US3817694A

US3817694A - Ignition device

Info

Publication number: US3817694A
Application number: US00259710A
Authority: US
Inventors: M Makino
Original assignee: Tanita Corp
Current assignee: Tanita Corp
Priority date: 1971-06-11
Filing date: 1972-06-05
Publication date: 1974-06-18
Anticipated expiration: 1991-06-18
Also published as: DE2227668A1; FR2140514B1; FR2140514A1; JPS5025871B1; GB1386107A

Abstract

A lighter ignition mechanism includes a solenoid connected to a pair of normally closed electrodes mounted on resilient arms and located adjacent a lighter burner nozzle. A magnetic yoke includes a leg about which the solenoid is wound, a permanent magnet leg, and a leg swingable between yoke opening and closing positions. A camming wedge is located on the swingable leg and moves between followers located on the resilient arms to separate the electrodes following the opening of the yoke and during the interval of induced current in the solenoid to produce a discharge between the electrodes of long duration. A capacitor, in one form of the mechanism, is connected across the solenoid.

Description

g I 22 Filed:

21 Appl. No.1 259,710

[ IGNITION DEVICE [75] Inventor: Minoru Makino, Tokyo, Japan [73] Assignee: Kabushiki Kaisha Tanita 1 Seisakusho, Tokyo-to, Japan June 5, 1972 [30] Foreign Application Priority Data June 11, 1971 Japan 46-40957 [52] us. c1 431/255, 317/81, 317/93, 317/97, 431/257, 431/264 51 1m. (:1. F23q 3/01 [58] Field of Search 317/79, 80, 81, 92, 93, 317/96, 97; 431/255, 257, 264; 335/229 [56] References Cited UNITED STATES PATENTS 2,076,418 4/1937, Smith, 317/93 3,021,455 2/1962 Weber ..'317/191 3,147,401 9/1964 Wotring 317/97 3,166,689 1/1965 Buntenbach 317/80 3,222,576 12/1965 Thompson 317/97 3,323,019 5/1967 Takahashi 317/93 3,384,78 5/1968 Oyamada et al 317/81 x 1 June 18, 1974 Primary Examiner-Volodymyr Y. Mayewsky Attorney, Agent, or Firm-Welder & Gross [57] ABSTRACT A lighter ignition mechanism includes a solenoid connected to a pair of normally closed electrodes mounted on resilient arms and located adjacent a lighter burner nozzle. A magnetic yoke includes a leg about which the solenoid is wound, a permanent magnet leg, and a leg swingable between yoke opening and closing positions. A camming wedge is located on the swingable leg and moves between followers located on the resilient arms to separate the electrodes following the opening of the yoke and during the interval of induced current in the solenoid to produce a discharge between the electrodes of long duration. A capacitor, in one form of the mechanism, is connected across the solenoid.

4 Claims, 13 Drawing Figures PAIENTEDM 1a m snztr m a Ila) PAIENIEDJun w 1014 saw 2 or 3 IGNITION DEVICE BACKGROUND OF THE INVENTION The present invention relates generally to improvements'in electrical ignition devices and it relates particularly to an improved electromagnetic mechanism for producing an electrical discharge in the proximity of a lighter fuel outlet or burner nozzle.

Many forms of electromagnetic lighter ignition mechanisms have been proposed and these generally include a step up transformer whose secondary winding is connected to spaced discharge electrodes in the vicinity of the lighter nozzle. The transformer includes a primary winding which is rapidly energized or deenergized by an associated battery and switch arrangement or a transformer magnetic yoke includes a permanent magnet and a movable leg in the yoke magnetic path so that a discharge is produced between the electrodes attendent to the separation of the movable yoke leg whereby to ignite the fuel, which may be, for example in gaseous form.

The conventional and proposed ignition mechanisms of the above type possess numerous drawbacks and disadvantages, being generally characterized by an electrical discharge of such short duration as to necessitate a very close time correlation between the opening of the lighter fuel nozzle and the establishment of the electrical discharge and hence very close manufacturing tolerances and frequently complicated mechanisms and very low reliability; Furthermore, in the type of electromagnetic ignition mechanism heretofore proposed the high voltage step up transformer required a primary as well as secondary winding which is of considerable bulk so it has been impractical to produce a lighter employing this type of ignition system which is compact enough for use as a conventional pocket lighter but is limited to use as a stationary type of lighter and otherwise leaves much to be desired.

SUMMARY OF THE INVENTION It is a principal object of the present invention to provide an improved ignition mechanism.

Another object of the present invention is to provide an improved electromagnetic ignition mechanism in which the need for batteries is obviated and which is so compact as to be suitable for portable pocket lighters.

A further object of the present invention is to provide an ignition mechanism of the above nature characterized by its simplicity, ruggedness, high reliability, obviation of close operational tolerences, low cost and high versatility.

The above and other objects of the present invention will become apparent from a reading of the following description taken in conjunction with the accompanying drawings which illustrate preferred embodiments thereof.

In a sense the present invention contemplates the provision of an ignition device comprising a solenoid, a pair of discharge electrodes movable between normally closed contacting and open separated positions and coupled to opposite terminals of the solenoid, means for producing a current inducing pulse of varying magnetic flux through the space delineated by the solenoid, and means for opening the electrodes following the initiation of said magnetic pulse and during the presence of induced current.

In its preferred form the discharge electrodes are positioned proximate the free ends of parallel resilient arms which normally urge the electrodes into engagement and carry respective follower members. The solenoid is wound about a leg of a magnet yoke which includes, as sections thereof forming a normally closed magnetic path, a permenent magnet and a leg movable between a yoke closing and opening positions and normally being in a closed position completing the magnetic path. A lever is provided for swinging the movable leg to its open position and a wedging cam is located on the movable leg and is advanced between the follower elements during the opening of the movable yoke leg to separate the electrodes following the opening of the yoke and while the magnetically induced current is present in the solenoid. A capacitor may advantageously shunt the solenoid.

The electrical discharge by reason of the separation of the electrodes following the start of and during the presence of the induced current is of such a nature that it is hot and of relatively long duration so as to reliably insure the ignition of the fuel and the mechanism is simple, rugged, compact and inexpensive.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1(a) is a top plan view of the discharge electrodes of an ignition mechanism embodying the present invention.

FIG. 1(b) is a fragmentary schematic front elevational view of the improved mechanism;

FIG. 1(0) is a schematic view of the improved mechanlsm;

FIG. 2(a) and 2(b) are diagrams showing the characteristic curve of the discharge voltage as related to the air gap formed between the discharge electrodes;

FIGS. 3(a) to 3(d) are diagrams showing the variation in magnetic flux passing through the ignition coil upon the opening of the magnetic yoke, the time of separation of the discharge electrodes and the variation of electric current and output voltage respectively in the coil as related to time;

FIG. 4(a) is a plan view showing the discharge electrodes of another embodiment of the present invention;

FIG. 4(b) is a view similar to FIG. 1(b) of the embodiment of FIG. 4(a);

FIG. 4(a) is a circuit diagram of the burner lighter ignition mechanism shown in FIG. 4(b); and

FIG. 5 is a graph showing the variation of voltage and current with time in the operation of the mechanism of FIGS. 4a to 40.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now the drawings and particularly FIGS. 1(a) to 1(c) thereof, the improved ignition mechanism comprises a magnetic yoke l for affording a low reluctance closed magnetic path for the magnetic field effected by a suitable high strength permanent magnet 2 which constitutes a leg of the yoke and extends upwardly from one end of a horizontal bottom leg of the yoke 1. Also projecting upwardly from the yoke bottom leg and transversely spaced from permanent magnet leg 2 is a magnetic leg la about which is wound a suitably insulated coil or solenoid 4. Completing the yoke 1 is an iron piece or magnetic leg 3 which extends between the top faces of and bridges legs 1a and 2, being hinged to the top outer corner of leg 2 so as to be swingable out of engagement with the top face of leg 1a from its closed position to a positionopening the yoke 1 and thereby sharply reducing the magnetic field through solenoid 4 by way of leg 1a to produce a sharply dropping magnetic flux pulse through the solenoid. To facilitate the rapid opening of leg 3 a lever or handle 3b is secured to the outer face of and separated from leg 3 by a spacer 2a so that inward pressure on handle 3b effects the snap opening of leg 3.

It is important to note that the coil 4 is wound around the yoke leg 1a with a minimum of distributed capacity in order to facilitate the development of an arc and to suppress any spark quenching action. The output terminals of coil 4 are connected with suitable shielding to a pair of discharge electrodes 6 and 7, respectively, which are kept in separable contact with each other as shown by FIG. 1(a). The electrodes 6 and 7 are located above leg 3 and, as shown by FIG. 1a, include a pair of spaced parallel resilient arms, one pair of the ends of which are fixed to the opposite faces of an insulator block6a. One electrode 7 has a pointed tip 7a directed toward and normally in contact with the other electrode 6. The electrodes 6 and 7 preferably comprise leaf spring members provided with confronting followers and, as'the movable iron piece 3 is swung out of contact with the yoke leg 1a, a wedge shaped cam member 3a projecting upwardly from iron piece 3 is advanced between the followers on electrodes 6 and 7 so that thepointed tip 7a of the electrode 7 is retracted out of contact with the electrode 6. In FIGS. la and 1b, 8 designates a burnerv nozzle for gaseous fuel which is opened as the movable iron piece 3 is brought out of contact with the yoke leg 1a by depression of the lever 3b in any suitable manner and is disposed slightly spaced from the electrode 6 and the pointed tip 7a of the electrode 7, as shown. It should be noted that discharge electrode 6 and pointed tip 7a of the discharge electrode 7 are preferably returned into contact with each other as rapidly as possible and that the returning movement of the movable iron piece 3 after the lever 3b is released is smoothly and reliably accomplished by themagnetic attractive force.

Considering now the operation of the ignition mechanism described I above, the lever 3b is depressed to swing the movable iron piece 3 out of contact with the yoke leg l a, about the upper end of the permanent magnet 2 to insert and advance the cam or wedge defining projection 3a located on movable iron piece 3 between the followers on discharge electrodes 6 and 7 to thereby retract the point tip 7a of discharge electrode 7 out of contact with discharge electrode 6, as shown by FIG. 2(a). A discharge voltage is developed between the separated electrode 6 and the pointed tip 7a of the electrode 7, as shown by FIG. 2(b), due to the variation of magnetic flux passing through the coil 4 as the movable iron piece 3 is moved out of contact with the yoke leg la. FIG. 2(b) shows a characteristic curve of the discharge voltage developed between electrode 6 and the pointed tip 7a of electrode 7, wherein t, the time elapsing from the moment at which movable iron piece 3 has left yoke leg la, is the abscissa and Vd, the discharge voltage, is the ordinate. In FIG. 2(a), (i) corresponds to the state in which electrode 6 is in contact with pointed tip 7a of the electrode 7 (ii) to (iv) corresponds to the states in which both discharge electrodes 6 and 7- are spaced from each other with air gaps 1d,,

Id and Id respectively. The discharge voltage Vd developing between the electrode 6 and the pointed tip 7a of the electrode 7 which varies depending upon the air gap formed between electrode 6 and pointed tip 7a experiences the following sequence. First,'in the state of air gap 1d,, the discharge voltage Vd consists of an oscillating voltage of high frequency and small amplitude as shown by (ii) in FIG. 2b, which effects a socalled shower discharge; when the state of air gap [d2 is attained, there is developed a discharge voltage which uniformly rises and an arc occurs as the air gap across the electrode 6 and the pointed tip 7a of the electrode 7 increases; and finally the discharge voltage Vd reaches the maximum level (approximately 2,500 to 2,700V) when the state of air gap hi is attained (i.e., when the lever 3b is depressed substantially to the final stage of depression) and thereafter a state of resonance occurs which is a function of the inductance and distributed capacity, substantially corresponding to self inductance and distributed capacity of the coil 4, in which state a damped oscillation voltage occurs.

The time point at which the maximum voltage level is developed is within the range between 800p. and 1,200p. seconds after the separation of the electrode 6 and the pointed tip 7a and the first peak of the damped voltage appears approximately 200p. seconds after the time of the maximum voltage level/The nozzle 8 for "gaseous fuel, therefore may be opened approximately from the moment at which an air gap across the electrode 6 and the pointed tip 7a occurs corresponding to the state shown by (ii) in order that the ignition of the gaseous fuel is assured by the discharge voltage under the conditions of resonance voltage at the steps (ii) to (iv) and the following conditions as shown in FIG. 2b.

FIGS. 3a to 3d illustrate the variation in magnetic flux passing through coil 4 from the moment at which the opening of movable iron piece 3 is initiated, the time point at which the electrode 6 and the pointed electrode tip 7a are separated from each other, and the variation of electric current and output voltage respectively in coil 4 as related to time it. As is seen from FIG. 3(b), the variation of electric current and output voltage reaches a maximum at the moment at which the electrode 6 and the pointed tip 7a are separated from each other.

The point tip 7a of the electrode 7 and the portion of the electrode 6 that is engagable by pointed tip 7a, including the area adjacent to tip 7a, are susceptible to soot and the other dust which progressively accumulates thereon with repeated ignitions. This soot and dust are, however, removed under cleaning effect not only of the chattering phenomenon occurring during the separation of both electrodes 6 and 7 which serves to clean these contact surfaces but also by reason of a metal catalytic action during combustion of the gaseous fuel, so that effective and reliable ignition is always assured.

The embodiment shown in FIG. 4 differs from that first described in that a capacitor 5 is connected in parallel with the coil 4 and the points at which capacitor 5 is connected in parallel with coil 4 are connected to discharge electrodes 6 and 7 which are nonnally in contact with each other. The discharge voltage Vd developed between the electrode 6 and the tip 7a of the electrode 7 which varies depending upon the air gap formed between electrode 6 and tip 7a experiences the following sequence. First, in the state of air gap 1d,, the discharge voltage Vd is an oscillation voltage of high frequency and small amplitude as shown by (ii) in FIG. 2b; when the state of air gap ld is attained, there is developed a discharge voltage which uniformly rises, and finally the discharge voltage Vd reaches maximum value when the state of air gap Id is attained and thereafter a state of resonance occurs which is substantially a function of the inductance and capacitance valves of the coil 4 and the capacitor 5, in which state a damped oscillation voltage occurs.

The nozzle 8 for gaseous fuel, therefore, may be opened approximately from the moment at which an air gap between the electrode 6 and the tip 7a is effected corresponding to the state as shown by (ii) in order that ignition of gaseous fuel is assured by the dis charge voltage under the influence of the resonance voltage as the steps (ii) to (iv) and the following conditions as shown in FIG. 2b. FIG. 5 shows curves illustrating the voltage v induced by the coil 4 and the discharge current Id varying in accordance with the time lapse t after the movable iron piece 3 has left the yoke leg 1a.

According to the present invention, as will be understood from the aforegoing description in reference to the accompanying drawing, the electrode 6 and the pointed tip 7a of the other electrode 7, these being normally in contact with each other, are brought out of contact with each other in response to separation of the movable iron piece 3 from yoke leg la and, in response to the separation of the electrodes, a discharge is effected between the electrodes under the influence of the induced voltage produced in the coil 4, so that it is possible, as shown by FIG. 2b, to maintain the dis charge for an extremely long interval of time with a lower voltage and to thereby accomplish the ignition of the gaseous fuel in a reliable manner. The electromagnetic igniting mechanism in accordance with the present invention further includes the lever 3b which may be depressed with a suitable force to swing the movable iron piece 3 out of contact with the yoke leg la, improving the ignition operating requirements. Furthermore, the present mechanism permits the provision of a portable electromagnetic lighter of an extremely compact construction since a single coil or solenoid suffices and many other components have been obviated.

A relatively high internal resistance of the coil 4 avoids any problem of contact resistance between the electrode 6 and the pointed tip 7a of the electrode 7 and the maximum discharge output during ignition may reach approximately three to four times the electrodeopen-circuit voltage by suitable adjustment of the timing with which the movable iron piece 3 is separated from the yoke leg 1a.

While there have been described and illustrated preferred embodiments of the present invention it is apparent that numerous alterations, omissions and additions may be made without departing from the spirit thereof.

I claim:

1. In combination with a fuel nozzle, a fuel ignition device comprising a solenoid, a pair of separable discharge electrodes, means including an insulator member supporting said electrodes proximate and exposed to fuel from said nozzle, said electrodes being moveable between normally closed contacting and open separated positions and coupled to opposite terminals of said solenoid, one of said electrodes being resiliently biased into contacting engagement with the other electrode, means for producing a current inducing pulse of varying magnetic flux through the space delineated by said solenoid including a magnetic yoke transferrable between an open and closed condition and having a first leg registering with said solenoid and a permanent magnet second leg and a third leg supported for swinging between a yoke closed and a yoke open position, means including an actuating handle for swinging said third leg from said closed to said open position, and means for opening said electrodes in operative association with the initiation of said magnetic pulse and during the presence of said induced current to produce an electric discharge between said electrodes to ignite said fuel and including a follower movable with said biased electrode and cam element movable with said third leg and engageable with said follower to retract said biased electrode from the other electrode with the opening of said third leg.

2. The ignition device of claim 1 including a capacitor connected across said solenoid.

3. In combination with a fuel nozzle, a fuel ignition device comprising a solenoid, a pair of discharge electrodes movable between normally closed contacting and open separated positions and electrically coupled to opposite terminals of said solenoid, means including an insulator member supporting said electrodes proximate and exposed to fuel from said nozzle, means for producing a current inducing pulse of varying magnetic flux through the space delineated by said solenoid and comprising a normally closed magnetic yoke including a first section which registers with said solenoid and a permanent magnet second section and a third section swingable between a yoke closed first position and a yoke open second position, means including an actuating handle for swinging said third section from its first position to its second position, and means for opening said electrodes in operative association with the initiation of said magnetic pulse and during the presence of said induced current to produce an electrical discharge between said electrodes to ignite said fuel, one of said electrodes being normally resiliently biased into contact with the other of said electrodes, said electrode opening means separating said electrodes in response to the opening movement of said yoke third section and including a spring arm supporting said resiliently biased electrode and including a follower and a cam element mounted on said yoke third section and movable with the opening of said third section to engage said follower and separate said electrodes.

4. The ignition device of claim 3 including a capacitor connected across said solenoid.

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