This invention relates to diver-propulsion units.

The invention is concerned especially with diver-propulsion units which are for use by divers principally when swimming underwater, and which are of the kind to be held by the diver or for attachment to them.

According to the present invention there is provided a diver- propulsion unit comprising a propeller for providing propulsion thrust of the unit, mounting means defining a cylindrical duct, means mounting the propeller for rotation coaxially within the cylindrical duct, a motor mounted on the mounting means externally of the duct, and coupling means for coupling the motor to the propeller to drive rotation of the propeller.

The mounting means may have a forward part for intake of water, and a rear part defining the duct. The forward part may extend to the duct for defining a path into the duct for the intake- water. This intake-water path may be of reducing cross-sectional area towards the duct for increasing the inflow velocity of water to the propeller.

The coupling means of the diver-propulsion unit of the invention may include drive means that extends radially with respect to the rotational axis of the propeller for coupling the motor drivingly to the propeller. The drive means may comprise a belt-drive, a chain-drive or a shaft-drive.

The diver-propulsion unit may have an external casing that encloses the mounting means and the motor. This external casing may comprise a front-casing for defining a water inlet to the diver-propulsion unit, and a rear-casing for defining a water outlet from the unit.

A diver-propulsion unit according to the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view from the front of the diver- propulsion unit according to the invention;

Figures 2 to 6 are, respectively, a front elevation, a side elevation, a plan view from above, a plan view from below, and a rear elevation of the diver-propulsion unit of Figure 1;

Figures 7 and 8 are sectional elevations on the lines VII-VII and VIII-VIII respectively of Figures 2 and 3 ;

Figure 9 is a front elevation of the diver-propulsion unit of Figure 1 with its front-casing and main seal part removed;

Figure 10 is a sectional elevation of the diver-propulsion unit of Figure 1, the section being taken on the line X-X of Figure 4;

Figure 11 is a front perspective view of a nozzle-mount that provides a core structural element of the diver-propulsion unit of Figure 1; and

Figures 12 to 14 are, respectively, a front elevation, a sectional side elevation, and a plan from below of the nozzle- mount of Figure 11, the section of Figure 13 being taken on the line XIII-XIII of Figure 12.

The diver-propulsion unit to be described is for use by a scuba or other diver principally when swimming underwater, for the purpose of achieving increased progress and manoeuvrability. Referring to Figures 1 to 6, the diver-propulsion unit 1 is of a compact, short-cylindrical or ring form having front- and rear- casings 2 and 3 respectively that are of moulded plastics (for example, acrilonitrile-butadiene-styrene, otherwise known as 1ABS') - The front-casing 2 has a peripheral rim 4 that is supported by radial ribs 5 which extend from a radial cover-shell 6. The cover-shell 6 is integral with the rim 4 at the bottom of the unit where there is a downward bulge 7 in the rim 4 that closes onto a motor-housing 8 of the rear-casing 3.

The propulsion unit 1 is to be held with both hands by the diver, and to facilitate this, hand-grips 9 are mounted diametrically opposite one another on the rear-casing 3. The hand-grips 9 are inclined upwardly at 45 degrees towards the front of the unit 1 so as to enable the swimming diver to hold the unit underwater with both hands forward and just below him/her keeping drag to a minimum and allowing exhaust of water from the unit 1 to be unobstructed by the diver's body. Water is drawn into the front of the unit 1 through the gaps between the ribs 5 and is forced rearwardly out through gaps between ribs 10 of the rear-casing 3 to provide propulsion. Turning from forward propulsion is achieved simply by using the hands on the grips 9 to turn the unit 1 to the required extent in the desired direction, and ascent or descent can be achieved likewise by inclining the unit 1 up or down.

Referring to Figures 7 and 8, the front- and rear-casings 2 and 3 are clamped within the propulsion unit 1 to a substantially- cylindrical nozzle-mount 11 (for example, of ABS) with a circumferential flange 12 of the mount 11 sandwiched between them. The nozzle-mount 11, which is shown more clearly in Figures 9 to 14, has a "top-hat" form with the flange 12 extending outwardly from the periphery of a cylindrical rim 13 that is reduced in diameter rearwardly within the propulsion unit 1 down to a cylindrical duct-portion 14 of near-constant internal diameter (a draft angle of one degree is involved for injection- moulding purposes) . A propeller 15 for providing the propulsion thrust of the unit 1 is mounted on an axial drive-shaft 16 for close rotation within the duct-portion 14. The shaft 16 is journalled at its rear-end 17 in a central socket 18 of the rear- casing 3 and at its forward-end within a central hub 19 of the casing 3. Input-drive to the shaft 16 is provided via epicyclic- gearing 20 that is housed within the hub 19.

An input shaft 21 to the gearing 20 is driven from an electric motor 22 mounted in the housing 8 of the rear-casing 3 at the periphery of the propulsion unit 1. Drive from the motor 22 is transmitted from an output shaft 23 of epicyclic gearing 24 mounted with the motor 22, to the input shaft 21 of the epicyclic gearing 20 via a belt 25 (of ^V V- or multiple 'V -section, or toothed) . The belt 25 runs between two pulleys 26 mounted respectively on the output shaft 23 and the input shaft 21. The shafts 21 and 23 are journalled in respective sockets 27 and 28 of the front-casing 2, and the belt 25 and its pulleys 26 are housed within a radial channel-shell 29 of the nozzle-mount 11 that is closed by the cover-shell 6 when the front- and rear- casings 2 and 3 are clamped together onto the flange 12 of the nozzle-mount 11.

The forward-part of the nozzle-mount 11 is configured internally for streamline or venturi-style intake-flow to the propeller 15 in the duct-portion 14. This is achieved by means of fairing 30 (see Figures 1 and 8) of the front-casing 2 that projects into the cylindrical rim 13 of the nozzle-mount 11. The fairing 30 establishes an intake-water flow path of reducing cross-sectional area into the duct-portion 14 so as to provide for increase in the inflow velocity of water to the propeller 15. The electric motor 22 is powered for driving the propeller 15 from re-chargeable batteries (preferably lithium-ion batteries) housed in streamlined and watertight projections or pods 31 spaced from one another round the external periphery of the rear- casing 3 of the propulsion unit 1. Powering of the motor 22 from the batteries is via a motor-energizing circuit that in addition to including battery-control circuitry (not shown) incorporates a plug-in-socket link. This link comprises a socket 32 mounted in the rear-casing 3 to open rearwardly of the unit 1, and a plug 33 that is secured by a strap 34 to the casing 3 adjacent the socket 32. Until the plug 33 is engaged in the socket 32, the motor- energizing circuit remains open, but even with the plug 33 engaged in the socket 31, the circuit is not closed to energize the motor 22 until two switches 35 associated with the two hand- grips 9 respectively, are both actuated concurrently in gripping the hand-grips 9. Thus, as a safety precaution, the propeller 15 is not driven by the motor 22 unless the plug 33 is in engagement with the socket 32 and the diver has hold of both hand-grips 9 with both switches 35 actuated.

Re-charging of the batteries is carried out by plugging a power source into the socket 32. The plug (not shown) used in this case links through the socket 32 into a charging circuit that includes the battery-control circuitry but by-passes the motor 22 and the switches 35. The socket 32 may be re-located to a position elsewhere in the rear-casing 3; for example to a location under the right-hand handle 9.

The operating voltage of the motor 22 is, for example, 18 volts, and the unit 1 includes provision for ensuring that it is cooled sufficiently to avoid over-heating. In this respect, the pods 30 projecting from the casing 3 add to the internal and external surface-areas of the unit 1 to give an added cooling effect of the water-flow, and this is supplemented by further increase in the surface-areas resulting from indentations 36 elsewhere round the rear-casing 3 (see Figures 3 and 5) . The latter further increase in surface areas may be achieved by providing projections from the casing 3 instead of the indentations 36 in it.

The front and rear-casings 2 and 3 are sealed water-tightly to the nozzle-mount 11 with pairs of sealing rings 37 and 38 (see Figures 7 and 8) located within respective pairs of circumferential grooves 39 and 40 (see Figures 11, 13 and 14) of the rim 13 and duct-portion 14. Although there is normally adequate water-tight sealing between the cover-shell 6 of the front-casing 2 when closed onto the radial shell 29 of the nozzle-mount 11, this is not critical in that transmission of drive by the belt 25 via the pulleys 26 is largely unaffected by entry of water into this part of the casing. Even if water floods this part of the casing, flooding of the main chamber housing the motor 22 and its batteries and electronics, is blocked by a rotary-shaft seal of the shaft 23 (a quad seal or an 'O'-ring may be used instead).

Although a belt-drive is used in the present example, this could be replaced, for example, by a chain-drive, or by a shaft-drive involving a transmission shaft running within the closed radial shell 29. Coupling in this latter case from the output shaft 23 to the transmission shaft, and from the transmission shaft to the input shaft 21, might be by bevel gearing.

The diver-propulsion unit 1 described has significant advantages over previous proposals. In particular, the general layout of the unit with the motor and its batteries located peripherally enables a very compact construction with low drag and largely unobstructed in-flow to the propeller, to be realized. Moreover, by locating the motor peripherally it is readily possible to avoid over-heating, using external water-flow over the unit 1 to provide the cooling required without adding unnecessary bulk to the unit. Further in this respect, the distribution of the batteries peripherally of the unit avoids the necessity for a large battery pod. The use of a belt-drive (or a chain-drive) has the advantage of simplicity of drive-transmission, and the location of the belt (or chain) within the radial shell of the rear-casing provides for easy maintenance in that access to it can be gained simply by removing the front-casing, and with it the cover-shell, without breaking the main water-tight sealing within the unit of the rear-casing with the nozzle-mount.