Patent Abstract:
An electrically activated locking device is provided for use with an article of furniture of the type comprising a cabinet with an interior surface, at least one drawer in the cabinet moveable between an open position and a closed position, and a locking bar slideably mounted adjacent the interior surface for vertical movement and having at least one locking pin extending therefrom into locking engagement with the drawer and at least one lifting pin extending therefrom. The device includes an electrically powered actuator, an electronic module for controlling power to the actuator, a rotatable cam operatively connected to the actuator, and a lifting pin carrier in the path of and vertically moveable by rotation of the cam. The lifting pin carrier has an opening for receiving the lifting pin, whereby the locking bar is moveable into either an unlocked or locked position responsive to rotation of the cam.

Full Description:
FIELD OF THE INVENTION 
     The present invention relates generally to locks for articles of furniture such as case goods or cabinets, and more particularly, to an electronic locking mechanism for cabinets with multiple drawers and the like, and also to the lock itself. 
     BACKGROUND OF THE INVENTION 
     Many types of locking systems are known for articles of furniture having one or more drawers, including desks, credenzas, file cabinets, and the like. Many of these articles are designed wherein drawers are configured in a stacked relationship. Often it is desirable to lock each of the drawers with a single locking system that is operable from a single location. The most common locking scheme is known as a “gang lock” and includes an elongated metal bar or rod that is mounted to an inside wall of the article of furniture for sliding, vertical movement between locked and unlocked positions. The bar or rod typically includes multiple locking or arresting pins that engage catches mounted on the individual drawers when the drawers are in the closed position and the bar or rod is in the locked position. When the bar or rod is in the unlocked position, the arresting pins are disengaged from the drawer catches, thereby permitting the drawers to be opened. 
     The vertical movement of the locking bar or rod have, in the past, been actuated by mechanical means. Mechanical actuators typically include a linkage or cable system that, when manually actuated, move the locking bar or rod between locked and unlocked positions. The actuator is often operated manually using a mechanical keyed locking mechanism. While such purely mechanical locking systems are effective in securely locking multiple drawers, they require a mechanical key which may be lost or misplaced. Also, where multiple cabinets or desks, for example, are used in a single location, multiple keys are required or else each cabinet or desk must be similarly keyed at considerable expense. Further, such systems cannot be remotely operated from one or more locations or automatically lock at a prescribed time, such as after hours. 
     More recently, some electronic keyless systems have been introduced which require no mechanical keys. Some of these systems employ an electric motor and cam configuration to actuate the vertical motion of a locking bar or rod. However, these systems are not compatible with the mechanical gang lock described herein above and involve design changes in conventional cabinet drawer construction. 
     Most of the electronic locking systems heretofore known also require considerable space for installation. This results in special additional compartments that must be constructed within the article of furniture for placement of the locking system. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention is directed to an article of furniture having a cabinet with an interior surface and multiple drawers in stacked relation. Each of the drawers is moveable between an open position and a closed position and dimensioned to create a space between the drawer and the interior surface of the cabinet when the drawer is in the closed position. A locking bar is slideably mounted for vertical movement in the interior space between the drawers and the cabinet wall. Multiple spaced apart locking pins are positioned on the locking bar for locking engagement with each of the drawers when the drawers are in the closed position. An electrically activated locking system is operatively connected to activate a lifting pin on the locking bar. 
     Another aspect of the present invention is an electrically activated locking device for use with an article of furniture having a cabinet structure with at least one drawer that is moveable between an open position and a closed position, and a locking bar that is slideably mounted to in the cabinet for vertical movement. The electrically activated locking device is dimensioned to fit in the space existing between the interior surface of the cabinet and the drawer when the drawer is in a closed position. The locking device includes an electrically powered actuator, or motor, an electronic module for controlling power to the actuator, and a rotatable cam that is operatively connected to the actuator. Rotation of the cam moves a lifting pin carrier that moves a lifting pin mounted on the locking bar, which in turn moves one or more locking pins into either an unlocked or locked position. 
     In one embodiment of the locking device, when external power is supplied to the lock, the actuator (motor) is powered and the cam is rotated until the cam has reached its apex where the locking bar and lifting pin are at their highest travel points. When external power is removed from the lock, energy that is stored in one or more capacitors will discharge to again operate the motor. The motor will rotate the cam only a few degrees whereupon the locking bar will return to its normal (lowest) position. 
     As a result of the lock configuration, it can be so installed to cause a downward motion of the locking bar when power is supplied to the lock. 
     These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiments when considered in conjunction with the drawings. It should be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1   a  through  3  are illustrative of prior art mechanical locking systems; 
         FIGS. 4   a  and  4   b  are schematic illustrations of one embodiment of the present invention showing a cabinet with a plurality of drawers in the locked and unlocked positions; 
         FIG. 5  is an exploded perspective view of the gang-lock system of  FIGS. 4   a  and  4   b;    
         FIG. 6  is a detailed perspective view of the system of  FIG. 5  illustrating the lifting mechanism of the system; 
         FIG. 7  is a front view of the gear train with the lifting pin trolley in the bottom position; 
         FIG. 8  is a front view of the gear train with the lifting pin trolley in the top position; 
         FIG. 9  is a block diagram of the electronic module and interconnections; and 
         FIG. 10  is a simplified block diagram of the electronic module. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is directed to a electronically activated locking device that addresses the problems described above. 
     Turning first to  FIGS. 1   a  through  3 , known designs and configurations  20 ,  40  are shown for locking a plurality of drawers with a single locking bar. These are commonly referred to as “gang lock” system. These systems include a locking bar  22  or locking rod  48  that is vertically mounted to an inside surface of a cabinet, desk, or the like  21 ,  42  having a plurality of drawers  30 ,  44 ,  45 ,  46 . In the typical arrangement shown in  FIGS. 1   a  and  1   b , the locking bar  22  is movably mounted to the interior surface of the cabinet  21  by a plurality of guides  26  such that the locking bar  22  may slide vertically between a locked position ( FIG. 1   a ) and an unlocked position ( FIG. 1   b ). 
     The locking bar  22  further includes a plurality of locking, or arresting, pins  24 . As shown in  FIG. 2   a , a catch  32  is typically pivotally mounted on each drawer surface  30  which is adjacent to the locking bar  22 . As seen in  FIG. 2   b , when a drawer  30  is in a closed position, its associated arresting pin  24  engages the catch  32 , thereby preventing the drawer  30  from being withdrawn when the locking bar  22  and the associated arresting pin  24  are in the locked position. The catch  32  is biased by a spring  34  or by gravity toward a locking position. This arrangement permits a drawer  30  to be closed even when the locking bar  22  is in a locked position, since the catch  32  will pivot and slide over the arresting pin  24  as the drawer  30  is closed. As the drawer is fully closed, the catch  32  snaps downwardly behind the arresting pin  24 , thereby preventing the drawer  30  from being withdrawn until the locking bar  22  and corresponding arresting pin  24  are lowered to an unlocked position. As those skilled in the art will appreciate, the locking and unlocking scheme may be reversed so that the locking bar and arresting pin are lowered to locked position. 
     Alternatively, as shown in  FIG. 3 , a locking bar or rod  48  may include a plurality of arresting hooks  50 . In such an arrangement, each hook  50  engages a catch  54  on an associated drawer  44 ,  45 ,  46 . The hooks  50  may be flexible or pivot to permit a drawer to be closed when the locking bar  48  and hooks are in a locked position. Alternatively, the locking bar or rod  48  may include a spring which biases the rod toward a locked position (not shown). In this arrangement, if a drawer is closed when the locking bar is in a locked position, a tapered edge on the hook  50  and/or drawer urges the rod and hooks to move toward the unlocked position. Once the drawer is in a closed position, the spring returns the bar to its locked position, thereby engaging the arresting hooks with the catches to lock the plurality of drawers. 
     Conventional gang-lock systems are commonly actuated between locked and unlocked positions by a keyed mechanism  28 ,  43 , which operates to raise or lower the locking bar, generally through a lifting pin extending from the locking bar. Again, the locked position of the locking bars in such systems may be either up or down, depending on the placement of the arresting pins or hooks and their associates drawer catches. 
     The electrically activated locking system of the present invention is advantageous over known mechanical locking systems because it can be readily integrated into conventional gang-lock cabinet, desk, etc. designs, and with known electronic access systems, thus eliminating the need for mechanical keys to unlock the drawers. Such electronic access systems may provide access to drawers locked with the present invention by means of an electronic combination keypad, a magnetic card scanner, a radio frequency transponder, or the conventional electronic switch devices. One such electronic access system, for example, that can be used in conjunction with the present invention is the Dialock Furniture Terminal (DFT), available from Hafele GmbH &amp; Company. Such electronic access systems also may permit simultaneous operation of multiple electrically activated gang locking systems from a single remote electronic access control module. Another advantage of the electrically activated locking system of the present invention is that it operates with minimal electric power consumption or heat dissipation. 
     Turning now to  FIGS. 4   a  and  4   b , one aspect of the present invention is shown in simplified form.  FIG. 4   a  is illustrative of the present invention in a locked position and  FIG. 4   b  is illustrative of the present invention in an unlocked position. A rigid locking bar  16  is slidably mounted by a plurality of bar guides  18  to an interior surface  12  of a cabinet, desk, or the like  14  having a plurality of sliding drawers  102 . Vertical movement of the locking bar  16  is affected by the electrically activated device  19 , described in greater detail below, which is electrically interconnected to an external power source  100 . The device  19 , which is positioned over the locking bar  16 , raises and lowers the locking bar  16  between unlocked and locked positions by raising or lowering a lifting pin  15  on the locking bar  16 . A plurality of locking pins  17 , that are also positioned on the locking bar  16  at spaced positions corresponding to the positions of the individual drawers, cooperate with corresponding catches  104  on the drawers  102 . 
     As best seen in  FIG. 5 , the electrically activated device  19  includes a housing  9  which is mounted to an interior surface  14  of the cabinet by screws  8 . The housing  9  is mounted over a portion of the locking bar  16 . More particularly, the housing  9  for the device  19  has a thickness of less than about ½ inch so that it will fit within the ½ inch gap between the side of a drawer and interior of the cabinet that is typical in cabinet and drawer constructions. Thus, the typical cabinet does not have to be modified or enlarged for the device  19  of the present invention. As those skilled in the art will appreciate, the locking bar may be mounted in a recessed channel formed in the surface  14  of the cabinet, or the housing  9  may be formed to accommodate the clearance necessary when the locking bar is mounted directly to the interior surface  14 . The lifting pin  15  on the locking bar  16  extends through the device  19  and through the vertical aperture  13  in the housing  9 . A cover  9   a  likewise incorporates a vertical aperture  13  and is attached to the housing  9  by screws  52 . 
     Referring to  FIGS. 6 through 8 , operation of the electrically activated device  19  of the present invention is illustrated. As best seen in  FIG. 6 , the lifting pin  15  which is attached to the locking bar  16  is captured in a lifting pin carrier or trolley  51  through a clearance aperture  15   a  corresponding to the shape of the lifting pin  15 . The trolley  51  can slide vertically up and down a rail  59  that is integral to the housing  9 . The trolley  51  is forced upwardly by the counterclockwise rotation of a cam  31 . When the cam&#39;s surface  53   a  engages the arm of the trolley, the trolley, and thus the lifting pin  15 , are at their lowest point. When the cam&#39;s surface  53   b  engages the arm of the trolley, the trolley  51  and pin  15  are at their highest point. As will be appreciated, the device  19  of the present invention may be mounted upside down, in which case references to the direction of travel of the trolley  51  and pin  15  are reversed with reference to the ground. 
     The cam  53  is rotated by an electric motor  58  through gears  59 ,  57 ,  57   a ,  54   55 , and  55   a . One purpose of this gear train is to reduce the rotational speed of the cam. In one embodiment, the compact motor  58  is Model No. FF-N20PN, available from Mabuchi Motor Co., Ltd., which rotates at about 10,000 rpm at a nominal load. The cam  53 , however, must rotate at a substantially slower speed so that it can be stopped at a specified angle. Also, a speed-reducing gear train arrangement is needed since the motor alone provides inadequate torque to lift the weight of the locking bar  16  if the motor  58  were to drive the cam  53  directly. Thus, using a 1:N speed reduction provides a N:1 torque gain (less friction loss). In one embodiment, the gear train provides a 1:435 speed reduction. 
     The electrically activated device is configured to unlock, via the locking bar  16  and arresting pins  24 , the plurality of drawers in the cabinet when external power supplied to the device  19 . As described in greater detail below, control of the motor  58  is undertaken by an integral electronic module  90 . Referring to  FIG. 8 , it is assumed that the device begins in the locked position, which corresponds to the cam  53  being in contact with the trolley at point  53   a , and thus the trolley  51  being at its lowest point. When power is applied to the electronic module  90 , the motor  58  is started to drive the gear train and rotate the cam  53  in a counterclockwise direction. The increasing radius of the cam pushes the trolley  51  are upwardly. When the cam  53  reaches the point where its surface  53   b  is in contact with the trolley  51  arm, the motor is stopped automatically. 
     When external power is removed, the electronic module, via energy stored in at least one capacitor, powers the motor  58  which rotates the cam  53  slightly counterclockwise again. As shown in the Figures, due to the steep slope of the cam  53 , the trolley  51  drops to the lowest point after only a few degrees of rotation. The motor then is again stopped. The device  19  has now completed a complete cycle and returned to the locked position. 
     Turning to  FIG. 7 , the trolley  51  is biased against the cam  53  by means of a spring  61  which is housed within a channel in the trolley  51  and restrained by the housing  9  at one end. When the device  19  of the present invention is installed as shown in  FIGS. 5 through 8 , the weight of the locking bar  16  applies a downward force on the trolley  51  and thus against the cam  53 . As the motor  58  rotates the cam  53  counterclockwise from it lowest point to raise the locking bar  16 , the movement of the trolley  51  also compresses the spring  61 . Thus, in this orientation, the spring  61  serves to bias the trolley in a locked position. If it is desired to mount the device  19  upside down, the spring  61  serves to overcome the weight of the bar  16 , thus raising the bar. Without the spring  61 , the bar would remain at a low point in reference to the ground, preventing contact between the cam and the trolley to raise or lower the bar. 
     Referring to  FIG. 9 , the electronic module  90  is illustrated in greater detail. The electronic module  90  is mounted inside the housing  9  and is powered from an electronic access controller  100  as described above. Initial operation of the access controller  100  by a user supplies external power to the module  90  to unlock the drawers. When the user operates the access controller  100  to lock the drawers in the cabinet, external power is removed. In both cases, the electronic module  90  controls the power to the motor  58  to raise or lower the trolley  51 . 
     The position of the cam  53  and the trolley  51  is more precisely determined by a pair of limit switches  92  and  93 . Referring again to  FIG. 8 , at the end of the arm of the trolley  51  are a pin  51 c and a sleeve  51 d. The sleeve contacts the cam  53  and acts as a rotating bearing to reduce the friction between the cam  53  and the pin  51 c which is pushed up by the cam as the cam rotates in its clockwise direction. Limit switch  92  is an interrupter-type opto-sensor. The output of the sensor changes when an opaque material is moved in close proximity to the sensor so as to block the IR beam in the sensor. As seen in  FIG. 8 , the edge of the trolley  51  obstructs the IR beam when the trolley is in its highest position. Thus the sensor  92 , which is interconnected to the electronic module  90 , communicates to the module  90  when the trolley has reached this upper position. The module  90  then immediately turns off power to the motor  58 , thus stopping rotation of the cam. To further ensure that the cam is stopped and that the momentum of the inertia in the cam  53  is dissipated quickly, the electronic module  90  incorporates an electronic brake by applying a low resistance across the motor  58  in a fashion known in the art. 
     As will also be appreciated, tolerances in manufacturing and the need for clearances between the trolley  51  and the rail on which it travels, the precise position of the trolley  51  and cam  53  may not be sufficiently detected by sensor  92 . For example, if the top of the trolley  51  is detected too early, the cam may stop short of its highest point. Subsequent operation of the motor  58  and rotation of the cam  53  may be insufficient to move the cam beyond surface  53 b. The result would be that the locking bar  16  would be prevented from moving downwardly to lock the drawers. Likewise, if the cam  53  stops too late, the trolley  51  will return to its lowest point rather than at its highest point needed to unlock the drawers. For this reason, sensor  93  provides a fine position signal, complementing the coarse information transmitted by sensor  92 . Sensor  93  straddles gear  57 , its IR beam being blocked by the gear. A slot  57   e  in the gear, however, allows the IR beam to pass through the gear  57  when the slot  57   e  is aligned with the sensor  93 . This arrangement permits the position of the gear  57  to be determined with a 2 to 3 degrees of rotation through the sensor  93 . With a gear step-down between gears  57  and  54  of about 1:7 in one embodiment, the 2-3 degrees of tolerance in the position of gear  57  translates to less than a 1 degree tolerance on gear  54 , and thus the cam  53 . In operation, the electronic module  90  will stop the motor  58  only when it receives a signal from sensor  93  that corresponds to an unblocked IR beam, which will have been preceded by a signal from sensor  92  corresponding to a blocked IR beam. 
     As previously described, the electronic module  90  must power the motor  58  when external power to the module  90  has been removed. To move from an unlocked to a locked position, the motor is required to move the cam  53  only a few degrees to move the trolley from point  53   b  to point  53   a . In one embodiment, the required rotation is less than 5 degrees. This corresponds to a time period of only about 0.1 seconds that the motor must be powered. The power to operate the motor and the module  90  while external power has been removed is obtained from at least one large value capacitor  91 , shown in  FIG. 9 . The capacitor  91  is charged when external power is supplied to the module  90 , and discharges when external power is removed. In one embodiment, capacitors with a combined value of 3,000 microfarads were found to provide adequate power to rotate the cam  53  to its low starting point. 
       FIG. 10  provides a simplified block diagram of the electronic module  90 . External power (voltage) is supplied through wires  110  and  111  from the access controller (not shown). The incoming voltage is provided to capacitor  114  through a diode  113 . The voltage on capacitor  114  powers a microprocessor  118 . The microprocessor  118  checks the state of the inputs from limit switches/sensors  92  and  93 . If the input indicates that the cam  53  is not in the top position, the microprocessor powers an electronic switch  112  through circuit  117  and connects the motor  58  to the supply voltage  110 ,  111 . 
     When limit switches  92  and  93  indicate that the cam  53  has reached its peak position, switch  112  is returned to its middle position, thus disconnecting the power from the motor. Immediately afterwards, switch  115  is closed through circuit  116 . The closed switch  115  acts as a short across the motor  58 , which acts to brake the motor. The cam  53  then comes to a stop at its upper position and the locking bar  16  is in its unlocked position. Switch  115  is then released to minimize the power consumption of the device  119  so that it remains in the unlocked position as long as external power is connected. 
     When external power is removed from the electronic module  90 , the microprocessor  118  detects the loss of power through circuit  119 . The microprocessor remains powered by capacitor  114  which is prevented from being discharged into input  110 ,  111  through diode  113 . The microprocessor activates switch  112  so that motor  58  is connected to capacitor  114 . The motor discharges the capacitor as it rotates and returns the cam  53  to its starting low point. When the capacitor is discharged, the microprocessor  118  powers down and the device  119  becomes dormant until external power is again supplied to the electronic module  90 . 
     In the embodiments described above, drawers are locked when the locking bar  16  and arresting pins  17  are in a fully downward position, as shown in  FIG. 4 . Accordingly, the arresting pins  15  engage catches  104  on the drawers  102  when the drawers are fully closed, and lock the drawers when external power is removed from the electronic module  90 . Conversely, drawers are unlocked when external power is supplied to the electronic module  90  and the arresting pins  17  are in a fully upward position. This “fail locked” arrangement ensures that the drawers will be locked if power is inadvertently lost. Alternatively, the locking system and device  19  described above may be installed as a “fail unlocked” system. This can be achieved by installing the device  19  upside down so that its cover  9   a  is in contact with the interior surface  14  of the cabinet. In this position, applying power to the electronic module  90  will force the trolley  51  downwardly, thus locking the cabinet. When external power is removed, the trolley  51  will rise to its highest position with respect to the ground, and the cabinet will become unlocked. 
     The locking system described herein can be readily combined with known drawer interlock systems which prevent more than one drawer in a stack of drawers from being withdrawn when the drawers are unlocked. Further, multiple gang locks can be included in a single cabinet, desk, or the like which include more than one stack of drawers. Each of the multiple gang locks may be operable from a single electronic access module, or each may be separately controlled. 
     Although the present invention has been described by reference to a preferred embodiment, it is to be understood that modifications and variations may be utilized without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the appended claims and their equivalents.

Technology Classification (CPC): 4