US3421368A - Ignition system safety circuit for internal combustion engines and the like - Google Patents

Description

J. B. STEPHENS IGNITION SYSTEM SA Jan. 14, 1969 FETY CIRCUIT FOR INTERNAL COMBUSTION ENGINES AND THE LIKE Sheet Filed Jan. 23, 1967 INVENTORZ .JOE BARON STEPHENS BY hz/MM ATTYS.

J. B. STEPHENS IGNITION SYSTEM SAFETY CIRCUIT FOR INTERNAL Jan. 14, 1969 COMBUSTION ENGINES AND THE LIKE Sheet Filed Jan. 23. 1967 ATTYS.

Jan. 14, 1969 Filed Jan. 25,1967

J. B. STEPHENS IGNITION SYSTEM SAFETY CIRCUIT FOR INTERNAL COMBUSTION ENGINES AND THE LIKE zff DETECTOR l Sheet 3 of '3 hr'f 1 i V204 l )..J

- mvewron:

JOE BARON STEPHENS Y /rww/ 95W ATTYS.

United States Patent 16 Claims ABSTRACT OF THE DISCLOSURE A safety circuit for internal combustion engines which makes high frequency ignition systems compatible with conventiontl safety monitoring networks so that existing safety monitoring networks may be used without modication thereof.

The present invention relates to a safety circuit for ignition systems suitable for use with internal combustion engines, and, particularly, to an improved safety circuit for ignition systems employing electronic circuitry for high frequency operation.

In recent years, ignition systems have been developed which replace the prior art breaker point apparatus and mechanical distributor with electronic circuitry for performing similar functions in response to electrical timing pulses produced in synchronism with engine operation. Many of these recent ignition lsystems employing electronic circuitry lare referred to as high frequency systems since capacitive means is employed to store energy and discharge such energy quickly into windings of a stepup transformer to re associated fuel ignition means. The quick discharge of energy from the capacitive means, providing high frequency operation, makes possible the use of transformers with fewer turns of conductors as compared to conventional transformers employed with conventional magneto ignition systems. The duration of the pulse of energy rapidly discharged from the capacitive means is less than that produced in conventional ignition systems where the energy is sustained from a magneto. One such high frequency ignition system is disclosed in a copending application entitled Ignition Apparatus for Internal Combustion Engines and the Like, Ser. No. 358,015, tiled Apr. 7, 1964, now U.S. Patent 3,311,783 of Leslie E. Gibbs et al. and of common assignee herewith.

In ignition systems of the high frequency type with which the present invention is primarily concerned, these high frequency ignition systems have proved highly durable and reliable in use and are desirable to use for replacement of conventional magneto ignition systems on medium and large size internal combustion engines. These medium and large size engine installations often include a very elaborate safety network to protect the engine and/ or engine driven devices, such as generators, alternators or power plants. In installations of this type, the engine often operates unattended and, therefore, should a malfunction occur in either the engine or engine driven de* vice, it is imperative that the malfunction be detected immediately and the engine stopped promptly.

The safety monitoring network for such engines includes detector devices to sense, for example, engine temperature, engine oil pressure, and engine speed, or excess current and voltage in the engine driven device. The safety network may also include various types of relay circuits which are energized by completion of the circuit through the detecting device or devices. The relay circuits serve to carry the relatively high surge of current from the conventional magneto when a malfunction is detected and to 31,421,368 Patented Jan. 14, 1969 actuate, for example, means for stopping engine operation or means for providing a visual indication of the malfunction of the engine.

When high frequency ignition systems are substituted for conventional magneto ignition systems, the energy dlscharged from the capacitive means is normally not sufficient to accurately and dependably actuate the relay c1rcu1ts used with conventional magneto ignition systems. It has been found that because of the short energy duration produced by discharge of the capacitive means, the high frequency ignition systems -are not directly interchangeable with conventional ignition systems because of the engine safety monitoring network employed for ldetecting and indicating malfunction of the engine. Accordlngly, it is an objective of the present invention to provide a safety adapter circuit with a high frequency ignition system to make the high frequency ignition system readily capable of substitution for conventional ignition systems.

In accordance with the invention, a safety circuit is pr0- vided to make high frequency ignition systems compatible with conventional safety monitoring networks for internal combustion engines. The ignition system safety circuit comprises charge storage means and unidirectional current flow means for connecting the means for charging the capacitive means of the high frequency ignition system to the charge storage means for charging the charge storage means. The conventional detecting means of the safety network is actuatable to complete a circuit upon detecting a malfunction in the engine system, such as, undesirable engine oil pressure. Control means is employed for electrically connecting the charge storage means to the circuit of the conventional detecting means, and the control means is provided with malfunction indicating apparatus. In the arrangement of the present invention, when a malfunction occurs closing the circuit of the detecting means, the charge storage means will discharge through the control means for actuating the malfunction indicating apparatus.

The control means preferably includes an electro-mechanical transducer, such as a relay, energized by discharge of the charge storage means and a visual indicator which is actuated upon energization of the electromechanical transducer for providing a visual indication of the malfunction of the engine. Detecting means and control means is preferably provided for each function of the engine desired to be monitored and they are connected to the charge storage means for receiving energy to accu- -rately and dependably actuate the associated malfunction indicating apparatus. Preferably, the charge storage means includes a capacitor of larger value than the capacitive means for storing more energy to energize the control means when a malfunction is detected. The electromechanical transducer of the control means may preferably be employed to actuate a valve to stop iiow of fuel to the ignition means of the engine, thereby stopping engine operation upon any malfunction of the engine sensed by the detecting means.

The safety adapter circuit of the present invention may be employed in a high frequency ignition system employing two separate capacitive means which are separatel-y connected by controllable switch means to an equal plusrality of different sets of fuel ignition means for the engine, each of whiclh ignition means may include the usual spark plug as the fuel igniting element, for example. Thus, in a twelveecylinder engine, six of the igniting elements may be connected to one of the two capacitive means and the other six to the other of the two capacitive means. When using two capacitive means, first gasoline in the cylinder in one set of six cylinders is ignited by discharge of one of the capacitive means, and then gasoline in a cylinder in the other set is ignited by discharge of the other capacitive means and so on. In this arrangement, the unidirectional current flow means could connect the charge storage means to one of the means for charging one of the two capacitive means to also charge the charge storage means. The other of the capacitive means could be connected by circuit means to the control means, whiclh is actuatable to connect the other capacitive means to electrical ground upon e-nergization of an electromechanical transducer in the control means to stop engine operation, for example.

For a better understanding of the present invention, reference is made to the following drawings, in which:

FIG 1 is a block diagram illustrating an overall ignition system and safety circuit in accordance with one form of the present invention;

FIG. 2 is a block diagram illustrating another overall ignition system and safety circuit in accoindance iwith another form of the invention and showing an alternative connection for the circuit means;

FIG. 3 is a schematic diagram illustrating one form of the safety circuit of FIG. 1;

FIG. 4 is a schematic diagram illustrating one form of the safety circuit of FIG. 2;

FIG. 5 is a schematic diagram illustrating another form of the safety circuit of FIG. 2; and

FIG. 6 is a schematic diagram illustrating still another form of the safety circuit of FIG. 2.

Referring now to the embodiment of the invention illustrated by way of example in FIG. 1, there is represented therein an ignition system and safety circuit in use in conjunction with ian engine 10 which may be a conlventional gasoline engine. For purposes of illustration, it will be assumed that the engine 16 has six cylinders each Witlh an associated spark plug for igniting combustible I fuel in the corresponding cylinder and that the engine is of the usual four-cycle type. The proper timing relation for firing the fuel in the engine cylinders is provided by yengine ignition means 12 which will ordinarily comprise circuitry including six spark plugs, one for each cylinder of engine .10. The function of the remainder of the ignition system of FIG. 1 is to provide appropriate voltage pulses to the engine ignition means in sequence so that each voltage pulse fires the proper spark plug at the proper time.

To accomplish proper timing, there is provided an alternating voltage generator 14 =which is driven from the engine vcrank shaft 16 b-y Way of appropriate gearing 18, so as to produce at its output terminal 20 a train of pulses of alternating polarity in synchronism with rotation of cnank shaft 16. The gearing 18 is such 'as to provide the desired integral multiple relationship between the frequency of rotation of crank shaft 16 yand the frequency of recurrence of pulses at the output of generator 14, which may be provided by any suitable voltage generator.

The alternately opposite polarity voltage pulses from voltage generator 14 are supplied to rectifying means 22. 'Ilhe rectifying means 22 may be provided by a diode which passes positive polarity pulses, for example. The pulses from the rectifying means 22 are applied to capacitive means 24, which is responsive to the input pulses supplied thereto from the rectifying means 22 to charge 'a capacitor therein. The capacitor in the capacitive means is electrically connected to switch means 26 which has, in this example, six output connections 28, 30, 32, 34, 36 and 38, each of wlhich is effective to produce a capacity discharge from capacitive means 24 through a dilferent particular one of the spark plugs in the engine ignition means 12, depending upon which of input lines 40, 42, 44, 46, 48 and 50 is supplied with a trigger control pulse for triggering the discharge. More specifically, input lines 40, 42, 44, 46, 48 and 50 conduct input trigger pulses to different ones of six silicon-controlled rectiers, for example, to actuate a particular one of the silicon-controlled rectiers to connect the capacitive means to re one of the six spark plugs connected to output lines 28, 30, 32, 34, 36 `and 38, respectively, between the switch means and engine ignition means. Therefore, to produce firing of any one of the six cylinders by engine ignition means 12, it is only necessary to apply a trigger control pulse to the appropriate one of tihe trigger input lines 40-50 to render conductive the appropriate one of the silicon-controlled rectifiers in the switch means 26, thereby permitting current to flow from the capacitor to the appropriate spark plug.

To generate the necessary trigger pulses at the required times in relation to the phase of engine operation for which fuel combustion is desired, there is preferably ernployed trigger pulse generator 52 having output leads 40-50. In general, the trigger pulse generator may preferably comprise a number of conductors equal to the number of cylinders of the engine, spaced from each other circumferentially around a center, and a magnet having a pole which is Irotatable about its center so as to induce pulses sequentially in the several conductors. The rotatable element in the trigger induction generator may be feared to crank shaft 16 of engine 10 by way of gearing 18 so that trigger pulses are produced by the generator at a rate in sequence with engine operation to actuate the switch means to discharge the capacitor therethrough to fire the appropriate spark plug. The triggering induction generator would Abe arranged so that trigger control pulses iare produced at its output lines on the proper lines for effecting the desired sequences of spark plug firing, this sequence being selected in appropriate fashion for the particular engine application according to principles well known in the art.

The details of the circuitry and construction of an overall ignition system in accordance with the block diagram described above is disclosed in detail in the abovementioned copending application of Gibbs et al. This type of high frequency ignition system has proved to be very advantageous and it is desirable to use such ignition systems for replacement of conventional magneto ignition systems employing breaker point apparatus and distributors. However, due to the short energy duration upon discharge of the capacitive means, the high frequency ignition systems have not been directly interchangeable with conventional ignition systems only because of the often encountered engine monitoring safety network. In order to provide the interchangeability of the high frequency ignition system for the conventional magneto ignition system of the prior art, and further to insure accurate and dependable operation of the ignition system safety devices, a safety adapter circuit is provided with the conventional detecting network.

A preferred overall safety circuit generally designated 6) in FIG. l embodying the present invention comprises unidirectional current flow means 62 connected to the output of rectifying means 22 and in parallel with capacitive means 24. The positive output pulses from the rectifying means are passed through the unidirectional current flow means and applied to charge storage means 64. The charge storage means is responsive to the input pulses to charge, for example, a capacitor, in response to each of the input pulses. The charge storage means 64 is discharged through control means 66 upon actuation of detecting means 63, the control means providing an electrical connection between the charge storage means and the detecting means. Detecting means 68 is preferably part of the engine monitoring network employed to detect malfunction of the engine. Preferably, when a malfunction is detected the detecting means is actuated to complete a circuit from the control means to electrical ground so that the charge storage means may discharge through the control means to provide a pulse of sulcient energy to actuate relays or other apparatus in the control means. The control means may be employed to cause stopping of operation of the engine upon the occurrence of a malfunction and actuate a visual indicator to immediately indicate the malfunction of the engine detected by the particular detecting means.

Referring to FIG. 3, there is shown a preferred ernbodiment of `a safety circuit, which could be employed as safety circuit 60 in the system of FIG. 1. The unidirectional current ow means is provided by a diode 80 having its anode element connected to the output of the rectifying means 22 (not shown) and its cathode element connected to the charge storage means 82, a capacitor, to charge the capacitor with positive pulses from the rectifying means. Capacitor 82 is connected by electrical lead 84 to control means 86, which is connected to detecting means 88. A plurality of other electrical leads 90, 92 and 94, for example, may connect other control means and detectors to capacitor 82, as indicated in FIG. 3, control means 86 and detecting means 88 being shown as representative of each unit. Each detector would be provided to monitor a desired operation of the engine, such as, engine temperature, oil pressure, speed, etc.

In the present instance, the control means 86 comprises a conventional electromechanical transducer or relay 100 having a coil 101 connected in electrical line 84 and an armature 102 which serves to move a pivoted latch arm 104 upon energization of the coil to permit release of a spring biased lever 106. The lever 106 is electrically conductive and is connected to and pivots about terminal 108, which is connected to electrical line 84. Lever 106 when released from latch arm 104 is moved by spring 109 to the alternate position indicated in FIG. 3 to contact terminal 110, which is connected to electrical ground. Lever 106 also actuates pushbutton indicator 112 to move its plunger 112a outwardly to provide a visual indication of the particular malfunction of the engine sensed by detector 88, as indicated by the alternate position of the plunger in FIG. 3.

The detector 88 for sensing `a particular malfunction of the engine may comprise, for example, a meter 114 for indicating oil pressure by a movable element or pointer 116 on dial 118 in a conventional manner. Meter 114 has an input terminal 120 connected to the coil 100 and an output terminal 122 connected to electrical ground. Movable element 116 of meter 114 is connected to input terminal 120 `and is movable to contact output terminal 122, when the oil pressure drops below a predetermined minimum level to complete the circuit through the meter. When the movable element completes the circuit through the meter, capacitor 82 discharges through coil 100 and the meter circuit. Upon this occurrence, armature 102 in the coil will be actuated to disengage latch arm 104 from lever 106 permitting the spring biased lever 106 to contact terminal 110 and the plunger of indicator 112, thereby providing a visual indication of the malfunction. In addition, in this arrangement, when the circuit is completed through the meter to connect capacitor 82 to electrical ground, the capacitive means of the ignition system is also connected to electrical ground to stop engine operation before the engine is damaged. After the oil pressure is brought up to a suitable level, movable element 116 moves away from output terminal 122. However, the ignition system will remain grounded and the engine stopped until the plunger of indicator 112 is depressed to move lever 106 to a position where interlocking of latch arm 104 and lever 106 occurs, at which time the ignition system is in proper order for operation. The ignition system will normally work in the manner described unless manual kill switch 124 is closed between electrical lead 84 and electrical ground to connect capacitor 82 and capacitive means 24 to electrical ground, stopping engine operation.

The capacitor 82 employed in the safety circuit is preferably of a larger value than the capacitor in the capacitive means of the ignition system in order to store more energy to accurately and properly actuate the electromechanical transducer or relay in the control circuit for providing the desired visual indication of the cause of malfunction of the engine and for providing stoppage of engine operation. The pushbutton indicator, latch arm and lever arrangement in the control circuit 86 may be provided by a conventional safety switch, such as manufactured by Frank W. Murphy Mfg., Inc., of Tulsa, Okla.

Referring to FIG. 2, there is shown an ignition system which is characterized by a split bridge rectifier circuit especially adapted for use with engines having a large number of cylinders. The ignition system shown in FIG. 2 is similar to that shown in FIG. 1 except the alternating current generator in FIG. 2 is connected to two separate capacitive means to charge them and the capacitive means are separately connected by controllable switch means to corresponding different sets of six. fuel ignition means for the engine, each of which ignition means may include the usual spark plug as the fuel igniting element, for example. More specifically, there is represented in FIG. 2 a gasoline engine 150, and, in this example, it will be assumed that the engine has twelve cylinders each with associated spark plug for igniting gas in the corresponding cylinder and that the engine is of the usual fourcycle type. There is provided an alternating voltage in generator 154 which is driven from the engine crank shaft 156 by way of appropriate gearing 158, so as to produce at its output terminal 160 a train of pulses of alternating polarity in synchronism with rotation of thet crank shaft 156.

The pulse train from generator 154 is applied in parallel to a first rectifying means 162 and a second rectifying means 164, first rectifying means 162, for example, being responsive only to positive pulses from generator 154 and second rectifying means 164 being responsive only to negative pulses to pass current therethrough.

In the ignition system Yof FIG. 2, the pulses from first rectifying means 162 are applied to rst capacitive means 166, While the output of second rectifying means 164 is connected to second capacitive means 168. The first ca-` pacitive means 166 is electrically connected to first switch means and the second capacitive means 168 is electrically connected to second switch means 172. In this example, first switch means 170 has six output connections each of which is effective to produce capacity discharge from capacitive means 166 through a particular one of the spark plugs in engine ignition means 150, depending upon which of the input lines from triggering pulse generator 174 is supplied with a control pulse for triggering the discharge through a particular silicon-controlled rectifier associated with one of the six connections. Similarly, second switch means 172 has six output connections, each of which is effective to produce capacity discharge from capacitive means 168 through a different particular one of the spark plugs in the engine ignition means 152, depending upon wsich of the input lines from triggering pulse generator 174 is supplied with a control pulse for triggering the discharge of a particular siliconcontrolled rectifier, associated with a particular output connection. First switch means 170 and second switch means 172 are each eifective to produce firing of a different set of six spark plugs in the engine ignition means by Iway yof their associated output connections to the ignition means. Accordingly, to produce firing of any one of the twelve cylinders by the ignition means 152, it is only necessary to apply a trigger control pulse to the appropriate corresponding one `of the input lines to one of the rst or second switch means. The triggering pulse generator in this example may comprise a number of conductors equal to the number of cylinders in the engine, spaced from each other circumferentially around a center, and a magnet having a pole which is rotated about said center so as to induce pulses sequentially in the several conductors. The triggering pulse generator may have its rotating element geared to crank shaft 156 by way of gearing 158. The connections from the triggering pulse generator to the twelve input connections for the two switch means circuits are so arranged that trigger control pulses are produced at the output leads of generator 174 on the proper leads for effecting the desired sequences of spark plug firing, this sequence being selected in appropriate fashion for the particular engine application according to principles well known in the art. The details of circuitry and construction of an overall ignition system which corresponds to the parts thus far described in FIG. 2 are shown and described in the above-mentioned copending application of Gibbs et al.

The block diagram f FIG. 2 has a safety circuit generally designated 180 electrically connected to the circuit of the ignition system. In this instance, safety circuit 180, which includes the present invention, comprises unidirectional current fiow means 182 electrically connected to the output of first rectifying ymeans 162 and in parallel with first capacitive means 166. The positive output pulses from the first rectifying means pass through the unidirectional current fiow means and are applied to charge storage means 184, which is responsive to the input current pulses to charge a capacitor therein to store the energy. Charge storage means 184 may be discharged through control means 186 upon actuation of detecting means 188, the control means providing an electrical connection between the charge storage means and the detecting means. The safety circuit of FIG. 2, which is somewhat similar to the safety circuit of FIG. 1, preferably has the detecting means as part of the engine monitoring system employed to detect malfunction of the engine.

Circuit means 190 is provided as part yof the safety circuit of FIG. 2 and is electrically connected to the output of second rectifying means 164 and in parallel with second capacitive means 168. The circuit means provides an electrical path, for example, to facilitate grounding of the second capacitive means through the control means so that the engine will be stopped upon detecting a malfunction. The circuit means could be alternatively connected, as shown in FIG. 2, to the charge storage means 184 or to the control means 186 to provide the desired function of stopping engine operation, for example.

The details of circuitry to provide preferred safety circuits operable with the ignition system of FIG. 2 will now be described with specific reference to more detailed showings of other drawings. Referring to FIG. 4, there is illustrated one form for safety circuit 180 of FIG. 2. The Safety circuit of FIG. 4 comprises a diode 200 providing unidirectional current iiow means having its anode element connected to the output of first rectifying means 162 and its cathode element connected to charge storage means 202, which is a capacitor, whereby pulses from the first rectifying means charge the capacitor. Control means 204 electrically connects capacitor 202 to detector 206. Similar control means and detectors could be connected to the capacitor by leads 210 and 212, for example, to monitor any number of functions associated with the engine. The detector of FIG. 4 may be of any conventional type and it will be assumed in this example that it is used to measure engine temperature. The detector shown has an input terminal 214 connected to the control means, an output terminal 216 connected to electrical ground and a movable indicator 218 to provide an indication of engine temperature. When the engine temperature reaches a predetermined undesirable level, the movable element will contact output terminal 216 to complete a circuit through the detector.

The control means in this instance comprises a conventional electromechanical transducer 220 including a coil 221 connected between line 208 and the input of the detector `and an armature 222, similar to the transducer of FIG. 3. When the coil is energized, it moves associated :armature 222 to actuate a latch member 224, which is adapted to hold a spring biased lever arm 226 in fixed position until the latch is released. When the latch arm 224 is actuated by movement of armature 222 upon energization of coil 220, spring biased lever arm 226 will be moved to actaute pushbutton indicator 228, which indicates the particular malfunction of the engine. In this arrangement, when the movable element of the detector provides a circuit therethrough, the capacitor 202 will be grounded through the control circuit and detector, and output of the first rectifying means will be connected to electrical ground through diode 200, control circuit 204 and detector 206.

Circuit means 190 of FIG. 2 in this instance is provided by a diode 230. The anode element of diode 230 is connected to the output of the second rectifying means of FIG. 2 (not shown) and its anode is electrically connected to the capacitor 202. Current pulses from the second rectifying means pass through diode 230 to charge capacitor 202 but discharge of the capacitor through diode 230 is prevented. Diode 230 provides an electrical path from second rectifying means 164 to the control means and detector for grounding the other set of ignition pulses when a malfunction of the engine is detected to stop engine operation.

Capacitor 202 is preferably of a larger value of either of the capacitors of the first and second capacitive means in order to store more energy for accurately and dependably actuating electromechanical transducer 202 which actuates apparatus for providing an immediate indication of the malfunction of the engine. The system will normally work in the manner described unless manual kill switch 232 connected between line 208 and electrical ground is closed to provide a circuit to electrical ground for capacitor 202, first rectifying means 166 and second rectifying means 168 so that appropriate ignition pulses are prevented from being applied to the engine ignition means.

FIG. 5 illustrates an alternative form of the safety circuit of FIG. 2. The modified safety circuit shown in FIG. 5 has parts similar to those in the safety circuit of FIG. 4 and similar parts in FIG. 5 are identified by the same number designators with the addition of primes thereto. The primary difference lies in the circuit means for providing a connection from the output of the second rectifying means of FIG. 2 to the control means 204'. In the present instance, the circuit means comprises electrical lead 240 for providing a connection between the output of second rectifying means 164 of FIG. 2 (not shown) and a contact 242 in the control circuit. The pivotally mounted lever arm 226' in the control circuit 204' is adapted to contact 242 when `released by latch arm 224'. Also, lever arm 226 is adapted to contact contact 244, which is connected to el-ectrical ground, when contact 242 is contacted, to provide a circuit from the second rectifying means through latch arm 226 to electrical ground so that both the first and second rectifying means are connected to electrical ground when coil 220 is energized for stopping engine operation and indicating a malfunction in the engine.

FIG. 6 illustrates still another form for the safety circuit 180 of FIG. 2. The modified safety circuit shown in FIG. 6 has parts similar to those in the circuit of FIG. 4, land parts similar to those in the system of FIG. 4 are identified `by the same number designator with the addition of double primes thereto. The primary difference lies in the control means 204 for controlling engine operation. In the present instance, coil 220" connected between capacitor 202 and detector 206 is energized to actuate armature 222, which is mechanically connected to an engine fuel shut-off valve 250 in engine fuel supply line 252. Capacitor 202 is of a value to store sufficient energy to assure accurate and dependable actuation of the coil 220 to move the armature to close valve 250. When a malfunction in the engine is detected by detector 206, capacitor 202 will discharge through the coil and detector to close valve 250 in the engine fuel supply line to assure that the engine will not receive fuel, avoiding any possible diesel action in stopping the engine.

In using high frequency capacity-discharge ignition systems, a steep-rising and narrow pulse is applied to the spark plugs to provide greater accuracy of firing the spark plugs. With these narrow pulses, less electrical energy is dissipated through the spark plug With a resultant Ireduction in erosion of the electrodes of the plug and, hence, increased service life of the plugs. Also, in such ignition systems, more reliable firing of the spark plugs fouled by a partially-conductive film is obtained, due to the rapid rise time of the pulse which apparently prevents energy of the pulse from leaking off through the film. It will be observed that the safety circuit of the present invention provides means capable of accurately and dependably actuating safety control means employed with conventional magneto ignition systems. The safety adapter circuit of the present invention enables high frequency capacity-discharge ignition systems to be compatible with, and readily capable of substitution into, engine systems of existing types to provide the desired stopping of the engine and actuation of indicators for immediate determination of the engine malfunction.

The present invention has been described with reference to specific embodiments and alternative embodiments of various portions of the system. It should be understood that each of the specific embodiments can employ substitution of parts disclosed in alternative embodiments, land substitution of equivalent parts from specific embodiments, without departing from the basic concept.

Other modifications of the present invention and its forms described herein will occur to those skilled in the art. All such modifications are intended to be within the scope and spirit of the invention as dened by the appended claims.

I claim:

1. In an ignition system safety circuit for an internal combustion engine including capacitive means, means for charging the capacitive means, engine fuel ignition means, switch means for connecting the capacitive means to the ignition means, and means for actuating the switch means to connect the capacitive means to the ignition means for discharging the capacitive means through the' ignition means in synchronism with engine operation, the combination therewith of charge storage means; unidirectional current ow means for connecting the means for charging the capacitive means to the charge storage means to charge the charge storage means; detecting means actuatable to complete a circuit upon detecting a malfunction in the engine system; and control means for electrically connecting the charge storage means to the circuit of the detecting means and having malfunction indicating apparatus, whereby when a malfunction occurs the charge storage means will rdischarge through the control means for actuating the malfunction indicating apparatus.

2. The ignition system safety circuit of claim 1 in which the charge storage means includes a capacitor of larger value than the capacitive means for storing more energy to energize the control means when a malfunction is detected.

3. The ignition system safety circuit of claim 1 in which the unidirectional current iiow means includes a diode.

4. The ignition system safety circuit of claim 1 in which the control means in response to discharge of the charge storage means actuates means for providing a visual in dication of the malfunction.

5. The ignition system safety circuit of claim 1 in which the control means comprises an electromechanical transducer and a pair of contacts which are actuated closed for short-circuiting the capacitive means upon energization of the electromechanical transducer by discharge of the charge storage means, thereby stopping engine operation.

6. The ignition system safety circuit of claim 1 in which the control means comprises an electromechanical transducer and a valve means which is actuated closed for stopping iiow of fuel to the ignition means upon energization of the electromechanical transducer by discharge of the charge storage means, whereby upon closing of the valve the engine will be stopped.

7. The ignition system safety circuit of claim 1 in which the control means comprises an electromechanical transducer and a visual indicator actuated upon energization of t'he electromechanical transducer by discharge of the charge storage means for providing visual indication of the malfunction of the engine.

-8. In an ignition system safety circuit for an internal combustion engine including means for generating a series of pulses of alternating polarity, iirst capacitive means, tirst means selectively responsive to the pulses of one polarity for charging the first capacitive means, second capacitive means, second means selectively responsive to the pulses of the other polarity for charging the second capacitive means, a first and a second set of engine fuel ignition means, rst Switch means for connnecting the first capacitive means to the iirst set of ignition means, second switch means for connecting the second capacitive means to the second set of ignition means, and means for actuating the rst and second switch means to discharge the first and second capacitive means through the respective ignition means of the first set and second set in synchronism with engine operation, the combination therewith of: charge storage means, unidirectional current iiow means for connecting the first means selectively responsive to pulses to the charge storage means for charging storage means, detecting means actuatable to complete a circuit upon detecting a malfunction in the engine system, control means for electrically connecting the charge storage means to the circuit of the detecting means and having malfunction indicating apparatus, whereby when a malfunction occurs the charge storage means will discharge through the control means actuating the malfunction indicating apparatus.

9. The ignition system safety circuit of claim 8 furthe comprising circuit means for connecting the second means selectively responsive to pulses to electrical ground upon discharge of the charge storage means so that when a malfunction is detected the rst and second capacitive means will be connected to electrical ground stopping engine operation.

10. The ignition system safety circuit of claim 9 in which the circuit means includes second unidirectional current iow means for connecting the second means selectively responsive to pulses to the charge storage means so that when the charge storage means is discharged the second means selectively responsive to pulses will be connected to electrical ground.

11. The ignition system safety circuit of claim 10 in which the first-mentioned unidirectional current flow means and the second unidirectional current flow means each include a diode.

12. The ignition system safety circuit of claim 9 in which the control means comprises an electromechanical transducer energized by discharge of the charge storage means yand the circuit means compirses a pair of contacts which are electrically connected upon energization of the electromechanical transducer fol connecting the second means selectively responsive to pulses to electrical ground to stop engine operation.

13. The ignition system safety device of claim 12 in which the malfunction indicating apparatus includes a visual indicator and the electromechanical transducer when energized actuates the visual indicator.

14. The ignition system safety circuit of claim 8 in which the charge storage means includes a capacitor of larger value than either of the capacitive means for storing more energy to energize the control means when a malfunction is detected.

15. The ignition system safety circuit of claim 8 in which the control means comprises an electromechanical 1 1 1 2 transducer and a visual indicator which is actuated upon References Cited energization of the electromechanical transducer by dis- UNITED STATES PATENTS charge of the charge storage means for providing Visual indication of the malfunction of the engine. /[ellerttegl 73-117'3 16. The ignition system safety circuit of claim 8 in 5 3316449 4/1967 Quinn 315 226 X which the control means comprises an electromechanical transducer and valve means which is `actuated closed for RICHARD C. QUEISSER, Primary Examiner.

stopping flow of fuel to the ignition means upon energiza- TERRY W. MYRACLEI ASSI-Smm Examinertion of the electromechanical transducer by discharge 'of the charge storage means, whereby upon closing of the l0 U-S. Cl- X-R- valve the engine will be stopped. 340. 4195 324 19 315 352 UNITED STATES PATENT OFFICE CERTIFICATE 0F CGRRECTION Patent No. 3,421, 368 January l4 1969 Joe Baron Stephens It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column l, line l5, "conventiontl" should read conventional Column 4, line 24, "feared" should read geared Column 6, line 29, "thet" should read the line 56, "wsich" should read which Column 8, line 48, "to contact 242" should read to Contact Contact 242 Column lO, line 40, "the comprising" should read ther comprising Signed and sealed this 24th day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

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