Abstract:
An automatic shut-off valve suitable for watering of batteries is disclosed. The valve is formed by a chamber having an inlet and an outlet. A seat surrounds the outlet. A spring biased piston within the cylinder is movable into and out of sealing engagement with the seat to open and close the valve. A flow deflecting surface is positioned between the inlet and the piston. Water flow is directed around the piston to eliminate drag that would force the piston into engagement with the seat. A second deflector surface directs flow against the piston to bias it open. An actuator cup, fed by a nozzle extending from the outlet, draws the piston into engagement with the seat when the cup is sealed by engagement with the electrolyte surface. The valve may also employ a float actuator connected to the piston.

Description:
FIELD OF THE INVENTION 
     This invention relates to automatic shut-off valves for controlling liquid flow to batteries for aqueous electrolyte replenishment. 
     BACKGROUND OF THE INVENTION 
     Automatic watering systems for batteries employ independent valves in each cell of the battery to control the flow of water into the cells for replenishing the aqueous electrolyte that is lost during battery charging. Such batteries typically comprise a casing containing a number of individual cells, each holding an electrolyte solution in which plates are immersed. Examples of batteries having an aqueous electrolyte include nickel-cadmium batteries or lead-acid type batteries. Oxygen and hydrogen gases are produced during charging as a result of electrolysis of the water. The electrolysis causes a loss of water from the electrolyte solution, and, as a result, such batteries require periodic replenishment of the lost water. 
     It is advantageous for the valves to operate effectively across a wide range of water pressures. They should be sensitive enough to operate at low pressures of about 4 psi, but stable enough to operate at high pressures of about 50 psi. 
     Valves currently in use for battery watering may be classified in one of two categories, i.e., hydrostatic or hydrodynamic. Hydrostatic valves typically rely on a float buoyed by the electrolyte to open and close the valve, while hydrodynamic valves rely on a venturi-based mechanism for actuation. Both types of valves can employ a positive stop configuration. Positive stop valves have a closing member, typically a piston, that moves within a pressurized chamber through which the water or other fluid flows. Upon actuation by the float or venturi mechanism, the piston engages with or disengages from a seat within the chamber to close and open the valve. In the positive stop configuration, the piston moves into the closed position with the water flow or pressure. Positive stop valves, be they hydrostatic or hydrodynamic, suffer from the same disadvantage, in that hydrodynamic drag on the piston engendered as water flows through the valve can cause the piston to close the valve prematurely in response to the water flow or pressure, and not in response to the fluid level as intended. Positive stop valves in particular, tend to close prematurely when operated at high pressures which generate high drag forces on the piston and its actuating mechanism. This characteristic limits the range over which positive stop valves may be effectively employed to the lower pressures. There is clearly a need for a valve that can operate over a large pressure range, encompassing both high and low pressures and flow rates, without premature closing due to high hydrodynamic drag. 
     SUMMARY OF THE INVENTION 
     The invention concerns a valve for controlling fluid flow, and particularly positive stop valves operable over a wide range of pressures and flow rates useful for automatic battery watering. The valve according to the invention comprises a chamber having a fluid inlet and a fluid outlet. A valve seat surrounds the outlet. A valve closing member is positioned within the chamber. The closing member is movable between a closed configuration in sealing engagement with the seat, thereby stopping flow of the fluid through the outlet, and an open position in spaced relation away from the seat. A biasing member is engaged with the closing member. The biasing member biases the closing member into the open configuration. An actuator is engaged with the closing member. The actuator is adapted to apply a force moving the closing member into the closed configuration. A first deflector surface is positioned within the chamber between the inlet and the closing member. The first deflector surface deflects the flow of the fluid around the closing member to prevent flow of the fluid from engaging and moving the closing member into the closed configuration. 
     The valve according to the invention may also include a second deflector surface positioned within the chamber downstream of the valve closing member. The second deflector surface deflects the flow of the fluid against the closing member so as to further bias the closing member into the open configuration. Preferably the second deflector surface is positioned surrounding the seat in facing relation with the closing member. 
     In one hydrodynamic embodiment of the valve, the actuator comprises a cup having a first end positioned outside of the chamber adjacent to the outlet. A second, open end of the cup is positioned distally to the outlet. A nozzle extends from the outlet into the cup through an opening in the first end. The cup is slidably movable along the nozzle. A tether having a first end attached to the cup extends through the nozzle. A second end of the tether is attached to the closing member. Flow of fluid through the nozzle creates a partial vacuum within the cup when the open end engages a fluid surface. The vacuum draw the cup along the nozzle away from the chamber, and the tether draws the closing member into the closed configuration in sealing engagement with the seat, thereby halting the flow of fluid through the chamber. 
     In another hydrostatic embodiment of the valve, the actuating member comprises a float positioned outside of the chamber. A link member attaches the float to the closing member. The float, when buoyantly supported by the electrolyte or other fluid, applies a force, by virtue of its buoyancy, to the closing member through the link member. The force moves the closing member into the closed configuration. 
     The invention also includes a battery incorporating a valve as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of a valve according to the invention; 
         FIGS. 2 and 3  are longitudinal sectional views taken at line  2 - 2  of  FIG. 1  depicting a portion of a battery cell using the valve shown in  FIG. 1 ; 
         FIG. 4  is a cross-sectional view taken at line  4 - 4  of  FIG. 2 ; and 
         FIGS. 5 and 6  are longitudinal sectional views of a portion of a battery cell using another embodiment of a valve according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows an embodiment of a hydrodynamic valve  10  according to the invention. Valve  10  comprises a chamber  12 , preferably in the form of an elongated cylinder. A cap  14  is positioned at one end of chamber  12 , the cap having one or more fluid inlets in the form of slots  16  allowing fluid flow into the chamber. A fluid outlet  18  is positioned at the opposite end of chamber  12 . A valve seat  20  surrounds the outlet, and as shown in  FIG. 2 , a nozzle  22  extends from the outlet. A valve closing member in the form of a piston  24  is positioned within the chamber  12 . Piston  24  is slidably movable within chamber  12  between an open position (shown in  FIG. 2 ) where it is in spaced relation away from seat  20 , and a closed position (see  FIG. 3 ) where it is engaged in sealing relation with the seat. A biasing member, preferably a spring  26 , is attached between the cap  14  and the piston. Spring  26  biases the piston into the open configuration. An actuator, preferably in the form of an elongated cylindrical cup  28 , is located at the outlet end of the chamber  12 . Cup  28  is coaxially aligned with chamber  12  and has an opening  30  in one end through which nozzle  22  passes. The opposite end  32  of cup  28  is open. A tether  34  has one end  36  attached to the cup  28 , preferably near the open end  32 . The other end  38  is attached to the piston  24 . As described in detail below, the cup is slidably movable along the nozzle  22  and acts as an actuator to pull the piston from the open to the closed position against the biasing action of spring  26  through the tether  34 . 
     As shown in  FIG. 1 , a deflector surface  40  is positioned within the chamber  12  between the inlet slots  16  and the outlet  18 . Deflector surface  40  may have any practical shape suitable for a particular valve design, and in this embodiment, the deflector surface preferably comprises an elongated cylinder  42  positioned within chamber  12  and extending from cap  14 . Inner cylinder  42  surrounds the piston  24  and preferably is coaxially aligned with the outer cylinder forming the chamber  12 . As shown in  FIGS. 2 and 4 , this configuration produces an annular duct  44  providing fluid communication between the inlet slots  16  and the outlet  18 . The deflector surface  40  functions to deflect the flow of fluid around the piston  24  and thereby prevent hydrodynamic drag on the piston by high pressure/high flow rate fluid flows through chamber  12 . Thus, there is less tendency for the piston to close prematurely in response to the fluid pressure or flow. 
     As shown in  FIG. 2 , a second deflector surface  46  is positioned downstream of the piston  24 . In this embodiment, the second deflector surface is formed by the end  48  of chamber  12  that surrounds seat  20 . The surface may be flat as shown or may be curved or otherwise shaped so as to provide hydrodynamic enhancements to the fluid flow. The second deflector surface  46  directs a portion of the fluid flow through the chamber against the piston  24  to provide dynamic fluid biasing of the piston as described below. 
     Operation of the valve  10  is described with reference to  FIGS. 2 and 3 . In  FIG. 2 , valve  10  is shown positioned within a battery cell  50  having an aqueous electrolyte  52 . A fitting  54  connected to a water source (not shown) is attachable to the valve  10  and supplies water  56  to the cell through valve. Water  56  flows into the valve through inlet slots  16  and through the annular duct  44 , the water being deflected around the piston  24  by the surrounding deflector surface  40  (cylinder  42 ). The water  56  impinges on the second deflector surface  46  at the end  48  of chamber  12  and a portion of the flow  58  is deflected toward the piston  24 . The remainder of the flow  60  exits through nozzle  22  into cup  28  where it enters battery cell  50  to replenish water lost to electrolysis during battery charging. 
     The water flow slows as it exits the annular duct  44  due to the sudden increase in cross sectional area of the chamber  12 . By Bernoulli&#39;s principle, this causes a region of higher pressure to form beneath the piston. The higher pressure acts to augment the biasing force of spring  26 . The greater the rate of flow, the higher the pressure in this region. Furthermore, the portion of the flow  58  that is deflected by the second deflector surface  46  experiences a change in momentum that directs the flow portion  58  against the piston, further biasing it in the open position. This dynamic biasing force also increases with increasing pressure and flow rate. The effect of the pressure and flow impingement on the piston is equivalent to having a higher biasing force on the piston at high pressures and flow rates when the pressure and momentum changes will be highest, but a lower biasing force on the piston, due mainly only to the spring  26 , during low pressure and low flow rates. This renders the valve very sensitive at low pressure and flow rates and, in conjunction with the effect of the deflector surface  40 , provides great stability preventing premature closure of the valve at high pressures and flow rates. Laboratory test results show that the ratio of high to low pressure that the valve can accommodate increases from about 6 to 1 to about 20 to 1, better than a three fold increase in the pressure range. 
     The portion  60  of the water flow that exits through nozzle  22  works in conjunction with the actuator cup  28  to close the valve. Water  60  fills the cell  50  and the level of the electrolyte  52  rises until it contacts and seals the open end  32  of the cup. Continued flow of water through nozzle  22  draws a vacuum within the cup  28 . This allows gas pressure on the outside surface  28   a  of the closed end of cup  28  to force the cup downwardly into the electrolyte as shown in  FIG. 3 . Motion of the cup  28  pulls the tether  34 , drawing the piston  24  into engagement with the seat  20  thereby halting the flow of water through the valve  10 . 
       FIGS. 5 and 6  show an example of a hydrostatic valve embodiment  62  according to the invention. Valve  62  is mounted in fluid communication with a battery cell  50  and a conduit  64  connectable to a water source (not shown). Valve  62  comprises a chamber  66  having an inlet  68  connected to the conduit  64  and an outlet  70  in fluid communication with cell  50 . A seat  72  surrounds the outlet  70 . A valve closing member, preferably a piston  74  is movably mounted within the chamber. The piston may move between an open position in spaced relation away from seat  72  ( FIG. 5 ), and a closed position wherein the piston is engaged in sealing relation with the seat ( FIG. 6 ). Preferably, the piston  74  slides within a cylinder  76  positioned between the inlet  68  and the outlet  70 . The end  78  of cylinder  76  that faces the inlet is closed, thus forming a deflector surface that deflects the water flow  80  around the piston and prevents the generation of hydrodynamic drag on the piston that would otherwise tend to force it into the closed position regardless of the fluid level within the cell  50 . 
     A second deflector surface  73  is positioned within chamber  66 . Deflector surface  73  faces piston  74  and, as described previously, deflects a portion of the water flow  80  against the piston to augment the biasing of the piston in the open position shown. Again, deflector surface  73  may be shaped to enhance the fluid flow against the piston. 
     An actuator in the form of a float  82  is buoyantly supportable by the electrolyte  52  within cell  50 . Float  82  is connected to piston  74  through a pivoting link member  84 . Weight of the float  82  acting through the link member  84  applies a force to piston  74  pushing it away from engagement with seat  72 , opening the valve  62  and allowing water  80  to flow into the cell  50 . Because of the presence of the deflecting surface  78  the float does not have to push the piston  74  against the flow of water through the chamber  68 , enabling the float to be lighter and thus more responsive that if it had to open the valve against the water flow. 
     As shown in  FIG. 6 , when the electrolyte  52  reaches the desired level the float  82  is buoyantly supported and exerts a force on piston  74  through link member  84  that closes the valve by engaging the piston  74  with the seat  72 , thereby halting the flow of water to the cell. 
     Positive stop valves according to the invention, whether hydrodynamic or hydrostatic in design, can be operated over greater pressure ranges more reliably due to the presence of the deflector surface that deflects the flow of fluid around the valve closing member, thereby virtually eliminating hydrodynamic drag on the piston that would otherwise tend to close the valve regardless of the desired fluid level. In hydrodynamic valves, the addition of a second deflector surface downstream of the valve closing member provides further dynamic biasing augmenting the forces that keep the valve in the open position. These forces are greatest when they are most needed, i.e., under high pressure and high flow rates that would otherwise engender premature valve closing.