Abstract:
An eductor assembly includes an inlet connectable to a high pressure water source useful in firefighting, an outlet connectable to a fire hose and/or nozzle, and a venturi therebetween. An additive inlet communicates with the venturi so that a chemical additive, such as a foam concentrate, is educed into the output stream. A check valve is positioned at the additive inlet to open under venturi flow conditions and remain closed otherwise. An actuator is provided that holds the check valve in its open position while water flows through the eductor assembly under non-venturi conditions to produce a back flow through the additive inlet and ultimately through the additive fluid circuit, including the additive metering valve components. A return element may be disposed within the eductor body to return the check valve to its closed position when the back flow ceases.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to fire-fighting equipment, and more specifically to equipment coupled to a fire hose or pipeline for integrating an additive to a water stream. 
   Fire fighting systems typically include a fire truck, such as truck T in  FIG. 1 , which includes a pumping unit P that pumps water under high pressure from a tanker truck or a nearby fire hydrant, through a fire hose H 1 , H 2  and nozzle N. While water alone is sufficient for most fires, some fires cannot be efficiently controlled or extinguished by water alone. In this case, certain chemical additives are introduced into the water line to be discharged onto the particular type of fire. Incidents involving flammable liquids or hazardous materials often require the use of a foam that is spread over the fire to starve the fire of oxygen or to suppress noxious vapors. For instance, Class A foam concentrates are used for wildland, rural and urban fire suppression on Class A fuels, such as wood, paper and other solid materials. Class B foam concentrates are primarily intended for Class B materials, such as flammable liquids containing hydrocarbons or polar solvents, and can be used for vapor suppression or extinguishment. 
   There are numerous approaches to introducing chemical additives or foam concentrates into the flow through firefighting water lines. Some systems utilize additive pumps for forced injection of the chemical into the water line. Such systems are generally complicated and are not portable. On the other hand, portable systems rely upon the movement of water through the fire hose to educe the chemical. In the context of the present invention, educe or induct means that liquid is drawn into the system, such as by the flow of another liquid. In one typical arrangement, a foam bucket F contains a liquid foam concentrate that is induced into the fire hose H 2  by a foam eductor valve E. This typical eductor valve E relies upon venturi flow to draw the foam concentrate from the foam bucket F into the water stream passing through the eductor E. 
   The chemical additives or foam concentrates are often corrosive and usually expensive. Thus, the typical eductor valve E includes a check valve system to prevent backflow of water into the chemical supply. For instance, the by-pass eductor described in U.S. Pat. No. 5,960,887, includes a ball check valve integrated into a foam concentrate metering valve. 
   While the check valve is important to prevent water backflow, it can be problematic with respect to cleaning the eductor valve E. In fire-fighting equipment back-flow typically occurs when the discharge nozzle N is shut off or when the hose H 2  is kinked so that fluid discharge is terminated. Without cleaning, the chemicals passing through the valve may congeal and foul the valve or the metering orifice used to control the quantity of chemical introduced into the water stream. In an extreme case, the valve may be stuck open or closed. Prior devices require disengaging the eductor valve from the water line, connecting the water supply hose H 1  to the chemical inlet of the eductor valve E, and flushing the valve with water. This process is cumbersome, but perhaps more significantly this approach can be hazardous. In particular, disengaging a eductor valve filled with a chemical additive of foam concentrate will necessarily result in a chemical spill. 
   What is needed is an eductor valve apparatus that satisfies all of the necessary functions of an eductor, but that is easy and safe to clean. Such an apparatus would allow controlled flushing so that the chemicals can be safely collected without risk of spilling. A further need is the ability to readily determine the position of the check valve and to manually alter it. 
   SUMMARY OF THE INVENTION 
   To address this unmet need, the present invention contemplates a system for preventing actuation of a check valve within an eductor assembly. In one embodiment, the present invention contemplates an eductor assembly for use with firefighting equipment that comprises an eductor body defining a fluid inlet connectable to a source of a firefighting fluid (e.g., high pressure water), a fluid outlet for dispensing fluid therefrom in fluid communication with the fluid inlet, and an additive inlet connectable to a source of an additive to the firefighting fluid and in fluid communication with the fluid outlet. The additive can be, for example, a foam concentrate that is educed to mix with the high pressure water under venturi flow. 
   The eductor assembly further comprises a check valve disposed between the additive inlet and the fluid outlet that is moveable, in response to a flow of water through the fluid inlet, between a first position operable to prevent back flow of water through the additive inlet and a second position to permit flow of additive through the additive inlet to the fluid outlet. In other words, the check valve is open to permit the eduction of the additive under proper venturi conditions, but otherwise closes the additive inlet. 
   In one important feature of the invention, means are provided for holding the check valve in its open position while allowing water back flow through the additive inlet. This feature allows the additive fluid circuit to be back flushed and thus cleaned after use. In one embodiment, this means includes an actuator operable from outside the eductor body to move the check valve to the second position. In a more specific embodiment, this actuator is an elongated pin having a proximal end manually accessible outside the eductor body and an opposite working end engageable with the check valve to move the check valve to the second position. The actuator preferably includes a push button mounted to the proximal end of the pin to facilitate manual operation of the actuator. 
   Preferably, the actuator pin is sized so that it does not contact the check valve in its non-actuated position. In the preferred embodiment, means are provided for biasing the pin to this non-actuated position away from engagement with the check valve. When the push button is manually pressed, the pin moves against this biasing means to contact and push the check valve to its open position. 
   The eductor assembly further comprises a metering head in fluid communication with the additive inlet, in which the metering head includes a metering inlet connectable to the source of the additive and an adjustable metering element disposed between the metering inlet and the additive inlet. The actuator is supported by the metering head to engage the check valve to move the check valve to the second position. Where the actuator is an elongated pin, the pin is slidably disposed within the metering head and has a proximal end manually accessible outside the metering head and an opposite working end engageable with the check valve to move the check valve to the second position. 
   In one embodiment, the metering element is connected to a proportioning knob movably mounted to the metering head, and the knob defines a recess for receiving the push button and a bore communicating with the recess slidably receiving the pin therethrough. In a further feature, the eductor assembly includes a mating assembly between the metering head and the additive inlet of the eductor body for removably coupling the metering head thereto. This mating assembly allows removal of not only the additive metering components, but also the actuator pin and push button. 
   Preferably, the actuator includes a spring between the push button and the proportioning knob within the recess. The spring is arranged to bias the pin away from engagement with the check valve. In certain embodiments, the pin extends through the metering element, which can comprise a hollow proportioning ball defining a plurality of differently sized metering openings arranged to be selectively aligned with the metering inlet, and a hollow stem coupled to the proportioning ball and defining a passageway to slidingly receive the pin. A fluid sealing element or seal ring may be disposed between the pin and the hollow stem. 
   In the preferred embodiment, the check valve includes a valve disc sized to close the additive inlet in the first position and a number of alignment wings projecting from the valve disc into the additive inlet when the check valve is in either of the first and second positions. Thus, the wings maintain the position of the check valve as it moves between its open and closed positions. The wings are sufficiently dispersed to allow substantially unimpeded flow of additive of water back flow through the additive inlet. In a specific embodiment, the number of wings defines a hub arranged to be engaged by the actuator pin when the actuator is operated to move the check valve to the second position. 
   The invention further contemplates a method of cleaning an eductor assembly used to introduce an additive to a flow of water through a venturi nozzle. The eductor assembly includes an eductor body defining the venturi nozzle, an additive inlet in fluid communication with the venturi nozzle and a check valve disposed between the additive inlet and the venturi nozzle that is open when the venturi nozzle produces suction to educe additive through the additive inlet, and is otherwise closed to prevent back flow through the additive inlet of water passing through the venturi nozzle. The preferred embodiment of the method comprises the steps of moving the check valve to its open position, holding the check valve in that position and then flowing water through the venturi with the check valve open to produce back flow of water through the additive inlet. Preferably, the holding step includes manually depressing an actuator pin slidably disposed within the eductor assembly to push the check valve into its open position. 
   It is one object of the present invention to provide a system and method for cleaning an eductor assembly that is used for introducing a chemical additive, such as foam concentrate, into a flow of water used to battle a fire. 
   One benefit of the invention is that the inventive eductor valve apparatus satisfies all of the necessary functions of an eductor, but is easy and safe to clean. A further benefit of the apparatus is that it allows controlled flushing so that the chemicals can be safely collected without risk of spilling. Yet another benefit is provided by the ability to readily determine the position of the check valve and to manually alter it. 
   Other objects and benefits of the invention will become apparent upon consideration of the following written description, taken together with the accompanying figures. 

   
     DESCRIPTION OF THE FIGURES 
       FIG. 1  is a pictorial representation of a fire truck equipped for dispensing a foam for fire or vapor suppression or extinguishment. 
       FIG. 2  is a perspective view of the components of an eductor assembly in accordance with one embodiment of the invention. 
       FIG. 3  is an exploded view of the eductor assembly depicted in  FIG. 2 . 
       FIG. 4  is a side partial cross-sectional view of the eductor assembly shown in  FIGS. 2-3 . 
       FIG. 5  is an enlarged perspective view of a check valve for use in one embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the invention is thereby intended. It is further understood that the present invention includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the invention as would normally occur to one skilled in the art to which this invention pertains. 
   In accordance with one embodiment of the invention, the eductor valve E shown in  FIG. 1  includes an eductor assembly  10 , as illustrated in  FIG. 2 . This assembly includes a main body  11  having a water inlet  13  and an outlet  15 . A foam inlet  17  intersects the inlet and outlet and is configured to mate with a metering head  20 . The metering head  20  is connected to a suction hose  22  that terminates in a wand  23 . The wand  23  is configured to engage the foam bucket F ( FIG. 1 ) in a conventional manner to draw foam concentrate from the bucket by venturi flow of water through the main body  11 . The metering head  20  includes a mating ring assembly  27  that is configured for quick connect and disconnect to the foam inlet  17 . A proportioning knob  25  can be rotated to adjust the quantity of chemical additive fed through the metering head  20  into the main body  11 . 
   As shown in the detail view of  FIGS. 3 and 4 , the eductor assembly as thus far described is of known construction. For instance, the main body  11  is hollow and defines a plenum  12  ( FIG. 4 ) into which the chemical or foam additive is drawn. A blending tube  35  is situated at the inlet  13  of the body  11 , terminating in a nozzle end  37  within the plenum  12 . A coupling assembly  39  mounts the blending tube  35  within the body and provides an interface for engagement to a fire hose H 1  ( FIG. 1 ). The coupling assembly  39  can be of known construction, including, for instance, a ball bearing mounted threaded coupling ring sized to mate with a 1½ inch fire hose connection. The coupling assembly  39  facilitates ready removal and replacement of the blending tube  35  to substitute a tube sized for different water flow rates. 
   At the outlet  15 , the body  11  mates with a discharge nozzle  42 . The nozzle  42  terminates in a nozzle end  44  within the plenum  12  and is arranged to receive water or a water/chemical mixture when water is supplied under pressure at the inlet  13 . The discharge nozzle  42  includes a coupling end  45  that is configured in a known manner for engagement to a hose H 2  or nozzle N. The discharge nozzle  42  is configured for threaded engagement within the main body  11 . Different discharge nozzles can be provided with differently sized outlets  15  to achieve selectable exit flow rates. In addition, the size of the inlet  13  to the eductor is preferably correlated to the discharge nozzle outlet size to achieve these flow rates. 
   The metering head  20  mates with the additive or foam inlet conduit  47  of the main body  11 . The mating ring assembly  27  can be configured in a known manner to provide a quick connect/disconnect fitting arrangement, as depicted in  FIG. 3 . The mating ring assembly  27  allows a number of metering heads to be engaged to an eductor body depending upon the desired chemical/foam flow rate. 
   The metering head  20  includes a metering body  50  that defines a foam inlet  52 . A fitting assembly  24  connects the suction hose  22  to the metering body in a known manner. The metering body defines a cavity  51  that communicates with the inlet  52 . A proportioning ball  54  resides in and is rotatable within the cavity to align a plurality of differently sized metering orifices  56  with the inlet  52 . In a specific example, the proportioning ball includes five orifices of different sizes and shapes to correspond to different proportional settings for foam consumption, as well as a no flow or “off” setting in which the foam inlet  52  is blocked. In this specific example, the orifices correspond to ¼%, ½%, 1%, 3% and 6% ratios of foam concentrate to water volume. The two smaller settings correspond to small orifice diameters and are typically better suited for Class A foams. The larger settings are typically better suited for Class B foams. 
   The proportioning ball  54  includes a stem  60  that extends through a bore  53  in the metering body. The stem  60  is connected to the proportioning knob  25  to rotate with the knob. In a specific embodiment, the stem  60  extends through a bore  76  in the knob and includes a notch  61  that can interlock with a rib (not shown) within the bore so that the two components rotate together. An O-ring  58  between the proportioning ball  54  and the metering body helps prevent leakage through the bore  53 . As best seen in  FIG. 4 , the metering ball  54  provides a fluid path from the foam inlet  52  through a selected metering orifice  56  and into the cavity  51  of the metering body. The knob preferably includes indicia corresponding to the position of the proportioning ball  54  relative to the foam inlet  52 . 
   When the metering head  20  is mounted on the eductor main body  11 , the metering cavity  51  communicates with the plenum  12  through a passageway  49  defined in the additive inlet conduit  47 . As is known in the art, water flowing from the nozzle end  37  of the blending tube  35  into the nozzle end  44  of the discharge nozzle  42  causes a pressure drop within the plenum. This pressure drop pulls or educts fluid from the foam bucket F through the wand  23 , creating a high speed flow of the chemical additive or foam concentrate. This educed fluid mixes with the water as it is discharged through the discharge nozzle  42 . 
   In order to prevent unwanted backflow of water from the plenum into the metering head  20 , a check valve  30  is provided within the foam inlet conduit  47 , as shown in  FIGS. 3-4 . In a preferred embodiment of the invention, the check valve  30  includes a valve disc  85  that has a diameter greater than the diameter of the passageway  49  defined in the inlet conduit  47 . More specifically, the valve disc  85  is sized to engage a valve seat  49   a  to completely close the passageway  49  to prevent the backflow of water into the inlet conduit and metering head. 
   The check valve  30  includes an arrangement of wings  87  projecting upward from the disc  85  into the passageway  49 . The wings are configured to constrain and guide the check valve so that it translates along the axis of the passageway and so that the valve disc  85  seats flush with the valve seat  49   a  in the main body  11  to close the passageway  49 . The upper surface of the disc  85  can include a resilient seal ring  91  to improve the sealing capability of the check valve. Alternatively, the disc itself can be formed of a resilient material that deforms slightly under fluid pressure to form a tight seal against the main body. In the preferred embodiment, the check valve, including the disc  85  and wings  87 , is formed of a plastic material. 
   The wings  87  have a height calibrated so that the wings remain substantially disposed within the passageway even when the valve disc  85  is in contact with one or both of the nozzle ends  37 ,  44 . Under normal operating conditions, the valve disc  85  will remain trapped between the nozzle ends and the additive inlet as the venturi suction pulls the disc downward and induces chemical fluid flow through the metering head  20 . However, once the venturi suction falls below a threshold value, or when no fluid is flowing through the metering head, the inlet water pressure will push the check valve upward until the valve disc seals against the main body and closes the inlet passageway  49 . This condition will occur in response to a termination of the flow downstream, such as when the nozzle N is shut off or when the hose H 2  is kinked. Under normal operating conditions, the check valve will remain closed (preventing backflow into the metering head) when the fire hose nozzle N ( FIG. 1 ) is off, since there is no flow through the eductor to produce venturi suction. However, once the nozzle is opened, water flow commences and the check valve opens to draw the chemical additive or foam concentrate into the plenum  12 . 
   As thus far described, the check valve  30  presents the same problem experienced by the prior eductor valves with respect to cleaning the eductor assembly  10 . In order to alleviate this problem, the present invention contemplates a system for holding the check valve  30  in an open position—i.e., with the valve disc  30  unseated or offset from the eductor body, leaving the passageway  49  substantially unobstructed even under water pressure. In order to achieve this objective, the preferred embodiment of the invention includes a back flush pin  65  ( FIGS. 3-4 ) that bears against a contact hub  89  defined at the peak of the wings  87  (see  FIG. 5 ). The pin  65  is slidably disposed within a passageway  62  defined in the stem  60  of the proportioning ball  54 . Thus, while the proportioning ball is fixed in translation along the cavity  51 , the pin  65  is free to move vertically downward into contact with the hub  89  of the check valve  30  to push the valve downward away from the passageway  49 . For the purposes of the present disclosure, the “vertical” direction is defined as along the axis of the metering body  50 , and “downward” is movement toward the eductor body  11 . 
   In the illustrated embodiment, the proportioning knob  25  defines a recess  75  within the metering body  50  that communicates with the bore  76 . As explained above, the stem  60  of the proportioning ball  54  interlocks with the knob  25  within this bore. O-ring  58  provides a fluid tight seal between stem  60  and metering body  50 . A cross pin  69  passes through a bore  68  ( FIG. 3 ) in the back flush pin to set an upper limit for the travel of the pin. An O-ring  73  is mounted within a seal ring groove  74  in the pin  65  to provide a fluid-tight seal between the pin and the passageway  62  as the pin translates within the bore. 
   A push button  79  is threaded onto the end of the back flush pin  65 , trapping a return spring  77  within the recess  75 . The top end of the back flush pin  65  defines an internally threaded bore  71  to receive a locking screw  81  for fixing the back flush pin  65  to the push button  79 . The push button  79  is accessible above the proportioning knob  25  so that the button can be manually depressed when it is desired to clean the eductor assembly  10 . When the button is pushed, the back flush pin  65  is driven downward to push against the check valve  30 . With the button  79  fully depressed, the check valve is clear of the passageway, creating a back flush flow path from the water inlet  13  through the eductor assembly  10 . The eductor assembly does not need to be disconnected from the water supply, but instead remains connected as it was during the firefighting action. Water from the pumping unit P of the fire truck T, through fire hose H 1 , can be supplied directly to the eductor assembly to flush all of the chemicals out of the assembly components. The flushed liquid is discharged through the suction hose  22  and wand  23 , which means that the wand can be placed within an appropriate receptacle to receive the back flush liquid waste. 
   In a typically cleaning process after use, the wand is removed from the foam supply F and optionally placed in a discharge container. The water flow through the supply hose H 1  is significantly reduced from the typical fire-fighting water pressure and flow rate. In a specific embodiment, the back flush water pressure is reduced to below 45 psi (as compared to a typical operating pressure of about 200 psi). With the nozzle N closed (to prevent water flow through the hose H 2 ), the back flush button  79  is depressed to release the check valve  30  and allow the water to flow back through the metering body  50 , suction hose  22  and suction wand  23 . The proportioning knob  25  rotated as the water continues to back flush so that water passes through every foam metering orifice  56  in the proportioning ball  54 . Back flushing continues at each metering setting until there is no visible foam in the flush water. At that point, the water supply is stopped and the metering head  20  is removed from the main body  11  by manipulating the mating ring assembly  27 . The residual water within the metering body  50  and main body  11  can be gravity drained. 
   Under certain conditions, the check valve  30  may not properly engage the valve seat  49   a  ( FIG. 4 ) to fully close the passageway  49 . In order to ensure a proper sealing engagement, the check valve  30  may be provided with a return element  100 , as shown in  FIG. 5 . The return element  100  includes a ring  102  that defines an opening that is preferably larger than the flow path through the outlet  15  so as not to impede the flow of fluid through the eductor  10 . A base  104  is provided on the ring to bear against the wall of the plenum  12 . 
   The element  100  further includes an elongated stem  106  projecting upward from the ring  102 . The stem passes through a bore  107  defined in the hub  89  of the check valve  30 . In the preferred embodiment, the stem  106  is long enough to pass completely through the check valve bore  107 . 
   The ring  102  is formed of a corrosion resistant material that is flexible and resilient. In a preferred embodiment, the ring is formed of a thermoplastic elastomer, such as ALCRYN®. When the back flush pin  65  is depressed, the check valve  30  bears against the ring  102  to deform the ring. In a preferred embodiment, the ring  102  is circular in its installed shape, and becomes generally oval as it is deformed under pressure from downward movement of the check valve. The return element is configured so that it can be deformed when the check valve opens under venturi pressure. In the preferred embodiment, the opening force due to venturi pressure is about ½ ounce. In addition, when the back flush pin  65  is depressed, the check valve  30  bears against the ring  102  to deform the ring. When the back flush pin is release, the ring  102  seeks its neutral shape so that it springs back to its original oval shape. In so doing, the ring  102  pushes the check valve  30  upward into engagement with the valve seat  49   a . Moreover, as the ring  102  pushes the valve upward, the stem  106  keeps the check valve in proper alignment so the disc  85  bears fully against the valve seat. 
   In certain embodiments, the ring  102  is sized so that in its neutral or un-deformed shape the base  104  contacts the wall of the plenum  12  while the top of the ring is also in contact with the disc  85  of the check valve. Alternatively, the ring may be sized so that the top of the ring  102  is slightly offset from the disc  85  so as not to impede the downward movement of the check valve under venturi pressure only. However, in this alternative, the ring is sized so that the ring may be deformed when the back flush pin  65  is fully depressed. 
   In the preferred embodiment, the return element is in the form of a ring so that the return spring force produced by the element  100  will be directed substantially along the axis of the elongated stem  106 . Other forms of the return element may be contemplated provided that the element does not interfere with the flow of fluid through the eductor and that the element operates to accurately return the check valve to the valve seat. For example, in lieu of the complete ring  102 , the return element  100  may include a pair of resilient legs extending downward and outward from the check valve to contact the side walls of the plenum  12 . 
   The internal components of the eductor assembly  10  are formed of materials that are compatible with the types of chemical additives or foam concentrates flowing through the assembly. The component materials are preferably non-reactive with the chemicals and resistant to the corrosive effects of these chemicals. In a specific embodiment, the wand  23  and the back flush pin  65 , and ancillary hardware are formed of stainless steel, as is the back flush pin  65 . On the other hand, the blending tube  35  can be formed of a high density plastic. Preferably, all the other components are formed of a metal, such as aluminum that has been hard anodized. The proportioning ball  54  and integral stem  60  are also preferably formed of a high density plastic, which beneficially provides a smooth sliding surface for the O-ring  73  as the back flush pin  65  reciprocates within the passageway  62 . 
   While the invention has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the invention are desired to be protected. 
   For instance, while the illustrated embodiment of the check valve contemplates a disc valve, other one-way valves can be utilized. For instance, a ball valve can be situated within the plenum  12  so that the ball seals against the passageway  49 . A cage may contain the ball in alignment with the passageway. The same back flush pin  65  described above can be arranged to bear against the check ball to prevent it from seating over the passageway. In this instance, the pin  65  and inlet conduit  47  would be commensurately sized so that the pin is clear of the ball valve during normal use but is capable of extension into contact with the ball when it is desired to back flush the eductor assembly. 
   Similarly, the check valve can be a resilient valve, such as a duckbill valve. With this type of valve, the working end of the back flush pin can be modified to hold open the duckbill when the pin is pushed through the valve. 
   As a further example, the illustrated embodiment contemplates a push button feature for actuating the back flush pin  65 . Other means and mechanisms for actuating the pin are contemplated by the present invention. For instance, a pivoting or sliding lever can be integrated into the side wall of the metering body so that manipulation of the lever will push the check valve to its open position. Non-contact actuation is also contemplated, such as a magnetically coupled valve.