Abstract:
An automated mixing drink dispenser ( 10 ) establishes a preselected feed rate of concentrate from a concentrate hopper ( 42 ) and ratio of concentrate to mixing water fed into a mixing chamber ( 42 ) through the Venturi effect created by swirling water fed into a mixing chamber ( 42 ) at a preselected water pressure ( 66 ) and preselected regulated flow rate ( 68 ) associated with the preselected feed rate of the concentrate. Concentrate is fed to a mixing chamber ( 42 ) from a concentrate hopper ( 42 ) having an open drain hole ( 50 ) openly connected to the mixing chamber ( 42 ). A stirring mechanism ( 106, 100, 101, 102, 104 ) mechanically mixes the concentrate within the concentrate hopper ( 42 ) to maintain a uniform density and viscosity and a gas pressure mechanism ( 92, 94, 96, 86 ) maintains a uniform head pressure of concentrate to facilitate maintenance of the preselected concentrate flow rate over time. Nitrogen gas in air is pumped through a nitrogen passing filter to fill the space ( 90 ) above the concentrate to both maintain head pressure and to reduce deterioration of the concentrate due to interaction with oxygen.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. 119(e) of U.S. provisional patent application No. 61/264,083, filed Nov. 24, 2009. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to an electric, automatic mixing drink dispenser for mixing liquid drink concentrate with water to make a mixed drink on demand and methods of mixing and dispensing drinks with such a mixing drink dispenser 
     2. Discussion of the Prior Art 
     Electrical, commercial mixing drink dispensers of type that mix liquid drink concentrate with carbonated or noncarbonated mixing water on demand to make and dispense a mixed drink are well known, but suffer from a number of disadvantages. When a manual switch is actuated, mixing water and drink concentrate from a concentrate hopper are injected into a mixing chamber where they are mixed together to make a mixed beverage and then dispensed. In some cases, actuation of the start switch starts a timer that fixes a preselected total quantity of mixed drink to be dispensed. In other dispensers, the mixing and dispensing proceeds continuously as long as a dispense switch is manually held in an actuated state. 
     In some cases, the mixing is achieved with rotating mixing blades that disadvantageously become dirty and need to be cleaned periodically or become worn and need replacement. In some cases, a drain valve, subject to wear and clogging may be used to block dispensing of the beverage from the mixing chamber until for a preselected time period until fully mixed. The concentrate is generally maintained within a concentrate hopper with a drain hole, while the mixing water is generally obtained from a public source of pressurized water from a faucet. Both the mixing water and the concentrate are fed to a proportional valve to maintain a preselected ratio of concentrate to mixing water over the mixing of the many mixed drinks that are made from the a single hopper load of concentrate. Again, such proportionate valves are expensive and require periodic cleaning and maintenance if the concentrate to mixing water is to be maintained. Other computer controlled valves based on mixing water quantity measurements and concentrate quantity measurement may also be used, but the need for a valve for each of the concentrate and water is still required as well as the higher cost of a computer and associated interfaces. 
     In mixing drink dispensers that rely upon the measured length of time that a concentrate outlet valve is open to determine the quantity of concentrate that is dispensed to the mixing chamber, a problem exists with respect to maintaining the rate of concentrate dispensing because of the lowering of the concentrate head pressure at the concentrate hopper drain hole as the concentrate in the hopper is gradually depleted and the level becomes lower. As the level of the concentrate in the hopper becomes lower, the head pressure forcing the concentrate out of the drain hole becomes less and the rate of concentrate flow gradually decreases. Such change in concentrate flow rates disadvantageously results in a non-uniform drink product which may be too strong when the concentrate hopper is first filled and is too weak when the concentrate hopper is nearly depleted. 
     The inventor has also noted that the concentrates fail to maintain a uniform density throughout the normal periods of storage within the concentrate hopper between concentrate refills. Consequently, even if the same fluid volume per drink is maintained over the plurality of drinks that are made, the uniformity of flavor intensity varies. Over time, the heavier elements of the concentrate gradually settle toward the bottom. Accordingly, after a period of time, the first drinks are made with a more highly concentrated concentrate than the drinks that are made later. 
     Another problem noted by the inventor with existing mixing drink dispensers is that in some cases the same concentrate may be stored within the drink dispenser over a substantial length of time. Even with cooling of concentrate, this long term storage of the concentrate exposed to the oxygen in the air causes gradual deterioration of the taste, smell and other flavor elements of the concentrate and eventually spoilage due to mold and aerobic bacteria. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention that overcomes or ameliorates the disadvantages of the known concentrate mixing drink dispensers noted above. 
     The is objective is achieved in part by providing a mixing drink dispenser with a mixing chamber for receipt of mixing liquid drink concentrate with water for mixing together into a beverage, said mixing chamber having an upper cylindrical section with a water inlet directed for flow of streaming water tangentially against an interior surface of the cylindrical section at a first level, and a concentrate inlet directed for flow of streaming concentrate generally perpendicularly against the interior surface at a second level beneath the first level; a source of mixing water connected with the water inlet, and a concentrate hopper for holding liquid drink concentrate connected with a drain hole connected to the concentrate inlet. 
     In the preferred embodiment, the mixing chamber includes a lower section joined to a bottom of the upper cylindrical section having a drain hole with a diameter substantially smaller than a diameter of the upper cylindrical section. The lower section has an interior lower surface joined to the interior surface of the upper cylindrical section at a location beneath the second level and extends inwardly and downwardly to the drain hole. This inwardly, downwardly lower section advantageously speeds the flow beverage around a perimeter for enhanced mixing. Also, the interior lower surface is at least a partly planer surface to increase turbulence for improved mixing. 
     Preferably, the concentrate inlet is an open end of an elongate concentrate inlet tube located within the mixing chamber and extending from one side of the upper cylindrical section toward a side opposite the one side to locate the open end directly opposite a concentrate inlet closure at another side of the upper cylindrical section diametrically opposite the sealed tube opening at the one side. The concentrate inlet is slid into engagement with the inlet closure or the closure is moved into engagement with the inlet to close the inlet when beverage is not being mixed. In the case of a movable concentrate inlet tube, the stationary closure member is an inwardly directed cone that facilitates the rapid spread of the concentrate over the interior wall from which it is washed by a relatively elevated swirling stream of mixing water created by the tangentially directed water inlet. 
     The object of the invention is also acquired in part by provision of a mixing drink dispenser, having a mixing chamber; a concentrate hopper; means for selectively passing mixing water into the mixing chamber from a source of mixing water at a preselected water flow rate and preselected water pressure required to establish a preselected flow rate of concentrate into the mixing chamber; means for selectively passing concentrate contained within the hopper to the mixing chamber at a preselected flow rate established at least in part by the preselected water flow rate and the preselected water pressure. 
     In the preferred embodiment, the mixing drink dispenser has a start switch, and the selective water passing means and the concentrate passing means are both actuated simultaneously in response to actuation of the start switch. Passage of concentrate and water into the mixing chamber and associated mixing continues so long as the switch is held in an actuated state. An adjustable water pressure regulator connected between the source of mixing water and the mixing chamber regulates the water pressure of the mixing water while an adjustable flow rate regulator establishes a preselected flow rate of the mixing water. The preselected flow rate and water pressure of the inlet water establishes the flow rate of the concentrate into mixing chamber and thus also determines the ratio of concentrate to mixing water. 
     Also, the object of the invention is partly obtained by providing in a mixing drink dispenser having a source of mixing water, a hopper for holding drink concentrate for mixing with the water to make a consumable drink and a mixing chamber within which the mixing water and the concentrate are fed for mixing together into the beverage, an improvement having means for selectively passing mixing water under pressure into the mixing chamber; means openly connecting the concentrate hopper with the mixing chamber; means for maintaining a preselected head pressure within the mixing chamber to maintain a uniform flow rate of concentrate for different levels of concentrate within the mixing chamber for a given mixing water flow rate and a given mixing water pressure. In the preferred embodiment, the head pressure maintaining means includes a relatively air tight closure for a load opening of the mixing chamber, a sensor for detecting the gaseous pressure within the mixing chamber above the concentrate, a gas pump controlled by the sensor for pumping gas into mixing chamber when the detected pressure falls beneath a preselected minimum level until the pressure rises to another preselected maximum level higher than the one preselected level. 
     Achievement of the objective is also acquired in part by providing in a mixing drink dispenser having a source of mixing water, a hopper for holding drink concentrate for mixing with the water to make a consumable drink and a mixing chamber within which the mixing water and the concentrate are fed for mixing together into the beverage, an improvement having means for selectively passing mixing water under pressure into the mixing chamber; means openly connecting the concentrate hopper with the mixing chamber; and means for mixing concentrate in the hopper to maintain a substantially uniform density and viscosity of all the concentrate to help maintain a uniform flow rate of concentrate out of the concentrate hopper over time. 
     Preferably, the concentrate mixing means includes a mixing blade mounted on a rotary base member mounted on the bottom of the hopper for relative rotary movement, an electric rotary motor mounted outside of the hopper with a rotor located adjacent to the bottom of the hopper and the rotary base member, and means for toolessly linking the rotor with the rotary base to rotate the rotary base with rotation of the rotor. 
     Moreover, the objective of the invention is partly achieved by providing a mixing drink dispenser having a source of mixing water, a hopper for holding drink concentrate for mixing with the water to make a consumable drink and a mixing chamber within which the mixing water and the concentrate are fed for mixing together into the beverage, with an improvement having means for selectively passing mixing water under a preselected pressure into the mixing chamber, means openly connecting the concentrate hopper with the mixing chamber and means for maintaining the mixing chamber above the concentrate substantially oxygen free relative to air. 
     Preferably, the inert gas is nitrogen, and the maintaining means includes a gas pump for pumping nitrogen gas into the mixing chamber from the outlet of a nitrogen passing filter that passes nitrogen into the mixing chamber but blocks passage of oxygen. The maintaining means also includes a cover for an open top load opening of the mixing chamber that is sufficiently gas tight to maintain the nitrogen gas within the mixing chamber and to keep oxygen laden air from leaking into the mixing chamber. 
     Additionally, the objective is partly acquired by provision of an automated mixing drink dispenser, with means for feeding water into a mixing chamber at a preselected water pressure and regulated flow rate, means for passing concentrate to the mixing chamber from a concentrate hopper having an open drain hole openly connected to the mixing chamber at a preselected flow rate at least partly determined by the preselected water pressure and regulated flow rate, means for mechanically mixing the concentrate within the concentrate hopper to maintain a uniform density and viscosity to facilitate maintenance of the preselected concentrate flow rate over time and means for maintaining a preselected head pressure of the concentrate in the hopper to facilitate maintenance of the preselected concentrate flow rate over time. 
     Preferably, means associated with the preselected head, pressure maintaining means for also fills the concentrate hopper with an inert gas. The pressurizing means includes a nitrogen filter and a pump for drawing nitrogen from the air through the filter and into the concentrate hopper. 
     Additionally, the objective is achieved in part by providing a method of mixing and dispensing a mixed drink with a mixing drink dispenser, by performance of the steps of injecting mixing water from a source of water through a tangentially directed water inlet of an upper cylindrical section of a mixing chamber against an interior surface of the cylindrical section at a first level to create a spiraling flow of streaming water around the interior surface and injecting concentrate from a drain hole of a concentrate hopper though a concentrate inlet of the mixing chamber directed for flow of streaming concentrate generally radially against the interior surface at a second level beneath the first level. 
     Also, achievement of the object is acquired partly by providing a method of mixing and dispensing a mixed drink with a mixing drink dispenser, by performance of the steps of selectively passing mixing water into a mixing chamber from a source of mixing water at a preselected water flow rate and preselected water pressure required to establish a preselected flow rate of concentrate into the mixing chamber and selectively passing concentrate contained within the hopper to the mixing chamber at a preselected flow rate established at least in part by the preselected water flow rate and the preselected water pressure. 
     Acquisition of the object of the invention is also partly obtained by providing a method of mixing and dispensing a mixed drink with a mixing drink dispenser having a source of mixing water, a hopper for holding drink concentrate for mixing with the water to make a consumable drink and a mixing chamber within which the mixing water and the concentrate are fed for mixing together into the beverage, by performing the steps of selectively passing mixing water under pressure into the mixing chamber; openly connecting the concentrate hopper with the mixing chamber and maintaining a preselected head pressure within the mixing chamber to maintain a uniform flow rate of concentrate for different levels of concentrate within the mixing chamber for a given mixing water flow rate and a given mixing water pressure. 
     Moreover, the object is partly achieved by providing a method of mixing and dispensing a mixed drink with a mixing drink dispenser having a source of mixing water, a hopper for holding drink concentrate for mixing with the water to make a consumable drink and a mixing chamber within which the mixing water and the concentrate are fed for mixing together into the beverage, through performance of the steps of selectively passing mixing water under pressure into the mixing chamber, connecting the concentrate hopper with the mixing chamber; and mixing concentrate in the hopper to maintain a substantially uniform density and viscosity of all the concentrate to help maintain a uniform flow rate of concentrate out of the mixing chamber over time. 
     Additionally part achievement of the invention is obtained by providing a method of mixing and dispensing a mixed drink with a mixing drink dispenser having a source of mixing water, a hopper for holding drink concentrate for mixing with the water to make a consumable drink and a mixing chamber within which the mixing water and the concentrate are fed for mixing together into the beverage, by performance of the steps of selectively passing mixing water under a preselected pressure into the mixing chamber; openly connecting the concentrate hopper with the mixing chamber and maintaining the mixing chamber above the concentrate substantially oxygen free relative to air. 
     Preferably, the method includes the steps of pumping nitrogen gas into the mixing chamber from the outlet of a nitrogen passing filter that passes nitrogen into the mixing chamber but blocks passage of oxygen; and covering an open top load opening of the mixing chamber with means sufficiently gas tight to maintain the nitrogen gas within the mixing chamber and to keep oxygen laden air from leaking into the mixing chamber. 
     The object is also partly acquired by providing a method of mixing and dispensing a mixed drink with a mixing drink dispenser, by performance of the steps of feeding water into a mixing chamber at a preselected water pressure and regulated flow rate; passing concentrate to the mixing chamber from a concentrate hopper having an open drain hole openly connected to the mixing chamber at a preselected flow rate at least partly determined by the preselected water pressure and regulated flow rate, mechanically mixing the concentrate within the concentrate hopper to maintain a uniform density and viscosity to facilitate maintenance of the preselected concentrate flow rate over time and maintaining a preselected head pressure of the concentrate in the hopper to facilitate maintenance of the preselected concentrate flow rate over time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The forgoing objects, features and advantages of the liquid beverage concentrate mixing beverage dispenser and methods of the present invention will be described and others made apparent in the detailed description given below with reference to the several figures of the drawings, in which: 
         FIG. 1  is a perspective view of a preferred embodiment of the liquid concentrate mixing and dispenser, or mixed drink dispenser, of the present invention; 
         FIG. 2  is a front elevation view of the mixed drink dispenser of  FIG. 1 ; 
         FIG. 3  is a sectional side elevation view of one from of the drink dispenser; 
         FIG. 4  is sectional plan view of the mixing chamber of the drink dispenser of  FIG. 3  in which a water dispense valve is in a closed position; 
         FIG. 5  is a sectional plan view of the mixing chamber of drink dispenser of  FIG. 3  in which the water dispense valve is in an open position; 
         FIG. 6  is a sectional side elevation view of another from of the drink dispenser in which the top cover is opened and another type of dispense valve, different from that of  FIGS. 3-5 , is in a closed position; 
         FIG. 7  is a sectional side elevation view, the same as that of  FIG. 6 , but in which the cover is closed and the other type of valve of  FIG. 6  is in an open position; 
         FIG. 8  is an enlarged sectional plan view of the mixing chamber of  FIG. 7  showing the valve in the open position; 
         FIG. 9  is an enlarged sectional plan view of the mixing chamber of  FIG. 6  showing the valve in the closed position; and 
         FIG. 10  is a functional block diagram of the operating systems of the drink dispenser  10 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIGS. 1 and 2 , a preferred embodiment of the drink dispenser  10  of the present invention is seen to include a housing  12  with an aft concentrate housing section  14  with a generally rectangular cross section, a top  16  and a bottom  18 . Extending forwardly from the front of the bottom  18  is a generally semicircular drip tray  20  with a removable, perforated cup support  22  supported at the top of an upwardly facing drip container body  24 . A finger hole  25  in the cup support  22  functions as a handle to facilitate removal of the cup support  22  from the top of drip container body  24  for cleaning. 
     Located above the cup support  22  is an overhanging, forward, upper, dispenser housing section  26  cantilever mounted to a central, upper part of the front  28  of the aft housing  14 . The forward, upper dispenser housing section  26  has a curved front  30 , a flat bottom  32  and a downwardly, inwardly slanted beveled section  34  extending between the front  30  and the bottom  32 . Extending downwardly from the bottom  32  is a beverage dispense tube  36  from which the beverage is dispensed into a suitable serving container, such as a glass or cup (not shown) supported on the cup support  22 . 
     The beverage is dispensed when a push-button dispense switch  38  is pushed inwardly to a dispense position and continues to be dispensed while the push-button dispense switch  38  is manually held in the inward dispense position. The push-button switch is spring loaded to return to an outward, off, or valve closed, position when not being manually held in the inward dispense position. Consequently, when the user releases the dispense push-button switch  38 , dispensing of the beverage automatically ceases. 
     Referring now to  FIGS. 3-5 , the internal workings of the drink dispenser  10  is described. As seen in  FIG. 3 , the aft concentrate housing section  12  protectively houses a concentrate hopper  42  within which a supply of liquid beverage concentrate  44  is temporarily stored before being dispensed. The concentrate hopper  42  has a cylindrical upper section  46  and a lower conical section  48  that slants downwardly and inwardly to a centrally located, downwardly extending, hollow, cylindrical tube connector  52  with a concentrate drain hole  50 . One end of a flexible Teflon® tube  54 , or the like, schematically illustrated by a single line, is connected to the concentrate tube connector  52 . The flexible concentrate tube  54  is directly connected at its opposite end to an inlet connector  56  of a concentrate solenoid controlled valve  58 , best seen in  FIGS. 5 and 6 . The outlet of the solenoid controlled valve is located within a mixing chamber  74 , as seen in  FIG. 3 . 
     A water line  60 , schematically illustrated by a single line, is directly connected at an inlet  62  to a public water supply through a suitable flexible hose, not shown. The inlet  62 , in turn, is connected to an inlet of a solenoid controlled water inlet valve  64 . The outlet of the solenoid controlled water inlet valve  64 , in turn, is connected in series with both a pressure regulator  66  and a flow regulator  68 . The output of the flow regulator  68  is connected directly to a water inlet connector  70  via an elongate flexible tube  69 . As best seen in  FIGS. 4 and 5 , the water inlet connector  70  is a rigid, elongate, hollow, cylindrical tube that extends outwardly from a side of the cylindrical top section  72  of the mixing chamber  74  in a generally tangential direction. 
     The outlet  69  merges into the interior cylindrical sidewall of the mixing chamber  74 . This entry location of the water inlet connector  70  causes the water to enter the cylindrical top section  72  in a tangential direction and then swirl around the interior cylindrical surface of the cylindrical top section  72 . Centrifugal forces press the water against the upper interior surface and tends to hold the water there, but gravity causes the swirling water to gradually fall downwardly along the interior side. Advantageously, a spiraling, swirling vortex of water closely covering the interior side of the cylindrical top section  72  that moves downwardly is thereby created. 
     Unlike the tangential connection used for the water, the solenoid controlled concentrate valve  58  has an outlet  78  that directly faces in a radial direction at a fixed conical valve closure  76 . Advantageously, the conical valve closure  76  performs a dual function. The peak  77  of conical valve closure  76  is directly aligned with and located opposite and adjacent to the concentrate outlet  78 . Accordingly, when the concentrate valve  58  is struck by a stream of concentrate, the conical shape of the valve closure  76  splits and widens the concentrate stream to causes the concentrate to splatter and spray against the sides of the conical valve closure  76  and the surrounding interior surface  73  of the cylindrical top section  72 . The concentrate is thus spread out in an area directly beneath and forward of the entry point of the falling swirling water from the water outlet of the water inlet valve  70  for enhanced and rapid mixing of the beverage concentrate with the mixing water. Once the water drops down to and impacts against the conical, concentrate valve closure  76  and the surrounding concentrate, swirling laminar flow of the water ends and the fluid motion converts to a more turbulent flow ideal for mixing. 
     As the swirling water drops down to and through a non-cylindrical lower section the reduced diameter causes an increase in velocity of the mixed water and concentrate. Moreover, the non-cylindrical lower section  81  has a rearwardly located section  80  that is planer. This planer section  80  creates additional source of turbulence, and because the planer section  80  slants inwardly towards the opposite side, the volume containing the mixed beverage is reduced and the mixing more concentrated. Finally, after complete mixing, the mixed beverage falls downwardly toward a drain hole  82  at the cylindrical side of the mixing chamber  74  that is opposite planer section  80 . The drain hole  82  is connected to a top, distal end of the beverage dispense tube  36 . Thus, first the swirling water captures the concentrate splattered on the interior surface and then vigorously mixes occurs as the mixture moves downwardly and faster and more turbulent flow occurs. 
     In keeping with an important aspect of the invention, by controlling both the water pressure, with the pressure regulator  66 , and the water flow rate, with the flow regulator  68 , the mixing ratio between drink concentrate and water is controlled without the need of proportional valves or other measuring devices. In addition to the viscosity and density of the liquid concentrate, the size of the concentrate drain hole  50 , frictional characteristics of the interior of the concentrate tube  54  and other factors remain fixed. In accordance with the invention, the amount of concentrate that flows into the mixing chamber  74  is determined, in part, by a Venturi effect created by the entry of the water into the mixing chamber  74 . The degree that this Venturi effect is created depends upon the rate and pressure at which the water enters the mixing chamber  74 . Thus, the rate at which the concentrate enters the mixing chamber  74  is dependent upon the rate and pressure at which the water enters the mixing chamber  74 . The rate of entry and pressure of the water, once the water inlet valve  64  is opened, is determined by the pressure regulator  66  and the flow regulator  68 . Accordingly, the drink ratio of concentrate to mixing water may be controlled by appropriate settings of the flow rate and water pressure. 
     Specifically, in keeping with the method of the invention, the pressure regulator  66  and flow regulator  68  are preset to preselected limits empirically determined to establish a preselected concentrate flow rate, or mixing ratio. Different drink concentrates may have different levels of viscosity and density thus different regulation settings may be needed for different concentrates to achieve the same mixing ratio. Likewise, different regulation settings are needed to achieve different mixing ratios for the same concentrate or different concentrates with the same flow characteristics. 
     In keeping with another important aspect of the present invention, another problem with known mixing drink dispensers is overcome. The problem noted by the inventor is that as the level of the concentrate  44  becomes lower during dispensing of beverage from the drink dispenser  10 , the head pressure within the concentrate decreases. Decreases of head pressure, without adjustment, results in decreased flow rate of the concentrate for given pressure and flow regulation settings. Disadvantageously, this reduced concentrate flow rate results in a gradual decline in the mixing ratio of concentrate to mixing water. Reduced mixing ration disadvantageously results in a corresponding weakening of the beverage as the level of the concentrate in the concentrate hopper  42  drops. 
     In accordance with the present invention, this problem is overcome by means of a head pressure regulation assembly that includes a gas pump  84  drawing ambient air through an inlet  85 , a gas pressure regulator  86 , and a concentrate hopper  42 , gas pressure sensor  88  connected with the regulator  86 . The head pressure regulation assembly automatically operates to regulate the gas pressure in the head space  90  above the concentrate  44  when the cover  40  is sealed closed. 
     In order to facilitate control the pressure, the cover  40  is preferably provided with a relatively air tight seal. As best seen in  FIG. 6 , the cover  40  has a neck  92  that extends into and fits snuggly against the interior surface at the top of the upper cylindrical section  46  of the concentrate hopper  42 . In addition, an annular shoulder  94  formed between the neck  92  and an upper section  96  of the cover  40  presses downwardly onto the upwardly facing edge of the top of the concentrate hopper  42  to provide another air tight sealing surface. The annular shoulder is also preferably provided with an O-ring seal or other resilient sealing member or the like that presses against the top. When the cover  42  is closed, as shown in  FIGS. 3 and 7 , the relatively air tight seal, enables the gas pump  84  and the gas pressure regulator  86  to increase the pressure in head space  90  to a level greater than atmospheric pressure as needed to maintain a uniform concentrate flow rate regardless of the level of concentrate  44 . 
     In the absence of gas being pumped into the head space  90 , as the level of the concentrate goes down, the volume of the head space  90  increases. This increase in volume causes the pressure within the head space  90  to decrease. This pressure decrease is detected by the sensor pressure  88 . When the pressure decreases to a preselected minimum level, a signal is sent to the gas pump  84 . The gas pump continues to operate until the sensor  88  detects that the pressure in the head space has again been elevated to a preselected maximum level needed for uniform flow. After the pump  84  is turned off, the pressure again declines as the level of the concentrate  44  drops until it again reaches the minimum level which causes the gas pump  84  to again turn on. 
     In keeping with another aspect of the invention, the ambient air inlet  85  is preferably covered by a nitrogen filter  98  that filters out oxygen from the ambient air and passes only nitrogen through the pump  84  and regulator  86  to reduce the amount of oxygen in contact with the concentrate  44  within the head space  90 . As best seen in FIG.  6 , the flexible nitrogen gas line  85  passes into the neck  94  of the cover  40  and is passed to the head space  90  from the gas pump  86  though the cover  40 , except when the cover is hinged open, as shown in  FIG. 6 . This reduction of oxygen helps to reduce the deterioration of the concentrate due to interaction with oxygen, which is a relatively active gas, as opposed to nitrogen, which is relatively inert and non-reactive with the concentrate. Consequently, the chemical integrity and original fresh flavor of the concentrate may be maintained for a much longer time as compared to when it unfiltered air is used to maintain the head pressure. Other inert gasses could be used but only nitrogen is plentiful, free and may be obtained by simple filtering. 
     Another problem with known concentrate drink dispensers that interferes with maintenance of uniform concentrate flow rates and control over the concentrate to mixing water ratio is that no compensation is provided for the non-homogeneity of the concentrate. With most concentrates, over a period of time, the heavier constituents of the concentrate gradually settle toward the bottom. This causes the density of the portion of the concentrate near the bottom to increase relative to that at the top and relative to the average density. This increase in density decreases the viscosity of the concentrate that is passed to the mixing chamber. The decreased viscosity tends to uncontrollably reduce the flow rate while also uncontrollably increasing the concentration of the concentrate. As the level goes down, the diminished remaining concentrate uncontrollably increases in viscosity while uncontrollably decreasing in concentration levels. This again disadvantageously results in a non-uniform beverage product being produced. 
     In accordance with the present invention, this problem is overcome by means of concentrate mixing assembly that includes an electrical motor  100  fixedly mounted within the upper cylindrical housing  42  and having hollow, central, electrical core though which the tube connector  52  is slidably received, as best seen in  FIGS. 6 and 7 . The electrical motor  100  located outside of the concentrate hopper  42  rotates about the tube connector  52  and carries fixed magnets or ferromagnetic elements, or magnetic elements,  101  which are also rotated. The fixed magnets or ferromagnetic elements  101  are magnetically attracted to mating ferromagnetic elements or fixed magnets, or magnetic elements,  103  of a blade rotor  102 . The blade rotor  102  is rotatably mounted to rotate in a cylindrical housing section located beneath the conical section  48  of the concentrate hopper  42 . Extending upwardly from the circumferential edge of the blade rotor  102  is a plurality of mixing blades  104 . When the motor  100  is energized by an electrical timer switch  106 , the motor  100  rotates the magnetic elements  101  and the magnetic link between magnetic elements  101  and the magnetic elements  103  carried by the blade rotor  102 , cause the blade rotor to rotate  102 . The rotation of the blades  104  mixes the concentrate  44  to maintain homogeneity and prevent settling of the concentrate  44 . The electrical timer  106  may be set to different cycles, but generally, it has been found that mixing for a few minutes every few hours is sufficient to maintain the concentrate in a sufficiently homogenous condition. 
     Referring to  FIG. 4 , the solenoid controlled concentrate valve  58  is closed, as shown, when the solenoid  79  is not energized. In such case, a spring  83 , schematically illustrated only in  FIG. 4 , automatically forces the distal open end  78  of the slidably mounted tube  75  against the conical valve closure  76 . The conical valve closure  76  is fixedly mounted to the inside wall of the cylindrical section  46  of the mixing chamber  42  directly opposite the distal end  78 . A water seal, preferably an O-ring  71 , from a water tight seal between the sides of the tube  75  and the mourning hole in the side of the mixing chamber  42  through which it is slidably mounted. 
     Referring to  FIG. 5 , when the solenoid  79  is energized, a resultant electromagnetic force overcomes the spring bias provided by the spring  83 ,  FIG. 4 , and the tube  75  is moved to the open position in which the open end  78  is spaced laterally from the conical valve closure  76 , as shown in  FIG. 5 . In this position, concentrate flows out of the end  78  at a rate determined by the water pressure regulator  66 , the water flow regulator  86  and head pressure regulation assembly including the pressure sensor  88 , the gas pump  84  and the gas pressure regulator  86 . 
     Referring to  FIG. 6-9 , another embodiment of a drink dispenser  120  is shown which is substantially identical to the drink dispenser of  FIG. 3  and which has an outward appearance identical to that of drink dispenser  10  shown in  FIG. 3 . The only difference is that a concentrate solenoid controlled valve  122  is employed that is different from the solenoid controlled valve  58  of  FIGS. 5 and 6 , and the mixing chamber  126  has a slightly different configuration to accommodate the differences in the valves  58  and  122 . All other features are the same. 
     Referring specifically to  FIGS. 8 and 9 , the solenoid controlled concentrate valve  122  has a fixedly mounted inlet or discharge tube  124  that may be integrally formed with the body of the mixing chamber  126 . Instead of a solenoid moving the tube  124 , another solenoid  128  is mounted to the mixing chamber  126  at the side opposite the discharge tube  124 . When the solenoid  128  is not energized, a resilient, flexible membrane  130  holds a slidable mounted plunger, or actuator rod,  132  in an open retracted position. As seen in  FIG. 8 , in the open retracted position, the end  134  of the tube  124  is uncovered to allow concentrate to flow into the mixing chamber  126 . When the solenoid  128  is energized, however, as seen in  FIG. 9 , the actuator rod  132  is forced inwardly toward the end  134  and pushes the flexible, resilient membrane  130  into a blocking, plugged relationship with the end  130  to close the end  130  against the release of concentrate. 
     An advantageous feature of the present invention is that the operation is obtained without the need for a microcomputer, ASICS card or other expensive and sometimes unreliable electronics. Instead, as illustrated in the functional block diagram of  FIG. 10 , the various functions are performed substantially independently or passively. The water pressure regulator  66  and the water flow rate regulator  68  are preferably entirely mechanical and head pressure regulation and concentrate homogenization maintenance are all achieved with simple switches, automatically actuating sensors and actuating timers operating independently but in concert. 
     Control of the concentrate dispense rate and thus the mixing ratio is achieved automatically each time the dispense push button switch  38  is manually actuated. The water pressure regulator  66  and the flow regulator  68  are preferably entirely mechanical and need no control signals to perform the respective functions. They are passive in the sense that they function automatically without any external controls whenever the water pump  64  is energized in response to manual actuation of the dispense push button switch  38 . Both the water pressure regulator  66  and the water flow regulator  68  are manually set to preselected levels of pressure and flow rate. These preselected set levels are not changed unless manually changed when needed to accommodate a different concentrate with a different liquid viscosity or to otherwise change the mixing ratio. While the dispense switch  38  is manually held actuated, an energization signal is sent to the concentrate solenoid controlled valve  58  or  128  to open a passage to the mixing chamber  74  and another signal is sent to energize the water pump  64  and the regulators  66  and  68  function automatically in response to the pressurized water from the pump to pass the water to the mixing chamber  74  at a controlled pressure and rate. 
     Likewise, oxidation prevention is also automatically achieved by the passive nitrogen passing, oxygen blocking filter  98 . This filter  98  only passes predominately nitrogen gas from the atmosphere to the head space  90  above the top surface of concentrate  44  whenever the gas pump  84  is energized. 
     The gas pump  84  is energized and controlled solely by the pressure sensor  88 . After the concentrate has been added to the concentrate hopper  42 , the cover  40  is manually moved from the open position, as shown in  FIG. 6 , to the sealed closed position shown in  FIG. 7 . After there has been removal to the mixing chamber  74  of some of the original amount of concentrate added to the hopper  42 , a resultant decrease in pressure to a preselected minimum pressure is detected. When this preselected minimum pressure is detected, the pressure sensor generates a low pressure energization signal. The gas pump  84  begins pumping nitrogen through the nitrogen filter  98  in response to the low pressure energization signal. The gas pump  84  continues to pump nitrogen into the head space  90  until the low pressure energization signal is terminated by the pressure sensor  88  when the sensed pressure increases to a preselected maximum head pressure. 
     The operation of the mixing motor on the other hand is strictly controlled by the electronic periodic timer  106 . The timer  106  automatically, periodically generates energization signals to the electric motor to cause the mixing blades  104  to rotate for a few minutes every few hours as may be needed. The degree of mixing is chosen to keep the concentrate from significantly separating and losing a homogenous condition needed to maintain a uniform concentrate density throughout all the contents of the hopper  42  and thus maintain a uniform concentrate flow rate and uniform flow rate. 
     Thus, it is seen that a concentrate mixing drink dispenser is provided that overcomes the disadvantages of know drinking dispenser that lack the novel features of the present invention. Different mixing ratios may be selected from different concentrates by selectively varying and maintaining preselected pressure and flow rates at which the mixing water enters the mixing chamber. Once these settings are established, variations in the water pressure of the public water supply do not result in varying the mixing ratio as happens in known mixing dispensers. The uniform ratio is also maintained in part by maintaining a uniform head pressure in the hopper and by maintaining the concentrate in a uniform homogenous state by periodic mixing.