US2289865A - Radial pump or motor - Google Patents

Description

July 14, 1942- E. K. BENEDEK RADIAL PUMP 0R MOTOR Filed Sept. 28, 1940 5 Sheets-Sheet l l m@ .QQ 1 i NNW 7A@ (www QN V NN mw n mm. mm w n@ w ww Nm, .wm ,1 QN n Q NNWN l -l Wmv* .QH Q v Q@ E. vw u Q mm. .w p1, .mwwmv w n www@ wm @n NW SQ if- Qn N n www n m W www@ www e. /M "Nm n W hw e u, mw H l e m RADIAL UMP 0R MOTOR v EVek llBenecZQ/f July 14, 1942. E. K. BENEDEK RADIAL PUMP OR MOTOR Filed Sept. 278, 1940 3 Sheets-Sheet 3 www Nh. mw mm kn "WKN,

' l Sylva/who@ Ele/f fnenedfeff @M @www v O l GMM/migo Patented July 1,4, 1,942

UNITED STATES PATENT OFFICE RADIAL PUMPOR MOTOR Elek K. Benedek, Cleveland, Ohio, assigner, by mesne assignments, to Midland Machine Corporation, a corporation of Illinois Application September 28, 1940, Serial No. 358,911 14 claims. (ci. ics- 161) This invention relates to hydraulic pumps or motors, and more particularly to hydraulic pumps or motors of the type including a plurality of radially disposed piston and cylinder assemblies.

Machines of the kind referred to, in general, comprise a stationary pintle provided with fluid transfer passages or con-duits, a cylinder barrel rotatable about the pintle and being formed with a plurality of radially disposed, circumferentially spaced cylinders adapted to have valved communication with the pintle conduits, pistons in the cylinders, and vmeans for effecting reciprocation of the pistons relatively to the respective cylinders when the cylinder barrel is rotated. Because f their substantially continuous, positive pressure discharge characteristics, such pumps latelyhave found wide application in various fields, use for driving machine tools and hydraulic presses being representative examples of useful applications. Pumps of the general char- -acter'refe'rred to are well known, and most of those heretofore availablehave been found satisfactory for many uses. They have, however, left something to be desired where required to operateat high rotative speed to discharge fluid under high pressure and at high volumetric rate.

Pumps of this general class heretofore proposed most commonly have included a single set of circumferentially deployed radial piston and cylinder assemblies. For such machines to deliver fluid at high volumetric rates without operating at prohibitive speeds, it has been necessary to use large pistons and cylinders, increasing the diameter of the rotating assemblies and surrounding parts so that inordinate centrifugal forces have beenl produced, resulting in high thrust bearing pressures and rapid wear, .and necessitating ineonvenientlylarge overall radial dimensions.

To overcome these diiliculties it heretofore has been proposed to provide a plurality, e. g. two, sets of piston and cylinder assemblies spaced from each other longitudinally of the pump pintle and to operate the pistons in pairs, each pair including a piston of each of the two sets of assemblies. In this way provision may be made for discharge of fluid at high volumetric rates without the use of very large pistons and cylinders, and consequently without unduly large diameter of rotative assemblies. However, the piston thrust transmitting means or mechanism of such known pumps has been subject to high friction losses, and in some cases has been susceptible to misalignment or skewing of certain parts in operation.

An object .of the present invention is to provide a pump vor motor of the general class referred to above including improved thrust-transmitting means for operating in pairs the pistons of two adjacent sets of piston and cylinder assemblies.

Another object is to provide a pump or motor of the kindreferred to in which the thrust-trans mitting means for each pair of pistons has threepoint support on a cooperating reactance member;

Another object is to provide the pairedpistons with thrustetransmitting pins having rolling contact simultaneously with three annular reactance tracks in three radial planes or zones spaced longitudinally of the pump pintle. A correlative object is so to form and mount the rolling pins as to assure constant rolling of the pins on the tracks without;y slipping or sliding and without skewing.

A further object is so to form and arrange the pins with respect to the pistons' and the reactance member as to give the pins the greatest resistance to deflection in the zone of greatest bending stress.

Other objects will become apparent from a reading of the following description, the appended claims, and the accompanying drawings, which:

Figure 1 is a longitudinal, horizontal, sectional view of a pump or motor embodying the invention, the section being taken on the line i-l of Figure 2';

Figure 2 is a transverse, vertical, sectional View taken on the line 2 2 of Figure 1;

Figure 3 is a detailed sectional view taken on the line 3-3 of Figure l;

Figure 4 is another detailed sectional view taken on the line 6-4 of Figure 1;

Figure 5 is a fragmentary vertical sectional view taken on the line 5-5 of Figure 1; and

Figure 6 is a fragmentary sectional view of a piston crosshead and thrust-transmitting pin, drawn onan enlarged scale.

For the purposes of illustration l'. have shown a pump capable of delivering one hundred gallo-ns per minute at twelve hundred revolutions per minute. It comprises two end plate sections `7 and 3 and an intervening ring section 4 secured between the end plate sections by means of screws 5. The opposed inner faces of the peripheral portions of the end 4plates 2 and 3 are recessedy to provide shoulders 6 and 'l which serve accurately to locate the end plates 2 and 3 and the ring member 4 in assembled relation.

I6 of which is held in place by an end cap I1 secured to the hub portion I4 by screws I8. The inner race I9 of the bearing assembly I5 is mounted on an inner end portion 2liv of a drive shaft generally designated 2|. At the extreme inner end of the shaft 20 is an enlarged flange 22 providing a shoulder 23 against which the inner ball race I9 is clamped by a nut 24 engaging a threaded portion 25 of the shaft 2|.

- The shaft ilange 22 is secured to the cylinder barrel by means ofl screws 26. The shaft 2| may be used to impart positive driving effort to the cylinder barrel I3 ifthe machine is to be used` n as a pump, and may be used to transmit power Irom the rotating cylinder barrel I3 to external apparatus to be driven when the machine is to be used as a hydraulic motor.

The cylinder barrel is formed with two sets, generally designated A and B, of radially disposed circumferentially deployed, piston and cylinder assemblies, the sets being spaced longitudinally of the pintle axis. The set A of piston and cylinder assemblies, shown at the right in Figure 1 and also shown in Figure 2, includes a plurality of circumferentially spaced cylinders 21 respectively communicating with ports 28 in turn adapted to have valved communication with cutouts or ports 29 in the pintle, the ports 29 having constant communication with bored pintle passages 30. The passages 30 communicate with combined inlet and outlet openings on opposite sides of the pintle and one, 3|, of which is shown at the left in Figure l. Pistons 32 are mounted respectively for reciprocation in the cylinders 21. When the cylinder barrel and pistons are rotated, the pistons will be reciprocated relatively to the associated cylinders in a manner to be described latter, and the valved intake and discharge of fluid through the opening 3|, the passages 39, the cut-out ports 29, and the cylinder end ports 28 will take place in a manner well understood in the art. The other set B of piston and cylinder assemblies is spaced axially to the left (as viewed in Figure 1) of the set A and includes a plurality of cylinders 21 in which pistons 32' are mounted for reciprocation to take in and discharge uid through end ports 28', pintle cut-out passages 29', the bored pintle passages 30, and the pintle intake and outlet openings 3|.

In accordance with the invention, individual piston and cylinder assemblies of the set A are paired, respectively, in parallelism with individual piston and cylinder assemblies of the set B, and means are provided for reciprocating the paired pistons of the two sets in unison. The pistons 32 of the set A are formed with crossheads 33 mounted to@ slide in guides formed in a flange 34 integral with xlthe cylinder barrel. Similarly. the pistons 32' of the set B are formed with crossheads 33' slidable in guides formed in a flange 34 integral with the cylinder barrel. The crossheads 33 and 33' of the sets A and B are paired, and are formed respectively with bores equipped with elongated roller bearings 35-35' which anti-frictionally mount hardened thrust-transmitting pins 36 each having an enlarged diameter central portion 31 and smaller diameter end portions 38 and 38'.

For transmitting thrustto and reciprocating the pins 36 and the pistons of both sets A and B. reactance means surrounding the piston and cylinder assemblies of both sets A and B is provided with annular tracks engaged by the pins 36 in three zones spaced from each other longitudinall'y of the pintle axis; and means are provided for mounting the three tracks of the reactance means eccentrically with respect to the pintle axis, so that, as the cylinder barrel, the pistons, and the pins 36 rotate about the pintle axis, the engagement of the pins simultaneously with the three eccentrically disposed tracks will move the pistons in to their respectively associated cylinders. In the form shown, the reactance means includes a shiftable, non-rotating reactance stator 39 comprising end sections 40 and 40' secured to a central ring section 4| by means of-screws 42-42'. The ring section 4| is formed with flat pads 43 mounted to slide on pads 44 formed on the inner surface of the casing ring 4 so as to mount the stator 39 for shifting movement to vary its eccentricity with respect to the pintle axis. Rodsn45 secured to the central ring section 4| of the'stator 39 extend through the casing and are adapted to be connected to suitable handles or mechanism for shifting the stator. It is usual to mount the reactance stator in pumps of this class so that it may shift to vary its eccentrlcity, and,` hence, the rate of discharge of the pump, but it will be understood that the invention may be embodied in rotary `radial pumps wherein the reactance stator is mounted in a iixed eccentric position.

The stator end sections 40 and 40 are formed, respectively, with bearing race seats 46 and 46' which respectively receive outer races 41 and 41' of bearing assemblies generally designated 48 and 48', and which assemblies also include inner races 49 and 49 respectively. The bearing assemblies 48 and 48 serve antifrictionally to mount a rotary reactance member 50 comprising end plate sections 5| and 5|' secured by screws 52 and 52', respectively, to a hardened central ring section 53. The end sections 5I and 5| are formed with bearing race seats 54-54' in which are received the inner races 49 and 49' of the bearing assemblies 48 and 48'.

The end plate sections 5| and 5|' are formed respectively with annular tracks 55 and 55' disposed in the radial planes or zones of the pin ends 38 and 38. Outwardly'beyond the tracks 55 and 55' the end plate sections 5I and 5|' lare formed, respectively, with outer radial surfaces 56 and 56' which lie alongside and serve to guide the outer portions of the crossheads 33 and 33'. Inwardly of the annular tracks 55 and 55' the end plate sections 5I and 5I' are formed, respectively, with inner radial surfaces 51 and 51' which lie alongside the extreme end portions of the pins 36 with working clearance between the radial surfaces and the at pin ends. 'I'he central section 53 of the rotary reactance 56 is formed with an inwardly extending, centrally disposed ange 58 located between the radial planes of the sets A and B. 'I'he inner face ofl the ange 58 constitutes a track 59 upon which the enlarged central portions 31 of the pins 36 are adapted to roll. Opposed, outwardly directed,

radial faces 60 and 60' of the track flange 58 11e alongside andrespectively guide the outer portions of the piston crossheads 32 and 32'.

When the machine is operated as a pump, the centrifugal force acting on the pins 36, pistons 32 and 32', and associated crossheads tends to move them outwardly with respect to their cylinders so as to perform suction strokes. To assist in this outward movement,` and, more particularly, to maintain the pins in engagement with the reactance tracks 59, 55, and 55 when the pump is at rest and while it is being brought up to operating speed, floating return-thrust-transmitting rings 6I yand 6| are disposed respectively within the circle defined generally by the outer end portions of the pins 36. The rings 6I and `6| are supported radially solely by their engagement with the pins 36, and are confined against movement longitudinally of the piston by the piston crossheads and the adjacent inner radial surfaces 51 and 51' of the reactance rotor end plate sections I and 5I'.

In operation, when the reactance stator 39 and the rotary reactance member 50 carried thereby are ,shifted to be eccentric to the pintle axis, rotation of the cylinder barrel, the pistons of both sets A and B, and the pins will cause the pins to roll in three zones on the tracks 55, 55', and 59; and the pins 36 and the Vpistons of both sets A and B will be reciprocated radially to effect valved intake and discharge of fluid through the ports and passages previously described- The relative arrangement of the piston crossheads 33 and 33', the thrust-transmitting pins `36, and the three reactance tracks is such that thethrust load transmitted from each of the end tracks55 and 55 to the pin ends 38 and 38', respectively, is considerably less than the thrust transmitted from the middle track 59 to each enlarged diameter central pin portion 31. Thus, the pins and tracks will be subjected to substantially equal wearing influences in all three thrust zones. An unequal Wearing of the pins with resultant disturbance of the proportioning 0f the parts and misalignment or skewing is prevented.

at the ends of the'pins 36 is commensurate with i the smaller load on the pin ends, so that subslipping or sliding cfa pin on its associated track, even if only momentary, would produce a fiat spot of microscopic dimensions on the pin large enough, however, to encourage the pin to stop rotating again at the same point, so as again to slide on the at spot, which then would become larger. Very soon, the flat spot would absolutely prevent any rotation of the pin, and the heat generated by the sliding friction would cause rapidI and fatal destruction of the parts. It is for this reason that the absolute assuring of constant rolling 4of the pins resulting Vfrom the construction disclosed is of such importance.

Supporting of the pins 36 throughout their entire length by engagement with the piston crossheads and the tracks 55, and 59 tends to prevent pin deflection. However, but for the novel proportioning of the pins, some deflection could occur within the limits allowed by working clearances of the bearing parts. Even such slight deflection is substantially eliminated because of the enlarged diameter central portions 31 of the pins being located to provide the maximum resistance to deilection in the lzone of maxstantially equal unit stresses are borne at different sections along the pins.

The track flange 58 serves not only to provide the track 59 properly located to engage the enlarged diameter roller portions 31, but also to reenforce and stillen the rotary reactance assembly in the zone of greates load. Consequently, deflection of the rotary reactance member is minimized and, for all practical purposes, is eliminated.

The construction shown herein for the purposes of illustration embodies the invention in itsnow preferred form, but it will be apparent that changes in the construction and relative arrangement of the parts may be made without departing fromthe invention as delined in the claims.

I claim:

1. In a rotary hydraulic pump or motor, two sets of rotatable radial piston and cylinder assemblies, each set including a plurality of circumferentially deployed piston and cylinder assemblies, said assemblies each comprising a p iston element and a cooperating cylinder element, one element of each assembly being reciprocable radially relative to the axis of rotation of said assemblies and said sets of assemblies being spaced from each other longitudinally of the axis of rotation, individual assemblies of one set being paired respectively in parallelism with individual assemblies of the other set; reactance means surrounding the axis of rotation and comprising three axially spaced continuous annular working-thrust-transmitting tracks, the radial planes of the'reciprocable elements of the assemblies of said two sets respectively being disposed between the radial planes of the middle track and the end tracks, and'rolling-thrust-transmitting pins respectively journaled in and extending through pairs of said reciprocable elements and having simultaneous thrust-transmitting rolling engagement with all three tracks.

2. In a rotary hydraulic pump or motor, two sets of rotatableradial piston and cylinder assemblies, each set including a plurality of circumferentially deployed piston and cylinder assemblies, said assemblies each comprising a piston element and a cooperating cylinder element, one element of each assembly being reciprocable radially relative to the axis of rotation of said planes of the reciprocable elements of the assemblies of said two sets respectively being disposed between the radial planes of the middle track and the end tracks; and rolling-thrusttransmitting pins respectively journaled in and extending through pairs of said reciprocable elements and each having a central enlarged diameter portion in rolling engagement with said middle track, and end portions of equal relatively smaller diameter in rolling engagement `with said end tracks, said pins engaging all three tracks simultaneously for thrust transmission.

3. In a rotary hydraulic pump or motor, two sets of rotatable radial piston and cylinder assemblies,each set including a plurality of circumferentially deployed piston and cylinder assemblies, said assemblies each comprising a piston element and a cooperating cylinder element, one element of each assembly being reciprocable radially relative to the axis of rotation of said assemblies and said sets of assemblies bemg spaced from each other longitudinally of the axis of rotation, individual assemblies of one set being paired respectively in parallelism with individual assemblies of the other set; reactance means surrounding the axis of rotation and comprising three axially spaced annular workingthrust-transmitting-tracks all having surfaces facing in the same direction radially with respect to the axis of rotation, the radial planes of the reciprocable elements of the assemblies of said two sets respectively being disposed between the radial planes of the middle track and the end tracks; rolling-thrust-transmitting pins respectively journaled in and extending through pairs of said reciprocable elements and having simultaneous thrust-transmitting rolling engagement with all three tracks; and returnthrust-transmitting track means having an annular surface facing radially in the direction opposite said working-thrust-transmitting surfaces and being adapted to have rolling engagement with said pins.

4. In a rotary hydraulic pump or motor, two sets of rotatable radial piston and cylinder assemblies, each set including a plurality of circumferentially deployed piston and cylinder assemblies, said assemblies each comprising a piston element and a cooperating cylinder element, one element of each assembly being reciprocable radially relative to the axis of rotation of said assemblies and said sets of assemblies being spaced from each other longitudinally of the axis of rotation, individual assemblies of one set being paired respectively in parallelism with individual assemblies of the other set; reactance means surrounding the axis of rotation and comprising three axially spaced annular working-thrust-transmitting tracks all having surfaces facing in the same direction radially with respect to the axis of rotation, the radial planes of the reciprocable elements of the assemblies of said two sets respectively being disposed between the radial planes of the middle track and the end tracks; rolling-thrust-transmitting pins respectively journaled in and extending through pairs of said reciprocable elements and having simultaneous thrusttransmitting rolling engagement with all three tracks; and return-thrust-transmitting track means comprising two axially spaced annular surfaces facing radially in the direction opposite said working-thrust-transmitting surfaces and being adapted to have rolling engagement with said pins respectively at opposite ends of said pairs of reciprocable elements.

5. In a rotary hydraulic pump or motor, two sets of rotatable radial piston and cylinder assemblies, each set including a plurality of circumferentially deployed piston and cylinder assemblies, said assemblies each comprising a piston element and a cooperating cylinder element, one element of each assembly being reciprocable radially relative to the axis of rotation of said assemblies and said sets of assemblies being spaced from each other longitudinally of the axis' of rotation, individual assemblies of one set being paired respectively in parallelism with individual assemblies of the other set; reactance means surrounding the axis of rotation and comprising three axially spaced annular working-thrusttransmitting tracks, the radial planes of the reciprocable elements of the assemblies of said two sets respectively being disposed between the radial planes of the middle track and the end tracks; rolling-thrust-transmitting pins respectively journaled in and extending through pairs of said reciprocable elements and having simultaneous thrust-transmitting rolling engagement with all three tracks; means mounting said reactance means independentL of said assemblies for rotation about a predetermined axis eccentric to the axis of rotation of said assemblies; and a pair of floating return-thrust-transmitting rings having axially spaced annular surfaces facing radially in the direction opposite said working-thrust-transmitting surfaces and being adapted to have rolling engagement with said pins at opposite ends of said pairsv of reciprocable elements and being thereby radially supported by said pins.

6. In a rotary hydraulic pump or motor, two sets of rotatable radial piston and cylinder assemblies, each set including a plurality of circumferentially deployed piston and cylinder assemblies, said assemblies each comprising a pisa ton element and a cooperating cylinder element, one element of each assembly being reciprocable radially relative to the axis of rotation of said assemblies and said sets of assemblies being spaced from each other longitudinally of the axis of rotation, individual assemblies of one set being paired respectively in parallelism with individual assemblies of the other set; reactance means surrounding the axis of rotation and comprising three axially spaced annular working-thrusttransmitting tracks, the radial planes of the reciprocable elements of the assemblies of said two sets respectively being disposed between the radial planes of the middle track and the end tracks and the middle track being extended radially to intervene between and engage adjacent radial faces of paired reciprocable elements for guiding said elements radially; and rollingthrust-transmitting pins respectively journaled in and extending through pairs of said reciprocable elements and having simultaneous thrusttransmitting rolling engagement with all three tracks.

7. In a rotary hydraulic pump or motor, two sets of rotatable radial piston and cylinder assemblies, each set including a plurality of circumferentially deployed piston and cylinder assemblies, said assemblies each comprising a piston element and a cooperating cylinder element, one element of each assembly being reciprocable radially relative to the axis of rotation of said assemblies and said sets of assemblies being spaced from each other longitudinally of the axis of rotation, individual assemblies of one set being paired respectively in parallelism with individual assemblies of the other set; reactance means surrounding the axis of rotation and comprising three axially spaced annular workingthrust-transmitting tracks, the radial planes of the reciprocable elements of the assemblies of said two sets respectively being disposed between the radial planes of the middle track and the end tracks; radial surfaces on said reactance means engaging and guiding said reciprocable elements on two sides of each element facing in opposite directions parallel to the axis of rotaaasases spectively journaled in and extending through pairs of said reciprocable elements and having simultaneous thrust-transmitting rolling engagement with all three tracks.

v8. In a rotary hydraulic pump or motor, two sets of lrotatable radial piston and cylinder assemblies, each set'including a plurality' of circumferentially deployed piston and cylinder assemblies, said assemblies each comprising a pisthree annular tracks spaced from each other axially of the pintle, the middle track being disposed between said sets of piston and cylinder a longer radius than the end tracks, the radial y planes of the reciprocable elements of the assemblies of said two sets respectively being disposed between the radial planes of the middle track and the end tracks; and rolling-thrust-transmitting pins respectively journaled in and extending through pairs of said reciprocable elements and each having a central enlarged diameter portion in rolling engagement with said mlddle track, and end portions of equal relatively smaller diameter in rolling engagement with said end tracks, said pins engaging all three tracks simultaneously for thrust transmission, radial surfaces at opposite ends of said enlarged diameter central pin portion abutting respectively adjacent radial faces of paired reciprocable elements. l

9. In a rotary pump or motor, a pintle; a

' cylinder barrel rotatable about said pintle; two

sets of radially extending cylinders in said barrel spaced from each other Aaxially of the pintle, the cylinders of each set being deployed circumferentially about said pintle and individual cylinders of one set being paired respectively in parallelism with individual cylinders of the other set; similarly paired pistons reciprocable in the cylinders of both sets and projecting outwardly beyond said cylinders; a reactance member surrounding the pistons of both setsv and comprising three continuous annular tracks spaced from each other axially of the pintle, the middle track being disposed between said sets of piston and cylinder assemblies, and the two end tracks respeetively being disposed beyond said two sets of cylinders and pistons; and thrust-transmitting pins respectively extending through and journaled in the projecting portions of each Vtwo paired pistons to rotate about individual axes disposed radially inwardly of said tracks and having rolling engagement with all three of said tracks.

10. In a rotary pump or motor, a pintle; a cylinderbarrel rotatable about said pintle; two

Ysets of radially extending cylinders in said barrel spaced from each other axially of the pintle, the cylinders of each set being deployed circumferentially about said pintle andindividual cylindersv of one set being paired respectively in parallelism with individual cylinders of the other set; similarly pairedlpistons reciprocable in the cylinders of both sets and projecting outwardly beyond said cylinders; a reactance member surrounding the pistons of both sets and comprising assemblies, and the two end tracks respectively being disposed beyond said twosets of cylinders and pistons; ythrust-transmitting pins respectively extending through and journaled in the projecting portions of each two paired pistons to rotate about individual axesV disposed radially inwardly of said tracks and having rolling engagement with all three of said tracks; and an` nular return-thrust transmitting means comprising annular track means disposed radially inwardly with respect to said pins' and with which said pins are adapted to have rolling engagement. g

1l. In a rotary pump or motor, a pintle; a cylinder barrel rotatable about said pintle; two sets of radially extending cylinders in said barrel spaced from each other axially of the pintle, the cylinders of each set being deployed circumferentially about said pintle and individual cylinders of one set being paired respectively in parallelism with individual cylinders of the other set;

similarly paired pistons reciprocable in the cylinders of both sets and projecting outwardly beyond.

said cylinders; a reactance member surrounding the pistonsof both sets and comprising. three annular tracks spaced from each other axially of the pintle, the middle track being disposed between said sets of piston and cylinder assemblies, and the two end tracks respectively being disposed beyond said two sets of cylinders and pistons; thrust-transmitting pins respectively extending through and journaled in the projecting portions of each two paired pistons to rotate about individual axes disposed radially inwardlyv of said tracks and having rolling engagement with all' similarly paired pistons reeiprocable in the cylin-v ders of both sets and projecting outwardly beyond said cylinders; a reactance member surrounding the pistons or both sets and comprising three annular tracks spaced from each other axially of the pintle, the middle track being disposed between said sets of piston and cylinder assemblies, and the two end tracks respectively being disposed beyond said two sets of cylinders'and pistons, said end tracks-being of equal relatively small diameter and said middle track being of larger diameter; and thrust-transmitting pins respectively extending through and journaled in the projecting portions of each two paired pistons and having enlarged diameter central portions krollingly engaging said middle track and having smaller diameter end portions rolllngly engaging said end tracks.

13. Ina rotary pump or motor, a pintle; a cylinder barrel rotatablel about said pintle; two sets of radially extendingv cylinders in said barrel spaced from each other axially of the pintle, the cylinders of each set being deployed circumferentially about said pintle and indilvdual cylinders of one set being paired respectively in parallelism with individual cylinders of the other set; similarly paired pistons reciprocable in the cylinders of both sets and projecting outwardly beyond said cylinders; a reactance member surrounding the pistons of both sets and comprising a ring section surrounding the projecting portions of said pistons, two annular end plate sections secured to opposite ends of said ring sections and respectively extending inwardly alongside the projecting portions of said sets of pistons, said ring section being formed with an annular flange extending inwardly between the projecting portions of the pistons of said sets, radial faces of said flange respectively engaging said projecting piston portions and the inner face of said ange constituting an annular track, said end plates respectively having radial portions respectively engaging the projecting piston portions of said sets and said end plates also having annular tracks respectively beyond the piston projecting portions of said sets; and thrust-transmitting pins respectively extending through and being journaled in the projecting portions of each two paired pistons and each pin having rolling engagement with all three of said tracks.

14. In a rotary pump or motor, a pintle; a cylinder barrel rotatable about said pintle; two sets of radially extending cylinders in said barrel spaced from each other axially of the pintle, the cylinders of each set being deployed circumferentially about said pintle and individual cylinders of one set being paired respectively in parallelism with individual cylinders of the other set; similarly paired pistons reciprocable in the cylinders of both sets and projecting outwardly beyond said cylinders; a reactance member surrounding the pistons of both sets and comprising a ring section surrounding the projecting portions of said pistons, two annular end plate sections secured to opposite ends of said ring sections and respectively extending inwardly alongside the projecting portions of said sets of pistons, said ring section being formed with an annular flange extending inwardly between the projecting portions of the pistons of said sets, radial faces of said flange respectively'engaging said projecting piston portions and the inner face of said flange constituting an annular track, said end plates respectively having radial portions respectively engaging the projecting piston portions of said sets and said end plates also having annular tracks respectively beyond the piston projecting portions of said sets; and thrust-transmitting pins respectively extending through and being journaled in the projecting portions of each'two paired pistons and each pin having rolling engagement with all three of said tracks, said ange track being of larger diameter than said end plate tracks and said pins respectively having enlarged diameter central portions between the projecting piston portions of said sets to engage said iiange track. Y

ELEK K. BENEDEK.

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