EP3643422A1 - Pressing device for work pieces - Google Patents

Abstract

The present invention relates to a press machine 10 for pressing workpieces, comprising a hydraulic pump 27 for conveying a hydraulic fluid 70; an electric motor 20 for driving the hydraulic pump 27; a working cylinder 25 which is in hydraulic connection with an outlet of the hydraulic pump 27; a pressure relief valve 50, which is in hydraulic connection with the outlet of the hydraulic pump 27 and which opens at a certain preset pressure Pv of the hydraulic fluid 70; an electronic controller 40 for actuating the electric motor 20 and a sensor 60 which monitors the state of the pressure relief valve 50 and outputs a signal which describes the state of the pressure relief valve 50 to the electronic controller 40. A method for operating such a press machine 10 is also claimed.

Description

Technical field

The present invention relates to a press machine, in particular a hand-held press machine, for pressing workpieces, and a method for operating a press machine.

State of the art

Methods for pressing workpieces, for example tubular workpieces, in particular pipes in installation technology, are known in the prior art. In a known method, two pipes are permanently connected to one another by means of a press fitting. For this purpose, the pipes are inserted into openings of a press fitting, which has polymer seals for sealing with the pipes. After inserting the pipes to be connected, the press fitting is pressed using a suitable press machine, i.e. plastically deformed so that the inserted pipes can no longer be pulled out and the seals seal securely.

The pressing is carried out with a hand-held and motor-driven press machine, which can have interchangeable tools, such as press jaws with different sizes and geometries. In addition, press machines are also known for other tasks. For example, press machines are used for pressing, crimping or cutting workpieces, for example in the electrical industry when connecting cable lugs to cables.

In a hand-held press machine, the press jaws are arranged around the press fitting for pressing. To close the press jaws, a user presses an operating button and thereby starts an electrically operated hydraulic pump. This creates a pressure in a hydraulic fluid that acts on a working piston. The working piston generates a high pressing force, which is exerted on the surface of the press fitting by means of pressing tongs, so that this is radially compressed and plastically deformed. The plastic deformation of the press fitting securely connects the workpieces, for example the press fitting and pipe. The inner tubes can also experience plastic deformation.

The pressing process is usually ended in the case of press machines of the prior art by opening a pressure relief valve when a certain maximum pressure is reached, reducing the hydraulic pressure and returning the working piston to its starting position. The specified maximum pressure ensures that a suitably high pressing force has been exerted on the workpiece in order to ensure sufficient pressing. When the end of the pressing process is reached, the operator can release the operating button and switch off the electric motor of the hydraulic pump. Such manual control of the hydraulic pump by the operator can mean an unnecessary consumption of electrical energy and requires that the operator keep the operating button pressed until the end of the pressing process. If the operator releases the operating button before the end of the pressing process, there is no guarantee that the workpieces have already been pressed sufficiently.

From the publication EP 2 501 523 B1 is a hand-held press device for pressing a press fitting in installation technology and for pressing cable lugs. In order to generate the required high pressing forces, the pressing tool is connected to an electro-hydraulic conversion device. A brushless electric motor is used as the drive motor. As soon as the required pressing force is reached, a pressure relief valve opens, causing the engine speed to skyrocket. This increase in the engine speed is recognized by a controller of the pressing device and the electric motor is then switched off. Such a pressing device therefore requires complex monitoring and evaluation of the engine speed.

It is therefore the object of the present invention to provide a press machine which overcomes the disadvantages mentioned above and has a simple and effective control. Furthermore, a corresponding method for operating a press machine is to be provided.

Summary of the invention

The above-mentioned problems are solved according to the invention by a press machine according to claim 1 and a method for operating a press machine according to claim 11.

In particular, the above-mentioned problems are solved by a press machine for pressing workpieces, comprising a hydraulic pump, for conveying a hydraulic fluid; an electric motor for driving the hydraulic pump; a working piston which is in hydraulic connection with an outlet of the hydraulic pump; a pressure relief valve which is in hydraulic connection with the outlet of the hydraulic pump and which opens at a certain preset pressure of the hydraulic fluid; an electronic control for controlling the electric motor; and a sensor that monitors the state of the pressure relief valve and outputs an electrical signal that describes the state of the pressure relief valve to the electronic control.

By monitoring the status of the pressure relief valve through the sensor, the electronic control recognizes the status of the pressure relief valve, for example whether it is closed or open, and can control the press machine accordingly. In particular, the pressing process can thus be carried out automatically to the end by the control unit operating the electric motor until the pressure relief valve is triggered and then the electric motor stops. This ensures that the necessary pressing pressure is reached and electrical energy is saved since the electric motor is only operated as long as necessary. This is particularly advantageous in the case of battery-operated pressing devices. In addition, it can be recognized whether the required pressing pressure has been reached or not with manual control of the pressing machine by the user.

The pressure relief valve preferably has a movable valve piston which is biased against a valve seat by means of a spring. A spring-biased pressure relief valve is particularly reliable in operation and allows the desired release pressure to be set by adjusting the spring preload.

The sensor preferably has a magnetic sensor which is influenced by a magnet on the pressure relief valve. Magnetic actuation of the sensor is particularly reliable and easy to implement. All that is required is to attach a magnet to a movable part of the pressure relief valve, such as the valve piston. The magnet then moving with the valve piston acts on the magnetic sensor via its magnetic field without a mechanical or electrical contact being necessary for this. This increases the reliability of the detection and of the press as a whole. The Hall sensor itself can also contain a magnet, in which case the detection takes place by changing the magnetic field, e.g. by the movement of a ferro-magnetic piston

The magnetic sensor preferably has a Hall sensor. The magnetic sensor can have a Hall sensor that can detect a magnetic field very reliably. The output signal is dependent on the size of the magnetic field, so that the distance between the magnet and the Hall sensor can be recorded continuously. This enables a particularly accurate and reliable detection of the state of the pressure relief valve, since both the closed and the open state of the pressure relief valve can be detected by a clear electrical signal.

The magnetic sensor preferably has a reed contact. A reed contact is a particularly inexpensive type of magnetic sensor.

The magnetic sensor preferably has an inductive sensor. When using an inductive sensor, the change in a magnetic field can preferably be detected. The moving magnet on the pressure relief valve preferably induces a voltage in an inductive sensor, for example in a coil. This voltage can be detected by the control.

The valve piston preferably has a permanent magnet. The state of the pressure relief valve can be detected particularly easily by means of a permanent magnet on the valve piston. The permanent magnet moves together with the valve piston when the pressure relief valve is opened or closed, as a result of which the magnetic field generated by the permanent magnet is related to a fixed magnetic sensor changes. This magnetic field or the change in the magnetic field can be detected by the magnetic sensor.

The valve piston can preferably also contain an inversely arranged magnet, for example a permanent magnet, which, in combination with a further magnetic sensor, increases the security of the signaling. In this case, for example, the open position of the valve piston can be actively detected by the first magnetic sensor and the closed position of the valve piston can be actively detected by the second magnetic sensor. This means that precisely defined signals are applied to the control for both states of the pressure relief valve, and the control of the press machine becomes insensitive to external magnetic fields.

Preferably, both the normally arranged magnet and the inversely arranged magnet can also be an electromagnet, which only generates a magnetic field after the pressing process has started. This enables the controller to evaluate the signals from the magnetic sensors even in the idle state and compare them with those after starting. This makes it possible to identify and filter out interference signals from external magnetic fields.

The sensor preferably has an optical sensor. The state of the pressure relief valve can also be optically detected. An optical sensor is used here, which preferably responds to the change in the incidence of light due to a mechanical movement of the valve piston. For example, a diaphragm could be attached to the valve piston, which enters the space between a fork light barrier when the valve piston moves.

The sensor preferably has an electrical switch. An electrical switch is a particularly inexpensive type of sensor. For example, the electrical switch can be arranged such that the valve piston acts directly on the electrical switch when it is displaced.

The sensor preferably has a capacitive sensor. The status of the pressure relief valve can also be monitored capacitively. For this purpose, a capacitive sensor can be formed, for example by the valve piston movable part and a fixed electrode forms a fixed part of a capacitive sensor. The distance between the valve piston and the electrode and thus the switching state of the pressure relief valve can then be determined by determining the electrical capacitance between the valve piston and the electrode.

The electric motor is preferably a brushless DC motor. Such a brushless DC motor can be controlled very precisely and is very low-maintenance with high performance.

1. 1. Antreiben einer Hydraulikpumpe mittels eines Elektromotors;
2. 2. Fördern einer Hydraulikflüssigkeit mittels der Hydraulikpumpe;
3. 3. Öffnen eines Überdruckventils, welches mit dem Ausgang der Hydraulikpumpe in hydraulischer Verbindung steht, bei einem bestimmten voreingestellten Überdruck der Hydraulikflüssigkeit;
4. 4. Überwachen des Zustands des Überdruckventils mittels eines Sensors;
5. 5. Ausgeben eines elektrischen Signals an eine elektronische Steuerung, wobei das Signal den Zustand des Überdruckventils beschreibt; und
6. 6. Ansteuern des Elektromotors durch die elektronische Steuerung basierend auf dem Signal.

The above-mentioned problems are further solved by a method for operating a press machine for pressing a workpiece, comprising the following steps:

1. 1. driving a hydraulic pump by means of an electric motor;
2. 2. Pumping a hydraulic fluid by means of the hydraulic pump;
3. 3. Opening a pressure relief valve, which is in hydraulic connection with the outlet of the hydraulic pump, at a certain preset pressure of the hydraulic fluid;
4. 4. monitoring the status of the pressure relief valve by means of a sensor;
5. 5. Outputting an electrical signal to an electronic control, the signal describing the state of the pressure relief valve; and
6. 6. Control of the electric motor by the electronic control based on the signal.

By means of the method according to the invention, the electronic control system can also monitor the state of the pressure relief valve and determine whether it is closed or open and can control the press machine accordingly. In particular, the pressing process can thus be carried out automatically to the end by the control unit operating the electric motor until the pressure relief valve is triggered and then the electric motor stops. This ensures that the necessary pressure is reached. In addition, electrical energy is saved since the electric motor is only operated by the control for as long as necessary. The method preferably has the step of determining the distance between a movable part of the pressure relief valve and a part which is fixed with respect to the press machine by the sensor. The state of the pressure relief valve can be determined particularly easily and reliably by means of the distance between a part of the pressure relief valve, in particular the valve piston, and a part which is stationary with respect to the press machine.

1. a. optisch, wobei der Sensor ein optischer Sensor umfasst;
2. b. magnetisch, wobei der Sensor einen Magnetsensor umfasst;
3. c. magnetisch, wobei der Sensor einen Hallsensor umfasst;
4. d. magnetisch, wobei der Sensor einen Reedkontakt umfasst;
5. e. induktiv, wobei der Sensor einen induktiven Sensor umfasst;
6. f. elektro-mechanisch, wobei der Sensor einen elektrischen Schalter umfasst; und/oder
7. g. kapazitiv, wobei der Sensor einen kapazitiven Sensor umfasst.

The step of determining the distance preferably takes place:

1. a. optically, the sensor comprising an optical sensor;
2. b. magnetic, the sensor comprising a magnetic sensor;
3. c. magnetic, the sensor comprising a Hall sensor;
4. d. magnetic, the sensor comprising a reed contact;
5. e. inductive, the sensor comprising an inductive sensor;
6. f. electro-mechanical, the sensor comprising an electrical switch; and or
7. G. capacitive, the sensor comprising a capacitive sensor.

The sensor can preferably detect both the closed and the open state of the pressure relief valve. This increases the reliability of the control, since the failure of the sensor or a fault in the connection between the sensor and the control can then be detected. In addition, interference from external magnetic fields can be detected and filtered out.

Instead of a single sensor, two or more sensors can preferably also be used for this purpose.

The sensor can preferably continuously detect the distance between the movable part of the pressure relief valve and the part which is stationary with respect to the press machine. A continuous determination of the distance enables the detection threshold for the states of the pressure relief valve to be set electronically. As a result, no mechanical settings on the sensor are necessary.

Brief description of the figures

Fig. 1

eine schematische Darstellung einer Ausführungsform einer Pressmaschine in der Form eines hydraulisches Handpressgeräts gemäß der vorliegenden Erfindung;

Fig. 2A

eine Schnittansicht eines Teils der Pressmaschine mit geschlossenem Überdruckventil; und

Fig. 2B

die Schnittansicht nach Fig. 2A mit geöffnetem Überdruckventil.

Preferred embodiments of the present invention are illustrated below with reference to the attached figures. It shows:

Fig. 1

a schematic representation of an embodiment of a press machine in the form of a hydraulic hand press device according to the present invention;

Figure 2A

a sectional view of part of the press machine with the pressure relief valve closed; and

Figure 2B

the sectional view after Figure 2A with open pressure relief valve.

Detailed description of preferred embodiments

Preferred embodiments of the present invention are described in detail below with reference to the attached figures.

Fig. 1 shows an embodiment of a hydraulic hand press device 10 with hydraulic power transmission unit. In this hydraulic hand press device, an electric motor 20 drives an eccentric 24 connected to it via a gear 22. The electric motor 20 is preferably a brushless DC motor that is supplied by a controller 40 with correspondingly modulated current from a battery or a wired power supply (not shown). A commercially available DC motor 20 with a commutator can also be used. The gearbox 22 reduces the speed of the electric motor 20 and increases the torque for actuating a hydraulic pump 27. The eccentric 24 connected to the gearbox converts the rotary movement of the output shaft of the gearbox 22 into a one-dimensional oscillating motion, around the hydraulic pump 27, which is designed as a piston pump is to drive.

Due to its movement, the hydraulic pump 27 pumps a hydraulic fluid 70 from a reservoir into a working cylinder 25, as a result of which the hydraulic pressure in the working cylinder 25 increases. The increasing hydraulic pressure presses a working piston 28 movably guided in the cylinder 25 in the illustration of FIG Fig. 1 to the left, in the direction of the fastening area for exchangeable pressing jaws 30 (not in detail shown). By using a large piston diameter, the working piston 28 can transmit a very high pressure to the press jaws.

The working piston 28 is mechanically connected to rollers 29 which move with the movement of the working piston 28. The rollers 29 move in a conventional manner between inclined ends of press jaws 30, which are thus closed and can plastically deform the workpiece with high force. In operation, the hydraulic pressure is transmitted directly proportional to the connected pressing jaw 30, and generates a pressing force directly proportional to the hydraulic pressure on the workpiece.

To start the pressing process, the user can actuate an operating button 41 which is electrically connected to the controller 40. The controller 40 recognizes the actuation of the operating button 40 and then controls the electric motor 20 in a suitable manner, so that it drives the hydraulic pump 27 via the eccentric 24. The hydraulic pump 27 pumps the hydraulic fluid on the output side into the working cylinder 25 in order to move the working piston.

Due to the increasing hydraulic pressure P during the pressing and the increasing pressing force on the workpiece or fitting, the workpiece is pressed and plastically deformed.

At the end of the pressing process, the hydraulic pressure has risen to a predetermined maximum pressure at which a secure pressing of the workpieces is ensured. When the predetermined pressure is reached, a pressure relief valve 50 opens, as a result of which the hydraulic pressure in the working cylinder 25 is reduced and the working piston 28 returns to its starting position due to a spring preload.

The opening of the pressure relief valve 50 when the predetermined pressure is reached is detected by a sensor 60, which is connected to the controller 40 for signaling purposes. The control 40 is thus signaled to open the pressure relief valve 50 so that it can stop the electric motor 20.

Details of the relief valve 50 and an exemplary sensor 60 are shown in FIGS Figures 2A and 2B shown. Figure 2A shows the pressure relief valve 50 in its closed state. The pressure relief valve 50 comprises a movable valve piston 52, which is biased against a valve seat 51 by means of a spring 56, here a spiral spring. The preload of the spring 56 can be adjusted by means of an adjusting screw 58 in order to thereby set the preset pressure P _v at which the pressure relief valve 50 is to open at the end of the pressing process. The pressure relief valve 50 is hydraulically connected to the outlet of the hydraulic pump 27 and therefore experiences the hydraulic pressure which acts on the working cylinder 25. At a pressure P ₁ <P _v , the pressure relief valve 50 is closed, the valve piston 52 sealing against the valve seat 51.

With a hydraulic pressure of P ₂ > = P _v , as in Figure 2B shown, the pressure relief valve 50 opens by the valve piston 52 being moved to the right against the force of the spring 56. Hydraulic fluid 70 can escape from the annular gap between valve piston 52 and valve seat 51, as shown by reference numeral 72. As a result, the pressure on the outlet side of the hydraulic pump 27 or the pressure acting on the working cylinder 25 drops, and the working piston 28 can move back into its starting position.

In the schematically illustrated embodiment, the valve piston 52 has a dynamic pressure surface 57, which causes the pressure relief valve 50
remains open when hydraulic fluid 72 emerges from the annular gap between valve piston 52 and valve seat 51. The pressure in the working cylinder 25 can thus decrease so far and the hydraulic fluid 70 can escape so far that the working piston 28 can move back into its starting position.

In an alternative embodiment (not shown), the valve piston 52 has no dynamic pressure surface 57 and the pressure relief valve 50 will close again as soon as sufficient pressure has been released for this. The working cylinder 25 can then be emptied by a separate hydraulic valve (not shown), which can be controlled electrically, for example, by the controller 40.

In addition, in a further alternative embodiment (not shown), it is possible for the valve piston 52 to have no dynamic pressure surface 57, and for the controller 40 to hold the valve piston 52 in its open position in a controlled manner, for example by electromagnetic means.

In addition, in a further alternative embodiment (not shown), it is possible for the valve piston 52 to have no dynamic pressure surface 57, but to engage mechanically in its open position. The detent can then be released again when the working piston 28 has moved back into its starting position.

The state of the pressure relief valve 50 can be monitored by a sensor 60. In particular, the sensor 60 outputs an electrical signal to the controller 40 when the pressure relief valve 50 opens after reaching the preset pressure P _v . In addition, the sensor 60 can also output another signal when the pressure relief valve 50 is closed. It is also possible for the sensor 60 to output a corresponding signal when the pressure relief valve 50 changes from the closed to the open state, or from the open to the closed state.

In the preferred embodiment, the sensor 60 consists of a magnetic sensor which is attached to a fixed housing component 62 and is electrically connected to the controller 40. The sensor 60 reacts to a magnetic field 55 which is generated by a permanent magnet 54 which is arranged at one end of the valve piston 52. The magnetic field 55 between the permanent magnet 54 and the sensor 60 changes when the valve piston 52 moves when the pressure relief valve 50 is opened or closed. Here, the distance between the permanent magnet 54 and sensor 60 changes from a length L ₁ in the closed state to a smaller length L ₂ in the open state of the pressure relief valve 50.

The sensor 60 can have an inductive sensor with an induction coil which, when the magnetic field 55 changes, generates an induced voltage which can be evaluated. For example, controller 40 may integrate the induced voltage to detect a relative change in the signal. This integrated voltage is then compared by the control with a threshold value which is characteristic of the opening of the pressure relief valve 50.

The sensor 60 can also have a Hall sensor that reacts to the changes in the magnetic field. Here too, the sensor signals can be evaluated in the manner described above.

Alternatively, the sensor 60 can have a reed contact that opens or closes an electrical contact at a certain strength of the magnetic field 55, that is to say from a certain distance between the permanent magnet 54 and the sensor 60. This switching of the reed contact can be recognized by the controller 40.

Alternatively, the sensor 60 can also have an optical sensor (not shown) which detects the change in an optical property, for example a change in a light intensity. For example, a diaphragm could be attached to the valve piston 52, which enters the space between a fork light barrier when the valve piston 52 moves when the pressure relief valve 50 is opened.

Alternatively, the sensor 60 can also have an electrical switch (not shown) which is actuated by the valve piston 52 in a mechanical manner. For example, the electrical switch can be arranged such that the valve piston 52 acts directly on the electrical switch when it is displaced and switches it.

Alternatively, the sensor 60 can have a capacitive sensor (not shown). With this, the status of the pressure relief valve 50 can also be monitored in a capacitive manner. The controller 40 then measures the variable electrical capacitance of a capacitive sensor which is formed, for example, from the valve piston 52 as a movable part and an electrode connected to the housing as a fixed part. Then the distance between valve piston 52 and electrode and thus the switching state of pressure relief valve 50 can be determined by determining the electrical capacitance between valve piston and electrode.

Based on the signal from the respective sensor 60, the controller 40 controls the pressing process of the press machine 10. When the necessary pressing pressure has been reached and the pressure relief valve opens when the preset pressure P _{v is reached} , the Control 40 stop the movement of the electric motor 20 immediately or after a certain overrun time. As a result, the electric motor 20 is automatically switched off by the controller 40 at the end of the pressing process, without the user having to take any action. On the one hand, this increases the user-friendliness of the press machine 10 and reduces the energy consumption. Furthermore, the controller 40 can thereby control the pressing process fully automatically until it has been successfully completed.

Reference list

10th

Pressing device

20th

Electric motor

22

transmission

24th

eccentric

25th

Working cylinder

26

hydraulic system

27

Piston pump

28

piston

29

roll

30th

Fastening area for interchangeable tools

40

control

50

Pressure relief valve

51

Valve seat

52

Valve piston

54

Permanent magnet

55

Magnetic field

56

feather

57

Back pressure area

58

Adjusting nut

60

sensor

62

fixed part / housing part

70

Hydraulic fluid

Claims (15)

Press machine (10) for pressing workpieces, comprising: a. a hydraulic pump (27) for conveying a hydraulic fluid (70); b. an electric motor (20) for driving the hydraulic pump (27); c. a working cylinder (25) which is in hydraulic connection with an outlet of the hydraulic pump (27); c. a pressure relief valve (50) which is in hydraulic communication with the outlet of the hydraulic pump (27) and which opens at a certain preset pressure (P _v ) of the hydraulic fluid (70); d. an electronic controller (40) for driving the electric motor (20); and e. a sensor (60) that monitors the state of the pressure relief valve (50) and outputs a signal that describes the state of the pressure relief valve (50) to the electronic control (40). Press machine according to claim 1, wherein the pressure relief valve (50) has a movable valve piston (52) which is biased by means of a spring (56) against a valve seat (51). Press machine according to one of claims 1 or 2, wherein the sensor (60) has a magnetic sensor (60) which is influenced by a magnet (54) on the pressure relief valve (50). Press machine according to claim 3, wherein the magnetic sensor (60) comprises a Hall sensor. Press machine according to claim 3, wherein the magnetic sensor (60) has a reed contact. Press machine according to claim 3, wherein the magnetic sensor (60) comprises an inductive sensor. Press machine according to one of claims 2 to 6, wherein the valve piston (52) has a permanent magnet (54). Press machine according to one of claims 1 or 2, wherein the sensor (60) comprises an optical sensor. Press machine according to one of claims 1 or 2, wherein the sensor (60) has an electrical switch. Press machine according to one of claims 1 to 9, wherein the electric motor (20) is a brushless DC motor. Method for operating a press machine (10) for pressing a workpiece, comprising the following steps: 1. Driving a hydraulic pump (27) by means of an electric motor (20); 2. Pumping a hydraulic fluid (70) by means of the hydraulic pump (27); 3. Opening a pressure relief valve (50), which is in hydraulic connection with the outlet of the hydraulic pump (27), at a certain preset pressure (P _v ) of the hydraulic fluid (70); 4. monitoring the state of the pressure relief valve (50) by means of a sensor (60); 5. Outputting a signal to an electronic controller (40), the signal describing the state of the pressure relief valve (50); and 6. Control of the electric motor (20) by the electronic controller (40) based on the signal. A method according to claim 11, comprising the step of determining by the sensor (60) the distance (L) between a movable part (52) of the pressure relief valve (50) and a part (62) fixed with respect to the press machine (10). The method of claim 12, wherein the step of determining the distance (L) is: a. optically, the sensor (60) comprising an optical sensor; b. magnetic, the sensor (60) comprising a magnetic sensor; c. magnetic, the sensor (60) comprising a Hall sensor; d. magnetic, the sensor (60) comprising a reed contact; e. inductive, the sensor (60) comprising an inductive sensor; f. electro-mechanical, the sensor (60) comprising an electrical switch; and or G. capacitive, the sensor (60) comprising a capacitive sensor. Method according to one of claims 11 to 13, wherein the sensor (60) can detect both the closed and the open state of the pressure relief valve (50). A method according to claim 12, wherein the sensor (60) can continuously detect the distance (L) between the movable part (52) of the pressure relief valve (50) and the part (62) which is stationary with respect to the press machine (10).

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