Folding Propeller for a Water Vehicle

Abstract

The present disclosure relates to a folding propeller (10) for a water vehicle, comprising a hub (12) which is drivable about a rotation axis (D) via a drive shaft, and a propeller blade (14) which is arranged on the hub (12) to be pivotable about a pivot axis (S) between a maximum closed position (P1) and a maximum open position (P2), wherein the pivot axis (S) defines, together with a normal (N.sub.D) to the rotation axis (D) which intersects the pivot axis (S), a maximum opening plane (E.sub.Max), wherein in the driven state and a pivot position of the propeller blade (14) in the region of the maximum open position (P2), at least one opening force acts upon the propeller blade (14) which results from rotation of the folding propeller (10) and in relation to the rotation axis (D) is directed substantially radially outwardly, wherein an effective force application point (EAP) of the opening force is arranged spaced from the maximum opening plane (E.sub.Max) and is substantially arranged in the closing direction (SR) of the propeller blade (14). The present disclosure further relates to a folding propeller (10) comprising a propeller blade (14) which has a reversal element (143) which is configured such that during rearward drive a reversed thrust (F.sub.reverse) acts upon the reversal element (143) and is directed substantially perpendicularly to the propeller blade longitudinal axis (L.sub.P) in the opening direction (OR) of the propeller blade (14).

Claims

1. A folding propeller for a water vehicle, the folding propeller comprising: a hub drivable about a rotation axis via a drive shaft, and a propeller blade arranged on the hub to be pivotable about a pivot axis between a maximum closed position and a maximum open position, wherein the pivot axis defines, together with a normal to the rotation axis which intersects the pivot axis, a maximum opening plane, wherein in a driven state and a pivot position of the propeller blade in a region of the maximum open position, an opening force acts upon the propeller blade which results from rotation of the folding propeller and in relation to the rotation axis is directed substantially radially outwardly, wherein an effective force application point of the opening force is arranged spaced from the maximum opening plane and is substantially arranged in a closing direction of the propeller blade.

2. The folding propeller according to claim 1, wherein the effective force application point of the opening force corresponds to a center of mass of the propeller blade, wherein one or both of the opening force is a centrifugal force or the effective force application point of the opening force corresponds to the center of pressure of an uplift body arranged on the propeller blade, wherein the opening force is an uplift force.

3. The folding propeller according to claim 1, wherein the folding propeller has a stop apparatus which defines the maximum open position of the propeller blade and the effective force application point of the opening force is arranged outside the maximum opening plane in the closing direction such that in the maximum open position of the propeller blade, an opening moment acts which presses the propeller blade against the stop apparatus.

4. The folding propeller according to claim 1, wherein the propeller blade has an additional body that is one or both of configured as an uplift body or configured as a mass body, wherein the uplift body is configured as a winglet and the mass body has a curved cylinder.

5. The folding propeller according to claim 1, wherein the propeller blade has a first propeller blade portion that is distally arranged, and a second propeller blade portion that is proximally arranged, wherein the first propeller blade portion is offset relative to the second propeller blade portion substantially in the closing direction.

6. The folding propeller according to claim 1, wherein the propeller blade has a propeller blade tip portion, a propeller blade shaft portion and a propeller blade root portion, wherein the propeller blade shaft portion is arranged between the propeller blade tip portion and the propeller blade root portion, and wherein one or both of the propeller blade shaft portion or the propeller blade tip portion is offset relative to the propeller blade root portion substantially in the closing direction of the propeller blade.

7. The folding propeller according to claim 6, wherein the propeller blade is configured such that a center of mass of the propeller blade is arranged distally in relation to a centroid of the propeller blade, wherein the center of mass of the propeller blade is arranged either in the propeller blade tip portion or in the propeller blade shaft portion.

8. The folding propeller according to claim 1, wherein the propeller blade has a propeller root, wherein the propeller root has a mounting apparatus for attaching the propeller blade to the hub and the mounting apparatus defines the pivot axis.

9. The folding propeller according to claim 6, wherein the propeller blade has an additional body that is configured as one or more of an uplift body or as a mass body, wherein one or both of the propeller blade tip portion or the additional body is formed of metal.

10. The folding propeller according to claim 9, wherein the propeller blade or the propeller blade tip portion is configured integrally with the additional body.

11. The folding propeller according to claim 6, wherein one or both of the propeller blade shaft portion or the hub is formed at least partially of plastics.

12. The folding propeller according to claim 6, wherein the propeller blade tip portion is one or both of connected form-fittingly or frictionally to the propeller blade shaft portion.

13. The folding propeller according to claim 6, wherein the propeller blade tip portion has a tongue which is one or both of cast into the propeller blade shaft portion or is connected to the propeller blade shaft portion via a releasable connection, in particular a screw connection.

14. The folding propeller according to claim 1, wherein a metal insert is embedded in the propeller blade.

15. A folding propeller for a water vehicle, the folding propeller comprising: a hub drivable about a rotation axis via a drive shaft, and a propeller blade arranged on the hub to be pivotable about a pivot axis, wherein the propeller blade has a reversal element, which is configured such that during rearward drive, a reversed force acts upon the reversal element and is directed substantially perpendicularly to a propeller blade longitudinal axis in an opening direction of the propeller blade.

16. The folding propeller according to claim 15, wherein the reversal element is arranged in a propeller blade tip portion.

17. The folding propeller according to claim 15, wherein the reversal element is arranged on the propeller blade to be pivotable about the pivot axis which is substantially parallel to the propeller blade longitudinal axis.

18. The folding propeller according to claim 15, wherein the reversal element is pivotable between a maximum folded-in position and a maximum folded-out position, wherein the reversal element assumes a maximum folded-in position when the folding propeller is in forward drive, wherein in the maximum folded-in position, the reversal element is oriented substantially aligned with the propeller blade, wherein the reversal element assumes the maximum folded-out position when the folding propeller is in rearward drive, wherein in the maximum folded-out position, the reversal element experiences the reversed force.

19. The folding propeller according to claim 15, wherein the reversed force generates an opening moment on the propeller blade via a lever to the pivot axis.

20. A drive for a water vehicle having a folding propeller comprising: a hub which is drivable about a rotation axis via a drive shaft, and a propeller blade which is arranged on the hub to be pivotable about a pivot axis between a maximum closed position and a maximum open position, wherein the pivot axis defines, together with a normal to the rotation axis which intersects the pivot axis, a maximum opening plane, wherein in a driven state and a pivot position of the propeller blade in a region of the maximum open position, an opening force acts upon the propeller blade which results from rotation of the folding propeller and in relation to the rotation axis is directed substantially radially outwardly, wherein an effective force application point of the opening force is arranged spaced from the maximum opening plane and is substantially arranged in a closing direction of the propeller blade.

21. A drive for a water vehicle having a folding propeller comprising: a hub drivable about a rotation axis via a drive shaft, and a propeller blade arranged on the hub to be pivotable about a pivot axis, wherein the propeller blade has a reversal element, which is configured such that during rearward drive, a reversed force-acts upon the reversal element and is directed substantially perpendicularly to a propeller blade longitudinal axis in an opening direction of the propeller blade.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Exemplary embodiments of the present disclosure are explained in detail below with the following description of the drawings. In the drawings:

[0077] FIG. 1 is a schematic partially sectional plan view of a folding propeller according to one embodiment;

[0078] FIG. 2a is a partially sectional plan view of a propeller blade of the folding propeller shown in FIG. 1 in a maximum closed position and in a middle open position;

[0079] FIG. 2b is a continuation of the view of FIG. 2a;

[0080] FIG. 3a is a schematic front view of a folding propeller according to a further embodiment;

[0081] FIG. 3b is a schematic side view of a propeller blade tip portion of a propeller blade;

[0082] FIG. 3c is a schematic side view of a propeller blade tip portion of a propeller blade;

[0083] FIG. 3d is a schematic front view of a tongue of a propeller blade tip portion of the propeller blade shown in FIG. 3a according to one embodiment;

[0084] FIG. 3e is a schematic front view of a tongue of a propeller blade tip portion of the propeller blade shown in FIG. 3a according to a further embodiment;

[0085] FIG. 4 is a schematic front view of a folding propeller with a propeller blade having a metal inlay according to a further embodiment;

[0086] FIG. 5 is a schematic partially sectional plan view of a folding propeller with a winglet according to a further embodiment;

[0087] FIG. 6 is a schematic cross-sectional view of an embodiment of the winglet shown in FIG. 5;

[0088] FIG. 7 is a perspective view of an embodiment of the winglet shown in FIG. 5;

[0089] FIG. 8 is a perspective schematic view of a water vehicle during rearward drive with a folding propeller according to a further embodiment;

[0090] FIG. 9a is a schematic front view of the propeller blade shown in FIG. 8;

[0091] FIG. 9b is a schematic side view of the propeller blade shown in FIG. 9a;

[0092] FIG. 10a is a schematic front view of the propeller blade shown in FIG. 8 during forward drive; and

[0093] FIG. 10b is a schematic side view of the propeller blade shown in FIG. 10a during forward drive.

DETAILED DESCRIPTION

[0094] Exemplary embodiments are described below making reference to the drawings. Herein, identical, similar or similarly acting elements are provided with the same reference signs in the different drawings, and repeated description of these elements is in part dispensed with for the avoidance of redundancy.

[0095] FIG. 1 shows a schematic partially sectional plan view of a folding propeller 10 according to a first embodiment. The folding propeller 10 comprises a hub 12 and two identical propeller blades 14.

[0096] In the text below, the present embodiments are illustrated for simplification on the basis of an individual propeller blade 14. For greater clarity, the reference signs in FIG. 1 are shown distributed over both propeller blades 14, although the two propeller blades 14 do not differ functionally or structurally.

[0097] The propeller blade 14 has a propeller root 15 which has a mounting apparatus 16 for attaching the propeller blade 14 to the hub 12. The hub 12 is rotatable about a rotation axis D and drivable via a boat drive shaft (not shown) to which it is connected for conjoint rotation. The mounting apparatus 16 defines a pivot axis S which is arranged perpendicularly to the rotation axis D. The propeller blade 14 is pivotable about the pivot axis S between a maximum closed position (P1, not shown) and a maximum open position P2. In the contact region of the propeller root 15 and the hub 12, the folding propeller 10 has a stop apparatus 18 which limits the opening of the propeller blade 14 and thus defines the maximum open position P2.

[0098] A normal N.sub.D to the rotation axis D crossing the pivot axis S defines, together with the rotation axis D, a maximum opening plane E.sub.Max of the propeller blade 14 or of the folding propeller 10. The maximum opening plane E.sub.Max can arbitrarily but does not necessarily correspond to the maximum open position P2, since the latter is defined by the stop apparatus 18, whereas the maximum opening plane E.sub.Max substantially depends upon the pivot axis. Rather, the maximum opening plane E.sub.Max serves to define the arrangement of effective force application points, for example, the center of mass MSP of the propeller blade 14. The center of mass MSP is spaced from the maximum opening plane E.sub.Max and is substantially arranged and/or displaced in the closing direction SR of the propeller blade 14. The opening direction OR and the closing direction SR correspond substantially to arc-shaped pivot movements of the propeller blade 14 when it is pivoted about the pivot axis S. The stop apparatus 18 is configured so that the center of mass MSP in the maximum open position P2 is spaced, in the closing direction SR, from the maximum opening plane E.sub.Max.

[0099] The propeller blade 14 has a first, distally arranged propeller blade portion 14a and a second, proximally arranged propeller blade portion 14b wherein the first propeller blade portion 14a is offset relative to the second propeller blade portion 14b substantially in the closing direction SR.

[0100] Accordingly, an advantageous spacing of the center of mass MSP in the closing direction SR in relation to the maximum opening plane E.sub.Max is achieved or increased. The center of mass MSP represents an effective force application point EAP of a centrifugal force that is suitable for generating an opening moment (see FIG. 2a, b).

[0101] Furthermore, the propeller blade 14 has a propeller blade tip portion 144, a propeller blade shaft portion 146 and a propeller blade root portion 148. In the embodiment shown in FIG. 1, the propeller blade tip portion 144 is connected to the propeller blade shaft portion 146 form-fittingly and frictionally and together they form the first propeller blade portion 14a, whereas the propeller blade root portion 148 forms the second propeller blade portion 14b. The first and second propeller blade portions 14a and 14b are firmly connected to one another so that a transmission of the propeller thrust forces is assured.

[0102] The propeller blade tip portion 144 has an additional body 142 which forms a propeller blade tip 19. In the present example, the additional body 142 is formed integrally with the propeller blade tip portion 144. The additional body 142 can be present in the form of an uplift body 142a, for example, in the form of a winglet 13 (see FIG. 5). The uplift body 142a can be configured such that, when the folding propeller 10 is driven, it experiences a dynamic uplift which is applied to the center of pressure DP of the uplift body 142a. The center of pressure DP thus represents an effective force application point EAP of the dynamic uplift that is suitable for generating an opening moment (see FIG. 5).

[0103] In the embodiment shown, due to the offset described above of the first propeller blade portion 14a relative to the second propeller blade portion 14b in the closing direction SR, an advantageous spacing of the center of pressure DP in the closing direction SR relative to the maximum opening plane E.sub.Max is also achieved or increased.

[0104] In the regions in which different propeller roots 15 can make contact with one another or can overlap one another, the propeller roots 15 of the two propeller blades 14 have spur gear toothing (not shown). This enables an interlocking of the propeller blades 14 and thus a synchronization of the pivot movements of the propeller blades 14.

[0105] Furthermore, in the embodiment shown, the propeller blade 14 is configured such that the center of mass MSP is arranged distally in relation to the centroid VSP of the propeller blade 14. In other words, the material density in the distal region of the propeller blade 14 is greater than in the proximal region. This is achieved, for example, in that the additional body 142 is present in the form of a mass body 142b (see FIGS. 3a and 3c). For example, the mass body 142b and/or the propeller blade tip portion 144 may thus be formed of metal. In general, the additional body 142 and/or the propeller blade tip portion 144 can be made of a material of higher density than the remainder of the propeller blade portions (for example, the propeller blade shaft portion 146 and propeller blade root portion 148). In the embodiment shown, the propeller blade shaft portion 146 consists of plastics.

[0106] The embodiment described above has the advantage that the folding propeller can be configured particularly weight-optimized, whereas the desired centrifugal force can be influenced by an arrangement of the center of mass as far distally as possible.

[0107] Additionally, the hub 12 is formed of plastics. This reduces the moment of inertia of the hub 12 and the hub 12 can be constructed with a larger diameter. By this means, the pivot axis S defined by the mounting apparatus 16 can be arranged with a greater spacing h (see FIG. 2) from the rotation axis D. This has the result that, in an opened pivot position of the propeller blade 14, the center of mass MSP and the center of pressure DP have a greater spacing from the rotation axis D, which in turn leads to an increase in the desired opening forces.

[0108] In the description of the following drawings, the relevant forces and moments will be considered, inter alia.

[0109] FIG. 2a shows a schematic plan view of the folding propeller 10 of FIG. 1, wherein a single propeller blade 14 is shown in two different pivot positions, specifically the maximum closed position P1 and a middle open position Pm. Starting from the maximum closed position P1, due to the rotation of the hub 12 about its rotation axis D, a centrifugal force F.sub.centrifugal,1 acts upon the center of mass MSP which is spaced at a distance r.sub.centrifugal,1 (not shown) from the rotation axis D, wherein the centrifugal force F.sub.centrifugal,1 is directed radially outwardly, i.e. in the direction of a normal (not shown) extending through the center of mass MSP to the rotation axis D. The centrifugal force F.sub.centrifugal,1 has an opening force component F.sub.centrifugal,lever,1 which is applied to the center of mass MSP and is directed perpendicularly to a lever with the length of the spacing a.sub.MSP-S from the center of mass MSP to the pivot axis S. The opening force component F.sub.centrifugal,lever,1 thus generates, via said lever, an opening moment M.sub.opening,1 (not shown). By this means, the center of mass MSP, disregarding the translational travel motion of the boat, is accelerated tangentially relative to the pivot axis S and is thus pivoted out of the maximum closed position P1.

[0110] The relationship just described applies for both possible rotations DR of the hub 12, that is, for forward travel and rearward travel of the boat.

[0111] As a result, the propeller blade 14 pivots in the opening direction OR, wherein the representation of the middle open position Pm in FIG. 2a makes clear that with increasing spacing r.sub.centrifugal,m of the center of mass MSP from the rotation axis D, the centrifugal force F.sub.centrifugal,m has also increased in relation to F.sub.centrifugal,1. F.sub.centrifugal,m can be determined as follows:

F.sub.centrifugal,m=m*ω.sup.2*r.sub.centrifugal,m,

[0112] where m=mass of the propeller blade 14, ω=angular velocity of the hub rotation and

r.sub.centrifugal,m=pivot axis spacing h+a.sub.MSP-S*cos(α.sub.m);

wherein h=spacing of pivot axis S from rotation axis D, and
α.sub.m=opening angle in the middle pivot position.

[0113] In general, the opening angle α represents the angle between the maximum opening plane E.sub.Max and the lever, i.e. the distance from the center of mass MSP to the pivot axis S.

[0114] FIG. 2b shows a continuation of the pivot movement of FIG. 2a, wherein the propeller blade 14 is pivoted into the maximum open position P2.

[0115] In particular, in this maximum open position P2, an opening force component F.sub.centrifugal,lever,2 acts upon the center of mass MSP and generates an opening moment M.sub.opening,2 as described above. Therein, M.sub.opening,2 and F.sub.centrifugal,lever,2 can be determined as follows:

M.sub.opening,2=F.sub.centrifugal,lever1,2*a.sub.MSP-S

where F.sub.centrifugal,lever,2=F.sub.centrifugal,2*sin(α.sub.2)

[0116] The opening force F.sub.centrifugal,lever,2 thereby presses the propeller blade 14 against the stop apparatus 18. In addition, the opening moment M.sub.opening is greater than a closing moment M.sub.close (not shown) acting overall simultaneously. This applies, in particular, for the rearward drive and the braking.

[0117] FIG. 3a shows a schematic front view of a folding propeller blade 14 of a folding propeller 10 according to a further embodiment. The additional body 142 can be configured as a mass body 142b, for example, as a cylinder (see FIG. 3c), in some embodiments as a curved cylinder or as an uplift body 142a (see FIG. 3b) or in another suitable form. The propeller blade tip portion 144 is therein in some embodiments formed integrally with the additional body 142. Furthermore, the propeller blade tip portion 144 may be formed of metal.

[0118] In some embodiments, the propeller blade tip portion 144 is connected form-fittingly or frictionally to the propeller blade shaft portion 146. As shown dashed in FIG. 3a, the propeller blade tip portion 144 has a tongue 1440 which is cast into the propeller blade shaft portion 146 and/or is connected to the propeller blade shaft portion 146 via a screw connection or a rivet connection or another suitable connection. Furthermore, the propeller blade shaft portion 146 is in some embodiments formed of plastics.

[0119] The tongue 1440 is in some embodiments formed integrally with the propeller blade tip portion 144. The tongue 1440 can be configured such that the propeller blade tip portion 144 has a stepped form from a separation edge 145 in the proximal direction (see FIG. 3b, 3c), in order to be received in a corresponding distally oriented recess in the propeller blade shaft portion 146.

[0120] In order to configure the possible connection interfaces of additional bodies 142 to the propeller blade 14 or from the propeller blade tip portion 144 to the propeller blade shaft portion 146, a person skilled in the art would accordingly take account of the radii R1 and R2 shown in FIG. 3a.

[0121] FIGS. 3b and 3c show, in a schematic side view, a further embodiment of the propeller blade tip portion 144. It has an additional body 142 which in FIG. 3b is present in the form of a uplift body 142a and is inclined in the rearward travel direction. Such an inclination of the uplift body 142a can be used to generate dynamic uplift (see FIG. 5). In FIG. 3c, the additional body 142 is present as a mass body 142b, in this case in the form of a curved cylinder with the curvature of radius R2 (see FIG. 3a). The mass body 142b can be used for increasing the centrifugal force. The tongue 1440 serves for the aforementioned connection of the propeller blade tip portion 144 to the propeller blade shaft portion 146.

[0122] The separation edge 145 can be used for the design or for improving the connection of the aforementioned propeller blade portions.

[0123] FIG. 3d, 3e show schematic frontal views and cross-sections of the tongue 1440 of the propeller blade tip portion 144 which serves for the form-fitting and/or frictional connection to the propeller blade shaft portion 146. In FIG. 3d, the tongue 1440 has bores 1442 which can serve in the aforementioned connection, for example, as through holes or threaded holes for a screw connection, bolt connection or rivet connection. In FIG. 3e, by contrast, the tongue 1440 has webs 1444 which can advantageously be used in the aforementioned connection, for example, for the aforementioned injection molding or casting connection.

[0124] As shown in FIGS. 3a, 3d and 3e, the tongue 1440 can be trapezoid or rectangular, but can also have any other shape suitable for the connection described.

[0125] FIG. 4 shows a schematic front view of a plastics propeller blade 14 with a metal inlay 20 according to a further embodiment of the folding propeller 10. Herein, the metal inlay 20 is embedded in the plastics propeller blade 14. For example, the metal inlay 20 can be cast into the plastics propeller blade 14. In this way, advantages are achieved with regard to corrosion and servicing, while due to the metal inlay 20, the arrangement of the center of mass MSP and a sufficient stiffness of the plastics propeller blade 14 can be ensured. The embodiment shown in FIG. 4 can have, in particular, the previously and subsequently described features, for example, an additional body 142, even if this is not explicitly shown in FIG. 4.

[0126] FIG. 5 shows a schematic plan view of a further embodiment of a propeller blade 14 of the folding propeller 10 in the maximum closed position P2. In this example, the propeller blade 14 has an uplift body 142a in the form of a winglet 13. The winglet 13 has, in its cross-section (see FIG. 6), an airfoil profile with a correspondingly formed winglet upper side 13a and winglet underside 13b. Furthermore, the winglet 13 has a first, distal portion 131 and a second, proximal portion 132 wherein the latter is suitably equipped, in particular, for connecting to the remainder of the propeller blade 14. The winglet longitudinal axis L.sub.W is inclined relative to the remainder of the propeller blade 14 in the closing direction SR, in particular, inclined by the angle β relative to the longitudinal axis L.sub.shaft of the propeller blade shaft portion 146. The winglet 13 is configured (see FIG. 6) such that, in particular, when surrounding water flows over the winglet 13, a dynamic uplift force F.sub.uplift acts upon the winglet and, associated therewith, an openingly acting uplift force component F.sub.uplift,lever acts upon the propeller blade 14. F.sub.uplift,lever is the component of the uplift force F.sub.uplift which generates an opening moment M.sub.uplift,opening that acts perpendicularly via a lever to the pivot axis on the propeller blade 14.

[0127] Shown schematically in FIG. 5 is an effective application point EAP of the uplift force F.sub.uplift acting overall upon the winglet 13 in the form of a projection of the center of pressure DP of the winglet profile. Accordingly, the relevant lever results from the spacing of the center of pressure DP from the pivot axis S, that is the distance app-s. In the design of the folding propeller 10, a person skilled in the art can thus easily create a model to describe the moment M.sub.uplift,opening which acts openingly due to the uplift and which comprises the parameters shown in FIG. 5. A person skilled in the art can thus determine, for a given configuration, an advantageous winglet inclination angle β. The winglet 13 is configured such that the effective force application point EAP of the uplift force F.sub.uplift is clearly spaced from the maximum opening plane E.sub.Max and is offset in the closing direction SR.

[0128] The arrangement shown in FIG. 5 of the winglet 13 in relation to the propeller blade shaft portion 146 is geometrically simple and here is substantially described by means of the two longitudinal axes L.sub.W and L.sub.shaft and their inclination angle β to one another. However, the winglet arrangement can deviate therefrom substantially. Alternatively, the winglet 13 can be configured elliptical or annular, for example, as a spiroid or a split-wing loop. Furthermore, the winglet 13 can have a plurality of portions and therefore a plurality of portion longitudinal axes (for example, a T-shape or a Y-shape) and can accordingly be arranged on the propeller blade shaft portion 146 or on the propeller blade 14.

[0129] FIG. 6 shows schematically an exemplary profile in a section A-A of the winglet 13 of FIG. 5. In some embodiments, the winglet profile is configured as a normal profile, wherein the winglet upper side 13a is configured convex and the winglet underside 13b is configured s-shaped. If a normal profile is used, this can in some embodiments be oriented toward the folding propeller 10 such that during rearward drive, the flow of the surrounding water, represented here as the flow AS, and thus the dynamic uplift, is particularly advantageously used. A reinforcement of the opening moment M.sub.opening is particularly preferred for rearward drive. Alternatively, the winglet profile can be configured as a symmetrical profile or can have any further advantageous, uplift-generating profile shape. As shown by way of example in FIG. 6, the surrounding water flows faster on the upper side 13a than on the underside 13b, so that the dynamic uplift force F.sub.uplift acts upon the winglet 13, is applied to the center of pressure DP or the effective force application point EAP and is directed perpendicularly to the flow AS and away from the winglet upper side 13a.

[0130] FIG. 7 shows a schematic perspective view of the winglet 13 according to one embodiment. In this example, the winglet 13 is formed integrally. In this way, by simple design means, a hydrodynamically optimized propeller blade can be provided.

[0131] FIG. 8 shows a perspective schematic view of a water vehicle 100 during rearward drive with a folding propeller 10 according to a further embodiment. The folding propeller 10 comprises a hub 12 and two identical propeller blades 14. The propeller blade 14 is attached in the region of its propeller root (not shown) via a mounting apparatus (not shown) to the hub 12. The hub 12 is rotatable about a rotation axis D and is drivable via a boat drive shaft (not shown) to which it is connected for conjoint rotation. The mounting apparatus (not shown) defines a propeller blade pivot axis S which is arranged perpendicularly to the rotation axis D. The propeller blade 14 is pivotable about the propeller blade pivot axis S between a maximum closed position (not shown) and a maximum open position P2. In a contact region of the propeller root (not shown) and the hub 12, the folding propeller 10 has a propeller blade stop apparatus (not shown) which limits the opening of the propeller blade 14 and thus defines the maximum open position P2.

[0132] The propeller blade 14 is configured as an airfoil which means that, on rotation of the hub 12 in the rotation direction DR or contrary to the rotation direction DR, it undergoes uplift forces through the displacement of the surrounding water and transmits said forces in the form of a resultant thrust via the hub 12 to the drive.

[0133] In the propeller blade tip portion 144, a reversal element 143 is arranged to be pivotable about a reversal element pivot axis S.sub.U which is substantially parallel to the propeller blade longitudinal axis L.sub.P. The propeller blade 14 has a front edge 150 and a rear edge 151.

[0134] In FIG. 8, the hub 12 is rotated in the rotation direction DR which corresponds to a rearward drive, so that due to the linear velocity v.sub.linear, a flow AS impacts upon the propeller blade rear edge 151. The flow AS presses against the reversal element 143, which pivots or is pivoted accordingly in the direction of the maximum folded-out position U2. The stream AS henceforth impinging upon the reversal element 143 brings about the reversed force F.sub.reverse which acts via an effective force application point EAP on the propeller blade 14 and via a lever of length a.sub.U-S to the propeller blade pivot axis S, generates an opening moment M.sub.opening,reverse.

[0135] By means of the rotation of the hub 12 in the rotation direction DR, the propeller blade 14 experiences uplift forces F.sub.uplift,rearward directed in the rearward direction of travel, the sum of which results in a thrust F.sub.thrust,rearward directed in the rearward direction of travel. In addition, the uplift forces F.sub.uplift,rearward cause a moment (not shown) having a closing effect on the propeller blade 14, the lever of which is significantly smaller, substantially half as great as the lever a.sub.U-S of the previously described openingly acting moment M.sub.opening,reverse.

[0136] In the design of the folding propeller 10, on the basis of the arrangement disclosed, a person skilled in the art can thus easily create a model to quantify the openingly and closingly acting moments, comprising the elements and parameters shown in FIG. 8. A skilled person can therefore, for example, configure the propeller blade 14 and the reversal element 143 such that a desired opening moment for particular parameter configurations results.

[0137] FIG. 9a shows a schematic front view and FIG. 9b the corresponding side view of the propeller blade 14 shown in FIG. 8 during rearward drive of the folding propeller 10. In the example shown, the reversal element 143 is arranged in the propeller blade tip region, that is, at the distal end of the propeller blade 14. Through the rotation of the propeller blade 14, the reversal element 143 moves with the linear velocity about the rotation axis. Thereby, a flow AS lies continuously against the reversal element 143. Thereby, an uplift results which generates the reversed force F.sub.reverse which acts upon the reversal element 143 and pivots the reversal element 143 about its pivot axis S.sub.U into its maximum folded-out position U2. This pivoting is limited by a stop apparatus (not shown) which therefore defines the maximum folded-out position U2. Furthermore, a transmission apparatus (not shown) is provided on the propeller blade 14 in the region of the reversal element 143, which is configured to transmit the reversed force F.sub.reverse engaging upon the reversal element 143 to the propeller blade 14, so that F.sub.reverse—as described in relation to FIG. 8—generates via the lever a.sub.U-S to the propeller blade pivot axis S, the opening moment M.sub.opening,reverse. The stop apparatus can therein be configured integrally with the transmission apparatus. In particular, the transmission apparatus can be configured to transmit the reversed force F.sub.reverse applied to the reversal element 143 via suitable elements to the propeller blade 14 by means of compression forces and/or tensile forces.

[0138] As FIG. 9b shows, the reversal element 143 can have a form in its distal end region which is suitable to catch the flow AS during rearward drive such that the reversal element 143 is pivoted out of a maximum folded-in position (see FIG. 10a, b) automatically or autonomously in the direction of its maximum folded-out position 143.

[0139] FIG. 10a shows a schematic front view and FIG. 10b the corresponding side view of the propeller blade 14 shown in FIG. 8 during forward drive of the folding propeller 10. Due to the flow AS against the propeller blade front edge 150, the reversal element 143 remains substantially in its maximum folded-in position U1. If braking is carried out during forward travel, the vector of the linear velocity V.sub.linear,forward rotates accordingly into the opposite direction and consequently also the flow AS. By this means, the reversal element 143 is pivoted into the maximum folded-out position U2, so that, as described above, the reversal element 143 can provide a moment acting closingly on the propeller blade 14.

[0140] As far as practicable, all the individual features which are described in the exemplary embodiments can be combined with one another and/or exchanged without departing from the scope of the present disclosure.

REFERENCE SIGNS

[0141] 10 Folding propeller [0142] 12 Hub [0143] 13 Winglet [0144] 13a Winglet upper side [0145] 13b Winglet underside [0146] 14 Propeller blade [0147] 14a First, distal propeller blade portion [0148] 14b Second, proximal propeller blade portion [0149] 15 Propeller root [0150] 16 Mounting apparatus [0151] 18 Stop apparatus [0152] 19 Propeller blade tip [0153] 20 Metal inlay [0154] 100 Water vehicle [0155] 131 First, distal winglet portion [0156] 132 Second, proximal winglet portion [0157] 142 Additional body [0158] 142a Uplift body [0159] 142b Mass body [0160] 143 Reversal element [0161] 144 Propeller blade tip portion [0162] 145 Separation edge [0163] 146 Propeller blade shaft portion [0164] 148 Propeller blade root portion [0165] 150 Propeller blade front edge [0166] 151 Propeller blade rear edge [0167] 1440 Tongue [0168] 1442 Bore [0169] 1444 Web [0170] a.sub.MSP-S Spacing/distance center of mass MSP to pivot axis S [0171] a.sub.DP-S Spacing/distance center of pressure DP to pivot axis S [0172] AS Flow [0173] D Rotation axis [0174] DP Center of pressure [0175] EAP Effective force application point [0176] E.sub.Max Maximum opening plane [0177] F.sub.uplift Uplift force [0178] F.sub.centrifugal Centrifugal force [0179] F.sub.reverse Reversed force on the reversal element [0180] h Spacing rotation axis D to pivot axis S [0181] L.sub.P Propeller blade longitudinal axis [0182] L.sub.shaft Longitudinal axis of propeller blade shaft portion [0183] L.sub.W Winglet longitudinal axis [0184] M.sub.opening Opening moment [0185] M.sub.closing Closing moment [0186] MSP Center of mass of propeller blade [0187] N.sub.D Normal to the rotation axis D [0188] OR Opening direction [0189] P1 Maximum closed position of the propeller blade/folding propeller [0190] Pm Middle open position of the propeller blade/folding propeller [0191] P2 Maximum open position of the propeller blade/folding propeller [0192] r.sub.centrifugal Spacing rotation axis D to center of mass MSP (radius of centrifugal force) [0193] R1 Outer radius of propeller blade shaft portion [0194] R2 Outer radius of folding propeller or curvature of cylinder [0195] S Pivot axis [0196] S.sub.U Pivot axis of reversal element [0197] SR Closing direction [0198] U1 Maximum folded-in position of reversal element [0199] U2 Maximum folded-out position of reversal element [0200] α Opening angle of propeller blade/angle between a.sub.MSP-S and E.sub.max [0201] β Inclination angle of winglet/angle between L.sub.w and L.sub.shaft