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Title:
LIGHTER WITH A CAPACITOR DISCHARGE IGNITION SYSTEM AND MEANS FOR PREVENTING AUTOMATIC RECHARGING OF SAID CAPACITOR
United States Patent 3781163
Abstract:
A smoker's lighter having a capacitor discharge electric ignition in which the recharging of the capacitor is prevented by means of a two transistor semiconductor switch. Reactuation of a manual ignition switch is necessary before the capacitor can be recharged. Automatic discharge of the capacitor is achieved by use of a trigger diode controlling a thyristor.


Inventors:
OVENS C
Application Number:
05/271670
Publication Date:
12/25/1973
Filing Date:
07/14/1972
Assignee:
Dunhill Lighters Limited (London, EN)
Primary Class:
Other Classes:
315/209T, 315/209CD, 361/256, 431/132, 431/255
International Classes:
F23Q2/28; (IPC1-7): F23Q3/01
Field of Search:
317/79,81,93,95,96,97 292
View Patent Images:
US Patent References:
3612736SYSTEM FOR ACTUATING CIGARETTE LIGHTERSOctober 1971Steuerhagel
3442598GAS LIGHTER WITH ELECTRIC SPARK IGNITIONMay 1969Halm
3399948Solid state ignition circuit for fuel brunersSeptember 1968Myers et al.
3338288Electronic spark ignitorAugust 1967Walker
3323019N/AMay 1967Takahashi
3311789Gas cigarette lighter with spark ignitionMarch 1967Remy
2219186Magnetic latchOctober 1940Hornfeck
Primary Examiner:
Mayewsky, Volodymyr Y.
Claims:
1. A smoker's lighter comprising:

2. A lighter as claimed in claim 1 wherein the semiconductor switch means comprises a first transistor of one conductivity type and a second transistor of the opposite conductivity type, the base of the first transistor being connected to the collector of the second transistor, and the base of the first transistor.

3. A smoker's lighter comprising a housing mounting and enclosing:

4. A lighter as claimed in claim 3 wherein the voltage step-up means comprises a transistorised multivibrator oscillator connected to a step-up transformer, the transformer having a feedback winding to provide feedback for the oscillator.

5. A lighter as claimed in claim 3 wherein means are provided to actuate the discharge means when a predetermined voltage across the capacitor is reached.

6. A smoker's lighter comprising a housing mounting and enclosing:

7. A lighter as claimed in claim 3 whrein the semiconductor switch means is connected to the capacitor by pulse conducting means so that discharge of the capacitor actuates the semiconductor switch means.

8. A lighter as claimed in claim 7 wherein the pulse conducting means is a capacitor.

Description:
This invention relates to electric lighters of the type having an internal fuel reservoir and primarily intended for lighting such items as cigars, cigarettes and pipes. Such a lighter will be termed herein a "smoker's lighter".

A known type of smoker's lighter includes an electric cell, a switch to control spark production and a capacitor to store energy for the production of the spark at ignition electrodes. In the intersts of saving the life of the electric cell it is undesirable that the capacitor should be kept charged during periods of non-use, for the circuit will always take some "leakage" current particularly if a high quality (and hence relatively expensive) capacitor is not used. Thus the manually operable switch has been designed to have a normal "off∞ position and on actuation the capacitor is first charged to its working voltage and then discharged to produce the spark. Such a switch can have two "on" positions, a first position to charge the capacitor and a second position to discharge the capacitor. This arrangment has, however, the disadvantage that special design is needed to ensure that the capacitor is adequately charged in the first position. On the other hand if the switch merely has one "on" position (charge followed by discharge) the capacitor will begin to charge again after its discharge if the switch remains actuated. This arrangement can, of course, be wasteful of the life of a cell.

The present invention provides a smoker's lighter having an electric ignition system for operation from one or more electric cells and including a manually operable switch, and a capacitor to store energy for the production of a fuel-igniting spark, the production of a spark being in response to actuation of the manually operable switch, wherein semiconductor switch means are provided operative to prevent recharging of the capacitor for further spark production until a further actuation of the manually operable switch is performed.

Preferably means are provided to change the level of voltage supplied during use by the cell or cells to a substantially higher level for charging the capacitor.

The means to change the level of voltage can comprise inverter means (that is, a direct voltage to alternating voltage converter) connected to rectifier means.

The inverter means can comprise a multivibrator oscillator connected to a step-up transformer. Feedback for the oscillator can be obtained from a feedback winding on the transformer and the output of the transformer can be connected to a full-wave rectifier. A thyristor can be provided to discharge the capacitor into a pulse transformer under control of a trigger diode responsive to the voltage across the capacitor.

In a smoker's pocket-lighter embodying the invention it is preferred that the inverter, capacitor and a pulse transformer shall be arranged in tandem fashion along the length of the lighter. It is also preferred that the lighter shall include a fuel tank for butane gas fuel moulded to correspond to the contours of adjacent components.

The invention can equally well be embodied in a table lighter, in which case the greater available space compared with a pocket ligher allows the use of larger electric cells and greater fuel capacity. A more squat arrangement of internal parts than in a pocket lighter can prove desirable in a table lighter.

It is to be understood that the term "smoker's lighter" is intended to embrace an assembly of lighter parts for insertion in an outer casing or sheath.

By way of example only, a preferred embodiment of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 shows an isometric view of a pocket smoker's lighter embodying the invention,

FIG. 2 is a part sectional view illustrating the internal arrangement of parts of the lighter with certain parts omitted for clarity,

FIG. 3 shows an isometric view of potted electronic circuitry employed in the lighter and cells used for powering the lighter,

FIGS. 4a, b and c show the arrangement of components in the potted electronic circuitry,

FIG. 5 is a diagrammatic isometric view of a lid catch for the lighter,

FIG. 6 is an "exploded" view of some of the component parts of the lid catch,

FIG. 7 corresponds generally to FIG. 2 but shows different details of construction,

FIGS. 8 and 9 show to an enlarged scale details of construction of a base plate used in the lighter, FIG. 8 being a sectional view and FIG. 9 a plan view,

FIG. 10 illustrates the fuel tank and burner assembly of the lighter,

FIG. 11 shows a side elevation of the fuel tank,

FIG. 12 shows a view from beneath of the fuel tank,

FIG. 13 shows a plan view of the fuel tank,

FIG. 14 shows an "exploded" isometric view of the top of the fuel tank and part of a switch mechanism,

FIG. 15 shows an "exploded" isometric view of flame regulation components,

FIG. 16 shows a partly sectional view of flame regulation components,

FIG. 17 shows an insulator used in the lighter and

FIG. 18 shows the electronic circuit of the lighter.

It should be noted that the Figures are not all to the same scale and that in the interests of clarity parts may be omitted or simplified.

Referring to FIG. 1, the butane gas smoker's lighter there shown comprises a hollow rectangular casing 1 having a sprung lid 2 and base plate 3, a slide switch 4, a flame adjustment wheel 5, a burner assembly 6 (only a part of which can be seen in FIG. 1) and an ignition electrode 7. When the ligher is not in use the sprung lid 2 is retained closed by a magnet 8. As will be appreciated the external parts of the lighter are desirably given a high quality ornamental finish to appeal to the eye. In particular the casing 1 and base plate 3 can be made of, or plated with, a precious metal. The lid 2 is required to be in part at least of a ferromagnetic material so as to be attracted by the magnet 8 but can of course be plated with a precious metal.

Assuming the lid 2 to be closed, the lighter is operated by depressing the slide switch 4 towards the base of the lighter whereupon the lid 2 flies open, an electrical contact is made within the lighter and a valve in the burner assembly 6 opens to allow gas to exit for ignition. The slide switch is maintained in a depressed condition and after a very short period of time (scarcely perceptible to the user) a spark is generated at the ignition electrode 7 and the gas ignites. The flow of gas is pre-set to some convenient level by means of the flow adjustment wheel 5. Pipe smokers will generally use a higher flow rate setting than cigaretter smokers. After use of the lighter the sprung lid 2 is manually closed and the magnet 8 retains the lid closed until the next occasion on which the slide switch 4 is operated. Closure of the lid 2 stops the flow of gas through the burner assembly 6.

Now that a general description of the lighter has been given its component parts will be described in detail. For this purpose the description can be dealt with under seveal separate headings, viz. general internal layout; lid catch; fuel tank; bas-plate; gas control mechanism; electronic circuitry and mechanical aspects of the electronic circuitry.

GENERAL INTERNAL LAYOUT

FIG. 2 show most the major internal component parts of the lighter although certain parts are omitted for clarity of illustration. Most of the internal space is taken up by a gas tank 9 and electronic circuitry 10 potted in an epoxy resin or other suitable material. The electronic circuitry 10 is connected to a switch contact wire 11 and to a transformer 12 (T2 in the circuit diagram). The electronics circuitry 10 is potted so as to be in the shape of a rectangular box with a "step" therein as can be seen in FIG. 3. The "step" is used to accommodate two electric cells 13 which are held in a plastics material tray (not shown) including means for making connection to the cells. The cells are connected in series and the positive pole of the series connected cells is connected to the casing 1.

The arrangment of parts within the potted circuitry 10 is shown in FIGS. 4a, b and c. FIG. 4a shows the component layout with a direction of view corresponding to that of FIG. 2. FIG. 4b and 4c show views at right angles to the direction of view of FIG. 4a, FIG. 4b being a side view and FIG. 4c an end view. The component reference numbers are the same as those used in the circuit diagram FIG. 18. The layout shown in FIGS 4a, b and c is thus considered to be self-explanatory.

LID CATCH

FIG. 5 shows a diagrammatic view of the lid catch. A compression spring 14 shown in broken outline is provided to urge the lid 2 open, the lid being provided with a hinge (not shown) at 15. As may best be seen in FIG. 6, the magnet 8 is generally `U` shaped with a north pole piece 16 and a south pole piece 17 and has a base portion 18 which is received in a rectangular yoke 19. Screws 20 and 21 are provided to bear upon and so retain the magnet 8 in the yoke 19. The slide switch 4 is attached to the yoke 19 by means of a push-fit location lug 22 received in a hole 23 in the yoke 19.

FIG. 7 shows the mechanical arrangements for biassing the slide switch 4 in its UP position (it should be noted that the magnet 8 is omitted from FIG. 7). A helical compression spring 24 disposed coaxially about a tube 39 forming part of the burner assembly 6 acts at its lower end against a washer 25 positioned directly beneath the yoke 19. The yoke 19 is shaped at 26 so as to conform to the shape of the tube 39 against which it lies so that the yoke can slide vertically. It will be seen that the casing 1 is recessed at 27 to provide a sliding surface for the slide switch 4. When the slide switch 4 is in its UP position and the lid 2 is closed the poles of the magnet 8 are in contact with the under surface of the lid. The lid 2 which (as previously explained) is at least in part of ferromagnetic material is retained closed against the action of the spring 14 by the force of magnetic attraction. When the slide switch 4 is depressed the poles of the magnet 8 are moved away from the lid and the force of the spring 14 becomes more powerful than the magnetic attraction and the lid springs open to assume a vertical position. The return of the lid 2 to its closed position is achieved manually.

FUEL TANK

Details of the fuel tank 9 are shown in FIGS. 10 and 14. The fuel tank is moulded from a plastics material such as that known as `DELRIN` (registered Trade Mark). The burner assembly 6 and filler valve 40 are moulded during manufacture of the tank into the positions shown. Burner tubes and filler valves are components quite familiar to those skilled in the art of making smoker's lighters and hence a detailed description is not necessary here. The burner assembly 6 is preferably of the type described in British Patent No. 822,374 or No. 828,813 and the filler valve can, for example, be of the type described in British Patent Specification No. 784,357 or No. 966,967.

The fuel tank 9 includes a hole 41 for reception of switch components as will be further described later. Typically the wall thickness of the tank will be 0.04 inches.

BASE-PLATE

Details of the base-plate 3 and the means by which it is retained in position are shown in FIGS. 8 and 9. Referring to FIG. 8, the lower end of the casing 1 is provided with recessed portions 28 and 29. The base-plate 3 is provided with a projection 30 for entry into the recessed portion 30 and a retractible projection 31 for entry into the recessed portion 29. The base plate 3 has a groove 32 formed therein which acts as a mounting for the retractible projection 31. The retractible projection 31 consists of a short length of springy wire of slightly smaller diameter than the width of the groove 32. The shape of the wire could generally be described as a flattened "Ω". One end, 33, of the wire is secured in the groove 32 by stamping the upper wall of the groove at that point to bend the upper wall towards the lower wall to trap the wire in position. A threaded screw hole 34 is provided in the base-plate 3 to receive a retaining screw 35 (shown in broken outline). When the screw 35 is removed from its hole the natural springiness of the wire causes its end 36 (shown in broken outline) to move into a position a little to the right (as shown) of the position normally occupied by the central axis of the screw 35 so that the projection 31 is retracted to allow the base-plate 3 to be removed from the casing 1 for cell replacement and refuelling. When (with the base-plate 3 in position) the screw 36 is inserted the point of the screw (which is suitably shaped) displaces the end 36 of the wire so that the projection 31 is thrust outwards into the recessed portion 29 so retaining the base-plate 3 in the casing 1.

It will be understood that other types of base-plate can be used. For example, a base-plate which requires to be slid sideways against spring pressure to disengage a projection from a recess can be used. Alternatively a "snap-in" type base-plate can be used. If desired a hole and dust cap, corresponding in position to the filler valve, can be provided in the base-plate so that the lighter can be refuelled without removing the base-plate.

GAS CONTROL MECHANISM

Gas control mechanisms for smokers' lighters are well known to those skilled in the art and therefore a lengthy description is not necessary here. As previously stated, the burner assembly 6 is preferably of the type described in British Patent No. 822,374 or No. 828,813. FIG. 10 shows a view of the fuel tank 9; flame adjustment wheel 5 and burner assembly 6 with other components omitted. The burner assembly 6 comprises a central spring mounted rod 42 fitted coaxially within the tube 39. The rod 42 is able to move longitudinally against the action of the spring (not shown) which urges the rod 42 upwards (as seen in the drawing). The rod 42 is connected to a valve (not shown) which allows gas from the fuel tank to exit through the tube 39 when the rod is in its "UP" position. The top end of the rod is arranged to act against the lid 2 of the lighter. When the lid 2 is closed the rod 42 is depressed against the action of the spring and the valve (not shown) is closed. When the lid is open the rod 42 moves upwards, the valve opens and gas flows out of the fuel tank 9. Closure of the lid once more depresses the rod against its spring and shuts off the gas. By this means, opening and closure of the lid 2 of the lighter is made to provide a simple but effective on/off control over the flow of gas.

The component parts of the lighter used for flame regulation are shown in FIGS. 15 and 16 (FIG. 16 being to a larger scale than FIG. 15) with other parts omitted. Flame regulation in smokers' lighters is within the knowledge of those skilled in the art so that a simple description here will suffice.

The flame adjustment wheel 5 is of a resilient plastics material and has a knurled front 43 for operation by the user and a hole 44 with projections 45 arranged to push onto and mate with a splined shaft 46 on an screw member 47. Gas from the fuel tank 9 exists to the tube 39 by way of a slot 48 in a housing 49, thence through a wick 50 and a central passage 51 in a compression member 52, and thence by way of the gas on/off valve (not shown) to the tube 39. The wick 50 lies between the compression member 52 and a seating comprising a rubber pad 53 and a lower compression member 54. The screw member 47 has an external thread 55 arranged to mate with a corresponding thread in the part (not shown) in which it is fitted. Thus operation of the flame adjustment wheel 5 causes axial movement of the screw member 47 so that the wick 50 is compressed to a greater or lesser degree according to the sense of movement of the flame adjustment wheel 5. As will readily be understood, the wick 50 in a highly compressed condition will resist the passage of gas therethrough to a greater extent than when the wick is less compressed and control over the rate of flow of gas is thus achieved.

ELECTRONIC CIRCUITRY

Referring to FIG. 18, a battery E is connected to supply the ignition system of the lighter which comprises an ignition switch SW1; an inverter constituted by transistors VT1 and VT2, and a transformer T1 ; an inverter control circuit constituted by transistors VT3 and VT4; resistors R1, R2, R3 and capacitors C2 and C3 ; a full-wave bridge rectifier constituted by diodes D1, D2, D3 and D4 ; a triggering circuit constituted by triggering diode D6 and resistors R4 and R6 ;and a discharge circuit constituted by a capacitor C1, a step-up transformer T2, a thyristor D5, and ignition electrodes IE. As will be explained in more detail later, operation of the switch SW1 causes the production of an electric spark at the ignition electrodes IE to ignite the fuel of the lighter. Examples of suitable types and values of components for the circuit are set out in the table below.

Component Type or Value E Two mercury cells each type MP625H VT1, VT2, VT3 each 2N3794 VT4 2N4291 R1 180Ω ± 5% 0.1W R2 10kΩ ± 5% 0.1W R3 68kΩ ± 5% 0.1W R4 R5 each 1kΩ±5% 0.1W C1 33μF 40V electrolytic C2, C3 each 0.01μF 30V D1, D2, D3, D4 each IN 4148 D5 TIC 45 D6 D 32 T1 first primary P1 16 turns centre-tapped second primary P2 16 turns centre-tapped secondary S2 200 turns on an 8 mm diameter toroidal ferritecove T2 primary 12 turns secondary 2500 turns SW1 normally open single pole switch

Transformer T2 is preferably of the type described in British Patent Application No. 5981/72 entitled "Formers for Inductive Devices and Devices and Apparatus Employing Same".

The inverter is designed to have a high efficiency so that the time taken to charge the capacitor C1 can be kept low. In this respect, silicon transistors selected for low collector-emitter saturation voltage at the operating currents involved are employed in conjunction with a toroidal ferrite transformer. The bridge rectifier diodes are high frequency types also chosen to maintain high efficiency. In this respect a full-wave rectifier arrangement is preferred to a half wave arrangement.

The collectors of transistors VT1 and VT2 are connected to respective ends of the primary winding P1 of transformer T1 and their emitters are connected in common to the negative pole of battery E. The bases of transistors VT1 and VT2 are connected to respective ends of the primary winding P2 of transformer T1. As will be explained in more detail later, transistors VT3 and VT4 are connected to control the base current to transistors VT1 and VT2 and so control operation of the inverter. The inverter functions in a known manner as a multivibrator square-wave oscillator with transformer coupling to provide the necessary feedback.

The secondary winding of transformer T1 has one end connected to the cathode of diode D1 and the anode of diode D4 and its other end connected to the cathode of diode D2 and the anode of diode D3. The anodes of diodes D1 and D2 are connected in common to the negative pole of the battery E. The cathode of diodes D3 and D4 are connected in common to one end of trigger diode D6 whose other end is connected to one end of resistor R4 whose other end is connected through resistor R5 to the negative pole of the battery E. Thyristor D5 has its anode connected to the cathodes of diodes D3 and D4 and its cathode connected to the negative pole of the battery E. The trigger electrode of thyristor D5 is connected to the junction of resistors R4 and R5. The full-wave rectified output of transformer T1 thus appears across thyristor D5.

Components VT3, VT4, R1, R2, R3, C2 and C3 constitute the inverter control circuit. The emitter of transistor VT3 is connected to the centre-tap of primary-winding P2 of transformer T1 and its collector is connected to the base of transistor VT4. The collector of transistor VT4 is connected in common to the base of transistor VT3, one end of capacitor C2, one end of capacitor C3 and one end of resistor R3. The emitter of transistor VT4 is connected to one end of resistor R1 the other end of which is connected to the end of capacitor C2 remote from the base of transistor VT3. The end of resistor R3 remote from the base of transistor VT3 is connected to the negative pole of the battery E. Resistor R2 is connected from the junction of resistor R1 and capcitor C2 to the negative pole of battery E. The common ends of resistors R1 and R2 and capacitor C2 are connected to the centre-tap of primary winding P1 of transformer T1 and to the pole of switch SW1 remote from the battery E. The end of capacitor C3 remote from transistor VT3 is connected to the positive output (cathodes D3 and D4) of the bridge circuit constituted by diode D1, D2, D3, D4.

The positive pole of electrolytic capcitor C1 is connected to the cathodes of diodes D3 and D4 and its negative pole is connected to one end of the primary winding of transformer T2. The other end of the primary winding is connected to the negative pole of the battery E. One end of the secondary winding of transformer T2 is connected to the negative pole of the battery E. The other end of the secondary winding of transformer T2 is connected to the ignition electrode 7. The other ignition electrode is constituted by the rod 42 which is connected to the positive pole of the battery E. The positive pole of battery E is connected to the casing 1.

On closure of the switch SW1 the positive pole of the battery E is connected to the top end (as shown) of capacitor C2 and a positive going waveform consequently appears at the base of transistor VT3. The emitter of transistor VT3 is connected to the negative pole of the battery E by way of the centre-tap of the primary winding P2 so that the said positive going waveform tends to turn transistor VT3 ON. As a result collector current for transistor VT3 is drawn from the base of transistor VT4 which tends to turn VT4 ON. Collector current from transistor VT4 feeds the base of transistor VT3 which in turn draws more current from the base of transistor VT4. THus, transistors VT3 and VT4 form a complementary pair switch and closure of switch SW1 results in both of transistors VT3 and VT4 turning ON.

Transistor VT3 feeds base current to transistors VT1 and VT2 of the inverter which oscillates and continues oscillating so long as the switch SW1 is closed to supply collector current and so long as transistor VT3 supplies base current to the transistors of the inverter.

When the inverter is functioning a square-wave output appears at the secondary winding S1 of transformer T1 of approximately 70V peak to peak amplitude at a frequency of approximately 40kHz. The output of the circuit will, of course, be somewhat less if the battery has deteriorated through age or use. The inverter and rectifier change the battery voltage from a level of a few volts to a level considerably greater.

The full-wave rectified output of the secondary winding S1 charged capacitor C1 through the primary winding of transformer T2. Trigger diode D6 remains non-conducting until its breakdown voltage is reached and so long as the voltage across trigger diode D6 is less than the breakdown voltage the voltage drop across resistors R4 and R5 is effectively zero. A point is soon reached as capacitor C1 charges when the voltage across trigger diode D6 is equal to its breakdown voltage, whereupon the diode D6 conducts and a signal appears at the junction of resistors R4 and R5 which triggers the thyristor D5 into a state of conduction. Capacitor C1 now rapidly discharges through the primary winding of transformer T2 and thyristor D5 (which, of course, remains conducting until the current through it become equal to zero) and as a result a very high voltage (about 7kV) is induced in the secondary winding of tranformer T2. The high secondary voltage cause a fuel-igniting spark to occur between the ignition electrodes IE.

The energy required to ignite the butane gas of the lighter is approximately 2mJ and in the present circuit at least 15mJ would be stored in capacitor C1. While the energy available in the spark depends upon the efficiency of the transformer T2 this value of stored energy in capacitor C1 more than compensates for expected losses in transformer T2.

The use of trigger diode D6 and thyristor D5 allows a high charging rate of capacitor C1 to be employed since the open circuit output voltage of the inverter and rectifier can be made significantly greater than the maximum working voltage of the capacitor C1. This fact is advantageous because the size of capacitors of a given value increases with their rated working voltage.

The discharge of capacitor C1 also results in a negative going spike being applied through capacitor C3 to the base of transistor VT3. This negative going spike causes both transistors VT3 and VT4 of the inverter control circuit to turn OFF. As a result the flow of base current to the transistors of the inverter ceases and the inverter stops oscillating. The negative going spike will charge capacitor C in such a manner as to maintain the transistors VT3 and VT4 OFF. This charge decays through the resistances associated with capacitor C2 but the transistors VT3 and VT4 remain OFF until a positive going waveform is again applied at the base of transistor VT3 by a further actuation of the switch SW1.

It will be appreciated that to obtain the spark discharge the user must continue to operate the switch SW1 for the multivibrator to function sufficiently long for the voltage on capacitor C1 to be built up. Once capacitor C1 has discharge it will be observed that the inverter is turned off. Thus, for a single actuation of the switch the inverter runs for a sufficient time to produce the spark, after which it remains off irrespective of whether or not the user keeps the switch depressed.

The switch action does not need to be mechanically timed -- providing the contact is made the inverter will run only for the time necessary to charge the capacitor with sufficient energy to create one ignition spark. This means that no energy is wasted after the capacitor is fully charged (a fixed time charging system would have to allow sufficient time for a partially used battery to charge the capacitor, which would thus be more than necessary for a fresh battery). The time (normally scarcely perceptible to the user) required for the capacitor to charge and a spark to be produced will increase as the battery ages and can serve as a useful indication of the necessity to renew the battery. Nevertheless, the ignition system should continue to operate even with fairly extended charging times.

MECHANICAL ASPECTS OF THE ELECTRONIC CIRCUITRY

The mechanical details of the switch SW1 are illustrated in FIG. 2 and 14. A helical compression spring (not shown) is located in the hole 41 (FIG. 14,) so as to act against the switch contact wire 11 (FIG. 2). A contact pin 56 is inserted in the end of the hole 41 remote from the contact wire 11 and is biased by the spring into contact with the internal face of the slide switch 4. The slide switch 4 is made of an insulating material with a fluted front face and an area 58 of conducting material on its inside face. The conducting area 58 is connected to the positive pole of the battery through the casing 1 (the area 58 slides against the casing 1). When the slide switch 4 is in its UP position the contact pin touches the insulated part of the slide switch 4, but when the switch 4 is depressed the pin 56 comes into contact with the area 58 and connection is made through the spring in hole 41 to contact wire 11 which in turn is connected to the electronic components.

The high voltage parts of the circuit need careful insulation to ensure that unwanted discharges do not occur. The shaping of the insulation about the ignition electrode 7 can be seen in the Figures. A shield 57 (FIGS. 1 and 17) of a ceramic or other heat resistant insulating material is placed about ignition electrode 7 to help avoid such unwanted discharges. The burner assembly 6 is connected to the positive pole of the battery E through the yoke 19 (which is of metal) and the casing 1.

It will be appreciated that the described embodiment has many advantages over prior art lighter. The provision of the inverter and rectifier to change the level of voltage supplied by the battery to a higher level enables a smaller capacitor to be employed for the storage of a given amount of energy than if the capacitor has been charged by the battery alone. This provides an advantageous economy in the space required within the lighter for the electrical components (the height of the lighter shown in FIG. 1 can be as little as 7 cms). Further, low voltage cells are employed which are relatively cheap and easily obtainable. The use of the inverter also provides a rapid means for charging the capacitor which is desirable in respect of repeated operation of the lighter and further no load is imposed on the cells during a period of non-use. The use of the trigger diode is particularly advantageous in respect of the speed of charging the capacitor and the use of the thyristor ensures a rapid discharge of the capacitor without any problems of the `contact bounce` type (a thyristor, once triggered, remains conducting until the voltage across it drops to zero).

Other forms and modifications are possible within the scope of the invention. For example, the invention can be embodied in a table lighter. In a table lighter a more squat arrangement of components would generally be desirable. The thyristor can if desired be replaced by a mechanical switch contact and the trigger diode can be omitted, but the use of the components shown to provide automatic ignition is preferred. Transistors of the opposite conductivity types to those shown can be employed and other inverter arrangements are possible. For example, an oscillator employing a single transistor could be used. The inverter could employ a piezo-electric solid-state transformer. It is also contemplated that a voltage multiplier of the diode voltage-doubler type could be used. At least some of the electrical components of the lighter could be made in integrated circuit form. One or more rechargeable cells could be used to power the lighter. It is not essential for the electronic components to be potted as described.