In the field of transporting, the invention refers to hoisting, lifting or hauling appliances, in particular to winches, namely to construction details thereof.

The purpose of the invention is to create a forestry winch suitable for attachment to a tractor, by which coiling of a towing cable should be performed in a controlled manner, which means that each disposable windings of said cable on the surface of a winding drum should be arranged side by side relatively to each other and without any transpositioning or overlapping, and that each overloading of said towing cable and other components of a driving assembly due to towing of too heavy load should be excluded.

A forestry winch as such is described e.g. in SI 9600339 A2. Such winch comprises a casing, which is on the one hand furnished with beams for establishing a required connection with a three-point mechanism of an usual tractor, as well as with an end portion of a shaft suitable for connection with a joint shaft of a tractor. The opposite side of said housing is furnished with a deflecting surface, a so-called board, which essentially forms a part of casing of a driving and towing unit in such winch, which moreover comprises a winding drum with a brake and a clutch, as well as a reduction gearbox, via which said shaft is connected to said end portion of the shaft for connection with said joint shaft of each tractor. A towing cable is wound around said drum, which is optionally directed over an upper pulley block or over a lower pulley block towards each load, which shall be towed. An upper pulley block is mounted on said winch frame above an lower pulley block and is furnished with a motor-driven pulley. Such upper pulley block is described e.g. in SI 22800 A and is furnished with a pulley, which is driven by means of a hydraulic motor and is moreover adapted for guiding of a towing cable and in particular also for decoiling of said towing cable from each belonging winding drum.

Such forestry winch is generally suitable for coupling to a tractor and is furnished with a winding drum, on which a towing cable is coiled. Prior to towing of each load, the drum needs to be directed in the opposite direction, by which the cable is decoiled from the drum and extended towards the load in order to attach the load to the cable. As soon as each load, e.g. a timber or several timbers coupled to each other, starts to be towed, rotation of said winding drum in appropriate direction results in coiling of the towing cable onto said drum and consequently to towing of said load towards the winch.

In particular in some larger winches the towing cable is relatively thick, and the force required for decoiling of the cable is quite high due to friction and inertia of the drum together with the towing cable wound thereon. Of that reason, a motor-driven upper pulley block is extremely useful for each user. The upper pulley block is usually mounted onto the winch frame, so that a direction of extending the towing cable placed over said upper pulley is normally defined in advance. Redirecting of the towing cable, depending on each position of the load relative to the winch and also relative to each direction of approaching said load towards the winch, is enabled by means of the lower pulley block, which is also mounted onto said winch frame in the area below said upper pulley block and with the possibility of rotating around its vertical axis. Such redirecting leads to displacement of acting direction of tensioning forces closely to the ground and improves the stability of both the winch and the tractor.

On the other hand, a direction of the other section of the towing cable, which extend from a fixed upper pulley block, which us unable to rotate around its vertical axis, towards the winding drum. A direction in which the towing cable extends, is namely depending on current location of decoiling area, in which the towing cable is coiled on or decoiled from the winding drum, e.g. on its one or its opposite end portion, or in the middle of said winding drum. Due to central arrangement of the upper pulley block, said direction of running the towing cable via the upper pulley block is approximately aligned with a direction of coiling the cable onto the drum, it decoiling it therefrom, only when said cable is coiled or decoiled in the central region of the winding drum. By increasing distance between said coiling/decoiling area and the central region of the winding drum, a tendency of undesired deflecting the cable away from desired direction and concentrating said cable in the central region of the winding drum, where windings are then coiled over each previous windings instead to the surface of the winding drum, or by multi-layered coiling onto each previous layer of regularly coiled windings. When the towing cable is already damaged, for example flattened, intruded, folded, or otherwise deformed, the probability of irregular coiling becomes still essentially greater. Each cross-like overlapping of windings on the winding drum leads to essentially increasing of tension loadings within particular wires forming said towing cable, while the bottom winding is exposed to essential flattening. By towing heavy loads, said loadings in particular locations may reach enormous values, which can lead to durable damages of the towing cable, or even to completely destroying thereof.

Various appliances with controlled coiling of a towing cable and preventing thereof from overloading are also described in JP 2004 217 422 A, FR 2 506 277 A1, CH 666 472 A5, JP S49 143688 U and SU 594 031 A1.

The proposed invention as defined in claim 1 refers to a forestry winch with controlled coiling of a towing cable and preventing thereof from overloading. Such winch comprises a frame, on which a rotatable winding drum is mounted together with said towing cable which is wound thereon, wherein said winding drum is preferably driven by means of a tractor cardan joint shaft and is controlled by means of a clutch and a brake, and wherein moreover an upper pulley block is also mounted on said winch frame, so that said towing cable extends from the winding drum via the upper pulley block and optionally via at least one additional pulley block towards each disposable load.

A directing assembly is arranged between the winding drum and the upper pulley block, namely above the winding drum, which is rotatably around its horizontal geometric axis mounted on the winch frame, and below the upper pulley block, which is by means of its casing fixedly mounted in the upper area of the winch frame and is furnished with a pulley which is also allowed to rotate around its horizontal geometric axis, wherein said directing assembly is with the possibility of freely rotating or at least pivoting at each required angle around its vertical axis connected to the upper pulley block, or optionally to the winch frame. Said directing assembly comprises a casing, in which two pulleys are embedded, which are each per se freely rotatable around their rotational axles, which are arranged horizontally and parallel to each other, wherein the distance between the rotational axle of the lower pulley and said vertical axis of the directing assembly is greater than the distance between the rotational axle of the upper pulley block and said vertical axis of the directing assembly. Consequently, said pulleys are suitable for guiding the towing cable from the upper pulley block along said vertical axis of the directing assembly towards the upper pulley and then via the lower pulley towards the winding drum, or in the opposite direction.

Said rotational axle of the upper pulley is arranged in such manner that a tangent to said upper pulley is aligned with said vertical geometric axis of the directing assembly, and both sections of the towing cable in the area of said upper pulley , namely the section of the cable on the side of the upper pulley block and the section of the cable on the side of the lower pulley, when observed in a direction towards the axis of the upper pulley, are arranged at angle between 100° and 170°.

According to the invention, said upper pulley is embedded within the casing of the directing assembly displaceable in a direction of the resultant force of tension forces in both sections of the towing cable in the area of said upper pulley, and is moreover in said direction supported by means of a dynamometer.

The invention further provides that said casing of the directing assembly in said winch is rotatably around said vertical axis, which is mounted on a bearing member by means of at least two bearings, which are vertically spaced apart from each other, and said directing assembly is by means of said bearing member mechanically attached either to the upper pulley block or to the winch frame. Said bearing member is preferably available in the form of a tube, through which the towing cable is inserted, when extending from the upper pulley block towards the upper pulley of the directing assembly, or in the opposite direction.

The previously mentioned dynamometer preferably consists of a hydraulic cylinder, by which the upper pulley is supported in a direction of acting the resultant force of tensioning forces in both sections of the towing cable in the area of said upper pulley of the directing assembly, as well as of a pressure sensor which is adapted for measuring of pressure within said hydraulic cylinder. Said winding drum is at least by rotating around its rotational axis in a direction of coiling the towing cable thereon driven and controlled under consideration of each tension loading within the towing cable, as measured by means of said dynamometer.

The invention will be described in more detail by means of an embodiment, which schematically presented in the attached drawings, wherein

Fig. 1

is a schematic spatial presentation of a concept as well as of relevant components of the forestry winch according to the invention, in particular of a winding drum, an upper pulley block as well as of an lower pulley block; and

Fig. 2

is a front view of detailed and partially sectioned directing assembly of the winch according to the invention.

The present invention refers to a forestry winch with controlled coiling of a towing cable 2 and preventing thereof from overloading, wherein such winch comprises a frame, which is not shown in the drawings and on which a rotatable winding drum 1 is mounted together with a towing cable wound thereon; said drum 1 is driven by means of a tractor cardan joint shaft and is controlled by means of a clutch and a brake, and wherein moreover an upper pulley block 3 with a preferably motor-driven pulley is also mounted on said winch frame above the lower pulley block, which is not shown in the drawing and is furnished with a freely rotatable pulley, so that said towing cable 2 extends from the winding drum 1 via the upper pulley block 3 and via the lower pulley block towards each disposable load.

For the purposes of better understanding of the arrangement and orientation of relevant parts of the winch it shall be especially annotated that the winding drum 1 is rotatable around its horizontal rotation axis 10, which is aligned with longitudinal geometric axis of a driving shaft 11 of said drum 1, which is via a corresponding clutch (not shown) and brake (not shown) connectable with a not shown cardan joint shaft of each disposable tractor.

Besides, just for better understanding, the upper pulley block 3 is by means of its casing 31 fixedly mounted in the upper area of the winch frame and is furnished with a pulley, which is allowed to rotate around its horizontal geometric axis 30 and is preferably a motor-driven one, and is in the shown embodiment preferably driven by means of a hydraulic motor 32.

In accordance with the present invention, a directing assembly 4 is foreseen in the area between the upper pulley block 3 and the winding drum 1, namely above said drum 1 and below said pulley block 3, and is intended to guide said towing cable 2, namely a section of said towing cable 2, which is located between the winding drum 1 and the upper pulley block 3.

Said directing assembly 4 comprises a casing 41, which is either rotatable, or may optionally be - depending on the length of the winding drum 1 and each disposable distance between it and the redirecting assembly 4 - just pivoted at corresponding angle around the vertical geometric axis 40, the position and direction of which corresponds to a position and direction of the towing cable 2 in the area below the upper pulley block 3, when extending towards the winding drum 1. To this aim, the casing 41 of the directing assembly 4 is by means of two vertically spaced bearings 42', 42" embedded on a bearing member 43, which is in the shown embodiment conceived as a tube, through which the towing cable 2 can be inserted and by means of which the casing 41 of the directing assembly 4 is mechanically connected with the upper pulley block 3 and attached thereto with the possibility of the previously mentioned rotation or at least pivoting around said axis 40.

Instead to said upper pulley block 3, said directing assembly 4 could generally or optionally also be mounted directly to a winch frame, and is furthermore furnished with two pulleys 44, 45, which are each per se freely rotatable and embedded on corresponding rotational axles 440, 450, which extend horizontally and parallel to each other, wherein the distance between the rotational axle 440 of the upper pulley 44 and said vertical axis 40 of the directing assembly 4 is smaller than the distance between the rotational axle 450 of the lower pulley 45 and said axis 40, and in addition to that, said upper pulley 44 is arranged in such manner that said vertical geometric axis 40 of the directing assembly 4 corresponds to a tangent to said upper pulley 44.

Thanks to such arrangement of said pulleys 44, 45 and their rotational axles 440, 450 within said casing 41 of the directing assembly 4, which is rotatable around the vertical axis 40, the invention provides such arrangement of the towing cable 2, which allows automatically directing of the towing cable 2 during coiling thereof onto the winding drum 1. When coiling of the towing cable 1 takes place, the towing cable 2 is usually intensively tensioned due to towing of a not shown load, wherein the towing cable 2 (Fig. 1) extends from the load either directly or via at least one lower pulley block, and then via the pulley of the upper pulley block 3 vertically downwards and preferably within said tubular bearing member 43 along said axis 40 and then tangentially towards the upper pulley 44 of the directing assembly 4, where the cable 2 is at a pre-determined angle α, which is, when observed in a direction towards the rotational axle 440 of the upper pulley 44, between 100° and 170°, in particular between 120° and 150°, redirected towards the lower pulley 45 of the directing assembly 4 and then only towards the surface of the winding drum 1. Thanks to said freedom of rotation said directing assembly 4 around said vertical axis 40, the casing 41 of the directing assembly 4 can slightly pivot after each winding of the towing cable 2 around the winding drum 1 in order to enable each subsequent winding of the cable 2 to slide down from each previous winding and to rest onto the surface of the winding drum 1, or by multi-layer coiling, onto each previous layer of windings, which are side by side and closely to each other already coiled on the surface of the winding drum 1.

As evident in Fig. 2, both components of forces F₁, F₂ in corresponding sections of the towing cable 2 generate a single resultant force F, which is directed along the axis of symmetry in the middle of said angle α between said sections of the wowing cable 2 in the area of the upper pulley 44. Said acting direction of the resultant force F can always be exactly determined in advance, depending on the geometry and location of pulleys 44, 45, namely on position of axles 440, 450 and diameters of pulleys 44, 45, which are preferably equal, but may generally also differ with respect to each other. The invention further provides that the rotational axle 440 of the upper pulley 44 is embedded within said casing 41 along the direction of said resultant force F and is supported by means of dynamometer 46, which in the shown embodiment consists of a hydraulic cylinder 461 as well as of a pressure sensor 462 which is adapted for measuring of pressure within said cylinder 461. Said dynamometer 46 enables permanent measuring and controlling of tension in the towing cable 2, wherein in the case of overloading of the towing cable 2 i.e. tensioning thereof beyond each pre-determined threshold, a signal is generated in the dynamometer 46, on the basis of which the power supply to the winding drum 1 is interrupted.