Abstract:
A flow control includes a conduit and a flow control washer disposed in the conduit between the conduit&#39;s inlet and the outlet. A gas inlet passage opens into the conduit, preferably at a location just downstream of the flow control washer, to permit a gas (typically ambient air) to enter a liquid stream flowing through the flow control washer. The admission of a gas into this liquid stream reduces noise generated by liquid flow through the flow control washer. Gas induction and noise reduction capabilities may be enhanced by admitting the gas fluid into a low pressure region of a venturi located in the conduit downstream of the flow control washer. The flow control is particularly useful in a wastewater drain of a water softener control valve, but is also useful in a variety of other applications. A method of reducing noise in a flow control is also provided.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to flow control devices and, in particular, to a flow control having a flow control washer that maintains a generally constant volumetric flow rate through a liquid stream despite fluctuations in supply pressure. 
     2. Description of the Related Art 
     Flow controls are commonly used in appliances such as dishwashers, drinking fountains, and water softeners to compensate for variations in water supply pressure. The typical flow control comprises an annular flexible flow control washer mounted in a conduit such that water flowing through the conduit must flow through a central orifice in the flow control washer. The flow control washer and its support in the conduit are configured so that the orifice constricts as the water pressure increases, thereby maintaining a generally constant volumetric liquid flow rate through the conduit despite variations in supply pressure. A flow control of this general type has been used in water softeners as is detailed in U.S. Pat. No. 4,210,532 to Loke and in U.S. Pat. No. 5,162,080 to Dragger. 
     Flow controls of the above-mentioned type tend to be very noisy in operation, possibly due to cavitation caused by the pressure drop across the washer and/or to vibrations of the washer itself. In fact, in the case of a water softener, the whistling noise generated by the flow of water through the flow control can often proprogate through the pipes and be heard throughout much of the building. 
     This noise problem has been recognized and addressed, but never satisfactorily. For instance, U.S. Pat. No. 5,226,446 to Cooper proposes a rather complex anticavitation arrangement disposed downstream of the flow control washer. U.S. Pat. No. 3,250,342 to Petry proposes an expansion duct having apertures to recycle a portion of the fluid flow. U.S. Pat. No. 3,712,341 to Constantin proposes a flow separator for separating a downstream fluid influx from an upstream fluid flow. All of these arrangements are relative complex, are relatively expensive to manufacture and install, and are of questionable effectiveness. 
     In view of the foregoing, it would be desirable to provide a flow control that solves the noise problems associated with prior flow controls in a simple and effective manner. 
     SUMMARY OF THE INVENTION 
     The invention, which is defined by the claims set out at the end of this disclosure, is intended to solve at least some of the problems noted above. In accordance with a first aspect of the invention, the above-identified need is satisfied by providing a flow control comprising a conduit and flow control washer disposed in the conduit between its inlet and its outlet. “Conduit,” as used herein, means an enclosed passageway capable of receiving a flow control washer. An ambient fluid passageway opens into the conduit, preferably at a location just downstream of the flow control washer, to permit a gas (typically ambient air) to enter a liquid stream flowing from the flow control washer. The admission of the gas into this liquid stream reduces noise generated by liquid flow through the flow control washer. Gas induction and noise reduction capabilities may be enhanced by admitting the gas into a low pressure region of a venturi located in the conduit adjacent the flow control washer. The venturi may be formed integrally with the conduit or provided as a separate insert fitted in the conduit. 
     A method of reducing noise in a flow control is also provided. In the method, liquid flows through a flow control washer of a flow control conduit at a volumetric flow rate that remains generally constant, despite pressure fluctuations in the flowing liquid, due to operation of the flow control washer. A gas (typically ambient air) is drawn into the liquid flow to reduce the noise that would otherwise be generated by operation of the flow control. 
     The flow control can be used in any application where the flow rate is controlled within a particular pressure range. Examples of uses for the flow control include, but are not limited to, water softeners, water fountains, eye washes, dishwashers, and safety showers. If used on conjunction with a simple on/off valve, it can also be used do measure or dispense a given volume of fluid, without having to make volumetric measurements, simply by relying the flow control to maintain a desired fluid flow rate therethrough and automatically or manually closing the valve at the appropriate time. Hence, if a flow control maintains a flow rate therethrough at 2 gpm, 20 gallons can be reliably measured or dispensed simply by closing an associated valve after 10 minutes of flow through the flow control. 
     These and other objects, advantages, and features of the invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred exemplary embodiments of the invention are illustrated in the accompanying drawings, in which like reference numerals represent like parts throughout and in which: 
     FIG. 1 is a sectional elevation view of a vessel incorporating a flow control constructed in accordance with a first embodiment of the invention; 
     FIG. 2 is a side elevation view of a second, more practical embodiment of a flow control in accordance with the invention; 
     FIG. 3 is a sectional perspective view of the flow control of FIG. 2; 
     FIG. 4 is a perspective view of a third preferred embodiment of a flow control in accordance with the invention; 
     FIG. 5 is a sectional elevation view of the flow control of FIG. 4, taken generally along line  5 — 5  in FIG. 4; 
     FIG. 6 is a sectional elevation view of the flow control of FIG. 4, taken generally along line  6 — 6  in FIG. 5; and 
     FIG. 7 is a perspective view of a water softener that incorporates a flow control constructed in accordance with the invention. 
     Before explaining embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. 
    
    
     DETAILED DESCRIPTION 
     1. Resume 
     Pursuant to the invention, a flow control is provided that is configured to reduce or even eliminate noise associated with previous flow controls. The flow control includes a bore that draws a gas into a liquid stream in the vicinity of a flow control washer of the flow control for purposes of noise reduction. It has been discovered that the noises caused by the flow of liquid through the washer can be reduced or even eliminated simply by including a small bore in the flow control just downstream of the flow control washer for the admission of the gas, typically ambient air. 
     2. System Overview and First Embodiment of Flow Control 
     Referring to the drawings and initially to FIG. 1, a vessel  10  is schematically illustrated that employs a flow control  12  that is constructed in accordance with a preferred embodiment of the invention. The vessel  10  may be any system or structure from which water or another liquid is intended to flow at a generally constant volumetric flow rate. Examples of such structures are drinking fountains and eye washers. The vessel  10  could also be a backwashable filter, in which case the flow control  12  would be used in a control valve used to help control the backwashing process. The vessel  10  includes an outlet port  14  for the discharge of liquid, typically water, to another location, typically the ambient atmosphere. The liquid could also be discharged to a pressurized outlet. The outlet port  14  is coupled to a discharge line (not shown) by an elbow fitting  16 . The elbow fitting  6  includes an annular lip  18  around its outer periphery that rests against a shoulder  20  of the outlet port  14 . An O-ring  22 , which is disposed in a groove  24  in the outer periphery of the elbow  16 , forms a seal between an inner periphery of the outlet port  14  and the elbow  16 . 
     The flow control  12  may be provided as a standalone item as in the illustrated embodiment or as part of a more complex valve assembly. The flow control  12  also may be formed integrally with an existing conduit or inserted into that conduit. In the embodiment of FIG. 1, the flow control  12  is inserted in a lower, vertical leg  26  of the elbow fitting  16 . The flow control  12  of the embodiment of FIG. 1 comprises 1) a tubular conduit in the form of a plastic tube  28  and 2) a flow control washer  30  mounted in the tube  28  . The tube  28  has an inlet  32 , an outlet  34 , and an outer peripheral surface  36 . The outer peripheral surface  36  is press-fit into the lower leg  26  of the elbow  16  and sealed to the elbow  16  by an O-ring  38  mounted on a groove  40  in the outer peripheral surface  36  of the tube  28 . As is conventional, the flow control washer  30  comprises an annular elastomeric washer having an outer periphery  42  and a center orifice  44 . The outer periphery  42  is held in place within the tube  28  and sealed against an inner peripheral surface  46  of the tube  28  in a conventional manner. Alternatively, and as is more typically the case in flow controls, the washer  12  could simply rest on a shelf-like seat and be sealed to the seat during operation by the pressure differential thereacross. The center orifice  44  forms a flow path for water or another liquid through the washer  30 . The flow control washer  30  is configured so that the diameter of the orifice  44  constricts generally proportionally as the pressure drop across the washer  30  increases, thereby maintaining the volumetric flow rate of liquid through the washer  30  at least generally constant regardless of variations in supply pressure. Hence, fluid travels through the orifice  44  in the flow control washer  30  at a generally constant volumetric flow rate, exiting the tube  28 , and is discharged from the fitting  16 . 
     The flow control  12  also includes a passageway  52  that admits a gas into the flow control  12  in a low pressure region of the flow control. The passageway  52  extends through the elbow  16 , through the tube  28  and into the interior of the tube  28  at a location downstream of the flow control washer  30 . The passageway  52  of the embodiment comprises a simple bore drilled through the fitting  16  and tube  28 . The bore  52  permits a gas to enter the liquid stream flowing from the flow control washer  30 , as is shown by arrow  53 . The gas will typically comprise ambient air and, therefore, will hereafter be referred to as “air” for the sake of convenience. It has been observed that the flow of liquid through the flow control washer  30  causes a venturi effect that produces low pressure that draws air into the bore  52  and discharges a frothy air/liquid mixture from the outlet  46 . The manner in which the bore  52  actually eliminates the noise that is associated with the flow control washer  30  is unknown. While applicant does not wish to be restricted to a particular theory of how the bore  52  in the inventive flow control  12  reduces or even eliminates noise, the following theory explanation of how the bore  52  functions. 
     In conventional flow controls, air is distilled or otherwise removed from the liquid passing through the flow control washer. This and/or other factors generate noise, possibly by 1) cavitation in the low pressure region of the flow control downstream of the flow control washer and/or 2, vibration of the flow control washer at its resonant frequency. These noises can be carried and amplified throughout a building that includes the device having the flow control. It is believed that the introduction of air into the flow control  12  detunes the rubber of the flow control washer  30 . The detuning is believed to change the natural frequency of the flow control washer  30  sufficiently to avoid resonance. It is also believed that, in the inventive flow control  12 , the bore  52  negates a low pressure created by the accelerated liquid. That is, the flow of air into the liquid stream raises the minimum pressure in the system to a level that prevents cavitation. 
     The desired upper diameter of the bore  52  is limited by the production of noise from the air induction itself, while the desired lower diameter of the bore  52  is limited by the ability of the flow control  12  to draw enough ambient air into the flow control  12  to achieve the desired noise reduction effect in the tube  28 . When the discharged liquid is water and the tube  28  has a diameter on the order of 0.5″ to 2.0″, the bore diameter preferably is between 0.020″ and 0.060″, and preferably about 0.035″. 
     Flow controls constructed in accordance with the invention can accommodate a variety of volumetric flow rates. Depending on the sizing of the flow control flow rates of from about 0.5 gpm to about 25 gpm or even higher can be accommodated. They can also accommodate a wide range of supply pressures of, e.g., from less than 20 psig to more than 12.5 psig, for a typical application in which the liquid is discharged to the atmosphere at 14 psig. 
     3. Second Embodiment of the Flow Control 
     A second preferred embodiment of the flow control  112  is shown in FIGS. 2-3. The flow control  112  of the second preferred embodiment is similar to the flow control  12  of first preferred embodiment. Elements of the flow control  112  of FIGS. 2-3 corresponding to elements of the flow control  12  of FIG. 1 are incremented by 100. Flow control  112  therefore includes a tubular conduit  128  and a flow control washer  130 . The conduit  128  has an inlet  132  and an outlet  134 . A passageway  152  is formed in the conduit  128  downstream of the flow control washer  130  to admit gas into the conduit  128  for noise reduction purposes. However, the flow control  112  of this embodiment is significantly different from the embodiment of FIG. 1 in some respects. 
     For instance, the conduit  128  is configured to be mounted in series between two other conduits (not shown) and to facilitate mounting of the flow control washer  130  in the conduit  128 . The conduit  128  therefore is formed from a connector having female and male sections  154 ,  156  secured to each other via a swage fitting  158  threaded onto the female section  154  and secured to male section  156  by locking ring  172 . The washer  130  is positioned between a downstream axial end  166  of the male section  156  and a shoulder  168  on the female section  154 . The female section  154  is sealed to the male section  156  by an O-ring  170  disposed radially between the sections  154 ,  156  in the vicinity of the swage fitting  158 . 
     In addition, the interior of the female fitting  160  is shaped to enhance the venturi effect of liquid flow though the flow control  112  in order to enhance airflow into the flow conduit  128  and the resultant noise reduction. Specifically, a venturi  174  is formed in the conduit  128  downstream of the washer  130 . The venturi  174  includes a conically tapered inlet  176 , a conically tapered outlet  178 , and a relatively narrow throat  180  disposed between the inlet  176  and the outlet  178 . The bore  152  opens into the interior of the conduit  128  at the throat  180  of the venturi  174 , where the pressure drop of fluid flowing through the flow control  112  is a maximum. 
     A one-way valve  182  is also provided in this embodiment to prevent liquid from back flowing out of the bore  152 . Suitable valves include, but are not limited to, check valves, flapper valve, and duck-billed valves. The illustrated valve  182  is a duck-billed valve disposed in a boss  184  containing an outer end portion of the bore  152 . The valve  182  is formed from a rubber or other elastomeric material that is slit down its middle. The rubber halves of the valve  182  move apart to admit air into the bore  152 , but close to prevent the egress of liquid from the bore  152 . 
     In use, a liquid such as water enters the inlet  132  of the conduit  128  as represented by the arrow  148  in FIG. 3, flows through a central orifice  144  in the flow control washer  130 , flows through the venturi  174 , and exits the outlet  134  of the conduit  128 . Supply pressure fluctuations are accommodated by expansion and constriction of the orifice  144  to maintain a substantially constant volumetric flow rate through the flow control washer  130  and downstream components of the flow control  112 . The pressure drop created by liquid flow through the washer  130  and augmented by the venturi  174  draws a gas such as ambient air through the bore  152  and into the throat  180  of the venturi  174  as represented by the arrow  153 , thereby attenuating noises that otherwise would be generated by operation of the flow control  112 . The rubber halves of the duckbill valve  182  move apart to admit air into the bore  152  during this process, but close to prevent the egress of liquid form the bore  152 . 
     4. Third Embodiment of the Flow Control 
     A third preferred embodiment of the flow control  212 , which is illustrated in FIGS. 4-6, differs from the second preferred embodiment in that the venturi  274  is configured for installation in a separate fitting rather than being formed integrally with a fitting. Elements of the flow control  212  of FIGS. 4-6 corresponding to elements of the flow control  112  of FIGS. 2 and 3 are incremented by 100. The flow control  212  therefore includes a conduit  228  incorporating an integral venturi  274  and a flow control washer  230  mounted in the conduit  228  and having a central orifice  244 . 
     The flow control  212  of this embodiment is configured to minimize redesign of a flow control used in a drain fitting of a water softener control valve such as the valve  186  illustrated in FIG.  7 . The water softener control valve  186  includes a brine port  188  connected to a brine tank  190 , a service port  192  connected to a resin tank  194  containing a treatment medium, an inlet port  196  connected to an untreated water inlet line  198 , an outlet port  300  connected to a treated water outlet line  302 , and a wastewater discharge port  304  opening into a wastewater discharge fitting  306  connected to a drain line  308 . The flow control  212  is disposed in the wastewater discharge fitting  306 . 
     Referring back to FIGS. 4-6, the discharge fitting  306  comprises an elbow  216  incorporating the flow control  212 . The elbow  216  includes 1) a vertical upstream leg  226  configured for mounting in the wastewater discharge port  304  (FIG. 7) and 2) a horizontal downstream leg  308  configured for threaded connection to the drain line  308  (FIG.  7 ). The flow control  212  is formed in an insert  310  that is installed into the vertical leg  226  of the fitting  216  from the inner end. An outer peripheral surface of the insert  310  is sealed to an inner peripheral surface of the vertical leg  226  by a pair of spaced O-rings  316 ,  317 . Sliding movement of the insert  310  due to pressure differential from operation of the flow control into the vertical leg  226  of the fitting  216  is limited by engagement of an annular ring  314  on the insert  310  with the upstream end of the fitting  216 . The fitting is otherwise held in place by friction from O-rings  314  and  316 . A boss  315  extends upstream from the ring  314  and is configured to extend into the discharge port  304  of the water softener control valve  186 . The flow control washer  230  is also positioned loosely within the boss  315  adjacent the ring  314 . 
     The venturi  274  includes a conically tapered inlet  276 , a conically tapered outlet  278 , and a relatively narrow throat  280  disposed therebetween. An air inlet passage connects the ambient atmosphere to a low pressure region of the venturi  274  to permit air to flow into the low pressure region as represented by the arrow  253 . In the illustrated embodiment, the passage is formed from a bore  251  through a boss  284  on the fitting  216 , through an annular space  208  formed between the outer peripheral surface of the insert  310  and the inner peripheral surface of the fitting  216 , and through a bore  252  opening into the outlet portion  278  of the venturi  274  near the throat  280 . As with the embodiment of FIGS. 2 and 3, the venturi  274  augments the venturi effect caused by the flow of liquid through the flow control washer  230  to maximize the noise reduction effects of airflow into the flow control  212 . Finally, and also as in the second embodiment, a duck-billed one-way valve  282  is mounted in the boss  284  to prevent water from flowing out of the flow control  212  via the air inlet passage. 
     5. Noise Reduction 
     The data shown in the Tables 1-4 below demonstrate the difference in noise reduction using a relatively small (0.5″ diameter) elbow for fitting in a water softener drain port fitting constructed in accordance with the third embodiment of the invention. Data are shown as “A weighted,” which is used for scientific purposes, and “C weighted,” which approximates the human ear. The fitting was connected to the water softener control valve  185  and to the drain line  203  with flexible tubes to isolate the flow control  212  from external noise sources. Noise levels were tested at various flow rates in gallons per minute (GPM). Noise was measured with air introduced via the bore  252  of the flow control (WITH AIR) and without air introduced (W/O AIR). The difference between the two noise measurements is shown in the column labeled “DIFF.” 
     
       
         
               
             
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 NOISE TEST WS1 CONTROL VALVE (inlet pressure 70 PSI) 
               
               
                 BACKGROUND NOISE WAS 53 (37) dB AT 
               
               
                 18″ TEST C (A) WEIGHTED 
               
             
          
           
               
                   
                 18 INCHES TO THE LEFT SIDE OF VALVE @ 57″ HIGH 
               
             
          
           
               
                   
                 C WEIGHTED 
                   
                 A WEIGHTED 
                   
               
             
          
           
               
                   
                 WITH 
                   
                   
                 WITH 
                   
                   
               
               
                 GPM 
                 AIR 
                 W/O AIR 
                 DIFF. 
                 AIR 
                 W/O AIR 
                 DIFF. 
               
               
                   
               
             
          
           
               
                 0.7 
                 72.0 
                 78.5 
                 6.5 
                 77.0 
                 80.9 
                 3.9 
               
               
                 1.0 
                 69.5 
                 80.0 
                 10.5 
                 68.6 
                 82.5 
                 13.9 
               
               
                 1.3 
                 74.0 
                 81.5 
                 7.5 
                 72.3 
                 80.5 
                 8.2 
               
               
                 1.7 
                 70.8 
                 80.0 
                 9.2 
                 68.2 
                 80.5 
                 12.3 
               
               
                 2.2 
                 70.5 
                 80.0 
                 9.5 
                 73.4 
                 82.0 
                 8.6 
               
               
                 2.7 
                 68.0 
                 78.0 
                 10.0 
                 68.5 
                 80.2 
                 11.7 
               
               
                 3.2 
                 68.5 
                 79.3 
                 10.8 
                 69.5 
                 81.0 
                 11.5 
               
               
                 4.2 
                 69.0 
                 78.5 
                 9.5 
                 70.8 
                 81.0 
                 10.2 
               
               
                 5.3 
                 71.0 
                 78.0 
                 7.0 
                 72.0 
                 79.5 
                 7.5 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 NOISE TEST WS1 CONTROL VALVE (inlet pressure 70 PSI) 
               
               
                 BACKGROUND NOISE WAS 52 (35) dB AT THE 36″ POSITION C 
               
               
                 (A) WEIGHTED 
               
             
          
           
               
                   
                 36 INCHES IN FRONT OF VAVLE @ 57″ HIGH 
               
             
          
           
               
                   
                 C WEIGHTED 
                   
                 A WEIGHTED 
                   
               
             
          
           
               
                   
                 WITH 
                   
                   
                 WITH 
                   
                   
               
               
                 GPM 
                 AIR 
                 W/O AIR 
                 DIFF. 
                 AIR 
                 W/O AIR 
                 DIFF. 
               
               
                   
               
             
          
           
               
                 0.7 
                 69.0 
                 74.0 
                 5.0 
                 72.1 
                 75.9 
                 3.8 
               
               
                 1.0 
                 68.0 
                 75.0 
                 7.0 
                 67.9 
                 76.8 
                 8.9 
               
               
                 1.3 
                 71.5 
                 76.0 
                 4.5 
                 72.0 
                 76.3 
                 4.3 
               
               
                 1.7 
                 67.0 
                 75.5 
                 8.5 
                 64.8 
                 74.5 
                 9.7 
               
               
                 2.2 
                 67.0 
                 75.0 
                 8.0 
                 71.5 
                 75.5 
                 4.0 
               
               
                 2.7 
                 66.0 
                 73.0 
                 7.0 
                 67.3 
                 74.5 
                 7.2 
               
               
                 3.2 
                 67.0 
                 74.0 
                 7.0 
                 67.0 
                 75.0 
                 8.0 
               
               
                 4.2 
                 68.0 
                 73.0 
                 5.0 
                 68.0 
                 74.2 
                 6.2 
               
               
                 5.3 
                 69.0 
                 72.5 
                 3.5 
                 69.5 
                 73.7 
                 4.2 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 NOISE TEST WS1 CONTROL VALVE (inlet pressure 70 PSI) 
               
               
                 BACKGROUND NOISE WAS 53 (37) Db AT 
               
               
                 18″ TEST C (A) WEIGHTED 
               
             
          
           
               
                   
                 18 INCHES TO THE LEFT SIDE OF VALVE @ 57 HIGH 
               
             
          
           
               
                   
                 C WEIGHTED 
                   
                 A WEIGHTED 
                   
               
             
          
           
               
                   
                 WITH 
                   
                   
                 WITH 
                   
                   
               
               
                 GPM 
                 AIR 
                 W/O AIR 
                 DIFF. 
                 AIR 
                 W/O AIR 
                 DIFF. 
               
               
                   
               
             
          
           
               
                 0.7 
                 62.2 
                 66.0 
                 3.8 
                 62.3 
                 68.5 
                 6.2 
               
               
                 1.0 
                 58.0 
                 67.8 
                 9.8 
                 58.0 
                 70.0 
                 12.0 
               
               
                 1.3 
                 59.8 
                 69.1 
                 9.3 
                 60.5 
                 70.7 
                 10.2 
               
               
                 1.7 
                 69.0 
                 75.8 
                 6.8 
                 71.5 
                 77.0 
                 5.5 
               
               
                 2.2 
                 60.0 
                 74.0 
                 14.0 
                 61.6 
                 75.1 
                 13.5 
               
               
                 2.7 
                 61.5 
                 72.2 
                 10.7 
                 61.7 
                 74.2 
                 12.5 
               
               
                 3.2 
                 62.8 
                 72.5 
                 9.7 
                 62.1 
                 73.8 
                 11.7 
               
               
                 4.2 
                 64.2 
                 72.0 
                 7.8 
                 65.0 
                 74.0 
                 9.0 
               
               
                 5.3 
                 66.2 
                 72.2 
                 6.0 
                 67.5 
                 75.0 
                 7.5 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 NOISE TEST WS1 CONTROL VALVE (inlet pressure 70 PSI) 
               
               
                 BACKGROUND NOISE WAS 52 (35) dB 
               
               
                 AT THE 36″ POSITION C (A) WEIGHTED 
               
             
          
           
               
                   
                 36 INCHES IN FRONT OF VAVLE @ 57″ HIGH 
               
             
          
           
               
                   
                 C WEIGHTED 
                   
                 A WEIGHTED 
                   
               
             
          
           
               
                   
                 WITH 
                   
                   
                 WITH 
                   
                   
               
               
                 GPM 
                 AIR 
                 W/O AIR 
                 DIFF. 
                 AIR 
                 W/O AIR 
                 DIFF. 
               
               
                   
               
             
          
           
               
                 0.7 
                 60.0 
                 62.4 
                 2.4 
                 61.8 
                 63.4 
                 1.6 
               
               
                 1.0 
                 57.0 
                 64.0 
                 7.0 
                 58.1 
                 65.5 
                 7.4 
               
               
                 1.3 
                 63.7 
                 68.7 
                 5.0 
                 64.7 
                 71.6 
                 6.9 
               
               
                 1.7 
                 67.0 
                 70.6 
                 3.6 
                 68.5 
                 72.0 
                 3.5 
               
               
                 2.2 
                 59.3 
                 67.6 
                 8.3 
                 59.4 
                 68.4 
                 9.0 
               
               
                 2.7 
                 59.8 
                 66.3 
                 6.5 
                 59.8 
                 67.8 
                 8.0 
               
               
                 3.2 
                 60.3 
                 67.2 
                 6.9 
                 61.0 
                 68.0 
                 7.0 
               
               
                 4.2 
                 61.8 
                 67.0 
                 5.2 
                 62.0 
                 68.3 
                 6.3 
               
               
                 5.3 
                 63.2 
                 66.5 
                 3.3 
                 64.1 
                 67.5 
                 3.4 
               
               
                   
               
             
          
         
       
     
     As can be seen from the data of Tables 1-4, introducing air via the air inlet passage of the flow control  212  significantly reduces noise levels under all conditions tested. 
     It is understood that the various preferred embodiments are shown and described above to illustrate different possible features of the invention and the varying ways in which these features may be combined. Apart from combining the different features of the above embodiments in varying ways, other modifications are also considered to be within the scope of the invention. 
     The invention is not intended to be limited to the preferred embodiments described above, but rather is intended to be limited only by the claims set out below. Thus, the invention encompasses all alternate embodiments that fall literally or equivalently within the scope of these claims.