FUEL DISTRIBUTOR DEVICE WITH STEAM EXTRACTION
DESCRIPTION OF THE INVENTION The invention is concerned with a method for the removal of displaced fuel vapor during the simultaneous operation of at least two fuel distributing units using a gas pump device. In accordance with national and international regulations to limit environmental pollution, fuel dispensing devices such as fuel pumps must be provided with a steam extraction. During the filling of a vehicle's fuel tank, the fuel vapor present in this tank is displaced by the fuel transported to the tank. This displaced steam must be discharged and fed back to the fuel supply tank of the oil station. The same amount of fuel is discharged from this supply tank as the vapor is displaced from the vehicle tank, so that the vapor displaced from the vehicle's fuel tank can easily be taken to the fuel supply tank. When the fuel supply tank is refilled, the displaced vapor is received in a similar way in the fuel tank of the tank truck, which in turn carries this vapor to a fuel tank, where a device is available. to process this steam. A closed system is thus obtained where little or no fuel vapor enters the environment. In known fuel dispensing devices a gas pump is present which extracts the fuel vapor displaced from the vehicle's fuel tank and pumps it to the fuel supply tank of the filling station. Because there is an open connection between the exhaust duct and the vehicle's fuel tank in the position of the fuel filler opening, the exhaust flow velocity of the fuel vapor must be adjusted precisely at the speed of flow of fuel that is pumped by the distributor unit to the vehicle tank. In order to obtain this, each fuel distributing device is provided in the steam extraction duct with a gas pump and a control valve. This control valve is adjusted in such a way that the correct amount of steam is extracted. The control apparatus comprises for this purpose a memory in which the characteristics of the relationship between the position of the control valve and the flow velocity of the extracted vapor are stored. Devices are known per se, with which, the fuel can be distributed simultaneously with two fuel distributing units. There is then usually a choice between different types of fuels. These devices are usually designated as multiproduct distributors (MPD). In order to obtain a good extraction of the fuel vapors, also when the fuel is distributed simultaneously with for example two fuel distributing devices, each unit is provided in the prior art with its own gas pump and control valve which is controlled in the manner summarized above. The distribution of fuel on one "side" does not influence the extraction on the other "side". Such a multiple mode of steam discharge encompasses a relatively high cost of the fuel dispensing device. The object of the invention is to provide a method for extracting displaced fuel vapor during the simultaneous operation of at least two fuel units using a gas pump device, such method can be carried out with a fuel distributor device. which can be manufactured at a lower cost. This object is obtained according to the invention by the application of the method according to the invention as characterized in claim 1. Only one gas pump device required in the present, even when the fuel is distributed simultaneously from a plurality of fuel distributing units. When the fuel is distributed simultaneously by a plurality of fuel distributing units, the pump device will have to transport more steam. By applying the method according to the invention a specific underpressure is created by the pump device. The control valve of each fuel distribution unit is adjusted in such a way that the correct amount of steam, corresponding to the amount of fuel distributed by the relevant fuel distribution unit, is extracted at the specific underpressure. For this purpose the valve characteristics of each control valve are determined at the specific underpressure. According to a preferred embodiment of the invention, the pump device is controlled in such a way that the specific underpressure is created on the suction side substantially independently of the extracted flow rate. Therefore, the characteristic of the valve simply needs to contain only the relation between the position of the valve and the flow velocity of the steam allowed through this specific underpressure. Therefore the operation of the control valve is simple.
The method according to claim 3 is preferably applied herein. In order to create the specific underpressure independently of the extracted flow rate, a feedback valve is controlled which is received in a feedback line connected to the suction and discharge side of a gas pump of the pump device. The control of this feedback valve is carried out in such a way that a measured pressure on the suction side of the gas pump is kept constant. An appropriate additional embodiment is characterized in claim 4. Although control of the control valves is more complicated, a separate feedback valve with associated control is unnecessary in this embodiment. Also, the invention is concerned with and provides a device for the multiple and simultaneous distribution of the fuel as described in claim 5. Advantages and additional features of the invention will become apparent from the following description with reference to the accompanying drawings of several modalities Figure 1 shows a schematic representation of a first mode.
Figure 2 shows a schematic representation of a second embodiment. Figure 3 shows a cross section through a part of the pump device according to a third embodiment. Figure 1 shows a first embodiment of the device 1 for simultaneous multiple fuel distribution. The device comprises three double distribution units 2. Each double distribution unit 2 can simultaneously distribute a particular fuel, in this case, for example, oil with a low octane number, oil with a high octane number and unleaded oil, for means of two distributor nozzles 3. One of the three dispensing nozzles available is therefore chosen in each case either on one side or the other of the double distributor unit 2. In a manner that is also known per se and therefore not shown, the fuel is transported from a fuel supply tank 6 to the relevant dispensing nozzle 3, from where it is transported to the fuel tank of a vehicle. Each fuel nozzle 3 is provided with a steam duct 4 which opens near the outlet opening of the nozzle 3. The fuel v displaced from the vehicle fuel tank is removed via this steam duct 4. The steam duct be received in the usual manner in the hose that supplies fuel to the nozzle. The steam duct 4 comprises a valve 5 which is closed when the associated fuel nozzle 5 is not used. Each steam duct 4 is connected to a collector line 9 or 10. Each collector line is located on one side of the device, such that during simultaneous multiple fuel distribution with the device 1, both collector lines 9, 10 are in use for steam extraction. A control valve 11, 12 is received in each collection line 9 and 10. Together with its outputs, the control valves 11, 12 are connected to the steam extraction conduit 7. Accommodated in this steam extraction conduit are find a gas pump device 8 that can extract gas from the steam extraction duct and transport it to the supply tank 6. Present for each distribution nozzle in each of the distribution units 2 is a detector that measures the flow velocity of the distributed fuel. These sensors are connected via signal lines 15 to the control device 16 and more particularly to the computer 17 of the same. This computer 17 processes the measurement signals in the usual way so that the distributed amount of fuel can be displayed in the connected counters, optionally simultaneously with the cost associated with it. The counting computer 17 is implemented in such a way that it feeds the flow rate signal for each of the sides of the device 1 via the signal line 19 to the control device 18 of the control device 16. Via the lines 19 these signals of Flow rate are fed by a part to a port Y20 and by another to a so-called switch to be described further. The control device 18 further comprises two memories. A first memory 22, which includes a valve characteristic of the valves 11 and 12 to be further described and a second memory 21 including a feature of the gas pump device 8. The amount of fuel distributed on both sides of the device 1 is therefore totalized in the port Y 20. This total amount of the fuel is fed to a part of the control device 18 comprising the memory 21. The pump characteristic maintained in this memory is concerned with the relation between the underpressure on the suction side of the pump 8. and the vapor flow rate extracted. As is known, the underpressure on the suction side of the gas pump device 8 will decrease as more gas must be extracted by the gas pump device. This relationship between the underpressure and the quantity of extracted steam, which is characteristic for the specific pump 8, is predefined and stored in the memory 21. In, the control device 18 is now determined by means of the characteristic in the second memory 21. , what will be the underpressure in the duct 7 during the extraction of a quantity of steam equal to the amount of fuel supplied. This underpressure signal is fed to the first memory 22 which comprises a characteristic of the valves 11 and 12. This characteristic is concerned with the relationship between the position of the valve, the underpressure and the vapor flow velocity allowed through the valves. same. The underpressure, which will be adjusted, is determined based on the characteristic of the pump in the second memory 21 and the vapor flow rate for the relevant distributor unit is likewise fed to the first memory 22. The position of the valve a to be applied to the momentary flow rate and the underpressure follows from the characteristic of the valve in the memory 22. A control signal for this position of the valve is fed to the relevant control valve 11 or 12 via the control line 24 The switch 23 ensures that the flow rates associated with the relevant valves are fed alternately to the first memory 22 and the given control signal is simultaneously fed to the relevant control valve 11 or 12. This is carried out using a frequency appropriate alternating such that the valves 11 and 12 are put into operation almost continuously. When the distributed quantity of fuel changes on one or both sides of the device 1, the position of the two control valves 11, 12 is adjusted by the control apparatus 16, in such a way that the correct amount of steam continues to be discharged for the sides in question. When the fuel distribution is for example stopped on one side of the device 1, in which the control valve 11 is arranged, the amount of steam to be extracted is limited to the amount corresponding to the amount of fuel distributed on the other side . The underpressure in the extraction duct 7 will be increased by this and the control valve 11 must be controlled in the closing direction to still allow the same flow rate to pass. Figure 2 shows a second embodiment 31 of the device for simultaneous multiple fuel distribution. The device comprises three double distributor units 32. Each double distributor unit 32 can simultaneously distribute a particular fuel by means of two distributor nozzles 33.
Each fuel nozzle 33 is provided with a steam duct 34 which opens near the outlet opening of the nozzle 33. The fuel vapor displaced from the vehicle fuel tank is removed via this steam duct 34 and finally enters the tank of fuel supply 36. The steam duct 34 comprises a valve 35 which is closed when the associated fuel nozzle 33 is not used. Each steam duct 34 is connected to a manifold line 39 or 40. Each manifold line is located on one side of the device, such that during simultaneous multiple fuel distribution using the device 31, both manifold lines 39, 40 are in use for steam extraction. A control valve 41, 42 is arranged in each manifold line 39, 40. Together with its outlets, the control valves 41, 42 are connected to the steam extraction conduit 37. The steam extraction conduit 37 is connected to the suction side of the pump device 43. A gas pump 38, a feedback control valve 44 and a pressure measuring device 45 are arranged in this pump device. The gas pump 38 can extract gas from the steam extraction duct and transport it to the supply tank 36. The pressure measuring device 45 is connected to the suction side of the pump device 43 and measures the underpressure in the steam extraction duct 37. The feedback control valve 44 is connected to the suction and discharge side of the gas pump 38. By means of the feedback control valve 44 the gas can flow back from the discharge side of the gas pump. 38 next to suction. Present for each distributor nozzle in each of the distributor units 32 is a sensor or detector that measures the flow velocity of the distributed fuel. These detectors are connected via signal lines 46 to the control device 47 and more particularly to the counter computer 48 thereof. This counting computer 48 processes the measurement signals in the usual manner and forms the first measurement unit. The counting computer 48 is implemented in such a way as to feed the flow rate signal for each of the sides of the device 31 via the signal line 49 to a control device 50 of the control device 47. The control device 50 comprises a memory 54 containing the valve characteristic of the valves 41 and 42 at the specified specific underpressure. This characteristic is concerned with the relationship between the position of the valve and the vapor flow velocity allowed through them. After processing this information from the memory 54, a control signal results for each control valve 41, 42 that determines a position for the relevant control valve according to the required extraction flow rate. This control signal is fed to the relevant valve 41 or 42 via a switch 52 and the control line 53. The switch 52 ensures that the flow rates associated with the relevant valves are fed alternately to the memory unit 22 and the signal The determined control is simultaneously fed to the valve 41 or 42. This is carried out using an appropriate alternating frequency in such a way that the valves 41 and 42 are put into operation almost continuously. The gas pump 38 has a pump capacity that is sufficient to process the amount of steam for extraction at the total maximum flow rate of the fuel distributing device. At a sub-pressure set at 200 mbar the gas pump can for example draw an amount of steam at a combined maximum flow rate of the two fuel nozzles 33 of for example 2 x 45 1 / minute. The pressure measuring device 45 measures the underpressure at the inlet of the gas pump 38. In the control unit 50, this measurement signal is compared with a reference signal stored in the memory 54. The difference signal is used to control the control valve 44 in such a way that the difference tends toward zero. Thus, a fixed underpressure can be established at the intake of the gas pump 38 using the choice of the reference signal. When the underpressure is too high, the position of the control valve 44 is changed in such a way that the underpressure decreases and vice versa. When the distributed amount of fuel changes on one or both sides of the device 31, the position of the relevant valve 41 and / or 42 is adjusted by the control apparatus 47, such that for the side in question the correct amount of steam continues to be downloaded. When the fuel distribution is stopped, for example, on the side of the device 1 in which the control valve 41 is arranged, the amount of steam for extraction is limited to the amount corresponding to the amount of fuel distributed on the other side . In order to maintain the underpressure at the determined specific value, the adjustment of the feedback control valve 44 is modified in such a way that the specific underpressure is restored. The control valve 41 is closed. There is no change for the control valve 42. The pump device can be implemented with a mechanical pressure measuring device and control valve instead of with an electronic control device. Figure 3 shows such mechanical control apparatus in cross section. The assembly 61 comprises a two-part box 62, 63 with a space divided into two chambers 64, 65. The chambers are separated by a membrane 66. The chamber 64 is connected to both the suction side 67 and the discharge side 68 of the chamber. a gas pump 69. The underpressure created by the gas pump prevails in this chamber 64. According to this underpressure, the membrane 66 will make the chamber 64 larger or smaller. The membrane 66 is arranged for this purpose between two spring means 70, 71 arranged on both sides of the membrane 66 in the two chambers 64 and 65. The spring means 70 comprises a spring 72 arranged between two spring cups 73 and 74 The cup 73 is fixed to the membrane 66. The cup 74 is engaged on an adjusting screw 75 projecting outwardly through the box part 63. The adjusting screw 75 can be tightened, whereby the means of Docks 70 and 71 are compressed and the resting position of the membrane is changed. When using adjusting screw 75, a predetermined specific value can be set for underpressure according to the function of the pump device as described above. The membrane 66 is connected to one end of a lever 76 which is mounted on a prominent arm 77 fixedly screwed to the box part 62. The other end of the lever is connected to a valve element implemented as the slide 78. This slide 78 is placed on a tube projection 79 connected to the discharge side 68 of the gas pump 69. The projection 79 of the tube is provided with holes 80 that connect the chamber 64 to the discharge side 68 of the gas pump 69. holes 80 and chamber 64 form the feedback duct. The slider 78 forms the feedback control valve, which opens the feedback duct to a lesser or greater degree by closing the orifices 80 to a greater or lesser degree. When the underpressure on the suction side becomes too strong, the membrane 66 will move to the left as seen in figure 3. Via the lever 76, the slide 78 is then moved to the right as seen in figure 3 , whereby the holes 80 are further opened. By this, more gas will flow from the discharge side 68 of the gas pump 69 to the suction side 67, whereby the underpressure becomes less strong. When a sub-pressure is too low, the inverse action occurs, whereby the underpressure is reinforced once again. A substantially constant underpressure is thus maintained on the suction side of the gas pump 69, independently of the amount of steam extracted. The advantage of this control apparatus and of the apparatus shown in Figure 2 is that changes in the capacity of the gas pump that occur over time, due for example to wear or fouling, are compensated, since the Specific underpressure is nevertheless maintained by the control apparatus. The mechanical embodiment of Figure 3 also has the advantage of a relatively low cost price. It is noted that, with regard to this date, the best method known to the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.