METHOD FOR OPERATING A HYDRAULICALLY ACTUATED WORK TOOL

Abstract

A method for operating a hydraulically actuated work tool having a work jaw is provided. Once an increase in force applied as a result of a hydraulic pressure has been reached, the work process does not require any further force or a maximum permissible hydraulic pressure has been reached. The hydraulic pressure is applied by a pump piston that travels through a pump path and a return path in each pump cycle. The hydraulic pressure is recorded over a time for a change from a pressure increase range to a pressure-maintaining range corresponding substantially to a specific pressure value from the pump path into the return path. At the end of a pump cycle, if the reached pressure-maintaining range exceeds a predefined pressure-maintaining range, an indication is concluded that the tool needs to be checked for a break in the work jaw.

Claims

1. A method for operating a hydraulically actuated work tool with a work jaw, 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, with a pump piston that travels through a pump path and a return path in each pump cycle, wherein, while the hydraulic pressure is recorded over time given a change from the pump path to the return path, a change takes place from a pressure increase range to a pressure-maintaining range that essentially corresponds to a specific pressure value, characterized in that the work tool is set up to monitor for a break in the work jaw, to which end a reached pressure-maintaining range is compared with a predefined pressure-maintaining range in a predefined pressure interval, or an acquired number of pressure-maintaining ranges in a pressure interval is compared with a number of pressure-maintaining ranges predefined for this pressure interval, wherein relative to the reached pressure-maintaining range, it is concluded that checking the tool for a break in the work jaw is indicated if the reached pressure-maintaining range exceeds the predefined pressure-maintaining range.

2. The method according to claim 1, wherein if the reached pressure-maintaining range exceeds the predefined pressure-maintaining range, the user of the work tool is given a visual and/or acoustic indication.

3. (canceled)

4. The method according to claim 2, wherein a range of between one fifth and one twentieth of the permissible maximum pressure is predefined as the pressure interval.

5. The method according to claim 4, wherein in relation to the recording of pressure over time, an interval starting with an initial pressure up to a time at which the end of a work process has arisen, and thus the last complete pressure interval comes about, is used as the pressure interval for evaluation purposes.

6. (canceled)

7. The method according to claim 1, wherein 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.

8. The method according to claim 1, wherein a range of between one fifth and one twentieth of the permissible maximum pressure is predefined as the pressure interval.

9. The method according to claim 8, wherein in relation to the recording of pressure over time, an interval starting with an initial pressure up to a time at which the end of a work process has arisen, and thus the last complete pressure interval comes about, is used as the pressure interval for evaluation purposes.

10. The method according to claim 1, wherein in relation to the recording of pressure over time, an interval starting with an initial pressure up to a time at which the end of a work process has arisen, and thus the last complete pressure interval comes about, is used as the pressure interval for evaluation purposes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] While the invention is explained below based upon the attached drawing, the latter only shows exemplary embodiments. A part that is only described with reference to one of the exemplary embodiments and is not replaced by another part in an additional exemplary embodiment based upon the characteristic emphasized therein is thus also described as an at least possible present part for this additional exemplary embodiment. The drawing shows:

[0031] FIG. 1 a perspective view of a hydraulically actuatable work tool in the form of a crimping tool with a work jaw;

[0032] FIG. 2 the work tool according to FIG. 1 in a partially cut side view;

[0033] FIG. 3 the magnification of area III on FIG. 2, relating to a position upon reaching the end of the work process given a proper work jaw;

[0034] FIG. 4 an illustration corresponding to FIG. 3, but with a work jaw having a break;

[0035] FIG. 5 an illustration of the pressure increase in a hydraulic means of the work tool while performing a work process given a proper and broken work jaw;

[0036] FIG. 6 the magnification of area VI on FIG. 5;

[0037] FIG. 7 a sectional view according to FIG. 2 relating to an alternative embodiment of the work jaws.

DESCRIPTION OF THE EMBODIMENTS

[0038] Initially shown and described with reference to FIGS. 1 and 2 is a hydraulically actuatable work tool 1, herein in the form of a crimping tool.

[0039] The work tool 1 can have a handle 2, and further an accumulator 3 if the tool is to be operated wirelessly. A connection by means of an electric cable to a supply via an electrical network is also possible, however.

[0040] The hydraulic work tool 1 can further have a hydraulic tank 4. A pump, for example a piston pump 5, can be used to pump hydraulic means out of the hydraulic tank 4 into a hydraulic cylinder 6. By pumping the hydraulic means into the hydraulic cylinder 6, a hydraulic piston 7 can be moved into the hydraulic cylinder 6 between an initial position and a final position, with the latter being exemplarily shown on FIG. 2. The hydraulic piston 7 can be exposed to the action of a restoring spring 8. FIG. 7 relates to a work tool 1 in another embodiment, and depicts the initial piston position. FIG. 2 also shows a piston illustration corresponding to FIG. 3 with proper work jaws.

[0041] By moving the hydraulic piston 7, a movable work jaw 9 in the exemplary embodiment according to FIGS. 1 to 3 can be shifted against a fixed work jaw 10.

[0042] As evident from the illustrations, the fixed work jaw 10 can be essentially L-shaped in relation to a longitudinal section depicted on FIGS. 2 and 3, with a longer leg 11 that faces in the displacement direction r of the hydraulic piston 7 and is fixed on the cylinder wall 12 of the work tool 1, and an L-leg that runs transverse to the leg 11 and essentially forms the fixed work jaw 10 that acts against the movable work jaw 9.

[0043] Overall, this results in a pressing space enclosed in essentially a C-shaped manner in the basic work position, which can accommodate a part to be crimped, a pellet 13. For example, the pellet 13 can consist of a sleeve and a tube, which are to be crimped together, or also of a cable and a cable lug, as depicted.

[0044] In the work tool 1 shown on FIG. 7, movable work jaws 9 can be swiveled against each other by the hydraulic piston 7 for crimping purposes. The respective swiveling axis x of the work jaws 9 runs transverse to the displacement direction r.

[0045] The piston pump 5 can be driven by means of an electric motor 14, which can receive its power supply via the already mentioned accumulator 3, or for example also via the also mentioned network cable.

[0046] As also preferred, the work tool 1 can further have a data processing device 15 suitable for evaluating transmitted measured values, which is schematically illustrated on FIG. 2. Such a tool preferably also has a control device 16. The latter is connected by a cable to the data processing device 15.

[0047] The functions of the data processing device 15 and the control device 16 can also be performed by a uniform electronic component. For example, the control device can directly conclude a work process autonomously of any devices.

[0048] The hydraulic work tool 1 can further have a sensor 17 for acquiring a pressure in the hydraulic means. The pressure of the hydraulic means is preferably measured by the sensor 17 in the hydraulic cylinder 6.

[0049] The sensor 17 delivers respective measured values in very short time intervals. In particular, the time intervals measure under one second, further preferably under one tenth of a second. Such a time interval can also measure only one or several milliseconds.

[0050] Involved in particular is an electronic sensor, for example which can likewise be supplied with electrical power by the accumulator 3.

[0051] For example, concluding a work process can involve moving a work part, such as the movable work jaw 9 in a crimping tool, back into an initial position upon reaching a predefined pressing force, or initiating such a return movement. In a hydraulic pressing tool of the kind described, the initiation can in particular involve retracting the hydraulic piston 7 while returning hydraulic means from the hydraulic cylinder 6 into the hydraulic tank 4. As a rule, this involves in particular opening a return valve, and preferably also turning off the pump simultaneously with the mentioned opening.

[0052] While performing a crimping process (work process), for example with the hydraulic work tool in the form of a crimping tool, a hand-actuated switch 18 is used to initiate a crimping operation after inserting the pellet 13 into the pressing space. As it performs a plurality of piston strokes, the piston pump 5 then begins to pump hydraulic means out of the hydraulic tank 4 into the hydraulic cylinder 6.

[0053] FIG. 5 shows a first pressure increase curve K, relating to a proper crimping of a pellet 13 using undamaged work jaws 9, 10.

[0054] In the illustration, the pressure is recorded on the ordinate, and the time t is recorded on the abscissa. A specific increase in pressure over time t takes place, wherein different slopes arise relative to the pressure increase curve K.

[0055] As also evident in particular from the magnified illustration on FIG. 6, a change between a pressure increase range a and pressure-maintaining range b takes places while recording the hydraulic pressure in the pressure increase curve K as a function of the pump path and return path of the hydraulic piston 7.

[0056] This yields an overall stepped progression of the pressure increase curve K.

[0057] The storage of the data processing device 15 and/or the control device 16 can store a specific absolute value, which relates to a stiffness of the tool, in particular of the hydraulic cylinder 6, can be provided as a tool constant, and is drawn upon for comparison purposes with respect to an actually acquired pressure-maintaining range b, b′. Exceeding the value of the predefined pressure-maintaining range b.sub.max, for example by 5 percent or more, but possibly already by less than 5 percent, for example 1 percent or 2.5 percent, can lead to a signal for ending the work process, if necessary additionally or also alternatively to triggering a visual and/or acoustic signal. If the value for the predefined pressure-maintaining range b.sub.max is exceeded, it can be concluded that there is a break 19 in the work jaw 10.

[0058] Such a constellation with a broken work jaw 10 is exemplary shown on FIG. 4. In particular, the break 19 in the form of a tear arises in the connection area of the work jaw 10 or of the respective leg to the leg 11 that is essentially subjected to a bending stress.

[0059] The formation of a break can result in an incomplete and improper crimping of the pellet 13 (see magnified view on FIG. 4, in which the pressing jaws are not moved together).

[0060] In this improper design of the work jaw 10, the free edge of the piston wall 20 can further hit the facing floor of the hydraulic cylinder 6 on the end face (see additional magnified view on FIG. 4). This hitting position is not reached during a conventional crimping with a proper work jaw 10 according to the illustration on FIG. 3. Rather, the permissible maximum pressure in the hydraulic cylinder 6 is reached before the piston wall 20 comes into contact with the cylinder floor, after which the hydraulic piston 7 is made to return by the spring force (after opening the return valve).

[0061] FIG. 5 shows another pressure increase curve K′, relating to the pressure gradient using a work jaw 10 in which a break 19 is present.

[0062] As evident in particular from the magnified view on FIG. 6, a proper crimping with correspondingly intact work jaws 9 yields pressure-maintaining ranges b, whose acquired values (heights) always lie below the value of the predefined pressure-maintaining range b.sub.max until the specific or general work force C has been reached. As a result, the exemplary pressing process can be properly executed until the work force C has been reached.

[0063] By contrast, if a pressure-maintaining range b′ is acquired whose pressure value exceeds the maximum pressure value of the predefined pressure-maintaining range b.sub.max according to the pressure increase curve K′ shown on FIG. 6, the measurement and comparison result derived therefrom leads to the stored measure (acoustic and/or visual signal and/or, as schematically depicted, deactivation, etc.). With respect to the aforementioned measurement diagram, a dashed line on FIG. 6 shows the additional pressure value measurement course that at least theoretically arises without deactivation.

[0064] In an alternative method or one combined with the concept described above, the number of pressure-maintaining ranges b can be acquired within a pressure interval D that comprises a plurality of pressure increase and pressure-maintaining ranges a and b, and hence a plurality of pump cycles P.

[0065] In the exemplary embodiment shown, the pressure interval D comprises roughly the area on the order of 10 percent relative to a maximum pressure leading to a deactivation or maximum pressure reached as the upper end. For example, if this maximum pressure measures 750 bar, this results in a pressure interval D over a pressure increase of 75 bar.

[0066] With respect to recording the pressure in the pressure increase curve K over time t, the pressure interval D starts with an initial pressure E, and ends in a final pressure F, which is preferably also the cut-off pressure for the pump.

[0067] As evident in particular from the magnified view on FIG. 6, a lower number of pressure-maintaining ranges b′ by comparison to the predefined number of pressure-maintaining ranges as shown in the pressure increase curve K arises in relation to the pressure increase curve K′ given a broken work jaw 9, 10 over the same pressure interval D, here as well correspondingly over the same exemplary pressure range of 75 bar up until the end of the work process in the final pressure F. According to the illustration, only two pressure-maintaining ranges b′ can thus arise within the pressure interval D given a broken work jaw 10. By contrast, the reference value for an intact work jaw is three according to the pressure increase curve K. The respective measurement correspondingly yields a number of pressure-maintaining ranges b′ that corresponds to two thirds of the predefined number of pressure-maintaining ranges b.

[0068] Given an evaluation of both the measured values for the pressure-maintaining ranges b, b′ in comparison to the predefined pressure-maintaining range b.sub.max as well as the number of pressure-maintaining ranges b, b′ within a pressure interval D, the measurement that deviates from the predefined value first in time can already result in an immediate deactivation, for example.

[0069] The above statements serve to explain the inventions encompassed by the application overall, which further develop the prior art at least via the following feature combinations and also each taken separately, wherein two, several or all of these feature combinations can also be combined, specifically:

[0070] A method, characterized in that the respectively reached pressure-maintaining range b, b′ is compared with a predefined pressure-maintaining range b.sub.max as relates to its pressure difference hereby given for the pump cycle P, and that 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.sub.max.

[0071] A method, characterized in that if the reached pressure-maintaining range b, b′ exceeds the predefined pressure-maintaining range b.sub.max, the user of the work tool 1 is given a visual and/or acoustic indication.

[0072] A method, characterized in that the work tool 1 is set up to monitor for a break 19 in the work jaw 9, 10 by comparing a reached pressure-maintaining range b, b′ with a predefined pressure-maintaining range b.sub.max in a predefined pressure interval.

[0073] A method, characterized in that a range of between one fifth and one twentieth of the permissible maximum pressure is predefined as the pressure interval D.

[0074] A method, characterized in that the evaluation is performed using a pressure interval D relating to the recording of pressure over time t, starting with an initial pressure E up to a last complete pressure interval D, in which the end of the work process has arisen.

[0075] All disclosed features (taken separately or in combination with each other) are essential to the invention. The disclosure of the application hereby also incorporates the disclosure content of the accompanying/attached priority documents (copy of preliminary application) in its entirety, also for the purpose of including features in these documents in claims of the present application. Even without the features of a referenced claim, the subclaims characterize independent inventive further developments of prior art with their features, in particular so as to initiate partial applications based on these claims. The invention indicated in each claim can additionally have one or several of the features indicated in the above specification, in particular those provided with reference numbers and/or included on the reference list. The invention also refers to embodiments in which individual features mentioned in the above specification are not realized, in particular to the extent they are obviously unnecessary for the respective intended application, or can be replaced by other technically equivalent means.

REFERENCE LIST

[0076]

TABLE-US-00001 1 Work tool 2 Handle 3 Accumulator 4 Hydraulic tank 5 Piston pump 6 Hydraulic cylinder 7 Hydraulic piston 8 Return spring 9 Work jaw 10 Work jaw 11 Leg 12 Cylinder wall 13 Pellet 14 Electric motor 15 Data processing device 16 Control device 17 Sensor 18 Switch 19 Break 20 Piston wall a Pressure increase range b Pressure-maintaining range .sup. b′ Pressure-maintaining range   b.sub.max Pressure-maintaining range (predefined) r Displacement direction t Time x Swiveling axis C Work force D Pressure interval E Initial pressure F Final pressure K Pressure increase curve .sup. K′ Pressure increase curve P Pump cycle