US2155638A - Carburetor - Google Patents

Description

April 25, 1939.

CARBURETOR Filed Feb. 6, 1955 R. F. BRACKE Patented Apr. 25, 1939 u-,lxxiriso- STA-TES PATENT OFFICE-,f

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GARBURETOR' Robert F. Bracke, chicago, Ill. Application February 6, 19,35, Serial No. 5,203

' 1 claim.` (o1. '2t-1772 v This ,invention relates tocarburetors and 'par-v' ticularly to carburetorsof thefuel lift type in whichthe suction 'of` the engine applied to the carburetor is adapted -through suitable 'depres-v sionramplifying means toraise the necessary'supply of fuel from the fuel tank. 1

One of thel objects of the inventionvis to 'pro- A furtherv object of theinvention is to lprovide a fuel lift carburetor'adapted'to exert a substantially uniform vfuellift suction, irrespective of engine speed and without means connected to the engine controls;

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

In the drawing, the ligure is a vertical section through a preferred embodiment of my invention and diagrammatically shows this embodiment connected to the main fuel tank.

Referring to the drawing, the carburetor is designated by the reference numeral IIJ and the fuel tank, which is normally located at the rear end of the vehicle and at a lower level than the carburetor, is designated by the reference numeral II.

The carburetor comprises a main body p0rtion I2 which is provided with an annular seat I3 against which abuts the upper edge of a removable shell I4 forming a fuel chamber I4a. The shell I4 is provided with a central opening through which is adapted to pass a cylindrical stem I5 depending from the carburetor body I2. The shell I4 is connected to the stem I5 by means of a knurled nut I6. Suitable gaskets are employed at the seat I3 and the upper end of the nut I6 to render the shell I4 liquid-tight in assembled relation. 'I'he stem I5 is internally shouldered at I1 and I8. The portion of the stem above the shoulder I8 is internally threaded to receive a correspondingly threaded portion of a Venturi tube or nozzle I9. The Venturi tube I9 is conformed so as to establish an annular passage 20 located between the shoulders I1 and I8. This annular passage communicates through a duct 2| with a low point within the chamber I4a. The Venturi tube I9 is provided with ducts 22 which lead from the annular passage 20 into the throat of the Venturi tube, The stem I5 terminates inside a secondary air chamber 23. The Venturi tube I9 extends through this chamber and terminates thereabove in the throat of a Venturi tube 24 formed in the body I2"of the carburetor. The Venturi tube 24'is 1Q,- cated at the bottom of a mixing chamber 25,".tlie' outletfr'om whichv is controlled by a throttle L. valve: 2liI which maybe vof the k,usual -butterfl'yj type'. 5 l/Vithin the chamber. I 4a is provided Aa float'` 21"of1 known 4type Vwhich actuates'a valve 28 Itf; controlr the outlet of a pipe 29 v`andmaintai'n a substantially constant levelkof liquid fuel withinM the `shell. i4. The pipe 29 leads back'to theA fuel 10 3| Visfprovided to control the admission. of this .15`

air.' The valve 3l is provided with a'stem 32,4 which stem is supported in a boss 33 carried by a spider 34 mounted in the port 30. An abutment member 35 is mounted on the outer end of the stem 32 and a coil spring 3B is located 20 around the stem 32 so as to bear against the boss 33 and against the abutment member 35 so as to tend to move the valve 3| outwardly to closed position.

In the wall of the chamber 23 opposite the port 25 39, and preferably substantially in the center of said port, a duct 31 is provided which communicates with a downwardly directed bore 38, the upper end of which is threaded to receive the correspondingly threaded end of a small Venturi 30 tube 39. The lower end of the bore 38 is enlarged so as to provide, in cooperation with the Venturi tube 39, an annular chamber 4I). The annular chamber 40 communicates through ducts 4I with the throat of the venturi 39 and by 35 means of a duct 42 in the body I2 of the carburetor, with the upper portion of the chamber Illa. A screw 43 provided with a knurled nut 44 is provided for the purpose of constricting, to

an adjustable extent, the outlet of the Venturi 40 tube 39. A lock nut 45 isprovided to maintain the screw 43 in the desired position of adjustment.

The operation of the carburetor is as follows. At low and idling speeds the suction of the en- 45 gine draws primary air through the stem I5, and the Venturi tube I9 draws fuel through the conduit 2| from the chamber I4a. The suction of the engine is communicated through conduit 31 to Venturi tube 39 with the result that a greater 50 suction is produced in the conduit 42 and, consequently, in the upper portion of the chamber I4a. As liquid fuel is taken from the chamber I4a, the float 21 falls and the valve 28 is opened so that this suction may elevate liquid through 55 pipe 29 from fuel tank This operation maintains a substantially constant level of liquid in the chamber I4. The knurled nut 44 is adjusted so as to give the desired Vacuum lift in the chamber Ma.

When the speed of the engine is increased by opening the throttle Valve 26, the Vacuum within the mixing chamber 25 and Venturi tube 24 creates a greater flow of primary air through the stem I5 and consequently a greater supply of liquid fuel through the duct 2|, The vacuum in the secondary air chamber 23 is surliicent to open the valve 3| against the closing tendency of the spring 36. The degree of opening of the valve 3l depends upon the speed of the engine, being greater for high speeds and less for lower speeds. I have round that the air coming in past the lower edge of the valve 3| impinges against the opposite Wall of the chamber 23 and creates a relatively high pressure in the bottom zone of the chamber 23. The Vacuum in the upper portion of the chamber 23 is considerably greater. By entering the duct 31 into the secondary air chamber 23 at a point of intermediate height, I

am enabled to subject the duct 31, and conse- =quently the Venturi tube 40, to a vacuum or depression of intermediate degree, which is substantially constant for all speeds of the engine. The result is that the vacuum Within the chamber |4a is substantially constant and supply of liquid fuel in large quantity to the venturi I9 at high speeds is not interfered with by an excessive Vacuum in the chamber |4a.

It will be noted that the secondary air is admitted into the chamber 23 from one side and that the duct 31 opens into a side opposite thereto, the secondary air passingv to the engine through the top intermediate these two sides. 'Ihat is, the incoming secondary air is subjected Within the secondary air chamber to a change in direction which has the eiect of establishing pressure differences therein. The fuel lift Venturi tube connects to the secondary air chamber at a point of intermediate pressure.

Although the invention has been described in connection with the specific details of a preferred embodiment thereof, it must be understood that such details are not intended to be limitative of the invention except in so far as set forth in the accompanying claim.

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

A fuel lift carburetor comprising a body por-A tion having formed thereinL at its upper end a mixing chamber, the lower end of said mixing chamber being of Venturi tube formation, a secondary air chamber in said'body below said Verif-A turi tube and open at one side for'the admisu.l sion of secondary air, a fuel chamber removably, secured to the lower end of said body, aI primary] air inlet extending through said chamber and a, main Venturi tube extending through,l the geg. ondary air chamber into first said Venturi tube formation, and a fuel lift Venturi tube commu.. nicating with the secondary air chamber at a point opposite and substantially ,Y central with respect to the secondary air inlet, said point being free from local interruptions to the normal ow of air through said chambers.

ROBERT F. BRACKE.

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