US1136946A - Pump. - Google Patents

Description

W. B. ERB.

PUMP.

APPLICATION FILED 0CT.2 1913.

Patented Apr. 27

1915. 3 SHEETS-SHEET I.

Ma @7. l/

W. B. ERB.

PUMP.

APPLICATION FILED ocT.2. 1913.'

Patented Apr. 27, 1915.

3 SHEETS-SHEET 2.

W. B. ERB.

PUMP.

APPLICATION FILED ocT.2. 1913.

Patented Apr. 27, 1915.

3 SHEETS-SHEET 3.

W ieg. 0, Y {N WQ 2 M N i ie WILLIAM B. ERB, OF CHICAGO, ILLINOIS.

PUMP.

ineen-ie.

Specication. of Letters Patent.

Patented Apr. 2?, 1915.

Application led October 2, 1913. Serial No. 792,954.

T0 all whom it may concern Be it known that I, WILLIAM B. ERB, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented new and useful Improvements in Pumps, of which the following is a specification, reference being had to the accompanying drawings, forming a part thereof.

'Ihe purpose ofthis invention is to provide an improved construction of pumps specially designed for deep wells, operable in others, by which the water is elevated by thev use of compressed air both operating a piston for positive lift of the water, and also acting upon' the water by injection ofthe air thereinto for inlating and elevating it.

It consists of the elements and features of construction shown and described, as indi'- cated in the claims.

In the drawings z--Figure 1 is a vertical axial section of a well tube and pump apparatus connected therewith embodying this invention. Figs. 2, 3 and 4 are vertical sections ona larger scale than Fig. 1 of three vertically successive portions of the entire device. Fig. 5 is a section at the line, 5,- 5, on Fig. 6. Fig. 6 is a section at the line, 6,-6, on Fig. 5. Fig. 7 is a section at the line, 7,-7, on Fig. 4. y

'Ihe well tube, 1, is presumed to be driven or sunken in the usual manner in the well bore into the water-bearing stratum.- At its lower end it terminates in an inlet fitting, 2, provided with a strainer, 3, below its inlet port, and a ball check valve, 4, above said port, the valve seat, 5, being screwed into an inlet port after the inspection of the ball valve there-through into a cage, 5a, which forms the upper part of said fitting and through which the water which passes the ball valve enters the well tube. The inlet fitting also supports the pump cylinder, 6, whose lower end is closed bythe coupling plug, 7, screwed into the cylinder, and onto the upper-end of the inlet fitting.

8 is a rubber cushion let into the upper end of the coupling plug, 7, to serve as a buer or yielding stop for the down strokeof the piston. The well tube at its upper end is connected by a coupling, 10, with an uplead pipe, 11, the cylinder, 6, being at its upper end fitted within the coupling, 10, so

f that the latter which is screwed into the upper end of the well tube, 1, 'closes at the upper end* the annular-chamber, 12, whichis formed between the cylinder and the well tube. 'Ihe piston, 14, as will be hereinafter more fully explained, is operated by compressed air admitted below it into the cylinder, lifting it to a pre-determined point as hereinafter explained, and the piston on its descent, however caused, is followed by the water entering from the chamber, 12, through ports, 15, at the upper end of the cylinder so that the cylinder above the piston is filled with water ready to be lifted upon the next upwardl stroke of the piston.

In pumps. employing compressed air for operating the piston to elevate the water, as such -pumps have been heretofore constructed, it has been customar to release the compressed air after each lifting stroke in orderto vacate the cylinder for the return stroke of the piston. A specific purpose of this invention is to avoid wasting the compressed air, and to utilize for further up-lifting and discharge of the water the expansive force of the compressed air below the piston which remains after the piston has been thus lifted by the compressed air for positively lifting the water above it. For this purpose the cylinder, 6, is provided withra multiplicity of relatively small perforations, 16, at a level in the height of the cylinder which will be passed by the piston and exposed below its lower end by the time the pistons upper end reaches and laps slightly upon the'ports, 15, leaving said ports still mainly uncovered, for communication between the water space, 12,1and the cylinder chamber. When the parts, 16, are thus uncovered by the upward movement of the piston, the compressed air bclowf the latter in the cylinder is discharged in a multiplicity of jets into the water in the chamber, 12, and thence through the ports, 1 5, into the cylinder and the up-lead pipe, 11, inflating and elevating the water and continuing and increasing its delivery upward to ultimate discharge.

At a distance above the highest position of the pump piston in the cylinder which will be desirably varied according to the different circumstances of each case, as, the depth of the well, the depth of submergence of the cylinder below the level of the waterbearing stratum ,and the degree of air pressure to be employed, there is located in the up-lead'pi'pe a column-retaining check valve,

17. Since the .piston stem must extend up within the-up-lead pipe, the water passage therein is necessarily annular, and the check valve and its seat are conformed to this circumstance. Inasmuch as the check valve is to be mounted variably as to, its distance above the cylinder, the up-lead pipe is furnished at its lower part with a thin sleeve lining, lla, whose length covers the full range of probable variation of position of the check valve, and the check valve seat, 17a, being secured into a bushing ring, 17h, gripping an annular packing. ring, 17, is tted by means of said packing snugly within the said lining sleeve, 11a, and is held lixedly suspended therein, in addition to its close fit in the sleeve, by means of a piston stem housing tube, 18, which is coupled at its lower end to the upper end of a sleevelike hub, 17d, with which the check Valve seat is provided, and through which the piston stem extends, said housing being screwed at its upper end into a hollow boss, 19, which projects from the top wall of a water chamber, 19, which is mounted on the top of the up-lead pipe, and from which the final water discharge pipe 19e, leads olf. The check valve is seated by a spring, 17, coiled around the sleeve stem, 17, of said valve, said sleeve stem being mounted for sliding freely on the sleeve hub, 17d, of the valve seat. The spring bears at its lower end upon the valve, 17, and is stopped at its upper end by the lower end of the coupling, 18a. The pump piston stem, 20, passes loosely through the hub sleeve, 17d, of the valve seat, the clearance around the stem being small so that the water passes only to a limited extent around the stem through the housing, 18. The boss, 19a, is provided with vent apertures, 19, opening into the chamber, 19, at a point close to the top of said chamber. The primary purpose of these vent apertures is to permit the escape of air which may remain temporarily trapped below the check valve, 17 after the tension of the compressed air, originally operating, as above described, for lifting the water, has become reduced in such action so that it does not immediately find its way up'through the 4 Water. This residue of air remaining in the passages below the check valve would diminish the capacity of the pump at each stroke thereafter, and it is important, therefore, that it should be allowed to escape, and this is eilected through the space around the rod, 20, in the tubular connection of the check valve seat with the chamber, 19. In addition to this function, tlie ports, 19", serve to permit the easy upward movement and discharge from'the space around the piston stem in the connecting pipe, 18, of the water, which may under some conditions of submersion be therein instead of the air above mentioned. This is desirable because the piston stem, 20, may have a coupling, 20a, located in said pipe, 18, which would operate more or less as a piston displacing the water in the movement of the piston in either direction, and thereby causing considerable resistance to the movement of the piston.

rlhe compressed air is introduced into the cylinder through the piston stem, which is for that purpose hollow, and which for the same purpose extends up through the water chamber, 19, a stuling box, 22, being provlded on the upper side of said chamber through which the piston extends upward. Upon the upper side of said chamber, 19, there is mounted a housin the purpose of which is to afford means for giving the compressed air access to the cavlty of the piston stem, and controlling entrance of the compressed air therethrough, as will hereinafter appear. For this purpose the pump piston stem at its upper end comprises a valve member, 24, and a cam member, 25, the two being in one piece which is hollow from its lower end upward to a point near its upper end, which is tapered, as shown, at 25, to form a cam for the purpose hereinafter explained; and in said tapered portion an aperture, 25, leads from the surface to the vinterior cavity of said member. Saidl valve-and-cam member is screwed at its lower end onto the upper end of the lower tubular portion of the pump piston stem, and immediately above the valve portion, 24, by which it is thus attached, it is cut. away at opposite sides to form the lateral openings, 25, 25, leading from its interior cavity into the chamber of the piston stem housing, 2 3. Onto the upper end of the piston-stem-housing, 23, there is bolted fast a member, 30, the lower end of said member and the upper end of the housing, 23, being provided with mated flanges for securing them together. The member, 30, is, or comprises substantially a continuation of the piston housing, but with a cavity of such diameter as to beI fitted snugly piston-wise by the valve-andcam-member, 24,-25, of the pump piston stem; and said stem is extended upward, but without being hollow, in the rod portion, 26, and terminates in a second cam member` 27.

The member, 30, has mounted upon it at a position of its length intermediate the lower end in which the piston cam member,

g, 23, for the Vupper end portion of the plston,

25, is seated and the upper end portion in which the cam member, 27, is seated, oppositely transversely projecting valve chamanaemia anced valve, 34, which has a short range of reciprocation in said chamber and has in each of its opposite heads a small port, 34, leading from the cavity of the valve into the cavity of the. valve chamber. The valve chamber is furnished at its upper side with a compressed air inlet port, 31, at which is connected a compressed air supply pipe, 35, provided with a manually operable shut-olf valve, 36. It will be understood that the pipe, 35, leads to a compressed air supply chamber not shown, the pipe, 35, bein hereinafter referred to as the source o compressed air. 'lhe valve chamber, 31, has an exit port, 31h, diametrically op osite the inlet port, 3l, and the valve, 34, as corre-- sponding inlet and exit ports, 34b and 34,-

whic'h register with the ports, 31a and 31h, respectively, when the valve, 34, is at one limit,-(the right hand in `Fig. 5)-of its longitudinal movement in the chamber, 31. 'llhe valve, 34, is guided in said longitudinal movement and prevented from rotating in the chamber by a guide stud, 37, which projects from the upper side of the chamber w all into a slot, 34, of the valve which is, in fact, a continuation of the port, 34", and has the effect of causing the interior cavity of the valve to be at all times in communication with the inlet port, 31, leading from the. compressed air source. rlhe chamber, 31, is in communication at its opposite ends, respectively, with valve\ chambers, 28 and 29, said communication being effected by the passages, 28 and 29, respectively, leading laterally from said balanced valve chamber and entering laterally into the valve chambers, 28 and 29, respectively, at the inner ends of said valve chambers, respectively. lln said last mentioned valve chambers there are provided piston valves, 28", 29", which are normally held seated over the inlet ports, 28a and 29, by springs, 28e, 29. Said valve chambers open axially with respect to the bosses in which they are formed, radially into the cavity of the piston stem housing, 30, and said valves are provided respectively with stems, 28 and 29d, which lit the extension of said valve chambers into the cavity of said pump piston stem housing, said stems havin axial bores from their inner `ends terminating in said housing chamber back of the point at which the stems join the body of the valve, and said axial ports are there connected by laterallyleading ports, 28e, 29", with the valve chambers, respectively; so that when the valves are pushed back in their chambers against the resistance of their respective springs, communication is opened between the chambers-.of 'said yalves respectively and the cavity of the piston stem housing in the member, 30; and thence throughthe piston stemto the pump cylinder below the pump piston; and the valves, 28b and 29", are by the same movement moved to uncover the ports,

28a 'and 29, leading from the balanced valve chamber, 31, which is thus put in communication alternately at opposite ends with the pump cylinder below the piston. The cam members, 25 and 27, on the pump piston stem at the opposite extremities of the rod portion, 26, thereof, are adapted to encounter the ends of the hollow valve stems, 28d and 29d, in the opposite strokes of the piston so as to open said valves, 28b and 29", alternately at opposite stages of the pump pistons movement.

The operation of the valve mechanism above described is as follows z-Assuming the, piston, 14, to be at the bottom of its stroke in the cylinder, the cam member, 27, will be in a position at which having encountered the stem of the valve, 29h, and

thrust that valve open, it is holding the same in open position maintaining air communication between the cavity of the housing, 30, and the right hand end of the balanced valve chamber, 31. At this stage, the balanced valve, 34, is at the position shown in Fig. 5, opening communication from the source of compressed air into the passage,

39, leading from the lower side of the balanced valve chamber and thence horizontally in the lower side of the casting forming said chamber, `to the face thereof by which it is mounted upon the member, 30, where said passage registers with a duct, 40, formed in the latter and leading to the lower end thereof Where it opens into the cavity of the housing, 23. By this passage the compressed air is admitted through 'theports, 25, into the axial cavity of the hol^ low piston stem, 20, and thereby into the cylinder, 6, belowy the piston. 'llhe several parts being at rest in this position, upon the operator opening the valve, 36, and admitting the compressed air, the iston will be forced upward inthe cylin er, lifting the water above itin the cylinder, and in the up-lead pipe past the check valve, 17, and,-assuming the up-lead pipe and chamber, 19, and passage pipe, 20, to be already full of water,.-the water will be by this movement discharged from the upper-end of said discharge pipe. When in this movement the lower end of the piston passes and uncovers the ports, 16, the compressed air below the piston forcing its way past the check valve, 50, is .discharged in a multiplicity of jets out through the ports, 16, out 1nto the chamber, 12; and thence, passmg around the piston back and through the pots, 15, inflating the Water inthe cylinder i .an

11p-lead pipe above the piston, and thereb uplifting the body of the water therea ove, it causes further discharge from the discharge pipe, 19. In the upward movement of the piston and about the time it passesJ and uncovers the ports, 1 6,

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the'lower end of the piston valve cam member, 25,--that is, the portion thereof below the ports, ,enters the housing member, 30, and, operatingy as a valve therein, shuts o' the communication of the compressed air with the cavity of the hollow piston stem.

Substantially simultaneously with the cut- -ting oif of the compressed a1r communication with the piston stem, whichuis effected by means of the valve end, 24, as described, the upper cam end, 25, encounters the stem of the valve, 28", and thrusts the same inward, opening that valve. The supply of compressed air being cut oiil and the compressed air expanding by discharge into the .water for inating and lifting the same, as described, the tension of the air in the cylinder below the piston and in the cavity of the piston stern, will be reduced and the valve, 2 8", being open establishingcommunication for said air under reduced tension withthe left hand end' of 'the balanced valve chamber, 31, the tension of the air in that. end of thechamber being reduced will imbalance the valve and cause it to be moved tothe left, cutting yoii" the communication whichy it controls withv the compressed air source. 'Ihe movements described of the balanced valve result because of the relatively small communication alorded by the port, 34, from the interior of the valve to the right hand end of the chamber, in compari'son Iwith the vent for escape of compressed air ailorded by the passages 28a and 29B. The compressed air in the cylinder below the piston continuing to expand and inflatie, elevate 'and discharge the water from above the piston, the tension of said air will eventually be reduced so that it will no longer-support the piston and its stem and its .a-ppurtenantt members, and the piston will descend in the cylinder to the bottom thereof. In the last short increment of the descending movement ofthe pump piston, the cam member, 27, at the upper end of the rod member, 26, of the piston stem encounters the Stem 4of the valve, 29", and opens said valve; thereby effecting communication from` the chamber of the housing, 30, to

the vright hand end of the balanced valve chamber, causing said valve to be again unbalanced, which will result in its movement .in the opposite direction from that previously occurring, and its arrival at the position shown in Fig. 5 at which free4 communication is opened through it from the compressedl airsource to the cavity of the housing, 23'. The piston continuing to descend, the valve member, 24, onthe piston stem emerges from its seat in the housing,

@30, and the ports, 25, are uncovered, admitting the compressed air to the cavity of the` hollow stem, and .thence into the cylinder below the piston, whereupon the cycle of movement above described will be repeated.

The pump piston'is provided at its lower end with a check valve, 50, which controls ports, 51, in the lower end section of the piston through which the water is admitted to pass the check valve and enter the space, 14D, between said lower section, 14, and the main body of the piston, 14. The purpose of this is to adapt the piston to pick up from the bottom of the cylinder any water which may have obtained entrance by leakage past the piston, or otherwise, so as to permit the piston at full stroke to descend to the bottom of the cylinder and thus obtain its full range of action upward. The water thus picked up and carried in the space, 14h, will be ejected by the air, as

'above described, when the piston rises so as to bring the space, 14", opposite the. perforations, 16.

I claim 1. In a pump, in combination with a pump piston and a cylinder in which it reciprocates, a by-pass from a lower to a higher point' on the cylinder chamber around a ,fcertaln position of the piston therein at the upper part of its stroke; a

hollow piston stem opening into the cylinder below the piston; a source of compressed ai-r and meansfor alternately admitting it to and excluding it from the piston stem, said means comprising av valve which is operated by the compressed air, and devices Operated by the up-and-down movement; of the piston stem for unbalancing the air pressure on said valve oppositely at.

opposite stages of the piston stems movement.

2. In combination with a pump piston and a cylinder in which it reciprocates, a bypass from a lower to a higher point .of the cylinder chamber around a certain position of the piston therein at the upper part of its stroke; a source ofcompressed air; a passage leading from the piston chamber below thel piston to said compressed air source; a device for controlling communication through said passage; a valve operated by the piston forcontrolling said passage at a point intermediate the first-mentioned controlling device and the pump cylinder; an auxiliary passagenot controlled by the lastmentioned valve connecting the previouslymentioned passage with the first-mentioned controlling device, and valves operated by the piston at opposite stages of its stroke for controlling the communication of said auxiliary passage with said first-mentioned controlling' device.

3. In-combination with a pump piston and a pump cylinder in which it reciprocates, an up-lead pipe connected to theupper end and" leading to a discharge; a check valve in the up-lead pipe opening dischargeauieaaae tain' position of the piston therein at the upper part of its stroke; a hollow piston stem opening into the 4cylinder below the piston; a source of compressed air and means for alternately admitting it to and releasing it from the piston stem, said means comprising a valve which is operated by the compressed air, andy devices operated by the up-and-down movement of the piston stem for unbalancing the air pressure on said valve oppositely at `opposite stages of the movement of the piston stem.

4. ln combination with a well tube or casing, a pump cylinder supported within the casing and positioned therein to afford water space between it and the casing wall; a check valve at thed foot of the caslng admitting water to said water space; a piston mounted for reciprocation in the cylinder, the latter having communication with Said water space near the upper limit of the pistons stroke in the cylinder, and also at its upper part below the pistons position at said limit,4 whereby a by-pass` is formed around the piston at said position; a hollow piston stem opening into the pump cylinder below the -piston; a source of compressed air and means for alternately admitting it to` and releasing it from the piston stem, said means comprising a valve which is operated by the compressed air, and devices operated by the up-and-down movement of the piston stem for unbalancing the air pressure on said valve oppositely at the opposite stages of the lpistons movement.

5. lln combination with a pump piston and a pump cylinder in which it reciprocates, a by-pass from a lower to a higher point of the cylinder chamber around a certain position of the piston therein at the upper part of its stroke; a hollow piston stem opening into the cylinder below the piston; a source of compressed air and means for alternately admitting it to and releasing it from the piston stem; Said means comprising a piston valve and its chamber provided with means for communieating with the source of ce mpressed air adapted to admit balanced pressure to the valve, passages aording communication from the pump piston chamber belew the pistonto the piston valve chamber at 'opposite sides of the valve therein, and means by vwhich the pump piston stem opens said communications alternately at opposite stages of its stroke. 4

6. lncombination with a pump piston and a pump cylinder in which it reciprocates, a by-pass from a lower to a higher point of the pump'cylinder around a certain position of the piston therein at the upper part of 'the stroke of the latter; a compressed-air-controlling device and a passage therefrom to the :pump cylinder below the piston, said controlling device comprising a balanced piston valve and its chamber, said chamber having two inlet ports at o-pposite sides of the piston valve; a valve device operating in the compressed-air passage which leads to the pump cylinder for cutting ofi' communication between the same and the compressedair-controlling device; air connections not controlled by said valve leading from said passage to said inlet ports; valves which control said connections respectively, and means by *which the piston operates said valves alternately at opposite stages of its stroke.

7. In combination with a pump piston and a pump cylinder in which it reciprocates, an up-lead pipe leading from its upper end; a by-pass from a lower to a higher point of the cylinder chamber around a certain position of the piston therein at the upper part of its stroke; a hollow piston stem opening into the cylinder below the piston; a housing for the piston stem above the uplead pipe and a iitting which closes communication of said housing with the up-lead pipe andV constitutes a stuiing box for the stem; a piston valve member on the stem above the stuiiing boX; a seat for said piston valve in the housing; a compressed-aircontrolling device and a passage therefrom 'leading into the piston-stem housing between said stuiing box and the piston valve seat, the piston stem having an opening leading from its cavity int the cavity of said housing for communication with said passage, said controlling device comprising a balanced piston valve and its chamber, the latter having ports for air communication at opposite sides of the piston valve vtherein; ducts from said ports to the piston housing above said piston valve member; valves controlling said ducts, the piston stem having means for operating said valves alternately -at opposite stages of its stroke.

v 8. In combination with a well tube.or casing, a pump cylinder supported within the casing and positioned therein to afford water space between it and the casing wall; a piston mounted for reciprocationin the cylinder, the latter having communication with said water space near the upper limit of the piston'Js stroke in the cylinder, and also at its upper part below the pistons position at said upper limit, whereby a by-pass for air is formed around the piston at said position, the last-mentioned of said communications being by means of a. multiplicity of relatively small perforations for subdividing the air into small jets at its emergence into the water; a hollow piston stem opening'into the pump cylinder below the piston; a source of compressed air and means for alternately admitting it to and releasing it from the piston stem.

9. lin combination with a pump piston and a cylinder in which it reciprocates; av

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previously-mentioned passage with the irst mentioned controlling device, and valves operated by the .piston at opposite stages of its stroke for controlling the communication of said auxiliary passage with the first-mentioned controlling device.

10. In a pump, in combination with a pump piston and a cylinder in which it reciprocates, an up-lead pipe from the upper end of the cylinder for water discharge; a hollow piston stem opening into the cylinder below the piston; a source of compressed air and means for alternately admitting it to and excluding it from the piston stem;

means for opening communication for the compressed air from the piston stem into the up-lead pipe at a pre-determined point in the rising movement f the piston, and

means for controlling the admission o fcompressed air to the piston stem comprising a valve and two air connectionsfor operating it in opposite directions, said air connections leading from the piston stem; valves which control said connections respectively, and means carried by the piston stem for operating said valves respectively at opposite stages of the pistonsmovemen 11. In a pump, 1n 'combinatlon with a I p ump piston and a cylinder in which it reclprocates, a well tube within which the cylinder is positioned having access for water to the space around the cylinder, the cylinder having communication near its upper end with said Water space for receiving water therefrom above the piston; means for supplying and .intermitting the supply of compressed air to the cylinder below the piston to cause reciprocation of the piston, the cvlinder having ports for communication from its chamber with the water space around it in the well tube at a positionto be uncovered by the upward movement of the piston near the upper limit of its stroke, for admitting the compressed air from below the lpiston into the water space around the cylinder and thence back into the cylinder above the piston.

12. In a pump, in combination with a pump piston and a cylinder in which it 15eciprocates, a well tube within which the cylinder is positioned having access for water to the space around the cylinder, the cylinder having communication near its upper end with said water space for receiving water therefrom above the piston; means for supplying and intermitting the supply of compressed air to the cylinder below the piston to cause reciprocation of the piston,

'the cylinder having ports for communication from its chamber with the water space around it in the well tube at a position to be uncovered by the upward movement of the piston near the upper limit of its stroke, for admitting the compressed air from below the piston into the water space around the cylinder and thence back into the cylinder above the piston; a supplemental plston below the main piston having ports extending through it, and a check valve above said supplemental piston opening upward, whereby water which may accumulate in the bottom of the cylinder may be lifted by said supplemental piston and discharged by the air through said ports. l

13. Incombination Awith a pump piston and a cylinder in which it reciprocates, an up-lead pipe connected to the upper end of the cylinder; a water chamber at the up er end of the up-lead pipe; means by which the piston stem is extended water-tight through the top of said chamber; a houslng for the piston stem above said chamber; a conduit leading from a source of compressed air opening into the housing, the piston stem ,having an openin into its cavity for compressed air to said conduit.

14. In a pump, in combination with a pump piston and a cylinder in which it reciprocates, a source of compressed air and means for alternately admitting it to and excluding it from the cavity of the cylinder below the piston, said means comprising a balanced valve device; air connections leading from the cylinder below the piston to opposite sides of such valve for unbalancing the latter; valves controlling said communications, and cams on the piston stem for operating said valves alternately at opposite stages of the pistons movement.

15. In a pump, in combination with a cylinder and piston therein and means for discharging compressed air into the up-take water passage `above the piston, a check .valve in said up-take passage; a housing which supports the check valve seat extend- License `ing to the top of said 11p-take pipe, the piston stem extending loosely through said housing and the housing having vent apertures at its upper end above the up-take plpe.

16. In a pump', in combination with the pump piston, a cylinder in which it reciprocates; a source of compressed air; a conduit therefrom to the cavity of the cylinder below the piston; means for opening communication from said cavity into the space above the piston at a pre-determined point in the upward movement of the piston; a balanced yvalve device for alternately admitting and excluding compressed air from said conduit; means for `operating said balanced valve comprising air connections from the space in the vcylinder below the piston to opposite sides of the balanced valve; valves which control said connections, and means operated by the pistons movement for opening said valves `alternately at opposite stages of the pistons movement.

In testimony whereof, ll have hereunto set my hand at Chicago, llllinois, this 29th day of September, 1913.

WllLLIAM B. ERB. Witnesses: p

BoBT. N. BURTON,

EDNA M. MACINTOSH.

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