Apparatus for converting buoyancy forces of a gas in a liquid into mechanical torque

Abstract

A buoyancy-powered motor is disclosed. The motor comprises a liquid chamber 2 and an output shaft 5 extending beneath the tank 2. A buoyancy vessel 16 is arranged to receive gas from a manifold 18 and

Description

Paul Stewart APPARATUS FOR CONVERTING BUOYANCY FORCES OF A GAS IN A LIQUID INTO MECHANICAL TORQUE TECHNICAL FIELD OF THE INVENTION This invention relates to apparatus for converting buoyancy forces of a gas in a liquid into mechanical torque which can, for example, be used to drive an electricity generator. BACKGROUND Electricity generators are used in remote locations in many parts of the world where there is no convenient access to an electricity supply grid, such as on ships for example. Such generators are commonly driven by a petrol or diesel engine which provides the torque to operate an AC or DC generator. However, with fossil fuels in increasingly short supply, and environmental concerns over atmospheric pollution, there is a requirement for a clean, efficient and compact apparatus for producing the necessary torque. Whilst various kinds of “buoyancy engine” are already known for converting gas pressure into torque there is still a requirement for a relatively compact, reliable and efficient form of apparatus. SUMMARY OF THE INVENTION When viewed from one aspect the present invention proposes apparatus for converting buoyancy forces of a gas in a liquid into mechanical torque: - a liquid chamber (2), - an output shaft (5) extending beneath the liquid chamber, - a gas manifold (18) in the liquid chamber, - a gas supply (3) for the gas manifold, - a buoyancy vessel (16) movable in the liquid chamber and arranged to receive gas from the gas manifold, - a rotatable member (8) mounted at the bottom of the liquid chamber (2) and passing through a wall of the liquid chamber, - a one-way clutch arrangement (12a, 12b) coupling the rotatable member (8) to the output shaft (5), - a first flexible element (13) wound about the rotatable member (8) within the liquid chamber (2) and tethered to said buoyancy vessel (16) such that the buoyancy vessel rotates the rotatable member, - a return arrangement (14, 25, 26) located outside the liquid chamber (2) and arranged to rotate the rotatable member (8) in an opposite sense to the buoyancy vessel (16) such as to rewind the first flexible element (13) onto the rotatable member (8). The configuration of the apparatus is both compact and efficient. Apart from electricity generation, the apparatus is particularly suitable for low profile uses such as driving boat or ship propellers, for example. Further advantageous features of the apparatus are specified in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings: Figure 1 is a general view of apparatus for converting the buoyancy forces of a gas in a liquid into mechanical torque; Figure 2 is a general view of part of a drive arrangement which is provided for each chamber of the apparatus; Figure 3 is another general view showing part of the interior structure of the chambers; Figure 4 is a general external view of one of the chambers; Figure 5 is a ghost view of the lower part of the chamber; Figure 6 is a similar ghost view of the upper part of the chamber. DETAILED DESCRIPTION OF THE DRAWINGS Referring firstly to Fig. 1, the apparatus include a panel-like casing 1 which contains a number of vertically disposed chambers 2. The chambers may be open at the top and are conveniently arranged side-by-side in a row. An air supply 3, e.g. an air blower, pump, compressor, or pressurised air tank, is located at one end of a branched pipe 4 to supply air to each of the chambers 2. At the opposite end of the casing 1 an output shaft 5 which extends beneath the chambers 2 supplies mechanical torque to drive an AC or DC generator 6 of the kind which produces electricity by electromagnetic induction. The opposite end of the output shaft 5 may be provided with a starter 7 such as a small starter motor or hand crank for example. Referring to Fig. 2, at the bottom of each of the chambers a respective rotatable member in the form of a drive shaft 8 is mounted in bearings 9. The drive shaft extends through opposite walls of the chamber, one of which ends turns the output shaft 5 via enmeshed gears 10 and 11. Gear 10 and / or gear 11 is mounted on the respective shaft via a suitable one-way clutch bearing 12a, 12b such as a ratchet, needle roller, sprag clutch etc. First and second flexible elements 13 and 14 are wound about each drive shaft 8, the first element 13 being contained within the chamber 2 and the second element 14 being located outside the chamber. The flexible elements may be cables, chains, lines, ropes etc., and are wound in opposite directions on the drive shaft such that one element unwinds from the shaft as the other winds onto the shaft. As shown in Fig. 3, each chamber 2 contains a buoyancy vessel 16 which can move up-and-down within the chamber 2 with sufficient space between the buoyancy vessel and the wall of the chamber for liquid to move freely around the buoyancy vessel. The buoyancy vessel is open at its bottom end 16a and is provided with an air escape valve 17 at its top end. Beneath the buoyancy vessel 16 an air manifold 18 is fixed within the chamber supplied with air from a branch 19 of the air pipe 4 via an inlet control valve 20 (e.g. solenoid-operated) and a non-return valve 21. An air transfer pipe 22 passes through the top of the air manifold with its bottom end terminating within the manifold. When the buoyancy vessel 16 is in the position shown, the top of the transfer pipe 22 passes into the buoyancy vessel through the open bottom end 16a. There is sufficient space between the transfer pipe 22 and the open end 16a for liquid to simultaneously flow out of the buoyancy vessel as gas enters the buoyancy vessel through the transfer pipe. The bottom end 23 of the manifold 18 may be open allowing the first flexible element 13 to pass into the air manifold 18 and travel upwards through the air transfer pipe before being tethered to the buoyancy vessel 16 by a cross-pin 24. As can be seen in the external view of Fig. 4 and the ghost views of Fig.s 5 and 6, the second flexible element 14 is wound on the portion of the drive shaft 8 which projects outside the chamber 2 and travels upwards alongside the chamber until it reaches the top of the chamber where the element passes over a pulley 25. The flexible element 14 then enters a guide tube 26 where the element is fixed to a counterweight (not shown) which can slide up-and-down under gravity within the guide tube 26. In use, each of the chambers 2 is filled with water up to a level 27, as indicated in Fig. 6. The buoyancy vessel 16 may be guided within the chamber 2 by spaced runners 29 which allow water to flow between them. Similarly, as shown in Fig. 5, apertured supports 30 may be provided for the air manifold 18, which also allow water to flow beneath the manifold. Air is fed under pressure through the branch pipe 19 so that the manifold 18 starts to fill with air. The water level in the manifold 18 falls to a level 28 (Fig. 3) and air travels up through the transfer pipe 22 displacing water from the bottom of the buoyancy vessel 16. As its buoyancy increases due to the air entry the buoyancy vessel rises through the water causing the first flexible element 13 to unwind making the drive shaft 8 rotate, which in turn imparts torque to the output shaft 5. At the same time, rotation of the drive shaft 8 causes the counter-wound second element 14 to wind onto the drive shaft which in turn raises the counterweight within the guide tube 26. When the buoyancy vessel 16 reaches the water surface 27 in the chamber 2, air exits through the escape valve 17 so that the vessel re-fills with water until the buoyancy falls sufficiently to allow the vessel to sink back towards the starting position shown. Such return is assisted by the action of the counterweight within the guide tube 26 which causes the rotation of the drive shaft 8 to reverse and re-winds the first flexible element onto the drive shaft. The one-way bearings 12a and / or 12b (Fig. 2) ensure that the reverse rotation does not produce reverse torque on the output shaft 5. These bearings also act such that torque is only applied to the output shaft when the buoyancy of the vessel 16 is sufficient to exceed the rotational speed of the output shaft 5. In its simplest form the apparatus could comprise a single chamber 2, but by providing multiple chambers the torque on the output shaft can be increased considerably. Furthermore, by using an electronic or mechanical control system to time the opening of the inlet control valves 20 (Fig. 3) the filling of the manifolds can be operated sequentially to ensure that a substantially smooth and continuous torque is produced. The use of multiple chambers may also improve efficiency and enable lower gas supply pressures to be used. Furthermore, the method of gas entry into the open-bottomed buoyancy vessels through the manifolds 18 and wide bore transfer pipes 22 allows rapid filling under low gas pressures with gas entering and liquid leaving simultaneously. In consequence, the overall height of the apparatus can be reduced which, combined with the low level output shaft configuration, makes the apparatus particularly suitable for use in restricted locations such as boats or ships. Although above example describes solenoid valves used to control gas entry from the branch pipes a purely air operated sequenced mechanical solution might be an equally good option. Other options include: Provision of a reverse gearing arrangement. Combination of the apparatus with an air blower. Operation by means of cryogenically liquefied gas. Addition of a heat source to maximise gas expansion. Although the water chambers 2 may have a separate watertight casings it is possible for multiple chambers to be interconnected. Indeed, multiple chambers 2 may be provided within a single common watertight casing which contains multiple buoyancy vessels 16 along with their associated components. The number and volume of the liquid chambers 2 and the type of air supply used is determined by the depth of water and the air pressure and flow required to create the required output torque. In one form the escape valve 17 could be a small hole which allows air to escape from the buoyancy vessel 16 at a controlled rate, but a valve which only opens when the buoyancy vessel reaches the water surface is preferable. A simple ball valve or a float-operated valve may be used. Although the above example describes an air and water system it will be appreciated that any gas could be used with any liquid which provides sufficient buoyancy. In most cases a starter 7 will not be necessary although it might be useful in dry simulations for example. Some form of starter will most likely be needed in the generation of electricity using larger apparatus, and quite likely on smaller versions, similar to those used to provide starting torque on commercial wind turbines. An important application of the apparatus is in shipping, where the apparatus is eminently suited to directly drive a propeller shaft on a ship or boat by using pressurised air tanks, by using a smaller fossil fuel engine to power a blower, or using cryogenically liquefied gas. Another potential application is electricity generation using compressed air energy storage, e.g. on container ships with container sized air tanks. The apparatus could also be situated alongside wind farms for example, providing an alternative means of power generation. Whilst the above description places emphasis on the areas which are believed to be new and addresses specific problems which have been identified, it is intended that the features disclosed herein may be used in any combination which is capable of providing a new and useful advance in the art. x Xx Xx x kx x x xk

Claims

CLAIMS 1. Apparatus for converting buoyancy forces of a gas in a liquid into mechanical torque: - a liquid chamber (2), - an output shaft (5) extending beneath the liquid chamber, - a gas manifold (18) in the liquid chamber, - a gas supply (3) for the gas manifold, - a buoyancy vessel (16) movable in the liquid chamber and arranged to receive gas from the gas manifold, - a rotatable member (8) mounted at the bottom of the liquid chamber (2) and passing through a wall of the liquid chamber, - a one-way clutch arrangement (12a, 12b) coupling the rotatable member (8) to the output shaft (5), - a first flexible element (13) wound about the rotatable member (8) within the liquid chamber (2) and tethered to said buoyancy vessel (16) such that the buoyancy vessel rotates the rotatable member, - a return arrangement (14, 25, 26) located outside the liquid chamber (2) and arranged to rotate the rotatable member (8) in an opposite sense to the buoyancy vessel (16) such as to rewind the first flexible element (13) onto the rotatable member (8).

2. Apparatus according to claim : wherein the return arrangement includes a second flexible element (14) which is wound about the rotatable member (8) in an opposite sense to the first flexible element (13) such that one element unwinds from the rotatable member as the other winds onto the rotatable member.

3. Apparatus according to claim 2 wherein the second flexible element (14) is connected to a counterweight arrangement (26).

4. Apparatus according to claim 3 wherein the second flexible element (14) travels upwards alongside the liquid chamber (2), passes over a pulley (25) at the top of the liquid chamber, and then enters a guide tube (26) in which the second flexible element (14) is fixed to a counterweight which can slide up-and-down under gravity within the guide tube.

5. Apparatus according to any preceding claim wherein the rotatable member (8) is a drive shaft which is mounted in bearings (9).

6. Apparatus according to any preceding claim wherein the rotatable member (8) is drivably coupled to the output shaft (5) via enmeshed gears (10 and 11).

7. Apparatus according to any preceding claim wherein the one-way clutch arrangement (12a, 12b) comprises a ratchet, needle roller or sprag clutch.

8. Apparatus according to any preceding claim wherein the gas manifold (18) is fixed within a bottom portion of the liquid chamber (2). S. Apparatus according to any preceding claim wherein the buoyancy vessel (16) is open at its bottom end (16a) and includes an escape valve (17) at its top end to release gas therefrom.

10. Apparatus according to claim 9 wherein a gas transfer pipe (22) extends upwards from the gas manifold (18) and passes into the buoyancy vessel (16) through the open end (16a) with sufficient space between the transfer pipe (22) and the open bottom end (16a) for liquid to simultaneously flow out of the buoyancy vessel as gas enters the buoyancy vessel through the transfer pipe.

11. Apparatus according to claim 10 wherein the first flexible element (13) passes into the gas manifold (18) through an open bottom (23) of the gas manifold, travels upwards through the gas transfer pipe (22), and is tethered internally to the buoyancy vessel (16).

12. Apparatus according to any preceding claim wherein the gas manifold (18) is supplied with gas via an inlet control valve (20) and a non-return valve (21).

13. Apparatus according to any preceding claim wherein a plurality of such liquid chambers (2) have their respective rotatable members (8) coupled to the output shaft (5). x x x x x x x x

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