US2881587A

US2881587A - Electrical apparatus having means to control the supply of energy from a coil to a plurality of circuits

Info

Publication number: US2881587A
Application number: US530073A
Authority: US
Inventors: Donald C Loudon
Original assignee: Bendix Aviation Corp
Current assignee: Bendix Aviation Corp
Priority date: 1955-08-23
Filing date: 1955-08-23
Publication date: 1959-04-14
Anticipated expiration: 1976-04-14

Description

April 14, .1959 D. c. LoUDoN ELECTRICAL APPARATUS HAVING MEANS To CONTROL. THE SUPPLY 0E ENERGYfERoM A con. To A RLURALITY 0E cxRcUITs Filed Aug. 23, 1955 Om/ mi United States Patent O ELECTRICAL APPARATUS HAVING MEANS TO CONTROL THE SUPPLY OF ENERGY FROM A COIL TO A PLURALITY OF CIRCUITS Donald C. Loudon, Sidney, N.Y., assignor to Bendix Aviation Corporation, Sidney, N.Y., a corporation of Delaware Application August 23, 1955, Serial No. 530,073

17 Claims. (Cl. 60-39.14)

This invention relates to electrical apparatus and more particularly to a system which utilizes electrical energy for controlling the ilow and eiecting the ignition of fuel in an engine or the like.

One of the objects of the present invention is to pro vide a novel ignition and fuel flow control system for combustion engines or the like, such as so-called jet and gas turbine type engines.

Another object of the invention is to provide novel apparatus of the above character wherein a continuously operating magneto generator is utilized in a novel manner to supply energy for an intermittently operating ignition system.

A further object is to provide novel electrical apparatus in an engine or the like wherein the output of a single magneto generator is simultaneously employed for supplying energy to an ignition system for the engine and controlling the flow of fuel to be ignited.

Still another object is to provide novel apparatus for starting jet and gas turbine type engines and the like which is relatively light in Weight, safe in operation, simple in construction and low in cost.

A still further object is to provide a combined ignition and fuel ow control system which will accomplish results electrically in a more simple manner and more eiiiciently than similar results can be mechanically attained.

The above and further objects and novel features of the present invention will more fully appear from the following detail description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a deiinition of the limits of the invention.

In the drawings, Fig. l is a diagrammatic illustration of one form of ignition and fuel ow control system embodying the present invention and Fig. 2 is a detail view showing a modification thereof.

One embodiment of the invention is illustrated in Fig. l of the drawings, by way of example, in the form of an ignition and fuel ow control system for a so-called gas turbine or jet type of engine wherein electrical ignition means are required for starting purposes only and wherein such ignition is utilized for igniting an auxiliary or primer injection of fuel. Such injection and ignition is usually efected in a small supplemental combustion chamber adjacent to land in communication with the main combustion chamber of the engine in which continuous combustion is maintained during normal operation. Combustion in the main chamber is sometimes unintentionally or accidentally interrupted, such as during ight in an aircraft, and it becomes necessary to start it again with the electrical system of the present invention. During normal engine operation, the ignition system is preferably ineffective and the supply of primer or starting fuel is preferably interrupted while the ignition system is not functioning.

icc

In the form shown, a magneto generator 5 of the multipole rotating magnet type has a rotor 6 driven by a rotating part of the engine (not shown) on which the system is used. Although an eight-pole rotor is illustrated, the number of poles is not critical. The stator of the magneto generator comprises a coil or winding 7 which is divided into three parts 8, 9 and 10 by taps 11 and 12, the latter of which is connected to ground.

The upper end of section 8 of the coil 7, as viewed in the drawing, is connected for supplying energy to an ignition unit which comprises two parallel connected circuits for energizing two spark or igniter plugs 14 and 15 which are preferably of the shuntedsurfacegap type, such 'is the type shown in U. S. Patent No. 2,684,665, having a shunting resistance or semiconductor 16 bridging the sparking electrodes. The circuit for plug 14 comprises rectifier means 17, 17 which may be of any suitable known type to pass current of one polarity only and charge a relatively large storage condenser 18 which is connected between the rectiers and ground G. A rcsistance 19 may be connected in shunt with condenser 18 to dissipate residual energy when the engine is not in use. The illustrated rectiers are of the point to plane type but other known types, such as selenium rectiiiers, may be used.

Any suitable known means may be provided for controlling the discharge of storage condenser 18 across the electrodes of plug 14. In the form shown, said means comprises a three-electrode spark gap device 20 having a

shuntedsurface type gap

21, 22, the shunting resistor or semi-conductor being diagrammatically illustrated at 23, and a

main gap

21, 24, the latter having its electrodes so spaced that the maximum voltage attainable by condenser 18 will not normally initiate a discharge thereacross. A sealed control gap 25 designed to break down or become conductive when a voltage of predetermined magnitude is impressed across its electrodes is connected in series with a relatively small condenser 26 between gap electrode 22 and ground G. A resistance 27 may be connected across condenser 26 to dissipate any residual charge thereon between successive operating cycles to be hereinafter described. The electrode 24 of the spark gap device 20 is connected to the .ungrounded electrode of spark plug 14.

The circuit for spark plug 15 is identical with the circuit above described for spark plug 14 except that the rectifier means 17', 17 are connected to pass current of `a polarity opposite to that of the current passed by the rectiliers 17, 17. The corresponding parts of the circuits for the two sparking plugs are indicated by the same numerals, except that those in the circuit for spark plug 1S are primed. Also, a resistance 28 may be placed in the input lead for the rectifier tubes 17 Thus, during operation of the magneto generator 5, condensers 18 and 18 will receive, alternately, pulses of energy from winding 8, 9. When the relatively large storage condenser 18, for example, has been charged by a series of incremental charges to a suiciently high predetermined voltage to bridge the electrodes of control gap 25, said condenser will release a portion of its charge across

gap

21, 22 and the control gap 25 into the relatively small condenser 26. This iiow of energy between

electrodes

21 and 22 ionizes the gaseous medium between

electrodes

21 and 24 so that the remaining charge on the storage condenser 18 will bridge the

main gap

21, 24 and cause current ow across the gap between the shunted-surface electrodes of spark plug 14 in a known manner, creating a high energy ignition spark. It will be understood that at the same time-a charge is being built up on and discharged from condenser 18 to create an ignition spark across the electrodes of spark plug 15'.

Although the' sparks at plugs 14 and 15 may not be simul-V taneous, the sparking rate at each is substantially the same.

The components of the above ignition circuit are such that when the magneto generator rotor is driven by a starting motor or its equivalent at a relatively low speed, sucient energy will be supplied by winding 8, 9 to bring condensers 13 and 18' up to or above the predetermined voltage which will bridge .the control gaps 25 and 25', respectively. After discharge of each condenser, the cycle is repeated at a frequency which can be regulated by properly choosing the electrical constants of the circuit.

In order to preserve some of the less durable parts of the system, such as the spark gaps and igniter plugs, means are provided for rendering the above described ignition circuits ineffective while the engine is operating normally. Said means as shown comprise a switch 29 which is responsive to the speed of the engine and hence to the speed of the magneto rotor which is driven by the engine so that the ignition system is rendered inelective to create sparks at plugs 14 and 15 when the engine is operated above a selected predetermined speed. Switch 29 is normally open, but is actuated to closed circuit position at a predetermined engine speed by centrifugal or other suitable means in a manner well understood in the art. Any of many well known centrifugally actuated switches may be used for this purpose or the switch may be controlled `by other forces, such as fluid or gas pressures, which are functions of the engine speed. Switch 29 is connected in a lead between tap 11 and ground G through a second switch 30 that is normally closed and preferably manually actuated. Switch 30 is known as an air start switch when the system is used on aircraft and is used for rendering speed responsive switch 29 ineffective at all engine speeds when it becomes necessary or desirable to use the ignition system in flight, vsuch as when the llame in the main burner of the engine is blown out.

When switches 29 and 30 are both closed, thus connecting tap 11 to ground G, the central portion 9 of the magneto winding is shorted out and renders the winding incapable of charging condensers 18 and 18 to a sutilciently high voltage to break down

control gaps

25 and 25. sparking across any of the gaps, including the gaps of the igniter plugs 14 and 15.

Novelly associated with the above described ignition system are means subject to the same control for determining the flow of fuel to the combustion chambers which contain igniter plugs 14 and 15. As shown, said means comprises a solenoid, the coil 35 of which is connected at one end to ground and at its other end to the opposed or ungrounded ends of coil sections 9 and 10 through half

wave rectifier tubes

36 and 37, respectively. The latter are so. connected that pulses of like polarity pass alternately therethrough to energize solenoid coil 35. A condenser 38 connected between ground 4and the high potential end of coil 35 serves to smooth out the pulsating ow of energy to the coil. As shown, the rectiers are of the type commercially known as CKSS 17 tubes having starting electrodes connected to the supply line through

resistors

40, 40. The

small condensers

41, 41 connected between ground and the input terminals of

rectiers

36 and 37 are regulating condensers which aid in balancing the spark rate between igniter plugs 14 and 15.

Within or otherwise magnetically associated with coil 35 is a solenoid core or valve stem 42 which embodies a valve 43 for controlling the passage of fuel through supply line 44. When coil 35 is energized core 42 will be lifted to eiect opening of valve 43 and permit fuel ow to the combustion chamber in which sparking plugs 14 and 15 are installed.

If desired, the speed responsive control switch 29 and manual switch 30 may be replaced, as illustrated in Fig. 2,

Accordingly, under those conditions, there is no' by a speed responsive switch 29 and a manual switch 30', respectively, connected in series between ground and the output from

rectifiers

36, 37. In this event, it is desirable to interpose between said switches a lter comprising a series connected inductance 50 flanked by condensers 51 and 52 connected between ground and opposite ends of the inductance. This modified type of circuit has advantages from the radio shielding point of view, but it requires a relatively heavy flow of current through

rectiiiers

36, 37 at all times. In the embodiment illustrated in Fig. l of the drawings, the rectifier tube 36 is by-passed and but little, if any, current ows through rectiiier tube 37 when switches 29 and 30 are both closed, thus enlarging the operating life of the tubes.

The various elements of the above described circuits may vary rather widely, depending upon the application and requirements. In one satisfactory ignition circuit for a jet or gas turbine type engine, the windings S, 9 and 10 of the magneto coil 7 comprised 20,000, 4,500 and 4,500 turns of numbers 40, 33 and 34 wires, respectively. The

resistances

19, 27 and 28 were 20 megohms, 100,000 ohms and 1,000 ohms, respectively, while the capacities of condensers 1S and 26 were .5 microfarad and .01 microfarad, respectively. The control gap 25 was constructed to break down or become conductive at 2,500 volts, and the

main gap

21, 24 was designed to normally withstand a potential of 3,500 to 4,000 volts in the absence of ionization of the surrounding gases by the flow of energy between

electrodes

21 and 22 in the manner above described. In the fuel ow control circuit, the condensers 38 and 41 had capacities of about .5 microfarad and .025 microfarad, respectively. The resistors 40 were of about 5 megohm each, and solenoid coil 35 contained 45,000 turns of No. 39 wire.

In operation, when` the engine is not running, the magneto rotor may be driven by a starting motor or its equivalent. With switch 29 in its normally open position, the energy generated in coil 7 charges condensers 18, 18 through rectiiiers 17, 17 to a sufciently high voltage to spark across

control gaps

25, 25 and thereby initiate sparking across the electrodes of igniter plugs 14 and 15 in the manner hereinabove described. At the same time solenoid coil 35 is energized through

rectiers

36, 37 to open fuel valve 43. The fuel ow is thus automatically coordinated with the sparking of the plugs 14 and 15 to start the engine. When the engine is thus started, ignition sparks and the ow of starting fuel are no longer necessary or desired. Accordingly, at a predetermined engine speed, switch 29 will be moved to closed position in response to said speed while switch 30 is lclosed, thereby shorting out winding 9 of the magneto coil and rendering the entire coil ineffective to suitably energize either the ignition circuits or the fuel ilow control circuit. Thus, while switches 29 and 30 are closed, the igniter plugs 14 and 15 will not re and fuel will not ilow through supply line 44 to the combustion chamber. Switch 30 may be opened atk any time to render the system operative, independently of the position of speed responsive switch 29 in the event combustion in the main burner of the engine should cease and require starting.

Tap 11 of the magneto coil may also be connected to ground through a manually operable switch 45. The latter may be and preferably is connected for operation by the throttle 46 which controls the main supply of fuel to the engine. When the throttle is closed, switch 45 is likewise closed to render the ignition system and the starting fuel flow control means ineffective in the same manner as when switches 29 and 30 are closed. When the throttle is open, the switch 45 is open and the apparatus is ready to operate for starting the engine.

There is thus provided a novel electrical control system which coordinates in a simple manner the control of` ignition and the supply of starting fuel for an engine of the so-called jet or gas turbine type. The system is novelly electrically and mechanically designed to insure a maximum operating life for the least durable elements thereof and to afford maximum safety in the event of an operating failure in the electrical portion thereof. Additionally, the novel apparatus comprehended by the invention is of simple and inexpensive construction which may be condensed into relatively small units of lightweight.

Although only a single embodiment of the invention is illustrated in the drawings and described in detail in the foregoing specification, it is to be expressly understood that the invention in its broadest scope is not so limited. For example, other suitable types of magnetos or sources of electrical energy may be used in place of the specific 8-pole magneto shown and other types of rectiers may replace those illustrated. Other similar but specically different known types of condenser discharge ignition circuits may be used in place of the circuits connected to winding 7, such as systems embodying high voltage igniter plugs, in which case a transformer would be provided to step up the voltage of the discharges from the storage condensers. Various other changes may also be made in the specic system illustrated in the drawings without departing from the spirit and scope of the invention as will now be apparent to those skilled in the art.

What is 4claimed is:

l. Electrical apparatus comprising a magneto generator having a winding in which electrical energy is generated, an ignition circuit operatively connected across a portion of said winding, a control circuit including a solenoid operatively connected across a diterent portion of said winding, and means for short circuiting a portion of said winding to thereby render said ignition and control circuits ineffective to provide ignition and to operatively energize said solenoid, respectively.

2. Electrical apparatus as defined in claim 1 wherein said short circuited portion of the winding is common to both the rst-named and second-named portions thereof.

3. Electrical apparatus as deiined in claim 1 wherein said short circuiting means includes normally open switch means automatically operable when the magneto generator is operating above a predetermined speed.

4. Electrical apparatus as defined in claim 1 wherein said solenoid actuates a fuel ow control valve.

5. Electrical apparatus as defined in claim 1 comprising means for rendering said short circuiting means inoperative.

6. Electrical apparatus as defined in claim 1 wherein the ignition circuit comprises a storage condenser, an igniter gap connected across said condenser, and means for controlling the discharge of the condenser across the gap.

7. Electrical apparatus as defined in claim 6 wherein said winding is a primary Winding and said condenser is charged in increments through a rectifier.

8. In a gas turbine type engine or the like having a rfuel supply line and a valve for controlling the ow of fuel in said line, the combination of a magneto generator drivably connected to the engine, said generator including a coil winding in which electrical energy is generated, an ignition circuit including an igniter gap operatively connected across at least a portion of said winding, a solenoid for actuating said valve to open position, a control circuit including the coil of said solenoid connected across at least a portion of said winding, and means for short circuiting only a portion of said winding to thereby render said ignition and control circuits ineffective to energize said igniter gap and said solenoid sufciently to create sparks and to open said fuel valve.

9. A combination as dened in claim 8 wherein said short circuited portion of the winding is common to the two rst-named portions of said winding.

10. A combination as delined in claim 8 wherein said short circuiting means is operable only when the engine `speed exceeds a predetermined minimum.

ll. A combination as dened in claim 10 comprising means for rendering said short circuiting means inoperative.

12. In electrical apparatus, a source of electrical energy including a coil winding, a first circuit connected across a portion of said winding, a second circuit connected across a different portion of said winding, said portions `each including a central section of said winding, and means for short circuiting said central section to reduce the energy supplied to each of said circuits to below a predetermined eiective amount.

13. Electrical apparatus as defined in claim 12 wherein said source is a magneto generator and said short circuiting means includes switch means operable in response to the speed at which the magneto is driven.

14. Electrical apparatus as defined in claim 12 wherein said short circuiting means comprises switch means operable in response to the speed or other function of an engine or the like.

15. In ignition and fuel supply apparatus for starting gas turbine type engines or the like, means for supplying starting fuel including ow control valve means, electromagnetic means for opening said valve means, means including an igniter gap for igniting said fuel, a source of electrical energy, a circuit including said igniter gap operatively connected to said source, a circuit including an element of said electro-magnetic means connected to said source, and means including switch means operable in response to the speed of the engine to suiiciently limit without interrupting the supply of energy from said source to said circuits when the engine is operating above a predetermined speed to render said igniter gap and electromagnetic means inoperative.

16. Apparatus as dened in claim l5 wherein the source of electrical energy is a magneto generator drivably connected to the engine.

17. Apparatus as defined in claim 16 wherein the means for limiting the supply of energy to the circuits comprises means for short circuiting a portion only of the output coil of the magneto generator.

References Cited in the le of this patent UNITED STATES PATENTS 2,377,591 Taylor June 5, 1945 2,546,919 Carington et al Mar. 27, 1951 2,602,149 Brunelle et al July 1, 1952 2,633,511 Stamford Mar. 31, 1953 2,643,511 Briggs June 30, 1953 2,667,742 Kuzmitz Feb. 2, 1954 2,742,759 Flanigen et al. Apr. 24, 1956