WO2018090078A1

WO2018090078A1 - Safety system

Info

Publication number: WO2018090078A1
Application number: PCT/AU2017/051227
Authority: WO
Inventors: Philip Louis Peach; Jonathan David Bernard POINT
Original assignee: Pivot Electronics Pty Ltd
Priority date: 2016-11-15
Filing date: 2017-11-08
Publication date: 2018-05-24

Abstract

Described herein is a safety system comprising an electrically non-conductive temperature responsive element and an actuator in communication with the temperature responsive element. The electrically non-conductive temperature responsive element is arranged in working relationship with each of a plurality of electronic components, and causes the actuator to be activated when a temperature in at least one of the plurality of electronic components reaches, or exceeds, a predetermined threshold value.

Description

"Safety system"

Technical Field

[0001] The present disclosure relates, generally, to estimating or detecting electronic component degradation or compromise. In one form the disclosure relates to a safety system for predicting failure of electronic components in an electronics unit.

Background

[0002] Electronic components can be compromised by a number of factors such as excess current or voltage, mechanical impact or excess temperatures. In systems that are typically subject to adverse conditions, for example trackside circuitry used in railway signalling, there is an increased risk of component damage, and there may also be serious or even dangerous consequences if circuits malfunction. In some instances, the adverse conditions may not necessarily result in immediate failure of electronic components, but may cause some damage that ultimately affects the component life and may lead to accelerated component failure.

[0003] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.

Summary

[0004] One of the causes of component degradation, for example in trackside circuitry, is power surges. Even if components are able to withstand a power surge and continue operating, the increased component temperature resulting from the power surge may impact the integrity of the components, resulting in accelerated component failure. We have found that component temperature may therefore prove a useful indicator in pre-empting possible component failure, and we therefore describe herein a system that monitors and responds to component temperature.

[0005] In one aspect of the disclosure, there is provided a safety system comprising: an electrically non-conductive temperature responsive element arranged in working relationship with each of a plurality of electronic components; and an actuator in communication with the temperature responsive element; wherein the temperature responsive element causes the actuator to be activated when a temperature in at least one of the plurality of electronic components reaches, or exceeds, a predetermined threshold value.

[0006] The predetermined threshold value may be associated with at least potential component damage or a reduced component life expectancy.

[0007] The actuator may be retained in an inactive position by the temperature responsive element, and the temperature responsive element may release the actuator to an active position when the actuator is activated. The actuator may comprise a mechanical indicator of component condition.

[0008] The system may further comprise a housing fixedly containing the actuator and the electronic components. As used herein, "fixedly" refers to a fixed relative position of contents, components and/or parts inside and/or on the housing.

[0009] The temperature responsive element may comprise an elongate body configured to be in contact with each of the electronic components, the elongate body having a first end anchored relative to the housing, and a second end connected to, and retaining, or causing the actuator to be or remain, in an inactive position. The temperature responsive element may comprise a stretch-resistant fibre. The temperature responsive element may break upon the temperature in the at least one of the plurality of electronic components reaching, or exceeding, the predetermined threshold value. In an embodiment, the temperature responsive element will break without first stretching.

[0010] When activated, the actuator may provide an indication of potential electronic component damage and/or failure of the unit comprised of the housing and the components contained in the housing. The system may further comprise a

communication interface in data communication with a remote location, the data communication interface being responsive to the actuator to communicate the indication to the remote location. The communication interface may comprise a switch. In an embodiment, the switch may be a micro-switch.

[0011] The system may be vibration resistant up to a force of about 100N per unit mass or greater.

[0012] In another aspect of the disclosure, there is provided an electrical terminal block assembly comprising an electrical terminal block; and an electronics unit comprising the system as described above.

[0013] In another aspect there is provided a remote monitoring unit in communication with one or more safety systems, the remote monitoring unit being configured to provide an indication of potential electronic component damage and/or failure in response to a signal received from the one or more safety systems. The indication may be provided to a remote location.

[0014] In another aspect there is provided a thermal sensing device for providing an alert at a threshold temperature, the thermal sensing device comprising: an actuator configured to communicate with a remote monitoring device; and an electrically non- conductive temperature responsive element comprising an elongate body, the elongate body being held in tension between an anchor position at a first end of the elongate body and the actuator at a second end of the elongate body; wherein the temperature responsive element breaks at the threshold temperature, thereby activating the actuator to generate the alert at the remote monitoring device. [0015] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Brief Description of Drawings

[0016] Embodiments of the disclosure are now described by way of example with reference to the accompanying drawings in which:-

[0017] Figure 1A is a sectional side view of an embodiment of a thermal sensing device before activation;

[0018] Figure IB is a sectional side view of the thermal sensing device of Figure 1A after activation;

[0019] Figure 2A is a sectional top view of an electronics unit including an electronic circuit board and an embodiment of a safety system;

[0020] Figure 2B is a sectional side view of the unit with the safety system;

[0021] Figure 3 is a perspective view of an embodiment of an electrical terminal block assembly including the electronics unit, in the form of a cassette, positioned in a terminal block;

[0022] Figure 4 is a sectional side view of the unit with an actuator retained in an inactive position;

[0023] Figure 5 shows a sectional end view of the cassette taken along line A-A in Fig. 4 of the drawings;

[0024] Figure 6A is an exploded view of an embodiment of a cassette with the electronic circuit board omitted for the sake of clarity; [0025] Figure 6B shows a cassette shell of the cassette of Figure 6A, and a circuit board configured to slot into the cassette shell;

[0026] Figure 7 is a sectional side view of the unit with the actuator released to an active position;

[0027] Figure 8 shows a sectional end view of the cassette of Figure 7 taken along line B-B in Fig. 7 of the drawings; and

[0028] Figure 9 is a schematic representation of a remote monitoring system. [0029] In the drawings, like reference numerals designate similar parts. Description of Embodiments

[0030] Referring to Figure 1A of the drawings, an embodiment of a thermal sensing device 10 used for providing an alert at a threshold temperature is shown. The thermal sensing device 10 has an actuator 14 configured to communicate with a monitoring device via a communication interface 12 (such as a micro-switch). The thermal sensing device 10 has a temperature responsive element 16 with an elongate body 17, the elongate body 17 being held in tension between an anchor position at a first end 18 of the elongate body, and the actuator 14 at a second end 20 of the elongate body 17. The temperature responsive element 16 breaks at the threshold temperature (as shown in Figure IB), thereby activating the actuator 14 to generate the alert at the monitoring device. The alert may be communicated via communication link 22 (such as a cable transmitting a signal from a micro-switch or from a fireproof switch to, for example, a processor or alarm which may be at a remote or physically removed location).

[0031] As shown in Figure 1A, the thermal device 10 is housed in an enclosure 24 which may be mounted in an area to be monitored, for example adjacent equipment to be monitored for overheating. In this embodiment, the body 17 is held in tension with the use of a biasing means such as a coil spring 26. In some embodiments the monitoring device may be a remote monitoring device located remote from the enclosure 24 and the area to be monitored. In other embodiments, the monitoring device may be substantially collocated with the enclosure 24. In some embodiments the monitoring device may include an alarm and/or other be configured to activate auxiliary functions or auxiliary equipment, such as a sprinkler system.

[0032] The temperature responsive element 16 is a fibre that breaks at around a threshold temperature (for example within a temperature range of 130 and 160°C), does not stretch so that the fibre may be held taught under tension, is non-flammable, and is electrically non-conductive. One example of a suitable fibre is a high-strength, multifilament polyethylene fibre, such as Ultra High Molecular Weight Polyethylene (UHMWPE) fibre. As the temperature responsive element is flexible it may be arranged along a distance and path as appropriate for the application, for example traversing a zone adjacent a complex area, or multiple areas, for which the temperature is to be monitored. The temperature responsive element may then be guided around waypoints or bends with, for example, pulleys, hooks, eyelets, or the like.

[0033] This type of thermal sensing device may be used in a wide number of applications where the specific properties of the proposed temperature responsive element would be useful, for example within any number of locations where excessive heat is to be sensed. Examples of such locations may include relatively inaccessible locations such as building attic or roof areas, marine craft bilges or engine rooms, building plant rooms, mine shafts or tunnels, underground cable ways, including areas unsuitable or inconvenient for human entry and/or for human habitation.

[0034] Referring to Figure 2A of the drawings, an embodiment of a safety system 100 comprises a temperature responsive element, in this embodiment a fibre 102, arranged in working relationship with each of a plurality of electronic components 104, for example passing adjacent to or being in contact with the components 104. The system 100 comprises an actuator 206, shown in Figure 2B, in communication with the fibre 102. The fibre 102 causes the actuator 206 to be activated when a temperature in at least one of the plurality of electronic components 104 reaches, or exceeds, a predetermined threshold value.

[0035] In some embodiments, the safety system 100 includes a switch, such as micro- switch 106, that is responsive to the actuator 206 to communicate an indication of potential electronic component damage and/or failure of the electronic components (or of the circuit that includes the components) to a remote location. In some embodiments the remote location is a remote monitoring site in communication with the safety system 100 via a remote monitoring unit 904, as described elsewhere herein with reference to Figure 9. The remote monitoring site may include, for example, a remote processor that raises an alarm.

[0036] In one embodiment the temperature responsive element has an elongate body configured to be in contact with one or more of the electronic components, for example a flexible fibre 102 wrapped around or passing against or close to the electronic components being monitored for overheating, as shown in Figure 2B of the drawings. These components may be any relevant components that have specific operational temperature ranges, for example resistors and diodes, etc., and the components selected to be arranged in working relationship with the fibre 102 or other type of temperature responsive element would typically be components expected to fail under overload or fault conditions. The fibre 102 is positioned with the help of guides 116 (such as metal or plastic hooks formed on or protruding from a circuit board 112).

[0037] The fibre 102 has a first end 108 anchored relative to a housing 110 that houses the system 100 and the circuit board 112 with the components 104. The housing 110 also contains the actuator 206, and may contain other parts specific to the application. In particular, the housing 110 fixedly contains at least the actuator 206 and the electronic components 104, i.e. in a fixed position relative to one another and the housing. A second end 400 (shown in Figure 4) of the fibre 102 is connected to, and retains, the actuator 206 in an inactive position while the fibre 102 is intact. [0038] In some embodiments, in order for the fibre 102 to be able to hold the actuator 206 in the inactive position, the fibre 102 includes a stretch-resistant fibre.

[0039] Furthermore, in order for the fibre 102 to act as a temperature responsive element, it reacts when exposed to temperature within a certain temperature range, ΔΤ, or when exposed to a temperature above a temperature threshold, Tth, associated with at least potential component damage. In some embodiments, the fibre 102 has a failure temperature range ΔΤ stretching from above the normal operating temperature of the relevant electronic components being monitored, to below the failure temperatures of the components. Electronic components that have overheated to above their normal operating temperature range may not necessarily fail immediately, and may continue operating, but these components may have been compromised due to the overheating and should be replaced. Typical components may have a normal operating temperature below 75 °C, and may have a failure temperature of around 180 °C to about 200 °C. Therefore, the responsive failure temperature range ΔΤ may be between about 130 °C and about 160 °C, for example a range from about 140 °C to about 150 °C.

[0040] In some embodiments, the fibre reacts to a temperature that falls within the temperature range, ΔΤ, or is above the temperature threshold, T^ by breaking. For example, when the temperature in at least one of the electronic components 104 that the fibre 102 passes close to or lies against reaches, or exceeds, the predetermined threshold value T_th, the fibre 102 breaks relatively quickly, for example within a few minutes, or in less than a minute.

[0041] In the embodiment shown in the drawings, the fibre 102 used for the temperature responsive element 102 therefore has three specific characteristics. Firstly, the fibre is stretch resistant in order to retain the actuator 206 in its inactive position. Secondly, the fibre has a temperature responsive temperature range ΔΤ or threshold T_th that coincides with a temperature range or threshold indicative of potential electronic component damage, and not necessarily component failure (though in some

embodiments the threshold may be selected to be indicative of components failure conditions). In an embodiment, the fibre 102 maintains its stretch resistant properties even while it heats up, until the temperature of the fibre 102 reaches the temperature range, ΔΤ, or reaches the temperature threshold, Τ_¾. Thirdly, the fibre is non- conductive, and therefore does not add any complexity with respect to maintaining electrical isolation of the fibre. One example of a suitable fibre is a high- strength, multi-filament polyethylene fibre, such as commercially available Ultra High

Molecular Weight Polyethylene (UHMWPE) fibre.

[0042] In other embodiments, the temperature responsive element may include one or more thermal fuses, for example fusible thermal protection components. In railway signalling applications, however, the thermal fuses would need to be able to withstand the high currents and voltages typical of that application and environment without triggering a response before the temperature reaches the predetermined threshold T_th or responsive temperature range ΔΤ, as described above. In embodiments that use thermal fuses, the fuses are used in a temperature responsive circuit that triggers an electronic indicator for communicating the state of the circuit to the remote location.

[0043] Referring to Figure 3 of the drawings, in one embodiment the system 100 described above is implemented in a terminal block assembly 300 that includes an electronics unit, in the form of a cassette, 302 positioned in a base unit, or terminal block, 304. The terminal block 304 receives cabling in the connectors 306, and the cables are secured by closing the latches 308 on the connectors 306. The connectors 306 may be any type of connector suited to the cables used.

[0044] The cassette 302 comprises the housing 110 and the circuit board 112 containing the components 104, the temperatures of which are monitored by the system 100. In the illustrated embodiment, the terminal block 300 is used as part of a trackside railway signalling system. The environment in which these terminal blocks are implemented may typically be subjected not only to high currents and voltages in normal operation, but also strong vibrations around the order of 10G to 11G (or a force of about 100N per unit mass), and also periodic power surges. In order to protect against possible power surges, the cassette 302 contains a circuit board with surge protection circuitry, for example. This is the type of circuitry shown schematically in Figures 1 and 2, where the components 104 include a metal-oxide varistor (MOV) 118, a gas discharge tube (GDT), resistors and/or TVS diodes. Other types of surge protection circuits known to those skilled in the art having the benefit of this disclosure may also be monitored using the system described herein.

[0045] Figure 4 of the drawings shows a section through the terminal block 300 of Figure 3. In this embodiment, the actuator 206 includes an indicator flag body 402 (which can be seen in more detail in Figure 6A of the drawings), with a protruding catch 404 to which the second end 400 of the fibre 102 is connected (e.g. looped and hooked onto). The fibre 102 holds the indicator flag body 402 in a first position that is inactive. Referring to Figure 5, in the inactive position, the protruding catch 404 of the indicator flag body 402 holds a lever arm 506 of the micro-switch 106 in a closed position. The micro-switch 106 acts as a communication interface and has switch connectors 502 that communicate the active or inactive state to the remote location. The inactive state is associated with normal operation, and the active state is associated with a compromised circuit as described in more detail below.

[0046] The indicator flag body 402 is biased toward an active position by an indicator urging device which, in this embodiment, is in the form of a flag compression spring 410. During normal operation, while the fibre 102 is intact, the fibre 102 overcomes the bias by pulling the protruding catch 404 so as to compress the indicator flag spring 410.

[0047] Figure 6A shows an exploded view 600 of the housing 110 of the cassette 302. The housing 110 consists of two mating shells 610a, 610b, typically made of a moulded plastic, that mate together and are fixed together with connectors such as a screw or a snap-fit mechanism. Each side of the cassette housing 110 of the cassette 302 carries a cassette release arm 612 and a cassette release pin 614 that enable the insertion into and removal from the terminal block 304. The release of the cassette 302 is facilitated by a cassette release spring 616. As shown in Figure 6B, a row of apertures 630 in the wall 628 on the terminal block end of the shell 610b receives a matching row of fingers 618 on the end of the circuit board 112, thereby stabilising the position of the circuit board 112 when the assembled cassette 110 is installed into the terminal block 304. In addition, each release pin 614 is shaped to include a tapered end 615 that wedges against a ridged retaining formation 704 on the terminal block 304 (see Figure 7), and this contributes to reducing vibration of the cassette 302 when installed in the terminal block 304.

[0048] The circuit board 112 is fixedly mounted within the housing 110 in any suitable way, for example, by clamping shaped edges 631 of the circuit board 112 between one or more sets of opposing ribs 632 located on the inside of the side walls 634 of the shell 610b (see Figure 6B). In addition, a two-leaf release spring 620 is positioned in the housing 110 on the terminal block end, and the release spring 620 cooperates with posts 702 (shown in Figure 7) that form part of the terminal block interface with the cassette 302. When the cassette 302 is positioned in the terminal block 304, the posts 702 bear against the ends of the spring 620, and flex the spring 620 as shown, for example, in Figure 7.

[0049] The cassette 302 is retained and locked into place by the release pins 614 that catch the ridged retaining formations 704 on the terminal block 304. When the release arms 612 are urged upward, the release pins 614 are withdrawn from engagement with the terminal block 304, and the release spring 620 then urges the cassette 302 out of the interface with the terminal block 304.

[0050] The force applied by the spring 620 causes the cassette 302 to be held fast against the release pins 614. The spring 620 thereby aids in reducing vibrations of the circuit board 112 due to the environmental vibrations, thereby reducing micro pitting and/or other fatigue and stress related defects.

[0051] The indicator flag body 402 has a bicoloured indicator 602, one colour of which is generally externally visible via the window 604 at a time (for example, green when the indicator flag body 402 is in the inactive position, and red when the indicator flag body has shifted across to the active position). The indicator flag body 402 is received in an indicator flag housing 606 and biased within the housing by the flag spring 410 toward the active position (i.e. where the red portion of the indicator surface 602 is visible through the window 604). The protruding catch 404 of the indicator flag body 402 protrudes through a slot in the flag housing 606 (not visible in Figure 6A) and, as described above, the micro- switch 106 is responsive to movement of the protruding catch 404 which interacts with the lever arm 506, either holding the lever arm 506 down or releasing it to trigger the micro- switch 106.

[0052] Figures 7 and 8 of the drawings illustrate an active position of the indicator flag body 402 resulting from the failure of the fibre 102, by rupturing, across one of the electronic components, in this instance the GDT 120. When the tension in the fibre 102 is lost due to the break in the fibre 102, the indicator flag spring 410 is released. This biases the indicator flag body 402 into the active position so that the lever arm 506 of the micro-switch 106 is released, thereby triggering the micro-switch 106 to send a signal indicative of the changed state to the remote location.

[0053] Referring to Figure 9 of the drawings, in some embodiments, two or more devices 902 (each consisting of a terminal block 304 and a cassette 302), are co-located at a trackside location, forming part of a remote monitoring system 900. The cassettes 302 that form part of each device 902 each house an electronic circuit board (typically a surge protection circuit) and a respective safety system as described herein. The remote monitoring system 900 also includes a remote monitoring unit 904 that is in communication with each of the devices 902 that are configured in a daisy chain test loop 906.

[0054] The remote monitoring unit 904 has an independent power supply 908 that converts DC or AC power (for example 1 lOVAC or 240V AC) to 24VDC. A test loop current source 910 provides a current to the test loop 906, and monitors the loop current. Overheating of a monitored component in any one of the devices 902 will cause an indication of potential electronic component damage and/or failure of one or more electronic components to be communicated from the relevant device 902, so that the loop current is altered. [0055] Based on the monitored loop current, a local loop indicator 918 displays the state of the devices 902 as either operating normally or a fault being detected. A corresponding signal is provided to a relay 914 via circuit 912. The relay 914 in turn switches a local fault indicator 920 or System OK indicator 922 (depending on a fault being detected, or normal operation being detected, respectively). The relay 914 also provides an output signal 916 to the remote monitoring location in order to activate an alert and/or an alarm.

[0056] The system provides a dual indication of component compromise, both locally and remotely. Locally the bicoloured indicator 602 is a mechanical indicator that provides an indication of the state of the system 100, i.e. inactive (normal operation) or active (compromised, with the fibre 102 broken). At the same time, the indicator flag body 402 also triggers the micro- switch 106 to send an indication of the state of the system 100 to the remote location. The use of the indicator 602 enables a technician to determine, at a glance, which unit in a cabinet containing a large number of the units has failed.

[0057] In addition, the change of state that alerts the remote location (a central processor and database, and/or operator/s) can advantageously occur before any electronic components necessarily malfunction and actually cause a disruption in operation (e.g. signalling operations for railway trackside applications). This is due to the selected temperature range, ΔΤ, or temperature threshold, T^, at which the relevant temperature responsive element is configured to respond being below the typical failure temperature of the components. Consequently the system described herein provides an early warning system, encouraging replacement of compromised components based on at least potential component damage, and in anticipation of potential component failure.

[0058] The use of the fibre described herein as a temperature responsive element provides the additional advantage of not being conductive, so that no additional circuit structures are required to ensure insulation between the fibre and the circuit board being monitored. Using a multi-filament polyethylene fibre also means that the fibre is strong enough to withstand a high level of vibration without breaking. The fibre (for example in comparison to a thermal fuse with a higher thermal mass) also does not absorb heat from the components, so that the temperature of quite small components can be monitored. A single fibre can be used to monitor multiple components at once, so that the number of parts (and associated cost) does not increase linearly with respect to the temperature responsive element for circuit boards with more components. Using a fibre in this way also means that the monitoring component does not take up much additional space on the circuit board.

[0059] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A safety system comprising: an electrically non-conductive temperature responsive element arranged in working relationship with each of a plurality of electronic components; and an actuator in communication with the temperature responsive element; wherein the temperature responsive element causes the actuator to be activated when a temperature in at least one of the plurality of electronic components reaches, or exceeds, a predetermined threshold value.

2. The system of claim 1 wherein the predetermined threshold value is associated with at least potential component damage.

3. The system of claim 1 or claim 2, wherein the actuator is retained in an inactive position by the temperature responsive element, and the temperature responsive element releases the actuator to an active position when the actuator is activated.

4. The system of any one of the preceding claims wherein the actuator comprises a mechanical indicator of component condition.

5. The system of any one of the preceding claims, which further comprises a housing fixedly containing the actuator and the electronic components; and wherein the temperature responsive element comprises an elongate body configured to be in contact with each of the electronic components, the elongate body having a first end anchored relative to the housing, and a second end connected to, and retaining, the actuator in an inactive position.

6. The system of claim 5 wherein the elongate body is flexible.

7. The system of any one of the preceding claims, wherein the temperature responsive element comprises a stretch-resistant fibre.

8. The system of any one of the preceding claims, wherein the temperature responsive element breaks upon the temperature in the at least one of the plurality of electronic components reaching, or exceeding, the predetermined threshold value.

9. The system of any one of the preceding claims, wherein, when activated, the actuator provides an indication of potential electronic component damage and/or failure of a unit comprising the plurality of electronic components.

10. The system of claim 9, wherein the system further comprises a data communication interface in data communication with a remote location, the data communication interface being responsive to the actuator to communicate the indication to the remote location.

11. The system of claim 10, wherein the communication interface comprises a switch.

12. The system of any one of the preceding claims, wherein the system is vibration resistant up to a force of about 100N per unit mass.

13. An electrical terminal block assembly comprising: an electrical terminal block; and an electronics unit comprising the system of any one of the preceding claims.

14. The assembly of claim 13, wherein the electrical terminal block is a trackside railway terminal block.

15. A thermal sensing device for providing an alert at a threshold temperature, the thermal sensing device comprising: an actuator configured to communicate with a remote monitoring device; and an electrically non-conductive temperature responsive element comprising an elongate body, the elongate body being held in tension between an anchor position at a first end of the elongate body and the actuator at a second end of the elongate body; wherein the temperature responsive element breaks at the threshold temperature, thereby activating the actuator to generate the alert at the remote monitoring device.