APPARATUS AND METHOD FOR SPLICING SUBSTANTIALLY FLAT CONTINUOUS MATERIAL

Abstract

The apparatus and method for splicing substantially flat continuous material comprises a transport unit for transporting a first substantially flat continuous material and a second substantially flat continuous material to a splicing location. The transport unit is adapted to transport the first substantially flat continuous material and the second substantially flat continuous material parallel to each other forming an overlap portion of the first substantially flat continuous material and the second substantially flat continuous material in the splicing location. A pressure unit is arranged in the splicing location. The pressure unit is adapted to apply a mechanical impact onto at least a part of the overlap portion of the first substantially flat continuous material and the second substantially flat continuous material, thereby at least partially merging the first substantially flat continuous material with the second substantially flat continuous material.

Claims

1. Method for splicing substantially flat continuous material, the method comprising the steps of: providing a first substantially flat continuous material and providing a second substantially flat continuous material; aligning the first substantially flat continuous material and the second substantially flat continuous material in an overlapping manner forming an overlap portion, and applying a mechanical impact to the overlap portion, thereby merging the first substantially flat continuous material with the second substantially flat continuous material, wherein the step of applying a mechanical impact is performed outside of a transport path of a transport system.

2. Method according to claim 1, wherein the step of applying a mechanical impact to the overlap portion comprises applying the mechanical impact over a width of the overlap portion and onto discrete longitudinal positions of the overlap portion.

3. Method according to claim 1, wherein the step of applying a mechanical impact to the overlap portion comprises applying the mechanical impact perpendicular to a plane spanned by the first substantially flat continuous material and the second substantially flat continuous material.

4. Method according to claim 1, applying the mechanical impact on two lateral sides of the transport path of the transport system in the splicing location.

5. Method according to claim 1, wherein a length of the overlap portion is in a range between about 15 millimeter and about 50 millimeter.

6. Method according to claim 1, further comprising the step of cooling the first substantially flat continuous material and the second substantially flat continuous material during or after performing the combining step.

7. Method according to claim 1, the method comprising the further steps before applying the mechanical impact: cutting the first substantially flat continuous material and the second substantially flat continuous material such as to provide the first substantially flat continuous material and the second substantially flat continuous material with edge cuts; aligning the edge cuts of the first substantially flat continuous material and of the second substantially flat continuous material such that the edge cuts overlap each other.

8. Method according to claim 7, further comprising the step of dispensing a liquid to at least the first substantially flat continuous material or the second substantially flat continuous material.

9. Method according to claim 1, further comprising the steps of providing a gas stream and directing the gas stream into a moving direction of at least the first substantially flat continuous material or the second substantially flat continuous material, thereby guiding at least the first substantially flat continuous material or the second substantially flat continuous material into the moving direction.

10. Method according to claim 1, wherein the first substantially flat continuous material and the second substantially flat continuous material is any one of a polylactic acid sheet and a tobacco sheet.

Description

[0059] The invention is further described with regard to embodiments, which are illustrated by means of the following drawings, wherein

[0060] FIGS. 1-3 show top views of two webs of substantially flat continuous material before and after splicing;

[0061] FIG. 4 shows a mechanical pressure unit;

[0062] FIG. 5 shows a hammer of the pressure unit of FIG. 4;

[0063] FIG. 6 shows an apparatus according to the invention.

[0064] In FIGS. 1 to 3 the splicing process is shown. A first continuous flat material web 70 and a subsequently following second continuous flat material web 71 are transported along the transport direction 100. Both sheet material 70,71 have the same width and are aligned along their longitudinal middle axis. The end portion of the first web and the head portion of the second web have been cut to provide predefined edge cuts 700 having a form complementary to each other. Knifes (not shown) are arranged such that the webs are cut at an angle 102 to the width of the webs or with respect to the direction perpendicular 101 to the transport direction 100. As shown in FIG. 2 the webs 70 71 are then overlapped to form an overlap portion 701. Due to the obliquely cut webs the overlap portion 701 forms a parallelepiped. The angle 102 at which the webs are cut influences the size of the overlap portion. Especially, a longitudinal extension 702 of the overlap portion may be kept small with small cutting angles 102. A cutting angle may be in a range of between about 10 degree and about 60 degree, preferably between about 15 degree and about 45 degree, for example degree. The longitudinal extension 102 of the overlap portion is preferably within a range of 10 millimeter and 100 mm, for example 40 millimeter to 80 millimeter.

[0065] In FIG. 3 the two webs have been spliced by partly merging the overlap portion. The connection of the two webs is formed by a merged portion 703 in the form of two parallelepipeds arranged on the two lateral sides of the webs 70,71. The two parts extend to the lateral side edges of the webs but leave a space in between the two parts. It has been shown that a continuous merged portion 703 continuously merging the entire width of the webs is not necessarily required for a reliable splicing. In addition, in the space between the merged parts, a conveyor belt 10, for example a vacuum belt for transporting the webs, is arranged below the webs, which is indicated by dotted lines. The merged portion 703 is produced by applying a mechanical impact onto the webs by two hammers impacting against an anvil, wherein no mechanical impact is applied onto the conveyor belt arranged in between the hammers. The hammers are arranged to extend over the width of the webs, however also at an angle to the direction perpendicular 101 to the transport direction 100. In the embodiments shown, cutting angle 102 and splicing angle are substantially identical. A splicing angle may also differ from a cutting angle and may be in a range of between about degree and about 60 degree, preferably between about 15 degree and about 45 degree, for example 40 degree.

[0066] FIG. 4 shows a pressure unit 3 with two hammers 31 and drive means 32, such as, for example, a pressurized air source. The drive means 32 drive a piston 30, which piston drives the hammers. Therefore, the piston comprises an enlarged head portion 300, where the two hammers 31 are mounted to. The hammers 31 each comprise a longitudinal hammer surface 310 for acting upon the flat material to be spliced. The hammers 31 are aligned such that the two hammer surfaces 310 lie on a same imaginary line. The hammers 31 are distance from each other on this imaginary line. The hammers 31 comprise two spring washers 313 each or bellows for damping the hammers. Each hammer is provided with external connections 312 for heating or cooling or heating and cooling the hammers 31. The pressure unit further comprises longitudinal guiding means 24 in mechanical connection with the enlarged head portion 300 of the piston 30. The guiding means 24 guide the piston 30 when in hammering action, that is, when applying a mechanical impact via the hammers 31 onto the web material. They support a balancing of the force distribution onto the hammers 31 and may prevent unintended rotation of the hammers. The pressure unit 34 is mounted to the apparatus via support 35.

[0067] The transport direction of webs to be spliced is indicated via arrow 100. The position of the hammers 31 is skew to the transport direction 100 and skew to the direction perpendicular to the transport direction at a splicing angle corresponding to the cutting angle 102. The piston 30 is fixed against rotation, however, preferably, this rotational position may be varied. Thus, the piston 30 may be rotated around its longitudinal axis to change the position of the hammers 31, that is, to change the splicing angle.

[0068] In FIG. 5 one of the two hammers 31 of the pressure unit of FIG. 4 is shown. The hammer 31 has a hammer edge 310 with a hammer surface acting upon the web materials to be spliced. The hammer 31 also comprises openings 311 for connecting heating or cooling connections to the hammer. Such heating connections may for example be electrical connections or tube connections for introducing a heating or cooling fluid into or through the interior of the hammer. Exemplary values for the hammer may be: weight 120 grams; size: 1051835 millimeters; width of hammer surface 6 millimeters.

[0069] Preferably, a substantially flat hammer edge 310 is used for merging the web material. For example, for thin materials having a low melting temperature, that is, having a melting temperature that is reached or exceeded upon a mechanical impact, a flat profile may preferably be used for splicing. The melting of the material may suffice to create a strong merging portion. Thus, the flat hammer surface guarantees the formation of a reliable connection between the two webs without the risk of creating holes or thin spots that tend to weaken the material in the merged portion 703.

[0070] However, depending on the web material to be spliced, for example a thicker material, for example thicker than 200 microns per web, also a structured hammer surface may be used. A structured hammer surface may, for example, comprise a three-dimensional serrated profile or be a grid structure of pyramid-shaped protrusions. A structure may support the merging of the material of one web into the material of the second web.

[0071] FIG. 6 shows the transport unit 1 comprising two transport belts 10, each for transporting a substantially flat continuous material, such as a for example webs of paper or plastic, metal foil or tobacco webs. The transport belts 10 pass below a cutting unit 2, are then guided via deflection rollers 12 to be led parallel to each other through the pressure unit 3 and through embossing rollers 5 arranged downstream of the pressure unit 3. Over drive rollers 11, the conveyor belts may be guided again via the deflection rollers 12, thereby forming continuous belt loops.

[0072] The cutting units 2 each comprise a knife holder holding a knife 20 for cutting a continuous web transported on the conveyor belt below the cutting unit 12. The cutting units 2 are also provided with a water dispenser 21 each for supplying water to the webs in the cut area or onto a web portion being part of a future overlap portion 701 for example as shown and described above relating to FIGS. 1 to 3. The water dispenser may for example comprise a nozzle. Preferably, water is dispensed or sprayed onto one web only, preferably a future lower lying web such that one water dispenser may be optional or only one water dispenser may be active at a time.

[0073] The pressure unit 3 comprises an actuator 32 for actuating a piston 30 comprising one or several hammers 31 arranged at the distal end of the piston. An anvil 33 is arranged opposite the piston 30 and hammer 31. The webs transported via the transport belts 10 are guided in parallel through the splicing location 36 located between hammer 31 and anvil 33. In the splicing location 36 the webs are arranged having an overlap portion required for reliably splicing the webs. The pressure unit 3 is then actuated to apply a mechanical impulse such as a blow from the hammer 31 against the anvil 33, where the overlap portion is arranged between hammer and anvil. By this, the two webs are merged together and may further downstream be provided with a structure, for example an embossing structure, crimping structure or folding structure, while passing between the embossing rollers 5. As shown in FIG. 6 the webs are transported vertically downwards into and through the pressure unit 3. The transporting and overlapping of the webs is thereby supported by gravitational force. The merged and embossed continuous web is further transported vertically out of the apparatus while belts 10 are guided by the drive rollers 11 back to supply a further web material to be spliced to an upcoming end of the web material actually in use.

[0074] A control unit 4 is provided to control and actuate the pressure unit 3 and the drive rollers 11. Preferably, the webs are stationary while being spliced. Thus, via the control unit 4 the drive rollers 11 may slow down or stop the conveyor belts 10 for the splicing process. After the splicing process at least one of the conveyor belts 10 is started to continue the transport of the now spliced web. Preferably, this is done by slowly raising the velocity of the belt or belts until a final velocity is reached.

[0075] An exemplary embodiment of a splicing set-up is:

[0076] Material: two polylactic acid webs with a thickness of 50 microns plus or minus 5 microns; the obliquely cut webs, cut at a cutting angle of 40 degree, are made to overlap with a longitudinal extension of the overlap portion of about 80 millimeter;

[0077] Pressure unit: 2.4 bar air pressure is applied to piston 30 having a cross section of 50 millimeter and 20 square centimeter piston surface; two hammers 31 with a hammer edge surface of about 6 square centimeter each are heated to about 100 degree Celsius; a mechanical impulse with a force of 450 Newton and of 350 millisecond duration is applied to the overlapping PLA webs.

[0078] While the embodiments as shown in the drawings comprise two hammers, variations of this set-up may be envisages without departing from the scope of the invention. For example, one or three hammers may be provided, while one, two or more conveyor belts are guided outside of a merging zone. For example, the conveyor belts may be laterally displaced in view of an outside of the position of the hammer(s), as well as may be arranged in between neighbouring hammers.