Power control circuit assembly for an electric door latch mechanism

A power control circuit assembly for an electric door latch mechanism comprises a load control circuit module configured to distribute a DC operating voltage to power an electromechanical door latch mechanism and its associated access control device. An energy storage device such as a rechargeable battery 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 energy storage device voltage 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 an energy storage device recharge voltage. An energy storage device voltage detection module is configured to interrogate a DC voltage supplied by the energy storage device.

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 '332 publication”), the entirety of which is incorporated herein by reference. As disclosed in the '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.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In describing the preferred embodiment of the present invention, reference will be made herein toFIGS. 1-6of 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 toFIGS. 1-3, a power control circuit assembly in accordance with an embodiment of the present invention is generally indicated by reference numeral10. Unlike a comparatively large power control box typically located above ceiling panels, as known in the prior art, power control circuit assembly10is configured to reside within a standard-in-the-industry double gang electrical box12that 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. Box12may be secured to an interior framing member14between opposing panels of drywall16,18, 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 cap20is secured to box12by a pair of cap screws22. To improve aesthetics of the installed assembly, box12may include a cover plate24configured to overlap any gaps between the edge of the hole cut in drywall panel16and the outer surface of box12. A rechargeable energy storage device26, such as for example a rechargeable battery, is housed within electrical box12while a printed circuit board (PCB)28and associated components (seeFIG. 4) is housed within a case30which is secured within box12and assembly cap20via case screws32.

As seen inFIG. 4, and with additional reference toFIG. 5, PCB28includes AC inputs34configured to receive grid input AC voltage36. Grid input AC voltage36is converted by rectifier38to input DC voltage40. As an aside, it should be noted that an alternative input DC voltage41may be provided using alternative energy sources43, such as solar or wind energy. Input DC voltage40is routed through load control circuit module42to supply a charge voltage44to energy storage device26. Energy storage device26then routes a DC voltage46to load control circuit module42where it is conditioned by load control circuit module42to be output as one or more DC operating voltages, such as DC output voltages48,50. By way of example, DC output voltage48may 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 voltage50may power an electric door latch mechanism (not shown), such as that described within the '332 publication discussed above.

Distribution of DC output voltage48,50may be directed by a microprocessor (MP)52powered via a microprocessor voltage66supplied by energy storage device26at terminal53on PCB28. For instance, DC output voltage50may be directed to the electric door latch mechanism after MP52receives an authorized control signal entered via the access control device and transmitted to MP52via access control input54. MP52may also provide supervisory pathways58,60which monitor DC output voltages48,50to ensure that load control circuit module42is operating properly and outputting the requisite DC output voltage48,50. The status of DC output voltages48,50may be indicated visually such as through LED's49,51, respectively. MP52may also monitor energy storage device operation via supervisory pathways62,64. Pathway62interrogates the magnitude of energy storage device charge voltage44directed from load control circuit module42to energy storage device26while pathway64monitors the DC voltage being supplied by energy storage device26to load control circuit module42. Should the energy storage device need frequent recharging or should the energy storage device fail to provide the requisite DC voltage, MP52will 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 buzzer55to emit a chirp or other noise).

In the event of a failure of the rechargeable energy storage device (i.e., MP52determines through measurements received via supervisory paths62and64that the energy storage device needs frequent recharging or the energy storage device fails to provide the requisite DC voltage), DC output voltages48,50may be supplied directly via input DC voltage40. To that end, PCB28includes an energy storage device voltage detection module65that detects whether DC voltage46supplied 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 module42, via line67, to supply DC voltage40directly to DC output voltages48,50, 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 MP52, 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'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 voltages48,50until the new energy storage device has been charged and can then provide the necessary DC voltage to power the electric door lock.

PCB28may further include fire alarm input78wherein input78is configured to receive a fire alarm activation signal from a remote fire alarm system. In this manner, DC output voltage50used 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 assembly10functionality, PCB28may include one or more switches in communication with MP52, such as dipswitch80. While described as a dipswitch, switch80may be any suitable electrical connection, for instance, a jumper block. Dipswitch80may include switches controlling various functionalities, such as an access control switch80ato selectively configure the access control input54as normally open (NO) or normally closed (NC); a fire alarm switch80bto selectively configure fire alarm input78as NO or NC; a lock behavior switch80cto selectively configure the electromechanical door latch mechanism to be fail secure or fail safe; and a latching switch80dto selectively activate fire alarm latching. Fire alarm latching is required by law in certain jurisdiction, such as Canada, wherein once a fire alarm input78is 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, MP52automatically resets the lock mechanisms once the fire alarm has been disabled.

FIG. 6shows a process flow diagram for initializing and operating power control circuit assembly10(seeFIGS. 1-5). In a first step100, upon initialization of the circuit, (energy storage device26is depleted) in-line controller74is active such that input DC voltage40is operating to power DC output voltages48,50. In step102, MP52interrogates whether energy storage device26is present within circuit10. If energy storage device26is present, in step104, MP52places the in-line controller74in standby mode and interrogates energy storage device voltage to determine whether the energy storage device has at least 10 V of charge (step106). If the energy storage device has less than 10 V of charge, MP52interrogates its internal memory to determine the last time energy storage device26was recharged with charge voltage44(step108). If the last charging of energy storage device26occurred longer ago than a selected length of time (i.e. more than 2 hours), energy storage device26is charged with charge voltage44(step110). However, if the last charging occurred more frequently than the selected length of time, MP52will interpret the instant lack of energy storage device voltage as indicative of an energy storage device failure needing replacement and will initialize an alarm signal55such as for example, a buzzer to emit a chirp (step112).

Alternatively, if energy storage device26holds a voltage greater than 10 V (or if energy storage device26is not present (step102), MP52determines whether fire alarm input78has been activated (step114). If fire alarm input78has not been activated, MP52determines whether access control input54has been activated with an authorized access code (step116). If an authorized access code has been entered (step118), MP52authorizes load control circuit module42to supply DC output voltage50to the electromechanical door latch mechanism thereby changing the state of the electric door lock (step120). If the access control input54has not been activated or after the state of the lock has been changed after authorization, MP52reverts to step104wherein the in-line controller is in standby mode and the charge of the energy storage device is interrogated.

If MP52determines that fire alarm input78has been activated (step114), MP52will then determine, in step122, whether active fire alarm latching has been selected (such as by way of dipswitch80d, discussed above). If fire alarm latching is active, step124has MP52changing the status of DC output voltage50(i.e. placing it in the unpowered default state) and energizing LED82to indicate the active fire alarm input78. DC output voltage50and LED82will remain in these conditions until dipswitch80dis manually reset. To manually reset the fire alarm latch, cap20is removed to expose dipswitch80dwherein a small tool may be used to reset the switch. Alternatively, cap20may be configured to include small access holes wherein a small tool may be inserted through cap20to access the one or more switches80a-80deither directly or indirectly through connecting buttons80a-80d. If fire alarm latching is inactive, MP52will change the status of DC output voltage50(i.e. place it in the unpowered default state) and energize LED82to indicate the active fire alarm input78(step126). MP52will then query whether the fire alarm input is still activated (step128), wherein if the input78is still active MP52reverts to step122. If fire alarm input78is no longer active, MP52returns power control circuit assembly10to normal operation (step130).

From the above description, it should be evident to those skilled in the art that the power control circuit assembly10of the present invention utilized DC voltage supplied by energy storage device26to power the associated electric door lock. Input AC voltage36is utilized only to recharge energy storage device26when needed or to provide DC output voltage48,50should energy storage device26be inoperable and requiring of replacement. In this manner, energy efficiency may be maximized.