HK1202096B - A process and a device of plasma perforation of tipping paper - Google Patents

Abstract

The present invention relates to a process and a device of plasma perforation of tipping paper (4). The process mixes gases under the action of a point energy source, ionizes the gases on the surface of the tipping paper (4), immediately produces low temperature plasma (3). During this process, the mixed gases are ionized only on a minimal defined region of the surface of the tipping paper (4). The energy source of the device is docking the tipping paper (4) at 90 angle. The energy source has a tip. The energy light is emitted from this tip of the energy source docking the tipping paper (4). The energy source is configured in a hollow tube (1) in which a nozzle (1.1) is mounted at one end docking the tipping paper (4), being an outlet for the mixed gases under the action of pressure, the tip of the energy source is placed in the nozzle (1.1) and is concentric and coaxial with the nozzle. The present invention relates to laser perforation and mechanical perforation, plasma perforation can produce a very small aperture, as compared with the electrostatic perforation, very precise aperture and position can be obtained, avoiding visible burn marks at the edge of the hole.

Description

Method and apparatus for plasma drilling of tipping paper

Technical Field

The present invention relates to a method and apparatus for plasma perforating tipping paper.

Background

The five basic parts of a conventional filter-tipped cigarette are the tobacco leaf segment, the cigarette paper wrapping the tobacco leaf segment, the filter, the plug paper and the tipping paper (tipping paper).

Tipping paper, also known as "tipping paper", wraps the filter and plug wrap. It is that part of the person whose lips touch the filter cigarette when smoking. The tipping paper typically extends in the longitudinal direction of the filter cigarette, slightly towards the longitudinal extent of the tobacco leaf segment, wrapping around the paper and being adhered thereto by glue. The filter portion and tobacco segment portion are mechanically joined together on the machine by the creation of a bond. The tipping paper is most often paper in nature and it may be a film or foil. In the case where the tipping paper is formed as a film or foil, it may contain cellulose hydrate.

Typically the printing of the tipping paper should be visually appealing. Such printing is often used with universal patterns. The tipping paper is typically partially perforated near one end of the tobacco segment, so that ambient air can enter the filter during smoking to mix with smoke generated by the tobacco segment and reduce the amount of smoke inhaled.

The tipping paper is typically perforated after printing, in order to avoid that if it is perforated before printing, the holes will become clogged again.

Perforation of paper, paper webs or other materials, according to the prior art three perforation modes can be applied:

-mechanical punching;

-laser drilling;

-electrostatic drilling.

Mechanical perforation uses a sharp needle or needle pad to pierce the tipping paper. Such a method is described in EP 0222973a1 in connection with perforating of paper. The diameter of the vent hole (hole size) in this way is about 0.05 to 0.4 mm. The disadvantage is that the needles are subject to mechanical wear and the size of the holes fluctuates, so that the needles need to be replaced frequently to ensure uniform hole sizes.

During laser drilling, paper is penetrated by a beam. Such processes are described in DE2751522a1 and DE 102004001327a 1. The size of the hole is equivalent to that of mechanical punching, and the diameter of the hole can be 0.05mm at minimum. The advantage compared to mechanical punching is that the device does not wear and the diameter and position of the hole can be controlled very accurately. The disadvantage is that holes with a diameter of less than 0.05mm cannot be punched.

Electrostatic drilling is performed by burning paper by spark discharge. A needle electrode was used, placed on one side of the web. On the other side a flat counter electrode is placed, or again a plurality of pin electrodes. The needle electrode and the counter electrode are separated by a paper web and a narrow air gap. A high voltage is applied to the electrodes and discharges through the air gap and the web. The small area of the web burns to form pores due to the high heat energy generated by the arc discharge. Advantageously, very small holes with a diameter of 0.01mm can be produced. The disadvantages are visible marks (burning edges) at the edge of the hole due to burning, uneven hole size distribution due to difficulties in controlling the discharge, and spark splatter due to the discharge, resulting in the desired very small hole next to the hole. Electrostatic drilling is exemplified in DE3016622(A1), US4094324(A) and DE2934045 (A1).

Disclosure of Invention

The invention aims to invent a punching method which can generate a hole with a diameter as small as 0.01mm and can avoid the defects of electrostatic punching.

To accomplish this task, it is proposed to perforate the paper wrapper by generating a low temperature plasma with specific properties.

The challenge faced by the present invention is to create a controllable, reproducible low temperature plasma so that precise hole size and location can be achieved on the tipping paper. Plasma is generated by the ionization of a gas or gas mixture. In addition to the energy source and pressure supplied, the composition of the gas and the ionized gas mixture is also of particular importance for the degree of ionization and the plasma temperature.

If a solid is exposed to a low temperature plasma, two reactions occur at its surface, namely sublimation and oxidation. Sublimation is the direct transition of a substance from a solid state to a gaseous state. Oxidation is a chemical reaction formed by the release of electrons from a chemical substance. Oxidation of chemical species upon exposure to oxygen can be observed upon flame formation, i.e., combustion. The starting material is altered by oxidation to produce a new chemical composition.

If a low temperature plasma in the mixture is formed adjacent to the surface of the tipping paper, a hole will be formed in the low temperature plasma region by the two effects mentioned above. The sublimation effect is superior to the oxidation (combustion) effect, since oxidation may lead to undesirable combustion products, which, depending on the composition of the starting material, may also be toxic. The combustion products may be visible as combustion residues, thereby affecting the visual effect and, in some cases, altering the taste of the cigarette. The solid matter of the tipping paper evaporates when sublimed, leaving no residue. Thus, in the present invention, a low-temperature plasma is generated and its properties are controlled so that almost only a sublimation reaction occurs.

Technically, this conversion is the application of a defined gas mixture or a specific gas, which is ionized by a beam of energy supplied for a defined time, to a localized surface area of the tipping paper. The mixture and the supplied energy can therefore meet only in a very limited region, i.e. the low temperature plasma can be generated only in a very small region and can come into contact with a relatively small portion of the surface of the tipping paper. This results in a very small aperture and a very high accuracy of the positioning of the holes.

The present invention is superior to the prior art because plasma drilling can produce very small apertures relative to laser drilling and mechanical drilling, and can achieve very precise apertures and positions compared to electrostatic drilling. There is also an advantage over electrostatic drilling in that the visibility of burning marks at the hole edges can be avoided.

Drawings

FIG. 1: examples of cross-sectional views of the device of the present invention.

FIG. 2: example 2 of a cross-sectional view of the inventive device.

FIG. 3: examples of the apparatus of the present invention in which a laser beam is used as the energy source.

Detailed Description

The technical solution of the present invention is further described below by specific examples.

In fig. 1, an apparatus according to the invention is shown for plasma perforation of a paper web, in particular of a tipping paper web or tipping paper 4. On the flat side of the tipping paper 4 is placed an energy source of as small an area as possible. In this example, a needle-shaped electrode 2 is used as an energy source, and more precisely a voltage is applied between the two electrodes 2 and 5. The electrode 2 is mounted on the tube 1. The pipe 1 is used for conveying a pressurized gas or gas mixture. For a better understanding, the gas flows in the figures are marked with arrows. At the front end of the tube 1 there is a nozzle 1.1 for narrowing the gas flow. This nozzle 1.1 is mounted at its tip opposite the tipping paper 4, concentric with the electrode 2. Through the cavity 1.2, which is closed by the tube 1 and the nozzle 1.1, the pressurised gas or gas mixture is directed annularly around the electrode 2 in the direction of the tipping paper 4. On the other side of the tipping paper 4 there is also a needle-shaped counter electrode 5 or, as shown in figure 2, a flat counter electrode 5.

When a high concentration of inert gas or gas mixture is injected into the cavity 1.2, the gas stays in the middle of the empty tube and meets another portion of the gas mixture at the top of the electrode 2 and the narrow portion of the tipping paper 4. This region has a slightly lower concentration of inert gas than the concentration of gas directly ejected from the nozzles 1.1 and therefore it is relatively easy to ionize the gas in this region and generate plasma 3 in a limited region which sublimes to perforate the tipping paper 4. Since the inert gas concentration in the plasma gas 3 is relatively high, oxidation on the surface of the tipping paper 4 is not easy, and therefore, no visible burning trace is generated around the hole. By varying the width of the nozzle 1.1, or by varying the distance the electrode 2 is exposed from the nozzle 1.1, the extent of the region of lower inert gas concentration can be adjusted to increase or decrease the amount of plasma. The optimum configuration of the apparatus, the optimum composition of the inert gas or gas mixture, is obtained experimentally since these are closely related to the characteristics of the material to be perforated, and in particular the tipping paper 4.

Figure 3 depicts the inventive device with a laser. The lowermost end of the hollow tube 1 is likewise connected to a nozzle 1.1. The center of the nozzle is provided with a lens 7 which has two main functions. The first function of the lens 7 is to focus the laser light emitted by the laser 6 onto the surface of the tipping paper and the second function is to adjust the gas flow emitted by the nozzle 1.1 as required so that the gas flow annularly surrounds the lens 7. In order for the inert gas or gas mixture to be ejected around the lens 7, the lens must be attached to the hollow tube 1 with a very thin wire, or the lens 7 is located at the end of a straight optical fiber that must pass vertically through the hollow tube as does the electrode 2. In this case, the plasma 3 is only in a region where the energy of the laser 6 is sufficiently strong so that the mixed gas concentration in this region is sufficient but as low as possible, and then is ionized. The burning point of the lens 7 is the location where the laser 6 has the highest energy and the inert gas concentration is the lowest, so that a regional, small area plasma 3 can be generated.

The inert gas can be nitrogen (N)₂) Argon (Ar), or carbon dioxide (CO)₂) And the like. The inert gas or gas mixture leaves the nozzle 1.1 under pressure and the annular gas concentration formed at the electrode or mirror 7 is higher than the concentration immediately after leaving the electrode 2 or mirror 7. The concentration of a gas is about high and the energy required to ionize the gas is about large. In addition, the airflow can also play a role in washing away ions and electrons. These two effects also actually act to confine the plasma 3 region. Above all, it is sufficient to use the laser 6 as an energy source and compressed air as a gas mixture, since the sublimation of the laser-generated plasma 3 exceeds the oxidation.

While the foregoing is directed to the preferred embodiment of the present invention, and not to any one of the preceding forms or essential limitations thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Those skilled in the art can make various changes, modifications and equivalent arrangements, which are equivalent to the embodiments of the present invention, without departing from the spirit and scope of the present invention, and which may be made by utilizing the techniques disclosed above; meanwhile, any changes, modifications and variations of the above-described embodiments, which are equivalent to those of the technical spirit of the present invention, are within the scope of the technical solution of the present invention.

Claims (8)

1. A process for plasma drilling of tipping paper (4) by means of an ionizable gas mixture which is ionized in real time on the surface of the tipping paper (4) under the action of a punctiform energy source to generate low-temperature plasma (3), characterized in that an inert gas or a gas mixture containing a high-concentration inert gas is introduced under pressure and forms a ring around the tip of the energy source facing the tipping paper (4), so that the ionizable gas mixture is ionized only in a very small, limited area of the surface of the tipping paper (4), i.e. in the area in front of the center of the tip of the energy source, and the ionizable gas mixture is annularly surrounded by the introduced inert gas or the gas mixture containing a high-concentration inert gas which is not ionized by the energy source.

2. A process according to claim 1, in which the source of energy comprises two spaced electrodes (2, 5), the tipping paper (4) and the ionizable gaseous mixture being located in a gap between the electrodes, the ionizable gaseous mixture being ionized when a voltage is applied across the electrodes (2, 5).

3. A process of plasma perforation of tipping paper (4) according to claim 2, characterised in that both electrodes (2, 5) are needle-shaped.

4. A process according to claim 2, wherein one electrode (2) is needle-shaped and the other opposing electrode (5) is flat-headed.

5. A process according to claim 1, wherein the energy source is a laser (6) directed towards the tipping paper (4).

6. The process according to claim 5, characterized in that the laser of the laser (6) is focused by means of a lens (7) on the zone containing the lowest concentration of inert gas.

7. Device for plasma perforation of tipping paper (4) with an energy source directed at the tipping paper (4) at an angle of 90 DEG and having a tip from which the energy light emerges, characterized in that the energy source is arranged in a hollow tube (1) and that the end directed at the tipping paper (4) is fitted with a nozzle (1.1) as outlet for an inert gas or a gas mixture containing a high concentration of inert gas under pressure, the energy source being arranged in the outlet of the nozzle (1.1) concentrically and coaxially with the nozzle, said tip being the tip of an electrode (2) or an optical element emitting a laser beam.

8. An apparatus for plasma perforating tipping paper (4) as claimed in claim 7, characterized in that the tip of the energy source is directed towards the tipping paper (4) beyond the outlet of the nozzle (1.1).