Strapping device with an electric drive

Abstract

The present invention relates to a mobile strapping device. The mobile strapping device comprises a tensioning device for applying strap tension to a strap and a welding device for creating a connection between two regions of the strap. The welding device can be moved from a rest position to a welding position and from the welding position to the rest position by means of a toggle lever device.

Description

[0001] The invention relates to a mobile strapping device for strapping packaged goods with a strapping band, which has a tensioning device for applying a band tension to a loop of a strapping band, as well as a connecting device for creating a connection at two superimposed areas of the loop of the strapping band, and a rechargeable energy store for storing energy that can be released as drive energy for motor drive movements at least for the connecting device and / or for the tensioning device.

[0002] Such mobile strapping devices are used to strap packaged goods with plastic strapping. For this purpose, a loop of the respective plastic strap is placed around the packaged goods. The plastic strapping is usually pulled from a supply roll. Once the loop has been completely placed around the packaged goods, the end of the strap overlaps with a section of the strap loop. The strapping device is then applied to this two-layer section of the strap. The strap is clamped in the strapping device, tension is applied to the strap loop using the tensioning device, and a closure is created on the loop between the two strap layers using the connecting device. Various closure technologies are possible, including friction welding. In the latter case, an oscillating friction shoe is pressed onto the strap in the area of ​​two ends of the strap loop.The pressure and heat generated by the movement melt the strap, which is usually made of plastic, locally for a short time. This creates a permanent bond between the two layers of strapping that can only be broken with considerable force. The loop is then cut from the supply roll. The packaged goods are then strapped.

[0003] Such strapping devices typically have a rechargeable and, if necessary, replaceable battery for powering DC motors. In portable, mobile strapping devices, the DC motors are used to generate drive movements for the tensioning device and / or the welding device.

[0004] Such mobile strapping devices are often used continuously in industry for packaging goods. Therefore, the aim is to make the strapping devices as simple to operate as possible. This should ensure, on the one hand, high functional reliability of the strapping device combined with the production of high-quality straps, and, on the other hand, the lowest possible stress for the operators. Previously known strapping devices cannot fully satisfy this requirement.

[0005] The invention is therefore based on the object of creating a generic mobile strapping device of the type mentioned at the outset which, despite the possibility of at least largely automated production of strapping, has a high level of functional reliability and good handling properties.

[0006] This object is achieved according to the invention in a strapping device of the type mentioned above by a brushless DC motor as the drive for the tensioning device and / or connecting device. As will be explained in more detail below, brushless DC motors have electrical and mechanical properties that offer particular advantages in connection with mobile strapping tools. Furthermore, such motors are largely wear- and maintenance-free, which contributes to the high functional reliability of the strapping tools.

[0007] Furthermore, a speed-dependent or speed-controlled tensioning process, as is now possible with brushless DC motors, also enables a fast first tensioning process, i.e., tensioning with a high belt retraction speed, followed by a second tensioning process with a reduced belt retraction speed compared to the first tensioning process. Particularly with such brushless motors, the belt retraction speeds can be adapted to the desired conditions required for the two tensioning processes due to the ability to adjust the speed of the motor shaft and the motor torque independently of one another within certain ranges. The described division into a first and at least one second tensioning process allows particularly high belt tensions to be achieved.

[0008] A strapping tool according to the invention can further comprise an energy storage device embodied as a lithium-ion battery, which can provide energy to drive a connecting device embodied as a friction welding device. It has been shown that such batteries also achieve particularly good functional reliability, as these batteries provide sufficient energy to perform a high number of strapping cycles with mobile strapping tools, even when high strap tensions are applied and strapping processes are to be carried out at least largely automatically with motorized drive movements.

[0009] It has also been shown that lithium-ion batteries in combination with friction welding systems can be considered an ideal complement compared to other electrical energy storage devices. The friction welding process itself depends on the pressure between the two strips and the frequency of the oscillating welding shoe or welding element. For welding PP or PET straps, welding shoe frequencies of approximately 250–300 Hz with a contact pressure of 300–350 N are desired. To achieve these values, an eccentric drive driving the welding shoe requires a speed of approximately 6,000 to 7,000 rpm on the drive side. Ideally, with these starting values, a welding process takes between 1.5 and 2 seconds. If the eccentric shaft speed drops below 6,000 rpm, the quality of the strap closure deteriorates significantly.

[0010] It has now been shown within the scope of the invention that the premature decline in the quality of the seals observed with conventional hand strapping tools, even when the batteries are not even 60% discharged, does not occur in this way with lithium-ion batteries. Lithium-ion batteries can provide the voltage values ​​required for high rotational speeds for significantly longer. This means that lithium-ion batteries, compared to other batteries of a comparable size, can continue to enable friction-welded seals with the desired strength for a significantly longer time, i.e. with a significantly higher number of strappings. Only shortly before the stored energy is completely used up does the supply voltage provided by lithium-ion batteries drop to values ​​that should be avoided in friction welding processes.Since the point in time at which the user should be prompted to recharge the battery by a corresponding signal from the strapping device due to the imminent complete discharge of the lithium-ion battery corresponds approximately to the point in time from which the battery no longer enables good quality friction fasteners to be produced, in contrast to conventional batteries the signal for recharging can also be provided as a warning to the user that from now on the required quality of the strappings produced subsequently is no longer guaranteed.

[0011] Since lithium-ion batteries have a significantly higher energy density than conventional batteries, these advantages can be achieved even with smaller batteries. The resulting lower weight of the batteries used is another significant advantage, especially for use in mobile, portable strapping devices.

[0012] Particular advantages can be achieved by using lithium-ion batteries in conjunction with at least one brushless DC motor as a drive for the clamping device and / or friction welding device. This can be further enhanced by a planetary gear system, particularly when the at least one planetary gear system is arranged together with the brushless DC motor and the lithium-ion battery in the drive train for the clamping device and / or friction welding device.

[0013] A design of the strapping device in which the tensioning device and the welding device are provided with a single common drive can also be of independent significance. This single drive can preferably be designed as an electric motor, with the drive movement of which the tensioning device and the friction welding device can be driven one after the other. Preferably, this single motor not only drives the drive movement of the welding process itself, but also moves the friction welding device from a rest position to a welding position in which a welding element of the friction welding device applies pressure to the strap layers to be welded together and creates a friction weld connection on the strap layers through an oscillating movement. In this case, the welding element of the friction welding device is preferably inactive in the rest position and is preferably only activated when a movement from the rest position begins.

[0014] According to a further aspect of the present invention, which can also have independent significance, the strapping device is provided with means by which rotational positions of the motor shaft or positions of components of the strapping device that are dependent on the motor shaft can be determined. The information about one or more rotational positions can preferably be used by a controller of the strapping device to control components of the strapping device, such as the friction welding device and / or the tensioning device. If a brushless DC motor is used as the drive, this can be done in a particularly simple manner. Such motors must already determine information about the current positions of the rotating component of the motor, which is usually designed as a rotating armature, for their commutation. For this purpose, detectors orSensors, such as Hall sensors, are provided to determine the rotational positions of the rotating engine components and provide them to the engine control unit. This information can also be advantageously used, in particular, to control the friction welding device.

[0015] Thus, in a preferred embodiment of the strapping device, it can be provided that a number of revolutions of the rotating component of the motor is determined in order to perform a switching operation when a predetermined value for the revolutions is reached. This switching operation can, in particular, involve switching off the friction welding device to terminate the creation of a friction weld. In a further advantageous embodiment of the invention, it can be provided that the motor cannot be switched off at one or more specific rotation positions, or can only be switched off at one or more specific rotation positions.

[0016] Finally, it has proven advantageous to provide a toggle lever device for moving the welding device from the rest position to the welding position and back. The levers of the toggle lever device, which are connected to one another via a joint, can be moved into their two end positions by overcoming two dead center positions, in which they hold the welding device in the rest position or in the welding position. Advantageously, the toggle lever device is held at least in the two end positions by a force, preferably by a force emitted by a mechanical spring. The toggle lever device should only be able to move from one end position to the other by overcoming this force. The toggle lever device has the advantage that the end positions of the welding device can only be changed by overcoming comparatively high torques.Since this applies particularly to the welding position, the toggle lever device contributes to further increasing the functional reliability of the strapping device. Furthermore, the toggle lever device advantageously complements the drive train of the strapping device, which in one embodiment of the invention, in addition to the toggle lever device, also features a brushless DC motor and a planetary gear for automated transfer of the welding device to its welding position, since all components are capable of generating high torques or only execute movements when high torques are present.

[0017] Further preferred embodiments of the invention emerge from the claims, the description and the drawing.

[0018] The invention is explained in more detail using exemplary embodiments shown purely schematically in the figures, which show: Fig. 1 a perspective view of a strapping device according to the invention; Fig. 2 the strapping device from Fig. 1 without housing; Fig. 3 a partially sectioned view of the motor of the strapping device from Fig. 1 together with components arranged on the motor shaft; Fig. 4 a highly schematic representation of the motor together with its electronic circuit for commutation; Fig. 5 a perspective partial representation of the drive train of the strapping tool from Fig. 1 ; Fig. 6the drive train from Fig. 5 in a representation from a different perspective; Fig. 7 a side view of the drive train from Fig. 5 with the welding device in a rest position; Fig. 8 a side view of the drive train from Fig. 5 with the welding device in a position between two end positions; Fig. 9 a side view of the drive train from Fig. 5with the welding device in a welding position; Fig. 10 a side view of the tensioning device of the strapping tool without housing, in which a tensioning rocker is in a rest position; Fig. 11 a side view of the tensioning device of the strapping tool without housing, in which a tensioning rocker is in a tensioning position; Fig. 12 the tensioning rocker of the strapping tool shown partially in section Fig. 10 in a side view; Fig. 13 the clamping rocker from Fig. 12 in a front view; Fig. 14 a detail from Fig. 12 according to line C - C.

[0019] The Fig. 1 and 2The exclusively manually operated strapping tool 1 according to the invention shown has a housing 2 that encloses the mechanism of the strapping tool and on which a handle 3 is formed for handling the tool. The strapping tool is further provided with a base plate 4, the underside of which is intended for placement on an object to be packaged. All functional units of the strapping tool 1 are attached to the base plate 4 and to the strapping tool support (not shown in detail) connected to the base plate.

[0020] With the strapping tool 1, a Fig. 1A loop (not shown in more detail) of a plastic strap, for example made of polypropylene (PP) or polyester (PET)), which has previously been placed around the object to be packaged, is tensioned by means of a tensioning device 6 of the strapping device. For this purpose, the tensioning device has a tensioning wheel 7 with which the strap can be gripped for a tensioning process. The tensioning wheel 7 interacts with a rocker 8 which, by means of a rocker lever 9, can be pivoted about a rocker pivot axis 8a from one end position at a distance from the tensioning wheel to a second end position, in which position 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 sufficiently high for the packaging purpose.The tensioning process and the rocker 8 which is advantageously designed for this purpose will be explained in more detail below.

[0021] Subsequently, at a point on the strap loop where two layers of strap lie on top of each other, the two layers can be welded together using the friction welding device 8 of the strapping machine. This permanently seals the strap loop. For this purpose, the friction welding device 10 is equipped with a welding shoe 11, which melts the two layers of strapping by applying mechanical pressure to the strapping band and a simultaneous oscillating movement at a predetermined frequency. The plasticized or melted areas flow into one another, and after the band has cooled, a connection is formed between the two strap layers. If necessary, the strap loop can then be cut from a supply roll of strap using a cutting device (not shown in detail) of the strapping machine 1.

[0022] The actuation of the clamping device 6, the delivery of the friction welding device 10 by means of a transfer device 19 ( Fig. 6 ) of the friction welding device 10 as well as the use of the friction welding device itself and the actuation of the cutting device are carried out using only a common electric motor 14, which provides a drive movement for each of these components. For its power supply, an exchangeable accumulator 15 is arranged on the strapping device, which can be removed, in particular for charging. A supply of other external auxiliary energy, such as compressed air or additional electricity, is possible with the strapping device according to the Fig. 1 and 2 not provided.

[0023] In the present case, the portable mobile strapping device 1 has an actuating element 16 designed as a pressure switch, which is intended for starting the motor. Three modes can be set for the actuating element 16 using a switch 17. In the first mode, by actuating the actuating element 16, both the tensioning device 6 and the friction welding device 10 are triggered sequentially and automatically, without any further action by the operator. To set the second mode, the switch 17 is switched to a second switching mode. In the second possible mode, only the tensioning device 6 is triggered by actuating the actuating element 16. To trigger the friction welding device 10 separately, a second actuating element 18 must be actuated by the operator.In alternative embodiments, it can also be provided that in this mode the first actuating element 16 is actuated a second time to trigger the friction welding device. The third mode is a type of semi-automatic mode, in which the tensioning button 16 is pressed until the tensioning force or tensile stress in the strap, which can be preset in stages, is reached. In this mode, it is possible to interrupt the tensioning process by releasing the tensioning button 16, for example to attach edge protectors to the strapping material under the strapping band. The tensioning process can then be continued by pressing the tensioning button. This third mode can be combined with either a separately initiated or an automatically subsequent friction welding process.

[0024] On a Fig. 3A gear mechanism 13 is arranged on the illustrated motor shaft 27 of the motor, which is designed as a brushless, slotted internal rotor DC motor 14. In the exemplary embodiment shown here, a type ECI40 motor from Maxon Motor AG, Brünigstrasse 20, 6072 Sachseln, is used. The brushless DC motor 14 can be operated in both directions of rotation, with one direction of rotation being used to drive the clamping device 6 and the other direction of rotation being used to drive the welding device 10.

[0025] The Fig. 4The brushless DC motor 14, shown purely schematically, is designed with a slotted internal rotor 20 with three Hall sensors HS1, HS2, HS3. This EC motor (electronically commutated motor) has a permanent magnet in its rotor 20 and is provided with an electronic controller 22, which is provided for electronic commutation in the stator 24. The electronic controller 22 determines the respective instantaneous position of the rotor 20 via the Hall sensors HS1, HS2, HS3, which in the exemplary embodiment also assume the function of position sensors, and switches the electric magnetic field in the windings of the stator 24. The phases (phase 1, phase 2, phase 3) can thus be switched depending on the position of the rotor 20 in order to cause a rotational movement of the rotor in a specific direction of rotation, with a predeterminable variable speed and torque.In this case, a so-called "1-quadrant motor drive amplifier" is used, which supplies the motor with the voltage, as well as the peak and continuous current, and regulates them. The current flow for the coil strands of the stator 24 (not shown in detail) is controlled, i.e., commutated, via a bridge circuit 25 (MOSFET transistors). Furthermore, a temperature sensor (not shown) is provided on the motor. This allows the direction of rotation, rotational speed, current limit, and temperature to be monitored and controlled. The commutation is implemented as a separate printed circuit board and is housed separately from the motor in the strapping device.

[0026] The power supply is ensured by the accumulator 15, which is designed as a lithium-ion battery. Such batteries are based on several independent lithium-ion cells, in each of which chemical processes take place at least essentially separately from one another to generate a potential difference between two poles of the respective cell. In the exemplary embodiment, this is a lithium-ion battery from the manufacturer Robert Bosch GmbH, D-70745 Leinfelden-Echterdingen. The battery of the exemplary embodiment has eight cells and a capacity of 2.6 ampere hours. Graphite is provided as the active material or negative electrode of the lithium-ion accumulator. The positive electrode of the accumulator often comprises lithium metal oxides, particularly in the form of layered structures. Anhydrous salts such as lithium hexafluorophosphate or polymers are usually used as the electrolyte.The voltage delivered by a conventional lithium-ion battery is typically 3.6 volts. The energy density of such batteries is approximately 100 Wh / kg - 120 Wh / kg.

[0027] The transmission device 13 has a freewheel 36 arranged on the motor-side drive shaft, on which a sun gear 35 of a first planetary gear stage is arranged. The freewheel 36 transmits the rotational movement to the sun gear 35 only in one of the two possible directions of rotation of the drive. The sun gear 35 meshes with three planet gears 37, which mesh with a stationary ring gear 38 in a conventional manner. Each of the planet gears 37 is in turn arranged on a shaft 39 assigned to it, each of which is integrally connected to an output gear 40. The rotation of the planet gears 37 about the motor shaft 27 results in a rotational movement of the output gear 40 about 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 located on the freewheel 36 and is thus also mounted on the motor shaft.This freewheel 36 ensures that both the sun gear 35 and the output gear 40 rotate only in one direction of the rotational movement of the motor shaft 27. The freewheel 29 can, for example, be of the type INA HFL0615, as offered by Schaeffler KG, D-91074 Herzogenaurach.

[0028] The transmission device 13 further comprises, on the motor-side output shaft 27, a toothed sun gear 28 belonging to a second planetary gear stage. Although the shaft 27 passes through the recess of the sun gear 28, the shaft 27 is not connected to the sun gear 28. The sun gear is fastened to a disk 34, which in turn is connected to the planet gears 37. The rotational movement of the planet gears 37 about the motor-side output shaft 27 is thus transmitted to the disk 34, which in turn transmits its rotational movement to the sun gear 28 at identical speeds. The sun gear 28 meshes with several planet gears, namely three gears 31, each arranged on a shaft 30 running parallel to the motor shaft 27. The shafts 30 of the three gears 31 are stationary, i.e., they do not rotate about the motor shaft 27.The three gears 31, in turn, mesh with an internally toothed gear ring, which has a cam 32 on its outer side and is referred to below as cam gear 33. The sun gear 28, the three gears 31, and the cam gear 33 are components of the second planetary gear stage. The input-side rotational movement of shaft 27 and the rotational movement of cam gear 33 in the planetary gear are at a ratio of 60:1, i.e., the two-stage planetary gear provides a 60-fold reduction.

[0029] At the end of the motor shaft 27, a bevel gear 43 is also arranged on a second freewheel 42, which meshes with a second bevel gear (not shown in detail). This freewheel 42 also transmits the rotary motion only in one direction of rotation of the motor shaft 27. The directions of rotation in which the freewheel 36 of the sun gear 35 and the freewheel 42 transmit the rotary motion of the motor shaft 27 are opposite to each other. This means that in one direction of rotation, only the freewheel 36 rotates, and in the other direction, only the freewheel 42 rotates.

[0030] The second bevel gear is arranged at one end of a tension shaft (not shown in detail), which carries another planetary gear 46 at its other end ( Fig. 2). The drive movement of the electric motor in a specific direction of rotation is thus transmitted via the two bevel gears 43 to the tensioning shaft. Via a sun gear 47 and three planetary gears 48, the tensioning wheel 49 of the tensioning device 6, designed as an internally toothed ring gear, is thereby set in rotation. The tensioning wheel 7, which has a surface structure on its outer surface, entrains the respective strapping band during its rotational movement through frictional engagement, whereby the required strap tension is applied to the strap loop.

[0031] The output gear 40 is designed in the area of ​​its outer circumferential surface as a gear on which a toothed belt 50 of a sheath drive is arranged ( Fig. 5 and Fig. 6). The toothed belt 50 also wraps around a pinion 51, which is smaller in diameter than the output gear 40 and whose shaft drives an eccentric drive 52 for an oscillating back and forth movement of the welding shoe 53. Instead of a toothed belt drive, any other form of enveloping drive could be provided, for example a V-belt or chain drive. The eccentric drive 52 has an eccentric shaft 54, on which an eccentric 55 is arranged, on which in turn a welding shoe arm 56 with a circular recess is seated. The eccentric rotational movement of the eccentric 55 about the rotational axis 57 of the eccentric shaft 54 ​​leads to a translational oscillating back and forth movement of the welding shoe 53. Both the eccentric drive 52 and the welding shoe 53 itself can also be designed in any other previously known manner.

[0032] The welding device is further 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 is provided with a longer toggle lever 61 pivotally connected to the welding shoe arm 56. The toggle lever device 60 is further provided with a pivot element 63 pivotally connected about a pivot axis 62, which functions as a shorter toggle lever in the toggle lever device 60. The pivot axis 62 of the pivot element 63 runs parallel to the axes of the motor shaft 27 and the eccentric shaft 57.

[0033] The pivoting movement is initiated by means of the cam 32 of the cam wheel 33, which rotates counterclockwise - referring to the illustrations of the Fig. 7 to 9 - the cam wheel 33 passes under the swivel element 63 ( Fig. 8). A ramp-like surface 32a of the cam 32 contacts a contact element 64 inserted into the pivoting element 63. The pivoting element 63 is thereby rotated clockwise about its pivot axis 62. In the area of ​​a concave recess in the pivoting element 63, a two-part, longitudinally adjustable toggle lever rod of the toggle lever 61 is arranged according to the "piston-cylinder" principle and is pivotable about a pivot axis 69. The latter is also pivotally connected to a pivot point 65 of the welding shoe arm 56, designed as a further pivot axis 65, near the welding shoe 53 and at a distance from the pivot axis 57 of the welding shoe arm 56. A compression spring 67 is arranged between the two ends of the longitudinally adjustable toggle lever rod, by means of which the toggle lever 61 is pressed both against the welding shoe arm 56 and against the pivoting element 63.The pivoting element 63 is thus operatively connected with the toggle lever 61 and the welding shoe arm 56 with respect to its pivoting movements.

[0034] As in the representations of the Figs. 7 and 9 As can be seen, in the rest position there is an (imaginary) connecting line 68 of the two articulation points of the toggle lever 61, running through the toggle lever 61, between the pivot axis 62 of the pivot element 63 and the cam wheel 33, i.e. on one side of the pivot axis 62. By actuating the cam wheel 33, the pivot element 63 - with reference to the representations of the Fig. 7 to 9 - rotated clockwise. The toggle lever 61 is driven by the swivel element 63. 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 pivot axis 62 of the pivot element 63. In the Fig. 9In the end position of the movement (welding position) shown, the toggle lever 61 with its connecting line 68 is then located in relation to the cam wheel 33 and the rest position on the other side of the pivot axis 62 of the pivot element 63. During this movement, the welding shoe arm 56 is transferred by the toggle lever 61 from its rest position into the welding position by rotating about the pivot axis 57. In the latter position, the compression spring 67 presses the pivot element 63 against a stop (not shown in detail) and the welding shoe 53 onto the two layers of strip to be welded together. The toggle lever 61 and thus also the welding shoe arm 56 are thus in a stable welding position.

[0035] The representation of Fig. 6 and 9The counterclockwise drive movement of the electric motor is transmitted by the toothed belt 50 to the welding shoe 53, which is now moved into the welding position by the toggle lever device 60. The welding shoe 53 is pressed onto the two belt layers and moves back and forth in an oscillating motion. The welding time for creating a friction weld is determined by counting the adjustable number of revolutions of the cam wheel 33 from the time at which the cam 32 actuates the contact element 64. For this purpose, the number of revolutions of the shaft 27 of the brushless DC motor 14 is counted in order to determine the position of the cam wheel 33 at which the motor 14 is to be switched off and thus the welding process is to be ended. This is to prevent the cam 32 from remaining below the contact element 64 when the motor 14 is switched off.Therefore, for shutting off the motor 14, only relative positions of the cam 32 relative to the pivoting element 63 are provided in which the cam 32 is not located below the pivoting element. This ensures that the welding shoe arm 56 returns from the welding position back to the rest position (. Fig. 7 ) can pivot. This avoids in particular a position of the cam 32 in which the cam 32 would arrange the toggle lever 61 in a dead center position, ie in a position in which the connecting line 68 of the two articulation points the pivot axis 62 of the pivot element 63 - as in Fig. 8 shown - cuts. Since such a position is avoided, the rocker ( Fig. 2 ) from the tensioning wheel 7 and in the process the toggle lever 61 is moved in the direction of the cam wheel 33 into the Fig. 7The strapping tool can be swiveled to the position shown. Once the strap loop has been removed from the strapping tool, it is ready for another strapping process.

[0036] The described sequential processes of "tensioning" and "welding" can be triggered simultaneously in one switching state of the actuating element 16. To do this, the actuating element 16 must be actuated once, causing the electric motor 14 to initially rotate in the first direction, thereby (exclusively) driving the tensioning device 6. The strap tension to be applied to the respective strap can be adjusted on the strapping tool, preferably using a pushbutton, in nine steps corresponding to nine different strap tension values. Alternatively, a continuously variable adjustment of the strap tension could also be provided. Since the motor current depends on the torque of the tensioning wheel 7, which in turn depends on the current strap tension, the strap tension to be applied can be adjusted in the form of a limit value of the motor current in nine steps using pushbuttons on the control electronics of the strapping tool.

[0037] After reaching an adjustable and thus predeterminable limit value for the motor current or the belt tension, the motor 14 is shut down by its control unit 22. Immediately thereafter, the motor is operated by the control unit 22 in the reverse direction of rotation. As a result, the welding shoe 53 is lowered onto the two superimposed belt layers in the manner described above, and the oscillating movement of the welding shoe is carried out to create the friction welded joint.

[0038] By pressing switch 17, the actuating element 16 can be assigned the function of triggering the tensioning device. Once this setting has been made, pressing the actuating element activates only the tensioning device and deactivates it again once the preset belt tension is reached. To initiate the friction welding process, the second actuating element 18 must be activated. However, except for the separate activation, the function of the friction welding device is identical to the other mode of the first actuating element.

[0039] As already explained, the rocker 8 can be moved by operating the Fig. 2 , 10 , 11 The rocker arm 9 shown in the drawing performs pivoting movements around the rocker axis 8a. For this purpose, the rocker is pivoted by means of a bolt located behind the tensioning wheel 7 and therefore in Fig. 2not visible, rotating cam disc. Via the rocker lever 9, the cam disc can rotate by approximately 30° and move the rocker 8 or tensioning plate 12 relative to the tensioning wheel 7, which enables the strap to be inserted into the strapping device or between the tensioning wheel 7 and tensioning plate 12.

[0040] This also allows the toothed clamping plate 12 arranged in the area of ​​the free end of the rocker to be moved by a Fig. 10 shown rest position into one of Fig. 11The clamping plate 12 can be pivoted into the tensioning position and back again. In the rest position, the clamping plate 12 has a sufficiently large distance from the tensioning wheel 7 so that a strapping band can be arranged in two layers between the tensioning wheel and the clamping plate, as is necessary for forming a closure on a strap loop. In the clamping position, the clamping plate 12 is pressed against the tensioning wheel 7 in a manner known per se, for example by means of a spring force acting on the rocker, whereby, unlike in Fig. 11 As shown, during a strapping process, the two-layer strap is located between the tensioning plate and the tensioning wheel, and thus no contact should occur between the latter two. The toothed surface 12a (clamping surface) facing the tensioning wheel 7 is concavely curved, with the radius of curvature corresponding to the radius of the tensioning wheel 7 or being slightly larger.

[0041] As particularly in the Fig. 10 and11 as well as in the detailed representations of the Fig. 12 - 14 As can be seen, the toothed clamping plate 12 is arranged in a groove-shaped recess 71 of the rocker. The length - in relation to the belt running direction - of the recess 71 is greater than the length of the clamping plate 12. In addition, the clamping plate 12 is provided with a convexly curved contact surface 12b, with which it is mounted in the recess 71 of the rocker 8 on a flat support surface 72. As can be seen in particular from the Fig. 11 and 12 The convex curvature runs in a direction parallel to the strip direction 70, while the contact surface 12b is flat transverse to this direction ( Fig. 13). Due to this configuration, the clamping plate 12 is capable of performing tilting movements relative to the rocker 8 and the tensioning wheel 7 in the strap travel direction 70. Furthermore, the clamping plate 12 is fastened to the rocker 8 by a screw 73 passing through the rocker from below. For this purpose, the screw is located in an elongated hole 74 in the rocker, the longitudinal extension of which runs parallel to the strap travel 70 in the strapping device. In addition to being tiltable, the clamping plate 12 is also longitudinally displaceable on the rocker 8.

[0042] During a clamping process, the clamping rocker 8 is first moved from the rest position ( Fig. 10 ) into the clamping position ( Fig. 11). In the tensioning position, the spring-loaded rocker 8 presses the tensioning plate 12 in the direction of the tensioning wheel and in doing so clamps both strap layers between the tensioning wheel 7 and the tensioning plate 12. Due to different strap thicknesses, different distances of the tensioning plate 12 from the circumferential surface 7a of the tensioning wheel 7 can result. This not only results in different pivoting positions of the rocker 8, but also in different positions of the tensioning plate 12 in relation to the circumferential direction of the tensioning wheel 7. In order to nevertheless achieve uniform contact pressure, the tensioning plate 12 aligns itself automatically during the pressing process against the strap by a longitudinal movement in the recess 71 and a tilting movement via the contact surface 12b on the support surface 72 so that the tensioning plate 12 exerts as uniform pressure as possible on the strapping strap over its entire length.If the tensioning wheel 7 is now engaged, the teeth of the tensioning plate 12 hold the lower belt layer in place, while the tensioning wheel 7, with its toothed peripheral surface 7a, grips the upper belt layer. The rotational movement of the tensioning wheel 7 and the lower coefficient of friction between the two belt layers then cause the tensioning wheel to retract the upper belt layer, thus increasing the tension in the belt loop to the desired tensile stress value.

[0043] Further embodiments: 1. A mobile strapping device for strapping packaged goods with a strapping band, comprising a tensioning device for applying band tension to a loop of a strapping band, a connecting device for creating a connection at two superimposed areas of the loop of the strapping band, and a rechargeable energy storage device for storing energy that can be released as drive energy for motorized drive movements at least for the connecting device and / or for the tensioning device. 2. A strapping device according to embodiment 1, characterized by a connecting device designed as a friction welding device. 3.Strapping device according to embodiment 1 or 2, characterized in that the energy storage device comprises a lithium-ion accumulator, with which energy can be provided to drive a connecting device designed as a friction welding device. 4. Mobile strapping device according to at least one of the preceding embodiments, characterized by means for automatically shutting off the electric drive. 5. Mobile strapping device according to at least one of the preceding embodiments, characterized by means for determining the rotational position of the motor shaft or the position of an element arranged in the drive train of the welding device, dependent on the position of the motor shaft. 6. Mobile strapping device according to embodiment 5, characterized by at least one, preferably several, in particular at least three, detectors arranged on the electric drive for determining the rotational position of the motor shaft.Mobile strapping device according to embodiment 6, characterized by detectors for determining the rotational position of the motor shaft, which are also part of a circuit for controlling an electronically generated commutation of the electric drive. 8. Mobile strapping device according to at least one of the preceding embodiments, characterized in that a duration of a welding cycle during which the friction welding device is in use is adjustable, wherein the duration is predeterminable as a function of a number of revolutions of the electric drive. 9. Strapping device according to at least one of the preceding embodiments, characterized by a planetary gear for transmitting and changing the speed of a drive movement provided by an electric drive of the friction welding device. 10.Mobile strapping device according to at least one of the preceding embodiments, characterized in that the friction welding device is provided with a toggle lever device that can be pivoted between two end positions, wherein one end position of the toggle lever device defines a friction welding position and the other end position defines a rest position in which the friction welding device is not in use. 11. Mobile strapping device according to at least one of the preceding embodiments, characterized by a speed-controlled tensioning cycle of the tensioning device, during which the electric drive is operated at least temporarily at different speeds with at least substantially constant torque. 12.A method for strapping packaged goods with a strapping band using a mobile, battery-operated strapping device, in which a loop of a strapping band is placed around packaged goods, then a band tension is applied to the loop using a tensioning device of the strapping device, and a connection is created at two superimposed regions of the loop of the strapping band using a connecting device of the strapping device, characterized in that drive movements for a speed-controlled first tensioning process and a subsequent second tensioning process are provided by means of a brushless DC motor, wherein the second tensioning process is carried out at a reduced band retraction speed compared to the first tensioning process. 13.Method according to embodiment 12, characterized in that the first and second tensioning processes are carried out with essentially constant strip retraction speeds. List of reference symbols 1 Strapping tool 1 31 gear 2 Housing 32 cam 3 Handle 32a Area 4 Base plate 33 cam wheel 6 clamping device 35 sun gear 7 tension wheel 36 Freewheel 7a circumferential area 37 planetary gear 8 seesaw 38 ring gear 8a Rocker swivel axis 39 Wave 9 rocker lever 40 Output gear 10 Friction welding device 42 Freewheel 11 welding shoe 43 Bevel gear 12 clamping plate 46 Planetary gear 12a clamping surface 47 sun gear 12b Contact surface 48 planetary gear 13 Gearbox 49 tension wheel 14 electric DC motor 50 Timing belt 15 accumulator 51 pinion 16 Actuating element 52 Eccentric drive 17 Switch 53 welding shoe 18 Actuating element 54 Eccentric shaft 19 Transfer facility 55 eccentric 20 rotor 56 Welding shoe arm HS1 Hall sensor 57 Rotation axis eccentric shaft HS2 Hall sensor 60 Knee lever device HS3 Hall sensor 61 longer knee lever 22 electronic control 62 Swivel axis 24 stator 63 Swivel element 25 Bridge circuit 64 Contact element 27 engine-side output shaft 65 Swivel axis 28 sun gear 66 Swivel axis 30 Wave 67 compression spring 68 connecting line 73 screw 69 Swivel axis 74 slot 70 Band direction 71 recess 72 Support surface

Claims

1. A mobile strapping device (1), comprising: a tensioning device (6) for applying strap tension to a strap; a welding device (10) for creating a connection at two regions of the strap; wherein the welding device (10) can be transferred from a rest position to a welding position and from the welding position to the rest position by means of a toggle lever device (60).

2. Mobile strapping device (1) according to claim 1, wherein: the toggle lever device (60) is held in the rest position by a first force; and the toggle lever device (60) is held in the welding position by a second force; preferably by a force delivered by a mechanical spring (67).

3. Mobile strapping device (1) according to claim 2, wherein the toggle lever device (60) is designed such that transferring the welding device (10) comprises: overcoming the first force when the welding device (10) is transferred from the rest position to the welding position by means of the toggle lever device (60); and overcoming the second force when the welding device (10) is transferred from the welding position to the rest position by means of the toggle lever device (60).

4. Mobile strapping device (1) according to one of claims 1 to 3, wherein the toggle lever device (60) comprises levers (61, 63) connected to one another via a joint.

5. Mobile strapping device (1) according to claim 4, wherein the levers (61, 63) of the toggle lever device (60) are movable between a first configuration and a second configuration and between the second configuration and the first configuration; wherein the levers (61, 63) of the toggle lever device (60) hold the welding device (10) in the rest position when the levers (61, 63) are in the first configuration; and wherein the levers (61, 63) of the toggle lever device (60) hold the welding device (10) in the welding position when the levers (61, 63) are in the second configuration.

6. Mobile strapping device (1) according to one of claims 1 to 3, wherein the toggle lever device (60) comprises: a pivoting element (63); a toggle lever (61) connected to the pivoting element (63) and the welding device (10); wherein the pivoting element (63) and the toggle lever (61) are movable between a first configuration and a second configuration; wherein the first configuration is different from the second configuration; wherein the welding device (10) is in the rest position when the pivoting element (63) and the toggle lever (61) are in the first configuration; wherein the welding device (10) is in the welding position when the pivoting element (63) and the toggle lever (61) are in the second configuration.

7. Mobile strapping device (1) according to claim 6, further comprising a spring (67) configured to exert a first force on the pivot element (63) and a second force on the toggle lever (61) when the pivot element (63) and the toggle lever (61) are in the second configuration.

8. Mobile strapping device (1) according to claim 7, wherein the spring (67) at least partially encloses the toggle lever (61).

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