SAFETY STRUT ASSEMBLY FOR HYDROFOIL CRAFT

Abstract

Safety strut assembly (9) for a hydrofoil craft (1) comprising a strut (12), which is attached to the hull (10) of the craft by means of a transverse oriented strut axle (40) for pivotal movement with respect to the hull, the assembly further comprising: a control rod (33) passing down through the strut (12); a linear actuator assembly (28); a hydrofoil (13) pivotally mounted to the bottom portion of the strut (12) about a transverse oriented foil axle (35); first linkage means (34) connecting the hydrofoil (13) to the control rod (33); wherein the first linkage means (34) comprises a first drive ring (48) mounted around the foil axle (35), wherein the first drive ring is provided with one first ring cam element (45), and wherein the foil axle (35) is provided with one foil axle cam element (46).

Claims

1. A safety strut assembly for a hydrofoil craft comprising: a strut, which is attached to a hull of a craft by means of a transverse oriented strut axle for pivotal movement with respect to the hull; a control rod passing down through the strut; a linear actuator assembly; a hydrofoil pivotally mounted to a bottom portion of the strut about a transverse oriented foil axle; first linkage means connecting the hydrofoil to the control rod to vary angular orientation thereof; and second linkage means connecting the linear actuator assembly to the control rod; wherein the first linkage means comprises a first drive ring mounted around the foil axle, wherein the first drive ring on its radial inner surface is provided with at least one first ring cam element, wherein the foil axle on its radial outer surface is provided with at least one foil axle cam element, and wherein the at least one foil axle cam element and the at least one first ring cam element are arranged to mutually engage and disengage.

2. The safety strut assembly according to claim 1, wherein the at least one first ring cam element is arranged to engage the at least one foil axle cam element and pivot the foil axle when a pulling force is exerted on the first linkage means by the control rod.

3. The safety strut assembly according to claim 1, wherein the foil axle freely pivotable away from the engaging position of the at least one foil axle cam element with the at least one first ring cam element.

4. The safety strut assembly according to claim 1, wherein each of the foil axle and the first drive ring is provided with three first cam elements that are equally spaced apart, so that foil axle and the hydrofoil freely pivotable over at least 85° degrees.

5. Safety strut assembly (9) according to claim 1, wherein the second linkage means comprises a transverse oriented actuator axle, the actuator axle being coaxial with the strut axle, the second linkage means further comprising: a second drive ring mounted around the actuator axle, wherein the second drive ring on its radial inner surface is provided with at least one second ring cam element, and wherein the actuator axle on its radial outer surface is provided with at least one actuator axle cam element, wherein the at least one actuator axle cam element and the at least one second ring cam element are arranged to mutually engage and disengage.

6. The safety strut assembly according to claim 5, wherein the at least one actuator axle cam element is arranged to engage the at least one second ring cam element and pivot the second drive ring when a pushing force is exerted on the second linkage means by the linear actuator assembly.

7. The safety strut assembly according to claim 5, wherein the second drive ring freely pivotable away from the engaging position of the at least one second ring cam element with the at least one actuator axle cam element.

8. The safety strut assembly according to claim 5, wherein the actuator axle and the second drive ring each are provided with three second cam elements that are equally spaced apart, so that the second drive ring of the second linkage means is freely pivotable over at least 85° degrees.

9. The safety strut assembly according to claim 5, wherein a foil spring is provided between the strut and the foil axle, wherein the foil spring is tensioned by retracting the strut into a horizontal hull-borne position within a recess of the hull, so that the tensioned foil spring rotates the foil axle and the attached hydrofoil into a safe vertical transport position.

10. The safety strut assembly according to claim 1, wherein the linear actuator assembly is arranged for exerting pushing forces to the second linkage means and the control rod.

11. The safety strut assembly according to claim 10, wherein the second linkage means comprises a spring element, biasing the second linkage means in the pushing direction of the linear actuator assembly.

12. The safety strut assembly according to claim 11, wherein the spring element is a compression spring.

13. The safety strut assembly according to claim 1, wherein the assembly further comprises a retraction assembly comprising a retraction actuator and retraction linkage means connected to the strut, the retraction assembly being adapted to pivot the strut aftward and forward in a keel direction about the strut axle.

14. The safety strut assembly according to claim 13, wherein the foil axle, being a centre of rotation of the hydrofoil, is not coinciding with the centre of pressure of the hydrofoil in the keel direction of the craft, thereby enabling varying the angular orientation of the hydrofoil by a single direction displacement of the control rod and the first linkage means in a height direction of the craft.

15. The safety strut assembly according to claim 14, wherein the centre of rotation of the hydrofoil is located before the centre of pressure of the hydrofoil in the keel direction of the craft.

16. The safety strut assembly according to claim 15, wherein the first linkage means is located before the centre of rotation of the hydrofoil in the keel direction of the craft, thereby enabling varying the angular orientation of the hydrofoil by a puling force and displacement of the control rod in the height direction of the craft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention and the following detailed description of certain embodiment thereof may be understood by reference to the following figures.

[0043] FIG. 1 shows is a side view of a typical hydrofoil craft in foil-borne operation;

[0044] FIG. 2 shows a perspective view of the hydrofoil craft of FIG. 1;

[0045] FIG. 3 shows a side view of the bow strut with retraction means of FIGS. 1 and 2;

[0046] FIG. 4 shows a side view of the bow strut AoA control assembly;

[0047] FIG. 5 shows a perspective view of the bow strut with hydrofoil;

[0048] FIG. 6 shows a bottom view of the hydrofoil of the bow strut;

[0049] FIG. 7 shows a fragmentary sectional view, detailing the second linkage means of the bow foil axle;

[0050] FIG. 8 shows a rear view of the bow strut with retraction assembly and actuator assembly;

[0051] FIG. 9 shows a cross-sectional view of the bow strut with control rod and first and second linkage means;

[0052] FIG. 10 shows in more detail the first linkage means of FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

[0053] The invention is now described by the following aspects and embodiments, with reference to the figures.

[0054] For convenience of interpretation of the figures, the following terms are used. The terms vertical, horizontal and straight are to be understood as substantially vertical, horizontal respectively straight, whereby horizontal meaning: in the transverse direction of the width of the craft parallel to the waterline, whereby vertical meaning: in de height direction, perpendicular to the water surface, whereby the keel direction meaning: perpendicular to the transverse direction parallel to the water surface, from the stern to the bow.

[0055] FIGS. 1-2 show an overview of a hydrofoil craft for the safety strut assembly according to the invention.

[0056] Arrow V indicates the vertical direction, directing upwards from the water; arrow H indicates the transverse direction, directing from starboard to port side of the craft; arrow K indicates the keel direction, directing from the stern to the bow.

[0057] FIG. 1 shows a side view of a typical hydrofoil craft 1 which is here illustrated in foil-borne operation, traveling at high speed, indicated by arrow 11, above the water surface 17. Safety strut assembly 9 at the bow of the craft comprises a strut 12, which is supported on the hull 10 of the craft in a manner to permit pivotal movement in the aft direction of arrow 20 but is normally held against such movement during foil-borne operation by substantially rigid restraining means. The strut is retracted in the aft direction indicated by arrow 20 in a recess in the hull when hull-borne operation of the craft is desired. For foil-borne operation of the flight, the strut is repositioned in the extended position. If an impact force, or a force in excess of the normal load, is applied to the strut, it is adapted to yield and permit pivotal movement in the aft direction indicated by arrow 20.

[0058] Furthermore, a floating (semi)submerged object 18 is shown that could cause a collision, indicated by arrow 19.

[0059] FIG. 2 shows a perspective view of the typical hydrofoil craft 1 of FIG. 1, which craft is illustrated here as including a pair of hydrofoils, there being a bow foil 13 mounted on the bow strut 12 beneath the bow of the craft and a second hydrofoil 15 mounted on two vertical struts 14 beneath the stern of the hull 10 of the craft. The stern struts 14 are provided with propellers 16 for propulsion of the craft. The type of propulsion for the craft is not essential for the invention. A mechanical propulsion may be provided, but also alternative propulsions may be provided, like a hybrid diesel electrical propulsion, a waterjet or an electrical propulsion including batteries for storage of electrical energy. Nevertheless, it has to be understood that other means of propulsion may be employed without departing of the gist of the invention.

[0060] FIG. 3 shows a side view of the bow strut retraction mechanism 7, here illustrating the movement indicated by arrow 20 of the bow strut 12 with the bow foil 13 when being retracted into the boat's hull.

[0061] The bow strut retraction mechanism 7 comprises a retraction actuator 25 and retraction linkage means 24. When hull-borne mode operation is required, the bow strut 12 can be retracted aftward and upward about a bow strut axle 40 into a recess 8 provided in the hull 10, by means of the retraction linkage means 24. When foil-born mode operation is desired, the bow strut 12 is moved into the upright, extended position by the bow strut retraction mechanism 7.

[0062] A safety release system (also indicated by mechanical fuse device) is provided to the bow strut retraction mechanism, which release system ensures that the bow strut retracts and moves aftward and upward upon meeting an obstruction such as submerged object 18 (see FIG. 1). The safety release system may be of any suitable type, it may be designed simply to rupture and release the strut, permitting it to swing in the aft direction in response to the impact force. The safety release system thus functions as a mechanical fuse device by rupturing or failing in a predetermined manner. The mechanical failure is thus confined to an easily replaceable element or device and any other structural damage is prevented or minimized. In the embodiment shown, a breaking pin 23 is mounted between the retraction actuator 25 and the retraction linkage means 24. The breaking pin 23 ruptures upon striking a sizable submerged object 18 by the bow strut 12 permitting the bow strut and the bow foil 13 to yield and to move aftward and upward into recess 8 according to arrow 20.

[0063] This safety release system limits or reduces the possible structural damage by providing a predetermined failure path. However, when during the retraction movement in the direction of arrow 20 the bow foil 13 remains in fixed position and orientation with respect to the bow strut, a large negative AoA will occur which will decelerate the craft and will cause a downward deceleration dragging the craft downwards into the water. The linkage system according to the invention permits the bow strut 12, in response to the impact force of arrow 19 of a floating or submerged object 18, to make a pivotal movement in the direction of arrow 20 in the aft direction, while keeping the foil in the horizontal position 21 in the water flow 26. As a result, abrupt deceleration is prevented, allowing the craft to slow down and to settle onto the water 17 at a safe rate of deceleration.

First Embodiment

[0064] FIGS. 4-6, 9 show a first embodiment of the safety strut assembly for the hydrofoil craft 1 according to the invention.

[0065] FIG. 4 shows a side view of the foil Angle of Attack (AOA) control mechanism of the bow strut, here illustrating the position of the main components, including the foil 13, second linkage means 27, actuator axle 41, spring element 29 and linear actuator assembly 28.

[0066] FIG. 5 shows a perspective view of the foil 13 and the strut 12, with a fragmentary sectional view illustrating: the mechanism to control the AOA of the foil 13, control rod 33, first linkage means 34, foil axle 35, the Center of Pressure (COP) line 36, the Center of Rotation (COR) line 37, and foil spring 44.

[0067] FIG. 6 shows a bottom view of the foil 13, illustrating that the position of the Center of Rotation (COR) line 37 is placed in front of the Center of Pressure (COP) line 36. FIG. 9 shows the strut 12 of the retractable safety strut assembly according to the invention, with second linkage means 27 and first linkage means 34 connected by control rod 33.

[0068] FIGS. 4 and 9 show in more detail the hydrofoil control mechanism in the strut 12 for maintaining the optimal orientation of the craft during foil-borne mode traveling of the craft. Linear actuator assembly 28 is connected with second linkage means 27 to control rod 33. Control rod 33 extends downward through the bow strut 12 to first linkage means 34. First linkage means 34 connects the control rod 33 to the hydrofoil 13. The linear actuator assembly 28 is now able to adjust the AoA of the hydrofoil 13 and maintain the optimal position of the craft during foil-born travel.

[0069] In FIGS. 5-6 is shown, that according to the invention the Center of Rotation (COR) line 37 of the hydrofoil 13 is not coinciding with line of the Center of Pressure (COP) 36 of the hydrofoil 13. Thus, during travel/flight or movement through the water of the hydrofoil, the pressure of the water, exerted on the hydrofoil, will force the hydrofoil into an (safe) orientation determined essentially by the mutual distance and position of the COR and the COP.

[0070] The non-coinciding placement of the COR 37 and the COP 36, compared to a coinciding COR 37 and COP 36, has the advantage that a single direction displacement of the control rod 33 is sufficient in controlling the orientation of the foil 13. If the COR 37 and COP 36 were coinciding, e.g. were located in the same position, this would result in requiring both push and pull forces for controlling the orientation and the AoA of the foil 13, so that the control rod 33 must be a fixed connection between the linear actuator assembly 28 and the foil 13. Having non-coinciding COR and COP, and a single direction displacement of the control rod 33, allows for an intrinsically safe foil 13, which has the freedom to return to its safe orientation by the pressure exerted by the flowing water.

[0071] In a more advanced embodiment as shown in FIGS. 5-6, the Center of Rotation (COR) line 37 is positioned in front of the line of the Center of Pressure (COP) 36 of the bow foil 13. Thus, during travel/flight, the trailing portion 51 of the bow foil is moved upward and the leading portion 50 is moved downward into a negative AoA creating a downward acceleration of the craft.

[0072] Positioning the COR 37 of the hydrofoil before the COP 36 creates an intrinsically safe negative AoA of the hydrofoil during travel/flight of the craft and a force on the control rod during movement of the foil-borne craft through the water. As a result, the negative AoA will force the craft to switch to the intrinsically safe hull-borne mode, e.g. in case of fault or breakdown of the electric systems. Furthermore, the intrinsically safe orientation of the foil 13 is advantageous during the start of the travel of the craft, when the craft is hull-borne. The intrinsically safe negative AoA of the foil 13, when not actuated, ensures that switching from hull-borne mode to foil-borne mode is only possible with electrical control systems working properly.

Second Embodiment

[0073] FIGS. 5-6 and 9-10 show in more detail the first linkage means 34 according the invention for maintaining the foil 13 in a safe horizontal position, parallel to the water surface 17 and in the direction of movement 11 of the craft, during retraction of the bow strut 12.

[0074] FIGS. 5 & 10 show the bottom part of the strut 12 and the foil 13 at the bow of the craft. The control rod 33 passes down through the strut 12 (see FIG. 9) from the linear actuator assembly 28 (see FIG. 4). The foil 13 is pivotally mounted on the strut 12 in a manner that it is controlled by the linear actuator assembly 28 by means of control rod 33 and generates lift when the strut is in the extended position and locked in place. In case the strut 12 makes a pivotal movement 20 in the aft direction, the foil 13 can move freely with the flow of the water 26 (see FIG. 3) thus not generating lift or decelerating the craft. Control rod 33 is connected through first linkage means 34 with foil axle 35. The first linkage means 34 comprise a first drive ring 48 mounted around the foil axle 35. The first drive ring 48 on the radial inner surface is provided with at least one first ring cam element 45 and the foil axle 35 on the radial outer surface is provided with at least one foil axle cam element 46. The first ring cam element 45 and the foil axle cam element 46 are arranged to mutually engage and pivot the foil axle 35, when the control rod 33 exerts a pulling force on the first linkage means 34 in the direction of arrow 47. A pulling force of the control rod 33 pivots the foil axle clockwise in FIGS. 5-6 and 10, thereby moving the leading portion 50 of the foil 13 upward and the trailing portion 51 downward creating an upward acceleration of the craft. The foil axle 35 is permitted to pivot freely counter-clockwise when the pulling force of the control rod 33 is removed or the strut 12 is retracted and moves aftward and upward into recess 8 of the hull 10 according to arrow 20 (see FIG. 3). As a result, the horizontal, parallel orientation of the foil 13 with respect to the water surface and the direction of the water flow 26 is maintained, so that abrupt deceleration of the craft is prevented and the craft can slow down and settle onto the water 17 at a safe rate of deceleration. In the embodiment of the invention shown in FIGS. 5, 9 and 10 three sets of engaging cam elements are provided, equally spaced apart, thereby permitting the foil axle 35 and the connected foil 13 to pivot freely over at least 85 degrees.

[0075] In FIG. 10 (circle X of FIG. 4) a foil spring 44 is mounted between the strut 12 and the foil axle 35. The foil spring 44 is tensioned when the strut is retracted and rotating aftward and upward in the direction of the recess 8 in the hull (see FIG. 3). When the strut 12 has reached position 22 after intermediate position 21, the foil spring 44 will rotate the foil axle 35 and the attached foil 13 counter clockwise into a safe vertical transport position.

Third Embodiment

[0076] FIGS. 7, 9 and 10 show a third embodiment of the hydrofoil craft 1 according to the invention.

[0077] FIG. 7 shows in more detail (circle VII of FIG. 4) the second linkage means 27, which connects the linear actuator assembly 28 (see FIG. 4) to the control rod 33. The second linkage means 27 comprises a second drive ring 54 mounted around the actuator axle 41. The radial inner surface of the second drive ring is provided with at least one second ring cam element 55. The actuator axle 41 on its radial outer surface is provided with at least one actuator axle cam element 56. The actuator axle cam element 56 and the one second ring cam element 55 are arranged to mutually engage and disengage. When a pushing force is exerted by the linear actuator on the second linkage means 27, the actuator axle 41 will pivot the second drive ring 54 counter clockwise, and will pull the control rod 33 upward in the direction of arrow 57. The second drive ring 54 is permitted to pivot freely further counter-clockwise when the strut 12 is retracted and moves aftward and upward into recess 8 of the hull 10 according to arrow 20 (see FIG. 3). Accordingly, by allowing free pivoting of the second drive ring 54 of the strut 12, the actuator axle 41 and the linear actuator assembly 28 are permitted to maintain their position and are not forced to follow the pivoting movement of the strut 12. Because the second ring cam element 55 disengages from the actuator axle cam element 56 of the actuator axle 41, the linear actuator assembly is allowed to maintain its position within the hull of the craft during the aftward pivoting of the strut 12.

[0078] In the embodiment of the invention shown in FIGS. 7 and 9 three sets of engaging cam elements are provided, equally spaced apart, thereby permitting the second drive ring 54 of the second linkage means 27 to pivot freely over at least 85 degrees.

[0079] The actuator axle 41 is coaxial with the strut axle 40, e.g. an axle in axle construction extending on two sides of the strut in the transverse direction of the craft. The actuator axle 41 is coaxial with the strut axle 40 to be able to retract and rotate the strut with the control rod.

[0080] FIG. 9 shows the strut 12 of the bow of the craft, as seen from port side, provided with a control rod 33 connected to first linkage means 34 comprising a first drive ring 48, and connected to second linkage means 27 provided with a second drive ring 54. Advantageously, this construction for the safety strut assembly allows for a safe and swift retraction of the strut, while minimizing the chance on damage to the control mechanism for the bow hydrofoil.

[0081] FIG. 8 is a cross-sectional view over line VIII-VIII in FIG. 1, which shows a rear view of the strut 12 with retraction assembly 7 and actuator assembly 28. Seen from starboard, a cross-section of retraction assembly 7 over line III-III is shown in FIG. 3. Seen from port side, a cross-section of actuator assembly 28 over line IV-IV is shown in FIG. 4. FIG. 9 is a cross-sectional detailed view over line IX-IX in FIG. 8, as viewed from port side of the craft.

[0082] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “to comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The term “and/or” includes any and all combinations of one or more of the associated listed items. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The article “the” preceding an element does not exclude the presence of a plurality of such elements. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.