NO163892B - HYDRAULIC SYSTEM, PRINCIPLES FOR OPERATING WINDS. - Google Patents

Description

The invention relates to a hydraulic system, preferably for operating winches, as indicated in 1 of the introduction to patent claim 1.

From US-PS 26 65 081 it is known a device mounted on an electrically driven vehicle for winding on and unwinding of electric cables attached to a fixed point. The system is such that the electric cable is automatically wound on or off the drum, depending on whether the vehicle moves towards or from the attachment point for the electric cable. When using this hydraulic system for operating winches, a suspended load can be lifted from a fixed surface by starting the pump. However, a suspended load cannot be stopped without simultaneously stopping the pump. However, the pump will then be driven in the opposite direction as the motor and thereby drive the electric motor, diesel engine or similar in the opposite direction. The load will go down in an uncontrolled manner.

With this hydraulic system, the motor's torque is limited by a valve when the motor for winding the cable acts as a motor. The motor's torque is limited by a second valve when the wire winding motor acts as a pump. The hydraulic system is an open system. This means that the return oil flows back to the tank. The pump's filling pressure in the line will therefore be limited to the atmospheric pressure minus the loss due to flow resistance in the line. When the engine is operated as a pump, you get an unfavorable filling pressure in the engine, because the filling pressure is limited by the atmospheric pressure minus the pressure drop in the lines and in the valve. The lower filling pressure in the engine constitutes a strong limitation for the engine speed before cavitation.

The system is designed so that when the engine is operated as a pump, not only is the engine's oil quantity throttled through the valve, but also the oil quantity from the actual pump is throttled in the valve pump. When using the system for operating a winch, one would therefore get a disproportionately high heat development and an unnecessary power loss with regard to the operation of the pump.

From DE-AS 12 77 526, a hydraulic winch drive is known which consists of at least one pump, a motor for operating the winch drum and a manual control valve, the control valve serving to control the amount of liquid supplied to the motor from the pump. An adjustable proportion of the amount of liquid transported by the pump passes through a bypass line and outside the hydraulic motor. Furthermore, there is a switching valve for the transition from cargo to mooring operation, as for the automatic mooring operation an overflow valve is arranged between the pressure line and the engine's outlet line. This overflow valve can be set to an opening pressure that is below the maximum load. However, the overflow valve can only throttle small effects, as the purpose of the overflow valve is to be able to reduce the system's working pressure under very specific conditions.

The purpose of the present invention is to provide a hydraulic system, preferably for operating winches, with the possibility of winding and unwinding steel rope in one as well as in the other direction of rotation, with the possibility of braking the unwinding.

This is achieved according to the invention with a hydraulic system as stated in patent claim 1, with the special features stated in the characteristics.

With the invention, it is achieved in a simple way that the winch can be used for different conditions in different places on board a ship. Thus, a winch unwinding a steel rope can rotate in a certain direction, while another winch, of the same type, can rotate in the opposite direction when unwinding a steel rope. Thereby, the need for several winch types is avoided and major savings are achieved with regard to the storage of parts. Two identical winches can be used on board a trawler, one of which is placed on the starboard side, while the other is placed on the port side, for setting and retracting the trawl. The winches are set up symmetrically relative to the vessel's centreline. When setting and retracting, they rotate in opposite directions, preferably powered by one and the same pump. When setting the trawl, the winches are braked, so that the trawl ropes can be kept taut. The winch can thus act in one or the other direction of rotation as a hauling device and in the opposite direction of rotation act as a launching or unwinding device. At the same time, the hydraulic system is such that the braking effect, which each winch can exert, will be independent of the pump's capacity.

The hydraulic motor itself can act as a coupling, since the hydraulic motor is short-circuited by draining a pilot-controlled overflow valve with the help of a 2-way valve, so that the hydraulic motor can rotate almost without pressure, for example when the trawl under the tow should get stuck in the seabed.

The invention will be explained in more detail below with reference to the drawings, where fig. 1 shows the hydraulic system during setting - or inhaling, fig. 2 shows the hydraulic system during the setting of the trawl and Fig. 3 shows the hydraulic system during braking with maximum braking torque.

The pump 1, which is driven by an electric motor, a diesel engine or another power source, supplies oil to the hydraulic motor 2, which in turn drives the winch. A 4/3 valve 3 controls oil to and from the hydraulic motor 2.

The engine's 2 rpm is determined by means of a throttle regulation, as the amount of oil that is fed through the valve's 3 bypass channels can be continuously regulated from full pump delivery to zero. The motor's 2 dreleretnlng is rerouted by crossing the wires.

In the system there is a pressure reduction valve 4 which enables a controlled release when the operating lever of the valve 3 is brought to the extreme position "release". The pressure reduction valve slide will, when the maneuvering valve lever is in the stop position, be held in the open position by the pump's "circulation pressure" which will act against a relatively weak spring plus a pressure determined by the height difference of the expansion tank.

During lifting operation, the pressure reduction slide will likewise be kept open by the pump pressure so that return oil from engine 2 flows freely back to pump 1.

In case of four operation, the maneuvering slide will "gradually" reveal the maneuvering valve's return channel and throttle pressurized oil from the hydraulic motor 2, which is then driven by the load as a pump. The speed of the hydraulic motor is regulated in this way steplessly corresponding to an oil quantity from zero up to the actual pump's oil delivery. The part of the actual pump's oil delivery that flows through the maneuvering valve's bypass channel will also decrease accordingly.

If the valve's 3 maneuvering lever is moved to the extreme position, the maneuvering valve slide will reveal the maneuvering valve's return channel. The pressure will then propagate to the pressure reduction valve 4 and the lowest set pilot valve 8 on the overflow valve 6. The pressure reduction valve 4 will then throttle a quantity of oil from the hydraulic motor 2, corresponding to the oil supply of the actual pump 1, with a pressure drop in excess of what the load dictates. The slide in the pressure reduction valve 4 will "float" in a position determined by a spring force plus the actual pump's feed pressure determined by the oil level in the expansion tank 5, balancing with a desired and highly intended feed pressure for the hydraulic motor 2, on the actual pump's 1 delivery side . If the pressure in the pump's delivery line drops, the pressure reduction valve's output pressure, which is approximately constant and determined by the spring plus the expansion tank's oil level, will control the slide so that it throttles more. If the pressure in the pump's delivery line rises above the desired value, the pressure reduction valve will automatically throttle less, so that the pressure in the pump's delivery line drops again. The pressure reduction valve 4 will thus ensure that the hydraulic motor 1, when it functions as a pump at "full four", for example when shooting a trawl, receives sufficient feed pressure to prevent cavitation. Furthermore, the pressure reduction valve will prevent the actual pump 1, which can be of a structurally simple type with a fixed displacement and a delivery direction, from getting unwanted pressure on the return side. The pressure reduction valve is of known construction, but the application, which appears from the above, is special, as the actual pump's pressure will keep the pressure stop valve slide in the open position during lifting operation, while the pressure reduction valve's output pressure, determined by the relatively weak spring plus the expansion tank's oil level, will determine the actual pump's pressure and thus the hydraulic motor's feed pressure at "full four". The actual pump's feed pressure will thus under all conditions be determined by the height difference between the pump and the expansion tank's oil level.

As mentioned above, the pressure from the hydraulic motor 2 when the maneuvering valve lever is fully extended will propagate to the pilot valve 8. This pilot valve 8, which is set to a relatively low opening pressure, then controls the overflow valve 6, for example when launching a trawl. The hydraulic motor 2 will then act as a pump and brake the load with a torque determined by the relatively low set opening pressure of the pilot valve 8, and deliver an amount of oil equal to the sum of the actual pump's oil delivery, plus a variable amount of oil that flows over the overflow valve 6. The amount of oil that flows from the engine's pressure side to the suction side above the overflow valve 6, will be automatically varied in accordance with variations in the load, for example variations in the boat's speed and the boat's movements 1 rough weather when shooting a trawl. An increasing tendency in the load will cause the overflow valve to open more, alternatively a decreasing tendency in the load will result in the overflow valve opening less. The energy supplied during the braking period will thus, by throttling the pressure reduction valve 4 and the overflow valve 6, be converted into heat which is supplied to the system.

By moving the maneuvering valve lever, off, outer position which provides automatic control with. a r.e-latlvt low,tr. braking torque, towards the zero position, the maneuvering valve slide will increasingly cover the maneuvering valve's return channel. The pressure in the hydraulic motor 2' and thus the braking torque will then increase immediately, and the speed will decrease accordingly. As the throttling of the oil flow from the hydraulic motor is transferred from the pressure reduction valve 4 to the maneuvering valve's return channel, the pilot valve 8 will "lose" the opening pressure. If the maneuvering valve slide throttles so much that the pressure increases to the set opening pressure of the pilot valve 7, the overflow valve 6 will open and the hydraulic motor will then brake with full braking torque. By placing the maneuvering valve lever in the stop position, the hydraulic motor speed will decrease towards zero, except for the motor's internal leakage.

The system used on a trawl winch can be used as an example. When the firing period has ended, the boat's speed is reduced, while the maneuvering valve lever is moved from the outer position, which provides automatic control with relatively low wire tension, to the stop position. The maneuvering valve lever in the stop position involves automatic control with a relatively high wire tension, and the wire speed will decrease towards zero, determined by the speed of the boat.

By draining the overflow valve 6 using a two-way valve 9, the hydraulic motor will be short-circuited. The hydraulic motor can thereby act as a coupling.

When "towing" the trawl, only the mechanical brakes should "hold" the drums. If the trawl gets stuck on the bottom, the brake must slip. By short-circuiting the hydraulic motor 2, this will be able to act as a coupling and rotate almost without pressure.

Claims (2)

1. Hydraulic system, preferably for the operation of winches based on the principle of a pump (1) supplying oil to a hydraulic motor (2), where the speed and direction of rotation of the hydraulic motor are determined by a four-way valve (3) with a non-return valve and equipped with a maneuver lever and with an "open center" of known construction, characterized in that a pressure reduction valve (4) connected in series with the pump provides controlled loading of the load in both four directions when the maneuver valve lever is held in the respective extreme position, the pressure reduction valve being controlled by the pressure in the engine's (2 ) inlet, pressure oil from the hydraulic motor (2) is throttled which then acts as a pump and brake with a pressure drop large enough to give the motor sufficient feed pressure, as the actual pump (1) acts as a feed pump for the hydraulic motor (2) and prevents that the actual pump (1) gets unwanted pressure on the return side and so that an amount of oil corresponding to the actual pump's oil delivery is choked and the energy thus converted into heat which is supplied to the hydraulic system, and that a pressure limiting valve (6) placed between the four-way valve and the engine and connected in parallel with this will open at two different, preferably adjustable opening pressures, determined by the position of the maneuvering valve lever and by two pilot valves (7, 8), so that the braking torque of the hydraulic motor can be regulated steplessly from the maximum set braking torque to the minimum set braking torque by moving the maneuvering valve lever from the stop position to the extreme position and that the system with the maneuvering valve in the extreme position provides automatic control with a desired, relatively low braking torque for example when shooting a trawl, determined by the pilot valve (8), and that the system with the maneuvering valve lever in the stop or lift position provides automatic control of the maximum braking torque determined by the pilot valve (7) during final braking. 2. Hydraulic system as specified in claim 1, characterized in that the hydraulic motor (2) itself functions as a coupling, as the hydraulic motor is short-circuited, e.g. by means of a two-way valve (9) by draining the pilot-controlled pressure limiting valve (6), whereby the hydraulic motor will be able to rotate almost without pressure.