This invention relates to marine propulsion apparatus. This invention has particular but not exclusive application to the propulsion of boats, and for illustrative purposes reference will be made to such application. However, it is to be understood that this invention could be used in other applications, such as the propulsion of amphibious vehicles.

There are a number of techniques in use for boat propulsion, most of which operate by thrusting water rearward from the boat. For the purposes of this specification, a boat is to be. taken to mean any type of marine craft, including ships. Over the years since the invention of engines suitable for boats, many different thrust devices have been applied to boats, including propellers, water jets, paddle wheels and paddle tracks. Most existing boats utilise propellers as their thrust devices, b;ut the efficiency of a propeller falls at speeds above and below its optimum speed and the resulting power transfer may be quite inefficient at speeds, commonly used.

Paddle wheels and paddle tracks are known to provide high propulsive efficiency at low speeds, but suffer from the problem that as their speed rises they entrap and carry increasing volumes of water as they exit the water and thus they have hitherto been useful only for low speed operation. The present invention aims to alleviate the above disadvantages and to provide marine propulsion apparatus which will be reliable and efficient in use. Other objects and advantages of this invention will hereinafter become apparent.

With the foregoing and other objects in view, this invention in one aspect resides broadly in marine propulsion apparatus including:- a supporting frame; an endless conveyor supported by said supporting frame whereby a lower

run part thereof may be immersed in water, said endless conveyor supporting a plurality of longitudinally-spaced drive elements disposed along its outer surface; drive means for driving said endless conveyor, and said lower run portion including a trailing part arranged to exit the water at an acute angle to the water surface during forward drive operation.

Preferably, the endless conveyor passes about a front pulley and a rear pulley- and the rear pulley is fully disposed above the water surface such that the endless conveyor may exit the water at an acute angle to the water surface during normal forward drive operation.

Preferably, an intermediate pulley is mounted on the supporting -Frame and contacts the lower segment of the endless conveyor intermediate the front pulley and the rear pulley, -forming a leading part of the endless conveyor between the front pulley and the intermediate pulley, and a trailing part of the endless conveyor between the intermediate pulley and the rear pulley. The drive element may be in the form of a transversely extending fin which also extends outwardly from the endless conveyor. The fin may be vertical, or inclined forward with respect to the conveyor. Preferably, however, the fin is inclined rearwardly with respect to the conveyor ^" when exiting the water to minimise water carryover and to enhance forward thrust. Apertures may be formed in the fin whereby air entrapped during immersion of the fin may be released.

Alternatively, the drive element may be in the form of a transversely extending fin movable about an axis transverse to the endless conveyor between a stowed attitude at which the fin lies along the endless conveyor and an operating attitude at which the fin extends outwardly from the endless conveyor. The fin may be held in the operative attitude by

interaction between the fin and the surface of the endless conveyor along the leading part and may be released from the operative attitude along the trailing part of the endless conveyor. The interaction may be controlled by contouring the front pulley and the intermediate pulley transversely such that the endless conveyor is selectively raised or manipulated along the leading part to produce the interaction, and by contouring the rear pulley such that the transverse shape of the endless conveyor is changed along the trailing part between the intermediate pulley and tfie rear pulley whereby the interaction ceases along the segment of endless conveyor between the intermediate pulley and the rear pulley. Reverse tabs or lugs may be provided whereby a fin may be re-oriented during a change between forward drive and reverse drive.

Alternatively, a control conveyor may be provided which passes around the front pulley and the intermediate pulley whereby the control conveyor may interact with the fin to maintain it in an operative position along the leading part of the conveyor. If desired, a conveyor may pass around a front pulley and a rear pulley having different respective transverse contours whereby interaction between the conveyor and the fins may produce the desired control of the attitude of the fins. The fin may be provided with a lug or a cam formed along a part of the transverse edge nearest the transverse axis about which it pivots whereby the fin may interact with the conveyor such that it may be held in an operative attitude. Fins may be formed such that they may be held in alternative operating attitudes, whereby drive may be provided in forward or reverse directions as required, or separate fins adapted for forward and rearward drive respectively may be provided. Biassing means may be provided associated with the fin,

whereby the fin may be biassed into a selected attitude in the absence of external forces. The biassing means may be in the -Form of a spring arranged to hold the fin in an operative attitude relative to the conveyor. Fin control means may be attached to the frame and utilised to control the attitude of the fin. The fin control means may be in the form of a slide which engages with the fin and holds it in a selected attitude such as along the conveyor for a selected portion of a run of the conveyor. In a further alternative embodiment, the drive element may be formed from a flexible or elastic material as a pocket which may be supported in an extended operative position by water pressure within the pocket and which may collapse into a -folded attitude when the water pressure is released from the pocket. The pulleys may be contoured transversely into shapes which interact with the conveyor and the pockets to selectively open and close the pocket as the conveyor passes around the pulleys. The pocket may have an opening at the rear to facilitate the release of water -From the pocket as it passes along the trailing part of the conveyor. Drive elements may be oriented for optimum operation in forward drive, and further drive elements may be added to the conveyor in opposite orientation for reverse operation. Drive elements may be formed with a plurality of pockets such that pockets for forward drive are operable during forward travel o-F the conveyor and pockets for reverse drive are operable during reverse travel of the conveyor.

The pulleys may be profiled transversely to engage complementarily with the profiled inner surface of the endless conveyor. The pulleys may be provided with flanges, and the endless conveyor may be provided with complementary longitudinal grooves. Preferably, however, the pulleys are grooved circumferentially, and the endless conveyor is

provided with complementary ribs, teeth or lugs along its inner surface. Circumferential grooves may be formed in the pulleys whereby hydrodynamio separation between the conveyor and the pulleys may be minimised. The pulleys may be formed as open assemblies through which water may flow. If desired, however, pulleys may be formed with sealed internal voids such that flotation forces are imparted to the pulleys when immersed in water.

The endless conveyor may operate within the water with its side edges exposed. Preferably, however, the endless conveyor is enclosed between channel side walls such that circulation of water from the high-pressure side of an immersed fin to the low-pressure side of the fin is minimised. If desired, the side walls may be retractable, such that they may be retracted for operation in shallow water. Portions of the side walls may be formed of flexible materials, whereby damage due to contact with solid articles may be minimised.

The frame may be mounted within a slot within a boat hull, and the side walls of the slot may be utilised as the channel side walls. Of course, the side walls may be utilised as the frame if desired, and may be formed integral with the hull of the boat. Alternatively, the frame may be adapted for mounting external to a boat, such as at the rear, the sides, the front or the underside of the boat. The frame may be mounted to the boat via mounting means such that the frame is tiltable about a transverse axis whereby the tilt angle of the frame may be adjusted to improve the performance of the propulsion Unit or to stow the propulsion unit when it is not in use.

The frame may also be mounted on support means such that it may be raised or lowered to control the height of the propulsion apparatus relative to the water level.

The tilt may be controlled by supporting a portion of the frame remote from the transverse axis by tensioning means the length of which may be adjustable. Alternatively, an actuator, a spring, or damper may be placed between the frame and the boat to control the tilt. A transverse fin or foil may be mounted on the frame, and may be independently tiltable to produce vertical force components whereby the attitude of the boat or the propulsion unit may be controlled. The transverse fin may also function as a water deflector if desired, and may be made buoyant or non-buoyant as desired.

The boat may be fitted with a conventional rudder for steering. Preferably, however, the frame* is rotatable with respect to the boat about a vertical axis and steering means is associated with the frame whereby the propulsion unit may be rotated transversely to steer the boat. Alternatively, steering may be effected by means of a vertioal fin pivotably mounted about a vertical axis on the frame.

A deflector may be disposed rearward of the endless conveyor, extending rearwardly and upward from the endless conveyor whereby water splash from the endless conveyor as it exits the water is deflected rearwardly.

In another aspect, this invention resides in an amphibious vehicle having a plurality of marine propulsion units substantially as defined above. The propulsion units may be adapted to support and propel the vehicle on land, and the propulsion units may include pneumatically-tyred wheels mounted co-axially with the pulleys. The amphibious vehicle may have further wheels adapted to drive or steer. The drive elements may be flexible or collapsible such that the weight of the vehicle may be supported on the ground through the endless conveyors with minimal damage to the drive elements. The pulleys around which the endless conveyors pass may be

conventional rigid pulleys, but preferably the pulleys are formed from dual pneumatic tyre assemblies, the gap between the dual tyres engaging with lugs or ribs on the internal surfaces of the endless conveyors to locate the endless conveyors transversely. Alternatively, a single pneumatic tyre formed with a circumferential groove may be used.

Alternatively, a pulley may be mounted in conjunction with a pneumatically-tyred wheel or wheels, and the diameter of the pulley may be smaller than the outside diameter of the pneumatic tyre. The vehicle may then be supported on the ground on the tyre or tyres such that the endless conveyor is supported clear of the ground, and the pulley and the wheel may be driven by common drive means.

In a further aspect, this invention resides in sub-marine propulsion apparatus including:- a supporting frame; an endless conveyor having upper and lower runs and supported by said supporting frame, said endless conveyor supporting a plurality of longitudinally-spaced drive elements disposed along its outer surface; drive means for driving said endless conveyor, and said drive elements being adapted for driving during motion along one run of said endless conveyor.

Preferably, the drive elements are in the form of fins which may be erected by erection means such that they may be adapted for driving along one run of the conveyor and which may be collapsed into a non-driving attitude along the other run of the conveyor. Of course, if desired, other means of providing differential drive forces along the two runs, such as shrouding one run to minimise water entry along that run, may be used. The shrouding means may be in the form of a top cowling adapted to entrap air during submergence, or to be filled with air or gas to minimise water intrusion.

In order that this invention may be more easily understood and put into practical effect, reference will now be made to

the accompanying drawings which illustrate a preferred embodiment of the invention, wherein:-

FIG. 1 is a pictorial view of a marine propulsion apparatus; FIG. 2 is a pictorial view of an alternative marine propulsion apparatus;

FIG. 3 is a pictorial view of a further alternative marine propulsion apparatus;

FIG. 4 is a side view of marine propulsion apparatus adapted for mounting outboard of a boat;

FIG. 5 is a side view of an amphibious vehicle;

FIG. 6 is a pictorial view of another alternative marine propulsion- apparatus, and

FIG. 7 is a pictorial view of yet another alternative marine propulsion apparatus.

The marine propulsion apparatus 10 shown in FIG. 1 has a frame 11 on which are rotatably mounted a front pulley 12, an intermediate pulley 13 and a rear pulley 14.

A belt 15 passes around the pulleys 12, 13 and 14, and a tensionβr 16 forces the shaft carrying the rear pulley 14 along the frame 11 to tension the belt 15. The belt 15 has a rib 17 projecting from its inner surface and the rib 17 engages with circumferential grooves 18 in the pulleys 12, 13 and 14 to locate the belt 15 transversely. A hydrostatic drive motor 19 is mounted on the frame 11 and drives the front pulley 12. Fins 20 are attached through fin flanges 21 to the outer surface of the belt 15 by means of fasteners 22. Fin side plates 23 brace the fins 20, and are also attached to the belt 15 with fasteners 22. The frame 11 has apertures 24 in its mounting plate 25 to enable it to be attached to a boat hull.

In use, the hydrostatic drive motor 19 is energised to rotate the front pulley 12, and the belt 15 is drawn around

the pulleys 12, 13 and 14. In the belt section between the front pulley 12 and the intermediate pulley 13, the fins 20 react with the water to produce a thrust on the frame 11. In the section of belt between the intermediate pulley 13 and the rear pulley 14, the fins 20 exit from the water at an acute angle, and the majority of the water carried ahead of the fins 20 is ejected to the rear of the apparatus.

The marine propulsion apparatus 30 shown in FIG. 2 has a frame 31 on which are rotatably mounted a front pulley 32, an intermediate pulley 33 and a rear pulley 34.

A belt 35 passes around the pulleys 32, 33 and 34, and a tensioner 36 forces the shaf carrying the rear pulley 34 along the frame 31 to tension the belt 35. The belt 35 has a rib 37 projecting from its inner surface and the rib 37 engages with circumferential grooves 38 in the pulleys 32, 33 and 34 to locate the belt 35 transversely.

Pocket fins 39 are formed with rear faces 40 and side faces 41, and are attached to the belt 35 through flanges 42 by means'of fasteners 43. The use of the marine propulsion apparatus 30 is similar to the use,of the marine propulsion 10, but the pocket fins 39 may collapse to permit the lower run of the belt 35 to be supported on land.

The marine propulsion apparatus 50 shown in FIG. 3 has a frame 51 on which are rotatably mounted a front pulley 52, an intermediate pulley 53, and a rear pulley 54. The rear pulley 54 has a recess 55 formed centrally in its circumferential surface.

A belt 56 passes around the pulleys 52, 53 and 54, and a tensioner 57 forces the shaft carrying the rear pulley 54 along the frame 51 to tension the belt 56. The belt 56 has a rib 58 projecting from its inner surface and the rib 58 engages with circumferential grooves 59 in the pulleys 52 and

53 to locate the belt 56 transversely.

Fins 60 are attached to the side portions of the outside surface of the belt 56 by flexible hinges 61, and have lugs 62 extending downward from the fins 60 in the centre portion of the belt 56. Springs 64 bias the fins 60 into an upright attitude with respect to the belt 56.

In use, the belt 56 is tensioned by operating the tensioner 57. The tensioned belt 56 develops a central groove 63 in the runs 64 and 65 which lead away from the recessed rear pulley 54. The drive is then operated to drive the belt in forward rotation from the front pulley 52 to the intermediate pulley 53 and then on to the rear pulley 54. As the belt 56 passes between the rear pulley 54 and the front pulley 52, the centre portion of the belt 56 rises, engaging with the lugs 62 on the fins 60, thus causing the fins 60 to be raised into an attitude extending away rom the belt 56 and braced in this attitude.

The fins 60 remain propped in the extended position as they pass around the front pulley 52 and the intermediate pulley 53. As they approach the rear pulley 54, the belt 56 falls away from the lug 62 as the central groove 63 forms, and the fin 60 is no longer propped in place. The fin 60 then pivots about the hinges 61 and swings backward along the belt 56 under the pressure of the passing water. The fin 60 remains in this position until it passes over the rear pulley 54, and then as the central groove 63 is pulled out of the surface of the belt 56, the process of erecting the fin 60 begins again.

While passing between the front pulley 52 and the intermediate pulley 53, the fin in its extended attitude exerts a force on the water whereby a forward thrust is produced on the frame 51. As the fin passes between the intermediate pulley 53 and the rear pulley 54 and begins to

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fold back, the fin 60 no longer engages with the water, and thus water carryover as the fin 60 exits the water is minimised.

The outboard propulsion apparatus 100 shown in FIG. 4 has 5 a frame 101 on which pulleys 102 are rotatably mounted. An endless belt 103 passes around the pulleys 102 and carries drive elements 104. The frame 101 is pivoted on a trunnion 105 mounted on the transom 106 of a boat 107. A control bracket assembly 108 limits the travel of the frame 101 as it iO pivots about the trunnion 105. A rudder 109 is pivoted vertically on the rear of the frame 101, and a trim foil 110 is pivoted horizontally on the rear of the frame.

A water deflector 111 deflects water spray from the apparatus away from the rear of the hull. 15 Referring now to FIG. 5, it will be seen that the amphibious vehicle 70 has a hull 71 with a pair of propulsion assemblies 72 mounted beneath the hull 71. Each of the propulsion assemblies 72 has a front pulley 73, an intermediate pulley 74, a rear pulley 75, and a series of 20 idler pulleys 76 rotatably mounted on shafts to a frame 77. An endless belt 78 passes around the pulleys 73, 74, 75 and 76, and drive pockets 79 are attached to the outer surface of the endless belt 78. The drive pockets 79 adopt a extended attitude when travelling along the lower run 80 of 25. the endless belt 78, and are adapted to fold into a contracted position along the angled run 81 of the endless belt between the intermediate pulley 74 and the rear pulley. A trim foil 82 is mounted in a lower position at the rear of the hull 71, and a deflector 83 is mounted above the water 0 level at the rear of the hull 71.

The propulsion apparatus 90 shown in FIG. 6 has flexible pockets 91 attaohed along opposed edges 92 to a belt 93 with fasteners 94. The belt 93 is used in conjunction with a

front pulley 95 and an intermediate pulley 96 of concave profile and a rear pulley 97 of cylindrical profile. Reversing pockets 98 are attached to the belt 93 in the reverse orientation to the pockets 91 to provide drive thrust in reverse operation.

In use, the propulsion apparatus 90 is partly immersed in water and then operated in forward drive mode by using drive means to rotate the pulleys 95, 96 and 97 and thus cause the belt 93 to travel around the pulleys 95, 96 and 97. As the pockets 91 pass around the concave front pulley 95, the belt 93 assumes the concave shape of the pulley 95, allowing the distance between the opposed edges 92 to foreshorten and permitting the pocket 91 to open. In passing between the concave intermediate pulley 96 and the cylindrical rear pulley 97, the belt 93 flattens and the pocket 91 contracts, expelling the entrapped water.

The marine propulsion apparatus shown in FIG. 7 has a front pulley 120 and an intermediate pulley 121 with cylindrical outer surfaces and a rear pulley 122 with a central recess 123. Outer belts 124 pass around the front, intermediate and rear pulleys 120, 121 and 122, and an inner belt 125 passes around the front and intermediate pulleys 120 and 121 between the outer belts 124.

Fihs 126 are attached to the outer belt 124 by hinges 127, and lugs 128 project downward from the centre portion of the fins 126.

In use, the drive is operated to drive the outer belts 124 in forward rotation from the front pulley 120 to the intermediate pulley 121 and then on to the rear pulley 122, and the inner belt 125 from the front pulley 120 to the intermediate pulley 121. As the outer belts 124 pass around the rear pulley 122, the fins 126 are free to pivot around the hinges 127. As the outer belts 124 approach the upper

side of the intermediate pulley 121, the lugs 128 engage with the inner belt 125, thus causing the fins 126 to be raised into an attitude extending away.from the belts 124 and 125. The fins 126 remain propped in this attitude, as the belts 124 and 125 pass along the run between the front pulley 120 and the intermediate pulley 121. After the inner belt 125 has passed around the intermediate pulley 121, the fin 126 is no longer propped by. its lug 128, and oan swing back around the hinges 127 to lie along the belts 124 such that the fins 126 no longer provide drive through the water.

It will of course be realised that while the above has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the.broad scope and ambit of this invention as is defined in the appended claims.