US3190224A

US3190224A - Hydraulic machines of the piston-operated type

Info

Publication number: US3190224A
Application number: US257997A
Authority: US
Inventors: Billington William Peter; Howson David Frank
Original assignee: Nat Res Dev
Current assignee: National Research Development Corp UK
Priority date: 1962-02-15
Filing date: 1963-02-12
Publication date: 1965-06-22
Anticipated expiration: 1982-06-22
Also published as: GB1029659A; DE1453593A1; FR1351688A

Description

HYDRAULIC MACHINES OF THE msmomorrsmmn TYPE Filed Feb. 12, 1963 June 1955 w. P. BILLINGTON ETAL 3 Sheets-Sheet 1 FIG. 4.

INvENToRS WILLIAM P. BILLINGTON DAVB F. HowaoN ATTORNEY J1me 1965 w. P. BILLINGTON ETAL 3,190,224

HYDRAULIC MACHINES OF THE PISTON-OPERATED TYPE Filed Feb.'12, 1963 3 Sheets-Sheet 2' 9 MN QM. VN oN MN QN mfi/ w w Q flwwlm -f x a a 3 O MW 3 o Wm M a a 3% 2 AW INVEN TOR 5 WILLIAM F. BILLINGTON DAwb F. HowsoN ATTORNEY June 965 w. PQBILLINGTON ETAL 3,190,224

HYDRAULIC MACHINES OF THE PISTON-OPERATED TYPE Filed Feb. 12, 1963 s Sheets-Sheet 5 '57 52 43 saif 3s 49 J9 o- 2' /5 53' :2 F16. 3. 4a- 45 48 27 I7 29 J3 J7 INVEN'TQRS WILLIAM PBILUNGTON DAVID F. Henson United States PatentfO 3,196,224 HYDRAULIC MACHINES OF THE PISTON- OPERATED TYPE 7 William Peter Billington, Flitwiclr, and David Frank Howson, Brickhill, England, assignors to National Research Development Corporation, London, England, a British corporation Filed Feb. 12, 1963, Ser. No. 257,997 Claims priority, application Great Britain, Feb. 15, 1962,

5,862/62 6 Claims. (Cl. 103-37) V This invention relates to hydraulic machines of the piston type, for example swashplate or eccentric-operated piston-type rotary motors or pumps, each cylinder of which is provided with an auxiliary piston arranged either to slide with'the main piston in the cylinder or to be locked against sliding movement in the cylinder, for the purpose of altering the swept volume of the machine to vary the speed or the delivery of the machine as the case may be. Thus for example in the case of a hydraulic motor, for low-speed high-torque operation the auxiliary piston slides with the main piston in the cylinder, but it remains fixed in the cylinder and thereby decreases the swept volume of the motor for high-speed operation with lowertorque at the same input of hydraulic fluid.

According to the present invention, in a hydraulic pump or motor of the type specified the means provided for selecting the auxiliary piston to remain stationary in the cylinder or to move with the main piston comprises hydraulic locking means associated with the auxiliary piston, the locking action of which means is performed not by a solid locking bolt but by the resultant thrust produced by incompressible. pressurised hydraulic fluid acting on one or more surfaces of the auxiliary piston.

The operation of the hydraulic locking means, may be controlled by mechanical means if desired, but in a preferred arrangement it is arranged to take place automatically in response to a variation of hydraulic pressure .in a hydraulic system connected to the machine.

For example, where themachine is incorporated in a hydraulic transmission system maintained at an elevated base pressure to reduce cavitation, the locking or release of the auxiliary piston by e hydraulic locking means may be selected in response to a change in the base pressure, sometimes referred to as the boost pressure.

. Hitherto, in such machines the. control of the auxiliary piston has been efiected by mechanical means by which the auxiliary piston is either positively locked by means of a mechanical latch or bolt to the main piston to slide therewith in the cylinder, or is similarly locked mechanically in the cylinder against movement with the main piston. Such mechanical controlmeans however is subject to variousgdisadvantages, including'the considerable mechanical shock introduced by the operation of the locking means.

In one arrangement of the present invention the auxiliary piston comprises a movable hydraulic valve shuttle member arranged to move in response to variatiouin the base pressure in the applied. hydraulici system between a position in whichitadmits the full working pressure of the system to one side of the auxiliary piston but shuts 1 ed the system pressure from the other side thereof, thereby hydraulicallylocking the auxiliary piston in an extreme position against movement in the cylinder, and a second position in which the system pressure is admitted in balance to both sides of the auxiliary piston to permit it to move with the main piston.: e

the bore of the sleeve. An alternative arrangement has been devised however, in which the sleeve comprises the main piston and is coupled to the input or output member of the machine, as the case may be, whilst the auxiliary piston comprises a free piston which slides in the bore of the sleeve. 7

The invention may be carried into practice in various ways, but two specific embodiments will now be described by way of example only with reference to the accompanying drawings, in which FIGURE 1 is a general view of a hydraulic motor, FIGURE 2 is a fragmentary sectional view of one cylinder of the motor of FIGURE 1 with the auxiliary piston sleeve hydraulically lockedgto the main cylinder, 7

FIGURE 3 is a view similar to FIGURE 2 but showing the auxiliary piston sleeve free to slide with the main piston, and

, FIGURE 4 is a view similar to FIGURE 2 of one cylinder of a modified embodiment of motor.

In the embodiment of FIGURES 1 to 3, a hydraulic motor generally. indicated at 10 comprises an annular housing 11 in which are formed a number of radiallyextending cylinders 12 each provided with itsassociated detachable cylinder head 13 secured by means of bolts orstudsld to the top of the associated projectingcylinder block 15. As seen in FIGURES l and 2 the annular housing 11'is formed with an external circumferential channel 16 in which the cylinder heads 13 and projecting cylinder blocks 15 lie. r t

The motor 10 has a corresponding number of pistons 17 each slidable radially in one of the cylinders 12 in the housing 11. The pistons 17 operate an eccentric 18 which is mounted on the main output shaft 19 of the motor in a central cylindrical recess 20 within the housing 11. The cylindrical eccentric 18 is mounted with its axis 21 radially displaced from the axis 22 of the output shaft. Each piston 17 is formed at its radially inner end with a part spherical bearing foot 23 which sits in acor- .respondingly formed bearing recess of a rocker: shoe 24, the, radially inner surface of each rocker shoe 24 being of part-cylindrical form and being in contact with abearing ring 25 coaxially journalled on the eccentric 18, so that reciprocating movement of the pistons 17 in the radial direction producesrotation of the eccentric 18 and ,ofthe "output shaft 19 about the axis 22 of the latter. The

rocker bearings, 23, 24 are lubricated by pressure fluid supplied from the interior of the cylinder via passages 26 formedin the piston '17. V

As shown in FIGURES. 2 and 3, each piston 17 is surrounded by a cylindrical sleeve 27, in the bore 28 of which sleeve the piston 17 is a close sliding fit. Each sleeve 27 ,is itself a close sliding lit in the associated cylinder 12 and thus constitutes an auxiliary piston. Each sleeve 27 has an iu-turned flange 29 at its radially outer end which. ex-

tends over the crown of ,the main piston=17 and acts as a stop, to limit relative sliding movement in one direction. The cylinder block 15 of each cylinder 12 is formed 'with a main inletpassage 30 which is connected to a source of hydraulic fluid under pressure via suitable porting or valvingtnot shown), ofconventional design. The assoe oiated cylinder head 13 is also forme'dwith a miain'inlet passage 31 aligned with the. passage 30, through which passage 31 hydraulic fluid under pressure is admitted to the interior of the cylinder 12 above the piston 17 through an extension tube 32 which projects radially inwardly into a recess 33 formed in the' crown of the piston '17. A movable valve sleeve 35'surrounds the extension tube 32 and is spring-lbiassed in a radially outward directionby a valve spring 36 acting between an external flange 37 on the inner end of'the tube 3 2 and an internal flange 38 formed in the ,bore of the valve sleeve, 35. The cylindricalbody 3-9 of the valve sleeve across the cylinder 12 at its upper end, and the outer part of the valve sleeve 35 outside the cover plate 40 is formed as a piston 41 which is a close sliding fit in the cylindrical bore 42 formed in the cylinder head 13. Thus the valve 35 is a close sliding fit in 'an aperture formed in a cover plate 40 which extends sleeve 35 is movable in thecylinder head in radially 'ina ward and outward directions coaxially with the main piston '17.

Sealing rings

43,44 and 45 are providedto seal the valve sleeve 35 in sliding contact with the surfaces of the cylinder head bore .42, the aperture in the cover" plate 40 and the flange 29 of the auxiliary piston sleeve '27. 1

An auxiliary passage 48 formed ineach cylinder block 15 is connected to a point of a hydraulic system associated with .the motor at the system base or boost pressure. The passage 48 is inalignment with a'corresponding auxwill thus close the open inner. edge, of the narrow annular V clearance 52 between the pistonsleeve 27 and the'cover plate 40, sealing off this clearance space from the working 7 pressure applied to the crown of the main piston 17. However the working pressure will still acton the radially inner face of the flange 29 of the piston sleeve 27, so that the sleeve 27 will be subject to an outwardly-directed hydraulic thrust which will keep it hydraulically clamped against thecoverplate 40.; 'Now the piston sleeve 27 will be retained locked in the main cylinder 1 2 by this hydrau-lic clamping force, and the main piston 17 willieciprocate alone within the bore 28 of the piston sleeve 27,

sliding relatively to the'lockedpiston sleeve 27 which surili-ary passage'49 formed 'in the cylinder head 'l3 and leading into the bore 42, so. that this'steady hydraulic base pressure is applied to the interior of the cylinder head bore 42 beyond the piston 41 of the valve sleeve 35. The

strength of the valve spring 36 is so chosen in relation to the base pressure and to the efleot-ive areaof the piston 41 ,7

on the valve sleeve 35 that whenthe base pressure is at a 'predeterminedhigh value, say 100 p.s.i.,'the resultant hy-.

draulic thrust on the piston 41 of the valve sleeve35 over-' comes the force of the spring 36-and moves the valve sleeve 35 radially inwardly to its innermost position as illustrated in FIGUREZ. In this positionthe inner face of the piston 41 engagesagainst the outer face of the cover head bore 42 is reduced to a predetermined low value, say

50 p.s.i. the valve spring 36 prevails and moves the valve sleeve 35 radially outwardly to the position shown in FIGURES. 7

The radially outer end of the sleeve 27 constituting cumferential flange 51 which abuts against the inner face of the cover plate 40 to limit the outward movementof the, auxiliary piston sleeve 27. In the outermost position of the piston sleeve 27 as illustrated in 2 and 3, a narrow annular clearance 52 is defined between the inner face of the cover plate 40 and the outer end face of the s auxiliary piston is formed with an axially projecting cirplate to limit the radially inward movement of the valve sleeve 35. -However when the hydraulic base'pres-sure supplied through the passage-s48 and 49 to the cylinder position of the valve sleeve 35 the annular clearance 52 is thus subjected to the hydraulic working pressure prevailing in the cylinder head inlet passage 31 and, via the bore of the extension tube 32, in the recess 33in the crown 'ofthe piston 17, which working pressure acts on the piston 17. Since'the-annular area thus exposed at the radially outer end of the auxiliary piston sleeve 27 is greater than -the oppositely facing annular meant the inner side of the flange 29 of the sleeve 27, the sleeve" 27 will thus be sub-- ject to a resultanthydraulic thrust in the radially inward,

' directionand will thus move radially inwardly together with the main piston 17 sliding in the main cylinder 12 1 7 under the thrust'of the working pressure, so that the two pistons together apply a driving torque to the'outpu't'shaft 19 via the eccentric 18. g

However when the base pressure in the system is.

changed to as higher va-lue of 100 p.-s.i. and moves the -valve sleeve 35 to its radially inner position as illustrated in FIGURE 2, thenasthe piston sleeve' 27 is returned to its outer position by the next outward stroke of the main piston 17, the cylindrical body 39 of thevalve sleeve 35 will slide into the cylindrical aperturedefined by the in-; turned flange 2.9 at the top of the piston sleeve 27 and roundsit.

To prevent hydraulicfluid being trapped between-the cover plate 40 and the outerv end face of the piston sleeve 27 as the latter approaches its extreme outer position, a

bypass passage 53 is formed in the flange 29 of the piston:

sleeve 27 and incorporates a nonreturn valve 54 of the ball type. Any trapped fluid can thus escape'fromthe annular clearance 52 through the bypass passage, but the iballvalve prevents the flow of'fiuid through the bypass passage 53 in the opposite direction into the clearance 52.1 "A bleed passage 57 extends through the wall ofthe cylinder head 13 to prevent fluid becoming trapped beneath the piston 41, and a second bleed passage 58 provided with anon-return valve 59 extends from the bore .42 of the cylinder head back into the inletpassageB l. Theauie iliary passage 48 in the cylinder block 15 is provided with its own non-return valve 50.

Thus by the simple operation of changing the system 1 'base pressure from one value to the other, which can be done by a simple two-position hydraulic slide valve,zthe movable valve sleeve in each cylinder head '13 canwbe caused to move from' its outer position of FIGURE 3 to its inner position of .FIGURE. 2, or vice versa, there- 'by causing the auxiliary piston sleeve '27 either to remain stationary in a locked position in the cylinder 12 whilst the main piston 17 reciprocates alone in the cylindenfor high speed; operation of the motor, or to slide with the main piston 17 in the cylinder 12 for low speed operation with greater output torque.

In the modified embodiment illustrated in FIGURE 4, in which similar parts are given the same. reference num-i ber's, each-cylinder 12 is provided with a main piston which is in the formof a'cylindrical sleeve 60 which'is slidable within the cylinder 12, the piston sleeve'60 being formed with a bearing foot 61 at its inner end whichacts on the bearing ring 25 of the eccentric 18 via a rocker shoe 24', whilst the auxiliary piston in this case c0m-, prises a solid cylindrical piston 62 which is slidable-inthe bore 63 of the main piston sleeve 60. The auxiliary piston 62 is formed at its outer end with an" external "radially-protruding circumferential flange 64 which overlies the annular end face 65. of the piston sleeve 60 and limits relative sliding movement between the sleeve 60 and the auxiliary piston 62 in one direction. The mov-' able valve member in this case comprises a valve collar 66 "slidably mounted on a fixed mushroom-shaped stud- 67 fo rmed integrally with the cylinder head 13 and protruding'inw'ardly within itsjbore 42, the valve collar 66.

being spring-biassed in the radially outward direction by means of. a helical compression. spring 68... The valve collar 66 is formed-with a depending skirt 70, and when. theicollar 66 is moved to its radially innermost position. as illustrated in'FIGURE4 by theaction of the systemv base pressure when-the'latter is selected to its-highi value sufiicient to overcome the action of the spring 68, 1 the skirt 70 slides over the edge of the flange 64 of the auxiliary piston 62and thereby cuts 01f from ther hydraulic working pressure the clearance 71 between the crown ot the auxiliary piston 62 and the ,head lot the stud 67, this'clearance 71' being maintained by an axially protruding flange 72 formed circumferentially around the outer. edge of the crownof the auxiliary piston :62.

Thus the auxiliary piston 62 will be hydraulically locked to the stud 67 with its flange 72 held in abutment against the head of the stud 67 by thehydraulic working of the system acting on the inner annular face of the flange 64.

However when the system base pressure, is changed to its predetermined lower value, so that the valve'collar 65 is raised by its spring 68 to lift the valve skirt 70 clear of the flange 64 and thus to admit the working pressure of the system to the clearance 71 between the head of the stud 67 and the crown of the auxiliary piston 62, the auxiliary piston 62 'will thereupon be released and will be subject to the system pressure so that it will reciprocate with the main piston sleeve 60 and increase the swept volume of the motor, thereby producing a corresponding speed reduction and increase in torque of the motor. a

In this embodiment the main working pressure of the hydraulic system is admitted to the interior of the cylinder .head through a pipe 73, whilst the system base pressure is admitted into a cylindrical recess 74 formed at the inner end of the interior of the cylinder head 13, through a separate pressure line 75 leading to an auxiliary passage '76 formed in the'wall of the cylinder head 13. The valve collar 66 when raised to its radially-outer position by its spring 68 is a close sliding fitin the cylindrical recess 74, but when the collar 66 is moved inwardly to its innermost position as shown in FIGURE 4, it clears the edge of the recess 74 to allow communication between the interior of the recess and the main bore 42 of the cylinderhead. A non-return valve 77 is providedat the entrance to the auxiliary passage 76. Moreover a bleed passage 78 provided with a non-return valve 79 extends between the auxiliary passage 76 and the main pressure inlet '73 to the head, to release hydraulic fluid trapped in the recess 74 when the valve collar 66 moves to its radially outer position. A bypass passage 80, also provided with a non-return valve 81 extends through the wall of the cylinder head 13 and through the shank of the stud 67 to allow the escape of hydraulic fluid trapped in the clearance 71 between the auxiliary piston 62 and the head of the stud 67, the escaping fluid after passing through the non-return valve 81 being released into'the bore 42 of the cylinder head outside the valve collar 66.

It will be understood that either of the two embodiments of motor described and illustrated may equally Well be employed as a pump, by connecting the main shaft carrying the eccentric to a suitable driving motor. The base pressure used for controlling the

valve shuttle member

35 or 66 may be derived from the output of the pump using one or more selectively-controlled restn'ctor valves to provide the required pressure variations.

The pressure input passage 30, when the machine is used as a pump, will become the pressure delivery or output passage. The same valve mechanism (not shown) which controls the inlet of pressure fluid into the cylinder during the downward movement of the piston or pistons, and permits fluid to be exhausted from the cylinder during the upward movement of the piston or pistons, merely needs to be re-timed in order for the machine to operate as a pump. When operating as a pump this valve mechanism will allow discharge of fluid under pressure, when the piston or pistons are ascending, and will allow fresh fluid to be drawn into the cylinder from a return line when the piston or pistons are decending.

What we claim as our invention and desire to secure by Letters Patent is: i

1. A hydraulic machine having a cylinder, a cylinder head, a main piston and an auxiliary piston both movable reciprocally within the cylinder, to vary the volume of the free space within the cylinder between the pistons and the cylinder head, means constraining the auxiliary piston to a piston stroke of substantially the same length as the overall stroke of the main piston, means for admitting hydraulic fluid to the said free space within the cylinder t 6 to'coact simultaneously with both the-said pistons; and control means for altering the swept volume of the machine, the said control means having a hydraulic pressure inlet for connection to a source of hydraulic control pressure, and including a selectively-operable hydraulic shuttle valve connected to the pressure inlet for operation in response to predetermined changes in control pressure, the

'-'shuttle valve including a sliding shuttle member subject 'to the said control pressure and movable selectively into a movable selectively into a second position in which it admits balanced hydraulic pressures to both sides of the auxiliary piston, whereby the auxiliary piston, is freed to move in the cylinder together with the main piston.

2. A hydraulic machine as claimed in claim 1 in which the auxiliary piston is formed with an end face adapted to abut against a cooperating face of the fixed abutment, and in which the auxiliary piston and the abutment have circumferential edges surrounding their respective said faces which edges lie mutually in register with one another in side-by-side relationship when the said faces are in abutting engagement, and in which the shuttle member when moved into its said first position slides transversely across the said registering edges and seals them against the ingress of hydraulic fluid between the abutting faces.

3. A hydraulic machine as claimed in claim 2 in which the auxiliary piston is a sleeve mounted within and in sliding contact with the cylinder, the sleeve having an internal bore and in which the main piston is mounted within and in sliding contact with the bore of the sleeve, and in which the shuttle member is slidable through aligned apertures in the said faces of the abutment and of the auxiliary piston to seal the adjacent circumferential edges of the said apertures against the ingress of hydraulic pressure fluid between said faces.

4. A hydraulic machine as claimed in claim 2 in which the main piston is a sleeve mounted within and in sliding contact with the cylinder and having an internal bore, and in which the auxiliary piston is mounted within and in sliding contact with the bore of the sleeve, and in which the shuttle member has a depending tubular skirt arranged to slide over the external circumferential surfaces of the auxiliary piston and of the fixed abutment to seal the outer circumferential edges of the said abutting faces against the ingress of hydraulic pressure fluid between said faces.

. 5. A hydraulic machine having'a cylinder, a cylinder head, a main piston and an auxiliary piston both mov-v able reciprocally in the cylinder to vary the volume of the free space within the cylinder between the pistons and the cylinder head, means for admitting hydraulic fluid to the'said free space within the cylinder to coact with the pistons, and control means for altering the swept volume of the machine, the said control means including a selectively-operably hydraulic locking device by which the auxiliary piston is either subjected to an unbalanced hydraulic pressure thrust on one end face thereof by which pressure thrust the auxiliary piston is held fixedly clamped against a fixed abutment in the cylinder, or is freed to move in the cylinder together with the main piston, the locking device comprising a hydraulically controlled shuttle valve,'having a connection to a source of hydraulic control pressure, and including a sliding shuttle member subject to the said control pressure and movable between a first position in which it admits unbalanced hydraulic pressure to one side only of the auxiliary piston and shuts off the said hydraulic pressure from the other side of the auxiliary piston, and a second position in which it admits balanced hydraulic pressures to both sides of the auxiliary piston.

7 r I v a r 6. A hydraulic machine as claimed in glaim'5, in which V 7 References Cited by the'Examiner thefauxiliary piston is formed with an end face adapted V t UNI toabut against a eooperating'face of the fixedabutment, STATES PATENTS 7 and in which the auxiliary piston and the abutment have 10/46 3 '-"'T""'+ 91167 circumferential edges surrounding their respective said 15' 2182556 5/42 Bowen 91.412 faces which edges lie mutually in register with one another 2285476 *6/42 Wahlmark 9 1*169 in side-by-sidemelationship when the said faces are in a l abutting engagement, and in whichthe shuttle member t when moved into its said first position slides transversely FRED ENGELTHALER V i r acrosslthe said registeringredges and seals them against' m SAMUEL LEVINE, Examiner.

the ingress of hydraulic fluid between the abutting faces. 7

2,716,965- 9/55 Klamp 91168'

Claims

1. A HYDRAULIC MACHINE HAVING A CYLINDER, A CYLINDER HEAD, MAIN PISTON AND AN AUXILIARY PISTON BOTH MOVABLE RECIPROCALLY WITHIN THE CYLINDER, TO VARY THE VOLUME OF THE FREE SPACE WITHIN THE CYLINDER BETWEEN THE PISTONS AND THE CYLINDER HEAD, MEANS CONSTRAINING THE AUXILIARY PISTON TO A PISTON STROKE OF SUBSTANTIALLY THE SAME LENGTH AS THE OVERALL STROKE OF THE MAIN PISTON, MEANS FOR ADMITTING HYDRAULIC FLUID TO THE SAID FREE SPACE WITHIN THE CYLINDER TO COACT SIMULTANEOUSLY WITH BOTH THE SAID PISTONS, AND CONTROL MEANS FOR ALTERING THE SWEPT VOLUME OF THE MACHINE, THE SAID CONTROL MEANS HAVING A HYDRAULIC PRESSURE INLET FOR CONNECTION TO A SOURCE OF HYDRAULIC CONTROL PRESSURE, AND INCLUDING A SELECTIVELY-OPERABLE HYDRAULIC SHUTTLE VALVE CONNECTED TO THE PRESSURE INLET FOR OPERATION IN RESPONSE TO PREDETERMINED CHANGES IN CONTROL PRESSURE, THE SHUTTLE VALVE INCLUDING A SLIDING SHUTTLE MEMBER SUBJECT TO THE SAID CONTROL PRESSURE AND MOVABLE SELECTIVELY INTO A FIRST POSITION IN WHICH IT ADMITS UNBALANCED HYDRAULIC