US2165963A - Constant flow nonpulsating pump - Google Patents

Description

July' 11, 1939.1

w. H. CUR-ris 2,165,963

CONSTANT FLOWNONPULSATING PUMP Filed April 25', 1958 3 sheets-sheet 1 July11,1939. 7 n W H `URT,S l2,165,963

coNsTANT mow NONPULSATING Puur Filed April 25f 1938 s sheets-sheet 2 66. i 54? 7c` 6062 72 v a l.f2.2 .43

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July 11, 1939. w. H. CURTIS CONSTANT FLOW NoNiULsATING PUMP Filed April 51',y 1938-v s sheets-sheet s larly to vane type rotary outer ends or the vanes oscillate toward and humedll 11.- 1939 n Y'narrati sr-A'rss 2.10am coNs'rAN'r now NoNrmsA'rma Pour wimmncuraesiniaomo, .aimeraientis Pump Company, Dayton, Ohio, a corpora- Ation lf-Ohio Application April es, 1m,- snlai No. msgs 1o emma (ci. Ica-its) 'ihis invention relates to pumps and particupumps wherein the away from, thev center of rotation ofthe rotor.

o! this character in which the volume of iluid transferred, from the low to the high pressure side of the pump, is exactly the same per unit of angular movement at any point in a' revolution 1.0 of the shaft, to the end that there will`be no oscillatory velocity I -be present.- even whenV the pump 2g objects have not been going objects are attained, each without sacriiic- 39 wherein,

ing iull attainment of the other.

.Further objects and meritoriousfeatures wm'.

become evident as the invention is described in detail, reference being had to the drawings,

Fig. 1 is section thrul a rotary pump oi' that type vnow known in the art in which the 'attainment of non pulsating delivery may be had only by auchv modification in the structure as'will cause mechanical shock, and the elimination of mechanical shock may be eiiected only. by permitting-pulsating deliver. Fig. l is included for illustrative purposes only and not as a part of this invention.

Fig. 2 is a diagram of a developed portion of the interior of` a pump cylinder applicable tothe upump shown in Fig. 1, land used where non pulsating delivery is to beachieved and mechanical shock permitted.

Fig. 3 is `a Ndiagram of a developed portion of the interior of a pump cylinder applicable to the pump shown in Fig. 1, and used where mechanical .shock iseto beeliminated and pulsatlngdelivery permitted.

Figs. 4,'5 and 6 are'diagrams o! a developed portion of the interior surface of a pump cylin- -der made according to this invention, with vanes positioned at different places in theirv travel `across the developed surface. These diagrams are intended to illustrate the operation of the structure shown in Fig. 7.

Fig. 'I is a cross section taken at 1-1 of Fig. 8 thru a pump made according to this invention, the structure being such as to secure non pulsatfAn object of the invention is to provide a pump the two foregoing round since AD=CF=BE. The cylinder bore is" l D eects a uniform delivery ing delivery and-at the same time be free frommechanical shock.-

meals-an analsecuonmk'en at s-a orma. 'zi

thru the improved pump structure.'

Figs.- 9l and 10 are side views of two of the s vanes.

Fig. 11 is a diagram employed to illustrate the mathematics of the curve of a portion of the interior of the pump cylinder.

Fig. 12 is a section thru a modiiied form of pump in which the lprinciples oi this 'invention may be embodied. I f

Fig. 13 shows an optional form of vane having sealing members at the ends.

Similar numerals refer only to similar parts thruout(` the several views. L j

Referring particularly to Fig. 1, the body 2l, of a rotary pump has a circular bore 22 into which the pump cylinder Il is press iitted. The

rotor 26 is rotatable on a sh lft 2l about the center l which is also the center of the outside of the cylinder 24. i

The`rotor 28 isl provided with slots 30 at right angles to each other and with lvanes 32 and 34 which 'are slidableradially in these slots. The vanes 32 and 34 are cut away as at to clear each other, the cut away portionbeing sumcient to permit the maximum radial movement o! thev .vanes without interference with each other.

The vanes 32 and 3l are longer than the rotor l.. diameter and consequently project radially'therefrom, the bore of the cylinder 24 being so' fashf. i

loned as to permit rotation of the vanes with theI rotor. For convenience in description, the centerl lines of the vanes are vdesignated by letters AD` and CF.

Since both ends of a vane must contact the,v cylinder at any point o! rotation'of theroto'r,A obviously the interior of the cylinder may not be` in fact madeA with the arc AF equal to the radius of the rotor, the arc CD having a radius equal to the rotor radius plus the excess oi thevane length i over the rotor diameter, and the c urves'AC and DF being necessarily such as to pass thru B and E respectively and such as to contact both ends of a vane at any point in its rotation. Ihe arcs AF and CD both have their centers at '0 which is the axis oi the rotor.

Now since the fluid 'occupying the space 38 is bounded by two4 arcs having the same center, it follows that uniform rotation of a vane from C to.

the space Il` into the space Il, so that were this the only consideration, non pulsating delivery would'be achieved. i

It must be noted however, that while one vane is 'passing from AC to D, another is passing from Dto F.

It avane could passiromDtoF without re-A of the -fluid within tracting into the rotor, it would neither` add to the volume in space 40 nor subtract from it, but the fact is, that while a vane passes from D to F it retracts into the rotor thereby increasing the space 40 by a volumeV equal to the volume of that part of a. vane which extends from the rotor when 4the vane is at D. It follows that the delivery from the discharge end 42 per quarter turn of the rotor is equal to the fluid in space 38 minus a volume of fluid equal to the vane extension at D.

It has been shown that the delivery of the fluid `in space 38 is constant when the rotor speed is constant,thatis,every degreeof rotor rotation will transfer the same volume from 38 to 40 as every other degree. It follows that if the ultimate discharge from the end 42 is to be constant, the vane extension must retract an equal amount per degree of turn, i. e., each degree of turn of the 90 degrees between D and F must retract the vane extension $60 of the whole retraction.

To satisfy the foregoing conditions mechanl ically, the cylinder curve from D to F must be plotted from a diagram as in Fig, 2, where the retraction velocity of a vane 32 between D and F is exactly the same thruout, with uniform movement of the vane from D to F. In such a structure the vane 32 after moving from C toD without retraction, instantly changesat D from no retraction to the maximum rate of retractionv and then without acceleration or deceleration maintains `this constant rate of retraction from D to F, then at F instantly changes from the maximum rate of retraction to zero retraction.

If the curve from D to F were plotted on this basis, the rotor could not be revolved at any practicable speed without destructive mechanical shock at points D and F.

Itis therefore obvious that, in order to attain non pulsating delivery at the discharge end 42 an objectionable mechanical construction was necessarily adopted.

In order to avoid this mechanical shock, the curves of pump cylinders are usually plotted from a diagram as shown in Fig. 3. Here a vane 32 leaving point D, has a very small rate of retraction at the beginning, acceleration of retraction taking place betwen D and E where the maximum rate of retraction is reached. From E deceleration of retraction takes place until F is reached where a zero rate of retraction isagain had.

This acceleration and deceleration of the rate of retraction, however, provides a decided pulsation in the fluid delivery particularly in noncompressible fluids for it will berecalled that for non pulsating delivery-it was required that there be no acceleration or deceleration in the rate of retraction of a vane passing from D to F, but that the rate of retraction must be constant between these points in order that the ultimate discharge at 42 may be constant and therefore without pulsation.

It will be seen that a structure which provides non pulsating delivery is subject to mechanical shock and that a structure which avoids this mechanical shock introduces a decided pulsation into the delivery. It-is therefore necessary, in employing existing art, to make'a choice as to which of the two evils is to be endured, or provide a new structure not heretofore known which eliminates them both. Such a new structure is the substance of this invention and will now be described.

Referring now to Figs. '7 to 10, a. pump body 48 has a circular bore 48 with a pump cylinder 50 press tted therein. An end head 5| is held to the body 48 by screws 53' thereby closing the one end of the body.

The rotor 52 comprises a ringy which is slotted at 60 degree intervals leaving a series of segmental 1ugs154 between which the three vanes 56, 58 and 60 are transversely slidable.

The lugs 54 are formed integral with a disc 82 from which the shaft 64 extends, the shaft having rotative bearing inthe hub 66 of body 46. The vanes are notched out to clear each other, the vane 56 from the bottom upward as at 88, the vane 58 from the top downward as at 10, the vane 60 being notched from both top and bottom as at 12 and 14 Fig. 8. Thevanes 56, 58 and 68 are longer than the diameter of the rotor and consequently project radially therefrom.

'Ihe axis of the rotor 52 and the axis of the outside of the cylinder 50 coincide at 0, but the inner contour of the cylinder is offset with the outside to such an extent that when the rotor touches one side of the cylinder bore it is as far from the opposite side as the difference between the rotor diameter and .the vane length. The center linesof the vanes are designated by letters AD, BE and CF.-

Since AD=BE2CF is obvious that the cylinder bore 48 may not be round. The cylinder bore is composed of an arc AF ldrawn to the radius of the rotor, an opposite arc CD drawn to a radius which is as much longer than the radius of the rotor as the difference between the rotor diameter and the vane length, and the curves ABC and DEF which must be such that'a straight line drawn from any point on ABC thru to its intersection DEF will equal AD=BE=CF.

'I'he cylinder 50 is slotted at 'I6 and 'I8 to provide suction and discharge ports respectively, the slots being of considerably less width than the cylinder, leaving ample bearing for the ends of the vanes to contact when passing over the ports'. Both parts-16 and 18 subtend an angle t of 120 degrees centered at 0.

`according to the line DEF, Fig. 3, to avoid mechanical shock, an objectionable pulsation in the delivery would inevitably result.

It is now the purpose to show how and why the curve DEF, Fig. 7, may be plotted according to lines DEF in Figs. 4, and 6 to avoid mechanical shock, and at the same time secure nonpulsating delivery.

The line DEF, Fig. 4 represents diagrammatically the curve DEF Fig. 7, a vane 58 being positioned at D and a vane 60 at E. When the vanes 58 and 50 move laterally in the direction of the arrow 80 across DEF, obviously they will retract vertically in the direction of the arrow 82. It. will be observed that when the vane 58 rst moves laterally away from D the rate of vertical retraction is yery small per unit of lateral movement, but that the farther lateral movement progresses the more rapid the rate of vertical retraction until the vane 58 reaches E as in Fig. 6. At E the rate of vertical retraction is at a maximum and begins to diminish with further lateral movement of the vane. Thus there is acceleration of vertical retraction from D to E and deceleration or negative acceleration ofvertical retraction from E to F.

Now it will be observed that, since the vanes i arcanes are spaced 60. degrees apart and the curve DE!" extends over 120 degrees, there are at all times two vanes within the extremities of the curve. -It will be further observed that when a vane Il leaves the -point D, whre the rate oi retraction is lowest, the vane Il is leaving -l! where the rate of retraction is.highest (see Fig. 4), and

- when vanes. i8 and Il are midway between DE y to the problem.

and EF respectively the rate ot retraction is the same for both vanes (see Fig. 5), and that when the vanes 5l and Si are at E and F respectively,v the rate of retraction of vane Il is highest and o! vane Il lowest. r

The curve DEF must therefore be so formed thruout its 120 degrees that the 60 degree spaced varies will at any stage in their movement across the curve have a rate of retraction in one vane as much below the average rate as the rate of retraction of the other vane is above the average rate, i. e., -when the retraction rate is being accelerated in one vane it is being decelerated or negatively accelerated in ,the other. Stated in another way, i! the-sum of the two vane retrac'tive-velocities isto .be constant, the

- algebraic' sum c! the accelerations of4 retraction of the two blades which are at the same timev on the curve must equal zero, and the form oi" curve `:required is one, the equation oi' which will have its second derivative equal to a constant.

` This obviously indicates a parabola.

Two forms of polar equations, which are-the most convenient in the analysis, are well -known and applicable:

It remains to select the equation best Referring tcrlg. 11, BE and cr represent constant-length blades of zro thickness, and having in this instance an equal angular spac- .ing of 60 degrees. AF isan arc with radius AO=F O, and CD is an arc with radius CO=DO. Since the vanes are to' be of constant length,

" and the center line of any vane must always paas thru I, it is required only tu-'developl the portion AB -of the curve, from which DE may ,be obtained by subtracting the respective AB ricaldispositionfof, the values of AB and DE ordinatesv from the 'constant representing the blade length.

EF and BC may then be obtained by symmetwith respect to thevertical axis MN.

Two boundary values for the. curve Vare obvious from the At A the polar, ordinate r muet =2a0l=rate of r with respect t0 0..

d6s=2=acceleration of r with respect to 0'.

If 0 represents angular velocity of blade and is uniform, it may be replaced by t==time, and

gg=2a0= velocity of blade (retractive),

d=h=acceleration of blade (retractive),

lwhich are the respective velocities and accelcrations of retraction in either zones AB or FE depending' on the direction of rotation. Also ,the corresponding ordinates for zonesjDll and BC are equal to L-r where L the vane length, and it we let u equal the 'ordinate Y which snows `that the'relctive ve1cc1t1es and sc- -celerations in these zones are equal to those in the primaryzones but opposite in 7sigr'x. Thismust be-tr'nel for otherwise vanes o! constant length couldnot be used.

Now let us apply the actual condition'in a pump' of the form. of Fig. 7, having counter clock-- rotation with inlet port extending from -A to C, and discharge port extending from D to F.'

Assume van'es D and E to have moved to Di and E1 (see Fig. ll) and still in motion. Then the sum oi! their retractive velocities is fza rc1-Ho which is obviously a constant for any position ot- D and 'E. .in the none DEF, since 014-0: the angle DOE inrradians a constant. 'I'he condition till holds vtrue when D, reaches the position-E, I or then 01 radians DOE and oz zero.

Moreover the acceleration of D and E, with respect tg'each other are plus 2a and minus 2a which A`algebraically equal zero. Stated Aotherwise there is constant acceleration in zone DE and constant deceleration in zone EF, while at points D, E andi' there is neither acceleration 6r deceleration. Y c

Thus a curve is provided in which all of the cnditidns for uniform non pulsating discharge are met. Also, since the eiiect is obtained by reason'of constant retractivevane velocity summation, it is independent ofvane thickness. The -f discharged, the thicker the vane the smalierjthe volume discharged.

Obviously the number of vanesineed not be coniined to the six, i. e., three thru vanes shown..

but may comprise any reasonable number greater than four single vanes or two thru vanes. The inlet` and outlet portsmust span two or a 'multi- -`vane thickness will, of course, aect the volume u ple of two vane angles, the curve of the equas tion one or more vane angles, the pumping sone arc less'than one vane `angle andthe seal whatever remains of the bore.

It will be apparent that the vanes may com.- priseeither thru vanes, as shown, or, may comprise the older type-oi' vane construction in againstthe cyii'riderbore' by springs or 'similar Vmeans-"placed between them.

. which -single vane: in individual slots are urgedl n Ffcr simplicity'in illustration, in the embodi ment shown, plain vanes with rounded ends are employed, but obviously'vanes-ii t ted with rockers 84, Fig. 13, may be employed to good advantage, since the rockers have the capacity to adjust themselves to the varying curvature of the cylinder bore and thereby reduce the vane to a theoretical plane having length BE.

Where such rockers are not used it may be necessary to adjust the curves of .the cylinder bore to allow for vane thickness, as otherwise the vanes would be more or less sharp at the ends on the center line. It is 'entirely possible, however, to employ vanes with appropriately rounded ends and retain all the advantages of this invention if suitable adjustments are made in the theoretical cylinder bore to compensate for the curvature on the vane ends, as by drawing, from a theoretical bore, a series of small arcs with radius the same as the vane ends, and fitting an actual bore to the outside of these small arcs. v

The modification shown in Fig. 12 is shown to illustrate how the invention may be applied to a balanced rotor type of pump. Here a pump body 86 has a circular bore 88 centered at 8, the outside of a cylinder S being closely fitted therein;

The cylinder 98 is slotted to provide suction ports 92 and 9i and discharge ports 96 and 98, which communicate respectively with passages 00, |02, |04 and H36 in the body 86.

The cylinder ports are so spaced as to leave e two opposite sealing portions |08 and lill, the curves of which are tangent, make a line contact therewith, and to the rotor at C and H and two opposite pumping zones H2 and H4. at right angles to the sealing portions. The center linesA of the ten vanesgare'at AO, BO, CO, etc., the

pumping zones H2 and IH extending from A to J and from E to F respectively. Obviously the sealing zones or the pumping zones may be increased in angular extent by increasing the number of vanes.v

The rotor lli is slotted to receive the vanes slidably. Single vanes are employed because, the distance C-H must of necessity be less than either A-F or J-E precluding the use of solid thru vanes. Any of the meanscommonly employed to keep the outer ends of the vanes in contact with the inner wall of the cylinder are applicable. In the embodiment shown, a pin H8 extends from each vane into an appropriately formed track in the bearing head for this purpose.

In this balanced pump, Fig. 12, the hydraulic loads are equal and opposite and therefore lighten the load on the 'rotor and bearings, which is highly advantageous where high pressures are involved.

The two suction passages may with appropriate structural design be combined into one, as may also the two discharge passages. The outer ends Voi.' the vanes may be arcuate as shown, or fitted with rocker seals 84, as in Fig. 13.

The curve ABC is developed in two sections, but with the same basic equation as heretofore employed.

angle from CO toward BO in radians.

the angle froxnAO toward BO in radiana.

memes symmetry. The portions AJ and EF are circle arcs of not less than one vane span.

In order that these pumps may be operated at exceptionally high speeds, the cylinder bore must be free from sharp 'changes of curvature. This requires common tangents wherever the bore changes in contour. That common tangents exist in the bores described may be proven as follows:

Let 4 .equal the angle between r and the tangent to the curve, then in zone AB and the curves have a common tangent with arc AJ and adjacent curve CD.

Also at point B, c+m92=c1a0z and 0 equals the same value in each case, therefore the tangent angles are equal and the curves have a common tangent vat B. Therefore the cylinder bore is without sharp changes in curvature. Moreover, a vane in passing from Ato B is u nder constant acceleration, while in the passage from B to C it is under constant deceleration. By applying the same reasoning here used to a flow analysis of the pump of Fig. 7 it will appear that the algebraic sum of the accelerations actingiupon the vane or vanes inthe zone ABC is constant and equal to zero, wherefore the vsum of their retraction velocities must be a constant whereby non pulsating ow conditions are provided. By the same method it may be shown that common tangents exist at all juncture joints between calculated curves and `circle arcs in the forms shown in Figs. 7 and 11.

It should be noted vthat in the type of pump herein disclosed, the vanes do not move radially in the rotor when under load, i. e., when passing thru the pumping zone, all sliding movement of a vane in the rotor occurring when the vane is passing over a port and doing no work. Excessive loads between surfaces` in rubbing contact 'are therefore avoided whereby .wear is held at a minimum. s

Further it should be noted that functions developed and proven for the discharge port zone exist with opposite sign but similar effect over y the intake zone.

In the claims, two thru vanes will be referred tft: as four vanes Vand three thru vanes as six vanes, e c.

Having shown and described several embodiments of the invention,

I claim:

1. In a pump of the oifset rotor sliding vane type, a Dump body having a right somewhat cylindrical bore, a normal cross section of which is defined by two' opposite concentric arcs of unequal radii, with vane. extending and retracting curves joining adjacent ends of said arcs, there being tangents |common to the arcs and curves at their-points of juncture, a cylindrical rotor having a diameter of twice the smaller of the two radii, rotatably positioned with its, axis at the centers of the arcs, said rotor having radial vane slots, vanesslidable in saidl slots, the number of vanes being an even number necessarily greater than four, the ends of the vanes being always in contact with said bore;. the surfaces denned by the arcs of the smaller'and larger radii respectively constituting a sealing' and pumping zone, each subtending any whole number of vane spans,

vand the surfaces deiined by lthe vane extending t and retracting curves having ports circumferentially equal to said curves which must subtend at least two or a multiple of two vane spans, said curves being so formed that, with 'constant angular velocity of the. rotor, there will be uniform acceleration of the movementl of a vane ina slot as the end of the vane passes over the ilrst half of thecurve and uniform deceleration of the movement of said vane in its slot as its end passes Aover the second half of the curve.

2. The structure defined in claim 1 with opposite vanes ofthe same rotor slot being formed integral.

3. In a pump of the sliding vane type, a pumpv body having a right somewhat cylindrical bore, l

a rotor smaller than said bore rotatably mounted in said bore with at least one side of the rotor in contact with said bore to form a seal, said rotor having axially extending vane slots spaced around its periphery, vanes having their outer ends always in contact with said bore siidablein said slots toward or away from the rotor axis, the number of vanes being any'number greater than four, said bore comprising atleast one pumping zone, said zone being defined by a radius drawn from the rotor axis but greater than the rotor radius and subtending an arc equal to not less' than one vane span and -vane extending or retracting curves beginning at the ends of the pump- Gil the r'st half or the curve, and uniform deceleration of the movement of said vane in its slot as itsend passes over the second half of the curve.

4. The structure defined in claim 3 wherein the acceleration of the extension or retraction velocity of a vane. begins when a vane starts over a port and remains-constant until it reaches a point angularly midway in s aid p ort, whence deceleration of the extension or retraction velocity begins at the same rate as it leaves the said midwaypoint and remains constant until it reaches the end of said port.

5. The structure defined m claim' 3 wherein the said extending and retracting curves are of such length and so formed and the vanes are so spaced with respect thereto that when one vane is at a position which is causing minimum retraction velocity to a vane, another vane is atl a position which is causing maximum retraction` velocity to a vane.'

6. The structure deilned in claim 3 wherein the saidy extending and retracting curves' are of such length and'so formed and the vanes so spaced with respect thereto, that when one vane is leaving the zone wherein there is zero extension or retraction velocity of a vane in its slot, 4another vane is entering a zone whereinthere is zero 'extension or retraction velocity o the vane in its slot, and -another vane is midway between the A -i'lrst -and secondi said vanes and is leaving a point on said extending or retracting curve where there is maximum extension or retraction velocity.

'1. The structure dened in claim 3 wherein the extending and retracting curves are of such length and so formed and the vanes are so spaced with respect thereto, that when two vanes are within the boundaries of the same curve, one is receiving acceleration of-its velocity of sliding movement, the other is receiving deceleration of its velocity oi sliding movement and said acceleration and deceleration are always numerically equal. 8. The structure defined in claim 3 wherein the said extending or retracting curves are of such length and so formed, and the vanes are so spacedwith respect thereto, that when two spaced apart vanes .pass over a curve and are thereby extended or retracted radially, the sum of their extension -or retraction velocities at any point in the rotation of said vanes is a constant.

9. The str ucture dened in claim 3 wherein the extending and retracting curves are 'or such length and so formed, and the vanes are so Aspaced with respect thereto, lthat the sum of the extension or retraction velocities of all vanes which may be passing over a curve at the same time is a constant.

10. The structure deilned in claim 3 wherein the extending and retracting curves are of such llength and so formed, and the vanes so spaced with respect thereto, that the algebraic sum oi all accelerations of extension and retraction velocities of. all vanes passing at the same time-over said curves is equal to zero.

v WILLIAM. H. CURTIS.

Certificate of Correction Patent No. 2,165,963. y July 11, 1939.

. H. CURTIS It is hereby certied that errors appear in the rinted-speciication of the above numbered patent re uiring correction as follows: age 2, second column, line l26,l `before the word'is'msert it; line 35, before DEF insert with; line 41, for the word parts read rts; page 3, second column, line 65, before less insert not; page 4, first column, lles 32 and 33, for the Words tangent, make a line contact therewith, and to the rotor at C and H and read tangent to the rotor at O ami H and make a line contact therewith, and; line 69, in the equation, forrAB=c1-I'a02 5 read rAB=c1-'a02; and

second column, line 29, for in the passage read in passing; and that the said Letters Patent should be read with these corrections therein that the same may `conform to the record of the case in the Patent Office.

Signed and sealed this 17th day of October, A. D. 1939.

l [Sw] HENRY VAN msnm,

Acting O'oHarri/issienesl of Paen'ts.

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