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 adapted for attachment to a tractor, wherein a power transmission between a driving joint shaft of said tractor and a driven winding drum of said winch could be performed more efficiently by simultaneously reducing loads on each exposed bearing parts, and wherein the transmission gearing should be preferably integrated within said winding drum.

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 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. Such winch 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 towards each load, which shall be towed. The winding drum is embedded within a casing and is mounted on a shaft, on which in addition to said drum also a driving gear of the winding drum is mounted.

A transmission gear as such is also described in SI 23429 A, which actually concerns a two-step transmission gear with cylindrical gears, wherein a splined shaft is connectable with a cardan joint shaft of a tractor and is furnished with a gear with a relatively small number of teeth, which is adapted to mesh with the first gear with essentially larger number of teeth, which is mounted on an intermediate, shaft.- Said intermediate shaft is moreover furnished with a further gear with relatively small number of teeth, which is intended to mesh with said gear on the shaft of the winding drum wherein the lastly mentioned gear is also provided with relatively high number of teeth. Accordingly, the torque i.e. power transmission from the cardan joint shaft onto the winding drum shaft is performed via a two-step reduction gear, which is actually embedded within a casing of the winch, but completely outside of the winding drum, the diameter of which can be consequently relatively small. The winch is basically intended wither for tensioning each towing cable and winding said cable onto the winding drum, or also to release the cable and dispense it from the drum. Each particular position of the tensioning force and consequently also each stresses and stability of the complete appliance depend on position of the towing cable. Each corresponding position of the winding drum within the casing is therefore adjusted to each disposable position of the tensioning force, which then also determines appropriate position of the input shaft, which is connectable to the tractor cardan joint shaft. When considering all these circumstances, in the practice the cardan joint shaft is offset in two planes, which actually undesired, since the dynamic stresses involving undesired impacts and vibrations of particular components are relatively high. Consequently, also the overall efficiency of power transmission from the tractor towards the winding drum of the winch is then correspondingly decreased.

The invention refers to a forestry winch with improved transmission gear for power i.e. torque transmission from the input shaft, which is in detachable manner connectable to a tractor cardan joint shaft, towards the winding drum, which is intended for tensioning or releasing of a towing cable, wherein said transmission gear is adapted to cooperate with alternatively operating clutch and brake, so that by activated clutch the brake is deactivated and the torque can be transmitted from the input shaft onto the winding drum, which is then rotated in one or another direction, or vice versa, and that by activated brake the clutch is deactivated, by which rotation of the winding drum is blocked and at the same time the transmission of torque from the input shaft onto the winding drum is interrupted.

The invention provides that said transmission gear is formed as a two-step planetary gear consisting of a first planetary assembly and a second planetary assembly, which are embedded within a common casing. In the first planetary gearing, a sun gear is with the possibility of torque transmission mounted on a primary shaft and is by means of the last via said clutch connectable with said input shaft of the transmission gear and is moreover adapted to mesh with corresponding planet gears meshing with inner teeth of an outer ring gear within the casing of the transmission gear. Axle bearings of said planet gears of the first planetary assembly are jointly and with the possibility of torque transmission via a secondary shaft connected with a sun gear of the secondary planet gear, which is capable to mesh with corresponding planet gears, which are capable to mesh with corresponding teeth of an outer ring gear within said casing and axle bearings thereof are jointly and with the possibility of torque transmission connected with the winding drum, by which the casing of the transmission gear is at least partially surrounded, so that said casing of the transmission gear and said winding drum are arranged coaxially with each other and at the same time the winding drum is rotatable relative to said casing.

Said clutch comprises at least a primary friction disc, with which the input shaft of the transmission gear is connected, and a secondary friction disc, with which said planetary gear is connected. In a preferred embodiment of the invention, the input shaft is connected, in addition to the primary friction disc of the clutch, the secondary friction ^" disc Of which is connected with the -primary- shaft of the planetary gear, also with at least one further transmission gear, via which by means of said input shaft and independently with respect to operation of said clutch, at least one further powered means is driven, in particular a hydraulic media pressurizing pump.

The invention will be described in more detail on the basis of an embodiment, which is schematically illustrated in Fig. 1.

A forestry winch according to the invention comprises an improved transmission gearbox 1, which is intended for transmission of torque i.e. power from the input shaft 3 onto a winding drum 3, on which a towing cable 4 is wound.

Said input shaft 2 is on the one hand detachably, however with the possibility of torque transmission, interconnectable with a cardan joint shaft of each tractor and on the other hand with a clutch 5, namely with a primary friction disc 5' of said clutch 5, while its secondary friction disc 5" is connected with a planetary gear 8, namely with a primary shaft 80' thereof, to which in addition to said secondary friction disc 5" also a brake 7 and a sun gear 811 of the first planetary assembly 81 are connected, which planet gears 812 in the shown embodiment mesh with the inner teeth of the outer ring gear 812 within the casing of said gearbox 1.

Bearings 812' of axles of said planet gears 812 of the first planetary assembly 81 are jointly connected with a secondary shaft 80", on which a sun gear 821 of the second planet assembly is attached, which in the shown embodiment via planet gears 822 meshes with inner teeth of the outer ring gear 823 within the casing 9 of the transmission gear 1. Bearings 822' of axles of said planet gears 822 of the second planetary assembly 82 are connected with said winding drum 3 with which said casing 9 of the transmission gear 1 is at least partially surrounded. The casing 9, within which said first and second planet assembly 81, 82 are embedded, and said winding drum 3 are arranged coaxially with each other, and at the same the winding drum 3 is rotatable relative to the casing 9.

The clutch 5 with friction discs 5', 5" and the brake 7 are operating in alternative manner. When the clutch 5 is activated, which means that the primary friction disc 5' and the secondary friction disc 5" are brought in contact with each other in order to establish a required torque transmission via the clutch 5, then the brake 7 is released and allows rotation of the winding drum 3 in one or another direction. As soon as the brake 7 is activated in order to prevent said rotation of the winding drum 3, said friction discs 5', 5" are separated from each other and the clutch 5 is deactivated in order to disable the torque transmission from the input shaft 2 onto a primary shaft 80' and the secondary shaft 80' of the planetary gear 8 of the gearbox 1 and consequently to the winding drum 3, although said shaft 2 continues rotating together with the tractor joint shaft. Whenever the forestry winch is controlled by means of a not-shown hydraulic assembly, a hydraulic pump 100 for pressurizing each hydraulic media is foreseen adjacent to the casing 9 and is be driven by means of the input shaft 2 via appropriate transmission assembly 101.

Since thanks to previously described concept the transmission gear 1 with its casing 9 is embedded within the winding drum 3, the winch according to the invention, when compared with state-of-the art winches, allows essential change of position of the input shaft 2 in each desired position of the towing cable 4 with respect to each position of the towing force, so that the input shaft 2 can be located within the same plane as the cardan joint shaft, namely in the central vertical plane, - which means that the cardan joint shaft is located within a single plane instead of being offset in two planes, as known from the prior art, which essentially reduces vibrations and mechanical stresses, to which machine parts are exposed, and at the same time also the efficiency of power transmission can be essentially improved.

In comparison with known winches, said integration of the planetary gear 8 into the generally pretty wide winding drum 3 might result in certain increasing diameter thereof, which shall however not be understood as a deficiency. On the contrary, bending of the towing cable 4 is less intensive, since the radius of the bending curve is correspondingly enlarged, and besides, enlarging the diameter of the winding drum 3 by winding the same length of the cable leads to reduction of layers of the cable on the surface of the drum, which leads to still further decreasing of loadings, to which the cable is exposed, and moreover also to reduction of variations in diameter of windings, by which also the towing force can be much more uniform. Precisely controlling the operation of the clutch 5 and the brake 7, and herewith accurate operation of the winding drum 3, can be easily achieved by means of cooperation of the clutch 5 and the brake 7 with the first planetary assembly 81 of the transmission gear 8 of the winch. Consequently, the parts are exposed to essentially lower stresses, by which their dimensions and weight can be essentially reduced.

In particular, the transmission gearbox 1 of the winch according to the invention is an independent construction assembly, which is available within its own casing 9, and can therefore be manufactured separately and independently from any other components in mass production processes, and can therefore be separately assembled, tested, inserted, removed, repaired, or replaced, when appropriate.