Patent Publication Number: US-11662192-B2

Title: Mechanical energy harvesting devices with safety and event detection for munitions and the like

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit to U.S. Provisional Application No. 62/963,242, filed on Jan. 20, 2020, the entire contents of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates generally to low profile self-powered electrical initiators and electrical energy generation devices for munitions and the like with safety and firing event detection capability, and more particularly to devices that detect firing acceleration or target impact shock event without requiring external power sources and begin to generate electrical energy upon such shock loading events to initiate electrical initiators and/or power other system electronic and electrical circuits and devices. 
     2. Prior Art 
     All existing and future smart and guided gun-fired munitions and mortars that are equipped with electronics for fuzing or other similar purposes require electric power for their operation. Due to safety and the long shelf life of munitions, the electrical energy required for their operation is either provided by reserve batteries or onboard electrical generators. Reserve batteries, primarily the so-called liquid reserve and thermal batteries, are designed to be inert until they are activated. As a result, they have very long shelf life, sometimes well over 20 years that is required for most munitions power sources. 
     The amount of power required for proper operation of certain components in gun-fired munitions, for example for the operation of certain fuzing electronics, is small enough to be provided by harvesting electrical energy from firing setback and/or set-forward acceleration or from shock loading of target impact. The outset of the electrical energy generation by such devices may also be used as a signal indicating detection of the firing or target impact event for fuzing purposes and the like. 
     In general, such event detection and electrical energy generators harvest mechanical energy during the firing acceleration or target impact and store it as mechanical energy in certain mechanical energy storage devices as potential and/or kinetic energy and then convert it to electrical energy following the experienced shock loading event. The amount of electrical energy that such devices can provide is generally enough for initial powering of fuzing electronics until reserve power sources are activated and in some cases enough power is provided for the munitions entire mission. 
     Such event detection and electrical energy generators provide a very high degree of safety in munitions since they provide electrical energy that could operate onboard electronics only post firing. These devices therefore eliminate the need for a primary battery or a capacitor that needs to be charged on board munitions and their related safety and shelf life problems. 
     All weapon systems require fuzing systems for their safe and effective operation. A fuze or fuzing system is designed to provide as a primary role safety and arming functions to preclude munitions arming before the desired position or time, and to sense a target or respond to one or more prescribed conditions, such as elapsed time, pressure, or command, and initiate a train of fire or detonation in a munition. 
     Fuze safety systems consist of an aggregate of devices (e.g., environment sensors, timing components, command functioned devices, logic functions, plus the initiation or explosive train interrupter, if applicable) included in the fuze to prevent arming or functioning of the fuze until a valid environment has been sensed and the arming delay has been achieved. 
     Safety and arming devices are intended to function to prevent the fuzing system from arming until an acceptable set of conditions (generally at least two independent conditions) have been achieved. 
     A significant amount of effort has been expended to miniaturize munitions components to maximize their payload and their effectiveness. In the case of gun-fired munitions, it is highly desirable to have event detection and electrical energy generators that can be highly miniaturized and have minimal height. These devices are to harvest mechanical energy during the firing acceleration or target impact and store it as mechanical energy in mechanical energy storage devices as potential and/or kinetic energy. The device must then begin to generate electrical energy from the stored mechanical energy to electrical energy rapidly following gun firing or target impact event. The generated electrical voltage/current provides the event detection sensory functionality. The generated electrical energy can be used directly by the munition electronics and/or stored in certain electrical energy storage device such as a capacitor or super-capacitor for use during the flight and as required for the munitions mission. 
     A need therefore exists for the development of methods and devices that efficiently utilize the firing acceleration (or the target impact induced acceleration) to accumulate mechanical potential and/or kinetic energy in the device and only after the firing (target impact) event has ended, to rapidly begin to generate electrical energy. The generated electrical voltage/current can then be detected by the munition electronics and provide the firing (target impact) event detection sensory input to the munition electronics. The generated electrical energy is then used to power the munition electronics and other devices and stored in certain electrical storage devices for use post firing (target impact). 
     Piezoelectric-based mechanical event detection devices have also been developed that upon detection of the prescribed firing or target impact acceleration level and duration, i.e., the firing event or target impact, would harvest mechanical energy from firing setback or set-forward acceleration event and provide electrical energy to activate reserve batteries and/or for initial powering of fuzing electronics until reserve power sources are activated. 
     Piezoelectric-based energy harvesting device, however, can only generate a very small amount of electrical energy in munitions. This is the case since the firing setback acceleration provides a single shock loading pulse, which quickly deform the piezoelectric element to its maximum deformation level (harvested mechanical energy), i.e., the maximum generated charge level. For example, if the firing setback acceleration is 10-15 msec, the piezoelectric element deforms to its maximum allowable deformation level in a small fraction of one msec, and no mechanical energy is harvested during the remaining setback acceleration event time. 
     A need therefore exists for the development of methods and devices that can efficiently extract and accumulate a significant amount of mechanical energy during the entire period of setback acceleration (or the target impact induced acceleration) in the form of mechanical potential and/or kinetic energy that can then be used to generate electrical energy. The generated electrical energy may then be used to initiate reserve batteries and/or power the munition electronics and other devices and stored in certain electrical storage devices for use post firing (target impact). The generated electrical voltage/current may also be detected by the munition electronics as firing (target impact) event detection sensory input. 
     Such event detection and electrical energy generators provide a very high degree of safety in munitions since they provide electrical energy that could operate onboard electronics only post firing. These devices also eliminate the need for a primary battery or a capacitor that needs to be charged onboard munitions and their related safety and shelf life problems. 
     All weapon systems require fuzing systems for their safe and effective operation. A fuze or fuzing system is designed to provide the primary role of safety and arming functions to preclude munitions arming before the desired position or time, and to sense a target or respond to one or more prescribed conditions, such as elapsed time, pressure, or command, and initiate a train of fire or detonation in a munition. 
     The above fuzing functions require electrical energy to power the system sensory and related electronic and electrical devices. Event detection and electrical energy generators, particularly if they can generate significantly larger amounts of electrical energy that is possible with piezoelectric-based devices or other similar generators that cannot harvest and store the harvested mechanical energy during the entire setback acceleration cycle and convert the stored mechanical energy to electrical energy, would not only eliminate the need for a primary battery or a capacitor that needs to be charged onboard munitions before firing, but could also (at least partially) power the munitions electronics and electrical systems until onboard reserve batteries are activated. This is particularly beneficial for longer range munitions in which high electrical power that is supplied by the munition reserve batteries is needed only later during the flight. In such munition applications, the larger amounts of harvested electrical energy allow for the munitions reserve batteries to be activated later during the flight. As a result, the reserve battery rise time can be longer and significantly smaller thermal batteries would generally be required for the relatively long missions. 
     A significant amount of effort has been expended to miniaturize munitions components to maximize their payload and their effectiveness. In the case of gun-fired munitions, it is highly desirable to have safety and firing event detection, electrical reserve battery initiation and electrical energy generators that can be highly miniaturized. The achievement of this goal is greatly assisted by the development of devices that can harvest a significant amount of mechanical energy during the firing acceleration or target impact and store it as mechanical energy in mechanical energy storage devices as potential and/or kinetic energy for conversion to electrical energy. The generated electrical energy from the stored mechanical energy can then be used to power the system electronics, initiate reserve battery or initiation trains (with a prescribed delay if necessary), and/or store in a capacitor or super-capacitor for later use by munitions electronics and electrical devices. 
     A need therefore exists for the development of methods and devices that efficiently utilize the firing acceleration (or the target impact induced acceleration) to accumulate mechanical potential and/or kinetic energy in the device and only after the firing (target impact) event has ended, to rapidly begin to generate electrical energy. 
     The developed devices must not generate any electrical energy if the accelerations that do not correspond to the prescribed all-fire acceleration or target impact, i.e., a minimum acceleration threshold that lasts a prescribed period of time. 
     The generated electrical energy can then be used to initiate the device electrical initiator with or without a prescribed time delay or after receiving a command signal. The generated electrical voltage/current can also be detected by the munition electronics and provide the firing (target impact) event detection sensory input to the munition fuzing electronics. The remaining generated electrical energy may be used to power the munition electronics and/or stored in certain electrical storage devices for use post firing (target impact). 
     The developed devices must not accumulate any mechanical energy and generate no electrical energy if it is subjected to any accidental acceleration events, such as short duration but high acceleration levels due to accidental drops on hard surfaces or other object impacts (usually durations of the order of 0.5 msec or less) or low peak accelerations due to transportation vibration or the like. 
     A need also exists for the development of methods and devices that allow mechanical energy to be harvested from the munitions firing setback acceleration during essentially the entire duration of the setback acceleration to maximize the amount of mechanical energy available for conversion to electrical energy. 
     A need therefore exists for self-powered electrically initiated igniters for thermal batteries and the like, particularly for use in gun-fired smart munitions, mortars, small missiles and the like, that operate without external power sources and acceleration sensors and electrical and electronic circuit and incorporate the advantages of both electrical igniters with self-powered decision making electronics and microprocessors and inertial igniters that are currently available. 
     A need also exists for mechanical energy harvesting devices that can harvest mechanical energy from firing setback acceleration during essentially the entire duration of the setback acceleration and converting it to electrical energy upon the termination of the firing setback acceleration. 
     Such devices may also be used to harvest mechanical energy from firing set-forward acceleration in munitions and from impact induced accelerations. 
     A need also exists for self-powered munitions firing and impact event detection sensors for munitions fuzing applications. 
     Mechanical delay mechanisms for miniature inertial igniters have been described in U.S. Pat. Nos. 7,587,979 and 8,191,476 and 8,434,408, the entire disclosures thereof are incorporated herein by reference. This prior art mechanical delay mechanism and its operation is herein described by the “finger-driven wedge design” mechanism of  FIGS.  1   a - 1   d   , which as can be seen is a multi-stage mechanical delay mechanism. 
     The schematic of the prior art three-stage embodiment  80  is shown in  FIG.  1   a   . The device  80  can obviously be designed with as many fingers (stages) as is required to accommodate any desired delay time. The mechanism may have three fingers (stages)  81 ,  82  and  83 , each of which provides a specified amount of delay when subjected to a certain amount of acceleration (in the vertical direction of the arrow  89  as viewed in  FIG.  1   a   ). The fingers are fixed to the mechanism base  84  on one end. Each finger is provided with certain amount of mass and deflection resisting elasticity (in this case in bending). Certain amount of upward preloading may also be provided (with preloaded springs—not shown) to delay finger deflection until a desired acceleration level is reached. When at rest, only the first finger  81  is resting on the sloped surface  87  of the delay wedge  85 . The delay wedge  85  is provided with a resisting spring  88  to bring the system back to its rest position, if the applied acceleration profile is within the no-fire regime of the inertial igniter and to offer more programmability for the device. The delay wedge  85  is positioned in a guide  86  which restricts the delay wedge  85  motion along the guide  86 . 
     The operation of the device  80  is as follows. At rest, the delay wedge  85  is biased to the right by the delay wedge spring  88 , and the three fingers  81 ,  82  and  83  are biased upwards with some pre-load. The ratio of pre-load to effective finger mass will determine the acceleration threshold below which there will be no relative movement between components. The positions of the three fingers  81 ,  82  and  83  are such that finger  81  is above the sloped surface  87  of the delay wedge  85  and fingers  82  and  83  are supported by the top surface  90  of the delay wedge  85 , and are prevented from moving until the delay wedge  85  has advanced the prescribed distance. This is illustrated in  FIG.  1     a.    
     If the device  80  experiences an acceleration in the direction  89  above the threshold determined by the ratio of initial resistances (elastic pre-loads) to effective component masses, the primary finger  81  will act against the sloped surface  87  of the delay wedge  85 , advancing the delay wedge  85  to the left. 
       FIG.  1   b    shows the first finger  81  fully actuated and the delay wedge  85  advanced one-third of its total finger-actuated travel distance. At this instant, the second finger  82  is no longer supported by the top surface  90  of the delay wedge  85  and is free to move downwards provided that the acceleration is still sufficiently high to overcome the preload for the second finger  82  and the delay wedge spring  88  force at the aforementioned one-third travel distance. 
     If the acceleration continues at an all-fire profile, the second finger  85  will drive the delay wedge to two-thirds of its total finger-actuated travel distance, allowing the third finger  83  to act on the top surface  87  of the delay wedge  85 . This is shown in  FIG.  1     c.    
     If the acceleration terminates or falls below the all-fire requirements, the mechanism will reverse until balance is achieved between the acceleration reaction forces and the elastic resistances. This may be a partial or complete reset from which the mechanism may be re-advanced if an all-fire profile is applied or resumed. 
     Full actuation of the mechanism will occur once all three fingers  81 ,  82  and  83  have driven the delay wedge  85  to its full travel in succession. This non-linear progression will be carried out as a continuation of the partial actuations described above. The full actuation of such a mechanism is shown in  FIG.  1     d.    
     Obviously, the amount of preloading and/or resistance to bending of the fingers  81 ,  82 ,  83  may vary such that the first finger  81  bends under a certain acceleration profile, finger  82  bends under a larger acceleration profile than the first finger  81  and the third finger  83  bends under the largest acceleration profile. Furthermore, the delay wedge  85  can be configured to provide the ignition of the thermal battery upon full activation. 
     The above multi-stage mechanical delay mechanism  80  may obviously be configured in a wide variety of configurations. This method of providing a mechanical time delay mechanism via sequential travel of inertial elements provides devices that occupy very short heights while achieving very long-time delays. The significance of the multi-stage design in reducing the height of the mechanical time delay mechanisms, thereby the size (particularly the height) of inertial igniters can be described as follows (U.S. Pat. Nos. 7,587,979 and 8,191,476 and 8,434,408). 
     The mathematical model that can be used to evaluate the delay time as a function of the total vertical distance that the inertial (mass) element(s) of the various mechanical delay mechanisms have to travel due to the vertical travel distance of the inertial elements of the device using the delay mechanism, i.e., the minimum height of the resulting device, is based on an expansion constrained mass-spring model as shown in  FIG.  2   , consisting of a mass (inertia) element  101  and spring element  102 . The spring element  102  is attached to the base  103 , which in turn is fixed to the accelerating platform  105 . The spring element  102  is preloaded in compression and is constrained to expand from its preloaded position shown in  FIG.  2    by the stop  107 , which is fixed to the accelerating platform  105 . 
     When the base is accelerated upwards in the direction of the arrow  106 , the mass  101  will experience a reaction inertial force downward. Since the spring  102  is preloaded in compression, a threshold will exist below which the reaction force on the mass will not be high enough to deflect the spring from its preloaded position. Beyond this acceleration threshold, the mass  101  will move downward. For relatively high preloads and relatively small spring  102  deflections (such as those employed in the prior art embodiment of  FIGS.  1   a - 1   d   ), the spring  102  force can be assumed to be constant throughout the deflection. The net force on the mass is then equal to the difference between the reaction inertial force from the acceleration and the constant spring  102  force. 
     To generate a generic model applicable to a system without a predetermined mass or spring rate, the preload force may be expressed in terms of a force equivalent to the supported mass under some acceleration
 
 F   p   =m A   p   g  
 
where F p  is the preload force, A p  is the equivalent preload acceleration magnitude in G&#39;s, and g is the gravitational acceleration constant. This acceleration, A p , may now be subtracted from the acceleration which is producing the reaction force on the mass  101 . In other words, we specify the preload not in terms of force, but in terms of the threshold of acceleration below which there will be no spring  102  deflection. If the net equivalent acceleration on the mass  101  in G&#39;s is A, the displacement of the mass  101 , i.e., the deflection of the spring  102 , y, as a function of time t, can be expressed as
 
 y= ½ A g t   2   (1)
 
     Now, from the equation (1) we can compare the necessary axial displacement of the inertial elements (mass  101  in the model of  FIG.  2   ) in a single stage mechanical delay mechanism with the axial displacement of the inertial elements (mass  101  in the model of  FIG.  2   ) in a multi-stage mechanical delay mechanism. In the plot of  FIG.  3   , a 2000 G pulse is considered to be applied to the base  103  in the direction of the arrow  106  for 0.5 millisecond duration. The mass elements  101  is supported by constant-force springs  102  with preload forces equivalent to a movement threshold of 700 G. The vertical displacement of the mass (inertial) elements  101  have been scaled such that the displacement of the mass  101  in the single-stage mechanical delay mechanism (indicated by the curve  110  in the plot of  FIG.  3   ) at the end of the aforementioned acceleration pulse has a magnitude of one. Considering a three-stage mechanical delay mechanism, the vertical displacement of the first, second and third mass elements  101  of the first, second and third stages are shown in  FIG.  3    by the curves  111 ,  112  and  113 , respectively. The total vertical displacement required for the three stages (in fact for any number of stages) of a multi-stage mechanical delay mechanism is seen to be limited to the displacement of one of its stages alone. From the plot, the advantage of the three-stage design is clear: the total vertical displacement of a three-stage design nearly 90% smaller than that of the single-stage (currently available) designs. 
     It is noted that the reason behind a significant advantage of the disclosed multi-stage inertial mechanical delay mechanisms is the fact that for a single mass subjected to an acceleration, the resulting displacement is a quadratic function of the time of travel, equation (1). A quadratic function, curve  110  in  FIG.  3   , is more or less flat at the beginning, i.e., during the first relatively small intervals of time the displacement is small since the inertial element  101  has not gained a considerable amount of velocity. The present multi-stage inertial igniters take advantage of this characteristic of the aforementioned quadratic delay time vs. displacement relationship, equation (1), by limiting the total (vertical) displacement of the inertial elements  101  of each individual stage, thereby achieving very small vertical height requirement. 
     SUMMARY 
     Accordingly, methods and devices for harvesting and storing mechanical energy during essentially the entire duration or the desired portion of the duration of the firing setback acceleration or impact induced acceleration events is provided. The provided methods and devices may have the capability to ensure that mechanical energy is stored in the device and electrical energy is generated only if the device is subjected setback acceleration levels that are at or above the prescribed firing threshold or the prescribed impact induced acceleration threshold for the prescribed minimum durations and not when the device is subjected to any accidental acceleration events, such as short duration but high acceleration levels due to accidental drops on hard surfaces or other object impacts (usually durations of the order of 0.5 msec or less) or low peak accelerations due to transportation vibration or the like. 
     The generated electrical energy may then be used to initiate the provided electrical initiator(s) with or without a prescribed time delay. In which case, the device would thereby function as a self-powered electrical initiator with the added functionality of providing firing or impact event detection sensory input to the munitions fuzing and electrical energy to power munitions electronics and in some applications eliminate the need for onboard battery. 
     The device may also be provided with electronic circuit and logic and microprocessor(s) that can be programmed to initiate the provided electrical initiator(s) after certain amount of time or after receiving a command signal from the munitions control system or other sensory and the like inputs. 
     The device may also be used only for harvesting mechanical energy from the firing setback acceleration or impact events and generating electrical energy for direct use by the system electrical and electronics and/or storage in a storage device such as a capacitor or a super-capacitor. The device electrical output voltage/current may still be used to detect firing or impact events. 
     The device may also be used only for harvesting mechanical energy from the firing setback acceleration or impact events for direct use by the system mechanical systems such as safe and arm mechanisms following the detection of the prescribed all-fire or impact induced acceleration profile, i.e., a setback acceleration level that is at or above the prescribed firing acceleration threshold (or the prescribed impact induced acceleration threshold) for the prescribed minimum duration and not when the device is subjected to any accidental acceleration events, such as short duration but high acceleration levels due to accidental drops on hard surfaces or other object impacts or low peak accelerations due to transportation vibration or the like 
     An objective is to provide a new class of “mechanical energy harvesting devices” that can efficiently harvest mechanical energy from acceleration events, such as the firing setback acceleration of munitions, and store it in a mechanical energy storage device for later conversion to electrical energy or for other purposes, such as for actuating certain mechanical mechanisms or devices. 
     The disclosed new classes of “mechanical energy harvesting devices” may be provided with the capability of differentiating a prescribed minimum acceleration level and its duration, such as all-fire conditions in munitions or impact induced minimum acceleration level and minimum duration, and then begin to generate electrical energy. The electrical energy may then be used to initiate an electrical initiator with or without time delay or other sensory or control signal input; or may be at least partially stored in an electrical energy storage device such as a capacitor or supercapacitor for powering certain electrical and/or electronics. 
     The disclosed “mechanical energy harvesting devices” that are designed to directly transfer their mechanical energy to an electrical generator to generate electrical energy and at least partially use the generated electrical energy to initiate an electrical initiator and are provided with the previously described all-fire event detection capability are hereinafter referred to as “self-powered electrically initiated inertial igniters”. The “self-powered electrically initiated inertial igniters” may be provided with decision making electronics and/or microprocessors for initiating the electrical initiator, for example to activate a reserve battery or a munitions initiation train after certain time delay or when a sensory signal is received. 
     The disclosed “self-powered electrically initiated inertial igniters” utilize the firing acceleration to harvest mechanical energy and store it in a mechanical energy storage device and after the firing acceleration has ceased, convert it to electrical energy with the provided electrical generator(s) and at least partially use the generated electrical energy to initiate the provided electrical initiator. 
     The disclosed “self-powered electrically initiated inertial igniters” can be miniaturized and produced using available mass fabrication techniques and should therefore be low cost and reliable. 
     To ensure safety and reliability, all inertial igniters, including the disclosed “self-powered electrically initiated inertial igniters” must not initiate during acceleration events which may occur during manufacture, assembly, handling, transport, accidental drops, etc. 
     Additionally, once under the influence of an acceleration profile particular to the firing of the ordinance, i.e., a previously described all-fire condition, the igniter must initiate with high reliability. In many applications, these two requirements compete with respect to acceleration magnitude, but differ greatly in their duration. For example:
         An accidental drop may well cause very high acceleration levels—even in some cases higher than the firing of a shell from a gun. However, the duration of this accidental acceleration will be short, thereby subjecting the “self-powered electrically initiated inertial igniters” to significantly lower resulting impulse levels.   It is also conceivable that the “self-powered electrically initiated inertial igniters” will experience incidental long-duration acceleration and deceleration cycles, whether accidental or as part of normal handling or vibration during transportation, during which it must be guarded against initiation. Again, the impulse input to the igniter will have a great disparity with that given by the initiation acceleration profile because the magnitude of the incidental long-duration acceleration will be quite low.       

     The need to differentiate accidental and initiation acceleration profiles by their magnitude as well as duration necessitates the employment of a safety system which is capable of allowing initiation of the “self-powered electrically initiated inertial igniters” only when all-fire acceleration profile conditions are experienced. 
     The need to differentiate accidental and initiation acceleration profiles by their magnitude threshold as well as minimum duration necessitates the employment of a safety system which is capable of allowing accumulation of mechanical energy and its conversion to electrical energy only when the aforementioned all-fire acceleration profile conditions are experienced 
     In addition to having a required acceleration time profile as was previously described which should initiate generation of electrical energy and/or initiate an igniter, the all-fire and no-fire conditions may also be described by prescribed acceleration profiles, particularly for testing purposes. For example, the design requirements for initiation for one application may be summarized as:
         1. The device must fire when given a half sine pulse firing setback acceleration with a peak acceleration of 1,200 G±200 G for 20 msec.   2. The device must not fire when subjected to a half since acceleration of 3000 G for 0.5 msec in any direction.       

     The individual components of the disclosed “mechanical energy harvesting devices”, “electrical energy generator” and “self-powered electrically initiated inertial igniters” have been used in munitions, therefore the disclosed devices should be capable of readily satisfying most munitions requirement of 20-year shelf life and operation over the military temperature range of −65 to 165 degrees F., while withstanding high G firing accelerations. 
     Some of the features of the disclosed “electrically initiated inertial igniters” for use in reserve batteries, such as thermal batteries, initiation trains, and for providing electrical energy or all-fire detection functionality for gun-fired projectiles, mortars, sub-munitions, small rockets and the like include:
         1. The disclosed “self-powered electrically initiated inertial igniters” are capable of being readily “programmed” to almost any no-fire and all-fire requirements or multiple predefined setback environments. For these reasons, the disclosed “self-powered electrically initiated inertial igniters” are ideal for almost any reserve battery and initiation train applications, including conformal small and low power reserve batteries for fuzing and other similar munitions applications.   2. The disclosed “self-powered electrically initiated inertial igniters” do not require any external power sources for their operation.   3. In those applications in which the reserve battery power is needed for guidance and control close to the target, the disclosed “self-powered electrically initiated inertial igniters” can be set (programmed) to initiate battery activation long after firing or be commanded by onboard control system or sensory input or the like to initiate battery activation, thereby significantly increasing the battery run time, particularly in the case of thermal batteries.   4. The disclosed “self-powered electrically initiated inertial igniters” are readily packaged in sealed housings using commonly used mass-manufacturing techniques. As a result, safety and shelf life of the igniter and the reserve battery and initiation train using the igniters and the projectile is significantly increased.   5. The design of the “self-powered electrically initiated inertial igniters” and their capability of being hermetically sealed should easily provide a shelf life of over 20 years and the components used in their design allow for their proper operation within the military temperature range of −65 to 165 degrees F.   6. The disclosed “self-powered electrically initiated inertial igniters” can be designed to withstand very high-G firing accelerations in excess of 50,000 Gs.   7. The disclosed “electrical energy harvesters” can be set (programed) to generate electrical energy when subjected to a prescribed all-fire event, i.e., a prescribed minimum acceleration level and minimum duration, and not generate any electrical energy when subjected to any no-fire acceleration events, such as the previously described no-fire conditions. The disclosed “electrical energy harvesters” can therefore be used for initiation of almost all available electrical initiation devices for reserve batteries, initiation trains or other similar applications.   8. The disclosed “self-powered electrically initiated inertial igniters”, “mechanical energy harvesting devices” and “electrical energy harvesters” can be designed to conform to almost any geometrical shape of the available space in reserve batteries and munitions.       

     Accordingly, methods to design “mechanical energy harvesting devices” that harvest mechanical energy from the acceleration of the object to which they are attached, such as the firing setback acceleration of a gun-fired munition and store it in a mechanical energy storage device as potential and/or kinetic energy are provided. 
     Also provided are methods to design “mechanical energy harvesting devices” that can efficiently harvest mechanical energy from the acceleration of the object to which they are attached during almost the entire duration of the acceleration. 
     The “mechanical energy harvesting devices” may be provided with the means of differentiating a prescribed acceleration profile, with the prescribed acceleration profile being indicated as a minimum acceleration level and its duration, such as firing setback acceleration in munitions or target impact. In which case, if the prescribed acceleration profile is not detected, the “mechanical energy harvesting devices” either do not begin to harvest mechanical energy from the applied acceleration or discard the stored mechanical energy. 
     Also provided are “electrical energy generators” that use the above “mechanical energy harvesting devices” and convert the stored mechanical energy to electrical energy. Thereby providing “mechanical energy harvesting devices” that harvest mechanical energy from the acceleration of the object to which they are attached, such as the firing setback acceleration of a gun-fired munition, and convert the stored mechanical energy to electrical energy for direct use or for storage in an electrical energy storage device such as a capacitor and/or super-capacitor and/or rechargeable battery. 
     Also provided are “self-powered electrically initiated inertial igniters” that use the disclosed “mechanical energy harvesting devices” that are provided with the means of detecting prescribed acceleration profiles, with the prescribed acceleration profile being indicated as an acceleration level threshold and its minimum duration, such as firing setback acceleration in munitions or target impact, and upon detection of the prescribed acceleration profile would convert the stored mechanical energy to electrical energy, and use at least a portion of the generated electrical energy to initiate an electrical initiation device. 
     The electrical energy generating device can be an electromagnetic based electrical generator. The “mechanical energy harvesting device” may be provided with gearing and flywheel to increase the efficiency with which the stored mechanical energy is converted to electrical energy. 
     In addition, in certain applications, the electrical energy that is generated by the electrical energy generator of the “self-powered electrically initiated inertial igniter”, for example an electromagnetic electrical generator, may be desired to be partially or completely stored in an electrical energy storage device such as a capacitor for later use by the system electronics or the like, such as for powering a timing and/or sensory circuitry for initiation of a reserve battery after a prescribed amount of time has elapsed and/or after a certain event has been detected. In such applications, it is highly desirable for the mechanical energy harvesting and the electrical energy generation be highly efficient to make it possible to minimize the size of the overall device. 
     It is appreciated by those skilled in the art that when harvesting mechanical energy from high G accelerations that last relatively long time, for example several thousand G over ten or more milliseconds, or other similar very high G and similar duration events, mechanical energy harvesting over close to the entire duration of the high G acceleration is very challenging. This is the case since mechanical energy is harvested by either displacement of a mass element or gained velocity, which would both be extremely high for a reasonably sized mechanical energy harvesting device. For example, if the firing acceleration is 4,000 G and its duration is 10 msec, the device mass would be displaced a distance d, given as:
 
 d =(0.5) a t   2 =(0.5)(4000×9.8)(0.010) 2 =1.96 m  
 
And the final velocity V becomes:
 
 V=a t =(4000×9.8)(0.010)=392 m/sec
 
     Thus, as can be seen, the resulting mass displacement and velocity are both too high for a direct mass displacement and/or velocity-based mechanism to be used for mechanical energy harvesting in munitions and almost all envisioned applications. In addition, currently used electrical energy collection and capacitor storage methods are inefficient when the input (“pulse”) duration is very short. 
     Thus, methods and means are highly desirable to be developed for efficient harvesting of mechanical energy from short duration but high G accelerations and for storing the harvested mechanical energy in a mechanical energy storage device as potential and/or kinetic energy. The developed mechanical energy harvesting and storage devices must also be capable of transferring the stored mechanical energy to an electrical energy generator, such as an electromagnetic generator, to generate electrical energy for direct use and/or for storage in an electrical energy storage device such as a capacitor, super-capacitor or rechargeable battery. 
     Accordingly, methods and devices are provided for highly efficient harvesting of mechanical energy from short duration but high G accelerations and for storing the harvested mechanical energy in a mechanical energy storage device as potential and/or kinetic energy. Such short duration and high G accelerations are routinely encountered in munitions due to firing setback and target impact. The provided methods and devices provide the capability of transferring the stored mechanical energy to an electrical energy generator, such as an electromagnetic generator, to generate electrical energy for direct use and/or for storage in an electrical energy storage device such as a capacitor, super-capacitor or rechargeable battery. 
     There is also a need for methods for the design of devices that could detect prescribed acceleration event, the prescribed acceleration event defined as an acceleration level threshold and its minimum duration, and upon detection of the prescribed acceleration event to begin to generate electrical energy, the voltage and/or current produced by the generate electrical generator of the device may be used to provide the sensory input to the system electronics as the indication of the detection of the prescribed acceleration event, i.e., the all-fire condition in munitions. 
     Accordingly, methods and devices are provided for detecting prescribed acceleration events, the prescribed acceleration event defined as a minimum acceleration level and its duration, and upon the detection of the prescribed acceleration event to begin to generate electrical energy, the voltage and/or current produced by the generate electrical generator of the device would then provide the sensory information to the system electronics as an indication of the detection of the prescribed acceleration event. 
     A need also exists for methods to design battery-free inertially activated electrical initiation devices (i.e., the previously described “self-powered electrically initiated inertial igniters”) with integrated safety to differentiate prescribed initiation acceleration profiles, defined as a minimum acceleration level and its duration (all-fire condition in munitions) from all accidental or short duration and large magnitude accelerations, such as those experienced in accidental drops, or long duration and low magnitude accelerations, such as those experienced during transportation (no-fire conditions in munitions). The said “self-powered electrically initiated inertial igniters” may be required to ignite the device pyrotechnic material a certain amount of time following detection of the aforementioned prescribed initiation acceleration profile (all-fire conditions in gun-fired munitions or after target impact), i.e., be provided with a time delay mechanism. 
     Accordingly, methods and devices are provided for “self-powered electrically initiated inertial igniters” that with integrated safety that can differentiate prescribed initiation acceleration profiles by their magnitude level threshold as well as minimum duration from all accidental or other short duration and large magnitude accelerations or long duration and low magnitude accelerations. The devices may be provided with ignition time delay capability. 
     In addition, there is a need for the said battery-free inertially activated electrical initiation devices (“self-powered electrically initiated inertial igniters”) be capable of being miniaturized and protected from electromagnetic interference (EMI) and electromagnetic pulse (EMP). 
     Still further provided is methods for detecting the aforementioned prescribed initiation acceleration events by their magnitude threshold and minimum duration and then generating electrical energy and the onset of the generated electrical energy (usually detected voltage or current through a load element) indicating the detection of the said prescribed initiation acceleration event (firing event for the case of munitions or target impact), and providing electrical power to an internal component of the munition. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the apparatus of the present embodiments will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
         FIG.  1   a    illustrates an isometric view of a prior art embodiment of a multi-stage mechanical delay mechanism. 
         FIGS.  1   b - 1   d    illustrate the prior art multi-stage mechanical delay mechanism of  FIG.  1   a    in various stages of acceleration. 
         FIG.  2    illustrates an expansion constrained mass-spring model for evaluating delay time as a function of total vertical distance that the inertial (mass) element(s) of the various mechanical delay mechanisms have to travel. 
         FIG.  3    illustrates a plot of the expansion constrained mass-spring model of  FIG.  2    where a 2000 G pulse is applied to the base for 0.5 millisecond duration. 
         FIG.  4    illustrates a plot of the force vs. displacement of the mass-spring of  FIG.  2    as the unit is subjected to increasing acceleration. 
         FIG.  5    illustrates the schematic of the first “mechanical energy harvesting device” embodiment. 
         FIG.  6    illustrates the schematic of the first “mechanical energy harvesting device” embodiment of the  FIG.  5    after harvesting mechanical energy from the applied acceleration. 
         FIG.  7    illustrates the schematic of the first “mechanical energy harvesting device” embodiment of the  FIG.  5    with a mechanism for releasing the stored mechanical energy. 
         FIGS.  8 A- 8 B  illustrates the schematic of a modified “mechanical energy harvesting device” embodiment of  FIG.  5    that is designed to release the stored mechanical potential energy if a prescribed acceleration level and its duration is not detected. 
         FIG.  9 A  illustrates the schematic of the normally open electrical switch embodiment constructed with the “mechanical energy harvesting device” embodiment of  FIG.  7   . 
         FIG.  9 B  illustrates the schematic of the normally closed electrical switch embodiment constructed with the “mechanical energy harvesting device” embodiment of  FIG.  7   . 
         FIG.  9 C  illustrates the schematic of percussion primer initiator embodiment constructed with the “mechanical energy harvesting device” embodiment of  FIG.  7   . 
         FIG.  9 D  illustrates he schematic of an electrical energy harvesting embodiment constructed with the “mechanical energy harvesting device” embodiment of  FIG.  7   . 
         FIG.  10    illustrates the schematic of the second “mechanical energy harvesting device” embodiment. 
         FIGS.  11  and  12    illustrates the schematic of the third “mechanical energy harvesting device” embodiment. 
         FIGS.  13  and  14    illustrates the schematic of the fourth “mechanical energy harvesting device” embodiment. 
         FIG.  14 A  illustrates the schematic of a mechanical energy collecting unit for the embodiments of  FIGS.  5  and  8 A  with increased mass. 
         FIG.  15    illustrates the schematic of a mechanical energy collecting unit for the embodiments of  FIGS.  5  and  8 A  that begin energy harvesting only after an acceleration threshold has been reached. 
         FIG.  16    illustrates the schematic of a mechanical energy collecting unit for the embodiment of  FIGS.  13  and  14    that begin energy harvesting only after an acceleration threshold has been reached. 
         FIG.  17    illustrates the schematic of the fifth “mechanical energy harvesting device” embodiment. 
         FIG.  18    illustrates the side view of one of the mechanical energy collecting units of the “mechanical energy harvesting device” embodiment of  FIG.  17   . 
         FIG.  19    illustrates the schematic of the top view of the “mechanical energy harvesting device” embodiment of  FIG.  17   . 
         FIG.  20    illustrates the schematic of the sixth “mechanical energy harvesting device” embodiment. 
         FIG.  21    illustrates the schematic of the top view of the “mechanical energy harvesting device” embodiment of  FIG.  20   . 
         FIG.  22    illustrates the schematic of a mechanical rotary actuator unit for the “mechanical energy harvesting” embodiment of  FIG.  20    that begins energy harvesting only after an acceleration threshold has been reached. 
         FIG.  23    illustrates the schematic of the side view of the seventh “mechanical energy harvesting device” embodiment that is used to initiate a percussion primer or pyrotechnic material. 
         FIG.  24    illustrates the schematic of the view B-B of the embodiment of  FIG.  23    as used to initiate a percussion primer or pyrotechnic material. 
         FIG.  25    illustrates an alternative release mechanism for the “mechanical energy harvesting device” embodiment of  FIG.  23    that is used to initiate a percussion primer or pyrotechnic material. 
     
    
    
     DETAILED DESCRIPTION 
     It is appreciated that the prior art method and devices disclosed in the U.S. Pat. Nos. 7,587,979 and 8,191,476 and 8,434,408, and as described above with regard to  FIGS.  1   a - 1   d   , were developed for the design of mechanical delay mechanisms that are compact, low height, and that can be used for initiation of pyrotechnic materials or percussion caps or for performing electrical switching actions upon the detection of a prescribed minimum acceleration level with minimum duration (prescribed firing setback acceleration profile in munitions) and not when the device is subjected to any accidental acceleration events, such as short duration but high acceleration levels due to accidental drops on hard surfaces or other object impacts or low peak accelerations due to transportation vibration or the like. 
     In the present disclosure, a method of providing for sequential travel of mass elements of a multi-stage mechanism as the mechanism is subjected to an acceleration event is used to develop novel “mechanical energy harvesting devices” for efficiently harvesting mechanical energy from acceleration and storing it in mechanical energy storage devices; “electrical energy generators” that convert the mechanical energy stored in the “mechanical energy harvesting devices” to electrical energy for direct use by system electrical and electronic devices; and “self-powered electrically initiated inertial igniters” that use a portion of the electrical energy generated by the “electrical energy generators” to initiate electrical initiators directly or with a time delay or upon command from a sensory device or system controls. 
     Now consider the mass-spring shown in the schematic of  FIG.  2   . The compressive spring  102  is considered to have a constant spring rate k. The spring is constrained in its preloaded position by the stop  107 . Let the mass of the element  101  be indicated by m. Now when the base  103  of the unit is subjected to an acceleration α in the direction of the arrow  106 , the acceleration a acts on the mass m of the element  101 , applying a downward force F to the mass m equal to:
 
 F=mα   (2)
 
If the spring  102  is preloaded to a force F p , then if the acceleration α is high enough to generate a downward force F that is larger than the preload force F p , then the element  101  is displaced down a distance d to balance the downward force F, where the displacement d is determined from:
 
 F−F   p   =kd   (3)
 
     If we now plot the force F as a function of the spring deflection d from its free length, i.e., no preload condition) to its maximum deflection allowed by the  103  of the unit,  FIG.  2   , the plot of  FIG.  4    is then obtained. In the plot of  FIG.  4   , the d p  is the deflection of the spring  102  from its free length due to the applied preloading force F p  and the deflection d max  is considered to be the maximum deflection that the spring  102  can undergo due to the available space of the unit structure, at which time the maximum spring force F max  is reached. It is appreciated by those skilled in the art that in the plot of  FIG.  4   , the deflection of the spring  102  from its free length to the deflection d p  is due to the preloading of the spring  102  and the deflection from d p  to d max  is due to the acceleration α in the direction of the arrow  106  acting on the mass m of the element  101  as indicated by the equation (2). 
     In the plot of  FIG.  4   , the preloading deflection d p  is set as half of the maximum possible deflection d max  of the spring  102  for the purpose of making it easier to show the advantage of preloading springs in “mechanical energy harvesting devices” to be described later in this disclosure. Here, since the spring constant k of the spring  102  is considered to be constant, the spring force and deflection relationship is linear and is shown with the line  152  in  FIG.  4   . The area under the line  152  also indicates the amount of the work that is done on the spring to achieve the indicated spring deflection. For example, the area  151  is the amount of the work done by the force F to deflect the spring  102  distance d p  from its free length, at which point the force has a magnitude of F p . Once the spring is deflected a distance d p , the work done by the force F to deflect the spring is stored in the spring as mechanical potential energy E p  as:
 
 E   p =(½) F   p   d   p   (4)
 
However, if the spring  102  is preloaded by deflecting it a distance d p  and is then deflected the same amount (as was assumed above that d max =2 d p ), then the area under the line  150  (cross hatched), i.e., the work done by the force to deflect the spring  102  from the deflection position d p  to d max  will be three times larger than that area  151 , i.e., three times more mechanical potential energy is stored in the spring  102  for the same amount of spring deflection.
 
     As a result, when vertical height of the “mechanical energy harvesting device” is desired to be low, then preloaded spring elements should be used for harvesting mechanical potential energy from acceleration events. 
     The method being disclosed for the design of “mechanical energy harvesting devices” that harvest mechanical energy from acceleration of the object to which they are attached can be used to store the harvested mechanical energy in linear springs or torsional (power) springs. Herein, the method is described by its application to a “mechanical energy harvesting device” that harvests mechanical energy from acceleration and stores it in a linear spring. This embodiment  160  of the “mechanical energy harvesting device” is shown schematically in  FIG.  5   . 
     The “mechanical energy harvesting device” embodiment  160  of  FIG.  5    is designed to harvest mechanical energy from acceleration of the object to which the device is attached in the direction of the arrow  153  and store it in the compressive spring  154  as mechanical potential energy. The compressive spring  154  is appropriately preloaded as is described later in this enclosure to maximize the amount of mechanical energy that can be harvested from the acceleration. 
     The “mechanical energy harvesting device” embodiment  160  consists of a sliding member  156  that can slide in the provided guide  157  in the body  155  of the device. The sliding member  156  is provided with the notches  158  on at least one of its sliding surfaces as shown in  FIG.  5   . The notches  158  are used to engage the pawl  159 , which is attached to the device body by the hinge  161  and is provided with the biasing compressively preloaded spring  162  that in normal conditions presses it against the provided stop  163 , which is provided in the device body  155 . The pawl  159  and its assembly with the spring  162  and stop  163  and the notches  158  that are provided on the sliding surface of the member  156  constitute a well-known ratchet mechanism that allows for the movement of the member  156  to the left as seen in the view of  FIG.  5   , i.e., in the direction of deflecting (i.e., compressing) the mechanical potential energy storage spring  154  of the device, but prevents its movement to the right. 
     The “mechanical energy harvesting device” embodiment  160  is also provided with multiple “mechanical energy collecting” units  164  (in the schematic of  FIG.  5    three of such units are shown). The “mechanical energy collecting” units  164  may be identical, but as is described later in this disclosure, for optimal mechanical energy transfer and storage in the mechanical potential energy storage spring  154  they may have different effective mass and/or springs  169  with different levels of preloading. 
     Each “mechanical energy collecting” units  164  consists of a sliding member  165 , which is free to slide up or down as viewed in the schematic of  FIG.  5    in the guides  168  provided in the structure of the “mechanical energy harvesting device” embodiment  160 . On the sliding member  156  side, the sliding members are provided with rollers  166 , which are free to rotate about the shaft  167  that attaches them to the sliding member  165 . On the opposite side of the sliding members  165 , compressive springs  169  may be provided to keep the roller  166  in contact with a surface  170 ,  171  of the sliding member  156  as shown in  FIG.  5   . The compressive spring  169  can be selected to have low spring rate and can be slightly preloaded in compression to ensure roller contact with the top surface of the sliding member  156 . 
     The “mechanical energy harvesting device” embodiment  160  functions as follows. Initially, the roller  166  of the first (right-most) “mechanical energy collecting” units  164  is in contact with the inclined surface  170  of the sliding member  156 , while the other “mechanical energy collecting” units  164  (second and third from the right in  FIG.  5   ) are in contact with the top straight surface  171  of the sliding member  156 . When the object to which the device is attached is accelerated in the direction of the arrow  153 , the acceleration acts on the total mass (inertia) of the sliding member  165  and roller  166  assembly and the contributing (equivalent) mass of the spring  169 , resulting in a dynamic force (mass times acceleration) that in addition to the preloading force of the compressive spring  169  is applied by the roller  166  to the inclined surface  170  of the sliding member  156 . The horizontal component (as seen in the view of the  FIG.  5   ) of the dynamic and preloaded spring force applied by the roller  166  to the inclined surface  170  will then tend to displace the sliding member  156  to the left, thereby further deflecting the mechanical potential energy storage spring  154  in compression. The work done by the roller  166  force on the sliding member  156  is thereby stored in the spring  154  as mechanical potential energy. 
     In the meanwhile, the pawl  159  of the aforementioned ratchet mechanism is moved to one or more notches  158  of the sliding member  156  to the right. Thereby, if at this point of time the acceleration of the object to which the “mechanical energy harvesting device” embodiment  160  is attached is ceased, the said ratchet mechanism would prevent the sliding member  156  from returning to its initial position. The mechanical potential energy that is harvested from the acceleration of the said object would therefore stay stored in the mechanical potential energy storage spring  154 . 
     Then as the roller  166  of the first “mechanical energy collecting” units  164  nears the bottom surface  172  of the guide  157  of the sliding member  156 , the roller of the next “mechanical energy collecting” units  164  is positioned on the inclined surface  170  of the sliding member  156  and, if the acceleration continues, the roller of the next “mechanical energy collecting” units  164  continues to similarly force the sliding member to the left and further compress the mechanical potential energy storage spring  154 , thereby storing more mechanical potential energy in the mechanical potential energy storage spring  154 . In the meanwhile, the pawl  159  advances further to the notches  158  that are closer to the sliding surface  170 , thereby preventing the mechanical potential energy stored in the mechanical potential energy storage spring  154  to be released when the acceleration in the direction of the arrow has ceased or has dropped below the level at which the pressing roller  166  cannot overcome the opposing force of the mechanical potential energy storage spring  154 . 
     Then when the acceleration in the direction of the arrow  153  has ceased or has dropped below the level at which the pressing roller  166  cannot overcome the opposing force of the mechanical potential energy storage spring  154 , the mechanical potential energy stored in the spring  154  is available for the intended function(s). These functions may include: (1) conversion to electrical energy; (2) transfer of the stored mechanical energy to another device, such as accelerating a striker mass to impact a percussion primer to initiate it, or displacing or rotating a link or an object; or (3) a combination of the two. Examples of embodiments performing such functions are described later in this disclosure. 
     It is appreciated by those skilled in the art that after the “mechanical energy harvesting device” embodiment  160  of  FIG.  5    is subjected to an acceleration event in the direction of the arrow  153  that is strong enough and lasts long enough to actuate at least one of the device “mechanical energy collecting” units  164 , the mechanical potential energy stored in the mechanical potential energy storage spring  154  is retained by the action of the “ratchet” mechanism of the notches  158  and pawl  159 . Therefore, if the “mechanical energy harvesting device” is subjected to a next similar acceleration event, the mechanical potential energy gets accumulated in the mechanical potential energy storage spring  154  until the device reaches its maximum limit, generally when the last “mechanical energy collecting” unit  164  has been actuated as shown in  FIG.  6    or when the storage spring  154  is fully engaged (i.e., compressed). 
     Such “mechanical energy harvesting devices” are suitable for many applications. For example, for applications in which the device is subjected to numerous acceleration events with high enough levels and duration and the amount of stored mechanical potential energy has to reach a certain threshold level before it should be transferred to another device for performing certain task(s). Examples include devices used to generate electrical energy and that a minimum amount of electrical energy is needed to perform a certain task or for the electrical generator to operate efficiently. 
     One mechanism for releasing the mechanical energy stored in the mechanical energy storage spring  154 ,  FIG.  6   , is shown in the schematic of  FIG.  7   . In this embodiment, the mechanical energy stored in the mechanical energy storage spring  154  is intended to be released and transferred to the sliding member  178 , which is free to slide in the direction arrow  179 , The sliding member  178  is then used to perform one or more functions, such as generating electrical energy or performing other intended tasks. 
     In the embodiment of  FIG.  7   , the sliding member  156  is provided with an actuating pin  175  which is used to drive the mechanism that would release the mechanical energy stored in the storage spring  154 . The release mechanism consists of the link  176 , which is attached to the device body  155  by the rotary joint  177 . A link  180  is then attached to the free end of the link  176  via the joint  181  on one end and to the sliding block  182  via the joint  183  on the other end. The block  182  is provided with a guide (not show) that restricts it to movement against the device body as shown in  FIG.  7   . The member  184  is fixedly attached to the block  182  as shown in  FIG.  7   , which engages a slot  185  provided in the sliding member  178 , preventing its movement while the mechanical energy storage spring being compressed by the sliding member  156  as a result of the device acceleration in the direction of the arrow  153 ,  FIG.  5   , as was previously described. 
     In the configuration of  FIG.  7   , the sliding member  156  is shown to have been pushed to the left by the previously described action of the “mechanical energy collecting” units  164  so that the actuating pin  175  has come into contact with the link  176 . Now further leftward movement of the sliding member  156  by the engaging “mechanical energy collecting” unit,  FIG.  7   , would cause the link  176  to be rotated in the counter-clockwise direction as shown by the arrow  186 , thereby forcing the block  182  to be moved downward by the connecting link  180 , thereby disengaging the member  184  from the slot  185  in the sliding member  178 , thereby allowing the mechanical energy stored in the mechanical energy storage spring  154  to be transferred to the sliding member  178 . The sliding member could then transfer the mechanical energy to other devices and/or perform certain function that requires mechanical energy input. 
     In certain applications, such as in gun-fired munitions applications, the “mechanical energy harvesting device” must be capable of differentiating a prescribed minimum acceleration level with minimum duration (prescribed firing setback acceleration profile in munitions) from all accidental acceleration events, such as short duration but high acceleration levels due to accidental drops on hard surfaces or other object impacts (usually durations of the order of 0.5 msec or less) or low peak accelerations due to transportation vibration or the like. Such a capability is readily provided to the “mechanical energy harvesting device” embodiment  160  of  FIG.  5    by the simple modification to the sliding member  156  as shown in the schematic of  FIG.  8 A . 
     In the modified “mechanical energy harvesting device” embodiment  160  of  FIG.  5   , notches  158  are positioned in the sliding member  156  away from the pawl  159  enough so that if the prescribed acceleration threshold and its duration are not reached, the “mechanical energy collecting” units  164  would not displace the sliding member  156  to the left as viewed in the schematic of  FIG.  8    enough for the pawl  159  to engage the first notch  158 , such as shown in  FIG.  8 B . In the schematic of  FIG.  8 B , the first “mechanical energy collecting” units  164  is shown to be fully actuated and the second “mechanical energy collecting” units  164  is half-way actuated under the applied acceleration to the device in the direction of the arrow  153 ,  FIG.  5   . At this point, the acceleration has dropped or ceased so that the sliding member  156  cannot be further displaced to the left,  FIG.  8 B . Once the acceleration in the direction of the arrow  153  has ceased or dropped further, the mechanical energy storage spring  154  would force the sliding member  156  to return to its initial positioning of  FIG.  8 A . As a result, if the device is not subjected to the prescribed acceleration threshold and its duration (all-fire condition in munitions), no mechanical energy would remain stored in the mechanical energy storage spring  154 . 
     Now consider the mechanical energy harvesting embodiment of  FIG.  7   . It is appreciated by those skilled in the art that once the sliding member  178  is released, the mechanical potential energy stored in the “mechanical energy storage” spring  154  begins to be transferred to the sliding member  178  via the spring  154  force acting on the mass (inertia) of the sliding member  178 . The sliding member  178  may then be used to perform certain tasks, such as actuate certain mechanism or transfer the mechanical energy to an electrical generator to generate electrical energy. Examples of such use of the released mechanical energy, particularly for switching or initiation of certain actions are described below. 
     In one such embodiment, the mechanical energy harvesting embodiment of  FIG.  7    is used to close or open an electrical switch as shown in  FIGS.  9 A and  9 B , respectively. In  FIGS.  9 A and  9 B , the mechanical energy harvesting embodiment of  FIG.  7    is shown as a dotted box and is indicated by the numeral  190 , except for the sliding member  178  which is released following the previously described process of actuation by the “mechanical energy collecting” units  164  and forced out in the direction of the arrow  179  ( 198  in  FIGS.  9 A and  9 B ) by the “mechanical energy storage” spring  154 . 
     In the schematic of  FIG.  9 A , the normally open electrical switch is configured to close an electrical circuit once the sliding member  178  of the mechanical energy harvesting embodiment of  FIG.  7    is released. In the normally open electrical switch of  FIG.  9 A , an element  187 , which is constructed of an electrically non-conductive material is fixed to the device structure  188  ( 155  in  FIG.  7   ). The element  187  is provided with two electrically conductive elements  191  and  192  with contact ends  193  and  194 , respectively. The electrically conductive elements  191  and  192  may be provided with extended ends as shown in  FIG.  9 A  to form contact “pins” for direct insertion into provided holes in a circuit board or may alternatively be provided with wires  195  and  196  for connection to appropriate circuit junctions. The sliding member  178  is then provided with a flexible strip of electrically conductive material  189 , which is fixed to the sliding member as shown in  FIG.  9 A  by the fasteners  197  or other commonly known method in the art. 
     The normally open electrical switch of  FIG.  9 A  functions as follows. Once the sliding member  178  of the mechanical energy harvesting embodiment of  FIG.  7    is released, the mechanical energy storage spring  154  would force the sliding member  178  to move in the direction of the arrow  198  until the flexible electrically conductive strip  189  come into contact with the contacts  193  and  194 , thereby causing the circuit through the wires  195  and  196  (or electrically conductive elements  191  and  192 ) to close. 
     The normally open electrical switch of  FIG.  9 A  can be readily modified to provide a “normally closed” electrical switch. All the components of the “normally closed” electrical switch embodiment of  FIG.  9 B  are the same as those of the “normally open” embodiment of  FIG.  9 A , except the following electrical circuit closing elements. The “normally closed” electrical switch of  FIG.  9 B  is provided with two electrically conductive contact elements  199  and  200 , which are fixed to the electrically non-conductive member  187 , which is fixed to the device structure  188  as shown in  FIG.  9 A . The electrically conductive contact elements  199  and  200  are similarly provided with the extended ends or wires  195  and  196 ,  FIG.  9 A , for connection to appropriate circuit junctions. 
     To the electrically conductive contact elements  199  and  200  are fixedly attached flexible conductive strips  201  and  202  as shown in  FIG.  9 B , which are normally in contact, thereby causing the contact elements  199  and  200  (and wires  195  and  196 ,  FIG.  9 A , when provided) to close the electrical circuit to which they are connected to. The sliding member  178  is provided with a non-conductive element  203  as shown in  FIG.  9 B . 
     The normally closed electrical switch of  FIG.  9 B  functions as follows. Once the sliding member  178  of the mechanical energy harvesting embodiment of  FIG.  7    is released, the mechanical energy storage spring  154  would force the sliding member  178  to move in the direction of the arrow  198  until the non-conductive element  203  come into contact with the flexible conductive strips  201  and  202  and inserting the non-conductive element  203  between the contacting surfaces of the flexible conductive strips  201  and  202 , thereby rendering their contacts open, thereby opening the electrical circuit to which the contact elements  199  and  200  (and wires  195  and  196 ,  FIG.  9 A , when provided) are connected. 
     The electrical contacts can also be provided directly on an electronic/electrical device and the wiring can be integrally formed on a substrate in or on the device. 
     In another embodiment, the mechanical energy harvesting embodiment of  FIG.  7    is used to initiate a percussion primer (or other similarly provided pyrotechnic material) as shown in  FIG.  9 C . In  FIG.  9 C  the mechanical energy harvesting embodiment of  FIG.  7    is still shown as a dotted box and is indicated by the numeral  190 , except for the sliding member  178  which is released following the previously described process of actuation by the “mechanical energy collecting” units  164  and forced out in the direction of the arrow  179  ( 198  in  FIG.  9 C ) by the “mechanical energy storage” spring  154 ,  FIG.  7   . 
     In the schematic of  FIG.  9 C , the percussion primer initiator is configured to ignite the percussion primer  204  once the sliding member  178  of the mechanical energy harvesting embodiment of  FIG.  7    is released. In the percussion primer initiator of  FIG.  9 C , a percussion primer (or similar impact-initiated igniter) is fixed to the device structure  188  ( 155  in  FIG.  7   ) or to another element, such as a thermal battery. The element  187  is provided with a tip element  205  that is sized to ignite the percussion primer  204  upon impact. 
     The percussion primer initiator embodiment of  FIG.  9 C  functions as follows. Once the sliding member  178  of the mechanical energy harvesting embodiment of  FIG.  7    is released, the mechanical energy storage spring  154  would force the sliding member  178  to move in the direction of the arrow  198  and gain speed until the tip element  205  impacts the percussion primer  204  and causes it to ignite. If element  188  is another device, the same can have a hole behind the primer  204  such that, when ignited, flame/sparks can pass through the hole to another device, such as the thermal battery. 
     In yet another embodiment, the mechanical energy harvesting embodiment of  FIG.  7    is used to generate electrical energy as shown in  FIG.  9 D . In  FIG.  9 D  the mechanical energy harvesting embodiment of  FIG.  7    is still shown as a dotted box and is indicated by the numeral  190 , except for the sliding member  178  which is released following the previously described process of actuation by the “mechanical energy collecting” units  164  and forced out in the direction of the arrow  179  ( 198  in  FIG.  9 D ) by the “mechanical energy storage” spring  154 ,  FIG.  7   . 
     In the schematic of  FIG.  9 D , the sliding member  178  is attached to a link  206  via a rotary joint  207 . The other end of the link  206  is attached to another link  208  via a rotary joint  209 . The other end of the link  208  is then fixedly attached to the inner rotating component of a rotary one-way clutch  210 , which is attached to the support member  211  via the shaft  212 . The support member  211  is fixedly attached to the device structure  188 . The outer race of the one-way clutch  210  is fixedly attached to a flywheel member  213 . The one-way clutch  210  is mounted such that the counter-clockwise rotation of the link  208  would engage the clutch and force the flywheel  213  to rotate in the counter-clockwise direction, but clockwise rotation of the link  208  relative to the flywheel  213  causes the clutch  210  to disengage. As a result, the flywheel  213  is always free to rotate in the counter-clockwise direction. The flywheel  213  is provided with an engaging surface, such as a gear (not shown and can be on the outside diameter of the flywheel  213 ), which engages a corresponding surface of a pinion  214  (such as mating gear teeth, not shown), which is free to rotate about the shaft  215 , which is mounted in a bearing in the support member  216 , which is fixedly attached to the device structure  188 . The gear  214  is then use to drive an electrical generator (not shown), which might be integral to the gear or driven by the shaft  215  that is connected fixedly to the gear  214  or via another engaging gear as are all well known in the art. 
     The electrical energy generator embodiment of  FIG.  9 C  functions as follows. Once the sliding member  178  of the mechanical energy harvesting embodiment of  FIG.  7    is released, the mechanical energy storage spring  154  would force the sliding member  178  to move in the direction of the arrow  198 . The sliding member  178  would then begin to drive the link  206 , which would then drive the link  208 , thereby transferring the mechanical energy stored in the mechanical energy storage spring  154  to the flywheel  213  as mechanical kinetic energy. Once the sliding member  178  has reached its maximum extent, which is can be configured to be before the links  206  and  208  become lined-up, the one-way clutch  210  would allow the flywheel  213  to continue to rotate in the counter-clockwise direction and for the flywheel (through its attached engagement surface or gear previously described) to rotate the pinion  214 , thereby the electrical generator is driven by the pinion  214 . The mechanical kinetic energy of the flywheel  213  is thereby transferred into electrical energy that can be used directly or stored in an electrical energy storage device such as a capacitor or a rechargeable battery for later use. 
     It is appreciated that the “mechanical energy harvesting device” embodiment  160  of  FIG.  5    uses multiple “mechanical energy collecting” units  164  (in the schematic of  FIG.  5    three of such units are shown) to force the sliding member  156  to compress the mechanical potential energy storage spring  154  when the device  160  is subjected to high enough acceleration in the direction of the arrow  153  to store mechanical potential energy in the spring  154  as was previously described. The same function of harvesting mechanical energy from the device acceleration and storing it in a mechanical energy storage spring can be performed by using mechanisms other than the previously described “mechanical energy collecting” units  164 . One example of such an alternative “mechanical energy collecting” mechanism is shown in the schematic of  FIG.  10   . 
     The “mechanical energy harvesting device” embodiment of  FIG.  10    is constructed by the modification of the embodiment of  FIG.  8 A . In the embodiment of  FIG.  10   , the “mechanical energy collecting” units  164  are replaced by rollers or balls (four of which are shown in  FIG.  10   ) as described below. The remaining elements of the embodiments of  FIG.  10    are identical to those of the embodiment of  FIG.  8 A  and perform the same functions, except for the added elements that are herein described. The rollers (balls)  217  can be kept apart by a “cage” member  218 , as is commonly used in roller (ball) linear and circulating bearings. The rollers (balls) are free to move in the guide  219  above the sliding member  156  provided in the device structure  155 . The guide  219  in the structure  155  of the device is continued as indicated by numeral  220  which ends as can be seen in  FIG.  10    inside the device structure  155 . 
     The “mechanical energy harvesting device” embodiment of  FIG.  10    is also configured to harvest mechanical energy from acceleration of the object to which the device is attached in the direction of the arrow  222  ( 153  in  FIG.  8 A ) and store it in the compressive spring  154  as mechanical potential energy. The compressive spring  154  is appropriately preloaded as was previously described to maximize the amount of mechanical energy that can be harvested from the device acceleration. 
     The “mechanical energy harvesting device” embodiment of  FIG.  10    functions as follows. Initially, the right most roller (ball)  217  is in contact with the inclined surface  170  of the sliding member  156 , while the other rollers (second to fifth in  FIG.  10   ) are in contact with the top straight surface  171  of the sliding member  156 . When the object to which the device is attached is accelerated in the direction of the arrow  222 , the acceleration acts on the mass (inertia) of the roller (ball)  217 , resulting in a dynamic force (mass times acceleration) that is applied by the roller (ball)  217  to the inclined surface  170  of the sliding member  156 . The horizontal component (as seen in the view of the  FIG.  10   ) of the dynamic force applied to the inclined surface  170  will then tend to displace the sliding member  156  to the left, thereby further deflecting the mechanical potential energy storage spring  154  in compression. The work done by the roller (ball)  217  force on the sliding member  156  is thereby stored in the spring  154  as mechanical potential energy. 
     In certain applications, such as in gun-fired munitions applications, the “mechanical energy harvesting device” must be capable of differentiating a prescribed minimum acceleration level with minimum duration (prescribed firing setback acceleration profile in munitions) from all accidental acceleration events, such as short duration but high acceleration levels due to accidental drops on hard surfaces or other object impacts or low peak accelerations due to transportation vibration or the like. Such a capability is provided for the “mechanical energy harvesting device” embodiment of  FIG.  10    as was described for the embodiment of  FIG.  8 A . If such a feature is not desired, then the notches  158  in the sliding member  156  can be arranged as shown in the embodiment  160  of  FIG.  5    to allow accumulation of the harvested mechanical energy. 
     It is appreciated that the “mechanical energy harvesting device” embodiments of  FIGS.  5 ,  8 A and  10    are designed to linearly displace a sliding member  156  to deform the compressive spring  154  (however, a linear tensile spring may also be used but needs to be attached to the opposite end of the sliding member  154 , i.e., to the side of the inclined surface  170 ), thereby harvesting mechanical energy from the acceleration of the device and store it in the spring  154  as mechanical potential energy. 
     A “mechanical energy harvesting device” operating on the same principle may, however, be configured with a rotary sliding member to harvest mechanical energy from the acceleration of device and store the harvested mechanical energy in a torsion or linear spring as mechanical potential energy. Such an embodiment  225  of a rotary type “mechanical energy harvesting device” is shown in the schematics of  FIGS.  11  and  12   . An advantage of using a rotary type as compared to the previously disclosed linear type “mechanical energy harvesting device” is that they can be configured to be significantly smaller. In addition, rotary type devices can be less prone to friction related energy losses and geometrical design restrictions. 
       FIG.  11    shows the schematic of the side view of the “mechanical energy harvesting device” embodiment  225 .  FIG.  12    shows the top view of the embodiment  225  as herein described. The “mechanical energy harvesting device”  225  consists of a main shaft  221 . The shaft  221  is fixedly attached on one end to the intended object  224 , which is subjected to the acceleration in the direction of the arrow  226 , from which mechanical energy is intended to be harvested. On the other end, the shaft  221  is fixedly attached to a “cylindrical cup” shaped cover  223 , the cross-section of it is shown in the schematic of  FIG.  11    so that the internal components of the mechanical energy harvesting device can be seen. The shaft  221  is provided with a step member  227 , over which the cylindrical cover  223  is shown to rest. The step member  227  is provided with an extended member  229 , which is more clearly seen in the top view of  FIG.  12   . 
     It is appreciated that the shaft  221 , the step member  227  and the cylindrical cover may be integral, but for manufacturing considerations, the cylindrical cap  223  may be a separate element with the central hole  228 , which is positioned over the step member  227  and fixedly attached to the shaft by welding or other known methods in the art. 
     In the top view of the “mechanical energy harvesting device” embodiment  225  shown in the schematic of  FIG.  12   , the cylindrical cap  223  is not shown so that the internal components of the device can be clearly seen. The step member  227  is provided with an extended member  229 ,  FIGS.  12  and  11   . 
     The “mechanical energy harvesting device” embodiment  225  is provided with the member  230 ,  FIGS.  11  and  12   , which is attached to the shaft  221  by a bearing  231 , allowing it to rotate freely around the shaft  221 , which is fixedly attached to the device  224  to which the “mechanical energy harvesting device” embodiment  225  is attached. The bearing  231  may be ball or other type of anti-friction bearing or formed by providing a small clearance between the shaft  221  and the inside diameter of the member  230 , in which case a thrust bearing or the like should be provided to prevent displacement of the member  230  along the shaft  230 . In general, particularly when high acceleration levels in the direction of the arrow  226  are involved, a ball or roller thrust bearing combination or properly mounted tapered roller bearing can be for mounting the member  230  on the shaft  221 . 
     The “mechanical energy harvesting device” embodiment  225  is provided with “actuating” balls  232  (similar to the balls  217  in the embodiment of  FIG.  10   ), which can be kept apart by the “cage” members  233 , as is commonly used in roller (ball) linear and circulating bearings. The balls  232  are free to move on the surface  234  of the member  230  in the configuration shown in  FIGS.  11  and  12    as guided by the outer surface  235  of the step member  227 , the bottom surface  236  and inner surface  237  of the cylindrical cap  223  ( FIG.  11   ). The top surface  234  of the member  230  is provided with a sloped portion  238  which drops to the surface  239  as shown in  FIGS.  11  and  12   , which continues up to the step  240  ( FIG.  12   ), which rises back to the top surface  234  of the member  230 . It is noted that in the schematics of  FIGS.  11  and  12   , five balls  232  are shown, the right most of which as viewed in these schematics is positioned on the sloped portion  238 . A torsion spring  241  is provided and is fixedly attached to the member  230  on one end  242  and to the device  224  on the other end  243 . 
     The “mechanical energy harvesting device” embodiment  225  shown in  FIGS.  11  and  12    is configured to harvest mechanical energy from acceleration of the object to which the device is attached in the direction of the arrow  226  and store it in the torsion spring  241  as mechanical potential energy. The torsion spring  241  may be preloaded as was previously described for the embodiment of  FIG.  5    to maximize the amount of mechanical energy that can be harvested from the device acceleration. In which case, a stop extension  244  can be provided on the member  230  that is pressed against a provided member  245  on the structure of the device  224  to which the embodiment  225  is attached to prevent counter-clockwise rotation (as viewed in  FIG.  12   ) of the member  230  relative to the device  224  to relieve the preloading of the torsion spring  241 . 
     The “mechanical energy harvesting device” embodiment  225  of  FIGS.  11  and  12    functions as follows. Initially, the right most ball  232  is in contact with the inclined surface  238  of the member  230 , while the other balls (second to fifth in  FIGS.  11  and  12   ) are in contact with the top straight surface  234  of the member  230 . When the object to which the device is attached (indicated by the ground  224 ) is accelerated in the direction of the arrow  226 , the acceleration acts on the mass (inertia) of the balls  232 , resulting in a dynamic force (mass times acceleration) that is applied by the balls on the contacting surfaces of the member  230 , including the ball  232  that is positioned on its inclined surface  238 . The tangential component (tangent to the circle centered at the center of the shaft  221  with a radius equal to the distance from the center of the shaft  221  to the point of contact between the ball  232  and the inclined surface  238 ) as seen in  FIG.  12    of the dynamic force applied to the inclined surface  238  will then tend to rotate the member  230  in the clockwise direction, while the ball  232  presses against the surface  246  of the extended member  229  of the step member  227 ,  FIG.  12   . The torsion spring  241  is thereby wound and the work done by the ball  232  force on the member  230  is stored in the torsion spring  241  as mechanical potential energy. The first ball  232  would then reach the surface  239 ,  FIGS.  11  and  12   , at which time the second ball  232  is positioned over the inclined surface  238  and as long as the acceleration in the direction of the arrow  226  persists and is high enough to overcome the resisting force of the torsion spring  241 , would keep forcing the member  230  to rotate in the clockwise direction, thereby adding more potential mechanical energy to the torsion spring  214  to store. 
     It is appreciated by those skilled in the art that a ratchet mechanism similar to those shown for the embodiments of  FIGS.  5  and  8 A  may also be provided between the member  230  and the shaft  221  to perform the same tasks for the embodiment  225  of  FIGS.  11  and  12   . It is appreciated that in certain applications, such as in gun-fired munitions applications, the “mechanical energy harvesting device” must be capable of differentiating a prescribed minimum acceleration level with minimum duration (prescribed firing setback acceleration profile in munitions) from all accidental acceleration events, such as short duration but high acceleration levels due to accidental drops on hard surfaces or other object impacts or low peak accelerations due to transportation vibration or the like. Such a capability is provided for the “mechanical energy harvesting device” embodiment of  FIGS.  11  and  12    with the added ratchet mechanism (not shown) as was described for the embodiment of  FIG.  8 A . If such feature is not desired, then the ratchet mechanism notches ( 158  in  FIG.  5   ) would be arranged as shown in the embodiment  160  of  FIG.  5    to allow accumulation of the harvested mechanical energy. 
     The “mechanical energy harvesting device” embodiment  225  of  FIGS.  11  and  12    may be modified as shown in the schematics of  FIGS.  13  and  14    and identified as the “mechanical energy harvesting device” embodiment  250 . The embodiment  250  is intended to be constructed with fewer parts and occupy a smaller volume, which is of much interest in applications such as munitions. 
     The construction of the “mechanical energy harvesting device” embodiment  250  shown in the top and side views of  FIGS.  13  and  14   , respectively, is identical to that of the embodiment  225  shown in  FIGS.  11  and  12   , except for the following modifications. Firstly, the cylindrical cap  223  and the step member  227 ,  FIG.  11   , are eliminated as can be seen in the schematic of  FIG.  14   . Secondly, the balls  232  of the embodiment  225 ,  FIG.  12   , are replaced by “contact members”  247 , which are fixedly attached to the shaft  221  by members  248 , which are flexible in bending (in and out of the plane of the view of  FIG.  13   ), but relatively rigid in bending sideways. The configuration options for the shape and size of the “contact members”  247  and the flexible members  248  are described below. 
       FIG.  14    shows the schematic of the side view of the “mechanical energy harvesting device” embodiment  250 . Similar to the embodiment  225  of  FIGS.  11  and  12   , the “mechanical energy harvesting device”  250  is fixedly attached to the intended object  224 , which is subjected to the acceleration in the direction of the arrow  249 , from which mechanical energy is intended to be harvested. 
     The “mechanical energy harvesting device” embodiment  250  is provided with the same member  230  as the embodiment  225  of  FIGS.  11  and  12   , which is also attached to the shaft  221  by a bearing  231 , allowing it to rotate freely around the shaft  221 . The bearing  231  may be ball or other type of anti-friction bearing or formed by providing a small clearance between the shaft  221  and the inside diameter of the member  230 , in which case a thrust bearing or the like should be provided to prevent displacement of the member  230  along the shaft  230 . In general, particularly when high acceleration levels in the direction of the arrow  249  are involved, a ball or roller thrust bearing combination or properly mounted tapered roller bearing can be for mounting the member  230  on the shaft  221 . 
     As was shown in the embodiment  225  of  FIGS.  11  and  12   , the top surface  234  of the member  230  is provided with the same sloped portion  238 , which drops to the surface  239  and continues up to the step  240 , which rises back to the top surface  234  of the member  230 . It is noted that in the schematics of  FIGS.  13  and  14   , five “contact members”  247 , which are fixedly attached to the shaft  221  by members  248  are shown, the right most of which as viewed in  FIG.  14    is positioned on the sloped portion  238 . A torsion spring  241  is similarly provided and is fixedly attached to the member  230  on one end  242  and to the device  224  on the other end  243 ,  FIG.  14   . 
     The “mechanical energy harvesting device” embodiment  250  of  FIGS.  13  and  14    is also configured to harvest mechanical energy from acceleration of the object to which the device is attached in the direction of the arrow  249  and store it in the torsion spring  241  as mechanical potential energy. The torsion spring  241  may be preloaded as was previously described for the embodiment  225  of  FIGS.  11  and  12    to maximize the amount of mechanical energy that can be harvested from the device acceleration. In which case, the stop extension  244  is also provided on the member  230  that is pressed against a provided member  245  on the structure of the device  224  to which the embodiment  250  is attached to prevent counter-clockwise rotation (as viewed in  FIG.  13   ) of the member  230  relative to the device  224  to relieve the preloading of the torsion spring  241 . 
     The “mechanical energy harvesting device” embodiment  250  of  FIGS.  13  and  14    functions as follows. Initially, the right most “contact member”  247  is in contact with the inclined surface  238  of the member  230 , while the other contact members (second to fifth in  FIGS.  13  and  14   ) are in contact with the top straight surface  234  of the member  230 . When the object to which the device is attached (indicated by the ground  224 ) is accelerated in the direction of the arrow  249 , the acceleration acts on the mass (inertia) of the contact member  247  (neglecting the inertia of the flexible connecting member  248 ), resulting in a dynamic force that is applied by the contact members to the surfaces of the member  230 , including the contact member  247  that is positioned on its inclined surface  238 . The tangential component (tangent to the circle centered at the center of the shaft  221  with a radius equal to the distance from the center of the shaft  221  to the point of contact between the contact member  247  and the inclined surface  238 ) as seen in  FIG.  13    of the dynamic force applied to the inclined surface  238  will then tend to rotate the member  230  in the clockwise direction as viewed in the schematic of  FIG.  13   . The torsion spring  241  is thereby wound and the work done by the contact member  247  on the member  230  is stored in the torsion spring  241  as mechanical potential energy. The first contact member  247  would then reach the surface  239 ,  FIGS.  13  and  14   , at which time the second contact member  247  is positioned over the inclined surface  238  and as long as the acceleration in the direction of the arrow  249  persists and is high enough to overcome the resisting force of the torsion spring  241 , would keep forcing the member  230  to rotate in the clockwise direction, thereby adding more potential mechanical energy to the torsion spring  214  to store. 
     In a modification of the “mechanical energy harvesting device” embodiment  250  of  FIGS.  13  and  14   , at least one of the (five) “contact members”  247  are hinged (instead of being fixedly attached) to the shaft  221 , allowing the contact member  247  and the connecting member  248  to rotate in and out of the plane of view of  FIG.  13   , thereby performing the same function as described above. 
     It is appreciated by those skilled in the art that a ratchet mechanism similar to those shown for the embodiments of  FIGS.  5  and  8 A  may also be provided between the member  230  and the shaft  221  to perform the same tasks for the embodiment  250  of  FIGS.  13  and  14   . It is appreciated that in certain applications, such as in gun-fired munitions applications, the “mechanical energy harvesting device” must be capable of differentiating a prescribed minimum acceleration level with minimum duration (prescribed firing setback acceleration profile in munitions) from all accidental acceleration events, such as short duration but high acceleration levels due to accidental drops on hard surfaces or other object impacts or low peak accelerations due to transportation vibration or the like. Such a capability can also be provided for the “mechanical energy harvesting device” embodiment of  FIGS.  13  and  14    with the added ratchet mechanism (not shown) as was described for the embodiment of  FIG.  8 A . If such is feature is not desired, then the ratchet mechanism notches ( 158  in  FIG.  5   ) would be arranged as shown in the embodiment  160  of  FIG.  5    to allow accumulation of the harvested mechanical energy. 
     In the schematics of the “mechanical energy harvesting device” embodiment  250  of  FIGS.  13  and  14   , the contact members  247  are shown as a ball, which are connected to the shaft  221  by the member  248 , which is relatively flexible in up and down bending (in the direction parallel to the axis of the shaft  221 ) and relatively rigid in lateral bending. The ball shaped depiction of the contact members is only for the purpose of showing similarity of this embodiment to that of the embodiment  225  of  FIGS.  11  and  12   . It is appreciated by those skilled in the art that the contact members  247  may be configured in almost any shape as long as their center of mass is nearly located along the neutral axis of the member  248  so that the applied acceleration in the direction of the arrow  249  would not generate a twisting torque on the connecting members (beams)  248  and that the surfaces of the contact members with the surfaces of the member  230  is close to being spherical to minimize contact friction. As an example, a possible side view of the contact member  247  and the connecting member  248  is shown in  FIG.  14 A , in which the lower section of the contact member is spherical, while the top has a square cross-section. Such designs would allow the designer to choose a desired mass for the contact member  247  (such as indicated by the numeral  247   a  in  FIG.  14 A ) to achieve the desired dynamic force based on the applied acceleration level in the direction of the arrow  249  and also vary the contact mass (usually increase) sequentially as the mechanical energy storage spring  241  is wound to counter its increasing resistance to wounding. 
     It is appreciated that when the “mechanical energy harvesting device” embodiments of  FIGS.  5  and  8 A  are subjected to accelerations in the direction of the arrow  153 , the acceleration acts on the combined inertia of the “mechanical energy collecting” units  164  and apply the resulting dynamic force to the sliding member  156  by the roller  166 . The provided preloaded compressive spring  169  applies an additional preloading force to the sliding member  156 . This is also the case for the “mechanical energy harvesting device” embodiment  250  of  FIGS.  13  and  14    and when the device is subjected to acceleration in the direction of the arrow  249 , the dynamic force due to the inertia of the contact member  247  is applied to the surface of the member  230 . It is also appreciated that the flexible connecting member (beam)  248  may also be preloaded to keep the contact member  247  in contact with the surface of the member  230  and apply a desired level of force to the surface at all times. 
     It is, however, appreciated that in some applications, such is in many munitions applications, it is highly desirable that the “mechanical energy collecting” units  164  of the “mechanical energy harvesting device” embodiments of  FIGS.  5 - 9    to begin to apply force to the sliding member  156  or the contact member  247  of the embodiment  250  of  FIGS.  13  and  14    to begin to apply force to the surface of the member  230  after a certain acceleration level threshold has been reached. It is appreciated that the prescribed acceleration threshold may be the same for all “mechanical energy collecting” units  164  and contact member  247  or may be different for each of the units. The following modifications to the design of the “mechanical energy collecting” units  164  and the contact member  247  and its connecting member  248  described below provides the above capability to the related “mechanical energy harvesting device” embodiments. 
     To prevent the “mechanical energy collecting” units  164  from applying a force to the sliding member  156  before a prescribed acceleration threshold has been reached, the configuration of the units can be modified as shown in the schematic of  FIG.  15    and indicated by the numeral  251 . The “mechanical energy collecting” unit  251  consists of a member  252 , to one end of it the sliding member  253  is fixedly attached. The sliding member  253  is free to move in the guide  256  that is provided inside the housing  254 , which is fixedly attached to the structure  255  of the “mechanical energy harvesting device” (for example, the structure  155  of the embodiment  160  of  FIG.  5   ). As can be seen in  FIG.  15   , the member  252 , which is smaller in diameter, passes through a smaller diameter hole  257  that is provided at the bottom of the guide  256  of the housing  254 . A preloaded compressive spring  258  is positioned between the sliding member  253  and the bottom of the guide  256  to bias the sliding member  253  against the structure  255  of the device  251  as can be seen in  FIG.  15   . On the other end of the member  252  that is extended outside the housing  254 , a roller  259  is provided that is free to rotate about the shaft  260 . 
     The “mechanical energy collecting” unit  251  will then function as follows. When the “mechanical energy harvesting device” in which the units  251  are used to actuate their sliding members, for example the sliding members  156  of the embodiment of  FIG.  5  or  8 A , is subjected to acceleration in the direction of the arrow  261 , the acceleration acts on the effective inertia of the entire moving assembly of the “mechanical energy collecting” unit  251 , i.e., the members  253 ,  252 , wheel  256  and pin  260  and the contribution of the inertia of the spring  258 , and generate a dynamic force that is applied to the compressively preloaded spring  258 . If the level of acceleration in the direction of the arrow  261  is below the preloading level of the compressive spring  258 , i.e., below the previously indicated prescribed acceleration threshold, the preloading force of the compressive spring  261  will not be overcome and the roller  259  is not displaced downward. However, if the level of acceleration is above the prescribed acceleration threshold, the preloading force level of the spring  261  is overcome, and the roller  259  begins to be displaced downward and if the acceleration level is high enough, the roller  259  will reach the surface of the sliding member  156  and begins to cause mechanical potential energy to be accumulated in the device as was previously described for the embodiments of  FIGS.  5  and  8 A . As a result, the “mechanical energy harvesting device” embodiments would harvest mechanical energy only if the applied acceleration is above the prescribed threshold. 
     To prevent the contact member  247  from applying a force to the member  230  before a prescribed acceleration threshold has been reached, the design of the contact member  247  and connecting member  248  assembly can be modified to as shown in the schematic of  FIG.  16   . The contact member  247  and connecting member  248  assembly is provided with a stop member  262 , which is also fixedly attached to the device shaft  221  ( FIG.  13   ), which prevents their upward deflection as seen in the view of  FIG.  16   . Another member  263 , which is also fixedly attached to the shaft  221  is provided a certain distance below the connecting member  248  as can be seen in  FIG.  16   . A preloaded compressive spring  264  is positioned between the member  263  and the connecting member  248 . 
     The contact member  247  and connecting member  248  assembly of  FIG.  16    will then function as follows. When the “mechanical energy harvesting device” embodiment of  FIGS.  13  and  14    in which the assembly is used is subjected to acceleration in the direction of the arrow  265 , the acceleration acts on the effective inertial of the entire moving assembly, i.e., the members  247  and  248 , and generate a dynamic force, which would tend to cause the connecting member  248  to bend downward. If the level of acceleration in the direction of the arrow  265  is below the preloading level of the compressive spring  264 , i.e., below the previously indicated prescribed acceleration threshold, the preloading force of the compressive spring  264  will not be overcome and the connecting member  248  will stay unmoved against the stop member  262  as shown in the configuration of  FIG.  16   . However, if the level of acceleration is above the prescribed acceleration threshold, the preloading force level of the spring  264  is overcome, and the connecting member  248  will begin to bend downward, displacing the contact member  247  downward and if the acceleration level is high enough, the contact member  247  will reach the surface of the member  230  and begins to cause mechanical potential energy to be accumulated in the device as was previously described for the embodiments of  FIGS.  13  and  14   . As a result, the “mechanical energy harvesting device” embodiments would harvest mechanical energy only if the applied acceleration is above the prescribed threshold. 
     It is appreciated by those skilled in the art that the mechanical potential energy stored in the mechanical energy storage spring  241  of the embodiments  225  and  250  of  FIGS.  11  and  14   , respectively, may then be released to perform a desired function, such as generate electrical energy, for example, by retracting the stop  245  ( FIGS.  12  and  13   ), to allow the mechanical energy storage spring  241  to transfer the stored mechanical potential energy to the member  230 , which could act as a “flywheel” to rotate a pinion with a provided gear (not shown) to rotate an electrical generator to generate electrical energy. In another example, the base of the shaft  221  ( FIGS.  11  and  14   ) are provided with a ratchet or a one-way clutch (not shown), that once released would transfer the mechanical potential energy stored in the spring  241  to a flywheel, which would rotate an electrical generator to generate electrical energy. Such arrangements for transferring stored mechanical potential energy in torsion springs to electrical energy generation devices are well known in the art. 
     It is appreciated by those skilled in the art that the flexible connecting member  248  may also be preloaded in bending and kept in its preloaded condition by the stop member  262  as shown in  FIG.  16   . In which case, the total preloading forces of the connecting member  248  and the compressive spring  264  determines the acceleration preloading that has to be overcome by the device acceleration in the direction of the arrow  265  before the contact member  247  would start to move downward. 
     The fifth embodiment  270  of the “mechanical energy harvesting device” is shown in the schematic of  FIG.  17   . The embodiment  270  is with rotary “mechanical energy collecting” units rather than linearly displacing units such as those of the embodiment of  FIG.  5   . 
     The construction of the “mechanical energy harvesting device” embodiment  270  is shown in the side view of  FIG.  17   . As can be seen in the schematic of  FIG.  17   , the embodiment  270  consists of a shaft  266 , which is mounted in the bearings  267  and  268 , which are in turn fixedly attached to the structure of the “mechanical energy harvesting device” embodiment  270  as indicated as ground  269 . The bearings  267  and  268  may be sleeve type or anti-friction type such as ball bearing or the like, which are intended to indicate that they allow for free rotation of the shaft  266 , while allowing its minimal longitudinal displacement. 
     Mounted on the shaft  266  are “mechanical energy collecting” units  271 ,  FIG.  17   . In the schematic of  FIG.  17    only one unit  271  is shown for the sake of clarity, but in general several such units can be mounted on the shaft  266  and interact for sequential action as is described below. The view A-A of the “mechanical energy collecting” unit  271  is shown in  FIG.  18   . Each unit consists of a cylindrical sleeve  272 , which is mounted on the shaft  266  via a one-way clutch  273 , which allows the shaft  266  to turn in the counter-clockwise direction with respect to the unit  271  as viewed in the schematic of  FIG.  18   . The “mechanical energy collecting” unit  271  is provided with a mass element  274 , which is fixedly attached to the cylindrical sleeve  272  by the relatively rigid member  275 . In the configuration of the “mechanical energy harvesting device” embodiment  270  shown in the schematic of  FIG.  17   , the mass element  274  is positioned as shown in the view A-A of  FIG.  18   , as slightly to the left of a vertical plane passing through the center of the shaft  266 . A relatively rigid but thin and lightweight “release” plate  276  is also fixedly attached to the cylindrical sleeve  272  as shown in  FIGS.  17  and  18   . At least on one end of the shaft  266  is provided with a member  279  (such as a disc shaped member), to which one end  280  of a torsion spring  278  is fixedly attached. The other end  281  of the torsion spring  278  is attached to the structure  269  of the “mechanical energy harvesting device” embodiment  270  as shown in  FIG.  17   . 
     The “mechanical energy harvesting device” embodiment  270  is considered to be fixedly attached to the intended object  267 , which is subjected to the acceleration in the direction of the arrow  277  as shown in the schematic of  FIG.  17   , from which mechanical energy is to be harvested. 
     The “mechanical energy harvesting device” embodiment  270  of  FIGS.  17  and  18    is also designed to harvest mechanical energy from acceleration in the direction of the arrow  277 ,  FIG.  17   , of the object to which the device is attached and store it in the torsion spring  278 . 
     The “mechanical energy harvesting device” embodiment  270  of  FIGS.  17  and  18    functions as follows. Here, the operation of the embodiment  270  with only one “mechanical energy collecting” unit  271  is described and its operation with multiple units  271  is described below. Initially, the one “mechanical energy collecting” unit  271  is in the configuration shown in  FIG.  18   , i.e., with the mass element  274  slightly to the left of the axis of the shaft  266 . When the object to which the device is attached (indicated by the ground  269  in  FIG.  17   ) is accelerated in the direction of the arrow  277 , the acceleration acts on the mass (inertia) of the mass element  274  (neglecting the inertia of the connecting member  275  and the release plate  276 ), resulting in a dynamic force that is applied to the center of mass of the mass element  274 , generating a torque that tends to rotate the shaft  266  in the counter-clockwise direction as viewed in  FIG.  18   . It is noted that as can be seen in the schematic of  FIG.  18   , the distance between the center of mass of the mass element  274  and the center of the shaft  266 , i.e., the moment arm of the generated dynamic force (indicated by the numeral  282 ) is relatively small, thereby causing the acceleration in the direction of the arrow  277  to generate a relatively small torque, but the moment arm increases as the shaft  266  is rotated by the generated torque, reaching a peak at the mass element position  283  (when the moment arm is perpendicular to the direction of the applied acceleration) and diminishing as the moment arm becomes parallel to the direction of acceleration at the mass element position  284 . The torsion spring  278  is thereby wound and the work done by the generated dynamic force is stored in the torsion spring  278  as mechanical potential energy. 
     The top view of the “mechanical energy harvesting device” embodiment  270  of  FIG.  17    (as viewed in the opposite direction of the arrow  277  is shown in the schematic of  FIG.  19   . In this view, four “mechanical energy collecting” units  271  are shown as mounted as was previously described on the shaft  266 . In the top view of  FIG.  19   , all four “mechanical energy collecting” units  271  are in the position seen in  FIGS.  17  and  18   . 
     The “mechanical energy harvesting device” embodiment  270  is provided with a mechanism to sequentially release the “mechanical energy collecting” units  271 . In the schematic of  FIG.  19   , for the sake of clarity, the mechanism is shown with solid lines between the first (right hand side) and the second “mechanical energy collecting” units  271  and with light dashed lines between the second and third units  271  and between the third and fourth units  271 , and would be provided similarly between other units when present. Also, for the sake of clarity, the mechanisms used for sequential release of the “mechanical energy collecting” units  271  are not shown in the schematics of  FIGS.  17  and  18   . 
     The mechanism for sequential release of the “mechanical energy collecting” units  271  consists of a link  286 , which is attached to the structure  269  of the “mechanical energy harvesting device” embodiment  270  by the joint  293  via the support  285  as shown in  FIG.  19   . To one side of the free end  294  of the link  286  is attached the member  288 , which can be a small diameter element with a rounded tip as can be seen in  FIG.  19    for ease of sliding against the surface  290  of the release plate  276  of the first (right hand side) “mechanical energy collecting” unit  271  in the “mechanical energy harvesting device” embodiment  270  configuration depicted in  FIGS.  17 ,  18  and  19   . In this configuration, the preloaded compressive spring  295  is provided to bias the link  286  to keep the rounded tip of the member  288  in contact against the surface  290  of the release plate  276  of the first “mechanical energy collecting” unit  271  as shown in  FIG.  19   . The positioning of the member  288  relative to the release plate  276  is shown by dashed line circle  296  in the view A-A of  FIG.  18   . The preloaded compressive spring  295  is attached to the structure  269  of the “mechanical energy harvesting device” embodiment  270  as seen in  FIG.  19   . To the other side of the free end  294  of the link  286  is attached the member  287 , which in the “mechanical energy harvesting device” embodiment  270  configuration depicted in  FIGS.  17 ,  18  and  19   , is positioned in front of the edge  291  ( FIG.  18   ) of the release plate  276  of the second “mechanical energy collecting” unit  271  as shown in  FIG.  19   . 
     Identical mechanisms for sequential release of the “mechanical energy collecting” units  271  are provided between each pair of units  271 , in the case of the embodiment  270  shown in the top view of  FIG.  19   , between the second and third and third and forth “mechanical energy collecting” units  271  as shown with dashed lines. 
     The “mechanical energy harvesting device” embodiment  270  of with multiple “mechanical energy collecting” units  271  shown in the top view of  FIG.  19    would then function as follows. Initially, all “mechanical energy collecting” units  271  are in the configuration shown in the top view of  FIG.  19   , as also seen in the view A-A of  FIG.  18   , i.e., with the mass elements  274  slightly to the left of the axis of the shaft  266 . When the object to which the device is attached (indicated by the ground  269  in  FIG.  17   ) is accelerated in the direction of the arrow  277 ,  FIGS.  17  and  18   , the acceleration acts on the mass (inertia) of the first (right most) mass element  274  (neglecting the inertia of the connecting member  275  and the release plate  276 ), resulting in a dynamic force that is applied to the center of mass of the mass element  274 , generating a torque that tends to rotate the shaft  266  in the counter-clockwise direction as viewed in  FIG.  18    as was previously described. Now as the first “mechanical energy collecting” unit  271  is rotating in the counter-clockwise direction ( FIG.  18   ), the “mechanical energy collecting” units  271  stays in contact with the surface  290  of the release plate  276 ,  FIG.  19   , thereby keeping the member  287  in front of the edge  291  ( FIG.  18   ) of the release plate of the second “mechanical energy collecting” unit  271 , thereby preventing the dynamic force acting on the mass  274  of the second “mechanical energy collecting” unit  271  to cause it to similarly rotate in the counter-clockwise direction. The third and fourth “mechanical energy collecting” unit  271  are similarly prevented from being forced to rotate in the counter-clockwise direction. As the first “mechanical energy collecting” unit  271  is rotating in the counter-clockwise direction ( FIG.  18   ), the one-way clutch  273  ( FIG.  17   ) forces the shaft  266  to rotate with the unit  271 . The torsion spring  278  is thereby wound and the work done by the generated dynamic force is stored in the torsion spring  278  as mechanical potential energy. 
     Now as the mass element  274  of the first “mechanical energy collecting” unit  271  reaches close to its lowest position  284  ( FIG.  18   ) indicated by dashed lines, the edge  292  of the release plate passes the member  288  (shown by dashed lined circle  296  in  FIG.  18   ), thereby allowing the link  286 ,  FIG.  19   , to be rotated in the clockwise direction by the preloaded compressive spring  295 , thereby disengaging the member  287  from the release plate  276  of the second “mechanical energy collecting” unit  271 . The second “mechanical energy collecting” unit  271  is thereby freed to begin to rotate as was described for the first “mechanical energy collecting” unit  271 , thereby storing more mechanical energy in the torsion spring  278  as mechanical potential energy. The link  286  in the meanwhile rotates in the clockwise direction until it is stopped against the provided stop  289 ,  FIG.  19   . The third and the fourth “mechanical energy collecting” units  271  are similarly released to further harvest mechanical energy from the applied acceleration and accumulate it in the torsion spring  278 . 
     It is appreciated that in the “mechanical energy harvesting device” embodiment  270  as shown in the schematics of  FIGS.  17  and  18   , when the acceleration of the device in the direction of the arrow  277  has ceased or has dropped below a level that the generated dynamic forces on the mass members  274  cannot overcome the reacting torque of the mechanical potential energy accumulated in the torsion spring  278 , then the torsion spring would tend to rotate the shaft  266  together with the mass members  274  in the clockwise direction as viewed in  FIG.  18    (here the effect of gravity is not being considered). To prevent the mechanical potential energy from being released to rotate the shaft  266 , a one-way clutch or ratchet mechanism may be provided between the shaft  266  and one of the bearings  267  or  268  (not shown) that would allow for counter-clockwise rotation of the shaft  266  relative to the said bearings but prevents its rotation in the clockwise direction as viewed in  FIG.  18   . 
     It is appreciated by those skilled in the art that the in the “mechanical energy harvesting device” embodiment  270  of  FIGS.  17 - 19   , the mechanical potential energy stored in the mechanical energy storage spring  278  and then be released to perform a desired function, such as generate electrical energy. As an example, the base  269  ( FIGS.  17  and  19   ) may be provided with a ratchet or a one-way clutch (not shown), that once released would transfer the mechanical potential energy stored in the spring  278  to a flywheel, which would rotate an electrical generator to generate electrical energy. Such arrangements for transferring stored mechanical potential energy in torsion springs to electrical energy generation devices are well known in the art. 
     It is appreciated that in certain applications, such as in gun-fired munitions applications, the “mechanical energy harvesting device” must be capable of differentiating a prescribed minimum acceleration level with minimum duration (prescribed firing setback acceleration profile in munitions) from all accidental acceleration events, such as short duration but high acceleration levels due to accidental drops on hard surfaces or other object impacts or low peak accelerations due to transportation vibration or the like. The “mechanical energy harvesting device” embodiment  270 , however, due to the provided one-way clutches  273 ,  FIG.  17   , does not allow the return of the mass member  274  back to its initial configuration shown in  FIG.  18    after experiencing an acceleration event in the direction of the arrow  277  and rotating the shaft  266  in the counter-clockwise direction. A modification of the design of the “mechanical energy harvesting device” embodiment  270  presented in  FIG.  20    and indicated as the “mechanical energy harvesting device” embodiment  300  provides the capability of harvesting and accumulating mechanical energy only when a prescribed acceleration profile with a minimum acceleration level and minimum duration is detected. 
     The “mechanical energy harvesting device” embodiment  300  uses a combination of features from the above described embodiments as shown in the side view of  FIG.  20   . As can be seen in the side view of the “mechanical energy harvesting device” embodiment  300  of  FIG.  20   , this embodiment is constructed by modification of the embodiment of  FIG.  10   . In the embodiment of  FIG.  20   , the actuating rollers or balls  217  of the embodiment of  FIG.  10    are replaced by the “rotary actuators”  301 . The remaining elements of the embodiment  300  of  FIG.  20    are identical to those of the embodiment of  FIG.  10    and perform the same functions. The top view of the embodiment  300  showing only the “rotary actuators”  301  components and the actuated sliding member  302  ( 156  in  FIG.  10   ) are shown in  FIG.  21   . 
     As can be seen in the side view of  FIG.  20    and the top view of  FIG.  21    of the “mechanical energy harvesting device” embodiment  300 , the “rotary actuators”  301  consists of a cylindrical or spherical roller  303 , which is mounted on the shaft  304  which is an extension of the link  305 . A sleeve or anti-friction bearing  306  ( FIG.  20   ) can be used to mount the roller  303  to the shaft  304  to allow for its rotation with minimal friction. The links  305  are in turn mounted on the shaft  307  by sleeve or anti-friction bearings  308  to allow for their rotation with respect to the shaft with minimal friction resistance,  FIG.  21   . The shaft  307  is attached to the structure  309  of the “mechanical energy harvesting device” embodiment  300  by bearings  310  for ease of device assembly or is fixedly attached to the structure  309 . 
     The “mechanical energy harvesting device” embodiment  300  is also configured to harvest mechanical energy from acceleration of the object to which the device is attached in the direction of the arrow  311  ( FIG.  20   ) and store it in the compressive spring  312  ( 154  in  FIG.  10   ) as mechanical potential energy. The compressive spring  312  is appropriately preloaded as was previously described, for example for the embodiments of  FIGS.  5 ,  8 A and  10   , to maximize the amount of mechanical energy that can be harvested from the device acceleration. 
     The “mechanical energy harvesting device” embodiment  300  of  FIGS.  20  and  21    functions as follows. Initially, the right most roller (ball)  303  is in contact with the inclined surface  313  ( 170  in  FIG.  10   ) of the sliding member  302  ( 156  in  FIG.  10   ), while the other rollers (second to fourth) are in contact with the top straight surface ( 171  in  FIG.  10   ) of the sliding member  302 . When the object to which the device is attached is accelerated in the direction of the arrow  311 , the acceleration acts on the effective inertia of the roller (ball)  303  and link  305  and shaft  304  assembly, resulting in a dynamic force that is applied by the roller (ball)  303  to the inclined surface  313  of the sliding member  302 . The horizontal component (as seen in the view of the  FIG.  20   ) of the dynamic force applied to the inclined surface  313  will then tend to displace the sliding member  302  to the left, thereby further deflecting the mechanical potential energy storage spring  312  in compression. The work done by the roller (ball)  303  force on the sliding member  302  is thereby stored in the spring  312  as mechanical potential energy. 
     It is appreciated that similar to, for example, the embodiment  160  of  FIG.  5   , preloaded compressive springs  315  ( 169  in  FIG.  5   ), which are positioned between the link  305  and the structure  309  of the device, may be provided to keep the roller  303  in contact with top surface  314  of the sliding member  302  as shown in  FIG.  20   . The preloaded compressive spring  315  is usually selected to have low spring rate and is slightly preloaded in compression to ensure roller contact with the top surface  314  of the sliding member  302 . 
     In certain applications, such as in gun-fired munitions applications, the “mechanical energy harvesting device” embodiment  300  must be capable of differentiating a prescribed minimum acceleration level with minimum duration (prescribed firing setback acceleration profile in munitions) from all accidental acceleration events, such as short duration but high acceleration levels due to accidental drops on hard surfaces or other object impacts or low peak accelerations due to transportation vibration or the like. Such a capability is provided for the “mechanical energy harvesting device” embodiment  300  of  FIG.  20    as was described for the embodiment of  FIG.  8 A . If such a is feature is not desired, then the notches  316  ( 158  in  FIG.  8 A ) in the sliding member  302  ( 156  in  FIG.  8 A ) would be arranged as shown in the embodiment  160  of  FIG.  5    to allow accumulation of the harvested mechanical energy. 
     To prevent the “rotary actuator” units  301  ( FIGS.  20  and  21   ) from applying a force to the sliding member  302  before a prescribed acceleration threshold has been reached, the design of the units can be modified to as shown in the schematic of  FIG.  22    and indicated by the numeral  317 . Each “rotary actuator” units  317  are constructed with the same components as the “rotary actuator” units  301 , with the exception that the preloaded compressive spring  315  is removed and a stop element  318 , which is fixedly attached to the structure  309  of the “mechanical energy harvesting device” embodiment  300  ( FIG.  20   ), is added together with a preloaded compressive spring  319 , which is used to bias the link  305  of the “rotary actuator” units  301  against the stop  318 . 
     The “rotary actuator” units  317  will then function as follows. When the “mechanical energy harvesting device”  300  ( FIGS.  20  and  21   ) in which the units  317  are used to actuate their sliding members  302  is subjected to acceleration in the direction of the arrow  311 , the acceleration acts on the effective inertial of the entire rotating assembly of the “rotary actuator” unit  317  and generate a dynamic force that is initially applied to the compressively preloaded spring  319 . If the level of acceleration in the direction of the arrow  311  generates a dynamic force that is below the resisting preloading level of the compressive spring  319 , i.e., below the previously indicated prescribed acceleration threshold, the preloading force of the compressive spring  319  will not be overcome and the roller  303  is not displaced downward. However, if the level of acceleration is above the prescribed acceleration threshold, the preloading force level of the spring  319  is overcome, and the roller  303  begins to be displaced downward and if the acceleration level is high enough, the roller  303  will reach the surface  313  of the sliding member  302 ,  FIG.  20   , and begins to cause mechanical potential energy to be accumulated in the device as was previously described for the embodiment  300  of  FIGS.  20  and  21   . As a result, the “mechanical energy harvesting device” embodiments  300  would harvest mechanical energy only if the applied acceleration is above the prescribed threshold. 
     It is appreciated by those skilled in the art that the mechanical energy storage spring  312  may be preloaded as was described for the embodiments of  FIGS.  5  and  8 A  to increase the amount of mechanical potential energy that can be stored. The stored mechanical potential energy may then be used to perform the same functions as were described for these mechanical energy harvesting devices. 
     It is also appreciated by those skilled in the art that the mechanical energy storage springs as well as the actuating unit springs (e.g.,  169  in  FIGS.  5  and  315    in  FIG.  20   ) may be designed with nonlinear stiffness characteristics to maximize the harvested mechanical energy for a given device acceleration profile. 
       FIG.  23    is the schematic of the side view of the seventh embodiment  320  of the mechanical energy harvesting embodiment that is used to initiate a percussion primer or properly configure pyrotechnic material via impact. The view B-B, which shows the lateral view of the various components of the embodiment  320  is shown in  FIG.  24   . 
     The “mechanical energy harvesting device” embodiment  320  that is configured for initiating percussion primer or properly configure pyrotechnic material via impact shown in  FIG.  23    uses at least one “mechanical energy collecting” units  321 , which is similar to the “mechanical energy collecting” units  271  of embodiment  270  of  FIG.  17   . Similarly, the “mechanical energy collecting” units  321  are mounted on the shaft  322  by bearings  323 , which allow for free rotation of the units  277  relative to the shaft  322 . The bearings  323  may be an anti-friction bearing, such as a ball bearing, or may be a clearance that is provided in the cylindrical sleeve  324 ,  FIGS.  23  and  24   . The shaft  322  is either fixedly attached to the structure  337  of the embodiment  320  or is mounted in the bearings  329  as shown in  FIG.  23   . 
     The view B-B of the “mechanical energy collecting” units  321  is shown in  FIG.  24   . Each unit consist of a cylindrical sleeve  324 , which is are mounted on the shaft  322  via the bearing  323 . The “mechanical energy collecting” units  321  are provided with mass elements  325 , which are fixedly attached to the cylindrical sleeve  324  by the relatively rigid member  326 . In the configuration of the “mechanical energy harvesting device” embodiment  320  shown in the schematic of  FIG.  23   , the mass element  325  is positioned as shown in the view B-B of  FIG.  24   , as slightly to the left of a vertical plane passing through the center of the shaft  322 . 
     The “mechanical energy harvesting device” embodiment  320  is also provided with the striker unit  327 , which is similarly mounted on the shaft  322  by the member  328  via the bearing  329 . The bearing  329  allows for free rotation of the striker unit  327  relative to the shaft  322 . The bearings  323  may be an anti-friction bearing, such as a ball bearing, or may be a clearance that is provided in the member  328 . The striker unit  327  is provided with a striker mass  330 , which is fixedly attached to the member  328 . On the striker mass  330  side seen in the side view of  FIG.  23   , the striker mass is provided with the extension  331  over which the middle loop  332  of the “double wound” torsion spring  333  rests as shown in  FIGS.  23  and  24    (the helical section of the torsion spring  333  is not shown in the view B-B of  FIG.  24    for sake of clarity). On the other side of the striker mass  330  (indicated by the numeral  334  in  FIG.  24   ), the striker mass is provided with the sharp member  335 , which is designed for initiating the percussion primer  336  upon impact as described below. 
     The “mechanical energy harvesting device” embodiment  320  is considered to be fixedly attached to the intended object  337  (shown as ground in  FIGS.  23  and  24   ), which is subjected to the acceleration in the direction of the arrow  338  as shown in the schematics of  FIGS.  23  and  24   , from which mechanical energy is to be harvested and used to initiate the primer  336 . 
     The “mechanical energy harvesting device” embodiment  320  of  FIGS.  23  and  24    functions as follows. Initially, “mechanical energy collecting” units  321  and the striker unit  327  are in the configuration shown in the view B-B of  FIG.  24    and the torsion spring  333  is in free configuration shown in  FIG.  23   . The counter-clockwise rotation of the striker unit  327  is limited by the removable stop  340  that as shown in the configuration of  FIG.  24   , engages the top of the striker mass  330 . In the initial configuration shown in  FIG.  24   , the mass elements  325  of the “mechanical energy collecting” unit  321  are seen to be positioned slightly to the left of the axis of the shaft  322 . When the object to which the embodiment  320  is attached is accelerated in the direction of the arrow  338 , the acceleration acts on the mass (inertia) of the mass elements  325  (neglecting the inertia of the connecting member  326 ), resulting in a dynamic force that is applied to the center of mass of the mass element  325 , generating a torque that tends to rotate the “mechanical energy collecting” units  321  in the counter-clockwise direction as viewed in  FIG.  24   . It is noted that as can be seen in the schematic of  FIG.  24   , the distance between the center of mass of the mass element  325  and the center of the shaft  322 , i.e., the moment arm of the generated dynamic force (indicated by the numeral  282  in  FIG.  18   ) is relatively small, thereby causing the acceleration in the direction of the arrow  338  to generate a relatively small torque, but the moment arm increases as the shaft  322  is rotated by the generated torque, reaching a peak when the moment arm is perpendicular to the direction of the applied acceleration and diminishing as the moment arm becomes parallel to the direction of acceleration at the mass element position  343  shown by dashed lines in  FIG.  24   . The torsion spring  333  is thereby wound and the work done by the generated dynamic forces is stored in the torsion spring  333  as mechanical potential energy. The mechanical potential energy stored in the torsion spring  333  can then be used to perform a prescribed function, such as to generate electrical energy as was described for the previous embodiments. 
     The “mechanical energy harvesting device” embodiment  320  as illustrated in the view B-B of  FIG.  24    is used to initiate a percussion primer. To perform this task, the embodiment  320  is usually designed so that as the device using the embodiment  320  is accelerated in the direction of the arrow  338  and the “mechanical energy collecting” units  321  in the counter-clockwise direction, as the mass element  325  approaches the position  343  and that the torsion spring has stored enough mechanical potential energy, the striker mass  330  is released by the displacing the removable stop  340  in the direction of the arrow  342 . The striker unit  327  is thereby accelerated in the counter-clockwise direction as viewed in the schematic of  FIG.  24   . The striker mass would thereby gain certain velocity and impact the percussion primer  336  by the sharp member  335 . The percussion primer  336  would then initiate and the ignition flames and sparks would exit from the hole  344  that is provided in the structure of the embodiment  320 . 
     In general, a mechanical mechanism, such as a cable mechanism (not shown) may be used to pull the removable stop  340  in the direction of the arrow  342  or a link mechanism (not shown) that is actuated by the mass element  325  when it has rotated in the counter-clockwise direction to the desired location (at which position enough mechanical potential energy is stored in the torsion spring  33  for initiating the percussion primer  336 ). Such mechanical mechanisms are well known in the art and may be used. However, a simpler alternative mechanism for releasing the striker mass is shown in the schematic of  FIG.  25   . 
     In the alternative release mechanism shown in the schematic of  FIG.  25   , the removable stop  340 ,  FIG.  24   , is replaced by a relatively flexible beam element  345 , which is fixedly attached to the structure  337  of the embodiment  320 . The tip  346  of the striker mass  330 , which is in contact with the flexible beam stop is also provided with a sharp edge as seen in  FIG.  25   . Then as the “mechanical energy harvesting device” embodiment  320  is subjected to acceleration in the direction of the arrow  338  and the “mechanical energy collecting” units  321  is rotated in the counter-clockwise direction as was previously described and when the torque level in the torsion spring  333  reaches a prescribed level, the stiffness of the flexible stop beam element  345  is designed to allow the beam element  345  to bend enough (as shown by the dashed line  347 ) to release the striker mass  330 . The striker unit  327  is thereby accelerated in the counter-clockwise direction as viewed in the schematic of  FIG.  25    as was previously described and the striker mass  330  would thereby gain certain velocity and impact the percussion primer  336  by the sharp member  335 . The percussion primer  336  would then initiate and the ignition flames and sparks would exit from the hole  344  that is provided in the structure of the embodiment  320 . 
     It is appreciated that the level of force that needs to be applied to the flexible beam element  345  to release the striker mass  330  can be designed to correspond to an acceleration level in the direction of the arrow  338 , which must also be applied long enough for the striker unit  327  to rotate far enough in the counter-clockwise direction for the torsion spring to apply the said designed force level to the beam element  345 . The “mechanical energy harvesting device” embodiment  320  would then only initiate the percussion primer  336  if the acceleration in the direction of the arrow that is applied to the device has the prescribed minimum level and duration. Otherwise the striker unit  327  would return back to its initial positioning following an acceleration event that lower than the prescribed level or is relatively short in duration even if its level is relatively high. 
     It is appreciated by those skilled in the art that the torsion spring  333  may be preloaded with the “mechanical energy collecting” units  321  positioned as shown in  FIG.  25   , in which case, a stop  348  must be provided in the structure  337  of the embodiment  320  to constrain clockwise rotation of the “mechanical energy collecting” units  321 . By preloading the torsion spring, the “mechanical energy collecting” units  321  would then begin its counter-clockwise rotation only after acceleration in the direction of the arrow  338  has reached the level at which the torque generated by the dynamic force acting on the mass element  325  would overcome the preloading torque of the torsion spring. 
     It is also appreciated by those skilled in the art that the “mechanical energy harvesting device” embodiment  320  may also be used to construct normally open and normally closed electrical switches as was described for the embodiments of  FIGS.  9 A and  9 B , respectively. To this end, for the normally open electrical switches, the electrically non-conductive member  187  with contacts  193  and  194 ,  FIG.  9 A , replaces the percussion primer  336  and the flexible electrically conductive strip  189  will be attached to the striker mass  330  in place of the sharp member  335 . For the normally closed electrical switches, flexible conductive strips  201  and  202  as mounted in the electrically non-conductive member  187 ,  FIG.  9 B , replaces the percussion primer  336  and the non-conductive element  203  will be attached to the striker mass  330  in place of the sharp member  335 . Both electrical switches will then operate as was described for the embodiments  9 A and  9 B. 
     While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.