JPS6253278B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to forging and pressing operations,
More specifically, the present invention relates to a method of controlling a hydraulic screw press and an apparatus for implementing the method.

[Prior Art] The field of application of hydraulic screw presses has been expanding more and more in recent years.

During operation of a hydraulic screw press, a ram is often driven. The ram is first driven through the entry stroke of its stroke and is then accelerated until the required speed is reached, at which time the acceleration of the ram is terminated.

Therefore, the speed of the ram when impacting the workpiece is primarily dependent on the length of the further stroke the ram travels after stopping the supply of working fluid.

However, experiments have shown that the point in the stroke at which the ram reaches the required speed is not always the same, but changes due to changes in the viscosity of the working fluid, changes in press lubrication conditions, pressure fluctuations in the pressure accumulator, etc. Tend.

As a result, the distance between the point at which drive energy injection stops and the point of impact changes, and the speed of the ram at impact also changes. The resulting impact energy is therefore different from the intended one.

The above conventional method includes a speed sensor connected to the ram of the press through a mechanical transmission, and a speed comparator, the input of which is connected to the main speed controller and the speed sensor; The output of this speed comparison device is connected to a solenoid that controls a fluid distribution device located in the middle of a hydraulic line connecting the pressure accumulator to the hydraulic drive cylinder of the press. However, such a configuration cannot eliminate the above-mentioned drawbacks.

[Problems to be Solved by the Invention] One of the drawbacks of the conventional control method is that the magnitude of the impact energy actually applied to the workpiece deviates from the intended value. This is because after accelerating the ram to the required speed, the fluid distribution device is deactivated, thus reducing the speed of the ram.

This will be explained in more detail with reference to FIG. The working fluid is supplied from the pump 7 to the hydraulic cylinder 2 via the valve 8.
When the piston 40 is supplied, the position of the piston 40 moves and pushes the screw 3 and the ram 5 to rotate the flywheel 4.

The speed of the ram 5 steadily increases as shown in FIG. When the required speed V1 is reached, the valve 8 closes at time A. At this point, the fluid flow stops and the speed of the screw 3, flywheel 4, and ram 5 decreases. Since the piston 40 is firmly connected to the screw 3, it continues to move within the cylinder due to inertia even if the supply of working fluid is cut off, creating a considerable vacuum inside the cylinder. As a result, the speed of the ram 5 rapidly decreases as shown in FIG. 8A-B. The impact on the workpiece then occurs at a speed V2 lower than the speed V1. As can be seen from the figure, the larger the portion A-B, the lower the speed of the ram 5 at the time of impact. Therefore, it is necessary to make the distance between A and B as short as possible, ideally zero. That is, it is necessary to accelerate the ram 5 so that it reaches the required speed at time B when the ram 5 collides with the workpiece.

SUMMARY OF THE INVENTION The main objects of the invention are a method for reaching the required speed at a point just before the ram of a press travels in its travel path and begins forming the workpiece, and an apparatus for carrying out this method. The goal is to provide the following. The purpose of this is to accelerate the moving part of the press in order to obtain the impact energy required to form the workpiece, measure the moving speed of the moving part (ram), and use such acceleration to determine the speed corresponding to the given impact energy. This is accomplished by a method of controlling a hydraulic screw press that terminates acceleration when achieved. In this method, the planned point at which acceleration will end is determined in advance, and the point at which the required speed will be reached is predicted by how much it will deviate from this planned point based on the speed, and the point at which the required speed will be reached is compared to the point at which the desired speed will be reached. Using the deviation value (distance, velocity) with respect to the point, one of the motion parameters (acceleration, acceleration stroke, etc.) of the movable part is changed to achieve the required velocity at the point of impact.

Another object of the present invention is to provide a device capable of measuring impact energy with high accuracy.

Another object of the invention is to provide a method for controlling a hydraulic screw press in which impact energy can be measured with high precision.

Yet another object of the invention is to reduce tool wear and extend the service life of the press.

[Example] One method of this example is to first drive the movable part or ram at a constant speed through the approach stroke, then accelerate it at a constant acceleration to the required speed, and compare the planned point at which the acceleration ends and the actual required point. The length of the approach stroke (i.e. the travel stroke of the ram before starting acceleration) is changed depending on the deviation from the point where the speed is reached, and therefore the length of the stroke in which acceleration occurs changes. become.

Another method is to determine the planned point at which the acceleration will end, and calculate the deviation between this planned point and the point at which the required speed is reached according to the speed at this planned point.
This deviation is used to change the acceleration of the movable part while keeping the length of the acceleration stroke constant.

In this case, the acceleration is changed by changing the pressure of the working fluid of the hydraulic screw press acting on the movable part.

Now, with reference to FIG. 1, let us touch upon the essence of the present invention. FIG. 1 illustrates the speed changes during the stroke of the ram 5 within the press.

The travel of the ram 5 starts at point O and is moved at a constant rate to point A. The process up to this point will be called the approach process. This movement is accomplished by supplying working fluid from a pump directly into the cylinder of the press. At point A, the supply of working fluid from the hydraulic pressure accumulator is started, and the fluid pressure provides a constant driving effect to the movable body of the hydraulic cylinder. The ram 5 of the press is therefore driven with constant acceleration. That is, the speed of the ram 5 increases from point A to point B. The process up to this point will be called the acceleration process.

When the ram 5 reaches the required speed, point B, the supply of working fluid from the hydraulic pressure accumulator to the hydraulic cylinder is cut off, and the ram 5 remains at full speed for the rest of the process up to point C, where the forming of the workpiece begins. move by the inertia exerted on it.

Point B is selected to be a short distance BC from point C, and ram 5 is used for braking by cutting off the working fluid supplied to the hydraulic cylinder.
The motion of the robot is designed so that it is hardly affected.

However, if the required velocity V is achieved at point B1, which is farther from point C by a distance B1C which is greater than BC, this means that the ram 5 has gained the required energy before reaching point B.
Then, distance B1B can be considered as a deviation value from the point where the required speed is achieved. The length of the acceleration stroke is shortened by moving the acceleration start point A to the right (the direction in which the ram 5 collides with the workpiece) in accordance with this value. That is, the length of the approach stroke is increased by ΔS1, which is the same as B1B.

If, on the other hand, the required velocity V is achieved at point B2, which is closer to point C, this means that after the ram 5 has reached point B, the required energy has been obtained. Distance B2B is the deviation, whereby the length of the acceleration stroke is increased by moving point A to the left (i.e. in the direction of point O), i.e. by changing or adjusting the length of the approach stroke to the planned point The objective of achieving the required speed in is achieved.

However, the same objective can be achieved by changing other parameters of the motion, namely the acceleration. This will be explained with reference to FIG.

The stroke of the ram 5 is started at O by supplying fluid from the hydraulic accumulator, acceleration begins and the speed of the ram 5 begins to increase from here. When the ram 5 reaches the required speed at point D, the speed sensor sends a signal to cut off the supply of working fluid to the hydraulic cylinder, the acceleration is terminated and the workpiece is then struck at point E. distance
ED is determined based on the same reasons as distance BC.
If the required speed is achieved at point D1, this means that the required energy has been stored in ram 5 before it reaches point D. That is, the acceleration of the moving part is changed by reducing the pressure in the hydraulic accumulator to a value that ensures that no deviation of D1D occurs in the next ram actuation cycle. Similarly, if the required velocity is achieved at point D2, the pressure is increased. It will be apparent to those skilled in the art that various combinations of the methods described herein may be employed. The idea of the present invention is that the point at which acceleration ends is selected to be a certain distance away from the point of impact, and by shortening this distance, it does not have a large effect on the ram speed at the time of impact in practice. This point is established reliably by measuring the speed and changing the motion parameters of the ram 5.

(First Example) This is a control method for changing the length of the approach stroke. FIG. 3 schematically shows an embodiment of a hydraulic screw press 1 comprising a hydraulic cylinder 2, a screw 3, a flywheel 4, and a ram 5.

The device for controlling this press includes a hydraulic accumulator 6 and a pump 7 communicating with the hydraulic cylinder 2 via a solenoid-controlled valve 8, and the pump 7 communicating with the hydraulic accumulator via a check valve. , perform pressure adjustment.

The control device further includes an electrical control system 10,
It has the ability to change the length of the acceleration stroke whenever necessary. Electrical control system 10 is connected to ram 5 via a mechanical part. It includes a speed sensor 11, such as a speed measuring generator, and a main speed controller 12, such as a voltage divider. The speed sensor 11 and the main speed controller 12 are connected to a speed comparator circuit 13, for example in the form of a null detector, which is well known in the field of automatic control. The electrical control system 10 includes a transmitter or sensor 14 for sensing the ram 5 passing the end of its approach stroke, which operates as a suitable limit switch, either of the contact or non-contact type. The limit switch is connected to a reversible stepping motor 15 which is the actuator for setting the limit switch in the desired position.

The sensor 14 is a valve 8 controlled by a solenoid.
When the sensor 14 sends a signal, the valve 8 is activated and the hydraulic pressure accumulator 6 is connected to the hydraulic cylinder 2.

The electrical control system 10 also includes a sensor 16 responsive to the displacement of the ram 5 (i.e. the distance traveled by the ram 5).
and a sensor 17 that detects the ram 5 passing through the planned point where acceleration ends. The sensor 16 is in the form of a suitable known linear displacement transducer, such as a circular pulse transducer connected to the ram 5 of the press via a mechanical part, and the sensor 17 is in the form of a suitable known orbital switch. It is of the form. The outputs of the sensors 16 and 17 are connected to a logic control circuit 18,
The logic control circuit 18 is adapted to control the reversible stepping motor 15 of the sensor 14. The logic control circuit 18 includes the speed comparison circuit 13
If the signal from the sensor 16 and the signal from the sensor 17 arrive at different moments, the signal is passed from the sensor 16 to the reversible stepping motor 15; if the two signals arrive at the same time, the signal from the sensor 16
The signal from the reversible stepping motor 15 is prohibited.

FIG. 4 shows an embodiment of this logic control circuit. This circuit consists of three AND elements 19, 20, 2
1, one input terminal of the AND element 19 is connected to the sensor 16, and the other input terminal is connected to the sensor 17 that senses the ram 5 passing a predetermined acceleration end point. One input terminal of the AND element 20 is connected to the sensor 16, and the other input terminal is connected to the speed comparison circuit 1.
Connected to 3. One input terminal of the AND element 21 is connected to the speed comparison circuit 13, and the other input terminal is connected to a sensor 17 responsive to the ram 5 passing a predetermined point at which acceleration ends.

Note that this logic control circuit includes two two-input inhibition gates 22, one input terminal of each gate is connected to the output of AND element 21, and the other input terminal is connected to the outputs of AND elements 19 and 20, respectively. , the outputs of the two inhibition gates 22 drive the windings of a reversible stepping motor 15 which moves a sensor 14, which is connected to an annular commutator 23 and detects the end point of the approach stroke (i.e. the start point of acceleration), to a desired position. Switch.

This device operates as follows.

Working fluid is supplied to the hydraulic cylinder 2 by a pump 7 through a solenoid-controlled valve 8. Ram 5 then begins its approach. Ram 5 is sensor 14
When actuated, the sensor 14 sends a signal to the solenoid-driven valve 8 to switch the valve and supply actuating pressurized fluid from the hydraulic accumulator 6 to the hydraulic cylinder 2. In this way, from the ram 5 to the speed comparison circuit 13
The sensor 16, which senses the displacement of the ram 5 by increasing the signal sent to its input, sends a pulse signal to the logic control circuit 18. When the ram 5 reaches the required speed, the speed comparison circuit 13 sends an output signal to the solenoid-controlled valve 8 and the supply of working fluid from the hydraulic accumulator 6 to the hydraulic cylinder 2 is stopped. The acceleration of the press ram 5 is terminated and the ram 5 hits the workpiece with stored kinetic energy.

Regarding the acceleration of the ram 5, the following three cases can occur.

(1) When the ram 5 reaches the required speed at the point where the sensor 17 is activated.

In this case, the respective signals of the speed comparator circuit 13 and the sensor 17 reach the respective inputs of the AND element 21 at the same time, which causes the AND element 21 to send an output signal to each input of the two inhibit gates 22 and to the respective inputs of the sensor 21. The pulses from 16 are not transmitted to the input of the toroidal commutator 23 controlling the stepping motor 15. Therefore, since there is no need to modify the position of the sensor 14, no such position modification occurs.

(2) If the ram 5 reaches the required speed before the sensor 17 is activated.

In this case, the signal arriving at the input of the AND element 20 from the speed comparison circuit 13 does not inhibit the signal from the sensor 16. No prohibition signal is sent from the AND element 21 to the prohibition input of the prohibition gate 22. This is because AND element 21 receives only the signal from speed comparison circuit 13. Therefore, sensor 1
The pulses from 6 are sent to the positive (+) input of the toroidal commutator 23, which distributes these pulses to the windings of the reversible stepping motor 15. Therefore, the reversible stepping motor 15 rotates and the sensor 1
4 in a direction so that the instantaneous point at which the required speed is reached coincides with the planned point. As the ram 5 continues to move further, the sensor 17 operates, and the signal from the sensor 17 becomes
Since the signal is supplied to the input of the AND element 21, the AND element 21 sends a signal to the inhibit input of the inhibit gate 22. The signal to the annular commutator 23 is then terminated,
The reversible stepping motor stops. The new position of the sensor 14 thus determined is the position at which the ram 5 can reach the desired speed at the expected point where it finishes accelerating during the next operating cycle of the press.

(3) When the ram 5 reaches the required speed after the sensor 17 is activated.

Now, when the output signal of the sensor 17 is sent to the AND element 19, a pulse can be transferred from the sensor 16 to the input of the inhibit gate 22. At this point, since there is no signal coming from the speed comparator circuit 13 to the input of the AND element 21, there is also no signal coming to the inhibit input of the inhibit gate 22. Yotsute AND
Pulses from the output of the element 19 are supplied to an annular commutator 23 for the reversible stepping motor, which rotates in the opposite direction to the direction (2) above and moves the sensor 14. During this time, the ram 5 moves while being accelerated, and when the required speed is reached, the speed comparator circuit 13 sends an output signal to the input of the AND element 21, and the AND element 21 sends an output signal to the inhibit input of the inhibit gate 22. do. This causes the stepping motor to stop when the sensor 14 is at a position where it can just reach the required speed at the intended point of termination of acceleration during the next cycle of operation of the ram 5.

(Second Embodiment) Next, a control method performed by changing acceleration will be described.

FIG. 5 shows an example thereof. Most of the constituent units of this device are the same or similar to those of the embodiment shown in Fig. 3, and the difference between the two is the electric circuit for pressure control and the oil supply path between the hydraulic pressure accumulator and the hydraulic cylinder. This electric circuit has a built-in means for changing the pressure of the pressure control circuit 2.
4, the input of this pressure control circuit is connected to the output of logic control circuit ^18- and the output of pressure transducer 25, and the output of this pressure control circuit is connected to a regulator. This regulator includes a solenoid-controlled valve 26 that allows communication between the pump 7 and the hydraulic pressure accumulator 6, and when it is necessary to increase the pressure of the oil supply line through which working fluid is supplied to the hydraulic drive, the pump 7 and the hydraulic pressure accumulator 6 are connected to each other. The hydraulic pressure accumulator 6 is communicated with the oil drain pipe when the pressure in the oil supply path is lowered.

The logic control circuit ^18- of this embodiment is slightly different from that shown in FIG.

A block diagram of the logic control circuit ^18- is shown in FIG. This circuit is the AND circuit explained in the previous example.
In addition to the elements 19, 20, 21 and the inhibit gate 22, it further includes a reversible pulse counter 27, the input of which is connected to the output of the inhibit gate 22, and the output of this counter is connected to the output of the inhibit gate 22. 1 input, respectively. The second input of this D/A converter 28 is connected to the AND element 21 and also to the D/A converter 2.
The output of 8 is connected to a pressure control circuit 24.

This device operates as follows. When the press is started, a solenoid-controlled valve 8 is actuated to connect the hydraulic cylinder 2 to the hydraulic accumulator, thereby starting the acceleration of the ram 5. As the ram 5 accelerates, the speed sensor sends an increasing signal to the input of the speed comparison circuit 13, while the sensor 16
A pulse signal proportional to the distance traveled by the logic circuit 18- is applied to the logic circuit ^18- .

When the ram 5 reaches the required speed, the output of the speed comparator circuit 13 is supplied to the valve 8 which stops supplying pressurized working fluid from the hydraulic accumulator 6 to the hydraulic cylinder 2. Acceleration of the moving parts of the press is stopped and the movement of the ram 5 is then determined by inertia, ie stored kinetic energy, up to the point where it impacts the workpiece.

The following three cases can occur regarding the acceleration of the ram 5.

(1) When the required speed is reached at the moment when the sensor 17 that responds to the ram 5 passing the planned point at which acceleration ends is activated.

In this case, from the sensor 16 to the AND elements 19 and 2
The signals to each input of 0, (Fig. 6) are reversible counter 2.
It is not sent to the input of 7. This is because signals from the speed comparison circuit 13 and the sensor 17 arrive at the input of the AND element 21 at the same time, and the AND element 21 sends a signal to the inhibit gate 22 to inhibit pulse transmission. The electrical control system ^10- therefore does not generate a correction signal.

(2) Before the sensor 17 sends out the output signal, the ram 5
reaches the required speed.

If this case occurs, speed comparison circuit 1
An output signal from 3 is sent to the input of AND element 20 and a pulse is transmitted from sensor 16 to the input of inhibit gate 22. On the other hand, no signal is applied from the AND element 21 to the inhibit input of the inhibit gate 22. This is because the AND element 21 receives the signal only from the speed comparator circuit 13. The pulse from sensor 16 is therefore applied to the count-up input of reversible counter 27. As the ram 5 advances more and more, the sensor 17 responds and a signal is also input to the other input of the AND element 21, so that the AND element 21 outputs a signal to the inhibit input of the inhibit gate 22.

Pulsing to the reversible counter 27 is stopped and the counter stores the value corresponding to the movement of the ram 5 from the point at which the required speed is reached to the point at which the sensor 17 responds. This value is converted by the D/A converter 28 into a voltage value proportional to the required pressure change, and when the D/A converter 28 receives the output signal from the AND element 21, the pressure control circuit 24 supplied to the input. The pressure control circuit 24 outputs a signal that opens the valve 26 at the moment this voltage is applied to its input, so that the hydraulic pressure accumulator is connected to the drain side, so that:
Signal coming from pressure transducer 25 and D/A converter 28
The pressure there decreases until the signal coming from the As soon as they are equal, the valve 26 is closed and the pressure is reduced to such a value that in the next press cycle the ram 5 reaches exactly the required speed at the intended point of ending the acceleration.

(3) If the ram 5 reaches the required speed after the sensor 17 is activated.

In this case, the signal coming from the sensor 17 is applied to the AND element 19. This causes a pulse to be applied from the sensor 16 to the input of the inhibit gate 22. At this moment, from the speed comparison circuit 13 to the AND element 21
No signal is input to the input of , so the pulse is
Proceeding from the output of the AND element 19 to the countdown input of the counter 27, this counter 27 performs a countdown. As the ram 5 advances more and more, its speed increases, and when the required speed is reached, the speed comparison circuit 13
sends an output to the AND element 21. As a result, the inhibit input of the inhibit gate 22 receives a signal and pulse counting is stopped. At the same time, the output of the AND element 21 is applied to the input of the D/A converter 28, and transmission of the voltage signal to the pressure control circuit 24 is started. The output signal of the pressure control circuit 24 opens the valve 26 so that the pump 7 is connected to the hydraulic pressure accumulator 6. Then, the pressure in the hydraulic pressure accumulator 6 increases. Pressure transducer 2
At the moment when the signal coming from ram 5 and the signal coming from D/A converter 28 become equal, pressure control circuit 24 closes valve 26 and the pressure is applied to ram 5 in the next press operation cycle.
will rise to a value at which the required velocity will be reached at the planned point, and this pressure increase will stop.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a method (first embodiment) for controlling a hydraulic screw press by changing the length of the acceleration stroke, and Figure 2 is a diagram showing how to control a hydraulic screw press by changing the acceleration of the movable part. A line diagram showing a control method (second embodiment), FIG. 3 shows an outline of a device for controlling a variable acceleration stroke hydraulic screw press, and a system diagram showing an outline of the hydraulic screw press 1, Figure 4 is a system diagram of one embodiment of the logic circuit in Figure 3, Figure 5 is a system diagram of another device that controls a variable pressure hydraulic screw press, and Figure 6 is a diagram of the control circuit in Figure 5. FIG. 7 is a diagram showing the principle of a conventional press, and FIG. 8 is an explanatory diagram showing changes in the speed of the ram shown in FIG. 7. 5... Ram (ram) of hydraulic screw press, 1
0...Electrical control system, 13...Speed comparison circuit, 1
4...Sensor responsive to the ram passing the end point of its approach stroke, 16...Speed sensor for the ram, 17...Sensor responsive to the ram passing the point ending acceleration, 18...Logic control circuit. , 23... annular commutator, 19, 20, 21... AND element, 24
...Pressure control circuit, 22...Prohibition gate, 28...
...D/A converter.

Claims (1)

[Claims] 1. Implementing an acceleration stroke of a movable part of the press in order to obtain the necessary impact energy to form a workpiece, changing the speed of movement of the movable part, and applying a certain preset impact energy. In the method of controlling a hydraulic screw press, the method includes: terminating the acceleration when a speed corresponding to the speed is reached; presetting points B and D at which the acceleration is to be terminated; and presetting the points B and D at which the required speed is reached. measuring a displacement value ΔS from an acceleration end point, and varying at least one kinematic parameter of the movable part depending on this value, thereby increasing the preset speed. A method for controlling a hydraulic screw press, characterized in that: is achieved at a point of impact on a workpiece. 2. A method according to claim 1, characterized in that a constant acceleration value is maintained over the acceleration stroke and the length of the acceleration stroke is varied. 3 Before the acceleration stroke, an approach stroke is provided in which the movable part advances at a constant speed, and the movable part is first moved at a constant speed through the approach stroke, and then this is preset at a constant acceleration. and varying the length of the approach stroke accordingly depending on the displacement of the point at which the preset speed is reached from the preset acceleration end point. 3. A method according to claim 2, characterized in that the length is varied. 4. The method according to claim 1, characterized in that the acceleration of the movable part is varied over the acceleration stroke while the length of the acceleration stroke remains unchanged. 5. A method according to claim 4, characterized in that the hydraulic pressure acting on each movable part to be accelerated is changed in order to change the acceleration. 6 A hydraulic pressure accumulator 6 and a working fluid supply pump 7 communicating with the hydraulic cylinder 2 driving the ram 5 of the press via a solenoid-controlled valve 8, respectively, and the ram of the press connected to the actuator and passing through the end of the approach stroke. 5 and a speed comparator circuit 13 which generates a signal sent to the solenoid-controlled valve 8 and which interrupts communication between the pressure accumulator 6 and the hydraulic cylinder 2 of the press.
In a hydraulic screw press control device of the type for varying the length of the acceleration stroke, the control device includes a sensor 11 responsive to the speed of the press ram 5 and a main speed controller 12 presetting the speed of the ram 5 of the press. a system 10 for controlling the actuator of a sensor 14 responsive to the ram 5 passing through a point, a sensor 17 responsive to the ram 5 passing a preset acceleration end point, and a ram displacement sensor; 16 and a logic control circuit 18 connected to the output of said sensor and the output of said speed comparator circuit 13 so that when signals are supplied by said speed comparator circuit and acceleration endpoint sensor 17 at the same time, a RAM and a logic control circuit 18 that prohibits the displacement sensor 16 from transmitting a signal and allows the ram displacement sensor 16 to transmit a signal when only one of the signals is supplied. Control device for screw press. 7. The invention as claimed in claim 6, characterized in that the logic control circuit 18 includes means for determining the direction of action of the actuator of the sensor 14 in response to the ram 5 of the press passing through the end of its entry stroke. Device. 8. The logic control circuit 18 includes three AND type logic elements, the first AND element 19 is connected to a sensor 17 whose input is preset with the ram displacement sensor 16 and responsive to the passage of the ram 5 at the end of acceleration. and the output of the second AND element 20 is sent to the ram displacement sensor 16.
and the speed comparison circuit, and the third AND element 2
1 input is connected to the speed comparator circuit 13 and a sensor 17 responsive to passage of the ram 5 at a preset acceleration end point;
including two inhibit gates 22, each of which inhibit inputs are connected to the output of the third AND element 21,
Other inputs are connected to the output of the first AND element 19 and the output of the second AND element 20, respectively,
The output of the prohibition gate 22 is the stepping motor 1 of the actuator of the sensor 14 at the end point of the approach stroke.
8. A device according to claim 7, characterized in that it is connected to an annular commutator (23) controlling the flow rate. 9 A hydraulic pressure accumulator 6 connected to the hydraulic cylinder 2 driving the ram 5 of the press via a solenoid-controlled valve 8 and a speed comparison circuit 13 connected to the pressure accumulator 6.
a sensor 11 responsive to the speed of the ram 5 generating a signal to the solenoid-controlled valve 8 which interrupts communication between the hydraulic cylinder 2 and the hydraulic cylinder 2, and a main speed controller 12 presetting the ram speed throughout the acceleration stroke. A control device for a hydraulic screw press of the type that changes the acceleration of a movable part by moving the hydraulic pressure accumulator 6 to the hydraulic cylinder 2, the control system ^10- comprising ^: A sensor 17 that responds to the ram 5 passing through a preset acceleration end point, a ram displacement sensor 16, and a sensor 17 connected to the output of the sensor and the output of the speed comparison circuit 13 to detect the required pressure fluctuation to obtain the desired speed. a logic control circuit that generates a signal proportional to the pressure control circuit, the signal being sent to a second input of the pressure control circuit, the second input of the pressure control circuit being connected to the pressure transducer 25; The output of another solenoid-controlled valve 2 controls the communication between the hydraulic accumulator and the pump or drain.
6 to increase or decrease the pressure in the hydraulic path. 10. The apparatus of claim 9, wherein the logic control circuit ^18-- includes means for determining the direction of pressure variations in the hydraulic path. 11 The logic control circuit 18 ^- is an AND of three
includes a logic element, the input of the first AND element 19 being connected to a ram displacement sensor 16 and a sensor 17 responsive to the ram 5 passing through a preset acceleration end point, and the input of the second AND element 20 being connected to a ram displacement sensor 16 and a sensor 17 responsive to the ram 5 passing through a preset acceleration end point Sensor 1
6 and the speed comparison circuit 13, and the input of the third AND element 21 is connected to the speed comparison circuit 13 and the sensor 1 responsive to the ram 5 passing through a preset acceleration end point.
7, the logic control circuit further includes two inhibit gates 22, each inhibit input being connected to the output of the third AND element 21;
The other inputs are the first AND element 19 and the second AND element 19, respectively.
The output of the inhibition gate 22 is connected to one input of the D/A converter 28, and the other input of the D/A converter 28 is connected to the input of the third AND element 21. 10. Apparatus according to claim 9, characterized in that the output of the inhibit gate (22) is connected to a pressure control circuit (24).