Method and arrangement for feeding wood batches into a pressure grinder

A method of feeding a wood batch into a pressure grinder, the method comprising first collecting the wood batch to be fed into the grinder into a separate batch chamber above a side feeding chamber, from which the wood batch is lowered vertically by means of a separate supporting plate to the side feeding chamber. Thereafter, the wood batch is transferred from the side feeding chamber into the feeding chamber. An arrangement for feeding a wood batch into a pressure grinder comprises a batch chamber above a side feeding chamber and in which the wood batch to be fed into the pressure grinder is formed before it is lowered into the side feeding chamber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for feeding a wood batch into a pressure grinder, according to which method the wood batch is transferred first into a side feeding chamber, which is pressurizable to the same pressure as a continuously pressurized grinding chamber, and thereafter from the side feeding chamber into a feeding chamber where the wood batch is during grinding pushed into contact with a grinding element, such as a pulp stone, rotating in the grinding chamber, whereby the wood batch is transferred substantially horizontally from the side feeding chamber into the feeding chamber in the direction of the rotation axis of the grinding element.

The invention also relates to an arrangement for feeding wood batches into a pressure grinder, the arrangement comprising a frame forming a pressurizable grinding chamber, a rotating grinding element in the grinding chamber, a feeding chamber opening to the grinding chamber, feeding equipment for pushing a wood batch against the grinding element in the grinding chamber, a side feeding chamber on the side of the feeding chamber, a transfer apparatus for feeding the wood batch from the side feeding chamber into the feeding chamber in the direction of the shaft of the grinding element, and a feeding sluice for pressure-tight closing of a feed opening between the feeding chamber and the side feeding chamber.

2. Description of Related Art

CA Patent 1 255 530 discloses a method and equipment, wherein a wood batch is fed into a pressure grinder from the side substantially horizontally and in the direction of the rotation axis of the grinding element. This solution provides the advantage that feeding problems caused by a conventional way of dropping wood batches from above can be avoided. However, as to transferring and feeding the wood batches in particular, this solution has certain limitations, since wood must be transported and fed into the feeding chamber from the side to avoid the problems caused by the dropping. In case of grinder replacements, in particular, this means that the entire wood transportation mechanism has to be replaced, which, on one hand, increases costs and, on the other hand, causes problems in groundwood mill traffic and other functions.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and an arrangement for feeding wood batches from a wood feeding conveyor moving above a grinder from the side of the grinder into a feeding chamber simply and easily and without problems.

The method of the invention is characterized by collecting the wood batch to be fed first into a separate batch chamber above the side feeding chamber, by lowering said wood batch vertically by means of a separate supporting plate from the batch chamber to the side feeding chamber and only thereafter transferring it from the side feeding chamber into the feeding chamber.

The arrangement of the invention is characterized in that the arrangement comprises a batch chamber which is above the side feeding chamber and in which the wood batch is formed before it is fed into the side feeding chamber, that between the batch chamber and the side feeding chamber there is an inlet opening provided with a closing sluice which can be closed pressure-tightly, through which opening the formed wood batch can be transferred into the side feeding chamber, and a supporting plate which can be lifted and lowered by using transfer means and by which the wood batch formed in the batch chamber can be lowered as one whole to the side feeding chamber to transfer it from there into the feeding chamber.

The essential idea of the invention is that wood is dropped from a conveyor first to a separate batch chamber above a side feeding chamber, wherefrom the wood batch is lowered by means of a separate supporting element moving inside the side feeding chamber down to the side feeding chamber, from which the wood is then transferred in a known manner to a feeding chamber of a grinder to be ground.

The invention provides the advantage that a wood batch can be collected into a separate batching chamber, after which the wood batch, supported on the side walls of the batching chamber, can be transferred with a separate supporting element in a controlled manner from the batching chamber via an opening, which is located between the batching chamber and a side feeding chamber and can be opened and closed by means of a separate sluice, down to the side feeding chamber, and, after the sluice is closed, the wood batch can be transferred to the feeding chamber of the grinder without falling freely at any stage of the transfer. In this way, feeding problems due to free falling of a wood batch can be avoided easily and simply.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1aand1bshow a partial section of a prior art grinder from the side and from above, respectively. The grinder typically comprises a pressure-tight frame1, inside of which there is a grinding space2. A pulp stone3is rotatably mounted in the grinding space2to rotate around a shaft4. The shaft4, for its part, is connected to a non-shown rotation motor known per se, which is used for rotating the pulp stone3. The frame1is further connected with a feeding chamber5which is open towards the pulp stone3and has a rectangular cross-section and at the other end of which there is a feeding shoe8operated by a hydraulic cylinder7of feeding equipment6.

On the other side of the feeding chamber5there is a side feeding apparatus9, which is provided with a side feeding chamber10having preferably a rectangular cross-section. Bottoms10aand5aof the side feeding chamber10and of the feeding chamber5are in the same level, or the bottom10aof the side feeding chamber can be located a bit higher than the bottom of the feeding chamber5.

In the prior art, a side of the side feeding chamber10comprises an inlet opening11, in connection of which there is a closing sluice13operated by a separate pressure-medium cylinder12. The closing sluice13provides the inlet opening11with pressure-tight closure. The end of the side feeding chamber10facing the feeding chamber5comprises a transfer opening14, which leads to the feeding chamber5and can, correspondingly, be closed pressure-tightly by means of a feeding sluice16operated by a pressure-medium cylinder15. The end of the side feeding chamber10opposite to the feeding chamber5is provided with a transfer apparatus17, which comprises a transfer piston18inside the side feeding chamber10and a pressure-medium cylinder19connected thereto, which can be used for pushing a wood batch from inside of the side feeding chamber10to the feeding chamber5one batch at a time.

FIGS. 2aand2bschematically show a partial section of an arrangement of the invention from the side and from an end, respectively. As appears from the figures, in the arrangement of the invention the sides of the side feeding chamber10are uniform, and an inlet opening11′ for feeding a wood batch into the side feeding chamber10is formed in the upper part of the side feeding chamber. Above the side feeding chamber there is, respectively, a closing sluice13′, by which the inlet opening11′ above the side feeding chamber10can be closed pressure-tightly. Above the side feeding chamber10there is a batch chamber20, to which a wood batch to be fed into the grinder at one time can be fed by using a separate wood conveyor21. The upper side of the batch chamber20is open so that cut-to-size logs of wood supplied from the conveyor21can, one at a time, fall freely thereto. The figure also shows a supporting plate22, which is located on the bottom of the side feeding chamber and arranged to be lifted and lowered by means of a suitable power unit. The supporting plate22is located on the bottom of the side feeding chamber10, thus forming a basal surface, along which the wood batch in the side feeding chamber10is pushed into the feeding chamber5. The lifting and lowering mechanism of the supporting plate22can be, for instance, a pressure-medium cylinder23or another lifting and lowering mechanism functioning in a manner known per se and forming the transfer means for the supporting plate22.

FIGS. 3ato3cschematically illustrate operation of a method and arrangement of the invention from the direction ofFIG. 2b.FIG. 3aillustrates a situation where the feeding chamber5of the grinder contains a wood batch, which is pushed against the pulp stone3in a manner known per se during the grinding while the pulp stone is rotating. Simultaneously, water is fed to the grinder in a conventional way to form a fiber pulp mixture and to cool the pulp stone. Correspondingly, the side feeding chamber10contains a new wood batch waiting to be transferred into the feeding chamber5. The sluice13′ of the inlet opening11′ above the side feeding chamber is pushed into its place so that the inlet opening11′ is closed. The batch chamber20is empty, since the wood batch it contained has been transferred to the side feeding chamber10.

FIG. 3billustrates a situation where the grinding of the wood batch which was in the feeding chamber5is now completed and a new wood batch is transferred from the side feeding chamber10to the feeding chamber5. In this case, the feeding sluice16closing the transfer opening14between the side feeding chamber10and the feeding chamber5is moved to the side so that the transfer opening14is open and the wood batch is pushed by means of the transfer piston18of a pushing device17so that the wood batch is transferred to the feeding chamber5. In this case, the feeding shoe8, which can be seen inFIGS. 1aand1b, is pulled accordingly to its rearmost position to transfer the wood batch to the feeding chamber5. When the wood batch is pushed to the feeding chamber5, the transfer piston18is pulled back and the feeding sluice16is pushed into its place so that the feeding chamber5and the side feeding chamber10are separated from each other pressure-tightly.

FIG. 3c, for its part, shows how a new wood batch is fed into the side feeding chamber. The closing sluice13′ above the side feeding chamber is moved to the side so that the supporting plate22on the bottom of the side feeding chamber10is lifted as high as to the lower part of the batch chamber20. Thereafter, cut-to-size logs are brought with the conveyor, the logs falling onto the supporting plate22, until the number of logs in the batch chamber20corresponds to that of one wood batch. Supported by the supporting plate22, this wood batch is lowered down to the side feeding chamber10, after which the closing sluice13′ is closed pressure-tightly so that when a new wood batch is fed, the side feeding chamber can be pressurized to the same pressure as the feeding chamber5and the grinding chamber2before the transferring of the wood batch into the feeding chamber is started.

FIGS. 4ato4c, in turn, show a second embodiment of the method and arrangement of the invention. In this embodiment, asFIG. 4ashows, a wood batch is dropped onto the closing sluice13′ of the batch chamber20to wait until it is possible to lower the batch to the side feeding chamber10. The wood in the side feeding chamber10was already transferred into the feeding chamber5earlier in a manner shown inFIGS. 3ato3cand the transfer piston18is brought back to the end of the side feeding chamber10. The supporting plate22, for its part, is lifted up in a manner shown in the figure so that it is immediately under the closing sluice13′ ready to receive a wood batch from the batch chamber20.

FIG. 4bshows a situation where the closing sluice13′ is pulled to the side from under the wood batch and the wood batch is lowered onto the supporting plate22so that the walls of the batch chamber20keep it in good order.

FIG. 4c, in turn, shows a situation where a wood batch is lowered with the supporting plate22down to the side feeding chamber10, after which the closing sluice13′ can be closed so that the side feeding chamber10is closed pressure-tightly in respect of the outside air and, to feed the wood batch into the feeding chamber5, can be pressurized in a known manner to the same pressure as the feeding chamber and the grinding chamber2. At the same time, the batch chamber20can be filled again by feeding logs of wood from the conveyor21to the batch chamber.

FIG. 5schematically shows a third embodiment of the method and arrangement of invention, which otherwise corresponds to the embodiment ofFIGS. 3ato3c, but the operational distance of the supporting plate22is longer than in the other embodiments. In this embodiment, the supporting plate22can be lifted nearly as high as to the level of the conveyor21. In this case, logs of wood supplied from the conveyor21to the supporting plate22fall only a short distance, and therefore they do not move restlessly nor are they set obliquely onto the supporting plate22. When new logs are fed onto the supporting plate22in the batch chamber20, the supporting plate22is simultaneously lowered so that the falling distance of new logs remains quite short, until a suitable batch of wood is formed on top of the supporting plate22and it can be lowered through the opening11′ to the side feeding chamber10.

FIGS. 6ato6cshow a fourth embodiment of the method and arrangement of the invention, which may be a solution based on one of the embodiments of the invention shown above, whereby the numbering of the parts corresponds to the numbering previously used for identical parts. This embodiment of the invention differs from the previous embodiments in that it comprises a separate transfer support24, which is used for maintaining a wood batch in a suitable shape during the transfer. The transfer support24is a trough provided with an opening on its upper side or a supporting frame formed by sides connected to each other in the transverse direction, into which transfer support a wood batch is lowered by means of the supporting plate22so that it is supported by the side walls24aof the transfer support24. When the wood batch is transferred from the side feeding chamber10into the feeding chamber5, the transfer support24, along with the wood batch, is simultaneously transferred by using the transfer means, such as a transfer cylinder25until the entire wood batch is in the feeding chamber5. After this, most preferably the transfer support24is first pulled out of the feeding chamber back to the side feeding chamber10, while the transfer piston18supports the wood batch at its end and thus hinders it from moving back along with the transfer support24.FIG. 6billustrates this. When the transfer support24is pulled back to the side feeding chamber10and the transfer piston18is pulled out of the feeding chamber5, the sluice16can be closed and the grinding of the wood batch in the feeding chamber5can be started.

In the above description and drawings, the invention is described only by way of example and it is not restricted thereto in any way. It is essential that a wood batch is collected from a conveyor above a grinder, specifically to a batch chamber above a side feeding chamber, and then transferred from the batch chamber in a controlled manner, supported by a supporting plate or a similar supporter, to the side feeding chamber so that the shape of the wood batch is maintained, after which the side feeding chamber is closed pressure-tightly in respect of the outside air and, when the wood batch is transferred into the feeding chamber, the side feeding chamber is pressurized to the same pressure as the feeding chamber and the grinding chamber to transfer the wood batch in a controlled manner in the direction of the grinder shaft from the side feeding chamber to the feeding chamber to be fed against the pulp stone.