Abstract:
A positive control fill valve for dispensing fillable materials which eliminates dripping, splashing, sloshing and contamination of fill materials is provided with a fluid activiated fill piston having a substantially cylindrical piston sealing head cooperating with a tapered seat for receiving the piston filling head in combination with a leak detection port for positively detecting potential leaks between the fluid activated fill piston and the product fill chamber. The novel fill valve preferably includes at one end, a pneumatic means for opening and closing the fill valve piston and at the other end, a fill chamber having a tapered seat for positively seating the sealing head of the pneumatically activated piston with a product inlet means disposed therebetween and a two seal arrangement separating the pneumatic chamber at one end from the product dispensing chamber at the other end and a leak detection port disposed intermediate the two seals. The novel fill valve assembly provides rapid and positive control in dispensing fill materials of various viscosities and densities, while at the same time, preventing a contamination of fill materials with fluid activation fluid by employing a leak detection port for immediately detecting and identifying the position of a potentially defective seal.

Description:
This application claims the benefit of No. 60/165,788, filed Nov. 16, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to a novel positive control fill valve, particularly suited for application in the dispensing of flowable materials in hygienic or sanitary dispensing operations, such as used in the food, medical and pharmaceutical industries. More particularly, the novel fill valve assembly provides for the positive control over the dispensing of a wide range of liquids having varying degrees of viscosity by utilizing a positive control valve activated by a pneumatically activated piston, having a substantially cylindrical shaped sealing head in combination with a tapered cylinder for providing a positive control over the dispensation of fluids dispensed through the fill assembly. 
     The novel fill assembly includes at one end, a reservoir for activating the positive controlled product dispensing piston and at the other end, an outlet having a tapered sealing seat for dispensing the product and seating the sealing head of the product dispensing piston. A leak detection port for positively identifying seal failure is disposed between a positive seal means having a first seal disposed between the leak detection port and the reservoir for activating the product dispensing piston and a second seal disposed intermediate the leak detection port and the product dispensing outlet. The novel hygienic and sanitary fill valve assembly further includes flanges for connecting the reservoir which in the best mode is a chamber for activating the product dispensation piston with a corresponding flange around the bottom of the dispensation chamber to allow the novel fill valve assembly to be cleaned or sterilized in place, as is preferred in the pharmaceutical, medical and food processing industries. 
     The flanges for connecting the product dispensing outlet from the pneumatic activation chamber, as well as for the cleaning in place mechanism, provide a hygienic and sanitary environment, which allows for effective cleaning of the valve, piston and internal components of the novel fill valve assembly to prevent the build up of contaminants in threads, seams, welds, or other surface irregularities in the novel fill valve assembly. The novel fill valve assembly is typically constructed of high quality stainless steel or other material that is compatible with food processing equipment. 
     2. Description of Related Prior Art 
     The prior art includes many types of product dispensation valves for dispensing product. Many of these prior art valves do not include a tapered sealing seat in combination with a pneumatically activated piston for providing a positive shut-off of viscous fill materials. Many of the prior art valves result in a dripping or sloshing of a fill material around the filled container. None of the prior art includes a tapered seat in combination with a substantially cylindrical sealing head for positively shutting off the flow of dispensed material by seating the substantially cylindrical head of a product dispensing piston in a tapered seat when the valve is in the closed position and the placement of the sealing head is in the flow path of the dispensed product to circulate the fill material around the sealing head to prevent sloshing of the fill material during dispensation. Further, none of the known prior art dispensing valves includes a novel leak detection port disposed intermediate the ends of the product dispensing piston in combination with a novel positive seal means which includes, at one end, a seal between the piston activation chamber and the leak detection port and a second seal disposed between the product dispensation chamber and the leak detection port so that failure of the seal at either side of the leak detection port results in a positive identification of the exact portion of the seal that is damaged. 
     The best known prior art fill assembly valves typically employed in the food processing industry are not known to have a leak detection port in combination with a piston with a tapered seat and nozzle combination for positively dispensing liquid products without sloshing or dripping. 
     The best known fill valve assemblies uncovered in the course of the prior art search is Copas, et al. U.S. Pat. No. 4,518,021 which discloses a similar type of flanged fill machine having a product dispensing nozzle with a side inlet. The nozzle includes a tapered nozzle end and product,dispensing piston in the up position does not remain in the flow to prevent sloshing and does not employ a sealing head forming a dual function. Further Copas, et al. does not contain a leak detection port or a pneumatic means to positively control the dispensation of the product or provide a system for assuring that the fluid activation of the product dispensing piston would not contaminate the fill product material to assure the highest quality of product dispensing and handling. 
     The prior art includes also a variety of leak detection ports for a variety of applications. Leak detection ports have been provided for gas flow applications such as Matthews U.S. Pat. No. 3,999,932, Kurtz, et al U.S. Pat. No. 4,648,874 and Steeper U.S. Pat. No. 4,888,979. None of these prior art patents teach or suggest the utilization of a leak detection port in a filling machine such as Copas, et al. U.S. Pat. No. 4,518,021. Further, none of the known prior art leak detection port devices utilizes a double seal arrangement around a piston to identify the failure of a seal to prevent the contamination of a fill product. The closest of the known leak detection port apparatus is Steeper U.S. Pat. No. 4,888,979, which pertains to leak detection across an O-ring sealing a flanged connection. This leak detection provided in Steeper U.S. Pat. No. 4,888,979 pertains to leak detection radially along the O-ring as opposed to axially as is provided in accordance with the novel fill valve assembly of the invention. 
     SUMMARY OF THE INVENTION 
     A novel sanitary fill valve assembly providing positive control over dispensed liquids and preventing contamination between the dispensed liquids and the means for activation of the piston is provided by a novel leak detection port for providing the positive identification of seal failure before contamination of a dispensed product. The novel hygienic fill valve assembly includes, at one end, a fluid chamber for providing the positive control over a piston for providing for the dispensation of a fill material through a product outlet chamber to a fill material outlet or nozzle disposed at the other end for dispensing the fill product and a product inlet port disposed intermediate the fluid chamber and the product dispensation outlet or nozzle. A positively controlled fluid activated piston is disposed intermediate the fluid chamber and the product outlet chamber, which includes a substantially cylindrical sealing head, which provides positive sealing by mating with a tapered sealing seat in the product outlet chamber. In the best mode of the invention, the fluid chamber for activating the product dispensing piston is pneumatically controlled. 
     A first seal is provided intermediate a leak detection port and the fluid chamber and a second seal is provided intermediate the leak detection port and the product outlet chamber to provide positive identification of seal failure and to prevent contamination of the product with air or fluids which activate the fluid control product dispensing piston. The leak detection port in combination with different fluids, i.e., gas and liquid or fluids of different color, serves to positively identify the defective seal and provide a failsafe seal system to prevent contamination. In the preferred application of the invention, the product dispensing piston is activated by air as the fluid activation means and in the preferred application the identification of the defective seal is provided by the release of a fill liquid or a gas from the leak detection port while preventing cross contamination. 
     The novel positive control fill valve assembly can include an optional nozzle having one or more fluid ports provided in the outlet nozzle. In this embodiment of the invention, the substantially cylindrical seating head is designed to mate with the tapered outlet so that fluids remaining in the channels of the nozzle are positively controlled by the seating of the cylindrical shaped piston head in the tapered nozzle head so that the viscosity of the fluid in combination with the size and number of channels in the nozzle prevent fluids from dripping much in the same manner as trapping liquid in a straw prevents fluid displacement in the straw. The combination of the sealing head together with the tapered seat in proximity to the channels of the nozzle similarly prevents further fluid from displacing the fluid captured in the channels of the nozzle. 
     In another embodiment of the invention, where fluids having high viscosities and low densities such as alcohol are dispensed, the product outlet chamber, at its upper end, may include an inwardly tapering wall which provides a seat for the upper surface of the substantially cylindrical head of the product dispensing piston. In this embodiment, a nozzle with a single large opening may be utilized to provide for the dispensation of the product. In either embodiment, the substantially cylindrical head of the product dispensing piston is designed to remain in the path of flow in the product dispensation chamber to assist in the dispensation of the product into the container in a manner that prevents sloshing, spilling or dripping into a container disposed below the novel positive control fill valve assembly. 
     The novel positive control fill valve assembly is preferably made of stainless steel or other material that provides the highest purity and hygienic standards for the sanitary dispensing of flowable materials, particularly medicines and food products. As such, the novel positive control valve assembly is typically made of high grade non-corrosive stainless steel that is without seams, threads, welds or other surface imperfections that would allow accumulation or accretion of any particles that would result in contamination of the dispensed product. Preferably, the novel positive control fill valve assembly includes a flange disposed at the nozzle or dispensation end of the positive control fill valve assembly to allow the entire nozzle, valve, product outlet and product inlet chambers to be cleaned in place (CIP capability) by the backflow circulation of cleaning solutions through and around the tapered valve seat and cylindrical piston head of the product dispensing piston and in and through the product inlet. 
     The novel leak detection port provides a positive identification of the precise location of a pending seal failure that would result in contamination of the dispensed product or the fluid activation means for activating the product dispensing piston. This positive identification of the breaking down of one of the two seals in the novel positive control fill valve assembly prevents not only contamination of the piston activation fluid, but even more importantly product contamination and prevents costly recall of products packaged in prior art equipment that have been contaminated due to seal failure. This positive identification of the deterioration of the seal, as well as whether the seal is on the pneumatic side of he piston or on the product side of the piston prevents the packaging and possible shipment of contaminated products by employing a failsafe system to prevent the subsequent expensive recall of defectively filled and contaminated packaged products. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages of the invention will become more apparent to those skilled in the art in conjunction with the detailed description of the preferred embodiment of the invention, in which: 
     FIG. 1 is an exploded view of the preferred embodiment of the novel positive control fill valve assembly of the invention; 
     FIGS. 1A and 1B are exploded views of the best mode of the fill valve assembly similar to FIG. 1 illustrating the novel control fill valve assembly in greater detail; 
     FIG. 2 is a side cut away elevational view of the novel positive control fill valve assembly of FIG. 1; 
     FIG. 3 is a side cut away elevational view of an alternative embodiment of the novel positive control fill valve assembly; 
     FIG. 4 is a perspective view of an alternative embodiment of the product dispensing piston; 
     FIG. 5 is a side elevational view of an alternative embodiment of the sealing head of the product dispensing piston of FIG. 4; 
     FIG. 6 is a perspective view of the sealing head of FIG. 5; 
     FIG. 7 is a side elevational view of an alternative embodiment of the sealing head of FIG. 6; and 
     FIG. 8 is a side elevational view similar to FIG. 3 illustrating the application of multiple seals in combination with the leak detection port. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The novel positive control fill valve assembly is designed to positively control the dispensation of flowable materials in a product container and in particular a variety of viscous fluids, such as yogurt, milk, water, ice cream beverages and other such flowable food products or pharmaceutical preparations or medical and medicines which require a positive control fill valve for dispensing and metering precise quantities of a liquid product into a container requiring hygienic and sanitary dispensation of the liquid product fill material. 
     The novel positive control fill valve assembly provides for not only the positive metering and control of fluids into packages and containers, but also prevents the sloshing and splashing during the dispensation of the flowable product and prevents dripping at the end of the fill cycle by providing a positive control over the closing of a valve provided by the combination of the tapering piston valve seat in combination with the sealing head of the product dispensing piston. In addition, the novel fill valve assembly provides positive control and identification of the location of seal deterioration before seal deterioration can result in contamination of food, pharmaceutical, medicine or medical material with oils, fluids or airborne materials utilized to activate the product dispensation piston for activating the positive control fill valve assembly. The novel fill valve assembly is designed to operate over a wide range of operative pressure conditions required for dispensing a variety of liquid products having a wide range of viscosities. Typically the product dispensing piston operates at pressure of from about 2 to 60 psi for dispensing fluid products while providing a positive control over the quantity of material dispensed without dripping and without contamination of the fill material with fluids employed to activate the product dispensing piston. 
     Referring now to FIGS. 1,  1 A and  1 B, the novel positive control fill valve assembly  1  includes, at one end, a cylinder housing assembly  2  and at the other end, a product dispensation cylinder  4 . The product dispensation cylinder  4  includes a product inlet  6 , which, at one end, includes a flange  8  and a groove  10  for receiving an O-ring  12  (FIG.  1 B), which is connected to a product reservoir (not shown) by means of a flange clamp (not shown) to provide a good metal to metal plus O-ring seal that is sometimes not achieved in the prior art that utilize flexible hoses attached to prior art nozzles. Further, the novel fill valve assembly  1  is of a compact design and does not require the utilization of flexible hoses to connect to the novel fill valve assembly  1  from the product manifold which has resulted in leaking in the prior art fill assemblies. 
     Referring now to FIGS. 1A,  1 B and  2 , the novel positive control fill valve assembly  1 , includes a flange  14  (FIG. 1A) on the cylinder housing assembly  2  and a corresponding flange  16  on the main valve body  18 , which together form a groove  20  (FIG. 2) for receiving a gasket seal  22  to provide an airtight seal between cylinder housing assembly  2  and main valve body  18  which are held together by flange clamp  24  (FIG.  1 A). Flange clamp  24  is preferably a Triclover flange clamp as manufactured by Triclover, Inc. of Kenosha, Wis. The Triclover clamp  18  is pivoted at end  26  and includes an adjustable key nut  28  for firmly securing the flange clamp around flanges  14  and  16  to provide an airtight seal. 
     In the best mode of the invention a second flange  30  is provided on main valve body  18  in the preferred embodiment of the invention to connect main body  18  to cylinder housing assembly  2  (FIG. 1B) in accordance with the preferred embodiment of the invention. The purpose of providing a second flange  30  and the corresponding flange  32  on product dispensation cylinder  4  is to assist in the disassembly and removal and replacement of the novel leak detection port assembly as will be described hereinafter in greater detail. The second flange  30  on main valve body  18  is secured to corresponding flange  32  on product dispensation cylinder  4  by a second flange clamp  34 , which also preferably is a Triclover flange clamp similar to Triclover flange clamp  24 . A fluid tight seal is provided between main valve body  18  and product dispensation cylinder  4  by a gasket  36 . Where the optional second flange is utilized it is placed near or below the leak detection port  38  to assist in the disassembly and replacement of product seal O-ring  40 . Alternatively, main valve body  18  can be constructed as a single piece as part of cylinder housing assembly  2 , as illustrated in FIGS. 1 and 2. 
     A product dispensing piston rod  42  is provided for dispensing a viscous product from chamber  44  (FIG. 2) in product dispensation cylinder  44 . Product dispensing piston rod  42  is activated by fluid, which, in the best mode is pneumatic air pressure supplied by fitting  46  through port  48  in cylindrical housing assembly  2 . Air pressure introduced through port  48  into chamber  50  of cylinder housing assembly  2  is designed to force a cylinder cup or piston  52  down to the bottom of chamber  50  to force substantially cylindrical seal  54  on product dispensing piston rod  42  into tapered seat  56  of product dispensing cylinder  4 . The seat between the tapered wall forming tapered seat  56  provides a positive control for shutting off product dispensed through nozzle  58  of product dispensing cylinder  4 . 
     Nozzle  58  may be configured in a variety of ways depending upon the physical characteristics of the liquid fill material. Nozzle  60  is designed to contain a plurality of channels  60 , the number and size of which are related to the viscosity of the product being pumped into product inlet  6  and dispensed through the channels  60 . The higher the density and the lower the viscosity of the liquid fill product, the greater the number of channels since the seating of substantially cylindrical seal  54  in tapered seat  56  provides a fluid tight seal. This fluid tight seal prevents further product from being dispensed through channels  60  in which trapped product in channels  60  prevents dripping of product through the nozzle  58  or channels  60 . Further the product under pressure from product inlet  6  and product chamber  44  exerts a positive force on the top  55  of substantially cylindrical seal  54  which forces the substantially cylindrical seal  54  into the tapered seat  56 . The density and constant pressure over fill material introduced into product chamber  44  increases the positive control over the positive control fill valve assembly. Conversely, where less dense and fluids of high viscosity are dispensed through the novel positive control fill valve assembly, the nozzle may be modified as well as the seating arrangement of the piston sealing head in the tapered sealing seat as will be described hereinafter in greater detail with respect to FIG.  3 . 
     A cap screw  62  (FIG. 1A) connects cylinder cup  52  to product dispensing piston rod  42  through a pair of washers  64  and  66 , through a pair of adaptor rings  68  and  70  and through a second cylinder cup or piston  72 , through washer  74 . Cap screw  62  is received in threaded opening  76  of product dispensing piston rod  42 . The action of fluid pressure on cylinder cup  52  forces seal  54  into tapered seat  56  and the action of fluid pressure on cylinder cup  72  retracts piston  42  and removes seal  54  from tapered seat  56 . 
     Product dispensing piston rod  42  is guided in main valve body  18  by a bushing  78 , which is fitted into opening  80  of main valve body  18 . Bushing  78  is preferably made of a plastic material and preferably composed of a Delrin, Teflon or Delrin Teflon composition which assists product dispensing piston rod in reciprocating in chamber  50  and product chamber  44 . Disposed below bushing  78  is pneumatic air seal O-ring  82 . Disposed intermediate product seal O-ring  40  and pneumatic air O-ring seal  82  is leak detection port  38 , which provides a positive indication as to whether pneumatic air O-ring seal  82  or whether product seal O-ring  40  is defective. The combination of leak detection port  38  with pneumatic air O-ring seal  82  and product seal O-ring  40  prevents contamination of the product with the product dispensing piston rod  42  activation fluid in a manner that will be described hereinafter in greater detail. 
     Cylinder housing assembly  2  includes a pad  84  that is designed to fit in opening  86  of cylinder housing assembly  2 . Pad  84  can be optionally threaded into opening  86  to provide adjustment of product dispensing piston rod  42  in chambers  50  and  44 . Alternatively adjustment may be provided by adaptor rings  68  and  70  in combination with the threads on cap screw  62  to accommodate adjustment in the amount of travel of product dispensing piston rod  42  in chambers  50  and  44 . 
     The activation of product dispensing piston rod  42  to remove the substantially cylindrical seal  54  from tapered seat  56  is accomplished by the introduction of air pressure through fitting  88 , which is connected to opening  90  through passage  92  (FIG.  2 .). Passage  90  communicates with second cylinder cup  72  to push second cylinder cup  72  up into chamber  50  until cap screw  62  contacts pad  84 . As will be recognized, the opening of product dispensing piston rod  42  allows product from product inlet  6  to travel around the sides of product dispensing piston rod  42 , as well as around substantially cylindrical seal  54  and out of channels  60  and nozzle  58 . The passage of a viscous product from inlet  6  into chamber  44  and around retracted product dispensing piston rod  42  and substantially cylindrical seal  54  prevents sloshing or undue turbulence of the dispensed product as it enters nozzle  58  and through channels  60 . Dispensed product from product inlet  6  is substantially under constant pressure which assists in urging cylindrical seal  54  in tapered seat  56  when the fill valve is closed. The novel product dispensing piston rod with the sealing head thereby provides two functions; not only does it provide a positive seal for the novel positive control fill valve assembly, but it also assists in preventing the product from undue turbulence and spilling and sloshing as it enters nozzle  58  and exits channels  60 . 
     As will be recognized by those skilled in the art, air pressure in chamber  50  controls the position of the product dispensing piston rod  42  in product chamber  44 . This provides numerous advantages in not only preventing sloshing or undue turbulence but also for maintaining the substantially cylindrical seal  54  in any desired intermediate position. This is particularly advantageous where liquids of varying temperature, density, viscosity and compressibility are dispensed since the difference in air pressure introduced through fitting  88  and/or pressure port  48  can be used to control the position of substantially cylindrical seal  54  in chamber  44  in relation to the density, viscosity, and compressibility of the dispensed fluid. This is particularly the case where foods such as ice cream are dispensed in the novel fill valve since temperature variation of the ice cream varies the density and viscosity of the food product. 
     The novel positive control fill valve assembly further prevents contamination of dispensed products with oils, gases and other contaminants present in activation fluids necessary to activate product dispensing piston rod  42 . Even where air pressure is utilized in chamber  50  to open and close product dispensing piston rod  42 , such air, even when filtered, contains trace amounts of contaminants, oils and other materials that are deleterious to foods, medicines and other products dispensed through fill valve assemblies. The contamination of product has resulted in contamination and recall of food products and substances and pharmaceutical materials, as well as other hygienically packaged products. This contamination is eliminated by the novel leak detection port  38  disposed intermediate the product seal O-ring  40  and the O-ring seal  82 . 
     The purpose of the dual seal, in combination with the leak detection port, is to allow accurate and quick assessment of seal condition by determining whether product O-ring seal  40  is defective, in which case product passes through seal  40  and is stopped by O-ring seal  82  causing the product to exit leak detection port  38  positively identifying seal  40  as defective. Alternatively, if O-ring seal  82  is defective, air pressure or activation fluid travels down the side of product dispensing piston rod  42  and is prevented from contaminating the product by product seal O-ring  40  causing air pressure or activation fluid to exit leak detection port  38  to indicate the requirement for maintenance on seal  82 . Where an activation fluid other than gas is used to activate product dispensing piston rod  42  such activation fluid can be dyed in an indicator color different from the dispensed product to assist in defective seal identification. In the preferred application of the invention, a product seal  40  and seal  82  are quad seal rings, such as may be obtained from McMaster, Inc. manufacturer of Norwalk, Calif. 
     The substantially cylindrical seal  55  may be modified to have a rubber of elastomeric sealing head  57  as illustrated in FIGS. 4,  5  and  6 . Sealing head  57  includes a hole  59  for attachment to product dispensing piston rod  42 . Sealing head  57  can include a taper  61  to assist in sealing in tapered seat  56  as illustrated in FIG.  7 . Alternatively, product dispensing piston rod  42  may have a metal head  54  as illustrated in FIG. 1B together with a groove  96  for receiving an O-ring seal  98  to provide additional advantages in dispensing various types of products and providing a seal in tapered seat  56 . 
     The novel positive control fill valve assembly  1  further optionally includes a cleaning flange  100  with an O-ring seal groove  102  (FIG. 2) for receiving a cleaning assembly (not shown), which mates with cleaning flange  100  to provide clean in place CIP capabilities by the backflow of cleaning fluid through channels  60  in nozzle  58  and in and through product chamber  44  and around substantially cylindrical seal  54  and around product dispensing piston rod  42  and out through product inlet  6  to provide for the periodic cleaning of all of the internal components of the novel positive control fill valve assembly that are in contact with dispensed fill product. 
     Referring now to FIG. 3, an alternative embodiment of the novel positive control valve is illustrated in which product dispensing piston rod  42  has been slightly modified by utilizing a modified cylindrical sealing head  104  made of rubber or an elastomeric material similar to FIGS. 4,  5  and  6  which provides a seal at the modified tapered seat  106 . Modified cylindrical sealing head  104  can be constructed like substantially cylindrical seal  54  in which case groove  96  and O-ring seal  98  would be attached to product dispensing piston rod  42  with O-ring seal  98  facing modified tapered seat  106 . 
     The pneumatic activation of the product dispensing piston rod  42  in FIG.  3  and the components for the activation of the product dispensing piston rod  42 , as well as the leak detection port  38  are all identical to the components previously described with respect to FIGS. 1 and 2. Further the product inlet into the product chamber  44  remains also the same, except that, as illustrated in FIG. 3, the seal between the modified cylindrical sealing head  104  and tapered seat  106  occurs at the top of the cylindrical sealing head  104  and the bottom of chamber  44 . The novel positive control fill assembly valve, as illustrated in FIG. 3, is primarily used for less dense liquids having a greater viscosity such as alcohol and other such products where a nozzle  58  is not required due to the physical characteristics of the liquid dispensed. In such cases, where alcohol or other liquids of a greater viscosity are dispensed, the open end  108  of the product dispensing chamber allows such liquids to drain from the sides  110  of the product dispensing nozzle  112 , while the seal between modified cylindrical sealing head  104  and modified tapered seat  106  provides a positive control fill valve. Similarly, the modified novel product positive control fill valve, as illustrated in FIG. 3, may include a cleaning flange  102  to provide for the cleaning of nozzle  112 , interior of sides  110  modified cylindrical sealing head  104 , modified tapered seat  106 , chamber  104 , as well as the product inlet  6 . 
     Referring now to FIG. 8 a further embodiment of the leak detection port  38  is illustrated. The leak detection port  38  includes a first O-ring seal  82  and a second O-ring seal  120  in axial alignment with the first O-ring seal  82 . This arrangement serves to increase the sealing area between the leak detection port and the pneumatic chamber for activating product dispensing piston rod  42 . This arrangement of a second seal is similar to the utilization of a quad seal as heretofore discussed. It is possible to utilize multiple seals not only between the lead detection port and the pneumatic chamber for activating piston rod  42 , but also between the leak detection port  38  and the product chamber  44 . The desirability of employing multiple seals is not only related to the relationship between the activation fluid employed and the dispensed fluid but also the efficiency of bushing  78  in slidably engaging piston rod  42 . 
     As will be recognized from the foregoing, the novel positive control fill valve assemblies of the invention provide numerous advantages over the prior art fill valves by providing, not only a positive control over the volume of fluids dispensed, but also reducing the amount of sloshing, spilling and frothing of product as it is dispensed by the utilization of the novel sealing head in combination with the tapered sealing seat provided in the novel positive control fill valve assembly. Numerous modifications may be made in the components and activation of the product dispensing piston as well as the materials of which the novel sealing head is constructed, as well as modifications in the shape of the novel sealing head as heretofore been discussed. 
     Numerous modifications and changes can also be made to the novel leak detection port for preventing contamination of food product with piston activation fluids to suit particular arrangements and machine requirements. Also changes and modifications can be made in the nozzle and the arrangement of the tapered sealing seat and cylindrical sealing head, as well as the types of nozzles and channels provided in the nozzles to provide a wide range of adaptability to various types of fluids to suit particular requirements. These and other such modifications, as are made by those skilled in the art, are deemed to be included within the scope of the claims. 
     As used herein and in the following claims, the word ‘comprising’ or ‘comprises’ is used in its American technical sense to mean the enumerated elements include but do not exclude additional elements which may or may not be specifically included in the dependent claims. It will be understood such additions, whether or not included in the dependent claims, are modifications that both can be made within the scope of the invention. It will be appreciated that these and other modifications can be made within the scope of the invention as defined in the following claims.