Propulsion device for a vessel The invention relates to a propulsion device for a vessel, said device comprising a number of propeller blades each being provided with a shaft extending in longitudinal direction of the blade, said blade shafts being rotatably mounted between two parallel and oppositely arranged discs and said shafts being circumferentially distributed and being square to the planes of the discs, said discs being connected directly or indirectly to each other, means being present for rotatably supporting and rotating said discs, further means being provided for rotating the blades around their shafts in such a way that rotation of a blade during a revolution of the discs can be controlled in dependence of certain parameters being measured during operation of the propulsion device.

Such a device is known from NL-A-100008. With this known device, the means for rotating the blades around their shafts are constituted by levers connected to the blade shafts, said levers being provided with rollers situated in curve tracks, parts of which being adjustable.

Here, two curve track systems, each provided with two curve tracks, are mounted substantially at both sides of the vertical plane extending through the axis of rotation of the discs and are adjustable in such a way that they can be moved toward and away from each other. The facing ends of the curve tracks of the curve track systems touch a common line and connect to each other in the position in which they are the closest to each other, an adjustable bridging part provided with at least one curve track being situated in a plane extending parallel to the curve tracks, for guiding the rollers when the ends of the curve track systems are spaced apart. For achieving a stable position of the blades, the lever connected to the axis of rotation of a blade can be provided with two rollers situated at some distance from

each other as seen in the plane of the discs to which the shafts are connected.

Practice has shown that such a control of the blades gives rise to difficulties. On the transfer of the rollers from one curve track onto the other, shocks occur that are difficult to absorb and that make a gradual rotation of the blades impossible.

Said patent specification indicates further possible embodiments of the means for rotating the blades. However, these too have proven to operate not fully satisfactory or they result in complicated structures.

A further important objection of the known device is that the course of the adjusting angle of the blades across a revolution or the disc is fixed by the shape of the curve tracks. Due to that, it is not possible to bring the blades in any position at their optimum adjusting angles at any speed of the vessel and at any speed of the discs.

The object of the invention is to provide a device having a simple structure and enabling gradual rotation of the blades, in which each blade is able to take up de desi- red adjusting angle at any moment.

According to the invention this is achieved in that the shaft of each blade is provided with a chain wheel, which, by means of a chain, is connected to an adjusting chain wheel having the same number of teeth which is rotatably mounted on the portion of the driving shaft extending outsi- de the discs connected to each other, said adjusting chain wheel being connected to means for rotating it forward and backward across a limited angle.

Thus, the adjusting chain wheel and the means for rotating it forward and backward are situated in a more or less fixed position. Due to that, said means can be realized in a simple way. The adjusting chain wheels for a number of blades need only be next to each other on the drive shaft, as a result of which said drive shaft and the shaft of a number of blades too will have a greater length.

Preferably, it will be provided for, that half the number of chain wheels connected to the blades through the shafts, and half of the adjusting chain wheels connected to them are situated near the one disc and the other half of the chain wheels near the other disc.

Due to this, the distance across which the shafts of the blades protrude beyond the discs can be limited and it will less quickly be necessary to support the portions of the shafts protruding beyond the discs in bearings.

Although the above refers to chain wheels and chains, toothed belt discs and belts as they are generally known may be applied as well.

One could also utilize engaging gear wheels, but they will generally require more space and will entail a consid- erably more expensive construction.

For rotating an adjusting chain wheel, one can use e.g.

a hydraulic cylinder, the cylinder and piston rod of which being pivotably connected to the adjusting chain wheel and a fixed portion of the supporting structure of the propulsion device, respectively. The hydraulic cylinders are thus situated in substantially fixed positions so that operating them does not present any difficulties. Naturally, the cylinders could also be fixedly arranged. Then, one could utilize a connecting link between the cylinder and the adjusting chain wheel. Naturally, the adjusting chain wheel can be provided with an arm directly or indirectly connected to the hydraulic cylinder.

Applying the hydraulical cylinders is possible in that the adjusting chain wheel need only be rotated forward and backward across a limited angle. The hydraulic cylinders can also be operated in such a way, that they take up positions between both outermost positions.

For rotating the adjusting chain wheel forward and backward, one might also use an electric stepping motor.

However, this will generally require more space in axial direction of the blades.

A further possibility is the use of a planetary gear box being driven by the main shaft and providing for rotati- on of a blade by means of pins. Here, a fully mechanical rotation of the blades is achieved, which under certain circumstances may offer advantages in relation to other ways of controlling rotation.

Further, it should be stated that by positioning the shafts in the centre of pressure of the profiled blades, the moments exerted on the blades can be kept low. The loads exerted on the chain wheels and the parts for adjusting them can therefore be kept low as well.

Further, DE-A-3040508 is referred to, which shows a propulsion device in which a propeller blade is rotatably mounted on a shaft having its ends supported by arms which are in turn rotatably connected to the rotatably supported discs being locally discontinued at their circumference. The rotary shaft of the propeller blade bears a chain wheel being connected to a chain wheel by a chain, said chain wheel being mounted on the rotary shaft of the arm. Said rotary shaft of the arm is provided with a chain wheel across which a chain runs, which is coupled to an adjusting chain wheel that is situated on the central shaft and is used for controlling the position of the propeller blades.

Said latter chain wheel can be rotated from the outside. As long as this is not realized, all propeller blades will take up a certain angular position at a certain location during a revolution. On rotating the adjusting chain wheel, the position of all blades during one full revolution of the discs will be changed to a certain degree. As a result of that, it is not possible to bring each blade on any location in the optimum angular position, in the way it is possible with the help of the device according to the invention.

A further objection of said known device is that the blades exert a torque on the arms, in which said torque should be accomodated by the adjusting chain wheel.

Further, US-A-5082423 is referred to, from which it is known that the propeller blades are always kept in the vertical position by means of gear wheels engaging a central gear wheel. Such a device can only be used in that the upper part of the device is covered by a cap, since otherwise the action of the blades situated at the top side will counter- act the action of the blades situated at the bottom side.

From GB-A-1052763 it is known to employ hydraulic cylinders for adjustment of the propeller blades. However, these are controlled from a central location, so that it is again impossible to bring each blade at any place in the desired position.

The invention is further explained by means of an embodiment shown in the drawing, in which: Fig. 1 schematically shows a side view of part of a propulsion device according to the invention with a part of the vessel to which the device is mounted; Fig. 2 schematically shows a rear view of a part of the vessel with a part of the propulsion device according to Fig. 1; and Fig. 3 schematically shows a possibility of the move- ments the blades of the propulsion device according to the Figs. 1 and 2 can make in relation to their supporting discs.

Figs. 1 and 2 show a propulsion device 1 mounted to a vessel 2 to which end it is provided with a cavity 3.

The propulsion device 1 comprises the discs 4 between which the shafts 5 extend, that serve for supporting the blades 6. Only some of said blades 6 have been indicated schematically. The shafts 5 of the blades 6 are rotatably mounted in relation to the discs 4. The discs 4 are connec- ted to the drive shaft 7 which is supported by the hull portions 8 laterally defining the cavity 3. The shaft 7 can be driven in a way not further indicated by a motor arranged in the vessel.

For rotating a blade 6 in relation to the discs 4, the shaft 5 of a blade 6 can be provided with a chain wheel 9 across which a chain 10 runs and further extends across an adjusting chain wheel 11 rotatably mounted on the drive shaft 7. The adjusting chain wheel 11 is provided with an arm 12 being pivotably connected to the piston rod 13 of a hydraulical cylinder 14 having its other end pivotably connected to a portion of the hull 8.

It will be obvious that a chain wheel 9, connected to the shaft 5 of another blade 6, must be situated next to the chain wheel 9, or chain wheels, of the other shafts 5.

Correspondingly, the adjusting chain wheels 11 will be situated next to each other on the shaft 7.

Possibly, in a way not further indicated in the dra- wing, an adjusting chain wheel 11 can be connected to a bush being rotatable on the drive shaft 7 and extending outwardly so that operation thereof can occur at some distance from adjusting chain wheel 11. Then, the adjusting chain wheel 11 of another shaft 5 can likewise be provided with a bush being rotatable on the bush of another adjusting chain wheel. In this way it can be achieved, that the means for rotating the various chain wheels 11 and the lines extending towards them, not further indicated, are situated close to each other.

Figure 3 shows the way in which the blades 6 are rotat- ed in relation to the discs 4. The direction of drive of the vessel is indicated by a V and the direction of rotation of the discs by S. The cross-section of a blade is profiled and the nose of the profile is always situated at the foremost end of the arrows P.

On movement of the blades through the water, an over- pressure, indicated by +, is locally generated at the blade surface, and an underpressure, indicated by -, is generated at the opposite surface of the blade.

As appears from Fig. 3, the blades 6 only perform a relatively small rotation in relation to the horizontal plane. Most of the propulsion force is generated by a blade on movement thereof across the two areas indicated by the word "lift". On movement across the lowermost and uppermost area, little or no propulsion is generated, or only resis- tance will be generated.

It will be obvious, that in the left part of Fig. 3, the blade is loaded in another way than in the right part thereof. The fact is that the overpressure is present at the other side of the blade. Therefore it will be desirable to form the blade symmetrically in relation to the middle plane extending through the chord. The efficiency of such a blade may possibly be somewhat lower than of a blade having a non- symmetrical cross-section.

It is not necessary, that the discs 4 are connected to each other by means of said drive shaft 7. There is the possibility of supporting the discs by some circumferential- ly distributed rollers. These may be executed in the form of e.g. gear wheels engaging a gear of the discs. At least one of the gears bearing the discs can be driven and the gear wheels can be supported by portions of the vessel. Then, there will substantially be no fixed connection between the discs, but only a connection by the shafts 5 of the propel- ler blades 6, said blades being rotatable in relation to the discs.

It will be obvious, that only one possible embodiment of a propulsion device according to the invention has been shown in the drawing and described above and that, as alrea- dy indicated above, changes can be made without departing from the inventive idea, as it has been indicated in the claims.

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