Fuel dispensing device with vapour extraction

Abstract

The invention relates to a method and device for extracting fuel vapour displaced during the simultaneous operation of at least two fuel-dispensing units using a gas pump device. Each fuel-dispensing unit comprises a vapour extraction conduit in which a control valve is arranged. The different vapour extraction conduits are connected to a single gas pump device. The underpressure to be created by the gas pump device and essential for discharge of the correct quantity of vapour is determined, whereafter the control valves are adjusted such that they each allow through the correct quantity of vapour at the specific underpressure.

1 . Method for extracting fuel vapour displaced during the simultaneous operation of at least two fuel-dispensing units using a gas pump device, comprising of providing a vapour extraction conduit for each fuel-dispensing unit which are each provided with a control valve and are together connected to a suction side of the gas pump device, and further comprising of 
 measuring the individual fuel flow rate dispensed by each fuel-dispensing unit,    having the pump device create a specific underpressure on the suction side of the pump device, wherein a vapour flow rate substantially equal to the total of the individual fuel flow rates is pumped away,    predetermining a valve characteristic for each control valve of the relation between the valve position and the vapour flow rate allowed through at least at the specific underpressure,    determining on the basis of the valve characteristic for each control valve the valve position at the specific underpressure and the individual fuel flow rate of the fuel-dispensing unit with which the relevant control valve is associated, and    adjusting each control valve to the determined valve position.    
     
     
         2 . Method as claimed in  claim 1 , wherein the pump device is controlled such that the specific underpressure is created on the suction side substantially irrespective of the extracted flow rate.  
     
     
         3 . Method as claimed in  claim 2 , wherein the pump device comprises a gas pump with a suction and discharge side, a feedback conduit provided with a feedback valve and connected to the suction and discharge side, and a pressure measuring device connected to the suction side, and further comprising of 
 measuring the underpressure on the suction side during operation, and    adjusting the feedback valve such that the specific underpressure is substantially maintained.    
     
     
         4 . Method as claimed in  claim 1 , further comprising of 
 predetermining a pump characteristic of the relation between different underpressures on the suction side and the extracted vapour flow rate,    wherein the determined valve characteristic comprises the relation between the valve position, the vapour flow rate allowed through and the different underpressures, and    wherein for the specific underpressure the underpressure is taken on the basis of the gas pump characteristic at a vapour flow rate equal to the total of the individual fuel flow rates.    
     
     
         5 . Device for simultaneous multiple dispensing of fuel, comprising a number of fuel-dispensing units which each comprise a fuel conduit and a dispensing nozzle connected to the fuel conduit, wherein a fuel pump is arranged in the fuel conduit, a collector line for displaced vapour connected to each dispensing nozzle, in each of which lines is received a control valve, a pump device which is connected on a suction side to the collector lines and which can create a specific underpressure on the suction side, and a control apparatus comprising 
 a first measuring unit for measuring the fuel flow rates dispensed with each fuel-dispensing unit,    a first memory containing a valve characteristic for each valve of the relation between the valve position and the vapour flow rate allowed through at least at a specific underpressure, and    a first control unit which on the basis of the valve characteristic for each valve can determine the valve position at the specific underpressure and the individual fuel flow rate of the fuel-dispensing unit with which the relevant valve is associated, and can adjust each valve to this determined valve position.    
     
     
         6 . Device as claimed in  claim 5 , characterized in that the pump device comprises gas pump and wherein the first memory contains a valve characteristic for each valve of the relation between a valve position, an underpressure and a vapour flow rate allowed through, and the control apparatus further comprises 
 a second memory containing a pump characteristic of the relation between the underpressure on the suction side and the extracted vapour flow rate,    a second control unit which on the basis of the pump characteristic can determine the underpressure on the suction side of the gas pump at a vapour flow rate equal to the total of the individual fuel flow rates.    
     
     
         7 . Device as claimed in  claim 5 , characterized in that the pump device comprises a gas pump, a feedback device connected to the suction and discharge side of the gas pump and a pressure measuring device connected to the suction side of the gas pump.  
     
     
         8 . Device as claimed in  claim 7 , characterized in that the feedback device comprises a feedback conduit and a feedback control valve, and the memory also contains a determined specific value for the underpressure, and the control apparatus further comprises 
 a second measuring unit for measuring the underpressure,    a second control unit which can determine a setting for the feedback control valve such that the specific underpressure can be maintained.    
     
     
         9 . Device as claimed in  claim 7 , characterized in that the feedback device comprises a feedback conduit and a feedback control valve, and the pressure measuring device comprises at least two chambers separated by a membrane, wherein one chamber is connected to the suction side of the gas pump and the feedback conduit such that the underpressure on the suction side can be determined with the position of the membrane, and that the membrane is connected by means of a lever to the feedback control valve to enable adjustment of the feedback control valve so that the specific underpressure can be maintained.  
     
     
         10 . Control apparatus evidently intended for a device as claimed in claims  5 - 9 .