EP0038977A2 - Method and apparatus for perforating paper - Google Patents

Abstract

Method and apparatus for producing perforated paper, especially cigarette paper and tip-covering paper. The perforations are produced by guiding the paper between two electrodes to which a voltage sufficient for spark-over is applied. The paper is passed through continuously between the electrodes and the time interval between the spark-overs depends, on the one hand, on a predetermined value and, on the other hand, on the web speed of the paper passed through. In one embodiment, provision is made for different zones to have different perforation densities, for these perforation densities to be measured and for the desired perforation density to be maintained at all times via a controlled system. <IMAGE>

Description

The present invention relates to a process for the production of perforated paper, in particular cigarette and tip paper, in which the paper is placed between two electrodes, to which a voltage sufficient for arcing is applied.

Furthermore, the invention relates to a device for performing the method.

From DE-AS 11 63 216 it is known to perforate cigarette paper by passing the paper through a field of electrical sparks. From DE-OS 25 31 285 it is also known to also perforate cigarette paper only in certain zones by high-voltage spark erosion.

'The object of the present invention is to provide a way to adjust the ratio between the area of the perforations or air inlets in the paper and the paper area itself according to the requirements.

The task. is achieved in that the paper is continuously moved in a web, a signal which is dependent on the web speed is obtained, and the time interval between the sparkovers is controlled by a predetermined setting value and the speed-dependent signal. In this way, the paper can be perforated without stopping it for perforation, the web speed of the paper and the hole spacing being made dependent on one another in such a way that the desired hole spacing is achieved at every web speed occurring during operation. The hole spacing and thus the perforation density can be selected by a predefined setting value, the hole spacing and thus the frequency the holes determine the effective ventilation area.

One possibility here is that the speed-dependent signal is a DC voltage proportional to the web speed, which is adapted to the operating conditions by a control and converted into a pulse train, the individual pulses each causing a sparkover after amplification. The DC voltage, which is dependent on the web speed, can be obtained without difficulty, and the adaptation to the operating conditions, for example to the desired porosity, can easily be achieved by regulating this DC voltage to a desired value using a potentiometer. This DC voltage can be converted into a pulse train by conventional electrical components, the frequency of which depends on the level of the DC voltage. These individual pulses can then be used to generate the sparkover, each stabilized by amplification.

It is preferred that the pulses of the pulse train are reshaped to adjust the hole size before they are amplified. Through this process step, the effective ventilation area is determined not only by the number of holes, but also by the size of the individual holes.

In certain areas of application, in particular in the case of cigarette paper and mouthpiece covering paper, it is desirable, regardless of material fluctuations and component tolerances, to achieve a ventilation which is predetermined for all areas as precisely as possible in the individual areas.

This adjustment can be adjusted by adjusting the DC voltage after the control additionally sets the DC voltage for each zone individually. The supplied DC voltage value, which is representative of the web speed, is thus influenced again before it is converted into a pulse train, and this time separately for each zone, so that the subsequent voltage-frequency converters deliver a pulse train set separately for each zone.

A preferred form of the method provides that the ventilation for each zone is measured, this actual value is compared with a target value and, in the event of a deviation between the actual value and the target value, the DC voltage for each zone is changed individually until the actual value and the target value match. In this way, a controlled system is set up which uses known methods to check the perforation generated to determine whether the perforation value has assumed the desired value. By influencing the DC voltage, the perforation density can be changed in this controlled system until it is adjusted to the desired value.

In addition, a method provides for the ventilation of the individual zones to be measured simultaneously and the deviations of the actual values from the setpoint to be corrected by automatically changing the DC voltage for each zone. In this way, a control loop is set up for each zone, so that the perforation generated is automatically adapted to the desired value.

Another possibility provides that a pulse train is obtained as the signal dependent on the web speed, the frequency of which is a measure of the web speed, the pulse train drives a changeable gate signal, and that a pulse train with a fixed, at least five times the frequency of the signal dependent on the web speed to the electrodes for the arcing. This method does not increase the perforation density, i.e. the number of holes per unit area, but rather sets the hole size. For this purpose, a pulse train is taken, which is related to the web speed. This pulse sequence can either be achieved, as described above, by obtaining a DC voltage and then converting it into a frequency, or by mechanically driving parts for the web speed mechanically by opening and closing contacts or via magnetic, optical or similar sensors Generate pulse train. The pulses trigger gate signals, which are therefore dependent on the frequency of the pulses. Furthermore, a pulse train of high frequency is provided, and the gate signal opens the connection between the generator for the pulse train of high frequency and the electrodes, so that for the duration of the gate signal this pulse train of high frequency generates sparks after appropriate amplification. Ultimately, a sequence of sparks, also at a high frequency, is thus obtained on the spark gap, this frequency being chosen so high that not several holes are formed in succession on the paper web, but that the spark following the first spark is the hole created by the first spark expand. The strength of the extension depends on the gate signal, so the setting of the device signal can influence the hole size.

An order of magnitude of approximately 100 kHz has proven to be a favorable value for the pulse sequence with a fixed high frequency. A typical value for the web speed of the paper is 60 meters per minute, and the paper moves only 0.01 mm between two 100 kHz discharges. This ensures that the successive sparks only form a hole.

A simplification of the method is achieved if each start of a pulse of the signal dependent on the web speed triggers the gate signal and the fixed frequencies are generated only during the application of the signal dependent on the web speed. Since the clock ratio of the pulses, which depend on the web speed, can be set to approximately 0.5, holes are produced which are separate from one another and which do not merge into one another, as long as the fixed frequency is generated only when the signal, which is dependent on the web speed, is present. The method is further simplified in that each start of a pulse of the signal dependent on the web speed triggers the gate signal, since intermediate elements such as counters or frequency dividers can be omitted in this way.

The simplest possibility for setting the hole size has been found to be that the width of the gate signal can be changed. During the time duration of the gate signal, the sparks are on the electrodes supplied by the high-voltage transformer, and the width of the gate signal can be easily adjusted depending on the desired hole size.

The invention further provides an apparatus for carrying out the method, with a paper web which is guided between electrodes which are connected to the high-voltage connections of a high-voltage transformer.

Such devices are known from the above-mentioned prior art. The object on which the invention is based is achieved in that a measuring device detects the speed of the paper web and converts it into an electrical signal, a frequency generator is connected to the measuring device and, depending on the electrical signal, supplies a pulse train to a first amplifier, and the amplifier the Forward pulses to the primary side of the high voltage transformer.

Preferred embodiments are described in the subclaims.

• Fig. 1 ein Blockschaltbild einer erfindungsgemäßen Schaltung zur Einstellung des Verhältnisses zwischen der Fläche der Lüftungsöffnungen und der Fläche, des Papiers;
• Fig. 2 Regelkreise zur Einstellung des Verhältnisses in mehreren voneinander getrennten Zonen;
• Fig. 3 ein Schaltungsaufbau zur Einstellung der Lochgröße;
• Fig. 4 die Arbeitsdiagramme, abgegriffen an einigen Punkten des Schaltungsaufbaus nach Fig. 3;
• Fig. 5 einen erfindungsgemäßen Schaltungsaufbau zur Regelung von Lochdichte und Lochgröße.

The invention is described in detail below with reference to the associated figures. Show it:

• Figure 1 is a block diagram of an inventive circuit for adjusting the ratio between the area of the ventilation openings and the area of the paper.
• Fig. 2 control loops for setting the ratio in several separate zones;
• 3 shows a circuit structure for setting the hole size;
• FIG. 4 shows the working diagrams, tapped at some points in the circuit construction according to FIG. 3;
• 5 shows a circuit structure according to the invention for regulating hole density and hole size.

In Fig. 1, an adjustment path for adjusting the porosity is shown, with several identical paths lying in parallel in order to be able to adjust different zones of the paper passing through. A speed-proportional analog signal in the form of a DC voltage is generated with a tachometer generator 10. With an actuator 11, for example in the form of a potentiometer, the input voltage is set jointly for all routes lying parallel to one another, thereby fixing the porosity level.

This section has a second actuator 12 with which the porosity is adjusted separately for each channel, that is to say separately for each perforation zone, in accordance with a previously determined measured value. The voltage set with the actuator 12 reaches a voltage frequency converter 16. This converter 16 generates a separate frequency for each channel, which determines the hole spacing. In the further course of the route, a single device 17 for adjusting the hole size can be provided, the signal then passes to an amplifier 18. The amplifier 18 supplies the necessary energy, which is brought to the necessary ignition voltage with the output transformer 19 and at the discharge pins 20 Discharge.

The channel that is routed in parallel with it has the same switching elements, each designated by a deleted reference numeral in FIG. 1. It is therefore possible to continuously bring the porosity to the desired value by adjusting the hole spacing separately for each channel using the potentiometers 12, 12 '.

FIG. 2 shows, partly using the same switching elements as in FIG. 1, the same elements being designated by the same reference numbers, the structure of a control circuit for the porosity. The speed-proportional voltage signal of the tachometer generator 10 is set to a desired level with the actuator 11 for all channels. The porosity of the zone is measured by the transducer 13 of a known type, passed as an actual value to the comparator 14 and compared there with the target value given to all channels by the target value transmitter 15. The setpoint of the setpoint generator 15 is set by hand. If desired, however, it is conceivable that each channel is assigned its own setpoint, and thus different porosities are generated in the individual zones. The output signal of the comparator 14 changes the actuator 12, the output voltage of the voltage-frequency converter 16 is converted into a frequency that determines the hole spacing and thus the porosity of the zone.

1, via an actuator 17 for the hole size and the amplifier 18, reaches the high-frequency transformer 19, which tightens the pulses, so that a sparkover occurs at the electrodes 20. The actuators 12 are changed until the target value and the actual value match. In this way, the porosity fluctuations for each channel are corrected.

Fig. 3 shows a circuit structure by means of which the hole size can be adjusted. The hole size can only be influenced to a small extent by the intensity of the discharge. Extending the discharge in an arc has not proven to be feasible, since generally visible fire edges develop very quickly because the paper is very strongly heated at certain points. The sudden discharge of a high-voltage capacitor can only be changed in terms of energy, and this sudden discharge also leads to a torn hole shape and to the appearance of paper fibers, so that the holes are closed again in an uncontrolled manner during further processing. This in turn leads to an uncontrolled decrease in porosity.

3, the hole size is changed over a wide range by using a pulse generator 10 driven by the paper web to generate a speed-proportional frequency F ₁ (G) which, depending on the web speed, is between 0 Hz and 20 kHz can. The frequency can be obtained either directly by opening and closing mechanical contacts, by magnetic encoders and reed relays, by optical devices with photocells or similar structures, the voltage-frequency converter 16 according to FIG. 1 or 2 can also be used. The duty cycle of the Frequency f ₁ is of the order of 0.5. With this signal G, on the one hand, an oscillator 21 is synchronized, which delivers a fixed frequency f ₂ (0), the frequency of which is significantly higher than f. A reasonable order of magnitude for this frequency is 100 kHz.

Furthermore, a time stage 22 is triggered via f ₁ , which emits an adjustable gate time T. The gradual setting of this gate signal has proven to be sufficient in practice; a continuous change is of course also conceivable. Via a gate 23, for example an AND gate, the 100 kHz signal 0 now only reaches an amplifier 18 during the gate time T. This control signal S at the output of the AND gate thus consists of a number of 100 kHz that can be set by changing the gate signal Pulses that are repeated periodically with the fundamental frequency f1 (G) proportional to the web speed. The number of pulses is generally between 1 and 10. The amplifier 18 controls, as in the previous embodiments, the high-voltage transformer 19, which outputs the ignition voltage to the discharge pins 20.

As many discharges take place on the pins 20 in a 100 kHz rhythm as there are pulses set by the gate signal T '. However, this occurrence of high-frequency discharges only creates a hole in the paper web, since the paper web speed is low compared to 100 kHz. At a web speed of 60 meters per minute, which is a practical value, the paper only moves by 0.01 mm between two 100 kHz discharges. Depending on the length of the gate signal, a hole of different size is created in the paper web, the hole size can therefore be adjusted in other areas. The hole size is very constant reproducible with one setting, so that only very small fluctuations in the porosity can be obtained.

FIG. 4 shows the signals which are obtained at the individual points in the circuit structure according to FIG. 3. In the first line, G represents the signal which is derived from the tachometer generator 10, a rectangular pulse sequence, the frequency of which is representative of the speed of the paper web. The square-wave pulse sequence which is obtained from the fixed frequency generator 21 is represented by 0, wherein it should be mentioned that the fixed frequency is only present when the signal tapped at G is at logic 1. T represents a rectangular pulse, the width of which can be adjusted continuously or in discrete steps. In order to achieve a reasonable circuit structure and a functionality of the circuit, the signal T must be at least as wide as a pulse of the fixed frequency 0, but not wider than the pulse of the speed-dependent signal G. The signal S is at the output of the AND gate 23 removed, and shows that the signal 0 only passes the AND gate 23 when the signal T is present at the same time. This signal S is amplified in a corresponding manner in the amplifier 18 and fed to the discharge pins after transformation.

5 ultimately shows a complex circuit structure which is composed of the circuit structures according to FIGS. 2 and 3. The arrangement of the elements 10 to 15. corresponds to the arrangement of FIG. 2, the speed-dependent DC voltage signal is then converted into a frequency in the frequency converter 16. This frequency is fed to a unit 17 for setting a hole width which corresponds to the structure according to FIG. 3. The setting of the width of the gate signal in the circuit element 22 can be carried out separately for each channel, as shown in FIG. 5, but if the ratio of the If the effective ventilation openings are to be made only by the number of openings, not by the hole size, a single setting would suffice for all channels. The rest of the circuitry does not differ from that of the temporary examples.

Claims (13)

Process for the production of perforated paper, in particular cigarette and mouthpiece covering paper, in which the paper is placed between two electrodes, to which a voltage which is sufficient for arcing is applied, characterized in that a) the paper moves continuously in a path, b) a signal dependent on the web speed wins, and c) controls the time interval between the arcing by a predetermined setting value and the speed-dependent signal. 2. The method according to claim 1; characterized in that the speed-dependent signal is a DC voltage proportional to the web speed, which is adapted to the operating conditions by a control and converted into a pulse train, the individual pulses each causing a sparkover after amplification. 3. The method according to claim 2, characterized in that the pulses of the pulse train are formed prior to their amplification to adjust the hole size. 4. The method according to claims 1 to 3, characterized in that a plurality of adjacent sparkover zones produce a perforation which can be set in the individual regions, the DC voltage additionally being set individually for each zone after the control for adapting the DC voltage. 5. The method according to claim 4, characterized in that the perforation density is measured for all zones, this actual value is compared with a target value and, in the event of deviations between the actual value and target value, the DC voltage for each zone is changed individually until the actual value and target value match. 6. The method according to claim 1, characterized in that a pulse train is obtained as the signal dependent on the web speed, the frequency of which is a measure of the web speed, the gate train controls a gate signal, and a pulse train for the duration of the gate signal fixed, at least five times the frequency of the signal dependent on the web speed to the electrodes for the sparkover. 7. The method according to claim 6, characterized in that each start of a pulse of the signal dependent on the web speed triggers the gate signal and the fixed frequency is generated only during the application of the signal dependent on the web speed. 8. Device for performing the method according to claims 1 to 7, with a paper web which is guided between electrodes which are connected to the high-voltage side connections of a high-voltage transformer, characterized in that a) a measuring device (10) detects the speed of the paper web and converts it into an electrical signal, b) a frequency generator (16) is connected to the measuring device (10), which is dependent on the electrical Signal delivers a pulse train to an amplifier (18,
and c) the amplifier (18) forwards the pulses to the primary side of the high-voltage transformer (19). 9. The device according to claim 8, characterized in that the measuring device (10) outputs a DC voltage, which is fed to a voltage adjuster (11), and the frequency generator (16) converts the DC voltage into a pulse train. 10. The device according to claim 8, characterized in that - between the frequency generator (16) and the amplifier (18), a device (17) for adjusting the hole size is connected. 11. The device according to claims 8 to 10, characterized in that a transducer (13) for. Measurement of the porosity of the treated paper web and a setpoint generator (15) for the porosity are provided, and the outputs of the transducer (13) and the setpoint generator (15) are fed to a comparator (14), the output signal of which from an adjusting device (12) the measuring device (10) influences the signal emitted to detect the web speed. 12. Device according to claims 9 to 11, characterized in that for several zones of the paper web each have a route with frequency generator (16, 16 '), Hole size adjustment (17, 17 '), amplifier (18, 18'), high-voltage transformer (19, 19 ') and electrodes (20, 20') is provided, and in each section the signal dependent on the web speed via an adjustment (12, 12 ') can be set separately. 13. The apparatus according to claim 8, for adjusting the hole size, characterized in that a transmitter (10) provides a pulse train (G) low frequency depending on the paper web speed, a gate signal generator (22) is connected downstream of the transmitter (10), the gate signals (T) provides adjustable width, a fixed frequency generator (21) provides a fixed frequency (0), the gate signal (T) is fed to one input and the fixed frequency (0) to the other input of an AND gate (23), the output of which Input of the amplifier (18) is connected.

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