CABLE WINCH WITH AUTOMATICALLY CONTROLLED REGULATION OF SPEED OF UNWINDING OF A HAULAGE CABLE

Abstract

 The object of the invention is a cable winch with automatically controlled regulation of speed of unwinding of a haulage cable. The cable winch of the invention is used as a drive unit of a device for haulage of timber on a poorly accessible terrain. The cable winch of the invention also provides for a remote control of the cable winch and based on the speed of the carriage (10) the brake force of the cable winch can be controlled by a brake (3) that acts via a braking cylinder (4) on the speed of unwinding of a drum (2) with a haulage cable (6) by means of an electronic circuit (7), in which a comparison between a desired value of speed of the carriage (10) and the actual speed measured by a sensor (1) on a pulley (11), an estimate of terrain inclination and that of load mass on the carriage (10) is made possible.

Description

[0001] The object of the invention is a cable winch with automatically controlled regulation of speed of unwinding of a haulage cable. A cable winch of the invention is used as a drive unit of a device for hauling of timber on a poorly accessible terrain. It allows access with a working machine, a tractor or a lorry only from the top of a terrain, so timber must be hauled uphill.

[0002] When a classic cable winch is used as a drive unit a problem of returning of the haulage cable downhill appears (the cable needs to be hauled manually from an upper point of a terrain to a lower point). A solution is an additional bearer cable and a carriage, with which a haulage cable is lowered downhill and timber is then hauled lifted from the ground uphill. Round timber does not get stuck into the ground and understorey is therefore not destroyed. A variant with an additional bearer cable and a carriage will be hereinafter called a "cableway".

[0003] Various variants of cableways for hauling of timber are nowadays available commercially. There exist the most basic variants of a cableway, where a mechanical or a hydraulic cable winch is used as a drive unit (lower price range) and professional cableway systems consisting of a standalone drive unit (higher price range).

[0004] In the continuation, a focus will be made on a variant of a cableway of a lower price range with a mechanical or hydraulic cable winch as a drive unit.

[0005] In currently known variants of cableways lowering of a carriage down a terrain is carried out by way of a brake on a cable winch. An operator influences the speed of a carriage by controlling the brake, whereas he must rely on his visual estimate of the speed of the carriage. A further disadvantage of such operation can be caused by a variegated terrain that does not allow monitoring of the carriage along the entire terrain. This variant is schematically shown in Figure 1.

[0006] Three workers are most frequently needed to manage a cableway. A first worker is located at a site where round timber is fastened, a second worker releases the round timber and a third worker is in charge of lowering the carriage downhill and of lowering the round timber in the upper point. The mass of the round timber to be lowered to the ground is of key importance in pulling a brake. The worker needs to monitor the speed of lowering of the round timber and to adequately react by using a mechanical lever of the brake. The mass of round timber to be lowered can be in a range of up to 1,500 kg. While lowering the carriage the lower worker and the one operating the brake usually need to communicate since the worker operating the cable winch in the lower section of the terrain does not see how rapidly the carriage moves.

[0007] The embodiment of a cableway with a cable winch with automatically controlled regulation of the speed of unwinding of a haulage cable of the invention allows for a more simple automated process of cableway operation. This embodiment also allows for a remotely controlled operation of the cable winch, wherein the operator does no longer have to manually control the braking force of the cable winch based on an estimated speed of the carriage. The embodiment of the cableway with the cable winch of the invention calls only for two workers in order to keep the same functionality of the cableway. The embodiment of the cableway is schematically shown in Figure 2.

[0008] When the bearer cable is adequately arranged, an initial clip and a final clip (CLIP_1 and CLIP_2) need to be arranged. The clips make it possible to release a cable from the carriage when they come in contact with the carriage. The final section of the cable is fixed into the carriage between both clips. It is herewith ensured that the round timber is lifted from the ground during the entire uphill hauling.

[0009] The cable winch with automatically controlled regulation of speed of unwinding of a haulage cable of the invention will be explained in more detail by way of an embodiment and the enclosed drawings representing in:

Figure 1 schematic presentation of cableway operation (old embodiment);

Figure 2 schematic presentation of cableway operation (new embodiment);

Figure 3 block diagram of a cable winch of the invention;

Figure 4 block diagram of a speed regulator of a carriage of the cable winch of the invention.

[0010] A cable winch with automatically controlled regulation of speed of unwinding of a haulage cable of the invention is represented in a block diagram in Figure 3.

[0011] The task of such cable winch is to automatically regulate the speed of unwinding of a haulage cable 6 and consequently the speed of movement of a carriage 10 along a bearer cable 5. The haulage cable 6 is wound on a drum 2 of a hydraulic winch 8. In a classic operation of a hydraulic winch a brake 3 is fully pulled until a hauling function (winding of the haulage cable onto a drum - haulage of round timber towards the winch) or an unwinding function (unwinding of the haulage cable from the drum - lowering of the haulage cable downhill) is used. If the speed of unwinding of the haulage cable 6 is to be changed continuously, also the force, with which the brake 3 brakes the speed of rotation of the drum 2, needs to be changed continuously. A hydraulically operated brake 3 is used for this purpose and its brake force can be defined by the pressure in a braking cylinder 4. To change the pressure in the braking cylinder 4 a hydraulic proportional valve 9 is used. An electronic circuit 7 is provided to change a reference value of the proportional valve, based on an operating algorithm, which is based on a measured value of movement of the haulage cable 6 that is measured by a sensor 1. The speed of movement of the haulage cable 6 is measured on a pulley 11, through which the haulage cable 6 is led. The pulley 11 is provided with holes that are detected by the sensor 1.

[0012] The task of the electronic circuit 7 is to measure the speed of movement of the haulage cable 6 when going downhill in the first phase and to influence the pressure in the proportional valve 9 in the second phase.

[0013] To calculate the speed 22 of movement of the haulage cable 6 a signal from the sensor 1 and the holes on the pulley 11 are used. While the pulley 11 is rotating the sensor 1 detects a hole in the pulley 11: With the sensor 1 above a hole, the output status of the sensor 1 is logical '0' otherwise the output status is logical '1'. Based on the changing of the logical value of the sensor 1 output, the speed of movement of the haulage cable 6 can be determined by using data on:

• number of logical changes in a certain time interval, and
• time between two changes of the logical status of the sensor 1.

[0014] The electronic circuit 7 can have influence on the speed of movement of an empty carriage and also on the movement of a loaded haulage cable at the top of the cableway where an unknown quantity of round timber (various loads) is lowered.

[0015] To reach a constant speed of movement of the carriage or the load, the force of the brake 3 needs to be regulated. The force of the brake depends on various factors such as load mass, terrain inclination, setting of a pre-brake, current speed of the carriage and quantity of the haulage cable on the drum.

[0016] The electronic circuit 7 also provides for a function of load weighing. The force needed on the braking cylinder 4 for the load to start moving should be determined (a rough value needed for such load on the braking cylinder is thus determined). By determining this force the following factors in the system are done away with: load mass, terrain inclination and pre-brake setting. The pressure in the braking cylinder 4 is gradually increased for weighing purposes. As the pressure is increased, the braking cylinder 4 gets gradually opened. The position of the haulage cable 6 changes during the entire opening interval. When the haulage cable 6 moves, the electronic circuit 7 records the current pressure needed to make the load (attached to the haulage cable 6) start moving. Due to various loads, different pre-settings of the brake 3, different terrains this value can considerably vary between situations.

[0017] The electronic circuit 7 consists of a comparator 13 of desired speed 12 of the haulage cable 6 and of the actual speed 20 of the carriage 10, and an output of a proportional regulator 14 is connected to the first part of an adder 15 and the second part of the adder - pre-controller 17 is an output of an additional function of weighing a load 18 that is determined on the basis of pulse counts from the sensor of movement 21 that is monitored while the ramp 19 function is controlled, and the output of the additional function of weighing of the load 18 is also a function of changing the proportional parameter of the regulator 14.

Example:

[0018] At a load of 100 kg, an average inclination of the terrain and an average setting of the pre-brake, a pressure of 120 bar is needed to release the brake.

[0019] At a load of 1000 kg, an average inclination of the terrain and an average setting of the pre-brake, a pressure of only 50 bar is needed.

[0020] Such method of weighing the load provides an indication on an approximate pressure value that is needed for the brake 3 to brake very smoothly (pre-control). And yet, the speed of the carriage and the load would remain uncontrolled if only such mode of control (without a regulator) were used.

[0021] Figure 4 shows a block diagram of a regulator for controlling a speed of the carriage. In order to have a regulated control the current data on the speed of movement of the haulage cable 6 are needed apart from the pre-control. A regulation scheme of operating such system contains a P speed regulator with an added pre-control that is determined by the function of load weighing.

[0022] The used linear P-regulator changes the reference value of the proportional valve 9 on the basis of a difference between the reference and actual speed of movement of the haulage cable 6. A parameter of the P-regulator changes with respect to the mass of the regulated load.

[0023] The output value of the regulator is limited within the range determined by a proportional hydraulic valve that is controlled via D/A converter.

[0024] In the method of releasing the load in the upper position of the cableway (CLIP_1), a further function is used that provides for an undisturbed releasing of the load by preventing a too huge amplitude of oscillation of the bearer cable 6.

Claims

1. A cable winch with automatically controlled regulation of speed of unwinding of a haulage cable, where a remotely controlled operation of the cable winch is possible and based on the speed of a carriage a brake force of the cable winch can be controlled
characterized in that
the speed of a haulage cable (6) that is wound on a drum (2) and led through a pulley (11) and attached to a carriage (10) is regulated by way of a hydraulically operated brake (3) via braking cylinder (4) controlled by a hydraulic proportional valve (9), wherein an electronic circuit (7) controls the proportional valve (9).

2. Cable winch according to claim 1
characterized in that
the electronic circuit (7) consists of a comparator (13) of desired speed (12) of the haulage cable (6) and of the actual speed (20) of the carriage (10), and an output of a proportional regulator (14) is connected to the first part of an adder (15) and the second part of the adder (pre-controller (17) is an output of an additional function of weighing a load (18) that is determined on the basis of pulse counts from the sensor (21) of movement that is monitored while the ramp (19) function is controlled, and the output of the additional function of weighing of the load (18) is also a function of changing the proportional parameter of the regulator (14).

3. Cable winch according to claim 2
characterized in that
the electronic circuit (7) can compare the desired value (12) of the speed of the carriage (10) and the actual speed (20) measured by a sensor (1) on the pulley (11), estimate the inclination of the terrain and load mass on the carriage (10), wherein the output signal of the electronic circuit (7) is connected to the proportional valve (9) that controls the brake (3) via the braking cylinder (4).

4. Cable winch according to claims 1 to 3
characterized in that
the pulley (11) is provided with holes that allow detection of the speed of rotation of the pulley by the sensor (1), based on which the speed and the movement of the haulage cable are measured.

Drawing