EP0837283A1 - Système de commande automatique avec une protection de sécurité double pour des brûleurs à gaz à fonctionnement intermittant - Google Patents

Système de commande automatique avec une protection de sécurité double pour des brûleurs à gaz à fonctionnement intermittant Download PDF

Info

Publication number
EP0837283A1
EP0837283A1 EP96830531A EP96830531A EP0837283A1 EP 0837283 A1 EP0837283 A1 EP 0837283A1 EP 96830531 A EP96830531 A EP 96830531A EP 96830531 A EP96830531 A EP 96830531A EP 0837283 A1 EP0837283 A1 EP 0837283A1
Authority
EP
European Patent Office
Prior art keywords
state
thermocouple
burner
voltage
ignition
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP96830531A
Other languages
German (de)
English (en)
Other versions
EP0837283B1 (fr
Inventor
Gianpiero Turrin
Stefano Fandella
Ettore Rossi
Danilo Briarava
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sit La Precisa SpA
Original Assignee
Sit La Precisa SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sit La Precisa SpA filed Critical Sit La Precisa SpA
Priority to EP96830531A priority Critical patent/EP0837283B1/fr
Publication of EP0837283A1 publication Critical patent/EP0837283A1/fr
Application granted granted Critical
Publication of EP0837283B1 publication Critical patent/EP0837283B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
    • F23N5/10—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermocouples
    • F23N5/102—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermocouples using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2223/00—Signal processing; Details thereof
    • F23N2223/14—Differentiation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2227/00—Ignition or checking
    • F23N2227/22—Pilot burners
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2227/00—Ignition or checking
    • F23N2227/22—Pilot burners
    • F23N2227/24—Pilot burners the pilot burner not burning continuously
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2227/00—Ignition or checking
    • F23N2227/36—Spark ignition, e.g. by means of a high voltage
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2231/00—Fail safe
    • F23N2231/20—Warning devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2235/00—Valves, nozzles or pumps
    • F23N2235/12—Fuel valves
    • F23N2235/14—Fuel valves electromagnetically operated
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2235/00—Valves, nozzles or pumps
    • F23N2235/12—Fuel valves
    • F23N2235/18—Groups of two or more valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/24—Preventing development of abnormal or undesired conditions, i.e. safety arrangements
    • F23N5/242—Preventing development of abnormal or undesired conditions, i.e. safety arrangements using electronic means

Definitions

  • the present invention relates to an automatic control system with double intrinsic safety protection for intermittently-operating gas burners, for example, of the type used in gas boilers for domestic heating and, in particular, in a system for automatically igniting a pilot light for a burner under the control of an external signal, for automatically re-igniting the pilot light should it go out accidentally, and for closing both a safety valve and a regulation valve in the event of failure to re-ignite.
  • thermocouple the electromotive force of which supplies a solenoid-valve winding keeping the valve in the open position.
  • thermocouple A reduction of the e.m.f. of the thermocouple, which is indicative of the flame going out, is detected by suitable sensors and causes the activation of a control circuit which, before closing the safety valve, operates an ignition-spark generator for a predetermined period of time.
  • thermocouple e.m.f. which ensures closure of the valve.
  • thermocouple voltage In the absence of which the safety valve should close.
  • the safety valve also performs a regulation function and, as well as being opened for the ignition of the burner, can also be closed intermittently by the controlled opening of the thermocouple circuit or by the generation of a current pulse to neutralize the magnetisation current generated by the thermocouple.
  • a further disadvantage is that the burner is automatically ignited or re-ignited by the opening of the safety and regulation valve for a predetermined period of time, of the order of 60s, so that if the operation is not successful the volume of gas which flows from the burner throughout this time is not negligible and constitutes a risk factor.
  • the present invention overcomes these serious disadvantages and provides an automatic control system with double intrinsic safety, or redundancy protection, for intermittently-operating or even continuously-operating gas burners, with a minimal leakage of gas even in the event of a failure to ignite or re-ignite, in which two valves are provided in cascade, of which one has exclusively a safety function and the other has a regulation function.
  • the opening of the regulation valve is dependent on the actual presence of a pilot light supplied by means of the safety valve, as detected by a voltage of a thermocouple heated by the pilot light being above a preset threshold value.
  • Double intrinsic safety protection is thus provided, in the sense that even if the safety valve fails to operate automatically, as a result of the lack of a pilot light (first protection), the regulation valve (second protection) is in any case closed.
  • the failure of the regulation valve to operate for any reason is remedied by the operation of the safety valve; as is known from probability theory, the probability of a simultaneous failure to operate of both valves is the product of the probabilities of the two individual events and is thus much lower than the probability of a single valve failing to operate, and is practically zero.
  • an automatic control system comprises, essentially, a first, safety solenoid valve 1 in series with a regulation solenoid valve 2, a control unit 3 supplied by a supply P.S. 4, a spark-generating device 6, a thermocouple 7 and acoustic or visual alarm indicator means 29.
  • the safety solenoid valve 1 comprises a plug 8 which closes a gas-flow path from an inlet 9 to an outlet 10.
  • the plug 8 which is fixed to the armature 11 of an electromagnet 12, is biased towards the closure position by a spring 13.
  • the electromagnet 12 has a first winding 14 supplied by the voltage developed by the thermocouple 7 and at least one second winding 15 supplied by a signal EV1 generated by the control unit 3.
  • the regulation solenoid valve 2 which operates intermittently with ON-OFF regulation comprises a plug 20 which closes a gas-flow path from the output 10 of the valve 1, which constitutes the input of the valve 2, to an outlet 151 connected to a gas burner 16.
  • a pipe 17 connected to the inlet/outlet 10 and terminating in a nozzle 18 opening near the burner 16 supplies a pilot light 19 which, when ignited by the spark-generator 6, heats the thermocouple 7.
  • the plug 20, which is fixed to the armature 21 of an electromagnet 22 is biased towards the closure position by a spring 23.
  • the electromagnet 22 has a winding 24 supplied by a signal EV2 generated by the control unit 3.
  • thermocouple 7 terminals are connected to an input of the control unit 3.
  • the regulation valve may be of the combined type with a solenoid valve and valve with a diaphragm actuator, the activation of the former producing a differential pressure on the diaphragm which causes the latter to open.
  • the control unit 3 is supplied by the supply 4 when it is connected to the electrical mains by a manual switch 25.
  • the manual switch 25 may also consist of a thermostatic switch for supplying the automatic control system only when there is a demand for the burner to operate.
  • thermostatic regulation switch 26 is provided in addition to the general manual switch, in the line of the signal EV2 output by the control unit.
  • the control unit 3 comprises, essentially, electrical circuits which operate as a logic system with finite states, a thermocouple-voltage amplifier 5, a comparator 28 which receives, as an input, the voltage output by the amplifier 5 and compares it with a reference voltage in order to generate a binary logic signal, of which the levels, on (or true) and off (or false), indicate, respectively, that the thermocouple voltage is above or below a predetermined value, for example 5mV and, preferably (but not necessarily), a timing circuit 27.
  • thermocouple 7 When the thermocouple 7 is not heated by the pilot light, the thermocouple voltage is practically zero and when it is heated, the voltage rises to a level of the order of 10-15mV (without a load).
  • the threshold value of 5mV is advantageously selected as the voltage value above which the magnetomotive force developed by the winding 14 is sure to be sufficient to oppose the action of the spring 13 and the armature 11, if closed, is held by the electromagnet 12.
  • the first operative mode is represented by the state diagram of Figure 2.
  • the control unit 3 changes to a state 31 (PILOT IGNIT) in which the pilot light is ignited when a heat demand signal TH-ON is applied to the unit.
  • This signal advantageously consists of the supply voltage which is applied to the unit 3 (by the supply 4) by the closure of the switch 25 ( Figure 1).
  • control unit 3 activates an internal timing circuit (START-TIM) and turns on (EV1-ON) the signal EV1 for energizing the solenoid valve 1 ( Figure 1), which is opened, as well as a signal SPARK-ON for energizing the ignition spark-generator 6 ( Figure 1).
  • STT-TIM internal timing circuit
  • EV1-ON the signal EV1 for energizing the solenoid valve 1
  • SPARK-ON for energizing the ignition spark-generator 6 ( Figure 1).
  • the signal EV2 for energizing the regulation solenoid valve 2 is turned off (EV2-OFF).
  • thermocouple 7 As a result of the signals which are turned on, the nozzle 18 is supplied with gas and the pilot light 19 is ignited, heating the thermocouple 7.
  • thermocouple voltage V exceeds the predetermined threshold level (5mV) which is sufficient to ensure that the solenoid valve 1 is kept open
  • the condition V>5mV recognized by the unit 3 causes it to change from the state 31 to a state 32 (BURNER COMM), with a delay which is normally of the order of a few seconds (5-15 sec).
  • control unit 3 turns off the signal for energizing the solenoid valve 1 (EV1-OFF) and the spark-generator 6 (SPARK-OFF) and turns on the signal for energizing the regulation valve (EV2-ON).
  • the burner is thus lit.
  • control unit 3 changes from the state 32 (BURNER COMM) to the state 30 (IDLE-OFF) when the thermostatic supply switch 25 is opened (TH-OFF).
  • thermocouple circuit During the transition from the state 32 to the state 30, a voltage pulse SWITCH-OFF is generated and applied to the thermocouple circuit and neutralizes the thermocouple voltage, closing the solenoid valve 1 and extinguishing the pilot light.
  • thermocouple voltage V falls below the predetermined threshold level (5mV) for any reason, the control unit 3 returns to the state 31 in order to re-ignite the pilot light.
  • this change of state may also be dependent on a rate of decrease of the thermocouple voltage greater than a predetermined value S, that is, on the condition - ⁇ V/ ⁇ T>S , as described, for example, in the document WO 9312378 already cited, instead of on a threshold voltage.
  • the two criteria may also be combined, the change of state taking place upon the occurrence of at least one of the two events.
  • the control unit 3 in the state 31 If the ignition or re-ignition operation carried out by the control unit 3 in the state 31 is not successful and the control unit 3 does not change to the state 32, at the end of the time interval defined by the timing circuit 27, (TIME-END), the control unit changes from the state 31 to an alarm state 33 (ALARM).
  • control signals for energizing the two solenoid valves 1 and 2 are both turned off (EV1-OFF, EV2-OFF) and a signal ALARM-ON for activating the optical and/or acoustic alarm-state indicator is turned on.
  • the lock-out and alarm state may be volatile or permanent.
  • the alarm state is maintained until the demand for ignition of the burner (that is, the supply voltage in the embodiment described) is turned off.
  • the system thus changes from the state 33 to the state 30 completely automatically without any manual intervention when the condition TH-OFF occurs.
  • the transition from the alarm state to the state 30 is dependent on an electrical or electro-mechanical operation (MAN-RES) to reset a lock-out device, carried out by the user and represented by the broken transition line 34.
  • MAN-RES electrical or electro-mechanical operation
  • control unit 3 in the case of the permanent-pilot mode of operation will now be considered with reference to Figure 3, in combination with Figure 1.
  • control unit 3 changes from an inactive state 37 (IDLE-OFF) without a supply to an active state 38 (PILOT IGNIT) for the ignition of the pilot light upon the closure (ON signal) of the supply switch 25 ( Figure 1).
  • the control unit 3 turns on the signal EV1-ON for energizing the safety valve 1 and the signal SPARK-ON for energizing the spark-generator, whereas the signal EV2-OFF for opening the regulation valve 2 is turned off.
  • the control unit After the ignition of the pilot light, which is detected by a the thermocouple voltage V above the threshold voltage, the control unit changes to the burner-operating state 39 (BURNER COMM) in which the signals for energizing the solenoid valve 1 and the spark-generator 6 are turned off (EV1-OFF, SPARK-OFF), whereas the signal for energizing the solenoid valve 2 is turned on (EV2-ON).
  • BURNER COMM the burner-operating state 39
  • the control unit 3 leaves the state 39 in order to change to the IDLE-OFF state 37 upon the removal (OFF) of the supply voltage, as a result of the opening of the switch 25 ( Figure 1).
  • a current pulse (SWITCH-OFF) is also generated upon the transition from the state 39 to the state 37, neutralizing the thermocouple current and ensuring closure of the solenoid valve 1.
  • thermocouple voltage V decreases below a predetermined threshold value (5mV) (as when the pilot light goes out) or with a rate of change - ⁇ V/ ⁇ T greater than a predetermined value S
  • the control unit is put in an alarm state 40 (ALARM) in which the signals for energizing the solenoid valves 1 and 2 are both turned off (EV1-OFF, EV2-OFF), whereas an alarm signal ALARM-ON is turned on and activates an optical and/or acoustic alarm indicator.
  • the alarm state 40 may be a permanent lock-out which the system leaves (transition line 41) by a manual resetting operation in the presence of the supply voltage (MAN.RST & ON) or a volatile lock-out which the system leaves (transition line 42, alternative to line 41) upon the removal (OFF) of the supply voltage.
  • a timing circuit may also be provided and activated when the control unit 3 is in the state 38 in order to bring about the change from the state 38 to the state 40 (transition line 44, signal TIME-END) if a thermocouple voltage above a predetermined value is not detected within a predetermined period of time determined by the timing circuit.
  • thermocouple voltage falls below a threshold value
  • the permanent-pilot mode of operation thus differs substantially from the intermittent-pilot mode of operation solely in that the pilot light is lit permanently throughout the time for which the automatic control system is supplied, irrespective of an actual demand for ignition of the burner imposed intermittently by a thermostatic switch (switch 26 of Figure 1).
  • This mode of operation which requires a permanent electrical supply to the system and a continuous supply of gas to the pilot-light nozzle and hence a continuous although low consumption of electrical energy and gas which, in the previous case, is strictly limited to the stages in which the pilot flame is ignited and the burner is supplied, is particularly advantageous for automatic control systems for so-called “combined” or water-heating automatic boilers in which it is necessary to have an almost instantaneous supply of hot water upon demand by the user.
  • the supply takes place without delay since it does not even have to be preceded, upon each demand, by a short pilot-flame ignition stage of the order of 10-15 sec.
  • the regulation solenoid valve 2 also has to ensure a continuous opening regulation which is achieved, for example, by means of a differential diaphragm actuator acting on the obturator 20 in an OR logic arrangement with the electromagnet 22 in dependence on the required flow-rate of hot water.
  • the automatic control system provides for the use of two valves (safety and regulation) in cascade which, except for the holding ensured by the thermocouple voltage if it is greater than a predetermined threshold value, are opened mutually exclusively, and that the absence of flame is detected positively, where appropriate after an ignition attempt, in order to close both solenoid valves and to adopt an alarm and lock-out state (volatile or permanent).
  • Double intrinsic safety is thus ensured, as already explained since, in the event of the pilot light going out, the supply of gas is stopped not only as a result of the automatic operation of the safety valve but also by the supplementary closure action imparted to the regulation valve.
  • Figure 4 shows schematically and by way of an example of the various possible embodiments, a preferred embodiment of a control unit 3 for the automatic control system of the present invention in the case of the intermittent-pilot mode of operation.
  • a conventional supply 4 activated by the closure of the thermostatic switch 25 outputs an alternating voltage V ⁇ used for energizing the solenoid valves and the spark-generator 6, which is also conventional, a first, unregulated direct voltage V1 of the order of 20V, and a second, regulated direct voltage V2 of the order of 15V.
  • the control unit comprises essentially the following functional blocks:
  • the release block 50 comprises a diode 54, a resistor 55 and a capacitor 56 connected in series between the voltage V1 and the positive thermocouple terminal 7.
  • the node between the resistor 55 and the capacitor 56 is connected to earth by a limiting resistor 59 and a first, normally-closed, switch contact 57 of a relay 58 of the piloting block 52.
  • the monitoring block 51 comprises essentially a first operational amplifier 60 supplied with the voltage V2 and receiving the thermocouple voltage as an input (through suitable resistors), and a comparator 61, also supplied by the voltage V2, with its non-inverting input connected to the output of the amplifier 60 and its inverting input connected to a reference voltage VR (obtained, for example, from V2 by a resistive divider).
  • a reference voltage VR obtained, for example, from V2 by a resistive divider
  • Input capacitances and feedback circuits define the gain and frequency-response of the amplifier and comparator, in known manner.
  • thermocouple voltage At the output of the comparator 61 there is a positive electrical signal if the thermocouple voltage is above 5mV, and a zero electrical signal if the thermocouple voltage is below 5mV.
  • thermocouple voltage The optional modifications necessary to take account, additionally or solely, of any decreases of more than a predetermined value in the thermocouple voltage can easily be inferred from the document WO9312378 cited.
  • the piloting block 52 comprises essentially a transistor 62 with its collector connected to the voltage V1 by means of a load constituted by the winding of the relay 58 with two toggling switch contacts 57, 63, its emitter connected to earth, and its base driven, in known manner, by the signal output by the comparator 61.
  • a freewheeling diode 64 with reverse polarity is connected between the voltage V1 and the collector of the transistor 62.
  • the timing and alarm block 53 comprises essentially an RC network formed by a resistor 65 and a capacitor 66 in series between the voltage V2 and earth, a comparator 67 which is supplied by the voltage V2 and receives as inputs the charge voltage of the capacitor 66 and a reference voltage VRR obtained, for example, from V2 by a resistive divider, and a transistor 68 connected like the transistor 62 in order to drive the winding of an alarm relay 69 in parallel with which an LED 70 or equivalent alarm indicator is connected.
  • the normally-closed contact 71 of the relay 69 is opened with a delay determined by the time constant of the RC network 65, 66 after the supply of voltage to the circuit.
  • the alternating voltage V ⁇ is transferred by means of the normally-closed contact 71 to the switch contacts 63 as a signal EV1 or EV2 for the mutually exclusive supply of the two solenoid valves 1 and 2 ( Figure 1).
  • the de-energized relay 58 supplies the solenoid valve 1, which is opened, and the spark-generator.
  • thermocouple voltage exceeds 5mV
  • the relay 58 is energized and the supply is switched to the solenoid valve 2 by means of the switch contacts 63.
  • the switching of the contacts 57 of the relay 58 causes the capacitor 66 to be discharged, consequently resetting the timing block and allowing charging of the capacitor 56, the function of which will be explained below.
  • thermocouple voltage does not exceed 5mV
  • the comparator 67 makes the transistor 68 conductive and the relay 69 is supplied and opens the contact 71, removing the supply from both of the solenoid valves 1 and 2 and indicating the alarm condition.
  • the relay 69 may be of various types; if a simple relay with an electromagnet is used, the lock-out and alarm condition is volatile and, if the supply is removed from the control circuit, for example, by the opening of the switch 25, the de-energizing of the relay causes the control circuit to return to the rest condition (block 30 of Figure 2).
  • the relay 69 has a manual lock-out with a manual release, the lock-out condition is maintained even if the supply is removed and, in order to return to the rest condition, a manual operation is necessary to release the mechanical lock-out.
  • the release may also be electro-mechanical and brought about by a push-button which closes an electrical release circuit.
  • the release is dependent on the presence of a voltage and the system changes from the lock-out state 30 to the pilot-light ignition state 31 ( Figure 2).
  • the contact 57 of the relay 58 switches and connects the positively-charged plate of the capacitor 56 to earth.
  • the capacitor 56 thus applies to the thermocouple circuit a negative voltage pulse which opposes the thermocouple voltage and neutralizes the current which holds the solenoid valve 1 open, so that it closes.
  • control unit for the permanent-pilot mode of operation shown in Figure 5 may not differ greatly from the previous embodiment.
  • the solenoid-valve piloting block is also the same as that of Figure 4, differing therefrom solely in that, when the contact 57, which is normally closed to earth, is opened, it supplies a supply voltage to an alarm block 73.
  • the alarm block 73 which replaces the timing block 53 of Figure 4, comprises a lock-out and alarm relay 75 of the mechanical lock-out type with two contacts 80, 81 (of which one 81, which is normally closed, has the same function as the contact 71 in the block 53, at least with regard to the activation of the release block 50), a first excitation winding 76 connected between earth and the collector of a PNP-type transistor 77 and a second resetting winding 79.
  • the emitter of the transistor 77 is supplied, by means of a delay network formed by a capacitor 72 and a resistor 74, by a voltage supplied, for example but not necessarily, by the block 50 when the contact 57 in the block 52 is open.
  • the base of the transistor 77 is polarized, through a resistor 78, by the output voltage of the comparator 61 of the block 51 which makes the transistor 77 conductive if the thermocouple voltage is below 5mV and, of course, if the contact 57 is open and the transistor 77 is supplied.
  • An LED 82 or equivalent indicator connected in series between the voltage V1 and earth to a current-limiting resistor and to the normally-open contact 80, supplies an alarm signal when the relay 75 is put in the alarm state.
  • the second winding 79 of the relay 75 which is energized by the voltage V1 when a push-button switch 83 is closed, provides a reset control signal for the lock-out and alarm device.
  • circuits of Figures 4 and 5 represent only preferred examples of the many possible embodiments and many variations may be applied.
  • thermocouple voltage the rate of decrease of the thermocouple voltage is greater than a certain value
  • control system described can also be used in gas-burning equipment having a pilot light and protection against depletion of supporters of combustion, known by the acronym ODS (for oxygen depletion system), in which the design of the pilot-light nozzle and its spatial relationship with the thermocouple are such that the pilot light heats the thermocouple only when there is an adequate supply of supporters of combustion; otherwise, in the presence of a stale atmosphere, and hence with a smaller supply of supporters of combustion, the rate of propagation of the flame is reduced and the pilot flame generated moves away from the thermocouple and cannot heat it sufficiently.
  • ODS oxygen depletion system
  • control system described is used in combination with an ODS device, it is advantageous, for reasons of safety, to avoid any attempt to reignite the pilot light in the event of its going out, which may be due to combustion-air depletion.
  • the alarm and lock-out condition 33 is also advisable for the alarm and lock-out condition 33 to be permanent and for a manual operation to be required to reset it.
  • thermocouple voltage which can be detected even before the threshold voltage value is reached, whereas depletion of supporters of combustion in an enclosed environment and the consequent movement of the pilot flame away from the thermocouple are much slower and more gradual phenomena which bring about a slower and more gradual decrease in the thermocouple voltage.
  • thermocouple voltage is below a predetermined threshold value that the safety valve closes, extinguishing the pilot light, if it is lit, and causing a further subsequent rapid drop in the thermocouple voltage.
  • Figure 6 shows, as a state diagram, the operation of a preferred embodiment of the control unit 3 which operates according to these concepts in a system such as that of Figure 1.
  • an inactive state 90 in which the unit 3 is preferably but not necessarily, not supplied electrically, the system changes to a state 91 (PILOT IGNIT) for the ignition of the pilot light when a heat demand signal TH-ON is applied to the unit.
  • control unit 3 activates an internal timing circuit (START-TIM), and turns on (EV1-ON) the signal EV1 for energizing the solenoid valve 1 ( Figure 1) which is opened, as well as a signal SPARK-ON for energizing the ignition spark-generator 6 ( Figure 1).
  • STT-TIM internal timing circuit
  • EV1-ON the signal EV1 for energizing the solenoid valve 1
  • SPARK-ON for energizing the ignition spark-generator 6 ( Figure 1).
  • the signal EV2 for energizing the regulation solenoid valve 2 is turned off (EV2-OFF).
  • thermocouple 7 As result of the signals which are turned on, the nozzle 18 is supplied with gas and the pilot flame 19 is ignited, heating the thermocouple 7.
  • thermocouple voltage V exceeds the predetermined threshold level (5mV) which is sufficient to ensure that the solenoid valve 1 is kept open
  • the condition V>5mV recognized by the unit 3 causes it to change from the state 91 to a state 92 (BURNER COMM), with a delay which is normally of the order of a few seconds (5-15 sec.).
  • control unit 3 turns off the signal for energizing the solenoid valve 1 (EV1-OFF) and the spark-generator 6 (SPARK-OFF) and turns on the signal for energizing the regulation valve (EV2-ON).
  • the burner is thus lit.
  • control unit 3 changes from the state 92 (BURNER COMM) to the state 90 (IDLE-OFF) when the thermostatic supply switch 25 is opened (TH-OFF).
  • thermocouple circuit During the transition from the state 92 to the state 90, a voltage pulse SWITCH-OFF is generated and applied to the thermocouple circuit and neutralizes the thermocouple voltage, closing the solenoid valve 1 and extinguishing the pilot light.
  • Any failure of one of the open valves to close does not constitute a dangerous condition because gas is prevented from flowing to the burner, if not to the pilot-light nozzle, by the operation of the other valve.
  • thermocouple voltage V undergoes an abrupt decrease ( - ⁇ V/ ⁇ T>S ), probably due to accidental extinguishing of the light, the control unit 3 returns to the state 91 in order to reignite the pilot light.
  • thermocouple voltage decreases slowly to a level below or equal to a predetermined threshold voltage (V ⁇ 5mV) the control unit is put in an alarm and permanent lock-out state (ALARM 1) which it leaves to change to the state 90 only by a manual resetting operation (MAN-RST).
  • a predetermined threshold voltage V ⁇ 5mV
  • thermocouple voltage is probably due to depletion of supporters of combustion.
  • control signals for energizing the two solenoid valves 1 and 2 are both turned off (EV1-OFF, EV2-OFF) and a signal ALARM1-ON for activating an optical and/or acoustic indicator of the alarm state is turned on.
  • the control unit 3 in the state 91 If the ignition or re-ignition operation carried out by the control unit 3 in the state 91 is not successful and the control unit 3 does not change to the state 92, at the end of the time interval defined by the timing circuit 27 (TIME-END), the control unit changes from the state 91 to an alarm state 94 (ALARM 2).
  • control signals for energizing the two solenoid valves 1 and 2 are both turned off (EV1-OFF, EV2-OFF) whereas a signal ALARM2-ON for activating an optical and/or acoustic alarm-state indicator is turned on.
  • the lock-out and alarm state may be volatile or permanent.
  • the alarm state is maintained until the demand for ignition of the burner (that is, the supply voltage in the embodiment described) is turned off.
  • the system thus changes from the state 94 to the state 90 completely automatically without any manual intervention when the condition TH-OFF occurs.
  • the alarm state 94 is functionally equivalent and corresponds to the state 93.
  • Figure 7 shows, by way of example, a practical embodiment of a control unit which operates according to the states of Figure 6.
  • control unit is constituted essentially by the same functional blocks as those described with reference to Figures 4 and 5 and only the very small variations are shown and described in detail.
  • the functional blocks and elements equivalent to those of Figures 4 and 5 are identified by the same reference numerals.
  • the block 51 for monitoring the thermocouple voltage differs from that of Figures 4 and 5 solely in that, in addition to the comparator 61, there is a second comparator 95 the inverting input of which is connected to the output of the amplifier 60.
  • the non-inverting input is connected to the output of the amplifier 60 by means of a resistor 96. It is also connected to earth by means of a resistor 97 and a capacitor 98 in parallel with one another.
  • the output of the comparator 95 is normally at an electrical level 0 and is brought to a positive electrical level (V2) only by a relatively rapid decrease in the voltage output by the amplifier 60.
  • the block 52 for piloting the solenoid valves differs from that of Figures 4 and 5 in that, as well as being controlled by the transistor 62 which closes one terminal of the winding to earth when it is made conductive by the comparator 61, the excitation winding of the relay 58 is also controlled by a PNP transistor 99 of which the emitter is connected to the voltage V2 (by suitable measures also to the voltage V1) and the collector is connected to the other terminal of the winding.
  • the base of the transistor 99 is connected to the output of the comparator 95 by means of a resistor, so that the transistor 99, which is normally conductive, is cut off when the output of the comparator 95 is brought to a positive electrical level, that is, in the presence of a relatively rapid drop in the thermocouple voltage.
  • the relay 58 is energized when the thermocouple voltage is greater than a predetermined threshold value and is de-energized, not only if the thermocouple voltage falls below the threshold value, but also if it drops rapidly.
  • the control unit comprises both a timing and alarm block 53 identical to that of Figure 4 and an alarm block 73 identical to that of Figure 5.
  • the supply of the voltage V ⁇ to the solenoid valves is controlled jointly by the two blocks 53 and 73, by the connection in series of the relay contact 71 in the block 53, of the relay contact 81 in the block 73, and of the diverter switch contact 63 of the relay 58 in the block 52.
  • the energizing of the relay 58 brings about resetting of the timing circuit in the block 53 by the switching of the contact 57.
  • the two alarm blocks 53 and 73 may be replaced by a single alarm and timing block, with a single intervention and permanent lock-out relay activated both by the operation of the timing circuit and by the falling of the thermocouple voltage below the threshold level.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Combustion (AREA)
EP96830531A 1996-10-16 1996-10-16 Système de commande automatique avec une protection de sécurité double pour des brûleurs à gaz à fonctionnement intermittant Expired - Lifetime EP0837283B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP96830531A EP0837283B1 (fr) 1996-10-16 1996-10-16 Système de commande automatique avec une protection de sécurité double pour des brûleurs à gaz à fonctionnement intermittant

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP96830531A EP0837283B1 (fr) 1996-10-16 1996-10-16 Système de commande automatique avec une protection de sécurité double pour des brûleurs à gaz à fonctionnement intermittant

Publications (2)

Publication Number Publication Date
EP0837283A1 true EP0837283A1 (fr) 1998-04-22
EP0837283B1 EP0837283B1 (fr) 1999-12-22

Family

ID=8226037

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96830531A Expired - Lifetime EP0837283B1 (fr) 1996-10-16 1996-10-16 Système de commande automatique avec une protection de sécurité double pour des brûleurs à gaz à fonctionnement intermittant

Country Status (1)

Country Link
EP (1) EP0837283B1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2772463A1 (fr) * 1997-12-16 1999-06-18 Europ Equip Menager Dispositif d'aide a la gestion du fonctionnement d'un bruleur domestique par detection de flamme
DE10029234A1 (de) * 2000-06-14 2001-10-25 Rolf Kresel Mehrstufige Gasarmatur
EP1215441A2 (fr) * 2000-12-18 2002-06-19 BSH Bosch und Siemens Hausgeräte GmbH Commande de brûleur de séquence d'impulsions avec une soupape
ES2310491A1 (es) * 2007-06-21 2009-01-01 Bsh Electrodomesticos España, S.A. Disposicion de mando para una cocina de gas.
FR2944337A1 (fr) * 2009-04-10 2010-10-15 Barriere Procede de mise en securite d'un generateur de flammes et generateur de flammes equipe d'un dispositif de mise en oeuvre d'un tel procede
US8668490B2 (en) * 2003-02-13 2014-03-11 Mertik Maxitrol Gmbh & Co. Kg Method and arrangement for igniting a gas flow
IT201800005549A1 (it) * 2018-05-21 2019-11-21 Apparecchio di riscaldamento con bruciatore a gas combustibile

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU2013293033A1 (en) * 2012-07-16 2015-02-05 Bromic Pty Ltd Gas heater
US10655891B2 (en) 2017-12-14 2020-05-19 Emerson Electric Co. Gas valve control system for a water heater

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4360338A (en) * 1980-05-19 1982-11-23 Robertshaw Controls Company Control system for dual coil pilot valve burner system
JPS58117915A (ja) * 1982-01-07 1983-07-13 Matsushita Electric Ind Co Ltd 湯沸器の燃焼制御装置
EP0109155A1 (fr) 1982-09-22 1984-05-23 Webber Electro Components Plc. Vanne électromagnétique avec commande par capteur externe
GB2170932A (en) * 1985-02-07 1986-08-13 Stelrad Group Ltd Status indicators for fuel burning appliances
FR2616887A1 (fr) * 1987-06-19 1988-12-23 Theobald Sa A Dispositif thermo-electrique de surveillance de flamme et de securite a l'allumage et a l'extinction pour bruleur a gaz
JPH01318809A (ja) * 1988-06-17 1989-12-25 Matsushita Electric Ind Co Ltd 火力切換装置
EP0439417A1 (fr) 1990-01-26 1991-07-31 Société Anonyme CONSTRUCTIONS ELECTRIQUES R. V. Dispositif de sécurité pour le fonctionnement d'un brûleur
WO1993012378A1 (fr) 1991-12-13 1993-06-24 Aktiebolaget Electrolux Dispositif assurant le reallumage automatique d'un bruleur eteint
EP0573222A1 (fr) * 1992-05-30 1993-12-08 BLUE CIRCLE HEATING LIMITED (formerly MYSON GROUP PLC) Appareils de chauffage

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4360338A (en) * 1980-05-19 1982-11-23 Robertshaw Controls Company Control system for dual coil pilot valve burner system
JPS58117915A (ja) * 1982-01-07 1983-07-13 Matsushita Electric Ind Co Ltd 湯沸器の燃焼制御装置
EP0109155A1 (fr) 1982-09-22 1984-05-23 Webber Electro Components Plc. Vanne électromagnétique avec commande par capteur externe
GB2170932A (en) * 1985-02-07 1986-08-13 Stelrad Group Ltd Status indicators for fuel burning appliances
FR2616887A1 (fr) * 1987-06-19 1988-12-23 Theobald Sa A Dispositif thermo-electrique de surveillance de flamme et de securite a l'allumage et a l'extinction pour bruleur a gaz
JPH01318809A (ja) * 1988-06-17 1989-12-25 Matsushita Electric Ind Co Ltd 火力切換装置
EP0439417A1 (fr) 1990-01-26 1991-07-31 Société Anonyme CONSTRUCTIONS ELECTRIQUES R. V. Dispositif de sécurité pour le fonctionnement d'un brûleur
WO1993012378A1 (fr) 1991-12-13 1993-06-24 Aktiebolaget Electrolux Dispositif assurant le reallumage automatique d'un bruleur eteint
EP0573222A1 (fr) * 1992-05-30 1993-12-08 BLUE CIRCLE HEATING LIMITED (formerly MYSON GROUP PLC) Appareils de chauffage

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 007, no. 223 (M - 247) 4 October 1983 (1983-10-04) *
PATENT ABSTRACTS OF JAPAN vol. 014, no. 121 (M - 0946) 7 March 1990 (1990-03-07) *

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2772463A1 (fr) * 1997-12-16 1999-06-18 Europ Equip Menager Dispositif d'aide a la gestion du fonctionnement d'un bruleur domestique par detection de flamme
EP0924467A1 (fr) * 1997-12-16 1999-06-23 Compagnie Europeenne Pour L'equipement Menager "Cepem" Dispositif d'aide à la gestion du fonctionnement d'un brûleur domestique par détection de flamme
DE10029234A1 (de) * 2000-06-14 2001-10-25 Rolf Kresel Mehrstufige Gasarmatur
DE10029234C2 (de) * 2000-06-14 2003-11-27 Rolf Kresel Gasregel- und Sicherungsarmatur für einen mehrstufigen Gasbrenner
EP1215441A2 (fr) * 2000-12-18 2002-06-19 BSH Bosch und Siemens Hausgeräte GmbH Commande de brûleur de séquence d'impulsions avec une soupape
EP1215441A3 (fr) * 2000-12-18 2003-10-15 BSH Bosch und Siemens Hausgeräte GmbH Commande de brûleur de séquence d'impulsions avec une soupape
US8668490B2 (en) * 2003-02-13 2014-03-11 Mertik Maxitrol Gmbh & Co. Kg Method and arrangement for igniting a gas flow
ES2310491A1 (es) * 2007-06-21 2009-01-01 Bsh Electrodomesticos España, S.A. Disposicion de mando para una cocina de gas.
FR2944337A1 (fr) * 2009-04-10 2010-10-15 Barriere Procede de mise en securite d'un generateur de flammes et generateur de flammes equipe d'un dispositif de mise en oeuvre d'un tel procede
IT201800005549A1 (it) * 2018-05-21 2019-11-21 Apparecchio di riscaldamento con bruciatore a gas combustibile
WO2019224128A1 (fr) * 2018-05-21 2019-11-28 Sit S.P.A. Appareil de chauffage comprenant un brûleur à gaz combustible

Also Published As

Publication number Publication date
EP0837283B1 (fr) 1999-12-22

Similar Documents

Publication Publication Date Title
US6322352B1 (en) Gas burner system
US7112059B2 (en) Apparatus and method for shutting down fuel fired appliance
CA1166719A (fr) Circuit de commande a commutateur de securite auto-verificateur
US4360338A (en) Control system for dual coil pilot valve burner system
US7083408B1 (en) Apparatus and method for shutting down a fuel fired appliance
EP0837283B1 (fr) Système de commande automatique avec une protection de sécurité double pour des brûleurs à gaz à fonctionnement intermittant
GB2036946A (en) Fuel ignition and supply systems
US4106889A (en) Burner ignition system
US4077762A (en) Fuel ignition system having contact interlock protection
US3484177A (en) Igniter and control means
US4235586A (en) Gas ignition control
US4482312A (en) Burner control system
US3660005A (en) Fail-safe electric ignition systems
US5277575A (en) System and method for controlling the operation of a primary burner
GB2196500A (en) Time delay pulse circuit
US4147496A (en) Safety ignition means for burner installations
JP2000088246A (ja) 燃焼装置
US4025283A (en) Electrical ignition systems for gas fired equipment
JP3588245B2 (ja) 燃焼装置
US5704775A (en) Auxiliary igniter and control for a furnace
KR0143695B1 (ko) 가스렌지버너의 자동착화 및 소화장치
JPS6130046Y2 (fr)
JP2675507B2 (ja) 燃焼装置
CN108072056B (zh) 燃气器具
JPS584041Y2 (ja) 燃焼制御装置

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): FR GB IT

AX Request for extension of the european patent

Free format text: AL;LT;LV;SI

ITCL It: translation for ep claims filed

Representative=s name: JACOBACCI CASETTA & PERANI S.P.A.

EL Fr: translation of claims filed
17P Request for examination filed

Effective date: 19980417

AKX Designation fees paid

Free format text: FR GB IT

RBV Designated contracting states (corrected)

Designated state(s): FR GB IT

REG Reference to a national code

Ref country code: DE

Ref legal event code: 8566

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

17Q First examination report despatched

Effective date: 19990326

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: SIT LA PRECISA S.P.A.

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): FR GB IT

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY

Effective date: 19991222

ITF It: translation for a ep patent filed
ET Fr: translation filed
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20001016

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20001016

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.

Effective date: 20051016