EP3643422B1 - Pressing device for work pieces - Google Patents

Description

technical field

The present invention relates to a press machine, in particular a hand-held press machine, for pressing workpieces, and to 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 each other by means of a press fitting. For this purpose, the pipes are introduced 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 pressing machine, i.e. plastically deformed in such a way 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 pressing machine, which can have interchangeable tools, such as pressing 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 pressing machine, the pressing jaws are arranged around the press fitting for pressing. To close the press jaws, the user presses an operating button, which activates an electrically operated hydraulic pump. This generates 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 pliers, so that it is radially compressed and plastically deformed in the process. through the Plastic deformation of the press fitting securely connects the workpieces, such as the press fitting and pipe. In this case, the inner tubes can also undergo plastic deformation.

In press machines of the prior art, the pressing process is usually ended in that when a specific maximum pressure is reached, a pressure relief valve opens, the hydraulic pressure is reduced and the working piston moves back to its initial 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 baling 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 waste electrical power and requires the operator to hold the power button down until the end of the crimping cycle. If the operator releases the operating button before the end of the pressing process, there is no guarantee that the workpieces have already been sufficiently pressed.

From the pamphlet EP 2 501 523 B1 a hand-held pressing device for pressing a press fitting in installation technology and for pressing cable lugs is known. In order to generate the necessary high pressing forces, the pressing tool is connected to an electrohydraulic 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 increase dramatically. This increase in 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.

The pamphlet EP 1 337 016 A2 discloses a battery powered hydraulic tool including a frame forming a hydraulic fluid conduit system; a power supply connected to the frame; a drive system connected to the frame, the drive system including an engine and a hydraulic pump connected to the hydraulic fluid piping system; one with the hydraulic valve connected to hydraulic fluid line system; and a controller adapted to sense a drop in electricity to the motor when the valve opens and adapted to disable the motor for a predetermined period of time.

The pamphlet EP 3 243 604 A1 discloses a motor-driven hand-held crimping tool with a pressure sensor that detects the pressure of a hydraulic medium in a hydraulic cylinder. In this case, a pressure drop when a return valve opens automatically can be detected by means of the pressure sensor in order to check the actual setting and function of the automatically opening return valve.

It is therefore the object of the present invention to provide a press machine which overcomes the above disadvantages 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 problems are solved according to the present 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 problems are solved by a press machine for pressing workpieces, having a hydraulic pump for delivering a hydraulic fluid; an electric motor for driving the hydraulic pump; a working piston in hydraulic communication with an outlet of the hydraulic pump; a pressure relief valve which is in hydraulic communication with the outlet of the hydraulic pump and which opens at a certain preset overpressure of the hydraulic fluid; an electronic controller for driving the electric motor; and a sensor that monitors the condition of the relief valve and outputs an electrical signal indicative of the condition of the relief valve to the electronic controller.

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

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

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

The magnetic sensor preferably has a Hall sensor. The magnetic sensor can have a Hall sensor that can very reliably detect a magnetic field. The output signal depends on the size of the magnetic field, so that the distance between the magnet and the Hall sensor can be continuously recorded. A particularly precise and reliable detection of the state of the pressure relief valve is thus possible, 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. In this case, 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 controller.

The valve piston preferably has a permanent magnet. The status of the pressure relief valve can be detected particularly easily by a permanent magnet on the valve piston. The permanent magnet moves with the valve piston when the pressure relief valve opens or closes, changing the magnetic field generated by the permanent magnet in relation to a stationary magnetic sensor. 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 reliability of the signaling. Here, 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 present at the controller for both states of the pressure relief valve and the control of the press machine becomes insensitive to external magnetic fields.

Both the normally arranged magnet and the inversely arranged magnet can preferably also be an electromagnet, which generates a magnetic field only after the pressing process has started. This means that the controller can evaluate the signals from the magnetic sensors even when the vehicle is at rest and compare them with those after it has started. This makes it possible to detect and filter out interference signals caused by external magnetic fields.

The sensor preferably has an optical sensor. The status of the pressure relief valve can also be detected optically. Here, an optical sensor is used, which preferably reacts to the change in the incidence of light due to a mechanical movement of the valve piston. For example, a screen could be attached to the valve piston, which screen enters the space between a forked 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 in such a way 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. A capacitive sensor can be formed for this purpose, for example by the valve piston forming a movable part and a fixed electrode forming a fixed part of a capacitive sensor. Then, by determining the electrical capacitance between the valve piston and the electrode, the distance between the valve piston and the electrode and thus the switching state of the pressure relief valve can be determined.

The electric motor is preferably a brushless DC motor. Such a brushless direct current motor can be regulated very precisely and requires very little maintenance while at the same time having 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 problems are further solved by a method for operating a press machine for pressing a workpiece, having the following steps:

1. 1. Driving a hydraulic pump by means of an electric motor;
2. 2. Conveying a hydraulic fluid by means of the hydraulic pump;
3. 3. Opening a pressure relief valve, which is in hydraulic communication with the outlet of the hydraulic pump, at a certain preset overpressure of the hydraulic fluid;
4. 4. Monitoring the status of the pressure relief valve using a sensor;
5. 5. Outputting an electrical signal to an electronic controller, the signal describing the state of the pressure relief valve; and
6. 6. Controlling the electric motor by the electronic controller based on the signal.

With the method according to the invention, the electronic control can also monitor the status of the pressure relief valve and determine whether it is closed or open and can control the pressing machine accordingly. In particular, the pressing process can be carried out automatically to the end in that the controller operates the electric motor until the pressure relief valve is triggered and then stops the electric motor. This ensures that the necessary pressing pressure is achieved. In addition, electrical energy is saved because the electric motor is only operated by the controller for as long as necessary.

Preferably, the method includes the step of determining, by the sensor, the distance between a movable part of the relief valve and a part that is stationary with respect to the press machine. The state of the pressure relief valve can be determined particularly easily and reliably via the distance between a part of the pressure relief valve, in particular the valve piston, and a part that is stationary with respect to the pressing 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. optical, wherein the sensor comprises an optical sensor;
2. b. magnetic, wherein the sensor comprises a magnetic sensor;
3. c. magnetically, the sensor comprising a Hall sensor;
4. i.e. magnetically, the sensor comprising a reed contact;
5. e. inductive, wherein the sensor comprises an inductive sensor;
6. f. electro-mechanical, wherein the sensor comprises an electrical switch; and or
7. G. capacitive, wherein the sensor comprises 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 then the failure of the sensor or a fault in the connection between the sensor and control can be recognized. In addition, interference from external magnetic fields can be detected and filtered out.

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

Preferably, the sensor can continuously detect the distance between the movable part of the pressure relief valve and the part that is stationary with respect to the press machine. A continuous determination of the distance enables a continuous electronic adjustment of the detection threshold for the states of the overpressure valve. This means that no mechanical settings are required on the sensor.

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 presented below with reference to the accompanying figures. It shows:

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

Figure 2B

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

Detailed description of preferred embodiments

In the following, preferred embodiments of the present invention are described in detail with reference to the attached figures.

1 shows an embodiment of a hydraulic manual pressing device 10 with a hydraulic power transmission unit. In this hydraulic manual pressing device, an electric motor 20 drives an eccentric 24 connected to it via a gear 22 . Preferably, the electric motor 20 is a brushless DC motor of a controller 40 with appropriately modulated power from a battery or a wired power supply (not shown) is supplied. A commercially available commutator DC motor 20 may also be used. The gearbox 22 reduces the speed of the electric motor 20 and increases the torque to actuate a hydraulic pump 27. The eccentric 24 connected to the gearbox converts the rotational movement of the output shaft of the gearbox 22 into a one-dimensional oscillating movement in order to drive 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 pushes a working piston 28, which is movably guided in the cylinder 25, in the representation of FIG 1 to the left, towards the mounting area for interchangeable press jaws 30 (not shown in detail). By using a large piston diameter, the working piston 28 can transfer a very high pressure to the pressing 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 the usual way between inclined ends of press jaws 30, which are thus closed and can plastically deform the workpiece with great force. During operation, the hydraulic pressure is thereby transmitted directly proportionally to the connected pressing jaws 30 and generates a pressing force on the workpiece that is directly proportional to the hydraulic pressure.

To start the pressing process, the user can press 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 . On the output side, the hydraulic pump 27 pumps the hydraulic fluid into the working cylinder 25 in order to move the working piston.

The workpiece is pressed and plastically deformed due to the increasing hydraulic pressure P during pressing and the resulting increasing pressing force on the workpiece or the fitting.

At the end of the pressing process, the hydraulic pressure has risen to a predetermined maximum pressure at which reliable pressing of the workpieces is guaranteed. If 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 initial position due to spring preload.

The opening of the overpressure valve 50 when the predetermined pressure is reached is detected by a sensor 60 which is connected to the controller 40 in terms of signals. The opening of the overpressure valve 50 is thus signaled to the controller 40 so that it can stop the electric motor 20 .

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

At a hydraulic pressure of P ₂ >= P _v , as in Figure 2B shown, the pressure relief valve 50 opens in that the valve piston 52 is displaced to the right against the force of the spring 56 . Here, hydraulic fluid 70 can escape from the annular gap between valve piston 52 and valve seat 51, as represented by reference number 72. As a result, the pressure on the output side of the hydraulic pump 27 or the pressure acting on the working cylinder 25 falls and the working piston 28 can move back into its starting position.

In the embodiment shown schematically, the valve piston 52 has a dynamic pressure surface 57 which causes the overpressure valve 50 to remain open when hydraulic fluid 72 emerges from the annular gap between the valve piston 52 and the valve seat 51 . The pressure in the working cylinder 25 can thus be reduced to such an extent that the hydraulic fluid 70 can escape to such an extent 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 will close the pressure relief valve 50 again as soon as sufficient pressure for this has been reduced. The working cylinder 25 can then be emptied by a separate hydraulic valve (not shown), which can be controlled electrically by the controller 40, for example.

In addition, it is possible in a further alternative embodiment (not shown) 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 electromagnetically.

In addition, it is possible in a further alternative embodiment (not shown) that the valve piston 52 does not have a dynamic pressure surface 57 but mechanically engages in its open position. The detent can then be canceled again when the working piston 28 has moved back to its starting position.

The status 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 the preset pressure P _v has been reached. In addition, the sensor 60 can also output a different signal when the pressure relief valve 50 is closed. It is also possible for the sensor 60 to emit 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 attached to a fixed housing member 62 and electrical connected to the controller 40. The sensor 60 is responsive to a magnetic field 55 generated by a permanent magnet 54 located 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. The distance between permanent magnet 54 and sensor 60 changes from a length L ₁ when the pressure relief valve 50 is closed to a shorter length L ₂ when it is open.

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, the controller 40 can integrate the induced voltage to detect a relative change in the signal. This integrated voltage is then compared by the controller to a threshold representative of the relief valve 50 opening.

Sensor 60 may also include a Hall effect sensor that responds to 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, which opens or closes an electrical contact at a certain strength of the magnetic field 55, ie from a certain distance between the permanent magnet 54 and the sensor 60. This switching of the reed contact can be detected 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 light intensity. For example, an aperture could be attached to the valve piston 52, which diaphragm enters the intermediate space of a forked light barrier when the valve piston 52 moves when the overpressure valve 50 opens.

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

Alternatively, the sensor 60 can have a capacitive sensor (not shown). In this way, the status of the pressure relief valve 50 can also be monitored capacitively. 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 moving part and an electrode connected to the housing as a fixed part. Then, by determining the electrical capacitance between the valve piston and the electrode, the distance between the valve piston 52 and the electrode and thus the switching state of the overpressure valve 50 can be determined.

Based on the signal from the respective sensor 60, the controller 40 controls the pressing process of the pressing machine 10. If the necessary pressing pressure is reached and the pressure relief valve opens when the preset pressure P _v is reached, the controller 40 can stop the movement of the Stop electric motor 20. 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 is successfully completed.

Reference List

10

pressing device

20

electric motor

22

transmission

24

eccentric

25

working cylinder

26

hydraulic system

27

piston pump

28

Pistons

29

roll

30

Mounting area for interchangeable tools

40

steering

50

pressure relief valve

51

valve seat

52

valve piston

54

permanent magnet

55

magnetic field

56

Feather

57

dynamic pressure area

58

adjusting nut

60

sensor

62

fixed part/housing part

70

hydraulic fluid

Claims (15)

1. Pressing machine (10) for pressing workpieces, having:

   a. a hydraulic pump (27) for delivering a hydraulic fluid (70);

   b. an electric motor (20) for driving the hydraulic pump (27);

   c. a working cylinder (25) in hydraulic communication with an output of the hydraulic pump (27);

   d. a pressure relief valve (50) in hydraulic communication with the output of the hydraulic pump (27) and opening at a predetermined preset pressure (Pv) of the hydraulic fluid (70);

   e. an electronic controller (40) for driving the electric motor (20); characterised by

   f. a sensor (60) monitoring the state of the pressure relief valve (50) and outputting a signal describing the state of the pressure relief valve (50) to the electronic controller (40).
2. Pressing machine according to claim 1, wherein the pressure relief valve (50) has a movable valve piston (52) biased against a valve seat (51) by means of a spring (56).
3. Pressing machine according to one of claims 1 or 2, wherein the sensor (60) has a magnetic sensor (60) influenced by a magnet (54) on the pressure relief valve (50).
4. Pressing machine according to claim 3, wherein the magnetic sensor (60) has a Hall sensor.
5. Pressing machine according to claim 3, wherein the magnetic sensor (60) has a reed contact.
6. Pressing machine according to claim 3, wherein the magnetic sensor (60) has an inductive sensor.
7. Pressing machine according to one of claims 2 to 6, wherein the valve piston (52) has a permanent magnet (54).
8. Pressing machine according to one of claims 1 or 2, wherein the sensor (60) has an optical sensor.
9. Pressing machine according to one of claims 1 or 2, wherein the sensor (60) has an electrical switch.
10. Pressing machine according to one of claims 1 to 9, wherein the electric motor (20) is a brushless DC motor.
11. Method for operating a pressing machine (10) for pressing a workpiece, having the following steps:

    1. driving a hydraulic pump (27) by means of an electric motor (20);

    2. delivering a hydraulic fluid (70) by means of the hydraulic pump (27);

    3. opening a pressure relief valve (50) in hydraulic communication with the output of the hydraulic pump (27) at a predetermined preset pressure (Pv) of the hydraulic fluid (70); characterised by the following steps:

    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. driving the electric motor (20) by the electronic controller (40) based on the signal.
12. Method according to claim 11, comprising the step of determining the distance (L) between a movable part (52) of the pressure relief valve (50) and a part (62) fixed with respect to the pressing machine (10) by the sensor (60).
13. Method according to claim 12, wherein the step of determining the distance (L) is carried out:

    a. optically, wherein the sensor (60) comprises an optical sensor;

    b. magnetically, wherein the sensor (60) comprises a magnetic sensor;

    c. magnetically, wherein the sensor (60) comprises a Hall sensor;

    d. magnetically, wherein the sensor (60) comprises a reed contact;

    e. inductively, wherein the sensor (60) comprises an inductive sensor;

    f. electromechanically, wherein the sensor (60) comprises an electrical switch; and/or

    g. capacitively, wherein the sensor (60) comprises a capacitive sensor.
14. 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).
15. 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) fixed with respect to the pressing machine (10).

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