DISPLAY PANEL ASSOCIATING SERIES CIRCUIT INTERLOCK SWITCH CONDUCTION STATUS INDICATORS WITH CIRCUIT TOPOLOGY

Abstract: An expanded annunciator of the status of individual switches in a series circuit of interlock switches, has a schematic of the series circuit printed on its display panel face. Display elements such a light-emitting diodes are juxtaposed to the switches, and emit light to symbolize that the switches are conducting. Preferably, the schematic is printed with individual switch symbols arranged in a line, and lines are drawn on the panel face from individual display elements to the lines symbolizing the conductors whose voltage level is displayed by the display element involved.

Description: DISPLAY PANEL ASSOCIATING SERIES CIRCUIT INTERLOCK SWITCH CONDUCTION STATUS INDICATORS WITH CIRCUIT TOPOLOGY < 5 BACKGROUND OF THE INVENTION + Many types of control systems are used to operate apparatus which has the potential for causing harm or injury if various parameter levels are outside of predetermined ranges. A simple example is the automobile whose engine will be severely damaged if the oil pressure is too low or the coolant temperature is too high. 10 In this situation the system relies on the good judgment of the driver to stop the auto as soon as the warning light or gauge indicates the problem. In many of these systems however, human monitoring of the apparatus parameters may be unacceptable because the apparatus is intended to operate automatically, or because the result of improper, that is to say human, monitoring 15 may result in serious damage or injury. Neither is it desirable to rely on the control system to monitor every one of these parameter levels and shut down of the system when needed because this adds substantial complexity to the controller. Also, the control system can on occasion fail, for example because of power outages. Instead, in most systems these parameters are used to directly control interlock switches which 20 open if the parameter level is outside of the predetermined range. In these systems, the interlock switches are typically arranged in a series circuit which passes the current for operating the apparatus (and parts of the control system as well in many cases) so that if any of the parameter levels are outside the range specified for it, the apparatus will not receive power and cannot operate. Examples of these series 25 circuits of interlock switches are found in a number of different types of apparatus and their controls, including as one example burner systems and controls. In burner controls, the interlock switch series circuit is used to control power which operates the fuel valves. If any of the burner system parameters are outside the specified ranges, power is not available to the fuel valves, with the result that the burner cannot 30 operate. There are as many as a dozen or more of these individual interlock switches employed in a typical installation. These switches will usually be physically located at various sites in the installation which are separated from each other. Thus, switches which are adjacent to each other in the series circuit sequence, may be 35 physically separated by many feet or even yards. This is because the most convenient or logical arrangement for the sequence of switches in the series circuit will typically have no relationship to the physical locations of these switches. A problem which arises in these systems is determining the cause of a malfunction. If an interlock switch opens, power to the system is interrupted of course, but the problem can be in any of the parameters controlling the interlock switches or in other aspects of the system. For example, in burner systems flame failure does not control an interlock switch. In this particular situation, the control system itself interprets the flame sensor signal and shuts down the fuel valves when flame is detected as absent. When the shutdown is caused by an open interlock switch, by the time a repairer arrives to correct the problem, the original cause of the shutdown may no longer exist. As one example of this situation, a low fuel pressure parameter which opens an interlock switch may have been restored within a few seconds and thus will not be apparent to the repairer. In order to simplify and improve troubleshooting of malfunctions in these systems, improved annunciators have been designed which display the status of each of the interlock switches in the interlock switch string. There are annunciators available which show by a series of labelled lights the conduction status for a number of switches in a series string. Another example is U.S. Patent No. 4,295,129 (Cade), which describes a circuit connected to individual interlock switches and the main and pilot valve actuators, to detect abnormal conditions by sensing the status of the fuel valves and to record the identity of the first interlock switch or fuel valve to open at the time the abnormal condition was detected. U.S. Patent No. 3,967,281 (Dageford) attempts to determine the earlier of two detected failures and record the identity of the switch which first opened. These will typically be related, but may happen in either order, and an indication of the earlier allows easier detection of the underlying problem. None of these references associate individual switch status directly with a schematic of the switches in the series circuit. Accordingly, it is often difficult for the operator to gain an accurate mental image of the status of the series circuit when having no more than a display identifying the conduction status of the individual switches. BRIEF DESCRIPTION OF THE INVENTION A special panel is provided which shows graphically or schematically the conduction status of the switches in an series circuit of interlock switches. These interlock switches each have first and second contacts and are connected by a plurality of conductors to form therefrom a series circuit of interlock switches in a preselected sequence for connection by an end interlock switch thereof to a power source to pass current through the series circuit to a load. Each of a plurality of voltage sensors are associated with a single interlock switch and are connected to a conductor connected to the interlock switch with which the voltage sensor is associated. Each voltage sensor provides a status signal having a first state responsive to presence of power voltage on the conductor to which it is connected and a second state otherwise. Each of a a plurality of display elements are associated with a single one of the voltage sensors. Each of the display elements receive a display signal and entering a first display state responsive to a first state of the display signal and a second display state responsive to a second state of the display signal. Each of a plurality of display drivers are associated with a single display element, that display element's corresponding interlock switch, and that interlock switch's associated voltage sensor. Each display driver provides to its associated display element a display signal having its first and second states responsive respectively to the first and second states of the status signal provided by the display driver's associated voltage sensor. The improvement comprises the special display panel having printed on its face a circuit schematic depicting with switch symbols the series circuit of interlock switches. The display elements are mounted on the panel with each display element in adjacent association to the circuit schematic switch symbol representing the switch with which the display element is associated. The schematic analogy is extended in one improvement where there are printed lines symbolizing the conductors connecting the individual switch contacts. BRIEF DESCRIPTION OF THE DRAWING The Fig. shows a representation of the display panel and the circuitry providing display signals to the display elements mounted on the display panel face. DESCRIPTION OF THE PREFERRED EMBODIMENT The Fig. shows a power terminal 10 connected to one end of a series circuit of interlock switches 14. These switches are controlled by the physical parameters necessary for the proper operation of a load 20. The load 20 is shown as operating under the control of a control unit 24 which may be a conventional burner controller if the load is the individual elements such as the valves and igniter of a burner itself. If a parameter is not within the proper range, its switch opens, removing power from the load. Individual switches each have two contacts, and are connected to form the series circuit by conductors as at 13 each connecting a contact of one switch to a contact of another. In the commercial embodiment of this invention, four separate series circuits of varying numbers of switches are connected together with two of the series circuits connected in parallel with each other and this parallel circuit connected between the two other series circuits. Each conductor 13 is connected to an input terminal of a voltage sensor 16. Each voltage sensor 16 is associated with one of the switches to which its input terminal is connected through the conductor. Each voltage sensor 16 provides a status signal having a first state when line voltage is present on the conductor 13 to which its input terminal is connected and a second state otherwise, and each voltage sensor has its output terminal connected to the input terminal of a display driver 18. The output terminals of display drivers 18 are connected to conductors 25a-25f to provide to a plurality of display elements 32a-32f , display signals having first and second states accordingly as the voltage sensors provide status signals having first and second states. Each of these display drivers is associated with the voltage sensor 16 from which it receives its status signal, the display element 32a-32f to which it is connected, and the interlock switch 16 with which its associated voltage sensor 16 is associated. A display panel 30 is shown having printed on its face a circuit schematic shown generally at 38 and having individual switch symbols as at 33, each symbol corresponding to an actual one of the switches 14. The printed circuit schematic 38 further shows the switch symbols 33 in a linear arrangement with connection lines 34 printed on the display panel 30 face between switch symbols 33 to symbolize the conductors 13 between the individual switches 14. Each of the plurality of display elements 32a-32f are associated with one of the voltage sensors 16, and are mounted on the display panel 30 in adjacent association to the switch symbol 33 representing the switch with which the display element is associated. A line 36 may be printed between a connection line 34 symbolizing a conductor 13, and the display element 32a-32f which is associated with the voltage sensor connected to that conductor. Each display element 32a-32f is connected to receive a display signal on the one of the conductors 25a-25f from the display driver 18 with which the display element is associated. The display elements 32a-32f are preferably LED elements which are connected so that light is emitted which its associated voltage sensor 16 receives voltage at its input terminal. The dotted line portions of the conductors 25a-25f are intended to indicate that all or a part of their lengths are concealed behind panel 30. A legend (Burner Switch, Operating Ctrl, etc.) specifying the purpose of each switch may be placed adjacent to the display element 32a-32f associated with that switch. In fact, other than for the reference numbers, the dotted lines symbolizing conductors 25a-25f , and the circles symbolizing the display elements 32a-32f , all of the art work shown within the box symbolizing display panel 30 is printed on a typical panel face. When a single one of the interlock switches 14 is open, voltage will be sensed by voltage sensors 16 only on conductors between the power terminal 10 and that open switch. Each of the voltage sensors 16 sensing voltage will cause its associated display element 32a-32f to enter a distinct first state, and those display elements associated with conductors 13 which are not receiving voltage from power terminal 10 will have their second state. If more than one interlock switch 14 is open, the conductors between the switch closest to power terminal 10 all have voltage on them, and their associated display elements will indicate this fact. One can see how a user's understanding and insight into the status of the switches in the series circuit is substantially improved by bright red light emitted from those LED elements which are graphically connected by the printing on the display panel 30 face to the symbols for voltage-carrying conductors connecting sequentially adjacent interlock switches. At the same time, LED elements which are not lit indicate non-voltage - carrying conductors. Where there are a number of series circuits connected in topologically more complex arrangements as, for example shown in the cross- referenced applications identified above, the display of switch status according to these principles becomes even more useful. In this way, the organization of the display elements and the printing of the series circuit schematic on display panel 30 cooperate to provide an intuitive and understandable indication of the status of the various switches comprising a series circuit. While display drivers 18 are shown as providing display signals encoding the current status of the associated switch, it is possible to include in them means which record a current status and then provide a display signal encoding this status at a later time as a fault or history display. This is a first out switch display which is very helpful in determining the cause of a malfunction, or for other purposes. At any rate, it should be clearly understood that applicants do not wish to limit this apparatus to simply showing current status of the series circuit. The preceding has described our invention. What we wish to claim by letters patent as our invention is:

Claims: CLAIMS 1. In an annunciator of the status of a plurality of interlock switches each having first and second contacts and connected by a plurality of conductors to form therefrom a series circuit of interlock switches in a preselected sequence for connection by an end interlock switch thereof to a power source to pass current through the series circuit to a load, and including a plurality of voltage sensors each associated with an interlock switch and connected to a conductor connected to the interlock switch with which the voltage sensor is associated and each voltage sensor providing a status signal having a first state responsive to presence of power voltage on the conductor to which it is connected and a second state otherwise; a plurality of display elements with each display element associated with one of the voltage sensors, each of said display elements receiving a display signal and entering a first display state responsive to a first state of the display signal and a second display state responsive to a second state of the display signal; and a plurality of display drivers, each display driver associated with a single display element, that display element's corresponding interlock switch, and that interlock switch's associated voltage sensor, each display driver providing to its associated display element a display signal having its first and second states responsive respectively to the first and second states of a status signal provided by its associated voltage sensor, wherein the improvement comprises: a display panel having printed on the face thereof, a circuit schematic depicting with switch symbols the series circuit of interlock switches, and with the display elements mounted on the panel with each display element in adjacent association to the circuit schematic switch symbol representing the switch with which the display element is associated. 2. The annunciator of claim 1, wherein the series circuit schematic is printed with the switch symbols in a linear arrangement with connection lines symbolizing the conductors between sequential switches printed between the switch symbols. 3. The annunciator of claim 2, wherein the display elements are mounted on the display panel in a linear sequence. 4. The annunciator of claim 3, wherein the display panel has printed on it a line from each display element to the connection line symbolizing the conductor to which is connected the voltage sensor with which the display element is associated. 5. The annunciator of claim 1 , wherein the display elements are mounted on the display panel in a linear sequence. 6. The annunciator of claim 1, wherein the display panel has printed on it a line from each display element to the connection line symbolizing the conductor to which is connected the voltage sensor with which the display element is associated.

Inventors: MERTEN GREGORY J, PATTON PAUL B, MERTEN, GREGORY, J., PATTON, PAUL, B.
Applicants: HONEYWELL INC, HONEYWELL INC.
Application year: 1993
Main classification: G08B25
IPC codes: F23N5, G08B25