Folding propeller and methods of use

The present disclosure relates to a folding propeller, comprising a hub, which may be driven via a drive shaft around a rotation axis, at least two propeller blades, which are pivotably arranged on the hub between a folded position and an unfolded position, and a propeller blade arresting means, which is configured for arresting the propeller blades in the unfolded position, wherein the propeller blade arresting means is movable relative to the hub in rotation direction between a starting position and an arresting position.

RELATED APPLICATIONS

This application claims the benefit of and priority to German Application No. DE 10 2020 129 938.9, filed Nov. 12, 2020, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a folding propeller comprising a hub that can be driven via a drive shaft around a rotation axis, and at least two propeller blades pivotably arranged on the hub between a folded position and an unfolded position. Such folding propellers are typically used in motor drives for sailing boats.

BACKGROUND

It is known to use auxiliary drives with folding propellers in sailing boats because of their advantageous flow characteristics when not in use. These are normally folding propellers, which have two or more propeller blades, which usually are mounted transverse to the propeller hub and are substantially freely movable. This principle basically allows two operating states. The first operating state exists when the propeller blades are axially folded backwards, which is for example the case when the drive shaft is standing still. The second operating state occurs when the drive shaft rotates and is defined in that the propeller blades are radially folded outwards in order to be able to apply thrust to the boat in this way.

In the simplest case the propeller blades are unfolded during forward as well as during reverse travel thanks to centrifugal forces. In most cases the propeller blades are coupled to each other at their root end to guarantee a synchronous opening of the propeller blades. This prevents that strong imbalances occur at the drive shaft when opening the propeller blades. If the folding propeller is rotated in a direction that equals forward travel, the thrust generated by the propeller blades pushes the propeller blades into a completely opened position from a certain opening angle of the propeller blades. Centrifugal force as well as thrust therefore generate an opening torque at the propeller blades.

This works very well during forward travel. However, during reverse travel an unfolding of the propeller is more difficult to realise, which reduces the efficiency of the known folding propellers during reverse travel. The thrust generated at the propeller blades effects a closing torque at the propeller blades during reverse travel. If a flow equalling forward travel is also applied to the folding propeller, this inflow also effects a closing torque at the propeller blades. Only centrifugal force effects an opening torque and therefore counteracts thrust and also inflow. As a result the propeller blades often reach only a partly unfolded position during reverse travel. Relatively high speeds are therefore necessary during reverse travel, and in particular when halting, to counteract the centrifugal force of the other closing torques. The efficiency of the folding propeller is therefore normally quite low during reverse travel.

SUMMARY

Based on known prior art it is an objective of the present disclosure to provide an improved folding propeller.

This objective is solved by a folding propeller with the features of claim1. Advantageous further developments result from the subclaims, the description and the Figures.

Accordingly, a folding propeller is suggested, comprising a hub that can be driven via a drive shaft around a rotation axis, at least two propeller blades, which are arranged pivotably mounted on the hub between a folded position and an unfolded position, and a propeller blade arresting means, which is configured for arresting the propeller blades in the unfolded position.

According to the disclosure the propeller blade arresting means is movable relative to the hub in rotation direction between a starting position and an arresting position.

The arrangement of the propeller blades on the hub that is pivotable between a folded position and an unfolded position enables two operating states. In the folded position of the propeller blades the folding propeller is in a first operating state, in which the alignment of the propeller blades is oriented axially backwards. This state substantially occurs only when the drive shaft is standing still. In the unfolded position of the propeller blades the folding propeller is in a second operating state, which occurs when the drive shaft rotates. The alignment of the propeller blades is oriented radially outwards in this second operating state. The folded position and/or the unfolded position can be predetermined end positions here, between which the propeller blades can be pivoted.

The pivotability of a single propeller blade can be uncoupled from further propeller blades here, or the propeller blades can be coupled with each other with regard to pivotability. Particularly, the folding propeller can have two or three propeller blades, wherein the pivotability of each one is uncoupled from the pivotability of the further propeller blades or is coupled with the same.

Not all propeller blades present need to be arrested directly by the propeller blade arresting means in the sense of the present disclosure. Notwithstanding, all propeller blades present may be arrested above the propeller blade arresting means.

An arresting position in the sense of the present disclosure is understood as a position of the propeller blade arresting means that is relative to one propeller blade or to several propeller blades, in which the pivotability of the propeller blade or the propeller blades is limited compared to the pivotability of the propeller blade or the propeller blades in the starting position.

The arresting position may be a position in which the propeller blades are wholly or partly unfolded and are secured against folding by the propeller blade arresting means. In particular the arresting position may be a position in which the propeller blades are completely unfolded and are arrested in this position by the propeller blade arresting means in such a way that a pivoting of the propeller blades cannot occur as long as the propeller blade arresting means is in the arresting position relative to the hub.

According to an advantageous further development the propeller blade arresting means is connected with the drive shaft in a torsion proof (German expression:“drehsteif”) way, wherein the hub is uncoupled from the propeller blade arresting means in rotation direction, wherein the propeller blade arresting means preferably has a sleeve.

According to some embodiments, the folding propeller therefore has two components that are movable relative to each other in rotation direction, wherein the first component comprises the drive shaft and the propeller blade arresting means, and the second component comprises the hub and the propeller blades.

The drive shaft and the propeller blade arresting means may therefore be designed as one component, which may be a single piece or consist of several parts.

The fact that the propeller blade arresting means may have a sleeve means that the hub that is uncoupled from the propeller blade arresting means in rotation direction may for example be arranged in the interior of the sleeve. This guarantees a simple positioning and assembly of the hub including the propeller blades pivotably arranged on the hub.

The hub is advantageously configured to be movable in such a way that a movement of the hub from the starting position into the arresting position is enforced when applying a torque.

The term enforced may mean that a stop may be provided between two parts which are movable relative to each other.

The term torque is to be understood in the sense of the present disclosure as a torque acting on the drive shaft, from which a corresponding movement of the hub relative to the propeller blade arresting means occurs.

In other words, the hub may be configured together with the propeller blades arranged on the same in such a way that a movement of the hub from the starting position into the arresting position, in which the propeller blades are arrested, is enforced when a torque is applied to the drive shaft, and thus also to the propeller blade arresting means that is connected in a torsion proof way with the same.

According to an advantageous further development the hub may be configured to be movable in such a way, that by utilisation of a torque applied to the hub by the propeller blade arresting means, a movement of the hub from a starting position into an arresting position, in which the propeller blades are arrested, is enforced.

The torque of the drive shaft and the propeller blade arresting means acts against the stoppage here, which is generated by the—at least partly—unfolded propeller blades, so that the propeller blade arresting means is forced against the hub by applying the torque in such a way that the above-mentioned movement is achieved.

According to an advantageous further development the hub may be configured to be movable in such a way that a movement of the hub from the starting position into the arresting position, in which the propeller blades are arrested, is enforced by utilising the mass inertia of the hub.

This way, the mass inertia of the hub and the propeller blade arranged on the same may be utilised to support the movement of the propeller blade arresting means into the arresting position if a relative acceleration is applied between the components uncoupled from each other.

Mass inertia is generally to be understood as an inertia moment, also mass inertia moment or inertial moment, which specifies the inertia of a body in question in relation to a change in its angular speed whilst rotating around the rotation axis (torque divided by angular acceleration).

Utilising mass inertia means that mass inertia substantially causes the movement of the propeller blade arresting means from its starting position into its arresting position, relative to the hub. This may be realised in that an inert body, the mass inertia of which is used to force the hub into the arresting position when rotation of the hub is accelerated, has sufficient mass and a suitable mounting. The detailed implementation of this will further depend on the angular speed and dimensions, which may be determined with the aid of simple trials. Decisive is that the hub is placed in the arresting position for a specific application from a desired angular acceleration of the drive shaft and the propeller blade arrangement means based on its mass inertia torque relative to the propeller blade arresting means.

According to another advantageous further development the hub is connected with the drive shaft in a torsion proof way, wherein the propeller blade arresting means is uncoupled from the hub in rotation direction, wherein the propeller blade arresting means preferably has a sleeve.

In some embodiments, only the propeller blade arresting means is for example uncoupled in rotation direction, wherein the drive shaft, the hub and the propeller blades pivotably mounted on the hub are connected in a torsion proof way with each other. This has the advantage that the force flow from the shaft to the propeller blades remains unchanged, which may lead to avoiding a re-design of the drive train.

The sleeve may preferably be arranged on the outside of the hub in some embodiments. The propeller blade arresting means may be easily integrated into the hub in this way without having to make substantial changes to the hub. The propeller blade arresting means may also be integrated into the hub without the flow in the vicinity of the folding propeller being significantly influenced. Lastly a sleeve is a cost effective and easily manufactured component, which can simply be replaced or retrofitted if necessary.

It is of further advantage if the propeller blade arresting means is configured to be movable in such a way that a movement of the propeller blade arresting means from a starting position into an arresting position, in which the propeller blades are arrested, is enforced by means of utilising mass inertia that occurs when rotating the hub.

In some embodiments, mass inertia substantially causes the movement of the propeller blade arresting means from its starting position into its arresting position relative to the hub. Sufficient acceleration or sufficient angular acceleration must accordingly be applied for this, which leads to the relative movement being performed.

It can further be of advantage if the propeller blade arresting means may be configured to be movable in such a way that its mass inertia is utilised in a targeted way to enforce the movement of the propeller blade arresting means from the starting position into the arresting position.

The function of arresting may thus be guaranteed with the propeller blade arresting means alone. The propeller blade arresting means may therefore also be designed as a retrofit component, with which conventional folding propellers may be equipped. In addition, the remaining components of the folding propeller do not need to be modified, or only a little, to guarantee the function of arresting the propeller blades.

According to an advantageous further development the effect of the mass inertia of the propeller blade arresting means may be supported or replaced through flow bodies that generate flow forces. Such flow bodies may for example be blades, ribs, lamellae or other devices on the propeller blade arresting means. These flow bodies are preferably configured in such a way that they, much like the inertia of the propeller blade arresting means, counteract a change in rotation speed (in particular in a reverse direction) in order to make the propeller blade arresting means stand still whilst the propeller starts to rotate backwards.

According to some embodiments, such flow bodies, in particular blades, may be of a collapsible or foldable design, so that the same may lie against the hub during forward rotation (low water resistance), whilst they stand upright during reverse travel to support inertia. This has the advantage that the propeller blades may be locked reliably during reverse travel rotation and that the flow body folds up again during a hydrogeneration of the flow bodies because the same then rotates forwards. A direction dependent enforcement of any effect may thus be created, which also gives rise to mass inertia.

According to an advantageous further development the rotation direction equals a reverse operation of the propeller blades. An unfolding of the propeller blades may in principle take place during forward travel as well as during reverse travel, therefore in both directions.

When the propeller blades are driven via the drive shaft and set to rotate, they induce impulse forces corresponding to their blade geometry onto the adjacent fluid. During forward travel the counter forces acting on the propeller blade increase the unfolding of the propeller blades. However, during reverse travel it may happen that the counter forces occurring during the same cause a closing torque on the propeller blades, which will lastly lead to a folding of the propeller blades into the folded position. This disadvantageous effect may be suppressed by the propeller blade arresting means.

Approaches of adapting the profiles of the propeller blades in such a way that a folding of the propeller blades during reverse gear becomes more unlikely are known from prior art. If the buoyancy generated is for example lower in reverse gear, the speed for a specific thrust must be correspondingly higher, which causes the correspondingly higher centrifugal forces to make a folding more unlikely. The presence of the propeller blade arresting means has the advantage that the propeller blades may also be configured in such a way that a high thrust is generated in reverse gear at low speed, as a folding into the folded position is indirectly prevented.

As a result, the propeller blades may be configured in such a way that they generate optimal buoyancy even during reverse travel. In this way reverse travel may also be reliably induced at low speeds. The often-used practice of specifically increasing the speed of the hub for inducing reverse travel in order to provide sufficient centrifugal force may thus be omitted. The folding propeller may therefore be used in a more environmentally friendly, reliable and quieter way.

The fact that the arresting position is enforced by means of using mass inertia that occurs when the hub rotates means that a self-adjusting arresting of the propeller blades may be realised, which occurs solely through rotating the hub. In addition, a controlled opening during reverse travel and during towing is guaranteed. The efficiency and also the calculability of the folding propeller is improved in this way.

Further, efficiency during hydrogeneration (recuperation), for example during sailing operation, may be improved by using the suggested arrestable folding propeller. Hydrogeneration operation may be implemented particular efficiently in this way.

In some embodiments, the propeller blades are mounted on a bearing pin arranged transverse to the rotation axis. The propeller blades may firstly be folded up in an axis-parallel way, and secondly pivoted onto a rotation plane that lies orthogonal to the rotation axis. The propeller blades of this construction type may also be replaced easily and fitted to the hub by means of commercially available bolts and/or safety devices.

According to an advantageous further development the propeller blade arresting means is configured in such a way that the same is in the starting position when the drive shaft stands still, wherein the propeller blades are freely pivotable between the folded position and the unfolded position in this case. If there is therefore no rotation of the drive shaft, and if no mass inertia torque is induced by the same, the propeller blade arresting means is located relative to the hub in the starting position and the propeller blades of the folding propeller are freely pivotable.

The propeller blade arresting means therefore does not act as an arresting component when the drive shaft stands still, which means the folding propeller acts like a conventional folding propeller when the drive shaft stands still. Established assembly, maintenance and cleaning work can consequently be carried out in the same way.

According to an advantageous further development the sleeve of the propeller blade arresting means has a recess and a catch in the area of each propeller blade, wherein the catch is preferably formed on a downstream end of the sleeve.

In the sense of the present application an end of the sleeve is to be understood as a facing side of the sleeve in an axial direction. The downstream end of the sleeve is the end which is oriented downstream during forward travel of the folding propeller. The recess is preferably a part area cut out of the shell surface of the sleeve, in which a propeller blade or a propeller blade root of a propeller blade is held in the unfolded position.

The catch is preferably part of the sleeve. The catch is for example formed in that the recess on the shell surface of the sleeve extends only partly up to the facing side of the downstream side end of the sleeve. The remaining gap between the end of the catch and the adjacent shell surface of the sleeve is preferably so large that a propeller blade may be inserted into and withdrawn from the recess through this gap.

According to some embodiments, where the propeller blade arresting means is connected with the drive shaft in a torsion proof way, the unfolding of the propeller blades is affected or supported by the shape of the recess or the catch in such a way that the propeller blades are unfolded by means of form closure, which results from the forces between the driven propeller blade arresting means and the inert hub.

It may therefore be guaranteed in a simple way that the sleeve is rotated relative to the propeller hub during rotation, utilising mass inertia, is forced into the arresting position and a catch is simultaneously pushed before each propeller blade.

In some embodiments, the propeller blade arresting means has an insertion bevel, which is designed in such a way that a folding of the propeller blades leads to the propeller blade arresting means being reset into its starting position in a state in which the propeller blade arresting means is not yet completely in the arresting position. Vice versa the bevel leads to the propeller blades being pressed down by the bevel during reverse travel.

The insertion bevel can for example be formed on the catch, in particular on one side of the catch, which simultaneously is an edge structure. The catch can for example have a width that tapers towards its free-standing end, wherein the width relates to a dimension that lies on the level of the shell surface. The insertion bevels improve the reliability of the function of the propeller blade arresting means.

According to an advantageous further development the propeller blade arresting means is made from one piece. The propeller blade arresting means can be manufactured cost effectively in this way. Sleeve and catch can for example be milled from one piece, whilst any type of forming, in particular casting, forging or suchlike, is feasible in principle. Alternatively, the sleeve and/or the catch can however also be connected with any kind of joining. The catch can be adapted to follow the shape of the sleeve or can also be freely connected with the same.

The propeller blade arresting means and/or the propeller blades preferably include a metallic material. With regard to the propeller blade arresting means a use of a metallic material has the advantage that the mass inertia torque of the same is increased. As a result, the reliability and calculability of the propeller blade arresting means, and lastly of the folding propeller, is improved with such a one.

According to an advantageous further development the propeller blade arresting means is designed to arrest the propeller blades in an unfolded position when towing the folding propeller, so that an automatic rotation of the propeller blades takes place, wherein the propeller blade arresting means is preferably designed to enable an automatic rotation of the propeller blades for recycling energy from around 5 kn of speed. The propeller blade arresting means can for example have a recess and/or a catch for this, which are designed in such a way that arresting is also guaranteed during forward travel.

In one advantageous further development the propeller blades are configured in such a way that the initial opening of the propeller blades takes place by utilising centrifugal force, preferably wherein the propeller blades include a metallic material, in particular a metal alloy. The initial opening of the propeller blades may take place from an early folded position by utilising centrifugal forces. A reliable and calculable function of the folding propeller may be achieved in this way on the one hand. On the other hand, utilising centrifugal forces for the initial opening of the propeller blades allows the omission of further technical means for opening the propeller blades. The propeller blades may therefore be arranged on the hub pivotable freely.

Use of a metallic material for the propeller blades has the advantage that the initial opening of the blades, which is based on centrifugal force, is simplified by the corresponding mass of the propeller blades. This improves the reliability and the calculability of the propeller blade arresting means, and lastly the folding propeller, with such a one.

An example of a movement cycle of a folding propeller, according to some embodiments, is disclosed in the following for explaining the function of the propeller blade arresting means in more detail by means of an example, according to which the propeller blade arresting means is connected with the drive shaft in a torsion proof way, and the hub is uncoupled from the drive shaft in rotation direction:

The propeller blade arresting means is driven together with the drive shaft from standstill around a rotation axis in a rotation direction, which equals reverse travel.

The angular acceleration of the propeller blade arresting means and the mass inertia of the hub may create a contact between the propeller blade arresting means and the hub. The hub may then be towed by the propeller blade arresting means together with the propeller blades.

Due to the centrifugal forces that act on the propeller blades the propeller blades pivot out of their early folded position into an unfolded position.

When pivoting the propeller blades out of the unfolded position these may each be driven into a recess of the propeller blade arresting means, which forms a corresponding opening. The propeller blades may pass a catch during this, which may be formed on the facing side end of the sleeve.

Upon reaching the unfolded position the propeller blades may be located completely in the recess.

Caused by the rotation of the propeller blade arresting means the torque applied to the hub and the unfolded propeller blades may lead to propeller blades being moved from a starting position into an arresting position within the recess. The arresting may lastly be realised by means of a catch, which may affect an indirect arresting of the propeller blade.

If the rotation is stopped, the propeller blade may move into the starting position thanks to the mass inertia of the hub. The catch in particular is configured such that the same releases the propeller blade, which is in abutment here. The propeller blade may thus be pivoted back out of the unfolded position into the folded position in this abutment.

In some embodiments, in which the hub is connected with the drive shaft in a torsion proof way and the propeller blade arresting means is uncoupled from the hub in rotation direction, functionality is as follows:

The hub is driven by a drive shaft from standstill around a rotation axis in a rotation direction that equals reverse travel.

The rotation of the hub may be transferred directly to the propeller blades, which may pivot from the early folded position into an unfolded position due to centrifugal forces acting on the same.

Upon pivoting into the unfolded position, the propeller blades may each go into a recess in the propeller blade arresting means, which may form a corresponding opening on the facing side end of the sleeve. The propeller blades may pass a catch here, which may be formed on the facing side end of the sleeve.

Upon reaching the unfolded position the propeller blades may be located completely in the recess.

Caused by the rotation of the propeller blades and the hub the mass inertia of the propeller blade arresting means may induce the propeller blades being moved from a starting position into an arresting position within the recess. The arresting may lastly be result from a catch, which may affect an indirect arresting of the propeller blade.

If the rotation is stopped or reduced, the propeller blade arresting means may move into the starting position due to its mass inertia. The catch in particular is designed in such a way that the same may release the propeller blade, which is in abutment here. The propeller blade may thus pivot back out of the unfolded position into the folded position in this abutment.

The functionalities of the propeller blade arresting means described herein are examples and should not be understood as limiting.

The objective of the present disclosure is further solved by means of a drive for a boat with a folding propeller, as described herein. The objective of the present disclosure is further solved by means of a boat with such a drive.

DETAILED DESCRIPTION

Exemplary embodiments are described in the following with reference to the Figures. Identical, similar or identically acting elements are identified with identical reference numbers in the various Figures, and a repeated description of these elements is partly omitted to avoid redundancies.

FIG.1shows a schematic view of a folding propeller10according to some embodiments in a folded position Z1.

The folding propeller10comprises a hub2, which is uncoupled from the drive shaft4in rotation direction D. Two propeller blades6a,6bare pivotably arranged on the hub2. The hub2may be driven around a schematically illustrated rotation axis A via the drive shaft4, namely via a propeller blade arresting means8, which is permanently, and therefore connected in a torsion proof way with the drive shaft4.

The hub2and the propeller blades6a,6barranged on the same therefore form a first component, which is supported in an uncoupled way in rotation direction D in a further component, formed by the drive shaft4and the propeller blade arresting means8.

The propeller blades6a,6bare pivotably arranged on the hub2between a folded position Z1and an unfolded position Z2(for example shown inFIG.2).

The propeller blade arresting means8is equipped for arresting the propeller blades6a,6bin the unfolded position Z2in order to prevent a (partial) folding of the propeller blades6a,6b, for example during reverse travel, when halting or during hydrogeneration, in this way. The propeller blade arresting means8is designed as a sleeve14here. The sleeve14has a recess16formed in its shell surface as well as a catch18, which is formed on the downstream end of the sleeve14. The propeller blade arresting means8designed as a sleeve14is movable relative to the hub2in rotation direction D between a starting position Z10and an arresting position Z20(for example shown inFIG.3) together with the drive shaft4attached to the same.

Accordingly, a relative movement between the hub2and the sleeve14may for example be achieved by utilising the torque applied by the sleeve14to the hub2, which occurs when rotating the drive shaft4, and therefore rotating the propeller blade arresting means8in form of the sleeve14. The hub2is inhibited together with the propeller blades6a,6barranged on the same by its movement through water, so that correspondingly, it provides a counter torque, and by means of which the torque applied by the propeller blade arresting means8to the hub2induces a movement between the propeller blade arresting means8and the hub2. This way, a movement of the sleeve14relative to the hub2may be enforced from a starting position Z10, as illustrated inFIG.1, into an arresting position Z20, as illustrated inFIG.3.

A schematic view of the folding propeller10according to some embodiments in an unfolded position Z2is illustrated inFIG.2, wherein the propeller blade arresting means8is still located in the starting position Z10relative to the hub2. The illustration shown inFIG.2approximately equals the case that occurs when the folding propeller10is in forward travel. Rotation direction D is therefore one that equals forward travel.

The unfolding of the propeller blades6aand6bfrom the folded position Z1shown inFIG.1into the unfolded position Z2is realised through rotating the drive shaft4together with the propeller blade arresting means8, which lastly acts on the hub2across the propeller blades6a,6b. As soon as the propeller blades6a,6bare set to rotate a centrifugal force acts on the same, which promotes an unfolding of the propeller blades6a,6band thus generates an opening torque on the propeller blades6a,6b. In addition, an opening torque is applied to the propeller blades6a,6band acts on the propeller blades6a,6bwhen applying a rotation of the hub2and the simultaneous application of a forward thrust resulting from the same.

As can be gathered from the illustration inFIG.2, in particular from the orientation of the vane profile, that a rotation of the folding propeller10in rotation direction D generates a forward thrust Sv, generated upwards in the drawing. The resulting counter force, which acts on the propeller blades6a,6b, supports the unfolding of the propeller blades6a,6b. In other words, the propeller blades6a,6bare moved into the unfolded position Z2by centrifugal force as well as by the reaction forces from the forward thrust generated by means of rotation.

As the forward thrust Svis applied in this rotation direction D of the drive shaft and no closing torque acts on the propeller blades6a,6b, an arresting of the folding propeller10across the propeller blade arresting means8is not provided and is not necessary either. The propeller blades6a,6bare being pushed into the unfolded position Z2at any point in time when a forward thrust is to be applied.

In this state, the propeller blade arresting means8in the form of a sleeve14therefore remains, as illustrated inFIG.2, typically in its starting position Z10. Alternatively, or additionally the propeller blade arresting means8may also be designed in such a way that an arresting of the folding propeller10across the propeller blade arresting means8also takes place in rotation direction D, which equals forward travel. In this way the propeller blades6a,6bmay be arrested through a “sharp” reverse switch-on as well as a “sharp” forward switch-on.

A schematic view of the folding propeller10according to some embodiments in an unfolded position Z2and a propeller blade arresting means8in an arresting position Z20is illustrated inFIG.3. The illustration depicted inFIG.3for example equals the case that comes about when the folding propeller10is driven during reverse travel. Rotation direction D therefore equals reverse travel here. As an additional delivering torque acts on the propeller blades6a,6bin this rotation direction D via reverse thrust SR—for example through an inflow of surrounding water as well as exercising the reverse thrust SRdirected in the closing direction of the propeller blades6a,6b—the closing torque on the propeller blade competes with the centrifugal force acting on the propeller blade. An arresting of the folding propeller10across the propeller blade arresting means8is therefore necessary or provided, respectively.

To this end, the suggested propeller blade arresting means8in the form of a sleeve14as well as the hub2are designed such that a movement of the hub2relative to the sleeve14into the arresting position Z20is enforced by utilising the torque applied to the hub2, which occurs when rotating the drive shaft4. In this position, the propeller blades6a,6bare arrested in the arresting position Z20. The difference between the starting position Z10and the arresting position Z20can be graphically deduced from a comparison ofFIGS.2and3. From this it can be seen that the change in rotation direction D from forward travel into reverse travel results in the sleeve14being rotated relative to the hub2in such a way in the latter case, seeFIG.3, that the sleeve14abuts on the propeller blade6awith another flank, namely with the opposite flank of the recess16, in which the propeller blade in question6bis located. This is realised in that the torque applied to the hub2, which occurs when turning the drive shaft4, is utilised for enforcing a relative movement of the hub2relative to the sleeve14from a starting position Z10into an arresting position Z20.

A schematic view of a folding propeller10according to some embodiments is illustrated in a folded position Z1inFIG.4.

The folding propeller10comprises a hub2, which may be driven around a rotation axis A via a schematically illustrated drive shaft4. The folding propeller10further comprises at least two propeller blades6a,6b, which are pivotably arranged on the hub2between a folded position Z1as illustrated, and an unfolded position Z2(for example shown inFIG.5). The folding propeller10further comprises a propeller blade arresting means8movably coupled with the hub2, which is configured for arresting the propeller blades6a,6bin the unfolded position Z2in order to prevent a (partial) folding of the propeller blades6a,6b, for example during reverse travel, when halting or during hydrogeneration, in this way. The propeller blade arresting means8is designed as a sleeve14here. The sleeve14has a recess16formed in its shell surface as well as a catch18, which is formed on the downstream end of the sleeve14. The catch18has an insertion bevel20. The propeller blade arresting means8designed as a sleeve14is freely moveable relative to the hub2in rotation direction D between a starting position Z10and an arresting position Z20(for example shown inFIG.6).

A relative movement between the hub2and the sleeve14may accordingly be realised by means of utilising the mass inertia of the sleeve14, which occurs when accelerating the hub2. A movement of the sleeve14from a starting position Z10, as illustrated inFIG.4, into an arresting position Z20, as illustrated inFIG.6, may then be enforced.

A schematic view of the folding propeller10according to some embodiments is illustrated in an unfolded position Z2inFIG.5, wherein the propeller blade arresting means8is still in the starting position Z10. The illustration shown inFIG.5approximately equals the case that comes about when the folding propeller10is in forward travel. Rotation direction D is accordingly one that equals forward travel.

The unfolding of the propeller blades6aand6bfrom the folded position Z1shown inFIG.4into the unfolded position Z2is realised through a rotation of the hub2and the centrifugal force thus acting on the propeller blades6a,6b. An opening torque additionally acts on the propeller blades6a,6bwhen applying a rotation of the hub2and the simultaneous applying of a forward thrust resulting from the same to the propeller blades6a,6b. In other words, the propeller blades6a,6bare moved by the centrifugal force and the forward thrust applied in the unfolded position Z2.

As no closing torque acts on the propeller blades6a,6bin this rotation direction D of the hub2in forward thrust direction, an arresting of the folding propeller10across the propeller blade arresting means8is not provided and is not necessary either. The propeller blades6a,6bare driven into the unfolded position Z2at any point in time when a forward thrust is to be applied.

The propeller blade arresting means8therefore remains in this state, as illustrated inFIG.2, in the form of a sleeve14, typically in its starting position Z10. Alternatively, or additionally the propeller blade arresting means8may also be designed in such a way that an arresting of the folding propeller10via the propeller blade arresting means8also takes place in rotation direction D, which equals forward travel. In this way the propeller blades6a,6bmay be arrested through a “sharp” reverse switch-on as well as a “sharp” forward switch-on.

A schematic view of the folding propeller10according to some embodiments in an unfolded position Z2and a propeller blade arresting means8in an arresting position Z20is illustrated inFIG.6. The illustration depicted inFIG.6for example equals the case that comes about when the folding propeller10is driven during reverse travel. Rotation direction D therefore equals reverse travel here. As a closing torque acts on the propeller blades6a,6bin this rotation direction D—for example through an inflow of surrounding water as well as exercising the thrust directed in the closing direction of the propeller blades6a,6b—an arresting of the folding propeller10via the propeller blade arresting means8is therefore necessary or provided, respectively.

To this end the suggested propeller blade arresting means8in the form of a sleeve14is designed in such a way that a movement of the sleeve14into the arresting position Z20is enforced by utilising the mass inertia of the sleeve14, which occurs when accelerating the hub2. In this position, the propeller blades6a,6bare arrested in the arresting position Z20. The difference between the starting position Z10and the arresting position Z20can be graphically deduced from a comparison ofFIGS.5and6. It becomes apparent from this that the change in rotation direction D from forward travel into reverse travel results in the sleeve14being rotated relative to the hub2in such a way in the latter case, seeFIG.6, that the sleeve14abuts on the propeller blade6a. This is realised in that the mass inertia of the sleeve14, which occurs when accelerating the hub2, is utilised for enforcing a relative movement of the sleeve14from a starting position Z10into an arresting position Z20.

This is achieved not only when reversing the rotation direction, but at any increase of the speed of the hub2in rotation direction that equals reverse travel. It may for example be achieved with a rapid rotation of the hub2that the propeller blades6a,6bstraighten up and it may then be achieved with a further acceleration of the rotation of the hub2that the hub2quasi turns under the sleeve14that remains in its current movement condition due to its inertia, so that an arresting of the propeller blades6a,6bis achieved.

FIG.7shows a schematic view of the folding propeller10according to some embodiments in a position that lies between the folded position Z1and the unfolded position Z2.FIG.7substantially serves for demonstrating a transition state of the unfolding process of the propeller blades6a,6b. It can be seen from the illustration inFIG.7that the arresting of the propeller blades6a,6bis achieved by means of the catch18as long as the hub2is driven in reverse travel. The latter can grip the propeller blades6a,6bby means of the insertion bevels20before these are completely unfolded.

FIG.8shows a schematic view of the folding propeller10according to some embodiments in an unfolded position Z2, and a propeller blade arresting means8in a starting position Z10. It can be seen from the illustration ofFIG.8that the propeller blades6a,6bare each mounted above a bearing pin12that is arranged transverse to rotation axis A. The illustration depicted inFIG.8in turn equals the case according to which the folding propeller10is driven in rotation direction D, which equals forward travel. As no closing torque acts on the propeller blades6a,6bin this rotation direction D, an arresting of the folding propeller10via the propeller blade arresting means8is not absolutely necessary. In this state, the propeller blade arresting means8in the form of a sleeve14may therefore remain in a starting position Z10, as illustrated inFIG.5. Alternatively, or additionally the propeller blade arresting means8may also be designed in such a way that an arresting of the folding propeller10is achieved via of the propeller blade arresting means8in rotation direction D as well, which equals forward travel.

FIG.9shows a schematic side view of the folding propeller10according to some embodiments in an unfolded position Z2and a propeller blade arresting means8in an arresting position Z20. Analogous toFIG.6the illustration depicted inFIG.9equals the case of reverse travel of the folding propeller10. In this case the folding propeller10is driven in rotation direction D, which equals reverse travel. As a closing torque acts on the propeller7blades6a,6bin this rotation direction D, an arresting of the folding propeller10via the propeller blade arresting means8is necessary or provided, respectively.

To this end, the propeller blade arresting means8is designed in the form of a sleeve14, so that a movement of the sleeve14into the arresting position Z20is enforced by utilising the mass inertia of the sleeve14that occurs when rotating the hub2. In this position, the propeller blades6a,6bare arrested in the arresting position Z20.

FIG.10shows a schematic side view of a folding propeller10according to some embodiments in a first position Z110. The folding propeller10according to some embodiments also comprises a hub2, which may be driven around a rotation axis A via the drive shaft4. Some embodiments further comprise two propeller blades6a,6b, which are pivotably arranged on the hub2between a folded position Z1(illustrated as a dotted line) and an unfolded position Z2. Some embodiments further comprise a propeller blade arresting means8coupled with the hub2, which is configured for arresting the propeller blades6a,6bin the second, unfolded position Z2. The propeller blade arresting means comprises a thread22for this.

The propeller blade arresting means8according to some embodiments is therefore designed to move relative to the hub2in rotation direction D in such a way that a movement of the propeller blade arresting means8from a starting position Z10into an arresting position Z20(not illustrated inFIG.10) is enforced by utilising mass inertia that occurs when rotating the hub2.

An attachment and a thread22is arranged on the drive shaft4. The hub2may be screwed onto the thread22. The special feature of the hub2is characterised in that the entire hub2can be screwed onto and unscrewed from the drive shaft4by means of the thread22in the direction of the rotation axis of the drive shaft4. This screwing mechanism is activated on the basis of the mass inertia of the hub2and the drive shaft4.

Screwing and unscrewing the hub2relative to the drive shaft4means that the propeller blades6a,6bare mounted freely pivotable transverse to the rotation axis A via the bearing pin12in the first state according toFIG.10. The propeller blades6a,6bare pivoted along their propeller blade roots via a gear rack24in a synchronised way. The propeller blades6a,6bmay also be controlled via the gear rack24in the first state illustrated inFIG.10. The propeller blades6a,6bare further influenced via a rod26, which communicates with the gear rack24.

A further force for opening the propeller blades is introduced in this way, which improves the reliability and optimisation of opening. It is for example possible with this force, which acts only in one direction, to fold the propeller blades6a,6bduring forward travel.

The hub2, the propeller blades6a,6band the rack24may be made from any material here and may in particular include plastic or also metal alloys.

The thread22must however consist of a metal alloy in order to withstand the torques and guarantee a sliding along the thread surface. The thread22is preferably made from a material, the hardness of which differs from that of the hub2. This may prevent an occurrence of cold welding.

FIG.11shows a schematic side view of the folding propeller10according to some embodiments of a second position Z220. According to the illustration ofFIG.11the propeller blades6a,6bare controlled via the gear rack24in such a way that the same is in the unfolded position Z2. In addition, the folding propeller10is in an arrested position, the second position Z220, which is achieved in that the two components are screwed onto each other due to the mass inertia of the drive shaft4and the hub2.

FIG.12is a schematic perspective view of a folding propeller10according to some embodiments in an unfolded position. According to some embodiments the folding propeller10comprises a hub2, which has a first hub element2aand a second hub element2b, wherein the hub2may be driven via a drive shaft (not illustrated) around a rotation axis A. Some embodiments further comprise two propeller blades6a,6b(6bnot illustrated), which are pivotably arranged on the hub2, as well as a propeller blade arresting means coupled with the hub2in the form of a forced hub28, which is configured for arresting the propeller blades6a,6bin the unfolded position Z2.

The propeller blade arresting means in the form of a forced hub28is designed to move relative to the hub2, in particular the hub element2b, in rotation direction D in such a way that a movement of the propeller blade arresting means in the form of a forced hub28into an arresting position Z20, in which the propeller blades6a,6bare arrested, is enforced by utilising mass inertia that occurs when rotating the hub2.

In some embodiments, the reverse driving torque may be used for arresting instead of or in addition to mass inertia.

Two hub elements2aand2bmay twist freely to each other within 90° here. This twisting is induced and controlled by the mass inertia. A forced hub28, which generates a lift when twisted by 90° and therefore drives a gear rack24between the two propeller blades6a,6b, is located in the first hub element2aand may thus control its end position. Some embodiments further have a recess30at the forced hub28, which is located at the tapering end of the 90° twisting and thus acts as an additional resistance against folding.

Additional force for opening the propeller blade6a,6bis therefore introduced, which is to improve the reliability and optimisation of opening. This force acts in one direction only and further allows folding during forward travel. The first hub element2a, the forced hub28, the gear rack24and the propeller blades6a,6bhave no material restrictions. These may include plastic as well as metal alloys or consist of the same. The hub element2bhas the only restriction that it should be heavier than the hub element2ato realise optimal results. The forced hub28as well as the gear rack24must be made of materials of a different hardness to avoid cold welding.

Where applicable, all individual features illustrated in the embodiment examples can be combined with and/or exchanged for each other without departing from the scope of the disclosure.

LIST OF REFERENCE NUMBERS

A Rotation axis

D Rotation direction

2aFirst hub element

2bSecond hub element

8Propeller blade arresting means