Abstract:
The invention relates to a robot for handling loads, comprising an end effector, three actuators, each with a single degree of freedom, three arms, each of them pivotably connected to an actuator and on pivotably connected to the end effector, a frame carrying the actuators; and a control unit connected to the actuators. The invention also relates to an assembly of plural of these robots.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to The Netherlands Patent Application No. 2010312 filed Feb. 15, 2013, the disclosure of which is hereby incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a robot for handling loads, comprising an end effector, three actuators, each actuator designed for initiating a movement with a single degree of freedom, three arms, each of the arms on one side pivotably connected to a different actuator and on the other side pivotably connected to the common end effector, a frame carrying the actuators; and a control unit connected to the actuators. The present invention also relates to an assembly of plural of these robots. 
         [0004]    2. Description of Related Art 
         [0005]    Robots of this type are also known as “delta robots” and are specific designed for manipulating relative light and small objects at a high speed. Use is made of delta robots in industrial environments to handle products, for instance in selection and packaging of products. Normally in such circumstances the frame and actuators, also referred to as the robot&#39;s base, is mounted above a workspace. From the actuators three arms extend downwards and at the ends of the arms a manipulator is held. The manipulator is also referred to as end effector. The actuators move the end effector via the arms along the X, Y and Z direction. As the actuators are mounted to the frame and can thus be stationary the arms can be made of a light material, e.g. a composite material. As a result of this the robot can be constructed so that the moving parts have a small inertia. This allows the end effector to be moved with high speed and high acceleration. Such a delta robot is for instance known from US 2004/143876. 
         [0006]    Such a robot is also known from WO 03/059581, which describes an industrial robot for moving an object on a platform in space. The robot is thereto provided with three rotatable arms, wherein the axis of rotation of the three arms lies essentially in the same plane. Such arrangement of arms allows the platform to be moved in a relative small area. 
         [0007]    EP 1 125 693 describes a parallel kinematic system to move an end effector by at least two actuators. The actuators of EP 1 125 693 are mounted on a frame along which the actuators move in vertical direction. Such arrangement allows a working area inside the frame. 
         [0008]    EP 2 517 841 describes a device for moving and positioning a member in space. The device thereto comprises a frame, along which two actuators can slide, and a rotating actuator, which actuators are connected to the member in order to move the member in space. The vertically oriented frame limits the area in which the member can be positioned, since the two sliding actuators can only be moved in vertical direction. 
         [0009]    The object of the present invention is, to provide a robot of the delta type that can be used more efficient than the prior art delta robots while at least maintaining the effectiveness of the prior art delta type robots. 
       SUMMARY OF THE INVENTION 
       [0010]    To realise the enhanced efficiency the invention provides a robot for handling loads comprising an end effector, three actuators, each actuator designed for initiating a movement with a single degree of freedom, three arms, each of the arms on one side pivotably connected to a different actuator and on the other side pivotably connected to the common end effector, a frame carrying the actuators, and a control unit connected to the actuators, whereby at least two of the actuators are rotary actuators, connected to the frame with their axes of movement substantially parallel to each other, whereby the axis of movement of one of the actuators is lying outside and nonparallel to a plane through the substantially parallel axes of movement of the other actuators. Traditionally the actuators are positioned in a triangle setting with equal angles between the axes of movement of the three actuators. An advantage of the robot construction according the present invention is that the field of activity, also referred to as the “working volume”, of the end effector changes compared to the prior art robots of this type. Instead of the field of activity of the end effector having a circular projection to a working surface the comparable field of activity of the end effector of the robot according the present invention has a more oval shape. In more detail the working surface in this respect is in a specific embodiment parallel to the plane through the substantially parallel axes of movement has a oval shape. In practise such oval shaped field of activity of the end effector is often more suited for the purposes the robot is used. E.g. in practise these robots are often used for picking up articles from a conveyor belt and moving them sideward to put them in or on a product carrier as for instance a packing. Such handling requires a field of activity that is normally wider than long (compared to for instance the conveyor belt as mentioned before). Even more: the field of activity of the handling ideally is in the centre of the oval is larger (higher) than in the outskirts of the oval. The robot according the present invention fits such handling requirements better than the prior art robots of this type. 
         [0011]    The actuators with parallel axes of movement are in rotary actuators with or without reductions (direct drive) and the arms connected to the rotary actuators can be pivotably connected to the actuator at a distance of the axis of rotation. 
         [0012]    The axis of movement of one of the actuators is lying outside a plane through the substantially parallel axes of movement two of the other actuators. As in the traditional robots the manipulators were place in a common plane the present invention enables it also for instance to put one manipulator (especially the manipulator with the non-parallel axis of movement above or under the other two manipulators with the substantially parallel axes of movement. This further enhances the compactness of build and enables close assembly of plural of these robots. In such build the distance of the actuators with the substantially parallel axes of movement to the end effector will be different from the distance of the third actuators to the end effector. In case the third manipulator is placed above the two manipulators with substantial parallel axes of movement the two actuators with the substantially parallel axes of movement will be closer to the end effector than the third actuator thus also the arms connecting to the two manipulators with substantial parallel axes of movement will have to be shorter than the arm of the third (“non-parallel”) manipulator. 
         [0013]    A further advantage of the robot according the present invention is that the specific orientation of the manipulators of the robot enable a compacter assembly of the combined manipulators. Instead of the traditional triangular orientation now other builds are also possible that can be compact in one or more directions dependent on the specific requirement in which the robot is to be used. The change in field of activity and the change in the possibilities of assembly of the manipulators enable also a different (more compact) assembly of plural cooperating robots. This will be elucidated later in more detail. 
         [0014]    In yet a further embodiment for controlling the orientation of the end effector at least one of the actuators is connected with dual arms to the end effector. Use of parallelograms in arms connecting one or more of the manipulators to the end effector enables to maintain the orientation of the end effector, e.g. to keep it in a horizontal orientation. The use of parallelograms also enable to restrict the movement of the end effector to a pure translation so also without orientations. The arms can be connected to the end effector with universal joints. 
         [0015]    The actuators with their axes of movement substantially parallel to each other are ideally fully parallel to each other but the effect sought for can also largely be realised when the angle enclosed between the substantially parallel axes of movement of two of the actuators is in the range of 0°-20°, preferably in the range of 0°-15°. 
         [0016]    The end effector is normally provided with a handling element. The choice of the specific type of handling element is dependent of the required handling specifications. The handling element may be a passive element (e.g. a pusher) but it is also possible that the end effector carries an active handling element (e.g. a gripper) that is separately controlled, preferably also by the control unit. To realise such independent control a wireless control can be used but also a wired control line connecting to the end effector can be used. 
         [0017]    The invention also provides an assembly of plural robots as specified above which robots are positioned together wherein the field of activity of their arms and/or end effectors (handling elements) is overlapping or separated from each other. The combined robots can in such embodiment be considered as a modular handling system that can be expanded to a capacity, thus a number of robots, as required in a specific situation. To prevent the arms and/or end effectors of the robots to collide (even when they are centrally controlled) these arms and/or end effectors (handling elements) can be separated from each other such that they can never contact so their fields of activity are not overlapping. To make the assembly of robots as compact as possible the distance of the fields of activity of the arms and/or end effectors (handling elements) of two adjoining robots is less than 0.1 m., preferably less than 0.05 m. 
         [0018]    When the field of activity of their arms and/or end effectors (handling elements) is overlapping a central controller can be used such that the arms and/or end effectors will not collide during use. 
         [0019]    In a specific embodiment the assembly of robots also comprises at least one conveyor and the robots are positioned above and in line with at least one conveyor belt. In such configuration the advantage of the relative dense combination of the robots is made use of as here above a specific part of the conveyor (e.g. a belt conveyor) the handling capacity of the robot assembly according the present invention can be higher than the handling capacity of a robot assembly according the prior art. Also, when the same handling capacity compared to the prior art robot assembly is required, this can be achieved with the same amount of robots, where each robot requires less space compared to the prior art robot. Therefore resulting in a reduction of the footprint of the robot assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The present invention is further elucidated on the basis of the non-limitative exemplary embodiment shown in the following figures. Herein shows: 
           [0021]      FIG. 1A  a perspective view on a robot according the present invention; 
           [0022]      FIG. 1B  a side view of the robot of  FIG. 1 ; 
           [0023]      FIG. 2  a perspective view on a part of the robot as shown in  FIG. 1  from a different point of view; 
           [0024]      FIGS. 3A-3G  schematic views on the orientation of the actuators of a robot according the present invention; 
           [0025]      FIG. 4  a schematic top view of an assembly of robots according the present invention; and 
           [0026]      FIG. 5  a schematic top view of an assembly of robots compared to the prior art robots. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0027]      FIG. 1A  shows a delta robot  1  according the present invention with three rotary actuators  2 ,  3 ,  4  that are mounted on a robot frame  5 . The rotary drives  2 ,  3 ,  4  all have a crank  6  that is rotated for changing the position of the dual arms  7 ,  8 ,  9  connected to these cranks  6 . The dual arms  7 ,  8 ,  9  are all connected to an end effector  10 . The arms  7 ,  8 ,  9  are all double constructed as this enables to control not only the position but also the orientation of the end effector  10 . Here the end effector  10  is embodied as a platform. As also illustrated in  FIG. 2  the rotary actuators  2  and  3  are connected to the frame  5  with their axes of movement  11 ,  12  parallel to each other. The parallel axes of movement  11 ,  12  of two of the actuators  2 ,  3  results in a field of activity  13  of the end effector  10  that has a oval shape. 
         [0028]      FIG. 1B  shows the delta robot  1  wherein the field of activity  13 , also referred to as the “working volume”, of the end effector  10  is further indicated. The oval shape as shown in  FIG. 1A  reduces in size when the effector  10  reaches lower, as indicated by the tapered field of activity  20 . 
         [0029]    Further attention is drawn to the position of the third rotary actuator  4  being located above the “parallel” lower rotary actuators  2 ,  3 . Such positioning of the actuator  4  enables a compact build of the frame/actuator assembly  2 , 3 , 4 , 5 . An axis of movement  13  of the higher rotary actuator  4  is perpendicularly intersecting the axes of movement  11 ,  12  of the two lower actuators  2 ,  3 . The arms  7 ,  8  connecting to the two lower actuators  2 ,  3  are shorter than the arms  9  connected to the higher actuator  4 . 
         [0030]      FIG. 3A  shows a schematic view on the orientation of the actuators  2 ,  3 ,  4  of the robot  1  as shown in  FIGS. 1 and 2 . Also the axes of movement  11 ,  12 ,  13  of the actuators  2 ,  3 ,  4  are shown in this figure. 
         [0031]    In line with the schematic view of  FIG. 3A  in  FIG. 3B  is an schematic view shown on an alternative orientation of actuators  30 ,  31 ,  32  with axes of movement  33 ,  34 ,  35 . Here the axes of movement  33 ,  34  of the actuators  30 ,  31  are parallel but now the axis of movement  35  of the actuator  32  is crossing the axes of movement  33 ,  34  of the actuators  30 ,  31 . The actuators  30 ,  31 ,  32  are all placed in a single plane. Also this first alternative configuration of the actuators  30 ,  31 ,  32  is part of the present invention. A choice for the orientation as shown in this figure can for instance be made in case there is limited space in height on the location where a delta robot is to be placed but still the advantages of the present invention are sought for. 
         [0032]    In  FIG. 3C  a second alternative orientation of actuators  40 ,  41 ,  42  with axes of movement  43 ,  44 ,  45  is shown. Here the axes of movement  43 ,  44  of the actuators  40 ,  41  are placed in line (and are thus also parallel). The axis of movement  45  of the actuator  42  is crossing the axes of movement  43 ,  44  of the actuators  40 ,  41 . 
         [0033]    In  FIG. 3D  a third alternative orientation of actuators  50 ,  51 ,  52  with axes of movement  53 ,  54 ,  55  is shown. Here the axes of movement  53 ,  54  of the actuators  50 ,  51  are placed substantially in line (and are thus also substantially parallel). The angle enclosed by the axes of movement  53 ,  54  of the actuators  50 ,  51  is less than 20°, preferably less than 15°, even more preferably less than 10°. 
         [0034]    In  FIG. 3E  a fourth alternative orientation of actuators  500 ,  501 ,  502  with axes of movement  503 ,  504 ,  505  is shown. Here the axes of movement  503 ,  505  of the actuators  500 ,  502  are placed substantially in line (and are thus also substantially parallel). The angle enclosed by the axes of movement  503 ,  505  of the actuators  500 ,  502  is less than 20°, preferably less than 15°, even more preferably less than 10°. 
         [0035]    In  FIG. 3F  a robot according to the invention is shown wherein the actuators comprise two rotary actuators ( 510 ,  511 ) with their axis of movement ( 512 ,  513 ) substantially parallel and one linear actuator ( 514 ). The use of linear actuators may save space, resulting in the possibility of placing multiple robots closer together. 
         [0036]      FIG. 3G  discloses a robot according to the invention wherein the actuators comprise two linear actuators ( 520 ,  521 ) with their axes of movement ( 522 ,  523 ) substantially parallel and one rotary actuator ( 524 ). The use of linear actuators may save space, resulting in the possibility of placing multiple robots closer together. 
         [0037]      FIG. 4  shows schematic top view of an assembly of robots  60 ,  61 ,  62 ,  63  according the present invention with their with the fields of activity  64 ,  65 ,  66 ,  67  separated from each other. The robots  60 ,  61 ,  62 ,  63  are located above two conveyor belts  68 ,  69  moving in the direction as indicated by arrows P1, P2. On conveyor  68  individual products  70  are supplied and the successive robots  60 ,  61 ,  62 ,  63  pick individual products  70  from the conveyor belt  68  and place these individual products  70  in packages  71  as empty supplied by the conveyor belt  69  to be filled after passage of the complete assembly of robots  60 ,  61 ,  62 ,  63  with the individual products  70 . As the fields of activity  64 ,  65 ,  66 ,  67  of the robots  60 ,  61 ,  62 ,  63  are separated from each other there is no possibility of undesired interference of the robots  60 ,  61 ,  62 ,  63 . Also schematically shown is a common control unit  72  steering the robots  60 ,  61 ,  62 ,  63 . 
         [0038]      FIG. 5  shows a schematic view of an assembly of robots  80 ,  81 ,  82 ,  83  according to the prior art and an assembly of robots  84 ,  85 ,  86 ,  87  according to the present invention which are placed above two conveyor belts  88 ,  89 . The effective placement of the robots of the present invention reduced the required footprint on the factory, as indicated by the difference between X and Y, while maintaining the handling capacity of the assembly.