US2698585A

US2698585A - Radial piston-type hydraulic pump

Info

Publication number: US2698585A
Application number: US201018A
Authority: US
Inventors: John C Cotner; Warren R Tucker
Original assignee: HPM Development Corp
Current assignee: HPM Development Corp
Priority date: 1950-12-15
Filing date: 1950-12-15
Publication date: 1955-01-04
Anticipated expiration: 1972-01-04

Description

Jan. 4, 1955 J. c. COTNER ET AL 2,698,585

RADIAL PISTON-TYPE HYDRAULIC PUMP Filed D60. 15, 1950 4 Sheets-Sheet l INVENTORS Wrren R. er

Jbizn L. 601 ner BY M ATTORNEY J. C. COTNER ET AL RADIAL PISTON-TYPE HYDRAULIC PUMP Jan. 4, 1955 4 Sheets-Sheet 2 Filed Dec. 15, 1950 INVENTORS V Zv'r'en J2. Tuckcr John 6? Gathe BY 7W ATTORNEY m u E Jan. 4, 1955 J. c. COTNER -T L 2,698,585

RADIAL PISTON-TYPE. HYDRAULIC PUMP Filed Dec. 15, 1950 4 Sheets-Sheet 5 INVENTOR %7'762 3. 540i? FIGS- ATTORNEY Jan. 4, 1955 J. c. COTNER ETAL 2,698,585

RADIAL PISTON-TYPE HYDRAULIC PUMP Filed D80. 15, 1950 4 Sheets-Sheet 4 INVENTORS U] Warren E. Tuci'er' John C. dolner BY Wd KW ATTORNEY United States Patent M RADIAL PISTON-TYPE HYDRAULIC PUMP John C. Cotner and Warren R. Tucker, Mount Gilead, Ohio, assi nors to H-P-M Development Corporation, Mount Gilead, Ohio, a corporation of Delaware Application December 15, 1950, Serial No. 201,018

3 Claims. (Cl. 103-161) The present invention relates generally to hydraulic pumps and/or motors, and has particular reference to an improved radial piston-type hydraulic pump or motor which is characterized by a structurally simple and rugged construction, and which incorporates an improved and mechanically eflicient connecting rod structure between the pumping pistons and the eccentrically movable rotor member of the pump.

In the past, the ordinary type of radial piston hydraulic pump comprised, among other elements, a primary shaftdriven rotor formed with a plurality of radially disposed cylinders, a like number of pumping pistons reciprocable in the cylinders, and an outer or secondary rotor to which one end of the pumping pistons was slidably connected, in order that the secondary rotor might be rotated in unison with the primary rotor, while at the same time providing for shifting movement of the secondary rotor to positions of eccentricity with respect to the primary rotor to impart a pumping reciprocating action to the pistons. In previously known constructions of this type, connection between the primary and secondary rotors was accomplished solely through the pumping pistons which were slidably connected with the secondary rotor to permit relative shifting of the rotor with respect to the primary rotor to obtain a pumping action within the cylinders. The sliding connection between the pumping pistons and the secondary rotor necessarily increased the amount of wear within the moving elements of the pump and in many cases resulted in a binding of the outer rotor in its shifting movement with respect to the primary rotor with consequent operating difliculties in varying the displacement of the pump. Further, due to the sliding connection between the primary and secondary rotors, a relatively large number of parts were necessary to accomplish the desired movement of the secondary rotor in varying the fluid output of the pump, and extremely accurate machining of the relatively movable parts was necessary to prevent undesired excessive friction and binding of the relatively movable parts. Also, in the ordinary type of radial piston pump, there is generally provided a stationary valve spindle having passages arranged to communicate with the separate cylinders of the primary rotor during relative rotation of such rotor about the stationary spindle. This feature of the pump further presents mechanical difficulties and greatly increases the cost of the pump due to the accurate machining necessary to accomplish the desired relative rotation between the stationary spindle and the primary rotor, and obviously, such relative rotation increases the friction produced in the operation of the pump and the normal wear of the parts thereof.

It follows, therefore, that the primary object of the present invention is to provide an improved radial pistontype pump which entirely eliminates a sliding connection between the reciprocating piston members and the secondary rotor of the pump, and which provides for the simultaneous unified rotation of the primary and secondary rotors and the valving structure associated with the pressure chambers or cylinders of the pump, thereby to greatly reduce the number of relatively movable elements within the pump structure, and consequent wear to the parts thereof.

It is another object of this invention to provide a radial piston-type pump or motor which comprises a primary shaft-driven rotor in which, is formed a plurallty of radially disposed pumping cylinders communicating at 2,698,585 Patented Jan. 4, 1955 one end with separate fluid passages extending in planes parallel to the axis of the rotor and in alignment with relatively stationary separate fluid inlet and outlet ports formed in the casing of the pump, a secondary rotor arranged for movement between concentric and eccentric positions relative to the primary rotor, a plurality of rodconnected pumping pistons reciprocable in the cylinders of the primary rotor and pivotally connected with the secondary rotor, and a free floating compensator ring disposed in laterally offset relation to the rotors and connecting the primary and secondary rotors for unified rotation, while at the same time providing for shifting movement of the secondary rotor between concentric and eccentric positions relative to the primary rotor to thus provide for reciprocation of the pumping pistons within the pressure cylinders of the primary rotor and the consequent variable displacement of fluid between the inlet and outlet ports of the pump.

Yet another object of the invention is to provide, as a sub-combination within a radial piston-type pump, a floating ring and connecting rod assembly between the primary and secondary rotors of the pump providing for the simultaneous unified rotation of the primary and secondary rotors while permitting shifting movement of the secondary rotor to various positions providing variable and reversible discharge of pressure fluid from the pump.

For a further and more detailed understanding of the present invention and the various additional objects and advantages realized therefrom, reference is made to the following description and the accompanying drawings, wherein:

Fig. l is a medial longitudinal vertical sectional view taken through a hydraulic pump formed in accordance with the present invention;

Fig. 2 is a transverse vertical sectional view taken along the line 2-2 of Fig. l;

3 is a similar view taken along the line 3-3 of 1g.

Figs. 4-7 are diagrammatic views showing the various positions taken by the compensator ring of the present pump as the same rotates when the pump is conditioned for displacement of fluid in one direction;

Fig. 8 is a transverse vertical sectional view taken along the line 88 of Fig. l and showing the relation between the inlet and outlet ports of the pump casing and the respective fluid passages leading from the pumping cylinders of the pump.

Referring now to the drawings, the present pump comprises an outer sectional casing consisting of a substantially rectangular central frame section 10 and

opposite end sections

12 and 14 which are suitably rigidly joined with the central frame section 10 in any suitable manner, such as by bolts, not shown, which pass transversely through the end sections and the central frame. The end sections and central frame are formed to provide an internal chamber 16 which houses the elements of the pumping mechanism to be hereinafter more fully described. At one end, the end section 14 is provided with a reduced hub portion 18 in which is formed a pair of oppositely disposed fluid inlet-outlet ports 20. Each of the ports 20 terminates at its inner end in an arcuate manifold chamber 22 which opens into an axially disposed bore 24 extending through the hub portion 18. Positioned within the bore 24 of the hub portion 18 is an annular valving member 26 which is formed with a pair of radially disposed arcuate manifold ports 28 in registration with the arcuate manifold chambers of the inlet-outlet ports 20. Each of the arcuate ports 28 of the valving member 26 terminates at its inner end in a relatively reduced perpendicularly extending arcuate passage 30 which opens at one end of the valve member 26 inwardly of the pump casing. Advantageously, the valving member 26 is provided with packing rings 32 at its periphery to provide a fluid-tight fit between the valving member 26 and the inner walls of the hub section 18 defining the bore 24. Adjoining the relatively enlarged bore 24 of the hub section 18 is a reduced diameter bore 34 formed with a shouldered region 36 and defining a chamber for the reception of a pair of anti-friction ball bearings 38. The bore 34 is closed at its outer end by an end cap 40 which is SCUI 1 to the outer face of the hub section 18 as by cap screws 42. The end cap is formed with an axial shaft-receiving opening 44 through which extends a drive shaft 46. The shaft 46 is rotatably carried within the inner races of the ball bearings 38, and may advantageously be formed with a diametrically enlarged shoulder region 48 which functions to maintain a separation between the separate ball bearings 38. The shaft extends inwardly of the casing through an axial bore 50 'formed in the valve member 26, and terminates centrally of the pump casing in a splined outer end portion 52. The splined portion 52 of the shaft 46 is received within a cooperatively splined bore 54 extending axially through an annular primary rotor 56.

As shown particularly in Fig. l of the drawings, the shaft 46 terminates intermediate the ends of the bore 54 of the primary rotor 56, and a second shaft 58 extends into the bore 54 from the opposite end thereof to abut the inner end of the shaft 46. The outer end of the second shaft 58 extends through a bushing block 60 positioned within a recess 62 formed upon the inner side wall of the casing section 12. The extreme outer end of the second shaft 58 is relatively diametrically enlarged and rotatably extends within a bore 64 formed axially through the end casing section 12. Advantageously, the bore 64 of the end section 12 is covered by a removable face plate 66 to provide access to the end of the shaft 58 to enable the same to be removed upon disassembly of the pump.

The primary rotor 56 is supported within the casing by anti-friction bearings 68 which, in turn, are supported within annular recesses 69 formed in the inner side Walls of the

end sections

12 and 14. The intermediate portion of the primary rotor 56 is relatively diametrically enlarged with respect to the end hub portions thereof and is formed with a plurality of spaced radially disposed pumping cylinders or bores 70. Each of the cylinders 70 opens along the periphery of the rotor 56 and communicates at its inner end with separate fluid passages 72 extending longitudinally through the primary rotor 56 parallel to the axis thereof and terminating in the plane of the arcuate passages 30 formed in the valving member 26. The primary rotor 56 is formed at the juncture of the cylinders 70 and passages 72 with relatively enlarged recesses 74 opening into the passages 72 and providing for the unrestricted flow of pressure fluid from the cylinders to the passages 72.

It will be understood that the primary rotor 56 is carried in rotation with the drive shaft 46, and that upon rotation, the separate passages 72 are sequentially brought into registration with the separate arcuate passages 30 formed in the valving member 26, whereby fluid may be transfcrred from and to each of the passages 72 by way of the arcuate passages or ports 20 of the valving member which, in turn, communicate with the separate inlet-outlet ports 20 of the pump.

Extending within each of the cylinders 70 of the primary rotor is a pumping piston 76 which is formed on its inner end with a piston head and which includes a hollow cylindrical skirt region opening unrestrictedly at its opposite end. Positioned within the skirt region of each piston 76 is a bearing block 78 which is formed with a semispherical recess for the partial reception of the spherical head portion 80 of a connecting rod 82. The head portion 80 of each rod is retained within the piston by means of an annular split-ring collar 84 which is provided with a semispherical recess engagcable with the opposite side of the spherical head 80 of the connecting rod 82. The collar 84 is abutted by a coil compression spring 86 which has its opposite end retained within the piston by a split-ring retaining collar 88 carried within an inner circular recess formed in the skirt portion of the piston 76. The block 78 and collar 84 provide a pivotal support between the spherical head 80 of the connecting rod and the piston 76 and permit limited swinging movement of the connecting rod within the skirt portion of the piston. The opposite end of each of the connecting rods 82 terminates in a relatively enlarged cylindrical boss region 90 which is formed with an axial bore 92 for the reception of a wrist pin 94. The wrist pin 94 extends outwardly on either side of the connecting rod and is nonrotatively carried within the bore 92 of the connecting rod by means of a set screw 96. The outer end portions of the wrist pin 94 extend within axially aligned and opposed roller bearings 98 which are positioned within bearing-receiving openings 100 formed in an annular secondary rotor 102.

The secondary rotor 102, in the regions of the connecting rods 82, is formed with radially disposed channeled recesses 104 which receive the circular boss regions 90 of the connecting rods. The opposing walls of the recesses 104 are formed with the bores 100 which receive the bearings 98 and support the wrist pins 94 therebetween. The outer peripheral surface of the annular secondary rotor 102 slidably abuts the inner side surface of a circular ring 106 whose outer surface rides upon a multiplicity of roller bearings 108 interposed between the outer surface of the ring 106 and the circular inner surface of a rectangular flow-controlling block 110. The flow-controlling block 110 is mounted within the outer casing for limited longitudinal shifting movement and has its upper and lower surfaces slidably supported by a plurality of wear plates or blocks 112 carried upon the inner side surface of the central casing frame 10 in substantially the corner regions thereof. At either end, the flow-controlling member 110 is provided with outwardly extending control shafts or rods 114 extending through openings formed in the central casing frame 10. The control rods 114, in the usual manner, may be mounted within a servomotor control of any suitable type, not shown, which functions to impart shifting movement to the block 110 through the rods 114.

Rigidly bolted to one side of the secondary rotor, as at 115, is a ring 116 which is formed with a pair of diametrically opposed bores 117 in which are carried a pair of radially extending rods 118. The rods 118 are suitably secured within the bores of the ring 116 by means of set screws 120 and are arranged to have their inner end portions extend through a pair of radially disposed and diametrically opposed bores 121 formed in a circular and annular compensator ring 122. The ring 122 is positioned in laterally offset relation to the primary and secondary rotors and is carried in spaced relation to the diametrically enlarged intermediate region of the primary rotor. The ring 122 is formed in 90 relation to the bores 121, which receive the rods 118, with a second set of bores 124 which slidably receive a second pair of radially disposed rods or posts 126 which, at their inner ends, are rigidly connected with the relatively reduced hub portion of the primary rotor 56. With reference to Fig. 3, it will be seen that the rods 118, which are carried by the ring 116, occupy relatively diametrically opposed positions in 90 relation to each of the rods 126 carried by the primary rotor 56. This assembly, comprising the ring 122 and

rods

118 and 126, permits limited shifting movement of the flow-controlling block 110 and of the secondary rotor 102 between concentric and eccentric positions with respect to the primary rotor and the drive shaft 46. As the rods 118 which are carried by the secondary rotor are shifted in either direction laterally with respect to the primary rotor, the compensator ring 122 likewise shifts and slides relative to the rods 126 carried by the primary rotor. At the same time, the rods 126 rotate with the primary rotor, thus transmitting direct rotation to the ring 122, through the rods 118, and thence to the secondary rotor. In this manner, there exists a unified rotation between the primary and secondary rotors of the pump, yet the secondary rotor is permitted to move relative to the primary rotor to an eccentric position-on either side of the primary rotor to cause relative reciprocation of the pistons 76 within the pumping chambers of the primary rotor and the consequent displacement of fluid between the separate inlet-outlet ports 20 of the pump. The outer ring 116 is slotted, as at 128, on either side of the rods 126 to permit the ring 116 to be moved radially and eccentrically with respect to the primary IOl6Ol without interference by the outer ends of the rods 12 Fig. 3 of the drawings illustrates the various elements of the pump in their neutral positions, wherein the primary and secondary rotors are concentric to one another to prevent the reciprocation of the pistons during rotation of the rotors. In this neutral position, there is no circulation of fluid between the separate ports 20 of the pump.

Figs. 4-7 illustrate the flow-controlling block 110 in a position providing for full displacement of fluid between the separate inlet and outlet ports of the pump. The separate figures show the relative positions of the free floating compensator ring 122 as the rotors are driven in rotation with the flow-controlling block 110 shifted to its full left hand position. It will be seen from these latter figures that the compensator ring is rotated in unison with the rotors of the pump, but at the same time the axis of the compensator ring moves in a circular path relatlve to the axis of the primary rotor and drive shaft 46, thus permitting free shifting movement of the flowcontrolling block 110 and the secondary rotor 102 during rotation of the rotors of the pump.

Advantageously, the central frame of the casing may be formed along its lower sides to provide laterally and downwardly projecting base leg portions 130 by which the pump casing may be suitably rigidly anchored to a supporting structure. Further, the central frame section '10 may be formed upon its upper surface with an access opening 132 through which lubricants may be introduced to the interior of the casing to lubricate the sliding block or flow-controlling member 110. Also, for lubricating purposes, the end faces of the pistons 76 may be provided with relatively small orifices or passages 134 through which hydraulic fluid may pass from the passages 72 to lubricate the pivotal connection between the spherical heads 80 of the connecting rods and the associated bear ing surfaces of the blocks and collars 78 and 84.

Bolted on the side of the secondary rotor 102 opposite the ring 116 is a second retaining ring 136 which overlaps the left hand end of the wrist pins 94, as viewed in Fig. l, to maintain such wrist pins against undue longitudinal shifting movement within the bearings 98, and thereby to maintain the cylindrical boss regions 90 of the connecting rods in spaced relation to the inner side surfaces of the bearings 98 and prevent end wear thereto.

In operation, the mechanism constitutes a variable displacement reversible hydraulic pump, the secondary rotor being movable to either side of a concentric position relative to the primary rotor to reverse the direction of flow of fluid between the separate inlet and outlet ports of the pump. The rate of displacement of fluid between such ports is controlled by the extent of movement of the second rotor eccentrically of the primary rotor.

Assuming the drive shaft 46 to be drivingly connected with a suitable power source, such as an electric motor, not shown, the shaft, primary and secondary rotors, and the compensator ring 122 are rotated in unison. With the flow-controlling block 110 occupying its neutral position as shown in Figs. 2 and 3, there is no transfer of fluid between the separate ports 20 of the casing due to the concentric disposition of the primary and secondary rotors and the consequent immobility of the pumping pistons within the pressure cylinders of the primary rotor. However, when a discharge of pressure fluid through the upper inlet-outlet port 20 is desired, the flow-controlling block 110 is shifted leftwardly to its full line shown in Figs. 4-7. Such shifting movement imme diately moves the secondary rotor 102 to its maximum left hand position of eccentricity with respect to the primary rotor 56, and as the rotors continue to rotate in unison, the pistons 76 are caused to ing cylinders of the primary rotor to draw fluid into each of the cylinders through the lower inlet-outlet port 20 of the casing, the lower arcuate port of the valving member 26, and through the longitudinal passages 72 as the latter are brought into registration with the lower arcuate port 30 during rotation of the primary rotor. As the primary rotor continues to rotate, each of the pistons 76, in its turn, moves inwardly of its associated cylinder to force fluid within the cylinder outwardly throu h the passages 72 and the upper in et-outlet port 20 of the casing as the individual passages 72 are brought into registration with the upper arcuate port 30 of the valving member 26. As shown in Fig. 8 of the drawings, the ends of the separate arcuate ports or passages 30 of the valving member 26 are disposed in relatively closely spaced relation to minimize any tendency to compress fluid within the individual cylinders or to create a vacuum therein as the passages 72 are closed ofl by the area of the valving member 26 during rotation of the primary rotor relative thereto. Thus, the arcuate ports 30 of the valving member are arranged to register with each of the passages 72 associated with the individual cylinders 70 in a manner to permit flow of fluid to and from the passages during actual movement of the pistons within the cylinders and to close the passages 72 as the pistons reach top and bottom dead center positions. The degree of shifting movement of the flow-controlling block 110 controls the length of stroke of each piston, and by increasing the eccentricity of the secondary rotor with respect to the primary rotor, the strokes of the mdivrdual position as reciprocate within the pump- 2 pistons are correspondingly increased with the result that the volume output of the pump is also increased,

The discharge of the pump is reversed in the usual manner by reversing the position of the flow-controlling block 110, and it will be understood that by shifting the flow-controlling block rightwardly, as viewed in Figs. 27, a reversal of the direction of flow of fluid would result, the upper inlet-outlet port 20 serving to supply fluid to the pump, while the lower inlet-outlet port 20 of the casing functions as the pressure outlet of the urn p In view of the foregoing, it will be seen that the present invention provides an improved and mechanically eflicient radial piston-type hydraulic pump or motor which is characterized by its simplicity of construction and the employment of relatively few and simple movable parts. The provision of the novel free floating compensator ring as a means for joining the separate primary and secondary rotors of the pump for unified rotation greatly reduces the amount of friction and wear in comparison with previous types of radical piston pumps, and enables the individual pumping pistons to be mounted upon relatively simple connecting rod and wrist pin assemblies. Further, the generally rectangular outer configuration of the flow-controlling member of the present pump and the cooperative four-corner support of the flow-controlling member within the outer casing greatly reduces the amount of wear between the sliding surfaces of such members and effectively resists any tendency of the flow-controlling member to cock due to torque forces transmitted upon rotation of the rotors of the pump. A further advantage ambient to the present pump construction stems from the provision of the valving member 26 of the pump which remains stationary with respect to the rotating primary rotor and its associated fluid passages 72. In utilizing the stationary valving member 26, the ordinary valve spindle, which usually rotatively supports the primary rotor of the pump, is eliminated in its entirety, thereby enabling the primary rotor to be directly keyed or splined to an axially disposed drive shaft, thereby eliminating the necessity for an axially offset connection between the drive shaft and the primary rotor of the pump.

While a single preferred embodiment of the present invention has been disclosed in detail, it will be understood that various modifications respecting constructional details may be resorted to without departing from the spirit of the invention or the scope of the following claims.

We claim:

1. In a fluid displacement pump: in combination, a casing formed with an internal chamber, a fluid inlet, and a fluid outlet; a circular primary rotor journaled for axial rotation within the chamber of said casing, said primary rotor being formed with a plurality of radially disposed pumping cylinders and a plurality of fluid-conducting passages disposed in parallel but radially oflset relation to the axis of said primary rotor, each of the passages of said primary rotor communicating with one of the pumping cylinders formed in said primary rotor and being arranged for alternate communication with the fluid inlet and outlet of said casing upon rotation of said primary rotor; a drive shaft extending into said casing and drivingly connected with said primary rotor; a secondary rotor positioned in the chamber of said casing around said primary rotor; piston means carried by said secondary rotor and reciprocable in the pumping cylinders of said primary rotor; a first set of diametrically opposed radially and outwardly extending rods carried by said primary rotor; a second set of diametrically opposed radially and inwardly extending rods carried by said secondary rotor in right angular relation to said first set of rods; a ring having diametrically opposed sets of openings slidably receiving said first and second sets of rods and thereby joining said primary and secondary rotors for unified rotational movement while permitting movement of said secondary rotor between concentric and eccentric posi tions relative to said primary rotor, the movement of said secondary rotor to positions of eccentricity with respect to said primary rotor providing for reciprocation of said piston means within the cylinder of said primary rotor and the displacement of fluid between the inlet and outlet of said casing; and means in the chamber of said casing engaging said secondary rotor for moving the latter between concentric and eccentric positions with respect to said primary rotor.

2. In a fluid displacement apparatus: a casing having an internal Chamber fl T smarter: seats; at as; r axia rotation, said primary rotor b a plurality of radially a'ran d eing formed w th ducting P ges commu nicat i? cy-mder-s h said lmd d extending longitudinally i Witd y ers an alternate communi ation with th l; Primary rotor r d mlet and [1 means of said casing upon IOIZIIOI I of d Du et a piston reciprocable in each of t Sai pnmary rotof; Sald ne cylinders formed in marria es;astreamers:arte s relation to the outer perimeter of said prim ary rg gl ifi e lng rods pivotally connected at one end with each of sald R means pivotally connecting said rods at their opposite ends wlth said secondary rotor; flow-controlling means surrounding said secondary rotor and movable Within said casing to shift said secondary rotor between concentric and eccentric positions with respect to the axis of said primary rotor; and means independent of said connecting rods uniting said primary and secondary rotors for rotation and permitting shifting movement of said secondary rotor during rotation thereof between concentric and eccentric positions relative to said primary rotor to cause reciprocation of said pistons within the cylinders of said primary rotor and the displacement of fluid between the inlet and outlet means of said casing, said lastnamed means comprising a plurality of radially and outwardly extending rods carried by said primary rotor, a plurality of radially and inwardly extending rods carried on said secondary rotor, and a floating ring member having radially disposed openings slidably receiving said rods. 3. In hydraulic fluid displacement apparatus: a casing formed with an internal rotor-receiving chamber, a fluid inlet port, a fluid outlet port, and passage means connecting the inlet and outlet ports with the rotor-receiving chamber; shaft means journaled in said casing and extending axially through the rotor-receiving chamber thereof; a first primary rotor positioned in the chamber of said casing and drivingly connected with said shaft means, said primary rotor being formed with a plurality of radially arranged and relatively spaced pumping chambers opening inwardly from said primary rotor and a plurality of se ar said prima i ii 523 22 3 exhendlng qngltudmally of chambers formed therein t l i e c l i iiiigls g Pumping rotor being arranged fofzlte t P ry the Passage means of said casin a e commum-catlon and outlet ports u on g assqclatefi with the Inlet annular secondary iotoi g i n e i r l ih t r ii zfme l fi g casing around said primary rotor and m b a] concentric and eccentric positions with 22 1e betweqn nmar pect to said {it the gu iifiiii iif r s i iii iiifii i f mg Qds pivotally connected at one end ti' ler e f vv fli li of Sald Plstons; means Pivotally connecting the g t ends of said rods with said secondary rotorfio z -cizt n trolling means slidable within the chamber of said casing and engageable with said secondary rotor for moving the latter between concentric and eccentric positions With respect to said primary rotor; and means other than said connecting rods positioned within the chamber of said casing and drivingly connecting said primary and secondary rotors for unified rotation but providing for movement of said secondary rotor between concentric and eccentric positions with respect to said primary rotor during rotation of said rotors, said last-named means comprising a pair of diametrically opposed rods carried by and projecting radially outwardly on one side of said primary rotor, a second pair of diametrically opposed rods carried by and projecting radially inwardly on one side of said secondary rotor, and a floating ring having a plurality of radially arranged openings slidably receiving said first and second pairs of rods.

References Cited in the file of this patent UNITED STATES PATENTS 697,019 Richardson Apr. 8, 1902 2,173,432 Benedek Sept. 19, 1939 2,273,468 Ferris Feb. 17, 1942 2,381,741 Grosser Aug. 7, 1945 2,397,314 Grosser Mar. 26, 1946 2,419,059 De Villiers Apr. 15, 1947