Abstract:
An electronic lock box contains a mechanical structure that allows the lock box to work in several different mechanical states. A first state is a key compartment door unlocking state, while a second state is a shackle release state. A third state is a “soft lock” state, which allows the key compartment door to be closed, or the shackle to be re-installed, and once this has occurred, the door will not fall open, and the shackle will not fall out. A fourth state is a “hard lock” state in which the key compartment door and the shackle are not easily disturbed by vibration or intentional impact by a would-be thief, who is attempting to unlawfully open the door or remove the shackle.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to electronic lock equipment and is particularly directed to an electronic lock box of the type that contains a secure compartment for storing keys that allow entry to a structure. The invention is specifically disclosed as an electronic lock box that includes an internal movable actuator that moves in one direction to open the door to a secure compartment containing a key to the structure, and moves in the opposite direction to release a shackle that holds the lock box to the structure, such as a door handle. Much of the theory of operation of a similar movable actuator is disclosed in U.S. Pat. No. 7,086,258, by the same inventor. 
         [0003]    In the present invention, improvements are made to the previous cost efficient design, including a more secure mechanical actuator and locking mechanisms. In addition, the present invention maximizes the “power budget” for operating the secure actuator mechanisms. 
         [0004]    2. Description of the Related Art 
         [0005]    In U.S. Pat. No. 7,086,258, a prime mover apparatus moves a movable actuator which engages latches that retain either a key compartment door or a shackle for attaching the lockbox to a fixed object. The prime mover typically is a high performance micro-motor with a spur gear attached which interfaces with a set of “rack” teeth that translate the rotational energy of the motor shaft into linear motion. This cost efficient design works well, however, improvements can be made. 
         [0006]    Lockboxes require increasing levels of security as the homes they protect have increasingly valuable contents. Thieves may try multiple means at their disposal to gain entry into a lockbox so a robust latching system to thwart the would-be attacker would be a decided improvement. 
       SUMMARY OF THE INVENTION 
       [0007]    Accordingly, it is an advantage of the present invention to provide an improved movable actuator design that increases the mechanical security of the device. 
         [0008]    It is another advantage of the present invention to provide an improved movable actuator design for an electronic lock box that increases its reliability. 
         [0009]    It is a further advantage of the present invention to provide an improved electronic lock box design that improves the economic use of battery power for driving the actuator motor. 
         [0010]    Additional advantages and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. 
         [0011]    To achieve the foregoing and other advantages, and in accordance with one aspect of the present invention, a locking apparatus is provided, which comprises: (a) a movable actuator that travels in a substantially linear direction between a first end travel position and a second end travel position, the movable actuator having a first end and a second end and a central area therebetween, and the movable actuator having a longitudinal axis which runs between the first and second ends; (i) the movable actuator having a first spaced-apart pair of sloped surfaces that, proximal to the first end, are farther apart from one another, and that, at the central area, are closer to one another, wherein the first pair of sloped surfaces are at angles that are not perpendicular to the longitudinal axis; (ii) the movable actuator having a second spaced-apart pair of sloped surfaces that, proximal to the second end, are farther apart from one another, and that, at the central area, are closer to one another, wherein the second pair of sloped surfaces are at angles that are not perpendicular to the longitudinal axis; (iii) the movable actuator having a first spaced-apart pair of blocking members that are located proximal to the first end, and which are spaced apart from the first pair of sloped surfaces; (iv) the movable actuator having a second spaced-apart pair of blocking members that are located proximal to the second end, and which are spaced apart from the second pair of sloped surfaces; (b) a transverse first control arm that exhibits a first control protrusion, a transverse second control arm that exhibits a second control protrusion, and a first mechanical bias member that tends to push the first and second control arms apart from one another; (c) a transverse third control arm that exhibits a third control protrusion, a transverse fourth control arm that exhibits a fourth control protrusion, and a second mechanical bias member that tends to push the third and fourth control arms apart from one another; (d) a housing that holds the first control arm, the second control arm, the third control arm, the fourth control arm, and the movable actuator in their proper physical orientations with respect to one another; (e) wherein: (i) when the movable actuator is at a first position of its travel, the first control protrusion and the second control protrusion make contact with the first pair of sloped surfaces which cause the first and second control protrusions to move inward, thereby retracting the first and second control arms, and allowing a first mechanical member to be unlocked; (ii) when the movable actuator is at a second position of its travel, the third control protrusion and the fourth control protrusion make contact with the second pair of sloped surfaces which cause the third and fourth control protrusions to move inward, thereby retracting the third and fourth control arms, and allowing a second mechanical member to be unlocked; (iii) when the movable actuator is at a third position of its travel, the first control protrusion and the second control protrusion do not make contact with the first pair of sloped surfaces which allow the first and second control arms to extend outward, and causing the first mechanical member to be locked; and (iv) when the movable actuator is at the third position of its travel, the third control protrusion and the fourth control protrusion do not make contact with the second pair of sloped surfaces which allow the third and fourth control arms to extend outward, and causing the second mechanical member to be locked. In accordance with another aspect of the present invention, a lock box apparatus is provided, which comprises: an enclosure; a detachable holding member actuatable by a first movable control arm; a secure compartment within the enclosure, having a movable door actuatable by a second movable control arm; a movable actuator; and a driving member that causes the movable actuator to move along a substantially linear travel pathway between a first end travel position and a second end travel position; wherein: (a) the first movable control arm includes a first control protrusion that, in first predetermined conditions, makes contact with a first control surface of the movable actuator; (b) the second movable control arm includes a second control protrusion, in second predetermined conditions, makes contact with a second control surface of the movable actuator; (c) the movable actuator includes a first blocking member, which may engage the first control protrusion; (d) the movable actuator includes a second blocking member, which may engage the second control protrusion; (e) when moved to a first position along the substantially linear travel pathway, the movable actuator causes the first movable control arm to be actuated, by way of contact between the first control protrusion and the first control surface, so as to release the holding member, thus allowing the lock box apparatus to be detached from a fixed object; (f) when moved to a second position along the substantially linear travel pathway, the movable actuator causes the second movable control arm to be actuated, by way of contact between the second control protrusion and the second control surface, so as to disengage the door, thus allowing access to the secure compartment by opening the door; (g) when moved to a third position along the substantially linear travel pathway, the movable actuator causes the first movable control arm to be actuated so as to allow the holding member to be reinstalled to the lock box apparatus, and once the holding member has been reinstalled, the first movable control arm prevents the holding member from falling out from the lock box apparatus, thereby obtaining a “soft lock;” (h) when moved to the third position along the substantially linear travel pathway, the movable actuator causes the second movable control arm to be actuated so as to allow the door to be closed, and once the door has been closed, the second movable control arm prevents the door from falling open, thereby obtaining a “soft lock;” (i) when the movable actuator is moved to a fourth position along the substantially linear travel pathway, the first control surface of the movable actuator and the first blocking member substantially hold the first control protrusion within a first predetermined range of movement, and thus prevent the holding member from being detached from the lock box apparatus, thereby obtaining a “hard lock;” and ( 0 ) when the movable actuator is moved to the fourth position along the substantially linear travel pathway, the second control surface of the movable actuator and the second blocking member substantially hold the second control protrusion within a second predetermined range of movement, and thus prevent the door from being opened, thereby obtaining a “hard lock.” 
         [0012]    In accordance with a further aspect of the present invention, a method for using a lock box is provided, in which the method comprises the following steps: (a) providing a lock box apparatus that includes an enclosure; a detachable shackle actuatable by a first movable control arm; a secure compartment within the enclosure, having a movable door actuatable by a second movable control arm; a movable actuator having first and second control surfaces; and a driving member that causes the movable actuator to move along a substantially linear travel pathway between a first end travel position and a second end travel position; (b) driving the movable actuator to a first predetermined position such that the first control surface of the movable actuator causes movement of the first movable control arm so as to release the shackle; (c) driving the movable actuator to a second predetermined position such that the second control surface of the movable actuator causes movement of the second movable control arm so as to allow the door to be opened; (d) driving the movable actuator to a third predetermined position creating a “soft lock” state, such that: (i) the first movable control arm is positioned to allow the shackle to be reinstalled, and to prevent the shackle from falling out from the enclosure, and (ii) the second movable control arm is positioned to allow the door to be closed, and to prevent the door from being reopened; and (e) driving the movable actuator to a fourth predetermined position creating a “hard lock” state, such that: (i) the first control surface of the movable actuator and a first blocking member of the movable actuator combine to limit movement of the first movable control arm, such that the shackle cannot be released, and (ii) the second control surface of the movable actuator and a second blocking member of the movable actuator combine to limit movement of the second movable control arm, such that the door cannot be opened. 
         [0013]    Still other advantages of the present invention will become apparent to those skilled in this art from the following description and drawings wherein there is described and shown a preferred embodiment of this invention in one of the best modes contemplated for carrying out the invention. As will be realized, the invention is capable of other different embodiments, and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of at least one embodiment of the invention taken in conjunction with the accompanying drawings. The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description and claims serve to explain the principles of the invention. In the drawings: 
           [0015]      FIG. 1  is a perspective view of the outer enclosure of an electronic lock box, as constructed according to the principles of the present invention. 
           [0016]      FIG. 2  is a perspective view of the electronic lock box of  FIG. 1 , in which the key compartment door is in its open state. 
           [0017]      FIG. 3  is an exploded view in perspective of the electronic lock box of  FIG. 1 . 
           [0018]      FIG. 4  is a front elevational view of a shackle used with the electronic lock box of  FIG. 1 . 
           [0019]      FIG. 5  is a perspective view of the shackle of  FIG. 4 . 
           [0020]      FIG. 6  is an elevational view of a drive screw used with the electronic lock box of  FIG. 1 . 
           [0021]      FIG. 7  is a top view of the drive screw of  FIG. 6 . 
           [0022]      FIG. 8  is a perspective view of a movable actuator that is used in the electronic lock box of  FIG. 1 . 
           [0023]      FIG. 9  is a perspective view from the opposite side of the movable actuator of  FIG. 8 . 
           [0024]      FIG. 10  is a front elevational view in cross-section of the movable actuator of  FIG. 8 , taken along the lines  10 - 10  of  FIG. 8 . 
           [0025]      FIG. 11  is a bottom plan view of the movable actuator of  FIG. 8 . 
           [0026]      FIG. 12  is a side elevational view of the movable actuator of  FIG. 8 . 
           [0027]      FIG. 13  is a front elevational view of the movable actuator of  FIG. 8 . 
           [0028]      FIG. 14  is a rear elevational view of the movable actuator of  FIG. 8 . 
           [0029]      FIG. 15  is a front plan view of a “mechanism box” that is used in the electronic lock box of  FIG. 1 . 
           [0030]      FIG. 16  is a perspective view of a lower control arm used in the lock box of  FIG. 1 . 
           [0031]      FIG. 17  is a side elevational view of the lower control arm of  FIG. 16 . 
           [0032]      FIG. 18  is a perspective view of an upper control arm used in the lock box of  FIG. 10 . 
           [0033]      FIG. 19  is a perspective view of the upper control arm of  FIG. 18 , taken from the opposite direction. 
           [0034]      FIG. 20  is a side elevational view of the upper control arm of  FIG. 18 . 
           [0035]      FIG. 21  is an end view of the upper control arm of  FIG. 18 . 
           [0036]      FIG. 22  is an end view taken from the opposite end, of the upper control arm of  FIG. 18 . 
           [0037]      FIG. 23  is a diagrammatic view of certain of the internal components of the electronic lock box of  FIG. 1 , in which the mechanism components are in a “hard lock” state. 
           [0038]      FIG. 24  is a diagrammatic view of certain of the internal components of the electronic lock box of  FIG. 1 , in which the mechanism components are in a “soft lock” state. 
           [0039]      FIG. 25  is a diagrammatic view of certain of the internal components of the electronic lock box of  FIG. 1 , in which the mechanism components are in a key compartment door unlocking state. 
           [0040]      FIG. 26  is a diagrammatic view of certain of the internal components of the electronic lock box of  FIG. 1 , in which the mechanism components are in a shackle release state. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]    Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings, wherein like numerals indicate the same elements throughout the views. The exemplifications set out herein illustrate at least one preferred embodiment of the invention, in at least one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
         [0042]    The terms “first” and “second” preceding an element name, e.g., first control arm, second control arm, etc., are used for identification purposes to distinguish between similar or related elements, results or concepts, and are not intended to necessarily imply order, nor are the terms “first” and “second” intended to preclude the inclusion of additional similar or related elements, results or concepts, unless otherwise indicated. 
         [0043]    The present invention provides a level of protection not found in any existing lock box design. Physical testing has shown that simple opposed latch designs used in other products are vulnerable to attack with simple hand tools such as hammers. Other designs have incorporated improvements such as opposing latches to improve security from impacts, however, none to date has incorporated a two-state locking system whereby, in the first state the latches utilized can be deflected with the normal operation of closing the door or inserting the shackle, and the second state immobilizes the latches such that external forces applied to the device restrict the latch movement, thereby significantly increasing attack resilience. The two-state locking system of the present invention provides maximum usability and security without a significant increase in cost. 
         [0044]    Additional resistance to the unwanted application of external forces can be found in the present invention, by use of a drive screw to couple power from the motor gear box to the movable actuator. As illustrated below, a retention collar in the drive screw prevents the coupled drive assembly from being forced by external linear pressure in a direction where undesired latch movement otherwise would result. 
         [0045]    The benefits of these improvements are greater protection against unwanted intrusion through: (a) hammer blows applied perpendicular to the axis of latch travel; (b) deflection of latches by first drilling a hole in the lockbox outer casing, and subsequent insertion of a screwdriver or other tool to force the latches inward and to release the retained shackle or key door; or (c) device impacts induced through sudden deceleration such as the lockbox being thrown against a hard surface. 
         [0046]    Another advantage of the invention is the actuation force created through the arrangement of a micro-motor with gear box and the Acme drive screw. Electronic lockbox designs require great attention to power consumption as all are battery operated. Electronic lock boxes are also subject to extreme cold found in northern climates. Such extreme cold limits the instantaneous power available from the battery supply. The Acme drive screw increases the drive ratio between the rotational speed of the micro-motor and the imparted physical movement of the latching system while minimizing frictional losses in the drive screw. A high drive ratio requires less current to operate at any given point in time making it ideally suited for situations where battery current is limited by temperature. This allows the lock box of the present invention to operate very close to the chemical reaction limits posed by the battery chemistry. Some of the other electronic lockboxes now in use utilize solenoids that have poor power consumption characteristics. 
         [0047]    Referring now to  FIG. 1 , an overall view of the outer casing of the electronic lock box is illustrated, in which the lock box is generally designated by the reference numeral  10 . The outer enclosure is hinged, and has a stationary rear case  12  and a movable (via the hinge) front case  14 . There is an opening  24  in the front case for a keypad (not shown), by which a user can enter commands and other information to the electronic controller of the electronic lock box  10 . 
         [0048]      FIG. 2  illustrates the electronic lock box  10  in the condition in which the front case  14  has been opened, and has been pivoted with respect to the rear case  12 . A hinge pin  30  can be seen, as well as the front case hinge leaf  32 , and the rear case hinge leaf  34 . An open space or volume  20  is made available to hold the mechanical components that will be described below, and this set of mechanical components is essentially to be affixed to the rear case  12 . There is also an open space or volume  22  that is made available for holding a mechanical key, or other important component or device that is to be retained within the electronic lock box. This is also sometimes referred to as the “key compartment” or the “secure compartment.” In  FIG. 2 , the secure compartment  22  is not illustrated in detail, as any type of relatively small container size and shape would suffice for holding a mechanical house key, or some other type of credit card-sized device that would hold building opening or access codes, for example. 
         [0049]      FIG. 2  also shows a pair of catching members  150  and  152 , which are used to hold the front case  14  closed against the rear case  12 . The first catching member  150  has an opening  160 , and the second catching member  152  has an opening  162 . These openings  160  and  162  will receive a spring-loaded movable member that, once in place within the openings  160  and  162 , will prevent the key compartment  22  from being exposed (i.e., the key compartment “door” will remain closed). The spring-loaded movable members are discussed below, in reference to  FIGS. 16 ,  17 , and  23 - 26 . 
         [0050]      FIGS. 1 and 2  also illustrate openings for allowing a shackle to be inserted along the top surface of the electronic lock box  10 . These shackle openings are at  46  and  48 , and the “barrels” of the shackle are inserted here. The shackle itself is not illustrated in these views, for the sake of clarity. 
         [0051]    Referring now to  FIG. 3 , the enclosure components and other certain components are illustrated in an exploded view. The hinge components  30 ,  32 , and  34  are visible, and the front case can be seen as comprising two separate covers  16  and  18 . The key door outer cover is reference numeral  16 , while the key door inner cover is reference numeral  18 . The use of two separate covers for the key compartment door is to increase the mechanical security of the electronic lock box of the present invention. 
         [0052]    A cross brace  40  is illustrated in  FIG. 3 , and its placement on the rear case  12  is depicted on  FIG. 1 . Also illustrated in  FIG. 3  are two side brackets  42  that are mounted into the rear case  12 , and there is also a weld nut  44  that is mounted (or welded) to the rear case  12 . Referring now to  FIGS. 4 and 5 , a shackle  50  is illustrated for use with the electronic lock box of the present invention. Shackle  50  has two extensions, a left shackle extension (or barrel)  52  and a right shackle extension (or barrel)  54  (as oriented in these views). The farthest tips (or ends) of the barrels  52  and  54  are angled (in a frusto-conical shape), as depicted at reference numerals  53  and  55 , respectively. 
         [0053]    In this particular mechanical embodiment of the present invention, the shackle barrels are virtually identical, and have the same length of extension and exhibit the same type of sloped surfaces that make up the latching surfaces. The latching surfaces for the left shackle barrel  52  are depicted at  64 , and the shackle latching surfaces for the right shackle barrel  54  are depicted at  66 . These shackle surfaces  64  and  66  are also sometimes referred to as first and second “notches,” and will be discussed below in greater detail, with respect to the overall mechanical latching design of the present invention. 
         [0054]    Shackle  50  has an upper portion  56 , and the overall “U” shape of the shackle can be seen as having a conformal cover  62 . Part of the conformal cover  62  comprises two rain caps; there is a left shackle rain cap  58  and a right shackle rain cap  60 . This helps to prevent water from entering the top openings  46  and  48  of the rear case  12  when the electronic lock box of the present invention is in actual use. 
         [0055]    Referring now to  FIGS. 6 and 7 , a drive screw  70  is illustrated in some detail. Screw  70  has Acme threads  72 , and has a specific type of screw head  74 . Screw head  74  has a D-slot at  76  (see  FIG. 7 ). Screw head  74  also has a collar surface at  78 . This collar surface  78  will act as a retention collar with respect to the other mechanical devices that will be described below. The drive screw  70  is used to position a movable actuator that will now be described in reference to  FIGS. 8-14 . 
         [0056]      FIGS. 8-14  illustrate in detail a movable actuator, generally designated by the reference numeral  80 . On one end of the movable actuator is a nut  82  that has internal Acme threads. These threads will mate with the external threads  72  of the drive screw  70 . In the central region of the movable actuator  80  is an oval opening  84 , that retains a bushing (not shown in these views). There are linear gear teeth  86  along the bottom portion of one of the sides of the actuator  80 . 
         [0057]    Movable actuator  80  has several sloped guiding surfaces that have the appearance of ramps, designated by reference numerals  90 ,  91 ,  92 , and  93 . These sloped guiding surfaces are best viewed in  FIGS. 8 ,  10 , and  13 . In  FIGS. 10 and 13 , the upper left ramp is at  90 , the upper right ramp is at  91 , the lower left ramp is at  92 , and the lower right ramp is at  93 . There is also a sloped (or ramped) outer edge  94  that can be seen in  FIGS. 8 ,  10 ,  13 , and  14 . Surfaces  90  and  91  are sometimes referred to herein as a “first spaced-apart pair of sloped surfaces;” surfaces  92  and  93  are sometimes referred to herein as a “second spaced-apart pair of sloped surfaces.” 
         [0058]    As can be seen in the figures, sloped surfaces  90 - 93  are at angles that are not perpendicular to a longitudinal axis of the movable actuator  80 . Furthermore, sloped surfaces  90  and  91  are closer to one another at a central area (near the opening  84  of the actuator  80 ), and are farther apart from one another at the upper end (a “first end”), on  FIG. 10 ; sloped surfaces  92  and  93  are closer to one another at the central area (near the opening  84  of the actuator  80 ), and are farther apart from one another at the lower end (a “second end”), on  FIG. 10 . 
         [0059]    Movable actuator  80  also has several blocking wall members, which are designated by the reference numerals  95 ,  96 ,  97 , and  98 . These “blocking members” protrude from one of the surfaces of the movable actuator  80 , and this is the surface that faces the viewer on  FIGS. 10 and 13 . The blocking members can also be seen in the perspective view of  FIG. 8 . In  FIGS. 10 and 13 , an upper left blocking member is at  95 , and a similar member for the upper right is at  96 . A lower left blocking member is at  97 , and a similar member is at the lower right at reference numeral  98 . Blocking members  95  and  96  are sometimes referred to herein as a “first spaced-apart pair of blocking members;” blocking members  97  and  98  are sometimes referred to herein as a “second spaced-apart pair of blocking members.” 
         [0060]    The purposes for the shapes and positions of the sloped guiding surfaces (or ramps)  90 - 93  and the blocking members  95 - 98  will be explained below. These surfaces and blocking members aid in the greater security of the electronic lock box of the present invention. 
         [0061]    Referring now to  FIG. 15 , a “mechanism box” is generally depicted by the reference numeral  100 , which is a type of housing with the overall enclosure of the electronic lock box  10 . Within this so-called mechanism box are several movable components that are important to the latching and locking operations of the present invention. Mechanism box  100  has a perimeter wall  102 , and within the perimeter of this wall are two battery wells at  104  and  106 . The outline of the movable actuator  80  is depicted on  FIG. 15  as a reference point  108  for some of the other components. It will be understood that movable actuator  80  is not fixed at this position  108  that is depicted on  FIG. 15 , but actually can travel in a substantially linear manner, in the vertical direction with respect to the depiction of  FIG. 15 . 
         [0062]      FIG. 15  illustrates four different control arms  110 ,  111 ,  120 , and  121 , which are illustrated in greater detail on  FIGS. 16-22 . With respect to  FIG. 15 , there are two springs  112  and  122  that are in mechanical communication with the control arm  110 ,  111 , and  120 ,  121 . In this view, the spring  112  will be referred to as the “upper spring,” and the spring  122  will be referred to as the “lower spring.” Spring  112  is also sometimes referred to herein as a “first mechanical bias member,” and spring  122  is also sometimes referred to herein as a “second mechanical bias member.” It will be understood that other types of mechanical biasing devices could be used in lieu of coil springs, without departing from the principles of the present invention. 
         [0063]    As can be seen in  FIG. 15 , the upper spring  112  is in mechanical communication with the upper control arms  110  and  111  while the lower spring  122  is in mechanical communication with the lower control arms  120  and  121 . Spring  112  tends to push the upper control arms  110  and  111  apart from one another, i.e., toward the outer perimeter  102  of the mechanism box. The same is true for the lower spring  122 ; i.e., it tends to push the lower control arms  120  and  121  apart from one another, toward the outer perimeter  102  of the mechanism box. 
         [0064]    For ease of assembly, the upper-left control arm  110  has an “L” depicted on the control arm itself, while the upper-right control arm  111  has an “R” depicted on it. These two control arms  110  and  111  have different shapes, and their orientation is important in this particular embodiment, while the lower control arms  120  and  121  are interchangeable in this embodiment. The upper-left control arm  110  is essentially a mirror image of the upper-right control arm  111 . 
         [0065]    Referring now to  FIGS. 16 and 17 , one of the lower control arms is depicted, and is designated by the reference numerals  120  and  121 . As noted above, these two control arms are interchangeable, and only a single one is illustrated in  FIGS. 16 and 17 . Control arm  120 ,  121  has an elongated, somewhat linear shape, and essentially has a square cross-section. There is a sloped control surface  124  or  125 , depending on whether this would be the “left” control arm or the “right” control arm  120  or  121 , respectively. The function of the sloped control surface  124 ,  125  will be discussed below. There is an interior opening  126  or  127  (again depending upon which control arm is being discussed), and this receives one of the ends of the lower spring  122 . In  FIG. 15 , lower spring  122  is illustrated as a coil spring, and its outer dimension will fit inside the inner diameter of these two interior openings  126  or  127 . 
         [0066]    There is a control protrusion  128  or  129  on one of the longitudinal surfaces of the control arm  120  or  121 , respectively. In  FIGS. 16 and 17 , there is a single control protrusion (either  128  or  129 ) that extends at a right angle from the longitudinal axis of the control arm itself. In addition, the control protrusion  128 ,  129  is near the opposite end from the sloped control surface  124  or  125 . The purpose of the control protrusion  128 ,  129  will be discussed below. 
         [0067]    Referring now to  FIGS. 18-22 , the upper right control arm  111  is illustrated in great detail. Control arm  111  is also elongated, and has a longitudinal axis with a cross-section that is approximately square, similar to the lower control arms  120  and  121 . However, in this embodiment control arm  111  is shorter along its longitudinal axis than the lower control arms  120  and  121 . This can be seen by referring to  FIG. 15 . 
         [0068]    On one end of the control arm  111  is a sloped control surface  115 . This is similar to the sloped control surfaces  124  or  125  on the lower control arms, although as can be seen in  FIGS. 17 and 20 , the angle of the slope is different for the sloped surface  115  compared to the sloped surface  124  or  125 . The upper-left control arm  110  has a similar sloped control surface  114 , which is visible on  FIG. 15 . 
         [0069]    Control arm  111  has an interior opening on one end, in which the interior opening is designated by the reference numeral  116 . This opening  116  is circular, and has an inner diameter that is larger in size than the outer dimension of the upper spring  112 . There is a similar interior opening  117  on the upper control arm  110 . 
         [0070]    There is a control protrusion  119  on the upper-right control arm  111 , which can be seen in each of the views of  FIGS. 18-22 . Control protrusion  119  is located near one of the ends along the longitudinal axis of control arm  111 , and it is the opposite end from the sloped control surface  115 . This is similar to the lower control arms  120  and  121 , with respect to their control protrusions  128  or  129 , respectively. The upper-left control arm  110  will have a similar control protrusion  118 , which can be seen on  FIG. 15 . The control protrusion  119  is positioned at a right angle with respect to the longitudinal axis of the control arm  111 . For the upper-left control arm  110 , the control protrusion  118  is similarly positioned at a right angle with respect to the longitudinal axis of arm  110 . 
         [0071]    There is a positioning pin  132  that also protrudes at a right angle with respect to the longitudinal axis of the upper-right control arm  111 . As can be best seen on  FIG. 19 , the positioning pin  132  protrudes from a different one of the longitudinal surfaces of the control arm  111 . It is still at a right angle with respect to the longitudinal axis, but it is also protruding at a right angle with respect to the axis of the control protrusion  119 . There is a similar positioning pin  131  on the upper-right control arm  110 , which can be seen on  FIG. 15 . The positioning pins  131  and  132  assist in preventing the upper control arms  110  and  111  from rotating when they move. The purposes of the control protrusions for the upper control arms  110  and  111  are discussed below. 
         [0072]    Referring now to  FIGS. 23-26 , the orientations of the latching and locking mechanical mechanisms with respect to the shackle and key compartment door mechanisms are illustrated. There are four different possible states for the latching/locking mechanisms, and  FIGS. 23 ,  24 ,  25 , and  26  each show one of those four states. 
         [0073]    Control arm  110  is sometimes referred to herein as a “transverse first control arm;” control arm  111  is sometimes referred to herein as a “transverse second control arm;” control arm  120  is sometimes referred to herein as a “transverse third control arm;” and control arm  121  is sometimes referred to herein as a “transverse fourth control arm.” 
         [0074]    Before discussing the various attributes of the four different mechanical states in  FIGS. 23-26 , certain other mechanical parts will be introduced. There is a bushing  140  that travels within the oval opening  84  of the movable actuator  80 . As can be seen in these views, the axis of the oval opening  84  is vertical, so long as the shackle is also held in a vertical orientation. As the movable actuator  80  is moved through its substantially linear travel, the bushing  140  will hold the movable actuator within a certain range of distances, and will also tend to hold it along the appropriate vertical axis with respect to the remaining portions of the electronic lock box of the present invention. 
         [0075]    There is a potentiometer gear  142  that has outer gear teeth or spline that mate with the linear gear teeth  86  of the movable actuator  80 . The gear  142  is in mechanical communication with a potentiometer (not shown), so that the physical position of the movable actuator  80  can be measured electrically, and an electrical signal can be produced based on that potentiometer resistance value. This is similar to an earlier version of an electronic lock box that has been sold by assignee, SentriLock LLC. 
         [0076]    In  FIGS. 23-26 , the outer wall of the rear case  12  is depicted by the reference numeral  154 . In each of these four views, two portions of this outer wall  154  are depicted, one on each side of the lower control arms  120  and  121  of the locking/latching mechanism. There are also two protruding “ears”  150  and  152  that are illustrated on  FIGS. 23-26 , and the brackets  42  are further illustrated on  FIGS. 23-26 . Brackets  42  are also seen on the earlier views of  FIGS. 1 and 3 . 
         [0077]    In the mechanism design of the illustrated embodiment, there are certain important mechanical components, which include the drive screw  70  with an “Acme” style thread (as noted above), a pair of opposable “latches” for the key compartment door (i.e., the “lower” control arms  120  and  121 ), a pair of opposable “latches” for the shackle (i.e., the “upper” control arms  110  and  111 ), and the uniquely shaped movable actuator  80 . 
         [0078]    Drive Screw 
         [0079]    As discussed above, the drive screw  80  has a ‘D’ shaped hole (or slot)  76  on one end. This hole  76  accepts the output shaft of a micro-motor gearbox (not shown). The Acme threads on the drive screw impart a desired rate of linear motion, and minimize frictional losses in the interface between the drive screw  70  and the movable actuator  80 . Drive screw  70  incorporates a collar  78 , which rides in a journal  88  located in the mechanism box housing. The collar  78  is also retained by a portion of journal  88  that is located in the mechanism box cover. The journal/collar arrangement resists the application of externally induced linear forces on the movable actuator  80  in its desired operating direction unless the drive screw  70  is rotated in the Acme nut  82 . 
         [0080]    Key Door Latches 
         [0081]    The key door latching members are the “lower” control arms  120  and  121 , which are mounted opposing each other in a track in the mechanism box  100  housing. These control arms (also referred to as “latches”) are extended by a compression spring (lower spring  122 ) such that the tapered ends of the latches (at sloped control surfaces  124  and  125 ) extend outside the mechanism box enclosure. Each latch  120 ,  121  has a protrusion  128 ,  129  on the top surface (as seen in  FIGS. 23-26 ) that interfaces with the ramped surfaces  92 ,  93  on the movable actuator  80 . As movable actuator  80  travels in a downward direction, the ramped surfaces  92 ,  93  deflect the key door latches  120 ,  121 , respectively, inward. 
         [0082]    The key door components (e.g., the case  14 , and inner and outer doors  18  and  16 ) can be referred to herein as a “first mechanical member” that is to be locked or unlocked, depending on the operating state of lock box  10 . When movable actuator is in a “first position” of its travel, the first mechanical member is unlocked. In other travel positions of the movable actuator, the first mechanical member may be locked, as discussed below. 
         [0083]    Shackle Latches 
         [0084]    The shackle latching members are the “upper” control arms  110  and  111 , which are mounted opposing each other in a track in the mechanism box  100  housing. These control arms (also referred to as “latches”) are extended by a compression spring (upper spring  112 ) such that the angled notched ends of the latches (at angled control surfaces  114  and  115 ) extend into cylindrical channels (starting at the openings  46  and  48 ) that the open ends of the shackle barrels (i.e., extensions  52  and  54 ) slide into. The angled control surfaces  114  and  115  allow the shackle barrels  52  and  54  to deflect upon shackle insertion, while the bottom edges of the control arms  110  and  111  engage the notches  64  or  66  in the shackle barrels, thereby providing interference such that the shackle  50  cannot put pulled out without retracting the shackle latches (i.e., control arms  110  and  111 ) far enough to clear the notched shackle ends (at  64  and  66 ). Each control arm  110 ,  111  has a protrusion on its top surface (as seen in  FIG. 23 ) that interfaces with one of the ramped surfaces  90  or  91  on the movable actuator  80 . As movable actuator  80  travels in an upward direction, the ramped surfaces  90 ,  91  deflect the shackle latches  110 ,  111  inward. 
         [0085]    The shackle (including the barrels  52  and  54 ) can be referred to herein as a “second mechanical member” that is to be locked or unlocked, depending on the operating state of lock box  10 . When movable actuator is in a “second position” of its travel, the second mechanical member is unlocked. In other travel positions of the movable actuator, the second mechanical member may be locked, as discussed below. 
         [0086]    Movable Actuator 
         [0087]    As seen in  FIG. 13 , the movable actuator  80  has an oval opening  84  in the middle, two pairs of ramped surfaces  92 ,  93  on the underside, a threaded “Acme” style nut  82  near its the bottom end, a set of rack teeth  86  on the right face of the lower section, and strategically placed blocking members  97  and  98  on the underside. The rack teeth  86  mesh with the teeth of a spur gear  142  which has a shaft (not shown) that connects into a potentiometer that is utilized in the previously disclosed closed loop feedback position monitoring system. (See U.S. Pat. No. 7,086258, which is incorporated by reference in its entirety.) The oval opening  84  in the center of movable actuator  80  is used to retain the movable actuator in the mechanism box  100 , while also providing guidance to help ensure that movable actuator  80  travels in a substantially straight line. The drive screw  70  retains the bottom end of the movable actuator  80  to assist in providing the desired substantially straight travel. 
         [0088]    Key Door Release 
         [0089]    To release (or open) the key door (i.e., the inner and outer door covers  16  and  18 ), power is applied to the micro-motor (not shown) causing the gear box output shaft (not shown) to rotate in a counterclockwise direction, thereby causing the Acme nut  82  on the movable actuator  80  to travel toward the micro-motor. (This would be the “down” direction on  FIGS. 23-26 .) 
         [0090]    As movable actuator  80  moves toward the motor, the key door latch protrusions (i.e., control arms  120 ,  121 ) engage the lower ramped surfaces  92 ,  93 , causing the key door latches  120 ,  121  to move inward at right angles to the movable actuator motion. When sufficient latch retraction occurs, the ends of the latches (at the sloped control surfaces  124  and  125 ) no longer interfere with the key compartment door catching members (or “ears”)  150  and  152 , thus allowing the door ears  150 ,  152  to pass by the latches  120 ,  121  and thereby allowing the key compartment to be opened (i.e., the front case  14  will be allowed to pivot with respect to the rear case  12 ). This operating state is illustrated by  FIG. 25  (showing the second position of travel of the movable actuator). 
         [0091]    In the illustrated embodiment of the present invention, the movable actuator  80  is moved to its lowermost travel position for door release, which can also be referred to as a “first end travel position.” It will be understood that the present invention is not limited to this precise travel position of the movable actuator  80 , and other configurations could be used without departing from the principles of the present invention. 
         [0092]    Shackle Release 
         [0093]    To release the shackle  50 , power is applied to the micro-motor (not shown) causing the gear box output shaft (not shown) to rotate in a clockwise direction, thereby causing the Acme nut  82  on movable actuator  80  to travel away from the micro-motor. (This would be the “up” direction on  FIGS. 23-26 .) As movable actuator  80  moves away from the motor, the shackle latch protrusions (i.e., the sloped control surfaces  114  and  115  of control arms  110 ,  111 ) engage the upper ramped surfaces  90  and  91 , causing the shackle latches  110 ,  111  to move inward at right angles to the movable actuator motion. When sufficient retraction of control arms  110  and  111  occurs, the ends  114 ,  115  of the shackle latches  110 ,  111  no longer interfere with the notches  64 ,  66  in the shackle ends (at shackle extension  52 ,  54 ), thus allowing the shackle  50  to be pulled out of the mechanism  10 . This operating state is illustrated by  FIG. 26  (showing the first position of travel of the movable actuator). 
         [0094]    In the illustrated embodiment of the present invention, the movable actuator  80  is moved to its uppermost travel position for shackle release, which can also be referred to as a “second end travel position.” It will be understood that the present invention is not limited to this precise travel position of the movable actuator  80 , and other configurations could be used without departing from the principles of the present invention. 
         [0095]    Soft Lock 
         [0096]    Returning the control arms (or “latches”)  110 ,  111 ,  120 ,  121  to a state in which the key compartment door  16 ,  18  can be latched closed, or the shackle  50  can be inserted into the lock box  10 , is performed by applying power to the micro-motor such that its output shaft (not shown) rotates in a direction so as to move the movable actuator  80  in a direction conducive to allowing the compression springs  112  and  122  to extend the latches  110 ,  111 ,  120 ,  121  back to their normal resting position. On  FIGS. 23-26 , this means that the movable actuator  80  is to be moved to a travel location that is near its bottommost position, and this orientation is illustrated by  FIG. 24 . Upon reaching this travel location (of  FIG. 24 ), the spring tension exerted by the compression springs  112  and  122  between the pairs of control arms (arms  110 ,  111  for spring  112 , and arms  120 ,  121  for spring  122 ) causes the control arms to extend as permitted by the ramp/latch protrusion interface. 
         [0097]    The actuator&#39;s substantially linear travel is stopped by terminating power to the micro-motor. The appropriate travel location is referred to as the “soft lock” state, and in this state the control arms can be compressed by outside forces, such as by inserting the shackle  50  or by closing the key compartment door  16 ,  18 . However, the “lower” control arms  120  and  121  cannot be compressed so far as to cause the key compartment door latching protrusions at  124  and  125  to be blocked by the blocking members  97  and  98 , found on the movable actuator  80 . Instead, this state of “soft lock” allows the key compartment door  16 ,  18  to be closed and latched to a sufficient extent such that it does not fall open. 
         [0098]    In the soft lock state, the third and fourth control protrusions  128  and  129  make contact with the third and fourth sloped surfaces  92  and  93 , respectively, and the third and fourth control arms  120  and  121  are retracted to a slight extent. As such, the sloped “third tip” and “fourth tip”  124 ,  125  of third and fourth control arms  120  and  121  can “slide” by the openings  160  and  162  in the catching members  150  and  152 , respectively. But once the control arms have reached these openings  160  and  162 , then the mechanical bias (due to the action of spring  122 ) will force control arms  120  and  121  outward, and their tips (ends)  124  and  125  will occupy the openings  160  and  162 , and the key compartment door  16 ,  18  will not be able to re-open. This operating state is illustrated by  FIG. 24 . 
         [0099]    In a similar manner, the “upper” control arms  110  and  111  cannot be compressed so far as to cause the shackle latching protrusions at  114  and  115  to be blocked by the blocking members  95  and  96 , found on the movable actuator  80 . Instead, this state of “soft lock” allows the shackle  50  to be inserted and latched to a sufficient extent such that it will be retained without falling out. The first and second angled tips  53  and  55  of the shackle barrels  52  and  54 , respectively, can slide past the angled surfaces  114  and  115 , respectively, at the tips (or ends) of the control arms  110  and  111 . But once the control arms have reached the notches  64  and  66 , then the mechanical bias (due to the action of spring  112 ) will force control arms  110  and  111  outward, and their tips (ends)  114 ,  115  will occupy the open areas of notches  64  and  66 , and the shackle barrels  52  and  54  will not be able to be disengaged from the lock box in this state. This operating state is illustrated by  FIG. 24  (showing a fourth position of travel of the movable actuator). 
         [0100]    The control arms  110 ,  112 ,  120 , and  121  are, respectively, sometimes referred to herein as a “first control arm,” a “second control arm,” a “third control arm,” or a “fourth control arm.” Their outer control surfaces  114 ,  115 ,  124 , and  125  are, respectively, sometimes referred to herein as a “first angled outer edge,” a “second angled outer edge,” a “third angled outer edge,” or a “fourth angled outer edge.” 
         [0101]    Hard Lock 
         [0102]    The movable actuator  80  can be moved to a position in which the latch protrusions  114 ,  115 ,  124 , and  125  (of control arms  110 ,  111 ,  120 , and  121 ) will contact the corresponding blocking members  95 ,  96 ,  97 , and  98  if any external action applies compressive force along the “latch axes” of the control arms. (In  FIGS. 23-26 , the latch axes are essentially horizontal. Of course, of the electronic lock box  10  of the present invention is placed in a different orientation, then the latch axes will vary accordingly, with respect to the vertical or horizontal directions.) In this state, the control arms are said to be “hard locked,” in that they cannot be sufficiently moved by an external force such that the key door ears  150 ,  152  can move past the control arm ends  124 ,  125 ; moreover, the shackle latching surfaces  64 ,  66  cannot move past the control arm ends  114 ,  115 , and thus the shackle cannot be removed from electronic lock box  10 . This operating state is illustrated by  FIG. 23  (showing a third position of travel of the movable actuator). 
         [0103]    By appropriate control over the amount of clearance between the blocking members and their corresponding control protrusions, the control arms simply cannot be forced to move far enough to allow the key compartment door to be opened, or to allow the shackle to be released, at least not without physically damaging the enclosure of the lock box  10  to such an extent that its appearance would be noticeably altered. In this manner, the blocking members and the control protrusions work in pairs: blocking member  95  and control protrusion  118 ; blocking member  96  and control protrusion  119 ; blocking member  97  and control protrusion  128 ; and blocking member  98  and control protrusion  129 . 
         [0104]    The amounts of clearance for each set of blocking members and their corresponding control protrusions are predetermined distances. As can be seen in  FIG. 23 , these clearances are very small as compared to the respective distances (or clearances) between these same mechanical members in the other operating states of electronic lock box  10 . The sloped “ramp surfaces”  90 - 93  control the positioning of the control arms, by forcing the control protrusions  118 - 119  and  128 - 129  to be at predetermined locations along the longitudinal axes of the corresponding control arms, while the springs  112  and  122  exert an “outward” force on the control arms (and thus, cause all the control arms to extend outward). 
         [0105]    It should be noted that the “ramp surfaces”  90 - 93  do not have to be straight in order to operate effectively with the control protrusions  118 ,  119 ,  128 , and  129  of the control arms  110 ,  111 ,  120 , and  121 , respectively. In fact, these control surfaces  90 - 93  could be curved to take advantage of a particular motor load profile, in order to save energy (particularly since the electric motor, which is the prime mover of the movable actuator  80 , is energized by a battery in most installations of a lock box). 
         [0106]    With regard to the above description of the “hard lock” state, it should be noted that the blocking members  97  and  98  exhibit sloped surfaces along their uppermost edges, as seen on  FIG. 23 . These upper sloped surfaces can assist in pushing the control arms  120  and  121  outward, to establish a hard lock state when the control arms  120  and  121  are to extend to their outermost positions. In effect, these upper sloped surfaces act as secondary ramps, and can make contact with the control protrusions  128  and  129 . This is useful in the event of a slight mis-positioning of the control arms  120 ,  121 , or to overcome any potential additional friction that otherwise might inhibit the lower spring  122  from doing its job (to extend these control arms). 
         [0107]    In addition to the above, the retention collar  78  of drive screw  70  is always confined to the mating area of the journal  88 . This arrangement resists externally induced forces on the drive screw, including any impact forces along the longitudinal axis of the drive screw itself. In essence, the movable actuator  80  cannot be moved along its “normal” substantially linear pathway except by rotation of the drive screw. Other (external) forces cannot cause the movable actuator to move, unless the amount of external force used is so great that the Acme threads  72  of the drive screw or the mating threads of the Acme nut  82  on the movable actuator become stripped, or they are literally broken. Again, this cannot easily occur, at least not without physically damaging the enclosure of the lock box  10  to such an extent that its appearance would be noticeably altered. 
         [0108]    It would typically be desirable for the electronic lock box  10  to enter the “hard lock” state soon after the “soft lock” state was achieved to allow a user to either insert the shackle  50 , or to close the key compartment door  16 ,  18 . The system controller of the electronic lock box could be programmed to cause the micro-motor to automatically be actuated after a predetermined time delay, once the soft lock state was achieved, if desired. Or perhaps the timer function would begin operating once the electronic lock box  10  had its key compartment door opened. The system controller would likely be programmed to move the movable actuator  80  to its soft lock position soon after either the door open state was achieved, or the shackle release state was achieved. In other words, the use would thereby only have a limited amount of time to physically open the key compartment door or pull out the shackle, once an appropriate command had been entered to the electronic lock box  10 . 
         [0109]    Alternatively, a door limit switch could be provided to “notify” the system controller that the key compartment door had been closed by the user, and then the controller could immediately cause the lock box  10  to enter the hard lock state, without waiting for a timer function to occur. A combination of these events could be used to allow the system controller to decide when the lock box  10  should enter the hard lock state. Of course, other types of sensing devices could be used, if desired, to determine whether the lock box  10  was “ready” for entering its hard lock state, without departing from the principles of the present invention. As an example, there could be a “continuity test” circuit for determining whether the shackle  50  was inserted in the lock box  10 . If the shackle  50  is made of an electrically conductive material (such as most metals), then the electrical resistance could be measured between the points within the shackle openings, and this information could be used as an input to the system controller. Once the shackle has been re-installed, the system controller could be programmed to immediately move the movable actuator  80  to its hard lock position. 
         [0110]    All documents cited in the Background of the Invention and in the Detailed Description of the Invention are, in relevant part, incorporated herein by reference; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention. Specifically, the following patents and patent applications by the same inventor are incorporated herein by reference in their entirety: U.S. Pat. No. 6,989,732, issued on Jan. 24, 2006, titled: “ELECTRONIC LOCK SYSTEM AND METHOD FOR ITS USE WITH CARD ONLY MODE;” U.S. Pat. No. 7,009,489, issued on Mar. 7, 2006, titled: “ELECTRONIC LOCK SYSTEM AND METHOD FOR ITS USE;” U.S. Pat. No. 7,086,258, issued on Aug. 8, 2006, titled: “ELECTRONIC LOCK BOX WITH SINGLE LINEAR ACTUATOR OPERATING TWO DIFFERENT LATCHING MECHANISMS;” U.S. Pat. No. 7,193,503, issued on Mar. 20, 2007, titled: “ELECTRONIC LOCK SYSTEM AND METHOD FOR ITS USE WITH A SECURE MEMORY CARD;” U.S. patent application Ser. No. 10/805,018, filed on Mar. 19, 2004, for ELECTRONIC LOCK BOX WITH MULTIPLE MODES AND SECURITY STATES; U.S. patent application Ser. No. 11/585,038, filed on Oct. 23, 2006, for ELECTRONIC LOCK BOX USING A BIOMETRIC IDENTIFICATION DEVICE; and U.S. patent application Ser. No. 11/584,940, filed on Oct. 23, 2006, for ELECTRONIC LOCK BOX WITH KEY PRESENCE SENSING. 
         [0111]    The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and the present invention may be further modified within the spirit and scope of this disclosure. Any examples described or illustrated herein are intended as non-limiting examples, and many modifications or variations of the examples, or of the preferred embodiment(s), are possible in light of the above teachings, without departing from the spirit and scope of the present invention. The embodiment(s) was chosen and described in order to illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to particular uses contemplated. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.