Abstract:
A system for monitoring and controlling the delivery of CO 2  from a bulk storage tank to at least one gas-driven pump is disclosed. By monitoring certain conditions, the flow of CO 2  can be quickly and easily terminated if necessary, thereby reducing or eliminating undesirable consequences of CO 2  gas flow in abnormal operational scenarios. The invention is particularly well suited for deployment in conjunction with beverage dispensing machines and can be configured to shut down the flow of CO 2  if a drop in pressure occurs due to a leak in the system or if a syrup delivery system runs out of product.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This non-provisional patent application claims the benefit of U.S. patent application Ser. No. 12/070,958, under 35 U.S.C. §120, which application was filed on 22 Feb. 2008, which application is now pending and which application is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention generally relates to systems for storing gas and relates more specifically to monitoring systems for bulk cryogenic storage systems. 
     2. Background Art 
     The use of bulk cryogenic storage systems for carbon dioxide (CO2) gas is a relatively recent historical development in the beverage industry. Vacuum jacketed storage containers delivering 300 pounds to 750 pounds or more of liquified CO 2  gas are widely used. These containers are configured to deliver gaseous CO 2  at pressures above 90 pounds per square inch by converting the liquid CO 2  to gas using a natural conversion process through a simple temperature increase effected by ambient temperatures at the location of use. 
     The gas delivered from such tanks is widely used in conjunction with beverage dispensing machines of the type commonly found in restaurants, convenience stores, theaters, amusement parks and the like. In these environments, the carbon dioxide (CO 2 ) is typically mixed with water to produce carbonated water under pressure. The carbonated water is then mixed with a syrup at the dispensing machine to produce the finished carbonated beverage. 
     CO 2  in its gaseous state is a tasteless, colorless, odorless gas which naturally displaces oxygen. If this gas is accumulated in sufficient density in a closed space, such as a storage room, it may be hazardous, if not lethal. In facilities that initially produce CO 2  gas for ultimate delivery and consumption, multiple safety procedures are generally employed. Among these are detectors that are configured to sense when the CO 2  gas level in a particular area exceeds a safe level and produce a warning alarm. 
     Bulk storage tanks, however, frequently are located in a confined area adjacent a beverage dispensing machine, frequently, in a small room one wall or in some other area which is frequented by employees of the establishment using the beverage dispensing machine. CO 2  sensors or safety devices are not typically employed where bulk storage tanks are used to supply CO 2  to a beverage dispensing machine. In such situations, both employees of the establishment and customers may be exposed to unsafe levels of CO 2  gas without their knowledge. 
     If the syrup box or container used to deliver the flavored syrup to the beverage dispensing machine is empty while the CO 2  dispensing line is connected to it, the resultant drop in pressure may allow CO 2  gas to pass outwardly into the surrounding area. Also, if a leak should occur in the gas line for delivering the gaseous CO 2  to the carbonator or beverage box of a beverage dispensing machine or, if for any reason, there is a failure to turn off the delivery of CO 2  gas, a drop in pressure, sometimes sudden, takes place at the bulk storage tank. 
     A sudden drop in pressure of CO 2  delivered from the tank will generally cause the liquid CO 2  in the bulk container to turn into “dry ice.” When this occurs, further delivery of gaseous CO 2  from the tank is precluded. This typically necessitates some type of a service call, since when this occurs, the beverage dispensing machine will cease to operate correctly. Service calls of this type are unscheduled and are may be quite expensive, driving up the operating costs of the entire system. Accordingly, without improvements to the current state of the art for bulk cryogenic storage systems, the operation of these systems will continue to be suboptimal. 
     BRIEF SUMMARY OF THE INVENTION 
     A system for monitoring and controlling the delivery of CO 2  from a bulk storage tank to at least one gas-driven pump is disclosed. By monitoring certain conditions, the flow of CO 2  can be quickly and easily terminated if necessary, thereby reducing or eliminating undesirable consequences of CO 2  gas flow in abnormal operational scenarios. The invention is particularly well suited for deployment in conjunction with beverage dispensing machines and can be configured to shut down the flow of CO 2  if a drop in pressure occurs due to a leak in the system or if a syrup delivery system runs out of product. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The preferred embodiments of the present invention will hereinafter be described in conjunction with the appended drawings, wherein like designations denote like elements, and: 
         FIG. 1  shows a system for monitoring and controlling the flow of CO 2  in accordance with a preferred exemplary embodiment of the present invention; 
         FIG. 2  shows a block diagram for a CO 2  shut-off circuit for use in conjunction with a system for monitoring and controlling the flow of CO 2  in accordance with a preferred exemplary embodiment of the present invention; 
         FIG. 3  shows a circuit diagram for a pump control circuit used in conjunction with a system for monitoring and controlling the flow of CO 2  in accordance with a preferred exemplary embodiment of the present invention; and 
         FIG. 4  shows a method for monitoring and controlling the flow of CO 2  in accordance with a preferred exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , a block diagram of a system  100  for monitoring and controlling the flow of CO 2  in accordance with a preferred exemplary embodiment of the safety system of the present invention is depicted. As shown in  FIG. 1 , system  100  is used in conjunction with a bulk cryogenic storage tank  10  of the type used to store and deliver liquid CO 2 , converted to a gaseous state, suitable for application in a variety of applications. 
     One such application is shown in  FIG. 1  is the use of bulk cryogenic storage tank  10  in conjunction with a beverage dispensing unit  32 . Beverage dispensing unit  32  is fairly common and is used in many fast food restaurants and the like to dispense soft drinks A gas delivery line  11  is connected to a conventional high pressure regulator  12 , which regulates the output gas flow from the tank  10  to a pressure in the approximate range of 90 to 110 PSI. Pressure regulator  12  and the pressure range for the CO 2  gas delivered from tank  10  is relatively conventional, in a range typically used by common beverage dispensing units, such as beverage dispensing unit  32 . 
     After the connection to regulator  12 , gas line  11  is connected to the input of a safety tank pressure monitor system or unit  14 . Safety tank pressure monitor unit  14  is configured to monitor the pressure of gas in line  11  and, in the most preferred embodiments of the present invention, includes controls for sensing low pressure, a condition that may be caused by a leak in gas line  11  or by an open CO 2  connection downstream from pressure monitor unit  14 . 
     Pressure monitor unit  14  typically includes user-adjustable electronic circuitry, or other suitable means, for continuously monitoring the pressure in line  11  as it flows through pressure monitor unit  14 . The operation of pressure monitor unit  14 , in conjunction with other portions of system  100 , is described in greater detail below. After gas line  11  has passed through safety tank pressure monitor system  14 , it is connected through a normally closed control valve  16 , from which it then is connected to a conventional carbonator  30 . Carbonator  30  is also supplied with water, as shown in  FIG. 1 . The output from carbonator  30  is supplied to the beverage  18  dispensing machine  32 , along with syrup for selected beverages from  19  a single beverage box or, as shown in  FIG. 1 , a beverage box cluster  34 . In the most preferred embodiments of the present invention, beverage box cluster  34  typically comprises a plurality of different beverage syrups, each contained in a separate beverage box, and the syrup from the beverage boxes can be combined with the output of carbonator  30  for use in providing carbonated beverages to consumers. 
     The manner in which syrup is delivered from the beverage boxes  34 , and in which carbonated water is delivered from carbonator  30  to machine  32  is well known to those skilled in the art, and therefore is not discussed in any detail here. As noted above, CO 2  gas from storage tank  10  is generally supplied to a normally closed valve  16 . 
     In order for valve  16  to be opened to deliver CO 2  gas to carbonator  30 , a relay  18  must be operated. Relay  18  is electrically actuated and whenever electrical power to relay  18  is interrupted, the power supply to normally closed valve  16  is disconnected and valve  16  closes to prevent flow of CO 2  gas through system  100  to carbonator  30 . This is the “fail safe” mode of operation for system  100  and is a safety mechanism that stops the flow of CO 2  in case of a problem. 
     Whenever the pressure sensed by a pressure sensor contained within safety pressure monitor unit  14  exceeds a pre-established pressure level (typically, in the normal pressure range of 90 PSI or more), a signal is supplied to close a normally open switch  22 . This is indicated by dotted line  36  in the drawing. This signal and the particular type of switch, and the manner in which the switch is closed, may be of any suitable type. Switch  22  is indicated in the drawing diagrammatically as a single-pole-single-throw mechanical switch of the type that may be operated by a relay. Switch  22 , however, may be a micro switch, or a transistor, electronic switch, or any other suitable type of switch. The particular type of switch is not critical to the invention; so it has been depicted functionally as shown in the drawing. 
     When switch  22  is closed by way of the link shown as the dotted line  36  in  FIG. 1 , power is applied from a suitable source of alternating current power  20 , through a rectifier  24 , to operate relay  18 . When relay  18  is operated, valve  16  is opened, allowing gas to pass through valve  16  to carbonator  30  causing the system to operate in its normal mode of operation. 
     So long as there are no leaks or an unintentionally left open demand for CO 2  gas from beverage dispensing machine  32 , system  100  operates as if safety tank pressure monitor unit  14  was not present. 
     In the event, however, that a sudden and/or prolonged drop in pressure as a result of a leak or other abnormal flow of gas out of tank  10  takes place, the low pressure condition is sensed by the safety tank pressure monitor unit  14 ; and switch  22  is opened. When switch  22  is opened, no further power is delivered to relay  18 ; and therefore, the normally closed valve  16  again closes. This terminates the delivery of CO 2  gas to carbonator  30 , so long as the low pressure condition exists. 
     With valve  16  closed, however, the pressure in system  100  can stabilize and pressure is allowed to build up naturally as CO 2  gas is delivered from tank  10 . The stabilization of system  100  at a preselected upper pressure automatically occurs as a result of the nature of the liquid CO 2  contained the tank  100 . If there is a significant leak in system  100  (e.g., a rupture in tank  10 ) then it is possible that the pressure in system  100  may never stabilize at a level that would be high enough to open valve  16  again. 
     When and if the desired operating pressure is sensed by safety tank pressure monitor unit  14 , switch  22  is closed and valve  16  is opened once again, thereby permitting flow of CO 2  gas to carbonator  30 . If the condition that caused the low pressure sensing from safety tank pressure monitor unit  14  again takes place, however, as a result of a leak or other uncorrected continuous dispensing of the CO 2  gas, the low pressure condition once again will be established. Safety tank pressure monitor unit  14  again senses the low pressure and causes the valve  16  to be closed. Even though the system may cycle back and forth between a closed valve  16  and an open valve  16 , freezing up or icing up of the system is prevented. Obviously, cycling back and forth between the open and closed operation of the valve  16  does not stop leakage, if the condition was caused by leakage. 
     Consequently, repair of whatever caused the CO 2  leak will still need to be performed. The safety monitor system, however, does provide for operation of beverage dispenser  32  until the necessary repairs can be made. The operation of dispenser  32  obviously will be interrupted whenever the valve  16  is closed so that the persons responsible for the system&#39;s operation are provided with a ready indication of some type of system malfunction. By employing the apparatus described herein, the malfunction however, will not result in a frozen condition of the CO 2  in tank  10 ; and by the nature of the operation of safety tank pressure monitor unit  14 , it is possible to schedule a repair and inspection of the system at a more convenient time, rather than under some type of “emergency” situation. 
     In addition to safety tank pressure monitor unit  14  as described above, another aspect of the present invention is the use of an apparatus to disable the flow of CO 2  gas under circumstances other than a drop in pressure sensed by safety tank pressure monitor unit  14 . For example, it is possible that the individual pumps associated with the beverage boxes may be pumping even though the product contained in the beverage box has been completely exhausted. This is an undesirable situation and may be addressed as set forth below. 
     Referring now to  FIG. 2 , a line cut-off system  200  is configured to detect any irregularity in the continuous operation or other change in the operational characteristics of the gas-driven beverage pump due to an empty supply bag or other fault. In the most preferred embodiments of the present invention, this is accomplished by detecting the sound from the exhaust port of the pump drive. 
     In most beverage dispensing systems, the bag pumps that are connected to the product dispensing bags are gas-driven and generally powered by a compressed gas, typically CO 2  or air. However, the apparatus of the present invention is universal in nature and may be deployed with any pressurized gas used in beverage dispensing systems known to those skilled in the art. In the most preferred embodiments of the present invention, system  200  uses one or more monitoring devices to detect operational abnormalities in the flow of the product in the beverage dispensing system. For example, in the most preferred embodiment of the present invention, one or more electret microphone pickups are used to monitor the exhaust sound emanating from each of the bag pumps. Based on the change in one or more operational characteristics of the gas-driven pump (e.g., the sound associated with the pumping of the product from the bag), problems in the operation of the system can be detected. When the bag connected to the pump is out of product (e.g., syrup) the pump will generally operate at a higher frequency and a louder volume level, attempting to pump product from the empty bag. 
     While the use of the microphone to detect system anomalies is one of the most preferred embodiments, those skilled in the art will recognize that various other methods could be used to detect operational abnormalities or changes in the operational characteristics of the gas-driven pump associated with the pumping of product from one or more bags (e.g., pressure or flow transducer or switch, or any other flow detection method that can be used to detect a change in the flow rate of the liquid being pumped by the gas-driven pump). In any case, when the monitoring system (e.g., micro-controller and other associated components) detects a change in the operational characteristics of the gas-driven pump or otherwise determines that a problem exists in the monitored system, it closes a solenoid control valve that is in line with the source of gas (e.g. CO2 or compressed air) that supplies power to the pump, effectively disconnecting the air source that drives the gas-driven pump, thereby disabling the pump and terminating the operation of the pump. Additionally, in at least some preferred embodiments of the present invention, an LED indicator light may be configured to be illuminated at some location near the gas-driven pump or at some remote location to indicate that one or more of the pumps has disabled by the monitoring circuit. When the problem is corrected, the operator will reset circuit  200  with a pushbutton switch and the microcontroller opens the control valve, allowing the pump to operate normally once more. This may mean, in most cases, that one or more new boxes of liquid have been connected to the appropriate gas-driven pump so that the beverage can be delivered to the beverage dispensing system. 
     As shown in  FIG. 2 , system  205  includes a gas supply line  201  is used to provide CO2 or air to one or more product supply boxes or beverage boxes  34 . For each beverage box  34 , gas supply line  201  will pass through a line cut-off system solenoid control valve  220 . Each beverage box  34  is connected to a gas-operated pump  240 . Each gas-operated pump  240  is used to pump the contents of its respective beverage box  34  to beverage dispensing machine  32  of  FIG. 1 . Once the beverage box  34  has been emptied, the pump exhaust  241 , which is coupled to a pump control circuit  230 , will trigger a solenoid control valve  220 , shutting off the flow of CO2 or air to gas-operated pump  240 . This will have the effect of disabling gas-operated pump  240 . In at least one preferred embodiment of the present invention, the output of pump exhaust  241  is the sound of gas-operated pump  240 . In other preferred embodiments of the present invention, pump exhaust may comprise a flow transducer that monitors and detects the decrease in product flow being delivered by gas-operated pump  240  or some other similar mechanism. In any case, there will be a mechanism positioned at or near beverage box  34  and gas-operated pump  240  that will detect the reduced flow of product to beverage dispensing machine  32  and activate pump control circuit  230 , thereby actuating solenoid control valve  220  and disabling gas-operated pump  240 . 
     Although a single beverage box  34  is shown in conjunction with system  205 , in most applications, there will be a plurality of beverage boxes, each connected to a pump control circuit  230  with each pump control circuit  230  being connected to electrical supply  36  and to beverage dispensing system  32  of  FIG. 1 . 
     Referring now to  FIG. 3 , a circuit schematic diagram  300  for implementing a specific preferred embodiment of system  200  of  FIG. 2  is presented in greater detail. Those skilled in the art will recognize that this is only one way of implementing a single preferred embodiment of the present invention and that many other circuits may be utilized to accomplish the same result. 
     24 VDC power is supplied to JP 1  from an external power supply, such as a wall transformer circuit. R 8 , C 1 , and Zener diode D 2  provide a low voltage, low current VCC supply. JP 2  is provided so that power may be connected from this circuit to the next in a daisy-chain fashion, reducing the length of wiring required for the system. 
     MK 1  is an electret microphone mounted near the pumps so that it will pick up the sound from the pump exhaust. R 2  provides bias current to the microphone. Q 1  and its associated components C 4 , R 3 , and R 5  amplify the signal from the microphone. R 3  and R 5  bias Q 1  so that its collector voltage in the absence of sound is approximately ½ the supply voltage, VCC. In the absence of sound, C 5  will also be charged by current through R 4  to approximately ½ the supply voltage, VCC. When the signal from MK 1  is strong enough, C 5  will be discharged through D 4  and the voltage on C 5  will be reduced. 
     C 5  is connected through R 6  to pin  1  of micro-controller U 2 . Pin  1  is the input to a comparator circuit in U 2 . Its threshold is set to 0.6V so that when C 5  is discharged below 0.6V the micro-controller recognizes that MK 1  is receiving the necessary level of sound to indicate a problem with the pump. The program in the microcontroller uses the duration and frequency of occurrence for the sound to determine that there is a fault or that the bag connected to the pump is out of product (e.g. syrup). 
     Pin  4  of the microcontroller is connected to the gate of mosfet Q 2 . In the absence of a pump fault, the micro-controller holds the gate of Q 2  high so that Q 2  conducts current through the solenoid valve connected to JP 3  and the valve is ON, allowing the pump to operate. Pin  2  of JP 3  is essentially at ground potential and pin  1  of JP 3  is connected to the 24V supply, supplying power to operate the solenoid valve. When the microcontroller determines that there is a fault, it pulls the gate of Q 2  low, turning it off and turning off the solenoid valve. Pin  2  of JP 3  is then pulled to 24V through the low resistance solenoid coil and LED D 3  lights. The current through D 3  is much too small to operate the solenoid valve. D 1  provides for suppression of transient voltages from the inductive energy stored in the coil of the solenoid valve when it is on. 
     Switch SW 1  is monitored by the micro-controller and when it is pressed, the micro-controller turns Q 2  on again, actuating the solenoid valve. 
     J 1  and R 1  provide a means of programming U 2  while in-circuit. This allows the micro-controller program to be easily changed for different conditions (e.g., adjusting the sound intensity or frequency for triggering the shut-off circuit). 
     Referring now to  FIG. 4 , a method  400  for monitoring and controlling the flow of CO2 in a beverage dispensing system in accordance with a preferred embodiment of the present invention is depicted. 
     As shown in  FIG. 4 , one or more gas powered pumps are monitored (step  410 ) to determine when the product being pumped by the gas powered pump has been depleted (step  420 ). As previously mentioned, there are a number of ways whereby the depletion of the product can be determined. In the most preferred embodiments of the present invention, the change in the sound of the operation of the gas powered pumps is detected by an electret microphone and used to activate a pump control circuit and a solenoid control valve, thereby disabling the flow of gas to the gas powered pump (step  430 ). As long as there is product available for the gas powered pump to pump, (step  420 =“NO”), then the pump will continue to operate and will be monitored by the system (step  410 ). 
     Once the system has been reset by the operator (step  440 =“YES”) then the gas flow to the gas powered pump can be restored (step  450 ) and the pump will continue to be monitored once again (step  410 ). If the system has not been reset (step  440 =“NO”) then the gas flow to the gas powered pump will remain disabled (step  460 ). 
     From the foregoing description, it should be appreciated that an enhanced apparatus and methods for monitoring CO2 is provided by the various preferred embodiments of the present invention and that the various preferred embodiments offer significant benefits that would be apparent to one skilled in the art. Furthermore, while multiple preferred embodiments have been presented in the foregoing description, it should be appreciated that a vast number of variations in the embodiments exist. Lastly, it should be appreciated that these embodiments are preferred exemplary embodiments only and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description provides those skilled in the art with a convenient road map for implementing a preferred exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in the exemplary preferred embodiment without departing from the spirit and scope of the invention as set forth in the appended claims.