Abstract:
An automatic door opening system utilizing wireless links to communicate from hazard or obstruction sensors to a controller to react to such conditions. The present invention allows the use of hazard, fault or obstruction switching devices which themselves utilize internal continuity monitoring in a wireless environment. Compressible hazard switch sensors which utilize internal, continuous conducting elements are continually monitored for breaks in such elements through continuity checks. A signal is generated from the wireless transmitter during door operation to indicate to the system that the link between the wireless transmitter and a wireless receiver is fully functioning at all times. The system can determine if an actual obstruction hazard is detected or if there is a loss of communications between the wireless transmitter and receiver link in the disclosed system while also allowing for wireless continuity checking between sensor switches utilized.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   The Applicants claim the benefit of their provisional application No. 60/464,810 filed on Apr. 23, 2003. 

   BACKGROUND OF THE INVENTION 
   The present invention relates generally to door systems, and more particularly to automatic door safety systems which use wireless links for sending information regarding the detection of a hazard condition or the operational status of the entire wireless system and hazard detection components of a system. 
   Automatic door operating systems are popular in commercial or residential settings. Such doors typically include the operation of overhead door systems, elevator doors or other automatic control systems to open and close doors in various categories. Such doors also typically provide for obstruction detection to prevent the door from continuing to close when the apparatus on the door senses an obstruction in the door&#39;s path. Such obstruction sensors and obstructions switches usually include means to activate internal contacting devices within such sensors when the switch is compressed when it strikes an obstruction during the operation of a door. Such switches may include normally open, compressible door edge cells which contain internal electrical conductors which contact each other upon compression of the cell. 
   Present systems utilize such door edge systems usually along the leading edge of the door in a location where the system is likely to become compressed when striking an object, compressing the internal conductors together causing an electrical path to be completed thereby providing a fault signal typically communicated by a control wire to the motor controller to stop operation of the door immediately. 
   In many environments it is desirable to monitor the safety switches and safety sensors typically utilized with power operated doors in a wireless environment, rather than require a 2-conductor or 4-conductor wire lead to track the operation of the door as it opens and closes. It is desirable to eliminate the wear and tear on such conductor as it tracks the door through many thousands of operations. In today&#39;s environment, motor operated doors typically are expected to last ten years or more thereby placing considerable physical wear and tear on the conductors which may track the motion of the door to facilitate the connection between safety edge sensors and the controller monitoring for obstructions indicated by such sensors. Eliminating such hard-wired connections is important, but maintaining failsafe reliability systemwide is paramount. Also important is an ability to continuously monitor a system regardless of whether the door being protected is actually in operation. The systems disclosed in the prior art lack such an important combination of features. 
   SUMMARY OF THE INVENTION 
   The present invention provides an automatic door control system which utilizes wireless links between the safety edge switches which detects hazard conditions to eliminate the need for control cable conductors to communicate between door edge sensors and the control unit monitoring the sensors. Desirable safety edge sensors typically also check for internal continuity on each side of the electrical switch which comprises elongated conductor foils within a safety edge switch to assure continuity on each side of the such switch. When a hazard condition is detected, a wireless signal is sent from the vicinity of the door edge safety sensor to the controller to stop operation of the door. 
   Further, the present invention disclosed allows for a fault signal to be generated should there be an internal failure of the door edge safety sensor such as to require communication of that fact, wirelessly, to the same controller. At the same time the system also provides for continuous fault monitoring of the wireless link between the sensor transmitter and the receiver utilized to communicate the transmitter signal to such controller. By providing a periodic signal from the transmitter to the receiver, the receiver recognizes that the communications path between the transmitter and receiver is operating. Such periodic monitoring can prevent failure of the entire system should the radio frequency link be disturbed because of equipment failure or such other environmental conditions such as electromagnetic interference created by other apparatus or equipment within the operating environment. Such a periodic signal provides a continuous status check. Depending on the battery life desired in the transmitter, such periodic status check signals should repeat on a short time basis to be assured that failure of the link during operation of the door will be noticed by the system quickly and a fault signal provided to stop operation of the door or take other action. 
   The system also provides a means to determine whether the door being protected is in motion, thereby signaling the transmitter to stay in continuous operation during the door movement to provide the ability for faster signaling to the receiver if a fault condition is detected. The door motion is detected using a secondary sensor such as a mercury switch or other vibration sensing switch to indicate to the transmitter that the door is moving and the transmitter should remain in an on condition through the entire operation. 
   After a predetermined period of time has passed since motion of the protected door has ceased, the transmitter is commanded back to a “sleep” mode to conserve battery power while continuing to periodically check the parameters of other safety features in the system such as the integrity of a door edge switch, battery voltage condition or other system tamper indicators. Further, the transmitter polls the receiver in the system on a periodic basis, in an exemplary embodiment five minute intervals, to assure that the transmitter and receiver are in communications and that all systems are nominal prior to the next cycling of the door being protected by the system. 
   The disclosed system consists of one or more transmitters and a receiver which communicate in the UHF radio range. Each transmitter is connected to a safety device, typically a two- or four-wire safety edge switch such as the Miller Edge™ switch, disclosed for example in U.S. Pat. Nos. 5,728,984, 4,785,143 and 4,396,814. The safety device is typically installed on the leading edge of a sliding door or garage overhead door. If a transmitter senses that it has hit an object, it communicates this to the receiver. The latter then actuates the associated relay as a control signal to the motion controller. Typically, a door/gate reversal is executed at this point. Speed of response and noise immunity are the most desired design features for transmitters and receivers employed in this type of system. 
   The transmitter and receiver used in the present invention has a unique radio frequency channel designator set by DIP switches. In addition each transmitter and receiver has an ability to uniquely address each other in the system so that multiple systems may coexist in one location. 
   In the example embodiment, each transmitter has a primary and a secondary switch input. Such connections may be for edge switches which are of the Normally-Open (NO) or Normally-closed (NC) types. It is anticipated that some users will have, for example, a secondary door “break-out” signal which must be responded to in a different manner as that of the primary signal from an edge obstruction switch device. A DIP switch controls the desired NO verses NC state. 
   Either two- or four-wire safety devices may be connected to the system. In the former case, shorting jumpers may be installed on the transmitter board to account for this type of edge switch device. In the latter case, four-wire, a fault to any of the input lines will cause the transmitter to issue a fault indication. 
   The transmitters in the system are battery powered and typically each will have a 9V Lithium battery. The transmitters are designed to be highly efficient and they spend a majority of time in a dormant or inactive state. The unit automatically wakens itself on a rapid cycle. One of the fundamental trade-offs in a system employed as with the present invention is speed of response and noise immunity vs. battery longevity. While it is desired to keep the transmitter size as small as possible, it is possible to accommodate larger capacity batteries of various types if necessary for a particular application if longer life is of importance for a given application. 
   The transmitter checks its inputs every 18 milliseconds. It radiates a status signal every five minutes in a typical installation, even if the status is “Everything Okay.” The receiver expects to hear from each transmitter within a preprogramed amount of time, typically 2 to 5 minutes. If the receiver does not receive a signal from the transmitter, this itself is defined as a fault. The receiver can be programmed to wait a longer time to hear from the transmitter if desired to account for momentary signal loss or other temporary problem. In the event the expected signal is not received, the appropriate channel relay will then be actuated. When the transmitter detects a fault it generates a train of 24 signals to assure reception and response. This feature can be used in facilities with high EMI backgrounds. 
   Both transmitter and receiver are controlled by Microchip PIC parts though those skilled in the art may recognize that there could be a large amount of flexibility in modifying the design to obtain the same function using a variety of different integrated circuit designs. 
   The communication protocol between transmitter and receiver is simple and is designed to be as minimal as possible to speed the reaction time of the system. It is possible to support different responses for different contingencies. The communication protocol lets the receiver know exactly what the fault is, even if the end result is the same, such as a relay closure at the receiver. For example, a Maintenance-Required LED may be included which will be activated (along with the appropriate relay) to indicate a low battery situation, a tamper attempt, a secondary input sensor trip, or other fault indication. 
   The present transmitter design supports two different possible radio frequency design schemes. One method is based on a Micrel MICRF102 device with a quartz crystal frequency base. This method consumes more power and necessitates a careful software controlled start-up sequence. The transmitter has an LED and a connection for a buzzer as sensory outputs of operation. 
   The transmitter employs a low-inductance PCB-loop antenna. The receiver employs a Quarter Wavelength monopole antenna on a coaxial connector. Both transmitter and receiver are enclosed in boxes comprised of lightweight, high impact materials which are easily installed in the field. 
   The receiver is powered by 24 VAC, which is industry standard. In the preferred embodiment of the invention, the receiver supports up to three different channels, each with a 1A relay and a red fault LED. The same receiver may be configured to operate with only one or two relays. Each relay may be jumper-selected as NO or NC output. Additions to the receiver can support a green “Signal Received” LED as well as a yellow “Battery-Low” LED. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of a typical installation of the various components used in the invention. 
       FIG. 2  is a block diagram illustrating an exemplary sequence of the operating steps of an exemplary embodiment of an automatic door safety system of the present invention. 
       FIG. 3  is a schematic diagram of an example of a multichannel wireless receiver utilized to practice the present invention. 
       FIG. 4  is a schematic diagram of a wireless transmitter utilized to practice the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following is a detailed description of the preferred embodiment of the Radio Frequency (“RF”) link system for an automatic door safety edge. The description is not intended to limit the scope, applicability or configuration of the invention in any way. However, the following description does provide a convenient illustration for implementing a preferred embodiment of the invention. Upon review of the following description it will occur to those skilled in the art that various changes may be made to the function and arrangement of the elements described in the preferred embodiment without departing from the spirit or scope of the invention as set forth herein and in the appended claims. 
   Referring now to  FIG. 1 , a block diagram of the entire system  10  is presented. Door edge switch  12  is a membrane type switch which utilizes a door edge safety sensor in the present invention, mounted on the lower edge of an overhead garage door or some other rolling door or movable door, which may be used in a variety of applications whether commercial or residential. In a typical installation, a movable door, whether overhead or in an elevator for closing laterally, the door moves between the open and closed positions in response to a command from a door controller mechanism which itself drives the motors or chain drives to actuate the door. It is always desirable that obstructions be automatically and instantly recognized to halt operation of the door as a safety feature. Door edge switch  12  is most frequently configured to be placed along the leading edge of a movable door, such as an overhead door, to acuate the switch upon compression of switch  12 . 
   In conventional systems the door switch is hardwired through physical contact with a controller which, sensing actuation of the switch, signals the controller to stop motion or, as may be desired, to reverse motion and open the door. The prior art describes a variety of different systems utilized to present obstruction signaling for overhead doors or other types of doors and elevator systems, and the like, whether pneumatically or electrically controlled. It is desirable in many situations to eliminate the hardwired cabling between the door edge switch or similar control switching apparatus to the door controller such that both the wear and tear and the inconvenience of having a cable tracking the motion of an operating door can be eliminated. Over time such cables will fail from continued motion day to day and therefore either reduce the protection provided by the system or place the door out of service until the cable can be repaired or replaced. 
   In the present invention, system  10 , the information conveyed by switch  12  regarding obstruction detection is conveyed to a wireless transmitter  14  which itself is communicating with a receiver  16  through a radio frequency link  22 . Such transmitters and receivers have been employed in the past for a variety of different applications including, but not limited to remote control systems for car alarms, burglary systems and control of overhead doors. 
   In applying wireless or radio frequency techniques to present link  22  in system  10 , a problem arises regarding the assurance of reliability of the system. If transmitter  14  is signaling an obstruction condition signaled by door edge switch  12 , it would be appreciated that receiver  16 , normally placed in the vicinity of the door controller  20 , must receive information from transmitter  14  in order to command the door controller to take what action is desirable. Receiver  16  communicates to door controller  20  through path  34  normally a wired path with a connection directly from the receiver  16  to the door controller  20 . While this operation may be straightforward, in the event that transmitter  14  or receiver  16  is not functioning or, should RF link path  22  be obstructed for any reason whether temporary or permanently, it is necessary to account for such occurrences to provide the failsafe operation of system  10 . In that regard, one way to do so is to have transmitter  14  continually connected to receiver  16  through link  22 . In such fashion, receiver  16  could be programmed to take action if transmitter  14  failed or RF link  22  became ineffective. Such an “always on” condition has obvious power consequences because transmitter  14  is necessarily battery operated to take advantage of the wireless condition of mounting transmitter  14  on a particular door or other protected portal which contains switch  12 . While some systems in the prior art are designed to have a transmitter poll a receiver on a regular basis, perhaps every few seconds, the obvious consequence of battery life makes such a design undesirable. Other systems only poll the receiver while a door is actually operating and does not check the “health” of the entire system while in a standby mode. 
   In the present invention, system  10  provides a means to enable transmitter  14  to send information continuously upon actual operation of the rolling door or other moving door such that there is a continuous monitoring of the status of switch  12 . While in this active mode, obstructions encountered by switch  12  will be immediately conveyed from transmitter  14  to receiver  16 . To do this, transmitter  14  must be commanded to remain in an active condition only when the door is in operation. By using motion sensor  18 , transmitter  14  can be commanded to remain in the on mode, continually monitoring the condition of switch  12 , while the door being protected is in motion. To do so, it is necessary for transmitter  14  to be activated when the door is moving so that the continuous operation mode can be implemented. 
   Motion sensor  18  can be a variety of different mechanisms, but in the preferred embodiment the most effective means is to use a mercury switch or other switching means which are very susceptible to any vibration. A mercury switch or reed switch is in a position on the door to be protected. Placement of sensor  18  should be placed in a position on the door which is subject to the most vibration or movement during the operation of the door. Sensor  18  can continually signal transmitter  14 , through path  32 , that the transmitter should remain in an active condition transmitting its status at all times to receiver  16  through link  22 . Upon completion of the motion of the door, motion sensor  18  will cease being active and will discontinue signaling transmitter  14  through path  32 . After a preselected “time out,” normally one or two minutes, transmitter  14  can return to a standby mode by conserving transmitter battery power. 
   Transmitter  14  is designed to have several different features to enhance the safety of the system. First, transmitter  14  includes a tamper switch system which will signal receiver  16  when transmitter  14  is either removed, opened, or otherwise tampered with. Other such incorporated monitoring capabilities include measurement of battery voltage as well as provisions for additional secondary sensors other than motion sensor  18 . Such additional or secondary inputs could be for Infrared beam sensors, ultrasonic or RF motion sensors or other specific sensors designed for special applications. Such sensors can be integrated into the control protocol for operating the door or to stop the door upon the currents of other designed events. Further, transmitter  14  is designed to generate a signal over RF link  22  which is addressable such that the transmitter can coexist on a given channel at a given facility with other systems  10  operating nearby on other doors. In such a fashion, it can be appreciated by those skilled in the art that transmitter  14  may be selectable on a number of different operating channels such that multiple systems  10  can operate within a given facility with minimal interference between the system. 
   Transmitter  14  can operate on one of several channels that can be selected during installation. Further, transmitter  14  can encode defined addresses on a given channel to enable receiver  16  (which is configured to respond to a given transmitter  14  specifically configured to address a given receiver  16 ), to operate on a common frequency used by other systems within the facility. Using frequency agile transmitters, along with the system of addressable receivers for a given frequency, it can be appreciated that multiple systems  10  can operate within radio range of each other with negligible interference and without a given transmitter  14  signaling an unintended receiver  16  from a different system, even if operating on the same frequency. In the preferred embodiment as disclosed, the transmitter and receiver frequency as well as the address encoding is performed by conventional DIP switches or other methods to configure a given system  10 . 
   Continuing to consider  FIG. 1 , one advantage of the present invention is the use of door edge switches  12  which utilize a failsafe system within the switch itself.  FIG. 1  is comprised of two conductors within a compressible structure which is designed to make electrical contact upon compression of the switch material to signal contact with an obstruction. First door switch element  24  would contact second door switch element  26  as shown in  FIG. 1  upon compression of the switch, thereby enabling a closed circuit, assuming that the configuration being used is a normally open switch configuration. It should be noted that the present invention can operate with a normally closed switch, a normally open switch or some other configuration because of the flexibility of the system as described below. In the preferred embodiment, a normally open switch  12  is used as suggested in  FIG. 1 . 
   Utilizing a closed loop system on both switch element  24  and switch element  26 , it can be seen that continuity of the conductor can be measured at all times to be certain that the switch is in operating condition. From time to time it is possible that door edge switch  12  may be damaged or worn out by continual use and failure may not be detected during a normal inspection. In the event that one of the conductors within the door edge switch fails, it can be seen from  FIG. 1  that continuity as measured across first switch conductor cable  28  or second switch edge conductor cable  30  would be broken. Transmitter  14  is designed to allow continuous monitoring of the continuity of switch element  24  and switch element  26 , thereby immediately being able to signal a fault condition if continuity of one side or the other side of the switch conductor is broken. Such an indication would not be possible in utilizing remote sensing or signaling systems which are configured only to work on more conventional door edge switches comprised of a single conductor on each side of the switching element. 
   Turning to  FIG. 2 , a block diagram illustrating an exemplary sequence of the operating steps of one embodiment of the system is presented. Transmitter  14  begins in a standby mode  42 . If transmitter  14  becomes active, a decision is made whether it is because of an automatic awakening  44  or because a motion sensor for the door  18  has commanded the transmitter to an active state. If it is determined the transmitter has become active  44 , the system determines whether the preprogrammed elapse time  48  has occurred. Elapsed time  48  is programmed to be between two and five minutes depending on how frequently the user of system  10  would desire transmitter  14  to poll receiver  16 , testing both the link  22  and the general condition of the entire system. If the program elapse time  48  has occurred, transmitter  14  gets turned on as shown at  46  in  FIG. 2 , and a short transmitter activation time results. If in fact the transmitter becomes active because of motion sensor  18 , evaluation of the program elapse time  48  is not necessary and the system proceeds to turn on the transmitter directly at  46 . As long as the door remains in motion at  50  the transmitter  14  remains active, checking to see if the door has hit something or encountered an obstruction  52  as well as continuing to check the system operation  54  during the period of time that the transmitter is in an active state. During this active state the transmitter conveys its status to the receiver at  56  and continues to operate through the loop as shown in  FIG. 2  until the door motion is terminated. At step  50  when the door motion has terminated and the preselected time-out delay has expired, the system returns to a standby mode  42  as shown in  FIG. 2 . 
   During the operation of the system, transmitter  14  can become active to transmit a fault condition such as low batter voltage, failure of the monitored edge sensing switches, tampering or other desired features. Transmitter  14  can be configured also to automatically awake into the active mode to convey such error or fault conditions to receiver  16  if desired to disable door controller  20  if desired. In a separate configuration, such fault conditions can present indicator outputs rather than a disabling condition. For example, both transmitter  14  and receiver  16  can provide fault indication LED light indicators showing a variety of conditions. A low battery condition on the transmitter  14 , tampering with the case of transmitter  14 , failure of door edge switch  12  continuity check, or failure of receiver  16  to be polled by transmitter  14  within a preprogrammed time period can provide fault indicator lights while at the same time disabling the operation of the door by signaling controller  20  and disabling operation until the system is inspected. 
   In a preferred embodiment, receiver  16  is designed to automatically signal controller  20  through path  34  if receiver  16  does not receive a signal from transmitter  14  while transmitter  14  is in the standby or inactive mode in between operation of the door. As an example, typical operation of the invention requires that receiver  16  be polled by transmitter  14  every five minutes when transmitter  14  is in the inactive or standby condition. Receiver  16 , failing to hear from transmitter  14  during preprogrammed time period would command the door controller to off or fault status shutting down system  10  until the system can be checked to determine the reason for the fault. In practice, it has been determined that receiver  16  can wait a multiple period of timed intervals to hear from transmitter  14  before determining that there has been a genuine fault in the system. It can be appreciated that the parameters to be used in a given system  10  would be dependent on the tolerance for a possible fault which the operator of the system determines is appropriate. 
   Turning now to  FIG. 3 , a schematic diagram of a typical multichannel receiver for use in the present invention is disclosed. Receiver  60  is of conventional design and is used in the operation of system  10  in an exemplary embodiment. The illustrative design shown at  60  for receiver  16  is configured to operate with transmitter  14  in system  10 . 
     FIG. 4  shows the typical transmitter design which can be used effectively with receiver  60 . Particular note should be given to the design of the transmitter board  62  which incorporates a 4-conductor connection at  64  which allows connection of a 4-terminal door edge switch as shown at  12  in  FIG. 1 .  FIG. 1  discloses first switch conductor cable  28  and the second switch conductor cable  30  as it is configured with transmitter  14 . Such connections used on board  62  are shown at  64 , which allows for continuity checking across the entire length of a given door edge switch  12 , as discussed above. Connector  64  is integrated into the design of integrated circuit  66  which presents terminals which can be effectively used to provide sensing of the continuity switch element  24  and switch element  26  to provide a fault indication in the event that there is a loss of continuity between each side of the switch element as described in more detail above. 
   With the above, an automatic door system according to the various aspects of the present invention has been disclosed with reference to a particular preferred embodiment. It will be obvious to those skilled in the art that the system disclosed may be comprised of diagnostic systems that may be altered slightly to provide for specific requirements of a given installation. While the principles of the invention have been described in an illustrative embodiment, it should be apparent that many modifications of structure, arrangement, proportions, specific elements, as well as materials and components can be used in the practice of the invention. Improvements or adjustments not specifically described may be varied and in particular adapted for specific applications that warrant different operating requirements without departing from those principles as set forth above.