WO2013167172A1

WO2013167172A1 - Ultrasonic bonding device

Info

Publication number: WO2013167172A1
Application number: PCT/EP2012/058450
Authority: WO
Inventors: Patrik FJELDSA
Original assignee: Sca Hygiene Products Ab
Priority date: 2012-05-08
Filing date: 2012-05-08
Publication date: 2013-11-14

Abstract

An ultrasonic bonding device includes an anvil (10) and a horn (20), wherein the anvil (10) includes an anvil element (11) and the horn (20) includes a horn element (21) facing the anvil element (11), so that a gap (G) is provided between facing surfaces of these elements (11, 21) for receiving the material to be bonded. At least one mechanical stop is provided in order to maintain a minimum size of the gap (G) which is larger than zero, so as to avoid contact between the anvil element (11) and the horn element (21). Alternatively or in addition, the anvil (10) further includes a jam protection unit which allows the gap (G) to be further increased in case a force acting within the gap (G) to separate the anvil element (11) from the horn element (21) exceeds a predetermined value.

Description

ULTRASONIC BONDING DEVICE

TECHNICAL FIELD

The present invention refers to an ultrasonic bonding device.

Ultrasonic bonding devices according to the present invention may be particularly, but not exclusively, used for forming ultrasonic seams during the manufacture of absorbent articles such as a pants-type diapers, sanitary pants or incontinence garments. These absorbent articles often include non-woven layers and/or film layers which are integrated with each other by means of ultrasonic seams.

BACKGROUND OF THE INVENTION

When ultrasonically bonding, the materials to be bonded together are worked mechanically by moving the end of an ultrasonic horn up and down, while in contact with the material, with a frequency that lies within the ultrasonic range. Heat is generated in the material as a result of the internal friction created by this mechanical working process, causing the material to melt in the worked area so that materials located in between horn and an opposing anvil will melt and therewith fuse together.

When bonding moving webs of material, the anvils often comprise a suitable pattern of projections on a pattern cylinder or drum, so as to provide a patterned seam. The specific pattern of such a seam may have an influence on the strength of the seam.

Ultrasonic bonding devices are used for bonding continuous material webs or discrete pieces of material. In the latter case, the material is intermittently fed through the gap between the anvil and the horn. During the intervals in which no material is present there between, a contact of the horn and anvil is to be prevented in order to avoid damage to the components. In prior art devices, a very stiff construction with a minimum extent of deflection in the mechanical parts has been required for this purpose. A known solution includes a gap force control with a step motor.

The use of an ultrasonic bonding technique for forming seams of absorbent articles of the type indicated above provides the advantages that the seams become relatively soft and less stiff than it is the case with other connection methods. The softer the seam, the smaller the probability that the seams will be uncomfortable for the wearer.

However, ultrasonic bonding devices are quite sensitive and can easily be damaged by high peak forces resulting from splices passing the bonding area or crashes occurring in the bonding area. In the case of a material jam, extremely high forces in the order of 10.000 N may act onto the anvil and horn, often resulting in damage to the components of the device. For this reason, ultrasonic bonding is presently avoided in product areas where the system could get damaged, and the layers are connected by other means instead, e.g. by means of glue.

DISCLOSURE OF THE INVENTION

In the light of the above, it is the object underlying the present invention to provide an ultrasonic bonding device in which a contact between the anvil and the horn is avoided at all times and by simple measures.

This object is solved by an ultrasonic bonding device according to claim 1. The ultrasonic bonding device includes an anvil and a horn. The anvil includes an anvil element, and the horn includes a horn element facing the anvil element, so that a gap is provided between facing surfaces of these elements for receiving the material to be bonded. At least one mechanical stop is provided in order to maintain a minimum size of the gap which is larger than zero, so as to avoid contact between the anvil element and the horn element.

Preferred optional features are recited in the associated dependent claims.

The at least one mechanical stop is suitably formed between opposing portions of the anvil and the horn.

At least one of the mechanical stops may provide a hinge about which the anvil and the horn may pivot relative to each other.

The anvil and the horn may be pivotable relative to each other about a pivoting axis which is parallel to a travelling direction of a material travelling through the gap, or about a pivoting axis which is perpendicular to said travelling direction.

At least one mechanical stop may further be adjustable so as to increase or reduce the size of the gap in accordance with the type of materials to be bonded and further process conditions.

In order to achieve this adjustability, the at least one mechanical stop may, for example, include a tapered element which is slidably received between facing portions of the anvil and the horn in order to set the size of the gap.

Alternatively or in addition, the device may include a set of adjustment elements of different sizes which can be selectively employed so as to set the size of the gap.

According to a preferred embodiment, several mechanical stops are used which are spaced apart from each other, e.g. along a support shaft of the anvil element or the horn element. The mechanical stops may together define three distinct contact points between the horn and the anvil. Three distinct contact points provide for a stable connection between the horn and anvil. For example, a first mechanical stop defines two distinct contact points between the horn and the anvil, and a second mechanical stop defines a third contact point between the horn and the anvil.

Another object of the present invention is to provide an ultrasonic bonding device which is able to endure a jam of material in the gap between the anvil element and the horn element .

This object is solved by an ultrasonic bonding device according to claim 11. The ultrasonic bonding device again includes an anvil and a horn, and the anvil includes an anvil element, while the horn includes a horn element facing the anvil element, so that a gap is provided between facing surfaces of these elements for receiving the material to be bonded. The anvil further includes a jam protection unit which allows the gap to be further increased in case a force acting within the gap, so as to separate the anvil element and the horn element from each other, exceeds a predetermined value.

Preferred optional features are recited in the associated dependent claims.

The anvil may further include an anvil bracket supporting the anvil element, and the horn may further include a horn bracket supporting the horn element. The anvil bracket may in turn be supported in a frame of the device, preferably in a pivotable manner. As an alternative, the anvil bracket could also be, for example, slidably supported. Further alternatively, it would generally also be possible to have the horn bracket movably supported while the anvil bracket remains stationary. However, the anvil bracket generally has a smaller mass and is therefore less inert than the horn bracket, which would allow the anvil bracket to move more quickly.

Furthermore, the device preferably includes means for urging the anvil element and the horn element towards each other with a force which is smaller than the predetermined value. These urging means may include at least one pneumatic cylinder, at least one spring, and/or alternative urging means as they are per se known in the art.

In case it is the anvil bracket which is movably supported relative to the horn bracket, the urging means are suitably so arranged and constructed as to press the anvil bracket against a fixed stop mounted to or integrated with a frame of the device. During normal operation, the anvil bracket is then pressed against this fixed stop. Only in the event of a splice passing the bonding area or a material jam in the bonding area, the anvil bracket may pivot away from the horn bracket against the force applied by the urging means.

Both the above measures can also be combined into an ultrasonic bonding device having both the at least one mechanical stop of claim 1 and the jam protection unit of claim 11.

Finally, the anvil element and/or the horn element may be stationary elements, or they may be provided in the form of rotatably supported rollers . Such rotary horns and/or anvils are often used when bonding moving webs of material.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic view of the main components of an ultrasonic bonding device according to a first embodiment of the present invention.

Figure 2 is a cross sectional view along the line A-A in Figure 1. Figure 3 is a cross sectional view along the line B-B in Figure 1.

Figure 4 is a schematic view of the main components of an ultrasonic bonding device according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Two different embodiments of an ultrasonic bonding device according to the present invention will now be described with reference to the attached drawings.

The ultrasonic bonding device may be particularly, but not exclusively, used for forming ultrasonic seams during the manufacture of absorbent articles such as a pants-type diapers, sanitary pants or incontinence garments. These absorbent articles often include non-woven and/or film layers which are integrated with each other by means of ultrasonic seams. For example, side seams or standing gathers of such absorbent articles are bonded.

In Figures 1 to 3, the main components of an ultrasonic bonding device according to a first embodiment of the present invention are shown in a schematic manner. The device includes an anvil 1 and a horn 2 (also known as sonotrode) which are supported in a frame, of which frame portions 3 and 4 are schematically illustrated. The frame is configured so that the horn 2 rests onto the anvil 1 with a certain pressure.

The horn 2 includes as an ultrasonic booster 5 as it is per se known in the art.

The Figures further show that the anvil 1 and horn 2 include an anvil bracket 10 and a horn bracket 20, respectively, which in turn accommodate an anvil element 11 and a horn element 21, respectively. The material to be bonded would be fed through a gap G formed between the facing surfaces of these elements 11, 21, The travelling direction T of the material runs into the plane of projection in Figure 1 or in the horizontal direction in the cross-sectional view of Figure 3, respectively. In the present embodiment, the horn element 21 is stationary, while the anvil element 11 is rotatable. The rotatable anvil element 11 is supported by means of an articulated shaft 12. The anvil element 11 and/or the horn element 21 may be patterned so as to achieve a patterned ultrasonic seam.

The device may be used for bonding continuous material webs or discrete pieces of material. In the latter case, the material is intermittently fed through the gap G. During the intervals in which no material is present between the elements 11 and 21, but the ultrasonic vibrations continue to be applied, a metal contact of the anvil and horn elements 11 and 21 with each other is to be avoided in order to prevent the elements from wearing.

For this purpose, the gap G between the anvil 1 and the horn 2 is maintained by means of mechanical stops. In the present embodiment, there are two mechanical stops which are spaced apart from each other along the axis of the articulated shaft 12, one employing a round bar 30 and the other one employing a tapered key 40 with a stop screw 41.

The first mechanical stop defines a distance between two support portions 13 of the anvil 1 and two support portions 23 of the horn 2 which are positioned opposite the support portions 13. The round bar 30 is disposed between the opposing anvil and horn portions 13, 23. The anvil support portions 13 are spaced apart from each other in a direction perpendicular to the axis of the articulated shaft 12, and the same applies to the horn support portions 23.

The second mechanical stop defines a distance between a single support portion 14 of the anvil and an opposing single support portion 24 of the horn. The tapered key 40 is disposed between the opposing anvil and horn portions 14, 24.

The front and rear stops together form an three point configuration (two contact pairs 13, 23 and one contact pair 14, 24).

Both stops are adjustable in order to set the distance between horn bracket 20 and anvil bracket 10 or the size of the gap G, respectively. In the present embodiment, the adjustment takes place by adjusting the vertical position of the horn support portions 23, 24 vis-a-vis the facing anvil support portions 13, 14.

More particularly, in order to adjust the first mechanical stop, the anvil support portion 13 has been divided into an approximately U-shaped base part 13a and two crown parts 13b positioned on top of the legs of the U-shaped base part 13a. The vertical extension of the anvil support portion 13 is determined by interposing shims 50 between the base part 13a of the anvil support portion 13 and each of the two crown parts 13b thereof. By using shims 50 of different thicknesses, the height of the anvil support portion 13 can be adjusted as desired so as to adapt the size of the gap. If compared with the fine adjustment effected by adjusting the second mechanical stop, which will be described further below, the use of the shims 50 allows for a coarse adjustment of the gap size, e.g. in reaction to a change in the dimensions of the anvil element 11 or the horn element 21. The shims 50, which may for example have the shape of rectangular platelets, may be fixed between the base part 13a and the crown parts 13b by means of screws or the like. By means of the shims 50, the size of the gap G can be adjusted in an easy but still accurate manner.

The second mechanical stop is adjustable by displacing the tapered key 40 perpendicular to the axis of the shaft 12 by means of the stop screw 41. For setting the gap G, one would set the first stopper first, and then adjust the tapered key 40 of the second stopper. By means of the tapered key 40, a very precise adjustment is possible. By slightly reducing or increasing the distance between the opposing anvil and horn portions 14, 24, the horn 2 is made to pivot about the round bar 30 as a pivoting axis. Insofar the round bar 30 has a double function as a stopper on the one hand and a hinge on the other hand. In addition, the round bar 30 also prevents the anvil and horn from rotating relative to each other in a horizontal plane.

If compared with, for example, the known gap force control mentioned above, the present solution provides the advantages that the unit is more compact, simpler in structure, less expensive, and has an improved mechanical stability.

In case the material is intermittently fed through the gap G, any metal contact of the anvil and horn elements 11 and 21 with each other is avoided during the intervals in which no material is present between the elements 11 and 21, but the ultrasonic vibrations continue to be applied, so that the elements 11 and 21 are prevented from wearing.

The advantages of the present invention do, however, not only become apparent when the material travels through the gap in a completely intermittent manner. There are also cases in which a relatively thin, continuous web of material is fed through the gap, and further layer (s) of material is/are intermittently placed onto said thin layer. The welding seam is only required in the area of these further layers, but he ultrasonic vibrations are continuously applied, i.e. also during the intervals in which only the thin material layer passes the gap. This could easily lead to the thinner material being welded through. Also in such cases, the gap G is securely maintained in the present device, so that any welding through of the thinner material in between these portions is avoided. In accordance with the present embodiment, the ultrasonic bonding device further includes a jam protection unit.

In the present embodiment, the jam protection unit employs a hinged support of the anvil bracket 10: The anvil bracket 10 is provided with shaft ends 60 (cf. Figs. 1 and 3), which engage with shaft support brackets 65 installed in the frame part 4 so as to form the hinge. In the case of a material jam in the gap G, the anvil bracket 10 can therefore pivot away from the horn bracket 20.

The support brackets 65 also prevent the hinged anvil bracket 10 to move sidewards.

In the device of the present embodiment, the force applied to the material being bonded at the gap G between the anvil element 21 and the horn element 11 is controlled by means of pressure-adjustable air cylinders 17 pushing against the anvil bracket 10. The force exerted at the gap G may thus be set to different levels for different materials through adjustment of the air pressure in the cylinders 17. To mention an example, two single acting, 50 mm diameter pneumatic cylinders 17 with 10 mm stroke could be used. In case there is sufficient space available, the cylinders could as well have a stroke of, for example, 15 or 20 mm. Instead of two cylinders one could also use only one or more than two cylinders.

Protrusions 15 formed on the anvil bracket 10 are pressed against fixed stoppers 16 mounted to the frame part 4 (cf. Figure 3) .

Figure 1 also shows a rigid plate 70 provided at the frame part 4 of the ultrasonic bonding device, to which the cylinders 17 are fixed.

The force which is applied onto the anvil bracket 10 by these cylinders 17 may, for example, be regulated by means of the air pressure in the cylinders 17 so as to be between 500 and 1500 N. The force could, however, also be as high as 2500 N, corresponding to an air pressure of 6 bars in the present configuration. In the case of a passing splice or a jam, the force acting in the gap G to separate the anvil element 21 from the horn element 11 will be larger than this predetermined force so that the anvil bracket 10 is pivoted away from the horn 20. The maximum movement of the anvil bracket 10, and therefore also of the cylinder pistons, in the case of a product jam is 8 to 9 mm.

Thanks to the jam protection unit of the present invention, the ultrasonic bonding of materials can now be taken into account also in cases in which passing splices and material jams are more likely to occur. In case a splice passes or a jam occurs, the device must not even necessarily stop, but could in principle continue the ultrasonic bonding operation or at least resume operation after a short break.

By means of the jam protection according to the present invention, damage to the components of the ultrasonic bonding device is avoided or at least reduced, and the number of machine shutdowns for repair reasons and corresponding resumptions of operation is also reduced accordingly, improving the efficiency of the device.

The second embodiment differs from the one shown in Figures 1 to 3 in the arrangement of the anvil support portions 13, 14 and the opposing horn support portions 23, 24: In the first embodiment discussed above, the support portions are configured so that the horn 2 is made to pivot about the round bar 30 as a pivoting axis which is parallel to the travelling direction T of the material. In the second embodiment of Figure 4, the support portions have been turned by 90° so that the horn 2 will now pivot about a pivoting axis which is perpendicular to the travelling direction T of the material.

This configuration has the advantage that the opposing faces of the horn element 21 and the anvil element 11 will always be in parallel with each other. In other words, the parallelism of these faces will not be affected by the pivoting of the horn 2.

The ultrasonic bonding device according to the present invention is not restricted to the particular structures of the above embodiments.

In particular, while the devices of the above embodiments employ both the mechanical stops and the jam protection unit, devices of the present invention could as well employ only one of these measures.

Secondly, in the above embodiments, two different types of mechanical stops are used, one employing the round bar 30 and the other one employing the conical key 40 and stop screw 41. This is, however, just an example. It would of course also be possible to use two similar mechanical stops for spacing both opposing anvil and horn portions 13, 23 and 14, 24.

The stops must also not necessarily be adjustable but could also be constructed so as to maintain one fixed gap size.

The devices of the above embodiments use a stationary horn element 21 and a rotary anvil roller 11. This is, however, also not mandatory, and the device could as well include nonrotary or rotary anvils and horns as they are per se known in the art.

The jam protection unit of the device according to the present invention is also not restricted to the particular structures of the above embodiments. For example, instead of using the pneumatic cylinders 17, the anvil bracket 10 could also be forced against the stoppers 16 by other means, e.g. by means of springs having a corresponding spring force which would be overcome by the force acting in the gap G in the case of a passing splice or a jam, so as to pivot the anvil bracket 10 away from the horn 20 against the force of the springs .

Claims

What is claimed is:

1. An ultrasonic bonding device including an anvil (1) and a horn (2), wherein the anvil (1) includes an anvil element (11) and the horn (2) includes a horn element (21) facing the anvil element (11) , so that a gap (G) is provided between facing surfaces of these elements (11, 21) for receiving the material to be bonded,

characterized in that

at least one mechanical stop is provided in order to maintain a minimum size of the gap (G) which is larger than zero, so as to avoid contact between the anvil element (11) and the horn element (21) .

2. The ultrasonic bonding device of claim 1, in which the at least one mechanical stop is formed between opposing portions (13, 14, 23, 24) of the anvil (1) and the horn (2).

3. The ultrasonic bonding device of claim 1 or 2, in which at least one mechanical stop provides a hinge (30) about which the anvil (1) and the horn (2) may pivot relative to each other. . The ultrasonic bonding device of any one of claims 1 to 3, in which the anvil (1) and the horn (2) are pivotable relative to each other about a pivoting axis which is parallel to a travelling direction (T) of a material travelling through the gap (G) .

5. The ultrasonic bonding device of any one of claims 1 to 3, in which the the anvil (1) and the horn (2) are pivotable relative to each other about a pivoting axis which is perpendicular to a travelling direction (T) of a material travelling through the gap (G) .

6. The ultrasonic bonding device of any one of claims 1 to 5, in which at least one mechanical stop is adjustable so as to increase or reduce the size of the gap (G) .

7. The ultrasonic bonding device of claim 6, in which at least one mechanical stop includes a tapered element (40) which is slidably received between facing portions (14, 24) of the anvil (1) and the horn (2) in order to set the size of the gap (G) .

8. The ultrasonic bonding device of any one of claims 1 to 7, further including a set of adjustment elements (50) of different sizes which can be selectively employed in order to set the size of the gap (G) .

9. The ultrasonic bonding device of any one of the preceding claims, in which several mechanical stops are used which are spaced apart from each other, preferably along a support shaft (12) of the anvil element (11) or the horn element (21) .

10. The ultrasonic bonding device of any one of the preceding claims, in which the mechanical stops together define three distinct contact points between the horn (2) and the anvil (1) .

11. An ultrasonic bonding device including an anvil (1) and a horn (2), wherein the anvil (1) includes an anvil element (11) and the horn (2) includes a horn element (21) facing the anvil element (11) , so that a gap (G) is provided between facing surfaces of these elements (11, 21) for receiving the material to be bonded,

characterized in that

the device further includes a jam protection unit which allows the gap (G) to be further increased in case a force acting within the gap (G) , to separate the anvil element (11) and the horn element (21) from each other, exceeds a predetermined value.

12. The ultrasonic bonding device of claim 11, in which the anvil (1) further includes an anvil bracket (10) supporting the anvil element (11) , and the horn (2) further includes a horn bracket (20) supporting the horn element (21) .

13. The ultrasonic bonding device of claim 12, in which the anvil bracket (10) is in turn supported in a frame (3, 4) of the device so as to be movable with respect to the horn bracket (20) , preferably in a pivotable manner.

14. The ultrasonic bonding device of claim 11, 12 or 13, further including means (17) for urging the anvil element (11) and the horn element (21) towards each other with a force which is smaller than the predetermined value, which urging means preferably include at least one pneumatic cylinder (17) and/or at least one spring.

15. The ultrasonic bonding device of claims 12 and 14, in which the urging means are arranged and constructed so as to press the anvil bracket (10) against a fixed stop (16) mounted to or integrated with a frame (3, 4) of the device.

16. The ultrasonic bonding device of any one of claims 11 to 15, further including the features of any one of claims 1 to 10.

17. The ultrasonic bonding device according to any one of the preceding claims, in which the anvil element (11) and/or the horn element (21) is provided in the form of a rotatably supported roller.