US3183958A - Gas igniter - Google Patents

Description

y 8, 1965 G. DAVIES 3,183,958

GAS IGNI'IER Filed July 11, 1961 (Trap/V575 United States Patent 3,183,958 GAS IGNITER George Davies, St. Brelade, Jersey, Channel Islands, assignor of one-half to Herbert Abraham Walford, St. Brelade, Jersey, Channel Islands Filed July 11, 1961, Ser. No. 123,199 16 Claims. (Cl. 158-115) This invention relates to gas igniters and one object is to provide means enabling a gas jet to be automatically and reliably ignited When the gas tap is turned on.

A further object is to provide an igniter which is safer than igniters currently used in that there is less likelihood of there being unlit gas issuing from a burner.

According to one aspect of the present invention a gas igniter includes a valve for controlling the supply of gas to a burner, an electrical ignition circuit for supplying current to a filament for igniting the gas at the burner by electro-catalytic action and means arranged to generate in response to the operation of a handle or manual switch for opening the valve, a pulse voltage in the ignition circuit.

With such an igniter the gas cannot be turned on without generating the ignition voltage and by proper design of the igniter it can be arranged that generation of the voltage is very reliable in effecting ignition of the gas. The use of a pulse as distinct from a continuous voltage can be adequate for effecting ignition of the gas but has the advantage that the filament is not energised for longer than is necessary and so is less likely to fail.

The burner could be a main gas burner but is preferably a burner for an initiating flame adjacent a main gas burner so that once the main jet has been lit the initiating flame can be allowed to go out so that the filament will not be subject to continuous heating. Then conveniently the supply of gas to both burners is controlled by operation of a single handle or manual switch.

In a preferred form of the invention the generator and the filament are related so that an electrical pulse of no greater than about one twentieth or even one hundredth joule energises the filament when the voltage is generated. If the filament is small enough this amount of energy is quite sufficient to raise the filament to the temperature necessary for catalytic ignition While yet causing little drain on the source of voltage and causing little damage to the filament. The filaments conventionally used in gas igniters require many times this amount of energy to be raised to the temperature for catalytic ignition because of their great relative weight. The current drawn by the filament may be rather less than half an ampere.

With such a small demand of the generator it could comprise a dry cell but preferably it comprises a magneto having an armature and a magnetic member between which relative movement is efiected by the operation of the handle or manual switch. Relative displacement could occur against a spring as the handle is operated to open the valve and then rapid return movement effected by the spring Will generate the ignition voltage pulse.

In a preferred form of the invention in which the burner is an initiating burner there may be means for allowing the pulse of gas to flow to the burner during a small overshoot movement of the handle or manual switch against a spring at the end of the valve opening movement. The handle can be held in the overshoot position until the main burner jet is lit and then can be released to stop the gas supply to the initiating burner.

Preferably a spring is arranged to return the gas Valve to the closed position if the handle or manual switch has not been operated sufficiently to generate the ignition voltage. This affords a protection against accidental knocking on of the handle.

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In the past it has been the custom to use a platinum coil in a portable gas lighter containing a very large battery and when the electrically heated filament has been inerted in the gas flowing from the burner catalytic ignition has occurred. It is, of course, possible for the tap to be turned on accidentally without igniting the gas and in any case it has been found necessary to manufacture very large filaments if they are to withstand thermal shock of being placed in the gas flame. The large filament has required a great deal of energy to heat it to the temperature for catalytic ignition and so a large battery has also been a necessity.

According to another aspect of the present invention a gas ignition head includes a conduit for the flow of gas and a filament for igniting the gas flowing from the conduit by electro-catalytic action in which the filament is very light compared with known filaments. If made wholly or principally of platinum a filament which is very light within the meaning of this specification would be less than about 10 millionths of an ounce in weight. The known platinum filaments for electro-catalytic ignition of gas have been of platinum wire of 0.0025" or 0.005 in diameter with a length uncoiled of from 1 to 2". Such a filament would have a weight of from 60-100 millionths of an ounce.

A preferred filament is of Wire of platinum with 10% of rhodium of 0.001 diameter, with a maximum length of about three-eighths of an inch. This filament will have a weight of no more than about 4 millionths of an ounce.

In order to protect the filament from the heat of the fiame and from chemical attack from the products of combustion it is preferably placed to one side of the direct line of gas flow through and from the conduit. Ignition can be effected by including means for directing a portion only of the gas flowing from the conduit to the filament and in a preferred form of head this means comprises a projection at the open end of the conduit oblique to the line of gas flow which ensures backward vortex currents of gas from the jet issuing from the conduit. Conveniently the filament is connected to the projection which thus constitutes one electrode for conducting current to the filament.

The conduit itself could then comprise one conductor and in a convenient construction the other conductor is a tube surrounding the conduit and spaced from it by an insulating spacer. A small housing may be arranged to afford mechanical protection for the filament and to define an ignition chamber in which a gas and air mixture can be ignited by the catalytic action. Thus a preferred ignition head is in four main pieces, the conduit, the outer conductor, the housing, and the filament.

The end of the conduit may comprise a main gas burner but is preferably adjacent a main gas burner, the jet from which is to be ignited by the flame from the end of the conduit. This means that once the main jet has been lit the gas supply to the conduit can be cut off and there is no further danger of heating the filament.

Damage to the filament can be rendered less likely by associating the head with a source of voltage capable of providing electrical pulses of energy of no more than about one-twentieth or even perhaps one fiftieth or even one hundredth of a joule. Satisfactory ignition has been effected in experiments with a current of 0.1 ampere from a voltage source of 1.25 volts for one-tenth of a second. This represents an energy in each pulse of oneeightieth of a joule. In most known igniters the current has been continued until ignition has been effected so that not only is there a much more rapid drain from the source but the filament is heated for much longer time. In general the source might be considered to be satisfactory if asting for less than half a it produces electrical pulses second.

There may also he means arranged to provide a pulse jet of gas from the conduit at the moment of the current pulses. This pulse can be arranged to terminate not long after the electrical pulses so that the ignited et w lt be extinguished and the lament will be no longer sub ected to heat. By this time, of course, a main burner can have been lit. 1

Conveniently the electrical pulse 1s produced througn the act of turning on a gas tap controlling the supply to a main burner so that the gas cannot be turned on without causing the ignition voltage to be generated.

The source of voltage could comprise an electric cell which would not require replacement at all frequently because of the very small demand in each li ht ng operation but prefer-ably the source of voltage comprise a mag neto, the energy for moving which is derived trorn the turning on of the gas tap.

According to an optional feature of the invention tne lea-d has two filaments as a precaution against failure of one of them. They could be electrically in parallel.

The invention may be carried into practice in various ways and a preferred embodiment together with certam modifications will now be described by way of example with reference to the accompanying drawings in which:

FIGURE 1 is a section of a preferred head for inmating lighting of a gas jet;

FIGURE 2 is a section of a gas tap incorporating a magneto for generating the voltage for electro-catalyt c ignition of a starting jet of gas at the head shown in FIGURE 1; 1

FIGURE 3 is a plan view of the tap of FIGURE 2 with a part removed; and

FIGURE 4 is a diagram corresponding to FIGURE 3 showing the arrangement of the parts in the tap of FIG- URES 2 and 3.

The ignition initiating head shown in FIGURE comprises coaxial copper tubes 11 and 12 with insulation 13 between them and a platinum alloy filament 14 welded to tongues 15 and 16 formed at the ends of the tubes 11 and 1.2 respectively. Conveniently the welding is effected using an intermediate piece of silver.

The inner copper tube 12 serves as a bypass passage for a temporary gas supply for initiating ignition of gas at a main burner and the two tubes constitute electrical conductors of current to the filament 14. The end of the tube 12 constitutes an initiating burner.

It is arranged that the current flows for about one tenth of a second at the same time as a puff of gas flows from the end of the inner tube 12. It will be seen that the filament is to one side of the jet of gas and this ensures that when the gas has been ignited the filament will not be in the path of the initiating flame and so will not be liable to thermal damage. In any case it is arranged, as will be described below, that the gas supply through the inner tube 12 is cut ofi when the flame has lasted for the brief period necessary to ignite the gas jet at the main burner which is in the neighbourhood of the initiating flame.

A metal shield or housing 17 surrounds the ends of the tubes 11 and 12 and gives mechanical protection to the filament and also defines a small filament chamber. The internal diameter of the chamber is 0.275" and it is about 0.3 long. The arrangement of the tongue or projection 1'6 shown, bending away from the axis of the inner tube 12 at an angle of about 40 towards the shield 17 has been found to cause just sufiicient turbulent flow of gas around itself to provide a suitable gas and air mixture in the filament chamber which will be ignited by electrocatalytic ignition when the small pulse of current flows. Once the mixture in the filament chamber has been ignited it ignites the initiating jet which in turn ignites the adjacent main jet and then is extinguished when the sup ly of gas is cut ed.

It will be noticed that the filament is protected mechanically and is kept away from the frame as much as possible and from the bi-products of combustion. This arrangement enables a very fine short filament to be used and this can be raised to the necessary temperature for ignition of the gas with a very light current for a very short time.

The head described is suitable for igniting coal gas.

For igniting butane or another gas which is heavier than air the ignition head may require modification. In one form, the gas supply conduit is horizontal and the gas leaving it will have a downward component to its horizontal motion due to the weight of the gas, and the filament is positioned in the path of this unignited gas. When the filament is energised and ignition takes place the ignited gas becomes less dense than air and rises so that the flame is immediately removed from the filament which is not liable to damage.

In another possible form of ignition head for butane, the gas conduit has a small initiating jet branching from the main supply to the end of the conduit and leading to the interior of a perforated housing comprising a draft shield and containing the filament. A gas air mixture is established in the housing and is ignited when the filament is energised and then the main jet issuing from the end of the conduit is ignited by flash from the initiating flame.

In either form, the flame at the end of the conduit could be a main flame or an initiating flame for igniting a main jet of gas.

It becomes at once apparent that because such a small mass has to be heated for such a short time to the temperature necessary for catalytic ignition, the large batteries normally used with gas lighters can become a thing of the past and a small mercury or other cell could be used. However, it is preferable to do without a battery at all and accordingly means are provided for generating the necessary electric power by use of a magneto using energy derived from the turning on of the gas tap. It is only because such a small current for such a small time can be used that a magneto system is possible.

The tap and magneto are shown in FIGURES 2, 3 and 4. When the tap 21 is turned an inlet 22 is put into communication with a main outlet 23 connected to a main burner 20 by way of passages 24 and 25 in cores 26 of the magneto, and co-operating ports in a stationary plate 27 secured to the free ends of the cores 26 and a rotary plate 28 secured to the tap 21.

The rotary plate has in its under surface a part annular groove 29 subtending an angle of about at the centre of rotation and it is at the same radius as the ports at the ends of the passages 24 and 25 in the cores. After about a half-turn of the tap 21 from the closed position, the leading end of the groove 29 starts to overlap the outlet port 25 and the main gas supply to the outlet 23 commences. During a short overshoot movement, at the conclusion of the opening movement of the tap 21 the leading end of the groove 29 comes into communication with a groove 31 formed in the stationary plate 27. The initiating head of FIGURE 1 is connected to the tap by the tubes 11 and 12 which are of appropriate length, and the inner tube is in communication with a passage 32 in the magneto body connected to the groove 31. Thus gas is supplied to the tube 12 from the inlet 22 just at the completion of the rotary opening movement of the tap.

While the tap is being opened the rotor 34 of the magneto is being turned and two permanent magnet pole pieces 35 move past the cores 26 on the stator. The cores 26 are joined at their ends remote from the tap 21 by a soft iron yoke 36 and this carries an electrical coil 37 whose ends are connected respectively to the ends of the inner and outer tubes 11 and 12 of the initiating head, which are secured in a bore in a boss 38 on the magneto body containing the passage 32 for the initiating gas jet. Of course, during the slow manual opening movement of the tap the voltage generated in the coil 37 is insufficient to produce a significant current in the filament 14.

As the tap 21 is opened the movement of the rotor 34 is effected through a catch 41 pivotally mounted on the rotary plate 28 in engagement with a shoulder 42 formed on a disc 43 secured to the end of the rotor shaft 44 where it protrudes through the plates 27 and 28. A coil spring 45 has its ends secured respectively to the disc 43 and the stationary plate 27 and so is wound up as the rotor moves with the tap 21. A small spring 46 between the pivot point of the catch 41 and the free arm 47 of the catch ensures that the catch is kept in engagement with the shoulder 42.

However, during the overshoot movement, just as the pilot gas starts to flow into the groove 31 and the passage 32, the free end 47 of the catch 41 comes into contact with a pillar 48 secured to the stationary plate 27 and is moved out of engagement with the shoulder 42. In consequence the coil spring 45 is released from the held tap and moves the rotor of the magneto rapidly back to its initial position. During the return movement the poles 35 move sufiiciently quickly in relation to the magneto core to generate a voltage which can cause a current of 0.1 ampere to fiow for one-tenth of a second through the filament 14. The voltage is, in fact, 1.25 volts.

This short current pulse occurs at the same time as the puff of initiating gas and effects ignition of the jet which in turn ignites the main jet as described above.

It will be apparent that if the tap 21 is released before it has been fully turned on to cause ignition of the initiating jet it will be returned with the rotor 34 and disc 43 by the spring 45 to the closed position in which the main supply is turned ofif. The actual overshoot which effects the flow of gas to the initiating head and the generation of the ignition voltage is against a bent leaf spring 51 connected at one end to a platform carrying the pillar 48 and capable of engaging at the other end the pivot pillar of the catch 41. The tap 21 will be held in the overshoot position against this spring until ignition of the gas at the main burner has been effected and then the hold on the tap is released and the initiating gas supply will cease with the main jet alight.

It is not until the ignition current is generated during the overshoot movement that the catch 41 is released from the shoulder 42 on the disc 43 and this means that unless the ignition current flows to ignite the gas jet the coil spring 45 will return the tap 21 to the off position when it is released. The arrangement is therefore quite safe in that the gas supply cannot be left on unlit.

It is possible that the initiating jet will be at some distance from the tap and magneto, and then the gas puff at the moment of overshoot would take so long to reach the head that the energisation of the filament would be over before the gas arrived. Accordingly a subsidiary gas supply can be arranged to commence as soon as the tap begins to be turned in order to clear air from the tube 12 and till it with gas.

For this purpose the inlet and outlet 24 and 25 of the main gas supply are connected through subsidiary grooves 53 in the stationary plate 27 and radial bores 54 by Way of a cock formed in the rotor shaft 44. The cock 44 is so arranged that once the tap begins to be opened, the gas main inlet 24 is connected to the initiating gas passage 32, and during the opening movement of the tap the gas can flow to the initiating jet clearing out the air. Then when at the moment of overshoot the additional puff of gas is passed through the passage 32 gas will be present at the jet for ignition at the moment of voltage generation. This arrangement is adequate even if the initiating jet is at a distance of several feet from the tap.

It may be desirable, for example for application to a gas cooker, to have a single magneto in conjunction with a number of taps and it can be arranged that whichever tap is opened the magneto will be operated and the generated voltage will be connected to the appropriate filament.

In the case of a portable gas appliance connected by way of a flexible gas supply tube to a tap secured to the Wall, the flexible pipe would include a separate gas channel for the initiating jet and electrical conducting wires for the filament. The magneto would be at the tap on the Wall and the subsidary gas supply through the separate channel would ensure that there was no air in this channel when the overshoot operated to produce the initiating puff of gas. I

In a modification of the invention as applied to an appliance having a pilot jet which is alight as long as the tap is on for relighting the gas at one of one or main burners by fiash back if the flame were accidentally extinguished, the overshoot feature is not necessary. This is because the initiating jet can be placed so close (say nearer than half an inch) to the pilot jet of the appliance, that ignition of the subsidiary supply, which ceases when the magneto rotor is released, can be relied upon to ignite the pilot jet. There is no need to hold the tap in the overshot position until ignition of a jet which may be some inches from the initiating jet.

in tests, a filament of the kind described has caused satisfactory ignition with only one failure in 50,000 attempts, without noticeable deterioration of the filament.

What I claim as my invention and desired to secure by Letters Patent is:

l. A gas igniter including a valve for controlling the supply of gas, a magneto for supplying a pulse voltage, a rotor in the magneto, a burner arranged to be supplied with the gas from the valve, a filament mounted adjacent the burner and connected to receive the pulse voltage for igniting gas at the burner, and a spring device connected to said valve and to said magneto rotor urging said valve to the closed position, and means operable in response to full opening of the valve for releasing said spring from connection to the valve and for permitting the spring to return and to drive said rotor, thereby supplying said pulse voltage.

2. A gas ignition head as claimed in claim 1 in which the filament extends parallel with the conduit.

3. A gas igniter as claimed in claim 1 in which the filament has a mass of less than ten-millionths of an ounce.

4. A gas ignition head as claimed in claim 1 in which the magneto is arranged to produce pulses lasting for less than /2 second.

5. A gas igniter as claimed in claim 1 in which the burner is for an initiating flame, and including a main gas burner adjacent the initiating burner and said valve including means to control the supply of gas both to the main burner and the initiating burner.

6. A gas igniter as claimed in claim 5 including means for cutting-off the gas supply to the initiating burner after the voltage has been generated.

7. A gas igniter as claimed in claim 5 including means for allowing a pulse of gas to flow to the initiating burner by movement of the valve against a spring through a small over-shoot movement at the end of the valve opening movement.

8. A gas igniter as claimed in claim 1 in which said filament is composed of 10 percent rhodium and percent platinum, is 0.001 inch in diameter, and has a maximum length of about of an inch and the current drawn by the filament from the magneto is less than one half ampere.

9. A gas ignition head including a conduit having an end for introducing a flow of gas, a filament for igniting gas flowing from the conduit, comprising a few spaced turns of wire, a part at least of the filament being positioned behind the end of the conduit in the direction of gas flow, means holding the filament adjacent the end of the conduit, a housing defining a restricted space around the end of the conduit and containing the filament and a tongue projecting obliquely from the end of the conduit into the housing for causing a portion only of the gas from the conduit to flow into the housing.

10. A gas ignition head as claimed in claim 9 in which the filament is principally of platinum.

11. A gas ignition head as claimed in claim 10 in which the filament is of an alloy of platinum with 10% of rhodium.

12. A gas ignition head as claimed in claim 11 in which the filament is made of Wire of a diameter of onethousandth of an inch.

13. A gas ignition head as claimed in claim 12 in which the filament is made from a length of wire threeeighths of an inch long.

14. A gas ignition head as claimed in claim 13 in which the filament is placed to one side of the conduit.

15. A gas ignition head as claimed in claim 9 in which the filament is connected to the tongue which thus con- 15 stitutes one electrode for conducting current to the filament.

16. A gas ignition head as claimed in claim 9 in a plurality of pieces, including an outer conductor, an insulating spacer and means holding the housing on the outer 20 conductor.

References Cited by the Examiner UNITED STATES PATENTS 613,990 11/98 Guyenot. 1,118,943 12/14 Lyon. 1,600,857 9/26 Woods. 2,475,534 7/49 Wales 219-3231 2,480,230 8/49 Elster 158-115 2,487,752 11/49 Cohn 6719 X 2,513,051 6/50 Ray 158-28X 2,667,605 1/54 Massier 158-415 2,865,441 12/58 Coupe 15828 2,896,704 7/59 Aleweld 158-115 FOREIGN PATENTS 7 70,485 3/57 Great Britain.

JAMES W. WESTHAVER, Primary Examiner.

FREDERICK L. MATTESON, In, ROBERT A.

OLEARY, Examiners.

Claims (1)

1. 9. A GAS IGNITION HEAD INCLUDING A CONDUIT HAVING AN END FOR INTRODUCING A FLOW OF GAS, A FILAMENT FOR IGNITING GAS FLOWING FROM THE CONDUIT, COMPRISING A FEW SPACED TURNS OF WIRE, A PART AT LEAST OF THE FILAMENT BEING POSITIONED BEHIND THE END OF THE CONDUIT IN THE DIRECTION OF GAS FLOW, MEANS HOLDING THE FILAMENT ADJACENT THE END OF THE CONDUIT, A HOUSING DEFINING A RESTRICTED SPACE AROUND THE END OF THE CONDUIT AND CONTAINING THE FILAMENT AND A TONGUE PROJECTING OBLIQUELY FROM THE END OF THE CONDUIT INTO THE HOUSING FOR CAUSING A PORTION ONLY OF THE GAS FROM THE CONDUIT TO FLOW INTO THE HOUSING.

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