EP2452078B1 - Device for providing a variable restriction for a fluid flow - Google Patents

Description

TECHNICAL AREA

The invention relates to a lift control valve, a hydraulic lift system with the lift control valve and a method for operating the lift system according to the preambles of the independent claims.

STATE OF THE ART

In hydraulic and pneumatic systems today a variety of arrangements for the provision of variable throttle cross sections for fluid flows therein are used, both for the regulation of pressures and / or flow rates as well as for their detection. The change in the throttle cross-section is carried out either by external Verstelling by means of mechanical, hydraulic, pneumatic or electric actuators, eg control valves, or by the pressure, a pressure difference and / or a flow force of the guided in the arrangement fluid, such as pressure relief valves or check valves. The latter arrangements have the advantage that a high operational reliability is achieved due to the relatively simple hydraulic / pneumatic coupling and the independence of auxiliary power. The disadvantage here, however, that these arrangements are typically used only in a flow direction. This poses a problem with lift control valves for hydraulic lift systems in which, depending on the operating situation, changing fluid flows occur in their direction of flow, which problem is solved today by using a plurality of such arrangements and an elaborate interconnection thereof. However, this is associated with a considerable financial and technical equipment and effort In addition, often leads to not inconsiderable maintenance costs.

Out US 3,981,478 a reversible flow control valve is known.

PRESENTATION OF THE INVENTION

It has as its object to provide a lift control valve, which does not have the aforementioned disadvantages of the prior art or at least partially avoids.

This object is achieved by the lift control valve according to claim 1.

Accordingly, the lift control valve has an arrangement for providing a variable throttle area for a flow of fluid, preferably a fluid flow, e.g. a stream of hydraulic oil, on. This arrangement includes a throttle assembly and a drive assembly. The throttle arrangement forms a variable by movement of a throttle body throttle cross-section. The drive arrangement has a drive element arranged movably in a housing, which is coupled to the throttle body of the throttle arrangement such that the throttle cross section of the throttle arrangement can be changed by changing the relative position of the drive element in the housing. Preferably, the coupling between the throttle body and the drive element takes place in a hydraulic or mechanical manner, advantageously by common, in particular one-piece construction of throttle body and drive element.

In this case, the arrangement is designed such that the drive element is permanently acted upon by a spring force (the claimed first spring force) or can be acted upon, for example by supplying auxiliary power, with such a spring force. The spring force acts in a claim according to the first direction on the drive element, in which this in the housing is mobile. For this purpose, it is conceivable, for example, that a spring element or a pressurized compressible medium in a suitable direction exerts a compressive force directly on the drive element and / or on the throttle body coupled to the drive element. The spring force causes the drive element is positioned in a basic position in the housing in the absence of at least equally large, acting in a direction opposite to the first direction claims according to the second direction on the drive element.

Furthermore, the arrangement is such that the drive element is fluidly in contact with a first side of the throttle cross-section or can be brought into fluidic contact with this first side due to fluid pressures in a first fluid space of the arrangement, and a second fluid space of the arrangement, which is permanently in fluidic contact with the other, second side of the throttle cross-section or can be brought into fluidic contact with this second side, with a second and a third force can be acted upon, both of which act in the second direction according to claim, ie against the spring force.

Also, the arrangement is designed such that due to a fluid pressure in a third fluid space of the arrangement, the drive element is acted upon by acting in the claim first direction fourth force, ie with a fourth force acting in the direction of the spring force.

This configuration results in that the drive element in the event that no further forces in the first and second claims claim the second direction act on this, and that from the second, the third and the fourth force results in a total force, which in the Spring force opposite claims second direction acts and the spring force in the basic position exceeds the basic position is moved out until an equilibrium of forces between the spring force acting on the drive element in the respective relative position and the resulting force acting from the second, the third and the fourth force in the direction against the spring force occurs or a maximum movement position of the drive element is reached.

Furthermore, the arrangement comprises a switching arrangement, e.g. a hydraulically operable 3/2-way valve, by means of which either either the first and the third fluid chamber of the arrangement or the second and the third fluid chamber of the arrangement are fluidically connectable to each other. When the first side of the throttle section is in fluid communication with the first fluid space and the second side of the throttle section is fluidically in communication with the second fluid space, the drive element is dependent on the switching state, i. depending on whether the third fluid space is connected to the first or the second fluid chamber, either on the occurrence of a positive or negative pressure difference between the first side and the second side of the throttle gap from the home position movable to open or enlarge the throttle cross-section.

In this way, an arrangement for providing a throttle cross-section for a fluid flow is provided, in which the throttle cross section is variable or openable depending on a pressure difference across this and in which the polarity of the pressure difference, by means of which the throttle cross section can be changed or opened is, is switchable.

In a preferred embodiment, the arrangement is designed such that the throttle cross section is completely closed when arranged in the basic position drive element, so the two sides of the throttle cross-section are separated from each other, so that in this position, the first fluid space from the second Fluid space is separated. This separation is preferably carried out such that there is a leak-free separation at the intended pressures and the intended fluids. This can be achieved, for example, in that the throttle arrangement is designed as a seat valve. Such embodiments of the arrangement may be used, for example, as reversible check valves, which is a preferred use thereof.

In a further preferred embodiment, the arrangement has means for determining the opening of the throttle cross section of the throttle arrangement, the relative position of the drive element in the housing and / or the relative position of the throttle body of the throttle arrangement, ie means with which a variable representing the respective throttle cross section can be determined. Preferably, these means comprise sensors with which the relative positions of the drive element and / or the throttle body can be converted into electrical signals, so that an electronic evaluation of the determined measured values is possible. Such embodiments of the arrangement may e.g. be used as flow meter with reversible flow direction, which is a further preferred use of the arrangement. Especially with non-compressible fluids, e.g. Water or with only very low compressible fluids such. Mineral oil has the advantage that, with known characteristics of the arrangement and known viscosity of the fluid all other required for the determination of the volume flow rates, that are the throttle cross-section, the hydraulic characteristic of the arrangement in this throttle cross-section and at the given viscosity of the fluid and the Pressure difference between the first and the second side of the throttle cross-section, with good accuracy from the determined, the throttle cross-section representing size result.

Particularly preferred are embodiments which the features of the two aforementioned embodiments combine with each other. These can be used as combined reversible flow and check valve units. These functionalities are required, for example, in lift control valves, where today they are provided in a complex manner by combining a plurality of individual arrangements.

In yet another preferred embodiment, the arrangement is such that the second force and the third force are approximately equal at identical fluid pressures in the first and second fluid spaces, e.g. It can be achieved by directly applying force without over- or reduction mechanisms, the effective areas used to generate the respective force are made the same size. In this way it can be achieved that the operating behavior of the arrangement in both switching states, i. both when the first and third fluid spaces are interconnected via the switching arrangement and when the second and third fluid spaces are interconnected via the switching arrangement, apart from the reverse polarity, the pressure differential required to actuate the drive element is substantially identical.

In yet another preferred embodiment, the arrangement is designed such that at identical fluid pressures in the first, second and third fluid space, the second, third and fourth forces cancel each other substantially. This can be achieved, for example, by the fact that, in the case of a direct introduction of force without over or reduction mechanisms, the active surfaces used to generate the second and third forces are of the same size as the active surface used to generate the fourth force. In this way, a particularly sensitive response of the arrangement can be achieved, such that even slight pressure differences between the first and the second Side of the throttle cross-section lead to an opening or increase the throttle cross-section.

If the drive element has axial surfaces which are fluidically connected to the first, the second and the third fluid chamber for generating the second, third and fourth forces, which is preferred, a direct and loss-free introduction of force into the drive element takes place.

Advantageously, the drive element of the drive arrangement and the throttle body of the throttle arrangement are formed by one and the same one-piece or multi-piece component. This allows a simple and compact design with a lossless coupling between the drive element and throttle body realize.

Furthermore, the inventive lift control valve has a first connection for a supply line for hydraulic fluid coming from a hydraulic pump, a second connection for a return of hydraulic fluid into a tank and a third connection for a hydraulic line leading to a hydraulic drive of a lift system. In addition, the lift control valve has a control arrangement with which the first side of the throttle cross section and the first fluid space of the arrangement can be fluidly connected either to the first port or to the second port, depending on whether the lift control valve is to be brought into a position which is intended to allow the passage of hydraulic fluid from a hydraulic pump to a hydraulic drive of a lift system (OPEN-drive operation) or the return of hydraulic fluid from a hydraulic drive a lift system in a tank (AB-ride operation) when used as intended. Further, the lift control valve is configured such that the second side of the throttle cross-section and the second fluid space of the arrangement are connected to the third terminal or can be connected thereto.

In this way, the arrangement is incorporated into the main line through which the hydraulic fluid flows in the event of normal UP-drive operation and AB-drive operation of the lift control valve and, if designed accordingly, can be used, for example. Perform tasks as a reversible check valve and / or as a reversible flow meter, which is preferred. It is particularly preferred if the arrangement, as stated at the outset, is designed in such a way that it forms a combined flow measuring and check valve unit which can be switched over with respect to the direction of flow, ie can simultaneously perform the two aforementioned tasks. As a result, the system engineering effort compared to previous lift control valves can be significantly reduced with the same functionality and save corresponding provisioning and maintenance costs.

In this case, in a preferred embodiment, the lift control valve is designed in such a way that, when the first side of the throttle cross-section and the first fluid space are connected to the first port, the second fluid space will inevitably also be connected to the third fluid space by the changeover arrangement and Connecting the first side of the throttle cross-section and the first fluid space with the second port inevitably leads to the first fluid space is connected by the switching arrangement with the third fluid space. This ensures that the arrangement is also switched in each case when switching the control arrangement of the lift control valve from OPEN-drive operation to AB-drive operation and vice versa and is thereby adapted to the respective flow direction.

Advantageously, as a control arrangement for enabling the selective connection of the first side of the throttle cross-section with either the first or the second port of the lift control valve is preferably provided steadily acting, preferably hydraulically actuated main valve used, which is preferably designed in piston valve design. Such control arrangements are proven, reliable and low maintenance.

Further, in embodiments in which the control arrangement of the lift control valve is a hydraulically actuated main valve, it is advantageous that the lift control valve has a valve with which the fluid supply to the hydraulic drive of the main valve on reaching or exceeding a certain pressure at the first port fluidly is connected to the second port, ie with the port which is provided for a return of hydraulic fluid in a tank. This makes it possible to allow certain positions of the main valve and thus certain operating conditions or operating state changes of the lift control valve only if there is no appreciable fluid pressure at the connection for the supply of hydraulic fluid from a hydraulic pump (demanding first port), e.g. when the hydraulic pump connected there is switched off or the hydraulic fluid flow is deactivated.

It is also in embodiments in which the control arrangement of the lift control valve has a hydraulically actuated main valve, preferably when the lift control valve has an electrically actuated pilot valve for the hydraulically actuated main valve, by means of which the hydraulic drive of the main valve fluidly with the second side of the throttle cross-section or connected to the third port or can be disconnected. In this way, in the proper use of the lift control valve, the fluid pressure generated by the weight of a lift operated therewith can be used in the line leading to the lift drive for actuating the main valve, resulting in the advantage shows that a controlled AB ride is possible even in case of failure of the hydraulic pump.

It is further preferred that the fluidic connection between the pilot valve and the hydraulic drive of the main valve to the second port, i. Having throttle leading to the tank connection. This throttle point advantageously has a variable depending on the valve position of the main valve throttle cross-section. When executed in piston valve design main valve, it is preferred that the throttle cross section is variable in dependence on the position of the spool, which is advantageously realized such that the throttle cross section between the spool and a fixed component of the main valve is formed. As a result, a pressure relief of the connecting line between the pilot valve and the main valve is ensured with a closed pilot valve. In versions with variable throttle cross section, it is also possible to specifically influence the response of the main valve.

In a further preferred embodiment, the lift control valve is designed in such a way that connection of the first side of the throttle cross section of the throttle arrangement to the second connection is not possible when hydraulic fluid is present under pressure at the first connection. In this way it can be ensured that an AB drive operation of a system formed with this lift control valve is possible only when the hydraulic pump or the hydraulic fluid flow is switched off.

In yet another preferred embodiment of the lift control valve, the switching arrangement of the arrangement has a hydraulically actuable changeover valve, which is switchable during normal operation by opening or closing a pressure relief opening. In this case, the control arrangement of the lift control valve is designed such that it when connecting the first side of the throttle cross-section of the throttle assembly with the second port (tank port) opens the pressure relief port of the switching valve. As a result, a coupling of the control arrangement and switching arrangement is possible in a simple and reliable manner.

In general, it is preferred that the lift control valve is designed in such a way that the actuation energy of the hydraulic fluid guided in operation in the lift control valve can be removed for the actuation of hydraulically operated valves contained in it. In this way can be dispensed with further supply and discharge lines for hydraulic fluid and there is a lift control valve unit with a minimum of interfaces.

A second aspect of the invention relates to a hydraulic lift system with a lift control valve according to the first aspect of the invention. The lift system has a hydraulic pump connected or connectable to the first connection of the lift control valve, a tank for hydraulic fluid connected or connectable to the second connection of the lift control valve and a hydraulic drive connected or connectable to the third connection of the lift control valve, with which a lift of the lift system is driven can. The hydraulic drive is preferably designed as a linear drive in the form of a hydraulic cylinder, but it may also be designed differently, e.g. as a rotary hydraulic motor. The formation of such a lift system represents a proper use of the lift control valve according to the first aspect of the invention.

In a preferred embodiment, the lift system has a lift control valve with an arrangement which is equipped with means for determining the opening of the throttle cross section of the throttle arrangement, the relative position of the drive element and / or the relative position of the throttle body of the throttle arrangement. Further, this embodiment of the lift system comprises a control for the driving operation of the lift, which is so connected to the aforementioned means and is configured that they operate via this means information about the opening of the throttle cross-section, the relative position of the drive element and / or the relative position of the throttle body can receive and this can take into account in the control or regulation of the driving operation of a lift of the lift, and preferably as a parameter representing the hydraulic fluid flow which flows through the throttle cross-section of the arrangement, and in particular the associated travel speed of the lift. With such hydraulic lifts it is possible to realize a very precise regulation of the travel speed of the lift with little system outlay.

• Anheben eines Lifts der Liftanlage durch Förderung eines Volumenstromes von Hydraulikflüssigkeit von der Hydraulikpumpe zum Hydraulikantrieb des Lifts, wobei die Hydraulikflüssigkeit den Drosselquerschnitt der Drosselanordnung der Anordnung von der ersten Seite des Drosselquerschnitt zur zweiten Seite des Drosselquerschnitts durchströmt und der zweite Fluidraum und der dritte Fluidraum der Anordnung fluidisch über die Umschaltanordnung miteinander verbunden sind und zudem fluidisch mit der zweiten Seite des Drosselquerschnitts verbunden sind, während die erste Seite des Drosselquerschnitts fluidisch mit dem ersten Fluidraum verbunden ist
• oder
• Absenken eines Lifts der Liftanlage durch Förderung eines Volumenstromes von Hydraulikflüssigkeit vom Hydraulikantrieb des Lifts in den Tank, wobei die Hydraulikflüssigkeit den Drosselquerschnitt der Drosselanordnung der Anordnung von der zweiten Seite des Drosselquerschnitt zur ersten Seite des Drosselquerschnitts durchströmt und der erste Fluidraum und der dritte Fluidraum der Anordnung fluidisch über die Umschaltanordnung miteinander verbunden sind und zudem fluidisch mit der ersten Seite des Drosselquerschnitts verbunden sind, während die zweite Seite des Drosselquerschnitts fluidisch mit dem zweiten Fluidraum verbunden ist;
• Ermitteln der Öffnung des Drosselquerschnitts der Drosselanordnung, der Relativposition des Antriebselements der Antriebsanordnung und/oder der Relativposition des Drosselkörpers der Drosselanordnung der Anordnung während der Förderung des Volumenstromes von Hydraulikflüssigkeit durch den Drosselquerschnitt;
• Vergleichen der ermittelten Öffnung des Drosselquerschnitts, Relativposition des Antriebselements, der Relativposition des Drosselkörpers der Drosselanordnung und/oder eines aus einem oder mehreren dieser ermittelten Werte errechneten Werts mit einem Sollwert; und
• Verändern des Volumenstromes der durch den Drosselquerschnitt geförderten Hydraulikflüssigkeit bei Feststellung einer Abweichung vom Sollwert derart, dass sich die Öffnung des Drosselquerschnitts, die Relativposition des Antriebselements, die Relativposition des Drosselkörpers und/oder der errechnete Wert dem Sollwert annähert.

A third aspect of the invention relates to a method for operating a lift system according to the second aspect of the invention. The method comprises the following steps:

• Lifting a lift of the lift system by promoting a volume flow of hydraulic fluid from the hydraulic pump to the hydraulic drive of the lift, wherein the hydraulic fluid flows through the throttle cross section of the throttle arrangement of the arrangement from the first side of the throttle cross section to the second side of the throttle cross section and the second fluid space and the third fluid space of the arrangement are fluidly connected to each other via the switching arrangement and are also fluidly connected to the second side of the throttle cross-section, while the first side of the throttle cross-section is fluidly connected to the first fluid space
• or
• Lowering a lift of the lift system by promoting a volume flow of hydraulic fluid from the hydraulic drive of the lift into the tank, wherein the hydraulic fluid is the throttle cross-section of the throttle assembly the arrangement flows from the second side of the throttle cross section to the first side of the throttle cross section and the first fluid space and the third fluid space of the arrangement are fluidly connected to each other via the switching arrangement and are also fluidly connected to the first side of the throttle cross section, while the second side of the throttle cross section fluidly is connected to the second fluid space;
• Determining the opening of the throttle cross section of the throttle arrangement, the relative position of the drive element of the drive arrangement and / or the relative position of the throttle body of the throttle arrangement of the arrangement during the promotion of the volume flow of hydraulic fluid through the throttle cross section;
• Comparing the determined opening of the throttle cross-section, relative position of the drive element, the relative position of the throttle body of the throttle arrangement and / or a value calculated from one or more of these determined values with a desired value; and
• Changing the volume flow of the conveyed through the throttle cross-section hydraulic fluid upon detection of a deviation from the desired value such that the opening of the throttle cross-section, the relative position of the drive element, the relative position of the throttle body and / or the calculated value approaches the target value.

It is preferred that the volume flow of hydraulic fluid delivered through the throttle cross-section of the throttle arrangement is determined by means of an algorithm exclusively from the determined opening of the throttle cross-section, the determined relative position of the drive element and / or the determined relative position of the throttle body of the throttle arrangement, possibly with additional consideration of a additionally determined temperature value of the hydraulic fluid.

This makes it possible to regulate the lift system according to the second aspect of the invention in the ON-drive operation and AB-drive operation precisely with respect to the speed of the elevator, without requiring the determination of system pressures is required, so that a cost-effective and particularly safe operation is possible.

In a preferred embodiment of the method, when the lift is lifted, the volume flow of hydraulic fluid delivered through the throttle cross section of the throttle arrangement is changed by the larger or smaller part of the volume flow conveyed by the hydraulic pump being diverted into the tank by the control unit of the lift control valve. In this way, the use of low-constant pumps is possible and the entire regulation via the lift control valve.

BRIEF DESCRIPTION OF THE DRAWINGS

• Fig. 1 einen Schnitt durch ein erfindungsgemässes Liftregelventil in einer ersten Betriebssituation;
• Fig. 2 einen Schnitt durch das Liftregelventil gemäss Fig. 1 in einer zweiten Betriebssituation; und
• Fig. 3 ein Hydraulikschema einer Liftanlage mit dem Liftregelventil gemäss den vorangehenden Figuren.

Further embodiments, advantages and applications of the invention will become apparent from the dependent claims and from the following description with reference to FIGS. Showing:

• Fig. 1 a section through an inventive lift control valve in a first operating situation;
• Fig. 2 a section through the lift control valve according Fig. 1 in a second operating situation; and
• Fig. 3 a hydraulic diagram of a lift system with the lift control valve according to the preceding figures.

WAYS FOR CARRYING OUT THE INVENTION

Fig. 1 shows a section through an inventive lift control valve in a de-energized rest state of the lift control valve. As can be seen, the lift control valve on a solid metal housing 3, within which by inserting various functional units from the outside a hydraulically actuated 3/4-way main valve 14, an electrically actuated pilot valve 15 for the main valve 14, a pressure relief valve 18, a unlockable check valve 22 and a switching valve 8 are formed for the check valve 22. The check valve 22, together with the switching valve 8, is a claimed arrangement for providing a variable throttle cross section for a hydraulic fluid flow to be controlled by the lift control valve for a hydraulic lift drive.

The main valve 14 is designed as a continuously acting slide valve, with a piston slide 17 which limits a control oil chamber 25 at its left end and forms at this end together with a control edge of the housing 3 a variable depending on the spool position throttle body 16. At its right end of the spool 17 limits a spring chamber 27, in which a return spring 26 is arranged, which pushes the spool 17 at unpressurized control oil chamber 25 to the left in a basic position. The spring chamber 27 is limited over a part of its axial extent and at its end facing away from the spool 17 end of a throttle sleeve 28, which relieves pressure on this space 27 via a throttle point formed by them to the second port 12 (tank connection). Within the piston slide 17 a central bore 30 is further arranged with a check valve 31, via which oil from a radial groove 32 on the circumference of the spool 17 in the spring chamber 27 can be passed.

The pilot valve 15 for controlling the main valve 14 is formed as a steadily acting seat valve, which forms a check valve in the illustrated currentless state in the direction of its intended flow direction.

The main valve 14 and the associated pilot valve 15 form the claim as appropriate control unit of the lift control valve.

The unlockable check valve 22 is formed in a seated construction, with a in the housing 3 against the force of a spring 23 (the claimed first force) slidable throttle body 2 and a fixedly arranged in the housing 3 valve seat body 9. The throttle body 2 and the valve seat body 9 formed throttle section 1 closed in a basic position with non-deflected throttle body 2 fluid-tight and changeable by deflection of the throttle body 2 from the basic position in dependence on the position of the throttle body 2.

The throttle body 2 forms in the present case at the same time the claimed drive element 4 by having axial surfaces which are in direct contact with a claimed first fluid chamber 5, a claim according to the second fluid chamber 6 and a claim according third fluid chamber 7, so that due corresponding second, third and fourth forces in and against the force direction of the spring 23 can be exerted on the throttle body 2 by fluid pressures in these fluid spaces 5, 6, 7. If the sum of these second, third and fourth forces, the force of the spring 23 in the opposite direction, the throttle body 2 is lifted from the valve seat body 9 and the throttle section 1 is opened so far that a balance between the spring force and the sum of the second, third and fourth forces in the direction opposite to the spring force is present. In the present arrangement, the ratios of the axial areas of the throttle body 2, 4 are selected such that the second, the third and the fourth force with identical fluid pressure in the first, second and third fluid chamber 5, 6, 7 cancel each other. As can also be seen, the throttle body 2 is coupled at its right end with a position sensor 10, with which its position in the housing 3 in the form of electrical signals can be determined, to determine the flow during operation through the throttle section 1 of the throttle valve 22 flow of hydraulic fluid.

The switching valve 8, which serves as a claim switching arrangement for switching the check valve 22 is formed as a switching 3/2-way valve in slide construction and is located in the in Fig. 1 illustrated situation in a position in which it fluidly connects the second fluid chamber 6 and the third fluid chamber 7 and separates them from the first fluid chamber 5. As a result, the throttle cross-section 1 of the check valve 22 can only be opened if a fluid pressure is generated in the first fluid chamber 5, which exceeds the fluid pressure in the second 6 and in the third fluid chamber 7 and additionally is large enough to the force of the spring 23 in the basic position to overcome.

As can be seen, the piston valve of the switching valve 8 is loaded by a spring in this way, so that it is held in the position shown in the absence of greater forces acting in the direction opposite to the spring force. This spring is arranged in a spring chamber 24, which is fluidically connected via a throttle point in the piston valve with the second 6 and third fluid chamber 7. Next, the spring chamber 24 is fluidly in contact with the end face of the throttle sleeve 28 of the main valve 14, to which a central pressure relief opening 19 for pressure relief of the spring chamber 24 is located, which in the in Fig. 1 shown operating situation is fluid-tightly closed by a spring-loaded ball, so that the spring chamber 24 is not depressurized in this operating situation. The spool 17 of the main valve 14 has at its right end to an actuating pin 29, by means of which he can open the pressure relief opening 19 by lifting the spring-loaded ball from its seat in a fully controlled position and thereby the spring chamber 24 of the switching valve 8 with the spring chamber 27 of the Main valve 14 can connect fluidly.

As further in particular in conjunction with Fig. 3 can be seen, which shows the hydraulic scheme of a hydraulic lift system formed with this lift control valve, the first fluid chamber 5, which is arranged on the claim Demand first side of the throttle section 1 of the check valve 22, via the main valve 14 optionally with a first port 11 for one of A supply line for hydraulic fluid coming from a hydraulic pump 33 can be connected to a second connection 12 for a return of hydraulic fluid into a tank 34. The second fluid space 6, which is arranged on the claimed second side of the throttle cross-section 1 of the check valve 22, is permanently connected to a third connection 13 for a hydraulic line leading to a hydraulic drive 35 of a lift system and to the inlet side of the pilot valve 15. In the illustrated basic position is the throttle gap 1 is completely closed, so that the first 5 and the second fluid chamber 6 are fluidly separated from each other via this.

The pressure relief valve 18 is located in the feed from the pilot valve 15 for the control oil to the control oil chamber 25 of the main valve 14 and is designed such that when exceeding a certain fluid pressure at the first port 11, this feed is connected to the second port 12 for the tank and thereby the control oil pressure collapses.

Will now, as in Fig. 3 represented, starting from the in Fig. 1 shown switching situation of the lift control valve of the first terminal 11 by means of a hydraulic pump 33 fed with hydraulic oil and the second port connected to a hydraulic oil tank 34, from which the hydraulic pump 33 promotes, the oil through the hollow main spool 17 of the main valve 14 to the second port 12 and back led to the tank 34, wherein adjusts a circulation pressure in the interior of the slider 17. This circulating pressure penetrates via columns into the first fluid space 5. By connected to the third terminal 13 of the lift control valve hydraulic drive 35 a lift system on which the weight of the lift loads, the fluid pressure in the second 6 and the third fluid chamber 7 is greater than the circulation pressure, so that the throttle cross section 1 of the valve 22 remains closed.

If the pressure present at the third connection 13 or in the second fluid chamber 6 is at least partially guided into the control oil space 25 of the main valve 14 by opening the pilot control valve 15 and the latter is thereby activated, then the main slide 17 of the valve 14 is displaced to the right, whereby Outlet closed to the tank and the first port 11 is connected to the first fluid chamber 5. At the same time the throttle cross section of the variable throttle point 16 is increased with increasing deflection of the main slide 17, via which a part of the control oil flow for the Main valve 14 to the second port 12 and into the tank 34 is passed. As a result, the pilot valve 15 must be opened disproportionately for an increasing deflection of the piston slide 17 of the main valve 14, so that a sensitive adjustment of the main valve 14 results.

As soon as the pressure in the first fluid chamber 5 has exceeded the fluid pressure in the second fluid chamber 6 and, in addition, has also neutralized the force of the spring 23, the throttle body 2 is deflected to the right. The throttle cross-section 1 opens and hydraulic oil flows under pressure from the first port 11 to the third port 13 and from there to the hydraulic lift drive 35, in the present case a one-way hydraulic cylinder. This state corresponds to the OPEN-drive operation of the lift control valve. In this case, the position of the throttle body 2 via the sensor 10 as an electrical position signal for an electronic control (not shown) can be tapped and is available for a determination of the flowing through the throttle cross-section volume flow hydraulic oil, without requiring a determination of pressure values.

The changeover valve 8 remains in its ON position during the OPEN-DRIVE operation, since the spring chamber 24 on the right-hand side of its piston valve, which is not relieved of pressure in this operating situation, is in fluid communication with the second fluid chamber 6 and third fluid chamber 7 via a throttle point in the piston valve and whose spring compensates for the slight overpressure in the first fluid space 5 with respect to the pressures in the second 6 and third fluid space 7 or in the spring space 24.

If the pilot valve 15 is closed again, the pressure builds up in the control oil chamber 25 of the main valve 14 via the throttle point 16 and the slider 17 of the main valve 14 is returned from the spring 26 in the in Fig. 1 pushed back starting position shown.

For a conversion of the lift control valve in the in Fig. 2 As shown, which shows the lift control valve in the AB drive mode, the slider 17 of the main valve 14, as can be seen, must be brought into a fully deflected position to the right.

However, this is only possible if the first port 11 is depressurized, so this is not connected to a running hydraulic pump 33, otherwise at the latest at a Kolbenschieberprosition in which the circumferential groove 32 with the annulus, in which the first port 11 opens, in Cover device, the spring chamber 27 of the main valve 14 would be pressurized and thereby further deflection to the right of the spool 17 would be hydraulically prevented.

If now the pilot valve 15 is fully opened when the first port 11 is depressurized and the third port 13 is pressurized, then the control oil pressure can push the spool 17 of the main valve 14 into the in-port valve 13 Fig. 2 Move shown position to the right, which lifts the spring-loaded ball, which closes the discharge port 19 fluid-tight, with its actuating pin 29 from its seat. As a result, the first fluid chamber 5 is connected directly via the main valve 14 and the spring chamber 24 of the changeover valve 8 indirectly via the discharge opening 19 and the throttle sleeve 28 with the second port 12 and the tank 34 and thereby relieved of pressure. As a result, the fluid pressure in the second fluid space 6 in conjunction with the axial surfaces of the spool of the switching valve 8, to which it acts, is sufficient to deflect this spool against the spring force to the right. This increases after lifting the piston valve of the switching valve 8 from its seat, the pressure in the first fluid chamber 5, which acts on the end face of the piston valve and then additionally helps to deflect it completely to the right in the position shown. As a result, the first fluid space 5 is connected to the third fluid space 7, while the second fluid space 6 is separated therefrom. By connecting the third fluid chamber 7 with the first fluid chamber 5, the fluid pressure in the second fluid chamber 6, which acts axially only on an annular surface of the throttle body 2, in conjunction with the fluid pressure in the first fluid chamber 5, which extends to the end face of the throttle body. 2 acts to move the throttle body 2 from the home position to the right and thereby open the throttle area 1. As a result, the hydraulic fluid flows from the second fluid chamber 6 via the throttle cross-section 1 in the first fluid chamber 5 and from there via the main valve 14 and the second port 12 in the tank 34. This state corresponds to the AB drive operation of the lift control valve, said Again, as already in the previously described ON-ride operation, the position of the throttle body 2 via the sensor 10 as an electrical position signal for an electronic control (not shown) can be tapped and so for a determination of the now in the reverse direction through the throttle section. 1 flowing volume flow hydraulic oil is available, again without the need for this purpose, a determination of system pressures.

If the pilot valve 15 is closed again, the pressure builds up in the control oil chamber 25 of the main valve 14 via the throttle point 16 and the slider 17 of the main valve 14 is returned from the spring 26 in the in Fig. 1 pushed back starting position shown. As a result, the discharge opening 19 is closed again by the spring-loaded ball and it builds up in the spring chamber 24 of the switching valve 8, a fluid pressure, which causes the spool of the switching valve 8 to the left back into the in Fig. 1 shown position, wherein it connects the second 6 and the third fluid chamber 7 with each other and the first fluid space 5 separates from them. This causes the pressure in the spring chamber 7 of the check valve 22 increases and the throttle body 2 to the left in the normal position shifts, in which this fluid-tight against the valve seat body 9 and the lift control valve again completely in Fig. 1 has shown idle state. In this state rests at the in Fig. 3 illustrated lift system of the piston of the lift drive 35 hydraulically on the check valve 22, the pilot valve 15 and the switching valve. 8

While preferred embodiments of the invention are described in the present application, it should be clearly understood that the invention is not limited to these and may be practiced otherwise within the scope of the following claims.

Claims (22)

1. Lift control valve with an arrangement for providing a variable throttle cross-section for a fluid flow, particularly for a liquid flow, the arrangement comprising
   a throttle arrangement (20) with a throttle cross-section (1) which can be varied by a motion of a throttle body (2),
   an actuation arrangement (21) with an actuation element (4) which is movable inside a casing (3), being coupled to the throttle body (2) of the throttle arrangement in order to vary the throttle cross-section (1) depending on its relative position inside the casing (3), wherein the arrangement is formed such
   that the actuation element (4) is permanently acted upon by a first spring force or can be acted upon by a first spring force which acts upon the actuation element (4) in a first direction of its mobility and positions the actuation element (4) in a base position in the casing (3) in the absence of at least equal forces acting upon the actuation element (4) in a second direction which is opposed to the first direction,
   that as a result of a pressure of a fluid in a first fluid chamber (5) of the arrangement, which is fluid-connected or fluid-connectable to a first side of the throttle cross-section, the actuation element (4) can be acted upon with a second force acting in the second direction,
   that as a result of a pressure of a fluid in a second fluid chamber (6) of the arrangement, which is fluid-connected or fluid-connectable to the second side of the throttle cross-section, the actuation element (4) can be acted upon with a third force acting in the second direction,
   that as a result of a pressure of a fluid in a third fluid chamber (7) of the arrangement, the actuation element (4) can be acted upon with a fourth force acting in the first direction,
   such that the actuation element (4), in case no further forces act upon the actuation element (4) in the first or the second direction and the sum of the second, the third and the fourth force is a resulting force which acts in the second direction and which is higher than the first spring force acting upon the actuation element (4) in the base position in the first direction, is moved away from the base position until a balance of forces between first spring force acting upon the actuation element (4) in its corresponding relative position and the resulting force is reached or a maximum motion position is reached,
   and wherein the arrangement further comprises a switching arrangement (8) by means of which optionally either the first fluid chamber (5) and the third fluid chamber (7) or the second fluid chamber (6) and the third fluid chamber (7) are fluid-connectable,
   wherein the lift control valve has a first connecting port (11) for an inlet line for hydraulic liquid coming from a hydraulic pump, a second connecting port (12) for conducting hydraulic liquid back into a tank and a third connecting port (13) for a hydraulic line leading to a hydraulic actuator of a lift installation as well as a control arrangement (14, 15) adapted such that the first fluid chamber (5) of the arrangement and the first side of the throttle cross-section (1) are fluid-connectable optionally with the first connecting port (11) or with the second connecting port (12), and wherein the second fluid chamber (6) of the arrangement and the second side of the throttle cross-section (1) are connected or are connectable with the third connecting port (13).
2. Lift control valve according to claim 1, wherein the arrangement for providing the variable throttle cross-section is formed in such a way that the throttle cross-section (1) of the throttle arrangement is entirely closed in case the actuation element (4) is arranged in the base position.
3. Lift control valve according to one of the preceding claims, wherein the arrangement for providing the variable throttle cross-section comprises means for determining the opening of the throttle cross-section (1) of the throttle arrangement, the relative position of the actuation element (4) in the casing (3) and/or the relative position of the throttle body (2) of the throttle arrangement, particularly sensors (10), by means of which the relative positions of the actuation element (4) and/or of the throttle body (2) can be converted in electric signals.
4. Lift control valve according to one of the preceding claims, wherein the arrangement for providing the variable throttle cross-section is formed in such a way that the second and the third force are substantially equal in the presence of identical fluid pressures in the first fluid chamber (5) and the second fluid chamber (6).
5. Lift control valve according to one of the preceding claims, wherein the arrangement for providing the variable throttle cross-section is formed in such a way that the second, third and fourth force cancel out in case of identical fluid pressures in the first, second and third fluid chamber (5, 6, 7).
6. Lift control valve according to one of the preceding claims, wherein the arrangement for providing the variable throttle cross-section is formed in such a way that the actuation element (4) has axial surfaces which are each fluid-connected with the first, the second and the third fluid chamber (5, 6, 7) in order to generate the second, the third and the fourth force.
7. Lift control valve according to one of the preceding claims, wherein the arrangement for providing the variable throttle cross-section is formed in such a way that the throttle arrangement is formed as a seat valve.
8. Lift control valve according to one of the preceding claims, wherein the arrangement for providing the variable throttle cross-section is formed in such a way that the actuation element (4) of the actuation arrangement and the throttle body (2) of the throttle arrangement are formed by a common component.
9. Lift control valve according to one of the preceding claims, wherein the lift control valve is formed in such a way that in the intended operation an automatic connection of the second fluid chamber (6) with the third fluid chamber (7) takes place by means of the switching arrangement (8) when the first fluid chamber (5) and the first side of the throttle cross-section are connected with the first connecting port (11) and an automatic connection of the first fluid chamber (5) with the third fluid chamber (7) takes place by means of the switching arrangement (8) when the first fluid chamber (5) and the first side of the throttle cross-section are connected with the second connecting port (12).
10. Lift control valve according to one of the preceding claims, wherein the control arrangement (14), for making it possible to optionally connect the first side of the throttle cross-section (1) with the first connecting port (11) or with the second connecting port (12), has a particularly continuously acting, particularly hydraulically actuated main valve (14), which in particular is executed in a piston slide way.
11. Lift control valve according to one of the preceding claims, wherein a valve (18) is present, which connects the fluid supply to the hydraulic actuator of the main valve (14) with the second connecting port (12) as soon as a certain pressure is reached at the first connecting port (11).
12. Lift control valve according to one of the preceding claims, wherein the lift control valve comprises a pilot valve (15) which can be actuated electrically for the main valve (14) which can be actuated hydraulically, by means of which the hydraulic actuator of the main valve (14) can be optionally fluid-connected with the second side of the throttle cross-section (1) and/or with the second fluid chamber (6) or can be fluid-disconnected therefrom, in order to actuate the main valve (14).
13. Lift control valve according to claim 12, wherein the fluid connection between the pilot valve (15) and the hydraulic actuator of the main valve (14) has a flow restriction (16) leading to the second connecting port (12).
14. Lift control valve according to claim 13, wherein the flow restriction (16) has a throttle cross-section which is changeable depending on the valve position of the main valve (14), particularly in case of a main valve (14) executed as a piston valve depending on the position of the piston (17), which is formed, particularly in case of a main valve (14) executed as a piston valve, between the piston (17) of the main valve (14) and a fixed component of the main valve (14).
15. Lift control valve according to one of the preceding claims, wherein the control arrangement (14, 15) is formed in such a way that in case of hydraulic liquid being under pressure at the first connecting port (11) a connecting of the first side of the throttle cross-section (1) of the throttle arrangement and/or of the first fluid chamber (5) with the second connecting port (12) is not possible.
16. Lift control valve according to one of the preceding claims, wherein the switching arrangement (8) has a switching valve (8) which can be actuated hydraulically, which in the intended operation can be switched by opening or closing, respectively, a pressure release opening (19) and wherein the control arrangement (14, 15) is formed in such a way that it opens the pressure release opening (19) of the switching valve (8) when the first side of the throttle cross-section (1) of the throttle arrangement and/or the first fluid chamber (5) are connected with the second connecting port (12).
17. Lift control valve according to one of the preceding claims, wherein the lift control valve is formed in such a way that the actuation energy required for actuating its hydraulic actuatable valves (8, 14) can be taken from the hydraulic liquid that is present in operation in the lift control valve.
18. Hydraulic lift installation with a lift control valve according to one of the preceding claims, wherein the lift installation has a hydraulic pump (33) which is connected or which can be connected with the first connecting port (11) of the lift control valve, a tank (34) which is connected or which can be connected with the second connecting port (12) of the lift control valve and a hydraulic actuator (35) which is connected or which can be connected with the third connecting port (13) of the lift control valve, particularly a hydraulic cylinder, by means of which a lift of the lift installation can be actuated.
19. Lift installation according to claim 18, wherein the lift control valve is formed with means (10) for determining the opening of the throttle cross-section (1) of the throttle arrangement, the relative position of the actuation element (4) and/or the relative position of the throttle body (2) of the throttle arrangement, and wherein the lift installation further comprises a controller for the driving operation of the lift, which is connected to these means and is adapted such that in operation it can receive information from these means (10) about the opening of the throttle cross-section (1), the relative position of the actuation element (4) and/or the relative position of the throttle body (2) and can consider these information during the controlling or regulating, respectively, of the driving operation of a lift of the lift installation, particularly as a parameter representing the hydraulic liquid flow flowing through the throttle cross-section (1) of the throttle arrangement, and particularly the driving speed of the lift associated thereto.
20. Method for operating a lift installation according to one of the claims 18 to 19, comprising the steps of
    lifting a lift of the lift installation by conveying a volume of hydraulic liquid from the hydraulic pump (33) to the hydraulic actuator (35) of the lift, wherein the hydraulic liquid flows through the throttle cross-section (1) of the throttle arrangement from the first side of the throttle cross-section (1) to the second side of the throttle cross-section (1) and the second fluid chamber (6) and the third fluid chamber (7) are fluid-connected to each other and to the second side of the throttle cross-section (1) whereas the first side of the throttle cross-section (1) is fluid-connected with the first fluid chamber (5);
    or
    lowering a lift of the lift installation by conveying a volume of hydraulic liquid from the hydraulic actuator (33) of the lift into the tank (34), wherein the hydraulic liquid flows through the throttle cross-section (1) of the throttle arrangement from the second side of the throttle cross-section (1) to the first side of the throttle cross-section (1) and the first fluid chamber (5) and the third fluid chamber (7) are fluid-connected to each other and to the first side of the throttle cross-section (1) whereas the second side of the throttle cross-section (1) is fluid-connected with the second fluid chamber (6);
    determining the opening of the throttle cross-section (1) of the throttle arrangement, the relative position of the actuation element (4) of the actuation arrangement and/or the relative position of the throttle body (2) of the throttle arrangement during the conveying of the volume of hydraulic liquid through the throttle cross-section;
    comparing the determined opening of the throttle cross-section (1), the determined relative position of the actuation element (4), the determined relative position of the throttle body (2) of the throttle arrangement and/or a value calculated from one or more of these determined variables with a target value; and
    changing the volume of the hydraulic liquid conveyed through the throttle cross-section (1) in case a deviation from the target value has been observed such that the opening of the throttle cross-section (1), the relative position of the actuation element (4), the relative position of the throttle body (2) and/or the calculated value converges with the target value.
21. Method according to claim 20, wherein during the lifting of the lift the volume of hydraulic liquid conveyed through the throttle cross-section (1) of the throttle arrangement is changed in such a way that a higher or lower part of the volume conveyed by the hydraulic pump (33) is redirected to the tank (34) by means of the controlling entity (14, 15) of the lift control valve.
22. Method according to one of the claims 20 to 21, wherein the volume of hydraulic liquid conveyed through the throttle cross-section (1) is determined by an algorithm solely from the determined opening of the throttle cross-section (1), the determined relative position of the actuation element (4) and/or the determined relative position of the throttle body (2) of the throttle arrangement optionally by additionally considering an also determined temperature value of the hydraulic liquid.

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