WO2012007971A1

WO2012007971A1 - Dampened propeller with pitch blades regulation during backward motion

Info

Publication number: WO2012007971A1
Application number: PCT/IT2010/000311
Authority: WO
Inventors: Massimilian Bianchi
Original assignee: Max Prop S.R.L.
Priority date: 2010-07-15
Filing date: 2010-07-15
Publication date: 2012-01-19

Abstract

There is described, a variable pitch propeller comprising at least one blade pivoted rotatably to a cylindrical propeller casing (3), a propeller hub (4) coupled to a propulsor and positioned coaxially inside the propeller casing, a kinematic mechanism for adjusting the rotary motion of said at least one blade about its axis of pivoting to the propeller casing as a function of the relative motion of the propeller hub assembly with respect to the cylindrical casing thereof, and elastic means (8) for opposing relative rotation of the hub (4) with respect to the cylindrical propeller casing (3), and vice versa, comprising at least a first(9) and at least a second end(10)for operation thereof. The first end of the elastic means is constrained to the cylindrical propeller casing or to the hub, while the second end of the elastic means is constrained to at least one guide integral with the propeller hub or with the cylindrical casing, and the guide has at least a first and at least a second position for temporary operation of the elastic means which are mutually spaced apart.

Description

"Dampened propeller with pitch blades regulation during backward motion" FIELD OF THE INVENTION

The present invention relates to a propeller, preferably for marine use, of the variable pitch type, i.e. capable of automatically modifying the fluid dynamic pitch of the blades during operation to ensure high performance in different conditions of use. In more detail, the present invention relates to a nautical propeller with automatic pitch variation that can also be used for navigation in reverse drive, capable of efficiently absorbing (dampening) accidental impacts to which the propeller may be subjected during use in forward drive and in reverse drive.

PRIOR ART

The market currently offers propellers in which the fluid dynamic pitch variation of the blades takes place automatically, by means of the propeller drive. Generally, these propellers comprises a cylindrical propeller casing, on which the propeller blades are pivoted according to a direction transverse to the axis of the propeller casing, or more generally perpendicular to the forward axis of the propeller, and a drive shaft, coupled coaxially to the propeller casing.

The propeller is also provided with means for transmitting rotary motion from the shaft to the propeller casing, and with a kinematic mechanism for adjusting the rotary motion of each blade about its axis of pivoting to the propeller casing, preferably adapted to transform the rotary motion of the drive shaft into a rotary motion of each blade about its axis of pivoting.

In order to allow operation of the aforesaid kinematic mechanism to transform rotation of the drive shaft into rotation of the blades, the motion transmission means allow the shaft to rotate idly with respect to the propeller casing at least for a predefined angular interval. Idle rotation of the drive shaft in this angular interval, with respect to the propeller casing, causes, due to the aforesaid kinematic mechanism for adjustment/transformation, relative rotation of the blades with respect to the propeller casing, with consequent variation of their angle of incidence with respect to the fluid and therefore of the fluid dynamic pitch.

A propeller of this type is described in the document WO 2008/075187, by Max Prop S.r.L, in which relative rotation of the drive shaft with respect to the propeller casing is adjusted by an elastic element interposed therebetween, which allows continuous pitch adjustment during operation in forward drive.

In particular, the elastic element allows the blades to be positioned to the optimal pitch during operation, balancing the forces acting on the propeller, mainly the drive torque generated by the propulsor and the drag torque, until reaching a balanced position. Moreover, the elastic element interposed between the drive shaft and the cylindrical propeller casing allows absorption of impacts to which the blades, or more in general the propeller, may be subjected during navigation in forward drive. In fact, as previously stated, the elastic element adjusts rotation of the drive shaft with respect to the cylindrical propeller casing, and vice versa, in a given angular interval and acts as a shock absorber in the event of accidental impacts that may occur during navigation in forward drive.

Although ensuring high performances in terms of output during forward motion of the watercraft, this type of propeller cannot be used to modify the pitch of the blades for navigation in reverse drive. In fact, the value of the pitch in reverse drive is linked to the value of the pitch in forward drive. In other words, the two pitches are not independent from each other and for this reason it is not possible to adjust the pitch for navigation in reverse drive as this modification would cause a variation in the pitch for forward drive with non optimal values.

However, the propeller may also be subjected to accidental impacts during reverse drive, for example while performing manoeuvres.

In this regard, some prior art propellers are also capable of providing protection against impacts during navigation in reverse drive by means of a specific device, separate from the device that allows variation of the fluid dynamic pitch of the blades, by means of a further elastic element.

This type of propeller is generally provided with two elastic elements. The first elastic element allows automatic pitch variation during forward drive, in relation to the torque that opposes rotation of the propeller, by means of the angular displacement, controlled by the elastic element, of the propeller casing with respect to the hub which determines rotation of each blade about its axis, as described above with reference to the document WO 2008/075187 by Max Prop S.r.L

The second elastic element is instead interposed between the propeller hub and the drive shaft and provides protection against impacts during forward drive and during reverse drive, allowing partial idle rotation of the hub about the drive shaft by means of elastic deformation of the elastic element interposed therebetween.

Therefore, propellers currently available allow automatic pitch variation to be obtained during use in forward drive and absorption of accidental impacts both in forward motion in forward drive and in that in reverse drive, through the use of distinct devices, and in particular distinct elastic elements, each of which is destined to perform a specific function.

These propellers suffer from some drawbacks; in fact, being provided with distinct devices, each comprising a different elastic element destined to perform a specific function, their dimensions are not very compact and they are also very complex and costly to produce.

The object of the present invention is to provide a variable pitch propeller with automatic pitch adjustment during forward drive that does not have the limitations and drawbacks of prior art described above and which can also be used for navigation in reverse drive.

Another object of the present invention is to provide a propeller that does not have the limitations and drawbacks of prior art described above and which allows automatic pitch adjustment during use in forward drive and, at the same time, allows absorption of accidental impacts to which the propeller, or its blades, may be subjected during motion in both directions of drive, both forward and reverse.

A further object is to provide a propeller that also allows modification of the pitch for navigation in reverse drive by the user, in a rapid and simple manner, without the need to disassemble the propeller or subject the internal parts thereof to mechanical machining operations.

SUMMARY OF THE INVENTION

These and other objects are achieved by the variable pitch propeller according to the first independent claim and the subsequent dependent claims.

The variable pitch propeller, according to the present invention, comprises at least one blade pivoted rotatably to a cylindrical propeller casing, a propeller hub coupled to a propulsor and positioned coaxially inside the propeller casing, a kinematic mechanism for adjusting the rotary motion of said at least one blade about its axis of pivoting to the propeller casing as a function of the relative motion of the propeller hub with respect to the cylindrical propeller casing, and elastic means for opposing relative rotation of the hub with respect to the cylindrical propeller casing, and vice versa, which comprise at least a first and at least a second end for operation thereof. The propeller is characterized in that the first end of the elastic means is constrained to the cylindrical propeller casing, or to the hub, while the second end of the elastic means is constrained to at least one guide integral with the propeller hub, or with the cylindrical casing, the guide having at least a first and at least a second position for temporary operation of the elastic means which are mutually spaced apart.

It must be noted that the distance between the two positions for temporary operation of the elastic means with which the guide is provided provides an angular space for rotation of the hub with respect to the cylindrical propeller casing, and vice versa, in which the elastic means are not operated.

According to a preferred embodiment, the first end of the elastic means is constrained to the cylindrical propeller casing and the second end is constrained to the guide, which is produced on the propeller hub, or on an element integral in rotation therewith.

According to a possible embodiment, the guide with which the propeller according to the present invention is provided is configured in an arc of circumference, and the elastic means are operated when the end thereof constrained to the guide is located at the ends of this guide. In this case the angular space for rotation of the hub with respect to the cylindrical propeller casing, and vice versa, is comprised between the ends of the guide.

When the elastic means are located in the positions for temporary operation thereof with which the guide is provided, at least part thereof is subjected to expansion, or contraction, and/or rotation with respect to the unstressed condition thereof during rotation in clockwise direction or in counter-clockwise direction of said hub with respect to said propeller casing, or vice versa. In other words, when the elastic means of the propeller are located in the positions for operation thereof, they are subjected to stresses that cause deformation thereof, thereby allowing relative rotation of the hub with respect to the cylindrical propeller casing, and vice versa, to be opposed. In this manner, the elastic means allow automatic adjustment of the fluid dynamic pitch during use of the propeller in forward drive as they allow adaptation of relative rotation between the hub and the cylindrical casing in the different conditions of use, balancing the forces acting on the propeller, and in particular the drive torque delivered by the propulsor and the drag torque due to the fluid dynamic forces that act on the propeller blades. Moreover, the elastic means allow absorption of the shocks to which the propeller is subjected during use in both directions of drive, forward and reverse.

The seat has greater dimensions with respect to those of the elastic means in a manner such that it can allow expansion and/or rotation of at least part thereof when they are located in at least one of the operating positions and relative rotation between the hub and the propeller casing produces the stresses that cause deformation thereof. The elastic means expand and/or rotate until contact with the internal surface of the seat inside which they are housed.

According to a possible embodiment of the propeller according to the present invention, the elastic means comprise at least one spring, preferably cylindrical, the first end of which is constrained to the cylindrical propeller casing and the second end is constrained in a manner sliding inside the guide.

It must be noted that, the first and the second end of the spring lie on planes parallel to each other and perpendicular to the longitudinal axis of the propeller.

In this manner, when the second end of the spring is located in the positions for temporary operation, at least part of the spring is subjected to expansion, or reduction, of the diameter thereof, and/or rotation with respect to the unstressed condition thereof during rotation in clockwise direction or in counter-clockwise direction of the hub with respect to the propeller casing, or vice versa. Instead, when the hub rotates with respect to the propeller casing, or vice versa, and the second end of the spring slides following the relative rotation motion between the two ends of the guide, the spring is not subjected to stresses and therefore is not subject to deformation.

According to the operating position and according to the direction of rotation of the hub with respect to the propeller casing which determines the direction of the deformation force that acts on the spring, this latter will be deformed in a different manner, expanding, or decreasing the diameter thereof.

According to a possible embodiment, the seat inside which the cylindrical spring is housed is annular in shape, and the axis of the annular seat and that of the cylindrical spring are coincident.

The cylindrical spring is housed inside the annular seat which has a larger external diameter than the external diameter of the cylindrical spring to allow expansion of the latter therein. The internal diameter of the annular seat is smaller with respect to the internal diameter of the spring to allow contraction of the spring.

The propeller according to the present invention also comprises means to adjust the distance between the positions for temporary operation of the elastic means, consisting, for example, of metal pins, or calibrated rods installed inside the guide. By varying the distance between the two positions for temporary operation of the spring and therefore consequently varying the rotation angle a of the hub with respect to the propeller casing, i.e. the rotation angle for which the end of the spring slides inside the guide between the ends thereof, it is possible to modify the fluid dynamic pitch of the blades for navigation in reverse drive.

In fact, it must be noted that relative rotation, equal to the angle a, and sliding of the second end of the spring inside the guide from the second position for operation thereof until reaching the first position for operation thereof, causes modification of the fluid dynmic pitch of the blades to obtain the pitch suitable for navigation in reverse drive.

In other words, relative rotation equal to the angle a of the hub with respect to the cylindrical propeller casing, and vice versa, necessary for sliding of the second end of the spring from one end of the guide to the other (corresponding to the distance between the two operating positions of the spring), allows modification of the fluid dynamic pitch of the blades taking it to a value suitable for navigation in reverse drive. The rapid and simple installation of one or more metal pins, or calibrated rods, inside the guide, allows -the space present between the two ends of the guide to be decreased, consequently decreasing the distance between the two positions for operation of the spring with which the guide is provided.

BRIEF DESCRIPTION OF THE DRAWINGS.

Further characteristics and advantages of the present invention will be more apparent from the following description, provided by way of example with reference to the accompanying drawings, wherein:

• Fig. 1 is a sectional view according to a plane passing through the longitudinal axis of the propeller, of a possible embodiment of the propeller according to the present invention;

• Fig. 2 is a view from the prow according to the plane A-A perpendicular to the longitudinal axis of the propeller, according to Fig. 1 ;

• Fig. 3 shows a possible embodiment of a spring that can be used in the propeller according to the present invention;

• Fig. 4 is a sectional view of the propeller according to Fig. 1 , in which means are installed to adjust the distance between the positions for temporary operation of the elastic means;

• Fig. 5 is a view from the prow according to the plane A-A perpendicular to the longitudinal axis of the propeller, according to Fig. 4.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE PRESENT INVENTION

Fig. 1 shows a sectional view according to a plane passing through the longitudinal axis of the propeller, of a preferred embodiment of the variable pitch propeller according to the present invention, preferably for marine use, which can also be used for navigation in reverse drive and is capable of absorbing accidental impacts to which it may be subjected during use both in forward drive and in reverse drive. The propeller according to present invention comprises a hollow cylindrical casing 3 and a hub 4 of the propeller coupled to a propulsor, not shown in the figures.

The propulsor is constrained according to know methods to the hub 4, or this latter can consist of an end of the drive shaft, not shown in the accompanying figures. The hub 4 of the propeller is coupled coaxially to the cylindrical casing 3 in a manner such as to allow, as will be better described hereinafter, the transmission of rotary motion from the drive shaft to the cylindrical casing.

The propeller blades, again not shown in the figures, are pivoted to the cylindrical propeller casing in a manner such as to rotate about their axis of pivoting; in other words, the blades can rotate along an axis orthogonal with respect to the axis defined by the hub 4 of the propeller, which coincides with the drive direction of the propeller during forward and reverse motion.

The propeller according to the present invention also comprises a kinematic mechanism for adjusting the rotary motion of each of the blades about its axis of pivoting to the propeller casing as a function of the relative motion of the hub assembly with respect to the cylindrical propeller casing.

In more detail, the kinematic mechanism determines rotation of the blades about their pivot axis, thereby varying the angle of incidence with respect to the fluid (and therefore the fluid dynamic pitch) when the drive shaft, and therefore the hub 4, rotates in relation to the cylindrical propeller casing 3 by a non-null rotation angle, or vice versa.

The kinematic mechanism for adjusting the rotary motion, not represented in the accompanying figures, is, for example, of the type comprising a truncated-cone shaped gear pinion, integral with the root of each blade, i.e. at the end of the blade housed inside the propeller casing.

The hub of the propeller is provided with a gear wheel integral with a central truncated-cone shaped pinion, which permanently meshes the pinions of the respective blades, so that rotation of the central pinion with respect to the cylindrical propeller casing causes corresponding rotation of the blades about the respective axes of pivoting to the propeller casing, or vice versa.

This rotation of each blade about its axis causes variation of the relative angle of incidence and therefore of the fluid dynamic pitch of the propeller.

Consequently, relative rotation of the hub 4 with respect to the cylindrical propeller casing 3 causes rotation of the blades, according to an angle that is naturally a function of the angle of relative rotation between the hub assembly and the cylindrical propeller casing.

The kinematic mechanism described above can naturally be replaced with equivalent means that, by means of relative rotation between the drive shaft, and therefore the hub 4, and the cylindrical propeller casing 3, allow variation of the fluid dynamic pitch, transforming the rotation motion imparted by the propulsor into rotation of the blades about their axis of pivoting, and vice versa.

As can be seen in the accompanying figures, the propeller comprises elastic means 8 to oppose rotation of the hub 4 with respect to the cylindrical propeller casing 3, and vice versa.

In fact, these elastic means 8 are provided with at least a first end and at least a second end which allow operation thereof.

In more detail, a first end of the elastic means 8 is constrained to the cylindrical propeller casing 3 or to the hub 4, while the second end is constrained to at least one guide integral with the hub 4 or with the cylindrical propeller casing.

According to a preferred embodiment, shown in the figures, the first end of the elastic means 8 is constrained to the cylindrical propeller casing 3 and the second end is constrained to a guide 1 1 integral in rotation with the hub 4.

It must be noted that the guide 1 1 can be produced directly on the hub 4 or on an element constrained to the hub and integral in rotation therewith. The guide 11 has a first and a second position for temporary operation of the elastic means 8 which are mutually spaced apart, in a manner such as to comprise therebetween, a rotation angle a of the hub 4 with respect to the cylindrical casing 3, and vice versa.

As will be described in more detail hereinafter, following relative rotation between the hub 4 and the cylindrical casing 3, the guide 1 1 moves with respect to the second end 10 of the spring 8 which therefore slides inside this guide, in a manner such as to reach the first or the second position for operation of the elastic means.

Although specific reference has been made to the embodiment in which one end of the elastic means 8 is constrained to the cylindrical propeller casing 3 while the other end is constrained in a manner sliding inside the guide 1 1 integral in rotation with the hub 4, the alternative embodiment in which the guide 1 1 is integral in rotation with the cylindrical propeller casing 3, or produced directly thereon, and the other end of the elastic means is constrained to the propeller hub 4 also come under the scope of protection of the present invention.

As shown in Fig. 2, which is a view from the prow from the plane A-A transverse to the longitudinal axis of the propeller, according to a preferred embodiment, the guide 1 1 is configured as an arc of circumference and is produced in a disc-shaped element 5 integral in rotation with the hub 4. The positions for temporary operation of the elastic means are mutually spaced apart and positioned at the ends 15 and 16 of the guide 1 1.

It must be noted that the term "position for temporary" operation has been used to indicate that the elastic means 8 oppose relative rotation of the hub with respect to the cylindrical propeller casing, and vice versa, only when the end of the elastic means constrained to the guide 1 1 is located in one of the positions for operation thereof.

In other words, the elastic means 8 are operated and oppose relative rotation between hub 4 and propeller casing 3 only when they are located engaged with the guide in the positions for operation with which it is provided, which as stated in the embodiment shown in the figures correspond to the position in which the end of the elastic means constrained to the guide are located at one of the ends 15 and 16.

Operation of the elastic means 8 is temporary, as following a rotation in counter- clockwise direction, seen from the stern, of the hub 4 with respect to the cylindrical casing 3, or vice versa, the end of the elastic means constrained to the guide 1 1 reaches the operating position at the end 15 of the guide 1 1 until the direction of rotation is inverted, or no further drive torque is delivered through the propulsor. Instead, when the hub 4 rotates in clockwise direction, seen from the stern, with respect to the propeller casing 3, or vice versa, the elastic means 8, following rotation of the guide 1 1, reach the second operating position at the end 16 of the guide 11 and remain in this position until the direction of rotation is inverted, or no further drive torque is delivered through the propulsor.

When the elastic means are located in the positions for operation thereof, the cylindrical propeller casing 3 and the hub 4 are coupled in rotation through the elastic means 8 which on the one side are constrained to the cylindrical casing 3 and on the other side are operated being temporarily engaged with the guide 1 1 integral with the hub 4.

In this manner, the elastic means 8 allow automatic adjustment of the fluid dynamic pitch during use of the propeller in forward drive as they allow adaptation of relative rotation between the hub 4 and the cylindrical casing 3 in the different conditions of use, balancing the forces acting on the propeller, and in particular the drive torque delivered by the propulsor and the drag torque due to the fluid dynamic forces that act on the propeller blades. Moreover, the elastic means 8 allows absorption of impacts to which the propeller is subjected during use in both directions of drive, forward and reverse.

As shown in the accompanying figures, according to a preferred embodiment the elastic means 8, with which the propeller according to the present invention is provided, comprise a spring 8 shown in detail in Fig. 3.

As can be seen in Fig. 3, the spring 8, preferably a cylindrical spring, is provided with a first end 9 constrained to the cylindrical propeller casing 3 according to known means, for example a specific slot 7, and a second end 10 constrained in a manner sliding inside the guide 1 1.

Following relative rotation between the guide 1 1 and the second end 10 of the spring 8, this latter can slide inside the guide 11 in a manner such as to provide an angle a of free rotation of the hub 4 with respect to the cylindrical propeller casing 3, and vice versa, in which the spring is not operated.

In fact, as already stated, the first end 9 of the spring 8 is constrained to the cylindrical propeller casing 3 and therefore, due to relative rotation between cylindrical propeller casing 3 and hub 4, the second end 10 will move inside the guide 1 1 according to the direction of rotation until reaching the first or the second position for temporary operation with the guide 1 1 which, as stated, preferably coincide with the ends 15 and 16 thereof.

In other words, according to the embodiment described above, the end 10 of the spring 8 is located in the operating position with the guide 1 1 when the end 10 is at one of the ends 15 or 16 of the guide 1 1. The two positions for temporary operation of the spring 8 are mutually spaced apart and therebetween there is present an angular space a for relative rotation between the hub 4 and the cylindrical propeller casing through which the second end 10 of the spring 8 moves, due to rotation of the guide 11 , from one end of the guide to the other, and vice versa, from one position for temporary operation to the other.

It is clear that when relative rotation between the hub 4 and the cylindrical propeller casing 3 causes sliding of the second end 10 of the spring 8 inside the angular space a between the two ends 15 and 16 of the guide 11, i.e. when the spring is not operated, it is not subjected to any stress and therefore does not sustain any deformation.

Instead, when following rotation of the hub 4 with respect to the cylindrical propeller casing 3, and vice versa, the spring 8 is located in one of the two positions for operation thereof with which the guide 1 1 is provided, and the cylindrical propeller casing 3 and the hub 4 are coupled in rotation by means of the spring 8, this latter is subjected to stresses that cause deformation thereof, and in particular, expansion or contraction in radial direction and/or rotation.

Preferably the ends 9 and 10 of the spring, constrained respectively to the cylindrical propeller casing 3 and to the guide 11 , lie on planes perpendicular to the longitudinal axis of the propeller parallel to each other.

Figs. 2 and 5 are view from the prows according to a plane A-A perpendicular to the longitudinal propeller axis, and show the second end 10 of the spring 8 at the end 15 of the guide 1 1 in the position for temporary operation.

Preferably, counter-clockwise rotation of the propulsor, seen from the stern, and therefore of the hub 4, is used for navigation in forward drive, while clockwise rotation, seen from the stern, is used for navigation in reverse drive.

Consequently, the end 10 of the spring 8 reaches the end 15 of the guide 11 in operating position of the spring, as shown in the accompanying Figs. 2 and 5, when the propulsor imparts rotation in counter-clockwise direction, seen from the stern, as stated, preferably used for navigation in forward drive. When the direction of rotation of the propulsor is inverted, in clockwise direction, seen from the stern, generally used for navigation in reverse drive, the end 10 of the spring 8, following rotation of the guide 1 1 , reaches the other end 16 of the guide 1 1 in the second operating position of the spring, not shown in the accompanying figures.

The propeller according to the present invention also comprises a seat 12 inside which the elastic means 8 are housed.

As will be apparent at this point of the description, as the first end of the spring 8 is constrained to the cylindrical propeller casing, when the second end 10 is located in one of the positions for temporary operation thereof following relative rotation between hub and cylindrical casing, the spring 8 is subjected to stresses that cause deformation thereof.

In other words, when the spring is operated, it opposes rotation of the hub 4 with respect to the cylindrical propeller casing 3, and vice versa, and is subjected to forces that cause deformation thereof, and in particular expansion (in radial direction), or reduction of the diameter thereof, and/or rotation. As will be better described hereinafter, according to the direction of relative rotation between the hub and the cylindrical propeller casing, the spring is subjected to different stresses that cause expansion thereof and/or rotation or contraction thereof (reduction of the diameter thereof) and/or rotation.

According to the embodiment shown in Fig. 3, the spring 8 is subjected to expansion and/or rotation when the hub rotates in clockwise direction, seen from the stern, with respect to the propeller casing, and vice versa, and the second end 10 of the spring 8 is located in operating position at the end 16 of the guide 1 1. Expansion of the spring 8 allows absorption of any impacts to which the propeller may be subjected during navigation in reverse drive.

Instead, when the hub 4 rotates in counter-clockwise direction, seen from the stern, with respect to the cylindrical propeller casing 3, and vice versa, and the second end 10 of the spring 8 is located in operating position at the end 15 of the guide 1 1, the spring 8 is subjected to contraction with consequent reduction of the diameter thereof and/or rotation. Contraction of the spring 8 and reduction of the diameter thereof allows control of the motion of relative rotation of the hub 4 with respect to the cylindrical propeller casing 3, and vice versa, allowing continuous adjustment of the fluid dynamic pitch of the blades and absorption of any impacts during navigation in forward drive. It must be noted that the seat 12 with which the propeller according to the present invention is provided allows limitation of the deformations to which the spring 8 is subjected when it is subjected to expansion, or contraction, due to relative rotation between the hub 4 and the cylindrical propeller casing 3, in a manner such as to allow automatic variation of the fluid dynamic pitch of the blades during forward drive and absorption of impacts both in forward drive and in reverse drive.

As stated, according to the operating position and according to the direction of rotation of the hub 4 with respect to the propeller casing 3 which determines the direction of the deformation force that acts on the spring, this latter will be deformed in a different manner with expansion, or reduction, of the diameter, and/or rotation. By modifying the space available for deformation of the spring inside the seat 12, it is possible to limit maximum rotation of the hub 4 with respect to the cylindrical propeller casing 3 and therefore to control and limit adjustment of the fluid dynamic pitch of the blades and absorption of impacts during motion in forward drive and in reverse drive.

In the embodiment shown in the accompanying figures, the seat 12, inside which the cylindrical spring 8 is housed, is annular in shape.

The cylindrical spring 8 is housed inside the anular seat in a manner such that the axis of the cylindrical spring and that of the annular seat are coincident.

It must be noted that the annular seat has a larger external diameter with respect to the external diameter of the spring in order to allow deformation (expansion and/or rotation) and therefore control relative rotation of the hub with respect to the propeller casing, and vice versa, to absorb impacts in reverse drive. The internal diameter of the annular seat 12 is instead smaller with respect to the internal diameter of the cylindrical spring 8 to allow contraction (reduction in diameter) of the spring, and therefore control relative rotation of the hub with respect to the propeller casing, and vice versa, to vary the fluid dynamic pitch of the blades and absorb impacts in forward drive.

As shown in the sectional view of Figs. 1 and 4, the cylindrical seat 12 is provided with a space 18 for expansion of the spring; instead, the numerical reference 19 indicates contraction, with consequent reduction of diameter, to which the spring is subjected during motion in forward drive in a manner such as to allow an angle of relative rotation of the hub with respect to the cylindrical propeller casing adapted for automatic modification of the fluid dynamic pitch of the blades during motion in forward drive.

It is apparent that the space 18 for expansion of the spring will depend on the difference between the external diameter of the seat 12 and that of the cylindrical spring in unstressed condition, while the contraction 19 to which the spring is subjected will depend on the difference between the internal diameter of the spring, in unstressed condition, and that of the annular seat 12.

The space 18 is produced and dimensioned in a manner such as to accommodate and limit deformation of the spring during motion in reverse drive, and provides a shock absorption transient for any impacts. As can be seen in Figs. 1 and 4, the space 18 inside the seat 12 adapted to accommodate expansion of the spring 8 during motion in reverse drive is smaller with respect to the space 19 available for contraction (reduction of diameter) of the spring during motion in forward drive.

As will be apparent at this point of the description, the spring 8 expands and/or rotates until coming into contact with the internal surface of the external diameter of the annular seat 12 inside which it is housed. Instead, when the spring is subjected to contraction, it will reduce the diameter thereof until coming into contact with the internal surface of the internal diameter of the annular seat 12.

The dimensions of the annular seat 12 determine the maximum deformation to which the spring 8 can be subjected, consequently limiting maximum rotation of the hub 4 with respect to the cylindrical propeller casing 3, and vice versa, and therefore allows automatic pitch variation during forward drive and a shock absorption transient for impacts during motion in forward drive and in reverse drive.

This particular configuration also makes it possible to prevent the spring 8 from being subjected to excessive deformations which would cause permanent deformation or even breakage thereof.

In fact, contraction of the spring will allow an angle of relative rotation between hub 4 and propeller casing 3 such as to allow adjustment of the fluid dynamic pitch of the blades and absorption of impacts during motion in forward drive. Instead, during motion in reverse drive the blades are positioned to a pitch suitable for this condition of use and the space 18 of the seat 12 adapted to accommodate and limit expansion of the spring 8 is such as to determine a more limited rotation of the hub 4 with respect to the cylindrical propeller casing 3 intended to provide a shock absorption transient for any impacts during use in reverse drive.

Operation of the propeller according to the present invention will now be described with reference to the accompanying figures.

Starting from the position shown in Figs. 1 and 4, in which the second end 10 of the spring 8 is located at the end 15 of the guide 1 1 in the operating position, the propulsor imparts rotation in counter-clockwise direction, seen from the stern, preferably used for navigation in forward drive.

As the other end 9 of the spring 8 is constrained to the cylindrical propeller casing 3, the hub 4 and the cylindrical propeller casing 3 are coupled in rotation by means of the spring 8 which opposes relative rotation thereof.

The spring 8, which operates by flexure, opposes relative rotation between the hub 4 and the propeller casing 3 and is subjected to stresses that determine contraction and/or rotation thereof.

As stated, as the angle of relative rotation between the hub 4 and the cylindrical propeller casing 3 correspondingly determines the rotation of the angle of incidence of the blades, when the external conditions vary, and specifically the drag torque on the blades and therefore the drive torque, the elastic response of the spring 8 and deformation thereof and/or rotation inside the seat 12, will vary correspondingly, and consequently the possible angle of rotation of the hub 4 with respect to the cylindrical propeller casing 3, and vice versa, will also vary.

This determines continuous rotation of the blades with corresponding variation in their angle of incidence with respect to the direction of forward motion corresponding to the axis of the drive shaft, or of the hub, when these external conditions change.

This relative rotation of the hub 4 with respect to the cylindrical propeller casing 3, adjusted by the spring 8 and by contraction thereof, causes rotation of the blades with respect to the cylindrical propeller casing towards an angle of incidence, and therefore an optimal fluid dynamic pitch for a given operating condition. By opposing relative rotation of the hub 4 with respect to the cylindrical propeller casing 3, the spring 8 allows the relative angular displacement of the hub 4 with respect to the cylindrical propeller casing 3 to be varied as a function of the forces acting on the spring 8, and therefore as a function of the drive torque of the propulsor and of the drag torque which, through the blades, is transmitted to this cylindrical propeller casing 3.

The spring 8 allows balancing of the forces acting on the propeller, and in particular the drive torque generated by the propulsor and the drag torque caused by friction and by resistance of the fluid, allowing automatic and continuous modification of the fluid dynamic pitch of the blades ensuring high performance during use.

It must be noted that the spring 8 also allows absorption of any impacts to which the propeller, or its blades, may be subjected during operation in forward drive.

Maximum contraction of the spring is limited by the difference between the internal diameter of the spring and that of the annular seat. In fact, following relative rotation between the hub and the cylindrical propeller casing, the spring 8 tends to reduce the diameter thereof until it comes into contact with the internal surface of the seat 12 on the internal diameter thereof.

When the direction of rotation of the propulsor is inverted, and the hub rotates in clockwise direction (seen from the stern) with respect to the propeller casing, and vice versa, the end 10 of the spring 8, following rotation of the guide 1 1 , leaves the position of temporary operation shown in Figs. 2 and 5 and, travelling along the entire guide 1 1 following relative rotation between the hub 4 and the cylindrical propeller casing 3, reaches the second operating position within the guide 1 1 at the end 16 of the guide 1 1.

Relative rotation, equal to the angle a, and sliding of the second end 10 of the spring 8 inside the guide 1 1 , caused by rotation of the guide 1 1 , until reaching the first position for operation thereof, determines modification of the fluid dynamic pitch of the blades and obtains the pitch suitable for navigation in reverse drive.

In other words, relative rotation equal to the angle a of the hub 4 with respect to the cylindrical propeller casing 3, necessary for sliding of the second end 10 of the spring 8 from one end of the guide to the other (corresponding to the distance between the two operating positions of the spring 8), allows modification of the fluid dynamic pitch of the. blades, taking it to a value suitable for navigation in reverse drive.

Once the first operating position has been reached, the spring 8 allows absorption of any impacts to which the propeller may be subjected during navigation in reverse drive. In fact, following relative motion between the hub 4 and the cylindrical propeller casing it is subjected to expansion and/or rotation inside the upper space 18 of the seat 12 which determines a shock absorption transient of any impacts during reverse drive.

The spring 8, which operates by flexure, opposes relative rotation between the hub 4 and the propeller casing 3 and is subjected to stresses that determine expansion thereof and/or rotation inside the seat 12 in which it is housed.

In fact, once the second end 10 of the spring 8 has reached the end 16 of the guide 11, further rotation of the hub 4 with respect to the cylindrical propeller casing 3 in clockwise direction, seen from the stern, and vice versa, subjects at least part of the spring 8 to stresses that cause expansion thereof and/or rotation inside the seat 12. As stated, deformation of the spring will take place in a given direction and the space 18 between the spring and the internal surface of the seat 12 will allow limitation of relative rotation between the hub 4 and the cylindrical propeller casing 3, providing a desired shock absorption transient.

Naturally, the dimensions of the space 18, and therefore the difference between the external diameter of the spring and that of the annular seat for expansion of the spring can be modified during the design stage of the propeller according to requirements and to the maximum variation desired, both to limit the shock absorption transient in reverse drive, and to prevent deformation thereof in the plastic range and therefore avoid possible breakage thereof. In the same manner, also the difference between the internal diameter of the spring and that of the annular seat which determines the space for contraction of the spring can be varied appropriately during the design stage to control and limit in the desired manner modification of the fluid dynamic pitch of the blades and the shock absorption transient in forward drive. Although having made specific reference to the embodiment provided with a seat of cylindrical shape, this can be produced in different shapes, also in relation to the shape and dimensions of the spring that must be housed therein, provided that the space necessary for deformation of the spring is guaranteed.

It must be noted that the fluid dynamic pitch for navigation in reverse drive of the propeller according to the present invention can be easily set by the user, through the use of adjustment means (25).

In fact, as will be better described hereinafter, the angular space a comprised between the two operating positions of the elastic means, with which the guide is provided, is adjustable by the user and allows the pitch of the blades to be modified in a rapid and simple manner for navigation in reverse drive.

Fig. 4 shows a sectional view according to a plane passing through the longitudinal axis of the propeller, of a possible embodiment of the variable pitch propeller identical to the one described previously with reference to Fig. 1 , with the exception of the presence of means 25 for adjusting the distance between the first and the second operating position of the elastic means with which the guide is provided. In other words, the angular rotation space (angle a) of the hub 4 with respect to the propeller casing 3, and vice versa, between the two positions for temporary operation of the spring 8, can be adjusted through appropriate means 25 with which the propeller according to the present invention is provided.

In more detail, starting from the first position for temporary operation shown in the accompanying figures, when the hub 4 rotates in clockwise direction, seen from the stern, until the end 10 of the spring travels along the entire guide 1 1 and reaches the second operating position, relative rotation of the hub 4 with respect to the cylindrical propeller casing determines modification of the pitch of the blades and obtains the pitch suitable for navigation in reverse drive.

This propeller pitch for navigation in reverse drive is established in advance and depends on the distance between the two positions for temporary operation of the spring with which the guide is provided.

In particular, in the embodiment shown in the figures, the two operating positions correspond to the two ends 15 and 16 of the guide 1 1, and therefore the fluid dynamic pitch of the blades for navigation in reverse drive will also depend on the length of the guide and consequently of the angle of relative rotation a of the hub 4 with respect to the cylindrical propeller casing 3 comprised between the two operating positions of the spring.

As stated, the propeller according to the present invention allows modification of the pitch suitable for navigation in reverse drive by the user without requiring to completely disassemble the propeller and carry out internal work thereon through replacement or mechanical machining of the drive shaft, of the hub or of the propeller casing.

In fact, the user can modify the pitch suitable for navigation in reverse drive manually, by varying the distance between the two positions for temporary operation of the ends of the spring and consequently varying the angle a of rotation of the hub 4 with respect to the propeller casing 3, i.e. the angle of rotation for which the end 10 of the spring 8 slides inside the guide 1 1 between the ends 15 and 16 thereof.

In fact, as can be seen with reference to Figs. 4 and 5, said means for adjusting the distance between the positions for temporary operation of the elastic means with which the guide 1 1 is provided, preferably comprise one or more pins 25, made of metal material, installed inside the guide 1 1 in the space comprised between the operating positions of the spring 8 with which the guide 1 1 is provided, in proximity of the end 16.

As shown in the figures, the pin or pins 25 reduce the space present between the two ends 15 and 16 of the guide 11, consequently allowing a reduction of the angle a of relative rotation between the hub 4 and the propeller casing 3.

The angle a of rotation of the hub 4 with respect to the propeller casing 3 can be modified by increasing or decreasing the angle γ equal to the dimension and to the number of metal pins 25 installed inside the guide 11.

Naturally, as will be apparent at this point of the description, during the design stage it is possible to establish the pitch suitable for navigation in reverse drive decreasing, or increasing, the dimensions of the guide 1 1 , and therefore basically varying the space between the two positions for temporary operation of the elastic means.

As stated, the user can proceed to modify the pitch of the blades for navigation in reverse drive according to personal using requirements and on the basis of the propulsor to which .the propeller will be coupled, in a simple and rapid manner, and in particular without requiring to disassemble parts of the propeller.

In fact, the guide 1 1 is easily accessible from the outside simply by removing the propeller tip 30.

For this reason, the user can carry out adjustment of the fluid dynamic pitch suitable for navigation in reverse drive by installing a variable number of metal pins 25 with a few simple operations.

In particular, as shown in Fig. 4, once the tip of the propeller has been removed the user has free access to the guide 11 and can proceed with replacement of the pins 25. According to an alternative embodiment of the propeller according to the present invention, the means for adjusting the distance between the first and the second operating position of the elastic means comprise a calibrated rod which is installed inside the guide 1 1.

The calibrated rod is secured to an insert, not shown in the accompanying figures, which is constrained to the guide 1 1 according to known means. The user has the choice of a plurality of inserts, each provided with a calibrated rod having different dimensions with respect to the others.

As described previously in relation to the pins 25, the rotation angle a of the hub 4 with respect to the cylindrical propeller casing is modified by increasing or decreasing the angle γ equal to the dimension of the calibrated rod installed.

Claims

A variable pitch propeller of the type comprising at least one blade pivoted rotatably to a cylindrical propeller casing (3), a propeller hub (4) coupled to a propulsor and positioned coaxially inside said propeller casing (3), a kinematic mechanism for adjusting the rotary motion of said at least one blade about its axis of pivoting to said propeller casing (3) as a function of the relative motion of said propeller hub (4) with respect to said cylindrical propeller casing (3), elastic means (8) for opposing relative rotation of said hub (4) with respect to said cylindrical propeller casing (3), and vice versa, said elastic means comprising at least a first and at least a second end for operation thereof, characterized in that said at least a first end of said elastic means is constrained to said cylindrical propeller casing, or to said hub, and said at least a second end of said elastic means is constrained to at least one guide (1 1) integral with said propeller hub, or with said cylindrical casing, said at least one guide having at least a first and at least a second position for temporary operation of said elastic means (8), mutually spaced apart.

The propeller according to claim 1, characterized in that said at least a first end of said elastic means (8) is constrained to said cylindrical propeller casing

(3) and said at least a second end is constrained to said at least one guide (1 1) made on said propeller hub (4) or on an element integral in rotation with said propeller hub.

The propeller according to claim 1 or 2, wherein the distance between said at least a first and said at least a second position for temporary operation of said elastic means (8) provides at least one angular space (a) for rotation of said hub

(4) with respect to said cylindrical propeller casing (3), and vice versa. The propeller according to any one of the preceding claims, wherein said at least one guide (1 1) is configured in an arc of circumference, said elastic means (8) being in said positions for temporary operation thereof when at least one end of said elastic means is located at the ends of said at least one guide, said at least one angular space (a) for rotation of said hub with respect to said cylindrical propeller casing, and vice versa, being comprised between said ends (15, 16) of said at least one guide (1 1).

5. The propeller according to claim 1 or 2, wherein at least part of said elastic means (8) is subjected to expansion or contraction and/or rotation with respect to the unstressed condition thereof during rotation in clockwise direction or in counter-clockwise direction of said hub (4) with respect to said propeller casing (3), or vice versa, when said elastic means are located in said positions for temporary operation thereof of said at least one guide (11).

6. The propeller according to any one of the preceding claims, characterized by comprising at least one seat (12) inside which said elastic means (8) are housed.

7. The propeller according to claim 6, wherein said at least one seat (12) is provided with larger dimensions with respect to said elastic means (8) to allow expansion thereof and/or rotation inside said seat when said elastic means are located in at least one of said positions for temporary operation thereof of said at least one guide (1 1).

8. The propeller according to claim 6 or 7, wherein said at least one seat (12) is annular, having axis parallel to the longitudinal axis of the propeller.

9. The propeller according to any one of the preceding claims, wherein said elastic means comprise at least one spring (8) provided with at least a first (9) and at least a second (10) end.

10. The propeller according to claim 9, characterized in that said at least a first end (9) of said spring (8) is constrained to the cylindrical propeller casing (3) and said at least a second end (10) of said spring (8) is constrained in a manner sliding inside said guide (1 1) integral with said propeller hub (4).

1 1. The propeller according to claim 9 or 10, wherein said at least a first and second end (9, 10) of said at least one spring (8) lie on planes parallel to each other and perpendicular to the longitudinal axis of the propeller.

12. The propeller according to claim 9 or 10, wherein said at least part of said at least one spring (8) is subjected to expansion or reduction of the diameter and/or rotation with respect to the unstressed condition thereof during rotation in clockwise direction or in counter-clockwise direction of said hub (4) with respect to said propeller casing (3), or vice versa, when said at least a second end (10) of said spring is located in said positions for temporary operation of said guide (11), said at least one spring (8) not being subjected to deformations when said at least a second end (10) slides inside said guide (1 1) between said ends (15, 16) of said at least one guide (1 1).

13. The propeller according to any one of claims 9 to 12, characterized in that said at least one spring is cylindrical.

14. The propeller according to claim 8 or 13, wherein said cylindrical spring is housed inside said at least one annular seat (12), said cylindrical spring being provided with a smaller external diameter with respect to the external diameter of said at least one annular seat to allow expansion thereof inside said seat, said cylindrical spring being provided with a larger internal diameter with respect to the internal diameter of said at least one annular seat to allow contraction of the spring inside the seat.

15. The propeller according to any one of the preceding claims, characterized by comprising means (25) for adjusting the distance between said at least a first and said at least a second position for temporary operation of said elastic means (8).

16. The propeller according to claim 15, wherein said means (25) for adjusting the distance between said at least a first and said at least a second position for temporary operation of said elastic means (8) comprise at least one metal pin inserted inside said at least one guide (1 1).

17. The propeller according to claim 15, wherein said means (25) for adjusting the distance between said at least a first and said at least a second position for temporary operation of said elastic means (8) comprise at least one calibrated rod mounted on an insert and inserted inside said at least one guide.