GB2172456A - A device for monitoring the operation of the lights circuit of a trailer of a commercial vehicle - Google Patents

Abstract

The device comprises a first and second processing means 3, 4 which can be located on the tractor and the trailer respectively, and having respective outputs connected together at a node 24 and further connected to a third processing means 27. This latter includes comparators 60, 65, 70 which detect the signal level coming from the first and second processing means and selectively control the activation of corresponding display elements 67, 69 and 72, 73 mounted in a position visible to the driver. The lamps 5, 6 on the trailer are connected to the supply 11 via the series circuit of a resistor 37 in processor 4 and a relay coil 12 in processor 3; coil 12 operates read switch contacts 14. The comparators 60, 65, 70 discriminate between three signal levels provided at node 24 by processors 3 and 4. A yellow LED 67 is turned on in response to a high level at node 24 obtained when information from the trailer processor 4 is not available, e.g. due the tractor and trailer being uncoupled, absence of a processor 4 on the trailer, malfunction of the processor 4 or an interruption in the connection of processor 4 to node 24. If the device and light circuit are normal, an intermediate level is provided at node 24 and a green LED 69 is turned on. In the presence of a failure in the supply circuit of lamps 5, 6, e.g. due to an interruption in the circuit or burning out of a lamp 5, or 6, node 24 is at a low level and green LED 69 and red LEDS 72, 73 are turned on. <IMAGE>

Description

SPECIFICATION A device for monitoring the operation of a trailer lights circuit for a commercial vehicle The present invention relates to a device for monitoring a trailer vehicle lights circuit for a commercial vehicle of the type having a tractor and trailer. More particularly, by lights circuit is intended both the side lights, sub-divided into two branches, and the stop lights, as well as the associated supply cables which extend from the trailer to the tractor via an electrical connection coupling.

Currently, devices for monitoring the operation of a trailer lights circuit do not exist. In fact, currently known commercially available devices can only be mounted on the tractors of commercial vehicles or else on motor vehicles in general. Monitoring the operation of the lights of a trailer is in general particularly difficult due to the fact that the electrical connection which establishes the connection between the tractor's wiring and that of the trailer has in general only a single cable available to pass all the signals relating to the operation of the above mentioned lights circuit.Moreover, it is necessary to take into account that a single tractor can be used to draw not only trailers provided with a lights monitoring circuit but also trailers which do not have such arrangements, and this must not detrimentally affect the correct operation of any possible monitoring device.

Finally, it will be necessary to take into account the different arrangements of lights which may be encountered on any possible trailer provided with means for monitoring its lights circuit; for example it could happen that it will be necessary to monitor, with the same device, two lights positioned in parallel rather than a single light.

The object of the present invention is that of providing a device for monitoring a lights circuit of a trailer, which is able to satisfy all the above listed conditions.

The said object is achieved with the present invention in that it relates to a device for monitoring a trailer lights circuit of a commercial vehicle of the type having a tractor and a trailer, characterised by the fact that it comprises: - first and second processing means respectively mountable on the said tractor and the said trailer in such a way as to be connected, in use, in series in a supply circuit for indicator lamps located on the said trailer; -third processing means having an input connected to the outputs of the said first and second processor means and including comparator means operable to generate control signals in dependence on the level of signals present at the said input; and -display means controlled selectively by the said comparator means and mountable in the cab of the tractor in a position visible to the driver.

For a better understanding of the present invention a preferred embodiment will now be described purely by way of non limitative example and with reference to the attached drawing, and in which: Figure 1 is an electrical diagram of a monitoring device formed according to the present invention; and Figure 2 is a front view of an indicator panel conveniently mountable within a driver's cab of a commercial vehicle.

With particular reference to Figure 1, a device for monitoring the operation of a lights circuit 2 of a trailer of a commercial vehicle of the type having a tractor and a trailer is generally indicated with the reference numeral 1. More particularly, the device 1 essentially comprises first and second processing means, mountable, respectively, on the tractor and the trailer in such a way as to be, in use, connected in series in the lights circuit 2, which essentially comprises, in this specific case, a pair of side lights 5, 6, located on the trailer and connected together in parallel.One terminal of these latter is connected to earth and another terminal is connected, by means of a connector 7, to the processing circuit 4 located on the trailer, a further connector 8, the processing circuit 3 located on the tractor, a further connector 9 and a switch 10, with a terminal 11 connected, in a manner not illustrated, to the positive pole of a DC supply source, such as, for example, an accumulator battery.

The processing circuit 3 includes a winding 12 connected between the connectors 8 and 9 in such a way as to be traversed, in use, by the current which flows in the lamps 5 and 6. This winding 12 is conveniently mounted in a casing 13 of a magnetically actuable switch 14 (for example a reed contact).

The switch terminals 14 are connected, respectively, on one side to the connector 9 and a terminal of a resistor 15 and, on the opposite side, to an earthed resistor 16 and a first input of a logic gate 17 of exclusive OR type a second input to which is connected to the second terminal of the resistor 15.

The connector 9 is likewise connected, as indicated in broken outline, to a circuit portion comprising voltage dropping resistors 18 and a suitable detector unit 19 for the purpose of monitoring, according to known methods, the operation of indicator lamps 20 located on the said tractor.

The output of the logic gate 17 is connected both to the anode of a diode 21 and to the input of an inverting gate 22 of NOT type. The output of this latter is connected to a node, indicated 24, to which there is connected, by means of a connector 25, the output of the processing circuit 4 mounted on the trailer; the node 24 is also connected, by means of a connector 26, to the input of a further processing circuit indicated 27. The cathode of the diode 21 is connected to a first terminal of a resistor 29 and to the output of a comparator 30; this latter has an inverting input (-) connected to the node 24 by means of a resistor 31 and, via a capacitor 32, to a terminal 33 connected in a manner not illustrated to a positive pole of a DC supply.To this terminal 33 there is likewise connected the second terminal of the resistor 29 as well as the first end of a divider constituted by two resistors 34, 35 the opposite end of which is earthed and an intermediate connection point of which is connected to the non-inverting input (+) of the comparator 30.

The processing circuit 4 essentially comprises a resistor 37 connected in series between the connectors 7 and 8 in such a way as to constitute a divider with the resistance of the lamps 5 and 6. A connection point between the resistor 37 and these lamps is connected, via a resistor 38, to the inverting input (-) of a comparator 40 which has a non-inverting input (+) connected to a connection point between three resistors 41,42,43 respectively, the opposite terminal of the first of which is connected to a terminal 44 and to the connector 8, whilst the opposite terminal of the second resistor is connected to a terminal 45 and the opposite terminal of the third resistor is earthed. The reference numeral 46 indicates a suitable horse-shoe-shape connector which can electrically connect the terminals 44 and 45 together.The output of the comparator 40 is connected to the connector 25, at which, via resistor 49, arrives a signal coming from a comparator 50 the inverting input (-) and non-inverting input (+) of which are connected to corresponding intermediate nodes of dividers formed by two respective pairs of resistors 51,52 and 53, 54 respectively connected between earth and a connector 55 atwhich, in use, arrives a positive DC supply voltage, for example from the said accumulator battery on the tractor.

The connector 26 is connected to a processing circuit 27 at a node to which are joined three resistors 56, 57 and 58 and a capacitor 59. The resistor 56 is likewise connected, at its opposite end, to an inverting input (-) of a comparator 60. The resistor 57 on the other hand is connected at its opposite end to a terminal 61 connected, in a manner not illustrated, to a positive supply terminal, whilst the other terminal of the capacitor 59 is earthed. Between the terminal 61 and earth there is, moreover, connected a voltage divider constituted by a set of three resistors 62,63,64 respectively.The junction point between the resistors 62 and 63 is connected both to the non inverting input (+) of the comparator 60 and to the non-inverting input (+) of a comparator 65 the corresponding inverting input (-) of which is connected to the output of the comparator 60 and likewise connected to the terminal 61 via a resistor 66 and a light-emitting diode 67 respectively.

The output of the comparator 65 is also connected to the terminal 61 via a corresponding resistor 68 and a light-emitting diode 69. The junction point between the resistors 63 and 64 is connected to the inverting input (-) of a comparator 70, the non-inverting input (+) of which is connected to a terminal of the resistor 58 and an output of which is connected via a resistor 71 and a pair of light-emitting diodes 72,73 located in parallel, to the said terminal 61. The light-emitting diodes 67, 69,72,73 constitute, as a whole, indicator means generally indicated 75 the selective illumination of which allows the driver to verify in the manner described hereinbelow, the operation of the lights circuit of the said trailer.

With particular reference to Figure 2, a display panel is generally indicated with the reference numeral 80, this having an essentially rectangular screen 81 which is sub-divided into different indicator areas. In particular, on the left side of the screen 81 there is formed an indicator area comprising a push-button 82 and an illuminable indicator 83, for example of green colour, located adjacent the lower edge. Along this edge and in three different indicator areas are spaced a corresponding number of illuminable indicators 84, 85, 86 for example of red colour, above which are positioned respective symbols which indicate, for example, the level of water in the radiator, the level of the engine oil, and the level of water for the screen washer.The illumination of any of such illuminable indicators indicates therefore that the level of the corresponding liquid is below a predetermined minimum value.

Finally, in the zone positioned above the areas containing the indicators 84, 85,86 there is, schematically indicated, the outline of a tractor 87 drawing a trailer 88. Connected to the tractor 87 are a number of illuminable indicators 89, for example coloured red, illumination of which indicates possible inoperability of the external indicator lights, side lights, stop lights, rear fog lamp and number plate light.

On the shape representing the trailer 88 there are, on the other hand, disposed illuminable indicators 67, for example coloured yellow, 69, for example coloured green, and 72,73 for example coloured red, already mentioned with reference to Figure 1. In particular, it is to be observed that the yellow indicator 67 is positioned in correspondence with the connection between the trailer 88 and the tractor 87, whilst the green indicator 69 is positioned at the centre of the trailer 88, and the red indicators 72, 73 are positioned in a rear zone of the trailer 88.The illuminable indicator 67 is therefore essentially in the position in which, in use, the electrical coupling connector between the tractor and trailer is located, which itself contains, with reference to Figure 1, the connectors 25, 55,8 and other connectors similar two the connector 8 and supplying, for example, the other branch of the position indicator lamps or else the stop lamps or other electrical services disposed on the trailer and which must be monitored from the tractor.

The operation of the device 1 is now illustrated by studying all the typical correct operation situations and the failure situations which can happen most frequently.

In particular, the condition in which the trailer is separated from the tractor, or else the trailer is uncoupled losing the processing circuit 4, or else the cable which leads to the node 24 via the connector 25 is broken causes illumination of the yellow light-emitting diode 67, which therefore indicates that it is not possible to obtain information from the trailer lights circuit. The illumination of the yellow light-emitting diode 67 takes place in the following manner. First of all, supply to the terminal 33 of the device 1 involves, via the capacitor 32, the maintenance of the inverting input of the comparator 30 at a positive level and this sets the associated output at the logic level zero. This holds the input of the logic NOT gate 22 at the logic level zero and therefore signals coming from the output of the exclusive OR logic gate 17 are not taken into consideration; as a consequence of this the output of the NOT gate 22 is at logic level 81 at the inverting input of the comparator 30 and ensures that a signal is sent to the inverting input of the comparator 60 which is at a higher level than the corresponding level present at the non-inverting input. Consequently a low output level of the comparator 60 is obtained with consequent illumination of the light-emitting diode 67, whilst for similar reasons the outputs of the comparators 65 and 70 are high and therefore the lightemitting diodes 69,70 and 73 are extinguished.

When the trailer is coupled and everything is functioning correctly the green light-emitting diode 69 of the device 1 is illuminated whilst all the others are extinguished. In fact, if everything is operating correctly it also signifies that the connector 55 of the trailer is receiving the supply voltage and involves, because the dividers supplying the inputs of the comparator 50 are so dimensioned, the displacemenu to logic level "0" of the output of the comparator 50 in such a way that the voltage at the node 24 is divided, becoming lower, taking into account essentally the division ratio between the resistors 57 (positioned in the processing circuit 27) and 49 (positioned in the processing circuit 4).Consequently, the voltage level sent to the inverting input of the comparator 60 is now less than the corresponding voltage level present at the non-inverting input of the comparator 60 so that the output of this latter commutes from the logic level "0" to the logic level "1" causing consequent commutation of the output of the comparator 65 and therefore illumination of the light-emitting diode 69. The lowering of the voltage at the node 24 also causes a lowering of the voltage present at the inverting input of the comparator 30 to an extend such that this voltage is now lower than that present at the corresponding noninverting input. Consequently the output of the comarator 30 commutes to the logic level "1" and in this conditions allows the passage of the electrical signal from the output of the exclusive OR gate 17 to the input of the NOT gate 22.Since it has been assumed that everything is working correctly, the output of the exclusive OR gate 17 is at logic level "0" because the respective inputs are both at logic level "0" (when the switch 10 is open) or else both at logic level "1" (when the switch 10 is closed). It is to be noted, moreover, that in these conditions the two dividers which, in the processing circuit 4 supply the inputs of the comparator 40, are adjusted such that the voltage at the non-inverting input is greater than that at the inverting input when the situation is normal, so that the output of this comparator is at logic level "1" in correct operating conditions, and therefore does not influence the potential of the node 24.

The condition in which the trailer is coupled and at least one of the lamps 5 and 6 is burned out is indicated by the device 1 by means of the illumination of the red light-emitting diode 69, which indi cates that the processing circuit 4 in the trailer is operating, and the illumination of the red light emitting diodes 72 and 73 which on the other hand indicate that there is a fault. This is possible because the burn out of at least one of the lamps 5 and 6 causes a raising of the voltage sent to the inverting input the comparator 40 by an amount sufficient to exceed the voltage level present at the non inverting input. Therefore the output of the comparator 40 commutes to logic level "0" and therefore forces the voltage of the node 24 also down to level "0".Consequently the voltage at the non-inverting input of the comparator 70 is lowered to a point below the voltage level present at the inverting input of the comparator 70, consequently causing commutation of the signal at the output from level "1 " to level "0" and therefore illumination of the lightemitting diodes 72 and 73.

The device 1 is moreover able to indicate, by illumination of the green light-emitting diodes 69 and the red light-emitting diodes 72, 73 the possible interruption of any of the cables which supply the lamps of the trailer or the supply cable for the processing circuit 4 leading tothe connector 55, in which case the yellow light-emitting diode 67 is illuminated. Supposing first of all, for example, that the supply cable is undamaged and that at least one of the two lamps 5 or 6 is operating and, moreover, that the supply cable which leads to the connector 55 is unbroken.In these conditions, supposing that the switch 10 is open, there are two signals at logic level "O" at the respective inputs of the exclusive OR logic gate 17 in that one input is connected to earth via the resistor 16 and the other input is connected to earth via the resistor 15, the winding 12, the connector 8, the resistor 37, the connector 7 and at least one of the lamps 5 or 6. Consequently the output of the gate 17 is at logic level "0" and maintains the output of the gate 22 at logic level "1".Since, as already seen, the presence of the correct supply voltage at the connector 55 maintains the output of the comparator 50 at "0", the node 24 is consequently at a potential which can be considered intermediate between the maximum value and the "0" value and is such as to cause a high level signal at the output of the comparator 60 and consequently a low level signal at the output of the comparator 65 with illumination of the lightemitting diode 69. This situation remains the same even after closure of the switch 10. In fact, in such conditions, the passage of the supply current directed towards the lamps 5 and 6 causes magnetic attraction of the contacts of the switch 14 and therefore puts both the inputs of the exclusive OR logic gate 17 to level "1" with consequent maintenance of the associated output at logic level "0".If the supply current to the lamps 5 and 6 cannot flow because the associated cable is ruptured or else both the lamps are burnt out or missing a fault indication is obtained through illumination of the green lightemitting diode 69 and the red light-emitting diodes 72 and 73. In fact, closure of the switch 10 causes the upper input of the exclusive OR logic gate 17 to be positioned at logic level "1" via the resistor 15, whilst the other input, not being able to close the switch 14 due to the lack of current in the winding 12, is held at earth level by the resistor 16. Consequently the output of the exclusive OR gate 17 is at logic level "1" and holds the output of the NOT gate 22 at logic level "0"; consequently the node 24 is at logic level "0" which means, as already seen hereinabove, illumi nation of the green light-emitting diode 69 and of the red light-emitting diodes 72 and 73. If the supply directed to the processing circuit 4 via the connector 55 is interrupted, the outputs of the comparators 40 and 50 are fluctuating and the potential setatthe output of the NOT gate 22 likewise fluctuates. In other words, we are back to the case already examined in which the connector 25 is interrupted, and therefore in this condition the yellow lightemitting diode 67 is illuminated which indicates the non-operation of the processing circuit 4 mounted on the trailer.

Finally, it is observed that the device 1, and in particularthe processing circuit 4, is capable of detecting whether one or two lamps on a two lamp installation is or are burnt out as described hereinabove, orwhethera single lamp is burntoutwhen this is the only one to be installed. Whilst the first case has been examined hereinabove, the detection of the burning out of a lamp on a single lamp installation requires an adjustment of the voltage reference level present at the non-inverting input of the comparator 40. This is possible by connecting the terminals 44 and 45 by means of the horseshoe connector 46 in such a way as to connect the resistor 42 in parallel with the resistor 41 and therefore obtain a raising of the intervention threshold of the comparator 40.

From a study of the characteristics of the device 1 formed according to the present invention, the advantages which can be obtained thereby are evident. First of all, the main part of this device, which is mounted on the tractor, provides an indication of the presence or absence of the processing circuit 4which may be mounted on the trailer coupled to the tractor at any one time. The device further provides an indication that the monitoring circuit mounted on the trailer is in operation and, in the case in which this circuit is operating there is also obtained an indication when any of the lamps burn out or if the supply cable to these lamps becomes interrupted.All these functions are obtainable by the exploitation of a single cable which leads to the connector 25 and the advantage of this is considerable in that it is not currently possible to make available any more separate cables. Moreover, it is observed that the device 1 is adaptable as far as the processing part located on the trailer is concerned, to indicate the failure of a single lamp when only one lamp is installed, or the failure of one or two lamps when two lamps are installed in parallel, and this is possible simply by acting on the horseshoe connector 46.

Finally it is interesting to note the advantageous arrangement of the light-emitting diodes 67, 69 and 72, 73 in the outline shape shown in the panel 80. In fact, the yellow light-emitting diode 67 is positioned at the connection point between the trailer 88 and the tractor 87 and its illumination indicates that the trailer 88 is not coupled, or is coupled and does not contain a processing circuit 4, or else that it contains such circuit but this latter is not functioning, whilst on the other hand the operation of this circuit is indicated by the green light-emitting diode 69 which remains correctly illuminated even when some of the quantities being monitored (lamps, connection cables etc.,) are subject to a failure indicated this time by the illumination of the red light-emitting diodes 72,73.

Finally, it is clear that the device 1 described above can be modified and varied without by this departing from the scope of the present invention.

Claims (32)

1. A device for monitoring the trailer lights circuit of a commercial vehicle of the type having a tractor and trailer, comprising: first and second processing means mountable on the tractor and the trailer respectively in such a way as to be, in use, connected in series in a circuit for supply of at least one indicator lamp located on the trailer; third processing means having an input connected to the outputs of the first and second processing means and including comparator means operable to generate control signals depending on the signal level present at the input; and display means selectively controlled by the comparator means and mountable in the cab of the tractor in a position visible to the driver.

2. A device according to Claim 1, in which the comparator means is able to discriminate between at least three different levels of the input signals, and, for each of the levels, is able to activate at least one corresponding display element belonging to the display means.

3. A device according to Claim 2, in which the first processing means generates, in the absence or failure of the second processing means, an output signal directed towards the third processing means at the first of the three levels, causing a corresponding comparator of the comparator means to activate an associated first display element.

4. A device according to Claim 2 or Claim 3, in which the first and second processing means, in conditions of correct operation of the device and of the lights circuit, generate in combination a signal at the second of the three levels, causing a corresponding comparator ofthe comparator means to activate an associated second display element.

5. A device according to any one of Claims 2 to 4, in which the first and second processing means, in the presence of a failure in the circuit for supply of the indicator lamps, involving for example the burning out of the lamp or interruption of the circuit, generate in combination an output signal atthethird level; causing a corresponding comparator of the comparator means to activate at least one associated display element.

6. A device according to Claims 3,4 and 5, in which the second level lies between first level and the third level.

7. A device according to Claim 3, in which the first level is close to a positive supply value of the device.

8. A device according to Claim 5 or Claim 6, in which the third level is close to a "zero" voltage value.

9. A device according to any one of the preceding Claims, in which the display means are of the light-emitting type.

10. A device according to Claim 9, in which the display means are essentially constituted by light emitting diodes.

11. A device according to Claim 10 when appendant to Claim 3, in which the first display element is constituted by a light-emitting diode of a first colour.

12. A device according to Claim 11, in which the first colour is yellow.

13. A device according to Claim 10 when appen dantto Claim 4 in which the second display element is constituted by a light-emitting diode of a second colour.

14. A device according to Claim 13,inwhichthe second colour is green.

15. A device according to Claim 10 when appendant to Claim -5, in which the third display element is constituted by at least one light-emitting diode of a third colour.

16. A device according to Claim 15, in which the third colour is red.

17. A device according to Claim 3, in which the display means are mounted on a display panel showing an outline of a tractor drawing a trailer, the first display element being located on the outline of the trailer in the region in which the trailer is coupled to the tractor.

18. A device according to Claims 4 and 17 in which the second display element is located in a centrai position in the outline of the trailer.

19. A device according to Claim 5 and to Claim 17 or 18, in which the third display element is located in a rear position on the outline of the trailer.

20. A device according to any one of the preceding Claims in which the second processing means includes at least a first threshold comparator having a first input connected to a first circuit branch having at least one resistor and at least one of the inidicator lamps, and a second input to which is directed a reference voltage generated by a second resistive divider.

21. A device according to Claim 20, in which the resistive divider generating the reference voltage has means for adjustment of the reference voltage.

22. A device according to Claim 21, in which the reference voltage adjustment means are essentially constituted by a further resistor, which can be connected in parallel with a resistor of the said resistive divider.

23. A device according to any one of the Claims 20, 21 or 22, in which the second processing means includes means for detecting the presence of the supply voltage to the second processing means.

24. A device according to Claim 23, in which the means for detecting the presence of the supply voltage includes at least one second comparator, the inputs of which are connected to a pair of resistive dividers supplied with the supply voltage.

25. A device according to Claim 24, in which a resistor is connected in series with the output of the second comparator.

26. A device according to Claim 25, in which the end of the resistor opposite that connected to the output of the second comparator is connected to the output of the first comparator in such a way that together they constitute the output of the second processing means.

27. A device according to any one of the preceding Claims, in which the first processing means includes means for detecting the passage of the current in the lights circuit.

28. A device according to Claim 27, in which the detector means essentially comprises a switch, the contacts of which are magnetically actuable, and a winding through which the current in the lights circuit flows and which is located in a position such as to control the closure of the contacts of the switch.

29. A device according to Claim 28, in which the opposite terminals of the switch are essentially connected to associated inputs of an exclusive OR logic gate; a first terminal of the switch being likewise connected to earth via a resistor and a second terminal of the switch being further connectable to a positive supply pole, via a switch, for control of the lights circuit.

30. A device according to Claim 29, in which the output of the exclusive OR logic gate is connected to the output of the first processing means by means of a NOT logic gate.

31. A device according to Claim 30 when appendant to Claim 4, having at least one comparator, the control input of which is connected, via at least one resistor, to one output of the first processing means; the comparator having an output connected to a connection zone between the output of the exclusive OR logic gate and the input of the NOT logic gate; a signal at the first level present at the output of the first processing means causing, in the comparator, a first output voltage value, whilst a signal at the second or third level causes a second output level of the signal generated by the comparator; the first output signal being at logic level "0" and the second output signal being at logic level "1".

32. A device as claimed in Claim 1 for monitoring the lights circuit of a trailer of a commercial vehicle substantially as described with reference to and as illustrated in the accompanying drawings.