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CROSS REFERENCE TO RELATED APPLICATIONS 
     The Applicants claim the benefit of their provisional application No. 61/401,034 filed on Aug. 6, 2010. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an electronic control system for an automatic motorized door operating unit to allow a switching safety edge to operate with a motorized door operating unit of the type which is designed for use with a photo eye obstruction detection system. 
     2. Description of the Related Art 
     Motorized doors are used for everything from residential garages to industrial moving, rolling or sliding doors and gates. For many years, it has been a best practice and usually a legal safety requirement to provide an obstruction protection mechanism to stop a motorized door moving along a given track when the door has an obstruction that will strike the door if the motor driving the door is not stopped. Many automatic doors or gates, particularly those such doors used in industry, have a door operating unit which controls the power to the door motor to open or close the motorized door along its normal path. 
     In many cases, light beam sensors such as a photo eye are used to monitor the continuity of an infrared light beam installed across the path of the motorized door so that obstructions to the door can be sensed by the breaking of the photo eye path thereby changing the always on, fail safe control signal which would normally be signaling continuously that the path of the door is not obstructed. A problem with such photo eyes is that they are by inherent design observing obstructions, or the lack thereof, only across the actual path of the light beam from a light emitter to a photo eye on the opposite side of the path. There are other disadvantages to a light beam obstruction sensor as well. Therefore, a moving edge of a door being closed may meet an obstruction that is outside the sensing range of a given photo eye pair therefore causing the door to strike the obstruction whether it is a vehicle, person or other object in the path of the moving door. 
     Door or gate edge sensors are known devices which are comprised of elongated conductive switches which are contained within an enclosed switch package which can be placed along the entire leading edge of a moving door. Such edge safety switch devices are commonly known as switch safety edges, safety switches, edge switches, switch sensing edges or just sensing edges. The switches operate by being compressed when striking an object thereby shorting parallel flexible conductors within the edge sensing strip to close a conduction loop or path to a control circuit. This action then indicates that the edge has struck an obstruction and therefore the motor should be de-energized. 
     Edge sensing strips or switches may also have fail safe configurations such that each side of a two-conductor elongated strip is checked for continuity to make sure that any operation of the switch because of an obstruction will actually allow a signal of continuity engagement to be transmitted back to a control module which is monitoring for an opened or closed condition in the edge sensing strip. This presents a continuous signal opportunity much as a photo-eye monitored door so that the motor operator for controlling the door is signaled that the obstruction protection remains operational. Such door operators otherwise default to a safe condition if the operator does not receive a signal from the photo-eye. Likewise, an edge switch must present monitored status by continuity checking in some fashion. Some monitored switching systems are sometimes referred to as 4-wire switches in which simple direct current continuity confirmation is accomplished by simple means. Other monitoring means might include placing a known component, such as a resistor of known value, in the switch edge to facilitate a known or expected measurement of the component, a change if which can be used to signal a change in the switch edge state from functioning to non-functioning. 
     Conventional, simple photo eye obstruction sensors generate a continuous signal output when no obstructions are blocking the path between light generator and the light beam receiver on the opposite end of the protected path. Photoelectric systems typically use a signal waveform with a designed and controlled amplitude, period and duty cycle, tailored to a particular door operator unit designed to work with a particular controller with a given style of signal output from a given photo eye system. In order to make an edge sensing switch compatible with a given door operator unit which expects to see a signal from the photo eye, a programmable and flexible interface device would be necessary to convert the expected direct current switching information from a 2 or 4-wire safety switching edge to the type of output signal a door operating unit would expect to see if it were observing a simple photo eye across the protected door entrance. Generating a signal expected as output from a functioning photo-eye system based on a retrofitted switch edge device would allow conversion of an existing installation of an automatic door controller which is using a photo-eye obstruction sensor to an edge switch sensor without the need to change the system components. It is also important to accomplish such a conversion utilizing the existing power provided by the motor operator, typically 24 volts for a photo-eye controlled operator. 
     Accordingly, a device and method is needed in which the user of a motorized door safety sensing system can use edge sensing switch devices to drive a motor controller which normally is expecting to see a digital signal from a compatible photo eye device commonly used in the industry. A system which allows retrofitting of existing door operating units which use conventional photo eye control signaling by providing an interface between the conventional switch sensing edge to the digital control signal emulating the output of a simple photo eye which otherwise would be used with a given control unit to protect from obstructions placed within the pathway of the moving motorized door would allow this and be useful. Such a conversion must maintain the safety conditions afforded by monitoring the operational readiness of the retrofitted switch edge when in standby mode. 
     Accordingly, it is the object of the present invention to provide an interface device which will allow retrofitting a motorized door operating unit from a simple photo eye obstruction sensor to a door edge sensing switch device which uses either a 2-wire or 4-wire continuity control system without changing or modifying the door operating unit already in place. 
     It is further the object of the present invention to provide a conversion device to change an opened or closed direct current switch condition in a door edge sensing device to a pre-determined digital signal output of a selected amplitude, periodicity and duty cycle to suit a given motorized door operating unit which would otherwise expect to be signaled by a defined digital signal emulating the output of a compatible photo eye sensing device and operate from the existing control voltage provided by the door operating unit. 
     It is also the object of the present invention to provide a method of retrofitting an existing photo eye type obstruction protection controller to use a door edge switch obstruction protection system without the requirement of changing the controller or applying different power requirements. 
     SUMMARY OF THE INVENTION 
     The Underwriter&#39;s Laboratory® (“UL”) standard for safety entrapment devices used on commercial doors and gates has been changed recently. While compliance to the standard is voluntary, the majority of commercial door and gate operators are modifying their products in order to be in compliance with the new standard. The most significant change to the standard requires door operators (the mechanical linkages, motors and control circuits) to have a “monitored” external entrapment device. The term “monitored” defines a device that generates a unique signal such that the monitoring equipment, i.e. the operator, can determine that the device is connected and working properly. A monitored entrapment device for motorized doors therefore applies a fail-safe protocol to assure that the safety device itself is always operational, and stops the system if the safety device reports a failed condition of the device. 
     In the field of door and gate operators the simplest monitored device that meets the UL requirements is a “monitored photo-eye”. Photo-eyes are available as both monitored and un-monitored varieties. Typically, a monitored photo-eye designed to function with a UL-325 compliant operator generates a square wave output signal with a frequency range from 300 Hz to 1000 Hz and a duty cycle of roughly 85% (High to Low ratio). Virtually all of the operator manufactures that build UL-325 compliant equipment made a decision to use a monitored photo-eye as their external entrapment device likely because of the relatively low cost. A safety edge switch type device could be used but only as an auxiliary device in conjunction with a monitored photo-eye. Thus the end user was required to purchase and install two entrapment devices in order to gain the superior protection of a safety edge switch such as offered by certain manufactures. 
     In order to solve this problem, it would be desirable to design a monitored safety edge that would generate the exact same signal as a monitored photo-eye and would look identical in operation to the operator to which it was connected. The optimum design would be a system consisting of a terminated edge switching device and a conversion module which serves as a solution to the described problem. Both a method and a system of retrofitting existing installations would be very advantageous. 
     A terminated edge switch is a elongated door edge switch which may include a type of terminating device, such as a resistor or a diode or a capacitor, connected to the switching type edge at the end opposite to the cable exit end. Four wire switching edges, wherein the extra wires are used to monitor continuity of the switch elements without a terminating device are still in use. The present invention can still be utilized in such a case. An existing four wire edge can be converted to a terminated edge by simple connecting the terminating element between one pair of the wires coming from the edge. 
     When the terminated edge is connected to the module described in this disclosure, the act of monitoring is carried out by the internal microprocessor. The microprocessor in the invention is configured to test the edge hundreds of times per second to insure that the termination is present. When the edge is activated by closure of the conductors which comprise the length of the switch, the electrical characteristics or value of the terminating device is effectively interrupted and the control then observes a short or closed conductor condition rather than the monitored value of the terminating device. When an obstruction is sensed, a microprocessor interrupts the output signal to the operator which causes the door to stop, reverse and go to the fully open position as such an operator normally reacts according to its design and/or programming. 
     In summary, the apparatus and method described both monitors a door or gate switch edge for its termination and checks the edge for activation. The invention controls the door operator in the same fashion as if the replaced photo-eye sensor was monitoring the same door and therefor eliminates the need for a new door operator or new power supply for the switch or the control module disclosed as the module will operate on the same voltage used to power the replaced photo-eye. A failed termination device or other change of the electrical conditions of the switch because of failure or an activation of the switch result in the loss of signal to the operator and the door stops and/or opens depending on the programmed set up of the door operator. The invention is a field replacement system for an existing photo-eye monitored automatic door which functions with the existing monitored door operator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a system pictorial diagram demonstrating the placement of the interface module containing a microprocessor between an edge sensing switch on a moving door or gate which is retrofitted from a simple photo eye obstruction monitoring device. 
         FIG. 2  is an electronic block diagram of a preferred embodiment of the interface module demonstrating the overall design method of the interface module for use in replacing an electric photo-eye with an edge sensing switch. 
         FIG. 3  is an electronic circuit schematic diagram with details of an embodiment for the module interface which is used to interface between a device terminated edge sensing switch and photo eye terminals of a motorized door operating unit. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     And now the invention will be described in detail with reference to the various drawings in which like numerals refer to like parts. Turning to  FIG. 1 , a pictorial diagram of the system presents the general placement and operation of control module  10 . In most automatic door operating systems, there is a door operator  12  which controls motor  14  which can drive a gate, overhead door or other automatic door opening system. 
     Many present systems utilize a photoelectric eye of either visible light, infrared light beams or other obstruction sensing photoelectric or similar devices are known to those skilled in the art. Such devices monitor the threshold of such automatic doors or gates to stop the door operating unit  12  in the event that motor  14  is driving the automatic door but an obstruction appears in its path. Such photoelectric devices and other beam sensing systems operate by providing a signal of known amplitude, period and duty cycle output  30 . Output  30 , depicted in the figure as square wave pulses in diagrammatic representation, is presented across operator photoelectric input  16  as shown in  FIG. 1 . As long as door operator  12  receives the expected signal  30  across input terminals  16 , shown in the figure as two wire terminals, operator  12  will continue to operate normally upon a command to open and close by activating motor  14  when a request is received by whatever control means is used. Such control means could be a button, or a wireless remote door control or the like. 
     Without the presence of signal  30 , operator  12  would assume that there has been a failure of the photoelectric safety system or an obstruction and will prevent operation of motor  14 . Any replace device must therefore both function from a typical 24 volt control voltage available across input terminal  16  and simulate the normal state signal output expected by operator  12  to truly be a retrofit capable system. 
     As described above, there is a need to substitute photoelectric devices with actual edge safety sensing systems which in many applications are an advantage from the perspective of being able to sense obstructions in front of the automatic door being operated by motor  14 . Sensing edge  40  is an elongated switch that run across the entire length of a typical automatic door or gate, compressing slightly when contacting an obstruction in the path of the automatic door. Sensing edge  40  is a switch design already known to those skilled in the art in the sense that such switches have been employed as a safety feature on many operating doors in the past. 
     Edge  40  operates differently than a typical photoelectric beam that may sweep the same threshold being protected in that edge  40  is a simple switch which is comprised of a flexible switch assembly  42 . Assembly  42  is comprised of elongated conductors such as foil sandwiched along the top of the strip at  44  with a bottom strip  46  essentially presenting a second conductor which can close a circuit upon compression of switch foil  44  into switch foil  46  when coming in contact with an obstruction. Accordingly, a circuit can be closed allowing a simple control type unit to switch off a door operator which is expecting a different type of signal input, (that is, an open or closed continuity condition) than those used for simple photo eyes. However, it can be appreciated that to be considered a monitored system, the simple continuity style switch must have facilities to reliably signal failure of the switch components. 
     Edge  40  can be constructed of different types of switch assemblies  42  to allow for actual monitoring of the continuity of foil  44  and  46  so that if they become open through wear and tear a simple system can sense that edge  40  is no longer protecting a door edge to which it is attached. A preferred method presently is the use of a terminating device  48  which is typically a resistor, diode and capacitor combination or other device which allows control models that are typically used for sensor edge  40  to measure an expected resistance across foil  44  and foil  46  thereby allowing a control module for a simple sensing edge to detect that it is no longer measuring the terminating resistor, typically 10,000 Ohms or, if diode and capacitor terminated, the direct current termination expected as device  48 . Direct current termination can take the form of a back to back diode such as a commonly known P6KE9.1CA in connection with a conventional capacitor placed in parallel across the diode. When the state of edge  40  changes because that the foil switch has failed in some aspect and is no longer in a protection mode, it can be appreciated that the resistance or voltage drop across terminals  20  and  21  will change. Module  10  measures this and will terminate the signal generated across terminals  18  which provide the constant state signal  30  to operator  12  as shown. 
     Another older method of measuring continuity of foil  44  and foil  46  which may still be in use is to replace terminating device  48  with a four-wire conductor as shown in  FIG. 1  which is comprised of the two conductor terminals from assembly  42  with the addition of sensing wires  22  and  24  which themselves can measure the continuity of foil  44  and  46 . By sensing continuity between terminal  20  and  22  shown on  FIG. 1 , one can determine whether foil  44  is in operation. Likewise, sensing continuity between terminal  21  and  24  in  FIG. 1  will indicate that switch foil  46  is likewise intact. This system of fail safe checking the integrity of flexible switch assembly  42  may still be in use but is presently losing popularity as a preferred switch monitoring technique. Voltage generation for continuity checking is not shown but is easily constructed using conventional techniques and can be intergrated into the module using the 24 volt control voltages typically used and presented by motor door operator  12  if desired. 
     To employ sensing edge  40  in a retrofit installation to replace a photoelectric eye which may be monitoring a threshold of a moving door, it can be appreciated that door operator  12  must receive an expected signal  30  across terminals  16  in order to allow door operator  12  to continue to operate normally as if a photoelectric threshold sensor that is being replaced is still in operation and is signalling that all is well with the safety sensing photoelectric device. 
     Accordingly, module  10  is a microprocessor based device which converts the simple continuity information available from edge  40  to a preprogrammed output of known amplitude, period and duty cycle at signal  30  to present to operator photoelectric signal input  16 . In such a fashion operator  12  continues to receive and expect a signal indicating that any threshold safety system is in operation and is therefore fail safe allowing the retrofitting of a photoelectric system with a sensing edge  40  without the need to change door operator  12  or other system components. 
     Module  10  as shown in  FIG. 1  contains a control circuit such as presented in block diagram form in  FIG. 2  and in more detail with an example in  FIG. 3  which can be adopted for direct current terminated switch edges or resistor terminated edges as may be desired in the installation of sensing edge  40 , discussed in more detail below. Module  10  is connected to flexible switch assembly  42  at terminals  20  and  21  and may include monitoring sensor wires shown at  22  and  24  to assure continuity of switch foil  44  and switch foil  46 . It can be appreciated that if terminating device  48  is going to be a resistor, for example, it is not necessary to also employ wire  22  and  24  for continuity since module  10  would be designed to measure the resistance of device  48  to determine whether assembly  42  is operationally ready. 
     Module  10  is comprised of terminal outputs  18  thereby providing an expected signal to door operator  12  without the need to change the entire door operator and associated systems when converting an existing photoelectric safety system to an edge sensing switching arrangement as described above. 
     Turning to  FIG. 2  now, a block diagram of the electronics implemented in  FIG. 3  is shown. Power supply  62  consists of 5 volt voltage regulator (shown as regulator  62  in  FIG. 3 ) and associated discrete components. Regulator  62  and  64  are commonly known as an LM3480-5V. However, regulator  64  is commonly known as an LM3480-15/12V when module  10  is configured for a DC termination  48  as described below. Module  10  can have an input voltage range across terminals  18  and  19  of 6 Volts DC to 30 Volts DC with a source resistor of 300 ohms to 800 ohms. The input voltage from operator  12  is polarity independent. Diode bridge  26  creates polarity independence providing simpler installation and preventing polarity errors. Voltage hold up circuit  72  maintains the stability of the voltage going to voltage regulator  62  (shown in schematic form in  FIG. 3 ) since the input voltage is pulsed by output driver  78  when a properly terminated edge  40  is connected and prevents the input voltage to regulator  62  from going to zero volts. Power to module  10  is indicated by a green LED  58 . 
     Voltage doubler  74  functionality, is used when module  10  is used with a direct current type termination device  48 . Voltage doubler  74  is bypassed when module  10  is used with a resistor termination device  48 . Use of a direct current type terminated edge  40  requires at least 12 volts to monitor edge  40 . However, the incoming voltage in case a diode and capacitor type direct current termination  48  is only between 10 volts and 12 volts, so incoming the voltage from door operator  12  needs to be boosted. Therefore, when a direct current termination of switch edge  40  is used, the 12 volt or 15 volt regulator is used and in the case of a resistor terminated device  48 , a 5 volt regulator is used. 
     Voltage divider circuit  76  divides the incoming voltage from edge  40 . Two different resistor divider networks are used in module  10 . One resistor network is used for the case in which termination device  48  is of the direct current type, and a second set is for use if termination device  48  is a resistor. Protection circuit  27  prevents damage to module  10  should an installer mistakenly connect switch edge terminals  20  and  21  to operator output terminals  18  and  19 . 
     Micro-controller  60  and output pulse driver  78  comprises the control block of module  10 . Micro-controller  60  performs two functions. Micro-controller  60  monitors edge  40  and if a properly terminated edge  40  is connected, micro-controller  60  toggles output pulse driver  78 , and controls red LED  59  to indicate edge fault. Micro-controller  60  monitors the output voltage of voltage divider  76 . If the voltage is between the specified voltage ranges then the pulse is generated and turns off red LED  59 . If the voltage is above the specified range then a pulse is not generated, resulting in red LED  59  being turned on. If the voltage is below the specified range then it doesn&#39;t generate the pulse red LED  59  is cycled through on and off to blink the LED. Use of a direct current terminating device  48  or a resistor termination device  48  result in different voltage ranges and pulse rate outputs. 
     Output pulse driver  78  is controlled by the micro-controller. It toggles the input voltage line by field effect transistor (“FET”)  66  shown in  FIG. 3 . It also has positive temperature coefficient (PTC) device  80  in the case of a direct current termination device  48 . PTC device  80  prevents FET  66  in the case of sudden surge of input current. Both FET  66  and FET  68  shown in  FIG. 3  are both commonly known as type number 2N7002ET1G. 
     In carrying out the invention it can be appreciated by those skilled in the art there would be a number of ways to implement control circuits for module  10 .  FIG. 3  shows a preferred embodiment of a typical electronic circuit which comprises module  10  for use for a direct current terminated edge  40  which utilizes the four-wire connection described above presenting operational continuity confirmation by measuring continuity between terminal  20  and line  22  and terminal  21  and line  24 . In the preferred embodiments,  FIG. 3  illustrates a typical electronic design for module  10  for terminated switch assemblies  42  with a resistor as device  48  or utilizing a diode and capacitor pair for termination. One difference would be adjustment of the values of resistors  50 ,  52 ,  54  in  FIG. 3 . 
     In  FIG. 3 , micro-controller or microprocessor  60  can be programmed to provide a signal output which is designed to match a particular motor controller system which may already be in place in a given installation. Jack  70  is used to program or service module  10 . One type of device employed effectively in the design is a Microchip Technology, Inc. model PIC12F683 micro-controller which is readily available. Once the expected signal input for a given photo eye output to an operator or controller is determined, a microprocessor device can be programmed to emulate the waveform or control information which the operator expects to see from a photo eye signal output. 
     Thereafter, an edge switching system connected to terminals  20  and  21  in both circuit examples can be used to control a motor operator or control system by discontinuing or altering the control signal which the operator circuit would expect to see for an unobstructed path. When an edge switching device is activated because it has hit an obstruction, the circuit examples presented will discontinue the emulated photo eye signal output expected by a given motor controller simulating the control signal disruption of a photo eye circuit for a similar obstruction. The control circuit disclosed provide typical component type and placement and identify typical terminal uses on the microprocessor device suggested, but different embodiments can be used to accomplish the purpose of the invention once the desirable end result is determined. 
     Programming a microprocessor, micro-controller or another type of peripheral interface controller device can be accomplished by loading firmware into the device which allows the flexibility of the invention to address the control requirements of a given photo eye driven motor control device. Such programming for generating an output signal of a desired pulse size, periodicity, amplitude or other characteristics is known to those skilled in the art. Accordingly, various similar methods could be designed to carry out the solution taught in this disclosure. Such solutions which allow the same result are within the scope of the present invention. It can be appreciated by those skilled in the art that the samples of the circuit diagrams given are a good solution to provide the control desired. However, other changes and circuit selections could be designed to accomplish the same conversion of control information to allow various styles of switching devices to operate with a motor controller or operator which expects to see a certain control information pattern of a selected frequency, period, pulse rate or pulse length. 
     Although the invention has been described in accordance with the preferred embodiment, it will be appreciated by those skilled in the art that the application of the present invention is useful in a variety of configurations and designs not specifically described above. All such designs and applications are considered to be within the scope of the present disclosure, and the invention is applicable across a wide variety of applications. Such applications are considered within the scope and spirit of the present invention.

Summary:
Apparatus and method to adapt a automatic door motor operator utilizing a photoelectric eye generating a digital pulse train of known amplitude, periodicity and duty cycle to a control signal created through the opening or closure of a moving door edge sensing device or strip which closes or opens when compressed. The invention relates to safety edges used on motorized doors to provide a conversion means to allow a sensing edge switch on the leading edge of a moving door to control a door operator control unit which expects to receive a control signal of a predetermined amplitude, period and duty cycle normally generated through use of a photo eye used to monitor obstructions within the path of the moving door. The invention allows field replacement of an obstruction protecting photo-eye sensor with an safety edge switch type device utilizing the existing door operator and the in-place power source.