US2969963A - Carburetor - Google Patents

Description

Jan. 31, 1961 INVENTOR. HERBERT K. BROWN CARBURETOR Herbert K. Erown, Trumbull, Conn assignor to Brown Engine Products, Inc, a corporation of Texas Filed May 7, 1958, Ser. No. 733,561

4 Ciairns. (Cl. 2614) This invention relates to carburetors in which fuel is introduced through a passage into a venturi charge-forming chamber. More particularly, it relates to diaphragm controlled carburetors and provides an improved carburetor body structure in which the fuel passage is formed.

There has been a growing demand for carburetors having flexible diaphragm fuel pumps mounted directly on the carburetor for use on portable gasoline engines. Further, diaphragm-controlled fuel reservoirs commonly are used in such carburetors when the engine must be operated in many different positions, to provide means for automatically regulating the flow of the fuel through the passage. Such reservoirs are partly defined by a flexible wall (diaphragm) which actuates a needle valve positioned in the passage between the fuel pump and the reservoir and thereby causes the flow of fuel to decrease or increase as required. Regulation of the outflow of fuel from the diaphragm is provided in many designs by an adjustable second needle valve=located in the fuel passage between the reservoir and the venturi'chargeforming chamber.

In most instances the body structure of the carburetor is designed to define the entire fuel passage from the pump to the charge-forming chamber inclusive. The fuel passage generally communicates with the venturi charge-forming chamber at a fuel delivery position located at or closely adjacent a butterfly valve shuttering the venturi.

.if the venturi is at one end portion of the carburetor body structure with the entire fuel passage to one side of the venturi axis, as is frequently the case, thebutterfiy valve axis usually extends laterally with respect to the body structure (i.e., ifthe venturi is in the top of the body structure with the fuel passage in the portions therebeneath, the butterfly valve axis usually extends horizontally through the wall of the venturi Fuel enters the charge-forming chamber in a direction perpendicular to the venturi axis at a point on the circumference of the venturi in the transverseclosed-position plane of the butterfly valve. Conventional carburetor body structures have not been of sufliciently versatile configuration to permit a fuel passage to extend around the circumference of the venturi to enter at any other fuel delivery position.

This limitation in known carburetor body structures has mitigated against optionally disposing the butterfly valve axis across the venturi at right angles to the ordinary position. For example, if the venturi is in the top of the body structure with the. fuel passage in the portions therebeneath, it has heretofore required a special redesign of the carburetor body to mount the butterfly valve axis vertically.

- The present invention provides an improved carburetor having a body structure of exceptionally versatile design. The newcarburetor is conventional in: that it includes a venturi charge-forming chamber shuttered by abutterfly valve,and has a passage for conducting liquid fuel from a fuel source pressurized by flexible diaphragm 2 pump means through a first needle valve to a fuel reservoir and from the fuel reservoir through a second needle valve to the charge-forming chamber. The passage opens into the charge-forming chamber at a fuel delivery position substantially in the plane of the butterfly valve and perpendicular to the axis thereof.

The improved carburetor body structure of this invention is characterized by defining paths for said passage along each of two courses extending from the second needle valve to two fuel delivery positions in the wall of the charge-forming chamber. Each of the fuel delivery positions is substantially in the plane of the butterfly valve when it is in its closed position, and is spaced angularly approximately 90 about the axis of the chamber. The body structure includes sufficiently extensive drilling surfaces at each of the fuel delivery positions to enable it to be drilled to receive a butterfly valve shaft extending diametrically through the chargeforming chamber, so that the butterfly valve may be positioned for operation about either of two axes at right angles to each other.

small, accommodates a reserve fuel supply for quick response of the engine when it'must accelerate, and it also serves as a surge chamber forthe fuel pump. Advantageously, a first removable filtering'element is positioned in the fuel well, and a second removable filtering element positioned in the passage between the fuel reservoir and the second needle valve.

. 'A preferred embodiment of the invention is described hereinbelow with reference to the accompanying drawings, wherein Fig. 1 is a side elevation in section and partly broken away of a schematic form of a carburetor having the contemplated body structure and illustrating the manner in which the removable filter elements are mounted in that structure;

Fig. 2 is a detailed section of one type of filtering element that may be seated in the body structure;

Fig. 3 is a section through an actual form of carburetor taken on a plane as indicated by the line 33 of Fig. 1, showing one arrangement of the butterfly valve axis and fuel deliveryposition; and

Fig. 4 is a section similar to Fig. 3 showing an alternative arrangement of the butterfly valve axis and. fuel delivery position.

Referring first to Fig. 1, the carburetor includes a body structure indicated generally by the reference numeral 10, which includes a main body portion 11, a diaphragm closure member 12, a fuel pump body 13, and an inlet cover 14-. The fuel pump body 13 and the diaphragm closure member 12 are held in position in relation to the main body portion 11 by any suitable fastening means which also hold a pump gasket 15 and a reservoir gasket 16 in position as shown. The inlet cover 14 is secured to the fuel pump body 13 by one centrally located screw 17, and a gasket 18 and filter element 19 are held in position thereby as shown. Fuel enters the carburetor through an inlet passage 20 in the inlet cover 14. By loosening the cap screw 17, the inlet cover 14 and the associated inlet passage 20 may be turned on the axis of the screw to whatever position is most convenient for attachment to a fuel delivery conduit.

After passing through the filter element 19 the fuel is admitted into a pumping chamber 25 through an inlet check valve 26. The upper surface of the pumping chamber is defined by one side of a flexible pump diaphragm 27, the opposite side of which partly defines a variable pressure chamber 28 in the diaphragm closure member 12. A passage 36 in the diaphragm closure member 12 and in the main body portion 11 provides for communication between the variable pressure chamber 28 and the fiuid pressure. The cyclic variations in such pressure, communicated to the chamber 28 through the passage 30, cause corresponding pulsations of the flexible pump diaphragm 27 so that fuel is intermittently drawn through the inlet check valve 26 into the pumping chamber 25, and is subsequently forced out under pressure through an outlet check valve 31.

After exiting under pressure through the outlet check valve 31, the fuel is forced through a passage 32 in the diaphragm closure member 12 and the main body portion 11. It then passes through a removable filtering element 33 seated in the main body portion of the carburetor body structure. The filtering element 33 is described in detail hereinbelow. After being filtered, the fuel issues through an inlet needle valve 34 into a fuel reservoir 35. The needle valve 34 is engaged by one end of a lever 36 which is pivoted about a pin 37 and urged toward a closed position by a helical compression spring 38. The needle valve 34 is slidably mounted in a seat 40 so that clockwise pivoting of the lever 36 against the force of the spring causes the inlet valve 34 to be opened to increase the flow of fuel into the reservoir 35. Conversely, counterclockwise pivoting of the lever 36 causes the needle valve 34 to close to reduce the flow of fuel. The end of the lever 36 remote from the needle valve rests on an abutment 41 secured to a flexible diathrough an idling passage 47 or a main outlet passage- 47'. Flow through the idling passage 47 into an auxiliary chamber 48 may be selectively controlled by an idle adjustment needle valve 49. The auxiliary chamber 48 is separated from the reservoir 35 by a removable plug 50. The fuel passes from the auxiliary chamber 48 into a charge-forming chamber 51 througheither a primary idling jet orifice 52 or a secondary idling jet orifice 53.

The charge-forming chamber 51 is at the outlet end of a conventional venturi 54 with the air entering under atmospheric pressure in the direction of the arrows and exiting to the engine cylinder or intake manifold at the left as viewed in Fig. 1.

Flow of fuel from the reservoir 35 through the main outlet passage 47' is controlled by a high speed adjustment needle valve 55. Fuel passing this needle valve enters a high speed jet chamber 56 (which is closed from the fuel reservoir by a plug 57) and passes into the throat of the venturi 54 through a high speed jet orifice 58.

A conventional choke butterfly valve 60 and a throttle butterfly valve 61 control the mixture and delivery respectively of the air-fuel charge which is delivered to the internal combustion engine. The throttle butterfly valve 61 is mounted on a shaft 62 extending horizontally across the venturi charge-forming chamber 51. In the closed position of the throttle butterfly valve 61 seen in Fig. 1, the lower edge of the valve is disposed between the primary and secondary idling jet orifices 52 and 53 respectively. The location of the jet orifices 52 and 53 where they open into the charge-forming chamber 51 constitutes what is referred to herein as the fuel delivery position on the circumference of the venturi charge-forming chamber 51.

Returning now to the first removable filtering element 33, the fuel passage 32 communicates with a substantially cylindrical well 65 drilled in the main body portion 11 of the carburetor body structure 10. As seen in Fig.

1, the well 65 extends downwardly from a flat drilling surface 66 on the main body portion 11 and is offset forwardly (toward the reader) with relation to the axis of the venturi 54. The inner diameter of the upper portion of the well 65 has internal threads formed therein.

' The filtering element 33 is a cylindrical plug of per- 'meable material such as felt, screening material, etc.,

shaped to be accommodated within the lower portion of the 'well 65, in position to intercept fuel forced through the passage 32 to the needle valve 34. The upper end of the filtering element 33 is advantageously seated in a recess formed in the lower surface of an externally threaded plug 67. This plug screws into the upper end of the well 65 with its head exposed on the exterior of the carburetor body structure. Thus, by unscrewing the plug 67 from the internally threaded portion of the well 65, the filtering element 33 may be removed from the well and may be replaced with a clean element when desired.

The lower portion of the well 65 is oversize relative to the cylindrical filtering element 33 and an annular space 68 is thereby defined in the fuel passage. This space forms a reserve fuel supply chamber from which fuel may be delivered when the engine is accelerated or started, during the first several engine crankshaft revolutions before the pumping effect of the fuel pump can make itself felt. In addition it functions as a pressure surge chamber which compensates for variations in fuel line pressure due to oscillation of the fuel pump.

The lower end of the filter plug 33 is pressed tightly by the plug screw 67 against its seat about the exit opening from the well 65 to the needle valve 34. Hence fuel in the annular chamber space about the periphery of the filter plug 33 must pass through the filter to enter the fuel reservoir 35.

Turning now to the second removable filtering element 46, a substantially cylindrical well 70 is drilled into the main body portion 11 of the carburetor body structure 10 from a flat drilling surface 71. The well 70 communicates with the passage at its inner end and with the idling passage 47 and the main outlet passage 47' about midway along its length. The removable filtering element 46 itself, which is positioned in the well 70, is a narrow tubular element formed with an internal bore 72 of substantial length closed at its inner end and communicating with the passage 45 at its outer end. The bore 72' also communicates with the interior of the well 70 through a pair of radial apertures 73 in its wall. These apertures are very fine, and of small diameter relative to the bore. A sealing flange 74 formed on the tubular filtering element 46 and a gasket 75 aid in sealing against leakage of fuel about the periphery of the tubular element 46. The filtering element also includes an externally threaded plug 75 which is exposed at the exterior of the body structure 10 and screw-threads into the outer end of the well 70.

Fuel forced from the fuel reservoir 35 through the passage 45 is admitted into the bore 72 and exits therefrom through the fine radial apertures 73 into the well 70. From there it proceeds into the idling passage 47 and the main outlet passage 47'. The small diameter of the bore 72 and the apertures 73 serve as the filtering means, and prevent any drill chips or other debris not intercepted by the filtering element 33 from being carried into position to prevent proper seating of either of the needle valves 49 or 55, or to plug the jet orifices 52, 53 or 58. The filtering element 46 may be readily removed when it becomes clogged by unscrewing the plug 75, and it can then be cleaned or replaced as desired. I

- Alternatively, as shown in detail in Fig. 2, a cylindrical plug 76 of felt or other permeable material may be inserted in the well 70, rather than the tubular element shown in Fig. l. The felt plug 76 fits snugly within the well 70, and is received in a recess 77 formed in a plug 78. The plug screw-threads into the well 70, and compresses the filter plug tightly therein. Fuel flows through the passage 45 to the idling-passage 47 and-the main outlet passage 47- directly through the felt material of the plug 76, which intercepts any chips, dirt, or other solid debris.

The unique design of the body structure permits the primary idling jet orifice 52 and the secondary idling jet orifice 53 to communicate with the venturi chargeforming chamber 51 at either one of two alternate fuel delivery positions as illustrated in Figs. 3 and 4. Such communication at two alternate positions is particularly advantageous in multi-cylinder engines where difficulties are sometimes encountered in distributing the air-gas charge to the cylinder. Also the design permits theshaft 62 of the throttle butterfly valve 61 to be disposed either horizontally or vertically;

In Fig. 3 a transverse section of the main body portion 11 of an actual carburetor is shown detached from the remainder of the body structure 10, with the throttle butterfly valve 61 in fully open position. In this view the valve shaft 62 is horizontal and is mounted within aligned cylindrical bearing surfaces 80 and 81' drilled through flat drilling surfaces 82 and 83 formed diametrically opposite each other on the exterior of the carburetor body structure. The idling jet orifices 52 and 53 (only the latter is shown in Fig. 3) are drilled upwardly through the body structure from the auxiliary chamber 48 to communicate with the venturi charge-forming chamber 51 substantially in the closed-position plane of the butterfly valve 61 at a location substantially 90 from the axis of the shaft 62 at the bottom of the venturi. The auxiliary chamber 48 is itself formed in a flat drilling surface 84 located in the fuel reservoir wall 90 around the circumference of the charge-forming chamber from the surfaces 82 and 83. After the idling jet orifices 52 and 53 are drilled, the plug 50 is pressed into place. Thus, to prepare the main body portion 11 for the arrangement illustrated in Fig. 3, the aligned bearing surfaces 80 and 81 are drilled from either of the drilling surfaces 82 or 83, and the idling jet orifices 52 and 53 are drilled directly upwardly from the auxiliary chamber 48.

Fig. 4 illustrates an alternative arrangement made possible by the carburetor body structure 10. Rather than being disposed horizontally, the butterfly valve shaft 62 is disposed vertically and the idling jet orifices 52 and 53 enter the venturi charge-forming chamber 51 horizontally from the side. From a flat drilling surface 85 on the top of the main body portion 11 of the carburetor diametrically opposite the drilling surface 84, a shaft bearing hole is drilled dovmwardly through the venturi charge-forming chamber 51 into its opposite wall to provide bearing surfaces 87 and 88. These bearing surfaces accommodate opposite ends of the butterfly shaft 62 to dispose the throttle butterfly valve 61 vertically. Since the idling jet orifices 52 and 53 cannot enter the venturi charge-forming chamber 51 at the bottom of the venturi as in the arrangement of Fig. 3, they are drilled horizontally into the charge-forming chamber from the drilling surface 83 to provide a fuel delivery position located 90 away from that of Fig. 3.

This fuel delivery position of Fig. 4 is provided by drilling the orifices 52 and 53 from the inner end of a small well 0 drilled in the flat drilling surface 83. A connecting passage 92 is drilled angularly upwardly from the auxiliary chamber 48 to communicate with this well and with the idling jet orifices 52 and 53 without interfering with either the adjacent bearing surface 88 or the venturi charge-forming chamber 51. A plug 93 is inserted in the well 90 to seal its outer end after the orifices 52 and 53 and the passage 92 are drilled.

It will be seen that by the unique disposition of the flat drilling surfaces 82, 83, 84, and 85, the main body portion 11 of the body structure 10 permits the butterfly valve axis to be positioned either horizontally or vertically in the carburetor assembly.

I claim:

1. In a carburetor having a venturi charge-forming chamber shuttered by a butterfly valve, and further hav-' ing a passage for conducting liquid fuel from a fuel source pressurized by flexible diaphragm pump means through a first needle valve to a fuel reservoir and from the fuel reservoir through a second needle valve to said charge-forming chamber, said passage opening into said charge-forming chamber at a single fuel delivery position substantially in the plane ofsaid butterfly valve and per endicular to the axis thereof, the improvement-which comprises a carburetor body structure defining the path for said passage and providing for said passage to ex tend along each of two courses from said s econd n'e'edle valve to two separatelocations in'the' wallof the chargeforming chamber, saidtwo -separate locations each being substantially in the closed-position plane-of the butter fly valve and being spaced angularly approximately apart about the axis of the-chamber, said single fuelde livery position being adapted to be located at either one of said two separate locations in the wall of said chamher, the body structure at each of said separate locations being sufficiently massive to be drilled to receive a but-terfly valve shaft extending diametrically through the chargeforming chamber, whereby said butterfly valve may be positioned for operation about either of two axes at right angles to each other, said body structure also defining a fuel well in said passage directly adjacent the inlet side of the first needle valve and providing accommodation for a removable filtering element in said passage between said fuel reservoir and said second needle valve.

2. In a carburetor having a venturi charge-forming chamber shuttered by a butterfly valve, and further having a passage for conducting liquid fuel from a fuel source pressurized by flexible diaphragm pump means through a first needle valve to a fuel reservoir and from the fuel reservoir through a second needle valve to said charge-forming chamber, said passage opening into said charge-forming chamber at a single fuel delivery position substantially in the plane of said butterfly valve and perpendicular to the axis thereof, the improvement which comprises a carburetor body structure defining the path for said passage and providing for said passage to extend along each of two courses from said second needle valve to two separate location in the wall of the charge-forming chamber, said two separate locations each being substantially in the closed-position plane of the butterfly valve and being spaced angularly approximately 90. apart about the axis of the chamber, said single fuel delivery position being adapted to be located at either one of said two separate locations in the wall of said chamber, the body structure at each of said two separate location being sufficiently massive to be drilled to receive a butterfly valve shaft extending diametrically through the charge-forming chamber, whereby said butterfly valve may be positioned for operation about either of two axes at right angles to each other.

3. In a carburetor having a passage for conducting liquid fuel from a fuel source pressurized by flexible diaphragm pump means through a first needle valve to a fuel reservoir, and from the fuel reservoir through a second needle valve to a venturi charge-forming chamber, said passage opening into said charge-forming chamber closely adjacent the periphery of a butterfly valve shuttering said venturi and at a single point substantially perpendicular to the axis thereof, characterized in that said passage is defined by a body structure including four exterior substantially flat drilling surfaces equally spaced circumferentially at intervals of substantially 90 about said mixing chamber to permit both the butterfly valve axis and the opening of said passage into said charge-forming chamber to "be located in either of two circumferential positions substantially 90 apart.

4. In a carburetor having a venturi charge-forming chamber shuttered by a butterfly valve, and further hav- 7 ing a passage for conducting liquid fuel from a fuel source pressurized by flexible diaphragm pump means through a first needle valve to a fuel reservoir and from the fuel reservoir through a second needle valve to said chargeforrning chamber, said passage opening into said chargeforming chamber at a single fuel delivery position substantially in the plane of said butterfly valve and perpendicular to the axis thereof, the improvement which comprises a carburetor body structure defining the path for said passage and providing for said passage to extend along each of two courses from said second needle valve to two separate locations in the wall of the chargelforming chamber, said two separate locations each being substantially in the closed-position plane of said butterfly valve and being spaced angularly approximately 90 apart about the axis of the chamber, said body structure comprising four relatively massive exterior flat drillring surfaces equally spaced circumferentially at intervals of substantially 90 about said mixing chamber, two of said drilling surfaces being positioned substantially at said two separate locations and the other two of said drilling surfaces being substantially diametrically opposite said two separate locations, whereby both the butterfly valve axis and the opening of said passage into said charge-forming chamber maybe located in either of two circumferential positions substantially 90 apart, said body structure also defining a well in said passage between the fuel source and the first needle valve to ac commodate a first removable filtering element through which the fuel must pass, said well being oversize relative to said first removable filtering element to define a reserve fuel supply and pressure surge compensation chamber therein, said body structure further providing accommodation fora second removable filtering element positioned in said passage between said fuel reservoir and said second needle valve.

References Cited in the file of this patent UNITED STATES PATENTS 2,774,582 Bracke Dec. 18, 1956 2,801,621 Anderson et a1. Aug. 6, 1957 2,823,905 Brown Feb. 18, 1958 2,841,372 Phillips July 1, 1958

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