US2981198A - Reciprocating variable delivery pump - Google Patents

Description

F. NETTEL April 25, 1961 RECIPROCATING VARIABLE DELIVERY PUMP Filed Aug. l2, 1958 INVENTOR.

2,981,198 REClPRO'CATING VARIABLE DELIVERY PUMP Frederick Nettel, 173 Chapel Road, Manhasset, N.Y. Filed Aug. 12, 1958, Ser. No. 754,613

Claims. (Cl. 103--41) This invention deals with piston or plunger pumps, particularly to such employed for delivering iluids of any kind, as well as gases or vapors in variable quantities while operating at substantially constant speed.

Known pumps of this general performance either employ rather complicated variable-stroke devices (variable crank radius, swash plates etc.) or the start of delivery is more or less delayed, beginning at points Where the piston has reached already appreciable or high velocities.

Special mechanical devices, as mentioned, are expensive to build and yto maintain, while the sudden start of delivery when the piston is moving, involves heavy hydraulic shocks which under certain conditions may even prove destructive.

It is the principal object of this invention to eliminate these drawbacks and the possibility of leakage of fluids or gases outside the pump.

It is another object of this invention to provide a simple and cheap means for sensitive and fast regulation of uid delivery at any operating speed, requiring a small actuating force.

Itis a further object of my invention to provide a pump which may furnish two iiuid streams of same or different pressures.

These and other objects and advantages of my invention will be apparent from the following specification when taken with the accompanying drawings, which show by way of non-limiting examples embodiments of my invention.

In the drawings, Fig.. l is a diagrammatic section through a pump with liquid storage tank. Fig. la is a sectional view through the cylinder of the pump as per Fig. l. Fig. 2 shows a modification depicting delivery control by a rotatable element. Fig. 3 indicates the design of the control sleeve Vfor the pump as perlFig. 2. Fig. 4'shows the same control sleeve with the secondary piston in position for maximum delivery. Fig. 5 shows another embodiment of my invention avoiding a high pressure seal. Fig. 6 depicts the control sleeve used in pump as per Fig. 5. e The main object of my invention is achievedlby theprovision of a primary cylinder in which-.a primary piston is reciprocable, the piston being provided with an axially extending aperture or recess, called for the purposes of this vspecification hereinafter secondary cylinder, the primary cylinder having an adjustable member, called hereinafter secondary piston, adjustable relative to the secondary cylinderin such manner, that in accordance with the selected positionof the secondary piston, effective fluid delivery will be terminatedV sooner or laterv during the working stroke of the primary piston.

-Revertng'now in more detail to Fig. 1: 1 indicates the body of a primary cylinder in which the primary piston 2 is reciprocable by the 'crank kdrive 3 with the stroke S. The primary piston 2 carries at its lower end piston rings 4 as seals, being connected YtoA the crank drive-by the wrist pin 5. The upper part of the piston' 2 is provided with y groovesA 6dat its circumferencey which are connected to a 2,981,198 Patented Apr. 25, 1961 ring-shaped space 7 Ifrom which a bore 8 is connected via the vertical duct 9 to the suction valve 10 which seals off toward lthe secondary cylinder 11. This valve is disposed centrally within the primary piston. Screwed into the-secondary cylinder is a control sleeve 12, equipped with radial ports 13 arranged round its circumference. Mounted above the secondary cylinder, and adjustable by screw in the cover 14 of the primary cylinder, is the secondary piston 15 which is in axial alignment with the control sleeve 12, closely fitting Within the latter. The secondary piston has a central bore 16 which connects via a radial bore 17 with a cylindric space l18 in the cylinder cover 14 and thence with the fluid delivery conduit 19. The screw thread of the secondary piston v15 permits the llatter to be moved vertically within the control sleeve 12 to any desired degree by the handwheel 20.

Interposed in the axial bore 16 is the delivery valve 21, as shown. The primary cylinder-is connected via Ithe pipe 21 with the uid source, for example the tank 22.

Briefly stated, heV pump operates as follows:

In Fig. 1 both the primary piston and the secondary piston `are shown in their lowest positions. Due to the connection with the tank 22 all spaces within the pump are assumed to be lled with iluid. If now the primary piston begins torise, the ports 13 will be opened and Yestablish connection between the secondary cylinder 11 and the primary cylinder 1, with the result that the whole content of the cylinder 11 is displaced back into the cylinder 1 and thence back into the tank 22. No appreciable pressure rise can take place Within the cylinderv 11, so that the valve 21 remains closed, and the delivery of the pump is zero.

If now, for example, the secondary piston 15 is screwed upward to a position higher by the stroke S, as indicated by the dash-dotted lines, the piston 15 will keep the ports 13`closed over the whole stroke, thus sealing the secondary cylinder 11 and forcing its contents under pressure out via lthe valve 21, the bores 16 and 17 and the delivery conduit 19. This position of the piston 15 corresponds to maximum pump delivery.

Obviously, in `any position of the secondary piston 15 between the two described above, the ports 13 will open more or less before the primary piston reaches its uppermost position, thus terminating delivery earlier, so that the pump will furnish partial volumes, as desired.

At this point it is necessary to point out a vital difference between the mode of operation of known pumps and my invention: In known pumps the start of the delivery is delayed at the beginning of the working stroke so that, when the effective stroke begins, the piston 2 has already a considerable velocityrelative. to 'the piston 15, or its equivalent in other designs. Sudden sealing of the cylinder 11 causes under such circumstances a sudden hydraulic shock which is most undesirable Iand may be destructive. Contrary to this, in Yapplicants pump, delivery always starts near the bottom dead centerwhere the velocity ofthe piston 2 is practically zero. The ports 13 open to relieve the pressure within'the'cylinder 11 sooner or later according to the adjustment' of the piston 15, which takes place without shock and ensures smooth operation also at high speeds.

The .seal between the piston 15 and the control sleeve 12`can be effected in any known manner', for example by close metal-to-metal fit by lapping or piston rings, soft seals etc. Any leakage from the cylinder 11 will be into the cylinder 1, i.e. not outside the pump. Fig. la shows a section through the pump as per Fig. l along the line A--A. Parts corresponding to parts in Fig. 1 are described in all figures by the same numerals.

Fig. 2 depicts Ian alternative embodimentlin which no axial adjustment of the secondary piston is used, but in which a rotary motion of this piston may Iachieve any pump delivery from zero to maximum. The cylinder part only is shown. In this case the primary and secondary cylinders are essentially the same as in Fig. l, except that the ports in sleeve l2 are arranged in echelon around the sleeve circumference, preferably in such manner that the maximum diderence in height of the ports corresponds to the stroke S, asV s-hown. ln Fig. 3 the sleeve l2 is shown removed `from the pump. In this ligure lthere is a second row of ports indicated which serves to increase the ow area between the primary and secondary cylinders. Fig. 2 the secondarypiston has its upper working edge cut at an angle to the horizontal which may -be the same as the echelon angle at which the ports are disposed in the sleeve i2.' The secondary piston has again a central bore i6 with an interposed delivery valve (not shown here), which ends at the delivery conduit 19. The shank of the piston l5 carries a ilange l5' which bears 'against the cylinder cover 14, forming a thrust bearing for the piston 15. The pin 23 protrudes into a groove of the piston shank to prevent its being moved downward during the suction stroke.

In Fig. 2 the piston 2 is again drawn in its lowest position. Obviously, when it begins to rise, the ports 13 begin to be opened gradually, with the piston 15 in the position as shown, and the pump delivery is consequently zero. If now the piston 15 is turned around its axis by 180 degrees, itcomes into the position as sho-wn in Fig. 4. The portal?, remain sealed by the piston l5 .during the full working stroke and the pump delivery is atA its maximum. If the piston is turned by angles smaller than 180 degrees, the ports .will begin t open at different points during the working stroke so that partial deliveries can be adjusted at will by operating the handwheel 20.

Fig. indicates a modilication of the design of Fig. 2 in which the piston consists of two parts, i.e. a center part 15 which is rigidly connected to the cylinder cover lill and a rotatable sleeve 15K surrounding it which carries a recess forming a working edge identical with the upper working edge of the piston l5 in Fig. 2. The lower end of part l5 is of conical shape against which a cone provided at the lower end of the sleeve 15 is pressed during the delivery stroke of the pump, forming a tight seal against any pressure, while allowing the sleeve to be rota-ted.. The sleeve i5 is prevented from moving downward during the suction stroke by the pin 23 protruding Vinto Va groove in part l5. This design has special merits for very yhigh pressures and high capacities because any movable high-pressure seal is eliminated. Fig. 6 shows the sleeve 15 partly in section with a gear rim 24 at its upper end which may be arranged to be operated by hand or automatically through a'conventional gear rack (not shown).

Reverting again to Pig. 2, attention is drawn to the spring loaded suction valve 10', and to the spring loaded delivery valve 2.1', both connected to the primary cylinder 2. The valve 1G is used where no fluid tank under Istatic pressure is available, in which case the surplus ininV take fluid is discharged through the valve 21'. Obviously, itis possible to operate thepurnp of the primary cylinder and primary piston Aas separateV pump of larg'ervolume, with theL secondary piston 15 set for zero delivery, for example. .Howeven deliveryl of iluid,

can also take l place simultaneously at i9 and through valve 21. This may be advantageous in certain hydraulic drives where two separate pumps are now used, one for high pressure at small volume, vthe other atlarger volume at lower pressure. The valves ill and 21 can be used with any of the embodiments shown. Y

The suction valve l0 in Fig. 1 is shown'without spring. While a springcan be used, it is not necessary, lbecause due to inertia the valve will close during acceleration upwards and open during deceleration. During 'downward motion the action is, of course, reversed. *.This is vadvantageous also for air or vapor pumps because the valve resistance is eliminated during the suction stroke.

It is immaterial for the purposes of this invention by what means the reciprocating motion of the pistons is eiiected: it may be by crank, cam, eccenter, swashplate, for examples. It is `also irrelevant what types of valves are used and how many units of pumps are used together and how these units are arranged to each other.

While in the lforegoing preferred embodiments of my invention have been described and shown, it is understood that further alterations and modifications may be made within the scope of the appended claims.

What I claim is:

l. In a reciprocating, constant speed, variable delivery pump for handling media such as liuids, gases or vapors comprising a source of such media, the combination of a primary cylinder, a primary piston disposed to operate reciprocably within said primary cylinder, a secondary cylinder centrally disposed and axially extending within said primary piston, a secondary piston extending into said primary cylinder in axial alignment with said secondary cylinder, said secondary cylinder disposed to operate reciprocably relative to said secondary piston, first conduit means for connecting the source of medium with the primary cylinder, an aperture between said primary and secondary cylinders, second conduit means for connecting said primary yandsecondary cylinders, a check valve interposed in said second conduit means permitting tlow of medium from the primary cylinder `into the secondary cylinder on movement ofthe secondary cylinder away fronrsaidsecondary piston, an axial passage in the secondary piston extending through it and connecting the secondary cylinder with the outside, a check valve interposed in said passage'permitting ow of medium from said secondary cylinder to the outside on movement of said secondary cylinder toward said secondary piston, said secondary piston being adjustable relative to said secondary cylinder for controllably opening said aperture between said primary and secondary cylinders at freely selectable points in the stroke of the secondary cylinder, the amount of medium displaced from said secondary cylinder to the outsideduring its movement toward said secondary piston being determined by specificposition of adjustment of the latter.

2.V Reciprocating pump as set forth in claim Vl, having said aperture between the primary and secondary cylinders in the form of ports disposed around the .circumference of the secondary cylinder, substantially in a plane at right angle'to the axis of said secondary cylinder, and means to adjust the position of said secondary piston in the direction of its axis.' i

3. Reciprocating pump as set forth in claim l, having said aperturebetweenrthe primary and secondary cylin derst Ain the form of ports disposed in echelonaround the circun'rferenceA of said secondary cylinder, said secondary piston `having axial sealing contact with `said secondary cylinder of varyinglengths at different points 'along"thercircumference' of said secondary piston, and

means for turning the latter around its axis. l4. Reciprocating pump as set forth in claim 3, having rotatable sleeve'means disposed around said secondary piston-andy forming part-of it, said sleeve having axial Contact withV said secondary" cylinder `of varying lengths at dile'rent points along' the Vcircumference of lsaid. secondary sleeve 'and means for rotatably adju'stingjthe positionl of said sleeve forcontrolling-'said aperture ,between the primary and 4secondary cylinders.

' 5.v Reciprocating pump 7as set f orth in claim l., having a heck valve interposedin saidliirst conduit means permitting ilow of medium fronrthe *source into the primary cylinder on movement Voat the primary pistonV out'of the' primary cylinder, third conduit means connecting the primary cylinder with theoutside, .a check valve .inter-` pos edj,in saidthirdfconduitmeans permitting ow of medium out of the primary cylinder on movement of the primary piston into the primary cylinder, to enable the primary cylinder with primary piston to act as pump independent of any pumping action taking place in the secoudary cylinder.

References Cited in the file of this patent UNITED STATES PATENTS

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