WO2011113477A1

WO2011113477A1 - Propeller

Info

Publication number: WO2011113477A1
Application number: PCT/EP2010/053376
Authority: WO
Inventors: Conny Thyberg
Original assignee: Berg Propulsion Technology Ab
Priority date: 2010-03-16
Filing date: 2010-03-16
Publication date: 2011-09-22

Abstract

The present invention relates to a propeller (10) comprising a boss (14) and at least one propeller blade (12). The propeller (10) further comprises an adjusting member (34) adapted to be displaced along a first dimension (L). The adjusting member (34) and the propeller blade (12) are operatively connected to one another such that a displacement, in the first dimension (L), of the adjusting member (34) results in a change in the pitch of the propeller blade (12). The adjusting member is adapted to be positioned in a first position in the first dimension (L) such that the propeller blade is in a feathering position. Said boss (14) comprises a rotational locking means (14a) adapted to, at least when said adjusting member (34) is in said first position, prevent said adjusting member (34) from being rotated around an axis of rotation (R) extending parallel to said first dimension (L).

Description

PROPELLER

TECHNICAL FIELD

The present invention relates to a propeller comprising a boss and at least one propeller blade. The propeller further comprises an adjusting member adapted to be displaced along a first dimension. The adjusting member and the propeller blade are operatively connected to one another such that a displacement, in the first dimension, of the adjusting member results in a change in the pitch of the propeller blade. The adjusting member is adapted to be positioned in a first position in the first dimension such that the propeller blade is in a feathering position.

BACKGROUND OF THE INVENTION

Floating vessels, in particular cargo vessels and supply vessels, of today are generally furnished with a propulsion system which includes an adjustable propeller. To this end, the propeller includes at least one propeller blade, but often a plurality of propeller blades, wherein the pitch of each one of the aforesaid blades is controlled by a servo

arrangement. The servo arrangement generally is a hydraulic arrangement the fluid chambers and piston of which generally are located in the boss of the propeller.

The piston of the aforesaid servo arrangement is generally connected to an adjusting member such that the adjusting member is adapted to be displaced in a longitudinal direction. Since the fluid chambers of the hydraulic arrangement may be subjected to high pressures, the adjusting member is preferably located outside the fluid chambers. The longitudinal displacement of the adjusting member is in turn transformed into a rotation - i.e. a change in pitch - of a propeller blade by means of a transformation arrangement. Normally, the transformation arrangement includes a control element, such as a pin, which is rigidly connected to the propeller blade and which engages with a slot in the adjusting member, which slot extends in a rectilinear slot extension direction which is substantially perpendicular to the longitudinal direction. Although the propeller as presented hereinabove generally is appropriate for many marine applications, there are some shortcomings associated with such propellers. For instance, it is generally difficult to obtain a feathering position of the propeller blades - i.e. a position with minimum drag of the blades. This is since a feathering position requires a relatively large displacement, in the slot extension direction, of the control member at the same time as the control member is slidably engaged with the slot which may result in that the control member may adhere to the structure delimiting the slot. In particular, the possibility of having propellers which are adapted to be put in a feathering position is desired for vessels provided with at least two propellers - a propeller system with exactly two propellers is sometimes referred to as a twin propeller system - wherein each one of the propellers is connected to an individual machine room. In order to reduce the risk of the control member adhering to the slot, prior art solutions, such as the ones disclosed in the documents GB821824, DE 3321968 and US5464324 teaches that the slot may be arcuate. By the provision of an arcuate slot, contact forces imparted on the control element from the slot are not perpendicular to the displacement direction of the control element when the adjusting member is displaced along the first dimension. However, the provision of the arcuate slot will in turn require that the length of the stroke of the adjusting member is increased - this is since the arcuate slot will provide for that a certain displacement in the first dimension of the adjusting member results in a smaller displacement in the first dimension of the control element - which in turn introduces the need for an increase in the size of the propeller hub, which increase generally is undesired.

As may be realized from the above, there is a need for improvements of the prior art adjustable propeller arrangements, in particular as regards prior art transformation arrangements including an arcuate slot and a control member.

It is also evident that for keeping the propeller blade in its feathering position it must be avoided that the adjusting member can make rotational movements around a rotational axes, which is substantially parallel to a first dimension, of the adjusting member. SUMMARY OF THE INVENTION

As such, the present invention relates to a propeller comprising a boss and at least one propeller blade, the propeller further comprising an adjusting member adapted to be displaced along a first dimension, the adjusting member and the propeller blade being operatively connected to one another such that a displacement, in the first dimension, of the adjusting member results in a change in the pitch of the propeller blade, the adjusting member being adapted to be positioned in a first position in the first dimension such that the propeller blade is in a feathering position, characterized in that the boss comprises a rotational locking means adapted to, at least when the adjusting member is in the first position, prevent the adjusting member from being rotated around an axis of rotation (R^ extending parallel to the first dimension.

According to a further embodiment of the present invention, the rotational locking means comprises an abutment surface adapted to abut against at least a portion of the adjusting member when the adjusting member is in the first position to thereby prevent the rotation of the adjusting member around the axis of rotation (R-i). The abutment surface adapted to abut against at least a portion of the adjusting member can abut directly or indirectly, preferably directly, against at least a portion of the adjusting member. According to another embodiment of the present invention, the boss comprises a hub body which in turn comprises a hub cavity in which the adjusting member is located, the rotational locking means being fixedly attached to the hub body.

According to a further embodiment of the present invention, the rotational locking means forms an integral part of the hub body.

According to another embodiment of the present invention, the propeller further comprises guide means adapted to guide the adjusting member to engagement with the rotational locking means as the adjusting member is displaced towards the first position.

According to a further embodiment of the present invention, the boss has a boss diameter, the propeller further comprising a transformation arrangement providing the operative connection between the adjusting member and the propeller blade, the transformation arrangement comprising a slot comprising a slot portion with a slot centre extending in a slot extension direction which direction is arcuate with a radius of curvature, the transformation arrangement further comprising a control element slidably engaged with at least the slot portion. Advantageously, the radius of curvature is within the range of 0.2 to 0.7 times the boss diameter. According to another embodiment of the present invention, the radius of curvature is within the range of 0.4 to 0.6, preferably within the range of 0.45 to 0.55, times the boss diameter. According to a further embodiment of the present invention, the propeller comprises a servo located in the boss, the servo comprising a piston which is displaceable along the first dimension, the piston being rigidly connected to the adjusting member.

According to another embodiment of the present invention, the control element comprises a block and a pin, the block comprising a block opening and being slidably engaged with the slot, the pin engaging with the block opening.

According to a further embodiment of the present invention, the slot is associated with the adjusting member and at least a portion of the control element is rigidly connected to the propeller blade.

According to another embodiment of the present invention, the adjusting member comprises a piston rod and a piston rod head, the piston rod being fixedly attached to the piston and the piston rod head being fixedly attached to the piston rod, wherein the slot is provided on the piston rod head.

According to a further embodiment of the present invention, the adjustment member has a body formed by at least two members. The adjustment member us advantageously a piston rod head, which comprises a plurality of piston rod head members, together forming the adjustment member. The adjustment member comprises advantageously a first piston rod head member and a second piston rod head member. At least one of the first and the second members comprises a portion of the slot. Optionally each one of the first and second piston rod head members comprises a portion of the slot. Preferably, at least one of the first and the second rod head members comprises a portion of the slot. Optionally each one of the first and second piston rod head members comprises a portion of the slot.

The first and second rod head members abut against each other in an abutment plane. In cases of more than two piston rod head members, the rod head members abut against each other in one abutment plane or optionally in at least two abutment planes, separate from each other.

According to another embodiment of the present invention, the abutment plane extends substantially perpendicularly to the first dimension.

According to another embodiment of the present invention, the abutment plane exhibits a three dimensional structure. In this embodiment, at least one protrusion extends from at least one of the first and second rod head to thereby form said three dimensional structure.

According to a further embodiment of the present invention, the adjusting member comprises an engagement region having at least one edge, advantageously at least two edges.

According to a further embodiment of the present invention, the adjusting member comprises an engagement region comprising a first, second, third and fourth edge, preferably substantially rectangular or square formed engagement region. The first and third edge being located on opposite sides of the engagement region and extending substantially parallel to the longitudinal dimension, the second and fourth edge being located on opposite sides of the engagement region and extending substantially transversal to the longitudinal dimension, the slot extending in the engagement region from the first edge to the second edge. According to another embodiment of the present invention, the slot extends in a slot extension (EDs) direction from the first edge, the slot having a width (SW) extending perpendicularly to the slot extension direction (EDs), the slot comprising a first slot portion and a second slot portion wherein the second slot portion is located downstream of the first slot portion in the slot extension direction (EDs), the first slot portion having a first slot width (SW1) and the second slot portion having a second slot width (SW2) such that the second slot portion is adapted to accommodate at least one component of the control element.

According to a further embodiment of the present invention, the boss comprises a cavity in which at least a portion of the adjusting member is located, the propeller further comprising an inlet duct (37) and an outlet duct (39) which ducts both are in fluid communication with the cavity, the inlet duct (37) and the outlet duct (39) being

interconnected outside the boss for circulating a lubrication fluid through the cavity. According to another embodiment of the present invention, the propeller comprises a plurality of propeller blades, each one of the plurality of propeller blades being provided with a corresponding transformation arrangement.

A second aspect of the present invention relates to a vessel comprising a propeller according to the first aspect of the present invention.

A third aspect of the present invention relates to a propeller comprising a boss and at least one propeller blade, the propeller further comprising an adjusting member, adapted to be displaced along a first dimension, and a transformation arrangement connecting the adjusting member to the propeller blade such that a displacement, in the first dimension, of the adjusting member results in a change in the pitch of the propeller blade, the transformation arrangement comprising a slot in the adjusting member, the adjusting member comprising a piston rod and a piston rod head, wherein the piston rod head comprises a first piston rod head member and a second piston rod head member, each one of the first and second piston rod head members comprising a portion of the slot, characterized in that the piston rod and the first piston rod head member form a unitary component.

According to a preferred embodiment of the third aspect of the present invention, the piston rod and the first piston rod head member are made of cast iron or cast steel.

A forth aspect of the present invention relates to a method for assembling a propeller having a boss with a boss diameter and a propeller blade having a blade root , with an adjustment member. The adjustment member is adapted to be displaced along a first dimension to enable a change in the pitch of the propeller blade upon the displacement of the adjustment member in the first dimension after assembly. The assembly is done at least partly inside of the boss. The boss comprises a rotational locking means adapted to, at least when the adjusting member is in a first position, prevent the adjusting member from rotation around an axis of rotation extending parallel to the first dimension and the adjustment member is inserted into the boss using a relative displacement with respect to the rotational locking means. The method enables a smooth assembly of the propeller which saves time and effort.

The rotational locking means can for example be an abutment surface arranged inside of the boss, the adjustment member is then moved relatively to the abutment surface during installation, sliding past, on, or next to, as the assembly is done at least partly inside the boss.

The adjustment member can comprises a plurality of piston rod head members, advantageously a first piston rod head member and a second piston rod head member.

According to an embodiment of the present invention, the method further comprises the step of; assembling a plurality of piston rod members, or a the first and the second rod head member, thereby forming the adjustment member. At least the first piston rod head member and the second piston rod head member are both inserted into the boss using a relative displacement with respect to the rotational locking means.

An arcuate formed slot is formed, or made operable, on the adjustment member when assembling the piston rod head members, such as the first piston rod head member (50) and the second piston rod head member (52). The arcuate formed slot is adapted to cooperate with the propeller (12), and preferably a pin on the propeller base, to enable a change in the pitch of the propeller blade upon the displacement of the adjustment member in the first dimension The propeller blade can comprises a pin and the assembly of the first and second piston rod members is done so as to engage the pin in the arcuate formed slot.

According to an embodiment of the present invention, the method further comprises the steps of; a) introducing the pin of the blade root to a slot portion of the first piston rod head member; b) forming the slot by displacing the second piston rod head member towards the first piston rod member and; c) attaching the first and second piston rod head members to each other.

According to an embodiment of the present invention, the method further comprises the of introducing the pin of the blade root into the slot portion of the first piston rod head member by a relative displacement in a first direction of the first piston rod head member while the pin remain stationary. Optionally step a) further comprises the step of moving the pin by imparting a rotational motion to the blade root to a first edge of the first piston rod head member. Optionally step a) further comprises the step of attaching a block to the pin.

BRIEF DESCRIPTION OF THE DRAWINGS Hereinafter the present invention will be described with reference to non-limiting embodiments shown in the accompanying drawings, in which:

Fig. 1 shows a partial cross-section of a side view of an embodiment of a propeller according to the present invention;

Fig.2 illustrates a propeller blade with an associated blade root of the propeller in Fig. 1 ;

Fig.3 shows in perspective an adjusting member incorporated in the propeller according to Fig. 1 ;

Fig. 4 is a top view of the adjusting member according to Fig. 3;

Fig. 5A - 5C illustrate in schematic top views a transformation arrangement in different pitch adjusting positions;

Fig. 6 is a diagram illustrating the torque imparted on a propeller blade as a function of a pitch angle;

Fig. 7 is a top view of the adjusting member of the Fig. 1 propeller;

Fig. 8 is a top view of a part of the adjusting member according to Fig. 7 during a portion of the assembly procedure;

Fig. 9 is a top view of a part of the adjusting member according to Fig. 7 after the assembly procedure; Fig. 10 is a top view of the adjusting member in a position referred to as A-A in Fig. 12; Fig. 1 1 is a top view of the adjusting member in a position referred to as B-B in Fig. 12;

Fig. 12 is a view corresponding to Fig. 1 and showing a modified embodiment of a propeller according to the present invention; and

Fig. 13 is an end view of the adjusting member in a propeller according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter the invention will be described as examples of embodiments, which are merely included for explaining principles of the invention, not limiting the scope of the invention as defined in the accompanying claims.

Fig. 1 illustrates a side view in cross section of a propeller 10 according to an embodiment of the present invention. The propeller comprises at least one propeller blade, in the implementation of the adjustable propeller illustrated in Fig. 1 propeller includes four propeller blades 12 of which only one is visible in Fig. 1. However, other embodiments of the propeller of the present invention may be provided with more or fewer propeller blades. The Fig. 1 propeller 10 is preferably used on a floating vessel (not shown), such as a ship, although the propeller 10 of the present invention may also be used in other applications, such as for wind power plants (not shown).

The Fig. 1 propeller 10 comprises a boss 14 which in turn comprises a hub cylinder 16 and a hub body 18. Within the hub cylinder 16, a servo 20 is arranged comprising a piston 22 and a piston rod 24. The piston 22 divides the interior of the hub cylinder 16 into two chambers, namely a forward pitch chamber 26 and a backward pitch chamber 28.

The boss 14 has a boss diameter 0_B which is defined as the largest diameter of the boss 14. As such, the propeller blades or any fixedly attached component thereof should not be considered when determining the boss diameter 0_B. In Fig. 1 , this largest diameter is indicated as being located between the propeller blade 12 and a drive shaft 19 to which the propeller 10 is connected. However, in other embodiments of the propeller 10 the largest diameter may be located in other positions. Purely by way of example, the largest diameter may be located in a portion of the hub body 8 from which portion the propeller blades 12 extends. Again, purely by way of example, the boss diameter 0_B may for supply vessels and cargo vessels range between 0.5 and 1.5 meters.

As may be understood from Fig. 1 , the piston rod 24 comprises a forward pitch duct 30 in fluid communication with the forward pitch chamber 26 and a backward pitch duct 32 in fluid communication with the backward pitch chamber 28. As such, fluid may be conveyed through the aforementioned ducts 30, 32 to thereby change the position, along a first dimension L, of the piston 22. Thus, the piston 22 is displaceable along the first dimension L. In order to simplify the explanation of features and functions of the propeller 10 of the present invention, the expression "forward" and "backward" are introduced. As used in the description hereinbelow, a forward displacement of the piston 22 is a displacement of the piston 22 away from the propeller blade 12 in the first dimension L. Consequently, a backward displacement of the piston 22 is a displacement of the piston 22 towards the propeller blade 12 in the first dimension L.

The propeller 10 further comprises an adjusting member 34 located at a distance D in the first dimension L from the piston 22. The adjusting member 34 - which in the Fig. 1 embodiment is exemplified as a piston rod head 34 - is fixedly attached to the piston rod 24, for instance by means of a bolt joint arrangement (not shown), and the piston rod 24 is in turn fixedly attached to the piston 22, also for instance by means of a bolt joint arrangement (not shown). As such, the piston rod head 34 is connected to the servo 22 - the piston rod head 34 is in Fig. 1 in fact fixedly attached to the servo 22 - such that a displacement along the first dimension L of the piston 22 results in a corresponding displacement of the piston rod head 34. As may be realized from Fig. 1 , the piston rod head 34 is located in a hub cavity 36 of the hub body 18. It should be noted that although the piston rod head 34 - in the embodiment of the propeller 10 illustrated in Fig. 1 - is located at a distance D from the piston 22 the piston rod head 34 may in other embodiments of the present invention instead be located in close connection to the piston 22 and in some embodiments, the piston rod head 34 may in fact constitute a portion of the piston 22 (not shown). Moreover, it should be noted that although the piston rod head 34 in the Fig. 1

embodiment is actuated by means of the servo 22, in other embodiments of the propeller 10 of the present invention, the piston rod head 34 may instead be actuated by other means. Purely by way of example, the piston rod head 34 may be actuated by an actuator (not shown) located outside the propeller and the piston rod head 34 may then be connected to the aforesaid actuator by means of a displacement transmission member - such as a rod - extending through the drive shaft 19 connected to the propeller 10.

However, irrespective of how a displacement is imparted on the piston rod head 34, the displacement will result in a change in pitch of the propeller blade 12. How this is achieved is presented hereinbelow.

Fig. 1 also illustrates that the propeller 10 comprises an inlet duct 37 and an outlet duct 39 which ducts both are in fluid communication with the hub cavity 36 cavity, the inlet duct 37 and the outlet duct 39 being interconnected outside the boss for circulating a lubrication fluid through the hub cavity 36. The benefit of circulating a lubrication fluid through the hub cavity 36 is that the fluid may be inspected outside of the propeller 10 in order to detect possible defects in the hub cavity 36. Purely by way of example, should the hub body 18 start leaking such that water is introduced in the hub cavity 36, water will enter the lubrication fluid circulated in the hub cavity 36 and the presence of water may be detected outside of the propeller, for instance by using a measuring device measuring the moisture content of the lubricant.

The boss 14 incorporates a rotational locking means arranged to prevent the adjusting member 34 from being rotated around an axis of propeller rotation r extending parallel to the first dimension L, at least when the said adjusting member 34 is in its first position, i.e. when the propeller blade is in its feathering position.

In one embodiment said rotational locking means can incorporate at least one abutment surface 14a adapted to abut against at least a portion of the adjusting member 34 when this is in its first position, for avoiding its rotation around the axis Ri, when the propeller blade is in its feathering position. In an embodiment with a four blade propeller there are two pair of opposed abutment surfaces 14A, although this is not a critical number of such rotation preventing means. As shown there are also guide means 14b adapted to guide said adjusting member 34 to engagement with said rotational locking means as said adjusting member (34) is displaced towards said first position. The rotational locking means can also be designed in other manners, e.g. by means of other mechanical means, by electro magnetic means, by hydraulics or the like.

When said adjusting member 34 is in its first position, i.e. where the propeller blade is in its feathering position, the rotation preventing function is effected by the rotational locking means only, whereas in a normal non feathering position, said rotation of the adjusting device 34 is prevented by a two point contact against the inside of the hub cavity 36 by a control element 62 and by a sliding disc 34a, which projects a short distance above the surface of the adjusting member 34. In an intermediate position the adjusting member 34 is prevented from rotation by the two point contact and also by the rotational locking means, such as the at least one abutment surface or the like. For ascertaining that the adjusting member 34 will enter in engagement with the rotational locking means, there is provided guide means adapted to guide said adjusting member to engagement with said rotational locking means as said adjusting member is displaced towards said first position.

Fig. 2 illustrates the Fig.1 propeller blade 12 fixedly attached to a blade root 38 (the blade root may also be referred to as a crank pin ring). The fixed attachment is preferably obtained by a bolt joint arrangement 40 which in Fig. 2 is constituted by six bolts.

Moreover, the blade root 38 is provided with a pin 42 protruding from a bottom surface 44 of the blade root 38. In the Fig. 2 implementation of the blade root 38, the pin 42 and the remaining portion of the blade root 38 together form a unitary component although in other implementations of the blade root 38, the pin 42 may instead be a separate component which for instance is attached to the blade root 38 by means of threads (not shown).

As may be understood from Fig. 2, the propeller blade 12 comprises a circumferentially extending outer slide surface 46 adapted to slidably abut against a circumferentially extending outer surface of the hub body 18 (not shown in Fig. 2), whereas the blade root 38 comprises a circumferentially extending inner slide surface 48 adapted to slidably abut against a circumferentially extending inner surface of the hub body 18 (not shown in Fig. 2). As such, if the pin 42 is subjected to a displacement in the first dimension L, the propeller blade 12 will be subjected to a rotation about an axis of rotation R- which axis is substantially perpendicular to the first dimension L. In order to obtain the aforesaid slidable abutments, the outer slide surface 46 and the inner slide surface 48 - as well as the corresponding surfaces of the hub body 18 - are preferably made of materials which provide appropriate sliding characteristics. Purely by way of example, the outer slide surface 46 and the surfaces of the hub body 18 may be 5 made of bronze. As for the inner slide surface 48, again purely by way of example, this may be made of bronze or steel.

Fig. 3 illustrates the Fig. 1 piston rod head 34 which - as previously indicated - is comprised in the adjusting arrangement of the Fig. 1 propeller 10. As may be seen from

10 Fig. 3, the piston rod head 34 comprises a slot 54 which in turn comprises a slot portion 56 with a slot centre C_s extending in a slot extension direction ED_S which direction is arcuate with a radius of curvature R_c. Fig. 3 further illustrates that a block 58 is located in the slot 54 which block comprises an opening 60 adapted to receive the pin 42 of the blade root 38. The block 58 is slibably engaged with at least the slot portion 56 of the slot

15 54. As such, the block 58 and the pin 42 together form a control element 62 which is slidably engaged with at least said slot portion 56. However, in other embodiments of the present invention, the control element 62 may be constituted in other ways. Purely by way of example, the block 58 may in some implementations of the control element 62 be omitted such that the pin 42 in itself is slidably engaged with the slot portion 56. Fig. 3

20 also illustrates that the piston rod head 34 has a longitudinal centre line L_c extending parallel to the first direction L.

The slot 54 and the control element 62 together form a transformation arrangement 64 for transmitting a displacement - in the first dimension L - of the piston rod head 34 to a

25 change in pitch of the propeller blade 12. It should be noted that although - in the Fig. 2 and Fig. 3 implementation of the transformation arrangement 64 - the slot is provided on the piston rod head 34 and the transformation arrangement 64 is associated with the propeller blade 12, this relation may in other implementations be the opposite such that the slot is provided on a member fixedly connected to the propeller blade 12 - such as the

30 blade root 38 - whereas the transformation arrangement 64 may be associated with the piston rod head 34.

Fig. 4 illustrates a top view of the piston rod head 34 of the Fig. 1 propeller 10. As may be seen from Fig. 4, the slot extension direction ED_S - which extension direction is arcuate - 35 has a centre of curvature C_c which is located forward of the piston rod head 34 in the first dimension L. Moreover, the radius of curvature R_c is within the range of 0.3 to 0.7 times the boss diameter 0_B. Preferably, the radius of curvature is within the range of 0.4 to 0.6, more preferably within the range of 0.45 to 0.55 times the boss diameter 0_B. In fact, Fig. 4 illustrates a slot extension direction ED_S with the most preferred radius of curvature R₀, namely 0.46 times the boss diameter 0_B.

Fig. 4 further illustrates that the adjusting member - i.e. the piston rod head 34 - comprises a substantially rectangular engagement region 66 comprising a first 68, second 70, third 72 and fourth 74 edge. The first and third edges 68, 72 are located on opposite sides of the engagement region 66 and extend substantially parallel to the longitudinal dimension L. The second and fourth edges 70, 74 are located on opposite sides of the engagement region and extending substantially transversally to the longitudinal dimension L. Fig. 4 further illustrates that the slot 54 extends in the engagement region 66 from the first edge 68 to the second edge 70.

Fig. 5A illustrates the transformation arrangement 64 of the Fig. 1 propeller 10 when the propeller blade 12 - indicated by dotted lines - is in a neutral, or zero pitch, position. As may be gleaned from Fig. 5A, when the propeller blade 12 is in the neutral position, the control element 62 is located in a top position - i.e. at a position with a largest distance from the longitudinal centre L_c of the piston rod head 34. When the control element is in the Fig. 5A position, the transformation arrangement 64 will provide a maximum available torque M_max for the propeller blade 12 wherein the maximum available torque M_max is calculated as the normal force F_N between the control element 62 and the slot portion 56 multiplied by the distance from the action point of the normal force F_N and the centre of rotation C_R of the propeller blade 12 (i.e. the lever of the normal force F_N).

Fig. 5B illustrates the transformation arrangement 64 when the propeller blade 12 is approaching a feathering position. In the implementation of the propeller blade illustrated in Fig. 5A, the feathering position is obtained when the pitch angle Θ reaches 90°.

As may be gleaned from Fig. 5B, the control element 62 has now been displaced rearwardly - in the first dimension L - with a first distance d₁. In order to achieve this rearward displacement, the piston rod head 34 has been displaced a second distance d₂ which second distance d₂ is larger that the first distance d-ι and this difference between the first and second distances is occasioned by the arcuate shape of the slot portion 56. Moreover, Fig. 5B illustrates that, since the slot portion 56 is arcuate with a radius of curvature R_c in the interval as defined hereinabove, the control element 62 is less prone to tilt in relation to the slot portion 56 as compared to transformation arrangement 64 including a rectilinear slot portion (not show). As may be realized by a person skilled in the art, the tilt may result in large contact forces resulting in large friction forces between the control element 62 and the slot portion 56 and these large friction forces may in turn result in that the control element 62 gets stuck in the slot portion 56 when the piston rod head 34 is imparted a displacement in the first dimension L. However, the risk of having the control element 62 locked to the slot portion 56 is significantly reduced when using a slot portion 56 having a radius of curvature within the interval of the present invention.

Fig. 5B also illustrates an unexpected effect of providing the slot portion 56 with a radius of curvature within the range of 0.3 to 0.7 times the boss diameter 0_B, namely that even when the propeller blade 12 is approaching a feathering position, the transformation arrangement 64 will impart a torque on the propeller blade 12. This is since the normal force F_N imparted on the control element 62 from the slot portion 56 will form an angle with the first dimension L. As such, even though the point of application of the normal force F_N on the control element 62 is located close to - or even on - an axis extending parallel to the first dimension L and intersecting the centre of rotation C_R of the propeller blade 12, the normal force F_N will nevertheless result in a torque - i.e. a moment around a axis of rotation A_R extending out of the plane in Fig. 5B, which axis is located at the centre of rotation C_R of the propeller blade 12. As may be gleaned from Fig. 5B, the same reasoning applies for a friction force F_{ imparted on the control element 62 from the slot portion 56, i.e. the friction force F_f will also result in a torque irrespective of the position of the control element 62 in relation to the slot portion 56.

Fig. 5C illustrates the Fig. 5A transformation arrangement 64 wherein the propeller blade 12 is in a backward pitch position. As may be realized by a person skilled in the art, the reasoning as regards the torque obtained from the normal force F_N and the friction force F_f imparted on the control element 62 will apply mutatis mutandis for the position illustrated in Fig. 5C.

Fig. 6 is a graph illustrating the available torque M_avai| as a function of the pitch angle Θ of the propeller blade 12 for three different implementations of the slot portion 56. The available torque M_aVaii is in Fig. 6 normalized by the maximum available torque M_max. In Fig. 6, the three different implementations slot portion 56 are denominated SPi, SP₂ and SP₃, respectively, wherein the first slot portion implementation SPi has a slot extension direction ED_S with a radius of curvature R_c of approximately 0.35 times the boss diameter 0B, the second slot portion implementation SP₂ has a radius of curvature R_c of approximately 0.60 times the boss diameter 0B and the third slot portion implementation SP₃ has an infinite radius of curvature, i.e. the third slot portion implementation SP₃ is rectilinear. As may be gleaned from Fig. 6, an implementation of the transformation arrangement 64 with the third slot portion implementation SP₃ will not be able to impart a torque on the propeller blade 12 if the pitch angle Θ exceeds a certain threshold angle which threshold angle is smaller than 90° (approximately 80° in Fig. 6). However, for a transformation arrangement 64 with the first or the second portion implementation SP^ SP₂ it is actually possible to impart a torque on the propeller blade 12 even if the pitch angle Θ equals, or even exceeds, 90°. As may be realized from Fig. 6, the first slot portion implementation SPi will provide that a high torque may be imparted on the propeller blade 12 for the whole range from 0 to 90° of the pitch angle Θ. Moreover, the second slot portion implementation SP₂ will provide a torque which decreases as the pitch angle Θ increases. However, as compared to the first slot portion implementation SPi, the second slot portion implementation SP₂ has the benefit of requiring a shorter hub body 18, i.e. a hub body 18 having a smaller extension in the first dimension L.

Fig. 7 illustrates an implementation of a piston rod head 34 - or adjusting member.

As may be gleaned from Fig. 7, the piston rod head 34 comprises a first piston rod head member 50 and a second piston rod head member 52 wherein the first 50 and second 52 rod head members are fixedly attached to one another - preferably by means of a bolt joint arrangement (not shown in Fig. 7) - and the members abut against each other in an abutment plane P_A which extends substantially perpendicularly to the first dimension L. Other extension of the abutment plane P_A is however possible. It should also be noted that each one of the first piston rod head member 50 and a second piston rod head member 52 comprises a portion of the slot 54. As for the piston rod head 34 illustrated in Fig. 4, the Fig. 7 piston rod head 34 comprises a substantially rectangular engagement region 66 comprising a first, 68 second 70, third 72 and fourth 74 edge. In an embodiment the first piston rod head member 50 comprises the slot 54 with an opening in the abutment plane. The second piston rod head member 52 is then effectively closing the slot 54 during assembly with the first rod head member 50.

5

Moreover, Fig. 7 illustrates that the centre Cs of the slot 54 extends in a slot extension direction ED_S from the first edge 68 to the second edge 70. The slot has a width S_w extending perpendicularly to the slot extension direction ED_S. The slot comprises a first slot portion 76 and a second slot portion 78 wherein the second slot portion 78 is located 10 downstream of the first slot portion 76 in the slot extension direction ED_S. The first slot portion has a first slot width S_Wi and the second slot portion has a second slot width S_W2 wherein the second slot width S_W2 is greater than the first slot width S_W2- As may be realized from Fig. 7, the second slot portion 78 is - in the implementation illustrated therein - substantially rectangular.

15

Some of the advantages of having a piston rod head 34 which is constituted by two parts or members, as well as having the wider second slot portion 78, are explained in the following. First of all, it should be noted that the separation of the piston rod head into two portions is useful in a propeller assembling procedure - and in particular in a

20 transformation arrangement assembly part of that procedure - a few steps of which are discussed below.

Generally the propeller is assembled by inserting the blade root 38 into the boss 14. The blade roots 38 can be stationary at their intended location by means of gravity if the boss

25 14 is positioned vertically with the dimension L pointing towards the ground/floor, see arrow L in figure 1. The piston rod 24 is inserted into the boss 14, separately or simultaneously with the piston rod head 34, also referred to as the adjustment member 34, sliding past the rotational locking means 14a. The rotational locking means 14a, in the form of an abutment surface in this case, is positioned in the proximity of the opening of

30 the boss 14. The blade root 38 is brought to cooperate with the piston rod head 34. In cases where a first and a second piston rod head member is used, the first piston rod head member is inserted into the boss 14, and the blade root 38, and the pin 42, is introduced to a portion of the slot extending parallel with the first dimension L, also referred to as the first direction L. The second piston rod head member can thereafter be introduced and assembled with the first piston rod head member. A more detailed assembly procedure is described hereafter.

Fig. 8 illustrates the first piston rod head member 50 when the transformation

5 arrangement 64 is in a pre-assembly position. As such, the first piston rod head member 50 is in Fig. 8 not attached to the second piston rod head member 52. In a first step of assembling the transformation arrangement, the pin 42 of the blade root 38 is introduced in the second slot portion 78. This is generally achieved by imparting a forward displacement in the first dimension L on the first piston rod head member 50 while the pin 10 42 remains stationary in relation to the propeller 10. The position of the pin 42 relative to the first piston rod head member 50 is indicated by the letter A in Fig. 8.

Next, the blade root 38 - and possibly also the propeller blade 12 if this has already been attached to the blade root 38 - is imparted a rotation such that pin 42 will be conducted 15 through the second slot portion 78 and at least a portion of the first slot portion 76 such that the pin 42 is located close to the first edge 68 of the first piston rod head member 50.

If the control element 62 - in addition to the pin 42 also comprises a block 58, the first piston rod head member 50 is - in a third step - preferably moved even further forward in

20 the first dimension L such that the block 58 may be connected to the pin 42. Then - in a fourth step - the first piston rod head member 50 is preferably moved backwardly in the first dimension L, such that the control element 62 is adjacent to the first piston rod head member 50. However, and as may be realized by a person skilled in the art, if the control element 62 is being constituted by only a pin 42, this third and fourth steps may be

25 omitted.

Then, and as is illustrated in Fig. 9, the second piston rod head member 52 is displaced towards the first piston rod head member 50 such that the slot 54 is formed. The first and second piston rod head member 50, 52 are then attached to one another, preferably by 30 means of a bolt joint arrangement (not shown in Fig. 9).

By the steps of the assembly procedure above, the control element 62 is now located in the slot 54 and the control element 62 is slidably engaged with at least a slot portion 56 of the slot 54. It should be noted that although the steps hereinabove have been described 35 for only transformation arrangement 64, for a propeller 10 comprising a plurality of propeller blades, and which thus generally comprises a plurality of transformation arrangements 64, the steps as defined hereinabove may be performed substantially simultaneously for each one of the transformation arrangements 64. Fig. 10 illustrates schematically, how the piston rod head 34 or adjusting member in a position illustrated A-A in Fig. 1 is not in engagement with the abutment surface 14a of the hub body 18, of which only a fragment is shown. As can be seen in Fig. 1 both the control element 62 and the sliding disc 34a in this position are in contact with the inner side face of the hub cavity 36 thereby preventing that the adjusting member 34 is rotated about the axis Ri . A non-limiting embodiment of guiding surfaces 14b is also illustrated in the figure.

Fig. 11 illustrates schematically in a view corresponding to Fig. 10, how the adjusting member 34 has been displaced to position B-B as illustrated in Fig. 12, in which it is in engagement with said abutment surfaces 14a.

Fig. 12 illustrates a second embodiment of a propeller 10 according to the present invention. In the position shown, the only visible propeller blade 12 is positioned in its feathering position, and the adjusting member 34 is here positioned in its first position B- B, where the rotational locking means, in this embodiment, the abutment surfaces 14a are in engagement with the adjusting member 34 and therefore prevent it from rotating about

In this embodiment of the propeller 10 according to the present invention, the piston rod head 34 - or adjusting member - incorporates a first piston rod head member 50a, which is an integral part of the piston rod 24. The second piston rod head member 52 is a separate part, which is fixedly attached to the integrated first piston rod member 50a for instance by means of a bolt joint arrangement. The assembly of this embodiment of the piston rod head or adjusting member 34 corresponds to that described with reference to Figures 8 and 9 except for the fact that the first piston head member 50a is an integral part of the piston rod 24, and the assembly of this embodiment of the propeller therefore is simplified.

In Fig. 13 is shown a cross section of a propeller according to the invention along lines A- A in Fig. 1 and B-B in Fig. 12, and this view illustrates how the adjusting member 34 in the B-B position, i.e. when the propeller blade 12 is in its feathering position, is prevented from rotation around its central axis of rotation R_{1 p} by inner abutment surfaces 14a. In position A-A the space between the inner surfaces is however bigger, whereby the surfaces of the adjusting member 34 will not be engaged by the abutment surfaces 14a, and as mentioned earlier, the two-point contact of the contact element 62 and the sliding disc 34a (which are not visible in this view) against the adjusting member 34, in this position will prevent rotation of the adjusting member 34. It should be mentioned that the propeller according to this view is intended to have four propeller blades 12, although for the sake of clarity, only one such blade is shown in the drawing. It should be realized that the present invention is not limited to the embodiments illustrated in the accompanying drawings and described in connection thereto. A person skilled in the art will realize that many changes and modifications can be performed within the scope of the appended claims, and it is also possible that many combinations of the different features can be made without departing from the scope of the claims.

Claims

1. A propeller (10) comprising a boss (14) and at least one propeller blade (12), said propeller (10) further comprising an adjusting member (34) adapted to be displaced along a first dimension (L), said adjusting member (34) and said propeller blade (12) being operatively connected to one another such that a displacement, in said first dimension (L), of said adjusting member (34) results in a change in the pitch of said propeller blade (12), said adjusting member being adapted to be positioned in a first position in said first dimension (L) such that said propeller blade is in a feathering position, characterized in that said boss (14) comprises a rotational locking means adapted to, at least when said adjusting member (34) is in a first position, prevent said adjusting member (34) from being rotated around an axis of rotation (Ri) extending parallel to said first dimension (L).

The propeller (10) according to claim 1 , wherein said rotational locking means comprises an abutment surface (14a) adapted to abut against at least a portion of said adjusting member (34) when said adjusting member (34) is in said first position to thereby prevent said rotation of said adjusting member (34) around said axis of rotation (Ri).

The propeller (10) according to claim 1 or 2, wherein said boss (14) comprises hub body (18) which in turn comprises a hub cavity (36) in which said adjusting member (34) is located, said rotational locking means being fixedly attached to said hub body (18) .

The propeller (10) according to claim 3, wherein said rotational locking

forms an integral part of said hub body (18).

The propeller (10) according to any one of the preceding claims, wherein said propeller (10) further comprises guide means (14b) adapted to guide said adjusting member (34) to engagement with said rotational locking means as said adjusting member (34) is displaced towards said first position.

6. The propeller (10) according to any one of the preceding claims, wherein said boss (14) has a boss diameter (0_B), said propeller (10) further comprising a transformation arrangement (64) providing said operative connection between said adjusting member (34) and said propeller blade (12), said transformation arrangement (64) comprising a slot (54) comprising a slot portion (56) with a slot centre (C_s) extending in a slot extension direction (ED_S) which direction is arcuate with a radius of curvature (R_c), said transformation arrangement (64) further comprising a control element (62) slidably engaged with at least said slot portion

(56), said radius of curvature (R_c) preferably being within the range of 0.2 to 0.7 times said boss diameter (0_B).

7. The propeller (10) according to claim 6, wherein said radius of curvature (R_c) is within the range of 0.4 to 0.6, preferably within the range of 0.45 to 0.55, times said boss diameter (0_B).

8. The propeller (10) according to any preceding claims, wherein said propeller (10) is operable with a servo (20), said servo (20) comprising a piston (22) which is displaceable along said first dimension (L), said piston (22) being rigidly connected to said adjusting member (34).

9. The propeller (10) according to claim 8, wherein said servo (20) is located in said boss (14).

10. The propeller (10) according to any one of claims 6 to 9, wherein said control element (62) comprises a block (58) and a pin (42), said block (58) comprising a block opening (60) and being slidably engaged with said slot (54), said pin (42) engaging with said block opening (60).

1 1. The propeller (10) according to any one of claims 6 to 10, wherein said slot (54) is associated with said adjusting member (34) and at least a portion of said control element (62) is rigidly connected to said propeller blade (12). 12. The propeller (10) according to any preceding claims, wherein said adjusting

member (34) comprises a piston rod (32) and a piston rod head (35), said slot (54) being arranged on said piston rod head (35).

13. The propeller (10) according to claim 12, wherein said piston rod (32) and at least parts of said piston rod head (35) is formed from a unitary piece of material.

14. The propeller (10) according to claim 12, wherein said piston rod (32) being fixedly attached to said piston (22) and said piston rod head (35) being fixedly attached to said piston rod (32), wherein said slot (54) is provided on said piston rod head (34).

15. The propeller (10) according to any of the claims 12-14, wherein said piston rod head (34) comprises at least a first piston rod head member (50) and a second piston rod head member (52).

16. The propeller (10) according to claim 15, wherein each one of said first and

second piston rod head members comprising a portion of said slot (54) and said first and second rod head member abut against each other in an abutment plane

17. The propeller (10) according to claim 16, wherein said abutment plane (A_P)

extends substantially perpendicularly to said first dimension (L).

18. The propeller (10) according to any one of the preceding claims, wherein said adjusting member (34) comprises an engagement region (66) comprising a first (68), second (70), third (72) and fourth (74) edge, said first (68) and third (72) edge being located on opposite sides of said engagement region (66) and extending substantially parallel to said longitudinal dimension (L), said second (70) and fourth (74) edge being located on opposite sides of said engagement region (66) and extending substantially transversal to said longitudinal dimension (L), said slot extending in said engagement region (66) from said first edge (68) to said second edge (70).

19. The propeller (10) according to claim 18, wherein said slot (54) extends in a slot extension (ED_S) direction from said first edge (68), said slot (54) having a width (Sw) extending perpendicularly to said slot extension direction (ED_S), said slot (54) comprising a first slot portion (76) and a second slot portion (78) wherein said second slot portion (78) is located downstream of said first slot portion (76) in said slot extension direction (ED_S), said first slot portion (76) having a first slot width (S_Wi) and said second slot portion (78) having a second slot width (S_W2) such that said second slot portion (78) is adapted to accommodate at least one component of said control element (62).

20. The propeller (10) according to any one of the preceding claims, wherein said boss (14) comprises a cavity (36) in which at least a portion of said adjusting member (34) is located, said propeller (10) further comprising an inlet duct (37) and an outlet duct (39) which ducts both are in fluid communication with said cavity (36), the inlet duct (37) and the outlet duct (39) being interconnected outside the boss (14) for circulating a lubrication fluid through said cavity (36).

21 . The propeller (10) according to any one of the preceding claims, wherein said propeller (10) comprises a plurality of propeller blades (12), each one of said plurality of propeller blades being provided with a corresponding transformation arrangement (64).

22. A vessel, characterized in that said vessel comprises a propeller (10) according to any one of the preceding claims.

23. A propeller (10) comprising a boss (14) and at least one propeller blade (12), said propeller (10) further comprising an adjusting member (34), adapted to be displaced along a first dimension (L), and a transformation arrangement (64) connecting said adjusting member (34) to said propeller blade (12) such that a displacement, in said first dimension (L), of said adjusting member (34) results in a change in the pitch of said propeller blade (12), said transformation arrangement (64) comprising a slot (54) in said adjusting member, said adjusting member (34) comprising a piston rod (32) and a piston rod head (35), wherein said piston rod head (35) comprises a first piston rod head member (50) and a second piston rod head member (52), each one of said first and second piston rod head members comprising a portion of said slot (54), ch a racte rized i n th at said piston rod (32) and said first piston rod head member (50) form a unitary component .

24. The propeller according to claim 19, wherein said piston rod (32) and said first piston rod head member (50) are made of cast iron or cast steel.

25. A method for assembling a propeller (10) having a boss (14) with a boss diameter (0_B), and a propeller blade (12) having a blade root (38), with an adjustment member (34),

said adjustment member (34) is adapted to be displaced along a first dimension (L) to enable a change in the pitch of said propeller blade (12) upon said displacement of said adjustment member (34) in said first dimension (L) after assembly,

characterized in

said assembly is done at least partly inside of said boss (14);

said boss (14) comprising a rotational locking means adapted to, at least when said adjusting member (34) is in a first position, prevent said adjusting member (34) from being rotated around an axis of rotation (R-i) extending parallel to said first dimension (L) and in that;

said adjustment member (34) is inserted into said boss (14) using a relative displacement with respect to said rotational locking means.

26. The method according to claim 24, wherein said adjustment member (34)

comprises at least a first piston rod head member (50) and a second piston rod head member (52) and; in that said method comprises the step of;

assembling said at least first and second piston rod members (50, 52) thereby forming said adjustment member (34), said at least first piston rod head member (50) and said second piston rod head member (52) being inserted into said boss (14) using a relative displacement with respect to said rotational locking means. 27. The method according to claim 26, wherein an arcuate formed slot (54) is formed, or made operable, on said adjustment member (34) when assembling said first piston rod head member (50) and said second piston rod head member (52), said arcuate formed slot (54) is adapted to cooperate with said propeller (12) to enable a change in the pitch of said propeller blade (12) upon said displacement of said adjustment member (34) in said first dimension (L).

The method according to claim 27, characterized in that said propeller blade (12) comprises a pin (42) and that said assembly of said first and second piston rod members (50, 52) so as to engage said pin (42) in said arcuate formed slot (54).

29. The method according to claim 28, characterized in that said method further comprises the steps of;

a) introducing the pin (42) of the blade root (38) to a slot portion (78) of said first piston rod head member (50);

b) forming said slot (54) by displacing the second piston rod head member (52) towards the first piston rod member (52) and;

c) attaching said first and second piston rod head members (50, 52) to each other.

30. The method according to claim 29, characterized in that step a) further comprises the step of introduction of said pin (42) of the blade root (38) into said slot portion (78) of said first piston rod head member (50) by a relative displacement in a first direction of the first piston rod head member (50) while said pin (42) remain stationary.

The method according to claim 30, characterized in that step a) further comprises the step of moving said pin (42) by imparting a rotational motion to said blade root (38) to a first edge (68) of the first piston rod head member (50).

32. The method according to claim 31 , characterized in that step a) further comprises the step of attaching a block (58) to said pin (42).