Patent Application
20080047973
Beverage dispensers for mixing together liquid beverage concentrate and liquid diluent in predetermined ratios, and for dispensing the mixture as a drink for service to consumers, are well known. Some such beverage dispensers serve fruit juice drinks, such as orange juice, apple juice, etc., in which case the diluent normally is plain water while the concentrate comprises concentrated fruit juice that usually is refrigerated, often has a relatively high and temperature dependent viscosity, and may contain pulp. For consistent quality of drinks, it is important that concentrate and water always be mixed together in a predetermined ratio, depending upon the particular fruit juice drink to be served. In an attempt to maintain a desired constant ratio of water to juice concentrate, conventional practice contemplates using a metering type delivery device, such as a peristaltic pump that is driven at a constant speed during delivery of a flow of concentrate to a mixing chamber, with a regulated water supply being portioned into the mixing chamber at a flow controlled to be in accordance with the speed of operation of the concentrate metering pump. However, such prior systems are less accurate than desired in maintaining a constant ratio of water to concentrate, in that they normally are of the open loop type and therefore are unable to compensate for naturally occurring changes in the flow of concentrate delivered by a peristaltic pump to the mixing chamber. Changes in the flow of concentrate to the mixing chamber can occur, for example, because a peristaltic pump, while capable of accurately metering and delivering a selected flow of a pumped liquid if the characteristics of the liquid remain constant, cannot necessarily deliver a constant flow of liquid when changes occur in the characteristics of the liquid, even though the speed of operation of the pump is maintained constant. For example, when the pumped liquid is fruit juice concentrate that often has a relatively high and temperature dependent viscosity, changes in temperature, and therefore in viscosity, of the concentrate, as well as the presence or absence of pulp in the concentrate, can significantly affect the pumped flow of concentrate to the mixing chamber, despite the operating speed of the metering pump being controlled to be constant. The net result is that variations in the characteristics of the concentrate affect the flow of the concentrate and, thereby, the ratio of water to concentrate in the prepared beverage, which adversely impacts the quality of drinks served to consumers.
In improving upon beverage component proportioning schemes for conventional fruit juice dispensers, the invention provides a flow control system that operates to precisely control the ratio of water to fruit juice concentrate as delivered to a mixer and served from a dispensing valve of a fruit juice dispenser, despite changes in the characteristics of either or both of the water and concentrate. To provide such precise control, the system monitors flows of the concentrate and water to the mixer and the pressure of water upstream from the mixer and controls the flow of one or both of the water and concentrate, in accordance with the pressure of the water, in a manner to compensate for variations in the flow of either, to thereby maintain a constant predetermined ratio of water to concentrate as delivered to the mixer.
To provide liquid fruit juice concentrate to the Y-tube inlet 24, a supply container of concentrate 30 is fluid coupled to an inlet to a metering pump 32, such as to an inlet to a motor driven peristaltic pump that may be of any suitable type known to those skilled in the art and that may be operated at various speeds to vary the flow of concentrate delivered by the pump to the Y-tube inlet 24. It is to be understood that the metering pump 32 need not necessarily be a peristaltic pump, and can be any suitable type of fluid delivery regulating pump, or fluid delivery regulating system that does not necessarily include a pump, that can be operated in a manner to control a flow of concentrate to the Y-tube inlet, although for convenience the invention will be described in terms of the metering pump being a peristaltic pump, an outlet from which is fluid coupled to the Y-tube inlet 24. An electronic control circuit or controller 34, which may be microprocessor based, operates the motor driven peristaltic pump 32 between off and on states and controls the speed of operation of the pump and thereby the flow of concentrate into the Y-tube inlet 24. From the Y-tube inlet, liquid fruit juice concentrate flows to the mixing chamber 28.
To provide water to the Y-tube inlet 26, a potable water line 36 is fluid coupled to an inlet to a dosing valve 38. The dosing valve advantageously is of a type as disclosed in U.S. Pat. No. 6,962,270, issued Nov. 8, 2005 and the teachings of which are specifically incorporated herein by reference. With reference also to
The controller 34 is electrically connected to the stepper motor 62 to operate the stepper motor in a manner to move the dosing valve piston 52 between positions fully closing and opening the valve as well as to positions therebetween to control a flow of water through the valve. When the controller operates the stepper motor to move the piston to its lowermost position as shown, the piston completely closes off, in conjunction with its lower seal 56, the central bore through the valve block 64, thereby closing the valve 38 and preventing a flow of water from the valve. When the controller operates the stepper motor to raise the piston, the valve block 64 is opened to allow a flow of water through the V-grooves 66 and from the valve outlet 44 into the Y-tube inlet 26. The further the piston 52 is raised, the greater the degree of opening through the dosing valve and the greater the flow of water into the Y-tube inlet 26. A signal generated by the flow meter turbine 46, representing of the flow of water through the dosing valve and thereby into the Y-tube inlet 26, is coupled via a lead 46a to the controller 34. A water pressure measuring device 68, which may be of any suitable type, is downstream from the metering valve 38 and upstream from the Y-tube mixing chamber 28 to sense the pressure of water upstream from the mixing chamber. A signal generated by the water pressure sensor, representing the pressure of water delivered to the mixer 28, is coupled to the controller 34 via a lead 68a.
Operation of the system 20 in maintaining a predetermined ratio of the flows of water and fruit juice concentrate delivered to the Y-tube mixing chamber 28 is predicated upon fluid dynamics. As is well known, if two flows of liquid are brought together, the upstream pressures of both flows will be affected. Thus, when a flow of concentrate and a flow of water are brought together in the Y-tube mixing chamber 28, the upstream pressure of each flow is affected. In the system 20, the water flow is introduced to the mixing chamber through the dosing valve 38, which valve has the capability of measuring and controlling the water flow. When concentrate is introduced to the mixing chamber 28 by the peristaltic pump 32, it affects the pressure of the water flow upstream from the mixing chamber, as detected by the pressure measuring device 68. The controller 34 receives from the dosing valve turbine flow meter 46 and the pressure sensing device 68 inputs representative of the flow and pressure of water delivered to the mixing chamber 28, and in response to the inputs provides control signals to the peristaltic pump 32 and to the dosing valve 38 to control the speed of operation of the pump and the degree of opening of the valve, in such manner as to introduce a selected ratio of concentrate and water into the mixing chamber.
When fruit juice concentrate is introduced into the Y-tube mixing chamber 28, in order to maintain a constant flow of water to the mixing chamber, the dosing valve must compensate by opening further and thereby increase the pressure of the water upstream from the chamber, which increase is detected by the pressure sensor 68 and applied to the control circuit 34. The amount of water pressure increase is proportional to the mass flow of concentrate introduced into the mixing chamber 28, so that by measuring the increase in water pressure, the mass flow of concentrate can be determined. In accordance with one contemplated operation of the system 20, concentrate flow is regulated by the control circuit 34 in accordance with sensed water pressure, by appropriately varying the speed of operation of the peristaltic pump 32.
To initialize or prepare the system 20 for delivering a predetermined ratio of water and fruit juice concentrate to the Y-tube mixing chamber 28, as a first step the peristaltic pump 32 is turned off and the dosing valve stepping motor 62 is operated to move the valve piston 52 to various ones of its positions between fully closed and open states of the valve, to determine water pressures that exist at the pressure sensor 68 for various flows of water in the absence of a flow of concentrate. These pressures are input to and stored by the controller 34. For any particular flow of water only and associated pressure of the water, there is a corresponding incremental change in pressure of the water that will occur at the pressure sensor 68 in response to flow of a known type of fruit juice concentrate, when the flow of concentrate is such as yields a desired ratio of water to concentrate being introduced into the Y-tube mixing chamber 28, and such incremental pressure changes as would occur at various combinations of flows of water and concentrate are entered into the controller 34. Target water pressures are then determined for the various combinations of water and concentrate flows that yield the desired ratio of water to concentrate, which target pressure for any particular combination equals the pressure of water sensed by the pressure sensor 68 when water only flows at the particular water flow rate plus the incremental pressure induced in the water when there is a flow of concentrate at the particular concentrate flow rate. Given the various target pressures, for any measured flow of water, the controller 34 can adjust the speed of operation of the peristaltic pump 32, and thereby the flow of concentrate, in a manner to provide the target pressure of water at the pressure detector 68, thereby to control the flow of concentrate such that the desired ratio of water to concentrate is delivered to the mixing chamber.
It is understood that while operation of the system has been described with respect to adjusting the speed of operation of the peristaltic pump 32 to vary the flow of concentrate in a manner to yield, for a particular water flow, a target pressure of water at the pressure detector 68, if desired the speed of operation of the peristaltic pump could be maintained constant and the dosing valve 38 could be operated to vary the water flow in a manner to reach a target water pressure as would exist at a different water flow. In other words, with the concentrate flow being maintained constant, the dosing valve 38 can be operated to bring the water flow and water pressure to one of the predetermined associated values of water flow and pressure as have been entered into the controller 34, which will then provide the desired ratio of water and concentrate in the mixing chamber 28, since for any given flow of concentrate from the peristaltic pump, only one set of associated water flow and water pressure values exists. Alternatively, both the peristaltic pump and the dosing valve could be operated to reach a previously predetermined set of associated of water flow and water pressure values as have been entered into the controller 34, thereby to again provide a desired ratio of water to concentrate in the mixing chamber 28. Also, while the invention has been describe in respect of a single system 20 for use in a fruit juice dispenser, depending upon the number of beverage dispensing valves employed, a corresponding number of systems could be used. Further, the invention is not limited to use with fruit juice dispensers, but may also be used with other types of beverage dispensers in order to maintain a selected ratio of two beverage components. The system may also be used to provide mixtures of non-beverage liquid components in selected ratios.
While embodiments of the invention have been described in detail, various modifications and other embodiments thereof may be devised by one skilled in the art without departing from the spirit and scope of the invention, as defined by the appended claims.
