DE102011114241B4 - Hydraulic drive device, hydraulic output stage of a hydraulic servo-control valve, servo-control valve and powder press - Google Patents

Abstract

Hydraulic drive device (1) for press pistons (17, 18) of hydraulic cylinders (2, 3) of a powder press (4) for producing multiply stepped compacts with more than one hydraulic pressure source (5) and with at least one hydraulic main control valve (9, 10), in which the hydraulic pressure sources (5) are hydraulically connected to at least one of the hydraulic cylinders (2, 3) via the main hydraulic control valve (9, 10) and in which at least one of the hydraulic pressure sources (5) a hydraulic pressure accumulator (6, 7, 8) for providing a first hydraulic working pressure (P0, P1, P2), characterized in that a (6) hydraulic pressure accumulator (6, 7, 8) bypassing the at least one hydraulic main control valve (9, 10) on at least one counterpressure pressure chamber of one of the hydraulic cylinders (2, 3) is directly hydraulic connected.

Description

The invention relates firstly to a hydraulic drive device for pressing pistons of hydraulic cylinders of a powder press for producing multi-stepped compacts with more than one hydraulic pressure source and at least one main hydraulic control valve, wherein the hydraulic pressure sources are connected via the main hydraulic control valve to at least one of the hydraulic cylinders and wherein at least one of Hydraulic pressure sources is a hydraulic pressure accumulator for providing a first hydraulic working pressure. On the other hand, the invention also relates to a hydraulic output stage of a hydraulic servo-control valve. The invention further relates to a servo-control valve with a pilot valve and a powder press for producing multi-stepped compacts comprising hydraulic cylinder with hydraulically driven plunger.

From the prior art generic powder presses for producing multi-stepped forms of powder are known, which have next to a main press cylinder for moving a main press piston along a main press axis further secondary press cylinder for the process of corresponding secondary press piston along related Nebenpressachsen. As a rule, the individual pressing pistons, in particular those of the secondary pressing axes, are hydraulically driven, wherein they are used as needed during a pressing cycle for producing a multi-stepped shape.

In particular, in order to be able to hold the individual secondary pressing pistons in the desired position control during the entire pressing cycle, it is often necessary for forces to be briefly provided on the secondary pressing cylinders that correspond approximately to half the main pressing force. Since the piston surfaces of the main press cylinder or the main press cylinder and the secondary press cylinder are usually different, the cylinder pressures are usually not in the same ratio. Frequently, similar cylinder pressures will be present at approximately half the piston area of the slave cylinders relative to the main jack cylinders. There are different drive concepts for this. Especially on the secondary press axes are usually only in one direction, namely in the pressing direction, high pressing forces and thus also correspondingly high cylinder pressures required.

In a very simple known embodiment, the secondary press cylinders are fed from a common hydraulic accumulator with a hydraulic fluid and a position control of the secondary piston is made via a respective servo-control valve. In this very simple hydraulic connection, the maximum pressure of the hydraulic accumulator must be present during the entire pressing cycle. The energy demand is correspondingly high in order to be able to permanently provide this maximum pressure.

A known in the prior art and, in contrast, more energy-efficient embodiment provides for a division of the common hydraulic pressure accumulator into a high-pressure accumulator and in a low-pressure accumulator, which can optionally be switched by means of a main hydraulic control valve a hydraulic system or switched off by this. The high-pressure accumulator is thereby switched on only in the respective pressing phase by means of a corresponding valve.

In a further embodiment, no hydraulic pressure accumulator are used, but in particular each secondary press cylinder has in addition to a servo-control valve via a pressure-controlled pump with a variable displacement. In this respect, only the required in the respective cycle phase working pressure, which also includes the pressure component for the hydraulic system bias. With this method, the energy consumption can be approximately halved compared to the more energy-efficient embodiment explained above.

However, a significantly improved energy efficiency can hardly be achieved because it is limited in its size to maintain a required minimum control accuracy of the servo control valve. In the usual or desired traversing speeds with respect to the plunger causes the size limitation due to flow resistance disadvantageous flow losses. However, these flow resistances can be significantly reduced if a small and a larger servo control valve are used in parallel for each pressing cylinder. However, this increases the structural complexity of the hydraulic drive device.

In summary, it can be stated that conventional hydraulic drives for fully position-controlled secondary pistons of powder presses are characterized either by a very high energy consumption or by a very complex design.

It is an object of the present invention to avoid the disadvantages mentioned above and to provide a generic hydraulic drive device, which operates in particular more energy efficient.

The object of the invention is a hydraulic drive device for plunger of hydraulic cylinders of a powder press for producing multi-stepped compacts with more than one hydraulic pressure source and having at least one main hydraulic control valve connected, wherein the hydraulic pressure sources are connected via the main hydraulic control valve to at least one of the hydraulic cylinders, wherein at least one of the hydraulic pressure sources is a hydraulic pressure accumulator for providing a first hydraulic working pressure and which is characterized in that a hydraulic pressure accumulator, bypassing the at least one main hydraulic control valve is connected directly to at least one counterpressure pressure chamber of the hydraulic cylinder directly hydraulically. As a result, the pressure of the one connected bypassing the main hydraulic control valve hydraulic pressure accumulator can be used in a structurally simple way energy efficient.

As already mentioned, working pressures in the cylinders of the order of magnitude of at least half the master cylinder pressures and usually even at least the whole master cylinder pressures must be applied for a short time to keep the existing plungers of the hydraulic cylinders connected to the hydraulic drive device in position control during a total press cycle to be able to.

On the other hand, during the working process, the high working pressures in the cylinders, in particular on the hydraulic auxiliary cylinders, must be applied only in the pressing direction. In particular, this can be used in the present invention.

Advantageously, by means of the hydraulic drive device according to the invention, only a correspondingly low backpressure can be used, if necessary, to completely return a plunger which has been hydraulically displaced in the pressing direction to its original position without having to permanently maintain a higher hydraulic working pressure by the hydraulic pressure accumulator bypassing the main hydraulic control valve is subjected to appropriate pressure. In this way, this energy can be saved to produce this higher hydraulic working pressure.

It is understood that the hydraulic pressure accumulator can be hydraulically separated by a closing valve or the like in terms of maintenance work or the like. However, this is preferably not done regularly to control or regulate the respective hydraulic cylinders during a press cycle.

The hydraulic pressure accumulator connected in bypassing the main hydraulic control valve is advantageously a counterpressure accumulator, which is connected directly to at least one of the hydraulic cylinders by means of a corresponding hydraulic pressure line, ie without the interposition of the main hydraulic control valve, so that this hydraulic cylinder is permanently supplied with the desired counterpressure ,

On the one hand, the main hydraulic control valve can establish or close a hydraulic connection between the hydraulic pressure sources and the hydraulic cylinders or a collecting reservoir for hydraulic fluid.

The term "hydraulic drive device" is understood in the context of the invention essentially all components of a hydraulic system on a powder press, which are required for operating hydraulic cylinders, in particular hydraulic auxiliary cylinders. In particular for producing multiply stepped compacts, a powder press with a plurality of pressing pistons, which divide into a main pressing piston and a plurality of secondary pressing pistons, is required. In this context, one often speaks of main or primary and secondary or secondary axes. The hydraulic drive device essentially serves to move a hydraulic fluid back and forth between a pressure reservoir and cylinder chambers of the hydraulic cylinders.

In the present case, the term "hydraulic cylinder" includes in particular auxiliary hydraulic cylinders of a powder press. However, hydraulic master cylinders of a powder press can also be hydraulically fed by means of the present hydraulic drive device if this is advantageous.

Advantageously, the present hydraulic cylinders are double-chamber hydraulic cylinders whose respective first pressure chambers are set under working pressure in order to move the respective plunger from a starting position in the main pressing direction. Subsequently, each of the first pressure chamber is relieved, and a prevailing in a second pressure chamber opposite the second pressure chamber lower working pressure moves the respective plunger with a backward movement back to its original position.

In this respect, a preferred embodiment provides that in each case a first pressure chamber of at least one of the hydraulic cylinders, in particular a pressing pressure chamber of at least one of the hydraulic cylinders, is hydraulically connected via the hydraulic main valve optionally with a hydraulic pressure accumulator for a low pressure or with a hydraulic pressure accumulator for a high pressure. As a result, different pressing pressures, in particular as working pressures, can be provided at the respective first pressure chamber of the hydraulic cylinders. This is done via the main hydraulic control valve by hydraulically coupled or decoupled different hydraulic pressure sources, if necessary, with the first pressure chamber.

Advantageously, in each case the second pressure chamber of at least one of the hydraulic cylinders is hydraulically connected to a hydraulic pressure accumulator for storing a back pressure, bypassing the at least one main hydraulic control valve, so that here too a simple construction is ensured.

The pressure chambers correspond in the present context cylinder spaces of the present hydraulic cylinder.

A particularly preferred embodiment provides that a first of the hydraulic pressure sources and a second of the hydraulic pressure sources are connected to a common hydraulic connection device to the at least one main hydraulic control valve, wherein between the second hydraulic pressure source and the main hydraulic control valve, a hydraulic closing valve is arranged.

On the one hand can be realized structurally simple and with fewer components by the common hydraulic connection device, the hydraulic drive device. On the other hand, the second hydraulic pressure source can be structurally easily decoupled from the common hydraulic connection device, in particular from the main hydraulic control valve, by means of the hydraulic closing valve, if a working pressure of the second hydraulic pressure source is not required.

Also, for energy-efficient operation in a hydraulic drive device for ram pistons of hydraulic cylinders of a powder press for producing multi-stepped compacts with more than one hydraulic pressure source and with at least one main hydraulic control valve, the hydraulic pressure sources may be hydraulically connected to at least one of the hydraulic cylinders via the main hydraulic control valve, a first one of the hydraulic pressure sources and a second one of the hydraulic pressure sources having a common hydraulic connection means is connected to the at least one main hydraulic control valve, and wherein the hydraulic closing valve is disposed between the second hydraulic pressure source and the main hydraulic control valve.

Structurally simple, a hydraulic drive device can be implemented in particular if a first of the hydraulic pressure sources and a second of the hydraulic pressure sources are connected to a common hydraulic connection device to the at least one main hydraulic control valve and the first hydraulic pressure source is hydraulically separated from the second hydraulic pressure source by means of a check valve.

By means of the check valve can be structurally easily prevented that the higher provided working pressure or the high pressure acts up to the hydraulic pressure source of the lower working pressure or the low pressure, so that both hydraulic pressure sources can advantageously use the common hydraulic connection device and only with a main hydraulic control valve with the individual hydraulic cylinders can be hydraulically connected.

For energy-efficient operation, in a hydraulic drive device for plunger of hydraulic cylinders of a powder press for producing multi-stepped compacts having more than one hydraulic pressure source and having at least one main hydraulic control valve, the hydraulic pressure sources may be hydraulically connected to at least one of the hydraulic cylinders via the main hydraulic control valve, a first of the hydraulic pressure sources and a second one of the hydraulic pressure sources having a common hydraulic connection means is connected to the at least one main hydraulic control valve, and wherein the second hydraulic pressure source is hydraulically separated from the first hydraulic pressure source by means of the check valve.

If the two hydraulic pressure sources are configured as two separate hydraulic pressure accumulators which can independently supply working pressures as constant hydraulic pressure pressures, wherein the two hydraulic pressure accumulators are connected to at least one of the hydraulic cylinders via the at least one main hydraulic control valve, in particular a counter press manufacturing process on the powder press can be designed particularly simply.

It should be assumed that the present invention initially has no immediate advantage in counterpressing. However, as a rule, several such drives are used and usually not all counterpress, present invention is still in embodiments in which is pressed against correspondingly advantageous.

Alternatively, one of the two hydraulic pressure sources has a hydraulic pressure accumulator and one of the two hydraulic pressure sources has a delivery pump for delivering a constant pressure Delivery volume, wherein both the hydraulic pressure accumulator and the feed pump is connected via the at least one main hydraulic control valves to at least one of the hydraulic cylinders, the present hydraulic drive device can be designed particularly advantageous for powder presses without Gegenpresszyklus.

In the latter, in particular, no larger oil volume with the same pressure level is absolutely necessary, so that it is possible to dispense with a special hydraulic pressure accumulator. Rather, the feed pump provides a substantially constant delivery volume, by means of which successively a pressure build-up can be achieved on the hydraulic cylinder, wherein when reaching the required hydraulic pressure a further increase in pressure by means of a corresponding pressure relief valve can be avoided. About the pressure relief valve excess conveyed volume can be advantageously redirected and collected in a corresponding reservoir.

Especially with regard to the energy-efficient embodiment described above, which provides a high-pressure accumulator and a back pressure accumulator, the object of the invention is also a hydraulic drive device for plunger of hydraulic cylinders of a powder press for producing multi-stepped compacts with two hydraulic pressure accumulators for providing a first working pressure and a second Operating pressure on the hydraulic cylinders and solved with at least one main hydraulic control valve, wherein the hydraulic drive device, a further hydraulic pressure supplier for providing or generating a further working pressure, such as the above-described feed pump or other pressure or hydraulic source, and wherein the further hydraulic pressure supplier, bypassing the at least one main hydraulic control valve is hydraulically directly connected to at least one of the hydraulic cylinders.

Preferably, this hydraulic pressure accumulator is a back pressure accumulator of the hydraulic drive device, by means of which in each case the second pressure chamber of the existing hydraulic cylinder can be energetically fed with counterpressure in order to achieve a corresponding backward movement of the relevant plunger.

Although this increases the structural complexity of the hydraulic drive device by at least one hydraulic pressure supplier over the prior art with two hydraulic pressure accumulators. However, the powder press can be energetically operated much cheaper by the provision of further hydraulic suppliers, so that the superficially considered disadvantage of the constructively complex designed hydraulic drive device ultimately proves to be an advantage.

A first related advantageous embodiment provides that the further hydraulic pressure supplier is designed as a further hydraulic pressure accumulator, which provides the further working pressure as a constant hydraulic pressure. This variant is particularly advantageous for press cycles involving a counterpressure movement.

In a working variant in which it is possible to dispense with such a counterpressure movement, an alternative embodiment is preferred in which the further hydraulic pressure supplier is a feed pump for conveying a constant delivery volume, the feed pump, bypassing the at least one main hydraulic control valve, being connected directly to at least one of the hydraulic cylinders is.

For the advantages and disadvantages of the two last-mentioned embodiments with and without counterpressing motion, reference is made to the solution described at the beginning in order to avoid repetition.

Moreover, it is advantageous for the reasons described above, if a hydraulic closing valve is arranged between the further hydraulic pressure supplier and the main hydraulic control valve.

Likewise, from the advantages already explained above, it is advantageous if one of the two hydraulic pressure accumulators and the further hydraulic pressure supplier are hydraulically separated from one another by means of a check valve.

Can or should all existing hydraulic cylinders are used in common mode, the hydraulic cylinders can be advantageously controlled only by means of a main hydraulic control valve. On the other hand, to be able to actuate the hydraulic cylinders individually particularly precisely, it is advantageous if each hydraulic cylinder is preceded by a main hydraulic control valve.

The present invention can be advantageously supplemented when the hydraulic cylinders each comprise a hydraulic cylinder piston having a press pressure chamber side surface area and a Gegenpressdruckkammerseitiger surface area, wherein the pressure-chamber-side surface area is greater than the Gegenpressdruckkammerseitige surface area. In such a chosen Surface ratio of the hydraulic cylinder piston can already be moved already in the pressing direction, if at least approximately equal pressure conditions prevail in the compression pressure chamber or in the compression direction acting in the compression chamber and in the counter-pressure chamber or in the counter to the pressing direction pressure chamber; or it can be correspondingly increased advantageously the resulting pressing force at the same pressure. In particular, as a result, among other things, the required total operating time of a high-pressure source can be further reduced on the hydraulic drive device, whereby the energy requirement can be further reduced.

The term "surface area" in the context of the invention describes that surface area of a pressing piston which forms a substantially transverse to a pressing piston movement direction extending chamber wall of a pressure chamber of a hydraulic cylinder.

It is understood that the main hydraulic control valves can be structurally varied.

In order to be able to set and control both a pressing piston position and a pressing piston movement extraordinarily well and precisely, it is advantageous if a servo-control valve is used for the main hydraulic control valves.

The term "servo control valve" essentially describes valves in which a small input signal causes a larger output signal. Such a power gain may be approximately at a height of 10 ⁴ to 10 ⁷ . In this respect, servo-control valves are characterized by better dynamics than, say, continuous directional control valves.

The design effort of the present hydraulic drive device can be further reduced if the main hydraulic control valve is a 4/3-way servo-control valve in which at least one port is blocked.

It is particularly advantageous if the main hydraulic control valve is a 3/3-way servo-control valve. A 3/3-way valve in the form of a servo-control valve is not known from the prior art. However, it can reduce the design effort advantageously further. The 3/3-way servo control valve is preferably designed as a two-quadrant control valve.

However, since an even less complex structure is desirable, a single-port servo-control valve is advantageous for a hydraulic connection to an end device such as a pressure chamber and a cylinder space of a hydraulic cylinder of the present invention. By means of this single connection, the hydraulic cylinder can be hydraulically connected or disconnected hydraulically in the simplest way either with a hydraulic pressure source or with a collecting container of the hydraulic drive device.

In this respect, it is exceptionally advantageous if the main hydraulic control valve comprises a hydraulic output stage of a servo-control valve, as described below.

According to another aspect, the object of the invention is also achieved by a hydraulic output stage of a hydraulic servo-control valve, which is characterized by a housing having a first lateral pressure chamber, with a second lateral pressure chamber, with a biased in a central position double-headed piston between the two pressure chambers and with a centric pressure chamber, wherein in the middle position the first piston head of the double-headed piston separates the first lateral pressure chamber from the centric pressure chamber and the second piston head of the double-headed piston separates the second lateral pressure chamber from the centric pressure chamber, the first lateral pressure chamber opening a first pilot valve opening to a pilot valve and the second lateral pressure chamber has a second pilot valve opening to the pilot valve, the central pressure chamber having a terminal connection and, on the one hand, a hydraulic fluid connection and a first pilot valve connection and others it has a sump connection and another pilot valve connection.

By means of this hydraulic output stage of the hydraulic servo-control valve, the hydraulic cylinders of a powder press can be moved and positioned particularly precisely during a pressing cycle with respect to multi-stage compacts with an exceptionally good response and moreover.

Advantageously, the hydraulic output stage of the hydraulic servo-control valve on the terminal side has only one hydraulic connection. In this respect, it is characterized by a very simple structure.

A preferred embodiment of the hydraulic output stage provides that, on the one hand, the hydraulic fluid port and the first pilot valve port and / or the other the reservoir port and the second pilot valve port are arranged in the longitudinal direction of the hydraulic output stage at the same height, and preferably also directly opposite one another.

The hydraulic output stage can advantageously correspond with a commercially available pilot valve as a hydraulic precursor, so that a new servo-control valve is created structurally simple way.

The object of the invention is alternatively achieved by a servo-control valve with a pilot valve and the power amplifier described above. Preferably, the servo control valve is designed as a two-quadrant control valve.

Finally, the object of the invention is also achieved by a powder press for producing multi-stepped compacts comprising hydraulic cylinder with hydraulically driven plunger, which is characterized by a hydraulic drive device, by a hydraulic output stage or by a servo-control valve with one of the features described above.

The teaching of the present invention is not limited to generic powder presses. The hydraulic drive device and in particular the hydraulic output stage can also be used advantageously in other hydraulically operating systems in connection with hydraulic cylinders.

Further advantages, objects and features of the present invention will be explained with reference to the appended drawings and their description in which hydraulic drive devices and components thereof are shown and described by way of example.

In the drawing show:

1 a schematic view of a first hydraulic powder press drive device with three separate hydraulic pressure accumulators;

2 a schematic view of another hydraulic powder press drive device with two separate hydraulic pressure accumulators and a separate feed pump of a hydraulic fluid;

three schematically a longitudinal section of a hydraulic output stage according to the invention; and

4 a schematic view of an alternative hydraulic powder press drive device again with three separate hydraulic pressure accumulators and a 4/3-way servo-control valve.

The in the 1 hydraulic drive device shown by way of example 1 one by two hydraulic cylinders 2 and three schematically indicated powder press 4 for producing multi-stepped compacts (not shown here) comprises a plurality of hydraulic pressure sources 5 in the form of a backpressure accumulator 6 for providing a back pressure P0, a low pressure accumulator 7 for providing a low pressure P1 and a high pressure accumulator 8th for providing a high pressure P2 and a first main hydraulic control valve 9 for the first hydraulic cylinder 2 and a second main hydraulic control valve 10 for the second hydraulic cylinder three ,

The main hydraulic control valves 9 and 10 are not commercially available in the present embodiment and each have a hydraulic power amplifier 250 (please refer three ), which will be described later.

Hydraulically connected are the hydraulic pressure sources 5 at the main hydraulic control valves 9 and 10 or the hydraulic cylinders 2 and three by means of a common hydraulic connection device 11 which in this embodiment comprises a plurality of hydraulic lines which are not further numbered here.

In the hydraulic cylinders shown here by way of example 2 and three the powder press 4 these are double-chamber hydraulic cylinders 12 and 13 each with a first pressure chamber 14 and a second pressure chamber 15 (numbered here only by way of example), by means of which the respective directions of movement 16 the plunger 17 respectively. 18 the hydraulic cylinder 2 and three with respect to a first secondary press axis 19 or a second secondary press axle 20 can be initiated. For this purpose, the pressure chambers 14 and 15 acted upon accordingly with hydraulic working pressures.

Here is the backpressure accumulator 6 bypassing any hydraulic main control valves 9 respectively. 10 and via a back pressure line 21 immediately respectively with the second pressure chamber 15 the hydraulic cylinder 2 . three hydraulically connected.

The second pressure chambers 15 Here are counterpressure pressure chambers that permanently with the back pressure P0 from the back pressure accumulator 6 are fed.

By means of the back pressure P0, in this embodiment permanently in the second pressure chambers 15 is applied, the respective plunger 17 respectively. 18 always in a backward motion 22 offset or held in a desired position control when the pressure conditions in the first pressure chamber 14 be adjusted accordingly.

Advantageously, by providing the backpressure accumulator 6 the hydraulic drive device 1 or the powder press 4 be operated much more energy efficient, whereby the multi-stage pellets can be produced much cheaper.

The first pressure chambers 14 are present pressure chambers of the hydraulic cylinder 2 and three , which can be acted upon with the necessary pressing pressures for pressing the compacts.

A forward movement 23 the plunger 17 respectively. 18 is achieved in that in the first pressure chamber 14 either a low pressure P1 or a high pressure P2 is provided.

The low pressure P1 is structurally simple by means of the low pressure accumulator 7 over a low pressure line 24 in the common hydraulic connection device 11 fed. The low pressure P1 is sufficient in the present embodiment to the plunger 17 . 18 to shift against the back pressure P0, as long as no external pressing forces act. Here, the low pressure P1 is selected so that in particular the flow resistance of the main hydraulic control valves 9 and 10 can be overcome.

Accordingly, a high pressure P2 by means of the high-pressure accumulator 8th via a corresponding high-pressure line 25 in the common hydraulic connection device 11 fed.

Feeding the low pressure P1 and the high pressure P2 into the hydraulic connection device 11 takes place in a node 26 ,

The node 26 is the respective main hydraulic control valve 9 . 10 directly upstream, in this embodiment between the high-pressure accumulator 8th and the node 26 a hydraulic closing valve 27 is arranged. In this respect, there is the hydraulic closing valve 27 between the high-pressure accumulator 8th and the respective main hydraulic control valve 9 respectively. 10 , Thus, the high-pressure accumulator 8th the common hydraulic connection device 11 If necessary, hydraulically switched on or from the common hydraulic connection device 11 be separated.

In addition, the high-pressure accumulator 8th by means of a check valve 28 from the low pressure accumulator 7 or from the low pressure line 24 hydraulically disconnected, leaving open hydraulic closing valve 27 a high pressure P2 in the common hydraulic connection device 11 only up to this check valve 28 present and beyond.

By means of two separate hydraulic pressure accumulators 7 and 8th can on the hydraulic cylinders 2 and three structurally particularly easy different high hydraulic pressures can be provided.

A hydraulic fluid that is no longer needed after a pressing operation can be used, in particular, during the reverse movement of the pressing pistons 17 respectively. 18 via the hydraulic main control valves 9 and 10 in a hydraulic fluid reservoir 29 and collected there for further use.

The back pressure accumulator 6 , the low pressure accumulator 7 and the high-pressure accumulator 8th be fed by means of one or more feed pumps in a conventional manner according to the hydraulic fluid.

In this embodiment, the hydraulic working pressures P0, P1 and P2 are selected such that the plungers 17 respectively. 18 preferably at a speed of 50 mm / s in both the forward motion 23 as well as in the backward movement 22 can move. It should be noted at this point that this is not necessarily a limiting feature and other speeds can be preset by a suitable choice of pressures.

The back pressure P0 is in this case proportional to the pressing piston surface, this being determined from the ratio of the pressing piston surfaces, which in the present exemplary embodiment is selected to be approximately 1, so that in the present exemplary embodiment the back pressure P0 is approximately 60 bar. At a ratio of the plunger surfaces of 2 with the back pressure on the smaller area of the back pressure would be approximately 120 bar. The back pressure P0 influences the energy balance of the powder press 4 advantageously hardly.

The low pressure P1 is not or only negligible depending on the ratio of the plunger surfaces and is ideally in about 120 bar and already has a greater impact on the energy balance.

The high pressure P2 decisively influences the energetic effectiveness of the hydraulic drive device 1 and is preferably more than 315 bar.

Accordingly, it is advantageous if the high pressure P2 is used only slightly, ie essentially only in one pressing phase or in one final pressing phase. In this respect, the above-mentioned movement speeds are not critical with respect to the pressing phase or in a final pressing phase per se, depend essentially on the materials and the shape of the compacts and can therefore deviate from the above-mentioned values.

It should be noted that not all plungers may be necessary 17 . 18 be operated against pressing or, in particular in the non-counteracting parts or cylinders of the drive device 1 the benefits described above have a corresponding impact on the energy balance.

The in the 2 shown hydraulic drive device 101 has substantially the same construction as the hydraulic drive device 1 from the 1 , In this respect, the same or equivalent components of the hydraulic drive devices 101 provided with final digits which the components of the hydraulic drive device 1 correspond, wherein the components in terms of the hydraulic drive direction 101 only to the extent that they differ from the hydraulic drive device 1 differ in order to avoid repetition.

In contrast to the hydraulic drive device 1 from the 1 is in the hydraulic drive device 101 on the high-pressure accumulator 8th (please refer 1 ) has been waived.

Instead of the high-pressure accumulator 8th alternatively occurs a feed pump, which provides a constant volume flow Q, which is chosen relatively small and if necessary via the common hydraulic connection means 111 and via the main hydraulic control valves 109 respectively. 110 in the first pressure chambers 114 can be fed.

Due to the constant delivery volume builds up within the common hydraulic connection device 111 , especially in the first pressure chambers 114 , a correspondingly desired hydraulic pressure, wherein the hydraulic pressure also via hydraulic main control valves 109 and 110 and a pressure relief valve 141 , which acts on the high pressure P2 pressure limiting, can be influenced or adjusted.

The pressure relief valve 141 is between a collection container 129 and a node 126 the common hydraulic connection device 111 hydraulically integrated.

This alternative hydraulic drive device 101 is particularly suitable when a counterpressure presses on the powder press 104 is not provided, so that the energy-related benefits in particular in this regard can be used accordingly.

The in the three shown hydraulic power amplifier 250 a 3/3-way servo valve controlled by a pilot valve (see main hydraulic control valves) 9 . 10 ; 109 . 110 ), as regards the two previously described hydraulic drive devices 1 respectively. 101 is used, has a housing 251 on, in which one in a middle position 252 preloaded movable double-headed piston 253 longitudinally displaceable (double arrow 254 ) is stored.

The double-headed piston 253 is characterized by two equal piston heads 255 and 256 with identical diameter, with the two piston heads 255 and 256 through a diameter-reduced piston rod 257 of the double-headed piston 253 spaced apart from each other.

The housing 251 is with a first lateral pressure chamber 258 , with a second lateral pressure chamber 259 and a centric pressure chamber 260 Mistake.

In the two lateral pressure chambers 258 and 259 is in each case a spiral spring 261 respectively. 262 placed, by means of which the double-headed piston 253 inside the case 251 biased in the middle position 252 is stabilized. In so far form the first spiral spring 261 and the second coil spring 262 together a mechanical spring return device 263 the hydraulic output stage shown here 250 out. It is understood that in modified embodiments, other restoring devices, for example, also by other media than springs conditional restoring devices, or other spring arrangements, can be used accordingly effectively.

The first lateral pressure chamber 258 has a first pilot valve opening 264 to a pilot valve, not shown here, the hydraulic power amplifier 250 ,

Accordingly, at the second lateral pressure chamber 259 a second pilot valve opening 265 arranged, which the second lateral pressure chamber 259 can hydraulically connect with the pilot valve.

With regard to the centric pressure chamber 260 are a first pilot valve connection 266 and a second pilot valve port 267 intended.

Since the pilot valve constructed here is a commercially available component whose mode of operation is known, a further explanation of the pilot valve and its function is dispensed with.

According to the illustration according to three are the two pilot valve openings 264 and 265 as well as the two pilot valve connections 266 and 267 pilot valve side 268 on the housing 251 the hydraulic power amplifier 250 arranged.

Furthermore, pilot valve are mutually side 269 the power amplifier 250 on the housing 251 a terminal connection 270 , a hydraulic fluid port 271 and a sump connection 272 available.

The terminal connection 270 is centered on the housing 251 or in the middle of the centric pressure chamber 260 placed while the hydraulic fluid port 271 closer to the first lateral pressure chamber 258 and the sump connection 272 closer to the second lateral pressure chamber 259 are arranged.

In this particular embodiment of the hydraulic power amplifier 250 On the one hand are the hydraulic fluid connection 271 and the first pilot valve port 266 and on the other hand, the sump connection 272 and the other pilot valve port 267 on the side of the centric pressure chamber 260 longitudinal 254 the hydraulic power amplifier 250 Seen at the same height and also arranged opposite.

If now the hydraulic fluid from the hydraulic fluid port 271 to the terminal connection 270 can flow to allow a pressure build-up in the hydraulic cylinders, by means of the pilot valve, not shown here, via the second pilot valve opening 265 a control pressure in the second lateral pressure chamber 259 initiated, by means of which the double-headed piston 253 in the direction of the first lateral pressure chamber 258 is moved. In this case, both the hydraulic fluid port 271 as well as the first pilot valve connection 266 open. Accordingly, hydraulic fluid may be supplied from the hydraulic fluid port to the terminal port 270 flow, whereby, for example, the first pressure chambers 14 the powder press 4 from the 1 can be set under appropriate hydraulic pressure. To prevent in such a case, the double-headed piston 253 due to the opening of the hydraulic fluid port 271 in the direction of the first lateral pressure chamber 258 By means of a pressure equalization via the first pilot valve connection 266 , via the pilot valve, not shown here, as well as via the first pilot valve opening 264 the pressure conditions in the first lateral pressure chamber 258 adjusted accordingly.

To the double-headed piston 253 again in the direction of the middle layer 252 to move, it requires a further control pressure in the first lateral pressure chamber 258 passing the first pilot valve opening 264 can be applied.

Is the double-headed piston 253 For example, again in the middle position 252 stabilized, in the context of the present invention, the hydraulic pressure can easily in the first pressure chambers 14 the hydraulic cylinder 2 respectively. three the powder press 4 being held.

To the first pressure chambers 14 again, the double-headed piston can relieve 253 further in the direction of the second lateral pressure chamber 259 be displaced, whereby the sump connection 272 and also the second pilot valve port 257 be exposed. This can then be a hydraulic pressure reduction from the terminal connection 270 via the sump connection 272 respectively.

The movement of the double-headed piston 253 in the direction of the second lateral pressure chamber 259 can be damped by applying a pressure equalization across the second pilot valve port 267 , the pilot valve and the second pilot valve opening 265 he follows.

When in the 4 shown alternative hydraulic drive device 301 are also a backpressure storage 306 , a low pressure accumulator 307 and a high-pressure accumulator 308 intended. Also in this alternative embodiment are also two hydraulic cylinders 380 two secondary press axles 381 a powder press 304 exemplified, but the rest of the hydraulic cylinders 2 . 102 . three . 103 The embodiments described above are operated and controlled in accordance with and substantially identical.

The three hydraulic accumulators 306 . 307 and 308 are by means of a common hydraulic connection device 311 with the two hydraulic cylinders 380 hydraulically connected.

In contrast to the two previously described hydraulic drive devices 1 (please refer 1 ) and 101 (please refer 2 ) is in the hydraulic drive device 301 each of the hydraulic cylinders 380 or their first pressure chambers 314 not a 3/3-way servo valve ( 9 . 10 , please refer 1 ; 109 . 110 , please refer 2 ) but each a 4/3-way servo valve 382 (numbered here only as an example) upstream, with each of the 4/3-way servo valves 382 a fourth valve outlet 383 (here only exemplified quantified) is closed.

Each of the 4/3-way servo valves 382 works similar to a hydraulic power amplifier 250 as they are in the three previously described.

In addition, in particular, the hydraulic structure of the hydraulic drive device 301 essentially identical to the structure of the hydraulic drive device 1 according to the 1 ,

The back pressure accumulator 306 is also here bypassing the 4/3-way servo valves 382 with second pressure chambers 315 directly hydraulically connected. For this purpose, the backpressure accumulator 306 via a corresponding counterpressure line 321 with the second pressure chambers 315 directly hydraulically connected.

The low pressure accumulator 307 is with a low pressure line 324 at the common hydraulic connection device 311 connected. In the low pressure line 324 there is a check valve 328 so that the low pressure accumulator 307 to higher hydraulic pressures in the common hydraulic connection device 311 is decoupled.

The high-pressure accumulator 308 is via a high pressure line 325 and a hydraulic closing valve disposed therein 327 the common hydraulic connection device 311 switchable.

The low pressure line 324 and the high pressure line 325 are in a common node 326 the common hydraulic connection device 311 of which in turn a corresponding pressure on the 4/3-way servo-control valves 382 is forwarded. The latter can, as explained in the embodiments described above, hydraulic fluid in a collecting container 329 dissipate.

LIST OF REFERENCE NUMBERS

1

driving device

2

first hydraulic cylinder

3

second hydraulic cylinder

4

powder Press

5

Hydraulic pressure sources

6

Backpressure memory

7

Low pressure accumulator

8th

High-pressure accumulator

9

first main hydraulic control valve

10

second main hydraulic control valve

11

Hydraulic connector

12

first double-chamber hydraulic cylinder

13

second double-chamber hydraulic cylinder

14

first pressure chambers

15

second pressure chambers

16

directions of movement

17

first plunger

18

second plunger

19

first secondary press axis

20

second secondary press axle

21

Against pressure line

22

regression

23

forward movement

24

Low pressure line

25

High-pressure line

26

junction

27

Hydraulic closing valve

28

check valve

29

Clippings

101

driving device

102

first hydraulic cylinder

103

second hydraulic cylinder

104

powder Press

105

Hydraulic pressure sources

106

Backpressure memory

107

Low pressure accumulator

109

first main hydraulic control valve

110

second main hydraulic control valve

111

Hydraulic connector

112

first double-chamber hydraulic cylinder

113

second double-chamber hydraulic cylinder

114

first pressure chambers

115

second pressure chambers

116

movement direction

117

first plunger

118

second plunger

119

first secondary press axis

120

second secondary press axle

121

Against pressure line

122

regression

123

forward movement

124

Low pressure line

125

High-pressure line

126

junction

128

check valve

129

Clippings

141

Pressure relief valve

250

hydraulic power amplifier

251

casing

252

center position

253

Double-headed pistons

254

longitudinal displacement

255

first piston head

256

second piston head

257

piston rod

258

first lateral pressure chamber

259

second lateral pressure chamber

260

centric pressure chamber

261

first spiral spring

262

second spiral spring

263

Spring return facility

264

first pilot valve opening

265

second pilot valve opening

266

first pilot valve connection

267

second pilot valve connection

268

pilot valve side

269

pilot valve each other

270

terminal connection

271

Hydraulic fluid port

272

collecting connection

301

driving device

304

powder Press

306

Backpressure memory

307

Low pressure accumulator

308

High-pressure accumulator

311

Hydraulic connector

314

first pressure chambers

315

second pressure chambers

321

Against pressure line

324

Low pressure line

325

High-pressure line

326

junction

327

Hydraulic closing valve

328

check valve

329

Clippings

380

hydraulic cylinders

381

Secondary press axis

382

4/3-way servo-control valve

383

valve outlet

Claims (14)

Hydraulic drive device ( 1 ) for plunger ( 17 . 18 ) of hydraulic cylinders ( 2 . three ) a powder press ( 4 ) for producing multi-stepped compacts with more than one hydraulic pressure source ( 5 ) and with at least one main hydraulic control valve ( 9 . 10 ), in which the hydraulic pressure sources ( 5 ) via the main hydraulic control valve ( 9 . 10 ) on at least one of the hydraulic cylinders ( 2 . three ) are hydraulically connected and wherein at least one of the hydraulic pressure sources ( 5 ) a hydraulic accumulator ( 6 . 7 . 8th ) for providing a first hydraulic working pressure (P0, P1, P2), characterized in that a 6 ) Hydraulic pressure accumulator ( 6 . 7 . 8th ) bypassing the at least one main hydraulic control valve ( 9 . 10 ) on at least one counterpressure pressure chamber of one of the hydraulic cylinders ( 2 . three ) is connected directly hydraulically. Hydraulic drive device ( 1 ) according to claim 1, characterized in that a first ( 7 ) of hydraulic pressure sources ( 5 ) and a second ( 8th ) of hydraulic pressure sources ( 5 ) with a common hydraulic connection device ( 11 ) on the at least one main hydraulic control valve ( 9 . 10 ) are connected, wherein between the second hydraulic pressure source ( 8th ) and the main hydraulic control valve ( 9 . 10 ) a hydraulic closing valve ( 27 ) is arranged. Hydraulic drive device ( 1 ) according to claim 1 or 2, characterized in that a first ( 7 ) of hydraulic pressure sources ( 5 ) and a second ( 8th ) of hydraulic pressure sources ( 5 ) with a common hydraulic connection device ( 11 ) on the at least one main hydraulic control valve ( 9 . 10 ), the first hydraulic pressure source ( 7 ) from the second hydraulic pressure source ( 8th ) by means of a check valve ( 28 ) is hydraulically isolated. Hydraulic drive device ( 1 ) according to one of claims 1 to 3, characterized in that two ( 7 . 8th ) of hydraulic pressure sources ( 5 ) as two separate hydraulic accumulators ( 7 . 8th ), which independently of one another can provide working pressures (P1, P2) as constant hydraulic pressures, the two hydraulic pressure accumulators ( 7 . 8th ) via the at least one main hydraulic control valve ( 9 . 10 ) on at least one of the hydraulic cylinders ( 2 . three ) are hydraulically connected. Hydraulic drive device ( 1 ; 101 ) according to one of claims 1 to 3, characterized in that a ( 7 ; 107 ) of the two hydraulic pressure sources ( 5 ; 105 ) a hydraulic accumulator ( 7 ; 107 ) and a ( 140 ) of the two hydraulic pressure sources ( 5 ; 105 ) has a feed pump for conveying a constant delivery volume, wherein both the hydraulic pressure accumulator ( 7 ; 107 ) and the feed pump via the at least one main hydraulic control valve ( 9 . 10 ; 109 . 110 ) on at least one of the hydraulic cylinders ( 2 . three ; 102 . 103 ) is hydraulically connected. Hydraulic drive device ( 1 ) according to one of claims 1 to 5, characterized in that each hydraulic cylinder ( 2 . three ) a main hydraulic control valve ( 9 . 10 ) is connected upstream. Hydraulic drive device ( 1 ) according to one of claims 1 to 6, characterized in that in each case a first pressure chamber ( 14 ) at least one of the hydraulic cylinders ( 2 . three ), in particular a pressing pressure chamber of at least one of the hydraulic cylinders ( 2 . three ), via the main hydraulic control valve ( 9 . 10 ) optionally with a hydraulic accumulator ( 7 ) for a low pressure (P1) or with a hydraulic accumulator ( 8th ) is hydraulically connected for a high pressure (P2). Hydraulic drive device ( 1 ) according to one of claims 1 to 7, characterized in that in each case a second pressure chamber ( 15 ) at least one of the hydraulic cylinders ( 2 . three ) with a hydraulic accumulator ( 6 ) for storing a back pressure (P0) bypassing the at least one main hydraulic control valve ( 9 . 10 ) is hydraulically connected. Hydraulic drive device ( 1 ) according to one of claims 1 to 8, characterized in that the hydraulic cylinders ( 2 . three ) each have a hydraulic cylinder piston ( 17 . 18 ) having a pressure-surface-side surface portion and a pressure-surface-side surface portion, the pressure-pressure-chamber-side surface portion being larger than the pressure-surface-side surface portion. Hydraulic drive device ( 1 ) according to one of claims 1 to 9, characterized in that the main hydraulic control valve ( 9 . 10 ) is a 3/3-way servo control valve. Hydraulic power amplifier ( 250 ) of a hydraulic servo-control valve of a hydraulic drive device according to claim 10, characterized by a housing ( 251 ) with a first lateral pressure chamber ( 258 ), with a second lateral pressure chamber ( 259 ), with one in a central position ( 252 ) prestressed double-headed pistons ( 253 ) between the two pressure chambers ( 258 . 259 ) and with a centric pressure chamber ( 260 ), whereby in the middle position ( 252 ) the first piston head ( 255 ) of the double-headed piston ( 253 ) the first lateral pressure chamber ( 258 ) from the centric pressure chamber ( 260 ) and the second piston head ( 256 ) of the double-headed piston ( 253 ) the second lateral pressure chamber ( 259 ) from the centric pressure chamber ( 260 ), wherein the first lateral pressure chamber ( 258 ) a first pilot valve opening ( 264 ) to a pilot valve and the second lateral pressure chamber ( 259 ) a second pilot valve opening ( 265 ) to the pilot valve, wherein the central pressure chamber ( 260 ) a terminal connection ( 270 ) and on the one hand a hydraulic fluid connection ( 271 ) and a first pilot valve connection ( 266 ) and, on the other hand, a sump connection ( 272 ) and another pilot valve connection ( 267 ) having. Hydraulic power amplifier ( 250 ) according to claim 11, characterized in that on the one hand the hydraulic fluid connection ( 271 ) and the first pilot valve connection ( 266 ) and / or on the other hand, the sump connection ( 272 ) and the further pilot valve connection ( 267 ) longitudinal ( 254 ) of the hydraulic power amplifier ( 250 ) Seen at the same height, and preferably also directly opposite, are arranged. Servo control valve with a pilot valve, characterized by a hydraulic output stage according to one of claims 11 or 12. Powder press ( 4 ) for producing multiply stepped compacts comprising hydraulic cylinders ( 2 . three ) with hydraulically driven plungers ( 17 . 18 ), characterized by a hydraulic drive device ( 1 ) according to one of claims 1 to 10, by a hydraulic output stage ( 250 ) according to claim 11 or 12 and / or by a servo-control valve according to claim 13.

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