A HYDRAULIC SYSTEM WITH ADDITIONAL PROTECTION OF OPERATION OF CLUTCH AND DRUM BRAKE HYDRAULIC CIRCUIT IN A FORESTRY WINCH

Abstract

 The invention belongs to the field of mechanical engineering, more precisely to the field of hydraulic systems with a hydraulic accumulator as an additional source of hydraulic pressure/compressive energy in particularly suitable for machines with unequal consumption. At the same time, the invention also belongs to the field of forestry winches with hydraulically controlled brake and clutch of a winding drum in a forestry winch.
The hydraulic system with additional protection of operation of the hydraulic circuit of the clutch and drum brake in a forestry winch comprises an oil reservoir 1, a filter 2, a pump 3, a check valve 4, a pressure relief valve 5, a control valve 6, a check valve 7 with a throttle 8, a valve 11, a hydraulic accumulator 9, a check valve 12 with an adjustable throttle 13, a valve 19 with a throttle 18, a hydromotor 19, a cylinder 14 of the brake and a cylinder 15 of the clutch. The entire hydraulic system is mechanically integrated into the housing of a forestry winch.

Description

Field of the invention

[0001] The invention belongs to the field of mechanical engineering, more precisely to the field of hydraulic systems with a hydraulic accumulator as an additional source of hydraulic compressive energy in particularly suitable for machines with unequal consumption. At the same time, the invention also belongs to the field of forestry winches with hydraulically controlled brake and clutch of a winding drum in a forestry winch.

The technical problem

[0002] The technical problem, which is solved by the present invention, is a constructional solution of a hydraulic system for controlling the winding drum of a winch, which will enable reliable control of the clutch and the brake even in the most critical moments of winch operation. During use of a winch a situation can occur, in which the tractor is lifted from the ground due to an oversized load if the basic valve is stuck and the user stops the winding function. Because in such situations the winding function would not be terminated, the tractor could overturn as the winch would still pull. The construction must enable additional control option in the process of winch steering.

State of the art

[0003] Slovene patent no. 22392 discloses a solution of a hydraulic aggregate for supply and control of hydraulic consumers, in particular a brake and a clutch in a forestry winch. The hydraulic aggregate for supply and control of smaller hydraulic consumers, particularly cylinders for the control of a brake and a clutch in a forestry winch comprises at least a hydraulic medium tank, a pump to assure a required pressure of the hydraulic medium and a control assembly consisting of at least one control valve and at least one cylinder. It is foreseen according to the invention that a piston pump is included into the hydraulic aggregate circuit, and is connected with the control assembly and the hydraulic medium tank via a non-return valve transmitting hydraulic medium in the direction away from the pump but not in the direction towards the pump on the one hand, and on the other hand, is connected in series to the hydraulic circuit together with a pressure accumulator and the previously mentioned non-return valve either via a switchover valve comprising a non-return valve transmitting hydraulic medium in the direction towards the pump but not in the opposite direction, or, in the case of exceeding the set-in-advance pressure due to automatic rerouting of the switchover valve, to the hydraulic circuit comprising the mentioned pump, the switchover valve, the control assembly and the mentioned non-return valve in the series connection. The hydraulic aggregate excels in small dimensions, exceptionally low quantity of applied hydraulic medium and low hydraulic losses.

[0004] Patent SI 22877 discloses a solution of a hydraulic aggregate for a forestry winch with an integrated electromagnetic valve for controlling the brake cylinder and the clutch cylinder. The hydraulic generator includes a pump for pumping the hydraulic media under pressure, an electromagnetic valve for controlling the brake cylinder and the clutch cylinder as well as a hydraulic assembly, which features a return valve, a safety valve and a choke features an electromagnetic valve integrated into the hydraulic assembly and the brake cylinder as well as the clutch cylinder by way of a hydraulic piping attached to the terminals of the hydraulic block leading from the integrated electromagnetic valve.

[0005] Patent SI 22937 discloses a hydraulic generator of the forestry winch with added hydraulic engine for rotating the driving device for unrolling the pulling rope from the winding drum, which features an added valve in front of the cylinder. In front of the hydraulic engine there is also an additional valve. The valve is in the shutdown position open and requires for its locking an electrical signal from the direction of the cylinder, while the valve is closed in the shutdown position in the direction of the hydraulic engine and requires an electrical signal in order to open. The triggered electrical signal for the flow direction of the hydraulic medium into the cylinder and the hydraulic engine switches the control valve and the valve on, while after a certain time lapse the valve is triggered. The time lapse is larger than the required time for the cylinder to ensure the shutdown of the brake.

[0006] Slovene patent no. 23104 describes a hydraulic aggregate of a forestry winch with an added hydraulic motor for rotating a driving device for unwinding a traction rope from a winding drum, which comprises a pump for pumping a hydraulic medium under pressure, a gas accumulator and a reservoir, and a hydraulic block with a control valve for the control of a clutch cylinder and/or a brake and a hydraulic motor cylinder. The hydraulic motor is linked with a pipe to the outflow connection of the brake cylinder, while the inflow connection of the brake cylinder with a pipe to the control valve. The flow of the hydraulic medium through the hydraulic motor is only possible, when the control valve is open for the flow into the cylinder and the cylinder is in the state with the brake unlocked.

[0007] According to the utility patent DE202005020694U1 by company Ritter the user cannot release the brake and at the same time drive the tractor forwards, when a non-moving load is on the rope, because the hydromotor is connected in parallel with the brake. If the hydromotor spins faster than the available flow, the pressure in the duct leading to the brake cylinder drops, which blocks unwinding of the drum.

[0008] The solution according to the invention differs from the above mentioned known solutions in that the invention is much more reliable from the perspective of security. When winding-towing is activated, two valves activate simultaneously. If one of the valves is blocked after towing is stopped, this may lead to an accident as the winch continues to pull. Protection with two valves prevents such events, as it is highly unlikely that both valves would be blocked at the same time.

Description of the solution of the technical problem

[0009] The essence of the hydraulic system with an additional protection of operation of the hydraulic circuit of the clutch and the drum brake in a forestry winch is in that it comprises a hydraulic accumulator, which stores enough energy for multiple releases of the brake or the clutch in case the hydraulic system malfunctions, a pump with a pressure relief valve, which is a safety valve at the same time. The system mostly operates at a low pressure up to 20 bar, a time delay of activation of the brake cylinder can be set with an adjustable throttle. A flow regulator ensures approximately constant rotation speed of the hydromotor regardless of the load on it.

[0010] The hydraulic system will be described in further detail based on figures, which show:

Figure 1

A basic hydraulic scheme of the system

Figure 2

A hydraulic scheme with an additional protection of clutch release

[0011] The hydraulic system with additional protection of operation of the hydraulic circuit of the clutch and the drum brake in a forestry winch comprises an oil reservoir 1, a filter 2, a pump 3, a check valve 4, a pressure relief valve 5, a control valve 6, a check valve 7 with a throttle 8, a valve 11, a hydraulic accumulator 9, a check valve 12 with an adjustable throttle 13, a valve 19 with a throttle 18, a hydromotor 19, a cylinder 14 of the brake and a cylinder 15 of the clutch. The entire hydraulic system is mechanically integrated into the housing of a forestry winch.

[0012] The pump 3 fills the accumulator 9 through the check valves 4 and 7 to a working pressure, which is set on the pressure relief valve 5. When the oil in the hydraulic accumulator 9 reaches the set working pressure, the pressure relief valve 5 opens and remains in this position until the pressure in the hydraulic accumulator 9 drops under a specified value, which is approximately 10 to 15 bar. The oil freely runs to the flow regulator 16 and the control valve 6, when the valve 5 is open. Because the smaller resistance is on the side of the valve 6, the oil runs through it into the oil reservoir 1. Due to such execution of the hydraulic equipment the pump 3 works most of the time at a lower pressure, namely at a pressure up to 10 bar. If the user selects the function of rope unwinding, valves 6 (right) and 11 (right) are simultaneously switched. The oil runs from the pump through the valve 6 to the flow regulator 16, the check valve 17 to the hydromotor 19, which drives the unwinding sheave, via which the rope from the winch drum is lead. At the same time the oil from the hydraulic accumulator through the throttle 8, the valve 11 and the adjustable throttle 13 activates the brake cylinder 14 and consequently releases the drum brake, so that the drum starts to unwind due to the pulling force in the rope, caused by the hydromotor 19. Pressure in the inlet line to the hydromotor 19 increases to 50 to 70 bar.

[0013] When the user turns on winding of the rope, only the valve 11 (left) is switched and the oil runs from the hydraulic accumulator 9 through the throttle 8 and the valve 11 and activates the clutch cylinder 15. In case that the pressure in the hydraulic accumulator drops below a specified value, the pressure relief valve 5 closes and the pump fills the hydraulic accumulator 9 to the set working pressure.

[0014] If the user activates the function of unwinding, releases the brake and simultaneously drives the tractor forwards and a non-moving load is attached to the rope, the driving speed of the tractor is higher than the peripheral speed of the rope on the unwinding sheave and the hydromotor 19 in this case works as a pump, so that the oil runs from the reservoir 1 through the motor 19, the throttle 18, the flow regulator 16, the valve 6 back to the reservoir 1. The throttle 18 creates resistance, so that the sheave and the drum do not unwind too quickly due to dynamics. In case the drum rotates too quickly, the rope may unwind without control or the coils may loosen due to inertia of the drum. The throttle 18 is intended to create resistance in the circuit of the drive of the hydromotor 19 in the case of winding the rope onto the drum. The driven sheave in this case drives the hydromotor 19, which operates in the mode of a pump so that the oil runs form the reservoir 1 through the hydromotor 19 and through the throttle 18 and the regulator 16 back to the reservoir 1. The larger the resistance of oil on the throttle 18 the larger the force of pretensioning between the sheave and the drum. This force is important for steady winding of the rope onto the drum in the form of a helix in layers, even when there is no load attached to the rope or if only rope is to be wound.

[0015] One of the essential safety elements of this scheme is that in an event that the user would like to release the rope in case of an emergency (for example when the load increases to such extent that the tractor with the winch is pulled towards an abyss), the drum may unwind to the end as the brake is always released. This characteristic cannot be found in any of the existing solutions.

[0016] The hydraulic scheme with additional protection of the clutch is shown in figure 2. The essential element is the 2/2 control valve 20, which is connected in parallel with the hydraulic cylinder 15 of the clutch. In case of winding the valves 11 and 20 have to be simultaneously switched so that the hydraulic cylinder 15 of the clutch is turned on. When winding is switched on, the left part of the valve 11 and the right part of the valve 20 are simultaneously switched. The oil from the accumulator runs towards the hydraulic cylinder 15 of the clutch, thereby activating it, while at the same time the oil cannot run through the right part of the valve 20. When winding is stopped, the valves 11 and 20 are switched to their starting positions as shown in figure 2. If one of the valves is blocked, the oil can freely run to the reservoir through the valve 11 or through the valve 20. In this way safety during work is not compromised as in older solutions, in which only one valve is used and if this valve is blocked, the winch pulls regardless of the winding function being terminated or not.

[0017] The key role in the system according to the invention has the pressure relief valve 5, which is simultaneously a relief and a safety valve. Because the system is designed so that it operates most of the time at a low pressure up to 20 bar, heating is lower and therefore the energy consumption is also lower. The hydraulic accumulator 9 stores enough energy for multiple release of the brake or the clutch in case of malfunction of the hydraulic system or the pump. A time delay for activation of the brake cylinder 14 can be set with the adjustable throttle 13. The flow regulator 16 ensures approximately constant rotation speed of the hydromotor 19 regardless of the load on it.

[0018] When winding-pulling is activated, two valves are simultaneously activated. If one of the valves is blocked after termination of the command, which is possible, this can potentially lead to an accident, as the winch continues to pull. Because the system has two valves 11 and 20, in case one of them malfunctions the other valve remains active, allowing execution of a command for interruption of pulling. Flow regulator 16 allows adjustment of desired revolution of the unwinding sheave or the motor 19, respectively, and therefore minimizes energy loss. The unwinding hydromotor 19 is not connected in parallel with the hydraulic cylinder of the brake 14, which allows the user to decide to release the load and the rope, wherein the rope may freely unwind to the end and the load may detach the rope from the empty drum. The characteristic that the brake may be released all the time in case an emergency situation occurs, is novel in the field of control of the hydraulic circuit of the clutch and the drum brake in a forestry winch.

[0019] If one of the valves 11 or 20 is stuck in the position for winding, one is always returned to the starting position after the function is terminated, so that the oil freely runs to the reservoir 1. This ensures double protection of rope pulling by the winch.

Claims

1. A hydraulic system with an additional protection of operation of clutch and drum brake hydraulic circuit in a forestry winch characterized in that it comprises an oil reservoir (1 ), a filter (2), a pump (3), a check valve (4), a pressure relief valve (5), a control valve (6), a check valve (7) with a throttle (8), a valve (11), a hydraulic accumulator (9), a check valve (12) with an adjustable throttle (13), a valve (17) with a throttle (18), a hydromotor (19), a brake cylinder (14) and a clutch cylinder (15).

2. The hydraulic system according to claim 1, characterized in that the pump (3) fills the accumulator (9) through the check valves (4 and 7) to a working pressure, which is set on the pressure relief valve (5); that when the oil in the hydraulic accumulator (9) reaches the set working pressure, the pressure relief valve (5) opens and remains in this position until the pressure in the hydraulic accumulator (9) drops under a specified value, which is preferably 10 to 15 bar; that the oil freely runs to the flow regulator (16) and the control valve (6), when the valve (5) is open; that because the smaller resistance is on the side of the valve (6), the oil runs through it into the oil reservoir (1); that when the user selects the function of rope unwinding, the right part of the valve (6) and the left part of the valve (11) are simultaneously switched; that the oil runs from the pump through the valve (6) to the flow regulator (16), the check valve (17) to the hydromotor (19), which drives the unwinding sheave, via which the rope from the winch drum is lead; that at the same time the oil from the hydraulic accumulator through the throttle (8), the valve (11) and the adjustable throttle (13) activates the brake cylinder (14) and consequently releases the drum brake, so that the drum starts to unwind due to the pulling force in the rope, caused by the hydromotor (19).

3. The hydraulic system according to claim 1, characterized in that when the function of rope winding is selected, the left part of the valve (11) opens and the oil runs from the hydraulic accumulator (9) through the throttle (8) and the valve (11) and activates the clutch cylinder (15).

4. The hydraulic system according to claim 2, characterized in that in case of a large load on the rope, when rope unwinding is selected and the brake is released, the hydromotor (19) operates as a pump, so that the oil runs from the reservoir (1) through the hydromotor (19), the throttle (18), the flow regulator (16), the valve (6) back to the reservoir (1); that the throttle (18) creates resistance, so that the sheave and the drum do not unwind too quickly due to dynamics.

5. The hydraulic system according to claim 2, characterized in that the throttle (18) is used to create resistance in the drive circuit of the hydromotor (19) in the case of winding the rope onto the drum; that the driven sheave in this case drives the hydromotor (19), which operates in the mode of a pump so that the oil runs form the reservoir (1) through the hydromotor (19) and through the throttle (18) and the regulator (16) back to the reservoir (1); that the larger the resistance of oil on the throttle (18) the larger the force of pretensioning between the sheave and the drum.

6. The hydraulic system according to any of the claims from 1 to 5, characterized in that 2/2 control valve (20) is connected in parallel with the hydraulic cylinder (15) of the clutch; that in case winding is switched on, the left part of the valve (11) and the right part of the valve (20) are simultaneously switched, the oil from the accumulator (9) runs towards the hydraulic cylinder (15) of the clutch, thereby activating it, while at the same time the oil cannot run through the right part of the valve (20); that when winding is terminated, the valves (11 and 20) are switched to their starting positions.

7. The hydraulic system according to any of the claims from 1 to 5, characterized in that the hydromotor (19) is not connected in parallel with the hydraulic cylinder (14) of the brake, which allows unwinding of the rope to the end.

8. The hydraulic system according to any of the claims from 1 to 6, characterized in that in case one of the valves (11 or 20) is stuck in the position for winding, one of them always returns to the starting position after the function is terminated, so that the oil freely runs to the reservoir (1).

Drawing