US1808032A - Out of water propeller - Google Patents

Description

June 2, 1931. r GEBERS 1,808,032

OUT- OF WATER PROPELLER Filed Jan. 12, 1925 Patented June 2, 1931 UNITED STATES PATENT OFFICE.

FRIEDRICH GEBEBS, OF VIENNA, AUSTRIA our on WATER, rnor'ELLEn Application filed January 12, 1925, Serial No. 1,974, and in Germany January 22, 1924.

By partially immersed propellers are understood those shipsscrews which only dip into the water with a rather small lower part of their peripheral surface, while the boss is located above the surface.

The object of the partially immersed propeller is twofold (1) to impart a favourable driving action to very fast ships, by eliminating the resistance of the propeller-shaft bearing projecting from the hull and of the boss of the screw, and in some cases also of the inner inefiective parts of the blades;

' (2) to ensure for ships of shallow draught, particularly in water ofv limited depth, a greater effective blade area and a more favourable screw race than for ordinary ships screws, and above all to enable ships even when lightly loaded and therefore not immersed to their normal depth in the water to employ the full power of their engines without exceeding the most favourable angular velocity of the propeller shaft.

In both cases the entranceof the blade into the water should be as'free from shock as possible and the centrifugal scattering of masses of water should be kept as small as possible. I

The present invention is adapted to comply with these requirements by virtue of the fact that the leading edge of the blade is drawn as far forward as possible in the direction of rotation, so that first the front outer parts of the blade, with a somewhat rounded tip and then gradually the'other inner parts of the inlet edge become immersed. Theshape or design of the single propeller blade is asymmetrical with respect to the radius drawn through the attachment point .of the propeller. The entering tip of the blade represents approximately an angle of 4060 measured through the entering edge and a tangent at the said tip and laid against the propeller circle. The, angle, which the radius of the propeller circle at the tip forms for the normal with the entering edge is at least 20. This formation of the blade is also for the object of strengthening the tendency to drive the water inwards, in the case of ships of limited draught, in which two partially immersed propellers rotate in such a direction as to produce this tendency, the dipping propeller blade which is farthest out from the hull catching the water first.

The centrifugal scattering of the water, however, has to be reduced by running out the trailing part of the propeller at the outer edgeinto a scallop or tongue which remains as long as possible in the water.

Since the wake behind a ship is in general greater above in the neighbourhood in the surface of the water than below, in deeper layers, this fact can be taken into consideration in a novel manner in constructing the out of Water propellers insofar as the pitch 7O osition of the blades (the construction pitc may be diminished from the outside towards the inside.

The application of the force against theblade of a partially immersed propeller while working is of an alternating character. When entering the water the dipping part first experiences a powerful torque in the direction of travel and when emerging the emerging part receives a similar torque. On this account it is necessary in order to take of the arrangements of reversing propellers hitherto known, and on this account also the removal thereof to the outside of the boss casing is necessary.

Since furthermore the total propeller thrust is distributed amongst fewer blades than in the case of a completely immersed propeller and is applied at. a considerably greater radius, the support of the blades must be longer than for the completely immersed propeller.

The design of out of water propeller gradually evolved in the two accompanying drawings is in accordance with the basicvideas herev developed. In these drawings:

Figure 1 is a view from the pressure side of a partially immersed propeller with three fixed blades.

Figure 2 is a side view of this propeller. Figure 3 is a view according to Figure 1 but only towards the lower blade in a somewhat modified form.

Figure 4 illustrates a further modified form of the blade and shows greater rounding of the dipping tip.

Figure 5 is a View according to Figures 1 to 4, wherein however, only the outer part of the blade surface is still retained, attached to a special blade-holder or arm.

Figures 6, 7 and 8 show sections through the lower propeller blade of a propeller according to Fig. 1 on the lines 66, 77 and 88 respectively viewed in the direction of the arrows A.

According to the invention the shape of the leading edge of'the projected blade area is such that it or a prolongation of it forms an acute angle of for instance 4060 with the tangent to the outer blade circle passing through the point of intersection of the leading edge with the outer blade circle (Figures 1, 3, 4 and 5) if the slight rounding off of the tip is no longer regarded as an outlet edge (Figure The outer boundary line of the blades may in this case difl'er if desired from the outer blade circumference (Figures 3 and 4). On the trailing edge, at its point ofconta'ct'with the external blade boundary, is formed a scallop of the blade (Figures 1, 3 and 5) which however may in special cases be omitted (Figure 4). This may for example be the case at high angular velocities when it would then be ineffective.

Figure 5 shows how the special blade form can be retained even ifin a known manner the propeller consists of a boss with individual arms to which the individual blades are secured.

Further in connection with Figs. 1 to 5 it will be noted that the entering edge of each bladeis provided with a leading tip.

The exit edge is also preferably provided with a tip which enables a good loosening of the blade surface from the water.

This structure of theblades has a special advantage for ships which move in limited water depth and where the out-of-water propellers have such direction of rotation that the water is brought by them from the outside inwardly. This bringing in of the water is increased by the structure according to the invention as the immersing propeller blade being far remote from the boss first enters the water.

In the constructional form of the out-ofwater propeller according to Figure 3, the leading tip is somewhat rounded oil. In this case, the exit edge also tapers to a point.

In the constructional form according to Figure 4, a leading tip is provided on the entering edgeas according to the subject mat- -1,8o8,osa

ter of Figure 1while a special tip is omitted on the exit edge. A gentle loosening from the water is effected according to this structure by a very wide curvature of the exit edge.

In the constructional form according to Fig. 5, a blade surface is used, which extends into the water substantially only within the range of the depth of immersion and is connected to the boss by a special arm. In this case, a leading tip is also provided on the entering edge and a tip on the exit edge.

With broad blades in particular, they will be given increase that increases from the leading edge in a known manner.

lVhat I claim is 1. An out-of-water propeller designed to operate simultaneously in water and air, consisting in the combinationof a hub which is normally above water, blades on said hub with an asymmetrical surface distribution with respect to the radius drawn through the attachment point on the hub, and a point sharpened in the rotation direction as to about 4060 and essentially extending before the radial partof the propeller causing the gradual immersion from the air into the water at the cntering edge of each blade, said entering edge forming with a radius through the utmost point of they blade an acute angle of at least 20.

2. An out-of-water propeller designed to operate simultaneously in water and air comprising .a plurality of blades, each of said blades being provided with a radially extending portion, the entering edge of which extends forwardly and is provided with a leading tip, the exit edge of each blade being also provided with a relatively small and comparatively sharp tip.

3. An out-of-water propeller designed to operate simultaneously in water and air comprising a plurality of blades, each of said blades being provided with a radially extending portion, the entering edge of which extends forwardly and is provided with a leading tip, the exit edge of each blade being also provided with a relatively small and comparatively sharp tip, wherein the pitch of each blade decreases from the outside inwardly.

In testimony whereof I havesigned my name to this specification. 1

FRIEDRICH GEBERS.

Images