CN117897333A

CN117897333A - Propeller for driving watercraft

Info

Publication number: CN117897333A
Application number: CN202180100215.9A
Authority: CN
Inventors: L·卡托; J·杜斯; S·罗施曼; T·霍普; R·舒尔兹; G·佩辛格; F·伊戈
Original assignee: Albert Hantmann Eltka Co ltd
Current assignee: Albert Hantmann Eltka Co ltd
Priority date: 2021-05-05
Filing date: 2021-05-05
Publication date: 2024-04-16
Also published as: WO2022233407A1; EP4334204A1; CA3218695A1; JP2024516315A

Abstract

A propeller for driving a watercraft is described, having propeller blades (2, 6, 9, 15) and a metal hub (1, 7, 8, 14, 31) for connection to a marine propulsion shaft, and a method for manufacturing the propeller. The propeller blades are made of polyamide 12C or of a composite material of polyamide 12C and long-and/or short-fiber inlays. The propeller blades or the assembly of propeller blades are fitted at the hub or the propeller as a whole is composed of polyamide 12C or of a composite of polyamide 12C and long and/or short fibre inlays and of a hub overmolded with PA 12C. Improved propulsion power and reduced acoustic characteristics compared to metal propellers can thereby be achieved.

Description

Propeller for driving watercraft

Technical Field

The present invention relates to a propeller for driving a watercraft according to the preamble of claim 1 and a method for manufacturing such a propeller according to the preamble of claim 9.

Background

According to the prior art, propellers for watercraft with considerable dimensions and drive power are made of metallic materials such as propeller bronze, brass, steel or stainless steel. In these propellers, each of the blades and the hub for application to the marine propulsion shaft and for torque transmission are composed of metal. Depending on the dimensions, the propeller is made of a cast part or the individual blades are connected to one another in a force-fit, material-fit or form-fit manner. It is well known that propellers for larger watercraft are mainly made of metallic materials.

However, a disadvantage is that the rotation of the metal propeller produces significant electrical, magnetic and acoustic signatures (signature) in the water. These features are undesirable in both civilian and military shipping. In the field of commercial shipping, the emission of propeller sounds is severely evaluated, especially ecologically, because of their biological impact in water and the serious interference of such noise by, for example, communication and identification of whales or dolphins. In the field of military shipping, these electric, magnetic and acoustic emissions are responsible for the positioning of ships. The goal here is also to keep as few features as possible, for example, to make submarines difficult to find.

Furthermore, larger propellers with carbon fibre reinforced fins, consisting of plastic, are known. However, due to the nature of the matrix and the long fibers used, these propellers are very prone to delamination and therefore find no important application. Propellers composed of different plastics are used only for smaller watercraft with lower drive power. These propellers are usually made entirely of plastic, or metal hubs are cast in plastic.

It is also known that in propellers according to the prior art, any desired geometry of the fins may be manufactured, not in order to avoid cavitation of the material used. The service life of the airfoil is too short in the case of certain geometries due to erosion of the metal material by the air pocket. While attempts have been made to minimize the effects caused by cavitation by the shape and surface design of the airfoil and to obtain maximum performance from a given marine engine, hull and propeller arrangement, this still prevents optimization of propeller geometry.

In case of damage to one or more of the propeller blades, it is necessary for the prior art propeller to replace the entire propeller during the mooring time in the dry dock. The propeller and the propeller blades are difficult to assemble with the corresponding cranes due to their high specific gravity. Repair is time consuming and the associated direct and indirect costs are high. Another disadvantage is that the watercraft cannot be used during this time. Quick repairs in water are virtually impossible.

The propellers according to the prior art are often vulnerable to barnacles, shellfish and other organisms, which can continue and significantly reduce the driving power in a short time and thus increase the fuel consumption. To slow down this growth, conventional propellers are equipped with a special anti-fouling coating. However, the biocides contained in such coatings are often toxic and are therefore undesirable for ecological reasons. Coating itself can lead to costs due to the docking time of the dry dock, the materials used and the corresponding effort. Other coating methods, such as by non-toxic and washable paints or underwater cleaning, are also not widely used for economic purposes.

Finally, galvanic corrosion may also adversely affect the service life of the propeller.

Disclosure of Invention

The object of the present invention is to significantly reduce the electrical, magnetic and acoustic characteristics from various types of watercraft, and/or to improve the propulsive power of the propellers and thus also to achieve a further reduction of the characteristics, and/or to enable propeller replacement or replacement of individual propellers under water, and/or to slow down the intrusion of barnacles or shellfish and to reduce the use of biocides resulting therefrom, and/or to avoid galvanic corrosion.

This object is achieved with a propeller according to claim 1 and a method according to claim 9.

The propeller according to the invention is mainly composed of cast polyamide 12 plastic or of a composite material of cast polyamide 12 plastic with suitable long-fiber and/or short-fiber inlays.

Long fibers are well known to be understood as fibers having an average fiber length exceeding 50 mm. In contrast, the short fibers have an average length of 0.1mm to at most 50mm, in particular 1mm to 15 mm.

The propeller comprises one or more fins with a preferably structured surface.

The fins are mounted to the metal hub for assembly on the marine propulsion shaft and for force introduction, for example, in the following manner, or all the fins are cast in one piece, wherein the hub is then cast in together. For this purpose, all the blades and the hub are preferably cast in simultaneously.

The solution according to this object involves the selection of materials for so-called PA12C (Cast) or fiber composites composed of suitable long and/or short fibers and PA-12-C matrix as materials for propeller blades.

The mechanical, physical and chemical properties of such polyamides enable a durable use of the propeller in water due to low hygroscopicity, reduced cavitation due to the toughness of the materials used, an optimized design of the propeller, and an easier replacement of the propeller blades due to the relatively low specific gravity and the design of the surface for slowing down barnacle intrusion. For example, the propeller blades may be fastened by the described technique to a metal hub which in turn is pushed onto the marine propulsion shaft and fastened there.

By using new propeller materials, the electrical, magnetic and acoustic characteristics of various types of watercraft can be significantly reduced and the efficiency of the propeller is improved by the configuration of the geometry which is optimised by the particular structure of the materials selected, whereby a further reduction in characteristics is thus also achieved. It is also possible to realize propeller replacement or replacement of individual propeller blades under water. The infestation of barnacles or shellfish can be slowed down and thus the use of biocides reduced. This is achieved, on the one hand, by the characteristics of the propeller material polyamide 12C itself, and, on the other hand, the structure of this material enables the construction of an optimised propeller geometry.

Furthermore, from polyamide 12C, in particularThe constructed propeller blades/wings have a significantly increased elasticity with respect to such propeller blades/wings constructed of a metallic material, so that an elastic displacement (wegfedern) of the load peaks of the rear flow field of the ship in one complete propeller rotation (360 deg.) can be achieved.

The invention thus relates to the use of polyamide 12C plastic or a composite material of cast polyamide 12 plastic with suitable long-fiber and/or short-fiber inlays for producing individual propeller blades or complete propellers.

Polyamide 12C (also referred to as PA 12G) is a polymeric material that is directly melted and cast as a low viscosity melt into a mold prior to processing from a suitable mixture of monomers and additives. In the manufacture of fiber-reinforced components, long or short fibers are introduced into a mold before filling with plastic and then surrounded by the melt. The filling of the mould is carried out in a non-pressurized manner as is the subsequent polymerization and curing and therefore has special properties compared to extruded, injected or deep drawn workpieces. This can be achieved by: significantly improved electrical and magnetic characteristics can be achieved by using PA12C and avoiding surrounding metallic components (propeller blades); the structural design of the propeller blades enables the characteristics of sound to be significantly improved with increased resistance to cavitation and excellent internal damping of the casting matrix by means of the propeller blades; and a significantly higher efficiency of the propeller can be achieved by a technical design optimized due to minimized cavitation.

The material PA12C differs from other plastics in terms of mechanical, physical and chemical properties and is therefore particularly suitable for the design and construction of propellers for watercraft. When placed in water, the material has a minimum hygroscopicity of only 1.4 weight percent and is therefore suitable for use in water. PA12C has the best notched impact toughness (especially even at low temperatures) among all polyamides and can therefore achieve particular advantages in terms of cavitation and resistance of the matrix (composite variant) to external impacts. The low specific gravity of the components and thus the neutrality of the buoyancy are a prerequisite for the replacement of the propeller blades under water. Internal damping of the workpiece by PA12C or by a composite material having a matrix composed of PA12C reduces the acoustic signature of the component. The wide temperature range, chemical resistance, creep strength and/or electrical properties of this material, compared to other materials, which are technically reasonable, also demonstrates the special applicability of PA12C as a propeller material for watercraft.

In the case of composite materials composed of PA12C and long and/or short fibers, a fiber volume content of more than 65% and thus a very good stiffness-to-weight ratio of the corresponding component with suitable mechanical properties is achieved by the low viscosity of the melt. This material also has significant cost advantages over conventional fiber composites due to the short cure time of a few minutes. Due to these material advantages, the propeller for a watercraft made of PA12C is superior to the propeller according to the prior art.

Another component of the invention may be a propeller blade and a blade made of a metallic materialSpecial coupling of hubs. Force and torque transmission from the marine propulsion shaft to the propeller is typically via e.g. an oil pressure jointThe sliding key or the locating pin is realized by the shape fit connection or the force fit connection of two metal materials of the clamping sleeve. This principle is preserved in principle in the present invention, since certain material properties of the PA12C (e.g. low E-modulus or creep properties at high local surface pressures) do not support a direct coupling of the propeller at the corresponding marine propulsion shaft. The invention can thus also be derived from the type of coupling of the propeller blades at the hub, depending on the desired force transmission and torque transmission as well as the size of the propeller.

Another component of the invention may be in the design of the surface of the propeller blade to avoid the use of an anti-fouling coating. In this case, the shark skin-like surface is preferably shaped by a suitable design of the casting mould and by incorporating special particulate material into the plastic close to the surface. Thus, the growth of barnacles and shellfish is retarded and mechanical cleaning of the surface can be simplified even without lifting the watercraft from the water.

The invention can be implemented in a technically and commercially advantageous manner, for example, using the following embodiments.

Drawings

The preferred embodiments of the present invention are illustrated by the accompanying drawings. In which:

fig. 1 shows a section of a propeller in a first preferred embodiment, based on assembling the propeller blades/propeller vanes on a metal hub;

fig. 2 shows the propeller in a second preferred embodiment together with a cast-in metal hub in a manner that the profile of the propeller blades is seen from the front;

fig. 3 shows a propeller in a variant of the second embodiment similar to fig. 2;

fig. 4 shows a section of a propeller according to a variant of the first embodiment;

fig. 5 shows the propeller in a third embodiment in a schematically shown surface characteristic of the sum of the profiles of the propeller blades viewed from the front;

fig. 6 shows an oblique view of the assembly of the propeller according to the first embodiment.

Detailed Description

The propeller can be seen in fig. 1 together with a metal hub 1. By means of (so-called) hoops 4And a peg 3 introduced into the propeller blade 2 mounts the propeller blade/propeller vane 2 of the propeller on the metal hub by means of a nut 5.

The outline of the propeller can be seen in fig. 2, wherein all the propeller blades 6 are produced in a casting process, and the associated metal hub 7 is overmolded during this casting process, so that a one-piece propeller is produced.

The outline of the propeller can also be seen in fig. 3, wherein all the propeller blades 9 are produced in a casting process, and wherein a metal hub 8 prefabricated for this purpose is overmolded, for example by etching, sandblasting, knurling, cleaning and/or planing, so that a one-piece propeller is produced.

In order to better guide the forces from the metal hub 8 into the individual propeller blades 9, structural elements may be provided, which are represented, for example, in different forms as rods 10, profiles 11, metal structural members 12 (e.g. rods) and/or cores 13. The mounting of these structural elements by means of a material fit (illustratively at the rod 10 and the metallic structural part 12) and/or a form fit (illustratively at the profile 11) is also illustratively and schematically shown.

Fig. 4 shows a propeller in section, in whose propeller blades 15 at least one insert 19 each having two threaded rods 18 is cast into each case. The respective propeller blades 15 are fitted by means of screws 17 between the flange of the metal hub 14 and a (so-called) hoop 16 screwed onto the hub 14 by means of threaded rods 18.

In fig. 5 a preferred embodiment of a propeller is shown, in which the surface 20 of one or more propeller blades is designed such that it resembles a shark skin in hydrodynamic technology. This is generally understood to mean that the surface has so-called corrugations (Riblets) which reduce the frictional resistance when turbulent flow across the surface compared to a smooth surface. As is known, such surface geometries are a plurality of sharp-edged ribs, the longitudinal axes of which lie essentially in the flow direction preset there.

One embodiment of a propeller having a rotor made of PA12C (e.g., under the trademark PA12C can be seen in fig. 6) The resulting propeller blade/propeller vane 30 together with the metal hub 31 together with the (so-called) hoop 32 together with the fastening screw 34 for the hoop 32 and together with the bolt for fastening the propeller blade/propeller vane 30 and the associated nut 33.

Reference is made below to the reference numerals mentioned above and used in fig. 1 to 6.

For the construction and manufacture of propellers composed of PA12C or of PA12C reinforced with long and/or short fibers, for example, the following embodiments are possible:

1.1 an embodiment with one or more propeller blades 2, which are individually or in plurality cast with a low-viscosity PA-12 melt in a non-pressurized manner in a suitable, respectively temperature-regulated casting mould (which corresponds approximately to the outer contour of the blade or blades) and then polymerized and cured by suitable temperature control.

1.2 an embodiment with a metal hub 1 which can be pushed onto a marine propulsion shaft with, for example, an oil pressure fitting, a sliding key, a locating pin and/or a clamping sleeve by means of a form-fitting connection or a force-fitting connection and fastened there for transmitting forces and torques.

1.3 an embodiment of connecting a plastic fin with a metal hub that is pushed onto and connected to a marine propulsion shaft is as follows: one or more metal pins 3 for force transmission and torque transmission are respectively inserted into each propeller blade 2. The metal bolt is fastened on one side in the flange of the metal hub 1 by means of a corresponding nut 5. After all individual tabs have been preassembled at the metal hub 1 in this way, a so-called hoop 4 is fitted on the end of the hub 1 opposite the flange by means of a suitable screw connection. In which ring an opening is provided which is adapted to the metal bolt 3. The bolt 3 is tightened with a suitable torque relative to the collar 4 by means of the nut 5. A suitable cover plate at the end of the hub 1 preferably covers the screw connection and thus by its design simultaneously achieves an optimized flow in the inertial motion of the shaft.

1.4 an embodiment of a structural design with individual propeller blades at the propeller foot is as follows: the temperature dependent variation of the propeller thickness due to the choice of the propeller thickness at room temperature (depending on the hub flange, the bolt and the hoop) is done in such a way that the stress is so small at high temperature that the creep properties of the PA12C are not overdriven, while on the other hand the pre-stress is still so large at low temperature that the propeller blades are clamped firmly.

1.5 an embodiment of the design with a hole for the bolt 3 is as follows: one or more recesses are introduced throughout the length of the hole to thereby reduce stress peaks in the material and improve creep characteristics.

1.6 one embodiment is as follows: by heating the plastic and pressing the pins in at room temperature; cooling the pins and pressing into the plastic fins at room temperature; or a combination of both assembly methods to couple the peg 3 at the propeller blade 2. However, in principle, other joining methods are also conceivable.

For the construction and production of propellers composed of PA12C or of PA12C reinforced with long or short fibers, for example, the following embodiments are possible:

2.1 an embodiment with a metal hub 7 which can be pushed onto the marine propulsion shaft with, for example, an oil pressure fitting, a sliding key, a locating pin and/or a clamping sleeve and fastened there for transmitting forces and torques by means of a form-fitting connection or a force-fitting connection.

2.2 an embodiment with a metal hub 7, which is prefabricated (for example as shown in fig. 2) at the surface of the hub facing the plastic by etching, sandblasting, knurling, cleaning with special cleaning agents, application of planing, is for over-casting with PA 12C.

2.3 an embodiment with a metal hub 8 for transmitting forces and torques from the hub 8 into the propeller blades 9 (as shown for example in fig. 3) has structural elements such as rods 10, profiles 11, metal structural parts 12 or inserts 13 which are fastened to the hub by force fit, form fit and/or material fit and are completely surrounded by plastic during casting.

2.4 an embodiment with a metal hub 7, 8 according to embodiment 2.2 and/or 2.3, which is completely over-molded with a PA12 melt of low viscosity in a non-pressurized manner in a suitable, correspondingly temperature-regulated casting mold (which corresponds to the outer contour of the one-piece propeller to be produced) and then polymerized and solidified by suitable temperature control.

2.5 an embodiment of the propeller manufactured according to embodiment 2.4, which propeller is machined in a cutting manner after curing and shaping in order to obtain a precise final profile. One or more heat treatments may be performed between the individual cutting processes to relieve possible stresses in the material.

3.1 an embodiment with one or more propeller fins 15, which are cast singly or multiply in a temperature-regulated mould (which corresponds approximately to the outer contour of the fin or fins) with a PA-12 melt of low viscosity in a non-pressurized manner, and then polymerized and cured by suitable temperature control.

3.2 an embodiment with an insert 19 cast into each propeller blade, at which a threaded rod 18 is mounted prior to casting.

3.3 an embodiment with a metal hub 14 which is pushed onto the marine propulsion shaft by means of a form-and/or force-fitting connection, for example together with an oil pressure fitting, a sliding key, a locating pin and/or a clamping sleeve, and fastened there for transmitting forces and torques.

3.4 an embodiment of connecting a plastic fin 15 with a metal hub 14 that is pushed onto and connected to a marine propulsion shaft is as follows: the insert 19 and the threaded rod 18 cast into the respective propeller blade 15 are each pushed through the opening of the hub 14 and then fastened thereto with the screw 17. After all individual fins have been preassembled at the metal hub in this way, a (so-called) hoop 16 is fitted on the end of the hub 14 opposite the flange by means of a suitable screw connection. An opening for a threaded rod 18 is formed in the hoop 16. The bolt is then tightened with a suitable torque against the collar 16 by means of a suitable nut 17. A suitable cover plate at the end of the hub 14 covers the screw connection and by its design simultaneously achieves an optimized flow in the inertial motion of the shaft.

3.5 an embodiment of a structural design with individual propeller blades at the propeller foot is as follows: the temperature dependent variation of the propeller thickness due to the choice of the propeller thickness at room temperature (depending on the hub flange, the bolt and the hoop) is done in such a way that the stress is so small at high temperature that the creep properties of the PA12C are not overdriven, while on the other hand the pre-stress is still so large at low temperature that the propeller blades are clamped firmly.

4.1 an embodiment with one or more propeller blades, which are individually or in plurality cast with a low-viscosity PA-12 melt in a non-pressurized manner in a suitable, correspondingly temperature-regulated casting mould (which corresponds approximately to the outer contour of the blade or blades), and then polymerized and cured by suitable temperature control.

4.2 an embodiment of the design of the surface 20 with one or all propeller blades/propeller foils according to embodiment 4.1 is as follows: a surface structure resembling shark skin can be cast within the scope of the casting process by shaping of the casting mould and/or incorporation of a suitable particulate material into the surface. The surface structure thus has so-called furrows which reduce frictional resistance against a smooth surface when turbulent flow through the surface structure and thus slow down the growth of barnacles and other organisms and simplify mechanical cleaning. This facilitates long-term maintenance of the required propeller power.

Claims

1. Propeller for driving a watercraft, with a propeller blade (2, 6, 9, 15) and a metal hub (1, 7, 8, 14, 31) for connection with a marine propulsion shaft, characterized in that the propeller blade is made of polyamide 12C or of a composite material of polyamide 12C and a long and/or short fibre inlay, and that the propeller blade or an assembly of the propeller blade is fitted at the hub or in that the propeller as a whole is made of polyamide 12C or of a composite material of polyamide 12C and a long and/or short fibre inlay and a cast hub is overmolded with PA 12C.

2. Propeller according to claim 1, wherein each of the propeller blades or blade pairs formed thereof is fastened by means of a metal peg (3) placed in the propeller and its tightening in the flange of the hub and a collar (16) fitted onto the hub.

3. Propeller according to claim 2, wherein an opening for the metal pin (3) is formed in the hoop and the pin is tightened with respect to the hoop (4, 16, 32) by means of a nut (5).

4. A propeller according to claim 3, wherein the propeller blades comprise holes for the pegs (3) and are correspondingly configured with one or more recesses for reducing material stresses over the length of the holes.

5. Propeller according to claim 3 or 4, further having a cover plate mounted at an end of the hub for covering the nut/screw connection and in particular for optimizing the flow in inertial motion of the marine propulsion shaft and/or the hub.

6. Propeller according to claim 1, further having a structuring element for transmitting forces and torques from the hub to the propeller blades, wherein the structuring element, in particular in the form of a rod (10), a profile (11), a metallic structural part (12) or an insert (13), is fastened at the hub (8) by force fit, form fit and/or material fit and is entirely overmolded by polyamide 12C.

7. Propeller according to claim 6, wherein the hub (7, 8) has a surface prefabricated for over casting with PA12C by etching, sandblasting, knurling and/or application of planing.

8. The propeller of at least one of the preceding claims, wherein one or more propeller blades have a surface structure resembling shark skin.

9. Method for manufacturing a propeller for driving a watercraft, which propeller has propeller blades (2, 6, 9, 15) and a metal hub (1, 7, 8, 14, 31) for connection with a marine propulsion shaft, characterized in that the propeller blades are made of polyamide 12C or of a composite material of polyamide 12C and long and/or short fibre inlays and that the propeller blades or an assembly of propeller blades are fitted at the hub or in that the propeller, which is made of polyamide 12C or of a composite material of polyamide 12C and long and/or short fibre inlays, is manufactured by surrounding the metal hub of the propeller simultaneously and shaping all propeller blades during casting.

10. Method according to claim 9, wherein a metallic peg (3) for force and torque transmission is placed in the propeller blade (2) by heating the polyamide 12C and pressing in the peg at room temperature and/or by cooling the peg and pressing in at room temperature.

11. Method according to claim 9, when simultaneously surrounding the hub (7, 8) prefabricated therefor and shaping all propeller blades during casting, wherein the structuring element for introducing forces from the hub into the respective propeller blade is fastened at the hub and completely surrounded by PA12C during casting.

12. The method according to claim 11, wherein the hub (7, 8) is prefabricated for over casting at the surface facing the polyamide 12C by etching, sandblasting, knurling and/or application of a planing.

13. Method according to at least one of claims 9 to 12, wherein the propeller formed and cured by casting is machined in a cutting manner to produce its final profile.

14. Method according to any of claims 9 to 13, wherein a shark skin-like surface structure is cast by shaping of the casting mould and/or incorporation of particulate material into the surface within the scope of the casting process to shape the surface (20) or parts of the surface of one or more propellers.