GB2415913A

GB2415913A - Underwater propulsion unit

Info

Publication number: GB2415913A
Application number: GB0415526A
Authority: GB
Inventors: Dimitri Rembisz
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-07-10
Filing date: 2004-07-10
Publication date: 2006-01-11
Anticipated expiration: 2024-07-10
Also published as: GB0415526D0; GB2415913B

Abstract

An underwater propulsion unit comprises two sections, one of which contains the motor and battery A, and the other the propeller D. The two sections are magnetically coupled together and attached to the air tank B. An on/off switch E is attached by a wire to the motor housing and comprises a reed switch (69, fig 6) and a light emitting diode (67, fig 6) in the handle (63, fig 6).

Description

Field of the invention:

The invention relates to underwater propulsion apparatus. Particularly, but not exclusively, the invention applies to underwater propulsion apparatus for use by scuba divers.

As prior art in the field of underwater propulsion apparatus, there may be mentioned: US3635188; US3995578; US3422787; US4938722; US3745961; US4467742; US4700654; US5984739; US6341993

Background of the invention:

The existence of underwater propulsion apparatus is well known and has many users within the diving world. For example, over the last decade or so, scuba tank mounted propulsion apparatus has been developed and introduced to the market. Detailed descriptions of tank mounted diver propulsion units are given in, inter alla, U.S. Pat Nos. 4,467,742 and 5,984,739. From these and other prior art documents, it can be seen that it can enhance the diver's comfort and speed as well as increase the effective use of the diver's diving time.

It is also desirable for a tank mounted diver propulsion unit to be both compact and reliable over a wide range of water depths.

In some known arrangements, the tank mounted diver propulsion unit has been placed above the scuba tank, resulting in an offset between the thrust of the propulsion unit and the diver's main longitudinal body axis (see for example, U.S. Pat. No. 5,984,739).

This has the tendency to induce a downward force on the diver's attitude during its motion and could create an unwanted increase in the diver's depth.

In arrangements of the type showed in U.S. Pat. No. 4,467,742 the motor is snugly fitted into a sealed housing. The output shaft extends to the propeller through a watertight sealing arrangement, hence providing a dynamic seal against water ingress thus protecting the electrical motor. However, in the current art, the increase in depth against a dynamic seal will increase friction against the output shaft, hence reducing the motor efficiency as depth increases. Furthermore, a dynamic sealing arrangement will have a pressure limitation, as depth increases, and be subjected to wear caused by the rotation of the output shaft resulting in a less than desirable reliability.

Summary of the invention:

The present invention provides an underwater propulsion system, which is free of the problems of existing systems of water ingress through the dynamic seals, by the elimination of this seal and, by the provision of a pressure equalization system which further increases its operational water depth range. .: Although the application of the invention includes all forms of underwater propulsion requirements, it is particularly applicable to propulsion units for scuba divers, as it is amenable to attachment to a scuba air tank. This application is used as an example to describe the invention in the detailed description.

The invention comprises:- 1) An electrically driven propulsion unit. 2) A battery power pack with battery switching and state indication circuitry. 3) A remote control lead/switch assembly for the remote operation of the propulsion unit.

Figures 1 and 2 show the typical arrangement of the system fitted to a scuba diver.

Detailed description of the invention:

Description of the drawings:

Fig 1 shows a side view of a diver equipped with the propulsion system.

Fig 1 shows a top plan view of a diver equipped with the propulsion system.

Fig 3 shows a schematic of the propulsion unit.

Fig 4 shows a schematic of the magnetic coupling arrangement.

Fig 5 shows a sectioned view drawing of a practical implementation of the propulsion unit.

Fig 6 shows the arrangement of the remote on/off power switch and battery status indicator.

Fig 7 shows a schematic of the electronics installed within the power battery pack.

Fig 8 shows a typical battery voltage depletion versus time curve.

1. Propulsion Unit (refer to figures 3 & 5) The propulsion unit is divided into two sub-assemblies operating together, but capable of working in different environments. The environments in which said sub- assemblies operate are distinctively called internal and external sub- assemblies. The workings of the sub-assembly, which is subjected to the internal environment, are protected, whereas the workings of the sub- assembly, which is subjected to the external environment, are exposed to seawater.

1.1. Said Internal sub-assembly includes: Pressure compensated housing means encasing a rotation motion producing means coupled with an internal magnetic coupling means.

1.1.1 Said pressure compensated housing means comprising: Housing means; Said housing means is made of a housing (26) closed at one end by a bulkhead (21).

Said bulkhead (21) is sealed by an o'ring (20) against said housing (26).

Opposite end of said housing (26) is close by a diaphragm (28). Said diaphragm (28) is sealed by o'ring (22) against said housing (26). Said diaphragm (28) is fastened to housing (26) by a clamping ring (29). Shape of said diaphragm (28) may be, but is not restricted to, a flat disc. A nominal value of 1.5mm or less may be used for the diaphragm thickness. Material of said diaphragm (28) must be electrically non conductive. A typical material suitable for the purpose is phenolic fabric laminated plastic.

Variable volume means; A bladder or a closed bellow (27) may form said variable volume means. Said variable volume means is fitted to a pressure port present on the inner side of said bulkhead (21). Seawater pressure is transmitted via above mentioned pressure port to variable volume means. (As shown by arrow A of figure 3) Pressure medium; Said pressure medium (18) is a fluid kept within the enclosure formed by said housing (26) said bulkhead (21) said diaphragm (28) and said variable volume means. Said pressure medium bathes said rotation motion production means coupled with said internal magnetic coupling means. Said pressure medium has dielectric and lubricating properties.

1.1.2 Said rotation motion producing means comprising: Electrical motor; Said electrical motor (17) may be coupled with gearbox (34). The mechanical arrangement of said geared motor (17, 34) is fitted to the inner side of said bulkhead (21) in order to provide a torque reaction path. Means of attachment of said geared motor (17,34) to bulkhead (21) might use a mounting plate (19) and pillars (35) as part of this torque reaction path.

The electrical lead terminations of said motor (17) are fed through the thickness of bulkhead (21). The engineer will find in the current art means of forming an electrical path isolated from bulkhead (21). To this effect proprietary items such as glass to metal type connectors or other types of waterproof connector assemblies may be used.

The output end of gearbox (34) is coupled to driving member (12) of said internal magnetic coupling means.

1.1.3 Said internal magnetic coupling means comprising: Driving member (12) Said driving member (12) is fitted with a polar array of four magnets (14). The magnetic array may be populated with more than two magnetic pairs. Said magnets (14) are arranged on one face of said driving member (12) so that each adjacent magnet has alternate polarities (refer to items 14 of figure 4).

The material of driving member (12) has magnetic properties. A typical material suitable for the purpose of driving member (12), is mild steel. This choice of material is purposeful in order to increase magnetic field strength.

Each magnet is glued to said driving member (12) using metal-loaded epoxy glue.

To enable a smooth motion of said external magnetic coupling means within the environment of said pressure medium (18), the polar array is encapsulated to said driven member (12), up to the height of the magnets. The encapsulant (16) used may be Duralco 4525, which is a potting compound available from Cotronics Corporation of Brooklyn, N.Y.

Magnetic face of said driving member (12) is kept to within a narrow gap of said diaphragm (28) inner face. The magnets are of the permanent magnet variety made out of neodymium-iron boron, a rare earth material. A nominal gap of 0.5mm may be used as a separation between the magnet face and said diaphragm (28) inner face. To this effect a thrust bearing (15) provides support to said driving member (12) in order to keep the above mentioned gap constant. Said thrust bearing (15) is itself supported by said housing (26).

The above mentioned arrangement provides an axial load reaction path against the magnetic attraction emanating from the reciprocal driven magnetic member (11).

1.2 Said external sub-assembly includes: External magnetic coupling means coupled with a propeller shaft sub-assembly means.

Said propeller shaft sub-assembly means is guided by bearing sub-assembly means, which is itself mounted into back-end sub-assembly means.

1.2.1 Said external magnetic coupling means comprising: Driven member (11) ; Said driven member (11) is fitted with a polar array of magnets (13) matching driving member's (12) magnetic array. Said magnets (13) are arranged so that each adjacent magnet has alternate polarities (refer to items 13 of figure 4).

The magnets are of the permanent magnet variety made out of Samarium cobalt, a rare earth material.

Each said magnet (13) is glued to the face of said driven member (11) using metal- loaded epoxy glue. To enable a smooth motion of said external magnetic coupling means within the seawater environment, the polar array is encapsulated to said driven member (11), up to the height of the magnets. The encapsulant (16) used may be Duralco 4525, which is a potting compound available from Cotronics Corporation of Brooklyn, FLY.

Material of said driven member (11) has magnetic properties and may be protected against corrosion by a film of epoxy paint. Said driven member (11) may also be made of precipitation hardening martensitic stainless steel that satisfies both the magnetic and corrosion resistance requirements. This choice of material is purposeful in order in

increase magnetic field strength.

1.2.2 Said propeller shaft sub-assembly means comprising: Drive shaft (33) ; Said drive shaft (33) mechanically links said driven member (11) to propeller (23).

Castle nut (24); Said castle nut (24) is fitted to a threaded portion of said drive shaft (33). Said castle nut (24) has dual purpose. Said castle nut (24) firstly reacts against the axial load from said magnetic coupling means magnetic attraction. Secondly said castle nut (24) enables a narrow gap to be set between said driven member (11) magnetic face and said diaphragm (28) outer face. A nominal value of 0.5mm may be used as a separation between these two later mentioned items.

1.2.3 Said bearing sub-assembly means comprising: Axial bearing (36); Said axial bearing (36) is tolerant of seawater environment and may be made of self lubricating polymer. Said axial bearing (36) supports said propeller shaft sub-assembly means in its rotational motion. Said axial bearing (36) is fitted to said back-end sub assembly means.

Thrust bearing (30); Said thrust bearing (30) is tolerant of seawater environment and may be composed of thrust washers made of selflubricating polymer. Said thrust bearing (30) may also be composed of a shaft washer with raceway groove, a ball and cage thrust assembly and a housing washer with raceway groove. The later mentioned components may be made of materials showing galvanic compatibility. As far as material choice is concerned, ceramic balls associated with aluminium bronze for both raceway-grooved washers, may be used.

Said thrust bearing (30) is fitted to said backend sub-assembly means and completes the axial load reaction path in conjunction with castle nut (24) .

1.2.4 Said back-end sub-assembly means comprising: Back-end housing (37); Said back-end housing (37) is a receptacle for said external magnetic coupling means said propeller shaft sub-assembly means and said bearing sub-assembly means. Said back-end housing (37) may be made of polymeric material. Said back-end housing (37) is fastened against clamping ring (29).

Propeller guard (31); Said Propeller guard (31) is placed around the propeller fins to protect the diver. Said Propeller guard (31) is attached to said back-end housing (37).

2. Battery Switching and State Indication - Electronic Assembly The electronic assembly is placed within the sealed battery power pack. Inside the battery power pack is typically a plurality of rechargeable batteries such as 1.2V NiMH (nickel metal hybrid) 13 amp cell batteries suitably interconnected in series. Electrical penetrations for power and remote control leads are sealed. To this effect, proprietary items such as glass to metal type connectors or other types of waterproof connector assemblies may be used. The inside of the battery power pack remains at atmospheric pressure.

The electronic assembly has several purposes: (refer to figure 7) 2.1 The electronic assembly acts as an electronic power relay. The closing of the reed switch (item SW1 Figure7) is switched on by a Field Effect Transistor (Q1), also known in the current art as FET. Once Q1 is ON, it closes the circuit between battery cells and motor of the propulsion unit.

2.2 The electronic assembly monitors the voltage level of the battery cells. As long as the voltage supplied to Q2 through Zener diode ZD2 remains stable above 1.15V per battery cell (refer to arrow F of figure 8) , the bipolar transistor Q2 remains ON and energise the green section of the tri-colour LED while Q3 is OFF since there is no base current flowing through R7. If the voltage drops below 1.1 5V per cell, Q2 will turn OFF, de-energise the tri-colour LED green section, and Q3 will turn ON, due to its base current flowing through R7, R5 and R6, thus energising the red section of the LED. The third colour of the LED, amber, is not utilised since both anodes of the LED are not energised at the same time.

The arrow F shown on Figure 8 highlights the point on the battery cell voltage depletion curve where the LED is switched from green to red.

2.3 The circuit is further protected against accidental failure by: Zener diode ZD1, which protects the gate of field effect transistor Q1 against undesirable voltage increases (for example due to a battery over-charge, or a failure of the 1 OA fuse whilst charging).

2.3 Diode D1 protects the drain of FET Q1 against accidental polarity reversal during battery charging and excessive voltage during switching of the motor.

3. ON/OFF Switch Assembly The ON/OFF switch assembly (refer to figure 6) is attached to the end of the remote control lead (61). The opposite end of said control lead (61) is fed to one end of the power battery pack (refer to item E of figure 1) and is connected internally to the electronic assembly. For easy reach by the diver, the on/off switch assembly is routed over the diver's shoulder and clipped to the diver's BCD, also known in the current art as Buoyancy Control Device or Stab jacket.

The ON/OFF switch assembly comprises the following main components: 3.1 A magnetic switch, also know in the current art as a reed switch.

In essence, a reed switch is a self-contained electrical device of which contacts are contained within an airtight capsule. The contacts are inherently protected from corrosion by the above-mentioned capsule. In this application, the reed switch (69) is further protected against the effects of hydrostatic pressure. To achieve this, the switch connected to said control lead (61) is placed within switch embodiment (70). Said switch embodiment (70) is filled with a transparent epoxy encapsulant (68) . The compression strength of the encapsulant is chosen to match the prerequisites dictated by deep sea diving.

3.2 A magnet (64) placed within a handle (63) is fitted to the above mentioned switch embodiment. The magnet actuates the reed switch to an on status when the handle is manually slid along said embodiment (70). A recoil spring (65) moves said switch embodiment (70) back to its original position once released and puts said reed switch (69) to an off status.

3.3 A tri-colour light emitting diode (67) also known in the current art as an LED is also fitted within the above mentioned switch embodiment. In first instance, the purpose of said LED (67) is to give the diver a visual indication that the battery pack is still healthy. Said LED (67) changes automatically to another colour when the battery power pack energy reserve starts to run low.

As well as the reed switch, the LED is further protected against the effects of hydrostatic pressure. To achieve this, the LED connected to its lead is placed within the above-mentioned switch embodiment (70) and is encapsulated within the embodiment, together with the Reed switch.

3.4 To enable the diver to monitor the status of said LED (67) said transparent epoxy encapsulant (68) will be vacuum moulded to form a protective lens which will enable said LED (67) to remain visible in either of the operating positions of said switch embodiment (70).

The encapsulant (68) used may be Duralco 4462, which is a potting compound available from Cotronics Corporation of Brooklyn, N.Y.

The logic of the electronic assembly attached to the above switch and LED is explained in detail in section 2.

Claims

Claims What is claimed is: 1. A subsea propulsion system comprising: A

motorised underwater propulsion unit rendered immune to water ingress and the effects of water pressure increases, an on/off switch assembly means connected to a battery power pack associated with an electronic assembly.
2. A device according to claim 1 where said underwater propulsion unit is mounted on a scuba air tank.
3. A device according to claim 1 where said underwater propulsion unit uses a magnetic coupling means between two separate sub-assemblies working together into two different pressurised media.
4. A device according to claim 1 where said underwater propulsion unit comprises a pressure compensated housing means encasing a rotation motion producing means coupled to the driving member of said magnetic coupling means.
5. A device according to claim l where said underwater propulsion unit includes a back-end assembly means, which provides housing and bearing means to the driven member of said magnetic coupling means.
6. A device according to claim 5 where said driven member of said magnetic coupling means is mechanically coupled to a propeller.
7. A device according to claim 1 where said underwater propulsion unit is electrically connected to said electronic assembly means of said battery power pack.
8. A device according to claim 1 where said on/off switch assembly means provides a waterproof embodiment to a reed switch, said reed switch is electrically connected to said electronic assembly means of said battery power pack.
9. A device according to claim 1 where said on/off switch assembly means provides a waterproof embodiment to a light emitting diode, said light emitting diode is electrically connected to said electronic assembly means of said battery power pack.
10. A device according to claim 8 where said on/off switch assembly means includes a handle housing a magnet, which slides along the assembly to operate said on/off switch.
11. A device according to claim 9 where said light emitting diode remains visible to a diver in either position of said handle.
12. A device according to claim 9 where a lens made from a transparent epoxy encapsulant protects said light emitting diode.
13. A device according to claim 10 where said handle returns automatically to an off position once released.
14. A device according to claim 7 where said electronic assembly monitors the battery energy level.