US3587681A - Apparatus for debranching and/or debarking felled trees - Google Patents

Abstract

D R A W I N G
AN APPARATUS FOR DEBRANCHING AND/OR DEBRAKING FELLED TREES COMPRISING UPPER AND LOWER VERTICALLY DISPLACEABLE SUPPORTS EACH HAVING STATIONARY, ROTATABLY MOUNTED GUIDE PINIONS, INPUT PINIONS AND OUTPUT PINIONS FOR EACH OF AT LEAST TWO ENDLESS CHAIN CUTTERS PASSING BETWEEN THE SUPPORTS. TWO MOTORS ARE OPERATIVELY CONNECTED TO EACH CHAIN TO DRIVE IT IN TRACTION AND THRUST. THE INPUT AND OUTPUT PINIONS ARE ARRANGED TANGENTIALLY TO THE PERIPHERY OF THE TRUNK SO THAT THE CUTTERS RUN IN OPPOSITE DIRECTIONS ALONG OVERLAPPING, OPPOSED PERIPHERAL PORTIONS OF THE TRUNK. TENSIONING MEANS ARE ALSO INCLUDED TO APPLY TENSION TO THE CHAIN CUTTERS SO THAT THEY WILL FOLLOW THE PROFILE OF THE TRUNK DURING PROCESSING.

Description

United States Patent APPARATUS FOR DEBRANCHING AND/OR DEBARKING FELLED TREES 23 Claims, 18 Drawing Figs.

U.S. Cl 144/2, 144/208 Int. Cl 827! 1/00 Field of Search 1' 44/208,

Primary Examiner-Gil Weidenfeld Attorney-Stevens, Davis, Miller & Mosher ABSTRACT: An apparatus for debranching and/or debarking felled trees comprising upper and lower vertically displaceable supports each having stationary, rotatably mounted guide pinions, input pinions and output pinions for each of at least two endless chain cutters passing between the supports. Two motors are operatively connected to each chain to drive it in traction and thrust. The input and output pinions are arranged tangentially to the periphery of the trunk so that the cutters run in opposite directions along overlapping, opposed peripheral portions of the trunk. Tensioning means are also included to apply tension to the chain cutters so that they will follow the profile of the trunk during processing.

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SHEET 13 0F PATENTED JUN28 I97! pmmwmzam 3587381 sum 1n or 15 Fig 76 PATENTED JUN28 |97| SHEET 15 0F SPEED MONITOR I NVENTORS GEORG warm GOTTHOLD e'cirzs HANS HEESCH AMPEREMETER CONTROL VALVE 6+0 AXIAL PLUNGER L B/W ,M: w z tg APPARATUS FOR DEBRANCHING AND/OR DEBARKING FELLED TREES The invention relates to an apparatus for debranching and/or debarking felled trees, or tree trunks, by means of chain cutters.

In order to facilitate transportation and, especially in the case of conifers, to avoid insect attack, trees felled in wood exploitation are as a rule debranched and debarked in situ immediately after felling and, if necessary, they are also cut to lengths ready for the market. Apparatuses are already known by means of which some of this work can be carried out, among others, for instance, apparatuses using a chain cutter as the debarking element.

Many difficulties arise in building such apparatuses. Above all, account must be taken of the totally asymmetrical configuration of the tree to be processed, which is not brought about merely by the presence of branches but is also the consequence of the irregular configuration of the trunk itself, since the trunk tapers from bottom to top, exhibits an axis curved to a greater or lesser degree in all possible directions, and at any level has a totally asymmetrical cross section. It should furthermore be borne in mind that the requirement is not merely to debark by mechanical means trunks already debranched, but both to debranch and debark felled tree trunks with one apparatus; and finally, that it is important that the branches be severed and the bark removed as completely as possible, i.e. in many cases as far as the inner most peel, but without damaging the wood. These facts show why development in this field has not yet ceased and why better solutions are being sought, taking all of these difficulties into account as far as possible.

It is an object of the invention to produce an apparatus for debranching and/or debarking felled tree trunks lying horizontally, which apparatus operates safely and reliably, i.e. which debranches felled trunks of different growths and/or debarks them as far as the inner most peel without damaging the wood of the trunk, thus making possible continuous operation with the smallest possible number of operators.

This aim is accomplished with an apparatus for debranching and/or debarking felled trees or tree trunks by means of chain cutters, the apparatus being characterized, according tothe invention by at least two endless chain cutters which, in the operating position lie, running in opposite directions, with a .portion of their length, against the trunk along a peripheral section greater than 360ln (n= number of chains), The chain cutters are each driven by two motors, one driving the traction run and the other driving the thrust run, the one motor being arranged on the upper, and the other motor upon the lower, of two transverse supports vertically displaceable in relation to each other and adjustable from the top and bottom to the moving trunk. Each of the supports exhibiting stationary, rotatably mounted guide pinions for the chain cutters and, for each chain cutter, a pair of adjacent rotatably mounted input pinions and output pinions movable in tangential direction with respect to the periphery of the moving trunk, A tensioning device is furthermore provided for each chain and is associated with one of the two supports and consists of a pair of rotatably mounted tensioning pinions, the distance of which from a stationary guide pinion, located in the chain run between the tensioning pinions, is variable in accordance with the periphery of the moving trunk located between the supports.

This provides a plurality of advantages. For one thing, it ensures that no torque is exerted on the trunk passing through the apparatus by the cutting elements, i.e. the chain cutters, during debranching and/or debarking, that is tosay the trunk does not rotate. It also results in the start of the chain being smoother and easier, while at the same time excluding any disadvantageous softness, i.e. unduly low tension in the chain cutters. This causes the chain cutters to run more smoothly in the guideand drive-pinions. The arrangement of two superimposed chain supports not only ensures that the apparatus according to the invention is of relatively small dimensions and thus requires a small amount of space, but also makes it possible to accommodate the more sensitive parts of the apparatus in the upper support, so that the functioning of the 'parts is not impaired by waste bark and branches. Moreover the pairs of input and output pinions make it possible to open the chain cutters without interrupting the runningof the chain, so that, immediately following a debranched and/or debarked trunk, a new trunk may be introduced into the apparatus, and may be processed continuously and even completely automatically. The tensioning devices ensure reliable functioning of the apparatus for each diameter of trunk located between the chain supports.

A further advantageous embodiment of the invention provides an additional, lower, immobile transverse support and an upper transverse support vertically displaceable in relation thereto, independently of the previously mentioned chain supports, and capable of being pressed against the moving trunk. The supports are equipped with motor-driven rollers to feed the trunk forward. Thus the apparatus according to the invention has a bearing point for the moving trunk which always remains at the same height, this being of advantage because the devices for feeding the trunks to, and removing them from, the apparatus are usually set once and for all at a certain height, after which they are not altered. The above-mentioned pairs of displaceable and tensionable input and output pinions provided, according to the invention, tangentially movable to the moving trunk, and the also previously mentioned mobility of the two chain supports in the vertical direction, ensure that each trunk periphery, regardless of its configuration and size, and in spite of the constant height of its lowermost point in the apparatus, is always reliably debranched and/or debarked.

In further perfecting the invention, the chain-cutter drive motors may be provided with a speed monitor which allows the trunk feed-rolls to be driven only when the motor is running at a specific adjustable number of revolutions per minute. This makes it impossible for the chain cutters to operate at a speed which is too low in relation to the trunk feed velocity, i.e. they cannot engage the trunk and tear.

In a similar way, it has been found advantageous to connect a contact ammeter to the current-supply line to the chaindrive motors, the ammeter cooperating with the feed rolls drive in such a manner that when the chain drive motors draw an increased amount of current, the rpm. of the feed rolls decreases until a normal current is drawn, whereas the current drawn increases when the r.p.m. rises. This also prevents undue stressing and tearing of the chain cutters. Moreover, optimal throughput times for the trunks is ensured in this way.

In a further advantageous configuration of the invention, an apparatus having two lateral chain cutters'engaging the moving trunk may be provided, at the upper and lower chain supports, with twoguide columns sloping laterally outwards at 45. The columns at the upper support and the columns at the lower support are staggered in relation to each other in the direction of feed of the moving trunk. The columns of the upper and lower supports which lie on the same side extend over the same with and at the same'distance from the vertical center line of the supports and are provided with a carrier displaceably mounted on both columns at the same time and exhibiting a support for the traction run, lying against the moving trunk, of one or the other chain cutter, it being possible for the support to be a pinion engaging in the relevant chain cutter. These precautions have made it possible to keep the support, in the simplest manner, in a position corresponding to the trunk section located in the apparatus, and to ensure satisfactory guidance of the chain-cutter section cooperating therewith and embracing the adjacent half of the trunk, thus ensuring satisfactory debranching and/or debarking even at high feed speeds.

In a further embodiment of the invention, each chain cutter may have at least one guide pinion for the thrust run rotatably mounted on acarrier connected to the central joint of a twomember scissor, the ends of which remote from the central joint are hinged to the upper and lower chain supports. This prevents any change in the distance travelled by the thrust run of the chain cutters when the two chain supports move; instead they remain constant in relation to each other, independently of the position of the two chain supports. The functioning of the chain-tensioning devices described, which only have to compensate for the change in length of the path travelled by the traction run of the chain resulting from a change in the distance between the upper and lower chain support, when the chains are opened or when the diameter and/or periphery of the trunk in that apparatus changes is thus assisted. The scissor may also be designed (more members, appropriate leverage, etc.) in such a manner that compensation is also provided for the change in length of the path travelled by the traction run of the chain, e.g. the increase in trunk periphery resulting from increasing trunk diameter may be fully compensated for without the use of hydraulic tensioning devices, additional compensation for deviations from the normal, geometrically correct shape or diameter being effected by means of springs or the like.

Moreover, the above-mentioned lower feed support may be provided, for the purpose of centering the trunk introduced into the apparatus for p ocessing, with two trunk guides arranged on both sides of the vertical center line of the support (.r), and capable of being swung in and out jointly. When the upper feed support is brought down, these elements, which are swung laterally outwards when the apparatus according to the invention is open, swing inwards, forcing the section of trunk introduced into the apparatus laterally into the desired central position, when the trunk section does not lie centrally in case the trunk is curved, as it usually is. It is of particular advantage to introduce the trunk top first. In the desired position in the vertical direction, and with the trunk section clamped between the previously mentioned feed rollers at the lower or upper feed support, the trunk section is guided by the upper feed roller, which may for this purpose be designed as a dou ble cone, i.e. with its diameter increasing towards the lateral faces. Centering of the incoming tree trunk is effected by bringing down the upper feed support of the apparatus, during which time the two trunk guides and the upper, double-cone.

feed roller move simultaneously to the center of the opening in the apparatus.

The trunk guides may, with advantage, be carried through a linkage by a shaft rotatably mounted in the lower feed support, to which shaft a lever arm is attached .and secured against rotation, the lever arm being hinged to the free end of a rod rotatably attached to the upper feed support.

in the case of an apparatus having chain cutters engaging the moving trunk laterally, it has been found of particular advantage to provide a common drive motor for the two thrust runs of the two chain cutters and a common drive motor for the two traction runs of the two chains. This ensures a particularly economical, light, and space-saving design.

It is also of advantage to arrange the above-mentioned tensioning devices for the chain cutters on the upper chain support. This arrangement above the trunk to be processed prevents the functioning of the tensioning devices from being impaired by waste, i.e. severed branches, pieces of bark, and wood chips.

According to another characterizing feature of the invention, in the case of an apparatus having two chain cutters engaging laterally with the moving trunk, the thrust runs of the two chain cutters, seen in the direction of feed of the moving trunk, may lie exactly one behind the other, and the corresponding stationary guide pinions for the chains may be rotatably mounted one behind the other on the same axis, on the upper and lower chain supports. With this arrangement, a two-member scissor only is provided on the side of the chain supports on which the thrust runs of the chain cutters run, the carrier fitted to the central joint exhibiting a guide pinion for each chain. In this arrangement, furthermore, the tensioning devices for the chain cutters may also be arranged, with advantage, one behind the other in the direction of feed of the moving trunk. This provides a particularly compact and spacesaving design of the apparatus.

In a further embodiment of the invention, a roller running on a horizontal axis perpendicular to the direction of feed of the moving trunk may be fitted to each of the chain supports, the roller coming to rest against the moving trunk, and being eccentrically mounted in the upper and lower chain supports for the purpose of altering the distance between the surface of the trunk and the pairs of input and output pinions.

In the apparatus according to the invention, the moving and preloading of the chain supports, the upper feed support, the pairs of chain input and output pinions, and the tensioning devices is best carried out by means of hydraulically actuated piston/cylinder units. it has similarly been found particularly advantageous to provide a hydrostatic motor to drive the trunk feed rollers.

According to another characterizing feature of the invention, the oil for the piston/cylinder units and, if necessary, for the hydrostatic motors may be accommodated in two containers which are vertically mobile and are each connected to the upper chain support by means of a chain. When full, these containers act as counterweights for the support, which may thus be moved with a minimal expenditure of force. Four oil containers arranged in this manner may also be provided, two being allotted to the upper chain support and two to the lower, as counterweights. In this way, the lower chain support is also easily displaceable.

The chain supports may, with advantage, run on four vertical guide columns in a frame which, for the purpose of adjusting the planes in which the chain cutters lie, is adjustable in relation to the longitudinal axis of the moving trunk, about a horizontal axis perpendicular to the direction of feed. This assists in the smooth running of the chain cutters and especially avoids their cutting into the moving trunk.

According to another characterizing feature of the invention, each pinion of the pair of input and output pinions of the foremost chain cutter, seen in the direction of feed of the moving trunk, may be equipped with a cutting head. This prevents branches from running out over the ends of the pinions, which would block the passage of the trunk. These cutting heads, in conjunction with the overlapping, in the direction of feed of the trunk, of the chain-cutter sections lying against the trunk to be processed, already mentioned above, render unnecessary the provision of special precutting elements for removing all branches from the trunk to be processed, or even only of branches in a specific section of the periphery of the trunk, or for severing the outer portions of the branches.

Furthermore, the overlapping of the chain-cutter sections lying against the trunk to be processed, previously called traction runs, ensures reliable removal of the bark from the entire periphery of the trunk.

A shutoff valve may, with advantage, be inserted into the oil lines of the piston/cylinder units for the pairs of input and output pinions of each chain. This ensures reliable control of the pair of input and output pinions of each chain, i.e. they may be locked in any desired position.

The apparatus according to the invention may be set up on a stationary table, but is preferably rigidly mounted on a vehicle, for example, a motor-vehicle trailer, so that it may easily be transported. Auxiliary devices may also be mounted on the trailer, for example an operating pulpit, an electric switchbox and a hydraulic switchbox, the hydraulic pumps and their drive motors, a blower for blowing away the waste from the trunk-input end of the apparatus, and finally an output conveyor belt, the latter being swung downwards while the trunk is passing through the apparatus according to the invention, and is swung up under the processed trunk only when the latter has left the feed rollers in the apparatus.

The apparatus cooperates with devices for feeding the felled trunks to be processed, and for removing the debarked and/or debranched trunks. Thus when the apparatus is in its operating position, a guide frame is provided in front of the apparatus in alignment with the feed passage, the frame having a capstan table exhibiting one or more winches. A discharge frame, also aligned with the passage through the apparatus, is also arranged behind the apparatus and has a topping saw and -If the apparatus is in the form of a transportable unit, i.e. at-

tached, for example, to a motor-vehicle trailer, these connections are made easily detachable, so that both the frames. and the capstan table may be transported to the desired site in a suitable vehicle.

Preferably, however, the guide frame and the discharge frame themselves are made as mobile units, the' guide frame being provided with oblique runup surfaces for the trunk to be processed, so that a separate special capstan table is unnecessary. This provides particularly rapid and simple transportation for the two frames. 7

Easy transportability and rapid setting up of the apparatus according to the invention with its auxiliary devices is still further promoted in that the necessary generator installation is also made mobile and is accommodated in a protective motorvehicle trailer enclosed on all sides, and in that a branch-conveyor belt with an appropriate surface for removing the branches and other waste severed by the apparatus according to the invention is provided and is also designed for road travel.

Thus the apparatus according to the invention is preferably used in the form of a wood-harvesting train consisting of five roadworthy, preferably single-axle units, namely the debranching and/or debarking apparatus, the guideor inputframe, the discharge frame, the generator installation, and the branch conveyor.

The means for accomplishing the foregoing objects and other advantages, which will be apparent to those skilled in the art, are set forth in the following specification and claims, and are illustrated in the accompanying drawings dealing with a .basic embodiment of the present invention. Reference is made now to the drawings in which:

FIG. 1 is a schematic end view of the guidance and arrangement of the chain cutters in an apparatus according to the invention having two such cutting elements;

FIG. 2 is a schematic front elevation of an apparatus according to the invention having the chain-cutter arrangement of FIG. 1, e.e. a view looking at the apparatus in the direction of feed of the moving trunk;

FIG. 3 shows a side elevation of the apparatus in FIG. 2;

FIG. 4 is a view of the feed unit of the apparatus in fig. 2, corresponding to FIG.3;

FIG. 5 shows a front elevation of the left-hand portion of the feed unit of FIG. 4;

FIG. 6 is a view corresponding to that in FIG. 3 of the chaincutter carrier unit of the apparatus illustrated in FIG. 3;

FIG. 7 is a front elevation of the upper one of the two chaincutter supports shown in FIG. 6 merely as blocks, portions of the support being omitted for the sake of clarity;

FIG. 8 shows a section along the line 8-8 in FIG. 7;

FIG. 9 shows a section along the line 9-9 in FIG. 7;

FIG. 10 shows a view corresponding to that in,FIG. 6 of the chain-cutter support unit, the front portions of the chain-carrier support being omitted, as well as the left-hand chain support with its associated guides;

FIG. 11 is a schematic illustration of the arrangement of the left and right-hand chain-cutter support in front elevation;

FIG. 12 shows the lower, stationary feed support, with the device provided thereon for lateral centering of the trunk;

FIG. 13 is a view corresponding to those in FIGS. 6 and 10, showing in particular the arrangement of the oil containers serving as counterweights for the weights for the upper chain support;

FIG. 14 is a schematic illustration of the hydraulic circuit of the apparatus according to FIGS. 1 to 13;

FIGS. 15 and 16 show a plan view and side elevation, respectively, of a mobile embodiment of the inventive apparatus;

FIG. 17 is a schematic representation of the eccentric mounting of the rollers; and

FIG. 18 is a schematic representation of the present invention including a speed monitor.

The apparatus illustrated in-FIGS. 1 to 16, for debranching and/or debarking felled trees and tree trunks, comprises two chain cutters 1 and 2 which carry out the debranching and/or debarking'As may be seen in FIG. 1, they engage around moving trunk 3, running in opposite directions, along a section of the periphery greater than They run over guide pinions 4 rotatably mounted on the front of a lower and an upper transverse support 5 and 6. They also run over a guide pinion 7 rotatably mounted on the central joint of a scissor 8 hinged at one end to transverse support 5 and at the other end to transverse support 6.

Chains l and 2 run in two planes 9 and 10 lying one behind the other, as seen in the direction of feed of trunk 3, chain cutter l embracing the right-hand side of trunk 3 running in front plane 9, and chain cutter 2 embracing the left-hand side of trunk 3 lying in rear plane 10. These planes may be seen very clearly in FIGS. 3, 6 and 10, in which they'are shown in chain-dotted lines.

Guide pinions 4 and 7 are accordingly arranged in such a manner that the two pinions for each chain cutter 1 and 2 correspond to each other in the run of the chain and are rotatably mounted on the same axis of rotation in planes 9 and 10, provided on lower transverse support 5 and upper transverse support 6, and on the central joint 7 of scissor 8.

Chain cutters l and 2 are respectively driven by two motors 11 and 12. Each motor 11 and 12 is provided with two drive pinions located in chain planes 9 and 10, by means of which chains 1 and 2 are engaged. In this way, while two motors act upon each chain, not four but only two motors are required for two chain cutters. Motor 11 pulls the section of the chain cutters designated as traction run 1 and 2' lying between motor 11' and motor 12 which does not engage with trunk 3, i.e. it runs back over guide pinion 7. Motor 12 pulls the section of the chain cutters designated as traction run 1", and 2" located between motor 11 and motor 12 and lying against the moving trunk.

Traction runs 1" and 2" run respectively over a pair of adjacent rotatably mounted input pinions 13 and 14 above trunk 3 to be processed, running thence over a pair of output pinions l5 and 16 similarly arranged one beside the other below the trunk 3. Pinion pairs 13 to 16 can be moved from the cutting or operating position shown in FIG. 1 in full lines, into the open-chain position shown in dotted lines, when a new trunk 3 is to be introduced between transverse supports 5 and 6. Pinion pairs 13 and 15 lie in chain plane 9 in front of pinion pairs 14 and 16 in chain plane 10.

Also provided on transverse support 6 for each chain cutter l and 2 are two pinions 17 which, like pinion pairs 13 to 16, are displaceable on a common carrier from the position shown in FIG. 1 in full lines, to the position shown in dotted lines. Pinion pair 17 serves to tension chain cutters l and 2, which is necessary for adaptation to various diameters of trunk periphery. Provided for each chain cutter 1 and 2 is a separate pinion pair 17 independent from the other, which forms a tensioning device with stationary guide pinion 4 lying in the same chain plane 9 or 10 enclosed by pinions 17 in the run of chain 1 or 2.

It emerges with particular clarity from FIGS. 2 and 3 that chain supports 5 and 6 are displaceably mounted on four vertical guide columns 18 with hard-chromed surfaces, by ballbearing sleeves 19. Columns 18 are part of a frame 20 which can be adjusted by means of a wedge 21 about a horizontal axis 22, so that chain planes 9, l0 always lie perpendicular to the axis of moving trunk 3 (of FIG. 3). Movement of chain supports 5 and 6 on columns 18 is accomplished with the aid of hydraulically-actuated piston/cylinder units 23 provided on both sides and engaging on the one side with supports 5 and 6 and on the other with frame 20, as may be seen above all in FIG. 2. Provided on the lower transverse member of frame 20 are rubber buffers 24, upon which lower chain support may rest via its ball-bearing sleeve 19 when the support is moved down to its lowest position.

From FIGS. 2 and 3 it way also be gathered that there is another frame, in addition to frame 20, which also exhibits four vertical guide columns 25, with hard-chromed surfaces, which are attached to lower transverse support 26 and carry ball bearing sleeves 27 of an upper transverse support 28 which is vertically displaceable, in relation to lower support 26, with the aid of two symmetrically arranged piston/cylinder units 29. On lower support 26, a cylindrical roller 30 is mounted to rotate about a horizontal axis, while upper support 28 carries a double-cone-shaped rotatable roller 31. Each of these two rollers 30 and 31 is driven by a hydrostatic motor 32, and they move trunk 3 through the apparatus.

The frame carrying feed rollers 30 and 31 is shown alone in FIGS. 4 and 5.

FIG. 6 is a side elevation of frame 20 showing chain supports 5 and 6 which are displaceable therein, the supports being shown only as blocks. This figure shows particularly clearly the configuration of scissor 8 carrying guide pinions 7 for chain cutters l and 2. The pinions 7 are rotatably mounted on the same shaft 33 on a carrier 34 which in turn is fitted to central hinge 35 of scissor 8. The two scissor members 36 and 37 are hingedlaterally by their free ends to transverse supports 5 and 6. I

FIGS. 7 to 9 show the construction of upper chain support 6 which, apart from the already-mentioned tensioning device for each chain cutter l and 2, corresponds to the construction of lower chain support 5. In FIG. 7, motor 11 and its drive pinions are omitted. From FIG. 7 in conjunction with FIG. 9 it emerges that tensioning pinions 17 for chain cutters 1 and 2 are rotatably mounted on carriers 38 which can be displaced on parallel guide columns 39. According to FIG. 9, carriers 38 lie one in front of the other and are connected respectively to piston/ cylinder units 40 and 41 attached to support 6, in the case of rear carrier 38 by a rod 42 attached thereto, to the end of which is hinged the free end of the piston rod of piston/cylinder unit 41. On the other hand, piston/cylinder unit 40 lies directly between front carrier 38 and support 6.

Whereas FIG. 9 shows the two tensioning devices or pairs of tensioning pinions 17 provided in the apparatus according to the invention, FIG. 7 shows only the rear pair of tensioning pinions 17 for chain cutter 2. The tensioning device for chain cutter 1 is omitted from FIG. 7 for the sake of clarity.

It emerges from all three FIGS. 7 to 9 that both input-pinion pairs 13 in front chain cutter 1 and input-pairs 14 of rear chain cutter 2 are mounted respectively on carriers 43 and 44, which are displaceable on two horizontal, parallel guide columns 45 and 46 on upper chain support 6. Rear carrier 44 of pinion pair 14 is hinged to the free end of the piston rod of hydraulically actuated piston/cylinder unit 47, the cylinder of which is held by upper support 6, as may be seen in FIG. 8. Carrier 43 exhibits an arm 48 lying in front of input-pinion pair 14 for rear chain cutter 2 and carrying input-pinion 13 of front chain cutter 1. Carrier 43 is hinged by a rod 49 to the free end of the piston rod of hydraulically actuated piston/cylinder. unit 50, the cylinder which is also held by upper support 6, as may be seen clearly in FIG. 8. By means of units 47 and 50 input-pinion pairs 14 and 13 may be moved from the position shown in FIGS. 7 to 9, in which chain cutters 1 and 2 lie against the trunk 3 to be processed, in the direction of arrows 51 and 52 in FIG. 8, so that they assume the position shown in dotted lines in FIG. 1, in which a new trunk may be introduced into the apparatus.

As already mentioned and as shown in FIG. 2, lower chain support 5 is of similar construction to upper support 6. Thus rear output-pinion pair 16 of chain cutter 2 is arranged behind front output-pinion pair of chain cutter l, pinions 15 being held by arm 53 of carrier 54 which is displaceably mounted on two horizontal guide columns 55 parallel with each other on lower support 5, and output pinions 16 being furthermore rotatably mounted on a common carrier 56 which is also displaceable on two horizontal guide columns 57 parallel with each other on lower support 5.' Hydraulically actuated piston/cylinder units 59, engaging in the case of carrier 54 through a rod 58, and in the case of carrier 56 directly, with the free ends of their piston rods, and attached by the cylinders to lower support 5, serve to move output-pinion pairs 15 and 16.

The apparatus according to the invention is equipped with a chain-supporting device which, for the sake of clarity, is not shown in FIGS. 1 to 9, but may be seen in FIGS. 10 and 11. It consists of four guide columns 60 arranged at an angle of 45 to the horizontal and enclosing a quadrangle in front elevation (cf. FIG. 11). According to FIG. 10, the two lower guide columns 60 lie in front of the two upper guide columns 60 are carried by upper chain support 6. Columns 60 are held at their ends by blocks 61 which in turn are flanged to upper and lower chain supports 6 and 5.

FIG. 10 shows the two right-hand guide columns 60 of FIG. 11 with their associated blocks 61 and flanges 62. From this, and from FIG. 11, it emerges that the two guide columns 60 lying on the same side of the vertical center line of the apparatus jointly hold a displaceable carrier 63 exhibiting a countersupport 64 for the traction run of chain cutters 1 and 2. Right-hand columns 60 carry counter support 64 for front chain cutter 1 while left-hand columns 60 guide the countersupport for rear chain cutter 2. 'Countersupports 64 may be mounted in carriers 63 to pivot about a vertical axis 65 and may be preloaded, by means of springs, not shown, towards the center of the apparatus, i.e. towards each other against stops provided on carrier 63.

Columns 60 are arranged on supports 5 and 6 in such a manner that the two chain countersupports 64 always lie between abutments 66 (cf. FIG. 3) on lower support 5 and upper support 6, with which these supports lie against trunk 3 when chain cutters l and 2 are in the cutting position. Furthermore, the arrangement of guide columns 60 described above and illustrated in FIGS. 10 and 11 ensures that each chain countersupport 64 is always spaced from the vertical center line of supports 5 and 6 by a distance equal to half the distance between abutments 66. Thus countersupports 64 lie against the periphery of trunk at its horizontal diameter, supporting chain cutters 1 and 2 at this location. This ensures particularly smooth running of the chain cutters, even when the trunks are passed through the apparatus at extremely high speeds of up to 50 m/min.

FIGS. 10 and 11 show the apparatus in the open position i.e. with chain supports 5 and 6 moved away from each other, although in FIG. 11 upper feed support 28 and its associated feed roller 31 are not shown in their highest positions.

Chain cutters l and 2 are, for example, duplex link chains, i.e. two-row chains, equipped on their front sides with cutting teeth. These chains lie with their backs against countersupports 64.

The apparatus according to the invention cooperates with a guide frame to feed-in the trees or tree trunks to be processed, and a discharge frame to remove the processed trunks. The bearing elements in these frames for the trunks are arranged at the height offeed roller 30. Thus a trunk passes from the guide frame in the direction of arrow 67 (cf. FIG. 3), through the apparatus of the invention, on to the discharge frame. As soon as a trunk has been debranched and/or debarked, the apparatus opens. i.e. input-pinion pairs 13 and 14 and output-pinion pairs 15 and 16 move apart on chain supports 5 and 6 which themselves simultaneously move apart. A new trunk for processing is then introduced into the apparatus by the guide frame, usually with the treetop first. Since the trunk is usually curved to a greater or lesser degree, the top of the trunk introduced does not lie in the middle of the apparatus, as required. In order to compel this central position, according to FIG. 12 two trunk guides 68 are provided on lower feed support 26. The guides are cooperating with feed roller 31 on the

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