DE102012008559B4 - Robot arm module for a robot arm or robot arm - Google Patents

Abstract

Robot arm module (14, 15) for a robot arm (13) with
- a module body (17),
- At least three joint devices (18) on the module body (17),
- At least three connecting devices (16) which are arranged pivotably on the module body (17) by means of one of the joint devices (18), and
- coupling devices (20, 21) for pivotably coupling the connecting devices (16) to such a connecting device (16) of an adjacent module body (17) or an adjacent drive module (21),
- wherein each of the connecting devices (16) has two such coupling devices (20, 21) spaced apart from one another, and
- Each of the hinge devices (18) being arranged between two such spaced-apart coupling devices (20, 21), characterized in that the hinge devices (18) support the connecting devices (16) in through openings (19) passing through the module body (17).

Description

The invention relates to a robot arm module for a robot arm according to claim 1 or to a robot arm with at least one such module according to claim 8.

There are robot arms in which a plurality of modules are arranged between a first end section and an opposite second end section, which modules form an articulated connection between the two end sections. The modules are connected to one another via articulated connections. For example, describes EP 2 243 994 Al an arm structure in which a large number of rigid elements are connected to one another via elastic elements in the form of springs.

To move the first end section relative to the second end section, drives are usually used, which act directly on individual rigid elements or modules or via pulling mechanisms on modules or the opposite end section. For example, describes WO 2011/104038 Al a gear arrangement, which between two
Module bodies is arranged. On each of the module bodies, three connecting devices are attached in an articulated manner in the direction of the opposite module body. The end sections of the connecting devices opposite the module body are provided with corresponding ones
End portions of connecting devices of the opposite module body are articulated. In each case a drive is connected in an articulated manner between a central point of one of the two module bodies and an articulation point at which two such connecting devices are connected to one another. This arrangement is made possible by
Adjusting at least one of the drives tilting or uniform parallel movement of the first module body relative to the second adjacent module body. However, such an arrangement is only suitable for adjusting two module bodies which are adjacent to one another in relation to one another. Due to the arrangement of the drives between the module bodies, a large amount of space is also required.

From the DE 34 31 453 C2 a mechanical manipulator arm is known which has a module body with at least three joint devices on the module body and at least three connecting devices which are each pivotably arranged on the module body by means of one of the joint devices. Furthermore, this prior art shows coupling devices for pivotably coupling the connecting devices to such a connecting device of an adjacent module body. Each of the connecting devices has coupling devices which are spaced apart from one another. Each of the joint devices is arranged between two such coupling devices which are spaced apart from one another.

the DE 10 2004 058 450 A1 relates to a movement device with a serial-parallel structure in the sense of parallel kinematics with at least one driven axis per parallel kinematics element. The end points of moving axes span a triangle in which three guide elements are arranged in such a way that they intersect their axes of movement in a marked point of the triangle and / or marked normal vector of the plane of the triangle at an always constant angle.

From the FR 2 896 847 A1 a structure with triple parallel kinematics is known, which is connected in an articulated manner to a tiltable platform.

the EP 0 344 185 B1 shows a modular robot that allows the displacement of an end piece from an initial position to an end position.

The robot is built up in steps. A first stage is firmly attached to a base. A last step carries the end piece at the opposite end. Each stage has a platform and six linear moving members. The moving members are attached to the platform of the relevant step by means of a ball joint and to the opposite end by means of an identical joint.

From the WO 01/98 039 A1 an arrangement for moving and positioning objects in space in the sense of a parallel manipulator is previously known. Any movement of an object in space can be carried out via a joint construction and coupling devices as well as the modular structure provided there.

the U.S. 3,580,099 A discloses a movement mechanism with articulated rods and coupling joints for executing movements in space in a wide variety of directions, including a rotation or a torsional movement.

The object of the invention is to further develop a robot arm module for a robot arm or a robot arm with at least one such module. In particular, with a simple structure, even adjustment of a sequence of individual modules connected one behind the other should also be fixed relative to an end section or another
Point within the robot arm are made possible. In particular, a number should be adjustable Components are reduced and still a stable and at the same time space-saving structure are made possible.

This object is achieved by the robot arm module with the features of claim 1 or by a robot arm with at least one such robot arm module according to claim 8. Advantageous configurations are the subject of the dependent claims.

Accordingly, a robot arm module is preferred for a robot arm with a module body, with at least three joint devices on the module body, with at least three connection devices which are pivotably arranged on the module body by means of one of the joint devices, and with coupling devices for pivotably coupling the connection devices to such a connection device of an adjacent module body or an adjacent drive module, each of the connecting devices having two such coupling devices which are spaced apart from one another and wherein each of the articulation devices is arranged between two such coupling devices which are spaced apart from one another.

In other words, the connecting devices extend in a direction parallel to the longitudinal axis on both sides of the module body. In particular, the module body is arranged centrally between two opposite end sections of each of the connecting devices.

The longitudinal axis is to be understood as an imaginary axis which extends in the longitudinal direction of an arm formed from a plurality of such modules. In particular, the longitudinal axis leads through each of the module bodies transversely to its main body extension, so that the module bodies are arranged with their main body extension in a basic position parallel to the main body extension of adjacent module bodies. In the

In the basic position, the longitudinal axis extends, for example, along a straight line. In other adjustable positions, however, the longitudinal axis has a curved course.

A coupling device is understood to mean an in particular articulated connection which enables pivoting about at least one axis. However, connections in which the connecting devices coupled to one another are arranged rotatably with respect to one another about an axis are also not excluded. Such a coupling device can form a fixed and non-releasable connection between two connection devices, but is preferably to be understood in the sense of a jointly coupled connection which is releasable again. This enables the arm length of a robot arm to be adjusted subsequently by removing individual modules or adding further modules. One embodiment is a module in which in one
Basic position a first such module body of a first module is arranged along a longitudinal axis parallel to a second such module body of a second module, in which the connecting devices in the module body of the first module at a first angle with respect to one to
the longitudinal axis are pivotably mounted at least parallel to the axis and in which the connecting devices in the module body of the second module are pivotably mounted at a second angle with respect to the longitudinal axis, the first angle and the second angle being inclined with respect to their longitudinal axes in different directions. In other words, the connecting devices in the first module body are inclined to the left, for example, when viewed in the circumferential direction, and the
Connecting devices in the second module body inclined to the right as seen in the circumferential direction. This creates an accordion-like structure of the robot kinematics or the arm.

Such a module can also be implemented in which a first such coupling device is mounted or formed on one end section of such a connecting device and in which a second such coupling device is mounted or formed on an opposite end portion and is configured as a counter-coupling device to a second such coupling device . By means of such a configuration, a section of such a connecting device can be coupled to an opposite end section of a similar connecting device of an adjacent module. In particular, at least one of the coupling devices is on their

Connection device stored or forms an articulated connection in cooperation with the opposite coupling device of an adjacent module. As a result, according to a preferred embodiment, the modules that are adjacent to one another can be adjusted towards and away from one another along their longitudinal axis. According to the preferred embodiment, two modules that are adjacent to one another can thereby be pivoted to one another at an angle of the longitudinal axis leading through one of the modules.

One embodiment consists in that at least one swivel drive for swiveling one of the connecting devices assigned to it is arranged or fixed on the module body is formed, in particular three pivot drives are arranged or fixed, and each such pivot drive is connected or coupled to one of the connecting devices. Such a module thus forms a drive module which, by uniformly activating three drives, pivots all three connecting devices relative to the module body. As a result, a sequence of modules connected parallel to one another is moved in a straight line away from one another or towards one another along the longitudinal direction leading through them. Due to the fixed arrangement of the drives on the module body and the mounting of the individual connecting devices in this way with, in particular, a central joint device, external clamping or other fixed guidance is not required for this. If only one drive or two drives are activated, this causes a pivoting of the module bodies adjacent to one another and thus a curvature of an arm formed by them. By activating three drives of different strengths, a superimposed movement can take place at the same time, in which an arm formed from a plurality of mutually adjacent modules can be adjusted both in terms of its length and in terms of its curved course.

A further development consists in one on the module in which at least one end section of such a connecting device has an obliquely running region for the longitudinal extension of the connecting device, on which the coupling device is arranged or supported. Such a configuration enables a simple and at the same time space-saving structure. However, with such an arrangement, the connecting devices of two mutually adjacent modules are to be designed with the respective opposite inclination direction of the connecting devices.

According to one embodiment, it is preferred if, in the module, the hinge devices are arranged along tracks arranged in a star shape in the module body and the hinge devices support the connecting devices for pivoting along a circular track. Such an arrangement enables a particularly well-coordinated adaptation of the connecting devices in a module to those in an adjacent module in the installed state.

According to the invention, all of the configurations have in common that the joint devices mount the connecting devices in passage openings passing through the module body. It is equivalent to this that projections, in which the hinge devices are arranged, protrude from the module body adjacent to the passage openings.

According to one embodiment, at least one feed-through opening leads through the module body. Such a feed-through opening is advantageously used to feed lines or cables in the interior of a robot arm from one module to the next.

According to another embodiment, the coupling devices are designed to be rotated and / or given away about at least two axes. In other words, such an arrangement offers two kinematic degrees of freedom, which can be implemented, for example, by designing it as a cardan or universal joint. Such an articulated connection can also be made possible in a simple manner by tensioning the cable if, for example, one end of a steel cable is firmly mounted on the end section of a connecting device and the other end of the steel cable is fixedly mounted on an opposite end section of the connecting device of the adjacent module. The provision of two degrees of freedom not only enables the arm to be extended in a straight longitudinal extension, but also enables the arm to pivot.

According to an independent embodiment, a robot arm with at least one such module, in particular a multiplicity of modules configured in this way, is preferred. In an embodiment of the simplest type, such a module is placed between two end modules which, starting from a module body, have three connecting devices pivotably mounted thereon, these connecting devices not having to pass through the module body. However, robot arms with a large number of such preferred modules are preferred.

In particular, in such a robot arm, at least one such module is designed as a drive module and such a drive module is or are several such drive modules 35 are spaced from end portions of the arm.

In principle, a single drive module is sufficient to adjust the arm with regard to its longitudinal extension and at least one curvature movement. The drive module can be arranged in any position within the arm and is not necessarily limited to the arrangement as the first or last module body.

The use of more than one drive module, with several such drive modules preferably each having a plurality of further modules without a pivot drive between them, enables additional curvatures. For example, with two drive modules, an S- shaped arch adjustable. In order to enable an S-shaped bend, the link chain is particularly interrupted when changing from the first to the second, oppositely bendable “C” bend. In other words, if there are two drives on a link chain, the link chain as such is interrupted somewhere between the drives.

According to one embodiment, such a robot arm or a device with such a robot arm is equipped with a control device for controlling pivoting drives on the at least one drive module. Such a control device can indeed be part of the robot arm itself, but individual components of a suitable control device or an entire control device can also be arranged in a higher-level device or external to a robot with the robot arm.

According to one embodiment, one of the modules arranged between other modules or next to an end module is fixedly, in particular rigidly connected to an external stationary component in the vicinity of the robot arm. This enables any particular module to be attached as a fixed point in the room. In such a case, all other modules move relative to this module.

According to an advantageous embodiment, a gripper or tool is attached to one end of the robot arm.

These components enable the construction of a bionically inspired robot kinematics similar to a worm, a snake or a trunk. Due to the modular structure, in particular the length of such a robot arm can be freely designed. By using several drive modules, bends in different directions can be generated within the length of the robot arm, so that not only a simple bend is made possible, but also S-shaped bends or even more complex bend patterns are made possible. Essentially, a module consists of a base plate as a module body and three rotatably attached levers in the manner of connecting devices, each with a connecting piece and, on the first joint or first module, preferably three additional drives for moving the lever. A modular construction kit can be provided in particular from a module with the base body and the connecting devices as a standard module and a further module as a drive module with one to preferably three drives for adjusting the respective connecting devices relative to the module body. Depending on the design, for example with beveled end sections or specially arranged coupling devices, provision can also be made for a second standard module with a base body and three connecting devices and correspondingly modified coupling devices.

According to such a particularly simple structure, there are. different possibilities of movement of the first end section
relative to the second end section. Changing the length is easy to implement by controlling all three drives equally. Flexion or curvature can be achieved by unevenly controlling the drives.

In particular, a combined movement with change in length and curvature is also possible in that the three drives are controlled accordingly. As a result, kinematics with just one drive module can already generate a "C" curve with a variable length and a variable radius of curvature. If two kinematics are coupled one behind the other or two drive modules are arranged within the total length of the arm, an "S" curve can be created, for example.

This enables safe human-robot interaction, which enables a common work area for humans and robots. Such a biokinetic configuration of the individual components can in particular be surrounded by a cover, for example in the form of a bellows, so that the individual components of the modules are protected from environmental influences. At the same time, a cover ensures that there are no jamming points and no shearing points, which can lead to injuries to people or damage to other surrounding objects. In contrast to a simple articulated arm robot with only one joint between two elongated rods, there are no clamping points and no shearing points. The use of such a robot arm enables a comprehensible range of motion and no reconfiguration, as is necessary with articulated arm robots. Since the drives within the system are preferably stationary, only a very small moving mass needs to be moved, which reduces collision energy.

• 1 einen Roboterarm, der aus einer Vielzahl aneinander gekoppelter Module ausgebildet ist, wobei eine länglich erstreckte Stellung des Roboterarms skizziert ist,
• 2 den Roboterarm gemäß 1 in einer gekrümmten Stellung,
• 3 den Roboterarm in einer geradlinig zusammengezogenen Stellung und
• 4A - 4F verschieden ausgestaltete Modulkörper mit unterschiedlichen Lageranordnungen für Verbindungseinrichtungen.

An exemplary embodiment is explained in more detail below with reference to the drawing. Show it:

• 1 a robot arm which is formed from a plurality of modules coupled to one another, an elongated position of the robot arm being sketched,
• 2 the robot arm according to 1 in a crooked position,
• 3 the robot arm in a straight-line contracted position and
• 4A - 4F differently designed module bodies with different bearing arrangements for connecting devices.

How out 1 seen extends between a first end portion 11 and a second end portion 12th an arm 13th made up of a large number of first modules 14th and second modules 15th is trained. For example, the first end section is used 11 to be coupled to a stationary body, while the second end portion 12th serves to be a tool 29 or to hold a gripper.

The different modules 14th , 15th , 22nd each consist of a rigid module body 17th . The module bodies are preferred, but not absolutely necessary 17th disc-shaped. In each case two adjacent module bodies 17th are among each other by means of three connecting devices 16 connected with each other. The connecting devices 16 are each made of a rigid material and have an elongated, for example rod-shaped, configuration. Each of the connecting devices 16 is by means of a hinge device 18th on the module body assigned to it 17th pivoted.

Here is the connecting device 16 through a passage opening 19th of the module body 17th passed through. The connecting device 16 thus protrudes from the module body on both sides 17th out and is on or in its passage opening 19th so by means of the hinge device 18th stored that a pivoting of the connecting device 16 is made possible relative to the module body. As a result of a pivoting, when viewed axially through the joint device, for example, the upper part of the connecting device tilts 16 to the right, while the underside part of the connecting device 16 pivoted to the left. If the pivoting direction is reversed, the sequence is the opposite.

All three connecting devices are preferred 16 in such a way on the module body 17th stored. The joint devices 18th are in particular star-shaped from a center point of the module body 17th leading so that the three connecting devices 16 along an imaginary circular path around the hinge devices 18th are pivotable.

When coupling a first module to one another 14th and a second module 15th the respective adjacent end sections are each of two of the connecting devices 16 coupled to one another or articulated. The connection is made in such a way that when the two adjacent modules that are coupled to one another move towards one another 14th , 15th the three connecting devices 16 of the first module 14th Pivot along the imaginary circular path, for example in the clockwise direction, while the connecting devices coupled therewith viewed from the coupling point 16 of the second module 15th Swivel counterclockwise. In other words, in this refinement, from the point of view of the space between the first and the second module 14th , 15th the connecting devices 16 in the module body 17th of the first module 14th at a first angle α with respect to one to the longitudinal axis X , which is centered vertically through the module body 17th leads, at least parallel axis or longitudinal axis X ' pivoted. Correspondingly, from the point of view of the module body 17th of the second module 15th its connecting devices 16 at a second angle ß opposite the longitudinal axis X or a longitudinal axis parallel to it X " pivoted. By moving the two adjacent module bodies 17th of the first and second module 14th , 15th become their connecting devices 16 inclined so that the first angle α and the second angle β with respect to their respective longitudinal axes X ' , X " are inclined in mutually different directions.

The ends of the two connecting devices coupled to one another 16 are due to various configurations of coupling devices 20th , 21 connectable to each other. The coupling is such that the two connecting devices coupled to one another 16 on the one hand can be pivoted and / or rotated relative to one another and on the other hand one in the longitudinal direction of the arm 13th Form a sufficiently firm connection. In addition to embodiments with a coupling of the two connecting devices connected to one another which cannot be released or cannot be released without effort 16 Couplings can also be designed which can be separated from one another again with little effort, if necessary, by coupling and uncoupling.

The coupling devices sketched as an example 20th , 21 engage in each other in a U-shape and are, for example, through 35 through bolts connected to each other. Embodiments with a spherical or partially spherical end section of one of the coupling devices and a shell-shaped structure or ring-shaped structure of the opposite coupling device that at least partially encompasses the ball can also be configured.

To support a contracted position of the two adjacent modules that are as close as possible to one another 14th , 15th and a strong inclination required for this of the connecting devices are the end sections of the connecting devices 16 with sloping areas 27 educated. The corresponding sloping areas 27 the end sections of two such connecting devices coupled to one another 16 preferably run in the opposite direction to the pivoting direction of the respective connecting device 16 inclined. In this refinement, there are thus two mutually different first and second modules 14th , 15th provided, which in sequential alternation within the arm 13th can be used.

The very first module of the arm is exemplary 13th as a drive module 22nd educated. With the drive module 22nd are on its module body 17th up to three swivel drives in particular 23 firmly arranged. As swivel drives 23 In particular, electric motors can advantageously be used, although other types of drive, for example hydraulic drives, can also be implemented. The swivel drives 23 have drive shafts 30th on, which are preferably designed at the same time as a cardan shaft and fixed to the body of the connecting device located in the longitudinal direction 16 are coupled or connected to it or formed in one piece with it in a guiding manner through its pivot axis. When the drive shaft 30th one of

Swivel drives 23 by the swivel drive 23 is set in rotation, the connecting device connected to it thus rotates automatically 16 what a forced pivoting of the connecting device attached to it 16 of the adjacent first module 14th has the consequence. The pivoting is based on the design of the arm 13th through the entire sequence of all connection devices coupled therewith 16 continued, which when driving a single one of these drives to a pivoting of the arm in a direction to the drive or from the pivoting drive 23 leads away. With uniform drive of all three swivel drives 23 this leads to movement of the entire arm 13th along a central longitudinal axis leading through this X . Each of the swivel drives 23 thus controls a first, second and third link chain 24 , 25th , 26th each of a plurality of connecting devices coupled to one another in series 16 at. While 1 and 3 a straight extension of the arm 13th through uniform control of all three swivel drives 23 outlines, shows 2 a situation which is caused by the uneven control of the three swivel drives 23 relative to each other. In this case, the arm bends 13th around its central longitudinal axis X or with this from module body 17th to module body 17th .

At the two end sections 11 , 12th are exemplary module bodies 17th shown through which through their passage openings 19th the respective connecting devices 16 protrude through. Instead of such a configuration, however, any other body can also be attached to the end sections, on which such three connecting devices are only pivotably mounted, with these not protruding through the respective body to its rear side. This enables a space-saving structure, even if a further type of end module may have to be provided.

The module bodies shown 17th each have a passage opening 19th for each of the connecting devices 16 on, whereby this feature is also not to be seen as a mandatory feature. Such passage openings 19th offer the advantage of mounting the connecting devices 16 on both sides of their pivot axis. In particular, such through openings 19th can also be formed at other positions in the module body 31-34. How this is based 4A is sketched, the passage openings are 19th arranged along a particularly circular path. How this is based 4B is sketched, the passage openings are 19th Arranged in a star shape. How this is based 4C and 4D is sketched, the passage openings are 19th arranged parallel to one another with two directly parallel to one another or two arranged one behind the other on a line. How this is based 4E is sketched, the passage openings are 19th arranged without a recognizable system, with sufficient pivotability of the connecting devices mounted thereon, of course, being given. How this is based 4A is sketched, the passage openings are 19th arranged along a particularly circular path. The joint devices not shown in these configurations again run correspondingly transversely to the passage openings 19th and mount the connecting devices in such a way that the connecting devices can be pivoted in a plane which, in particular, has a plane axis through the longitudinal extent of the passage openings 19th . runs.

In principle, however, module bodies can also be provided which on the outside have a protruding axis or bearing connection as a joint device of this type 36 have, so that corresponding connecting devices on the outside of the module body 35 are stored sedentarily, as this is based on 4F is sketched. In the case of frame-like configurations, however, such connecting devices can also be arranged on one side on the inside of frame elements.

Connection devices constructed like a frame are shown 16 from two mutually parallel plates, which at their outer end sections by the respective coupling devices 20th , 21 are firmly connected to each other 10. Instead, full profile rods or other configurations can also be used.

Instead of one or more drives on a single module body 17th , which is used as a drive module 22nd at the beginning or at the end of the arm 13th is arranged, such or additional drive modules 22nd also at any other position within the arm 13th be arranged. This allows pivoting of the arm 13th not only enable in 'C' form. In principle, the three pivoting drives, in particular, can also be distributed over different modules of this type and do not necessarily have to be all three on the same module body 17th be arranged. Instead of the electrical drives on the base body, drives outside the actual arm can also be used 13th be arranged and with, for example, linkage or hydraulic systems, each with one of the link chains 24 - 26th be connected.

List of reference symbols

11

first end section

12th

second end section

13th

poor

14th

first modules

15th

second modules

16

Connecting devices

17th

Module body

18th

Joint device

19th

Passage opening

20th

first coupling device

21

second coupling device

22nd

Drive module

23

Swivel drive

24

first link chain

25th

second link chain

26th

third link chain

27

sloping area

28

Feedthrough opening

29

tool

30th

Drive shafts

31-35

Module body

36

Joint device

X

central longitudinal axis

X '

Longitudinal axis in FIG. 14 parallel to the central longitudinal axis

X "

Longitudinal axis in Fig. 15 parallel to the central longitudinal axis

α

first angle with respect to the longitudinal axis X

β

second angle with respect to the longitudinal axis X

Claims (9)

Robot arm module (14, 15) for a robot arm (13) with - a module body (17), - at least three joint devices (18) on the module body (17), - at least three connecting devices (16), which are connected by means of one of the joint devices ( 18) are arranged pivotably on the module body (17), and - coupling devices (20, 21) for pivotably coupling the connecting devices (16) to such a connecting device (16) of an adjacent module body (17) or an adjacent drive module (21), - wherein each of the connecting devices (16) has two such coupling devices (20, 21) which are spaced apart from one another and - each of the joint devices (18) being arranged between two such coupling devices (20, 21) which are spaced apart from one another, characterized in that the joint devices (18) the Store connecting devices (16) in through openings (19) passing through the module body (17). Robot arm module Claim 1 , characterized in that - in a basic position a first such module body (17) of a first module (14) is arranged along a longitudinal axis (X) parallel to a second such module body (17) of a second module (15), - the connecting devices ( 16) are pivotably mounted in the module body (17) of the first module (14) at a first angle (α) with respect to an axis at least parallel to its longitudinal axis (X ') and - the connecting devices (16) in the module body (17) of the second module (15) are mounted pivotably at a second angle (β) relative to its longitudinal axis (X "), - the first angle (α) and the second angle (β) relative to their longitudinal axes (X ', X") in relation to one another are inclined in different directions. Robot arm module Claim 1 or 2 , characterized in that a first such coupling device (20) is mounted or on an end section of such a connecting device (16) and in which a second such coupling device (21) is mounted or configured on an opposite end section and is configured as a counter-coupling device to a second such coupling device (21). Robot arm module according to one of the preceding claims, characterized in that at least one pivoting drive (23) for pivoting one of the connecting devices assigned to it is arranged or fixed on the module body (17), in particular three pivoting drives (23) are arranged or fixed, and each such pivot drive (23) is connected or coupled to one of the connecting devices (16). Robot arm module according to one of the preceding claims, characterized in that the joint devices (18) are arranged along star-shaped tracks in the module body (17) and the joint devices (18) support the connecting devices (16) for pivoting along a circular track. Robot arm module according to one of the preceding claims, characterized in that at least one feed-through opening (28) passes through the module body (17). Robot arm module according to one of the preceding claims, characterized in that the coupling devices (20, 21) are designed to be rotated and / or given away about at least two axes. Robotic arm (13) with at least one module according to a preceding claim, or with a plurality of modules (14, 15, 22) according to a preceding claim. Robot arm (13) Claim 8 , characterized in that at least one such module is designed as a drive module (22) and such a drive module or several such drive modules (22) is / are arranged at a distance from end sections of the arm (13).

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