Patent Application
20120224987
The present invention relates generally to pumps and valves and, in particular, to a magnetically driven piston pump and a magnetically driven flow control valve.
Precision fluid metering is demanded in many industries. A common denominator is the need to meter or dose working fluids at flow rates generally less than 10 liters per hour, sometimes referred to as the “micro flow” range. End users frequently require very high accuracy fluid delivery provided at a low cost. High accuracy is synergistic with the continual advancement of digital technologies that make it possible to achieve more precise control of electric motors and solenoids. Information transfer using wireless technology, WIFI Internet, radio frequency identification tags, bar codes, etc., are also pushing system developers to offer more customized user interfaces that demand increased fluid delivery or dose precision.
Typical market segments and applications may include: medical diagnostics, medical fluids delivery, food dosing/packaging, beverage equipment, industrial dosing, paint and ink dosing, fuel cells, water analysis, semi-conductor electronics, chemical/gas analyzers, cleaning and disinfectant dosing.
Working fluids are as diverse as their respective applications and may include liquids and gases such as water, 1V drugs and solutions, food and beverage concentrates, soaps and detergents, dyes, and analysis chemicals to name a few. Precise adjustment of flow rate is often required between as little as 1.0 ml/hr to as high as 10,000 ml/hr. Delivered fluid pressures are generally very close to atmospheric pressure, but may range upward to 15-30+ pounds per square inch (103-206+ kilopascal) in some applications.
Precision fluid metering solutions often fall into three (3) general categories. One category employs a variable speed pump, electronic flow meter and a closed loop feedback controller. The controller makes incremental adjustments to the pump speed to correct for flow rate deviations from a pre-defined set point. A second category may involve using constant speed pump, and applying an electronically actuated, variable orifice downstream of the pump. The controller makes incremental adjustments based the measured flow rate, but instead of adjusting pump speed, opens or closes the variable orifice to throttle the flow rate and maintain the flow at pre-defined set point. A third category applies open loop control using a variable speed pump that is powered using continuous or pulse width modulated DC supply voltage. Open loop control may be used where there is a known relationship between the DC supply voltage, pump speed, and the volumetric displacement rate of the pump. Open loop control is desirable because it is generally simpler to operate, has fewer components and is lower in cost.
However, the flow accuracy of open loop control is limited by the volumetric displacement accuracy of the pump and accuracy of the pump motor speed. Each pump type provides its own set of features and benefits that include trade-off in size, cost, power, material compatibility, reliability, and flow accuracy. There is generally a large trade-off between cost and accuracy. For example syringe pumps with precise stroke and volumetric precision may be used to deliver intravenous drugs and solutions with exceptional dose accuracy, but they are very expensive and not convenient to use. On the other hand, peristaltic pumps provide good value and are easy to use. However peristaltic pumps offer greatly reduced accuracy as compared to syringe pumps due to inconsistent tubing elasticity that may result in variable fluid delivery rate.
Each market application has its own set of demands and challenges. Some markets are also beginning to consider a new demand disposability of the wetted pump components. Precision disposable pumps are of keen interest in the medical market where it is cost prohibitive to clean and sterilize recyclable components after contact with medical fluid media. While the tubing set of a peristaltic pump is disposable, it cannot deliver acceptable dose accuracy, especially in the lower micro flow range. Disposable medical applications may include but are not limited to drug delivery, IV solutions, peritoneal dialysis, hemodialysis, and anesthesia delivery. Disposable pumps may also be attractive in other markets, for example integration with disposable fluid containers such as the “bag-in-box” used in the food, beverage, and personal care products industries. The beverage market provides an added challenge wherein a precise amount of concentrate must be continuously mixed with flowing water to maintain an accurate volume ratio of water-to-concentrate for good beverage quality and customer satisfaction. A major difficulty is caused by the fact that water flow rate may vary widely due to variation in water supply pressure. However, a general theme across all markets is that customers increasingly demand high accuracy, ease of use, and reliability, all provided with a low cost.
Positive displacement pumps, such as diaphragm pumps or more preferably piston pumps, may offer precision dosing as long as a suitable control system is employed to trigger precisely timed linear, cyclic movements that drive the diaphragm or piston, respectively. In general the piston pump is more suitable for low dose and/or low flow rate because the stroke volume can be scaled down by reducing the diameter and stroke of the piston. Also the stroke volume of a piston pump is precise as compared to a diaphragm pump. Diaphragms being made from flexible elastomers may cause the stroke volume to vary with changes in the stoke speed, fluid viscosity and pressure rise across the pump. Conventional diaphragm and piston pumps are not considered disposable because the pump cost is too high for one time use. The most expensive component of the pump is the drive motor assembly. Recovery of the drive motor assembly from the pump head is cost prohibitive due to the high amount of labor needed to remove the motor from the pump head, and then reassemble and re-qualify a new pump head with the recycled drive motor assembly.
Many micro dosing fluid delivery applications involve liquids that are stored in a plastic bag at atmospheric pressure. Such bags are equipped with fittings that allow for a tube to connect the liquid contents of the bag to the inlet port of the fluid delivery pump. Examples are the common “bag-in-box” containers used in the beverage industry to store drink products and beverage concentrates. “IV bags” are also used to store intravenous solutions and drugs in the medical field. Of concern is the infiltration of air into the pump inlet or suction tube when the bag becomes depleted and must be disconnected from the tubing to install a new, replenished bag of liquid. Air bubbles pulled into the pump suction and then delivered into the pump discharge tube is problematic. In beverage applications this may result in poor delivered drink quality. In medical applications air delivered with IV fluids may be harmful to the patient under some conditions.
The present invention provides a new and improved magnet-based drive method and system which may form part of a pump, control valve or other device. According to one embodiment, the apparatus includes a shaft which is operative to rotate at least one drive magnet. An actuating piston head sub-assembly includes a driven magnet that is carried by a carriage with the carriage forming part of a piston that is reciprocally, linearly movable in a piston housing. The piston is movable between two positions. A drive module housing includes structure for receiving the piston head and is arranged such that the driven magnet is located in proximity to the drive magnet so as to create alternating attracting and repelling force between the drive and driven magnets as the drive magnet is rotated about the axis of the shaft. As the shaft is rotated, the carriage moves to one extreme position when the drive magnet is in one predetermined position and moves to its other extreme position when the drive magnet rotates to another predetermined position. In one embodiment, this magnetic-based apparatus serves as a pump assembly and includes a pump head in which the piston head is reciprocally mounted, such that when it reciprocates, it pumps fluid from an inlet to an outlet in cooperation with inlet and outlet check valves.
According to this embodiment, the shaft, which is operative to rotate the drive magnet, may be rotated by an electric motor or a fluid-driven turbine.
In another embodiment, the magnetic-based drive apparatus forms part of a shut-off type control valve. In this latter embodiment, the piston carries a seal. The seal carried by the piston is movable between a fluid blocking position which blocks flow through a passage and a spaced position which allows fluid flow through the passage. According to this embodiment, the drive magnet may be rotated in one direction to move the piston assembly into the blocking position and may reverse rotate, due to magnet repulsion, in order to allow the piston to move to the spaced position.
According to another feature of the invention, an air bleed accumulator may form part of the apparatus and functions to remove air from fluid being delivered to the inlet of a pump head. The accumulator includes a chamber for receiving fluid, a dip tube through which fluid is delivered to an inlet port and a membrane and check valve which are operative to bleed air from the accumulator chamber so that it does not enter the fluid stream entering the pump inlet.
According to another embodiment, the drive magnet may be rotated by a fluid-driven turbine. In this disclosed application, the pumping apparatus serves as a ratio pump and can be used to mix two fluids, one fluid being used to drive the turbine, whereas the other fluid is pumped by the pumping apparatus. This ratio pump may form part of a fluid dispensing system, such as a beverage dispenser. In the case of a beverage dispenser, the ratio pump can be used to mix beverage syrup with carbonated water.
In order to provide additional precision for pumping applications, the positions of the drive and/or driven magnets may be monitored by a sensor, such as a Hall Effect Sensor. The sensors are used to determine the positions of the associated magnet and the frequency with which the magnets are moving. When used in a pumping application, the extent of motion of the piston assembly determines the volume being pumped. Thus, knowing the stroke frequency of the piston assembly, as sensed by the sensor, can be used to precisely determine the volume of fluid pumped.
The invention also contemplates incorporating an RFID device in the housing in which the piston assembly is supported so that data can be transferred to an associated drive or control module.
A control module is also disclosed in which a drive module is located. The drive module is designed to accept a pump head such that when the pump head is installed, an associated driven magnet in the pump head is located in proximity to a drive magnet forming part of the drive module. The control module performs control functions on the drive module and, thus, controls the pumping function of the pump head.
According to the invention, a magnet pump is offered to provide the high accuracy of a closed loop feedback pump control system using a simple, feed forward control method. A pump head subassembly is self-contained, modular and magnetically coupled to a power source. It is capable of metering the flow rate of liquids, vapors and/or gases. The disclosures that follow are primarily focused on description of how the pump operates with incompressible liquids for simplicity. However, the pump may be applied with equal advantage processing vapors and/or gases.
The pump head is inherently of low cost construction, rendering it operationally and economically feasible to use the pump as a disposable product. While the pump head may be disposed after one use, its construction is durable enough for usage in permanent or semi-permanent applications. Should the pump head become worn out, it may be easily removed from a drive module and quickly replaced in a matter of seconds.
Another embodiment will be shown to offer unique benefit in the beverage market, wherein beverage concentrate is continuously adjusted or matched to the changing water flow rate in a very simple, reliable and yet cost effective manner as compared to presently available technology.
Yet another embodiment will be shown wherein the magnetic coupling mechanism applied to the magnet pump may be used to shut off flowing fluid in a valve application.
Additional features and a fuller understanding of the invention will become apparent in reading the following detailed description made in connection with the accompanying drawings.
Pump head subassemblies of different volumetric capacities may be universally adapted to the motor drive module 10b, thus extending the volumetric pumping range of the drive module subassembly 10b.
Unless otherwise noted in the foregoing detailed description, the pump and valve components are preferably fabricated from molded thermoplastic resins. There are many candidate resins that will satisfy the durability and reliability requirements including but not limited to various grades of acetals, nylons, nylons, polycarbonate/polyester blends, polysulfones, polyphenylene sulfides, and others. The thermoplastics may also be blended with PTFE Teflon additive to reduce friction between moving components. Inert fillers such as glass fibers and glass beads may also be compounded with the base resin to improve strength and dimensional accuracy of the molded pump components.
The motor drive module 10b includes an actuator or drive motor 16 with constant or variable speed. Motor 16 may be selected as a stepper motor to provide a source of precision rotary motion that may be controlled in degree or even fractional degree rotational movement. However, other drive motor types such as variable speed DC motors or constant speed AC synchronous motors may be adapted depending on the pump application. A preferred embodiment of the pump assembly 10 applied as a piston pump is shown in
The motor drive module 10b may serve as a mounting base for the pump head 10a. As seen in
While the drive magnet 18 and the caddy 19 may be directly mounted on the motor shaft 20, in some applications it may be desirable to rotate the drive magnet 18 at a different speed than the motor shaft speed. Thus another embodiment is envisioned wherein a gear train may be positioned between the motor 16 and the drive magnet 18 to provide for a customized ratio of motor rotation speed to the drive magnet rotation speed.
A reciprocally movable “driven” magnet 22 is encapsulated inside the pump head 10a. The driven magnet 22 is also bi-polar and preferably shaped as a cylinder, cube or a disc. However unlike the drive magnet 18, the driven magnet 22 is preferably axially magnetized with opposing poles located at respective axial ends of the magnet.
Referring to
There are many different choices available for type of check valve that may be used for the check valves 27, 29 including ball checks and elastomeric duckbill checks. Ideally the check valve should have zero backflow leakage. The check valves may be specified for opening or “cracking” pressure in the forward flow direction to prevent upstream pressure from pushing fluid forward through the pump head when the pump is idle.
Assuming the drive magnet 18 has 2-poles (N and S), one 360 degree rotation of the drive magnet causes one complete stroke (forward and reverse) of the driven magnet 22 and the piston carriage 24. The drive magnet 18 may be specified with multiple, even numbers of poles, i.e., 2, 4, 6 or 8. For example, a 4-pole magnet (with 2 N's and 2 S's) will result in 2 complete strokes of the driven magnet 22 for each 360 degree rotation. Regardless of the number of poles in the drive magnet 18, the driven magnet 22 is always specified with 2 poles.
An alternate embodiment included in the scope of the present invention includes the configuration of an array multiple bi-polar drive magnets that are radially positioned about the axis of shaft 20 and mechanically coupled with said shaft. The pole axes of each of said magnets are also radially oriented and sequenced with alternating polarity. Such embodiment provides ability to greatly increase the stroke rate of the driven magnet by increasing the number of alternating magnet poles presented to the driven magnet for each revolution of shaft 20. In such embodiment, an alternate drive magnet caddy structure is necessary to position and mechanically couple said multiple bi-polar magnets to shaft 20 in the manner described. The description of the preferred embodiment that follows is limited to application of a single bi-polar drive magnet 18.
Both drive and driven magnets 18, 22 are preferably permanent and may be made from any suitable magnetic material, and most preferably of the rare earth element type which provides superior magnetic strength and longevity. Alternatively the driven magnet may be made from a magnetically susceptible material such as iron in order to reduce cost. In this case the magnetic field imparted by the drive magnet temporarily induces the formation of opposing magnetic poles in the driven magnet. Magnet shapes other than cylindrical may be alternately used to customize the magnetic field strength and shape to meet specific application requirements.
Referring to
It should be noted here that the carriage 24, in which the driven magnetic 22 is located, forms a reciprocally movable piston assembly 23. This piston assembly moves between two extreme positions, the upper position shown in
Preferably the lower portion 24b of the piston carriage is designed to allow the driven magnet 22 to be easily press fitted into the piston carriage 24 Both upper and lower portions 24a and 24b of piston carriage 24 are coaxially centered inside the upper and lower bore/cylinder sections 32a and 32b, with each cylinder section respectively cored inside a lower body portion 35b of pump head sub-assembly 10a. The driven magnet 22 being coaxially centered inside lower carriage section 24b, is also coaxial with lower cylinder section 32b. The linear motion of the piston assembly 23 is guided by both the upper and lower cylinder sections 32a and 32b of the stepped bore 32, respectively. A surface 34 represents the bottom surface of lower cylinder section 32b and is the inside surface defined by a bottom wall 38 of the lower body section 35b of the pump head 10a. A surface 37 represents the transition between upper and lower cylinder sections 32a and 32b, respectively and is the top of lower cylinder section 32b. Accordingly, the stroke ΔX (
A mechanical impact occurs each time the carriage portion 24b is momentarily stopped by the fixed surfaces 37 and 34. The mechanical impact is characterized by a repeating tapping or clicking noise. The strongest impact occurs when the driven magnet 22 is pulled toward the drive magnet 18 at the bottom of the stroke. This is because the two magnets are in closest proximity and the attractive forces between the magnets are maximized. The impact of carriage portion 24b against the surfaces 37 and 34 may also cause hydraulic pressure pulsations inside the pump head 10a if the working fluid is an incompressible liquid such as water. These pressure pulsations may be large enough to cause premature opening or “cracking” of check valves 27 and 29 resulting in the incremental forward flow of liquid greater than the volumetric displacement of the piston. This effect is undesirable because it causes other than a 1:1 relationship between piston stroke volume and the volumetric flow rate, thus reducing the pump's predictive pumping accuracy based on the stroke volume.
To reduce this tapping noise that may be objectionable, and to ensure that the pump flow rate is exactly equal to the volumetric displacement of the piston, a flexible shock absorbing disc may be fastened to one or both of the top and bottom surfaces of lower carriage 24b. A shock absorbing disc 39 is preferably glued to the bottom surface of lower carriage 24b and is a thin silicone foam or sponge or other elastomers, approximately 0.040″ to 0.080″ thick, such as manufactured by Stockwell Elastomerics, that are flexible, durable and resist compression set to ensure repeatable stroke distance. The momentary compression distance of disc 39 is inclusive in the stroke distance ΔX.
The pump cycle may be referenced with the piston carriage 24 starting its linear cyclic motion at TDC and drive magnet 18 at 0 degrees (reference) rotation position as shown in
As the drive magnet 18 continues rotation from 180 to 360 degrees completing a full revolution, the driven magnet 22 likewise is pushed by the drive magnet 18 back to the original starting position TDC (
An important characteristic of the pump is its ability to create a high negative pressure (vacuum condition) at the pump suction (inlet port) in order to prime the pump with a liquid working fluid, and especially when the suction line to the pump and the pump itself is void of liquid and is considered “dry”. In order to maximize the dry suction lift capability of the pump, the volume of cavity 47 must be minimized when the piston carriage is at the TDC position. According to the Boyle's Law, the negative vacuum pressure that may be achieved inside of cavity 47 is expressed by the following equation:
Vacuum Gage Pressure=(Atmospheric Pressure)×(1−((Cavity Volume@TDC)/(Cavity Volume@BDC)).
In order to achieve the maximum priming capability, vacuum pressure must be maximized and thus cavity volume at TDC position must be minimized according to the above equation. Thus it is desirable for the top surface 24d (shown in
The optimal cyclic speed range of the piston assembly is estimated to be a range up to 10 Hz. This is based on the observed operation of driven magnets applied in the size range of 0.50″ diameter by 0.50″long and applied with a stroke distance of 0.100″. Above 10 Hz it is possible the piston may not complete full strokes because the inertia of the piston carriage assembly overcomes the magnetic attracting and repulsing forces induced by the drive magnet. Smaller driven magnets (with lower inertial mass) combined with larger drive magnets (having greater magnetic field strength) may allow speeds substantially higher than 10 Hz while maintaining full strokes with zero or minimal stroke slippage. Higher speed may also be achieved by reducing the stroke distance.
In an alternate embodiment the driven magnet 22 may directly serve as the piston without need for a piston carriage, wherein the driven magnet 22 is coated in a material such as electrolous nickel that is inert and suitable for direct contact with medical fluids, food and beverage concentrates. This embodiment also requires an O-ring 31 to provide a dynamic seal between the magnet 22 and the inside surface of upper cylinder wall 32a. A circumferential groove may be formed directly on the driven magnet to secure O-ring about said magnet.
Another embodiment may adapt to a diaphragm pump. The piston or driven magnet 22 may be over molded integral with the rubber diaphragm. Cyclic linear motion of the driven magnet 22 may cause the diaphragm to flex back and forth to create the volumetric pumping action.
Referring to
In order for the accumulator assembly 130 to properly function, the highest elevation of fluid contained in the liquid reservoir bag must be positioned slightly higher than the elevation of the inlet port 134 (at least 24 mm and preferably greater than 100 mm). This is to provide enough hydrostatic pressure to allow the free flow of liquid from the bag into the accumulator when a full bag of liquid is initially connected by tubing to the accumulator inlet.
Membrane 140 is semi-permeable and may be a material such as chemically inert PTFE Teflon (manufactured by Porex Technologies or W.L. Gore & Associates) with pore size preferably ranging between 5 and 30 micron and thickness ranging between 0.10 and 1.0 mm. Membrane 140 allows the free flow of gases such as air to pass through unimpeded with low pressure loss. The membrane however blocks the flow of liquids. The hydrostatic pressure of the liquid reservoir acting on the suction accumulator inlet port pushes trapped air ahead of advancing liquid exiting the bag and moving towards the accumulator inlet. As both liquid and trapped air bubbles enter the accumulator through inlet port 134, the liquid and air separate by gravity with the liquid on the bottom and air on the top. As liquid fills the accumulator, hydrostatic pressure pushes air through the membrane 140, check valve 142 and vent hole 146 to exhaust to atmosphere.
Check valve 142 must be provided with low cracking pressure, preferably less than 24 mm of water column to facilitate the exhaust of unwanted air without requiring excessively high air pressure inside body 132, that would otherwise require an increase in the elevation of the fluid reservoir bag to increase the hydrostatic pressure inside body 132.
Accumulator outlet port 136 connects directly to the pump inlet or suction port 28′. Thus as the pump operates it creates a reduced pressure at port 136 that draws fluid contained inside accumulator body 132 into the pump. Dip tube 138 is provided so that liquid is drawn from the bottom of the accumulator. As long as liquid is maintained above the dip tube inlet 138a, only liquid is drawn into the pump suction.
As the pump operates and the fluid reservoir bag becomes nearly depleted, it may be possible for the pressure inside accumulator body 132 to fall to less than atmospheric pressure. This is the result of a loss in positive hydrostatic pressure maintained at inlet 134. Accordingly check valve 142 is provided to prevent back flow of atmospheric air into the accumulator. The accumulator body should be sized with enough fluid containing capacity to prevent the accumulator from becoming empty as the reservoir bag becomes depleted. This of course requires the depleted bag to be replaced in a timely manner. Upon connection of a new, replenished bag, any air drawn into the tubing connecting the bag to the accumulator inlet will then become expelled as the fluid contents in the bag start to flow towards the accumulator inlet.
It should be noted here that the disclosed pump head sub-assemblies 10a of the various disclosed embodiments include an upper body section 35a that includes inlet and outlet ports 28 and 30, check valves 27 and 29, plus lower body section 35b, the exterior portion of which provides a precise interface 35 for mounting or “docking” the pump head 10a with the drive module 10b. Lower body portion 35b of the pump head is precisely positioned inside mating receptacle or cavity 14 internally formed as part of housing 12 of motor drive module 10b. Inlet and outlet check valves 27 and 29 are positioned inside the pump head near respective inlet and outlet ports 28 and 30 to prevent back flow, and to facilitate accurate delivered fluid volume for each stroke of the driven magnet.
The motor drive module 10b is activated by selective application of voltage to power the motor 16. Depending on the type of motor applied (DC motor, AC synchronous motor, or stepper motor), suitable electronic controls, software, and operator interfaces, must be provided to program and activate the voltage to motor 16 which in turn causes the drive magnet 22 to rotate and thereby activate the pumping action of pump head 10a. Collectively the electronic controls, software and operator interfaces are referred to as the “Control Module”. The control module may be 1) located remotely from the drive module assembly 10b and electronically connected via suitable cables as shown in
Referring to
The pump head 10a′ may also be designed to mount radio frequency identification (RFID) tag 76 (shown schematically in
In some medical applications, an independent confirmation of positive pump action may be required by U.S. Food and Drug Administration rules for medical devices. The proposed pump system provides for such requirement. Referring in particular to
H1 is a sensor that detects either the N or S, or both N and S poles of the radially magnetized drive magnet. H2 is a sensor that detects just one pole N or S of the longitudinally magnetized driven magnet. In the relative position shown in
Leads L1 and L2 communicate electronic signals between Hall Sensors 80 and the Control Module. There may be more than 2 leads. The number of leads is determined by the sensor model and type of output signal created, for example digital or analog.
An example of a Hall Effect sensors that may be applied with the magnet pump are model HSC sensors as manufactured by Sensor Solutions Corp. of Steamboat Springs, Colo. (see www.sensorso.com).
The microelectronics contained in the control module 60 may use the Hall Effect sensor input in two important ways: 1) calculate the stroke rate, corresponding pumping rate, compare to a desired set point, and then make adjustments of motor speed to correct for set point deviations, and 2) maintain a timed history of the number of pump strokes completed and use this information to calculate and display flow rate and total dispensed volume. In an embodiment wherein motor 16 is a stepper motor, the electronic controller in the control module 60 will always know the precise angular location of the drive magnet 18, and by association driven magnet 22. Should the Hall Effect sensor H2 not respond as expected by the control module 60 at the time the driven magnet 22 is calculated to be at the top (or bottom) of its stroke, then an alarm condition will sound notifying the operator that there has been a malfunction. When in an “alarm condition”, the control module may selectively disable the pump or otherwise revert to a pre-defined fail safe mode of operation.
In
Returning to
Another embodiment provides for integration of multiple docking stations parallel to each other and for simultaneous operation of multiple pump heads. The motor assembly contained inside the control module 60 or as part of a remote drive module 10b′, may include a lengthened drive magnet caddy (not shown) to provide room to mount multiple drive magnets, or to mount a single drive magnet with increased length. Either embodiment facilitates the ability to drive more than one pump head from a single motor. This way the multiple pump heads are synchronized to operate at the same speed provided for by the common, lengthened the drive magnet caddy. Each pump head may be selected for a customized stroke volume as required for the application. Synchronizing the operation of multiple pump heads is useful in applications that require multiple fluids to be delivered at precise flow rate and in precise volumetric ratio to one another. Use of a single control module 60 or drive module negates the need for multiple drive modules, thus reducing cost and complexity, while increasing ease of use. Of course the operator interface (LCD display, push buttons, and software) would all be custom designed to accommodate operation of parallel, synchronous pumps heads.
The control module 60 may be programmed to operate the drive module under two modes of operation: Uniform Dosing Mode and Intermittent Dosing Mode. When set to Uniform Dosing Mode, the control module 60 may be selectively programmed to pump uniformly (or continuously) at a specified flow rate. When set to Intermittent Dosing Mode, the control module 60 may be selectively programmed to incrementally dispense a pre-set volume of fluid at a programmed time interval and at a specified flow rate.
Uniform and Intermittent Dosing Modes may be achieved using either DC or AC motors to rotate the drive magnet 18. Using a DC motor or stepper motor provides the flexibility for the control module to adjust the motor speed through selective adjustment of the DC voltage. In other applications it may be desirable achieve a highly precise, constant motor speed by using an AC synchronous motor. In this case the desired flow rate is established by the volumetric capacity of the selected pump head in combination with the highly accurate, constant speed provided by the synchronous motor.
Before considering the modes of operation in more detail, it must be recognized that the magnetic flux field developed between the proximal poles of the drive and driven magnets is known to be non-linear with respect to rotation position of the drive magnet. This causes a non-linear relationship between the angular rotation position of the drive magnet and the intra-stroke position of the piston. Stroke-to-stroke volume consistency is not impacted by this intra-stroke non-linearity. In very low flow rate situations requiring partial intra-stroke steps, the non-linearity must be compensated for to provide uniform volume displacement as the piston advances in incremental, intra-stroke steps. Intra-stroke step compensation can be accomplished by programming the control module 60 to correct for the true relationship between the angular rotation position of the drive magnet and the intra-stroke position of the piston. The true relationship may be determined either through theoretical modeling of the dynamic magnetic forces, or through empirical testing. Theoretical modeling is a very complex endeavor and must ultimately be validated by empirical testing. Thus empirical testing is deemed to be the most accurate and direct method to establish the true relationship between angular rotation position of the drive magnet and intra-stroke position of the piston.
With consideration to full piston strokes or inter-stroke operation, the volumetric flow rate is calculated as the pump stroke rate times the pump's volume displacement per complete stroke. The mass flow rate is the volumetric flow rate multiplied by the fluid density which is constant for an incompressible fluid. If the working fluid is a gas, then a calculation correction would be required to determine mass flow rate using the Ideal Gas Law (PV=RT, where P=absolute pressure, V=specific volume of gas, R=ideal gas constant, and T=absolute temperature) and factoring the pump's internal pressure rise. The following description is oriented to application of an incompressible working fluid wherein the mass flow rate is directly proportional to volumetric flow rate.
The operator may set the desired volumetric flow rate through the user interface display pad positioned on the control module. For example, in the case of pumping an incompressible liquid, consider a piston pump head with a bore diameter of 5 mm (0.5 cm) and a stroke of 5 mm (0.5 cm) The stroke volume is the cylinder cross section area multiplied by the stroke distance (0.20 cm2×0.5 cm=0.10 cm3=0.10 ml). If a uniform flow rate of 1 liter per hour is desired, then the strokes per hour required is calculated as follows: Strokes per hour=1,000 ml per hour/0.10 ml per stroke=10,000 strokes per hour. This equates to a manageable 167 completed strokes per minute. Assuming the drive magnet 18 is a 2-pole configuration where one revolution corresponds to one round trip piston stroke, and then the required rotation speed of the drive magnet is 167 revolutions per minute. In the case of applying a variable speed DC motor or stepper motor, the control module will accordingly operate the motor at a speed which satisfies the demand for 167 revolution per minute to provide one pumping stroke every 0.36 seconds.
While the mode of operation is considered “uniform”, the actual flow is accomplished in very short duration increments or flow pulses. If “uniform” flow duty is very low, the time increment between pulses may be significantly lengthened as seen in the next example. Consider the same piston pump head, but the required flow rate is 1 ml per hour. This represents a reduction in flow rate of 1,000 times the previous example. Stroke rate=1 ml per hour/0.10 ml per stroke=10 strokes per hour. This equates to one stroke every 6 minutes. In a medical delivery application, a stroke period of 6 minutes (360 seconds) may be deemed too long or infrequent. Assuming a 60 second stroke period is acceptable, the Control Module may be programmed to complete partial strokes, wherein the stepper motor is controlled in fractional (discrete) rotational steps. While a full 360 degree shaft rotation is required to facilitate one complete stroke every 6 minutes (360 seconds), an incremental rotational step of 60 degrees every 60 seconds is equivalent to delivering an average or effective flow rate of 0.017 ml every 60 seconds. Thus the operator may set the flow rate and minimum period between stepper motor increments as needed for the application. The controller will also automatically apply the intra-stroke corrections as required to compensate for the known non-linearity between drive magnet rotation position and the intra-stroke position of the piston.
In some cases the user may wish to dispense a fixed volume or dose of fluid at regular or irregular time intervals. This may be satisfied by setting the Control Module to operate in Intermittent Dosing Mode, where the user may set a customized dose volume and the time interval. The Control Module is interactive with the user, and thus the user may set virtually unlimited dosing instructions. Examples include fixed dose dispensed at regular time intervals, fixed dose dispensed at variable time intervals, variable does dispensed at regular time intervals and variable dose dispensed at variable time intervals.
The user may also program the total number of doses to be dispensed, start time, and/or finish time. Or the user may input a table of times and doses to be dispensed. The user may also specify the uniform flow rate at which the dose is to be dispensed.
A special application is envisioned wherein the disposable pump head contains a RFID tag that may be programmed with patient specific dosing information as prescribed by the doctor, in addition to the information that identifies the pump model and stroke volume. Or, the control module may be electronically integrated with a bar code reader that reads the patient's dosing prescription as printed on the bag containing the prescribed medical fluid. The control module 60 will then automatically confirm that the pump head is appropriate for the dose via communication with the RFID tag, and will ensure that the patient's dosing instructions are automatically programmed into the control module 60 as read from the bar code. This will eliminate dosing errors resulting from operator programming errors. Furthermore the control module may be linked to an external data network to provide the doctor with real time monitoring of the patient's dosing progress.
The pump assembly of the present invention provides an integrated fluid management platform with capability to deliver accurate flow rate and fluid dosing over a wide range of operator set parameters. The control module 60 can be programmed to provide Uniform Dosing (continuous flow rate) or Intermittent Dosing. Relatively high flow rates can be achieved with the Drive Module rotating the drive magnet such that the driven magnet advances in full strokes. However, extremely low flow rates may also be achieved by rotating the drive magnet 18 such that the driven magnet 22 advances in fractional strokes. The pump head is low cost, easy to mount to the drive module 10b or to the control module 60 (integrated with the drive module) and is potentially disposable. The pump port orientation may be fixed, may be universally set to any position, or may be allowed to freely rotate.
The pump head 10a may be adapted to a suction accumulator or air bleed assembly 130 to expel air pulled into the suction tubing in the special case of pumping liquids that are stored in an atmospheric storage vessel or flexible plastic bag or pouch.
Pump heads of different volumetric capacity may be interchangeably mounted or docked to a motor drive module 10b or to a control module 60 providing a wide range flow rate capability. Multiple pump heads may be docked to a single drive module or control module to provide concurrent metering of multiple fluids and to maintain precise volume ratio of the multiple fluids to one another. RFID tags may be affixed to the pump head 10a (or 10a′) to allow the control module 60 to automatically identify the volumetric capacity of the pump head, and accordingly provide for automatic and error free compensation of all calculations used to control the motor function. The control module 60 may also be integrated with a bar code reader to input error free, customized dosing information into the control module. Positive sensing of the piston position can be achieved using a Hall Effect sensor 80 (See
The magnet drive system that includes the motor 16, shaft 20, rotating drive magnet 18 and the linear motion driven magnet 22 is not to be construed as being limited to the pumping applications described above. The disclosed magnet drive principle may be applied anywhere the linear motion of a piston and a piston carriage assembly may provide a beneficial function. Citing just one example, the magnet drive system/principle described above may be applied to replace conventional electric solenoids used in fluidic shut-off valve assemblies. In prior art solenoid operated valves, the solenoid provides the electro-magnetic force to move a magnetically susceptible pole piece in linear motion. The pole piece is connected to an elastomeric seal that is used to block or constrict the valve's orifice. When the solenoid is not energized, a spring acts upon and positions the pole piece such that the valve's orifice is selectively blocked or dosed by the seal. When the solenoid is energized, the resulting electro-magnetic field acts on the pole piece. The pole piece pushes against the spring and moves the seal away from the orifice thus opening the valve. A limitation of conventional solenoid valves is the ability for the solenoid to move the pole piece and open the valve when there is high upstream pressure. The high upstream pressure presses against the seal and resists movement of the pole piece upon activation of the solenoid to open the valve. Solenoid power must be managed to prevent high current and overheating of the solenoid. Thus solenoid activated shut-off valves are often limited from being applied when high inlet pressure is presented to the valve.
The magnet drive system/principle described above in connection with a pumping application may be applied to replace the conventional solenoid and pole piece system. The disclosed magnet drive system may also provide increased ability to open the valve when there is high upstream pressure due to favorable power-torque characteristics of DC electric motors and gear motors used to rotate the drive magnet as compared to conventional solenoid valves.
According to this embodiment, the modular valve assembly 110a replaces the modular pump head 10a shown in
According to this embodiment, a valve seal 114 is over molded or affixed with flexible rubber on upper carriage portion 124a. The seal is preferably tapered to press with adequate force against valve orifice 112 and thereby facilitate shut-off when the driven magnet 122 is moved to the TDC position as referenced in
The rotational range of motion of drive magnet 118 and caddy 119 must be limited to 180 degrees (or ½ revolution) which corresponds to the motion of driven magnet 122 and of piston carriage assembly 124 between TDC and BDC positions. This may be accomplished through the application of a tab 119a affixed to caddy 119 and of a strategically placed mechanical stops 116 affixed to or defined by the drive module housing 112a in proximity to the caddy 119. A torsion spring (not shown) may also be adapted to resist the rotation of caddy 119 when motor 116 is energized. The opening and closing cycle of the valve assembly 110a may be described with the valve starting in the open position, the motor de-energized, and piston carriage assembly 124 and driven magnet 122 in the BDC position as defined in
When the motor is energized and the valve is closed, the motor is stalled against the mechanical stop 116 and driven magnet 122 and piston carriage assembly 124 are in the TDC position. Of course the motor must be selected so as to operate continuously in a stalled condition without over heating. In the case of a reversible motor, for example a DC motor, the polarity of voltage applied to the motor may be reversed to reverse the rotation direction of the motor. In this case, the torsion spring may be eliminated, and the motor may be opened and closed by selectively reversing the polarity of the applied voltage presented to the motor.
A more preferred embodiment for eliminating the need for a torsion spring is illustrated in
In
However, upon removing voltage or de-energizing motor 116, the opposing force V1 acting on drive magnet 118 is no longer balanced by the applied motor torque, thus causing an imbalance of forces. This force imbalance causes a reversing (counterclockwise) rotation that backdrives motor 116, shaft 120, caddy 119 and drive magnet 118. The reverse rotation continues until the north pole (N) of the drive magnet 118 and the south pole (S) of the driven magnet 122 are moved into closest proximal positions as shown in
Yet another embodiment of the present invention is its adaptation as a linear actuator. This embodiment directs the linear motion of the piston carriage assembly 124 into any useful function. The motion of piston carriage assembly 124 may be directed through a forward stroke motion by energizing motor 116, and a reverse stroke motion by de-energizing motor 116, in a manner similar to the motion described for the shut-off valve embodiment shown in
Many other applications of the magnet drive system principle are envisioned. It is not the intent of this disclosure to list all possible applications. The motor powered magnet drive system disclosed herein as an integral part of the disclosed pumping system may be applied wherever the motion of the piston may provide a useful outcome.
While not limited to one industry, the beverage industry in particular has a long standing need to provide precise ratio of liquid constituents, specifically the volumetric ratio of water-to-beverage concentrate components. The post-mix beverage dispensing process is applied in the vast majority of fountain beverage systems. Post-mix is the process of blending 2 or more beverage components on demand. The beverage components—usually water and flavoring syrup (beverage concentrate)—are dispensed through post-mix beverage valves mounted on a fountain beverage dispensing tower. Mixing the beverage components at the point of dispense provides freshest mixed drink possible. The water and syrup are chilled to ice cold temperature before entering the valve. The water may be carbonated as in the case of soft drinks, or it may be non-carbonated as in the case of fruit juice or tea beverages. The flow rate of beverage dispensed through post-mix valves typically ranges between 3 and 6 volumetric ounces per second.
The water-to-syrup volume ratio is a critical element to obtain a quality tasting drink. Post-mix beverage valves generally use independent flow control mechanisms, one for water and one for syrup, in order to meter the syrup and water, and thereby control the dispensed beverage flow rate and the water-to-syrup volume ratio. While there are many different approaches to flow control, the most traditional approach is to employ a relatively economical pressure compensating piston-sleeve-spring flow control mechanism. Other flow control methods may include electronic means to measure the flow rate of water and/or syrup components and then apply proportional feedback control to an electromechanical valve or metering device to achieve the specified flow rate. Electronic controls provide increased flow accuracy. However the cost of the beverage valve may increase 2 to 3 times the cost of a valve that uses the traditional piston-sleeve-spring flow control mechanism.
The purpose of the flow control, regardless of its method of operation, is to maintain specified flow, even as upstream supply pressure to the beverage valve varies over a wide range. For example non-carbonated water pressures often vary between 30 to 70 psig. Carbonated water pressure is generally more reliable due to constant pressure maintained in the upstream carbonator. However, even carbonated water pressure can drop precipitously should 2 or more beverage valves operate simultaneously and cause high pressure drop in the supply tubes connecting the carbonator to the beverage valves.
Syrup is usually pumped using pressurized CO2 gas driven diaphragm pumps. Diaphragm pumps discharge the syrup at pressures set to approximately 60 psig. However instantaneous pressures experienced in the diaphragm pump cycle may vary an additional 20 psig above and below the 60 psig set point. In many applications pumps are installed a very long distance from the beverage dispensing tower in the remote “backroom” (up to 100 feet away). Sometimes the backroom is located in a basement up to 30 feet below the dispensing tower. Variability in both horizontal and vertical (elevation) distance between the pump and the tower can result in variable pressure loss and variable pressure delivered to the dispensing valve. Sometimes the syrup pumps are mounted very close to the dispensing valves, just a few feet away under the counter. In such applications the upstream instantaneous pressure fluctuations presented by the diaphragm pump cannot be fully compensated for by the flow control, and resultant pulses in syrup flow are observed as varying color streams in the dispensed beverage.
Another variable that affects how well the flow control operates is the viscosity of the syrup which may fluctuate depending on its temperature and formulation. Chilled sugared syrups are highly viscous with the consistency of molasses. Artificially sweetened diet syrups flow very easily and with the viscosity near that of water. Room temperature syrups flow more easily than chilled syrups.
Unfortunately, due to the wide range of water and syrup conditions experienced, the traditional piston-sleeve-spring flow control mechanism is not able to maintain specified flow rate and ratio without frequent manual adjustments to or calibration of the flow control. Each post-mix dispensing valve must be adjusted during the initial installation to obtain the specified water-to-syrup volume ratio. The installation of a single beverage system can require initial calibration of as many as 24 dispensing valves. The valve calibration time is considered significant to the installation cost of the fountain beverage system.
There are many millions of post-mix beverage valves installed today, the majority using piston-sleeve-spring flow controls. Unfortunately, the valves are not maintenance free. After the initial installation the valves may come out of adjustment and cause drinks to be dispensed with incorrect volume ratio and poor drink quality. Flow control adjustment is typically the largest category of service calls for fountain beverage systems and is a major cost to the operators of such systems.
The ratio pump of this embodiment of the invention provides for fixed water-to-syrup volume ratio. The disclosed ratio pump is intended to replace conventional post-mix dispensing valves mounted on the beverage tower. In applications where there is not unreasonable restriction or vertical elevation between the syrup supply and the ratio pump, the ratio pump may also eliminate conventional, pressurized gas or electric motor driven syrup pumps that are remotely installed in the backroom. The ratio pump may fit the same or smaller footprint as a conventional post-mix dispensing valve. There is generally is no need to adjust the ratio either during the initial installation or during the operating life of the pump. The ratio of the pump is factory set, but may be changed to a new setting through very simple replacement of a modular pump head to be described.
The advantages are considerable and include elimination of cost to service the beverage dispensing system (associated with beverage valve maintenance and calibration), improved customer satisfaction through improved dispensed drink quality (ratio control) and reduced installation and capital equipment of the beverage dispensing system.
Before engaging the turbine wheel 148, the incoming water is accelerated to high velocity by directing the water through an appropriately sized flow restrictor 150 with reduced flow area. Flow restrictor 150 may be configured as an orifice or nozzle to cause development of a high velocity water jet 152 downstream of the restrictor. Accordingly the restrictor converts potential energy held in the lower velocity, pressurized water upstream of the flow restrictor into kinetic energy represented by the high velocity water jet 152 downstream of the restrictor. The high velocity water jet impinges on the vanes or paddles 154 of the turbine wheel 148. Resultant deceleration of the water jet causes a transfer of momentum from the water jet to the turbine paddles and thus the development of a normal force that acts on the turbine paddles causing the turbine wheel to rotate in direction 156.
Paddles 154 of the turbine wheel are preferentially evenly spaced around the circumference of the wheel. “Water buckets” 174 of fixed volume are formed by the interior surfaces of adjacent paddles and the interior side walls of the hermetic enclosure 168. As water impinges on a first paddle the wheel rotates forward and the paddle advances away from the water jet until it is no longer exposed to the jet. At this point a next successive second paddle becomes exposed to the water jet. The advancing water bucket formed between the first and second paddles is filled with water that has fully decelerated, transferred its momentum to the turbine wheel, and created the force required to rotate the wheel. As long as the clearances between the paddles and the turbine enclosure are sufficiently small, water entering the turbine must advance to the turbine discharge 186 by the forward rotational movement of successive buckets filled with water. Accordingly a proportional relationship exists between the angular rotation of the turbine wheel and the volume of water processed by the turbine wheel. By proportional association and factoring the synchronous relationship between the turbine wheel and the pump head sub-assembly, a fixed proportional relationship (or ratio) also develops between the volume of syrup pumped by modular pump head 170 and the volume of water flowing through the turbine wheel.
Referring to
Water flow rate and flow rate of dispensed product 204 will vary in proportion to changes in upstream water pressure presented to the ratio pump. Thus the rotation speed of the turbine wheel will lessen with lowered water pressure and increase with higher water pressure. However the change in water flow rate does not impact ratio because the volume of the syrup flow changes in the same proportion as changes in the turbine wheel speed and water flow rate.
The ratio pump being integrated with the modular magnet pump is effective for pumping high viscosity fluids such as sugared syrups. Increase in syrup viscosity (causing more frictional pressure drop) and/or increase in the lifting height (between the syrup supply and the ratio pump 147 require more pumping power. While increased pumping power increases load on the turbine wheel causing lower speed, a proportional reduction in both water and syrup flow rate maintains a constant water-to-syrup volume ratio of dispensed beverage.
The volumetric capacity (per stroke) of the pump head 170 in combination with the fixed physical geometry (or capacity) of the water turbine sets the volumetric ratio of the ratio pump 147. However, the water flow rate processed through the ratio pump will vary with the upstream water pressure presented to the ratio pump, as will the dispensed beverage flow rate. During the initial installation the operator may want the flexibility to adjust the dispensed beverage flow rate higher or lower depending on the available water supply pressure. Referring to
The primary strategy of the ratio pump 147 is to set a fixed ratio according to selection of the volumetric capacity of the modular pump head 170 and the size of the water turbine 148. In some applications it may not be practical to offer standard capacity modular pump heads for all conceivable ratio settings required for different beverages, and it may be necessary to fine tune the ratio of a given pump head 170. Referring to
Low water pressure in the non-carbonated water supply is a major problem when traditional piston-sleeve-spring flow controls are used. Water pressure in non-carbonated systems is highly variable and less reliable as compared to carbonated water systems, wherein relatively constant head pressure is maintained by the carbonator. So called “ambient” and “cold” carbonations systems generally maintain stable carbonated water supply pressures of 110 psig and 70 psig, respectively.
Traditional flow controls lose virtually all ability to regulate water flow at pressures below 35 psig and the delivered water flow rate can fall precipitously. The standard industry recommendation in this case is to install an expensive water pressure booster upstream of water supply 158 to regulate the pressure to a level above 35 psig, and preferably in the range of 60 to 70 psig.
When applied in non-carbonated water systems that experience very low water pressure, the ratio pump may offer a special advantage and negate installation of an expensive water pressure booster. A relatively low cost water pressure regulator 206 may be installed upstream of the ratio pump between supply 158 and inlet solenoid valve 176. It may be possible to set the regulator and the ratio pump to operate at a very low pressure, for example as low as 10 psig at turbine inlet 184. The theoretical pressure drop across the turbine wheel is on the order of 5 psig based on the hydraulic energy (flow rate×pressure rise) required to pump the syrup in a typical application. Thus 10 psig is theoretically or ideally enough water pressure to drive the turbine wheel and pump the syrup. Even as the water pressure upstream of the regulator may vary from as high as 100+ psig to as low as 10 psig, the pressure regulator will present a constant pressure of 10 psig to inlet 184 (of course factoring any pressure drop across valves 176 and 178), while maintaining constant flow rate of delivered beverage and constant water-to-syrup volume ratio. The adjustable inlet restriction 178 must be opened to provide a very low level of restriction to achieve the desired beverage flow rate because the inlet pressure is set so low. If the beverage flow rate is still too low, then the regulator 106 can be set to a pressure higher than 10 psig as may be necessary to achieve the required beverage flow.
This same water regulating approach may be applied in carbonated systems if there is concern with the stability of the carbonator head pressures. In summary, the ratio pump may be applied to deliver constant water flow through the use of an upstream pressure regulator set at suitably low pressure. This allows the ratio pump to operate over a wide range of system water pressures with a constant flow rate. In non carbonated systems application of the ratio pump may negate the use of an expensive water pressure booster.
The control Module 200 may be physically integrated with the ratio pump 147 or remotely positioned away from the ratio pump. A Hall Effect Sensor 208 may be adapted to the ratio pump to optionally sense the magnetic field of drive magnet 166 and/or of the driven magnet 122 contained inside the pump head 170. The signal generated from the Hall Effect Sensor provides a mechanism for the control module 200 to count pump strokes and accordingly calculate the volume of dispensed beverage. This provides the opportunity for the user to select a desired dispensed drink portion size (for example, small, medium, and large) using an interface such as a push button pad that is integrated with Control Module 200.
Optionally two Hall Effect Sensors may be concurrently applied, one to sense the drive magnet and the other to sense the driven magnet. This way the control module 200 may discern a malfunction of the pump head if the counts developed from each sensor do not match. In this case the control module may develop an override to stop the dispensing function and/or develop an Alarm Condition to indicate there is a malfunction.
The control module 200 may also be optionally connected to an external data network to transmit information such as number of drinks dispensed, portion size, time of day dispensed, alarm condition, etc. that may be useful to the store owners and/or beverage concentrate suppliers.
The disclosed ratio pump and system integrates the syrup pumping function with the dispensing function. The ratio pump concurrently pumps the syrup from remote location while also metering the syrup and water in pre-set ratio. The elimination of conventional syrup pumps greatly reduces the complexity of the fountain beverage system, and provides an opportunity for large reduction in installed cost and annual maintenance costs, while reducing system complexity and increasing overall reliability.
The ratio pump has numerous advantages as compared to conventional post mix beverage valve technology. The ratio pump provides for proportional changes in water flow rate, turbine wheel speed and magnet pump stroke rate. Accordingly water-to-beverage concentrate ratio is held constant even as the water flow rate changes due to variable water pressure. Pump volumetric flow per stroke is constant, and is impervious to changes in viscosity caused by temperature variability or by changes in syrup composition (diet vs. sugared syrups). The ratio pump may replace the function of expensive “backroom” beverage concentrate pumps. The energy required to pump the concentrate is derived from the water turbine which converts water pressure to useful pumping energy. The ratio pump head 170 is modular and quickly replaced.
This feature provides a great degree of operational flexibility to accommodate changeover to beverages with different mix ratios and/or to replace a broken pump head. Maintenance cost to periodically adjust the flow controls of conventional post-mix vales is greatly reduced.
The disclosed ratio pump provides improved portion control technology. A Hall Effect sensor can be added to the pump body to allow for electronic counting of magnetic piston strokes. Integrated with a “smart” electronic control module, the volume of syrup and water dispensed may be instantly calculated. Accordingly the user may select a custom portion size at the operator interface.
The potential for cost reduction using the disclosed ratio pump cannot be understated. Elimination of the syrup pumps also eliminates expensive carbon dioxide used to drive the pumps and associated tanks, hoses, fittings, pressure regulators, valves, etc. A single beverage installation may save thousands of dollars in installed cost. The improved reliability of the disclosed ratio pump may also save thousands of dollars in reduced maintenance cost over the life of the installation.
While this description is specifically oriented to application of the disclosed ratio pump for dispensing post mix beverage, it is not to be construed as limiting its application. The disclosed ratio pump may be applied in any application requiring the delivery of two fluid components in fixed proportion to one another, and when the first fluid component is presented at sufficient pressure and flow rate to provide the energy source to pump the second fluid.
Although the invention has been described with a certain degree of particularity, it should be understood that those skilled in the art can make various changes to it without departing from the spirit or scope of the invention as hereinafter claimed.
This application claims priority from U.S. Provisional Application Ser. No. 61/448,722, filed Mar. 3, 2011, the subject matter of which is incorporated herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61448722 | Mar 2011 | US |
