US2991748A - Ship stabilizers - Google Patents

Description

July 11, 1961 F. H.Mu1Rl-1EAD ErAL 2,991,748

SHIP STABILIZERS Filed Dec. l?, 1959 4 Sheets-Sheet 1 July 11, 1961 F. H. MUIRHEAD ETAL 2,991,748

SHIP STABILIZERS Filed Dec. 17, 1959 4 Sheets-Sheet 2 JUIY 11, 1951 F. H. MUERE-[EAD ErAL 2,991,748

SHIP STABILIZERS Filed Dec. l?, 1959 4 Sheets-Sheet 3 atb-.Gid-

` B Figb KM C July Il, 1961 F. H. Mum-EAD ETAL 2,99L748 SHIP smBmzERs FiiO.

Filed Dec. l?, 1959 4 Sheets-Sheet 4 ,saws

Patented .Iuly 11, 1961 hice 2,991,748 SHIP STABILIZERS Francis Heron Muirhead, .lohnBell, and .lohn Victor Foll, Beckenham, England, assignors to Muirhead &

Co. Limited, Beckenham, England Filed Dec. 17, 1959, Ser. No. 860,187 Claims priority, application Great Britain Aug. 4, 1959 2 Claims. (Cl. 114-126) This invention relates to ship stabilizers of the kind in which ns or hydrofoils projecting from the hull of a ship below the water-line are tilted or oscillated to react with the water when the ship is in forward motion in such a way as to produce a torque which continuously opposes the torque due to sea force causing the ship to roll.

The present invention particularly relates to a ship stabilizer system of the kind comprising a plurality of small ins attached to the ship in the region of the bilge, each iin being provided with an integral actuating means, the motion of said actuating means being governed by a common roll-sensing means.

A feature of the invention is the use, in the construe` tion of the fins, of various moulding techniques and materials.

In one construction the fin mounting member, which may be a shaft adapted to rotate in a bearing or, alternatively, a bearing part adapted to rotate round a xed shaft, is extended laterally to form a skeleton or framework for supporting the n. The iin itself is made from an elastomer, for instance, rubber, polyvinyl chloride or similar substance moulded around and in intimate contact with the supporting framework. The framework is deliberately kept to a minimum size both in chord length and outreach with the object of making the iin resilient against overload forces such as may be encountered if the ship is proceeding in Water such as harbours and estuaries which may be fouled by floating or submerged objects or should the ship make contact with the ground or a river bank or with another ship. Under the normal forces of fin lift and drag imposed on the iin due to passage through the water, its shape is not signicantly altered, but under direct impact it yields to the force of the impact and so reduces the risk of damage.

The fin shaft or, alternatively, the shaft on which the n is adapted to rotate, may be constructed with a section of reduced diameter to act as a safety device by limiting the force that may be imposed on the ship in the event of impact of a fin or fins with a solid object by permitting the iin or ns to break off.

In a still further construction a iin may be moulded to the correct form around a metal center or insert in hard-setting materials such as fibreglass and nylon. In iin construction and the hydraulic actuators co-operating therewith all metal parts coming in contact with the sea water may be fabricated from non-corrodible metal, for instance, stainless steel, bronze and Monel metal. Bearing surfaces and particularly those employing water lubrication may alternatively be made of Tufnol (Registered Trade Mark), nylon, polyetetrailuoroethylene or similar materials. In small equipments the tins may be contructed of Wood.

Another feature of the invention is the adoption of a rotary hydraulic jack or vane motor as the n actuating means. This device is cheap to manufacture, takes up little space and is easily integrated into the iin construction.

A further feature is a locking device to hold the lin in a neutral position with respect to the water ow when not required for active stabilizing. For this purpose the fin is pivoted forward of its center of pressure so that when not -controlled by the actuating means it will automatically assume the neutral position. However, to maintain the iin in neutral position when the ship is stationary a` springaloaded and hydraulically operated bolt coi-operating with a catch or detent is provided. When the stabilizer' is in operation the bolt is withdrawn from the catch by hydraulic pressure opposing the spring pressure. But when the stabilizer is stopped the hydraulic pressure is released and the spring urges the bolt in the direction of the catch. As soon as the Water How aligns the iin in the neutral position the bolt enters the catch and the lin is locked against further movement. The fins then func# tion as a bilge keel giving passive roll damping.

The invention also consists in a stabilizing arrangement for ships comprising a set of fins on each side of the ship in which the proportional control of the stabilizing force is effected by operating the tins sequentially to their maximum angle of tilt.

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

FIGURE 1a is a side elevation and Y FIGURE lb is a cross-section of a flexible n construction.

FIGURE 2a is a longitudinal section and FIGURE 2b a cross section on the line A-A of FIGURE 2a and FIGURE 3a is a plan in partial section.

FIGURE 3b is an elevation and FIGURE 3c a section on the line B-B of FIGURE 3b of a hydraulic control device.

FIGURE 4 shows diagrammatically a ship stabilizer system employing hydraulic actuating means with oil as the hydraulic liuid.

FIGURE 5 is a diagrammatic plan view of the ships hull showing its relationship to part of FIGURE 4 in one arrangement.

FIGURE 6a is a graph showing the operation of the arrangement of FIGURE 5 for light rolling, and

FIGURE 6b is a similar graph for heavy rolling.

FIGURE 7 is a ship stabilizer system similar to that .slhown in FIGURE 4 but using sea water as the hydraulic uid.

FIGURE 8 shows a modification of part of FIGURE 4.

FIGURE 9` is a frontal view of an alternative oam actuated by the device sensitive to rolling of the ship, and

FIGURE l0 shows diagrammatically the operation of a hydraulic relay system connecting the ns with the cam.

FIGURE 11 is a diagrammatic showing of a six n stabilizer corresponding to FIGURE 5 but activated by the alternative means of FIGURE 9.

In FIGURE la the iin shaft 1 bearing 1in 2 is rigidly att-ached to the ship structure 3 by flanges 4. Hydraulic actuating means which may be of the rotary jack or vane motor kind is located within the annulus 5a between lin shaft 1 and tin sleeve 5. Fin sleeve 5 terminates about half-way along the rotational axis of the fin 2 and is formed with lugs 6 and 7 conforming to the streamline section ot the iin. rIhe fm proper is moulded from suitable plastic material such as vulcanised rubber or polyvinyl-chloride to the correct fm contours and completely surrounds the outboard end of the fin sleeve and the lugs 6 and 7. It will be seen from the construction that the inner part of fin 2 is given the support of iin sleeve 5 and lugs 6 and 7 whereas the outer part of the fin between x and x is not reinforced. This outer part, however, is suf'liciently rigid to withstand the normal forces of lift and drag but it will yield to abnormal forces due to contact Iwith floating objects or grounding.

A hydraulic jack or rotary vane motor according to the invention is shown in FIGURES 2a and 2b. Shafft 8` which also forms the stator element of the rotary vane motor is attached to ship structure 3. Part 9 is rotatably mounted on shaft 8 and forms the rotor of the vane motor and also supports iin 2. By means of annular ring 10 screwed to shoulder 11 on the stator part 8 and annular ring 12 abutting shoulder 13 on the stator part 3 and bolted to it, and `also abutting a shoulder on part 9 an annular space or chamber 14 is 'formed between the stator and the rotor. This chamber is sealed by O-rings 15 and 16. Annular rings 10 and 12 abut adjacent shoulders on the inside surface of rotor part 9 as shown in the drawing thereby providing a positive location of rotor part 9 on stator part 8. Vanes or lands 17 and 18 attached to rotor part 9 and corresponding vanes or lands 19 and 20 attached to stator part 8 divide chamber 14 in four compartments a, a1, b, b1. Compartments aand a1 are connected to the hydraulic pressure source over channel 21 and channel 22 while compartments b and b1 are connected to exhaust over channel 23 and channel 24. It will be appreciated that when pressure oil is admitted to chambers a and a1, these chambers will expand by forcing vanes 17 and 18 to rotate in a clockwise direction as viewed in FIGURE 2b until arrested by `resilient stops 25. At the same time, oil contained in chambers b and b1 which are contracting is exhausted over channels 23 and 24. It is eas-ily seen that when oil is admitted to chambers b and b1 the reverse sequence of events takes place. Resilient stops 25 and 26 comprise coil springs of wire or strip material such that by slight deformation of their cylindrical form, they absorb the shock of impact at the end of travel of the moving vanes.

The iin locking device comprises piston 27 operating in cylinder 28. Spring 29 in the lower portion of cylinder 28 urges piston 27 and bolt 30 attached thereto into engagement with slot 31 in rotor part 9 indicated by broken lines -thereby securely locking the n. rPhe travel of the bolt is limited by perforated collar 32 coming up against shoulder 33 in stator part 8. Application of pressure oil to the top side of piston 27 over channel 23a forces bolt 30 out of engagement against the pressure of spring 29 and so releases the iin for rotary motion. Extension 34 of piston 27 limirts the travel of the bolt in the downwards or outwards direction.

FIGURES 3a, 3b and 3c show a hydraulic valve unit embodying a plurality of Valves of the piston type adapted for Iiin operation. The cylinder block 35 in which a number of cylinders 36 are bored comprises a solid block of metal. Ports 37 in cylinders 36 are connected over pipe lines lto hydraulic actuators in their respective ns as shown in FIGURE 4. High pressure oil is supplied over duct 38 to ports 39 in each cylinder. The tops of cylinders 36 are closed by plate 4i) provided with holes 41 registering with the axes of each cylinder. The bottoms of said cylinders `are closed with another plate 42 provided with holes 43 also registering with the axes of the cylinders.

The action of a valve may best be explained with reference to FIGURE 3c in which piston 44 is shown in the normal or nnoperated position at Athe top of its stroke urged thereto by spring 45. Piston 44 has an extension 46 passing through hole 41 and terminating in adjustable tappet head 47. Pressure oil is fed to the cylinder over duct 38 and port 39. Port 37 is in communication with one side of a hydraulic actuator which may be of the forms shown in FIGURE 2a or FIGURE 10 (not shown) over pipe 48. When tappet 47 is depressed so that land 49 of piston `44 is below port 37, pressure oil passes to the hydraulic actuator and causes the fin to proceed to full tilt. Releasing the tappet causes piston 44 to return to its original position, urged thereto by spring 45 so that pressure is released in the hydraulic actuator and the pressure oil may exhaust through port 43 as the n returns automatically to the neutral position in aligning itself with the streamline water ow. It will be seen that after land 49 has uncovered port 37 the piston may travel further in a downwards direction while still maintaining the oil supply to the hydaulic actuator. This feature be seen to be necessary to the proper functioning of the stabilizer as will be described hereinafter.

In FIGURE 4 a roll sensing device 50 of known kind which may embody a rate gyroscope to detect the velocity of roll has an output shaft 50a which operates tilting arm 5l by lever 52 and link 53. Hydraulic valve units 35 and 35 of the kind shown in FIGURES 3a, 3b and 3c are disposed to co-operate with extensions 56 and 457 of rocking lever 51. The said hydraulic valve units are partly immersed in a tank 58 of hydraulic fluid such as oil. Said hydraulic iiuid is drawn `from tank 58 by pump 59 driven by electromotor `60 and passed at yhigh pressure to ducts 38 (FIGURES 3a, 3b and 3c) over pipe 61.

Outlet ports of valve unit 35 are connected in sequence over pipe lines 48 rto one side of the appropriate iin actuator and each outlet port of valve unit 35 is similarly connected to the other side of the iin actuators over pipe lines 68.

Conveniently, each pipe line may include a shut-oli valve 63 and a iluid flow indicator 64. Pipe lines 62 extend from lthe high pressure side of pump 59 to the bolt actuating cylinders associated with each n. When the stabilizer is in operation high pressure fluid in pipelines 62 retracts the bolts in the said bolt actuating cylinders thereby allowing free movement of the fins. It will be appreciated that when the stabilizer is put out of action, as by stopping the pump 59, the pressure in the pipelines 62 will be removed and the bolts will engage the slots in the iin urged thereto by spring pressure as hereinbefore explained. Six valves are shown in the gure. This would correspond to lan installation having three tins on each side or six iins on one side, or as desi-red. Larger numbers of Valves may be employed. For a larger installation Afins may be operated in pairs or other groups from one valve.

FIGURE 5 shows one arrangement of the stabilizer employing six tins actu-ated to progressively counter the roll of a ship. 'Ihe six ns a-f are arranged in a symmetrical manner as shown in the figure, each iin being actuated by a hydraulic motor connected over pipe lines 48 to hydraulic valves a to f respectively and over pipe lines 48 to hydraulic valves a" to j" respectively. Thus it will be seen that as extension 56 of tilting arm 51 descends the said iins will be operated to full tilt in the following sequence, the signs indicating the incidence or lift of the fins: a+, b-, c+, d-, c+, f-. When extension 56 has completed its movement three ns on one side of the ship bave been tilted to positive incidence and three fins on the other side to negative incidence, all tins combining to produce a torque in one direction. It will be further seen that as extension 56 returns to the central or neutral position lthe tins will return to their neutral positions in reverse sequence. Now when the extension 57 descends the iins will be operated to full tilt in the sequence a-, 24-, c-, d+, e-, ;f-{-, and as said arm returns to neutral the iins will again return in reverse sequence to their neutral position. Tappets 47 may be adjusted to provide a smooth transition from one sequence to the other.

The movement off tilting arm 51 is controlled by a sensing device of known kind responsive to the roll velocity and FIGURES 6a and 6b illustrates by graphs the action of the ins for one complete oscillation or roll of the ship assuming the roll to be sinusoidal.

In FIGURE 6a, curve A represents the magnitude of the roll angle plotted against time and cunve -B (which corresponds -to roll velocity) the magnitude of the iin power (as expressed by the number of fins in action) to counter the roll, in circumstances where the fm power or torque just sutlicient to 'balance the rolling torque. It will be understood that forV light rolling in moderate seas less than the maximum number of ns will be brought into operation to counter the reduced roll. When, however, the magnitude of the roll, and consequently the roll torque, exceeds the maximum iin power or torque all of the tins will proceed to their tilted positions to develop maximum n power in the time that the roll torque builds up to a corresponding value and all the tins will remain fully tilted until later, the roll torque falls to the value of the iin torque. This is shown by the graphs in FIG- URE 6b where the hatched area represents fin torque.

It must be understood that the fins may be any in number, they may be arranged differently, for example, all on one side of the ship, and they may operate in various sequences since such variations will not eifect or alter the fin torque law as represented in FIGURES 5 and 6a and 6b. Furthermore, a signal responsive to other derivatives of the roll, for example, acceleration and displacement, may be introduced into the lin control signal in known manner to improve the eiciency of the stabilizer for non-sinusoidal roll displacements.

Various sequences of operation of the ns may be arranged depending on the manner in which the hydraulic valves are connected to the iin actuators. The underside or operating faces of rocking arm extensions 56 and 57 as shown in FIGURE 3 are at. Using this configuration and by adjusting the heights of the tappets 47 (FIGURE 3) in an appropriate manner the valves may be made to operate according to a linear sequence. By changing the contour of the operating `faces and/ or the heights of the tappet, sequences obeying other laws may be arranged.

The sequence of operation of the tins to counter a roll to port may, if desired, be different from the sequence to counter a roll to starboard.

FIGURE 7 shows a construction in which sea water is used as the hydraulic uid.

Pump 59 driven by electromotor 60 draws sea water through filter 65 and passes it under pressure to valve units 35 and 35. Low pressure exhaust water from the iin actuators is collected in tank 58 and flows by gravity back tothe sea via pipe 66.

It is sometimes advantageous to introduce an element of control whereby the number of -ns in operation is reduced with increased speed of the ship.

FIGURE 8 illustrates the manner in which this type of control may be adjusted to the stabilizer according to the present invention.

In this flgure, box 69 represents the control sensitive to ship speed, output rod 70 being adapted for linear movement related to ship speed. Roll sensing device 50 operates tilting arm 51 over lever 52 and link 53 as previously described but in the present construction lever 71 and link 72 are interposed between lever 52 and link 53. Lever 71 is provided with a slot in which fulcrumV 73 attached to output rod 70 is slidably mounted.

Thus for a given movement of lever 52, the amount by which arm 51 is tilted, and consequently the number of iins brought into operation is dependent upon the position of yfulcrum 73, which in turn is dependent on ship speed.

FIGURES 9, 10 and l1 show an alternative iin operating arrangement wherein cam means are caused to rotate fin hydraulic control valves of the known 3-position kind and the fins are actuated by piston means.

As shown -in the FIGURES 9 and 10, the cam 74 is carried on the shaft 50a and is provided with a radial face having three steps 74a, 74b and 74C. The middle step b corresponds to the neutral position of the ns, whilst one of the other steps a or c corresponds to a tilting upwards of the fins on one side of the ship and in the opposite direction on the other side of the ship, and the third step corresponds to a tilting of ns opposite to this. Six spring-loaded rods 75 are provided for actuating six three-way valves 76 one of which is shown in FIGURE l0.

The valve 76, when operated by push rod 75, can allow liquid arriving from the pump or reservoir by a supply pipe 77 to ow into a pipe 78 or a pipe 79. When in the neutral position shown, both pipes are connected to eX- haust. The pipes 78 and 79 are tted with locking valves 6 and 81 and thence lead to the position in the bilge keel where the corresponding tin is mounted.

FIGURE 10` shows a tin operating means alternative to that shown in FIGURES 2a and 2b namely, hydraulic jacks comprising two pistons or plungers contained in corresponding cylinders in a cylinder block. The cylinder block may be attached to the fin, the pistons reacting with an attachment to the iin pintle as shown. Alternatively, the cylinder block may be attached to the tin pintle, the pistons` reacting with an abutment of the iin. In the figure, pipes 78 and 79 are connected with the two hydraulic jacks 82 and 83 mounted in the n by two ilexible pipes 84 and 85. Ilhe plungers 86 and 87 of the jacks are arranged to abut against the ends of a thrust block 88 fixed integrally on the n pintle 89.

All the valves controlled through push rods 75 are con.. nected with ns on one side of the ship.

FIGURE ll shows a six-fin stabilizer corresponding to that of FIGURE 5 but actuated by the alternative means. In the figure in which like references represent like parts where applicable the cam 74 is represented for clarity of presentation as a linear device having identical cam lfaces on each side. Such a cam device may be alternatively used where the output :from the control is a linear motion. Pipes 78 and 79 lead directly to the fin hydraulic jacks on one side of the ship while pipes 78 and 79 leading to the lin hydraulic jacks on the other side of the ship are crossed over. The stabilizer functions in the following manner: When all the rods 75 rest onstep 74b of cam 74, valves 76 are in the neutral or central position and the corresponding ins occupy neutral or horizontal positions by virtue of the ow of Water over them as previously explained. When cam 74 moves downwardly rods 75 progressively rise onto step 74e and the leftJhand ns in the gure tilt in one direction and because pipes 78 and 79 are crossed, the right-hand fins are tilted in the opposite direction to the Ins on the left to add to the stabilising torque. When, however, cam 74 moves from :the central position upwardly rods 75 progressively descend on to step 74a urged thereto by their respective springs. Valves 76 now move in the opposite direction and consequently the -tilt of the iin is reversed.

We claim:

1. A ship stabilizer system comprising a ships hull, a plurality of stub axles rigidly attached in spaced positions along the hull in the region of the bilge, tins mounted on the stub axles for oscillation about a neutral position, individual hydraulic motors for oscillating the respective ns, hydraulic pump means, hydraulic lines for circulating hydraulic iiuid from the pump through the hydraulic motors, individual valve means for controlling the fluid flow from the pump to the respective hydraulic motors, sensing means mounted to respond to roll of the hull, means for operating the valve means in sequence from the roll-sensing means, land means responsive to ships speed for limiting the number of ns brought into operation.

2. A ship stabilizer system comprising a ships hull, a plurality of ins attached in spaced positions along the hull in the region of the bilge for oscillation about a neutral position, individual hydraulic motors for oscillating the respective tins, hydraulic pump means, hydraulic lines ttor circulating hydraulic iluid from the pump through the hydraulic motors, individual valve means for controlling the fluid flow from the pump to the respective hydraulic motors, sensing means mounted to respond to roll of the hull, means for operating the valve means in sequence lfrom' the roll-sensing means, and means responsive to ships speed for limiting the number of ns brought into operation.

References Cited in the le of this patent UNITED STATES PATENTS

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