US2818707A - Rotary pump and motor hydraulic transmission - Google Patents

Description

ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION Original Filed Oct. 9, 195D E. STURM 2 Sheets-Sheet 1 Jan. 7, 1958 lhven for:

A Harney E. STURM Jan. 7, 1958 2,818,707

ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION Original Filed Ost. 9. 1950 2 Sheets-Sheet 2 .Inventar United States Patent() ROTARY PUMP AND MOTOR' HYDRAULIC TRANSMISSION Erwin Sturm, Boll, near Goppingen,Germany Original' application October 9, 1950, Serial No. 189,207,

nowf Patent No. 2,750,895, dated June 19, 1956.l Di- ;gletzlszind this applicationy Aprilj 24, 1956, Serial No.

2 Claims. (Cl. 60?-53) The present invention is a division of my co-pending application Serial No. 189,207, tiled' October 9, 1950, now Patent No. 2,750,895, dated June'19, 1956.

This invention relates to a rotary pump and7 motor hydraulic transmission, in which the vane drums of both the pump and the motor, including the vanes, are enclosed by freely rotatable casings, which are eccentrically adjustable relative to said drums and which de'ne the working chambers of the pump and the motor. By this known arrangement the friction between said rotary casing on the one hand and the vanes on the other isrestrict'- edi to a limited motion which is due tothe eccentricity between the rotary casing and the vane drum. Therefore, frictional losses are extremely small.

The rotary casing makes it possible to use higher pressures of the driving medium. However, this important' advantage has been limited by the fact that the guide shaft or distributor shaft connecting' the workingchambers of the pump and the motor, was capablewithin' certain limits only to absorb higher pressures ofthe driving medium, since it was found that the rotary vane drum after a certain period of time would seize the distributor shaft and thus become immobilized' thereto.

It is an object of this invention tolprevent the rotatable vane drum from seizing the stationary distributor shaft and to decrease the wearing of -the pivots ofthe distributor shaft in suchV a manner that' it-v remainswithin permissible deviation.

A further object of the invention is to prevent admission ofair through the suction passage of the distributor shaft into the workingy chambers of` pump and' motor with the result, that higher pressures' may. befusedf and the outputmay be increased.

The-inventor has discovered' thatv the rigid*y attachment of the: -distributor shaft withiny the machine housing as proposed in his U. S.. A'. Patent' 2,049,092v of Iuly 28, 1936, andwhich has been customary practicef'orfseveral decades, introduces said serious drawbacks and he has found that according to his invention said: drawbacks can be eliminated and further advantages are attainable by az pump.- and' motor hydraulic drive, in` whichJ the vane drums of both the pump, andthe motor aref enclosed by: freely rotatable casings which are eccentrically. adjusta'ble'relativev to said drums incombination' with adis'.- tributorl shaft, which connects by transferu passagesthere'- in the working chambers of the pump and motor andA is supported in the hubs of the vane drums'without xed connection with the outer'housing and soibeing adapted to' follow movements of the vanedrums. Saiddistributor shaft is also provided with at least one projection; which is' in .loose contact with the machine housing to prevent the rotation of the distributor shaft but" to' give it' limited movement relative to the machine-housing,

n An object of they present invention is to overcome above mentioned disadvantages of hydraulic drives in a satisfactory manner.

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Other objects and structural details ofthe invention will be apparent from the following description when read in.- conjunction with the accompanying' drawings forming part of this specification, wherein:

Fig. l is a vertical sectional view of a hydraulic drive according to. the invention,taken on line I-I of Fig. 2;

Figi 2 is a sectional view of the hydraulic device, taken on line Il ll of Fig. l;

Fig.' 3 is a sectional view of the hydraulic drive, taken on line III-III of Fig. 1;

Fig.y 4 shows the left portionof the movable mounted distributor shaft and its radialV displacement caused' by thebearing play ofthe ball bearings of the vane'drums.

.Referring now to the drawings, the housing of the hydraulic drive comprises a lower portion 1 and an upper portion' 2 connected with each other by a plurality Another object of the present invention isto improve v I l tricall'y t'o-the-main-- axis of the drive; the threadedI end of otr the artv of rotary machines asl now ordinarily made:

of'bolts 3. As best show-n in Fig. 3,v the line of separation between said two portions 1 and 2 of the housing is in' the same horizontal plane as the main longitudinal axis'of the drive. As best shown in Fig. l, the hydraulic drive has two equal component parts, one` of which is employed. as. a pump, the other as a motor. These component partsiare connected with each other, in a manner well known,` by conduits extending throughy the guide or Adistributor shaft 4 andv connecting the working chambers of the pump andthe motor. Each component part includes a vanedrum, the hub 5 of which encircles the .associated end or bearing portion of the guide shaft 4; each vane drum is rotatably mounted inthe housing 1, 2 by means of ball bearings 6. The inner ball bearings 6 are engaged withV semicircular lugsA 1' and 2' arranged on the lower and upper portions 1y and 2 respectively of' the housing.. The input-or output-stud 7 is` connected. with the hub 5l by a pin or the like in ak manner known per se. The wheel-like portion 8 of the vane drum receives the vanes 9 in a manner known per se.- According to the embodiment shown in the drawings, the vane drum of each component part isv providedwith seven vanes- 9. A casing comprising two front covers 10` and` a jacketv 11 rigidlyV connected with eachother by bolts` 124 enclose Athe vane drumy and the vanes arranged therein. A ballv bearing 13 or 14, respectively, is arranged between eachvfront cover 10 of theY casing.Y and a support 15` The inner races of said ball. bearings l13: and 14'` snugly tit on the hubs of the casing 10, 11, while thelouterraces of said. ball bearings snugly tit intol the recesses of the support 15. Said support 15 is provided with two' journals 16 and 17 (see Fig. 2), inserted into aperturesv of the housing` closed` by covers 18 and 19; Furthermore, as. best shown inFig. 1, the outer surfaces of the covers 10 of the rotary casing 10, 11 beyondtheir contact with the inner races of the ball bearings 13, 1'4 are of conical shape, while the inner surfaces of the support 15 are in a plane perpendicular to the longitudinal.' axis ofthe vane drum, whereby spaces increasing in width towards the circumference of the casing 10,11 are formed between the covers 10 and the inner walls ofy the support 1'5.. Therefore, the support 15 being slidably mounted in the housing 1 2 by the journals 1'6, 1'7v (Fig. 2) may perform. oscillations in the direction of the double arrow X (see Fig. 1) about an axis of rotation determined by the line of intersection between the' horizontal center plane located inthe axis of the vaine` drum and' a vertical center planelocated centrally with reference to the' ends of the vane drum.

The support 15 ofthe casing 10, 11 comprises two symmetrical halves 20 and 21 connected with each other by set. pins 22 and bolts 23. The cylindrical journals' 16 and 17' are integral' with the associated support 1'5 ofthe casing 10, 1'1.

` To' adjust the support 15 of the casing 10, 11 eccen'- 19 and provided with a setting handle 24 is engaged with a threaded bore of the support 15. Thus, the support maybe `displaced by` a rotation of the handle 24 along anA axis of adjustment identical with the above described axis of rotation of the support.

The guide or distributor shaft 4 consists of a center piece 26 and cylindrical bearing portions 27 and v28, respectively, into which the center piece 26 continues axially at each of its sides, said center piece 26 is integral wlth. said bearings portions 27 and28. Said bearing portions of the distributor shaft 4 snugly fit into the bores of the hubs of the vane drums with a minimum of operating clearance, which secures a tight fitting without dlsturbmg the rotation of the vane drums. At least'one projecting` piece 29 carried by the center piece 26 passes through an aperture of the portion 2 of the housing 1,V 2 of the drive in loose contact therewith, whereby the distributor shaft 4 is prevented from rotation.

Check valves 29a projecting into the oil chamber arev arranged at the lower side of the center piece 26; one of sa1d check valves 29a is associated with the suction conduit, the other one is associated with the pressure con-l duit. In a similar manner two safety valves 29b are arranged at the upper side of said center piece 26, one of sald safety valves 29]; being associated with the suction conduit, the other one being associated with the pressure conduit. As the bearing portions 27 and 28 t into the bores of the hubs of the vane drums with the smallest play and the distributor shaft is not in any rigid connection with the housing, the distributor shaft may follow the radial movements of the vane drums caused by the bearing play of the ball bearings.

The projecting piece 29 communicates with the suction and pressure conduits 32 by means of bores 31 extending transversely through the center piece 26. To obtain a pressure relief, the bearing portions 27 and 28 of the shaft 4 are formed with arcuate shallow recesses 33 corresponding, with respect to area, to the openings of the suction and pressure conduits 32. In Fig. 1, it will be seen that each of the recesses 33 is connected with the opposlte conduit by a bore 35 whereby the pressure in the opposite conduit is led to the associated recess. This particular arrangement is a contributing factor in reducing to a minimum the friction between the shaft 4 and the vane drums.

It is well known, that ball bearings require a certain amount of operating clearance or play, which will increase in the course of time due to wear. For several decades it has `been'practice rigidly to connect the distributor shaft with the machine housing as shown especially 1n Figs. 1 and 4 of my earlier U. S. A. Patent No. 2,049,092 of July 28, 1936. That known arrangement has the drawback that the differences in the operating clearance of the ball bearings of the vane drums cannot egualize, therefore the operating clearance between the pivots of the distributor shaft and the bores in the hubs of the vane drums must be made wider than the minimum of clearance to obtain a tight fitting in said bores. 'Ihough it is admitted that the operating clearances amount to fractions of a millimeter only, the increased clearance is necessary to avoid a seizing of the distributor shaft, but is sufficiently great to permit air to enter into the suction sides of the working chamber and such to cause air to be entrained by the driving medium. The commingling of air with the driving medium causes both a reduction in eticiency and an increase in noise level.

This is the point at which the invention comes into its own, according to which the distributor shaft 4 is no longer rigidly mounted in the machine housing but is supported in the hubs of the vane drums with a minimum of operating clearance. It is evident, that by this arrangement the distributor shaft 4 and the two vane drums rotatably mounted upon their pivots 27 and 28 form a movable system, being only under the inuene o f the operating clearances of the ball bearings 6 by which the vane drums are supported. In said movable system the 1distributor shaft 4 is adapted to perform a radial displacement and a tilting movement as far as these movements are permitted by said operating clearances of the ball bearings 6. The distributor shaft is provided with at least one projection 29 in loose contact with the machine housing 2, whereby the distributor shaft 4 is prevented from rotation but is not prevented from following radial and tilting movements of said vane drums.

In order to explain the operation of the new arrangement, the Fig. 4 shows in a schematic manner the left portion of the distributor shaft 4, the adjacent hub 5 of the vane drum and the inner ball bearing 6 of the vane drum, whereby the upper balls of the ball bearing 6 are in a tipped up position in consequence of the operating clearance shown in exaggerated scale. Therefore,

ythe distributorshaft 4, which is no. more in a rigid connection with the machine housing, can follow the radial displacements b and slopes of the vane drums. Such a position of the distributor shaft is shown in Fig. 4 and marked by the angle a. Now the pivots 27 and 28 of the distributor shaft may snugly lit into the bores of the f' vaneV drums with` a minimum of operating clearance.

' distributor shaft has thus been eliminated, As a result it is now possible to use very high pressures of the driving medi-um. Only now can the full benefits be derived from the advantages afforded by the rotary casing. From this fact there will be appreciated the inherent relationship between the arrangement of an eccentrically adjustable freely rotatable casing enclosing the vane drums of both the pump and the motor of a hydraulic drive in combination with a distributor shaft which has transfer passages extending between the pump and the motor, whereby said distributor shaft is supported by the hubs of the vane drums, said distributor shaft being provided with at least one projection being in loose contact with the machine housing to prevent the rotation of the distributor shaft but to give it free for a movement relative to the machine housing.

Preferably, oil is used as driving medium for the hydraulic drive described above. The operation of hydraulic drives of this kind is known, so that a detailed description there of is unnecessary.

The construction, according to the invention may also be applied to drives equipped with pumps or motors with rotating pistons.

I claim:

1. A hydraulic drive comprising a housing, ball bearings mounted in the housing, a liquid pump and a liquid motor, said pump and motor each including a vane drum, a hub for each drum rotatably supported by the bearings, an axial bore in each hub, said hubs and bores being axially aligned, a casing surrounding each vane drum, a carrier supporting each casing for free rotation, means slidably mounting each carrier in the housing, each casing being adjustable eccentrically with respect to its vane drum by sliding movement of each carrier, each of said casings and its vane drum defining a working chamber, means forming alternate radial slots and passages in each vane drum, a vane slidably mounted in each of said radial slots, a distributor shaft closely tted into the bores of the hubs, said distributor shaft having longitudinal passages therein to establish communication between the working chambers of the pump and motor through the radial passages in said vane drums, and complementa! s means on the distributor shaft and housing preventing rotation of the shaft yet allowing the shaft to follow radial movements and tilting movements of the vane drums.

2. The hydraulic drive as dened in claim 1, wherein said complemental means includes a projection on the distributor shaft extending perpendicularly therefrom and of a length to project through an opening of greater perimetric area in the housing.

References Cited in the le of this patent UNITED STATES PATENTS

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