US2138020A - Carburetor - Google Patents

Description

Nov. 29, 1938.

R. F. .BRACKE CARBURETOR Filed March 22, 1935 2 Sheets-Sheet 1 laI,

NOV. 29, R F BRACKE CARBURETOR Filed March 22, 1935 2 Sheets-Sheet 2 ysa-md Nov. 29, 193e UNITED STATES PATENT ori-ICE csmsumrrort Robert F. Bracke, chicago, n1. Application Maren zz, 1935, serial No. 12,463

s claims. (o1. zen- 34) My invention pertains tov carburetors and is more particularly concerned with carburetors of the fuel-lift type.

An object of my invention is to provide a carburetor which will afford more rapid acceleration for the internal combustion engine to which it is attached.

Another object is to provide an improved carburetor of this type which is simple and economical to manufacture and which is durable and trouble-free in service.

Other objects and advantages will become apparent as the description proceeds.

In the drawings,

Figure l is a vertical elevation, partly in section, showing a carburetor embodying my invention;

Figure 2 is a vertical section through the carburetor of Figure l, being taken on the line 2-2 of Figure 1; and

Figure 3 is a fragmentary cross-sectional view taken on the line 3-"3 of Figure 2.

My improved carburetor is illustrated as comprising an upper casting A and a lower casting B secured together by bolts Il) and having an airtight gasket I2 confined between adjacent portions of the two castings.

'I'he casting A includes an air horn I4 having its upper end4 of reduced external diameter to facilitate the attachment of any usual form of air cleaner and silencer where the use of such a device is deemed desirable or necessary.

Part of the air entering the air horn I4 passes into the nozzle Venturi tube I6 where it mixes with fuel supplied through diagonal ducts I8 communicating with the throat of the nozzle I6. Annular space 20 and passageway 22 connect the ducts I8 with a fuel chamber 24 which constitutes a source of fuel supply for the nozzle I6.

'I'he lower end of the nozzle I6 is surrounded by the upper end 26 of an air valve 28 which controls the admission of secondary air from the air horn I4 into the mixing chamber 38. A spring 32 urges the air valve 28 toward closing position. The nozzle I6 discharges against the flat upper surface of an inverted cup-shaped portion 34 provided by the air valve 28, and this flat surface causes the primary mixture delivered by the nozzle I8 to flowradially outward where it mixes with secondary air admitted past the air valve 28.

I'he upper portion of the air valve which surrounds the lower end of the nozzle I6 is preferably provided with heat insulating packing 36. The inverted cup-shaped portion 34 of the air valve, together with the air valve guide 88, Hforms a closed chamber 89 into which suction may'be introduced for opening the air valve against the l tension of its spring 82.

'I'he chamber 39 communicates withthe upper 5 l end of throttle bore 40 by means of passage 4I l .and the small orifice 43 provided by the plug 45A g press-fitted into one end of the passage 4I. By this means the suction existing in the upper part of throttle bore 48 is communicated to the cham- 10 ber v39, and the valve 28 is opened an amount proportional tothe degree of suction obtaining in the upper end of throttle bore 48. v

The combustible mixture flows `from the mixing chamber 30 into the throttle bore 48 which 15 is provided with the usual throttle valve 42 carried by a shaft 44 pivotally mounted in the lower f casting B.' One end of theshaft 44 has an arm 46 adapted to be connected to the usual accelerator pedal of an automobile, and a second arm 20 48 adapted to be connected to the usual hand throttle of the automobile. The arm 46 can'ie the usual adjustable stop 50.

Part of the air entering the air horn I4 passes through a lateral opening 52 at one side of the 25 air-horn and flows downwardly through a conduit 54 into a chamber 56 provided by a sheet-metal cup 58 secured in place by a star-shaped spring plate 60 and screw 62. A booster Venturi tube 64 has its inlet end in communication with the 30 chamber 56. This booster discharges into a duct 86 communicating with throttle bore 48 through an orifice 68 in which there is a tapered pin 'I8 having an enlarged upper head confined between a plate 12 and the adjacent portion of the air 35 valve 28 so that the pin 'l0 reciprocates with the air valve.

The throat of the booster 64 is provided with radial ducts communicating with a passage 82 connecting'with the top of the fuel chamber 24. 40 'I'he function of this booster 64 is to draw fuel into the fuel chamber 24 through pipe 84 which connects with the main fuel tank of the automobile usually located at the rear of the vehicle and below the carburetor. 'I'he fuel chamber v24 45 is provided with the usual inlet valve 86 controlled by the float 88.

A choke plate'14 is located between the metal cup 58 and the adjacent portion of the casting B. This choke plate has an L-shaped opening 'I6 50 which maintains communication at all times' between the chamber 56 and the conduit 54. 'Ihis choke plate has a second opening 18 which controls'the inlet to the booster Venturi tube 64. In the normal position of the choke plate, there is 55 free communication between the inlet to the booster 64 and the chamber Il, but when the choke plate is moved to full or part choke position, the inlet to the booster 'I8 is correspond.- ingly reduced so that the suction created in the fuel chamber 24 by the booster 34 varies with the position of the choke plate 14.

When the choke plate 'I4 is in substantially the full choke position, the end 88 of the L-shaped slot 13 establishes communication between the chamber i8 and a duct 82 leading to the chamberV 39 formed beneath the secondary air valve 28 so that under full choke conditions atmospheric air is admitted beneath the air valve 28. The duct 92 admits air to the chamber 38 faster than the air in the chamber can be withdrawn through the small oriilce 43, and the-result is that the air valve 28 remains closed and an extremely rich mixture is supplied to the engine.

The choke plate 'I4 has a stop 84 which rests against a pin 96 when the choke plate is in the position it assumes when the engine is operating normally. 'I'he choke plate 14 has an arm 98 adapted for connection to the usual choke control mechanism for moving the choke plate to any desired position. When the choke plate is in the full choke position, the arm 88 rests ,against A that the full power of the engine will immediately become available for accelerating purposes. To insure full opening of the secondary air valve at such times, I provide a source of vacuum which is connected to the chamber 33 beneath the secondary air valve whenever rapid engine accelera: tion is desired.

At one side of the mixing chamber 33 I provide a vacuum chamber Ill having its lower end in communication with a cylinder |82 connected to a part of the throttle bore 4l beneath the throttle valve 42 by means of a duct |84. The upperend of vacuum chamber |88 is provided with a valve seat |06 and valve |88 controlling communication between this chamber'and a passageway Il. leading to the chamber 38 beneath the secondary air valve 28.

A piston ||2 is located in the cylinder |32 and has a piston rod I I4. 'I'he valve |83 is mounted on the upper end of the piston rod ||4. A spring lli is confined between the valve seat |83 and a washer |I8 supported on a shoulder suitably provided by the piston rod II4.

In the normal operation of the engine, the piston ||2 and valve |03 assume the position shown in Figure 2 of the drawings. The piston ||2 does not make a perfect seal with its cylinder |32 so that air is exhausted from the chamber |88 by the suction existing in the throttlebore 43 beneath the throttle valve 42 until the degree of vacuum obtaining in the chamber |38 is substantially equal to that existing on the engine side of the throttle valve 42.

When the throttle valve is quickly opened to obtain rapid engine acceleration, the pressure in the throttle bore 4I| rises to almost atmospheric pressure, and this is communicated to the underside of the piston 2. Because of the relatively high vacuum existing in the chamber |00, the substantially atmospheric pressure acting on the under side of-the piston ||2 moves this piston upwardly against the tension of spring IIS and -This immediately produces complete or substantially complete opening of the air valve 28, thus permitting the maximum now of secondary air therepast and supplying the engine cylinders with the maximum amounts of combustible mixture. 'I'he piston ||2 fits sufficiently tightly in its cylinder |82 to greatly restrict the leakage of air into the chamber |03 past the piston ||2, so that the eii'ect of the vacuum chamber Ill on the secondary air valve is not immediately dissipated but continues over an appreciable period of time.

. Because of the rise in pressure in the throttle bore 43 during periods of acceleration, the booster becomes ineffective during such accelerating periods to draw fuel from the main'fuel tank into the fuel chamber 24. `This fuel chamber 24 therefore mu'st be madek large enoughto supply all oi' the fuel needed by the engine during periods of acceleration without replenishment from the main fuel tank during such acceleratingperiods.

The carburetor is further provided with a fuel pump |23 comprising a cylinder |22 extending downwardly into the fuel chamber 24, and a piston |24 located in the cylinder |22 and operated by a piston rod |28. 'Ihe lower end of piston rod |23.rests on one end of an Aadjustable stop |23 provided by one of the two arms of a lever |38 which is pivoted on the casting B at |32 and which has its second arm adapted for engagement by a cam I 34 rotatable with the throttle valve shaft 44.

'I'he piston |24 is moved downwardly by a spring |36 confined between the upper side of the piston and an opposing part of the casting A. The piston is provided with ports |38 which are practically closed during the pumping movement of this piston by a valve disk I 40. 'Ihe valve disk |48 has a small orifice to provide the necessary fuel for engine idling, and when the engine is operating at greater' than idling speed, the disk |43 is drawn upwardly away from the ports |38 to permit the passage of additional fuel to the engine.

Ihe upper end of cylinder |22 communicates with passage 22 through an orifice |42 in which there is located a metering pin |44 attached to and reciprocable with the piston |24.

Leakage of air into the fuel chamber 24 around the piston rod |23 is prevented by4 a duct |48 which connects an intermediate portion of the guide for this piston rod with the portion of the throttle bore 48 which is beneath the throttle valve 42.

The operation of my improved carburetor is as follows:

Part of the air entering the horn I4 passes through the nozzle IC where it mixes with fuel drawn from the fuel chamber 24 and delivers this mixture against the inverted cup-shaped portion 34 of the air valve 28. 'I'his mixture then flows radially and mixes with any secondary air flowing past the air valve 28. From the mixing chamber 33 the resulting combustible mixture flows to throttle bore 4II and past throttle valve 42 to the engine cylinders.

When the engine is operating at part or full throttle, the suction existing in the upper part of throttle bore 4II draws air from chamber 38 through orifice 43 and passage 4|, and the resultant suction created in this chamber 39 moves secondary air valve 28 downwardly a distance proportional to the suction existing in the upper part of throttle bore 40. At the same time pin is moved downwardly and restricts the discharge from booster 64 to a greater extent so that the booster 64 always maintains substantially the same degree of vacuum in the fuel chamber 24. Under normal operating conditions, this vacuum -is suiiicent to draw fuel from the main fuel tank when the float 88 drops sufficiently to permit the inlet valve 86 to open.

When the throttle valve 42 is quickly opened to provide rapid engine acceleration, the suction chamber I00 is placed in communication with the chamber 39 beneath the secondary air valve by the resulting upward movement of the piston I I2 and valve |08. This results in drawing the secondary air valve 28 downwardly to admit the maximum volume of secondary air, whereupon the engine cylinders receive a maximum charge of combustible mixture and the engine produces its maximum torque. The quick opening of the throttle valve 42 actuates the accelerator pump |20, whereupon additional fuel is supplied to the nozzle I6 which delivers an exceptionally rich mixture best suited for rapid acceleration.

During the accelerating period, the booster 64 becomes ineiective to supply fuel, and the fuel maintained at all times in the fuel chamber 24 suiices to carry the engine through the accelerating period, at the termination of which the booster 64 again functions to rell the fuel chamber 24. During this accelerating period, however, the booster 64 still exerts a regulating or calibrating influence on the nozzle I6, thereby insuring that the latter supplies the propermixture for acceleration.

When the choke is applied, the chamber 38 beneath the air valve is connected with atmosphere through duct 92 and end 90 of opening 16 in choke plate 14, with the result that the spring 32 holds the secondary air valve in closed position. At the same time the available air supply for the booster 64 is materially decreased so that the booster creates a negligible vacuum in the fuel chamber 24. This permits the nozzle I6 to supply a richer mixture to the engine, thereby facilitating starting when the engine is cold.

The carburetor disclosed and claimed herein is an improvement over that disclosed and claimed in my prior application, Serial No. 6,421, led February 14, 1935.

While I have disclosed and claimed only one embodiment of my invention, it is to be understood that my invention may assume numerous forms and that the scope of my invention is limited solely by the following claims.

I claim:

l. In a carburetor of the class described, the combination of a nozzle for supplying a mixture of fuel and air, a mixing chamber into which said nozzle discharges, a valve for admitting air directly to said mixing chamber, a vacuum chamber, means for creating a vacuum therein, and means for utilizing the vacuum in said chamber to open said valve, said means becoming effective only when the carburetor is conditioned for rapid engine acceleration.

2. In a carburetor of the class described, the combination of a fuel supply nozzle, a mixing chamber into which said nozzle discharges, a suction actuated valve for admitting secondary air to said chamber, a suction chamber beneath said valve, a spring for closing said valve, a throttle bore communicating with said mixing chamber, a restricted conduit connectingsaid throttle bore with said suction chamber whereby said valve is opened an amount proportional to the degree of suction existing in the upper part of said bore, a vacuumchamber, a conduit connecting said vacuum chamber with said suction chamber, a valve normally closing said conduit, means for opening said last-named valve'when the carburetor is conditioned for rapid engine acceleration, and an accelerator pump for simultaneously supplying said nozzle with an additional quantity of fuel.

3. In a carburetor of the class described, the combination of a fuel-feeding nozzle, a mixing chamber into which said nozzle discharges, a throttle bore communicating with said mixing chamber, a throttle valve located in said bore, an air valve for admitting secondary air to said mixing chamber, a spring for closing said valve, suction-operated means for opening said valve, a restricted conduit connecting said last-named means with said throttle bore on the inlet side of saidA throttle valve, a vacuum chamber, a conduit connecting said chamber with said suctionoperated means, a valve in said conduit, a passage connecting said vacuum chamber with a part of .the throttle bore on the engine side of said throttle valve, a restriction for limiting ow through said conduit, and a piston for opening said last-mentioned valve when rapid engine acceleration is desired.

4. In a carburetor of the class described, the combination of a fuel-feeding nozzle, a mixing chamber into which said nozzle discharges, a throttle bore communicating with said mixing chamber, a throttle valve located in said bore, an air valve for admitting secondary air to said mixing chamber, a spring for closing said valve, suction-operated means for opening said valve, a restricted conduit connecting said-lastnamed means with said throttle bore on the inlet side of said throttle valve, a vacuum chamber, a conduit connecting said chamber with said suctionoperated means, a valve in said conduit, a cylinder in communication with said vacuum chamber, a passage connecting said cylinder with said throttle bore on the engine side of said throttle valve, a piston in said cylinder permitting slow leakage of air therepast in either direction, and means connecting said piston and said conduit valve whereby movement of said piston in one direction opens said valve.

5. In a carburetor of the class described, the combination of a fuel-feeding nozzle, a-mixing chamber into which said nozzleA discharges, a throttle bore communicating with said mixing chamber, a throttle valve located in said bore, an air valve for admitting secondary air to said mixing chamber, a spring for closing said valve, suction-operated means for opening said valve, a restricted conduit connecting said last-named means with said throttle bore on the inlet side of said throttle valve, a vacuum chamber, a conduit connecting said chamber with said suctionoperated means, a valve in said conduit, a cylinder in communication with said vacuum chamber, a passage connecting said cylinder with said throttle bore on the engine side of said throttle valve, a piston in said cylinder permitting slow leakage of air therepast in either direction, means connecting said piston and said conduit valve for conjoint movement, and a springv for urging said piston and valve in one direction.

6. In a carburetor, the combination of a-.fuel feeding nozzle, a mixing chamber into which said nozzle discharges, a throttle valve controlling communication between said mixing chamber and the manifold of an engine to which said carburetor is connected, an air valve for admitting air to said mixing chamber, said valve normally opening in response to mixing chamber suction, suction means independent of mixing chamber suction and responsive to sudden opening of said throttle valve for opening said air valve during acceleration, and an accelerator pump operated by said throttle valve for supplying said nozzle with an additional quantity of fuel.

7. In a carburetor, the combination of a fuel feeding nozzle, a mixing chamber into which said nozzle discharges, a throttle valve controlling communication between said mixing chamber and the manifold of an engine to which said carburetor is connected, an air valve for admitting air to said mixing chamber, yielding means for closing said air valve, a suction dashpot associated with said air valve for opening said air valve, said dashpot having a restricted communication with said mixing chamber, a suction cham- Y,

scribed, the combination of a fuel feeding nozzle,-

a mixing chamber into which said nozzle discharges, a fuel chamber for said nozzle, a booster for supplying fuel to said fuel chamber, a throttle valve controlling communication between said mixing chamber and the manifold of an engine to which said carburetor is connected, an air valve for admitting air to said mixing chamber, said valve normally opening in' response to mixing chamber suction, an accelerator pump, said accelerator pump being simultaneously operated by said throttle valve for supplying said nozzle with an additional quantity of fuel, and suction means independent of mixing chamber suction and responsive to sudden opening of said throttle valve for opening said air valve during acceleration.

9. In a carburetor of the class described, the combination of a fuel supply nozzle, a mixing chamber into which said nozzle discharges, a suction actuated valve for admitting secondary air to said chamber, a suction chamber beneath said valve, a spring for closing said valve, a throttle bore communicating with said mixing chamber, means whereby said valve is opened an amount proportional to the degree of suction existing in the upper part of said bore, a vacuum chamber, a conduit connecting said vacuum chamber with said suction chamber, a valve normally closing said conduit, means for opening said last-named valve when the carburetor is conditioned for rapid engine acceleration, and an accelerator pump for simultaneously supplying said nozzle with an additional quantity of fuel.

ROBERT F. BRACKE.

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