Patent Publication Number: US-2016245380-A1

Title: Pull and / or push rod

Description:
This nonprovisional application claims priority under 35 U.S.C. §119(a) to German Patent Application No. 10 2015 102 724.0, which was filed in Germany on Feb. 25, 2015, and which is herein incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a pull and/or push rod. Such machine parts are often used in clamping and gripping technology to perform an axial motion, i.e. a motion oriented along a longitudinal axis, in order to switch the relevant clamping or gripping device between a clamping configuration and a release configuration. 
     2. Description of the Background Art 
     A known process is to trigger the axial movement of the components by means of threaded joints between threaded rods or threaded hollow bars. This process is described for a release unit, for example in DE 10 2011 116 818 A1, wherein the axial movement of the release rod is realized by a screw mechanism of two interlocking trapezoidal threads. These threaded connections have the disadvantage that the external threaded hollow bar often tilts because of the large prevailing play. The tilting is also caused because depending on the position of the threaded nut, the thread flanks are engaged with each other at different degrees, which means that possibly only minor thread engagement is present. Small thread engagement in cooperation with large prevailing play in the overall design can lead to an unwanted blocking of the system. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a pull and/or push rod which overcomes the disadvantages mentioned above. 
     This object is achieved in an exemplary embodiment by a pull and/or push rod which is adjustable along a rod longitudinal axis and which comprises a cam for guiding a control member. The cam comprises a coil section that is at least partially spiral and has one or more slope portions. 
     Thus, along the rod longitudinal axis of the pull and/or push rod, instead of a thread, a cam is formed which routinely includes a guide groove. The width of the guide groove or of the coil section of the cam is configured much wider than the threads of a trapezoidal thread, whereby when using a cam, a tilting of the elements engaging into the cam is virtually impossible. Further, a cam has the particular feature that it does not have to be shaped like a screw with threads having a constant pitch, but instead may also comprise slope portions having different gradients. 
     The cam can comprises at least one idle stroke section which is adjacent to the coil section and substantially radially extends to the rod longitudinal axis. Within the idle stroke section, a control member slides such in the cam of the pull and/or push rod that these experience no axial displacement. 
     This has the advantage that the pull and/or push rod can be fixed in its axial position when a control member is within the idle stroke section. 
     To manufacture the pull and/or push rod in a particularly simple manner, it has proven to be preferable when the cam is formed on an outer periphery of the pull and/or push rod. Preferably, the pull and/or push rod is additionally coated with a friction-reducing coating. In order to create a low-abrasion overall system, a DLC 4000 coating (DLC=Diamond-Like-Carbon; hard coating based on carbon) for the pull and/or push rod is conceivable. Further, the pull and/or push rod can be hardened, wherein the sliding surfaces of the cam are subsequently ground. 
     An embodiment provides that the pull and/or push rod is at least partially formed as a hollow rod and that the cam is formed in an inner periphery of the hollow rod. This has the advantage that the outside of the pull and/or push rod is available as a sliding surface within a housing, wherein the outer contour is also designed with a non-circular shape to provide an anti-rotation safeguard for the pull and/or push rod. The outer surface may hereby also be grafted or coated with materials having special sliding properties. 
     In order to rotationally drive the pull and/or push rod in a simple manner, it has proven to be useful when an extension of a non-circular cross-section or an inner receptacle of a non-circular cross-section is provided. 
     Further, a rotatable cap and/or a thrust bearing arranged on the pull and/or push rod on the side facing away from the extension or the inner receptacle is useful for decoupling rotational movements. 
     One potential application for the pull and/or push rod is in an electrical release unit. 
     The electrical release unit provides a pull and/or push rod according to the invention, and an electric motor which is at least indirectly rotationally coupled with the pull and/or push rod. Furthermore, the electrical release unit has a control member at least axially fixed in a housing, which engages in the cam of the pull and/or push rod for the axial adjustment of the pull and/or push rod between a clamping position and a release position. This electrical releasing unit, too, has the advantage that a tool clamping system-actuating release bar, which is thereby switched between a clamping position and a release position, is not formed with a threaded joint, but with an axially formed cam and with a control member engaging in the cam. 
     To ensure safe shifting between the two positions, it has proven to be particularly useful if the control member is formed as a control pin or as a cam. The prevailing rotational symmetry of the control member thereby allows for a simple sliding of the control member within the cam or within the guide groove. 
     In order to exercise a high torque to the pull and/or push rod, it has proven advantageous if the output of the electric motor is associated with an eccentric gear, which is at least indirectly rotationally coupled with the pull and/or push rod. In this context, a rear drive-free harmonic drive has been found particularly advantageous, which can provide a relatively large gear reduction in order to achieve high torque. A reduction between 1:60 and 1:40 has proven to be preferred, more preferably a reduction of 1:50. 
     In addition, it has proven to be useful if a driving flange is connected with a drive spindle of the electric motor, which comprises an axially extending drive collar. This drive collar can be coupled with other rotationally driven components. 
     For a simple transmission of the rotational movement, it has proven to be advantageous when the drive collar is associated with a driving flange having a non-circular cross-section for rotationally driving the pull and/or push rod. 
     In order to be able to monitor the axial position of the pull and/or push rod, it has proven to be preferable if the drive collar is non-rotatably coupled to a sensor sleeve having a sensor target which is eccentrically arranged relative to the rod longitudinal axis or formed with a circumferential pitch. It is advantageous in this case, if the sensor target is associated with a distance sensor, wherein the distance of the distance sensor to the sensor target is formed proportional to the axial position of the pull and/or push rod within the housing. 
     In order to be able to adjust the pull and/or push rod axially in a simple manner and in order to lose the least possible force during adjustment, it has proven advantageous if a slide bearing and/or a slide bush is arranged in the housing coaxially to the rod longitudinal axis. 
     A further advantageous application of the pull and/or push rod according to the invention is its use in an electrical separating device. This device is characterized in that it is formed with a pull and/or push rod which is guided non-rotationally but axially displaceable in a housing, and associated with a separating finger. Further, an electric motor is provided which is at least indirectly non-rotatably coupled to an actuating element, as well as a control member arranged on the actuating element, which engages in the cam for the axial adjustment of the pull and/or push rod between a separating position and an open position. Also in separating devices, no tilting of threaded joints occurs which could lead to a blockage or to damage to the separating device. 
     The separating position is the configuration of the separating device in which a single component (e.g. a magazined workpiece) is separated from further components (further magazined workpieces). The open position is the configuration of the separating device in which the components may pass through the separating device unseparated (non-isolated) from one another. This position is also often referred to as neutral because the workpieces can escape unhindered from the magazine. 
     In order to avoid damage to the separating device, it has proven to be preferable if in the pull and/or push rod a resilient element or a spring or a spring package is arranged for damping axial forces acting on the separating finger. 
     A further application of the inventive pull and/or push rod relates to its use in an electrical gripping device. This is characterized in that it has gripper base jaws which are guided in gripper grooves radially designed to the gripper longitudinal axis, and are adjustable. Via splines which extend in a sloped manner to the gripper longitudinal axis, the gripper base jaws interact with an axially adjustable wedge hook or wedge cone which according to the present invention is connected to a pull and/or push rod. Furthermore, an electric motor is at least indirectly non-rotatably coupled with an actuating element at which a control member is arranged, which engages in the cam for the axial adjustment of the pull and/or push rod between an open position, a clamping position and a closed position. The clamping position is located between the open position and the closed position and its position depends on the respective application of the gripping device. 
     To prevent damage to the gripper base jaws or the electric gripper device, it has proven advantageous if on the pull and/or push rod, a resilient element or a spring or a spring package is arranged for damping forces that radially act on the gripper base jaws. 
     It has been found preferable when top jaws for the releasable attachment to the gripper base jaws are provided, which are designed with radially inward gripper surfaces for external gripping of workpieces and/or with radially outward gripper surfaces for an internal gripping of workpieces. The top jaws can thereby have a shape that is adapted to the gripping workpiece so that this can be safely and securely gripped externally or internally. 
     Another application of the inventive pull and/or push rod relates to its use in an electric parallel gripper. 
     The electrical parallel gripper is hereby to be equipped with at least two gripper arms of which at least one can be actuated with a pull and/or push rod according to the present invention. Further provided is an electric motor which is at least indirectly non-rotatably coupled with an actuating element. At the possibly multi-part actuating element, a number of control members are arranged that, if necessary, may correspond to the number of pull and/or push rods which engage in the cam for axial displacement between a closed position and an open position. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein: 
         FIGS. 1 a  to 1 e    illustrate an embodiment of the inventive pull and/or push rod, 
         FIGS. 2 a  and 2 b    illustrate an axial positioning system with a pull and/or push rod according to  FIGS. 1 a    to  1   e,    
         FIGS. 3 a  to 3 e    illustrate an embodiment of the inventive pull and/or push rod, 
         FIGS. 4 a  and 4 b    illustrate an axial positioning system with a pull and/or push rod in accordance to  FIGS. 3 a  to 3 e    with a control member formed as a control pin, 
         FIGS. 5 a  and 5 b    illustrate the system of  FIGS. 4 a  and 4 b    with a control member formed as a control ball, 
         FIGS. 6 a  to 6 e    illustrates an embodiment according to the inventive pull and/or push rod, 
         FIGS. 7 a  to 7 e    illustrates an embodiment of the inventive pull and/or push rod, 
         FIGS. 8 a  to 8 e    illustrates an embodiment of the pull and/or push rod having a cam formed as a spiral groove, 
         FIGS. 9 a  and 9 b    illustrate an axial positioning system with a pull and/or push rod according to  FIGS. 8 a    to  8   e,    
         FIG. 10  illustrates a longitudinal cross-section through an electrical release unit, 
         FIG. 11  illustrates the release unit of  FIG. 10  in a partially sectioned, perspective view in the clamping position, 
         FIG. 12  illustrates the electrical release unit of  FIGS. 10 and 11  in the release position, 
         FIG. 13  illustrates a separating device shown in the open position in a perspective view, partly sectioned, 
         FIG. 14  illustrates a longitudinal section of the separating device in  FIG. 13 , 
         FIG. 15  illustrates the separating device of  FIG. 13  in the separating position, 
         FIG. 16  illustrates a longitudinal cross-section through the separating device of  FIG. 15 , 
         FIG. 17  illustrates a gripping device, partly shown for internal gripping in the open position in a perspective view section, 
         FIG. 18  illustrates a longitudinal cross-section through the gripping device of  FIG. 17 , 
         FIG. 19  illustrates the gripping device of  FIG. 17  in the closed position (the clamping position is between the open and the closed position) in a partly sectioned, perspective view, 
         FIG. 20  illustrates a longitudinal cross-section through the gripping device of  FIG. 19 , 
         FIG. 21  illustrates a longitudinal cross-section through a parallel gripper in the closed position, 
         FIG. 22  illustrates the parallel gripper of  FIG. 21  in a partly sectioned, perspective view, 
         FIG. 23  illustrates a longitudinal section through the parallel gripper of  FIG. 21  in the open position, 
         FIG. 24  illustrates the parallel gripper of  FIG. 23  in a partly sectioned, perspective view, 
         FIG. 25  illustrates a perspective view of a sensor system for controlling the axial position of a Pull and/or push rod, 
         FIG. 26  illustrate a plan view of the sensor system of  FIG. 25 , and 
         FIG. 27  illustrate a front view of the sensor system according to  FIG. 25 . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 a  to 1 e    show a pull and/or push rod  1  which is adjustable along the longitudinal axis of a rod. This has a cam  2  for guiding a control member  3  which comprises an at least partially spiral-shaped coil section  8  having at least one or several slope portions  4 ,  5 ,  6 ,  7 . 
     The cam  2  further comprises at least one idle stroke section  9 ,  10  which adjoins the coil section  8 , substantially radially extending to the rod longitudinal axis and preferably arcuate in shape. In the embodiment, exactly two of the idle stroke sections  9 ,  10  are provided, of which a first idle stroke section  9  is disposed at a first end of the coil section  8 , and of which a second idle stroke section  10  is arranged at the second end of the coil section  8 , which lies opposite the first end. Preferably, the idle stroke sections  9 ,  10  of the pull and/or push rod  1  extend radially by up to 90 degrees, relative to the rod longitudinal axis. In other words, the idle stroke section  9 ,  10  thus extends such that it substantially always lies on a normal, relative to the rod longitudinal axis. 
       FIGS. 1 a  to 1 e    further show that the cam  2  is formed on an outer circumference  12  of the pull and/or push rod  1 . Further, the pull and/or push rod  1  has an extension  14  having a non-circular cross-section ( FIG. 1 d   ). This extension  14  extends axially and has a rectangular cross-section with rounded corners. Due to the non-circular shape of the extension  14 , a rotary motion can be transmitted to the pull and/or push rod  1 . 
       FIG. 1 e    shows the spiral characteristic  39  of the pull and/or push rod  1 . It provides a first slope portion  4  with a low pitch and a second slope portion  5  with a higher pitch, relative to the low pitch. The first slope portion  4  of the coil section  8  is inclined between 2 degrees and 6 degrees relative to the normal to the rod longitudinal axis, preferably it is arranged inclined by exactly 4 degrees relative to the normal of the rod longitudinal axis. The second slope portion  5  of the coil section  8  is inclined between 14 degrees and 22 degrees relative to the normal of the rod longitudinal axis, preferably it is arranged inclined by exactly 18 degrees to the normal of the rod longitudinal axis. 
     The first slope portion  4  having a low pitch thus leads to a low axial stroke of the pull and/or push rod  1 , wherein a high force can be achieved (release stroke). The second slope portion  5  with a high gradient causes an axial stroke of the pull and/or push rod  1  in a shorter time, but with a lower force (fast stroke). 
     The spiral characteristic  39  also shows that a first idle stroke section  9  connects to the first slope portion  4  of the coil section  8 . Furthermore, it is shown that a second idle stroke section  10  connects to the second slope portion  5  of the coil section  8 . If a control member  3  is located within the respective idle stroke sections  9 ,  10 , the axial movement of the pull and/or push rod  1  is blocked and the pull and/or push rod  1  is axially fixed in its position. 
       FIGS. 2 a  and 2 b    show an axial positioning system  40  with a pull and/or push rod  1  according to  FIGS. 1 a    to  1   e.  Here, a control member  3  formed as a control pin  19  engages in the cam  2  of the pull and/or push rod  1 . The cross section of the pull and/or push rod  1  is in this case formed rotationally symmetrical. The control pin  19  is axially fixed in the housing  18 . Furthermore, a driving flange  24  is shown which can be rotationally driven by an electric motor  17  and which is non-rotatably connected to the extension  14  of the pull and/or push rod  1 . This driving flange  24  thereby allows an axial relative movement of the pull and/or push rod  1 . This means that the connection between the driving flange  24  and the pull and/or push rod  1  is designed non-rotatable but axially displaceable. If the pull and/or push rod  1  is rotated by the driving flange  24 , the control pin  19  glides along the cam  2 , whereby the pull and/or push rod  1  is moved axially forward, i.e. out of the housing  18 , or axially rearward, i.e. into the housing  18 . 
       FIGS. 3 a  to 3 e    show a second pull and/or push rod  1  which in its basic structure corresponds to that of  FIGS. 1 a    to  1   e.  In contrast to the pull and/or push rod  1  according to  FIGS. 1 a    to  1   e,  however, it does not include an extension  14  having a non-circular cross-section, but instead has an inner receptacle  15  having a non-circular cross-section. Thus, the overall length of the pull and/or push rod  1  of this embodiment is designed very short, in particular compared to those of the embodiment shown in  FIGS. 1 a    to  1   e.  The outer contour, in particular the cam  2 , is consistent in both the coil section  8  as well as the idle stroke section  9 ,  10  to that of  FIGS. 1 a    to  1   e.  Similarly, the pull and/or push rod  1  has the same spiral characteristic  39  as that of  FIGS. 1 a    to  1   e.    
       FIGS. 3 a  to 3 c    show that the pull and/or push rod  1  has a closed configuration at the end facing away from the inner receptacle  15 . This has the advantage that no contamination can occur in those drive connections which cause a rotational and/or axial movement of the pull and/or push rod  1 .  FIG. 3 d    also shows that the cross section of the inner receptacle  15  is formed as a polygon, shown here as a square. 
       FIGS. 4 a  and 4 b    show an axial positioning system  40  having a pull and/or push rod  1 , comprising a cam  2 , and in which a control member  3  (guide member) formed as a control pin  19  (guide pin) engages. The control pin  19  is axially fixed in a housing  18 . 
     This control pin  19  can also be mounted rotatably around its longitudinal axis pin in the housing  18 , whereby the adjustment of the pull and/or push rod  1  takes place in a friction-reducing manner. Further, a driving flange  24  rotationally drivable by an electric motor  17  is provided which has an actuating extension  41  which in its cross-section corresponds to the cross-section of the inner receptacle  15  of the pull and/or push rod  1 . The advantage of this embodiment of an axial positioning system  40  is the short overall length, especially as compared to those of the axial positioning system  40  shown in  FIGS. 2 a    and  2   b.  The actuating extension  41  of the driving flange  24  is designed in such a way that it forms a non-rotatable but axially displaceable connection with the pull and/or push rod  1 . If the pull and/or push rod  1  is rotated by the driving flange  24  or by the actuating extension  41 , then the control pin  19  slides along the cam  2 , whereby the pull and/or push rod  1  is displaced axially forward, i.e. out of the housing  18 , or backward, i.e. into the housing  18 . 
       FIGS. 5 a  and 5 b    show a system corresponding to the one in  FIGS. 4 a    and  4   b,  whereas here, instead of a control pin  19 , a control member  3  formed as a control ball  20  (guide ball) is positioned in the cam  2  of the pull and/or push rod  1 . This control ball  20  is axially fixed in a receiving pocket  42  in the housing  18  and can slide along the cam  2 . Likewise, it is possible that the control ball  20  rotates in the receiving pocket  42  about its own axis, so that the friction of the entire system is reduced. 
       FIGS. 6 a  to 6 e    show a third pull and/or push rod  1 , which in its basic structure corresponds to the structure of the pull and/or push rod  1  according to  FIGS. 1 a    to  1   e.  Here, however, the spiral characteristic  39  has been changed such that several, in this case exactly two, coil sections  8  are provided, which are separated from each other by an idle stroke section  10 . The cam  2  formed at the outer periphery  12  of the pull and/or push rod  1  accordingly has a first idle stroke section  9 , followed by a first slope portion  4 . A second slope portion  5  formed as a fast stroke adjoins the first slope portion  4  formed as a release stroke. A second idle stroke section  10  connects to the coil section  8  formed from the first slope portion  4  and the second slope portion  5 . A third slope portion  6  of a further coil section  8 , also formed as a fast stroke, in turn connects to this second idle stroke section  10 . A fourth slope portion  7  formed as a release stroke (also power stroke) is disposed downstream of the third slope portion  6 . A third idle stroke section  11  connects at the fourth slope portion  7 . 
     The pull and/or push rod  1  (or tension and/or pressure bolt) shown in  FIGS. 6 a  to 6 e    is also formed with an extension  14  having a non-circular cross-section, which serves for the transmission of rotary movements. Like the pull and/or push rod  1  according to  FIGS. 1 to 5 , the pull and/or push rod  1  of  FIGS. 6 a  to 6 e    is also formed such that it is axially adjusted, provided that a control member  3  engages in the cam  2  and provided that a relative rotation takes place with respect to the control member. When rotated counterclockwise, the rod moves axially in the direction of the extension  14 . It moves axially opposite the direction of the extension  14  when rotated in the clockwise direction. Of course, it is also possible to reverse the sense of rotation of the cam  2  so that if the pull and/or push rod  1  is rotated counterclockwise, an axial displacement is carried out against the direction of the extension  14 . 
       FIGS. 7 a  to 7 e    and  FIGS. 8 a  to 8 e    show further embodiments of a pull and/or push rod  1  which are adjustable along a rod longitudinal axis and which have a cam  2  for guiding a control member  3 . The pull and/or push rod  1  shown here has an inner recess  43 . It is further partially formed as a hollow rod, wherein at the inner periphery of the hollow rod  13 , i.e. in the wall of the inner recess  43 , the cam  2  is formed. The cam  2  shown here has a coil section  8  having one or more slope portions  4 ,  5 , according to the embodiment of  FIGS. 7 and 8 , further comprising a first idle stroke section  9  adjoining the coil section  8  and a second idle stroke section  10  adjoining the coil section  8 . Further, the outer contour of the pull and/or push rod  1  is non-circular in shape so that it can be non-rotatably fixed but axially displaceable in a housing  18 . The inner recess  43 , however, is cylindrical in shape so that it can engage with an actuating element  31  having a round cross-section. 
     The spiral characteristic  39  illustrated in  FIG. 7 e    shows that the coil section  8  comprises a first slope portion  4  with low pitch (power stroke or release stroke) and a second slope portion  5  with high pitch (fast stroke). 
       FIGS. 8 a  to 8 e    show a pull and/or push rod  1  of which the cam  2  is formed in the shape of a closed spiral groove. The spiral characteristic  39  in  FIG. 8 e    shows that the cam  2  includes a first idle stroke section  9 , to which a first coil section  44  connects. The first coil section  44  is followed by a second idle stroke section  10 . A second coil section  45  adjoins at this second idle stroke section  10 , which again merges into the first idle stroke section  9  due to the spiral groove  5  (cam) that is formed circumferentially to the inner recess  43 . Further, the inner recess  43  is continuously designed so that the pull and/or push rod  1  is formed as a pressure sleeve. 
     The spiral characteristic  39  of the pull and/or push rod  1  according to  FIGS. 8 a  to 8 e    means that the pull and/or push rod  1  constantly switches between the release position and the clamping position when a control member  3  rotationally driven in only one direction slides in the spiral groove. This has the advantage that to switch the pull and/or push rod  1  between the release position and the clamping position, the reversal of rotational direction of a motor is not required. In this way, switching times of the system are shortened and programming effort is reduced. 
       FIGS. 9 a  and 9 b    show an axial positioning system  40  which comprises a pull and/or push rod  1  as shown in  FIGS. 7 a    to  7   e.  The housing  18  has an inner contour which is adapted to the outer contour of the pull and/or push rod  1 , whereby the pull and/or push rod  1  is non-rotatably guided inside the housing  18 . In order to facilitate the axial sliding of the pull and/or push rod  1 , either its outer contour and/or the inner contour of the housing  18  can be provided with a friction-reducing coating. In order to maintain functionality, however, alternatively play can be left between the housing  18  and the pull and/or push rod  1  in such a way that in principle, a rotational movement of the pull and/or push rod  1  is prevented, but enough space remains to permit an axial movement of the pull and/or push rod  1  within the housing  18 . The driving flange  24  of the system comprises an actuating element  31  which engages in the rotationally symmetrical, in particular cylindrical, inner recess  43  of the pull and/or push rod  1 . At the actuating element  31 , the control member  3  is arranged in the form of a calotte  46  or in the form of a control ball  20 . The control member  3  is preferably fixedly connected to the actuating element  31 . If the driving flange  24  is now rotationally driven, the actuating element  31  is rotated with the control member  3  within the inner recess  43  of the pull and/or push rod  1 . In this case, the control member  3  slips along the spiral groove, forcing the hollow pull and/or push rod  1  in an axial movement, which results from its rotationally fixed mounting within the housing  18 . Also in this embodiment, the hollow rod is cup-shaped, i.e. formed closed on one side, so that a pressure or traction surface  47  is available on the side facing away from the driving flange  24 . 
       FIGS. 10 to 12  show an example of an electric release unit which is actuated by means of an electric motor  17 . The electric motor  17  preferably has a rotationally driven drive spindle. The electric release unit also provides a pull and/or push rod  1  which is movable along a rod longitudinal axis within a housing  18  and which has a cam  2  for guiding a control member  3  with an at least partially spiral, coil section  8  having one or more slope portions  4 ,  5 . 
     In the present embodiment, the control member  3  is axially fixed in the housing  18 . If the pull and/or push rod  1  is spindled, it is axially displaced within the housing  18 . In order to decouple the spindle movement, a rotatable cap  16  or a thrust bearing is disposed on the side facing away from the electric motor  17 . The pull and/or push rod  1  is preferably formed in accordance with the embodiment of  FIGS. 1 a  to 1 e    and comprises a first idle stroke section  9 , which essentially extends radially to the rod longitudinal axis and which adjoins the coil section  8 . Further, a second idle stroke section  10  also substantially formed radially to the rod longitudinal axis, is connected to the coil portion  8 . 
     On the side of the pull and/or push rod  1  facing away from the rotatable cap  16 , an extending projection  14  having a non-circular cross-section is provided, via which the rotational movement of the electric motor  17  is transferable to the pull and/or push rod  1 . 
     In the present embodiment, the control member  3  which engages in the cam  2 , is formed as a control pin  19 , which is axially fixed in the housing  18  of the electric release unit. It is also possible, that the pin is mounted to rotate about its longitudinal pin axis, whereby the cam  2  is also prevented from blocking or tilting the control pin  19 . 
       FIG. 11  shows the electrical release unit in the clamping position, wherein the control pin  19  is positioned in the second idle stroke section  10  (upper end position). When the control pin  19  is in an idle stroke section  10 , the pull and/or push rod  1  is axially locked in the housing  18 . 
     In order to move the pull and/or push rod  1  to the release position shown in  FIG. 12 , the electric motor  17  is driven, which in turn transfers its rotary motion to the extension  14  of the pull and/or push rod  1 . The rotation of the pull and/or push rod  1  causes the control pin  19  to slide along the idle stroke sections  10 —initially without a stroke movement of the rod. Thus, the electric motor  17  can build up its full torque or its full speed—stroke-free—before the control pin  19  reaches the coil section  8 . Only the sliding of the control pin  19  in the coil section  8  effects a stroke movement of the pull and/or push rod  1  relative to the housing  18 . 
     In the present embodiment, the control pin  19  first reaches the second slope portion  5  of the coil portion  8  with a large pitch with respect to the normal to the rod longitudinal axis, which provides a fast stroke. If the pull and/or push rod  1  is rotated further, the control pin  19  reaches the first slope portion  4  of the coil section  8  with a slight pitch with respect to the normal to the rod longitudinal axis, which provides a power stroke. 
     In other words, using a high pitch at a slope portion  4 ,  5 ,  6 ,  7  means the occurrence of a large axial stroke with a small force, whereby a slight pitch of a slope portion  4 ,  5 ,  6 ,  7  results in a low axial stroke with a high force. 
     Once the control pin  19  has passed through the first slope portion  4  (power stroke), the guide pin  19  reaches the first idle stroke section  9  of the cam  2 , causing the pull and/or push rod  1  to be locked in the release position, no longer allowing axial travel (rear end position of the rod). 
     In order to move the electrical release unit from the release position back into the clamping position, the pull and/or push rod  1  needs to be rotated in the opposite direction, whereby the guide pin  19  passes through the cam  2  in the opposite direction until it has again reached the second idle stroke section  10  (front end position of the rod). 
     So that a high torque can be transmitted to the extension  14  or the pull and/or push rod  1 , it has proven useful when an eccentric gear, preferably a harmonic drive, is arranged between the output or the drive spindle of the electric motor  17  and the pull and/or push rod  1 . Preferably, the eccentric gear thereby provides a relatively large reduction, for example, 1 to 50 in the present example. 
     The electric motor  17  or the drive spindle of the exemplary embodiment includes a mounting flange  21  which is at least indirectly non-rotatably coupled with the pull and/or push rod  1 . In the present case, the drive spindle is thus connected via the harmonic drive to the mounting flange  21 , which is in turn connected with the driving flange  22 , which has an axially extending drive collar  23 . Inside the housing  18 , a sealing ring  48  or sliding ring is disposed, which is arranged coaxially to the output of the electric motor  17  and serves to seal the interior or alternatively, serves as a slide bearing of the driving flange  22 . A driving flange  24  with a non-circular cross-section is connected to the drive collar  23 , which is coupled non-rotatably but axially displaceable to the extension  14  of the pull and/or push rod  1 . In this context, the driving flange  22 , the drive collar  23  and the driving flange  24  can be designed separately, but also at least in some cases, integrally. The mounting flange  21  generally constitutes a part of the electric motor  17 . 
     In order for the adjustment of the pull and/or push rod  1  to require the least possible force within the housing  18 , the housing  18  includes a slide bush  29  which encloses the pull and/or push rod  1 . In the present case, the slide bush  29  is screwed to the end face of the housing  18 . Within this slide bush  29 , additionally a stripping mechanical seal  49  is included in a sliding ring receptacle, which, for example, is formed from a self-lubricating plastic. The mechanical seal  49  seals inwards and prevents the penetration of dirt from outside (stripping). For weight reduction or for conducting media (fluids), the pull and/or push rod  1  has a channel  50  which is configured in the longitudinal direction. 
     The electric release device shown is further advantageously developed in that the drive collar  23  is non-rotatably coupled to a sensor sleeve  25 , which has a sensor target  27  with a peripheral slope  26 . The sensor sleeve  25  is configured in multiple parts with a target holder  51 , with which the sensor target  27  is releasably or fixedly connected. 
     The sensor target  27  as such is part of a sensor system  52  for measuring the axial position of an element, e.g. of a pull and/or push rod  1  of the present invention. Below, the sensor system  52  separately disclosed herein is explained in more detail with reference to  FIGS. 27 to 29 . The sensor system may also be used in separating devices, gripping devices or parallel grippers, or in systems where accurate detection and resolution of a rotation is of an advantage. 
     The sensor target  27  has a peripheral slope  26 , i.e. the sensor target  27  is formed with a rising or falling radius, depending on the rotational position and rotational direction. Preferably, the radius r (A) on the outer periphery of the sensor target  27 , which is dependent of the rotation angle A, can be expressed by the following formula: radius r(A)=r 0 +(Y×A/360 degrees), wherein A is the angle of rotation, r 0  the basic radius and Y is the maximum surcharge to the radius r 0 . Thus, depending on the rotational position of the sensor target  27 , another radial distance  66  from a stationary distance sensor  53  (displacement sensor), preferably arranged on the housing  18 , is present. Likewise, the distance between the outer side to the center  54  of the target is dependent on the angle of rotation A. 
     At its front end  55 , i.e. its side facing away from the electric motor  17 , the sensor target  27  has an elevation  56  which at least partially extends circumferentially. This elevation  56  is higher than a base  57 , preferably by an amount between 2 and 4 mm, preferably by exactly 3 mm. At the front side, a distance sensor  58 , in particular an inductive proximity switch, is disposed which detects the distance  67  to the front end  55  of the sensor target  27 . The distance  67  is less if the sensor target  27  is in a rotary position, in which the elevation  56  sits opposite the distance sensor  58 . Conversely, the distance  67  is greater if the base  57  sits opposite the distance sensor  58 . 
     This has the advantage that it now can be determined whether the rotational movement corresponds to an idle stroke or to an actual axial adjustment (stroke movement). Here, the arc portion  59  communicates to the elevation  56  by how many degrees the respective idle stroke section  9 ,  10 ,  11  of the cam  2  radially extends relative to the rod longitudinal axis. The opening angle B of a line extending from the center point  54  of the sensor target  27  to the first stage  60  of the elevation  56 , and a line extending from the center point  54  of the sensor target  27  to the second stage  61  of the elevation  56  are thereby identical to the opening angle under which the idle stroke section or sections  9 ,  10 ,  11  extend. Thus, when the idle stroke section  9 ,  10 ,  11  extends by 90 degrees, the opening angle between the first stage  60  and the second stage  61  relative to the center  54  of the target  27  is also 90 degrees. Therefore, the elevation  56  in the end face can detect whether an axial stroke is performed. 
     The amount by which the axial stroke takes place, is, however, detected by the radial distance between the sensor target  27  and the radially disposed distance sensor  53 . The more the sensor target  27  is rotated, the smaller the distance  66  between the displacement sensor and the sensor target  27 , due to the circumferentially arranged peripheral slope  26 . In the embodiment shown, the measurement of the axial stroke is recorded over 270 degrees. Only when a 270-degree rotation is reached does the end-face distance  67  of the sensor target  27  again decrease towards the front-side distance sensor  58 , thereby detecting that a control member  3  has again reached an idle stroke section  9 ,  10 ,  11 . Combining distance measurements by the radial distance sensor  53  and the axial inductive proximity switch  58 , the respective end positions (upper or lower end position) can be clearly detected. 
       FIGS. 13 to 16  show an electrical separation device with a pull and/or push rod  1 , non-rotatably but axially displaceably guided in a housing  18  and connected to a separating finger  30 . This pull and/or push rod  1  is adjustable along a rod longitudinal axis and has a cam  2  for guiding a control member  3 , having a coil section  8  which is at least partially spiral-shaped and includes one or more slope portions  4 ,  5 . 
     In the illustrated embodiment, an idle stroke section  9 ,  10  essentially radially extending to the rod longitudinal axis adjoins the coil section  8  of the cam  2 . In the present case, two idle stroke sections  9 ,  10  are provided, wherein the cam  2  is formed as a spiral groove. The pull and/or push rod  1  is additionally at least partially formed as a hollow rod, wherein the cam  2  is formed in an inner periphery  13  of the hollow rod. 
     The pull and/or push rod  1  of the electrical separation device essentially corresponds to the tension and/or compression bar  1  of  FIGS. 8 a    to  8   e.  A rotationally symmetrical actuating element  31  which is fixedly connected to the drive spindle of an electric motor  17 , engages in the cylindrically shaped interior recess  43 . A control member  3  in the form of a calotte  46  is arranged at this actuating element  31 , which engages in the cam  2  for axial adjustment of the pull and/or push rod  1  between a separating position and an open position. 
       FIGS. 13 and 14  show the electrical separation device in the open position;  FIGS. 15 and 16  show it in the separating position. The pull and/or push rod  1  is connected to a separating finger  30  and simultaneously non-rotatably but axially displaceably guided in the housing  18 . In the present case, its outer periphery  12  is formed non-circular as a polygon, in particular as a hexagon. The inner contour of the housing  18  is formed such that the pull and/or push rod  1  is guided non-rotatably but axially displaceable in the housing  18 . 
     Additionally, a protective cap  62 , preferably formed from plastic, is attached to the separating finger  30 . To damp forces axially acting on the separating finger  30 , a spring package is arranged in the tension and/compression rod  1 . In the present case, a cup-shaped recess  63  is formed on the side of the pull and/or push rod  1  facing away from the electric motor  17 , in which a spring  32 , in this example a spiral spring (compression spring), is inserted. This compression spring is supported by a collar  64  of the separating finger  30 , which in this case is removably attached on the separating finger  30  by a screw. This collar  64  is in turn secured to the spring cup of the pull and/or push rod  1  by means of a snap ring. If forces that are too large act on the separating finger  30  in the direction of the electric motor  17  when in the clamping position, the spring  32  is compressed and the collar  64  moves back into the pull and/or push rod  1 , i.e. towards the electric motor  17 . 
     If the electric motor  17  is driven, the control member  31  is rotated, whereby the control member  3  slides in the cam  2  to the position (separation position) shown in  FIGS. 15 and 16 . In this position, the control member  3  formed as a ball is in an idle stroke section  9 , so that the pull and/or push rod  1  is axially locked. Axial movement of the separating finger  30  is now only possible against the spring force of the spring  32 . Since the cam  2  is formed as a spiral groove, the electric motor  17  can be driven in the same direction, i.e. without needing to change the rotating direction, whereby the pull and/or push rod  1  is again returned to the position shown in  FIGS. 13 and 14  (open position). An alternative embodiment of the separating device does without the use of a spring. 
       FIGS. 17 to 20  show a further embodiment of the inventive pull and/or push rod  1 . These figures show an electric gripping device with gripper base jaws  34 , which are radially adjustable to the gripper longitudinal axis and are guided in gripper grooves  33 , and which interact with an axially adjustable wedge hook  35  over splines  68  which extend in a sloped manner to the gripper longitudinal axis. This wedge hook  35  is connected to a pull and/or push rod  1 . This pull and/or push rod  1  is adjustable along a rod longitudinal axis and has a cam  2  for guiding a control member  3 , which comprises an at least partially spiral coil section  8  having one or more slope portions  4 ,  5 . 
     According to the present embodiment, the pull and/or push rod  1  is at least partially formed as a hollow rod, wherein the cam  2  is formed in an inner periphery  13  of the hollow rod. Alternatively, of course, the cam  2  can also be formed on an outer circumference  12 . The pull and/or push rod  1  substantially corresponds to the pull and/or push rod  1  of  FIGS. 8 a    to  8   e.  In the present case, an electric motor  17  is provided which is non-rotatably coupled with an actuating element  31 , at which a control member  3  is arranged. The control member  3  engages in the cam  2  which is formed as a spiral groove for axial adjustment of the pull and/or push rod  1  between a closed position and an open position (and if needed, a clamping position which sits between the closed position and the open position). If the pull and/or push rod  1  is adjusted axially forward, i.e. in the direction of the gripper grooves  33 , the wedge hook  35  or wedge cone forces the gripper base jaws  34  radially outwardly within the gripper grooves  33 . In a gripper according to  FIGS. 17 to 20 , this corresponds to a motion in the clamping position or closed position. In this case, the control member  3  slides within the cam  2  along the coil section  8  towards a first idle stroke section  4  which adjoins the coil section and substantially extends radially to the rod longitudinal axis. Within this first idle stroke section  4 , an axial movement of the pull and/or push rod  1  is prevented, therefore axially locking it. If the actuating element  31  is rotated further, the guide member  3  within the guide groove  2  slides back toward the second idle stroke section  5 , whereby according to  FIGS. 17 to 20 , the gripper re-opens to the open position. 
     As soon as the control member  3  has again reached the first idle stroke section  4 , the pull and/or push rod  1  is again axially fixed, i.e. locked, in the housing  18 . 
     In this embodiment of an electric gripper device, a spring  32  is arranged in the pull and/or push rod  1  to damp forces which act radially on the gripper base jaws  34 . The spring assembly, in turn, corresponds to the arrangement which was already described for the separating device. By altering the arrangement of the spring assembly, the gripper is adapted for external gripping. 
       FIGS. 21 to 24  show a gripping device in the form of an electric parallel gripper. This parallel gripper comprises two gripper arms  38  with a number of pull and/or push rods  1  which correspond to the number of gripper arms  38 . In the present embodiment, one gripper arm  38  each is releasably connected with each pull and/or push rod  1 . The pull and/or push rods  1  are partially formed as a hollow rod, wherein at the inner periphery  13  of the hollow rod, a cam  2  for guiding a control member  3  is formed which has an at least partially spiral coil section  8  having one or more slope portions  4 ,  5 . 
     As shown clearly in  FIGS. 22 and 24 , the pull and/or push rod  1  has a rotationally symmetrical interior recess  43 , in which an actuating element  31  engages which is at least indirectly non-rotatably connected with an electric motor  17 . The two-piece shaped actuating element  31  has two control members  3 , each of which engage in one of the cams  2  of the pull and/or push rods for axial adjustment of the pull and/or push rods  1  between a closed position or a clamping position ( FIGS. 21 and 22 ), and an open position ( FIGS. 23 and 24 ). The clamping position is preferably situated between the open position and the closed position. The closed position may alternatively also correspond to the clamping position. 
     In the present embodiment, two individual actuating elements  31  engaging in the respective hollow rods are provided, whereas the two individual actuating elements can also be integrally molded. This simplifies the transmission of the rotational movement from the electric motor  17 , which in this case is formed as a torque motor  65 , to the actuating elements  31 . The pull and/or push rods  1  thereby essentially correspond to the pull and/or push rod  1  shown in  FIGS. 7 a    to  7   e.  In order to store the pull and/or push rods  1  axially displaceable but rotationally fixed in the housing  18 , these also have a non-circular outer contour, a polygon in the present example, in particular a hexagon. The cam  2  is formed with a first idle stroke section  9 , which is followed by a coil section  8 . At the other end of the coil section  8 , a second idle stroke section  10  is arranged, which predetermines the final position (clamping position). If the centrally arranged torque motor  65  is actuated, it powers the actuating elements  31  with the control members  3 . In this way, the control members  3  can be slidably switched within the cam  2 , between the clamping position and the release position. 
     In an alternative embodiment, it is provided that one of the gripper arms  38  is formed as a fixed, i.e. fixed relative to the housing  18 , gripper arm  38 . The fixed gripper arm  38  cannot be operated with a pull and/or push rod. The at least one other not fixed gripper arm  38 , however, can be operated by means of a pull and/or push rod  1  according to the present invention in order to switch the parallel gripper between a closed position and if necessary, a clamping position, and an open position. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.