EP1103349B2 - Press tool and method for controling the same - Google Patents

Abstract

The control method has the compression tool (1,5) operated after fitting or replacement of the clamp plates (2) for compression of the coupling element, with detection of the movement path of the hydraulic pistons (12) until a given pressure is reached, for use as a reference value for comparison with the effective path value for each subsequent compression operation, for providing a signal when the difference between the compared values is outside a given tolerance range. An Independent claim for an electrically-operated compression tool is also included

Description

The present invention relates to a method for controlling an electrically operated pressing tool device for pressing coupling elements with a clamping pliers.

Press tool devices of the type mentioned are used for pressing of coupling elements, such as press sleeves, press fittings, pipe sleeves, nested pipe sections and the like. The press tool devices have a clamping pliers with clamping jaws, which form a pressing space for receiving the coupling element to be pressed. The pressing pressure necessary for the compression is supplied by a, generally hydraulic, drive.

After each compression, it should be checked whether the coupling element has been pressed to the desired mass or whether the compression has been too strong or too weak. This check is carried out by a visual inspection.

However, if the strength of the compression is only just outside the tolerance limit, this can not be detected by mere visual inspection. In addition, it depends on the reliability of the worker, whether and how carefully he performs the visual inspection.

Press tools are implements that have an increased risk of accidents. There have already been several accidents at work in which the clamping forceps was thrown uncontrollably and the fork-shaped receptacle was spread and deformed.

It has therefore been proposed according to EP-A-0'712'696 to provide a Ueberwachungselement which monitors the connecting pin in its fully inserted position and is connected via a switching element with the drive motor in connection.

Even if the clamping forceps are held correctly in the press tool, so this alone does not guarantee proper compression of the tubular workpieces. Reasons for inadequate crimping can be extremely diverse. In addition to reasons related to the function of the pressing tool device, there are reasons which have to do with the insufficient processing. For example, the clamp or its jaws may be dirty, whereby a sufficient closure of the clamp is not achieved or the dimensions of the pipe sleeve or compression sleeve used does not correspond to the dimension which is provided for the corresponding pliers.

For these reasons, according to EP-A-0'858'850 a press tool device has been proposed in which the applied pressing pressure is determined and it is determined whether this pressing pressure is within the predefined tolerance limits. From this it is concluded that a complete closure of the clamp has been achieved. However, for such monitoring to be done correctly, the press tool must recognize which clamp is used. Such Klemmzangenerkennung requires an electronic exchange of information between clamping pliers and press tool, as well as a spe electronic logic, by means of which the information can be evaluated for corresponding signals indicating a correct or incorrect compression. Such electronic monitoring can then easily connect with other electronic information that also indicates the correct operation and the perfect condition of the press tool.

Because these press tools are often used in construction, contamination of the clamping pliers are difficult to avoid. Such contamination then often lead to interruptions of the electronic transmission and thus to misinformation.

Moreover, as is known, for example, from DE-A-19'631'019, pressing tool devices in which the final pressing position of the pressing jaws is monitored. Accordingly, the clamping tongs have means which perceive this final pressing position and forward it to a display device. Again, an information transfer from the clamp to the press tool must be done. In addition, appropriate electronic means must be integrated into the jaws in addition to also delicate mechanical elements.

Finally, EP-A-0'941'813 also shows a pressing tool of the type of interest here. Here it was recognized that both the mechanical and the electrical detection of the clamping pliers is problematic. Therefore, a non-contact data transmission from the clamping tongs to the pressing tool was made contactless here by magnets interact in the clamping tongs with Erkennu ngssensoren the pressing tool.

According to the hitherto known state of the art, information must therefore always be supplied by the clamping tongs to the pressing tool device until today. It is therefore an object of the present invention to provide a method which does not require electrical or electronic data transmission from the clamping tongs to the pressing tool device and procures itself selbstdiese this information.

This object is achieved by a method having the features of claim 1. Further advantageous method steps are evident from the dependent claims 2 to 3 and their meaning is explained in the following description.

Figur 1

eine Vorrichtung, bei der die Wegmesssensorik zwischen Rollenhalter und gabelförmiger Aufnahme angeordnet ist und

Figur 2

ein Presswerkzeuggerät, bei dem die Wegmesssensorik in der Kolben/Zylindereinheit integriert ist.

In the drawing, two embodiments of press tool devices are shown, which can operate according to the inventive method. It shows:

FIG. 1

a device in which the Wegmesssensorik between roller holder and fork-shaped receptacle is arranged and

FIG. 2

a pressing tool device in which the Wegmesssensorik is integrated in the piston / cylinder unit.

In the following, the press tool apparatus will be explained for the time being with reference to the drawing, and then the method according to the invention will be described.

In FIG. 1, only the pressing tool device designated by 1 is shown, while in FIG. 2 the pressing tool device 1 and an inserted clamping pliers 2 are shown. The press tool 1 consists essentially of an electro-hydraulic device that is designed pistol-shaped. The device has a housing 3 with a handle 4. On the handle 4, the release switch 5 is arranged, via which a pressing operation is triggered. The accommodated in the housing 3 electromotive drive 6 acts via a gear 7 to a hydraulic pump 8, which presses hydraulic oil from a reservoir into the cylinder and thus moves the piston.

The piston / cylinder unit is designated overall by 10. It comprises the cylinder 11 and the piston 12 movable therein. The piston 12 is engaged by a piston rod 13, which is guided through a two-part bearing 14. At the opposite end of the piston 12, a roller holder 15 is arranged on the piston rod 13. The roller holder 15 has the shape of a yoke in which two rollers 16 are mounted.

The extension of the cylinder housing 11 is milled in the longitudinal direction and thus forms two cheeks 17, which form the fork-shaped receptacle 20. Transversely to the longitudinal direction of the cheeks 17, the fork-shaped receptacle 20 is penetrated by a securing bolt 18. By a monitoring sensor 19, the correct position of the securing bolt 18 is monitored. This safety pin 18 passes through the bearing plates or a connecting plate of the clamping jaw 2. To replace the clamping jaw 2 each of the safety pin 18 must be removed.

Upon actuation of the trigger switch 5, hydraulic oil is injected through the cylinder head 9 into the cylinder 11. Accordingly, the piston 12 is moved in the drawing to the right. Of course, the piston rod 13 moves with the attached roller holder 15 to the right in the same mass. The rollers 16 come on ramp-like surfaces 25 on the inner surfaces of the two jaws 21 of the clamping jaw 2 for concern. In this case, the two jaws 21 pivot about the two corresponding pivot bearing 22, which are arranged in the bearing plates 23. The Lagerplattemn 23 may themselves be designed so that they are penetrated by the safety pin 18 or it may be arranged a corresponding fastening tab between the two bearing plates 23, which is penetrated by the safety pin 18. In the latter version, correspondingly larger and wider clamps can be realized. In the position of the piston shown in Figure 2 and according to the position of the roller holder or the rollers, the clamping jaw 2 can be opened. If the rollers 16 move to the right on the ramp-like surfaces 25, the jaws 21 are pressed apart on this side of the pivot bearing 22 and pressed together on the other side, wherein the clamping space 26 is reduced, so that the tubular workpiece lying therein is compressed ,

In the embodiment according to FIG. 1, a recess 27 is mounted in one of the two cheeks 17 of the fork-shaped receptacle 20, in which a sensor 28 determining the stroke is arranged. This may be a magnetic sensor, a magnetoresistive angle sensor, a displacement sensor or a Hall sensor. In the present case, it is a displacement sensor, which is in corresponding operative connection with a magnetic strip 29, which is fastened on the reel holder 15. The magnetic strip is a small plate. which is divided in a dense arrangement alternately strip-shaped in plus and minus poles. Upon actuation of the device, the roller holder 15 and thus the magnetic strip 29 located thereon moves past the sensor 28, which receives counting pulses corresponding to the alternating poles. The number of detected counts is directly proportional to the stroke of the piston 12 and the roller holder 15. With the same clamping length of the constant stroke corresponds to the constant closing movement of the clamp, which leads to a consistent compression.

When using a magnetoresistive angle sensor, this can be accommodated in the cylinder seal, through which the piston rod 13 is guided. The piston rod can then be provided with magnetized regions, the magnetization directions being different. The magnetoresistive angle sensor detects a vector corresponding to an absolute position of the piston rod. This preferred embodiment completely eliminates destruction in jaw replacement.

In terms of method, work is now carried out in such a way that, after the insertion of the clamping jaw 2, the triggering lever 5 is actuated, but without a workpiece to be pressed being introduced into the clamping space 26. Accordingly, the clamping forceps 2 can close completely unhindered. If the clamping jaw 2 is completely closed, the pressure in the cylinder chamber increases up to a limit defined by a built-in, not shown, overpressure valve. When the corresponding pressure is reached, the valve automatically switches over and the hydraulic oil can flow back from the cylinder 11 directly into the storage oil tank. Because usually a torsion spring or return spring is integrated, which returns the pliers in the untensioned position, the piston 12 is also pushed back to the starting position accordingly. Of course, it is also possible with the switching of the overpressure valve umzupolen the direction of rotation of the hydraulic pump and actively return the oil.

The number of signals detected during the first tongs closure is supplied to an electronic unit housed at 30 in the housing 3. The electronic circuit contains a data memory, a comparator and possibly further conventional means for storing the desired path value on the one hand and inputting tolerance ranges below and / or above this and one arithmetic unit which compares the determined actual path values with the specified target path value and checks whether the actual travel value is within of the specified tolerance range.

The particular advantage of the inventive solution is mainly to be seen in the fact that the determined Sollwegwert represents a relative value, which is dependent on the Klemmzangentyp and even each individual clamping pliers, since such clamps also show signs of wear, whereby the tolerance would practically always be greater. For systems that assume absolute values, the clamps must either be replaced earlier or readjusted accordingly. Each time the clamping tongs are used again, the actual closing path is determined by the empty closing as described in the citation and is newly recorded as a reference path value. Because neither mechanical scanning elements nor electronic data transmission elements are required on the clamping pliers themselves, the entire system is extremely insensitive in daily use and all suitable clamping pliers can be used and monitored.

FIG. 2 shows a second embodiment. The second embodiment differs from the first described embodiment only with respect to the arrangement of the sensor and the type of the sensor. Centrally in the cylinder head 9, a hollow cylindrical pin 31 is arranged. This fixed in the cylinder head 9 pin 31 protrudes into the piston 12 and the piston rod 13 in a blind hole. The corresponding blind bore 32 is so large in diameter that the pin 31 can protrude without contact therein. In the head of the piston 12, an enlarged bore 33 is arranged, in which a magnetic ring 34 is held fixed. In the hollow pin 31, a straight or wound arranged wire is attached, which induces a signal during movement along the magnetic ring 34, which in turn is evaluated at the arranged at 30 electronic circuit. Again, the signal is proportional to the stroke of the piston. The evaluation of the signal is exactly the same as in the solution described above. Again, the clamp itself determines the Sollhubweg and the corresponding tolerances can be programmed in the circuit from the manufacturer. The user has no access to the setpoint tolerance setting.

In contrast to known systems, the control system disclosed here for monitoring the clamping tongs is not regulated by the pressure. The hydraulic pressure is subject to considerable fluctuations, which are dependent on external influences, which are hardly considered. In particular, the viscosity represents a significant parameter. The viscosity of the hydraulic oil is also dependent on the temperature. In the case of the solution described here, only one overpressure valve is present, which only switches when a certain safety value has been reached. This value can be relatively high above the possibly required compression pressure. The pressure is in principle set so high that the pliers can safely close. Accordingly, this value is completely uncritical for the actual pressing. This is again a significant advantage of the inventive solution.

In order to avoid misinformation, the electronic circuit in the pressing tool device can be switched so that the stored setpoint path value expires when the voltage on the pressing tool device disappears. This is to ensure that if the clamp is replaced while the power is off, it will not start from a wrong stored value when the power is turned on again. Although this would not be a tragedy, because then the input Sollwegwert either below, whereupon the device perceives this pressure as a new Leerpressung and store the value thus determined as a new Sollwegwert and also visually and / or acoustically identifies this process. However, it is certainly desirable that when resuming work after replacing the clamping pliers, a new Leerpressung or Vollverpressung takes place and this empty pressure is determined as a reference.

In an analogous manner, in principle, the changing of the clamping tongs can be monitored and deleted according to the stored Sollwegwert when removing the clamp. This can be done most simply by using the removal or replacement of the securing bolt 18 as information. This is completely unproblematic possible, because anyway the sensor 19 is present, which monitors the safety pin. Accordingly, the information of the sensor 19 only has to be logically coupled to the information of the sensor 28.

Claims (3)

1. A method for controlling an electrically operated pressing tool apparatus (1) for pressing coupling elements with a clamping pincer (2), wherein the pressing tool apparatus moves a hydraulically actuatable piston (12) until reaching a predetermined pressure and with this closes the clamping pincer (2), characterised in that with the insertion or exchange of the clamping pincer (2) the stored nominal displacement value is deleted and thereafter the pressing tool apparatus (1,5) is actuated carrying out a empty pressing, wherein the displacement which the piston (12) covers up to reaching a predetermined safety value of the pressure which lies above the required pressing pressure is registered and as a nominal displacement value up to settable tolerances is compared to each effective displacement value of every subsequent pressing procedure. wherein deviations from the nominal displacement value activate a signal.
2. A method according to claim 1, characterised in that the stored nominal value displacement is deleted with the cessation of the voltage at the pressing tool apparatus (1).
3. A method according to claim 2, characterised in that on falling short of the stored nominal displacement value this lower value is recognised as an erroneous pressing and is optically and/or acoustically displayed.

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