Filling nozzle

Abstract

Filling nozzle for delivering a fluid, comprising an inlet (13) for connection of a fluid feed line, an outlet (14), a main conduit (15) connecting the inlet to the outlet, a main valve device (16) for controlling a flow of fluid through the main conduit (15), a control lever (17) for actuating the main valve device (16), an automatic safety shut-off designed to move the main valve device (16) to a closed position independently of a position of the control lever (17) when a fluid pressure at the inlet (13) falls below a minimum value, and comprising a preloading device (18) which preloads the main valve device (16) into the closed position and effects a variable opening cross-section of the main valve device (16) depending on a fluid pressure at the inlet. According to the invention, the preloading device (18) is designed to produce a discontinuous opening characteristic of the main valve device (16) in such a way that a closing force acting on a valve body (20, 20', 20", 22) of the main valve device is reduced in a first opening cross-section range extending from the closed position of the main valve device (16) to a limit opening cross-section.

Description

[0001] Zapf en til

[0002] The subject matter of the present invention is a nozzle valve for dispensing a fluid, having an inlet for connecting a fluid supply line, an outlet and a main channel connecting the inlet to the outlet. The nozzle valve also comprises a main valve device for controlling a fluid flow through the main channel and a control lever for actuating the main valve device. Furthermore, the nozzle valve comprises an automatic safety shut-off which is designed to move the main valve device into a closed position regardless of a position of the control lever if a fluid pressure at the inlet falls below a minimum value. Finally, the nozzle valve comprises a prestressing device which prestresses the main valve device into the closed position and brings about a variable opening cross-section of the main valve device depending on a fluid pressure at the inlet.

[0003] Such a fuel pump is known from EP 2 386 520 B1. It can be used, in particular, to dispense fuel into a vehicle's tank. A user can operate the fuel pump using the control lever to open the main valve and close it again after dispensing the desired amount of fuel. The fuel is supplied by a feed pump, which is typically connected to the fuel pump via a fuel hose.

[0004] The feed pump regularly allows the desired fuel quantity to be pre-selected. In this case, the user can wait for the pre-selected quantity of fluid to be dispensed after hooking the nozzle's outlet pipe into a filler neck on the vehicle and then securing the control lever using a locking device. Once the pre-selected quantity of fluid has been dispensed, the feed pump switches off automatically and the fuel dispensing stops. It is not absolutely necessary for the control lever and with it the main valve to be moved back to the closed position after the feed pump has been switched off. If the main valve remains in the open position, there is a fundamental risk that fuel will escape uncontrollably during a subsequent refueling process.To avoid this risk, the known nozzle has the automatic safety shutdown described above, which moves the main valve into the closed position when the pressure at the inlet falls below a minimum value, in particular after the feed pump has been switched off.

[0005] The above-mentioned pre-tensioning device creates an increased back pressure in front of the main valve in the previously known nozzle during the discharge of the fluid, which pressure disappears once the feed pump is switched off. The pre-tensioning device therefore helps to create a sufficient pressure difference that can be exploited in a known manner within the automatic shut-off device to ensure safe shutdown. In addition, the pre-tensioning device ensures that any fuel still present in the fuel hose cannot leak out uncontrollably, even if the fuel hose is full of fluid after the feed pump is switched off and the automatic shut-off device has not (yet) been triggered.

[0006] A problem can arise in this context, however, if the pressure at the inlet and within the fuel hose in full-hose operation (i.e. when the feed pump is switched off and the fuel hose is full of fluid) does not fall below the minimum pressure or even increases again, for example if fuel pumped from a cold underground tank heats up in a fuel hose exposed to the sun. In EP 2 386 520 B1, it was proposed to solve this problem that the main valve is pushed into the closed position at an angle under the effect of the pre-tensioning device in such a way that its tightness is reduced. Due to the reduced tightness, the pressure present in full-hose operation can be reduced in a controlled manner, so that this previously known solution ensures safe shutdown.However, it has been shown that the components that contribute to the canting of the main valve require low manufacturing tolerances and a high level of testing effort.

[0007] Based on this prior art, it is the object of the present invention to provide a nozzle which at least partially avoids the disadvantages mentioned above. This object is achieved with the features of the independent claims. Advantageous embodiments are specified in the subclaims. According to the invention, the pretensioning device is designed to generate a discontinuous opening characteristic of the main valve device such that a closing force acting on the main valve device is reduced in a first opening cross-sectional area extending from the closed position of the main valve device up to a limit opening cross-section.

[0008] First, some terms used in the context of the invention will be explained. The term fluid includes liquid, gaseous or substances in a mixed phase. The main valve device can have exactly one or two or more valve bodies. An opening cross section of the main valve device is a cross-sectional area that depends on the opening state of the one valve body or the multiple valve bodies of the main valve device and is available for the flow of the fluid through the main valve device. When the main valve device is in the closed position, all valve bodies of the main valve device are in a closed position. When the main valve device is closed, it therefore has an opening cross section of zero.

[0009] Due to the discontinuous opening characteristic according to the invention, the closing force acting on a valve body is reduced from the closed position to the limit opening cross-section (i.e., within the first opening cross-section range). The minimum pressure prevailing at the inlet required to open the main valve device is thereby reduced. The main valve device can thus be opened more easily by the valve body, whose closing force is reduced, performing a corresponding opening movement.

[0010] This ensures that, in full-hose operation, even a low pressure upstream of the main valve is sufficient to open the main valve. In this way, the pressure can be reliably reduced below the minimum pressure at which the automatic shut-off device is triggered.

[0011] On the other hand, the fluid supplied by a feed pump hits the main valve device with a significantly greater pressure during normal delivery operation, so that the limit opening cross section is regularly exceeded. The discontinuity of the opening characteristic is evident in the fact that the reduction in closing force disappears when the limit opening cross section is exceeded. If the limit opening cross section is exceeded, a larger pressure difference is therefore necessary to further increase the opening cross section. Therefore, if the limit opening cross section is exceeded, a high pressure builds up upstream of the main valve device, which can be used in a known manner to actuate the automatic shut-off device. The operational reliability of the automatic shut-off device can be improved in this way.

[0012] In a preferred embodiment, the pretensioning device is designed such that a minimum pressure required to open the main valve device lies in a range between 0.01 bar and 0.5 bar, preferably between 0.05 bar and 0.3 bar. Furthermore, it can be provided that a pressure threshold value, above which the opening cross-section exceeds the limit opening cross-section, lies in a range between 0.075 bar and 0.5 bar. Preferably, the pressure threshold value is at least 5% greater, more preferably at least 20%, particularly preferably at least 50% greater than the minimum pressure.If, in this design, the pressure prevailing at the inlet lies between the minimum pressure and the pressure threshold, the main valve device opens in a controlled manner (up to the limit opening cross section at most) and thus enables a controlled pressure reduction below the minimum pressure, below which the automatic shutdown device is triggered. The minimum pressure can be, for example, between 0.075 bar and 0.45 bar. The automatic safety shutdown and the preloading device are preferably designed such that the minimum pressure lies between the minimum pressure and the pressure threshold. The limit opening cross section can, for example, be in a range between 1 mm. 2 and 12 mm 2 , preferably between 2 mm 2 and 8 mm 2In one embodiment, the main valve device has a main valve body, a main valve seat, a pressure reduction channel and a pressure reduction valve body designed to close the pressure reduction channel. In this embodiment, the main valve device therefore has two valve bodies. The pretensioning device can be designed to urge the main valve body and the pressure reduction valve body independently of one another into a closed position, wherein a change in the opening cross-section of the main valve device in the first opening cross-sectional area is brought about by a movement of the pressure reduction valve body and wherein a change in the opening cross-section of the main valve device beyond the limit opening cross-section is brought about by a movement of the main valve body relative to the main valve seat.In this embodiment, an opening cross-section of the main valve device can therefore be changed by changing an opening state of the pressure reduction valve body and / or moving the main valve body relative to the main valve seat.

[0013] The pressure reduction channel preferably runs through the main valve body. In addition, the pretensioning device for urging the main valve body into the closed position can have a first return element, which is preferably designed as a solid hose spring. Furthermore, the pretensioning device for urging the pressure reduction valve body into the closed position can have a second return element, which is preferably designed as a pressure reduction spring. By the main valve device having two independent valve bodies and the pretensioning device having a separate return element for each of these valve bodies, the described discontinuity of the opening characteristic can be realized in a simple manner.In particular, it can be provided that the main valve device is opened by the fluid pressure in full hose operation in that only the pressure reduction valve body opens, while the main valve body remains in a closed position in which it rests sealingly against the main valve seat. When the pressure reduction valve body is fully open, an opening cross-section can preferably be achieved which corresponds to the limit opening cross-section. Any excess pressure present in front of the main valve device in full hose operation can then be reduced in a controlled manner via the pressure reduction channel. During normal delivery operation (i.e. when the delivery pump is switched on), the opening cross-section of the main valve device is (additionally) increased by a movement of the main valve body relative to the main valve seat, so that an increased dynamic pressure predetermined by the first return element or the full hose spring is created in front of the main valve device.

[0014] In an alternative embodiment, the main valve device comprises a main valve body which is prestressed by the prestressing device against a main valve seat into a closed position, wherein the first opening cross-sectional area corresponds to a first actuating range of the main valve body and a second opening cross-sectional area extending beyond the limit opening cross-section corresponds to a second actuating range of the main valve body adjoining the first actuating range. An actuating range of the main valve body refers to a movement range (deflection range) extending along an axial direction of the main valve body, within which the main valve body can be moved relative to the valve seat in order to open or close the main valve device.Preferably, the discontinuous opening characteristic is also achieved in that the preloading device has a smaller reset constant in the first adjustment range than in the second adjustment range. The “reset constant” is a measure of the relationship between the force required to move the main valve body and the resulting deflection of the main valve body. Due to the smaller reset constant of the preloading device in the first adjustment range, the main valve body is urged less strongly into the closed position in this adjustment range. This means that even a lower fluid pressure upstream of the main valve device can cause the main valve device to open until the end of the first adjustment range and thus the limit opening cross-section is reached.If the main valve device is subjected to a greater fluid pressure during normal delivery operation, the main valve body moves further within the second actuating range against a restoring force predetermined by the greater restoring constant.

[0015] For example, the pretensioning device can comprise a first return element and a second return element, wherein a movement of the main valve body in the first adjustment range in the opening direction occurs predominantly or exclusively against a return force of the second return element and wherein a movement of the main valve body in the second adjustment range in the opening direction occurs predominantly or exclusively against a return force of the first return element.

[0016] The above-mentioned separate action of the return elements in the various adjustment ranges can be achieved, for example, in that the first return element prestresses the main valve body relative to a displaceable holding element, wherein the second return element prestresses the displaceable holding element relative to the main valve seat of the main valve device. A movement of the main valve body in the first adjustment range in the opening direction can in this case take place by a joint movement of the holding element and the main valve body counter to a restoring force of the second return element, wherein a movement of the main valve body in the second adjustment range in the opening direction can take place by a movement of the main valve body relative to the holding element counter to a restoring force of the first return element.

[0017] In the embodiment described above, the displaceability of the displaceable holding element relative to the main valve seat can be limited by a first stop positioned on the main valve seat. Furthermore, the mobility of the displaceable holding element relative to the main valve body can be limited by a second stop formed on the main valve body. If only a slight pressure prevails upstream of the main valve device, the main valve body is tensioned against the displaceable holding element by the first return element until the holding element strikes the second stop of the main valve body. At the same time, the holding element is spaced from the stop present on the main valve seat due to the return force of the second return element.If the main valve body is moved from the closed position within the first adjustment range, this is accompanied in this case by a displacement of the holding element relative to the main valve seat and a corresponding deflection of the second return element. If the fluid pressure upstream of the main valve device increases, the holding element is deflected counter to the restoring force of the second return element and comes to rest on the first stop. A subsequent further increase in pressure then leads to an opening movement of the main valve body (within the second adjustment range) relative to the holding element with simultaneous deflection of the first return element. In a further alternative embodiment, the pretensioning device comprises a first return element with a first return constant, which urges the main valve body relative to the main valve seat into the closed position.In addition, in this embodiment, the preloading device comprises a second reset element with a second reset constant, which urges the main valve body relative to the main valve seat in the opening direction. In this case, the second reset element counteracts the first reset element, whereby a reduction in the closing force can be achieved in the first actuating range, which enables a controlled pressure reduction. If the limit opening cross-section is exceeded (i.e., in the second actuating range), the opposing effect of the second reset element can be eliminated, whereby the discontinuity of the opening characteristic according to the invention can be realized.In particular, the reset constant of the pretensioning device in the first adjustment range can result from a combination of the reset constants of the first and second reset element, wherein the reset constant of the pretensioning device when the limit opening cross-section is exceeded (i.e. in the second adjustment range) can result predominantly or exclusively from the reset constant of the first reset element.

[0018] Furthermore, it can be provided that a restoring force of the first restoring element acting on the main valve body in the first actuating range is greater than a restoring force of the second restoring element acting on the main valve body in the first actuating range. This ensures that the main valve body is moved completely into the closed position in the absence of fluid pressure.

[0019] The second return element preferably has a first end and a second end lying opposite one another in a deflection direction, the first end being fixed to the main valve body and the second end resting against a stop fixed relative to the main valve seat during a movement of the main valve body in the first adjustment range, and the second end being released from the stop during a movement of the main valve body in the second adjustment range. Preferably, moreover, a deflection of the second end of the second return element in the upstream direction is limited by a limiting projection fixed to the main valve body. This exemplary embodiment makes it possible for only the first return element to act on the main valve body in the second adjustment range.

[0020] The invention further relates to a fuel pump with a feed pump for dispensing a fluid and with a dispensing hose which connects the feed pump to a dispensing valve according to the invention.

[0021] Advantageous embodiments of the invention are explained below by way of example with reference to the accompanying drawings.

[0022] It shows :

[0023] Figure 1: a fuel pump according to the invention, to which a fuel nozzle according to the invention is connected, in a partially sectioned side view;

[0024] Figure 2 : a partial section of the embodiment of the figure

[0025] 1 in a lateral sectional view;

[0026] Figure 2A: an enlarged section of Figure 2; Figure 2B: an enlarged section of Figure 2;

[0027] Figure 3: a partial section of Figure 2, wherein the nozzle is in a different operating state;

[0028] Figure 3A: an enlarged section of Figure 3;

[0029] Figure 3B: an enlarged section of Figure 3;

[0030] Figure 4: the view of Figure 3, with the nozzle in a different operating state;

[0031] Figure 5 : the view of Figure 3 in yet another

[0032] operating condition;

[0033] Figure 6: a part of a second embodiment of a nozzle according to the invention in a sectional side view;

[0034] Figure 6A: an enlarged section of Figure 6;

[0035] Figure 7: a partial section of Figure 6 in a side sectional view in a different operating state;

[0036] Figure 7A: an enlarged section of Figure 7;

[0037] Figure 8: the view of Figure 7, with the nozzle in a different operating state; Figure 9: the view of Figure 7, with the nozzle in a different operating state;

[0038] Figure 10: a part of a third embodiment of a nozzle according to the invention in a sectional side view;

[0039] Figures 11-13: Partial sections from Figure 10, with the nozzle valve in different operating states.

[0040] Figure 1 shows a partially sectioned side view of a fuel pump 8 according to the invention, to which a fuel pump valve according to the invention is connected for dispensing a fuel. The fuel pump valve comprises a housing 12 with an inlet 13 which is connected to a fuel hose 9. The fuel hose 9 leads to the schematically illustrated fuel pump 8. Inside the fuel pump 8 there is a feed pump (not shown) which is designed to pressurise the fuel and convey it to the fuel pump valve. Inserted into the housing 12 is an outlet pipe 11, at the front end of which is an outlet 14. A main channel 15 extends through the fuel pump valve from the inlet 13 to the outlet 14 and can be closed by a main valve device 16.

[0041] The main valve device 16 has a main valve body, which, in the state of Figure 1, is held in a closed position in a known manner by a closing spring 28 and a piston assembly 29 actuated by the closing spring. The main valve device 16 can be actuated via a control lever 17 in a known manner by displacing the piston assembly 29 to the left with the aid of a control lever pin 27 against the force of the closing spring 28. This releases the main valve body in a fundamentally known manner, so that a fluid pressure prevailing upstream of the main valve device can move the main valve body into an open position.

[0042] Additionally and independently of the closing spring 28 and the piston assembly 29, the main valve device is urged into the closed position by a preloading device 18. After actuation of the control lever 17, the fluid pressure at the inlet 13 must be sufficiently high to overcome the resistance of the preloading device 18 in order to discharge the fuel. The interaction of the preloading device 18 with the main valve device 16 is explained in detail below in conjunction with Figures 2 to 5.

[0043] The nozzle further comprises an automatic shut-off device 10 which is designed to move the main valve device 16 into the closed position regardless of the position of the control lever 17 when a fluid pressure at the inlet 13 falls below a minimum value. In particular, the shut-off device 10 is designed in a fundamentally known manner (see, for example, EP 2 386 520 B1) to decouple the control lever pin 27 from the piston arrangement 29, so that the main valve body is moved into the closed position by the closing spring 28 and held there regardless of the position of the control lever. Upstream of the main valve device 16, a pressure connection channel 30 opens into the main channel 15.The pressure connection channel 30 interacts with the automatic shut-off device 10 in a known manner such that a pressure drop below the minimum value occurring upstream of the main valve device 16 triggers the shut-off device 10 and thus leads to the above-described decoupling of the control lever 17 from the piston arrangement 29. Figure 2 shows a partial section of the embodiment of Figure 1 in a lateral sectional view. The partial section shows the area of ​​the nozzle according to the invention in which the main valve device 16 and the pretensioning device 18 are arranged and interact with one another. In Figure 2, the areas A and B are also marked, which are shown enlarged in Figures 2A and 2B.

[0044] The main valve device 16 of this embodiment has a main valve body 20' and a main valve seat 23. The piston assembly 29 presses the main valve body 20' against the main valve seat 23 into a closed position in the operating state shown in Figure 2.

[0045] Independently of this, the main valve body 20', which is connected to a valve rod 31, is also tensioned into the closed position against the main valve seat 23 by the pretensioning device 18. The valve rod 31 runs along an axial direction of the main valve body 20'. The pretensioning device 18 comprises a full-hose spring 18a, a pressure-relieving spring 18c and a displaceable holding element 24. The two springs 18a, 18c are compressed compared to their rest position (i.e. they press the elements against which they rest apart), the pressure-relieving spring 18c exerting a smaller closing force on the main valve body 20' and having a smaller spring constant than the full-hose spring 18a. To effect a predetermined deflection of the pressure-relieving spring 18c, a smaller force is therefore necessary than with the full-hose spring 18a.

[0046] The main valve seat 23 is integrally connected to retaining projections 32, which slidably support the displaceable retaining element 24 and enable displacement of the retaining element 24 along the axial direction. The valve stem 31 is also slidably guided through a through-opening provided in the displaceable retaining element 24. The mobility of the valve stem 31 or of the valve body 20' connected thereto relative to the retaining element 24 in the closing direction is limited by a stop 35, which is formed at the rear end of the main valve body 20'.

[0047] The pressure reduction spring 18c tensions the holding element 24 relative to the holding projections 32 (and thus relative to the valve seat 23) in the closing direction (i.e. to the left in Figure 2). At the same time, the full hose spring 18a engages an outwardly pointing projection 34 of the valve stem 31 and the upstream end of the holding element 24 and thus tensions the valve body 20' relative to the holding element 24 upstream in the closing direction, but only until the front end of the holding element 24 comes to rest on the stop 35. The stop 35 is positioned in such a way that the main valve body 20' can be moved completely into the closed position not by the full hose spring 18a alone, but only under the additional effect of the pressure reduction spring 18c (or under the additional effect of the piston device 29 and closing spring 28).When the piston device 29 releases the main valve body, the main valve body 20' is therefore only moved completely into the closed position by the pressure relief spring 18c. To do this, the pressure relief spring 18c presses the holding element 24 away from the holding projections 32, so that a gap 33 forms between the holding element 24 and a stop 26 of the holding projections 32 (see Figure 2A). In this state, the main valve body 20' lies completely against the valve seat 23, so that an opening cross section of zero results. This is indicated in Figure 2B by the reference numeral 36. Figure 3 shows a section of Figure 2 in a different operating state, in which the piston arrangement 29 is spaced from the downstream end of the main valve body 20' and the main valve body is thus released. In addition, the fuel hose is full of fluid so that there is a corresponding fluid pressure in front of the main valve device.This condition can occur, for example, if the control lever is locked in an open position and the feed pump has been switched off after a preselected amount of fuel has been delivered. When the feed pump is switched off, the fluid pressure upstream of the main valve device 16 drops significantly, although in this case (because the fuel hose is still full of fluid) it still remains above the minimum pressure at which the automatic switch-off device is triggered. The main valve body 20' is thus tensioned into the closed position by the full hose spring 18a and the pressure reduction spring 18c (to the left in Figure 3).

[0048] In the state shown in Figure 3, therefore, a fluid pressure initially remains upstream of the main valve device 16 which is sufficient to move the main valve body 20' together with the holding element 24 into an open position against the restoring force of the pressure reduction spring 18c until the holding element 24 abuts the stop 26 (see Figure 3A). The gap 33 shown in Figure 2B is thereby closed (see Figure 3A). In this way, an opening cross-section of the main valve device 16 is created which corresponds to the limit opening cross-section. This can be seen in Figures 3A and 3B, in which the sections marked with the letters A and B in Figure 3 are shown enlarged. In particular, it can be seen in Figure 3B that the main valve body 20' is slightly lifted off the main valve seat 23 (see gap 43).In this way, a fluid pressure prevailing upstream of the main valve device 16 can be reduced in a controlled manner until the fluid pressure drops below the minimum pressure at which the shut-off device is triggered. When the holding element 24 rests against the stop 26, the pressure reduction spring 18c can no longer be compressed during a further opening movement of the main valve body 20'. Such a further opening movement (with which an opening cross-section is generated which exceeds the limit opening cross-section) must therefore take place against the restoring force of the solid hose spring 18a. The opening characteristic of the pretensioning device 18 is therefore discontinuous when the limit opening cross-section is exceeded.While in the first opening cross-sectional area, a reduced restoring force generated by the pressure-reducing spring 18c must be overcome, the further opening movement beyond the limit opening cross-section occurs against the greater restoring force of the solid hose spring 18a. This is explained below in connection with Figure 4.

[0049] Figure 4 shows the section of Figure 3 in a different operating state of the nozzle valve. In the state of Figure 4, the control lever 17 is in a middle opening position, which corresponds to a predetermined axial position of the piston arrangement 29. Furthermore, in the state shown in Figure 4, the feed pump is switched on, so that the fluid pressure prevailing upstream of the main valve device 16 is sufficient to move the main valve body 20' downstream in the axial direction against the restoring force of the full-hose spring 18a until the main valve body 20' strikes the piston arrangement 29. This results in an opening cross-section of the main valve device that exceeds the limit opening cross-section.

[0050] Figure 5 shows the section of Figures 3 and 4 in yet another operating state of the nozzle. The control lever 17 is in a fully open position. The piston assembly 29 is accordingly displaced further to the right compared to the position in Figure 4. The fluid pressure generated by the feed pump can therefore move the main valve body 20' even further to the right compared to the state shown in Figure 4, so that the opening cross-section is further increased.

[0051] Figure 6 shows a main valve device 16 and a preloading device 18 of a second embodiment of a nozzle according to the invention. Elements that are essentially identical to those in the first embodiment of the invention are provided with the same reference numerals. The differences between the first embodiment and the second embodiment are explained below.

[0052] In the embodiment of Figure 6, the main valve device 16 comprises a main valve body 20'' which is urged into the closed position by a biasing device 18, wherein the biasing device 18 has a full-tube spring 18a and a pressure relief spring 18d. In addition, retaining projections 32' are integrally connected to the valve seat 23, on which the main valve piston 31 is mounted so as to be sliding and displaceable along its axial direction. The full-tube spring 18a engages an upstream end of the retaining projections 32' in order to bias the main valve in the closing direction. The pressure reduction spring 18d is connected with its downstream end to the main valve body 20 '' and has at its opposite upstream end a sliding ring 37 which is displaceable relative to the main valve body 20 '' up to a limiting projection 38 when the pressure reduction spring 18d is deflected.In the state shown in Figure 6, the sliding ring 37 rests against a downstream stop 25 of the holding projections 32', so that the main valve body 20' is biased in an opening direction relative to the valve seat 23 by the pressure relief spring 18d. In the state shown in Figure 6, however, the control lever 17 is in the closed position, so that the main valve cone 20' is additionally biased into the closed position by the piston arrangement 29 acted upon by the closing spring 28. In the position shown, there is a gap 39 between the sliding ring 37 and the limiting projection (see Figure 6A, in which section A of Figure 6 is shown enlarged).

[0053] Figure 7 shows a section of Figure 6 in a state in which the piston arrangement 29 is spaced from the downstream end of the main valve body 20'' and the main valve body is correspondingly released. This state can occur, as already explained above, for example when the control lever is locked in an open position, the feed pump is switched off after a preselected amount of fuel has been dispensed and the automatic switch-off device has not yet been triggered. In this case, as explained above, the main valve body 20'' is tensioned in the closing direction by the full hose spring 18a and in the opening direction by the pressure reduction spring 18d. The closing force exerted on the main valve body 20'' by the full hose spring 18a is correspondingly reduced by the pressure reduction spring 18d and a minimum pressure required for opening is also reduced.The main valve body 20" can therefore be moved in the opening direction under the action of a slight fluid pressure until the sliding ring 37 comes to rest on the limiting projection 38 (see Figure 7A). This opening movement corresponds to a first adjustment range of the main valve body 20" and the opening cross-section achievable thereby corresponds to the limit opening cross-section. By slightly opening the main valve device (illustrated in Figure 7 by the gap 44), the fluid pressure can be reduced in a controlled manner until the pressure falls below the minimum and the automatic shut-off device is triggered.

[0054] If, however, the main valve device is actuated with the aid of the control lever 17, a further opening movement of the main valve body 20'' (beyond the limit opening cross-section) occurs against the full restoring force of the full-hose spring 18a and therefore requires a significantly higher pressure difference, since the pressure reduction spring 18d no longer counteracts the restoring force of the full-hose spring 18a in the subsequent second actuating range. In this way, a discontinuity in the opening characteristic of the main valve device is generated when the limit opening cross-section is exceeded.

[0055] Figure 8 shows the section of Figure 7 in a different operating state of the nozzle. In the state of Figure 8, the control lever 17 is in a middle opening position, which corresponds to a predetermined axial position of the piston arrangement 29. Furthermore, in the state shown in Figure 8, the feed pump is switched on, so that the fluid pressure prevailing upstream of the main valve device 16 is sufficient to move the main valve body 20'' downstream in the axial direction against the restoring force of the full-hose spring 18a until the main valve body 20' strikes the piston arrangement 29. This results in an opening cross-section of the main valve device which exceeds the limit opening cross-section. In this state, the pressure reduction spring 18d is no longer in contact with the stop 25.

[0056] Figure 9 shows the section of Figures 7 and 8 in yet another operating state of the nozzle valve. In the state of Figure 9, the control lever 17 is in a fully open position. The piston arrangement 29 is accordingly displaced further to the right compared to the position of Figure 8. The fluid pressure generated by the feed pump can therefore move the main valve body 20'' even further to the right compared to the state shown in Figure 8, so that the opening cross-section is further increased.

[0057] Figure 10 shows a main valve device 16 and a preloading device 18 of a third embodiment of a nozzle according to the invention. Elements that are essentially identical in the first or second embodiment of the invention are provided with the same reference numerals. The differences from the other embodiments are explained below.

[0058] In the embodiment of Figure 10, the main valve device 16 comprises a main valve body 20 which is tensioned in the closing direction against a main valve seat 23 by the pretensioning device 18. The main valve device 16 also comprises a pressure reduction channel 21 extending through the main valve body 20, as well as a pressure reduction valve body 22 which is designed to close the pressure reduction channel 21. The main valve device 16 thus comprises two valve bodies 20, 22, each of which can contribute to opening the main valve device 16. Just as in the embodiment of Figures 6 to 9, the nozzle valve has holding projections 32' which are connected in one piece to the valve seat 23 and on which the main valve piston 31 is mounted so as to slide and be displaceable along its axial direction.The pretensioning device 18 comprises a full-tube spring 18a, which biases the main valve body 20 against the valve seat 23, and a pressure relief spring 18b, which biases the pressure relief valve body 22 against the main valve body 20. For this purpose, the pressure relief spring 18b is clamped in a compressed state between a downstream end of the pressure relief valve 22 and an outwardly projecting collar 40, which is fixed to the main valve body 20.

[0059] In the operating state shown in Figure 10, the piston arrangement 29 presses both the main valve body 20 against the main valve seat 23 and the pressure relief valve 22 against the main valve body 20 into a closed position.

[0060] Figure 11 shows a section of Figure 10, wherein the piston arrangement 29 is spaced from the downstream end of the main valve body 20 and the pressure reduction valve body 22. In addition, the feed pump has been switched off after the delivery of a preselected amount of fuel, and the automatic switch-off device has not yet been triggered. In this case, the main valve body 20 is biased in the closing direction by the full hose spring 18a. In addition, the pressure reduction valve 22 is biased in the closing direction by the pressure reduction spring 18b. The reset constants of the elements 18a and 18b are selected in the present case such that a movement of the pressure reduction valve body 22 relative to the main valve body 20 in the opening direction requires a lower minimum pressure at the inlet 13 than a movement of the main valve body 20 relative to the main valve seat 23 in the opening direction.The presently prevailing low pressure is therefore just sufficient to move the pressure reduction valve 22 in the opening direction until it hits a stop 41 fixed relative to the main valve body. This creates a gap 42 between the main valve body 20 and a sealing surface of the pressure reduction valve body 22, through which gap the fluid can flow. With this opening movement, an opening cross-section of the main valve device 16 increases up to a limit opening cross-section. By slightly opening the main valve device, the fluid pressure can be reduced in a controlled manner until the pressure falls below the minimum and the automatic shut-off device is triggered.A further opening movement of the main valve device 16 (beyond the limit opening cross-section), which is achieved by a movement of the main valve body 20 relative to the main valve seat 23 in the opening direction, requires a significantly higher pressure, which only occurs when the feed pump is switched on. By opening the main valve device 16 before reaching the limit opening cross-section against the smaller closing force of the pressure reduction spring and after exceeding the limit opening cross-section against the greater closing force of the full hose spring 18a, a discontinuous opening characteristic of the main valve device 16 is realized in the region of the limit opening cross-section.

[0061] Figure 12 shows the section of Figure 11 in a different operating state of the nozzle valve. In the state of Figure 12, the control lever 17 is in a middle opening position, which corresponds to a predetermined axial position of the piston arrangement 29. Furthermore, in the state shown in Figure 12, the feed pump is switched on, so that the fluid pressure prevailing upstream of the main valve device 16 is sufficient to move not only the pressure reduction valve 22 but also the main valve body 20 in the opening direction against the restoring force of the full-hose spring 18a, until the main valve body 20 abuts the piston arrangement 29. This results in an opening cross-section of the main valve device 16 that exceeds the limit opening cross-section.

[0062] Figure 13 shows the section of Figures 11 and 12 in yet another operating state of the nozzle valve. In the state of Figure 13, the control lever 17 is in a fully open position. The piston assembly 29 is accordingly displaced further to the right compared to the position of Figure 12. The fluid pressure generated by the feed pump can therefore move the main valve body 20 even further to the right compared to the state shown in Figure 12, so that the opening cross-section is further increased.

Claims

Patent claims 1. Dispensing valve for dispensing a fluid, with an inlet (13) for connecting a fluid supply line, an outlet (14) , a main channel (15) connecting the inlet (13) with the outlet (14) , a main valve assembly (16) for controlling a fluid flow through the main channel (15) , a control lever (17) for actuating the main valve assembly (16) , an automatic safety shutdown designed to shut off the main valve assembly (16) to move into a closed position independently of the position of the control lever (17) when the fluid pressure at the inlet (13) falls below a minimum value, and with a pre-tensioning device (18) which pre-tensions the main valve assembly (16) into the closed position and causes a variable opening cross-section of the main valve assembly (16) depending on the fluid pressure at the inlet (13), characterized in that the pre-tensioning device (18) is configured to generate a discontinuous opening characteristic of the main valve assembly (16) such that a closing force acting on the main valve assembly (16) is reduced in a first opening cross-section area extending from the closed position of the main valve assembly to a limit opening cross-section.

2. Dispensing valve according to claim 1, wherein the pre-tensioning device (18) interacts with the main valve device (16) such that - the border opening cross-section in a range between 1 mm 2 and 12 mm 2 lies and / or - a minimum pressure required to open the main valve assembly, in a range between 0.01 bar and 0.5 bar, preferably between 0.05 bar and 0.3 bar. Dispensing valve according to claim 1 or 2, wherein the pre-tensioning device (18) interacts with the main valve assembly (16) such that a pressure threshold, above which the opening cross-section exceeds the limit opening cross-section, lies in a range between 0.075 bar and 0.5 bar, wherein the pressure threshold is preferably at least 5% greater, more preferably at least 20% greater, and particularly preferably at least 50% greater than a minimum pressure required to open the main valve assembly.A dispensing valve according to any one of claims 1 to 3, wherein the main valve assembly (16) comprises a main valve body (20), a main valve seat (23), a pressure relief channel (21), and a pressure relief valve body (22) designed to close the pressure relief channel (21), wherein the preloading device (18) is configured to force the main valve body (20) and the pressure relief valve body (22) independently into a closed position, wherein a change in the opening cross-section of the main valve assembly (16) in the first opening cross-section region is effected by a movement of the pressure relief valve body (22), and wherein a change in the opening cross-section of the main valve assembly (16) beyond the limit opening cross-section is effected by a movement of the main valve body (20) relative to the main valve seat (23). A dispensing valve according to claim 4, wherein the pressure relief channel extends through the main valve body (20). Dispensing valve according to claim 4 or 5, wherein the pre-tensioning device (18) has a first return element (18a) for forcing the main valve body (20) into the closed position and a second return element (18b) for forcing the pressure relief valve body (22) into the closed position.Dispensing valve according to one of claims 1 to 3, wherein the main valve assembly (16) comprises a main valve body (20', 20'') which is biased into a closed position by the biasing device (18) against a main valve seat (23), wherein the first opening cross-sectional area corresponds to a first actuating area of ​​the main valve body (20', 20'') and a second opening cross-sectional area extending beyond the limit opening cross-section corresponds to a second actuating area of ​​the main valve body (20', 20'') adjoining the first actuating area, wherein the discontinuous opening characteristic is realized by the fact that the biasing device (18) has a smaller restoring constant in the first actuating area than in the second actuating area.Dispensing valve according to claim 7, wherein the pre-tensioning device (18) comprises a first return element (18a) and a second return element (18c), wherein a movement of the main valve body (20') in the first actuation range in the opening direction occurs predominantly, preferably exclusively, against a return force of the second return element (18c), and wherein a movement of the main valve body (20') in the second actuation range in the opening direction occurs predominantly, preferably exclusively, against a return force of the first return element (18a). Dispensing valve according to claim 8, wherein the first return element (18a) biases the main valve body (20') relative to a displaceable retaining element (24), wherein the second return element (18c) biases the displaceable retaining element (24) relative to the main valve seat (23) of the main valve assembly (16). Dispensing valve according to claim 9, wherein the displaceability of the displaceable retaining element (24) relative to the main valve seat (23) is limited by a first stop (26), wherein preferably the displaceability of the displaceable retaining element (24) relative to the main valve body (20') is limited by a second stop (35).Dispensing valve according to claim 7, wherein the pre-tensioning device (18) comprises: a first return element (18a) with a first return constant that forces the main valve body (20'') into the closed position relative to the main valve seat (23), and a second return element (18d) with a second return constant that forces the main valve body (20'') in the opening direction relative to the main valve seat (23). Dispensing valve according to claim 11, wherein the return constant of the pre-tensioning device (18) in the first actuation range results from a combination of the return constants of the first and second return elements (18a, 18d), and wherein the return constant of the pre-tensioning device (18) in the second adjustment range only results from the restoring constant of the first restoring element (18a). Dispensing valve according to claim 11 or 12, in which a restoring force of the first restoring element (18a), which acts on the main valve body (20'') in the first adjustment range, is greater than a restoring force of the second restoring element (18d) that acts on the main valve body (20'') in the first actuation range. Dispensing valve according to one of claims 11 to 13, wherein the second restoring element (18d) has a first end and a second end opposite along a deflection direction, the first end being on the main valve body (20'') is fixed and wherein the second end restrains against a stop (25) fixed relative to the main valve seat (23) during a movement of the main valve body (20'') in the first positioning range and wherein the second end is released from the stop (25) during a movement of the main valve body (20'') in the second positioning range, wherein a deflection of the second end of the second return element (18d) is preferably limited in the upstream direction by a limiting projection (38) fixed to the main valve body (20''). Dispensing pump with a delivery pump for dispensing a fluid and with a dispensing hose connecting the delivery pump to a dispensing valve according to any one of claims 1 to 14.

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