Abstract:
A valve assembly is disclosed comprising an elongate body comprising a lumen and an output aperture near a distal portion thereof, a plunger positioned in the lumen and movable to a first position and a second position, and a toner path formed at least partially within the lumen and extending from a toner input to a toner path end located proximate the output aperture. When the plunger is in the first position, the output aperture is not fluidly coupled to the toner path. When the plunger is in the second position, the outlet aperture is fluidly coupled to the toner path such that a toner in the toner path can exit the valve assembly.

Description:
BACKGROUND 
     This specification relates to dispensing toner. 
     A toner is a pure color of paint including several elements including a pigment, a solvent, and a resin. Liquid toners include paints, inks, colorants and other fluids used to dye or color a base material. Toners are often mixed together in order to produce a particular result. For example, automotive paints are typically created using a precise mixture of toners. The mixture for a particular color is defined by a recipe. The recipe identifies the toners, as well as the amounts of each toner. Failure to mix the correct amount of toner results, for example, in a paint that does not exactly match the desired color. 
     Conventional paint mixing is a manual process. A human user reviews the recipe and then manually pours each toner into a container, e.g., on a scale, until the specified amount of each toner has been poured. However, human pouring often leads to inaccurate pours, especially when a precise amount of each toner is required to form a specific toner mix. 
     Motorized toner dispensing apparatuses typically use one or more motors to control a spout for a container of toner. However, conventional motorized toner dispensers do not adjust quickly and often over or under pour the toner. Conventional motorized toner dispensing apparatuses use a type of pump activated, for example, by a motor, air driven or electric, which due to the nature of the pump, requires occasional calibration. Since toners contain pigments that can be abrasive, the pumps are subject to wear, leading to the need to calibrate the pump. Additionally, conventional spouts are poorly sealed leading to dripping and introduction of contaminants into toner containers as well as curing of toner within the containers. Thus, conventional spouts require periodic cleaning, especially when changing empty toner containers. 
     SUMMARY 
     This specification describes technologies relating to dispensing toner. 
     In general, one aspect of the subject matter described in this specification can be embodied in a cap and valve assembly including a movable valve assembly, the movable valve assembly having a first position and a second position; a toner path, which when open is configured to allow toner to flow from a toner container to an output aperture; and an air inlet path, which when open is configured to couple an air source to the toner container; where in a first valve assembly position the toner path and the air inlet path are closed, and in a second valve assembly position the toner path and the air inlet path are open. 
     These and other embodiments can optionally include one or more of the following features. The cap and valve assembly further includes a toner container coupler configured to secure the cap and valve assembly to the toner container; a coupler configured to couple the cap and valve assembly to one or more air sources; and an elongate body positioned between the cap and the coupler, the elongate body holding a portion of the movable valve assembly such that the portion is movable within a lumen formed in the elongate body. The outlet aperture is positioned relative to the distal end of the elongate body and further comprising an anti-drip cap coupled to a distal end of the elongate body. 
     The cap and valve assembly further includes an anti-drip cap where the anti-drip cap is movable relative to the outlet aperture of the toner path such that in a first position the outlet is open allowing toner to pass through the outlet from the toner path and in a second position the outlet is closed sealing the toner path preventing substantially all toner from passing through the outlet. The anti-drip cap prevent air from entering the toner path through the outlet aperture when the anti-drip cap is positioned in the second position. The cap and valve assembly further includes an elongate body including an elongated outer tube and an elongated inner tube, the elongated inner tube being movable relative to the outer tube, the elongated outer tube including openings for the air intake path and the toner path, the inner tube including the air intake path and the toner path, where the movable valve assembly moves the inner tube relative to the outer tube such that the air inlet path and toner path are aligned with respective openings in the outer tube. The inner tube includes a channel along a portion of the length of the inner tube, the channel providing the toner path within the elongate body. The cap and valve assembly further includes a toner inlet tube coupled to the toner path for directing toner from a bottom portion of the toner container into the toner path. 
     Particular embodiments of the subject matter described in this specification can be implemented so as to realize one or more of the following advantages. A precise amount of a toner can be dispensed using a toner dispensing system. The toner dispensing system provides a high dispensing accuracy by using flow monitoring and a regulated dispenser coupled using closed loop signals from an electronic scale. The toner dispensing system replaces a container cap supplied from a toner manufacturer with a cap including a two position valve (e.g., a shuttle valve) for positive shut-off of toner flow and air pressure into the container. The valve cap also incorporates a moving wiping anti-drip cap to prevent drips after dispensing and to seal the end of the toner delivery device from air and containments and reduce curing of toner. The toner dispenser directs toner for dispensing from the bottom of the toner container, which avoids dispensing from the top surface where partial curing can occur due to air exposure. 
     The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the invention will become apparent from the description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of an example toner dispenser. 
         FIG. 2A  is a longitudinal cross-sectional view of an example cap and valve assembly in a closed position. 
         FIG. 2B  is a longitudinal cross-sectional view of an example cap and valve assembly in an open position. 
         FIG. 3A  is an isometric view of an example coupling between a housing and a cap and valve assembly. 
         FIG. 3B  is an isometric view of an example coupling between a housing and a cap and valve assembly with the cap and valve assembly inserted into the housing. 
         FIG. 3C  is an isometric view of an example coupling between a housing and a cap and valve assembly with the cap and valve assembly secured to the housing. 
         FIG. 4  is a flowchart of an example method for creating a toner mix. 
         FIG. 5  is a flowchart of an example method for dispensing a toner 
         FIG. 6  is a top view of an example toner dispenser. 
         FIG. 7  is a side view of an example toner dispenser. 
         FIG. 8  is a front view of the example toner dispenser. 
         FIG. 9  is a schematic diagram of an example system architecture. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 1  is an isometric view of an example toner dispenser  100 . The toner dispenser  100  includes first and second toner containers  102 , first and second cap and valve assemblies  104 , a scale  106 , an optional scale control interface  108 , and a housing  110 . 
     Each toner container  102  contains a volume of a respective toner (e.g., respective paint colors). The toner containers  102  can have different sizes depending on the application (e.g., half liter, liter, and two liter container volumes). Larger size containers can be remotely stored, and through use of an adapter and tubing, the contents of the larger containers can be dispensed using the cap and valve assemblies  104 . 
     Each of the toner containers  102  are coupled to a respective cap and valve assembly  104  using a cap  114 . Each cap and valve assembly  104  couples the respective toner container  102  to a horseshoe shaped coupling device  112  to allow dispensing of a particular toner. In some implementations, each valve assembly  104  has a flange molded on an end of a shuttle valve that engages with the coupling device  111 . The coupling device  112  is also coupled to an air cylinder that drives a plunger of the valve assembly  104  to open and close ports for air paths and toner dispensing. 
     In particular, the cap and valve assemblies  104  each provide a toner path for dispensing toner as well as an air path from the housing  110  for injecting air or another gas (e.g., an inert gas) into the corresponding toner container  102 . Injecting air or another gas generates pressure causing toner to move into an open toner path. The cap and valve assemblies  104  include an air regulated movable valve (e.g., a shuttle valve) that can be controlled along with the air provided to the toner container  102  to dispense precise amounts of toners from the corresponding toner container  102 . The structure of the cap and valve assembly is described in greater detail below with respect to  FIG. 2 . 
     The scale  106  provides weight measurements for dispensed toners. In particular, the scale  106  is positioned such that toners dispensed from the cap and valve assemblies  104  are collected in a container positioned on a surface of the scale  106 . The scale provides precise measurements of the amount of toner dispensed from one or more of the cap and valve assemblies  104 . For example, the toner dispensed can be controlled within one drop or substantially 25 thousands of a gram. The scale  106  can be coupled to the control interface  108 , for example, to provide weight measurements to the scale control interface  108  at a specified frequency (e.g., 100 times per second). 
     Additionally, or alternatively, the scale  106  can include a separate display providing a measurement readout (e.g., an LCD display of measured weight). The scale  106  or scale control interface  108  can also include a zeroing function to zero the scale, e.g., when an empty container is placed on the scale or for calibration in dispensing each toner. The scale can also provide information, e.g., scale readings, to a flow controller. The flow controller can be part of the scale control interface  108  or a separate flow controller, e.g., in the housing  110 . 
     The housing  110  provides an interface for controlling the toner dispensing system  100  with a host computer system including software from the toner manufacturer for storing one or more color recipes. Alternatively, the host computer system can be incorporated within the housing  110 , be coupled externally, or accessed over one or more computer networks to provide recipes. 
     A toner mixing recipe is a set of instructions for creating a particular toner mix. The recipe includes particular toners as well as the amounts, either by weight or parts of a ratio, of each toner. In some implementations, the recipe identifies the constituent toners in a particular mixing order. In some implementations, the recipe includes other instructions for creating the toner mix. For example, a recipe for 1989 Ford Performance White includes:
         1 [toner 1, Bright White], [138.00 grams of toner 1]   2 [toner 2, Dark Black], [0.6 grams of toner 2]   3 [toner 3 Chrome Yellow], [2.5 grams of toner 3].       

     In some implementations, the recipe is encoded, for example in XML format, that can be read by the dispensing system  100  (e.g., by the flow controller) to dispense the identified amount of each toner. An example XML recipe for generating a color “Dark Highland Green” is reproduced below: 
                                              &lt;?xml version=“1.0” encoding=“utf-8” ?&gt;             -  &lt;Tints&gt;             -  &lt;BatchInfo&gt;            &lt;NexaRef&gt;LFG2B&lt;/NexaRef&gt;            &lt;Color&gt;Dark Highland Green&lt;/Color&gt;            &lt;Manufacturer&gt;Ford&lt;/Manufacturer&gt;            &lt;Code&gt;PX&lt;/Code&gt;            &lt;Volume&gt;6.0 oz&lt;/Volume&gt;            &lt;NumTints&gt;9&lt;/NumTints&gt;             &lt;/BatchInfo&gt;             -  &lt;Tint&gt;            &lt;TintName&gt;p425-954&lt;/TintName&gt;            &lt;NonCumulative&gt;27.6&lt;/NonCumulative&gt;            &lt;Actual&gt;0.0&lt;/Actual&gt;            &lt;Adjustment&gt;0.0&lt;/Adjustment&gt;             &lt;/Tint&gt;             -  &lt;Tint&gt;            &lt;TintName&gt;p420-982&lt;/TintName&gt;            &lt;NonCumulative&gt;23.3&lt;/NonCumulative&gt;            &lt;Actual&gt;0.0&lt;/Actual&gt;            &lt;Adjustment&gt;0.0&lt;/Adjustment&gt;             &lt;/Tint&gt;             -  &lt;Tint&gt;            &lt;TintName&gt;p425-984&lt;/TintName&gt;            &lt;NonCumulative&gt;4.6&lt;/NonCumulative&gt;            &lt;Actual&gt;0.0&lt;/Actual&gt;            &lt;Adjustment&gt;0.0&lt;/Adjustment&gt;             &lt;/Tint&gt;             -  &lt;Tint&gt;            &lt;TintName&gt;p420-942&lt;/TintName&gt;            &lt;NonCumulative&gt;2.0&lt;/NonCumulative&gt;            &lt;Actual&gt;0.0&lt;/Actual&gt;            &lt;Adjustment&gt;0.0&lt;/Adjustment&gt;             &lt;/Tint&gt;             -  &lt;Tint&gt;            &lt;TintName&gt;p425-900&lt;/TintName&gt;            &lt;NonCumulative&gt;0.9&lt;/NonCumulative&gt;            &lt;Actual&gt;0.0&lt;/Actual&gt;            &lt;Adjustment&gt;0.0&lt;/Adjustment&gt;             &lt;/Tint&gt;             -  &lt;Tint&gt;            &lt;TintName&gt;p425-957&lt;/TintName&gt;            &lt;NonCumulative&gt;4.4&lt;/NonCumulative&gt;            &lt;Actual&gt;0.0&lt;/Actual&gt;            &lt;Adjustment&gt;0.0&lt;/Adjustment&gt;             &lt;/Tint&gt;             -  &lt;Tint&gt;            &lt;TintName&gt;p420-938&lt;/TintName&gt;            &lt;NonCumulative&gt;10.6&lt;/NonCumulative&gt;            &lt;Actual&gt;0.0&lt;/Actual&gt;            &lt;Adjustment&gt;0.0&lt;/Adjustment&gt;             &lt;/Tint&gt;             -  &lt;Tint&gt;            &lt;TintName&gt;p425-950&lt;/TintName&gt;            &lt;NonCumulative&gt;24.6&lt;/NonCumulative&gt;            &lt;Actual&gt;0.0&lt;/Actual&gt;            &lt;Adjustment&gt;0.0&lt;/Adjustment&gt;             &lt;/Tint&gt;             -  &lt;Tint&gt;            &lt;TintName&gt;p192-5600&lt;/TintName&gt;            &lt;NonCumulative&gt;78.9&lt;/NonCumulative&gt;            &lt;Actual&gt;0.0&lt;/Actual&gt;            &lt;Adjustment&gt;0.0&lt;/Adjustment&gt;             &lt;/Tint&gt;             &lt;/Tints&gt;                        
In the above XML recipe, there are nine different toners used to generate the final output of 6 oz of the “Dark Highland Green”. Each toner has a specified identifier and an amount of toner (e.g., in grams). Thus, the dispensing system is used to dispense each precise amount of toner in order generate the final color.
 
     In some implementations, the housing  110  includes a flow control interface for controlling the toners according to the selected recipe. The flow control interface can delay dispensing of a particular toner until a user input is received indicating that further dispensing can occur. For example, a user can confirm that the particular toner to be dispensed is in position and secured within a particular dispensing station of the toner dispensing system  100 . 
     When there are more toners in the recipe than the dispensing system  100  holds (e.g., more than two dispensing stations for dispensing system  100 ), the scale or flow control interfaces can be used to restart dispensing after swapping out toners. In particular, a given cap and valve assembly and toner container pair can be swapped out as a unit. 
     The scale control interface  108  can be coupled to the flow controller to dispense the correct amount of toner upon initiation by a user. The flow controller is coupled to one or more air supplies used to control toner dispensing from a particular toner container according to the recipe information and the scale data. 
     The housing  110  provides the support for the toner dispenser  100 . The housing  110  houses control lines including electrical circuitry providing information to and from various components of the dispensing system. For example, communication lines between the scale  110  and the scale control interface  108 , and communication from scale  110  or scale control interface  108  to the flow control. Additionally, the housing  110  can include one or more air lines providing air from an air supply (e.g., compressed air storage, an air compressor, or an exterior air supply connection) to each cap and valve assembly  104 . In some implementations, a single air source (air supply) is used to provide air to the system. The supply can be split into one or more regulated paths for controlling various components (e.g., the respective movable valves and input air flows to toner containers). 
     The housing  110  also houses support structures for the dispensing system  100 . For example, the housing  110  includes legs forming a stable base for the dispensing system  100 . Other support structures can provide support for holding components of the dispensing system  100  in position including the toner repositories, scale control interface  108 , and flow controller. Additionally, the housing  110  can include various computer circuitry, for example, as part of the flow controller. For example, the housing can include one or more processors and computer readable storage devices where the one or more computer readable storage devices can include recipes for toner mixes as well as instructions that, when executed by the one or more processors, perform operations including managing the flow controller or managing the scale control interface  108 . 
     The housing  110  can also provide external access connections for coupling the dispensing system  100  to one or more electrical sources, air sources, and computer or networking sources. For example, the scale control interface  108  can retrieve toner mixing recipes from an external computer through a network interface. 
       FIGS. 2A-2B  are longitudinal cross-sectional views of an example cap and valve assembly  200  in a closed position and cap and valve assembly  201  in an open position. The cap and valve assembly  200  includes a toner container coupler  202 , a housing coupler  204 , an input air path  206 , a toner path  208 , a movable valve  210 , and an anti-drip cap  212 . The cap and valve assembly  200  is coupled between a toner container  214  (partially shown) and a housing of a dispensing system (e.g., housing  110  of dispensing system  100  in  FIG. 1 ). The cap and valve assembly  200  provides an elongate portion  224  for dispensing precise toner amounts from a distal end of the elongate portion  224  to a container, for example, to be measured for mixing several toners together according to a recipe. 
     The toner container coupler  202  couples the cap and valve assembly  200  to the toner container  214 . In one implementation, the toner container coupler  202  includes a threaded coupler configured such that threaded toner container bottles can be screwed to the threaded coupler. For example, water based toners can be stored in toner containers made from plastic and having threaded tops. Alternatively, in another implementation, the toner container coupler  202  includes a clamping coupler for securely sealing the toner container to the cap and valve assembly  200  (e.g., for solvent based and other toners). 
     The housing coupler  204  couples the cap and valve assembly  200  to the housing of the dispensing system. In some implementations, the housing coupler  204  is configured to slide into a receiver of the housing. The receiving of the housing includes a valve coupler for coupling the housing to the movable valve  210  and an input air coupler for coupling the input air path  206  to the housing. In some implementations, the input air coupler includes a poppet valve to provide an airtight seal between the housing and the input air path  206  and to provide air to the input air path only when the cap and valve assembly  200  is secured to the housing. The housing coupler  204  is described in greater detail below with respect to the housing side of the coupler in  FIG. 3 . 
     The input air path  206  provides a path, when the movable valve  210  is in an open position, from the housing to the toner container  214 . In particular, the housing coupler  204  aligns an air line in the housing with an opening of the input air path  206 . When the movable valve  210  is in the open position ( FIG. 2B ), air can pass from the air line in the housing through a first aperture entering the input air path  206  and out a second aperture into the toner container  214 . The increased air pressure in the toner container  214  causes toner to move into the toner path  208  at a particular flow rate. When the movable valve  210  is in the closed position ( FIG. 2A ), the input air path  206  is blocked such that air cannot flow into the toner container  214 . The air pressure applied through the input air path  206  can be adjusted to control the flow rate of toner through the toner path  208 . Thus, the greater the air pressure applied to the toner container  214 , the greater the flow rate through the toner path  208 . Thus, a regulated air supply allows for control of the flow rate. 
     The toner path  208  provides a path, when the movable valve  210  is in an open position, from the toner container  214 , along a channel along the movable valve  210  in the elongate portion  224  of the cap and valve assembly  200 , to an output  216  (e.g., an aperture in the elongate portion  224 ) of the cap and valve assembly  200 . Specifically, the toner path  208  is formed from channel formed between an outer portion of the elongate body and the movable valve  210 . A valve body seal  228  can optionally form the end of the toner path  208 . 
     In particular, a toner input tube  218  is coupled to a toner channel  220  that runs along an interior portion of the elongate portion  224  of the cap and valve assembly  200 . In some implementations, the toner input tube  218  is part of the cap and valve assembly  200 . In other implementations, the toner input tube  218  is part of the toner container or a separate component coupled to the cap and valve assembly  200 . In some implementations, the toner input tube  218  extends to substantially the bottom of the toner container  214 . Positioning the toner input tube  218  toward the bottom of the toner container allows for the toner to be directed from the bottom of the toner container rather than the top, which can have a surface skin formed due to curing of the toner (e.g., due to exposure to air in the container or through evaporation in water based toners). 
     In some implementations, a filter is positioned on the toner path  208  to prevent impurities from passing through the toner path. For example, the filter can be coupled to the toner input tube  218 . The filter can be attached to the bottom of the toner input tube  218  as toners from the toner container enter the toner path  208 . Alternatively, the filter can be coupled between the toner input tube  218  and the toner channel  220 . 
     When the cap and valve assembly  200  is coupled to the toner container, toner can pass into the toner path  208 . However, when the movable valve  210  is in the closed position ( FIG. 2A ), the output  216  is blocked such that toner can not pass through the output  216 . When the movable valve  210  is in the open position ( FIG. 2B ), toner can flow along the toner path  208  and is dispensed through the output  216 . In particular, toner passes through the toner input tube  218  along the toner channel  220  and out the output  216  aperture. 
     The movable valve  210  moves between open and closed positions. The open position allows toners to flow through the toner path  208  and out the output  216 . In particular, the open position allows air to pressurize the toner container such that the toner flows up the toner input tube  218  and along the toner path  208 . The closed position of the movable valve  210  prevents air from entering the toner container and prevents toners from passing through the toner path  208 . The position of the movable valve  210  is controlled by application of air pressure. 
     The movable valve  210  is coupled to a moveable plunger  226  within a lumen formed in the cap and valve assembly  200 . In particular, the movable valve  210  slides along the elongated portion of the cap and valve assembly  200  in response to air pressure applied to the movable valve  210 . The amount of toner to be discharged through the output  216  is regulated by the amount of air pressure within the toner container. As the scale (e.g., scale  106  of  FIG. 1 ) measures a dispensed amount approaching the recipe amount of toner in a collection container, a programmable pressure regulator backs off the air pressure to reduce the amount of toner discharged from a stream to a series of toner droplets. When a particular amount of toner is weighed by the scale, the programmable pressure regulator vents to atmosphere thereby reducing the pressure within the toner container to zero and a solenoid valve within the housing shuttles the moving plunger to the closed position, which closes off both the air and toner paths. In some implementations, the maximum displacement of the movable valve  210  is substantially 10 mm. 
     The flow rates of various toners are dependent upon the air pressure within the toner container and the viscosity of the toner. Consequently, the flow rate of toners can be controlled for toners having a known viscosity by controlling the air pressure to the toner container. When air is not applied, or applied below a threshold pressure, the flow rate of the toner is zero. 
     Movement of the movable valve  210  to the open positions aligns paths in the movable valve  210  to the input air path  206  and toner path  208  by a specified amount. In particular, the toner channel  220  of the toner path  208  moves with the movable valve  210  (e.g., the toner channel  220  formed in the plunger of the movable valve). In the open position, the toner channel  220  is moved as part of the movable valve  210  to align with the output  216  formed in the elongate body  224  of the cap and valve assembly  200 . When the movable valve  210  is in the closed position, the toner channel  220  is not aligned with the output  216  such that toner does not pass from the toner channel  220  to the output  216   
     Similarly, when the movable valve  210  is in the open position, a portion of the movable valve  210  forming the air input path  206  is aligned with portions formed in the elongate portion  224  of the cap and valve assembly  200  such that air can pass through the cap and valve assembly and into the toner container. When the movable valve  210  is in the closed position, the portion of the movable valve  210  forming the air input path is not aligned with portions formed in the elongate portion  224  of the cap and valve assembly  200  such that air cannot pass through the cap and valve assembly  200  and into the toner container. 
     The anti-drip cap  212  is positioned at a distal portion of the movable valve  210  and moves in concert with the movable valve  210 . The anti-drip cap  212  is coupled to the movable valve  210  and includes a sealing portion that wraps around the outside of the elongate portion  224 . The anti-drip cap  212  is a moving wiping cap that prevents drips after dispensing and seals the end of the cap and valve assembly from air and containments. When the movable valve  210  is in the closed position, the anti-drip cap  212  extends along the outside of the elongate portion  224  beyond the output  216  of the toner path. Consequently, the output  216  is blocked from both sides by a combination of the anti-drip cap  212  and the non-alignment of the movable valve  210 . Blocking the exterior of the output  216  prevents dripping of excess toner from the output  216  when the movable valve  210  is in the closed position. Additionally, the anti-drip cap  212  can include one or more seals  230 , e.g., o-rings or other sealing structures. 
     When the movable valve  210  is in one of the open positions, the anti-drip cap  212  is positioned along the elongate portion  224  such that the output  216  is clear. The anti-drip cap  212  also seals the output  216  in order to prevent drying or curing of the toners in the toner path  208 . In particular, the sealed output  216  can prevent evaporation of particular toners (e.g., water based toners). In some implementations, an air cylinder is integrated into the cap for use in controlling the movable valve  210  and, correspondingly, the movement of the anti-drip cap  212 . 
       FIG. 3A  is an isometric view  300  of an example coupling between a housing  302  and a cap and valve assembly  304 . In particular, a housing coupler  306  of the cap and valve assembly  304  is shown about to be inserted into a receiver  308  of the housing  302  as indicated by the arrow. The receiver  308  includes a valve coupler  310  that couples the housing  302  to a movable valve of the cap and valve assembly  304  (e.g., movable valve  210  of  FIGS. 2A-2B ). The valve coupler  310  forms a seal between the movable valve and the valve coupler  310 . In particular, the movable valve is moved into communication with the valve coupler  310 , which has a horseshoe shaped recess, thereby coupling a flange on the end of the movable valve  210 . The valve coupler can include a T-slot coupled to an air cylinder. Additionally, the valve coupler  310  is movable in response to air pressure applied such that the valve coupler  310  and movable valve  210  move in concert with each other. 
     The receiver  308  also includes a clamp  312 , controlled by a lever  316 . The lever  316  is activated to clamp the housing  302  to the cap and valve assembly  304 . The lever  316  also activates an air valve (e.g., a poppet valve). Alternatively, one or more additional valves can be used to control the air flow to the toner container in place of the poppet valve. However, using the poppet valve reduces the cost of the assembly by eliminating the cost of electro-pneumatic valves and the circuits to activate the valves. Activation of the lever  316  is described in greater detail below with respect to  FIGS. 3B and 3C . The air valve allows air to flow into the cap and valve assembly  304 , in particular, an input air path. In some implementations, the air pressure is regulated by sending an analog electrical signal to a variable pressure regulator. The signal is developed using Pulse Width Modulation (PWM) and low pass filtering in the flow controller. The signal is frequently adjusted as during dispensing. 
       FIG. 3B  is an isometric view  301  of an example coupling between a housing  302  and a cap and valve assembly  304  with the cap and valve assembly  304  inserted into the housing  302 . However, the lever  316  has not been activated such that the housing  302  and cap and valve assembly  304  are not clamped together. Thus, while the cap and valve assembly  304  is positioned within the receiver  308 , it is not secured to the housing  302 . 
       FIG. 3C  is an isometric view  303  of an example coupling between a housing  302  and a cap and valve assembly  304  with the cap and valve assembly  304  secured to the housing  302 . In particular, the lever  316  has been articulated to a closed position that secures the cap and valve assembly  304  to the housing  302 . In particular, activating the lever  316  activates clamp  312  to clamp the housing  302  to the cap and valve assembly  304  by way of a downward clamping movement. 
     Additionally, activating the lever  316  activates an air path in the housing  302  to the input air path of the cap and valve assembly  304 . For example, the housing can include a poppet valve that is opened when the lever  316  is articulated to activate the lever  316 . When the poppet valve is opened, air is allowed to pass from an input air line along a path to the input air path of the cap and valve assembly  304 . However, air does not flow into the input air path of the cap and valve assembly  304  unless the movable valve is in an open position. 
       FIG. 4  is a flowchart of an example method  400  for creating a color mix. For convenience, the method  400  will be described with respect to a system (e.g., toner dispensing system  100  of  FIG. 1 ) that performs the method  400 . 
     The system receives  402  a selection of a color mixing recipe. Receiving the selection can include receiving a user input through navigation of a collection of color mixing recipes. The recipe identifies a number of toners and amounts to create a particular mix of color. In some implementations, the recipes are identified by a particular code for the resultant color mix. The code can be identified through a user interface to the system, or alternatively, using a book or other written collection of codes. Thus, the user can select the recipe by inputting the code to the system. 
     The system retrieves  404  the selected recipe. A number of recipes can be stored in a recipe collection. The recipe collection can be locally stored on the system or can be remotely located. Thus, retrieval of the selected recipe can include communicating with a remote server or other computing device to request the recipe and to receive the delivered recipe. In some implementations, the received recipe is simply a group of numbered recipe lines where each line identifies a toner for the mix and a weight of the toner to dispense. 
     The system receives  406  an input to initiate the toner dispensing. For example, the user can provide then input to a control interface on the dispensing system. The input can include selecting a “start” button on the control interface. 
     The system identifies  408  a current line of the recipe. The current line identifies a particular toner and toner amount (e.g., a weight amount of the toner to dispense). Generally, the current line initially identified is line one of the recipe. 
     The system determines  410  whether the current line number is odd or even. When the current line number is odd, the system prompts  412  the user to prepare the identified toner for a first dispensing station. The system can prompt the user, for example, using a screen display in the control interface that identifies the toner and the dispensing station for the toner. Colors can be identified by a name, a code, or some other identifier. In some alternative implementations, the system provides a verbal prompt instead of, or in addition to, displaying the prompt. 
     While the system can identify each toner at a time to dispense, the recipe information can be presented to the user before hand, e.g., as a list of toners needed for the particular toner mix. As a result, the user can obtain the needed toners and have them ready to install into the appropriate dispensing station as required. 
     When the current line is odd, the method  400  continues by receiving  416  a confirmation that the toner has been prepared for the first dispensing station. For example, the user can provide an input to the control interface indicating that the toner is ready to dispense. For example, a button can be provided in a control interface that, when selected, indicates that the dispensing of the first station should begin. When the confirmation has been received, the system dispenses  418  toner at the first dispensing station. 
       FIG. 5  is a flowchart of an example method  500  for dispensing a toner. For convenience, the method  500  will be described with respect to a system (e.g., toner dispensing system  100  of  FIG. 1 ) that performs the method  500 . 
     The system activates  502  a scale to measure the amount of toner dispensed into a container. Activating the scale can include zeroing the scale, for example, before dispensing the first toner. In some implementations, the scale is zeroed before each toner in the recipe is dispensed. Alternatively, the scale maintains a total relative to the ending weight of the previous toner dispensed. 
     The system activates  504  one or more air flows to the first dispensing station. For example, an input air path and air for controlling a movable valve are separate air flows having separate air sources. Alternatively, a single air flow is used that separates to the input air path and the movable valve. In some implementations, an air flow to the input air path is constantly activated. However, air is prevented from passing into a toner container because the input air path in the cap and valve assembly is closed and the valve in the housing is also closed (e.g., a poppet valve that is not open until a lever is activated). 
     The air flow to the movable valve is regulated such that a controllable amount of air is used to drive the movable valve. In particular, a flow controller controls an air path such that the movable valve can be controllably moved between the open and closed positions. 
     The air flows can be regular air (e.g., “shop air”) that is simply compressed outside air. In other implementations, however, the gas used for one or more air flows is different from outside air. For example, a less reactive gas can be used for the air flow input into the toner container (e.g., Nitrogen, Argon) in order to reduce adverse effects due to interaction between the gas and the toner. 
     The system activates  506  the movable valve to a dispensing position and opens the air input path to pressurize the toner container. In addition, the flow controller applies a specified amount of the regulated air flow to the toner container in order to pressurize the toner container so that the toner can flow from the toner container up the input tube and along the toner path to the output. 
     The system monitors  508  scale weight as toners are dispensed. Monitoring the scale weight provides frequent updates as to the amount of toner that has been dispensed. In some implementations, the system identifies the scale weight  100  times per second. 
     The system determines  510  that first threshold amount of toner has been dispensed. In some implementations, the first threshold is a specified weight threshold relative to the weight of the toner identified in the recipe. For example, the threshold can be identified when 0.5 grams of toner remains to be dispensed. In some alternative implementations, the dispensing system gradually reduces the flow rate over a range of weight data up to the first threshold amount (e.g., beginning with 1.0 grams to be dispensed and ending with the 0.5 gram first threshold). 
     When the threshold has been reached, the flow controller reduces the flow rate of the toner being dispensed. In particular, the air regulator reduces the air pressure within the toner container. The air is reduced to provide a particular flow rate (e.g., 2 drops per second) based on the air necessary to flow the toner with known properties of the toner being dispensed (e.g., a viscosity of the toner). In particular, fluid characterization data is retrieved for each toner being dispensed that identifies a flow rate for a particular output aperture. The characterization information can be stored locally in the dispensing system or retrieved from a remote location as needed. 
     The system determines  512  that a second threshold amount of toner has been dispensed. When the second threshold amount of toner has been dispensed, the system stops the one or more air flows to end toner dispensing. In particular, closing the movable valve engages the anti-drip cap to prevent further dispensing. In some implementations, the air in the toner container is vented through the input air path prior to closing the movable valve. In some implementations, the second threshold is a specified weight threshold relative to the weight of the toner identified in the recipe. For example, the second threshold can be identified when 0.05 grams of toner remains to be dispensed. 
     As shown in  FIG. 4 , the system determines  420  whether the dispensed toner was in the last line of the recipe. When the system determines that the toner from the last line has been dispensed, the system indicates  422  that the dispensing is complete. 
     When the system determines that the last line has not been dispensed, the system increments  424  the recipe line and returns to the determination  410  of whether or not the recipe line number is odd or even. 
     When the system determines that the recipe line number is even, the system prompts  426  the user to prepare the identified toner for a second dispensing station. For example, the user can attach the identified toner to the second dispensing station using a corresponding cap and valve assembly. 
     The system receives  428  feedback that the toner has been prepared for the first dispensing station. For example, the user can provide an input to the control interface indicating that the toner is ready to dispense. For example, a button can be provided indicating that the dispensing of the first station should begin. 
     The system dispenses  430  toner at the second dispensing station. The toner can be dispensed in a similar manner as shown in  FIG. 5  above. 
     The system again determines  420  whether the dispensed toner was in the last line of the recipe. When the system determines that the toner from the last line has been dispensed, the system indicates  422  that the dispensing is complete. 
     When the system determines that the last line has not been dispensed, the system again increments  424  the recipe line and returns to the determination  410  of whether or not the recipe line number is odd or even. The method then repeats as described above until the last line of the recipe has been dispensed. 
       FIG. 6  is a front view  600  of the example toner dispenser  100 . The front view  600  shows toner containers  102 , cap and valve assemblies  104 , scale control interface  108 , and scale,  106 . The front view  600  also shows the respective levers (e.g., levers  312  of  FIG. 3 ) for securing the cap and valve assemblies  104  to the housing  110 . 
     As shown in the front view, the scale  106  is positioned between the dispensing stations such that each cap and valve assembly  104  can dispense toners to a same container positioned on the scale  106 . Additionally, the front view  600  shows that the toner containers  102  are suspended by the cap and valve assemblies  104 . This allows the scale  106  to be positioned beneath the toner containers  102  so that they can be positioned closer together, reducing the size of the toner dispenser  100 . 
       FIG. 7  is a top view  700  of the example toner dispenser  100 . The top view  700  shows the scale  106 , the housing  110 , and scale control interface  108 . Additionally, elongate portions of the cap and valve assemblies  104 , including toner containers  102 , are shown extending at an angle toward each other and the center of the scale  106 . Thus, a single container placed in the center of the scale  106  can be used to capture toners dispensed from each cap and valve assembly  104 . 
     The top view  700  also shows the operation of respective levers coupling each cap and valve assembly  104 . In particular, lever  702  is shown in a first position and lever  704  is shown in a second position. The first position can be used when inserting and removing the cap and valve assembly  104 . Articulating a lever to the second position shown for lever  704  can be used to secure the cap and valve assembly to the housing as described above. 
       FIG. 8  is a side view  800  of the example toner dispenser  100 . The side view  800  shows a toner container  102 , cap and valve assembly  104 , scale  106 , scale control interface  108 , and housing  110 . Additionally, levers  702  and  704  for respective toner stations are shown. Additionally, the side view  800  shows that each toner container  102  can be suspended over the scale  106  so that the scale can be positioned beneath the toner containers  102  and the cap and valve assemblies  104 . 
     In some implementations, a dispensing system can have different numbers of dispensing stations. For example, the dispensing system can have a single dispensing station that couples a single cap and valve assembly. Alternatively, a single housing can include multiple dispensing stations in addition to two that can be used to provide additional toners for creating a mix without switching out toners. Additionally, in some implementations, a multiple station dispensing system can be used in combination with additional scales to create more than one mix at a time. 
     In some implementations, the dispensing system can be configured to dispense toners using a different orientation of toner containers. For example, the toner containers can be inverted and the housing modified such that the cap and valve assemblies are inserted into a housing receiver with the toner container turned upside down. 
     The dispensing system can be applied to dispensing various toners including different types of paints including water based and solvent based paints. Additionally, inks, dyes, and other fluids can be similarly dispensed. In particular, for each type of toner, particular characteristics (e.g., viscosity) can be calculated to determine flow control requirements during dispensing. 
       FIG. 9  is a schematic diagram of an example system architecture  900 . For example, the system architecture  900  can be used to identify recipes for toner mixes, monitor scale measurements, and provide flow control for cap and valve assemblies. 
     The system architecture  900  is capable of performing operations for dispensing toners. The architecture  900  includes one or more processors  902  (e.g., IBM PowerPC, Intel Pentium 4, etc.), one or more display devices  904  (e.g., CRT, LCD), graphics processing units  906  (e.g., NVIDIA GeForce, etc.), a network interface  908  (e.g., Ethernet, FireWire, USB, etc.), input devices  910  (e.g., keyboard, mouse, control interface, etc.), and one or more computer-readable mediums  912 . These components exchange communications and data using one or more buses  914  (e.g., EISA, PCI, PCI Express, etc.). 
     The term “computer-readable medium” refers to any medium that participates in providing instructions to a processor  902  for execution. The computer-readable medium  912  further includes an operating system  916  (e.g., Mac OS®, Windows®, Linux, etc.), a network communication module  918 , a dispensing module  922 , and other applications  924 . The operating system  916  can be multi-user, multiprocessing, multitasking, multithreading, real-time and the like. The operating system  916  performs basic tasks, including but not limited to: recognizing input from input devices  910 ; sending output to display devices  904 ; keeping track of files and directories on computer-readable mediums  912  (e.g., memory or a storage device); controlling peripheral devices (e.g., disk drives, printers, etc.); and managing traffic on the one or more buses  914 . The network communications module  918  includes various components for establishing and maintaining network connections (e.g., software for implementing communication protocols, such as TCP/IP, HTTP, Ethernet, etc.). 
     The dispensing module  920  provides various software components for performing the various functions for identifying recipes for mixing toners and dispensing the toners identified in the recipe including providing flow monitoring and control, as described with respect to  FIGS. 1-8 . Recipes can be stored as such on the computer-readable medium  912  for future use (e.g., to perform additional dispensing operations). Flow monitoring can include receiving inputs from a scale indicating measurements of dispensed toners. Flow control includes controlling air pressure within the toner containers to provide a specified flow rate and controlling movement of the movable valve. 
     The dispensing acts can be electronically controlled. Embodiments of the subject matter and the operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Embodiments of the subject matter described in this specification can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage medium for execution by, or to control the operation of, data processing apparatus. Alternatively or in addition, the program instructions can be encoded on an artificially-generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus for execution by a data processing apparatus. A computer storage medium can be, or be included in, a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of them. Moreover, while a computer storage medium is not a propagated signal, a computer storage medium can be a source or destination of computer program instructions encoded in an artificially-generated propagated signal. The computer storage medium can also be, or be included in, one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices). 
     The operations described in this specification can be implemented as operations performed by a data processing apparatus on data stored on one or more computer-readable storage devices or received from other sources. 
     The term “data processing apparatus” encompasses all kinds of apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, a system on a chip, or multiple ones, or combinations, of the foregoing The apparatus can include special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit). The apparatus can also include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, a cross-platform runtime environment, a virtual machine, or a combination of one or more of them. The apparatus and execution environment can realize various different computing model infrastructures, such as web services, distributed computing and grid computing infrastructures. 
     A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, object, or other unit suitable for use in a computing environment. A computer program may, but need not, correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub-programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network. 
     The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform actions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit). 
     Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for performing actions in accordance with instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. However, a computer need not have such devices. Moreover, a computer can be embedded in another device, e.g., a mobile telephone, a personal digital assistant (PDA), a mobile audio or video player, a game console, a Global Positioning System (GPS) receiver, or a portable storage device (e.g., a universal serial bus (USB) flash drive), to name just a few. Devices suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry. 
     To provide for interaction with a user, embodiments of the subject matter described in this specification can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, for displaying information to the user and a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. In addition, a computer can interact with a user by sending documents to and receiving documents from a device that is used by the user; for example, by sending web pages to a web browser on a user&#39;s client device in response to requests received from the web browser. 
     Embodiments of the subject matter described in this specification can be implemented in a computing system that includes a back-end component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a front-end component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the subject matter described in this specification, or any combination of one or more such back-end, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (“LAN”) and a wide area network (“WAN”), an inter-network (e.g., the Internet), and peer-to-peer networks (e.g., ad hoc peer-to-peer networks). 
     The computing system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. In some embodiments, a server transmits data (e.g., an HTML page) to a client device (e.g., for purposes of displaying data to and receiving user input from a user interacting with the client device). Data generated at the client device (e.g., a result of the user interaction) can be received from the client device at the server. 
     While this specification contains many specific implementation details, these should not be construed as limitations on the scope of the invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments of the invention. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
     Thus, particular embodiments of the invention have been described. Other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.