Hydraulic steering mechanism
United States Patent 3911847
A hydraulic operator for ships' rudders and like control surfaces, whose operation calls for the application of rising torque with increase of movement from a mid position, employing a pair of double-acting rams powered from a constant pressure source through linked valves which operate to reverse fluid addmission to each ram as its piston achieves top dead center coincident with the rudder or the like reaching a chosen displacement from the mid position.
US Patent References:
Steering gear
Lamond - May 1942 - 2282194
Automatic steering device for boats and planes
Dunning - March 1950 - 2499471
Automatic follow-up system for successive application of power sources
Mercier - June 1959 - 2892310
Ship stabilizers
Muirhead et al. - July 1961 - 2991748
Valve actuator apparatus
Hopkins - August 1966 - 3269676
Steering gear
Lamond - May 1942 - 2282194
Automatic steering device for boats and planes
Dunning - March 1950 - 2499471
Automatic follow-up system for successive application of power sources
Mercier - June 1959 - 2892310
Ship stabilizers
Muirhead et al. - July 1961 - 2991748
Valve actuator apparatus
Hopkins - August 1966 - 3269676
Application Number:
05/508617
Publication Date:
10/14/1975
Filing Date:
09/23/1974
View Patent Images:
Export Citation:
Assignee:
N. Worthing & Co. Ltd. (London, EN)
Primary Class:
Other Classes:
244/99.500
International Classes:
B63B39/06; B63H25/22; B63H25/34; B64D37/02; F15B9/12; B63B39/00; B63H25/06; B64D37/00; F15B9/00; B63H25/22
Field of Search:
114/126,150,144R 244/78
US Patent References:
Primary Examiner:
Blix, Trygve M.
Assistant Examiner:
Sotelo, Jesus D.
Attorney, Agent or Firm:
Witherspoon, And Lane
Parent Case Data:
This is a continuation of application Ser. No. 337,766, filed Mar. 2, 1973, now abandoned.
Claims:
I claim
1. A hydraulic steering mechanism comprising:
2. The hydraulic steering mechanism as defined in claim 1 wherein said control surface is a ship's rudder.
3. The hydraulic steering mechanism as defined in claim 1 wherein said control surface is a ship's stabilizing fin.
4. The hydraulic steering mechanism as defined in claim 1 wherein said control surface is part of an aircraft.
5. The hydraulic steering mechanism as defined in claim 1 wherein said cylinder of each said ram of said pair of double acting rams is pivoted and said piston of each said ram of said pair of double acting rams transmits movement directly through an associated piston rod.
6. The hydraulic steering mechanism as defined in claim 1 wherein said cylinder of each said ram of said pair of double acting rams is fixed and said piston of each said ram of said pair of double acting rams transmits movement through an associated crosshead and connecting rod.
1. A hydraulic steering mechanism comprising:
2. The hydraulic steering mechanism as defined in claim 1 wherein said control surface is a ship's rudder.
3. The hydraulic steering mechanism as defined in claim 1 wherein said control surface is a ship's stabilizing fin.
4. The hydraulic steering mechanism as defined in claim 1 wherein said control surface is part of an aircraft.
5. The hydraulic steering mechanism as defined in claim 1 wherein said cylinder of each said ram of said pair of double acting rams is pivoted and said piston of each said ram of said pair of double acting rams transmits movement directly through an associated piston rod.
6. The hydraulic steering mechanism as defined in claim 1 wherein said cylinder of each said ram of said pair of double acting rams is fixed and said piston of each said ram of said pair of double acting rams transmits movement through an associated crosshead and connecting rod.
Description:
BACKGROUND OF THE INVENTION
This invention concerns hydraulic mechanism for operating the steering gear of ships, stabiliser fins of the ailerons or aircraft, for convenience referred to hereinafter as steering mechanism.
It is well-known that the torque which must be exerted on the rudder stock of a ship travelling at a given speed increases rapidly with the angle of rudder from its mid position. The same applies to the movements of ships stabilisers and the ailerons of aircraft.
The object of this invention is to provide a simple hydraulic steering mechanism which develops the characteristic of an appropriate increasing torque with angle-of-movement, when supplied with hydraulic fluid from a constant pressure source.
In combination with a hydraulic accumulator and a recharging pump the proposed steering mechanism provides a system which is economical in power consumption. This is because the volume of fluid used per degree of control surface movement near its mid position is only a small fraction of that used per degree of movement near its hard over position.
SUMMARY OF THE INVENTION
The invention provides a hydraulic steering mechanism consisting of at least one pair of double acting rams powered from a constant pressure source, the said rams acting on crankpins on an arm fixed to a control surface, so arranged that one crankpin passes through top dead center when the surface is partially deflected in one direction and the other crankpin passes through top dead center when the surface is partially deflected in the opposite direction, said mechanism incorporating at least one pair of linked reversing valves each one reversing pressure fluid connections to the ends of each double acting ram of a pair as a piston thereof passes through its top dead center.
In one preferred form of mechanism the ram cylinders are fixed and the movement of their pistons is transmitted to the control surface arm through cross heads and connecting rods. In an alternative form the ram cylinders are pivotally mounted and their piston rods act directly upon the control surface arm.
Approaching its top dead center the ram pulls its crankpin and produces a torque on the rudder stock or other control surface which steadily diminishes to zero. Beyond its top dead center the ram pushes its crankpin and produces a steadily increasing torque in the same direction as before. Staggering the top dead center positions of the two rams by a few degrees either side of the rudder (or other control surface) mid position ensures that the sum of the two torques has a constant small value over this range of movement. Outside this range the total torque increases with the angle of movement from the midposition.
To reverse the torque and the rotation of the rudder stock or like element it is only necessary to reverse the fluid supply and return connections to both change-over valves simultaneously by a single control valve.
A number of such mechanisms can be arranged around the element to operate in parallel or to act as a stand-by.
BRIEF DESCRIPTION OF THE DRAWING
The above and other features of the invention are embodied in alternative forms of mechanism which will now be described in some detail with reference to the accompanying drawings in which: FIG. 1, is a horizontal cross-section of a first form of mechanism in the mid position;
FIG. 2, is a similar view of the mechanism of FIG. 1 in the hard-over position;
FIG. 3, is a horizontal cross-section of an alternative arrangement of rams used in the mechanism of FIGS. 1 and 2;
FIG. 4 is a sketch of a ship having a rudder and a stabilizer operated by the steering mechanism of this invention;
FIG. 5 is a sketch of a ship having two stabilizers operated by the steering mechanism of this invention; and
FIG. 6 is a sketch of an aircraft having an aileron operated by the steering mechanism of this invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows schematically one form of the mechanism having rams with fixed cylinders and with a ship's rudder amidships while FIG. 2 shows the rudder hard over to starboard.
Pistons 1a, 1b in double-acting cylinders 2a, 2b are connected by piston-rods 3a, 3b to cross-heads 4a, 4b. The cross-head pins 5a, 5b are linked by connecting rods 6a, 6b to crank pins 7a, 7b on the tiller arm 8 which is keyed to the rudder stock 9. Piston 1a and crankpin 7a pass through top-dead-center when the control surface 40 in this case a rudder 40 as shown in FIG. 4 (referenced TDC in FIGS. 1, 2 and 3) is 15 degrees to port and piston 1b and crankpin 7b pass through top-dead-center when the rudder 40 is 15° to starboard. When the rudder is near its mid position the top end of cylinder 2a and the bottom end of cylinder 2b are connected through reversing valves 10a, 10b to the lower port 11 of the control valve 12, while the bottom end of cylinder 2a and the top end of cylinder 2b are connected through reversing valves 10a, 10b to the upper port 15 of the control valve 12.
When the control valve 12 is moved down from the central position in which it is shown, port 11 is connected to pressurised fluid supply pipe 14 and port 13 is connected to the return pipe 15. Supply pipe 14 and return pipe 15 are connected to a constant pressure source 24 as shown in FIG. 1. For purposes of clarity, constant pressure source 24 is not shown in FIGS. 2 and 3; however, it is obvious how this pressure source would be coupled in these figures from the showing in FIG. 1. Constant pressure source 24 may be any suitable constant pressure source. Constant pressure fluid sources are well known in the art. Connecting rod 6a is in compression and connecting rod 6b is in tension. Both rams produce a counterclockwise torque and the rudder 40 moves to starboard. At 15° to starboard, as the crankpin 7b is passing top-dead-center TDC, the linked repeater lever 16 and link 17b operate valve 10b to reverse the connections to cylinder 2b. At this point the torque contribution of piston 1b is zero, but, as the rudder 40 moves further to starboard, its torque contribution increases again in the same direction, the connecting rod 6b now being also in compression.
The combined torque potential is nearly constant at all rudder angles below 15°, but it increases with the rudder angle between 15° and full rudder. This potential torque characteristic of the steering mechanism matches the rudder torque requirement and provides economy of fluid consumption and pumping power when the fluid is supplied from a system comprising an hydraulic accumulator and a recharging pump.
When the control valve 12 is moved up from its central position in which it is shown, port 13 is connected to pressurised fluid supply pipe 14 and port 11 is connected to the return pipe 15. The rudder 40 moves from starboard to port. Valve 10b reverses back to the midships condition as the rudder re-passes the 15° to starboard position, and valve 10a reverses as the rudder passes the 15° to port position.
Normally the control valve 12 is operated by a differential lever 18 which receives the required rudder input from the local steering wheel 19 via lead-screw 20, nut 21 and link 22. When the rudder 40 has reached the required position the feedback link 23 recenters the control valve 12 and motion ceases.
FIG. 3 shows another form of the mechanism in which the cylinders 2a, 2b of the rams are independently pivoted on pins 31a, 31b in bearings fixed to the deck. The ends of the piston-rods 3a, 3b have bearings for the crankpins 7a, 7b. The valvegear is not shown but is identical to FIG. 1, except that the connections between each cylinder and its reversing valve must either be made with flexible piping or incorporate swivel joints.
While the steering mechanism of this invention has been described in detail with reference to the rudder of a ship such as rudder 40 of FIG. 4, as has been previously mentioned, the steering mechanism of this invention can be used to operate other control surfaces such as the stabilizing fins of a ship and the ailerons of aircraft. FIG. 4 shows a stabilizer fin 40a that is operated by the steering mechanism of this invention and FIG. 5 shows a pair of stabilizer fins 40a that are operated by the steering mechanism of this invention. FIG. 6 shows an aileron 40b operated by the steering mechanism of this invention. Thus, it should be evident that generally any control surface can be operated by the steering mechanism of this invention.
This invention concerns hydraulic mechanism for operating the steering gear of ships, stabiliser fins of the ailerons or aircraft, for convenience referred to hereinafter as steering mechanism.
It is well-known that the torque which must be exerted on the rudder stock of a ship travelling at a given speed increases rapidly with the angle of rudder from its mid position. The same applies to the movements of ships stabilisers and the ailerons of aircraft.
The object of this invention is to provide a simple hydraulic steering mechanism which develops the characteristic of an appropriate increasing torque with angle-of-movement, when supplied with hydraulic fluid from a constant pressure source.
In combination with a hydraulic accumulator and a recharging pump the proposed steering mechanism provides a system which is economical in power consumption. This is because the volume of fluid used per degree of control surface movement near its mid position is only a small fraction of that used per degree of movement near its hard over position.
SUMMARY OF THE INVENTION
The invention provides a hydraulic steering mechanism consisting of at least one pair of double acting rams powered from a constant pressure source, the said rams acting on crankpins on an arm fixed to a control surface, so arranged that one crankpin passes through top dead center when the surface is partially deflected in one direction and the other crankpin passes through top dead center when the surface is partially deflected in the opposite direction, said mechanism incorporating at least one pair of linked reversing valves each one reversing pressure fluid connections to the ends of each double acting ram of a pair as a piston thereof passes through its top dead center.
In one preferred form of mechanism the ram cylinders are fixed and the movement of their pistons is transmitted to the control surface arm through cross heads and connecting rods. In an alternative form the ram cylinders are pivotally mounted and their piston rods act directly upon the control surface arm.
Approaching its top dead center the ram pulls its crankpin and produces a torque on the rudder stock or other control surface which steadily diminishes to zero. Beyond its top dead center the ram pushes its crankpin and produces a steadily increasing torque in the same direction as before. Staggering the top dead center positions of the two rams by a few degrees either side of the rudder (or other control surface) mid position ensures that the sum of the two torques has a constant small value over this range of movement. Outside this range the total torque increases with the angle of movement from the midposition.
To reverse the torque and the rotation of the rudder stock or like element it is only necessary to reverse the fluid supply and return connections to both change-over valves simultaneously by a single control valve.
A number of such mechanisms can be arranged around the element to operate in parallel or to act as a stand-by.
BRIEF DESCRIPTION OF THE DRAWING
The above and other features of the invention are embodied in alternative forms of mechanism which will now be described in some detail with reference to the accompanying drawings in which: FIG. 1, is a horizontal cross-section of a first form of mechanism in the mid position;
FIG. 2, is a similar view of the mechanism of FIG. 1 in the hard-over position;
FIG. 3, is a horizontal cross-section of an alternative arrangement of rams used in the mechanism of FIGS. 1 and 2;
FIG. 4 is a sketch of a ship having a rudder and a stabilizer operated by the steering mechanism of this invention;
FIG. 5 is a sketch of a ship having two stabilizers operated by the steering mechanism of this invention; and
FIG. 6 is a sketch of an aircraft having an aileron operated by the steering mechanism of this invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows schematically one form of the mechanism having rams with fixed cylinders and with a ship's rudder amidships while FIG. 2 shows the rudder hard over to starboard.
Pistons 1a, 1b in double-acting cylinders 2a, 2b are connected by piston-rods 3a, 3b to cross-heads 4a, 4b. The cross-head pins 5a, 5b are linked by connecting rods 6a, 6b to crank pins 7a, 7b on the tiller arm 8 which is keyed to the rudder stock 9. Piston 1a and crankpin 7a pass through top-dead-center when the control surface 40 in this case a rudder 40 as shown in FIG. 4 (referenced TDC in FIGS. 1, 2 and 3) is 15 degrees to port and piston 1b and crankpin 7b pass through top-dead-center when the rudder 40 is 15° to starboard. When the rudder is near its mid position the top end of cylinder 2a and the bottom end of cylinder 2b are connected through reversing valves 10a, 10b to the lower port 11 of the control valve 12, while the bottom end of cylinder 2a and the top end of cylinder 2b are connected through reversing valves 10a, 10b to the upper port 15 of the control valve 12.
When the control valve 12 is moved down from the central position in which it is shown, port 11 is connected to pressurised fluid supply pipe 14 and port 13 is connected to the return pipe 15. Supply pipe 14 and return pipe 15 are connected to a constant pressure source 24 as shown in FIG. 1. For purposes of clarity, constant pressure source 24 is not shown in FIGS. 2 and 3; however, it is obvious how this pressure source would be coupled in these figures from the showing in FIG. 1. Constant pressure source 24 may be any suitable constant pressure source. Constant pressure fluid sources are well known in the art. Connecting rod 6a is in compression and connecting rod 6b is in tension. Both rams produce a counterclockwise torque and the rudder 40 moves to starboard. At 15° to starboard, as the crankpin 7b is passing top-dead-center TDC, the linked repeater lever 16 and link 17b operate valve 10b to reverse the connections to cylinder 2b. At this point the torque contribution of piston 1b is zero, but, as the rudder 40 moves further to starboard, its torque contribution increases again in the same direction, the connecting rod 6b now being also in compression.
The combined torque potential is nearly constant at all rudder angles below 15°, but it increases with the rudder angle between 15° and full rudder. This potential torque characteristic of the steering mechanism matches the rudder torque requirement and provides economy of fluid consumption and pumping power when the fluid is supplied from a system comprising an hydraulic accumulator and a recharging pump.
When the control valve 12 is moved up from its central position in which it is shown, port 13 is connected to pressurised fluid supply pipe 14 and port 11 is connected to the return pipe 15. The rudder 40 moves from starboard to port. Valve 10b reverses back to the midships condition as the rudder re-passes the 15° to starboard position, and valve 10a reverses as the rudder passes the 15° to port position.
Normally the control valve 12 is operated by a differential lever 18 which receives the required rudder input from the local steering wheel 19 via lead-screw 20, nut 21 and link 22. When the rudder 40 has reached the required position the feedback link 23 recenters the control valve 12 and motion ceases.
FIG. 3 shows another form of the mechanism in which the cylinders 2a, 2b of the rams are independently pivoted on pins 31a, 31b in bearings fixed to the deck. The ends of the piston-rods 3a, 3b have bearings for the crankpins 7a, 7b. The valvegear is not shown but is identical to FIG. 1, except that the connections between each cylinder and its reversing valve must either be made with flexible piping or incorporate swivel joints.
While the steering mechanism of this invention has been described in detail with reference to the rudder of a ship such as rudder 40 of FIG. 4, as has been previously mentioned, the steering mechanism of this invention can be used to operate other control surfaces such as the stabilizing fins of a ship and the ailerons of aircraft. FIG. 4 shows a stabilizer fin 40a that is operated by the steering mechanism of this invention and FIG. 5 shows a pair of stabilizer fins 40a that are operated by the steering mechanism of this invention. FIG. 6 shows an aileron 40b operated by the steering mechanism of this invention. Thus, it should be evident that generally any control surface can be operated by the steering mechanism of this invention.