US2233551A - Fluid pump - Google Patents

Description

March 4,1941. R. w. OTT 2,233,551

FLUID PUMP Filed 001:. 20, 1938 2 Sheets-Sheet 1 INVENTOR PoBL'Rr T/V/u/AM Orr BY 772M.

ATTORNEYS March 4, 1941. R O T 2,233,551

FLUID PUMP Filed Oct. 20, 1938 2 Sheets-Sheet 2 INVENTOR PQBERT ML/AM Orr Patented Mar. 4, 1941 UNITED STATES PATENT OFFICE Norman Machine Tool Company,

a corporation of Massachusetts Mass,

Springfield,

Application October 20, 1938, Serial No. 236,047

Claims.

This invention relates to a rotary, variable displacement, hydraulic pump.

One object of the invention is to provide a pump of this character which will be unusually compact in proportion to its performance. A further object is to provide such a pump which will practically eliminate what is known as slippage, or leakage of the liquid being pumped past the pumping elements. A further object is to provide such a pump which will be very quiet in operation. A further object is to provide a pump of this character which will improve its tightness by use. A further object is to provide a pump in which the valve mechanism will be balanced so that binding and wearing will be eliminated and a tight seal produced. A further object is to provide a mechanism by which the output pressure of the pump may be regulated, automatically if desired, throughout its complete range without stopping the power means; or by which the pump may be used at a constant but adjustable volume output. Additional advantages and objects will appear from the following description and claims.

Referring to the drawings:

Fig. 1 is a central longitudinal section through the pump, showing the parts positioned for producing maximum volume output;

Fig. 2 is a section on line 2-4 of Fig. 1;

Fig. 3 is a detail section on line 33 of Fig. 2;

Fig. 4 is a detail section on line 44 of Fig. 1;

Fig. 5 is a section on line 5-5 of Fig. 1;

Fig. 6 is a section on line 6--6 of Fig. 1;

Fig. '7 is a fragmentary section corresponding to a portion of Fig. 1 but with the parts in neutral position; and

Figs. 8 and 9 are perspective details of certain pump parts.

The pump mechanism is carried by a housing or frame constructed in two parts l0 and H see cured together as by screws [2 (Fig. 3). The frame part I0 is apertured at l3 to receive with a press fit the body l4 of a tapered valve member IS. A flange I6 on the valve member abuts the frame part ill to give a definite location to the valve member. The valve member is provided with a pair of parallel passages l1, l8 (Fig. 4), drilled in from the end of the member and closed by plugs l9. Passages 20, 2| (Fig. 6) extend laterally from the passages I1, I 8, and merge into similar passages 22, 23 in the frame member which may be connected to the hydraulic circuit in which the pump is to be located. At an intermediate point the opposite sides of the valve member are grooved as at 24, 25 deeply enough to enter the passages l1, l8 and thus form ports serving respectively as inlets or outletsdepending upon the setting of the pump.

A drive shaft 30, keyed at 3| to any source of power, is provided with a tapered socket 32 fitting snugly over the valve member l5 and provided with ports as will be described below so that it acts as a cooperating valve element. The drive shaft abuts a washer 33 which bears against the flange I6, so that by choosing a washer of correct thickness the tightness of fit of the drive shaft socket upon the member l5 can be regulated. A positioning flange 34 on the drive shaft bears against the end of the inner race of a ball bearing. 35, the outer race of which fits in a cylindrical bOre in the frame part II) so that it will not interfere with the positioning of the shaft by the washer 33. The opposite end of the shaft is shouldered to receive a flanged spacing collar 36 held in' place by a jam nut 31. A radial-thrust ball bearing .38 has its inner race carried by the spacing collar, and has its outer race forced axially by a jam nut 39 threaded into the end of the frame part II By tightening the latter jam nut the bearing 38 can be preloaded to hold the shaft firmly against the washer 33 and prevent any en'd play in the parts.

Keyed at 40 to the shaft 30 are a pair of end closure disks 4|, 42 and an intermediate ring 43, all of course rotating with the shaft. The ring 43 serves to keep the disks a definite distance apart, and forms the inner wall of the pump chamber, of which the disks form the end walls. The outer wall of the chamber is formed by a second ring 44, ground to a length that will just permit it to slide between the disks while-preserving fluid-tight contact with them. In the chamber thus formed are located a circumferential series of blocks arranged in two altemating and staggered series and 46. The'blocks of the former set are shaped generally like a ear tooth with sides in the form of circular arcs, while the blocks of the latter set have straight sides converging towards .each other and making contact with the curved sides of blocks 45. The ends of the blocks of both sets are ground so as to permit them to move snugly in contact with the closure disks 4|, 42 in the-same manner as the ring 44, and their peripheral surfaces are ground to make tight but sliding contact with rings 43 and 44, respectively.

The ring 44 can be shifted from a position concentric with the shaft as in Fig. 7 to'an eccentric position on either sidethereof, one of which is shown'in Figs. 1 and 2, by a shifting registration with one port to registration with member having a series of rollers 5| in contact with a channeled race in the ring. The

'shifting member has block-like extensions 52 or lowered, carrying the outer ring 44 to a moreor less eccentric position on either side of the axis. Before considering the details of the automatic control, however, the operation of the pumping mechanism itself will be described.

The alternating blocks form pumping chambers externally of the blocks 45 and chambers lil internally of the blocks 46, as is best shown in Fig.

'7. If the ring 44 is shiftedto an eccentric position, as in Fig. 2, the block or blocks 45 on the side from which the ring is moved are forced between the wedge blocks 46, causing the latter to slide slightly on the outer ring. A complete readjustmentof the blocks throughout the chamber follows, as is clearly indicated by a'compari son between Figs. '7 and 2. The pumping chambers 60 and'6l adjacent the point where the rings approach each other most closely become smaller, and those on the opposite side larger. As the chambers enlarge they draw in a supply of fluid, and as they contract they force it out. This action is permitted by the coaction of certain valve ports with the ports 24 and 25.

As is best shown inFig. 5, the tubular portion of the drive shaft is provided with a series of 'portS 62 passing through it and coming into registry alternately with the ports 24-and 25 as the shaft rotates. Intermediate its passage from the other of the pair 24, 25, each port 62 passes across a portion 63 of the drive shaft which seals it off. With the number of blocks shown there are always two ports .62 incontact with each of the ports '24, 25. The ports 62 connect with passages 64 formed in the closure plate 42'. Since this plate is keyed to the shaft, the passages always remain in registration with" the ports. Each passage 64 communicates with the chamber 6| between one of the wedge blocks 46 and the ring 43. While the wedge blocks move circumferentially with-respect to the ring during the pumping action, they are restricted in this motion so that the pumping chambers 6| never depart from communication with the passages 64 (see Fig. 2)

The chambers 60 are each in communication with one adjacent chamber 61 For this purpose each block 46 has a passage 65 extending from one side into a central outer recess 66. This latter recess communicates with the chamber 6| between the block and ring 43 by channels 61 extending down the side of the block. Besides the described function of connecting the chambers 60 and 6|, the recess 66 performs another purpose by balancing, to the extent of the pressure of liquid acting on it, the outward pressure, on the block and, therefore, decreasing the frictional resistance between the block 46 and the outer ring 44.

It was stated above that the blocks 45 have a loose connection with the disks 4|, 42 and hence and the wedging action of the two sets of blocks will cause the blocks to grip the rings firmly enough to cause rotation with no other aid, but in starting the pump it is necessary to hold the blocks temporarily in 'place to avoid slippage. For this purpose each block 45 isprovided with a through hole 10 receiving apin "H of somewhat smaller diameter and received in arcuate slots 12 (Fig. 5) in the disks 4!, 42. Free motion of the blocks is thus permitted within limits. If a block forces its pin to the end of its slot, however, further pressure on the block makes the bottom of the hole I0 (which is preferably'eccentric with the pin for this purpose) ride on the pin and cams the block .against ring 43. With one block' thus held, the wedging action of the pairs of blocks causes the remainder to grip the rings tightly.

One aspect of the pumping action deserves special mention, because of its important relation .to the fluid tightness of the pump. It might appear at first that each chamber 60 and GI, or at least each pair of chambers connected by passages 65, function separatelyand that it must for that reason be necessary to maintainfluid-tight contact between adjacent blocks 45 and 46 in all positions. It is desirable to' design the wedge surfaces of blocks 46 and the curved surfaces of blocks 45 so that the two sets of blocks always fill snugly the annular chamber between the rings 43 and 44, irrespective of the position of the latter with regard to eccentricity, in order to reduce lost motion and thus the noise of the pump. In actual practice, however, the blocks do'not fill the chamber tightly, either because of manufacturing tolerances (which .must 'be chosen so that the blocks at the high pressure side ofthe pump on the high side the block's do not quite fill the v will be forced apart bythe fluid pressure and the blocks onthe opposite side of the pump forced together by their resulting shifting.

No leakage is introduced by the action just described since the chambers 60, 6| through the high pressure zone are all connected together through two ofthe passages 64 and the common port 24; or 25, whichever inay be acting as the high pressure side. The important place for the blocks to be in tight contact is at the transition points between the ports, and the separation of the blocks at the high pressure side insures this by crowding the blocks together thrqighout the Y remainder of the chamber. The tightnessthus secured becomes more pronounced after the pump has been in operation, for the rubbing of the parts smooths off any tiny inequalities left by the surface finishing operation. A further feature of importance in making a fluid-tight pump is they faces of blocks 46 is of importance in securing:

proper operation of the pump. This angle should be large enough for a given size of pump so that a positive wedging action between the two sets of blocks will occur. On the. other hand it should not be so large thatthe angle of' contact between adjacent blocks is steep enough'to cause locking by either radial or circumferential pressure, or

tdcause the corners of any block to bind on an adjacent block. A further'consideration is that the size of the blocks and the angle 15 are preferably so coordinated that the chambers 80 and SI will be of approximately equal volume. In gen eral this angle may be in the range of 10 to 25, depending upon the pump size.

It is desirable, in order to reduce the friction and wear of the parts, and to prevent leakage, that all parts be balanced hydrostatically in order to avoid excessive pressures. The manner in which this is accomplished for blocks 45 and 46 has already been considered. Aside from the blocks the only part of the present pump which requires hydrostatic balancing is the bearing of the taper socket 32 on the valve plug l5. While the plug -is held in the frame and the shaft is journaled in ball bearings slight deflections due to the pressure adjacent the high pressure port could still cause wear and leakage were not precautions taken to balance the pressure conditions. In the present case this balance is achieved by passages 16 (Figs. 1 and 4) leading from each duct l1, l8 to a port 11 on the opposite side of the plug |5. There are four ports ll, two on each side, each being connected to the duct I! or 18 on the opposite side; and the area of the two ports 11 .on one side is made equal to that of the port 24 or 25 on the other side. The hydrostatic pressure tending to cause lateral relative displacement of the members l5 and 32 is thus balanced. If oil is the liquid being pumped these ports 11 may also serve as lubricatingmeans.

The pump described lends itself readily to automatic control of its displacement, so that it maybe used to deliver fluid under constant pressure. One such arrangement is shown in Figs. 1 and 6. Fixed to the shaft 54 is a gear 80 meshing with a rack 8| formed integral with a piston 82 sliding in a cylinder 83. To provide for accurate adjustment of the mesh between the gear and rack the cylinder 83 is preferably formed as an eccentric sleeve rotatable in a bore 84. A

passage 85 extends from one end of the cylinder to the passage 23, which in this case is connected as the high pressure side of the pump. The piston is held against the fluid pressure in the cylinder by a spring 86 backed up by an adjustable plug 81. The pressure'on the head of the piston will shift the piston, and thus changethe position of the member to vary the output of the pump, until the total pressure on the piston head is equal to that of the spring. Since this can bevaried the pressure can be maintained at any predetermined level. If, for example, the output of the pump is completely shut off the member 50 will be shifted to a position in which the rings 43 and 44 are coaxial, in which case the output will be zero. By placing a second pistonin tandem with piston 82 and connecting its cylinder periodically with a second point in the hydraulic system which is under different pressure conditions the pressure output of the pump may be varied automatically.

It may be pointed out again that the chambers 60, 6| on the high pressure side act as one large chamber due to the passages 65, 66, 61, to the separation of the blocks, and to the interconnection of the exhaust passages. Oneresult of this is that pressure is built up practically instantaneously when the'pump is put into operation.- The operation of the dered exceptionally smooth.

What I claim is: 1. A variable displacement rotary pump of the type having a rotatable annular chamber with end walls and with inner and outer circumferpump is also renential walls one of which is of variable eccentricity and valve means connected to said chamber; characterized by pumping mechanism within the chamber consisting ofv a circumferential series of blocks arranged for contact with each other in two alternating and staggered sets slidable between the end walls, the blocks of one of said sets being in slidable contact with the outer circumferential wall and having their side surfaces inwardly convergent and the blocks of the other of said sets being in slidable contact with the inner circumferential wall and having their side surfaces outwardly convergent.

2. A variable displacement rotary pump of the type having a rotatable annular chamber with end walls and with inner and outer circumferential walls one of which is of variable eccentricity and valve means connected to said chamber; characterized by pumping mechanism within the chamber consisting of a circumferential series of blocks arranged for contact with each other in, two alternating and staggered sets slidable between the end walls, the blocks of one of said sets being in slidable contact with the outer circumferential wall and having their side surfaces inwardly convergent and the blocks of the other of said sets being in slidable contact with the inner circumferential wall and having their side surfaces outwardly convergent, the blocks of at least one set having their side surfaces curved to produce line contact with the blocks of the remaining set.

3. A rotary pump comprising an annular chamber, a circumferential series of blocks slidably arranged within the chamber for contact with each other in two alternating and staggered sets, the blocks of one set having their side sur faces inwardly convergent and the blocks of the other set having their side surfaces outwardly convergent, means for exerting a radial Wedging force progressively throughout the circumferential series of blocks, and valve means for aci-v mitting fluid. to and discharging it from the chamber at opposite sides thereof.

4. A rotary pump comprising an annular chamber, a circumferential series of' blocks slidably arranged with respect to the chamber and within the chamber for contact with each other .chamber formedby end Walls and inner and outer circumferential walls one of which is slidable between the end walls, a circumferential series of blocks slidably arranged with respect to the chamber and within the chamber for contact with each other in two alternating and staggered sets, the blocks of one set being in slidable contact with the end walls and with the outer circumferential wall and having their side surfaces inwardly convergent, the blocks of the second set being in slidable contact with the end walls and with the inner. circumferential wall and having their side surfaces outwardly convergent,

the blocks of at least one set having their side surfaces curved to produce line contact with the blocks of the remaining set; means for rotating the chamber and the blocks thereima bearing for one of the circumferential ,,walls, means'for shifting said bearing transversely of the axis of rotation of the chamber to vary the eccentricity of said wall with respect to the other wall and thus to exert a radial wedging force passing progressively throughout the circumferential series of blocks to cause them to approach circumfer ential alinement on one side of the axis and to increase their staggered relationship on the other, and valve means connecting to the pump inlet a sector of the chamber in which the staggered relationship of the blocks is increasing and connecting to the pump outlet a sector of the chamber in which the staggered relationship of the blocks is decreasing.

6. A rotary pump comprising an annular chamber formed by end walls and inner and outercircumferential walls, a circumferential series of blocks slidably arranged' with respect ,to the chamber and within the chamber for contact with each other in two alternating and sta gered .sets, the blocksof one set having their side surfaces inwardly convergent and the blocks of the other set having their side surfaces outwardly convergent, means for exerting a radial force on one of said circumferential walls to produce a radial wedging force passing progressively throughout the circumferential series of blocks,

and valve means for admitting fluid to and discharging it from the chamber at opposite sides thereof.

7. A rotary pump comprising an annular chamber composed by end walls and inner and outer circumferential walls, a circumferential series of blocks slidablyarranged with respect to the chamber and within the chamber for contact with each other in two alternating and staggered sets, the blocks of one set having their side' surfaces substantially plane and inwardlyconvergent and the blocks of the other set having their side surfaces curved and outwardly convergent, means for rotating said chamber and the blocks therein, means for adjusting one of said circumferential walls along a straight line at right angles to the axis of rotation of said chamber to thereby regulate the eccentricity of said wall with respect to saidaxis of rotation, and to exert thereby a radial wedging force passing progressively throughout the circumferential series of blocks, and valve means for admitting fluid to' and discharging it from ,7 the chamber at opposite sides thereof.

8. A rotary pump comprising an annular chamber, a circumferential series of blocks slidably arranged with respect to the chamber and within the chamber forcontact with each other in two alternating and staggered sets, the blocks of one set having their side surfaces inwardly convergent and the blocks of the other set having their side surfaces outwardly convergent, means for exerting a radial wedging force progressively throughout the circumferential series of blocks, valve means for admitting fluid to and discharging it from the chamber at opposite sides thereof, and means automatically controlled by the pressure delivered by the pump for varying the amplitude of said radial wedging force.

9. A rotary pump comprising an annular chamber formed of end walls and inner'and outer circumferential walls, a circumferential series of blocks slidably arranged with respect to the chamber and within the chamber for contact with each other in two alternating'and' staggered sets, the blocks of one set having their side surfaces inwardly convergent and the blocks of the other set having their side surfaces outwardly convergent, means for varying the eccentricity of one of said circumferential walls to produce a radial wedging force passing progressively throughout the circumferential series of blocks, valve means for admitting fluid to and discharging it from the chamber at opposite sides thereof, and mean automatically controlled-by the pressure delivered by the pump for controlling the eccentricity varying means.

10.'A rotary pump. comprising 'anannular chamber, a circumferential series of blocks slidably arranged with respect to the chamber and within the chamber for contact with each other in two alternating and staggered sets, the blocks of one set having their side surfaces substantially plane and inwardly convergent and the blocks of the other set having their side surfaces J curved and outwardly convergent, one of said sets of blocks having passages formed therein to form a communication between the -.space within one series of blocks and the space outside of the other series of blocks, means for exerting a radial wedging force progressively throughout the circumferential eries of blocks, and valve means for admitting fluid to and discharging it from the chamber at opposite sides thereof, said valve means being. formed to permit'communication between at least two of said adjacent pumping chambers.

11. A rotary pump comprising wall members defining an annular chamber having closed end wallsand cylindrical inner and outer walls, a

guide holding one of said cylindrical walls in a position eccentric to the other cylindrical wall, valve means having ports, certain of the wall members being apertured to communicate therewith, means for causing relative rotation between the chamber on the one hand and the valve means on the other hand, and a plurality of blocks located in the chamber. in two alternat- I ing sets in sliding contact with the closed ends of the chamber and in sliding contact respectively with the outer and the inner cylindrical walls, the blocks of the first set having their side surfaces inwardly convergent and the blocks of the second set having their side surfaces outwardly convergent, and in contact with the ,side surfaces of the blocks of the first set.'

12. A rotary pump! comprising wall members defining an annular chamber having closed end walls and cylindrical inner and outer walls, a

guide holding oneof said cylindrical walls in a position eccentric to the other cylindrical wall, valve means having two diametrically opposed ports, certain of the wall members being apertured to communicate therewith, means for causing relative rotation between the wall members on'the one hand and the guide and the valve means on the other hand, and a plurality of blocks located in the chamber in two alternating sets in sliding contact with the closed end walls, of the chamber and in sliding contact respectively with these outer and inner cylindrical walls, the blocks of the first 'set having their side surfaces substantially plane and inwardly convergent and the blocks of the second set having their side surfaces outwardly convergent and cu ved to produce line contact with the blocks of the otherset.

13. A rotary pump comprising wall members defining an annular chamber having closed end walls and cylindrical inner and outer walls, a guide holding one of said cylindrical walls in a position eccentric to the other cylindrical wall,

' pair of closure disks keyed to the socketed mem-' 'an' adjacent block of the other set.

valve means on the other hand, and a plurality of blocks located in the chamber in two alternating sets in sliding contact with the closed end walls of the chamber and in sliding contact respectively with the outer and the inner cylindrical walls, the blocks of'the first set havingtheir side surfaces substantially plane and inwardlyconvergent and the blocks of the second set having their side surfaces outwardly convergent and curved to produce line contact with the blocks of the other set, the convergence of the side surfaces of the blocksof the first set bein sufficient to produce non-locking wedge contact between the blocks of the two sets.

14. A rotary pump comprising wall' members defining an annular chamber-having closed end walls and cylindrical inner and outer walls, a guide holding one of. said cylindrical walls in a position eccentric to the other cylindrical wall, valve means having two diametrically opposed ports, certain of the wall members being apertured to commun cate therewith, means for causing relative rotation between the wall members on the one hand and the guide and the valve means on the other hand, and a plurality of blocks located in the chamber in two alternating sets insliding contact with the closed end walls of the chamber and in sliding contact respectively with the outer and the inner cylindrical walls, the blocks of the first set having their side surfaces plane and inwardly convergent so that the included angle between the adjacent side surfaces of adjacent blocks lies between 10 and 25, and the blocks of the second set having their side surfaces formed as cylindrical segments having line contact with the plane surfaces of the blocks of the first set throughout the motion of the blocks.

15. A rotary pump comprising wall members defining an annular chamber having closed end walls and cylindrical inner and outer walls, a guide holding one of said cylindrical walls in a position eccentric to the other cylindrical wall, valve means having two diametrically opposed ports, certain of the wall members being apertured to communicate therewith, means for causing relative rotation between the wall members on the one hand and the guide and the valve means on the other hand, and a plurality of blocks located in the chamber in two alternating sets in sliding contact with the closed end walls of the chamber and in sliding contact respectively with the outer and the inner cylindrical walls, the blocks of the first set having their side surfaces inwardly convergent and the blocks of the second set having their side surfaces outwardly convergent and in contact with the side surfaces of the blocks of the first set, one set of blocks being formed with passages connecting the space outside a block of one set with the space inside 16. A rotary pump comprising a stationary tapered valve plug, a socketed member revolving around the plug and fitting closely thereon, a pair of fluid conducting passages in the plug, oppositely opening ports in the plug connected to said passages, ports in the socketed member positioned to register with the ports in the plug, a

ber, a spacing sleeve between the disks, a'ring spaced outwardly from the sleeve and slidable into concentric or eccentric relation between the disks in fluid tight relation therewith, a plurality of blocks slidable between the disks between the sleeve and the ring, said blocks being arranged in two alternating sets, passages in at least one of the closure disks from the ports in the socketed member to adjacency with at' least one set of blocks, the blocks of one set being in sliding contact with the ring and the blocks of the other set being in sliding contact with the sleeve, the blocks of the first set having their side surfacesinwardly convergent and the blocks of the second set having their side surfaces outwardly convergent and in contact with the side surfaces of the blocks of the first set.

17. A rotary pump comprising 'a stationary tapered valve plug, asocketed member revolving around the plug and fitting closely thereon, a pair of fluid conducting passages in the plug, oppositely opening ports in the plug connected to said passages, ports in the socketed member positioned to register with the ports in the plug, a pair of closure disks keyed to the socketed member, a spacing sleeve between the disks, a'ring spaced outwardly from the sleeve and slidable into concentric or eccentric relationbetween the disks in fluid tight relationtherewith, means for varying the eccentricity of the ring with respect to the sleeve, a circumferentially complete series of blocks slidable between the disks in the space between the sleeve and the ring, said blocks being arranged in two alternating sets, passages in at least one of the closure disks extending from the ports in the socketed member into adjacency with at least one set of blocks, the blocks of one set being in sliding contact with the ring andjthe blocks of the other set being in sliding contact with the sleeve, the blocks of the first set having their side surfaces inwardly convergent and the blocks of the second set having their side surfaces outwardly convergent and in contact with the side surfaces of the blocks of the first set.

18. A rotary pump comprising a stationary tapered valve plug, a socketed member revolving around the plug and fitting closely thereon, a pair of fluid conducting passages in the plug, oppositely opening ports in the plug connected to said passages, ports in the socketed member positioned to register with the ports in the plug, a pair'of closure disks keyed to the socketed member, a spacing sleeve between the disks, a ring spaced outwardly from the sleeve and slidable into concentric or eccentric relation between the disks in fluid tight relation therewith, a plurality of blocks slidable between the disks between the sleeve and the ring, said blocks being arranged in two alternating sets, passages inat least oneof the closure disks from the ports in the socketed member to adjacency with at least one set of blocks, the blocks .of one set being in sliding contact with the ring and the blocks of the other set being in sliding contact with the sleeve, the blocks of the first set having their side surfaces substantially plane and inwardly convergent and the blocks of the second set having their side surfaces outwardly convergent and curved to produce line contact with the blocks of the other set.

19. A rotary pump comprising a stationary tapered valve plug, a socketed member revolving around the plug and fitting closely thereon, a pair of fluid conducting passages in the plug, oppositely opening ports in the plug-connected to said passages, ports in the socketed member positioned to register with the ports in the plug, a pa r of closure disks keyed to the socketed member,

a spacing sleeve between thedisks, a ring spaced outwardly from the sleeve and slidable between the disks in fluid tight relation therewith, means for varyingthe eccentricity of the ring with respect to the sleeve, 9. circumferentially complete series of blocks slidable between the disks between the sleeve and the ring, said blocks being arranged in two alternating sets, passages in at least one of the closure disks from the ports in the socketed member to adjacency with at least one set of blocks, the blocks of one set being in slidingcontact with the ring and the blocks of 'the other set being in sliding contact with the sleeve, the blocks of the first set having their,

side surfaces planeand inwardly convergent so that the included angle between the adjacent side surfaces of adjacent blocks lies between 10 and 25, and the blocks of the second set having their side surfaces formed as cylindrical segments having line contact with the plane surfaces of the blocks of the first set throughout the motion of the blocks. n

20. A rotary pump comprising a stationary tapered valve plug, a socketed member revolving around the plug and fitting closely thereon, a pair of fluid conducting passages in the plug, oppositely opening ports in the plug connected to said passages, ports in the socketed member positioned to register with the ports in the plug, a'

pair of closure disks keyed to the socketed member, a spacing sleeve between the disks, a ring spaced outwardly from the sleeve andslidable between the disks in fluid tight relation therewith,

of the other set being in sliding contact with the sleeve, the blocks of the first set having their side surfaces inwardly convergent and the blocks .of the second set having their side surfaces outwardly convergent, and in contact with the side surfaces of the blocks of the first set, one 'set of blocks being formedwith passages connectingthe space outside a block of one set with the space inside an adjacent block of the other set.

ROBERT WM. 011'.

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