US2835239A - Fuel pump - Google Patents

Description

May 20, 1958' K. J. DICKRELL 2,835,239

FUEL PUMP Filed Feb. 3, 1955 FIG. 3.

INVENTOR. MMNUHJ. DIUY/Pfll ATTORNEY United States Patent FUEL PUMP Kenneth J. Dickrell, Chilton, WiS-, assignor to Kiekhaefer Corporation, Cedarburg, Wis.

Application February 3, 1955, Serial No. 485,950 1 Claim. (or. 123-139) This invention relates generally to pumps and more specifically to an improved diaphragm pump for internal combustion engines operating on the two-stroke cycle.

One of the requirements of a diaphragm pump for an internal combustion engine is that it produce a substantially continuous flow of liquid at a substantially constant positive pressure. I-Ieretofore, diaphragm pumps for internal combustion engines actuable by the fluid pressure intermittently developed in the crankcase thereof, have developed a fluctuating liquid output corresponding to the fluctuations of fluid pressure developed within the crankcase.

It is therefore an object of the present invention to provide an improved diaphragm pump for an internal combustion engine of the two-cycle type having a liquid output at a substantially constant pressure.

Another object of the invention is the provision of an improved diaphragm pump for an internal combustion engine having adjacent chambers exposed to the substantially 180 degrees out of phase crankcase fluid pressure developed in respective adjacent crank chambers.

Another object of the invention is to provide an im proved diaphragm pump for an internal combustion engine of the two-cycle type having a greater liquid pumping capacity for its size than prior known diaphragm pumps.

Another object of the invention is to provide an improved crankcase actuated fluid diaphragm pump for an internal combustion engine wherein the liquid output is continuous.

Objects and advantages other than those set forth above will be obtained from the following description when read in connection with the accompanying drawing, in which:

Fig. 1 is a front elevation view showing the fuel system comprising a fuel supply tank, a fuel pump and a carburetor for a two cylinder, two-cycle engine;

Fig. 2 is an elevation view of the engine of Fig. 1 shown partially in section;

Fig. 3 is a section view taken along line 33 of Fig. 1;

Fig. 4 is an enlarged view of the part of the housing of the fuel pump adapted to be mounted on the crankcase;

Fig. 5 is an enlarged view of the remaining part of the housing of the fuel pump adapted to be secured to the part of the housing of Fig. 4; and

Fig. 6 is a section view taken along line 6-6 of Fig. 1.

As shown in the drawings, a preferred embodiment of this invention is illustrated as applied to a two-cycle internal combustion engine 7. The engine 7 shown in the drawings includes a crankcase 8 secured to a cylinder block 9 and carrying a crankshaft 11. Pistons 12 are each connected by a rod 13 with a corresponding crank throw of the crankshaft 11 and carried in a correspond ing cylinder 16 of the block 9 for alternate reciprocation. A bearing member. 17 intermediate the crank throws of the crankshaft 11 divides the crankcase 8 into upper and lower crank chambers 18, 19 respectively asice 2 sociated with the lower ends of the corresponding cylinders 16. The bearing member 17 includes an induction passage 21 shown in dotted lines and which opens into chambers 18, 19. A carburetor 22 secured to the crankcase 8 includes a mixing passage 26 which communicates through the crankcase 8 with the passage 21 in the bearing member 17 for the delivering of air and carbureted fuel to the chambers 18, 19 in the operation of the engine 7. i

In the operation of the engine 7, the upward stroke of each piston 12 compresses the fuel charge in a combustion chamber 23 above the piston 12. At the same time, the air and fuel mixture from the curburetor passage 26 is drawn into the respective crank chambers 18, 19. During the downward power stroke of each piston 12 following ignition of the compressed charge in the respective combustion chamber 23, the fuel and air mixture in the corresponding crank chamber 18, 19 is compressed for transfer to a communicating passage 24 shown in Fig. 3 which opens through the intake ports 27 above the piston 12 into the cylinder 16. The exhaust ports 28 of each cylinder 16 are controlled by the respective pistons 12 and are uncovered by the pistons 12 for the discharge of the exhaust through the ports 28 slightly in advance of a similar opening of the intake ports 27 for the re-charging of the cylinder with fuel and air mixture from the respective crank chamber 18, 19 as described. The action of the alternately reciprocating pistons 12 produces a constantly changing fluid pressure in the respective crank chambers 18, 19 varying substantially sinusoidally through 360 degree pressure cycles and substantially 180 degrees out of phase with one another.

Liquid fuel is supplied to the carburetor 22 by means of a diaphragm pump 29 in which the present invention is embodied having a supply line 31 connecting a fuel tank 32 to the inlet of the pump 29 and a conduit 33 connecting the outlet of the pump 29 to the carburetor 22. The fuel pump 29 is of the diaphragm type having a housing formed of an upper section 36 and a lower section 37 with a diaphragm 38 interposed therebetween. The housing sections 36, 37 may be formed of cast metal or any other suitable material and are provided with openings 39 shown in Figs. 4 and 5 in registry through which bolts 41 are inserted to engage tapped openings,

not shown, in the crankcase 8 to connect the housing sections 36, 37 together and mount the pump 29 on the crankcase 8 of the engine 7. The housing sections 36, 37 are constructed with recesses 42, 43 and 44, 46 therein respectively, each section 36, 37 having a transverse Wall portion extending between such recesses 42, 43 and 44, 46. When the housing sections 36, 37are connected together, the respective recesses 42,. 44 and 43, 46 are in registry forming chambers 47, 48 as shown in Fig. 3. The chamber 48 is substantially larger than chamber 47 and constitutes the primary pumping chamber Whereas chamber 47 functions primarily as a surge chamber to provide a smoother or less fluctuable liquid pump output. The diaphragm 38 which is assembled between the housing sections 36, 37 as shown in Fig. 6 may be in the form of a disc having a central. portion dividing the chambers 47, 43 and having an outer or marginal portion 49 adapted to be clamped or held between the cooperating portions of the housing sections 36, 37. This diaphragm 38 is formed of an elastic, rubher-like material, such as synthetic rubber, or any other suitable elastic substance which will Withstand the deteriorating effects of gasoline or other liquid fuel being pumped.

An inlet opening 51 and outlet opening 5.2 of the fuel pump 29 shown in Figs. 3, 5 and 6 is formed by the housing section 36 with each opening 51, 52 connected to "a respective bore '53, "54 disposed in the lower portion of the recess 43. Each of the bores 53, 54 is provided with an annular valve seat 56 for mounting a check valve 57. Each of the check valves 57 comprises a valve housing 53 having a seatportion mating withthe valve seat 56 and a valve disc 5'9 urged iuto ,sealing engagement with the valve housing 58 'by means of a spring 61 interposed between the valve disc '59 and the valve housing 58 asis well'known in the art. The check valves 57 are secured tothe housing section 37 by means of a clamp plate '62, shown dotted in Pig. '5, which fits over a portion of the valve housing 53 and rigidly clamps the valve 57 to the housing section 37 by means of screws 63 also shown dotted. The check 'valve 57in the bore 53 connected to the inlet opening 51 permits movement of the liquid into the recess 43 but prevents the movement of liquid out thereof into the liquid inlet opening 51 whereas the che'ck valve 57 in the bore 54 connected to the pump outlet opening 52 permits liquid-to leave the recess 43 but not to enter'therein through the pump outlet opening 52. The housing section 36 is also provided with a passageway 64 shown in Fig. 5 connecting the outlet opening 52 of the pump 29 to the recess 42. The lower section 37 of the housing is provided with openings 66, 67 as shown in Figs. 3 and 4 leading into the respective recesses 44, 46.

The fuel pump 29 is positionedon the crankcase 8 of 'the engine 7 so that the openings 66, 67 formed by the housing section 37 are in registry with corresponding openings 63, 69 as shownin Fig. 3 leading into the passages 24 which connect the crank chambers 18, 19. Therefore, the diaphragm .38 dividing the respective chambers 57, 48 will be acted upon by crankcase actuated fluid pressures that are 180 degrees apart; that is, when pressure acting upon the diaphragm 33 of one chamber '47 is positive or at the highest value, the pressure acting upon the diaphragm 38 of the other chamber "48 will be negativeor at the lowest value.

In operation, movement of the piston 12 downwardly in the upper cylinder 16 and upwardly in the adjacent cylinder 16 produces a successively increasing fluid pres sure in the upper crank chamber '18 and a successively decreasing fluid pressure in the lower adjacent crank chamber 19. The decreasing fluid pressure in the crank chamber 19 causes the diaphragm in the chamber 48 to move inwardly drawing liquid through the fuel pump inlet opening 51 and check valve 57 into the recess 43. During this action, the outlet check valve 57 is closed. The increasing fluid pressure in the adjacent crank chamber 18 causes the diaphragm in the chamber 47 to move outwardly expelling the liquid outof the recess 42 through the passageway 64 to the pump outlet opening 52. Upon completion of the engine cycle with the upper piston 12 moving upwardly and the adjacent piston 12 moving downwardly, the increasing fluid pressure developed in the lower crank chamber 19 causes the diaphragm 38 in thechamber 48 to move outwardly closing the inlet check valve 57 and opening the outlet check valve 57 expelling the liquid from the recess 43 through the outlet opening 52. The decreasing fluid pressure in the adjacent chamber 18 causes the diaphragm 38 in the chamber 47 to move inwardly causing some of the liquid to be drawn into the recess 42. A push-pull type of pumping action is developed with the surge chamber 47 functioning as an auxiliary pump to increase the pump capacity and provide a pump output that is continuous and at a substantially constant pressure.

Although but one embodiment has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claim.

It is claimed and desired to secure by Letters Patent:

A fuel pump for supplying fuel from a fuel source to the carburetor of a two cycle internal combustion engine, said engine employing crankcase precompression and having adjacent crankcase chambers intermittently pressurized in alternate relation, comprising a first and a second chamber, a pressure responsive diaphragm extending across each of said chambers, conduit means connecting the portion of the first chamber on one side of the diaphragm to the fuel source, second conduit means connecting said portion of the first chamber with the second chamber and the carburetor, respectively, valve means controlling the flow of fuel into and out of said portion of the first chamber in response to actuation of the diaphragm therein, passage means connecting the portion of the first chamber on the opposite side of the diaphragm from the conduit means connections to one of the adjacent crankcase chambers whereby the inter mittent crankcase pressures serve to flex the diaphragm to pump fuel from the fuel source into the second chamber and carburetor, respectively, and second passage means connecting the portion of the second chamber on the opposite side of the diaphragm from the conduit means connection to the other of the adjacent crankcase chambers whereby the diaphragm in said second chamber is flexed oppositely to the flexing of the diaphragm in said first chamber, said second conduit being open from said valve means to both the carburetor and one portion of said second chamber, .and said second chamber being substantially smaller than said first chamber whereby only a part of the fuel discharge from said first chamber enters said second chamber and the remainder of the fuel is forced into the carburetor at a time when said second chamber is being expanded by the actuation of its diaphragm and the alternating pressures between said first-and second chambers providing a relatively continuous flow of fuel to the carburetor at a relatively constant pressure.

References Cited in the file of this patent UNITED STATES PATENTS 2,713,858 Armstrong et al. July 26, 1955

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