Spark-producing arrangement for a lighter with a battery

Abstract

A spark-producing circuit arrangement having a source of D.C. voltage, an oscillating portion including a spark gap in the operating region of the flame and sensing the presence of the flame for turning off the oscillating portion when a flame is present.

Description

FIELD OF INVENTION

The present invention relates to a spark-producing device employing a battery for use especially in lighters having voltage transducers capable of oscillations for producing a high voltage spark and including a cut-in and cut-out switch which is operable by the operating member of the spark-producing device itself so as to throw the voltage transducer into and out of the circuit.

BACKGROUND OF THE INVENTION

Spark-producing arrangements employing batteries are already known in which a storage capacitor is charged up directly from the battery and is discharged through a high voltage ignition transformer by operating an actuating contact. Such an arrangement has a disadvantage in that the ignition transformer must have a very high transformer ratio and a multi-cell battery is necessary. For such reasons a spark-producing device of the above kind is relatively bulky.

Another spark-producing device employing a battery became known which has a voltage transducer capable of oscillations and through which a storage capacitor is charged to a voltage which is several times higher than the battery voltage itself. After charging up the capacitor, the storage capacitor becomes discharged through an ignition transformer after a switch becomes operated. As is evident from the above, an additional transformer is necessary for the oscillating part of the voltage transducer. However, the last mentioned arrangement operates with a single cell battery and its ignition transformer requires a relatively small transformer ratio and, therefore, its volume can be kept relatively small. The disadvantage of the above-mentioned spark-producing arrangement resides in that it remains in operation for as long as the operating switch of the lighter is closed, even after ignition has taken place. In the case of pocket lighters, such repeated and superfluous ignition will lead to a quick exhaustion of the battery.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide an improved spark-producing arrangement employing a battery which does not have the above-mentioned disadvantages of known spark-producing devices and which is capable of increasing thereby the operating life of the battery.

According to the present invention, a flame sensing means is provided within the spark-producing arrangement which controls a cut-out member of the ignition device.

According to the present invention, a spark-producing arrangement employing a battery and having a transistorized voltage transdusing arrangement therein, the cut-out member is preferably provided in the feedback path of the voltage transducer and located in the base circuit of the transducer.

According to the present invention it is preferred that the flame sensing means forms the cut-out member itself.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more readily apparent from the following description of preferred embodiments thereof shown in the accompanying drawing, in which:

FIG. 1 illustrates the circuit connections of a spark-producing device employing a battery according to the present invention; and

FIGS. 2a-f illustrate various flame sensing devices which can be used in connection with this spark-producing arrangement according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the circuit diagram of FIG. 1, it is seen that it includes a battery 1, which preferably has a voltage of 1.5 volts, and an electrolyte capacitor 2, which is connected parallel to the battery 1. The fact that such a type of capacitor is used has the advantage that even when the battery has been relatively fully discharged, the spark-producing arrangement of the present invention will still be capable of proper functioning. The circuit diagram further includes a npn-type transistor 5, which obviously can also be a pnp-type and, in the latter case, it is required only to change the voltage polarities. The emitter of the transistor 5 is connected to the negative terminal of the battery 1, while the collector is connected over the primary winding 6 of an oscillation transformer 9, with the make-contact of an operating switch 10, the other contact point of which is returned to the positive terminal of the battery 1.

The oscillating transformer 9 further includes a feedback winding 7 as well as a secondary winding 8. The feedback winding 7 is connected with one end thereof to the base of the transistor 5 and with the other end thereof to a tap-joint of a voltage divider circuit feeding the base of the transistor 5 and comprising the resistors 3 and 4. One end of the voltage divider circuit is connected to ground, namely, at one end of the resistor 4, whiile the other end of the voltage divider circuit is connected to the make-contact side of switch 10 at the end of resistor 3.

The secondary winding 8 of the oscillating transformer 9 has a Villard-type rectifier arrangement coupled thereto which includes a storage capacitor 11, diodes 12 and 13 and another storage capacitor 14.

Through the storage capacitor 14, the primary winding 15 of a high voltage ignition transformer 17 is connected through a series circuit, including a thyristor 18.

The secondary side 16 of the high voltage ignition transformer 17 is in circuit connection with a spark gap 21.

According to the present invention, a flame-sensitive sensing means is provided which controls a cut-out switch member of the ignition arrangement. For this purpose the resistor 3 in the voltage divider circuit feeding the base of transistor 5 is replaced by a switch member which is placed in the operating range of the burning flame which includes a resistive part, the resistance of which increases with increasing flame temperature. Such switching members are illustrated in FIGS. 2a and 2d and which, for example, can be a resistor with a PTC resistance characteristic (PTC=positive temperature co-efficient) or as illustrated in FIG. 2d, a bimetall switch which can be arranged to be a normally closed contact. Instead of the above arrangement, one may replace the resistor 4 in the circuit diagram of FIG. 1 by a switching member which has a resistance characteristic decreasing with increasing temperature. Such switching member is illustrated in FIGS. 2c and 2b in alternatives and one is known as NTC-type resistors (NTC=negative temperature co-efficient) the other operative as a bimetall switch as illustrated in FIG. 2b arranged as a normally open contact.

Another embodiment possible for sensing the flame temperature and to acting as a cut-out switch is when the resistor 4 is replaced by an infra-red sensor, such as, by an infra-red sensitive photo-resistor. This type of arrangement is illustrated in FIG. 2e.

Also, as a further possibility, one may place, near the ignited flame, a so-called ionization gap 22, illustrated in FIG. 2f, which can be in the form of a pair of wire tips placed at a small distance with respect to each other. Such an ionization gap could then be used to replace the resistor 4. It is, however, assumed and required that the resistor 3 always has a value which is considerably larger than the resistance of the ionization gap 22. The resistance of the gap 22 at an operating flame lies between 1 and 20 M ohms. It is also noted that that, for the generally illustrated transistor 5, it is preferred to use a FET-type transistor which requires a very slight base current.

Instead of replacing resistor 4 directly by the ionization gap 22, one may arrange the gap 22 in such a manner that the gap 22 controls a switching member such as an FET transistor which lies parallel with the resistor 4.

In each of the above-described cases, the circuit of the oscillating arrangement must be designed in such a manner that when the operating switch 10 is closed, then the oscillation will start. The above requirement can be obtained by the appropriate dimensioning of the switching elements, especially by appropriately selecting the bias voltage for the base of the transistor 5, the winding ratio of the primary winding 6 and the feedback winding 7.

The circuit arrangement illustrated in FIG. 1 operates as follows:

When the operating switch 10 is closed, a current will flow through the voltage divider circuit consisting of resistors 3, 4. Consequently, a base current flows through the transistor 5 and through the return or feedback winding 7 of transformer 9. As a result, there will also be a collector current flowing through the primary winding 6 and, due to the fact that there is an inductive effect between the windings of transformer 9, and such effect is being fed-back through the feedback winding 7, the base voltage will increase further. Such a process will continue until the collector current reaches its maximum. Then, the magnetic flux density cannot increase anymore in the oscillating transformer 9 and the feedback winding 7 will not have any further induced voltage therein, therefore, the transistor 5 will become turned off.

Due to the increase of the collector current, until the maximum value of it is attained, there will be induced a voltage in the secondary winding 8 which, through diode 12, will charge the storage capacitor 11 to at least a partial value.

When the transistor 5 is turned off, as above-mentioned, then in the secondary winding 8 there will be an oppositely poled induced voltage present which will add to the voltage on the storage capacitor 11 and through diode 13, will charge up the storage capacitor 14. When there is no further charging current flowing into the storage capacitor 14, then the diode 13 will block and the energy stored in the winding capacity of the secondary winding 8 of transformer 9 will discharge itself through the oscillating transformer 9 and will induce a voltage in the feedback winding 7 of the transformer 9, which voltage will turn on again the transistor 5 and will thereby introduce a new oscillating cycle. It follows from the above that the oscillated portion includes elements 3-9, while the charging circuit includes elements 11-14.

The above described charging and discharging cycles repeat themselves until the storage capacitor 14 will carry a charge corresponding to the breakdown voltage of the thyristor 18. At such instant, the storage capacitor 14 will discharge through the high voltage ignition transformer 17 whereupon there is a spark produced across the spark gap 21.

The circuit diagram illustrated in FIG. 1 is designed in such a manner that the oscillations will continue after the storage capacitor 14 has discharged and the above described oscillating process keeps repeating itself.

According to a preferred embodiment of the present invention, the voltage transducer or oscillator will turn itself off only when the gas or whatever fuel is used is already burning. For this purpose, the resistor 3, as above described, can be made as a PTC resistor which is placed in the operating range of the flame. Due to the heat produced by the flame, the resistance of the PTC resistor 3 will increase itself considerably within a short period of time so that the bias voltage of the transistor base will be reduced to a value which is too small for another cycle of oscillation. It is assumed that the oscillating state of the voltage transducer or oscillator portion is relatively difficult to upset by changing the bias voltage of the transistor base. However, it is relatively easy to prevent a starting of the oscillation directly after the storage capacitor 14 has been discharged just by changing the bias voltage on the base of transistor 5.

As already has been mentioned above, instead of the PTC resistor 3, one may use a bimetall switch illustrated in FIG. 2d. In such a case, as soon as the flame starts to burn, the bimetall switch of FIG. 2d becomes heated and will open up so that the base of transistor 5 will become grounded through the resistor 4 and the further oscillations of the transducer or oscillator portion is prevented.

In the event that in the switching arrangement of FIG. 1 the resistor is a NTC resistor, as illustrated in FIG. 2c, then the resistance value of such a reistor will decrease considerably through the exposure to the heat of the flame and thereby the bias voltage to the base of transistor 5 will be reduced with the consequence, as mentioned above in connection with the PTC resistor, namely the oscillation will stop.

A similar effect will be attained when the NTC resistor 4 is replaced by a normally open bimetall switch, such as illustrated in FIG. 2b, which will become closed under the effect ot the heat of the flame.

The resistor 4 can be replaced by an infra-red sensitive photo-resistor as illustrated in FIG. 2e. Such a photo-resistor reduces its resistance value when radiation hits it, so that it will have a similar effect as when a NTC resistor is used.

In the event that an ionization gap 22 is used as the flame sensor, the tips of the electrodes of which are exposed to the immediate region of the flame, but outside the spark gap 21, then using such an ionization gap 22 instead of the resistor 4 will have the same effect as the use of an NTC resistor.

The switching arrangement illustrated in FIG. 1 can be modified several ways. For example, a self-cleaning or wiping contactor can be used, which, after having been operated once allows the sparking to go on only for a certain number of times before the switch can be operated again. As a result, an excessive use of the battery is avoided and this is especially advantageous in the event other operating deffects are present or when the fuel tank is empty.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

Claims

Having thus described the invention, what I claim as new and desire to be secured by Letters Patent, is as follows:

1. A spark-producing circuit comprising a source of D.C. voltage, an oscillating means including spark means coupled to said course of D.C. voltage, a sensing means placed adjacent said flame and sensing the presence of the flame for turning off said oscillating means when a flame is present, said oscillating means comprises a voltage transducer means having a primary, a secondary and a feedback winding, a transistor device having a base electrode connected to said feedback winding, a primary winding connected to said collector electrode, a voltage dividing circuit including said sensor means connected through said feedback winding to the base electrode of said transistor device, an operating switch means connecting said voltage divider circuit to one terminal of said D.C. voltage source, a discharge circuit connected to said secondary winding and including a storage capacitor means and a thyristor device connected in a series therewith and capable of producing a high voltage pulse when the charge in said storage capacitor attains a predetermined breakdown voltage of said thyristor means, a high voltage step-up transformer means having a primary winding connected in series with said storage capacitor means and said thyristor means and a secondary winding, a spark gap means connected in series with said secondary winding of said step-up transformer means, whereby a spark is produced in said spark gap means when said storage capacitor discharges over said thyristor device.