Patent ID: 12221238

The exclusively manually operated strapping device1in accordance with the invention shown inFIGS.1and2has a casing2, surrounding the mechanical system of the strapping device, on which a grip3for handling the device is arranged. The strapping device also has a base plate4, the underside of which is intended for placing on an object to be packed. All the functional units of the strapping device1are attached on the base place4and on the carrier of the strapping device which is connected to the base plate and is not shown in further detail.

With the strapping device1a loop of plastic strap, made for example of polypropylene (PP) or polyester (PET), which is not shown in more detail inFIG.1and which has previously been placed around the object to be packed, can be tensioned with a tensioner6of the strapping device. For this the tensioner has a tensioning wheel7with which the strap can be held for a tensioning procedure. The tensioning wheel7operates in conjunction with a rocker8, which by means of a rocker lever9can be pivoted from an end position at a distance from the tensioning wheel into a second end position about a rocker pivoting axis8a, in which the rocker8is pressed against the tensioning wheel7. The strap located between the tensioning wheel7and the rocker8is also pressed against the tensioning wheel7. By rotating the tensioning wheel7it 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 rocker8advantageously designed for this, is described in more detail below.

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 welder8of the strapping device. In this way the strap loop can be durably connected. For this the friction welder10is provided with a welding shoe11, 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 device1cutter which is not shown.

Operation of the tensioner6, assignment of the friction welder10by means of a transitioning device19(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 motor14, which provides a drive movement for each of these components. For its power supply, an interchangeable storage battery15, 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 withFIGS.1and2.

The portable mobile strapping device1has an operating element16, in the form of a press switch, which is intended for starting up the motor. Via a switch17, three operating modes can be set for the operating element16. In the first mode by operating the operating element16, without further action being required by the operator, the tensioner6and the friction welder10are started up consecutively and automatically. To set the second mode the switch17is switched over to a second switching mode. In the second possible operating mode, by operating the operating element16, only the tensioner6is started up. To separately start the friction welder10a second operating element18must be activated by the operator. In alternative forms of embodiment it can also be envisaged that in this mode the first operating element16has 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 button16must 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 button16, 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.

On a motor shaft27, shown inFIG.3, of the brushless, grooved rotor direct current motor14a gearing system device13is arranged. In the example of embodiment shown here a type EC140 motor manufactured by Maxon Motor AG, Brünigstrasse 20, 6072 Sachseln is used. The brushless direct current motor14can be operated in both rotational directions, whereby one direction is used as the drive movement of the tensioner6and the other direction as the drive movement of the welding device10.

The brushless direct current motor14, shown purely schematically inFIG.4, is designed with a grooved rotor20with three Hall sensors HS1, HS2, HS3. In its rotor20, this EC motor (electronically commutated motor) has a permanent magnet and is provided with an electronic control22intended for electronic commutation in the stator24. Via the Hall sensors, HS1, HS2, HS3, which in the example of embodiment also assume the function of position sensors, the electronic control22determines the current position of the rotor20and controls the electrical magnetic field in the windings of the stator24. The phases (phase1, phase2, phase3) can thus be controlled depending in the position of the rotor20, 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 stator24, which are not shown in more detail, is controlled via a bridge circuit25(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.

The power supply is provided by the lithium-ion storage battery15. 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.

On the motor side drive shaft, the gearing system device13has a free wheel36, on which a sun gear35of a first planetary gear stage is arranged. The free wheel36only transfers the rotational movement to the sun gear35in one of the two possible rotational directions of the drive. The sun gear35meshes with three planetary gears37which in a known manner engage with a fixed gear38. Each of the planetary gears37is arranged on a shaft39assigned to it, each of which is connected in one piece with an output gear40. The rotation of the planetary gears37around the motor shaft27produces a rotational movement of the output gear40around the motor shaft27and determines a rotational speed of this rotational movement of the output gear40. In addition to the sun gear35the output gear40is also on the free wheel36and is therefore also arranged on the motor shaft. This free wheel36ensures that both the sun gear35and the output gear40only also rotate in one rotational direction of the rotational movement of the motor shaft27. The free wheel29can for example be of type INA HFL0615 as supplied by the company Schaeffler KG, D-91074 Herzogenaurach,

On the motor-side output shaft27the gear system device13also has a toothed sun gear28belonging to a second planetary gear stage, through the recess of which the shaft27passes, though the shaft27is not connected to the sun gear28. The sun gear is attached to a disk34, which in turn is connected to the planetary gears. The rotational movement of the planetary gears37about the motor-side output shaft27is thus transferred to the disk34, which in turn transfers its rotational movement at the same speed to the sun gear28. With several planetary gears, namely three, the sun gear28meshes with cog gears31arranged on a shaft30running parallel to the motor shaft27. The shafts30of the three cog gears31are fixed, i.e. they do not rotate about the motor shaft27. In turn the cog gears21engage with an internal-tooth sprocket, which on its outer side has a cam32and is hereinafter referred to as the cam wheel33. The sun gear28, the three cog gears31as well as the cam wheel33are components of the second planetary gear stage. In the planetary gear system the input-side rotational movement of the shaft27and 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.

At the end of the motor shaft27, on a second free wheel42a bevel gear43is arranged, which engages in a second bevel gear, which is not shown in more detail. This free wheel42also only transmits the rotational movement in one rotational direction of the motor shaft27. The rotational direction in which the free wheel36of the sun gear35and the free wheel42transmit the rotational movement of the motor shaft27is opposite. This means that in one rotational direction only free wheel36turns, and in the other rotational direction only free wheel42.

The second bevel gear is arranged on one of a, not shown, tensioning shaft, which at its other end carries a further planetary gear system46(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 gear47as well as three planetary gears48the tensioning wheel49, in the form of an internally toothed sprocket, of the tensioner6is rotated. During rotation the tensioning wheel7, 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.

In the area of its outer circumference the output gear40is designed as a cog gear on which is a toothed belt50of an envelope drive (FIGS.5and6). The toothed belt50also goes round pinion51, smaller in diameter than the output gear40, the shaft of which drive an eccentric drive52for producing an oscillating to and fro movement of the welding shoe53. Instead of toothed belt drive any other form of envelope drive could be provided, such as a V-belt or chain drive. The eccentric drive52has an eccentric shaft54on which an eccentric tappet55is arranged on which in turn a welding shoe arm56with a circular recess is mounted. The eccentric rotational movement of the eccentric tappet55about the rotational axis57of the eccentric shaft54results in a translator oscillating to and fro movement of the welding shoe53. Both the eccentric drive52as well as the welding shoe53it can be designed in any other previously known manner.

The welding device is also provided with a toggle lever device60, 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 device60is attached to the welding shoe arm56and provided with a longer toggle lever61pivotably articulated on the welding shoe arm56. The toggle lever device60is also provided with a pivoting element63, pivotably articulated about a pivoting axis62, which in the toggle level device60acts as the shorter toggle lever. The pivoting axis62of the pivoting element63runs parallel to the axes of the motor shaft27and the eccentric shaft54.

The pivoting movement is initiated by the cam32on the cam wheel33which during rotational movement in the anticlockwise direction—in relation to the depictions inFIGS.7to9—of the cam wheel33ends up under the pivoting element63(FIG.8). A ramp-like ascending surface32aof the cam32comes into contact with a contact element64set into the pivoting element63. The pivoting element63is thus rotated clockwise about its pivoting axis62. In the area of a concave recess of the pivoting element63a two-part longitudinally-adjustable toggle lever rod of the toggle lever61is pivotably arranged about a pivoting axis69in accordance with the ‘piston cylinder’ principle. The latter is also rotatably articulated on an articulation point65, designed as a further pivoting axis65, of the welding shoe arm56in the vicinity of the welding shoe53and at a distance from the rotational axis57of the welding shoe arm56. Between both ends of the longitudinally adjustable toggle lever rod a pressure spring67is arranged thereon, by means of which the toggle lever61is pressed against both the welding shoe arm56as well as against the pivoting element63. In terms of its pivoting movements the pivoting element63is thus functionally connected to the toggle lever61and the welding shoe arm56.

As can be seen in the depictions inFIGS.7, in the rest position there is an (imaginary) connecting line68for both articulation points of the toggle lever61running through the toggle lever61between the pivoting axis62of the pivoting element63and the cam wheel33, i.e. on one side of the pivoting axis62. By operating the cam wheel33the pivoting element63is rotated clockwise—in relation to the depictions inFIGS.7to9. In this way the toggle lever61of the pivoting63is also operated. InFIG.8an intermediate position of the toggle lever61is shown in which the connecting line68of the articulation points65,69intersects the pivoting axis62of the pivoting element63. In the end position of the movement (welding position) shown inFIG.9the toggle lever61with its connecting line68is then on the other side of the pivoting axis62of the pivoting element63in relation to the cam wheel33and the rest position. During this movement the welding arm shoe56is transferred by the toggle lever61from its rest position into the welding position by rotation about the rotational axis57. In the latter position the pressure spring67presses the pivoting element63against a stop, not shown in further detail, and the welding shoe53onto the two strap layers to be welded together. The toggle lever61, and therefore also the welding shoe arm56, is thus in a stable welding position.

The anticlockwise drive movement of the electric motor shown inFIGS.6and9is transmitted by the toothed belt50to the welding shoe53, brought into the welding position by the toggle lever device60, 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 wheel33being counted as of the time at which the cam32operates the contact element64. For this the number of revolutions of the shaft27of the brushless direct current motor14is counted in order to determine the position of the cam wheel33as of which the motor14should switch off and thereby end the welding procedure. It should be avoided that on switching off the motor14the cam32comes to a rest under the contact element64. Therefore, for switching off the motor14only relative positions of the cam32with regard to the pivoting element63are envisaged, a which the cam32is not under the pivoting element. This ensures that the welding shoe arm56can pivot back from the welding position into the rest position (FIG.7). More particularly, this avoids a position of the cam32at which the cam32would position the toggle lever61at a dead point, i.e. a position in which the connecting line68of the two articulation points intersects the pivoting axis62of the pivoting element63—as shown inFIG.8. As such a position is avoided, by means of operating the rocker lever the rocker (FIG.2) can be released from the tensioning wheel7and the toggle lever61pivoted in the direction of the cam wheel33into the position shown inFIG.7. After the strap loop has been taken out of the strapping device, the latter is ready for a further strapping procedure.

The described consecutive procedures “tensioning” and “welding” can be jointly initiated in one switching status of the operating element16. For this the operating element16is operated once, whereby the electric motor14first turns on the first rotational direction and thereby (only) the tensioner6is 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 wheel7, 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.

After reaching a settable and thus predeterminable limit value for the motor current/strap tension, the motor14is switched off by its control device22. Immediately afterwards the control device22operates the motor in the opposite rotational direction. As a result, in the manner described above, the welding shoe52is 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.

By operating switch17the operating element16can 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 element18must be operated. However, apart from separate activation, the function of the friction welding device is identical the other mode of the first operating element.

As has already been explained, the rocker8can through operating the rocker lever9shown inFIGS.2,10,11carry out pivoting movements about the rocker axis8a. For this, the rocker is moved by a rotating cam disc which is behind the tensioning wheel7and cannot therefore be seen inFIG.2. Via the rocker lever9the cam disc can carry out a rotational movement of approximately 30° and move the rocker8and/or the tensioning plate12relative to the tensioning wheel7which allow the strap to be inserted into the strapping device/between the tensioning wheel7and tensioning plate12.

In this way, the toothed tensioning plate arranged on the free end of the rocker can be pivoted from a rest position shown inFIG.10into a tensioning position shown inFIG.11and back again. In the rest position the tensioning plate12is at sufficiently great distance from the tensioning wheel7that 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 plate12is pressed in a known way, for example by means of a spring force acting on the rocker, against the tensioning wheel7, whereby, contrary to what is shown inFIG.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 surface12a(tensioning surface) facing the tensioning wheel7is concavely curved whereby the curvature radius corresponds with the radius of the tensioning wheel7or is slightly larger.

As can be seen in particular inFIGS.10and11as well as the detailed drawings ofFIGS.12-14, the toothed tensioning plate12is arranged in a grooved recess71of the rocker. The length—in relation to the direction of the strap—of the recess71is greater than the length of the tensioning plate12. In addition, the tensioning plate12is provide with a convex contact surface12bwith which it is arranged on a flat contact surface71in the recess71of the rocker8. As shown in particular inFIGS.11and12the convex curvature runs in a direction parallel to the strap direction70, while the contact surface12bis designed flat and perpendicular to this direction (FIG.13). As a result of this design the tensioning plate12is able to carry out pivoting movements in the strap direction70relative to the rocker8and to the tensioning wheel7. The tensioning plate12is also attached to the rocker8by means of a screw72passing through the rocker from below. This screw is in an elongated hole74of the rocker, the longitudinal extent of which runs parallel to the course of the strap70in the strapping device. As a result in addition to be pivotable, the tensioning plate12is also arranged on the rocker8in a longitudinally adjustable manner.

In a tensioner the tensioning rocker8is initially moved from the rest position (FIG.10) into the tensioning position (FIG.11). In the tensioning position the sprung rocker8presses the tensioning plate in the direction of the tensioning wheel and thereby clamps the two strap layers between the tensioning wheel7and the tensioning plate12. Due to different strap thicknesses this can result in differing spacings between the tensioning plate12and circumferential surface7aof the tensioning wheel7. This not only results in different pivoting positions of the rocker8, but also different positions of the tensioning plate12in relation to the circumferential direction of the tensioning wheel7. In order to still achieve uniform pressing conditions, during the pressing procedure the tensioning plate12adjusts itself to the strap through a longitudinal movement in the recess71as well as a pivoting movement via the contact surface12bon contact surface72so that the tensioning plate12exerts as even a pressures as possible over its entire length on the wrapping strap. If the tensioning wheel7is then switched on the toothing of tensioning plate12holds the lower strap layer fast, while the tensioning wheel7grasps the upper strap layer with its toothed circumferential surface7a. The rotational movement of the tensioning wheel7as 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.

LIST OF REFERENCES1.Strapping device37.Planetary gear2.Casing38.Socket3.Grip39.Shaft4.Base plate40.Output gear6.Tensioner42.Free wheel7.Tensioning wheel43.Bevel gear7a.Circumferential surface46.Planetary gear system8.Rocker47.Sun gear8.Rocker pivoting axis48.Planetary gear9.Rocker lever49.Tensioning wheel10.Friction welder50.Toothed belt11.Welding shoe51.Pinion12.Tensioning plate52.Eccentric drive12a.Tensioning surface53.Welding shoe12b.Contact surface54.Eccentric shaft13.Gear system device55.Eccentric tappet14.Electric direct current motor56.Welding shoe arm15.Storage battery57.Rotational axis eccentricshaft16.Operating element60.Toggle lever device17.Switch61.Longer toggle lever18.Operating element62.Pivoting axis19.Transitioning device63.Pivoting element20.Rotor64.Contact element24.Stator65.Pivoting axis25.Bridging circuit66.Pivoting axis27.Motor side output shaft67.Pressure spring28.Sun gear68.Connecting line30.Shaft69.Pivoting axis31.Cog wheel70.Strap direction32.Cam71.Recess32a.Surface72.Contact surface33.Cam wheel73.Screw35.Sun gear74.Elongated hole36.Free wheelHS2Hall sensorHS1Hall sensorHS3Hall sensor