US2904026A

US2904026A - Fuel injection system

Info

Publication number: US2904026A
Application number: US655631A
Authority: US
Inventors: Alfred C Korte
Original assignee: ACF Industries Inc
Current assignee: ACF Industries Inc
Priority date: 1957-04-29
Filing date: 1957-04-29
Publication date: 1959-09-15
Anticipated expiration: 1976-09-15

Description

Sept. 15, 1959 A. c. KORTE FUEL INJECTION SYSTEM Filed April 29, 1957 yl-lff fr INVENTOR. ALFRED C. KORTE ATTORNEY United States Patent FUEL INJECTION SYSTEM Alfred C. Korte, St. Louis, Mo., assignor to ACF Industries, Incorporated, New York, N.Y., a corporation of New Jersey Application April 29, 1957, Serial No. 655,631

Claims. (21. 123-479 This invention is an engine fuel charging device operating as a continuous flow system adapted for intake port injection, in which system the fuel is pressurized, measured under pressure in accordance with engine requirements, and distributed under pressure to points adjacent the intake valves of the several cylinders or combustion chambers of the engine. This application shows an improvement applicable to the basic system shown in the prior patent to James, Fred Armstrong, No. 2,785,669, dated March 19, 1957, entitled Injection Carburetion.

A more complete understanding of the invention herein disclosed will be hadby reference to prior applications of James Fred Armstrong, Serial No. 632,798, filed January 7, 1957, for Fuel Injection System, and Serial No. 646,062, filed March 14, 1957, for Fuel Injection System, now Patent No. 2,846,994. I

The improvement disclosed herein may be applied to any of these prior inventions, as well as others which function on similar principles.

This application is specifically directed to features including a fuel delivery cut-off operated by the ignition switch, an engine load operated means for shutting oil. the fuel during deceleration of the engine from high speeds, and a control for changing the fuel delivery from the nozzles during engine cranking, which normally increases the flow to prime the engine, or, on full throttle opening, cuts off the fuel flow completely.

These features are all disclosed in the last-mentioned application by James Fred Armstrong, and the improveand has a metering screw 78 for adjusting the amount of ment here includes electrical circuits for performing the DESCRIPTION Air flow metering The air metering or measuring part of this system, indicated as B in Fig. 1, may be placed anywhere near the engine and connected with the inlet of the engine intake manifold, which has several branches (not shown) leading to the separate intake ports of the engine. This air measuring or metering part, termed the air horn, has a tubular body constructed for connection at its lower or outlet end to the intake manifold of the engine. The outlet of the air horn is controlled by a suitable throttle 50 mounted on a throttle shaft 51, and controlled by athrottle arm 52 actuated by a linkage R from the throttle pedal T.

Above the throttle is a balanced air valve 37 mounted on a suitable shaft 36 journaled in the walls of the air hem B. On the lower leading edge of the air valve 37 is Patentd Se t. 15, 1959v 55-.- The valve 37 is moved in the opening. direction by j a Servo-motor which has a diaphragm 40 operating against a calibrated spring 43 and a connection 39 with the air valve 37. The servo-motor is powered by the pressure drop across the air valve 37 as sensed -by two- Pitot tubes 44 and 45 upstream and downstream of the" A slotted baffle 49 extends. between the air valve shaft 36 and the throttle shaft 51.

air valve 37, respectively.

in a manner to eliminate aerodynamic interference of the air bypassing the air valve 37 in the idle range of displacements of this valve so as to adjust the mixture ratio at idle.

The air valve 37 is displaced by the power operated servo-motor so that it takes up an angular position indicating the rate of air flow past the throttle 50 to the engine. Shaft 36, upon which it is mounted, is in turn connected to the fuel metering part A by means of a magnetic clutch 35 to control the displacement of a plu rality of tapered fuel metering rods which are calibrated displacements of the air;

to flow fuel at a rate to give the full throttle power mixture throughout the range of angular displacement of the air measuring valve 37.

To get a part throttle economy mixture, the response of air valve 37 to air flow is modified to produce a de- Part throttle mixture Air valve response is modified for the above purpose by an air bleed connection 205 in the air horn B which connects the plurality of

ports

202 and 203 above the air valve 37 to the suction side 42 of the servo-motor. In this connection is a diaphragm operated valve 212 which is'held open against the closing force of the spring 211 by suction connection 209 extending posterior of the throttle valve 50. When the throttle is open far enough 7 so that manifold depression is less than six inches Hg,- forexample, valve 212 is closed by the spring 211 against: the force of suction acting on the diaphragm 208, thus: cutting off the air bleed 205 from communication with. the suction side 42 of the servo-motor. The response of the air valve 37 is thus changed to increase its opening and the displacement of the fuel metering rods to in-- crease the fuel delivery rate to a full rich mixture.

If, on the other hand, engine speed increases in thepart'throttle range of engine operation, angular air valve displacement is decreased for the same rate of air flo'w, giving a lesser displacement to the metering rods 33 so as.

to lean out the mixture for part throttle operation. '.As

engine speedincreases, however, angular airvalve displacements will also increase as a result of increasing air flow, so that the edge of the air valve 37 and deflector 37a m swings over the

ports

202, and 203. This places the

ports

202 and 203 in a zone of decreasing air pressure due to high velocity flow to reduce the effectiveness "of the air,

bleed on the action-"ofthe servo-motor. spouse is accordingly modified to increase air valve open Air'valve 're-' consequently, the rate of fuel flow to the engine,

giving a richer mixture at higher engine speeds to eliminate the possibility of part throttle detonation.

Mixture control for acceleration If the particular engine. requires a richer mixture on suddenthrottle opening, some kind ofa connection m ay. bed esirable, between the throttle, and the, fuel metering; rods to, increase. thefuel flow temporarily, In this device, it is more convenient to use an equivalent structure which;

operatesthe-air valve in an openingvdirectionupon opening oflthethrottle. Forexarnple, the air horn B has a pump with a .diaphragm127 spring-powered by a suitable ooil spring 128,-. and held in: operative position with the spring; ;128 compressed bya connection .130 ,to the;.suc-. tion sideof the air horn below. or downstream of'the throttle valye 50. The pressure side of the pump 125 is connected-by a passage 129 with'the pressure side 41 of the servo-motor. A leaf type of check valve 200 controls the eseape of pressure from the Pitot= tube 44.

:Duringoperation of the engine at-idle. speeds, suction compressesthe spring 128, but on throttle opening-this suction force largely disappears, allowing the spring 128 to; expand, pumping air into the chamber 41 of. the servomotor to. displace the valve 37 in an-opening direction, thus .withdrawing the metering rods33 to increasethe fuel mixture ratio, temporarily.

Starting mixture enrichment At low engine temperatures, fuel flow should be increased for starting and engine warm-up. This result is accomplished in the instant device by modification ofthe response of the air valve 37 instead of by direct connection with the fuel metering rods 33 which is, of course, possible. hornB' mounts a thermostatic spring 102 concentric with respect to one end of the air valve shaft 36. One end As illustratedvschematically herein, the air-- of the spring 102 is held fast in a slot in a pivoted lever 101,.which in turn is angularly movable by a suction operated piston 105 in a cylinder 106 against the force of'a calibrated spring 107. Suction is communicated to the cylinder 106 through a line 108 communicating with the manifold downstream of the throttle 50. The free end of the-thermostat 102, indicated as 103, abuts a lever100- fast on one end of the shaft 36, and, as the engine cools,

the thermostat 102 winds up, exerting a'force in a clockwise direction on the lever 100 to urge the valve 37 toward an open position. The force of the thermostat depends upon the temperature, but at temperatures below those encountered in normal operation of the engine this force either actually opens theair valve 37 or decreases theforce necessary to open the valve, so that the servomotor produces a greater degree of valve opening andmetering rod movement for increasing the fuel flow to the engine during cranking. As soon as the engine starts, suction rotates the arm 101 to decrease this opening force exerted by the thermostat spring 102 on the arm ing .;the,throttle 50 at lowengine temperaturesis shown ina copending application of James Fred Armstrong,

Serial No. 622,917, filed. November 19, 1956,;and.entitled; Fuel lnjection System. Figs. 25 and 26 iof thisiappli cationillustrate the fastidlecontrol mechanism. The i structu e eanbe r sed e er al ug it is netshe m i.

n orms- 0 Part. ofi hisu nr nt on-q Fuel metering system This part of the injection system may be conveniently described as having a fuel charging circuit and a datum pressure circuit. Both circuits are supplied with fuel under pressure from a pump P connected with a fuel tank by the line 19. The output side of the pump P connects by way of a check valve to a combined filter and pressure regulator 22 of the type shown and described in the prior applications of James Fred Armstrong above mentioned. The discharge from the pressure regulator 22 connects with a fuel chamber A by way of a line 20a.

The engine charging circuit includes the pressure chamber A and a plurality of discharge lines 24 connecting the chamber with individual nozzles 25 which discharge adjacent the intake valves of the engine in the branches of the manifold. The inlet of each fuel line 24 is supplied with fuel at the same pressure from the fuel chamber A through separate fuel metering jets or orifices 23, one for each of the fuel lines 24. Each meteringjet or orifice is variable in area by an individual, tapered metering rod '33, all supported on a. common carrier 34' for moving all of the rods in or out of the jets in unison.

Angular movements of the air valve 37 are mechanicah 'ly transmitted from the shaft 36 outside the chamber A to move the commoncarrier 34 inside the chamber A bymeans of a, magnetic clutch having elements 35 dis-. posedinside and outsideof the fuel chamber A. Movement of the rods in unison varies the area of all of the fuel metering orifices 23 simultaneously and equally.

Each of the fuel nozzles 25 is, in effect, a pressure regulatingtype of valve with an operating diaphragm 28, ex-

posed to the action of the pressure downstream of each. metering jet 23 in the separate lines 24. Fuel pressure in each line 24 acts on the diaphragm of the valve in a valve opening direction.

The datum pressure circuit The opposite side of each of the diaphragms 28 of each nozzle 25is connected toa by-pass fuel passage 56, 58 having the branches 58a, b, c, and a connecting with the individual fuel nozzles 25. The datum circuit is maintained under a pressure which bears a constant relation to the chamber pressure (about a half to one-anda-half pounds gauge lower during operation). Since all of the nozzles are connected with the by-pass 58, the pressure on the diaphragms 28 resisting valve opening is equal in all of the nozzle valves. When the pump and engine are in operation, each nozzle valve will open until the pressures on opposite sides of each diaphragmbalance, or, stated another way, each nozzle valve 25 maintains the pressure downstream of each metering jet 23 equal to datum pressure. The pressure downstream of each metering jet is thereby maintained equal in allthe lines 24 by interconnection of all the'nozzle valves 25 to the datum system. Each jet is likewise exposedto thesame pressure in the common supply chamber A,

so that equal division of the how through the branchesis obtained with jets of equal area operating at equalpressure drop.

In the datum pressure system is a pressure regulator C which controls the pressure upstream of the small metering orifice 61 at the by-pass outlet from the line 58. Between the orifice 61 andthe pump inlet is a second pressure regulator 60.

Regulator C is supplied with fuel through a connection to the-fuel chamber A by line 56, and is set to maintain a constant relative pressure in the line 58 (about onehalfto one-and-a-half pounds gauge) below the pressure of fuelin the chamber A, Whatever that pressure may be.

The regulator 60 is set to maintain a certain minimurmv pressure in the datum line or by-pass, about twenty to twenty-two pounds. Together, these two regulators maintaina small, continuous flow throughthe by-passorv datum circuit and out orifice 61 to the pump. This.

am nes flaw insures circulation in the entire fuel metering system.

When fuel flow increases through the jets 23 in lines 24, the nozzle valves must open. In order to avoid lag in fuel delivery as the metering rods 33 are withdrawn from the jets 23, some provision must be made to ac commodate the fuel displaced into the datum system circuit by movement of the diaphragms 28 of each nozzle 25. This movement will be accompanied with a slight pressure increase in the datum circuit 58, causing diaphragm 71 of pressure regulator C torespond, closing inlet valve 75 and opening outlet vavle 76, allowing the fuel to escape through a line 79 downstream of the metering restriction 61.

The preferred details of construction for the pressure regulators C and 60 have been described in the prior applications of James Fred Armstrong above mentioned. A further description here would be repetitious and serve no useful purpose, since the construction is not a feature of this invention.

Engine priming circuit In this system, the mixture ratio furnished may not only be affected by modifying the response of the air valve, as above described, but also by varying the pressure drop across the metering restrictions 23, and since this pressure drop or pressure differential is controlled directly by datum pressure, the mixture ratio can be varied one Way or the other, rich to lean, by changes in the datum pressure regulation. Because of this inherent characteristic of the system, it is possible to add to it the many desirable auxiliary features necessary to adapt the system to the needs of the engine.

, For example, the particular engine might require a rich mixture during cranking in order to facilitate engine starting. This function can be built into the present system by a control which acts upon datum pressure. The following detailed description is explanatory.

The usual starter and ignition circuit for the engine includes the battery 194 connected at one terminal to ground, and at the other terminal to the ignition key switch 197, which switch, when closed, energizes a circuit to the starter switch S, which is connected, in turn, by a lead 198 with the starter motor 195. Connected with the lead 198 is a second lead 189 extending to the Winding on solenoid 173 in the pressure regulator 60 and to ground through the lead 188.

Operation of priming circuit To crank the engine, both the ignition switch 197 and the starter switch S are closed, so as to complete the circuit to the engine starter motor 195. This circuit, in turn, energizes the circuit through the solenoid 173 by way of the

leads

189 and 188, energizing the solenoid 173 and producing a magnetic force attracting the armature 172. The force of the solenoid 173 tends to open the valve 167 against the force of spring 166, and thus change the minimum pressure setting of the pressure regulator 60, so as to lower the pressure downstream of the metering orifice 61 and increase the flow through the datum system 58. This brings into operation the effect of the metering restriction 58H to restrict the fuel flow in the datum system upstream of the metering restriction 61. The increase in flow through the datum system creates a pressure drop between the restriction SSH and the metering restriction 61, thus lowering the datum pressure acting on each of the nozzle diaphragms of the nozzles 25. When the datum pressure is lowered, the pressure downstream of the metering restrictions 23 is likewise lowered, increasing the pressure drop and the fuel flow past the metering rods 33 to the nozzles at any particular position of the rods 33. This priming function is accomplished only when both the ignition switch and the starter switch are closed.

Ignition switch fuel cut-0f) circuit In this system, the datum circuit forms a remote control for the discharge from the nozzles. When the pressures between the charging system and datum system are equalized, the fuel discharge from the nozzles is effectively cut off. One manner contemplated for utilizing this inherent feature is illustrated in Fig. 1.

In this particular embodiment, datum line 58 is directly connected with the fuel chamber A by a pressure equalizing line 300. Communication through the line 300 is in turn controlled by a solenoid operated valve SV, which is spring-biased to an open position and closed by energization from either of two electric circuits con-' nected with separate windings in the solenoid valve SV;

The first of these circuits comprises a line 299 connected with the ignition switch 197 and extending to one of the solenoid windings of the switch SV. The lead 298 connects the same winding to the opposite side of the starter switch S. In this circuit is a vacuum operated switch VS, which is held closed by spring pressure from the spring 250 under normal engine operating conditions.

Operation of ignition switch controlled fuel cut-ofi In the following discussion of the operation of the above-described circuit, the function of the vacuum operated switch VS will be ignored.

The ignition switch 197 controls the energization of the lead 299, which in turn, when closed, furnishes the necessary current to one of the windings in the solenoid valve SV to close the valve against the resistance of the spring 303, which tends to maintain the valve open. If the starter switch is open, as would be the case when the engine is running, then this circuit is grounded through the starter motor by way of the leads 298 and 198. With the ignition switch 197 closed, therefore, solenoid operated valve SV is energized and closed by the circuit grounding through the starter motor, as described, and the pressure equalizing passage 300 is. inoperative. It will be understood that the current flowing through this circuit is necessarily very small, due to the resistance of the solenoid winding, so that it has no efiect upon the operation of the starter motor 195. It requires a much greater amperage to operate the starter motor 195 than it does to operate the small solenoid operated valve SV.

When the ignition switch 197 is open, however, the circuit through the leads 299 and 298 is de-energized, allowing spring 303 to open the solenoid operated valve SV. This equalizes the pressure between the fuel chamber A and the datum line 58, so that each of the valves in the fuel nozzles 25 closes and discharge of fuel immediately ceases.

Conversely, when the ignition switch 197 is turned on, valve SV closes.

Operation of deceleration fuel cut-ofi In the circuit above described is a switch VS operated in response to a negative load on the engine for opening the circuit 299298. Preferably, the switch VS has a diaphragm 251 connected through a rod 252 to the switch. The diaphragm 251 is subject to atmospheric pressure on one side, tending to open the switch, and to manifold pressure on its opposite side through the line 108. A spring 250 may be calibrated so that the switch 253 remains closed until manifold suction exceeds the normal range of variations encountered in operating the engine under its own power. In other words, switch 253 remains closed until manifold suction exceeds 21 or 22 inches Hg. When this occurs, the force of spring 250 is overcome, opening the switch 253 and de-energizing the circuit 299 and 298 to the solenoid operated valve SV. Spring 303 opens the valve, equalizing the pressure between the chamber A and the datum line 58, so

that fuel discharge from the nozzles 25 is effectively out Unloading If, for any reason, the starting mixture is too rich so that the engine will not fire during cranking, it is necessary to provide for'some means to unload the engine of fuel. Under these circumstances,'continued delivery of fuel from the fuel nozzles 25 is not desirable. Here, again, datum pressure regulation forms a convenientmanner for .remotecontrol 'of the discharge from the fuel nozzles 25.

Whenthe ignition switch 197 and starter switch S are closed, the circuit 299 and 298 is short-circuited, so that it becomes inoperative and the current flows directly from the switch S to the starter motor 195 through the line 198.

The unloading circuit connects with the line 198, which is energized under these conditions, through lines 298 and 304-to the switch TS, and from thence through the line 301 through a second winding on the solenoid valve SV to ground. Thus, normally, 'the valve 8V is maintained closed, even though the circuit 298299 is inoperative.

Operation of unloader on the solenoid valve SV is likewise energized, maintaining the pressure equalizing passage closed, so thatthe priming system remains'inoperation until the throttle is opened wide. This movement of the throttle engages the lug 152 on the throttle arm 52 with the throttle operated switch TS, which opens the circuit between line 304, which is energized, and line 301, which extends to the Winding on the valve SV. Spring 303 then opens pressure equalizing passage. 300, and the pressurein the charging and datum circuits becomes equalized, closing the nozzle valves 25 to shutoff the discharge of fuel to, the engine.

As above explained, the starter switch S short-circuits the electric circuit through the lines 298 and 299, so that there is no closing force exertedagainst the spring 303, and the valve'remains open while the throttle is held wide open and thestarter switch remains closed.

, The foregoing describes a structure which performs all the functions and attainsv all the results set forth above, but it is contemplated that other. modifications will occur to those skilled in the art which come withinthe terms of the appended claims.

I claim:

1. Ina pressurized fuel charging system for a spark ignition type of internal combustion engine having a source of electric power and an electric circuit from the source to the ignition-and to the engine starter motor including an ignition switch and a starter switch, said system including a fuel'inlet, a fuel nozzle discharging fuel to the engine, a pumpsupplyingfuel' under pressure to'said fuel inlet, a fuel line normally pressurized from said pump connecting said inlet and said fuel nozzle, a pressure'regulator having amovable wall controlling a valve-in said fuel nozzle, a datum" pressure system, opposed expansible chambersseparated by said movable wall and connected with said datum system and said fuel line, respectively, whereby said regulator maintains the fuel in said fuel line at a pressure proportional to the controlled pressure in said datum system, means for establishing a controlled pressure in said datum system at a fixed differential with respect to'said pump supply pressure, a pressure equalizing line extending between said fuel line andsaiddatumipressure system and a normally open, solenoid closed valve in said pressure equalizing chamber; the combination therewith comprising a pair of windings on said solenoid controlled valve, an electric circuit extending from. said ignition switch for energizignition type of internal combustion. engine having a source of electric power, an electriccircuit from said source to the ignition, an ignition switch, a starterrnotor, a starter motor circuit, and a starter switch insaid starter motor circuit for energizing the starter motor from the power source, said system including afuel inlet, a fuel nozzle for discharging fuel-to the engine, a pump supplying fuel under pressure to said inlet, a fuel line normally pressurized from said pump connecting said inlet. and said fuel nozzle, a pressure regulator having amovable wall controlling a Valve in said nozzle, a datum pressure system, opposed expansible chambers separated by rsaid movable wall and connected with said datum system and said fuel line, respectively, whereby said regulator maintains the fuel in said fuel line at a pressure proportional to the control pressure in said datum system, means for establishing a controlled pressure in said datum system at a fixed differential with respect to said pump supply pressure, a-pressure equalizing passage, and a normally open, solenoid closed valve in said 'pressureequalizing passageythe combination'therewith comprising apairiof windings in said solenoid for, operating said .valve,.an electric circuit energized byvoperation of said ignition switch .connected with one-of. said windings, .an,,electric circuit energized .by. said :starter switch connected to the other-of said'iwindin gs, and aconnection for short-circuiting=said.first circuit onloperationof said starter'switch.

3.;l'n a pressurized fuel charging system for. atspark ignition type of internal combustion. engineahaving, a battery and a'starter-i-gnition system including an ignition switch and a starter switch in series between-the battery and the startermotor, said system including a, fuelinlet, a-fuei nozzlefor discharging fuel totheengine, a pump supplying fuelv under pressure to said inlet, a fuelline normally: pressurized from said pump. connecting :said inlet and saidfuel nozzle, a pressure regulatorhaving .a movable wall controlling a valve. in said nozzle, a datum pressure system, opposed expansible chambers separated by'rsaidmovable wall andaconnected with :said. datum system and said fuel .line, respectively, whereby said regulator maintains the fuel in said fuel line at a pressure proportional to the control. pressure in saicLclatum system, means for establishing acontrolled pressure insaiddatum system at a fixed diiferential with respect to said pump supply pressure, aprcssurecqualizingapassage between said fuel inlet and said datum system, and a normally open, solenoid operated valve in said-pressure equalizing passage;-the combination therewith comprising a pair of windingsfor said solenoid operated valve, a first electric circuit energized from said ignition switch and connected toground-through one of said windings and said starter motor whereby said circuit is energized only during operation of the enginebut not during crankin a switch in said first circuit responsive to negative load on the engine to open'said circuit, and asecond circuit energized from said starter switch and connected to ground through said second solenoid winding for retaining-said pressure equalizing passage closed during operation" of the starter motor.

4. ln aprcssurized fuel charging system'for a; spark ignition type of internal combustion engine having a throttle controlled air inlet, a battery and'an ignition switch and starter switch connected in series in-anelectric circuit extending from the battery tothe starter motor, said system including a fuel-inlet, a fuel nozzlefordischarging fuel to-the engine, apump supplying-fuel under pressure to said inlet, a fuelline normally pressurized from said pump connecting saidinletand said'fuel nozzle, a pressure regulator having a movable wall controlling a valve in said nozzle, a datum pressure system, opposed expansible chambers separated by said movable wall and connected with said datum system and said fuel line, respectively, whereby said regulator maintains the fuel in said fuel line at a pressure proportional to the control pressure in said datum system, means for establishing a controlled pressure in said datum system at a fixed differential with respect to said pump supply pressure, a pressure equalizing passage between said fuel inlet and said datum system, and a normally open, solenoid operated valve in said pressure equalizing passage; the combination therewith comprising a pair of windings in said solenoid operated valve, a first circuit energized from said ignition switch and extending to ground through one of said windings and said starter motor whereby said circuit is short-circuited during operation of said starter switch, a second circuit energized by closing of said starter switch and extending to ground through said second winding, and a switch in said second circuit operated by full opening movement of the throttle for de-energizing said second circuit during cranking of the engine.

5. In a pressurized fuel charging system for a spark ignition type of internal combustion engine having a throttle controlled air inlet, a battery, an electric circuit extending from the battery to a starter motor, and an ignition switch and starter switch in series in said circuit, said system including a fuel inlet, a fuel nozzle for dischanging fuel to the engine, a pump supplying fuel under pressure to said inlet, a fuel line normally pressurized from said pump connecting said inlet and said fuel nozzle, a pressure regulator having a movable wall controlling a valve in said nozzle, a datum pressure system, exposed expansible chambers separated by said movable wall and connected with said datum system and said fuel line, respectively, whereby said regulator maintains the fuel in said fuel line at a pressure proportional to the control pressure in said datum system, means for establishing a controlled pressure in said datum system at a fixed differential with respect to said pump supply pressure, a pressure equalizing passage between said fuel inlet and said datum system, and a normally open, solenoid operated valve in said pressure equalizing passage; the combination therewith comprising a pair of windings in said solenoid operated valve, a first circuit energized by said ignition switch and extending to ground through one of said windings and said starter motor, a switch in said circuit opened in response to negative load on the engine, a second circuit energized by said starter switch and extending to ground through said second winding, and a switch in said second circuit operated upon movement of said throttle to the wide-open position for de-energizing said ,second circuit.

References Cited in the file of this patent UNITED STATES PATENTS 2,785,669 Armstrong Mar. 19, 1957