Devices for operating variable-pitch propellers

A propeller includes a hub having mounted on the central end part thereof a rotating fitting which permits the passage therethrough of a fluid circulating within two conduits which pass longitudinally of the fitting. The fluid operates on opposite ends of an annular piston to impart thereto rectilinear movement, which in turn is transformed into rotation of the blades of the propeller due to lugs extending from the piston and being eccentrically engaged with the blades. The hub of the propeller is completely free to turn without affecting the driving shaft. The assembly is positioned completely outside the stern of the ship.

BACKGROUND OF THE INVENTION 
As is known, greater or lesser speeds of a ship are obtained by increasing 
or decreasing the rotative speed of the engine, that is the number of 
revolutions at which the propeller turns per unit of time. 
It will be understood that, due to the fact that the driving torque is 
reduced as the rotative speed of the engine is reduced, certain rotative 
speeds cannot be utilized. 
The design of the propeller of a ship is directly related to the engine, 
depending on the power and rotative speed thereof. 
When the ship is to convey a particular cargo at a particular speed, the 
propeller and the engine are designed according to these needs. However, 
when the ship must use the complete power of its engine at speeds 
differing from the predetermined speed, a suitable response is not 
obtained due to the lack of adaptability of the propeller in view of this 
contingency. 
The existence of variable-pitch propellers has put an end to such problem. 
In short, a variable-pitch propeller consists of a propeller having blades 
the pitch of which can be oriented without having to stop the ship. 
In view of this innovation, an optimum driving torque is obtained at 
different engine speeds. 
One of the most suitable applications of the variable-pitch propeller is 
its use in hauler fishing vessels which, due to their characteristics, 
have a sailing speed and another speed, which could be referred to as a 
working speed, for hauling the net during fishing. 
In the first case, the ship should sail with an optimum driving torque 
which permits a rapid and economical speed. 
In the second case, the speed is slower but the power needed is higher, due 
to the additional load resulting from the weight of fish being hauled or 
carried. 
The variation in the draft of the blades of the propeller is the best 
solution and as such it was put into practice immediately by shipbuilders, 
so that newly constructed ships incorporate variable-pitch propellers. 
The use of such propellers calls for the ship to already be designed 
therefore, since it is necessary to adapt the transmission shafts so that 
the necessary mechanisms which act on the blades to orient their draft are 
arranged therein. 
Ships which have already been constructed must be modified so that 
variable-pitch propellers can be adapted thereto. However, the necessary 
modifying operations to be carried out affect the internal structure of 
the ship, they require a prolonged time in the shipyard, and the cost is 
high. For these reasons shipbuilders are unwilling to make such 
adaptations. 
It is, therefore, desirable to find a solution which permits already 
existing ships incorporating a propeller having fixed blades to be 
transformed into ships incorporating a propeller having variable-pitch 
blades. However, this transformation should not affect the structure of 
the ship too greatly, to thereby reduce the expenses resulting from the 
inactivity of the ship and from the adaptation. 
SUMMARY OF THE INVENTION 
The object of this invention is to provide improvements in devices for 
operating the blades of variable-pitch propellers, the adaptation to which 
does not require the handling of the internal transmission system, and, 
consequently, whereby all the operations of adaptation are carried out 
outside the hull of the ship, with the consequent advantages to a 
shipbuilder in order to modify already existing ships provided with fixed 
pitch propellers. 
The improvements of this invention mainly consist in arranging in the 
interior of the hub of the propeller a double effect annular piston which 
is eccentrically, by means of lugs, joined to rotating bases which are 
embedded and guided in the hub and which support the blades of the 
propeller. 
The double effect piston is activated hydraulically from the interior of 
the ship, and guided double-acting no-return valves, which facilitate 
handling, are placed between those elements which give the necessary 
pressure to displace the annular piston and the annular piston itself. 
Pressure fluid is introduced against either of opposite end faces of the 
piston, so that the same is linearly displaced. This movement is 
transformed, due to the eccentric connection between the lugs and the 
blade bases, into simultaneous rotational movement of all the bases of the 
blades, thereby varying their orientation to another and different pitch 
which modifies the advance of the propeller. 
The manner in which the hydraulic fluid is led to the annular piston 
furthermore constitutes an important feature of the invention, since the 
assembly is included in the hub and it therefore turns therewith. 
The present invention provides two alternative mechanical solutions. The 
first solution consists in mounting on the hub of the propeller, at the 
end central portion thereof, a rotating fitting which permits, through a 
fixed core thereof, the inflow and outflow of a fluid circulating within 
two ducts which cross the fitting longitudinally, the hub of the propeller 
being completely free to turn. 
All this takes place without affecting in the least the integrity of the 
driving shaft, and with the assembly remaining completely outside the 
stern of the ship. 
The second solution does not in any way modify the essential features of 
the invention and consists in causing the fluid to reach the no-return 
valves through a collar fixed and adjusted to the hub, which collar is 
provided with grooves into which the fluid ducts open. 
The interior of the collar is fitted in a recess in the hub. Ducts are 
connected to the grooves and extend longitudinally through the hub to be 
joined to the guided double no-return valves. 
It is also possible to withdraw from the interior of the hub the guided 
double no-return valves and to place them next to the collar, so that the 
ducts made in the hub could be directed directly to the respective fronts 
of the annular piston. 
In any of the above solutions, the main feature of the invention is to move 
the annular piston at will and without having to stop the ship, thereby 
varying the pitch of the blades of the propeller according to the required 
needs.

DETAILED DESCRIPTION OF THE INVENTION 
The FIGURE shows an annular piston arranged in a chamber into which 
communicate ducts through which fluid passes to and from guided double 
no-return or one-way valves. 
At the inlet of the no-return valves are provided feeding conduits. 
Adjacent the feeding conduits are unconnected ducts which may be employed 
in a second application and which extend from grooves provided in a fixed 
collar arranged about a recess or reduced size portion formed in the hub. 
It is thus clear that, although there are two alternatives for introducing 
the fluid, the principle of the invention is basically the same in either 
case. 
The various reference numerals shown in the FIGURE correspond to the 
following parts: 
1. Shaft of the propeller; 
2. Locking key for locking the shaft 1 to the hub 3; 
3. Hub of the propeller; 
4. Locking nut attaching the hub 3 to the shaft 1; 
5. Annular piston; 
6 and 6a. Varying volume chambers formed at opposite ends of the piston 5; 
7. Lugs by means of which the annular piston 5 is joined to the bases 8 of 
propeller blades 9 and which transform rectilinear movement of the annular 
piston 5 into rotational movement of the bases 8 of the blades 9; 
8. Bases of the blades; 
9. Blades; 
10 and 10a. Fluid inlet ducts to chambers 6 and 6a; 
11a and 11b. Guided double-acting no-return valves; 
12 and 12a. Feeding conduits for the guided double-acting no-return valves, 
coming from a rotating fitting; 
13. Core of the rotating fitting; 
13a and 13b. Stationary supply ducts supplying fluid to core 13 and then to 
conduits 12 and 12a; 
14. Sleeve which is solidly fastened to the stern-post of the ship and 
which constitutes a protecting shell for the ducts 13a and 13b; 
15. Collar fixed to the ship; 
16 and 16a. Grooves in collar 15 and facing the recess of the hub 3; 
17 and 17a. Feeding conduits extending to the grooves 16 and 16a; and 
18 and 18a. Ducts which extend longitudinally through the hub 3 and which, 
according to the second embodiment, are joined to the feeding inlets of 
the guided double no-return valves. 
By means of conventional valve elements, fluid is made to pass under 
pressure from a hydraulic power station situated in the ship through the 
duct 13a and core 13 into feeding conduit 12. The pressure fluid opens the 
guided double-acting no-return valve 11a and then passes through duct 10 
and into the chamber 6, thus displacing the annular piston 5 rightwardly 
as shown in the FIGURE. 
The guided double-acting no-return valve 11a simultaneously opens its twin 
valve 11b and opens a path therethrough, so that the fluid displaced by 
the annular piston 5 is discharged from the chamber 6a and passes through 
duct 10a, valve 11b, conduit 12a, core 13, and duct 13b into the tank of 
the hydraulic power station. 
Upon the above described linear displacement of the annular piston 5, 
rotation of the blades 9 takes place due to the eccentric connection of 
the lugs 7 with their respective bases 8. 
When the action of the hydraulic fluid ceases, the guide double-acting 
no-return valves are closed, and the blades of the propeller are locked in 
the position reached without possibility of being varied, unless they are 
again hydraulically activated. 
By supplying fluid through duct 13b, core 13 and feeding conduit 12a, the 
blades will be rotated in a direction opposite to that described above. 
When the second embodiment of the invention is employed, the ducts 18 and 
18a will be connected to the guided double-acting no-return valves. Thus, 
a circuit different from that described above is formed. 
When hydraulic fluid passes through one of the conduits 17 or 17a, supplied 
from the hydraulic power station on the ship, the blades are rotated in 
the same manner as previously described. 
Thus, for example, if the fluid is supplied through the conduit 17, it then 
reaches the groove 16 and passes through the duct 18 and opens the valve 
11a, from where, through duct 10, it penetrates into the chamber 6 and 
moves piston 5 rightwardly as shown in the FIGURE. 
The activation of the annular piston, and therefore the variation in the 
pitch of the blades, is achieved with the same ease and precision using 
either of the above two described fluid supply circuits. It should only be 
taken into account that according to the second solution the collar 15 
which is provided with the grooves 16 and 16a must be fitted about the hub 
in a manner to withstand the fluid pressure necessary to move the blades. 
The rotating fitting 13 is applicable to any type of propeller.