FI77700B - FOERFARANDE OCH ANORDNING FOER MAETNING AV MATNINGSHASTIGHETEN AV TRAE I EN KONTINUERLIG SLIPANORDNING. - Google Patents

Description

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The invention relates to a method and an apparatus for measuring the feed rate of wood in a continuous grinder for producing wood chips, in which device there is an opening above the grinding stone, into which the direction.

German patent publication 18 13 287 discloses a control device for a feed motor which automatically adjusts the feed rate for the grinding stage to an optimum value of 15. In such plants, the speed of the goods, e.g. due to the difference between the actual feed rate. In order to precisely adjust the material density and to evaluate the grinding work, it is necessary to know the actual feed and in order to adjust the specific grinding work. In previous installations, mechanical identification methods were used almost exclusively to measure wood input. These could not withstand the uneven operating conditions or air conditions at the opening.

The present invention is therefore based on the object of creating a method and an apparatus which make it possible to measure the actual feed rate of wood and to withstand uneven operating conditions.

35 The problem is solved with respect to the 2 77700 method of the type described above by measuring the time required by at least one tree trunk for a given feeding distance in front of small logs and detecting the speed via an interpretation unit. Preferably, at the time of the sauna, the actual speed of the three logs is detected and the average speed of the three small logs is observed. The motion of one or more small trunks can be transmitted by optical means and the interpretation of the transmitted signal. Thus, the interpretation of the wood feed could be performed with a video camera or equivalent, which can achieve a high degree of interpretation. However, the structural elements used for this purpose are currently very expensive.

Suitably, the feed distances are given via the distance of the two non-contact signal sensors in the wood log feeder. The movement of one frame is preferably monitored by more than two non-contact signal sensors arranged in the feed direction of the tree frame, each measuring the time between two adjacent signal sensors and each time detecting the speed between the two signal sensors. As a particularly preferred embodiment of the method according to the invention, the movement of one tree frame is detected by five signal sensors arranged in the feed direction of the tree frame.

The movement of the wood frame can be detected by ultrasonic sensing signal sensors or optically sensing signal sensors. Infrared cells, in particular reflection infrared cells, are preferably used as signal sensors. Preferably, sensing devices that are not sensitive to high temperatures, dusting or vibration must be used. The palpable wood frames have a wide variety of colors on the surface and are often contaminated with soot, so that reliable detection of the measured value can be difficult. It has been found that among the possible spectral ranges of infrared cells, infrared cells with a spectral range of 900 to 1000 nm, preferably with a maximum at 930 nm, give particularly reliable results.

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3 77700 In order to eliminate sources of interference, it has proved expedient to synchronize the signal for infrared light sources. A clock frequency of 20 kHz has proven to be particularly reliable. In addition, the reflection infrared cells 5 have good optical accuracy and relatively small coverage areas.

Conveniently, the detection takes place as close as possible to the grindstone and in the center of the opening wall as far away as possible from the guide members, because when measured too far in the top opening, the feed measured there does not match the feed at the grindstone, as the wood stack becomes even more compacted. On the other hand, it must be avoided that the signal sensor becomes contaminated by the fiber sprayer, which occurs especially when it is fitted too close to the grindstone.

It has been found that if the grindstone runs perfectly in water, a distance of about 50 cm between the measuring cells and the grindstone is sufficient, and if there is only so much water in the gutter that the grindstone only comes into contact with water from the bottom 20, the distance between the measuring cells and the grindstone should not less than about 1 m. The distance from the underside of the upper chain sprocket should not be less than 50 cm.

In one device for carrying out the method 25 according to the invention, at least two signal sensors arranged at the bottom in the feed direction of the wooden frame are fixed to the opening wall, which together form a measuring distance for the wooden frame, which are electrically connected to the interpretation unit. Preferably, more than one measuring distance is arranged, expediently three measuring distances to the opening wall. The measuring distances are arranged side by side, preferably offset side by side. The measuring distance or distances are arranged in the center of the opening wall and as close as possible to the grindstone.

Preferably, the measuring distance consists of optical signal sensors, in particular reflective infrared cells. Infrared cells have a spectral range of 900 to 1000 nm, preferably up to 980 nm. The measuring distance can also consist of ultrasonic signal sensors. The distance between the two signal sensors is expediently in the range 10-50 mm, preferably 30-40 mm. To avoid connection errors, attention must be paid to the correct distance of the sensor from the tree trunk and the correct maximum range of the sensing devices. The interpretation unit shall be constructed in such a way that error measurements due to landing chips and lateral wood pledging are excluded.

An optical receiving means arranged in the aperture wall, such as a television camera, for example, can also be used with the interpretation unit. Another possibility is to use a photodiode camera.

The advantages of the new method and device are that the actual wood feed rate is measured despite the unfavorable air conditions in the orifice, so that it is possible to meaningfully adjust the density of the material in the trough and to make a meaningful adjustment of the specific energy for the production of groundwood.

The invention will be described in more detail with the aid of the drawings and the following description.

25 The drawings show: Fig. 1 a schematic description of a continuous grinder, Fig. 2 a schematic adjustment of the measuring distance, Fig. 3 a time course of a signal in two signal sensors, Fig. 4 a schematic description of a wood grinder with several measuring distances and an interpretation unit, Fig. 5 a block diagram showing adjusting the material density of the tray in a continuous grinder, and 11 5 77700 Fig. 6 is a block diagram showing the basic adjustment of the specific energy via the actual feed rate.

The wood frames 1 are fed by automatic feed 5 5 to a continuous grinding device. A wooden stack 3 is formed above the grinding stone 2. The necessary additional feed is provided via grinding chains 4 arranged on both sides of the grinding stone. The speed of the chains is measured with a tachometer 6. The speed of the chains was also deduced from the feed rate of the wood in the 10 hitherto used devices, so that certain inaccuracies have been associated with slip to evaluate the grinding work and determine the material density.

Figure 2 shows, for example, a schematic operating structure consisting of five signal-15 sensors 7 for measuring input. Five superimposed signal sensors form a measuring distance for one small wood wire 1. As the signal sensor, infrared reflection cells are used, which, in the case of the reflection of the beams, give off the signal under the influence of the tree trunk, so that a signal flow is generated, as shown in Fig. 3 in the example of two signal sensors. The cells are arranged at equal distances from each other. The cells have a spectral range of 900 to 1000 nm with a maximum at 930 nm.

Such a feature is, for example, with a GA-As diode of the type CQY 35. The distance is 10-50 mm, preferably 30-40 mm. The distance should be less than the diameter of the smallest tree trunk in order to accurately measure the speed of the tree trunk. As shown in Fig. 2, several wooden frames 30 can be located simultaneously in the pushing direction during the measuring distance.

When the tree trunk enters the measurement range and reflects the infrared rays, the output signal from the signal sensor, i.e. the cell, changes its value, either from logic 0 to logic 1 or vice versa. Looking at the feed direction, the second measuring cell does not at this time still receive any reflected light, because the infrared beam emanating from it is exactly on the opening 8 between the two wooden frames. If now the edge of the tree trunk comes into the infrared beam of the second cell, the output-5 signal in this cell also changes corresponding to the first cell, as shown in Fig. 3. The time from the input of the first infrared beam of the tree frame to the input of the second infrared beam can be determined by means of jump-varying output signals in the interpretation unit, which then detects the actual speed via the distance detected between the cells. The same measurement takes place when the infrared beam passes through a tree trunk. In this way, within the measuring distance, depending on the number of cells in each case, the speed of the tree trunk in the area between the two cells in question can be detected momentarily. In the case of several offset-matched measuring distances, the instantaneous detected speed value is detected.

Since in practice it may happen that the individual frames move so that the tree frame 20 in the measuring area leaves the measurement distance laterally during the measurement, it is advantageous to make the distance between the individual cells smaller than the smallest diameter of the tree frame. Then the errors during the signal, as shown in Fig. 3, can be detected as error measurements.

25 It must be considered in the error measurement if the signal flow of the first cell has two groups of pulses within one time span, the signal flow of the second cell has only one group of pulses within 30 within the time span transmitted until the input of the same sphere. As long as the same pulse train is given, the velocities of frames with diameters smaller than the distance of the cells are also measurable. In addition, the distance of the cells is further determined by the switching speed of the infrared reflection cells, so that the cells 35 cannot therefore be arranged arbitrarily close to each other.

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Figure 4 schematically illustrates a continuous grinding device with built-in signal sensors, which in each case form a measuring distance 9. The measuring distances are arranged above the grinding stone in the front opening wall 10 of the wooden frame 5 and connected to the interpretation unit 11 by cables. on the other hand, there is no further substantial compaction of the wood in the opening due to 10 displacements. The interpretation unit uses the average method to determine the measured value for the adjustment, because several measured values arrive at the same time.

As the measured value sensors, a photodiode field could be used, which also provides corresponding signals to the interpretation unit on the basis of the light / dark connections, or ultrasonic measured value sensors. Another possibility consists, for example, in detecting tree trunks by means of a television camera, transmitting the image with a pixel converter and interpreting the pixels via the interpretation unit 20. However, the method and device according to the invention have proved to be very advantageous.

Figure 5 shows the practical use of measuring the actual wood feed rate. The actual feed rate of the wood determines the material density in the grinder tray if the spray water volume of the grinder remains constant. However, since the material density of the trough is an important parameter for the behavior of the grinder, this should be adjusted. This adjustment is shown in the block diagram in Figure 5.

After the feed rate EV has been observed, 30 of the amount of spray water is sprayed onto the grindstone and the actual material density IS is measured in a flow meter DM. The new spray water setpoint SWS is obtained from the ratio of the material density setpoint SS to the actual material density IS multiplied by the old spray water setpoint. 35 The difference between the new injection water setpoint SWS and the actual value of the injection water 8 77700, measured in the flow meter DM, is fed to the controller R, which controls the motor valve M, to change the injection water volume SWM. Limiter B ensures that 5 minimum amounts of water are not exceeded.

Another use of the measurement method of the present invention is illustrated in Figure 6 in a block diagram and will be described below. In order to produce wood chips, it makes technological sense to produce it according to a specific 10 energy uses. The degree of grinding and the fraction of this wood chips then work to determine the specific energy setpoint. The following adjustment is possible by measuring the actual feed rate:

The specific reference energy IE is calculated from the intake power N of the grinder 15 and the actual wood feed rate IHV. After smoothing the setpoint SE for the specific energy, the ratio of the ratio of the specific setpoint energy to the specific actual energy multiplied by the actual wood feed rate is observed as the guide wood feed rate SHV. The difference between the guide wood feed rate SHV and the actual wood feed rate IHV is fed to the controller R, which changes the chain speed NSK of the grinder chains. The chain speed is limited by the maximum chain speed or a maximum of 25 slips between the chain and the tree. The slip is defined as the difference between the actual feed speed of the wood and the twist speed.

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Claims (13)

A method for measuring the feed rate in a continuous wood grind for the production of wood pulp, which has a shaft above the grinding stone, in which are arranged horizontally on each other wooden sticks, which move in the direction of the grinding stone by means of means at the sides of the shaft and by their own weight. , characterized in that the time necessary for a given feed distance for at least one log is measured at the gable side of the log and the speed is calculated by means of an evaluation unit. Method according to claim 1, characterized in that the actual speed of three logs is recorded simultaneously and the average speed is calculated. 3. A method according to claim 1 or 2, characterized in that the motion of one or more logs is transmitted by optical means and the transmitted image is evaluated. 20 4. A method according to claim 1 or 2, characterized in that the feed distance is obtained by the distance between two contactless signal transducers in the feed direction of the log. 5. A method according to claim 4, characterized in that the motion of a log is obtained by more than two contactless signal transducers arranged in the feed direction of the log, by measuring the time between two adjacent signal transducers and the velocity is calculated everywhere between two signal transducers. 30 6. A method according to claim 4 or 5, characterized in that the movement of a log is recorded by optical sensing signal transducer. 7. A method according to claim 6, characterized in that reflection infrared cells are used for the detection.