Patent Abstract:
A self-powered electric lock includes a lock bolt and a first engagement element having disengaged and engageable positions. An electric actuator includes an output operative to move the first engagement element to its engageable position. A manually operated rotatable member is operatively coupled to the first engagement element when the first engagement element is in its engageable position. A lock bolt drive mechanism is coupled to the lock bolt and to the first engagement element when the first engagement element is in its engageable position. The movable output moves the first engagement element to its engageable position upon input of correct electronic data. An electricity generator is coupled to the manually operated rotatable member. The electricity powers the electric actuator and an electronic data input device. The manually operated rotatable member is also used to actuate the lock bolt drive mechanism and retract the lock bolt.

Full Description:
[0001]     This application is a continuation of application Ser. No. 10/965,305 filed on Oct. 14, 2004 (pending) which is a continuation of application Ser. No. 10/391,830 filed on Mar. 19, 2003 (now U.S. Pat. No. 6,813,917) which is a continuation of application Ser. No. 09/985,975 filed Nov. 7, 2001 (now U.S. Pat. No. 6,546,769) which is a continuation of application Ser. No. 09/409,760 filed Sep. 30, 1999 (now U.S. Pat. No. 6,314,773) which is a continuation of application Ser. No. 08/985,901 filed Dec. 5, 1997 (now U.S. Pat. No. 5,960,655) which is a continuation of application Ser. No. 08/593,725 filed Jan. 29, 1996 (now U.S. Pat. No. 5,720,194), which is a division of application Ser. No. 08/371,319 filed Jan. 11, 1995 (now U.S. Pat. No. 5,487,290), which is a continuation of application Ser. No. 07/819,216 filed Jan. 13, 1992 (abandoned). 
     
    
     TECHNICAL FIELD OF THE INVENTION  
       [0002]     This invention relates to a high security lock mechanism and, more particularly, to an electronically controlled combination lock and lock-bolt operable by a very small amount of self-generated electrical power.  
       BACKGROUND OF THE PRIOR ART  
       [0003]     Items of extremely sensitive nature or very high proprietary value often must be stored securely in a safe or other containment device, with access to the items restricted to selected individuals given a predetermined combination code necessary to enable authorized unlocking thereof. It is essential to ensure against unauthorized unlocking of such safe containers by persons employing conventional safe-cracking techniques or sophisticated equipment for applying electrical or magnetic fields, high mechanical forces, or accelerations intended to manipulate elements of the locking mechanism to thereby open it.  
         [0004]     Numerous locking mechanisms are known which employ various combinations of mechanical, electrical and magnetic elements both to ensure against unauthorized operation and to effect cooperative movements among the elements for authorized locking and unlocking operations.  
         [0005]     One example of such recently-developed devices is disclosed in U.S. Pat. No. 4,684,945, to Sanderford, Jr., which relates to an electronic lock actuated by a predetermined input through a keyboard outside a safe to a programmable control unit within a housing of the safe. The device has an electric motor for driving a lock-bolt for locking a safe door to the safe housing, and means for displaying codes entered by the user, with a facility for selectively changing the necessary code. The device also has a battery-powered backup circuit maintained in a dormant state to conserve energy until an actuation key is operated. A microprocessor of the unit is programmed to activate a relatively high frequency of power output pulses at the start of movement of a locking bolt by the electric motor, to overcome inertia and any sticking forces on the bolt, and a lower frequency of power pulses to complete the movement of the bolt.  
         [0006]     Another example is provided in U.S. Pat. No. 4,674,781, to Reece et al., which discloses an electric door lock actuator and mechanism having manual and electrically driven locking means. This device utilizes a combination of a lost motion coupling and resilient springs for driving a motive means to a neutral position, to thereby isolate an electric motor and gearing from the locking means so that the locking means may be operated manually without back-driving of the electric motor and intermediate gearing.  
         [0007]     A major problem with such devices is that they require substantial amounts of electric power to perform their locking and unlocking functions. For securely storing and accessing highly sensitive or valuable items, it is important to avoid depending on the ready availability of sufficient electrical power for driving the locking mechanism. In fact, for many applications, the use of long-life batteries, even to power a small microprocessor, may also be deemed unacceptable.  
         [0008]     The stringency of relevant U.S. government specifications is readily appreciated from Federal Specification FF-L2740, dated Oct. 12, 1989, titled “FEDERAL SPECIFICATION: LOCKS, COMBINATION” for the use of all federal agencies. Section 3.4.7, “Combination Redial”, for example, requires that once the lock-bolt has been extended to its locked position “it shall not be possible to reopen the lock without completely redialing the locked combination”, and defines the locked position as one in which the bolt has been fully extended. Section 3.6.1.3, “Emanation Analysis”, requires that the lock shall not emit any sounds or other signals which may be used to surreptitiously open the lock within a specified period. Section 4.5.2.2.4, “Surreptitious Entry”, requires that for any lock to be deemed acceptable, attempts shall be made to unlock the lock through manipulation, radiological analysis and emanations analysis, further including the use of computer enhancement techniques for signals or emanations. Even further, Section 6.3.2 defines surreptitious entry as a method of entry such as manipulation or radiological attack which would not be detectable during normal use or during inspection by a qualified person.  
         [0009]     In short, for high security storage of sensitive or valuable material, in light of the availability of sophisticated computer-assisted means and methods for unauthorized operation of locking mechanisms, there exists a need for an autonomous locking mechanism that does not require batteries or external sources of power for any purpose, receives and recognizes only specific user-selected combination code information for access, emanates no information useful to persons attempting unauthorized operation, and is made to resist unauthorized operation even when subjected to strong externally imposed electrical, magnetic or mechanical forces, and satisfies other U.S. government specifications. Most important, once the mechanism is put in its locked position it loses all “memory” of the input combination code and requires a totally new and correct provision of the complete combination code to be unlocked again.  
         [0010]     The present invention, as more fully disclosed hereinbelow, meets these perceived needs at reasonable cost with a geometrically compact, electrically autonomous, locking mechanism.  
       SUMMARY OF THE DISCLOSURE  
       [0011]     It is an object of this invention to provide a locking mechanism which remains securely in a locked state until, following receipt of a predetermined combination code, a very small amount of electrical power is employed to put it in condition to be manually unlocked thereafter.  
         [0012]     It is another object of this invention to provide a locking mechanism actuated by the input of a selected combination code followed by the delivery of a very small amount of electrical power generated during input of a user-selected combination code to a low friction engagement means to put the same in a position to enable purely manual unlocking of the mechanism thereafter.  
         [0013]     Yet another object of this invention is to provide a locking mechanism which upon being put into a locked state remains in that state immune to electrical, magnetic, thermal or mechanical inputs accompanying attempts at unauthorized unlocking thereof.  
         [0014]     It is an even further object of this invention to provide a secure locking mechanism which is unlocked by the provision of a preselected combination code within a specified time followed by the provision of a very small amount of electrical power to move an engagement element to a position to enable solely manual unlocking of the mechanism thereafter.  
         [0015]     It is an even further object of this invention to provide a locking mechanism which utilizes a very small amount of electrical power, generated during input of a user-provided combination code, to be put into condition for manual unlocking, the mechanism, upon being manually put into a locked state, remaining in such a locked state until a predetermined combination code is entered.  
         [0016]     These and other related objects are realized, according to a preferred embodiment of the invention, by providing a locking mechanism which comprises a first means for moving an engagement element from a disengaged position to an engageable position thereof solely upon receipt of a controlled predetermined electrical power output, a manually operated second means for engaging the engagement element when the latter is in its engageable position for thereby manually moving the first means further in a first direction and back in a second direction, and third means for driving a lock-bolt engaged by the further movement of the first means to drive the lock-bolt to locking and unlocking positions thereof in correspondence with movements of the first means in the first and second directions respectively. Movement of the first means in the second direction restores security by returning the engagement element to its disengaged position when the lock-bolt reaches its locked position.  
         [0017]     In still another aspect of the invention, the first means comprises an electrical stepper motor having a rotor supporting the engagement element and having stable positions determined by magnetic detents which correspond to the disengaged and engageable positions of the engagement element. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is a perspective view of an exemplary safe having a generally rectangular casing and a hinged door, with a lock mechanism according to this invention mounted to the door of the safe.  
         [0019]      FIG. 2  is a horizontal cross-sectional view of the door and the lock mechanism at line II-II in  FIG. 1 .  
         [0020]      FIG. 3  is an exploded perspective view of a lock mechanism according to a preferred embodiment of this invention as viewed from a location behind a casing of the lock mechanism.  
         [0021]      FIG. 4  is a vertical elevation view of elements of the lock mechanism which are mounted to a rear cover of a casing of a lock mechanism according to  FIG. 3 .  
         [0022]      FIG. 5  is a plan view of the elements illustrated in  FIG. 4  in the direction of arrow V therein.  
         [0023]      FIGS. 6A, 6B  and  6 C are elevation views of elements of the lock mechanism operationally supported to and within the casing of the lock mechanism of  FIG. 3  to explain coaction of the elements at various stages as the lock-bolt is moved to an unlocked disposition thereof.  
         [0024]      FIGS. 7A, 7B  and  7 C are vertical elevation views illustrating, for a second embodiment of this invention, how various elements of the invention coact at various stages as the lock-bolt is moved from its locked position to its unlocked position.  
         [0025]      FIGS. 8A, 8B  and  8 C are elevation views, according to a third embodiment of this invention, illustrating various stages in the movement of the lock-bolt thereof from its locked to its unlocked position.  
         [0026]      FIG. 9  is a partial vertical cross-sectional view of one embodiment of another aspect of this invention, in which a voice coil is employed to ensure against unauthorized magnetically induced unlocking of the mechanism.  
         [0027]      FIG. 10  is a partial vertical cross-sectional view of another embodiment of the aspect shown in  FIG. 9 .  
         [0028]      FIG. 10A  is a vertical cross-sectional view at section XI-XI in  FIG. 10 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     A typical safe for securely storing valuable items, e.g., sensitive documents, precious jewelry or cash, hazardous materials such as radioactive or biologically dangerous substances, and the like, conveniently has a generally cubical form, with an opening closable by a single hinged door. Such a safe also typically has a multi-walled construction, both for the principal sides and for the door. As best seen in  FIG. 1 , such a safe  100  generally has a principal side wall  102  to which a door  104  is locked by operation of a lock mechanism  200 .  
         [0030]     As best seen in  FIG. 2 , a lock mechanism  200  according to a preferred embodiment of this invention has an external user-accessible hub  202  conveniently provided with an easily viewable combination code input display window  204  and a manually rotatable combination input knob or dial  206 . Hub  202  is attached to the outer surface  106  of door  104  in any known manner. Similarly, a casing  208  is securely attached to an inside surface  108  of door  104  in known manner. Door  104  may be kept hollow or may have an inner space filled with a thermally insulating material (not shown) to protect the contents of the safe in the event of a local fire.  
         [0031]     A shaft  210 , rotatable by knob  206 , extends through the thickness of door  104  and into casing  208  to cooperate thereat with a combination of important elements of the present invention as described more fully hereinbelow. A lock-bolt  212  is slidably supported by casing  208  to be projected outwardly into a locking position, or to be retracted substantially within casing  208  to an unlocking position, upon appropriate manual operation of combination-input knob  206  by a user. Casing  208  is provided with a detachable cover  272  which also serves to provide support to various components of the lock mechanism according to this invention.  
         [0032]      FIG. 3  is an exploded view of a lock mechanism according to a preferred embodiment of this invention, as viewed in looking toward the inside surface  108  of door  104 . Persons of ordinary skill in the art can be expected to appreciate that it is not critical to the utility of the present invention that lock mechanism  200  be mounted to a door since, without difficulty, the lock mechanism can be easily mounted to a wall of safe  100  in such a manner that lock-bolt  21   2  projects in its locking position into the safe door to lock it to the body of the safe. Details of such an alternative construction are simple and easy to visualize, hence illustrations thereof are not included. Such structurally obvious variations are contemplated as being within the scope of this invention.  
         [0033]     Referring again to  FIG. 3 , an aperture  110  extends through the entire thickness of door  104  to closely accommodate therein shaft  210  extending from combination-input knob  206  into a space  214  defined inside casing  208 . Located in correspondence with aperture  11   0  in door  104 , in casing  208  there is provided an annular journal bearing  216  to closely receive and rotatably support shaft  210  via  266  projecting therethrough into space  214 .  
         [0034]     Casing  208  is conveniently formed, e.g., by machining, molding or otherwise in known manner, to provide a pair of guide slots  218 ,  218  which are shaped, sized and disposed to closely accommodate lock-bolt  212  in a sliding motion between its locked and unlocked positions. While an important object of this invention is to provide its locking function in a highly compact manner, which inherently necessitates the selection of strong materials for forming the casing  208  and lock-bolt  212 , guides  218 ,  218  and lock-bolt  212  must be shaped and sized to provide the necessary strength to resist any foreseeable brute-force to open door  104 . Persons of ordinary skill in the art are expected to know of suitable materials for such purposes. For example, although the safe walls and door may be made of highly tempered steel or alloy, the lock bolt itself may be made of a softer metal such as brass or an alloy such as “ZAMAK,” and so may other elements of the mechanism.  
         [0035]     As also illustrated in  FIG. 3 , within space  214  inside casing  208  there are also provided attachment points for biasing means such as springs  222 ,  222  to be employed as discussed hereinbelow. In the embodiment illustrated in  FIG. 3 , there are also provided at an inside surface of casing  208  a small reed switch  224  and a socket  226  disposed to enable push-in electrical connection of a plurality of electrical connector pins  282  which are best seen in  FIG. 5 . Also provided on a wall surface of casing  208  near biasing springs  222 ,  222  is a guide pin  228  which closely fits into an elongate parallel-sided aperture  230  in the sliding element  232  which is generally flat and slides along an inner surface of casing  208 . Sliding element  232  is provided with a pair of spring-engaging pins  234 ,  234  which engage with biasing springs  222 ,  222 , whereby sliding element  232  is biased in a preferred direction, an upward direction in the illustration per  FIG. 3 .  
         [0036]     Note that sliding element  232  is also provided with a cam-engaging pin  236 , at least one elongate straight side  238  which may be used in known manner to provide additional sliding guidance, one or more weight-reducing apertures such as  242  which may also be shaped to perform cam functions, a circular aperture  244  close to cam-engaging pin  236 , and a cam-notch  246  at the end of sliding element  232  opposite the end closest to cam-engaging pin  236 .  
         [0037]     Lock-bolt  212 , as best seen in  FIG. 3 , is provided with a pivot-mounting aperture  248  into which is mounted a pivot  250 , to pivotably connect a lever arm  252  to lock-bolt  212  to communicate a manual force for moving the lock-bolt, guided by guides  218 ,  218 , between its locked and unlocked positions.  
         [0038]     Lever arm  252  is provided with a lateral pin  254  which is disposed to be engaged by cam-notch  246  of sliding element  232  so as to be forcibly moved thereby, in a manner to be described more fully hereinbelow, when sliding element  232  is itself caused to be slidingly moved as guided by the coaction of guide pin  228  and the parallel sides of elongate aperture  230 . The distal portion of lever arm  252  extending beyond the location of lateral pin  254  is formed as a hook  256 , the shape of which is provided with an outside edge having a plurality of contiguous portions  258 ,  260  and  262  which coact with a downwardly depending fixed cam portion  264  formed at an inside surface of casing  208 . This coaction, at different stages in the course of moving lock-bolt  212  between its locked and unlocked positions, is best understood with successive reference to  FIGS. 6A, 6B  and  6 C and is described more fully hereinbelow.  
         [0039]     An end portion of shaft  210  which extends into space  214  preferably has a square cross-section, to which is mounted a rotary element  266  via a matchingly shaped and sized central fitting aperture  268 , as best seen in  FIG. 3 . Accordingly, when a user of the safe manually applies a torque to the combination-input knob  206  (see  FIG. 2 ), he or she transmits the torque to shaft  210  to thereby forcibly rotate rotary element  266 . A split ring  270 , for example, may be utilized to retain the rotary element  266  to shaft  210  in known manner. Other known techniques or structures may be used, instead of such a split ring, for such retention. By this arrangement there is readily available, through rotary element  266 , a manually provided torque at a point inside space  214  of casing  208 , i.e., within the secure containment space inside safe  1   00 , even when door  104  is locked. This is a feature essentially common to the various embodiments disclosed and claimed herein. The exact structural form of the manually-torqued rotary element is different, and is somewhat differently utilized, in the various embodiments.  
         [0040]     In the best mode of this invention, exemplified by the preferred embodiment illustrated in exploded view in  FIG. 3 , rotary element  266 , in a portion closest to an inside surface of cover  272  of casing  208 , is provided an internal ring gear  274 . Outwardly of ring gear  274 , there is provided a periphery having a toothed arcuate portion  276 , a smooth circumferential portion  278  and a radially relieved smooth circular portion  280 .  
         [0041]     At a side of rotary element  266  between internal ring gear  274  and annular journal bearing  216  is a circular cam portion  400  provided with a radially-relieved mechanical detent  402  shaped and sized to receive hook  256  when lever arm  252  is pivoted to a predetermined degree about pivot  250  by a sliding movement of sliding element  232  and a corresponding coaction between lateral pin  254  of lever arm  252  and cam notch  246  of sliding element  232 . A small magnet  245  is mounted to rotary element  266 , at a predetermined angular disposition vis-a-vis mechanical detent  402 , at a radius such that it passes by reed switch  224  to activate it under conditions selected by microprocessor  288  as described hereinafter.  
         [0042]     As best seen in  FIG. 4 , cover  272  on the side facing space  214  of casing  208  supports a plurality-pinned electrical plug element with pins  282  located to be electrically engageable with socket  226 , an electrical power generator  284 , a power storage capacitor  286 , a microprocessor  288 , and assorted wiring  290  forming part of an electrical circuit. Details of this electrical circuit and various aspects of its functions, e.g., how a predetermined combination code may be provided to and stored in microprocessor  288 , how segments of a selected combination code are displayed in window  204  as they are input by a user operating manually rotatable combination-input knob  206 , and the like, are disclosed in U.S. Pat. No. 5,061,923, which is expressly incorporated herein by reference for all such relevant disclosure therein.  
         [0043]     Cover  272 , as best seen in  FIG. 3 , is provided with countersunk apertures  292  and one or more location-indexing projections  294  to facilitate precise fitting of cover  272  with casing  208  and secure affixation therebetween by screws  296 . When cover  272  is thus indexed and affixed to casing  208 , a sun-and-planet gear train  298 , best seen in  FIG. 4 , meshes with internal ring gear  274  of rotary element  266  to be rotated thereby, plus element  282  fits to socket  226 , and lock-bolt  212  then is slidably movable in a closely fitting aperture of closed casing  208 .  
         [0044]     As described in detail in U.S. Pat. No. 5,061,923, incorporated herein by reference for such details, such affixation of cover  272  to casing  208 , upon manual rotation of combination-input knob  206 , causes rotation of shaft  210  and rotary element  266  mounted thereto, resulting in manual rotation of planetary gear train  298  to generate electrical power in electrical generator  294 . Some of this electrical power is conveyed via a plurality of fine wires (not illustrated) which are disposed along shaft  210 , to provide a liquid crystal display of numbers relating to a combination code in display window  204 . A portion of the power generated by electrical power generator  284 , under the control of microprocessor  288 , is stored in power storage capacitor  286 . Some of this stored electrical power is thereafter available for a period of time under the control of microprocessor  288 , upon determination thereby that a correct combination code has been provided by a user, to perform a vital function of the present invention. This vital function is to create such a coaction of the above-described elements that lock-bolt  212  is positively and controllably moved, solely by a manually-provided force, from its locked position to its unlocked position.  
         [0045]     In the best mode of this invention, as best understood with reference to  FIG. 3 , there is a very low-friction, rotary, electric motor  300  provided with magnetic detents symbolized by the reference character “D” in the figure, which give a rotor  302  at least two stable positions which are angularly separated with respect to an axis of the rotor by a predetermined angle, preferably approximately 36°. Such motors are known; one example is a Seiko model. Hence, detailed illustrations of the internal structure of motor  300 , etc., are not believed necessary for an understanding of the structure or specific functioning of the present invention in any of the embodiments disclosed and claimed herein.  
         [0046]     What is of particular importance is that motor  300  is electrically connected by a portion of circuit wiring  290  so as to be able to receive from power storage capacitor  286  at least one predetermined small pulse of electric power at a time controlled by microprocessor  288 . Microprocessor  288  is initially provided a user-input reference combination code which, thereafter, serves as reference data until and unless it is replaced or changed as is fully described in copending application U.S. Ser. No. 07/250,918, incorporated herein by reference for relevant details disclosed therein. Subsequently, when a user rotates combination-input knob  206  to actuate the lock mechanism, rotation of shaft  210  (regardless of direction of its sense of rotation), generates electrical power to display elements of the combination code as they are being input and, simultaneously, enables the storage of a quantity of power in power storage capacitor  286 . Then, upon microprocessor  288  recognizing that a correct combination code has ben provided, e.g., upon receipt of a predetermined ordered set of three numbers, a portion of the power stored in power storage capacitor  286  is released to motor  300  when further rotation of rotary element  266  in a predetermined direction next brings magnet  245  close enough to reed switch  244  to actuate it. Alternatively, power can be supplied to the motor  300  by a separate capacitor (not shown).  
         [0047]     This motor  300  has very low-friction bearings rotatably supporting rotor  302 , preferably with no grease, oil or other lubricant being utilized therein to avoid deterioration thereof over prolonged period of time. The coaction of ring gear  274  and gear train  298  generates sufficient electric power during the process of inputting the requisite combination code to enable power storage capacitor  286  to store and deliver an adequate electrical power pulse (or more than one pulse, as needed) to cause rotor  302  to move from a stable disengaged position corresponding to a first magnetic detent to a stable engageable position corresponding to a second magnetic detent thereof. Motor  300  thus functions as a transducer in which a small amount of received electrical power is converted, i.e., transduced, to a small mechanical rotation of rotor  302 .  
         [0048]     A variation of this arrangement can be realized using simple modifications to the circuitry, so that power to actuate the motor  300  is provided directly from power generation elements to the motor without first storing that quantity of electrical charge in one or more capacitors. Power to operate the microprocessor, however, may still be stored in and provided through one or more capacitors.  
         [0049]     As best seen in  FIG. 6A , rotor  302  has an arcuately relieved portion  304  disposed to be closest to and accommodating of the outer peripheral portion  276  of rotary element  266  when rotor  302  is in its disengaged position. In the best mode illustrated in  FIGS. 6A-6C , a peripheral arcuate portion  306  of rotor  302  is provided with a plurality of teeth shaped and sized to be positively engageable with the teeth of toothed outer peripheral portion  276  to rotor element  266 . Upon the provision of the requisite electric power pulse from power storage capacitor  286 , as previously described, rotor  302  promptly rotates to its stable engageable position, this being one in which its toothed outer portion  306  is rotated to become engageable by teeth of peripherally toothed portion  276  of rotary element  266 , i.e., when rotary element  266  is turned counterclockwise in  FIGS. 6A, 6B  and  6 C to engage said teeth of portion  276  with the teeth of rotor  302 .  
         [0050]     Once such an engagement is initiated, further manual rotation of rotary element  266 , due to manual torque provided by a user rotating combination-input knob  206 , rotor  302  is forcibly and positively rotated in a rotational direction opposite to that of shaft  210 . In other words, simply by the provision of a very small electrical power pulse, which is preferably in the range of only a few microwatts, rotor  302  becomes drivable solely by the manual rotary input under the control of the user, and this occurs only after the input of a correct combination code as recognized by microprocessor  288  with reference to its prestored reference combination code data.  
         [0051]     Rotor  302 , as best seen in  FIG. 6A , in a face thereof closest to sliding element  232 , has two arcuate, diametrally opposed, generally kidney-shaped openings  308 ,  308 . These recesses are shaped and sized to non-bindingly receive therein a pair of drive pins  310 ,  310  provided on a rotatable cam element  312  which is mounted to be freely rotatable about the same axis as rotor  302  within angular limits imposed by arcuate recesses  308  coacting with drive pins  310 . In other words, drive pins  310 , when disposed to be located near corresponding ends of arcuate recesses  308  while rotor  302  is in its disengaged position, remain unmoved while the aforementioned electric power pulse causes rotor  302  to rotate to its stable engageable position, at which point drive pins  310  are located at the corresponding opposite ends of their respective recesses  308 ,  308 . Note that this ensures that with only a few microwatts of power, rotor  302  rotates from its disengaged position to its engageable position. This is an important aspect of the present invention and is common to all disclosed embodiments. However, upon further manually forced rotation of rotor  302 , arcuate recesses  308 ,  308  each forcibly engage with corresponding drive pins  310 ,  310  to forcibly rotate rotatable cam element  312 . Rotatable cam element  312  is located so as to then, and only then, force a portion of its outer peripheral edge into contact with cam-engaging pin  236  of sliding element  232 .  
         [0052]     In this manner, further solely manual rotation of rotatable cam  312  will generate a forced sliding motion of sliding element  232 , as guided b guide pin  228  engaging with elongate aperture  230 , by overcoming of a biasing force provided by bias springs  222 ,  222 . In the structure as illustrated in  FIG. 3  and  6 A- 6 C the sliding element  232  thus is manually moved downward.  
         [0053]     As previously noted, cam notch  246  at the upper distal end of sliding element  232  engages with lateral pin  254  of lever arm  252 . Thus, as best understood with reference to  FIGS. 6A, 6B  and  6 C, as sliding element  232  is forced downward, cam notch  246  thereof applies a downward pull on the hooked end of lever arm  252  to correspondingly pull hook  256  thereof downwardly toward a mechanical detent  402  provided on rotary element  266 . In the illustrations per  FIGS. 6A, 6B  and  6 C, as lever arm  252  is drawn downward to engage with mechanical detent  402 , edge portion  260  thereof coacts with a sloping edge of fixed cam portion  264  to be further moved downward into a positive engagement with mechanical detent  400 . Thus, as best seen with reference to  FIG. 6B , the downward motion of sliding element  232 , contact between the sloping edge of fixed cam portion  264  and the outside edge portions  258 ,  260  and  262  of lever arm  252 , and the eventual engagement of hook  256  with mechanical detent  402  of rotary element  266  all, eventually, lead to a manually-provided force being transmitted by lever  252 , through pivot  250 , to forcibly draw lock-bolt  212  into casing  208 . Ultimately, lock-bolt  212  becomes substantially drawn into casing  208  to its unlocked position.  
         [0054]     Also, as best understood with reference to  FIG. 6C , when this state of affairs is reached, lever arm  252  can rotate no further about pivot  250  because it is then in forced contact with the radially outermost portions of the detented side of rotary element  266 . Therefore, once lever arm  252  is engaged with rotary element  266  to draw lock-bolt  212  to its unlocked position, further forced rotation of combination-input knob  206  is prevented. Under these circumstances, door  104  may be opened and access may be had by the user to the contents of safe  100 .  
         [0055]     Once the user has completed his or her business with the contents of the safe, door  104  may be put in a position to close safe  100  and the combination-input knob  206  rotated in the opposite sense, i.e., in a direction opposite to that which enabled lock-bolt  212  to be manually moved to its unlocked position. As best understood with reference to  FIG. 6A , as the relieved detent portion of rotary element  266  is thus rotated, coaction between the same and the outer edge portion  262  of lever arm  252  forces lever arm  252  upward and in a direction that will drive lock-bolt  212  out of casing  208  toward a locked position. In this process, as the distal end of lever arm  252  slips past fixed cam portion  264  of casing  208 , lateral pin  254  of lever arm  252  is placed into engagement with cam notch  246  and serves to move sliding element upward while the biasing force provided by springs  222  also acts upward on sliding element  232 . At the same time, as rotating element  266  rotates, the meshed teeth of peripheral portion  276  of rotating element  266  and the teeth of toothed portion  306  of rotor  302  move in engagement until rotor  302  is rotated to such an extent that arcuate relieved portion  304  thereof abuts the relieved portion of the periphery of rotary element  266 .  
         [0056]     Again, as best seen with reference to  FIG. 6A , this united action of the above-described elements is such that when sliding bolt  212  eventually reaches its locked position, rotor  302  is returned to its stable disengaged position and will, thereafter, be retained there by the corresponding magnetic detent of motor  300 .  
         [0057]     Note that the rotation of rotary element  266  required to thus project lock-bolt  212  out of casing  208  into a locked position is minimal, and that very little electrical power is generated as an incident thereto. Consequently, the electrically discharged circuit does not acquire sufficient stored electrical charge to be able to influence stepper motor  300  while lock-bolt  212  moves from its unlocked to its locked position. A very important consequence of this, in the context of the present invention, is that the entire lock mechanism becomes totally deactivated upon lock-bolt  212  reaching its locked position. Once this happens, lock-bolt  212  can not be moved to its unlocked position without the provision of the correct and entire combination code which must be found satisfactory by microprocessor  288  to enable the unlocking process as described hereinabove. In short, once the door is locked, the only way to unlock it is to correctly provide the entire combination code.  
         [0058]     The basic concept of this invention, as realized in the preferred embodiment described hereinabove, may also be practiced with other embodiments. One such embodiment  700  is illustrated, in various operational stages, in  FIGS. 7A-7C . A detailed description of this second embodiment follows.  
         [0059]     Referring to  FIGS. 7A-7C , a view intended to be generally comparable to the view of the first embodiment, per  FIG. 6A , a lock-bolt  212  is slidably guided within guides  218 ,  218  and a pivot  250  pivotably connects lock-bolt  212  to a lever arm  702  which has a hook  704  at a distal end thereof. The extreme distal end of lever arm  702  ends in a frontal surface  706 , the shape of hook  704  being defined by an elongate curved surface  708  which meets a rear hook surface  710  at a point  712  of the hook. These surfaces are polished smooth. Lever arm  702 , at a point intermediate its ends, is provided with a spring connection pin  714 . A first spring  716 , of selected length and stiffness, is hooked at one end to spring connection pin  714  and at another end to a first spring attachment point  718  at an upper portion of lock casing  208 . Absent the application of an externally applied force, first spring  716  provides a sufficient biasing force to hold lever arm  702  with its smooth front surface  706  in contact with a matchingly inclined face of fixed cam  264  formed as part of casing  208 .  
         [0060]     In this second embodiment, as in the first embodiment illustrated in  FIGS. 3-6C , there is provided a shaft  210  rotated by a user manually operating combination-input knob  206 , as will be understood by reference to  FIG. 2 . Keyed to rotate with shaft  210  is a rotary cam element  720  which has an outer diameter such that when lever arm  702  is in its uppermost position, point  71   2  of hook  704  clears the circumferential rim of rotary cam element  720 . In this circumferential periphery, there is provided a generally triangular detent  722  having inclined sides forming a vertex directed toward a rotational axis of rotary cam element  720 , as best understood with reference to  FIGS. 7A-7C . Rotary cam element  720  is also provided with a hook-engaging detent  724  formed and shaped to be able to accommodate hook  704  of lever arm  702  under conditions described hereinafter.  
         [0061]     A low-friction, low-power, electric motor  300  is provided to receive a controlled electrical power pulse under the same conditions and is substantially the same manner as was described in detail for the first embodiment. Rotation of shaft  210  by a user, through a sun and gear train mounted on shaft  210 , will generate and store some electrical power under the control of a microprocessor. Upon satisfactory reception of a correct combination code input from a user, the microprocessor will release from an electrical storage capacitor a small controlled pulse of electrical power to cause a rotor of electric motor  300  to rotate from a first stable “disengaged” position to a second stable “engageable” position, these positions being defined by corresponding magnetic detents. For the sake of conciseness, a detailed description is not repeated herein of the manner in which the electrical power is generated and how, upon being provided the correct combination code input the microprocessor provides the necessary small electrical power pulse to motor  300  to cause the rotor thereof to turn. These details are believed to be comprehensible to a person of ordinary skill in the art upon a study of the earlier provided detailed description.  
         [0062]     In the second embodiment  700 , as best seen in  FIGS. 7A-7C , the rotor of electric motor  300  is provided with a generally radially extending engagement lever  726  and a radially eccentric elastic cam element  701 . Engagement lever  726  and eccentric cam  701  are thus mounted to be rotatable with the rotor (not expressly shown) of motor  300 . When the rotor of motor  300  is in its disengaged position, eccentric cam  701  has its periphery close to but not in contact with the circumferential periphery of rotary cam element  720  and the distal end of engagement lever  726  is located away therefrom. However, reception of the predetermined small electrical power pulse by motor  300 , (clockwise in  FIGS. 7A-7C ) causes eccentric cam  701  to contact the periphery of rotary cam element  720 . Frictional force thus generated causes the rotor to be turned manually thereafter, and engagement lever  726  is thus positively moved to extend into triangular detent  722 . Continued manual rotation of the rotary cam element  720  thereafter forcibly and manually rotates the rotor of motor  300 .  
         [0063]     It will be recalled that the location of a small magnet on the rotary element of the first embodiment actuates a reed switch  224  when the rotary element  266  turned to a predetermined position after reception by the microprocessor of a correct and complete combination input signal. For the sake of conciseness and clarity the details of such operation are not repeated and such elements are not illustrated in  FIGS. 7A-7C , but it will be understood that such components are present and cooperate in the manner previously described. Thus, upon reception of a complete and correct combination input by the microprocessor in the second embodiment, motor  300  receives the required small electrical power pulse and rotates its rotor so that the distal end of engagement lever  726 , assisted by movement of the elastic eccentric cam  701  caused by the power pulse to the motor  300  and subsequent rotor rotation friction between the elastic eccentric cam  701  and the contacting periphery of rotary cam element  720  permitting rotation of the rotary cam element  720 , rotates into triangular detent  722  of manually rotated rotary sam element  720 .  
         [0064]     As was the case in the first embodiment, there is provided a rotatable element (not shown in  FIGS. 7A-7C , but similar to  312  in  FIG. 3 ) mounted to rotate freely about the axis of motor  300 . Thus, when motor  300  has rotated its rotor by a predetermined small amount after receiving the small electrical pulse, the rotatable cam element  312  engages, and rotates a radial arm ending in a transverse cam pin  728 . See  FIGS. 7A-7C . Rotation of cam pin  728  about the axis of the motor is thus obtained by the application of a manual torque by coaction of the rotary cam element  720  and engagement lever  726  engaged therewith.  
         [0065]     A second spring  730  is engaged at one end to spring connection pin  714  of lever arm  702  and has a second end disposed to be pulled by cam pin  728 . The length of second spring  730  is selected such that it is put under tension only after engagement of engagement lever  726  by detent  722  of rotary cam element  720  as described in the immediately preceding paragraphs. Until that happens, second spring  730  is not subjected to any external force. However, once cam pin  728  is manually moved, as described above, it turns about the axis of motor  300  to a point where it begins to exert a force along second spring  730  and this force is to spring connection pin  714  of lever arm  702 . This force, manually provided, is sufficient to overcome the biasing force of first spring  716 , and eventually draws lever arm  702  in a pivotable motion about pivot  250 , so that point  712  of hook  704  is received within the hook engaging profiled detent  724 . Once this happens, co-action between the appropriately shaped hook engaging profiled detent  724  and rear hook surface  710  causes lever arm  702  to be drawn forcibly to thereby draw lock bolt  212  from its locking position to its unlocking position (as best seen in  FIG. 7C ).  
         [0066]     The second embodiment thus operates in the manner just described in accordance with the same basic principles as were earlier described with reference to the first embodiment.  
         [0067]     When the user wishes to lock the mechanism, he or she simply needs to turn combination-input knob  206 , and thus shaft  210  and rotary cam element  720 , in a clockwise direction as would be seen with reference to  FIG. 7C , i.e., in a direction contrary to that in which it was turned to bring lock bolt  212  into its unlocking position. When this is done, forcible co-action between the profiled hook engaging detent  724  and the elongate curved leading face  708  of hook  704  causes lever arm  702  to rotate about pivot  250  while applying a manually provided force to drive lock bolt  212  to its locking position. Eventually, when rotary cam element  720  has rotated sufficiently, co-action between triangular detent  722  and engagement lever  726  will cause the tension force in second spring  730  to be relieved and the rotor of motor  300  will return to its disengaged position as controlled by the corresponding magnetic detent. Once this is accomplished, the biasing force provided by first spring  716  will return lever arm  702  to the position best seen in  FIG. 7A . Since hook  704  is then no longer in contact with rotary cam element  720  at this time, any unauthorized rotation of shaft  21   0  will not succeed in unlocking the locking mechanism. Only the provision of a complete and correct combination code input can thereafter reactuate the mechanism and cause it to move to its unlocking position. There is, thus, provided an alternative simple structure for a locking mechanism.  
         [0068]     The third embodiment  800 , operating to the same basic principles, is illustrated in  FIGS. 8A-8C . In this embodiment, the elements for generating electrical power and controlling its delivery to motor  300  are as previously described. Lock bolt  212  is slidingly guided in guides  218 ,  218  as before. Lever arm  802  is pivotable about pivot  250  and has, as in second embodiment  700 , a hook  804  at a distal end. A rotary cam element  806  is manually rotatable by affixation to shaft  210 . Rotary cam element  806  has a hook-engaging profiled detent  808 , with an otherwise smooth circumferential periphery  810  smoothly contiguous therewith.  
         [0069]     The rotor of electric motor  300  has a gear wheel  812  the teeth of which are continuously engaged with the teeth of an arcuate toothed sector  814  of an element  816  pivotably mounted at a pivot  818  attached to an inside surface of casing  208 . Element  816 , on the side opposite to toothed sector  814 , has a sideways extension  820  having a generally triangular internal opening  822  and an external edge surface cam comprising a first straight portion  824 , an obtuse angle  826 , a short external edge portion  828 , a substantially right angled corner  830 , and a second straight edge portion  832 , as illustrated in  FIGS. 8A-8C .  
         [0070]     Lever arm  802  has a spring connection point  834 , a short rotatable arm  836  pivotably mounted on a pivot  838  and a stop pin  840  against which short rotatable arm  836  rests under a biasing force provided by a spring  842 .  
         [0071]     As illustrated in  FIG. 8A , when lock bolt  212  is in its locking position, i.e., projecting outwardly of casing  208 , lever arm  802  has its distal end and hook  804  in their uppermost position, with hook  804  barely touching the smooth circumferential periphery  810  of rotary element  806 . At this time, a cam pin  844 , extending transversely of short rotatable arm  836  near an end opposite to an end attached to spring  842 , is close to but not contacting the cam surface edge of element  816  at obtuse angle  826  thereof. See  FIG. 8A .  
         [0072]     When a user inputs the correct and complete combination code, as with the previously discussed embodiments, a microprocessor acts in combination with the reed switch and a magnet (not shown) mounted to the rotary element  806  in the manner previously described with respect to the other embodiments. A small electrical power pulse is then provided to electric motor  300  when hook-engaging detent  808  is at a predetermined position with respect to hook  804 . Pivotably supported element  816  is very light in weight, therefore has a small mass inertia, and is supported at pivot  818  with very little friction, preferably without the use of lubricants that could deteriorate over time. It is also intended to be balanced about pivot  818  so that, even with a very small electrical power pulse, motor  300  can turn gear wheel  812  and, thereby, element  816 . At this time, in the disposition illustrated in  FIG. 8A , a lever arm cam pin  846  is at a first corner of opening  822  of element  816 .  
         [0073]     Upon receiving the small electrical pulse, motor  300  causes rotation of its rotor and gear wheel  812  mounted thereto, and toothed sector  814  engaged therewith causes rotation of element  816  in a clockwise direction, preferably by about 30°, as illustrated in  FIGS. 8A-8C . The short cam surface edge portion  828  then slips away from under cam pin  844 , lever arm cam pin  846  coacts with an inside edge of triangular opening  822  to pivot lever arm  804  about pivot  250  so that hook  804  can then make contact against circumferential periphery  810 .  
         [0074]     Eventually, as rotary cam element  806  is manually turned counterclockwise, hook  804  enters hook-engaging detent  808  of manually rotated rotary element  806 . Once this occurs, further counterclockwise manual rotation of rotary element  806  forcibly pulls lever arm  802  leftward, and thus lock bolt  212  slides into casing  208 . An uppermost outer edge of the hooked distal end of lever arm  802  slips under fixed cam  264  provided at an upper portion of casing  208 . The dimensions of the various elements are selected so that when lock bolt  21   2  has reached its “unlocking” position detent  808 , the hook engaging detent  808  cannot pull on lever arm  802  any further, as best understood with reference to  FIG. 8C . The locking mechanism is now in its unlocked state.  
         [0075]     Note that, as with the two previously described embodiments, in this third embodiment the basic principle utilized is to employ a very small electrical power pulse to cause a light-weight, low-friction electric motor to cause a small rotatable element to rotate to initiate an engagement between a lever arm and a manually driven rotatable rotary element to enable delivery of a manual force to drive lock bolt  212  from its locking to its unlocking position. Note also that, as with the previous embodiments, such an engagement becomes possible only after the microprocessor has received a correct and complete combination code input from the user, and only when the user manually torques rotary element  806  thereafter.  
         [0076]     In order to put the locking mechanism in its locking state, the user must manually rotate rotary element  806  in the contrary direction, i.e., clockwise in  FIG. 8C . Co-action between the smooth, curved, outer edge of hook  804  and hook-engaging detent  808  will then cause a manually provided force to drive lock bolt  212  to its locking position rightward and, at the same time, once cam pin  844  contacts the second straight edge portion  832 , element  816  will be caused to also rotate in a clockwise manner under a bias force conveyed from spring  842 . Due to the engagement between toothed sector  814  ad gear wheel  812  of motor  300 , the motor also is thus returned to its disengaged detent-controlled position. At this time, under the urging of spring  842  acting on rotatable arm  836 , cam pin  844  will again return to its location inside obtuse angle  826  of the cam surface edge of element  816 . Rotary element  806  will have rotated so that its smooth outer circumferential periphery is now immediately adjacent hook  804 .  
         [0077]     Further uncontrolled, e.g., unauthorized, rotation of shaft  210  and rotary element  806  will not cause a lock-opening engagement between hook  804  and hook-engaging detent  808  until and unless element  816  is again caused to rotate out of the way of cam pin  844 , this being possible only under the control of the microprocessor after the microprocessor receives a correct and complete combination code input. The lock is thus safe from unauthorized opening once lock bolt  212  is put in its “locking” position, i.e., once it is extended outwardly of casing  208  as best illustrated in  FIG. 8A .  
         [0078]     As will be appreciated, to ensure against forcible or clever attempts at unauthorized unlocking operation of the locking mechanism, additional security elements may be provided. Two embodiments of such an aspect of an improving addition to th above-described invention are illustrated in  FIGS. 9, 10  and  10 A, as described more fully hereinbelow.  
         [0079]      FIG. 9  illustrates a mechanism that can act in combination with any of the above-described embodiments to further ensure against attempts at unauthorized operation of the locking mechanism by the imposition of an external magnetic field.  
         [0080]     This security device  900  preferably has its principal components disposed within a common casing  902  shared with the electrical windings  904  and rotor  906  of the electrical motor (otherwise used in the same manner as electric motor  300  of the previous embodiments). Rotor  906  is supported on an axle  908  mounted in low friction bearings (not shown) and has an external gear wheel  910  which mechanically coacts with other elements as previously described.  
         [0081]     At the inside end of rotor  906 , within casing  902 , there is provided a blocking member formed as a non-magnetic disk  912  which clears the inside surface of casing  902  and is rotatable with rotor  906  and shaft  908  to which external gear wheel  910  is mounted. Therefore, when blocking member disk  912  is prevented from rotating, so is external gear wheel  910  which, by its coaction with other elements previously described, is operable to put the lock in condition for unlocking.  
         [0082]     Non-magnetic locking member disk  912  is preferably provided with a slight recess  914 , as best seen in  FIG. 9 , with a through aperture  916  passing through the recessed portion to selectively receive a pin therethrough.  
         [0083]     Also mounted within casing  902  is a small magnetic coil, e.g., a voice coil  918  mounted concentrically with an extending portion of axle  908  supported at a rear wall of casing  902  in a bearing  920 . The voice coil is free to move axially of axle  908  and is biased toward rotor  906  and blocking member disk  912  by one or more springs  922  acting against the back end of and within casing  902 . At the end of voice coil  918  closest to blocking member disk  912 , there is mounted a cantilevered pin  924  which normally extends through aperture  916  in blocking member disk  912 , as shown in  FIG. 9 . This is the normal situation when the lock is in its locked state. Voice coil  918  is not rotatable about or with axle  908  but can merely slide axially thereof.  
         [0084]     A permanent magnet  926  is mounted inside casing  902  with its north and south poles aligned in such a manner that when an electric current is provided to voice coil  918 , an electromagnetic field generated therein produces a pole of like kind so that mounted permanent magnet  926  repells voice coil  918  axially of axle  908 . Consequently, when a sufficient electric current is provided to voice coil  918 , and the magnetic field thereof interacts with permanent magnet  926  to overcome the biasing force of springs  922 , voice coil  918  bodily moves away from blocking member disk  912 . In doing so, it causes pin  924  to be totally extracted from aperture  916  in blocking member disk  912 . So long as such a current continues to be provided to voice coil  918 , and pin  924  remains retracted entirely out of aperture  916  in blocking member disk  912 , blocking member disk  912 , rotor  906 , shaft  908  and external gear wheel  91   0  are then free to rotate. On the other hand, so long as such an electrical current is not being provided to voice coil  918 , springs  922  force it in such a direction that when the distal end of pin  924  becomes aligned with aperture  916  in blocking member disk  912  it projects therethrough and prevents rotation of axle  908  and external gear wheel  910  mounted thereto.  
         [0085]     In know manner, voice coil  918  is connected in conjunction with windings  904  of the electric motor (not numbered), which is used in the same manner as electric motor  300  of the previous embodiments. The electric current which activates voice coil  918  into retracting pin  924  out of blocking member disk  912  does so just before passing of electric current through windings  904  causes rotor  906  to turn axle  908  and, thus, external gear wheel  910 .  
         [0086]     As will be appreciated, to avoid binding between pin  924  and th edges defining aperture  916  in blocking member disk  912 , the pin must be retracted before windings  904  generate enough torque on rotor  906  and blocking member disk  912  to turn them inside casing  902 . As a practical matter, there are numerous known mechanisms and techniques for delaying the flow of electrical current to coils  904  until pin  924  has been entirely retracted from aperture  926 , thereby setting rotor  906  free to turn.  
         [0087]     In practice, the security device illustrated in  FIG. 9  acts to prevent rotation of external gear wheel  91   0  under the action of an external spurious or intentionally applied magnetic field, which, otherwise, might actually cause rotation of rotor  906 . Thus, if an unauthorized person positions equipment capable of generating a strong rotating field immediately adjacent the locking device of this invention, and rotor  906  rotates by coacting with the imposed rotating field, the lock might be engaged and unlocked without the input of an authorized combination code. The security device illustrated in  FIG. 9  would prevent such unauthorized opening of the lock. Since the externally imposed unauthorized rotating electromagnetic field would have no influence on the non-rotatable voice coil  91   8  and its pin  924  extended through aperture  916 , such a very small light pin  924  very effectively prevents unauthorized rotation of axle  908  and external gear wheel  910 .  
         [0088]     It may be theoretically possible to apply a strong inertial force, e.g., by a violent blow, to the lock along the direction of the axis of axle  908 , sufficient to cause voice coil  918  to compress springs  922 . While doing so, in theory one could retract pin  924  from aperture  916  while, simultaneously, applying a strong rotating external magnetic field to rotate rotor  906 . However, since most safes are very heavy or are built into a structure, the likelihood of such a complex contrivance putting the lock into condition for unlocking for practical purposes is eliminated by the presence of the security device per  FIG. 9 .  
         [0089]     Persons of ordinary skill in the art will appreciate that the performance of the voice coil and pin  924  attached thereto, involving retraction during the provision of a small electric current to the voice coil, can be utilized under other comparable circumstances to prevent movement of an element capable of coacting with pin  924 , e.g., a sliding element that may be employed as a magnetic key, or the like.  
         [0090]     Voice coil  918  is preferably connected in series with winding coils  904  of the electric motor in such a manner that when an electrical current is provided under the control of the microprocessor to enable rotor  906  to turn, the same current causes voice coil  918  to act against springs  922  to withdrawn pin  924  from aperture  916  of disk  912 . Only then can disk  912  and the rotor  906  turn to rotate the toothed element  910  into an engageable position to allow the user to apply manual force to lock bolt  212  to move it to its unlocking position. Rotation of rotor  906  by the imposition of an external magnetic field is prevented by this simple structure, while normal authorized opening of the lock mechanism is automatically made possible.  
         [0091]     In this manner, by the use of relatively inexpensive and commonly available elements, e.g., a voice coil, springs and essential wiring, additional security can be provided against unauthorized unlocking of the locking mechanism as described hereinabove.  
         [0092]     An alternative security device is illustrated in  FIGS. 10 and 10 A. In such a device, shown sharing a common ferrous casing  1002 , electric motor  300  utilizes a small rotor  1004  mounted coaxially to the motor axle  1006 , rotor  1004  having a knurled or otherwise roughened outer peripheral surface  1008 . Surrounding rotor  1004 , but at a small distance radially outward therefrom, is an annular ring  1010  of a non-ferrous material tightly fitted within ferrous casing  1002 .  
         [0093]     As best seen in  FIG. 10A , at four equally separated radial locations in non-ferrous annular ring  1010 , there are provided four radial holes  1012  having axes in a common plane. Inside each radial hole  1012 , there is provided a small hardened linear magnet  1014  which is shaped and sized to be freely slidable within radial hole  1012 . Each of the hardened magnets  1014  has a sharp point at its end nearest to the knurled surface  1008  of rotor  1004 . These magnets  1014  are disposed in pairs, with the two magnets of each pair having “like magnetic poles” opposite to each other in a substantially radial direction with respect to the axis of axle  1006  of electric motor  300 . By this arrangement, the two magnets in each pair of magnets tend to repel each other so that they remain loosely held within their corresponding radial holes  1012  but with their respective sharp points magnetically maintained away from the knurled surface  1008  of rotor  1004 .  
         [0094]     Under the above-described circumstances, with the magnets, by pairs, staying away from the knurled surface  1008 , the rotor of electric motor  300  remains free to operate as described previously, i.e., to turn between its two detent positions upon the reception of the required small electrical power pulse under the control of the microprocessor. However, should an unauthorized attempt be made to unlock the locking mechanism by the imposition of a large magnetic field upon the locking mechanism, the pairs of magnets will no longer balance each other radially outwardly and, therefore, their sharp ends will come into contact with knurled surface  1008  of rotor  1004  and will prevent rotation thereof. Consequently, the rotor of electric motor  300  also cannot turn and the mechanism cannot be put into condition for operation in any of its embodiments as described hereinabove. This mechanism thus insures safety against attempts at unauthorized opening of the locking mechanism by the imposition of extraneously provided large magnetic or electrical fields.  
         [0095]     It should be appreciated that persons of ordinary skill in the art, armed with the above disclosure, will consider variations and modifications of the disclosed embodiments and various aspects of this invention. Consequently, the disclosed embodiments are intended to be merely illustrative in nature and not as limiting. The scope of this invention, therefore, is limited solely by the claims appended below.

Technology Classification (CPC): 8