MULTIPLIER

FIELD OF THE INVENTION

The present invention relates to a modular piezoelectric based energy harvesting apparatus with mechanical force multiplier to harvest energy from forces applied to a roadway, railway, airport runway or pedestrian walkway, system for using said apparatus and method for implementation said apparatus.

BACKGROUND OF THE INVENTION

Piezoelectricity is the ability of certain crystalline materials to develop an electrical charge proportional to an applied mechanical stress. The converse effect can also be seen in these materials where strain is developed proportional to an applied electrical field. The Curie's originally discovered it in the 1880's. Some of the commercially used piezoelectric materials for industrial applications are lead based ceramics, available in a wide range of properties. However, other piezoelectric materials are also available. Piezoelectric materials are the most well known active material typically used for transducers as well as in adaptive structures.

Mechanical compression or tension on a poled piezoelectric ceramic element changes the dipole moment, creating a voltage. Compression along the direction of polarization, or tension perpendicular to the direction of polarization, generates voltage of the same polarity as the poling voltage. Tension along the direction of polarization, or compression perpendicular to the direction of polarization, generates a voltage with polarity opposite that of the poling voltage. These actions are generator actions - the ceramic element converts the mechanical energy of compression or tension into electrical energy. This behavior is used in fuel-igniting devices, solid state batteries, force-sensing devices, and other products. Values for compressive stress and the voltage (or field strength) generated by applying stress to a piezoelectric ceramic element are linearly proportional up to a material-specific stress. The same is true for applied voltage and generated strain. The review article "Advances In Energy Harvesting Using Low Profile Piezoelectric Transducers"; by Shashank Priya; published in J Electroceram (2007) 19:165-182; provides a comprehensive coverage of the recent developments in the area of piezoelectric energy harvesting using low profile transducers and provides the results for various energy harvesting prototype devices. A brief discussion is also presented on the selection of the piezoelectric materials for on and off resonance applications.

The paper "On Low-Frequency Electric Power Generation With PZT Ceramics"; by Stephen R. Piatt, Shane Farritor, and Hani Haider; published in IEEE/ASME Transactions On Mechatronics, VOL. 10, NO. 2, April 2005; discusses the potential application of PZT based generators for some remote applications such as in vivo sensors, embedded MEMS devices, and distributed networking. The paper points out that developing piezoelectric generators is challenging because of their poor source characteristics (high voltage, low current, high impedance) and relatively low power output.

The article " Energy Scavenging for Mobile and Wireless Electronics"; by Joseph A.

Paradiso and Thad Starner; Published by the IEEE CS and IEEE ComSoc, 1536-1268/05/; reviews the field of energy harvesting for powering ubiquitously deployed sensor networks and mobile electronics and describers systems that can scavenge power from human activity or derive limited energy from ambient heat, light, radio, or vibrations.

In the review paper "A Review of Power Harvesting from Vibration using Piezoelectric Materials"; by Henry A. Sodano, Daniel J. Inman and Gyuhae Park; published in The Shock and Vibration Digest, Vol. 36, No. 3, May 2004 197-205, Sage Publications; discusses the process of acquiring the energy surrounding a system and converting it into usable electrical energy - termed power harvesting. The paper discusses the research that has been performed in the area of power harvesting and the future goals that must be achieved for power harvesting systems to find their way into everyday use.

Patent application WO07038157A2; titled "Energy Harvesting Using Frequency

Rectification"; to Carman Gregory P. and Lee Dong G.; filed: 2006-09-21 discloses an energy harvesting apparatus for use in electrical system, having inverse frequency rectifier structured to receive mechanical energy at frequency, where force causes transducer to be subjected to another frequency. US patent 5,265,481; to Sonderegger, Hans C, et. al.; titled "Force sensor systems especially for determining dynamically the axle load, speed, wheelbase and gross weight of vehicles"; discloses sensor system incorporated in road surface - has modular configuration for matching different road widths.

US patent 7830071 ; to Abramovich, et. al.; titled "Power harvesting apparatus, system and method, discloses a method for harvesting the deformation of the roadway caused by passing vehicles, by piezoelectric elements loaded in compression.

US patient 7812508; to Abramovich, et. al. ; titled" Power harvesting form railway;

apparatus, system and method, discloses and energy harvesting, discloses a method for harvesting the deformation of the railway caused by passing trains, by piezoelectric elements loaded in compression.

PCT application PCT/IL2011/000395; titled: Piezoelectric Stack Compression Generator, filing date: May 18, 2011

SUMMARY OF THE INVENTION

The present invention relates to a modular piezoelectric based energy harvesting apparatuses with a mechanical force multiplier to harvest energy from forces applied to a roadway, railway, airport runway, vibrating machinery or pedestrian walkway; to systems for energy harvesting using said apparatus; and to methods for implementation said apparatuses. As vehicles, trains, planes and/or pedestrians move along their ways, part of their mechanical energy is spent in deformation of the way. This wasted energy is usually dissipated as heat. This invention harvests this usually wasted energy.

The amount of energy generated by the piezoelectric generator depends on its construction, material properties and the force applied to the transducer. Generally, the larger the force, the larger the generated energy. The current invention discloses exemplary embodiments for mechanical force multipliers that increases the force applied to piezoelectric generators within a piezoelectric module, thus increasing the amount of harvested energy.

In some exemplary embodiments, using a force multiplier increases the generated energy from a piezoelectric module by increasing the number of generators exposed to the effective force. When large forces are applied to the transducer, there is a need to protect the transducer from catastrophic filature due to forces exceeding its maximal loading, or from loss of performance and mechanical fatigue and failure due to repeated loading cycles. In some exemplary embodiments the disclosed invention comprises mechanisms for protecting the piezoelectric generators from being overstressed.

The piezoelectric transducers may be made of a single layer of piezoelectric material, or from a stack of layers. Stacks may comprise of several layers, fused (co-fired) together; or separate layers positioned in a stack configuration. In some embodiments, some layers may be fused stacks.

To be maximally efficient, the piezoelectric elements are preferably loaded within ranges of strains where their mechanical-electrical conversion is maximal and stable in multiple loading cycles. The same piezoelectric generator may therefore not be equally efficient in harvesting energy from widely different loads. Some exemplary embodiments of the present invention comprise a method to efficiently harvest these varying loads, for example from both heavy trucks and passenger cars passing on a roadway. A dual-load piezoelectric apparatus and module is disclosed, comprising at least two types of piezoelectric generators. A mechanical load-managing system is presented, capable of directing forces generated by light loads to light-load piezoelectric generators, and directing forces generated by heavy loads to heavy-load piezoelectric generators. In an exemplary embodiment of the invention, the dual-load piezoelectric apparatus and module comprises at least one force multiplier. In an exemplary embodiment of the invention, the dual-load piezoelectric apparatus comprises at least a heavy-load force multiplier and a light-load force multiplier. In an exemplary embodiment of the invention, the dual-load piezoelectric apparatus comprises one light-load force multiplier and two heavy-load force multipliers. In an exemplary embodiment of the invention, the dual-load piezoelectric apparatus comprises at least one force limiter for limiting the force applied to at least one piezoelectric generator.

In some of the exemplary embodiment, the module comprises one or combinations of the following components: a rigid upper and a rigid lower plate made of metal or plastic, a mechanical linkage connected to the upper plate that divides vertical force into two components subtending an angle β with the vertical axis by which the force is conveyed in compression to piezoelectric elements. In some of the exemplary embodiment, the modular generator may have one or more sets of these coupled components.

In some of the exemplary embodiment, the piezoelectric elements loaded are composed of either solid rods or stacked rods of piezoelectric elements.

In some of the exemplary embodiment, the piezoelectric elements are composed of sintered

(co-fired) stacks

In some of the exemplary embodiment, the piezoelectric elements are composed of stacks composed of piezoelectric rods stacked one on top of the other with interfaces of softer material than the piezoelectric material and include electrodes.

In some of the exemplary embodiment, the height of the stack is determined by spatial considerations and the stability of the stacks.

In some of the exemplary embodiment, the amount of piezoelectric material in the module is adjusted so as to deform the piezoelectric material at the desired Pascal level of stress.

In some of the exemplary embodiment, the modular generator can be made to efficiently harvest energy at both high and low vertical forces by the addition of a second mechanical linkage as illustrated in figures 5A(i)-5C. This is especially applicable when harvesting forces in the roadway that are used by both high wheel loads as exemplified by those produced by heavy trucks and low wheel loads as exemplified by those produced by passenger cars.

In some of the exemplary embodiment, the module is preferably sealed and protected from moisture and water.

In some of the exemplary embodiment, the module may have an internal electrical energy conversion or utilization unit or use an external electrical energy harvesting system.

In some of the exemplary embodiment, the modular piezoelectric power harvesting apparatus further comprising at least a first and a second force multipliers arranged in back-to-back configuration.

In some of the exemplary embodiment, the first force multiplier comprises a first mechanical linkage generating two compressive forces at an angle with respect the applied force, the second force multiplier comprises a second mechanical linkage generating two compressive forces subtending at an angle with respect the applied force, and said first mechanical linkage transfers force to said second mechanical linkage substantially in the direction of the applied force. In some of the exemplary embodiment, the device further comprises a box holding said first and second force multipliers.

It is an object of the current invention to provide a piezoelectric power harvesting device having force multiplier comprising: at least one force-distribution member; at least one common support structure; at least a first and a second piezoelectric generators, each of said piezoelectric generators is in mechanical communication with said force-distribution member at a first end, and each of said piezoelectric generators is in mechanical communication with said common support structure at a second end, each of said piezoelectric generators is capable of generating electrical power in response to compressive reactive force applied between said first end and said second end of said generator, wherein said mechanical communication with said force-distribution member and said communication with said common support structure is configured to produce compressive reactive forces on said piezoelectric generators in response to compressive force applied between said least one force-distribution member and said at least one common support structure.

In some embodiments each of the reactive forces is at an angle with respect to said applied force.

In some embodiments the reactive forces are substantially given by:

Fl=F2=F/(2*Cos[Beta]), wherein: Fl and Fl are the reactive forces on said first and second piezoelectric generators respectively, F is the applied force acting between said least one force- distribution member and said at least one common support structure, and Beta is the angle between the directions of said reactive forces with respect to the direction of said applied force.

In some embodiments the reactive compressive force on said piezoelectric generators is not smaller than said compressive force applied between said least one force-distribution members and said at least one common support structure.

In some embodiments at least one of said piezoelectric generators comprises a stack of piezoelectric elements.

In some embodiments the stack of piezoelectric elements comprises at least one sintered (co-fired) stacks.

In some embodiments the stack of piezoelectric elements comprises at least one stack composed of piezoelectric rods stacked one on top of the other within a matrix of material softer than the piezoelectric material. In some embodiments at least one of said piezoelectric generators comprises at least one single crystal piezoelectric element.

In some embodiments the amount of piezoelectric material in the device is adjusted so as to deform the piezoelectric material at the desired Pasqual level of stress for efficient energy production.

In some embodiments the output of the generator is used as a sensor to provide information.

In some embodiments the face of at least on of said at least one force-distribution member is curved and is capable of sliding against said first ends of said first and a second piezoelectric generators.

In some embodiments at least one force-distribution member is linked to said first ends of said first and second piezoelectric generators via friction reducing elements.

In some embodiments the second ends of said at least first and second piezoelectric generators are linked to said common support via friction reducing elements.

In some embodiments at least one of said friction reducing elements is a bearing.

In some embodiments at least one of said bearing is a ball bearing.

It is another object of the current invention to provide a piezoelectric power harvesting apparatus comprising: at least a first and a second piezoelectric power harvesting devices having force multiplier, each of said first and second piezoelectric power harvesting devices having force multiplier comprising: at least one force-distribution member; at least one common support structure; at least a first and a second piezoelectric generators, each of said piezoelectric generators is in mechanical communication with said force-distribution member at a first end, and each of said piezoelectric generators is in mechanical communication with said common support structure at a second end, each of said piezoelectric generators is capable of generating electrical power in response to compressive reactive force applied between said first end and said second end of said generator, wherein said mechanical communication with said force-distribution member and said communication with said common support structure is configured to produce compressive reactive forces on said piezoelectric generators in response to compressive force applied between said least one force-distribution member and said at least one common support structure. In some embodiments the first device and second device are placed side by side such that their common supports acts as a single base.

In some embodiments the first device and second device are placed one on top of the other such that their force-distribution members are in mechanical communication.

In some embodiments the first device and second device are of different mechanical and electrical properties, wherein said first device is configured to efficiently harvest energy at a first range of applied forces, wherein said second device is configured to efficiently harvest energy at a second range of applied forces, and wherein said first range of applied forces is lower than said second range of applied forces, such that said apparatus is capable of efficiently harvesting energy at both said first and second ranges of applied forces.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. In the drawings:

Figure 1 schematically depicts the mechanical basis for the amplification of forces in the modular piezoelectric module according to an exemplary embodiment of the current invention.

Figure 2 schematically depicts several views of a module according to an exemplary embodiment of the current invention,

Figure 3 schematically depicts several views of a railroad sleeper having embedded module according to an exemplary embodiment of the current invention,

Figure 4A schematically depicts several views of a light load super-module 400 according to an exemplary embodiment of the current invention.

Figure 4B schematically depicts a side view of an encased light load super-module according to an exemplary embodiment of the current invention.

Figure 4C schematically depicts a side view of an energy harvesting system using a plurality of light load super-modules according to an exemplary embodiment of the current invention.

Figure 5A(i) schematically depicts several views of the assembled dual-load module according to an exemplary embodiment of the current invention.

Figure 5A(ii) schematically depicts isometric view of the assembled dual-load module according to an exemplary embodiment of the current invention.

Figure 5B schematically depicts the dual- load module according to an exemplary embodiment of the current invention with the heavy-load force-distributing member removed, exposing the light-load piezoelectric generators and the light-load force-distributing member 530.

Figure 5C schematically depicts enlarged cross sectional views of dual-load module according to an exemplary embodiment of the current invention.

Figure 6A schematically depicts an isometric view of a force multiplying module according to another exemplary embodiment of the current invention.

Figure 6B schematically depicts an isometric view of a section of a piezoelectric stack used in the force multiplying module according to an exemplary embodiment of the current invention.

Figure 7A schematically depicts a cross-sectional view of a force multiplying device using two force multiplying modules in a back- to -back configuration according to an exemplary embodiment of the current invention. Figure 7B schematically depicts an isometric outer view of a force multiplying device of figure 7A according to an exemplary embodiment of the current invention.

Figure 7C schematically depicts another cross-sectional view of a force multiplying device using two force multiplying modules in a back-to-back configuration according to an exemplary embodiment of the current invention.

Figure 7D schematically depicts yet another cross-sectional view of a force multiplying device using two force multiplying modules in a back-to-back configuration according to an exemplary embodiment of the current invention.

Figure 8A schematically depicts a side view of a force multiplying device using friction reducing bearings according to yet another exemplary embodiment of the current invention.

Figure 8B schematically depicts a cross-sectional view of the force multiplying device using friction reducing bearings according to yet another exemplary embodiment of the current invention.

Figure 8C schematically depicts a top view of the force multiplying device using friction reducing bearings according to yet another exemplary embodiment of the current invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a modular piezoelectric based energy harvesting apparatus with a mechanical force multiplier to harvest energy from forces applied to a roadway, railway, airport runway or pedestrian walkway, system for using said apparatus and method for implementation said apparatus.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

In discussion of the various figures described herein below, like numbers refer to like parts.

The drawings are generally not to scale. For clarity, non-essential elements were omitted from some of the drawings. Energy harvesting using piezoelectric transducer from mechanical repeated stresses is well known. The amount of energy generated by the piezoelectric generator depends on its construction, material properties and the force applied to the transducer. Generally, the larger the force - the larger the generated energy. For clarity, the components used for transmitting, receiving and using the generated electrical energy were omitted from the drawings.

When large forces are applied to the transducer, there is a need to protect the transducer from catastrophic filature due to forces exceeding its maximal loading, or from loss of performance and mechanical fatigue and failure due to repeated loading cycles. It may be advantageous to match the forces to the characteristic mechanical and piezoelectric properties of the transducer used.

The piezoelectric transducers may be made of a single layer of piezoelectric material, or from a stack of layers. Stacks may comprise of several layers, fused (co-fired) together; or separate layers positioned in a stack configuration. In some embodiments, some layers may be fused stacks.

Piezoelectric materials used for energy harvesting may be piezoelectric ceramic materials, piezoelectric single crystal, or piezoelectric polymers. Some piezoelectric polymers exhibit inferior energy generation properties in comparison to the best piezoelectric ceramic materials, as well as degradation of performance after about 30,000 loading cycles. Stress on some currently used ceramic elements should be kept below 50 MPa, else degradation occurs after -100,000 cycles. Thus it is advantageous to adopt the design of the generator to the intended application.

In some cases, generated energy from a piezoelectric generator may be increased by increasing the effective force applied to the generator, and/or increasing the number of generators exposed to the force.

Figure 1 schematically depicts the mechanical basis for the amplification of forces in the modular piezoelectric module according to an exemplary embodiment of the current invention.

Supposing there is a force 101 having magnitude F which is applied to a force-distributing member 102. For clarity, force 101 is drawn in the downward (-Y), but it should be realized that the coordinate system is arbitrary.

In the depicted exemplary embodiment, force 101 results in two reaction forces Fl and F2 (103a and 103b respectively) that are at equal angles of inclination β in respect to the Y axis. Reaction forces Fl and F2 are applied to two (preferably identical) piezoelectric generators and the energy is harvested from these two generators.

The summation of forces in the vertical Y direction can be expressed as follows:

∑ F _Y = 0 ; Thus in this example F = Fl ^■ Co (β) + F2 ^■ Cos{ )

The summation of the forces in the X direction can be expressed as follows:

F _X = 0 ; Thus in this example: Fl■ Ξίη(β) = F2■ Ξίη(β) ; resulting in Fl = F2

And accordingly:

F = Fl ^■ Cos(p) + Fl ^■ Cos(p) = 2 - Fl - Cos(p)

Or F1 = F2 =

2 - Cos{p)

Note that when the angle β is equal to 60° the applied force is equal to each of the reaction forces F=F1 ; and thus F1+F2=2F.

Note that when the angle β is larger than 60° the reaction force on each of the generators is larger than the applied force.

Note that for any angles of inclination 90° > β > 60 the sum of energy harvested by both generators is larger than the energy that would have been harvested by applying force F to a single generator since Fl + F2 = F ^' ICos(P) > F

As the angle β is increased, for example from 60° up to 90° the reaction forces Fl and F2 are increased.

In the exemplary embodiment case, when this forces is applied to piezoelectric ceramic material of the same area more energy will be produced

It should be noted that the configuration seen in figure 1 is for illustration only. Asymmetric reaction forces may be used wherein unequal angels between the applied and reaction forces are used. Additionally or alternatively, more than two reaction forces may be used. Specifically, the reaction forces may not be confined to the X-Y plane, for example, two additional reaction forces may be placed in the Y-Z plane (not seen in this figure).

The generator may be used on streets, road, railway, airplane runway or taxiways, under vibrating machinery and pedestrian walkways for harvesting the wasted energy imparted by passing motor vehicles, trains and pedestrians as they deform the roadway, railway and pedestrian walkways. .

Figure 2 schematically depicts several views of a module 200 according to an exemplary embodiment of the current invention,

In this figure, 200a 200b, 200c and 200d are: front, side, top and isometric views of module 200 respectively. The applied and reaction forces (100, 103a and 103b respectively) are schematically depicted in side view 200a. The coordinate system (X, Y, Z) are schematically depicted in isometric view 299d.

When applied force 101 is applied to force-distribution member 102, generators 203a and

203b are pressed between the force-distribution member 102 and the base 205 (which acts a common support for generators 103a and 103b) such that reaction forces 103a and 103b are applied by the generators 203 a and 203b on force-distribution member 102.

In this exemplary embodiment, the generators 203 are depicted as single elements of sintered stacks; however other types of generators may be used. In the depicted embodiment, optional retaining structures 209 (only few of these retaining structures are marked or seen for drawing clarity) hold the generators 203 in place. Retaining structures 209 may be secured with screws, but other means of securing the generators may be used such as adhesives. Optionally, force-distribution member 102 is pre-loaded against the base 205 such that generators 203 are held in place.

Optionally, base 205 comprises a protrusion 211 such that a gap 213 is left between the top of protrusion 211 and the bottom of force-distribution member 102. When a large force F is applied to force-distribution member 102, generators 203 are compressed until gap 213 is closed and the force if applied directly to the base, preventing excessive force from being applied to the generators.

The general construction of the module seen in figure 2 may be adapted to various applications by selecting the relevant parameters such as the dimensions, the angles, the size and shape of the generators, the construction materials and so on. The rigid parts such as the base and force-distribution member 102 may be made of metal such as aluminum iron or steel, or from polymeric material or plastic or composite materials. A pluraKty of modules may be combined in a super-module comprising few modules. A plurality of modules or super-modules may be assembled to a system.

Force may be applied directly to the force-distribution member, for example in a railroad application where the rail is in contact (directly, or separated by a thin elastic pad) with the force- distribution member. Similarly, vibrating machinery may be placed modules such that it is supported by the force-distribution members.

Alternatively, a top plate may be used for transferring the load to the force-distribution members in the modules. Such is the case when the modules or super-modules are used in a walkway to harvest energy from passing pedestrians. In this case, top plate may be covered by tiling, planks or other covering for providing esthetic appearance and wear protection. Optionally the modules or super-modules are sealed for moisture and weather protection. In some cases, the top plate acts as a protective cover.

Similarly, a top plate may be used when the modules or super-modules are used for harvesting energy from cars. In this case, the top plate may be covered by a layer of asphalt, or bitumen if they are installed in an asphalt road. If the road in concrete then they may be covered wither by a layer of concrete or asphalt.

Similarly, a top plate may be used when the modules or super-modules are used for harvesting energy from airplanes. In this case, the top plate may be part of the runway structure.

For drawing clarity, all electrodes, leads and electronics that are connected to, and associated with the piezoelectric generators were omitted from the drawings.

Figure 3 schematically depicts several views of a railroad sleeper having embedded module according to an exemplary embodiment of the current invention,

In this figure, 300a and 300b are a top view and a cross-section view of sleeper 300 respectively.

Sleeper 300 is manufactured with two cavities 305, each sized to fit a module 200.

A pad 310 may be placed on top of the force-distributing member 102 and the rail 315 (only one seen for clarity) rests on the pad.

In some exemplary embodiments modules 200 are embedded in the cast concrete sleeper 300 during its manufacturing or in a steel sleeper during its manufacture. Figure 4A schematically depicts several views of a light load super-module 400 according to an exemplary embodiment of the current invention.

In this figure, 400a 400b, 400c and 400d are: front, side, top and isometric views of light load super-module 400 respectively.

According to an exemplary embodiment of the current invention each light load super- module 400 comprises two light load modules 410 joined by common support 470.

Similar to the construction of module 200, light load module 410 comprises a force- distribution member 402.

According to an exemplary embodiment of the current invention each light load modules 410 comprises four smaller generators 403 arranged in pairs, each pair supported by a base 405.

According to an exemplary embodiment of the current invention each light load modules 410 uses generators 403 having small cross section, and uses large angles β' such that appropriate stress is applied to the generators 403 when light load such as created by a passing pedestrians is applied to the force-distribution member 402.

Optional gap 413 between force-distribution member 402 and base 405 acts in a similar way to gap 213 seen in figure 2. When a large force is applied to force-distribution member 402, generators 403 are compressed until gap 413 is closed and the force if applied directly to the base 405, preventing excessive force from being applied to the generators. The drawing also depicts additional optional structures such as load fastener holes 481 , common support fastening holes 483, base securing holes 485, and generator cushions 487.

Force may be applied directly to the force-distribution member, for example in light vibrating machinery which may be placed on a plurality of modules such that it is supported by the force-distribution members.

Alternatively, a top plate may be used for transferring the load to the force-distribution members in the modules. Such is the case when the modules or super-modules are used in a walkway to harvest energy from passing pedestrians. In this case, top plate may be covered by tiling, planks or other floor covering for providing esthetic appearance and wear protection.

Optionally the modules or super-modules are sealed for moisture and weather protection. In some cases, the top plate acts as a protective cover. Similarly, a top plate may be used when the modules or super-modules are used for harvesting energy from airplanes. In this case, the top plate may be part of the runway structure.

Figure 4B schematically depicts a side view of an encased light load super-module 490 according to an exemplary embodiment of the current invention.

In this embodiment a cover 491 is used for protecting the light load modules 410 as well as transferring the applied force to the force-distribution members 402.

Optionally seal 492 prevents moisture from entering the encased light load super-module

490.

A plurality of encased light load super-module 490 may be used for creating an energy harvesting system having a large surface.

Figure 4C schematically depicts a side view of an energy harvesting system 495 using a plurality of light load super-modules 490 according to an exemplary embodiment of the current invention.

In this embodiment a top cover 496 is used for creating a surface used for protecting the light load modules 410, well as transferring the applied force to the force-distribution members 402, and a floor on which pedestrian may be traveling. Cover 496 may be made of planks or tiles and the system may be extended in one or two dimensions using a large numbers of light load super-module 410.

Figures 5A(i), 5A(ii), 5B and 5C depict a dual-load module 500 according to an exemplary embodiment of the current invention.

Dual-load module 500 comprises two substantially identical sub-units 501, each having one pair of heavy-load piezoelectric generators 503 and two pairs of Kght-load piezoelectric generators 505. For clarity, elements of subunits 501 may be marked on only one of the sub-units. The two sub-units 501 rest on common foundation 509 (which acts a common support for generators 503). The coordinate system (X,Y, Z) is marked in figures 5A(i) and 5A(ii). In these figures: 500a. 500b, 500c and 500d are top view, side view, A— A cross section, and isometric views respectively. View 500d schematically depicts an enlarge detail. Some elements already marked in figures 5A(i) and 5A(ii) may not be marked in figures 5B or 5C for drawing clarity.

Dual-load module 500 may be used in situation where the forces applied to the module may vary over a wide range.

Figure 5A(i) schematically depicts several views of the assembled dual-load module according to an exemplary embodiment of the current invention.

Figure 5A(ii) schematically depicts isometric view of the assembled dual-load module according to an exemplary embodiment of the current invention.

Figure 5B schematically depicts the dual-load module 500 according to an exemplary embodiment of the current invention with the heavy-load force-distributing member 520 removed, exposing the light-load piezoelectric generators 505 and the Kght-load force-distributing member 530.

Figure 5C schematically depicts enlarged cross sectional views 500c and 500e of dual-load module 500 according to an exemplary embodiment of the current invention.

Each heavy-load force-distributing member 520 is connected to two light-load force- distributing members 530 with connecting screw 532.

Force is applied to the dual-load module 500 by pressing on one of, or both heavy-load force-distributing members 520. Each heavy-load force-distributing member 520 is connected to the two light-load force-distributing members 530 with screw 532. Thus, the force is transferred to the four Kght-load piezoelectric generators 505. Force amplification is created in the light-load piezoelectric generators 505 in as disclosed in figure 1. The reactive forces created in the Kght-load piezoelectric generators 505 are in the Z-Y plane. Note that Kght-load piezoelectric generators 505 have small cross sections and thus relatively small force creates large stress within the Kght-load piezoelectric generators 505. The large stresses in Kght-load piezoelectric generators 505 are advantageous for efficient energy generation at light loading.

Additionally, each heavy-load force-distributing member 520 is connected to two heavy- load piezoelectric generators 503. Force amplification is created in the heavy- load piezoelectric generators 503 in as disclosed in figure 1. The reactive forces created in the heavy-load piezoelectric generators 503 are in the X-Y plane. Note that heavy-load piezoelectric generators 503 have large cross sections and thus relatively even large applied force cannot create stress that exceeds the maximal tolerable stress within the heavy- load piezoelectric generators 503. The large cross sections of heavy- load piezoelectric generators 503 are advantageous for efficient energy generation at heavy loading.

The exemplary embodiment depicted in figures 5 shows the stack construction of light-load piezoelectric generators 505 and heavy-load piezoelectric generators 503. However, it should be noted that single elements, co-fired stacks or stacks made of subunits separated by softer material containing electrodes may be used.

In another exemplary embodiment, a heavy-load module or sub-unit may be constructed by omitting all the light-load components, or only the light-load generators from the dual-load module or sub-unit respectively.

In another exemplary embodiment, a light-load module or sub-unit may be constructed by omitting all the heavy-load components, or only the heavy-load generators from the dual-load module or sub-unit respectively. Alternatively, or additionally, a light-load module or sub-unit may be constructed by replacing the heavy-load generators with light-load generators having smaller cross section in a dual-load module or sub-unit respectively.

Dual-load module 500 and/or subunits 501 may be used for example in application where the applied forces vary over a wide range. For example, in a road where passenger cars and heavy track travel, an energy harvesting system comprises a plurality of dual-load modules 500 can be used. The Dual -load module 500 may be designed such that heavy-load piezoelectric generators 503 are effectively active when large forces are applied by a passing loaded track, while light-load piezoelectric generators 505 are effectively active when smaller forces are applied by a passing car. The application to road should be viewed as exemplary and other applications may be apparent to a man skilled in the art. For example, in multi-lane roads where the majority of track travel in the right hand lanes, only heavy-load modules may be used in the right lane or lanes where tracks primarily travel, dual-load modules in the central lane or lanes where the traffic is mixed, and light- load modules in the left lanes where the majority of the traffic comprise cars.

For airport applications, a dual-load modules or heavy-load modules may be installed under a runway tarmac or in taxiways. Figure 5C schematically depicts enlarged cross sectional views 500c and 500e of dual-load module 500 according to an exemplary embodiment of the current invention.

This figure depicts the safety mechanism protecting the light-load generators 505 from being overstressed when heavy loads are applied to the dual-load module.

Then heavy-load is applied to the heavy-load force-distributing member 520, light-load generators are compressed until gap 598 is closed and light-load force-distributing member 530 make contact with the light-load generator-support 596 (which acts a common support for generators 505) , relieving the stress applied to the light-load generators. Any larger load causes the light-load force-distributing member 530 to push the light-load generator- support 596 against the flexible disks 595 which compress under pressure against the common foundation 509, decreasing the gap 599. In an exemplary embodiment of the current invention, the dual-load module is designed such that when force is applied to the dual-load module, the force is first affects the light-load generators and when the force exceeds a predetermined value it transferred to the heavy-load generators. It should be noted that the number of flexible disks 595 their dimensions and compliances may be selected according to the required performance, for example the maximal force that may be applied to light-load generators 505.

Figures 6-7 schematically depicts yet another exemplary embodiment using a mechanical force multiplier according to the current invention.

The force multipliers used in the embodiments depicted in figures 6-7, and their operation, are similar to the force multiplies depicted in figures 2, 4 and 5. Therefore, the main differences are detailed herein to avoid duplication of the explanation.

Figure 6A schematically depicts an isometric view of a force multiplying module 600 according to another exemplary embodiment of the current invention.

Force multiplying module 600 rests on a base 620 to which left side anchor 640a right side anchor 640b and central anchor 450 are firmly attached. In between two anchor is a central support 630, also firmly attached to base 620 (central support 630a between anchors 640a and 645, and central support 630b between anchors 645 and 640b). Figure 6B schematically depicts an isometric view of a section of a piezoelectric stack used in the force multiplying module 600 according to an exemplary embodiment of the current invention.

Each of piezoelectric stacks 610a, 610b, 610c and 610d rests on an anchor on one side and on a central support at the other side. Each piezoelectric stack 610 comprises a plurality of layers 611 for example as depicted in US20100045111 "multi-layer modular energy harvesting apparatus, system and method" or in US20110291526 "piezoelectric stack compression generator". For drawing clarity, details of the stacks and their electrical connections are not seen in these figures. However, the stacks may be sintered of made of discrete layers. Each layer may be made of piezoelectric material elements in a supporting matrix.

Optionally, each stack 610 comprises a bottom end 614 (not seen in figure 6B. In figure 6A, bottom ends 614a and 614d are marked for stacks 610a and 610d respectively). Bottom end 614 of stack 610 is connected, or rest on side anchor 640 or central anchor 630. Alternatively, stack 610 rests directly, or connected to side anchor 640 or central anchor 630.

Additionally, each piezoelectric stack 610 has a top end 612 (seen in figure 6B. In figure

6A, top ends 612a and 612d are marked for stacks 610a and 610d respectively). Top end 612 rests on sliding face 632 of central support 630. When force 680 is exerted on pressure transferring member 650 (two such member are marked in figure 6A: 650a and 650b), the force is transferred by the curve surface 655 of on pressure transferring member 650 to the top end 612 of stack 610. Top end 612 of stack 610 is capable of sliding on sliding face 632 of central support 630 creating a compression force 685 in stack 610 which is larger than the applied force 680.

In the depicted embodiment, holes 674 in top end 612 accommodate pins or screws (not seen in this figure) that are optionally attached or screwed to bottom end 614 that holds the layers of stack 610. Preferably, the screw heads of these pins or screws are below the top surface 613 of top end 612, such that top surface 613 of top end 612 is in contact with curve surface 655 of on pressure transferring member 650. Optionally the screws in holes 674 apply bias compression on the stacks such that energy is generated from the moment force is applied to the stack. Optionally the bias compression keeps the layers and/or piezoelectric elements in the layers in contact with each other and with electrical contact layers there between. Additionally, screws in holes 674 may helps keeping the integrity of the stack. In the depicted embodiment of figures 6, the basic structure 690 which comprises anchors (640, 645), two stacks 610, central support 630 and pressure transferring member 650 is repeated twice. However, a single basic structure 690 or any number of its repetitions may be used to create a single force multiplying module 600.

In some embodiments of the invention, force 680 is applied directly on pressure transferring member 650, or to a plate (not seen in this figure) which rests on or connected to pressure transferring member 650a and 650b.

Force multiplier module 600 may use a single layer force multiplier having one layer of piezoelectric stacks 610 as seen in figure 6A. It should be noted that module 600 may be placed upside-down (e.g. as 600b in figure 7A). It also should be noted that a multilayer structure may be formed by stacking modules 600, one on top of the other, thus increasing the energy generated when the same force (or weight) is applied. Figures 7 schematically depict an exemplary embodiment of dual-layered force multiplier created by stacking two modules 600 in a back-to- back configuration. However, other configurations (such as tandem stacking, large number of layers and odd number of layers) may be used.

It should be noted that in this exemplary embodiment, pressure transferring member 650 acts as a force-distributing member for the two generators 610, while base acts a common support for generators 610.

Figure 7A schematically depicts a cross-sectional view of a back-to-back force multiplying device 700 using two force multiplying modules 600a and 600b in a back-to-back configuration according to an exemplary embodiment of the current invention.

Back-to-back force multiplying device 700 comprises a force multiplying modules 600a on which a second force multiplying modules 600b is resting in an upside-down fashion. Pressure transferring members 650 of force multiplying modules 600a are connected to pressure transferring members 750 (acting as force-distributing member for generators 710) of force multiplying modules 600b (optionally using pins or screws inserted in holes 651 seen in figure 6 A) such that a force 780 applied to cover 720 of back-to-back device 700 creates compression forces in stacks 710 of modules 600b. The compression forces in stacks 710 of modules 600b transfers downward forces to pressure transferring members 750 which presses on pressure transferring members 650 modules 600a.

It should be noted that pressure transferring members 650 and 750 may be manufactured as one structure and the division to two members is an exemplary embodiment practiced for manufacturing convenience. In an optional exemplary embodiment, the curved face 655 of pressure transferring members 650 and 750 is substantially a cylindrical surface.

Similarly, base 620 (which acts a common support for generators 610) and/or cover 720 (which acts a common support for generators 710) may be manufactured with some or all of anchors 640, 645 and supports 630 already integrated in them.

It should be noted that the structure may be repeated vertically to accommodate more modules 600, or a plurality of back-to-back devices 700 stacks one on top of the other. Similarly, it should be noted that the structure may be repeated horizontally in one or two dimensions to accommodate more modules 600, or a plurality of back-to-back devices 700 positioned one on adjacent to other to crate a row of devices or to tile a large surface.

Optional springs 780a and 780b are optionally used to push pressure transferring members 650 and 750 away from central supports 630 once the force 780 is no longer applied to cover 720, thus releasing the compression forces on stacks 610 and 710. Optionally, springs 780 are in a form of spring disks.

As will be seen in the next figure, back-to-back devices 700 may be housed in a box to keep moisture out and protect the device. In this case, seal 725 may be used to flexibly seal cover 720 to box walls 810 (seen in the next figures). Figure 7B schematically depicts an isometric outer view of a force multiplying device 700 of figure 7A housed in a box according to an exemplary embodiment of the current invention.

The box in which device 700 is houses comprises the base 620, the cover 720 and walls 810a, 810b, 810c and 810d. Holes 722 in cover 720 are used for screws holding anchors 640 to cover 720. Holes 726 in cover 720 are used for screws holding support 630 to cover 720. Holes 724 in cover 720 are used for screws or pins that hold the cover 720 in place. Optionally these pins are forcing cover 720 to move vertically when force 780 is not evenly or centrally applied to cover 720.

Figure 7C schematically depicts another cross-sectional view of a force multiplying device 700 using two force multiplying modules in a back-to-back configuration in its house, according to an exemplary embodiment of the current invention.

This vertical cross section is parallel to wall 810a, along the line A— A in figure 7B.

Figure 7D schematically depicts another cross-sectional view of a force multiplying device 700 using two force multiplying modules in a back-to-back configuration in its house, according to an exemplary embodiment of the current invention.

This vertical cross section is parallel to wall 810a, along the line B— B in figure 7B.

Pins 920a and 920b are optional pins used to assist accurate assembly of the central support 630 to base 620 and central support 630 to cover 720 respectively. Optionally other such pins exist, but not seen for drawing clarity.

Screws 910a and 910b holds together pressure transferring members 650 to base 620 and pressure transferring members 750 to cover 720 respectively. The holes 931a and 931b in 650 and 750 respectively is deep enough to create a gap 933 between the heads 935a and 935b of screws 910a and 910b respectively, thus allowing the cover 720 to be pushed towards the base 620 when force 780 is applied.

In the embodiments depicted in figures 2-7, the force-distributing member (e.g. 102, 402, 520, and 530), and pressure transferring members (650 and 750) directly pushes against the piezoelectric generators (e.g. 203, 403, 503, 505, 610, 710) or on end structures (e.g. 612) connected to the ends of the piezoelectric generator. When the piezoelectric generators are compressed under the stress applied by the load, a lateral motion (substantially normal to the reaction forces Fl and F2) is created. For example as can be seen in figure 7A, top end 612 slides against the curve surface 655 of pressure transferring member 650 and the face of central support 630 as piezoelectric stacks 610 compresses. Such lateral movements may cause loss of energy due to friction, may generate heat, and may cause wear of the moving parts. To overcome these shortcomings, friction reducing structures or elements may be used. In some embodiments elastic members may be used which elastically distort under the stress instead of sliding one against the other. In other embodiments lubrication may be used, or the surfaces mat be made of polished or made of low friction material. Preferably, bearings are used to transform the lateral motion into a low-friction rotation motion.

Figure 8A schematically depicts a side view of a force multiplying device 800 using friction reducing bearings (with the side wall removed) according to yet another exemplary embodiment of the current invention.

Figure 8B schematically depicts a cross-sectional view of the force multiplying device using friction reducing bearings according to yet another exemplary embodiment of the current invention.

Figure 8C schematically depicts a top view, with cover 820 off, of the force multiplying device using friction reducing bearings according to yet another exemplary embodiment of the current invention.

Applied force 810 is applied to the cover 820 (which acts a common support for generators 840) of force multiplying device 800. Cover 820 presses 811 on top members 830. Wheels 821, connected to top members 830, slide 812 on the oblique surface 832 of side supports 834 as they rotate around axis 832 connected to top members 830. As a result, strong reaction forces 813 are applied on piezoelectric stack 840 which is sandwiched between top member 830 and bottom member 838. The piezoelectric stack may be a rigid co-fired stack. Alternatively stack 840 comprises of layers, held together by screws 899. Preferably, low friction bearings such as ballbearings are used between wheels 821 and axis 832. Bottom members 838 are anchored to central support 841 via bearings 844 which allow bottom members 838 to rotate about axis 845 in respect to central support 841.

Preferably, side supports 834 and central support 841 are connected to a housing 850. Preferably, a seal 855 between housing 850 and cover 820 prevent moisture and other

contaminants from entering the force multiplying device 800.

It should be noted that although in the exemplary embodiment depicted in figures 8A-8C, the applied force is seen as applied on cover 820, we can view the opposing force 810' applied by the supporting foundation (not seen) on housing 850 and split into two opposing reaction forces 813' acting on piezoelectric generators 840. Similar forces develop in the "upside-down" multiplying modules 600b seen in figures 7A and 7C. It should be noted that the devices 200, 400, 500, 600, 700, and 800 may be placed in any orientation and will react to forces or vibration applied between their opposing top and bottom sides regardless of orientation.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub combination.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent appKcation was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this appKcation shall not be construed as an admission that such reference is available as prior art to the present invention.