among those filters is one of “silver wool . . . for the control of bacterial growth” (col. 5, lines 54-60).  
         [0008]     A water cooler is described in U.S. Pat. No. 6,101,835. The cooler includes an in-line  E - coli  purification module  88  and particulate filter module  89  (col. 7, lines 25-29 and FIG. 3). The primary purification in module  88  is accomplished using an “electron curtain [which] will kill  E - coli  bacteria and contaminated water as the water passes through the electron curtain” (col. 7, lines 54-59 and FIG. 9). This patent also discloses use of a “silver screen structure” to assist in destruction of  E - coli  bacteria (Col. 8, lines 5-15).  
         [0009]     A drinking cup lid with various filter media, including silver, is disclosed in U.S. Pat. No. 4,999,109. One of the filter media is antibacterial and comprises “an asbestos screen coated with additional bactericidal medium, preferably silver nitrate . . . ” (Col. 4, lines 34-38 and FIG. 3).  
         [0010]     U.S. Pat. No. 4,287,057 issued Sep. 1, 1981 discloses a portable sink top water conditioner for filtering tap water. Mechanical screens  38  help to contain activated charcoal within the filter. “[O]ne or more of the screens may be silver plated” to reduce the bacteria count in the water (Col. 2, lines 51-65).  
       SUMMARY OF INVENTION  
       [0011]     An object of this invention is to prevent contamination of automatic faucets containing large particle water inlet screens or other particulate removal means. Such means have a tendency to trap bacteria, e-coli and other contaminants that are difficult to physically remove or neutralize. The contamination is particularly prevalent with automatic faucets in which water flow occurs only occasionally and for short periods of time. For example, in a hospital setting automatic faucets are typically only used to wash hands, for example, at a surgical scrub sink. In such an application water may only run through the faucet a few minutes a day and may sit quiescent within the faucet for long periods, e.g. overnight or over weekends.  
         [0012]     Almost all automatic faucets must have inlet screens or filters to avoid clogging of small internal passages used in such faucets. Typically these faucets use a pressure balanced diaphragm with minute bleed holes to control flow through the faucet, for example, as described in U.S. Pat. No. 4,948,090 incorporated herein by reference. As illustrated in this and like patents, free flow of water through these bleed holes is essential to distribute pressure across an operating diaphragm. Thus, particulate matter in a water supply can seriously impair operation of such valves by impeding movement of parts or clogging passages. Accordingly, screens or filters are essentially mandatory in such valves. Such screens or filters, however, are a natural habitat for growth of bacteria and other contaminants. This problem is exacerbated in those situations where the water supply has been compromised by flood, problems at a water utility&#39;s filtration plant or inflow of farm runoff into artesian wells.  
         [0013]     The current invention solves these and other contamination problems by providing an antibacterial coating on the automatic valve inlet screen, filter, or other particulate removal means. The efficacy of this coating as a means of limiting contamination of water passing through the inlet screen has been established by careful laboratory testing.  
         [0014]     The inlet screen or filter preferably comprises a stainless steel foraminous member coated with a pure silver coating. In a typical application the inlet screen or filter is formed as a cylindrical sleeve having a diameter of about one half inch (1.2 cm.) and height of about one inch (2.5 cm.). The screen or filter is provided with structural integrity by embedding the open edges of the circular sleeve in a plastic or rubber housing to form sealing washers at each open end thereof. Further structural integrity can be provided for the screen or filter housing by molding reinforcing ribs along the length of the sleeve.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a side elevational view of the automatic faucet assembly of this invention;  
         [0016]      FIG. 2  is a fragmental exploded cross-sectional view in elevation showing the faucet water inlet; the filter screen housing, the silver coated filter screen and the faucet water inlet closure;  
         [0017]      FIG. 3  is a fragmental cross-sectioned view of the assembled components of  FIG. 2 ;  
         [0018]      FIG. 4  is a top plan view of the filter screen housing;  
         [0019]      FIG. 5  is a bottom plan view of the filer screen housing; and  
         [0020]      FIG. 6  is a front elevational view of the filter screen.  
     
    
     DETAILED DESCRIPTION OF INVENTION  
       [0021]      FIG. 1  illustrates a typical automatic faucet  10  arrangement in which the inlet screen of this invention can be utilized. The structure and operation of automatic faucet  10  are set forth in the specification and drawings of commonly assigned U.S. Pat. No. 6,082,407 which is incorporated herein by reference. In the typical automatic faucet assembly, a faucet spout  12  is angled upward and over a sink (not shown) to discharge water from faucet outlet  13 . The faucet spout  12  is typically mounted on a deck plate  14  to facilitate mounting of faucet  10  to a solid surface or deck  16  surrounding the sink.  
         [0022]     Potable water is supplied to faucet  10  at water inlet  18  which typically includes a threaded or sweated connection for attachment of water supply tubing or piping (not shown). Flow through faucet  10  from water inlet  18  to faucet outlet  13  is controlled by solenoid operated valve  20  which is typically activated by an optical or infrared sensor  15  for sensing the presence of a user of the faucet  10 .  
         [0023]     A water inlet housing  22  is located downstream of water inlet  18  and upstream of solenoid operated valve  20 . This housing  22  is depicted on  FIGS. 2 and 3  and typically comprises a central bore  24  therein which is in fluid communication with water entering the faucet  10  through inlet  18 . The water entering through inlet  18  passes through bore  24  of the housing  22  and exits through water outlet port  19 . Water passing through outlet port  19  then enters solenoid  20  where its further passage through faucet  10  to water outlet  13  is controlled by solenoid valve  20 . One end of the bore  24  of water inlet housing  22  typically contains a threaded end closure  28 . Mating threads  26  in the housing  22  allow ready removal and replacement of closure  28 .  
         [0024]     The removal and replacement of closure  28  is necessary to accommodate the placement of an inlet screen or filter  30  within bore  24  of water inlet housing  22  to collect particulate matter in the water entering inlet  18 . This particulate removal means  30  is typically used in most, if not all, automatic faucets to filter out particles or other debris that might interfere with the operation of solenoid valve  20 , as explained above. The particles and debris that collect on particulate removal means  30  must be periodically removed to prevent clogging thereof that would impede flow of water through faucet  10 . Accordingly, closure  28  may be periodically opened to allow removal and cleansing of particulate removal means  30 .  
         [0025]     This means  30  is coated with silver to reduce water borne contamination. Particulate removal means  30  can be fabricated from any foraminous material that will support this silver coating, but is preferably made of stainless steel.  
         [0026]     To facilitate insertion, retention and removal of particulate removal means  30  in water inlet housing  22 , it is preferably placed in a housing  34  as illustrated in  FIGS. 2-6 . As shown in this preferred embodiment, particulate removal means  30  within housing  34  is a stainless steel mesh coated with silver formed as a circular sleeve having a diameter of about one-half inch (1.2 cm) and length of about one (1) inch (2.5 cm). Each end of the housing  34  includes molded washers  36  and  38  which are dimensioned to provide a sealing engagement with the top  25  of inlet housing bore  24  and the inlet housing closure  28 , respectively. A central opening  37  (See  FIG. 2-4 ) in molded washer  36  facilitates passage of water out the housing  34  into water outlet  19  of the water inlet housing  22 . A smaller opening  39  in washer  38  facilitates seating of the housing  34  on housing closure  28 . The structure of housing  34  is preferably strengthened with vertical ribs  40  extending between washers  36  and  38 .  
       EXAMPLE  
       [0027]     The efficacy of using silver coated particulate removal means in automatic faucets to reduce water contamination is confirmed by the following test results commissioned by the assignee of this application.  
         [0028]     Eight identical automatic faucets were exposed to contaminated water. Two of the faucets had “standard” uncoated inlet screens (100×100 mesh). Two had “coarse” silver plated internal screens made of coarser than standard screen which was silver plated; and four had “fine” silver plated internal screens (same screen mesh as the standard screens). After a three week exposure to contaminated water having a relatively high bacteria count (HPC&gt;10,000 CFU&#39;s/ml) and a relatively low particulate level (TSS&lt;10 mg/l), non-chlorinated well water having a relatively low bacteria count (HPC of 1) was run through the faucet for 60 minutes. Samples were collected at 15, 30, 45 and 60 minutes. Results are summarized below:  
                                                                                                                                                                           Draw Off           Standard Inlet Screen   Coarse Silver Screen   Fine Silver Screen   Valve            Time       Mean HPC   Std.       Mean HPC   Std.       Mean HPC   Std.       HPC       (min.)   n   (CFU/ml)   Dev.   N   (CFU/ml)   Dev.   n   (CFU/ml)   Dev.   n   CFU/ml                    15   2   435   35.6   2   79.5   43.1   4   144   125.2   1   28       30   2   291   210   2   113   77.8   4   126   28.5   1   31       45   2   55.0   1.41   2   39.5   6.36   4   40.0   9.93   1   26       60   2   71.5   9.19   2   48.0   1.41   4   42.5   12.4   1   28                  
 
         [0029]     The above results confirms that water contaminants are substantially reduced by coating the automatic faucet inlet screen with silver. For example, after fresh water (HPC of 1 or less) is run through the inlet screens for 15 minutes after contaminated water (HPC of &gt;10,000) is run through the inlet screens, there is a substantial reduction in the HPC count (435 reduced to between 79.5 and 144) in the faucet with silver coated screens versus uncoated screens. As more clean water passes through the faucet, e.g. after one hour, the reduction in contamination, (71 reduced to 48) is lesser because the clean water has flushed out much of the contamination. But the 15 minute test in this table best illustrates the conditions that might be experienced in actual use where contamination grows during non-use of a faucet followed by a short period of fresh water passing through the faucet.