WATERJET PROPULSION APPARATUS

Abstract

A waterjet propulsion apparatus comprising a motor, an impeller driven by the motor via a drive shaft, and a power source. A fluid flow-path is formed through the apparatus, the flow-path extending from at least one fluid inlet, through two propulsion passages, each propulsion passage extending from a propulsion inlet to an outlet located at a rear end of the apparatus. The impeller is located within the flow-path, after the at least one fluid inlet, and before the propulsion inlet of the each of the propulsion passages. The motor is located outside of the flow-path, between the two propulsion passages, and behind the impeller. The apparatus is advantageous in that it provides a compact and lightweight construction that can, for example, be used as part of a personal marine propulsion device that can be used by an individual.

Claims

1. A waterjet propulsion apparatus for a propulsion device comprising a motor, an impeller driven by the motor via a drive shaft, and a power source; wherein: a fluid flow-path is formed through and contained within the apparatus, the flow-path extending from at least one fluid inlet located at a front end of the apparatus through two propulsion passages, each propulsion passage extending from a propulsion inlet to an outlet located at a rear end of the apparatus; the impeller is located within the flow-path, after the at least one fluid inlet, and before the propulsion inlet of the each of the propulsion passages; and the motor is located outside of the flow-path, within a rear portion of the apparatus, between the two propulsion passages, and behind the impeller.

2. An apparatus according to claim 1, wherein each propulsion passage reduces in cross-section from its propulsion inlet to its outlet.

3. An apparatus according to claim 1, wherein the outlets of the propulsion passages are substantially cylindrical or rectangular.

4. An apparatus according to claim 1, wherein the propulsion passages are defined within a splitter formed as a unitary component.

5. An apparatus according to claim 4, wherein the motor is mounted to the splitter and the drive shaft extends through the splitter into the flow-path.

6. An apparatus according to claim 1, further comprising a heat-sink that is in thermal connection with motor and is arranged such that the heat sink is in direct contact with water when the device is in use.

7. An apparatus according to claim 1, wherein radially extending fins are located within the propulsion passages to direct water expelled from the device.

8. An apparatus according to claim 1, wherein the at least one fluid inlet is formed at a front end of the housing and the outlets of the propulsion passages are formed at a rear end of the housing.

9. An apparatus according to claim 8, wherein the housing has one or more handles located on an outer surface to allow a user to hold on to the device when in use.

10. An apparatus according to claim 8, wherein the housing is formed as a back-pack and comprises one or more straps to allow a user to wear the device.

11. An apparatus according to claim 8, wherein one or more components of the apparatus are mounted to the housing by means of vibration mounts.

12. An apparatus according to claim 1, wherein the impeller is formed by solid laser sintering.

13. An apparatus according to claim 1, wherein the drive shaft is mounted within the apparatus on ceramic bearings.

14. An apparatus according to claim 1, wherein the drive shaft is mounted within the apparatus by means of at least one thrust bearing.

15. An apparatus according to claim 1, wherein the motor is water-proof and can be operated when in direct contact with water.

16. An apparatus according to claim 1, wherein a rigid mesh is provided across the at least one fluid inlet to prevent solid objects entering the fluid flow-path.

17. An apparatus according to claim 16, wherein the mesh is heat-staked to the fluid inlet.

18. An apparatus according to claim 15, wherein the mesh is formed of epoxy coated metal.

19. An apparatus according to claim 1, wherein a grating is provided in the at least one fluid inlet.

20. An apparatus according to claim 1, wherein the apparatus is engaged with a personal marine propulsion device.

Description

DRAWINGS

[0027] FIG. 1 is an image of a device according to an embodiment of the present invention;

[0028] FIG. 2 is a partial cross-section of components of the embodiment of FIG. 1;

[0029] FIG. 3 is a three-dimensional view of a splitter of the embodiment of FIG. 1; and

[0030] FIG. 4 is a side view of components of the embodiment of the previous Figures.

[0031] A personal marine propulsion device 1 substantially consisting of a waterjet propulsion apparatus according to an embodiment of the present invention is shown in the Figures. An upper side of the complete device 1 is shown in FIG. 1. The housing 2 encloses most of the components of the device 1 such that all that is visible in FIG. 1 are outlets 4 of propulsion passages 3, a fluid inlet 9, and a top part 26 of the fluid inlet 9. Internal components of the device are illustrated in the other Figures and described further below. The housing 2 is formed of plastic and is moulded to substantially enclose the internal components. The device 1 is formed as a backpack and comprises shoulder straps (not shown) attached to a lower side of the housing 2 to allow the device to be worn by a user. A battery pack (not shown) is mounted within the housing to power a motor 7.

[0032] A partial cross-section through components of the device 1 of FIG. 1 is shown in FIG. 2. In particular, this Figure illustrates the relative positioning of an impeller 6, a motor 7, a drive shaft 8, the propulsion passages 3, and the fluid inlet 9. A pre-mesh part 9.1 of the fluid inlet and a post-mesh part of the fluid inlet are shown. A flow path 10 of fluid passing through the device 1 when it is in use is also shown.

[0033] An intake mesh 21 is position in the fluid inlet 9 and acts to prevent solid objects entering the flow path 10. The intake mesh 21 is a hexagonal mesh formed of epoxy coated metal that is heat staked to the fluid inlet 9 for strength and to minimise any gaps or protruding edges that could affect flow efficiency through the flow path 10. The intake mesh extends completely across the fluid inlet 9.

[0034] An intake grate 22 is also provided within the fluid inlet. The intake grate 22 comprises three vertically oriented plates that extend along the flow path 10 from a rear side of the intake mesh 21. The intake grate 22 is formed of a thin corrosion resistant material and each plate is bolted within the fluid inlet 9 at a bottom end and are fixed in position at an upper end by means of a fastening bolt 27 that extends through each plate. The intake grate 22 provides support to the top part 26 of the fluid inlet by transferring vertical force away from said top part 26. The intake grate 22 also acts to improve laminar flow through the flow path 10, thereby increasing the efficiency of the apparatus.

[0035] The flow path 10 through the device is defined by the fluid inlet 9, the impeller 6 and a splitter 11, which itself defines the propulsion passages 3. Details of the splitter 11 are best seen in FIG. 3. Both the fluid inlet 9 and the splitter 11 are unitary moulded components and the fluid inlet 9 and the splitter 11 are connected together around the impeller 6. The splitter 11 and the fluid inlet 9 may be 3D printed components. The unitary moulding of the splitter 11 allows a bearing seat 24 to be formed in which ceramic bearings 13.1, 13.2 of the drive shaft 8 are slotting into position. A radial groove in the splitter 11 also allows a securing ring 23 to be positioned around an outer end of the drive shaft 8.

[0036] The impeller 6 is located directly in front of the motor 7 and is driven by the motor 7 by means of the drive shaft 8, which extends from the motor, to the impeller. The impeller 6 is connected to the drive shaft 8 by means of a shaft fastener 19. The drive shaft 8 is mounted in the splitter 11 by means of two ceramic bearings 13.1, 13.2 that allow the drive shaft to freely rotate. In particular, the drive shaft 8 is mounted within a radial bearing 13.1 and an angular bearing 13.2. Ceramic bearings are used as they do not require watertight sealing. The motor 7 is fixed to the splitter 11 at a front end of the motor. The motor 7 is located between the propulsion passages 3 of the splitter 11.

[0037] The motor 7 is a waterproof motor that is used in direct contact with water when the apparatus 1 is in use. Contact with water acts to cool the motor 7 such that no heat sink or other cooling means is required.

[0038] The propulsion passages 3 of the splitter 11 are positioned either side of the motor 7 and each extend from a propulsion input immediately behind the impeller 6 to an output 4 at a rear end of the device 1. The propulsion passages 3 are substantially symmetrically positioned within the splitter 11 and are mirror images of one another. The propulsion passages 3 are substantially circular in cross-section and gradually reduce in diameter from their propulsion input to their output 4. This reduction in diameter helps increase and direct thrust generated by the device 1. Each propulsion passage 3 has sixradially extending fins 14 located therein in order to reduce the radial flow of water exiting the passages and to thereby preserve the thrust generated by the impeller 6. As the device 1 is intended for use as a backpack the device 1 does not include steering means. Instead the device 1 can be steered by the user orienting their body appropriately.

[0039] Further details of the device 1 can be seen in FIG. 4. In particular FIG. 4 shows the relative position of the splitter 11, the motor 7, the mesh 21, and an intake grate 22. As can be clearly seen, the motor 7 is positioned between the propulsion passages 3 of the splitter 11. The motor 7 is positioned and the housing 2 are formed such that an outer surface of the motor 7 is in direct contact with water when the device 1 is in use and submerged and thereby provide cooling to the motor. The motor 7 is fixed to a motor mount 20 at a front end. The motor mount 20 is in turn fixed to the splitter 11 to thereby hold the motor 20 in an appropriate position. The motor 20 is connected to the drive shaft 8 by means of a shaft coupler 15. A shoulder 25 is provided on the drive shaft 8 adjacent the shaft coupler 15 to locate the drive shaft 8 in position within the angular bearing 13.2.

[0040] The splitter 11 is connected to the housing 2 by means of four joint profiles 17 provided on each lateral side of the splitter 11. The joint profiles 17 have eyelets 18 through which the splitter 11 can be mounted to the housing 2 by vibration mounts (not shown) that act to reduce noise and to reduce wear and tear.

[0041] When in use the impeller 6 is driven by the motor 7 to rotate via the drive shaft 8. The motion of the impeller 6 creates a reaction force from water, which is transferred axially into the drive shaft 8 via the shaft fastener 19. The shaft shoulder 25 transfers the thrust into the angular bearing 13.2. The thrust transferred into the angular bearing 13.2, from there the reaction force is transferred via the bearing seat 24 into the splitter 11 and then into the housing 2 via the joint profiles 17.

[0042] In use the device 1 is strapped to a user's back and when the user is submerged in water it is turned on. The impeller 6 is then driven by the motor 7 via the drive shaft 8 to draw water through the flow-path 10. In particular, water is drawn in the fluid inlet 9, through the impeller 6 and out of the device via the propulsion passages 3. This provides a waterjet propulsion system that acts to propel the user forward. By controlling the Speedof the motor 7 the propulsion provided can be controlled appropriately. The user can then steer themselves by moving their body appropriately. In order that a user can control the speed of the motor and can turn the motor on and off control means (not shown) are provided as a handheld controller.