FI84733B - FOERFARANDE FOER REGLERING AV ETT SLIPVERK. - Google Patents

Description

84733

METHOD FOR ADJUSTING THE GRINDING MACHINE - FÖRFARANDE FÖR REGLE-RING AV ETT SLIPVERK

The present invention relates to a method according to the preamble of claim 1. One such method is known from DE-OS 33 25 049. As is generally known, in such a method, the abrasive stone is placed at a certain height in the wood chips accumulated in the abrasive basin with a consistency (density) of 2-3%. In principle, it is known, e.g. from DE-OS 36 00 203, to grind, i.e. to adjust the determined dependence of the wood grinding power in relation to the amount of wood chips obtained, so that the specific working requirement of the grinder, i.e. kWh used per ton, is as constant as possible.

The former publication further influences, depending on the specific work requirements, the temperature of the wood chips either in the sanding basin or in the spray water or in the wood shaft in order to keep the sanding conditions as constant as possible. Namely, the disturbances of the wood chips process, after reaching certain proportions, are usually very difficult (i.e. only over a long period of time) to adjust, so that on average the process result becomes relatively poor. The breaking strength or drying properties of wood chips at least partially meet only poor requirements.

It is an object of the present invention to improve the adjustment so that the adjustment operations can take place in a timely manner or so efficiently as to avoid major disturbances in the production of wood chips in the grinder.

This object is solved according to the invention by the features defined by the claim.

In the following, the invention will be explained in detail by means of an exemplary embodiment thereof with reference to the accompanying drawing, in which 2 84733

Fig. 1 shows a cross-section of a grinding machine according to the invention to which a control component is connected.

Fig. 2 shows a part of the cross-section enlarged at the grinding basin.

Figure 1 shows a basically continuous grinding machine in which wood logs are fed by a conveyor belt 31 into a feed shaft delimited on the sides by conveyor chains 30.

The conveyor chains 30, driven by the motors 33, press the wood pellets in the shaft 26 against the grinding stone 2, which processes the wood pellet suspension accumulating in the sanding basin from the wood pellets, under the action of a water jet through the nozzles 25. The height of the wood grinding pension at the outlet of the grinding basin 8 is adjusted by means of a pressure sensor 11 by a regulator 22 which controls the valve 10 of the control motor 12 in the grinding basin discharge line 9. Due to the roughing of the surface boards, a chip shredder 24 With 23. Dilution water is fed into the grinding basin via line 3 and sprayed by nozzles 7. The temperature of the dilution water, which is usually the return water of an industrial plant, can be regulated by cold water make-up by means of line 4 and a valve 5 controlled by controller 1.

The sensor 6 indicates the temperature in the grinding pool to the controller 1, with which the temperature of the wood grinding suspension in the grinding pool is kept substantially constant, for example about 85 °. It has been found that a very high temperature (grinding pool temperature) of the wood grinding suspension in the grinding pool is very advantageous for a good grinding process. It can be said that the higher the temperature in the grinding pool, the higher the temperature in the grinding zone at the grindstone. Correspondingly, the quality of wood chips also improves. However, the temperature must not be chosen or raised so high as to lead to intense evaporation in the grinding zone, which evaporation is known to occur in part. In that case, the stone is provided with a coarse fiber loose end. fibrous pieces or short fibers from the wood joint, however, in order to obtain a wood grinding suspension containing relatively long fibers by uniform grinding. However, the temperature in such an open-ground grinder, which only operates at normal atmospheric pressure, must in no case exceed the limit of about 90-95 °. The temperature sensor 6 and the controller 1 ensure that the temperature in the grinding pool does not rise too much.

It is known that the control of the constant specific work requirement has a connection between the stone's operating power and the wood supply, in which case an upper limit must be set for the stone's operating power if possible. However, due to the desired constant constant specific work need, a situation arises in which the operating power of the stone exceeds this upper limit. Depending on the roughness (steel depth) of the grindstone 2, a more or less intense heating of the wood takes place in the grinding zone, i.e. covered by wooden sticks, in the upper surface area of the grindstone 2. The above measures limit the temperature rise to such an extent that it does not lead to "burning" of the wood, i.e. browning. Despite this, the operating power of the grinding stone and thus also the operating power of the wood feed cannot always be controlled in this way in a timely manner. The current consumption of the feed motor is a function of the torque and thus also indirectly a function of the grinding pressure. A momentary change in the grinding of the working stone will inevitably lead to a change in the grinding pressure and the operating power of the stone. If the stone's operating power exceeds a value that is above the adjustment limit for a constant specific work requirement, the grinder will operate at the maximum wood feed, which can then be so high that 4 84733 unstable or otherwise unacceptable conditions may arise for the grindstone.

The immersion depth of the grinding stone 2 thus affects the instantaneous bite of the working stone and thus also the energy requirement of the grinding machine.

As shown in Fig. 2, the immersion depth of the grinding stone 2 in the wood grinding suspension accumulated in the grinding pool 8 can be adjusted by a shut-off flap 15 pivotally attached to the partition 14 depending on the stepper motor 17 mounted on the grinding wheel bracket 18 In this case, the rack 20 moves the shut-off flap 15 via the intermediate levers 21 articulated to both ends.

According to the invention, the shut-off valve control, depending on the supply current i of the drive motors 33, includes the chains 30 in the control concept as follows:

An upper and lower limit value is given for the supply current i, which must be freely selectable for each grinder. When the supply current i moves within these limits, the closing flap 15 remains in the middle position, which according to experience corresponds to the optimal depth of immersion of the stone. If the supply current i exceeds the upper limit for longer than a given (variable) period by a given (variable) amount, the shut-off flap 15 moves a certain amount to the right and the level of wood chips in the basin 8 decreases. If, after a certain (variable) time, the upper limit is still exceeded, the shut-off flap 15 lowers a certain amount again. If the upper limit is exceeded for a longer period, the process continues until the closing flap has reached its deepest position, which corresponds to the minimum permissible depth of immersion of the stone. Also for safety reasons, an additional, preferably mechanical downward limiter is necessary.

In the case of underspending of the supply motor current, in principle the same adjustment process takes place, but in the opposite direction, i.e. by means of the shut-off flap 15, the level of the wood chips suspension in the basin 8 is gradually increased up to the maximum position. If the supply current returns to the normal range for a certain time after the limit value triggered by the control process is undershot or exceeded, the shut-off flap moves back to its middle position (usually the home position).

Claims (1)

6 84733 CLAIMS A method for adjusting a wood grinder in which the specific working requirement of a wood grinder is adjusted to a constant value as constant as possible so that there is a connection between the stone power (, P2) and the wood feed power, the wood with adhesive pushers, characterized in that when the upper limit value of the current input of the wood supply (chains 30) drive motor (33) is exceeded, the pool level is reduced stepwise to the minimum pool limit until the upper limit is exceeded and that the lower limit of the wood supply drive motor is lowered . 7 84733 For the purpose of adjusting the slip network, the colors and the adjusting of the specifics of the slip network, the head of which is a constant value with the same value, and the same value as the three-way drive (P overhead line or line and stepping stone with rounding element in the operating element, kännetecknatav att vid över-skridande av ett övre gränsvärde hos strömupptagningen hos drive drivmotorn (33) förtre grille (number 30) the minimum number of grids in the treadmill, which means that the number of grids in the traction unit has been removed from the traction unit.