US482944A - Force pump - Google Patents

Description

(No Model.) 7 Sheets--Sheet 1.

v M. W. HALL.

FORGE PUMP.

No. 482,944. Patented Sept. 20,1892.

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By his Azfomeys,

(No Model.) 7 Sheets-Sheet 2.

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FORCE PUMP.

No. 482,944. Patented Sept. 20,1892.

INVENTOR:

(No Model.)

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FORGE PUMP.

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FORCE PUMP. No. 482,944. Patented Sept. 20, 1892.

INVENTOR:

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" NITED STATES PATENT OFFICE.

MILAN WV. HALL, OF PLAINFIELD, NEWV JERSEY, ASSIGN OR TO- OTIS BROTHERS & COMPANY, OF NEW YORK, N. Y.

FORCE-PUMP.

SPECIFICATION forming part of Letters Patent No. 482,944, dated September 20, 1892.

Application filed March 25, 1391- Serial No. 386,297. (No model.)

To all whom it may concern.-

Be it known that I, MILAN W. HALL, a citizen of the United States, residing in Plainfield, in the county of Union and State of New Jersey, have invented certain new and useful Improvements in Force-Pumps, of which the following is a specification.

This invention provides a power-driven pump for raising Water or other liquid to a higher level or for forcing it through mains. It is designed with special reference to the requirements of pumps driven by electric motors, but may be otherwise drivenas, for example, by a belt from shafting or by being coupled direct to a motor-engine.

One important object of my invention is to provide a pump with the minimum of valves and inclosed working parts and of such construction that the pistons and valves are made readily accessible for examination and repair. To this end the pump is constructed with two cylinders, in each of which works a piston fitted with a valve, the two cylinders being connected at one end, so that one forms a continuation of the other and the opposite ends of the cylinders being connected, respectively, with the suction and discharge, so that the water column enters one cylinder by the suction-pipe, passes through that into the other cylinder, back through the latter, and The pistons are made to act alternately on the column of water, so that the valve of each forms a check-valve for the other to prevent backflow while the other piston is on its return stroke, so that the stationary check-valves usually provided for this purpose and Which are ordinarily difficult of access are omitted. The connected ends of the two cylinders are joined through the medium of an intervening passage formed in a removable cap or cylinderhead, by moving which access is gained to both pistons and their valves, so that the pistons and valves may be taken out for repair or renewal of packings. This is practically of great advantage over the constructions heretofore used, wherein ordinarily separate induction and eduction valves are provided located in distinct boxes or chambers, access to which is obtained by taking off manholeplates distinct from the cylinder-heads, so

that ordinarily at least three plates or heads must be removed to gain access to the pistons and all the valves.

Another object of my invention is to construct the pump to perform a uniform work and oifer a-uniform load or resistance to its driving-motor in successive uniform intervals of time. Pumps as ordinarily constructed impart an intermittent movement to the column of water, the column being first lifted by the thrust of the piston and coming to rest and remaining seated against the check-valve during the return stroke of the piston, so that upon the beginning of the next stroke the column has to be again started against the resistance offered by its inertia. In single-acting pumps the entire column of water is thus started and stopped; but in double or triple acting pumps as ordinarily constructed the water column is divided into two or more branches, each acted upon by a piston and so arranged that one piston is acting to lift the main column while another is making its idle or return stroke, so that in this case the main column is kept moving at a tolerably-uniform speed, and it is only the branches of the column in the respective cylinders which-are subject to intermittent movements. This arrangement ordinarily equalizes the work to a great extent, but not entirely; but this equalization is obtained at the cost of considerable complication and involves more or less loss of power by reason of frictional resistance. Another important disadvantage with most force-pumps is the liability to hammering, so called, whenever the pump is driven beyond a certain speed, this hammering being caused by the piston moving faster than the water column in starting from a state of rest can follow it, since the inertia of the latter is greater at such an excessive speed of the piston than can be overcome by atmospheric pressure, so that the piston reaches the end of its strokein advance of the water column, and the latter, overtaking it, strikes solidly against it, or in case the piston has already commenced its return stroke the water column and the piston collide. This defect is found in all pumps wherein the water column is moved within the cylinder first in one direction and then in the opposite direction. To overcome these objections and equalize the work of the pump without involving disadvantages of complication or inaccessibility of parts, my invention provides for acting upon the column of water by two valved pistons working in succession and each commencing to lift the column before the lifting efiort of the other ceases, so that the column is kept in continual motion in the same direction and all disadvantages due to the stopping and starting or reversing of the flow of the water column overcome. .To accomplish this result, it is essential that eachpiston shall haveacomparatively slow working stroke and a comparatively quick return stroke, in order thatduring the time that one piston is making its working stroke the other may first cease its workingstroke, come gradually ,to a stop, then execute a rapid return stroke and recom- 'menceits working stroke, reaching fullspeed at or before the time when the other piston onnearing'the end of its stroke commences materially to reduce its speed. Hence the working strokes of the pistons overlap, so to speak, so that-each picks up the column of water before the other lets go'thereof. Each piston during its return stroke moves back through the moving column of water and in the opposite direction, its valve being unseated to permit the water to pass through it. To accomplish this peculiarmovement of the pistons, various different mechanisms may be employed; but my invention provides a special novel driving mechanism whereby the rotation of a driving-shaft at uniformspeed is converted through the medium of cranks and levers into the requisite differential movement of the pistons. Each piston executes its working stroke during approximately twothirds of a revolution of the driving-shaft and its returnstroke duringapproximately onethird thereof, so that the working strokes overlap for a period oftime equal approximately to one-sixth of a revolution at each-end.

My invention is peculiarly adapted to the construction of pumps to be operated by electricmotors. It is well known that such motors work to the best advantage when the load or work to be performed remains uniform orinvariableaslongasthework continues. Electric pumps as heretofore made have been but partiall y successful, for the reason that the pumps have been constructedto alternately stop and start the column of wateror branch columns thereof, so that the load or resistance varied greatly during different phases of the stroke or cycle of strokes in pumping. This variation of load not only results in a waste of power generated by the motor, but is injurious to the motor itself. 7

A-pump constructed to embody my present inventionnot only avoids waste of power and utilizes the power to advantage in the continued lifting of the water column, but also ofiers a resistance which is practically 'unvarying during the entire cycleof movement-abet is modification.

to say, its variation amounts to but an exceedingly small percentage, constituting but a minute fraction of the variation of resistance offered by previous electric pumps.

Having now indicated generally the nature of my invention, I will proceed to describe one preferred construction and also some modified forms with reference to. the accompanying drawings, wherein Figure 1 is a side elevation of the pump, looking from the left. Fig. 2 is a plan partly in horizontal section. Fig. 3 is a vertical longitudinal mid-section looking from the right. Fig. 3 is a fragmentary view showing a slight Fig. 4 is a vertical transverse section through the driving-movement, taken on the line 4 .4 in Figsrl and 3 and looking away. from the pump end. Fig. 5 is an end elevation of the pump-cylinders, the connect ing cap or head being removed to give access to the cylinders and pistons. Fig. 6 is a side elevation on a smaller scale looking from the right and showing the manner of driving the pumpfrom an electric motor. Fig. 7 is a diagram showing the relativemovements of the parts of the operating. mechanism for working the pistons, these part sbein g viewed-from the right, as in Fig. 3. Fig. 8 is a chartshowing, graphically, the relative movements of the pistons, the vertical lines being spaced apart to represent equal intervals of time-namely, thirty-sixths of a revolution, or ten degreeswhile thecurved lines indicate the positions of the respective pistons at the successive intervals of time. The remaining figures illustrate modifications. Fig. 9 is a vertical section through the cylinders of a modified construction ofpump, and Fig. 10is a horizontal section thereof on the line 10 10 in Fig. 9.

I will first describe the preferred construction shown in Figs. 1 to 7, inclusive. In this construction a-casting A isformed to include the two. pump-cylinders and to form bearings for the several Working-parts. The cylinders B B areformed in this casting one above the other with their axesparallel. They are constructed, preferably, with cylinder-linings C.

O, constituting thecylindersf-proper, in which work the pistons, (lettered D and D, respectively.) These pistons are hollow, so as to form a water-passage throughthem from end to end,-and are formed with valve-seats d d, respectively, against. which seat valves a a, pressed up, preferably, by springs b b. The

pistons are-packed in any suitable manner,

and are fixed on the ends of piston-rods, (let-- tered E E, respectively,) which pass out through stuffing-boxes at the front ends ofthe cylinders. These rods are expanded outside of the cylinders to form yokes F F, respectively, and their opposite ends are guided by passing through sliding bearingsca, formed in the opposite end of the casting or frame A. The rear ends of the cylinders are closed by a cap or head G, which is formed with a wator-passage Gflwithin-it,constituting a connection between the rear ends of the respective cylinders, as clearly shown in Fig. 3. This cap or head also serves to hold in place the flanges of the cylinder-linings C C, which are clamped between its flange and a corresponding flange on the end of the cylindercasting. It will be seen that the linings are shorter than the cylinders, soas to leave free water-channels between the ends of the linings and the ends of the cylinders, and that they are smaller in diameter than the cylinders, also, so as to permit a free flow of the water to or from the ends of the lining and between the said ends and the water inlets or ports. It will be seen that the linings extend over the water inlets or ports, so that it is not necessary to make the cylinders as long as would be required if the water inlets or ports were between ends of the linings and the heads of the cylinders or between the points to which the piston travels and the heads of the cylinders, which would be the case if no linings were used. The water-inlet or suction-opening H is formed at one side of the lower cylinder B, and the water outlet or discharge opening H is formed in the side of the upper cylinder B, both these openings being formed close to the front ends of the cylinders. The course of the water consequently extends from thesuction-pipe, entering the lower cylinder at H, passing rearwardly through this cylinder and through the piston D, thence through the curved passage G, thence forwardly through the upper cylinder and its piston D, and out through the discharge-opening H on the front end thereof. The front end of this cylinder is also formed with an opening e, extending upwardly and communicatin'gwith the usual air chamber or dome I.

I will now describe the mechanical movement for driving the pistons and imparting to each a comparatively slow working stroke at substantially uniform speed and a quick return stroke. 7

A driving-shaft J is mounted in bearings in the main frame A, extending transversely of the pump in the manner best shown in Fig. 4. A continuous rotary motion at suitable speed is imparted to this shaft through any suitable means. On one end of this shaft is mounted a crank K, the crank-stud of which is engaged by two links, (lettered L and L, respectively.) The link L is jointed at its other end to the end of a lever-arm M, which is fixed to a transverse shaft N, arranged beneath the driving-shaft and mounted to oscillate in suitable bearings in the main frame A. On this shaft N is fixed a lever-arm O, (or pair of arms) connected by a link P with a transverse stud fixed in the yoke F of the pump piston-rod E. As the shaft J revolves in the direction of the arrow in Fig. 1 its motion is communicated through the link L to the arm M, thereby oscillating this arm, the shaft N and arm 0 and communicating reciprocating movements to the piston -rod. The other link L connects in similar manner to a lever-arm M, fixed on a rock-shaft N, extending transversely across the machine above and parallel with the driving-shaft, and on this shaft is fixed an arm 0', which connects by a link P with the yoke F of the piston-rod E. The rotation of the crank oscillates M N O and communicates longitudinal reciprocating movements to the piston-rod. I will endeavor to explain the relative movements of the two pistons which are imparted to them by these mechanisms.

The working stroke of the lower piston D is its rearward stroke and that of the upper piston is its forward stroke. At mid-stroke both pistons move inthe same direction, the one executing its active stroke and the other its return stroke. The latter, however, is traveling much faster than the working piston and reaches the end of its stroke and comes to rest before the stroke of the working piston is completed. I will commence with the position of the pistons shown in Fig. 3. The lower piston D has just come to rest at the end of its working stroke and the upper piston D' has commenced its working stroke and is carrying the load of the column of water, its valve being seated. As it moves forward it forces the water with it, drawing the stream of water through the lower cylinder and through the piston thereof, the valve (1 of which is unseated. The piston D executes its working stroke at substantially uniform speed.

When it has completed about one fourth of its stroke, the lower piston starts on its return stroke and, traveling at greater speed, overtakes and passes the upper or working piston, reaching the end of its stroke and coming to a stop before the upper piston has completed its working stroke. As the upper piston approaches the end of its working stroke and its speed is materially reduced the lower piston has commenced its working stroke and has acquired a speed equal to that of the upper piston, at which instant its Valve seats under the tension of its spring, and for an instant both pistonsact together upon the column of water, the upper one having neared the end of its stroke and the lower one having but shortly before commenced its stroke. From this instant the upper piston slackens speed slightly before stopping, thereby transferring the load of the column of water easily and without shock or jar to the lower piston, which, having obtained substantially full speed, continues without intersame direction, the upper one at accelerating speed until shortly before the lower piston reaches the end 'of its stroke the upper piston equals it, and the valve of the upper piston, being then traveling at the same speed as the column of water, comes to its seat, and for an instant the two pistons both act together on the column of water until in the next instant the lower piston begins to reduce its speed preparatory to stopping, whereby the load of the water column is transferred to the upper piston, which is then traveling at substantially full speed and which continues the column of water uninterruptedly in motion. We have now followed the action of the pistons through an entire revolution of the crankshaft. The means by which these differential movements are imparted will be made more apparent by an inspection of the diagram Fig. 7, where J N N indicate the respective shafts. K designates the path of travel of the crank center, and the lines L, M, O, and P are the center lines of the like-lettered parts for operating the lower piston, while the lines L, M O' and P are the center lines of the parts for working the upper piston. The travel of the crank is marked off in tendegree intervals.

Let us follow first the movements of the parts for operating the lower piston. This piston is shown in Figs. 3 and 7 as at rest at the end of its working stroke. The crank is in position marked zeroor360. In this position the link L extends diametrically f the driving shaft axis, connecting with the armlti at'f. As the shaft revolves in the direction of the arrow its crank exerts a thrust through the link L against this pivotal pin f, which causes the lever-arm M to swing to the position shown in dotted lines at M This movement is completed in about one hundred and fifteen degrees, or approximately one-third of a revolution of the crank. Atthistime the link L again assumes a position radially of the driving-shat't center, as shown by the dotted line L After passing this center the working stroke commences, slowly at first, and by the timethe crank center reaches 140 the arm M has attained full speed, which it maintains during nearly its entire forward stroke, the speed reducing slightly toward the end of the stroke, as shown by the grad uations onthe outer side of the are 0:, which correspond to the different positions ten degrees apart of the crank-pin. As the crank-pin center approaches 360 the movement of the joint center f is slower until it stops in the position shown. Commencing the second revolution, the crank-pin exerts first a slow and then a rapid thrust through the link, causing the arm M to swing backward at a speed indicated by the graduations on the innerside of the are m, which indicate the positions of the center f atthe difierent ten-degree positions of the crank. Thus it is apparent that the return stroke is executed at about three times the speed of the working stroke. These diflerential movements are due to the relative positions of the centers of the shafts J and N, the relative radial lengths of thecrank K and the arm M, and the length of the link L. It

will be observed that by reason of these relative positionsand arrangements the angular position of the armM varies during the working stroke in such manner relatively to the successive positions of the crank radius that the latter acts upon it through the link at very nearly the same mechanical advantage or ratio of leverage for a period of timeexceeding ahalf-revolution of the crank, thus imparting to the arm in successive time intervals a nearly uniform succession of angular advance movements. The crank also acts during this working stroke at a considerable advantage of leverage, so that the movement imparted is a slowone. During the return stroke, while the crank is moving from 0to 115, however, the conditions are changed,

,the crank working at a considerable disadvantage of leverage, and thereby imparting a quick movement to the arm, and the angular relations'between the crank, link, and arm varying constantly and widely with the successive angular positions of the crank;

The movements of the parts L M O are substantially the same as those of the corresponding parts already described. It is to be noted that the lever-arm M is here arranged relatively on the opposite side of the drivingshaft axis from the arm Mthat is to say, since the arm M is arranged to the left of the shaft-axis in Fig. 7 the arm M would be arranged to the right thereof, if exactly, like movements were essential; but in factitis arranged to the left of the shaft-axis, as shown. This is done only for the sake of compactness and symmetry of the working parts, and it might as well be on the opposite side. This change of position results in a slight modification of the movements of the arm M, and consequently of the upper piston, as compared with the corresponding movements of the lower piston,as will beevident by comparing the graduations on the outer and inner sides of the are x withthe corresponding graduations on the are x. The speed of neither piston is exactly uniform, that ofthe lower piston being at its maximum during approximately the first two-thirds of the stroke andbecoming slightly slower during the remaining one-third, while that of the upper piston is slowest during the first part of the stroke or for about one-third thereof, and the maximum speed being maintained duringthe remaining lJWOrthlI'd-S of the stroke. These variations, however, are so slight as to be without intervals being numbered with graduations corresponding to the graduations on thecrankpath K in Fig. 7. The slight dissimilarity in the speed of the working strokes of the two pistons is rendered apparent in this diagram. The two rising and falling curves indicate the movements of the pistons, the rising portions of the curves indicating the working strokes and the falling portions the return strokes. The portions of the curves drawn witha heavy line indicate those portions of the working stroke in which the piston is actually lifting the load of the column of water, while the portions drawn with a light line indicate the idle movements at the beginning and end ofthe working stroke and during the return stroke. It will be seen from this diagram that the outward or lifting thrust against the column of water is continuous and at very nearly the same speed at all times. The lower piston D commences its thrust at about one hundred and forty degrees and continues it until about three hundred and twenty degrees, at which instant the load is transferred to the upper piston, which carries it till the succeeding position of one hundred and forty degrees is reached, whereupon it is again transferred to the lower piston, and so on. The transfer of the load from one piston to the other may be actually a very brief time interval subsequent to these positions by reason of the time necessitated for the seating of the valves; but as these valves are seated with great promptness by their springs this time interval is so brief that it may practically be disregarded.

The mechanical movement thus described for imparting the differential movements to the pistons is very simple, embodying the minimum of working parts and the minimum of friction, all the joints or bearing connections being rotative o-r oscillatory, and the only reciprocating or sliding bearings being those of the two piston-rods and their pistons. This movement is thus practically superior as compared with mechanical movements involving cams on the one hand or sliding blocks working in grooves toward and from the center of oscillation on the other, such being the ex pedients most commonly resorted to for securing such differential movements as my invention provides. All such mechanisms are subject to excessive friction and rapid wear, and difficulty is experienced in taking up the wear as it occurs. With the compound link-movement provided by my invention the wear, which will be slight, can easily be taken up by resorting to known expedients for that purpose applicable to rotative and oscillatory bearings. I have myself invented a self -tightcning bearing for this purpose adapted to automatically take up the wear, and which will be made the subject of a future application for patent.

By my improved pump the arrangements of the partsare such as to insure the greatest possible accessibility and convenience. The

' speed to the desired extent.

link-movement is arranged outside the frame and at one side, Where the parts can easily be put together or taken apart, and the other side of the frameis left free for the projection of the driving-shaft to receive a pulley or other means for driving it. The piston-rods are thoroughly guided, and the stuffing boxes through which they pass are readily accessible within the frame. The suction and discharge openings are duplicated at opposite sides of the pump and the pipes arranged parallel with one another to afford the greatest convenience in piping; but the most important advantage of the arrangement provided by my invention is in the ready accessibility of the pum p-pistons and valves. To get access to them, it is only necessary to remove the one cylinder head or cap G, whereupon both pistons and their valves are rendered accessible through the open ends of the cylinder, as clearly shown in Fig. 5. Any dirt or other material clogging the valves may be readily removed and the valves may be easily taken out and replaced. The lower valve may be removed without disturbing its piston by unscrewing the check-screw g and screw-thinlble h. Either of the pistons may be easily slipped out by unscrewing the fastening which unites it to the end of the piston-rod. This fastening for the lower piston consists of the collar h and set-screw g, while that for the upper one consists of a collar h and set-screw g. The removal of the upperpiston enables its valve to be taken out and replaced. In any ordinary use of the pumps no other parts will ever require to be removed in order to gain complete access to the interior of the cylinders. Hence in' this respect my pump is a great improvement over force-pumps as ordinarily constructed, wherein the valves are arranged in distinct valve boxes or chambers closed by manhole-plates, and wherein to gain access also to the pistons it is necessary to re movein addition one or more cylinder-heads.

Fig.6 shows my improved pump connected to an electric motor for operation as an electric pump. The electromotor Q may be geared to the .pump in various ways. It is desirable that the motor revolve at a high speed, while the pump is driven at a comparatively low speed. The speed may be reduced by interposing worm-gearing; but this involves the disadvantage of the loss of a large percentage of the power byfriction. Spur-gearing is also objectionable on account of its complication, noise, and wear. To overcome these disadvantages,lhave devised the arrangement of beltgearing shown in Fig. 6. A large belt-pulley J is fixed on the shaft J and a suitable drivingbeltj is carried over this pulley and over a small pulley 7c, fixed on the end of the armature-shaft of the electromotor, the two pulleys being suitably proportioned to reduce the To insure a considerable wrap of the belt around the pulleys and at the same time to afford a means for taking up slack in the belt, I provide an idlerpulley l, nearly filling the space between the pulleys J and 7.; and adjustable up or down to impart the requisite tension to the belt. Whenever the beltj becomes slack, it may be tightened by adjusting the bearing-block of the pulley l, as shown in dotted lines in Fig. 6,. downwardly, this block being provided with slotted connections to admit such adj ustment; or the pulley Z may be otherwise hung.

to prevent vertical movement.

My invention may be modified in various ways without departing from its essential features; be arranged within the casing-as, for in.- stance, within the cylinders B Band connect directly to the pistons by connecting rods or links. A modified construction embodying this plan is shown in Figs. 9 and 10.

The modified pump shown in Figs. 9 and 10 has in general the same arrangement of cylinders and pistons as that shown in Figs. 1 to 6; but the pump is made much more compact by moving shaftsJ N N closer to the pistons and arranging the shaftsNN' and theirarms O O to work within the pump-cylinders. The arms 0 O are connected to the pistons directly by the connecting rods or pitmen R R. For convenience the pump is arranged with its cylinders upright, so that the enlarged ends of the cylinders, in which work the arms 0 0, may be utilized to constitute a base for the pump, being provided with a suitable foot.

The suction and discharge openings are ar-' ranged at opposite sides, so that the suction and discharge pipes extend in line. The driving-gear is the same as that first described, except that in order to render the pump as compact as possible the lever-arms M M, in-

. stead of being arranged on the side of the crank remote from the cylinders, as shown in Fig. 3, are arranged on the opposite sidethat is to say, above the driving-shaft-in Figs. 9 and 10. This construction afiords the same advantages of easy access to the cylinders by removing the cylinder-head or cap G, as in the construction first described. If desired, the two cylinders may be arranged end to end, forming one continuous straight water-passage.

I have stated that the arrangement of the lever-arms M M on one side or other of the driving-shaft J is a matter of choice. With both arms arranged on one side of the shaft the movements of the two pistonsvary slightly, as indicated by a comparison of the curves of the lower and upper pistons in Fig. 8. By transferring the upper arm M in Figs. 1 to 7 to the opposite side of the driving-shaft the movements of both pistons will be made alike, the movements of both being that indicated by the curve marked lower piston D in Fig. 8. On the other hand, if the arm M be left in the position above shown in Figs. 1 to 7 and the lower arm M be moved to the opposite side of the crank the movements of both pistons will be the same as that denoted by the curve marked upper piston D in Fig.

For example, the lever-arms O 0' may 8. The difierence in the effect of t h ese movements is so slight as to be-practicallymapwater.

The links P and arms 0 may be replaced by toothed sectors and racks, as indicated in Fig.3. i

I do not here claim the combination, with a pump of the character described, of an electromotor having an armature revolving in one stantially as hereinbefore specified, namely: 1. The combination, in a pump, of twovalved pistons workingin alternation to pro-v pel a column of liquid and a driving-gear for imparting to each a comparatively slow working stroke and a quick return stroke,

consisting, of a driving crank-shaft, two rocklevers M M, connected each to the corresponding piston, and two links connecting said levers with the crank, whereby the Ievers are vibrated from the crank at varying speeds, substantially in the manner and to the elfect specified.

2. The combination, in a pump, of two valved pistons working in alternation to propel a column of liquid and a dr ving-gear for imparting to each a comparatively slow working stroke and a quick return stroke, consisting of a drivingcrank-shaft and two rock-levers connected to the respectlve p1stons and driven fromthe crank through interconnectinglinks, said levers having their axes arranged beyond the crank radius and the lengths of the lever-arms and links relatively to the crank radius and the distances between the. respective axes being proportioned to bring the positions of the crank at the opposite extremes of the movement of either lever approximately one-third of a revolution apart,

substantially as specified.

3. The combination, in a pump, of two valved pistons working in alternation to propel a column of liquid and a driving-gearfor imparting to each a comparatively slow working stroke and a quick return stroke, consisting of a driving crank-shaft and two rocklevers connected to the respective pistons, ar ranged with their axes on opposite sides of the driving-shaft, and links connecting the crank with the respective levers, the lengths of the lever-arms, links, crank radius, and distance between axes being relatively proportioned to drive the respective levers on the working strokes of their pistons through an arc of about two-thirds of a revolution and to begin the working stroke of each at approximately one-sixth of a revolution before the termination of the working stroke of the other, substantially as specified.

4. The combination, in a pump, of two valved pistons working in alternation to propel a column of liquid and a driving-gearfor preciable in its efiect upon the column of imparting to each a comparatively slow working stroke and a quick return stroke, consisting of a driving crank-shaft, two rock-levers comprising each two lever-arms connected by a rock-shaft, one of said arms connected to the corresponding piston and the other arm of each lever connected to the crank by a link, the lengths of the lever-arms, links, crank radius, and distance between axes being relatively proportioned to drive each lever on the working stroke of its piston during approximately two-thirds of a revolution and to drive it on its return stroke within the period of working stroke of the other, whereby the durations of workingstrokes of the respective levers are made to overlap and the load of lifting the column of water is transferred successively from each piston to the other while the column is kept in uninter- MILAN WV. HALL.

Witnesses:

ARTHUR G. FRASER, GEORGE I-I. FRAsER.

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