GB2347471A

GB2347471A - Protecting highway maintenance personnel working ahead of a stationary support vehicle

Info

Publication number: GB2347471A
Application number: GB0004137A
Authority: GB
Inventors: Norman Harold George Palmer
Original assignee: DANOR ELECTRONICS
Current assignee: DANOR ELECTRONICS
Priority date: 1999-03-05
Filing date: 2000-02-23
Publication date: 2000-09-06
Also published as: GB0004137D0; GB9904936D0

Abstract

A highway maintenance support vehicle 1 is fitted with an impact sensor 2 for sensing an impact of another vehicle with the vehicle 1, when stationary. Control circuitry 4 responsive to the sensor 2 enables the actuation of the vehicle brakes B 1, B2 when an impact is sensed, thereby opposing any tendency of the impact to move the vehicle 1. The sensor 2 comprises a flexible tube 6 connected to a pressure switch (P1, Fig. 2). The control circuitry 4 is only energised when warming lamps 10a, 10b at the rear of the vehicle 1 are switched on, the tube 6 is deployed and an activation switch 12 in the vehicle cab is on. An indicator 16 in the cab informs the driver that the control circuitry 4 is energised.

Description

Protection Apparatus The invention relates to protection apparatus particularly for a vehicle with brakes.

It is common for highway maintenance personnel to protect themselves whilst working by positioning a support vehicle between them and any oncoming traffic. Thus, the vehicle, commonly known as a block vehicle acts as a barrier and may be provided with a bumper or crash cushion to absorb the impact of any traffic which happens to collide with it. However, the bumper or crash cushion may have only a limited impact absorbency and, if the momentum of the colliding traffic is such that this absorbency is exceeded, the vehicle may be forced towards the maintenance personnel, potentially causing them injury.

There is therefore, a need for protection apparatus for a blocking vehicle which, in the event of a high momentum impact, reduces the risk of injury.

The invention provides protection apparatus for a vehicle with brakes comprising means for sensing an impact with the vehicle and means responsive to the sensing means for controlling the actuation of the vehicle brakes. The apparatus according to the invention enables the vehicle brakes to be applied in the event of an impact, thereby opposing any tendency of the impact to move the vehicle.

The vehicle may be moving or stationary immediately prior to the moment of an impact. The vehicle brakes may act upon one or more of the wheels and the vehicle may have one or an unlimited number of wheels.

The sensing means may be located in the region of the likely point of impact of another object with the vehicle and the apparatus may further comprise at least one warning lamp wherein the responsive means includes means for preventing the activation of the apparatus until the sensing means is deployed and at least one warning lamp is illuminated.

Activation of the apparatus may be notified by an audible or visible indicator which may operate in an intermittent mode prior to an impact and a continuous mode following an impact.

Preferably, the sensing means comprises a deformable member which deforms in response to an impact causing the pressure within the member to increase. Also preferably, the member is hollow and deformation increases the air pressure within the member.

Further preferably, the responsive means includes means for periodically relieving increases in pressure within the member caused by effects other than impacts. In the case of a hollow member, relieving the pressure may involve venting the hollow to atmosphere. The means which periodically relieves pressure may also be used to relieve the increase in pressure within the member caused by an impact.

The member may comprise a tube, closed at both ends, which may be substantially U-shaped in profile and ribbed so as to provide a combination of ruggedness and flexibility. The tube may be deployed as a bumper.

The invention will now be described, by way of example, with reference to the following drawings in which: Figure 1 is a schematic representation of a vehicle fitted with protection apparatus according to the invention; and Figure 2 is a diagram of the circuitry utilised in the protection apparatus shown in figure 1.

With reference to figure 1, a highway maintenance support vehicle indicated generally at 1 is fitted with protection apparatus comprising an impact sensor 2 and control circuitry 4. The impact sensor 2 comprises a hollow, polymeric material tube 6, closed at both ends, substantially U-shaped in profile and having transverse ribs to provide a combination of ruggedness and flexibility. The tube 6 is deployed as a bumper at the rear of the vehicle 1, at the likely point of impact from other traffic. The hollow in the tube 7 is connected via a nylon pipe 8 to a pressure actuated switch PI in the control circuitry 4 (see figure 2). Also deployed at the rear of the vehicle are four warning lamps 10 a-d (only two of which l Oa-b, are shown) The vehicle has wheels Wl-4 (only two of which, Wl-2, are shown) and air brakes B 1-4 (again, only two of which, B1-2, are shown) which act thereon. The actuation of brakes is controlled by a BASV valve BV1.

With reference also to figure 2, the control circuitry 4 is only energised when the four warning lamps 10 a-d at the rear of the vehicle 1 are switched on, the tube 6 is deployed and an activation switch 12 in the vehicle cab is on. When these conditions are met, current will flow through the reverse polarity diode D1 and energise the main positive rail 14.

Resistor R 1, Zener diode ZD 1 and capacitor C 1 form a stabilised power supply which is used to supply two 555 timer circuits with a transient free 12 volt supply.

A cab indicator circuit controls a visual and/or audible indicator 16 in the vehicle cab to inform the driver that the control circuitry 4 is energised. The cab indicator circuit is protected against short circuits at the cab indicator or interconnected wiring and operates as follows : The integrated circuit IC1 is a 555 timer connected in the astable mode. When the control circuitry 4 is first switched on, capacitor C2 will be discharged and ICI pin 3 will rise to nearly 12 volts. Capacitor C2 will charge via resistors R2 and R3 on a 0.5 sec time constant and when the voltage across it reaches 8 volts, the output of IC 1 at pin 3 will go low as will the voltage at the discharge pin 7 of IC 1. Capacitor C2 will then discharge via resistor R3 until the voltage across it drops to 4 volts. At this instant, the output of IC1 will go high again and the discharge path into pin 7 of IC1 will be blocked. The output of IC1 comprises an essentially symmetrical square wave with a periodic time of approximately 1 second.

When the output of IC1 goes high, capacitor C3 will charge via resistor R4, diode D4 and the base emitter junction of transistor TRI. This will cause transistor TR1 to turn on and enable current to flow out of the base of the Darlington transistor pair TR2. Transistor TR2 will then turn on and energise the cab warning light and/or buzzer 16.

The voltage across the cab indicator 16 will rise and reverse bias diode D3 and enable current to flow from IC 1 pin 3 through resistor R5 and diodes D2 and D4 into the base of transistor TRI to augment the charging current of capacitor C3 which drops to a very low value after 0.5 milliseconds. The cab indicator 16 will continue operating until the end of the pulse when it will turn off until the next pulse occurs.

When the pressure actuated switch PI operates, the voltage at the cathode of the diode D5 will rise to the voltage of the positive rail 14. Current will then flow through diode D5, resistor R6 and diode D4 into the base of transistor TR1 thus causing it to conduct continuously. The cab indicator 16 will therefore change from a flashing mode to a continuous mode when the braking system is actuated.

If a short circuit should occur across the cab indicator 16, the voltage at the anode of diode D3 will be held at zero volts with its cathode consequently limited to 0.6 volts which is insufficient to maintain transistor TR1 in conduction. Transistor TR1 will therefore turn off and prevent transistor TR2 from conducting approximately 0.5 milliseconds after the beginning of each pulse. Transistor TR2 provides pulses of current 0.5 milliseconds wide once a second into the short circuit repetitively.

The nylon pipe 8 is connected to the pneumatic low pressure switch PI. An electropneumatic REEDEX valve RV1 has its pneumatic path connected across the pneumatic section of the low pressure switch PI.

When the control circuitry 4 is de-energised the REEDEX valve RV1 will be open and any increase in air pressure within the tube 6 will leak away to atmosphere and thus be unable to operate the low pressure switch. When the system is energised the REEDEX valve RV1 will close and seal the pneumatic system. However, if the pressure in the tube 6 increases sufficiently, whether it be due to impact or any other cause, the contacts of the low pressure switch PI will close and initiate the actuation of brakes B 1-4.

The control circuitry 4 may be energised for hours at a time. The temperature of the air within the tube 6 and the other pneumatic elements can rise considerably during this period of time, particularly if bright sunshine is shining on the tube 6, and the pressure can rise sufficiently to close the contacts of the pressure switch PI and initiate the actuation of the brakes.

This problem can be avoided by periodically de-energising the REEDEX valve RV1 every few minutes. This is achieved by the use of a second timer circuit based on another 555 timer, IC2, which operates as follows: When the control circuitry 4 is first energised, the 12 volt stabilised supply will be established. The output of IC2 will rise to nearly 12 volts and capacitor C7 will start to charge via resistors R21 and R22 on a 220 second time constant. When the voltage across capacitor C7 reaches 2/3rd of the supply voltage, i. e. 8 volts, the output at pin 3 will go low and capacitor C7 will start to discharge via resistor R22 on a 470 m sec time constant. The output of IC2 will therefore be high most of the time but will go low for approx 0.5 second every 220 seconds.

When the output of IC2 is high, base current will flow into the base of transistor TR6 which will conduct and energise the REEDEX valve RV1 thereby blocking the bleed across the low pressure switch. When the output of IC2 goes low, transistor TR6 will turn off thus deenergising the REEDEX valve RVI and allowing any build up of pressure in the pneumatic system to bleed away to atmosphere.

If another vehicle (not shown) collides with the vehicle 1 and impacts upon the tube 6, the increase in air pressure within the tube 6 will be transmitted via the nylon pipe 8 to the low pressure switch P 1. The switch PI contacts will close and allow current to flow via resistor R10 into the base of transistor TR3 which will turn on and enable current to flow out of the base of the Darlington transistor pair TR5. This will turn on and energise the BASV valve BV 1 which will cause the vehicle brakes B 1-4 to actuate. The action of the brakes will oppose the tendency of the vehicle 1 to move under the effect of the colliding vehicle.

When transistor TR5 turns on, the voltage at its collector will rise nearly to the rail voltage.

Current will then flow via zener diode ZD4 and diode D7 into the base of transistor TR3 via resistor RIO. This latching circuit ensures that the vehicle brakes remain operated even if the low pressure switch P 1 contacts open. The brakes B 1-4 will remain applied until the positive supply to the control circuitry 4 is removed.

Transistor TR5 is protected against overload or short circuit across the BASV valve BV 1 as follows : A transistor TR4 has its base connected to a potential divider consisting of resistors R12, R13 and R14 between the positive rail 14 and the collector of transistor TR3. The resistor values of this potential divider are such that, alone they would cause transistor TR4 to conduct heavily and clamp the base of the transistor TR5 thereby preventing it from conducting.

In order to enable transistor TR5 to conduct a capacitor C5 is connected between the base and emitter of transistor TR4. This prevents transistor TR4 from conducting for a short period after transistor TR3 conducts. This enables transistor TR5 to conduct and the voltage at its collector to rise. Current will then flow through diode D9 to the junction of resistors R13 and R14. This increases the voltage at the junction of resistors R12 and R13 to a level which prevents transistor TR4 from conducting and hence allows transistor TR5 to continue conducting.

As the current through transistor TR5 increases so does the collector-emitter voltage ie the voltage at the collector will drop. The voltage at the anode of diode D9 will drop by a similar amount.

When the current through transistor TR5 reaches the current limit level, the voltage at the anode of D9 will have dropped sufficiently to enable TR4 to start to conduct. This will reduce the base current of transistor TR5 which will cause its collector-emitter voltage to increase even more. This will increase the conduction of transistor TR4. Positive feedback occurs and the transistor TR5 will turn off very rapidly.

The same operation occurs if a short circuit occurs across the BASV valve BV1.

When an impact occurs at the tube 6, considerable pressure can occur. The low pressure switch P1 can withstand substantial overpressure. However, in order to reduce the pressure as much as possible, after the BASV valve BV1 has operated, the REEDEX valve RV1 is arranged to open as follows : When the BASV valve BV1 has operated, there will be a voltage almost equal to the rail voltage across it. This voltage will cause current to flow into the base of transistor TR7 via resistor R19. Transistor TR7 will turn on hard and clamp the base of transistor TR6 thus causing it to turn off and de-energise the REEDEX valve RV1. The REEDEX valve RV1 will open and release the pressure in pneumatic system to atmosphere.

Claims

CLAIMS 1. A protection apparatus in or for a vehicle for the protection of highway maintenance personnel comprising vehicle brakes, sensing means for detecting an impact with the vehicle by a second, moving vehicle, and means responsive to the sensing means for controlling the actuation of the vehicle brakes.
2. A protection apparatus as claimed in claim 1 in which the sensing means comprises a deformable member which deforms in response to an impact with the vehicle.
3. A protection apparatus as claimed in claim 2 in which the deformable member is -hollow, deformation of the member causing an increase of pressure within the member.
4. A protection apparatus as claimed in claim 3 in which the sensing means further comprises a pressure switch for detecting any increase in pressure in the deformable member.
5. A protection apparatus as claimed in claim 3 in which the pressure switch is a low pressure switch.
6. A protection apparatus as claimed in claim 5 in which the contacts of the low pressure switch are caused to close by an increase in pressure in the deformable member caused by an impact, the closing of the switch causing an electrical power supply to be provided to the responsive means to actuate the vehicle brakes, thereby opposing any tendency of the impact to move the vehicle.
7. A protection apparatus as claimed in claim 6 in which a latching circuit maintains the vehicle brakes in the actuated position after an impact has been detected by closing of the low pressure switch, even if the contacts of the switch open.
8. A protection apparatus as claimed in claim 7 in which the brakes remain actuated until the electrical power supply to the responsive means is removed.
9. A protection apparatus as claimed in claim 3 in which an electro-pneumatic valve is provided for periodically relieving increases in pressure within the member caused by an impact and/or effects other than impacts.
10. A protection apparatus as claimed in claim 9 in which the electro-pneumatic valve is controlled by means of a timing circuit.
11. A protection apparatus as claimed in claim 10 in which the electro-pneumatic valve is closed when the valve is energised thereby sealing the deformable member and open when the valve is de-energised thereby venting the deformable member to atmosphere.
12. A protection apparatus as claimed in claim 11 in which the timing circuit energises the electro-pneumatic valve most of the time, and periodically de-energises the valve momentarily.
13. A protection apparatus as claimed in claim 12 in which the electro-pneumatic valve is de-energised for substantially 0.5 seconds every 220 seconds.
14. A protection apparatus as claimed in claim 2 in which the deformable member comprises a tube, closed at both ends, ribbed and substantially U-shaped in profile.
15. A protection apparatus as claimed in claim 14 in which the tube is formed as a bumper.
16. A protection apparatus as claimed in claim 1 in which the responsive means includes means for preventing actuation of the vehicle brakes until the sensing means is deployed and at least one warning lamp is illuminated.
17. A protection apparatus as claimed in claim 16 in which an audible or visible indicator is provided which indicates when the protection apparatus is operational.
18. A protection apparatus for protection of highway maintenance personnel substantially as herein described with reference to and as illustrated in figures 1 and 2 of the accompanying drawings.