The above type of debarking mechanism is disclosed e. g. in US patents 4 685 498 and 5 394 912.

A problem with the above type of prior art debarking mechanisms is how to control the time that the trees to be debarked dwell or reside in the debarking mechanism. Excessive dwell time results in wood loss and, on the other hand, insufficient dwell time leaves too much bark on the trees. Dwell time should be readily changeable, depending e. g. on the type of wood to be barked and whether the wood is frozen or unfrozen.

Another drawback in the prior known solutions is that, due to the debarking mechanism having a closed end, the trees must be supplied into the debarking mechanism from above, i. e. the trees must be first hoisted up and then lowered or dropped into the debarking mechanism.

In order to eliminate these drawbacks, there is provided a debarking mechanism which is characterized in that the debarking mechanism has its end provided with an opening for feeding trees into the debarking mechanism in a direction which corresponds to the advancing direction of the trees within the debarking mechanism itself, and that for feeding the trees, the debarking mechanism has its admission side provided with a conveyor, said conveyor being adapted to positively feed the trees through the opening formed in the end of the debarking mechanism onto said support surface of the debarking mechanism carrying the trees, particularly onto its lower section.

By virtue of this arrangement, the degree of admission for a debarking mechanism, as well as dwell time for trees in a debarking mechanism, can be readily controlled.

The advancement of trees within a debarking mechanism itself can be made totally dependable upon the positive feed of a conveyor functioning as a supply system for the debarking mechanism. Another way of designing a debarking mechanism is of course that, in addition to the feeding action of the conveyor, the debarking mechanism itself provides either an encouraging or discouraging effect on the advancement of trees, e. g. by adjusting the inclination of the debarking mechanism.

The conveyor has a feed rate and, if necessary, also a feed force which are preferably regulable. At its simples, the feed rate regulation may comprise a mere switch for switching the conveyor on or off.

In one preferred embodiment of the invention, the conveyor is adapted to function as a storage for trees to be fed into the debarking mechanism.

Thus, trees can be supplied onto the conveyor at highly irregular intervals while maintaining a constant wood flow into the debarking mechanism itself.

Another influencing factor in terms of the operation of a debarking mechanism is the thickness of a layer of trees supplied onto the conveyor.

The maximum distance of an active conveyor section from the admission end of a debarking mechanism is preferably no more than a distance which complies with the average length of trees to be barked in the debarking mechanism. The proper selection of this distance in accordance with the average length of a tree ensures impeccability of the feeding of trees effected by means of a conveyor. For the same reason, the conveyor has its feeding direction and profile arranged in view of allowing also a free movement for trees in the upstream section of a debarking mechanism.

Between the conveyor and the debarking mechanism is preferably provided a guide element, comprising one or more guide surfaces for delivering trees into the debarking mechanism. In order to ensure proper guidance for the trees, the guide surface of the guide element guiding the trees is preferably designed, at least in its bottom section, so as to substantially comply with the cross-section of the support surface bearing the trees.

The opening provided in the end of the debarking mechanism is dimensioned, at least in its lower part, to be substantially equal to the size of a chute formed by the support surface present in the debarking mechanism, upon which the trees to be processed travel through the debarking mechanism.

The invention will now be described in more detail with reference to the accompanying drawings, in which: Fig. 1 shows in a schematic side view a junction between a debarking mechanism and a feeding mechanism.

Fig. 2 shows a section along a line II-II in fig. 1.

Fig. 3 shows a section along a line III-III in fig. 1.

The drawings depict a debarking mechanism 1 which is intended for the excortication or pretreatment of trees 2 for separately performed final barking and for the expulsion of at least some of the removed barks from a wood flow passing through the debarking mechanism.

The debarking mechanism 1 is provided with a number of debarking shafts 3, which extend parallel to an advancing direction A of the trees 2 to be fed therethrough and which are rotatable in the direction of an arrow 12 by means of a motor and drive elements, not shown.

The debarking shafts 3 are provided with a number of teeth 4 extending beyond the circumferential surface of the shaft 3, which are adapted to strip bark off the presently processed trees 2 transversely to the lengthwise direction of the trees and at the same time to convey the trees transversely relative to the debarking shafts 3.

The debarking shafts 3, together with their teeth 4, constitute a section of a support surface upon which the trees 2 to be processed travel through the debarking mechanism 1. The illustrated example includes four debarking shafts 3, which are fitted relative to each other so as to provide an inclined plane. Other than that, the support surfaces are solid surfaces, which are designed to form, together with the support surface constituted by the debarking shafts, an open-ended chute covering the debarking mechanism 1 from end to end. The chute may have an open top or it may be covered.

The debarking mechanism 1 has its end 5 provided with an opening 6 for feeding the trees 2 into the debarking mechanism 1 in a direction S, which is

consistent with the advancing direction A for the trees in the debarking mechanism 1 itself. Except for the opening 6, the end 5 is closed by a panel 9 in the illustrated example.

The opening 6 provided in the end 5 of the debarking mechanism 1 is dimensioned, at least in its lower part, to be equal to the size of a chute constituted by the support surface present in the debarking mechanism 1, upon which the trees 2 to be processed travel through the debarking mechanism 1.

In order to feed the trees 2 into the debarking mechanism 1, its admission side is provided with a conveyor 7. The conveyor 7, which can be any conventional type of conveyor, for example a chain conveyor, is adapted to positively feed the trees 2 through the opening 6 formed in the end 5 of the debarking mechanism 1 onto said support surface of the debarking mechanism bearing the trees 2, especially onto its bottom section.

The conveyor 7 has its feed rate and/or feed force adapted to be regulable in a per se known manner.

The conveyor 7 is adapted to function as a storage for the trees 2 to be fed into the debarking mechanism 1.

The maximum distance for an active section of the conveyor 7 from the admission end of the debarking mechanism 1 is no more than a distance L, which corresponds to the average length of trees to be treated in the debarking mechanism 1.

The feeding direction S of the conveyor 7 is at least roughly the same as the wood advancing direction A within the debarking mechanism 1.

The support surface of the conveyor 7, used for guiding the trees 2, has a cross-section which is designed, at least in its bottom part, to substantially comply with that of the support surface of the debarking mechanism 1 used for bearing the trees 2. The actual conveyor 7 is provided alongside the same, at least over the section near the end 5 of the debarking mechanism 1, with side panels 10,11.

Between the conveyor 7 and debarking mechanism 1 is provided a guide element 8, comprising one or more guide surfaces for guiding the trees 2 into the debarking mechanism 1. The guide element 8 has its guide surface, at least in its lower section, designed to be substantially consistent with the cross-section of the support surface of the debarking mechanism 1 used for bearing the trees.