GB2170068A

GB2170068A - Line break detector

Info

Publication number: GB2170068A
Application number: GB08500668A
Authority: GB
Inventors: Walter Haworth
Original assignee: Hollingsworth GmbH
Current assignee: Hollingsworth GmbH
Priority date: 1985-01-11
Filing date: 1985-01-11
Publication date: 1986-07-23
Also published as: GB8500668D0; GB2170068B

Abstract

A circuit including a LED 15 and a relay 20 indicates a break in a line 1, which is itself a monitor line for a device 5 such as a clutch drive in a spinning installation. When clutch 5 is operated by switches 7, 8 the line 1 energises an indicator 1a through a resistor 1b. A break in line 1 allows a diode 11 to become conductive and current to flow through a resistor 14, diode 11, resistor 1b, resistor 1c, to -12v DC. This turns on a transistor 12 to operate the LED 15. <IMAGE>

Description

SPECIFICATION Line break detector This invention relates to a device which is capable of detecting when a break in an electrical signal line has occurred.

In one prior type of line break detector, the presence of both AC and DC signals indicate the integrity of a line and the absence of one of the two signals indicates that the line has broken. This technique, however, is rather complex because of the necessity for both types of signal and for their associated generating means. Such a line break detector might use a current loop for the detection.

However, this technique necessitates that a current loop be used for each and every line that is to be monitored.

It is an object of the present invention to provide a line break detector which can be used to monitor a number of lines and which is simple in construction.

In accordance with the present invention, there is provided a line break detector which is capable of simultaneously monitoring a number of electrical lines provided with DC signals, said detector indicating when any one or more of said lines are broken by providing a DC current in a part of each of said broken lines.

The present invention will be now more fully described by way of example with reference to the sole drawing in which there is shown a diagrammatic layout of the line break detector as applied to a specific system.

As shown in the Figure, the signal line 1 and the cut signal lines 2, 3 and 4 are the lines which are to be monitored. Signal line 1, connected to a specific system which we describe below, and signal lines 2, 3 and 4 are each connected to other systems which, for brevity and simplicity, will not be described. However, one application for the line break detector in accordance with the present invention is in the operation of an automated spinning installation comprising a plurality of modular loops each having several spinning stations or positions, with all the loops connected to a central controller. The monitoring of the continuity of the connections between the loops is important.

The system line 1 is connected to a clutch control mechanism. When the two switches 7 and 8 are closed, the diode 6 is reverse biassed and the clutch 5 is operating. Opening of any of the switches 7 or 8 breaks the flowing current to the respective clutch and so turns it off.

The other end of the line 1 is connected to a light emitting diode (LED) and optical coupler device 1a which serves the purpose of indicating when the clutch is on or off by virtue of the either high or low voltage, respectively, at point 9. The presence of the resistor 1 b serves to limit the current to the LED and optical coupler.

In this embodiment of the invention, lines 2, 3 and 4 are identically connected to couple devices 2a, 3a and 4a via respective resistors 2b, 3b and 4b. These various coupler devices 2a, 3a and 4a also serve to indicate whether the clutches connected to the lines 2, 3 and 4 are either on or off.

An essential aspect of this invention is always to maintain a current through the lines being monitored. In this case this is achieved by the respective resistors 1c, 2c, 3c and 4c which are in parallel with the respective LED and optical coupler devices 1a, 2a, 3a and 4a. By virtue of the distal ends of these resistors being connected to a point of lower potential than the operating potential of the clutch a current is always made to flow down the lines irrespective of whether the clutches are on or off.

Thus, specifically with respect to line 1 when either or both of switches 7 and 8 are open clutch 5 is off but current flows from ground via diode 6 through line 1 and the resistors 1b and 1c to the negative rail at -12 volts DC. Thus in this condition point 9 is essentially at 0 volts and LED 1a is off, correctly indicating that the clutch is inoperative. Alternatively, when switches 7 and 8 are made, clutch 5 is working and LED la is on because of the high voltage at point 9.

Thus, as can be seen in this system, because there is, in effect, a low impedance in the line 1 there will always be a current through this line and through the resistors 1b and 1c regardless of whether the clutch is operating or not. If, in any instance, line 1 gains a high impedance this would indicate a break in the line. The circuit that can be used to detect the presence or absence of high impedance is connected to the lines 1, 2, 3 or 4 by a diode AND gate 11. The first part of this impedance detecting circuit comprises a PNP transistor 12 coupled to the AND gate via the resistor 13. A further resistor 14 connects from the other end of resistor 13 to a ground line. The emitter of transistor 12 is also connected to ground, and the collector is connected to LED 15 which feeds to the -12 volts DC rail through a resistor 16.In the second part of the circuit the PNP transistor 17 has a base which connects to ground via the resistor 18 and also connects, via another resistor 19, with the collector of the transistor 12. The emitter of transistor 17 is connected to ground and the collector is connected to a relay 20, the purpose of which will be described later.

The way the impedance detecting circuit works will be explained below with specific reference to Figure 1.

When switches 7 and 8 are made the clutch 5 is on and the voltage at point 9 is high. Therefore, the voltage at point 10 is also high and because the resistor 14 is connected to the ground the first diode in the AND gate 11 is reverse biased. This in turn means that the transistor 12 is off. In this situation, no current is flowing in the collector of transistor 12. The transistor 17 is correctly biassed and there is a consequent flow in the relay device 20. A small base current is also flowing through resistors 19, 21 and 16 but this is not large enough to light the LED 15. This situation stays constant as long as the clutch is operating.

When the clutch is turned off via one of the switches 7 or 8, point 9 immediately drops to almost ground potential. Point 10 will, of course, be at the same potential and, this means that the uppermost diode in the AND gate 11 is reverse biassed. As will be clear, this condition mirrors that of when the clutch is operating and so the impedance detecting circuit is in the same state as described above. This state continues as long as line 1 is intact.

When line 1 breaks, the controlling voltages from the clutch drive circuit are removed. This means that a current path is opened via resistor 14, the uppermost diode in the AND gate 11, and the resistors 1 b and 1 c. Due to this flow of current a voltage drop occurs across resistor 14 and correctly biasses the transistor 12, turning it on. The collector current through transistor 12 turns on the LED 15 and causes the transistor 17 to turn off. In this condition, the LED 15 is on but no current flows through the relay device 20. Both of these effects indicate to the operator of the system that a line 1 has broken. The use of the relay device 20, although not essential to the invention, means that any other process which is occurring synchronously with the clutch driving system can be turned off when a break in the line 1 occurs.

By incorporating the diode AND gate in the detecting circuit, any number of lines can be monitored simultaneously with only a single detecting circuit. This means that an effective cheap and easy to maintain monitoring system is provided by the present invention.

Claims

1. A line break detector which is capable of simultaneously monitoring a number of electrical lines provided with DC signals, said detector indicating when any one or more of said lines are broken by providing a DC current in a part of each of said broken lines.

2. A detector according to claim 1 wherein, when the lines are intact, the DC voltage signal in the line is always such as to stop the flow of current from the detector into the line.

3. A detector according to claim 1 or 2 in which the detector is coupled to the line via a respective diode which is reverse biased when the line is intact.

4. A detector according to claim 3 wherein the respective diodes are all connected to a common point in the detector, which point is at a voltage which forward biases the respective diode connect to a broken line.

5. A detector according to claim 4 wherein a transistor is coupled to said common point in the detector and the flow of current through any one of said diodes correctly biases the transistor which in turn provides a current for an indicating device to indicate that one or more of said lines is broken.

6. A line break detector constructed and arranged substantially as hereinbefore described with reference to the accompanying drawing.

6. A detector according to claim 5, wherein at least one other transistor is present in said detector and coupled to said first transistor in such a way as to be on when said first transistor is off and to be off when said first transistor is on, said second transistor offering a second signalling means for indicating the integrity or break of a line.

7. A line break detector constructed and arranged substantially as hereinbefore described with reference to the accompanying drawing.

New claims or amendments to claims filed on 19th November 1985 Superseded claims 1 to 7 New or amended claims:

1. A line break detector which is capable of simultaneously monitoring several electrical lines each provided with first and second DC signals of a first polarity in different operating states of the lines, said detector indicating when any one or more of said lines is broken by providing a DC current of second polarity in a part of each of said broken lines.

2. A detector according to claim 1, in which the detector is coupled to each of the lines via a respective diode which is reverse biased when the respective line is intact.

3. A detector according to claim 2 wherein the respective diodes are all connected to a common point in the detector, which point is at a voltage which forward biases the respective diode connected to a broken line.

4. A detector according to claim 3, wherein a transistor is coupled to said common point in the detector and the flow of current through any one of said diodes correctly biases the transistor which in turn provides a current for an indicating device to indicate that one or more of said lines is broken.

5. A detector according to claim 4, wherein at least one other transistor is present in said detector and coupled to said first transistor in such a way as to be on when said first transistor is off and to be off when said first transistor is on, said second transistor offering a second signalling means for indicating the integrity or break of a line.