US2455275A - Fuel pump drive for diesel engines - Google Patents

Description

Nov. 30, 1948. R. H. SHEPPARD FUEL PUMP DRIVE FOR DIESEL ENGINES 2 Sheets-Sheet 1 Filed July 9, 1946 -ld X Nov. 30, 1948. R. H. SHEPPARD 1 2,455,275

FUEL PUMP DRIVE FOR DIESEL ENGINES Filed July e, 1946 2 Sheets-Sheet 2 I Patented Nov. '30, 1948 UNITED STATES PATENT OFFICE 2,455,275 FUEL PUMP DRIVE FOR DIESEL ENGINES Richard H. Sheppard, Hanover, Pa. Application July 9, 1946, Serial No. 682,398

4 Claims.

This invention relates to the starting of Diesel motors and has for its principal object the provision of a mechanism which will insure that the fuel is delivered to the combustion chamber of the Diesel engine at a greater speed than would be had if the starter were directly connected to the fuel pump shaft. As a corollary the invention includes the provision of a spring member in the chain of gearing between the crank shaft of the engine and its fuel pump shaft, particularly one in which power is stored in-the spring during a portion of the revolution of the large starting gear and when the spring is released a sharp motion or impulse is given to the fuel pump shaft whereby the fuel is discharged in nearer accord with the manner in which fuel is discharged while the engine is under load.

A still further object of the invention consists in the insertion in 9, Diesel engine starting mechanism of a quick impulse device which wil1 automatically become inoperative as soon as the engine approaches normal speed.

In the drawings:

Figure 1 is an elevation.

Figure 2 is a vertical section through the axis of the fuel pump shaft.

Figure 3 is a section on line 33 of Figure 1.

Figure 4 is a section on line 5-3 of Figure 1.

Figure 5 is a section on line 5-5 of Figure 4.

Figure 6 is an elevation of the cup.

Figure 7 is a detail on line l'l of Figure 4.

The fuel pump shaft of the sists, as is usual, of an inner member Ill and an outer member Ii, which, while they have relative movement, as far as the present invention is concerned, may be considered as a. single member. In any event, the two members invariably rotate together. The outer member turns in a bushing i2 in the fuel pump casing i 3 and carries at its end a screw member i5 secured to the fuel pump shaft as by the bolts l 6. This extension i5 of the fuel pump shaft turns in a bushing ll between the screw extension and the timing device plate l9, which itself is fast to the large bushing or hearing secured as by the bolts 2| to the back wall 22 of the gear case. 5

The member'20 has the usual oil hole 23 and the usual oil outlet 25 and the forward extension, that is, to the left in Figure 2, of the bushing 20, furnishes a bearing as at 26 for the hollow hub 21 of the gear 28 which receives power from the crank shaft 30 through an idler 3 7 A cup 33 is permanently secured as by the rivets It to a plate 36 fitting snugly the gear 28 and fast to it as by the .bolts 31.

Diesel engine con-' A retaining nut 39 presame radius as the outside of vents movement of the gear 28, the plate and the cup 33, away from the fuel pump shaft.

The forward portion 40 of the) screw member I5 which maybe considered as a part of the fuel pump shaft is slabbed off to afford a seat for the floating washer 4| which fits the stub shaft portion 40, rather snugly, the latter being threaded at its free end to receive the nut 39.

The small washer 36 turns freely on the stub shaft and its function is to prevent too great movement of the pawl 60.

A spring 50 is anchored at one end as at 5i to the washer 4| which always turns with the fuel pump shaft. At its other and larger end the spring 50 is anchored as at 52 to an extending portion 53 of the cup 53. As best seen in Figure 4, the cylindrical flange of the cup is cut away on both sides leaving two extensions 53. The purpose of these two oppositely disposed members 53 is to wind the spring and to release the spring. Within the cup is a driven plate 55 which generally is circular, but has two portions 56 of greater radius and just clearing the inside wall of the flange cup and having its outside arc of exactly the the cup. The driven plate 55 may therefore have relative movement of rotation with respect to the cup from one edge 5! of an extension 53 to the adjacent edge 53 of the opposite flange extension 53. A pawl 63 is pivoted as at '6! to the driven plate 55. The larger end 62 of the pawl acts as a weight and holds the shorter arm 63 of the pawl so that it extends beyond the outer mangin of the cup 33. A small point 63 on the pawl is merely for convenfence in restoring the pawl to operative position I when the centrifugal force of rotation throws the heavy arm 62 outward against the inner wall of the flange extension 53 at which time of course the short arm 63 is well within the cup. A fixed spacer 65 is mounted on the plate 55 to extend exactly the same distance as the top of the pivot pin 6| the better to position the real thin washer 67.

A stud 66 is fixed to the timing plate i9 so as to be engaged by the short arm 53 of the pawl as the driven plate 55 rotates. The engagement of the pawl and the stud hold the driven plate against movement and since this driven plate has no relative movement with respect to the fuel pump shaft the latter is held stationary as long as the pawl engages the stop. The driving cup, however, is continuously rotated in counter clockwise direction as seen in Figure 4 and in time the leading edge 58 will make contact withthe now stationary pawl and will camthe short end 63 inwardly. The release of this short end of the lowing edge 51 of the flange extension 53 of the cup. The net result of this action is to give far greater speed of rotation to the fuel pump shaft than would be had if the drive from the crank shaft were constant. Hence, while the fuel discharge is in perfect timing there is in every revolution of the fuel pump shaft one sharp impulse per cylinder and this results in a far more desirable discharge of Diesel fuel to the combustion chamber. Due to the centrifugal eflect on the pawl the impulse ceases just as soon as engine gets up to normal speedas at such time the larger end 62 of the pawl is thrown outward with the point 64 in engagement with the inner surface of the flange extension 53 of the cup 35.

'Except for the point there would be a danger of the pawl wedging against the cup flange.

I claim:

1. In a device to facilitate the starting of 8. Diesel engine, a fuel pump shaft, a gear coaxial therewith and adapted to be driven from the crank shaft of the engine, mechanism for connecting the gear with the shaft including a spring connection, means for winding thespring as the gear turns without rotating the shaft, and trip means for releasing the wound spring to rotate the shaft at a higher rate of rotation than the gear after the gear has rotated through a chosen angle of movement, said trip means including a centrifugally controlled member whereby the winding device is rendered inoperative when the gear reaches a chosen speed of rotation.

2. The device of claim 1 in which a plate fast to the shaft carries a pawl which at slow speeds engages a stop, and the gear carries a cup, the spring is fast to the cup at one end and to the shaft at the other end, and a projection on the cup cams the pawl from the stop and frees the plate and shaft so that the spring now wound rotates the shaft.

3. In a device for facilitating the starting of a Diesel engine, a casing, a fuel pump shaft journaled in said casing, a stop fixed to the casing. a plate fast to the shaft and having two extending ears, a pawl pivoted to the plate and having one end movable into engagement with the stop at slow speeds of the plate, a cup coaxial with the shaft and having a flange partly cut away to provide an opening to receive the two ears and the pawl with lost motion in excess of 45, a spring fast at one end to the cup and connected at the other end to the shaft, means for rotating the cup in timed sequence with the engine shaft, whereby the fuel pump shaft, which is held against movement while the pawl engages the stop and the cup winds the spring, is driven at a more rapid rotation than that of the cup by the transfer of stored power in the spring when the flange cams the pawl from the stop, thus freeing the shaft and permitting the spring to unwind.

4. In a device for facilitating the starting of a Diesel engine, a fuel pump shaft, 9. gear rotating in fixed relation to the engine shaft, and means for transferring power from the gear to the fuel pump shaft including a spring connection alternately wound and released, to give a series of quick impulse movements to the fuel pump shaft while the engine is being started, whereby in starting the engine, the fuel is delivered at a greater speed than if the fuel pump shaft were directly connected to the gear, and thus the fuel is delivered in starting in sharp impulses corresponding more nearly to the manner in which the fuel is delivered while the engine is under load.

RICHARD H. SHEPPARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,394,938 Schmidt et a1. Feb. 12, 1946 FOREIGN PATENTS Number Country Date 505,014 Great Britain May 5, 1939

Images