GB2501239A

GB2501239A - Wave operated pump with secondary chamber providing restoring force

Info

Publication number: GB2501239A
Application number: GB1204779.1A
Authority: GB
Inventors: Robert Tillotson
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-03-19
Filing date: 2012-03-19
Publication date: 2013-10-23
Also published as: GB201204779D0

Abstract

A wave actuated pump comprises an outer cylinder 4 and a piston rod 3, 7 with a piston head 6, defining a primary pump chamber 5 between the cylinder 4 and the piston rod 7 and a secondary pump chamber 8 within the connecting rod 7. The secondary chamber 8 is permanently connected to the pressurised fluid via inner tube 12 without a non-return valve, so the piston 6 is biased to the retracted position. There may also be an additional chamber 9, which draws water in via inlet filter 20 on the upstroke, and returns water to the primary chamber on the downstroke. Because the additional chamber 9 has a greater volume than the primary chamber (because of the connecting rod) some of the water will flow out to back flush the filter.

Description

Wave Actuated Pump The present invention relates to a wave actuated pump that allows the action of waves above the pump to cause the pump to pump water. The invention enables the harnessing of a wave's kinetic energy in a body of water. In addition this invention provides a method of pumping water using such a pump. The method relies upon the kinetic energy in waves, that energy being extracted by use of a buoy floating on the surface of the water and a wave actuated pump below it, the pump being connected to an anchored piston, e.g. on the seabed.

BACKGROUND OF THE INVENTION

Many devices have been devised to harness the energy of waves, e.g. to produce electricity, but very few have become commercially successful. One reason for thié is that many of the devices are highly complex. This results in high production costs, reducing their commercially viability when compared to other energy devices, such as those that use fossil fuels or other renewable sources. Their compLexity also can reduce their reliability which can limit their service life or cause high repair or maintenance costs.

Further, many devices are undesirable since they attempt to produce the electricity in situ, i.e. under the water. Such an approach again increases the complexity and requires the use of a large number of potentially unreliable components, thus again increasing the frequency of maintenance required, or reducing their service life.

Reliability is a major factor in the success of any such device. This is due to the fact that by their very nature and their location of operation, maintenance is costly.

Such devices are generally located offshore and so reaching and retrieving them requires substantial time and cost. Further the ability to reach them is often weather dependent. Therefore there can be extended periods of maintenance or downtime, i.e. when no pumping is achieved. This can therefore reduce their practical efficiency compared to other energy solutions, such as land-based solutions. It is therefore imperative for the success of any wave powered device that it be robust and reliable.

Seabed anchored wave actuated pumps are one solution known in the art that can reliably pump water in response to the action of waves above the pumps. See for example G62461859 and EF'0421010, the whole contents of which are incorporated herein by way of reference.

The present invention seeks to improve upon or compliment such prior art pumps, by providing an alternative or more reliable and durable embodiment, which can hopefully then achieve a commercially viable embodiment. It would also be desirable to optimise the speed with which pump can react to changes in wave heights, thereby increasing the efficiency of the pump in terms of the amount of energy captured from any given set of waves.

Further, by connecting the pump to a generator the pump of the invention may enable electricity to be attained from the wave movement above it. This might be achieved by Locating the generators on land. See, for example, the disclosure of GB246 1859. However, the generator could be located elsewhere. For example it might be connected to the water outlet of the pump, e.g. near the head of the pump, or on the seabed, or in or on or under a buoy in the water, or connected to the water inlet of the pump.

It will be appreciated from the above, therefore, that it is the intention of the invention to provide a simple, reliable and efficient pump which can provide a supply of pressurised or pumped water, e.g. to drive a generator, and which pump will be driven by wave power. It is also hoped to achieve this with a compact device that can be economically manufactured.

SUMMARY OF THE INVENTION

According to the present invention there is provided a wave actuated pump for harnessing the energy of waves via a flotation device due to the buoyancy of the flotation device, the pump comprising a primary pump chamber and a secondary pump chamber, the pump comprising a connecting rod that extends from a first end of the primary pump chamber, through the primary pump chamber, and to a common piston member at the opposite end of the primary pump chamber, wherein the common piston member is a piston head for both the primary and the secondary pump chambers and the secondary pump chamber is contained wholly within the connecting rod.

Preferably the secondary pump chamber has a crosssectionaI area that is less than that of the primary pump chamber.

Preferably the secondary pump chamber is substantially wholly contained within the outer perimeter of the primary pump chamber. By substantially wholly contained within we mean that at least 80% of its fully expanded volume is contained within the outer perimeter of the primary pump chamber.

Preferably the primary pump chamber is an upper pump chamber.

Preferably the secondary pump chamber is a pump chamber contained in the core of the primary pump chamber.

Preferably the primary pump chamber is defined by an upper open space within an outer housing of the pump.

Preferably that outer housing is formed from a metal pipe. It can be cylindrical.

Preferably, the distal end of the pump, e.g. the housing, is anchored to the sea bed or to some other fixed object below the water's surface. The anchoring may be via a connection member at the bottom of the pipe. The anchoring may be disconnectable or adjustable for allowing retrieval of the pump for servicing or for allowing adjustment of the height of the pump relative to the sea bed or the like for accounting for tidal variations.

Said prEmary pump chamber Es preferably generally elongated, i.e. with a longer length than diameter when fully extended, and more preferably with a length that is at least 2x the diameter when fully extended.

Preferably the piston is disposed within the housing to provide a standard fit within an outer cylinder of the pump. However, it will be appreciated that other elongated shapes will be suitable and are included within the scope of the invention.

The outer cylinder can provide an outer wall for both the primary pump chamber (usually an upper pump chamber) and a further pump chamber, e.g. a lower pump chamber.

The outer waU will typically be made from a metal, e.g. stainless steel. It will be designed with a sufficient thickness or strength to withstand the elevated pressures of the water caused by the pumping action of the pump.

The primary pump chamber has a cross sectional area, in this arrangement, that is defined as the area which lies within the internal perimeter of the outer housing (typically a cylinder), excluding the area defined by the outer perimeter of the secondary pump chamber, i.e. the connecting rod of the pump in this arrangement (also typically a cylinder, and usually a concentric one.

Likewise, the further or lower pump chamber has a cross sectional area, in this arrangement, that is defined as the area which lies within the internal perimeter of the outer housing, i.e. without the excluded area of the secondary pump chamber's structure. As such it has the largest of the three cross sectional areas.

The further pump chamber is separated from both the primary pump chamber and the secondary pump chamber by the common piston, and that piston is likewise the piston for the further pump chamber.

Preferably the flotation device would comprise a buoy, however other suitable devices I: will be well known to the person of ordinary skill in the art.

Said flotation device will be suitably sized to provide an adequate buoyancy force to contract the volume of the primary and secondary pump chambers so as to eject water therefrom towards a common mains or accumulator. It is this buoyancy driven water pumping process that provides pressurized water to further devices, e.g. to drive generators for producing electricity.

Preferably the secondary pump chamber is located entirely within the confines of the perimeter of the primary pump chamber, although other embodiments may have the secondary pump chamber arranged to extend therefrom, e.g. above the top of the primary pump chamber, or below the bottom thereof..

Preferably the connecting rod is hollow and it extends from a connecting element that in use will be connected to a flotation device. Further, its other end can be connected to the piston. As such, the connecting rod can extend substantially the full length of the pump (when the primary pump chamber is fully extended), i.e. from the connection end at the top (for the floatation device) to the anchorage end at the bottom of the housing end (for the ground anchor).

Preferably the secondary pump chamber is concentric with the primary pump chamber.

Preferably the primary secondary and further pump chambers all share a common axis, although the further pump chamber is linearly spaced along that axis from the primary and secondary pump chambers by the depth of the piston.

The secondary pump chamber, like the primary pump chamber, is preferably sealed or closed at its distal end by the piston head.

An advantage of the present invention over the prior art is that the design utilises a compact arrangement for combined unit of the primary and secondary pumps. Further, the moving parts are largely contained in a single housing, thus reducing the exposure of moving parts to the water surrounding the pump -only the connecting rod is likely to be exposed to that water. The internal components only get exposed to the pumped water, which water is preferably filtered by a filter -see the second aspect of the invention defined below. This arrangement therefore reduces the chance of degradation and minimises wear1 maximising service life.

Preferably, on the distal side of said piston head there is a lower pump chamber.

Preferably it has a cross sectional area greater than that of the primary pump chamber, and more preferably equal to or greater than that of the total cross sectional area of the primary and secondary pump chambers combined. This can be readily achieved when the secondary pump terminates at the piston head, whereby the entire region on the distal side of the piston head can comprise the lower pump chamber, whereas above the piston head the same area is occupied by both the primary and secondary pump chambers, and the mechanisms/walls of the secondary pump chamber.

Preferably both the primary and secondary pump chambers partially empty their chambers to a common mains or accumulator. Such an accumulator or common mains could be located on the shore. Likewise, such an accumulator or common mains could lead to one or more generator.

The common mains or accumulator in use will preferably store or hold a volume of pumped water at an elevated pressure i.e. as it gets expelled from the primary and secondary pumps on the upstroke. That elevated pressure can be used by the secondary pump chamber to provide an assist force to the piston head upon the down stroke commencing.

Preferably the primary pump chamber empties a volume of water therefrom on an upstroke.

Preferably the primary pump chamber has an outlet port towards its upper end.

Preferably the primary pump chamber is is connected to an outlet check valve, through which it can empty a volume of water as it pumps water from itself. The outlet check valve is provided to prevent water from the mains or the accumulator from re-entering the primary pump chamber, e.g. on the down stroke. Such check valves are well known in the water-pumping industry.

Preferably the secondary pump chamber is connected to the common mains or accumulator by means of an inner tube contained therein. Preferably the inner tube extends through the piston head and into the secondary pump. Preferably this tube is held stationary with respect to the outer housing of the pump. Preferably it has a port for fluidly connecting it to the secondary pump chamber. Such an inner tube can provide a conduit through which water from the secondary pump chamber can be carried to and from the accumulator or common mains.

The conduit may comprise multiple elements. For example, the inner tube could be a straight tube. A side port may then be provided in the bottom or base member of the housing, with the inner tube being fluidly connected to it at the tube's distal end An outlet recycle pipe might then be fluidly connected to the outlet of the side port for directly connecting to the mains' pipework. That connection will be beyond the outlet check valve for the primary pump chamber, whereby water from the secondary pump chamber will not circulate into the primary pump chamber -the outlet check valve prevents such entry into the primary pump chamber.

Preferably the inner tube runs through the piston head and the connecting rod in the centres thereof. HoweverE it will be appreciated that non circular or non concentric arrangements are possible too.

Preferably the piston head is assisted in its movement towards the distal end of the pump, i.e. the outer housing of the pump, by reactive expansion of the secondary pump chamber resulting from the increased pressure of the water contained in the mains or accumulator -e.g. by stored forces in the pipework thereof. This is achieved as the secondary pump is arranged to be openly connected to the accumulator, i.e. there is always an elevated pressure, thus creating a force to tend to try to expand the secondary pump chamber by moving the piston towards the distal end of the pump.

During the primary pumping process, i.e. the upstroke, the buoyancy force of the buoy is larger than the opposing force of the secondary pump chamber, as caused by that pressure within the secondary pump chamber, so the pump will cause water to be pumped. However once the wave has passed and the buoyancy force reduces, the pressure within the secondary pump chamber will cause the force on the piston head to be Farge enough to assist in the expansion of the primary and secondary pump chambers, i.e. in the moving of the piston downwards relative to the housing of the pump.

Such a mechanism for assisting the down stroke of the piston has many advantages over alternative forms of permanent bias, such as a spring, or simply just relying upon gravity. For example, a spring will require maintenance and has a risk of failure. Using gravity, on the other hand, would not provide sufficiently rapid response speeds to maximise the ability to capture the energy in consecutive waves.

Preferably the primary pump chamber and the further (or lower) pump chamber are both connected to a common inlet feed. Preferably that inlet feed has an inlet filter.

Preferably the feed for the primary pump chamber passes into the primary pump chamber through an inlet port positioned near the top of the pump's housing.

Preferably the feed for the primary pump chamber is controlled by an inlet check valve.

The inlet check valve is adapted to prevent water flowing out of the primary pump chamber through the inlet port. The water therefore instead flows out through the primary pump chamber's outlet port. In other words, the combination of the inlet and outlet check valve insures that water can only move in one direction through the inlet and outlet ports, i.e. upon a downstroke, from the inlet filter, through the inlet check valve and through the inlet port into the expanding primary pump chamber, and upon pumping the pump, i.e. an up stroke, out through the outlet port, through the outlet check valve, and on through to the common mains or accumulator.

Preferably the movement of said piston head in response to the up stroke or down stroke also pumps water into and out of the further pump chamber, respectively. Given the relative sizes of the primary and further pump chambers, there will be a greater volume of water cycling through the further pump chamber than the primary pump chamber. It is preferred, therefore, that the link pipe (an inlet recycle pipe) between the further pump chamber and the inlet filter be connected to the inlet filter outside the control of the inlet check valve. Then, as the piston moves towards the distal end of the pump,, and as the primary pump thus expands, the flow of water will enter the primary pump chamber, perhaps from the further pump chamber, or else from the inlet filter, or a combination of both. However, since there will be an excess of water venting from the further pump chamber, that excess will be vented out through the inlet filter thus flushing or back-washing the filter, whereupon the filter will be cleaned, which is of course advantageous -existing wave actuated pumps do not have a self cleaning filter, whereby over time the filter will get clogged, whereupon the efficiency of the pump reduces. In the present invention, there would be less of a need for human intervention to clean, replace or maintain the cleanness of the inlet filter, thus resulting in the pumps of the present invention requiring less maintenance and ultimately having longer service lives, making them a more commercially viable option when compared to existing renewable energy sources.

According to a second aspect of the invention, therefore, there is additionally provided a wave actuated pump for harnessing the energy of waves via a flotation device due to the buoyancy of the flotation device, the pump comprising a primary pump chamber, a further pump chamber, a connecting rod that extends from a first end of the primary pump chamber, through the primary pump chamber, and to a common piston member at the opposite end of the primary pump chamber, wherein the common piston member is a piston head for both the primary and the further pump chambers, and being arranged Sich that movement of the piston member in a first direction expands the primary pump chamber and contracts the further pump chamber, the further pump chamber having a larger cross sectional area than the primary pump chamber, and both the primary and further pump chambers being connected to a common inlet filter, wherein upon that movement of the piston member in the first direction, water that has passed through the inlet filter is drawn through an inlet port of the primary pump chamber into the primary pump chamber and excess water expelled from the further pump chamber is expelled back out through the inlet filter.

Preferably the the piston member is also arranged such that movement of the piston member in a second direction, opposite to the first direction, contracts the primary pump chamber to expel water out of the primary pump chamber via an outlet port and expands the further pump chamber to draw into it a volume of additional water through the inlet filter.

Preferably the inlet port and the outlet port are both fitted with one way flow control valves.

The pump of this second aspect can additionally have any of the features of the first aspect.

Further aspects of the present invention include wave powered apparatuses comprising a wave actuated pump as defined above, or such apparatuses where there is provided a floatation buoy attached to the pump, and/or an anchor attached to said wave actuated pump for anchoring the pump to a fixed surface in a body of water, such as a sea bed.

Also according to the present invention there is provided a method of pumping water, comprising providing a pump as discussed above attached to an anchor for anchoring the.pump to a fixed surface underwater and to a flotation device for engaging with the waves on the water's surface, wherein movement of the floatation device causes the pump's piston to move relative to the outer housing of the pump for pumping water from the primary pump chamber.

The present invention also provides a method of cleaning an inlet filter for a wave powered pump, comprising providing a pump as disclosed above, attached to an anchor for anchoring the pump to a fixed surface underwater and to a flotation device for engaging with the waves on the water's surface, wherein movement of the floatation device causes the pump's piston to move relative to the outer housing of the pump for pumping water from the further pump chamber back through the filter.

SPECIFIC EMBODIMENT

The present invention will now be described in further detail, purely by way of example, with reference to the accompanying drawing, Figure 1, which shows an embodiment of the invention in cross section.

Figure 1 illustrates a wave actuated pump 1 comprising a connection element 2 at its proximal end for connecting to a buoy (not shown, but see, for example1 the buoy illustrated in Figure 1 of GB2461 859.

Descending from the connection element, the pump I also has a primary rod 3, a part of which acts as a connecting rod 7 of a piston of the pump 1. The buoy and and the primary rod 3 in use will be configured such that the buoy will float on the surface of the body of water (not shown) in which the pump 1 is installed, with the primary rod extending down towards the sea bed. This is similar to the arrangement in GB2461859, in which the buoy is also floating on the surface of the body of water in which its pump is installed, and with a primary rod extending down towards the sea bed.

Referring again to Figure 1, the pump 1 is arranged such that it is anchored to a floor, a sea bed or some other fixed surface or object in the water, below the water's surface.

Such an anchoring, although not shown, can be similar to the arrangement disclosed in 032461 859. However1 the connection to the anchor arrangement in the present case's illustrated embodiment is by means of an anchorage point or connection 11 at the pump's distal end.

The pump, being for pumping water, is then arranged to be connected to a common mains or accumulator 14, whereby water from the pump can be directed out of the pump to that common mains or accumulator 14. An arrangement for that common mains or accumulator connection is also shown in GB2451359.

Duo to the many similarities in application for the present invention as compared to that of GB2461859, the whole contents of GB2461859 are incorporated herein by way of reference.

Referring again to Figure 1 of the present case, the pump 1 is further defined by an outer cylinder 4 which houses a piston head 6 and upper and lower pump chambers 5, 9.

The piston head 6 is formed at the distal end of the connecting rod 7.

A proximal face of the piston head 6 defines a lower end of the upper pump chamber 5 and a distal face of the piston head 6 -the face that is nearer to the anchorage point or 7. connection 11 -defines an upper end of the lower pump chamber 9.

The piston head 6 is disposed within the outer cylinder 4 to separate the lower pump chamber 9 and the primary pump chamber 5, but through longitudinal sliding within the outer cylinder 4, it can contract and expand the upper and lower pump chambers 5, 9 in opposition to one another.

The primary rod 3, and particularly its part that forms the connection rod 7, is arranged in this embodiment in a concentric manner relative to the outer cylinder. As such it extends along (here around or concentrically with) the central axis of the outer cylinder 4. Likewise it extends along (here around or concentrically with) the central axis of the upper pump chamber 5. However, at its distal end it terminates before it enters the lower pump chamber 9. Instead its distal end is rigidly attached to the piston head 6.

In this embodiment the primary rod 3 is provided as a hollow cylinder. Hence it defines a cylindrical hollow region B within it. At the proximal or upper end of this region 8 there is fitted a sealing unit 10 which is maintained stationary with respect to the outer cylinder 4 by an inner tube 12, on which the sealing tube in mounted -at the inner tube's proximal or upper end. The sealing unit 10 is provided to cap the proxima] or upper end of the hollow region 8.

The hollow region 8 forms a secondary pump chamber 8 that is concentric with the upper pump chamber 5. Its purpose during use is described in further detail below.

The upper pump chamber 5 and the secondary pump chamber 8 are both connected to the common mains or accumulator, shown here only schematically as element 14. This common mains or accumulator 14 will most likely be connected to shore by further pipework, or it might itself be located on the shore, it being itselfconnected to the pump I via pipework. See again GB246 1859.

When the pump l is pumping, i.e. on the up-stroke of the pump 1, the common mains 14 will contain pumped water, i.e. water at an elevated pressure. For that purpose the upper pump chamber 5 is connected to the common mains or accumulator 14 through an outlet port 16-located at the upper pump chamber's proximal end.

An outlet check valve 15 is located between the common mains or accumulator 14 and the outlet port 16 to prevent the pumped water from re-entering the upper pump chamber Son the down-stroke of the pump 1.

The secondary pump chamber 8 is also connected to the common mains or accumulator 14. That connection, however, is provided by the inner tube 12, which is hollow. The inner tube extends along the secondary pump chamber's central axis from the sealing unit 10 at its proximal end to the connection 11 at the bottom of the lower pump chamber 9.

The mounting of the inner tube 12 at the connection 11 is static with respect to the outer cylinder 4, thus holding the inner tube 12 and the sealing unit 10 stationary with respect to the outer cylinder 4, while the primary rod 3 and its connecting rod 7 and piston head 6 provide the pumping movements in response to movementsof the float (not shown) above the connection element 2.

Towards the proximal end of the inner tube there is provided a bi-directional port 19 which allows the passage of water between the secondary pump chamber 8 and the inner tube 12. The inner tube 12 then connects that wateruiow, at its distal end 22, to a outlet recycle pipe 13 via a side port 23 in the connection 11, i.e. at the distal end of outer cylinder 4. Hence secondary pump chamber 8 is also connected to the common mains or accumulator 14, but in this arrangement not via a check valve. As such the secondary pump chamber 8 can adopt the same water pressure as the common mains or accumulator 14 i.e. the elevated water pressure. This is in addition to the arrangement allowing the water contained in the secondary pump chamber 8, the inner H tube 12 and the outlet recycle pipe 13 to flow in both directions in response to the pumping action of the pump 1. That elevated pressure helps to draw down the primary rod 3 and its connecting rod 7 as the float above the pump 1 drops off a wave, thus improving the response or recovery rate of the pump, and in turn enabling it to pump more efficiently in response to variable or higher frequency wave-forms.

As for the water inlet side of the pump 1, it also has an advantageous mode of operation, which will be described in further detail betow.

H The water inlet side comprises an inlet filter 20, an inlet check valve 18 and an inlet port 17. In the illustrated arrangement the inlet port 17 is provided at the proximal end H of the outer cylinder 4, and in this instance is provided by way of an opening that matches and opposes the outlet port 16.

During the down-stroke of the pump 1, the upper pump chamber 5 draws water into the pump 1 through the inlet filter 20, via the inlet check valve 18 and the inlet port 17. Due to the provision of the inlet check valve 18, water can only flow in through the inlet port 17, rather than out of it, thus forcing the water within the upper pump chamber 5 to be pumped out through the outlet port 16 upon the up-stroke of the pump 1. Likewise, due to the outlet check valve 15, water can only flow out through the outlet port 16, rather than in through it, thus forcing the water to be pulled into the upper pump chamber 5 through the inlet port 17 upon the down-stroke of the pump 1. As such the upper pump chamber 5 onLy ever draws water in from the inlet filter 20 and it then expels that water only to the common mains or accumulator 14.

The lower pump chamber 9 is also connected to the inlet filter 20 but not via the check valve 18. Instead it bypasses that check valve 18 in a similar fashion to the secondary pump chamber 8-it is achieved by an inlet recycle pipe 21 that links the lower pump chamber 9 to the inlet filter 20 through a hole 24 in the sidewall of the outer cylinder 4.

That hale 24 and inlet recycle pipe 21 allows water to flow in both directions to and from the lower pump chamber.

In use, upon being affected by a wave, the buoy provides an upwards force on the primary rod 3. This upwards force, where greater than the force generated by the pressure in the secondary pump 8, causes the buoy to rise with the wave, pulling the piston head 6 up towards the proximal end of the pump 1. This simultaneously causes the upper pump chamber 5 and secondary pump chamber 8 to contract and so partially to empty the water from them at an elevated pressure. The larger amount of that water empties through the outlet port 16 to the common mains or accumulator 14. The smaLler volume of the secondary pump chamber 8, however, exits through the bi-directional port 19 and the inner tube 12, and out through the side port 23 and the outlet recycle pipe 13. Further, as the piston head 6 moves upwards, the lower pump chamber 9 expands in volume and hence draws fresh water into itself through the inlet recycle pipe 21 and The inlet filter 20.

Then, when the wave has passed and the buoyancy force is reduced, the weight of the moveable mechanism (e.g. the piston head 6, the primary rod 3, the connection element 2), together with the elevated pressure inside the secondary pump chamber 8 (caused by its open connection to the mains 14), causes the piston head 6 to move back downwards towards the distal end of the pump 1. This in turn expands the upper pump chamber 5 and the secondary pump clamber 8, and reduces the volume of the lower pump chamber 9.

Water from the accumulator or common mains 14 can freely enter the secondary pump chamber 8 through the inner tube 12 and bi-directional port 19. Further, water enters the upper pump chamber 5 from the inlet filter 20 via the check valve 18 and the inlet port 17. Further, the lower pump chamber expels its water at least partially out through the inlet filter 20 -due to the geometry of the secondary pump chamber 8, and its arrangement inside the upper pump chamber 5, the cross sectional area of the lower pump chamber 9 is larger than that of the upper pump chamber 5, whereby more water is expelled from the lower pump 9 than is drawn into the upper pump chamber 5, that expulsion necessarily being out through the filter 20, thus providing a filter backwash function that can remove dirt and debris deposits from the inlet filter 20.

Then, after the buoy 2 passes the trough of the wave, the moving parts of the pump 1 again begin to rise and so the upstroke starts, once again drawing in water to the lower pump chamber 9 and expelling the newly captured water from the upper pump chamber to the common mains or accumulator 14.

The present invention has been described above with an elongated, concentric pump chamber arrangement. Alternative shapes and arrangements, however, will also be understood to be within the scope of the invention.

The present invention has been described above purely by way of example.

Modifications to the invention may nevertheless be made thereto within the scope of the claims.

Claims

CLAIMS: 1. A wave actuated pump for harnessing the energy of waves via a flotation device dLIe to the buoyancy of the flotation device, the pump comprising a primary pump chamber and a secondary pump chamber, the pump comprising a connecting rod that extends from a first end of the primary pump chamber, through the primary pump chamber, and to a common piston member at the opposite end of the primary pump chamber, wherein the common piston member is a piston head for both the primary and the secondary pump chambers and the secondary pump chamber is contained wholty within the connecting rod.
2. The pump of claim 1, wherein the secondary pump chamber has a cross-sectional area that is less than that of the primary pump chamber.
3. The pump of claim 1 or claim 2, wherein the secondary pump chamber is substantially wholly contained within the outer perimeter of the primary pump chamber.
4. The pump of any one of the preceding claims, wherein the distal end of the pump is connected via an anchor to a sea bed.
5. the pump of any one of the preceding claims, wherein said primary pump chamber is generally elongated when fully extended, with a length that is at least 2x the diameter.
6. The pump of any one of the preceding cLaims, wherein an outer housing provides an outer wall for both the primary pump chamber and a further pump chamber:
7. The pump of claim 6, wherein the primary pump chamber has a cross sectional area that is smaller than that of the further pump chamber.6. The pump of claim 6 or claim 7, wherein the further pump chamber is separated from both the primary pump chamber and the secondary pump chamber by the common piston1 and that piston is likewise the piston for the further pump chamber.9. The pump of any one of the preceding claims, provided with a flotation device in the form of a buoy.10. The pump of any one of the preceding claims, wherein the secondary pump chamber is located entirely within the confines of the perimeter of the primary pump chamber.11. The pump of any one of the preceding claims, wherein the connecting rod is hollow and it extends from a connecting element that in use will be connected to a flotation device all the way to the piston.12. The pump of any one of the preceding claims, wherein the secondary pump chamber is concentric with the primary pump chamber.13. The pump of any one of the preceding claIms, wherein the primary, secondary and further pump chambers all share a common axis.14. The pump of any one of the preceding claims, comprising a further pump chamber, wherein the further pump chamber has a cross sectional area greater than that of the primary pump chamber and the secondary pump chamber combined.15. The pump of any one of the preceding claims, wherein both the primary and secondary pump chambers partially empty their chambers to a common mains or accumulator upon operation of the pump's piston in a first direction.16. The pump of claim 15, wherein the common mains or accumulator, in use, will store or hold a volume of pumped water at an elevated pressure, which elevated pressure can be used by the secondary pump chamber to provide an assist force to the piston head upon the piston becoming free to travel back in a second direction.17. The pump of any one of the preceding claims, herein the primary pump chamber empties a volume of water therefrom on an upstroke of the pump's piston.I 6. The pump of any one of the preceding claims, wherein the primary pump chamber is is connected to an outlet check valve, through which it can empty a volume is of water upon movement of the piston in a first direction, the outlet check valve being provided to prevent water from then re-entering the primary pump chamber through the outlet check valve.19. The pump of any one of the preceding claims, wherein the secondary pump chamber is connected to a common mains or accumulator by means of an inner tube contained within the secondary pump chamber's structure.20. The pump of claim 19, wherein the inner tube extends through the piston head and into the secondary pump chamber's structure.21. The pump of claim 19 or 20, wherein the inner tube Is held stationary with respect to an outer housing of the pump.22. The pump of any one of claims 19 to 21, wherein the secondary pump chamber Es In fluid communicat[on with a port for fluidly connecting the secondary pump chamber to the inner tube.23. The pump of any one of claims 19 to 22, further comprising a side port in a bottom or base member of a housing of the pump and an outlet recycle pipe, with the inner tube being fluidly connected to the side port at the inner tube's distal end, and the side port then being fluidly connected to the outlet recycle pipe, which outlet recycle pipe is then for connection to a common mains or accumulator.24. The pump of any one of the preceding claims, wherein the pIston head is assisted in its movement for expanding the volume of the secondary pump chamber by an elevated pressure of the water contained in a mains or accumulator to which the secondary pump chamber is connected.25. The pump of any one of the preceding claims, wherein the feed for the primary pump chamber is controlled by an inlet check valve.26. The pump of any one of the preceding claims, comprising the primary pump chamber, the secondary pump chamber and the further pump chamber, wherein the primary and further pump chambers are both connected to a common inlet feed.27. The pump of claim 26, wherein that inlet feed has an inlet filter.28. The pump of claim 27, wherein movement of said piston head in a direction to pump water out of the further pump chamber1 likewise pumps water into the into the primary pump chamber, and wherein the relative sizes of the primary and further pump chambers are such that there will be a greater volume of water cycling through the further pump chamber than the primary pump chamber upon such movement, whereby at least a part of the water from the further pump chamber will backwash out through the inletfilter.29. A wave actuated pump for harnessing the energy of waves via a flotation device due to the buoyancy of the flotation device, the pump comprising a primary pump chamber, a further pump chamber, a connecting rod that extends from a first end of the primary pump chamber, through the primary pump chamber, and to a common piston member at the opposite end of the primary pump chamber, wherein the common piston member is a piston head for both the primary and the further pump chambers, and being arranged such that movement of the piston member in a first direction expands the primary pump chamber and contracts the further pump chamber, the further pump chamber having a larger cross sectional area than the primary pump chamber, and both the primary and further pump chambers being connected to a common inlet filter, wherein upon that movement of the piston member in thefirst direction, water that has passed through the inlet filter is drawn through an inlet port of the primary pump chamber into the primary pump chamber and excess water expelled from the further pump chamber is expelled back out through the inlet filter.30. The pump of claim 29, wherein the piston member is also arranged such that movement of the piston member in a second direction, opposite to the first direction, contracts the primary pump chamber to expel water out of the primary pump chamber via an outlet port and expands the further pump chamber to draw into it a volume of additional water through the inlet filter.31. The pump of claim 29 or claim 30, wherein the inlet port and the outlet port are both fitted with one way flow control valves.32. A pump substantially as hereinbefore described with reference to the accompanying drawing.33. A wave powered apparatus comprising a wave actuated pump according to any one of the preceding claims, a floatation buoy attached to the pump, and an anchor attached to said wave aotLlated pump for anchoring the pump to a fixed surface in a body of water.34. A method of pumping water, comprising providing a pump according to any one of claims I to 32, attached to an anchor for anchoring the pump to a fixed surface underwater and attached to a flotation device for engaging with the waves on the water's surface, wherein movement of the floatation device causes the pump's piston to move relative to an outer housing of the pump for pumping water from the primary pump chamber.35. A method of cleaning an inlet filter of a wave powered pump, comprising providing a pump according to any one of claims I to 32, attached to an anchor for anchoring the pump to a fixed surface underwater and attached to a flotation device for engaging with the waves on the water's surface, the pump comprising a further pump chamber with a cross sectional area larger than the primary pump chamber of the pump, and the piston being a common piston head for both the primary pump chamber and the further pump chamber, wherein movement of the floatation device causes the pump's piston to move relative to an outer housing of the pump for pumping water from the further pump chamber back through the filter.