DE2012998A1 - Electric ignition system for burners - Google Patents

Description

PATH IiTAIiWAII !. ■ row. «1378 DIPL. ING. Β · JiOJLj25Jfi-K «■ 9 A UGSRTJIiG PHILIPPINE-WELSEIt-STBA8S «IA ""

771

Augsburg, March 18, 1970

i-iobertshaw Controls Company, 1701 Byrd Avenue, Richmond, Virginia, United States of America

Electric ignition system for burners

The invention relates to electrical ignition systems for burners and, more particularly, to electrical ignition systems in which an electrical ignition element with a positive temperature coefficient of resistance at the same time both as an igniter and as a temperature sensor for monitoring the relevant Burner leading fuel flow is used.

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Hire different types of information than electrical ones Detonators usable materials with desirable for commerce-fourth Properties have made electrical ignition systems having such detonators increasingly important to win. One of the many primary goals pursued by engineers in the field is to create one Circuit, which is relatively simple, consists of a few! 'Rushes and under abnormal operating conditions safely stops puncturing.

Electrical circuits are characteristic of such facilities with a heat sensor element to monitor the relevant Burner flame, jas the thermosensitive element is often either a thermistor or photoelectric light detector which responds to the heat of the light emitted by the burner flame in question responds. As well as the control circuit associated with these elements as well these elements themselves are quite complicated and often work with a considerable delay, which is under Certain circumstances in the room immediately surrounding the burner lead to explosive states can *

Various attempts to solve the above-mentioned difficulty and the associated further difficulties

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abilities led to circuits, polygamy as a result of their complexity, . Their difficult production and / or as a result In the absence of adequate security properties, they are only partially satisfactory '.

The invention is intended to solve the problem "* · in an electrical ignition system of the type mentioned above, a relatively "simple, few-part J

existing. Circuit and one in all circumstances to achieve safe puncture in any relationship.

This object is achieved in an electrical ignition system for burners according to the invention by an electrical power source, further by electrical ballast means connected to it, further by an electric igniter which can be attached close to the burner in question and is connected to both the power source and the ballast means with a positive * resistance temperature coefficient, 'and solved by an electrically actuatable valve connected to the igniter, forming an excitation circuit, for controlling the flow of fuel leading to the burner ^; in such a way that the valve is closed in the absence of electrical excitation and is opened when a voltage of a certain minimum level is excited, the said excitation circuit causing a voltage drop

00984171201

■ which is directly proportional to the respective temperature of the detonator and then one of the named Minimum voltage has the same value if the temperature of the Igniter is above the minimum ignition temperature required for the fuel.

Two preferred embodiments of the electrical ignition system according to the invention are hereinafter referred to as Examples are described with reference to the accompanying drawing. They represent:

Fig. 1 is a circuit diagram of a particular

simple embodiment of the electrical ignition system according to the invention for burners,

Fig. 2 is a circuit diagram of another

Embodiment of the electrical ignition system according to the invention with a flame monitoring device and

Fig. 3 is a diagram for explaining the

basic function of the electrical ignition system shown in FIGS. 1 and 2 according to the invention.

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The preferred embodiment shown in Fig. 1 of the electrical ignition system according to the invention comprises an electrical igniter 10 with a positive resistance * - Temperature coefficient, which with the excitation winding of an electromagnetic relay 12, a ballast resistor and a switch 16 is connected in series. The entire series connection is connected to an electrical power source " connected, which, for the sake of simplicity in the drawing is only indicated by lines 18. Instead of the special ™ Ballast resistor 14 and the illustrated winding of the Relay 12 can, if desired, also be a relay with a Ballast winding can be used, i.e. the ballast resistor and the relay winding are only the one in the drawing Drawn separately for clarity of illustration.

A series circuit is connected in parallel with the igniter 10, consisting of an electrically operated fuel supply valve 20, a switch '22 and a sentence usually |

open relay contacts or working contacts 24 exist, which latter in the manner shown in each case then are open when the relay 12 is not energized, while they are closed when this relay is energized. The electrically operated fuel supply valve 20 may be of any known type and may include any actuating device such as a heat engine

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Have electromagnets or the like. The valve, 20 is accordingly designed so that it only opens when it is excited by a voltage which is greater or is equal to a fourth "V", the latter being explained in more detail below with reference to the illustration in FIG. When the valve 20 is open, fuel flows over from a fuel source not shown in the drawing a line 26 and the opened valve 20 to a burner 28, which is in the vicinity of the ignition of the electric igniter lies.

In Fig. 2 are the parts also shown in Fig. 1, respectively again assigned the same reference numbers. In this embodiment of the invention shown in Fig. 2 is the Igniter 10 via power source 18 with a hot wire ballast relay 30, a switch 16 and a thermistor .Connected in series with a positive temperature coefficient. The hot wire ballast relay 30 has a ballast arm 34 which acts as a series ballast resistor and expands to close a set of contacts 36, when it heats itself up from the current flowing through it. The contacts 36 are connected to the switch 22 and the excitation winding are connected in series with 3 electromagnetic relays. The relay 38 magnetically actuates the Normally open contacts 24 and a set of normally closed

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Normally closed contacts 4.0, which the thermistor 32 directly connected in parallel. The relay 38 closes at his Excitation the contacts 24 while at the same time the ~ Contacts 40 opens. - '

The in the Eig. 1 and 2 illustrated circuits work in a similar way according to the principle according to the invention Way. Both circuits can be used in connection with any burner system, but will their mode of operation is described below as an example in connection with a central heating system. In such a The system can use the switch 16 either as an electrical main switch used when it is desired that the igniter is continuously energized, or as a system thermostat to serve. If switch 16 is effective as a system thermostat in a particular installation, it is Switch 22 is not required and can be omitted. Note that switches 16 and 22 are either can be operated normally or automatically according to the special requirements of the installation. aside from that the switches 16 and 22 can be operated either directly or indirectly as with a conventional thermostat which the switching element on a temperature-sensitive Device that responds to the temperature of the surrounding Room monitored. The switches 16 and 22 are only off

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Shown as a single-pole off switch for illustrative reasons.

To explain the mode of operation of the circuit shown in Fig. 1, a typical installation of an ignition system with a central heating furnace is assumed, in which the switch 16 acts as an electrical main switch and the switch 22 as a thermostatically operated switch. If no heat is requested and the main switch 16 is switched off, the ignition system is in the cows shown in the drawing That an increase in temperature is required, this switch 22 is closed, inter alia, this enables the excitation of the valve 20. Under these circumstances, closing the main switch 16 causes current from the power source 18 to flow through the igniter 10, the winding The relay 12 energized thereby closes the working contacts 24 so that the electrically operated valve 20 is connected in parallel to the igniter 10, if the igniter 10 is still cold, its resistance increases proportionally with the temperature still small in relation to the total resistance of the series circuit, which acts as a voltage divider.

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waste at the igniter 10 is therefore initially still small. Since the valve 20 is connected in parallel with the igniter 10 which is present on the igniter 10 as a result of the voltage drop Voltage directly to the valve 20, what a Causes excitation of this valve. Jf it - increasing temperature of the igniter 10 also increases in a corresponding manner the "resistance and thus the voltage drop of this initiator.

To further explain the mode of operation of the ignition system according to the invention shown in FIG Reference is made to the diagram shown in FIG. 3, in which a curve 42 shows the change in the igniter temperature as a function of time when the igniter is initially energized. The curve 42 also shows the temperature-dependent change in the voltage drop across the igniter 10. In the sequence of that in the previous one The operations described in paragraph correspond to those in diagram Λ specified time "t" the time at which the main switch 16 is switched on. As can be seen from Fig. 3, after the switch 16 is closed, both the Igniter temperature as well as that occurring at the igniter 10 Voltage drop bi3 to a point at which the with "T" designated ignition temperature required for igniting the fuel has been reached. At this point lies however, the voltage drop that is your across the valve 20

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pending potential, below a value "V", v / which corresponds to the lowest voltage required for actuation of the valve 20 in the sense of opening the same is required. As a result, the valve 20 only allows fuel at a time to the burner 28 when the temperature of the igniter 10 is above the said value "T", which latter the corresponds to the minimum temperature required to ignite the fuel. The igniter 10 consequently acts both as an ignition element as well as a heat sensor device, thereby preventing unburned fuel from flowing out.

The circuit described above also ensures that the ignition system according to the invention behaves safely in the event of malfunctions or sets its puncture in a safe manner, since a failure of any of the electrical parts in the sense of a short circuit or an interruption of the circuit rapidly de-energizes the valve 20 and thus a rapid interruption of the fuel flow leading to the burner 28 results. If, on the other hand, the igniter 10 short-circuits, the potential across the valve 20 becomes zero. It should also be noted that the relay 12 can be constructed so that it is so sensitive to current that it is only actuated when a current of sufficient strength flows through this valve to thereby heat the

- 10 -

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Ensure igniter 10 to ignition temperature. The inventive Ignition system therefore has its own safety properties which cannot be achieved with the known ignition systems in that the relay 12 is in the above-mentioned Way current-sensitive and the valve 20 is voltage-sensitive in the aforementioned manner.

The operation of the training shown in Fig. 2, etc.

The guide shape is similar to that of the embodiment shown in FIG. When the main switch 16 is closed, current flows from the power source 18 through the ballast arm 34 of the hot wire ballast relay 30 and the igniter 10 and via the contacts 40 past the resistor 32. The current flowing through the ballast arm 34 causes self-heating and expanding the same such that the contacts 36 are closed. If heat is requested, the thermostatically operated switch 22 is closed so that parallel to the igniter 10 relays can flow 38 flow through the exciter winding "of the N & N ^K more. In the in Fig. 2 illustrated embodiment, 38 is the relay as a voltage-sensitive Element which, when actuated, closes the contacts 24 and thereby connects the valve 20 to the power source, so that the valve is excited

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insofar as the one in Pig. I embodiment shown, as the igniter lü with increasing temperature causes increasingly larger voltage drop across the winding of the relay 3ö, this voltage drop in each case is sufficient to cause actuation of the heater 38 only when the igniter temperature is higher than the minimum ignition temperature required for the fuel.

The embodiment shown in Fig. 2 of The invention also has a further safety function. When the relay 38 is energized, they are normally closed Normally closed contacts 40 open, whereby the thermistor 32 with the igniter 10 is connected in series. The thermistor 32 has a positive temperature coefficient and has a sufficiently high resistance value to reduce the voltage drop occurring across the relay winding 38 to one Reduce the value at which the relay 38 is no longer is held in its actuated state unless a burner flame is present. When a burner flame is present, it heats the igniter 10, which increases the temperature of the igniter and thus also its resistance Increase to a value at which, even with the increased resistance of the in this series connection Thermistor 32 on to energize relay 38 is sufficient

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If, however, the burner flame goes out, the resistance of igniter 10 becomes smaller and the potential across the winding of relay 38 is no longer sufficient to maintain the flow of fuel, which prevents unwanted leakage of unburned fuel is * It should be noted that due to the positive temperature coefficient characteristics ^of:? 3 herini.stors lor the igniter 10, a delay time is given, through which 10 f the igniter each fuel ignition temperature is reached and the burner flame © ignites before the flame monitoring property occurs »

The invention thus makes a simple-and yet reliably working electrical ignition system given which the igniter is used both as a fuel igniter and also acts as a fast-acting heat sensing element. In this way, the failure of the device g

the effective security properties of such a system are increased, while at the same time reducing the number of individual parts required. The electrical ignition system is applicable to a wide variety of facilities as a result of the training according to the invention, which a high Must have security and a small manufacturing cost.

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The electrical ignition system according to the invention is in its individual parts and in partial combinations in the frame The invention can be modified in many ways, i.e. the description relating to the drawing is only for Explanation of examples of the electrical according to the invention Ignition system and is not to be understood in a limiting sense.

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Claims (12)

jut Claims I 1. ^ Electrical ignition system for burners, characterized by an electrical power source (18), further by electrical ballast means (14 or 30) connected to this, further by a near the relevant burner attachable, both to the power source and to the ballast means connected electrical igniter (10) with a Λ positive resistance temperature coefficient, and through an electrically operated valve (20) connected to the sinner to form an excitation circuit for controlling the fuel flow leading to the burner in such a way that the valve in the absence of a electrical excitation is closed and opened when excited by a voltage of a certain minimum level, "said excitation circuit causing a voltage drop which is directly proportional to the respective temperature of the detonator and has one of said minimum voltage equal to fourth when the temperature of the detonator is above the the minimum ignition temperature required for the fuel. 2. ignition system according to claim 1, characterized in that that the said ballast means one on the one mentioned - 15 0 0 9 8 A 1/1 2 0 2 Excitation circuit having flowing current responsive arrangement and that a responsive to this ötromsensoranordnung Switch arrangement is provided which is connected in series with said valve (20) and the latter goes out of operation when the strength of the said current falls below a certain threshold value lies. 3. Ignition system according to claim 2, characterized in that said current sensor arrangement is a ballast relay excitation winding having. 4. Ignition system according to claim 2, characterized in that said current sensor arrangement is a relay excitation winding and said electrical ballast means are connected in series with this relay excitation winding Have ballast resistance (14). 5. Ignition system according to claim 2, characterized in that said current sensor arrangement · a hot wire ballast relay (30) and said switch arrangement comprises an electromagnetic relay (38), the latter is provided with an excitation winding and at least one set of working contacts (24), which with the aforementioned Valve (20) are connected in series and each at BATH ORIGINAL -Ib- 009841/1202 excitation of the electromagnetic relay must be closed. 6. Ignition system according to claim 5> characterized by an Elammenüberwachungseinriehtung (32 ₃ 40) connected to said electromagnetic relay (38) and to said exciter circuit for reducing the voltage drop occurring in the exciter circuit to a value which is below the value of said minimum voltage Excitation of the electrically 'operable valve (20) is when the burner flame is extinguished. 7. ignition system according to claim 6, characterized in that ~ ' that the flame monitoring device has a thermistor connected in series with said excitation circuit positive temperature coefficient and a set of normally closed contacts connected in parallel to this thermistor (40) has, which each upon excitation of said electromagnetic relay (38) are opened, and that i the electric igniter (10) is kept at a temperature above the minimum ignition temperature required for the fuel when the burner flame has not been extinguished . 8. Electric ignition system for burners, in particular according to one of claims 1 to 7 »characterized by a electrical power source (18), further .by one to this - 17 - 009841/1202 ■ Η - Electric igniter (10) connected to the power source, the voltage drop of which increases with temperature and at ignition temperature this igniter has a certain value, furthermore by an electrically operated valve (20) for control the fuel flow leading to the relevant burner, furthermore by control means (12, 14, 16 or 32, 30, 16) connected in series with the igniter, which have a constant Represent load and respond to the current flowing through the igniter, and finally by a switch arrangement (22), which is then connected in parallel to the igniter by the control means when the control means to the respond to said detonator current in such a way that the electrically actuatable valve is then connected to the power source and is excited by this when the voltage drop occurring across the detonator is greater than said specific one Voltage drop value. 9. ignition system according to claim 8, characterized in that said control means is a Ballaat relay excitation winding contain. 10, ignition system according to claim 8, characterized in that that said control means have a ballast resistor (14) and a relay excitation winding connected in series with this (at 12) included '(Pig. I). BAD ORJOSMAL - 18 - 009841/1202 11 »Ignition system according to claim S _3, characterized in that the said control means contain a hot wire ballast relay (30) ■ and that the said switch arrangement (22, 38) is an electromagnetic relay (38) with an excitation winding and at least one set of normally open contacts (24) have, which latter are connected in series with said electrically operated valve (20) and are each closed when the electromagnetic relay is energized (Fig. 2), ... 12. Ignition system according to claim 11, characterized by a flame monitoring device connected to said electromagnetic relay (38) and to the electric igniter (10) (32, 40) to reduce the voltage drop occurring at the electric igniter a value which is below the specified voltage drop value when the burner flame is extinguished. . ■. . '■ ■. 13, ignition system according to claim 12, characterized in that that said burner flame monitoring device a thermistor (32) connected in series with the electric igniter (10) and having a positive temperature coefficient and Has a set of normally closed contacts (40) connected in parallel with the thermistor, each of which when the said electromagnetic relay (38) are opened, . - 19 - BAD origins ID Q 9 8 A 1/1 2 0 2 "I" and that the temperature of the electric igniter when the burner flame is not extinguished is above that for the fuel minli.ial required ignition temperature is maintained. BATH ORIGINAL 00984 1/1 202