DE4219670C1 - Paper strip cutter with adjustable positioning system - moves knife slides along rail past first pre-positioned sensor, then travels on to second pre-positioned sensor, thus being accurately positioned - Google Patents

Abstract

The position of the cutting tool in one of the slides is determined by passing over a sensor with a predetermined position fed in. This slide then travels to the position of an adjacent and pre-positioned second sensor. The adjacent second knife slide then travels to the now known position of the second sensor, and is thereby accurately positioned. The above operations are then repeated, until all sensors and knife slides have performed their functions. ADVANTAGE - Requires only moderate amount of software and can be installed in existing equipment.

Description

The invention relates to a method according to the Method claim 1 and a device according to the Preamble of claim 3.

Such a device is known from DE 41 06 069.

The stress of cutting devices at very high Speeds of up to 3000 m / min is quite considerably. For this reason, a very high one arises Wear, which is a frequent regrinding of the Cutting device conditional, whereby inaccuracies in the exact position of the cutting edges of the Cutting device arise.

If the positioning is limited to the To bring sled to a certain place and yourself by grinding the position of the cutting edge opposite changed the sled, this shift goes into the width of the partial webs generated and generated Deviations by corresponding amounts from their target size. In many cases, this is not permitted.

The change in the position of the cutting edges is known by grinding with the help of washers balance. This process is time consuming and error prone, because the required inserts through measurements to be taken for each pair of knives must be, errors due to tolerances remain.

• 1) The basic idea of wear of the circular knife Taking the control into account is self-explanatory taken from the published patent application DE 31 44 714 forth. It is a device in which each sled has its own Has displacement drive motor. Every sledge wear electrodes are assigned to the Control electrical signals to adjust the concerned slide to compensate for the Feed knife wear. Like this in detail to be accomplished and how in particular one appropriate measure on a generic Slitting device to be realized, does not appear from this document.
• 2) According to patent specification DE 34 17 042, each knife carriage has a fixed (carriage-fixed) mark which, measured in the direction of travel of the carriage, is at a certain distance from the cutting edge of the lower knife. If a lower knife is reground and reassembled on the slide, the slide is guided past a fixed position sensor. Two signals are generated: one when passing the cutting edge on the position sensor, and the other when passing the carriage-fixed mark on the position sensor. Both signals are fed into a microprocessor control. This control is intended to ensure precise positioning, taking into account the material decrease on the lower knife generated by grinding, by producing a correction measure. Here, a relative dimension is first obtained, from which an absolute dimension for the actual knife position must first be determined by the control.
  This known device and the associated method have the following disadvantages: Due to the necessity to record the exact position of all position sensors, or to be able to position the position sensors precisely, a high mechanical effort is required and also not always possible or too expensive in the case of retrofitting.
• 3) According to the publication mentioned at the beginning DE 41 06 069 uses a method which used a special measuring head, which over the can traverse the entire width of the machine and one offers very high absolute measurement accuracy. Here the cutting edge of the knife is scanned and thereby determining the absolute position of the knives. The advantages are great: high accuracy of the Calibration, quick and easy calibration and Detection of the actual cutting edges of the Knife. The disadvantages are also big: higher additional effort (mechanical and electrical, Control software), resulting high additional costs; very poor upgradeability in the existing systems, since the measuring head and the Traversing device already in the construction must be taken into account.

The invention has for its object a method and a device according to the preamble of claim 3 to be designed in such a way that a positioning device arises, which requires moderate software effort, in existing systems can be retrofitted and at a reasonable price Cost to produce.

This object is achieved by method claim 1 and characterizing features of claim 3 solved.  

The key idea here is just know the exact position of a single position marker to have to and about the successive start-up fixed position marks by various knives To determine the position of the other fixed brands and thus again measure the position of the individual knives precisely to be able to.

One type of embodiment can be as follows:
Several stationary sensors (e.g. optical reflex light barrier / laser switch or inductive proximity switch) are installed in the cutting section, which can detect the cutting edges of the knives. Each sensor must be able to be approached by at least 2 knives, if there is a previous / following sensor for this sensor, at least one knife must be present that can approach both the current and the previous / following sensor. These requirements result in a number of approx. 4 sensors for small to approx. 8 sensors for large cutting sections. Only the position of the first sensor needs to be known precisely enough. This is not particularly critical, since this position has to be empirically corrected in the commissioning phase anyway, because the paper runs easily from the cutting station to the roll-up sleeves, depending on the machine. The absolute positions of the other sensors within the machine are not important, they are determined automatically in the course of the calibration process, only good reproducibility of the sensors is required.

The sensors are on the same hardware side Control computer connected to the measured values of the Reads in the encoder and the one that is normally available  automatic knife positioning also the Controls positioning motors.

algorithm

It is e.g. B. started with the knife 1 (edge knife) lying first sensor A, the position of this sensor is known. The knife moves over (manually or automatically) the sensor in such a way that the actual cutting edge of the knife comes first into the sensor area. The position read in simultaneously by the travel sensor of the knife is used to calculate the offset required to correct the absolute position of the knife cutting edge. This is the procedure for all other knives that can also approach this sensor. Now a knife that can also approach the next sensor is again moved with the corresponding cutting edge over this sensor first, but this time the sensor signal is used to calibrate this sensor, since the absolute position of the corresponding knife is already from the measurement on the previous one Sensor is known. Then all knives that can approach this calibrated sensor are calibrated on this sensor, and so on.

The advantages of the method and the The device according to the invention are:

• - very little additional hardware expenditure;
• - no mechanically moving components;
• - Low mechanical assembly requirements Sensors;
• - simple wiring (everything stationary, no Cable towing);
• - non-contact measurement;
• - low absolute accuracy requirement Sensors;  
• - only the first sensor must be known fairly precisely be;
• - small number of sensors (approx. 4 to 8 sensors);
• - simple and inexpensive sensors (e.g. Reflex light barrier, inductive proximity switch);
• - relatively easy to retrofit existing ones Investments;
• - only one scale (e.g. angle encoder / tooth pole);
• - in the case of linearity errors of this scale, only this must Getting corrected;
• - Errors caused by changing knives are automatic corrected;
• - no dependency on the operating personnel;
• - simple procedure on the control side;
• - The process is easy to use and automate;
• - Procedure is quick (just a few minutes for everyone Knife);
• - If only one knife is calibrated, this is a procedure abbreviated;
• - Plausibility check for displacement sensors / sensors easy to implement;
• - Control or review of the travel area (Graycode).

The invention is explained in more detail with reference to the drawing: It also shows the following:

Fig. 1 schematic representation of a knife rail with positioning device.

Fig. 1 shows the basic diagram of a knife bar with the positioning means for the knife carriage. A knife rail MS can be seen across the width of the figure, on which there are seven knife carriages M1 to M7 by way of example. The knife slides can be moved in the travel areas F assigned to them. The assignment of the knife carriage to driving range F is shown by a dotted line. Furthermore, the calibration points 1 to 4 are located below the knife rail, the distance S from the zero point of the knife rail to the calibration point 1 being measured precisely during assembly. The calibration points 2 to 4 shown here by way of example are exactly determined in their position as described above by moving the knife slides and are then again available as calibration points.

It is crucial here that each calibration point at least has an adjacent calibration point to which one Connection through an overlapping driving area there is at least one knife carriage.

Claims (7)

1. Method for precise positioning of cutting devices for fabric webs, in particular paper webs, with variable cutting positions with the following features:

• 1.1 at least two, automatically movable, knife slides are used on a rail;
• 1.2 at least two position sensors are attached, distributed over the length of the rail;
• 1.3 the position of at least one position sensor is exactly determined;
• 1.4 the relative change in position of a slide is measured by displacement sensors;

characterized by the following features:

• 1.5 the position of the cutting tool of one of the knife slides is determined by passing one of the position sensors with an exactly predetermined position;
• 1.6 the measured knife carriage moves to the position of an adjacent, second sensor, with which this position is exactly determined;
• 1.7 the adjacent, second knife carriage moves to the now known position of the newly determined second sensor, as a result of which the position of the second knife carriage is determined;
• 1.8 Process steps 1.6 and 1.7 now begin in a repetitive manner until all position sensors and knife slides have been processed.

2. The method according to claim 1, characterized in that that more knife slides, their range of motion only in the area of a single position sensor by passing the person concerned Knife carriage on this position sensor exactly be positioned. 3. Device for performing the method according to claim 1 with:

• 3.1 at least two knife slides carrying the knives;
• 3.2 at least one rail carrying the knife carriage;
• 3.3 at least two fixed position sensors along the range of movement of the knife carriage;
• 3.4 means that measure the travel of the knife carriage;

characterized by the following features:

• 3.5 at least one position sensor is fixed at a precise known position;
• 3.6 for each pair of adjacent position sensors there is at least one knife carriage, the travel range of which intersects both position sensors.

4. Apparatus according to claim 3 and for carrying out the Process claim 2, characterized in that at least one further knife carriage is provided there is only one in its driving range Calibration point is located. 5. Apparatus according to claim 3 and 4, characterized characterized in that knife slides are provided, in their driving range there are more than two calibration points are located.