WO 2020/224773 PCT/EP2019/061802

A controllable pitch propeller, method of assembling and disassembling a controllable pitch propeller

Technical field

5 [001] The present invention relates to a controllable pitch propeller according to preamble of claim 1.

[002] The present invention relates to method of assembling and disassembling a controllable pitch propeller.

10 Background art

[003] Marine vessels are generally provided with a propulsion system which includes a propeller. The propeller may be a controllable pitch propeller (CPP propeller) in which the blades of the propeller are rotatable in respect of a longi tudinal direction of a blade. CPP propeller provides advantages such as the least 15 drag depending on the speed used, the ability to move the sea vessel backwards by providing astern thrust, and the ability adopt a feathering position.

[004] EP 2323902 A1 discloses a propeller comprising a boss with a boss di ameter and at least one propeller blade. The propeller further comprises an ad justing member, which comprises a piston rod head, adapted to be displaced 20 along a first dimension, and a transformation arrangement connecting the piston rod head to the propeller blade such that a displacement, in the first dimension, of the piston rod head results in a change in the pitch of the propeller blade. The transformation arrangement comprises a slot comprising a slot portion with a slot centre extending in a slot extension direction which direction is arcuate with a 25 radius of curvature. The transformation arrangement further comprises a control element slidably engaged with at least the slot portion. There is at least one gen eral problem relating to the propeller disclosed in EP 2323902. Namely, the struc ture requires that particularly the piston rod head needs to be constructed of two P38333PC00 201905081312

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parts in order to make possible the assembly of the adjusting member. This un duly, for example, makes the assembly difficult and causes a potential decrease of its strength.

[005] As may be realized from the above, there is a need for improvements of 5 the prior art adjustable propeller arrangements. An object of the invention is to provide a controllable pitch propeller in which the performance is considerably improved compared to the prior art solutions. It is a further object to provide a method of assembling and disassembling controllable pitch propeller.

10 Disclosure of the Invention

[006] Objects of the invention can be met substantially as is disclosed in the independent claims and in the other claims describing more details of different embodiments of the invention.

[007] According to an embodiment of the invention a controllable pitch propeller 15 comprises

a hub,

a number of propeller blades arranged to be rotatable in respect to a rotational axis of the propeller blade to the hub, and

a blade adjusting system for each propeller blade configured to rotate the propel- 20 ler blade in respect to the hub, the blade adjusting system comprising

a yoke having a longitudinal axis and a longitudinal side wall, which yoke is arranged to the hub movably in the direction of the longitudinal axis and a force transmission system configured to rotate the propeller blades in respect to the hub by movement of the yoke in the longitudinal direction, 25 and wherein the force transmission system comprises

a curved, elongated depression arranged on the side wall of the yoke, and a guide member arranged in connection with the propeller blade eccentrically to the rotational axis of the propeller blade, the guide member extending into the depression, and

30 a sliding block arranged slidably in the depression, to which sliding block the guide member is coupled rotatably, WO 2020/224773 PCT/EP2019/061802

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wherein the elongated depression and the sliding block are formed so as to allow the sliding block to enter into, and exit from the elongated depression via a pas sageway at an end of the depression, by relative movement between the yoke and the hub in the direction of the longitudinal axis.

[008] This makes the assembly and disassembly of the propeller advantageous because there is no need to dismantle the yoke.

[009] According to an embodiment of the invention the longitudinal side wall of the yoke is substantially planar and parallel with the longitudinal axis, and the depression in the side wall comprises a control section having a first control edge with a first radius of curvature and a second control edge with a second radius of curvature having a common center point, and the depression comprises an as sembly section having a passageway opening for the sliding block at the axial end of the yoke, which assembly section has a width greater than the difference between the first and the second radius of curvature.

[0010] According to an embodiment of the invention the depression comprises a first control edge with a first radius of curvature and a second control edge with a second radius of curvature having a common center point, and the sliding block is provided with a first guide edge with the first radius of curvature and a second guide edge with the second radius of curvature.

[001 1 ] According to an embodiment of the invention the sliding block is provided with a circular recess and the guide member is provided with circular pin which is configured to fit into the recess, and the sliding block is arranged to be asym metrical in respect to a line running through the center point of the curvatures and the center of the circular recess.

[0012] According to an embodiment of the invention the depression comprises a control section having a first control edge with a first radius of curvature and a second control edge with a second radius of curvature having a common center point, and the sliding block is provided with a circular recess and the guide mem ber is provided with circular pin which is configured to fit into the recess, and the sliding block is arranged to be asymmetrical in respect to a line running through the center point of the curvatures and the center of the circular recess. P38333PC00 201905081312

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[0013] According to an embodiment of the invention the depression comprises at its end, i.e. at the assembly section a first assembly edge and a second as sembly edge parallel to each other wherein the distance between the first and the second assembly edges is such that the depression can accommodate the

5 sliding block in inclined position which the block reaches at the assembly posi tion, where the block is brought to the end of the second control edge against the second assembly edge.

[0014] The sliding block is provided a first side edge and a second side edge extending between the first guide edge and the second guide edge. The sliding

10 block is generally of rectangular shape, formed by the side edges and the guide edges. The sliding block is provided with a circular recess into which the guide member is fitted rotatably. The guide edges are formed to be in conformity with the shape of the depression whereas the side edges may be formed more flexibly to meet functional requirements of the force transmission system.

15 [0015] According to an embodiment of the invention the first side edge of the sliding block is arranged at an angle in respect to a line running through the cen ter point of the radiuses of the curvatures of the guide edges and the center of the circular recess.

[0016] According to an embodiment of the invention in the sliding block a dis

20 tance between a corner of the first side edge and first guide edge and the a line running through the center point of the curvatures of the guide edges, and the center of the circular recess is longer than a distance between a corner of the first side edge and second guide edge, and the a line running through the center point of the curvatures of the guide edges and the center of the circular recess.

25 [0017] According to an embodiment of the invention the yoke is of a monolithic structure.

[0018] According to an embodiment of the invention the sliding block is provided with four main corners wherein a first diagonal line linking two opposite corners and a second diagonal line linking two other opposite corners are of different

30 length.

[0019] Method of disassembling a controllable pitch propeller comprising WO 2020/224773 PCT/EP2019/061802

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a hub,

a number of propeller blades arranged to be rotatable in respect to a rotational axis of the propeller blade to the hub, and

a blade adjusting system for each propeller blade configured to rotate the propel ler blade in respect to the hub, the blade adjusting system comprising

a yoke having a longitudinal axis and longitudinal side wall, which yoke is arranged to the hub movably in the direction of the longitudinal axis and a force transmission system configured to rotate the propeller blades in respect to the hub by movement of the yoke in the longitudinal direction, and wherein the force transmission system comprises

a curved, elongated depression arranged on the side wall of the yoke, and a guide member arranged in connection with the propeller blade eccentrically to the rotational axis of the propeller blade, the guide member extending into the depression, and

a sliding block arranged in the depression, to which sliding block the guide mem ber is coupled rotatably,

wherein the method comprising

changing the relative position between the yoke and the hub thereby moving the sliding block and the guide member near a passageway at the end of the elon gated depression,

changing the relative position between the yoke and the hub and departing the sliding block from the depression via the passageway in the direction of the lon gitudinal axis.

According to an embodiment of the invention the sliding block is guided to near the passageway at the end of the elongated depression until one of the corners of the sliding block is at the end of a second control edge of the depression and changing the relative position between the yoke and the hub in the direction of the longitudinal axis and thus repositioning the sliding block from the depression.

According to an embodiment of the invention the movement of the guide member is linear movement.

[0020] Method of assembling a controllable pitch propeller comprising

a hub, WO 2020/224773 PCT/EP2019/061802

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a number of propeller blades arranged to be rotatable in respect to a rotational axis of the propeller blade to the hub, and

a blade adjusting system for each propeller blade configured to rotate the propel ler blade in respect to the hub, the blade adjusting system comprising

a yoke having a longitudinal axis and longitudinal side wall, which yoke is ar ranged to the hub movably in the direction of the longitudinal axis and

a force transmission system configured to rotate the propeller blades in respect to the hub by movement of the yoke in the longitudinal direction, and wherein the force transmission system comprises

a curved, elongated depression arranged on the side wall of the yoke, and a guide member arranged in connection with the propeller blade eccentrically to the rotational axis of the propeller blade, and

a sliding block

wherein the method comprising

assembling the guide member into the sliding block,

positioning the guide member and the sliding block in front of a passageway at the end of the depression at the yoke

changing the relative position between the yoke and the hub in the direction of the longitudinal axis and thereby guiding the sliding block in to the depression.

[0021 ] According to an embodiment of the invention the sliding block is guided by linear movement to the elongated depression until one of the corners of the sliding block is at the end of a second control edge of the depression.

[0022] According to an embodiment of the invention the movement of the guide member is linear movement.

[0023] The exemplary embodiments of the invention presented in this patent ap plication are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. The novel features which are considered as charac teristic of the invention are set forth in particular in the appended claims. P38333PC00 201905081312

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Brief Description of Drawings

[0024] In the following, the invention will be described with reference to the ac companying exemplary, schematic drawings, in which

Figure 1 illustrates a controllable pitch propeller according to an embodiment of 5 the invention,

Figure 2 illustrates a yoke of a controllable pitch according to an embodiment of the invention,

Figure 3 illustrates a sliding block according to still an embodiment of the inven tion, and

10 Figure 4 illustrates an assembly position of the sliding block in the yoke according to an embodiment of the invention.

Detailed Description of Drawings

[0025] Figure 1 depicts schematically main parts and operation of a controllable 15 pitch propeller 10, which is in the following generally referred to as a propeller 10. In the view A the pitch is adjusted towards a first direction and in the view B the pitch is adjusted towards a second direction. It should be noted that the figure 1 is illustrated for purpose of generally describe the concept of controllable pitch propeller. The propeller blades are continuously adjustable between astern, 20 ahead, feathering and neutral positions.

[0026] The propeller 10 comprises a hub 12 which forms a body of the propeller 12. The hub 12 is coupled to a propeller shaft 14 at its first end 12’ by means of for example a hub mounting flange 16 arranged at the end of the propeller shaft 14. There is an end cover 18 arranged at a second end 12” of the hub 12. The 25 shaft 14 has a center axis 20 and the hub 12 is connected to the shaft 14 coaxi ally. The center axis 20 may be referred to as a longitudinal axis in the following.

[0027] There are number of blades 22 arranged to the hub 12 such that each blade 22 is arranged to be rotatable in respect to a rotational axis of the propeller WO 2020/224773 PCT/EP2019/061802

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blade 23 to the hub 12. The number of blades 22 can naturally vary according to the practical application. The blade 22 comprises at its root a base 26 by means of which it is rotatable coupled to the hub 12. The base is for example a circular disk-like part arranged perpendicularly to the rotational axis 23 of the blade. The base is configured to allow the rotational movement but substantially prevent movement in the direction of the rotational axis 23 of the blade. As is shown in the figure 1 the base is provided with locking part 28 which extends radially into a mating surface in the opening of the hub 12. The blade, or its base 26 is ad vantageously attached to the locking part 28 in removable manner using for ex ample a screw joint. The rotational position of the blade 22 rules the pitch of the propeller and in practise the blade in the propeller 10 according to the invention can be positioned in neutral position providing zero thrust, feathering position providing minimized water resistant for ahead moving vessel (the blades are gen erally turned such that their mid-to-edge section is aligned with waterflow), ahead position and astern position, and in any position between those, providing a con tinuous adjustment of the blade angle.

[0028] The propeller 10 comprises a blade adjusting system 30 in connection with each propeller blade configured to rotate the propeller blade in respect to the hub 12. The blade adjusting system 30 comprises firstly a yoke 32 which is arranged into an internal space 24 of the hub 12. The internal space 24 is sub stantially coaxial with the longitudinal axis 20 of the shaft 14. The yoke 32 ar ranged into the space 24 movably in the direction of the longitudinal axis 20. The yoke is respectively generally coaxial to the hub at least as far as is needed for operation of the blade adjusting system 30. The yoke 32 can also be referred to as a piston head due to its principle of operation. The yoke 32 is arranged to move in the direction of the longitudinal axis 22, actuated hydraulically. The yoke has a longitudinal axis which coincides with the longitudinal axis 22 of the shaft 14. The yoke 32 is provided with one or more seals 34 which extend around the periphery of the yoke 32 for sealing the gap between the yoke 32 and the inner wall of the hub 12 and the shaft 14. In the figure 1 the yoke 32 comprises a piston part 27 which arranged in a space 25 in the end cover 18 of the hub.

[0029] The piston part 25 divides the space 25 into partial spaces 25’, 25” and the spaces operate as hydraulic work spaces. The propeller shaft 14 comprises WO 2020/224773 PCT/EP2019/061802

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a first conduit 36 and a second conduit 38 for hydraulic liquid to operate the piston part 27. There is also a third conduit 37 for lubrication. In the view A pressure is applied in the first conduit 36 and hydraulic fluid flow in the partial space 24” behind the yoke 32 and hydraulic fluid is allowed to flow from the partial space 24’ in front of the yoke 32 causing the movement of the yoke in the direction of the longitudinal axis 20 towards the propeller shaft 14. In the view B pressure is applied in the second conduit 38 and hydraulic fluid flow in the partial space 24’ in front of the yoke 32 and hydraulic fluid is allowed to flow from the partial space 24” behind of the yoke 32 causing the movement of the yoke in the direction of the longitudinal axis 20 away from the propeller shaft 14.

[0030] The yoke 32 and the blade 22 are coupled with each other by a force transmission system 31 configured to rotate the propeller blades 22 in respect to the hub 12 by movement of the yoke 32 in the longitudinal direction i.e. in the direction of the longitudinal axis 20. The force transmission system 31 comprises a depression 40 arranged on a side wall of the yoke 32, a guide member 42, such as a pin, arranged in connection with the propeller blade 22, which guide member 42 is arranged eccentrically to the rotational axis of the propeller blade 23. In the figure 1 the blade adjusting system 30 is in a position where the guide member 42 is in line with the rotational axis of the propeller blade 23. The guide member extends into the depression and is therefore controlled by the depression 40. The force transmission system comprises further a sliding block 44 between the guide member 42 and the depression 40. The depression 40 and the sliding block 44 are configured to allow the sliding block to move along the elongated depression thereby rotating the propeller blade. In the embodiment of the figure 1 the yoke 32 supported by the hub 12 and the shaft 14.

[0031 ] Figure 2 discloses a front and side views of a yoke 22 of the blade adjust ing system in the propeller having five blades. This shows an alternative embod iment to support and move the yoke 22 in the hub 12 to the embodiment shown in the figure 1. As can be seen the yoke 22 maybe supported by the hub 12 and an end of the shaft 14. In the embodiment shown in the figure 2 the yoke 22 itself constitute the piston part so that the hydraulic force is subjected directly to the yoke 32. The internal space 24 in the hub is fluidly separated into two partial spaces, 24’, 24”. The partial spaces are partly bordered by the yoke 32 and the WO 2020/224773 PCT/EP2019/061802

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spaces operate as hydraulic work spaces. The propeller shaft 14 comprises a first conduit 36 and a second conduit 38 for hydraulic liquid. Hydraulic fluid can be fed via the first conduit 36 into and from the partial space 24” behind the yoke 32 and through the second conduit 38 into the partial space 24’ in front of the yoke 32 causing the movement of the yoke in the direction of the longitudinal axis 20.

[0032] What comes to the structure, operation and intended use of the blade adjusting system according to the invention, the yoke 22 adjusts each one of the propeller blades simultaneously in synchronized manner. Like in the figure 1 the yoke 32 in the figure 2 is arranged inside the hub 12 which is removably fastened to a hub mounting flange 16 at the end of the shaft 14. In the figure 2 the depres sion 40 of the yoke is disclosed in more detailed manner and this applies also the yoke shown in the figure 1 . The force transmission system configured to ro tate the propeller blades in respect to the hub comprises a sliding block 44 be tween the guide member (not shown) and the depression 40. The sliding block 44 is shown assembled into the depression 40 and its movement is controlled - in addition to the guide member arranged in connection with the propeller blade eccentrically (not shown) to the rotational axis of the propeller blade - by edges 40’, 40” of the depression 40 when the yoke 32 is moved in the direction of the longitudinal axis 22. The depression 40 and the sliding block 44 are configured to allow the sliding block to move along the elongated depression thereby rotating the propeller blade. As is shown in the figure 2 the depression is of curved and elongated shape. The total stroke of the yoke will be shorter when the depression is curved instead of being straight, and the torque is more uniform in all pitch angles.

[0033] The depression 40 arranged on a longitudinal side wall 32’ of the yoke 32, which depression 40 has an open passageway at its end. Thus the depres sion may be referred to as a groove also. The side wall 32’ of the yoke 32 is substantially planar and it is parallel to the longitudinal axis 20. It is further shown in the figure 2 that the depression in the side wall comprises a control section having first control edge 40’ with a first radius of curvature R1 and a second con trol edge 40” with a second radius of curvature R2 having a common center point C. The depression 40 has substantially planar bottom 41 between the control WO 2020/224773 PCT/EP2019/061802

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edges which is parallel to the side wall 32’. The radiuses are of constant length and therefore the depression has constant width W1. Further, the depression 40 comprises an assembly section 46 which has the open passageway at the axial end of the side wall 32’ of the yoke 32 extending over an edge of the side wall 32’. The assembly section 46 is generally parallel to the longitudinal axis 20.

[0034] Figure 3 shows the sliding block 44 of the figure 2 in more detailed man ner. There is also depicted the elongated depression 40 of the yoke 32 and the first control edge 40’ and the second control edge 40” of the depression which together with the sliding block 44 are configured to allow the sliding block 44 to move along the elongated depression 40. The sliding block 44 comprises a first guide edge 48 which is arranged against the first control edge 40’ of the depres sion in the yoke. Advantageously the thickness (the dimension in the direction of the normal of the plane of the figure 3) of the sliding block 44 is equal to or less than the depth of the depression 40. This way the sliding block does not interfere with the base of the propeller blade when the propeller is assembled for use. The sliding block 44 comprises also a second guide edge 50 which is arranged against the second control edge 40” of the depression in the yoke 32.

[0035] The first guide edge 48 of the sliding block 44 substantially coincides with the form of the first control edge 40’ of the depression 40 and the form of the second guide edge 50 coincides with the form of the second control edge 40” of the depression 40. Thus, the control edges are curved. The radius of curvature R1 of the first guide edge 48 of the sliding block 44 substantially equals to the radius of curvature of the first control edge 40’ of the depression 40 and respec tively, the radius of curvature R2 of the second guide edge 50 of the sliding block 44 substantially equals to the radius of curvature of the second control edge 40” of the depression 40. Naturally there must be some tolerance to allow the sliding block movement in the depression 40. Also, curvatures of the control edges 40’, 40” in the depression of the yoke and the guide edges 48, 50 of the sliding block have a common center point C of the radiuses of the curved control edges.

[0036] The sliding block is provided with a circular recess 52 or a through hole into which the guide member (see figure 1 reference 42), such as a pivot pin, is configured to fit rotatably. Even if not shown here it is advantageous to use a separate bearing bush between the pivot pin and the wall of the sliding block. WO 2020/224773 PCT/EP2019/061802

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Using the sliding block which is coupled rotatably with the guide member in creases the contact area between the parts, decreasing surface pressure in force transmission.

[0037] In the figure 3 the radius line R2 runs through the center point the curva ture C and the center of the circular recess 52. As can be seen in the figure the sliding block 44 is asymmetrical in respect to a line R2 running through the center point of the curvatures C and the center of the circular recess. This facilitates the insertion and removal of the sliding block 44 into and from the depression 40 by moving it, while being guided by the bottom 41 (see figure 2) of the depression 40, over an end edge 43 of the depression via the passageway at the longitudinal end of the planar side wall 32’ of the yoke 32. Also the width W2 of the depression opening at the axial end is minimized.

[0038] The shape of the sliding block 44 is generally rectangular, though it is advantageous to provide the corners with rounding. In addition to the control edges 48, 50 the sliding block 44 is provided a first side edge 58 and a second side edge 60 extending between the first guide edge 48 and the second guide edge 50. The corners can be referred to with the illustrated radius of curvature of the corner. For example the corner between the first control edge 48 and the first side edge 58 is referred to with reference R3. In the figure 3 it is shown that corners R3 and R4 are provided with greater radius of curvature than the corners R5 and R6. This also facilitates the insertion and removal of the sliding block 44 into and from the depression 40. According to an embodiment of the invention the radius of curvature R3 equals to R4 and it is 15 - 25 % of the diameter of the recess 42 of the sliding block, while the radius of curvature R5 equals to R6 being about 25-35% of the radius of curvature R3.

[0039] In the sliding block shown in the figure 3 the first side edge 58 is arranged at an angle a in respect to a line R2 running through the center point C of the curvature’s radiuses R1 , R2 and the center of the circular recess 52. The angle is such that first control edge 48 of the sliding block 44 is longer than the second control edge 50 of the sliding block 44. The first side edge 58 can by formed suitably such that the sliding block 44, can be move farther to position to upwards in the figure 2, i.e. to very proximity of an end of the depression 40 which facili tates the guide member 42 of propeller blade to reach an extreme position in WO 2020/224773 PCT/EP2019/061802

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respect to the longitudinal side wall 32’ of the yoke. The side edge can be pro vided with e.g. suitable cut-outs or a bevel for that purpose.

[0040] The form of the sliding block is also such that a distance from a corner of the first side edge 58 and first guide edge 48 to the center line R2 is longer than a distance from a corner of the first side edge 58 and second guide edge 50 to the line R2.

[0041 ] The asymmetrical state of the sliding block 44 can be by seen by a feature that the shortest distance L1 between perimeter of the recess 52 and first side edge 58 is shorter than the shortest distance L2 between perimeter of the recess 52 and second side edge 60 of the sliding block 44.

[0042] Figure 3 illustrates also that being generally rectangular the sliding block 44 is provided with four corners wherein a first diagonal line 54 linking two oppo site corners and a second diagonal line 56 linking two other opposite corners are of different length. Also the crossing point of the line diagonals deviates from the center of the circular recess 52.

[0043] Method of assembling a controllable pitch propeller according to the in vention can be rationalized with a reference to the Figure 4. Figure 4 shows a section of the planar side wall 32’ of the yoke according to the Figure 2. There is also shown the depression 40 and the sliding block 44 arranged into the depres sion. As can be seen in the figure 4 the depression 40 comprises an assembly section 46 which opens at the axial end of the planar wall 32’ of the yoke 32 between a first assembly edge 40”’ and a second assembly edge 40””. An end of the curved first control edge 40’ intersect with a first assembly edge 40”’ of the depression at the assembly section, which first assembly edge 40”’ is parallel to the longitudinal axis 20. Respectively, an end of the curved second control edge 40” intersect with a second assembly edge 40”’ of the depression at the assem bly section, which second assembly edge is parallel to the longitudinal axis 20 also. In the figure 4 the yoke 32 is positioned in the direction of the longitudinal axis 22 such that the sliding block 44 is guided to the assembly section 46, near the passageway at the end of the elongated depression 40, as is depicted by the arrow A. At this position one of the corners of the sliding block is at end of the WO 2020/224773 PCT/EP2019/061802

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second control edge 40”, and also at the intersection of the second assembly edge 40”” and the second control edge 40”.

[0044] This position may be reached by moving the yoke 32 to the direction to wards the flange 16 of the hub 32 (as seen in the figure 2). So, it is the first necessary step in disassembling the propeller, to position the sliding block 44 at position shown in the figure 4 i.e. laterally in respect to the planar side wall 32’ at the opening location of the depression 40, that is near the passageway at the end of the depression 40 at the edge of the planar wall 32’. The assembly section 46 of the depression 40 at the area of the opening of the depression is used for assembly or disassembly of the propeller, and the position of the elements shown in the figure 4 may be referred to as an assembly position. In other words the depression is provided with an opening in the direction of the longitudinal axis 20. The width W2 of the opening, i.e. the distance between the first and the sec ond assembly edges is greater than the difference between the first R1 and the second radius R2 of curvature, i.e. the width Wl .The the distance between the first and the second assembly edges is such that is can accommodate the sliding block therein in inclined position which the block reaches at the assembly position where the block is brought to the end of the second control edge 40” against the second assembly edge 40””.

[0045] Next, what is important is the relative movement of the yoke 32 in respect to the hub 12, or mutual movement between the yoke 32 and the hub 12. That is so, because the blade is supported by the hub and the rotational position of the blade is ruled by the relative position between the yoke and the hub, and the geometry of the blade adjusting system. It should be understood that in the posi tion shown in the figure 4 the pivot pin 42 is still in the recess 52 of the sliding block 44. Now, when the sliding block 44 is at the assembly position in the de pression 40 of the yoke 32, the mutual position of the yoke and the hub 21 is changed in the direction of the longitudinal axis 20 - while the rotational position of the propeller blades is fixed - such that the sliding block 44 comes out of or is departed from the depression 40 via the longitudinal end of the planar side wall 32’ of the yoke 32 without rotation in respect to the pivot pin 42. The movement of the pivot pin is linear movement. As is depicted by the arrows B in the figure 4 the yoke is moved from the position B1 to B2. However, the relative position WO 2020/224773 PCT/EP2019/061802

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between the yoke and the hub 21 can also be changed moving the hub, to which the pin 42 and the sliding block 44 are coupled, in respect to the yoke 32. After the sliding block is out of the depression, longitudinally departed from the planar side wall 32, there is enough room to separate the hub from the yoke even more and complete the disassembly as desired. The most critical part of the disassem bly is the detachment of the sliding block from the depression, which is accom plished by means of the invention is very advantageous manner.

[0046] This way the sliding block 44 can be inserted into the depression and removed from the depression 40 by relatively moving it against on the bottom 41 of the depression 40 over an end edge of the depression at the longitudinal end of the planar side wall 32’ of the yoke 32. Removal or inserting the sliding block does not require any substantial radial movement of the block 44 nor dismantling of the yoke itself, should it be constructed of multiple pieces. This make it also possible to construct the yoke 32 of one piece i.e. according to an embodiment of the invention the yoke 32 is monolithic structure. This makes the assembly of the propeller even more effective.

[0047] While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred em bodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features, and several other applications included within the scope of the in vention, as defined in the appended claims. The details mentioned in connection with any embodiment above may be used in connection with another embodi ment when such combination is technically feasible.