GB2024331A - Hydraulic control valve for a winch - Google Patents

Abstract

An hydraulic control valve arrangement for coupling to pressure and return lines for an hydraulic winch motor 51 which controls a load 52 through a drum 50, comprises a brake slide 41, an anticavitation valve 33 and a combined safety and mooring valve 49, all combined in a unitary construction. The valve controls lifting and lowering of the load in both directions of rotation of the winch drum. <IMAGE>

Description

SPECIFICATION Hydraulic control valve arrangement The present invention pertains to a hydraulic control valve, for a hydraulic winch or the like, which can perform the following functions: control the lowering speed, when a hydraulic motor, owing to the effects of the load, is driven as a pump; ensure the refilling of the hydraulic motor as the load is being decelerated during lowering; relieve fluid pressure shock; and maintain a selected pulling force during mooring (hauling) by means of a preset mooring-fluid pressure.

The common practice up to now has been that these functions are performed by several separate valves, and the collective valve system has thus been complicated and relatively expensive to produce and to install. This in turn has meant that during control and maintenance, the work involved in demounting and re-installing the valves has been especially time-consuming.

With the present invention, the above-specified valve functions are performed by one valve unit.

Some types of winches, e.g., a winch for pivoting a derrick or crane arm, must be capable of lowering a load in both directions of rotation; in such cases, it will be necessary to provide two valve units. Such an embodiment is illustrated on the accompanying drawings.

The valve arrangement of the invention is illustrated schematically in the figures, where Figure 1 shows how the valve unit functions when a load is being lowered, the hydraulic motor, owing to the effect of the load, then operating as a pump, Figure 2 shows how the valve unit functions in decelerating a load during a lowering operation, where the hydraulic motor must obtain the necessary refilling from the return side to prevent cavitation, Figure 3 shows how the valve unit functions in response to a pressure shock, which can occur if the hydraulic motor becomes overloaded when the manoeuvering valve is set on stop, for example, on a hauling winch, or during a sudden stop of the load, and Figure 4 shows how the valve unit functions when the hydraulic motor is to maintain a constant tension in a cable, for example, when operating a mooring winch.

A detailed description of the valve's construction and method of operation will be given in the following.

Figure 1 shows an example of a valve embodiment for use in a hydraulic winch installation. The system illustrated on the drawing is an open system, having a pump 10 which delivers a constant pressure which is maintained by the valve 1 liThe system can also operate with no load on the pump, the hydraulic motor being set on stop, if the manoevering valve 20 is adapted accordingly. A closed system could also be utilized.

The valve units 30 and 40 are of the same embodiment; the symmetrical construction shown here is necessary when the hydraulic motor 50 is supposed to be capable of lifting and lowering a load in both directions of rotation. The description given below of the valve unit 40 thus also applies for the valve unit 30.

The hydraulic motor 50 is coupled to a winch drum 51 which is affected by a load 52. The valve unit 40 comprises a slide 41 which is affected by a spring 45. With a build-up of pressure in the chamber40f, the slide will be pressed against the spring 45.

The filling valve 43, which is position in the chamber 40i, is held against the seat by the spring 44. If the pressure in port 40e becomes lower than the pressure in port 40b, the filling valve 43 will open. The check valve 46 prevents a back-flow from the hydraulic motor if the direction of rotation for lifting a load is the opposite of that shown on Figure 1.

The throttle valve 47 regulates inflow and outflow to the chamber 40f and thus damps the movement of the slide 41 when it is regulating the backflow from the hydraulic motor 50, between the ports 40e and 40b, during a lowering operation. To prevent an undesirable increase in pressure in the chamber40f, from ports 40a and 40e, caused by a leak over the slide land nearest the chamber 40f, this slide land is provided with a groove 42 which via channel 48 and port40c communicates with the return side. The pressure-limiting valve 49 is a combined safety valve and mooring valve. This valve, together with the throttle valve 47 and the check valve 46, are built into the valve body, together with the associated port connections.

The operation of the valve unit during the respective manoevering situations will be described in detail below.

Figure 1 shows a lowering of the load 52 when the hydraulic motor 50 has been supplied with the maximum amount of fluid by setting the manoevering valve 20 at the max. lowering position. Fluid then flows from the pump 10 through the manoevering valve 20, and further through the check valve 36 to port 30a, around the spool portion on the slide 31 to port 30e, and further to the port on the hydraulic motor 50 which during lifting is its discharge port.

This presupposes that the weight of the load 52 is of such magnitude that it will drive the hydraulic motor 50 as a pump. Fluid flows from the hydraulic motor 50 to the valve unit 40, through port 40e, around the spool portion on the slide 41 and is choked between the slide land 40j and port 40b.

From there, the fluid flows to the reservoir 12.

This throttling of the fluid flow between the slide land 40j and port 40b is adapted to control and provide an even lowering speed for the load 52. This is obtained in that the throttle valve 47 is adjusted such that the slide 41 obtains a damped movement.

The slide 41 is held in axial balance because the pressure in the chamber 40f, which affects the end surface on the slide, is balanced against the spring 45. If the load 52 tends toward a greater lowering speed than that which corresponds to the amount of oil supplied to the hydraulic motor 50, the fluid pres sure in ports 30e and 30a will decrease. The fluid pressure will then also sink in the line 30k and in the chamber 40f. This makes the spring 45, which has a certain tension, push the slide 41 nearer the chamber 40f. The slide land 40j will then assume a position whereby it restricts the outflow opening to port 40b, reducing the amount of outflow, with the result that the number of revolutions on the hydraulic motor 50 will be reduced.As a result of this, the fluid pressure will increase in the hydraulic motor's supply line and in ports 30e and 30a. This increase in pressure propagates further through the line 30k to the chamber 40f. The slide 41 will stop its movement toward the chamber40f. If the lowering speed for the load 52 tends to be too low, there will be a further increase of the pressure in chamber 40f, and the slide 41 will move in the opposite direction, toward the spring 45, and the lowering speed will increase.

In other fords, the slide 41 will assume a balanced position which ensures an even lowering speed even at maximum loading, and prevents cavitation in the supply line for the hydraulic motor by ensuring that a certain pressure is always maintained therein, such that the number of revolutions in the hydraulic motor corresponds to the amount of oil supplied when the load is being lowered.

Figure 2 shows the situation that arises when the load 52 is decelerated during lowering, i.e., just before the load is stopped. The slide 41 has in this situation the same function as in Figure 1. The sliding spool in the manoevering valve 20 is on Figure 2 shown near the center position, where flow to the check valve 36 is greatly reduced. As the hydraulic motor 50 must be ensured a supply of fluid while the shaft rotates, the supply will therefore be taken from port 30b, which communicates with port 40b and the reservoir 12. The check valve 33 will open, such that cavitation in the hydraulic motor's working chambers and supply line is prevented. Cavitation can lead to an uncontrolled lowering of the load, and to noise and knocking in the hydraulic motor and drive gears.

Figure 3 shows an overload situation, which can occur, for example, on a winch hauling a load in heavy seas, or with a sudden stop of the load. The manoevering valve 20 is set in the stop-position such that the supply of fluid to the check valve 36, and thus to the hydraulic motor 50, is cut off. The increased loading, via the drum 51, will cause an increased torque on the hydraulic motor 50, which thereby operates as a pump. The fluid pressure will rise in ports 40e and 40a, and the check valve 46 will close. The increase in pressure in port40e will propagate to the pressure-limiting valve 49. If the preset pressure level is exceeded, an inflow and an increase in pressure in chamber 40f will occur. The slide 41 presses against the spring 45 and moves closer until the slide land 40j begins to uncover the port 40b.A flow from port 40e to port 40b will then occur, with the resultthatthe pressure in port 40e will be reduced. The drum 51 will begin to rotate and pay out cable until the pressure in port 40e has been reduced below the pressure to which valve 49 is set and the inflow into chamber 40f is blocked. When such an outflow from port 40e to port 40b takes place, the hydraulic motor must be refilled in the same way as described above in connection with Figure 2.

Figure 4 shows the operation of the valve unit dur ing mooring, i.e., when the tension in the cable is to be held constant, with a consequent hauling in or paying out of cable in response to a decrease or increase in the force affecting the cable, for example, in the operation of a mooring winch. The sliding spool in the manoevering valve 20 is put in a position which provides a suitable speed for hauling in cable.

The pressure-limiting valve 49 is set to a suitable mooring pressure, depending on the pullling power which is desired on the winch. The pressure fluid from the pump 10 flows through the manoevering valve 20, check valve 46 and through port 40a, and further over the spool portion on the slide 41 to port 40e and to the intake side of the hydraulic motor 50.

The fluid pressure in port 40e also affects the pressure-limiting valve 49.

When the fluid pressure in port 40e exceeds the preset fluid pressure on valve 49, an inflow into chamber 40f will occur. As an outflow also takes place from this chamber through the throttle valve 47, which has a fixed, set choke aperture, an increased throughflow in the valve 49 will produce an increase of pressure in the chamber 40f.

The slide 41 presses against the spring 45 and moves, depending on the pressure in chamber40f, until the slide land 40j begins to uncover port 40b A flow from port 40e to port 40b will then take place. In other words, if the valve 49 is set for a small throughflow (high mooring pressure), the fluid pressure in chamber 40f will be low and the spring 45 will not be compressed to a great degree. The slide land 40j will therefore uncover only a little part of port 40b, and the fluid pressure in port 40e and the torque on the hydraulic motor 50 can be held near maximum.

If the valve 49 is set for a large throughflow (low mooring pressure), the fluid pressure will rise in chamber 40f and the spring 45 will be compressed so much that a large part of port 40b will be uncovered. The fluid pressure will then decrease in port 40e and produce a reduced torque on the hydraulic motor 50.

If tension in the cable increases, such that the fluid pressure in port 40e increases above the preset fluid pressure for valve 49, the drum 51 will pay out cable and the hydraulic motor 50 will operate as 8 pump.

An outflow from port 40e into port 40b will then occur. The hydraulic motor 50 will be refilled through ports 30b and 30e.

If the tension in the cable is reduced, such that the fluid pressure in port40e is higher than the fluid pressure which the tension in the cable dictates, the drum 51 will pull in cable. The cable, in other words, will be pulled in or payer out until a balance between the tension in the cable and the preset fluid pressure on the valve 49 has been obtained.

Claims (3)

1. A hydraulic control valve arrangement which is coupled to pressure and return lines for the drive medium for a hydraulic motor which is affected by a load via a drum, characterized in that the control valve is constructed as a composite unit containing a brake slide (slide 41) for lowering of a load, an anticavitation valve (filling valve 33) to prevent cavitation in the event of a sudden deceleration of the load, and a combined safety valve and mooring valve (pressure-limiting valve 49) to counteract overloading resulting from a sudden stop of the load and during automatic mooring.

2. A valve arrangement according to claim 1, characterized in that on the slide land in that end of the regulating slide which is affected by fluid pressure, a groove is provided in the periphery of the side land (42) with communication to the return side through bores (48 and 40c) to prevent an undesired increase of pressure in the chamber (40f) which affects the end of the slide, in the event of a leak over the slide land as a result of pressure build-up on the spool portion of the slide.

3. An hydraulic control valve arrangement substantially as described with reference to the accompanying drawings.