dispensing valve

Description

[0001] The present invention relates to a dispensing valve for a fluid, comprising an inlet for connecting a fluid supply line, an outlet, and a main channel connecting the inlet to the outlet. The dispensing valve also includes a main valve assembly for controlling the fluid flow through the main channel and a control lever for actuating the main valve assembly. Furthermore, the dispensing valve includes an automatic safety shut-off designed to move the main valve assembly to a closed position, regardless of the position of the control lever, when the fluid pressure at the inlet falls below a minimum value. Finally, the dispensing valve includes a pre-tensioning device that pre-tensions the main valve assembly to the closed position and causes a variable opening cross-section of the main valve assembly depending on the fluid pressure at the inlet.

[0002] Such a dispensing nozzle is known from EP 2 386 520 B1. It can be used, in particular, for dispensing fuel into the tank of a vehicle. A user can operate the dispensing nozzle using the control lever to open the main valve and close it again after dispensing the desired quantity of fuel. The fuel is supplied by a delivery pump, which is usually connected to the dispensing nozzle by means of a fuel hose.

[0003] The fuel pump allows the user to pre-select a desired amount of fuel. In this case, the user can wait for the pre-selected amount to be dispensed after inserting the nozzle into the vehicle's filler neck and locking the control lever in place. Once the pre-selected amount has been dispensed, the fuel pump automatically shuts off, and fuel dispensing ceases. It is not strictly necessary to return the control lever and the main valve to the closed position after the fuel pump shuts off. However, leaving the main valve open poses a risk of uncontrolled fuel leakage during subsequent refueling.To avoid this danger, the known dispensing valve has the automatic safety shut-off described above, which moves the main valve into the closed position when the pressure at the inlet falls below a minimum value, especially after the delivery pump has been switched off.

[0004] The aforementioned pre-tensioning device generates an increased back pressure upstream of the main valve in the known dispensing nozzle during fluid delivery. This pressure dissipates after the fuel pump is switched off. The pre-tensioning device thus contributes to generating a sufficient pressure differential, which can be utilized in a known manner within the automatic shut-off device to ensure reliable shutdown. Furthermore, the pre-tensioning device prevents fuel remaining within the fuel hose from leaking uncontrollably, even if the fuel hose is full of fluid after the fuel pump has been switched off and the automatic shut-off device has not yet been triggered.

[0005] However, a problem can arise in this context if the pressure at the inlet and within the fuel hose does not drop below the minimum pressure during full-hose operation (i.e., when the fuel pump is switched off and the fuel hose is full of fluid) or even increases again, for example, if fuel pumped from a cold underground tank warms up in a fuel hose exposed to the sun. EP 2 386 520 B1 proposed a solution to this problem by having the main valve, under the action of the pre-tensioning device, be forced into the closed position at an angle, thus reducing its sealing capacity. Due to this reduced sealing capacity, the pressure present during full-hose operation can dissipate in a controlled manner, ensuring reliable shut-off with this previously known solution.However, it has been shown that the components that contribute to the tilting of the main valve require tight manufacturing tolerances and a high level of testing.

[0006] Based on this prior art, the object of the present invention is to provide a dispensing valve that at least partially avoids the aforementioned disadvantages. This object is achieved by the features of the independent claims. Advantageous embodiments are specified in the dependent claims. According to the invention, the pre-tensioning device is configured to generate a discontinuous opening characteristic of the main valve assembly such that a closing force acting on the main valve assembly is reduced in a first opening cross-sectional area extending from the closed position of the main valve assembly to a limit opening cross-section.

[0007] First, some terms used in the context of the invention will be explained. The term fluid includes substances in liquid, gaseous, or mixed states.

[0008] The main valve assembly can have exactly one, two, or more valve bodies. The opening cross-section of the main valve assembly is the cross-sectional area available for fluid flow through the assembly, depending on the opening state of the one or more valve bodies. In the closed position of the main valve assembly, all valve bodies are in a closed position. Therefore, when the main valve assembly is closed, it 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 up to the limit of the opening cross-section (i.e., within the first opening cross-sectional area). This reduces the minimum pressure at the inlet required to open the main valve assembly. The main valve assembly can therefore be opened more easily, as the valve body, whose closing force is reduced, performs a corresponding opening movement. This ensures that, in full hose operation, even a low pressure upstream of the main valve assembly is sufficient to open it. In this way, the pressure can be reliably reduced below the minimum pressure at which the automatic shut-off device is triggered.

[0010] On the other hand, the fluid supplied by a feed pump strikes the main valve assembly at a significantly higher pressure during normal 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 when the limit opening cross-section is exceeded ceases. Therefore, a greater pressure differential is required to further increase the opening cross-section when the limit opening cross-section is exceeded. Consequently, a high pressure is built up upstream of the main valve assembly when the limit opening cross-section is exceeded, 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 thus be improved.

[0011] In a preferred embodiment, the pre-tensioning device is configured such that the minimum pressure required to open the main valve assembly lies in a range between 0.01 bar and 0.5 bar, preferably between 0.05 bar and 0.3 bar. Furthermore, a pressure threshold, above which the opening cross-section exceeds the limiting opening cross-section, may be provided in a range between 0.075 bar and 0.5 bar. Preferably, the pressure threshold is at least 5% higher, more preferably at least 20% higher, and particularly preferably at least 50% higher than the minimum pressure.In this configuration, if the inlet pressure lies between the minimum pressure and the pressure threshold, the main valve opens in a controlled manner (up to the maximum opening cross-section), thus enabling a controlled pressure reduction below the minimum pressure, below which the automatic shut-off device is triggered. The minimum pressure can, for example, be between 0.075 bar and 0.45 bar. The automatic safety shut-off and the pre-tensioning device are preferably designed such that the minimum pressure lies between the minimum pressure and the pressure threshold. The maximum opening cross-section can, for example, be in a range between 1 mm² and 12 mm², preferably between 2 mm² and 8 mm².

[0012] In one embodiment, the main valve assembly comprises a main valve body, a main valve seat, a pressure relief channel, and a pressure relief valve body designed to close the pressure relief channel. Thus, in this embodiment, the main valve assembly has two valve bodies. The pre-tensioning device can be configured to force the main valve body and the pressure relief valve body independently into a closed position, whereby a change in the opening cross-section of the main valve assembly in the first opening cross-section region is effected by a movement of the pressure relief valve body, and wherein a change in the opening cross-section of the main valve assembly beyond the limiting opening cross-section is effected by a movement of the main valve body relative to the main valve seat.In this embodiment, the opening cross-section of the main valve assembly can therefore be changed by changing the opening state of the pressure relief valve body and / or by moving the main valve body relative to the main valve seat.

[0013] Preferably, the pressure relief channel runs through the main valve body. Furthermore, the pre-tensioning device for forcing the main valve body into the closed position can have a first return element, which is preferably designed as a solid coil spring. The pre-tensioning device for forcing the pressure relief valve body into the closed position can also have a second return element, which is preferably designed as a pressure relief spring. By having the main valve assembly with two independent valve bodies and the pre-tensioning device with a separate return element for each of these valve bodies, the described discontinuity in the opening characteristic can be easily achieved.In particular, it can be provided that, during full-hose operation, the main valve assembly is opened by the fluid pressure by opening only the pressure-reducing valve body, while the main valve body remains in a closed position, sealing against the main valve seat. With the pressure-reducing valve body fully open, an opening cross-section corresponding to the limiting opening cross-section can preferably be achieved. Any overpressure present upstream of the main valve assembly during full-hose operation can then be released in a controlled manner via the pressure-reducing channel. During normal pumping operation (i.e., with the pump switched on), the opening cross-section of the main valve assembly is (additionally) increased by movement of the main valve body relative to the main valve seat, resulting in an increased back pressure upstream of the main valve assembly, determined by the first return element or the full-hose spring.

[0014] In an alternative embodiment, the main valve assembly comprises a main valve body which is biased into a closed position by the biasing device against a main valve seat, wherein the first opening cross-sectional area corresponds to a first actuating area of ​​the main valve body and a second opening cross-sectional area extending beyond the limiting opening cross-section corresponds to a second actuating area of ​​the main valve body adjoining the first actuating area. An actuating area of ​​the main valve body denotes a range of movement (displacement 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 assembly.Preferably, the discontinuous opening characteristic is also achieved by the preload device having a smaller restoring constant in the first actuation range than in the second actuation range. The "restoring constant" is a measure of the ratio between the force required to move the main valve body and the resulting deflection of the main valve body. Due to the smaller restoring constant of the preload device in the first actuation range, the main valve body is forced less forcefully into the closed position in this range. This allows even a lower fluid pressure upstream of the main valve assembly to cause it to open until the end of the first actuation range, and thus the limiting opening cross-section, is reached.If the main valve assembly is subjected to a higher fluid pressure during normal delivery operation, the main valve body will move further within the second adjustment range against a restoring force determined by the larger restoring constant.

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

[0016] The aforementioned separate action of the return elements in the different positioning ranges can be achieved, for example, by having the first return element preload the main valve body relative to a movable retaining element, while the second return element preloads the movable retaining element relative to the main valve seat of the main valve assembly. In this case, movement of the main valve body in the opening direction in the first positioning range can be effected by a joint movement of the retaining element and the main valve body against a return force of the second return element, while movement of the main valve body in the opening direction in the second positioning range can be effected by movement of the main valve body relative to the retaining element against a return force of the first return element.

[0017] In the embodiment described above, the displacement of the movable retaining element relative to the main valve seat can be limited by a first stop positioned on the main valve seat. Furthermore, the movement of the movable retaining element relative to the main valve body can be limited by a second stop formed on the main valve body. If only a small pressure exists upstream of the main valve assembly, the main valve body is clamped against the movable retaining element by the first return element until the retaining element abuts the second stop on the main valve body. Simultaneously, the retaining element is spaced apart from the stop on the main valve seat due to the return force of the second return element.When the main valve body is moved from the closed position within the first adjustment range, this is accompanied by a displacement of the retaining element relative to the main valve seat and a corresponding deflection of the second return element. Therefore, if the fluid pressure upstream of the main valve assembly increases, the retaining element is deflected against the restoring force of the second return element and comes to rest at 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 retaining element, with a simultaneous deflection of the first return element.

[0018] In a further alternative embodiment, the pre-tensioning device comprises a first return element with a first return constant, which forces the main valve body into the closed position relative to the main valve seat. In this embodiment, the pre-tensioning device also comprises a second return element with a second return constant, which forces the main valve body in the opening direction relative to the main valve seat. In this case, the second return element thus opposes the first return element, thereby reducing the closing force in the first actuation range and enabling controlled pressure release. When the limit opening cross-section is exceeded (i.e., in the second actuation range), the opposing effect of the second return element can cease, thus realizing the discontinuity of the opening characteristic according to the invention.In particular, the restoring constant of the pre-tensioning device in the first adjustment range can result from a combination of the restoring constants of the first and second restoring elements, whereby the restoring constant of the pre-tensioning device when the limit opening cross-section is exceeded (i.e. in the second adjustment range) can result predominantly or exclusively from the restoring constant of the first restoring element.

[0019] Furthermore, it can be provided that the restoring force of the first restoring element, acting on the main valve body in the first adjustment range, is greater than the restoring force of the second restoring element, also acting on the main valve body in the first adjustment range. This ensures that the main valve body is moved completely into the closed position in the absence of fluid pressure.

[0020] Preferably, the second return element has a first end and a second end opposite the direction of deflection, wherein the first end is fixed to the main valve body and wherein, during movement of the main valve body in the first actuation range, the second end rests against a stop fixed relative to the main valve seat, and wherein, during movement of the main valve body in the second actuation range, the second end is released from the stop. Preferably, the deflection of the second end of the second return element in the upstream direction is also limited by a limiting projection fixed to the main valve body. This exemplary embodiment makes it possible to ensure that, in the second actuation range, only the first return element acts on the main valve body.

[0021] The invention further relates to a fuel dispenser with a pump for dispensing a fluid and with a dispensing hose that connects the pump to a dispensing valve according to the invention.

[0022] Advantageous embodiments of the invention are explained below by way of example with reference to the accompanying drawings.

[0023] They show: Figure 1: A fuel dispenser according to the invention, to which a dispensing valve according to the invention is connected, in a partially cutaway side view; Figure 2: A partial detail of the embodiment of the Figure 1 in a side sectional view; Figure 2A: a section from the Figure 2 in enlarged view; Figure 2B: a section from the Figure 2 in enlarged view; Figure 3: a partial section of the Figure 2 , where the dispensing valve is in a different operating state; Figure 3A: a section of the Figure 3in enlarged view; Figure 3B: a section from the Figure 3 in enlarged view; Figure 4: the view of the Figure 3 , where the dispensing valve is in a different operating state; Figure 5: the view of the Figure 3 in yet another operating state; Figure 6: a part of a second embodiment of a dispensing valve according to the invention in a sectional side view; Figure 6A: a section from the Figure 6 in enlarged view; Figure 7: a partial section from the Figure 6 in a side sectional view in a different operating state; Figure 7A: a section from the Figure 7 in enlarged view; Figure 8: the view of the Figure 7 , where the dispensing valve is in a different operating state; Figure 9: the view of the Figure 7, wherein the dispensing valve is in a different operating state; Figure 10: a part of a third embodiment of a dispensing valve according to the invention in a cutaway side view; Figures 11-13: partial sections from the Figure 10 , whereby the dispensing valve is in different operating states in each case.

[0024] Figure 1Figure 1 shows a fuel dispenser 8 according to the invention, to which a dispensing nozzle according to the invention is connected for dispensing fuel, in a partially cutaway side view. The dispensing nozzle comprises a housing 12 with an inlet 13, which is connected to a fuel hose 9. The fuel hose 9 leads to the fuel dispenser 8, which is shown schematically. Inside the fuel dispenser 8 is a delivery pump (not shown) designed to pressurize the fuel and deliver it to the dispensing nozzle. A discharge pipe 11 is inserted into the housing 12, at the front end of which an outlet 14 is located. A main channel 15 extends through the dispensing nozzle from the inlet 13 to the outlet 14 and can be closed by a main valve assembly 16.

[0025] The main valve assembly 16 has a main valve body which, in the state of Figure 1The main valve assembly 16 is held in a closed position by a closing spring 28 and a piston assembly 29 actuated by the closing spring in a known manner. The main valve assembly 16 can be actuated in a known manner via a control lever 17 by moving the piston assembly 29 to the left against the force of the closing spring 28 using a control lever pin 27. This releases the main valve body in a generally known manner, allowing a fluid pressure upstream of the main valve assembly to move the main valve body into an open position.

[0026] In addition to and independently of the closing spring 28 and the piston assembly 29, the main valve assembly is forced into the closed position by a pre-tensioning 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 pre-tensioning device 18 in order to discharge the fuel. The interaction of the pre-tensioning device 18 with the main valve assembly 16 is described below in conjunction with the Figures 2 to 5 explained in detail.

[0027] The dispensing valve further comprises an automatic shut-off device 10, which is designed to move the main valve assembly 16 into the closed position independently of the position of the control lever 17 when the fluid pressure at the inlet 13 falls below a minimum value. In particular, the shut-off device 10 is configured in a generally known manner (see, for example, EP 2 386 520 B1) to decouple the control lever pin 27 from the piston assembly 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 assembly 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 assembly 16 leads to the activation of the shut-off device 10 and thus to the decoupling of the control lever 17 from the piston assembly 29 as described above.

[0028] Figure 2 Figure 1 shows a partial section of the embodiment in a side sectional view. The partial section shows the area of ​​the dispensing valve according to the invention in which the main valve assembly 16 and the pre-tensioning assembly 18 are arranged and interact with each other. Figure 2 Furthermore, areas A and B are marked, which are enlarged in the Figures 2A and 2B are shown.

[0029] The main valve assembly 16 of this embodiment comprises a main valve body 20' and a main valve seat 23. The piston assembly 29 presses the main valve body 20' into the Figure 2 The operating condition shown is against the main valve seat 23 in a closed position.

[0030] Independently of this, the main valve body 20', which is connected to a valve stem 31, is also biased into the closed position against the main valve seat 23 by the preloading device 18. The valve stem 31 runs along an axial direction of the main valve body 20'. The preloading device 18 comprises a solid coil spring 18a, a pressure relief spring 18c, and a sliding retaining element 24. The two springs 18a and 18c are compressed relative to their rest position (i.e., they push apart the elements against which they rest), with the pressure relief spring 18c exerting a smaller closing force on the main valve body 20' and having a smaller spring constant than the solid coil spring 18a. Therefore, a smaller force is required to effect a predetermined deflection of the pressure relief spring 18c than with the solid coil spring 18a.

[0031] The main valve seat 23 is integrally connected to retaining projections 32, which slidably support the movable retaining element 24 and allow the retaining element 24 to move along the axial direction. The valve stem 31 also slides through a through-opening in the movable retaining element 24. The movement of the valve stem 31, or of the associated valve body 20', relative to the retaining element 24 in the closing direction is limited by a stop 35 located at the rear end of the main valve body 20'.

[0032] The pressure relief spring 18c tensions the retaining element 24 relative to the retaining projections 32 (and thus relative to the valve seat 23) in the closing direction (i.e. in Figure 2(to the left). Simultaneously, the solid coil spring 18a engages an outwardly projecting projection 34 of the valve stem 31 and the upstream end of the retaining element 24, thus tensioning the valve body 20' relative to the retaining element 24 in the closing direction upstream, but only until the front end of the retaining element 24 comes to rest against the stop 35. The stop 35 is positioned such that the main valve body 20' cannot be moved completely into the closed position solely by the solid coil spring 18a, but only under the additional action of the pressure-relieving spring 18c (or under the additional action of the piston assembly 29 and the closing spring 28). Thus, when the piston assembly 29 releases the main valve body, the main valve body 20' is only moved completely into the closed position by the pressure-relieving spring 18c.For this purpose, the pressure relief spring 18c pushes the retaining element 24 away from the retaining projections 32, so that a gap 33 is formed between the retaining element 24 and a stop 26 of the retaining projections 32 (see . Figure 2A The main valve body 20' rests completely against the valve seat 23 in this state, resulting in an opening cross-section of zero. This is in Figure 2B indicated by the reference number 36.

[0033] Figure 3 shows an excerpt from the Figure 2In another operating state, the piston assembly 29 is spaced from the downstream end of the main valve body 20', thus releasing the main valve body. Furthermore, the fuel hose is full of fluid, so that a corresponding fluid pressure exists upstream of the main valve assembly. This state can occur, for example, when the control lever is locked in an open position and the fuel pump has been switched off after dispensing a preselected quantity of fuel. Switching off the fuel pump causes the fluid pressure upstream of the main valve assembly 16 to drop significantly, although in this case (due to the fuel hose still being full of fluid) it remains above the minimum pressure at which the automatic shut-off device is triggered. The main valve body 20' is thus held in place by the full-hose spring 18a and the pressure relief spring 18c (in Figure 3 (to the left) into the closed position.

[0034] In the Figure 3 In the state shown, a fluid pressure therefore initially remains upstream of the main valve assembly 16 which is sufficient to move the main valve body 20' together with the retaining element 24 into an open position against the restoring force of the pressure relief spring 18c, until the retaining element 24 abuts the stop 26 (see Figure 3A ). The one in Figure 2B The gap shown, 33, is thereby closed (see Figure 3A In this way, the opening cross-section of the main valve assembly 16 is established, which corresponds to the limit opening cross-section. This is the Figures 3A and 3B recognizable in which the in Figure 3 The sections marked with the letters A and B are shown enlarged. In particular, in Fig. 3BIt is evident that the main valve body 20' is slightly lifted from the main valve seat 23 (see gap 43). In this way, the fluid pressure upstream of the main valve assembly 16 can be reduced in a controlled manner until it falls below the minimum pressure at which the shut-off device is triggered. When the retaining element 24 rests against the stop 26, the pressure-reducing spring 18c cannot be compressed further during any further opening movement of the main valve body 20'. Such a further opening movement (which creates an opening cross-section exceeding the limit opening cross-section) must therefore occur against the restoring force of the solid coil spring 18a. Consequently, the opening characteristic of the preloading device 18 is discontinuous when the limit opening cross-section is exceeded.While a reduced restoring force generated by the pressure relief spring 18c must be overcome in the first opening cross-sectional area, the further opening movement beyond the limit opening cross-section occurs against the greater restoring force of the solid coil spring 18a. This will be discussed below in conjunction with . Figure 4 explained.

[0035] Figure 4 shows the section of the Figure 3 in a different operating state of the dispensing valve. In the state of Figure 4 The control lever 17 is in a central opening position, which corresponds to a predetermined axial position of the piston assembly 29. Furthermore, in the Figure 4In the depicted state, the feed pump is switched on, so that the fluid pressure prevailing upstream of the main valve assembly 16 is sufficient to move the main valve body 20' axially downwards against the restoring force of the solid coil spring 18a, until the main valve body 20' abuts the piston assembly 29. This results in an opening cross-section of the main valve assembly that exceeds the limit opening cross-section.

[0036] Figure 5 shows the section of the Figures 3 and 4 in yet another operating state of the dispensing valve. The control lever 17 is in a fully open position. The piston assembly 29 is accordingly in the opposite position to the Figure 4 further shifted to the right. The fluid pressure generated by the feed pump can therefore shift the main valve body 20' relative to the one in Figure 4Move the shown position further to the right, so that the opening cross-section increases further.

[0037] Figure 6 Figure 1 shows a main valve assembly 16 and a pre-tensioning assembly 18 of a second embodiment of a dispensing valve according to the invention. Such elements, which are essentially identical in the first embodiment according to the invention, are provided here with the same reference numerals. The differences between the first and second embodiments are explained below.

[0038] In the embodiment of the Figure 6The main valve assembly 16 comprises a main valve body 20'', which is forced into the closed position by a pre-tensioning device 18, the pre-tensioning device 18 having a solid coil 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 slidably mounted and displaceable along its axial direction. The solid coil spring 18a engages at an upstream end of the retaining projections 32' to tension the main valve in the closing direction. The pressure relief spring 18d is connected at its downstream end to the main valve body 20'' and has a sliding ring 37 at its opposite upstream end, which is displaceable relative to the main valve body 20'' up to a limiting projection 38 when the pressure relief spring 18d is deflected. In the Figure 6In the state shown, the sliding ring 37 rests against a downstream stop 25 of the retaining projections 32', so that the main valve body 20" is tensioned 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 closing position, so that the main valve cone 20" is additionally tensioned in the closed position by the piston assembly 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 the Figure 6 (shown enlarged).

[0039] Figure 7 shows an excerpt from the Figure 6in a state in which the piston assembly 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 explained above, for example, when the control lever is locked in an open position, the fuel pump is switched off after dispensing a preselected quantity of fuel, and the automatic shut-off device has not yet been triggered. In this case, as explained above, the main valve body 20" is tensioned by the solid coil spring 18a in the closing direction and by the pressure relief spring 18d in the opening direction. The closing force exerted on the main valve body 20" by the solid coil spring 18a is correspondingly reduced by the pressure relief spring 18d, and the minimum pressure required for opening is also reduced.The main valve body 20" can therefore be moved in the opening direction under the influence of a small fluid pressure until the sliding ring 37 comes to rest against the limiting projection 38 (see . Figure 7A This opening movement corresponds to a first adjustment range of the main valve body 20", and the resulting opening cross-section corresponds to the limit opening cross-section. Due to the slight opening of the main valve assembly (in Figure 7 (illustrated by the gap 44) the fluid pressure can be reduced in a controlled manner until the minimum pressure is undershot and the automatic shut-off device is triggered.

[0040] If, however, the main valve assembly is actuated using the control lever 17, a further opening movement of the main valve body 20" occurs (beyond the limit opening cross-section) against the full restoring force of the solid coil spring 18a and therefore requires a significantly higher pressure differential, since the pressure relief spring 18d no longer counteracts the restoring force of the solid coil spring 18a in the subsequent second actuation range. In this way, a discontinuity in the opening characteristic of the main valve assembly is created when the limit opening cross-section is exceeded.

[0041] Figure 8 shows the section of the Figure 7 in a different operating state of the dispensing valve. In the state of Figure 8 The control lever 17 is in a central opening position, which corresponds to a predetermined axial position of the piston assembly 29. Furthermore, in the Figure 8In the depicted state, the feed pump is switched on, so that the fluid pressure prevailing upstream of the main valve assembly 16 is sufficient to move the main valve body 20" axially downwards against the restoring force of the solid coil spring 18a, until the main valve body 20' abuts the piston assembly 29. This results in an opening cross-section of the main valve assembly that exceeds the limit opening cross-section. In this state, the pressure relief spring 18d is no longer in contact with the stop 25.

[0042] Figure 9 shows the section of the Figure 7 and 8 in yet another operating state of the dispensing valve. In the state of Figure 9 The control lever 17 is in a fully open position. The piston assembly 29 is accordingly in the position of the Figure 8further shifted to the right. The fluid pressure generated by the feed pump can therefore shift the main valve body 20" relative to the one in Figure 8 Move the shown position further to the right, so that the opening cross-section increases further.

[0043] Figure 10 Figure 1 shows a main valve assembly 16 and a pre-tensioning assembly 18 of a third embodiment of a dispensing valve according to the invention. Such elements, which are essentially identical in the first or second embodiment according to the invention, are provided with the same reference numerals here. The differences from the other embodiments are explained below.

[0044] In the embodiment of the Figure 10The main valve assembly 16 comprises a main valve body 20, which is pre-tensioned against a main valve seat 23 in the closing direction by the pre-tensioning device 18. The main valve assembly 16 also comprises a pressure relief channel 21 extending through the main valve body 20, and a pressure relief valve body 22 designed to close the pressure relief channel 21. The main valve assembly 16 thus comprises two valve bodies 20 and 22, each of which can contribute to opening the main valve assembly 16. As in the embodiment of Figures 6 to 9The dispensing valve has retaining projections 32' integrally connected to the valve seat 23, on which the main valve piston 31 is slidably mounted and displaceable along its axial direction. The preloading device 18 comprises a solid coil spring 18a, which preloads the main valve body 20 against the valve seat 23, and a pressure relief spring 18b, which preloads 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.

[0045] In the Figure 10 In the operating state shown, 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.

[0046] Figure 11 shows an excerpt from the Figure 10The piston assembly 29 is spaced apart from the downstream end of the main valve body 20 and the pressure relief valve body 22. The feed pump was also switched off after the delivery of a preselected quantity of fuel, and the automatic shut-off device had not yet been triggered. In this case, the main valve body 20 is biased in the closing direction by the solid coil spring 18a. The pressure relief valve 22 is also biased in the closing direction by the pressure relief spring 18b. The return constants of elements 18a and 18b are selected such that movement of the pressure relief valve body 22 relative to the main valve body 20 in the opening direction requires a lower minimum pressure at the inlet 13 than movement of the main valve body 20 relative to the main valve seat 23 in the opening direction.The low pressure present is therefore just sufficient to move the pressure-reducing valve 22 in the opening direction until it abuts 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-reducing valve body 22, through which the fluid can flow. With this opening movement, the opening cross-section of the main valve assembly 16 increases until it reaches a limit opening cross-section. This slight opening of the main valve assembly allows the fluid pressure to be reduced in a controlled manner until the minimum pressure is undershot and the automatic shut-off device is triggered.A further opening movement of the main valve assembly 16 (beyond the limit opening cross-section), 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. Since the opening of the main valve assembly 16 occurs against the smaller closing force of the pressure relief spring before reaching the limit opening cross-section and against the larger closing force of the solid coil spring 18a after exceeding the limit opening cross-section, a discontinuous opening characteristic of the main valve assembly 16 is realized in the region of the limit opening cross-section.

[0047] Figure 12 shows the section of the Figure 11 in a different operating state of the dispensing valve. In the state of Figure 12The control lever 17 is in a central opening position, which corresponds to a predetermined axial position of the piston assembly 29. Furthermore, in the Figure 12 In the state shown, the feed pump is switched on, so that the fluid pressure prevailing upstream of the main valve assembly 16 is sufficient to move not only the pressure relief valve 22 but also the main valve body 20 in the opening direction against the restoring force of the solid hose spring 18a, until the main valve body 20 abuts the piston assembly 29. This results in an opening cross-section of the main valve assembly 16 that exceeds the limit opening cross-section.

[0048] Figure 13 shows the section of the Figures 11 and 12 in yet another operating state of the dispensing valve. In the state of Figure 13 The control lever 17 is in a fully open position. The piston assembly 29 is accordingly in the position of the Figure 12further to the right. 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 increases further.

Claims

1. 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 (13) to the outlet (14), 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 (13), characterized in that 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 the main valve device (16) is reduced in a first opening cross-sectional range extending from the closed position of the main valve device to a limit opening cross section.

2. Filling nozzle according to Claim 1, wherein the preloading device (18) cooperates with the main valve device (16) such that - the limit opening cross section ranges between 1 mm2 and 12 mm2 and / or - a minimum pressure which is required for opening the main valve device ranges between 0.01 bar and 0.5 bar, preferably between 0.05 bar and 0.3 bar.

3. Filling nozzle according to Claim 1 or 2, wherein the preloading device (18) cooperates with the main valve device (16) such that a pressure threshold value from which the opening cross section exceeds the limit opening cross section ranges between 0.075 bar and 0.5 bar, wherein the pressure threshold value is preferably at least 5% greater, further preferably at least 20%, particularly preferably at least 50% greater than a minimum pressure which is required for opening the main valve device.

4. Filling nozzle according to one of Claims 1 to 3, wherein the main valve device (16) has a main valve body (20), a main valve seat (23), a pressure reduction conduit (21) and a pressure reduction valve body (22) which is configured for closing the pressure reduction conduit (21), wherein the preloading device (18) is designed to urge the main valve body (20) and the pressure reduction valve body (22) independently of one another into a closed position, wherein a change in the opening cross section of the main valve device (16) in the first opening cross-sectional range is effected by a movement of the pressure reduction valve body (22), wherein a change in the opening cross section of the main valve device (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).

5. Filling nozzle according to Claim 4, wherein the pressure reduction conduit runs through the main valve body (20).

6. Filling nozzle according to Claim 4 or 5, wherein the preloading device (18) has a first restoring element (18a) for urging the main valve body (20) into the closed position and a second restoring element (18b) for urging the pressure reduction valve body (22) into the closed position.

7. Filling nozzle according to one of Claims 1 to 3, wherein the main valve device (16) comprises a main valve body (20', 20'') which is preloaded by the preloading device (18) against a main valve seat (23) into a closed position, wherein the first opening cross-sectional range corresponds to a first adjustment range of the main valve body (20', 20") and a second opening cross-sectional range beyond the limit opening cross section corresponds to a second adjustment range of the main valve body (20', 20") subsequent to the first adjustment range, wherein the discontinuous opening characteristic is implemented by the preloading device (18) having a smaller restoring constant in the first adjustment range than in the second adjustment range.

8. Filling nozzle according to Claim 7, wherein the preloading device (18) comprises a first restoring element (18a) and a second restoring element (18c), wherein a movement of the main valve body (20') in the first adjustment range in the opening direction takes place primarily, preferably exclusively, counter to a restoring force of the second restoring element (18c), and wherein a movement of the main valve body (20') in the second adjustment range in the opening direction takes place primarily, preferably exclusively, counter to a restoring force of the first restoring element (18a).

9. Filling nozzle according to Claim 8, wherein the first restoring element (18a) preloads the main valve body (20') relative to a displaceable holding element (24), wherein the second restoring element (18c) preloads the displaceable holding element (24) relative to the main valve seat (23) of the main valve device (16).

10. Filling nozzle according to Claim 9, wherein a displaceability of the displaceable holding element (24) relative to the main valve seat (23) is delimited by a first stop (26), wherein preferably a displaceability of the displaceable holding element (24) relative to the main valve body (20') is delimited by the second stop (35) .

11. Filling nozzle according to Claim 7, wherein the preloading device (18) comprises: a first restoring element (18a) with a first restoring constant which urges the main valve body (20'') into the closed position relative to the main valve seat (23), and a second restoring element (18d) with a second restoring constant which urges the main valve body (20") in the opening direction relative to the main valve seat (23).

12. Filling nozzle according to Claim 11, wherein the restoring constant of the preloading device (18) in the first adjustment range results from a combination of restoring constants of the first and second restoring elements (18a, 18d) and wherein the restoring constant of the preloading device (18) in the second adjustment range results only from the restoring constant of the first restoring element (18a).

13. Filling nozzle according to Claim 11 or 12, wherein a restoring force of the first restoring element (18a), which acts in the first adjustment range on the main valve body (20''), is greater than a restoring force of the second restoring element (18d) which acts in the first adjustment range on the main valve body (20'').

14. Filling nozzle according to one of Claims 11 to 13, wherein the second restoring element (18d) has a first end and an opposing second end in a deflection direction, wherein the first end is fixed to the main valve body (20") and wherein during a movement of the main valve body (20'') in the first adjustment range the second end bears against a stop (25) which is fixed relative to the main valve seat (23), and wherein during a movement of the main valve body (20") in the second adjustment range the second end is released from the stop (25), wherein a deflection of the second end of the second restoring element (18d) in the upstream direction is preferably delimited by a limit projection (38) which is fixed to the main valve body (20'').

15. Filling pump with a feed pump for delivering a fluid and with a filling hose which connects the feed pump to a filling nozzle according to one of Claims 1 to 14.