US2258055A - Fuel pump - Google Patents

Description

- Oct. 7, 1941. J, HOLLOWAY .ET AL 2,258,055

FUEL PUMP Filed April 29, 1938 zai INVENTORS ATTOY.

Patented Oct. 7, 1941 FUEL PUMP John H.. Holloway, Green .Bay, and Moyes J. Murphy, Milwaukee; Wis., assignors to Murphy Diesel Company, acorporation of Delaware Application April 29, 1938, Serial No. 204,974 f I *The'invention relates to fuel pumps.

The object of the "invention is to provide improvements in the cut off construction of that type of fuel pump having a constant stroke but a variable cut off which is produced by a groove or scroll on the plunger registering with a relief port.

Heretofore the cut off scroll on the plunger has been of relatively large volume, and in some pumps having a vertically disposed plunger and a discharge valve at the lower end of the pump barrel it has been'necessary to use two ports in order to properly fill the pump and free it of en trained air. The object of the present invention is to provid a cut off groove or scroll on the plunger of small width and depth so as to keep the volume of the pump chamber a minimum and just sufficient to handle the flow. Furthermore; the improved cut off groove acts to vent air from the pump barrel during the outward stroke of the plunger andalso makes the pump self cleaning. Furthermore, the cut off of this invention acts to quickly reduce the pressure at the end of the effective stroke of the plunger. Also because of the small area of the groove there is a minimum of leakage and side thrust against the plunger. I 1

A further object of theinvention is to provide aninclined cut off groove on the plunger, the projection of whose inclined portion may 'be within the width of the relief port, so that the pump may be set to an idling position. j

, A'further object of the invention is to provide a cut off relief on the plunger which is cheap and easy to make and easy to measure and hold -end of its stroke said port I! is uncovered so.

er, so that the pressures on the same may be bal- 3 Claims. (01. 1031- 41) taken at substantially right angles to thr" if F 1; V Fig. 3 is a viewsimilar to Fig.2 showing the plunger in an intermediate position;

I Fig. .4 is a detailed sectional View similar to, Fig. 2 showing certain modifications;

Fig. 5 is a detailed sectional view taken on the line 5-5 of Fig. 4';

Fig. 6. is a detailed sectional view similar Fig. 5 showing certain modifications;

Fig. 7 is a'detailed sectional view similar to Fig. 5 showing certain modifications.

Referring to the drawing, we have shown a pump, including a casing 4, a barrel 5 mounted in said casing, .a valve seat member 6 mounted in the reduced end of said casing and clamped thereto by a sleeve nut I which also clamps a flanged nozzle member 8 against said member 6.-

The nozzle member has the spray orifices 9. and

thestepped bores lll, II, and I2 leading to said A ball valve I3 is normally held against its seat in the member 6 at the end of the discharge passage l41therein by means of a grooved pin 15 andfla" Spring l6 holding said pin against. said valve.,

The barrel forms .an inlet and a relief port and is controlled by a plunger l8 working in the barrel 5, it being noted that when said plunger is at th inward that fuel may flow freely into the barrel, it being noted that a partial vacuum may exist in the pump chamber under some conditions before th port I1 is uncovered- As previously noted the pump is of the type having a constant stroke and variable cut off, the cut off being controlled by a scroll or relief on the plunger cooperating with a relief port. The plunger I8 has a shallow cut off groove l9 formed therein by grinding or milling and having straight end portions 20 and 2| and a spirally inclined portion 22 connecting said end portions. It will be noted from Fig. 2 that the pitch of the portion 22 is such that the displacement of the edge 23 of the end portion 20 of the groove from the edge 24 of the end portion 2| of said groove is less than the width of the port l1, so that when the plunger is in its idling position as shown in full in Fig. 2, some portion of the groove Will at all times overlap th port I! during the entire stroke of the plunger, so that fuel taken into the barrel will be by-passed back into the port l1 during the entire stroke of the plunger. If now the plunger l8 and th barrel 5 be ro- 5 is provided a port l'liwhich i

Images