Field of the invention

The present invention belongs to the field of engineering, more precisely to the field of forestry winches and mechanisms for controlling tractive force of a winch. The invention relates to a system for ensuring a constant tractive force of a winch.

Background of the invention and the technical problem

When a winch is in use, the diameter of the drum changes depending on the number of layers of the wound wire rope, which consequently affects the tractive force of the winch. Situations, in which the tractive force must be regulated according to a specific situation in a work process, can occur during use of the winch. If the tractive force of the winch decreases due to the increase of rope radius on the drum to a such extent that the force of resistance is larger than the tractive force, the load stops, as the lamellae of the coupling (clutch) start to slide. This represents a problem in practice. Modem professional winches are designed to keep the tractive force during winding of the rope from smaller to larger diameter essentially the same, which enables optimal operation of the coupling. These winches are called constant traction force winches, wherein said constant traction force may be ensured in different manners. The main disadvantage of known solutions is that settings are challenging. In addition, known solutions are dimensionally extensive, which represents a further problem for ensuring compactness.

The technical problem, which is solved by the present invention, is construction of a compact system for controlling and managing the winding drum of a winch that will enable maintenance of constant tractive force of the winch. The task of the present invention is constructional arrangement of individual functional winch elements system, which will enable maintenance of constant tractive force of the winch even when the rope is completely wound on the drum as well as when the winding rope is almost fully unwound from the drum.

Prior art

The winch described in patent application EP 2 565 144 comprises a drive shaft, a drum for winding rope, a drum coupling provided for transmitting rotating movement of the drive shaft, a drum break for breaking the rope drum and a rope ejector with a drivable pulley. The drivable pulley stands for connecting a powertrain with the drive shaft over a rope ejection clutch. The drum coupling and the drum brake are formed as a hydraulic drum coupling and a hydraulic drum brake, respectively for operating an assigned valve. This is the characteristic of the invention. The present invention differs from this solution, as the hydraulically driven mechanism is involved in ensuring a mechanical shift of handles aimed to maintain almost constant tractive force of the winch.

According to the Slovenian patent 24108 a forestry winch with controlled winding of the rope is known, wherein the coils are arranged side by side relatively to each other and without any transpositioning or overlapping, while at the same time overloading of said towing cable and other components of a driving assembly due to towing of too heavy load is prevented. To this aim, the winch is provided with a directing assembly, which is arranged between an upper pulley block and said winding drum and is freely rotatable or least pivotable at certain angle around the vertical geometric axis, wherein said winch further comprises a dynamometer suitable for measuring of tensioning force within said towing cable, so that also the winding drum can be controlled depending on each measured loading of the towing cable.

A mechanical-hydraulic system with a pressure regulator for maintenance of constant tractive force of a winch, as described in patent EP 3 093 264 comprises a drum, a rope, the pressure regulator, a coupling comprising a hydraulic cylinder, and is characterized in that it further comprises a pushing cylinder installed on forks, spring and a shaft, wherein the pushing cylinder is pushed away with each new layer of a towing rope on a winch drum. Consequently, the cylinder rotates the axis of forks, which carry the pushing cylinder; that rotation of the forks' axis causes movement of a pole, which pushes a piston of a pressure regulator for one step, consequently causing an increase in oil pressure, which causes an increase of the cylinder piston pressure on couplings, resulting in an increase of the drum momentum. Distances »e«, »f« and »g« change with each movement of the pushing cylinder or the forks' axis due to a new layer of the towing rope on the drum, resulting in closing or opening of the pressure regulator with movable part of attachments, which consequently increases or decreases oil pressure in the hydraulic system. The distance »e« is the distance between the centre of the axis and attachment size of the first part of the pole in the groove, the distance »f« is the length of the pole, i.e. , the distance between the first part of the pole and the centre of the mounting of the second part of the pole in a holder, which is in contact with the piston of the pressure regulator, and the distance »g« is the distance between the centre of the axis, where the bottom part of an attachments is installed and the centre of the upper part of the attachment, where the pre-tensioned spring is mounted, said spring pulling the forks and thus pushing the pushing cylinder onto the drum. In accordance with changes in distances »e«, »f« and »g« and directly connected forks of the pushing cylinder, a spring and the pole, an almost constant tractive force of the winch is maintained.

Known solutions do not solve the technical problem in the same manner as the present invention and require complex settings and significant space.

Description of the solution to the technical problem

The solution disclosed in EP 3 093 264 is efficient, but the system is complex. Therefore, it is the main aim of the invention to simplify the system for ensuring constant tractive force of the winch regardless of the amount of rope wound on the drum. It is also desired that the construction of the system allows control with one controller, i.e., the winch controller that controls all winch operations. The essence of the system for maintaining constant tractive force of a winch is in that for ensuring a constant tractive force of a winch a pushing cylinder is provided for pushing onto a drum or a tube of the drum, on which a rope is wound, wherein said pushing cylinder is mounted on a holder, which is via an axis rotatably mounted on a housing of the winch. The pushing cylinder is arranged to rotate and shift away during layer-wise winding of the rope onto the drum, until the drum is fully wound. The angle of the pushing cylinder to the housing of the winch changes during winding and unwinding of the rope to and from the drum, respectively. If more wire is wound on the drum, the pushing cylinder is farther away from the drum. The cylinder is connected to a Hall angle sensor, which detects the angle of the cylinder and/or its holder on the housing of the winch. The Hall sensor is a contact-less sensor of magnetic field, comprising a plastic housing, an electronic microcircuit, and a permanent magnet. The Hall sensor is mounted on the winch housing in a fixed manner, using screwing or a similar method, wherein the cable connecting the sensor with the winch controller is installed along the winch housing in any suitable manner. Thus, the cable is protected against possible damage. In case the Hall sensor was movably installed, the cable would be damaged due to movements, which is not desired as high reliability of operation is the aim of the Hall sensor. Alternatively, securing the cable due to movement of the sensor could require a complex solution, which is not desired as well. The permanent magnet is usually installed together with its plastic housing in any suitable manner. With the movement of the cylinder, the permanent magnet also moves, wherein the semiconductor microcircuit detects the magnetic field during magnet rotation. As a result, certain voltage is created, which is proportional to the strength of the magnetic field. Said magnet is installed on the axis or on the holder of said pushing cylinder. Namely, several different embodiments are possible:

- the axis may be mounted on the winch housing in a fixed manner, and he holder is rotatably mounted on the axis, wherein the magnet of the Hall sensor is installed on the holder near the axis, to allow detection of its magnetic field with the microcircuit installed on the housing of the winch near or at one end of said axis,

- the axis is rotatably mounted in the winch housing and the holder is connected to the axis in a fixed manner, so the axis and the holder rotate together, wherein the magnet is installed on the axis and the sensor is installed on the housing of the winch at the end of the axis.

So designed system may measure the angle of the cylinder to the winch housing, where the Hall sensor is mounted, and via the sensed magnetic field the Hall sensor can send this information to the controller in order to provide status of the winding (amount of rope on the drum).

When the position of the cylinder is changed, the sensor sends to the controller voltage that is proportional to the rotation of the magnet, said controller based on the measured values assigns to a pressure valve, preferably proportional pressure valve a suitable electrical signal for changing the pressure with which the clutch presses on the drum. When the cylinder is open for a maximal angle, the pressure is increased to the highest value, while in case the cylinder is at a minimal deflection, the pressure is minimal. The maximal and minimal value are programmed in the controller based on the dimensions of the drum. Calibration is done via the controller, which simplifies management of the system. By using the Hall angle sensor precise control of the change in the diameter of the wound rope on the drum is achieved, and thus precise regulation of the constant pulling force. The Hall sensor is the most suitable for this function, as it is precise and insensitive for dirt, liquids, and large temperature changes. Its operation is therefore not sensitive for external conditions that occur during work with winch.

Further, use of the Hall sensor enables additional safety functions for preventing damage to the wire rope, unwanted movement or detachment of the load and winch operation stoppage (standstill).

By sensing the first layer of the rope on the drum detachment of the rope from the drum can be prevented. As the winch has a preferably system for measuring speed and rotation direction of the drum, a precise time of termination of unwinding can be defined in order to prevent full unwinding of the rope. The Hall sensor is arranged to detect the first layer of the rope on the drum,

The second safety function achieved with the Hall sensor is detection of the outermost diameter of the fully wound drum. Pulling with the winch is terminated once the maximal diameter set on the controller has been exceeded. Thus, over-winding of the rope is prevented. Pulling is also terminated in case the rope is wound on only one part of the drum, in case the maximal diameter is exceeded.

The system as described above is simple, with a small number of components and compact, so that it may be installed in any winch.

As an alternative to the Hall sensor a suitably mounted potentiometer, a measuring rod or an incremental encoder may be used. In case the measuring rod is used, the latter is installed in such manner that it converts rotational movement of the holder of the pushing cylinder into a linear movement that can be measured with the measuring rod. Conversion of the movement may be achieved in any suitable manner known to the skilled person. For example, it may be achieved by installing a small pulley on a pivot of the holder of the pushing cylinder, said pulley being arranged to receive a wire rope that moves linearly at the exit and returns to the initial position with a spring. An element detectable with the measuring rod is mounted on the wire rope.

The system for ensuring a constant tractive force of a winch will be described in further detail based on an exemplary embodiment and figures, which show:

Figure 1 Assembly and elements of the system for ensuring constant tractive force of a winch

Figure 2 Cross-section of the axis and the Hall sensor

A pulling rope is wound or unwound from a drum 1 . For better winding of the rope onto the drum 1 a pushing cylinder 2 is provided, said pushing cylinder being rotatably mounted, preferably with a ball bearing, on a holder 3. The holder 3 is mounted in an axis 6, so that it moves together with the axis as depicted with the arrow on figure 1 , i.e. , towards the drum or away from it, depending on the amount of rope wound on the drum 1 . The axis 6 is rotatably mounted on the housing of the winch. On one end of the axis 6 a holder 4 of a Hall sensor 5 is attached, while the axis 6 of the holder 3 of the pushing cylinder 2 is directly connected to a magnet 5a of a Hall sensor 5. The Hall sensor 5 itself is mounted in a fixed manner, preferably by screwing on the holder 4 and the housing of the winch. The holder 4 of the sensor is mounted in a fixed manner on the housing of the winch, while at the same time the holder 3 of the pushing cylinder is mounted on the holder 4 in a rotatable manner. A part 3a of the holder 3 is configured for mounting a spring (not shown in the figure), which pushes the pushing cylinder 2 onto the drum. The rope, which is wound on the drum, exits between the drum and the pushing cylinder in the vertical direction upwards.

The pushing cylinder 2 functions as a sensor for the number (amount) of wound layers of rope on the drum 1 , wherein its position is determined with the Hall sensor 5. The voltage of the latter related to the detected magnetic field is read by the controller, which suitably adjusts the electrical signal for the pressure valve regulating the pressure of the coupling.

Figure 2 shows a cross-section of the axis 6 and the Hall sensor 5 with the magnet 5a, which is installed on one end of the axis 6, so that it rotates together with the axis 6. The magnet 5a is surrounded with the holder 4, which is mounted in a fixed manner and does not rotate together with the axis, thus preventing the magnet 5a from disengagement from the axis 6. On the holder 4 the Hall sensor 5 with its housing and semiconductor circuit is installed, which is arranged to detect the magnetic field generated by the magnet 5a in dependence on rotation of the axis 6 and thus the holder 3 of the with the pressing cylinder 2. On the left side of the sensor 5 a cable or wiring is provided (not shown in the figure) for connection of the sensor 5 with the controller. The controller has a set maximal and minimal value of the pressure of the coupling on the drum, wherein all intermediate values are adjusted with regards to the detected position of the pushing cylinder 2, which depends on the amount of the rope wound on the drum 1 .