Abstract:
A dispensing valve assembly with a housing having a plurality of inlet passageways connectable at a respective upstream end to a respective supply source. Each inlet passageway is in communication with a pressure responsive valve element. The valve element is biased to abut a discharge valve seat in a closed position about an upstream end of an outlet passage. The valve element is moveable to an open position when pressure in its respective inlet passageway exceeds a predetermined value. Each outlet passage is in fluid communication with a common dispensing outlet.

Description:
TECHNICAL FIELD 
     This invention relates to a backflow prevention valve and more particularly to a dispensing valve with backflow prevention. 
     BACKGROUND OF THE INVENTION 
     Vending machines have long been popular for dispensing food snacks because of the convenience. At first, vending machines were limited to dispensing packaged goods but have now been developed for dispensing goods that are prepared at the vending machine such as hot coffee, and chocolate. The trend continues to provide vending machines that mix and make the food product on demand rather than merely dispensing prepared and stored products. By mixing and making the product at the vending machine, a wider selection of flavors and choices are possible than from a vending machine that stores limited inventory of prepared products. 
     When such products are made on demand, valves need to control the addition of various flavors to the base ingredient. For example, flavored syrup added to a base ice-cream is usually provided in liquid form. Displacement pumps and control valves need to control the addition of such different flavored syrups. Back flow prevention valves are also needed to prevent air from back flowing into the supply line to contaminate the supply. Previous valves were overly complex and often resulted in intermixing of different flavors. Known selector valves that rotate from one inlet to another and have a null or off position tend to get gummed up and stuck when viscous sugary fluids are used as the sugar crystallizes in the valve. 
     What is needed is a dispensing valve that can control the flow of multiple supplies such as different flavors and be closeable and provide for a quick cleaning of the common downstream passages that receive the flow of a different supply with each dispensing. What is also needed is a valve capable of supplying a plurality of liquids with no rotary selector valve that provides for backflow prevention for preventing crystallization of any liquid syrups. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention, a dispensing valve assembly with back flow protection has a housing having a plurality of inlet passageways connectable at a respective upstream end to a respective supply source. Each inlet passageway is in communication with a pressure responsive valve element. Each valve element is biased to abut a discharge valve seat in a closed position about an upstream end of an outlet passage. The valve element is moveable to an open position when pressure in the respective inlet passageway exceeds a predetermined value. Each outlet passage is in fluid communication with a common dispensing outlet. 
     In one embodiment, the valve element is in the form of a diaphragm. The inlet passageways terminate at and are in fluid communication with a pressure chamber that seats the diaphragm. The diaphragm has its outer periphery mounted between two seating shoulders of the housing. The pressure chamber also seats the discharge valve seat. It is further desirable that the housing is constructed such that the common dispensing outlet is at an axial end of the housing. Desirably, the plurality of inlet passageways are circumferentially spaced about the common dispensing outlet and radially extend outwardly transversely therefrom. The distances from the common dispensing outlet to the respective upstream ends of the outlet passages are approximately equal. 
     In one embodiment, pairs of pressure chambers are circumferentially spaced about in the housing with each pressure chamber in a respective pair being axially spaced from each other with a pair of passageways interposed between each of the pairs of axially spaced pressure chambers. 
     In accordance with another aspect of the invention, a dispensing valve with back flow prevention has a housing with a common dispensing outlet. A plurality of diaphragm backflow prevention valves has a discharge outlet in fluid communication with the common dispensing outlet and an inlet in communication with separate supply ports. Preferably, the housing includes a manifold plate, a spring cup retainer plate on each axial side of the manifold plate, and a cup plate that abuts a second side of each spring cup retainer plate. The common dispensing passage axially extending through the plates. The spring cup retainer plate houses a plurality of springs and spring cups. Each diaphragm back flow prevention valve includes the spring cup abutting against a respective diaphragm with the spring biasing the spring cup and diaphragm to a closed position against a discharge outlet seat. Each diaphragm is seated about its periphery between the spring cup retainer plate and the manifold plate. The manifold plate has a respective inlet passage in continuous communication with the diaphragm about the discharge outlet seat. The common dispensing passage is in selective fluid communication with the respective inlet passage when the diaphragm is in an open position with respect to the discharge outlet seat. 
     In one embodiment, the common dispensing outlet passage is at a radial center of the housing. The diaphragm back flow prevention valves are circumferentially spaced about the common dispensing outlet passage and being equidistant from the common dispensing outlet passage. The inlet passages are all at the same axial level on the manifold plate. 
     In accordance with another aspect of the invention, a back flow prevention valve has a housing with an inlet passageway terminating at a pressure chamber. A diaphragm valve element is mounted in the pressure chamber and has its periphery sealingly mounted between opposing seating shoulders in the housing. The diaphragm valve element is biased to close on a discharge outlet seat but openable away from the discharge outlet seat if pressure in the pressure chamber from the inlet passage overcomes the diaphragm valve bias to the closed position. Preferably, the housing includes a manifold plate and closure plate with the opposing seating shoulders being on the manifold plate and the closure plate. The closure plate has a bore for a spring cup retainer and a spring which abuts and biases the diaphragm to the closed position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference now is made to the accompanying drawings in which: 
         FIG. 1  is a perspective view of a dispensing valve assembly in accordance with one embodiment of the invention; 
         FIG. 2  is a top plan view of the valve shown in  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of the valve shown in  FIG. 1 ; 
         FIG. 4  is a cross-sectional view taken along lines  4 - 4  shown in  FIG. 2 ; 
         FIG. 5  is a cross-sectional view taken along lines  5 - 5  shown in  FIG. 2 ; 
         FIG. 6  is an enlarged fragmentary plan view of the manifold plate shown in  FIG. 3 ; and 
         FIG. 7  illustrates another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIGS. 1 and 2 , a dispensing valve assembly  10  for dispensing a selection such as different flavors has a housing  12 . The housing  12  has a generally polygonal shape with twelve sides but other shapes such as polygons with a different number of sides or a cylindrical shape are also acceptable. The housing  12  has a sandwich construction with a central manifold plate  14  and spring cup retainer plates  16  mounted on each axial end of the manifold plate  14 . Cap plates  18  are then mounted on the outer ends of the spring cup retainers  16 . 
     A plurality of supply inlets  20  and a plurality of flush inlets  22  are circumferentially positioned about the manifold plate  14 . A dispensing outlet  24  as shown in  FIGS. 3-5  is located centrally on the bottom side  25  of the housing  12 . An additional flush inlet  27  is located on the top side  29  of the housing. Preferably two supply inlets  20  are on a side  26  and a single flush inlet  22  is on alternating sides  28  of the housing  12 . 
     Referring now to  FIG. 4 , each inlet  20  has a supply passage  30  that leads to a pressure chamber  32  in the manifold plate. The pressure chambers  32  are at each end  34  of the manifold plate  12  and are also circumferentially arranged within the manifold plate. The chambers  32  at each end  34  are axially aligned. As shown in  FIGS. 4 and 2 , spring cup retainer plates  16  also have circumferentially spaced bores  38  therein aligned with the chambers  32 . The chambers  32  have a smaller diameter such that a seating edge  42  is about chamber and seals a diaphragm  40  against a corresponding rim  44  in cup retainer plate  16 . 
     The sandwich construction of the housing  12  is secured by threaded fasteners  46  which tighten the cap plates  18 , cup retainer plates  16  and manifold plate  14  into a secure assembly. The periphery of the diaphragm  40  is engaged by the cup retainer and manifold plates  16 ,  14  in a sealed manner against leakage. The cap plates  18  have vent grooves  39  to allow venting the coil spring side of the cups  46  as the cups move within bores  38  to alleviate any resisting pressure build up. 
     Referring to  FIGS. 4 and 5 , the diaphragm  40  is flexible enough to move between an open position as illustrated by the upper right diaphragm of each figure and a closed position as indicated by the other three diaphragms. As shown, in the closed position, the diaphragm abuts against a raised annular valve outlet seat  50  that has an outlet  52  therethrough. The retainer cups  46  are spring biased by coil springs  48  which move the diaphragm to the closed position against the valve seat  50 . However, when pressure is exerted in passage  30 , the pressure is communicated to pressure chamber  32  to act on the diaphragm  40  with sufficient force to move the diaphragm to an open position against the spring bias force exerted through the spring cups  46  by the coil springs  48 . The opening of the diaphragm  40  allows fluid to then pass through the open outlet  52  and into outlet passage  54  which radially extends to the central axial dispensing outlet  24 . 
     As shown in  FIGS. 5 and 6 , each pressure chamber  32  has the outlet passage  54  centrally located with respect to the pressure chamber  32 . As shown in  FIGS. 4 and 6 , the supply inlets  20  terminate in open communication with pressure chamber  32  through an off center aperture  58 . 
     In operation, each supply inlet  20  is connected to a different supply source, for example a different flavored syrup for ice cream that is connected to a conventional displacement pump (not shown). The flush inlets  22  are all connected to an actuable air pressure supply. When a flavor is selected, the appropriate pump is turned on which supplies the selected syrup through the supply inlet  20  and into pressure chamber  32  which opens the diaphragm  40  and passes through the outlet passage  54  and to dispensing outlet  24 . Air pressure is turned on and flows through inlets  22  and  27  to help assist the movement of the syrup. 
     When the pump for supply inlet  20  is turned off, the diaphragm closes due to the bias of spring  48 . Increased air pressure then passes through inlets  22  and  27  and to the outlet passage  54  to flush clean the lines of any syrup. The coil spring  48  has sufficient force to resist the force of the air pressure from undesirably opening the diaphragm  40 . 
     The valve according the embodiment shown in  FIGS. 1-6  can also be used with a plurality of gravity fed supplies all located above the valve and preferably at the same height. Secondly, preferably the short outlet passages  54  all have the same length which improves the timing of the dispensing of the flavored syrup. The air pressure assist during dispensing is particularly helpful for flavors with a greater viscosity such as mocha or chocolate. The higher air pressure flush after the dispensing of a syrup flavor also is improved due to the short distance needed to flush each flavor. The diaphragm valve remains closed during the high pressure flush to prevent air from entering into the pressure chamber  32  or the supply inlets  20 . Air is particularly undesirable for sugary supplies such as flavored syrups because entry of air will cause the syrup sugars to crystallize within the inlet passage  30 . 
     While the above described embodiment with a rotary shaped housing assembly has certain advantages, the diaphragm valve construction of the invention can be applied to other shaped housing valve assemblies such as the linear valve  60  shown in  FIG. 7 . In this embodiment the internal positioned pressure chamber  32 , diaphragm, spring cups and coil springs all have the same construction and operate in the same fashion as in the first embodiment. The most substantial difference is that the pressure chambers are linearly arranged and the supply inlets  20  have different effective distances from each outlet  52  to the dispensing outlet  24  for each pressure chamber  32 . 
     Other variations and modifications are possible without departing from the scope and spirit of the present invention as defined by the appended claims.