Boat propeller blade pitch changing

Abstract

 Variable-pitch screw propeller, the pitch of which can be varied and adjusted during traveling, suitable for motor-boats and sailing-boats, of the type provided with a pinion gear at the end of the driving shaft, inmeshing with central gear wheels integral with the blades, and a screw propeller hub of sleeve shape, housing said driving shaft and said gear wheels and supporting, with possibility of free rotation, the shafts integral with the blades, which screw propeller is provided with a mobile element, with said mobile element being movable according to a direction parallel to the axis of the driving shaft and interposed between said sleeve-shaped hub made integral with said driving shaft and said central gear wheels, with said mobile element being provided with at least two coupling elements, wherein one of said coupling elements is in engagement with said central gear wheels, and the other one is in engagement with said sleeve integral with the driving shaft, with the mutual engagement of said coupling elements being accomplished by means of the coupling, with possibility of translation, of said coupling elements inside corresponding grooves respectively provided on said sleeve and on said pinion gear, with at least one of said grooves being provided inclined to the axis of shifting of said mobile element, in such a way as to cause, by means of the axial shift of said mobile element by means of control means consisting of a pressurized fluid, or of mechanical nature, the central gear wheels to rotate relatively to the driving shaft, with the inclination of the blades, and therefore of the pitch of the screw propeller, being consequently changed.

Description

[0001] The present invention relates to a variable-pitch screw propeller, the pitch of which can be varied and adjusted during the traveling, having such a structure as to be suitable for use on motor-boats in general, and for auxiliary motors of sailing-boats using screw-­propellers which can be put in feathered position.

[0002] It is well-known that the motor-boats, and, in particular, the yachts, generally use fixed-pitch screw propellers, i.e., screw propellers in which the inclination of the blades is fixed and pre-established by the manufacturer. The main drawback affecting the fixed-pitch screw propellers is due to the fact that not always the adopted pitch results to be the optimum under the various traveling and operating conditions of the boat; in fact, the parameters which condition the pitch of a screw propeller are many, and among these, the revolution speed (revolutions per minute) of the screw propeller, the horse-power of the motor, the shape and speed of the hull, the carried load, the direction of wind, and the cleanliness conditions of the keel of the boat, can be mentioned.

[0003] Inasmuch as these parameters can vary, the fixed pitch can consequently result, during traveling, either too high, or too low, with thus the possibility existing, that the correct revolution speed (revolutions per minute) of the motor relatively to the required traveling conditions may not be taken advantage of.

[0004] In order to obviate this drawback, types of variable-­pitch screw propellers were proposed, the pitch of which can be varied and adjusted in various ways, e.g., in certain cases, by partially dismantling the screw propeller and changing the angle of the position in which the inner gear wheels, integral with the shafts of the blades, are keyed, and, in other cases, by means of control devices which axially run along the driving shaft, in order to continuously vary the inclination of the blades during traveling. These solutions result to be, in the first case, obviously inconvenient and complex and, in the second case, cause strong structural complications and a considerable increase in weight and in overall dimensions of the same screw propeller.

[0005] Furthermore, also the presently known and most widely diffused feathering screw propellers for sailing-boats (i.e., those screw propellers in which the blades, when the motor is stationary, are automatically arranged coplanar with one another, on the same plane also containing the axis of the driving shaft, in order to offer the lowest resistance possible during the sailing, are endowed with a variable pitch, which can be varied and adjusted in a discontinuous way, under stationary motor, and after dismantling the screw propeller.

[0006] A particular feathering screw propeller which is capable of rendering easy and quick the adjustment in pitch as a function of the traveling conditions is disclosed in Italian patent N. 1,062,990; in this case, the screw propeller has such a structure as to make it possible, always with stationary motor, an adjustment of the pitch to be carried out with gradualness, i.e., with small steps of values of blade inclination, within a wide range of desirable values, with the same blades being left free to automatically reach their feathered condition upon stationary driving shaft. The structural and functional characteristics of this feathering screw propeller are discussed in the following in greater detail.

[0007] Summing up, therefore, the types of variable-pitch screw propellers known from the prior art, the pitch of which is continuously variable during traveling, result to be practically complex and cumbersome, and so structured as to be unable to be used on all motor-boat types, whilst in all types of feathering variable-pitch screw propellers hitherto known, the adjustment in pitch is discontinuous and can be only carried out with the driving shaft being stationary.

[0008] Therefore, a purpose of the present invention is to provide a variable-pitch screw propeller, the pitch of which can be varied and adjusted in continuous during traveling, which is capable of obviating the limitations and the drawbacks displayed both by the screw propellers known from the prior art, either with fixed pitch, or with adjustable pitch for motor-boats in general, and by the variable-pitch, feathering screw propellers, the pitch of which is stepwise adjustable, for sailing-boats.

[0009] Another purpose of the invention is to provide a variable-pitch screw propeller which has such a structure, as to make it possible fine variations in blade inclination, and consequently in screw propeller pitch, to be carried out during traveling in order to adapt the characteristics of the screw propeller to the various boat traveling conditions, and to the motor running conditions, and therefore such as to result advantageosuly suitable for use on boats with outboard or on-board motor, as well as for auxiliary motors for sailing-boats with feathering screw propellers.

[0010] A further purpose of the present invention is to provide a variable-pitch screw propeller, the pitch of which can be varied and adjusted during the traveling, which is also capable of making it possible the blades to be positioned at high values of inclination, with the pitch being adjusted at high values, such as to enable the orientation of the blades to be changed in order to turn from the position of forwards traveling to the position of rearwards traveling, without reversing the revolution direction of the driving shaft.

[0011] A not least purpose of the present invention is to provide a screw propeller of the above specified type, which is such as to make it possible the changes in blade inclination to be accomplished by means of structurally simple and reliable control means, with the overall dimensions of the blade propeller being maintained approximately equal to the dimensions of the traditional screw propellers known from the prior art and having same characteristics, and such, in any case, as to be actuated from aboard the boat.

[0012] These, and still further purposes, which can be evidenced with greater clearness by the following disclosure, are achieved by a variable-pitch screw propeller, the pitch of which can be varied and adjusted with continuity during traveling, of the type provided with a pinion gear, installed at the end of the driving shaft, and inmeshing with central gear wheels of satellite type, integral with the blades, and a screw propeller hub of box-like, sleeve shape, housing said driving shaft and said central gear wheels and supporting, with possibility of free revolution, the shafts integral with the blades, which screw propeller is provided, according to the present invention, with at least one mobile element, with said mobile element being movable according to a direction parallel to the axis of the driving shaft and being interposed between said sleeve-shaped hub made integral with said driving shaft and said central gear wheels, with said mobile element being provided with at least two coupling elements, wherein one of said coupling elements is in engagement with said central gear wheels, and the other one is in engagement with said sleeve integral with the driving shaft, with the mutual engagement of said coupling elements being accomplished by means of coupling, with the possibility of translation, of said coupling elements inside corresponding grooves respectively provided on said sleeve and on said pinion gear, with at least one of said grooves being provided inclined to the axis of shifting of said mobile element, in such a way as to achieve, by means of the axial shift of said mobile element by means of control means consisting of a pressurized fluid, or of mechanical nature, the rotation of the central gear wheels relatively to the driving shaft, with the inclination of the blades, and therefore the pitch of the screw propeller, being consequently changed.

[0013] More precisely, said mobile element is constituted by a cylindrical-sleeve-shaped piston, freely housed, under tight-sealing conditions, inside a cylindrical hollow provided in said hub integral with the driving shaft, and provided with a toothing translatable inside grooves provided in the sleeve, and with a toothing inmeshing with a corresponding toothing provided on the pinion gear, in its turn inmeshing with said central gear wheels, with at least one of said toothings or grooves being made inclined to the axis of the driving shaft, and therefore also to the direction of sliding of said sleeve-shaped piston, in order to make it possible, at each translation in both directions of said sleeve-shaped pinion gear, relative rotations between the pinion gear integral with the central gear wheels and the sleeve integral with the shaft to take place.

[0014] Furthermore, said sleeve-shaped piston, sliding inside said cylindrical hollow provided in the sleeve integral with the shaft, is controlled to drive in both translation directions opposite to each other, by means of a pressurized fluid fed, in the one case, to one single end of said cylindrical hollow, with return by means of spring elements, and in the other case, to both ends of said cylindrica hollow, so as to translate said piston as if it was a slide valve, with said pressurized fluid being fed by means of feed means installed both outside the body of the screw propeller, and inside the driving shaft.

[0015] The present finding is now disclosed in the following in greater detail, according to some preferred, non-­exclusive forms of practical embodiment thereof, with reference to the hereto attached drawing tables, supplied for merely indicative purposes, wherein:

Figure 1 shows an axial sectional view of a variable-­pitch screw propeller, the pitch of which can be varied and adjusted during traveling, accomplished according to the present invention, and suitable for use on motor-boats;

Figure 2 shows a sectional axial view of a type of feathering, variable-pitch screw propeller, the pitch of which can be varied and adjusted during the traveling, also according to the present invention,

Figure 3 shows an exploded view of the main structural elements used in order to adjust the pitch of the screw propeller during the traveling of the boat;

Figures 4 and 5 show a sectional view according to path VI-VI of Figure 2, according to two different forms of practical embodiment; and

Figures 6 and 7 show two different forms of practical embodiments of the screw propellers respectively shown in Figure 1 and in Figure 2.

[0016] Referring to such figures, and, in particular, to Figure 1, the variable-pitch screw propeller, the pitch of which is variable and adjustable during the traveling, according to the present invention, is of the type provided with a driving shaft 1, a sleeve 2 mounted integral with the shaft by means of a key 3 and butt-fastened to the end of the same shaft, in order to prevent axial relative movements, by means of a nut 4.

[0017] Coaxial with the shaft 1, a pinion gear 5 is provided, which is in engagement with two or three or more opposite gear wheels 6-6a-and so forth (substantially two or more satellites), which are mutually opposite and freely rotatable around an axis 7, perpendicular to the axis 8 of the driving shaft, or also inclined to the same axis 8.

[0018] With the satellites 6-6a-and so forth, the pivots 9-9a- and so forth, are associated, which bear the usual blades 10 of the screw propeller.

[0019] The group constituted by the gear wheels 6-6a-and so forth, and the relevant pivots 9-9a-and so forth, are housed inside two mutually opposite substantially ring-­shaped retainer bodies 11 and 12, coaxial with the sleeve 2 integral with the shaft 1, with the outermost body 12 of said bodies ending with a usual spinner 12a. The ring-shaped bodies 11 and 12, after the positioning of the greawheels and of the relevant pinion 5 inmeshing with each other with a pre-established initial angle of inclination of the blades, are butt-­fastened to the end of the sleeve 2 by means of axial screws 13, so as to render the whole blade-holder hub integral with the shaft 1, leaving the same blades free of rotating around their axis.

[0020] In order to make it possible a gradual and continuous variation in blade inclination, i.e., in pitch, to take place during the traveling, the present invention provides, inside the sleeve 2, a cylindrical hollow 14, inside which a piston 15, having the shape of a cylindrical hollow body, is mounted freely translatable, under tight sealed conditions, in both directions and coaxially with the driving shaft 1. The piston 15 is provided with an internal toothing 16 (with either straight teeth or inclined teeth, owing to the reasons which will be better specified in the following) destined to always remain inmeshed with a corresponding toothing 5a of the pinion gear 5 during the translation of the piston 15; the same piston 15 is also provided with external peripheral teeth 17 suitable for being coupled, with possibility of translation, into grooves 18, provided in the inner surface of the sleeve 2 integral with the driving shaft.

[0021] Said grooves 18 can be provided both parallelly to the axis of the driving shaft 1, and inclined at a pre-­established angle to the same axis. In order to make it possible the ring-shaped piston 15 to translate by the necesary stroke, variable according to the screw propeller types and to the required amplitude of change in angular orientation of the blades - as it is better clarified in the following - the grooves 16 and 18 are given an adequate length for the intended purposes.

[0022] The translation movement of the piston 15 is driven by delivering - from aboard the boat 19 - see Figure 1) a pressurized fluid, such as oil or pressurized air, into the ring-shaped cylindrical chamber 14 through a longitudinal duct 20 provided inside the sleeve 2, which is placed in communication, through a revolving distributor 21 made integral with the boat 19 by means of a hooking device 22, with a duct 23 provided inside the sleeve, and the driving shaft, and connected with a source of pressurized fluid installed aboard the boat. Furthermore, between said ring-shaped piston 15 and the ring-shaped body 11 integral with the sleeve 2, return springs 24 are interposed, which are positioned along the periphery of the head of the piston, and with their axis being substantially parallel (or also inclined, in case of inclined grooves and/or toothings) to the axis of the same piston 15.

[0023] Therefore, with particular reference to Figure 1, if the grooves 16 of the translatable piston 15, or the grooves 18 of the sleeve 2, or both of them, are made inclined at a pre-established angle, or if said grooves are made straight and parallel to the direction of movement of the piston 15 and, on the contrary, either of toothings 17 or 5a of the pinion gear, or both of said toothings, are made inclined, the delivery of pressurized fluid into the chamber 14 causes a translation of the piston 15, which, in its turn, causes the toothed pinion gear 5 to rotate relatively to the sleeve 2 integral with the drivig shaft by a certain angle; as a consequence, the gear wheels or satellites 6-6a, with which the same pinion gear inmeshes, cause a change in inclination (in the reverse direction) of the blades 10, i.e., a change in screw propeller pitch. By suitably selecting the length and the angle of inclination of the grooves 16-18, or of the corresponding toothings 17-5a, the maximum value and the minimum value of the change in inclination of the blades in correspondence of a given stroke of the piston 15 can be prefixed. Inasmuch as the above disclosed screw propeller is particularly suitable for use on motor-boats (equipped with either outboard or on-board motors), by starting from an initial prefixed and preset pitch, during the traveling of the boat in screw propeller pitch continuous variations can be accomplished in both directions, which are such as to make it possible the boat to travel under optimum conditions of motor running, as regards the screw propeller, and the exploitation of motor power.

[0024] So, for example, longer grooves 16 and 18 will enable the ring-shaped piston 15 to move along a longer stroke, and therefore will allow the blades to change in orientation by larger angles. This form of embodiment may also make it possible, in special cases, and with a suitable length of said grooves, changes in screw propeller pitch to be obtained, which are so large, as to make it possible the pitch to be adjusted both when traveling forwards, and when traveling in reverse direction, it being possible the blades to be oriented up to their zero, viz., idling position, without reversing the direction of revolution of the driving shaft, and then reverse their inclination. Furthermore, with a very long stroke of piston 15, the blades can be positioned, by suitably controlling the position of the same piston, in their feathered position.

[0025] Still according to the invention, said ring-shaped piston 15 can be actuated like a slide valve, by alternatively delivering the control fluid at both of its ends, with the return springs 24 being hence got rid of. An example of a screw propeller equipped with a piston driven at both of its ends by means of pressurized oil, is depicted in Figure 6, which is explained in greater detail in the following.

[0026] Furthermore, the feeding ducts used for feeding the pressurized fluid 20-23 can be positioned coaxial with the driving shaft 1 until they reach the distribution chamber 14, with the external revolving distributor 21 and the hooking block 22, by means of which the herein disclosed structure is hooked to the boat, being therefore got rid of. These possibilities render the screw propeller suitable for use both on outboard motors, and on on-board motors.

[0027] In practice, it was observed that it is sufficient, in most applications on motor-boats, have available angles of change in blade inclination which are rather small, i.e., of approximately +/-5° relatively to the initial preset angle, which normally is of about 20°, a fact that, in practice, reduces the overall dimensions of the screw propeller, its weight and, obviously, its cost.

[0028] Still according to the present invention, a type of feathering screw propeller for auxiliary motors for sailing-boats is also provided, in which the inclination of the blades, and consequently the screw propeller pitch, can be changed during traveling in a gradual and continuous way, while the blades being left free to move to reach their feathered position (i.e., coplanar with one another, on the same plane which contains the axis of the driving shaft) when the driving shaft is stationary.

[0029] In Figures from 2 to 6a, a type of feathering screw propeller according to the present invention is shown, which exploits the general structure of a feathering screw propeller, which is the subject-matter of the prior patent for industrial invention N. 1,062,990.

[0030] The improved feathering screw propeller according to the instant invention is shown in Figure 2 and, as regards the kinematic systems for controlling the change in pitch during the traveling of the boat, reference is herein made to figures from 3 to 6.

[0031] This type of feathering screw propeller is constituted (Figure 2) by a driving shaft 1, a sleeve 2 integral with the shaft by means of keys 3, and butt-fastened to the head of the shaft 1 by means of the nut 4. At the end of the shaft 1, there is positioned a coaxial pinion gear 5, equal to the pinion of Figure 1, which is constantly inmeshing with two or more gear wheels 6-­6a, and so forth (satellites), opposite to each other, and freely rotatable around an axis 7, which may be either perpendicular, or inclined to the axis 8 of the driving shaft. With the gear wheels 6-6a, and so forth, the respective revolution shafts 9-9a, and so forth, supporting the blades 10, are then associated.

[0032] The unit constituted by the driving shaft 1, and the relevant sleeve 2, as well as the pinion gear 5 and gear wheels 6-6a, etc., with which the blades are integral, is housed inside two half-shells, or half-­spinners 11; both half-shells are given such a shape, that the various components housed inside them result to be freely rotatable.

[0033] Said half-shells, fastened to each other by means of screws 12a, form a blade-bearing hub rotatable relatively to the sleeve 2 integral with the driving shaft, when the driving shaft is stationary, as well as when it is running, as is better clarified in the following.

[0034] Also for this screw propeller, which has the structure as depicted in Figure 2, in order to make it possible the pitch to be varied while the boat is traveling, anyway allowing the blades to automatically move to reach their feathered position when the driving shaft is stationary, a piston device 15a is provided according to the invention, which is installed, with the possibility of freely translating, inside a chamber 14a (see figures 3 and 4), by being controlled in its movement by means of a pressurized fluid fed by means of the ducts 20a and 23a and the relevant revolving distributor 21a, connected with a source of pressurized fluid, installed aboard the boat.

[0035] As Figures 3 and 4 clearly show, the sleeve 2, integral with the driving shaft, is provided, at its end facing the pinion gear 5, with a bell-shaped, or cup-shaped enlarged portion 2a, inside which said cylindrical chamber 14a destined to contain the mobile piston 15a, is provided.

[0036] Inside the cylindrical body of the bell 2a, slots 18a are provided, which run in a direction parallel to the axis of the mobile piston 15a, or also inclined relatively to this same axis. Inside said grooves, the teeth 17a, correspondingly protruding from the movable piston 15a, enter with sliding possibility. Said piston 15a is provided with an inner toothing 16a (which may be either straight, or inclined to the axis of the same piston 15), inside which the toothing 5a of the gear pinion 5 is mounted, under constant inmeshing conditions, and with the possibility of translation, with said gear pinion 5 being in its turn inmeshing with the gear wheels 6-6a, etc., integral with the blades.

[0037] In case of figures 2, 3, 4 and 5, the mobile piston 15a is depicted as a simple-effect piston, so that, in order to enable it to perform its return stroke, springs 24a are provided (see figure 5), which are housed inside hollows 18b peripherally provided inside the end portion of the bell-shaped body 2a, in correspondence of the slots 18a. An end of each spring is positioned against an end stop 18c, and the opposite end thereof 24b is anchored to the translatable tooth, translating inside the corresponding slot, as clearly shown in figure 5.

[0038] The hollows 18b which house said return springs can be provided inclined at an angle substantially equal to the angle of inclination of the respective slots 18a, when these are provided, in order to make it possible, as already said in case of figure 1, the relative rotation between the sleeves 2-2a and the gear wheels 6-6a integral with the blades, to take place.

[0039] In order to prevent the teeth 17a of the mobile piston 15a from colliding against the inner shoulder 11a of the hub 11, when the same piston 15a reaches its stroke end, thus hindering or hampering the rotation of the hub relatively to the sleeve 2a, and therefore preventing the blades from freely moving to reach their feathered position, a stop ring 25 is provided, which is positioned at the end of the slots 18a, and is such as to stop the teeth 17a of the mobile piston before say teeth may bump against said shoulder 11a of the hub.

[0040] The feathering screw propeller disclosed by referring to Figure 2 is furthermore provided with a ring-shaped hollow 26 (Figures 2 and 6), provided between the sleeve 2 and the rotatable blade-holder hub 11; inside said hollow 26, two stop teeth 27 and 28 are provided; the stop 28 tooth is integral with the shaft 1, and the stop tooth 27 is interal with a half-shell of the blade-holder hub. Such stop teeth are so positioned as to come into mutual engagement after the starting-up of the driving shaft, and thereby maintain (both in case of forwards traveling and in case of reverse traveling, by reversing the direction of revolution of the driving shaft) the initially prefixed pitch; the position of maximum distance of the stops 27, 28 from each other corresponds to the position of the blades in their feathered position, with stationary driving shaft, with such position being automatically reached owing to the effect of the possibility left to the blade-holder hub of freely rotating around the driving shaft.

[0041] Therefore, the special structure of the screw propeller of Figure 2 makes it possible the inclination of the blades, and therefore the pitch of the screw propeller, to be adjusted, while the boat is traveling, relatively to the initially pitch, by actuating the mobile piston 15a, as it occurs in case of the screw propeller of Figure 1, useable on motor-boats, and also the blades to automatically reach their feathering position. The adjustment of the initial pitch, i.e., with stationary screw propeller and dismantled half shells, can be advantageously carried out quickly, and for small angles of inclination of the blades, by using both toothings 5a and 5b of the pinion gear 5 which, if they are made, as disclosed in above cited patent N. 1,062,990, with a number of teeth different from each other, make it possible very fine changes in blade inclination angle, even of 1° only, to be achieved.

[0042] The feathering screw propeller shown in Figure 2, by exploiting its advantage of having a sturdier structure, and of allowin a more rapid assembling as compared to the screw propeller of Figure 1, can also be used as a screw propeller for motor-boats equipped with either an outboard or an on-board motor. In this case, it is enough to fasten, as shown in Figure 6, the blade-holder hub 11-11b and the hub 2 integral with the driving shaft to each other, by means of couplings 29-­30, or the like, thus the possibility of the blades taking their feathered position being excluded.

[0043] Still according to the present invention, in Figure 6 a screw propeller of the same type as of that of Figure 1 is shown, which in practice has shown to be very suitable for power boats, and the like, is shown. The screw propeller depicted in Figure 6 is structurally similar to that of figure 1, so the corresponding parts are indicated by the same reference numerals.

[0044] In this type of screw propeller, the piston 15 is substantially a double-effect piston, sliding inside two mutually opposite chambers 14 and 14b, in both of which a tight seal being provided; the chamber 14b is defined by a cylindrical extension 15b of the piston 15, whose end is tightly sealed by a cylindrical ring 31 interposed between the inner end of the sleeve 2 and the end of the extension 15b.

[0045] In this form of practical embodiment, which results not to contain return springs, the piston 15 is driven to move in both directions by means of a pressurized fluid fed to the chamber 14 through a duct 20 equal to that of Figure 1, and, to the opposite chamber 15b, through a duct 20b. Both of these ducts are connected, through a double slide valve 21b, with two ducts 23b-23c supported in their turn by a device or block 22, of an elastically yielding type, connected with the boat.

[0046] A double-effect cylindrical piston 15 can also be used in a type of screw propeller like the one shown in Figure 7.

[0047] This type of screw propeller results in practice to be endowed with smaller overall dimensions in length, and only slightly stockier, and can be advantageously used for particular boats, e.g., for boats equipped with an outboard motor, or the like.

[0048] This screw propeller, only partially shown in Figure 7, is substantially constituted by a shaft 1 with the relevant hub 2 and butt nut 4, as in case of Figure 1, but it has a shorter sleeve 2, and a pinion gear 5c substantially constituted by a sleeve, or a ring-like body, coaxial with the shaft 1, and provided with an outer toothing 5d and an inner toothing 5e; the outer toothing 5d inmeshes with the toothing of the satellites 6-6a, and so forth, as Figure 7 clearly shows. The inner toothing 5e of the pinion gear inmeshes with the outer toothing 17b of the piston 15 and the inner toothing 17c of the piston inmeshes with the toothing 18b provided in the sleeve 2. This solution enables the piston 15 to translate in both directions, with the pitch of the screw propeller being adjusted exactly as it occurred in case of the screw propeller depicted in Figure 1 and in Figure 2, and shows the advantage that a screw propeller is obtained, which is much shorter than the hereinabove disclosed screw propellers.

[0049] Obviously, also the feathering screw propeller of Figure 2 can be made with a double-effect piston 15a, by providing two tightly sealed chambers at both piston ends, and two ducts for pressurized fluid feeding.

[0050] From what is hereinabove disclosed by referring to the figures, it clearly appears that the adoption, according to the invention, of a mobile element consisting of a piston, inserted between the sleeve integral with the driving shaft, and gear wheels rotatable integrally with the shafts of the blades, makes it possible the pitch of the screw propeller to be adjusted with gradualness and continuity while traveling, by only adjusting the pressure of the control fluid; furthermore, the above disclosed practical embodiments make it possible variable-pitch screw propellers to be obtained, the pitch of which can be varied and adjusted during the traveling, both for outboard motors and on-board motors, and for auxiliary motors of sailing-boats.

[0051] Obviously, in practice, to the invention as hereinabove disclosed according to some preferred forms of practical embodiment thereof, further structurally and functionally equivalent variants and modifications can be supplied, without departing from the scope of protection of the same invention.

Claims

1. Variable-pitch screw propeller, the pitch of which can be varied and adjusted during traveling, for motor-­boats in general, of the type provided with a pinion gear, installed at the end of the driving shaft, and inmeshing with central gearwheels of satellite type, integral with the blades, and a screw propeller hub of sleeve shape, housing said driving shaft and said central gearwheels and supporting, with possibility of free revolution, the shafts integral with the blades, characterized in that said screw propeller is provided with at least one mobile element, with said mobile element being movable according to a direction parallel to the axis of the driving shaft and being interposed between said sleeve-shaped hub made integral with said driving shaft and said central gearwheels, with said mobile element being provided with at least two coupling elements, wherein one of said coupling elements is in engagement with said central gearwheels, and the other one is in engagement with said sleeve integral with the driving shaft, with the mutual engagement of said coupling elements being accomplished by means of the coupling, with possibility of translation, of said coupling elements inside corresponding grooves respectively provided on said sleeve and on said pinion gear, with at least one of said grooves being provided inclined to the axis of shifting of said mobile element, in such a way as to achieve, by means of the axial shift of said mobile element by means of control means consisting of a pressurized fluid, or of mechanical nature, the rotation of the central gearwheels relatively to the driving shaft, with the inclination of the blades, and therefore the pitch of the screw propeller, being consequently changed.

2. Screw propeller according to claim 1, characterized in that said mobile element is constituted by a cylindrical, sleeve-shaped piston, coaxial with said driving shaft, freely housed, with tight sealing, inside a cylindrical hollow provided inside said sleeve integral with the driving shaft, and provided with a toothing translatable inside grooves, or the like, provided in said sleeve, as well as with a toothing inmeshing with a corresponding toothing provided on said pinion gear, in its turn inmeshing with said central gearwheels, with at least one of said toothings and grooves being made inclined relatively to the axis of the driving shaft, in order to make it possible, at each translation of said cylindrical piston, relative rotations to take place between said pinion gear integral with said central gearwheels and said sleeve integral with the drive shaft.

3. Screw propeller according to claim 1, characterized in that said cylindrical, sleeve-shaped piston is controlled by means of a pressurized fluid fed to an end of said hollows inside which said piston slides, with the return stroke of said piston being caused by elastic return elements.

4. Screw propeller according to claim 1, characterized in that said cylindrical piston is controlled by means of a pressurized fluid fed to both of the opposite ends of said hollow inside which said piston slides, in order to accomplish both to-and-fro strokes.

5. Screw propeller according to claim 1, characterized in that said pressurized fluid is fed to said cylindrical chamber of said sleeve integral with the driving shaft by means of ducts external to the body of the screw propeller and with the interposition of a rotary distributor kept stationary by means of elements for disengageable hooking to the hull of the boat.

6. Screw propeller according to claim 1, characterized in that said ducts for feeding the pressurized fluid to said cylindrical chamber are coaxially positioned inside the driving shaft.

7. Screw propeller according to claim 1, characterized in that said sleeve integral with the driving shaft is made as one single body, and with its end, annular elements are associated with possibility of disengaging, which are so shaped as to contain, freely rotatable, the shafts of the gearwheels integral with the blades.

8. Screw propeller according to claim 1, characterized in that said sleeve integral with the shaft is housed inside two mutually opposite half-shells or half-­spinners, which have such a struxture, and are so fastened to each other, as to form a blade-holder hub rotatable relatively to said sleeve integral with the shaft, with stop elements being provided between said hub and said sleeve, which are suitable for rendering the same hub and the relevant sleeve rotatably integral with each other during traveling, and for enabling the blades to automatically move to reach their feathered position during the sailing, with the driving shaft being stationary.

9. Screw propeller according to claim 1, characterized in that said grooves, provided in the sleeve integral with the shaft, as well as inside said cylindrical piston, can be made of such a length as to make it possible to vary the stroke of the piston and such as to allow fine adjustments of the variation of the screw propeller pitch while travelling as well as large changes, suitable for enabling the blades to reach their feathered position upon control of the piston, and in any case without reversing the revolving direction of the driving shaft.

10. Variable-pitch screw propeller, the pitch of which can be varied and adjusted during traveling according to claim 1, characterized in that said screw propeller is designed for use on motor-boats in general, and on auxiliary motors of sailing-boats.

Drawing