US2551993A - Pump and motor - Google Patents

Description

y 8, 1951 E. K. BENEDEK 2,551,993

PUMP AND MOTOR Filed Nov. 5, 1944 4 Sheets-Sheet 1 IN VEN TOR.

y 1951 E. K. BENEDEK 2,551,993

PUMP AND MOTOR Filed Nov. 3, 1944 I 4 Sheets-Sheet 2 FIELZ- INVENTOR May 8, v E K BENEDEK PUMP AND MOTOR Filed NOV. 5, 1944 4 Sheets-Sheet 3 INVENTOR.

4 edQ -32 E. K. BENEDEK PUMP AND MOTOR May 8, 1951- Filed Nov. 5, 1

4 Sheets-Sheet 4 A N I *3? z'ze/gfrfieygggb BYMQ 1 WI Patented May 8, 1951 N IT o STAT PAT ENT OFF les- AND MOTOR Elek K. Benedek, Chicago-J11.

Application'Novem'b'er 3, 1944; Serial No. 561,736

8 Claims. 1..

This invention relates to variable delivery pumps and motors, such: as-described and claimed in my co-pending application, Seria1 -No.. 694,1 79; dated November 18, 1933, .now-P-atent2,255,962 grantedseptember 16:, 1941-". One Object of the present invention is to. provide: improved re'-- actance means for greater operating speed and pressure.

Further. object is to provide improved and selfcontained piston and cross pin assemblies-With permanent and life-long-lubrication therein,- Ice-- tween-the rolling cross pins and the cross pin bore of theradial heads-oi the pistons.-

Still further objects are the provision-of selfcontained piston and roller assemblies with permanent life long lubrication between thrust" rollers and stationary thrust pins of the radial piston heads.

still further objectswillbeapp-arent and more particularly described in connection withthe accompanying drawingsforming part of this specification.

In the drawings:

Fig. 1. isapartial longitudinal main section; taken on line l--I, in'Fig. 2, of the pump; con-- structedin-accordance to the spirit oi this invention- V Fig. 2 is atransverse main section, taken on line. 2-'2l of Fig. 1, some of the p-istons' beingshown in elevation; some of themin' partially sectional elevations, for the clearance of the illustration.

Fig. 3 is a longitudinal main section of" apump, constructed in accordance with the spirit of this invention, showing a modification thereof.

Fig. lls apartial longitudinal sectionalview of a self-contained piston and anti-frictiona-lly' mounted rolling cross pin assembly, showing parts or the piston and cross pin inelevation; taken thru line 4-4 in Fig. 5.

Fig. 5 is apartial sectional- View, takenon line 5-5 of Fig. 4, showing the piston and cross pin sub-assembly.

Fig. 6 shows the spring snap-ring, used con nection with the sub-assemblies of Fig. 4 and Fig. 5; for retaining the rolling crosspinsof-the piston sub-assemblies. in place.

Fig. '7 is a partial, longitudinalsectionalView of my novel self-contained piston'roller sub-assembly and. is. slightly modifiedrelative to the one shown in Fig. 1 and Fig. 2, taken on line 1-1 in Fig; 8;

Fig. 8 is a sectional view taken on line B -Bof Fig. 7.

Fig. 9 'is a springlsnap. ring, used to retain -the rollers on the protruding ends. of'theirigidacrosspinsiin Fig.7..

Figure-102 is a transverse vertical sectionion the line' I 01 l Dfof l liguiretli.

Figure lliis a; fragmentary section onithe line? H--lt of Figure '1.

Figure 12Lis a-fragmentary section-on the line lZe-[Zi of ?Fig.ure"3;

Referring. to::Eigs;.1 and ZJofL'the drawings; they show. the: inside ofzrareversibl'e =variable*de.- livery pum in which. the'cylinderiblock Zand'a rotary reactances. I 4 -l51 are: associated by the medium oft'the pistons 8-9:andzcylinderiassem blies 1, including: the cross-pins l0.of.the"pis.-= tons, and the coacting thrustzrollerszil;

Each. piston' ithasza. largetradia-l head as at. 9, having; cylindrical. or fiat: torque. transmitting: and guiding: surfaces as at. 9a,. which. cooperate with: complementary radial. guiding andi torquetransmitting; surfaces 20h of: the: central circu'+-= lar: flange-2i ofiithetbarrel 2"; Itiwill be: noted; that. in case of: a: hydraulic motor, the entire torque and. therefore. the. entire: utility: of the motoriwilllbe concentrated on these surfaces and consequently theyv must be large enough to sus tain an effective oi-Lfilm; duringi-maximum pres== sure operation. periods. For this reason thei radial headseflcare-notl only. long; at least as-longas.- the? length. oithe pistons: 8 but they arealso larger thanzthe; diameter *of their piston.

In the. embodimentofrFig. 1', Fig; 2; Fig. 7'to Fig. 9 andFig'; 11 inclusive, the r'eactance haltes H and. [5. are bolted togetherasat Hi; to form atfluid." tight reservoir for. the Slipfi uidof the pump;..and collect this slip fluid, for the purpose" of full andeffective lubricationof the guide20'w' and: piston head 9'. r

Itwill be seen that bythe virtue of this-rotary liquid. tight reactance drum l4'l 5 the thrust elements ofthe piston-head 9;such astherigidly secured. cross-pin f0,- lll'a, [0b and Inc, and the associated roller. bearing assembly I3 and the roller sleeve: H, all willoperate during -all sustained pressure cycles: in a bathof oil. At higher' spee'ds such-as 1000- to 2500 R. P; M., this-lubri eating rotary oil bath will-be subject to-substan tial-centrifugalpressure, and it will additionally help the lubrication and cooling of the elengated ceive a spring snap ring l2, to retain elongated roller bearings I3, which support the pin-ends lea-10a by means of roller sleeves ll-H on coacting circular thrust shoulders, of the reactance halves l4 and [5. In this embodiment the pin ends are of the same diameter as the thrust ends of the pin ID, and the snap retainer ring i2 retains the rollers l3 in assembly, when the piston is removed from its cylinder. The diameter of the snap ring I2 is greater however than the bore of the roller sleeve ll, so that the snap ring retains not only the roller bearings, but also the roller sleeve I I on the thrust pin H].

The large piston head 9 readily accommodates the enlarged central portion of the pin H], to minimize elastic deflection of the pin ends ice-40a. This is very essential, since the roller bearings i3 and the sleeve ll take up substantial space radially of the pin and the pin ends themselves must be substantially weaker than the middle portion.

The radical piston load of the rotary pistons will be transmitted during each revolution to the reactance shoulders of I l and I in form of a sharp shock-load, since the time element of one pressure stroke is very small. Assuming conventional pump speeds of 1200-1800 R. P. M.s, the entire compression stroke will take ,/20 /3o of a second. The shock itself has much shorter duration however, even at the special V-notch pintle port construction, which is directed to absorb shock by the V-notch port openings. Considering the duration of the shock itself, it is a mere fraction only of the entire pressure stroke.

To absorb the above destructive shock, and yet to apply anti-friction elongated roller bearings for load and primary torque transmission, I submerge the entire roller bearings 13 in the above specifically described oil bath, so that at least at higher pressure when the pressure slip maintains the bath, continuously during pressure cycles, the rollers will be submerged in oil. At lower pressures the centrifugal force retains the oil bath in the drum, and therefore it may be said that the thrust roller bearings of the pistons are submerged in an oilbath during substantial periods of all working cycles.

The tenacious oilfilm surrounding the closely disposed but freely rotating needle rollers in such a manner that each bearing will have a high load carrying capacity combined with shock absorbing quality. In addition, the rolling frictional engagement between cylinder block 2 and reactance ring 14-45, in case of hydraulic motors will behave consistently with respect to starting torque under variable temperature conditions of the oil, when the variation of viscosity causes serious variations in starting torques of conventional motors, applying sliding oil film bearings as thrust means at the outer ends of the pistons.

. Since in case of deflection of the cross pins I!) under heavy loads, the cageless elongated rollers trend to skew considerably and move axially against the snap rings l2-l2, in Figs. '7 and 8 I make a primary shoulder as at 02) to withhold the needles and a secondary shoulder as at [0a to withhold the snap ring i2. Under all conditions, the elastic deflections of the pin ends Illa-40c must be prevented, to eliminate destructive skewing of the rollers. I accomplished the above objectives by providing heavier portions in the middle than at the ends of the pins, and additionally by pressfitting the pins H) in the piston heads 9 so that deflections really start, where the enlarged middle portion ends and the pin ends begin. This connection of the small ends with the enlarged center portions must be additionally relieved from shearing stresses by a radius as shown at [0d, which radius further facilitates the elimination of the skewing of the roller bearings, by keeping the pin ends straight and permitting the concentration of bending forces to the radius itself. The ends [2a of the snap rings l2 do not touch each other so that it may be freely expanded or contracted for its insertion into the complementary groove of the pin ends.

The elongated rollers are disposed with a capillary circumferential clearance with respect to each other in the bearing assembly, so that once the bearing is lubricated, capillarity will hold the lubricant in the bearing, for long periods of times, some times for the entire life of the machine. This is important after transportation or shut down of the pumps, when ordinarily the lubrication is stopped or destroyed, so that during the next full load operation the bearings would wear or burn out rapidly, before the necessary lubrication is supplied.

The embodiments of Fig. 3 to Fig. 6, Fig. 10 and Fig. 12 show a modification of the invention, wherein for radial space limitation neither the roller sleeves Il|l nor the liquid tight drum construction as at l4-I5 can be used. In this instant, the rollers l3 are disposed in the piston head 9 itself and the snap rings are disposed in such a manner that one ring 12 prevents the movement of the pin in one direction while the other ring l2 prevents the movement of the pin in the opposite direction, by being pushed against one or the other recess 9c9c, employed in the lateral faces of the head 9. The outside diameter of the recess is greater than the diameter of the bore of the crosshead, so that the snap rings 12 may be inserted into the grooves of the pin I0, by spreading the ring slightly under its elastic tension. For this purpose the inner inside edges of the snap rings are chamfered at about 30 to start them up easily on the pin ends I00. The arrangement is such that the outer faces of the rings and the transverse faces of the piston crossheads will be flush with each other and lie in the same plane. This will facilitate the guiding of the piston and its head between the opposed plain faces of the reactance rings 33 and 34 of Fig. 3, thereby effecting a relative rotation for the pin l0 parallel not only with the axis of pintle I, but also about its own axis and in such a manner, that this axis will remain parallel with itself and with the main axis of rotation of the pump in all adjusted stroke position of the pump.

It is important that by this guided arrange- .ment of the piston head, during the absolute and relative rotation of each crosshead pin, skewing of the pin itself as well as skewing of the individual elongated rollers will be limited to a practical minimum.

In this solution it is further of utmost importance to keep the pins in parallel with the axis of the pintle and evenly distribute the load on each end of each pin, because in case of transverse misalignment of the pins, one or the other ends of the needle rollers will be pinched between the pin and the bearing bore, with consequent result of vehement skewing of the needles.

; In my U. S. Patents 2,101,829 and 2,111,657 the accuses:

51.. roller bearings are disposed inzth'e. samemanner: as in Fig. 3. to Fig; of this application, with. the exception that inthe said patents the roller bearings are retained by. end rollers: rigidly secured to the: pin ends.

In my co-pendi'ng: application Ser. No. 716,451, filed March 20, 1934, now Patent 2,166,717 granted July 8, 1939 the roller bearings are disposed also in a similar manner, with the exception, that the pins andthe pistons do not form. a self contained sub-assembly, therefore in case of a disassembly or assembly of the pump, the needles may fall out with. the pins from the crossheads, and get lost or it' takes. additional time for their reassembly. It will be noted; that the solution of Figs. 4, 5- and Fig. 12 affords av stronger pin, but itis. necessary in this. case, since the elastic deflection of each pin now will be proportional to the entire working length of' the pin, while in case Figs. 7', 8; and llthedeformation extends only to the short stub. ends. of the walled-in pins.

In case of the latter solution, as shownv in Figs. 4, 5 and 12, the deflection is the greatest in. the middle, just where the roller bearings are, but here the rigid head bore comes to reduce the deflection. At the same time the curvature of the pin'ends at Hie-40c will not matter much. In both instances I obtained a compactness in combination with a self contained piston-thrust mechanism, for high speed, high pressure and consistent. torque performance of the. motor which was unknown heretofore. Additionally, the arrangement issuch, that capillary oilfilm lubrication and accompanying shock-absorbing qualities of the thrust roller bearings are assured at all speed and operating pressures.

These shock-absorbing qualities will be appreciated in view of the well known facts, that ordinary widely spaced roller bearings dig into the race tracks-at short strokes and high pressures.

In variable pitch propellers, the thrust bearings dig in deeply into the race, while the pro-- peller pitch remains constant, unless there are used 5 to 6 sets of thrust bearings, This galling phenomenon of molecular affinity, which exists between point contacts of widely spaced rollers and steel races,- prevented heretofore successful application of anti-friction elements-at thethrust transmitting ends of the pistons in high pres-- sure pumps and motors, and limited the safe maximum pressure in variable displacement pumps and motors. It must be borne in mind that the utility of motors-is particularly bound to good starting torque and eflicient running torque characteristics which from the other hand is identical with successful application of antifriction thrust transmission at the pins Iii, or pin endsliic.

Figs. 3 and 10 show particularly such an efiicient thrust transmitting arrangement for hydraulic pumps and motors. It is now well illustrated in Fig. 10 that rotary crosspins l0 and rotary reactance groove-ways formed between innerand outerreaetancehalves-2222 and 3334 form an efficient rolling device which is capable for high speed and heavy rolling load transmission. Such arolling device is'not only-capable of performingaccording to up-to-date standards, but due to the reduced masses of the straight cylindrical rolling pins it they introduce new avenues in pump design with their reduced size, weight and reciprocating" inertia. These new features and'their usefulnessis further enhanced by the ability of'the' light retainer means; such as 12-12 as: in Fig. 12,. to keep the. pins centered.

radial walls-of reactance halves 33 and 34. It

will be seen that the possibility of the maintenance of this free space at the pin-ends, and the elimination of the scraping action between the sidewallsof the reactance and the pin-ends is greatly dependent on the effective cooperation of retainer means 2l:2. Also the effective end retention of needle rollers. and the reduction of their tendency to skew is greatly accomplished b-ythe same retainer rings I2-l-2.

Fig. 10 shows the piston and reactance assemblies in neutral position, therefore the circumferential spacing-of pin-ends lilo-I00 in the grooveways is uniform. During operation this spacing however changes, and it will be appreciated that the tendency of the pin-ends Illcl0c to skew will be greatly minimized if the pins will be centralized with respect to the center lines of the pistons; the end scraping of the side walls.

of the reactance 33-34 will be eliminated by the guiding and retaining means I2--I2. In accordance with the spirit of the invention, in high speed machinery astraight crosspin I is used having intermediate bearing portion as at it in Fig. 12, and the endportions l0cliic, hardened and ground to assume the role of antifriction bearing rollers, while the side. portion iitwill assume the role of an inner race or shaft of an anti-friction rollerv bearing. The smaller the diameter.ofthecrosspin it andthe associated bearing. structure, such as Hie-I3 and. 9b, the better will this thrust transmitting. structure approach the ideal. conditions, the conditions ofa precision,anti-friction, high speed roller hearing.

In the. above described invention this galling iseliminated by bath and capillary lubrication, combined with centrifugal pressure lubrication. Additionally the elongated roller bearings, although they do operate asroller bearings in metal to metal rolling contact with the thrust rollers, are enveloped. at all times with full oil film, and even without the bath, are able to operate efiiciently, under heavy loads. Good lubrication eliminates redrawing of the hardness of the needles, pins andraces, and reduces wear to a commercial minimum.

To this effect, reactance halves 33 and 34 are covered with sheet metal shell as at 35 to retain slip fluid inall inter spaces of the reactance assembly includingrthe cylinder barrel and piston assemblies. Even when rotation stops, the lower half. of the fluid tightreactanceretains sufiicient fluid. to supply good. lubrication again, upon the.

restarting of the pump, when the retained fluid will be spreadout over all of the enclosed parts within. the halvesv 2324 and the oil retainer shell 35 respectively.

The pump is enclosed in a cylindrical housing, comprising a body portion 29 and two end plates as at 39 and 35 in a conventional manner. A reactance ring [9, stationarily mounts bearing supports 2'T2'i and associated ball bearings l'i'-- [Tin a well known manner. Finally these bearings will rotatabl'y support the reactance halves 33-34'and' the entire reactance thrust assembly in the stationary reactance i9 during all' adjusted position of the stationary reactance ring in the housing. It remains an outstanding featureof my invention, that the stationary react ance l 9is supported throughout its entire length in the main body 29 of the pump, to thereby distribute the reactance load on a large area and in the zone of the working reaction of the pistons.

Pintle l, barrel 2 and impeller shaft 3 are arranged in a conventional manner. A key element 4 engages the shaft 3 and the barrel 2 for joint rotation.

Snap rings 26 and 28 retain the bearings l7 and the bearing rings 21 in their proper assembly against transverse forces such as the axially floating adjustment of the barrel and reactance assembly, by means of the impeller shaft. Cap screws 32 secure the end plates to the body so that the pintle I may be secured and supported at one end in one of the end plates while the drive shaft 3 and the adjoining end of the pintle be indirectly supported in the other of the end plates.

Various changes may be made in the embodiment of this invention, without departing from or sacrificing the advantages as hereinabove specifically described and claimed in the appended claims.

I claim:

1. In a rotary radial piston pump or motor, a rotor; radial cylinders and cooperating pistons carried thereby; operating head portions on the pistons respectively and having radially disposed side faces; each of said head portions having a bore extending parallel to the axis of the rotor; a plurality of thrust pins one received in each bore and protruding therefrom at each end; elongated roller bearings intervening between each thrust pin and the associated bore wall; reactance means surrounding said cylinders and including imier and outer trackways on opposite sides of the piston head portions, said reactance means comprising axially separable side members respectively providing said radially extending portions and said outer trackways, a pair of intervening ring members between said side members on opposite sides of the pistons and cylinders and providing the inner trackways, and means for securing said inner and outer trackways in assembled relation; the protruding ends of the thrust pins bein adapted for rolling engagement with the inner and outer trackways, and lying respectively between the side faces of the reactance side members, means to maintain operative relation between said roller bearings and said pins in the bores of said head portions respectively, each piston and associated pin and roller bearing assembly forming a unitary piston-roller structure, said means comprising snap rings lying in face to face relation to the ends of the associated bores and being of greater diameter than said bores for retaining the elongated roller bearings and the thrust pins in operative position with the pistons and piston heads re spectively, said pin ends being grooved to receive said snap rings and hold them against axial movement.

2. In a rotary radial piston pump or motor, a rotor; radial cylinders and cooperating pistons carried thereby; operating head portions on the pistons respectively and having radially disposed side faces; each of said head portions having a bore extending parallel to the axis of the rotor; a plurality of thrust pins one received in each bore and protruding therefrom at each end; elongated roller bearings intervening between each thrust pin and the associated bore wall; reactance means surrounding said cylinders and including inner and outer trackways on opposite sides of the piston head portions, said reactance means comprising axially separable side members respectively providing said radially extending portions and said outer trackways, a pair of intervening ring members between said side members on opposite sides of the pistons and cylinders and providing the inner trackways, and means for securing said inner and outer trackways in assembled relation; the protruding ends of the thrust pins being adapted for rolling engagement with the inner and outer trackways, and lying respectively between the side faces of the reactance side members, means to maintain operative relation between said roller bearings and said pins in the bores of said head portions respectively, each piston and associated pin and roller bearing assembly forming a unitary piston-roller structure, said means including a pair of removable snap rings, a re-' cess in each protruding end of the thrust pins to engage said snap rings, the outer diameter of said ring being larger than the bore of the head portions to engage the lateral faces of said head portion, and thereby retain said pin and said head portion in a unitary piston roller structure, said pins having substantially the same diameter throughout their entire length.

3. In a rotary radial piston pump or motor, a rotor; radial cylinders and cooperating pistons carried thereby; operating head portions on the pistons respectively and having radially disposed side faces; each of said head portions having a bore extending parallel to the axis of the rotor; a plurality of thrust pins one received in each bore and protruding therefrom at each end; elongated roller bearings intervening between each thrust pin and the associated bore wall; reactance means surrounding said cylinders and including inner and outer trackways on opposite sides of the piston head portions, said reactance means comprising axially separable side members respectively providing said radially extending portions and said outer trackways, a pair of intervening ring members between said side members on opposite sides of the pistons and cylinders and providing the inner trackways, and means for securing said inner and outer trackways in assembled relation; the protruding ends of the thrust pins being adapted for rolling engagement with the inner and outer trackways, and lying respectively between the side faces of the reactance side members, means to maintain operative relation between said roller bearings and said pins in the bores of said head portions respectively, each piston and associated pin and roller bearing assembly forming a unitary piston-roller structure, said means lying in face to face relation to the ends of the associated bores and being of greater diameter than said bores, for retaining the elongated roller bearings and the thrust pins in operative position with the pistons and piston heads respectively, and including a pair of circular recesses in the end portions of the pin, a snap ring having radially disposed walls and adaptable in said recess, a complementary recess in the radial faces of the head portion adjoining the bore, the lateral depth of said recess being equal to the thickness of said ring, said circular recess of the pin engaging the inner portion, said outer recess of the head the outer portion of the radial walls of said snap ring, the diameter of said outer recess being greater than the diameter of the ring to acconn'nodate the insertion of said ring into the inner recess of the pin during assembly.

4. In a rotary radial piston pump or motor, a rotor; radial cylinders and cooperating pistons carried thereby; operating head portions on the pistons respectively and having radially disposed side faces; each of said head portions having a bore extending parallel to the axis of the rotor; a plurality of thrust pins one received in each bore and protruding therefrom at each end; elongated roller bearings intervening between each thrust pin and the associated bore wall; means to maintain operative relation be tween said roller bearings and said pins in the bores of said head portions respectively, each piston and associated pin and roller bearing assembly forming a unitary piston-roller structure, said means comprising snap rings lying in face to face relation to the ends of the associated bores and being of greater diameter than said bores for retaining the elongated roller bearings and the thrust pins in operative position with the pistons and piston heads respectively, said pin ends being grooved to receive said snap rings and hold them against axial movement.

5. In a rotary radial piston pump or motor, a rotor; radial cylinders and cooperating pistons carried thereby; operating head portions on the pistons respectively and having radially disposed side faces; each of said head portions having a bore extending parallel to the axis of the rotor; a plurality of thrust pins one pressfitted in each bore and protruding therefrom at each end; elongated roller bearings intervening between each thrust pin and the associated bore wall; means to maintain operative relation between said roller bearings and said pins in the bores of said head portions respectively, each piston and associated pin and roller bearing assembly forming a unitary piston-roller structure, said means comprising snap rings lying in face to face relation to the ends of the associated bores and being of greater diameter than said bores for retaining the elongated roller bearings and the thrust pins in operative position with the pistons and piston heads respectively, said pin ends being grooved to receive said snap rings and hold them against axial movement.

6. In a rotary radial piston pump or motor, a barrel having radial cylinders therein, valve means for the cylinders, pistons in the cylinders respectively, heads on the pistons respectively, a transverse bore in each head, a rotary reactance surrounding the barrel in eccentric relation thereto and having radial side walls and normally aligned circular trackways respectively lying alongside the heads of the pistons, load transmitting rollers rotatably mounted at their center portion in the bores of the heads and having end portions in load transmitting rolling engagement with the trackways of said reactance, and retainer means carried by said center portions of the rollers and engaged by the end of said bores to retain said center portion in operative position in said bore.

7. In a rotary radial piston pump or motor,

a barrel having radial cylinders therein, valve means for the cylinders, pistons in the cylinders respectively, heads on the pistons respectively, a transverse bore in each head, a rotary reactance surrounding the barrel in eccentric relation thereto and having radial side walls and normally aligned circular trackways respectively lying alongside the heads of the pistons, load transmitting rollers rotatably mounted at their center portion in the bores of the heads and having end portions in load transmitting rolling engagement with the traclnways of said reactance, and retainer means carried by said center portions of the rollers and engaged by the end of said bores to retain said center portion in operative position in said bore, said retainer means being arranged in paired assemblies at opposite ends of the center portions of said rollers.

8. In a rotary radial piston pump or motor, a barrel having radial cylinders therein, (valve means for the cylinders, pistons in the cylinders respectively, heads on the pistons respectively, a transverse bore in each head, a rotary reactance surrounding the barrel in eccentric relation thereto and having radial side Walls and normally aligned circular trackways respectively lying alongside the heads of the pistons, load transmitting rollers rotatably mounted at their center portion in the bores of the heads and having end portions in load transmitting rolling engagement with the trackways of said reactance, and retainer means carried by said center portions of the rollers and engaged by the end of said bores to retain said center portion in operative position in said bore, said retainer means being arranged -in paired assemblies at op;- posite ends of the center portions of said rollers, each of said retainer means including a rollergroove and a retainer ring, the outside diameter of said ring being greater than the diameter of said bore, the inside diameter of said ring being smaller than the diameter of said roller.

ELEK K. BENEDEK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,041,172 Ernst May 19, 1936 2,074,202 Benedek Mar. 16, 1937 2,097,830 Benedek Nov. 2, 1937 2,101,730 Benedek Dec. 7, 1937 2,101,829 Benedek Dec. 7, 1937 2,103,313 Benedek Dec. 28, 1937 2,103,314 Benedek Dec. 28, 1937 2,111,657 Benedek Mar. 22, 1938 2,115,296 Benedek Apr. 26, 1938 2,159,244 Benedek May 23, 1939 2,166,717 Benedek July 8, 1939 2,189,773 Benedek Feb. 13, 1940 2,215,134 Rehnberg Sept. 17, 1940 2,248,738 Benedek July 8, 1941 2,250,147 Benedek July 22, 1941 Benedek Sept. 16, 1941

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