EP0668441B1 - Drive control for a two-cylinder pump for viscous fluid - Google Patents

Abstract

The drive control is for a two-cylinder, high density medium pump. It has pre-control valves (66,67) which are mechanical, 2-position valves which are lockable in the switched position (I) via the pressure actuation of a control chamber (76,77). The release of pressure from the chamber is achieved via a flow pad (79,78) located on the pre-control valve, which is released in the function/switched position (I) of the valve. Both valves are operated by an axial sliding rod (71,72).

Description

The invention relates to a device for controlling the drive of a two-cylinder thick matter pump, the pump pistons of which can be driven by means of a drive cylinder for filling and delivery strokes, which are hydraulically connected in series, and with the further pumps mentioned in the preamble of claim 1. generic characteristics.

Such a device for drive control is known in connection with a concrete pump from DE 38 14 824 A1.

In the known drive control device, a hydraulically controllable changeover valve is provided for the cyclical control of the filling and delivery strokes carried out alternately by the two delivery cylinders, which changeover valve can be switched between alternative functional positions 0 and I by alternately acting with control pressure and pressure relief, in which the piston in each case one of the drive cylinders executes the working strokes corresponding to the filling stroke of the conveying cylinder driven by the latter and the pistons of the other drive cylinder perform the working strokes corresponding to the conveying stroke of the conveying cylinder driven thereby.

To pressurize the control chambers of the changeover valve in this regard, two pressure-controlled pilot valves are provided which alternately emit a control pressure pulse to one of the two control chambers of the main changeover valve whenever the piston moves one of the two drive cylinders into its end of the filling stroke of the feed cylinder driven by it or the end positions corresponding to the end of the delivery stroke of this delivery cylinder. The level of these control pressure pulses is determined by the pressure difference that can be tapped in the respective end position of the drive cylinder piston between the bottom-side and the rod-side drive pressure space of the respective drive cylinder as soon as and as long as the drive cylinder piston assumes a position between radial pressure-sensing bores, one of which in each case must be run over by the piston. So that the changeover valve between the successively generated changeover pressure pulses remains in its switching position 0 or I provided for the respective operating phase of the thick matter pump, a latching device is provided, the holding force of which must be overcome by the control pressure pulses being applied to the control chambers.

The known drive control device has at least the following disadvantages due to its construction and the function resulting from it:

If the thick matter pump is operated at a relatively low drive pressure level, which is the case if the pumped medium is relatively low-viscosity and / or only slight differences in height have to be overcome, e.g. When pumping liquid screed or mortar, with the result that the pressure difference between the bottom and rod-side drive pressure chamber of the respective drive cylinder remains correspondingly low, switching errors can occur, the avoidance of which requires additional technical effort, e.g. monitoring of the piston positions using electrical limit switches is required.

A further disadvantage is that in order to detect the pressure difference between its bottom-side and its rod-side drive pressure chamber in the two possible end positions of the piston of the drive cylinder which is used for stroke monitoring, it is necessary that the drive piston must pass over a radial housing bore , which inevitably leads to wear of the piston seals, which can only be kept fairly low by using expensive and expensive piston seals in order to achieve acceptable service life of the drive cylinder. Nevertheless, relatively frequent replacements of piston seals consisting of resistant and relatively hard material are required, which requires additional work and undesirable downtimes of the pump.

In addition, such, relatively hard seals, compared to so-called soft seals, have a poorer sealing effect, with the result that the volume of the rocking oil between the drive pressure spaces of the two drive cylinders, which are in constant communication with one another through the hydraulic connection in series, is relative can change significantly, mainly by a transfer of hydraulic oil from the rod-side drive pressure chambers of the two drive cylinders, which are under higher pressure during operation, into their bottom-side drive pressure chambers, so that accordingly a readjustment of the optimal rocking oil volume or additional effort for an automatic volume correction is required.

It is therefore the object of the invention to improve a device of the type mentioned at the beginning which is suitable for driving control of a thick matter pump in such a way that with the same simple construction an increased functional reliability of the thick matter pump is achieved and the need for maintenance work is significantly reduced.

This object is achieved by the characterizing features of claim 1.

According to this, the pilot valves provided for controlling the changeover valve are as by the piston (s) At least one of the two hydraulic drive cylinders, which can be actuated mechanically against the restoring force developed by a restoring element and which pushes the respective pilot valve into its basic position, is designed to be hydraulically locked in the switching position assumed by the mechanical actuation by the drive cylinder piston by pressurizing a control chamber.

In addition to the hydraulic locking mechanism, a mechanical latching device that supports its function and is effective with moderate holding force can be provided, which provides a force-locking fixation of the hydraulically locked switching position.

This mechanically, as it were, positively controlled and therefore independent of the operating pressure that occurs, reliable switching of the pilot valves and thus switching of the switching pressure mediating the drive pressure supply of the two hydraulic drive cylinders is achieved, thus ensuring extensive protection against incorrect switching. Since it is not necessary to sense the pressure difference between the respective rod-side drive pressure chamber and the bottom-side drive pressure chamber of the respective drive cylinder, and consequently there are no orifices of radial housing channels to be run over by the piston seals, seals made of relatively soft material can be used as piston seals without further ado, which increases the height Sealing effect can unfold, so that an increased functional reliability of the thick matter pump is achieved as a whole, since corrections to the rocking oil volume are required less frequently and also the periods of time after which the piston seals have to be replaced are significantly increased.

The hydraulic locking and unlocking of the pilot valves is achieved in a simple manner in that the pressurization of the control chamber of the pilot valve to be locked in each case takes place via a flow path released in the basic position of the other pilot valve, via which the output pressure of the pressure supply unit into the control chamber of the valve to be locked can be coupled in, and that the pressure relief of the control chamber of the pilot valve, in the basic position of which the control chamber of the pilot valve to be locked is acted upon by control pressure, takes place via a flow path of the pilot valve to be locked or locked, which is released by the mechanical actuation of this pilot valve.

In the construction of the pilot valves and the way in which they are actuated, which are indicated by the features of claim 2, these can be mounted in a position favorable for assembly outside the housing of the drive cylinder (s) on the floor and / or the rod-side end wall of the cylinder housing.

If the two pilot valves are each mounted on the outside of the bottom of the respective drive cylinder, they can, as proposed according to claim 4, also with the changeover valve and / or an ON / OFF switching valve provided for initiating and ending the conveying operation of the thick matter pump to form a control valve block be summarized, which can be attached to the two drive cylinders as a pre-assembled unit. The same applies mutatis mutandis, albeit with the restriction of a reduced installation space for an arrangement of such a control valve unit on the end face of the drive cylinder at which the piston rods emerge from the cylinder housing.

As an alternative to this, the arrangement of both control valves on a drive cylinder indicated by the features of claim 5 can also be expedient, e.g. when the pump is mounted on a vehicle and the hydraulic control elements are to be accessible from a vehicle side.

In combination with the simplest possible and functionally reliable design of the changeover valve specified by the features of claim 6, the hydraulic functional coupling of the pilot valves provided according to claim 7 is particularly simple and expedient.

In combination with the alternative design of the changeover valve according to the feature of claim 8 with two control chambers, which allows the use of a return spring with a relatively low preload and spring rate for selecting the starting position of the changeover valve, the hydraulic function coupling of the pilot valves provided according to claim 9 is particularly suitable.

Simple pilot valves designed as 3/2-way valves of the same type are suitable for both applications.

An ON / OFF switching valve designed according to claim 11 is suitable both as a manually controlled valve and also as an electrically controllable valve for integration into a control valve unit comprising the pilot valves and the changeover valve.

The same applies mutatis mutandis to a compensating valve arrangement outlined by the features of claim 12, the function according to, by the features of claims 13 and 14 in structural and hydraulic-circuit details, by means of which the setting in a simple manner - by manual operation - during operation of the thick matter pump the optimal rocking oil volume is possible.

A pressure relief valve which is generally expedient for safety reasons and hydraulically connected in parallel with the pressure supply pump can also be used for feeding rocking oil as required. which is carried out in such a way that a maximum amount of rocking oil is fed into the hydraulically connected drive pressure chambers of the drive cylinders, so that the pistons of both drive cylinders reach their end positions associated therewith and then one of the two drive cylinders is subjected to drive pressure in such a way that the portion absorbed by it the rocking oil is pushed back through the pressure relief valve into the reservoir of the pressure supply unit.

Also starting from a device for controlling the drive of a two-cylinder thick matter pump according to the preamble of patent claim 16, in which the pressure supply unit also takes over the function of the changeover valve and is in turn provided with an actuating device, the activation of which with the pressure output signals of the pilot valves determines the direction of delivery Pressure supply unit for one or other drive cylinder of the thick matter pump can be determined, the object on which the invention is based, is achieved by the combination of features corresponding to the characterizing features of patent claim 1. In a corresponding modification of this drive control, a single-acting hydraulic cylinder can also be used as an actuating device for the reversing pump provided as the operating pressure source.

Fig. 1

eine mit einer erfindungsgemäßen Einrichtung zur Antriebssteuerung betreibbare Zweizylinder-Dickstoffpumpe in schematisch vereinfachter Draufsicht, teilweise im Schnitt längs einer die zentralen Achsen ihrer Antriebs- und Förderzylinder enthaltenden Längsmittelebene und

Fig. 2 und 2a

das Hydraulikschaltbild des hydraulischen Antriebs-und Steuerteils der Dickstoffpumpe gemäß Fig. 1 in verschiedenen Konfigurationen der Funktionsstellungen von Steuerventilen und Antriebskolben, zur Erläuterung der Funktion der Einrichtung zur Antriebssteuerung der Dickstoffpumpe gemäß Fig. 1 und

Fig. 3

das Hydraulikschaltbild des hydraulischen Antriebs- und Steuerteils eines weiteren Ausführungsbeispiels, bei dem als Druckversorgungsaggregat eine in zwei alternativen Förderrichtungen betreibbare Verstellpumpe vorgesehen ist, deren Förderrichtungen mittels eines hydraulisch ansteuerbaren Stellzylinders einstellbar sind.

The invention is described below in the drawing illustrated embodiments explained both in terms of the basic idea and in terms of structural and functional details. Show it:

Fig. 1

a two-cylinder thick matter pump operable with a device for drive control according to the invention in a schematically simplified plan view, partly in section along a longitudinal central plane and containing the central axes of its drive and delivery cylinders

2 and 2a

The hydraulic circuit diagram of the hydraulic drive and control part of the thick matter pump according to FIG. 1 in different configurations of the functional positions of control valves and drive pistons, to explain the function of the device for driving control of the thick matter pump according to FIG. 1 and

Fig. 3

the hydraulic circuit diagram of the hydraulic drive and control part of a further exemplary embodiment, in which a variable-displacement pump operable in two alternative delivery directions is provided as the pressure supply unit, the delivery directions of which can be set by means of a hydraulically controllable actuating cylinder.

The thick matter pump, designated overall by 10 in FIG. 1, is a piston pump with two linear delivery cylinders 11 and 12 are formed, for the drive two hydraulic drive cylinders 13 and 14 designed as double-acting differential cylinders are provided, the pistons 16 and 17 of which are rigidly connected via pistons 18 and 19 to the pistons 21 and 22 of the feed cylinders 11 and 12, each individually .

The conveying cylinders 11 and 12 of the thick matter pump 10 can be driven by means of the hydraulic drive cylinders 13 and 14 in such a "push-pull" manner that their pistons 21 and 22 alternately carry out filling and conveying strokes, through which the material to be conveyed from a material feed container (not shown) For example, concrete - taken into the pump chambers 23 and 24 of the delivery cylinders 11 and 12 and displaced from them into a single delivery line 26, which, for example, uses a pipe switch 27, only indicated schematically, in time with the delivery strokes with the pump chambers 23 and 24 of the two delivery cylinders 11 and 12 comes into communicating connection. A slide element which mediates the communicating connection of its pump chamber 23 or 24 with the material feed container during the filling stroke of the respective delivery cylinder 11 or 12 and which shuts off this connection again during the delivery stroke of the respective delivery cylinder 11 or 12, and the pipe switch 27, which in turn communicates with the delivery line 26 mediated with each of the pump chamber 23 or 24 of the delivery cylinder 11 or 12 whose piston 21 or 22 executes the delivery stroke can be driven together, for example by means of another not shown, double-acting drive cylinder. The two delivery cylinders 11 and 12 can also be designed in the manner of piston pumps, which are each provided with an inlet and an outlet check valve, which can be designed as ball or plate check valves.

Between the feed cylinders 11 and 12 and their drive cylinders 13 and 14, which are arranged with their parallel central longitudinal axes 28 and 29 directly next to each other, there is a water box 31 through which free sections 18 'and 19' of the piston rods pass, within which there is Conveyed material, which may have passed due to unavoidable leaks in the pistons 21 and 22 of the delivery cylinders 11 and 12 into the space of the delivery cylinders 11 and 12 penetrated by the piston rods 18 and 19, can settle and, if it got caught on the piston rods 18 and 19 should be, by their movements within the water contained in the water tank 31 can be rinsed, thereby reliably avoiding that material to be conveyed into the rod-side drive chambers 32 and 33 of the drive cylinders 13 and 14 can be "dragged". This water box 31 also lubricates the pistons and cools both the drive cylinders 13 and 14 and the feed cylinders 11 and 12.

For the drive control of the drive cylinders 13 and 14 of the thick matter pump 10, one is only in FIG. 1 2, to which reference is now also made, provided with a hydraulic control unit, designated overall by 34, which, in the sense of a sequential control, automatically a periodically changing connection of the rod-side drive chambers 32 and 33 of the drive cylinders 13 and 14 to the high pressure outlet 36 of a pressure supply pump 37 and its pressureless reservoir 38, such that while one rod-side drive chamber 32 or 33 of the respective drive cylinder 13 or 14 is exposed to the high output pressure of the pressure supply pump 37, the rod-side drive chamber 33 or 32 of the other Drive cylinder 14 or 13 to the unpressurized reservoir 38 of the pressure supply unit is depressurized.

The bottom-side drive chambers 39 and 41 are permanently connected to one another by a pressure line 42, the orifices 43 and 44, via which the pressure line 42 opens into the bottom-side drive chambers 39 and 41 of the two drive cylinders 13 and 14, in the immediate vicinity of the respective cylinder base 46 and 47 or are arranged on the cylinder base itself and cannot be run over by the pistons 16 and 17 of the two drive cylinders 13 and 14 when they enter their end positions on the base side.

This hydraulic connection between the two drive cylinders 13 and 14, these are hydraulically connected in series, so that a single changeover valve 48 is sufficient for drive control of both drive cylinders 13 and 14.

This changeover valve 48, via which in the conveying operation of the thick matter pump 10, which essentially consists of the two drive cylinders 13 and 14 existing hydraulic power circuit, is formed in the illustrated embodiment as a pressure-controlled 4/2-way valve, which by filling alternately and in time - and delivery strokes of the delivery cylinders 11 and 12 and their drive cylinders 13 and 14 alternating pressurization and discharge of two control chambers 49 and 51 can be switched between its possible functional positions 0 and I; In one of these functional positions, which is also used as the basic position 0 for the start-up operation of the thick matter pump 10, the changeover valve 48 is pushed by a valve spring 52, which is only able to develop a relatively weak (return) actuating force, which is greater than that from an action the one, as shown in FIG. 2, left control chamber 51 of the changeover valve 48 with the output pressure of the pump 37 resulting actuating force, by means of which the changeover valve 48 can be switched into its functional position I, is small, but is sufficient in amount to the changeover valve in the functional position Hold 0 as long as the two control chambers 49 and 51 are depressurized or pressurized with the same control pressure, the one resulting from the application of pressure to the other right control chamber 49 of the changeover valve 48 with the outlet pressure the actuating force resulting from the pressure supply pump 37, which forces the changeover valve 48 into its functional position 0, corresponds approximately to the actuating force resulting from the pressurization of the left control chamber 51 and is therefore also large compared to that of the valve spring 52.

To secure the changeover valve 48 against disengagement from its respective assumed functional position 0 or I in the event of a pressure drop in the control chamber 51 or 49 acted upon by control pressure, latching devices (not shown) can be provided which act in a force-locking manner and develop a moderate holding force which corresponds only to part of the maximum restoring force of the restoring spring 52.

In the basic position 0 of the changeover valve 48, the drive pressure which can be provided at the high pressure outlet 36 of the pressure supply pump 37 is via a flow path 56, which is released in this basic position 0 and connects the P supply connection 53 of the changeover valve 48 to its B output 54 and a B output 54 of the Changeover valve 48 with the rod-side drive chamber 32 of the pressure medium line 57 connecting according to FIG. 2 right drive cylinder 13 can be coupled into the rod-side drive chamber 32 of the drive cylinder 13 and at the same time the rod-side drive chamber 33 of the left drive cylinder 14 according to FIG. 2 via a second pressure medium line 58 and one A-outlet 59 of the changeover valve 48 with its flow path 62 connecting its unpressurized T connection 61 to the unpressurized reservoir 38 of the pressure supply pump 37 relieved of pressure.

This functional position 0 of the changeover valve 48, which is also its spring-centered basic position, is assigned to the operating state of the thick matter pump 10 in which one, "right" drive cylinder 13 executes its intake stroke and thus the one delivery cylinder 11 performs its filling stroke, while the piston 17 accordingly Fig. 2 left drive cylinder 14 its outward stroke and thus the movement-coupled piston of the other delivery cylinder 12 executes its delivery stroke.

In switch position I, which the changeover valve 48 assumes when its left control chamber 51, as shown in FIG. 2, is exposed to the high output pressure of the pressure supply pump 37 and its right control chamber 49 is depressurized, the rod-side is via a flow path 63 of the changeover valve 48 that is released in this functional position I. The drive chamber 33 of the left drive cylinder 14 can be acted upon by the high output pressure of the pressure supply pump 37, while the rod-side drive chamber 32 of the right drive cylinder 13 is relieved of pressure via the further flow path 64 released in this functional position I of the changeover valve. This functional position I of the changeover valve 48 is that operating state of the thick matter pump 10 assigned, in which the "left" drive cylinder 14 executes its pull-in stroke and the feed cylinder 12 driven by it carries out its filling stroke, while the right drive cylinder 13 executes its outward stroke and the feed cylinder 11 driven by the right drive cylinder 13 performs its feed stroke.

For the hydraulic actuation of the switching valve 48 by means of alternative pressurization and relief of its control chambers 49 and 51, two pilot valves 66 and 67, each assigned to the latter and to the two drive cylinders 13 and 14, are provided, which can be actuated mechanically by the pistons 16 and 17 of the two drive cylinders, ie from a spring-centered basic position 0 against the restoring force of a valve spring 68 or 69 can be switched to a switching position I and hydraulically locked in this switching position I. In addition to the hydraulic locking mechanism, a mechanical latching device that supports its function and is effective with moderate holding force can be provided, which provides a force-locking fixation of the hydraulically locked switching position. In the exemplary embodiment according to FIGS. 1 and 2, these pilot valves 66 and 67 are mounted on the outside on the cylinder bottoms 46 and 47 of the drive cylinders 13 and 14 and are provided with actuating plungers 71 and 72 projecting axially into the bottom-side drive pressure spaces 39 and 41 of the drive cylinders 13 and 14 provided, which can be displaced in a pressure-tight manner through central bores 73 and 74 of the respective cylinder base 46 and 47 step through. The switching of the respective pilot valve 66 and 67 from its basic position 0 to its switching position thus takes place when the piston 16 or 17 of the right drive cylinder 13 or the left drive cylinder 14 approaches its end position on the bottom, in this case striking the valve actuating plunger 71 or 72 and axially displaces this for the switching actuation of the respective pilot valve 66 or 67, the end position being reached as soon as the respective pilot valve has switched and has thereby switched the switching valve for reversing the movement of the drive cylinder pistons 16 and 17.

The respective pilot valve 66 or 67 is hydraulically locked in the switching position I assumed by the changeover by coupling control pressure into a respective control chamber 76 or 77 of the respective pilot valve 66 or 67.

The pilot valves are designed as 3/2-way valves, in the basic position 0 of which a flow path 78 or 79 is released, via which the high output pressure of the pressure supply pump 37 is coupled into one of the two control chambers 49 or 51 of the changeover valve 48, whereby this can be switched into its functional position 0 or its switching position I, and on the other hand is coupled into the control chamber 76 or 77 of the respective other pilot valve 66 or 67, whereby this pilot valve 66 or 67 in each case is locked in its switching position I.

In the switching position I of the respective pilot valve 66 or 67, the control chambers 49 or 51 of the changeover valve 48 which can be controlled via this and the control chamber 77 or 76 of the respective other pilot valve 67 or 66 are relieved of pressure, as a result of which the respective pilot valve returns to its basic position 0 arrives and is thus prepared for a mechanical switchover, as it were.

To switch the conveying operation of the thick matter pump 10 on and off, a manually switchable or electrically controllable ON / OFF switching valve 81 is provided, which is designed as a 2/2-way valve with an open basic position 0 and a blocking switching position I, in which Home position 0 of this switching valve 81, the high-pressure output 36 of the pressure supply pump 37 is connected to the unpressurized reservoir 38, so that the pump 37 works in circulation mode in the basic position 0 of the switching valve 81 and the drive cylinders 13 and 14 cannot be acted upon by drive pressure while in In the blocking switching position I of the switching valve 81, the output pressure of the high-pressure pump 37 is present at the P connection 53 of the changeover valve 48 and, via the pilot valves 66 and 67, also into one of the control chambers 49 or 51 of the changeover valve 48 and one of the control chambers 76 and 77 of the pilot valves 66 and 67 is coupled.

To explain the function of the thick matter pump 10 described in this respect with reference to FIGS. 1 and 2, let us assume the functional state of its hydraulic drive device represented by FIG. 2 as the initial state from which the conveying operation of the thick matter pump 10 is to begin, in which the switching valve 48 and the pilot valves 66 and 67 assume their illustrated basic positions 0, in which the control chambers 49 and 51 of the switching valve 48 and the control chambers 76 and 77 of the pilot valves 66 and 67 are depressurized. A position between their possible end positions is assumed for the drive pistons 16 and 17 of the two drive cylinders 13 and 14. The high-pressure pump 37 is already in operation, but the on / off switching valve 81 is still in its basic position 0, in which the pump 37 operates in circulation mode and therefore there is no drive pressure at the P-connection of the switching valve.

By switching the ON / OFF switching valve 81 in its blocking functional position I, the circulation operation of the pressure supply pump 37 is ended and its pressure supply operation is initiated in which the high pressure at the high pressure outlet 36 of the pump 37 builds up at the P connection 53 of the Changeover valve 48 is present and via its flow path 56 and the pressure medium line 57 is coupled into the rod-side drive chamber 32 of the "right" drive cylinder 13, and the rod-side drive chamber 33 of the other - "left" - drive cylinder 14 via the pressure medium line 58 and the other flow path 62, which is released in the basic position 0 of the changeover valve 48, is connected to the tank connection 61 of the changeover valve and via the return line 82 to the unpressurized reservoir 38 of the pressure supply unit 37, 38. The piston 16 of the right-hand drive cylinder 13 executes the pull-in stroke linked to the filling stroke of the feed cylinder 11 and directed towards the bottom 46 of the drive cylinder 13, as a result of which pressure medium from the bottom-side drive chamber 39 of this drive cylinder 13 via the pressure line 42 into the bottom-side drive chamber 41 of the other drive cylinder 14 is displaced, the piston 17 thereby executing its outward stroke linked to the conveying stroke of the conveying cylinder 12.

Via the pilot paths 66 and 67, which are initially in their basic position 0, both control chambers 49 and 51 are initially acted upon via their flow paths 78 and 79 with the pressure building up at the pressure outlet 36 of the high-pressure pump 37, the changeover valve, however - essentially - by the action the valve spring 52 remains in its basic position 0. At the same time, the control chambers 76 and 77 of both pilot valves 66 and 67 are acted upon by the high output pressure of the pump 37, with the result that the two pilot valves 66 and 67 switch into their switching positions I, whereby the control chambers 49 and 51 of the switch valve 48 are relieved of pressure again are, as well as the control chambers 76 and 77 of the pilot valves 66 and 67, with the result that in During this start-up phase, the changeover valve 48 remains in its basic position 0 and the two drive cylinders 13 and 14 continue to execute their intake stroke or their outward stroke.

When the piston 16 of the right drive cylinder 13 runs into its bottom end position, the pilot valve 66 mounted on this drive cylinder 13 is switched to its switching position I, in which the control chamber 77 of the pilot valve 67 mounted on the bottom of the left drive cylinder 14 via a valve in the switching position I of the pilot valve 66 of the right drive cylinder 13, the flow path 83 and a relief line 84 to the reservoir 38 are relieved of pressure, and that control chamber 49 of the changeover valve 48 is relieved of pressure, by the pressurization of which a switching force which is rectified with the force of the valve spring 52 can be generated. Due to the pressure relief of its control chamber 77, the pilot valve 67 of the left control cylinder 14 is now held securely in its basic position 0 by its valve spring 69, in which the outlet pressure of the pump 37 also flows into the control chamber 76 of the right drive cylinder 13 via the flow path 79 of this pilot valve 67 mounted pilot valve 66, which is hereby hydraulically locked in its switching position I - against the action of its valve spring 68. Furthermore, the pilot chamber 51 of the changeover valve 48 is now also in the basic position 0 of the pilot valve 67 pressurized with high pressure, whereby the changeover valve 48 is switched into its switching position I, in which the rod-side drive chamber 33 of the left drive cylinder 14 is now exposed to the high output pressure of the pressure supply pump 37 via the flow path 63 of the changeover valve 48 released in this functional position I of the changeover valve and the rod-side drive chamber 32 of the right drive cylinder 13 via the pressure medium line 57 and the second flow path 64 released in the switching position I of the changeover valve 48 to the reservoir 38 of the pressure supply unit 37, 38 is relieved of pressure, with the result that now the left drive cylinder 14 has its filling stroke of a feed cylinder 12 linked pull-in stroke and the piston 16 of the right drive cylinder, driven by the bottom drive chamber 41 of the left drive cylinder 14 and the pressure line 42 into the bottom drive comb r 39 of the right drive cylinder 13 displaced rocking oil, executes its outward stroke linked to the delivery stroke of the delivery cylinder 11 connected to it.

The configuration of the switching positions of the changeover valve 48 and the two pilot valves 66 and 67 associated with this functional state of the thick matter pump 10 and the positions of the drive cylinder pistons 16 and 17 immediately after the movement reversal, the piston 16 of the right drive cylinder 13 being mounted on it by the actuating plunger 71 Pilot valve 66 has already taken off again, but remains in its switching position I because of the hydraulic locking, is shown in FIG. 2a.

As soon as the piston 17 of the left drive cylinder 14 reaches its end position on the bottom side, the pilot valve 67 which it can actuate is mechanically switched to its switching position I, in which the control chamber 76 of the other pilot valve 66 is relieved of pressure via the flow path 86 which is released in it , whereby the previously existing hydraulic locking of this pilot valve 66 in its switching position I is canceled and this pilot valve 66 switches back to its basic position 0, in which the control chamber 77 of the previously mechanically actuated pilot valve 67 with a high level is activated via the flow path 78 released in this basic position 0 Pressurized and this pilot valve 67 is thereby locked in its switching position I and on the other hand that control chamber 49 of the switching valve 48 is exposed to high pressure, the pressure of which causes the switching valve 48 to return to its basic position 0 is definable. At the same time, the other control chamber 51 of the changeover valve 48 is relieved of pressure via the pilot valve 67 mounted on the left drive cylinder 14 to the reservoir 37 of the pressure supply unit, so that the changeover valve 48 also switches reliably into its basic position 0, in which the two drive cylinders 13 and 14 now again with reverse direction of movement their pistons 16 and 17 are driven. The hydraulic drive system of the thick matter pump 10 is now in its "steady" operating state, in which the two delivery cylinders 11 and 12 perform their filling and delivery strokes alternating periodically, which are automatically controlled by the hydraulic sequence control described.

Since the amount of hydraulic oil flowing into the bottom-side drive chambers 39 and 41, which is constantly displaced as so-called rocking oil during operation of the thick matter pump, can change from one chamber to another, be it in the sense of an enlargement, because hydraulic oil in the rod-side Drive chambers 32 and 33 of the two drive cylinders 13 and 14 are under higher pressure than in their bottom-side drive chambers 39 and 41 and therefore are more likely to pass into them, be it in the sense of a reduction that can result from leakage oil losses or damage-related leaks in the rocking oil circuit , it is necessary to be able to compensate for such changes in quantity.

This problem is the same if, as indicated by dashed lines, the drive control of the drive cylinders 13 and 14 takes place via their bottom-side drive chambers 39 and 41, to which the drive pressure can be supplied via the pressure supply lines 57 'and 58' and the rod-side drive chambers 32 and 33 of the two drive cylinders 13 and 14 via a pressure line 42 ' are permanently communicating and the rocking oil is pushed back and forth between them.

To adjust and adjust the amount of rocking oil required in each case, a manually switchable compensation valve 87 is provided in the exemplary embodiment selected for explanation, which is designed as a 3/3-way valve, which has a central position as the blocking neutral position 0 and two alternative switching positions I and II, in one of which - the switching position I - hydraulic oil can be displaced into the bottom-side drive chambers 39 and 41 of the two drive cylinders 13 and 14 by means of the high-pressure pump 37 via a compensating line 88, which is connected to the connecting line 42, and in the other - the switch position II - hydraulic oil can be drained from the two bottom drive chambers 39 and 41 via the compensating line 88 and a flow path 89 released in this switch position II to the unpressurized reservoir 38 of the pressure supply unit 37, 38.

Between the compensating valve 87 and the compensating line 88, a check valve 91 is connected, which can be actuated in the opening direction by relatively higher pressure at the line-side connection 92 than in the compensating line 88 or the bottom-side drive chambers 39 and 41 of the two drive cylinders 13 and 14, and by relatively higher Pressure in the compensation line 88 is pushed into its blocking position at this valve connection 92 and is mechanically unlocked in the switching position II of the compensating valve 87, in which hydraulic oil must be able to be drained from the rocking oil circuit.

Furthermore, a pressure relief valve 93, which is hydraulically connected in parallel with the high pressure pump 37, is provided, by means of which the outlet pressure of the pump 37 is reduced to a predetermined limit value of e.g. 200 bar is limited, when the excess pressure valve 93 opens a relief path 94 leading to the reservoir 38.

If the amount of rocking oil contained in the bottom drive chambers 39 and 41 of the two drive cylinders 13 and 14 increases, this leads to the thick matter pump 10 "stopping" at some point because one of the two drive cylinder pistons 16 or 17 is no longer so can get far near its bottom end position that the respective pilot valve 66 or 67 can still be operated. In this malfunction it can be assumed that one of the two drive cylinder pistons 16 or 17 is in its end position remote from the floor. In order to remedy this malfunction state, it is then only necessary, while the high-pressure pump 37 is operating in the pressure supply mode, to switch the compensating valve 87 into its functional position II until the thick matter pump 10 starts again.

The other possible malfunction is that the amount of rocking oil, e.g. has decreased due to a leak in the rocking oil circuit, it can be seen that the delivery and filling strokes of the thick matter pump 10 decrease in amount. This malfunction can - while the thick matter pump 10 is in operation - thereby eliminated - compensated for - that the compensating valve 87, if necessary several times, is switched over to its functional position I for a short period of time in the hydraulic oil via a flow path 96 released in this functional position I. the compensating line 88 can be displaced into the connecting line 42 and via this into the bottom drive chambers 39 and 41 of the two drive cylinders 13 and 14. Such a switching of the compensation valve 87 is repeated until the maximum values of the filling and delivery strokes of the thick matter pump are achieved again.

As an alternative to the design of the thick matter pump 10 described so far, in which the pilot valves 66 and 67 of their hydraulic drive unit are each mechanically actuated and hydraulically locked in the functional positions achieved by the mechanical actuation when the pistons 16 or 17 of the two hydraulic drive cylinders 13 and 14 run into their bottom setting, a design of the hydraulic drive unit 13, 14, 48, 36 with an equivalent function is possible in that the pilot valves 66 and 67 are assigned to a single one of the drive cylinders 13 or 14 and one of these two pilot valves is actuated when the drive cylinder piston 16 or 17 enters its bottom end position and the other of the two pilot valves is actuated when the same drive cylinder piston 16 or 17 enters its end position away from the ground.

If, for the alternative connection of the delivery cylinders 11 and 12 to the delivery line 26, a pipe switch is provided, as explained at the beginning, this pipe switch can also be controlled by the pressure output signals of the pilot valves 66 and 67.

To explain a further exemplary embodiment of a device for drive control of a two-cylinder thick matter pump 10 explained in terms of its basic structure according to FIG. 1, reference is now made to FIG. 3, in which a hydraulic control unit as a whole analogous to the hydraulic control unit 34 according to FIG. 2 is denoted by 34 '.

Insofar as the structural and functional elements of this hydraulic control unit 34 'shown in FIG. 3 and the drive cylinder are provided with the same reference numerals as the element of the control unit 34 shown in FIGS. 2 and 2a, this is intended to indicate their structural and functional equality or analogy and, at the same time, the reference to them with reference to FIGS given description to avoid repetition and to be able to limit the description of the embodiment of FIG. 3 essentially to its structural differences compared to the embodiment of FIG. 2.

In the hydraulic control unit 34 'according to Fig. 3, the pressure supply pump 37' is a reversible variable displacement pump, e.g. designed as a swash plate axial piston pump which, depending on the position of its swash plate represented by arrow 97, can be operated in two alternative conveying directions, in which one of the two supply connections 36 'and 36' 'each has the high pressure outlet and the other the return connection of the variable displacement pump 37' form.

To set the respective conveying direction, a hydraulic actuating cylinder 98 designed as a double-acting hydraulic linear cylinder is provided, whose piston 99, which forms the axially movable, pressure-tight delimitation of the two drive chambers 101 and 102 of the double-acting actuating cylinder 98, via one or both of them to the Piston rods 103 and 104 emerging from the end faces of the cylinder housing and sealed against this in a pressure-tightly displaceable manner, as illustrated by a schematically indicated mechanical actuating element 106, are coupled in motion to the swivel plate 97 of the variable displacement pump 37 '.

Here are with deflections of the actuating cylinder piston 99 to the right linked deflections of the swivel plate 97 in a clockwise direction, the pump 37 'assuming an angularly positive (clockwise) angular distance (+ Mittel) from a neutral central position, which is marked by the dash-dotted reference plane 107, when its swivel plate 97 3 right supply connection 36 'and the pressure medium line 57 hydraulic fluid displaced into the rod-side drive pressure chamber 32 of the right drive cylinder 13 and hydraulic fluid flowing out of the rod-side drive pressure chamber 33 of the left drive cylinder 14 via its left supply connection 36''to the reservoir 108 of the pressure supply unit returns, and in the event that the swivel plate 97 from the reference plane 107 takes a counterclockwise negative distance (- ϕ), via its left supply connection 36 '' as a high pressure outlet hydraulic fluid via the pressure displaced the central line 58 to the rod-side drive pressure chamber 33 of the left drive cylinder 14 and discharges hydraulic fluid flowing from the right drive cylinder 13 to the reservoir 108 via its supply connection 36 ', which now acts as a return connection.

Due to the position of the swivel plate 97 shown in solid lines and its swivel position shown in broken lines, which is represented by the arrow 97 ', the positions with the maximum delivery volume of the pressure supply pump 37' are marked.

Between the input connections 111 and 112 of the two pilot valves 66 and 67, which are permanently connected to one another via a pressure medium line 109, in their respective basic position 0 the respective input connection 111 or 112 via a flow path 78 or 79 with the control chamber 77 or 79 released in this basic position 0. 76 of the respective other pilot valve 67 or 66 is connected and the two pressure medium lines 57 and 58, via which the one supply connection 36 'of the pressure supply pump 37' to the rod-side drive chamber 32 of the right drive cylinder 13 and the left supply connection 36 '' of the pressure supply pump 37 'are connected to the rod-side drive chamber 33 of the left drive cylinder 14, a check valve 113 or 114 is switched, which is due to relatively higher pressure at the supply connection 36' and 36 '' of the pressure supply pump 37 'than at the input connections 111 and 112 of the two Pilot valves 66 and 67 in Opening direction is applied and is otherwise blocking. These two check valves 113 and 114 ensure that, regardless of the delivery seal of the pressure supply pump 37 ', the respective output pressure of the pressure supply pump is present at both input ports 111 and 112 of the pilot valves 66 and 67 and as a control pressure for the hydraulic locking of the pilot valve 66 to be locked or 67 is usable.

The control output 116 connected to the control chamber 77 of the left pilot valve 67, which in the basic position 0 of the right pilot valve 66 is connected to its input port 111, is connected via a control line 117 to the left drive chamber 102 of the actuating cylinder 98 according to FIG. 3, during the in the basic position 0 of the left pilot valve 67 with its output port 112 communicating control output 118 of the left pilot valve 67 is connected via a further control line 119 to the right drive chamber 101 of the actuating cylinder 98 according to FIG. 3.

By means of a weakly preloaded actuating spring 121, the actuating force of which is significantly less than the actuating forces which can be generated by pressurizing the right drive chamber 101 while simultaneously relieving pressure on the left drive chamber 102 of the actuating cylinder 98 or relieving pressure on the left drive chamber 102 and relieving pressure on the right drive chamber 101, In the exemplary embodiment shown, that pivot position of the swivel plate 97 of the pressure supply pump 37 'is distinguished as the starting position in which the pressure supply pump 37' when the thick matter pump 10 starts up first allows its right delivery cylinder 11 to carry out its filling stroke, ie the right drive cylinder 13 executes its inward stroke.

In stationary operation, the embodiment according to FIG. 3, as can be seen immediately, works completely anazum Embodiment according to FIGS. 2 and 2a.

Claims (16)

1. Device for controlling the drive of a two-cylinder sludge pump, the pump pistons of which are drivable so as to execute push-pull filling and delivery strokes by means of, in each case, one drive cylinder, the drive cylinders being hydraulically connected in series, there being provided for cyclic control of said strokes a hydraulically controllable changeover valve having at least one control chamber, as a result of the alternate pressurization with control pressure and pressure relief of which control chamber the changeover valve is switchable into alternative operating positions 0 and I, in which the piston of one of the drive cylinders executes the working stroke corresponding to the filling stroke of the delivery cylinder driven by said drive cylinder and the piston of the other drive cylinder executes the working stroke corresponding to the delivery stroke of the delivery cylinder driven by said drive cylinder, there being provided for controlling the pressurization and pressure relief of the control chamber of the changeover valve two pilot valves, which are switched over upon movement of the pistons of the drive cylinders into their alternative end positions,
   characterized by the following features:

   a) the pilot valves (66 and 67) take the form of 2-position valves, which are mechanically operable by the piston(s) (16 and/or 17) of at least one of the two drive cylinders (13 and/or 14) counter to the resetting force, which is developed by a resetting element and urges the respective pilot valve (66, 67) into its basic position (0), and are hydraulically lockable in the position (I) assumed as a result of mechanical operation by pressurization of a control chamber (76 or 77), the hydraulic locking optionally being supportable by means of a mechanical detent device exerting a moderate retention force and acting in a force-locking and form-fit manner;

   b) pressurization of the control chamber (76 or 77) of the respective pilot valve (66 or 67) to be locked is effected via a flow path (79 or 78) which is released in the basic position (0) of the other pilot valve (67 or 66);

   c) pressure relief of the control chamber (76 or 77) of the pilot valve (66 or 67), in the basic position (0) of which the control chamber (77 or 76) of the pilot valve (67 or 66) to be locked is pressurized with control pressure, is effected via a flow path (79 or 78) of the pilot valve (67 or 66) which is to be locked or is locked, which flow path is released in the operating position (I) assumed by the pilot valve (67 or 66) as a result of its mechanical operation.
2. Device according to claim 1, characterized in that the two pilot valves (66, 67) are each operable by means of an axial plunger (71, 72), which plungers pass in a pressure-tight displaceable manner through axial bores of the cylinder housing(s) (73, 74), which are disposed in end walls of the cylinder housing(s), and project into drive pressure chambers (39, 41 and/or 32, 33) of the drive cylinders (13, 14), which drive pressure chambers are delimited in an axially movable manner by the pistons (16, 17) of the drive cylinders (13, 14).
3. Device according to claim 2, characterized in that the two pilot valves (66, 67) are mounted in each case on the outside of the bottom (46, 47) of the respective drive cylinder (13, 14).
4. Device according to claim 2 or claim 3, characterized in that at least the two pilot valves (66, 67) as well as the changeover valve (48) and preferably also an ON-OFF switching valve (81) provided for initiating and terminating the delivery mode of the sludge pump (10) are combined into a control valve block.
5. Device according to claim 2, characterized in that one of the pilot valves (66 or 67) is disposed at the bottom (46 or 47) of the cylinder housing of a drive cylinder (13 or 14) and the other pilot valve (67 or 66) is disposed at the end wall forming the housing-fixed axial delimitation of the rod-side drive pressure chamber (32 or 33) of the same drive cylinder.
6. Device according to one of claims 1 to 5, characterized in that the changeover valve (48) takes the form of a 4/2-way valve having only one control chamber (51), as a result of the pressurization of which control chamber the changeover valve (48) is switchable counter to the resetting force of a valve spring (52) out of its basic position (0) associated with the delivery mode of the one delivery cylinder (11 or 12) into its position (I) associated with the delivery mode of the other delivery cylinder (12 or 11), fixing of the valve body of the changeover valve (48) in its operating position (I) optionally being supported by means of a mechanical detent device exerting a moderate retention force and acting in a force-locking and form-fit manner.
7. Device according to claim 6, characterized in that in the basic position (0) of the one pilot valve (66 or 67) the high-pressure output (36) of the pressure supply pump (37) is introduced into both the control chamber (51) of the changeover valve (48) and the control chamber of the other pilot valve (67 or 66), in the position (I) of which the hydraulic locking of the pilot valve effecting the pressure triggering of the changeover valve (48) is cancelled.
8. Device according to one of claims 1 to 5, characterized in that the changeover valve (48) has two control chambers (49 and 51), as a result of the alternative pressurization and pressure relief of which the changeover valve (48) is switchable into its alternative operating positions (I and 0), and that a valve spring (52) urging the changeover valve into its basic position (0) is provided.
9. Device according to claim 8, characterized in that in the basic position (0) of the respective pilot valve (66 or 67) one of the control chambers (49 or 51) of the changeover valve (48) is connected to the control chamber (77 or 76) of the other pilot valve (67 or 66) as well as to the high-pressure outlet (36) of the pump (37) and said chambers are relieved of pressure in the position (I) of the respective pilot valve (66 or 67).
10. Device according to one of claims 1 to 9, characterized in that the pilot valves (66, 67) take the form of 3/2-way valves of the same type.
11. Device according to one of claims 1 to 10, characterized in that an ON-OFF switching valve provided for initiating and terminating the delivery mode of the sludge pump (10) takes the form of a 2/2-way valve, in the basic position (0) of which the high-pressure outlet (36) of the pressure supply pump (37) permanently connected to the high-pressure (P)-connection (53) of the changeover valve (48) is connected to the unpressurized storage container (38) of the pressure supply unit (37, 38) and in the position (I) of which the high-pressure outlet (36) of the pump (37) is shut off from the storage container (38).
12. Device according to one of claims 1 to 11, characterized in that a compensating valve arrangement (87, 91) is provided, by means of which the reciprocating oil quantity contained in the hydraulically interconnected drive pressure chambers (39, 41 or 32, 33) of the two drive cylinders (13, 14) is adjustable.
13. Device according to claim 12, characterized in that the compensating valve arrangement (87, 91) comprises a manually operable valve (86) in the form of a 3/3-way valve, which is movable out of a blocking basic position (0), in which a compensating line (88) which is in permanently communicating connection with the hydraulically interconnected drive pressure chambers (39, 41 or 32, 33) of the drive cylinders (13, 14) is shut off both from the high-pressure outlet (36) and from the unpressurized storage container (38) of the pressure supply pump (37), into a position (I), in which the high-pressure outlet (36) of the pressure supply pump (37) is connected to the compensating line (88), or alternatively into a position (II), in which said compensating line (88) is connected to the unpressurized storage container (38) of the pressure supply unit (37, 38).
14. Device according to claim 13, characterized in that the compensating valve arrangement comprises a check valve (91), which is inserted between the 3/3-way valve (87) and the compensating line (88) and is operable in opening direction by a relatively higher pressure at the cylinder-side valve connection (92) of the compensating valve (87) than in the compensating line (88) and is urged into its blocking position by a relatively higher pressure in the compensating line (88) than at the line-side connection (92) of the 3/3-way valve, and that said check valve is mechanically unblocked in the position (II) associated with the bleeding of reciprocating oil.
15. Device according to one of claims 1 to 14, characterized in that a pressure relief valve (93) hydraulically connected in parallel to the pressure supply pump (37) is provided.
16. Device for controlling the drive of a two-cylinder sludge pump, the pump pistons of which are drivable so as to execute push-pull filling and delivery strokes by means of, in each case, one drive cylinder, the drive cylinders being hydraulically connected in series, there being provided for cyclic control of said strokes a variable displacement pump operable in two alternative delivery directions, there being provided for adjustment of said pump a hydraulically controllable control cylinder having at least one drive chamber, as a result of the alternate pressurization with control pressure and pressure relief of which drive chamber operation of the variable displacement pump is controllable in its alternative delivery directions, in which the piston of one of the drive cylinders executes the working stroke corresponding to the filling stroke of the delivery cylinder driven by said drive cylinder and the piston of the other drive cylinder executes the working stroke corresponding to the delivery stroke of the delivery cylinder driven by said drive cylinder, there being provided for controlling the pressurization and pressure relief of the drive chamber of the control cylinder two pilot valves, which are switched over upon movement of the pistons of the drive cylinders into their alternative end positions, in particular according to one of claims 1 to 3, 5, 9, 10 as well as 11 to 15, characterized by the following features:

    a) the pilot valves (66 and 67) take the form of 2-position valves, which are mechanically operable by the piston(s) (16 and/or 17) of at least one of the two drive cylinders (13 and/or 14) counter to the resetting force, which is developed by a resetting element and urges the respective pilot valve (66, 67) into its basic position (0), and are hydraulically lockable in the position (I) assumed as a result of mechanical operation by pressurization of a control chamber (76 or 77);

    b) pressurization of the control chamber (76 or 77) of the respective pilot valve (66 or 67) to be locked is effected via a flow path (79 or 78) which is released in the basic position (0) of the other pilot valve (67 or 66);

    c) pressure relief of the control chamber (76 or 77) of the pilot valve (66 or 67), in the basic position (0) of which the control chamber (77 or 76) of the pilot valve (67 or 66) to be locked is pressurized with control pressure, is effected via a flow path (79 or 78) of the pilot valve (67 or 66) which is to be locked or is locked, which flow path is released in the operating position (I) assumed by the pilot valve (67 or 66) as a result of its mechanical operation.

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