Abstract:
In a control system for controlling traffic signal lights, normally supplied with power from the AC source, the combination comprising flasher means electrically connectible to the lights to cause the lights to come ON and OFF, repeatedly, an electrical power storage device electrically connectible to the flasher means for supplying electrical power to operate the flasher means when AC source power is not supplied to the traffic control system, and a charging device for charging the storage device when AC power is normally supplied to the traffic control system.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to traffic control systems, and more particularly to improvements in operating traffic signal lights at controlled roadway intersections during times when loss of electrical power occurs. 
     At the present time traffic control systems use a controller unit that energizes load switches that drive the signal lamps through a flash transfer relay. In the event that a conflicting signal should arise, a conflict monitor actuates the relay to transfer the traffic signal loads to a flasher module. When this transfer occurs, the controller unit and load switches are removed from causing the traffic signal lights to be turned ON and to be turned OFF. Once the relay is actuated to transfer the traffic signal loads to the flasher module, human intervention is required to restore the flash transfer relay to the state where the controller unit and load switches can cause the traffic signal lights to be turned ON and to be turned OFF, thereby removing the flasher module from operating the traffic signal lights. 
     The flasher module is capable of causing the traffic signal lights to alternate regularly OFF and ON. This is accomplished by the flasher module in such manner that traffic signal lights are flashed ON and OFF. In doing so, drivers of vehicles may see flashing red traffic signal light indications at the intersection, indicating for them to stop before proceeding through the intersection in a safe manner. 
     A traffic control system is normally considered as consisting of a traffic controller unit for the purpose of providing 24 volt DC input signals to one or more load switches used to turn traffic signal lights ON. A conflict monitor device is used to monitor the presence of proper alternating current field wire voltages supplied to power the traffic signal lights. When improper AC voltages exist, the conflict monitor causes an electro-mechanical relay to operate, which in turn causes the high current capacity flash transfer relay to remove traffic signal light power from the load switches and to connect the traffic signal light power to a flasher unit, which causes traffic signal lights to flash ON and OFF. 
     Operation of a traffic control system described above requires the supply of AC power to equipment. When AC power ceases to be supplied, the traffic control system ceases to operate and the traffic signal lights no longer emit light, thereby becoming dark. The result is that drivers of vehicles approaching the signalized intersection do not see any traffic signal lights. The drivers of vehicles approach what is typically referred to in the industry as “a dark intersection”. The Manual on Uniform Traffic Control Devices (MUTCD) of the Federal Highway Administration (FHWA), listed in the Federal Register, states that it is acceptable to operate a signalized intersection as “a dark intersection” and that, during such operation, drivers of vehicles are expected to interpret “a dark intersection” the same as they would an intersection having stop signs; stopping their vehicles before proceeding through the intersection. 
     One of the purposes of traffic signals is to make intersections more visible, and hence, safer. There has long been need for improvements in making “a dark intersection” more visible to drivers of vehicles for traffic control. Traffic signal lights may be difficult to see even when operating properly and lit. But when traffic signal lights are dark, intersections become very difficult for drivers of vehicles to see. The result is that accidents occur, causing property damage and bodily harm with potential loss of life. Power outages leading to loss of traffic signal light operation are most likely to occur as the result of inclement weather, which causes visibility to be degraded. Thus, the loss of traffic signal operation most commonly occurs when its reliable operation is needed most. Loss of traffic signal light operation during nighttime due to loss of power poses an all-too-common threat to the safety of drivers of vehicles, their passengers and bystanders. 
     Back-up power supplies with power storage capability have been used in traffic control systems at signalized intersections to maintain operation of the traffic control system as it would operate from the external AC power source. Use of such back-up power sources has been limited to only a few signalized intersections, due to space limitations and their high cost. 
     SUMMARY OF THE INVENTION 
     It is a major object of the invention to provide an improved system meeting the above needs. 
     The environment of the invention comprises a traffic control system for use at a roadway intersection, the system including traffic control lights, a light flasher means, and a plurality of load switches electrically coupled with the lights via relay means to which the flasher means is connected, the load switches having inputs, and a controller connected with the load switches for controlling normal operation of the lights and flashing of one or more of the lights by the flasher means in the event of a system malfunction. 
     In this environment, the invention provides: 
     a) flasher means electrically connectible to the lights to cause the lights to come ON and OFF, repeatedly, 
     b) an electrical power storage device electrically connected to the flasher means for supplying electrical power to operate the light flasher means when AC source power is not supplied to the traffic control system, and 
     c) a charging device for charging the storage device when AC power is normally supplied to the traffic control system. 
     Another embodiment of the invention provides a voltage disconnect device operatively connected with said storage device for preventing feed-back of stored power to selected elements of said control system when AC power is not being supplied to the system. 
     A further object is to provide a control system that includes
         i) load switches corresponding to said traffic control lights for supplying AC power thereto,   ii) a conflict monitor circuit,   iii) relay means operatively connected between said load switches and said control lights, and to said flasher means, and controlled by said monitor circuit, to remove a connection for power transmission via the load switches to the control lights, and to connect power transmission from the flasher means to said lights.       

     Yet another object is to provide a conflict monitor which includes measuring circuitry to measure the presence or absence of predetermined or selected AC field wire voltages at outputs defined by the load switches, whereby if the measured voltages are not at predetermined levels, the monitor determines that a malfunction has occurred, so that corrective action can be taken. 
     An additional object is to provide a controller or controllers, to control DC voltages that turn the load switches ON or OFF, the monitor operatively connected to said controller or controllers to monitor DC voltage, whereby if the DC voltage falls below a threshold level required for operation of the system, the monitor determines that a malfunction has occurred, and initiates corrective action. 
     These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which: 
    
    
     
       DRAWING DESCRIPTION 
         FIG. 1  is a preferred system block diagram; 
         FIG. 2  is a flasher block diagram; 
         FIG. 3  is a flasher detail diagram; 
         FIG. 4  shows waveform diagrams, at  4 ( a ),  4 ( b ) and  4 ( c ); 
         FIGS. 5 and 6  are modified block diagrams; 
         FIG. 7  is a further modified block diagram; 
         FIG. 8  shows a modified location of the  FIG. 3  circuitry; and 
         FIGS. 9 and 10  are circuit diagrams. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a traffic controller is indicated at  10 , as having output at  11 , connected at  12 - 16  with load switches  17 - 20 . Such switches have outputs at  21 - 24  connected at  25 - 29  with flash transfer relay means  30 , which is in turn connected at  31 - 36  with traffic control light units  37 - 40 . The latter are normally located at different corners of a roadway intersection. When a system malfunction or a power failure occurs, typically red lights in units  37 - 40  are placed in a flashing mode. This is accomplished by the high current capacity relay means  30 , which receives a flash initiating signal from a conflict monitor  41 , via connection  42 . The relay removes power transmission from the load switches normally connected via the relay to the respective four lights, and connects power transmission from the flasher circuit  43  to relevant light units. Relay means  30  is connected between  29  and  31 , as shown. 
     The conflict monitor  41  is shown as operatively connected with the load switches  17 - 20  via connection  44 , whereby the monitor  41  measures the presence or absence of predetermined or selected AC field wire voltages at the outputs  21 - 24  of the switches  17 - 20 , for example for appropriate AC voltage level supplied to the light units from the load switches. When AC field wire voltages at the outputs of the switches  17 - 20  are not appropriate, such as insufficient, the conflict monitor  41  determines that a malfunction has occurred and initiates corrective action. Also, the conflict monitor  41  monitors the DC voltage from the controller  10  that is used to turn each load switch output ON. If the DC voltage is below the minimum level required for operation of the traffic control system, the monitor  41  determines that a malfunction has occurred and initiates corrective action. Via AC connection  45 , the monitor  41  measures the AC supply voltage used to power equipment within the traffic control system which includes traffic controller  10 , load switches  17 - 20 , Flash Transfer Relay  30 , Flasher  43  and Conflict Monitor  41 , to ensure there is an adequate voltage level to operate the traffic control system. When the AC power voltage is below the minimum level required for operation of the traffic control system, the monitor  41  determines that a malfunction has occurred and initiates corrective action. In doing so, it is intended that monitor  41  causes the relay  30  to transfer electrical power connection to the traffic signal lights  37 - 40  from the load switches  17 - 20  to the flasher  43 , whereby the flasher then operates the signal lights  37 - 40 . 
     Transfer of operation of the traffic signal lights  37 - 40  to the flasher  43  will not cause operation of the lights if external AC power is insufficient to operate the flasher  43  and the traffic signal lights  37 - 40 . 
       FIG. 2  shows a block diagram of improvements provided by this invention for the flasher  43  which cause the traffic signal lights  37 - 40  to flash when AC power service supplied at  46  and  47  is below the voltage level necessary to operate the flasher  43  and the traffic signal lights  37 - 40 . This invention causes flasher unit operation under conditions when flasher units and traffic signal lights have previously been unable to operate, thus resulting in traffic signal lights becoming visible under conditions previously not possible. The flasher  43  is shown divided into two generalized circuit elements. One element indicated at  80  contains flashing logic and load power outputs connected as shown to the traffic signal lights  37 - 40 . The other element indicated at  81  contains back-up power charging, storage and switching circuitry for operating the flashing logic and load power outputs as well as the traffic signal lights, when AC power service at  46  and  47  is insufficient to cause traffic control system operation. 
       FIG. 3  presents further details describing improvements in operation. AC line voltage  46  and AC common voltage  47  enter the flasher  43  through a voltage disconnecting device  48  connected through paths  49  and  50  to voltage reduction circuitry  51 . The flasher unit  43  furthermore contains flashing logic  54  powered through connections  52  and  53  from the voltage reduction circuitry  51 . Such flashing logic  54  has outputs  55  and  56  connected at  57  and  58  to flasher load power output circuitry  57   a  and  58   a . Such flasher load power is delivered to the signal light loads through connections  61  and  62  from its outputs at  59  and  60 . Flasher power outputs  57   a  and  58   a  have sufficient current-carrying capacity to accommodate the traffic signal light loads  37 - 40 . Connection  61  supplies power to lights  37  and  38 ; and connection  62  supplies power to lights  39  and  40 . 
     Operation of the flasher  43  during times when AC line voltage  46  and AC common voltage  47  are below required levels occurs by virtue of the back-up power charging circuit  63 , the voltage rerouting control circuitry  64 , and the back-up power storage unit  65  for example interconnected as shown. During times when AC line voltage  46  and AC common voltage  47  are at levels sufficient to operate the flasher  43 , the back-up charging circuit or device  63  is activated through connections  66  and  67 . The back-up charging circuit or device  63 , such as an AC/DC converter, converts the AC line voltage  46  and AC common voltage  47  to DC voltage needed to charge the back-up power storage unit  65  such as a battery. The voltage rerouting circuitry is connected via connection  76  to the voltage disconnecting device. The voltage rerouting circuit  64  is also connected to the back-up power charging circuit  63  and to the back-up power storage unit  65 , through connections  68 - 71  as shown. The voltage rerouting control circuitry  64  provides several control functions. The first is to enable DC voltage produced from the back-up charging circuit  63  to be delivered to the back-up power storage unit  65  during times when the AC line voltage  46  and AC common voltage  47  are sufficient for operation of the flasher  43 , during which time it causes the voltage disconnecting device  48  to remain connected to the AC line voltage  46  and AC common voltage  47 . A second function occurs during times when the AC line voltage  46  and AC common voltage  47  are not sufficient for operation of the flasher  43  to cause the voltage disconnecting device  48  to remove the flasher elements from connection to the external power supply through  46  and  47  while simultaneously disconnecting from connections  68  and  69  and enabling connections  74  and  75  to connections  67  and  66 . This causes stored power from the back-up power storage  65  to be delivered through connections  72  and  73 , and ultimately to input connections  49  and  50 . A third function of the voltage rerouting control circuitry  64  is to convert the DC voltage output of the back-up power storage unit  65  into voltage needed to operate the flashing logic and load power outputs within the flasher  43 . Appropriate switches are contained within  64 . 
       FIG. 4  presents waveforms within which FIG.  4 ( a ) shows the standard AC voltage sine wave of peak voltage amplitude, V peak , and period, T, equal to 1/frequency. For 60 Hertz frequency AC the period is 16.6667 milliseconds. Industry standards such as those set by the FHWA define the period for the flasher  43  outputs  59  and  60  as 50 to 60 flashes/minute with an on period of 50+/−5 percent. FIGS.  4 ( b ) and  4 ( c ) present the waveforms for the flasher  43  outputs  59  and  60  where the AC waveform of FIG.  4 ( a ) would typically be observed to be superimposed upon the flasher load power outputs  59  and  60 . 
     The aforementioned elements, connections and functions may be implemented in separate units, within a single flasher unit or within the traffic signal light or lights and achieve the same desired results of self-powered flashing operation. Implementations in other structural ways, are contemplated. 
     It will be understood that the traffic signal lights may include LED&#39;s indicated at  201  which require minimum electrical power. Also, the housings  202  for the LED&#39;s at the signal lights may receive or house elements of the control circuitry referred to above, and indicated at locations  203 , within the housings. As a result, the back-up power storage unit  65  is required to supply only the minimum current needed for LED operation. 
     In  FIG. 7 , two single pole, double throw relays  225  and  226  are provided and connected as shown. The arm  225   a  of relay  225  is operated from circuitry  64 , via control line  225   b ; and arm  226   a  of relay  226  is operated from circuitry  64 , via control line  226   b . Relay  225 , when operated, enables connection of line  75  to connecting line  66 ; and relay  226 , when operated, enables connection of line  74  to connecting line  67 . The relays are equivalent to double pole, double throw relays. 
     The two relays  225  and  226  appear in position B. This would be the state when a power failure had occurred and  46  and  47  were below voltage thresholds established as sufficient for traffic control system operation. When the relays  225  and  226  are in position B, the back-up power system  81  will power flasher elements  51 ,  54 ,  57   a  and  58   a , thereby causing the traffic signals  37 ,  38 ,  39  and  40  to be lit. This is the state where the invention performs its novel, unique and useful function.  FIG. 7  shows element  43  (the flasher) connected to the traffic signal lights  37 - 40  as the result of flash transfer relay  30  being in the transferred state wherein the flasher is connected to the traffic signal lights. (The other state of the flash transfer relay  30  is where the load switches  17 - 20  are connected to the traffic signal lights  37 - 40 .) 
     While  FIG. 1  shows traffic signal lights  37 - 40  as being connected each by single connections  33 - 36 , it is clear from the symbols used for  37 - 40  that each traffic signal is comprised of three separate color indicating traffic signal light modules, i.e., R(=red), Y(=yellow) and G(=green). Application of the invention may also benefit from inclusion of a sub-figure detailing three separate electrical connections from the three separate outputs (R, Y and G) of one load switch to a traffic signal light. These connections could be referenced as  25   a ,  25   b  and  25   c  from load switch  17  and  33   a ,  33   b  and  33   c  to the traffic signal light  37 . FIG.  1  and subsequent figures need not be complicated by showing these additional lines. But, the sub-figure would then have laid the groundwork for describing the invention in its most commonly anticipated usage of flashing the red traffic signal light modules as opposed to unlikely use of flashing green traffic signal light modules. 
       FIG. 8  shows circuitry as in  FIG. 3 , located within a traffic light housing  84 . A traffic light lens and LED light array are indicated at  77  and  78 . The operational state shown is during AC power levels insufficient for traffic signal operation. Elements illustrated are listed as follows: 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                   FIG. 8  traffic signal light with LED module 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 46 
                 AC line voltage 
               
               
                 47 
                 AC common voltage 
               
               
                 48 
                 voltage disconnecting device 
               
               
                 63 
                 back-up power charging 
               
               
                 64 
                 voltage rerouting 
               
               
                 65 
                 back-up power storage 
               
               
                 68 
                 electrical connection 
               
               
                 69 
                 electrical connection 
               
               
                 70 
                 electrical connection 
               
               
                 71 
                 electrical connection 
               
               
                 72 
                 electrical connection 
               
               
                 73 
                 electrical connection 
               
               
                 74 
                 electrical connection 
               
               
                 75 
                 electrical connection 
               
               
                 76 
                 electrical connection 
               
               
                 77 
                 lens or cover 
               
               
                 78 
                 light emitting diode (LED) array 
               
               
                 79 
                 LED module internal power supply 
               
               
                 82 
                 electrical wire, line 
               
               
                 83 
                 electrical wire, common 
               
               
                 84 
                 housing 
               
               
                 85 
                 relay 
               
               
                   
               
             
          
         
       
     
     The voltage disconnecting device  48  in  FIG. 8  may be considered to be the equivalent of a relay, as shown in  FIGS. 9 and 10 .  FIG. 9  shows connections from AC line  46  and AC common  47  made to the flashing logic and load power outputs  80  when there is sufficient AC voltage to operate the traffic control system. When AC voltage drops below the threshold level, the voltage disconnecting device  48  removes  80  from  46  and  47 , as shown in FIG.  10 . Thus, AC voltage sensing circuitry is used in conjunction with  48 . 
     This invention enables the use of its elements, (herein stated as being separate), within fewer or combined elements, or may be separated further into additional elements, so as to still perform the same functions being described herein. In particular,  48  may be combined with the two relays  225  and  226 . Also, a plurality of relays may be used in various locations between the elements of this invention during its implementation, an example of such usage being shown in  FIG. 8 , the relays indicated at  230 ,  231 ,  232  and  233 . 
     Element  64  in  FIG. 8  also performs the useful function of generating proper voltages for use within the invention. Element  64  takes the DC voltage stored within element  65  and causes power to be delivered to flasher elements within  80  such that flashing of traffic signal lights will reliably result. In doing so, element  64  may act as an AC-inverter producing AC voltage of a type and form sufficient to allow for proper operation of flasher elements within  80 . One example of connections providing this capability is shown in  FIG. 3  with connection to element  51  via  49  and  50 . Another example of this invention is where element  64  produces reduced AC voltage of a type and form compatible to allow its connection to element  54  via  52  and  53 , such as indicated in FIG.  5 . Other examples of this invention encompass element  64  delivering pulsed DC voltage instead of AC voltage to element  54  via  52  and  53 , as well as to element  57   a  and element  58   a  whether both elements  57   a  and  58   a  are utilized or whether just one is incorporated within application of this invention. Accordingly, the invention is not limited to the shape or amplitude or periodicity of voltages supplied to cause flasher elements to operate, so long as the applied voltages are sufficient to cause the flasher to operate at all. 
     Elements  63  and  64  in  FIG. 8  may be combined to yield a DC charger/AC inverter with internal switching between these two functions and to charge/discharge the battery  65 . 
     The use of relay  230  at  85  is optional and is intended to isolate leakage of voltage from flasher output  61 , thereby preventing undesirable illumination of the LED array  78  at times when AC voltage at  46  and  47  are sufficient for normal operation of the traffic control system. Voltage leakage without incorporation of relay  230  may be expected to occur when the load switch connected to the traffic signal light module is in its OFF state (i.e., when traffic controller  10  has not caused the load switch to turn ON as the result of not having controlled DC voltage to be delivered to the load switch) and the flasher is in its OFF state. 
     Another embodiment of the invention provides traffic signal lights which include within them a:
         a) flasher means electrically connectible to the lights,   b) an electrical power storage device electrically connected to the flasher means,   c) a charging device for charging the storage device.       

     A further object is to provide a voltage disconnect device operatively connected with said storage device. 
       FIG. 3  shows connections  74  and  75  made to connections  67  and  66 . This implies that the voltage rerouting control circuitry  64  supplies AC voltage at a level comparable with that normally delivered through AC line voltage  46  and AC common voltage  47 . Another embodiment of the invention is where connections  74  and  75  are instead made to connections  52  and  53 , respectively. In this case, AC voltage having a lower voltage is delivered from voltage rerouting control circuitry  64  to flashing logic  54 . See FIG.  5 . The invention also encompasses modifications of examples shown and descriptions provided herein where defined flasher elements may be rearranged or reconnected, and also where DC voltages may be applied on-and-off so as to produce the same results of the invention described herein. An example is exhibited in FIG.  6 . 
     This invention may supply either AC, DC or DC on-and-off to the flasher  43  or to its elements. 
     Accordingly, the invention provides selective features such as:
         i) a voltage disconnect device operatively connected with said storage device of preventing feed-back of stored power to selected elements of said control system when AC power is not being supplied to the system,   ii) relay means operatively connected between said load switches and said control lights, and to said flasher means, and controlled by said monitor circuit, to remove power transmission via the load switches to the control lights, and to connect power transmission from the flasher means to said lights,   iii) a conflict monitor which includes circuitry to measure the presence or absence of predetermined or selected AC field wire voltages at outputs defined by the load switches, whereby if the measured voltages are not at predetermined levels, the monitor circuit determines that a malfunction has occurred, so that corrective action can be taken,   iv) a controller to control DC voltages that turn the load switches ON or OFF, the monitor operatively connected to said controller or controllers to monitor said DC voltages, whereby if the DC voltage falls below a threshold level required for operation of the system, the monitor circuit determines that a malfunction has occurred, and initiates corrective action,   v) LED traffic lights operable by the flasher means powered by an electric power storage device, in lieu of AC power supply.