US2353917A - Axial piston pump - Google Patents

Description

' 'UNITED Patented July 18, 1944 v AXIAL PISTQN y Hans'Molly, Berlin-Tempelhof,` Germany; vested e in the alien Property custodian 1:

1 f VApplication August 1o, 1940; serial No.' 352,146 f i In. Germany Augustll; 1939." v v Y scams. (otros-7162,),

The inventionl relates to axial piston pumps ywithl adjustable stroke.` A knownform'of priessure regulation i and pressure restrictionA in' such pumps consists in a pumpfpressureresponsive element, for instance a piston automatically adjusting the stroke adjusting member vin the sense of a stroke reduction as soon as a certain pressure is being exceeded; In such axial piston pumps two forces which balance one another are asta rule brought to bear upon the stroke adjusting member, namely an external force urging the stroke adjusting4 member towards vits maximum :stroke position and a force exerted by the pressure control element tending to return said member to the zero position.` Thusagcertainpump pressure'will always be automatically produced corresponding tothe respective amount o f the external force. Such devices are usedforinstance forldriving hydraulic machine tools, retracting devices for flandinggear or the like, i; e..in all cases where a for pressure restrictionltherefare, however, quite a number of cases in which `it'rnay `bedesirable forthe pump to possess predetermined pressure characteristici f' The invention isI based fon the perception that itis possible to introduce1an'essentialsimplifica-'V tion in the 'constructionof` pressureregulating devices inaxial piston 'pumps'in y ivh'icl'i the cylinder block carrier is i'swingablyfrnounted with; Va view to stroke adjustment.v :Instead o'f'ashitherto providing in the pressure conduit'A ofr the pump a special element A(cylinder with piston) @acting on'the stroke adjusting member, thefrequisite regulatingy forces mayfaccording Vto the invention be produced in the cylinder block carrier" itself.

This maybe done in such away that-adspercial pressure cylinder withl piston is` arranged invthe cylinder Iblock carrier, said piston kbeingheld ink a ilxe'd Support. In such an arrangement the pressure responsive regulating element moves with the Y:

cylinderv block, and special conduits i and lever systems may be dispensed with. It is Amerely necessary to provide the regulating A-cylinder with a short channel leadingto the contacting part/.of

the control surface. This ldirect connection of; the

regulating cylinder andthe .pressure duct yofthe control surface, beside its obvious, advantages, possesses theadditional advantage that the pump pressure is produced in the regulating cylinder f-.dri/vingfflange 2 whichis:support edin the nous 'without retardation-andthe regulation 'thus operates' free froinan'y pendulous tendency. lA particularly advantageous Varrangement, Yconsists in=the cylinder block` carrier being made swingableabo'ut anfexcentri'c axisfin such man- Vner thatthe pressure produced .in the'pump cylinders acts upon the cylinder blocl:4 carrier? in the sense of a stroke reduction. In such cases the pressure in theworking cylinder itself'is thus usedfor regulatinglwith the result that-special Yregulation devices are not required;v Hence pressure regulation isfachievedwithout anyspecial constructional-elements being necessary* The invention is 'deflnedin greaterdetail inthe following with reference to certain embodiments.

vinthe drawing: I i -.Fig. 1 is a longitudinal lsectional view showing the embodiment of yan axial piston pump in which the regulating force is produced by` av special cylinder with piston, and.y i

Fig. 2 is a similar view vo1' another such pump in .which the regulating-forcev is obtained by means of the cylinder block carrierwhichlisvswingable about an excentric axis; I -,Fig. 2a vis a diagramrand.. p

: Fig. 3y is Za longitudinal sectional viewsimilartto Fig. 2 except that the cylinder block is diilerently connected to thel driving -ilanga/ In al1-l figures the same reference characters designate identical parts.

1 the numeral I denotes theaxispi the ing 3 in ball bearings 5 andi. i Piston rods-are tarticulatelyconnected with the driving ilange 2, said piston rods 6 imparting to pistons 8,*.slidably `arrangedgin a cylinder .block 7.. a reciprocating motion' provided. lthe axis of.me'agun'ier` block 1 Ais deflectedrelative.v to thatof thedriving flange 2. In" the.` embodiment shown the pistons '6k vserve to imparta follow-up movement to Vthe .cylinder block lby means'of the pistons which is `not however an essential feature of t he invention. The cylinderblock 'Iv is rotatably supported in a cylinder lblock carrier 9, the latter being swingable about an axis I0. The plane control surface I I of thecylinder block "I, is yconnected on the onejhand to theflexible pipe conduitfl2 by means of refspective control orifices, said'conduit lI2`1ezatdingt'o a consumption apparatus(not`shown),-a`s for instance a pressure fluid 'motor-'Land is onfthe :which isfinturn supported against' a-ilx'edt stop -I5.--Thus afforce'acts upon the cylinder 4block carrier 9 which in dependence on the pump pressure produced actson said carrier in the sense ci' a strokeexecution. The action of the plunger I4 in response to the pressure vin ,cylinder I9 is resisted by a spring =I9 of a definite value acting upon the cylinder block carrier 9 at the point I1 and at a fixed point I8.

The pump operates as follows: The pressure set up in the conduit I2 by a certain pressure medium consumption by the piston I4 sliding in the cylinder I3 produces a force whichtends to deflect the cylinder block carrier into its zero position, as of course this piston is supported against a fixed point. This force is counteracted by an external force produced by the spring I6 tending to deflect the cylinder block carrier 9 towards its maximum stroke position. The two forces balance one another so that a ypressure may occur in the conduit Il' in dependence on the spring tension. The special piston I4 of Fig. l may be dispensed with if as shown in Fig. 2-the cylinder block carrier 9 is not arranged concentrically about an axis I9 but is swingable about an excentric axis I9. In the latter case the pressure produced in the pump cylinder acts on the cylinder block carrier 9 in the sense of a stroke reduction. Thisembodiment further differs from that of Fig. l in that the control surface is not plane ybut--as previously proposed elsewhere-has the form of a `sphere 20, in which case the support -axially guiding the cylinder block is dispensed with. Naturally, however, it is equally Vpossible to provide for a plane control surface. In any case it is, nevertheless, necessary that the cylinder block carrier 9 be articulately connected `with the driving flange 2 by means of a` special cen tering member 2I in a ball on said driving flange. In this way the supportof the cylinder block is free from static determination. This kind of support allows compensation for displacements due to conditions in the course of movement. f.'

the cylinder block carrier 9 is swingable around an excentric axis I9, this type of support is particularly important in -so far `as the position of the point of intersection of the cylinder block axis and the driving fiange axis is always precisely determined by the concentric guiding member '2I, and the slight motions caused'by the excentric position of the cylinder block carrier 9 relative to the cylinder block I due to the stroke adjustment are received by the control surface withoutdisturbing effects.

The centering member 2I is acted upon by the tension of a spring 22 ensuring constant contacting of the cylinder block I with the control surface 20. In this connection it is advantageous to have the spring 22 simultaneously act on a check valve 24 connected with the high pressure side of a pump by means of a duct 25 and thus exert a dampening effect on the reversing motion of the cylinder block 1.

As shown in Fig. 2a, the excentric pivot point I9 of the cylinder block carrier 9 lies in the normal N to the bisectrix W of the largest angle that is possible between the axis of rotation U and the cylinder block carrier axis V, because this normal N is the geometrical point for all circle centers touching the axis of rotation U and the cylinder block carrier axis V and because vin this position the smallest possible deviation of the axial intersection point from the desired intersection point is afforded with the result'that the 1l vplane ycontrol surface II.

vinder block by means of a piston 29.

above described sliding vmotion of the cylinder block 9 on the control surface 20 at stroke adjustments is reduced to the smallest possible amounts.

The embodiment acocrding to Fig. 3 is similar to that shown in Fig. 2, possesses an excentric support I9 of the cylinder block carrier 9 and a In distinction from the embodiments beforementioned the cylinder block 'I does not however follow the movement of the piston rods 6 .by means of the pistons B, a double cardan joint 25, 28 being provided for causing the follow-up movement by a member 28, which is non-rotatably mounted in the cyl- A double cardan joint is `required because, as mentioned above, the cylinderblock 1, during a stroke adjustment, undergoes slight displacements due to the excentric support at I9. As in contrast to Fig. 2 the cylinder block is not supported between two spherical surfaces, it is necessary to guide the plane control surface by means of a special centering member 21.

The invention is not restricted to the embodiments described, there being further possibilities of construction by suitable combination of the details described above with other known features.

What is claimed is:

1. In a hydraulic pump of the piston type, a cylinder block .formed with a plurality of cylinder bores, means for supporting said block for rotation about its axis, pistons in said bores, a driving ange mounted for rotation about its axis, mounting means for said flange, a centering ball concentrically connecting said block and said flange, the vcenter of said ball lying on both of said axes. piston rods operatively connecting said pistons and said ange, said pistons and said bores being so related as to cause said block and said ilange to rotate in synchronism, said supporting means for said block being pivotally connected with said mounting means for said flange to allow relative inclination of said axes to cause variations of the stroke of the pump in :response to variations of inclination of one of said axes relative to the other axis, the axis oi' the pivotal connection of said supporting means and said mounting means being spaced from said center of said ball and the axis of said driving iiange -to produce a lever arm which is subjeoted to the force exerted by said pistons when there is relative .inclination of the axes, to decrease the inclination and consequently the stroke of the pump, such force corresponding tothe fluid pressure of the pump, and resilient means for causing relative inclination of the axes by exerting a force to increase the relative inclination ofthe axesand consequently the stroke of the pump.

2. `In a hydraulic -pump of the piston type as claimed in claim 1, said centering ball being connected to a piston slidably mounted in a central bore of said cylinder block and provided with spring means for urging the end face of the block against its supporting means.

3. In a hydraulic pump of 'the piston type as claimed in claim 1, said centering ball being connected to a piston slidably mounted in a centering bore of said cylinder block, and said bore kcommunicating with the pressure side of the pump yby a check valve so as to `dampen the reversing motion of said cylinder block from its deflected position.

HANS MOLLY.

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