Title of Invention

CONTROL EQUIPMENT FOR AND PROCESS FOR THE CONTROL OF A HYDRAULIC PRESS

Abstract

The invention relates to a controller for a hydraulic press, comprising a pressing cylinder (1), a reservoir (2), a valve group (3), a pressure medium reservoir (7) and a hydraulic pump (6), connected together by means of a cylinder line (4), a reservoir line (5) and a tank line (8). According to the invention, a pressure converter (9) is arranged on the valve group (3), which may operate as a pressure amplifier or pressure reducer. The particular mode of action of said controller is achieved whereby the valve group (3) comprises a pre-press valve (11), a low-pressure chamber outlet valve (12), a low-pressure chamber inlet valve (13), a main press valve (14), a closing valve (15), a pressure release valve (16) and a 3-way valve (17), which may be operated by a particular control sequence. Said invention is applicable in hydraulic presses and of particular advantage in presses for the forming of ceramic pieces such as tiles.

Full Text

CONTROL EQUIPMENT FOR AND PROCESS FOR THE CONTROL OF A HYDRAULIC PRESS The present invention relates to control equipment for and process for the control of a hydraulic press. Such hydraulic presses are used when workpieces are to be shaped or reshaped. Hydraulic presses are also used for cutting purposes. The required force of the hydraulic press depends on the workpiece. In the ceramic industry, presses are used whose pressing force is 20,000 kN or more. Moreover, for the production to be economical, the cycle time for a pressing process should be as short as possible. Cycles of 20 strokes per minute are considered to be standard. The energy consumed by hydraulic presses is determined by the pressing force and the cycle time, which in turn are determined by the pumps and the electric motors driving these pumps. Accumulators used in the hydraulic presses are pneumatic-hydraulic accumulators or flywheels, as provided in prior art. A hydraulic press of the type mentioned herein is described in DE- A1-43 20 213. Here, a pneumatic-hydraulic accumulator is present in the feed circuit of the hydraulic press cylinder which is charged during the return stroke of the press and is actuated for the drive during the feed of the pressing tool. Consequently, energy can be saved during the main drive. A press described in JP-A-63 256 300, is operated with a multi-stage pressure converter. After an initial pressing at low pressure, the hydraulic oil is discharged into a tank which is followed by a high pressure pressing. Consequently, an energy regeneration is not possible in this case. A hydraulic drive system for a press is described in patent USA 5,852,933 and DE-A1 4436666 that contains a low and a high-pressure circuit. In this, three hydrostatic machines are present, of which two are mechanically coupled. For a satisfactory operation, these machines must be variable in their displaced and delivery volumes, which entails considerable cost. The system described here is used only if the press has a differential cylinder or synchronous cylinder. The use of the principle of secondary regulation for regulating the drive of a hydraulic press is known from (DE-A1-43 08 344). The different movements of the press ram are combined in such a way that the pressure network works in a closed circuit, in which the pneumatic-hydraulic accumulator determines the maximum pressure of the system. The fact that the hydraulic oil is quite compressible also plays a role in the regulation of a hydraulic press according to DE-A1-43 08 344. This has an effect in a pressing cycle both during the compression as well as during the decompression and is responsible for (energy) loss. Further, the problem of energy consumed by the mechanical parts of the press through elastic deformation of their components, has not been dealt with in the prior art. This energy is expended during the last stages of the pressing process. This energy is not recovered during the beginning of the process. The invention has attempted to make a hydraulic press whose hydraulic control is so constructed that it reduces the total energy requirement, without increasing the cost of the equipment. Besides, the hydraulic press control would also be useable for a press with plunger cylinders. The problem mentioned above is solved according to the invention. An embodiment of the invention based on the drawing is explained in detail below. Fig. 1 shows a hydraulic press control system, Fig. 2 to 6 are representations of individual steps within a stroke- cycle Fig. 7 shows a different embodiment of the press control. In fig.1, press cylinder is represented by 1, a storage tank 2 for the hydraulic fluid is placed over the press cylinder. A valve unit containing a series of valves is designated with reference number 3, to be described later. The hydraulic fluid is conveyed between the press cylinder 1 and the valve unit 3 via a cylinder conduit 4. An accumulator conduit 5 is connected to the valve unit 3. A hydraulic pump 6, which is driven by an electric motor, (not shown here), feeds the hydraulic fluid into this accumulator conduit. A -pneumatic-hydraulic accumulator 7 is connected to an accumulator conduit 5, which also runs within the valve unit 3, which means that the hydraulic pump 6 is in a position to deliver the hydraulic fluid to the pneumatic-hydraulic accumulator 7. A check valve, not shown, can be arranged in the conduit section between the hydraulic pump 6 and the accumulator conduit 5 to relieve the hydraulic pump from the pressure existing in the pneumatic-hydraulic accumulator 7 when the hydraulic pump 6 is not running. A tank conduit 8 leads from the valve unit 3 to the storage tank 2. A pressure converter 9 is connected to the valve unit 3 , which can work as a pressure intensifier on one hand and pressure reducer on the other. In addition, the pressure converter 9 has a piston 9K, which can slide within a cylinder 9Z and which separates a low pressure chamber 9.1 with a larger effective cross section and a high pressure chamber 9.2 with a smaller effective cross section. In order to achieve a lower effective cross section, there is a piston rod 9S connected to the piston 9K in the high-pressure chamber 9.2. The effective ratio between the pressure and the volume flow is determined at the cross sections of the two pressure chambers 9.1 and 9.2. The cross section is determined for the low pressure chamber 9.1 from the inner diameter of the cylinder 9Z according to A9.1 = 1/4*d9z2* and for the high pressure chamber by the difference of the inner diameter of the cylinder 9Z and the piston rod 9S according to A9,2 = 1/4*(d9Z-d9s)2* Here, A9.1 is the effective hydraulic cross section of the low pressure chamber 9.1, A9.2 that of the high pressure chamber 9.2, d9z the inner diameter of the cylinder 9Z and d9s the diameter of the piston rod 9S. The pressure ratio of the pressure converter 9 and correspondingly also the ratio of the volume flows is thus determined by A9 1:A9.2. The ratio A9.1:A9.2 is for example, 2:1. The position of the piston 9K is registered by means of a displacement gauge 9W. The low-pressure chamber 9.1 is connected to the valve unit 3 with a pressure converter-low-pressure conduit 10.1. There are three solenoid valves on this pressure converter-low-pressure conduit 10.1, namely admission pressure valve 11, whose second junction is connected to the cylinder conduit 4, a low pressure chamber-outlet valve 12, whose second junction is connected to the storage tank 2 via the tank conduit 8 and a low pressure chamber-inlet valve 13, whose second junction is connected to the accumulator conduit 5 and hence also to the pneumatic-hydraulic accumulator 7. The high pressure chamber 9.2 is connected to a pressure converter-high- pressure conduit 10.2 of the valve unit 3. Likewise, there are valves on this pressure converter-high-pressure conduit 10.2, namely a main-pressing valve 14, whose second junction is connected to the cylinder conduit 4, and a stop valve 15, whose second junction is connected to the accumulator conduit 5 and hence also to the pneumatic-hydraulic accumulator 7. A pressure release valve 16 lies between the cylinder conduit 4 and the tank conduit 8. Besides, there is a third valve in the pressure converter-high-pressure conduit 10.2, namely a 3-way-valve 17 connected to a normally closed check-valve 18, in which the 3-way-valve 17 is connected to the accumulator conduit 5 on the other side and hence also to the pneumatic-hydraulic accumulator 7 and, with its additional connection, to the tank conduit 8 and consequently to the storage tank 2. The conduit section between the check-valve 18 and the 3-way-valve 17 is designated as press conduit and with an indicator 19. The check-valve 18 is functionally a non-return valve. The functionality of the other valves 11, 12, 13,14, 15, 16 and 17 is reported in detail later based on figures 2 to 6. The valves can be actuated electrically and are controlled by the controlling device 20. The connecting conduits from the controlling device 20 to the valves 11, 12, 13, 14, 15, 16 and 17 are not shown in the figures for reasons of clarity. Only the essential elements of the invention are illustrated in the hydraulic diagram besides a press safety reduction and return control 21, which is necessary for the safe operation of the press cylinder 1 with regard to the invention but is not relevant. Likewise, a pressure sensor 22 is necessary, which registers the pressure in the cylinder conduit 4. The electrical connections between controlling device 20, displacement gauge 9W, pressure sensor 22, pressure reduction and return control 21 and additional safety-relevant elements on the press are also not illustrated for reasons of clarity. The first phase of the press operation, namely the development of the admission pressure, is described below based on fig. 2. The press cylinder 1 is filled as usual with hydraulic fluid from the storage tank 2 and this is shown by an arrow. Thus the upper pressing tool is lowered and this closes the unit. At the same time, the piston 9K is in an upper position near its end position A. Now, the 3-way-valve 17 is so actuated that it releases the flow from the connection of the accumulator conduit 5 to the connection of the press conduit 19. The actuation of the 3-way-valve 17 is marked in fig. 2 by its electrically operated drive (shown in solid black). Now, by means of this opening of the 3- way-valve 17, the hydraulic fluid can flow from the pneumatic-hydraulic accumulator 7 via the mentioned 3-way-valve 17 through the press conduit 19, through the check-valve 18 forced open by the pressure of the hydraulic fluid and through the pressure converter-high pressure conduit 10.2 to the high pressure chamber 9.2 of the pressure converter 9, which is marked by an arrow in fig. 2. At the same time, the admission pressure valve 11 is also actuated by its electrically operated drive (shown in solid black). With that, the hydraulic fluid can now flow from the low-pressure chamber 9.1 via the pressure converter-low-pressure conduit 10.1, through the admission pressure valve 11 and the cylinder conduit 4 to the press cylinder 1. Due to the ratio of the areas Ag2 to A9.1, the pressure converter 9 now works as a pressure reducer, in which the quantity of the hydraulic fluid is increased corresponding to the ratio of the areas A9.2 to A9.1. If, for example, the ratio of the areas A9.2 to A9.1 amounts to 1:2, then the pressure is reduced in the ratio of 1:2 by the pressure converter 9, but the quantity of hydraulic fluid is increased in the ratio of 1:2. The piston 9K is moved in direction B by the flow of the hydraulic fluid. It is to be noted that the 3-way-valve 17 is a variabally controllable valve, hence the drive of the 3-way-valve 14, for example, is a variable-magnet, so that the pressure in the press conduit 19 and in the pressure converter-high pressure conduit 10.2 and consequently also the pressure in the pressure converter-low pressure conduit 10.1, in the cylinder conduit 4 and in the press cylinder 1 is controllable or adjustable. If the desired admission pressure is reached, which is detected by the pressure sensor 22 and is transmitted to the controlling device 20 and is then determined by the controlling device 22, then the controlling device 20 causes the 3-way-valve 17 and the admission pressure valve 11 to be closed. Now, finally, the pressure release valve 16 is actuated and consequently opened. Due to this, a pressure drop occurs in the press cylinder 1 and in the cylinder conduit 4, which is detected by the pressure sensor 22. With that, the hydraulic fluid flows from the press cylinder 1 and the cylinder conduit 4 via the pressure release valve 16 and through the tank conduit 8 to the storage tank 2. If the pressure sensor 22 records a low pressure in the press cylinder 1 and the cylinder conduit 4, then the pressure release valve 16 will be closed again. An additional phase of admission pressure development can be useful. This is achieved in the same manner as described earlier, but now with a higher admission pressure, which is reached by a correspondingly modified actuation of the 3-way-valve 17. This phase can run while the upper tool lies on the pressed product (both not illustrated). But it can also be advantageous to lift the upper tool slightly. After the admission pressure or the admission pressures phase, the piston 9K is near the lower end position B in the cylinder 9Z, which is determined by the distance sensordisplacement gauge 9W. This position is necessary for creating the required pressure of the main press later. Now the next phase of press operation follows which is the development of main press pressure. This is explained below based on figs. 3 and 4. The first step of this phase is shown in fig. 3. Now, the actuated valves are represented in black and the flow of the hydraulic fluid is shown with arrows near the conduits. As can be seen from fig. 3 that following actuation the stop valve 15 and the main-pressing valve 14 are open now. These two valves are preferably electrically actuated OPEN-CLOSE valves. The admission pressure valve 11, low-pressure chamber inlet valve 13, low-pressure chamber outlet valve 12 and the pressure release valve 16 are also preferably of the same type. The flow of hydraulic fluid from the pneumatic-hydraulic accumulator 7 via the accumulator conduit 5, through the stop valve 15, the main pressing valve 14 and through the cylinder conduit 4 to the press cylinder 1 is made possible by the actuation of stop valve 15 and main pressing valve 14. Consequently, a pressure is developed in the press cylinder 1, which can be selected, but corresponds to the maximum pressure in the pneumatic- hydraulic accumulator 7. The second step in the development of pressure of the main press is shown in fig. 4. Now, the low pressure chamber inlet valve 13 and the main pressing valve 14 are open following actuation, the electrical drives of the valves 13, 14 are represented in black as in the previous figure. The flow of the hydraulic fluid resulting from that is again shown with arrows near the conduits. Now, the hydraulic fluid flows from the pneumatic-hydraulic accumulator 7 through the accumulator conduit 5, the opened low pressure chamber inlet valve 13 and through the pressure converter-low-pressure conduit 10.1 to the low pressure chamber 9.1 of the pressure converter 9. The pressure existing in the pneumatic-hydraulic accumulator 7 arises also in the low-pressure chamber 9.1 due to this. The ratio of areas A9.2 to A9.1 results in a higher pressure in the high-pressure chamber 9.2 at the same time, which is twice the pressure in the pneumatic-hydraulic accumulator due to an already mentioned 1:2 ratio of areas A9.2 to A9.1. But now, since the main pressing valve 14 is also open, the same pressure develops in the press cylinder 1 as well. At the end of this phase of the press operation, the pressure in the press cylinder 1 under the given conditions is thus twice as high as the pressure in the pneumatic- hydraulic accumulator 7. The pressure sensor 22 detects the pressure that develops in the press cylinder 1. As soon as the desired pressure is reached, the low-pressure chamber inlet valve 13 and the main pressing valve 14 are closed again. It is clear that this pressure development following a flow of hydraulic fluid from the pneumatic-hydraulic accumulator 7 to the low-pressure chamber 9.1 and from the high pressure chamber 9.2 via the cylinder conduit 4 to the press cylinder 1 is also related to the movement of the piston 9K in the direction A. Moreover, due to the ratio of areas A9.2 to A9.1, the quantity of hydraulic fluid that flows out from the high pressure chamber 9.2, with a 1:2 ratio of areas A9.2 to A9.1, is only half as much as the quantity of the hydraulic fluid that flows from the pneumatic-hydraulic accumulator 7 into the low-pressure chamber 9.1. Now, the press achieves its maximum pressure and carries out the pressing. Also, the stresses in the components of the press reach the maximum values under the action of this pressure. Since the components deform elastically, energy is also stored in these components. The compressible hydraulic fluid volume in the press cylinder 1, the press conduit 4, the pressure converter-high pressure conduit 10.2 and in the high pressure chamber 9.2 of the pressure converter 9 represents an additional energy potential. Now, a phase of release with stress reduction and decompression follows thereafter. This phase occurs in three steps, of which the first two are illustrated in fig. 5 and 6. The first step is shown in fig. 5. Now, the main pressing valve 14 and the stop valve 15 are opened, the drives of the valves 14, 15 are marked in black as in the previous figure. Now, the hydraulic fluid can flow from the press cylinder 1 to the pneumatic-hydraulic accumulator 7, for which it takes the path through the cylinder conduit 4, the main pressing valve 14, the stop valve 15 and the accumulator 5. The flow takes place because of the fact that, as mentioned before, the pressure in the press cylinder 1 is greater than that in the pneumatic-hydraulic accumulator 7. The first step lasts as long as the pressures in the press cylinder 1 and the pneumatic-hydraulic accumulator 7 are the same. By now a considerable portion of the energy stored in the components of the press is recovered, while the pressure in the pneumatic-hydraulic accumulator 7 is increased. This is a decisive advantage of the control equipment as per the invention and of the process for its operation. The second step of the release phase is described based on fig. 6, in which again the drives of the actuated valves are represented in solid black and the flow of the hydraulic fluid is shown with arrows on the conduits. This second step serves for the preparation of the next press cycle. For this, the pressure converter 9 must take up a definite position in the direction of the end position B. The volume still remaining in the low-pressure chamber 9.1 of the pressure converter is sufficient to realise the admission pressures for the next work- cycle. Tthis can be verified with the distance sensordisplacement gauge 9W. If this is not the case, then the remaining pressure existing in the press cylinder 1, in the cylinder conduit 4 and in the pressure converter-high-pressure conduit 10.2 is used to bring the piston 9K of the pressure converter 9 to the desired position by opening the main pressing valve 14 and the low-pressure chamber outlet valve 12. This desired position is shown in the fig. 6. Thereby, the high- pressure chamber 9.2 is also already filled again with hydraulic fluid remaining under pressure, so that it is not necessary to draw hydraulic fluid from the pressure accumulator 7, thus saving additional energy. The hydraulic fluid displaced from the low-pressure chamber 9.1 by the movement of the piston 9K reaches the storage tank 2 via the low-pressure chamber outlet valve 12 through the tank conduit 8. If the piston 9K has attained the desired position, which as mentioned, is determined by the distance sensordisplacement gauge 9W, then the low-pressure chamber valve 12 and the main pressing valve 14 are closed again. Finally, in the third step, the remaining pressure in the press cylinder 1 and in the cylinder conduit 4 is further released completely, by opening the pressure release valve 16 now. Moreover, the hydraulic fluid flows from the press cylinder 1 through the cylinder conduit 4, the pressure release valve 16 and the tank conduit 8 to the storage tank 2 under the action of the remaining pressure. The flow ceases as soon as the remaining pressure in the press cylinder 1 is fully released. Then, the pressure release valve 16 is closed again. But, at the same time, the pressure in the high pressure chamber 9.2 and in the pressure converter high-pressure conduit 10.2 is maintained at the same level. This pressure can be used in the next press cycle, which again results in an energy saving, since the pressure need not be built up again. In fig. 7, a variation of the press control as per the invention is shown. The only difference as against the example of fig. 1, is that the pressure converter 9' is of a different type than that of fig. 1 to 6. The pressure converter consists essentially of a pump 23, whose shaft 24 is coupled rigidly to a second pump 25, so that the shaft 24 is common to both the pumps 23 and 25. The first pump 23 is connected to the pressure converter low-pressure conduit 10.1 on one side, whereby this side of the pump 23 acts as low-pressure chamber 9.1, and to a tank 26 on the other side. The second pump 25 is connected on one side to the pressure converter high-pressure conduit 10.2, whereby this side of the pump 25 acts as high-pressure chamber 9.2, and likewise to the tank 26 on the other side. The two pumps 23, 25 are not driven by a motor but operate respectively, through the rigid connection, as units of pump and hydromotor. This combination of the two pumps 23, 25 is effective as pressure converter because of the fact that the specific output volume, that is the volume per rotation, is different, which is represented symbolically by the different sizes of the pumps 23, 25 in fig.7. This amounts to a ratio of 2::1. Also, by this means, the output of the hydraulic fluid by the two pumps 23, 25 to these effective areas correspond to the areas A9.1 or A9.2 according to the first embodiment. Accordingly, the pressure converter 9' behaves during the different phases of the press operation exactly like the pressure converter 9 as illustrated in the fig. 2 to 6 and can be explained based on these figures. During the first phase of the press operation mentioned before, the pressure converter 9' acts, for example, as pressure reducer, in which the second pump 25 works as hydromotor and the first pump 23 drives. For acting as pressure intensifier, the first pump 23 works as hydromotor, which the second pump 25 drives. The individual phases and their steps of a pressing cycle correspond to the earlier description. Moreover, it is also advantageous that the control process is simplified by the fact that a distance sensordisplacement gauge 9W is not required and the pressure converter 9' need not take up a definite position. In spite of the very simple construction of the control equipment as per the invention, energy can be recovered at various pressing steps. Thus, as described earlier, even the energy stored elastically in the press, in the pressed product and in the compressible hydraulic oil is recovered. Moreover, the control equipment does not require costly components, like variable pumps. It was determined through trials that a considerable energy can be saved through the control equipment as per the invention against the anticipated prior art. The energy saving can be upto about 40 %. The invention can be used with great advantage, basically for hydraulic presses of different types for various application areas. Besides, the press can be equipped with differential cylinders, constant speed cylinders or plunger cylinders. It is particularly advantageous when the control equipment as per the invention is used for presses for shaping of ceramic units, such as tiles. Both, the construction of the equipment as well as the mode of operation, hence the control process, are subjects of the invention, based on the construction and the mode of action described earlier. Reference list 1 Press cylinder 2 Storage tank 3 Valve unit 4 Cylinder conduit 5 Accumulator conduit: 6 Hydraulic pump 7 Pneumatic-hydraulic accumulator 8 Tank conduit 9 Pressure converter (First embodiment variant) 9' Pressure converter (Second embodiment variant) 9.1 Low-pressure chamber 9.2 High-pressure chamber 9Z Cylinder 9K Piston 9S Piston rod 9W Displacemnet gaugetance sensor 10.1 Pressure converter-low-pressure conduit 10.2 Pressure converter-high-pressure conduit 11 Admission pressure valve 12 Low-pressure chamber outlet valve 13 Low-pressure chamber inlet valve 14 Main pressing valve 15 Stop valve 16 Pressure release valve 17 3- way-valve 18 Check-valve 19 Press conduit 20 Controlling device 21 Press safety reduction and return control 22 Pressure sensor 23 First pump 24 Shaft 25 Second pump 26 Tank CLAIMS : 1. Control equipment for a hydraulic press with a press cylinder (1), a storage tank (2), a valve unit (3), a pressure converter (9; 9'), a pneumatic- hydraulic accumulator (7) and a hydraulic pump (6), wherein the press cylinder (1), the storage tank (2}, the valve unit (3), the pneumatic-hydraulic accumulator (7) and the hydraulic pump (6) are connected with each other by means of a cylinder conduit (4), an accumulator conduit (5) and a tank conduit (8), wherein - - the pressure converter (9; 91) is attached to the valve unit (3), - the pressure converter (9; 9') is a single-stage pressure converter (9; 9'), which can be operated as pressure intensifier and as pressure reducer, and - the pressure converter (9') consists of a first pump (23) with larger specific output volume and a second pump (25) with smaller specific output volume, which are connected rigidly by means of a shaft (24), wherein one side of the first pump (23) acts as low-pressure chamber (9.1) and one side of the second pump (25) acts as high- pressure chamber (9.2). Control equipment for a hydraulic press with a press cylinder (1) a storage tank (2), a valve unit (3), a pressure converter (9; 9') a pneumatic-hydraulic accumulator (7) and a hydraulic pump (6), wherein the press cylinder (1), the storage tank (2), the valve unit (3), the pneumatic-hydraulic accumulator (7) and the hydraulic pump (6) are connected with each other by means of a cylinder conduit (4), an accumulator conduit (5) and a tank conduit (8), wherein - - the pressure converter (9; 9') is attached to the valve unit (3), - the pressure converter (9, 9') is a single-stage pressure converter (9; 9'), which can be operated as pressure intensifier and as pressure reducer, wherein the pressure converter (9) consists of a piston (9K) sliding in a cylinder (9Z) and a piston rod (9S) rigidly connected to the piston (9K), wherein the pressure converter (9) has a low-pressure chamber (9.1) and a high-pressure chamber (9.2), which are separated from each other by the piston (9K), and the low- pressure chamber (9.1) has a larger cross section A91 than the high-pressure chamber, which has a cross section of A9.2 - the low-pressure chamber (9.1) is connected via a pressure converter low-pressure conduit (10.1) to the valve unit (3), and the pressure converter low- pressure conduit (10.1) is connected - -to a first connection of a pre-pressing valve (11), whose second connection is to the cylinder conduit (4), - to a first connection of a low-pressure chamber inlet valve (13), whose second connection is to the accumulator conduit (5), and - to a first connection of a low-pressure chamber outlet valve (12), whose second connection is to the tank conduit (8), and - the high-pressure chamber (9.2) is connected via a pressure converter high-pressure conduit (10.2) to the valve unit (3), and the pressure converter high-pressure conduit (10.2) is connected to - -a first connection of a main pressing valve (14), whose second connection is to the cylinder conduit (4), - to a first connection of a stop valve (15) whose second connection is to the accumulator conduit (5), and - via a first connection of a check-valve (18) and a press conduit (19) to a 3-way-valve (17), whose second connection is to the accumulator conduit (5) and whose third connection is to the tank conduit (8). 3. Control equipment as claimed in claim 2, wherein the 3-way-valve (17) can be controlled proportionately. 4. Control equipment as claimed in claim 2 or 3, wherein a pressure release valve (16) is arranged between the cylinder conduit (4) and the tank conduit (8). 5. Control device as claimed in claim 4, wherein the pre-pressing valve (11), low-pressure chamber inlet valve (13), low-pressure chamber outlet valve (12), main pressing valve (14), stop valve (15) and pressure release valve (16) are electrically controllable OPEN-CLOSE-valves. 6. Process for the control of a hydraulic press with a press cylinder (1), a storage tank (2), a valve unit (3), a pneumatic-hydraulic accumulator (7) and a hydraulic pump (6), wherein the press cylinder (1), the storage tank (2), the valve unit (3), the pneumatic-hydraulic accumulator (7) and the hydraulic pump (6) are connected with each other by means of a cylinder conduit (4), an accumulator conduit (5) and a tank conduit (8), wherein a pressure converter (9; 9') attached to the valve unit (3) can be operated as pressure intensifier and as pressure reducer, wherein the valves arranged in the valve unit (3) are operated in such a way that - in a first step, the pressure converter (9; 9') works as pressure reducer through the actuation of a 3-way-valve (17) and a pre-pressing valve (11) and an admission pressure is developed in the press cylinder (1), - in a second step, a pressure is developed in the press cylinder (1) through the actuation of a stop valve (15) and a main pressing valve (14), which can be selected beforehand and which corresponds to the maximum pressure in the pneumatic-hydraulic accumulator (7), - in a third step, the pressure converter (9; 9') works as a pressure intensifier through the actuation of the main pressing valve (14) and a low-pressure chamber inlet valve (13) and a pressure is developed in the press cylinder (1), which is higher than the pressure in the pneumatic- hydraulic accumulator (7), -in the fourth step, the existing pressure in the press cylinder (1) is released until it is as high as the pressure in the pneumatic-hydraulic accumulator (7) through the actuation of the main pressing valve (14) and the stop valve (15), - if necessary, in a further step, the piston (9K) of the pressure converter (9) is brought to the desired position for a next pressing cycle through the actuation of the main pressing valve (14) and a low-pressure chamber outlet valve (12), and -finally, the remaining pressure in the press cylinder (1) is released through the actuation of the pressure release valve (16). 7. Process as claimed in claim 6, in which the first step is repeated to develop a higher admission pressure using a modified actuation of the 3-way- valve. The invention relates to a controller for a hydraulic press, comprising a pressing cylinder (1), a reservoir (2), a valve group (3), a pressure medium reservoir (7) and a hydraulic pump (6), connected together by means of a cylinder line (4), a reservoir line (5) and a tank line (8). According to the invention, a pressure converter (9) is arranged on the valve group (3), which may operate as a pressure amplifier or pressure reducer. The particular mode of action of said controller is achieved whereby the valve group (3) comprises a pre-press valve (11), a low-pressure chamber outlet valve (12), a low-pressure chamber inlet valve (13), a main press valve (14), a closing valve (15), a pressure release valve (16) and a 3-way valve (17), which may be operated by a particular control sequence. Said invention is applicable in hydraulic presses and of particular advantage in presses for the forming of ceramic pieces such as tiles.

Documents:

367-KOLNP-2003-(03-01-2012)-FORM-27.pdf

367-KOLNP-2003-FORM 27 1.1.pdf

367-KOLNP-2003-FORM 27.pdf

367-kolnp-2003-granted-abstract.pdf

367-kolnp-2003-granted-assignment.pdf

367-kolnp-2003-granted-claims.pdf

367-kolnp-2003-granted-correspondence.pdf

367-kolnp-2003-granted-description (complete).pdf

367-kolnp-2003-granted-drawings.pdf

367-kolnp-2003-granted-examination report.pdf

367-kolnp-2003-granted-form 1.pdf

367-kolnp-2003-granted-form 13.pdf

367-kolnp-2003-granted-form 18.pdf

367-kolnp-2003-granted-form 3.pdf

367-kolnp-2003-granted-form 5.pdf

367-kolnp-2003-granted-gpa.pdf

367-kolnp-2003-granted-priority document.pdf

367-kolnp-2003-granted-reply to examination report.pdf

367-kolnp-2003-granted-specification.pdf

367-kolnp-2003-granted-translated copy of priority document.pdf