To release said type of biockage/stoppage, known devices have generally required that the production line is stopped for releasing or displacing the tree trunks by low- ering any type of lifting means into the hopper.

The object of the present invention is to provide a procedure and arrangements for the operator to release blockage occurring in the feed hopper, or for preventing blockage at an earlier stage.

This object is met according to the invention by providing a procedure, which is char- acterized by the momentary or controlled insertion of one or several lifting means, projecting from the inner side of the hopper. The lifting arrangement causes at least part of the timber in the feed hopper to be raised and thereby to release the timber which is wedged inside the hopper, or is used momentarily to limit the amount of tree trunks supplied to the hopper.

A remote-controlled lifting means will thereby make the operator able to release blockage occurring in the hopper, or more preferred, to prevent the occurrence of blockage at an earlier stage by the controlled and/or momentary operation of the lift- ing means, whereby an uninterrupted flow of timber is secured.

The lifting means of the invention comprises one or several lifting arms, operable to be inserted through an opening formed in the inner surface of the hopper. In the in- serted position, the free end of each lifting arm projects from the inner surface of the hopper, and in a retracted position the free end of the lifting arm is levelled with, or below, the inner surface of the hopper.

In a preferred embodiment of the invention, the opening for the lifting means is pro- vided in the bottom of the feed hopper. In this embodiment, the raising of the wedged timber is performed simply by a straight upward lifting motion of the lifting means.

In another preferred embodiment of the invention, the lifting means is formed as a curved lever arm. One end of the curved arm is rotatably secured outside of the hopper. In this second embodiment, the lifting means and associated drive means are arranged generally by the side of the hopper, an arrangement which is consid- ered to be mostly preferred in aspect of required mounting space.

In view of a most rapid operation for preventing additional tree trunks to be supplied to the hopper in case of a blockage, the invention provides, in yet another embodi- ment, an insertable limiting means. Said limiter is provided generally by the side of the feed hopper inlet, and arranged to be insertable in the supply line for stopping the flow of timber, supplied to the feed hopper.

The invention is more clearly disclosed below, reference being made to the attached drawings. In the drawings, Fig. 1 is a diagrammatic view from above, showing a feed hopper and associ- ated wood chipper equipped according to the invention; Fig. 2 is a sectional view of line ll-ll in fig. 1, and Fig. 3 is a sectional view according to fig. 2, the lifting means shown in a raised position.

In fig. 1, the reference number 1 represents a feed hopper for a wood chipper, the tree trunks being supplied to the hopper by a conveyor 11 on the right hand side of the drawing. From the hopper 1, tree trunks are introduced to the cutter or disc chip- per 2, on the left hand side of fig. 1.

The inventive device, generally referred to as 10, includes one or several lifting means 4. The lifting means 4 are arranged to be insertable through one or several openings 5, formed in the inner face of the hopper 1, on the side or in the bottom 7 of the hopper (as of the drawing, the bottom 7). In the inserted position (see fig. 3), the lifting means 4 projects with a free end 6 from the hopper inner face, and in a retracted position (see fig. 2) the free end 6 of the lifting means 4 is levelled with, or below, the inner face of the hopper. Preferably, the free end is levelled with the hop- per inner face in the retracted position.

In the embodiment shown in the drawing, the lifting means 4 includes a curved or bowshaped lever arm, one end of which is rotatably secured in a beam or other sup- porting structure of the hopper, outside of the hopper. Two lifting arms 4 are inter- connected by a connection beam 12 to provide a complete lifting arrangement, the raising and lowering of the lifting means being effected by a hydraulic cylinder 13.

One end of the cylinder 13 is connected to the connection beam 12, and the other end is connected to the supporting structure of the feed hopper. It should be appar- ent, that the lifting means 4 may be differently structured and may e. g. be shaped as a straight rod. Considering a limited building space, the curved or bowshaped con- figuration is more often the most preferred embodiment.

The lifting means 4 is here shown to be a structural element, controlled by the op- erator to be projected from the inner face of the hopper 1 as required for releasing wedged tree trunks, or momentarily for limiting the amount of tree trunks supplied to the disc chipper 2.

The embodiment of the inventive assembly 10 as shown in the drawings may addi- tionally include a limiting means 9, arranged by the side of the hopper inlet 8. The limiter 9 is controlled to be inserted above the conveyor, thereby stopping the flow of tree trunks supplied to the feed hopper.