GB2555711A

GB2555711A - Improvements to a propeller for a water craft

Info

Publication number: GB2555711A
Application number: GB1714859.4A
Authority: GB
Inventors: Shaw Christopher
Original assignee: Superprop Ltd
Current assignee: Superprop Ltd
Priority date: 2016-09-15
Filing date: 2017-09-15
Publication date: 2018-05-09
Anticipated expiration: 2037-09-15
Also published as: GB201615676D0; GB201714859D0; GB2555711B

Abstract

A propeller (16, figure 1) comprises a plurality of blades, (20a, 20b, figure 2a) formed from a core 4 of a selected metal or metal alloy, and a deformable material 6 such as a polyurethane rubber. The propeller may be formed so that the deformable material substantially encloses a cavity in the blade. In some embodiments, the blade may be formed by casting the core from a metal or alloy, then the deformable material poured in liquid form around the cast. Preferably, the deformable material deforms as the propeller spins, altering the locations of the stiffness and lift axes, (26, 28, figure 3c) of the blade, and altering its hydrodynamic properties. In some embodiments, the deformable material may be placed to form a pattern which mimics shark skin or the skin of a fish or mammal.

Description

(54) Title of the Invention: Improvements to a propeller for a water craft

Abstract Title: Propeller with a metal core and a deformable outer coating (57) A propeller (16, figure 1) comprises a plurality of blades, (20a, 20b, figure 2a) formed from a core 4 of a selected metal or metal alloy, and a deformable material 6 such as a polyurethane rubber. The propeller may be formed so that the deformable material substantially encloses a cavity in the blade. In some embodiments, the blade may be formed by casting the core from a metal or alloy, then the deformable material poured in liquid form around the cast. Preferably, the deformable material deforms as the propeller spins, altering the locations of the stiffness and lift axes, (26, 28, figure 3c) of the blade, and altering its hydrodynamic properties. In some embodiments, the deformable material may be placed to form a pattern which mimics shark skin or the skin of a fish or mammal.

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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Figure 2a t,'3/4

Figure 2b

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Improvements to a propeller for a water craft

The invention to which this application relates is improvements to a propeller of a type used to propel a craft through a body of water and, more typically, although not necessarily exclusively, to a propeller which is fitted to a yacht to act as a propulsion means when the sails of the yacht are not being used.

The provision of a propeller in connection with a splined shaft which, in turn, is driven to rotate by one or more engines provided on the craft, is known and the propeller typically includes at least first and second blades, or possible more blades, which are attached to a body and which rotate about a longitudinal axis of the body, with the longitudinal axis being in line with the longitudinal axis of the splined shaft to which the propeller is attached.

When the propeller is required to be used, the blades rotate and hence drive the craft through the body of water at a desired speed within a range of speeds. When not in use, the propeller blades of the conventional form of propeller, will still extend outwardly from the body and hence act as a drag to the speed of the yacht or other craft as it is propelled through the body of water by the other propulsion means. The Applicant, in their co-pending application, identifies an alternative form of propeller in which the blades, when the propeller is not in use, are moved to a retracted, storage position in which the same are substantially in line with the body and hence the drag on the movement of the craft, is significantly reduced.

A further problem which is experienced with propellers and particularly propellers which are used relatively infrequently, is the build-up of fouling on the external surfaces of the same and particularly on the blades of the propeller. The fouling, which is typically different forms of bacteria and crustaceans such as barnacles, act to reduce the speed of propulsion which can be achieved when the propeller is in use and can further add to the drag of the propeller when the same is not in use. A yet further problem is that if the blades of the propeller when in use, are not correctly aligned, in terms of their relative angle of twist with regard to the direction of the propulsion, then this can cause a further degradation of the speed of propulsion which can be achieved.

An aim of the present invention is therefore to provide improvements to a propeller which reduce the drag created by the propeller on the speed of propulsion which can be achieved when the propeller is in use and/or not in use.

In a first aspect of the invention, there is provided a propeller comprising a body and a plurality of blades connected to the body, said body connected to drive means to allow the same to be rotated and hence rotate the blades, wherein said blades have a stiffness axis and a lift axis and include a body formed of a metal material and at least part of which is coated with a deformable material which has a greater degree of deformability than the body.

In one embodiment, the provision of the deformable material on the external surface of the body of the blade is such that when the propeller is rotated, the respective locations of the stiffness axis and the lift axis of the blade, adjust to an optimal rotational position.

In one embodiment, the provision of the deformable material on the external surface of the blade is such that the axis of the blade that corresponds to its axis of twist, when stressed in a stationary position in air, (the stiffness axis) and the axis of the blade that corresponds to the water pressure generated by the blade as it moves through the water (the lift axis) are not coincident so that the angle of incidence of the blade can change as the pressure generated by the water changes.

Typically, the adjustment of the relative positions of the stiffness axis and the lift axis, allow the angle of the blade with respect to the direction of propulsion to adjust to a position which provides hydrodynamic advantage to the movement of the blade and hence propeller and, in turn, allows a reduction in drag and/or increase in speed of propulsion which can be achieved.

In one embodiment, the said material is polyurethane rubber.

In one embodiment, the said material is located outside a cavity within the blade and substantially encloses the cavity within which may be placed a material of a different stiffness value.

In one embodiment, the blade is first cast of the metal which is selected and the deformable material, which may be polyurethane rubber, is poured in a liquid form around the cast metal.

In one embodiment the particular form of the polyurethane rubber compound can be selected to suit the size and/or speed and/or further parameters of the particular blade on which the same is to be provided so as to allow a particular range of movement between the respective positions of the stiffness axis and lift axis to be achieved.

In one embodiment, when the propeller rotation ceases, the stiffness and lift axes return to their original respective locations.

In one embodiment, the exterior surface of the blade includes a portion of material, other than the metal material from which the blade is formed, said material including on the external surface thereon, a predetermined pattern which is provided to reduce the possibility of fouling of the said surface.

In one embodiment, a portion of the blade is provided with this material while, in another embodiment, substantially all of the external surface of the blade is enclosed in said material.

In one embodiment, the blade is initially formed of the metal material of a size which is a predetermined percentage less than the required final size of the blade and the blade is then coated with the said further material which, in one embodiment, is polyurethane rubber.

In one embodiment, the blade, when initially cast, is subsequently placed into a mould which defines the dimensions and pattern of the external surface of the finished blade when formed by the polyurethane rubber material which is introduced into the cavity between the walls of the mould and the walls of the metal blade so as to form the final external surface of the blade.

In one embodiment, the surface pattern which is created, mimics that of the external surface of a fish or mammal and includes a series of recesses and protrusions thereon.

In one embodiment, the blades are attached to the body of the propeller in a manner which allows the same to be pivotally moveable with respect to the body.

In one embodiment, the pivotal movement is such as to allow the blades to be moved between an in use position in which the same extend substantially perpendicular to the longitudinal axis of the body, and a storage condition in which the longitudinal axes of the blades are substantially in line with the longitudinal axis of the body.

In one embodiment, the movement of the blade between the said in-use and storage positions, is as a result of rotation, or lack of rotation of the body such that when rotated, the blades are moved to the in-use position and when the body is not rotating, the blades move to the storage position.

In one embodiment, the propeller is of a form as described in the Applicant’s co pending patent application GB2532694, the contents of which are included herein.

In one embodiment, the body of the propeller, includes a lubrication system which includes a first port into which a lubrication source can be connected and a second port, spaced from the first port which allows lubricant to leave the body and the first and second ports are interconnected by a series of channels, passages or the like formed within the body and which are provided to receive lubricant therein and therealong to allow the lubricated movement of the components of the body and the blades with respect to the body.

In one embodiment, the user can be certain that sufficient lubricant has entered and is contained within the body, by continuing to introduce lubricant into the first port until a time at which lubricant is seen to leave through the second port.

Typically the amount, thickness and/or shaping of the external coating with respect to the base is selected so as to allow the location of the respective blade axes to be selected.

In one embodiment the blade is formed such that in use the lift axis is not coincident with the stiffness axis and as a result the hydrodynamic characteristics of the blade are altered in an advantageous way.

Typically, in use, the change in the blade shape occurs as a result of the load so that the blade geometry alters in a manner which allows improved transmission of power supplied to the propeller in the form of revolutions per minute (RPM) and torque in the water so as to provide thrust and speed to the craft.

Specific embodiments of the invention are described with reference to the following drawings; wherein

Figure 1 illustrates a drive system incorporating a propeller in accordance with one embodiment of the invention.

Figures 2a and b illustrate the propeller of figure 1, in greater detail in accordance with one embodiment of the invention;

Figures 3a-c illustrate a propeller blade formed in accordance with one embodiment of the invention; and

Figure 4 illustrates a predetermined pattern of a propeller external surface formed in accordance with an embodiment of the invention.

Referring to Figures la and b there is illustrated a drive system for a yacht 52 in accordance with one embodiment in which there is provided in the hull 54 an engine 56, connected by shaft to gear box 60. This is in turn connected to shaft which is connected to gear box 64 and in turn drive shaft 66. Connected to the free end 68 of the drive shaft is a propeller 16 which has a body 70 with blades 72 which are driven by the rotation of the drive system.

In Figures 2a and b there is illustrated a propeller 16 in accordance with one embodiment of the invention in which the blades 20a and 20b are movable between a storage position shown in bold lines in Figure 2a and in Figure2b. The blades 20a, 20b move to an in use position about the pivot axis 24a as shown in broken lines in Figure 2a. The stiffness axis 18 of the propeller is in line with that of the shaft 66.

In Figures 3a and b there are illustrated views of a propeller blade 2 in accordance with one embodiment of the invention and the propeller blade is formed with a body 4 of a first material and an outer coating 6 of a second material. The first material which forms the body is a metal material such as aluminium bronze and which is cast into a predefined shape using a suitable casting method. In accordance with the invention, the metal casting is formed to act as a body 4 of the propeller blade and is therefore formed of a size which is less than the final required size of the blade 2. In one embodiment the casting process used is a lost wax method but other processes may be used. The blade body 4 is then placed into another mould having clearance volume around it and a deformable material such as liquid polyurethane rubber is poured into the volume to form the outer layer 6 of the blade 2.

The second component 6 of the blade, is an outer coating which is formed using a deformable material such as polyurethane rubber. The outer coating 6 is applied by placing the body 4 of metal into a mould of a suitable shape and in the space or cavity which is defined between the external face of the body and the internal face of the mould, the rubber material is poured as a liquid and, once formed, adheres and attaches to the body so as to form, in combination, an integral blade.

The blade body 4 is formed so as to allow the deformation of the external layer 6 formed by the deformable material when the blade is in use, i.e. as the propeller rotates. The effect of the rotation of the propeller acts to put load onto the blades which in turn causes the deformable layer 6 to alter shape within a predefined range of possible movement as is illustrated in an exaggerated manner by a comparison between the shape of the deformable material in Figure 3b when the blade is at rest and the shape of the deformable material 6 when the blade is moving as illustrated in Figure 3c. A comparison of the Figures 3b and c shows how the external surface shape changes and, as a result, the effective surface of the blade changes when it is rotated as shown in Figure 3c and will revert back to the shape shown in Figure 3b when the propeller comes to rest.

The effective surface geometry of the blade therefore alters so that it its shape is better suited to transmit more power for the propulsion of the craft through the water by allowing movement of the relative position of the stiffness axis 26 of the blade with respect to the lift axis 28 of the blade during use of the propeller and thereby allows the same to adjust to an optimal shape for its rotational position. Thus, the deformable material 6 on the external surface of the blade is such that the axis of the blade that corresponds to its axis of twist, when stressed in a stationary position in air, (the stiffness axis), and the axis of the blade that corresponds to the water pressure generated by the blade as it moves through the water (the lift axis) are not coincident as shown in Figure 3b, being spaced apart by a distance X when the blade is at rest, and then, when the blade is being moved as illustrated in Figure 3c, the deformable material shape changes and so the relative effective positions of the stiffness axis 26 and lift axis 28 of the blade change so that, in this example, the same are spaced apart by a greater distance Y. As a result of the deformable material change in shape when the blade is being moved through the water as a result of the propeller being driven via the drive shaft 16 so the angle of incidence of the blade can change as the pressure generated by the water changes and thereby allow improved performance of the blade 2 and hence propeller.

As shown in Figure 4, which illustrates a portion 10 of the external surface of the blade 2, then in one embodiment, there is provided a predefined pattern 8 of protrusions 12 and recesses 14 therein to reduce the ability for the fouling of the same. In one embodiment this can be achieved by the second mould in the moulding process described above, including the impression of the pattern which is to be formed.

The preconfigured pattern 10 is typically designed so as to have the effect, when the propeller is in use, of reducing the fouling of the external surface of the blade, most typically, by providing an uneven surface in a form which reduces the ability for matter to adhere to the same. The pattern 8 can be, in one embodiment be of a form so as to mimic the effect of a shark skin. In one embodiment, the pattern 8 is such so as to reduce the ability for crustaceans, such as barnacles, to achieve a vacuum seal with the surface and therefore reduce the possibility of the barnacles remaining in contact with the surface and hence fouling the same.

The said predetermined pattern which is formed therefore acts as an anti-fouling means.

Claims

1. A propeller for a water craft comprising a body and a plurality of blades connected to the body, said body connected to drive means to allow the same to be rotated and hence rotate the blades, wherein said blades have a stiffness axis and a lift axis and include a body formed of a metal material and at least part of which is coated with a deformable material which has a greater degree of deformability than the body.

2. A propeller according to claim 1 wherein the provision of the deformable material on the external surface of the body of the blade is such that when the propeller is rotated, the respective locations of the stiffness axis and the lift axis of the blade, adjust.

3. A propeller according to claim 1 wherein the provision of the deformable material on the external surface of the blade is such that the axis of the blade that corresponds to its axis of twist, when stressed in a stationary position in air, (the stiffness axis) and the axis of the blade that corresponds to the water pressure generated by the blade as it moves through the water (the lift axis) are not coincident so that the angle of incidence of the blade can change as the pressure generated by the water changes.

4 A propeller according to claim 3 wherein the adjustment of the relative positions of the stiffness axis and the lift axis, allow the angle of the blade with respect to the direction of propulsion to adjust to a position which provides hydrodynamic advantage to the movement of the blade and hence propeller.

5. A propeller according to any of the preceding claims wherein the deformable material is polyurethane rubber.

6 A propeller according to claim wherein the deformable material is located on the blade so as to substantially enclose a cavity in the blade.

7 A propeller according to claim 6 wherein a material of a different stiffness value than the deformable material is located in the cavity.

8 A propeller according to any of the preceding claims wherein the blade is cast from a selected metal or metal alloy and the deformable material is poured in a liquid form around the cast.

9. A propeller according to any of the preceding claims wherein the shape of the blade changes as a result of the movement of the deformable material as the blade rotates as a result of the load to allow an increase in the transmission of power supplied to the propeller in the form of revolutions per minute (RPM) and torque in the water so as to provide thrust and speed to the craft to which the propeller is connected.

10 A propeller according to any of the preceding claims wherein at least a portion of the exterior surface of the blade is formed by a material, other than the metal or metal alloy material from which the blade is formed, said material including on the external surface thereon, a predetermined pattern.

11 A propeller according to claim 10 wherein the cast metal or metal alloy is placed into a mould which defines the dimensions and pattern of the external surface of the blade when formed by the said material which is introduced into the cavity between the walls of the mould and the walls of the metal blade so as to form the external, patterned surface of the blade.

12. A propeller according to claim 11 wherein the said pattern mimics that of the external surface of a fish or mammal and includes a series of recesses and protrusions thereon.

13 A propeller according to any of the preceding claims wherein propeller includes a body which includes a lubrication system formed by a first port into which a lubrication source can be connected and a second port, spaced from the first port which allows lubricant to leave the body and the first and second ports are interconnected by a series of channels, passages or the like formed within the body and which are provided to receive lubricant therein and therealong to allow the lubricated movement of the components of the body and the blades with respect to the body.

14 A propeller according to any of the preceding claims wherein each of the propeller blades is provided with a portion of deformable material located thereon so as to provide said lift and stiffness axes on each of said blades.

15 A propeller according to claim 14 wherein when at rest the lift and stiffness axes on each blade are provided at first respective locations, said respective locations change as the propeller rotates and when the propeller rotation ceases, the stiffness and lift axes return to the first respective locations.

16 A propeller according to any of the preceding claims wherein the blades are attached to the body of the propeller in a manner which allows the same to be pivotally moveable with respect to the body.

17 A propeller according to claim 16 wherein the pivotal movement is such as to allow the blades to be moved between an in use position in which the same extend substantially perpendicular to the longitudinal axis of the body, and a storage condition in which the longitudinal axes of the blades are substantially in line with the longitudinal axis of the body.

18 A propeller according to claims 16 or 17 wherein the movement of the blade between the said in-use and storage positions, is as a result of rotation, or lack of rotation of the body such that when rotated, the blades are moved to the in-use position and when the body is not rotating, the blades move to the storage position.

19 A water craft including a propeller as defined in any of claims 1-18

Intellectual

Property

Office

Application No: GB1714859.4 Examiner: Mr Michael Shaw