A hydraulic piston pump assembly and a wave power system

Abstract

A hydraulic piston pump assembly and a wave power system comprising such hydraulic piston pump assembly, wherein the assembly comprises a pump housing (11) having a pump housing axis and comprising an inner pump housing surface; a piston comprising a piston head (12a) with a peripheral head surface adapted to seal against the inner pump housing surface and a piston rod (12b) connected to the piston head (12a), wherein the piston rod (12b) comprises an outer piston rod surface and an actuator rod (13). The piston comprises an axial piston channel (15) extending at least partially through the piston rod (12b), wherein the actuator rod (13) has a first actuator end portion (13b) and a second actuator portion (13c), wherein the first actutor end portion (13b) fully or partly extending into the axial piston channel (15) and is slidable in the axial piston channel (15) and wherein the second actuator portion (13c) is adapted to be engaged with an effector capable of being actuated by water waves.

Description

[0001] A HYDRAULIC PISTON PUMP ASSEMBLY AND A WAVE POWER SYSTEM

[0002] TECHNICAL FIELD

[0003] The invention relates to a hydraulic piston pump assembly suitable for converting energy from water waves as well as a wave power system for extracting energy from water waves and comprising one or more hydraulic piston pump assemblies.

[0004] BACKGROUND ART

[0005] For many years, there has been a high focus on environmentally friendly methods for generating energy, in particular extraction of energy from sun, wind and water waves.

[0006] Many different systems for extracting energy from water waves have been suggested. US 2007 / 0257491 discloses a wave power system comprising a plurality of generators comprising a float and a brake and a mechanical energy transmission system that harnesses wave energy and converts it into limited motion that is suitable for input to an electrical energy generator.

[0007] WO20257909 describes a wave energy harnessing system comprising a plurality of wave energy devices coupled together to form a high-capacity installation. The wave energy device includes a buoyant body, which maintains a permanent orientation relative to the surface of the ocean, while the power take-off (PTO) would self-al ign in the direction of the incoming waves. The power take-off is completely enclosed, above the waterline and easily accessible. The buoyant body is coupled to the buoyant bodies of other similar wave energy devices by flexible or articulating coupling means. The wave energy devices are arranged in arrays or any other suitable layouts, to form large connected floating structures. US2020088155 discloses a wave power device for extracting energy from water waves. The wave power device comprises a reference structure and effectors moving relative to the reference structure. Each effector is connected to two hydraulic rams, symmetrically positioned around each effector. The hydraulic rams have an effective hydraulic area which is stepwise increased as the length of the hydraulic rams are compressed and stepwise decreased as the length of the hydraulic rams are increased.

[0008] WO22214153 discloses a wave power system for extracting energy from water waves. The wave power system includes a basic structure, at least one effector movably engaged with the basic structure and adapted for being moved relative to the basic structure by water waves, and an energy harvesting arrangement arranged for harvesting energy from the relative movements between the energy collector and the basic structure The basic structure is a plurality of duct sections releasable connected to each other.

[0009] In many of the prior art systems for extracting energy from water waves, the energy from the waves is converted to pressurized water using a pump system. However, since the water waves vary greatly e.g., with respect to frequency, amplitude and energy content, it heretofore has been difficult to convert the energy with a desired high effect. In addition, the harsh environment in the water e.g. ocean water, both in respect of chemical and mechanical influences on the system is also a challenge for the extraction and conversion of the energy.

[0010] US 2010 / 0207390 describes a converter comprising a pump which is driven directly or indirectly by a natural force such as a water swell, it being possible for a hydraulic machine to be driven by the pump. The hydraulic machine is force-coupled to an electrical machine which may function as a generator or a motor. According to the present invention, the force acting on the pump is regulated via a control loop as a function of oscillation parameters of the natural force. The converter includes a pump which is driven by an oscillating natural force such as a water swell, via which a hydraulic machine system including at least one hydraulic machine may be driven, the hydraulic machine system being coupled to an electrical machine to convert mechanical energy into electrical energy. The converter includes a control loop via which the adjustable hydraulic machine may be adjusted such that the piston of the piston pump is acted upon using a predetermined force or a predetermined pressure differential.

[0011] DISCLOSURE OF INVENTION

[0012] An objective of the present invention is to provide a hydraulic piston pump assembly suitable for converting energy from water waves a wave power system, which is relatively robust and simultaneously effective for harvesting wave energy.

[0013] In an embodiment, it is an objective to provide a hydraulic piston pump assembly which is capable of operating mechanically without the use of electronic sensors or controllers.

[0014] In an embodiment, it is an objective to provide a hydraulic piston pump assembly which is self-adjustable.

[0015] In an embodiment, it is an objective to provide a hydraulic piston pump assembly which is very effective for extracting and converting energy from the water waves to hydraulic energy.

[0016] In an embodiment, it is an objective to provide a hydraulic piston pump assembly which is very durable and robust to both mechanical and chemical degradation

[0017] In an embodiment, it is an objective to provide a wave power system comprising one or more of the hydraulic piston pump assemblies, which water wave system thereby may provide a very effective conversion of energy from water waves to hydraulic energy and optionally further to use the hydraulic energy for desalination of water and / or for conversion to electricity.

[0018] These and other objects have been solved by the inventions or embodiments thereof as defined in the claims and as described herein. It has been found that the inventions or embodiments thereof have a number of additional advantages, which will be clear to the skilled person from the following description and claims.

[0019] It should be emphasized that the term "comprises / comprising" when used herein is to be interpreted as an open term, i.e. it should be taken to specify the presence of specifically stated feature(s), such as element(s), unit(s), integer(s), step(s) component(s) and combination(s) thereof, but does not preclude the presence or addition of one or more other stated features.

[0020] The phrase "applying a load" and "applying a force" are used interchangeably. Thus, applying a force to the paddle blade surfaces results in applying a force to the paddle blade surfaces.

[0021] The terms "liquid" and "water" may be used interchangeably.

[0022] The phrases "axial piston channel" and "piston channel" are used interchangeably.

[0023] Reference made to "some embodiments" or "an embodiment" means that a particular feature(s), structure(s), or characteristic(s) described in connection with such embodiment(s) is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases "in some embodiments" or "in an embodiment" in various places throughout the specification is not necessarily referring to the same embodiment(s). Further, the skilled person will understand that particular features, structures, or characteristics may be combined in any suitable manner within the scope of the invention as defined by the claims.

[0024] The term "substantially" should, unless otherwise specified or clear from the context, be taken to mean that ordinary product variances and tolerances are comprised.

[0025] Throughout the description or claims, the singular encompasses the plural unless otherwise specified or required by the context. All features of the invention and embodiments of the invention as described herein, including ranges and preferred ranges, may be combined in various ways within the scope of the invention, unless there are specific reasons not to combine such features.

[0026] The hydraulic piston pump assembly of the invention is adapted for forming part of a system for converting energy from water waves, such as a wave power system as further described below.

[0027] The hydraulic piston pump assembly comprises

[0028] • a pump housing having a pump housing axis and comprising an inner pump housing surface;

[0029] • a piston with a piston axis and comprising a piston head with a peripheral head surface adapted to seal against the inner pump housing surface and a piston rod connected to the piston head, wherein the piston rod comprises an outer piston rod surface and

[0030] • an actuator rod.

[0031] The piston rod may be connected to the piston head by being fixed e.g. by a mechanical e.g. threaded connection and / or a chemical e.g. glued connection or advantageously the piston rod is connected the piston head by the parts being integrated with each other.

[0032] The piston rod may be connected to the piston head by or via a sliding connection whereby the piston head is allowed to slide along a selected length portion of the piston rod.

[0033] The pump housing along the pump housing axis has a first pump housing end portion, a second opposite pump housing end portion and a pump housing operation portion located between the first pump housing end portion and the second pump housing end portion.

[0034] The piston head is located inside the pump housing and is axially slidable to move (drive) the piston head along the pump housing operation portion from a first piston pose where the piston head is at an innermost location at or adjacent to the first pump housing end portion and to a second piston pose where the piston head is at an outermost location adjacent the second pump housing end portion,

[0035] The piston rod is extending out of the pump housing through a piston passage at a piston passage location in the second pump housing end portion, wherein the piston passage is forming a seal against the piston rod surface.

[0036] The piston comprises an axial piston channel extending at least partially through the piston rod.

[0037] The actuator rod has a first actuator end portion and a second actuator portion which may or may not be or form part of an end portion. For example as it will be described further below the second actuator portion may conveniently be connected to or integrated with another rod, such as second actuator portion of another hydraulic piston pump assembly.

[0038] The first actuator end portion fully or partly extend into the axial piston channel and is slidable in the axial piston channel and the second actuator portion is adapted to be or is engaged with an effector capable of being actuated by the water waves.

[0039] The inventor of the present invention has provided an entire new concept comprising the actuator that is slidable in the axial piston channel. This concept ensures that the forces captured by the effector when actuated by the water waves may be transferred to the piston via the actuator rod which has shown to provide a very effective energy harvesting and at the same time may provide a high chemical and mechanical protection of the piston and the entire hydraulic piston pump assembly. Further the new concept enables a mechanical control and self-adjustment of the operation of the hydraulic piston pump assembly as it will be explained further below, such that a desired operation may be obtained without a need for sensors or electronic regulations.

[0040] The hydraulic piston pump assembly may preferably be configured for converting energy from ocean water waves and may advantageously be adapted for subsea operation, such as for generating pressurized water when forcibly moved by the effector, wherein the pressurized water among other things, may be applied for production of electricity and / or desalinated water.

[0041] The pump housing may in principle have any outer and inner cross-sectional shape, such as polygonal or round, e.g. square oval or circular. For ease production, it may be desired to provide the pump housing to have round or oval cross-sectional shape.

[0042] The pump housing may be either a simple monocoque structure or composed of several elements partly or fully bonded or connected together. In a particular and preferable version, the pump housing comprises a fibre reinforced composite pipe which is partly encased by a steel reinforcement.

[0043] The piston head is conveniently adapted to the inner pump housing surface to minimize distance and hereby enable sealing against the inner pump housing surface. The piston head may conveniently comprise a sealing, such as a piston seal e.g. a hydraulic piston seal e.g. as market by Trelleborg Sealing Solutions. Where the inner cross-sectional shape of the pump housing and thereby the inner pump housing surface is polygonal, such as square, it is desired that the peripheral head surface of the piston head has a corresponding shape to provide the desired sealing and in the same way where the inner cross-sectional shape of the pump housing and thereby the inner pump housing surface is round, such as circular, it is desired that the peripheral head surface of the piston head has a corresponding round shape to enable the desired sealing as a the piston heal slides in contact with the inner pump housing surface between the first piston head pose and the second piston head pose. The pump housing operation portion is defined by the portion of the pump housing in which the piston head can slide and be in sealing contact with the inner pump housing surface.

[0044] Advantageously the hydraulic piston pump assembly is adapted for pumping by pulling forces provided by the effector when water waves pull the effector away from the pump housing. It has been found that providing that the pumping is mainly provided by pulling the piston, so the piston head is pulled towards the outermost location (i.e. towards the second piston pose) a very effective energy transfer is provided and at the same time the potential wear applied to the piston is relative low.

[0045] In this embodiment, the hydraulic piston pump assembly is adapted to generate pressurized water when the water waves force the effector away from the pump housing hereby pulling the piston towards second piston pose, preferably from the first piston pose towards or even fully to the second piston pose to thereby provide a full piston stroke as it will be described further below.

[0046] The hydraulic piston pump assembly may advantageously be adapted for converting the energy from the water waves by the water waves actuating the effector by pulling the effector away from the pump housing. Thereby the effector engages and transfers pulling force to the second actuator portion providing the actuator to pull the piston towards second piston pose. The pulling of the piston towards second piston pose may be adapted to provide a pumping of liquid (preferably water) out of the pump housing, preferable to produce pressurized water.

[0047] In an embodiment, the piston rod and the piston head are connected to have a common symmetrical axis coincident with the piston axis. In an alternative embodiment the piston rod and the piston head are connected to not having a common symmetrical axis, the piston head may for example have a noncircular periphery, such as an oval periphery and / or the piston head may extend asymmetrically relative to the piston axis. In an embodiment, the first actuator end portion is slidable in the axial piston channel to move the first actuator end portion from a first actuator pose where it is fully located in the axial piston channel to a second actuator pose where the first actuator end portion is partly located in the axial piston channel. The actuator rod may for example be axially movable relative to the piston from the first actuator pose to the second actuator pose, wherein the actuator comprises an actuator protrusion located at the first actuator end portion of the actuator rod, wherein the actuator protrusion is preventing the actuator from slipping out of the piston channel. The second actuator pose will in this situation be a pose where the actuator protrusion is preventing the actuator from slipping out of the piston channel, for example wherein the actuator protrusion of the actuator rod in the second actuator pose geometrically engages with a radially inwards ledge of the piston rod.

[0048] To provide that the actuator rod is extending into the axial piston channel and is slidable in the axial piston channel, the piston conveniently comprises an access passage to the axial piston channel. The access passage may comprise a bearing to guide the actuator rod.

[0049] The bearing may form a seal, however it is not required that the bearing is leak proof. In an embodiment, it is desired that the bearing is a leaking bearing allowing water to pass, e.g. at a selected pressure.

[0050] In an embodiment the bearing is a linear bearing.

[0051] Advantageously, the bearing allow the actuator rod to tilt or even rotate to alleviate potential torsion caused by the water waves action on the effector engaged with the second actuator portion. Thereby the hydraulic piston pump assembly may be relatively robust towards torsion caused by the water waves

[0052] The pump housing may comprise a pump outlet located at the second pump housing end portion. This pump outlet is also referred to as a proximal pump outlet. The pump housing may advantageously comprise a pipe arrangement or be adapted to be connected to such pipe arrangement for pressurized liquid that passes through the pump outlet. Advantageously, the pump housing comprises means for connecting the second pump housing end portions to a pipe arrangement. Such means for connection may in practice be any kind of means, such as the means known in the art. The means for connecting may for example comprise an arrangement for a pipe connection, such as a lateral pipe connection e.g. a branch, a spigot and / or a socket.

[0053] The terms "proximal" and "distal" are seen in relation to locations in the pump housing, i.e. "distal" and "distally to" mean a location at or closer to the first pump housing end portion and "proximal" and "proximally" to mean at or closer to the second pump housing end portion or the terms "proximal" and "distal" are seen in relation to locations in the axial piston channel, i.e. "distal" and "distally to" mean a location at or closer to an innermost location in the axial piston channel and "proximal" and "proximally" to mean at or closer to access passage to the axial piston channel. Whether it is in relation to locations in the pump housing or in relation to locations in the axial piston channel will be clear from the context.

[0054] The pump outlet may be in fluid communication with a check-valve for preventing back flow. The outlet check-valve may be located at the pump outlet, at the pipe spigot or at any suitable location in the pipe arrangement for preventing backflow of liquid through the pump outlet.

[0055] In an embodiment, the outlet check-valve (preventing back-flow into the pump housing) is arranged at a location of the pipe arrangement adapted for transporting liquid towards the generator station.

[0056] In an embodiment, the outlet check-valve is located at the second pump housing end portion, preferably immediately adjacent to the pump outlet, such as at a pipe spigot of the pump housing.

[0057] In an embodiment, the outlet check-valve is located in the pipe arrangement adapted for transporting liquid towards the generator station. In an embodiment, the pipe arrangement adapted for transporting the liquid towards a generator station comprises a pipe spigot and / or a socket suitable for being mounted to the pump housing, such as to a pipe spigot and / or a socket of the pump housing.

[0058] In an embodiment, the hydraulic piston pump assembly or two or more hydraulic piston pump assemblies in combination comprises the pipe arrangement adapted for transporting the liquid towards a generator station.

[0059] The pump housing may comprise a distal liquid intake and outflow opening for intake and outflow of liquid distally to the piston head. The distal liquid intake opening is conveniently located at the first pump housing end portion, such as an open end face and / or one or more openings in a pump housing wall section of the first pump housing end portion. Optionally the liquid intake opening is covered by a filter for preventing blocking thereof e.g. by for preventing blockage caused by algae and seaweed.

[0060] In an embodiment, the pump housing comprises a proximal liquid intake opening for intake of liquid proximally to the piston head. The proximal liquid intake opening may be located proximally to the first pump housing end portion and / or in the piston head e.g. provided by one or more passages through the piston head. To prevent back flow through the proximal liquid intake opening, the assembly preferably comprises a one-way inlet checkvalve which may conveniently be arranged for preventing backflow when the piston head is sliding towards the second piston pose and producing pressurized water.

[0061] The inlet check-valve may in principle be any kind of check-valve. Advantageously, and for an effective operation the inlet check-valve may be a pressure activatable check-valve, which allows flow into an annular piston rod-pump housing space via the proximal liquid intake opening when the piston head is moved in distal direction towards the first piston pose and wherein the inlet check-valve is adapted to prevent outflow from the annular piston rod-pump housing space via the proximal liquid intake opening when the piston head is moved in proximal direction towards the second piston pose resulting in an increase in pressure in the annular piston rod-pump housing space. The annular piston rod-pump housing space is defined as the space between the piston rod and the inner pump housing surface, from the piston passage to the piston head.Thereby, when the piston head is moved in distal direction towards the first piston pose, liquid is flowing into the annular piston rod-pump housing space between the piston rod and the inner pump housing surface between the piston passage and the piston head via the proximal liquid intake opening and at the same time, liquid located distally to the piston head may flow out of the pump housing via the distal liquid intake and outflow opening.

[0062] In an embodiment, the inlet check-valve may an integral part of the piston. This may be realized by making the piston head slide between a first endstop at the first piston pose and a second endstop att the second piston. Thus, when the piston rod is pushed in one direction, the piston is pressed towards one of the endstops, whereas when the piston is pulled in the opposite direction the sliding piston is pressed towards an opposite of the endstops. One of the first and the second endstops is active during a suction stroke i.e. when water is pulled into the pump housing and the other endstop is active during a the power stroke, i.e. when water is pumped out of the housing.

[0063] The valve may then be realized by making a channel between the pumpchamber and the ambient, which is only exposed when the piston head is pressed towards or against the endstop that is active during the suction stroke. Thus, when the piston is pressed against the endstop which is active during the power stroke, the channel to the ambient is blocked.

[0064] When the piston head is moved in proximal direction towards the second piston pose, liquid in the annular piston rod-pump housing space is pressurized and pumped via the pump outlet and into the pipe arrangement, this is referred to as the power-stroke. Advantageously, the axial piston channel extends in the entire length of the piston rod. The first actuator end portion may comprise an actuator head located in, and slidable along the piston channel, from a distal actuator head location to a proximal actuator head location of the piston channel. The actuator head may be located in the distal location when the first actuator end portion is in the first actuator pose and the actuator head may be located in the proximal location of the piston channel when the first actuator end portion is in the second actuator pose.

[0065] In an embodiment, the actuator head constitutes or form part of the actuator protrusion which prevents the actuator from slipping out of the piston channel.

[0066] To alleviate the stroke that may be applied onto the actuator head when the actuator rod is pulled towards the second actuator pose caused by water waves acting on the effector, the actuator may advantageously comprise a shock absorber arrangement. The shock absorber arrangement may conveniently be adapted for at least partly absorbing forces when the actuator head reaches the proximal actuator head location in the piston channel and hits the radially inwards ledge of the piston rod. The resistance applied to a motion of the actuator head in the axial piston channel when the actuator rod is pulled towards the second actuator pose actuator head until it reaches the proximal actuator head location may be relatively low, which mean that the actuator head may hit the radially inwards ledge of the piston rod with a relative high impact force. The shock absorber arrangement may ensure that the risk of damaging the actuator head and the radially inwards ledge of the piston rod is reduced to a minimum.

[0067] Suitable materials and designs for shock absorber arrangements are known in the art and may for example comprise an elastic element, such as a viscoelastic element, e.g. comprising a spring element, a damping pot, a dashpot, a snubber and / or a rubber element. The actuator and the axial piston channel may form an actuator piston channel space between a channel surface of the axial piston channel and the actuator from the access passage to the channel to the actuator head and wherein the assembly comprises an actuator-piston check valve arrangement for at least partially control flow into and out of the actuator piston channel space.

[0068] Thereby the flow into and out of the actuator piston channel space may control the transfer of force from the actuator to the piston.

[0069] Advantageously, the actuator piston check valve arrangement allows liquid flow into the actuator piston channel space when the actuator head travels towards the proximate actuator head location. Thereby resistance to the motion of the actuator head towards the second actuator pose actuator head may be relatively low until it reaches the proximal actuator head location.

[0070] Advantageously, the actuator-piston check valve arrangement is adapted to close off when the pressure in the actuator piston channel space exceeds the pressure distally to the piston head, wherein the pressure distally to the piston head advantageously is ambient pressure. Thereby the pressure in the actuator piston channel space may increase which may ensure an effective transfer of forces from the actuator to the piston, which ensures that the piston is pushed into the first piston pose.

[0071] Thereby, even when the water waves are of moderate energy or even relative calm, the actuator may ensure that the piston repeatedly is moved to the first piston pose, thereby reducing the risk or even fully prevent marine biofouling, such as growth of barnacles and clams.

[0072] In an embodiment, the assembly comprises an actuator-piston relief valve comprising an activator adapted for allowing outflow from the actuator piston channel space when the piston is at or reaches a selected distance to the first piston pose, preferably the actuator-piston relief valve form part of the actuator-piston check valve arrangement. Advantageously, the actuator-piston check valve arrangement is adapted to provide that a motion of the actuator head towards the distal actuator head location provides an increase in pressure in the actuator piston channel space, which closes off the actuator-piston check valve arrangement and due to the incompressible liquid in the actuator piston channel space, provides a transfer of force to the piston to push the piston towards the first piston pose.

[0073] Thereby when the piston is at or reaches a selected distance to the first piston pose the actuator-piston relief valve is activated and allow liquid to flow from the actuator piston channel space to allow the actuator head to proceed towards the distal actuator head location. The actuator-piston check valve arrangement advantageously remains open for the actuator head to be pulled towards the proximal actuator head location without any significant resistance.

[0074] In an embodiment, the actuator-piston relief valve may form part of or be integrated with the actuator piston check valve arrangement.

[0075] In an embodiment, where the actuator head is slidable movable along the piston channel comprising a distally directed motion towards the distal actuator head location, the distally directed motion may fully or partly close the actuator-piston check valve arrangement and hereby provide that the distally directed motion of the actuator head is fully or partly transferred to the piston at least until the piston head is at or is at a selected distance to the first piston head pose.

[0076] The piston head may advantageously comprise a peripheral seal housing at its peripheral head surface that is housing a gasket, wherein the peripheral seal housing may be in the form of a recess.

[0077] The peripheral seal housing and the gasket may at least partly provide the seal against the inner pump housing surface. The piston head may comprise two or more gaskets located in same or in respective peripheral seal housings of the piston head. The gasket may e.g. be as the piston seals marketed by Trelleborg Sealing Solution e.g. as described on the home page https: / / www.seals- shop.com / eu / en / piston-seals.

[0078] The piston passage in the second pump housing end portion may advantageously comprise a seal housing, wherein the seal housing is housing a gasket. The seal housing may be in the form of a recess.

[0079] The gasket of the piston passage may be as described above for the gasket of the piston.

[0080] In an embodiment, wherein the first actuator end portion comprising the actuator head is extending into the axial piston channel and providing that the actuator head is slidable along the piston channel from the proximal actuator head location to the distal actuator head location of the piston channel, the actuator head when it is at its distal actuator head location is non-engaging with the piston head. Optionally the actuator head at its distal actuator head location is fully or partly located in the piston head but without being mechanically engaged with the piston head.

[0081] In a desired embodiment the assembly comprises a return mechanism adapted for returning the piston rod into the pump housing, preferably at least where a motion of the piston head towards the first piston head pose is ongoing and / or has a velocity less than a selected threshold and / or could not be completed without the return mechanism.

[0082] The return mechanism may advantageously be an active return mechanism. In an embodiment, the return mechanism is adapted for returning the piston rod into the pump housing even where the water wave is inadequate to actuate the effector to return the piston rod into the pump housing to provide that the piston head reaches the first piston head pose.

[0083] The return mechanism may preferably comprise a mechanical return mechanism a hydraulic return mechanism or a combination thereof. In an embodiment, the return mechanism comprises a mechanical return mechanism. The mechanical return mechanism may for example comprise a spring element and / or a rubber cord, wherein the spring element and / or rubber cord may be activatable by the axial motion of the piston when the piston head is moving towards the second piston head pose. The axial motion of the piston when the piston head is moving towards the second piston head pose may for example load the spring element and / or a rubber cord e.g. by stretching, and when the piston has reached the second piston head pose the element and / or a rubber cord may pull the piston back towards the second piston head pose optionally in cooperation with the forces transferred from the actuator to the piston as described above.

[0084] In an embodiment, the return mechanism comprises a return rod, wherein the return rod is fixed to or comprises a catcher for catching and fixing to the actuator rod when the actuator rod is moving away from the pump housing and wherein the return rod is engaged with the spring element and / or rubber cord to provide that the motion of the piston rod activates the spring element and / or rubber cord.

[0085] In an embodiment, the return mechanism comprises a hydraulic return mechanism comprising a return rod and a return housing wherein the return rod comprises a distal return rod portion having a distal return rod portion length and a proximal return rod portion, wherein the distal return rod portion comprises a return rod head located in the return housing and sealing against an inner return housing surface, the return rod head is slidable movable in the return housing between distally return housing head location, wherein the entire distal return rod portion is located in the return housing and a proximally return housing head location where a maximal part of the distal return rod portion is outside the return housing, wherein the proximal return rod portion is fixed to or comprises a catcher for catching and fixing to the actuator rod when the actuator rod is moving away from the return housing and wherein the return mechanism comprises a hydraulic controller arrangement connected to the return housing to control the pressure within the return housing proximally to the return rod head.

[0086] In an embodiment, the hydraulic controller arrangement comprises a return housing inlet path located proximally to the return rod head when the return rod head is at the return housing head location or at a distance to the return housing head location, which is up to 30 % of the distal return rod portion length.

[0087] Advantageously, a return annulus is provided between the return housing and the distal return rod portion and is extending from the return rod head and a return housing passage into the cylinder, wherein the hydraulic controller arrangement comprises a hydraulic return mechanism, comprising an arrangement for feeding pressurized liquid into the return annulus.

[0088] The hydraulic controller arrangement may for example comprise a return path for return pressurized water / liquid generated by the piston pump assembly. Conveniently the return path is adapted for returning pressurized water / liquid from the pump housing, from the outlet of the pump housing or from the pipe arrangement. Thereby a portion of the previously produced pressurized liquid may be used in the hydraulic return mechanism.

[0089] The return path may comprise a return path valve controllable by the hydraulic controller arrangement to prevent backflow.

[0090] The various elements of the hydraulic piston pump assembly may conveniently be made from materials that are suitable for use in water wave systems, such as materials that are suitable for use in sea water environments.

[0091] In an embodiment, the pump housing comprises a strength imparting layer (also called a reinforced pump housing) and an inner layer forming the inner pump housing surface of a polymer material. By providing the inner layer forming the inner pump housing surface of a polymer material a desired smooth inner pump housing surface may be provided in a relatively simple and cost effective way.

[0092] The strength imparting layer, may advantageously comprise at least one of a metal, such as carbon steel, stainless steel and / or aluminium; and / or a fiber reinforced polymer material, preferably comprising strength imparting fibers, preferably selected from polymer fibers, metal fibers and / or mineral fibers.

[0093] Any types of fiber may be useful, preferably fibers having a high hydrolysis strength and good adhesion to the matrix material.

[0094] Advantageously, the tensile strength of the strength imparting layer is at least 5 times the tensile strength of the inner polymer material, determined at an angle of 55° relative to the center axis of the housing. Optionally, the strength imparting layer comprises at least one of a metal containing layer and a layer comprising reinforcing fibres, tapes or wires (FTW) embedded in a polymeric matrix, wherein the fibres, tapes or wires comprises one or more of the materials selected from metals, ceramics and polymers.

[0095] In an embodiment, the inner layer comprises a polymer material comprising at least one of polyethylene (PE), cross-linked polyethylene PEX, polypropylene (PP), polyvinylchloride (PVC), Fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE) or polyoxymethylene (POM).

[0096] In an embodiment, the reinforced pump housing is in the proximal end reinforced by a steel-jacket, which also serves as mechanical anchor point for the pump wave energy device. The reinforced pump-housing and the reinforcing steel jacket may be joined in several ways, including mechanical locking and chemical bonding. Where the reinforced pump housing outer layer may be made from a polymer with inferior bonding properties, a locking pattern may be cut on the outside of the pump-housing, where after the pump-housing and the reinforcing jacket may be joined by casting a thermosetting resin in an annular space, which is defined by the inside of the casing and the outside of the pump-housing. In an embodiment, one or more of the actuator rod and / or the return rod is / are fully or partly of a metal, such as carbon steel, stainless steel, titanium, bronze and / or aluminium; and / or is / are fully or partly of a fiber reinforced polymer material, preferably comprising strength imparting fibers, preferably selected from polymer fibers, metal fibers and / or mineral fibers, such a glass fibers. In a specially preferred embodiment, the actuator rod connecting ends are made from a ductile metal, whereas the center part of the actuator rod is made from fibre reinforced polymers.

[0097] In an embodiment, the piston rod comprise a piston rod core coated with a piston rod coating, wherein the piston rod core is fully of partly of a metal, such as carbon steel stainless steel, titanium, bronze and / or aluminium; and / or is fully of partly of a fiber reinforced polymer material, preferably comprising strength imparting fibers, preferably selected from polymer fibers, metal fibers and / or mineral fibers.

[0098] In an embodiment the piston rod is made from a bare metal. Where the bare metal rod is duplex or super-duplex, grades like SAF2507 are preferred materials.

[0099] The piston rod core may be hollow for providing an axial piston channel as described above.

[0100] The piston rod coating may for example be of a polymer material comprising at least one of polyethylene (PE), cross-linked polyethylene PEX, polypropylene (PP), polyvinylchloride (PVC), Fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE) or polyoxymethylen (POM).

[0101] The hydraulic piston pump assembly as described above or two or more of such hydraulic piston pump assemblies may advantageously form part of a wave power system for extracting energy from water waves. The wave power system may advantageously comprise a basic structure, • at least one effector movably engaged with the basic structurer and adapted for being moved relative to the basic structure by water waves, and

[0102] • an energy harvesting arrangement arranged for harvesting energy from the relative movements between the effector and the basic structure,

[0103] -wherein the at least one effector comprises the effector engaged with the second actuator portion and

[0104] -wherein at least a part of the hydraulic piston pump assembly, form part of the energy harvesting arrangement.

[0105] Where the hydraulic piston pump assembly or assemblies comprises a part or all of the pipe arrangement, the pipe arrangement conveniently form part of the basic structure.

[0106] The invention also comprises a wave power system suitable for extracting energy from water waves.

[0107] The wave power system for extracting energy from water waves, comprises at least one hydraulic piston pump assembly as described above and at least one effector capable of being actuated by the water waves, wherein each of the at least one effector is engaged with at least one second actuator portion of one of the at least one hydraulic piston pump assembly.

[0108] The wave power system of embodiments of the invention may for example be as described in any one of US2011204643, US2020088155, WO22214153 WO23057028 and PCT / DK2022 / 050072 with the modification that the energy harvesting arrangement comprises at least one of the hydraulic piston pump assembly and wherein the at least one effector of the wave power system comprises the effector engaged with the second actuator portion.

[0109] Advantageously, the wave power system comprises a basic structure and wherein each of the at least one effector is movably engaged with the basic structurer and adapted for being moved relative to the basic structure by water waves and wherein the at least one hydraulic piston pump assembly forms part of an energy harvesting arrangement arranged for harvesting energy from the relative movements between the effector and the basic structure,

[0110] Preferably, the least one hydraulic piston pump assembly comprises a plurality of the hydraulic piston pump assemblies, wherein each effector, preferably is engaged with the second actuator portion of each of two of the hydraulic piston pump assemblies. Such two hydraulic piston pump assemblies wherein the respective second actuator portions are engaged with a common effector are also referred to as a pair of hydraulic piston pump assemblies.

[0111] Advantageously, each effector is engaged with the second actuator portion of each of a pair of the hydraulic piston pump assemblies. Preferably the second actuator portion of each of a pair of the hydraulic piston pump assemblies are integrated or fixed to each other. The pair of the hydraulic piston pump assemblies may conveniently be adapted to operate in opposite directions.

[0112] In a desired embodiment, each of the at least one effector comprises a wagon engaged with the basic structure and adapted for being moved forth and back along a path length section of the basic structure by a horizontal component of the water waves and / or by a vertical component of the water waves (rise and fall of the water).

[0113] The at least one effector may be engaged with the at least one hydraulic piston pump assembly or the pair of the hydraulic piston pump assemblies to provide that each back and forth motion along the path length section of the basic structure causes a pump stroke of each of the hydraulic piston pump assemblies engaged with the effector.

[0114] In use, the effector and the wagon engaged with the basic structure may be moved by the water waves along the entire path length section of the basic structure or only along a part of the path length section depending on the waves, such a wave energy and / or travelling direction(s) of the waves. For example, if the effector is stuck close to one end, repetitive oscillations may affect one of the hydraulic piston pump assemblies only. Even where the water waves is causing the effector and the wagon engaged with the basic structure to forth and back motions along a only a part of the path length section of the basic structure the one or more hydraulic piston pump assemblies may collect large amounts of energy.

[0115] In an embodiment, the at least one hydraulic piston pump assembly or the pair of the hydraulic piston pump assemblies is engaged with the at least one effector with the wagon adapted for being moved forth and back along the path length section of the basic structure, wherein the hydraulic piston pump assembly or the pair of hydraulic piston pump assembly is arranged with the respective pump housing axis parallel with the path length section.

[0116] For simplification and for cost effectivity it is desired that the pipe arrangement form part of the basic structure.

[0117] Each pair of the hydraulic piston pump assemblies and the engaged effector preferably with wagon may form an operation unit, wherein the forth and back motion along the path length section of the basic structure is adapted for moving the effector between a first effector location to a second opposite effector location. In the first effector location, the piston of a first of the pair of hydraulic piston pump assemblies is in the first piston pose and the piston of a second of the pair of hydraulic piston pump assemblies is in the second piston pose. In the second effector location, the piston of the first of the pair of hydraulic piston pump assemblies is in the second piston pose and the piston of the second of the pair of hydraulic piston pump assemblies is in the first piston pose. Thereby the two hydraulic piston pump assemblies of the pair of hydraulic piston pump assemblies are adapted for operation on opposite mode, i.e. pumping mode when the piston head is passing away from the first pose and towards the second piston pose and returning mode when the piston is head is passing away from the second pose and towards the first pose. Thus, when one of the hydraulic piston pump assemblies of the pair of hydraulic piston pump assemblies is operating in pumping mode, the other one of the hydraulic piston pump assemblies of the pair of hydraulic piston pump assemblies is operating in returning mode and vice versa. In the first effector location, the actuator of the first of the pair of hydraulic piston pump assemblies is advantageously in the first actuator pose, and the actuator of the second of the pair of hydraulic piston pump assemblies is in the second actuator pose in the second effector location, the actuator of the first of the pair of hydraulic piston pump assemblies is advantageously in the second actuator pose and the actuator of the second of the pair of hydraulic piston pump assemblies is in the first actuator pose

[0118] Advantageously, the forth and back motion along the path length section of the basic structure is adapted for repeatedly moving the effector from the first effector location to a middle effector location and further to the second effector location, from the second effector location to the middle effector location and further to the first effector location, wherein a motion of the effector wherein at the middle effector location each of the piston of the first and the piston of the second of the pair of hydraulic piston pump assemblies is in the respective first actuator pose and each of the actuator of the first and the actuator of the second of the pair of hydraulic piston pump assemblies is in the respective second actuator pose.

[0119] BRIEF DESCRIPTION OF THE EXAMPLES AND DRAWING

[0120] The invention will be illustrated further below in connection with examples and embodiments and with reference to the figures. The figures are schematic and may not be drawn to scale. The examples and embodiments are merely given to illustrate the invention and should not be interpreted to limit the scope of the invention.

[0121] Figure 1 is a schematic illustration of a wave power system according to an embodiment of the invention comprising a plurality of not shown hydraulic piston pump assemblies.

[0122] Figure 2a is a schematic, cross sectional side view of a portion of a hydraulic piston pump assembly of an embodiment of the invention. Figure 2b is a schematic, cross sectional side view of a portion of a hydraulic piston pump assembly of another embodiment of the invention

[0123] Figures 3a-3c are schematic cross sectional side views of a portion of a hydraulic piston pump assembly of an embodiment of the invention in different operation stages.

[0124] Figures 4a-4h are schematic cross sectional side views of a portion of another hydraulic piston pump assembly of an embodiment of the invention in different operation stages.

[0125] Figures 5a-5c are schematic cross sectional side views of a portion a wave power system of an embodiment of the invention in different operation stages.

[0126] Figures 6a-6f are schematic cross sectional side views of a portion hydraulic piston pump assembly with a return mechanism of an embodiment of the invention in different operation stages.

[0127] Figures 7a-7c are schematic cross sectional side views of a portion a wave power system of an embodiment of the invention wherein the hydraulic piston pump assemblies comprises respective return mechanism.

[0128] The wave power system of figure 1 comprises a basic structure 1 optionally in the form of pipes e.g. in the form of duct sections as described in

[0129] Figure 1 show a wave power system comprising a basic structure comprising three sets of elongate basic structure section also referred to as track sections 1 a, 1 b, 1 c. The track sections 1 a, 1 b, 1 c are connected to a common manifold 7 for transferring water pumped by the motions of the effectors 5 to a turbine generator 8. The common manifold 7 and the generator 8 form part of an energy harvesting arrangement arranged for harvesting energy from relative movements between the effectors 5 and the basic structurer.

[0130] The basic structure may conveniently comprise the pipe arrangement of a part thereof. A plurality of not shown hydraulic piston pump assemblies are connected at respective locations to the pipe arrangement for pumping pressurized into the pipe arrangement and further via the common manifold 7 to the turbine generator 8 for harvesting the energy.

[0131] Each set of elongate track sections 1a, 1 b, 1c comprises a number of elongate track sections portions each associated with an effector 5, which is movably engaged with the respective associated track section portions and adapted for being moved by water waves along the associated elongate track section portion in respective travelling length (also called a path length section) between not shown first and second locations.

[0132] Preferably each effector 5 is associated with a pair of hydraulic piston pump assemblies, preferably such that the effector is engaged with the second actuator portion of each of the pair of the hydraulic piston pump assemblies, e.g. as described above.

[0133] The elongate track section portions are arranged In in lengthwise extension of each other to form the three sets of elongate track sections 1 a, 1 b, 1c.

[0134] The sets of elongate track sections 1a, 1 b, 1c are moored by mooring lines M. The sets of elongate track sections 1a, 1 b, 1c may further comprises a number of buoyancy elements 3, where only a representative number of these are shown in addition or alternative to the buoyancy elements 3, the basic structure and / or the effectors 5 may comprise integrated light weight material, such as balsa and / or polymer foam e.g. embedded in thermoset polymer (advantageously epoxy), which thereby may have buoyancy effect.

[0135] The hydraulic piston pump assembly shown in figure 2a comprises

[0136] -a pump housing 11 having a pump housing axis A and comprising an inner pump housing surface;

[0137] -a piston with a piston comprising a piston head 12a with a peripheral head surface adapted to seal against the inner pump housing surface and a piston rod 12b connected to the piston head; and -an actuator rod 13 with an actuator head 13a.

[0138] The piston rod 12b is extending through a piston passage 14 at a piston passage location in the second pump housing end portion, wherein the piston passage 14 is forming a seal against the piston rod surface.

[0139] The piston head 12a is located in the pump housing and is axially slidable to move the piston head along the pump housing operation portion from a first piston pose where the piston head is at an innermost location at or adjacent to the first pump housing end portion and to a second piston pose where the piston head is at an outermost location adjacent the second pump housing end portion.

[0140] The pump housing 11 has a first pump housing end portion Pl, a second opposite pump housing end portion P2 and a pump housing operation portion P3 located between the first pump housing end portion Pl and the second pump housing end portion P.

[0141] The pump housing 11 has a branch 11a for connecting the second pump housing end portion P2 to a pipe arrangement for pumping pressurized water into the pipe arrangement.

[0142] The piston comprises an axial piston channel 15 extending at least partially through said piston rod 12b.

[0143] The actuator rod 13 has a first actuator 13b end portion and a second actuator portion 13c, wherein the first actuator end portion fully or partly extending into said axial piston channel 15 and is slidable in said axial piston channel and wherein the second actuator portion 13c is adapted to be engaged with a not shown effector capable of being actuated by the water waves.

[0144] In the shown embodiment, the axial piston channel 15 is extending in the entirely length of the piston through the piston rod 12b and the piston head 12a. Thereby water can move into and out of the piston channel distally to the actuator head with low or no resistance. In a desired embodiment the hydraulic piston pump assembly may comprise an actuator-piston check valve that is closing the water passage through the actuator head 13a when the actuator is moved in distal direction. The actuator head comprises a shock absorber arrangement 16 as described above.

[0145] The hydraulic piston pump assembly shown in figure 2b comprises

[0146] -a pump housing 21 having a pump housing axis A and comprising an inner pump housing surface;

[0147] -a piston with a piston comprising a piston head 22a with a peripheral head surface adapted to seal against the inner pump housing surface and a piston rod 22b connected to the piston head; and

[0148] -an actuator rod 23 with an actuator head 23a.

[0149] The piston rod 22b is extending through a piston passage 24 at a piston passage location in the second pump housing end portion, wherein the piston passage 14 is forming a seal against the piston rod surface.

[0150] The piston head 22a is located in the pump housing and is axially slidable to move the piston head along the pump housing operation portion from a first piston pose where the piston head is at an innermost location at or adjacent to the first pump housing end portion and to a second piston pose where the piston head is at an outermost location adjacent the second pump housing end portion. pump housing 21 has a first pump housing end portion Pl, a second opposite pump housing end portion P2 and a pump housing operation portion P3 located between the first pump housing end portion Pl and the second pump housing end portion P2.

[0151] The pump housing 21 has a branch 21a for connecting the second pump housing end portion P2 to a pipe arrangement for pumping pressurized water into the pipe arrangement. The piston comprises an axial piston channel 25 extending at least partially through said piston rod 22b.

[0152] The actuator rod 23 has a first actuator 23b end portion and a second actuator portion 23c, wherein the first actuator end portion fully or partly extends into said axial piston channel 25 and is slidable in said axial piston channel and wherein the second actuator portion 23c is adapted to be engaged with a not shown effector capable of being actuated by the water waves.

[0153] In the shown embodiment, the axial piston channel 25 is extending in the entirely length of the piston rod 22b and partially through the piston head 22a, wherein an actuator-piston check valve arrangement 27 is arranged to close the water passage through the actuator head 23a when the actuator is moved in distal direction.

[0154] A shock absorber arrangement 26 as described above is located at radially inwards ledge 28 of the piston rod 22.

[0155] The hydraulic piston pump assembly shown in figures 3a-3c is as the hydraulic piston pump assembly shown in figure 2a, with the difference that in figures 3a-3c, the shock absorber arrangement is not shown. Same or corresponding reference numbers are therefore used.

[0156] In figure 3a the not shown effector is pushed away from the pump housing 11 by action of water waves, thereby the actuator rod 13 including the actuator head 13a is pulled in proximal direction. It can be seen that there is a distance between the actuator head 13a and the piston head 12a that is increasing from the operation stage shown in figure 3a to the operation stage shown in figure 3b. Thus, the actuator rod is moved outwards of the piston channel, until the actuator head 13a hits the at radially inwards ledge 18 of the piston rod 12 where it reaches the second actuator pose as shown in figure 3b. Until this stage the piston may have been resting inside the pump housing in the first piston pose. During the motion of the actuator head 13a in distal direction, water can pass into the piston channel 15 distally to the actuator head 13a without providing any substantially resistance. Water located distally to the actuator head 13a may advantageously drain out of the piston channel 15 proximally to the actuator head 13a via an access passage 18a to the axial piston channel 15.

[0157] In figure 3c, the forces and the pulling acting on the actuator 13 is fully transferred to the piston, whereby water located in the annular piston rodpump housing space is pumped as pressurized water into the pump arrangement via the branch 11a.

[0158] The hydraulic piston pump assembly shown in figures 4a-4h is as the hydraulic piston pump assembly shown in figure 2b, with the difference that in figures 3a-3c, the shock absorber arrangement is not shown. Same or corresponding reference numbers are therefore used.

[0159] In figure 4a the not shown effector is pushed towards from the pump housing 21 by action of water waves, thereby the actuator rod 23 including the actuator head 23a is pushed in distal direction. Due to the pushing in distal direction, the pressure in the axial piston channel 25 distally to the actuator head 23a is increased, whereby the actuator-piston check valve arrangement 27 is closing the passage through the actuator head 23a when the actuator is moved in distal direction. The forces acting on the actuator 23 is thereby transferred to the piston which mean that the piston head 22a is moved distally towards the first piston pose. In figure 4b the piston head 22a has been moved closer to the to the first piston pose and in figure 4c the piston head 22a reaches it innermost location and thereby the first piston pose. As the piston reaches the first piston pose an actuator 27a is pushing the valve arrangement 27 to open, whereby the water located in the piston channel 25 is allowed to escape as the piston head 23a is travelling fully into the piston channel 25 to reach the first piston pose as further shown in figure 4d and 4e where the actuator 23 has reached the first actuator pose. In figure 4f, the motion direction has changed and the not shown effector is now pushed away from the pump housing 21 by action of water waves, thereby the actuator rod 23 including the actuator head 23a is pulled in proximal direction. It can be seen in figure 4f, that substantially no forces from the actuator rod 23 are transferred to the piston since there is no pressure build-up in piston channel 25.

[0160] First when the actuator head 23a hits the at radially inwards ledge 28 of the piston rod 22 the forces is transferred from the actuator rod 23 to the piston and the pumping of water located in the annular piston rod-pump housing space is pumped as pressurized water into the pump arrangement via the branch 21a as shown in figures 4g and 4h.

[0161] The wave power system shown in figures 5a-5c comprises a pair of hydraulic piston pump assemblies comprising a left hydraulic piston pump assembly 36 and a right hydraulic piston pump assembly 35. The second actuator portion 36a of the left hydraulic piston pump assembly 36 and the second actuator portion 35a of the right hydraulic piston pump assembly 35 are integrated or fixed to each other so that the two hydraulic piston pump assemblies 35, 36 are adapted to operate in opposite directions.

[0162] An effector 31 of the wave power system is engaged with the second actuator portion 36a of the left hydraulic piston pump assembly 36 and the second actuator portion 35a of the right hydraulic piston pump assembly 35. The effector 31 comprises a wagon 32 which may advantageously be slidably engaged with an elongate track section portion of the basic structure 37 to be capable of travelling a path length section L. The engagement may include wheels to reduce friction. The basic structure 37 may constitute or comprise the pipe arrangement as described above.

[0163] In figure 5a, the effector 31 is located in a center location between the pump housing of the left hydraulic piston pump assembly 36 and the pump housing of the of the right hydraulic piston pump assembly 35. Due to the operation of the actuator rod, the system will always be biased of having the respective pistons located in the first piston pose prior to having the actuator rod located in or moved towards the first actuator pose. Therefore, when there is no or only small waves the piston will remain in the first pose, reducing the risk of undesired fouling of the piston as described above.

[0164] In figure 5b the effector has travelled towards the pump housing of the right hydraulic piston pump assembly 35 to provide that the actuator of the right hydraulic piston pump assembly 35 is in the first actuator pose and at the same time the piston of the left hydraulic piston pump assembly 36 is in the second piston pose.

[0165] In figure 5c the effector has travelled towards the pump housing of the left hydraulic piston pump assembly 36 to provide that the actuator of the left hydraulic piston pump assembly 36 is in the first actuator pose and the piston of the right hydraulic piston pump assembly 35 is in the second piston pose.

[0166] The wave power system may advantageously comprise a plurality of operation units each comprising pair of the hydraulic piston pump assemblies and the engaged effector.

[0167] The figures 6a-6f illustrates a hydraulic piston pump assembly comprising a return mechanism and the operation mechanism of a return mechanism.

[0168] The hydraulic piston pump assembly comprises a pump housing 41 a piston 42 with an axial piston channel and an actuator rod 43 with an actuator head 43a. The hydraulic piston pump assembly further comprises a return mechanism comprising a return rod 44 and a return housing 49. The return rod 44 comprises a catcher 47 capable of engaging with the actuator head 43a as explained in the following.

[0169] In figure 6a the piston 42 is in the first pose, i.e. fully inside the pump housing the not shown effector engaged with the actuator rod 43 is moved away from the pump housing 41 by the water waves and thereby pulling the actuator rod 43 out of the axial piston channel until the actuator head hits the not shown radially inwards ledge of the piston rod 42. In figure 6a the actuator head 43a has reached the access passage to the axial piston channel and is about to transfer forces to the piston 42 for pulling the piston outward from the pump housing 41 towards the second piston pose.

[0170] When the motion is continued further as shown in figure 6b the catcher of the 47 of the return rod 44 engages with the actuator head 43, whereby the return rod 44 is pulled outwards from the return housing 59. At the same time the piston head 42a is moved in proximal direction and water is pumped to pressurized water as described above.

[0171] The return mechanism may comprise a mechanical return mechanism and / or a hydraulic mechanism as described above.

[0172] In figure 6c, the motion of the actuator rod 43 away from the pump housing 41 is continued and in figure 6d, the motion direction is switched. The not shown effector engaged with the actuator rod 43 is now moved towards the pump housing 41 by the water waves and thereby pushing the actuator rod in distal direction towards the pump housing 41. At the same time the return mechanism assist to ensure that the main part or even all of the forces of the return rod 43 is transferred to the piston 42 to provide that the piston head 42a is pushed towards the first piston pose. As shown in figure 6e, the actuator rod 43 is not pushed further into the axial piston channel. First, as shown in figure 6f, when the piston head 42a has reached the first piston pose and the return rod 43 is fully returned into the return housing 59, the pushing of the actuator further into the axial piston channel will start.

[0173] The wave power system shown in figures 7a-7c comprises a pair of hydraulic piston pump assemblies comprising a left hydraulic piston pump assembly 56 and a right hydraulic piston pump assembly 55.

[0174] The left hydraulic piston pump assembly 56 comprises a pump housing 51, a piston 52 with an axial piston channel and an actuator rod 53 with an actuator head 53a. The hydraulic piston pump assembly further comprises a return mechanism comprising a return rod 54 and a return housing 59. The return rod 54 comprises a catcher 47 capable of engaging with the actuator head 53a.

[0175] The right hydraulic piston pump assembly 55 comprises a pump housing 51', a piston 52' with an axial piston channel and an actuator rod 53' with an actuator head 53a'. The hydraulic piston pump assembly further comprises a return mechanism comprising a return rod and a return housing. The return rod comprises a catcher capable of engaging with the actuator head 53a'.

[0176] The actuator rod 53 of the left hydraulic piston pump assembly 56 and the actuator rod 53' of the right hydraulic piston pump assembly 55 are integrated or fixed to each other so that the two hydraulic piston pump assemblies 35, 36 are adapted to operate in opposite directions.

[0177] An effector 58 of the wave power system is engaged with the actuator rod 53 of the left hydraulic piston pump assembly 56 and the actuator rod 53' of the right hydraulic piston pump assembly 55. The effector 58 comprises a wagon 58a, which may advantageously be slidably engaged with an elongate track section portion e.g. as described above.

[0178] In figure 7a, the effector 51 is located in a center location between the pump housing 51 of the left hydraulic piston pump assembly 56 and the pump housing 51' of the of the right hydraulic piston pump assembly 55. Due to the operation of the actuator rod, the system will always be biased of having the pistons 52, 52' located in their respective first piston pose prior to having the respective actuator rods travelling towards or located in the respective first actuator pose. Therefore, when there is no of only small waves the piston will remain in the first pose, reducing the risk of undesired fouling of the pistons 52, 52a as described above.

[0179] In figure 7b the effector has travelled towards the pump housing of the right hydraulic piston pump assembly 55 to provide that the actuator rod 53' is passing further into the axial piston channel of the piston 52' to provide that the actuator head 53a' is passing distally towards the first actuator pose. At the same time the actuator 53 of the left hydraulic piston pump assembly 56 has started to pull the piston 52 outwards of the pump housing 51 and the catcher 57 of the return rod 54 has engaged with the actuator head 53a and started to pull the return rod 54 outwards from the return housing 59. In figure 7c the motion is continued and will continue until the piston 52 of the left hydraulic piston pump assembly 56 has reached the first piston pose and / or until the water waves changes the motion of the effector 58 to move in the opposite direction.

Claims

PATENT CLAIMS1. A hydraulic piston pump assembly for converting energy from water waves wherein the hydraulic piston pump assembly comprises• a pump housing having a pump housing axis and comprising an inner pump housing surface;• a piston with a piston axis and comprising a piston head with a peripheral head surface adapted to seal against the inner pump housing surface and a piston rod connected to the piston head, wherein the piston rod comprises an outer piston rod surface and• an actuator rod, wherein the pump housing along the pump housing axis has a first pump housing end portion, a second opposite pump housing end portion and a pump housing operation portion located between the first pump housing end portion and the second pump housing end portion, wherein the piston head is located in the pump housing and is axially slidable to move the piston head along the pump housing operation portion from a first piston pose where the piston head is at an innermost location at or adjacent to the first pump housing end portion and to a second piston pose where the piston head is at an outermost location adjacent the second pump housing end portion, wherein the piston rod is extending through a piston passage at a piston passage location in the second pump housing end portion, wherein the piston passage is forming a seal against the piston rod surface, wherein the piston comprises an axial piston channel extending at least partially through said piston rod, wherein the actuator rod has a first actuator end portion and a second actuator portion, wherein the first actuator end portion fully or partly extends into said axial piston channel and is slidable in said axial piston channel andwherein the second actuator portion is adapted to be engaged with an effector capable of being actuated by the water waves.

2. The assembly of claim 1, wherein the hydraulic piston pump assembly is adapted for pumping by pulling forces provided by the effector when water waves pull the effector away from the pump housing.

3. The assembly of claim 1 or claim 2, wherein the hydraulic piston pump assembly is adapted for converting the energy from the water waves by the water waves actuating said effector by pulling the effector away from the pump housing, thereby the effector is engaging and transferring pulling force to the second actuator portion providing the actuator to pull the piston towards second piston pose, preferably the pulling of the piston towards second piston pose is adapted to provide a pumping of liquid out of the pump housing.

4. The assembly of any one of the preceding claims, wherein said first actuator end portion is slidable in said axial piston channel to move the first actuator end portion from a first actuator pose where it is fully located in said axial piston channel to a second actuator pose where the first actuator end portion is partly located in said axial piston channel.

5. The assembly of claim 4 wherein the actuator rod is axially movable relative to the piston from the first actuator pose to the second actuator pose, wherein the actuator comprises an actuator protrusion located at the first actuator end portion of the actuator rod, wherein the actuator protrusion is preventing the actuator from slipping out of the piston channel, preferably wherein the actuator protrusion of the actuator rod in the second actuator pose geometrically engages with a radially inwards ledge of the piston rod.

6. The assembly of claim 4 or claim 5, wherein the piston comprises an access passage to the axial piston channel, wherein the access passage comprises a bearing to guide the actuator rod.

7. The assembly of any one of the preceding claims, wherein the pump housing comprises a pump outlet located at the second pump housing end portion, wherein the pump housing comprises a pipe arrangement or is adapted to be connected to a pipe arrangement for pressurized liquid passed through the pump outlet, preferably the pump housing comprises means for connecting the second pump housing end portion to a pipe arrangement, such an arrangement for lateral connection, e.g. a branch, a spigot and / or a socket.

8. The assembly of any one of the preceding claims, wherein the pump housing comprises a distal liquid intake and outflow opening for intake of liquid distally to the piston head, wherein the distal liquid intake opening is located at the first pump housing end portion, such as an open end face and / or one or more openings in a pump housing wall section of the first pump housing end portion, optionally the liquid intake opening is covered by a filter for preventing blocking thereof.

9. The assembly of any one of the preceding claims, wherein the pump housing comprises a proximal liquid intake opening for intake of liquid proximally to the piston head, wherein the proximal liquid intake opening preferably is located proximally to the first pump housing end portion and / or in the piston head, wherein the assembly preferably comprises a one way inlet check-valve arranged for preventing backflow when the piston head is sliding towards the second piston pose.

10. The assembly of claim 9, wherein said inlet check-valve is a pressure actuatable check-valve, which allows flow into an annular piston rod-pump housing space via the proximal liquid intake opening when the piston head is moved in distal direction towards the first piston pose and wherein the inlet check-valve is adapted to prevent outflow from the annular piston rod-pump housing space via the proximal liquid intake opening when the piston head is moved in proximal direction towards the second piston pose, wherein the annular piston rod-pump housing space is the space between the piston rodand the inner pump housing surface, from the piston passage to the piston head.

11. The assembly of any one of the preceding claims, wherein the axial piston channel extends in the entire length of the piston rod and wherein said first actuator end portion comprises an actuator head located in, and slidable along said piston channel from a distal actuator head location to a proximal actuator head location of the piston channel, preferably the actuator head is located in the distal location when the first actuator end portion is in the first actuator pose and the actuator head is located in the proximal location of the piston channel when the first actuator end portion is in the second actuator pose.

12. The assembly of claim 11, wherein the actuator head constitutes or form part of the actuator protrusion which prevents the actuator from slipping out of the piston channel, wherein the actuator head preferably comprises a shock absorber arrangement for at least partly absorbing forces when the actuator head reaches the proximal actuator head location in the piston channel and hits the radially inwards ledge of the piston rod.

13. The assembly of claim 12, wherein the shock absorber arrangement comprises an elastic element, such as a viscoelastic element, e.g. comprising a spring element, a damping pot, a dashpot, a snubber and / or a rubber element.

14. The assembly of any one of claims 11-13, wherein the actuator and the axial piston channel forms an actuator piston channel space between a channel surface and the actuator from the access passage to the channel to the actuator head, and wherein said assembly comprises an actuator-piston check valve arrangement for at least partially control flow into and out of the actuator piston channel space.

15. The assembly of claim 14, wherein the actuator piston check valve arrangement allows flow into the actuator piston channel space when the actuator head travels towards the proximate actuator head location.

16. The assembly of claim 14 or claim 15, wherein the actuator-piston check valve arrangement is adapted to close off when the pressure in the actuator piston channel space exceeds the pressure distally to the piston head.

17. The assembly of any one of claims 14-16, wherein the assembly comprises an actuator-piston relief valve comprising an activator adapted for allowing outflow from the actuator piston channel space when the piston is at or reaches a selected distance to the first piston pose, preferably the actuator-piston relief valve form part of the actuator-piston check valve arrangement.

18. The assembly of claim 15, wherein the actuator-piston check valve arrangement is adapted to provide that a motion of the actuator head towards the distal actuator head location provides an increase in pressure in the actuator piston channel space, which closes off the actuator-piston check valve arrangement provides a transfer of force to the piston to push the piston towards the first piston pose, wherein when the piston is at or reaches a selected distance to the first piston pose the actuator-piston relief valve is activated and allow liquid to flow from the actuator piston channel space to allow the actuator head to proceed towards the distal actuator head location and wherein the actuator-piston check valve arrangement advantageously remains open for the actuator head to be pulled towards the proximal actuator head location.19 The assembly of claim any one of claims 14-18, wherein said actuator head is slidable movable along said piston channel comprising a distally directed motion towards said distal actuator head location and wherein said distally directed motion is fully or partly closing said actuator-piston check valve arrangement providing that the distally directed motion of the actuatorhead is fully or partly transferred to the piston at least until the piston head is at or is at a selected distance to the first piston head pose.

20. The assembly of any one of the preceding claims, wherein the piston head comprises a peripheral seal housing at its peripheral head surface that is housing a gasket, wherein the peripheral seal housing may be in the form of a recess.

21. The assembly of any one of the preceding claims, wherein the piston passage in the second pump housing end portion comprises a seal housing that is housing a gasket, wherein the seal housing may be in the form of a recess.

22. The assembly of any one of claims 11-13, wherein the first actuator end portion comprising the actuator head is extending into the axial piston channel providing that the actuator head is slidable along said piston channel from the proximal actuator head location to the distal actuator head location of the piston channel, wherein the actuator head at its distal actuator head location is non-engaging with the piston head, optionally the actuator head at its distal actuator head location is fully or partly located in the piston head.

23. The assembly of any one of the preceding claims, wherein the piston comprises an access passage to the piston channel, wherein the access passage comprises a bearing to guide the actuator rod, the bearing is preferably a linear bearing.

24. The assembly of any one of the preceding claims, wherein the actuator is rotationally movable relative to said piston and / or relative to said pump housing, preferably the access passage to the piston channel and / or the bearing thereof allows the actuator to be rotationally movable with a selected mechanical impedance.

25. The assembly of any one of the preceding claims, wherein the assembly comprises a return mechanism adapted for returning the piston rod into the pump housing, preferably at least where a motion of the piston headtowards the first piston head pose is ongoing and / or has a velocity less than a selected threshold and / or could not be completed without the return mechanism.

26. The assembly of claim 25, wherein the return mechanism is adapted for returning the piston rod into the pump housing even where the water wave is inadequate to actuate the effector to return the piston rod into the pump housing to provide that the piston head reaches the first piston head pose.

27. The assembly of claim 25 or claim 26 wherein the return mechanism comprises a mechanical return mechanism, preferably comprising a spring element and / or a rubber cord, wherein the spring element and / or rubber cord preferably is activatable by the axial motion of the piston where the piston head is moving towards the second piston head pose.

28. The assembly of claim 27, wherein the return mechanism comprises a return rod, wherein the return rod is fixed to or comprises a catcher for catching and fixing to the actuator rod when the actuator rod is moving away from the pump housing and wherein the return rod is engaged with the spring element and / or rubber cord to provide that the motion of the piston rod activates the spring element and / or rubber cord.

29. The assembly of any one of claims 25-28, wherein the return mechanism comprises a hydraulic return mechanism comprising a return rod and a return housing wherein the return rod comprises a distal return rod portion having a distal return rod portion length and a proximal return rod portion, wherein the distal return rod portion comprises a return rod head located in the return housing and sealing against an inner return housing surface, the return rod head is slidable movable in said return housing between distally return housing head location, wherein the entire distal return rod portion is located in the return housing and a proximally return housing head location where a maximal part of the distal return rod portion is outside the return housing, wherein the proximal return rod portion is fixed to orcomprises a catcher for catching and fixing to the actuator rod when the actuator rod is moving away from the return housing and wherein the return mechanism comprises a hydraulic controller arrangement connected to the return housing to control the pressure within the return housing proximally to the return rod head.

30. The assembly of claim 29, wherein the hydraulic controller arrangement comprises a return housing inlet path located proximally to the return rod head when the return rod head is at the return housing head location or at a distance to the return housing head location, which is up to 30 % of the distal return rod portion length.

31. The assembly of claim 29 or claim 30, wherein a return annulus is provided between the return housing and the distal return rod portion and extending from the return rod head and a return housing passage into the cylinder, wherein the hydraulic controller arrangement comprises a hydraulic return mechanism, comprising an arrangement for feeding pressurized liquid into the return annulus.

32. The assembly of claim 31, wherein the hydraulic controller arrangement comprises a return path for return pressurized water / liquid generated by the piston pump assembly, preferably the return path is adapted for return pressurized water / liquid from the pump housing, from the outlet of the pump housing or from the pipe arrangement.

33. The assembly of claim 32, wherein the return path comprises a return path valve controllable by the hydraulic controller arrangement.

34. The assembly of any one of the preceding claims, wherein the pump housing comprises a strength imparting layer and an inner layer forming the inner pump housing surface of a polymer material.

35. The assembly of claim 32, wherein the strength imparting layer, comprises at least one of a metal, such as carbon steel, stainless steel and / or aluminium; and a fiber reinforced polymer material, preferably comprisingstrength imparting fibers, preferably selected from polymer fibers, metal fibers and / or mineral fibers.

36. The assembly of claim 34 or claim 35 wherein the tensile strength of the strength imparting layer is at least 5 times the tensile strength of the inner polymer material, optionally said strength imparting layer comprises at least one of a metal containing layer, a layer comprising reinforcing fibres, tapes or wires (FTW) embedded in a polymeric matrix, wherein the fibres, tapes or wires comprises one or more of the materials selected from metals, ceramics and polymers.

37. The assembly of any one of claims 34-36, wherein the inner layer comprises a polymer material comprising at least one of polyethylene (PE), cross-linked polyethylene PEX, polypropylene (PP), polyvinylchloride (PVC), Fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE) or polyoxymethylen (POM).

38. The assembly of any one of the preceding claims, wherein one or more of the actuator rod and / or the return rod is / are fully or partly of a metal, such as carbon steel stainless steel, titanium, bronze and / or aluminium; and / or is / are fully or partly of a fiber reinforced polymer material, preferably comprising strength imparting fibers, preferably selected from polymer fibers, metal fibers and / or mineral fibers, such a glass fibers.39 The assembly of any one of the preceding claims, wherein the piston rod comprise a piston rod core coated with a piston rod coating, wherein the piston rod core is fully of partly of a metal, such as carbon steel stainless steel, titanium, bronze and / or aluminium; and / or is fully of partly of a fiber reinforced polymer material, preferably comprising strength imparting fibers, preferably selected from polymer fibers, metal fibers and / or mineral fibers.

40. The assembly of claim 39, wherein the piston rod coating is of a polymer material comprising at least one of polyethylene (PE), cross-linked polyethylene PEX, polypropylene (PP), polyvinylchloride (PVC), Fluorinatedethylene propylene (FEP), polytetrafluoroethylene (PTFE) or polyoxymethylen (POM).41 The assembly of any one of the preceding claims, wherein the hydraulic piston pump assembly form part of a wave power system for extracting energy from water waves, preferably, the wave power system comprising:• a basic structure,• at least one effector movably engaged with said basic structurer and adapted for being moved relative to said basic structure by water waves, and• an energy harvesting arrangement arranged for harvesting energy from said relative movements between said effector and said basic structure, wherein said at least one effector comprises the effector engaged with the second actuator portion and wherein the hydraulic piston pump assembly form part of said energy harvesting arrangement.

42. A wave power system for extracting energy from water waves, wherein the wave power system comprises at least one hydraulic piston pump assembly according to any one of the preceding claims and at least one effector capable of being actuated by the water waves, wherein each of the at least one effector is engaged with at least one second actuator portion.

43. The wave power system of claim 42, wherein the wave power system comprises a basic structure and wherein each of the at least one effector is movably engaged with said basic structurer and adapted for being moved relative to said basic structure by water waves and wherein said at least one hydraulic piston pump assembly forms part of an energy harvesting arrangement arranged for harvesting energy from said relative movements between said effector and said basic structurer,44. The wave power system of claim 42 or claim 43, wherein the least one hydraulic piston pump assembly comprises a plurality of the hydraulic piston pump assemblies, wherein each effector, preferably is engaged with the second actuator portion of each of two of the hydraulic piston pump assemblies.

45. The wave power system of claim 44, wherein each effector is engaged with the second actuator portion of each of a pair of said hydraulic piston pump assemblies, preferably said second actuator portion of each of a pair of said hydraulic piston pump assemblies are integrated or fixed to each other, preferably the a pair of said hydraulic piston pump assemblies are adapted to operate in opposite directions.

46. The wave power system of any one of claims 42-45, wherein each of said at least one effector comprises a wagon engaged with the basic structure and adapted for being moved forth and back along a path length section of said basic structure by a horizontal component of the water waves and / or by a vertical component of the water waves (rise and fall of the water).

47. The wave power system of claim 46, wherein the at least one effector is engaged with said at least one hydraulic piston pump assembly or said pair of said hydraulic piston pump assemblies to provide that each back and forth motion along said path length section of said basic structure causes a pump stroke of each of the hydraulic piston pump assemblies engaged with said effector.

48. The wave power system of claim 46 or claim 47, wherein said at least one hydraulic piston pump assembly or said pair of said hydraulic piston pump assemblies engaged with said at least one effector with the wagon adapted for being moved forth and back along the path length section of said basic structure is arranged with said pump housing axis parallel with said path length section.

49. The wave power system of any one of claims 42-48, wherein the pipe arrangement form part of said basic structure.

50. The wave power system of any one of claims 46-49, wherein each pair of said hydraulic piston pump assemblies and the engaged effector with wagon form an operation unit, wherein the forth and back motion along the path length section of said basic structure is adapted for moving the effector between a first effector location to a second opposite effector location, wherein in the first effector location, the piston of a first of the pair of hydraulic piston pump assemblies is in the first piston pose, and the piston of a second of the pair of hydraulic piston pump assemblies is in the second piston pose and wherein in in the second effector location the piston of the first of the pair of hydraulic piston pump assemblies is in the second piston pose and the piston of the second of the pair of hydraulic piston pump assemblies is in the first piston pose.

51. The wave power system of claim 50, wherein in the first effector location the actuator of the first of the pair of hydraulic piston pump assemblies is in the first actuator pose, and the actuator of the second of the pair of hydraulic piston pump assemblies is in the second actuator pose and wherein in in the second effector location the actuator of the first of the pair of hydraulic piston pump assemblies is in the second actuator pose and the actuator of the second of the pair of hydraulic piston pump assemblies is in the first actuator pose.

52. The wave power system of claim 50 or claim 51 , wherein the forth and back motion along the path length section of said basic structure is adapted for repeatedly moving the effector from the first effector location to a middle effector location and further to the second effector location, from the second effector location to the middle effector location and further to the first effector location, wherein a motion of the effector wherein at the middle effector location each of the piston of the first and the piston of the second of the pair of hydraulic piston pump assemblies is in the respective first actuator poseand each of the actuator of the first and the actuator of the second of the pair of hydraulic piston pump assemblies is in the respective second actuator pose.

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