Patent Publication Number: US-2023150095-A1

Title: Screw clamp

Description:
1 DESCRIPTION 
     The invention relates to a screw clamp according to the preamble of claim  1 . 
     DE 82 14 309 U1 describes a generic screw clamp with an adjustable clamping arm and a fixed clamping arm between which a workpiece can be clamped. The fixed clamping arm has a threaded flange with an internal thread, which is in threaded engagement with a threaded spindle with pressure plate facing the adjustable clamping arm. The adjustable clamping arm has a slide rail which, in the unclamped state, can be guided smoothly in a loose fit through a recess in the fixed clamping arm. To prevent slipping, the slide rail of the adjustable clamping arm has a corrugation which, when the slide rail is tilted, cants with a counter-contour of the recess formed in the fixed clamping arm. 
     In the prior art, the pressure plate of the fixed clamping arm and the adjustable clamping arm are first brought into contact with the intermediate workpiece for a clamping process. This is followed by a rotary actuation of the threaded spindle, which builds up a clamping force acting against the workpiece. 
     In the above DE 82 14 309 U1, the threaded spindle together with the pressure plate is positioned laterally offset from the slide rail of the adjustable clamping arm by a lever arm length. Depending on the workpiece geometry, such a screw clamp setup can have interfering contours. 
     The object of the invention is to provide a screw clamp that is functionally extended compared to the prior art and, in particular, provides an alternative screw clamp structure for special workpiece geometries. 
     The object of the invention is solved by the features of claim  1 . Preferred further embodiments of the invention are disclosed in the dependent claims. 
     The invention is based on a screw clamp in which at least one of the two clamping arms is adjustable by an axial adjustment path by means of a clamping unit which is manually rotatable about an axis of rotation. During a clamping process, a clamping force acting on the workpiece is built up. According to the characterizing part of claim  1 , the clamping unit is realized as a threaded drive. This has a radially outer adjusting sleeve with at least one internal thread and with at least one radially inner threaded stroke element. The threaded stroke element is in threaded engagement with the internal thread of the adjusting sleeve by means of its external thread. In addition, the radially inner threaded stroke element is connectable to the adjustable clamping arm in a force-transmitting manner (in particular via an anti-slip device). During a clamping process, the adjusting sleeve is rotationally actuated. As a result of the rotary actuation of the adjusting sleeve, the threaded stroke element together with the clamping arm connected to it is adjusted against the workpiece by the axial adjustment path while tension is built up. 
     In a first embodiment, the threaded stroke element can be firmly connected to the adjustable clamping arm. However, it is preferable if the adjustable clamping arm has a slide rail which, in the unclamped state, can be guided smoothly and adjustably through a recess in the radially inner threaded stroke element. The slide rail of the adjustable clamping arm can have a corrugation to prevent slipping. If the slide rail is tilted, it can cant with a counter-contour of the recess formed in the threaded stroke element. The recess can be built axially continuous in the threaded stroke element. 
     In the above embodiment, only one clamping arm can be adjusted by means of the adjusting sleeve. In contrast, in the following second embodiment, it is preferred if the two clamping arms can each be adjusted by an axial adjustment path when the adjusting sleeve is rotated. In order to realize such an adjustment kinematics, the adjusting sleeve can have a first internal thread (e.g. right-hand thread) and an axially adjacent second internal thread in the opposite direction (e.g. left-hand thread). These are respectively threadedly engaged with a first threaded stroke element and with a second threaded stroke element. The first threaded stroke element and the second threaded stroke element can each be connected in a force-transmitting manner to one of the adjustable clamping arms. The clamping arms can each be positioned on axially opposite end faces of the adjusting sleeve. 
     During a clamping process, the two threaded stroke elements can each be moved towards each other by an adjustment path by means of rotary actuation of the adjusting sleeve. Conversely, when the adjusting sleeve is rotated in the opposite direction, the two threaded stroke elements can each be moved away from each other by an adjustment path. 
     In a technical implementation, the slide rail of the first adjustable clamping arm guided through the recess of the first threaded stroke element can extend beyond the first threaded stroke element with a slide rail projection. In this case, the slide rail projection may provide an interfering contour for the adjacent second threaded stroke element. Against this background, the second threaded stroke element can have a clearance into which the slide rail projection can project without interfering contours. 
     Conversely, the slide rail of the second adjustable clamping arm, which is guided through the recess of the second threaded stroke element, can also extend beyond the second threaded stroke element with a slide rail projection. In this case, the slide rail protrusion may form an interfering contour for the first threaded stroke element. Against this background, the first threaded stroke element can also have a clearance into which the slide rail projection can project without interfering contours. 
     The clearance in the first threaded stroke element and/or in the second threaded stroke element can be dimensioned in such a way that the clearance does not form an interfering contour during a tilting movement of the slide rail into its inclined position, in which the slide rail corrugation cants with the counter-contour of the recess in the respective threaded stroke element, in order to realize a slip protection. In a technical implementation, the recess of one threaded stroke element may be aligned in axial alignment with the clearance of the other threaded stroke element. It is preferable if the clearance cross-section in the respective threaded stroke element is substantially larger than the recess cross-section. 
     With regard to increased functionality of the screw clamp, it is preferred if a threaded flange provided with an internal thread is formed on at least one of the clamping arms. This can be in threaded engagement with a threaded spindle with pressure plate. The pressure plate can face the other clamping arm. During the clamping process, the pressure plate of the threaded spindle can be stroke-adjusted for additional tension buildup by rotating the spindle. 
    
    
     
       An example of an embodiment of the invention is described below with reference to the accompanying figures. 
       It shows: 
         FIGS.  1  and  2    the screw clamp in a construction position in different representations; 
         FIG.  3    the screw clamp in a schematic side section view; 
         FIG.  4    a detailed view of the screw clamp; and 
         FIG.  5    in a view corresponding to  FIG.  3   , the screw clamp in the clamped position. 
     
    
    
     In  FIGS.  1  and  2   , the screw clamp is shown in a non-clamped construction position. Accordingly, the screw clamp has two adjustable clamping arms  1 , with an intermediate clamping unit  6 . In  FIG.  1  or  2   , each of the two clamping arms  1 ,  3  has a threaded flange  7  provided with an internal thread, which is in threaded engagement with a threaded spindle  9  with pressure plate  11 , each of which faces the opposite clamping arm. 
     A workpiece  5  ( FIG.  5   ) can be clamped between the two clamping arms  1 ,  3 . For a clamping process, the two clamping arms  1 ,  3  can be adjusted by an axial adjustment path Δa 1 , Δa 2  ( FIG.  5   ) by means of the clamping unit  6 , which can be manually rotated about a rotation axis D ( FIG.  2   ), whereby the pressure plates  11  of the two clamping arms  1 ,  3  are pressed against the workpiece  5  and a clamping force is built up acting against the workpiece  5 . A tool attachment  13  for rotary actuation of the threaded spindle  9  is formed at the end of the threaded spindle opposite the pressure plate  11 . 
     In  FIGS.  1  and  2   , the two clamping arms  1 ,  3  are each formed with slide rails  15  extending in an axial direction through the clamping unit  6 . 
     The structure of the clamping unit  6  is described below with reference to  FIG.  3   : Accordingly, the clamping unit  6  is realized as a threaded drive, which has a radially outer adjusting sleeve  17  with a first internal thread  19  (e.g. right-hand thread) and with an axially directly adjacent, opposite second internal thread  21  (e.g. left-hand thread). Each of the two adjusting sleeve internal threads  19 ,  21  is in threaded engagement with a first threaded stroke element  23  as well as with a second threaded stroke element  25 . 
     In  FIG.  3   , the screw clamp is shown in the unclamped state. Accordingly, the two slide rails  15  (only one slide rail  15  is shown in  FIG.  3   ) of the left-hand, first clamping arm  1  are guided smoothly adjustably in a loose fit through a recess  27  of the left-hand, first threaded stroke element  23 . The slide rail  15  extends in the further course with a slide rail projection  29  beyond the first, left-hand threaded stroke element  23 . In  FIG.  3   , the slide rail projection  29  extends without interfering contour through a clearance  31  of the second, right-hand threaded stroke element  25 . 
     Similarly, the slide rail  15  of the second clamping arm  3  on the right side, which is not shown in  FIG.  3   , is guided smoothly and adjustably in a loose fit through a recess  27  of the second threaded stroke element  25  on the right side. In this case, the slide rail  15  extends further (to the left in  FIG.  3   ) with a slide rail projection  29  (not shown in  FIG.  3   ) beyond the second, right-hand threaded stroke element  25 . The slide rail projection  29  also projects without interfering contour through a clearance  31  (not shown in  FIG.  3   ), which is formed in the first, left-hand threaded stroke element  23 . 
     In  FIG.  3   , the slide rail  15  of the left-hand, first clamping arm  1  has a corrugation  33  to provide anti-slip protection. When the slide rail  15  is tilted ( FIG.  5   ), the corrugation  33  cants with a counter-contour  35  of the recess  27  formed in the first threaded stroke element  23 . In the same way, an anti-slip device is also provided between the slide rail  15  of the second clamping arm on the right and the second threaded stroke element  25 . 
     As indicated in the detailed view of  FIG.  4   , both the first threaded stroke element  23  and the second threaded stroke element  25  each have a recess  27  and a clearance  31 . The recess  27  of one of the threaded stroke elements  23  is aligned in axial alignment with the clearance  31  of the other threaded stroke element  25 . In addition, the clearance  31  in one threaded stroke element  23  is dimensioned so large that it does not represent an interfering contour during a tilting movement K of the slide rail  15  into its inclined position ( FIG.  5   ). In the inclined position ( FIG.  5   ), the slide rail corrugation  33  cants with the counter contour  35  of the recess  27  in the respective threaded stroke element  23 ,  25  in order to realize a slip protection. 
     For a clamping process, the workpiece  5  is first positioned between the two pressure plates  11  of the clamping arms  1 ,  3 . Then the two clamping arms  1 ,  3 , which have not yet tilted, are pressed smoothly into contact with the workpiece  5 . This causes a slight tilting movement K ( FIG.  5   ) of the two clamping arms  1 ,  3 , whereby the slide rail corrugations  33  cants with the corresponding counter contours  35  of the two threaded stroke elements  23 ,  25 . As a result, the respective clamping arm  1 ,  3  is frictionally connected to the associated threaded stroke element  23 ,  25 . 
     Subsequently, the adjusting sleeve  17  is rotated, causing the two threaded stroke elements  23 ,  25  to move towards each other from their initial position ( FIG.  3   ) by the adjustment path Δa 1 , Δa 2  (shown exaggeratedly large in  FIG.  5   ), while building up a clamping force acting on the workpiece  5 . 
     REFERENCE SIGNS 
     
         
           1 ,  3  clamping arms 
         workpiece 
         clamping unit 
         threaded flange 
         threaded spindle 
         pressure plate 
         tool attachment 
         slide rails 
         adjusting sleeve 
         first internal thread 
         second internal thread 
         first threaded stroke element 
         second threaded stroke element 
         recess 
         slide rail projection 
         clearance 
         corrugation 
         counter-contour 
         D rotation axis 
         E adjusting sleeve center cross plane 
         Δa 1 , Δa 2  axial adjustment paths 
         K tilting movement