Patent Abstract:
A keyless locking system for a cart includes a lock mechanism with a drive mechanism in the form of a solenoid that is electrically coupled to an integrated circuit and a long lasting power supply. In an unenergized state, an armature of the solenoid prevents operation of the lock mechanism to release drawers supported by the cart. Upon entry of a correct access code via a keypad associated with the integrated circuit, current is supplied to the solenoid to permit operation of the lock mechanism and thereby release the drawers. Advantageously, the lock mechanism only draws from the power supply to temporarily release the solenoid only thereby requiring minimal power and significantly reducing the re-charging, replacement and maintenance requirements for the power supply and the down time for the cart.

Full Description:
FIELD OF THE INVENTION 
     This invention pertains to carts with lockable drawers and more particularly to a keyless locking system for medical carts. 
     BACKGROUND OF THE INVENTION 
     Carts with lockable drawers are used for many applications. For example, a medical cart is used to administer medication to patients in hospitals or other care facilities. A typical medical cart has casters located at the bottom of the cart to permit easy movement of the cart by attending nurses to various patients&#39; rooms. The cart also has one or more drawers for storing patients&#39; medicines. Typically, each drawer is dedicated to storing the medication for an individual patient. Because the cart is used to store medications for several patients and is moveable from room to room, controlling access to the contents of the cart to prevent theft or misuse of medication and thereby protect the patients is important. One such medical cart, as described above, is disclosed in U.S. Pat. No. 5,743,607, to Teufel et al., which patent is commonly held by the assignee of the present invention and hereby incorporated by reference in its entirety. 
     Controlling access to medical carts in the past involved the use of manual key locks or complex electromechanical devices which permit a drawer locking tab to lock and unlock all of the drawers of the medical cart. U.S. Pat. No. 5,743,607, for example, discloses the use of a keypad with a system of locking tabs to lock the drawers of a cart. These prior art methods of locking carts or controlling access to medical carts, while being effective, do have certain limitations. For example, the keys for a manually locked cart can be lost or misappropriated by unauthorized persons. In the event that a key is lost and controlled access to the cart has been compromised, the changing of a keyed lock requires considerable time and expense during which time the cart cannot be used. In the case of electromechanical locks, prior art locking systems generally consume a considerable amount of power, requiring the systems to be charged daily for proper operation of the electromechanical locking mechanism. Furthermore, service, maintenance, and manufacture of prior art carts may be generally expensive and time consuming due to the complexity of the locking mechanisms. 
     Accordingly, there is a need for a simple, keyless cart locking system having low power consumption requirements and which is easy to manufacture and maintain, particularly for medical carts having lockable drawers. 
     SUMMARY OF THE INVENTION 
     This invention, in one embodiment, is a locking system for a cart with lockable drawers, such as a medical cart, and in another embodiment the invention is a cart with such a locking system. The locking system includes an integrated circuit which controls the actuation of a drive mechanism in the form of a solenoid to permit the operation by a user of a handle for release of the drawers. Advantageously, power to the solenoid is only provided to disengage the lock mechanism when a correct access code has been entered via a keypad or other user input device. Previously, locking mechanisms for carts of this type required a significant amount of power for actuation of the drive and lock mechanisms. Since this invention only briefly consumes power to disengage the drive mechanism, the system has very low power consumption requirements. The simple design of the locking mechanism also makes it easy to operate, manufacture and service. 
     The invention includes a lock mechanism having a handle which is manipulated by a user to disengage a locking tab of the medical cart. The lock mechanism includes a housing which supports the handle and a spring-loaded cam to disengage the locking tab. The lock mechanism further includes a drive mechanism in the form of a solenoid having a movable armature that positively engages the handle portion of the lock mechanism to prevent the lock mechanism from disengaging the locking tab when the solenoid is in an unenergized, or “no load” state. The solenoid is connected to an integrated circuit having a keypad to accept user input such as an access code, and also to a power supply which provides power to the solenoid when the correct access code has been entered into the keypad. In a preferred embodiment, the power supply includes four D cell batteries to energize the solenoid on demand when the cart is to be unlocked. 
     The locking system of this invention preferably includes a manual override device to gain access to the drawers of the cart in the event of a loss of power or in the event the access code has been lost. The manual override device includes a flexible yoke which is connected to the armature of the solenoid. The yoke is actuated to disengage the armature from the handle by a conventional key lock coupled to and remotely located from the lock mechanism. In a preferred embodiment, the yoke is coupled to the remote key lock by a cable. 
     In another aspect of the invention, the housing of the lock mechanism has a clam-shell design, with hinges that facilitate easy assembly. The lock mechanism also includes a rod and handle assembly for an operator to disengage the drawer locking tabs of the cart. In this regard, the rod has a cam at one end which protrudes from the housing to move the locking tabs from a locked configuration to an unlocked configuration. The handle is inserted into an end of the housing opposite from the cam and is coupled to the rod. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate presently preferred embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention. 
     FIG. 1 is a perspective view of a medical cart including a locking system that incorporates features of the present invention; 
     FIG. 2 is a partially broken perspective view showing detail of the locking system and cart of the encircled area  2  of FIG. 1; 
     FIG. 3 is a side elevational view of the lock mechanism of FIG. 2 with the outer housing shown in phantom; 
     FIG. 4 is an exploded view of the lock mechanism of FIG. 3; 
     FIG. 5 is a view similar to FIG. 3 showing the handle in the first, locked, position; 
     FIG. 6 is a view similar to FIG. 3 showing the handle in the second, unlocked, position; 
     FIG. 7 is partial side view of the lock mechanism of FIG. 3, showing movement of the handle upon initial assembly; 
     FIG. 8 is a section view of the lock mechanism of FIG. 7 taken along line  8 — 8 ; 
     FIG. 9 is a partial side view of the lock mechanism of FIG. 7 showing further movement of the handle upon initial assembly; and 
     FIG. 10 is a flow chart depicting the steps of a method of securing a cart using a keyless locking system of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIGS. 1-2, a medical cart  10  is shown including a locking system  11  incorporating features of the present invention. The cart  10  has an enclosure  12  which houses a number of drawers  14 , mounted on slides  15 , and a frame structure  16  including a drawer locking tab  18  which can be used to lock all of the drawers  14  in a closed position. The drawers  14  may be used to store medicine for individual patients and the cart  10  is provided with casters  20  to enable the cart  10  to be easily moved within a facility so that the cart  10  may be taken to individual patient rooms for administration of medicine. 
     As shown in FIGS. 2 and 3, the locking system  11  of the present invention includes a lock mechanism  22  which is selectively urged into contact with the drawer locking tab  18  of the cart  10 , to thereby secure or release the drawers  14  of the cart  10 . The locking system  11  includes a drive mechanism which is preferably a solenoid  24  having an armature  26  which is engageable with the lock mechanism  22  for operation from a locked configuration to an unlocked configuration, as will be described in further detail. While the solenoid is preferable, the drive mechanism  24  may alternatively be a motor, magnet or another mechanism known in the art. 
     The locking system  11  further includes a power supply  28  (shown in dashed lines in FIG. 1) and an integrated circuit  30  electrically coupled to the solenoid  24  by wires  31 . The integrated circuit  30  is coupled to a keypad  32  located within the enclosure  12  by which an operator may enter an access code to the integrated circuit  30 . If the access code corresponds to a stored code value, the integrated circuit  30  controls the flow of current to the solenoid  24  to disengage the armature  26  from the lock mechanism  22  and permit operation from the locked configuration to the unlocked configuration. 
     In one embodiment of this invention, the keyless locking system  11  further includes a manual override device  34  which is utilized in the event of a power failure, or alternatively in the event that the access code has been lost. The manual override device  34  has a yoke  36  which is coupled to the armature  26  of the solenoid  24  whereby the yoke  36  can be manually actuated to disengage the armature  26  from the lock mechanism  22 . In one embodiment, the yoke  36  is coupled to a conventional key-operated lock  37  (see FIG. 1) which is remotely located from the lock mechanism. The key-operated lock  37  is connected to the yoke  36  by a flexible cable  38 , having a return spring  39  (see FIG.  4 ), such that it can be manipulated using a key (not shown) inserted into the lock  37 . The yoke  36  is configured to accommodate tolerances between the yoke  36 , the cable  38 , and the armature  26  so that the manual override device  34  will operate efficiently. In the exemplary embodiment shown in FIGS. 3 and 6, the yoke  36  includes a pair of arcuate formations  40  which act as a living hinge to accommodate the tolerances. 
     Referring to FIGS. 3 and 4, the lock mechanism  22  of one embodiment of this invention includes a housing  42  which is fastened to the frame  16  of the medical cart  10  using bolts or other fasteners (not shown) projecting through holes  44 . The housing  42  includes two opposing halves  46 ,  48  having mating tabs  50  and slots  52  that fit together to form a hinge, whereby the housing  42  is assembled in a clamshell fashion and secured by fasteners (not shown) installed through holes  53 . The housing  42  defines first and second opposing apertures  54 ,  56 , and a central cavity  58  disposed between the apertures  54 ,  56 . A third aperture  60  in the housing  42  intersects the central cavity  58  between the first and second apertures  54 ,  56 . The lock mechanism  22  also includes a handle  62  and a rod  64  coupled together and slidably disposed within the central cavity  58  of the housing  42 . A spring  66  is disposed between the rod  64  and the handle  62  to axially bias the rod  64  and handle  62  toward an unlocked configuration of the lock mechanism  22 . The spring  66  also rotationally biases the rod  64  and handle  62  toward a locked configuration of the lock mechanism  22 . 
     A first end  68  of the handle  62  has a knob  70  which extends from the second aperture  56  of the housing  42  so that the handle  62  may be manipulated by a user. A second end  72  of the handle  62  is rotatably coupled to a second end  74  of the rod  64 . A first end  76  of the rod extends from the first aperture  54  of the housing  42 , and has a cam surface  78  which operatively engages the locking tab  18  such that latches  77  on the locking tab  18  may capture or release tines  79  fixed to the drawers  14 . Thus, the handle  62  may be rotatably and slidably manipulated by the knob  70  to move within the housing  42  to a first position, corresponding to a locked configuration in which the cam  78  engages the drawer locking tab  18  to capture tines  79  with latches  77  and thereby secure the drawers  14 . FIG. 3 depicts the handle  62  in the first, locked position. The handle  62  may further be moved to a second position, corresponding to an unlocked configuration (FIG.  6 ), wherein the cam  78  disengages the drawer locking tab  18  to release tines  79  from latches  77  and thereby unlock the drawers  14 . 
     Referring to FIGS. 3-6, the solenoid  24  is fixed to the housing  42  by a bracket  80 . A recess  82  is formed into a portion of the handle  62  contained within the housing  42 . When the handle  62  is in the first position, corresponding to a locked configuration, the armature  26  of the solenoid  24  is urged into positive contact with the recess  82  of the handle  62  through the third aperture  60  by a biasing spring  84  on the solenoid, as depicted in FIGS. 3 and 5. In this configuration, the armature  26  prevents manipulation of the handle  62  from the locked position. When the solenoid  24  has been energized, or the manual override mechanism  34  has been actuated, the armature  26  is retracted from the handle  62  so that the handle  62  may be freely rotated and slid within the housing  42  from the first position to the second or unlocked position (FIG.  6 ). 
     In another exemplary embodiment, shown most clearly in FIGS. 4 and 8, the housing  42  of the lock mechanism has a groove  86  formed into the corresponding portions of the opposing housing pieces  46 ,  48 . The groove  86  defines a channel proximate the second aperture  56  through which the handle  62  protrudes from the housing  42 . A boss  88  on the handle  62  is seated within the groove  86  upon assembly of the lock mechanism  22 . As shown in FIG. 7, the groove  86  is in communication with a slot  90  formed into one portion of the housing piece  48 . The slot  90  captures the boss  88  on the handle  62  to constrain the translational and rotational movement of the handle  62  from the first position to the second position. A tab  92  between the groove  86  and the slot  90  acts as a one-way stop to permit the boss  88  to pass from the groove  86  to the slot  90  during initial assembly of the lock mechanism  22  and to prevent the boss  88  from moving back into the groove  86  once the lock mechanism  22  has been assembled. The groove  86  defines a path along which the handle  62  may be manipulated upon initial assembly to preload the spring  66  disposed between the rod  64  and the handle  62 . The spring  66  biases the handle  62  axially toward the second position. In a preferred embodiment, the spring  66  is preloaded both torsionally and axially so that the handle  62  is biased rotationally toward the first, locked position and axially toward the second, unlocked position. 
     With reference to FIGS. 7-9, the torsional and axial preload of spring  66  upon initial assembly of the lock mechanism  22  will be further explained. Referring to FIG. 8, handle  62  is initial installed into housing  42  with boss  88  resting in groove  86  in the orientation A. Spring  66  is torsionally preloaded by rotating the handle  62  in the direction of arrows  94 , through orientation B to the stop at orientation C. At orientation C, handle  62  is urged axially toward tab  92  in the direction of arrow  96  as depicted by the phantom lines in FIG.  7 . When the boss  88  engages tab  92 , handle  62  is rotated in the direction of arrow  98  so that boss  88  enters slot  90 , as depicted in FIG.  9 . When boss  88  enters slot  90 , tab  92  prevents boss  88  from reentering groove  86 , such that boss  88  is constrained to move within slot  90 . The extreme locations of boss  88  within slot  90  correspond to the first and second positions of handle  62 , as depicted in FIGS. 3 and 6. 
     The integrated circuit  30  operatively coupled to the solenoid  24  by wires  31  acts as a switch to control the flow of current from the power source  28  to the solenoid  24 . A keypad  32  associated with the integrated circuit  30  accepts an access code input by a user and compares the entered access code to a stored value. If the stored value does not correspond to the entered access code, the switch remains open and the integrated circuit  30  does not provide power to the solenoid  24 . When a correct access code has been entered, the switch is closed to send current to the solenoid  24  for a specified time interval. During the specified time interval, the solenoid  24  is energized to move the armature  26  away from the recess  82  in the handle  62 . The knob  70  then may be manipulated by a user to move the handle  62  from the locked first position to the unlocked second position and thereby release the drawer locking tab  18  of the cart  10 . Advantageously, according to this invention power from the power source  28  is not utilized to manipulate the handle  62  from the locked position. Thereafter, the drawers  14  of the cart  10  may be freely opened and closed until the handle  62  has been moved from the unlocked second position to the locked first position. In the locked position, the handle  62  engages the cam  78  against the drawer locking tab  18  to secure the drawers  14  of the medical cart  10 . If no manipulation of the handle  62  occurs during the specified time interval, the current is discontinued to the solenoid  24  by the integrated circuit  30  and the armature  26  moves back into contact with the recess  82  in the handle  62  to prevent movement of the handle  62  from the locked to the unlocked configuration. 
     FIG. 10 shows a flow chart describing the steps involved in securing the contents of a medical cart having drawers, a drawer locking tab adapted to retain the drawers, and a keyless locking system according to one preferred embodiment of the present invention. The method includes the steps of receiving an access code into an input device  110 , comparing the entered access code with a stored value  112 , and supplying current from a power source to a solenoid when the entered access code corresponds to the stored value  114  so that an armature of the solenoid disengages the lock mechanism to permit the handle to be manipulated and thereby disengage the locking tab of the cart. 
     While the present invention has been illustrated by the description of an embodiment thereof, and while the embodiment has been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method and illustrative examples shown and described. For example, the keyless locking system disclosed herein may be operated using a remote signaling device, instead of a keypad, to cause the integrated circuit to energize the solenoid and permit manipulation of the handle. Accordingly, departures may be made from such details without departing from the scope or spirit of applicant&#39;s general inventive concept.

Technology Classification (CPC): 4