The invention refers to an auxiliary winch for a mobile hydraulic crane, namely to a winch, which is suitable for mounting onto an usual bearing construction of a mobile hydraulic crane and is intended for transporting of loads, which are located outside of the operational area of the crane i.e. of the reach of the grabber, towards said operational area of the crane. Simultaneously, the invention also refers to a mobile hydraulic crane, which is furnished with such a winch, and is thanks to features of said winch upgraded by benefits resulting from improved concept of said auxiliary winch.

Pursuant to the International Patent Classification such invention may on the one hand belong to the field of transporting, namely to winches, which are intended for special purposes, and would in such context belong to the Class B 66 D 1/60. On the other hand, such invention may also belong to hydraulic cranes, which are suitable for being mounted onto road of railway vehicles, and which comprise a column and at least one arm, which is equipped with a grabber, and which is pivotally attached to said column, but in such case, according to said Classification, the invention should belong to the class B 66 C 23/36 or B 66 C 23/70, or by taking into consideration pretty special construction concept thereof, probably even to the class B 66 C 25/00. The invention is based on a problem, how to conceive a winch, which should be mountable onto a commonly used mobile hydraulic crane, namely onto a crane with a column and an arm, which is furnished with a grabber and is pivotally attached to said column and is by means of a hydraulic cylinder pivotal relatively to said column, by which the operational area of the crane is determined, and moreover with at least two hydraulically driven telescopic supporting legs suitable for providing stability of such crane during its operation, wherein such winch, when mounted onto a crane, should on the one hand enable towing of a load, which is located outside of the operational area of said crane, towards said operational area of the crane, namely to the reach of said grabber, while on the other hand, simultaneous operation of the crane and the winch should be excluded, and each user should be able to select either automatic decoding of the rope from the winch drum by a pre-determined velocity, or manual decoiling of the rope from the winch drum with each desired velocity corresponding to the users actual needs.

Several conceptually similar solutions are known in the state of the art. For example, a mobile log yarder is disclosed in US 4,917,567, which in addition to a framework and a support vehicle includes a crane, which comprises a two-arm crane construction, wherein the first arm is by its first terminal portion pivotally attached to said framework and is pivotal by means of a hydraulic cylinder, which is on the one hand attached to said first arm and on the other hand to said framework. Quite similar, said second arm is by its first terminal portion pivotally attached to the first arm and furnished with a hydraulic cylinder, which is on the one hand pivotally attached to said second arm and on the other hand to the first arm. Moreover, said second arm in on its second terminal portion furnished with a grabber, which is suitable for cooperation with a load. As clear from said explanation, such machine is capable of manipulating with a load, which is located inside of its operational area, and the load can be lifted, displaced and dropped to another location, which must however still be located within the operational area of the crane arms. Whenever a manipulation with such load would be required, which is located outside of the operational area of the crane arms, then by means of such machine such manipulation would not be feasible. To this aim, the support vehicle would have to be displaced in a desired direction, if of course configuration of a terrain would allow such operation at all. Fortunately, such machine is also furnished with an auxiliary winch, which is mounted on the free terminal portion of the second arm in the neighborhood of the grabber. Said auxiliary winch comprises a casing, by means of which it is attached to said second arm. A winding drum with a properly strong towing rope wound thereon is placed on a shaft, which is rotatably mounted within said casing. Said winding drum is motor-driven, and by rotating thereof in one direction the rope is coiling thereon, while by rotating in the opposite direction the rope is decoding there-from. Whenever the load is located outside of the operational area of said arms with the grabber, then the rope is uncoiled from said winding drum to such extent that it may be extended towards the load in order to connect the load to an attaching means, which is available in the terminal portion of the rope. Upon that, the rope may be gradually coiled onto the drum, which leads to towing the load towards the auxiliary winch and also towards the operational area of the arms with the grabber. As soon as the load is displaced into the operational area of the arms and the grabber, then the connection between the load and the rope is eliminated, and the rope is coiled back onto the winch drum, upon which the load can be manipulated by means of the grabber and displaced to another place within the operational area of the crane. In this case, simultaneous operation of the crane and auxiliary winch is not excluded, since in certain cases it might be even useful, if during operation of the auxiliary winch also the support vehicle and/or the arms could be moved/elevated or rotated, since then the towing of the load could be performed even faster, or collision of the load with potential obstacles might easier be avoided sometimes. However, in such cases there is always a high risk, that the position or direction of the towing force may suddenly change, and such manoeuver could jeopardize stability of the machine on each particular ground configuration, so that there is a risk of turning-over the machine. This problem becomes serious when heavier loads should be manipulated on a complicated terrain and by means of a much more simple and less bulky machine. The other related problem of such concept refers to a motor-driven winding winch. The velocity of the rope by coiling or decoding is usually the same and is moreover determined in advance. When towing the load along the terrain, the load is usually town at certain distance, upon which the winch is switched-off, so that the load can be manually re-oriented and adjusted to the terrain, upon which by switching-on the drum the load may again be displaced at certain distance in a desired direction. But this problem may sometimes be even more serious by decoiling the rope from the winch. When the rope, namely a cable consisting of a plurality of thin steel wires, is decoiled with a pre-determined velocity, then the user must take care about the need on maintaining the rope in properly tensioned state all the time, since otherwise the rope would due to its elasticity tend to run in various directions, or would in its insufficiently tensioned state even tend to form loops. But in the practice, said maintaining of the rope in its tensioned state is not an easy task at all. By manipulating with timbers in forestry this would mean that the operator must walk 50 or even 100 m by simultaneously towing the free terminal portion of the rope. Now, if the velocity of decoding is too low, then the efficiency and concentration of the operator may become insufficient, but is the velocity is too high, then the rope might quickly become insufficiently tensioned and the previously discussed troubles would arise. A similar crane with an auxiliary winch is disclosed in EP 3 219 660 Bl, namely a crane of a mobile forestry accessory with a rotatable column, with a first arm attached to it, as well as with a second telescopic arm attached to the first arm. Such crane, the arms of which are displaceable by means of hydraulic cylinders, is furnished with a hydraulically driven auxiliary winch, which is embedded within a casing in the terminal area of said telescopic second arm closely to a grabber. In this solution, two separate and alternatively operating hydraulic circuits are foreseen, which means that during operation of the crane the winch cannot be used, or vice versa. In such case rotation of a winding drum with the rope coiled thereon in the auxiliary winch is performed by means of a hydraulic motor, and the direction of rotating said hydraulic motor san be changed by switching of control valves and changing of direction of flowing the hydraulic liquid towards said hydraulic motor. Consequently, the winding drum is rotated in one or another direction, by which the rope is coiling or decoiling, wherein decoiling of the rope is motor-driven anyway and the velocity of the rope is determined in advance on the basis of a pre-determined rotation speed of the drum, so that the factual velocity of the rope actually not constant but is varying in dependence of its position on the drum, namely on its current radius on the drum, where it is at certain moment positioned by resting on the residual rope windings there-below. Of course also in such case said constant turning velocity of the hydraulic motor and said mathematically correlated velocity of the decoiled portion of the rope in most cases do not match actual needs of the user in various situations by walking along the terrain, so that decoding may be either too fast or too slow, but the user has practically no other option or choice.

The proposed invention generally refers to an auxiliary winch, which is in particular intended for use on a mobile hydraulic crane. Such winch comprises at least

- a casing, which is furnished with at least one rigid and substantially plane primary wall and is adapted for mounting of said auxiliary winch onto said crane, in particularly on a primary arm of said crane;

- a hydraulic motor, which is furnished with a driving shaft and is hydraulically integrated into a hydraulic circuit of the auxiliary winch, and which is in the auxiliary winch, when it is mounted on said crane, arranged to operate alternatively with respect to the hydraulic circuit of the crane as such, and is therefore prevented from operating simultaneously with operation of the hydraulic circuit of the crane; as well as

- a winding drum, which is mounted on a driving shaft within said casing and is together with said shaft rotatable in one or another direction around its longitudinal geometric axis, and on which a towing cable is coiled, wherein said drum is via a transmission assembly driven by means of said driving shaft of said hydraulic motor.

As a solution of the previously mentioned technical problem, the invention proposes that said transmission assembly is on its primary side by means of a clutch mechanically, namely for the purpose of torque transmission, optionally connectable with said driving shaft of the hydraulic motor, while on the secondary side it is mechanically, again for the purpose of torque transmission, permanently connected with the shaft of the winding drum. In this, a primary part of said clutch is conceived as an integral part of the driving shaft of the hydraulic motor, and the secondary part of said clutch is conceived as an integral part of the transmission assembly, which is mounted adjacent to said primary wall of the casing of the auxiliary winch. Said primary part of the clutch is together with said driving shaft and the hydraulic motor displaceable along the central geometric axis of said hydraulic motor shaft in a direction towards the secondary part of the clutch and towards the transmission assembly, which is located adjacent to the primary wall of the casing, wherein said primary part of the clutch is permanently supported by springs, which are suitable for acting in said direction and for maintaining of a positively locked interconnection between the primary part and the secondary part of the clutch. On the other hand, said primary part is at least temporarily displaceable also in the opposite direction, namely apart from said primary wall of the casing and at least for such a distance, which is required that said positively locked interconnection between the primary part and the secondary part is dismissed and the torque transmission via the clutch is interrupted.

In a preferred embodiment of the invention, said transmission assembly comprises a pair of mutually cooperating gear wheels, namely a secondary gear wheel, which is mounted on said shaft of the winding drum in the area between the last and the primary wall of the casing of the auxiliary winch, and is rotatable together with said shaft and the winding drum, as well as a primary gear wheel, which is adapted to cooperate with said secondary gear wheel and is freely rotatable mounted on an axle, which is fixedly mounted on said primary wall of the casing at appropriate distance apart from said shaft of the winding drum, so that the longitudinal geometric axis of said axle extends parallel to the longitudinal geometric axis of said shaft of the winding drum and simultaneously also coaxially with the longitudinal geometric axis of the driving shaft of the hydraulic motor, wherein said secondary part of the clutch represents an integral part of said primary gear wheel, and the primary part of the clutch represents an integral part of the driving shaft of the hydraulic motor. In accordance with further aspects of the invention it is also preferred that, in addition to said primary wall of the casing, a secondary wall is arranged within the interior of the casing, and extends substantially parallel to said primary wall and at an appropriate distance apart from it, and that said secondary wall is furnished with a throughout passage, so that said primary gear wheel is located between the primary wall and the secondary wall, and the clutch between the shaft of the hydraulic motor and the primary gear wheel extends through said passage in said secondary wall. On the other hand, said hydraulic motor is mounted on a bearing member of the hydraulic motor, wherein said bearing member is mounted on said secondary wall by means of at least three guiding screws, which are arranged symmetrically with respect to said longitudinal geometric axis of the axle and are each per se supported by a spring, so that said bearing member is together with the hydraulic motor displaceable at a pre-determined distance along said guiding screws and along said geometric axis of the driving shaft and the primary gear wheel, and is by means of said springs on said screws pressed in a direction towards the secondary wall, while on the contrary, said bearing member is optionally also allowed to be displaced in opposite direction, namely apart from the secondary wall and against the force of said springs and at least for such distance, which is required that said positively locked interconnection between the primary part and the secondary part of the clutch is dismissed. In addition to that, at least three hydraulic cylinders are embedded within said bearing member of the hydraulic motor on its side which is faced towards the secondary wall, wherein said cylinders are arranged symmetrically with respect to said longitudinal geometric axis of the driving shaft of the hydraulic motor, and each of them is conceived as a blinded bore, in which a piston is inserted, which is displaceable towards the secondary wall and is sealed towards the cylinder by means of a gasket. Each of said cylinders is within its interior, namely in the area behind the belonging piston, furnished with a hydraulic conduit, which is via corresponding control means hydraulically connected with the hydraulic circuit of the auxiliary winch, so that each piston is due to the pressure of said hydraulic media displaceable out from the belonging hydraulic cylinder towards said secondary wall at least for such a distance, which is required for a previously mentioned movement of the bearing member apart from the secondary wall, so that upon decreasing hydraulic media pressure each piston is returnable back to its initial position within the hydraulic cylinder due to the force of said springs and pushing the bearing member of the hydraulic motor in a direction towards the secondary wall.

In an alternative embodiment of the invention, said transmission assembly is a chain gear, in which a secondary chain wheel is mounted on the shaft of the winding drum instead of the secondary gear wheel, and a primary chain wheel is freely rotatably mounted on the axle instead of said primary gear wheel. In this, said chain wheels are due to torque transmission synchronously rotatable by means of a chain. However, also in such case the secondary part of the clutch represents an integral part of the primary chain wheel.

In the previously explained embodiments said clutch should preferably be a dog clutch.

A further object of the invention is a mobile hydraulic crane, which generally comprises a bearing support with hydraulically extendable telescopic supporting legs, a column, which is rotatable around a vertical geometric axis mounted on said bearing support and is intended to be rotated by means of a hydraulic motor, a primary arm, which is pivotally around a horizontal geometric axis attached to said column in the terminal area thereof, a secondary arm, which is pivotally around a horizontal geometric axis attached to said primary arm and is on its free terminal portion furnished with a hydraulically operated grabber, which is optionally rotatable around its vertical geometric axis by means of a hydraulic rotating unit. Such crane is in the area of said supporting unit mountable on a suitable vehicle. Said primary arm is supported by a hydraulic cylinder, which is on the one hand pivotally connected to the column and on the other hand pivotally to the primary arm, while the secondary arm, which can also be telescopically extendable, is supported by a hydraulic cylinder, which is on the one hand pivotally connected to the primary arm and on the other hand pivotally to the secondary arm. Said hydraulic cylinders and the other disposable hydraulic driving means on the crane are hydraulically connected with the hydraulic circuit of the crane, which is either autonomous or is hydraulically connectable with the hydraulic circuit of the vehicle, on which the crane is mounted.

The invention proposes that such crane is equipped with a hydraulically driven auxiliary winch with the previously explained features, however under provision, that the hydraulic circuit of the crane and the auxiliary winch can only be alternatively activated, so that by activation of the hydraulic circuit of the crane serving for operation of the crane, the hydraulic circuit of the auxiliary winch serving for operation of the auxiliary winch is deactivated, or vice versa, that the hydraulic circuit on the auxiliary winch, which enables operation of the auxiliary winch, may be activated only when the hydraulic circuit on the crane, which enables operation of the crane, is deactivated.

In a preferred embodiment of said crane, said casing of the auxiliary winch is mounted on the primary arm of the crane, preferably adjacent to the crane column. The invention will be also explained on the basis of embodiments concerning the auxiliary winch and also the crane furnished with such a winch, which are presented in the attached drawings, wherein

Fig. 1 is a crane, furnished with an auxiliary winch, in isometric view;

Fig. 2 is a separately presented auxiliary winch, in front view;

Fig. 3 is said auxiliary winch, presented in cross-section along the central plane

I - 1 according to Fig. 2 in position, in which the clutch is activated and manual decoding of the rope is disabled;

Fig. 4 is said auxiliary winch, presented in cross-section along the central plane

I - 1 according to Fig. 2 in position, in which the clutch is deactivated and manual decoiling of the rope is enabled;

Fig. 5 is said auxiliary winch, presented in cross-section along a partially deflected plane II - II according to Fig. 2 in position, in which the clutch is activated and manual decoiling of the rope is disabled;

Fig. 6 is said auxiliary winch, presented in cross-section along a partially deflected plane II - II according to Fig. 2 in position, in which the clutch is deactivated and manual decoiling of the rope is enabled; and

Fig. 7 is said auxiliary winch, presented in cross-section along the transversal plane III - III according to Fig. 2 in position, in which the clutch is deactivated and manual decoiling of the rope from the winding drum of the auxiliary winch is enabled.

A mobile hydraulic crane 9, which is presented in Fig. 1, comprises a bearing support 91 with hydraulically extendable telescopic supporting legs 92’, 92”, and a column 93, which is rotatable around a vertical geometric axis 910 by means of a hydraulic motor, is mounted on said bearing support 91. A primary arm 94 is pivotally around a horizontal geometric axis 930 attached to said column 93, and in the terminal area thereof, a secondary arm 95, which is pivotal around a horizontal geometric axis 940, is attached to said primary arm 94 and is on its free terminal portion furnished with a hydraulically operated grabber 96, which is optionally rotatable around its vertical geometric axis 960 by means of a hydraulic rotating unit 97. Such a crane 9 is in the area of its supporting unit 91 mountable on a suitable vehicle, which is as such not presented in the drawings. Said primary arm 94 is supported by a hydraulic cylinder 934, which is on the one hand pivotally connected to the column 93 and on the other hand pivotally to the primary arm 94, while on the other hand, the secondary arm 95, which is optionally telescopically extendable, is supported by a hydraulic cylinder 945, which is on the one hand pivotally connected to the primary arm 94 and on the other hand pivotally to the secondary arm 95. Said hydraulic cylinders 934, 945 and the other disposable hydraulic driving means on the crane 9 are hydraulically connected with the hydraulic circuit of the crane 9, which in addition to a not-shown reservoir and a pump includes suitable control valves, which serve for adjusting of inflow or outflow of the hydraulic media to relevant components, as it is required for the purpose of either sole or synchronized operation of said components. Said hydraulic circuit of the crane 9 is either autonomous or is hydraulically connectable with the hydraulic circuit of the vehicle, on which the crane 9 is mounted.

As shown in Fig. 1, said crane 9 is equipped with an auxiliary winch 1, which comprises a winding drum 2 (Fig. 2 - 7) with a towing rope 100, which is coiled thereon and which is on its free terminal portion 101 furnished with a connecting means 102, which serves for connecting said rope 100 with a load, which is not shown in the drawing. As it will be later-on explained in more detail such auxiliary winch 1 among other also includes a hydraulic circuit, which may be hydraulically connected either with a hydraulic circuit of the crane 9, or directly or in indirectly with the hydraulic circuit on a vehicle, on which the crane 9 is mounted. However, in each case operation of the crane 9 and operation of the auxiliary winch 1 is always performed in an alternative manner, which means that the auxiliary winch can only operate when operation of the crane 9 is completely deactivated, or vice versa. Thus, when the auxiliary winch 1 is allowed to operate, then each potential operation of the crane 9 is made impossible, or vice versa, when the crane 9 is operating, then the auxiliary winch 1 is prevented from any operation.

Said auxiliary winch 1 comprises a casing 10, in the area of which the auxiliary winch 1 is mounted onto the crane 9. In the shown embodiment (Fig. 1), the casing 10 of the auxiliary winch 11 is mounted on the primary arm 94 of the crane 9 in the area adjacent to the column 93 of the crane 9, and appropriate attachment of the casing 10 is assured by means of suitable screws. A shaft 20 of the winding drum 2 is rotatably around its longitudinal axis 200 embedded within said casing 10 of the auxiliary winch I, and a secondary gear wheel 25 is mounted on said shaft 20, and is rotated together with the shaft 20 and the winding drum 2 and located between the casing 10 and the winding drum 2.

Moreover, an axle 3 is fixedly mounted within said casing 10 at a suitable distance apart from said shaft 20 of the winding drum 2, and the longitudinal geometric axis 300 of said axle 3 extends parallel to the geometric axis 200 of said shaft 20 of the winding drum 2, wherein a freely rotatable primary gear wheel 35 is placed on said axle 3 and is adapted for cooperation with said secondary gear wheel 25 as mounted on the shaft 20 of the winding drum 2. Said primary gear wheel 35 and said secondary gear wheel 25 together form a transmission assembly 235 and are located nearby the primary wall 11 of the casing 10, while on the opposite side of said primary gear wheel 35 there is a secondary wall 12 of the casing 10, on which the bearing member 5 of a hydraulic motor 4 is mounted. Said bearing member 5 of the hydraulic motor 4 is located at a pre-determined distance apart from said secondary wall 12 of the casing 10 and is connected there- with by means of guiding screws 51, 51’, 51 ”, along which said bearing member 5 is displaceable in a direction towards the secondary wall 12, or in opposite direction. Thanks to springs 52, which are placed on said screws 51, 51’, 51 ”, said bearing member 5 of the hydraulic motor 4 is constantly pressed in a direction towards the secondary wall 12 and consequently also towards the axle 3, in the area of which however a through passage 120 is available in the secondary wall 12. In the shown embodiment there are three screws 51, 51’, 51” available, which are arranged around said geometric axis 300 and are equidistantly spaced from each other in the circumferential direction.

Moreover, a group of hydraulic pistons 55, 55’, 55” is arranged on said bearing member 5 of the hydraulic motor 4, and each of them is by means of a gasket 57 sealed within a belonging cylinder 56 and is by means of a hydraulic media, supplied along a hydraulic conduit 58, displaceable from the interior of the bearing member 5 outwardly in a direction towards the secondary wall 12 of the casing 10. Similarly like the previously mentioned screws 51, 51’, 51 ” arranged equidistantly around said geometric axis 300, are also three pistons 55, 55’, 55” in the shown embodiment equidistantly arranged around said geometric axis 300, and each of them is located in the area between each two neighboring screws 51, 51’, 51 ”.

Each of said hydraulic cylinders 55, 55’, 55” is formed as a blind bore within the bearing member 5 of the hydraulic motor 4, and is in the area behind the piston furnished with a hydraulic conduit 58, through which the hydraulic media can flow. Each of said conduits 58 is hydraulically connected into a hydraulic circuit of the auxiliary winch 1. Whenever a properly compressed hydraulic media is supplied along the conduits 58, then the pistons 55, 55 ’,55” are pushed outwardly from the bearing member 5 of the hydraulic motor 4 in a direction towards the secondary wall 12 of the casing 10. By progressing said pistons 55, 55’, 55” out from the bearing member 5, the bearing member 5 together with the hydraulic motor 4 is displaced along the screws 51, 51 ’, 51’ ’away from the secondary wall 12, and at the same time the springs 52 are compressed. As soon as the pressure of the hydraulic media is reduced, then said springs 52 start releasing and pushing the bearing member 5 in a direction towards the secondary wall 12, wherein also the pistons 55, 55’, 55” are pushed back to their initial position by simultaneously returning the hydraulic media back to the hydraulic circuit of the auxiliary winch 1.

Similarly like said cylinders 56 with pistons 55, 55’, 55”, also the hydraulic motor 4 on the bearing member 5 is hydraulically connected with the hydraulic circuit of the auxiliary winch 1. by supplying of the hydraulic media into said hydraulic motor from one or another direction, said shaft 40 of the hydraulic media is rotated in one or another direction around the geometric axis 300, since the shaft 40 extends coaxial with the geometric axis 300 of the axle 3 and the primary gear wheel 35.

Said shaft 40 of the hydraulic motor 4 is on its free terminal portion furnished with a primary part 71 of a dog clutch 7, while the secondary part 72 of said clutch 7 is mounted on said primary gear wheel 35 on the axle 3. A required hub of the clutch 7, namely a distance, which is required for establishing of a positive mutual engagement of both parts 71, 72 of the clutch 7, substantially corresponds to a distance, for which said bearing member 5 of the hydraulic motor 4 is thanks to said pistons 55, 55’, 55” thereon movable along said screws 51, 51’, 51 ” against the force of springs 52 on said screws 51, 51 ’, 51 ”. When the clutch 7 is activated, and said positive mutual engagement between the primary part 71 and the secondary part 72 of the clutch 7 is established, the torque is transmitted from the shaft 40 of the hydraulic motor 4 onto the primary gear wheel 35. When the clutch is deactivated, the torque from the shaft 40 of the hydraulic motor 4 to the primary gear wheel 35 cannot be transmitted.

When the auxiliary winch 1 is in operation, the hydraulic motor 4 is supplied by hydraulic media and the shaft 40 is rotating with a pre-determined speed in each desired direction. The torque is via the clutch transmitted to the primary gear wheel 35, which cooperates with the secondary gear wheel 25 on the shaft 20 of the winding drum 2. By rotating said winding drum 2 in one direction, the towing rope is decoiled from the drum 2, and by rotating of the drum in opposite direction upon changing a direction of the hydraulic media, said towing rope 100 starts coiling onto the winding drum 2.

Whenever, regardless to still operating hydraulic motor 4 and rotating of the shaft 40, the user wishes to attempt to manual decoiling of the towing rope 100 from the winding drum 2 with a desired rope velocity, this can be achieved by means of activation of suitable control valves and enabling hydraulic media to enter into said hydraulic cylinders 56 within the bearing member 5 of the hydraulic motor 4, upon which the belonging pistons 55, 55’, 55” are pushed out from the bearing member 5, which is herewith pushed away from the secondary wall 12 within the casing 10 and against the force of said springs 56 on said screws 51, 51’, 51”. In such case, said positive mutual engagement between the primary part 71 and the secondary part 72 of the clutch 7 extending through said passage 120 is dismissed, which leads to interruption of torque transmission from the shaft 40 of the hydraulic motor 4 to the shaft 20 of the winding drum 2. Upon that, said primary gear wheel 35 on the axle 35 is freely rotatable, so that by uncoiling of the towing rope 100 from the winding drum 2 said primary gear wheel 35 can be freely rotated together with the shaft 20 of the winding drum 2 and the secondary gear wheel, and is rotated independently on rotation of the shaft 40 of the hydraulic motor 4. As soon as such manual decoiling of the towing rope 100 from the winding drum 2 is concluded, the pressure of the hydraulic media within said conduits 58 is reduced, and pistons 55, 55’, 55” may during returning of the bearing member 5 due to compression of the springs 52 be gradually returned back to their initial position within the cylinders 56, by which said positive mutual engagement between the primary part 71 and the secondary part 72 of the clutch 7 is re-established, and also a transmission of torque from the hydraulic motor 4 onto the winding drum 2.

The invention provides also for an alternative embodiment, which is not shown in the drawings, but shall be understood by a person skilled in the art also without that. According to said embodiment, said transmission assembly 235 is a chain gear, in which a secondary chain wheel is mounted on the shaft 20 of the winding drum 2 instead of the secondary gear wheel 25, and a primary chain wheel is freely rotatably mounted on the axle 3 instead of said primary gear wheel 35. Said chain wheels are due to torque transmission synchronously rotatable by means of a chain. In such case, the secondary part 72 of the clutch 7 represents an integral part of the primary chain wheel. In such case the distance between the geometric axis 300 of the shaft 400 of the hydraulic motor 4 and the geometric axis 300 of the shaft 200 of the winding drum 2 must be correspondingly longer, but also in such case such auxiliary winch 1 could operate quite successfully.