This invention concerns a feeding wheel or roller for wood processors and wood harvesters. In these machines tree trunks or logs are pulled or forced past branch re- moveing knives. With increasing size of the trees the branches can be of considerable thickness and as a con¬ sequence the necessary pulling force will also be quite considerable. This transporting or pulling of the trees past the debranching knives is obtained by means of feed¬ ing wheels or rollers.

These feeding wheels must at the same time obtain a very good grip on the tree in order to obtain the neces¬ sary pulling forces and they must also treat the tree trunk as gentle as possible since otherwise the quality of the tree is impaired. If the grip is too hard the fibers might be damaged which in turn leads to blueing wood and fungus attacs which leads to an impaired quality and a lower price. The feeding wheels existing today on the market is either massive rubber wheels or wheels provided with in¬ flated tyres.

For greater machines air filled tyres is a rather acceptable solution for smaller units this solution how- ever is too expensive. For ' smaller units massive rubber wheels or" rollers has been used. However the rubber quite frequently works itself lose from the metal hub portion. This is particularly the case when anti-skid chains are applied to the feeder wheels in order to improve the grip. In other words when the grip between tree and rubber improve forces will become too great between rubber and metal.

Furthermore the use of anti-skid chains easily give rise to the above mentioned damages to the wood and the rubber whether massive or air cushioned may easily

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become prematurly worn, resulting in undesirable costs.

The object of the invention is to provied a feed¬ ing wheel for wood processors and wood harvesters that can easily and at a rather low cost be fabricated even for small units and that provide a good wear resistance and a good grip. -This is in accordance with the invention achieved by means of a feeding wheel with an outer layer of an elastic material that is vulcanized to an inner supporting and carrying structure preferably of steel, and in turn connected to the hub. Furthermore radial holes extends through the rubbber layer as well as the support¬ ing layer.

Since the holes allow loose bark etc. to fall straight through the wheel its ability to function as a lubricant between tree and wheel is considerably diminshed. The wheel becomes self cleaning. As a result of this it is no longer necessary to use a high friction material for the outer layer. Instead an extreme wear resistent but low friction material can be used i.a. uretan rubber. Naturally also the holes will reduce the contact surface between wheel and wood thereby also increasing the grip. The grip is further enhanced by branch residues and other irregularities gripping into the holes. By preferably providing the hub in one end of the wheel bark and wood residues that enter into the wheel through the radial holes can easily fall out axially out of the wheel.

The radial holes may be arranged in different patterns and may be round or have other shapes. Of course also the outer surface as well as the connecting surfaces between elastic layer and supporting structure may be profiled to improve the grip.

To increase the elasticity (if desired) of the elastic layer this may of course be provided with cavities in one form or another i.a. axially extending holes.

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It should in this context also be mentioned that the use of polyuretan rubber enables the use of simple unexpensive fabrication methods.

Particularily in the spring when the bark of many trees is full of juice it may be very difficult to obtain a grip with conventional feeding wheels as well as the above described. The trees quite simply becomes too slippery. The conventional use of anti-skid chains lead as has been said above very easily to damages in the wood and to the feeding wheels. In a further development of the invention these set-backs are eliminated in a simple man¬ ner resulting in a good grip but without damages to the wood in a simple and unexpensive way. This is achieved by providing anti-skid means in the shape of hard gripping means extending through radial holes. These hard grip means can i.a. be of metal and extend through the holes and are fastened on inside and outside but in principle floating in the holes so that when a great force is excerted on them they are resiliently pushed into the elastic material. In a preferable development of the invention these hard grip means are U-shaped yokes, with their legs extending through two holes and then fastened on the inside. This fastening can be by means of screw ends and nuts, but also other fastening means is of course possible i.a. pins. Due to the resilient arrangements the risk of damage to the wood is eliminated. The grip in¬ creasing means are furter easily exchanged or mounted and demounted. In the case of U-shaped grip increasing means the corresponding holes are preferably arranged along the same generatrix.

Of course one can use up all the holes in the wheel to arrange metal grip increasing means but preferably some of the holes are left intact BO that wood residue bark etc. as before is allowed to enter into the wheel to pre- vent it from serving as a lubricant.

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Since the grip increasing means are not only coupled via the elastic mantle or layer of the wheel but directly to the inner carrying structure or steel mantle there is no risk of the grip increasing means tearing the elastic layer off from the inner supporting structure and in fact the friction or grip increasing means increase the grip between the elastic layer and the inner supporting layer. The floating character of the friction increasing means is enhanced by the use of a low friction elastic material i.a. polyuretan rubber.

In order to reduce wear on the grip increasing means the holes in the inner supporting mantel may be provided with a layer of the same material as the outer elastic low friction layer which so to say can protrude into the holes in the supporting structure. Preferably the supporting structure carrying the elastic layer is cylin¬ drical.

Further features and advantages of the invention are apparent from the following description of a preferred embodiment shown in the drawings. In the drawings fig 1 depicts the general use of the feeding wheels according to the invention, fig 2 shows a first feeding wheel, fig 3 a second feeding wheel and fig 4 an enlarged part section of the wheel in fig 3. In fig 1 is illustrated two feeding wheels 1. These are journaled with parallel rotational axis and are by not shown means pressed against a tree trunk 6. Rotation of the feeding wheels 1 pull the trunk 6 forward so that knives 7 arranged around the trunk 6 cut off the branches one by one.

The feeding wheels incorporate as can be seen from fig 1 and 2 an inner steel cylinder 2, which in its upper end is welded to a disk 5 provided with holes so that it can be fastened to a driving element (not shown). To the cylinder 2 a mantel or layer 3 _» likewise cylindrical of

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polyuretan rubber is vulcanized. Radial holes 4 extend through the polyuretan layer and the steel cylinder. The holes need not necessarily be radial but radial holes give the shortest way for bark wood debris etc. and is thus presumably to prefer. The holes also reduce the area that come in contact with the trunk 6 and thus increase the grip thereon. Furthermore however branch residues and the like can grip into the holes 4. A good grip with little or no turning or sliding of the tree trunk is obtained giving good working conditions for the knives 1. In fig 3 a second feeding wheel 11 is shown. This feeding wheel 11 is also constituted by a steel cylinder 12 with fastening disk 15 welded thereto and on the out¬ side of the steel cylinder 12 is vulcanized a thick layer 13 of polyuretan rubber. Holes 14 extending radially through steel cylinder and polyuretan layer are also present. In addition to these holes 14 provided for the communication of debris and water from the outside of the wheel to the inside further holes 18 are arranged in pairs. These holes also extend through uretan rubber layer and steel cylinder. Each pair of holes is placed on the same distance fr.om each other and on the same generatrix of the wheel. Into each pair of holes is inserted the legs of a U-shaped yoke 19 _* The ends of the legs are threaded and on the inside of the steel cylinder 12 a plate 17 is located over the legs and nuts 20 are fastened to the ends of the legs of the yoke 19« Ample clearance is provided between the legs of the yoke 19 so that the yoke 19 easily can be resiliently pushed into the elastic layer 13« This will of course in due time cause a certain wear on the yoke 19 but since it is moveing in a low friction material it will last very long. This in particular if the polyuretan rubber also covers the inside of the holes in the steel cylinder 12. The holes 18 provided for the yokes 19 need of

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course not be as big as the holes 14 may be allowed to be but of course also similar holes can be used for both purposes. In view of the enhanced grip of the yokes the need of open holes 14 is of course reduced and it is eventually also possible to arrange yokes in all holes. When a sufficient number of U-shaped yokes are used the wheel would continue to function even if the elastic layer works loose from the steel cylinder, the yokes holding the elastic layer on place. If the legs of the yokes are inserted into holes that are not located on the same generatrix the gripping parts of the yokes will be angled giving them a self cleaning effect.

Of course other gripping means and fastening methods for these may be employed without departing from the in¬ ventive idea.

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