US2038090A - Piston pump - Google Patents

Description

April 2 1, 1936. J. w. sMlTH 2,038,090

PISTON PUMP Filed March 14, 1932 Patented Apr. 21, 1936 UNITED STATES PATENT oFFi-CE PIsToN PUMP John w. smith, Philadelphia, Pa.

Application March 14, 1932, Serial No. 598,656

7 Claims. (C1. 103-38) This invention relates, in its broader aspect, to high pressure metering of liquids and, more particularly, to pumps for metering liquid fuel for internal combustion engines; ,while the specic metering mechanism herein shown forms the subject matter of a companion application.

The piston type of pump heretofore used in connection with fuel injection for Diesel engines was diilicult to manufacture and expensive to maintain. The precision fit between thepump cylinder and plunger could not be effectively maintained at the vicinity of the intake port.

The principal object of my invention is to provide a novel pump construction which eliminates the necessity of an intake port in the cylinder wall, thus eliminating leakage at the intake port.

My improved pump cylinder is sufficiently short to be ground on standard production grinding equipment, at the same time leakage is prac- 30 tically eliminated, while a large diameter piston and short stroke are made use of. 'I'he metering mechanism has a novel mechanically operated valve plunger which also actuates the pump piston.

g5 To illustrate my invention I have shown, by the accompanying drawing, an embodiment thereof which will be found in practice to give satisfactory and reliable results. It is, however, to be understood that the various instrumentali- 30 ties of which my invention consists may be otherwise arranged and organized, and that said invention is not limited to the precise form as herein shown and described.

In the drawing:

a5 Fig. I is a central vertical section through a piston pump embodying my invention.

Fig. II is a top plan view of the upper portion of the pump drawn to a reduced scale; and,

Fig. III is a detail section hereinafter fully ex- 40 plained.

Referring to Figs. I and II, the cam shaft 4 is mounted in a housing 5 on suitable anti-friction bearings 6, one only of which is shown; while the pump casing 1 is bolted to said cam housing 45 by suitable bolts, not shown. A roller 8 is journaled on a pin 9, which is securely held in the slide Ill, reciprocative in a guide II securely clamped into the pump or fluid supply casing 1 by suitable bolts, not shown. A diaphragm I 2 50 and metering nut I3 are also clamped in place bythe aforesaid bolts. A reciprocating valve member or plunger I4 has a threaded portion for clamping the diaphragm I2 by means of special washers I5 and I6.

55 A spring I1, under compression, is the means for causing the roller 8 to follow the eccentric motion of the cam shaft 4 as shown at point I8. The diaphragm I2 exes to either side of a neutral position and prevents the mingling of liquids in the pump casing 1 and housing 5. An adjuster 5 stop screw I9 is mounted in the metering nut I3;

while a gear is securely fastened to the screw I9 and meshes into a pinion 2|. A shaft 22 is secured to the pinion 2| and is rotated by a lever 23 keyed to said shaft by a key 24. 10

Fig. II shows the range of adjusting movement of the lever 23 to be from point 25 to point 26.

When the lever 23 is at point 26 there is no movement of pumping element 21 because then the screw I9 holds the pumping element or piston 15 member 21 all the time at the highest point to which the reciprocating plunger or valve member I4 can lift it. When the lever 23 is at point 25, on the other hand, then .the pumping element 21 has its maximum movement, indicated 20 in Fig. III at 29. This movement 29, it will be seen, is half the stroke of the plunger I4, indicated in Fig. I at I8. In other words, the screw I9 coacts with the piston member 21 to control its downstroke or outstroke; it never allows the 25 member 21 to move downward beyond its position at midstroke of the valve plunger I4, and may allow it a less range of downward movement, or even no movement at all.

In Fig. III, vthe valve plunger I4 has lowered 30 the pumping element 21 and the pump piston 28 a distance equal to the gap 29, which represents a normal pumping movement, and has left the element 21 resting on the screw I9 and itself moved on downward an equal distance, correspondingly drawing the valve I4 away from its seat. It is obvious that the adjuster screw I9 may be turned upward to bear hard against the spring loaded enlarged piston head on which is a. spring abutment cap 30, thus eliminating the gap 29 and preventing any pumping movement. 'Ihis condition would take place when the lever 23 is at point 26.

In Fig. I, the pump piston 28 has been withdrawn to the maximum point for taking in and delivering a full charge of liquid. This requires that the lever 23 be at the point 25 in Fig. II. The valve plunger I4 has been withdrawn from the ported valve seat 32, thus connecting passage 33 and orifice 3l, though still engaged in its bore 50 in the enlarged head portion of the piston member 21. 34 is a restricted circumferential strainer passage which may have an opening of less than .002, measured in a radial direction. This passage 34 is formed between the external surface 5F prevent grit and foreign particles from lodging on the valve seat 32.

Referring to Fig. I, the compression spring 35 around the piston member 21 acts on its head c ap 30 to cause the member 21 to follow the movements of the valve member I4 so far as permitted by the adjustable stop screw I8. The cylinder 36 is clamped in place in the pump cover 31, by a plug 38; while the ball valve 39 is held to its seat on the port or opening at the upper end of the cylinder 36 by a tension spring 40. The plug 38 is threaded for connection of a conventional pipe fitting used in conjunction with spray nozzles for internal combustion engines. 'I'he piston 28 has the fuel passage or orifice 33 through its center.

A hole 4I is threaded for a suitable pipe connection through which the liquid enters into the pump casing 1; while a pressure of five pounds per square inch above atmosphere is required to force the liquid into the pump through the restricted circumferential strainer gap 34. If the liquid is sluggish and the strokes per minute are high, considerably more pressure would be requisite.

In Fig. I, 42 is a bushing for mounting shaft 22 and is'provided with anti-leak packing 43; while said shaft is held in place by a spring 44. Fig. lII shows the vpump piston 28 as moved to the end of the stroke in the pump cylinder 36, thereby forcing the liquid past the ball valve 39. The space 29 represents the metered distance through which the piston 28 has moved; while the space I8 represents the movement of the slide I0 and valve plunger I4. 45 designates bolts which secure the cover 31 to the pump casing 1.

In operation, the rotation of the `cam shaft 4 causes reciprocation of the slide I0 and oi the valve member I4, the length of their stroke corresponding t-o the distance I3. At each upstroke, the valve member I4 strikes the piston member 21 and lifts it off the stop screw I8 a distance corresponding to the vertical position of the screw: i. e., a maximum distance 29 equal to half the valve stroke I8 vwhen the lever 23 is at 25 in Fig.,

l1 and the screw I9 at its position shown in Figs. I and III, and a distance of zero when the screw I9 is adjusted a distance 28 above its position in Fig. III, with the lever 23 at 26 in Fig. II. During the downstroke or outstroke of the valve member I4 and of the piston member 21, a partial vacuum is created in the cylinder 36 above the piston 28; and when the piston member 21 is arrested by the screw I9and the still descending valve member I4 draws away from its seat 32,

then liquid fuel is drawn in through strainer pasv sage 34 and passages 3| and 33 into cylinder 33 above piston 28. When valve plunger I4 rises again and closes against its seat 32 on element 21, its further rise forces out a corresponding metered amount of liquid from above piston 28 past ball valve 33,-this amount being determined by the adjustment of the lever 23 and screw I8.

It will, of course, be 'understood that various changes may be eil'ected in the details of construction within the scope 'of my invention as defined in the following claims.

Having thus described my invention, what I claim is:

l. In a pump the combination of a cylinder, a bored piston in the cylinder having a head with a valve seat in line with the bore, a cap around the piston head with an intervening clearance.

a passage through the piston head jointly defining valve member engageable with the seat aforesaid to shut-ofi such flow-communication and force the piston inwardly to effect the pumping operation. A

2. In a pump the combinationof a cylinder, an axially bored piston in the cylinder having an enlarged head with a valve seat therein in line with the piston bore, a cap around the piston head with an intervening annular clearance, a passageway through the piston head from the annular clearance to the valve seat and defining with the latter flow-communication to the piston bore and pump cylinder, a reciprocable valve member engageable with the valve seat to shut-ofi such flow-communication and force the piston inwardly of the cylinder during the pumping stroke, and means coacting with the cap aforesaid for returning the piston, on the out-stroke, to a predetermined position controlled by an adjustable stop mechanism.

3. The combination of claim 2 wherein the cap is supported by the piston head and embodies a portion surrounding said head with provision of an intervening annular strainer gap of such radial restriction that it prevents passage of any solids therethrough.

4. The combination of claim 2 wherein the enlarged piston head cap is oi' annular formation and has an inwardly-directed portion at one end for seating coaction at the back of the piston head, with an outwardly-directed circumferential shoulder at the other end, and a spring reacts between said shoulder and a stationary abutment.

5. In a pump the combination of a fluid supply casing with a flexible wall at one end and a pump cylinder at the other; an axially bored piston reciprocable in the cylinder and having a head extending into the casing with a valve seat at the outer end of the axial bore; an annular cap supported by and having a portion surrounding the piston head with provision of an intervening annular strainer passage; means providing con- -duit communication through the piston head from the strainer passage to the valve seat and axial bore for fluid flow from the casing into thepump cylinder; a valve member operatively connected to the flexible wall and coacting with the piston valve seat to control fluid admission to the pump cylinder; means for reciprocating the valve member; means in the casing around the pump cylinder and reactive between the annular cap aforesaid and a wall of said casing to normally hold the valve member in engagement with its seat and to cause said parts to reciprocate together; adjustable stop means in the casing around the valve member, intermediate the flexible wall and the piston member, and coacting with the latter to limit its out-stroke movement; and mechanism whereby the stop means is adjustable to vary the out-stroke of the piston member and thereby regulate the capacity of the pump. y

6. In a metering pump the combination of a pump cylinder; an axially bored piston reciprocable in the cylinder, said piston having an enlarged head at its outer end with a'valve seat therein, concentrically of the axial bore, and a passageway from such seat to the outer surface of said head; an annular cap supported by and having a portion surrounding the piston head with formation of an intervening strainer passage, whereby inlet communication through the piston into the cylinder is established; a reciprocating valve member engageable with the valve seat to move the piston member into and out of the cylinder, and to control fluid admission to said cylinder; a stationary metering means with an axially-adjustable stop device surrounding the valve member and coacting with the piston to variably control the out-stroke movement of the latter; and mechanism whereby the stop device is adjustable, while the pump is operating, toward and away from the confronting end of the cylinder to respectively reduce or increase the length of the piston stroke and the pump output.

7. A pump comprising a fluid supply casing and a pump cylinder; a piston member movable in said cylinder and having an enlarged head with a valve bore therein, a valve seat in line with said bore, with passage from said seat into said cylinder for fluid to be pumped and also from the surface of said head to the bore around said seat; a removable cap around said head with a strainer gap between them communicating with the last mentioned passage, for straining the liquid flowing from said casing into said seat; a valve member engaged' in said valve bore and coacting with said valve seat to control fluid passage between the supply casing and the cylinder; means for reciprocating said valve member; spring means acting on said piston head to hold its seat engaged with the valve member and cause it to reciprocate withU the latter; and adjustable stop means coacting with said piston head to control the out-stroke movement of the piston,

JOHN W. SMITH.

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