US2138590A

US2138590A - Carburetor

Info

Publication number: US2138590A
Application number: US4479A
Authority: US
Inventors: Robert F Bracke
Original assignee: Individual
Current assignee: Individual
Priority date: 1935-02-01
Filing date: 1935-02-01
Publication date: 1938-11-29
Anticipated expiration: 1955-11-29

Description

Nov. 29, 1938. R. F. BRACKE 2,138,590

CARBURETOR Filed Feb. 1, 1955 Patented Nbv. 29, 1938 UNITED .ATENT OFFICE 18 Claims.

This invention relates to carburetors adapted to supply carbureted fuel to internal combustion engines and the like.

One of the objects of the invention is to pro- 5 vide an improved carburetor.

A further object of the invention isto provide an improved carburetor of the fuel lift type.

A further objectof the invention is to provide a carburetor of the fuel lift type in which the degree of fuel lift vacuum is modified under idling. conditions. to provide an automatic selfcompensating idling control.

A further object of the invention is to provide an improved downdraft carburetor.

Afurther object of the invention is to provide an improved carburetor having an expanding Venturi tube which automatically adjusts itself to different conditions of engine operation.

Other objects, advantages, and capabilities of the invention will appear from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawing, which shows in cross-section, a carburetor embodying my invention.

Referring to the drawing, the carburetor comprises two principal portions l and H which may suitably be castings. The upper portion l0 comprises a relatively large cylindrical mouth l2 which serves for the admission of air. The mouth i2 is provided with a spider 13 which supports a central hub M. The hub I4 is bored axially, the lower portion of the bore being threaded to receive the exteriorly threaded surface of the primary Venturi tube or nozzle 15, which is directed downwardly. The upper end of the Venturi tube 15 is provided with a shoulder [6 which engages the upper face of the hub I4. The hub I4 and Venturi tube are conformed to provide an annular chamber l'l around the throat of the Venturi tube. Fuel supply jets l8, which are preferably sloped inwardly and downwardly, extend between the annular chamber I! and the throat of the Venturi tube l-5.

The annular chamber I1 communicates through a duct I9, which may extend through one of the spokes of the spider l3, with a vertical bore 20. The lower portion of this bore 20 is enlarged to receive a depending guidetube 2| and its intermediate portion is threaded to receive a plug 22, the upper end of which is provided with a relatively large metering orifice 23 for the passage of liquid fuel. The guide tube 2| may be secured within the lower portion of the vertical bore 20 in any suitable way. It is, however, preferred to secure the tube 2| to the casting ID by means of the plug 22, which may be provided at its lowerend with a flange which engages an inwardly extending flange at the upper end'of the tube 2|.

An economizer pin 24 is adapted to project upwardly through the orifice 23. At its lower end the pin is secured to an inverted cup 25 which has a sliding fit in the tube 2|. Above the cup 25 a relatively. Weak coil spring 26, of large diameter, is provided. This spring abuts against the flange at the upper end of. the tube 2! so as to tend tomove the cup 25 and pin 24 downwardly. The upper end of. the pin 24 is provided with an enlarged head 2:! which is located within the orifice 23 during the part throttle range of the carburetor, corresponding to speeds between idling and, for example, sixty-five miles an hour. In this range the clearance between the head 2? and the metering opening 23 is relatively small so that only a restricted passageway for fuel is provided. Below the head 21 the pin 24 comprises a restricted portion 28, which portion is located'within the orifice 23 when the throttle is wide open, as will'hereinafter be described. The cup 25 is. provided with an opening 29 which permits fuel to pass upwardly therethrough. The opening 29 :is sufiiciently. small so that the cup 25 serves as the accelerator pump, supplying an increased amount; of fuel when the accelerator is Will be understood that thesev two portions of the carburetor are assembled together in any suitable manner, a gasket 32 being provided between the contacting surfaces.

The lower portion of the carburetor comprises a stepped cylindrical body 34 which is 10- cated in alignment with the cylindrical mouth l2. The fuel chamber 3|, which is located below the fiat member 30 and the bore 20, is located alongside the stepped cylindrical body 34. The throttle valve 35rwhich may be a butterfly valve of the usual type, is located .within the lower narrower portion of the stepped cylindrical body 34. A sleeve 36 is slidably mounted within the cylindrical .body 34,: being provided with an annular bearing surface 31 whichhas-a sliding fit in the lower portion of the stepped cylindrical body 34 and an annular bearing surface 38 of greater diameter which has a sliding fit within the upper enlargedportion of the stepped cylindrical body34. The sleeve 36 and stepped cylindrical body 34 provide between them a chamber 39, in which is provided a coil spring 45 normally tending to press the sleeve 35 upwardly so that its upper edge is brought into sealing engagement with the hub l4 of the spider l3. A duct 4! extends from the chamber 39 to the interior of the sleeve 35, opening thereinto preferably at a point near the upper end of the sleeve.

The fuel chamber 3| is provided with a fioat 44 which controls a fuel inlet valve (not shown) in known manner. The bottom wall of thefuel chamber 3| is provided with an elongated vertical sleeve 45 which receives a rod 47 adaptedto bear upon the upper wall of the inverted cup at or near its center. The lower end of the rod rests upon an arm 45 pivotally mounted on the body of the carburetor at a suitable point. Intermediate its pivotal point and the point of contact with the rod 4?, the arm 48 rests on a cam 49 which is mounted on the shank of the throttle valve outside. the stepped cylindrical body 34. Thefcam 49 is configured so that when the throttle valve 35 is opened the arm 48 is raised to elevate the head 27 of the pin 24 within the .metering orifice 23. At-;a predetermined throttle opening the head. 2? emerges from. the orifice 23 and the clearancebetween the reduced portion 28 of the pin 24 and the opening 23 provides an enlarged passage for the liquid fuel to meet the great demand for power at high speeds. It will be noted that. the pin 24 is not positively connected to the rod 41 and that there is no necessityfor exact alignment between the rod be mounted and maintained incoaxial relation with the opening 23. The tube 2| projects below, and the sleeve 45 projects above the normal fuel level of the fuel chamber 3|, defined by'the float 44.

At one side, for example, the side opposite the fuel chamber 3|, the stepped cylindrical body 34 is provided with a solid Wall of enlarged thickness designated 55. This wall is provided with a transverse bore 5| for the accommodation of the fuel lift or booster Venturi tube 52. The inner end of the bore5| is reduced slightly as shown at 53. The adjacent portion .of the bore 5| is threaded so as to receive the correspondingly threaded portion'of the Venturi tube 52. On the inner side of the head 54 of. the Venturi tube 52, the bore5l and the Venturi tube 52 are conformed to provide an annular passageway 55 which surrounds the throat of the Venturi tube 52 and communicates therewith through openings 55. The outer end of'thebor'e 5! is enlarged so as to receive the head 54 of the Venturi tube 52 and provide a chamber 57. A duct 58 connects the annular passage 55 to the upper portion of the fuel chamber 3.! A duct 59 extends downwardly from the chamber 51 to a point below the The duct 59 is connected by drical body 34 below the closed position of the throttle valvei35, and preferably at a point closely adjacent said valve.

The effective area of the duct 30 is controlled by a needle valve52 which is provided with a milled head whereby it may readily be adjusted. The wall 50 is provided with a flat outer face 54 which contains the outer end of the chamber '51. A duct extends from the fiat face 54 into the annular chamber 39. A plate 55 is pivotally mounted on the flat face 54 by means of a screw 5l a spring 58 serving to hold the plate 65 against the face 54. The plate 55 is provided with a metering orifice 69 adapted to register with the chamber 51 during the normal operation of the engine to which the carburetor is attached. The plate 65 is connected to suitable means (not shown) for its operation in the usual manner of operating a choke. When thus operated, the metering orifice 59 is brought out of register with the chamber 5i so that the Venturi tube 52 is rendered inoperative for the time being. plate 55 is provided with an opening 15 which is adapted to be brought into register with the duct 55 in the choked position of the plate 65.

Inthe normal operation of the carburetor with the engine running, the metering orifice 59 is in register with the chamber 5'! and the opening 15 is out of register with the duct 55, which is. consequently closed, the throttle 35 is partly open, and the rod 47 and pin 24 are slightly elevated above the position shown in the drawing. The suction of the motor is sufficient to move the sleeve 35 downwardly somewhat away from= seated relation with the hub it of the spider. l3, so that secondary air is admitted through the mouth 12, the sleeve 35 and stepped cylindrical body 35 into the intake manifold of the engine. Air drawn through the-Venturitube 52 .bythe suction of the engine creates a vacuum in, the duct 58 which is communicated to the fuel cham ber 3 I. This vacuumin the fuelchamber effects the elevation of liquid fuel from the main fuel tank inknown manner, the float 44 closing the valve (not shown). when a predetermined level is attained. In this way a. constant level of fuel is maintained in the chamber 3!.

With variations in engine suction, the vacuum The vary considerably. The air flowing through the Venturi tube 52 impinges upon the lower end of r the sleeve 35 which is slightly reduced below the bearing surface 3'! to provide clearance for the passage of air downwardly towards the throttle valve 35. This reduced portion of the sleeve tapers downwardly slightly, as shown in I the drawing. the flow of air through the Venturi tube 52 and this resistance is increased at high speeds owing to the lower position of the sleeve .35, which results in the narrowing of the passage between the sleeve and the wall and also increases the length of restricted travel between the discharge of the air at 53 until it is mixed with the main stream floating downwardly past the throttle valve 35. As a consequence, the vacuum in the fuel chamber 3!, while it increases progressively with increase of enginespeed, does not increase at as great a rate as it would if the action. of the Venturi tube 'were not modified in this manner;

' The suction of the engine is partly satisfied by the secondary air entering the sleeve 35 around the hub I4, and partly by the rich'mixture of air and fuel delivered by the Venturi tube 55. primary air is drawn through thezVenturitube l5 by the suction of the engine and the momentum of the secondary air entering the mouth I2 imparts an initial velocity to the primary air which increases'the emciency of the Venturi tube I5. The Venturitube l5 elevates fuel through the tube 2!, the opening 29 in the cup 25, the open- The This sleeve introduces resistance to- 23. At greater speeds the head 21 is above the opening 23 and a less restricted passageway is provided for the liquid fuel.

The suction of the engine within the sleeve 35 extends through the duct 4| into the annular chamber 39 and causes a downward movement of the sleeve 36', against the action of the spring 40, proportionate to the intensity of the engine suction.

An important feature of my invention is the automatic self-compensating idling control. In order to understand this control, it is first necessary to appreciate certain fundamental relationships. The amount of fuel supplied by the Venturi tube or nozzle I5 is dependent both upon the volume of airflowing through this tube and also upon the degree of suction existing in the fuel chamber 3|, so that by varying the degree of suction in the fuel chamber 3| the amount of fuel supplied by the Venturi tube l5 can be varied for any given amount of air flowing therethrough.

The degree of suction existing in the fuel chamber 3| is controlled by the booster Venturi tube 54 and is proportional to the volume of air flowing through this booster tube. The volume of air flowing through this booster tube 54 in turn depends upon difference in pressure at the ends of this tube, and I Vary the degree of suction existing in the fuel chamber 3| and therefore the amount of fuel supplied by the Venturi tube l5, by varying the pressure differential between the ends of the booster Venturi tube 54. The Venturi tube 54 derives its air supply from the chamber 5'! which communicates with atmosphere through metered orifice 69 which restricts the flow of air into the chamber 51. The chamber 51 is also connected to that part'of the manifold on the engine side of throttle valve 35 by means of passageways controlled by needle valve 62.

When the throttle valve 35 is substantially open, there is very little suction communicated to chamber 51. by means of the passageways controlled by needle valve 62, but when the throttle valve 35 is moved to idling or substantially closed position, the manifold vacuum rises and consequently the suction existing in the chamber 51 is increased, thereby decreasing the degree of suction in the fuel chamber 3| and permitting the Venturi tube |5to supply a richer mixture. The carburetor is adjusted by means of the needle valve 52 so that a rich mixture is supplied to the engine at idling speed.

If the mixture suppliedto the engine during idling should temporarily become lean for any reason, such, for example, as the passage of a small amount of vapor instead of liquid fuel to the passages l8 in the Venturi tube I5, the effect of this lean mixture will be to cause the engine to speed up slightly. This speeding up creates a higher degree of suction in that part of the manifold on the engine side of the throttle valve, and this higher degree of suction is communicated to the chamber 51 through passages 59 and 6|]. The resulting increase in suction in chamber 51 reduces the pressure drop across the Venturi tube '54 and this .in turn reduces the degree ofsuction obtaining in the fuel chamber 3|. Accordingly, fuel feeding nozzle l5 draws more fuel from fuel chamber 3| and supplies a richer mixture to the engine, thus causingit to slow down again and resume its normal idling speed.

In a similar manner my improved idling contI'O1 Wi11 compensatefor temporary increases in the richness of the mixture, by causingcorresponding increases inthedegree of suction ex isting in the fuel chamber 3|, thereby reducing the richness of the mixture supplied by the fuel feeding Venturi tube l5. This leaning of the mixture speeds up the rotation of the engine and reestablishes normal idling speed.

When the plate 66 is moved to choked position, the chamber 39 is put in communication with the atmosphere through the duct 65 and opening 10. The chamber 51 is closed by the plate 55 and the Venturi tube 52 is rendered inoperative as a booster so that the degree of suction obtaining in the fuel chamber 3| becomes equal to that existing in the mixing chamber. Consequently, the suction of the engine draws a very rich mixture through the Venturi tube l5 and ease of starting results.

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 claims.

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

1. A downdraft carburetor comprising a stepped body, a sleeve having a pair of bearing surfaces of different diameters slidable in said body and providing a chamber of variable capacity between said sleeve and body, a spring tending to force said sleeve upwardly, a downwardly directed Venturi tube mounted in the upper part of said body,

and means surrounding said Venturi tube adapted to receive the upper end of said sleeve to exclude secondary air, said sleeve having an opening establishing communication between said chamber and a point within said sleeve.

2. A downdraft carburetor comprising a stepped body, a sleeve having a pair of surfaces of different diameters slidable in said body and providing a chamber of variable capacity between said sleeve and body, a spring tending to force said sleeve upwardly, a downwardly directed Venturi tube mounted in the upper part of said body, means surrounding said Venturi tube adapted to receive the upper end of said sleeve to exclude secondary air, said sleeve having an opening establishing communication between said chamber and a point within said sleeve, and said body having an opening establishing communication between said chamber and the atmosphere, and means adapted to be actuated to open and close said last-mentioned opening at will.

3. A downdraft fuel lift carburetor comprising a stepped body, a sleeve having a pair of bearing surfaces of different diameters slidable in said body and providing a chamber of variable capacity between said sleeve and body, a spring tending to force said sleeve upwardly, a downwardly directed Venturi tube mounted in the upper part of said body, means surrounding said Venturi tube adapted to receive the upper end of said sleeve to exclude secondary air, said sleeve having an opening establishing communication between said chamber and a point within said sleeve and said body having an opening establishing communication between said chamber and the atmosphere, a fuel lift Venturi tube discharging into said body, and means adapted to be actuated at will either to open the last-mentioned opening and close the fuel lift Venturi tube or to close said last-mentioned opening and open the fuel lift Venturi tube. V

l. A'downdraft fuel lift carburetor comprising a stepped body, a sleeve having a pair of bear 'ing surfaces of different diameters slidable in said body and providing a chamber of variable capacity between said sleeve and body, .the lower end of said sleeve being of reduced diameter to provide a clearance between itand the adjacent portion of the body, a spring tending to force said sleeve upwardly, a downwardly directed Venturi tube mounted in the upper part of said body, means surrounding said Venturi tube adapted toreceive the upper end of said sleeve to exclude secondary air, said sleeve having an opening establishing communication between said chamber and a point within said sleeve and said body having an opening establishing communication between said chamber and the atmosphere, a fuel lift Venturi tube discharging into said'body the discharge from which is adapted to impinge against said reduced portion of the sleeve so that resistance to flow through the fuel lift Venturi tube is increased by the downward movement of the sleeve, and means adapted to be actuated at will either to open the last mentioned opening and close the fuel lift Venturi tube or to close said last mentioned opening and open the fuel lift Venturi tube.

5. A carburetor comprising upper and lower portions secured together, a fuel chamber in the lower portion having a sleeve projecting upwardly above the fuel level, an actuating rod projecting through said sleeve, a tube projecting from the upper portion to below the fuel level and having a fuel outlet at its upper end, said tube and sleeve being in substantial alignment, and a perforated piston in said tube adapted to be actuated by said rod. i

6. A carburetor'comprising upper and lower portions secured together, a fuel chamber in the lower portion having a sleeve projecting upwardly above the fuel level, an actuating rod projecting through said sleeve, a tube projecting from the upper portion to below the fuel level and having a fuel outlet at its upper end, a perforated piston in said tube adapted to be'actuated by said rod, and a member carried by said piston and extending into said fuel outlet adapted to control the effective size thereof in accordance with the position'of the piston.

7; A carburetor comprising upper and lower portions secured together and having a throttle valve, a fuel chamber in the lower portion, a tube projecting downwardly from the upper portion to below the fuel level, and having a fuel outlet at its upper end, a piston in said tube adapted to be moved progressively with the throttle Valve, and means carried by the piston adapted to project through the fuel outlet to modify the effective size thereof in accordance with the throttle valve position.

8. In a carburetor, incombination, an accelerator pump having a perforated piston adapted to provide an enhanced supply of fuel on rapid acceleration, said fuel passing through said piston and through a metering orifice, and an economizer element rigidly carried by said piston and projecting through saidorifice to control the effective area thereof in accordance with throttle position.

9. A fuel lift carburetor comprising a main Venturi tube, a fuel lift Venturi tube, a mixing chamber into which said Venturi tubes deliver, a

I valve responsive to suction in the mixing chamher and adapted to impede the flow through the fuel lift Venturi tube to a degreedepending upon from the mouth of the fuel lift Venturi tube to the engine side of the throttle valve, and adjustable means adapted to control the flow through said duct.

10. A fuel lift carburetor comprising a fuel chamber, a main Venturi tube, a fuel lift Venturi tube, ducts connecting the throats thereof to the fuel chamber, a mixing chamber intowhich the Venturi tubes deliver, a throttle valve controlling the outlet from said mixing chamber, a duct extending from the outer end of said fuel lift Venturi tube to the engine side of'the throttle valve, and a screw for adjusting the flow through the last-mentioned duct. 7 i

11. A carburetor comprising a pair of complementary sections secured together, a fuel chamber in one section having a sleeve projecting upwardly above the fuel level in said chamber, an actuating rod projecting through said sleeve and guided thereby, a tube carried'by the other sectionand projecting into said chamber to a point below the fuel level therein, said tube telescoping the upper end of said sleeve and having a fuel outlet at its upper end, and pump means guided V by said tube, said means and said rod having surfaces conformed to provide a satisfactory, operative connection therebetween irrespective of misalignment between said tube and said sleeve.

12. A fuel lift carburetor comprising a main Venturi tube, a fuel lift Venturi tube, a mixing chamber into which said Venturi tubes deliver,

subatmospheric pressure in said chamber whereby fuel is drawn thereinto from a main fuelsupply tank located at a distance from said cham her, a mixing chamber into which said Venturi tubes deliver, a throttle valve in said mixing chamber, and a by-pass operable at nearly closed throttle positions for reducing the effectiveness of the fuel lift Venturi tube. i

14. A fuel lift carburetor comprising a main Venturi tube, a fuel chamber from which said main Venturi tube is supplied, a fuel lift Venturi tube for creating a subatmospheric pressure in said fuel chamber whereby fuel is drawn thereinto'from a main fuel supply tank, a mixing 'chamber into which said Venturi tubes deliver, a throttle valve in said mixing chamber, and a duct communicating between the inlet of the fuel lift Venturi tube and the engine side of the throttle valve.

15. A fuel lift carburetor comprising a main Venturi tube, a fuel chamber from which said Venturi tube is supplied, a fuel lift Venturi tube for creating a subatmospheric pressure in said chamber whereby-fuel is drawn thereinto from a main fuel supply tank, a mixing chamber into which said Venturi tubes deliver, a valve responsive tosuction in the mixing chamber and adapted to impede the flow through the fuel lift Venturi tubeto a degree depending upon said su"- tion, a throttle valve controlling the outlet from said mixing chamber, and a duct extending from the inlet of the fuel lift Venturi tube to the engine side'of the throttle valve.' 1 T 16. A carburetor comprising upper and lower portions secured together, a fuel chamber in the lower portion having a part projecting upwardly above the fuel level, an actuating rod projecting through said part, a second part projecting from the upper portion to a point below the fuel level and providing a cylinder, said cylinder having a fuel outlet at its upper end, said parts being in substantial alignment, and a perforated piston in said cylinder adapted to be actuated by said rod.

17. A fuel lift carburetor comprising a main Venturi tube, a fuel lift Venturi tube, a mixing chamber into which said Venturi tubes deliver, a throttle valve in said mixing chamber, a metering orifice limiting the admission of atmospheric air to said fuel lift Venturi tube, means for varying the size of said orifice, a chamber located between said orifice and the inlet to said last mentioned Venturi tube, and a duct establishing communication between said last mentioned chamber and the engine side of the throttle valve.

18. A fuel lift carburetor comprising a fuel chamber, a main Venturi tube supplied from said chamber, a fuel lift Venturi tube for creating sub-atmospheric pressure in said chamber, whereby fuel is drawn thereinto from a main fuel supply tank located at a distance from said chamber, a mixing chamber into which said Venturi tubes deliver, a throttle valve in said mixing chamber, a by-pass operable at nearly closed throttle positions for reducing the effectiveness of said fuel lift Venturi tube, and other means operable at open throttle positions for reducing the effectiveness of the fuel lift Venturi tube.

ROBERT F. BRACKE.