News Column

Patent Issued for Photo Eye to Switch Sensing Edge Control Conversion System

July 23, 2014

By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventors Miller, Bearge (West Chester, PA); Castello, Timothy (West Chester, PA); Provenzano, John (Hatfield, PA); Sao, Vinay (Rosemont, PA), filed on August 5, 2011, was published online on July 8, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8769878 is assigned to Miller Edge, Inc. (West Grove, PA).

The following quote was obtained by the news editors from the background information supplied by the inventors: "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.

"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."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "The Underwriter's Laboratory.RTM. ('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."

URL and more information on this patent, see: Miller, Bearge; Castello, Timothy; Provenzano, John; Sao, Vinay. Photo Eye to Switch Sensing Edge Control Conversion System. U.S. Patent Number 8769878, filed August 5, 2011, and published online on July 8, 2014. Patent URL:

Keywords for this news article include: Electronics, Legal Issues, Microprocessors, Miller Edge Inc.

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Source: Electronics Newsweekly

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