US2271115A

US2271115A - Carburetor

Info

Publication number: US2271115A
Application number: US273853A
Authority: US
Inventors: Robert F Bracke
Original assignee: Individual
Current assignee: Individual
Priority date: 1939-05-16
Filing date: 1939-05-16
Publication date: 1942-01-27
Anticipated expiration: 1959-01-27

Description

Jan. 27, 1942. R; F. B'RCKE cARBUREToR V Filed May 16, 1939 l 2 Sheets-Sheet 1 jade/afar zum CARBURETOR Fild May 1e, 1959 2' sheets-sheet 2 2 0 1 2 a il, 1 ,w w m m 6 M w lz 1/ u. 'Il A l-l 2 w@ r 2M ,im l M M. 2 j. M aj 2 @0,6 a@ #u @un M Patented Jan. 27, 1942 CARBURETOR Robert Bracke, Chicago, Ill.

Application May 16, 1939, Seral No. 273,853 1 claim. `(ci. zei-41) My invention pertains to carburetors and is more particularly concerned withA carburetors of the fuel lift type.

In non-fuel lift carburetors for automotive use, it is common to provide a main fuel supply nozzle and an idling jet. This idlingvjet is customarily located on th'e engine side of the throttle valve and takes care of the fuel requirements of the engine during idling operation. A needle valve or other adjustment means is commonly pro-r vided to adjust this idling jet. Both the main fuel supply nozzle and the idling jet receive their fuel requirements from the float bowl of the carburetor.

Various attempts have been made to provide a fuel lift carburetor with such an idling jet. In fuel lift carburetors, however, the float bowl of the carburetor is maintained under a degree of suction sufficient to draw fuel thereinto from the main fuel supply tank usually located at the rear of the automobile. At full throttle operation, the degree of suction obtaining in the carburetor iioat bowl is greater than that obtaining at the discharge end lof the idling jet, with the'result that there occurs a back feed of fuel and air from the idling jet to the float bowl of the carburetor. This is disadvantageous in that it destroys the delicate balance necessary to proper operation of a fuel lift carburetor.

An object of my invention is to provide a fuel lift carburetorwith an idling jet which overcomes the foregoing disadvantages.

Another object is to provide a fuel lift carburetor with an idling jet whose .fuel supply is automatically cut off when the throttle valve reaches a predetermined position.

Another object is to provide an idling jet mechanism for a fuel lift carburetor, which mechanism is equally applicable to single-nozzle and multi-nozzle carburetors. y

Another object is to provide a simplified and improved idling jet mechanism for a fuel lift carburetor,

Another object is to provide a carburetor which is economical to manufacture, which will provide long and trouble-free service, andwherein th'e various control mechanisms Amay be independently adjusted.

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

This application is a continuation in part of my copending application Serial No. 136,544 led April 13, 1937, patented June 13, .1939, Patent No. 2,162,056.

In the drawings, Figure lis a diagrammatic view of acarburetor embodying kone form of my invention. In this diagrammatic View the relative positions vof the parts are distorted but their functional relationship is easy to follow; and 'Y Figure 2 is a 'sectional view of a carburetor embodying a second form of my invention.

, Referring to the drawings, I have illustrated a carburetor having a float bowl I adapted to be connected by meansof a pipe I2 with the main fuel supply tank of an automobile or similar machine. The quantity of fuel admitted to the float bowl I8 is regulated by the usual neat-controlled inlet valve I4. In the particular carburetor shown, the flo-at bowl I0 supplies fuel to a pair of 'main fuel feeding nozzles I6 and I8, each of which is illustrated as discharging into a separate mixing chamber or 272. I

Air is admitted to the-mixing chambers 2i) and 22 by way of a pivoted air valve 24 illustrated as being biased in one -direction by weight26 and connected with a dashpot 28 which prevents-fluttering of the air valve 24. A pair of throttle valves 30and 32 illustrated as mounted on a common shaft 34 control communication between the mixing chambers 2D and 22` and the inlet manifold of the engine to which the carburetor is attached. The throttle valve shaft 34 is provided lwith an arm 36 adapted to be connected to the usual foot and hand controls of an automobile.

Arm 36 is also connected t0 a link 3S and lever 40, the latter being connected to'a second lever 42 by Way of bolt 44 and interposed spring 46 for eliminating lost motion from the connection between the two levers which may be mounted on a common pivot pin 48 or pivoted separately as desired. A link 50 connects lever 42 with rod 52 extending into the float bowl I0 and slidably mounted in a guide 54. The lower end of the rod 52 is connected to a base 56 carrying an economizer pin 58 which passes through an orifice 60 and regulates the quantity of fuel supplied to the nozzles I6 and I8. i

The base 56 also operates the piston 62 of an accelerator pump. This piston has a bolt 64 slidably received in an opening in the base and provided with a head 66 limiting separation of the piston and base under the influence of the spring 68 which yieldably advances the piston 62 when the throttle valves are opened.

The piston 62 has an inlet valve 'I0 controlling a passage through the piston and through which fuel from the oat bowl I0 enters the cylinder 12, When the throttle valves are opened suddenly, the advance ofthe piston 62 discharges fluid from the cylinder 12, past the outlet valve '14 and through passages 16 and 18 to accelerator jets 88 and 82 respectively.

I have illustrated my carburetor as provided with idling jets 84 and 86 controlled respectively by needle valves 88 and 98. The idling jets 84 and 86 communicate with vertical passages 92 and 94 respectively. Each vertical passage is provided with a. small diameter air inlet 96 and a small bore 98 immediately above its main idling jet. The bores 98 form auxiliary idling. jets and although smaller in diameter than the bores 98, prevent back bleed therethrough in the event the needle valves 88 and 98 are entirely closed.

The vertical passages 92 and 94 communicate with ducts |88 and |82 respectively, leading to a chamber |84 communicating with an annular recess |88 in the rod 52. The chamber |84 is provided with a very small airvent |81 to prevent siphoning of fuel from the float bowl through the idling jets. The part of the rod 52 below the recess |86 has a diameter two-thousandths of an inch less than the internal diameter of the guide 54 which permits the desired amount of fuel to flow from the float bowl VI8 upwardly along the rod 52 to recess IML-chamber |84, and thence to idling jets 84 and 86 during idling .operation of the engine.

The float bowl I8 is maintained under subi atmospheric pressure by a booster Venturi tube |88 having its restricted throat connected with the upper part of the float `bowl b y way of passage ||8. The booster Venturi tube |88 communicates with atmosphere through ports ||2 and ||4, and air inlet |16. The ports ||2 and ||4 are in a disc ||8 which may be rotated to choke the booster Venturi tube |88 and thereby facilitate starting in cold weather.

The booster Venturi tube |88 discharges through passageway |28 into both mixing chambers 28 and 22. The discharge from the booster Venturi tube |88 passes through `a restricted orifice |22 and is regulated by -a tapered pin |24 connected with the air valve 24.

The operation of the idling jets of the carburetor shown in Figure 1 is as follows: When the engine is idling, the throttle valves 38 and 32 are closed or nearly .so and a high degree of suction is exerted on the idling jets 84 and `86. This degree of suction is sufficiently greaterfthan the suction obtaining in the float bowl |8 to draw fuel from the float bowl upwardly along the rod 52 inA the small clearance between this rod and the guide 54, thence into chamber |84 and through ducts |88 vand |82 and passages 92 and '84 to the idling jets. As the throttle valves are opened, the degree of suction obtaining at the idling jets and available to draw fuel thereto from the float bowl I8 decreases. When the throttle valves are opened to such a degree that the idling jets are no longer necessary, as the main fuel nozzles |6 and |8 are alone capable of supplying all fuel needed by the engine,v the degree of suction obtaining at the idling jets has so decreased that it is no longer sufcient to overcome the resistance of the restricted passageway between the rod 52 and guide 54 and no further fuel is supplied to the idling jets.

As the throttle valves 38 and 32 are opened wider and wider, the degree of suction obtaining at the idling jets 84 and 86 is still further `decreased and at some point in the opening of the throttle valves, the suctionl obtaining at the idling jets just balances that existing inthe oat bowl I8. Further opening of the throttle valves means that the degree ofsuction obtaining in the float bowl is greater than that obtaining at the idling jets 84 and 86. This would normally produce objectionable back bleed from the idling jets to the float bowl, but this is prevented by the resistance of the small clearance between the guide 54 and rod 52 which functions as a restriction to prevent such back bleed. This structure is interposed between the float bowl and idling jets and flow of fuel through this restriction is automatically regulated by suction in accordance with engine requirements.

In the carburetor shown in Figure 2, I have further simplified the carburetor structure by partially combining the accelerating pump mechanism with the idling jet mechanism. nIn this figure I have shown a carburetor having a main air inlet |58 communicating by way of air valve |52 with dual mixing chambers |54, each of which is provided with a main fuel feeding nozzle |56 and a throttle valve |58 on a common shaft |68. 1

The throttle valve shaftl|68 is interconnected with a link |62 in a manner similar to that of Figure 1 whereby opening of the throttle valve raises the link |62. The lower end of this link is pivotally connected toa rod |64 and a spring |68 is located in the tubular link |62 and between the two pivotal connections thereof to eliminate lost motion.

The lower end of the cylinder |12 is provided Ywith fa passage controlled by a ball inlet valve |88 whereby the cylinder .is supplied with fuel from the carburetor float bowl |82.

The duct |96 also communicates ,with a pair of vertical ducts 288 each leading to an idling jet 282v controlledy by a needle valve 284. Valves |88 and |94 prevent back bleed through duct |96.

It will be understood that the air valve |52 is provided with a weight or spring for urging this lvalve toward closed `position and` the valve is shown as being connected to a dashpot 288 to reduce valve fluctuation. The air valve |52 also controls a tapered pin 218 located in a restricted orifice 2|2 through which the booster Venturi tube (not shown) discharges. This booster Venturi tube serves to maintain sufficient suction in the iioat bowl |82 to draw fuel thereinto from the main fuel supply tank as described more fully in connection with Figure 1.

In the operation of the carburetor of Figure 2, the throttle valves` 58 assume the position shown when the engine is idling. During such idling, the high degreev of suction :existing below the throttle valves is suicient to raise valves v|38 and |94 associated with the accelerator pump and draw fuel from the oat bowl,.past these valves and through the restricting plug |92, thence through duct |90 and ducts 200 to the idling jets 202. When the throttle valves |58 are opened to such a degree that all fuel requirements of the engine can be adequately cared for by the main fuel feeding nozzles |56, the degree of suction at the idling jets 202 has decreased to such an extent that it is insufficient to draw fuel past the valves |80 and |94 and restriction |92. It will be noted that the accelerator jets |90 function as anti-siphoning air inlets for the duct system leading to the idling jets 202.

When the throttle valves are opened suddenly, the spring |14 is compressed and urges the accelerator pump cylinder |12 upwardly. This forces fuel through the restriction |92 in the piston, past valve |94, and through duct |96 to the accelerator jets |98 through which is discharged mosi; of the fuel forced from the accelerator pump as a result of the sudden open-A ing of the throttle valves. A small proportion of this fuel may also be discharged through the idling jets 202, but this is not objectionable. In fact, the interconnection of the idling jets with the accelerator jets has a material advantage in addition to simplification of l the carburetor structure.

'I'hroughout the range of operation of the idling jets the duct system leading to the accelerator jets |98 is maintained full of fuel. Practically all acceleration starts from this range so that at the start of each acceleration the passages leading to the accelerator jets |98 are lled with fuel whereby discharge of fuel from the accelerating jets starts simultaneously with the opening movement of the throttle valve. This results in instantaneous response of the engine. In carburetors in which the accelerator pump mechanism is entirely separate from the idling jet system, it is common for the accelerator pump system to be partially drained of fuel when opening movement of the throttle valves rst begins. This results in a lag 'in the response of the engine to the accelerating movement of the throttle valve. p

The modification shown in Figure 2 has a further advantage over that shown in Figure 1. In the embodiment of Figure 1 a small amount of air leaks down along the rod 52 and into chamber |04, even though that part of rod 52 above groove |06 is designed to fit tightly in the carburetor body. As a result of this leakage, an

emulsion of fuel and air is supplied to the idling jets 84 and 86. This emulsion, however, is not necessarily uniform and sometimes contains slugs of fuel which offer greater resistance to flow through the passages to the idling jets than does the emulsion. The presence of such slugs in these passages therefore temporarily reduces the degree of suction existing in the float bowl I0 and creates uneven idling of the engine.

This disadvantage of the embodiment shown in Figure 1 is eliminated in the embodiment of Figure 2. In Figure 2 the ducts |96 and 200 are so located and designed that the only infiltration of air into these ducts is through the accelerator jets |98 which correspond to the air inlet bores 96 of Figure 1 and which do not produce the objectionable characteristics resulting from leakage of air past the rod 52 of Figure 1.

While I have illustrated both embodiments of my invention as being applied to carburetors having tw'o fuel feeding nozzles, it will be understood that both embodiments of my invention are equally adapted for application to a carburetor having only a single fuel feeding nozzle or any number of such nozzles. It is also to be understood that my invention is not limited to the details shown but may assume numerous other forms.

The claims herein are directed broadly to subject matter disclosed but not claimed in my said Patent No. 2,162,056, and also specifically to the two embodiments shown in the drawings of the instant application.

I claim:

In a fuel lift carburetor of the class described the combination of a float bowl adapted to hold a quantity of fuel, a booster Venturi tube for maintaining said float bowl under sub-atmospheric pressure, a main fuel feeding nozzle supplied with fuel from said float bowl, conduit means connecting said nozzle with said float bowl, a mixing chamber into which said nozzle discharges, an air inlet valve for said mixing chamber, a dashpot for said valve, a throttle valve controlling communication between said mixing chamber and an intake manifold of an engine to which said carburetor is adapted to be attached, an idling jet on the engine side of said throttle valve, a needle valve for adjusting said idling jet, a passage connecting said idling jet with said float bowl, means connecting said passage with said mixing chamber above said throttle valve, a ow restriction in said passage, the absolute pressure at said idling jet and in said mixing chamber being greater under certain conditions of carburetor operation than' the absolute pressure in` said flo-at bowl whereby under said conditions of carburetor operation back bleed into said oat bowl through said passage would normally occur and flowd control means in said passage preventing back bleed therethrough, said flow control means being designed and arranged to be overcome by suction at said idling jet when said engine is idling.

ROBERT F. BRACKE.