Marine propulsion – Screw propeller – Variable pitch
Patent
1989-04-05
1991-09-10
Sotelo, Jesus D.
Marine propulsion
Screw propeller
Variable pitch
416147, B63H 300
Patent
active
050469738
DESCRIPTION:
BRIEF SUMMARY
The invention refers to a ship propeller, in particular for motor boats, comprising at least two propeller blades. Each blade of which is mounted for being swivelable around an axis oriented in normal direction to the axis of the propelling shaft on a propeller star put onto the propelling shaft. For the purpose of effecting such swivelling movement there is provided an adjusting drive means guided along the propelling shaft. Each propeller blade carries a step bearing rotatably supported on the propeller star by means of a bolt extending in normal relation relative to the axis of the propelling shaft and that the propeller blade is connected with a cogging being in meshing engagement with a cogging of the adjusting drive means.
Marine propulsions are most frequently designed as submarine propellers. There are used, with consideration of effectivity and of economy, for bigger ships propeller arrangements operated with sub-cavitative rotating speed, i.e. with a rotating speed being geared down for a multiple relative to the motor speed. On the other hand, there are known for rapid racing boats, high-strength racing propellers of great pitch and small diameter and being frequently operated as surface propellers with the speed of the motor speed, which means that they rotate with super-cavitative speed. In this case, optimum operation of such a surface propeller is obtained if it extends below the water surface for half of its diameter.
For various reasons, it is frequently desired to be in the position to adjust the propeller blades. This is not accompanied by difficulties in case of ship propellers being operated with sub-cavitative speed. For this purpose, there is provided an adjusting propeller hub comprising a bipartite housing enclosing the adjusting mechanism and having a relatively great diameter on account of the necessity to bearingly support the propeller blades and to accommodate therein the propeller adjusting pinions and the toothed racks being in meshing engagement therewith. Thus, it becomes impossible to use the known adjusting propeller constructions for surface propellers, because the centrifugal forces would become too great on account of the high rotating speed of these propellers. This equally applies for a ship propeller arrangement of the initially described type U.S. application Ser. No. 2 715 446) in which the propeller star carries radial bolts, each of which forms a centering means for its propeller blade being in its interior connected in a non-rotatable manner with a bevel gear. A housing portion holding in position the propeller blade against the radially acting centrifugal forces extends between the step bearing and said bevel gear. Such a construction can not be used for ship propellers being operated with super-cavitative speed.
It is an object of the invention to avoid these drawbacks in such a manner that an adjusting propeller construction can be operated as surface propeller, i.e. with super-cavitative speed (motor speed). This task is, according to the invention, solved by the fact that the step bearing is fixed on the propeller star by the bolt in a tension-transmitting manner and that the step bearing carrying the cogging has its outer surface substantially exposed. In this manner, each bolt fulfills the role which has been fulfilled by the housing of the previously described known construction, so that this housing is omitted and the outer surface of the step bearing is thus substantially exposed. Thus, there results a compact construction, i.e. a construction in which all component parts required for adjusting the propeller blades are located as near as possible in proximity of the axis of the drive shaft, which results as compared with the known construction in a reduction of the centrifugal forces. On account thereof, it becomes possible to operate the construction according to the invention with such a high speed that its use as a surface propeller is possible.
In principle, it would be conceivable to provide the bolt at its both ends with one shoulder each, whic
REFERENCES:
patent: 1740077 (1929-12-01), Dumbleton
patent: 3092186 (1963-06-01), MacLean
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