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FIELD OF THE INVENTION

The present invention relates to a variable pitch boat propeller, of the type in which each blade is constrained, directly or indirectly, to the motor shaft of the boat in such a manner as to be able to rotate about an axis transverse with respect to the axis of the motor shaft, by means of an extemal cylindrical body. The extemal cylindrical body of the propeller is fitted coaxiaily onto an intemal cylindrical body, which in turn rotates integrally with the motor shaft of the boat. Here and hereafter, reference will be made without distinction to automatically or manually variable pitch boat propellers, provided with or without blades in "feathering" position, given that these distinctions, as will be clear to those skilled in the art, have no relevance in relation to the object of the present invention.

BACKGROUND ART

In the field of variable pitch boat propellers it is know in the art to constrain the rotating blades to the motor shaft of the boat by means of an extemal cylindrical body, appropriately shaped to allow pivoting of the blades, which is constrained to the motor shaft usually by means of interposing of an intemal cylindrical body, or sleeve, fitted coaxiaily onto the motor shaft.

Coupling of the extemal cylindrical body with the internal cylindrical body is generally produced using bolts, screws or other threaded securing means, with axis both transverse and parallel to the axis of the motor shaft, or of the propeller.

Moreover, the extemal cylindrical body is usually constituted by several complementary parts, which are mutually secured using bolts, or screws, or other threaded securing means, also having axis transverse and/or parallel to the axis of the propeller.

However, assembly by means of bolts, screws, or other threaded securing means of the various parts that form the boat propeller causes some problems. In fact, during use of the boat propeller, due to the vibrations that are transmitted along the whole kinematic chain from the boat motor to the blades, there is a strong possibility of loosening of the threaded securing means, with the consequent risk of losing the various parts of which the propeller is composed.

Moreover, the removal and installation of the propeller, for example to carry out maintenance, are difficult operations, given the need to loosen and tighten a substantial number of bolts, screws or other threaded securing means, as well as the nut that locks the internal cylindrical body to the motor shaft.

In fact, it must be borne in mind that the propeller is usually installed on the motor shaft by means of a lock nut which, at the rear (stem) of the propeller, is screwed onto a corresponding threaded end portion of the motor shaft and is shaped in such a manner as to keep the motor shaft and the intemal body of the propeller coupled, preventing the mutual release thereof. The intemational patent application WO-A-9011221 , by the applicant MARINE PROPELLER Sri, describes a propeller in which the external body of the propeller, designed to keep each blade coupled with the intemal body of the propeller, in turn fitted onto the motor shaft, is constituted by various mutually juxtaposed parts generally constrained by means of bolts, with the exception of a part destined to be translated by the installer, which is kept coupled with the remaining part of said external body by means of a spring, an elastic ring and a "Seeger" type metal circlip.

This propeller, which has a lock nut positioned inside the intemal cylindrical body, besides being somewhat difficult to install and remove, due to the specific arrangement of this lock nut, also has the drawbacks set forth above in relation to the presence of threaded means to secure the various parts constituting the external cylindrical body of the propeller.

Moreover, in the propeller by MARINE PROPELLER, when wishing to install or remove the propeller on or from the motor shaft, following removal/installation of the lock nut, which as stated may itself be somewhat difficult, there is a strong possibility that the components of the propeller, kept in place by mechanical opposing of parts, will be disassembled in an undesirable manner. In prior art there are also propellers in which the external cylindrical body of the propeller is constituted by a plurality of mutually juxtaposed, or interlocked, parts, kept in their correct position through mechanical retaining means by juxtaposing/opposing of complementary parts. These retaining means can, for example, be constituted by a front stop integral with the internal cylindrical body, and by one or more elastic sealing rings, with a relative "Seeger" ring, positioned at the rear of the propeller, and can act as constraining elements of the external cylindrical body to the corresponding internal cylindrical body.

A propeller of this type is described in the Italian patent application ITMI2008A001667, by the same Applicant, wherein the use of these mechanical retaining means for interlocking of complementary parts, between the external and internal cylindrical body of the propeller, makes it possible to avoid the use of bolts, screws or other threaded securing means of the various parts forming the external cylindrical body.

While providing retaining means between the external and internal cylindrical bodies, during installation/removal of this type of propeller on/from the motor shaft, there is the risk of losing or damaging the lock nut, which can be separated from the propeller.

Moreover, once the lock nut has been removed, although without requiring to loosen threaded retaining means of the parts forming the external cylindrical body, in the propeller described in ITMI2008A001667 it is still necessary to remove the retaining means acting by opposed parts, for example constituted by the aforesaid Seeger ring and by the sealing ring (or rings).

The object of the present invention is to produce a variable pitch boat propeller which overcomes the drawbacks of prior art indicated above.

A further object of the present invention is to provide a variable pitch boat propeller which is highly reliable and at the same time easy to install and remove without the use of screws, pins, bolts and similar constraining elements between the various propeller components.

A further object of the present invention is to produce a variable pitch boat propeller which has a simple structure, which eliminates or minimizes the possibility of its components, including the nut that locks the propeller on the motor shaft, becoming disassembled during the step to remove/install it from/on the motor shaft.

SUMMARY OF THE INVENTION

These and other objects are achieved by a variable pitch boat propeller according to the first independent claim and the subsequent dependent claims. The variable pitch boat propeller according to the present invention comprises at least one internal cylindrical body and at least one blade pivoted to an external cylindrical body of the propeller constituted by one or more juxtaposed parts, and coaxial to the internal cylindrical body which is in turn fitted coaxially on a motor shaft and constrained thereto by means of a lock nut.

The propeller also comprises retaining means, which cooperate with the internal cylindrical body of the propeller, to maintain in assembled position, with interlocking of complementary parts, at least the internal cylindrical body, the external cylindrical body and the blades.

The propeller is characterized in that it comprises means to constrain by coupling the lock nut - which as stated constrains the propeller to the motor shaft - to the external cylindrical body of the propeller, or at least a part thereof. The presence of retaining means, which cooperate with the internal cylindrical body, allow the components of the propeller to be kept in assembled position, with interlocking, so that it is particularly simple to install on/remove from the motor shaft.

In fact, after removal, all the components of the propeller remain in assembled position, ready to be re-installed on the motor shaft at the end of the maintenance or other operation that made it necessary to remove the propeller from the shaft.

Advantageously, the use of pins, bolts, screws or other similar securing means to constrain the various components of the propeller to one another, or to mutually constrain the parts forming the external cylindrical body and this latter to the internal cylindrical body, is also limited, or even completely eliminated. Moreover, it must be noted that in the propeller according to the present invention, the constraining means with which it is provided also keep the nut inside the propeller, coupled with the external cylindrical body of the propeller. In this manner, the nut used to constrain the propeller to the motor shaft also remains in assembled position inside the propeller following operations to remove it from the motor shaft.

To allow the components to be kept in assembled position, the internal cylindrical body of the propeller comprises at least one abutting portion for the external cylindrical body, or at least for a part thereof.

Moreover, according to one aspect of the present invention, the constraining means are constrained in a removable manner to the external cylindrical body of the propeller, or at least to a part thereof, and comprise, according to a possible embodiment, a circular flange constrained in the part positioned at the rear of the external cylindrical body.

It must also be noted that according to a particular aspect of the present invention, the retaining means to keep the propeller in assembled position, comprise at least one elastic element, positioned between the internal cylindrical body and the external cylindrical body, or at least a part thereof, which cooperates in retaining and keeping the components of the propeller mutually assembled. Preferably, this elastic element is an elastic ring positioned at the external surface of the internal cylindrical body of the propeller.

According to one aspect of the propeller according to the present invention, the retaining means comprise, alternatively or additionally to one or more elastic elements, at least one abutting surface of the lock nut on the external cylindrical body of the propeller, or on at least a part of the external cylindrical body of the propeller.

In more detail, according to a possible embodiment the nut that allows the propeller to be constrained to the motor shaft comprises a lateral skirt and the abutting surface on the external cylindrical body is positioned at the end of this lateral skirt.

As shall be clear to those skilled in the art, with the propeller according to the present invention it is possible to achieve simple, fast and safe installation and removal of the propeller on from the motor shaft, at the same time avoiding possible risks of damage to the propeller components, which are encountered each time the propeller requires to be removed from the shaft and which are well known to any motor mechanic.

In fact, all the components of the propeller, including the lock nut, remain in assembled position by means of the retaining means, and preferably by means of at least one elastic annular element and/or at least one abutting surface of the nut, cooperating with the internal cylindrical body of the propeller.

Moreover, the constraining means with which the propeller is provided also allow the nut for locking the propeller to the motor shaft to be kept in assembled position, and in particular, coupled with at least part of the external cylindrical body of the propeller, In this manner, during removal of the propeller, even if loosened, this nut will remain coupled with the external cylindrical body.

BRIEF DESCRIPTION OF THE FIGURES

There shall now be described, purely by way of non-limiting example, some preferred embodiments of the present invention, with reference to the accompanying figures, wherein:

• Fig. 1 is a partial sectional view of a variable pitch boat propeller according to the present invention;

• Fig. 2 is a partial sectional view of a variable pitch boat propeller according to the present invention provided with means to lock rotation of the nut.

DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE PRESENT INVENTION

With reference to the accompanying Figs. 1 and 2, the variable pitch boat propeller 1, illustrated herein, comprises an internal cylindrical body 2 having axis X-X (axis of the propeller 1) and internal variable diameter (i.e. with a tapered internal portion), an external cylindrical body 5.1, 5.2, 5.3, formed by a plurality of juxtaposed parts, which is constrained in a manner coaxial to the internal cylindrical body 2, and a plurality of blades 4 constrained in a manner rotating about the axis Y-Y thereof, by means of the external cylindrical body 5.1 , 5.2 and 5.3.

It must be noted that the propeller shown in Fig. 2 is identical to the one shown in Fig. 1 , with the addition of means 30 to prevent rotation of the nut 6 for locking the propeller to the motor shaft 3, and for this reason Figs. 1 and 2 will be referred to without distinction, with particular reference only to the second figure in the description of these means 30 for locking the nut 6.

It must be noted that, in the propeller 1 illustrated herein, modification of the fluid dynamic pitch of the blades 4, by means of rotation about the axis Y-Y thereof, can be controlled manually or automatically, by means of suitable kinematic mechanisms, known in the art and not shown in the accompanying figures.

The internal cylindrical body 2, or sleeve, of the propeller is mounted and fitted, for example using a key, coaxially to the motor shaft 3 of the boat on which the propeller is installed, in such as manner as to be able to convey rotational motion to the propeller.

Although specific reference has been made to installation of the propeller directly on the motor shaft 3, it is also possible to install the internal cylindrical body 2 on an extension of the motor shaft, or on rotating means kinematically connected thereto.

The internal cylindrical body 2 of the propeller 1 has a tapered internal surface complementary in shape to the shape of the external surface of the motor shaft 3 on which it is installed.

In general, the shape of the internal surface of the internal cylindrical body 2 is such as to allow insertion of the motor shaft 3 therein, and at the same time, such as to prevent movement of the motor shaft 3 in one direction (to the right in Fig. 1) with respect to the internal cylindrical body 2.

The internal cylindrical body 2 is secured to the motor shaft 3 by means of a lock nut 6 which is tightened on a corresponding threaded end 3a of the motor shaft 3.

As will be more apparent from the description below, the propeller according to the present invention also comprises retaining means 6h, 8 cooperating, by opposing of parts, with the internal cylindrical body 2 of the propeller, to keep in assembled position, through interlocking, the components of the propeller and at least the internal cylindrical body 2, the external cylindrical body 5.1, 5.2, 5.3, or the various components thereof, and the blades 4.

In other words, in the propeller 1 according to the present invention the internal cylindrical body 2, the external cylindrical body 5.1 , 5.2, 5.3 (composed of one or more parts), and the blades 4 pivoted thereto, are maintained in assembled position by means of the joined action of the internal cylindrical body 2 and of the retaining means 6h, 8.

The retaining means comprise, in particular, at least one elastic element 8, positioned between the internal cylindrical body 2 and the external cylindrical body 5.1 , 5.2, 5.3, or at least a part thereof, which cooperates with the internal body 2, and in particular with a abutting portion 20 thereof, and the external body 5.1, 5.2, 5.3 in retaining and keeping the various components of the propeller 1 mutually assembled.

Moreover, according to one aspect of the present invention, these retaining means comprise, alternatively or in addition (as shown in the figures) to the elastic element 8, at least one abutting surface 6h for at least part 5.3 of the external cylindrical body, the abutting surface 6h is positioned on the lock nut 6. In the embodiment shown in the accompanying figures, the retaining means comprise, in more detail, an elastic element 8 and a abutting surface 6h of the lock nut 6, which cooperate with the external cylindrical body 5.1 , 5.2, 5.3, or at least a part thereof, to maintain the components of the propeller in assembled position, through interlocking of parts between the aforesaid abutting portion 20 of the internal cylindrical body 2 of the propeller 1 and said retaining means. In more detail, the external cylindrical body 5.1 , 5.2, 5.3, or at least a part thereof 5.3, comprises a portion 50 adapted to engage, at least partially, the elastic ring 8 and/or the abutting surface 6h of the nut 6.

It is clear that the elastic ring 8 cooperates to keep the components of the propeller 1 in assembled position. In fact, once positioned at the external rear surface of the internal cylindrical body 2, and being in the position to engage with the portion 50 of the rear part 5.3 of the external cylindrical body, the elastic ring 8 contributes to preventing axial movement of the external cylindrical body 5.1 , 5.2, 5.3 with respect to the internal cylindrical body 2, given that this external cylindrical body 5.1 , 5.2, 5.3 is thus interposed between the abutting portion 20 of the internal body 2 and the elastic ring 8 of said retaining means.

In the same manner, the abutting surface 6h of the nut 6 cooperates in keeping the components of the propeller in assembled position, through contact with the portion 50 of the external cylindrical body.

It must also be stressed that, in order to allow the components to be kept in assembled position, the internal cylindrical body 2 is provided with at least one abutting portion 20 for at least one corresponding portion 21 of the external cylindrical body 5.1 , 5.2, 5.3, or of a part thereof. In the embodiment of the propeller 1 shown in the accompanying figures, the part 5.1 of the external cylindrical body, is in particular provided with a portion 21 adapted to cooperate with the abutting portion 20 of the internal cylindrical body.

In this manner it is possible to considerably simplify the operations to install and remove the propeller 1 on/from the motor shaft 3. In fact, all the components of the propeller 1 remain in assembled position, eliminating the risk of damage thereto during said installation/removal operations or of loss thereof following separation or disassembly.

Advantageously, as all the components of the propeller remain kept in assembled position, the propeller 1 according to the present invention can be installed on and removed from the motor shaft simply by acting on the lock nut 6, tightening or loosening this latter on the corresponding threaded portion 3a of the motor shaft 3.

Advantageously, the propeller according to the present invention also comprises means 10 to constrain by coupling the lock nut 6 to at least a part of the external cylindrical body 5.1 , 5.2, 5.3.

Preferably, in the rear portion of the propeller (right part in the accompanying figures), the constraining means 10, preferably constituted by an annular flange, are constrained in a removable manner to the external cylindrical body 5.1 , 5.2, 5.3 of the propeller 1 , or at least to a part 5.3 thereof.

In this manner, the lock nut 6 is also kept coupled at least with the external cylindrical body 5.1 , 5.2, 5.3 of the propeller 1 , and during operations to install and remove the propeller 1 on and from motor shaft 3, contrary to prior art propellers, the nut 6 must not be removed/inserted from the inside of the propeller, thereby simplifying performance of these operations and preventing this nut 6 from being accidentally damaged or lost.

Moreover, due to the constraining means 10, tightening or loosening of the nut 6 implies, as shall be clear to those skilled in the art, simultaneous removal of the whole external cylindrical body 5.1 , 5.2, 5.3 and of the related internal body 2, in perfectly assembled configuration, due to the aforesaid retaining means, from the motor shaft 3.

In the embodiment shown in the accompanying figures, the nut 6 also comprises at least one elongated portion 6a which extends, at least partially, inside said internal cylindrical body 2. Inside the elongated portion there is produced a threaded part, adapted to cooperate with the corresponding threaded portion 3a of the motor shaft.

Moreover, as can be seen in the accompanying figures, the nut 6 comprises a lateral skirt 6b which extends parallel to the elongated portion 6a, in such a manner as to form an annular seat 6c, comprised between the internal wall of the skirt 6b and the external surface of the elongated portion 6a.

As can be seen in the figures, the abutting surface 6h of the nut 6 on the external cylindrical body 5.1, 5.2, 5.3 is positioned on the lateral skirt 6b of the nut 6, and preferably corresponds with the lower end of this lateral skirt 6b. As already mentioned, according to a preferred embodiment of the present invention, the constraining means to keep the lock nut 6 coupled at least with the external cylindrical body 5.1, 5.2, 5.3, comprise a circular flange 10 constrained to the external cylindrical body 5.1 , 5.2, 5.3 of the propeller 1 , and in particular to the part 5.3 thereof positioned at the rear (stem). The flange 10 is constrained in a removable manner to the external cylindrical body 5.1 , 5.2 and 5.3 through suitable known means, which can comprise, for example, threaded means adapted to allow reversible constraining of the flange 10 to the rear part 5.3 of the external cylindrical body, which is thus provided with corresponding threaded seats to receive the constraining means, not shown in the accompanying figures.

The flange 10 is circular in shape and allows engagement of the upper surface 6e of the upper part of the nut 6.

In this manner, the flange 10 prevents axial movement of the nut 6 which, as already mentioned, remains kept in assembled position with all the other components of the propeller, and in particular, it remains coupled with at least part of the external cylindrical body 5.1 , 5.2 and 5.3.

In fact, the nut 6 is inserted at least partly inside the internal cylindrical body 2 and has dimensions such as to be able to rotate inside the internal cylindrical body 2, to make installation and removal operations of the propeller 1 on and from the motor shaft 3 possible by tightening or loosening thereof on the corresponding threaded portion 3a of the motor shaft.

The lock nut 6 is operated from the outside by means of a specific head 6d, appropriately configured to be engaged by a tool of corresponding shape, and projects to the rear of the propeller through the central opening of the circular flange 10.

As shall be clear at this point of the description, axial movement of the nut 6 is prevented by the flange 10, following the contact with the upper surface 6e of the nut, while the nut 6, kept in assembled position, can be rotated inside the internal cylindrical body 2 of the propeller 1 to allow tightening/loosening of the propeller 1 on the motor shaft 3.

Although specific reference has been made to a flange 10 of circular shape, the flange could be produced according to other shapes, provided that it is able to prevent axial movement of the nut 6 (to keep it constrained to at least part of the external cylindrical body and in assembled position inside the propeller) and at the same time allow rotation thereof to perform installation/removal of the propeller on/from the motor shaft 3.

In the embodiment shown in Fig.2, the propeller comprises means 30 to prevent undesirable rotation of the nut 6, which are constrained to the external cylindrical body of the propeller 5.1 , 5.2, 5.3, or at least to a part 5.3 thereof. As shown in Fig. 2, these means 30 comprise one or more screws 31 which are constrained in specific threaded seats 33 produced in the part 5.3 of the external cylindrical body.

After being installed, the screws 31 engage the nut 6 by means of corresponding grooves 32 produced thereon, at the outer surface of the skirt 6b.

Securing and removal of the screws 31 in and from the specific threaded seats 33 usually takes place after temporary removal of the flange 10; alternatively, the flange 10 can be provided with through holes to allow installation and removal of the screws 31 without prior removal of the flange from the external cylindrical body of the propeller.

Other mechanical retaining means, such as grub screws, pins or other threaded means cooperating with appropriate seats arranged on the external cylindrical body of the propeller 1 adapted to engage the nut 6 to prevent rotation thereof, can naturally be used without departing from the scope of protection of the present invention.

Obviously, when the circular flange 10 is released from the external cylindrical body 5.1 , 5.2, 5.3, the nut 6 can be removed, and then the single components of the propeller can be removed, should this operation be necessary.

As already mentioned above, the retaining means of the propeller according to the present invention, comprise at least one elastic element 8 positioned between the internal cylindrical body 2 and the external cylindrical body 5.1 , 5.2, 5.3, or at least a part thereof. According to a preferred embodiment, the elastic element is an elastic ring 8 positioned at the external surface of the internal cylindrical body 2 of the propeller.

It must be noted that, in the embodiment shown in the accompanying figures, the elastic ring 8 is housed inside the annular seat 6c of the nut 6 together with the end part of the internal cylindrical body 2, which preferably reaches the abutting position against the base 6f from which the skirt 6b of the nut extends. Naturally, different types of elastic rings 8 can be used in the propeller according to the present invention, for example "Seeger" type metal circlips, or also metal rings which are not open and elastically deformable.

It is evident that the steps to install/remove the propeller are extremely simple to perform and only require operation of the nut 6 which causes locking/release of the propeller, in which all the components are kept in assembled position, by the motor shaft.

As stated, the components of the propeller remain assembled, through cooperation of the retaining means 6h and 8 with the internal cylindrical body 2, eliminating the risk of possible damages during these operations.

Moreover, advantageously also the nut 6 remains kept in assembled position inside the propeller when this latter is removed from the motor shaft through the constraining means 10 with which it is provided.

Consequently, due to the present invention, installation/removal of the propeller 1 on/from the motor shaft 3 is simplified, as no complicated installation/removal of parts is required, and for this reason it does not necessarily require to be carried out in a workshop.

Finally, it must be noted that, although specific reference has been made to an external cylindrical body of the propeller composed of several juxtaposed parts, as indicated schematically with the reference numbers 5.1 , 5.2 and 5.3, any other type of external cylindrical body, known in the art, can also be used without departing from the scope of protection of the present invention.

In the same manner, although specific reference has been made to a variable pitch boat propeller of automatic or manual type, the manner of retaining the components of the propeller can also be used in fixed pitch propellers provided with several components which might be subject to the aforesaid problems during the steps to remove it from/install it on the motor shaft.