Marine steering control valve and system

Abstract

The subject invention is directed to a hydraulic control valve for use between a reversible pump and a rudder operating cylinder in a marine steering system. The valve assembly includes a valve body with first and second fluid passages extending through the body from first and second inlets to first and second outlets. First and second check valves are disposed at the outlets for checking reverse fluid flow through the outlets toward the inlets. Means are included in the body for unseating either of the check valves in response to an increase in pressure in the passage in which the other check valve is disposed. A fluid return passage network is included in the body for connection to a fluid reservoir and intercommunicates the first and second passages. First and second shuttle valves are slidably mounted in the body and are spring biased to an operative position for controlling the fluid flow through the passages.

Description

The invention relates to hydraulic control valves for use in marine steering systems and in particular to an improvement in the valve described in U.S. Pat. No. 3,576,192 of which the present applicant is the assignee.

The valve described in the above mentioned United States patent is intended for use between a reversible pump and a rudder operating cylinder in a marine steering system. It provides advantages over arrangements which had previously been used particularly in preventing malfunctioning due to the presence of dirt in the system and also in facilitating the purging of the system of air. Where this valve has been installed in a simple hydraulic steering system having a single reversible pump and rudder operating cylinder with the valve interconnected therebetween, satisfactory operation has been achieved. However, it has been found that under certain conditions unsatisfactory operation can result in systems where steering control is effected from more than one position in the vessel. In such systems, a number of control valves are connected in parallel to a single rudder operating cylinder. It is among the objects of the present invention to provide an improvement in the valve to overcome such unsatisfactory operation.

The invention therefore provides a hydraulic control valve for interposition between a reversible pump and a rudder operating cylinder in a marine steering system, said valve comprising a valve body, first and second fluid pressure passages extending through said body respectively from first and second inlets, for connection to opposite sides of the reversible pump, to first and second outlets for connection to opposite ends of said rudder operating cylinder, first and second check valves respectively at said first and second outlets for checking reverse fluid flow through said outlets towards said inlets, means mounted in said body for unseating the check valve at the outlet to either one of said first and second fluid pressure passages in response to a relative increase in pressure in the other passage, a fluid return passage network in said body having a return outlet for connection to a fluid reservoir, said network further including intercommunicating first and second return passages which respectively communicate with said first and second fluid pressure passages and first and second shuttle valves each slidably mounted in said body and spring biased from an operative position in which the respective fluid pressure passage is open and the fluid return passage is closed, towards an inoperative position in which the respective fluid pressure passages close and the fluid return passage communicates with the return outlet and the other fluid return passage, whereby the pressures in the fluid pressure passages are equalized when the shuttle valves are in their inoperative positions and the unseating means thereby rendered inoperable.

The invention will now be further described with reference to the accompanying drawings in which:

FIG. 1 is a semi-diagrammatic representation of a steering system incorporating two control valves according to U.S. Pat. No. 3,576,192 and,

FIG. 2 is a similar representation, but including valves according to the present invention,

FIG. 1 illustrates the unsatisfactory operating condition which can arise with the valve of the above-mentioned United States patent when used in tandem to control the rudder operating cylinder. Reference may be had to the United States patent referred to for a full description of the valve and its operation. The following description is intended to be merely sufficient for the purpose of the present explanation.

The system shown in FIG. 1 comprises a rudder operating cylinder 1 in which a piston 2 is movable in one of two directions R1 and R2 indicated by arrows. Inlets 3 and 4 are provided at the ends of the cylinder 1. The inlet 3 is connected by two pipe connections 5 and 6 to one inlet of each of a pair of hydraulic control valves 7 and 8. The inlet 4 is similarly connected by means of pipe connections 9 and 10 to the other outlets of the two valves 7 and 8.

Each of the two valves 7 and 8 is identical and one only will be described. The same reference numerals are given to corresponding parts in each valve.

Each valve consists of a body 11 in which a pair of parallel bores 12 and 13 are provided. The bore 12 is plugged at its end by a pair of screwthreaded plugs 14 each having an inwardly extending spigot 15. Inlets 16 and 17 enter the bore 12 adjacent its ends for connection to opposite sides, represented by the references P1 and P2, of a reversible pump. A return outlet 18 extends from the bore 12 at a central position for connection to a reservoir represented by the reference T1.

The reversible pump may be of any suitable type, for example a swash plate pump, and may be directly connected to a hand operated steering wheel so that reversible of direction of rotation of the wheel reverses the direction in which the pump discharges. The pump will normally draw fluid from the reservoir. Since the connections to the second valve will be from and to a different pump and reservoir these are represented by the references P3, P4 and T2 respectively.

The bores 12 and 13 are interconnected by a pair of fluid pressure passages 19 and 20 having offset sections 21 and 22 respectively entering the bore 12. Fluid return passages 23 and 24 each communicate at one end with the passages 19 and 20 respectively and at the other end enter the bore 12 between the entry points of the offset portions 21 and 22.

The bore 13 communicates at its ends with outlet 25 and 26 through spring loaded ball check valves 27 and 28 respectively. 28 respectively. A spool 29 having axially extending spigots 30 and 31 is slidable in the bore 13 so as to unseat either of the balls of the check valves 27 and 28 depending on the direction of movement.

Within the bore 12, a shuttle valve is provided comprising a pair of cylindrical valve members 32 and 33 connected by a rod 34. It will be seen from the drawing that the valve member can be moved so as to close either of the fluid pressure passage portions 21 or 22, the arrangement being such that when either of these passages is closed the corresponding fluid return passage 23 or 24 is open.

In operating the steering system shown in FIG. 1, if it is desired to move the piston 2 to the right as shown in the drawing by means of the left hand valve, the pump is operated in a direction to pump fluid through the inlet 16. The fluid moves the valve member in the bore 12 to the right into the position shown in broken lines. In this position, the passages 22 and 23 are closed whilst the passages 21 and 24 are open. The fluid then passes along the passages 21 and 19 and then lifts the ball of the ball valve 27 to pass through the outlet 25 and pipe 5 to the inlet 3 of the cylinder 1. At the same time, the pressure in the passage 19 moves the spool 29 to the right so as to unseat the ball of the ball valve 28. As the piston 2 moves to the right, fluid can then pass from the inlet 4 of the cylinder 1, through the pipe 9 and outlet 26 of the valve. From the valve 28, the fluid then passes directly through the passages 20 and 24 and thence via the return outlet 18 to the reservoir. To reverse the direction of movement of the piston 2, the pump is merely operated in the opposite direction. The valve member in the bore 12 and the spool 29 then moves leftwardly as shown in the drawing to reverse the operating condition of the valve.

Where the cylinder 1 is to be operated by a single control valve and pump, the valve of the kind shown in FIG. 1 will operate satisfactorily. However, in a tandem installation (i.e. where two or more valves are connected in parallel to the cylinder, a failure in operation can arise under certain conditions. Thus, if it is assumed that the left hand valve in the drawing has been operated so that the valve member and spool has been moved to the right in their respective bores as shown in broken lines, and left in this position, it will be seen that a clear passage will exist from the inlet 4 of the cylinder to the reservoir T1. With the lefthand valve in this position, if fluid is introduced from the pump outlet P4 and through the inlet 17 of the right hand valve, it will pass through the valve, out through the outlet 26 thereof and then through the pipe connection 9 to the reservoir of the first valve. Thus no pressure will be generated through the inlet 4 of the cylinder and the piston 2 will not move. Thus, it will be seen that with any one valve in a tandem system in an unbalanced condition, steering control cannot be effected through other valves of the same system.

Turning now to FIG. 2, this shows the modification proposed by the present invention in order to overcome the above described disadvantage. The valves shown in FIG. 2 are identical in all respects with those shown in FIG. 1 except for the form of the valve assembly which is slidable in the bore 12. In the valves of FIG. 2, this valve assembly comprises two cylindrical valve members 40 and 41 having spigots 42 and 43 extending axially therefrom towards the other valve member. In addition, a coil spring 44 is located between the valve members 40 and 41 and biases them apart.

With the modification above described, when pumping has ceased through the inlet 16, the spring 44 drives the valve member 40 leftwardly as shown in the drawing so that the passages 23 and 24 are brought into direct communication. This equalizes the pressure on both sides of the spool 29 so that the spool ceases to unseat the ball of the check valve 28. Under these conditions, fluid cannot flow from any of the other valves through the pipe connection 9 into the reservoir T1. Thus the other valves can function effectively to operate the cylinder 1.

A further disadvantage can also arise with the valves of the kind shown in FIG. 1 whether the valve is used singly or in tandem. When the rudder is in the hard over position, the valve which has been operated to bring it to that position will have its valve member and spool 29 in the offset positions shown in broken lines in FIG. 1. In this condition the action of the water on the rudder will cause the fluid in the cylinder 1 to firmly press the ball of the check valve 27 against its seat. If the helmsman now turns the wheel to straighten the rudder, fluid moves down the passages 22 and 20 and then through the check valve 28 and outlet 26 to the inlet 4 of the cylinder. The increased pressure in the passage 20 also moves the spool 29 to the left until the spigot 30 abuts the ball of the check valve 27.

The pressure in the passage 20 gradually increases and ultimately lifts the ball of the check valve 27 from its seat in a sudden movement. Oil under pressure then passes quickly from the pipe connection 5 into the chamber 19. This in turn causes a sharp drop in pressure on the other side of the piston 2 in the cylinder and thus in the passage 20. The spool 29 immediately flies to the right and the valve 27 closes rapidly. Continued movement of the wheel by the helmsman causes the above described sequence to repeat at very short intervals giving rise to a pronounced chatter in the system.

Turning now to FIG. 2, in order to overcome this second disadvantage, a constriction has been provided at 45 in the bore 13 where indicated so as to leave a small clearance with the spigot 30. The clearance between the constriction 45 and spigot 30 is sufficient to permit the passage of fluid during normal operation of the valve but insufficient to permit the rapid fluid movement which arises during the chattering action described above. The body of fluid between the constriction 45 and the spool 29 thus acts to dampen the movement of the spool.

Claims

What I claim is:

1. A hydraulic control valve assembly comprising; a valve body having first and second inlets and first and second outlets, said valve body having first fluid passage means extending between said first inlet and said first outlet and second fluid passage means extending between said second inlet and said second outlet, said valve body having a return outlet and fluid return passage means extending between said first and second fluid passage means and said return outlet, first check valve means in said first fluid passage means adjacent said first outlet and having a seated position for checking reverse fluid flow through said first fluid passage means toward said first inlet and movable to an unseated position for allowing fluid flow therepast, second check valve means in said second fluid passage means adjacent said second outlet and having a seated position for checking reverse fluid flow through said second fluid passage means toward said second outlet and movable to an unseated position for allowing fluid flow therepast, unseating means in said valve body for unseating each of said respective said check valves in response to a predetermined pressure in the fluid passage means in which the other check valve is disposed, first shuttle valve means disposed in said valve body and movable between an operative position in response to fluid pressure from said first inlet opening for establishing a first fluid communication between said first inlet and said first fluid passage means and an inoperative position for blocking said first fluid communication and establishing a second fluid communication between said first passage means and said return outlet, second shuttle valve means disposed in said valve body and movable between an operative position in response to fluid pressure from said second inlet for establishing a third fluid communication between said second inlet and said second fluid passage means and an inoperative position for blocking said third fluid communication and establishing a fourth fluid communication between said second passage means and said return outlet, and biasing means urging said first and second shuttle valve means toward said inoperative positions to move each of said shuttle valve means to said inoperative positions when said pressure from said inlets is less than said opening pressure to equalize the fluid pressures in said first and second fluid passage means for moving said unseating means to an inoperative position where both of said check valve means are in their respective seated positions.

2. An assembly as set forth in claim 1 including a constriction in said valve body between said unseating means and at least one of said fluid passage means for dampening movement of said unseating means.

3. An assembly as set forth in claim 2 wherein said valve body includes a spool bore extending between said first and second fluid passage means and between said check valve means, said unseating means comprises a spool slidable in said spool bore, and a spigot extending axially from each and of said spool for unseating said respective check valve means upon movement of said spool in response to said predetermined pressure at the other end of said spool.

4. An assembly as set forth in claim 3 wherein said constriction is disposed in said spool bore and surrounds one of said spigots extending from said spool.

5. An assembly as set forth in claim 1 wherein said biasing means is disposed to react between said first and second shuttle valve means.

6. An assembly as set forth in claim 5 wherein said valve body includes a valve bore, said first and second valve means being slidably disposed in said bore, said first and second fluid passage means extending through said bore and said fluid return passage means extending through said bore.

7. An assembly as set forth in claim 6 wherein said biasing means comprises a coil spring disposed in said bore between first and second shuttle valve means.

8. An assembly as set forth in claim 7 wherein said first and second shuttle valve means each comprise a body having a spigot extending therefrom towards the body of the other valve means for maintaining a minimum spacing between said bodies.

9. An assembly as set forth in claim 8 wherein said coil spring engages said bodies and is disposed about said spigots.

10. An assembly as set forth in claim 9 including a constriction in said valve body between said unseating means and at least one of said fluid passage means for dampening movement of said unseating means.