US3500759A - Fuel priming pump - Google Patents

Description

March 17, 1970 ,po-r ET AL 3,500,759

FUEL PRIMING PUMP Filed June 13, 1968 INVENTORS MILLARD D. POTTER JOHN H. PARKS ATTORNEYS United States Patent 3,500,759 FUEL PRIMING PUMP Millard D. Potter, Bartonville, and John H. Parks, Peoria, 111., assignors to Caterpillar Tractor (10., Peoria, 111., a corporation of California Filed June 13, 1968, Ser. No. 736,710 int. Cl. F04b 9/22, 21/08, 33/00 US. Cl. 103-175 1 Claim ABSTRACT OF THE DISCLOSURE A compact fuel priming pump having a reciprocable piston within a first cylinder, a second cylinder concentrically arranged about the first cylinder to form an annular passage in communicatiton with One end of the first cylinder and suitable check valves separately communicating the other end of the first cylinder and the annular passage between the two cylinders with a fluid outlet and a fluid inlet.

Fuel priming pumps are commonly employed with engine fuel systems to deliver a suflicient quantity of fuel for start-up of the engine. Many of these priming pumps are of the single action type for example, and while being simple in design, do not have the necessary pumping capacity to permit priming of large displacement engines within a short time. Larger capacity priming pumps, for example those with double action or wobble plate design, generally deliver priming fuel at a higher rate. However, these pumps are generally complex in design and are expensive because of precision machining requirements. The complex construction of the pumps also commonly results in a larger size than is readily compatible with many engine systems.

Accordingly, it is an object of the present invention to provide a compact, high capacity pump. It is also an object to provide such a pump which is further of simple and economical construction.

The present invention fulfills these objects by arranging a reciprocable member within a hollow pump body to form two opposing chambers of variable volume with check valve means for communicating each of the chambers with a fluid inlet and a fluid outlet. Preferably the hollow pump body is a first cylinder having a reciprocable piston disposed therein and having a second cylinder concentrically arranged about the first cylinder with an annular passage formed between the cylinders for communicating a variable chamber at one end of the first cylinder with the check valve means.

Other objects and advantages of the invention are made apparent in the following description having reference to the accompany drawing.

In the drawing:

FIG. 1 is a side view, with parts in section, of a priming pump constructed to the present invention;

FIG. 2 is a view taken along section lines IIII of FIG. 1 illustrating a base member of the pump; and

FIGS. 3 and 4 are views taken respectively along section lines IIl-III and IV-IV of FIG. 2 to illustrate internal construction of the base member.

A fuel priming pump constructed according to the present invention and illustrated in FIG. 1 comprises a plunger assembly 11 arranged for reciprocable motion within a first cylinder 12. The plunger assembly 11 comprises an elastomeric piston member 13 in fluid sealing relation with the inside diameter of the cylinder 12 and a rod member 14 upon which the piston 13 is mounted. A second larger cylinder 16 is concentrically spaced apart from the first or inner cylinder 12 to form an annular passage 17 between the two cylinders. The upper ice ends of the two cylinders are closed by means of a plug member 18 with the rod member 14 penetrating a bore 19 formed in the plug 18. Seal means 21 prevent fluid leakage between the plug and the rod 14. The lower ends of the two cylinders are closed by means of a base member 22 so that a first or lower chamber 23 of variable volume is formed within the inner cylinder 12 by means of the base member 22 and the bottom of the reciprocable piston 13. An opposing or upper chamber 24 is also formed within the inner cylinder 12 by means of the top of the reciprocable piston 13 and the plug 18. The extended end of the rod 14 is threaded to a resilient knob 26 to permit manual reciprocable operation of the plunger assembly 11. The knob 26 is normally secured in a position with the plunger 11 depressed within the pump shown in FIG. 1 by means of a spring lock 27 which is pivoted at 28 to the outer cylinder 16 and the plug 18. Both of the variable volume chambers 23 and 24 are in communication with a fuel source (not shown) and an engine fuel system (not shown) by means of check valve and internal passages arranged within the base member 22 and described below with reference to FIGS. 2-4. The lower chamber 23 is in direct communication with two of the check valves while the upper chamber 24 is communicated with two additional check valves by means of a passage 29 formed by the plug 18 and the annular passage 17 between the two cylinders.

Simple and economical constructiton of the present priming pump is apparent from consideratiton of the components described above. For example, the cylinders 12 and 16 may be of standard precision t-ubing while the plug member 18 and base member 22 are preferably formed with concentric, stepped surfaces 31, 32, and 33, 34 respectively of appropriate diameters for pressfit engagement with the ends of the two cylinders 12 and 16, respectively.

Construction of the base member 22 and the arrangement of check valves therein is more clearly seen in FIGS. 2-4. Referring particularly to FIGS. 3 and 4, the reciprocable piston 13 is in a raised position to simplify the figures and more clearly illustrate the lower variable volume chamber 23. A recessed inlet 36 is formed at the bottom of the base member 22 for communication with a fuel source (not shown). Another recessed passage 37 is similarly formed for outlet communication with an engine fuel system (not shown). Two inlet ball check valve arrangements 38 and 39 are in communication with the fluid inlet passage 36 to permit fuel to flow into the pump from the passage 36 when pressure behind the check valve is sufficiently reduced. Another pair of outlet ball check valve arrangements 41 and 42 are in communication with the outlet passage 37 to permit fluid flow from the pump into the passage 37 when the check valves experience a suificient pressure rise within the pump. The inlet check valve 38 and the outlet check valve 41 are in direct communicatiton with the lower chamber 23 by means of respective passages 43 and 44 formed by the base member 22. The inlet check valve 39 and the outlet check valve 42 are blocked from communication with the lower chamber 23 while being in communication with the annular passage 17 and the upper chamber 24 by means of cross-drilled passages 46 and 47, respectively, in the base member 22.

During normal operation while the priming pump is not in use, the spring lock 27 secures the knob 26 and the plunger assembly 11 in place within the pump as shown in FIG. 1. To prime an engine with fuel prior to startup, the spring lock 27 is released and the plunger assembly 11 is manually moved in reciprocable motion by means of the knob 26. As the piston 13 is raised within the cylinder 12 from its position shown in FIG. 1, presme in the lower chambers 23 tends to decrease while iuid pressure in the upper chamber 24 tends to increase. lhe decreasing pressure in chamber 23 causes the inlet :heck valve 38 to open while maintaining the outlet check valve 41 in a closed position. Fuel in the inlet passage 36 is then permitted to flow into and fill the chamber 23. [he upper chamber 24 is normally filled with fuel while the pump is in the position shown in FIG. 1. Simultaneausly with the pressure decrease and filling of the lower :hamber 23, increasing pressure in the upper chamber 24 is communicated to the inlet check valve 39 and the autlet check valve 42 by means of the annular passage 17 and the respective passages 46 and 47. The increased pressure closes the inlet valve 39 and opens the outlet valve 42 so that fuel from a chamber 24 is directed to the passage 37 and the engine fuel system. As the plunger assembly 11 completes its upward stroke and is then moved in a downward stroke, fluid which entered the lower chamber 23 during the upward pump stroke experiences increasing pressure while the upper chamber 24 experiences decreasing pressure. The positions of the check valves are then reversed with inlet valve 38 and outlet valve 42 being closed and inlet valve 39 and outlet valve 41 being opened. During this downward stroke, fuel from passage 36 is drawn through the annular passage 17 to fill the chamber 24 while fuel from the lower chamber 23 is directed to the engine fuel system. This reciprocating operation of the pump is continued to rapidly deliver an adequate amount of priming fuel to insure starting of the engine. Upon completion of the priming operation, the plunger assembly is again secured within the pump by means of the spring lock 27.

What is claimed is:

1. A fluid priming pump comprising a pair of cylinders including walls free of ports, said cylinders comprising a first inner cylinder surrounded by a second larger diameter cylinder spaced therefrom and of greater length then said first cylinder to define an annular passage therebetween, stepped plugs providing the sole support for said cylinders, said stepped plugs inserted in the respective ends of said cylinders, each said plug including a first surface in press fit engagement with the inner surface of an end portion of the outer cylinder, a shoulder, and a smaller diameter extension terminating in an end within said first cylinder and including a cylindrical surface the extreme portion only of which is in press fit engagement with the inner surface of an end of the inner cylinder to leave an area of said cylindrical surface between the end of said inner cylinder and said shoulder exposed to said annular passage, one of said plugs including a passage in free communication between said exposed area and said end of said plug, the other of said plugs including two sets of inlet and two sets of outlet passageways including check valves and arranged within the member, one of each set of said passageways communicating with said exposed area and the other of each set communicating with the inserted end of said plug, a reciprocable piston arranged within the inner cylinder and forming opposing chambers of oppositely varying volume during reciprocable motion of the piston, one of the chambers being formed on one side of the piston by the one end of said inner cylinder, the other chamber being formed on the other side of the piston by the other end of the inner cylinder in combination with the annular passage whereby substantially the entire internal volume of the two pistons is available for pumping operation, and rod means for operating the piston in reciprocable motion, the rod means being secured to the piston and slidably extending, in sealed relation, through the plug.

References Cited UNITED STATES PATENTS 411,810 10/1889 Harwick 103-456 586,736 7/1897 Diss 230188 2,174,805 10/1939 Raulerson 103156 3,142,258 10/1965 Rutherford 103-175 3,185,042 5/1965 Hastings 103-216 FOREIGN PATENTS 283,004 1/ 1928 Great Britain.

575,916 4/ 1944 Great Britain. 1,003,400 3/ 1962 Great Britain.

WILLIAM L. FREEH, Primary Examiner US. Cl. X.R. 103216, 230218

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