Patent Document

This Application claims the benefit of U.S. Provisional Application No. 62/044,780, filed Sep. 2, 2014. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a power control circuit assembly for use with an electric door latch mechanism. More specifically, the invention relates to an improved power control circuit assembly affording improved power efficiencies when powering the electric door latch mechanism. Still more specifically, the invention relates to an improved power control circuit assembly having an energy storage device such as a rechargeable battery which powers the door latch mechanism with minimal use of grid power. 
     BACKGROUND OF THE INVENTION 
     In the prior art, solenoids are generally used as the driver to lock or unlock electromechanical door latches or strikes. The solenoid is spring biased to either a default locked or unlocked state, depending on the intended application of the lock. When power is applied to the solenoid, the solenoid is powered away from the default state to bias a return spring. The solenoid will maintain the bias as long as power is supplied to the solenoid. Once power has been intentionally removed, or otherwise, such as through a power outage from the grid or as a result of a fire, the solenoid returns to its default locked or unlocked state. 
     In a fail-safe lock system, power is supplied to the solenoid to lock the door latch mechanism. With power removed, a return spring moves the latching mechanism to an unlocked state. Thus, as long as the latch remains locked, power has to be supplied to the solenoid to maintain stored energy in the return spring. Typically, this power requirement equates to about 0.5 A to hold the solenoid plunger in the latch-locked state. This hold power is in addition to the approximately 1.0 A needed to initially pull in the plunger upon energizing of the solenoid. 
     In a fail-secure system, the reverse is true. With power removed, the return spring moves the latching mechanism to a locked state. Thus, as long as the latch remains unlocked, power has to be supplied to the solenoid to maintain stored energy in the return spring. Again, about 0.5 A is required to hold the solenoid plunger in the latch-locked state (with about a required 1 A to initially pull in the plunger). 
     A system designed to overcome the shortcomings of solenoid lock systems is disclosed in the prior art disclosure of Sargent Manufacturing Company (WO2014/028332—herein referred to as “the &#39;332 publication”), the entirety of which is incorporated herein by reference. As disclosed in the &#39;332 publication, the solenoid used to drive the door latch mechanism is swapped out for a small DC motor that moves a latching plate. This change, in combination with the motor aligning with and engaging an auger/spring arrangement, reduced standby power consumption of the driver from about 0.5 A to about 15 mA. 
     Nonetheless, there still exists a need for a compact power control circuit assembly, offering further improved power efficiency for use with electric door lock systems. The present invention fills these and other needs. 
     SUMMARY OF THE INVENTION 
     The present invention has found that the improved system efficiencies may be generated by coupling a small DC motor to a system that utilizes a rechargeable energy storage device such as a battery to power the system most of the time while using grid AC only to charge the energy storage device, as needed, and to power the system when the energy storage device fails. The grid AC may also provide a small amount of background power to maintain a microprocessor (and to provide for fire alarm and access control input monitoring). While the present invention is directed toward a system which utilizes a small DC motor to drive a door latch mechanism, it should be understood by those skilled in the art that the present invention may also be adapted to a solenoid driver which would also exhibit measurable efficiency improvements and such coupling should be considered within the scope of the present invention. 
     The present invention is directed to a power control circuit assembly for an electric door latch mechanism. The power control circuit assembly comprises a load control circuit module configured to distribute a DC operating voltage to power an electric door latch mechanism and its associated access control device. An energy storage device is coupled to the load control circuit module and is configured to deliver a DC voltage to the load control circuit module wherein the DC voltage of the energy storage device supplies the DC operating voltage. A rectifier is configured to receive an input AC voltage and convert the input AC voltage to an input DC voltage. The input DC voltage is adapted to deliver a recharge voltage to the energy storage device. An energy storage device voltage detection module is configured to detect when DC voltage from the energy storage device drops below a threshold value. 
     In a further aspect of the present invention, when the detected DC energy storage device voltage has a first magnitude, the energy storage device is operable to deliver the DC voltage from the energy storage device to the load control circuit module. When the detected DC voltage from the energy storage device has a second magnitude indicative of a failure of the energy storage device, the input DC voltage, supplied by grid AC, supplies the DC operating voltage. 
     In still a further aspect of the present invention, the power control circuit assembly includes a printed circuit board (PCB), wherein the load control circuit module, the rectifier, the load detection module and the in-line controller are printed into or mounted onto the PCB. 
     In a further aspect of the present invention, the power control circuit assembly is configured to reside within a double gang electrical box. 
     In yet a further aspect of the present invention, the electric door latch mechanism includes a DC motor or a solenoid powered by the DC operating voltage. 
     In still a further aspect of the present invention, the power control circuit assembly includes a microprocessor configured to monitor the energy storage device recharge voltage, the DC voltage supplied by the energy storage device and the DC operating voltage to determine the condition of the energy storage device and its ability to hold a charge, and whether the DC voltage from the energy storage device is supplying the DC operating voltage. The microprocessor initiates a visual and/or auditory alert when the energy storage device is unable to provide or sustain a satisfactory voltage level to the load control circuit, indicating that input DC voltage is instead supplying the DC operating voltage. 
     In a further aspect of the present invention, the power control circuit assembly includes a fire alarm interface in communication with the microprocessor wherein the electric door latch mechanism is positioned in an unlocked state when the fire alarm interface is triggered. The power control circuit assembly may further include a fire alarm interface latch wherein the electric door latch mechanism is held in the unlocked state after the fire alarm interface has been triggered until the fire alarm interface latch has been manually disabled. 
     In a further aspect of the present invention, the power control circuit assembly comprises one or more switches in communication with the microprocessor. The one or more switches are operable to select a respective normally open (NO) or normally closed (NC) access control device input configuration; a NO or NC fire alarm interface input configuration; a fail-safe or fail secure door latch configuration; or a disabled or enabled fire alarm interface latch configuration. Each of the one or more switches may be a dipswitch or a jumper. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective environmental view of a power control circuit assembly for an electric door lock in accordance with an aspect of the present invention; 
         FIG. 2  is a side environmental view of the power control circuit assembly seen in  FIG. 1 ; 
         FIG. 3  is an exploded view of the power control circuit assembly seen in  FIGS. 1 and 2 ; 
         FIG. 4  is a schematic view of a printed circuit board used with the power control circuit assembly seen in  FIGS. 1-3 ; 
         FIG. 5  is a schematic of an exemplary power control pathway of the power control circuit assembly seen in  FIGS. 1-3 ; and 
         FIG. 6  is a process flow diagram operating the power control circuit assembly seen in  FIGS. 1-5 . 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate currently preferred embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In describing the preferred embodiment of the present invention, reference will be made herein to  FIGS. 1-6  of the drawings in which like numerals refer to like features of the invention. The term “electric door latch mechanism” as used herein means any electrically actuated door or gate locking device including but not limited to an electric strike, an electric latch or an electromagnetic lock. 
     Referring to  FIGS. 1-3 , a power control circuit assembly in accordance with an embodiment of the present invention is generally indicated by reference numeral  10 . Unlike a comparatively large power control box typically located above ceiling panels, as known in the prior art, power control circuit assembly  10  is configured to reside within a standard-in-the-industry double gang electrical box  12  that is sized to host two electrical components (such as a standard electrical switch or receptacle), made possible by the compact design of the load control circuitry module and rechargeable energy storage device. Box  12  may be secured to an interior framing member  14  between opposing panels of drywall  16 ,  18 , and conveniently disposed adjacent a door assembly and latching mechanism instead of in a remote location such as above ceiling panels as known in the prior art. An assembly cap  20  is secured to box  12  by a pair of cap screws  22 . To improve aesthetics of the installed assembly, box  12  may include a cover plate  24  configured to overlap any gaps between the edge of the hole cut in drywall panel  16  and the outer surface of box  12 . A rechargeable energy storage device  26 , such as for example a rechargeable battery, is housed within electrical box  12  while a printed circuit board (PCB)  28  and associated components (see  FIG. 4 ) is housed within a case  30  which is secured within box  12  and assembly cap  20  via case screws  32 . 
     As seen in  FIG. 4 , and with additional reference to  FIG. 5 , PCB  28  includes AC inputs  34  configured to receive grid input AC voltage  36 . Grid input AC voltage  36  is converted by rectifier  38  to input DC voltage  40 . As an aside, it should be noted that an alternative input DC voltage  41  may be provided using alternative energy sources  43 , such as solar or wind energy. Input DC voltage  40  is routed through load control circuit module  42  to supply a charge voltage  44  to energy storage device  26 . Energy storage device  26  then routes a DC voltage  46  to load control circuit module  42  where it is conditioned by load control circuit module  42  to be output as one or more DC operating voltages, such as DC output voltages  48 ,  50 . By way of example, DC output voltage  48  may be used to power an access control device (not shown), such as but not limited to a card reader, keypad or biometric sensor, while DC output voltage  50  may power an electric door latch mechanism (not shown), such as that described within the &#39;332 publication discussed above. 
     Distribution of DC output voltage  48 ,  50  may be directed by a microprocessor (MP)  52  powered via a microprocessor voltage  66  supplied by energy storage device  26  at terminal  53  on PCB  28 . For instance, DC output voltage  50  may be directed to the electric door latch mechanism after MP  52  receives an authorized control signal entered via the access control device and transmitted to MP  52  via access control input  54 . MP  52  may also provide supervisory pathways  58 ,  60  which monitor DC output voltages  48 ,  50  to ensure that load control circuit module  42  is operating properly and outputting the requisite DC output voltage  48 ,  50 . The status of DC output voltages  48 ,  50  may be indicated visually such as through LED&#39;s  49 ,  51 , respectively. MP  52  may also monitor energy storage device operation via supervisory pathways  62 ,  64 . Pathway  62  interrogates the magnitude of energy storage device charge voltage  44  directed from load control circuit module  42  to energy storage device  26  while pathway  64  monitors the DC voltage being supplied by energy storage device  26  to load control circuit module  42 . Should the energy storage device need frequent recharging or should the energy storage device fail to provide the requisite DC voltage, MP  52  will issue an alert indicating a need for replacement of the rechargeable energy storage device. The alert may be a visual alert (such as the powering of an LED) and/or may be an audible alert (such as the powering of a buzzer  55  to emit a chirp or other noise). 
     In the event of a failure of the rechargeable energy storage device (i.e., MP  52  determines through measurements received via supervisory paths  62  and  64  that the energy storage device needs frequent recharging or the energy storage device fails to provide the requisite DC voltage), DC output voltages  48 ,  50  may be supplied directly via input DC voltage  40 . To that end, PCB  28  includes an energy storage device voltage detection module  65  that detects whether DC voltage  46  supplied by the energy storage device drops below a threshold voltage via the supervisory paths and, when it does, sends a signal to load control circuit module  42 , via line  67 , to supply DC voltage  40  directly to DC output voltages  48 ,  50 , to satisfy the increased voltage demand caused by the failed energy storage device. 
     It should be noted that the DC voltage supplied by the energy storage device is monitored by MP  52 , even if the energy storage device is no longer operative. In this manner, once a new energy storage device has replaced a worn out one, if the replacement energy storage device&#39;s voltage level is below a threshold voltage (indicating that the replacement energy storage device itself needs recharging), the input DC voltage will continue to power DC output voltages  48 ,  50  until the new energy storage device has been charged and can then provide the necessary DC voltage to power the electric door lock. 
     PCB  28  may further include fire alarm input  78  wherein input  78  is configured to receive a fire alarm activation signal from a remote fire alarm system. In this manner, DC output voltage  50  used to power the electric door latch mechanism may be disabled during an emergency, thereby placing the door latch mechanism in a preselected and desired state. 
     To facilitate power control circuit assembly  10  functionality, PCB  28  may include one or more switches in communication with MP  52 , such as dipswitch  80 . While described as a dipswitch, switch  80  may be any suitable electrical connection, for instance, a jumper block. Dipswitch  80  may include switches controlling various functionalities, such as an access control switch  80   a  to selectively configure the access control input  54  as normally open (NO) or normally closed (NC); a fire alarm switch  80   b  to selectively configure fire alarm input  78  as NO or NC; a lock behavior switch  80   c  to selectively configure the electromechanical door latch mechanism to be fail secure or fail safe; and a latching switch  80   d  to selectively activate fire alarm latching. Fire alarm latching is required by law in certain jurisdiction, such as Canada, wherein once a fire alarm input  78  is activated by the fire alarm system and the door lock mechanisms have been placed within their unlocked default state, the fire alarm latch prevents repowering of the electromechanical door latch mechanism until the fire alarm latch is manually disabled by resetting the switch. For those jurisdictions not requiring fire alarm latching, MP  52  automatically resets the lock mechanisms once the fire alarm has been disabled. 
       FIG. 6  shows a process flow diagram for initializing and operating power control circuit assembly  10  (see  FIGS. 1-5 ). In a first step  100 , upon initialization of the circuit, (energy storage device  26  is depleted) in-line controller  74  is active such that input DC voltage  40  is operating to power DC output voltages  48 ,  50 . In step  102 , MP  52  interrogates whether energy storage device  26  is present within circuit  10 . If energy storage device  26  is present, in step  104 , MP  52  places the in-line controller  74  in standby mode and interrogates energy storage device voltage to determine whether the energy storage device has at least 10 V of charge (step  106 ). If the energy storage device has less than 10 V of charge, MP  52  interrogates its internal memory to determine the last time energy storage device  26  was recharged with charge voltage  44  (step  108 ). If the last charging of energy storage device  26  occurred longer ago than a selected length of time (i.e. more than 2 hours), energy storage device  26  is charged with charge voltage  44  (step  110 ). However, if the last charging occurred more frequently than the selected length of time, MP  52  will interpret the instant lack of energy storage device voltage as indicative of an energy storage device failure needing replacement and will initialize an alarm signal  55  such as for example, a buzzer to emit a chirp (step  112 ). 
     Alternatively, if energy storage device  26  holds a voltage greater than 10 V (or if energy storage device  26  is not present (step  102 ), MP  52  determines whether fire alarm input  78  has been activated (step  114 ). If fire alarm input  78  has not been activated, MP  52  determines whether access control input  54  has been activated with an authorized access code (step  116 ). If an authorized access code has been entered (step  118 ), MP  52  authorizes load control circuit module  42  to supply DC output voltage  50  to the electromechanical door latch mechanism thereby changing the state of the electric door lock (step  120 ). If the access control input  54  has not been activated or after the state of the lock has been changed after authorization, MP  52  reverts to step  104  wherein the in-line controller is in standby mode and the charge of the energy storage device is interrogated. 
     If MP  52  determines that fire alarm input  78  has been activated (step  114 ), MP  52  will then determine, in step  122 , whether active fire alarm latching has been selected (such as by way of dipswitch  80   d , discussed above). If fire alarm latching is active, step  124  has MP  52  changing the status of DC output voltage  50  (i.e. placing it in the unpowered default state) and energizing LED  82  to indicate the active fire alarm input  78 . DC output voltage  50  and LED  82  will remain in these conditions until dipswitch  80   d  is manually reset. To manually reset the fire alarm latch, cap  20  is removed to expose dipswitch  80   d  wherein a small tool may be used to reset the switch. Alternatively, cap  20  may be configured to include small access holes wherein a small tool may be inserted through cap  20  to access the one or more switches  80   a - 80   d  either directly or indirectly through connecting buttons  80   a - 80   d . If fire alarm latching is inactive, MP  52  will change the status of DC output voltage  50  (i.e. place it in the unpowered default state) and energize LED  82  to indicate the active fire alarm input  78  (step  126 ). MP  52  will then query whether the fire alarm input is still activated (step  128 ), wherein if the input  78  is still active MP  52  reverts to step  122 . If fire alarm input  78  is no longer active, MP  52  returns power control circuit assembly  10  to normal operation (step  130 ). 
     From the above description, it should be evident to those skilled in the art that the power control circuit assembly  10  of the present invention utilized DC voltage supplied by energy storage device  26  to power the associated electric door lock. Input AC voltage  36  is utilized only to recharge energy storage device  26  when needed or to provide DC output voltage  48 ,  50  should energy storage device  26  be inoperable and requiring of replacement. In this manner, energy efficiency may be maximized. 
     While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.

Technology Category: 5