Strapping device

Abstract

A strapping device including a tensioner operable to apply a strap tension to a loop of wrapping strap, a friction welder operable to produce a friction weld connection at two areas of the loop of wrapping strap disposed one on top of the other, a motor operable in a first rotational direction to drive the tensioner and in a second opposite rotational direction to drive the friction welder, and a control device. The control device is configured to, in response to receiving a first designated input: (1) operate the motor in the first rotational direction to drive the tensioner until a predetermined strap tension is reached in the loop of wrapping strap; and (2) afterwards, automatically operate the motor in the second different rotational direction to drive the friction welder to produce the friction weld connection.

Claims

1. A strapping device comprising: a tensioning wheel; a welding shoe movable from a rest position downward to a connecting position to connect overlapping upper and lower strap layers together; a transitioning device configured to move the welding shoe from the rest position downward to the connecting position; a rotatable component configured to rotate relative to the transitioning device about a rotational axis, the rotatable component comprising a protrusion positioned to contact the transitioning device, wherein the protrusion is shaped such that rotation of the rotatable component about the rotational axis while the protrusion contacts the transitioning device causes the protrusion to exert a force on the transitioning device to move the welding shoe from the rest position to the connecting position, wherein the protrusion comprises an outer surface; and a motor configured to rotate the rotatable component about the rotational axis, wherein at least part of the transitioning device extends between the welding shoe and the rotatable component, and wherein at least part of the outer surface of the protrusion is spaced apart from the rotational axis.

2. The strapping device of claim 1, wherein the outer surface of the protrusion is curved, wherein the protrusion is positioned such that rotation of the rotatable component about the rotational axis causes the curved outer surface to contact the transitioning device and exert the force on the transitioning device to move the welding shoe from the rest position to the connecting position.

3. The strapping device of claim 1, wherein the protrusion is sized such that continued rotation of the rotatable component about the rotational axis after the transitioning device reaches the connecting position results in the protrusion disengaging the transitioning device.

4. The strapping device of claim 1, wherein the rotatable component comprises a cam wheel and wherein the protrusion comprises a cam on the cam wheel.

5. The strapping device of claim 4, wherein the cam is on an outer surface of the cam wheel.

6. The strapping device of claim 5, wherein the cam wheel has an annular shape and comprises internal teeth.

7. The strapping device of claim 1, wherein the protrusion is sized such that, while the protrusion contacts the transitioning device, less than one complete rotation of the rotatable component about the rotational axis causes the protrusion to exert the force on the transitioning device to move the welding shoe from the rest position to the connecting position.

8. The strapping device of claim 1, further comprising one or more gears operably connecting the motor to the rotatable component, wherein the motor is configured to cause the one or more gears to rotate to cause the rotatable component to rotate about the rotational axis.

9. The strapping device of claim 8, wherein one of the one or more gears is rotatable about the rotational axis.

10. The strapping device of claim 9, wherein the rotatable component comprises a cam wheel and wherein the protrusion comprises a cam on the cam wheel.

11. The strapping device of claim 10, wherein the cam is on an outer surface of the cam wheel.

12. The strapping device of claim 11, wherein the cam wheel has an annular shape and comprises internal teeth.

13. The strapping device of claim 12, wherein the one of the one or more gears comprises external teeth that are meshed with the internal teeth of the cam wheel.

14. The strapping device of claim 1, wherein the transitioning device comprises: a rod having a first end and a second end opposite the first end; a first component at the first end of the rod; a second component at the second end of the rod; and a spring between the first component and the second component and circumscribing at least part of the rod.

15. The strapping device of claim 14, wherein the transitioning device is longitudinally adjustable via movement of (a) the rod and one of the first and second components relative to (b) the other of the first and second components via piston-cylinder action.

16. The strapping device of claim 15, wherein the protrusion is sized such that, while the protrusion contacts the transitioning device, less than one complete rotation of the rotatable component about the rotational axis causes the protrusion to actuate the transitioning device to move the welding shoe from the rest position to the connecting position.

17. The strapping device of claim 15, further comprising one or more gears operably connecting the motor to the rotatable component, wherein the motor is configured to cause the one or more gears to rotate to cause the rotatable component to rotate about the rotational axis, wherein one of the one or more gears is rotatable about the rotational axis.

18. The strapping device of claim 17, further comprising a control device configured to, when the overlapping upper and lower strap layers are positioned beneath the tensioning wheel and beneath the welding shoe: cause the tensioning wheel to rotate to move the upper strap layer over the lower strap layer to tension the strap; and after a tension in the strap reaches a designated tension, control the motor to rotate the rotatable component to cause the protrusion to exert the force on the transitioning device to move the welding shoe from the rest position to the connecting position to contact the upper strap layer and force it against the lower strap layer.

19. The strapping device of claim 18, wherein the control device is further configured to, after the tension in the strap reaches the designated tension, cause the welding shoe to oscillate to produce a friction weld between portions of the upper and lower strap layers.

20. The strapping device of claim 19, wherein the control device is further configured to cause the welding shoe to oscillate while the welding shoe moves from the rest position to the connecting position.

21. The strapping tool of claim 20, wherein the spring exerts a first pushing force on the first component and a second pushing force on the second component.

22. The strapping device of claim 21, wherein the control device is further configured to control the motor to rotate the tensioning wheel.

23. The strapping device of claim 21, wherein the control device is further configured to control the motor to oscillate the welding shoe.

24. The strapping device of claim 22, wherein the control device is further configured to control the motor to rotate the tensioning wheel.

25. The strapping device of claim 14, wherein the transitioning device further comprises a pivoting element.

26. The strapping device of claim 25, wherein the rod, the first component, the second component, and the spring comprise a toggle lever.

27. The strapping device of claim 26, wherein the protrusion is positioned to contact the pivoting element, wherein the protrusion is shaped such that rotation of the rotatable component about the rotational axis while the protrusion contacts the pivoting element causes the protrusion to exert the force on the pivoting element to cause the pivoting element to pivot and force the toggle lever to move to force the welding shoe to move from the rest position to the connecting position.

28. The strapping device of claim 27, wherein the pivoting element is pinned to the first component.

29. The strapping device of claim 1, wherein the motor comprises a motor shaft, wherein the motor is configured to rotate the motor shaft in a first direction to cause the rotatable component to rotate about the rotational axis.

30. The strapping device of claim 29, further comprising an eccentric drive operably connected to the welding shoe to oscillate the welding shoe, wherein the motor shaft is operably connected to the eccentric drive such that rotation of the motor shaft in the first direction causes the eccentric drive to rotate.

31. The strapping device of claim 30, wherein the motor is operably connected to the tensioning wheel such that rotation of the motor shaft in a second direction opposite the first direction causes the tensioning wheel to rotate.

32. The strapping device of claim 1, wherein the motor comprises a brushless direct-current motor.

33. The strapping device of claim 1, further comprising a welding shoe arm supporting the welding shoe, wherein the transitioning device is configured to pivot the welding shoe arm to move the welding shoe from the rest position to the connecting position.

34. The strapping device of claim 1, further comprising a control device configured to, when the overlapping upper and lower strap layers are positioned beneath the tensioning wheel and beneath the welding shoe: cause the tensioning wheel to rotate to move the upper strap layer over the lower strap layer to tension the strap; and after a tension in the strap reaches a designated tension, control the motor to rotate the rotatable component to exert the force on the transitioning device to move the welding shoe from the rest position to the connecting position to contact the upper strap layer and force it against the lower strap layer.

35. The strapping device of claim 34, wherein the tensioning wheel is rotatable about a tensioning-wheel axis, wherein the rotational axis is transverse to the tensioning-wheel axis.

36. The strapping device of claim 35, wherein the tensioning wheel and the welding shoe are positioned such that the longitudinal direction of the upper and lower strap layers is parallel to the rotational axis.

37. The strapping device of claim 35, wherein the transitioning device comprises: a rod having a first end and a second end opposite the first end; a first component at the first end of the rod; a second component at the second end of the rod; and a spring between the first component and the second component and circumscribing at least part of the rod, wherein the transitioning device is longitudinally adjustable via movement of (a) the rod and one of the first and second components relative to (b) the other of the first and second components via piston-cylinder action, wherein the protrusion is sized such that, while the protrusion contacts the transitioning device, less than one complete rotation of the rotatable component about the rotational axis causes the protrusion to exert the force on the transitioning device to move the welding shoe from the rest position to the connecting position, and wherein the strapping device further comprises one or more gears operably connecting the motor to the rotatable component, wherein the motor is configured to cause the one or more gears to rotate to cause the rotatable component to rotate about the rotational axis, wherein one of the one or more gears is rotatable about the rotational axis.

38. The strapping device of claim 35, wherein the motor comprises a motor shaft rotatable about a motor-shaft axis, the strapping device further comprising a gear rotatable about a gear axis and operably connecting the motor shaft to the rotatable component, wherein the motor is configured to rotate the motor shaft about the motor-shaft axis to cause the gear to rotate about the gear axis to cause the rotatable component to rotate about the rotational axis.

39. The strapping device of claim 38, wherein the gear axis and the rotational axis are collinear.

40. The strapping device of claim 38, wherein the gear axis is parallel to and offset from the motor-shaft axis.

41. The strapping device of claim 38, wherein the gear axis is parallel to and offset from the rotational axis.

42. The strapping device of claim 38, wherein the gear axis and the motor-shaft axis are collinear.

43. The strapping device of claim 38, wherein the gear comprises a first gear and the gear axis comprises a first gear axis, the strapping device further comprising a second gear rotatable about a second gear axis, wherein the first gear is operably connected to the second gear such that rotation of the first gear about the first gear axis causes the second gear to rotate about the second gear axis, wherein the second gear is operably connected to the rotatable component such that rotation of the second gear about the second gear axis causes the rotatable component to rotate about the rotational axis.

44. The strapping device of claim 43, wherein the second gear axis is parallel to and offset from the first gear axis.

45. The strapping device of claim 44, wherein the first gear axis and the motor-shaft axis are collinear.

Description

(1) The invention will be described in more detail by way of the examples of embodiment which are shown purely schematically.

(2) FIG. 1 is a perspective view of a strapping device in accordance with certain embodiments of the invention;

(3) FIG. 2 shows the strapping device in FIG. 1 with the casing;

(4) FIG. 3 shows a partial section view of the motor of the strapping device in FIG. 1, together with components arranged on the motor shaft;

(5) FIG. 4 shows a very schematic view of the motor along with its electronic commutation switch;

(6) FIG. 5 shows a perspective partial view of the drive train of the strapping device in FIG. 1;

(7) FIG. 6 shows the drive train in FIG. 5 from another direction of view;

(8) FIG. 7 shows a side view of the drive train in FIG. 5 with the welding device in the rest position;

(9) FIG. 8 shows a side view of the drive train in FIG. 6 with the welding device in a position between two end positions;

(10) FIG. 9 shows a side view of the drive train in FIG. 5 with the welding device in a welding position;

(11) FIG. 10 shows a side view of the tensioner of the strapping device without the casing, in which a tensioning rocker is in a rest position;

(12) FIG. 11 shows a side view of the tensioner of the strapping device without the casing in which a tensioning rocker is in a tensioning position;

(13) FIG. 12 a side view of the tensioning rocker of the strapping device in FIG. 10 shown in a partial section;

(14) FIG. 13 shows a front view of the tensioning rocker in FIG. 12;

(15) FIG. 14 shows a detail from FIG. 12 along line C-C;

(16) The exclusively manually operated strapping device 1 in accordance with the invention shown in FIGS. 1 and 2 has a casing 2, surrounding the mechanical system of the strapping device, on which a grip 3 for handling the device is arranged. The strapping device also has a base plate 4, the underside of which is intended for placing on an object to be packed. All the functional units of the strapping device 1 are attached on the base place 4 and on the carrier of the strapping device which is connected to the base plate and is not shown in further detail.

(17) With the strapping device 1 a loop of plastic strap, made for example of polypropylene (PP) or polyester (PET), which is not shown in more detail in FIG. 1 and which has previously been placed around the object to be packed, can be tensioned with a tensioner 6 of the strapping device. For this the tensioner has a tensioning wheel 7 with which the strap can be held for a tensioning procedure. The tensioning wheel 7 operates in conjunction with a rocker 8, which by means of a rocker lever 9 can be pivoted from an end position at a distance from the tensioning wheel into a second end position about a rocker pivoting axis 8a, in which the rocker 8 is pressed against the tensioning wheel 7. The strap located between the tensioning wheel 7 and the rocker 8 is also pressed against the tensioning wheel 7. By rotating the tensioning wheel 7 it is then possible to provide the strap loop with a strap tension that is high enough for the purpose of packing. The tensioning procedure, and the rocker 8 advantageously designed for this, is described in more detail below.

(18) Subsequently, at a point on the strap loop on which two layers of the wrapping strap are disposed one on top of the other, welding of the two layers can take place by means of the friction welder 8 of the strapping device. In this way the strap loop can be durably connected. For this the friction welder 10 is provided with a welding shoe 11, which through mechanical pressure on the wrapping strap and simultaneous oscillating movement at a predefined frequencies starts to melt the two layers of the wrapping strap. The plastified or melted areas flow into each other and after cooling of the strap a connection is formed between the two strap layers. If necessary the strap loop can be separated from a strap storage roll by means of a strapping device 1 cutter which is not shown.

(19) Operation of the tensioner 6, assignment of the friction welder 10 by means of a transitioning device 19 (FIG. 6) of the friction welder as well as the operation of the friction welder itself and operation of the cutter all take place using only one common electric motor 14, which provides a drive movement for each of these components. For its power supply, an interchangeable storage battery 15, which can be removed for charging, is arranged on the strapping device. The supply of other external auxiliary energies, such as compressed air or additional electricity, is not envisaged in accordance with FIGS. 1 and 2.

(20) The portable mobile strapping device 1 has an operating element 16, in the form of a press switch, which is intended for starting up the motor. Via a switch 17, three operating modes can be set for the operating element 16. In the first mode by operating the operating element 16, without further action being required by the operator, the tensioner 6 and the friction welder 10 are started up consecutively and automatically. To set the second mode the switch 17 is switched over to a second switching mode. In the second possible operating mode, by operating the operating element 16, only the tensioner 6 is started up. To separately start the friction welder 10 a second operating element 18 must be activated by the operator. In alternative forms of embodiment it can also be envisaged that in this mode the first operating element 16 has to be operated twice in order to activate the friction welder. The third mode is a type of semi-automatic operation in which the tensioning button 16 must be pressed until the tension force/tensile force which can preset in stages is achieved in the strap. In this mode it is possible to interrupt the tensioning process by releasing the tensioning button 16, for example in order to position edge protectors on the goods to be strapped under the wrapping strap. By pressing the tensioning button the tensioning procedure can then be continued. This third mode can be combined with a separately operated as well as an automatic subsequent friction welding procedure.

(21) On a motor shaft 27, shown in FIG. 3, of the brushless, grooved rotor direct current motor 14 a gearing system device 13 is arranged. In the example of embodiment shown here a type EC140 motor manufactured by Maxon Motor AG, Brnigstrasse 20, 6072 Sachseln is used. The brushless direct current motor 14 can be operated in both rotational directions, whereby one direction is used as the drive movement of the tensioner 6 and the other direction as the drive movement of the welding device 10.

(22) The brushless direct current motor 14, shown purely schematically in FIG. 4, is designed with a grooved rotor 20 with three Hall sensors HS1, HS2, HS3. In its rotor 20, this EC motor (electronically commutated motor) has a permanent magnet and is provided with an electronic control 22 intended for electronic commutation in the stator 24. Via the Hall sensors, HS1, HS2, HS3, which in the example of embodiment also assume the function of position sensors, the electronic control 22 determines the current position of the rotor 20 and controls the electrical magnetic field in the windings of the stator 24. The phases (phase 1, phase 2, phase 3) can thus be controlled depending in the position of the rotor 20, in order to bring about a rotational movement of the rotor in a particular rotational direction with a predeterminable variable rotational speed and torque. In this present case a 1st quadrant motor drive intensifier is used, which provides the motor with the voltage as well as peak and continuous current and regulates these. The current flow for coil windings of the stator 24, which are not shown in more detail, is controlled via a bridge circuit 25 (MOSFET transistors), i.e. commutated. A temperature sensor, which is not shown in more detail, is also provided on the motor. In this way the rotational direction, rotational speed, current limitation and temperature can be monitored and controlled. The commutator is designed as a separate print component and is accommodated in the strapping device separately from the motor.

(23) The power supply is provided by the lithium-ion storage battery 15. Such storage batteries are based on several independent lithium ion cells in each of which essentially separate chemical processes take place to generate a potential difference between the two poles of each cell. In the example of embodiment the lithium ion storage battery is manufactured by Robert Bosch GmbH, D-70745 Leinfelden-Echterdingen. The battery in the example of embodiment has eight cells and has a capacity of 2.6 ampere-hours. Graphite is used as the active material/negative electrode of the lithium ion storage battery. The positive electrode often has lithium metal oxides, more particularly in the form of layered structures. Anhydrous salts, such as lithium hexafluorophosphate or polymers are usually used as the electrolyte. The voltage emitted by a conventional lithium ion storage battery is usually 3.6 volts. The energy density of such storage batteries is around 100 Wh/kh to 120 Wh/kg.

(24) On the motor side drive shaft, the gearing system device 13 has a free wheel 36, on which a sun gear 35 of a first planetary gear stage is arranged. The free wheel 36 only transfers the rotational movement to the sun gear 35 in one of the two possible rotational directions of the drive. The sun gear 35 meshes with three planetary gears 37 which in a known manner engage with a fixed gear 38. Each of the planetary gears 37 is arranged on a shaft 39 assigned to it, each of which is connected in one piece with an output gear 40. The rotation of the planetary gears 37 around the motor shaft 27 produces a rotational movement of the output gear 40 around the motor shaft 27 and determines a rotational speed of this rotational movement of the output gear 40. In addition to the sun gear 35 the output gear 40 is also on the free wheel 36 and is therefore also arranged on the motor shaft. This free wheel 36 ensures that both the sun gear 35 and the output gear 40 only also rotate in one rotational direction of the rotational movement of the motor shaft 27. The free wheel 29 can for example be of type INA HFL0615 as supplied by the company Schaeffler KG, D-91074 Herzogenaurach,

(25) On the motor-side output shaft 27 the gear system device 13 also has a toothed sun gear 28 belonging to a second planetary gear stage, through the recess of which the shaft 27 passes, though the shaft 27 is not connected to the sun gear 28. The sun gear is attached to a disk 34, which in turn is connected to the planetary gears. The rotational movement of the planetary gears 37 about the motor-side output shaft 27 is thus transferred to the disk 34, which in turn transfers its rotational movement at the same speed to the sun gear 28. With several planetary gears, namely three, the sun gear 28 meshes with cog gears 31 arranged on a shaft 30 running parallel to the motor shaft 27. The shafts 30 of the three cog gears 31 are fixed, i.e. they do not rotate about the motor shaft 27. In turn the cog gears 21 engage with an internal-tooth sprocket, which on its outer side has a cam 32 and is hereinafter referred to as the cam wheel 33. The sun gear 28, the three cog gears 31 as well as the cam wheel 33 are components of the second planetary gear stage. In the planetary gear system the input-side rotational movement of the shaft 27 and the rotational movement of the cam wheel are at a ratio of 60:1, i.e. a 60-fold reduction takes place through the second-stage planetary gear system.

(26) At the end of the motor shaft 27, on a second free wheel 42 a bevel gear 43 is arranged, which engages in a second bevel gear, which is not shown in more detail. This free wheel 42 also only transmits the rotational movement in one rotational direction of the motor shaft 27. The rotational direction in which the free wheel 36 of the sun gear 35 and the free wheel 42 transmit the rotational movement of the motor shaft 27 is opposite. This means that in one rotational direction only free wheel 36 turns, and in the other rotational direction only free wheel 42.

(27) The second bevel gear is arranged on one of a, not shown, tensioning shaft, which at its other end carries a further planetary gear system 46 (FIG. 2). The drive movement of the electric motor in a particular rotational direction is thus transmitted by the two bevel gears to the tensioning shaft. Via a sun gear 47 as well as three planetary gears 48 the tensioning wheel 49, in the form of an internally toothed sprocket, of the tensioner 6 is rotated. During rotation the tensioning wheel 7, provided with a surface structure on its outer surface, moves the wrapping strap through friction, as a result of which the strap loop is provided with the envisaged tension.

(28) In the area of its outer circumference the output gear 40 is designed as a cog gear on which is a toothed belt 50 of an envelope drive (FIGS. 5 and 6). The toothed belt 50 also goes round pinion 51, smaller in diameter than the output gear 40, the shaft of which drive an eccentric drive 52 for producing an oscillating to and fro movement of the welding shoe 53. Instead of toothed belt drive any other form of envelope drive could be provided, such as a V-belt or chain drive. The eccentric drive 52 has an eccentric shaft 54 on which an eccentric tappet 55 is arranged on which in turn a welding shoe arm 56 with a circular recess is mounted. The eccentric rotational movement of the eccentric tappet 55 about the rotational axis 57 of the eccentric shaft 54 results in a translator oscillating to and fro movement of the welding shoe 53. Both the eccentric drive 52 as well as the welding shoe 53 it can be designed in any other previously known manner.

(29) The welding device is also provided with a toggle lever device 60, by means of which the welding device can be moved from a rest position (FIG. 7) into a welding position (FIG. 9). The toggle lever device 60 is attached to the welding shoe arm 56 and provided with a longer toggle lever 61 pivotably articulated on the welding shoe arm 56. The toggle lever device 60 is also provided with a pivoting element 63, pivotably articulated about a pivoting axis 62, which in the toggle level device 60 acts as the shorter toggle lever. The pivoting axis 62 of the pivoting element 63 runs parallel to the axes of the motor shaft 27 and the eccentric shaft 54.

(30) The pivoting movement is initiated by the cam 32 on the cam wheel 33 which during rotational movement in the anticlockwise directionin relation to the depictions in FIGS. 7 to 9of the cam wheel 33 ends up under the pivoting element 63 (FIG. 8). A ramp-like ascending surface 32a of the cam 32 comes into contact with a contact element 64 set into the pivoting element 63. The pivoting element 63 is thus rotated clockwise about its pivoting axis 62. In the area of a concave recess of the pivoting element 63 a two-part longitudinally-adjustable toggle lever rod of the toggle lever 61 is pivotably arranged about a pivoting axis 69 in accordance with the piston cylinder principle. The latter is also rotatably articulated on an articulation point 65, designed as a further pivoting axis 65, of the welding shoe arm 56 in the vicinity of the welding shoe 53 and at a distance from the rotational axis 57 of the welding shoe arm 56. Between both ends of the longitudinally adjustable toggle lever rod a pressure spring 67 is arranged thereon, by means of which the toggle lever 61 is pressed against both the welding shoe arm 56 as well as against the pivoting element 63. In terms of its pivoting movements the pivoting element 63 is thus functionally connected to the toggle lever 61 and the welding shoe arm 56.

(31) As can be seen in the depictions in FIGS. 7, in the rest position there is an (imaginary) connecting line 68 for both articulation points of the toggle lever 61 running through the toggle lever 61 between the pivoting axis 62 of the pivoting element 63 and the cam wheel 33, i.e. on one side of the pivoting axis 62. By operating the cam wheel 33 the pivoting element 63 is rotated clockwisein relation to the depictions in FIGS. 7 to 9. In this way the toggle lever 61 of the pivoting 63 is also operated. In FIG. 8 an intermediate position of the toggle lever 61 is shown in which the connecting line 68 of the articulation points 65, 69 intersects the pivoting axis 62 of the pivoting element 63. In the end position of the movement (welding position) shown in FIG. 9 the toggle lever 61 with its connecting line 68 is then on the other side of the pivoting axis 62 of the pivoting element 63 in relation to the cam wheel 33 and the rest position. During this movement the welding arm shoe 56 is transferred by the toggle lever 61 from its rest position into the welding position by rotation about the rotational axis 57. In the latter position the pressure spring 67 presses the pivoting element 63 against a stop, not shown in further detail, and the welding shoe 53 onto the two strap layers to be welded together. The toggle lever 61, and therefore also the welding shoe arm 56, is thus in a stable welding position.

(32) The anticlockwise drive movement of the electric motor shown in FIGS. 6 and 9 is transmitted by the toothed belt 50 to the welding shoe 53, brought into the welding position by the toggle lever device 60, which is pressed onto both strap layer and moved to and fro in an oscillating movement. The welding time for producing a friction weld connection is determined by way of the adjustable number of revolutions of the cam wheel 33 being counted as of the time at which the cam 32 operates the contact element 64. For this the number of revolutions of the shaft 27 of the brushless direct current motor 14 is counted in order to determine the position of the cam wheel 33 as of which the motor 14 should switch off and thereby end the welding procedure. It should be avoided that on switching off the motor 14 the cam 32 comes to a rest under the contact element 64. Therefore, for switching off the motor 14 only relative positions of the cam 32 with regard to the pivoting element 63 are envisaged, a which the cam 32 is not under the pivoting element. This ensures that the welding shoe arm 56 can pivot back from the welding position into the rest position (FIG. 7). More particularly, this avoids a position of the cam 32 at which the cam 32 would position the toggle lever 61 at a dead point, i.e. a position in which the connecting line 68 of the two articulation points intersects the pivoting axis 62 of the pivoting element 63as shown in FIG. 8. As such a position is avoided, by means of operating the rocker lever the rocker (FIG. 2) can be released from the tensioning wheel 7 and the toggle lever 61 pivoted in the direction of the cam wheel 33 into the position shown in FIG. 7. After the strap loop has been taken out of the strapping device, the latter is ready for a further strapping procedure.

(33) The described consecutive procedures tensioning and welding can be jointly initiated in one switching status of the operating element 16. For this the operating element 16 is operated once, whereby the electric motor 14 first turns on the first rotational direction and thereby (only) the tensioner 6 is driven. The strap tension to be applied to the strap can be set on the strapping device, preferably be means of a push button in nine stages, which correspond to nine different strap tensions. Alternatively continuous adjustment of the strap tension can be envisaged. As the motor current is dependent on the torque of the tensioning wheel 7, and this in turn on the current strap tension, the strap tension to be applied can be set via push buttons in nine stages in the form of a motor current limit value on the control electronics of the strapping device.

(34) After reaching a settable and thus predeterminable limit value for the motor current/strap tension, the motor 14 is switched off by its control device 22. Immediately afterwards the control device 22 operates the motor in the opposite rotational direction. As a result, in the manner described above, the welding shoe 52 is lowered onto the two layers of strap displaced one on top of the other and the oscillating movement of the welding shoe is carried out to produce the friction weld connection.

(35) By operating switch 17 the operating element 16 can only activate the tensioner. If this is set, by operating the operating element only the tensioner is brought into operation and on reaching the preset strap tension is switched off again. To start the friction welding procedure the second operating element 18 must be operated. However, apart from separate activation, the function of the friction welding device is identical the other mode of the first operating element.

(36) As has already been explained, the rocker 8 can through operating the rocker lever 9 shown in FIGS. 2, 10, 11 carry out pivoting movements about the rocker axis 8a. For this, the rocker is moved by a rotating cam disc which is behind the tensioning wheel 7 and cannot therefore be seen in FIG. 2. Via the rocker lever 9 the cam disc can carry out a rotational movement of approximately 30 and move the rocker 8 and/or the tensioning plate 12 relative to the tensioning wheel 7 which allow the strap to be inserted into the strapping device/between the tensioning wheel 7 and tensioning plate 12.

(37) In this way, the toothed tensioning plate arranged on the free end of the rocker can be pivoted from a rest position shown in FIG. 10 into a tensioning position shown in FIG. 11 and back again. In the rest position the tensioning plate 12 is at sufficiently great distance from the tensioning wheel 7 that a wrapping strap can be placed in two layers between the tensioning wheel and the tensioning plate as required for producing connection on a strap loop. In the tensioning position the tensioning plate 12 is pressed in a known way, for example by means of a spring force acting on the rocker, against the tensioning wheel 7, whereby, contrary to what is shown in FIG. 11, in a strapping procedure the two-layer strap is located between the tensioning plate and the tensioning wheel and thus there should be no contact between the two latter elements. The toothed surface 12a (tensioning surface) facing the tensioning wheel 7 is concavely curved whereby the curvature radius corresponds with the radius of the tensioning wheel 7 or is slightly larger.

(38) As can be seen in particular in FIGS. 10 and 11 as well as the detailed drawings of FIGS. 12-14, the toothed tensioning plate 12 is arranged in a grooved recess 71 of the rocker. The lengthin relation to the direction of the strapof the recess 71 is greater than the length of the tensioning plate 12. In addition, the tensioning plate 12 is provide with a convex contact surface 12b with which it is arranged on a flat contact surface 71 in the recess 71 of the rocker 8. As shown in particular in FIGS. 11 and 12 the convex curvature runs in a direction parallel to the strap direction 70, while the contact surface 12b is designed flat and perpendicular to this direction (FIG. 13). As a result of this design the tensioning plate 12 is able to carry out pivoting movements in the strap direction 70 relative to the rocker 8 and to the tensioning wheel 7. The tensioning plate 12 is also attached to the rocker 8 by means of a screw 72 passing through the rocker from below. This screw is in an elongated hole 74 of the rocker, the longitudinal extent of which runs parallel to the course of the strap 70 in the strapping device. As a result in addition to be pivotable, the tensioning plate 12 is also arranged on the rocker 8 in a longitudinally adjustable manner.

(39) In a tensioner the tensioning rocker 8 is initially moved from the rest position (FIG. 10) into the tensioning position (FIG. 11). In the tensioning position the sprung rocker 8 presses the tensioning plate in the direction of the tensioning wheel and thereby clamps the two strap layers between the tensioning wheel 7 and the tensioning plate 12. Due to different strap thicknesses this can result in differing spacings between the tensioning plate 12 and circumferential surface 7a of the tensioning wheel 7. This not only results in different pivoting positions of the rocker 8, but also different positions of the tensioning plate 12 in relation to the circumferential direction of the tensioning wheel 7. In order to still achieve uniform pressing conditions, during the pressing procedure the tensioning plate 12 adjusts itself to the strap through a longitudinal movement in the recess 71 as well as a pivoting movement via the contact surface 12b on contact surface 72 so that the tensioning plate 12 exerts as even a pressures as possible over its entire length on the wrapping strap. If the tensioning wheel 7 is then switched on the toothing of tensioning plate 12 holds the lower strap layer fast, while the tensioning wheel 7 grasps the upper strap layer with its toothed circumferential surface 7a. The rotational movement of the tensioning wheel 7 as well the lower coefficient of friction between the two strap layers then results in the tensioning wheel pulling back the upper band layer, thereby increasing the tension in the strap loop up to the required tensile force value.

(40) TABLE-US-00001 LIST OF REFERENCES 1. Strapping device 37. Planetary gear 2. Casing 38. Socket 3. Grip 39. Shaft 4. Base plate 40. Output gear 6. Tensioner 42. Free wheel 7. Tensioning wheel 43. Bevel gear 7a. Circumferential surface 46. Planetary gear system 8. Rocker 47. Sun gear 8. Rocker pivoting axis 48. Planetary gear 9. Rocker lever 49. Tensioning wheel 10. Friction welder 50. Toothed belt 11. Welding shoe 51. Pinion 12. Tensioning plate 52. Eccentric drive 12a. Tensioning surface 53. Welding shoe 12b. Contact surface 54. Eccentric shaft 13. Gear system device 55. Eccentric tappet 14. Electric direct current motor 56. Welding shoe arm 15. Storage battery 57. Rotational axis eccentric shaft 16. Operating element 60. Toggle lever device 17. Switch 61. Longer toggle lever 18. Operating element 62. Pivoting axis 19. Transitioning device 63. Pivoting element 20. Rotor 64. Contact element 24. Stator 65. Pivoting axis 25. Bridging circuit 66. Pivoting axis 27. Motor side output shaft 67. Pressure spring 28. Sun gear 68. Connecting line 30. Shaft 69. Pivoting axis 31. Cog wheel 70. Strap direction 32. Cam 71. Recess 32a. Surface 72. Contact surface 33. Cam wheel 73. Screw 35. Sun gear 74. Elongated hole 36. Free wheel HS2 Hall sensor HS1 Hall sensor HS3 Hall sensor