Патент USA US2129828код для вставки
.Sept. 13, 1938. w.'1-. bu-NN- $129,828. PUMP Filed July 5, 1935 4 Sheets-Sheet l . INVENTOR. Mllr'am 7.’ Dan’? Sept. 13, 1938.. 2,129,828 T. DUNN. ~ 7150MBv Y Filed July 5, 1955 ‘ 4 sneeté-sheet 2 70li-\|I ‘ c", - INVENTOR. -~ /44 _ M21121?” Z'Dzlzzn BY _ ._ wxm?w \ I ’ ATTORNEYS. ‘ ' 2.129.828 Patented Sept. 13, 1938 UNITED ‘STATES PATENT OFFICE 2,129,828 PUMP Detroit, Mich., assignor to William T. Dunn, Chrysler Corporation, Highland Park, Mich., a. corporation of Delaware Application July 5,_ 1935, Serial No. 29,777 2 Claims. (01. 103-162) showing a. modi?ed arrangement of springs for This invention relates to pumps and’ refers operating the pistons. ‘ more particularly to improvements in pumps _ Fig. 5 is a similar view of a further modi?ca adapted to produce and maintain pressure on a ?uid, such as oil, suitable for use in systems of tion of my invention. Fig. 6 is a sectional elevational view of another 5 modi?cation of my invention, the view being taken along line 1-1 of Fig. 6. Fig. 7 is a sectional plan view along line 1-—'I of Fig. 6. 10 Fig. 8 is a'sectional elevationalview of a fur ther embodiment of my invention. Fig. 9 is a sectional view taken as indicated by motor vehicle transmission control although my 5 improvements are adaptable to a wide variety of applications. As illustrative of one system of transmission control to which my pump is adapt able, reference is made to the copending applica 10 tions Serial No. 724,434 ?led May 7, 1934 and Serial No. 752,948 ?led November 14, 1934. One object of my invention is to provide an improved pump which will e?iciently and quickly provide a relatively high pressure of the oil, such 15 pressure being maintained preferably without re— line 9-9 of Fig. 8. _ . Fig. 10 is a view generally similar to Fig. 1 but showing another modi?cation of my improved quiring operation of the pump after the required pump. pressure is maintained. Further objects of my invention are to provide stator for the pump shown in Fig. 10. Fig. 11 is a sectional elevational view of the Fig. 12 is a sectional plan view through the a pump having improved characteristics of self 20 regulation in its delivery; improved balance of the ‘parts; a pump capable of long and continu pump of Fig. 10, the section being staggered at the stator as indicated by the line 12-12 of . Fig. 11. _ ous service, as is required in motor vehicle con trol, without undue heat generation, noise, wear or failure through other causes; and having im 25 proved means preventing the trapping of air in the pumping system. ‘ . operating springs. l6-l6 of Fig. 15. , I ' I Fig. 17 is a diagrammatic view of the pump corporating an improved'arrangement of control of the swash plate or wabble plate for operating 35 the pistons to produce'and maintain the oil pres. sure at the pump delivery without objectionable stator and rotor ports during cut-off of fluid pressure,delivery. ‘ “hunting” or ?uctuation in the control of the ?uid pressure. portion of a‘motor vehicle transmission casing ' my pump. 1 Fig. 2 is a sectional plan view along line 2--2 of Fig. 1. '. Fig. 3 is a sectional view taken as indicated by the staggered line ‘3-3 of Fig. 1. , Fig. 3A is a detail sectional view along 3A—-3A showing the porting action‘. _ Fig. 3B isa view corresponding to Fig. 3A but showing the parts in a later stage of the porting operation. . \ Fig. 4 is a view generally similar to ‘Fig. 1 but 35 . 'Referring to Figs. 1 to 3 the pump illustrated in this embodiment of my invention comprises a suitable supporting structure A which may be a Further objects andadvantages of my inven tion will be apparent from the following detailed 40 description of several embodiments of my invention, reference being had to the accompanying drawings in which: Fig. 1 is a sectional elevational view through 55 . Fig. 14 is a sectional elevational view of an— other modi?cation of my pump. Fig. 15 is a sectional plan view taken along line 30 |5-l5 of Fig. 14. Fig. 16 is a detail sectional view along line ' Another object of my invention is to provide a pump of relative simple construction, having its operating parts compactly arranged for manu 30 facture and assembly at relatively low cost. In carrying out the foregoing objects, I prefer ably provide a pump of the swash plate type in 45 , Fig. 13 is a fragmentary view in sectional ele vation of a portion of my Fig. 1 pump but illus- ' trating a further modi?ed arrangement of piston formed with the generally cylindrical portion 20 thereof adapted to house the cylindrical pump rotor 13. Rotor B comprises a lower enlarged body 2| and an upper body 22 secured together by fas-i teners 23. The upper body 22 is suitably driven by a gear 24 connected by interlocked teeth 25 with the upper end of body 22, the gear being rotatably journalled by an anti-friction bearing 26 mounted adjacent the-upper end of a stator C. The upper and lower ends of the stator are respectively centered and ?xed within the sup port conduit 21 ‘and the cylindrical boss 28 of a casting 29 which houses the lower parts of the pump mechanism, this casting being secured to 55 support A by fasteners 30. -' 2 9,129,828 The bodies 2| and 22 have the axial bores 3|, 32 I The plate D will thus assume an angle depend-' rotatably engaging the I stator C. Body 2| has ing on .the pumping requirements and normally an annular series of cylinders 33 extending there the pump, after producing the desired pressure, through parallel to the body axis, these' cylinders will become inoperative insofar as reciprocation each slidably receiving a piston plunger 34. Each of the pistons is concerned until such time as the piston has an upwardly opening bore 35 accom pressure falls for any reason. With the pump 'modating a spring 36 acting between the upper operating at maximum delivery capacity, pistons body 22 and the piston for yieldingly urging the 35 closely approach the upper body 22, thereby piston downwardly to maintain the lower round insuring against entry-of air into the system. 10 ed. end 31 thereof in contact with the upper ele The delivery pressure may be readily varied by ment or ring 36 of a swash plate D. The lower adjusting the tension of springs 51, 58 at the 10 element 39 rotatably supports the upper ring by abutment 55. . the anti-friction bearing 390 and is rigidly The passages 45, 5| are preferably milled saw mounted on spaced arms40 secured to a shaft 4| kerfs for low cost manufacture, these pairs‘of 16 journalled at its opposite ends at 42, 43 in cast‘ passages being preferably vertically communicat ing 29 for pivotal movement by an arm or lever ing whereby. passages 45. function alternately 15 44 ?xed to shaft 4i and thus movable with arms both as delivery and inlet passages for cyl 40 as will presently be apparent. Radiating inwardly from the upper ends of each 20 cylinder 33 is a slot-like conduit 45 providing an inlet for the ?uid to each cylinder. Stator C has an axial bore 46 for supplying the ?uid upwardly from a reservoir in support A, the ?uid level be ing well above Opening 47 to deliver the‘ oil 25 through transverse stator passage 48 communi cating with bore 46. The latter bore terminates at 49 just above the radially extending out - wardly ?aring delivery passage 50. The upper body 22 has its under face formed 30 with circumferentially spaced radially extending milled slots 5| forming pressure delivery pas sages between the respective cylinders 33 and the stator. The stator has an upwardly ex-' tending delivery bore 52 which terminates just 35 below a second radially extending outwardly ?aring passage 53 which extends 180° from pas sage 50. The upper end of bore 52 delivers ?uid to conduit 54 in the support 21 and is suitably conducted to the points of use of the fluid under 40 pressure produced by the pump. The arm 44 carries an adjustable abutment screw 55 pivotally seating spring abutment 56, a spring assembly 51, 58 acting between casing abut ment 59 andabutment 56 tending to yieldingly 45 tilt the plate D as shown in Fig. 1. The spring assembly determines the oil pressure maintained by the pump as will be presently apparent. ' In operation of the pump in Figs. 1 to 3 as thus far described, the bodies 2|, 22 are rotated as a unit by drive gear 24, pistons 34 -being reciprocated by swash plate D and springs 36. As the pistons pass passage 50 they are moving downwardly and thereby drawing oil from the reservoir to bore 46 for delivery through pas sage 50 and passages 45 then in communication therewith; the remaining pistons moving up-v wardly and delivering oil under pressure from their cylinders 33 through the associated passages - 5| and thence to the passage 53 and conduit 52. 60 The intake and delivery through conduits 46 and 52 is thus continuous and the pressure rapidly builds up to the desired value determined by the strength of spring assembly 51, 58 and theratio of the leverage of ‘arms 44 and 40 about, 65 pivot 4|. When the delivery pressure tends to exceed. the 'desired value, which may run in the neighbor hood of 500 pounds per square inch for trans mission control systems, the delivery pressure act ing through the upwardly reciprocating pistons 34 causes plate D to level off about pivot 4| fur ther compressing springs 51, 58 and thereby re ducing or eliminating reciprocating movements ' of the pistons depending on the rate of use of 75 the oil‘ pressure or rate of .fall in such pressure. inders 33. ' ' As a further feature of my invention, I have provided means for balancing the __side thrust 20 between stator C and body 22 occasioned by the radial high pressure passage 53. Thus, above passage 53 and extending 180° therefrom is a further similar passage 6'0 ‘between conduit 52 and the inner walls of body 22, it being apparent 25 that in this manner the side thrusts are balanced out. In the absence of my pressure balancing port“, the stator C and body 22 are relatively displaced by the ?uid pressure giving rise to leakage between these parts. This relative dis 30 placement exposes more area of these parts to the high pressure fluid which in turn produces more separation and more leakage. 4 Above the pressure thrust balancing passage 60, the stator is formed with a series of axially 35 spaced narrow circular grooves 6| forming a labyrinth seal against the escape of oil outwardly between body 22 and the stator. If desired, a cylindrical shield 39| may be sup ported between casing parts 20 and 25 to sur 40 round bodies 2| and 22 to prevent undue foam ing and splashing of any. oil thrown from the pump bodies. ' 1 By reason of the arrangement of ?uid circula tion through stator 0 whereby the oil enters at 45 the lower end and is delivered at the upper end, I have provided, a “uni?ow” action of the oil, preventing air hammer, air trapping, and air pounding. It is, of course, highly desirable to provide noiseless pump operation and my pump has improved characteristics, of quietness of 50 operation. Furthermore, since the pistons are not reciprocating the majority of the time, the life of‘ the pump is materially increased over prior known types of pumps adaptable to the 55 uses suggested hereinabove. ' In order to limit upward movement of pistons 34 under the action of springs 51, 53 and plate _D and to also adjustably vary themaximum stroke of the pistons with accompanying varia- , tion in the pump discharge, I have provided the element 39 with a second lever arm 392 which extends oppositely from arm 44 ‘but integral ' therewith. Arm 392 carries an adjustable set screw 393 which strikes a bracket stop 394 de pending from support A. The set screw pro vides the means for adjusting the stroke of the pump as aforesaid. - < , With the rotation of- body members 2|, 22 as indicated by the arrow in Fig. 3 the pistons 34 70 progressively move upward, pumping oil, for those cylinders which have their discharge slots 5| communicating with the stator pressure cham ber 53. When each of the slots 5| reaches the enduof chamber 53, the pressure discharge‘ 75 3 2,129,828 spring 3|;b surrounding the body 2|h for urging through such slot ceases at a point in the rota tion of body 2| where the piston is approxi mately at its uppermost limit of movement. The piston associated'with such slot is then momen tarily sealed from communication with stator chambers 53 and 55 by the stator walls between all of the pistons against the swash plate Db.’ To this end the pistons 3'4b are joined, for rela tive movement nevertheless, by a ring 63 passing holes in through the lower ends of the pistons. Seating on this ring and loosely receiving the pistons therethrough is a plate 64 on which spring these chambers. Continued rotation progres sively brings passages 45 into communication 3Gb acts. with stator intake passage 5|], the pistons mov ing inwardly. Slots 5| are closed ‘on from com munication with chamber 53 during the time slots 45, which are associated with such closed off slots 5|, are open to the intake chamber 5|]. Approxi mately half of the cylinders are continuously op erating for intake while approximately half are ends of cylinders 33*‘. The cylinders may thus be formed completely through body 33b which The upper end of the spring abuts the outer portion of a frusto conical ring 65 which seats on a similar face of body 33”, through 10 an intermediate gasket 56, for closing the upper is a unitary structure driven as before by a gear 24*’. . continuously operating for pressure discharge of the ?uid, assuming of course that the plate D is not levelled off. ?tted to the cylindrical part of body 2|b above I have further provided means for preventing what is known as a “wire drawing” e?ect in ?uid pumps. This effect is in the nature of a knock or hydraulic hammer resulting from too abrupt ly cutting off the pump ?uid pressure delivery. To a lesser extent these objectionable noises often occur at other points in the cycle of pump opera passages 53“ and 53'’, a threaded nut 61 holding the ring 65 in position. I The stator Cb has its lower end'formed with 20 a plate 53 formed with a supporting shaft 4|b on one side of the stator and a boss 69 on the. other side. Plate Db pivots on shaft 4|b and has a lever extension 44b provided with forked ends tion such as at intake cut-off for each cylinder. 10 receiving therebetween a cup 1| having a 25 lever flange 12 against which the lever ends 10 act. The boss threadedly receives the upstand To overcome these objectionable noises, I have provided a porting structure having a very grad ual actioh and a typical arrangement will be described in reference to the pressure delivery v cut-off. It will be noted'from Figs. 1 and 3 that the generally vertically extending walls of chambers 50 and 53 are curved. 15 . The ring 65 has an upper cylindrical portion ing pin 13 which passes through the upper end closure 14 of cup 1| and threadedly receives stop washer 15 and nut 16 adapted to adjustably limit 30 upper movement of cup 1|. This cup is urged upwardly by a spring 51b centered by boss 69 and surrounding pin 13. By adjusting the'nut 16 it will be apparent that the maximum. upward movement of pistons 34b is adjustably controlled 35 This produces a desired curved edge at the ends of these chambers where the stator controls porting events with passages 45 and 5|. For convenience the said curving is as well as the pump stroke in a manner similar carried across the chambers 50 and 53 although ‘The operation of the Fig. 5 embodiment is sub stantially similar to the Fig. 1 arrangement. 40 When the plate Db levels off under the pressure developed by pistons 34”, the lever ends 10 de press cup 1| against spring 51“, it being noted that in this instance the fulcrum 4|b of the plate Db is on the opposite side of stator Cb from the 45 spring 51b. The oil is suppliedv to conduit 46*’ through inlet passage 48*’ as before. Referring now to the‘Fig. 6 embodiment of my invention, the stator Cc surrounds the rotat disposed body 2|° driven by gear 50 _ able centrally 24°. ‘This body is formed with downwardly open the controlling edges alone provide the desired functions being now considered. Furthermore other edges than curved may be employed within keeping of the broader teachings of this phase of _ my invention just so action is obtained. long as a gradual porting - In Fig. 3A I have illustrated a passage 5| ap proaching cut-off from pressure chamber 53, the piston associated with such passage 5| nearing the top of its stroke. In Fig. 3B, the same pas~ sage has rotated or moved from the Fig. 3A po sition and is just completing the pressure cut-o?. 55 to the adjustment of the set screw 393 in the Fig. 1 embodiment. , This cut-off action is very gradual as the trail ing cylinders 33° receiving portions 34° urged ing edge of passage 5| progressively eclipses the curved edge of chamber 5|. A similar condition is preferably provided at the other porting events of the pumping cycle as will be readily under by springs 36° against the plate D° > pivotally supported at 4|° between the vertical axis 11 of the plate lever portion 44°. The 55 stood. ' In the Fig. 4 embodiment of my invention, most of the parts are identical to those in Fig. 1 as indicated by the same reference'numerals. However, in Fig. 4 the pistons 34“ are solid and 60 springs 36° associated therewith are located above the pistons, the body 22a being enlarged to pro vide the spring receiving pockets 62. Referring to the embodiment of my invention illustrated in Fig. 5, the stator Cb‘has its intake 65 bore 46” offset from the stator axis containing delivery bore 52*’. the inner ends of these bores overlapping axially and respectively communicat ing with radial outwardly ?aring intake and de livery passages 50b and 53b respectively. The 70 latter passages respectively communicate through a series of circumferentially spaced conduits 45b and 5|b with the similarly arranged cylinders 33“ having pistons 34b associated therewith. .In Fig. 5 I have provided a single common plate in this instance has a hardened wear re sisting insert 18 slidably engaging the pistons 34°. The stator is formed with the diametrically op posite fluid inlet and dischargev passages 50° and 53° respectively, these passages being alternately 60 open to cylinders 33°, as body 2 |0 rotates, through the radial passages 45°. The ?uid intake to pas sage 5|)c from the fluid reservoir is provided by a vertical conduit 46° provided in the stator while the pressure discharge in this instance .is di 65 rected downwardly through conduit 52°. The discharge passage 53° has an extension 19 ' at which the stator has upper and lower .bores 83, 8 |' communicating therewith. Bore 80 accom modates a pressure relief valve 82 seated by 70 spring 83, a relief discharge port 84 being pro vided for bore 80 above valve 82. Bore 8| slidably receives a control plunger 85 having its upper end exposed to the ?uid pressure _of passage 53° and having its lower end engaging 4 2,129,828 lever 44°. By reason of the offset between axis for operation on a- vertical axis of rotation instead 11 and pivot shaft HQ it will be apparent that » of horizontal. a majority ‘of the pistons 34° will act to urge plate " Referring to Figs. 10 to 12, I have illustrated D‘2 to its inclined position as illustrated in Fig. 6.‘ a further embodiment of my invention closely The pressure 'rise, above a predetermined amount similar to the Fig. 1 embodiment (as indicated depending on the diameter of plunger 85, strength by the use 'ofumany similar reference characters) of springs 36°, length of lever 440 and other fac but differing therefrom primarily in the manner tors, will act through the plunger to level off of balancing the stator and pump body against 10 the swash plate as before described. In this embodiment of my invention, the swash plate is arranged so that in leveling off toward its horizontal position the pistons 340 move up wardly (rather than downwardly as in Figs. 1, 4 and 5). This has the advantage of positioning 15 the pistons, when levelled off, at or very close to the cylinder closing walls 86 where the pistons normally lie at the tops of their working strokes. _. Thus the volume of oil trapped‘ above the pistons is a minimum resulting in reduced air trapping 20 and noise. Any leakage including ?uid pressure loss due to porting as the pump body rotates at the level off condition, results in the plate Dc adjusting itself for a small movement of pistons 34c and this sometimes produces objectionable 25 noises unless the clearance space above the pis tons is maintained relatively small. - The circular form of passages 450 provides gradual eclipsing with the edges of passages 50° and 53c to obtain the advantages set forth in connection with 30 Figs. 3A and 3B. Referring to the embodiment illustrated in Figs. 8 and 9 I have illustrated my pump rotat relative displacements resulting from the pres sure of the ?uid. - The oil is drawn into the stator Ce through inlets 486 to bore 468, thence to the inlet cham ber 50‘? for admission to cylinders 33 through pas sage slots 45. The cylinders deliver the oil under pressure to the chamber 538 whence the oil passes through delivery bore 528 to its points of use. One feature of‘ my present arrangement re sides in the provision of a compact structure occupying less space than usual together with less pump Weight and cost by overlapping the chambers 50° and 53e in the direction of the axis of stator C9 as is clearly shown in Figs. 10 and 11. - As another feature of this embodiment of my invention, the pressure balance for the stator and rotating bodies 2| and 22 is divided attwo points so that the opposing or counteracting pressure acts below the chamber 538 as well as thereabove as in Fig. 1 at chamber 60. Thus, pressure balancing stator chambers 66° and 601 respectively communicate by stator passages 90, 9| with bore 529 and chamber 53*’. In this man ably about a horizontal axis instead of a vertical ner the stator is relieved of any tilting‘ tendency axis. The transmission drive shaft 81 passes ' since the balancing forces do not produce a 35 freely through the rotatable body 2N driven as couple as in Fig. 1. At the same time separat before through coupling 251, this body having horizontally disposed cylinders 33d accommodat ing pistons 34d, the intake and delivery passages ll5d communicating alternately with the intake and delivery passages 5i!‘1 and 53d of stator C“. The body ‘Md may be driven with shaft 81 but is preferably driven separately at a higher speed from shaft 81 or other power source so that when ing tendency between the stator and rotating pump bodies with resulting leakage and binding is prevented. From Fig. 12 it will be noted that the pistons reach top dead center just prior to cut-off of , ?uid pressure delivery from»successive passages 5|. This condition is illustrated for the upper most cylinder in Fig. 12. In this manner I pre the motor vehicle idles or drives slowly, the pump 45 will be rotated su?iciently fast to build up and vent carrying over a pressure in the passages maintain the desired oil‘pressure. Oneof the complete evacuation without producing hydraulic ends of the pistons are loosely tied by a ring 63d (as in Fig. 5), the pistons acting against ring 33‘1 of plate D4. The latter plate comprises bear ing 390‘! and lower ring 38‘1 having a lever ex tension 44“. The plate ass'emblypd is pivotally supported by ears 394 projecting from plate 39d, these ears being pivotally supported at 4|d from the casing structure. 55 “ 1 Only every third piston 34d has a spring 364 urging the piston outwardly. However, the pis tons are tied together by ringj3dras aforesaid 5| to the intake passage 50e and allowing for hammer noises and shocks. A slight amount of vacumn is created in each passage 5| and associated cylinder between pressure cut-01f and intake thereby producing a rapid in?ow of ?uid at the start ofthe intake cycle for each passage 5|. n In the same manner the arrangement is such that for intake cut¢o? each piston reaches bottom dead center just before cut-o?' takes place, providing for more efficient intake an general pumping e?iciency. ‘ Referring to' Fig. 13, I have illustrated only so that movement of all pisto/n’s in following the - a portion of the pump structure intended to be inclination of the swash plate is assured. Plate identical to that of Fig. 1 excepting that the D‘ is pivoted at the horizontal axis of the pump pistons 341 have an individual spring 361 sur and the normal tendency for the plate to tilt as rounding each piston instead of being located in Fig. 8 is produced by a spring 5‘!‘1 opposed by within each piston as in Fig. 1. Each spring a plate controlling plunger 85[1 exposed at its in acts between an abutment 92 carried by a piston ner end to the discharge passage 53d.‘ The plung and a relatively ?xed abutment provided by cy 65 er functions similarly to plunger 85 of Fig. 6 lindrical recess 93 in the rotatable body 2|‘. in leveling oif plate Dd in response to abnormal Obviously any of my other embodiments may ‘rise in the ?uid delivery pressure. In Fig. 8 I have the pistons thereof provided with exterior it will be noted that the ?uid enters chamber individual springs if desired. 504 through intake 88 and leaves chamber 53d In Figs. 14 to 17 I have illustrated a. pump 70 through outlet 89, the ?uid travelling transversely structure embodying many of the novel features to the horizontal pump axis along a substantially particularly of the Fig. 6 embodiment, asiwell as 74 vertical plane, the delivery of the cylinders prer ' other embodiments. erably being at the highest points inwardly of the The stator Ct draws oil through bore 461 which cylinders, as before, to prevent airtrapping. ‘Ob opens to intake chamber 53'f passes oil under 75 viously, if desired, the pump may be positioned pressure through bore 52' and thence through 2,129,828 of the ?xed casing 211. The pistons site ends thereof, said stator inlet end project- » ing into a reservoir containing ?uid to be 34’, swash plate D1 pivotally mounted at M! with lever M’ "i=1 oil pressure operated leveling pumped, a rotor surrounding said stator coax off plunger 851 s.» -'--r.-~: as described in connection with parts corresponding thereto in Fig. 6. How ever, in Fig. 14 the plunger bore 8|! communi bore 54‘, a pressure relief valve ~ cates with the 821 being provided thereabove. In order to pre vent too sudden movements of control plunger 85‘ and plate D‘, the bore 8|‘ contains a ?xed 10 ba?le 94 having a restricting ori?ce 95. The baffle acts as a dash pot to check undesirable ?uctuations and sudden movements of the swash plate. 15 ially therewith, said rotor having a plurality of cylinders spaced around said axis, pistons in said cylinders respectively, a pivotally supported wabble plate surrounding ,sa'd stator in engage ment with one end of said pistons, said rotor having a plurality of ?uid conducting passages respectively opening to said cylinders, said stator 10 having inlet and delivery ports respectively come municating with said stator inlet and delivery conduits, said stator inlet and delivery ports be ing respectively positioned to successively regis , I have also provided a further improved port ing arrangement and construction for obtaining improved pumping efficiency and quietness of operation. . ter with a plurality of said rotor passages during 15 rotation of said rotor, said statorhavingaa?uid conducting passage communicating at oneend thereof with said ?uid, delivery conduit and hav ing its other end‘ disposed to subject said rotor Each of the chambers ill)t and 53I has at least one controlling edge thereof, such as the intake 20 cut-off and the pressure cut-off edges respec to the pressure of ?uid in said passage, means yieldably urging swinging movement of said wabble plate about its pivotal support toward a tively, constructed for improved operation with ‘ position inclined with respect to a plane perpen the cylinder passages 45‘. In Figs. 16 and 17 I have illustrated this arrangement in connection with the typical passage 53!. This passage is 25 generally rectangular in section except in the region adjacent the discharge controlling edge where'the'inner wall of the passage has a curved groove 96 which terminates outwardly in a rather sharp pointed generally elliptical edge as 30 shown in Fig. 1'7. As the circular port of pas sage 451 sweeps‘ across the edge 96 as the body 35 dicular to said axis, and means responsive to the pressure of the ?uid delivered by said pistons 25 for moving said wabble plate in opposition to said yielding means. 2. In a ?uid pump, a stationary structure hav ing ?uid inlet and delivery passages, a rotary structure formed with a plurality of cylinders extending in the direction of the axis of rota 2|t rotates, as indicated by the dotted line in Fig. 17, the discharge of ?uid from passage 451 to chamber 53‘ is very gradually cut off. ‘ . ' noted that when my piston is at its highest point, the rotor port Mit has just passed the stator port edge 96', the dis tion and spaced circumferentially thereof, a pis ton reciprocating in each of said cylinders, means for conducting ?uid from said inlet passage to said cylinders in response to movement of said pistons in one direction of reciprocatory move ment thereof and for delivering ?uid under pressure from said cylinders to said delivery pas sage in response to movement of said pistons in sible while pressure is being built up by the pis ton and while passage 45f is open to chamber their other direction of reciprocatory movement, 40 a wabble plate structure controlling movement of said pistons, wabble plate adjusting means 531. This provides relatively great pump e?i comprising a lever arm, common means for piv ciency and prevents carrying over a pressure of an increasing character, in any cylinder, to the otally mounting said wabble plate structure and charge passage 45‘ being carried as far as pos said lever, yielding means acting on said lever 45 intake chamber 50‘. 45 '. The inner ends of passages 45t which form‘ arm for imparting swinging movement to said 50' ports 451 at the region of ?nal ?uid discharge erably associated with said ?rst mentioned lever arm for limiting upward movement of said pis wabble platestructure, means carried by said circular ports preferably have a diameter smaller , lever arm and acting on said yielding means for 96 at the port ' adjustably conditioning the latter for predeter- ' than the height of the groove controlling outer edge so that leakage will- not mining the ?uid pressure maintained by said occur to any undesirable extent between adjacent pump, means including a second lever arm op to chamber 5i!t and at the same time to obtain as large a number of ports and cylinders as pos sible in the rotor. What I claim is: I . 1 1. In a ?uid pump, a substantially vertically disposed stator having axial ?uid inlet and de livery conduits respectively formed in the oppo tons under ‘the action of said yielding means, and adjustable means acting on said second lever arm for varying the upward movement of said pistons. ' WILLIAM T. DUNN.