US2568125A - Heater ignition system - Google Patents

Description

Sept. 18, 1951 G. JACOBS HEATER IGNITION SYSTEM Filed Nov. 18, 1948 Patented Sept. 18, 1951 UNITED STATES PATENT OFFICE HEATER IGNITION SYSTEM Application November 18, 1948, Serial No. 60,747

2 Claims. 1

The present invention relates to heating systems and more particularly to a spark ignition system intended to be used as a part of aircraft combustion type heaters. An aircraft heater of the type illustrated and described in the copending application of Seymour E. Heymann, Serial No. 610,978, now Patent No. 2,454,512, burns liquid fuel, usually the same fuel supplied for the aircraft engine and has an extremely high output considering its weight and size. One of the important accessories used with such a heater is the system for igniting the fuel. One system commonly used for this purpose includes a spark plug which is supplied with electric energy at high voltage so as to produce a spark of sufficient intensity to ignite the fuel and air mixture within the heater.

The present invention is concerned with the provision of such a spark ignition assembly and has as one of its objectives the provision of an improved spark ignition system which is extremely reliable.

Another object is to provide a novel spark ignition system which can be put into operation from a remote point and which can otherwise be controlled remotely.

Yet another object is to provide an improved spark ignition system which does not interfere with radio and radar equipment with which the airplane usually will be provided.

Still another object is to provide a novel heater ignition system in which the components of the system which are most likely to cause service difliculty may be changed at will during flight even though the heater is located in an inaccessible position.

Other objects and advantages will become apparent from the following description of a preferred embodiment of my invention which is illustrated in the accompanying drawing.

The single figure of the drawing is a diagrammatic representation of an electrical circuit which embodies the present invention.

The ignition system which comprises the present invention consists generall of a spark plug I located within the combustion heater and normally forming a part thereof, this spark plug being connected by a shielded cable to a quick disconnect I 2, the other half of which is mounted upon a box, not shown, which contains the major portion of the ignition system. High voltage electric current is supplied to the disconnect l2 and therefore to the spark plug III by the secondary ll of a step-up transformer [6, the primary I8 of which is supplied with pulsating di rect current from a battery 20 by way of vibrator type circuit interrupters 22 and 24, the battery being connected to the ignition box by way of a quick disconnect 26.

In such an ignition system the weak link, in other words, the element most likely to get out of order, is the vibrator 22 or 24. These devices which are commonly available consist in general of a tuned reed which vibrates in the field of an electromagnet and which rapidly makes and breaks an output circuit. Although these vibrators, so-called, are commonly available well engineered devices and well suited in general to their purpose, the constant sparking at the contacts together with the rather large electrical load imposed thereon by the transformer primary I 8 is likely to cause the vibrators to fail while in use. Such failure in an aircraft heater installation may have rather serious consequencies, particularly if the heater is used for anti-icing purposes. That is, in some applications high output heaters of the type mentioned are used for raising the temperature of the wings and tail surfaces of aircraft so as to prevent the formation of ice thereon. Any failure of the heating system thereof may result in the rapid accumulation of ice upon the aircraft.

It has been found in use that the basic heater,

the spark plug used therewith, the transformer and the other elements of the system are quite dependable and that, as mentioned previously, the principal service difliculty will be experienced with the vibrator. In order to contribute to the safety of this heater, therefore, I have provided two vibrators, indicated by the numerals 22 and 24, and have so arranged the circuit that either of these vibrators may be used at the will of the operator for operating the ignition system. Further, I have arranged for these vibrators to be located within the box usually attached to the heater which contains all of the ignition equipment so a to provide for better radio shielding and have arranged the circuit such that either of the vibrators may be used at will and such that an operator can switch from one vibrator to the other by merely actuating a momentary contact push button conveniently disposed at a remote location.

Specifically, the circuit comprises the aircraft battery 28, one side of which is grounded while the other side is connected by a lead 28 to the quick disconnect 25, half of which is secured. to the metal box containing the ignition equipment. From the disconnect 25 a lead 35 passes to a choke capacitor filter system 32 and thence by way of a conductor 25 to one side of each of the primary [8 and secondary [4 of the ignition transformer l6;

As previously mentioned, the other side of the transformer secondary i4 is connected to the disconnect l2 and thence to the spark plug [9. The other side of the transformer primary I8 is connected by a lead 34 to a terminal 35 of the vibrator 22 which in turn is connected by a branch 38 to the similar terminal 40 of the other vibrator 24. The vibrator 24 also has a second terminal 42 connected by a lead 44 to the similar terminal 46 of the other vibrator 22 and to ground. A 9.25 m. f. d. capacitor 48 is also connected between the ground point of the lead 44 and the lead'34 leading to the ignition transformer primary for the purpose of suppressing arcing at the vibrator contacts.

A stepping relay 59 which may be of any wellknown construction is of the single pole double throw type and comprises a swinging contact member 52 which in one position is associated with a stationary contact 54 while in the other position the movable member 52 is connected to another stationary contact 55. The movable member 52 is operated by an electromagnetic coil 58 and the mechanism is so arranged that when the coil 58 is momentarily energized the movable member 58 will be shifted from one position to the other. Whenever the coil 58 is again momentarily energized the movable member 52 will be shifted back to its original position and so on. One side of the coil 58 is grounded while the other side thereof is connected by a lead 59' through a normally open push button 52 to the previously mentioned lead 25.

The push button 52 is mounted upon the metal ignition box and the circuit is such that whenever the push button 62 is depressed rnomentarily the coil 58 will be momentarily energized, thereby shifting the position of the movable contact 52 of the stepping relay. The ungrounded side 28 of the battery 29 is also connected through a lead 54 and push button 66 to one-half of a quick disconnect 68. The other half of this disconnect is mounted upon the ignition box and internally of the box is connected to a lead 70 which passes through a choke capacitor filter network 12 and thence to the lead 60 at a point between the push button 92 and the coil 58. The push button 55 is remotely located within reach of one of the crew men of the aircraft and serves when actuated to energize the coil 58 momentarily so as to shift the position of the stepping relay 59 in the same manner that the position of the relay is shifted by the push button 52.

The stationary contact 56 of the stepping relay switch is connected by conductor '34 to a terminal of the vibrator 22 while a similar terminal 78 of the vibrator 24 is connected by a lead 59 to the other stationary contact 54 of the step-ping relay switch. The swinging element 52 of this switch is connected by a lead 82 to the lead by way of a resistor 84 which in the present instance has a resistance of approximately ohms.

The internal circuit of the vibrator 22 comprises the vibrating reed 85 previously referred to which is connected to the terminal 46. This reed is also electrically connected to one end of a magnetic coil 83, the other end of which is connected to the terminal 75. The vibrator has two stationary contacts therein adapted to be engaged by the vibrating reed 83 alternately when the reed is in the alternate extreme positions.

4 One of the stationary contacts is indicated by the numeral 99 and is connected to the terminal 36. The other stationary contact, indicated by the numeral 92 is, as is one end of the coil 88, connected to the terminal 16.

The elements of the vibrator 24 duplicate those of the vibrator 22 so that the vibrating reed 94 of the vibrator 24 is the counterpart of the reed 86 previously mentioned. Similarly, contacts 95 and 98 are counterparts of the contacts 99 and 92 and the coil Hill is the counterpart of coil 88.

The circuit operates in the following manner. Assuming that the disconnects 25, 28 and i2 are properly joined and that the stepping relay is in the position shown with movable contact '52 against stationary contact 54, it will be seen that electric power is supplied from the battery 29 through the disconnect 28 and filter system 32 to the lead 25 and thence to one side of the transformer primary [8. This lead is also connected to the secondary Hi. The lead 34 is therefore energized through the transformer primary and therefore raises the potential of the vibrator contacts 99 and 55 to that of the battery. No current flows through the circuit, however, since the contacts 99 and 99 are separated from their reeds 94 and 89 respectively. Current is also supplied from the lead 25 through the resistance 84 to switch blade 52 and thence by way of switch contact 54 to terminal is of the vibrator 24. The current passes from the terminal "l8 through the coil Hi8 and by way of the lead 94, terminal 42 and lead 44 to ground. The coil I59 is therefore energized. This attracts the reed 94 until it strikes contact 98 and results in both sides of the coil I99 being connected to the reed 94. The coil is therefore shorted out of the circuit and no longer attracts the reed 94.

The reed because of its spring action therefore swings in the opposite direction and although soon thereafter the contact 98 is separated from the reed. 94 so as to re-energize the coil I the reed overshoots the central position and strikes contact 95. The circuit through the transformer primary I 8 is therefore momentarily completed since the lead 34 is connected by way of terminal 36 and thence by lead 38 to terminal 49, the latter terminal in turn being connected through contact 96 and reed 94 to ground by way of the lead 44. Soon thereafter the reed 94 springs away from the contact 96, thereby opening the circuit of the transformer primary [8 so as to repeat the cycle. During the time the reed 94 and contact 98 short out the coil I09, the resistor 84 which is connected between the main line 25 and the movable contact 54 of the stepping relay switch protects the circuit against high current flow.

Inasmuch as the stepping relay switch contact 56 is not connected to the swinging member 52 thereof, the vibrator 22 does not operate since the coil thereof is not energized. Under these conditions the reed 86 maintains a central position between the contacts 90 and 92 such that no circuit is made from the battery through the transformer primary [8 to ground by Way of the vibrator 22. This latter vibrator therefore simply remains in reserve until needed. At any time by depressing either the push button 62 or the button 55 the stepping relay coil 58 can be energized in the manner previously described so as to shift the swinging contact 52 away from the contact 54 and against the contact 55. This removes the vibrator 24 from operation and causes current to flow through the resistor 84 by way of stepping relay switch contacts 52 and 56 to the lead 14 connected to the terminal 16. Since this latter terminal is connected to ground through the vibrator coil 88 the coil 88 will attract its vibrating reed and move it against the contact 92 so as to short out the coil 88, thus permitting the reed 86 to swing backwardly. Like the reed 94 it overshoots its central point and impinges against the contact 90 long enough to cause a surge of cur-- rent to pass from the line 25 through the transformer primary l8 and through contacts 90 and 86 to ground.

The periodic electrical surges in the transformer primary 18 of course induce like surges, excepting that they are at a stepped up voltage, in the transformer secondary [4. These high voltage surges in a well-known manner cause sparking at the spark plug l so as to produce ignition for the heater.

It will be seen that the system described provides for high voltage'operation of the heater spark plug by a step-up transformer, the primary of which receives low voltage current surges at high frequency and that the transformer primary circuit is made and broken by means of an independent vibrating switch, two of which are provided, such that either one may be used in the circuit and that whenever one of these is used the other is disconnected from the circuit and held in reserve and further that the choice as to which of the vibrators is to be in the circuit at any particular time can be determined by an operator located at a remote point simply by momentary actuation of an ordinary push button.

Having described my invention what I claim as new and useful and desire to secure by Letters Patent of the United States is:

1. A heater ignition system of high voltage type comprising a heater igniting spark plug, a transformer having a secondary connected for energizing said spark plug, a primary in said transformer for energizing said secondary, and a circuit for energizing said primary including a battery and means connecting one side of said battery to one side of said transformer primary, first and second stationary contacts arranged in spaced apart opposed relation, a vibratable reed disposed between said spaced apart contacts, electromagnetic means for attracting said reed to said second stationary contact when energized, said reed having sufiicient resiliency to spring from said second contact to said first contact when said electromagnetic means is de-energized; means duplicating said first and second contacts, said reed and said electromagnetic means; circuit means connecting the other side of said primary to both said first contacts, circuit means connecting one side of each of said electromagnetic means to both of said reeds and to the other side of said battery, means connecting the other side of each of said electromagnetic means to its co-operating said second contact, circuit means connected to said one side of said battery and including a current limiting resistor, switching means for connecting the last said circuit alternately to either one or the other of said second contacts, electromagnetic means for operating said switching means, and remotely operated circuit means for operating the last said electromagnetic means.

2. An ignition system for a heater to provide an uninterrupted succession of fuel igniting sparks, comprising a transformer having a high voltage secondary and a low voltage primary; a heater igniting spark plug connected with the secondary for energization; a first vibrator having first and second stationary contacts, a vibratable reed carrying a third contact positioned between the stationary contacts, and an electromagnet adjacent the reed for pulling it toward the second contact for vibrating the reed, the electromagnet being shunted across the second contact and the reed; a second similar vibrator; first and second direct current power input terminals, one side of the transformer primary being connected with the first input terminal and the reeds of both vibrators being connected with the second input terminal, the other side of the primary being connected with the first stationary contacts of both vibrators; a. current limiting resistor; a push button switch; a stepping relay including a pair of contacts respectively connected with the second contacts of the vibrators, contact means connected through the resistor with the first input terminal, and means including a magnetic coil for establishing a connection between the contact means and the respective relay contacts alternately in response to successive intervals of energization of the coil, for energizing the vibrators alternately, one side of the coil being connected with one of the power input terminals, and the other side of the coil being connected through the push button switch with the other power input terminal.

GERALD JACOBS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,102,593 Kettering July 7, 1914 1,275,047 Krantz Aug. 6, 1918 1,946,607 Afiel Feb. 13, 1934 2,221,521 Maycock Nov. 12, 1940 2,330,431 Klatsch Sept. 28, 1943 2,427,076 Tabecchi Sept. 9, 1947

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