WO1992018963A1

WO1992018963A1 - Traffic control device

Info

Publication number: WO1992018963A1
Application number: PCT/GB1992/000664
Authority: WO
Inventors: Desmond Martin Armstrong
Original assignee: Robo Signs Limited
Priority date: 1990-04-17
Filing date: 1992-04-13
Publication date: 1992-10-29
Also published as: IE903768A1

Abstract

A traffic control device comprises a base (14) which rotatably carries a sign (16). The sign (16) has two opposite sides respectively bearing 'STOP' and 'GO' indications. A motor on the base (14) is coupled to the sign (16) for rotating the latter. Control means in the base positions the sign (16) alternately in angular positions 180° apart in response to control signals issued from a remote handset (11). A traffic control system includes two such devices controlled by a common handset.

Description

Traffic Control Device

This invention relates to a traffic control device, especially but not exclusively for use for the temporary control of traffic in the vicinity of, for example, roadworks.

According to the present invention there is provided a traffic control device comprising a base, a sign rotatably carried by the base and having two opposite sides, one side bearing a "GO" indication and the other side bearing a "STOP" indication, a motor on the base coupled to the sign for rotating the latter, and control means for positioning the sign alternately in angular positions 180° apart.

By a "GO" indication we mean the word "GO" (in any language) and/or a green colour and/or any other symbol, word or colour which is generally recognised as permitting oncoming traffic to pass. Similarly, by a "STOP" indication we mean the word "STOP" (in any language) and/or a red colour and/or any other symbol, word or colour which is generally recognised as requiring oncoming traffic to stop.

Preferably, the motor is an electric motor which is powered by at least one battery mounted on the base.

In the preferred embodiment the control means is responsive to successive control signals such that each control signal causes the control means to rotate the sign through 180°.

In such embodiment the base carries two fixed sensors, and a sensor actuator is mounted for rotation with the sign so as to come into close proximity with alternate sensors every 180° rotation of the sign, the control means commencing rotation of the sign in response to a control signal and such rotation continuing thereafter until it is automatically halted when the sensor actuator comes into close proximity with the next sensor.

The sensors may be reed switches, and the sensor actuator a permanent magnet.

The invention further provides a traffic control system including two traffic control devices as aforesaid, and a remote unit such as a handset for issuing successive pairs of control signals to alternate devices.

Preferably, each control means includes means for automatically setting the sign of the associated device to a predetermined one of its two angular positions if the remote handset is disconnected.

Further, the remote handset preferably includes means for inhibiting the issuance of control signals to the other device if the battery power of one device fails or falls below a predetermined level.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic diagram of the main components of a traffic control system using two traffic control devices according to the embodiment of the invention; Figure 2 shows the traffic control system set up for use;

Figure 3 is a perspective view of one of the two traffic control devices shown in Figures 1 and 2 (both such devices being identical);

Figure 4 shows the traffic control device of Figure 3 with the base cover removed, and also the post and sign removed;

Figure 5 is a block diagram showing the main components in the handset which is common to the two devices of Figures 1 and 2;

Figure 6 is a block diagram showing the main components of the control circuit for each traffic control device of Figures 1 and 2;

Figure 7 is a flow diagram of the main program steps executed by the microprocessor in the control circuit of Figure 5;

Figure 8(a) is a block diagram of an automatic timer circuit which can be used to control the system shown in Figures 1 to 4 and 6; and

Figure 8(b) is a timing diagram showing the operation of the circuit of Figure 8(a).

Referring first to Figures 1 and 2, a temporary traffic control system comprises two identical traffic control devices 10, a remote handset 11 which is common to both devices 10, the handset 11 being connected in use to each device 10 via extension cables 12 wound on reels 13. The cables are typically 50 meters long, thus permitting the two devices 10 to be positioned up to 100 meters apart at opposite ends of a roadworks.

Each device 10 has a base 14, and a post 15 extends substantially vertically upwardly from the base and is rotatable about its own axis. A sign 16 in the form of a flat circular panel 16 is carried by the post 15, and this has on one side the work "GO" on a green background and on the opposite side the work "STOP" on a red background.

As will be described, a motor on the base 14 is coupled to the post 15 for rotating the latter, and control means responsive to successive control signals issued by the handset 11 (generated in response to successive pushes on a control button 17) rotate the post by 180° in response to each control signal to position the sign in alternate angular positions 180° apart.

In fact, the handset 11 is adapted to issue the control signals in pairs alternately to the devices 10, so that the complete control cycle consists of four consecutive control signals from the handset 11.

In the four-signal control cycle, the first control signal rotates one of the signs, say the left sign as shown in Figure 1, by 180°. The next control signal then rotates the same sign through a further 180° so that it returns to its original position. Then the next two control signals similarly cause the other sign (the right sign in Figure 1) to rotate through two successive 180° turns, returning it to the original position. This cycle repeats for each successive set of four control signals.

At this point it should be explained that each device 10 has a STOP position and a GO position. The STOP position is when the STOP side of the sign 16 is facing a particular direction relative to the base 14, for example away from the cable connector socket 18 (see also Figure 3), and the GO position is when the STOP side of the sign is facing towards the cable connector socket 18. Thus in Figure 1 the left hand sign is at the GO position whereas the right hand sign is at the STOP position. In Figure 2 both the signs are at the

STOP position, it being assumed that the cable connector sockets 18 are facing each other.

The aforesaid four-signal control sequence assumes the Figure 2 situation to be the starting positions for the signs, i.e. both the signs in their STOP positions with the STOP sides of the two signs 16 facing away from one another. Thus the first control signal will turn one of the signs to the GO position, the second control signal will then turn the same sign back to the STOP position, the third control signal will turn the other sign to the GO position and the fourth control signal will turn the same sign back to the STOP position.

This placement of the devices 10 prior to operation of the system is essential if there are not to be two GO signs simultaneously showing to oncoming traffic at opposite ends of a roadworks. At this point it should be mentioned that each device 10 is capable of independent operation by a dedicated handset in cases where the short length of roadworks does not warrant the use of two signs. Naturally in such a case it does not matter which way round the device is placed because, of course, there can never be a GO sign showing simultaneously in the two directions of traffic flow. The use of the device 10 as a single independent unit will be described later.

Turning now to Figures 3 and 4, each device 10 comprises a base frame 20 with carrying handles 21. A shaft 22 is mounted vertically in the base frame 20, in bearings 23, for rotation about its own axis. There is a pulley 24 fixed to the shaft 22, and the pulley 24 is coupled by a drive belt 25 to a motor pulley 26. The motor pulley 26 is connected to the drive shaft of an electric motor 27 mounted on the base frame 20. The belt 25 has a tensioner 28. The power for the electric motor 27 is derived from two 12-volt batteries 29 connected in parallel. The base further has a control box 30 containing control circuitry (Figure 5) for the device 10.

Just above and close to the upper surface of the pulley 24 there are fixed two position sensors in the form of reed switches 31 and 32 respectively. These are disposed 180° apart around the axis of the shaft 27. A small permanent magnet 33 is fixed to the upper surface of the pulley 24. Thus, as the shaft 27, and hence the post 15, rotates, the magnet 33 comes into close proximity with alternate reed switches 31 and 32 every 180° rotation of the post. The magnet 33 causes each reed switch 31 and 32 to close when it comes into close proximity with it. As will be described, it is the closure of a corresponding reed switch which terminates each 180° rotation of the shaft 27, rotation of the shaft 27 bein started in response to each control signal from the handset 11 and being automatically halted when the magnet 33 comes into close proximity with the next reed switch 31 or 32.

Thus the STOP position of the device 10 is defined by the angular position of the shaft 27 when th magnet 33 is closely adjacent a particular one of the two reed switches 31 or 32, and the GO position is defined when the magnet 33 is closely adjacent the othe of the two reed switches. In this embodiment it will b assumed that the reed switch 31 is that which defines the STOP position of the device, and the reed switch 32 is that which defines the GO position of the device.

For ease of transportation the pole 15 is removably mounted on the shaft 27, and the sign 16 is itself removably mounted on the pole 15. However, bearing in mind the need to establish unambiguous STOP and GO positions for the device, the pole 17 is only able to be fitted to the shaft 27 in one angular position, and likewise the sign 16 is only capable of being fitted to the pole 15 in one angular position.

Turning now to Figure 5, the handset 11 has three lines 50, 51 and 52 leading to each device 10 via a respective 3-core cable 12, Figures 1 and 2. Each line 50 connects to a respective LED 53 on the handset whose function will be described later. The lines 51 and 52 are connected to the positive and negative terminals respectively of the parallel connected batteries 29. A unit 54 derives power for the handset; it takes its input from both positive lines 51 because in certain circumstances the potential on one of the lines 51 drops to near ground, as will be described, so that handset power is ensured even when this happens.

When the control button 17 (see also Figure 1 ) is pressed by an operator, a short pulse is sent to a monostable 55 having a time constant of about 5 seconds. This ensures that even if the button 17 is pushed rapidly, pulses can only be passed on at intervals of 5 seconds or more. The reason for this will be explained later.

The pulses supplied by the button 17 enter a counter 56 which has four outputs 57, 58, 59 and 60, respectively. The counter 56 provides, for each set of four successive pulses from the button 17, an output signal on each of the outputs 57 to 60 in turn. Thus the first pulse in a set of four will provide a signal on output 57, the second pulse a signal on output 58, and so on, until the fifth pulse once again provides a signal on the output 57.

The signals on counter outputs 57 and 58 set and reset respectively a latched switch 61 , and the signals on counter outputs 59 and 60 set and reset respectively a latched switch 62. Setting the switch 61 by a signal on output 57 causes the switch 61 to short the lines 51 and 52 connected to the first device 10, and these lines are held shorted until a signal appears on output 58. Similarly, setting the switch 62 by a signal on output 59 causes the switch 61 to short the lines 51 and 52 connected to the second device 10, and these lines are held shorted until a signal appears on output 60. Thus for each sequence of four pulses from the button 17 which pass the monostable 55, first the two upper lines 51 and 52 in Figure 5 are shorted, then they are unshorted, then the two lower lines 51 and 52 in Figure 5 are shorted, and then they are unshorted. It is this shorting and unshorting of the pairs of lines 51 and 52 which constitute the control signals for the devices 10.

As will be described, shorting the upper pair of lines 51 and 52 will cause the corresponding device to turn from its STOP position to its GO position, unshorting them will cause the same device to turn back to its STOP position, then shorting the lower pair of lines 51 and 52 will cause the other device 10 to turn from its STOP position to its GO position, and unshorting them will cause that other device to turn back to its STOP position. Of course, this is the desired sequence, as described earlier in the Specification.

Turning now to Figure 6, the control circuit in each device 10 is shown. The lines 50 to 52 which lead to the handset are shown at lower right. The positive lead 51 has a solid state switch 81 and current limiter

82 connected in series, and a further solid state switch 83 and a load 84 are connected in series between the positive and negative leads 51 and 52 as shown. The switch 81 is normally closed (conducting) and the switch

83 is normally open.

The control circuit is based upon a 4-bit microprocessor (MPU) 80. This has inputs from the reed switches 31 and 32, from the positive supply line 51 at point P beyond the current limiter 82, and from the positive supply line at point between the batteries 29 and switch 81. There is also a conventional watchdog circuit 85 to monitor the correct operation of the MPU 80.

The MPU 80 has outputs controlling a solid state motor control switch 86, outputs which control the switches 81 and 83, and an output 50 to the corresponding LED 53 on the handset.

Turning now to Figure 7, the programmed operation of each device 10 when the traffic control system is connected up and the devices 10 powered on will now be described.

First, the device is initialised, step 100, inter alia by ensuring that the associated sign is in the STOP position. This it does by examining the reed switch 31 for being closed. At this point, if the device is not in the STOP position, the device may shut off, but preferably closes the motor control switch 86 until it senses that the reed switch 31 has become closed.

Next the MPU 80 performs a battery check, step 101. This is done by closing the switch 83, Figure 6, so that the battery voltage is applied across the test load 84, and measuring the potential at the point Q. If the battery is "good", which means that the battery level is at least 50% of its fully charged value, the MPU 80 continuously illuminates the corresponding LED 53 (step 102). If the battery is "bad", i.e. battery level of 50% or less, it makes a further determination at step 103 whether the battery level is less than 25%. If it is not, it flashes the LED 53 (step 104) which is a warning to the operator that the battery needs charging in the near future, but otherwise returns to the main loop. If the battery is less than 25%, the MPU 80 shuts off the power by opening the switch 81, step 105.

This has the effect of removing all power from the line 51 to the handset 11 (Figure 5). This in turn prevents operation of the other device 10, due to the cross couplings 70 between the switches 61 and 62. The cross couplings 70 are effectively "enable" lines, such that removal of all power from one of the lines 51 connected to switch 61 or 62 will disable (i.e. prevent closure of) the other switch 61 or 62. This ensures that the handset cannot issue control signals to either device 10 if the power on one device fails or is below the 25% level.

After the battery check, the MPU 80 moves to step 106, where it monitors the potential at point P, Figure 6, for going LO, meaning that the corresponding switch 61 or 62 in the handset has shorted the lines 51 and 52 leading to that device. At this point it should be noted that the handset has an in-built delay, not shown, before it is able to issue control signals to the counter 56, to permit each device 10 to perform the above-mentioned initialising and battery check.

When the MPU 80 detects the line 51 going LO, it starts the motor 27 by closing the switch 86, step 107, and then monitors the reed switch 32 for closing, step 108. When the MPU 80 detects the reed switch 32 closed it stops the motor 27, step 109, by opening the switch 86. Now the device is in its GO position. The MPU 80 now moves to step 110, where it again monitors the potential at point P, Figure 6, this time for going HI, meaning that the corresponding switch 61 or 62 in the handset has unshorted the lines 51 and 52 leading to that device.

When the MPU 80 detects the line 51 going HI, it again starts the motor 27 by closing the switch 86, step

111, and then monitors the reed switch for closing, step

112. When it detects the reed switch 31 closed, the MPU 80 stops the motor 27, step 113, by opening the switch

86. Now the device has returned to its START position, and the loop returns to step 106 looking for the next time the line 51 goes LO.

Since the counter 56 issues the control signals in pairs to the devices 10, a pair of control signals being the same set of lines 51 and 52 to a device first being shorted and then unshorted, although each device 10 does not "know" what state the other is in, it is ensured that each device will turn from its GO position and back to its STOP position before the other device leaves its STOP position.

The monostable 55, Figure 5, is important in this respect. The 5 second time constant is sufficient to ensure that, in response to a control signal from the handset 11, the corresponding sign will have moved to the next position (from GO to STOP or STOP to GO) before a following control signal can be issued. The 5 second delay is also long enough to permit a battery check to be performed at intervals throughout operation rather than just at the start, for example every 50 turns of the sign. This can be accomplished between steps 113 and 106 provided that the total time from steps 110 to 106 does not thereby exceed 5 seconds. Other routine tasks can also be performed during the period of the delay provided by the monostable 55.

A particular safety feature of the embodiment described is that if the remote handset 11 becomes disconnected from a device 10 by accident or design, th sign 16 will automatically turn to the STOP position if it is not already in the STOP position. This is becaus when the handset is disconnected the potential on the line 51 will go HI, and the MPU 80 will interpret this as a control signal from the handset 11 instructing it to turn to the STOP position.

The above has described the devices 10 used in pairs in a traffic control system. However, a single such device 10 may be used where appropriate, as discussed above. The handset for such a single device 10 operating on its own would consist essentially of an means to short and unshort the pair of lines 51 and 52.

Alternatively, such shorting and unshorting could be accomplished under control of an automatic timer, giving the possibility of an unattended traffic control device. An automatic timer could also be used with the traffic control system described above, instea of a manually operated handset.

One could also use infra-red or other cable-les communication between the handset and the devices 10.

Figure 8(a) is a block diagram of an automatic timer circuit which can be used to control the system shown in Figures 1 to 4 and 6 in place of the remote handset 11 whose circuit is shown in Figure 5. Figure 8(b) is a timing diagram showing the operation of the circuit of Figure 8(a). Each line of Figure 8(b) shows the signal occurring at the similarly referenced point in Figure 8(a) .

The automatic timer circuit comprises four so-called 555 timer chips T1 to T4 having respective trigger inputs TR1 to TR4 and respective outputs 0/P1 to 0/P4. The timers T1 to T4 are connected in series, with a feedback connection from the last timer T4 to the first timer T1. Thus the outputs 0/PI to 0/P3 of the timers TI to T3 are connected respectively to the trigger inputs TR2 to TR4 of the timers T2 to T4 via respective coupling capacitors C1 ' to C3' , and the output 0/P4 of the last timer T4 is connected to the trigger input TR1 of the first timer T1 via a coupling capacitor C4¹. A respective RC circuit R1,C1 to R4,C4 determines the time constant of each timer T1 to T4. It will be appreciated that instead of using four 555 timer chips the circuit may be implemented using two 556 timer chips, since a 556 timer chip contains within it two 555 timer circuits.

The outputs 0/P2 and 0/P4 of the timers T2 and T4 are connected to the bases of respective transistor switches 91 and 92. The emitter-collector path of the transistor switch SI is connected across the lines 51 and 52 leading to a first of the devices 10 (Figure 1), and the emitter-collector path of the transistor switch S2 is connected across the lines 51 and 52 leading to the other device 10. In the latter case the contacts of a normally-open relay RLY are connected in series with the emitter of the transistor switch S2, but for the moment the relay contacts will be assumed to be closed. The operation of the automatic timer circuit is as follows.

At time trj. Figure 8(b), the timer T1 is reset by a negative pulse applied to the reset input RST, which causes the voltage on the output 0/P1 of the timer T1 to go high. The capacitor C1 of the associated RC circuit R1,C1 charges up until it reaches the threshold voltage of the timer T1 , during which time the voltage on the output 0/P1 of the timer T1 remains high. At time t*| the capacitor C1 reaches the threshold voltage at which point the voltage at 0/P1 goes low.

The high-low transition occurring at O/Pl at time t*ι produces, via the coupling capacitor C1 ' , a negative-going pulse at the trigger input TR2 of the timer T2. This causes the voltage on the output 0/P2 of the timer T2 to go high. Similar to the case of the timer T1 , the capacitor C2 of the RC circuit R2,C2 associated with the timer T2 charges up until it reaches the threshold voltage of the timer T2, during which time the voltage on the output 0/P2 of the timer T2 remains high. At time t2 the capacitor C2 reaches the threshold voltage at which point the voltage at 0/P2 goes low.

The high-low transition occurring at 0/P2 at time t2 produces, via the coupling capacitor C2' , a negative-going pulse at the trigger input TR3 of the timer T3, whereupon the previously described sequence of events for timer T2 now occurs for timer T3, as shown in Figure 8(b), culminating at time tβ in a negative-going pulse at the trigger input TR4 of the timer T4. This in turn triggers the timer T4 and this too now goes through the described sequence ending at time t-j in a negative-going pulse appearing at the right hand side of the capacitor C4' . This pulse is fed back to the trigger input TR1 of the timer T1 , so that the cycle repeats again as from time to.

The output 0/P2 of the timer T2 is connected to the base of the transistor switch S1 , and the output 0/P4 of the timer T4 is connected to the base of the transistor switch S2. Thus, at time t-] the transistor switch S1 is turned ON, effectively shorting the two lines 51 and 52 leading to the first device 10, and at time t2 it turns OFF and unshorts the two lines. At time t3 the transistor switch S2 is turned ON, effectively shorting the two lines 51 and 52 leading to the second device 10, and at time t-} it turns OFF and unshorts the two lines. Thus, as the timer circuit cycles through its operation, first the pair of lines 51, 52 to one device 10 will be shorted and then unshorted, and then the pairs of lines 51, 52 to the second device 10 will be shorted and unshorted.

Thus, the first device 10 will turn to GO at time t*ι and return to STOP at time t2, and then the second device 10 will turn to GO at time t3 and return to STOP at time t.}. This is the required sequence, as described earlier in this Specification.

For safety reasons the outputs 0/P2 and 0/P4 from the timers T2 and T4 are respectively connected to the inputs of a NAND gate whose output controls the normally-open relay RLY. Normally, during correct operation of the timing circuit, the voltages on the outputs 0/P2 and 0/P4 will never be high at the same time, so that the output of the NAND gate will be high and the contacts of the relay RLY will be held closed. If, however, 0/P2 and 0/P4 should both become high at the same time, the output of the NAND gate will go low, releasing the relay contacts. This will unshort the lines 51, 52 leading to the second device 10, whatever the state of the transistor switch S2, so returning it to the STOP position. Naturally the relay RLY could be provided in series with the emitter of the switch S1 rather than S2.

The relay contacts will also open in the case of power failure of the automatic timing circuit. Preferably, the automatic timing circuit is battery powered, to permit use of the system independently of the need for mains power.

The timing of the GO/STOP cycle for the devices 10 is determined by the component values in the RC circuits R1,C1 to R4,C4. Clearly it is desirable to permit adjustment of the timing, and this is readily accomplished by providing each of R1 to R4 as a potentiometer.

The automatic timer circuit will include the lead 50 and LED 53 shown in Figure 5, but these are not shown in Figure 8(a).

It is to be understood that both in the case of the automatic timing circuit shown in Figure 8(a) and in the case of the handset 11 shown in Figure 5, one could use infra-red or other cable-less communication between the timing circuit or handset and the devices 10, instead of the lines 50 to 52.

Claims

CLAIMS :

1. A traffic control device comprising a base, a sign rotatably carried by the base and having two opposite sides, one side bearing a "GO" indication and the other side bearing a "STOP" indication, a motor on the base coupled to the sign for rotating the latter, and control means for positioning the sign alternately in angular positions 180° apart.

2. A traffic control device as claimed in claim 1, wherein the motor is an electric motor which is powered by at least one battery mounted on the base.

3. A traffic control device as claimed in Claim 1 or 2, wherein the control means is responsive to successive control signals such that each control signal causes the control means to rotate the sign through 180°.

4. A traffic control device as claimed in Claim 3, wherein the base carries two fixed sensors, wherein a sensor actuator is mounted for rotation with the sign so as to come into close proximity with alternate sensors every 180° rotation of the sign, and wherein the control means commences rotation of the sign in response to a control signal and such rotation continues thereafter until it is automatically halted when the sensor actuator comes into close proximity with the next sensor.

5. A traffic control device as claimed in Claim 4, wherein the sensors are reed switches, and the sensor actuator is a permanent magnet.

6. A traffic control system including two traffic control devices as claimed in Claim 3, 4 or 5, and a remote control unit for issuing successive pairs of control signals to alternate devices.

7. A traffic control system as claimed in Claim 6, wherein the control unit is a handset.

8. A traffic control system as claimed in Claim 6, wherein the control unit is an automatic timer.

9. A traffic control system as claimed in Claim 6, 7 or 8, wherein each control means includes means for automatically setting the sign of the associated device to a predetermined one of its two angular positions if the remote control unit is disconnected.

10. A traffic control system as claimed in Claim 6 or 7, wherein the control unit includes means for inhibiting the issuance of control signals to the other device if the battery power of one device fails or falls below a predetermined level.

11. A traffic control system substantially as described with reference to the accompanying drawings.