Patent Publication Number: US-8528500-B2

Title: Automatic dairy animal milker unit backflusher and teat dip applicator system and method

Description:
This application is a continuation of U.S. Pat. No. 8,025,029 issued on Sep. 27, 2011, which is continuation-in-part of pending application Ser. No. 12/157,924 filed Jun. 12, 2008, which is a continuation of U.S. Pat. No. 7,401,573 issued on Jul. 22, 2008, which claimed the benefit of Provisional 60/578,997 filed Jun. 12, 2004; and a continuation-in-part of application Ser. No. 12/215,706 filed Jun. 27, 2008, the disclosures of which are incorporated herein by reference. 
    
    
     FIELD AND BACKGROUND OF THE INVENTION 
     This invention relates generally to teat dip applicators and backflushing systems for dairy animal milker units, and more particularly to automatic milker unit backflushing systems, teat dip applicators, related components, and methods for safely and efficiently applying dips and backflushing milker units. 
     Dairy milking systems as they relate to the present invention include a cluster of teat cups, each of which is matched with a flexible teat cup liner that is attached to a teat of a dairy animal with a vacuum. Vacuum is applied in pulses between the shell and liner to facilitate movement of the flexible liner to milk the dairy animals. Milk flows from the cow through each flexible liner and then through a short milk tube to a milker unit collecting bowl assembly, which collects milk from all of the animal&#39;s teats. This combination of elements is known as a milker unit and can be used to milk cows, sheep, goats and other dairy animals. Each milker unit is used to milk multiple animals so it must be sanitized, at least periodically, to prevent transmission of dirt and germs into the milk, and to help prevent transmission of diseases from animal to animal. 
     Milk from individual animals flows from each collecting bowl assembly through a long milk tube and into a milk line that receives milk from all of the milker units in the dairy. The milk is then chilled and stored in a milk tank. The milk lines and storage systems must not be contaminated with dirt, debris, chemicals, pathogens, or contaminated milk. 
     Various methods have been used to clean milker units. For example, milker units have been immersed into a bucket filled with a disinfectant solution for cleaning. In a simple automated variation, milker units are pulled through a so-called “disinfection trough” or multiple troughs filled with disinfectant solution. Other systems include automatic rinsing that is usually done from the downstream end of the long milk tube and cleans the entire length of the long milk tube as well as the milker unit. This latter method involves very high consumption of water and cleaning chemicals, and can waste milk that is in the long milk tube that is otherwise salable. In all cases, a practically complete removal of the disinfectant solution from the milker unit must take place before it is applied to the next cow, so thorough rinsing and/or backflushing are necessary. 
     In addition, dairy animal teats have broadened milk ducts after milking that make them especially susceptible to new infection from mastitis pathogens. To combat these pathogens, the teats can be treated with a disinfectant solution that adheres well to the teats and which usually also contains a skin-care component. The application of this disinfectant solution is called dipping and can be done with a hand-held dipping cup into which the individual teats are introduced. Dip can also be applied using manual spray devices and foam applicators. Dipping with a cup is especially labor-intensive, but generally has a better success rate and a lower consumption of dipping solution than manual spraying methods. 
     Some spraying methods are automated to spray dip from a dipping arm or dipping bar. Automated sprayers are not precise and tend to consume much more dipping solution than manual dipping methods. Other early automatic teat dipping applicator systems applied dip upward from the short milk tube toward the bottom of a teat at the end of milking, but before detachment from the milker unit. This arrangement provided some protection, but it did not coat the entire teat uniformly. See U.S. Pat. No. 7,290,497. Others have suggested automated systems that apply dip to an upper teat portion, but most of these failed to provide: uniform dip coverage on teats; consistent volumes of dip application over time; and protection of downstream milk system components from being contaminated by dip and other chemicals. 
     In particular, most prior automatic teat dip applicators and milker unit cleaner systems fail to adequately ensure that teat dip compositions and backflushing fluids do not enter the long milk tube and contaminate the dairy milk lines. This problem can be caused by a number of factors, but one possible cause for contamination results from differential pressures that develop in dipping and backflushing devices that are connected to milk lines. Differential pressures between the milk lines, and dipping and backflushing devices can cause seepage even through closed valves and tight seals, so it is difficult to design, build, install, maintain, and use automated teat dip applicators and milker unit backflushing systems that are safe and prevent contamination of dairy systems. 
     Thus, there is a need to provide backflushing and teat dip application automatically and in a conveniently arranged system that also ensures that the dip solutions and backflushing fluids do not contaminate the dairy system and milk supply. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to systems and methods that automatically backflush milker units and can automatically apply teat dip to dairy animal teats. Generally, when dip application is to be performed with the present invention, it occurs automatically near the end of milking, when milk flow through the milker unit diminishes and vacuum is about to be shut off to detach the milker unit from a dairy animal. Before detachment from the animal, the invention isolates the milker unit from the rest of the dairy system and delivers teat dip near the top of an animal&#39;s teats. A dip applicator in accordance with the invention can include; a dip supply, a pump, suitable conduits, valves, and a manifold that directs substantially uniform volumes of dip to each animal teat. The invention can be adjusted to properly time dip delivery, teat coverage, and dip rinsing for most types of teat dips. 
     After dip application, backflushing is performed by the present invention by continuing to seal off the milker unit from the downstream dairy system components. Valves are operated and backflushing chemicals, water, and air are used to sanitize the milker unit. The backflushing operation begins near a downstream portion of the milker unit and is directed upstream toward the teat cups and liners. Cleaning the milker unit with the invention is more thorough than cleaning just the cup liner and yet it does not waste milk in the long milk tube. The milker unit and the invention itself can be rinsed with clean water after backflushing. 
     Automatically backflushing milker units cleans out milk and teat dipping solution and prepares the milker unit for the next animal with minimal or no operator effort. Reduced operator effort results in more consistent dipping and milker unit cleaning and improved dairy herd health. 
     In accordance with the invention, the synchronization of the dipping and backflushing operations and the protection of downstream milk system components can be performed by a system that includes; a main control, delivery hoses, an air supply, a water supply, a backflushing fluid supply, a dip supply, a stall control, and a safety valve to seal the downstream end of a milker unit from the rest of the dairy system. The system can also include valve and controls to deliver backflushing fluids, water, and air through the safety valve and into the milker unit. The dairy system downstream from the milker unit includes the long milk tube and the rest of the dairy milk collecting, chilling, and storage devices, and these are protected from contamination by the safety valve and other system components. 
     One main control per milking parlor can be used and comprises an electronic control, storage units and preparation of the dipping and disinfectant solution. The main control can also monitor overall system safety and can generate appropriate warning signals or shut-down signals. There can also be more than one main control, where each controls a number of stalls within the overall dairy. 
     A stall control unit controls the system at each related milking station. It can control the time and sequence of the dipping, backflushing, and rinsing operations for individual milking stations. The stall control can also store dipping solution in a dosing valve in preparation for each dipping process. The dip amount to be applied can be adjusted to accommodate variations in teat dips, weather conditions, herd health, and any other relevant conditions using a dosing valve in accordance with the present invention. 
     A safety valve in accordance with the invention can be formed integrally with a milker unit collection bowl or be mounted on or near a downstream portion of the milker unit. The safety valve automatically isolates the milker unit and dairy system from the dipping and backflushing devices during milking. The safety valve also automatically isolates the milker unit from the rest of the milking system during the dipping and backflushing processes to ensure that no dip or backflush fluids can flow into the milking system downstream from the milker unit. The safety valve and a dip valve can be formed in a single valve unit. The invention can be installed as an automatic backflush system or dip applicator only, or it can include both. Also, an automatic backflush system can be installed initially and later have an automatic teat dip applicator added. The safety valve can also be added to most existing milker unit types and styles. 
     As stated above, the teat dip applicator applies dipping solution after milking and before the milker unit is released from the animal. Dip travels from the dip valve components in the safety valve to the liners through dip channels that are mounted either inside or outside of the teat cups (or shells). Consumption of teat dip with the present invention is comparable to the low consumption realized during manual dipping with a dipping cup. The dip can be distributed through the head of the teat shell liner, whereby the disinfectant solution can be distributed all around by dome flow controllers formed in the inside of the head of the shell liners such as those disclosed in U.S. application Ser. Nos. 12/215,706 and 12/157,924, U.S. Pat. No. 7,401,573, and Provisional Application 60/578,997 the disclosures of which are incorporated herein by reference. In this way, a single introduction of teat dip to the shell liner is sufficient to distribute the dip uniformly in the area inside the liner head and onto the teat, and then it is wiped on the length of the teat as the teat cup is removed. Gravity, pressure differential, and the wiping action of the liner during detach all ensure full coverage of the teat from top to bottom. Controlling dip flow this way also reduces dip spray out of the milker liner as the milker unit falls from an animal. 
     The milker unit safety valve ensures that disinfectant and teat dip cannot flow downstream from the safety valve and into the milk line, despite differential pressures in the milk lines and safety valve. To prevent seepage past valves and seals, a safety valve in accordance with the invention can include a type of valve arrangement known as “block-bleed-block.” Standard valves and seals can fail or allow seepage due to differential pressure on opposite sides of seals used in milk, teat dip, and backflushing lines. The block-bleed-block function of the invention prevents migration of disinfectant and teat dip through valves and seals into the milk lines by supplying a pair of spaced apart valves and a vent or “bleed” to atmosphere, with the vent being disposed between two seals. Multiple block-bleed-block arrangements can be used in the invention to provide redundancy and added safety. 
     Also in accordance with the invention, there is provided a valve block that joins air, water, and backflushing supply lines and channels them to a common outlet for efficiency. The valve block also provides a pressure bleeding vent between a pair of seals to further protect milk lines from contamination. 
     Also, in accordance with the invention, a teat dip manifold can be used to ensure more equal and consistent distribution of the dipping solution to individual teat cups. The manifold can be disposed on or near the milker unit or safety valve The teat dip manifold can also include a valve arrangement that isolates each liner head dip tube or pairs of liner head dip tubes from the others in the milker unit to prevent adverse pressure differentials in the various tubes during milking. Adverse pressure differentials in these tubes can affect critical milking vacuum levels in the milker unit liner head, and the present invention eliminates or reduces these pressure differentials. 
     A method for backflushing a milker unit, in accordance with the present invention, includes the steps of: closing a safety valve to substantially seal off a downstream portion of the milker unit from a dairy pipeline system; pumping backflush fluid through a safety valve and the milker unit; pumping water through the safety valve and milker unit; forcing air through the safety valve and the milker unit; and opening the safety valve so that the milker unit is in fluid communication with the dairy pipeline system. 
     The step of closing the safety valve can include the step of: moving a backflushing piston from a milking position to a backflushing position, which can include the step of: forcing air into the safety valve to move a backflush piston from a milking position to a backflushing position. 
     The method for backflushing a milker unit can also include the step of: bleeding the safety valve at a safety valve vent, wherein the vent is disposed between an upstream seal and a downstream seal when the safety valve is in the milking position and/or the backflushing position, and the vent can be disposed between a backflush fluid supply in fluid communication with the safety valve and the downstream portion of the milker unit when the safety valve is in a milking position. 
     The present invention can perform the above steps for backflushing a milker unit in conjunction with a method for dipping dairy animal teats is performed. The method for dipping dairy animal teats can include the steps of: moving the backflushing piston to a backflushing position; and moving a dip valve piston to a dipping position to allow dip to flow from a supply of pressurized dip to a dip channel that is in fluid communication with an upper portion of a teat shell liner, and this step is performed before and/or during detachment of a milker unit from an animal. 
     The present invention can accomplish one or more of the following: automate the dipping process to increase operator efficiency and reduce operator fatigue; provide safe, individual disinfection of the teats to reduce pathogenic organisms on the teat; prevent transfer of infection from animal to animal, and thus improvement of udder health of the entire herd; reduce or minimize chemical consumption (as opposed to spray or other automated dipping systems); improve uniformity of teat dip application; prevent chemical contamination of the milk and of the downstream milk system lines; reduce water consumption during backflushing of the milker unit; and be retrofitted to nearly any available milking unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective schematic view of a dairy harvesting facility including a milker unit backflushing and teat dip applicator system in accordance with the present invention; 
         FIG. 1B  is a perspective schematic view of an alternate embodiment of a dip applicator and backflushing system in accordance with the present invention; 
         FIG. 2A  is a perspective view of a milker unit and safety valve in accordance with the present invention; 
         FIG. 2B  is a side view of the milker unit and safety valve of  FIG. 2A ; 
         FIG. 2C  is a side view of an alternate embodiment of a milker unit and safety valve arrangement in accordance with the present invention; 
         FIG. 3  is a front view of a main controller and supply tanks for a backflushing and teat dip applicator system in accordance with the present invention; 
         FIG. 4A  is a perspective view of a stall control and a milker unit in the milking position, the milker unit having the backflushing and teat dip applicator unit of the present invention; 
         FIG. 4B  is a perspective view of the milking stall and milker unit of  FIG. 3A , with the milker unit in a backflushing position; 
         FIG. 5A  is perspective view of a stall controller that can be used to control backflushing and teat dipping at an associated milking stall in accordance with the present invention; 
         FIG. 5B  is front view of the stall controller of  FIG. 5A ; 
         FIG. 6A  is a perspective view of a valve block in accordance with the present invention; 
         FIG. 6B  is a left side view of the valve block of  FIG. 6A  with solenoid valves removed; 
         FIG. 6C  is a side cross sectional left side view of the valve block of  FIG. 6A  with solenoid valves removed; 
         FIG. 6D  is a side cross sectional front view of the valve block of  FIG. 6A  with solenoid valves removed; 
         FIG. 7A  is a perspective view from the lower right of a dosage valve in accordance with the present invention; 
         FIG. 7B  is a side cross sectional right view of a dosage valve in accordance with the present invention; 
         FIG. 7C  is a front cross sectional right view of a dosage valve in accordance with the present invention in a dip ready position; 
         FIG. 7D  is a front cross sectional right view of a dosage valve in accordance with the present invention in a dipping position; 
         FIG. 7E  is a disassembled perspective of a dosage valve in accordance with the present invention; 
         FIG. 8A  is a perspective view of a hose combination for communicating multiple fluids between components of the present invention and computer that can program and reprogram the stall control; 
         FIG. 8B  is a cross sectional view of the hose combination of  FIG. 8A ; 
         FIG. 9A  is a cross sectional view of a dosing valve in accordance with the present invention in a milking position; 
         FIG. 9B  is a cross sectional view of the dosing valve of  FIG. 9A  in a backflush position; 
         FIG. 9C  is a side cross sectional view of the milker unit safety valve of  FIG. 9A  in the milking position and illustrating bleed paths; 
         FIG. 9D  is a partial side cross sectional view of the milker unit safety valve of  FIG. 9A  in a backflushing and dipping position in accordance with the present invention; 
         FIG. 9E  is a side cross sectional view of the safety valve of  FIG. 9A  in a backflush and dipping position; 
         FIG. 9F  is a cross sectional perspective view of the safety valve of  FIG. 9A  in a backflushing position and illustrating “bleed” paths in accordance with the present invention; 
         FIG. 9G  is the safety valve of  FIG. 9A  in the milking position and with the housing removed; 
         FIG. 9H  is the safety valve of  FIG. 9A  in the backflushing position with the housing removed; 
         FIG. 10A  is a perspective view of a seal insert in accordance with the present invention; 
         FIG. 10B  is a cross sectional perspective view of the seal insert taken along  10 B- 10 B in  FIG. 10A ; 
         FIG. 11A  is a perspective view of a backflush piston in accordance with the present invention; 
         FIG. 11B  is a side view of the backflush piston of  FIG. 11A ; 
         FIG. 11C  is a top view of the backflush piston of  FIG. 11A ; 
         FIG. 12A  is a perspective view of a backflush valve operation plate, in accordance with the present invention; 
         FIG. 12B  is a cross section of the plate taken along line  12 B- 12 B in  FIG. 12A ; 
         FIG. 12C  is a perspective view of an alternate embodiment of a backflush operation plate in accordance with the present invention; 
         FIG. 12D  is a cross section of the backflush operation plate taken along line  12 D- 12 D in  FIG. 12C ; 
         FIG. 13  is a perspective view of a safety valve piston connector in accordance with the present invention; 
         FIG. 14A  is a partial perspective view of an upper housing and related components in accordance with the present invention; 
         FIG. 14B  is a cross sectional perspective view of the safety valve and illustrating an air conduit through which pressurized air operates the backflush piston and the dip piston, in accordance with the present invention; 
         FIG. 14C  is a partial cross sectional and perspective view of the safety valve, and illustrating an air inlet through with pressurized air enters the safety valve to purge cleaning fluids from the safety valve and related components; 
         FIG. 14D  is a partial cross sectional and perspective view of the safety valve, and illustrating an air inlet through with pressurized air enters the safety valve to purge cleaning fluids from the safety valve and related components; 
         FIG. 14E  is a partial perspective view of the upper housing and illustrating a dip flow path through the safety valve; 
         FIG. 14F  is a cross sectional side view of the upper housing and some related components in a dip position; 
         FIG. 15  is an exploded perspective view of a dip valve and top plate in accordance with the present invention; 
         FIG. 16A  is an exploded perspective view of a top plate, and dip inlet and outlet chambers in the upper housing, of the present invention; 
         FIG. 16B  is a perspective view of a top plate, in accordance with the present invention; 
         FIG. 16C  is a cross sectional perspective view of the top plate of  FIG. 16B ; 
         FIG. 16D  is a perspective view of the underside of the top plate; 
         FIG. 17  is a perspective view of an umbrella valve for use in a safety valve in accordance with the present invention; 
         FIG. 18  is a perspective view of a safety valve cap in accordance with the present invention; 
         FIG. 19A  is a perspective view of a dip manifold in accordance with the present invention; 
         FIG. 19B  is the dip manifold of  FIG. 19A  with the cover removed to show a diaphragm valve in accordance with the present invention; 
         FIG. 19C  is the dip manifold of  FIG. 19B  with the diaphragm valve removed to show dip flow paths through the dip manifold; 
         FIG. 19D  is the drawing of  FIG. 19C  with the flow paths removed; 
         FIG. 19E  is a perspective view of an alternate embodiment of a dip manifold in accordance with the present invention with a cover removed to illustrate a diaphragm valve; 
         FIG. 19F  is a cross section of the dip manifold with the diaphragm valve removed to illustrate dip flow paths; 
         FIG. 19G  is the dip manifold of  FIG. 19F  with the flow paths removed; 
         FIG. 19H  is a diaphragm valve for use in the dip manifold; 
         FIG. 20A  is an exploded perspective view of a teat cup assembly with an internal dip channel for delivering dip, in accordance with the present invention; 
         FIG. 20B  is a cross sectional view of the teat cup assembly of  FIG. 20A ; 
         FIG. 20C  is a side view of an alternate teat cup assembly with an external dip channel for delivering dip, in accordance with the present invention; 
         FIG. 20D  is a perspective view of another alternate embodiment of a teat cup assembly and dip channel for delivering dip, in accordance with the present invention; 
         FIG. 21A  is a side elevational view of a milker liner in accordance with the present invention; 
         FIG. 21B  is a perspective view of a milker liner dome chamber in accordance with the present invention; 
         FIG. 21C  is a partial perspective cross-sectional view of a milker unit liner in accordance with the present invention; 
         FIG. 21D  is a cross section of a liner and a teat cup of the present invention; 
         FIG. 22A  is a portion of an embodiment of a control operation chart for use with the present invention; 
         FIG. 22B  is a second portion of the control operation chart of  FIG. 22A ; 
         FIG. 22C  is a third portion of the control operation chart of  FIG. 22A ; and 
         FIG. 22D  is a table of steps for practicing an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A , and  2 A through  5 B generally illustrate an automatic teat dip applicator and milker unit backflushing system  20  disposed in a dairy harvesting facility  22 , in accordance with the present invention. 
     The teat dip applicator and milker unit backflushing system  20  is referred to herein as “the system  20 ” and preferably includes: a main control  26 ; a compressed air supply  25 ; a backflush chemical supply  28 ; a water supply  29 ; a teat dip supply  30 ; a conduit  31  for housing appropriate hoses and piping  32 ; stall controls  36  for each milking stall; a stall supply hose  38 ; a milker unit  40  for each stall, and a safety valve  60  for each milker unit  40 . The main control  26  and other controls are connected to an appropriate electrical power supply (not illustrated). 
     The milker unit  40  ( FIGS. 1A ,  2 A,  2 B, and  2 C) includes: a milker bowl collector  44 ; four short milk tubes  46 ; four teat cups  48 ; four teat cup liners  50  disposed in the teat cups  48 ; a milker unit safety valve  60  for controlling fluid flow for teat dipping and backflushing operations; and teat dip delivery channels  62  ( FIG. 2A ) for delivering teat dip to upper portions of an animal&#39;s teats. The teat cups  48  with liners  50  are attached to a dairy animal&#39;s teats and alternating vacuum (pulsation) through hoses (not illustrated) is applied to milk the animal. Milk flows from the liners  50 , through the short milk tubes  46 , into the bowl and claw collector  44 , and through the long milk tube  41  to the main dairy milk lines. 
     The system  20  preferably combines teat dipping and backflushing processes, but the system  20  can be within the scope of the present invention by including only a milker unit backflushing feature without a teat dip applicator or vice versa. Having only a backflushing feature is useful for automatically backflushing each milker unit  40  after each milking or at least periodically to ensure optimum hygiene of the milker units  40 . In a preferred embodiment, the teat dip applicator is a part of the same unit as the backflusher, but the teat dip applicator components can be added to the backflusher even after the safety valve  60  has been installed on a milker unit  40 . The system  20  of the present invention can be used in dairy harvesting facilities of any configuration including rotary milking parlors. 
       FIG. 1B  illustrates another teat dip and backflushing system that includes an applicator  831  that applies dip to a cow or other dairy animal teat. The applicator  831  includes a control panel  832  and a dip manifold  834 . A teat cup shell  836 , a liner  838 , a first backflush valve  840 , a short milk tube  842 , a milker unit collection bowl  844 , milk line  846 , and a second backflush valve  848  are also provided to work as part of or in conjunction with the applicator  831 . 
     The control panel  832  remotely controls operation of the teat dip application system  830 . It can be automated with suitable manual overrides or it can be operated by manually engaging various control buttons in response to audible and/or visual signals reflecting the stage of a milking and backflush operation. 
     The control panel  832  controls the flow of air  837 , water  839 , teat dip  841 , and any appropriate three-way valve ventilation that may be necessary. A vent  845  is also provided. The control panel  832  can remotely control valves elsewhere within the system  830  or it can incorporate valves and hose connections for controlling air, water, teat dip, and valve ventilation. 
     The control panel  832  is in fluid communication with the dip manifold  834  via a manifold hose  850 . The dip manifold  834  is illustrated as feeding a single teat dip applicator and milker unit combination, but the manifold  834  preferably serves a number of liners  838  and milker unit combinations. The dip manifold  834  is in fluid communication with each teat dip liner  838  via a dip hose  852 . 
     The dip hose  852  preferably tracks along the short milk tube  842 , the first backflush valve  840 , and passes into the teat cup shell  836  where it is protected from damage. Alternatively, the dip hose  852  could travel an alternate route to the teat cup shell  836 . The dip hose  852  can also be routed on the exterior of the teat cup shell  836 , or be part of an integral duct (not illustrated) formed in the teat cup shell  836 . The dip hose  852  forms part of a fluid conduit through which teat dips, air, and water pass. 
     Once a sufficient amount of dip is applied, the dip manifold  834  shuts off the flow of dip. Dip cannot be left inside the liner  838  because it may contaminate milk from the next cow. Backflushing of the liner  838  is therefore desirable. There are at least two options to backflush the liner  838 . In one option, the second backflush valve  848  is opened to deliver a backflushing fluid  859  such as water or a suitable chemical into the milk line  846 , through the milker unit  844 , the short milk tube  842 , the first backflush valve  840  (if present), and out of the liner  838 . In a second option, the first backflushing valve  840  is used, and only the liner  838  is backflushed while the milk line  846  is isolated by the backflushing valve  840 . 
     Automatic operation of the system  830  relies on an end-of-milking signal from a milk sensor (not illustrated) that activates the control panel  832  to shut off vacuum to the milker unit  844 . The first backflush valve  840  is then closed to isolate the liner head nozzle  864  from the milker line  846  to protect the milk line  846  from being exposed to dip and backflushing fluid  859 . Preferably, only the second backflush valve  848  is used, and it is activated by the control panel  832  to shut off the milk line  846  from the milker unit collection bowl  844 . 
     The control panel  832  then operates a three-way valve to connect the control panel  832  to the manifold hose  850  and delivers dip into the manifold hose  850 , manifold  834 , dip hose  852 , liner head chamber  862 , and liner head opening  864 . The amount and pressure of the dip  851  is controlled by the valves and the pressure of the source of dip. 
     Air is then forced through the manifold hose  850 , manifold  852 , dip hose  852 , and liner head chamber  862  to force dip out of the liner head opening  864 . As the milker unit  844  then begins detachment via a standard detacher mechanism (not illustrated), the liner head  860  mouth wipes dip down the teat sides and deposits an excess dip amount on the teat end. 
     Next, normal backflush cycles are used as described above to sanitize the liner between milkings and rinse out any teat dip residue. The system  830  is now ready to repeat the cycle. 
     Main Control 
     Referring to the system  20  in more detail, as illustrated in  FIGS. 1 and 3 , the main control  26 , the air supply  25 , the water supply  29 , the dip supply  30 , and the backflush chemical container  28  are preferably in a room separate from where the milker units  40  and milking operations are located. This is a preferred arrangement for safety and hygiene considerations, but other system configurations are possible. 
       FIG. 3  illustrates more details of the main control  26  that delivers air, water, dip (when included as part of the system), and backflush solution in a precise controlled manner to the stall controls  36  located in the dairy parlor  22 . The main control  21  is preferably contained within a housing or cabinet for protection against harsh dairy conditions. The main control  26  includes a programmable device  21  that can, for example, store information, control operation sequences, monitor operations, receive data regarding the condition of the system  20 , analyze possible problems, generate maintenance prompts, and provide critical control in case of problems. If such problems arise, the main control  26  can be programmed to generate an appropriate signal, such as sound, light or written display. 
     The main control programmable device  21  is preferably programmed to monitor and control all of the functions of the devices associated with the main control  26 , as well as, communicate with, respond to and/or control; stall controls  36 , computers, other data input devices, including sensors and manual controls. For example, the main control  26  can monitors a number of system parameters such as: 1) dip application pressure; 2) water pressure; and 3) air pressure of one or more air supplies, and adjust these parameters by modifying operational controls or adjust one or more pressure regulators  68 . The programmable device  21  is preferably an I/O  88  PCB circuit board used as an electronic monitoring device, but other types of devices can be used to accommodate particular dairy installations and needs. There can also be mounted on the main control an on/off switch, indicator lights, signal lights, sound alarms, key pads, other input devices, signaling devices and/or any other type of interactive device. Grommets for wire/cable connectors can be part of a housing for the programmable device  21 , as well. 
     The dip application pressure should be kept relatively constant to maintain a consistent dipping process with minimum lag time, air bubbles, or other inconsistencies. Dip from dip supply  30  (not to scale in  FIG. 3 ) is pumped by a dip pump  33  and controlled by a regulator  35 . Dip pressure can be monitored at various locations and adjusted to account for pressure drops/increases through the dip application components, including a dip filter  39 , mounted on the main control  26 . The dip supply  30  can store a premixed dip, a dip concentrate, dry dip ingredient, or other dip ingredient, to be mixed automatically by the main control  26 . It can include more than one container and can include a water source for in situ mixing of dip. 
     Backflush fluids can be drawn from multiple sources including the backflush chemical container  28  which is not shown to scale, but is representative of a single chemical supply either premixed or concentrated, a liquid or solid chemical mixer, multiple chemical supplies or any other source of chemicals that may be desired for use in backflushing milker units. A backflushing flow or dosing meter and/or pump  53  is preferably used to mix a concentrate from chemical container  28  with water and to control flow of backflushing chemicals to the stall control or directly to a safety valve  60 . When concentrates are used, mixing with water or other fluids can take place at or be controlled by the main control  26 . Various types of mixing controls and vessels can be used, but a Dosatron, Model D25RE2 available from Dosatron International Inc. of Clearwater, Fla. 33765, U.S.A, is preferred. Appropriate filters, sensing devices, and sampling devices for all of the supplies can be used as well. 
     Air and water pressures should not be allowed to drift outside of predetermined ranges because insufficient air and water pressures can result in ineffective valve operations and inconsistent cleaning and/or teat dip application. If an unacceptable condition occurs, normal operation of the invention can be shut down and/or alarms can be initiated. 
     Air pressure is generated by one or more compressors (not illustrated) and regulated by a regulator  37 , controlled by an air monitoring switch  45 , and filtered by an air coalescing filter  47 . The air supply  25  is set at an appropriate outlet pressure, preferably between about 50 to 70 psi, to operate related components. Optimum air pressure will depend on a number of factors, including the number of milker units  40  being served and hose length from the air compressor  28  to the milker units  40 . More than one air supply line can be used and controlled by the main control  26 . 
     Water inlet pressure can be generated by local sources or a pump used as part of the system  20 . Water inlet pressure is monitored by switch  49  and be filtered. The water supply  29  can be any suitable source of water with temperatures, pH, and chemical properties that are compatible with the system  20  and related chemical solutions such as teat dip concentrates, backflushing chemical concentrates, or simply as a final rinse of milker units  40  after a backflushing operation. A conditioning system (not illustrated) can be included if the pH or other properties of the local water source is incompatible with the necessary chemical solutions and/or to minimize corrosion of system components. 
     In a preferred embodiment, one dip line, one water line and one backflush solution line extend between the main control  26  and the stall control  36  and can be combined as depicted with the hose combination such as the hose combination  38  illustrated in  FIGS. 8A and 8B . Two air lines are preferred because one air supply is used for reliable safety valve, valve block, and dosing valve, and the second air supply is used for slugging backflushing fluids through the safety valve and milker unit. A single air line can communicate pressurized air from the main control  26  to a convenient location in the dairy before splitting that line into two separate lines. The split should be at a location that results in each air supply line having pressurized air that is not adversely influenced by pressure fluctuations in the other air supply line. The lines are preferably “pass through” types that allow for arrangement of the stall controls in “series” to reduce the number of hoses leaving the main control  26 . 
     A liquid level assembly  57  is preferably used for the dip and backflush solution supply drums to provide information to the main control  26  regarding status of liquid levels. The assembly  57  preferably includes a draw tube  59  with inlet screen/filter, a standard drum interface connector, and a reed switch  61 . The reed switch  61  provides a signal to the main control  26  and to parlor management software, if desired, indicating when the supply drum is nearly empty. An example of such an assembly is illustrated in the drum  30  in  FIG. 3 . 
     Supply Conduits 
     The pipelines and hoses  32  are sized and configured to meet the requirements of individual dairy harvesting facility. They may be routed together through the conduit  31  for protection and efficiency and to accommodate the pass through supplies described above. The conduit  31  can be plastic, such as PVC, metal or other suitable material. 
     Stall Control 
     A stall control  36  is dedicated to each milking stall (See  FIGS. 4A ,  4 B,  5 A, and  5 B) in the dairy harvesting facility  22 . The stall control  36  can be mounted using a base unit  101  in any convenient location near its respective stall, including under a platform in a milking parlor as depicted in  FIGS. 4A and 4B . Visual confirmation of the physical safety features within the safety valve  60  and other components is preferred, and appropriate positioning of the components is, therefore, desired. The stall control  36  can also be mounted to a wall, under the curb  54  or on top of the vacuum lines in swing-over parlor applications. 
     The stall control  36  is responsible for initiating a teat dip application and/or backflushing at the end of milking. Other milking operations can also be controlled at each stall control  36 . Electrical power is supplied through a separate conduit (not illustrated).  FIG. 4A  illustrates a milking position and  FIG. 4B  illustrates a backflushing position. The stall control  36  is preferably located under the parlor curb  54  (in  FIGS. 4A and 4B ) where it is out of the way, yet readily visible to an operator. 
     Preferably, the electronic control  80  includes a protective housing or cabinet and a stall control card  86  such as a programmable circuit board (“PCB”) for storing control parameters, monitoring, and signaling is provided. A suitable control card  86  is an I/O  88  PCB circuit board. Other types of programmable controls can also be used. The stall control  36  preferably includes an interface for a computer  55  or other programming device, sensors or monitoring devices. The computer  55  can also be used to program and monitor data from the main control  26 . The electronic control  80  can also include grommets for connecting wires and cables, and it can include signaling lights, key pads, or other interactive components. 
     Referring to  FIGS. 5A and 5B , the stall control  36  activates the backflushing and/or dipping operations after sensing that milk flow from the animal has ended or after a detacher is activated to remove the milker unit  40  from an animal. The operations begin with the safety valve  60  being activated to close downstream milk lines, such as the long milk tube  41  and protect the milk supply. A dose of teat dip will be pushed preferably with an air operated piston for speed, reliability and reduced foaming from a dosing valve  84  through a manifold  540 , delivery channels  62  and a dome of a milker unit liner  50 , and applied to an animal&#39;s teats. 
     The stall control  36  illustrated in  FIGS. 5A and 5B  preferably includes three primary components: an electronic control  86 , a valve block  610 , and a dosing valve  84  (when a dip applicator is included). Each stall has a control  86  and all are preferably programmed identically to provide a sequence of safety valve operation that is necessary to perform dipping and backflush or backflush only functions. The electronic control  80  can include a circuit board such as a standard eight input eight output circuit board at each stall to interface with a milking control (not illustrated) so the dipping and backflush processes are performed at a proper time and in a proper sequence. There are several variables that allow the sequence of operation to be varied within predetermined safe ranges, including: dip viscosity and composition, backflush chemical viscosity and composition, the amount of available time to perform each task, and ambient conditions. 
     Further, some variables can be adjusted to customize the sequence based on particular equipment or operation needs, however all stalls are preferably set similarly within any particular operation to ensure uniform treatment of all milker units  40  and all dairy animals. Variables such as hose size, hose length, distance of stalls from the main control  26 , dip types, individual animal needs, condition of the equipment, ambient conditions, and many other variables can be considered and programmed into the electronic control  80  to provide consistent operation and optimum dairy animal health. Further, monitoring devices can be used at various points in the system  20  to signal the stall control cards  86  to adjust appropriate parameters. “Fuzzy logic” controllers can be used to continually adjust parameters as conditions change in a dairy and/or with the dairy animals. 
     The valve block  610 , programmable device  86 , and the adjustable dosing valve  84  ensure that equal and consistent amounts of backflush fluids and dip are used in each operational cycle. The manifold  540  is attached to a milker unit  40  and is desirable to ensure that each dose of dip is divided equally for each animal teat. 
     The stall control  36  controls delivery of air, water, and chemicals to the milker unit  40  through a hose or hoses  38 . These hoses  38  are of any suitable size and length and are preferably made of a material that is suitable for use in a harsh dairy environment, yet flexible enough to not influence the milker unit  40  while on a dairy animal Using combined hoses  38  minimizes the number of hose assemblies necessary to operate the system and facilitates a flexible bundling of hoses. A notch can be made in a hose bundle web for joining of all hoses using a standard plastic tie or other suitable means in an organized yet flexible way. Further, the hoses  38  are preferably arranged next to a long milk tube  41  through which milk flows from the milker unit  40  to the dairy harvesting facilities main milk lines. This arrangement reduces the chances of the hose  38  from being damaged by a dairy animal and it makes attachment of the milker unit  40  easier because the hoses  38  will not interfere a with an operator&#39;s movements. 
     The stall control  36  can be equipped with a manual ON/OFF-Reset switch  99  which can shut down the dipping and/or backflush processes for a given stall in case of problem. Power for the stall control  36  can be wired directly from a source or be relayed from the main control  26 . 
     Valve Block 
       FIGS. 6A through 6D  illustrate a valve block  610  in which a number of valves are provided for supplying multiple medias (air, water, and backflush fluids) through a common outlet  637  to a backflush inlet  186  on the safety valve  60  ( FIG. 14A ). The valve block  610  includes a housing  613  that defines an axial chamber  619  in which a spool  621  is disposed to slide between a milking position ( FIG. 6C ) and a backflushing position ( FIG. 6D ). The axial chamber  619  includes an upper bell portion  623  and a lower bell portion  625 . 
     The housing  613  is preferably oriented vertically, as depicted, to provide drainage of fluids through a drain  634  ( FIG. 6B ), but other orientations can be used. Preferably, the valve block  610  housing  613  is made of Radel R5000 from Piedmont Plastics, Inc. of Charlotte, N.C. and available from distributors throughout the United States, or other translucent plastic or glass material to provide superior chemical resistance and clarity for operation and maintenance inspections. The valve block  610  housing  613  is preferably arranged and molded as an integral piece as depicted. Other materials can be used for the valve block  610  and related components, and the valve block  610  can be formed from one or more parts. Flanges  609  or other connectors can be joined to or molded integrally with the valve housing  613  to permit convenient mounting with snap-in features, screws, or other suitable fasteners. 
     The valve block housing  613  includes several pass-through inlets  614  though which air, water or backflushing fluids flow. Pass though inlets  614  are used so that a number of valve blocks can be arranged in series and supplied with air, water, or backflushing fluids from a common source. Other arrangements can be used, but arranging valve blocks in series requires fewer hoses for air, water, and backflushing fluids and less demand on pumps and other supply components. Flow through the pass through inlets  614  can be in either direction to accommodate a variety of dairy layouts. 
     Most of the pass-through inlets  614  communicate with a corresponding and dedicated block inlet  614   a  that is controlled by its respective valve to permit entry of a predetermined fluid into a chamber  619  through conduits  614   b . One exception is the pass through inlet  614  for the second air valve  612 , which communicates with the lower bell portion  625  of the axial chamber  619  at a position under the spool  621  via passages  635   a  and  635   b  so that pressurized air can force the spool  621  into the backflushing position ( FIG. 6D ), when desired. 
     Preferably, the valve block  610  includes five valves, as depicted in  FIG. 6A  including: a first air valve  611  that provides air directly to operate the milker unit milk safety valve  60  for dipping and backflushing; a second air valve  612  that moves a valve block safety spool  621  into place and provides air pressure to push dip in the teat dip delivery tubes  62  between the safety valve  60  and the liner  50  onto a teat; a third air valve  620  provides air for slugging backflush fluids and for complete surface rinsing and vigorous scrubbing of interior safety valve  60  surfaces; a water valve  622  that provides water to be used to rinse the milker unit  40  after backflushing and the safety valve  60  in a self-rinse cycle; and a backflush solution valve  624  that provides one or more chemical solutions for backflushing the milker unit  40 . 
     All valves are preferably solenoid valves, including the third air valve  620 , which is preferably a pilot operated valve that ensures air flow for backflush slugging. Also preferably, the backflush valve  624  is made of stainless steel or other material that resists corrosion from the backflushing fluids. For ease of reference, each valve is joined to the valve block  610  at a seat and each seat is designated in  FIGS. 6B and 6C  with a numeral matching its respective valve and including the suffix “a”, so that valve  620  is mounted on seat  620   a , for example. 
     The first air valve  611  is reserved for only operating the safety valve  60  only to help ensure complete, independent, and safe operation of the safety valve  60 . The first air valve  611  operates independently from the other backflush valves on the valve block  610  because the safety valve  60  must operate during dipping operations, and before and during backflushing operations. The independent operation also avoids pressure fluctuations that could result in from sharing air supply pressure with other system components. The air from air valve  611  exits the valve block  610  through a separate outlet  615  for this reason. The first air valve  611  could be separate from the valve block  610  and mounted elsewhere in the system because it does not use the common outlet  637 . Nonetheless, the valve block  610  provides a convenient mounting location and helps keep all of the hoses for the pass-through inlets  614  organized. 
     The second air valve  612  supplies air to the dosing valve  84  (described below) through an outlet  617 . The air inlet  614   a  preferably receives air from the same air source that supplies valve  611  and the safety valve  60 . Air from this air supply can be supplied through suitable hoses, conduits, or the like. A single air supply for the safety valve  60 , the valve block  610 , and the dosing valve  84  is adequate because of the low air pressure demands of these devices. 
     The spool  621  ( FIGS. 6C and 6D ) includes an upper valve head  626  and a lower valve head  628 . The upper valve head  626  and the lower valve head  628  each define an annular groove in which seals  626   a  and  628   a  are disposed, respectively. The seals  626   a  and  628   a  are preferably u-cup seals oriented as depicted to provide a sealing function in one direction each. U-cup seals provide satisfactory sealing properties and reduce friction between the seals and the central housing  613  so that the spool  621  moves relatively easily with a relatively low air pressure. 
     The seals  626   a  and  628   a  oppose each other to seal the axial chamber  619  at their respective ends. This seal orientation can permit fluid to pass into the axial chamber  619 . The spool  621  can be made of any suitable material such as stainless steel, stable plastic, or other material. The seals  626   a  and  628   a  can be made of Viton (FKM) or any rubber, silicone or other suitable material or the seals can be formed integrally with the spool  621 . 
     A valve block spring  630  biases the spool  621  toward the milking position ( FIG. 6C ). The valve block spring  630  engages a seat  631  on the upper valve head  626  and is contained within cap  633 . An alignment rod  639  extending from the upper valve head  626  of the spool  621  fits in socket  641  ( FIG. 6C ) formed in a cap  633  to maintain proper alignment of the spool  621  when moving between the milking position ( FIG. 6C ) and the backflushing position ( FIG. 6D ). 
     In the milking position ( FIG. 8C ), the spool  621  is forced by the valve block spring  630  to engage the upper valve head seal  626   a  with the walls of the axial chamber  619  to seal the common outlet  637  from the chamber  619  with an end seal  627 . The lower valve head  628  is forced down into the lower bell portion  625  and does not engage the walls of the axial chamber  619 , but the lower valve head  628  includes a recess  629  that fits around and seals the air outlet  617  while permitting drainage of residual fluids through drain  634 . In the milking position, there is a space between the spool  621  and the walls of the axial chamber  619  that extends between most of the length of the axial chamber  619 . The drain (or vent)  634  is in communication with the axial chamber  619  to “bleed” any differential pressure between the valves and the milk line thereby minimizing migration of dips and backflush fluids into the milk lines. The drain  634  is preferably located near the bottom of the axial chamber  619  to provide a drain for any fluids in the axial chamber  619  when the spool  621  is in the milking position. 
     The valve block  610  is preferably controlled by the stall control  36  to move to the backflushing position after the dipping operation. In the backflushing position ( FIG. 6D ), the spool  621  is forced (upward as illustrated) against the bias of the valve block spring  630  by pressurized air entering the inlet  635  to move the lower valve head  628  into sealing engagement with the walls of the axial chamber  619  to seal the vent  634  and open the air outlet  617  to the dosing valve  84 . In the backflush position, the upper seal head  628  does not seal anything because it is disposed in the upper bell portion  623 , and opens the axial chamber  619  to the common outlet  637 . 
     The inlets for the air valve  620 , the water valve  622 , and the backflushing fluid valve  624  all communicate with the axial chamber  619  through inlets  614   a , so that all of these fluids can flow through the axial chamber  619  and out of common outlet  637  when their respective valves are opened and the spool  621  is in the backflushing position. The fluids do not typically flow together, instead the various valves fire in a predetermined sequence to supply air, water or backflushing fluid at the specific time needed by the safety valve  60 , as described below. All hose connections to the valve block  610  and other components of the system  20  can be made with any suitable connection, including a John Guest fitting, as depicted in outlet  617 . 
     Dosing Valve 
     When the system  20  includes a teat dipping option, it is preferred that one or more dosing valves  84  be used at each stall.  FIGS. 7A to 7E  illustrate an example of a dosing valve  84  for use in the present invention is preferably pre-wired to and mounted on the stall control  36 . The dosing valve  84  is filled with dip after each completed dipping operation in preparation for the next dipping operation. Each dosing valve setting should be adjusted to provide substantially the same amount of dip at each stall for consistent treatment of animals. The amount of dip desired will depend on the type of dip used and operator preference with regard to the amount of dip that will be visible on the teat after dipping. 
     Further, more than one dosing valve  84  can be used to apply different dips, dip concentrations, medicaments, and the like to individual teats. When this latter option is desired, the various controls, especially the stall control  36 , can receive cow identification information from automated cow identification systems, and provide specialized teat dip applications to individual animals. 
     The dosing valve  84  includes a housing  432 , a dip inlet  434 , a dip feed  436 , a dip outlet  438 , a chamber adjustment mechanism  440 , a solenoid valve  444 , and an air chase outlet  446 . The dosing valve  84  operates electronically and pneumatically. The housing  432  is preferably made of a translucent plastic material such as Radel R5000 or any FDA approved material, so that visual confirmation of the adjustment mechanism  440  position, the presence or absence of teat dip, and maintenance are all simplified. 
     The housing  432  defines a chamber  450  ( FIGS. 7B ,  7 C, and  7 D) in which teat dip is measured and stored prior to being pumped to the safety valve  60 . Generally, the volume of the chamber  450  can be changed by adjusting the chamber adjustment mechanism  440  in or out of the chamber  450 . The volume of the chamber  450  is preferably set by comparing the adjustment screw  440  position to embossments  451  ( FIG. 7A ) on the side of the housing  432 , in amounts from about six to about fourteen milliliters, for example. Other types of measuring markings or devices can be used. 
     The dip inlet  434  is connected via a hose (not illustrated) to a pressurized source of dip at the main control panel  26 . The dip outlet  438  is connected to the safety valve  60  via a hose or other suitable device. The housing  432  also defines a vent hole  439 , to vent air as dip enters the chamber  450  and to prevent air from getting into dip in case an internal seal leaks, which would reduce the volume of dip delivered to teats. 
     The dip feed  436  is connected via a hose to an adjacent stall&#39;s dosing valve  84 , so that the dosing valves  84  are arranged in series to receive pressurized dip from the main control  26 . Such an arrangement reduces the number and lengths of dip hoses from the main control  26 , and between stall controls  36 . 
     The chamber adjustment mechanism  440  preferably includes a screw housing  458 , a threaded shaft  460 , a shaft head portion  462   FIG. 7B ), a head seal  464 , and a hollow conduit  466  that extends through the length of the threaded shaft  460 . 
     The screw housing  458  has a u-shaped portion  467  ( FIG. 7E ) with a recess  469  that mates with an upper rim  468  of the dosing valve housing  432  to connect the two housings together. The screw housing  458  further includes flanges  472  with notches or holes  474  through which screws can be inserted to mount the dosing valve  84  to a wall or plate near the stall control  36 . 
     The housing  432  rim  468  is inserted laterally into a back side of the screw housing  458  so that the dosing valve  84  is unable to become disconnected when the screw housing  458  is mounted to a support surface with screws. Additionally, the threaded shaft  460  itself acts to prevent disconnection because the two housings are unable to move laterally relative to one another when the threaded shaft  460  extends into the chamber  450 . 
     A lower end of the threaded shaft  460  is formed with or joined to the head portion  462 . The head portion  462  is preferably sized to mate with the chamber  450 . A seal  464  is used to substantially seal an annular surface of the head portion  462  with the housing chamber  450 . The seal is preferably a u-cup seal. 
     The threaded shaft  460  includes exterior threads that mate with interior threads in the screw housing  458 . The exterior threads  480  are preferably discontinuous  480  to reduce tooling cost. The threaded shaft  460  also includes an upper knurled portion  482  to facilitate manual adjustment even when the operator is wearing gloves or the surfaces are wet. The knurl  482  also connects to an air line used to operate the dosage valve  84  to push a spool-shaped piston  500  down and the dip out of the dosing valve  84 . 
     As illustrated in  FIGS. 7C and 7D , the spool-shaped piston  500  is disposed inside the housing chamber  450 . The spool-shaped piston  500  includes upper and lower seals  502  that slidably seal a central portion  503  of the spool-shaped piston  500  with the inside of the chamber  450 . Pressurized dip is allowed into the chamber  450  through the dip inlet  434  by the valve  444 . The pressurized dip forces the spool-shaped piston  500  to slide toward the threaded shaft  460  where it is stopped to define a predetermined volume defined in the chamber  450  between the spool piston  500  and the dip outlet  438 . This is a “dip ready” position. 
     To apply dip, pressurized air is fed from the second air valve  612  in the valve block  610  ( FIG. 6A ) to enter the hollow conduit  466  and push the spool-shaped piston  500  toward the dip outlet  438  to force dip out of the outlet  438  toward the safety valve  60 . The dip outlet  438  preferably extends into the chamber  450 , as illustrated, to act as stop for the spool-shaped piston  500 . An air hose between the second air valve  612  in the valve block  610  is not illustrated in  FIGS. 6A-7E , but see  FIGS. 8A and 8B  for a representative hose example. 
     When the spool  500  reaches the bottom of the chamber  450 , the dosing valve is in a “the dip empty” position. With the spool piston  500  in this position, the air chase outlet  446  is no longer blocked, and pressurized air that moved the spool  500  now exits the chamber  450  through the chase outlet  446  and moves through a hose, and enters the safety valve  60  to provide an air chase for the dip moving from the safety valve  60  to the milker unit. Thus, the same source of pressurized air used to feed a pressurized volume of dip also, in precise sequence, provides a desired air chase for that dip without using controllers, extra valves or other devices. 
     After an appropriate air chase interval, the solenoid valve  444  operates to allow dip to flow through the dip feed inlet  436  to fill the chamber  450  and push the spool-shaped piston  500  to a “dip ready” position ( FIG. 7C ). The solenoid valve  444  includes electrical contacts  449 . After filling the chamber  450  with dip, the solenoid valve  444  closes to prevent pressurized dip from the main control  26  from damaging seals inside the dosing valve  84 . 
     In the overall system of the present invention, other forms of dosing valve mechanisms can be used, and dosing valves are not absolutely necessary. Nonetheless, the above-described dosing valve  84  is particularly effective, simple, and reliable for providing a consistent amount of dip and chase air in a timely fashion. 
     Hose to Safety Valve 
     As stated above, automatic teat dip applicator installations preferably include one set (or bundle) of four hoses  140  ( FIGS. 8A and 8B ) to connect the stall control  36  to the safety valve  60 . A backflush hose  142  provides air pressure to move the milk safety valve  60  into position during dipping and backflushing operations. The second hose  144  provides the large capacity connection for backflush solution. 
     A teat dip hose  146  provides dip to the milker unit  40  and a second small tube  148  for providing a fluid “dip chase” that is preferably air. As stated above, the dip chase  148  reduces the amount of dip required and more completely utilizes the dip required for each milking because once the dosing valve  84  has pushed the dip to the safety valve  60  and on to the liner  50 , any dip that remains in the hose between the safety valve  60  and the liner  50  would otherwise be flushed and wasted in the backflush process. The teat dip hose  146  is preferably emptied before milking to prevent any residual dip from getting into the milk. 
     Milker Unit 
     As depicted in  FIGS. 2 ,  2 B, and  2 C, the milker unit  40  can be used with the collection bowl  44  as depicted in WO 2009/077607 A1, WO 2008/138862 A2, US 2009/0050062 A1, US 2008/0276871 A1, as well as, other bowl and claw arrangements. The system  20  and/or any of the individual components of the system can be retrofitted to existing milker units  40  by connecting the safety valve  60  downstream from the milker unit  40 , and preferably near the milker unit  40  because any milk upstream from the safety valve  60  will be flushed out in the backflushing operation. 
     In  FIGS. 1 and 4A , the milker unit  40  is depicted in a milking position with the bowl  44  on the lower portion and the teat cups  48  and liners  50  directed upwardly. This is the position of the milker unit  40  during automatic teat dip application. The backflushing operation will take place when the milker unit  40  is disconnected from a dairy animal ( FIG. 4B ) and the teat cups  48  and liners  50  are opened sideways or downward for draining backflushing fluids. It is preferred that the entire milker unit  40  be upside down during backflushing for complete drainage. Alternatively, a vacuum purge method may be employed whereby the remaining backflush solution in the milk bowl  44  is drawn back through the backflush supply circuit to the stall control  36  with vacuum and then retained for future use or purged from the system  20 . 
     Safety Valve 
     Safety Valve Overview 
     The safety valve  60  of the present invention is situated on or near a milker unit to seal and protect downstream dairy milk lines from teat dip and cleaning fluids that are fed through the safety valve to upstream milker unit components. All of the fluids, including dip, cleansers, water, and air pass through the safety valve  60 . 
     The safety valve  60  has a housing with various inlets, outlets, and vents through which the fluids flow. These fluid flows are controlled by several moving parts including two pistons and a connector between the two pistons, all of which are moved by springs and an air-actuated operation plate. A set of three umbrella valves is also used inside the housing to control the flow of some of the fluids. A number of special seal and vent arrangements are used in the housing to prevent unwanted seepage of fluids through the safety valve. 
     Safety Valve Detailed Description 
     The milker unit safety valve  60  is placed at or near the downstream end of the milker unit  40 , milk remaining in the long milk tube will not be flushed. In new milker units  40 , the safety valve  60  can be joined to or molded integrally with the milker unit collection bowl so that the backflushing operation flushes out the milker unit  40  including the collection bowl  44 , the short milk tubes  46 , and the liners  50 . ( FIGS. 2A ,  2 B.) Further, a system  20  installed with only a backflushing function can later have an automatic teat dipping feature added, as described in more detail below. 
     Short milk tubes  46  are also flushed and they can be of any design because none of the system  20  components connects to or passes through the short milk tubes  46 . Nonetheless, the backflushing operation begins downstream from the short milk tubes  46 , so any milk or other material in the short milk tubes  46  will be cleaned out in the backflushing operation. 
     The safety valve  60  is depicted separate from any milker unit in  FIGS. 9A through 9F . Generally, the safety valve  60  ensures that backflushing fluids and teat dip do not contaminate milk in the dairy components downstream from the milker unit  40 . The safety valve  60  also dispenses backflushing fluid and teat dip at appropriate intervals, and is capable of flushing and rinsing itself to ensure proper hygiene at all points in the system. The safety valve  60  can be made integrally with the collection bowl  44  of a milker unit  40  or be a separate unit connected to an outlet of the milker unit  40  or be joined with a short section of milk tube  61  between the milker unit  40  and the safety valve  60 . (See:  FIG. 2C .) Dip passes through a tube  65  to the manifold  170 . 
     The safety valve  60  must move between a milking position ( FIG. 9A ) and a backflushing position ( FIG. 9B ) to prevent contamination of the milk supply. It is noted that the terms “milking position” and “backflushing position” are used to designate the position of a backflush piston  120 , and that functions other than milking and backflushing can take place when the backflush piston  120  is in these positions. 
     Due to pressure differentials between milk lines, backflush lines, dip lines, and atmospheric pressure, it is desirable to do more than simply seal such lines from the milk supply because fluids can seep or migrate past valves and seals when seals are used alone. With the present invention, the pressure differentials are avoided with vents exposed to atmospheric pressure to “bleed off” any pressure differential that may cause unwanted seepage past a seal. In this manner, pressures on each side of the safety valve  60  are isolated from one another and migration of chemicals, air, and other fluids into the milk supply is prevented. 
     Generally in the present invention, the vents that “bleed” the pressure differentials are disposed between pairs of seals. This arrangement results in a block at one seal, a bleed at the vent, and another block at the other seal for a “block-bleed-block” feature that prevents seepage and ensures safety of the milk supply from backflushing and dipping fluids. 
     As depicted in  FIGS. 9A through 9F , the safety valve  60 , a preferred embodiment generally includes a housing that is assembled from a lower housing  70 , and an upper housing  74 , and the upper housing  74  is covered by a cap  76 . These elements are secured to one another with screws  78  ( FIG. 9E ), or any other suitable connectors, including but not limited to snap fittings, threaded housing components or being molded integrally with one another. Separate housing portions are preferred for ease of manufacture and assembly, but other housing arrangements are possible. Also, the safety valve  60  can be joined to the milker unit  40  with a suitable connector such as a screw  81 . 
     Preferably, the lower housing  70 , upper housing  74 , and cap  76  are made of a translucent material such as Radel R5000 formulation poly-phenylsulfone material, or FDA and 3A approved material to provide for visual inspection without disassembly of the safety valve  60 . Further, translucent materials provide visual indication of a leak and/or if the leaked material exits a vent. It is preferred that any leakage will exit a vent that an operator can see. 
     The lower housing  70  includes a milk inlet  62 , a milk outlet  64 , a pair of pulsation conduits  82 , a pulsation outlet  83 , and a hanger  66 . The milk inlet  62  is sized and shaped as necessary to mate with and be secured by a screw  81  to a milker unit  40 &#39;s downstream outlet. Alternatively, the milk inlet  62  of the safety valve  60  can be connected to a short section of tube  61  ( FIG. 2C ) disposed between the safety valve  60  and the milker unit  40 . The short tube section  61  in such an embodiment is preferably short so that the safety valve  60  is close to the milker unit  40 . This arrangement places the safety valve  60  downstream from the milker unit  40  so that the milker unit  40  is backflushed after each milking operation, but the long milk tube  41  or only a small portion of the long milk tube  41  is backflushed to minimize the quantity of milk that will be rinsed out of the long milk tube. The safety valve  60  can also be an integral part of the milker unit  40  by molding, bolting, screwing, gluing or otherwise attaching the safety valve  60  to the milker unit  40 . 
     It is noted that the terms “upstream” and “downstream” refer to the direction milk flows (right to left and identified as “M” in  FIGS. 9A and 9B ), from the dairy animal to the milker unit  40 , through the long milk tube  41 , and to the dairy milk&#39;s collecting, chilling, and storing facilities. During backflushing operations, backflushing and rinsing fluids flow upstream in the opposite direction of the milk flow. Dip does not pass through the path M because dip travels through a separate tube toward the dip manifold. 
     The pulsation conduits  82  and outlets  83  mate with a pulsation port on the milker unit  40  to provide vacuum pulsation for the milking operation. This pass through of vacuum is not necessary in the  FIG. 2C  embodiment because there is adequate clearance between the milker unit  40  and the safety valve  60  to feed vacuum lines directly to the vacuum port  85  on the milker unit  40 . The hanger  66  can be secured to a milker unit detacher mechanism (not illustrated) so that the milker unit  40  is supported above the floor or deck when not attached to a dairy animal. The hanger  66  may be unnecessary if the milker unit  40  includes such a feature. 
     The lower housing  70  generally defines a chamber  90  that is preferably shaped as a cylindrical cavity, but other shapes could be used to ensure proper arrangement of parts. Milk flows through a lowermost portion of the chamber  90  during a milking operation, from the milk inlet  62  to the milk outlet  64 . 
     The lower housing  70  also defines one or more (preferably three laterally spaced apart) holes  92  to vent from the chamber  90  to atmosphere. The holes  92  should be large enough to ensure adequate drainage and venting. The holes  92  are depicted as being on a downstream side of the lower housing  70 , but can be other places as well. Positioning the holes  92 , as depicted, on the downstream side of the lower housing  70  prevents alignment with piston holes that are used to dispense backflushing fluids. 
     Disposed in the lowermost portion of the chamber  90  is a seal insert  94 . (See  FIGS. 10A and 10B ) In a preferred embodiment, the seal insert  94  includes an upper ring-shaped portion  96  and a lower u-shaped portion  98 . The upper ring-shaped portion  96  and lower u-shaped portion  98  are preferably formed as an integral unit made of silicone or other elastomeric material such as (EPDM), but they could be separate seals, if desired. 
     The upper ring-shaped portion  96  is disposed against an interior chamber  90  surface, and is preferably supported by a seat  102   f  ( FIGS. 9G and 9H ) formed in the interior of the lower housing  70 . When in the milking position, the upper ring-shaped portion  96  forms a seal with a lower portion of the backflush piston  120  to seal the milk flow outlet  64  from backflushing and dip valve components. See  FIGS. 9A and 9G , for example. 
     The lower u-shaped portion  98  of the seal insert  94  is disposed transversely to the flow of milk from the milk inlet  62  to the milk outlet  64 . As best seen in  FIGS. 9G and 10B , an interior surface of the lower u-shaped portion  98  includes an upstream flange  104  and a downstream flange  106  joined to and spaced apart by a web  108 . The lower u-shaped portion  98  can be supported by a mating recess in the lower housing  70  chamber  90  wall ( FIG. 9E ). The functions of these components are explained in detail below in connection with the operation of the backflush piston  120 , but the space defined between the upstream flange  104 , the downstream flange  106 , the web  108 , the backflush piston  120 , and necked-down portion  130  (when in the backflush position) is a vent that communicates with one or more of the vent holes  92  to provide a double seal or “block” and a space between for “bleeding” to atmosphere. 
     In addition, the use of seal flanges  104  and  106  as the only contact with the backflush piston  120  reduces sticking to one another in a way that would impede operation. Also, debris such as bedding material, dirt, and sand that moves through the milker unit  40  is less likely to prevent the backflush piston  120  forming a seal with the seal insert  94 . It also provides clearance for the backflush piston  120  which helps reduce damage to the backflush piston  120 . 
     The seal insert  94  is preferably secured to the lower housing  70  with a screw  109  and a reinforcing plate  110 , which is preferably molded integrally with the seal insert  94 . 
     Referring to  FIGS. 9A-E , disposed in the lower housing  70  chamber  90 , is the backflush piston  120 . The backflush piston  120  is sized and shaped to move up and down (in the illustrated orientation) between a milking position ( FIGS. 9A  and C) and a backflushing position ( FIGS. 9B ,  9 D and  9 E). The backflushing piston  120  operates during both backflushing and dipping operations, so its name and lower position are to be understood as generic terms for a piston and a closed position, respectively. As seen in  FIGS. 11A to 11C , the backflush piston  120  is substantially cylindrically shaped, but it can have other cross-sectional shapes to ensure that it is inserted into the chamber  90  with the proper orientation, for example. Also preferably, the backflush piston  120  is closed at its lower end  122 , open at its upper end  124 , and has a flange  126  extending radially outwardly from its upper end  124 . The flange  126  has gaps  128  to permit cleaning solution to flow past for enhanced cleaning of the seal. 
     Essentially, the backflush piston  120  is used to divide the chamber  90  and seal the portion above from the portion below and to at least partially define a flow path for backflushing fluids into the milker unit  40 . Also, the backflush piston  120  is in the backflushing position when applying teat dip and when backflushing, but not when the safety valve  60  is self-cleaning. 
     As best seen in  FIGS. 11A to 11C , the backflush piston  120  has an exterior shape that includes an annular necked-down portion  130  adjacent to the flange  126 . The necked-down portion  130  preferably has an outside diameter that is smaller than the outside diameter of the lower portion of the backflush piston  120 , and extends at least partially around the backflush piston  120 . 
     The exterior surface of the backflush piston  120  further includes two piston by-pass vents  134  on opposite sides of the backflush piston  120 . The piston by-pass vents  134  are essentially indented portions arranged transversely to the milk flow path from the milk inlet  62  to the milk outlet  64 , and are positioned high enough on the backflush piston  120  so that a lower portion of the backflush piston  120  can mate and seal with the upper ring-shaped portion  98  of the seal insert  94  when in the milking position, and mate and seal with upstream and downstream flanges  104  and  106  of the lower u-shaped portion of the seal insert  94 . The by-pass vents  134  do not seal with the upper ring-shaped portion  96  when in the backflush piston  120  is in the backflush position. This arrangement provides a vent for the chamber  90  to bleed off differential pressure. 
     Next, the backflush piston  120  includes one or more (preferably two laterally spaced) holes  138  oriented radially to the backflush piston  120 . The holes  138  are formed or machined into the backflush piston  120  so that they are directed toward the milk inlet  62  when the backflush piston  120  is in the backflushing (lowered) position ( FIGS. 9B and 9D ), and are above the upper ring-shaped portion  96  of the seal insert  94  when the backflushing piston  120  is in a milking (raised) position ( FIG. 9A ). With this arrangement, the holes  138  are sealed from the milk supply by the upper-ring shaped portion  96  of the seal insert  94 . 
     As best seen in  FIG. 11C , inside the backflush piston  120 , and adjacent to, but not blocking the holes  138 , are two longitudinally oriented and inwardly extending flow vanes  142  that ensure that the backflush fluids flow through the holes  138  in a desired direction. The flow direction is typically selected based on the shape and/or configuration of the milker collection bowl  44  of the milker unit  40 . This arrangement permits the backflush piston  120  to be part of a backflush fluid conduit that extends through the safety valve  60 . 
     Also formed on the interior surface of the backflush piston  120  are two pairs of longitudinally and inwardly extending key ribs  144  ( FIGS. 11A and 11C ). Each pair of key ribs  144  is disposed opposite the other. When the backflush piston  120  is disposed in the lower housing  70 , the key ribs  144  are arranged on interior sides of the backflush piston  120  that are transverse to the direction of milk flow, and slidably engage an upwardly extending connector  160 , described below. 
     Disposed in the lower housing  70  chamber  90  between the seal insert&#39;s  94  interior surface and an underside of the flange  126  of the backflush piston  120 , is a piston return spring  150 . The piston return spring  150  acts between the flange  126  of the backflush piston  120  and the upper ring-shaped portion  96  of the seal insert  94 . Preferably, a metal ring  152  is positioned between the piston return spring  150  and the top of the upper ring-shaped portion  96  of the seal insert  94  to transfer spring loads without undue pressure or abrasion on the seal insert  94 . 
     The piston return spring  150  is arranged to bias the backflush piston  120  upward toward the milking position ( FIGS. 9A and 9C ). The piston return spring  150  can be made of metal, plastic or other material, and preferably has just enough force that can move the backflush piston  120  over friction with the seal insert  94 , but can be overcome by pressurized air to move the backflush piston  120  downward. The piston return spring  150  and the other springs described herein can be any type of biasing device. 
     To compress the piston return spring  150  and move the backflush piston  120  toward the backflush position ( FIGS. 9B and 9D ), compressed gas, such as air, is fed into the safety valve  60 , via an air inlet  184 , which applies pressure to a backflush operation plate  230  (described in detail below) that, in turn, applies pressure to the backflush piston  120 . The piston return spring  150  is designed to yield to the pressure exerted by the compressed pressurized air/gas, but to also quickly return the backflushing piston  120  to the milking position ( FIGS. 9A and 9C ). 
     Also as stated, the backflush operation plate  230  transmits air pressure to the backflush piston  120 , when the pressurized gas is vented or removed by the piston spring  150 . One embodiment of a backflush operation plate  230  in accordance with the present invention is illustrated in  FIGS. 12A and 12B  has a central opening  231  positioned around a central shaft  198  of the upper housing  74 . The backflush operation plate  230  is essentially a disk defining a recess  238  for receiving the lip  239  of the top of the backflush piston  120  so that the backflush piston flange  126  is in bearing contact with a lower rim  242  of the backflush operation plate  230 . 
     An outer u-cup seal  234  ( FIGS. 12A and 12B ) fits on a mating seat  244  of the backflush operation plate  230 . Alternatively, the u-cup seal  234  could be replaced with a seal formed integrally with the backflush operation plate  230 . The outer u-cup seal  234  extends radially outwardly from the outer diameter of the backflush operation plate  230  for sliding and sealing engagement with the inner surface of the lower housing  70 . An inner stem seal  236  is disposed in an inner annular recess  246  on the backflush operation plate  230  and extends inwardly to be in sliding and sealing engagement with the upper housing central shaft  198 . 
     When in the milking position, pressurized air can flow from the air inlet  184  of the upper housing  74  to force the backflush operation plate  230  downward against the force of the piston return spring  150 , and move the backflush piston  120  into the backflushing position ( FIGS. 9B ,  9 C, and  9 D), while also preventing backflush fluids from flowing upward into the upper housing  74 . 
     A second embodiment of a backflush operation plate  230  is illustrated in  FIGS. 9A ,  9 B,  12 C and  12 D, and has a central opening  231  and a recess  238  for receiving the lip  239  of the backflush piston  120 . Reinforcing ribs  233  are formed above and below a wall  232 . 
     This embodiment of the backflush operation plate  230  includes integrally molded seals  235  and  237  around the outer annular surface and an integrally molded seal  239  and  241  around the inner annular surface. This design is less costly, requires fewer parts, and is easier to assemble and replace. 
     The upper seals  235  and  239  seal air pressure to move the backflush piston  120  into a backflush position. The lower seals  237  and  241  wipe dirt and debris from mating surfaces when moving to the backflushing position, and seal out water during a self-cleaning cycle. 
     Extending though the central opening  231  of the backflush operation plate  230 , is a central shaft  198  of the upper housing  74  (described in detail below). Extending through the central shaft  162 , is a connector  162  that engages the backflush piston  120  with the dip valve piston  268 . As illustrated in  FIG. 13 , the connector  160  includes a central shaft  162 , a shaft key  164  at the top of the central shaft  162 , and a pair of tabs  166 . The shaft key  164  joins to the dip valve piston  268  and the shaft tabs  166  to slidably fit into the piston connection rib pairs  144  formed on the inside of the backflush piston  120 . This allows for differential movement between the dip valve piston  268  and the backflush piston  120 . The bottom of the connector  160  bears on the inside of the lower end  122  of the backflush piston  120 . 
     When pressurized air is applied to move the backflush piston  120  downward, the connector  160  is not pulled down because of their sliding relationship, as described above. Instead, the backflush operation plate  230  continues to move down even after the backflush piston  120  engages and slightly compresses the seal insert flanges  104  and  106  to close off the milk passage. This additional downward movement results in the backflush operation plate  230  engaging the tops  169  of the connector tabs  166  to force the connector  160  downward. When the connector  160  moves downward, the dip valve piston  268  is pulled down to open the dip valve piston  268  due to the fixed connection between the two to release dip. 
     The sequence of the differential movement between the backflush piston  120  and the dip valve piston  268  ensures that the backflush piston  120  has sealed off the milk line before any possibility of the dip valve piston  268  opening. In addition, the backflush piston  120  requires a relatively large movement to close off the milk passage, but the dip valve piston  268  needs to move only a relatively small amount to open. For example, the backflush piston  120  moves about 0.75 inches, and the dip valve piston  268  moves about 0.15 inches. This differential movement is not absolutely necessary, but it reduces the overall height of the safety valve  60 , and provides to above-described safety factors. 
     The connector tabs  166  upper portions are spaced radially apart from the central shaft  198  so that when the connector  160  is in a milking position, the tabs  166  will not engage the central shaft  198  of the upper housing  74 . 
     When dipping and backflushing operations are finished, air pressure applied to the backflush operation plate  230  is released, and the dip valve spring  326  (explained in more detail below) urges the dip valve piston  268  (upward as seen in the figures). Due to their sliding relationship, the connector  160  does not pull the backflush piston  120  back up. Instead, the sliding relationship between the connector  160  and the backflush piston  120  leaves only the piston return spring  150  to urge the backflushing piston  120  back to a milking position, and when the backflush piston  120  approaches the top of its movement, it can engage the connector  160  to provide a redundant force against the dip valve piston  268 . 
     The central shaft  162  of the connector  160  defines a longitudinal channel  168  through which backflushing fluid flows down, into the backflush piston  120 , and out the backflush piston  120  holes  138 . A lower end of the longitudinal channel  168  also mates with the flow vanes  142  in the backflush piston  120  to define a backflush fluid conduit for flow efficiency. 
     The central shaft  162  also defines a slot  172  in an upper portion of the central shaft  162  through which cleaning fluid flows during backflushing and self-cleaning. 
     The connector  160  extends upward, out of the lower housing  70 , and into the upper housing  74  for connection to components described below. 
     Upper Housing 
     As depicted in  FIGS. 9A through 14A , for example, the upper housing  74  preferably includes connecting shafts  180 , two air inlets  184 ,  185 , a backflush inlet  186 , a teat dip inlet  188 , a teat dip outlet  190 , and a guard  192  for protecting the inlets from damage. 
     The air inlet  184  enters the upper housing  74  and turns downward ( FIG. 14B ) to operate the safety valve  60  by acting on the backflush operation plate  230 , and it is connected via a hose or other suitable fluid communication device to valve  611  and outlet  615  on the valve block  610  ( FIGS. 6A to 6D ). Air through the air inlet  185  enters the upper housing  74 , turns upward and through an umbrella valve  253   a  ( FIG. 14D ) to “slug” dip and other fluids through the safety valve  60 , related dip delivery tubes, and chambers. The air inlet  185  is in communication with the air chase outlet  446  on the dosage valve  84 . The backflush inlet  186  is in fluid communication with valve block outlet  637  on the valve block  610  to feed backflush fluid, water, and air to the safety valve  60 . The backflush inlet  186  enters the upper housing  74  and the flow is diverted into two paths. One flow path turns upward and enters through umbrella valve  253   b  to clean the dip components. The other flow path extends into the central shaft  198  and then flows down to clean the safety valve  60  and milker unit  40 . The dip inlet  188  is in communication with the dosage valve outlet  438 , and enters the upper housing  74  where it turns up through umbrella valve  253   c . The rest of the dip flow path is described below. 
     Generally, the interior of the upper housing  74  defines a longitudinally extending air conduit in the hollow central shaft  198 , a backflush chamber  200 , a dip inlet chamber  204 , and a dip outlet chamber  206 . A transverse wall  210  divides the upper housing  74  and at least partially forms some of the chambers  200 ,  204 ,  206 . 
     Like the lower housing  70 , the upper housing  74  is preferably made of the same translucent plastic described above for the upper housing  74 , and for the same reasons. The upper housing  74  is sized and shaped to mate with and be connected to the lower housing  70 , preferably using screws  78 , bolts, and/or bushings, but they can also be formed integrally with one another. A ring seal  214  is provided in an annular recess formed in the lower end of the upper housing  74  to seal the interface between the lower housing  70  and the upper housing  74 . 
     As best seen in  FIG. 14B , the first air inlet  184  communicates with the air conduit in the central shaft  198  to feed compressed air against the backflush operation plate  230  and into the lower housing  70  to force the backflush piston  120  into the backflushing position ( FIG. 9B ). 
     As depicted in  FIGS. 14C and 14D , the second air inlet  185  is in communication with the dip inlet chamber  204  via a hole  218  to provide pressurized air from the dosage valve  84  outlet  446  that purges cleaning fluids from the safety valve  60  and any related hoses, lines, and dip manifold, liner mouth piece (lipped portion in liner head), and dip channels. 
     The backflush inlet  186  extends radially inwardly to the upper housing  74  and communicates with the central shaft  198  and the longitudinal channel  168  in the connector  160  (see  FIG. 13 ) to supply backflush fluid to the backflush piston  120 , and out of the backflush piston holes  138 . Preferably, the backflush inlet  186  is arranged asymmetrically (slightly tangential) to the central shaft  198  to allow for adequate connection space for all of the hoses and to generate some beneficial cleaning turbulence when the safety valve  60  is cleaning itself. 
     As seen in  FIG. 14F , the dip inlet  188  extends into the upper housing  74  and turns upwardly through a third opening  224  into the dip inlet chamber  204 . 
     As described above, there is a backflush operation plate  230  that acts to move the backflush piston  120  down. The backflush operation plate  230  is disposed in the lower housing  70 , but slides on the central shaft  198  of the upper housing  74  because the central shaft  198  extends downward into the lower housing  70 . 
     Should the safety valve  60  only be used for backflushing or washing animal teats, there is only a need for the above-described items, and the cap  76  mates with the upper housing  74  and the safety valve  60  functions to seal and backflush the milker unit  40 . If teat dip application functions are desired, the items described below are included. 
     Dip Valve Components 
     When teat dipping is used as an option,  FIGS. 14E ,  14 F,  15 ,  16 A,  16 B,  16 C, and  16 D for example, show that the safety valve  60  have in its upper housing  74  dip valve components that include; the dip inlet  188 , the dip outlet  190 , the dip inlet chamber  204 , the dip outlet chamber  208 , as well as the elements described below. The dip inlet  188  is connected by a hose to be in fluid communication with the dosage valve outlet  438 , and the dip outlet  190  is connected to a dip delivery channel (described below). The safety valve  60  includes a top plate  262 , a top plate seal  264 , a dip valve piston  268  disposed in the top plate  262  for sliding movement between a dip position (down as viewed in  FIG. 14F  and a milking position (up as viewed in  FIG. 9A ), and a dip piston seal  270 . 
     The backflush inlet  186 , the dip inlet  188 , and the second air inlet  185  are each closed with flexible valves  253   a ,  253   b  and  253   c  that are preferably an “umbrella valve” made of silicone, and connected together at  254  for ease of manufacture and installation. (See:  FIG. 17 ) The valves  253   a - c  are one-way valves that are opened by air, water, or dip pressure to allow air, water, or dip to enter, but the valves  253   a - c  restrict flow in the opposition direction because the valves  253   a - c  are resilient and close when there is no dip, air or water pressure to keep them open. The valves essentially function as suction cups when no pressure is there to open them. Also, pressure from other fluids entering other valves contributes to keeping the valves  253   a - c  closed. 
     As depicted in  FIGS. 16A to 16D , the top plate  262  includes a cylindrical cup portion  272  with a transverse bottom wall  273  for slidably receiving the dip valve piston  268 . The top plate  262  also includes fastening tabs  274  through which screws  78  can extend to fasten the top plate  262  to the top of the upper safety valve housing  74 . The top plate  262  includes an outer annular seat  276  on which the cap  76  is positioned. The top plate  262  can be made of any suitable material including Radel R5000, other plastic or stainless steel. The materials used for the various parts of the safety valve  60  are preferably the same or at least have similar properties such as coefficient of thermal expansion and chemical resistance. 
     The top plate  262  and the top plate seal  264  are preferably formed together to reduce expense, avoid an assembly step, and to ensure alignment of the various holes. Alternatively, aligning these parts can be done with two seal alignment pins extending downward from the top plate  262  that are preferably of a different shape and/or orientation and/or spacing from one another and other functional components. Regardless of which method is used, the seals  324  and  325  must match with holes  288  and  289  in the bottom wall  273 . 
     In the bottom wall  273  of the top plate  262  there is an upstream dip opening  288 , a downstream dip opening  289 , and a central opening  290  through which the connector  160  extends for connection to the dip valve piston  268 . 
     Inside the cylindrical cup portion  272  of the top plate  262  and the top surface  294  of the bottom wall  273  defines a dip flow channel  296  with the bottom on the dip valve piston  268 . An additional recess can be formed in any of these surfaces to help control dip flow, but the space between the dip valve piston  268  and the top surface  294  of the bottom wall  273  is adequate between  312  and top  262 . The dip flow channel  296  can be any shape that provides efficient flow characteristics for dip, with the dip flow channel  296  extending between the dip openings  288  and  289 . Dip flows up through the upstream dip opening  288 , across and down through the downstream dip opening  289 . 
     The dip valve piston  268  is depicted in  FIGS. 9F ,  14 C,  14 F and  15 , and is sized to be slidably disposed in the top plate  262  cylindrical cup portion  272 , and includes a head  298  defining an outer annular seal recess  300  with a seal  301 , a central connector post  302  extending downward, a downwardly extending upstream dip valve pin  304 , a downwardly extending downstream dip valve pin  305 , a number of notches  308  that provides better rinsing of u-cup, and a grab point for assembly, an upper recess portion  310 , and a bifurcated post  312  that extends upward above the surface of the head  298  to form a stop. The post  312  is also preferably bifurcated for improved fluid flow for cleaning. 
     The central connector post  302  of the dip valve piston  268  is hollow and includes at its lower end a receptacle  316  that mates with the connector  160  preferably in a snap relationship. The receptacle  316  is open at one side and to receive the top end of the connector  160  by engaging a connector slot  318 . 
     A dip valve spring  326  ( FIG. 9E ) is disposed in the central shaft  198  of the upper housing  74  and is prevented from extending downward and out of the central shaft  198  by one or more spring seats  328 . The dip valve spring  326  is also positioned around the central shaft  162  of the connector  160  to bias the connector  160  and the dip valve piston  268  (upward) toward a milking position. 
     The backflush piston return spring  150  biases the backflush piston  120  upward and the dip valve spring  326  biases the dip valve piston  268  upward despite the use of the connector  160  joining these two pistons  150 ,  268 . The force of two springs  150 ,  326  is not necessary to move the pistons  150 ,  268  upward, but they provide a redundancy that ensures safe operation of the safety valve  60 . 
     The dip valve pins  304 ,  305  each include a stem  320  and a valve head  322 . The valve heads  322  are sized and shaped to substantially close and seal the dip openings  288  and  289  (with seals  324  and  325 ) in the bottom wall  273  of the top plate  262  when the dip valve piston  268  is in the milking (or closed) position ( FIGS. 9A and 9C ). 
     The dip openings  288  and  289  are sealed when the dip valve piston  268  is closed. On opposite sides of these seals, there may be differential pressures that could cause dip to seep past the seals  324  and  325 . Accordingly, a vent between the dip openings  288  and  289  and seals  324  and  325  is provided for the desired block-bleed-block feature that ensures safe operation of the invention. 
     To provide a suitable vent, there is a skirt  277  extending downward from the bottom wall  273  of the top plate  262 . The plate seal  264  is disposed within the skirt  277 . Formed in both the plate seal  264  and/or the skirt  277  are two slotted vents  282  that extend radially outwardly and vent/bleed to atmosphere at vent holes  279 . The slotted vents  282  and vent holes  279  are positioned between the upstream dip opening  288  and the downstream dip opening  289  to provide a block-bleed-block arrangement. 
     As seen in  FIG. 9F , two dip hole seals  324  and  325  enhance the seal between the dip openings  288  and  289  and the dip valve heads  322 , and provide initial and secondary seals or “blocks” In between the seals  324  and  325 , the top plate  262  is vented in two places. The first vent is B 5  that passes down and past the dip piston post  302  to vent/bleed the top plate  262  out of the lower housing vents  92  described above. The second vent is B 6  that vents upward and out of the cap  76  vents  334 . Thus, the blocks  324  and  325  are spaced apart with two bleeds B 5  and B 6  disposed in between to provide important block-bleed-block functions. 
     When the dip valve piston  268  is in the dipping position ( FIG. 14F ), the dip valve heads  322  move downward and no longer seal the dip openings  288  and  289  because the stems  320  of the dip valve pins  304  are smaller than the dip openings  288  and define annular openings through which dip flows. Dip flows up through the upstream dip openings  288 , across to the other side, and down through the downstream dip opening  289 . 
     Safety Valve Cap 
     The cap  76  of the safety valve  60  is best depicted in  FIG. 18 . The cap  76  is cup-shaped with four screw holes  330  for securing the cap  76  to the other portions of the safety valve  60 . Preferably, the cap  76  is made of a translucent plastic, such as Radel R5000 for the reasons stated above. 
     The cap  76  also includes a pair of cap vents  334  that are formed by gaps  336  in the cap  76  and vent hoods  338 . The vent hoods  338  extend downwardly from the cap  76  and ensure that the cap  76  is vented to atmospheric pressure. 
     A bottom edge  332  of the cap  76  rests on the top plate  262  of the dip safety valve  260  when present or onto the upper housing  74  when the dip safety valve  260  is not included. No seal is needed between the bottom edge  332  of the cap  76 . The cap  76  preferably includes an interior key  339  ( FIG. 18 ) that mates with a key-way on the upper housing  74  to ensure proper alignment and orientation of the vents  334 . 
     Safety Valve Operation 
     As stated above, the safety valve  60  must move between a milking position ( FIG. 9A ) and a backflushing position ( FIG. 9B ) to prevent contamination of the milk supply by the teat dip or backflushing fluids. Due to pressure differentials on opposite sides of the safety valve  60 , it is desirable to do more than simply seal off chemical, air, or other fluid lines from the milk supply. With the present invention, the pressure differential on each end of the safety valve  60  is avoided with vents exposed to atmospheric pressure to “bleed” off any pressure differential that may cause unwanted seepage past a seal. In this manner, pressures on each side of the safety valve  60  are isolated from one another and seepage of chemicals, air, and other fluids into the long milk tube and milk supply is prevented. Generally, seals are provided in pairs with a vent to atmosphere disposed between the seals of each pair. This arrangement provides a “block-bleed-block” function to ensure that fluid that seeps past one seal cannot seep past the other seal. 
     As seen in  FIG. 9C , to achieve the “block-bleed-block” function when the safety valve  60  is in the milking position ( FIGS. 9A and 9C ), a block is formed by the seal insert  94 , and specifically by the upper ring-shaped part  96  of the seal insert  94 . The upper ring-shaped part  96  seals an annular gap between the interior surface of the chamber  90  and a lower cylindrical portion of the backflush piston  120 . 
     The bleed function in the milking position ( FIGS. 9A and 9C ) is performed by two different paths between the safety valve chamber  90  and the atmosphere outside of the safety valve  60  and the milker unit  40 . It is only necessary to have one such “bleed” path, but the illustrated embodiment provides a bleed redundancy for added safety. 
     The first bleed path is illustrated in  FIG. 9C  and is designated as B 1 . This first bleed path B 1  is a path from the chamber  90  through backflush piston holes  138 , and through holes  92  in the lower housing  70 . The second bleed path B 2  is from the chamber  90  of lower housing  70  through a space between the central connector post  302  of the dip safety valve piston  268  and central opening  290  of the top plate  262 , through the cylinder  272  of the top plate  262 , past the outer annular seat  276  of the dip valve piston  268 , up into an interior portion of the safety valve cap  76 , and out cap vents  334 . The second line of “block” function is performed by seals in the valve block  610  that controls the flow of backflushing fluids, air, water and teat dip into the safety valve  60 . Also, the valve block  110  includes a block-bleed-block feature, as described above as a redundant safety feature. 
     As seen in  FIGS. 9B ,  9 D, and  9 E, the safety valve  60  is in the backflushing position with the backflush piston  120  in its lowermost position with a lower surface of the backflush piston  120  engaging the u-shaped  98  portion of the seal insert  94 . More specifically, the lower surface of the backflush piston  120  is in contact with the upstream flange  104  and the downstream flange  106  of the u-shaped  98  portion of the seal insert  94 . This arrangement provides a double block between the safety valve  60 , milk inlet  62 , and milk outlet  64 . 
     Between the upstream flange  104  and the downstream flange  106  is the web  108  of the seal insert  94 . The web  108  is spaced apart from the lower surface of the backflush piston  120  to define part of a “bleed” path B 3  ( FIG. 9E ) that by-passes the upper portion of the backflush valve  120  and the upper ring-shaped portion  96  of the seal insert  94  through the piston by-pass vents  134 , and through the holes  92  in the lower housing  70 . This block-bleed-block arrangement prevents backflushing fluid and teat dip from entering the milk supply because any seepage past either seal will drain through the gap  111 , which is a bleed path. ( FIG. 9E ). 
     The teat dip block-bleed-block function is performed by the upstream dip valve pin  304  in connection with a dip opening  288  in the top plate  262 , and the corresponding dip hole seal  324  of the top plate seal  264 . A second block is formed by the downstream dip valve pin  305  in connection with a dip opening  288  in the top plate  262  and the corresponding dip hole seal  324  of the top plate seal  264 . 
     In this arrangement, there are at least two bleed paths. Bleed path B 5  in  FIG. 9F  is defined by a space between the dip valve piston  268  and the interior portion of the top plate  262  cylindrical cup portion  272 . B 5  is further defined by a space between the dip piston central connector post  302  and the central opening  290  of the top plate  262 , the lower housing chamber  90 , and the three openings  220 ,  222 , and  224 . 
     Another bleed path B 6  ( FIG. 9F ) is defined by the space between the dip valve piston  268  and the interior portion of the top plate cylindrical cup portion  272 , upward into the cap  76  and out of the cap vent hoods  338 . 
     Yet another bleed path is formed in the valve block housing  613  by the spool  621 , so that differential pressure cannot pass the valves and into any of the feed lines to the safety valve  120 . 
     When it is desired to apply teat dip, the dip safety valve  260  is operated by compressed gas such as air or other suitable fluid, mechanical device or electrical device to move the dip valve piston  268  downward against the force of the dip valve return spring  326  so that the dip valve pins  304  and  305  no longer seal the dip valve holes  288 ,  289 . 
     As seen in  FIGS. 14A and 14E , teat dip is pushed through the dip inlet  188  in the upper housing  74 . The dip flows under pressure through the dip inlet chamber  204 , up through upstream dip hole  288 , through the flow channel  238 , through the downstream dip hole  289 , through the dip outlet chamber  208 , out through the dip outlet  190 , through tube  345  joined to the dip outlet  190  with an elbow  580  and toward the dip manifold  170 . 
     When backflushing fluid (such as wash chemicals, rinse chemicals, water, and/or air) are to be pumped from the safety valve  60  upstream into the milker unit  40 , the following operation takes place. It should be understood that during a backflush operation, the milker unit  40  will not be upright as illustrated in most of the drawings. Instead, the milker unit  40  will be upside down or at some generally downward angle, and hanging from a detacher mechanism as in  FIG. 4B . This position aids in draining backflush liquids from the milker unit  40  in addition to a final “air slug” that is pumped through the safety valve  60  and the milker unit  40 . 
     Backflushing fluid enters the upper housing  74  backflush inlet  186 , down through the central stem  168 , down through the backflush piston  120 , out of the holes  138  in the backflush piston  120  and “upstream” through the milk inlet  62  and into the milker unit  40 . The safety valve components as described define a backflush fluid conduit extending through the safety valve  60  between the backflush fluid inlet  186  and the milk inlet  62 . 
     When desired to clean and rinse the safety valve  60 , there can be alternating pulses of air and water for any desired number of sequences after the backflushing piston  120  returns to the milking position. Preferably, there are more than one pulse of both air and water to provide agitation, and efficient and thorough cleaning. Water used in rinsing the safety valve  60  also lubricates the seals for less friction and resistance in moving the various pistons and valves. For this reason, it is also desirable to wash or rinse the safety valve  60  prior to start-up. 
     Also, it is preferred to clean the safety valve  60  with the backflush piston  120  in its milking position because some milk may enter the bleed area next to the backflush piston  120  when the backflush piston  120  is in the upper position. This will clean backflush chemicals, teat dips, and residual milk from the safety valve  60 . This process is done automatically by blowing water and air through the safety valve  60  before attaching the milker unit  40  to another animal. 
     Control Operation charts that illustrate a sequence of all the various elements that take place in a typical single cycle of the safety valve  60  are illustrated in  FIGS. 22A ,  22 B, and  22 C. Charts  22 A,  22 B, and  22 C are each a portion of a complete backflush and dip application cycle. Chart  22 A is a dipping and backflushing portion of the cycle, Chart  22 B identifies additional steps in the backflush operation, and Chart  22 C shows the steps of a dosing valve recharged in preparation for the next dipping procedure. (The abbreviation “BF” in the charts refers to backflush.) From the end of milking, closing off the milk line, dipping a cow, backflushing the milker unit, and self-cleaning of the safety valve, to being ready for a next milking operation is about forty-five seconds, in the preferred embodiment. Chart  22 D illustrates steps in the system  20  operation and the function that each step serves. 
     Dip Manifold 
     A teat dip manifold  170  is preferably included to separate the dip dose into four substantially equal quantities. The dip manifold  170  also isolates vacuum in each liner head  172  from vacuum in other liner heads  172  (See  FIGS. 19A-E ). Preferably, a four quarter milker unit system includes a backflushing safety valve  60  pre-assembled to the milker unit  40 . When adding the dipping function to an existing system, the dip manifold  170  can be secured to a four quarter milker unit  40  with an air divider  174 , which is part of a liner securing device or it can be loosely attached in any convenient location. In the embodiment of  FIG. 1A , the manifold  834  is mounted on the milker unit collection bowl  844 . 
     Two manifold designs are shown in  FIGS. 19A-E  and  19 F-H respectively The primary functions in both embodiments are to prevent air flow from one teat cup  48  to the other during milking, and provide even distribution of dip to all teats, and to distribute substantially even volumes of dip to each teat. 
     The manifold  540  depicted in  FIGS. 19A-E  includes a base  542 , a cover  544 , alignment pins  546  in the base  542 , four outlets  550 , one inlet  552 , a bladder seal  554 , and outlet guards  556 . 
     The base  542  and cover  544  are preferably molded from plastic, but could be any suitable material. They are assembled by aligning the alignment pins  546  of the base  542  with recesses in the cover  544 . The base  542  and the cover  544  are joined by welding, adhesive, or mechanical fastener. 
     As seen in  FIGS. 19A through 19E , the base  542  includes a manifold channel  560  in fluid communication between the inlet  552  and the four outlets  550 . The manifold channel  560  in  FIGS. 19C and 19D  is preferably bifurcated adjacent to the inlet  552  to divert dip flow to each side of the manifold  540 , and then bifurcated again at each side of the manifold  540  for a total of four substantially equal doses of dip to flow through corresponding outlets  550 . 
     The alternate manifold channel  560  illustrated in  FIGS. 19F and 19G  is also bifurcated adjacent to the inlet  552 , but in this embodiment, there is no other bifurcation in the flow channel  560 . Other flow channel designs are also possible. 
     The base  542  further includes mounting tabs  564  ( FIG. 14 ) that are used to join the manifold  540  to any suitable location. Other mounting methods are also possible. 
     The manifold  540  also includes the flexible bladder  554  made of silicone or other elastomer, and disposed between the base  542  and the cover  544  to seal the interface between the two, but to also serve as a check valve for individual outlets  550 . The bladder  554  includes alignment holes  570  to ensure proper alignment with the base  542  and cover  544  during assembly, and is joined to the base  542  with screws  545  or other suitable fasteners. 
     The bladder  554  includes flexible vacuum isolation diaphragm seals  576  each of which is disposed in the channel  550  adjacent to a corresponding outlet  550  so that flow through the outlet  550  is possible in only one direction. This arrangement of bladder vacuum isolation diaphragm seals  576  adjacent to the outlets  550  blocks pressure differentials in individual dip outlets  550  from adversely affecting dip flow through other dip channels  550 . 
     The manifold  540  depicted in  FIGS. 19A through 19E  has four independent diaphragm seals  576  that each seal a separate outlet  550 . The manifold  540  depicted in  FIGS. 19F and 19G  has two independently operating diaphragm seals  576  that each seal a pair of outlets  550 . In both embodiments, the seal channel  560  is sized and shaped to receive a matching diaphragm seal  576 , which are preferably formed as embossments on the bladder  554 . 
     Each of the two vacuum isolation diaphragm seals  576  includes a pair of dip outlets to prevent pressure differentials between pairs of dip outlets  550  from affecting dip flow through neighboring pairs of dip outlets  550 . 
     Dip flows into the manifold  540 , through the inlet  552 , the manifold channel  560 , and urges the diaphragm seals  576  upward against their natural bias toward a closed position. Once the diaphragm seals  576  are open, dip flows out individual outlets  550 . 
     The base dip inlet  552 , preferably has joined to or molded integrally with it, a widened portion  580  to provide a gripping surface when attaching and detaching a hose, for example. 
     Shell for Internal Dip Channel 
     Illustrated in  FIG. 15  is an external teat dip delivery tube for delivering dip to the liner is to pass the dip tube up along the inside of the teat cup  48 . 
     Illustrated in  FIGS. 16 to 19  is an internal teat dip delivery tube  190  that is disposed inside of a teat cup  48 . The delivery tube  190  can be secured to the interior wall of the teat cup  48  or it may simply extend through the teat cup  48  with no connections. 
     Depicted in  FIGS. 20A and 20B , are teat cup assemblies  700  for use with the present invention or separately with other dip delivery systems. The teat cup assemblies generally include a shell  702  and liner  704 . The liner  704  can be the type disclosed in application Ser. No. 12/157,924 which is incorporated herein by reference. The shell  702  is preferably a stainless sleeve with a TPR (thermal plastic rubber) bottom end or cap  734 . Stainless is preferred for the shell  702 , but molded (clear, translucent or opaque) plastic or other materials can be used, making it a very simple molded part that could include a dip channel  708  within the shell  702 . This embodiment of the teat cup assembly is preferred because it is easier to manufacture, since the cap will be a simple injection molded piece with no welding required. Nonetheless, other teat cup assemblies can be used with the other components of the present invention. 
     The shell  702  is a simple tube. The only welding will be to tack weld the dip delivery channel  708  onto the inside, as illustrated or outside in an alternate embodiment described below. The dip delivery channel is well protected from top to bottom, making the teat cup assembly  700  very robust. The dip channel  708  connects a liner fitting  720  to transmit dip to an internal dome in the liner. In  FIG. 20A , the liner fitting  720  extends outside of the liner head  722 , and in  FIG. 20B , the liner fitting  720  is inside the liner head  722 . These two options provide different assembly methods and visibility while assembling the parts. 
     Positive keying of the liner  704  to the shell  702  is provided by two slots  712  and  714 , one for the dip tube connection and one to force proper alignment, enabling the dip channel  708  connection. Additional holes  716  will be used as snaps to help hold the liner head  722  onto the shell  702  as cows may step on it. 
     A nipple  730  on the bottom of the shell  702  connects to a dip delivery tube or a connection using individual fittings pressed into bosses within the TPR can be used to provide flexibility from cow abuse with reduced breakage. The shell  702  is snapped into the cap  734  to provide a solid one-piece feel, making liner  704  change as easy as with a single piece shell  702 . 
     With the dip channel  708  on the inside, a triangular, square or manipulated round liner is preferred, so the liner  704  will not collapse and contact the internal dip channel  708 . 
     Shells for External Dip Channel 
       FIG. 20C  illustrates one embodiment for a dip passage  748  on the outside of the shell  48 . The dip passage  748  connects to the liner  704  when the liner  704  is assembled to the shell  48  in the proper orientation. The dip passage  748  connects to a liner fitting  724  in a manner similar to the embodiments of  FIGS. 20A and 20B . 
       FIG. 20D  illustrates another embodiment for a dip passage  766  on the outside of a shell  742 . The dip passage  766  connects to the liner  704  when the liner  704  is assembled to the shell  48  in the proper orientation. The dip passage  766  connects to a liner fitting  764  in a manner similar to the embodiments of  FIGS. 20A and 20B . The external dip passage  766  is protected by a rubber, silicone, or other material joined to the shell. The short milk tube  46  can be integral with the liner  704 , and the short milk tube  46  preferably terminates at a knob  770  that connects to a milk collection bowl. 
     Shell Liners 
     As stated earlier, preferred shell liners for use in the present invention are disclosed in U.S. application Ser. No. 12/215,706, which is incorporated herein by reference.  FIGS. 21A ,  21 B, and  21 C depict representative examples of a shell liner  920 , from that application. 
     In  FIG. 21A , there is depicted a milker unit liner  920  in accordance with the present invention. The liner  920  includes a dome  922 , a skirt  924 , a barrel  926 , and a delivery channel  928 . The skirt  924  extends downward from the dome  922  and is spaced away from the barrel  926  to define a recess  927 . 
     The liner  920  is sized and shaped to fit into a conventional outer shell or “teat cup” (not illustrated) so that the top of the teat cup fits in the recess  927  between the skirt  924  and the barrel  926 , but other shell types and alignment aids can be used. This relationship secures the liner  920  to the teat cup and forms a seal for the vacuum. The liner barrel  926  may have any cross-sectional shape including round, triangular, and square, or any other shape. Alternatively, a liner can comprise a separate dome and barrel that are connected to each other directly or indirectly using a teat cup or the other suitable device. The present invention is directed to a dome  922  having an inner surface to which flow diverters are joined regardless of the type, size, or shape of barrel. The liner  920  can be made of rubber, silicone, or other suitable materials. 
     The delivery channel  928  can be formed integrally with the other liner components or attached after the liner  920  is formed. The delivery channel  928  may be any of the design types described above, or it can be a separate component so long as it is attached to the liner  920  to act as a conduit for teat dip or cleaning fluids being introduced into the dome  930  from the safety valve  60 . 
       FIG. 21B  illustrates an embodiment of a liner dome  930  in accordance with the present invention, and that is removed from the other liner components and inverted to show an inner surface  932 . This dome  930  includes a teat opening  934 , and an annular recess  936  for mating with the top of a teat cup (not illustrated). 
     The liner dome  930  further includes a teat dip distribution structure having an inlet  966  (not depicted in  FIG. 21B , but see  FIG. 21C ), a first flow diverter which is illustrated in this embodiment as a flow bifurcating vane  942 , and a second flow diverter which is illustrated as a pair of ridges  944 . The inlet  966  is preferably an opening that is the same diameter as the delivery channel  928 , but it can be any size or shape to obtain satisfactory flow characteristics or simply provide ease of manufacturing. The inlet  966  could also include a nozzle in the form of a slit, for example, that is either molded into the dome  930  during manufacture or cut into the dome  930  after molding. A slit shape acts as a one-way valve to inhibit the flow of milk, teat dip  967  ( FIG. 21C ), cleaning fluid, and debris from flowing in the wrong direction through the inlet  966 . 
     The inlet  966  can also be a simple opening in the dome  930 , and a delivery tube may be used in combination with the inlet  966  so that the delivery tube defines the flow characteristics or a valve and the inlet  966  simply provides an opening through which teat dip passes into the dome  930 . Regardless of its shape or size, the inlet  966  is preferably joined to the dome  922  by being formed integrally in the liner dome  922 , but the inlet  966  can be joined to the dome  922  in any other suitable manner. 
     The inlet  966  is connected via the delivery channel  928  to a teat dip source and/or a backflushing source (not illustrated). In this manner, teat dip  967  ( FIG. 21C ) is provided through the inlet  966  under pressure from a pump, air pressure or other suitable device. 
     If left to flow directly toward a teat, most of the dip would be applied to the side of the teat closest to the inlet  966 , with some flow possibly reaching other sides of the teat if the dosage quantity is high enough. It is unlikely in practice that dip would reach all teat sides and even less likely that teat dip application would be uniform as preferred. 
     To redirect the inward and radial flow, the flow bifurcating vane  942  is disposed adjacent to the inlet  966  and in a flow path defined by the inlet  966 . The flow bifurcating vane  942  is shaped to split and redirect the upward flow from the inlet  966  into a substantially annular flow path or pattern around the periphery of the dome inner surface  902 . As depicted, the flow bifurcating vane  942  splits the flow substantially evenly in each direction to define a pair of flow paths, but if other inlets are used or other conditions warrant, the flow could be split in other proportions or simply redirected in a desired flow path. 
     The inlet  966  preferably defines two ramped and arcuate surfaces  920  on which the teat dip flows as it is being redirected. In this embodiment, a raised central portion  922  is used to confine the flow so that teat dip is not flowing directly toward the teat. In alternate embodiments, it is possible to permit some of the flow to be applied directly to the teat without being substantially redirected. In such embodiments, the central portion  922  may include openings, slots or ramps through or over which teat dip can flow. It is even permissible for some of the dip to flow over the bifurcating vane  912  and directly toward the teat. Further, the arcuate surfaces  950  can be shaped so that teat dip flow is not directed around the periphery, but instead through a flow pattern or radius that is smaller than the dome chamber&#39;s  902  periphery. 
     The flow ridges  954  preferably have arcuate shapes and contact surfaces that are joined to the inner surface  902  of the dome  930  and arranged in the flow path. The flow ridges  954  are shaped and sized to redirect the peripheral teat dip flow inward toward a cow&#39;s teat. In a preferred embodiment, the flow ridges  954  have a height dimension that redirects all the teat dip flowing from the flow bifurcating vane  942 . In alternate embodiments, the height of the flow ridges  954  could be reduced to permit some of the flow to by-pass the flow ridges  954  and flow to the part of the inner surface  902  opposite the flow bifurcating vane  912  or to other flow diverters (as described below). Further, the flow ridges  914  are depicted as being symmetrical, but they could be different sizes, shapes, positions, or orientations to provide asymmetric flow, if desired. 
     Most types of teat dip that would be flowing through the dome  930  have an inherent surface tension that helps establish a desired flow characteristic by remaining adjacent to the dome  930  surface and to the cow&#39;s teat so that the dip will cover areas of the teat that are not in the direct flow path defined by the flow diverters. 
     The flow diverters of the present invention are joined to the inner surface of the dome by being molded integrally with the dome, or they may be joined to the inner surface of the dome with glue or any other suitable means. 
       FIG. 21C  is an alternate embodiment of the present invention illustrating a cross-section of an upper portion of a liner  980  having a dome  982 , a barrel  984 , and a teat opening  986 . A teat delivery channel  990  is formed integrally with the dome  992 . A hose, pipe, or tube (not illustrated) can be joined to the delivery channel  990  as a conduit between a source of teat dip and the delivery tube  990 , as described above. The delivery channel  990  has at its upper end an inlet  966  that may be the same diameter of the delivery channel  990  or in the form of a nozzle or slit that is either molded into the liner  980  or cut after the liner  980  is molded. Other types of dip applicators can be used in the invention, but a dome with flow diverters is preferred. 
     Illustrated in  FIG. 21D , is a cross section of a shell  702  with an internal dip delivery channel  708  and with the liner barrel  780  collapsed. Without special precautions, a liner barrel can collapse, make contact with the dip delivery channel  708 , and cause premature wear and failure of the liner. With the dip channel  708  on the inside, a triangular, square or manipulated round liner is preferred to control the shape orientation of the collapsed barrel, so the liner  704  will not collapse and contact the internal dip channel  708 . 
     The liner barrel  780  in  FIG. 21D  is formed, machined or molded with slight variations in wall thickness, such as a relatively thin wall at portions  786  and relatively thick at portions  788 , to control collapse of the liner barrel  780  into an oval shape around a longitudinal axis  784  that is perpendicular to a transverse axis  786  on which the dip delivery channel  708  is disposed. This arrangement ensures that the liner barrel  780  does not contact the dip delivery channel  708 . Attachment nubs  788  are shown in the head of the liner to secure it to the shell  702 . 
     Preferably, the difference in wall thickness for the two portions  786 ,  788  is only from about 0.005 inches to about 0.010 inches, and is created by increasing thickness at portion  788 . An elliptically machined mold can be used to create this difference. 
     The present invention can have many benefits, including but not limited to, one or more of the following: automate the dipping process to increase operator efficiency and reduce operator fatigue; provide safe, individual disinfection of the teats to reduce pathogenic organisms on the teat; prevent transfer of infection from animal to animal, and thus improvement of udder health of the entire herd; reduce or minimize chemical consumption (as opposed to spray or other automated dipping systems); improve uniformity of teat dip application; prevent chemical contamination of the milk and of the downstream milk system lines; reduce water consumption during backflushing of the milker unit; and be retrofitted to nearly any available milking unit. 
     The above detailed description is provided for understanding the embodiments described and, unless otherwise stated, is not intended to limit the following claims.