Abstract:
In order to produce a gripping device for a robot or for a gantry loader that can be employed in a flexible manner, it is proposed that the gripping device should comprise at least one linearly displaceable gripping jaw and at least one pivotal gripping connection. The gripping jaw may be linearly displaced along a longitudinal axis of the gripping device by means of a linear drive to grip and release a workpiece. The pivotal gripping connection can be pivotably rotated along a pivotal axis to likewise grip and release a workpiece. In an embodiment, the pivotable gripping connection can be arranged in a plurality of different positions with respect to the housing of the gripping device so that a plurality of different gripping orientations can be achieved.

Description:
RELATED APPLICATION 
   This application is a continuation application of PCT/EP2006/011036 filed Nov. 17, 2006, the entire specification of which is incorporated herein by reference. 

   FIELD OF DISCLOSURE 
   The present invention relates to a gripping device for a robot or a gantry loader. 
   BACKGROUND 
   The known gripping devices for robots are specially designed and manufactured for each application and for this reason re-jigging or setting up for a workpiece of completely new geometry involves very high expenditure which leads to high procurement costs and long delivery times for such gripping devices. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is to create a gripping device for a robot or for a gantry loader which is employable in a flexible manner. 
   In accordance with the invention, this object is achieved by a gripping device for a robot or a gantry loader which comprises at least one linearly displaceable gripping jaw and at least one pivotal gripping connection. 
   Due to the linearly displaceable gripping jaw, the gripping device is able to grip a workpiece by means of a gripping element that is arranged on the gripping jaw and is therefore linearly displaceable. 
   Due to the pivotal gripping connection, the gripping device is able to grip a workpiece by means of a gripping element arranged on the gripping connection in the course of a pivotal movement directly, or, by means of a mechanical reorientation. 
   Since both types of movement are already integrated into the gripping device and it is merely the gripping elements which come into contact with the work piece that have to be moved over from the gripping jaw to the gripping connection or moved in the reverse direction in order to reset the workpiece gripping movement from a linear movement into a pivotal movement or else from a pivotal movement into a linear movement, the gripping device in accordance with the invention is easily modifiable and employable in a particularly flexible manner. 
   The gripping device in accordance with the invention preferably comprises a linear drive for the at least one linearly displaceable gripping jaw. 
   Such a linear drive can comprise, in particular, at least one linearly displaceable actuating rod which engages the linearly displaceable gripping jaw. 
   Furthermore, the linear drive can comprise at least one drive piston which is displaceable in a drive cylinder by the effect of a hydraulic or pneumatic pressure. 
   In order to obtain a particularly precise straight-line motion for the linear movement of the gripping jaw, provision may be made for the linear drive to comprise at least one guide rod for controlling the linear movement of the linearly displaceable gripping jaw. 
   If the gripping device has at least two linearly displaceable gripping jaws, then it preferably also comprises a synchronisation member for synchronizing the linear movement of the linearly displaceable gripping jaws. In this way, both linearly displaceable gripping jaws are displaced in exact synchronism from the open position into the closed position or in the reverse direction. 
   Furthermore, the gripping device preferably comprises a pivotal drive for the at least one pivotal gripping connection. 
   In principle, provision may be made for the pivotal drive to be a drive that is formed separately from the linear drive for the linear movement of the linearly displaceable gripping jaw and one that is operated independently of the linear drive. 
   However, a particularly simple construction for the gripping device in accordance with the invention is obtained if the pivotal drive comprises at least one movement converting device which converts the linear movement of the at least one linearly displaceable gripping jaw into a pivotal movement of the at least one pivotal gripping connection about a pivotal axis. Thus, in this embodiment of the invention, the pivotal drive does not work independently of the linear drive of the gripping device, but rather, it derives its pivotal movement from the linear movement of the linearly displaceable gripping jaw. Thus, the already existing linear drive can also be used for producing the pivotal movement of the gripping connection. 
   In a preferred embodiment of the invention, provision is made for the movement converting device to be connected to the linearly displaceable gripping jaw. 
   In particular, provision may be made for the movement converting device to be connected to the linearly displaceable gripping jaw in releasable manner. 
   In a particularly preferred embodiment of the invention, provision is made for the movement converting device to be capable of being selectively arranged in at least one first position and in at least one second position relative to the linearly displaceable gripping jaw, whereby, in the second position of the movement converting device, the direction of the pivotal axis about which the pivotal gripping connection is pivoted by means of the movement converting device is rotated with respect to the direction of the pivotal axis in the first position of the movement converting device. In this way, it is possible to use the gripping connection in two different positions relative to the linearly displaceable gripping jaw; for example, the pivotal gripping connection can be arranged in a first position on a front wall of the gripping device and in a second position on a bottom wall of the gripping device. 
   Preferably, provision is made for the direction of the pivotal axis in the second position of the movement converting device to be rotated through an angle of approximately 90° with respect to the direction of the pivotal axis in the first position of the movement converting device. 
   In regard to the construction of the movement converting device, more detailed information has not as yet been given. 
   Thus, for example, provision can be made for the movement converting device to comprise a connection rod. 
   Furthermore, the movement converting device can comprise an eccentric cam. 
   Advantageously furthermore, provision is made for the movement converting device to comprise an articulated bearing for the pivotal gripping connection. 
   In a preferred embodiment of the gripping device in accordance with the invention, provision is made for the pivotal gripping connection to be capable of being arranged in at least one first position and in at least one second position relative to a housing of the gripping device. As already explained, the pivotal gripping connection can, for example, be arranged in a first position on a front wall of the housing and in a second position on a bottom wall of the housing. 
   In order to enable this flexible arrangement of the pivotal gripping connection on the housing of the gripping device, it is of advantage if the housing of the gripping device has a first through opening for the passage of the pivotal gripping connection in the first position and a second through opening for the passage of the pivotal gripping connection in the second position. 
   In this case furthermore, it is expedient for the gripping device to comprise a cover for closing the first through opening or the second through opening when the pivotal gripping connection is arranged at the second through opening or at the first through opening respectively. In this way, it is ensured that no contamination or foreign body can enter the interior of the housing from the outside through a not used opening in the housing. 
   The gripping device in accordance with the invention enables the gripping principle to be completely altered by means of small constructional changes and simple conversion measures. 
   If, for example, in the delivery state of the gripping device, the workpieces were gripped and transported by a linear gripping movement, then the workpieces can be gripped and fixed by being pivoted in or out after a simple alteration of the gripping device. 
   The gripping device in accordance with the invention is suitable, in particular, for employment in robotic applications in an industrial cleaning plant. 
   Further features and advantages of the invention form the subject matter of the following description and the graphical illustration of an exemplary embodiment. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a schematic side view of a robot with a gripping device incorporating linearly displaceable gripping elements on which a workpiece is held; 
       FIG. 2  a schematic plan view from above of the robot with a workpiece depicted in  FIG. 1 ; 
       FIG. 3  a schematic front view of the gripping device of the robot depicted in  FIGS. 1 and 2 , wherein the linearly displaceable gripping jaws of the gripping device are in a closed position; 
       FIG. 4  a schematic front view of the gripping device corresponding to  FIG. 3 , wherein the linearly displaceable gripping jaws are in an open position; 
       FIG. 5  a schematic perspective illustration of the gripping device with the linearly displaceable gripping elements removed; 
       FIG. 6  a schematic perspective illustration of the gripping device depicted in  FIG. 5 , wherein a right-hand side part of the gripping device and a right-hand gripping jaw of the gripping device are partly broken away in order to render visible the elements of the gripping device that are arranged inside the side part and the gripping jaw; 
       FIG. 7  a schematic perspective illustration of the gripping device in a second operational state wherein two pivotal gripping connections are arranged at the front end of the gripping device; 
       FIG. 8  a schematic perspective illustration of the gripping device depicted in  FIG. 7 , wherein the right-hand side part and the right-hand gripping jaw of the gripping device are partly broken away in order to render visible the elements of the gripping device that are arranged inside the side part and the gripping jaw; 
       FIG. 9  a schematic side view of the gripping device depicted in  FIGS. 7 and 8 , in the line of sight denoted by the direction of the arrow  9  in  FIG. 7 ; 
       FIG. 10  a schematic horizontal longitudinal sectional view through the gripping device depicted in  FIG. 9 , along the line  10 - 10  in  FIG. 9 ; 
       FIG. 11  a schematic front view of the gripping device depicted in  FIGS. 7 to 10 ; 
       FIG. 12  a schematic vertical cross sectional view through the gripping device depicted in  FIG. 11 , along the line  12 - 12  in  FIG. 11 ; 
       FIG. 13  a schematic horizontal longitudinal sectional view through the gripping device depicted in  FIG. 11 , along the line  13 - 13  in  FIG. 11 ; 
       FIG. 14  a schematic vertical longitudinal sectional view through the gripping device depicted in  FIG. 9 , along the line  14 - 14  in  FIG. 9 ; 
       FIG. 15  a schematic vertical cross section through the gripping device depicted in  FIG. 11 , along the line  15 - 15  in  FIG. 11 ; 
       FIG. 16  a schematic perspective illustration of the gripping device in a third operational state in which two pivotal gripping connections are arranged on a lower surface of the gripping device; and 
       FIG. 17  a schematic perspective illustration of the gripping device depicted in  FIG. 16 , wherein the right-hand side part and the right-hand linearly displaceable gripping jaw of the gripping device are partly broken away in order to render visible the elements of the gripping device that are arranged inside the side part and the gripping jaw. 
   

   Similar or functionally equivalent elements are designated by the same reference symbols in each of the Figures. 
   DETAILED DESCRIPTION OF THE INVENTION 
   A robot bearing the general reference  100  and illustrated in  FIGS. 1 and 2  comprises a plinth  102  with the aid of which the robot  100  is fixed to a foundation  104 , and a base member  106  which is rotatable relative to the plinth  102  about a vertical rotational axis  108  by means of a rotary drive. 
   A first pivotal member  110  of the robot  100  is held on the base member  106  such as to be pivotal about a horizontal first pivotal axis  112  by means of a pivotal drive. 
   At the end of the first pivotal member  110  remote from the base member  106 , a second pivotal member  114  is held on the first pivotal member  110  such as to be pivotal about a horizontal second pivotal axis  116  by means of a further pivotal drive. 
   A rotary member  118  is held on the second pivotal member  114  such as to be rotatable about its longitudinal axis serving as a second rotational axis  120  by means of a rotary drive. 
   A third pivotal member  122  is held on the end of the rotary member  118  remote from the second pivotal member  114  such as to be pivotal about a third pivotal axis  124  running perpendicularly to the second rotational axis  120 . 
   A gripping device  126  bearing the general reference  126  and illustrated in  FIGS. 3 to 17  is flange mounted on the free end of the third pivotal member  122  by means of a connection flange  128 . 
   As can best be seen from  FIG. 5 , the gripping device  126  comprises a substantially block-like centre section  130  which is arranged between a substantially block-like left-hand side part  132   a  and a substantially block-like right-hand side part  132   b.    
   A respective end plate  134   a  and  134   b  adjoins each of the two side parts  132   a ,  132   b  and each has a respective hollow cylindrical seating  136   a  and  136   b  for a respective substantially cylindrical left-hand gripping jaw  138   a  and a right-hand gripping jaw  138   b.    
   Each of the gripping jaws  138   a ,  138   b  is linearly displaceable relative to the respectively associated seating  136   a ,  136   b  in parallel with the longitudinal axis  140  of the gripping device  126 , namely, by means of a linear drive  142  which will be described in more detail hereinafter. 
   As can best be seen from  FIG. 10 , the linear drive  142  comprises a respective drive piston  144   a ,  144   b  for each of the linearly displaceable gripping jaws  138   a ,  138   b , wherein each drive piston comprises a connecting rod  146  and a radially projecting collar  148  which surrounds the connecting rod  146  in ring-like manner and is arranged approximately in the centre of the connecting rod  146 , and which is guided in displaceable manner in the longitudinal direction of the connecting rod  146  in a cylinder  150  provided in the centre section  130  of the gripping device  126 . 
   Each cylinder  150  is provided at its left-hand end and its right-hand end with a respective seal packing  152  which seals the interior of the cylinder  150  in fluid-tight manner. 
   The interior of each cylinder  150  is sub-divided into a left-hand sub-space  154   a  and a right-hand sub-space  154   b  by the collar  148  of the respective drive piston  144   a  and  144   b , whereby pressurised air can be supplied to the left-hand sub-space  154   a  by way of an air control channel  156   a  and pressurised air can be supplied to the right-hand sub-space  154   b  by way of an air control channel  156   b.    
   Both air control channels  156   a ,  156   b  are connected to a respective (not illustrated) pneumatic line. 
   One end of the connecting rod  146  extends through a through opening  158  in the respective gripping jaw  138   a  and  138   b  driven by the relevant drive piston  144   a  and  144   b  and is bolted thereto by means of a nut  160 . 
   The opposite end of the connecting rod  146  is guided in a blind bore  163  which is provided in the respectively opposite gripping jaw  138   b  or  138   a  such as to be displaceable in the longitudinal direction thereof relative to this gripping jaw  138   b  or  138   a.    
   Furthermore, the connecting rod  146  extends through cylindrical channels  162  in the two side parts  132   a ,  132   b  of the gripping device  126  and through circular through openings  164  in the end plates  134   a ,  134   b.    
   The connecting rod  146  is sealed against the end plates  134   a ,  134   b  and against the seal packings  152  by means of sealing rings  166 , and is guided in the channels  162  by means of slide sleeves  167 . 
   Due to the fact that the two sub-spaces  154   a ,  154   b  of the cylinder  150  are alternately subjected to compressed air, each drive piston  144   a ,  144   b  is displaced in the longitudinal direction thereof relative to the respectively associated seating  136   a  and  136   b  due to the compressive forces effective on the respective collar  148 . 
   If, for example, the sub-space  154   a  illustrated to the left in  FIG. 10  is subjected to compressed air, then the drive piston  144   a  is moved into the closed position illustrated in  FIG. 10  in which the gripping jaw  138   a  is seated in the appertaining seating  136   a.    
   If the sub-space  154   b  illustrated to the right in  FIG. 10  is now subjected to compressed air, then the drive piston  144   a  is moved to the left, and the gripping jaw  138   a  moves from the closed position into the open position illustrated in  FIG. 4  in which the gripping jaw  138   a  is to the most part located outside the seating  136   a.    
   Thereby, the drive pistons  144   a ,  144   b  are subjected to compressed air in opposite senses so that the drive pistons  144   a ,  144   b  always move in parallel with each other but in opposite directions and thus the gripping jaws  138   a ,  138   b  are moved mutually synchronously into the respective closed position and into the respective open position. 
   Furthermore, in order to achieve the effect that the gripping jaws  138   a ,  138   b  move as accurately as possible parallel to the longitudinal axis  140  of the gripping device  126 , each of the gripping jaws  138   a ,  138   b  is connected to a respective guide rod  168  which is bolted at one of the ends thereof to the respectively associated gripping jaw  138   a  and  138   b  by means of a nut  170 , said guide rod extending from this end thereof through an opening  172  in the associated gripping jaw  138   a ,  138   b , through substantially cylindrical channels  174  in the side parts  132   a ,  132   b , through a synchronisation chamber  176  in the centre section  130  and through openings  178  in the end plates  134   a ,  134   b , whilst the free end thereof remote from the nut  170  is guided in displaceable manner in the longitudinal direction thereof in a cylindrical blind boring  180  that is provided in the respective gripping jaw  138   a  and  138   b  which is not fixed to the associated guide rod  168  (see in particular  FIG. 10 ). 
   The two guide rods  168  that are fixed to the respective gripping jaws  138   a  and  138   b  are connected together by means of a synchronisation member  182  which is arranged in the synchronisation chamber  176  such as to be pivotal about a pivotal axis  183  running perpendicularly to the longitudinal directions of the guide rods  168  and which is connected at the two free ends thereof to one of the guide rods  168  in articulated manner so that the two guide rods  168  can only move through equal path lengths in mutually opposite and mutually parallel directions (see in particular  FIG. 12 ). 
   Due to the synchronisation member  182 , it is thus ensured that the mutually oppositely directed linear movements of the gripping jaws  138   a  and  138   b  always take place exactly synchronously. 
   The guide rods  168  are sealed against the end plates  134   a ,  134   b  by means of sealing rings  184  and are guided in the channels  174  by means of slide sleeves  185 . 
   The synchronisation chamber  176  is closed to the exterior of the gripping device  126  by means of a cover plate  186  which is fixed to the centre section  130  of the gripping device  126  in releasable manner by means of a suitable mounting means. 
   Furthermore, in order to hold together the housing  188  of the gripping device  126  that is composed of the centre section  130 , the side parts  132   a ,  132   b  and the end plates  134   a ,  134   b , there are provided a plurality of, three for example, connecting rods  190  which extend through the abovementioned components of the housing  188  and are provided at the free ends thereof with external threads onto which clamping nuts  192  are screwed in order to clamp together the end plates  134   a ,  134   b  and also the side parts  132   a ,  132   b  and the centre section  130  that are arranged between the end plates. 
   Furthermore, the housing  188  of the gripping device  126  is provided with a ventilation device  194  which is arranged on the upper surface of the left-hand side part  132   a.    
   In  FIGS. 1 to 4 , the gripping device  126  is illustrated in a first operational state in which a gripping element  196  is fixed to the outer face of each gripping jaw  138   a ,  138   b  in releasable manner, whereby the mutually oppositely located gripping elements  196  can be moved by the linear drive  142  for the gripping jaws  138   a ,  138   b  in the direction of the longitudinal axis  140  of the gripping device  126  either towards one another into a closed position or away from each other into an open position. 
   Provision may be made here for the gripping elements  196  to grip a workpiece that is to be gripped in the closed position and to release it in the open position; as an alternative thereto however, the gripping elements  196  could also be formed and arranged relative to the workpiece in such a way that the workpiece is gripped in the open position of the gripping elements  196  and released in the closed position of the gripping elements  196 . 
   In the closed position of the gripping elements  196  illustrated in  FIGS. 1 and 2 , the gripping elements  196  hold a workpiece  198  that is arranged therebetween and can be released by moving the gripping elements  196  into the open position. 
   From this first operational state, the gripping device  126  is transferable into the second operational state illustrated in  FIGS. 7 to 15  by a simple structural alteration, in which, in addition to the linearly displaceable gripping jaws  138   a ,  138   b , two pivotal gripping connections  200  are arranged at the front of the gripping device  126 . 
   These gripping connections  200  are pivotal in mutually opposite senses about their mutually parallel pivotal axes  202  and are respectively connectable to a (not illustrated) gripping element so that these gripping elements can be moved towards one another into a closed position or away from each other into an open position by the oppositely directed pivotal movements of the gripping connections  200 . 
   A separate pivotal drive for producing the pivotal movement of the gripping connections  200  is not necessary; rathermore, the pivotal movement of the gripping connections  200  is derived from the linear movement of the gripping jaws  138   a ,  138   b  by means of a movement converting device  204  (see in particular  FIG. 8 ). 
   Each of the movement converting devices  204  comprises a respective substantially hollow cylindrical articulated bearing  206  for the respectively associated substantially cylindrical gripping connection  200 , an eccentric cam  208  connected in mutually non-rotatable manner to an end of the gripping connection  200 , a connection rod  210  which is pivotal about a first pivotal axis  212  and is connected to the eccentric cam  208  at a position displaced radially outwardly with respect to the pivotal axis  202  of the gripping connection  200  and the eccentric cam  208  and which extends away from the eccentric cam  208  in a direction running perpendicularly to the pivotal axis  202 , and a substantially cylindrical connecting part  214  upon which the end of the connection rod  210  remote from the eccentric cam  208  is held such as to be pivotal about a second pivotal axis  216  running parallel to the first pivotal axis  212  and which comprises a radially outwardly projecting connection flange  218  that is provided with a plurality of, for example with four, through openings for mounting means  220 . 
   The respectively associated gripping jaw  138   a  and  138   b  each comprises a central substantially cylindrical recess  222  which accommodates the connection flange  218  in the installed state of the movement converting device  204 , said flange being fixed to the associated gripping jaw  138   a ,  138   b  in releasable manner by means of the mounting means  220 . 
   From the recess  222 , the connecting part  214  extends through a through opening in the associated gripping jaw  138   a ,  138   b  into the interior of the respectively neighbouring side part  132   a  and  132   b.    
   In the installed state thereof, the articulated bearing  206  of the respective movement converting device  204  extends through a through an opening in the front wall of the respectively associated side part  132   a  and  132   b  and rests externally on the front of the associated side part  132   a  and  132   b  by means of a connection flange  224  projecting from the articulated bearing  206  in the radial direction. 
   This connection flange  224  has a plurality of, four for example, through openings through which the mounting means  226  extend and by means of which the connection flange  224  is fixed to the associated side part  132   a  and  132   b  in releasable manner. 
   For the purposes of disassembling the movement converting device  204 , the eccentric cam  208  can be released from the gripping connection  200  in the interior of the respectively associated side part  132   a ,  132   b.    
   Subsequently, the eccentric cam  208 , the connection rod  210  and the connecting part  214  can be extracted through the through opening in the respectively associated gripping jaw  138   a ,  138   b  after the attachment of the connection flange  218  to the respective gripping jaw  138   a  and  138   b  has been released. 
   Furthermore, the articulated bearing  206  and the gripping connection  200  that is pivotally mounted therein can be extracted through the through opening in the front wall of the respectively associated side part  132   a ,  132   b  after the attachment of the connection flange  224  to the front wall of the respective side part  132   a  and  132   b  has been released. 
   Assembly of the movement converting device  204  is effected by reversing the steps mentioned above for the disassembly process. 
   In order to enable the requisite assembly or disassembly work to be carried out in the interior of the respectively associated side part  132   a ,  132   b , the side parts  132   a ,  132   b  are each provided with access openings  228  which are adapted to be closed by means of a respective cover plate  230  (see  FIG. 5 ). 
   In the first operational state in which the movement converting devices  204  are not installed, the through openings in the gripping jaws  138   a ,  138   b  as well as in the front walls of the side parts  132   a ,  132   b  are closed by respective covers  232  and  234  which are respectively fixed to the gripping jaws  138   a ,  138   b  and to the side parts  132   a ,  132   b  in releasable manner by means of mounting means (see  FIGS. 5 and 6 ). 
   In the second operational state of the gripping device  126 , a pivotal movement of the gripping connections  200  is effected by a linear movement of the gripping jaws  138   a ,  138   b  by means of the movement converting devices  204  since, for example, in the course of a movement of the gripping jaws  138   a ,  138   b  along the longitudinal axis  140  into the open position, the connection-side linkage point of the connection rod  210  is moved outwardly along the longitudinal axis  140 , this thereby resulting in a pivotal movement about its pivotal axis  202  of the eccentric cam  208  which is articulated to the respective other end of the connection rod  210 . In consequence, the gripping connection  200  that is connected to the eccentric cam  208  in mutually non-rotatable manner is also pivoted about the pivotal axis  202 . 
   As can be seen from  FIG. 8 , when the gripping jaws  138   a ,  138   b  move outwardly into the open position due to the effect of the linear drive  142 , the right-hand gripping connection  200   b  (as seen from the front of the gripping device  126 ) is then pivoted in the clockwise direction and the left-hand gripping connection  200  in the counter clockwise direction. 
   The (not illustrated) gripping elements, which are connected to the gripping connections  200 , likewise implement a pivotal movement due to the pivotal movement of the gripping connections  200 , whereby this pivotal movement can lead up to a closed position or an open position of the gripping elements in dependence on the design of the gripping elements and depending upon their arrangement on the gripping connections  200 . 
   Thus, the movement of the gripping jaws  138   a ,  138   b  into the open position can correspond to a movement of the gripping elements on the gripping connections  200  into an open position or into a closed position. 
   Conversely, a movement of the gripping jaws  138   a ,  138   b  into the closed position can correspond to a movement of the gripping elements arranged on the gripping connections  200  into a closed position or into an open position. 
   The third operational state of the gripping device  126  illustrated in  FIGS. 16 and 17  differs from the second operational state illustrated in  FIGS. 7 to 15  only in that the gripping connections  200  are not arranged on the front face of the gripping device  126 , but instead, on the lower surface thereof, i.e. at a position rotated through 90° relative to the second operational state. 
   In order to be able to use this third operational state of the gripping device  126 , the bottom walls of the side parts  132   a ,  132   b  are likewise provided with through openings for the articulated bearings  206  of the movement converting devices  204  as is the case for their front walls. 
   In the first operational state and in the second operational state, these lower through openings are closed by covers  236  (see  FIG. 7 ) which are fixed to the bottom wall of the side parts  132   a ,  132   b  in releasable manner by means of mounting means. 
   In order to transfer the gripping device  126  from the second operational state into the third operational state, the movement converting devices  204  need only be rotated through an angle of 90° relative to the housing  188  of the gripping device  126 . 
   To this end, it is only necessary to release the connection between the eccentric cam  208  and the respectively associated gripping connection  200 , to extract the articulated bearing  206  with the gripping connection  200  through the opening in the front face of the respective side part  132   a  and  132   b , to close this opening by means of the cover  234 , to release the connection flange  218  of the connecting part  214  from the respective gripping jaw  138   a ,  138   b , to rotate it through an angle of 90° and fix it again to the associated gripping jaw  138   a  or  138   b  in releasable manner when in the rotated position, to release the cover  236  from the opening in the bottom wall of the respective side part  132   a  and  132   b , to feed the articulated bearing  206  with the gripping connection  200  through the thus freed opening and then to re-establish the connection of the eccentric cam  208  to the gripping connection  200  in this new position. 
   After carrying out this conversion work, a pivotal movement of the gripping connections  200  that are now arranged on the lower surface of the gripping device  126  can be derived in the same way by means of the movement converting devices  204  from the linear movement of the gripping jaws  138   a ,  138   b  as has already been described hereinabove in connection with the second operational state of the gripping device  126 .