Abstract:
The present invention provides a fluid flow system and method according to which the fluid is pumped from a source through a conduit while the flow rate of the fluid is sensed and terminated in response to the fluid flow rate falling below a predetermined minimum. After a predetermined time delay the valve is re-opened to allow flow to resume.

Description:
BACKGROUND 
     The present invention relates to a gasoline dispensing system and method and, more particularly, to such a system and method in which relatively low flow rates are inhibited. 
     In fluid flow systems, such as gasoline services station installations, the gasoline is pumped from an underground storage tank, through a conduit, or tube, to a dispenser unit, and through a hose extending from the dispenser unit to a nozzle for dispensing the gasoline into a vehicle tank. A manually operable valve is provided on the nozzle to enable the customer to initiate the dispensing and control the flow of the gasoline during the complete dispensing cycle. 
     Although a system valve is also provided to control the gasoline flow, the system operates for most of the time at the full flow rate. However, when the system does operate at a low flow rate, such as when the customer partially shuts off the nozzle valve near the end of the dispensing cycle and/or tops off the vehicle tank, a cost-competitive flow meter is often inaccurate. This is significant since it is important that the customer be charged for exactly the amount of gasoline dispensed. Also, certain government regulations require relatively high accuracy of the metered flow during all flow conditions. 
     Therefore what is needed is a fluid flow system of the above type which inhibits the fluid flow below a predetermined rate and thus insures high accuracy metering of the flow that is metered. 
     SUMMARY 
     The present invention provides a fluid flow system and method according to which the fluid is pumped from a source through a conduit while the flow rate of the fluid is sensed and terminated in response to the fluid flow rate falling below a predetermined minimum. 
     A major advantage is achieved with the system and method of the present invention since a cost-competitive flow meter can be used without any danger of inaccurate fluid flow measurement. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of gasoline dispensing unit according to an embodiment of the present invention. 
     FIG. 2 is schematic view of the fluid flow system according to the embodiment of FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     With reference to FIG. 1, the fluid flow system of an embodiment of the present invention will be described, by means of example, as a gasoline dispensing system for dispensing gasoline to vehicles at a service station, or the like. To this end, the reference numeral  10  refers, in general, to a dispenser unit having an upper housing  10   a  and a lower housing  10   b  connected by two spaced upright support members  10   c  and  10   d.    
     Hydraulics are provided that include one or more conduits or tubes (not shown) connected to one or more underground tanks for storing the gasoline to be dispensed. These conduits extend from the lower housing  10   b  through one of the support members  10   c  and  10   d  to the upper housing  10   a  for passing gasoline to one end of a hose  12  which extends from the upper housing  10   a . The other end of the hose  12  is connected to a nozzle  14  for dispensing gasoline from the storage tank to a vehicle. The nozzle  14  has a valve (not shown) that is normally closed but can be opened by a trigger, or lever,  14   a  that can be manually actuated in a conventional manner. Although not shown in the drawings, it is understood that the nozzle  14  includes an interlock that prevents the opening of the nozzle valve under relatively low pressure conditions as will be described. A boot  16  is provided on the front panel of the lower housing  10   b  for receiving the nozzle  14  during non-use. 
     An electronics housing  18  is provided between the upper housing  10   a  and the lower housing  10   b , and contains various electronic components, including a credit card reader  20 , a receipt dispenser  22 , and a display  24  which displays the volume of gasoline dispensed and the cost of same. The respective fronts of the reader  20 , the receipt dispenser  22 , and the display  24  extend through the front panel, or bezel, of the housing  18 . 
     Although not shown in the drawing, it is understood that a boot, identical to the boot  16 , is provided on the opposite, or rear, panel of the housing  10   b  which receives a nozzle, identical to the nozzle  14 , which extends from a hose identical to the hose  12 . Also, the electronics housing  18  has a rear panel that receives a credit card reader, a receipt dispenser, and a display identical to the reader  20 , the dispenser  22 , and the display  24 , respectively. Since all of this is conventional, it will not be described in further detail. 
     Referring to FIG. 2, one of the above-mentioned conduits extending from a storage tank (not shown) and through the dispenser unit  10  is referred to by the reference numeral  30 . A pump  32  is provided at the storage tank or in the lower dispenser housing  10   b  and is connected to the conduit  30  for pumping the fuel from the storage tank, and a flow meter  34  is connected to the conduit  30  for metering the flow of the gasoline through the conduit. It is understood that the meter  34  is electrically connected to the display  24  (FIG. 1) for providing a display of the amount of gasoline dispensed and the cost of same, all in a conventional manner. 
     A flow control valve  36  is also connected to the conduit  30 , preferably downstream of the meter  34 , and operates in a conventional manner to control the flow of the gasoline through the conduit, and the amount that is dispensed into the vehicle tank under the additional control of the nozzle  14 . 
     The conduit  30  extends to a fitting, or adapter,  38  which permits the corresponding end of the conduit to be connected to the hose  12 , and therefore to the nozzle  14 , in fluid flow communication in a conventional manner. 
     The sections of the conduit  30  shown in FIG. 2, as well as the meter  34  and the valve  36 , are all located in the dispenser unit  10 . The fitting  38  is preferably located on the lower portion of the upper housing  10   a  of the dispenser unit  10 , and the hose  12  extends from the latter fitting and is in fluid flow communication with the conduit  30 . 
     A control unit  40 , preferably in the form of a computer, a microprocessor, a CPU, or the like, is provided and is electrically connected to the pump  32 , the meter  34 , and the valve  36 . The control unit  40  receives input signals from the meter  34  corresponding to the fluid flow rate in the conduit  30 , and includes a software program that enables it to generate output signals based on this input signal which output signals are used to close the control the valve  36  in a manner to be described. 
     In order to initiate operation of the dispenser unit  10 , the customer activates the main system switch, in the form of a push button, a lever, or the like, on the unit  10 . This switch is connected to the control unit  40  which functions to start the pump  32 , open the valve  36 , to permit dispensing of the gasoline. Gasoline is thus pumped through the conduit  30 , the hose  12  and to the nozzle  14  until the pressure rises to a value to permit dispensing of the gasoline. The gasoline can be manually dispensed by the customer by actuating the trigger  14   a  of the nozzle  14  to open the nozzle valve. 
     After dispensing some gasoline, in the event the customer partially releases the trigger  14   a  to partially close the valve of the nozzle  14  in order to top off the vehicle tank or slow down and/or stop delivery for whatever reason, the meter  34  will sense the fluid flow rate falling below a predetermined minimum value and the control unit  40  will respond accordingly and close the valve  36  to completely shut off the fluid flow. The control unit  40  then opens the valve  36  after a predetermined relatively short delay. This will allow the customer to continue dispensing the gasoline as long as the fluid flow rate extends above the above predetermined minimum rate. 
     As an example of the time periods that could be involved, the software for the control unit  40  can be programed so that the above-mention predetermined minimum fluid flow rate is between 2-5 liters per minute, and, if the flow rate is below the predetermined minimum, the valve  36  would be shut for periods extending between 0.5 to 1.5 seconds, after which it would be opened. Since the pump  32  is pumping gasoline during all this time, during the short times that the valve  36  is closed the pressure builds up in the conduit  30  causing a relatively high flow rate when the valve is opened. These values, and other comparable values, can be selected to allow the customer to top-off, or slow down and/or stop delivery after a specific amount of gasoline has been dispensed. 
     The control unit  40  can be programed to operate continuously to monitor the flow rate measured by the meter  34  or, alternatively, it could be programed to periodically monitor the flow rate every 0.5 seconds to 1.5 seconds. 
     If the flow rate is below the predetermined minimum and the valve  36  is closed and opened as described above, the customer may still try to dispense a large volume of gasoline at a slow flow rate, by continually starting and stopping the pump by activating and deactivating the above-mention main system switch. To prevent this, the control unit  40  can be programed to limit the number of starts, and restarts. 
     A major advantage is achieved with the system and method of the present invention since low flow rates over an extended period of time, and therefore the chance for inaccurate flow rate measurements are eliminated. Therefore, a cost-competitive flow meter can be used without any danger of inaccurate fluid flow measurement. 
     Of course, if multiple grades of fuel are provided in separate storage tanks, the number of conduits  30  extending from the tanks to the dispenser unit  10  would increase accordingly, and above system would be used with each conduit. 
     It is understood that variations may be made to the foregoing without departing from the scope of the invention. For example, the specific values set forth above are for the purpose of example only, it being understood that they can vary within the scope of the invention. Also, although reference is made to “conduits” it is understood that pipes, tubes, hoses, lines and any other type of fluid flow device could be used within the scope of the invention. Further, the specific location of the various components discussed above that are connected to the conduit  30  can be varied within the scope of the invention. For example, the meter  32  can be located downstream of the valve  34  rather than upstream as shown in FIG.  2 . Further, the spatial references, such as “upper” and “lower” are for the purpose of illustration only and do not limit the specific orientation or location of the structure described above. Still further, the system and method of the present invention are not limited to a gasoline dispensing system but are equally applicable to any fluid flow system. 
     It is understood that other variations, changes and substitutions are intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.