Gripper device, and method for operating a gripper device

Abstract

The invention relates to a gripper device comprising a carrier device and a cable gripper mounted thereon, said gripper device comprising a gripper frame which is held on the carrier device via a holding cable, at least two grapple buckets which are pivotally mounted on a lower end of the gripper frame between a closed position and an open position, and an actuating device comprising an actuating cable for pivoting the grapple buckets, wherein an actuating cable is guided from the carrier device to the actuating device, and the carrier device comprises a driven first cable winch for the holding cable and a driven second cable winch for the actuating cable. A control device is provided comprising an input unit, by means of which a control command can be entered to rotate the cable gripper about the longitudinal axis thereof. According to the invention, the control device is equipped with a control program, by means of which the first cable winch and / or the second cable winch is actuated according to the control command to rotate the cable gripper without detecting cable forces on the basis of control values stored in the control program such that the unwound length of the holding cable and / or of the actuating cable changes in relation to each other and the cable gripper is rotated about the longitudinal axis thereof.

Description

[0001] GRIPPER DEVICE AND METHOD FOR OPERATING A GRIPPER DEVICE

[0002] The invention relates to a gripper device with a carrier device and a cable gripper arranged thereon, which has a gripper frame which is held on the carrier device via a holding cable, at least two gripper blades which are pivotally mounted at a lower end of the gripper frame between a closed position and an open position, and an actuating device with an actuating cable for pivoting the gripper blades, wherein the actuating cable is guided from the carrier device to the actuating device, and the carrier device has a driven first cable winch for the holding cable and a driven second cable winch for the actuating cable, and a control device is arranged with an input unit through which a control command for rotating the cable gripper about its longitudinal axis can be entered, according to the preamble of claim 1.

[0003] The invention further relates to a method for operating a gripper device according to the preamble of claim 13.

[0004] Grab devices are used in specialized foundation engineering to create trenches in the ground. These trenches can be used, for example, to construct diaphragm walls for supporting and / or sealing excavations.

[0005] Grabber devices primarily comprise a grab with grab buckets, whereby the grab is suspended from a carrier device, typically a jib crane, via a holding cable. Using the holding cable, a grab can be lowered into the ground. By closing the grab buckets, soil material can be removed and collected in the grab. The grab is then retracted from the ground via the operating cable and the holding cable and pivoted with the carrier device to an emptying position, where the grab buckets are opened to discharge the soil material. The grab is then pivoted back into its working position and then reinserted into the narrow slot in the ground with precise positioning and angle of rotation for another grab operation.

[0006] There are two different types of grippers used on such gripper devices: hydraulic grippers and rope grippers. A so-called hydraulic gripper is known, for example, from EP 3 798 367 A1. In a hydraulic gripper, the movement for opening and closing the gripper blades is generated by a hydraulic cylinder mounted on the gripper frame.

[0007] Such hydraulic grabs are relatively easy to operate and control thanks to the hydraulic system. However, the supply and discharge of hydraulic fluid requires appropriate hydraulic lines, which run parallel to the support cable. Appropriate cable reels for the hydraulic lines, with appropriate winch drives, and a suitably designed hydraulic system must be provided on the carrier device. This makes the grab device larger and more expensive. The hydraulic system also requires additional maintenance.

[0008] In contrast, so-called rope grabs offer a significantly simplified design. One such rope grab is known, for example, from GB 2 126981 A. In a rope grab, the opening and closing movement of the grab buckets is controlled by an actuating cable. The actuating cable runs essentially parallel to the retaining cable from the actuating device of the grab buckets to the carrier device. Using a separate winch for the actuating cable, the grab buckets can be opened or closed by unwinding or winding the actuating cable onto the winch.

[0009] With a rope grab, the complex supply of hydraulic lines to the grab is eliminated. Only an additional operating cable with a corresponding winch is required. Such an operating cable is also considerably less maintenance-intensive than hydraulic lines with a corresponding hydraulic system.

[0010] However, operating a rope grab is not as easy as operating a hydraulic grab, and requires an experienced operator. One reason for this is that the use of rotating ropes for the holding rope and the actuating rope to rotate the grab around its longitudinal axis generates undesirable torques in various operating states, causing a certain amount of rotation of the rope grab around its longitudinal axis. However, a precise rotational position of the rope grab is essential to ensure that the rope grab can be reinserted into a previously created slot in the ground when returning it from the emptying position.

[0011] A machine operator can rotate the rope grab around its longitudinal axis by applying specific tensile forces to the holding rope and the actuating rope. This requires relatively sensitive operation of the corresponding rope winches. This requires a certain level of experience from the machine operator and also a high level of concentration during the process. Furthermore, the rope winches are often operated using foot pedals, making sensitive operation of the rope winches for several hours very strenuous for a machine operator.

[0012] EP 4134489 A1 discloses a gripper device in which the cable force on the holding cable and the cable force on the actuating cable are detected by means of detection devices. A control device controls the first cable winch and the second cable winch depending on the detected cable force on the holding cable and the detected cable force on the actuating cable, resulting in a desired twist. This allows for a targeted twisting of a cable gripper to be achieved efficiently. However, detecting the cable forces with the accuracy required for twisting on a construction machine during construction is complex. In certain cases, such as particularly harsh environmental conditions, insufficient measured values ​​may occur.

[0013] The invention is based on the object of specifying a gripper device and a method for operating the gripper device, in which a simple operation and particularly reliable rotation of a rope gripper are made possible with a simple construction of the gripper device.

[0014] The object is achieved, on the one hand, by a gripper device having the features of claim 1 and, on the other hand, by a method having the features of claim 13. Preferred embodiments of the invention are specified in the respective dependent claims.

[0015] The gripper device according to the invention is characterized in that the control device is designed with a control program by which, depending on the control command for twisting without detecting cable forces on the basis of control values ​​stored in the control program, the first cable winch and / or the second cable winch are controlled in such a way that a developed length of the holding cable and / or the actuating cable changes in relation to one another and rotates the cable gripper about its longitudinal axis.

[0016] A fundamental idea of ​​the invention is to move away from the detection of rope forces on the holding rope and the actuating rope to control the twisting of a rope grab. This is based on the realization that, under certain operating conditions of a rope grab, the detection of rope forces causing twisting can be inaccurate or distorted. If the rope force is measured, for example, using a detection device on a rope deflection pulley, the rope force measurement can be distorted by the rope entering the pulley at an angle. Irregularities in the rope winding on the winch drum of a rope winch can also lead to force measurements that can deviate significantly from the actual rope forces on the holding rope and / or the actuating rope.The arrangement of appropriate measuring devices for recording the correct rope forces is generally complex and cost-intensive and can be omitted in the design according to the invention.

[0017] Rather, according to the invention, the control device is equipped with a control program by which, depending on the control command for rotating a rope gripper, in particular in a desired direction of rotation, the first rope winch and / or the second rope winch are controlled based on or solely on control values ​​stored in the control program, so that an unwinding length of the holding rope and / or the actuating rope changes in relation to one another. The rope gripper can thus rotate about its longitudinal axis in the desired direction of rotation due to the resulting corresponding torque. Starting from an initial position of the rope gripper, values ​​for controlling the first rope winch or the second rope winch are stored in the control program for a desired rotation or direction of rotation.If a machine operator specifies a desired rotation of, for example, 30° clockwise, the control system will control the cable winches accordingly based on the values ​​stored for this angle of rotation. The values ​​can be easily recorded and saved in advance for each angle of rotation. Operation can be performed using a joystick or thumbwheel, with the values ​​for controlling the first cable winch or the second cable winch being selected based on the deflection / operation of the joystick or thumbwheel.

[0018] A preferred embodiment of the invention is that the control device is designed with a control program by which the first cable winch and / or the second cable winch are controlled depending on the control command for rotating the cable gripper in a desired direction of rotation and / or a desired angle of rotation, thereby generating a corresponding torque that rotates the cable gripper about its longitudinal axis in the desired direction of rotation. Thus, a defined direction of rotation or a defined angle of rotation can be specified.

[0019] According to a further development of the invention, particularly precise rotation can be achieved by providing a determination device with which it can be determined whether or not the rope gripper is in a balanced state. A balanced state within the meaning of the invention is understood in particular to be a state in which no torsional forces act on the rope gripper about its longitudinal axis. With regard to its rotational position, the rope gripper is in a stable rotational position in the balanced state. A balanced state is particularly present when there is an equilibrium of forces on the holding rope and the actuating rope. Based on such a balanced state of the rope gripper, particularly precise rotational settings on the rope gripper can be effected using the stored values.A preferred embodiment of the invention is that at least one detection device is provided, which is designed to detect a rotational movement of the cable gripper about its longitudinal axis. Such a detection device can, on the one hand, verify the presence of a balanced state, namely when no rotational movement of the cable gripper about its longitudinal axis is detected. On the other hand, such a detection device can also be used to verify whether a rotation of the cable gripper has occurred according to an entered value.

[0020] According to a further development of the invention, it is particularly advantageous for the detection device to comprise a camera and / or a rotation sensor. A camera can be arranged, in particular, on the carrier device in order to detect a rotational movement of the rope gripper. The camera can be arranged particularly expediently on a mast or a boom, particularly preferably in the region of the longitudinal axis of the rope gripper suspended from the mast or boom. A rotation sensor can be arranged either on the carrier device or on the rope gripper itself. In particular, a gyroscope can be arranged on the rope gripper to detect a rotational movement and a rotational position.

[0021] According to a further development of the invention, particularly good reproducibility of a twisting movement is achieved in that the control device is designed such that when the rope gripper is twisted, the gripper blades are moved into the closed position. The control device is particularly designed such that when a twisting command is input, the gripper blades are initially closed if they are still open. The control for the twisting movement thus always occurs under a largely identical initial situation.

[0022] According to a further advantageous embodiment of the invention, it is provided that the cable winches each comprise a hydraulic drive and that the hydraulic drives of the two cable winches can be hydraulically connected to create a balancing state. By such a hydraulic connection of the two hydraulic drives of the cable winches for the holding cable and the actuating cable, a force balance can be achieved between the hydraulic drives and thus between the holding cable and the actuating cable without the cable forces having to be measured. In this way, a balancing state can be achieved or ensured. A further embodiment of the invention lies in the provision of a coupling device for hydraulically coupling the two hydraulic drives. With a hydraulic coupling, in particular, the hydraulic connection can be adjusted to achieve the balancing state.This allows the hydraulic drives to be controlled as desired and largely independently of each other for normal rope grab operation. By activating the coupling device, the two hydraulic drives can then be coupled or hydraulically connected to achieve the desired balance.

[0023] According to a variant embodiment of the invention, it is advantageous that the hydraulic drives are each connected to a supply line for the hydraulic fluid, that the two supply lines are connected to one another via a compensating line which extends between the two supply lines, and that a control valve for opening and closing the compensating line is arranged in the compensating line.

[0024] Each hydraulic drive is supplied with hydraulic energy, i.e., hydraulic fluid, via an associated supply line. A compensating line can, in particular, extend directly between the two supply lines of the hydraulic drives for the first cable winch for the holding cable and the second cable winch for the actuating cable. The compensating line is preferably located on the feed or supply side of the respective hydraulic drives during lifting operation. The compensating line can be used to ensure that an identical condition for the supply of hydraulic fluid, in particular an identical hydraulic pressure, is set on this supply side to create the compensating state. A control valve is arranged in the compensating line to open and close the compensating line.

[0025] It is particularly preferred that the control valve can be controlled by the control device to open or close. In particular, a control valve with an electromagnetic actuating unit can be provided. In particular, the control valve is closed in an unactuated state, wherein opening of the control valve and thus setting of the balancing state only occurs when electrically actuated by the control device. In principle, the individual cables can be designed the same or differently. According to one embodiment of the invention, it is particularly advantageous that the holding cable on the first cable winch has a first winding which is opposite to a second winding of the actuating cable on the second cable winch. In particular, the holding cable and the actuating cable have an opposite lay direction to one another or a so-called cable lay.When a tensile force is applied, opposing torques are exerted on the ropes. This allows for torque compensation and position stabilization of the rope grab during operation.

[0026] In principle, the actuating cable can be directly linked to the grab buckets. To achieve the highest possible closing forces, according to a further development of the invention, it is advantageous for the actuating device to have an actuating carriage connected to the grab buckets via a linkage mechanism, and for the actuating carriage to be displaceable along the grab frame for pivoting the grab buckets. The actuating carriage is preferably mounted on the grab frame so that it can be displaced in a longitudinal or vertical direction. The linkage mechanism can comprise joints, linkage rods, or linkage cables. An actuating carriage can, in particular, ensure the most uniform opening and closing movement of the grab buckets. This is advantageous for stabilizing the position of the rope grab.

[0027] Particularly high closing forces can preferably be achieved by providing a pulley assembly on the actuating carriage, with which an increase in force for closing the grab buckets can be generated. By means of a pulley assembly, the force on the actuating cable for closing the grab buckets can be multiplied depending on the number of pulls. The pulley assembly is positioned in particular between the actuating carriage and the lower end of the grab frame. The pulley assembly's rollers, which are mounted on the actuating carriage on the one hand and on the grab frame on the other, can be wrapped by the actuating cable, the lower end of which is attached to the grab frame. This results in a corresponding extension of the cable's travel distance for actuating the actuating carriage, with the desired increase in force.According to a further embodiment of the invention, it is particularly advantageous that a display screen is provided for the control device for operation. The display screen can be designed, in particular, as a touchscreen on which at least some of the operating elements for a machine operator are implemented. Furthermore, the position of the rope gripper can be displayed in various representations on the display screen to further facilitate operation for a machine operator.

[0028] The method according to the invention for operating a gripper device is characterized in that a gripper device according to the invention is used, wherein by means of a control program of the control device, depending on a control command for twisting without detecting cable forces on the basis of control values ​​stored in the control program, the first cable winch and / or the second cable winch are controlled in such a way that a developed length of the holding cable and / or the actuating cable changes in relation to one another and the cable gripper rotates about its longitudinal axis.

[0029] The method enables the previously described advantages to be achieved in the gripper device according to the invention.

[0030] According to a further development of the invention, it is particularly advantageous that the first cable winch and / or the second cable winch are controlled by means of the control program of the control device depending on a control command for rotating the cable gripper in a desired direction of rotation and / or a rotation angle and a corresponding torque is generated which rotates the cable gripper about its longitudinal axis in the desired direction of rotation.

[0031] The grab device can be used for a variety of tasks. A preferred method variant involves removing soil using the cable grab and, in particular, creating a slot in the ground. The cable grab can be designed, in particular, as a so-called diaphragm wall grab, with which a slot can be created, for example, for a sealing and / or retaining wall in the ground, for example, for an excavation enclosure. The invention is further described below using a preferred embodiment, which is schematically illustrated in the drawings. In the drawings:

[0032] Fig. 1 is a perspective view of a gripper device according to the invention;

[0033] Fig. 2 is a front view of the rope grab of the grab device of Fig. 1 with closed grab blades;

[0034] Fig.3 a front view of the rope grab according to Fig. 2 with opened grab blades; and

[0035] Fig.4 a hydraulic circuit diagram for the hydraulic drives of the cable winches.

[0036] A gripper device 10 according to the invention, as shown in Fig. 1, comprises a mobile carrier device 12 with a crawler chassis as the undercarriage 14. A superstructure 16 with an operator's cabin 17 is mounted on the undercarriage 14, rotatable about a vertical axis of rotation. Located within the operator's cabin 17 is a control device including an input device for a machine operator.

[0037] A boom arm 18 is pivotally mounted on the superstructure 16 about a horizontal axis. A holding cable 24 is guided on a head 20 of the boom arm 18 with deflection pulleys, to the end of which a rope grab 30 with a grab frame 32 and lower grab buckets 34 is attached. The holding cable 24 can be actuated to raise and lower the rope grab 30 via a first cable winch 21 on the carrier device 12. Furthermore, a second cable winch 22 for an actuating cable 44 is located on the carrier device 12, which is also guided via the head 20 to the rope grab 30 for actuating the grab buckets 34 at the lower end of the grab frame 32.

[0038] The functioning of the gripper device 10 according to the invention is explained in more detail below in connection with Figures 2 and 3.

[0039] In a central region of the gripper frame 32, an actuating carriage 42 of an actuating device 40 for actuating the gripper blades 34 is mounted so as to be displaceable in a vertical longitudinal direction. The end of the holding cable 24 is attached to the upper end of the actuating carriage 42, so that the cable gripper 30 is held by the actuating carriage 42.

[0040] At a lower end of the actuating carriage 42, a linkage mechanism 46 with linkage rods 47 is arranged. The linkage rods 47 are pivotally connected, on the one hand, to the actuating carriage 42 and, on the other hand, to one of the grab buckets 34. The grab buckets 34 themselves are pivotally mounted on the lower end of the grab frame 32 via pivot bearings 35. By a relative displacement of the actuating carriage 42 with respect to the grab frame 32, the grab buckets 34 can be opened and closed. By a relative upward displacement of the actuating carriage 42, the linkage rods 47 are pulled upward, whereby the grab bucket 34 is pivoted about its pivot axes 35 into its open position, which is clearly illustrated in Fig. 3.

[0041] Below the actuating carriage 42, a pulley assembly 50 is provided for the actuating cable 44. The pulley assembly 50 has at least one upper roller 52, which is rotatably mounted on the actuating carriage 42, and at least one lower roller 54, which is rotatably mounted on a lower region of the gripper frame 32. The actuating cable 44, fed from above, wraps around the rollers 52, 54 several times, forming loops 56 or pulleys, with the lower end of the actuating cable 44 being firmly connected to the gripper frame 32 or the actuating carriage 42. The actuating carriage 42 is thus adjustably connected or coupled to the gripper frame 32 via the actuating cable 44.

[0042] Starting from the opening position shown in Fig. 3, the actuating carriage 42 is pulled downward relative to the gripper frame 32 by the pulley assembly 50 by pulling the actuating cable 44 upwards through the second cable winch 22. The connecting rods 47 thereby press the gripper blades 34 downwards with an increased closing force, pivoting the gripper blades 34 about their pivot bearings 35 into the closed position shown in Fig. 2.

[0043] When used in a slot in the ground, soil material can be gripped and enclosed between the grapple blades 34 with a closing force that is greater than the tensile force on the actuating cable 44. After the cable grapple 30 is pulled out of a slot in the ground and moved to an emptying position, the tensile force on the actuating cable 44 can be reduced. In this way, the grapple frame 32 moves downward relative to the actuating carriage 42 due to its weight, so that the grapple blades 34 are pivoted back into their open position via the linkage rods 47, as shown in Fig. 3.

[0044] This described arrangement is only an example. In principle, other pulley arrangements with different rope linkages and a different linkage mechanism can be selected, enabling comparable grapple bucket operation.

[0045] When operating the rope grab 30, it is necessary to coordinate the forces and movements between the holding rope 24 and the actuating rope 44 in order to control the torques in the individual ropes and thus the torques of the attached rope grab 30 about its longitudinal axis, particularly due to a so-called lay direction in wound rotating ropes, so that a desired rotation of the rope grab 30 only occurs when this is necessary for the construction process.

[0046] All that is required from the machine operator are appropriate inputs regarding a possibly desired compensation mode for position stabilization or inputs regarding a desired rotational position of the vertical gripper 30. Based on this, the control device can control the cable winches 21, 22 accordingly to effect a compensation mode or the desired rotational position of the cable gripper 30. This significantly simplifies and facilitates the control of a simply constructed cable gripper 30 for a machine operator.

[0047] According to the hydraulic circuit diagram of Fig. 4, the arrangement of a first cable winch 21 for the holding cable 24, which is driven by a first hydraulic drive 61, and a second cable winch 22 for the actuating cable 44 is shown, wherein the second cable winch 22 is driven via a separate second hydraulic drive 62. The two hydraulic drives 61, 62 are each connected to their own first supply line 71 and a second supply line 72, respectively. The two hydraulic drives 61, 62 are designed to drive the respective cable winch 21, 22 in both directions of rotation, i.e., both for winding / lifting and for unwinding / lowering. A supply direction of the hydraulic fluid in the respective supply line 71, 72 during lifting is indicated in Fig. 4 by an arrow labeled LIFT.

[0048] A compensating line 75 extends between the two supply lines 71, 72, which basically run separately from one another and directly connects the first supply line 71 to the second supply line 72. A control valve 77 is arranged in the compensating line 75 and can assume two positions: closing or blocking the compensating line 75 and opening or releasing the compensating line 75. In the open state, in particular, pressure equalization of the hydraulic fluid between the first supply line 71 and the second supply line 72 can take place, whereby a balance state can be set between the first cable winch 21 with the holding cable and the second cable winch 22 with the actuating cable.

[0049] Preferably, control is provided directly by the control device of the gripper device. For fail-safe operation, the electrically actuated control valve 77 can be spring-loaded, whereby the control valve 77 is only opened upon electrical actuation. When non-electrical actuation is discontinued, the control valve 77 is closed, thus blocking fluid flow through the compensation line 75.

Claims

PATENT CLAIMS 1 gripper device with a carrier device (12) and a cable gripper (30) arranged thereon, which has a gripper frame (32) which is held on the carrier device (12) via a holding cable (24), at least two gripper blades (34) which are pivotably mounted at a lower end of the gripper frame (32) between a closed position and an open position, and an actuating device (40) with an actuating cable (44) for pivoting the gripper blades (34), wherein the actuating cable (44) is guided from the carrier device (12) to the actuating device (40), the carrier device (12) has a driven first cable winch (21) for the holding cable (24) and a driven second cable winch (22) for the actuating cable (44), and a control device with an input unit is arranged, by means of which a control command for rotating the cable gripper (30) about its longitudinal axis can be entered, characterized in thatthat the control device is designed with a control program by which, depending on the control command for twisting without detecting cable forces on the basis of control values ​​stored in the control program, the first cable winch (21) and / or the second cable winch (22) are controlled in such a way that a developed length of the holding cable (24) and / or the actuating cable (44) changes in relation to one another and the cable gripper (30) rotates about its longitudinal axis., 2. Gripper device according to claim 1, characterized in that the control device is designed with a control program by which the first cable winch and / or the second cable winch are controlled depending on the control command for rotating the cable gripper in a desired direction of rotation and / or a desired angle of rotation, whereby a corresponding torque is generated which rotates the cable gripper (30) about its longitudinal axis in the desired direction of rotation.

3. Gripper device according to claim 1 or 2, characterized in that a determination device is provided with which it can be determined whether a balancing state of the cable gripper (30) is present or not.

4. Gripper device according to one of claims 1 to 3, characterized in that at least one detection device is arranged which is designed to detect a rotational movement of the cable gripper (30) about its longitudinal axis.

5. Gripper device according to claim 4, characterized in that the detection device comprises a camera and / or a rotation sensor.

6. Gripper device according to one of claims 1 to 5, characterized in that the control device is designed such that when the cable gripper (30) is rotated, due to the control command for rotation, the gripper blades (34) are moved into the closed position.

7. Gripper device according to one of claims 1 to 6, characterized in that the cable winches (21, 22) each comprise a hydraulic drive (61, 62) and that the hydraulic drives (61, 62) of the two cable winches (21, 22) can be hydraulically connected to create a balancing state.

8. Gripper device according to claim 7, characterized in that a coupling device for hydraulically coupling the two hydraulic drives (61, 62) is arranged.

9. Gripper device according to one of claims 1 to 8, characterized in that the hydraulic drives (61, 62) are each connected to a supply line (71, 72) for the hydraulic fluid, that the two supply lines (71, 72) are connected to one another via a compensating line (75) which extends between the two supply lines (71, 72), and that a control valve (77) for opening and closing the compensating line (75) is arranged in the compensating line (75).

10. Gripper device according to claim 9, characterized in that the control valve (77) can be controlled by the control device to open or close.

11. Gripper device according to one of claims 1 to 10, characterized in that the actuating device has an actuating carriage (42) which is connected to the gripper blades (34) via a linkage mechanism (46), and in that the actuating carriage (42) is displaceable along the gripper frame (32) for pivoting the gripper blades (34).

12. Gripper device according to claim 11, characterized in that a pulley arrangement (50) is provided on the actuating carriage (42), with which an increase in force for closing the gripper blades (34) can be generated.

13. A method for operating a gripper device, characterized in that a gripper device (10) according to one of claims 1 to 12 is used, wherein by means of a control program of the control device, depending on a control command for rotating the cable gripper in a desired direction of rotation, without detecting cable forces on the basis of control values ​​stored in the control program, the first cable winch (21) and / or the second cable winch (22) are controlled in such a way that an unwinding length of the holding cable (24) and / or the actuating cable (44) changes in relation to one another and thus a corresponding torque is generated which rotates the cable gripper (30) about its longitudinal axis in the desired direction of rotation.

14. The method according to claim 13, characterized in that the first cable winch (21) and / or the second cable winch (22) are controlled by means of the control program of the control device depending on a control command for rotating the cable gripper in a desired direction of rotation and / or a rotation angle and a corresponding torque is generated which rotates the cable gripper (30) about its longitudinal axis in the desired direction of rotation.

15. Method according to claim 13 or 14, characterized in that soil is removed by means of the rope gripper (30) and in particular a slot is created in the soil.

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