Patent Publication Number: US-9840011-B2

Title: Parallel robot

Description:
RELATED APPLICATIONS 
     This is a continuation application of application Ser. No. 13/386,856, filed Jan. 24, 2012, which is a national stage of PCT International Application No. PCT/DE2010/000914, filed Aug. 4, 2010, claiming the priority of German application 10 2009 035 992.3, filed Aug. 4, 2009, all three applications hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention is based on an industrial robot with parallel kinematics, which is equipped with a robot base, with a carrier element used as a receptacle for a gripper or a tool and with several actuating units for moving the carrier element. 
     BACKGROUND OF THE INVENTION 
     Industrial robots of this type with parallel kinematics are used to move, position and/or process an object in space. They include Delta robots, for example. These are equipped with at least two control arms as actuating units. Each control arm has an upper and a lower arm section, which are connected to one another in a moveable manner. Each of the upper arm sections is driven by a drive, for example, a motor-gear unit. The drives are arranged on the robot base. The movement of the upper arm sections is transferred via the lower arm sections to a carrier element. Each lower arm section has two parallel rods or struts running in the longitudinal direction of the arm section, which are moveably connected at their one end to the associated upper arm section and at their other end are moveably connected to the carrier element. For example, a gripper for picking up an object or a tool for processing an object can be arranged on the carrier element. To this end the carrier element is equipped with a receptacle for a gripper or a tool. The gripper or the tool arranged on the carrier element can be moved in several dimensions in a targeted manner by means of the movement of the driven upper arm sections coordinated with one another. The control arms effect a spatial parallelogram guidance of the carrier element. The parallel kinematics resulting therefrom render possible a rapid and precise movement of the carrier element and of the gripper or tool arranged thereon. A torque and/or a force can be transferred to the gripper or the tool by means of an additional transfer device arranged on the robot base. If the industrial robot is equipped with three control arms, the transfer device is referred to as a fourth axis. 
     In addition to Delta robots, industrial robots with parallel kinematics also include cable robots. Cable robots are equipped with cables as actuating units. Each cable is connected by its one end to a drive. The drives are embodied as rotation or linear drives which give the free length of the cables by winding and unwinding on a shaft connected to a cable end or by advancing or retracting a push rod connected to a cable end. At their end facing away from the drive, the cables are connected to a carrier element for a gripper or a tool. It must be ensured thereby that the cables are tensioned. The gripper or the tool arranged on the carrier element can be moved in several dimensions in a targeted manner by means of the movement of the drives coordinated with one another. 
     A gripper arranged on the carrier element or a tool arranged on the carrier element is actuated via a pneumatic, hydraulic or electric drive. For this purpose, the gripper or the tool is connected to the robot base via hydraulic, pneumatic, electric or optical supply lines, on which robot base the drive or a part of the drive for the actuation of the gripper or the tool is arranged. The supply lines are used for the transport of compressed air, a pressure liquid, electric current or light. Light can be necessary, for example, for a sensor arranged on the gripper or on the tool. The supply lines thereby connect the robot base to the carrier element freely and without guidance or they are guided along the actuating units or along the transfer device. 
     An industrial robot of this type with actuating units in the form of control arms is known, for example, from EP 250 470 A1. 
     Since industrial robots of this type are also used in the field of food production and food processing, they must satisfy high requirements in terms of hygiene, the harmlessness of materials from which the components of the industrial robot are made and the compatibility with the objects to be moved or processed. In particular the components of the industrial robot coming into contact with the objects must be regularly cleaned. It is important thereby that a cleaning fluid used for cleaning can flow around the components of the industrial robot. The cleaning of the supply lines in particularly has thereby proven to be disadvantageous. If they are guided along the actuating units or the transfer device, dirt can collect in the gaps between the supply lines and the actuating units or the transfer device, which is difficult to access for a cleaning. Furthermore, special demands are made on the supply lines, in particular on their coating or covering with regard to its harmlessness with respect to the objects processed with the industrial robot. Finally, there is a risk of the supply lines being damaged during cleaning. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide an industrial robot with parallel kinematics, which renders possible a reliable cleaning of all components, in which damage to the supply lines is avoided and in which no special demands are made on the material of the supply lines. 
     This object is attained through an industrial robot equipped with at least one elongated hollow body, which is connected directly or indirectly to the robot base. The elongated hollow body has a continuous cavity running in the longitudinal direction. Furthermore, the elongated hollow body is connected in a moveable manner to the carrier element via a joint embodied in an internally hollow manner with several degrees of freedom. The cavity of the hollow joint thereby adjoins the cavity of the elongated hollow body and forms a channel from the robot base to the carrier element. The supply lines are guided from the robot base to the carrier element through the cavities of the elongated hollow body and of the hollow joint. They are thus protected on the one hand from contamination and soiling and on the other hand from damage. The elongated hollow body or hollow bodies are open on the front faces but otherwise preferably closed, so that contaminants and cleaning fluids cannot penetrate into the elongated hollow body from outside and particles such as wear debris of the supply lines, for example, cannot penetrate to the outside. The supply lines are thus protected from outside influences. Moreover, the objects to be processed are protected from contaminants by the supply lines. Furthermore, compared to a guidance of the supply lines along the actuating units, the supply lines guided in the elongated hollow body and the hollow joint are subjected to wear to a much lower extent, since even with a deflection of the carrier element from the starting position, they run virtually in a straight line or curved by only a small angle. 
     The elongated hollow body can have as components, for example, at least two tubes that can be displaced within one another in a telescoping manner. These are supported inside one another secured against twisting. For this purpose, the tubes can have a circular cross section. An inner tube is thereby equipped with bosses projecting outwards, while the outer tube has grooves that are adapted to the bosses. Bosses and grooves run in the longitudinal direction of the tubes. Furthermore, the tubes can also have a cross section that deviates from a circular shape, for example, an oval or angular cross section. The elongated hollow body comprising at least two tubes arranged inside one another in a telescoping manner has the advantage that it is variable in its length and adapts to the variable distance between the robot base and the carrier element. The distance between the robot base and the carrier element changes with a movement of the actuating units. Furthermore, large torques can be transferred even by tubes with a low weight. However, there is also the possibility of using flexible drive shafts as elongated hollow bodies. These are likewise embodied as hollow bodies and can thus accommodate the supply lines. Furthermore, the elongated hollow body can have only one rigid tube. In order to take into account the variable distance between the robot base and the carrier element, the tube can be displaceably supported on the robot base. 
     The cavity of the joint adjoins the continuous cavity of the elongated hollow body. The internally hollow joint has several joint parts, which are moveable relative to one another. These ensure several degrees of freedom of the joint, so that the elongated hollow body connected via the joint to the carrier element can follow the movement of the carrier element. The carrier element is moved in a three-dimensional manner in space via the actuating units. The joint must therefore permit at least a movement in two dimensions. A movement with respect to a third dimension is rendered possible, for example, by a displaceable arrangement in the longitudinal direction of the elongated hollow body on the robot base or by a variable-length embodiment of the elongated hollow body. The joint parts preferably have a continuous cavity or are arranged around a cavity. If the joint parts are arranged inside one another, such as, for example, with a homokinetic joint or a constant velocity joint, the innermost joint part has a cavity through which the supply line is guided. The other joint parts are arranged around the innermost joint part and do not constrict the cavity. If the joint parts are arranged one after the other, such as, for example, with a universal joint or cardan joint with a central joint part and with fork-like joint parts attached thereto in various directions, the cavities of the individual joint parts adjoin one another. Joint parts that connect the joint to the elongated hollow body and to the carrier element or to a gripper or tool arranged on the carrier element, are likewise embodied in a hollow manner or arranged around a cavity so that a continuous cavity common to all joint parts is produced or a sequence of cavities arranged one behind the other, which in turn in total produce a common continuous cavity of all joint parts for the supply lines. In the starting position of the joint, in which the joint is not deflected, this continuous cavity runs in the axial direction. In this starting position the joint can connect two virtual shafts aligned in a parallel manner. The two shafts are aligned offset to one another only through the deflection of the joint. In the case of the joint connected to the elongated hollow body, the axial direction of the joint corresponds to the longitudinal direction of the elongated hollow body and of the cavity of the elongated hollow body. In this starting position the elongated hollow body is aligned vertically. 
     The elongated hollow body with the joint on its end facing towards the carrier element can have various functions: 
     Firstly, it accommodates the supply lines for a gripper or a tool arranged on the carrier element and guides them from the robot base to the carrier element, on which a tool or a gripper is arranged. Advantageously, the cavity runs in the axial direction in the joint. If the supply lines can be laid in the axial direction along the axis of rotation, no torque or at most only a very low torque, will act thereon. 
     Secondly, it can transmit a torque of a rotation drive arranged on the robot base to a gripper arranged on the carrier element or to a tool arranged on the carrier element. In this case, the elongated hollow body is embodied as a torque transmission device and is connected to the carrier element in a rotatable manner, so that the torque is transmitted to a gripper or a tool on the carrier element, not to the carrier element. For this purpose, the carrier element is preferably equipped with a hollow shaft, which is arranged on the carrier element in a rotatable manner. The elongated hollow body is connected via the joint and the hollow shaft of the carrier element to a tool or to a gripper. In order to ensure an exact positioning and alignment of a gripper or tool arranged on the carrier element, it is essential that the elongated hollow body as well as the joint render possible exact angles of rotation. 
     Thirdly, as a force transmission device, it can transmit a force in the longitudinal direction to the carrier element or a gripper arranged on the carrier element or a tool arranged on the carrier element, and thereby press either the carrier element, the gripper or the tool in a direction opposite to the robot base. In order to perform this function, the industrial robot is equipped with a drive or actuator, for example, a pneumatic cylinder or a linear drive, for example, an electric motor, to generate forces acting axially. This drive or actuator can also be arranged in the elongated hollow body. The elongated hollow body and the joint must be rigid and must not undergo any deformation under the forces generated. Axially acting forces of this type are important in particular with cable robots, in which the cables are tensioned in this manner. 
     In a preferred manner the elongated hollow body does not penetrate the robot base and the carrier element. On its end facing towards the robot base, the elongated hollow body is moveably arranged on the side of the robot base facing towards the carrier element. For this purpose, a hollow joint can likewise be provided, through which the supply lines are guided. Furthermore, the elongated hollow body is moveably connected via a hollow joint to the carrier element on the side of the carrier element facing towards the robot base. 
     According to an advantageous embodiment, the joint has several joint parts that are moveable relative to one another, of which a first joint part is connected to the elongated hollow body and of which a second joint part is connected to the carrier element or to a tool or gripper arranged on the carrier element. The first and the second joint part are thereby moveably connected to one another. The first joint part and the second joint part are equipped with a cavity and/or arranged around a cavity so that a common continuous cavity or a spatial sequence of continuous cavities arranged one behind the other is given. The cavities arranged one behind the other likewise produce in sum a common cavity of all joint parts. The supply lines are guided through this common cavity of the joint parts. 
     According to a further advantageous embodiment of the invention, the first joint part and the second joint part are connected to one another via at least a third joint part. The at least one third joint part is thereby equipped with a cavity and/or arranged around a cavity. This cavity of the third joint part together with the cavities of the first and second joint parts forms a common continuous cavity of the joint, through which the supply lines are guided. 
     According to a further advantageous embodiment of the invention, the joint is a cardan joint, which has a central tubular or annular joint part equipped with crossed axles or pairs of axle stubs. A cardan joint is also referred to as a universal joint due to the intersecting axles. The central annular or tubular joint part, according to the above distinction between a first, second and third joint part, can be a third joint part, which has a continuous cavity. The annular or tubular joint part can be round or angular in cross section. A first axle or a first pair of axle stubs of the crossed axles runs through the central joint part with its rotational axis and is supported in or on a first joint part connected to the elongated hollow body. A second axle or a second pair of axle stubs of the crossed axles likewise runs through the central joint part with its rotation axis and is supported in or on a second joint part connected to the carrier element. As a first joint part, for example, tongue-shaped axle receptacles can be arranged on the elongated hollow body, which project in the longitudinal direction on the elongated hollow body. The same applies to the second joint part with respect to the carrier element. The first joint part can be embodied in one piece with the elongated hollow body or as a separate component that is connected to the elongated hollow body. Likewise, the second joint part can be embodied in one piece with the carrier element or connected to the carrier element as a separate element. 
     According to a further advantageous embodiment of the invention, the joint is a cardan joint or universal joint, which has at least two rings or tubes as joint parts. These rings or tubes are rotatably connected to one another via crossed axles and to the elongated hollow body and/or the carrier element. Thus, for example, the elongated hollow body can be rotatably connected about a first axis at its end facing towards the carrier element to a first ring, wherein the first axis is aligned perpendicular to the longitudinal direction of the elongated hollow body. The first ring can be arranged in a rotatable manner, for example, inside the elongated hollow body. According to the above distinction between the first and second joint part, the first ring corresponds to the first joint part. Inside this first ring, a second ring is rotatably arranged about a second axis on the first ring. The first and second axes thereby intersect. The second ring is connected to the carrier element. According to the above distinction between the first and second joint part, it corresponds to the second joint part. The first ring can also be arranged on the outside of the elongated hollow body. The rings or tubes preferably have a round cross section. 
     According to a further advantageous embodiment of the invention, the joint is a constant velocity joint, in which the inner joint part has a continuous cavity, which penetrates the joint part completely. The other joint parts are arranged around the inner joint part. Constant velocity joints are also referred to as homokinetic joints. 
     According to a further advantageous embodiment of the invention, the carrier element is equipped with a hollow shaft rotatably supported in the carrier element. The hollow shaft is connected at its end facing towards the elongated hollow body to the hollow joint and at its end facing away from the elongated hollow body to a tool or gripper. 
     According to an advantageous embodiment of the invention, the industrial robot is equipped with a second joint, embodied in an internally hollow manner, with several degrees of freedom, via which the elongated hollow body is connected to the robot base or to a drive arranged on the robot base. The supply lines are thereby guided through the second joint. The supply lines are thus also completely shielded from the outside at the transition from the elongated hollow body to the robot base. The second joint, like the first joint arranged between the carrier element and the elongated hollow body, has several joint parts that are moveable relative to one another. Furthermore, the second joint can be embodied, for example, as a cardan joint or a constant velocity joint. The above statements on the first joint apply analogously. 
     According to a further advantageous embodiment of the invention, the elongated hollow body together with the joint or joints is embodied at its ends as a jointed shaft with length compensation for transmitting torques from a rotation drive arranged on the robot base to a gripper arranged on the carrier element or to a tool arranged on the carrier element. 
     According to a further advantageous embodiment of the invention, the at least one elongated hollow body is rigid. In this manner no deformation of the elongated hollow body takes place. Furthermore, forces can be transmitted to the carrier element or to a gripper or a tool arranged on the carrier element through the elongated hollow body by means of an additional drive. 
     According to a further advantageous embodiment of the invention, at least one pneumatic or hydraulic control element is arranged in the elongated hollow body for actuating a gripper or tool arranged on the carrier element. A control element of this type comprises one or more valves, for example. Due to the position in the elongated hollow body, the control element is located closer to a gripper or tool than with a positioning of the control element on the robot base. The closer the pneumatic or hydraulic control is arranged to the gripper or the tool, the shorter the distance the compressed air or a pressure liquid has to cover to move the gripper or the tool from the control to the gripper or to the tool. This leads to short reaction times. The valves of the pneumatic or hydraulic control are triggered by electrical signals, the propagation speed of which is much higher than the speed of compressed air or of a pressure liquid. The elongated hollow body shields the pneumatic or hydraulic control from the outside and serves as a housing. The elongated hollow body thus prevents the pneumatic or hydraulic control from being able to come into contact with the objects to be moved or processed. The control therefore does not need to meet any special requirements regarding hygiene. 
     According to a further advantageous embodiment of the invention, the supply line arranged in the elongated hollow body is wound up at least in some sections in a screw-shaped or spiral-shaped manner. It can thus follow the length adjustment of the device. The screw-shaped or spiral-shaped winding is drawn apart with an enlargement of the distance between the robot base and the carrier element and compressed with a shortening of the distance. The winding is thereby preferably around the central longitudinal axis of the elongated hollow body. The diameter of the winding is thereby preferably smaller than the inner diameter of the elongated hollow body. 
     The object is furthermore attained through the industrial robot characterized in that it is equipped with at least one actuating unit embodied in a hollow manner. This actuating unit in the form of a control arm has an upper and a lower arm section with respectively one continuous cavity. Furthermore, the actuating unit is equipped with a joint between the two arm sections, which has a continuous cavity. The joint between the lower arm section and the carrier element likewise has a continuous cavity. The cavities of the arm sections and of the joints thereby adjoin one another and form a continuous channel from the robot base to the carrier element. In these continuous cavities at least one supply line is arranged and guided from the robot base to the carrier element. The supply line is thereby protected from contamination and soiling and on the other hand from damage. The arm sections and the joints of the hollow actuating unit are open at the front faces, but otherwise preferably closed so that contamination and cleaning fluids cannot penetrate into the elongated hollow body from outside and particles such as wear debris from the supply lines cannot penetrate to the outside. The supply lines are thus protected against external influences. Moreover, the objects to be processes are protected from contamination by the supply lines. Furthermore, compared to a guidance of the supply lines along the actuating units, the supply lines guided in the at least one hollow actuating unit are subjected to wear to a much lower extent. 
     According to an advantageous embodiment of the invention, the upper arm section of the hollow actuating unit is embodied as a hollow body. The lower arm section has at least one hollow body. Typically, the lower arm section is composed of two tubes arranged in a parallel manner. It is sufficient thereby if one of the two tubes is a hollow body. 
     According to a further advantageous embodiment of the invention, the hollow joint is a cardan joint, which has a central tubular or annular joint part equipped with crossed axles or pairs of axle stubs. A first axle or a first pair of axle stubs is supported in or on a first joint part connected to an arm section. A second axle or a second pair of axle stubs is supported in or on a second joint part connected to the other arm section or to the carrier element. The first and second joint parts are likewise embodied as hollow bodies. They can furthermore be embodied in one piece with the associated arm section or carrier element. 
     According to a further advantageous embodiment of the invention, the hollow joint is a cardan joint, which as joint parts has two rings or tubes, which are rotatably connected to one another via crossed axles. One of the two rings or tubes is connected to an arm section and the other ring or the other tube is connected to the other arm section or to the carrier element. 
     According to a further advantageous embodiment of the invention, the joint ( 71 ,  72 ) is a constant velocity joint, in which the inner joint part has a cavity. This cavity penetrates the inner joint part completely. 
     Further advantages and advantageous embodiments of the invention are shown by the following description, the drawing and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawing shows an exemplary embodiment of the invention and is described in further detail below. They show: 
         FIG. 1  first exemplary embodiment of an industrial robot according to the Delta principle in sectional representation, 
         FIG. 2  industrial robot according to  FIG. 1  without gripper, with actuating units shown diagrammatically and with vertically aligned elongated hollow body, 
         FIG. 3  industrial robot according to  FIG. 1  without gripper, with actuating units shown diagrammatically and with elongated hollow body deflected from the vertical, 
         FIG. 4  joint of the industrial robot according to  FIG. 1  in sectional representation, 
         FIG. 5  section through the elongated hollow body of the industrial robot according to  FIG. 1  along the plane designated A-A in  FIG. 2 , 
         FIG. 6  section through the elongated hollow body of the industrial robot according to  FIG. 1  along the plane designated B-B in  FIG. 2 , 
         FIG. 7  section through the elongated hollow body of the industrial robot according to  FIG. 1  along the plane designated C-C in  FIG. 2 , 
         FIG. 8  lower arm section of an actuating unit of the industrial robot according to  FIG. 1  in perspective representation, 
         FIG. 9  second exemplary embodiment of an industrial robot with cables as actuating units in perspective representation, 
         FIG. 10  industrial robot according to  FIG. 9  in longitudinal section, 
         FIG. 11  third exemplary embodiment of an industrial robot with cables as actuating units in longitudinal section, 
         FIG. 12  universal joint for an industrial robot according to  FIGS. 1, 9 and 11  in various views, 
         FIG. 13  fourth exemplary embodiment of an industrial robot in longitudinal section. 
     
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENT 
       FIG. 1  shows a first exemplary embodiment of an industrial robot according to the Delta principle with a robot base  1 , a carrier element  2 , on which a gripper or a tool can be arranged, and two actuating units  4  embodied as control arms. The gripper and the tool are not shown in the drawing. The industrial robot has a total of three actuating units  4  embodied as control arms, but one of the actuating units cannot be seen in the representation. Each of the three actuating units is connected to a motor  6  via a drive shaft  5 . The actuating units  4  have an upper arm section  7  and a lower arm section  8 . The upper arm section  7  is thereby characterized by high stability and low weight. The lower arm section  8  has two rods  9  and  10  running in a parallel manner. In the drawing in each case only one of the two rods of an actuating unit  4  is discernible. The two rods  9  and  10  of the lower arm section  8  of an actuating unit  4  are connected via joints  11  at their upper end to the upper arm section  7  of the actuating unit  4  and via joints  12  to the carrier element  2 . The joints  11  coincide with the joints  12 . A joint of this type is shown in section in  FIG. 4 . Each of the joints  11  and  12  has a spherical joint head  13 . This joint head is arranged on the upper arm section  7  with the joints  11  and on the carrier element  2  with the joints  12 . For this purpose, a connection piece is provided on the joint head  13 . Furthermore, the joints  11  and  12  have a ring  14  in which two cylindrical receiving members  15  and  16  are arranged. For better clarity of the drawing, the ring is shown only in part in  FIG. 1 . It can be closed or have an opening as in  FIG. 1 . The two receiving members  15  and  16  have on their front face facing towards the spherical joint head a shape that represents part of a ball cup. The radius of this ball cup is adapted to the radius of the spherical joint head  13 . The receiving member  15  is rigidly arranged in the ring  14 . The receiving member  16  is guided in a displaceable manner in a receptacle  17  in the radial direction based on the radius of the spherical joint head  13 . It is pressed against the spherical joint head  13  via a coil spring  18 . Instead of a coil spring, a disk spring can also be used for this purpose. Manufacturing tolerances of the joint head  13 , the receiving members  15  and  16  and a wear of the respective parts can be compensated via the receiving member  16  displaceably guided in the receptacle  17  and the force applied to the receiving member  16  via the coil spring  18 . This ensures that the joint head is supported in the receiving members in a moveable manner and without play. The joint head  13  and the two receiving members  15  and  16  are embodied with respect to their material and their surfaces such that the receiving members  15  and  16  can move relative to the joint head  13  and thereby slide along the surface of the joint head  13 . Only slight friction occurs hereby, which minimizes wear. Due to the joints  11  and  12 , the lower arm sections  8  can rotate relative to the upper arm sections  7  as well as relative to the carrier element  2 . In order to thereby avoid a rotation of the rods  9  and  10  about their longitudinal axis, the two rods  9  and  10  of a lower arm section  8  are connected to one another via bridge element  19 . The bridge elements  19  are composed of a rigid material. However, they are connected to the two rods  9  and  10  in a moveable manner. 
     The industrial robot is furthermore equipped with an elongated hollow body  20 . It is used to transmit a torque of a rotation drive  31  arranged on the robot base  1  to a gripper (not shown in the drawing) or a tool (not shown) on the carrier element. The elongated hollow body  20  has two tubes  21  and  22  that can be displaced inside one another in a telescoping manner. Due to the displaceable bearing, changes in distance between the robot base  1  and the carrier element  2  during a movement of the actuating units  4  can be equalized. The upper tube  21  is connected to the robot base  1  via a first cardan joint  34  in a moveable manner. The first cardan joint  34  has two rings  23  and  24 , which are arranged in a rotatable manner about axles  27  and  28  running perpendicular to one another. The first ring  23 , the second ring  24 , the first axle  27  and the second axle  28  are discernible in the sectional representation according to  FIG. 7 . The lower tube  22  of the elongated hollow body  20  is moveably connected to the carrier element  2  via a corresponding second cardan joint  35 . This is shown in  FIG. 5 . By means of the two cardan joints  34 ,  35 , the elongated hollow body  20 , adjustable in length, can follow a deflection of the carrier element  2  relative to the robot base  1  from the starting position shown in  FIGS. 1 and 2 . A deflection of this type is shown in  FIG. 3 . 
     The robot base  1  is equipped with a first hollow shaft  32  rotatably supported on the robot base  1 . The end of the first hollow shaft  32  facing away from the elongated hollow body  20  is connected to the rotation drive  31 . The end of the first hollow shaft  32  facing towards the elongated hollow body  20  is connected to the first cardan joint  34 . The first hollow shaft  32  ensures that the torque is transmitted through the robot base to the elongated hollow body  20 . Furthermore, the carrier element  2  is equipped with a second hollow shaft  33  rotatably supported on the carrier element. The end of the second hollow shaft facing towards the elongated hollow body  20  is connected to the second cardan joint  35 . The end facing away from the hollow body  20  can be connected to a gripper or tool (not shown in the drawing). The two hollow shafts  32 ,  33  are embodied in a tubular manner and have a continuous cavity in the axial direction, through which the supply lines are guided. Due to the two hollow shafts  32  and  33 , the elongated hollow body  20  can be rotated with respect to the robot base as well as with respect to the carrier element. The elongated hollow body  20  does not penetrate the robot base  1  and the carrier element  2 . It extends merely from the side of the robot base  1  facing towards the carrier element  2  to the side of the carrier element  2  facing towards the robot base  1 . 
     A valve control  25  with several valves for the pneumatic or hydraulic control of a gripper or tool is arranged in the tubes  21  and  22  of the elongated hollow body  20 . Furthermore, the supply lines  26  for the supply and discharge of compressed air or pressure liquid to the valve control  25  and the gripper or tool are arranged in the tubes  21  and  22  of the adjustable-length device  20 . In order for the supply lines  26  to be able to follow a change in length of the adjustable-length device  20 , the supply lines are wound in in helical manner. With a change in length of the elongated hollow body  20 , the coils of the helical winding are drawn apart or compressed. 
       FIGS. 2 and 3  show the Delta robot in longitudinal section similar to  FIG. 1 , but in contrast to  FIG. 1  the robot base  1 , the carrier element  2  and the actuating units  4  are shown only diagrammatically.  FIGS. 2 and 3  show primarily the alignment of the variable-length elongated hollow body  20 .  FIG. 2  thereby shows the starting position, in which the carrier element  2  is located directly under the robot base  1  and the elongated hollow body  20  with its two tubes  21  and  22  is aligned vertically in the longitudinal direction.  FIG. 3  in contrast shows a position of the carrier element  2  deflected from this starting position, which is triggered by a movement of the actuating units  4 . Although the deflection shown of the carrier element  2  does not lead to an extension of the elongated hollow body  20 , it does lead to a tilting by an angle of 15° with respect to the vertical alignment shown in  FIG. 2 . Due to the cardan joints  34  and  35  with the rings  23  and  24  on the lower and upper end of the adjustable-length elongated hollow body  20 , the tilting is possible without the robot base  1  and the carrier element  2  thereby changing their alignment with respect to the horizontal or vertical. The supply lines  26  are composed of a flexible material. They can therefore follow the movement of the adjustable-length elongated hollow body  20  relative to the robot base  1  and to the carrier element  2 . For example, they are curved with the transition from the lower rube  22  to the carrier element  2 . 
       FIG. 5  shows a cross section through the elongated hollow body  20  at the lower end of the tube  22  of the elongated hollow body  20  in the region of the second cardan joint  35 . In the sectional representation, the two rings  23  and  24  of the cardan joint  35  are discernible. The first ring  23  is thereby rotatably connected to the tube  22  via a first axle  27 . Furthermore, the second ring  24  is connected to the first ring  23  via a second axle  28 . On the outside of the tube  22  the bosses  30  running in the longitudinal direction are discernible, which are used for securing against twisting between the tube  21  and the tube  22 . 
       FIG. 6  shows a corresponding cross section through the elongated hollow body  20  at the upper end of the tube  21  in the region of the first cardan joint  34 . In the sectional representation, the two rings  23  and  24  of the cardan joint  34  are discernible. The first ring  23  is thereby rotatably connected to the tube  21  via a first axle  27 . Furthermore, the second ring  24  is connected to the first ring  23  via a second axle  28 . Since the two cardan joints  34  and  35  are designed in an identical manner, the rings and the axles have the same reference numbers. On the inside of the tube  21 , the grooves  29  running in the longitudinal direction are discernible, which are used for securing against twisting between the tube  21  and the tube  22 . 
       FIG. 7  shows the elongated hollow body  20  in cross section in the region in which the two tubes  21  and  22  overlap. In this representation the bosses  30  projecting outwards are discernible on the outside of the tube  22 , which engage in the grooves  29  of the tube  21 . Grooves  29  and bosses  30  together form the securing against twisting which prevents the tube  21  and the tube  22  from being able to rotate relative to one another. In the sectional representations according to  FIGS. 5, 6 and 7 , moreover, the supply lines  26  are discernible. 
       FIG. 8  shows a lower arm section  8  of an actuating unit  4  in perspective representation. The lower arm section has the two rods  9  and  10 , which are equipped with parts of the joints on their upper and lower end and with the bridge element  19 . The bridge element connects the two rods  9  and  10  to one another. The rings  14  with the receiving members  15  and  16  are arranged at the upper and lower ends of the rods  9  and  10  as parts of the joints. The spherical joint heads  13  of the joints  11  and  12  are arranged on the upper arm sections and on the carrier element  2 . The joint heads  13  are discernible in  FIGS. 1 and 4 . 
       FIGS. 9 and 10  show a second exemplary embodiment of an industrial robot, in which, in contrast to the first exemplary embodiment, the actuating units  36  have cables  37 . A total of six rotation drives  39  are arranged on a robot base  38 . In the representation according to  FIG. 9 , the rotation drives  39  are located on the underside of the robot base  38 . In the representation according to  FIG. 10 , the rotation drives  39  are located on the top of the robot base  38 . A cable  37  is attached with its one end to a shaft  40  of a rotation drive  39 . The cable  37  is wound on the shaft  40  or unwound from the shaft depending on the rotational direction of the associated rotation drive  39 . The cable  37  is guided via a roll  41  arranged likewise on the robot base  38 . With its lower end, the cable is fastened to a carrier element  42 . A gripper or a tool can be arranged on the carrier element  42 . Gripper and tool are not shown in the drawing. An elongated hollow body  43  is arranged between the robot base  38  and the carrier element  42 . The total of six rotation drives  39  are controlled and release a certain cable section via a control, not shown in the drawing. The carrier element  42  is pressed downwards by the elongated hollow body  43  and thus tensions the cables  37 . A movement of the carrier element  42  in space is thus carried out by means of the rotation drives  39  coordinated with one another, the cables  37  and the elongated hollow body  43 . 
     The elongated hollow body  43  has two tubes  44  and  45  arranged in a telescoping manner which overlap in a central section. How far the two tubes overlap depends on the distance between the robot base  38  and the carrier element  42 . A pneumatic cylinder  52  with a piston rod  53  is arranged in the elongated hollow body. Via this pneumatic cylinder a force is applied acting in the axial direction of the elongated hollow body, with which force the elongated hollow body  43  presses the carrier element  42  downwards in a direction opposite to the robot base  38 . The rotation drives  39  of the cables  37  in turn apply a force acting in the opposite direction to the carrier element  42 . The pneumatic cylinder  52  thus tends to draw the two tubes  44  and  45  apart, while the rotation drives  39  of the cables  37  compress the tubes  44  and  45 . The elongated hollow body  43  is connected at its upper end via a first cardan joint  46  to a first hollow shaft  47  arranged rotatably in the robot base  38 . Due to the first cardan joint  46 , the elongated hollow body  43  is connected to the robot base  38  in a movable manner in several directions. A first hollow shaft  47  on the robot base  38  forms the connection between the first cardan joint  46  and a rotation drive  48  arranged on the robot base  38 . The torque of the rotation drive is transmitted via the first hollow shaft  47 , the first cardan joint  46 , the elongated hollow body  43 , a second cardan joint  49  and a second hollow shaft  50  to a tool, not shown in the drawing, or a gripper, not shown in the drawing either, on the second hollow shaft  50  of the carrier element  42 . The second cardan joint  49  is located at the lower end of the elongated hollow body  43 . Due to the second cardan joint  49 , the elongated hollow body  43  is connected to the carrier element  42  in a moveable manner in several directions. The two cardan joints  46  and  49  ensure that the elongated hollow body  43  can follow the movements of the carrier element  42  triggered by the actuating units  36 . 
     The elongated hollow body  43 , the cardan joints  46 ,  49  and the hollow shafts  47  and  50  coincide essentially with those of the first exemplary embodiment. They are all equipped with a continuous cavity, wherein each cavity of a component adjoins the cavity of the adjacent component. In this manner a continuous cavity is produced from the side of the robot base  38  facing away from the carrier element to the side of the carrier element  42  facing away from the robot base, in which cavity supply lines  51  are arranged shielded from the outside. The supply lines  51  are wound in a helical manner in sections in the elongated hollow body. 
     In order to able to apply a force acting in the axial direction to the carrier element  42 , the elongated hollow body is equipped with a pneumatic cylinder  52 . The pneumatic cylinder is arranged in the hollow body  43  and partially surrounded by the winding of the supply lines  51 . This is therefore an inner actuator. The pneumatic cylinder is moveably connected to the first hollow shaft  47 . The piston rod  53  is moveably connected to the second hollow shaft  50 . 
       FIG. 11  shows a third exemplary embodiment of an industrial robot in longitudinal section. This exemplary embodiment coincides with the industrial robot according to  FIG. 10  apart from the elongated hollow body  54 . Only the elongated hollow body is therefore described below. This is embodied as a pneumatic cylinder. The cylinder  55  and the piston rod  56  are embodied as hollow bodies, namely as tubes. The supply lines  51  are arranged inside the cylinder  55  and the piston rod. The pressure for displacing the piston rod in the cylinder is built up and relieved in a chamber  57  surrounding the elongated hollow body on the outside. This is therefore an outer actuator, in contrast to the exemplary embodiment according to  FIG. 10 . 
       FIG. 12  shows a further exemplary embodiment of a hollow cardan joint for an industrial robot according to  FIGS. 1, 9 and 11  in various views. The cardan joint has a central joint part  58 , which is equipped with a continuous cavity  59 . Two pairs of axle stubs  60 ,  61  are arranged on the central joint part  58 , the rotational axes of which intersect at an angle of 90°. The first pair of axle stubs  60  is rotatably supported in a first joint part  62 . The second pair of axle stubs is rotatably supported in a second joint part  63 . The first and the second joint part have a continuous cavity with corresponding diameter like the central joint part. The cavities of the three joint parts  58 ,  62 ,  63  adjoin one another. Supply lines  64  are arranged in this sequence of cavities. They penetrate the cardan joint from one end to the other. This is discernible in the side view. 
       FIG. 13  shows a fourth exemplary embodiment of an industrial robot according to the Delta principle with a robot base  65 , a carrier element  66 , on which a gripper or a tool can be arranged, and two actuating units  67  embodied as control arms. The gripper and the tool are not shown in the drawing. Each of the three actuating units is driven via a drive unit  68 . The actuating units  67  have an upper arm section  69  and a lower arm section  70 . The upper arm sections  69  are composed of a hollow body with continuous first cavity  73 . The lower arm section  70  has two rods running in a parallel manner, of which only respectively the rod facing towards the viewer can be seen in the drawing. One of the two rods has a continuous third cavity  75 . The two rods of the lower arm section  70  of an actuating unit  67  are connected via joints  71  at their upper end to the upper arm section  69  of the actuating unit  67  and via joints  72  to the carrier element  66 . The joints  71  coincide at least qualitatively with the joints  72 . A joint of this type is shown in  FIG. 12 . This is a cardan joint. In this context we refer to the upper description for  FIG. 12 . Furthermore, in accordance with  FIG. 5 , the hollow joints can also be composed of several rings which are connected to one another via intersecting axles and to the arm sections or the carrier element. 
     The hollow joint  71  has a continuous second cavity  74 . The hollow joint  72  has a continuous fourth cavity  75 . The cavities  73 ,  74 ,  75  and  76  of the upper and lower arm sections  69 ,  70  and the hollow joints  71 ,  72  adjoin one another and form a continuous channel from the robot base  65  to the carrier element  66 . A supply line  77  is arranged in this channel. It extends from the robot base  65  to the carrier element  66 . 
     In the fourth exemplary embodiment shown, both actuating units are embodied in a hollow manner. However, it is sufficient if one of the two actuating elements is hollow. 
     According to a further advantageous embodiment of the invention, the joint ( 71 ,  72 ) is a constant velocity joint, in which the inner joint part has a cavity. This cavity penetrates the inner joint part completely. A constant velocity joint is well known in the art. A double cardan joint, which is a cardan joint (also called a universal joint) joined to another cardan joint, is a constant velocity joint. Accordingly, two of the hollow cardan joints shown in  FIG. 12  joined together with one end of one joined to one end of the other is a constant velocity joint. The cavities of the individual joint parts  58 ,  62  and  63  adjoin one another in sequence to allow the supply lines  64  to penetrate the individual joints from one end to the other. 
     All of the features of the invention can be essential to the invention individually as well as in any combination with one another. 
     REFERENCE NUMBERS 
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 1 
                 Robot base 
               
               
                 2 
                 Carrier element 
               
               
                 3 
               
               
                 4 
                 Actuating unit 
               
               
                 5 
                 Drive shaft 
               
               
                 6 
                 Motor 
               
               
                 7 
                 Upper arm section 
               
               
                 8 
                 Lower arm section 
               
               
                 9 
                 Rod 
               
               
                 10 
                 Rod 
               
               
                 11 
                 Joint 
               
               
                 12 
                 Joint 
               
               
                 13 
                 Joint head 
               
               
                 14 
                 Ring 
               
               
                 15 
                 Receiving member 
               
               
                 16 
                 Receiving member 
               
               
                 17 
                 Receptacle 
               
               
                 18 
                 Coil spring 
               
               
                 19 
                 Bridge element 
               
               
                 20 
                 Elongated hollow body 
               
               
                 21 
                 Tube 
               
               
                 22 
                 Tube 
               
               
                 23 
                 Ring 
               
               
                 24 
                 Ring 
               
               
                 25 
                 Valve control 
               
               
                 26 
                 Supply line 
               
               
                 27 
                 Axle of the cardan joint 
               
               
                 28 
                 Axle of the cardan joint 
               
               
                 29 
                 Groove 
               
               
                 30 
                 Boss 
               
               
                 31 
                 Rotation drive 
               
               
                 32 
                 First hollow shaft 
               
               
                 33 
                 Second hollow shaft 
               
               
                 34 
                 First cardan joint 
               
               
                 35 
                 Second cardan joint 
               
               
                 36 
                 Actuating unit 
               
               
                 37 
                 Cable 
               
               
                 38 
                 Robot base 
               
               
                 39 
                 Rotation drive 
               
               
                 40 
                 Shaft 
               
               
                 41 
                 Roll 
               
               
                 42 
                 Carrier element 
               
               
                 43 
                 Elongated hollow body 
               
               
                 44 
                 Tube 
               
               
                 45 
                 Tube 
               
               
                 46 
                 First cardan joint 
               
               
                 47 
                 First hollow shaft 
               
               
                 48 
                 Rotation drive 
               
               
                 49 
                 Second cardan joint 
               
               
                 50 
                 Second hollow shaft 
               
               
                 51 
                 Supply line 
               
               
                 52 
                 Pneumatic cylinder 
               
               
                 53 
                 Piston rod 
               
               
                 54 
                 Elongated hollow body 
               
               
                 55 
                 Cylinder 
               
               
                 56 
                 Piston rod 
               
               
                 57 
                 Chamber 
               
               
                 58 
                 Central joint part 
               
               
                 59 
                 Cavity 
               
               
                 60 
                 First pair of axle stubs 
               
               
                 61 
                 Second pair of axle stubs 
               
               
                 62 
                 First joint part 
               
               
                 63 
                 Second joint part 
               
               
                 64 
                 Supply line 
               
               
                 65 
                 Robot base 
               
               
                 66 
                 Carrier element 
               
               
                 67 
                 Actuating unit 
               
               
                 68 
                 Drive unit 
               
               
                 69 
                 Upper arm section of the actuating unit 
               
               
                 70 
                 Lower arm section of the actuating unit 
               
               
                 71 
                 Joint between an upper and a lower arm section 
               
               
                 72 
                 Joint between a lower arm section and the carrier element 
               
               
                 73 
                 First cavity 
               
               
                 74 
                 Second cavity 
               
               
                 75 
                 Third cavity 
               
               
                 76 
                 Fourth cavity 
               
               
                 77 
                 Supply line