Abstract:
A strapping unit for wrapping a tightening strap around a packaged item has a base plate, a tensioning device, a sealing device and a separating device. The tensioning device is provided with an actuable tensioning tool being fastened releaseably to the strapping unit by at least one fastening element. The sealing device is provided with a single- or multi-part sealing tool being fitted on the strapping unit by at least one releaseable, further fastening element. The separating device has a blade which can be brought into contact with the strap. At least part of the separating device is fitted releaseably on the strapping unit by at least one further, releaseable fastening element. The fastening elements are of a design which enables the fastening elements to be actuated by the same tool. Worn parts can therefore be swapped with very little maintenance effort.

Description:
FIELD OF THE INVENTION 
     The invention relates to a strapping unit for wrapping a tightening strap around a packaged item. 
     BACKGROUND OF THE INVENTION 
     Such a strapping unit has a base plate which is provided with a supporting surface for arranging on a packaged item, the strapping unit furthermore has a tensioning device with which a strap tension can be applied to the tightening strap, for which purpose the tensioning device is provided with an actuable tensioning tool which can be brought into contact with the strap, the tensioning tool being fastened releasably to the strapping unit by at least one fastening means, also has a sealing device, which sealing device is provided with a single- or multi-part sealing tool with which two strap layers can be connected permanently to each other by contact with the strap, the sealing tool being fitted on the strapping unit by at least one releasable, further fastening means, the strapping unit is furthermore provided with a separating means with which the strap can be severed, for which purpose the separating means has a blade which can be brought into contact with the strap, at least part of the separating means being fitted releasably on the strapping unit by at least one further, releasable fastening means. 
     Strapping units of this type are frequently provided for mobile use so that a user can wrap a steel strap around a packaged item in any desired location. A first generic type of these strapping units typically has a sealing device which produces a connection of two layers of the steel strap by means of multiple notchings, without using an additional sealing element, such as, for example a lead seal. For this type of strapping unit it is also typical for both the strap tension and the formation of a seal to be produced manually without the assistance of outside energy, in particular electric or pneumatic energy. For this purpose, the operator of a strapping unit according to the generic type has only to provide his own muscular power. However, the invention is also suitable for another generic type of strapping unit, in which either a sealing element, such as the already mentioned lead seal, or auxiliary energy, such as, for example, electric or pneumatic energy, is used for producing a welding connection in the case of plastic straps. 
     However, a common feature of the described generic types of strapping units is that, as a rule, the required strap tension is applied to the strap by means of a rotating tensioning wheel. By means of a frictional lock between the tensioning wheel and the strap layer in contact with it, the strap layer can be moved in the direction of a supply reel of the strap, as a result of which the strap loop becomes smaller and the strap tension consequently becomes greater. Apart from the manually actuated tensioning devices which have already been discussed, tensioning devices which use electric, pneumatic or other auxiliary energy for producing the strap tension can also be provided in strapping units of the generic type. 
     Virtually all of the components which belong to strapping units of this type and are in contact with the strap are subject to wear. In particular, those components whose function is to act upon the strap, whether by means of friction, a frictional lock or by deformation of the strap, regularly wear out. Consequently, such worn parts have to be regularly replaced. In the case of the described, previously known strapping units, what may not be satisfactory in this connection is that a great maintenance effort is required in order to replace the worn parts. 
     SUMMARY OF THE INVENTION 
     The invention is therefore based on the object of providing a strapping unit in which worn parts can be swapped with as little maintenance effort as possible. 
     This object is achieved according to the invention in the case of a strapping unit of the type described at the beginning by it being possible for a plurality of worn parts of the strapping unit to be exchanged using the same, i.e. using just one, tool. According to the invention, fastening means of the worn parts are therefore intended to be of a design, at the points provided for engagement of the tool, which enables the said fastening means to be released and fitted using just one tool in total. According to the invention, it is intended, in particular, for it to be possible at least for the worn parts on the strapping unit to be released with the same tool, swapped for new parts and for the latter to be fastened again using the same tool, wherein it is conceivable that they can be swapped regularly on the one hand, and simultaneously, on the other hand. This may involve one or more worn parts of the sealing device and/or of the separating means. This may, for example, comprise a die-plate and a punch of a notching tool of the sealing device, which tool is provided for sealing a strap loop, and a blade of the separating means. Instead of one of the abovementioned worn parts, or in addition thereto, a tensioning wheel of the tensioning device may also be provided and can likewise be replaced using the same tool. 
     The invention is therefore based on the concept of simplifying the maintenance effort by reducing the required handling steps and reducing the number of tools to be stocked up on. In the most favorable case, just one single tool which, if possible, is to be a standard tool, is required for the replacement of all of the worn parts. The strapping unit and the tool suitable for it can also be understood to be the maintenance system. Since strapping units are generally used in industrial works in which standard tools of this type are present, virtually all over the world the maintenance work can be undertaken by the user himself. Particularly in the case of mobile, transportable strapping units, this affords the advantage that worn parts can be exchanged very rapidly by the user himself in situ without the service of the unit manufacturer or a workshop being required for this purpose. 
     The ease of maintaining strapping units according to the invention can be further increased if worn parts or their fastening means on the strapping unit are accessible from the outside. According to the invention, fastening means of the worn parts should be able to be released without other components connected to the corresponding worn part having to be removed for this. For example, coverings or components which are retained or clamped by the same fastening element are connected to the worn part. In particular, components of the strapping unit with which movements of the strapping unit are produced, for example shafts and levers, and which would have to be readjusted again after the swapping of the worn parts should not have to be removed. 
     In a preferred embodiment, the tool can be just one screwdriver of a certain size, for example of size  4 . Of course, other tools could also be provided, such as, for example, a spanner or the like. 
     Further preferred refinements of the invention emerge from the dependent claims, the description of the figures and the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be explained in greater detail with reference to exemplary embodiments illustrated schematically in the figures, in which: 
     FIG. 1 shows a perspective illustration of a strapping unit according to the invention; 
     FIG. 2 shows the strapping unit from FIG. 1 in a different perspective illustration; 
     FIG. 3 a  shows a longitudinal sectional illustration of the strapping unit from FIG. 1, in which the sealing-device lever is situated in an open end position; 
     FIG. 3 b  shows an illustration of the strapping unit according to FIG. 3 a , in which the sealing-device lever is shown in the sealing end position; 
     FIG. 4 shows a perspective exploded illustration of the strapping unit from FIG. 1; 
     FIG. 5 shows a perspective illustration of a die-plate and a separating device of the strapping unit from the front; 
     FIG. 6 shows a perspective illustration of the die-plate and the separating device from FIG. 5 from the rear; 
     FIG. 7 shows a longitudinal sectional illustration of the strapping unit from FIG. 1 during the wrapping of a packaged item; 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIGS. 1 and 2 an exclusively manually actuated, portable handling unit is illustrated. With the strapping unit, a strap loop which is placed around a packaged item can be tensioned, sealed and separated from a strap supply reel. 
     The strapping unit has, as a constituent part of a carrier  1 , a base plate  2  with whose lower supporting surface  2   a  the strapping unit can be arranged on a package item, which is shown purely schematically only in FIG.  7 . As can be gathered in particular from FIGS. 3 a  and  3   b , a punch  3  in the base plate  2  is inserted into a recess of the base plate  2  from above. The punch  3  is fastened to the base plate by means of at least one slotted screw  4 , which is introduced from the supporting surface  2   a  of the base plate  2 , and two bolt pins  5 , which are seated fixedly in the base plate. The punch  3  is a constituent part of a sealing device. A bearing surface  2   b  of the base plate  2  is provided directly behind the punch, in the direction of the rear end of the base plate. Finally, in the region of the rear end of the base plate a toothed plate  7 , which is profiled on an upper side, is inserted into the base plate and a retaining plate  8  bears against it. The retaining plate  8  is likewise fastened releasably on the base plate  2  from the supporting side  2   a  with two slotted screws  9 ,  10  (FIGS. 3 a ,  4 ) and therefore fixes the toothed plate  7  in place. A slot width and slot depth of the heads of the slotted screws  4 ,  9 ,  10  are designed identically. 
     In the region of a front end of the base plate, a die-plate carrier  11  is mounted on the bearing point of the carrier  1  in a manner such that it can pivot about a bearing axis  14  (FIGS. 2 and 3 a ). The die-plate carrier  11  can be pivoted between an open end position and a sealing end position and is a constituent part, inter alia, of a sealing device. The die-plate carrier has a two-part die-plate  15  shown in FIGS. 5 and 6. In the illustration of FIG. 3 a , only the front die-plate part  15   a  of the two die-plate parts  15   a ,  15   b  can be seen. As FIG. 3 a  shows, the die-plate  15  is inserted into a recess on a lower side  11   a  of the die-plate carrier  11 , which side faces the base plate. In order to secure the die-plate  15 , the latter is pushed onto a pin  16  of the die-plate carrier  11  and is screwed to the die-plate carrier  11  by means of two identical slotted screws  17 ,  18  (FIGS. 1,  3   a ,  5 ). A slot width and slot depth of the heads  17   a ,  18   a  of the two screws  17 ,  18  are identical with the slot width of the screw heads  4 ,  9 ,  10 . 
     Geometrical shapes of the die-plate  15  and of the punch  3  can be designed essentially corresponding to the sealing tools shown in DE 38 41 489 C2 or CH 659 221 A5. 
     A separating device, which is provided with an adjusting wedge  20  and a notching blade  21  as notching tool, is also arranged on the lower side  11   a  of the pivotable die-plate carrier, behind the die-plate  15  in the tensioning direction (arrow  19  in FIG. 3 a ). As can be seen in the detailed illustration of FIGS. 5,  6 , the adjusting wedge  20  is provided with an obliquely running adjusting surface  20   a . The adjusting wedge  20  is pushed into a recess of the die-plate carrier  11  (cf. FIG. 3 a ). Its insertion depth, which runs transversely with respect to the strap alignment, can be infinitely variably adjusted by an adjusting screw  24 . For this purpose, the adjusting screw  24 , which is accessible from the side of the strapping unit, engages in a thread of the die-plate carrier  11 . 
     The notching blade  21  is likewise pushed into the die-plate carrier  11  below the adjusting wedge  20  and is clamped in place there by two identical slotted screws  25 ,  26 . An oblique contact surface  21   a  of the blade lies opposite the adjusting surface. The inclination of the contact surface  21   a  corresponds to the inclination of the adjusting surface  20   a , as a result of which both surfaces  20   a ,  21   a  bear against each other. On its side facing the base plate  2 , the blade  21  has a notched cutter  21   b . The blade  21  is also provided with two lateral grooves  21   c  which are approximately in the shape of a circular arc and in which a screw head  25   a ,  26   a  is arranged in each case. By this means, the blade  21  bears, firstly, against circumferential surfaces of the screw heads  25   a ,  26   a  of the two screws. Secondly, the two screw heads  25   a ,  26   a , which act as stops, also define, in the direction of the insertion depth of the blade  21 , the position of the said blade in the die-plate carrier  11 . The same screwdriver which also matches the other screws  4 ,  9 ,  10 ,  17 ,  18  can be used to actuate the slotted screws  24 ,  25 . By this means, a notched cutter  21   b  of the notching blade can protrude by a predetermined length over the lower side  11   a . This projecting length can be adjusted in an infinitely variable manner by means of screw-in depths of the screws  24 ,  25 , particularly as a function of the wearing state of the blade  21  and of the positions of the surfaces with which the punch  3  and the die-plate  15  deform the strap. 
     On an upper side facing away from the base plate  2 , the die-plate carrier  11  has a receptacle  27  for a transmission element  28  (FIGS. 3 a ,  3   b ). For this purpose, the receptacle  27  is of approximately fork-shaped design, the two fork struts  27   a ,  27   b  being bent toward each other in each case. That fork strut  27   b , which is closer to the rear end of the base plate  2 , is provided with an inner rolling surface  27   c  which is shaped in such a manner that the transmission element  28  can roll on it for a certain distance during a pivoting movement of the die-plate carrier  11 . The shape of the other fork strut  27   a  is configured to the effect that the transmission element  28  can, on the one hand, move in the predetermined manner in the receptacle  27  during pivoting movements, but, on the other hand, is retained securely between the two fork struts  27   a ,  27   b.    
     In the exemplary embodiment illustrated, the transmission element  28  is a roller which is arranged eccentrically with its eccentric axis  29  with respect to a rotational axis  30  of a rotational bearing. The eccentricity is designated by E in FIGS. 3 a ,  3   b . The rotational bearing, and therefore the die-plate carrier  11 , can be actuated via a sealing-device lever  33  which is connected non-rotatably to a rotational shaft  31  (FIGS. 1 and 2) of the rotational bearing (for rotation in common). 
     As can be gathered from FIG. 2, a rocker  34  of the tensioning device is mounted rotatably at one end of the rotational shaft  31 , which end lies opposite the transmission element  28 . The rocker  34  is supported on the support  1  via a spring  35  (FIG. 3 a ). Since the rocker  34  is arranged on the same shaft as the sealing-device lever  33 , the rotational axis  30 , with which the sealing-device lever  33  causes the rotational shaft  31  to rotate, is aligned with a pivot axis of the rocker  34 . Since, however, the rocker  34  is arranged on the rotational shaft with radial bearings (not shown in greater detail), rotational movements of the rotational shaft are decoupled from the pivoting movement of the rocker  34 . Both the rotational axis  24  and the pivot axis coinciding with it run essentially-parallel to the bearing axis  14  of the die-plate carrier. 
     The rocker  34  has, on the side of the die-plate carrier  11 , a bearing plate  36  which is provided with a circular recess  36   a  and a peg  36   b  (FIGS.  2  and  4 ). The recess  36   a  is provided for arranging on one end of the rotational shaft  31  and of the peg  36   b  for pushing into the tensioning shaft  37 . There is a passage hole  38  in the bearing plate  36 , approximately between the recess  36   a  and the peg  36   b , the said hole being used in order to fasten the bearing plate  34  with a set screw  39  to an internal thread of an extension  40  of the carrier. The slotted head  39   a  of the set screw  39  can, owing to the width and depth of the slot, also be actuated by the screwdriver with which the other screws  9 ,  10 ,  17 ,  18 ,  24 ,  25 ,  26  can also be loosened and tightened. 
     According to FIGS. 1 and 3 a , a handle  41  is also connected fixedly to the rocker  34  and can be used to actuate the rocker  34  in the form of a pivoting movement around the rotational axis  30  or pivot axis. With the handle  41 , the rocker  34  can be pivoted counter to the action of the compression spring  35  from a tensioning position (shown in the figures), in which a tensioning wheel  44  (FIG. 3 a ) bears against the toothed plate  7  or against a strap guided over the toothed plate  7 , into a neutral end position (not shown in the figures) and back again into the tensioning position. In the neutral end position, the tensioning wheel  44  is arranged at a distance from the toothed plate  7 . Without acting on the rocker  34 , the latter always takes up the tensioning position on account of the spring force acting on it. 
     A tensioning lever  45 , with which the tensioning wheel  44  (FIG. 3 a ) can be caused to rotate, is fitted to an end of the rocker  34  lying opposite the rotational axis  30  (FIG.  2 ). As can be seen in particular from FIG.  1  and FIG. 4, the tensioning shaft  37  is mounted rotatably in a cylindrical part  46  of the rocker  34 . At the two ends of the tensioning shaft  37 , the tensioning lever  45  is situated at one end and the tensioning wheel  44 , which is arranged non-rotatably on the tensioning shaft  37  (for rotation in common), is situated at the other end. The tensioning lever  45  can be moved to and from a first end position into a second end position, in which case it is connected non-rotatably to the tensioning shaft  37  (for rotation in common) only in one direction of rotation. With regard to the other direction of rotation, there is no rotational connection to the tensioning shaft  37 , and so the tensioning lever  45  can be moved back from its second end position into the first end position without carrying along the tensioning wheel  44  in the process. It is therefore possible to use the tensioning lever  45  to always move the tensioning wheel only in the tensioning direction. 
     In order, with the illustrated strapping unit according to the invention, to tension a strap loop around a packaged item  47  (which is illustrated schematically only in FIG.  7 ), first of all the strap  48  can be placed loosely around the packaged item  47 , so that two strap layers  50 ,  51  lie one above the other in the region of the free strap end  49 . The strapping unit is then arranged with its supporting surface  2   a  of the base plate  2  on the packaged item  47 , the die-plate carrier  11  being arranged in its open end position and the tensioning wheel  44  being arranged in its neutral end position. As a result, the two strap layers  50 ,  51  lying one above the other can be guided over the base plate  2  of the strapping unit, so that the strap is situated between the die-plate  15  and the punch  3 . By means of a pivoting movement of the rocker  34  counter to the spring force of the compression spring  35  a gap can then also be provided between the tensioning wheel  44  and the toothed plate  7 . To this end, an operator can grasp the handle  41  and the sealing-device lever  33 , which is arranged in its open end position, with one hand and compress the handle  41  upward in the direction of the sealing-device lever  33 . After the two strap layers  50 ,  51  have been introduced into the gap, the handle  41  is released, as a result of which the compression spring  35  moves the rocker  34  back again toward the toothed plate  7  into its tensioning position. The two strap layers  50 ,  51  are thereby clamped in place between the tensioning reel  44  and the toothed plate  7 . In the process, the lower strap layer  51  rests with the free strap end  49  on the punch  3  and on the bearing surface  2   b  of the base plate  2 . The other strap layer  50  leading to a supply reel (not illustrated) is situated above the free strap end  49  and projects out of the strapping unit behind the tensioning wheel  44 . This situation is shown in FIG.  7 . 
     The strap loop can now be tensioned by actuation of the tensioning lever  45 . For this purpose, the tensioning lever  45  is pivoted to and from a number of times between its two end positions. During its pivoting movement in the anticlockwise direction (with regard to the illustrations of FIGS. 3 a ,  3   b ,  7 ) the tensioning lever  45  is coupled to the tensioning wheel  44 . The tensioning wheel  44  is therefore caused to rotate in the anticlockwise direction. By means of a frictional lock between the upper strap layer  50  and the tensioning wheel  44 , the upper strap layer  50  is pulled further out of the strapping unit and the strap loop is provided with tension. In contrast, the lower strap layer  51  is retained unchanged in position by means of the profiling of the toothed plate  7 . During the pivoting movement of the tensioning lever  45  in the clockwise direction, in contrast, the operative connection between the tensioning lever  45  and the tensioning wheel  44  is canceled. The tensioning wheel  44  therefore remains in its current rotational position. The oscillating movement of the tensioning lever is repeated until a sufficient tension has been applied to the strap. 
     The strap loop is subsequently sealed. For this purpose, the sealing-device lever  33  and the transmission element  28  are transferred from the open end position (FIG. 3 a ) into the sealing end position (FIG. 3 b ). In the exemplary embodiment illustrated, the sealing-device lever  33  covers a rotational angle α of approximately 140° in the process. The eccentrically mounted roller rolls here along the surface  27   c  of the receptacle  27 . The eccentricity E of the transmission element  28  rotates here in the same direction of rotation as the sealing-device lever  33 . 
     By this means, it is reliably ensured that an additive-free, i.e. in particular a lead-free and weld-free, seal is formed in the strap  48  itself by the die-plate  15  and the punch  3 , which seal is not loosened even at high strap tension. Directly before the sealing end position is reached, the cutter  21   b  of the blade  21  notches into the upper strap layer  50 , which is still connected to a strap supply, and severs it in the process from the strap supply. Subsequently, the sealing-device lever  33  can be transferred again into its open end position, the tensioning wheel can be lifted off the strap by actuation of the rocker  34  and the strapping unit can be removed from the strap loop, which is now finished, by guiding it away laterally. 
     After a multiplicity of such strapping operations, the components in contact with the strap  48  have to be changed due to wear. In this connection, the punch  3 , which is inserted in the base plate  2 , can be removed by releasing the slotted screw  4 , which is accessible from the supporting side  2   a , with the slotted screwdriver  54  and can be replaced by a new punch. In order to secure the new punch, the latter is to be placed under the two pins  5  and only the screw  4  is to be re-inserted. On account of the size of the screw head  4   a  or of the slot of the screw  4 , a screwdriver  54  of size  4  can be used for this. 
     In order to swap the two parts  15   a ,  15   b  of the die-plate  15 , the screws  17 ,  18 , which are accessible from one side of the strapping unit have to be released. The slot width and depth of the heads  17   a ,  18   a  of the screws  17 ,  18  correspond to the head  4   a  of the screw  4 , and so similarly the slotted screwdriver  54  of size  4  can be used for this purpose. The die-plate  15  can subsequently be removed from the pin  16  and swapped for a new die-plate. The latter is fastened again to the die-plate carrier  11  by means of the two screws  17 ,  18 . 
     The blade  21  of the separating device can be pulled out of the die-plate carrier  11  after the slotted screw  25  is released. The same screwdriver  54  with which the screws  4 ,  17 ,  18  have also been actuated can also be used for this purpose. After a new blade  21  and, in order to fasten and adjust it, the screw  25  has been re-inserted, the adjusting screw  24  of the adjusting wedge  20  (FIG. 5) of the separating device can be adjusted with the same screwdriver  54 . The slot width of this screw  24  also corresponds to the slot widths of the other screws  4 ,  17 ,  18 . An additional tool is therefore not required either for the adjusting of the notch depth of the separating device. 
     In order to change the toothed plate  7  of the tensioning device, the two slotted screws  9 ,  10 , which are accessible from the supporting side  2   a  of the base plate, have to be released. These screws  9 ,  10  have the same slot size as the screw  4  of the punch  3  and can therefore also be actuated with the same tool. After the screws  9 ,  10  have been released, the retaining plate  8  and the toothed plate  7  can be removed from the base plate  2  parallel to the tensioning direction (arrow  19 ). A new toothed plate and the previous retaining plate  8  are then inserted and the screws  9 ,  10  are again screwed into the base plate from the supporting side  2   a  by the screwdriver  54 . 
     In order to swap the worn tensioning wheel  44  for a new tensioning wheel, the set screw  39  has to be released, the screwdriver  54  of size  4  likewise fitting into the slot of its screw head  39   a . As can be gathered from FIG. 4, after that the bearing plate  36 , a first spacer ring  55 , a strap-guiding ring  56 , a second spacer ring  57  and subsequently the tensioning wheel  44  can be removed from the tensioning shaft  37 . After a new tensioning wheel has been pushed onto the tensioning shaft  37 , the previously mentioned components can likewise be fitted again in the reverse order onto the tensioning shaft  37  and the bearing plate  36  can be fastened to the extension  40  by means of the screw  39 .