Abstract:
A system for operating an electric door release having an actuator powered by an energy harvester. The actuator may be a piezoelectric actuator and the harvester may be a piezo harvester. The system may further include a power module, a rechargeable battery and a voltage boost circuit disposed between the energy harvester and the actuator. When a piezoelectric actuator is used, a recycle actuator discharge circuit may be disposed between the piezoelectric actuator and the power module battery for recapturing a portion of the energy delivered to the piezoelectric actuator. The piezoelectric harvester may include an energy input portion whereby the piezo electric harvester is excited by the energy input portion. The energy input portion may include a circular or linear driving gear for exciting the piezoelectric harvester or a stepper motor generator, driven by movement of a door. The harvester may also be a stepper motor/generator.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Patent Application No. 61/324,698, filed Apr. 15, 2010. U.S. Patent Application No. 61/324,698 is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to electrically operated devices associated with a door or closure, more particularly, to mechanisms for electrically locking or unlocking a door in a frame; further, to such mechanisms wherein the power to operate the electrical mechanism is collected and provided by an energy harvester; and most particularly, to an electric door release mechanism which may be actuated by a piezoelectric actuator powered by an energy harvester such as, for example, a piezoelectric energy harvester. 
     BACKGROUND OF THE INVENTION 
     So-called “energy harvesters” and “energy harvesting” refer generally to apparatus and methods for collecting and storing energy present in the environment, such as heat or solar energy, RF energy, and kinetic energy such as low frequency excitation or rotation. Such energies are referred to herein as “waste” or “free” energies. Storing is typically in the form of conversion of waste energy to electricity for subsequent storage in a battery. 
     Electrically operated devices that are mounted in or on a door or at a remote closure, such as, for example, electric door release mechanisms, illumination devices, video screen displays, keypads and signage, are known. Electric door release mechanisms in particular, such as electrically-operated door strikes or door locks, are useful in providing remote or hands-free unlocking operation of a door in a frame, or for providing selective security for items within an area bounded by such a door. In the most general prior art, an electric door release mechanism is powered by a remote electric source, such as an AC grid, connected by a cable, through a transformer, to the unlocking device. The electric door release mechanism may be configured for mounting and operation in the door frame, to engage a cooperative bolt in the door, or the electric door release mechanism may be mounted in the door itself, requiring the cable to pass through the door hinge area in some fashion. 
     In some specialized applications wherein a power source such as an AC grid is not available or readily connectable to the electric door release mechanism, it is known to power an electric door release mechanism via a battery incorporated in or immediately proximate the door release system. Such a configuration has the disadvantage that the battery either must be kept charged in some fashion or must be replaced periodically, with risk of security failure if not timely replaced or if the recharging means fails. Further, prior art electric door release mechanisms typically are actuated by a relatively large and powerful linear solenoid or motor. Thus, where hard wiring of the mechanism from a remote power source is not possible, practical or desired, an undesirably large and expensive battery pack for operation of the electric door release mechanism is required. 
     What is needed in the art is an electrically operated door device such as an electric door release system wherein the power to a device can be supplied by harvesting of “waste” energy available locally. 
     What is further needed in the art is an electric door release system wherein the actuator requires significantly less electric power than in the prior art. 
     It is a principal object of the present invention to provide a secure environment wherein security is dependent upon a locally available source of waste energy, and wherein periodic human intervention is unnecessary. 
     SUMMARY OF THE INVENTION 
     Briefly described, a system for powering an electrically operated door device such as an actuator in an electric door release system, in accordance with the present invention, comprises an energy harvester for providing power to the device. The system may include a voltage boost circuit operationally connected to the energy harvester, and a device such as a piezoelectric actuator connected to the voltage boost circuit. The system may further include a power module including a battery, such as a thin film battery, disposed in a circuit between the energy harvester and the voltage boost circuit, and an actuator discharge circuit disposed between the piezoelectric actuator and the power module battery for recycling back to the battery a portion of the power provided to, and not consumed by, the piezoelectric actuator. 
     In one aspect of the invention, this system is readily adaptable to an electric door release system wherein an electric door release mechanism is actuated by a piezoelectric actuator powered by an energy harvester. Such an electric door release system in accordance with the present invention comprises: a) a mechanical release mechanism including a piezoelectric actuator for locking or unlocking the mechanism, and b) an energy harvester for providing electric power to the piezoelectric actuator. The energy harvester may be a piezoelectric device or any other type of harvester for collecting waste energy, for example, a stepper motor/generator whose rotor is turned by a door hinge member. 
     For use in an environment having variable or relatively low frequency of local waste energy occurrences, a rechargeable battery may be included between the energy harvester and the actuator. Preferably, control circuitry limits the draw on the battery to only the actual amount of power required to energize the piezoelectric actuator. Further, a voltage recycling circuit may be used whereby a substantial amount of the power provided to the piezoelectric actuator may be re-captured and returned to the battery for storage. 
     For use in environments having a more continuous level of waste energy available, in another aspect of the invention, the battery may be supplanted by a compound Greinacher-type voltage doubler circuit having substantial electrical capacitance that multiplies the voltage output of an energy harvester up to voltage potential required to energize the piezoelectric actuator. 
     In either arrangement, the energy generated by the harvester must be sufficient to keep the battery or capacitors fully charged so as to satisfy future actuator requirements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a block diagram of a system for harvesting and utilizing sporadically available waste energy in accordance with the present invention; 
         FIG. 2  is a detailed exemplary circuit diagram of the system shown in  FIG. 1 ; 
         FIG. 3  is a circuit diagram of a system for harvesting and utilizing continuously available waste energy in accordance with the present invention; 
         FIG. 4  is an isometric view of a commercially-available piezoelectric energy harvester; 
         FIG. 5  is an edge view of the piezoelectric energy harvester shown in  FIG. 4 ; 
         FIGS. 6 and 7  are alternate cross-sectional views showing a rotatable actuating sprocket assembly in accordance with the present invention actuating a ballast of a piezoelectric energy harvester; 
         FIG. 8  is a cross-sectional elevational view of a mechanical actuator assembly in accordance with the present invention; 
         FIG. 9  is an isometric view of a first piezoelectric energy harvester system in accordance with the present invention comprising an energy input portion and an energy harvesting portion; 
         FIG. 10  is an isometric view showing the first piezoelectric energy harvester system shown in  FIG. 9 ; 
         FIG. 11  is an isometric view like that shown in  FIG. 10 , showing the energy harvesting module disposed within a hollow door frame; 
         FIG. 12  is a schematic cross-sectional view of a second piezoelectric energy harvester system in accordance with the present invention, showing an energy input portion, using a rack gear mounted on a door edge, beginning engagement with an energy harvesting portion; 
         FIG. 13  is a view like that shown in  FIG. 12 , showing the energy input portion in full engagement with the energy harvesting portion as would occur with the door closed; 
         FIG. 14  is a side elevational view of a piezoelectric actuator disposed in a door strike in accordance with the present invention; 
         FIG. 15  is an enlarged view of the mechanical operating portion of the door strike shown in  FIG. 14 ; 
         FIG. 16  is a perspective view of a portion of the keeper shown in  FIGS. 14 and 15 . 
         FIG. 17  is an elevational view of a prior art key operated door locking mechanism; 
         FIG. 18  is an elevational view showing the door locking mechanism of  FIG. 17  modified with a piezoelectric latch in accordance with the present invention; 
         FIG. 19  is an isometric view of the mechanism shown in  FIG. 18 . 
         FIGS. 20 and 21  are differing isometric views of the unlocking and rotatable portion of the mechanism shown in  FIGS. 18 and 19 ; 
         FIG. 22  is an elevational view showing the mechanism of  FIG. 18  becoming unlocked after activation of the piezoelectric cell; 
         FIGS. 23 and 24  are sequential views showing the mechanism of  FIG. 18  becoming unlocked by action of a key without activation of the piezoelectric cell; 
         FIG. 25  is an isometric view in partial cutaway showing a stepper motor generator harvester having a rotor-mounted pinion gear meshing with a stationary ring gear like that shown in  FIG. 11 ; 
         FIGS. 26 and 27  are cross-sectional horizontal views of the mechanism shown in  FIG. 25 , showing the door in closed and opened positions, respectively; 
         FIG. 28  is a door showing, in partial cut away, an energy harvester (exemplary stepper motor generator) mounted on a door hinge to provide energy to unlock the knob lock set mounted on the lock side of the door once an activation switch (not shown) is closed; and 
         FIG. 29  is a dual-bridge circuit and stepper motor generator for connection to the micro power module at terminals J 2 . 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate currently preferred embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a system  10  is shown for harvesting and utilizing waste energy to power an electrically operated door device such as a door release actuator in accordance with the present invention. System  10  comprises a device  12  such as a door release actuator  112 ; in one aspect of the invention, as described further herein, device  12  may be for example a low power consumption actuator, such as a piezoelectric actuator  212 . When piezoelectric actuator  212  is used to release a door latch, system  10  may be powered by a power management module  14  that powers a voltage booster  18  for increasing voltage to a level sufficient to energize piezoelectric actuator  212 . Power management module  14  is responsive to a door-release authorization signal  20  and receives power from any waste energy harvester  22 , such as, for example, RF or solar cell harvesters, or other known sources of waste energy as described above, or alternately from a piezoelectric energy harvester  24  which may be configured to harvest door motion energy or door or building vibration energy. In the specific example described below, piezoelectric energy harvester  124 , configured for releasing a door latch, may be incorporated into the hinge region of an electrically secured door for capturing the energy of any and all motion and vibration associated with the opening and closing of the door and other waste energy in the vicinity of the door available for capturing. In yet another specific example described below, a stepper motor generator  724  may be incorporated into the hinge region for capturing the energy associated with opening and closing the door. 
     Referring to  FIGS. 4 and 5 , piezo transducer  25  that may be used in piezo energy harvester  24  is preferably a Model M-8528-P2, available from Smart Materials Corp., Sarasota, Fla., USA, or a Model Volture V25w, available from Mide Technology Corp, Medford, Mass., USA. Either of these devices develops a damped sinusoidal voltage output when strained in either direction and allowed to vibrate about a fixed end point. Referring to  FIG. 2 , the damped sinusoid output from piezo transducer  25  is supplied to a schottky diode bridge rectifier (not shown), the output of which is used to charge a thin film battery (not visible) such as that found in micro power module (MPM)  14 , preferably a Model D-MPM101, available from Infinite Power Solutions, Inc., Littleton, Colo., USA. Additionally or alternatively, an ambient RF or light energy harvester or a stepper motor/generator  724  ( FIGS. 25-29 ), for example a model 17PU-H hybrid stepper motor available from Minebea Motor Corp., Tokyo, Japan, model 17PU-H, can also be used to harvest energy for charging MPM  14 . 
     In addition, RF energy  28   a  may be captured on a steel door frame and boosted by a charge pump in known fashion to provide a DC output which is then used on the DC charging input of MPM  14 . Similarly, ambient light levels can be detected by a solar cell  28   b  such as the Sanyo AM-1454 and the voltage output can be added into the DC charging input for MPM  14 . 
     MPM  14  has a regulated output voltage enable circuit which determines the period of time during which the battery is being drained as it supplies current to the voltage boosting circuit. Output energy from MPM  14  can be provided by something as simple as a switch, or by any set of contacts which are closed only after verification of credentials for the person desiring to enter the door. Another function provided by the MPM is to discontinue output voltage if the battery voltage has fallen to less than 60% of its fully charged voltage. Normally, this would never happen as it is the intent of this invention to keep the battery at or near full charge by applying more energy at the recharge inputs than the energy used by the piezo actuator and its control circuitry for each operation of the door. 
     Typically, a piezo actuator such as piezoelectric actuator  212  needs voltage on the order of about 225 volts for proper operation. This voltage level is accomplished by employing a capacitor charge device  30  ( FIG. 2 ), preferably a Maxim Max 8622, available, for example, from Maxim, Sunnyvale, Calif., USA, which converts a low voltage battery output to a voltage level needed by the piezo actuator. 
     Numerous piezo cells for use in piezoelectric actuator  212  are available today. A Servo Cell AL2, available from ServoCell, Ltd., Harlow, UK, is found useful as it is a fully integrated unit that provides mechanical blocking of its linear displacement, permitting the piezo actuator to replace an electric solenoid in a slightly modified current production electric strike, as described below. Other piezo actuators, such as the Mide Quick Pack qp2On, available from Mide, Inc., Medfor, Mass., USA, may be used as a means of moving a blocking element to accomplish door unlocking. 
     An interesting byproduct of the use of piezoelectric actuator  212  is that once charging of the piezo cell is complete and motion accomplished, it is possible to recapture a percentage of the energy expended in actuating the device by discharging the actuator&#39;s capacitance back into the DC charge input of the MPM. Theoretically, one can re-capture via recycle circuit  32  up to 60% of the original energy expended. Thus the actual power consumption of the piezoelectric actuator is substantially reduced. 
     The electronic circuitry used to capture the harvested energy and use it to power the piezoelectric actuator consists of two elements—the MPM  14 , and voltage booster  18 . 
     Referring to  FIG. 2 , MPM  14  contains three connectors, J 2 , J 3  and J 5 . The first two are used to recharge the battery from DC and AC sources respectively. J 2  collects recycled energy  34  from the discharge of piezoelectric actuator  212 . J 3  may be used to collect additional waste energy from a variety of waste energy sources including, for example, collected RF energy  28   a  and collected solar energy  28   b . When used to collect energy from piezoelectric energy harvester  24 , 124  or stepper motor/generator  724 , J 3  takes the harvested door motion energy via output  36 . Since energy recoverable from door motion is readily available, it is the primary source of harvested waste energy to recharge the battery. Connector J 5  is used for input and output signals. Pins  1  and  2  provide under voltage protection to ensure that the battery output never drops below 2.1 volts. Pins  3  and  4  receive enabling signals for the regulated 3.6 volt output provided at pin  7 . Pin  5  is an isolated ground that does not connect directly to the ground of the internal thin film battery. The output voltage from pin  7  MPM  14  provides a low voltage, such as 3.6 volts. Capacitors C 5  and CI filter some of the noise signal created by the switching regulator in the voltage booster. Voltage booster  18  includes a charge device that uses a switching regulator and output transformer to boost an input voltage to an output voltage, for example 200 v. to 250 v., which is needed by the piezoelectric actuator  212 . Resistor R 2  sets the output level which the unit is trying to achieve. In this case, it is set to 237 volts. Resistor R 1  establishes the maximum input draw for the unit which is set as low as possible. Diodes D 1  and D 2  ensure that no back current is supplied to voltage booster  18  when the piezo actuator is discharging. Diode D 3  and resistor R 6  limit the current which can be fed back to recharge the battery through the DC charging input J 2 . Switch  38 , designated SW 1 , applies the re-captured voltage to the battery after the unlock pushbutton is released. 
     The timing sequence is then:
     1) Unlock pushbutton switch  38  is depressed. This opens the re-charge feedback loop and enables the MPM output.   2) Charge device  30  of voltage booster  18  powers piezoelectric actuator  212  until the charge on the actuator reaches the preset level of 237 volts.   3) Unlock push button switch  38  is released and the discharge of piezoelectric actuator  212  is sent back to the battery via circuit  32 .   

     Referring now to  FIG. 3 , in an environment experiencing a continuously-available, ample source of waste energy wherein an energy harvester can have a continuous electrical output, it may be possible to use a simplified system  10 ′ for harvesting and using waste energy to power a low power consumption actuator such as piezoelectric actuator  112 . Note that a power module is not required, although the actuator discharge circuit can be used to support the charge on the doubling capacitors. System  10 ′ comprises a piezo harvester, such as for example piezoelectric energy harvester  124 , a voltage boost circuit  18 ′, an operating switch SW 1   38 ′, and a piezoelectric actuator  212 . Voltage boost circuit  18 ′ is preferably a Greinacher-type circuit comprising a plurality of capacitors and diodes as is known in the prior art to boost the harvester output to the voltage potential required to drive the piezoelectric actuator  212 . Obviously, in circumstances wherein waste kinetic energy is not continuously available, a battery and control circuitry as shown in  FIG. 2  are required to accumulate waste kinetic energy as it occurs and to energize actuator  212 . 
     Referring now to  FIGS. 4 and 5 , a piezoelectric transducer  25  is shown, such as the Mide Model Volture V25w cited above. Transducer  25  may be used in piezoelectric energy harvester  24 , 124 . This device converts vibration into electrical energy when the ballast  125 , mounted on base plate  127  which also contains the piezo device, is flexed in either direction from the rest position  129 . Transducer  25  has good elastic attributes that allow it to deflect  131  from center up to about 0.25 inches on either side of rest position  129 . 
     Referring now to  FIGS. 6 through 8 , a mechanical actuator assembly  200  is shown that may be used in conjunction with piezoelectric energy harvester  124 . Mechanical actuator assembly  200  comprises a base plate  202  and stanchion  204  for rotatably supporting a rotatable actuating sprocket assembly  206 . Sprocket assembly  206  comprises a yoke  208  mounted on a shaft  210  journalled in stanchion  204  and includes a plurality of actuators  211 , exemplarily four, mounted for both pivoting and translating in yoke  208  as described below. Each actuator  211  is provided with a rounded nose  214 , rides in a first radial slot  216  formed in yoke  208 , and is pivotably pinned by a pin  218  into a second slot  220  formed in yoke  208 . Each actuator  211  captures a bias spring  222  in second slot  220  such that each actuator is urged after perturbation to return to a rest position  224  as shown in  FIG. 8 . Thus, each actuator  211  during rotation of sprocket assembly  206  and sequential engaging with, and disengaging from, ballast  125  of a piezoelectric energy harvester  124  is free to move rotationally on pin  218  in either direction ( FIGS. 6 and 7 ) and to move translationally radially in first and second slots  216 , 220  in response to being perturbed by rotation of assembly  206  in either direction as described below. 
     Referring now to  FIGS. 9 through 11 , a first piezoelectric energy harvester system  300  in accordance with the present invention comprises an energy input portion  302  and an energy harvesting portion  304 . 
     Energy input portion  302  comprises a door hinge  306  mountable to a door  308  in door frame  310  to cause the door  308  to swing in the frame  310 . A hinge pin  312  extends beyond the leaves  314 , 316  of hinge  306  and fixedly supports a drive member such as a hinge pin spur gear  318 . Hinge pin  312  is attached to the door-mounting leaf  316  of hinge  306  such that pin  312  and gear  318  remain fixed and stationary with respect to door  308  but rotate about hinge pivot axis  320  when door  308  is swung on hinge  306 . 
     Energy harvesting portion  304  comprises a piezoelectric energy harvester  124  as shown in  FIGS. 4 and 5  mounted via a bracket  322  to base plate  202  of a mechanical actuator assembly  200 . Mechanical actuator assembly  200  comprises base plate  202  and first and second stanchions  204  for rotatably supporting a rotatable sprocket assembly  206 . Sprocket assembly  206  comprises first and second yokes  208  fixedly mounted on a shaft  210  journalled in stanchions  204 . First and second yokes  208  are opposed on shaft  210  and are crenellated to be mutually out of phase by 45° such that sprocket assembly  206  provides  8  actuators  211  for engaging harvester ballast  125 . Shaft  208  extends beyond stanchion  204  to support a driven member such as capture (pinion) gear  324  meshed with hinge pin (spur) gear  318 . 
     Energy harvesting portion  304  defines an energy harvesting module that preferably includes a cover (not shown) for protecting harvester  124  and sub-assembly  206  from the environment, as well as to reduce the noise of engagement of the gears and the actuators with the ballast. 
     An advantage of piezoelectric energy harvester system  300  is that the driver/driven ratios may be selected to maximize energy harvest for a particular application. Further, the mass of ballast  125  may be selected to match the anticipated door velocity and thus optimize the resonance periods between ballast/actuator engagements to maximize energy output of harvester  124 . 
     Referring now to  FIGS. 10 and 11 , an exemplary installation of harvester system  300  is shown. Energy input portion  302  is mounted to an edge of door  308 , and energy harvesting portion  304  is mounted within a hollow frame  310  which is slotted  326  to provide access for gear  318  to gear  324 . Energy is captured by harvester  124  during opening and closing motions of the door in the frame. 
     Referring now to  FIGS. 12 and 13 , a second piezoelectric energy harvester system  300 ′ in accordance with the present invention comprises an energy input portion  302 ′ and the energy harvesting portion  304  described above. Only capture pinion gear  324  of portion  304  is shown. 
     System  300 ′ harvests kinetic energy from the door-latch side of a door  308 ′ mounted in a hollow frame  310 ′, as opposed to embodiment  300  which harvests energy from the hinge side. In system embodiment  300 ′, energy harvesting portion  304  is mounted within frame  310 ′, and energy input portion  302 ′ includes a drive member such as linear rack gear  318 ′ mounted to the beveled edge of door  308 ′ for engaging the driven member (pinion gear  324 ) to drive energy harvesting portion  304  as in the first system embodiment  300 . It will be seen that energy is harvested both in opening and in closing door  308 ′. 
     Referring to  FIGS. 10 and 12 , with respect to systems  300  and  300 ′, to reduce cost and noise, it is understood and contemplated by this invention that drive gears  318 ,  318 ′ can be replaced with friction wheels having, for example, a resilient contact surface  330  and driven gears  324 ,  324 ′ can be replaced with a friction wheel or a friction rack having, for example, a mating resilient surface  332 . 
     Referring now to  FIGS. 14 through 16 , as one embodiment, an electric strike portion  400 - 2  of an electric door strike system in accordance with the present invention comprises an electric strike  402 , for example, a Model 5000 available from Hanchett Entry Systems, Inc., Phoenix, Ariz., USA, modified as described below to include a piezoelectric actuator  212  in place of a standard linear electric solenoid (not shown). For simplicity and clarity, only the mounting and actuation portion of strike  402  are shown. 
     Strike  402  comprises a formed metal frame  404  supporting piezoelectric actuator  212  having a shaft  406  extending longitudinally therefrom. Shaft  406  includes an actuation portion  408  extending through a linear bearing  410  mounted in frame  404 . Actuation portion  408  includes a collar  412  to limit axial motion of shaft  406  away from actuator  212  by engagement with a support bracket  414  also mounted on frame  404 . Actuation portion  408  further includes an annular groove  416  having a beveled side defining a shaft engagement slope  418  for receiving a keeper  420  having a mating engagement slope  422 . Keeper  420  is a blocking link in the linkage releasing or locking a latch (not shown) in strike  402 . 
     Referring to  FIG. 16 , keeper  420  includes pivot hole  424  for mounting to strike  402  and an arcuate slot  426  concentric with the axis of pivot hole  424 . The lands on either side of slot  426  are tapered to form engagement slope  422  as shown in  FIGS. 14 and 15 . 
     Referring again to  FIG. 15 , shaft  406  is shown in the blocking position wherein keeper  420  blocks the linkage from activating to unlock the latch. Shaft  406  is biased to the right in  FIG. 15  by one or more bias springs (not visible). The shaft bias springs are sufficiently powerful that, in combination with the de-energized piezo cell, the keeper is maintained in the locking position against a latch-opening force sufficient to resist unwanted unlocking of the lock, as for example, up to at least 1000 pounds of latch-opening force. When the piezo cell in actuator  212  is energized, the cell actuates a blocking element, permitting shaft  406  to move to the left, allowing keeper  420  to rotate to move groove  416  farther into slot  426 , in which position keeper  420  no longer blocks the linkage and the latch is thus unlocked. In this condition, a relatively small manual force applied to the latch as by a person attempting to open the door is sufficient to displace the shaft to the left and allow the keeper to be forced into the unlocking position by engagement of the engagement slopes  418 , 422 . Conversely, when the piezo cell is de-energized, the combined force of piezo cell expansion and the bias springs displaces the shaft to the right, causing the keeper to be returned via engagement slopes  418 , 422  to the locking position shown in  FIGS. 14 and 15 . 
     While energy harvester systems  300  and  300 ′ are shown utilizing sprocket assembly  206  having an array of spring-loaded actuators  212  for purposes of absorbing some of the contact forces that would be imparted on ballast  125 , it is understood that, within the scope of the invention, sprocket assembly  206  may be simply a wheel having a select number of radial teeth for making contact with ballast  125 . 
     Referring to  FIG. 17 , an exemplary, prior art handle-lock set  500 , for example, a commercially available key-in-knob-lock, comprises a hub  502  having first and second connecting posts  504  extending therefrom for receiving screws (not shown) extending through a door and bezel (not shown). A locking shaft  506  and latch engaging shaft  508  extend through an opening in hub  502 . Locking shaft  506  is connected to key  530  but is turnable independently of latch engaging shaft  508  which is attached to knob  509 . Cooperative with locking shaft  506  is a floating locking tab  510  having spaced-apart first and second locking tangs  512 , 514  straddling upper connecting post  504  within locking ring  515 . As shown below in  FIG. 21  in connection with the disclosure of the present invention, a cam plate  516  having an angled slot  518  is mounted to locking shaft  506 . A pin  520  attached to locking tab  510  extends through slot  518 . Slot  518  is formed such that upon rotation of locking shaft  506  (clockwise in  FIG. 21 ; counterclockwise in  FIG. 17 ), locking tab  510  is moved inwardly along a radius of hub  502  until tangs  512 / 514  no longer straddle connecting post  504  and can clear locking ring  515 , permitting knob  509  and latch engaging shaft  508  to be rotated, thereby actuating a door latch (not shown) to open the door (not shown). 
     Referring now to  FIGS. 18-21 , in a handle-lock set  600  in accordance with the present invention, floating locking tab  510  is modified to define a novel floating locking tab  610  in accordance with the present invention. Prior art tang  512  is retained, but prior art tang  514  is replaced by assembly  623  comprising a piezoelectric actuator  622  and a domed plunger  624 . Locking ring  515  is modified to define a novel locking ring  615  having a ramp  626  for engaging domed plunger  624  in the locked state. Piezoelectric actuator  622  is preferably of the type AL-2, available from Servocell Ltd., Harlow, UK. 
     Complete locking and unlocking control is still furnished by either the key  530  on the interior side or the thumb turn (not shown) on the exterior side. Note: The key and thumb turn may be positioned on respective interior and exterior sides as may be desired in any particular application. 
     When the lock has been placed in the locked state by either of the above, the locked state may be overridden in one of three ways: by energizing of actuator  622 , by rotation of key  530  or the use of thumb turn, not shown. 
     Referring to  FIG. 22 , when piezoelectric actuator  622  is energized, handle/knob  509  may be turned in one direction (unidirectional) to open the door despite the door&#39;s being mechanically key-locked. In its un-energized state, piezoelectric actuator  622  remains rigid with domed plunger  624  extended as shown in  FIG. 18 . Energizing of actuator  622  removes rigid support for plunger  624 . Torque on handle/knob  509  ( FIG. 19 ), locking shaft  506 , and floating tab  610  urges the dome of plunger  624  against ramp  626 , causing plunger  624  to be forced into assembly  623 . When the plunger has cleared the ramp, tab  610  may be turned as shown, unlocking the mechanism. Note that cam plate  516  is not activated and tab  610  has not been moved radially inwards of hub  502 . Note also that handle/knob  509  can be turned in only one direction to act against piezo actuator  622 . Turning the handle/knob in the other rotational direction, even with piezoelectric actuator  622  energized, will cause locking tang  512  and rotation of knob  509  to be blocked by post  504 . In a variation of the embodiment shown in  FIGS. 22-24 , and referring to  FIG. 23 , locking tang  512  may be replaced with a second piezo actuator assembly  623  and ring  615  may be further modified with a second mirror-imaged ramp  626  on the opposite side of post  504 . With this variation, handle/knob  509  may be turned in either rotational direction (bi-directional) to open the door upon energizing the actuators despite the door&#39;s being mechanically key locked. 
     Referring now to  FIGS. 23 and 24 , handle-lock set  600  may also be unlocked conventionally by the key. As described above, when key  530  and locking shaft  506  are turned, cam plate  516  urges tab  610  radially inwards of hub  502  such that tang  512  and plunger  624 , or a pair of plungers  624 , no longer straddle connecting post  504  ( FIG. 23 ), allowing latch engaging shaft  508  to be rotated ( FIG. 24 ). 
     Referring now to  FIGS. 25 through 27 , a further embodiment  700  of an energy harvester is shown. A stationary drive member such as drive gear  718  is mounted to a fixed hinge pin  712  of a door hinge  702  mounted on a frame  710 . An energy harvester mounted on a door  308  in the form of a stepper motor/generator  724  is provided with a driven member such as pinion gear  704  in meshing relationship with drive gear  718 . As door  308  is rotated in either the opening or the closing direction ( FIG. 27 ) on hinge pin  712 , pinion gear  704  is rotated causing lobes of the magnetic rotor (not visible) of stepper motor/generator  724  to serially pass by and excite the coils (not visible) within the stepper motor in known fashion, generating an output series of two-phase sinusoidal signals along wire leads  726  that may be captured as stored electrical energy by the thin film battery in power management module  14  ( FIGS. 1 and 2 ). Preferably, the sinusoidal signals are rectified by passage through a pair of bridge rectifiers  730  shown in  FIG. 29 . attached to the DC charging input of MPM  14  at connector J 2  ( FIG. 2 ). 
     To reduce cost and noise, it is understood and contemplated by this invention that drive gear  718  can be replaced with a friction wheel having, for example, a resilient contact surface  730  and driven gear  704  can be replaced with a friction wheel having, for example, a mating resilient surface  732  ( FIG. 26 ). 
     Referring to  FIG. 28 , in a door  308 , such as for example a Rite Door manufactured by Adams Rite Co. Pomona, Calif., an energy harvester (exemplarily a stepper motor/generator  724  in accordance with the present invention) is coupled to a micro power module  14 , as described above, and a piezoelectric door lock (exemplarily a key-in-the-knob lock set  600  in accordance with the present invention as shown in  FIGS. 18-24 ). While stepper motor/generator  724  is shown exposed through surface  309  of door  308 , it is understood that motor/generator  724  and interconnecting wires may be completely confined between opposing door surfaces  309 ,  311 , of the exemplary door so that motor/generator  724  is not readily visible or readily accessible from either surfaces. 
     While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.