BACKGROUND OF THE INVENTION There are many sources of water and the present invention is especially concerned with bodies of water which are non-flowing, for example naturally-occurring bodies of water such as the oceans, lakes and ponds, or artificial bodies of water, for example reservoirs.

Apparatus for displacing water using a weight of stored water above a piston is already known, for example in GB-A-2340553. However, the downward stroke of the piston relies upon water being delivered through inlets above the piston, which makes particular demands of the water supply.

SUMMARY OF THE INVENTION It is a primary object of this invention to make use of a standing body of liquid.

According to a first aspect of this invention I propose hydraulic apparatus for use in a body of liquid, comprising : a passage having an inlet at one end for receiving working liquid from the body of liquid and an outlet at the other end for discharging working liquid; a reciprocable press member disposed in the passage so as to move along the passage: in a forward stroke from a first position nearer the inlet to a second position nearer the outlet and thereby to displace, under pressure from the body of liquid, working liquid through the outlet; and in a return stroke from its second position to its first position, with pressure from the body of liquid reduced or removed and allowing transmission of working fluid from the inlet side of the press member to the outlet side, wherein the press member includes means to further increase the pressure differential on the working liquid during the inward stroke.

The apparatus of the invention presses the working liquid through the passage to the outlet and through the outlet. The apparatus may act as a prime mover and may be a turbine. The press member is a single acting piston in that only one side of the press member is used to pump liquid. The apparatus makes use of the natural weight of

liquid such as water in a piston arrangement to pressurise output liquid. The body of liquid may be static or slow- moving provided the natural weight of the water is able to push the press member down onto the base.

The pressurised liquid is led off to be used externally, such as to move another hydraulic piston or to be raised for example in land irrigation, or the pressurised liquid may be used to produce a further effect, such as by being passed through a turbine to generate electricity.

The press member preferably comprises a hollow elongate portion having a first end face at the inlet side, on which end face the body of liquid acts and which has a first surface area, and a second end face, at the outlet side, which end face displaces the working liquid and which has a second surface area. The press member is also known as a ram, a piston or a plunger.

In one form, the means to additionally increase pressure is provided by the second surface area being smaller than the first. As an example, the surface area of the face at the inlet end may be at least about five to one hundred times that of the plunger face, perhaps about ten to twenty five times.

The first end face may be spaced from the inlet of the passage at the start of the forward stroke and may be seated against the inlet at the end of the forward stroke, and the passage is complementary to the elongate portion of the press member. In one embodiment, the elongate portion

depends centrally from the outlet side of the first end face.

It is desirable that the press member and the passage have a close and sliding fit for smooth movement of the press member and to create a liquid-tight seal, which assists in the syringe-like output effect on the liquid being squeezed out through the passage and the outlet. This liquid-tight seal may be provided by other means known to the skilled person in the art.

Throughflow of liquid may be started by a valve, e. g. a one-way valve, at the outlet end of the passage, which is opened prior to the inward stroke and closed after the inward stroke.

In an embodiment of the invention, the press member may have a concentric outer wall surrounding the elongate portion; the outer wall may join the inlet end face of the press member at its perimeter.

The passage may be provided, preferably centrally, in a solid support base. The outer wall and inlet end face of the press member may cover the base complementarily and have a similar liquid-tight, sliding fit to the press member and the passage. The passage may be surrounded by an outer wall; the passage may have a main portion with an inlet opening perpendicular to the longitudinal dimension of the passage at the inlet end, i. e. perpendicular to flow of liquid, and an outlet opening similarly perpendicular to the passage at the other end.

The press member, the passage, the outer walls of the

press member and the base are all preferably cylindrical.

The press member and the base member engage together as a unit in a close, sliding unit, which provides effective reciprocal action of the press member. This is a relatively simple construction, with few moving parts, and will require minimal maintenance, which is an advantage underwater.

The outer wall of the base member may include at least one additional outlet passage. Surprisingly it has been found that at least one passage (e. g. four of such subsidiary passages) may be useful in regulating throughput of liquid.

These outlets may be vented in tubes or pipes towards the surface of the body of the liquid, at least as high as the inlet of the passage and preferably to or near the surface of the body of liquid.

The base and the press member are suitably made from a rigid material, which is not compressible by the liquid, e. g. aluminium. The material of the press member does not need to be denser than the surrounding liquid. If the base material is not denser than the surrounding liquid it would need to be fixed to make it stationary.

At least one aperture or hole may be disposed in at least one of the end faces of the press member. The or each hole may be controlled by valve means so that each is closed prior to the inward stroke and opened prior to the return stroke. The valve means may be operated by conventional electrical or electronic means.

At the end of each inward stroke the press member can be lifted, for example by winch means, which may be powered, for instance by a battery or a solar-powered cell, and may be operated by a timer or sensor. The timer may also operate a motor for opening and closing the holes in the end faces of the press member. When the holes are open, the press member is lightweight and easier to lift because the liquid falls through the holes, which act like a sieve.

A buoyancy aid, such as a float of material less dense than the surrounding liquid, may be attached to the exterior of the press member to assist in the return stroke of the press member. The buoyancy aid may include a rigid framework which resists a change in shape due to pressure variations. Buoyancy may be provided by the press member being made from a material of low density material or made lighter by including a gas. The press member could include an internal polythene liner to assist in its sliding movement.

The hydraulic apparatus according to the invention may be deployed, preferably vertically, on a surface at the bottom of a body of liquid, for instance on the bottom of a pond or a lake. Pumps according to the invention may be most suited to depths of at least 30cm. The pump can be housed in an isolating chamber, i. e. a chamber sealed from external influences, with a chimney of liquid above. The outlet of the passage of the pump may communicate with a water-operable, pressure take-off device such as a turbine.

Electrical power could be produced for use as required, for

example for lighting or aeration. The pump could be used on any desired scale; farms of such pumps could be employed underwater. However, it is especially suitable as a portable device because it can then be readily installed for use.

According to a second aspect of my invention, I propose hydraulic pumping apparatus for submersion in a body of liquid, comprising a cylinder and a piston configured to reciprocate in the cylinder, the cylinder having an outlet through which liquid is ejected from the cylinder by a forward stroke of the piston, the piston having a valve member for controlling flow of liquid into the cylinder from the body of liquid, the valve member being closed during the forward stroke and opened during a reverse stroke of the piston.

The piston may depend from a member defining a chamber in which the cylinder is a piston-like fit, with the cylinder reciprocating in the chamber simultaneously with reciprocation of the piston in the cylinder. Such an arrangement may aid operation of the unit and may particularly assist in discharging the liquid. The chamber may have an annular cross-section.

The member may include a valve member for controlling flow of liquid into the chamber from the body of liquid, the valve member being closed during the forward stroke and opened during a reverse stroke of the piston.

The cylinder may include at least one channel through which liquid in the chamber is ejected by a forward stroke

of the piston.

The at least one channel may extend to discharge ejected liquid to a height above the valve in the piston when raised for the forward stroke.

According to another aspect of the invention I propose hydraulic apparatus, comprising: a passage having an inlet end for receiving working liquid from a body of liquid and an outlet end for discharging working liquid; a reciprocable press member disposed in the passage so as to move along the passage: in a forward stroke towards the outlet from a first position to a second position and thereby to displace, under pressure from the body of liquid, working liquid on the outlet side of the press member through the outlet, and in a return stroke from its second position to its first position, with pressure from the body of liquid reduced or removed and allowing transfer of working fluid from the inlet side of the press member to the outlet side; and a device for taking the pressurised liquid from the outlet to do work of any suitable kind.

I also propose according to yet another aspect of the invention a method of operation of hydraulic apparatus according to the first and/or the second aspect of the invention, comprising the following steps: starting with the press member in an initial position above the base and spaced therefrom, closing the holes in the input and output end faces of the

press member, opening the one-way valve in the outlet, permitting downward movement of the piston head, opening the holes in the input and output end faces of the press member a preselected amount, raising the piston head to its initial position, closing the one-way valve, and repeating the cycle as required.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention are now described by way of example to illustrate the invention, with reference to the drawings, in which: Figure 1 shows a perspective, exploded view of a first preferred embodiment of apparatus for displacing liquid such as water; Figure 2 shows schematically the apparatus of Figure 1 in cross-section prior to an inward stroke thereof; Figure 3 is a schematic flow chart showing an example of a control arrangement for using apparatus according to the invention, including the apparatus of Figures 1 and 2; Figure 4 is a flow chart illustrating an example of a method of use of apparatus according to the invention, including the apparatus of Figures 1 and 2; Figure 5 is a diagram of a pair of perforated plates which may be used in the invention as described below; and Figure 6 shows diagrammatically a pond arrangement including apparatus according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in Figures 1 and 2, apparatus 100 for producing hydraulic pressure, by displacing water, consists of an upstanding cylindrical inner support base 102, and a press 104, which covers the base. The press fits together complementarily with the base to form a canister unit having a liquid-tight, piston-type sliding fit, with the interior 106 isolatable.

The unit may be portable, about 15cm high and 10cm in diameter, and weighing about lkg. The press and the base are each made from rigid non-compressible material such as metal, for example aluminium or steel. The press need be only slightly denser than water; the base needs to be stationary in the water due to its density or anchoring or both.

A passage 108 has a main portion 109 running through the base 102 from an upper inlet end 110 to an opposite lower outlet end 112, which may lead through an optional portion 113 in the wall perpendicular to the central passage 108, into the main outlet 114 of the apparatus 100.

A turbine 116 for producing electricity, using pressurised water from the outlet, may be located in the outlet 114 and a one-way valve 118 may be disposed on the inlet side of the turbine.

Four secondary u-shaped outlet passages 120 of smaller diameter than the main outlet passage 108, extend outwards from the inlet end 103 of the base 102. Each secondary passage has an internal portion 121 in the base leading into an external portion 122. The external portions 122

are provided in tubing attached to the base 102. The tubing is made from a non-compressible material, e. g. a plastics material.

The press member 104 serves as a piston head: at the inlet end 110 of the unit the press 103 has an input end face 124, on which pressure from the body of water above the unit acts, and a hollow, cylindrical elongate portion 126 extending centrally downwards from the outlet side of the upper end face. The bottom of the elongate member has an output end face 128, which acts on working liquid below.

A cylindrical outer wall 130 extends downwards as a skirt from the outlet side 125 of the upper end face 124 of the press concentrically with the elongate portion 126, thus providing the annular or ring-shaped space 106 between the elongate member 126 and the outer wall 130. The surface area of the upper end face 124, the first surface area, is greater than the surface area of the lower end face 128, the second surface area. The first surface area can be at least about ten times the second surface area.

The effect is to additionally increase the pressure differential on the working liquid below the elongate member.

The press 104 is seated over the inner, tubular base 102, so that the outer wall 130 slidingly fits, optionally with a lubricant seal, round the inner, tubular base 102 and the elongate member 126 is located in the passage 108.

The press can be raised by a winch mechanism 130, which may be powered by a battery or solar cell (not

shown), which is connected to the upper end face 124 of the press by a cable 132. The cable may have a density less than the density of water. The winch mechanism may be floating on the surface of the liquid; the mechanism may be made steady e. g. by an anchor.

A buoyancy aid 134, such as a ring of material less dense than water, e. g. low density solid, material or tube of low density liquid, is attached to the exterior of the outer wall 130 of the press.

The upper end face 124 of the head of the press 104 is perforated with at least one hole 136 leading into the elongate portion 126 and at least one hole leading into the interior cavity 106, which can be selectively opened and closed as needed. These holes are closed prior to downward movement of the plunger and opened prior to upward movement of the plunger. Minimal energy is needed to do this as the end face is perpendicular to gravity.

When the hole/holes in the upper end face leading into the cavity 106 is/are closed, the cavity is isolated from the exterior of the unit.

The bottom end face 128 of the elongate portion 126 has at least one hole 138, which may be similarly opened and closed to the holes in the upper end face.

Alternatively to the holes, flap-type or hinged trapdoor-type valves might be used, which could be electromagnetic or hydraulic (not shown).

Figure 5 shows a pair of mating valve plates 139,140 (one pair in each of the top and bottom end faces of the

press member), which can be relatively turned to completely open or close the holes 136,138 or to control the size of the holes, for example by a timed motorised mechanism (not shown).

The apparatus of the invention may be submerged in water or other suitable liquid at a suitable depth of liquid e. g. water, to be determined by experiment, so that the press 104 is moved down into the outlet passage 108 by water acting on the top of the upper end face 124. For example, a depth of 30cm allows downward movement of the plunger. The apparatus may be used in a system having a timer for operation of the valves and the winch. A control arrangement is shown in the flow diagram of Figure 3. The timing system could be computer-controlled.

The external portions of the secondary tubes 120 extend upwardly beyond the upper end face of the press towards the surface of the water and may go to or near to the surface. A turbine or other device to use hydraulic pressure may be provided in association with each tube.

A method of operation of the apparatus just described is given in the flow chart of Figure 4 and will now be further described.

The press 104 starts in its upper position at level A with all the holes 136,138 in the upper and lower faces 124,128 and the valve 118 in the main outlet 114 closed.

The elongate portion 126 is partially disposed in the outlet passage 108. Water surrounds the sides and the top of the unit. When the one-way valve 118 in the main outlet

114 is opened, the press is pushed down until the end face meets the top of the base.

During this stroke water beneath the elongate portion in the passage is forced down through the passage 108 under increasing pressure by the elongate member, which reaches its extreme downward position when the end face of the press member sits on the base. The water below the elongate portion 126 is forced out in a syringe/piston effect through the main outlet passage 108 and then through the outlet 114.

As a result of this inward, downward stroke, other water in the cavity 106 beneath the plunger head is also released and urged out through the secondary outlet passages 121.

At the end of this inward stroke, the holes 136,138 in the top and bottom faces of the plunger are opened and the return stroke is carried out. The winch 130 moves the plunger upwardly from its lowermost position to return to its uppermost position. It has been found that surprisingly little effort is required to move the plunger device back.

The one-way valve 118 is then closed.

The sequence above described is repeated according to the output required from the hydraulic pumping apparatus, which could be electricity if a turbine or turbines is employed. The system could be run on a continuous cycle basis.

One way of how this embodiment might be operated under the surface of liquid, such as water, with a turbine 116 in

the outlet 114 is now given, by way of non-limiting example.

One-way valve 118 at turbine 116 is closed: Step 1 Close gaps 136 in the upper end face 124 (the top piston head) 104.30cm height of water on the top piston head provides approximately 3 kg x 9.8ms- = 29.4 kg ms-2 (Force). However ignoring the acceleration due to gravity, it is 3 kg ms-2.

This force translates to the lower end face 128 (the bottom piston head) directly, which is 3 kg ms~2 x 0.0131 m2/0. 000573 m=68. 6 kg ms~2.

Open one-way valve 118 (initiates downward movement of plunger device).

This is the approximate minimum amount of force required to move the piston head down and raise the liquid in all the tubes up, as determined by experiment. This is the force required to overcome the frictional forces and forces of all the liquid in the tubes. (The forces of all the liquid in the tubes will be 30cm x 1.13cm2 x 4 (tubes) = 135. 6cm3 + (30cm x 4.15cm2) 260cm3= 0.26kg of mass per 30cm depth of water.

If an extra 1.8m height of water is added to the weight (force) of liquid above the top piston head, the force on the upper piston head becomes an extra 180cm x 113.1cm2 = 20400 cm3 or 20.4kg i. e. this translates to 402.7kgms-2 at the bottom piston head (ignoring the acceleration due to gravity of 9.81 ms-2). For one stroke

of 20cm this is 81.0 kgm2s-2 of work. If the stroke takes 1 second it is Watts and in an hour would generate 81 x 3600 = ca291. 6KW (kgm2s~3). (See Note 2) If a stroke takes 6 seconds in a hour, this would be 81 x 600 = 48.6 KWatts Since the pressure in Cavity 106 is'isolated'from the external pressures because of the'syringe or piston effects'any additional weight (force) on the top piston head will translate directly to the lower piston head and will exceed the increasing upward forces from the weight of liquid in the tubes to a greater and greater extent. (See Note 1) The effect of this will be to provide an ever increasing amount of force as the depth of the device increases to drive the turbine, producing power.

Step 2 The next stage in the process is to raise the piston heads back to their original position. The force required will be reduced by the application of a buoyancy adjuster device 134 or the use of material of suitable density which will give very low weight to the piston heads in the liquid such that the force required to raise the piston heads will be minimal.

Also to allow the movement of the piston heads upward without lifting the fluid on top, the holes 136,138 in the top and bottom heads will be opened.

The winch 130 will then be activated to raise the piston heads and because the force required to do this will be so low, hardly any power will be used, and this amount

of power will be much less than has been generated by the down stroke. (The weight of the cable 132 in water will also be small as its density will be the same or less than water). Close one-way valve.

NOTE 1 These figures do not take into account the inefficiency of the turbine or the extra friction and mass of the extra fluid (water) in the tubes as the depth increases. However, these should easily be covered by the increasing weight/force on the top piston head.

NOTE 2 If there are a number of units combined, they can act like a car engine and as one stroke finishes and another stroke starts: thus a stroke a second is possible.

In NASTRAN computational analysis experiments, I have found that the power produced by a unit as described above increases with depth of the unit.

Output power values have been computed for the device in operation pushing water through all the pipes at a series of varying depths for a prototype unit as shown in Figure 2, with the apparatus and its associated outlet tubes fully submerged in water.

The power to overcome viscosity, to open and close the valve holes in the two piston heads and to raise the piston head unit is not accounted for but there should still be a net gain with depth.

The calculations have been done for apparatus having the following dimensions: area of upper end face = 113cm2 area of lower end face = 5.73cm2

cross sectional area of main outlet = 4.15cm2 cross sectional area of each subsidiary outlet = 1. 13cm2, and length of elongate portion = 20cm.

At each of the following depths, the power computed was: 0.3m, the power = 26787W 3m, the power = 2.5534e + 5W 6m, the power = 6.3069e + 5W 9m, the power = 1.0917e + 6W 10m, the power = 1.2395e + 6W, where e = 10 An embodiment illustrating the principle of my invention has been described above and the man skilled in the art will be able to make any minor changes necessary.

The system could be employed on a small scale, for examine in a pond or tank, or on a larger scale, for example in a lake or in the sea.

An arrangement of an embodiment of the invention in a pond is shown in Figure 6.

Apparatus 1 for producing hydraulic pressure is located under the surface 140 and on the bottom 142 of a pond P. The apparatus 100 is a unit as described above, with a support base 102 resting on the bottom of the pond and a press member 104 covering the base such that the elongate member 126 is engaged in the main passage 108.

The press member and the base again have a close, sliding fit. The unit is exposed to the pond.

A filter 144 is disposed in the outlet of the apparatus for filtering the pond water. Another filter

could be used as well or alternatively on the top of press member to filter water before it enters the apparatus. The outlet filter may be used in conjunction with or replaced by an aeration device 146, e. g. a frit, for aerating the pond water through an outlet tube 148 attached to the outlet. Instead of a filter and/or aeration device, a turbine may be employed, as shown in Figure 2, to produce electricity to supply underwater lighting 150 in the pond.

As another option, the apparatus may be employed without any such pressure take-off device and the pressure produced hydraulically may itself be used to disturb and agitate the water in the pond.

The apparatus provides pressurised water as described earlier, with reference to Figures 1 to 4.

The apparatus of this invention may be located in a similarly submerged fashion in any other natural or man- made reservoir of suitable standing liquid, such as water, or below a supported column of liquid.