FR2583856A1 - TEMPORIZED CUTTING CIRCUIT OF A GAS BURNER - Google Patents

Abstract

TIMED SHUT-OFF CIRCUIT OF A GAS BURNER USING AN AUTOMATIC TIMED SWITCHING DEVICE 8. THE SHUT-OFF IS OBTAINED BY DISTURBING AN ELECTRIC CURRENT WHICH A THERMO-ELEMENT 6 HEATED BY THE BURNER'S FLAME PROVIDES AN SAFETY 7 IN THE GAS VALVE 1. A DELAYED CONTROL UNIT 10, 13 CAUSES THE INTERRUPTION DURING THE ACTIVE PHASE OF THE GAS VALVE 1. THIS ACTIVE PHASE DEPENDS ON TRIPPING BY THE AUTOMATIC TIMED SWITCHING DEVICE 8 AND D '' A PRIOR PROCESS FOR CHARGING A CAPACITOR 10. APPLICATION: ESPECIALLY TO GAS COOKERS.

Description

TIMED CUTTING CIRCUIT

FROM A GAS BURNER

  The present invention relates to a circuit for timed shutdown of a gas burner using an automatic timed switching device, by disturbing the passage of the electric current of a thermoelement heated by the flame of the burner to a

  safety element in the gas valve.

  The use of automatic timed switching devices has long been known, in many forms, in electric ranges, that is, in stoves with electric heating systems. In this case, the investment is limited to the additional automatic timed switching device with a suitable power switch. The use of timed automatic switching devices in gas ranges is substantially more expensive. It is then necessary to control not an electric power switch but a gas valve capable of reliably interrupting the influx of gas which is further controlled with respect to its flow. Furthermore, normal use of the burner, without timed switching device, must also be possible. It is known, and specified in various countries, to provide, in the gas valves, a suitable gas valve, namely a valve known as a "thermo-safety element". This thermo-safety element comprises a thermo-element which is heated by the flame of the burner and which delivers the current which excites an electromagnet in the gas valve, a gas shutoff valve being kept open thereby. When extinguishing the flame in the burner, the excitation of the solenoid in the valve

  gas stops, and the gas valve closes.

  This being so, it is possible to act on this circuit, an automatic switching device timed, and to interrupt the flow of gas through the gas valve with the aid of an automatic switching device timed, this being done by interrupting the excitation of the electromagnet of the gas valve. However, the control must be designed in such a way that normal operation of the thermo-safety element

not be compromised.

  The object of the present invention is to provide a circuit by means of which an automatic timed switching device for a gas burner may be

  employed using the thermo-safety device.

  Such an arrangement must satisfy the strict safety requirements relating to the use of the gas, and must furthermore offer advantageous conditions for the operation of the burner without using the device.

  automatic time switch.

  According to the invention, a control circuit for achieving the aforementioned objects has a timed control unit, having a time constant in the field of the second, this unit causing, during its active phase, a disturbance of the current flow. ranging from the thermoelement to the safety element in the gas valve, which active phase depends on a triggering process by the automatic timed switching device and a charging process, prior to this triggering process,

  for the timed control unit.

  A control circuit thus produced is distinguished by a particularly high functional reliability, accompanied by a relatively low expense. The switching on of the automatic time-delayed switching device has the effect of producing a charging process of the time-delayed control unit arranged according to the invention, that is to say that this timed control unit is put in a condition of functional availability. When a predetermined period of time has elapsed, this timed control unit is triggered by the automatic timed switching device, that is to say that the timed control unit is briefly subjected, for a few seconds, to an active phase during which the flow of current from the thermoelement heated by the flame of the gas burner to the safety element in the gas valve is disturbed. This disturbance can be a simple interruption of an electrical conductor. As a result, the electromagnet in the gas valve is no longer energized and the gas safety valve thus closes during this phase. This phase must have a duration such that the interruption of the operation of the burner is certain. After the relatively rapid cooling of the thermocouple in the region of the gas burner, thereafter there is no further excitation of the electromagnet in the gas valve. However, it is possible, without any other particular measure, to

  restart the burner by a known manual operation.

  It is also possible to re-initialize the

  automatic timed switching device.

  In a preferred embodiment, the arrangement according to the invention is such that the delayed control unit is constituted by a series circuit comprising a capacitor, a winding of a relay and a switching unit that the automatic switching device. time delay can control, and by a charge path to charge the capacitor, this path being connected to the capacitor when the switching unit is in a breaking condition of said series circuit, and the disturbance of the current path from the thermo-element to the security element is

  realized by means of the switching contact of the relay.

  In this context, the switching unit is preferably in the form of a switch, which is actuable by the automatic time switch device and can connect the capacitor alternately in series with the load path or with the winding of the switch. relay. Such arrangements allow the realization of a control arrangement simple to build and economic to achieve, with

  which one can achieve the objects of the invention.

  The activation of the automatic timed switching device causes the capacitor to be charged by direct current through said charging path. If, at the end of a cooking process, this end occurs in accordance with a pre-adjustment, the automatic delayed switching device is triggered, the capacitor is then separated from the charging path and, via the switching - for example by means of a switch - is connected to the relay winding. This series connection has the effect that the capacitor is discharged via the relay winding and that the current flowing in this winding exits the relay whose switching contact causes the disturbance of the current path from the thermoelement to the element. safety valve of the gas valve. Since, before being thus connected to the relay winding, the capacitor had taken its maximum state of charge, the excitation current available for

  producing the attraction of the relay is also maximal.

  This current decreases according to an exponential function. The relay is, however, kept in the attracted state for a predetermined time. This time is determined by the capacitance values of the capacitor and the

  resistance of the relay winding.

  In a preferred embodiment of the arrangement according to the invention, an AC outlet can be connected in parallel to the terminals of the thermo-element by the switching contact of the relay. As the thermoelement makes it possible to obtain only relatively low voltages, but on the other hand a relatively intense current, it is necessary to provide a transmitting member (transformer) between the voltage of the sector and the terminals of the thermoelement, to bring them this voltage. In principle, it would be conceivable that the conduction path from the thermocouple to the safety element in the gas valve is simply interrupted by the timed control unit acting as a switching element. The extremely low voltages available in this area, and the very high relative intensity currents passing through, have the effect that the use of such a switching element is very problematic. Therefore, for the case of interruption, it is appropriate that the alternating current is briefly applied, superimposed, adequately, to the winding of the electromagnet of the safety element of the valve. gas. Preferably, the supply of the primary winding of the transmitting member is controlled by the switching contact of the timed control unit. The characteristics and advantages of the invention

  will appear more fully in the description

  presented below, by way of non-limiting example, with reference to the appended drawing, the single figure of which shows a timed control circuit associated with

  a gas valve shown schematically.

  Fuel gas is fed in the direction of the arrow to the gas valve 1, via a supply line 2. A manual control knob allows, by adjusting its angular position, to manually adjust the flow rate of this gas . By pressing axially on this control button, a gas safety valve is opened, so that the gas leaving the gas valve via line 5, in the direction of the arrow, can flow to a burner and be there. ignited. The ignition pilot flame heats a thermoelement 6 arranged in its region. The resulting electrical voltage produces an electric current which, by energizing an electromagnet 7 in the gas valve 1, holds the gas safety valve 4 in position.

opening condition.

  During manual operation, the cooking or boiling process is terminated by turning the control knob 3 to its "zero" position, which has the effect of

  effect of interrupting the supply of gas to the burner.

  The extinguishing of the flame has the further effect that the gas safety valve is no longer attracted by

  the electromagnet 7 and also closes the gas channel.

  If it is desired that the cooking or boiling process be automatically terminated after a predetermined period of time, then an appropriate automatic timing switch device 8 must be properly preset. As a result, a switch 9 is set to the position shown in phantom in the figure, whereby a capacitor 10 is energized via a rectifier 11 and a load resistor. 12, so that this capacitor is correspondingly charged. When the instant of completion of the switching has arrived in the automatic timed switching device 8, the switch 9 is switched to the position shown in solid lines in the figure. As a result, the capacitor 10 is directly connected in series with the winding of a relay 13. The discharge current flowing then excites this relay 13, and the contact 14 of this relay is closed. Through a transmitting member (transformer) 15, transformed alternating current (in the direction of a lowering) is fed to the conductors connecting the thermocouple 6 to the electromagnet 7. The superposition of this alternating current to the DC current supplied by the thermoelement 6 causes a relaxation of the gas safety valve 4 of the electromagnet 7, so that the flow of gas through the valve 1, towards the burner, is interrupted. The contact 14 of the relay remains closed until the charging voltage of the capacitor 10 has decreased to such a point that the discharge current passing through the coil 13 of the relay is no longer able to maintain this relay at the position attracted. This period of time must be determined by a suitable dimensioning of the capacitor 10 and the resistance of the winding 13 of the relay, so that the closing of the gas safety valve, and consequently the end of the cooking process, be assured. Then, the relay 13 drops, and the contact 14 of this relay is reopened. The whole installation is in a neutral state, which means that a new cooking process can be re-initialized and then be finished again, both by manual intervention and by the automatic switching device.

timed 8.

Claims (6)

  1. Circuit for timed shutdown of a gas burner with the aid of an automatic timed switching device, said shutdown being caused by disturbance of an electric current from a thermoelement heated by the flame of the burner to an element safety device in the gas valve, characterized in that it comprises a timed control unit (10, 13), having a time constant in the range of the second, this unit, during its active phase, causing a disturbance of the flow of current from the thermocouple (6) to the safety element (7) in the gas valve (1) and in that this active phase depends on a triggering process by the automatic time-delayed switching device ( 8) and a charging process, prior to this process of   tripping, for the timed control unit.   2. Circuit according to claim 1, characterized in that the time-delayed control unit is constituted by a series circuit comprising a capacitor (10), a winding (13) of a relay and a switching unit (9) that the automatic timed switching device can be controlled, as well as by a charging path (11, 12) for charging the capacitor (10), this path being connected to the condenser (10) when the switching unit (9) is in a condition of said series circuit, and in that the disturbance of the current path from the thermocouple (6) to the safety element (7) is effected by means of the   switching contact (14) of the relay (13).   Circuit according to Claim 2, characterized in that the switching unit is in the form of a switch (14) which can be actuated by the automatic time-delayed switching device and can connect the capacitor (10) alternately in series with the charging path (11,12) or with the winding (13) of the relay.   4. Circuit according to any one of the preceding claims, characterized in that an AC outlet can be connected in parallel to the terminals of the thermo-element (6) by the   switching contact (14) of the relay.   5. Circuit according to claim 4, characterized by a transmitting member or transformer (15) between the mains voltage and the terminals of the thermo-element (6). 6. Circuit according to claim 5, characterized in that the supply of the primary winding of the transmitting member (15) is controlled by the contact   switching (14) of the timed control unit.