AU694711B1 - Device for strapping packages - Google Patents

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Signode Bernpak GmbH Actual Inventor(s): Karl-Hans Schuttler Address for Service: LPHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street S..:Melbourne 3000 AUSTRALIA Invention Title: DEVICE FOR STRAPPING PACKAGES Our Ref 520760 POF Code: 88757/88773 f The following statement is a full description of this invention, including the best method of performing it known to applicant(s): ft -1- I~c~=I The invention concerns a device to wrap packages with a thermoplastic strap, which is supplied from a strap supply to a strap guide channel surrounding the package and through the channel to a strap closing unit, which joins strap sections overlapping each other in the strap wrapping plane by means of frictional welding, s wherein before and after the overlapping region a strap clamp each is provided to press one strap section against a counter-support and in the region of overlapping of the strap sections an oscillator driven in an oscillating manner parallel to the plane of the strap displaces the strap section facing it relative to the other one in highfrequency oscillations which generate frictional heat and consequently welds the strap io sections to each other, wherein the clamping jaw of that strap section, which is grasped by the oscillator, is provided in a displaceable manner in or against at least one direction parallel to the plane of the strip.

The vibration welding by means of an oscillator driven at high frequency is achieved in the region of the strap closure as the oscillator moves one of the two overlapping strap sections with high frequency oscillations relative to the other strap section, thus generating frictional heat which melts the surfaces of the overlapping strap sections contacting each other, so that these will be joined with each other in a material-locking manner caused by melting.

It is known from DE 17 61 166 B1 to oscillate the oscillator, called vibrator, in 20 the longitudinal direction of the strap. Since the oscillator has to work against the tensile forces in the strap, no great tightening forces can be achieved particularly for packages which can be compressed only slightly or not at all. In addition, particularly high motive power is required for the oscillator. Incidentally, this is achieved so that at the joining position of the overlapping strap sections the tension prevailing in the 25 noose will be fully effective, since the strap material is clamped only between the vibrator and the gripper pressing against it from the other side of the strap. This type of strap closure formation is strongly afifected by wear.

S In the case of the device according to US 4,776,905 the overlapping strap sections are firmly pressed together on one side next to the oscillator, and the 30 oscillator moves the strap section, which is grasped by it, transversely to the longitudinal direction of the strap over the second strap section pressed against it by a counter-support. This transverse movement of the strap, in a manner different from CIWINWORI)tlGAYINODELTFl)7OD.nOC.

-I

that of the oscillation of an oscillator and the associated strap end in the longitudinal direction of the strap, leads in the production of the welded closure to a very high shear load of the strap section moved by the oscillator. This can easily tear during the formation of the closure particularly when great strap tensions are present.

To counteract this disadvantage, in the counter-support plate adjacent to the oscillator a button-shaped clamping body is provided, which can rotate freely about an axis which is perpendicular to the strap. However, this can absorb the transversal oscillations of the strap only to a limited extent, since it can execute only rotating movements at a distance from the oscillator moving linearly transversely to the strip.

Incidentally, in this frictional welding device there is the problem of the strap tearing earlier on that side of the oscillator which is facing away from the clamping device. As no second strap clamp is provided, and due to the thermal stress in the strap during the formation of the closure, only small tensioning forces can be achieved.

An applied development of the subject matter by US 4,776,905 provides that the button-shaped strap clamp, which can freely rotate about its longitudinal axis, is provided with an additional pivoting movement about a distant axis. Such a clamp can follow the transverse strap movement of the end of the strap carried by the oscillator on a larger radius and consequently slightly better, but still not to an optimum degree. Incidentally, the disadvantages mentioned in the case of the US 20 4,776,905 are present here also.

Furthermore, from EP 0 605 759, for example, a frictional welding device has become known, wherein the oscillator does not vibrate linearly in the longitudinal ~direction of the strap nor transversely to it, but is shaped as an annular disc, which, offset eccentrically, rotates about an axis which is perpendicular relative the surface of 25 the strap. The strap section, carried away by the oscillator, is thus subjected to a S tumbling or wobbling movement. In the annular body of the oscillator a pressure piece is integrated merely under spring pressure to guide the ends of the strap in the effective region of the oscillator and hold them against each other. In the case of the practical device strap clamps are provided in the direction of the strap's movement before and after this vibration welding unit, which basically permit to carry out the S closing of the strap while the wrapped around strap is under tension, but the strap in the closing region is under stress to a greater or lesser extent in all directions.

C:WINWORDIG/AYINODELTEi52(7().DOC ~II~ ~-IFIICIII~-~.il-C---- However, to limit the shear stresses occurring in the strap sections, strap clamps are present before and after the vibratory closing unit at great distance .from each other to have long freely displaceable strap sections available and make use of their expansion which are not illustrated in EP 0 605 795 Al, but are present in the case of the machine in practice, This has, however, the disadvantage that no small packages, e.g. bar material, can be wrapped.

DE 40 14 305 C2, on which this present invention is based, also addresses the problem of consequences of the strcp stress in a vibratory welding region, in which the strap sections to be joined with each other overlap each other and wherein before io and after this closing region one clamp each is provided which holds firmly only one section of the strap. This arrangement is achieved by that the strap clamp, which grasps that section of the strap which is acted upon by the oscillator, is itself driven by a mechanical active drive synchronously with the oscillator and moves on this occasion by taking with it the strap section parallel to the oscillating movement of the oscillator while this oscillating movement takes place at right angle to the longitudinal direction of the strap.

So that the driven clamping jaw would be able to carry effectively with it the strap section, on the side facing away from the clamping jaw it is pressed against a smooth counter-support surface. This will result, on the one hand, in great frictional S. 20 forces and consequent wear, and on the other the smooth surface of the countersupport leads, naturally, to smaller clamping forces. Because the clamping jaw is actively driven, the machine-related expense of the device is great, o•*.Proceeding from this, it would be desirable to provide a device for wrapping packages according to the frictional welding method which allows the formation of a 25 closure under great tensile forces in the strap, which also allows to wrap around S relatively small packages with great strap tension and whereby expensive additional drives for parts of the unit can be avoided.

According to an aspect of the present invention there is provided a device as described at the outset wherein the oscillator oscillates about an axis which extends 30 through the movable clamping jaw and wherein this oscillates about the same axis in the same direction as the oscillator, yet is moved by the oscillating strap section.

CI/WISWORD/GAYiNODEILETI21)gO.DOC.

I--asl II C IA Due to the fact that the oscillator oscillates about an axis which extends through the moving clamping jaw, the oscillator carries out about this axis a circular arc-shaped moved to and fro over a circular segment. Its movement is perpendicular to the longitudinal direction of the strap only at one point of the movement path, so that for this reason alone the section of the strap is subjected to a considerably smaller shear. When, according to the invention, the clamping jaw oscillates about the same axis in the same direction as the oscillator, there are no relative movements between the clamping jaw and the strap held by it. However, according to the invention the clamping jaw is not driven, but is merely moved by the oscillating strap section.

A moving of the clamping jaw in this sense had not been envisaged until now by the state-of-the-art under consideration.

According to a further development of the invention an optimum oscillatorsynchronous movement of the clamp jaw by the oscillating section of the strap is achieved when the counter-support, interacting with the moving clamping jaw, is a section of the oscillator itself. This will lead to the further advantage that all surfaces of the oscillator and clamping jaw, which are in contact with the surface of the strap, can have a friction-increasing construction, especially by being roughened or serrated, as no slippage is present between the surfaces contacting each other. The 20 result of this is that the clamping jaw can exert very great clamping forces. In .*addition, a very simple design is achieved.

The oscillator and the freely moving clamping jaw can be integrated particularly advantageously by that the oscillator is mounted on that end of a hollow shaft, which supports the moving clamping jaw both in an axially displaceable and rotatable 25 manner.

A further development of the invention provides that the frictional surface of the oscillator forms an angle of inclination with thL surface of an opposite situated oscillating counter-support, which is open in the direction of the oscillating axis of the oscillator towards the direction of the strap and has a magnitude of approx. 0.30 to 30 By virtue of this the different distance from the strap sections to the oscillating centre S is advantageously made use of in coordination with the pressures occurring.

Corresponding to the inclination of the angle the pressure decreases continuously C:IWINWOR~,GAY(NODMD-I b.O276DOC.

-a away from the oscillation axis with the increase of the oscillation path. Due to this extraordinarily uniform load on parts of the unit and the strap over the length of the closure to be produced and a completely homogeneous welding is achieved.

The angle of oscillation of the oscillator is, incidentally, small and is in the magnitude of approx. 40 to 5 0 According to a further feature of the invention the oscillator forms the head plate of the strap closing unit facing the package, it is mounted on the end of the hollow shaft and protrudes from there free into the strap wrapping plane. Based on this concept the entire strap closing unit can be pivoted away from the closing region, lo and by doing this the strap loop, wrapped around the package, can be released in a simple manner. The controlling means can also be executed in a simple manner. In this regard the features of claims 8 to 10 are of significance. A particularly essential advantage is that the drive shaft forms a central drive, by means of which all strokecontrolled operating parts of the strap closing unit can be controlled by the cycle.

The above features of the present invention will be more fully understood from the following description of a preferred embodiment of the invention with reference to the accompanying drawings, in which: Fig. 1 a schematic view of a wrapping machine, Fig. 2 a schematic illustration of the strap closing unit in a first position after inserting the strap surrounding a package, Fig. 3 an illustration of the closing unit corresponding to Fig. 2 with the strap tightened around the package, Fig. 4 an enlarged illustration from Fig. 3, showing only the closing region of the device, wherein for clarity's sake no surface roughenings are shown, 25 Fig. 5 a schematic cross-section through the closing unit in the region of the C C° oscillator, corresponding to the operating positions of Figs. 3 and 4, Fig. 6 an enlarged illustration to explain the geometry and the operation of the oscillator and the clamping jaw, and Fig. 7 an illustration, corresponding to Fig. 4, of the unit's position at the end S: 30 of a working cycle.

°A strap wrapping machine in its totality is designated in Fig. 1 by the reference numeral 10. On its machine base 11 there is a basically enclosed strap guide C. I1NWOR),'GAINODELTM4 760.DOC, llil4aal C- r i is channel 12, through which and around a package 13, indicated in dot-dash lines, a strap 14 made of a thermoplastic material is introduced to a strap closing unit 15. The task of this unit is to weld the overlapping end sections of the strap 14 guided around the package 13 to each other by means of frictional welding by means of heat generation.

The strap 14 is stored outside the machine stand 11 on a rotatably mounted strap winder (drum 55). First the strap 14 runs through a pair of rollers 16 on the entry side of the machine, the two rollers grasping by friction opposite situated strap surfaces, the rollers being tensioned against each other and held under pressure io against the strap 14. The motor drive of this pair of rollers 16 transports the strap 14 to a strap magazine 17, which stores without tensioning such a length of the strap 14 which comprises at least for the following wrapping and the length of the path of the strap 14 to the closing unit In the strap supply device a second pair of rollers 18 is provided on the strap magazine 17. These two rollers of this pair of rollers 18 also drive the strap by friction. This pair of rollers 18 is driven reversibly, as they serve on the one hand for the insertion of the strap 14 into the strap guide channel 12 and, in the reverse direction, for the withdrawing of the strap 14 and its tightening around the package 13.

In the last mentioned sense the pair of rollers 18 is a so called low tension tightening 20 device.

In the strap supply device a high tension tightening device, by means of a tensioning drum 19, is provided downstream to the insertion and withdrawing pair of rollers 18, which drum is the subject matter of another patent application and is of no further significance in this case. This tensioning drum 19 is followed by a special 25 strap clamp 20 and a guide channel 21, through which the strap 14 travels to the strap closing unit.

Fig. 2 shows details of the strap closing unit 15. According to this illustration the strap 14 is conveyed by means of the inserting pair of rollers 18 through the tensioning drum 19 and the strap guide 21 to the strap closing unit 15, until the 30 leading edge 14' of the strap abuts against a so called insertion switch 23.

On its way to this switch, the free leading edge 14' of the strap passes through a separator slot 24 in a first strap clamp 25 and then a separator 26 serving as a strap C.:WINWORIl)IGAY/NOl3E.Et5207(A).DOC.

a qt~ guide inside of a so called welding clamp 27. The purpose of both separator slots is to keep the sections of the strap in the region of their overlap (initially) away from each other and to enable an unhindered cutting off of the bottom strap section.

The actuation of the insertion switch 23 by the leading free edge 14' of the strap signals the machine control that the machine is in its initial position and carries out practically a 'reset'. This initial position is characterised in that a section of the strap 14, capable to be wrapped around, is already stored inside the strap guide channel 12 (Fig. 1).

The wrapping process commences by a machine command initiated by pressing a button, after which the package 13 is placed in the channel 12. The pair of rollers 18 receives the command to reverse the drive and pulls back the strap 14, which due to the frictional forces exerted by the pair of rollers 18, begins to tighten the package 13, because the first strap clamp 25 holds firmly the front section 14 of the strap by pressing it against the undersurface of the head plate 22.

If the package 13 is to be subjected to a strap tensioning greater than that which can be exerted by the low tension pair of rollers 18 against the strap 14, the S high tension tensioning drum switches on in the strap tensioning operation in a rotating manner and by this tightens the strap with a greater tension.

Fig. 3 shows such a tightened state of the strap, showing additionally that the 20 separator 26 (Fig. 2) has been pivoted out from its operating position laterally, S subsequently the welding clamp 27 and a second strap clamp 41, arranged on the outside next to it, are displaced upward, locking the strap 14.

A separating knife 46, mounted on the welding clamp 27, has separated the strap length required for the wrapping from the strap supply. At this stage the strap 14, tightened around the package 13, is situated in the welding position to form a strap closure.

According also to Fig. 4, which shows the essential operating position on a larger scale than Fig. 3, this position is characterised mainly in that the front edge of the strap is held by the clamping jaw 25' of the first strap clamp 25 interacting with the head plate 22 on one side of the closure forming zone, whereas the clamping jaw 41' of the strap clamp 41 presses the other end 14" of the strap against the other side of the strap closing zone against a clamping block 42. Accordingly, each clamping jaw ih),TDOC.

and 41' holds firmly only one strap section, and the overlapping strap sections 43 and 44, which are to be joined to each other, are between them in the strap closing zone. The strap closing zone is free of the strap tensioning forces resulting from the wrapping around.

The head plate 22 is simultaneously the oscillator or vibrator and is driven in an oscillating manner about the vertical axis, designated by 29. The axis of oscillation 29 is at the same time the central axis of the strap clamp 25 with the clamping jaw which can rotate freely about this axis. The arrangement is such, that the bearing shaft 30 of the strap clamp 25 is guided in a hollow shaft 31. As Figs. 5 and 7 show, lo the hollow shaft 31 is joined with the oscillator-head plate 22 as a unit moving together.

The drive of the oscillator 22 is carried out by means of a motor 33, flangemounted on a bearing block 32, the motor driving via an eccentric shaft 34 an oscillating fork 35 in an oscillating manner, which fork is joined to the hollow shaft 31 in a manner preventing their rotation relative each other. Consequently, the oscillator 22 carries out oscillating movements about the vertical axis 29. This is illustrated in Fig. 6, wherein one end position of the oscillation is indicated with a full line, the other one with a dot-dash line. A top view on the oscillator 22 is shown, which is partly broken to make the clamping jaw 25' of the strap clamp 25, situated below it, visible.

S 20 The oscillating movement of the oscillator 22 leads to that on the one hand the strap section 43, grasped by the oscillator 22, moves to and fro over a circular sector relative to the strap section 44 held firmly by the welding clamp 27, this resulting in frictional heat and consequently in the fusing of the surfaces of the overlapping strap sections facing each other. The angle of oscillation is held small at approx. 4-50, S 25 contributing to both the protection of the strap and parts of the unit and has a wear and noise reducing effect.

For an optimum distribution of the pressure forces which occur during the frictional welding process, the surface 28, which grasps the strap section 44, is inclined at an angle of w relative to the under-surface 22 of the oscillator, which grasps the strap section 43. The angle w, whose apex is in or near to the axis of oscillation 29, is open from there over the clamping path to the outside. By virtue of the inclination angle w, which is approx. 0.70, the friction path and the pressure are CfVINWOI(I)IOAYJNOr)ELTI!.52fl760.t) I I coordinated so that with the increasing oscillation travel, i.e. in the direction of the opening of the angle w, the force will become slightly smaller. This also contributes to a considerably lesser wear and noise of the device as well as to a homogeneous welding.

The strap section 43, oscillated by the oscillator 22, is also pressed against the underside of the oscillator 22 by the clamping jaw 25' of the first strap clamp 25, so that the strap section 43, driven in an oscillating manner by the oscillator 22, carries with it the clamping jaw 25' of the strap clamp 25, guided rotatably in the hollow shaft 31 of the oscillator 22. Consequently, the shearing forces acting on the strap section 43 will be kept so small, that they will not have a damaging effect on a reliable closure which can be carried out also with highly tensioned strap.

After the strap has been closed in the manner described above, the strap clamps 25 and 41 as well as the welding clamp 27 move downward from the position shown in the drawings, and all stroke-controlled devices of the closing unit, in particular the oscillator 22 and the strap clamp 25 integrated in it, are pivoted laterally from the plane in which the strap is closed. This is shown in Fig. 7, in which S: additionally the separator 26, pivoted in the opposite direction, can be seen.

The control of the moving operating parts is carried out centrally via a control shaft 45 with a control cam 47 for the stroke-controlled strap clamp 25, a control cam 20 48 for the welding clamp 27 and a control cam 49 for the second strap clamp 41. As a result of the outward pivoting of the parts of the unit the wrapped around package can be removed particularly simply from the machine table.

.9 C(WINWORD'GAYNODEI.T15.21nM).DOC.

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Claims (11)

1. A device to wrap packages with a thermoplastic strap, which is supplied from a strap supply to a strap guide channel surrounding the package and through the channel to a strap closing unit, which joins strap sections overlapping each other in the strap wrapping plane by means of frictional welding, wherein before and after the overlapping region a strap clamp each is provided to press one strap section against a counter-support and in the region of overlapping of the strap sections an oscillator driven in an oscillating manner parallel to the plane of the strap displaces the strap section facing it relative to the other one in high-frequency oscillations which generate lo frictional heat and consequently welds the strap sections to each other, wherein the clamping jaw of that strap section, which is grasped by the oscillator, is provided in a displaceable manner in or against at least one direction parallel to the plane of the strip, wherein the oscillator oscillates about an axis which extends through the movable clamping jaw and wherein this oscillates about the same axis in the same direction as the oscillator, yet is moved by the oscillating strap section.

2. A device according to claim 1, wherein the counter-support which interacts with Sthe moving clamping jaw is a section of the oscillator itself.

3. A device according to claim 1 or claim 2, wherein the oscillator is mounted on the end of a hollow shaft, which supports the moving clamping jaw both in an axially e*eoC* 20 displaceable and rotatable manner.

4, A device according to any one of claims 1 to 3, wherein the frictional surface of the oscillator forms an angle of inclination with the surface of an opposite situated oscillating counter-support (welding clamp), which is open in the direction of the oscillating axis of the oscillator towards the direction of the strap.

5. A device according to claim 4, wherein the angle of inclination has a magnitude of approx. 0.30 to

6. A device according to any one of claims 1 to 5, wherein the angle of oscillation S of the oscillator has a magnitude of approx. 40 to

7. A device according to any one of claims 1 to 6, wherein the oscillator forms the head plate of the strap closing unit facing the package, it is mounted on the end of the hollow shaft and protrudes from there unilaterally free into the strap wrapping plane. ('I'WINWORD,'GAYiNODELETW7b60.D(W.K' -e -I

8. A device according to any one of claims 1 to 7, wherein the moving strap clamp, which is associated with the oscillator, has a shaft passing through the hollow shaft, which shaft forms the push-rod for its stroke control, which push-rod can be acted upon on its face by a control surface as component of a control member like cam or cam plate, which control member is mounted on a drive shaft extending parallel to the plane of wrapping.

9. A device according to claim 8, wherein the drive shaft carries control members for all stroke-controlled operating parts of the strap closing unit and thus forms a central drive.

10. A device according to claim 8 or claim 9, wherein the stroke-controlled parts of the strap closing unit, like strap clamps, strap separating knife and oscillator counter- support as well as the stroke-constant operating parts interacting with them, like oscillator and clamp counter-support are guided or held firmly in a common carrier, which carrier is pivotably mounted about the axis of the central drive shaft and can be pivoted by means of additional control surfaces moved by it in such a manner that the strap closing unit can be moved out temporarily altogether from the strap wrapping plane.

11. A device to wrap packages with a thermoplastic strap substantially as herein described with reference to the accompanying drawings. DATED: 17th March, 1998 PHILLIPS ORMONDE FITZPATRICK Attorneys for: SIGNODE BERNPAK GmbH a dl CIWIN'WORD;fGAYiNODELLTI5217bUflO. I I ABSTRACT The invention concerns a device (10) to wrap packages with a thermoplastic strap which is supplied from a strap supply to a strap guide channel (12) surrounding the package (13) and through the channel to a strap closing unit which joins strap sections 14") overlapping each other in the strap wrapping plane by means of frictional welding, wherein before and after the overlapping region a strap clamp (25, 41) each is provided to press one strap section 14") against a counter-support (22, 42) and in the region of overlapping of the strap sections (43, 44) an oscillator (22) driven in an oscillating manner parallel to the plane of the strap (14) displaces the strap section facing it relative to the other one in high- frequency oscillations which generate frictional heat and consequently welds the strap sections (43, 44) to each other, and wherein the clamping jaw of that strap .0.0 section which is grasped by the oscillator is provided in a displaceable manner in or against at least one direction parallel to the plane of the strap. Having 15 the aim of a simple design for the apparatus, a device avoiding shear stresses on the i. end of the strap which is moved by the oscillator is produced in that the oscillator oscillates about an axis (29) which extends through the movable clamping j and that this oscillates about the same axis in the same direction as the oscillator, yet is moved by the oscillating strap section. 0 w 0 0 4.o ClWiWoa GIGhnAYiNOOEl.E'F-i20760.OC. ~L