This invention relates to apparatus for providing a propulsive force in water.

There are various known types of apparatus for providing a propulsive force in water. For example, the apparatus may be fins or flippers worn on the feet of swimmers. The apparatus may alternatively be hand paddles or webbed gloves worn on the hands of swimmers and for providing an increase in the effective area of the power stroke of swimmers. For speed, the preferred swimming stroke is the crawl, but the crawl has the disadvantage that the swimmer's head is under the water for much of the stroke, and there is little opportunity for the swimmer to look forwards. Whilst the crawl reduces the drag due to forward motion of the arms by raising them above the water, the crawl does involve the extra effort of lifting the arms above the water.

Other types of known apparatus for providing a propulsive force in water include hydrotherapy and aqua-fitness equipment such for example as fins and dumbbells. These types of equipment are usually of limited size on account of portability and storage.

Further types of known apparatus for providing a propulsive force in water may be oars or paddles which are of a one piece design with a rigid blade which is moved through water for a propulsive power stroke, and then lifted clear of the water for an idle stroke. The oars or paddles have a long handle which is used to increase the length of the stroke, but the long handle adds to the weight of the apparatus because it has to withstand bending stress. The blade has to be lifted against gravity on the idle stroke, or weight and inertia has to be added by using a counter-balanced handle at the rower end. A rowlock acts as a fulcrum for the oar. Traditional oars also have the disadvantage of requiring a waterway which is considerably wider than the water-borne craft, and they need skill in timing the removal, insertion and rotation of the blades during each part of a stroke.

Pedalo boats use a paddle wheel driven by a crank. The crank is driven by the feet of a user or users. Propellers on boats have shaped blades and the propellers are moved in a rotary fashion through water. The propellers are more expensive and more difficult to fabricate than oars and paddles. Generally paddle wheels and propellers all involve substantial mechanical components and expense in maintenance and repair.

Another type of known apparatus for providing a propulsive force in water is a punt pole for use in punting. The punt pole cannot be used in deep water, or when the water bed underneath the water is muddy or uneven.

It is an aim of the present invention to provide apparatus for providing a propulsive force in water, which apparatus reduces at least some of the above mentioned problems.

Accordingly, in one non-limiting embodiment of the present invention there is provided apparatus for providing a propulsive force in water, which apparatus comprises a frame, at least one flap, and at least one flexible tensile component, the apparatus being such that the flap is pivotally secured to the frame, and the flap is also connected to the frame such that when the apparatus is immersed in water and there is relative movement between the apparatus and the water, the flap moves about the frame according to the direction of relative flow, the flap rotates to an angle of lesser resistance in one direction of relative flow but to an angle of higher resistance in the opposite direction of relative flow, and the flap is restrained in the angle of higher resistance by the flexible tensile component thereby to transmit a force in the flexible tensile component to the frame, and the apparatus also being such that at least one of the frame, the flap and the flexible tensile component is made of polymer material.

The apparatus of the present invention is advantageous in that it is lightweight due to bending or buckling stresses being minimised in stressed parts during the pull mode.

The apparatus of the present invention may be used by swimmers and divers. The apparatus is able to be operated with a reciprocating motion without withdrawal of the apparatus into air. The apparatus of the present invention may also be used by persons who are unable to swim conventional strokes due to joint replacement, or the fitting of prosthetic limbs. The apparatus of the present invention may also form part of boats, paddle boats and other water-borne craft.

The apparatus of the present invention may be one in which there is at least one of the flaps on each of two different faces of the frame. The flaps may be symmetrically arranged on opposite sides of the frame. The flap may have a concave area on at least one side. Alternatively or in addition, the flap may have at least one strengthening formation. The strengthening formation may be a rim. Other types of strengthening formation may be employed.

The flap may have at least one aperture. The aperture may be adjustable in size. If desired however the aperture may be a fixed aperture.

The apparatus may be one in which the flexible tensile component is of elastic material, enabling variable forces to be transmitted to the frame according to the amount of extension of the elastic material from its natural length.

The apparatus may be one in which the flap is connected to the frame by the flexible tensile component.

The apparatus may be one in which the flexible tensile component is connected at one end to one of the flaps, and at the other end to another one of the flaps. The flexible tensile component may be secured to the frame by adjustable securing means.

The apparatus may be one in which the frame is an open-ended body, and in which the flap is mounted on the outside of the open-ended body. The open-ended body may be an open-ended cylinder.

Alternatively, the apparatus may be one in which the frame is an open- ended body, and in which the flap is mounted on the inside of the open-ended body. The open-ended body may be an open-ended cylinder.

The apparatus may include at least one inflatable compartment. The apparatus may include at least one compartment for being filled with buoyancy material for adjusting buoyancy of the apparatus.

The apparatus may include at least one hand holding formation on the frame.

The apparatus may include path-indicating means that protrudes above water level during use of the apparatus, and that indicates the direction of passage of the apparatus.

The apparatus may be one in which there is a plurality of the flaps facing in opposite directions, and in which the apparatus includes latching means for releasably latching at least some of the flaps in the lesser resistance position and at least some of the flaps in the higher resistance position, whereby the apparatus is able to operate in a forward direction and in a reverse direction consequent upon operation of the latching means. Additionally, if desired, the latching means may be for releasably latching all of the flaps in the lesser resistance position, whereby the apparatus is able to remain stationary. The stationary position of the apparatus may be regarded as a neutral position between forward and reverse direction positions. Preferably the latching means is a lever-operated device which has at least one recessed portion for receiving an edge of the flap.

The apparatus of the present invention may be used as or may form part of a swimming aid, an item of fitness equipment, an item for physiotherapy exercise, an item of survival equipment, a means of propulsive force, a means of propulsion, or a means of manoeuvre. The apparatus of the present invention is able to utilise forces required to move an object in the water. Minimum forces are required when the object is long, thin and smooth. When a flap plate of low mass is at right angles to the force, then movement of the plate involves a pressure being built up by the plate on one side, and a reduced pressure on the other side. These pressures reach a constant state when water flows around the plate and from surrounding areas of water. In the case of an open box that has filled with water and that is being moved in the direction of the opening, the object being moved has a mass corresponding to the mass of the water inside it. The object being moved then has inertia, and an additional force is required to move it. The additional force is equal to the mass multiplied by the acceleration. Such a force is limited only by the ability to apply it quickly over a distance. However, the energy so expended is negated when the object has to be pushed forward in the direction of motion again. In the apparatus of the present invention, the frame is the box, and an internal flap is able to be hinged at the forward end of the box. In this case, the flap can be arranged so as to enable the faster water to be discharged and replaced by still water, with little retarding effect during a forward stroke. The hinged flap in the forward end of the box is restrained by the flexible tensile component. In addition the flap may be restrained by a mesh across the forward end of the box, or by any protrusions or stops arranged on the flap and the body. Such additional restraint devices enable the flap to be made of a more flexible material.

When the apparatus of the present invention uses a single flap, then the flap may be hinged to the frame, and the apparatus may use the flexible tensile component such that the flap is able to rotate through an angle relative to the plane of the frame. Where pivoting is effected by a hinge or hinges, then the hinge or hinges may be at right angles to the preferred direction of motion, and the flap is able to present different resistance to motion according to its angle. In one direction of movement, the hinge or hinges are at the forward edges of the flap, and the flap is allowed to swing to a lower resistance angle so that there is little disturbance of the water. When the frame is moved in the opposite direction, i.e. during the power stroke, the force of water flow causes the flap to swing outward until it is restrained by the flexible tensile component or components extended between the flap and the frame. This is a position of greater resistance to the water. The remaining power stroke then causes an increased force of the water on the flap, and consequential propulsive force in the preferred direction.

An important feature of the apparatus of the present invention is that in use, it may have an outward swing that is in a direction such that it swings to the extent limited by the flexible tensile component. A means of ensuring a particular direction of swing may be employed, and such means may comprises spring components, stops on the frame restraining the swing in the lowest resistance angle, weights and curved features on the flap or the frame.

The flap and the frame may be finished in contrasting colours and patterns to assist in observation of the correct movements, to warn other users of its presence, and to increase visibility in rescue situations.

The pivot means, for example one or more hinges, is typically only required to open through an angle of up to 90° from an idle stroke position. The pivot means does not need precision since the flap does not have to fit closely into a frame. This enables straps or ties to be used which require less maintenance than conventional aligned hinges with bearings that have possible corrosion and lubrication effects.

The flexible tensile component may be pure tensile links such as lightweight strings, ribbons, elastic material, coil springs, ropes, wires, cables or chains. The flexible tensile component or components should not tangle when they are loose during the idle stroke of the apparatus. Restraining links can be provided with means for adjustment, thereby altering the maximum angle of the flap, the quantity of water affected, and the power of each stroke.

In the case that the flexible tensile component is of elastic material, such for example as a length of "shock cord" of natural length less than that when the flap is in the fully open position, then a different force may be applied during the power stroke which may be estimated from the angle of the flap. Moreover, the use of the elastic material also avoids the jerk which occurs when a non-elastic flexible tensile component reaches the conclusion of its movements. Such a steady application of force is beneficial to the user and involves less stress to the apparatus itself. When more than one flap on the apparatus is restrained by the elastic flexible tensile component, it naturally takes a proportion of the forces on the power stroke, such proportion of the force being observable by the angles of each flap.

In use of the apparatus of the present invention, the propulsive effect is obtained by applying a reciprocating motion to the frame. If forces are applied at the end of the frame away from the other pivot means, then the propulsive effect is to pull on the driving member. The frame pulls on the person or craft, and the forces in the frame are mainly tensile. If the forces are applied at the pivot end of the frame, then the device works as a pusher. Devices of this type can be positioned ahead or behind a person or craft for pulling or pushing a craft, a swimmer or a diver. Directional adjustments can be made by operating to one side of the direction of movement.

The apparatus of the present invention can be produced in right handed and left handed types for use on two sides of a craft, or for operation by right and left handed limbs of a swimmer or a diver, or for use on both limbs together if desired. If the apparatus is fitted to a craft, then the craft may be moved in the forward direction by the inertial energy of a reciprocating body, the natural backwards direction caused by the return stroke being resisted by the greater resistance of the flap.

The flap can be made to be self-compensating so that, at all parts of a stroke where the water speed is faster than the power stroke speed, the flap is maintained in its streamlined state.

For a flap that can only move in one direction from an idling position, the flexible tensile component may be fastened at any point on the flap, thus enabling the pivot means to take a different share of the forces. The shape of the flap can be varied as desired. Thus the shape of the flap may be varied from a flat rectangular shape in order to produce different degrees and areas of disturbance in the water. The flap may be larger at its bottom than its top, in order to provide a buoyant effect. The parameters controlling the propulsive forces are projected area at right angles to the frame, volume of water affected in each stroke, strength of components, and the difference between the resistance to the water when idling and when in a power stroke.

In the case of a flap which is free to swing to either side of an idle position, the positioning of the flexible tensile component or components may be determined by the need to prevent them wrapping around parts of the flap or the frame, and for the flap to have a useful effect whichever way the flap swings.

In the case of a flap hanging from a floating frame, the flap may have one or more weights in order to make a quicker transition from an idle position to a power position.

As indicated above, at least one of the components of the apparatus of the present invention is made from a polymer material. The polymer material may be a lightweight plastics material or a rubber. Depending upon the intended use of the apparatus of the present invention, the polymer material, for example the lightweight plastics material, may be chosen to comply with regulations for use in swimming pools, to resist chlorine and salt water, and to be resistant to fungal growth. The polymer material may be one that requires no surface finish or maintenance.

The apparatus of the present invention may take the form of a buoyant device that can be thrown to a person who is in danger of drowning, and thereby enabling the person to manoeuvre towards a place of safety.

The flap may be such that it has a very thin central portion, if the flap has stiffness or framing components. The stiffness or framing components can also affect the effective area of the flap when it is at different angles to the water flow direction. Since the flap is very simple and automatic in operation, the apparatus can be constructed to have large numbers of the flaps on submerged surfaces. Shorter flaps can be operated where the apparatus is to be used with shorter strokes. Short stroke apparatus is more suited to electrical and mechanical reciprocation at high frequencies. Such apparatus may have a propulsive effect from transmission of vibrational energy to the frame. In all embodiments of the invention, one or more flaps may be provided as desired.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which:

Figures 1a, 1b and 1c show first apparatus of the present invention;

Figures 2a, 2b and 2c show part of apparatus of the present invention;

Figure 3 shows second apparatus of the present invention;

Figures 4a, 4b, 4c and 4d show the operation of part of apparatus of the present invention;

Figure 5a shows further apparatus of the present invention;

Figure 5b and 5c show modifications to the apparatus shown in Figure 5a;

Figure 5d shows further apparatus of the present invention;

Figure 6a shows further apparatus of the present invention;

Figure 6b shows further apparatus of the present invention;

Figure 7 shows further apparatus of the present invention;

Figure 8 shows further apparatus of the present invention;

Figure 9 shows further apparatus of the present invention; Figure 10 shows further apparatus of the present invention;

Figure 11 shows yet further apparatus of the present invention; and

Figure 12a, 12b and 12c show reversible apparatus of the present invention.

Referring to the drawings, Figures 1a, 1b and 1c show apparatus of the present invention that employs a single flap. In Figure 1a, the frame 1 is stationary relative to a flow 12. A flap 2 hangs loosely. Flexible tensile components 3 are loose. Hinges 4 are in an intermediate position.

In Figure 1b, water 12a is flowing from left to right relative to the frame 1. The flowing water wafts the flap 2a towards the frame 1 with a light force, relative to an idle stroke. The frame 1 and/or the flap 2 have means to prevent the flap 2 from moving in an upwards direction.

In Figure 1c, water 12b is flowing from right to left relative to the frame 1 , forcing the flap 2b to take the position shown where the flexible tensile component 3 is tight. This relates to a power stroke.

Figure 2a, 2b and 2c show three unconventional hinge arrangements with two or more hinges being required for the flap 2. In Figure 2a, each hinge comprises a circular section nylon fishing line 4 passing through a hole 14 in the frame 1 , and through a hole 15 in the flap 2. The fishing line 4 is prevented by means of crimps 5 from pulling through the holes 14 and 15.

In Figure 2b, each hinge is formed by a nylon cable tie 4a that forms a loose loop when its end is pushed through a ratchet head 17. In Figure 2c, the margin 18 of the flap 2 is secured to the frame. The flexibility of the material of the flap 2, or a preformed angle, or a weakened area, allows the flap 2 to hinge to the idle and the power position.

Figure 3 shows an arrangement with the flaps 2 and 2a mounted symmetrically to opposite sides of the frame 1. The frame 1 is preferably in a vertical plane beneath the water surface. Whilst Figure 3 shows separate tensile components 3 connecting each to the frame 1 at position 19, an arrangement could be employed in which a single tensile component connects the flaps 2 and 2a.

Figure 3 also shows how the apparatus of the present invention comprising the frame 1 has flaps 2 that are able to swing to either side of an idle position. The apparatus has a suitable means for providing hinges or other pivots, and for attaching the flexible tensile component 3. The frame 1 is also shown in a vertical plane in order that the flaps 2 are equally submerged in each position of swing, even when the apparatus 2 is near the surface of the water.

There are many types of securing means that are able to secure the tensile components 3 to the frame and to the flap 2. Several such securing means are shown in Figures 4a, 4b, 4c and 4d. In Figures 4a, 4b, 4c and 4d, a tensile component 3 is fastened to the frame 1 and to the flap 2. Many other means of joining one component to another could be used.

In Figure 4a, the tensile component 3 is a plastics line which passes through holes 19 in the frame 1. The two ends then pass through holes 20 in the flap 2. The tensile component 3 is then secured by a plastic weld 21. In Figure 4b, the tensile component 3 is a plastics line which passes through holes 19 in the frame 1. The two ends then pass through two holes 20 in the flap 2, and they are secured by a crimp 5

In Figure 4c, the tensile component 3 is a plastics line which passes through holes 19 in the frame 1. The two ends pass through holes 20 and the flap 2, and they are secured by means of a screw clamp connector 22.

In Figure 4d, the tensile component 3 is a plastics line which is secured into a loop 23 by means of crimp 5. The loop 23 is then attached to the frame 1 by means of a replaceable fixing into the side of the frame 1 at one of the chosen points 25. The other end of the tensile component 3 is secured to the flap 2 by passing the tensile component 3 through a crimp 5 and holes 20 in the flap 2, and then securing to the end through the crimp 5. In an alternative embodiment (not shown) the loop 23 may be replaced by knots preventing the tensile component 3 from pulling through holes in the frame 1 and the flap 2.

The above description demonstrates various means for assembling the apparatus with the apparatus having a simple rectangular frame of the type shown in Figure 1. These means and others can be used to adapt the apparatus to have diverse forms of frame, with these forms being advantageous for particular applications in relation to a range of sizes, strengths and weights. Smaller sizes of frame for personal use may require means for attachment to persons in the case of amputees, or for holding in the hand by swimmers, divers or other pool or water users. Figure 5a shows a plate 25 having hand grips 26 at each end. The flaps 2 are attached to each side by a flexible section 27 permitting them to swing outwards until restrained by the flexible tensile components 3. Handles at each end enable the apparatus to be used in a push or pull exercise mode, or as a push or pull propulsion device operated with one or both hands. The apparatus can be used on the surface of water, or under water.

Figure 5b shows a flap 2 having cut-outs in the form of an array of holes 200 for the purpose of altering the resistance during that part of the stroke having higher resistance through the water. A flap with variable resistance may be achieved by fastening the plate 205 shown in Figure 5c by fastening means such for example as screws passing through slots 207 and 208 in the plate 205 and into holes 202 and 203 in the flap 2. The slots 207, 208 enable the plate 205 to be fastened to the flap 2 in positions from that shown by 204 where the holes are fully operated, to that shown by 201 where the holes are covered. Whilst these Figures illustrate a simple array of round holes in a flat flap 2 and a flat plate 205, it is to be appreciated that the principle may be applied to flaps of any shape and contour, and containing cut-outs of any shape and configuration.

Figure 5d shows a preferred adaptation of Figure 5a for use as a handheld swimming aid. A hand grip 126 is arranged at an angle to that of the hinges of the flap device 26 such that a swimmer holds them with their flaps in a near vertical plane, and the propulsive forces are in alignment with the swimmer's arm. A buoyant plate 125 is sandwiched between the two flap devices 27 such that the turning effect of one flap is opposite to the turning effect of the other flap. The flaps 2 are made of a thin plastics material such for example as polymers in the form of polypropylene, polyethylene, or polyvinyl chloride. Other thermoplastics and thermosetting compounds may be used. The flaps 2 are formed with ribs around their peripheries for added strength, and to improve the propulsive effect. A material such as polypropylene is suitable when a hinge or other pivot device is formed by reducing the thickness of surrounding material.

Figure 5d also shows a preferred water level 127 that is indicated on a plate 128 by a line 129. A swimmer is able more easily to use this adaptation of the invention, especially in waves of opaque open water. The illustrated square pattern 130 may be of a size known to spectators and trainers such that the distance and speed of a swimmer can be evaluated from a support vessel, or from onshore. The pattern 130 may also be used to show the plane of the hinges of the flap 2. The printed number 131 may be used to identify the swimmer, or the areas 130 and 131 may be used for any sort of advertising or illustrative graphic. A wrist strap (not shown) may be attached to the apparatus and to the swimmer. The flexible tensile components 3 may be formed of terylene ribbons. A closed cell foam may be used for the frame 125. The flaps may be attached to either side of the frame 125 by means of cable ties.

Figure 6a shows a flap 2 attached to the outside of a hollow cylinder 35, by similar means to the attachment to a flat frame. Further similar flaps can be attached at other positions. Such a construction has the advantage that certain flaps can be temporarily secured in the idle position using an elastic band 33 or other means. In the case of an amputee, the cylinder 35 can slip over the limb and be secured using suitable straps and padding. A handle 28 can be provided for a person to grip.

In Figure 6b, flaps 2 are attached to the inside of a hollow cylinder 25. A handle is attached to the outside of the hollow cylinder 35. The apparatus illustrated in Figure 6b has the advantage that the flaps 2 will not strike surrounding objects or persons. Also, added propulsive effort is produced from the movement of the contained body of water.

Figure 7 shows a square or rectangular open ended box section 30 with a flap 2 mounted inside it. Handles 31 can be provided in the different ends of the different sides. As in Figure 6, the design of the apparatus shown in Figure 7 benefits from the extra thrust of the contained body of water.

Referring to Figure 8, there is shown apparatus comprising flaps 2 which are attached to all four sides of a frame, and a handle 31 is fitted inside. Such a construction has the advantage that certain flaps can be temporarily secured in the idle position using the illustrated elastic band 34 or other means. This construction is suitable for a wide range of sizes due to its advantageous stress distribution. If required, the internal space 36 could contain buoyancy or ballast materials.

Figure 9 shows an example of the apparatus of the invention for use on the surface of water. In Figure 9, there is shown a frame 1 that mounts three flaps 2. The flaps 2 can be opened by weights 37. The flaps 2 may also be encouraged to open from the idle position by stops 38 in the frame 1. The apparatus shown in Figure 9 can be used in small size by swimmer, or in larger sizes operated by a man from a boat using a long handle attached to the frame at end 48 to pull the boat, or to push the boat by means of a handle attached to the other end 47. The flap 2 nearest the "pull" end 48 is connected to the frame 1 by means of tensile components 3. The other flaps may be connected one to the other by tensile components in positions 3b instead of being separately connected to the frame by the tensile components in positions 3a. The position of the tensile components in positions 3b could be any point on each flap.

Referring now to Figure 10, there is shown a floating craft 41 which contains a crank shaft 39 driven by feet 40. The crank shaft 39 drives a connecting rod 38 and thus propels the floating craft 41 by the reciprocating movement of a floating device 37. A frame enclosing a body of water as shown in Figure 6a or Figure 7 may be employed to give extra thrust. Also, the crank shaft 39 may be driven by an engine, an electric motor, or by a pneumatic or hydraulic device.

Figure 11 shows apparatus of the present invention comprising an inflatable frame 42. The frame 42 may be brightly coloured for visibility in rescue situations. The inflatable frame 42 may have compartments in order to provide dimensional stability to the positions of brackets 46 for securing flaps 44 at the hinge side and the flexible tensile component 3. Weights 45 are employed to ensure that the flaps 44 open at the start of each power stroke. Adjustable buoyancy may be obtained by having rigid compartments within the frame 42 that may be filled or part filled with water, liquid, sand or granular material. Referring now to Figures 12a, 12b and 12c, there is shown reversible apparatus 50 comprising a frame 52, flaps 54, 56 and flexible tensile components 58, 60. The flaps 54, 56 are hinged to the frame 52 at hinge points 62. The hinge points 62 are at opposite ends of the flaps 54, 56 with respect to the forward direction of the frame 52 as indicated by arrow 64. The flexible tensile component 58 connects the free end of the flap 54 to the frame 52. Similarly, the flexible tensile component 60 connects the free end of the flap 56 to the frame 52.

Figure 12a shows the apparatus 50 with opposing flaps 54, 56 as shown, and with no latching means. Figure 12b shows the apparatus 50 with latching means in the form of a lever-operated device 66. The lever-operated device 66 comprises an operating lever 68 to which is attached two recessed portions 70, 72. The recessed portion 70 is for receiving the pivoted end 74 of the flap 54. The recessed portion 72 is for receiving a pivoted end 76 of the, flap 56. In Figure 12b, the lever-operated device 66 has been operated such that the flap 54 is in the lesser resistance position, and the flap 56 is in the higher resistance position. This enables travel of the frame 52 in the forward direction as indicated by the arrow 64.

Figure 12c shows apparatus 78 which is like the apparatus 50 except that it has a lever-operated device 80 which is like the lever-operated device 66 but which has recessed portions 84, 86 for operating on the free ends 88, 90 of the flaps 54, 56 respectively. The apparatus 78 still operates in the forward direction of the frame 52 as indicated by the arrow 64. As shown in Figure 12c, the lever-operated device 80 is currently in a forward direction mode of operation indicated by the letter "F". If the lever-operated device 80 is moved to the left as shown in Figure 12 to the position marked "R", then the lever-operated device 80 causes the frame 52 to move in the reverse direction. An intermediate position of the lever-operated device between the forward movement position "F" and the reverse movement position "R" may be regarded as a neutral non-moving position and this position is indicated in Figure 12c by the letter "N".

It is to be appreciated that the embodiments of the description described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected. Individual components shown in the drawings are not limited to use in their drawings and they may be used in other drawings and in all aspects of the invention.