WATERJET PROPULSION APPARATUS

Abstract

 A waterjet propulsion apparatus comprising a motor (7), an impeller (6) driven by the motor (7) via a drive shaft (8), and a power source. A fluid flow-path (10) is formed through the apparatus, the flow-path (10) extending from at least one fluid inlet (9), through two propulsion passages (3), each propulsion passage (3) extending from a propulsion inlet to an outlet (4) located at a rear end of the apparatus. The impeller (6) is located within the flow-path (10), after the at least one fluid inlet (9), and before the propulsion inlet of the each of the propulsion passages (3). The motor (7) is located outside of the flow-path (10), between the two propulsion passages (3), and behind the impeller (6). 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 (1) that can be used by an individual.

Description

Field of the Invention

[0001] The present invention relates to a waterjet propulsion apparatus. The apparatus is particularly suitable for use in a personal marine propulsion device (sometimes known as dive propulsion vehicles) that can be held by an individual or otherwise attached to an individual to aid their propulsion through and under water. Such devices are generally used for leisure purposes but also have applications in any other situation in which it might be desirable to propel an individual through water without the use of a larger vehicle.

Background

[0002] Various personal marine propulsion devices are currently known. Typically, such devices consist of a propeller driven by a motor and a power supply contained within a watertight housing. The propeller is generally external to the housing but contained within a casing that allows water to be drawn through the propeller but protects the user from coming into contact with the propeller. The devices generally have handles formed on an outer surface of the housing to allow a user to hold onto the device during use. When in use, a user will hold the device out in front of them or between their legs in order to propel themselves through the water. These devices are relatively inefficient and provide only weak propulsion.

[0003] More recently personal marine propulsion devices using waterjet, rather than propeller, propulsion have become available. Waterjet propulsion is the method of propulsion utilised in jetskis. In waterjet propulsion, water is drawn through a flow-path formed through a device by means of an impeller located within the flow-path. Typically the flow-path consists of a passage having a single intake and a single outlet and the impeller is located centrally within the passage. Steering is achieved by changing the direction in which water leaving the outlet is directed using one or movable steering flaps or other equivalent means located in or at the outlet. The intake is generally positioned ahead of the impeller and is, for example, positioned on the lower side of a jetski. In a typical waterjet propulsion system the motor is positioned directly in front of the impeller outside of the flow-path and drives the impeller by means of a drive shaft that extends into the flow-path. In order to allow this construction the flow-path will typically deviate beneath or to the side the motor and the intake will be positioned beneath or to the side of the motor.

[0004] Personal marine propulsion devices having waterjet propulsion are desirable as the propulsion is generally more powerful and safer than propeller propulsion. However, the length of flow-path required to achieve efficient waterjet propulsion has been considered to make waterjet propulsion generally unsuitable for personal marine propulsion devices. In particular, currently available devices are excessively large and/or heavy.

Summary of the Invention

[0005] The present invention provides 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.

[0006] The present invention is advantageous in that it provides a waterjet propulsion apparatus that has a construction that allows it to be made to be very lightweight and compact. For example, the waterjet apparatus is suitable for use in a personal marine propulsion device and would allow such a device to be constructed to be lightweight and compact enough for it to be used by an individual without difficulty. The positioning of the motor at the rear of the apparatus the two propulsion passages results in a compact construction that can be significantly shorter in length than waterjet propulsion devices according to the prior art. Further, the flow-path having two propulsion passages after the impeller, rather than a single passage, allows the flow-path after the impeller to be provided in a more compact manner as compared to the prior art without reducing the outlet area, whilst still providing stable and directed propulsion.

[0007] The structure of the apparatus of the present invention also ensures that the fluid inlets can be substantially unobstructed by any other part of the apparatus. In particular, there is no need for any fluid inlet to deviate around the motor and/or the drive shaft as both the drive shaft and impeller are located behind, rather than in front of, the impeller.

[0008] The apparatus of the present invention comprises a suitable power source for driving the motor. In embodiments of the invention the power source may be a compact battery, such as used in similar existing apparatus.

[0009] In order to achieve a strong and directed thrust from the outlets of the propulsion passages, each propulsion passage may progressively reduce in cross-section from its propulsion inlet to its outlet. Forming the propulsion passages in this manner is advantageous in that results in a controlled decrease in pressure along each passage, and an increased velocity of the water exiting the propulsion passages, which can provide improved thrust at the outlets of the propulsion passage.

[0010] In order to achieve well directed thrust from the outlets of the propulsion passages said outlets may be substantially cylindrical, rectangular or any other suitable shape. If the apparatus of the present invention is used in a personal marine propulsion device there is no requirement for the apparatus or device to comprise means to change the direction of the water leaving the outlets of the propulsion passages. If no such means are present then a device comprising the apparatus of the present invention can be steered by the user directing the device appropriately. However, embodiments of the invention may comprise steering means located at or adjacent the outlets of the propulsion passages in order to vary the direction of the water exiting the outlets and thereby steer a device comprising the apparatus. Any such steering means can be formed in any manner apparent to the person skilled in the art, for example in the manner in which steering means of conventional jetskis are formed.

[0011] The propulsion passages may be formed in any manner apparent to the person skilled in the art. In embodiments of the invention both propulsion passages may be defined by a unitary splitter component that is mounted within the housing. For example, the unitary splitter may be a moulded component. In such embodiments the motor may be directly mounted to the splitter and the drive shaft will extend through the splitter into the flow-path.

[0012] In order to provide sufficient cooling to the motor when the apparatus is in use the apparatus may further comprise a heat-sink such as a heat conductive casing or heat exchanger that is in direct or indirect thermal connection with the motor and is arranged such that an outer surface of the heat sink is in direct contact with water when the apparatus is in use and submerged. In particular, it is advantageous that any such heat sink is not completely enclosed within any housing of the apparatus but includes a heat exchanger surface that is directly in contact with water when the apparatus is in use and submerged. As will be readily appreciated any such heat exchanger surface is advantageously arranged such that a user will not easily come into contact with the heat exchanger surface when a device comprising the apparatus is in use.

[0013] In order to minimise radial flow of water exiting the outlets of the propulsion passages it is advantageous that radially extending fins are located within the propulsion passages. In embodiments of the invention each propulsion passage may have one or more, preferably at least four, equally circumferentially spaced radially extending fins.

[0014] The apparatus may further comprise a housing substantially containing the components of the apparatus and 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.

[0015] A housing of an apparatus of the present invention may be formed in any suitable manner. If the apparatus forms part of a personal marine propulsion device the housing may be formed such that it can be used by an individual in a simple manner. For example, the housing may have one or more handles located on an outer surface to allow a user to hold on to the device when in use. Alternatively or additionally the housing may be formed as a back-pack and comprise one or more straps to allow a user to wear the device as a back-pack.

[0016] The components of the invention may be mounted to a housing in any suitable manner. In embodiments of the invention one or more of the components may be mounted to the housing by vibration mounts to reduce noise of the apparatus during operation and to reduce wear and tear of the components during operation of the apparatus. In embodiments of the invention the propulsion passages may be mounted to a housing by means of vibration mounts, this may be particularly advantageous if the propulsion passages are defined within a splitter formed as a unitary component.

[0017] The impeller of the present invention may be formed in any suitable manner. In embodiments of the invention the impeller may be formed by 3D printing using solid laser sintering.
The drive shaft of the apparatus of the present invention may be mounted within the apparatus in any manner apparent to the skilled person. Typically, the drive shaft will be mounted within one or more bearings. Such bearings may be of any suitable type including, but not limited to, waterproof bearings or ceramic bearings. Ceramic bearings may be preferred as waterproof sealing is not required thereby reducing the cost and complexity of the apparatus. The drive shaft may be mounted within the apparatus by means of one or more thrust bearings that act to transfer thrust from the drive shaft to the apparatus. Alternatively or additionally, the drive shaft may be mounted within the apparatus within one or more brass bushes.
The motor of the apparatus may be a waterproof motor that can be operated in direct contact with water. This may be preferred as it is not necessary to mount such motors in waterproof casing and waterproof motors can be operated in direct contact with water to provide cooling to the water, thereby reducing the need for complex and/or heavy heat sinks.

[0018] In order to prevent solid objects entering the fluid flow-path embodiments of the invention comprise a rigid mesh provided completely across the at least one fluid Inlet. A rigid mesh may be formed of any suitable material. In embodiments of the invention a rigid mesh formed of plastic coated metal is provided. This may be preferred as it can provide a sufficiently rigid and strong structure whilst also providing good corrosion resistance. A rigid mesh may have a hexagonal mesh. If formed of appropriate material a rigid mesh may be heat-staked to the at least one fluid inlet in order to avoid gaps or protruding edges around edges of the mesh, which could affect flow efficiency through the fluid flow-path.

[0019] In order to provide strength to the at least one fluid inlet and/or to help direct fluid flow through the fluid flow-path an intake grate may be provided in the at least one fluid inlet. An intake grate may comprise one or more support members extending across the at least one fluid inlet and arranged to extend in a direction of fluid flow through the at least one fluid inlet. Providing a suitably formed intake grate can increase laminar flow through the at least one fluid inlet. An intake grate can extend across a height of the at least one fluid inlet to transfer force to the intake grate and thereby prevent damage to the at least one fluid inlet during operation of the apparatus. An intake grate can be mounted within an at least one fluid inlet in any appropriate manner including, but not limited to, fastening bolts at or near a periphery of the intake grate.

[0020] Further features and advantages of the present invention will be apparent from the preferred embodiment that is shown in the Figures and described below.

Drawings

[0021] 

Figure 1

is an image of a device according to an embodiment of the present invention;

Figure 2

is a partial cross-section of components of the embodiment of Figure 1;

Figure 3

is a three-dimensional view of a splitter of the embodiment of Figures 1; and

Figure 4

is a side view of components of the embodiment of the previous Figures.

[0022] 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 Figure 1. The housing 2 encloses most of the components of the device 1 such that all that is visible in Figure 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.

[0023] A partial cross-section through components of the device 1 of Figure 1 is shown in Figure 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.

[0024] 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.

[0025] 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.

[0026] 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 Figure 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.

[0027] 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.

[0028] 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.

[0029] 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 six radially 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.

[0030] Further details of the device 1 can be seen in Figure 4. In particular Figure 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.

[0031] 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.

[0032] 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.

[0033] 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.

Claims

1. A waterjet propulsion apparatus for a propulsion device (1) comprising a motor (7), an impeller (6) driven by the motor (7) via a drive shaft (8), and a power source; wherein:

a fluid flow-path (10) is formed through and contained within the apparatus (1), the flow-path (10) extending from at least one fluid inlet (9) located at a front end of the apparatus through two propulsion passages (3), each propulsion passage (3) extending from a propulsion inlet to an outlet (4) located at a rear end of the apparatus (1);

the impeller (6) is located within the flow-path (10), after the at least one fluid inlet (9), and before the propulsion inlet of the each of the propulsion passages (3); and

the motor (7) is located outside of the flow-path (10), within a rear portion of the apparatus (1), between the two propulsion passages (3), and behind the impeller (6).

2. An apparatus according to claim 1, wherein each propulsion passage (3) reduces in cross-section from its propulsion inlet to its outlet (4).

3. An apparatus according to claim 1 or claim 2, wherein the outlets (4) of the propulsion passages (3) are substantially cylindrical or rectangular.

4. An apparatus according to any preceding claim, wherein the propulsion passages (3) are defined within a splitter (11) formed as a unitary component.

5. An apparatus according to claim 4, wherein the motor (7) is mounted to the splitter (11) and the drive shaft (8) extends through the splitter (11) into the flow-path (10).

6. An apparatus according to any preceding claim, wherein radially extending fins (14) are located within the propulsion passages (3) to direct water expelled from the device (1).

7. An apparatus according to any preceding claim comprising a housing (2) substantially containing the components of the apparatus and wherein the at least one fluid inlet (9) is formed at a front end of the housing (2) and the outlets (4) of the propulsion passages (3) are formed at a rear end of the housing (2).

8. An apparatus according to claim 7, wherein the housing (2) has one or more handles located on an outer surface to allow a user to hold on to the device (1) when in use.

9. An apparatus according to claim 7 wherein the housing (2) is formed as a back-pack and comprises one or more straps to allow a user to wear the device (1).

10. An apparatus according to any of claims 7 to 9, wherein one or more components of the apparatus are mounted to the housing (2) by means of vibration mounts (17).

11. An apparatus according to any preceding claim, wherein the drive shaft (8) is mounted within the apparatus on ceramic bearings (13) and/or at least one thrust bearing.

12. An apparatus according to any preceding claim, wherein the motor (7) is waterproof and can be operated when in direct contact with water.

13. An apparatus according to any preceding claim, wherein a rigid mesh (21) is provided across the at least one fluid inlet (9) to prevent solid objects entering the fluid flow-path (10).

14. An apparatus according to any preceding claim, wherein a grating (22) is provided in the at least one fluid inlet (9).

Drawing