US2713854A - Fuel pump and carburetor assembly for two-cycle engines - Google Patents

Description

July 26, 1955 w. c. CONOVER FUEL PUMP AND CARBURETOR ASSEMBLY FOR TWO-CYCLE ENGINES Filed June 18, 1951 x a a 5 (a 7 z 6 V 5 z x 0: |.l.5 IIZ d k 7 mm% N a lo 7 5 V Q 8% aw w n; 9 n

55 54 flrfi I 2 Inmcntor M9285 6. Cam/5 Gttomcus United States Patent FUEL PUMP AND CARBURETOR ASSEMBLY FOR TWO-CYCLE ENGINES Application June 18, 1951, Serial No. 232,110

Claims. (Cl. 123--73) This invention relates to a fuel pump and carburetor assembly for two-cycle engines.

The invention contemplates a pressure-operated diaphragm pump for lifting fuel through a carburetor from a supply tank in which the fuel is carried at a lower level. The pump uses as its motivating force changes of pressure developed in the crank case of the two-cycle engine during its normal operation. Since such engines are commonly operated at 4500 R. P. M. and at even higher speeds, the diaphragm is required to vibrate with correspondingly high frequencies and its displacement is relatively minute.

The displacement must, however, be sutficient to supply the needs of the engine under all conditions. It is not at all uncommon for the heat of the sun, plus the heat developed in the engine, to raise to temperatures of 125 F. the metal parts of the engine proper. These temperatures raise serious problems in connection with a fuel pump, inasmuch as the fuel commonly used for the operation of a two-cycle engine of an outboard motor or the like will develop substantial quantities of vapor at such temperatures. Actual tests have shown that the pump will require twenty times as great a volumetric capacity at 125 F. as it requires at 70 F. because of the necessity for pumping increased ratios of vapor to fuel at the higher temperature.

The present invention reduces the volumetric requirements of such a pump by so combining the pump with the carburetor that the metal parts of the pump are not only cooled by carburetor evaporation but have no direct metallic connection with the engine. Even the carburetor upon which the pump parts are supported has no metallic connection with the engine except through its mounting bolts, being thermally insulated from the crank case by the usual intervening gasket. Thereby the cooling eflect resulting from such evaporation is used to keep the pump well below the temperatures of the metal parts of the engine. In practice, the entire carburetor is supported by connecting its intake manifold portion with the crank case of the engine and the pump is dependent on the intake manifold for mechanical support. The connection of the pump diaphragm chamber with the crank case is made through a flexible tube of rubber or the like which conducts negligible heat.

The invention further contemplates a fast acting, manually operable priming pump for lifting fuel to the 2,713,854 Patented July 26, 1955 either pump may be operated Without interfering in any Way with the operation of the other.

In the drawings:

Fig. l is a view partially in plan and partially in horizontal section through a carburetor and pump assembly which is illustrated in mounted position on the crank case of a two-cycle engine, the crank case and engine cylinder and piston being shown diagrammatically on reduced scale.

Fig. 2 is a view in vertical section through the pump assembly and carburetor, the latter being diagrammatically shown in a developed view in which the float chamber and manifold are moved from their normal position in order to be included in the section. This view also includes, diagrammatically, a view in side elevation of the remote fuel tank.

As will be apparent from the foregoing outline of the nature of the invention, the specific design of the carburetor forms no part thereof. There is an intake manifold 5 through the end 6 of which air is admitted. The end 7 of the manifold is flanged for connection with the crank case 8 of a two-cycle internal combustion engine having a crank 9, connecting rod 10, piston 11 and cylinder 12. A gasket 13 is interposed between the crank case 8 and the end 7 of the manifold. This minimizes heat transfer. In commercial practice, the admission of air to the crank case is sometimes controlled by the engine piston, sometimes by a rotary valve connected with the crank shaft, and sometimes by a check valve. For convenience of illustration, I have shown in Fig. 2 a check valve 14 for this purpose.

Fuel is introduced into the central portion or throat of the manifold 5 in any desired manner to carburete the air passing therethrough. For example, there may be a fuel nozzle 15 projecting into the manifold at its upper end and deriving fuel from a body of fuel at 16 in the float chamber 17 in which the lower end of the nozzle 15 is immersed. The float 18 in the float chamber is connected with a lever 19 pivoted at 20 and carrying at its free end a valve 21 urged by the buoyancy of the float into contact with a valve seat 22 when the supply of fuel in the float chamber is adequate. Any other arrangement for delivering the fuel into the air stream would be equally serviceable for the purposes of the present invention, Whether or not such arrangement includes a float controlled valve or a float chamber.

The pump organization now to be described is in direct metallic connection with that portion of the carburetor in which fuel is evaporated. In the particular device disclosed, the pump assembly derives mechanical support through the manifold or throat structure 5 from the engine crank case.

The automatic pump comprises a diaphragm at 25 marginally confined between casing elements 26 and 27 which are mutually concave to provide a pump chamber at 28. The diaphragm may be urged to one side i of such chamber for contact with casing block 27 by carburetor so that the engine may be started to initiate automatic pumping through the medium of the diaphragm pump above referred to. In this regard, the invention contemplates an organization in which the diaphragm pump and the manually operable piston pump advance the fuel through the same set of passageways, regardless i of which pump is operative, the arrangement being such as to facilitate the assembly of the necessary valves, all of which are exposed by the separation of the diaphragm pump fromthe piston pump casing. Since the fuel is moved through the same filter and the same passages,

means of a compression spring at 29. This is the side of the chamber from which the port 30 opens into the crank case 8, the casing member 27 being provided with a sleeve at 31 and the crank case 8 with a complementary sleeve at 32. A rubber tube or the like shown at 33 connects these sleeves. When the crank case 8 is under pressure, as occurs once in each cycle when the piston 11 moves outwardly in cylinder 12, the pressure is com municated through the port 30 to the diaphragm 25, thereby displacing the diaphragm to the left as viewed in Fig. 2, against the compression of spring 29. This displaces from pump chamber 28 any fuel that may be trapped therein. The fuel escapes through the outlet port 34 past the spring loaded check valve 35 into the passage 36 which leads to the float chamber, subject to the control of the float valve 21. It will be observed that the bore in the casing block 26 which provides port 34 is of smaller diameter than the bore 37 in pump casing 38 within which the compression spring 39 is housed. Consequently, the valve 3;! may comprise a simple disk fully exposed when the casing block 26 is separated from the hand pump casing 38.

Within the hand pump casing 38, there is a cylinder cavity 40 in which the hand pump piston 41 is reciprocable manna ly by means of a piston rod 42 which is guided in closure 43 and provided externally with a handle 44. From the cylinder cavity 49, a duct 4-5 leads past a spring loaded check valve 46 through the valve chamber 47 and port 48 into the diaphragm pump chamber 28. Again, the valve seat for valve 26 is formed on the base of the hand pump casing member 28 so that the valve 46 is fully exposed when the casing block 26 is removed.

The fuel reaches the hand pump cylinder cavity 40 through a passage 49 in casing member 33 and a passage 50 in the casing block 26 from valve chamber 51 in block 26, wherein there is a spring loaded valve 52 seated against seat provided on the end face of the hand pump casing 38. Controlled by valve 52. is the duct 53 which leads through the casing member BS from a filter chamber cavity 54. The filter 55 spans the cavity 54 and marginally seats upon an annular gasket 56 engaged with the shoulder '7 provided by counterbore St in the casing member 38. The filter 55 is held in position by compression spring 59 seated upon the removable cap 69 which has a gasketed connection with casing member 38 as clearly shown in Fig. 2.

The fuel enters the removable cap 60 through duct 61 into which is threaded the pipe coupling 62 for the tube or pipe 63 from the remote tank 64.

If the hand pump is operated, the reciprocation of piston 41 by means of handle 44 will draw fuel from tank 64 through pipe 63, duct 61, filter cap 60, filter 55, filter chamber 54, duct 53, check valve 52 and passages 50 and 49 into the cylinder cavity 4%.

On the return reciprocation of piston 41, the check valve 52 will necessarily be seated both by pressure and by its biasing spring.

Accordingly, the displaced fuel moves through the port 45 and past the check valve 46 and duct 48 into the diaphragm pump chamber 28 and thence through duct 34 past check valve 35 and through duct 36, past the float valve 21 into the float chamber 16.

As soon as the float chamber is full, the manual operation of piston pump 41 will ordinarily cease. The engine will thereupon be started, using fuel from the float chamher 17 to carburete the air admitted to the engine crank case and delivered to the combustion cylinder. With the engine started, the flow of fuel will become automatic through the functioning of the diaphragm pump 25 which will operate by pressure as already described to make one cycle during each engine cycle. On the suction stroke of the diaphragm to the right as viewed in Fig. 2, in response to pressure differential and to its spring 29, the fuel will be drawn from the tank 64 through the filter and the check valves 52 and 46 on precisely the same path which it follows when advanced by the manually operable piston pump 41. The only difference lies in the fact that the displacement is effected by the diaphragm 25, the pump piston 41 being at rest.

On the pressure stroke of the diaphragm to the left as viewed in Fig. 2, the diaphragm is operated by crank case pressure against the bias of spring 29 to displace from pump chamber 28 past valve 35 and through duct 36 the charge of fuel previously drawn from the tank.

The pressure developed on the fuel by the diaphragm will not ordinarily be sufficient to displace the check valve 21 against the pressure of float 18. Consequently, if the float valve is closed, the back pressure on the fuel will prevent the diaphragm 25 from being moved by crank case pressure from the position shown in Fig. 2, and there will be no pumping action. As soon as the float valve opens as the result of use of fuel from the float chamber, it will again be possible for the crank case pressure to displace the diaphragm 25, thereby advancing fresh quantities of fuel to keep the float chamber filled to the level controlled by the float.

Inasmuch as there is a negligible conductivity of heat through the rubber tube 33 from the crank case, it will be apparent that the entire pump structure will be protected from deriving heat from any other than atmospheric sources. By reason of the direct metallic connection between the pump structure and the manifol or throat 5 in which fuel is being evaporated, it will be apparent that heat for fuel evaporation will quite largely come from the metal of the pump structure so that the entire pump will tend to be maintained at a temperature considerably below that to which the pump structure would normally be heated by the combined effect of the ambient air surrounding it, plus such heat as is derived by radiation from the sun or other heat sources.

By reason of the cooling effect above described, the diaphragm pump can not only be much smaller than would otherwise be required, but it is much more efiicient, since the larger the diaphragm, the larger will have to be the capacity of the chamber in which it operates and the greater will be the movement of gases from the crank case which are responsible for motivating the diaphragm.

When a two-cycle internal combustion engine shuts down, there is a substantial increase in the temperature of its crank case, the latter being evaporation-cooled during engine operation. In the present construction, the fact that the carburetor is thermally insulated from the crank case by its gasket, while the pump is supported by the carburetor, provides a very long path of heat travel to the pump, and one which is interrupted at the gasket, thereby minimizing any temperature rise at the pump, such as might otherwise make diflicult the re-starting of the engine.

The ease of access to the valve parts, and the ease of assembly are again emphasized. On removal of the cap screws 65, the diaphragm casing elements 26 and 27 are not only separable from each other but from the pump casing 38, thereby exposing completely the diaphragm 25, its spring 29 and the several valves 35, 46 and 52' and their respective springs. It will further be observed that with the device in operation, it is not even essential to have the check valve 46. The same inlet check valve 52 and discharge check valve 35 which serve the. automatic diaphragm pump 25 also serve the manually operable piston pump 41.

I claim:

1. In a two-cycle internal combustion engine having a crank. case from which carbureted air is transferred to the engine cylinders, carburetor means including an air inlet passage to said crank case, a fuel pump mounted directly on said means and wholly dependent thereon for support from said engine, said fuel pump being provided with a chamber and a diaphragm in said chamber, said carburetor means including a fuel orifice communicating with the pump and the passage and supplied by said pump with fuel for carbureting the air transversing said passage, said pump including a casing in direct physical connection with said passage and comprising means for conducting heat from said pump to said passage for dissipation incident to fuel evaporation during carburetion, and means forming a passage from said crank case to said pump diaphragm chamber for subjecting said diaphragm to crank case pressure for actuation thereof, said means comprising a flexible heat insulating pressure connection from the crank case to the fuel pump diaphragm chamber.

2. In a two-cycle engine having pistons, cylinders and a crank case to which carbureted air is supplied en route to said cylinders, said crank case being subject to fluctuating pressures in response to the action of the pistons in said cylinders, 21 fuel pump having a chamber and a diaphragm in said chamber, means forming a passage from said crank case to said pump diaphragm chamber for subjecting said diaphragm to fluctuating crank case pressure for actuation of said pump, said passage means comprising a heat insulated pressure communicating hose, a carburetor to which said pump supplies fuel, said carburetor and pump being provided with a common and heat conducting housing whereby evaporation of fuel in said carburetor cools the pump, and means forming an air passage from said carburetor to said crank case.

3. The device of claim 2 in which said crank case has a mounting to which the last mentioned means is coupled, said means constituting substantially the sole support for said carburetor and fuel pump from said engine.

4. A combination carburetor and pump assembly for connection with the crank case of a two-cycle engine having an admission port for carbureted air and a pressure-communicating port, the said assembly comprising a carburetor throat having means for its connection with the crank case at the mixture admission port, carbureting means physically connected with said throat to be supported thereby from the crank case, a pump casing physically connected with said throat to receive support thereby from the crank case and provided with a pressure-communicating port, and flexible means connecting the pressure-communicating port of the pump casing with the pressure-communicating port of the crank case, the said pump casing being provided with a diaphragm pump and with ducts leading to said carbureting means and with check valves controlling flow through said ducts, whereby pressure communicated to the diaphragm from the crank case will advance fuel to said carbureting means and whereby the evaporation of such fuel in the air stream in said throat will cool said pump casing.

5. The device of claim 4 in which said pump casing further includes a separate pump cylinder in communication with the ducts aforesaid, together with a manually operable piston reciprocable in the cylinder for advancing fuel independently of said diaphragm through said ducts subject to the control of said check valves.

6. A combined manual and automatic pump having valves and ducts in common, said pump comprising a cylinder casing having a cylinder cavity and inlet and discharge ducts, neither of which communicates directly with said cavity, and intermediate inlet and discharge ducts leading to and from said cavity, diaphragm pump casing elements having a diaphragm marginally clamped between them and having complementary cavities providing a diaphragm pump chamber, one of said elements having a pressure port opening into said chamber at one side of the diaphragm, and the other of said elements having ducts registering respectively with the four ducts of the pump casing first mentioned, one of said last mentioned ducts being provided with a check valve seating against the pump casing first mentioned and controlling the inlet duct aforesaid, another of said ducts leading beyond said check valve to the intermediate inlet duct and thence to the cylinder cavity aforesaid, a third duct opening from the intermediate discharge duct of the first mentioned pump easing into the diaphragm pump chamber and being provided with a check valve seating against the first mentioned pump casing, and the fourth duct leading from the diaphragm pump chamber to the first mentioned discharge duct, the latter being provided with a check valve seating against one of the diaphragm pump casing elements.

7. The device of claim 6 in which the first mentioned pump casing is provided with a filter chamber from Which the inlet duct leads, and has a filter seat about said chamber, a filter resting upon said seat, and a cap in removable connection with the pump casing and provided with spring means biasing the filter toward said seat, said first mentioned pump casing having a further supply duct leading to a point beneath said cap.

8. The device of claim 7 in which the pump casing first mentioned is provided with a carburetor bowl and throat and has a carburetor nozzle affording communication between the bowl and throat, the discharge duct aforesaid leading to said bowl.

9. The device of claim 8 in which the said throat comprises means for the physical support of said casing, and easing elements to withdraw therefrom the heat absorbed by the evaporation of fuel in said throat.

10. In a device for pumping fuel from a remote tank for the carburetion of air admitted to the crank case of a two-cycle engine in which there is cyclic pressure variation, the combination of an air admission throat provided with means for physically mounting it upon the crank case in valve-controlled communication therewith, a fuel suppiy nozzle opening into said throat, a series of first, sec- 0nd and third casing elements physically connected with said throat to receive support therethrough from said crank case, the first such element having a fuel admission passage with a pipe connection from the remote tank and having a fuel delivery passage in communication with the nozzle and having a cylinder cavity and intermediate fuel passages leading to said cavity and from said cavity, a check valve seating on said first casing element in registry with each of the fuel admission passage and the intermediate passage leading from said cylinder cavity, the second casing element having a valve chamber embracing the first mentioned check valve and another valve chamber embracing the second mentioned check valve and having a duct leading from the first valve chamber to that intermediate passage which leads toward said cylinder cavity, the third casing element being connected with the second casing element and the second and third casing elements having diaphragm chamber cavities, the second element having a duct leading from the second valve chamber to its said diaphragm cavity and another duct leading from its said diaphragm chamber cavity into registry with the discharge cavity of the first casing element, the first casing element having a valve chamber cavity positioned to receive the discharge to said discharge passage, a check valve in said last mentioned valve cavity, a diaphragm marginally connected between the second and third casing elements and disposed in the diaphragm chamber, the third casing element having a port and a flexible coupling for connection with said crank case, and a piston valve in the said cylinder cavity and provided with a manually operable valve stem.

References Cited in the file of this patent UNITED STATES PATENTS 994,687 Nageborn June 6, 1911 1,022,803 Troutt Apr. 9, 1912 1,096,819 Ahlberg May 19, 1914 1,105,298 Peterson July 28, 1914 1,289,006 Rowell Dec. 24, 1918 1,351,880 Thompson Sept. 7, 1920 1,371,260 Pagel Mar. 15, 1921 1,447,398 Pagel Mar. 6, 1923 1,881,860 Muzzy Oct. 11, 1932 1,999,520 Stout Apr. 30, 1935 2,228,292 Wood Jan. 14, 1941 2,598,147 Tescher May 27, 1952 FOREIGN PATENTS 396,833 Great Britain Aug. 17, 1933

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