US3501253A

US3501253A - Automatic ignition systems

Info

Publication number: US3501253A
Application number: US699546A
Authority: US
Inventors: Kenneth R Wade
Original assignee: United Gas Industries Ltd
Current assignee: United Gas Industries Ltd
Priority date: 1967-02-09
Filing date: 1968-01-22
Publication date: 1970-03-17
Anticipated expiration: 1987-03-17
Also published as: GB1171831A; BE710540A; FR1568107A; NL6801754A; DE1601324A1

Description

K. R. WADE AUTOMATIC IGNITION SYSTEMS- March 17, 1970 Filed Jan. 22, 1968 2 Sheets-Sheet 1 In venlor ZWA ffi/ Fae/Mm 175175 B a4 R/Q% A ttor w my;

' March 17, 1970 K. R. WADE 3,501, 3

AUTOMATIC IGNITION SYSTEMS Filed Jan. 22, 1968 z Sheets-Sheet 2 3A 5 20 -L,J 45

Attorneys United States Patent Office 3,501,253 Patented Mar. 17, 1970 3,501,253 AUTOMATIC IGNITION SYSTEMS Kenneth R. Wade, Liverpool, England, assignor to United Gas Industries Limited, London, England, a British company Filed Jan. 22, 1968, Ser. No. 699,546 Claims priority, application Great Britain, Feb. 9, 1967,

6,313/67 Int. Cl. F2311 9/08 US. Cl. 431-43 1 Claim ABSTRACT OF THE DISCLOSURE A gas appliance ignition apparatus wherein a main burner is ignited by a pilot flame, which is lit by an electrical igniter coil. When the pilot flame lights a flame switch is moved from the cold to the hot position which disconnects the igniter coil and connects the solenoid to open the main burner valve. A safety switch which is closed when potential exists across the pilot valve solenoid is then in circuit with the main and pilot valve solenoids. Upon electrical failure the safety switch opens, closes both valves and stops the pilot valve opening until the flame switch has moved to cold.

The present invention relates to automatic ignition systems which may be used, for example, in gas fired boilers, space heaters or water heaters.

It is conventional, in gas fired appliances, such as boilers, space heaters or water heaters, to ignite the main burner of the appliance, by means of a constantly burning pilot flame. It will be apparent that this pilot flame, which may use a gas consumption of the order of 700 B.t.u.s per hour, involves a considerable wastage of gas resources and also is an expense to the user, besides causing corrosive condensation in many instances. In balanced flue appliances the pilot is frequently extinguished by strong winds.

As a safety precaution, and to save wastage of considerable quantities of gas, the main burner of the ap pliance is supplied with gas through a main valve, operation of which is controlled by a flame sensitive device (not uncommonly a switch). This flame sensitive device may take a number of different forms, such as a simple thermostat or a mercury capsule bi-metal or thermo couple and is operated by the heat of-the pilot flame. Thus is the pilot flame is burning, the device becomes hot and this allows the main valve for supplying gas to the burner to be opened or opens it directly. If, on the other hand the pilot flame goes out, or is operating at too low a level, the flame sensitive device prevents gas being supplied to the main burner.

Attempts have been made to light the pilot flame, or the main burner flame, by means of an electrical igniter coil wherever the appliance is to be used, this thus reducing the use of the gas necessary for supply ing the pilot flame.

It is an object of the present invention to provide an improved automatic electrically operated ignition system.

According to the present invention there is provided an ignition apparatus for a gas appliance, such apparatus comprising a solenoid operated main valve for controlling the flow of gas to a main burner, a pilot burner, a solenoid operated pilot valve for controlling the flow of gas to said pilot burner, an electrically operated igniter for lighting the pilot "burner flame, a flame switch adjacent the pilot burner sensitive to the presence of a flame from said pilot burner and actuable between a hot position when a flame is present and a cold position when no flame is present, the pilot valve solenoid coil being connected to an electrical input via the flame switch, when the latter is in the cold position, the main valve solenoid coil being connected to the electrical input via a safety switch and the flame switch, when the latter is in the hot position, means being provided to close the safety switch only when there is an electrical potential across the pilot solenoid coil, the latter being connected to the electrical input via the safety switch when the flame switch is in the hot position, so as to maintain the safety switch closed.

Should the power supply fail for any reason, then the safety switch will open, and both the pilot and main valves will close, the pilot valve being incapable of being re-energised until the flame switch has moved to the col position. If the pilot valve were capable of operating before the flame switch had reached the cold position, and if there were an instantaneous breaking and remaking of the power supply circuit, the solenoid valve would open, and gas would be injected into the combustion space, for a short time until the flame switch had reached the cold position. If thiswere to happen, there would be a tendency for explosive conditions to arise in the combustion space, as soon as the igniter coil were energised by the closing of the flame switch.

The safety switch may be in the form of a magnetic reed switch positioned within the magnetic field of the coil of the solenoid of the pilot valve or alternatively may be a simple relay or electronic switch in series or parallel with the pilot valve solenoid or may be an contact operated by the movement of the solenoid valve armature.

In a preferred construction of the present invention, a neon is placed to bridge the main valve solenoid, to give an indication of operation of this solenoid. A thermostat or time switch may also be placed directly in series with the main valve. A second neon may be connected in parallel with the igniter coil to give indication of failure of the coil, since these coils have limited life.

The pilot valve is preferably placed between the gas supply and the main valve, the branch leading "to the pilot burner itself being positioned between the pilot and main valves. Thus, gas cannot be supplied to the main valve and burner, unless the pilot valve is itself open.

In order that the invention may more readily be understood, the following description is given, merely by way of example, reference being made to the accompanying drawings in which:

FIGURE 1 is a circuit diagram of one embodiment of control system according to the invention.

FIGURE 2 is a schematic view of the gas supply arrangement for use with the circuit of FIGURE 1;

FIGURE 3 is a schematic cross-section through one embodiment of pilot valve according to the invention illustrating the safety switch operated by the pilot valve solenoid coil armature;

FIGURE 4 is a fragmentary view of a safety switch in the form of a reed switch in the field of the pilot valve solenoid coil;

FIGURE 5 is a portion of the circuit diagram of FIG- URE 1, illustrating the safety switch constructed as an electronic switch; and,

FIGURE 6 is a view similar to FIGURE 5 illustrating the safety switch in the form of a simple relay.

Referring first to FIGURE 1 it will be seen that the system includes a transformer 10 having a primary Winding 11 and two

secondary windings

12 and 13. The first secondary winding 12 is connected to a bridge rectifier 14, to one side X of the output of which is connected a solenoid coil 15, controlling opening of a solenoid operated valve 16 illustrated in FIGURE 2.

The second secondary Winding 13 of the transformer 10 is connected to the other side Y of the rectifier and also to an igniter coil 17. Between the igniter coil 17 and the pilot valve solenoid coil 15, is a flame switch 18 which is movable between a cold" and a hot position. In the cold position, the circuit to the pilot valve solenoid coil 15 is completed via the igniter coil 17 and the second secondary of the transformer 13.

Between the said otherside Y of the rectifier 14 and a point between the flame switch 18 and the pilot valve solenoid coil 15, is a line 19 including a safety switch 20, which is closed when there is an electrical potential across the pilot valve solenoid coil 15.

A main valve solenoid coil 21 is connected between the hot position terminal of flame switch 18 and the one side X of the output of the rectifier 14. Bridging the main valve solenoid coil 21 is a resistance 22 and a neon 23. In series with the main valve solenoid coil 21 is a thermostat or time switch contact 24.

Referring to FIGURE 2 there is seen a gas supply line 25 having therein a governor 26 and the solenoid operated pilot valve 16. Downstream of the pilot valve, the line 25 divides to be connected first to the main valve 27, which is controlled by main valve solenoid coil 21, and secondly to the pilot burner 28. A flame sensitive device, such as a mercury capsule or thermostat is positioned at 29, i.e. immediately in the path of the flame emanating from pilot burner 28. If a flame is playing on the device 29, the fiame switch 18 of FIGURE 1 will move to the hot position. Connected to the main valve 27 is the main burner 30 which is positioned to be ignited by the pilot flame from burner 28.

In operation of the above described system, one will assume that the switch 24 is closed. If desired, the switch may be omitted and the thermostat and/or time switch arranged in the AC. mains supply to the system.

When the mains supply is connected, the transformer is energised and a DC potential will appear across the output terminals X, Y of the rectifier 14. With the flame switch 18 in the cold position, current will flow via pilot valve solenoid coil 15, the flame switch 18, the igniter coil 17, and the second secondary 13 of the transformer 10, to the terminal Y of the rectifier. This current flowing through the coil 15 will cause safety switch to close, and an AC. current will be induced by the second secondary 13 to flow through line 19, flame switch 18 and the igniter coil 17. By this time the. pilot valve would have been opened by the coil 15 and gas will flow to the pilot burner 28. The AC. current through igniter coil 17 will cause the latter to glow and will ignite the pilot flame.

When the flame switch has been heated to a suflicient temperature, it will snap over to the hot position and current will be allowed to flow through coil 21 and through resistance 22 and neon 23, which will glow to indicate that the main valve solenoid is opearting. With the main valve solenoid energised, main valve 27 opens, and gas flows to main burner 30 to be lit by the pilot flame. Should the thermostat or time switch 24 indicate that the main burner is no longer required, it -will open and main valve 27 will be closed to cut off supply of gas to the main burner 30.

If there is a power failure, or if for any other reason,

current is not supplied to the transformer 10, the rectifier output will be cut off, and current will cease to flow through coil 15. As soon as this happens, the pilot valve 16 will close and safety switch 20 will open. At this juncture and for a small time thereafter flame switch 18 will remain in the hot position. When the sensing device 29 has cooled off sufliciently, flame switch 18 will close and will enable the circuit to coil 15 to be completed, when power is restored. However, it will not be possible to re-energise either the pilot valve or the main valve solenoids until such time as the flame switch has reached the cold position.

It will be appreciated that as soon as the main valve coil 21 is de-energized, either by the switch 20 or the switch 24 opening, the neon 23 will cease to glow to indicate that no current is being supplied to the valve.

In place of the igniter coil 17, an electrical spark igniter may be used. Various forms of safety switch arrangements are illustrated in FIGURES 3 to 6.

Referring now to FIGURE 3, the pilot valve 16 is illustrated as comprising an inlet union 40 and an outlet union 41, a poppet valve 42 engaging in the inlet union to close the valve. The poppet valve 42 has, as its stem 43, the armature of the solenoid coil 15 of the pilot valve. An extension 43A of the armature 43 is formed of insulating material and carries the movable leaf 48 of the switch 20. When current is applied to the

leads

44 and 45 of the coil 15, the stem 43 is raised thus opening the valve 42 and raising the extension 43A. This presses the contact 46 carried by leaf 48 against the other contact 46 carried by the fixed portion 47 of the switch 20. Thus, if potential appears across the

leads

44, 45 of the coil 15, the switch 20 is closed.

In the second form shown in FIGURE 4, the magnetic field created by the coil 15 causes the

contacts

22 and 53 carried by the arms 49 and 50 respectively of the' reed switch to close. This reed switch constitutes the safety switch 20 illustrated in FIGURE 1.

In FIGURE 5, the safety switch 20 is in the form of an electronic switch, e.g. a thyristor 54, the trigger contact of which is connected across the pilot valve solenoid coil 15. When potential exists across the coil 15, the thyristor becomes conductive i.e. in effect it closes the switch 20.

Finally in FIGURE 6 is illustrated an arrangement in which a simple relay 55 is connected in a series with the coil 15, current flowing through the relay 55 closing the switch 20. In an alternative construction a voltage sensitive relay 55A is connected in parallel with the pilot so enoid coil 15.

I claim:

1. An ignition apparatus for a gas appliance, said ignition apparatus comprising, in combination:

(a) a main burner;

(b) a solenoid operated main valve controlling flow of gas to said main burner;

(c) a first solenoid coil effective to operate said main valve between an open and a closed position;

(d) a pilot burner located adjacent said main burner;

(e) a solenoid operated pilot valve controlling flow of gas to said pilot burner;

(f) a second solenoid coil effective to operate said pilot valve between an open and a closed position;

(g) an electrically operated igniter associated with said pilot burner;

(h) electrical input means;

(i) a flame switch adjacent said pilot burner sensitive to the presence of a flame from said pilot burner, effective to be actuated between a cold position when no pilot flame is present and a hot position when a pilot flame is present;

(j) a safety switch comprising a single relay switch in series with said second solenoid coil;

(k) means connecting said second solenoid coil to 5 6 said electrical input means via said flame switch, References Cited When thfi latter iS in the Cold position; (1) means connecting said first solenoid coil to said electrical input means via said safety switch and 2100308 5/1940 Beggs said flame switch, when the latter is in the hot 110- 5 2,261,092 10/1941 petefson 431' 46 Sition; 2,269,157 1/1942 Levine 431-46 (m) means closing said safety switch only when there 2,730,169 1/1956 DeubFl 43145 is an electrical potential across said second sole- 2,800,176 7/ 1957 Mormon 431-45 noid; and

(11) means connecting said second solenoid coil to 1 said electrical input means via said safety switch, when said flame switch is in said hot position, eflfcc-' tive to return said safety switch closed.

0 JOHN J. CAMBY, Primary Examiner