A wave powered porpulsion apparatus

Abstract

A wave propulsion apparatus (1) has a spine (2) extending in a longitudinal dimension from a proximal end to a distal end and supporting a series of fins (4) pivotally mounted (5) by hinges on the spine for rotation about a lateral hinge axis. The restraints (30, 40) each has an end stop (33, 43) and is slidably mounted to the spine for linear movement to set a limit for rotation of each fin. There is a drive (25) for actuating longitudinal movement of the restraints. There are a pair of restraints (30, 40) associated with each fin (4), one proximally of the fin and one distally of the fin, and each fin is mounted to the spine by a cross-member (5(b)) which spans the spine members (3) and is fixed thereto. The hinges have shock absorbing resilience, so that a combination of the hinges and the resilient end stops (33, 43) provide excellent shock absorbing capacity.

Description

[0001] “A Wave Powered Propulsion Apparatus”

[0002] Introduction

[0003] The present invention relates to a wave powered towing or propulsion apparatus.

[0004] It is known to provide such an apparatus, as described in WO2017 / 025544 and W02020 / 200846.

[0005] The present invention is directed towards providing enhancements in operation of wave-powered propulsion apparatus.

[0006] Summary of the Invention

[0007] We describe a wave propulsion apparatus comprising: a spine extending in a longitudinal dimension from a proximal end to a distal end, a series of fins pivotally mounted by hinges on the spine for rotation about a hinge axis, at least one restraint comprising an end stop and being slidably mounted to the spine for linear movement to set a limit for rotation of each fin, and a drive for actuating longitudinal movement of the restraints.

[0008] In some preferred examples, there are a pair of restraints associated with each fin, one proximally of the fin and one distally of the fin. In some preferred examples, the spine comprises at least two parallel spine members, which are preferably of round cross-sectional shape. In some preferred examples, each fin is mounted to the spine by a cross-member which spans the spine members and is fixed thereto. Preferably, each cross-member supports a hinge to which the fin is attached. Preferably, at least some hinges have shock absorbing resilience. This may for example be due to the fin having an integral flexible portion which is secured to the spine.

[0009] In some preferred examples, at least some hinges comprise an element of flexible material with natural hinge flexibility. In some preferred examples, each hinge comprises only a single element of flexible material, and optionally said element is supported by clamping to the cross member.

[0010] In some preferred examples, the drive comprises a push rod for causing longitudinal movement of each restraint under action of a drive actuator. In some preferred examples, there is at least one push rod for each of a plurality of spine elongate members. In some preferred examples, at least some of the restraints have a stop member which extends with a directional component in the longitudinal dimension so that the end stop is the closest part of the restraint to the associated fin in use. Preferably, at least some end stops are resilient.

[0011] In some preferred examples, at least some fins each comprise at least on lip extending away from a plane of the fin at an extremity furthest from the hinge. In some preferred examples, there are two opposed lips, one facing proximally and one facing distally.

[0012] In some preferred examples, at least some fins each have a follower member with a proximal and / or a distal contact surface for engagement with an end stop, each said surface being tapered to extend proximally or distally and towards the hinge. In some preferred examples, the follower member has a generally triangular shape in side view. In some preferred examples, the follower contact surface has a convex configuration in side view.

[0013] In some preferred examples, the apparatus comprises a plurality of steering fins which are mounted at an acute angle to the longitudinal dimension, and associated restraints and restraint actuators linked with the controller, and the controller is configured to actuate said actuators according to desired steering angle. Preferably, the apparatus comprises a pair of series of steering fins, each mounted at a different angle to longitudinal. Preferably the pair of series of steering fins are mounted are both at an angle to longitudinal having the same value but in the opposite sense.

[0014] In some preferred examples, the steering fins are provided in a steering module arranged to be coupled at the distal end to a series of propulsion modules in series.

[0015] In some preferred examples, the apparatus comprises a plurality of buoyancy elements which extend across, and are affixed to, spine members. In some preferred examples, at least some of said buoyancy elements are attached to fin hinges. In some preferred examples, at least one drive is mounted to the spine to overlie a spine member.

[0016] Additional Statements

[0017] We describe a wave propulsion apparatus comprising a spine extending in a longitudinal dimension from a proximal end to a distal end, a series of fins pivotally mounted by hinges on the spine for rotation about a hinge axis, at least one restraint comprising an end stop and being slidably mounted to the spine for linear movement to set a limit for rotation of each fin, and a drive for actuating longitudinal movement of the restraints. In some examples, there are a pair of restraints associated with each fin, one proximally of the fin and one distally of the fin. In some examples, the spine comprises at least two parallel spine members, which are preferably of round cross-sectional shape. In some examples, each fin is mounted to the spine by a cross-member which spans the spine members and is fixed thereto.

[0018] In some examples, each cross-member supports a hinge to which the fin is attached. In some examples, at least some hinges have shock absorbing resilience. In some examples, at least some hinges comprise an element of flexible material with natural hinge flexibility. In some examples, each hinge comprises only a single element of flexible material.

[0019] In some examples, the drive comprises a push rod for causing longitudinal movement of each restraint under action of a drive actuator. In some examples, there is at least one push rod for each of a plurality of spine elongate members.

[0020] In some examples, at least some of the restraints have a stop member which extends with a directional component in the longitudinal dimension so that the end stop is closest to the associated fin in use. In some examples, at least some end stops are resilient.

[0021] In some examples, at least some fins each comprise have at least on lip extending sway from a plane of the fin at an extremity furthest from the hinge. In some examples, there are two opposed lips, one facing proximally and one facing distally.

[0022] In some examples, at least some fins each have a follower member with a proximal and / or a distal contact surface for engagement with an end stop, each said surface being tapered to extend proximally or distally and towards the hinge. In some examples, the follower member has a generally triangular shape in side view. In some examples, the follower contact surface has a convex configuration in side view.

[0023] In some examples, the apparatus comprises a plurality of steering fins which are mounted at an acute angle to the longitudinal dimension, and associated restraints and restraint actuators linked with the controller, and the controller is configured to actuate said actuators according to desired steering angle.

[0024] In some examples, the apparatus comprises a pair of series of steering fins, each mounted at a different angle to longitudinal, and preferably they are both at an angle having the same value but in the opposite sense. In some examples, the apparatus comprises a plurality of buoyancy elements which extend across, and are affixed to, spine members. In some examples, at least some of said buoyancy elements are attached to fin hinges.

[0025] Detailed Description of the Invention

[0026] The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which:

[0027] Fig. l is a perspective view of a propulsion apparatus of the invention,

[0028] Fig. 2(a) is a side view showing one fin and its mounting arrangement in more detail, Fig. 2(b) is an exploded view of the fin mounting assembly, and Fig. 2(c) is an enlarged side view showing the fin mounting assembly in further detail,

[0029] Fig. 3 is a perspective view of a propulsion apparatus having a series of the apparatus’ of Figs. 1 and 2 in series as modules and also a leading steering system,

[0030] Figs. 4 to 6 inclusive are plan, side perspective, and front perspective views of the steering system,

[0031] Fig. 7 is a side view of an alternative propulsion apparatus, in this case having drives which overlap the spine, and

[0032] Fig. 8 is a perspective view of the apparatus of Fig. 7, Fig. 9 is a plan view, and Fig. 10 is an end view facing in the proximal direction.

[0033] Description of the Embodiments

[0034] Referring to the drawings a wave-powered propulsion apparatus 1 comprises an elongate spine 2 extending in a longitudinal dimension. The spine 2 comprises a pair of parallel rails 3 separated by a distance in accordance with the structural requirements of the scale and application.

[0035] The rails 3 support a series of blades or fins 4 each mounted to rotate about an axis perpendicular to the longitudinal dimension by a hinge 5 comprising a main body 57 supporting a flexible hinge element 55 of flexible material, namely a rubber-based composite. Each hinge body 57 is mounted to the rails 3 in a manner that locks them in their longitudinal positions.

[0036] There is an elongate buoyancy element 6 attached to and extending across the hinges 5. This provides buoyancy to the apparatus. The buoyancy elements 6, like the hinges 5, are not attached to the push rods 20 but are fixed on the rails 3. It is only restraints 30 and 40, described in more detail below, which slide on the rails 3.

[0037] As sown most clearly in Figs. 2(b) and (c) the hinge main body 57 has through openings 60 to accommodate the rails 3, and a lower slot 65 encloses elongate clamping elements 58 and 59, between which the flexible hinge element 55 is sandwiched within the groove 65. Bolts 63 are engaged vertically through the main hinge body 57 to engage in the top lip of the cross member 59 to clamp the hinge to the rails 3. The hinge main body 57 also has longitudinal through holes 61 to receive the push rods 20 in a manner that allows them to move longitudinally. The hinge element 55 has longitudinal slots 56 to receive the push rods 20, as do all of the parts of the hinge. As shown in Fig. 2(c) there is a gap 66 between the tops of the hinge elements 59, 58, 55 and the solid part of the hinge main body. This is to allow clearance if required.

[0038] The buoyancy element 6 has a slot 51 along its length to receive the hinge main body 57. Also, it has end caps 51 and longitudinal slots 52 to receive the rails 3.

[0039] Each blade 4 comprises a pair of lips 7 extending transversely from a lower edge, one lip 7 facing each longitudinal direction. At its upper end, each blade 4 comprises a follower 10 having a surface facing in each longitudinal direction, the follower being tapered so that the surfaces extend upwardly and longitudinally when the blade 4 is in a vertical orientation. These surfaces are indicated as 11 and 12, the surface 11 facing in a first direction, which is rearward for the use position shown in the drawings, and the second surface facing forwardly in this use. The followers 10 have plates or webs which are perforated with holes 12 to reduce weight without sacrificing strength.

[0040] The apparatus 1 further comprises an actuator drive 25 for each rail having a watertight enclosure 23 with housing components joined by flanges 24. The drive 25 pushes and pulls a connector 22 which in turn pushes and pulls a pair of pushrods 20 on each spine 3, one upper and one lower. For clarity, the end of the apparatus with the drive 25 is termed as being proximal and the spine 2 extends distally from the drive 25. For each blade 4 there is a pair of sliding restraints 30 and 40, mounted to, and extending across, both rails 3. The restraint 40 has a main body 41 which has sliding engagement with the rails 3, and also being fast on the top and bottom push rods 20 which are driven by the drive 25.

[0041] The restraint 40 comprises a push element 42 which extends downwardly and forwardly in the longitudinal dimension. The push element 42 has a rounded and resilient end stop 43 configured to engage the blade surface 11 to prevent it from rotating anti-clockwise as viewed in Fig. 2 to an extent greater than limited by longitudinal position of the end stop 43. On the distal side of the blade 4 there is a distal restraint 30 having a main body 31 akin to the main body 41 and having a push element 32 extending downwardly and proximally and terminating in a rounded and resilient end stop 33.

[0042] The restraint 30 operates in the opposite sense to the restraint 40, limiting clockwise pivoting of the blade as viewed in Fig. 2. This drawing shows that the surface 12 of the follower 10 is curved around towards the proximal direction near its top end. In general, it is preferred that the follower has a surface which is generally convex, either with a continuous curve or with comers as illustrated. These configurations allow the restraint 30 or 40 to set a limit on rotation of the blade in its associated direction.

[0043] A controller with digital data processors provides control signals to the drive 25, to cause the push rods 20 to move to achieve a desired orientation of the blades 4. In the position shown in Fig. 2 the distal restraints 30 are active, limiting clockwise rotations to hold the blades 4 in an orientation facing rearwardly so that there is propulsion distally to the left as viewed in Fig. 2. Of course, with applicable movement of the push rods 20 the angle can be changed, or indeed the proximal restraint may become active, and this may cause orientation distally so that there is wave propulsion in the proximal direction, to the right as viewed in Fig. 2. The controller may be locally housed within the housing 23 or it may be remote, but it works with control inputs received from a remote location such as onshore or on a ship.

[0044] The apparatus may be referred to as an ‘unmanned surface vessel’ (“USV”) constructed to convert the orbital motion of ocean waves into powerful propulsion forces.

[0045] There may be a series of multiple drives 25, each attached to the ends of the long structural spines 3 which are parallel to the ocean surface. Each drive module 25 can control a predetermined cohort of fins 4 that can be independently cycled through a range of positions. There are at least two types of drives, termed as: propulsion modules and steering modules.

[0046] Propulsion modules provide the USV 1 with the ability to select remotely or autonomously, on command, when suitable wave activity is present, fundamental maneuvers at sea such as moving forward on the surface of the ocean, neutralize propulsion forces to allow the USV to drift according to conditions, to move astern (reverse), and to hold position dynamically over the ground.

[0047] These maneuvers and operations are achieved by the use of the mechanically adjustable end stops 33 and 43, which are configured to restrict, or limit, the rotational movement of a number of the horizontally hinged fins 4 mounted at regular spacings on longitudinal, tubular (but not necessarily tubular) spine structures 3. The fins 4 can be constructed from sheet steel, alloy, or composite materials. The fins 4 are flat and rectangular in shape, their width being much greater than their depth, e.g., a depth of 2 m and a width of 13 m. The fins are flat sheets and have structural stiffening built in as appropriate. In general, the fins may preferably have a depth in the range of 1 m to 5 m, and a width of 5 m to 30 m.

[0048] The upper edge of the fin has a flexible material 5(a), such as rubber sheet, attached along its full length, providing a one-piece hinge for the fin, with no mechanical linkages. This isn’t made from the same material as the fin or upper crossmember and may be referred to as a built-in flexure. This material in turn is attached to the bottom edge of the crossmember 5(b) which also can be made of steel, alloy, or suitable composite materials. The horizontal hinge system is formed by the flexible joint between the upper fin edge and the lower edge of the crossmember and this forms the axis of the fin rotation.

[0049] The fins and crossmember assemblies are fitted with their own independent buoyancy elements 6 which are attached to the upper section of each crossmember 5(b). Each completed fin and crossmember assembly hangs vertically underneath the buoyancy.

[0050] The crossmembers 5(b) intersect the longitudinal spine rails 3, parallel to the surface at 90°. The rails 3 may provide additional buoyancy to the overall system, but the main buoyancy component is preferably provided by the buoyancy elements 6 of the crossmembers. The buoyancy elements are preferably compartmentalized, lightweight, tubes, with hydrodynamic cross section. This could be an inflatable system or constructed from steel or alloy. The cross members 57 and 59 are atached to each spine rail 3 by a clamping system which holds them securely in a fixed position relative to the spine, and this allows them to be independently attached or removed easily from it. The crossmembers 57 act as an important structural component, holding the spines at a fixed dimension relative, and parallel to each other so that they move as one unit on the ocean surface. The lower half 65 of the crossmember also acts as the upper, fixed side of the fin hinge 5, having the flexible hinge material 55 attached to it.

[0051] The end stops or restraints 30 and 40 are mounted on the same spine structure 3 as the fin crossmember 57 but are allowed to slide longitudinally on the spines, within a specific range of movement. These are mechanically operated using the pushrods 20, which are moved longitudinally by lead screws or cables in the drive 25.

[0052] Each fin 4 has at least two or more dedicated end stops 30, 40, the end stops having a range of movement, relative to the fins, which will allow them to mechanically limit the angle of the fin travel. Using the end stops to limit the angle of travel of the fins at specifically selected positions / degrees, determines the ability of a group or module of fins 4 to exert propulsion forces and in what direction these forces will be exerted.

[0053] Within the extent of the designed range of end stop movement will be a position where the end stop limitations are inactive and allow the fins to oscillate freely without any restrictions. In this setting the fins 4 will be unable to exert a propulsion influence and are moving but neutralized in terms of propulsion capability.

[0054] In addition to this neutral setting, two further settings are possible which lock the fins in a ‘feathered’ position, holding them at an angle of 10° to 11° from horizontal relative to the spine. This position is achieved in two directions and has many important benefits, for example it secures the fins in a stable position when the device is under tow from a powered and manned service vessel. This could be to change location quickly, or to be taken for maintenance. It would allow the vessel to be placed into a ‘sleep’ mode’ for long durations with no moving parts, therefore reducing wear and tear on components. It also can form part of the ability the device has to dynamically hold position.

[0055] Apparatus of the invention may have directional control also by way of modules attached to the propulsion modules typically at one or both ends of a propulsion module chain. While the primary purpose of a steering module is to alter or maintain direction as the USV moves on the surface of the ocean, it can also be used to yaw the device on the horizontal plane when dynamically holding position.

[0056] A steering module includes fins that are hinged in a similar manner to that of the propulsion fins 4, however they are not attached at 90° to the spines, they are split in two equal parts each part being a series of blades mounted on a spine at an angle of for example 20° to the longitudinal dimension. This split fin arrangement allows half of each fin to be controlled independently to the other half. This split arrangement, combined with the 20° offset to the central spines, provides the steering module with the ability to effect a directional alteration to the system as it moves through the water.

[0057] The steering module has the possibility to cycle through multiple permutations as each half of each fin can be controlled independently i.e., feathered, placed in forward & reverse, and in neutral. However, a number of these combinations tend to be the most effective, depending on the circumstances of the device and sea conditions.

[0058] In more detail, Fig. 3 shows a propulsion apparatus 100 comprising a plurality of the apparatus’ 1 in series, each apparatus 1 being a module. The number of modules being chosen according to the power requirements and so that each drive can handle the restraint control requirements, given that an excessive number of fins would lead to early failure. At the leading end of the apparatus 100 there is a steering system 101, shown in more detail in Figs. 4 to 6.

[0059] The steering system 101 comprises two pairs of rails 103, each pair supporting a series of at least one fin 104(a) or 104(b) mounted at an angle of 20° to lateral. Restraints 130 and 140 are provided for operation in the manner described above, however in this case the controller is programmed to control their positions to achieve a desired steering angle, the propulsion power being provided by these blades being minimal. Also, the end stops of the restraints 130 and 140 are at an angle of 20° to the lateral direction, for good surface contact with the followers 110 of the fins 104. The closer the blades 104(a) and 104(b) are to vertical the more steering power they provide. There are drives 125(a), 125(b), 125(c), and 125(d), one per rail 103, to activate pushrods 120 to achieve the desired control of end stop position. There is a buoyancy element 106(a) or 106(b) over each fin in an arrangement akin to that of the propulsion fins and hinges 4 and 5, the only difference being that they are at an angle of 20° to lateral (70° to the longitudinal dimension). Referring to Figs. 7 to 10 an alternative propulsion module 200 is illustrated. Parts like those of the apparatus 100 are indicated by the same reference numerals. In this case the drive is provided by an actuator drive 225 with a tubular housing 226 which overlies the associated rail 3. A proximal coupler 227 is fixed to the relevant rail 3, and a distal coupler 227 is secured to the pair of pushrods 20. A benefit of this arrangement is that overall length of an apparatus with multiple modules is reduced and there is less of the overall length without blades 4. Also, the fact that the drive actuators overlie the spines provides an added degree of stiffness to the spine.

[0060] Propulsion Module Control Systems

[0061] The controller implements a logic flow using load sensor feedback to adjust end stop positions. In addition to the control inputs for forwards, backwards, and neutral the controller may optimize energy absorption from fluctuating wave conditions when the measurement of specific data is acquired for feedback to logic control systems. This would include information such as:

[0062] The force being exerted by the fin as it pushes against the end stop. A load cell built into the end stop could measure the force exerted by the fin, this would be a constant data feed to the control unit.

[0063] The angle a fin has reached as it meets the end stop. The angle of the fin could be measured with an encoder installation, or by using infrared or ultrasonic measuring sensors.

[0064] The velocity of the fin during rotation. A combination of the above sensors, or a separate installation of time and distance sensor data.

[0065] The optimum fin angle setting will fluctuate with different sea states. When the control system can measure the forces being exerted by the fin against the end stop, the force can be maximized by tuning the angle of the fin around a set point. The sensitivity of this would typically have a gain control function.

[0066] Steering Control

[0067] This involves the use of sensors used for the propulsion modules with the additional capability of satellite GPS communications. This should allow for periods of autonomous operation, with semi- autonomous intervention as required, where the USV would follow a predetermined course set out by waypoints, as is common practice. When a course is set, the USV would follow as on autopilot, with control inputs altering the steering fins thereby navigating to waypoint position inputs as the system constantly establishes and updates its position plotting relative to them, in accordance with the desired course as set out.

[0068] Accelerometers installed on board the USV can provide feedback of wave condition telemetry, both to shore-based monitoring and directly to the USV control. Artificial Intelligence and Machine Learning software may be used to assist with automatic control. A steering module may be located at the front or rear of the apparatus.

[0069] The steering modules are particularly suited to altering the heading of the USV rather than to make tight turns. If a large course deviation is required, it may be carried out more effectively by changing direction, i.e., putting the complete system into reverse, and altering course as required after that. Most seagoing vessels have a hull or propulsion system design which favours one direction of travel over another, (most vessels do not have matching speed or control while going astern as in a forward hull direction). In the case of this apparatus, while it may achieve a greater velocity when moving in the same direction as the waves, the structural design and propulsion system do not discriminate between forward and reverse and perform equally in either direction. Because of this, large course alterations (greater than 45°) may be more easily carried out by reversing direction. This would depend on the type of activity that was being carried out in the moment, i.e., towing a sensor.

[0070] The effect of both a resilient hinge (5(a)) and the end stop resilient tip (33, 43) provide a double shock absorbing effect. The apparatus harnesses wave power by restricting the movement of the fins when a water stream is acting on it, and this power is converted into propulsion. The water particle flow associated with the orbital motion is created by the wave energy moving through it. Because of the orbital aspect, in relation to the position of the fin, it produces a bidirectional flow, so to harness energy and produce a unidirectional force for propulsion purposes the fin cannot be fixed, and it must be allowed to react to only one direction of flow at a time. The flow will exert force on the fin in one direction and then swing the fin clear with the other. Using fins to harness the wave energy in this way means that they preferably have a free arc of movement in only one direction at a time, to a horizontal extremity, and a defined limit in the other. It is preferred that the full pivoting range for propulsion is between 45° and 90°.

[0071] As the end stops are a mechanical solution to create defined limits for the fins, they are one of the most important mechanical control features of this system. How and where the fin reacts against the end stop to limit its movement is also important. The geometry gives the fin a significant mechanical advantage over the end stop, i.e., the end stop buffer point is close to the fin fulcrum axis. As a result, the forces that are exerted on the end stop can be very large. The apparatus dampens these forces by means of a thick walled, soft silicone, tubing, built into the tip of the end stop 33 and 43 at point of contact with the fin, to help absorb the impact of shock loading. In addition to this, the flexure hinge system 5 of the fin will absorb a significant portion of the force caused by the end stop impact.

[0072] The flexure hinge material will further dampen and absorb these forces without causing any damage to it. One of the most effective materials used, in terms of minimum stiffness and durability, was a composite of rubber and nylon.

[0073] Using pushrods 20 / 120 attached directly to drive actuators is very simple and effective. Advantageously, the end stops do not need to physically move or push the fins, the fins are already constantly moving due to wave action and consequently the time spent in contact with the end stops in the full cycle of movement is minimal. The end stops only need to limit the angle that the fins can achieve in a crucial moment. The control system power consumption can be more efficient when the linear velocity of the end stop movement is low.

[0074] It is advantageous to keep the longitudinal travel of the end stops 30, 40 to a minimum; this is important in terms of the overall operating length of the system, i.e., the end stop linear travel is provided by actuators, the greater the linear travel the longer the actuator needs to be. Electrically powered linear actuators are a very effective means of positioning the end stops, they can position end stops very accurately and form an effective interface between the mechanical hardware, the electronics and control architecture and so direct attachment to the end stops via pushrods was possible and preferable.

[0075] It is preferable that the point of impact of the fin and end stop is close to the fin hinge axis, preferably located in the range up to 20% of the vertical dimension.

[0076] To design this point of impact to occur at a greater distance from the hinge axis, it would mean having to make compromises on other aspects of the system, i.e. the length of required end stop travel, the structural complexity of the end stop, which would then in turn be subjected to increased forces by the fin impact. In other examples the apparatus may have a retractable end stop, which would provide the desired minimum linear end stop travel dimensions and consequently reduce the force transmitted to the fin hinge area. However, this would be more complex.

[0077] The physical and structural arrangement of the apparatus provides opportunities to mount an array of solar panels sufficient to produce electrical power and supply the demands of actuators and control hardware / software.

[0078] Electrical power is not required for the apparatus main propulsion; however, it will be needed to operate actuators and on-board control systems. The apparatus could travel for hundreds of km on a course with just one setting of the end stops, the end stops only requiring power when moving to a new position.

[0079] The steering modules, where present, would demand more power while maintaining active directional control over long distances, however the overall ratio of steering fins to propulsion fins needed to achieve this are relatively few in number, e.g., physical model tests demonstrated that 3 steering fins could effectively manage the directional control of 25 propulsion fins, but not necessarily limited to 25.

[0080] In any case power consumption would depend on the prevailing conditions, it would be practical, if possible, to navigate with prevailing conditions, wind / wave direction, tides / currents, rather than in conflict with them. This type of operational approach would mirror to some extent the approach that wind powered vessels would have taken for hundreds of years.

[0081] In some examples the apparatus has integrated watertight, hull type compartments at strategic intervals to house sensors or submersibles, with built in deployment and retrieval systems.

[0082] If necessary, in some applications, these watertight hull units could have hybrid power generation systems of solar panels or backed up with fossil a fueled generator for emergencies.

[0083] Components of embodiments can be employed in other embodiments in a manner as would be understood by a person of ordinary skill in the art. The invention is not limited to the embodiments described but may be varied in construction and detail. For example, it is envisaged that the fins are mounted about an axis which is not horizontal normal to the longitudinal axis, such as a vertical axis. The functionality of the restraints moving in a linear direction still provides the same benefits.

Claims

Claims1. A wave propulsion apparatus (1) comprising: a spine (2) extending in a longitudinal dimension from a proximal end to a distal end, a series of fins (4) pivotally mounted (5) by hinges on the spine for rotation about a hinge axis, at least one restraint (30, 40) comprising an end stop (33, 43) and being slidably mounted to the spine for linear movement to set a limit for rotation of each fin, and a drive (25) for actuating longitudinal movement of the restraints.

2. An apparatus as claimed in claim 1, wherein there are a pair of restraints (30, 40) associated with each fin (4), one proximally of the fin and one distally of the fin.

3. An apparatus as claimed in claim 1 or claim 2, wherein the spine (2) comprises at least two parallel spine members (3), which are preferably of round cross-sectional shape.

4. An apparatus as claimed in claim 3, wherein each fin is mounted to the spine by a crossmember (57, 58, 59) which spans the spine members (3) and is fixed thereto.

5. An apparatus as claimed in claim 4, wherein each cross-member supports a hinge (5) to which the fin (4) is attached.

6. An apparatus as claimed in any preceding claim, wherein at least some hinges have shock absorbing resilience.

7. An apparatus as claimed in claim 6, wherein at least some hinges (5) comprise an element (55) of flexible material with natural hinge flexibility.

8. An apparatus as claimed in claim 7, wherein each hinge (5) comprises only a single element of flexible material (55), and optionally said element (55) is supported by clamping (58, 59) to the cross member (57).

9. An apparatus as claimed in any preceding claim, wherein the drive comprises a push rod (20) for causing longitudinal movement of each restraint under action of a drive actuator (25).

10. An apparatus as claimed in claim 9, wherein there is at least one push rod (20) for each of a plurality of spine elongate members (3).

11. An apparatus as claimed in any preceding claim, wherein at least some of the restraints have a stop member (32, 42) which extends with a directional component in the longitudinal dimension so that the end stop (33, 43) is the closest part of the restraint to the associated fin in use.

12. An apparatus as claimed in any preceding claim, wherein at least some end stops (33, 43) are resilient.

13. An apparatus as claimed in any preceding claim, wherein at least some fins each comprise at least on lip (7) extending away from a plane of the fin at an extremity furthest from the hinge.

14. An apparatus as claimed in claim 13, wherein there are two opposed lips (7), one facing proximally and one facing distally.

15. An apparatus as claimed in any preceding claim, wherein at least some fins each have a follower member (10) with a proximal and / or a distal contact surface (11, 12) for engagement with an end stop (33, 43), each said surface being tapered to extend proximally or distally and towards the hinge.

16. An apparatus as claimed in claim 15, wherein the follower member (10) has a generally triangular shape in side view.

17. An apparatus as claimed in claim 15 or claim 16, wherein the follower contact surface (11, 12) has a convex configuration in side view.

18. An apparatus as claimed in any preceding claim, wherein the apparatus comprises a plurality of steering fins (104(a), 104(b)) which are mounted at an acute angle to the longitudinal dimension, and associated restraints (130, 140) and restraint actuators linked with the controller, and the controller is configured to actuate said actuators according to desired steering angle.

19. An apparatus as claimed in claim 18, wherein the apparatus comprises a pair of series of steering fins (104(a), 104(b)), each mounted at a different angle to longitudinal.

20. An apparatus as claimed in claim 19, wherein the pair of series of steering fins are mounted are both at an angle to longitudinal having the same value but in the opposite sense.

21. An apparatus as claimed in any of claims 18 to 20, wherein the steering fins are provided in a steering module (101) arranged to be coupled at the distal end to a series of propulsion modules in series.

22. An apparatus as claimed in any preceding claim, wherein the apparatus comprises a plurality of buoyancy elements (6) which extend across, and are affixed to, spine members.

23. An apparatus as claimed in claim 22, wherein at least some of said buoyancy elements are attached to fin hinges (5).

24. An apparatus of any preceding claim, wherein at least one drive (225) is mounted to the spine to overlie a spine member.

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