EP3894701B1 - Piston pump and method for operating a piston pump - Google Patents

Description

The invention relates to a method for operating a piston pump with a differential cylinder drive with at least two differential cylinders for driving at least two delivery pistons movable in delivery cylinders, wherein each delivery piston is driven via an associated differential cylinder of the differential cylinder drive to operate the piston pump, with a hydraulic circuit for controlling or driving the differential cylinder drive by applying hydraulic fluid.

When conveying concrete, for example, piston pumps are regularly used that have two conveying cylinders, each with a piston. The cylinders draw the pulpy mass to be conveyed in a suction stroke, for example from a filling hopper, and then convey the sucked-in pulpy mass in a pumping stroke into a conveying line connected to the piston pump. The pistons of the two cylinders are operated in opposite directions in order to convey the pulpy mass into the conveying line as evenly as possible. The conveying line of such a pumping device can be considerably long. It is often part of a crane boom and is used to convey the pulpy mass from the location of the pumping device to remote ends of the construction site. The length of the conveying line means that even the smallest interruptions in the flow of the pulpy mass lead to considerable swiveling movements of the conveying line due to the inertia of the mass. Efforts have therefore long been made to develop pumps and processes that allow the pulpy mass to be conveyed continuously.

The US 3,749,525 A discloses a pump designed to convey a material to be conveyed under pressure. For this purpose, the pump has rotary slide valves assigned to each of the conveying cylinders, at which three connection openings can be opened or closed as required. The three connection openings are an inlet opening connected to the conveying cylinder, an outlet opening connected to a conveying line, and a filling opening connected to a filling funnel. The rotary slide valves have at least three switching positions and are switched simultaneously in opposite directions to one another by an actuator. While the filling opening and outlet opening are simultaneously closed by the two rotary slide valves, the continuous conveying flow from the conveying cylinders is interrupted. A pressure drop caused by this is compensated by a compensating cylinder, which ensures continuous conveying in the conveying line even when the conveying pistons in the conveying cylinders periodically change direction. The disadvantages of such a solution are, on the one hand, the complex structure with a third cylinder and the complicated control of the three cylinders in order to maintain continuous conveying in the conveying line.

In the US 3,279,383 A a pump is described with at least two delivery cylinders with delivery pistons movable therein, each delivery cylinder being assigned a rotary slide valve which has a slide housing and a valve member rotatable therein about a rotation axis, the slide housing having at least three connection openings. The three connection openings are an inlet opening which is connected to the delivery cylinder, an outlet opening which is connected to a delivery line, and a filling opening which is connected to a filling funnel. The valve member selectively closes or opens the filling opening or the outlet opening in two switching positions.

By coordinating the movements of the two conveyor pistons moving in the conveyor cylinders, a continuous conveying of the conveyed material in the conveyor line is to be maintained. Since the only two switching positions of the rotary valves do not allow pre-compression of the conveyed material in the conveyor cylinders, when the full conveyor cylinders are opened Before the pumping process, there are interruptions in the flow of the mushy mass, which lead to considerable swivel movements of the delivery line due to the inertia of the mass.

Further efforts to achieve continuous conveying of the material being pumped with a two-cylinder piston pump are in EP 2 387 667 B1 disclosed. Here, each delivery cylinder is assigned an inlet slide and an outlet slide. The solution described here has the advantage that the slides can be opened and closed under optimal pressure conditions. However, a suitable hydraulic circuit for driving the delivery pistons in the delivery cylinders is not described here.

Also the EP 3 282 124 A1 discloses a solution for the continuous conveying of material to be conveyed in a two-cylinder piston pump. Here, each delivery cylinder is assigned an inlet slide valve and an outlet slide valve is provided that can be switched to three positions, whereby in a middle position simultaneous conveying via the two delivery pistons into the delivery cylinder is possible.

The US 5 458 470 A discloses a pumping device comprising two cylindrical pumping chambers which alternately receive and discharge material to be pumped, the reception being via openings of a common feed chamber and the discharge via a discharge line which moves to an opening of the pumping chamber which is to deliver. Pumping is carried out by hydraulically actuated pumping pistons in the pumping chambers, a hydraulic circuit being designed such that the pumping piston in the pumping chamber which receives the material reaches a fully charged position before the discharging pumping chamber reaches a fully discharged position.

Out of EN 10 2015 103 180 A1 A two-cylinder piston pump is known which has a switching device which sets a piston-side or rod-side operating mode of the two-cylinder piston pump by switching the hydraulic oil flow to chambers of differential cylinders. The switching device is here attached to the bottoms of the piston-side chambers of the Differential cylinders arranged as a bridge-forming connection between the differential cylinders.

The EP 0 167 635 A1 describes an open hydraulic circuit with an automatic sequence for the control of concrete pumps with two pumping cylinders and two cylinders controlling a diverter valve that alternately connects the pumping cylinders to a delivery line and a hopper, and hydraulic valves to control the cylinders. In this circuit, the hydraulic valves are controlled by auxiliary hydraulic valves that act as relays controlled directly by the flow that supplies the hydraulic cylinders that operate the pump, the auxiliary hydraulic valves being activated only when the end position of the stroke is reached.

The EN 10 2004 009 362 A1 relates to a method for operating a slurry pump, wherein each pumping stroke of a piston comprises at least one pre-compression phase, a first synchronous phase, a pumping phase and a second synchronous phase.

The EN 10 2005 024174 A1 discloses a method for controlling a pumping device for conveying mushy masses, wherein the reduction of a safety pressure of a hydraulic pump for pre-compression, switching of the slide system, high compression to the current delivery pressure and opening of the gate valve can be carried out in a time-fixed manner.

A hydraulic circuit for switching a differential cylinder drive to drive the delivery pistons in the delivery cylinders of a piston pump is shown in EP 0 808 422 B1 proposed. The differential cylinders of the differential cylinder drive disclosed here drive the delivery pistons that are movable in the delivery cylinders of the piston pump when the piston pump is in pumping operation. For this purpose, the differential cylinders are supplied with a hydraulic fluid flow from a main hydraulic pump by the proposed hydraulic circuit. The main hydraulic pump drives the differential cylinders when the material to be delivered is sucked into the delivery cylinders and when it is ejected. of sucked-in material from the delivery cylinders. In addition, the proposed hydraulic circuit provides a further hydraulic pump, which supplies the differential cylinders with hydraulic fluid via the hydraulic circuit during pre-compression of material to be conveyed in the delivery cylinders. The disadvantage of the solution described here is that the pressure of the main hydraulic pump exceeds the pressure of the auxiliary hydraulic pump. In this way, sufficient pre-compression cannot take place in the delivery cylinders of the piston pump, since the lower pressure of the auxiliary hydraulic pump is not sufficient to achieve pre-compression of the conveyed material in the delivery cylinders, which prevents the conveyed material from sinking back out of the delivery line due to the further compression of the conveyed material in the delivery cylinder and the vibrations caused by this when switching to the pumping process for ejecting the conveyed material from the delivery cylinder. In addition, the delivery pistons of the delivery cylinders can only be switched abruptly to eject sucked-in material using the proposed two-way valve on the drive lines between the main hydraulic pump and the differential cylinders of the differential cylinder drive. The abrupt loading of the differential cylinders of the differential cylinder drive by the main hydraulic pump causes further vibrations in the delivery line. In one embodiment, it is also proposed to drive the differential cylinders of the differential cylinder drive via separate hydraulic pumps. However, the timing of the switching of the control valves and the drive power of the two separate hydraulic pumps is particularly difficult here. Continuous conveying of material with a piston pump is therefore not possible with the hydraulic circuits for the differential cylinder drive proposed here.

It is therefore the object of the invention to provide an improved method for operating a piston pump with a differential cylinder drive controlled by a hydraulic circuit, which enables simple, error-free and uniform, ie continuous, delivery. In addition, a simplified piston pump is to be created which offers continuous delivery of conveyed material with counter-rotating delivery pistons in the delivery cylinders.

• Ansaugung von zu förderndem Gut mittels eines ersten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders und gleichzeitiges Ausstoßen von zu förderndem Gut mittels eines zweiten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders,
• Vorkomprimierung des angesaugten Gutes mittels des ersten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders und gleichzeitiges Ausstoßen des Gutes mittels des zweiten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders,
• Ausstoßen des vorkomprimierten Gutes mittels des ersten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders und gleichzeitige Ansaugung von zu förderndem Gut mittels des zweiten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders, und
• Ausstoßen des Gutes mittels des ersten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders und gleichzeitige Vorkomprimierung des angesaugten Gutes mittels des zweiten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders. Dieses Verfahren bietet eine einfache, fehlerunanfällige und gleichmäßige, d.h. kontinuierliche Förderung von Fördergut.

This object is achieved by a method for operating a piston pump with the features of claim 1. According to the invention, the method comprises the following cyclically executed steps:

• Suction of material to be conveyed by means of a first conveying cylinder by driving the associated differential cylinder and simultaneous ejection of material to be conveyed by means of a second conveying cylinder by driving the associated differential cylinder,
• Pre-compression of the sucked-in material by means of the first conveyor cylinder by driving the associated differential cylinder and simultaneous ejection of the material by means of the second conveyor cylinder by driving the associated differential cylinder,
• Ejection of the pre-compressed material by means of the first conveyor cylinder by driving the associated differential cylinder and simultaneous suction of material to be conveyed by means of the second conveyor cylinder by driving the associated differential cylinder, and
• Ejection of the material by means of the first conveyor cylinder by driving the associated differential cylinder and simultaneous pre-compression of the sucked-in material by means of the second conveyor cylinder by driving the associated differential cylinder. This method offers a simple, error-free and uniform, ie continuous, conveyance of material.

The invention relates to the fact that the pre-compression is divided into at least two phases, wherein in a first phase the hydraulic circuit effects the pre-compression of the sucked-in material in the delivery cylinder with a first delivery piston speed by applying the hydraulic fluid to the associated differential cylinder at a first volume flow and a first pressure, and in a second, subsequent phase the hydraulic circuit effects the pre-compression of the sucked-in material in the delivery cylinder with a second delivery piston speed that is lower than the first delivery piston speed by applying the hydraulic fluid to the associated differential cylinder at a second volume flow that is lower than the first volume flow and a second pressure that is higher than the first pressure. Because the pre-compression is divided into at least two phases, wherein in a In a first phase, the hydraulic circuit causes the pre-compression of the sucked-in material in the delivery cylinder at a first delivery piston speed by applying the hydraulic fluid to the associated differential cylinder at a first volume flow and a first pressure, and in a second, subsequent phase, the hydraulic circuit causes the pre-compression of the sucked-in material in the delivery cylinder at a second delivery piston speed that is lower than the first delivery piston speed by applying the hydraulic fluid to the associated differential cylinder at a second volume flow that is lower than the first volume flow and a second pressure that is higher than the first pressure, continuous delivery that is improved compared to the prior art can be achieved.

Advantageous embodiments and further developments of the invention emerge from the dependent claims. It should be noted that the features listed individually in the claims can also be combined with one another in any technologically reasonable manner and thus show further embodiments of the invention.

In the first phase of pre-compression, large quantities of hydraulic fluid are generally required to pre-compress the conveyed material in the conveying cylinders. In particular, if the filling level of the conveying cylinder is low at the end of the suction, i.e. the suctioning conveying cylinder is filled with air as well as thick material, the time period provided for pre-compression and the available hydraulic pressure are often not sufficient to carry out the pre-compression in such a way that the pre-compressed material is subjected to the same pressure as the conveyed material in the discharging conveying cylinder. Pressure fluctuations in the conveying line caused by this prevent continuous conveying. This is where the invention comes in, in that in the first phase of pre-compression the hydraulic circuit applies a first volume flow and a first pressure to the differential cylinders. At the start of pre-compression, only the air sucked in in the conveying cylinder usually needs to be compressed. For the first phase of pre-compression, a low hydraulic pressure is therefore sufficient, but this may require a longer piston travel, i.e. a larger volume of hydraulic fluid must also be provided for this first phase of pre-compression. When the first phase of pre-compression is complete, the pressure of the material being conveyed in the delivery cylinders must still be raised to the pressure level in the delivery line. To do this, in the second phase of pre-compression, the differential cylinders are driven by the hydraulic circuit via the assigned differential cylinder at a second delivery piston speed that is lower than the first delivery piston speed. For this, a second volume flow that is lower than the first volume flow and a second pressure that is higher than the first pressure are used. This pre-compression, which is divided into two phases, ultimately makes it possible to achieve continuous delivery of material, effectively reducing the sagging of material in the delivery line and thus vibrations in the delivery line. This is particularly due to the lower first pressure in the first phase, which is applied to the assigned differential cylinder by the hydraulic circuit at the start of pre-compression. This can prevent the delivery piston in the delivery cylinder from hitting the material that has been compressed too quickly with too high a pressure and too high a delivery piston speed. The transition between the first phase of pre-compression and the second phase of pre-compression can be continuous to further reduce vibrations in the conveyor line.

A particularly advantageous embodiment is one in which the hydraulic circuit has at least one main hydraulic source, in particular at least one main hydraulic pump, for driving, i.e. for supplying the differential cylinders with hydraulic fluid, whereby the associated differential cylinder is supplied with equal pressure via the hydraulic circuit from the main hydraulic source, in particular from the main hydraulic pump, for pre-compressing the sucked-in material in one delivery cylinder and the associated differential cylinder is supplied with equal pressure via the hydraulic circuit for simultaneously ejecting the material from the other delivery cylinder. Due to the fact that the associated differential cylinder is supplied with equal pressure via the hydraulic circuit for pre-compressing the sucked-in material in one delivery cylinder and the associated differential cylinder is supplied with equal pressure via the hydraulic circuit for simultaneously ejecting the material from the other delivery cylinder are subjected to equal pressure by the main hydraulic pump, a piston pump can be operated for the continuous conveyance of conveyed material. By simultaneously applying the same pressure provided by the main hydraulic pump to the differential cylinders in the ejection direction (for pre-compression or for ejecting material), it is particularly easy to adjust the pressure levels in the delivery cylinders during pre-compression. Applying equal pressure from the same pressure source ensures that the pressure conditions in the delivery cylinder are easily adjusted to the pressure conditions in the delivery line during pre-compression. By adjusting the pressure conditions, a continuous conveyance of conveyed material can be achieved very easily using a two-cylinder piston pump, which effectively prevents the material from sinking back in the delivery line and thus vibrations in the delivery line.

According to an advantageous embodiment of the invention, after the pre-compression of the sucked-in material by means of a feed cylinder by driving the associated differential cylinder via the hydraulic circuit, the material is ejected simultaneously by means of the first and second feed cylinders by parallel driving of the associated differential cylinders, before the material to be conveyed is sucked in again by means of a feed cylinder by driving the associated differential cylinder via the hydraulic circuit. The parallel driving of the associated differential cylinders enables simultaneous ejection of material to be conveyed via both feed pistons of the piston pump. With the parallel conveying from both feed cylinders, a smooth transition can be set up when transferring the flow generated by the piston pump in the feed line between the two feed cylinders.

A particularly advantageous embodiment of the invention relates to the hydraulic circuit comprising at least one main hydraulic source, in particular a main hydraulic pump, for driving the differential cylinders, in particular for supplying the differential cylinders with the hydraulic fluid, when the material to be conveyed is sucked into the conveying cylinders by the conveying pistons and the sucked material is expelled from the conveying cylinders by the Delivery piston, and an additional hydraulic source, in particular an additional hydraulic pump, for driving the differential cylinders during pre-compression of material to be conveyed in the delivery cylinders between the suction of material to be conveyed and the ejection of pre-compressed material. In order not to branch off too much hydraulic fluid volume from the main hydraulic source in this first phase and thereby cause delivery pressure fluctuations in the delivery line, the connection of the additional hydraulic source is proposed. For this purpose, a hydraulic source that has a sufficient delivery volume is basically sufficient. The oil pressure provided by the additional hydraulic source, on the other hand, does not have to be too high, in particular it does not have to reach the high pressure of the ejecting delivery cylinder. In the hydraulic circuit provided, an additional hydraulic source is provided for this purpose, which, at least in the first phase of pre-compression, together with the main hydraulic source, drives the differential cylinders to compress the material to be conveyed in the delivery cylinders. The first phase of pre-compression is completed when the additional hydraulic source no longer contributes to increasing the pressure level in the delivery cylinder. The main hydraulic source can provide the hydraulic pressure required for this without causing a drop in the hydraulic pressure at the associated differential cylinder of the delivery cylinder that is simultaneously delivering, because the amount of oil required in this second phase is only small. Because in this second phase of pre-compression only the main hydraulic source acts on the differential cylinders of the differential cylinder drive to drive the delivery pistons in the delivery cylinders, the pressure level during pre-compression in one delivery cylinder can be easily adjusted to the pressure level of the delivery cylinder that is already delivering and thus to the pressure level in the delivery line.

According to an advantageous embodiment of the invention, it is provided that the pre-compression is divided into at least two phases, wherein in a first phase the additional hydraulic source, in particular the additional hydraulic pump, and the main hydraulic source, in particular the main hydraulic pump, pre-compress the sucked-in material in the relevant conveyor cylinder by driving the associated differential cylinder and, in a second, subsequent phase, only the main hydraulic source, in particular only the main hydraulic pump, causes the pre-compression of the sucked-in material in the conveyor cylinder by driving the differential cylinder. In the first phase of pre-compression, large quantities of hydraulic fluid are generally required to pre-compress the material to be conveyed in the conveyor cylinders. In particular, if the filling level of the conveyor cylinder at the end of the suction is low, i.e. the suctioning conveyor cylinder is filled with air as well as thick material, the time period provided for pre-compression and the available hydraulic pressure are often not sufficient to carry out the pre-compression in such a way that the pre-compressed material is subjected to the same pressure as the material to be conveyed in the discharging conveyor cylinder. Pressure fluctuations in the conveyor line caused by this prevent continuous conveying. This is where the invention comes in. In the first pre-compression phase, the hydraulic circuit supplies the differential cylinders with hydraulic fluid via the main hydraulic pump and an additional hydraulic pump. At the start of pre-compression, only the air sucked in in the delivery cylinder usually needs to be compressed. For the first pre-compression phase, a low hydraulic pressure is therefore sufficient, but this may require a longer piston travel, which means that a larger volume of hydraulic fluid must also be provided for this first pre-compression phase. This pre-compression, which is divided into two phases, makes it very easy to achieve continuous delivery of material using a two-cylinder piston pump, effectively preventing material from sinking back in the delivery line and thus vibrations in the delivery line.

A particularly advantageous embodiment of the invention relates to the fact that by applying equal pressure through the main hydraulic source, in particular through the main hydraulic pump, at the end of the second phase of pre-compression, an equal pressure is established in the differential cylinders before the hydraulic circuit begins to eject pre-compressed material from the conveyor cylinder that has completed the pre-compression. By setting equal pressure at the end of the second During the pre-compression phase, pressure conditions can be generated in the conveyor cylinders which prevent the material from settling in the conveyor line and thus prevent vibrations in the conveyor line at the beginning of the discharge of the pre-compressed material.

A particularly advantageous embodiment of the invention provides that the differential cylinders are each additionally acted upon by the additional hydraulic source, in particular by the additional hydraulic pump, to drive the delivery pistons from the hydraulic circuit during suction in order to accelerate the suction of material to be conveyed into the delivery cylinders. By accelerating the suction by the additional hydraulic source or the additional hydraulic pump, the suction process of the delivery pistons can take place faster than the pumping process, so that the time for the pre-compression of the material to be conveyed in the delivery cylinders and preferably also the time for the parallel conveying by both delivery cylinders can be balanced out. By using the additional hydraulic source, in particular the additional hydraulic pump, during pre-compression and during suction, the additional hydraulic source, preferably a hydraulic pump, can be used for two different tasks at the same time, so that only one unit, preferably an additional pump, is required for the accelerated suction and the improved pre-compression.

An advantageous embodiment of the invention provides that the additional loading of the differential cylinders to accelerate the suction of material to be conveyed into the delivery cylinders from the additional hydraulic source, in particular from the additional hydraulic pump, takes place on the rod-side effective surfaces of differential pistons of the differential cylinders, wherein the rod sides of the differential pistons are connected via a rocker line, which is connected from the hydraulic circuit to the additional hydraulic source, in particular to the additional hydraulic pump, for the purpose of applying hydraulic fluid. By loading the differential cylinders on the rod-side effective surfaces of the differential pistons, an additional acceleration during the suction by the additional hydraulic source, in particular by the additional hydraulic pump, can be achieved very easily. To this end, the additional hydraulic source, in particular the Auxiliary hydraulic pump, advantageously the rocker line which connects the rod sides of the differential pistons.

A particularly advantageous embodiment is one in which the differential cylinders for driving the delivery pistons are acted upon by the hydraulic circuit from the main hydraulic source, in particular from the main hydraulic pump, on the piston-side effective surfaces of the differential pistons when material to be conveyed is ejected from the delivery cylinders. When the differential pistons are acted upon by hydraulic fluid on the rod side to accelerate the suction by the additional hydraulic source, in particular by the additional hydraulic pump, it is particularly advantageous if the differential cylinders for driving the delivery pistons are acted upon by the main hydraulic source, in particular from the main hydraulic pump, on the piston-side effective surfaces of the differential pistons when material to be conveyed is ejected from the delivery cylinders. By applying pressure to the differential pistons on both sides via the main hydraulic source, in particular via the main hydraulic pump, and the additional hydraulic source, in particular the additional hydraulic pump, which feeds additional hydraulic fluid into the rocking line, the suction of the material to be conveyed can be accelerated simply and effectively. In addition to the rocking fluid from the rod side of one differential cylinder, the rod side of the other differential cylinder is supplied with additional hydraulic fluid from the additional hydraulic source, in particular from the additional hydraulic pump. This makes it easy to achieve a particularly effective acceleration of the suction process.

An advantageous embodiment provides that the additional hydraulic source, in particular the additional hydraulic pump, provides a higher volume flow of hydraulic fluid, but a lower pressure compared to the main hydraulic source, in particular the main hydraulic pump, via the hydraulic circuit for driving the differential cylinders during the first phase of pre-compression. The higher volume flow of hydraulic fluid that the additional hydraulic source, in particular the additional hydraulic pump, provides for driving the differential cylinders during the first phase of pre-compression enables a rapid Compression of the material being conveyed in the conveying cylinders can be achieved even at low filling levels without the conveying pressure in the conveying line collapsing.

According to a preferred embodiment of the invention, a check valve in the hydraulic circuit closes as soon as a pressure is present during pre-compression that is higher than the pressure provided by the auxiliary hydraulic source, in particular by the auxiliary hydraulic pump, wherein the closing of the check valve represents the transition from the first phase of pre-compression to the second phase of pre-compression. By closing the check valve in the hydraulic circuit, the first phase of pre-compression can be completed in a simple manner by the auxiliary hydraulic source, in particular the auxiliary hydraulic pump, ceasing to drive the differential cylinders of the differential cylinder drive for pre-compression. As soon as a pressure is present at the check valve during pre-compression that is higher than the pressure provided by the auxiliary hydraulic source, in particular by the auxiliary hydraulic pump, the check valve closes and the pre-compression is completed by the main hydraulic source, in particular by the main hydraulic pump, in the second phase.

A particularly advantageous embodiment is one in which the additional hydraulic source, in particular the additional hydraulic pump, presses open the check valve during the loading of the differential cylinders in the first phase of pre-compression. By pressing open the check valve in the first phase of pre-compression, the additional hydraulic source, in particular the additional hydraulic pump, can very easily make its contribution to driving the differential cylinders during pre-compression.

A particularly advantageous embodiment of the invention provides that drive lines between the differential cylinders and the main hydraulic source, in particular the main hydraulic pump, can be controlled via proportional valves, whereby the proportional valves are closed at the end of the In the second phase of pre-compression, after equal pressure has been reached in the differential cylinders, the valves are slowly opened to expel pre-compressed material from the conveying cylinders and slowly closed after the material to be conveyed has been expelled from the conveying cylinders. By slowly opening the proportional valves, a particularly smooth transition between pre-compression and expulsion of the pre-compressed material can be achieved. The slow closing of the proportional valves also ensures that a smooth transition to the suction process is guaranteed after the pumping process has ended.

According to an advantageous embodiment of the invention, it is provided that the differential cylinders for pre-compressing material to be conveyed in the delivery cylinders by the delivery pistons are acted upon by the hydraulic circuit through the additional hydraulic source, in particular by the additional hydraulic pump, via a check valve of the hydraulic circuit and at the same time by the main hydraulic source, in particular by the main hydraulic pump, via a flow control valve of the hydraulic circuit. By actuating the differential cylinders via the check valve, it can be ensured that the additional hydraulic source, in particular the additional hydraulic pump, provides additional hydraulic fluid for the rapid piston movement in the first phase of pre-compression. Actuating the differential cylinders from the main hydraulic source, in particular from the main hydraulic pump, via the flow control valve ensures that only a defined volume flow from the main hydraulic source, in particular from the main hydraulic pump, is used for pre-compression. With the volume flow limited by the flow control valve, pre-compression to the pressure level in the delivery line can be achieved without significant pressure fluctuations occurring in the delivery line due to the pre-compression via the main hydraulic source, in particular via the main hydraulic pump. This makes it easy to raise the pressure level in the delivery cylinders to the pressure level in the delivery line by pre-compressing the material being conveyed. This effectively prevents the material being conveyed from sinking back in the delivery line, thereby preventing vibrations in the delivery line.

A particularly preferred embodiment provides that during the pre-compression of material to be conveyed in one conveying cylinder, the other conveying cylinder is driven via the associated differential cylinder to eject material to be conveyed, this differential cylinder being supplied with hydraulic fluid from the hydraulic circuit through the main hydraulic source, in particular through the main hydraulic pump, the hydraulic circuit supplying the differential cylinder with hydraulic fluid from the main hydraulic source, in particular from the main hydraulic pump, via a drive line branching off in front of the flow control valve. The associated differential cylinder can be driven by the main hydraulic source, in particular from the main hydraulic pump, when ejecting material to be conveyed from the conveying cylinder via the drive line branching off in front of the flow control valve, without the branching off of hydraulic fluid from the drive line leading to significant fluctuations in the delivery pressure when the material to be conveyed is ejected into the delivery line.

A particularly advantageous embodiment of the invention relates to the fact that, in order to simultaneously eject material to be conveyed from the conveying cylinders, the associated differential cylinders are supplied with hydraulic fluid in parallel via separate drive lines from the main hydraulic source, in particular from the main hydraulic pump, bypassing the flow control valve from the hydraulic circuit. By supplying the associated differential cylinders via separate drive lines, a simultaneous ejection of material to be conveyed from the conveying cylinders can be achieved by simultaneously driving the differential cylinders via the main hydraulic source, in particular via the main hydraulic pump. By bypassing the flow control valve, the drive power of the main hydraulic source, in particular the main hydraulic pump, can be easily divided by the hydraulic circuit between the differential cylinders driven in parallel.

Furthermore, the invention relates to a piston pump with the features of claim 10.

The design of the piston pump according to the invention relates to the hydraulic circuit being designed to effect, in a first phase, a pre-compression of the sucked-in material in a delivery cylinder with a first delivery piston speed by applying the hydraulic fluid to the associated differential cylinder at a first volume flow and a first pressure, and, in a second, subsequent phase, a pre-compression of the sucked-in material in the delivery cylinder with a second delivery piston speed that is lower than the first delivery piston speed by applying the hydraulic fluid to the associated differential cylinder at a second volume flow that is lower than the first volume flow and a second pressure that is higher than the first pressure.

A preferred embodiment of the piston pump relates to the hydraulic circuit having at least one main hydraulic source, in particular a main hydraulic pump, for driving the differential cylinders, wherein the differential cylinders can be supplied with hydraulic fluid at equal pressure from the hydraulic circuit at least at times simultaneously by the one main hydraulic source, in particular by the one main hydraulic pump, for driving the delivery pistons. By supplying the assigned differential cylinders with the same pressure provided by the main hydraulic pump, it is particularly easy to adjust the pressure levels in the delivery cylinders during pre-compression, as explained above. The supply of equal pressure from the same pressure source ensures that the pressure conditions in the delivery cylinder are easily adjusted to the pressure conditions in the delivery line during pre-compression. By adjusting the pressure conditions, the piston pump can easily and effectively deliver material continuously. which effectively prevents the material being conveyed from sinking back into the conveying line and thus vibrations in the conveying line.

• eine Haupthydraulikquelle, insbesondere eine Haupthydraulikpumpe, zum Antrieb der Differentialzylinder bei Ansaugung von zu förderndem Gut in die Förderzylinder und Ausstoßen von angesaugtem Gut aus den Förderzylindern, und
• eine Zusatzhydraulikquelle, insbesondere eine Zusatzhydraulikpumpe, zum Antrieb der Differentialzylinder bei einer Vorkomprimierung von zu förderndem Gut in den Förderzylindern vor Ausstoßen von vorkomprimiertem Gut. Die Erfindung schlägt vor, dass jeder der Differentialzylinder zumindest zeitweise zur Vorkomprimierung in dem zugeordneten Förderzylinder gleichzeitig von der Haupthydraulikquelle, insbesondere von der Haupthydraulikpumpe, und der Zusatzhydraulikquelle, insbesondere der Zusatzhydraulikpumpe, von der Hydraulikschaltung mit dem Hydraulikfluid beaufschlagbar ist.

A particularly preferred embodiment of the piston pump relates to the hydraulic circuit comprising at least:

• a main hydraulic source, in particular a main hydraulic pump, for driving the differential cylinders when sucking material to be conveyed into the conveying cylinders and ejecting sucked material from the conveying cylinders, and
• an additional hydraulic source, in particular an additional hydraulic pump, for driving the differential cylinders during a pre-compression of material to be conveyed in the conveying cylinders before ejecting pre-compressed material. The invention proposes that each of the differential cylinders can be supplied with hydraulic fluid from the main hydraulic source, in particular from the main hydraulic pump, and the additional hydraulic source, in particular the additional hydraulic pump, from the hydraulic circuit at least temporarily for pre-compression in the associated conveying cylinder.

Figur 1

erfindungsgemäße Hydraulikschaltung,

Figuren 2 bis 7

Hydraulikschaltung in verschiedenen Schaltstellungen und

Figur 8

Druckbegrenzungsschaltung für Zusatzhydraulikpumpe.

Further features, details and advantages of the invention will become apparent from the following description and from the drawings which show embodiments of the invention. Corresponding objects or elements are provided with the same reference numerals in all figures. They show:

Figure 1

hydraulic circuit according to the invention,

Figures 2 to 7

Hydraulic circuit in different switching positions and

Figure 8

Pressure relief circuit for auxiliary hydraulic pump.

In the Figure 1 Denoted by the reference number 1, a differential cylinder drive 1 with a hydraulic circuit 4 for operating a piston pump according to the invention is shown. The differential cylinder drive 1 comprises at least two differential cylinders 2, 3 for driving at least two delivery pistons of a piston pump that are movable in delivery cylinders. Each of the delivery pistons is driven via an associated differential cylinder 2, 3 of the differential cylinder drive 1 to operate the piston pump. The piston pump comprises the hydraulic circuit 4 for switching the differential cylinder drive 1. The hydraulic circuit 4 has at least one main hydraulic source 5, which is preferably designed as a main hydraulic pump 5, for driving the differential cylinders 2, 3 when material to be delivered is sucked into the delivery cylinders by the delivery pistons. The main hydraulic source 5 can, as indicated in the figures, be designed as a main hydraulic pump 5. Alternatively, the main hydraulic source 5 can also be designed as a hydraulic accumulator, which is preferably charged by a hydraulic pump. The ejection of sucked material from the delivery cylinders by the delivery pistons also takes place by driving the differential cylinders 2, 3 via the main hydraulic pump 5. The hydraulic circuit 4 also has an additional hydraulic source 6, which is preferably designed as an additional hydraulic pump 6, for driving the differential cylinders 2, 3 during a pre-compression of material to be delivered in the delivery cylinders by the delivery pistons. The additional hydraulic source 6 can, as indicated in the figures, be designed as an additional hydraulic pump 6. Alternatively, the additional hydraulic source 6 can also be designed as a hydraulic accumulator, which is preferably charged by the main hydraulic pump 5 and/or another hydraulic pump. In a particularly preferred embodiment, a hydraulic pump charges the main hydraulic source 5 designed as a hydraulic accumulator and the additional hydraulic source 6 designed as a hydraulic accumulator. The pre-compression advantageously takes place between the suction of the material to be conveyed into the conveying cylinders and the ejection of the pre-compressed material from the conveying cylinders and ensures that the material to be conveyed is continuously conveyed by the piston pump. The additional hydraulic pump 6 can also actuate the differential cylinders 2, 3 to drive the conveying pistons in order to accelerate the suction of the material to be conveyed into the conveying cylinders. By actuating the differential cylinders 2, 3 to accelerate the suction, the additional hydraulic pump 6 can shorten the suction via the hydraulic circuit 4. The hydraulic circuit 4 shown has two proportional valves. 12, 13, via which the drive lines 15, 16 between the differential cylinders 2, 3 and the main hydraulic pump 5 can be regulated. By using proportional valves 12, 13, the differential cylinders 2, 3 can be slowly pressurized with hydraulic pressure to eject pre-compressed material from the conveyor cylinders. To do this, the proportional valves are slowly opened. After the material to be conveyed has been ejected from the conveyor cylinders, the proportional valves 12, 13 can also be slowly closed to achieve a smooth transition between ejection and suction. To accelerate the pre-compression, the auxiliary hydraulic pump 6 can pressurize the differential cylinders 2, 3 with hydraulic pressure via two rapid motion valves 17, 18. Two check valves 10, 11 are each pressed open by the auxiliary hydraulic pump 6. These check valves 10, 11 of the hydraulic circuit 4 close as soon as a pressure is present during pre-compression that is higher than the pressure provided by the additional hydraulic pump 6. The hydraulic circuit 4 also has two return valves 19, 20, via which the pressure-free return flow of hydraulic fluid into a tank 21 can be released or blocked. In addition to the drive lines 15, 16 with the proportional valves 12, 13, the hydraulic circuit 4 has a branch 22 in which a flow control valve 14 is arranged. Via two creep speed valves 23, 24, the hydraulic flow of the main hydraulic pump 5, which is limited by the flow control valve 14, can be applied to the differential cylinders 2, 3 of the differential cylinder drive 1, bypassing the proportional valves 12, 13 in the drive lines 15, 16. The rocking line 9, which connects the rod sides of the differential pistons 7, 8 in the differential cylinders 2, 3, can be supplied with hydraulic fluid by the additional hydraulic pump 6 via a rocking oil inlet valve 25. This additional rocking oil can also be drained towards the tank 21 via a rocking oil drain valve 26. The hydraulic circuit 4 also preferably has two pressure gauges 26, 27, which measure the pressure in the drive lines 15, 16 in front of the differential cylinders 2, 3 of the differential cylinder drive 1. For emergency operation, the hydraulic circuit 4 also has two sensors 29, 20 or initiators on the stop of the differential pistons 7, 8 in the differential cylinders 2, 3. Furthermore the hydraulic circuit 4 preferably has a position measuring system 31, 32 for each of the two differential cylinders 2, 3.

• Ansaugung von zu förderndem Gut mittels eines ersten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders 2, 3 und gleichzeitiges Ausstoßen von zu förderndem Gut mittels eines zweiten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders 2, 3,
• Vorkomprimierung des angesaugten Gutes mittels des ersten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders 2, 3 und gleichzeitiges Ausstoßen des Gutes mittels des zweiten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders 2, 3,
• Ausstoßen des Gutes mittels des ersten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders 2, 3 und gleichzeitige Ansaugung von zu förderndem Gut mittels des zweiten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders 2, 3,
• Ausstoßen des Gutes mittels des ersten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders 2, 3 und gleichzeitige Vorkomprimierung des angesaugten Gutes mittels des zweiten Förderzylinders durch Antrieb des zugeordneten Differentialzylinders 2, 3,

um eine kontinuierliche Förderung von Fördergut durch die Kolbenpumpe zu erreichen. Nach der Vorkomprimierung des angesaugten Gutes mittels eines Förderzylinders durch Antrieb des jeweils zugeordneten Differentialzylinders 2, 3 über die Hydraulikschaltung 4 kann zudem ein Ausstoßen des Gutes mittels des ersten und des zweiten Förderzylinders gleichzeitig durch parallelen Antrieb der zugeordneten Differentialzylinder 2, 3 erfolgen, bevor wieder eine Ansaugung von zu förderndem Gut mittels eines Förderzylinders durch Antrieb des jeweils zugeordneten Differentialzylinders 2, 3 über die Hydraulikschaltung 4 begonnen wird. Die zum Betrieb der Kolbenpumpe hierzu erforderlichen Ventilstellungen in der Hydraulikschaltung 4 werden anhand der Figuren 2-7 erläutert, welche die Hydraulikschaltung 4 gemäß Figur 1 bei den einzelnen Schritten zeigen.With the hydraulic circuit 4 shown, the piston pump can be driven via the differential cylinder drive 1 in the following cyclic steps:

• Suction of material to be conveyed by means of a first conveying cylinder by driving the associated differential cylinder 2, 3 and simultaneous ejection of material to be conveyed by means of a second conveying cylinder by driving the associated differential cylinder 2, 3,
• Pre-compression of the sucked-in material by means of the first conveyor cylinder by driving the associated differential cylinder 2, 3 and simultaneous ejection of the material by means of the second conveyor cylinder by driving the associated differential cylinder 2, 3,
• Ejection of the material by means of the first conveyor cylinder by driving the associated differential cylinder 2, 3 and simultaneous suction of material to be conveyed by means of the second conveyor cylinder by driving the associated differential cylinder 2, 3,
• Ejection of the material by means of the first conveyor cylinder by driving the associated differential cylinder 2, 3 and simultaneous pre-compression of the sucked material by means of the second conveyor cylinder by driving the associated differential cylinder 2, 3,

in order to achieve a continuous conveying of conveyed material by the piston pump. After the pre-compression of the sucked material by means of a conveying cylinder by driving the respective associated differential cylinder 2, 3 via the hydraulic circuit 4, the material can also be ejected by means of the first and second conveying cylinders simultaneously by parallel driving of the associated differential cylinders 2, 3, before the suction of material to be conveyed by means of a conveying cylinder by driving the respective associated differential cylinder 2, 3 via the hydraulic circuit 4 is started again. The valve positions in the hydraulic circuit 4 required for operating the piston pump are determined using the Figures 2-7 which the hydraulic circuit 4 according to Figure 1 show the individual steps.

In the Figure 2 The switching positions of the valves in the hydraulic circuit 4 shown ensure that the material to be conveyed is sucked in by means of a first delivery cylinder by driving the left differential cylinder 2 and that the material to be conveyed is simultaneously ejected by means of a second delivery cylinder by driving the right differential cylinder 3. In the switching positions shown here, the main hydraulic pump 5 supplies the right differential cylinder 3 on the piston side with hydraulic fluid in order to drive the associated delivery cylinder of the piston pump for ejecting the material to be conveyed from the delivery cylinder. For this purpose, the right proportional valve 13 in the right drive line 16 is opened and the piston-side active surfaces of the right differential piston 8 are thereby acted upon by the main hydraulic pump 5. The left differential piston 7 is additionally acted upon by the auxiliary hydraulic pump 6 via the open rocking oil inlet valve 25 in order to accelerate the suction of the material to be conveyed. This additionally accelerates the delivery piston, which is driven by the left differential cylinder 2, when the material to be delivered is sucked in. By supplying the rod-side chamber in the differential cylinders 2, 3 with additional rocking oil, the piston 7 of the left differential cylinder 2 moves back more quickly during the suction process. The hydraulic fluid displaced from the piston side of the differential cylinder 2 can simply flow out towards the tank 21 via the open left return valve 19.

The Figure 3 shows the switching positions of the valves in the hydraulic circuit 4 in a subsequent step. Here, the left differential cylinder 2 is driven to pre-compress the sucked-in material by means of the first delivery cylinder, while at the same time the right differential cylinder 3 continues to be driven to expel the material to be conveyed by means of the second delivery cylinder. In the first phase of pre-compression shown here, the left differential cylinder 2 is driven by the auxiliary hydraulic pump 6 and the main hydraulic pump 5, i.e. it is supplied with hydraulic fluid. The left differential cylinder 2 is supplied to pre-compress material to be conveyed in the first delivery cylinder by the hydraulic circuit 4 through the auxiliary hydraulic pump 6 via a check valve 10 of the hydraulic circuit 4 and at the same time by the main hydraulic pump 5 via a flow control valve 14 of the hydraulic circuit 4. In this first phase of During pre-compression, the auxiliary hydraulic pump 6 provides a higher volume flow of hydraulic fluid at a lower pressure than the main hydraulic pump 5 via the hydraulic circuit 4 to drive the left differential cylinder 2. The auxiliary hydraulic pump 6 presses the left check valve 10 open as long as the pressure during pre-compression is lower than the pressure provided by the auxiliary hydraulic pump 6. During pre-compression of material to be conveyed in the delivery cylinder, the left differential cylinder 2 is therefore pressurized by the auxiliary hydraulic pump 6 via the check valve 10 by the hydraulic circuit 4 and at the same time is driven with hydraulic fluid by the main hydraulic pump 5 via a flow control valve 14 of the hydraulic circuit 4. For this purpose, the left creep speed valve 23 is open, while the right creep speed valve 24 is closed. The oil from the auxiliary hydraulic pump 6 overcomes the check valve 10 as long as the pre-compression pressure is still low and the oil pressure of the auxiliary hydraulic pump 6 at the check valve 10 is greater than the pressure from the main hydraulic pump 5 in the left differential cylinder 2 that builds up during pre-compression. This accelerates the pre-compression and the pre-compression can be completed before the right differential cylinder 3 reaches the stop when material to be conveyed is ejected from the associated delivery cylinder. In this phase, the flow control valve 14 ensures that only a constant minimum amount of hydraulic fluid from the main hydraulic pump 5 is used for pre-compression by the left differential cylinder 2. This means that the drop in pressure of the hydraulic fluid and thus the drop in delivery quantity for the right cylinder 3, which is still delivering, are minimal if the main hydraulic pump 5 contributes to the pre-compression at the same time. During pre-compression, the main hydraulic pump 5 could also be adjusted using a control algorithm. The amount of hydraulic fluid withdrawn from the main hydraulic pump 5 for pre-compression can also be adjusted at the main hydraulic pump 5. The flow control valve 14 preferably contains a pressure compensator so that the pressure difference Δp across the flow control valve 14 always remains constant. Therefore, the amount flowing through the flow control valve 14 always remains constant, regardless of the level of pressure upstream and downstream of the flow control valve 14. The Excess rocking oil is drained to the tank 21 via the open rocking oil drain valve 26. In order to be able to precisely meter the drain of the excess rocking oil, the rocking oil drain valve 26 is preferably designed as a proportional valve.

The Figure 4 shows the switching positions of the valves in the hydraulic circuit 4 in a subsequent step. Here, the left differential cylinder 2 continues to be driven to pre-compress the sucked-in material using the first delivery cylinder, while at the same time the right differential cylinder 3 is also driven to expel the material being conveyed using the second delivery cylinder. In the second phase of pre-compression shown here, the left differential cylinder 2 is only driven by the main hydraulic pump 5. The left check valve 10 in the hydraulic circuit 4 closes because the pressure generated during pre-compression is higher than the pressure provided by the auxiliary hydraulic pump 6. The auxiliary hydraulic pump 6 no longer contributes to pre-compression in this phase because its hydraulic pressure would not be sufficient anyway. This represents the transition from the first phase of pre-compression to the second phase of pre-compression. The main hydraulic pump 5 now continues to increase the pressure in the piston-side chamber of the left differential cylinder 2 on its own, while it also continues to supply the right pumping differential cylinder 3. During the second phase of pre-compression of the sucked-in material in one of the conveyor cylinders, the left differential cylinder 2 and the right differential cylinder 3 are pressurized with equal pressure via the hydraulic circuit 4 from the main hydraulic pump 5 for simultaneous ejection of the material from the other conveyor cylinder. At the end of this second phase of pre-compression, this results in equal pressure in the two differential cylinders 2, 3. At the end of the pre-compression, this equal pressure is determined by measuring the pressure with the pressure gauges 27, 28, so that the transition to the next phase can take place in the next step. At the same time, the pre-compression pressure also reaches the delivery line pressure of the concrete, which is why an outlet slide on the conveyor cylinder can be switched more easily when the pressure is equal on its inlet and outlet sides. The excess rocking oil in this phase is drained to tank 21 via the open rocking oil drain valve 26.

The Figure 5 shows the switching positions of the valves in the hydraulic circuit 4 in a subsequent step. Here, the left proportional valve 12 in the left drive line 15 is slowly opened in order to realize a particularly smooth transition between pre-compression and ejection of the pre-compressed conveyed material via the left differential cylinder 2. At the same time, the right proportional valve 13 in the right drive line 16 is slowly closed so that the right differential cylinder 3 can slowly end the pumping process. In this phase, the material is ejected by means of the first and second conveying cylinders simultaneously by parallel driving of the right 3 and the left differential cylinder 2. The excess rocking oil in this phase is drained to the tank 21 via the open rocking oil drain valve 26.

The Figure 6 shows the switching positions of the valves in the hydraulic circuit 4 in a subsequent step. Here, the right differential cylinder 3 has reached the stop, which is detected by the position measuring system 32 and alternatively by the sensor 30. The right proportional valve 13 in the drive line 16 of the right differential cylinder 3 now closes, while the left proportional valve 12 in the drive line 15 of the left differential cylinder 2 is fully open. From now on, the left differential cylinder 2 takes over the pumping process and the conveying of material to be conveyed into the conveying line alone and the right differential cylinder 3 goes over to drive the suction process for the assigned conveying cylinder.

The Figure 7 shows the switching positions of the valves in the hydraulic circuit 4 in a subsequent step. The switching positions of the valves in the hydraulic circuit 4 shown here ensure that the material to be conveyed is ejected by means of the first conveying cylinder by driving the left differential cylinder 2 and that the material to be conveyed is simultaneously sucked in by means of the second conveying cylinder by driving the right differential cylinder 3. In the switching positions shown here, the main hydraulic pump 5 supplies the left differential cylinder 2 on the piston side with hydraulic fluid in order to drive the associated conveying cylinder of the piston pump for the ejection of the material to be conveyed from the conveying cylinder. For this purpose, the left proportional valve 12 in the left drive line 15 is opened and the piston-side effective area of the left differential piston 7 is pressurized by the main hydraulic pump 5. The right differential piston 8 is additionally pressurized by the auxiliary hydraulic pump 6 via the opened rocking oil inlet valve 25 to accelerate the suction of the material to be conveyed. This additionally accelerates the delivery piston, which is driven by the right differential cylinder 3, when the material to be conveyed is sucked in. By supplying the rod-side chamber in the differential cylinders 2, 3 with additional rocking oil, the piston 8 of the right differential cylinder 3 moves back more quickly during the suction process. The hydraulic fluid displaced from the piston side of the differential cylinder 3 can simply flow out in the direction of the tank 21 via the open right return valve 20. After the material to be conveyed has been sucked in by the second delivery cylinder by driving the right differential cylinder 3, pre-compression then takes place in the second delivery cylinder in a similar way via the hydraulic circuit 4.

With Figure 8 a simple pressure limiting circuit 33 for auxiliary hydraulic pump 6 is disclosed. The pressure limiting circuit 33 shown here has a pressure limiting valve 34, which is followed by a pilot valve 35 for high pressure. A pilot valve 37 for low pressure can be used via a switch 36 to limit the hydraulic pressure of the auxiliary hydraulic pump 6 and to divert excess hydraulic fluid towards the tank 21. The pressure limiting circuit 33 shown here also has a hydraulic accumulator 38, which is followed by a pressure limiter 39.

List of reference symbols

1

Differential cylinder drive

2

Differential cylinder L

3

Differential cylinder R

4

Hydraulic circuit

5

Main hydraulic pump (A), main hydraulic source

6

Auxiliary hydraulic pump (B), auxiliary hydraulic source

7

Differential piston L

8th

Differential piston R

9

Swing line

10

Check valve L (m)

11

Check valve R (n)

12

Proportional valve L (a)

13

Proportional valve R (b)

14

Flow control valve (I)

15

Drive cable L

16

Drive line R

17

Rapid motion valve L (c)

18

Rapid motion valve R (d)

19

Return valve L (e)

20

Return valve R (f)

21

tank

22

Junction

23

Slow speed valve L (g)

24

Slow speed valve R (h)

25

Swing oil inlet valve (i)

26

Swing oil drain valve (k)

27

Pressure gauge L (o)

28

Pressure gauge R (p)

29

Sensor L (q)

30

Sensor R (r)

31

Position measuring system L (s)

32

Position measuring system R (t)

33

Pressure limiting circuit

34

Pressure relief valve

35

Pilot valve (high pressure)

36

Switching

37

Pilot valve (low pressure)

38

Hydraulic accumulator

39

Pressure limitation

Claims (13)

1. Method for operating a piston pump with a differential cylinder drive (1) with at least two differential cylinders (2, 3) for driving at least two conveying pistons movable in conveying cylinders, wherein each conveying piston is driven via an associated differential cylinder (2, 3) of the differential cylinder drive (1), with a hydraulic circuit (4) for controlling the differential cylinder drive (1) and / or for driving the differential cylinder drive (1) by applying hydraulic fluid, comprising the following cycling steps:

   - suctioning of goods to be conveyed using a first conveying cylinder by driving the associated differential cylinder (2, 3) and simultaneously ejecting the material to be conveyed by means of a second conveying cylinder by driving the associated differential cylinder (2, 3),

   - pre-compression of the suctioned material by means of the first conveying cylinder by driving the associated differential cylinder (2, 3) and simultaneous ejection of the material by means of the second conveying cylinder by driving the associated differential cylinder (2, 3),

   - ejecting the material by means of the first conveying cylinder by driving the associated differential cylinder (2, 3) and simultaneously suctioning of material to be conveyed by means of the second conveying cylinder by driving the associated differential cylinder (2, 3),

   - ejecting the material by means of the first conveying cylinder by driving the associated differential cylinder (2, 3) and simultaneous pre-compression of the suctioned material by means of the second conveying cylinder by driving the associated differential cylinder (2, 3),

   characterized in that
   the pre-compression is divided into at least two phases, wherein in a first phase the hydraulic switch (4) effects the pre-compression of the suctioned-in material in the conveying cylinder (2, 3) with the hydraulic fluid in a first mass flow and a first pressure and in a second, subsequent phase, the hydraulic switch (4) effects the pre-compression of the suctioned-in material in the conveying cylinder with a second conveying cylinder speed reduced relative to the first conveying cylinder speed by applying the associated differential cylinder (2, 3) with the hydraulic fluid in a second volume flow rate reduced relative to the first volume flow rate, and a second pressure higher with respect to the first pressure.
2. Method according to claim 1, characterized in that the hydraulic circuit (4) comprises at least one main hydraulic source (5), in particular at least one main hydraulic pump (5), for driving, i.e. for application of the differential cylinders (2, 3) with hydraulic fluid, wherein for pre-compression of the suctioned material in the one conveying cylinder, the associated differential cylinder (2, 4) and for simultaneous ejection of the material from the other conveying cylinder, the associated differential cylinder (2, 3) are applied with a constant pressure from the main hydraulic source (5), in particular by the main hydraulic pump (5), via the hydraulic circuit (4).
3. Method according to one of the preceding claims, characterized in that after the pre-compression of the suctioned-in material by means of a conveying cylinder by driving the respectively associated differential cylinder (2, 3) via the hydraulic circuit (4) the material is ejected by means of the first and second conveyor cylinders simultaneously by parallelly driving the associated differential cylinders (2, 3), before the material to be conveyed is suctioned-in again by means of a conveying cylinder by driving of the respectively associated differential cylinder (2, 3) via the hydraulic circuit (4).
4. Method according to one of the preceding claims, characterized in that the hydraulic circuit (4) has at least one main hydraulic source (5), in particular a main hydraulic pump (5), for driving the differential cylinders (2, 3), in particular for applying the differential cylinders (2, 3) with the hydraulic fluid, when material to be conveyed is suctioned into the conveying cylinders by the conveying pistons and the suctioned-in material is ejected from the conveying cylinders by the conveying pistons, and an auxiliary hydraulic source (6), in particular an auxiliary hydraulic pump (6), for driving the differential cylinders (2, 3 ) when the material to be conveyed is pre-compressed in the conveying cylinders, the time between suctioning the material to be conveyed and the ejection of the pre-compressed material occurs.
5. Method according to claim 4, characterized in that the pre-compression is divided into at least two phases, wherein in a first phase the auxiliary hydraulic source (6), in particular the auxiliary hydraulic pump (6), and the main hydraulic source (5), in particular the main hydraulic pump (5), a pre-compression of the suctioned-in material in the relevant conveying cylinder by driving the associated differential cylinder (2, 3) and in a second, subsequent phase only the main hydraulic source (5), in particular only the main hydraulic pump (5), cause the pre-compression of the suctioned-in material in the conveying cylinder by driving the differential cylinder (2, 3).
6. Method according to claim 1 or 5, characterized in that by applying constant pressure by means of the main hydraulic source (5), in particular by means of the main hydraulic pump (5), a constant pressure is established in the differential cylinders (2, 3) at the end of the second phase of precompression, before starting to eject pre-compressed material from the conveying cylinder that has completed the pre-compression.
7. Method according to one of claims 4 to 6, characterized in that the differential cylinders (2, 3) for accelerating the suction of material to be conveyed are additionally applied upon by the additional hydraulic source (6), in particular by the additional hydraulic pump (6), for driving the conveying pistons via the hydraulic circuit (4) during suction.
8. Method according to one of claims 4 to 7, characterized in that a check valve (10, 11) in the hydraulic circuit (4) closes as soon as a pressure of the hydraulic fluid is present during precompression which is higher than that of the additional hydraulic source (6), in particular the pressure provided by the additional hydraulic pump (6), the closing of the check valve (10, 11) representing the transition from the first phase of pre-compression to the second phase of pre-compression.
9. Method according to claim 8, characterized in that the auxiliary hydraulic source (6), in particular the auxiliary hydraulic pump (6), presses open the check valve (10, 11) during the application of the differential cylinders (2, 3) in the first phase of pre-compression.
10. Piston pump with a differential cylinder drive (1) with at least two differential cylinders (2, 3) for driving at least two conveying pistons of the piston pump that are movable in conveying cylinders, wherein each conveying piston is driven via an associated differential cylinder (2, 3) of the differential cylinder drive (1) for operating the piston pump, with a hydraulic circuit (4) for controlling the differential cylinder drive and/or for driving the differential cylinder drive (1) by applying hydraulic fluid,
    characterized in that
    the hydraulic circuit (4) is configured to effect a pre-compression of the suctioned material in one conveying cylinder with a first conveying cylinder speed by application of the associated differential cylinder (2,3) with the hydraulic fluid at a first volume flow and a first pressure and in a second, subsequent phase, to effect a precompression of the suctioned material in the conveying cylinder with a second conveying cylinder speed reduced with respect to the first conveying cylinder speed by applying the associated differential cylinder (2, 3) with the hydraulic fluid with a second volume flow reduced compared to the first volume flow and a second pressure higher compared to the first pressure.
11. Method according to claim 10, characterized in that the hydraulic circuit (4) has at least one main hydraulic source (5), in particular a main hydraulic pump (5), for driving the differential cylinders (2, 3), wherein the differential cylinders (2, 3) can be applied with hydraulic fluid by the hydraulic circuit (4) from the one main hydraulic source (5) in particular from the one main hydraulic pump (5) under constant pressure for driving the conveying pistons.
12. Method according to claim 10 or 11, characterized in that the hydraulic circuit (4) at least comprises:

    - a main hydraulic source (5), in particular a main hydraulic pump (5), for driving the differential cylinders (2, 3) when the material to be conveyed is suctioned into the conveyor cylinders and for ejecting the suctioned-in material from the conveyor cylinders, and

    - an additional hydraulic source (6), in particular an additional hydraulic pump (6), for driving the differential cylinders (2, 3) when the material to be conveyed is pre-compressed in the conveying cylinders before the pre-compressed material is ejected, and

    wherein each of the differential cylinders (2, 3) can at least temporarily be applied with the hydraulic fluid by the hydraulic circuit (4) for pre-compression in the associated conveying cylinder, simultaneously by the main hydraulic source (5), in particular the main hydraulic pump (5) and the auxiliary hydraulic source (6), in particular the auxiliar hydraulic pump (6).
13. Piston pump according to one of claims 10 to 12, characterized in that the piston pump is set up to perform the method according to one of claims 1 to 9.

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