Abstract:
Arm consisting of angularly displaceable linkages ( 1, 2, 3 ), such as a manipulator, having a fixed end carried by a support ( 4 ) and a free end carrying a tool or workpiece ( 7 ), whereby each hinge is provided with controllable blocking means for the purpose of immobilizing said linkages relative to each other, wherein a member counter-balancing the torque is arranged at one or more pivot axes to compensate the weight of said linkages freely movable relative to a hinge towards said free end.

Description:
FIELD OF THE INVENTION 
     This invention is related to a device for relative displacement of two elements comprising articulated links arranged between the elements and force-applying arrangements for applying force for the relative displacement of the elements. 
     The relative displacement of the two elements has the purpose to position them mutually in a manner aimed at by means of the force-applying arrangements. More specifically, the device according to the invention is intended to form a manipulator or robot. The second of the elements is intended to carry, directly or indirectly via a carrying arrangement, a working member to execute the function aimed at, for instance picking, placing, packing and palletising. However, it is remarked that the working member may be adapted to carry out also other work operations than those just mentioned. The first element may according to a first embodiment form a base member secured in space but could according to a second embodiment form a base member with the character of a carrier movable in relation to a carcass. A force-applying arrangement then serves for adjusting the position of the carrier in relation to the carcass. 
     PRIOR ART 
     A robot of the kind defined by way of introduction is described in U.S. Pat. No. 4,976,582. For the positioning of the second element, the robot comprises three force-applying arrangements, which in unison comprise three force-exerting members arranged in a triangular distribution on the first element. Each of the force members is connected to the movable second element via its own connection comprising two link arrangements and an intermediate connection arrangement. These three connections coupled in parallel are likewise arranged in a triangular distribution. Each of these connections comprises a first link arrangement including two first links pivotably connected to the second element and a second link, which is rigidly connected to a movable portion of the force-exerting member and which by means of a connection arrangement is connected to the two first links. The second link is movable with regard to one single degree of freedom relative to the stationary portion of the force-exerting member. The connection arrangement connects the first and second links in a hinged manner with two but not more than two degrees of freedom. The link arrangement formed by the first links is connected to the second element so that likewise two but not more than two degrees of freedom occur. In reality, the first link arrangements form parallelogram-shaped four-links systems. A disadvantage with this known type of robot is that it becomes comparatively bulky as a consequence of the triangular distribution discussed hereinabove. The angle between planes of pivoting for two adjacent second links must, namely, always be less than 180°. Thus, it is very difficult to arrange two or more of those robots closely to each other without collision. A further disadvantage is that all arms must be of equal length. This implies that it is not possible to optimise the robot to the pattern of movement in question. Performance will always be symmetrically distributed in a symmetrical working area, which is not cost efficient. 
     As a consequence of the equilateral triangular construction of the known robot it is also difficult to arrange to work horizontally above conveyors, loading pallets etc. 
     OBJECT OF THE INVENTION 
     This invention aims at devising routes to develop the device of the kind defined by way of introduction so as to eliminate or at least reduce one or more of the disadvantages mentioned hereinabove. A particular aim is to provide a greater flexibility as to the design of the device so that two or more devices may be placed to work comparatively close to each other. According to a further aspect, the aim is to provide an enhanced movability of the robot. 
     SUMMARY OF THE INVENTION 
     The object of the invention is achieved in that the articulated links form at least one four-links system, that the device also comprises at least one pivot arm arrangement and that the fourlinks system and the pivot arm arrangement are mutually connected by means of a connection arrangement. 
     The invention creates possibilities for an asymmetrical design of the device according to the invention and accordingly a design adapted for the purpose of the working area thereof. For instance, this asymmetrical character of the device according to the invention provides possibilities for a very dense packing of a plurality of robots. 
     Several preferable developments of the invention are defined in the dependent claims. These developments and advantages in connection with the invention are dealt with more specifically in the following description. 
     SHORT DESCRIPTION OF THE DRAWINGS 
     With reference to the enclosed drawings a more close description of embodiment examples of the invention follows hereunder. 
    
    
     In the drawings; 
     FIG. 1 is schematical perspective view of the robot according to the invention, 
     FIG. 2 is a view similar to FIG. 1, but illustrating a modified embodiment, 
     FIG. 3 is perspective view of a robot similar to the one in FIGS. 1 and 2, but in a modified embodiment, 
     FIG. 4 is a schematical view similar to the one in FIG. 1, but with modifications relating to design and function, 
     FIG. 5 is a perspective view illustrating an embodiment where three force-applying arrangements comprise force-exerting members arranged with stationary portions fixed to the first element and movable portions arranged to actuate the pivot arm arrangement via link arm arrangements, 
     FIG. 6 is a view in perspective of an earlier alternative, 
     FIG. 7 is a perspective view of an alternative, where the pivot arm arrangement is situated closest to the first element, 
     FIG. 8 is a perspective view of yet another embodiment, where a pivot arm arrangement is pivotable in all directions in relation to a connection arrangement, which is connected to the first element via a four-links system, 
     FIG. 9 is a schematical perspective view illustrating a robot provided with a transmission intended for turning a working member arranged on a pivot arm arrangement, 
     FIG. 10 is a perspective view illustrating an alternative transmission capable of transmitting drive force between two link members pivotable in all directions in relation to each other, 
     FIG. 11 is a schematical and perspective view illustrating how double force transmission may be realised at a joint with two degrees of freedom, more closely freedom to relative pivoting about two axes inclined in relation to each other, 
     FIG. 12 is a perspective view of an embodiment similar to the one in FIG. 10, but in a somewhat modified condition, and 
     FIG. 13 is a perspective view of an alternative similar to the embodiment in FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In order to simplify the understanding, like reference characters have been used in the following in different embodiments for similar or corresponding components but with addition of letters specific to the embodiments. 
     The robot illustrated in FIG. 1 is intended for relative displacement of two elements  1 ,  2 . The element  1  is in the example intended to form a base member, relative to which the element  2  is intended to be positioned in space. The element  2  is intended to carry, either directly as indicated in FIG. 1, or, as will be dealt with later, indirectly via a carrying arrangement, a working member  3 . 
     The robot comprises articulated links  4 ,  5  provided between the elements  1 ,  2  and force-applying arrangements  6 ,  7 ,  8  for applying force for the relative displacement of the elements. 
     The articulated links  4 ,  5  form in addition to two further links  9 ,  10  a four-links system FS 1 . The robot comprises further a pivot arm arrangement  11  and a connection arrangement  12  for mutual connection of the four-links system FS 1  and the pivot arm arrangement  11 . 
     The links  4 ,  5 ;  9 ,  10  are in the example comprised in the four-links system FS 1  parallel in pairs, and accordingly of equal length. Thus, the four-links system FS 1  forms parallelogram. 
     A first  6  of the force-applying arrangements is provided to pivot the link  4  and hence also the link  5  of the four-links system in first planes in order to change the form of the four-links system. These planes extend more closely substantially parallel to the planes, in which the links in the four-links system FS 1  are arranged. 
     The force-exerting arrangement  6  comprises a force-exerting member with a stationary portion rigidly connected to the link  9  and a movable portion rotationally rigid connected to the link  4 . The force-exerting member is more closely formed by a rotary means, the stator thereof being connected to the link  9  and the rotor thereof being connected to the link  4 . 
     A second force-applying arrangement  7  is arranged to pivot the four-links system FS 1  in other planes forming an angle, preferably substantially right angle, with the first planes. The force-applying arrangement  7  comprises a force-exerting member with a stationary portion rigidly connected to the element  1  and a movable portion rotationally rigid connected to the link  9 . The force-exerting member is in the example formed by a rotary means with a stator rigidly connected to the element  1  and a rotor connected to the link  9 . The rotary means comprised in the arrangements  6 ,  7  are denoted  13  and  14  respectively and their rotation axes are in the example extending with an angle, preferably substantially right angle in relation to each other. It should be noted that the rotary means  13  will follow the link  9  in the example when the four-links system FS 1  is pivoted by means of the rotary means  14 . 
     A third  8  of the force-applying arrangements is arranged to actuate the pivot arm arrangement  11  in order to cause it to pivot. The arrangement  8  comprises a force-exerting member  15  with a stationary portion fixed in relation to the element  1  and a movable portion arranged to actuate the pivot arrangement  11 . More closely, a link arm arrangement  16  is arranged between the movable portion of the force-exerting member  15  and the pivot arm arrangement  11 . This pivot arm arrangement comprises in the example an arm  17  rigidly connected to the movable portion of the force-exerting member  15  and a link arm  18  hingedly connected to the arm  17  and to the pivot arm arrangement  11  via joints  19  and  20  respectively. These joints must allow pivoting of the link arm  18  in all directions in relation to the arm  17  and the pivot arm arrangement  11  respectively, i.e. the joints must allow a relative pivoting movement about pivot axes inclined in relation to each other. Thus, the joints could be realised by means of cardan couplings. They could also be realised by means of ball joints, which implies that a further degree of freedom in the form of relative rotation is added. 
     The four-links system FS 1  is in FIG. 1 arranged between the connection arrangement  12  and the element  1  and the pivot arm arrangement  11  is arranged between the second element  2  and the connection arrangement  12 . 
     The pivot arm arrangement  11  is in the example performed by a simple pivot arm  21 . The connection arrangement  12  has the character of a structure, which in a hinged manner connects the pivot arm  21  to the link  10  comprised in the four-links system FS 1 . 
     The pivot arm  21  has two arm parts  22  and  23  respectively located on each side of the pivot axis of the pivot arm denoted  24 , wherein a first arm part  22  is connected to the second element  2  and a second arm part  23  is connected to the link arm arrangement  16  via the joint  20 . The pivot arm  21  is pivotably connected to the connection arrangement  12  and the link  10  with one single degree of freedom. The pivot axis  24  of the pivot arm  21  is in the example directed so that the pivot arm  21  receives pivotability in planes substantially perpendicular to planes, in which the links  4 ,  5  of the four-links system are pivotable. 
     It is in FIG. 1 illustrated a third link  25  forming other four-links systems together with each of the other links  4 ,  5 . This third link is connected to the element  1  by means of a joint  26  and to the link element  28  via a joint  27 , said link element  28  being connected to the link  10  in the four-links system FS 1  via joint  29 . Since the form of FS 1  may be changed in its own plane by pivoting the links  4 ,  5  and besides may be rotated in a rotation plane perpendicular to said pivoting plane, it is required that the joints  26 ,  27  of the link  25  are so arranged that the link  25  may pivot in all directions in relation to the element  1  and the link element  28  respectively. Joints with at least two non-parallel pivot axes or ball joints will thus be of interest. The link element  28  is however pivotably connected to the link  10  of the four-links system FS 1  with one single degree of freedom, i.e. the joint  29  allows pure pivoting about an axis. This axis must run perpendicularly to the adjacent joint axes of the four-links system in order to cause a parallelogram-function. This requires in addition that the link  25  is substantially parallel to the links  4 ,  5  and has substantially the same length as they have. 
     Thus, the working member  3  may by means of the robot illustrated in FIG. 1 be adjusted in Z-direction by means of the rotary means  13 . The working member  3  may further be adjusted in the XY-plane by means of a suitable operation of at least one of and suitably both of the rotary means  14 ,  15 . 
     The alternative illustrated in FIG. 2 corresponds regarding the substantial parts with the previous embodiment. The difference is in the first place that the link/link element denoted  25  and  28  respectively in FIG. 1 are not present in this case. These components are thus not necessary but may be added when there is a need for further stability of the four-links system FS 1 . The robot has in absence of those components a more slender design and besides a greater working area. 
     The alternative in FIG. 3 is closely related to the embodiment according to FIG.  2 . There are mainly only two differences; the first difference is that the pivot arm  21   a  is connected to the link arm  18   a  in the area between the ends of the pivot arm, i.e. the pivot arm  21   a  is connected to the connection arrangement  12   a  with one of its ends and its other end carries the working member  3   a.  The second difference is that also the force-exerting member  13   a  is fixed with the stationary portion thereof in relation to the first element  1   a.  The movable portion (drive axis) of the member  13   a  has instead a gear wheel  30 , which drives a further gear wheel  31  rigidly connected to one  4   a  of the links in the four-links system FS 1  in an inclined relation thereto. The gear wheels  30 ,  31  form in other words an angular gear, which permits this rotation when the links  4   a  and  5   a  are rotated about the rotation axis denoted  32  by means of the force-exerting member  14   a  provided that the force-exerting member  13   a  by rotation by means of the member  14   a  is driven to follow with the same angular velocity. The movable portion of the force-exerting member  14   a  is rotationally rigid connected to the link  9   a  as previously, said link  9   a  being hingedly connected to the links  4   a,    5   a.  It should hereby be noted that the gear wheel  31  suitably is rotationally mounted in relation to the link  9   a.    
     The alternative illustrated in FIG. 4 differs from the embodiment according to FIG. 1 by means of that each of the articulated links  4   b,    5   b  and  25   b  is connected to the first element  1   b  and the connection arrangement  12   b  respectively, which in this case, and also in the previous embodiment, may be regarded comprising the link  10   b,  by means of joints permitting the links to pivot in all directions in relation to the first element  1   b  and the connection arrangement  12   b.  It should also be noted that the component  28   b,  which in the embodiment according to FIG. 1 had the character of a link element hinged in relation to the link  10 , in this case forms a rigid component of the connection arrangement  12   b.  It is however within the scope of the embodiment according to FIG. 4 to also utilise the embodiment shown there. 
     It has already been mentioned that the joints  26   b,    27   b  are arranged so that they permit pivoting of the link  25   b  in all directions in relation to the element  1   b  and the connection arrangement  12   b.  Thus, it is here referred to joints with double, angularly disposed pivot axes, for example cardan joints, or ball joints. Corresponding considerations are valid for the joints denoted  33  between the links  4   b,    5   b  and the element  1   b  and the connection arrangement  12   b  respectively. The articulated connection of the link  4   b  to the element  1   b  is however somewhat special as a consequence of that the articulated connection takes place via the force-exerting members  13   b,    14   b  in on principle the same way as already have been discussed. Thus, the link  4   b  will be connected to the element  1   b  via the rotation axes of the two force-exerting members  13   b,    14   b,  which extend substantially perpendicularly to each other. Thus, the rotation axes of the members  13   b,    14   b  will provide the universal pivotability of the link  4   b  in relation to the element  1   b  provided of course that the members  13   b,    14   b  permit the pivoting movements in question. 
     Thus, the discussion above implies that the link  9  present in the embodiments according to FIG.  1  and comprised in the four-links system FS 1  in the embodiment according to FIG. 4 will be formed by the element  1   b  itself in combination with the force-exerting members  13   b,    14   b.    
     Two degrees of freedom are obtained in FIG. 1 between the link  5  and the first element  1  by the link between  5  and  9  in combination with the rotation axis of the member  14 . Two degrees of freedom are obtained in FIG. 4 for the link  5   b  by the joint  33 . 
     The alternative illustrated in FIG. 5 differs from the preceding alternatives by way of not only the force-applying arrangement  8   c  but also the force-applying arrangements  6   c  and  7   c  comprise link arm arrangements  16   c,    34  and  35  respectively, through which the force-exerting members  13   c,    14   c  and  15   c  respectively actuate the second element  2   c.  The link arm arrangements  34 ,  35  comprise respective arms  36 , 37  in similarity to what is valid for the link arm arrangement  16   c,  said arms being rotationally rigid connected to movable portions of the respective force-exerting members  13   c,    14   c  and links  38  and  39  respectively connected between these arms  36 ,  37  and the second element  2   c.  From what has already been described regarding the link arm  18   c,  the link arms  38 ,  39  are also hingedly connected in relation to the arms  36  and  37  respectively and the element  2   c  (the pivot arm  21   c ) via joints permitting pivoting of the link arms in all directions. It is once again concerning ball joints or other joint constructions, such as cardan joints, permitting pivoting about two pivot axes angularly displaced in relation to each other. 
     It is in the embodiment according to FIG. 5 in the first place the force-applying arrangement  6   c,  which effects movement of the second element  2   c  in Z-direction. The arrangement  7   c  effects movement in Y-direction while the arrangement  8   c  effects movement in X-direction. 
     It is in FIG. 5 illustrated how the pivot arm  21   c  is provided with a stabilising bar  40  causing the articulated base of the pivot arm  21   c  becoming comparatively wide and therefor stabile in relation to the connection element  12   c.    
     The four-links system FS 1  is in the alternative according to FIG. 6 arranged between the connection arrangement  12   d  and the second element  1   d.  The pivot arm arrangement  11   d  is pivotable in relation to the connection arrangement  12   d  about a pivot axis denoted  41 , which in this case, although it is not necessary, is substantially parallel to the pivot plane of the four-links system FS 1 . The latter may be pivoted by means of the force-exerting member  13   d.    
     The pivot arm arrangement  11   d  is in this case pivotable in relation to the connection arrangement  12   d  by means of a joint arrangement generally denoted  42  permitting pivoting of the pivot arm arrangement  11   d  in all directions in relation to the connection arrangement  12   d.  The pivot arm arrangement  11   d  is in this embodiment in reality formed as a further four-links system comprising a further link  43 , except for the link  21   d,  which corresponds to the previously mentioned pivot arm  21 , said link  43  in addition to two further links  44 ,  45  forming a four-links system in said way. It is thereby pointed out that the links  21   d  and  43  are pivotable in relation to the link  45 , which is the one to be rotatable about the previously mentioned axis  41 . By means of the pivotability of the links  21   d  and  43  in relation to the link  45  and the rotatability thereof about the axis  41 , the pivoting freedom of the pivot arm arrangement  11   d  in relation to the connection arrangement  12   d  is thereby provided in all directions. 
     The second element  2   d  is not arranged directly on the pivot arm  21   d  in this embodiment, but instead on the link denoted  44 , which is partly carried by the arm  21   d.  This implies that the direction of the elements  2   d  in space will be maintained as a consequence of that two four-links systems in reality will be coupled in series, but by a relative pivoting movement of the four-links systems about the axis  41 , the rotation position of the second element  2   d  will on the other hand be displaced. Force-applying arrangements  7   d  and  8   d  respectively with force-exerting members  14   d  and  15   d  are in this case, just as in the previous case according to FIG. 5, prevailing, which are connected to the second element  2   d,  here the link  44 , via link arm arrangements  35   d  and  16   d  respectively in order to operate the same. It is in the first place the force-applying arrangement  8   d  operating the second element  2   d  in Z-direction in the figure while the arrangement  7   d  is pivoting the pivot arm arrangement  11   d  about the axis  41 , which in FIG. 6 is substantially vertical so that the element  2   d  is displaced in X-direction. The force-applying arrangement  7   d  is finally displaceable via the element  2   d  of the FS 1  in Y-direction. 
     The four-links system FS 1  is provided between the connection arrangement  12   e  and the second element  2   e  in the alternative according to FIG. 7, and the pivot arm arrangement  11   e  is provided between the first element  1   e  and the connection arrangement  12   e.  The force-exerting member  15   e  effects pivoting of the pivot arm  21   e  about the axis denoted  46  and it causes the force-exerting member  13   e  to follow due to that the stator thereof is rotatably rigid connected to the rotor of the member  15   e.  The force-exerting member  14   e  has on the other hand its stator connected to the first element  1   e.    
     Thus, the four-links system FS 1  may be relocated by the pivot arm  21   e  so that the element  2   e  is displaced in Y-direction. The member  13   e  causes a pivoting movement in Z-direction of FS 1  and the element  2   e  via the associated link arm arrangement. The force member  14   e  causing FS 1  to pivot in horizontal direction via the associated link arm arrangement, i.e. substantially parallel to the pivoting plane of the pivot arm  21   e  so that the element  2   e  is displaced in X-direction. 
     The alternative in FIG. 8 mainly corresponds to the alternative in FIGS. 2 and 3 except for that the pivot arm  21   f  of the pivot arm arrangement is connected to the connection arrangement  12   f  by means of a joint  47  allowing pivoting of the pivot arm  21   f  in all directions in relation to the connection arrangement  12   f.  The force-applying arrangement  8   f  with the force-exerting member  15   f  and the associated link arm arrangement  16   f  serve for operating the pivot arm  21   f  in the horizontal plane. A further moment is in this case that the pivot arm  21   f  also may be pivoted in the vertical plane and more closely with the aid of the force-exerting member  14   f,  which is connected to the second element  1   f  with a stationary portion thereof and carrying the force-exerting member  15   f  with a movable portion thereof. The members  14   f  and  15   f  have their respective rotation axes running in an angle in relation to each other, more closely in a substantially right angle so that the pivot arm  21   f  thus may be pivoted as desired in space. This requires that the joint  19   f  between the arm  17   f  of the link arm arrangement  16   f  and the link arm  18   f  is arranged with only one degree of freedom, namely pivotability about one single axis. This axis should be substantially parallel to the pivoting axis of the member  15   f,  but inclined, suitably with substantially right angle, to the rotation axis of the member  14   f.  The four-links system FS 1  may with the aid of the force-exerting member  13   f  also be pivoted vertically in order to change the vertical position of the pivot arm  21   f.    
     In an embodiment illustrated in FIG. 9, a four-links system FS 1  is vertically pivotable by means of the force-exerting member  13   g  and a pivot arm  21   g  is horizontally pivotable in relation to the connection arrangement  12   g  with the aid of the force-exerting member  15   g.  A transmission  49  for rotation of the working member  3   g  arranged on the link  9   g  and driven by a drive motor  48  comprises force transmitting members in the form of shafts  51  and/or traction transmitting elements  52  placed around diverting wheels  53 , 54  extending along the four-links system FS 1  (the link  5   g  thereof) and the pivot arm  21   g  and angular gear members  55  provided between these shafts/diverting wheels for force transmission without effecting the relative movement between the pivot arm  21   g  and FS 1 . A shaft  51  is in the example extending along the link  5   g,  said shaft having a gear wheel driven by the motor  48  at one end thereof. The device is suitably arranged so that a gear wheel of the motor  48  and the shaft  51  respectively form a first angular gear. A gear wheel  56  at the other end of the shaft  51  is arranged in driving connection to a gear wheel  57 , in the example via third gear wheel  58  forming an angular gear with each of the other gear wheels  56 ,  57 . A shaft rigidly fixed to the gear wheel  57  is rotationally rigid connected to the break wheel denoted  53  so that by rotation thereof the traction transmitting element  52  will cause the diverting wheel  54  to rotate and thereby the working member  3   g  to turn. The working member may thereby be adjusted as desired. It is to be noted that naturally the diverting wheels  53 ,  54  and the traction-transmitting element  52  could be replaced by a gear arrangement with required shafts. The shaft  51  could similarly besides associated gear wheels be replaced by diverting wheels with traction transmitting elements. 
     The force-exerting member  14   g  is in the example arranged to turn the FS 1  around via the link  9   g.  The motor  48  arranged on the link  9   g  will thereby follow. The member  15   g  is suitably arranged substantially coaxially with the member  14   g.    
     It is to be noted that the solution illustrated in FIG. 9 naturally is applicable on the embodiments according to all the described alternatives according to FIGS. 1-8. 
     It is in FIG. 10 illustrated a further embodiment suitable to obtain turning of the working member  3   h  on the basis of the first element  1   h  so that its adequate turning position may be adjusted. Such an adjustment of turning position may also be required for different manipulative tasks which the working member is to carry out, which should be apparent from the discussion above, but the adjustment is usually also desirable by that the pivotable embodiment of the robot means that the working member  3   h  will change turning positions in space by such a pivoting movement. 
     It is in FIG. 10 illustrated how a force-exerting member  59  has a stationary portion fixed by the first element  1   h  and a movable portion connected to an arm  60 . An arm pivotable in relation to the same is denoted  61 . An arm or a link pivotable in relation to the same is denoted  62 . By suitable driving of the force-exerting member  59 , the working member  3   h  may thus be displaced via the arms  60 ,  61 . 
     A drive motor  114  is located on the first element  1   h  in order to generate energy for turning the working member  3   h.  The drive motor  114  has a stationary portion connected to the element  1   h  and a movable portion, here in the form of a drive shaft, arranged to cause the drive wheel  115  to rotate. A further wheel  116  is rotatably mounted on the outer end of the arm  60  and a traction-transmitting element  117  is placed around these two wheels  115 ,  116  in the form of a loop. The wheel  116  is connected to a shaft  118  and a conical gear wheel  119  is fixed thereon. The shaft  118  is rotatable in relation to the outer end of the arm  60 . A support element  120  is also mounted round the shaft  118 , which is movable around the shaft  118  with one degree of freedom, i.e. pure turning. This support member  120  is with one degree of freedom pivotably connected to a shaft  121 , which is also rotatable in relation to the arm  61 . A conical gear wheel  122  and a wheel  123  are rotationally rigid connected to the shaft  121 , wherein a traction transmitting element  124  in the form of a loop is placed round the wheel  123 , said element  124  also being placed round a further wheel  125  being rotationally rigid connected to a shaft  126  mounted in the arm  61  at an outer end thereof. 
     The gear wheels  119  and  122  form together an angular gear in that the shafts  118  and  121  extend substantially perpendicularly in relation to each other. The shaft  126  carries a rotationally rigid connected conical gear wheel  127 , which is in engagement with a conical gear wheel  128  forming a further angular gear, said conical gear wheel  128  being rotationally rigid connected to the working member  3   h.  The gear wheel  128  is rotationally rigid arranged on a shaft  129 . The shaft extends perpendicularly in relation to the shaft  126 . A further support element  130  is mounted to the two shafts  126  and  129  with a single degree of freedom, i.e. pure turning. 
     The embodiment according to FIG. 10 operates in the following way: the arm  60  may be turned by actuating the force-exerting member  59  and the arm  61  may thereby be caused to turn. The described connections/force transmissions via the angular gears and the support elements  120  and  130  pivotably connected to the gear wheel shafts implies that the transition between the arm  60  and the arm  61  on one hand and between the arm  61  and the arm  62  on the other hand, there is obtained movability in two degrees of freedom, namely turning in two in relation to each other perpendicular axes. This implies that the arm  60  rotatable in a plane may be caused to operate the arm  62  also when the latter is disposed away from the rotation plane for the arm  60 , which is indicated in FIG.  10 . The drive wheel  115  will be caused to rotate by driving of the drive motor  114 . The drive wheel  115  drives the traction-transmitting element  117  in the form of a belt, line, wire or chain around so that also the wheel  116  is caused to rotate. The shaft  121  is caused to rotate via the angular gear  119 / 122  and this also leads to rotation of the wheel  123 , which will drive the wheel  125  via the element  124  so that the shaft  126  is caused to rotate. This will cause turning of the working member  3   h  via the angular gear  127 ,  128 . 
     It is to be noted that the embodiment according to FIG. 10 is applicable by all the embodiments according to FIGS. 1-9. The arm denoted  60  in FIG. 10 may for example thereby be formed by the arm denoted  17  in earlier figures while the arm denoted  61  in FIG. 10 could be formed by the link arm  18 . The arm denoted  62  could thereby be formed by the pivot arm  21  itself or possibly by the link denoted  44 . The force member  59  should then correspond to the member denoted  17 . 
     A fundamental solution for achieving double force transmission between two parts of the device pivotable round double, non-parallel shafts in relation to each other is illustrated in FIG.  11 . Force transmission could in comparison with the force transmission between the arm  60  and the arm  61  illustrated in FIG. 10 with guidance of the embodiment according to FIG. 11 take place twice. The explanation thereto is that double sets of traction-transmitting elements  131 ,  132  driven by separate drive motors and placed over a respective drive wheel  133 ,  134  are arranged in FIG.  11 . The shaft  135  at the wheel  134  is formed as a tube shaft while the shaft  136  of the other wheel  133  extends through the tube shaft  135 . The tube shaft  135  is provided with a first conical gear wheel  137  and the shaft  136  is provided with a second conical gear wheel  138  on its end extending through the tube shaft  135 . The gear wheel  137  connected to the tube shaft  135  is in engagement with a conical gear wheel  139  placed on a tube shaft  140  forming an angular gear. A wheel  141  is rigidly connected to the tube shaft  140  and a traction-transmitting element  142  is placed over the wheel  141  and driven by the same. 
     A further conical gear wheel  143  is in engagement with the gear wheel  138 , the gear wheel  143  being fixed to a shaft  144  extending through the tube shaft  140  and being connected to a wheel  145  driving a traction-transmitting element  146 , which runs further to a wheel (not shown) driven thereby, which is also the question for the element  142 . 
     The transmission shown in FIG. 11 thereby permits double force transmission and a joint with two degrees of freedom is simultaneously formed, i.e. a joint permitting turning around two angularly disposed shafts. The transmission may be utilised for providing the associated robot structure with two degrees of freedom. The components  131 ,  133 ,  136 ,  138 ,  143 ,  144 ,  145  and  146  may for example be utilised for turning the working member  3  around and the other components may be utilised for another degree of freedom of the robot, for example displacing a part carrying the working member  3 . 
     It is to be noted that the shafts  135 , 136  and  140 ,  144  respectively naturally not need to be driven by and drive respectively diverting wheels for traction-transmitting elements. Gear wheels may instead of the diverting wheels be arranged on said shafts  135 ,  136  and  140 ,  144 , which via corresponding gear wheels arranged on rotatable shafts could be capable of effecting the corresponding driving function and driven function respectively. 
     It is in FIG. 12 illustrated an alternative to the embodiment discussed by guidance of FIG.  10 . Shaft transmissions  146 ,  147  arranged along the arms  60   i  and  61   i  are utilised instead of traction transmitting elements and them driving wheels and wheels driven by them respectively for force transmission. This implies that further angular gear functions have to be arranged in the joint transitions in ways apparent from FIG.  12 . 
     The alternative illustrated in FIG. 13 is similar to the one in FIG. 8 except for that the pivot arm arrangement  11   j  is of a more complex nature in similarity to what is the case for example in the embodiment according to FIG.  6 . The pivot arm arrangement  11   j  in FIG. 13 forms more closely an articulated four-links system where the pivot arm  21   j  forms one of the links. The connection arrangement  12   j  is in this case connected to the pivot arm arrangement  11   j  by means of a joint arrangement  47   j  formed by two in relation to each other angularly disposed pivot axes  47   ja  and  47   jb.  The pivot axis  47   jb  thereby connects a link  45   j  comprised in the four-links system  11   j  so that said link may be turned in relation to the connection arrangement  12   j  with only one degree of freedom. The pivot axis  47   ja  connects the pivot arm  21   j  to the link  45   j,  also here with only one degree of freedom. The remaining links in the four-links system are denoted  43   j  and  44   j  respectively. 
     The working member  3   j  is in the example connected to the link  44   j  in the four links system  11   j.  It suitably forms a parallelo-gram. 
     The pivot axis  47   jb  is in the example substantially parallel to the pivot plane for FS 1 . This is however not required. The axes  47   ja  and  47   jb  are suitably perpendicular in relation to each other. 
     Thus, the four-links system  11   j  is pivotable around the axis  47   jb  in relation to the connection arrangement  12   j  by means of the force member  14   j  in a way similar to what has been discussed regarding FIG.  8  and the pivot arm  21   f  illustrated there. The pivot arm  21   j  is by means of the force member  15   j  pivotable in relation to the link  45   j  around the axis  47   ja.  The force transmission in FIG. 13 between the force member  14   j  and the pivot arm  21   j  is arranged in on principle the same way as what has been described regarding FIG.  8 . 
     In common for all the described embodiments is that a suitable control unit, especially in the form of a computer, is arranged to control the force-exerting members of the different robot embodiments in order to cause the second element  2  or thereto directly or indirectly connected members  3  in desired movement paths. 
     POSSIBLE MODIFICATIONS 
     It is evident that the invention is not only restricted to the embodiments discussed hereinabove. Thus, detailed adaptations of the embodiments may be carried out depending on the circumstances without leaving the inventive concept appearing from claim  1 . 
     It is further noted that the idea illustrated in FIG. 3, to cause the four-links system FS 1  to pivot by means of an angular gear function between one of the links in the four-links system and the associated force-exerting member  13   a  of course is applicable on the embodiments according to FIGS. 1,  2  and  4 . The primary advantage with such an arrangement is that the force-exerting member  13  no longer needs to follow when the four-links system is turned around by means of the force-exerting member  14 . Thus, the mass needed to be caused to move and thereto related inertias will be reduced.