EP3829820B1 - Method for operating a hydraulically actuated work tool - Google Patents

Description

field of technology

The invention relates to a method for operating a hydraulically operated working device with a working jaw, with a working process requiring an increase in a force applied as a result of a pressure in a hydraulic medium, after which the working process no longer requires a higher force or a maximum permissible hydraulic pressure is reached, with further, the hydraulic pressure is applied with the aid of a piston pump, with a pump piston that travels a pumping path and a return path in each pumping cycle, with a recording of the hydraulic pressure over time when changing from the pumping path to the return path, there is a change from a pressure increase range to a essentially a certain pressure value corresponding pressure holding range results.

State of the art

The prior art is initially on the WO 2016/005838 A1 ( US 2017/0087709 A1 ) to refer. From this it is known, in the case of a pressing tool with two pressing jaws which are arranged pivotably relative to one another, to detect when the pressing jaws have reached a closed position by means of a sensor. The sensor system can consist in monitoring the pressure in the hydraulic medium and evaluating a gradient of the pressure increase that is greater than a predetermined gradient so that a closed position of the pressing jaws has been reached.

Something similar is also from the WO 2017/129385 A1 and the WO 2008/138987 A2 ( U.S. 8,056,473 B2 ) famous.

Summary of the Invention

Proceeding from the state of the art presented, the invention is concerned with the task of further improving a method for operating a hydraulically operated implement.

This object is achieved with the subject matter of claim 1, which is based on the working device being set up to monitor for a fracture in the working jaw, for which purpose a pressure maintenance range that has been reached is compared with a specified pressure maintenance range in a specified pressure interval or a detected number of pressure maintenance ranges in a pressure interval is compared with a predetermined number of pressure maintenance ranges for this pressure interval, with regard to the reached pressure maintenance range (b, b') exceeding the reached pressure maintenance range (b, b') over the predetermined pressure maintenance range (b _max ) is evaluated in such a way that a check of the device (1) with regard to a fracture (19) in the working jaw (9, 10) is indicated.

When a pressure is generated in the hydraulic medium using a piston pump, a pressure increase curve detected by a sensor system provided is composed of a sequence of stepped sections with high resolution, with each stepped section corresponding to a pump cycle made up of a pump and return path. As the pressure in the hydraulic medium increases, the height of the steps increases, resulting from a force of the pump piston required for a given pumping path and thus a corresponding increase in the distance between two successive pressure-retaining areas.

An evaluation of the step height results in force-displacement information practically immediately, especially when using a piston pump every pump stroke, in this case a piston stroke of the piston pump, in a first approximation the hydraulic piston travels a practically always the same path per stroke of the piston pump and thus the same amount of hydraulic medium is always pumped. The associated (mean) force over a stroke of the piston pump is reflected in the step height. This results in the measure of the step height as a direct measure of the mechanical rigidity against which the pump works in each case.

According to the invention, the value of the predetermined pressure maintenance range corresponds to a value at which the mechanical rigidity is practically only, but at least to a considerable extent, determined by the tool itself and practically no longer by the part to be pressed and/or one or the working jaws. The rigidity determined by the device itself can be caused in particular by the hydraulic piston coming into abutment with the hydraulic cylinder, ie by a direct action on a cylinder base. Such direct action is usually not possible if the working jaws are intact. In this case, even when the working jaws are closed, the path of force still goes through the jaw areas, which have a higher rigidity, but less than the rigidity of the working device itself. This absolute value, the rigidity of the implement itself, therefore usually also represents a device constant.

When a certain or a general worker is reached, which is preferably also detected via a sensor system, according to the initially cited WO 2008/138987 A2 ( U.S. 8,056,473 B2 ) a signal to end the work process can be triggered, with a termination of the pumping activity of the pump piston and, if necessary, as is also preferred, opening of a return valve for the hydraulic medium. It results in the pressure rise curve a spontaneous drop, starting from a pressure peak which, in the pressure rise curve, indicates the pressure when the specified or general working force is reached.

According to the invention, the mentioned device constant or the value of the specified pressure maintenance range specifies a maximum value. If, as a result of this, the respectively achieved value of the pressure maintenance range is evaluated without the value of the specific worker being recorded beforehand, as should be the case regularly, this is recognized as a break in the working jaw. The absolute value of the device constant (value of the specified pressure maintenance range) can be recognized quickly, from which the working device is preferably switched off immediately.

A control/monitoring unit with a microprocessor can compare the values of the pressure-maintaining ranges reached at the end of a pumping cycle with the specified value of the pressure-maintaining range, which is used as an absolute value in the comparison.

The value of the specified pressure maintenance range or the named device constant can be recorded (for the first time) by intentionally bringing about a work process in which the hydraulic piston acts alone or to a significant extent on the cylinder base facing it. The value recorded here can be stored as a reference value or device constant for the working device. A data memory can be provided for this purpose.

For example, the reference measurement used for the purpose of detecting device constants can be carried out with at least one working jaw removed, alternatively, for example, with one in an inoperative position with the other working jaw spent working jaw. Correspondingly, in this case no usual end position of the working jaws is reached, in which the path of force leads solely or for the most part through the working jaws. A breakage of a working jaw is simulated by the missing working jaw or by a working jaw or insert that has been taken out of action.

The work process can be, for example, pressing, in particular pressing with a hydraulic pressing device. In this case, two pressing jaws forming the working jaws are usually moved relative to one another, for example a movable pressing jaw against a stationary pressing jaw which is formed in the working jaw. A part to be pressed or a combination of parts to be pressed can be inserted between the pressing jaws. As long as the part or parts are elastically and/or plastically deformed by the closing of the pressing jaws, there is a—first—increase in the work force. When the jaws have moved together, a further increase in the work force practically only leads to the pressing jaws "moving to the block". Thus essentially only the elasticity or rigidity inherent in one or both pressing jaws or working jaws is then effective as resistance against the further increase in the working force. With regard to this further increase, there may be a changed - second - increase in the workforce.

In the pressure increase curve, the transition to the rigidity of the device as such, i.e. reaching the specified pressure maintenance range, can occur compared to an undamaged working jaw - starting from a lower pressure or a lower pressure stage. A comparatively abrupt transition from the lower pressure stage to the predetermined pressure maintenance range can result. In addition, this transition can also differ from a comparable pressure rise curve set earlier if the working jaw is undamaged, based on a triggering of the working process.

According to one possible embodiment, when the predefined pressure maintenance range is reached, a user of the working device can be given a visual and/or acoustic indication. A visual indication can, for example, be in the form of an activation of a light source, for example an LED or the like, alternatively in the case of a possible arrangement of a display on the implement by a corresponding display in the form of a warning symbol and/or a plain text display.

The working device can have a loudspeaker for an acoustic indication, for example for the output of a signal tone.

In a further possible embodiment, when the predetermined pressure maintenance range is reached or even exceeded, the working device can also be (possibly temporarily) deactivated, possibly accompanied by a visual and/or acoustic indication for the user.

With regard to an evaluation of the number of pressure maintenance areas in the pressure interval with a number of pressure maintenance areas specified for this pressure interval, a number of 90 percent or less of pressure maintenance areas than corresponds to the specified number of pressure maintenance areas can be evaluated to the effect that a check of the device in with regard to a fracture in the working jaw.

A significant increase in step height (pumping force) compared to a step height specified for the working jaw within the considered Pressure interval can thus indicate a crack or a fracture in the working jaw. If the height of the steps is increased, there is a correspondingly smaller number of pressure holding areas between an initial pressure and an end pressure of the pressure interval under consideration.

A pressure interval which is limited by the end of a work process is preferably used here for the comparison measurement.

The control/monitoring unit compares the number of pressure-maintaining ranges reached in the specified printing interval in the course of the work process with the number of target pressure-maintaining ranges stored in this regard. For example, a specification of two to five pressure hold ranges within the pressure interval can be specified. If, on the other hand, in the pressure interval used for the comparison measurement, a number of pressure maintenance areas that is 10 percent or more lower than the specified number is recorded, for example with a target value of three pressure maintenance areas only two recorded pressure maintenance areas, this can also indicate a break in the working jaw.

When the specified 90 percent or less of the pressure maintenance ranges are reached, the user of the working device can also be given a visual and/or acoustic indication here, with the working device also being able to be deactivated if the specified 90 percent or less of the pressure maintenance ranges are exceeded.

According to the method, the device is set up to monitor for a break in the working jaw. The device can have at least one sensor for detecting the hydraulic pressure, and preferably electronics for evaluation of the recorded sensor data, as well as electronics, for example in the form of a microprocessor, for comparing the recorded data with default data stored, for example, in an internal data memory, analysis and optionally outputting a signal.

A range beginning at one-fifth and one-twentieth of the permissible maximum pressure can, as is also preferred, be specified as the decisive pressure interval that is included in the assessment. With an exemplary permissible maximum pressure of 600 to 800 bar, there can be a pressure interval for checking that begins, for example, at 30 to 160 bar, further, for example, at 60 to 80 bar. The end of the pressure interval is preferably always given by the reaching of the pressure value leading to the switching off of the pumping process.

The application of the pressure in the pressure rise curve over a period of time, beginning with a point in time at an initial pressure and ending with a point in time at which the end of the work process has occurred and thus a last complete pressure interval results, can result in the relevant pressure interval that is evaluation is used.

The ranges or value ranges or multiple ranges specified above and below also include all intermediate values with regard to the disclosure, in particular in 1/10 increments of the respective dimension, ie possibly also dimensionless. For example, the specification 30 to 160 bar also includes the disclosure of 30.1 to 160 bar, 30 to 159.9 bar, 30.1 to 159.9 bar etc. This disclosure can on the one hand limit a specified range limit from below and/or above, alternatively or additionally serve to disclose one or more singular values from a respectively specified range.

Brief description of the drawings

Fig. 1

in perspektivischer Darstellung ein hydraulisch betätigbares Arbeitsgerät in Form eines Verpressgerätes mit einer Arbeitsbacke;

Fig. 2

das Arbeitsgerät gemäß Figur 1 in einer partiell geschnittenen Seitenansicht;

Fig. 3

die Herausvergrößerung des Bereiches III in Figur 2, betreffend eine Stellung bei Erreichen des Endes des Arbeitsvorganges bei ordnungsgemäßer Arbeitsbacke;

Fig. 4

eine der Figur 3 entsprechende Darstellung, jedoch mit einer einen Bruch aufweisenden Arbeitsbacke;

Fig. 5

eine Darstellung des Druckanstiegs in einem Hydraulikmittel des Arbeitsgerätes bei Durchführung eines Arbeitsvorganges bei ordnungsgemäßer und bei gebrochener Arbeitsbacke;

Fig. 6

die Herausvergrößerung des Bereiches VI in Figur 5;

Fig. 7

eine Schnittdarstellung gemäß Figur 2, eine alternative Ausführungsform der Arbeitsbacken betreffend.

The invention is explained below with reference to the attached drawing, which, however, only represents exemplary embodiments. A part that is only explained in relation to one of the exemplary embodiments and is not replaced by another part in a further exemplary embodiment due to the special feature highlighted there is thus also described as a possible existing part for this further exemplary embodiment. In the drawing shows:

1

a perspective view of a hydraulically actuated working device in the form of a pressing device with a working jaw;

2

the working device according to figure 1 in a partially sectioned side view;

3

the enlargement of area III in figure 2 , relating to a position when the end of the work process is reached with a proper working jaw;

4

one of the figure 3 Corresponding representation, but with a fractured working jaw;

figure 5

a representation of the pressure increase in a hydraulic medium of the implement when carrying out a work process with proper and broken working jaw;

6

the enlargement of area VI in figure 5 ;

7

a sectional view according to figure 2 , concerning an alternative embodiment of the working jaws.

Description of the embodiments

Shown and described, first with reference to the figures 1 and 2 , A hydraulically actuated working device 1, here in the form of a pressing device.

The working device 1 can have a handle 2 and a battery 3 if the device is to be operated wirelessly. However, a connection by means of an electrical cable to a supply via an electrical network is also possible.

The hydraulic working device 1 can also have a hydraulic tank 4 . Hydraulic medium can be pumped from the hydraulic tank 4 into a hydraulic cylinder 6 by means of a pump, for example a piston pump 5 . When the hydraulic medium is pumped into the hydraulic cylinder 6, a hydraulic piston 7 in the hydraulic cylinder 6 can be moved between an initial position and an end position, as shown in figure 2 is shown as an example to be moved. The hydraulic piston 7 can be under the action of a return spring 8 . In figure 7 , relating to a working device 1 in a further embodiment, the initial piston position is shown. In figure 2 is one too figure 3 Corresponding piston end position shown, with proper working jaws.

By the movement of the hydraulic piston 7, a movable working jaw 9 in the embodiment according to Figures 1 to 3 be moved against a fixed working jaw 10.

As can be seen from the illustrations, the fixed working jaw 10 with respect to one in the figures 2 and 3 The longitudinal section shown can be essentially L-shaped, with a longer leg 11 pointing in the direction of displacement r of the hydraulic piston 7, which is fixed to the cylinder wall 12 of the implement 1, and an L-leg running transversely to the leg 11, which holds the against the movable working jaw 9 acting fixed working jaw 10 essentially forms.

In the basic working position, the result is a pressing chamber which is essentially C-shaped and in which a part to be pressed, a compact 13, can be accommodated. The compact 13 can consist, for example, of a sleeve and a tube that are to be pressed together, or, as shown, of a cable and a cable lug.

At the in figure 7 Working device 1 shown are movable working jaws 9 pivoted by the hydraulic piston 7 against each other for compression. The relevant pivot axis x of the working jaws 9 runs transversely to the displacement direction r.

The piston pump 5 can be driven by an electric motor 14, which can receive its energy supply via the accumulator 3 already mentioned or, for example, via the mains cable also mentioned.

In addition, the working device 1 can, as is also preferred, have a data processing device 15 suitable for evaluating transmitted measured values, which in figure 2 is shown schematically. Such a device also preferably has a control device 16. This is connected by a line to the data processing device 15.

The functions of the data processing device 15 and the control device 16 can also be provided by a uniform electronic component. For example, a work process can be terminated directly and autonomously via the control device.

In addition, the hydraulic working device 1 can have a sensor 17 for detecting a pressure in the hydraulic medium. The pressure of the hydraulic medium is preferably measured by the sensor 17 in the hydraulic cylinder 6 .

The sensor 17 supplies measured values at very short time intervals. The time intervals are more preferably less than one second below a tenth of a second. Such a time interval can also be just one or more milliseconds.

In particular, it is an electronic sensor that can also be supplied with electrical energy via the accumulator 3, for example.

A work process can be terminated, for example, in that a work part, such as the movable working jaw 9 in a pressing tool, is moved back into an initial position after a predetermined pressing force has been reached, or such a return movement is initiated. In the case of a hydraulic pressing tool, as shown, the initiation can consist in particular in that the hydraulic piston 7 is retracted while hydraulic medium is fed back from the hydraulic cylinder 6 into the hydraulic tank 4 . For this purpose, in particular, a return valve is usually opened and, preferably, the pump is also switched off at the same time as said opening.

When carrying out a pressing process (work process), for example with the hydraulic working device in the form of a pressing device, a pressing operation is triggered via a manually operated switch 18 after the compact 13 has been inserted into the pressing chamber. The piston pump 5 then begins to pump hydraulic medium from the hydraulic tank 4 into the hydraulic cylinder 6 by carrying out a large number of piston strokes.

In figure 5 a first pressure increase curve K is shown, relating to proper pressing of a compact 13 using undamaged working jaws 9, 10.

In the illustration, the pressure is plotted on the ordinate and the time t is plotted on the abscissa. There is a certain increase in pressure over time t, with different gradients resulting in relation to the pressure increase curve K.

As also in particular from the enlargement in figure 6 As can be seen, when the hydraulic pressure is recorded in the pressure increase curve K as a function of the pumping path and return path of the hydraulic piston 7, there is a change between a pressure increasing range a and a pressure holding range b.

This results in an overall stepped progression of the pressure rise curve K.

In a memory of the data processing device 15 and/or the control device 16, a specific absolute value relating to the rigidity of the device, in particular of the hydraulic cylinder 6, which can be given as a device constant, can be stored, which with regard to an actually recorded pressure maintenance range b, b' is used for comparison. Exceeding the value of the specified pressure maintenance range b _max , for example by 5 percent or more, but possibly even less than 5 percent, for example 1 percent or 2.5 percent, can lead to a signal to end the work process, possibly additionally or alternatively to trigger a visual and/or acoustic signal. Exceeding the value of the specified pressure holding range b _max indicates a fracture 19 in the working jaw 10 .

Such a constellation with a broken working jaw 10 is an example in figure 4 shown. The fracture 19 in the form of a crack is particularly evident in the connection area of the working jaw 10 or the relevant leg to the leg 11 that is essentially subjected to bending stress.

Due to the formation of fractures, the compact 13 may not be pressed completely and properly (compare the enlarged view in Fig figure 4 , in which the pressing jaws have not moved together).

Furthermore, in this improper design of the working jaw 10, the free edge of the piston wall 20 can hit the front side of the facing base of the hydraulic cylinder 6 (see further enlarged view in Fig figure 4 ). This stop position is achieved during normal pressing with a proper working jaw 10 as shown in figure 3 not reached. Rather, the maximum permissible pressure in the hydraulic cylinder 6 is reached before the piston wall 20 comes into contact with the cylinder base, after which the hydraulic piston 7 retracts due to the spring force (after opening a return valve).

In figure 5 a further pressure increase curve K' is shown, relating to the pressure profile using a working jaw 10 in which a fracture 19 is present.

As can be seen in particular from the enlargement in figure 6 can be seen, with proper compression with correspondingly intact working jaws 9, pressure-maintaining ranges b result whose recorded values (heights) are always below the value of the specified pressure-maintaining range b _max until the specific or general working force C is reached. It is a proper execution of the pressing process, for example, until the worker C is reached is possible.

If, on the other hand, according to in figure 6 If the pressure increase curve K' shown on the left detects a pressure maintenance range b', the pressure value of which exceeds the maximum pressure value of the specified pressure maintenance range b _max , the measurement and comparison result derived from this leads to the stored measure (acoustic and/or visual signal and/or, as shown schematically, shutdown, etc.). In figure 6 With regard to the above-mentioned measurement diagram, the further pressure value measurement profile that results, at least theoretically, without switching off is shown in dashed lines.

In an alternative procedure or a procedure that is combined with the concept described above, the number of pressure-maintaining areas b can also be detected within a pressure interval D, which includes a large number of pressure-increasing and pressure-maintaining areas a and b and thus a number of pumping cycles P.

In the illustrated exemplary embodiment, the pressure interval D comprises approximately the range in the order of 10 percent based on a maximum pressure leading to shutdown or the maximum pressure reached as the upper end. If this maximum pressure is 750 bar, for example, this results in a pressure interval D over a pressure rise of 75 bar.

Based on the application of the pressure in the pressure rise curve K over time t, the pressure interval D begins with an initial pressure E and ends in an end pressure F, which is preferably also the switch-off pressure for the pump.

As can be seen in particular from the enlargement in figure 6 As can be seen, in relation to the pressure increase curve K' for a broken working jaw 9, 10 over the same pressure interval D, correspondingly here over the same pressure range of, for example, 75 bar up to the end of the working process in the final pressure F, one results compared to the specified one Number of pressure holding areas b, as shown in the pressure rise curve K, smaller number of pressure holding areas b'. Thus, according to the representation, in the case of a broken working jaw 10, only two pressure holding areas b′ can result within the pressure interval D. In contrast, the reference value according to the pressure increase curve K for an intact working jaw is three. The relevant measurement correspondingly results in a number of pressure holding areas b' which corresponds to two thirds of the specified number of pressure holding areas b.

List of References

1 implement a pressure rise area 2 Handle b pressure holding area 3 accumulator b' pressure holding area 4 hydraulic tank b _max Pressure holding range (specified) 5 piston pump 6 hydraulic cylinder right shift direction 7 hydraulic piston t time 8th return spring x pivot axis 9 working jaw 10 working jaw 11 leg C Worker 12 cylinder wall D print interval 13 compact E outlet pressure 14 electric motor f final pressure 15 data processing facility K pressure rise curve K' pressure rise curve 16 control device P pump cycle 17 sensor 18 Switch 19 fracture 20 piston wall

Claims (5)

1. A method for operating a hydraulically actuated work tool (1) with a work jaw (9, 10), wherein a work process requires an increase in a force applied as the result of a pressure in a hydraulic means, wherein once said increase has been reached, the work process requires no more higher force or a maximum permissible hydraulic force has been reached, wherein the hydraulic pressure is further applied with the aid of a piston pump (5), with a pump piston that travels through a pump path and a return path in each pump cycle (P), wherein, while the hydraulic pressure is recorded over time (t) given a change from the pump path to the return path, a change takes place from a pressure increase range (a) to a pressure-maintaining range (b) that essentially corresponds to a specific pressure value, characterized in that the work tool (1) is set up to monitor for a break (19) in the work jaw (9, 10), to which end a reached pressure-maintaining range (b, b') is compared with a predefined pressure-maintaining range (b_max) in a predefined pressure interval (D), or an acquired number of pressure-maintaining ranges in a pressure interval (D) is compared with a number of pressure-maintaining ranges (b, b') predefined for this pressure interval (D), wherein relative to the reached pressure-maintaining range (b, b'), it is concluded that checking the tool (1) for a break (19) in the work jaw (9, 10) is indicated if the reached pressure-maintaining range (b, b') exceeds the predefined pressure-maintaining range (b_max).
2. The method according to claim 1, characterized in that if the reached pressure-maintaining range (b, b') exceeds the predefined pressure-maintaining range (b_max), the user of the work tool (1) is given a visual and/or acoustic indication.
3. The method according to one of the preceding claims, characterized in that a range of between one fifth and one twentieth of the permissible maximum pressure is predefined as the pressure interval (D).
4. The method according to one of the preceding claims, characterized in that, in relation to the recording of pressure over time (t), an interval starting with an initial pressure (E) up to a time at which the end of a work process has arisen, and thus the last complete pressure interval (D) comes about, is used as the pressure interval (D) for evaluation purposes.
5. The method according to claim 1, characterized in that a number of 90 % or less of pressure-maintaining ranges than corresponds to the predefined number of pressure-maintaining ranges can be taken as indicating that the tool must be checked for a break in the work jaw.

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