Folding propeller and methods of use

Abstract

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.

Claims

1. A folding propeller comprising: a hub, which can be driven via a drive shaft around a rotation axis (A); at least two propeller blades pivotably arranged on the hub between a folded position (Z1) and an unfolded position (Z2); and a propeller blade arresting means 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 (D) between a starting position (Z10) and an arresting position (Z20).

2. The folding propeller according to claim 1, wherein the propeller blade arresting means is connected with the drive shaft in a torsion proof way, wherein the hub is uncoupled from the propeller blade arresting means in rotation direction (D), and wherein the propeller blade arresting means has a sleeve.

3. The folding propeller according to claim 2, wherein the hub is configured to be movable in such a way that a movement of the hub from the starting position (Z10) into the arresting position (Z20) is enforced when applying a torque to the drive shaft.

4. The folding propeller according to claim 1, wherein 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 (D), wherein the propeller blade arresting means has a sleeve.

5. The folding propeller according to claim 4, wherein 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 (Z10) into an arresting position (Z20), in which the propeller blades are arrested, is enforced by means of utilising mass inertia that occurs when rotating the hub.

6. The folding propeller according to claim 5, wherein the sleeve of the propeller blade arresting means has a recess and a catch in an area of each propeller blade, wherein the catch is formed on a downstream end of the sleeve.

7. The folding propeller according to claim 4, wherein the propeller blade arresting means is configured to be movable in such a way that its mass inertia is utilised in a targeted way for enforcing a movement of the propeller blade arresting means from the starting position (Z10) into the arresting position (Z20).

8. The folding propeller according to claim 1, wherein the rotation direction (D) equals a reverse operation of the propeller blades.

9. The folding propeller according to claim 1, wherein the propeller blades are mounted on a bearing pin arranged transverse to the rotation axis (A).

10. The folding propeller according to claim 1, wherein the propeller blade arresting means are located in the starting position (Z10) when the drive shaft stands still, and wherein the propeller blades are freely pivotable between the folded position (Z1) and the unfolded position (Z2) in this case.

11. The folding propeller according to claim 2, wherein the sleeve of the propeller blade arresting means has a recess and a catch in an area of each propeller blade.

12. The folding propeller of claim 11, wherein the catch is formed on a downstream end of the sleeve.

13. The folding propeller according to claim 1, wherein the propeller blade arresting means has an insertion bevel, which is configured such that, in a state in which the propeller blade arresting means is not yet completely in the arresting position (Z20), a folding of the propeller blades leads to a re-setting of the propeller blade arresting means into its starting position (Z10).

14. The folding propeller according to claim 1, wherein the propeller blade arresting means is made of one piece.

15. The folding propeller according to claim 14, wherein the propeller blade arresting means and/or the propeller blades include a metallic material.

16. The folding propeller according to claim 1, wherein the propeller blade arresting means is configured for arresting the propeller blades in an unfolded position (Z2) during drag operation of the folding propeller, so that an automatic rotation of the propeller blades takes place.

17. The folding propeller according to claim 16, wherein the propeller blade arresting means is configured to enable an automatic rotation of the propeller blades for energy recuperation from around 5 kn of speed.

18. The folding propeller according to claim 1, wherein the propeller blades are configured such that an initial opening of the propeller blades takes place by utilising centrifugal force.

19. The folding propeller according to claim 18, wherein the propeller blades include a metallic material, in particular a metal alloy.

20. A drive for a boat comprising a folding propeller, wherein the folding propeller comprises: a hub, which can be driven via a drive shaft around a rotation axis (A); at least two propeller blades pivotably arranged on the hub between a folded position (Z1) and an unfolded position (Z2); and a propeller blade arresting means 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 (D) between a starting position (Z10) and an arresting position (Z20).

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Preferred further embodiments of the disclosure will be explained in more detail in the following description of the Figures. Shown are:

(2) FIG. 1 a schematic view of a folding propeller according to some embodiments in a folded position;

(3) FIG. 2 a schematic view of the folding propeller according to some embodiments in an unfolded position and a propeller blade arresting means in a starting position;

(4) FIG. 3 a schematic view of the folding propeller according to some embodiments in an unfolded position and a propeller blade arresting means in an arresting position;

(5) FIG. 4 a schematic view of a folding propeller according to some embodiments in a folded position;

(6) FIG. 5 a schematic view of the folding propeller according to some embodiments in an unfolded position and a propeller blade arresting means in a starting position;

(7) FIG. 6 a schematic view of the folding propeller according to some embodiments in an unfolded position and a propeller blade arresting means in an arresting position;

(8) FIG. 7 a schematic view of the folding propeller according to some embodiments in a position that lies between the folded position and the unfolded position;

(9) FIG. 8 a schematic view of the folding propeller according to some embodiments in an unfolded position and a propeller blade arresting means in a starting position;

(10) FIG. 9 a schematic view of the folding propeller according to some embodiments in an unfolded position and a propeller blade arresting means in an arresting position;

(11) FIG. 10 a schematic side view of a folding propeller according to some embodiments in a first position;

(12) FIG. 11 a schematic side view of the folding propeller according to some embodiments in a second position; and

(13) FIG. 12 a schematic perspective view of a folding propeller according to some embodiments in an unfolded position.

DETAILED DESCRIPTION

(14) 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.

(15) FIG. 1 shows a schematic view of a folding propeller 10 according to some embodiments in a folded position Z1.

(16) The folding propeller 10 comprises a hub 2, which is uncoupled from the drive shaft 4 in rotation direction D. Two propeller blades 6a, 6b are pivotably arranged on the hub 2. The hub 2 may be driven around a schematically illustrated rotation axis A via the drive shaft 4, namely via a propeller blade arresting means 8, which is permanently, and therefore connected in a torsion proof way with the drive shaft 4.

(17) The hub 2 and the propeller blades 6a, 6b arranged 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 shaft 4 and the propeller blade arresting means 8.

(18) The propeller blades 6a, 6b are pivotably arranged on the hub 2 between a folded position Z1 and an unfolded position Z2 (for example shown in FIG. 2).

(19) The propeller blade arresting means 8 is equipped for arresting the propeller blades 6a, 6b in the unfolded position Z2 in order to prevent a (partial) folding of the propeller blades 6a, 6b, for example during reverse travel, when halting or during hydrogeneration, in this way. The propeller blade arresting means 8 is designed as a sleeve 14 here. The sleeve 14 has a recess 16 formed in its shell surface as well as a catch 18, which is formed on the downstream end of the sleeve 14. The propeller blade arresting means 8 designed as a sleeve 14 is movable relative to the hub 2 in rotation direction D between a starting position Z10 and an arresting position Z20 (for example shown in FIG. 3) together with the drive shaft 4 attached to the same.

(20) Accordingly, a relative movement between the hub 2 and the sleeve 14 may for example be achieved by utilising the torque applied by the sleeve 14 to the hub 2, which occurs when rotating the drive shaft 4, and therefore rotating the propeller blade arresting means 8 in form of the sleeve 14. The hub 2 is inhibited together with the propeller blades 6a, 6b arranged 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 means 8 to the hub 2 induces a movement between the propeller blade arresting means 8 and the hub 2. This way, a movement of the sleeve 14 relative to the hub 2 may be enforced from a starting position Z10, as illustrated in FIG. 1, into an arresting position Z20, as illustrated in FIG. 3.

(21) A schematic view of the folding propeller 10 according to some embodiments in an unfolded position Z2 is illustrated in FIG. 2, wherein the propeller blade arresting means 8 is still located in the starting position Z10 relative to the hub 2. The illustration shown in FIG. 2 approximately equals the case that occurs when the folding propeller 10 is in forward travel. Rotation direction D is therefore one that equals forward travel.

(22) The unfolding of the propeller blades 6a and 6b from the folded position Z1 shown in FIG. 1 into the unfolded position Z2 is realised through rotating the drive shaft 4 together with the propeller blade arresting means 8, which lastly acts on the hub 2 across the propeller blades 6a, 6b. As soon as the propeller blades 6a, 6b are set to rotate a centrifugal force acts on the same, which promotes an unfolding of the propeller blades 6a, 6b and thus generates an opening torque on the propeller blades 6a, 6b. In addition, an opening torque is applied to the propeller blades 6a, 6b and acts on the propeller blades 6a, 6b when applying a rotation of the hub 2 and the simultaneous application of a forward thrust resulting from the same.

(23) As can be gathered from the illustration in FIG. 2, in particular from the orientation of the vane profile, that a rotation of the folding propeller 10 in rotation direction D generates a forward thrust S.sub.v, generated upwards in the drawing. The resulting counter force, which acts on the propeller blades 6a, 6b, supports the unfolding of the propeller blades 6a, 6b. In other words, the propeller blades 6a, 6b are moved into the unfolded position Z2 by centrifugal force as well as by the reaction forces from the forward thrust generated by means of rotation.

(24) As the forward thrust S.sub.v is applied in this rotation direction D of the drive shaft and no closing torque acts on the propeller blades 6a, 6b, an arresting of the folding propeller 10 across the propeller blade arresting means 8 is not provided and is not necessary either. The propeller blades 6a, 6b are being pushed into the unfolded position Z2 at any point in time when a forward thrust is to be applied.

(25) In this state, the propeller blade arresting means 8 in the form of a sleeve 14 therefore remains, as illustrated in FIG. 2, typically in its starting position Z10. Alternatively, or additionally the propeller blade arresting means 8 may also be designed in such a way that an arresting of the folding propeller 10 across the propeller blade arresting means 8 also takes place in rotation direction D, which equals forward travel. In this way the propeller blades 6a, 6b may be arrested through a “sharp” reverse switch-on as well as a “sharp” forward switch-on.

(26) A schematic view of the folding propeller 10 according to some embodiments in an unfolded position Z2 and a propeller blade arresting means 8 in an arresting position Z20 is illustrated in FIG. 3. The illustration depicted in FIG. 3 for example equals the case that comes about when the folding propeller 10 is driven during reverse travel. Rotation direction D therefore equals reverse travel here. As an additional delivering torque acts on the propeller blades 6a, 6b in this rotation direction D via reverse thrust S.sub.R—for example through an inflow of surrounding water as well as exercising the reverse thrust S.sub.R directed in the closing direction of the propeller blades 6a, 6b—the closing torque on the propeller blade competes with the centrifugal force acting on the propeller blade. An arresting of the folding propeller 10 across the propeller blade arresting means 8 is therefore necessary or provided, respectively.

(27) To this end, the suggested propeller blade arresting means 8 in the form of a sleeve 14 as well as the hub 2 are designed such that a movement of the hub 2 relative to the sleeve 14 into the arresting position Z20 is enforced by utilising the torque applied to the hub 2, which occurs when rotating the drive shaft 4. In this position, the propeller blades 6a, 6b are arrested in the arresting position Z20. The difference between the starting position Z10 and the arresting position Z20 can be graphically deduced from a comparison of FIGS. 2 and 3. From this it can be seen that the change in rotation direction D from forward travel into reverse travel results in the sleeve 14 being rotated relative to the hub 2 in such a way in the latter case, see FIG. 3, that the sleeve 14 abuts on the propeller blade 6a with another flank, namely with the opposite flank of the recess 16, in which the propeller blade in question 6b is located. This is realised in that the torque applied to the hub 2, which occurs when turning the drive shaft 4, is utilised for enforcing a relative movement of the hub 2 relative to the sleeve 14 from a starting position Z10 into an arresting position Z20.

(28) A schematic view of a folding propeller 10 according to some embodiments is illustrated in a folded position Z1 in FIG. 4.

(29) The folding propeller 10 comprises a hub 2, which may be driven around a rotation axis A via a schematically illustrated drive shaft 4. The folding propeller 10 further comprises at least two propeller blades 6a, 6b, which are pivotably arranged on the hub 2 between a folded position Z1 as illustrated, and an unfolded position Z2 (for example shown in FIG. 5). The folding propeller 10 further comprises a propeller blade arresting means 8 movably coupled with the hub 2, which is configured for arresting the propeller blades 6a, 6b in the unfolded position Z2 in order to prevent a (partial) folding of the propeller blades 6a, 6b, for example during reverse travel, when halting or during hydrogeneration, in this way. The propeller blade arresting means 8 is designed as a sleeve 14 here. The sleeve 14 has a recess 16 formed in its shell surface as well as a catch 18, which is formed on the downstream end of the sleeve 14. The catch 18 has an insertion bevel 20. The propeller blade arresting means 8 designed as a sleeve 14 is freely moveable relative to the hub 2 in rotation direction D between a starting position Z10 and an arresting position Z20 (for example shown in FIG. 6).

(30) A relative movement between the hub 2 and the sleeve 14 may accordingly be realised by means of utilising the mass inertia of the sleeve 14, which occurs when accelerating the hub 2. A movement of the sleeve 14 from a starting position Z10, as illustrated in FIG. 4, into an arresting position Z20, as illustrated in FIG. 6, may then be enforced.

(31) A schematic view of the folding propeller 10 according to some embodiments is illustrated in an unfolded position Z2 in FIG. 5, wherein the propeller blade arresting means 8 is still in the starting position Z10. The illustration shown in FIG. 5 approximately equals the case that comes about when the folding propeller 10 is in forward travel. Rotation direction D is accordingly one that equals forward travel.

(32) The unfolding of the propeller blades 6a and 6b from the folded position Z1 shown in FIG. 4 into the unfolded position Z2 is realised through a rotation of the hub 2 and the centrifugal force thus acting on the propeller blades 6a, 6b. An opening torque additionally acts on the propeller blades 6a, 6b when applying a rotation of the hub 2 and the simultaneous applying of a forward thrust resulting from the same to the propeller blades 6a, 6b. In other words, the propeller blades 6a, 6b are moved by the centrifugal force and the forward thrust applied in the unfolded position Z2.

(33) As no closing torque acts on the propeller blades 6a, 6b in this rotation direction D of the hub 2 in forward thrust direction, an arresting of the folding propeller 10 across the propeller blade arresting means 8 is not provided and is not necessary either. The propeller blades 6a, 6b are driven into the unfolded position Z2 at any point in time when a forward thrust is to be applied.

(34) The propeller blade arresting means 8 therefore remains in this state, as illustrated in FIG. 2, in the form of a sleeve 14, typically in its starting position Z10. Alternatively, or additionally the propeller blade arresting means 8 may also be designed in such a way that an arresting of the folding propeller 10 via the propeller blade arresting means 8 also takes place in rotation direction D, which equals forward travel. In this way the propeller blades 6a, 6b may be arrested through a “sharp” reverse switch-on as well as a “sharp” forward switch-on.

(35) A schematic view of the folding propeller 10 according to some embodiments in an unfolded position Z2 and a propeller blade arresting means 8 in an arresting position Z20 is illustrated in FIG. 6. The illustration depicted in FIG. 6 for example equals the case that comes about when the folding propeller 10 is driven during reverse travel. Rotation direction D therefore equals reverse travel here. As a closing torque acts on the propeller blades 6a, 6b in 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 blades 6a, 6b—an arresting of the folding propeller 10 via the propeller blade arresting means 8 is therefore necessary or provided, respectively.

(36) To this end the suggested propeller blade arresting means 8 in the form of a sleeve 14 is designed in such a way that a movement of the sleeve 14 into the arresting position Z20 is enforced by utilising the mass inertia of the sleeve 14, which occurs when accelerating the hub 2. In this position, the propeller blades 6a, 6b are arrested in the arresting position Z20. The difference between the starting position Z10 and the arresting position Z20 can be graphically deduced from a comparison of FIGS. 5 and 6. It becomes apparent from this that the change in rotation direction D from forward travel into reverse travel results in the sleeve 14 being rotated relative to the hub 2 in such a way in the latter case, see FIG. 6, that the sleeve 14 abuts on the propeller blade 6a. This is realised in that the mass inertia of the sleeve 14, which occurs when accelerating the hub 2, is utilised for enforcing a relative movement of the sleeve14 from a starting position Z10 into an arresting position Z20.

(37) This is achieved not only when reversing the rotation direction, but at any increase of the speed of the hub 2 in rotation direction that equals reverse travel. It may for example be achieved with a rapid rotation of the hub 2 that the propeller blades 6a, 6b straighten up and it may then be achieved with a further acceleration of the rotation of the hub 2 that the hub 2 quasi turns under the sleeve 14 that remains in its current movement condition due to its inertia, so that an arresting of the propeller blades 6a, 6b is achieved.

(38) FIG. 7 shows a schematic view of the folding propeller 10 according to some embodiments in a position that lies between the folded position Z1 and the unfolded position Z2. FIG. 7 substantially serves for demonstrating a transition state of the unfolding process of the propeller blades 6a, 6b. It can be seen from the illustration in FIG. 7 that the arresting of the propeller blades 6a, 6b is achieved by means of the catch 18 as long as the hub 2 is driven in reverse travel. The latter can grip the propeller blades 6a, 6b by means of the insertion bevels 20 before these are completely unfolded.

(39) FIG. 8 shows a schematic view of the folding propeller 10 according to some embodiments in an unfolded position Z2, and a propeller blade arresting means 8 in a starting position Z10. It can be seen from the illustration of FIG. 8 that the propeller blades 6a, 6b are each mounted above a bearing pin 12 that is arranged transverse to rotation axis A. The illustration depicted in FIG. 8 in turn equals the case according to which the folding propeller 10 is driven in rotation direction D, which equals forward travel. As no closing torque acts on the propeller blades 6a, 6b in this rotation direction D, an arresting of the folding propeller 10 via the propeller blade arresting means 8 is not absolutely necessary. In this state, the propeller blade arresting means 8 in the form of a sleeve 14 may therefore remain in a starting position Z10, as illustrated in FIG. 5. Alternatively, or additionally the propeller blade arresting means 8 may also be designed in such a way that an arresting of the folding propeller 10 is achieved via of the propeller blade arresting means 8 in rotation direction D as well, which equals forward travel.

(40) FIG. 9 shows a schematic side view of the folding propeller 10 according to some embodiments in an unfolded position Z2 and a propeller blade arresting means 8 in an arresting position Z20. Analogous to FIG. 6 the illustration depicted in FIG. 9 equals the case of reverse travel of the folding propeller 10. In this case the folding propeller 10 is driven in rotation direction D, which equals reverse travel. As a closing torque acts on the propeller7 blades 6a, 6b in this rotation direction D, an arresting of the folding propeller 10 via the propeller blade arresting means 8 is necessary or provided, respectively.

(41) To this end, the propeller blade arresting means 8 is designed in the form of a sleeve 14, so that a movement of the sleeve 14 into the arresting position Z20 is enforced by utilising the mass inertia of the sleeve 14 that occurs when rotating the hub 2. In this position, the propeller blades 6a, 6b are arrested in the arresting position Z20.

(42) FIG. 10 shows a schematic side view of a folding propeller 10 according to some embodiments in a first position Z110. The folding propeller 10 according to some embodiments also comprises a hub 2, which may be driven around a rotation axis A via the drive shaft 4. Some embodiments further comprise two propeller blades 6a, 6b, which are pivotably arranged on the hub 2 between a folded position Z1 (illustrated as a dotted line) and an unfolded position Z2. Some embodiments further comprise a propeller blade arresting means 8 coupled with the hub 2, which is configured for arresting the propeller blades 6a, 6b in the second, unfolded position Z2. The propeller blade arresting means comprises a thread 22 for this.

(43) The propeller blade arresting means 8 according to some embodiments is therefore designed to move relative to the hub 2 in rotation direction D in such a way that a movement of the propeller blade arresting means 8 from a starting position Z10 into an arresting position Z20 (not illustrated in FIG. 10) is enforced by utilising mass inertia that occurs when rotating the hub 2.

(44) An attachment and a thread 22 is arranged on the drive shaft 4. The hub 2 may be screwed onto the thread 22. The special feature of the hub 2 is characterised in that the entire hub 2 can be screwed onto and unscrewed from the drive shaft 4 by means of the thread 22 in the direction of the rotation axis of the drive shaft 4. This screwing mechanism is activated on the basis of the mass inertia of the hub 2 and the drive shaft 4.

(45) Screwing and unscrewing the hub 2 relative to the drive shaft 4 means that the propeller blades 6a, 6b are mounted freely pivotable transverse to the rotation axis A via the bearing pin 12 in the first state according to FIG. 10. The propeller blades 6a, 6b are pivoted along their propeller blade roots via a gear rack 24 in a synchronised way. The propeller blades 6a, 6b may also be controlled via the gear rack 24 in the first state illustrated in FIG. 10. The propeller blades 6a, 6b are further influenced via a rod 26, which communicates with the gear rack 24.

(46) 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 blades 6a, 6b during forward travel.

(47) The hub 2, the propeller blades 6a, 6b and the rack 24 may be made from any material here and may in particular include plastic or also metal alloys.

(48) The thread 22 must however consist of a metal alloy in order to withstand the torques and guarantee a sliding along the thread surface. The thread 22 is preferably made from a material, the hardness of which differs from that of the hub 2. This may prevent an occurrence of cold welding.

(49) FIG. 11 shows a schematic side view of the folding propeller 10 according to some embodiments of a second position Z220. According to the illustration of FIG. 11 the propeller blades 6a, 6b are controlled via the gear rack 24 in such a way that the same is in the unfolded position Z2. In addition, the folding propeller 10 is 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 shaft 4 and the hub 2.

(50) FIG. 12 is a schematic perspective view of a folding propeller 10 according to some embodiments in an unfolded position. According to some embodiments the folding propeller 10 comprises a hub 2, which has a first hub element 2a and a second hub element 2b, wherein the hub 2 may be driven via a drive shaft (not illustrated) around a rotation axis A. Some embodiments further comprise two propeller blades 6a, 6b (6b not illustrated), which are pivotably arranged on the hub 2, as well as a propeller blade arresting means coupled with the hub 2 in the form of a forced hub 28, which is configured for arresting the propeller blades 6a, 6b in the unfolded position Z2.

(51) The propeller blade arresting means in the form of a forced hub 28 is designed to move relative to the hub 2, in particular the hub element 2b, in rotation direction D in such a way that a movement of the propeller blade arresting means in the form of a forced hub 28 into an arresting position Z20, in which the propeller blades 6a, 6b are arrested, is enforced by utilising mass inertia that occurs when rotating the hub 2.

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

(53) Two hub elements 2a and 2b may twist freely to each other within 90° here. This twisting is induced and controlled by the mass inertia. A forced hub 28, which generates a lift when twisted by 90° and therefore drives a gear rack 24 between the two propeller blades 6a, 6b, is located in the first hub element 2a and may thus control its end position. Some embodiments further have a recess 30 at the forced hub 28, which is located at the tapering end of the 90° twisting and thus acts as an additional resistance against folding.

(54) Additional force for opening the propeller blade 6a, 6b is 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 element 2a, the forced hub 28, the gear rack 24 and the propeller blades 6a, 6b have no material restrictions. These may include plastic as well as metal alloys or consist of the same. The hub element 2b has the only restriction that it should be heavier than the hub element 2a to realise optimal results. The forced hub 28 as well as the gear rack 24 must be made of materials of a different hardness to avoid cold welding.

(55) 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

(56) A Rotation axis

(57) D Rotation direction

(58) S.sub.R Reverse thrust

(59) S.sub.V Forward thrust

(60) Z1 Folded position

(61) Z2 Unfolded position

(62) Z10 Starting position

(63) Z20 Arresting position

(64) Z110 First position

(65) Z220 Second position

(66) 2 Hub

(67) 2a First hub element

(68) 2b Second hub element

(69) 4 Drive shaft

(70) 6a, 6b Propeller blade

(71) 8 Propeller blade arresting means

(72) 10 Folding propeller

(73) 12 Bearing pin

(74) 14 Sleeve

(75) 16 Recess

(76) 18 Catch

(77) 20 Insertion bevel

(78) 22 Thread

(79) 24 Gear rack

(80) 26 Rod

(81) 28 Forced hub

(82) 30 Recess