CN109404504B - Linear motion device with parallel arranged and connected lead screws - Google Patents

Abstract

The present invention relates to a linear motion device, comprising: a longitudinal axis (2); at least two threaded spindles (4) which extend side by side parallel to the longitudinal axis (2) and are mounted on a housing (8) of the linear movement device (1) so as to be rotatable about their respective longitudinal axis (6); and a cantilever (10) which is positively engaged in the spindle (4) and which is intended for conversion between a rotation (40) of the spindle (4) and a linear movement (42) of the cantilever (10).

Description

Linear motion device with parallel arranged and connected lead screws

Technical Field

The present invention relates to a linear motion device and a method for controlling a linear motion device.

Background

Linear movement devices are common structural elements in order to achieve translational movement with, for example, commercially available or available components. The linear motion device is determined by parameters such as displacement path, displacement speed and the force that can be applied. The increase in the force that can be applied represents a hindrance in fact, so that the weight or power requirement prevents the arrangement of a single, more robust linear motion device, whereas the arrangement of a plurality of linear motion devices in a rigid or comparatively rigid system leads to a static overdetermination. Static overdetermination often causes increased wear or seizure of the machine.

From EP 2 718 921 B1 a motion simulator is known having a hexapod stage comprising six linear motion devices and a swing stage comprising two linear motion devices. A total of eight linear motion devices are each arranged generally obliquely relative to one another, each having a separate electric motor as a drive and each being supported axially on both sides by a universal joint for torque in the support interior.

An actuator with a movable cantilever is known from DE 10 2007 043 391 A1. Such an actuator has a housing, a spindle and a cantilever which is inserted into the spindle via a nut, wherein a rotation stop is provided between the housing and the nut or the cantilever. The rotation stop should prevent the cantilever from rotating together with the rotary motion of the spindle by: the twist stopper receives a force in a circumferential direction. The disclosed design with a sliding contour projecting with respect to the spindle axis of rotation and a housing-side guide groove adapted thereto should lead to a reduction in wear.

Disclosure of Invention

In contrast, the object of the present invention is to increase the force that can be applied by the linear motion device. In this case, it should preferably be arranged with regard to advantageous manufacturability, such as simple assembly and processability suitable for mass production, as well as wide availability, such as low weight and/or low installation space and/or low wear.

This object is achieved by a linear motion device and a method for controlling a linear motion device. Advantageous developments are preferred subjects.

A linear motion device can be claimed independently, with: a longitudinal axis; at least two threaded spindles which extend parallel to the longitudinal axis and are mounted on the housing of the linear movement device so as to be rotatable about their respective longitudinal axis; and a (common) cantilever that is positively engaged in the spindle, and wherein the cantilevers and/or the positive engagement means are intended for converting (drive-connected) between a rotation (about their respective longitudinal axis) of the spindle and a linear movement (along the longitudinal axis) of the cantilevers. The force that can be applied is increased by the at least two threaded spindles. Compared to a single spindle with a similar force that can be applied, a reduced moment of inertia is present for the same overall cross section, so that overall a higher power can be achieved for a faster response and less energy consumption during repeated accelerations. In this case, a separate housing, for example, can be dispensed with by integrating the two threaded spindles in order to save weight and installation space. The at least two threaded spindles running parallel to the longitudinal axis side by side are at least two threaded spindles arranged and connected in parallel. By providing two threaded spindles in a parallel arrangement and connection, a worn rotation stop can be dispensed with. There are thus multiple benefits in terms of increased forces that can be applied, faster response, reduced energy consumption, weight savings and abandonment of wear parts.

A linear motion device can also be claimed independently, having: a longitudinal axis; at least two wire guides, which extend parallel to the longitudinal axis and are mounted on the housing of the linear movement device (preferably in a non-rotatable manner about their respective longitudinal axis); and a (common) cantilever that engages in a form-locking manner in the spindle, and wherein the cantilevers and/or the form-locking engagement means are/is provided for converting (drivingly connected) between a rotation (about the longitudinal axis of the respective spindle) of the form-locking engagement means of the respective spindle and a linear movement (along the longitudinal axis) of the cantilevers. Such a linear motion device achieves the same advantages as the aforementioned linear motion device. In contrast to the aforementioned linear movement devices with rotatably mounted threaded spindles, threaded spindles of this type have a threaded spindle which is fixed to a housing, and a rotational degree of freedom and/or a rotational drive and/or a rotational output in a form-fitting receptacle. This enables, for example, a small moment of inertia of the rotation from the beginning. Such a linear movement device is used in particular if the cantilever is fixed in a device and the housing is moved. In this case, a drive device arranged fixed to the boom can be provided in addition, which is used to drive the form-fitting engagement means.

A linear motion device can also be claimed independently, having: a longitudinal axis; at least two wires, which extend parallel to the longitudinal axis and are mounted on the housing of the linear movement device (preferably rotatably about their respective longitudinal axis and/or preferably non-rotatably about their respective longitudinal axis); and a (common) cantilever that engages in a form-locking manner in the spindle, wherein a relative rotation can be produced between the form-locking engagement of the cantilever and the corresponding spindle (about the longitudinal axis of the corresponding spindle), and wherein the cantilever and/or the form-locking engagement are/is intended for a (drive-connected) conversion between the relative rotation and a linear movement (along the longitudinal axis) of the cantilever. Such a linear motion device unifies the features of the aforementioned linear motion devices and obtains the same advantages as the aforementioned linear motion devices.

The direction along the longitudinal axis of the linear motion device and/or parallel to the longitudinal axis is referred to as "axial". The direction perpendicular to the aforementioned direction is referred to as "radial". The direction about the longitudinal axis of the linear motion device and/or about an axis parallel to the longitudinal axis is referred to as the "circumferential" or "circumferential direction". The spindle can also be referred to as spindle for short. The linear movement device can be in particular a lifting cylinder or can be used as such a lifting cylinder. The threaded spindle and the cantilever arm can be referred to together as a spindle drive or a spindle drive. The linear motion of the cantilever can be referred to as a force line. The cantilever can be prepared for coupling with a system to be driven and/or a system to be driven.

It can be provided that the form-locking engagement is a screw engagement, so that a proven production method can be used.

Provision can be made for the cantilever to be positively engaged in at least one of the spindles by means of a nut, a ball screw drive and/or a ball circulation spindle, so that a proven design of the engagement means for positive engagement can be used. Other screw drive technologies not explicitly mentioned here can also be used, the construction forms mentioned being merely examples which are presently preferred for practical reasons.

Provision can be made for the cantilever to surround each of the spindles (for example, around the respective longitudinal axis). This makes it possible to achieve a particularly stable engagement in the form-locking with reduced surface contact pressure.

It can be provided that the positive-locking engagement of the spindle and the cantilever is designed as a self-locking or non-self-locking construction. The self-locking embedding mechanism can realize the holding effect without energy input. A non-self-locking engagement mechanism is capable of converting translational motion to rotational motion.

Provision can be made for the cantilever to project from the housing at an angle to the longitudinal axis on an end face of the housing parallel to or along the longitudinal axis and/or on a non-end face of the housing. This results in a linear movement device that can be adapted to the situation.

Provision can be made for the threaded spindle to be mounted axially on the housing. This is achieved thereby: the axial force of the spindle can be dissipated in a concentrated manner.

Provision can be made for the threaded spindle to be supported axially on the housing with an axial bearing inserted in between. The axial bearings are capable of rotation about the respective spindle longitudinal axis. Axial bearings are proven structural elements.

Provision can be made for an elastic element to be inserted and/or connected in between the spindle and the axial bearing or between the axial bearing and the housing. This makes it possible to avoid static overdetermination particularly reliably. This reduces wear on the one hand and enables a proportional force transmission on the other hand, so that there is also a double advantage.

It can be provided by extension that "elastic element" means at least one spring and/or at least one disk spring and/or at least one coil spring and/or at least one leaf spring. Thereby drawing upon proven and advantageous components. In general, "elastic element" refers to a member or component that achieves the ratio between deformation and movement through its/their morphology and its/their material selection. The spring element preferably has a damping effect, as in the case of a disk spring pack, for example, by frictional contact of several layers with one another. Every elastic element mentioned in the description can have this property without this being explicitly mentioned again.

It can be provided that at least one of the threaded spindles is supported at least one axial end or at both axial ends from the outside at least by a bearing fixed to the spindle, an axial bearing and a bearing fixed to the housing. Such features can also be claimed independently. This is achieved thereby: the associated spindle is subjected to a tensile load. This makes it possible to dispense with a design that prevents longitudinal bending of the threaded spindle, as a result of which a thinner threaded spindle can generally be achieved. This saves weight and installation space and increases the power.

It can be provided that at least one of the threaded spindles is supported at least one axial end in the radial direction by a floating bearing which is fastened to the spindle or to the housing. A floating bearing supported in the radial direction can also be referred to as a loosely supported radial bearing. The radial bearing enables the transverse forces of the spindle to be dissipated, while the floating bearing enables the spindle to be axially movable, for example, to compensate for thermally induced expansions. The special advantage is produced in combination with the axial bearing arrangement described above for obtaining tensile loads, since the axial bearing (there) can thus be kept free of transverse forces.

It can be provided, for example, that the axial bearing and/or the radial bearing (radial bearing) is at least one ball bearing and/or at least one plain bearing and/or at least one hydrostatic bearing and/or at least one hydrodynamic bearing and/or a plurality of the aforementioned bearings and/or a combination of the aforementioned bearings. This results in a linear movement device that can be adapted to the application.

It can be provided that an even number of threaded spindles are provided. A particularly symmetrical force distribution is thereby obtained.

It can be provided, either extendedly or as an alternative, that an odd number of screws are provided. This results in a linear movement device that can be adapted to the situation in particular. For an odd number of threaded spindles, a symmetrical force distribution can also be achieved, for example, by setting different diameters of the threaded spindles, by compensating for the moment of inertia and/or by compensating for the reaction forces.

It can be provided, either by extension or independently, that a part of the threaded spindle is left-handed and another part of the threaded spindle is right-handed. This can be achieved by: the internal torque generated by friction in the form-fitting mechanism can be compensated at least partially in the interior of the linear movement device, so that the articulation and/or mounting of the linear movement device can be kept as torque-free as possible.

It can be provided, either by extension or independently, that, in the presence of an even number of threaded spindles, half of the threaded spindles are left-handed and the other half of the threaded spindles are right-handed. This allows torque compensation within the linear movement device to be achieved as far as possible.

Provision can be made for the drive device (for example in the case of a non-rotatably mounted spindle) to be arranged in a fixed manner on the boom and to be provided for the driven relative rotation. Such a system is advantageous for installations with fixed booms and movable housings, because the mass of the movement is low.

It can be provided, either extendably or independently, that the linear movement device comprises at least one drive device, which is provided for rotationally driving at least one of the threaded spindles. This makes it possible to realize an integrated unit which can be coordinated particularly advantageously, for example as a supply assembly. If exactly one drive is provided, the costs can be kept low.

It can be provided, either by extension or independently, that the linear movement device comprises at least two drives, each of which is provided for rotationally driving at least one of the threaded spindles. An integrated unit can thereby be realized with increased reliability.

Provision can be made for each of the threaded spindles to be assigned a drive with a drive connection. This results in high redundancy and reliability.

Provision can be made for at least two threaded spindles to be assigned a drive in the case of a drive connection. This results in a drive assembly which can be operated and/or serviced particularly advantageously.

It can be provided that the drives are drivable and/or controllable and/or settable independently of one another and/or individually. Thereby achieving still higher reliability.

It can be provided that the drive device or the drive devices are selected from the group consisting of electric motors and/or fluid motors and/or hydraulic motors and/or a plurality of the aforementioned motors and/or a combination of the aforementioned motors. This results in the use of validated, i.e. tested, components. In particular, the possibility of combining a hydraulic transmission, such as a closed hydrostatic circuit, with other motors, such as electric motors, is to be mentioned. In general, it can be provided that the drive comprises a directly driven motor or a motor which is driven indirectly, for example by means of a transmission. The transmission can be part of the drive.

The drive device can be prepared for operation for regeneration, thereby reducing system costs through energy savings.

The drive means can comprise a brake which can be prepared for slowing down the movement of the cantilever and/or for holding the cantilever in position, so that a safety function and/or energy saving can be achieved. The brake can be in particular a ventilated brake, i.e. a brake which is opened by energy input and is closed in the event of an interruption of the energy input and thus carries out a safety function. The brake can be part of the transmission, such as a throttle and/or a shut-off valve in the hydraulic circuit, and/or it can be part of the motor, such as a disc brake which is attached to the rotor of the electric motor, and/or it can be provided separately from the other drive components for meeting safety requirements. The brake can act on a central drive, it can act on each spindle and/or at least one spindle or spindle group, and/or it can act on the boom. The holding function can also be achieved by controlled clamping of the spindle, so that additional components can be dispensed with.

Provision can be made for at least two of the threaded spindles to be drivingly and/or rotationally connected to a common drive via a transmission and/or a differential transmission. This makes it possible to reduce the number of drives and thus to save costs. The differential gearing enables a torque balance which helps to avoid clamping and/or jamming of the cantilever arm between the two lead screws.

It can be provided, in an embodiment, that the linear movement device comprises a drive device which is controlled with a large amount of compensation torque and/or with compensation expansion and/or with rotation angle in synchronism with the respective spindle or spindles and/or with compensation rotation angle and/or as a function of the displacement path of the boom and/or a combination of the aforementioned drive devices. A torque-compensating controlled drive makes it possible to avoid clamping the cantilever arm between the two threaded spindles. Likewise, a drive controlled in an expansion-compensating manner, synchronously in terms of the angle of rotation and/or in an angle-compensating manner with respect to the respective spindle or spindles can avoid clamping the boom between the two spindles. When mechanical anti-jamming measures are used, such as differential gearing or individually elastically supported nuts, the drive controlled as a function of the displacement travel of the cantilever arm does not lead to the cantilever arm being clamped between the two threaded spindles either. Thus, it can be specified that the plurality of driving devices are controlled or feedback-controlled in such a manner that the lateral force is minimized inside the device.

Provision can be made for an elastic element to be inserted between the cantilever and a form-locking engagement in at least one of the spindles, so that a static overdetermination (220berberinting) can be avoided particularly reliably. This reduces wear on the one hand and enables a portion-wise force transmission on the other hand, so that there are double advantages. In addition, the spring element can effect a clamping of the linear movement device, for example for applying pressure in a system, for example, which is stationary.

Provision can be made for elastic elements to be arranged in and/or on the cantilever (10) in order to be able to achieve a clamping of the linear movement device.

Provision can be made for the housing to be provided for support with the interposition of an elastic element. Clamping of the linear movement device can also be achieved here.

A method for controlling (operating) a linear movement device, which comprises at least two leadscrews connected in parallel and arranged for the positive-locking displacement of a common boom, can also be claimed independently, wherein at least two drives for the rotary drive of the leadscrews are provided, wherein the drives are controlled and/or feedback-controlled in a torque-compensating manner and/or in an expansion-compensating manner and/or in a rotation-compensating manner with respect to the respective leadscrew or leadscrews and/or in a rotation-compensating manner and/or as a function of the displacement path of the boom. The aforementioned advantages can be achieved with the method.

A method for controlling a linear movement device, which comprises at least two leadscrews connected and arranged in parallel for the positive-locking displacement of a common boom, can also be claimed independently, wherein at least two drives for the rotary drive of the leadscrews are provided, wherein only one part of the leadscrews is driven for displacing the boom, wherein another part of the leadscrews is driven for following the movement of the boom, wherein the following part of the leadscrews is driven for displacing the boom in the event of a partial failure of the displacement of the leadscrews. This enables a safety function, which can be referred to as "reserve drive".

Drawings

Preferred embodiments of the invention are explained in detail below with the aid of schematic drawings. Wherein:

fig. 1 shows a linear motion device according to a first embodiment of the invention in a perspective, partly sectional view; and is provided with

Fig. 2 shows a longitudinal section through a spindle of a linear movement device according to a second embodiment of the invention.

The drawings are merely schematic in nature and are merely intended to provide an understanding of the present invention. Like elements are provided with like features within the scope of the drawings and the embodiments. A renewed description of the same features is largely dispensed with.

Detailed Description

Fig. 1 shows a linear movement device 1 with a longitudinal axis 2. The linear movement device has four threaded spindles 4, each having a spindle longitudinal axis 6 parallel to the longitudinal axis 2, a housing 8 and a cantilever arm 10. The threaded spindles 4 are mounted on the housing 8 at the respective axial end 12 of the threaded spindles 4 by means of bearings 14 so as to be rotatable about their respective axis of rotation 6. Specifically, the housing 8 comprises a cylinder tube 16, a cylinder bottom 18 and a cylinder head 20, which are fixedly connected to each other, wherein each screw spindle 4 is supported in/on the cylinder bottom 18 and the cylinder head 20, respectively, by a support structure 14.

Each spindle 4 is surrounded by at least one nut 22 which is positively engaged in one another in the form of a thread (not shown). The respective nut 22 can be referred to as a positive fit of the respective spindle 4 in the boom 10 and/or a positive fit of the boom 10 in the respective spindle 4. The spindle 4 and the nut 22 interact for converting between a rotation 40 of the spindle 4 and a linear movement 42 of the boom 10. The rotation 40 of the threaded spindle 4 about its respective longitudinal axis 6 is a relative rotation between the respective threaded spindle 4 and the respective nut 22. The region of the form-locking engagement can be referred to as a form-locking engagement or form-locking. The nut 22 is received in the cantilever foot 24 and is fixed for this purpose. The cantilever 10 is designed as a piston, and the cantilever base part 24 is also referred to as a piston base. In addition to the cantilever base 24, the cantilever 10 as a spring element comprises a cantilever spring arrangement 26, which is formed by a set of disk springs 28, i.e. a set of disk springs 28, which are folded up so as to bear against one another in the same direction in order to produce a damping friction, and which comprises a cantilever rod 30, which projects from the housing 8 on an end face 44 along the longitudinal axis 2 in a manner such that it can be displaced and displaced in order to displace a load (not shown).

At the axial end of the housing 8 opposite the cantilever arm 30, four drives 32 are provided, each of which is assigned to a spindle 4. The drive 32 is designed as a transmission electric motor 34 of the same type, which has an electrically ventable disk brake (not shown) acting on a rotor shaft (not shown), an electric motor 36 and a reduction gear 38. The drive means 32 are intended for rotationally driving the respective spindle 4. The drives 32 are subjected to a feedback control, together with torque compensation, wherein a corresponding control method is carried out by a control device (not shown).

Of the four threaded spindles 4, two threaded spindles 4 are right-handed and two threaded spindles 4 are left-handed. The threaded spindles 4 are arranged in turn or alternately one after the other.

Fig. 2 shows another embodiment of the present invention. The general configuration of the linear motion device 1 corresponds to that of the first embodiment. In the following, an advantageous bearing structure of the spindle 4 is explained, with reference also to the first embodiment. On the two axial ends 22, each of the threaded spindles is provided with an axial bearing 46 and a radial bearing 48, respectively. The radial bearings 48 are of the floating bearing type, which are provided in this embodiment fixed on the housing and which are designed as ball bearings.

The axial bearing 46 is a simply acting axial ball bearing which is in each case connected with respect to the length of the spindle from the axially outer side to the axially inner side, centrally between a bearing 50 provided axially on the outer side or on the end side and fixed to the spindle and a bearing 52 provided axially on the inner side and fixed to the housing. The bearing 50 fixed to the spindle can be designed as a single or multiple component with the spindle 4 and can be referred to, for example, as a spindle shoulder or spindle stop. The housing-fixed support 52 can be part of the cylinder bottom 18 or the cylinder head 20, respectively, or it can be fixed for this purpose (directly or also via the cylinder tube 16). The support structures 14 each comprise a spring device 54 in the form of an elastic element, which is connected in the middle between the respective axial bearing 46 and the respective bearing 52 fixed to the housing. This means that a static certainty is obtained in that one of the two axial bearings 46 is subjected to the axial forces of the spindle 4, and the transverse forces and tilting moments of the spindle 4 are subjected to the radial bearing 48. Thus, the 5 degrees of freedom of the spindle 4 are absorbed by the bearing structure 14, wherein a rotation of the spindle 4 can be realized by the bearing structure 14. The spindle 4 is thus subjected to a tensile load by the cantilever 10, so that bending can be ruled out. In order to avoid plastic deformation of the spring device 54 and/or too great an axial movement of the spindle 4, these can be short-circuited from a certain limit value of movement by means of a stop 56 which is arranged on the housing side and is connected parallel to the spring device 54.

Thus, a linear motion device 1 is disclosed having: a longitudinal axis 2; at least two threaded spindles 4 which extend parallel to the longitudinal axis 2 and are mounted on a housing 8 of the linear movement device 1 so as to be rotatable about their respective longitudinal axes 6; and a cantilever 10 which is positively engaged in the spindle 4 and which is intended for conversion between a rotation 40 of the spindle 4 and a linear movement 42 of the cantilever 10.

List of reference numbers:

1. linear motion device

2. Longitudinal axis

4. Screw rod

6. Longitudinal axis of spindle

8. Shell body

10. Cantilever arm

12. Axial end part

14. Bearing assembly

16. Cylinder tube

18. Cylinder bottom

20. Cylinder cover

22. Nut

24. Cantilever base member

26. Cantilever spring device

28. Disc spring

30. Cantilever bar

32. Driving device

34. Transmission-electric motor

36. Electric motor

38. Bevel gear transmission device

40. Rotate

42. Linear motion

44. End face

46. Axial bearing

48. Radial bearing

50. Support fixed on main shaft

52. Support fixed on shell

54. Spring device

56. A stop member.

Claims (11)

1. A linear motion device having: a longitudinal axis (2); at least two threaded spindles (4) which extend side by side parallel to the longitudinal axis (2) and are mounted on a housing (8) of the linear movement device (1); and a bracket (10) which is positively locked in the spindle (4), wherein a relative rotation (40) about the longitudinal axis (6) of the respective spindle (4) can be produced between the positively locking engagement (22) of the bracket (10) and the respective spindle (4), and wherein the positively locking engagement (22) is provided for converting between the relative rotation (40) and a linear movement (42) of the bracket (10), wherein at least one of the spindles (4) is supported at both axial ends (12) from the outside at least by means of a bearing (50) fixed to the spindle, an axial bearing (46) and a bearing (52) fixed to the housing, wherein an elastic element (54) is connected between the axial bearing (46) and the bearing (52) fixed to the housing.

2. The linear motion device according to claim 1, wherein the cantilever (10) protrudes from the housing (8) at an end face (44) of the housing (8) parallel to or along the longitudinal axis (2) and/or at an angle relative to the longitudinal axis (2) at a non-end face of the housing (8).

3. Linear movement device according to claim 1 or 2, wherein at least one of the threaded spindles (4) is radially supported at least one axial end (12) by a floating bearing (48) fixed to the spindle or to the housing.

4. Linear motion device according to claim 1 or 2, wherein an even or odd number of lead screws (4) is provided and/or wherein a part of the lead screws (4) is left-handed and another part of the lead screws (4) is right-handed.

5. Linear motion device according to claim 4, wherein half of the screw (4) is left-handed and the other half of the screw (4) is right-handed.

6. Linear movement device according to claim 1 or 2, wherein the linear movement device (1) comprises at least one drive device (32) which is prepared for rotationally driving at least one of the lead screws (4).

7. Linear movement device according to claim 1 or 2, wherein at least two of the threaded spindles (4) are drivingly connected to a common drive (32) by means of a transmission, and/or wherein the linear movement device (1) comprises a plurality of drives (32) which are controlled in a torque-compensating manner and/or in a manner compensating for expansion and/or in a manner compensating for rotation angles with respect to the respective threaded spindle (4) or threaded spindles (4) and/or in a manner compensating for rotation angles and/or in a manner compensating for a displacement path of the boom (10).

8. Linear motion device according to claim 7, wherein at least two of the lead screws (4) are in rotational driving connection with a common drive (32) via a differential transmission.

9. Linear movement device according to claim 1 or 2, wherein an elastic element (26) is inserted in the middle between the cantilever (10) and a form-fitting engagement (22) in at least one of the spindles, and/or wherein an elastic element is arranged in and/or on the cantilever (10), and/or wherein the housing is prepared for being supported with the elastic element inserted in the middle.

10. Method for controlling a linear movement device (1) according to one of claims 1 to 9, comprising at least two leadscrews (4) which are connected in parallel and are arranged for the form-fitting movement of a common boom (10), wherein at least two drive devices (32) for the rotary drive of the leadscrews (4) are provided, wherein the drive devices (32) are controlled in a torque-compensating manner and/or in an expansion-compensating manner with respect to the respective leadscrew (4) or leadscrews (4) and/or in a rotation-compensating manner and/or in a movement path of the boom (10).

11. Method according to claim 10, wherein the drive device (32) is subjected to feedback control in a torque-compensated manner and/or in an expansion-compensated manner with respect to the respective screw (4) or screws (4) and/or in a rotation-angle-compensated manner and/or as a function of a displacement path of the boom (10).

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