US3137243A - Hydraulic pumps or motors - Google Patents

Description

June 16, 1964 c5. BECK ETAL 3,137,243

HYDRAULIC PUMPS 0R MoToRs Filed June 5, 1959 5 Sheets-Sheet 1 GEORGE BECK ERIC HIDE BOWERS PETEI? HENRY BROWN OSWALD THOMA i Y Mm @www +4 ATTORNEYS June 16, 1964 G. BECK ETAL 3,137,243

HYDRAULIC PUMPS OR MOTORS Filed June 5, 1959 5 Sheets-Sheet 2 4/ 59 2/ 39 6/ J /V/ J 67( y J 68 1 e nu.

INVENTOES GEORGE BECK ERIC HIDEIZ, BOWERS' PETER HENRY BROWN BY OSWAL-D THOM A W w+ A'rToQNEYS June 16, 1964 G. BECK ETAL HYDRAULIC PUMPS 0R MoToRs 3 Sheets-Sheet 3 Filed June 5. 1959 INVENTOES GEORG E BECK.

ERIC HIDEIZ BOWERS PETER HENRY BROWN oswALD THOMA .,.wa/MAM BY W ATTORNEYS United States Patent 3,137,243 HYDRAULIC PUMPS OR MOTORS George Beck, Tewkesbury, Eric Hider Bowers, Cheltenham, Peter Henry Brown, Prestbury, and Gswald Thoma, Cheltenham, England, assignors to Dowty HydraulicUnits Limited, Tewkesbury, England, a British company, and Oswald Thoma, Cheltenham, England Filed .lune S, 1959, Ser. No. 818,291 l Claim. (Cl. S-162) This invention relates to hydraulic pumps or motors of the class comprising a rotary cylinder block having cylinders parallel or substantially parallel to the block rotation axis, a rotary thrust plate and drive shaft secured together and mounted for rotation about an axis intersecting the rotation axis of the cylinder block, pistons inthe cylinders, a connecting rod articulatingly secured between each piston and the thrust plate, a universal joint arrangement to interconnect the thrust plate and cylinder block to ensure that they rotate similarly, and valve means co-operating with the cylinder block ot connect the cylinders to supply and return ports during rotation in synchronism with reciprocation of the pistons within their cylinders. In this class of pump or motor the displacement may be fixed or variable by arranging that the cylinder block is either mounted so that its rotationV axis intersects the thrust plate axis at a xed angle or, alternatively, is hingedly mounted so that its rotation axis is angularly adjustable relatively to the thrust plate axis. In order to be able ,to obtain a large liquid flow rate in such a pump or motor it is desirable that it should be capable of high speed operation with a large angle between the rotation axes of the cylinder block and thrust plate. This requires that the universal joint should have exact constant velocity characteristics at any angle to avoid unduly large cyclic accelerating and decelerating forces being transmitted through the universal joint. It is known to provide two Hooke type universal joints in series between the thrust plate andcylinder block so arranged that their non-constant velocity characteristics oppose one another to give a substantially constant velocity relation. However, in such a case one of the joints is necessarily located partly within the cylinder block and it follows that its size and consequently the torque that it can transmit without substantial wear over a longL period is limited by the space available between the cylinders. Further, where the displacement is variable by varying the angle between the two axes the Hooke joint combination is not accurate in securing constant velocity relation over the whole range of displacement variation. Still further, lost motion may easily occur in the Hooke joint combination and create difculty in maintaining exact phase relationship between the cylinder ,block and the thrust plate.

The use of a single constant velocity universal joint to interconnect the thrust plate and the cylinder block would solve the difficulties mentioned above, in particular it would allow high speed operation with a large angle between the rotation axes of the thrust plate and cylinder block and, at the same time, maintain exact constant velocity characteristics. Further, such a joint would be located at the intersection of the two rotation axes which is at a position between the connecting rods where the largest space is available. Such a joint is known to the art, and in its general form is not a part of this invention. However, a further difficulty arises in its use in that, for successful operation, the geometric centre of the universal joint must coincide exactly with the intersection ofthe rotation axes of the thrust plate and cylinder block. In practice, this is never possible due to manufacturing tolerances and any attempt to use a pump or motor of the' class described having a known type of constant vep locity universal joint as the sole interconnection between ice thrust plate and cylinder block could only result in heavy stresses in the universal joint which would cause rapid wear.

The main object of the present invention is to provide a pump or motor of the class described having a constant velocity universal joint of known type as the interconnec* tion between thrust plate and cylinder block together with novel compensating means for manufacturing or other tolerances that will allow the constant velocity universal joint, despite displacements impossible to eliminate, to operate substantially as though it were located exactly at the intersection of the two rotation axes.

In accordance wih the present invention, in a pump or motor of the class described a constant velocity universal joint is provided to interconnect the thrust plate and the cylinder block and is located so that its geometric centre coincides substantially, or as nearly as is practicable, with the intersection point of the two axes of rotation, the connection between this universal joint and either the thrust plate or the cylinder block being arranged to allow at least of small degrees of lateral bodily movement of the part connected to the driving shaft relative to the part connected to the other element, and with relation to their common rotation axis. Where the constant velocity universal joint cannot permit of longitudinal movement of the cylinder block or thrust plate along their respective axes it is desirable to include in the connection to the thrust plate or cylinder block means to allow such longitudinal movement. It is, however, the relative bodily movement that distinguishes this invention, as distinct, from lateral ilexure. The constant velocity universal joint may enter a recess in the thrust plate having a diameter extending almost to the articulating connections of the connecting rods whereby the torque capacity of the joint may be made as large as possible. It is preferred that the constant velocity universal joint should be secured directly to the cylinder block and that the connection oifering relative movement should be between the universal joint and the thrust plate. The connection affording relative movement may be one such as is disclosed in the Brown Patent No. 2,900,921, where the movement is permitted by the spring in a shaft mounted within a bore in the driving shaft, modified, however, in that there is a splined connection between the spring shaft and the universal joint half to which it is connected whereby relative movement between the universal joint and the thrustplate may be not only lateral, due to the spring in the shaft, but also longitudinal relative'to the thrust plate axis, due to the splined connection, and hence in any direction, or universal-or there may be in actual fact a secondary universal joint between the thrust plate and its half of the primary universal joint half, whereby bodily relative universal movement of slight magnitude may occur. Preferably, and distinctive in this invention, the connection offering transverse angular and longitudinal relative movement is an elementary form of universal joint comprising a slot or slots and sliding member tting in the slots.

Five examples of the invention will now be described with reference to the accompanying drawings, in which:

FIGURE l is an axial section through a pump of the kind described embodying the flexible shaft extension which illustrates the principle of the invention, but with- Y out change over the Brown patent;

spectively still further examples, which also are entirely practical. Y n

Reference is made initially to FIGURE l to illustrate the principle underlying the more practical forms later described. In the drawing a driving shaft 1 of the pump is provided having splines 2 to facilitate positive connection to a driving means. This shaft extends into a housing 3 and increases in cross-section to terminate as the thrust plate 4. The driving shaft 1 and thrust plate 4 are made from a single piece of metal and xedly located by r'rieans such as the roller bearings 5 and 6 against radial movement and by the thrust roller bearing 7 against endwise movement. The shaft V1 and thrust plate 4 include a central bore 8 in which is located a shaft extension 9 constituting part of the connecting means referred to above which extends to one half 11 of a universal joint 12. This universal joint is a type known in the art as a constant velocityuniversal joint, the function whereof `is to maintain a constant rotational velocity of the driven element 29, with constant velocity of the driving element 4. The joint is located in an enlargement l@ at the outer end of bore 8 which is the largest space available havingl regard to the fact that the connecting rods 41 diverge from the cylinder block to the thrust plate, the circle containing ball ends 43 being larger in diameter than the circle of the cylinders 38. The shaft extension 9 includes a portion 13 of reduced diameter to allow of small lateral spring deflections of the half 11 of the universal joint withV relation to the driving shaft 1. The outer end of the shaft 13 is formed with a splined or serrated portion 14 which is of hardened metal, the ends or the serrations being sharp. The portion 14 is arranged to be a drive tit in a comparatively soft metal bush 15 located at the end of the bore 8. A small diameter drawshatt 16 is integral with and extends from the portion 14 through a small diameter hole 17 in shaft 1, terminating adjacent the outer end of the shaft in a screw-threaded portion 18. Arecess 19 in the outer end of shaft 1 accommodates a nut 21 in screwthreaded engagement with screw 1@ such that rotation of the nut relatively to the draw-shaft 1t? will pull the latter to cause the portion 14 to enter the metall bush 15 moving from left to right.

The above describes the shaft extension 9 as part of the connection between the driving shaft 1 and the thrust plate on the one hand, and the universal joint part 11 on the other. The invention is not limited to such a location and association, for in other forms the halt of the universal joint attached to the cylinder block might equally well be arranged for connection through a similar element.

The housing 3 extends on either side of the thrust plate 4 in the form of two circular discs 22 and 23. These discs are surrounded by roller bearings 24 and 25 which in turn fit into recesses formed in the ends of hollow arms 26 and 27. The arms 26 and 27 extend along the side of the cylinder block and are secured to a valve plate 2S on which the cylinder block 29 rotates. The valve plate includes two ports 31 and 32 which connect to passages 33 and 34 which extend through the hollow arms 27 and 26 respectively. The opposite ends of the hollow arms are locatedl in bearings respectively 35 and 36 formed in the pump casing 37, these two bearings being arranged to lie coaxially with the roller bearings 24 and 25 and with the geometric centre of universal joint 12.

A plurality of cylinders 38 are'formed in the cylinder block 29 arranged symmetrically in the block with their axes parallel to the axis of block rotation. In each cylinder a piston 39 is slidably located and from each piston a connecting rod 41 extends to the thrust plate. Each connecting rod is located in its respective piston by means of a ball end 42 whilst, at the same time, its opposite end is located in the thrust plate by means of a ball end 43. The block 29 is rotated by means of the universal joint 12 and that half 44 of the universal joint which co-operates with the half 11 is directly mounted on the end of the block 29 adjacent the thrust plate. The block is retainedl iirmly seated on the valve plate by means of a tixed shaft or stern 455 extending from the valve plate through a central bore 46 in the block. The end of the stem 45 is enlarged at 47 and forms a location for a sealing ring 48 which seals in the bore 46. vA passage 4g extends along the shaft 45 and supplies liquid under pressure into the bore 46 which then acts to urge the block on to the valve plate. Pressure liquid obtains access to the hole 49 through one or the other of two one-way valves 51 or 52 located respectively in the ports 32 and 31. A compression spring 53 located in the bore 46 acts through an axial thrust bearing 54 against the enlarged end 47 of stem 45 also to urge the block against the valve late.

p The passages 33 and 34 extend through bearings 36 and to iixed pipes 55 and 56 by which supply and return liquid may enter and leave the pump. The cylinder block 29, valve plate 28, and arms 26, 27 form a complete assembly which is movable about the common axis of the bearings 24, 25, 35 and 36 to vary the angular position about this axis of the thrust plate relatively to the cylinder block and so as to vary pump displacement. This angular position is controlled by means of a screw adjustment (not shown but known in the art) manually adjustable from externally of the casing 37 and acting through a pin 57 secured to arm 26.

In operation, the pump is driven at drive shaft 1 to cause both rotation of the thrust plate 4 and the cylinder block 29. Assuming that the axes of the thrust plate and cylinder block are inclined by a controlling force applied to pin 57, the rotational movement will cause reciprocation of the pistons within their cylinders. The arrangement of the valve plate 28 is such that cylinders having ascending pistons are connected to one of the ports 31 or 32 and cylinders having descending pistons are connected to the other of these ports, and liquid is pumped from one ot' the passages 33 and 34 to the other passage. The direction of pumping will depend on the direction in which the cylinder block has been inclined relatively to the thrust plate. For operation at high speeds it is essential that there should be constant velocity relationship in the universal joint between block and thrust plate. If, for example, a universal joint of the known Hooke type were used it would be subject to cyclic alternating torques because of the non-constant velocity relation and would rapidly wear out. The universal joint 12 shown is of a comparatively new but known form. Briefly, the two halves 11 and 44 of this universal joint are each of U- shape, the limbs interengaging one with the other through the medium of a plurality of pads 58 semi-cylindrical in shape which are arrangedto rock'on the limbs and slidingly engage one another. This form of universal joint gives a constant velocity drive between the two halves, whilst, at thersame time, it can allow considerable relative movement of the two halves of the joint along their rotational axes. In the pump embodiment as described the whole pump may be completely assembled with the shaft 9 and the half 11 of the universal joint displaced to the left from the position shown in the drawing so that the serrated portion 14 is in lposition to enter, but has not entered the soft metal bush 15. The final operation in the assembly of the pump isto ensure that the cylinder block is correctly alignedv vrelatively to the thrust plate before the nut 21 is tightened to pull the portion 14 intothe bush 15, which action will iix the half 11 of the universal joint relatively to the thrust plate 4 and thus will locate the cylinder block relatively to the thrust plate. The two halves 11 and 44 of the universal joint come apart leasily in the event that it is desired to take the thrust plate from the cylinder block during servicing or repair of the pump.

The function of the shaft extension 9 and its thin part 13 is to accommodate any slight inaccuracies in the positioning of universal joint 12, such accommodation being by transverse bending of the portion 13. Inaccuracies in commodate unavoidable lack of coincidence between the center of the universal joint and the point of intersection of the relatively inclined axes of the driving and driven elements, or disposition of these two axes so that they fail to intersect. This necessity for relative movement may arise regardless of the necessity for phase adjustment, and'may be accommodated by constructions other than that disclosed in the Brown patent, alternative constructions being disclosed herein.

A more usual` constant velocity joint may be used if` a sliding joint is provided in shaft extension 9. Such an arrangement is shown in the second example illustrated in FIGURE 2. The cross-section in this ligure is at right-angles to that shown in FIGURE 1 and the cylinder block is shown with its axis inclined to the axis of the thrust plate. Where possible, the same reference numerals will be used to indicate parts similar to those appearing in FIGURE 1. Thev constant velocity joint 12 is of a well-known type comprising i a hollow spherical outer member 61 positively secured by a support 62 to the end of the cylinder block, an inner spherical member 63, cooperating grooves'64 on the inside of the outer member 61 and the outside of the inner member `63 and a ball race 65 carried by a cage '66 which locates one ball in each pair of co-operating grooves 64. Whatever the angle between the axes of rotation of the inner member 63 and the outer member 61 the plane occupied by the ball race 65 will bisect this angle and give a constant velocity relation between thetwo parts 61 and 63.

For connection of the inner member 63 to the thrust platea splined hole 67 is formed` axially in member 63 which receives the splined end 68 of the thin spring shaft 13 extending back into the bore 8.` The shaft 13 terminates in the flange 59y which may be locked against a shoulder in the bore 8 by means of a drawbolt 16 extending through a small hole in the Vdrive shaft 1 and a nut 21 located at the outer end of the driveshaft.

vDuring rotation of the drive shaft 1 and cylinder block 29 any inaccuracies in the location of the universal joint 12p so that either its centre does not coincide with thev supposed point of intersection of the two rotation axes of the thrust plate 4 and cylinder .block 29, and/ or the two axes do not actually intersect, areV accommodated by the fact that the shaft'13 can bend so that the end 68 can move in any direction transversely to the rotation axis of the thrust plate 4 and thatthe inner member 63 of the universal j oint may'slide axially on the end 68 of shaft 13. It will be seen,however, that rotation of the drive shaft 1 is imparted directly to `the inner member 63 of the universal joint without any lost motion. The recess which accommodates the universal joint is larger in diameter than any other available space between the connecting rods or in the centre of the cylinder block'for the reason that the circle containing the centres of the connecting rod ball ends in the thrust plate is on a larger diameter than the circle of centres of the cylinders. This arrangement is essential in a pump or motor of the kind referred to to prevent the connecting rods, when in the positions seen in the drawings, especially FIGURE 1, from contacting the open ends of the cylinders.

Reference is now made to the example in FIGURES 3 and 4 in which equivalent parts are given the same reference numerals as used in connection with FIGURES 1 andA 2. The difference in construction from FIGURE 2 lies in the provision of a secondary universal joint for 3 4 connecting the inner member 63 of the universal joint 12 to the thrust plate 4. This allows free bodily universal movement. The form of FIGURES 3 and 4 represents the most practical form of the invention. The bore 8 extending from recess 10 is made comparatively shallow and within this bore a transverse pin 69 is inserted through a transverse hole 71. Within the bore 8 a square-section block 72 fits on pin 69 to engage accurately within a slot 73 which extends transverse to cylindrical plug 74 which is a loose fit within bore 8. A short shaft extension 75 extends from plug 74 and terminates as a splined end 68 engaging within the splined hole 67 in the centre member 63 of the universal joint. The spindle or shaft extension 7S is locked in position by means of a nut 76 screwthreaded on the end of the shaft 68 and a shoulder 77 which between them grip on the inner member 63 of the universal joint. The pin 69 is normally located in position by means of a sleeve 78 which surrounds shaft 1 and is located in position against a shoulder 79 by means of a circlip S1.

In operation,` it will be seen that the shaft extension 75 is capable of limited bodily transverse angular movement relative to the axis of shaft 1 and also capable of limited bodily longitudinal relative movement, but not of relative rotational movement about the shaft axis which is prevented by the accurate engagement of the block 72 over the pin 69 and within the slot 73. Any small errors in the position of the universal joint 12 so that its centre does not coincide with the intersection of the rotation axes of thrust plate and cylinder block are accommodated by virtue of the limited transverse angular bodily movements and longitudinal movements that shaft extension 75 may make relative to the thrust plate, whilst the fact that no relative rotation is allowed about the drive shaft axis means that the cylinder block and thrust plate are rotationally interconnected without lost motion. The pin 69 and the block 72 engaging in slot 73 form a secondary universal joint which need be capable only of very small compensating movement, but this is a bodily `movement as distinguished from the flexural movement in the forms of FIGURES 1 and 2. If it is desired to take the pump apart as during servicing or repair, it may be necessary to part the thrust plate and the cylinder block. For this purpose, the circlip 81 and sleeve 78 may be moved to allow pin 69 to be driven from the transverse hole 71 to release plug 74 from recess 8 thereby releasing the vcylinder block from the thrust plate.

Referring now to FIGURE 5 of the drawings, the example shows a modification of the secondary universal joint of the type shown in FIGURES 3 and 4 in that the plug 74 is provided with a transverse slot 73 which opens to the end of the plug. VThe purpose of this arrangement is to allow more easy parting of the cylinder block from the thrust Aplate for service or repair. It will be seen that thereV is `no need to remove pin 69 since the open-ended slot 73 will slide olf the block 72. Other than this feature operation is as described for FIGURES 3 and 4'.

Referring now to FIGURE 6, the example shows a further `modification of the secondary universal joint shown in FIGURES 3 and 4 which permits bodily movement. Within the recess 8 a plug 82 is positively xed by means of a pair of dowel pins extending through shaft 1 and within the plug a transverse slot 83 is formed which opens towards the universal joint 12. This slot is closed at its ends by the walls of recess 8 to form a substantially rectangular section opening. The shaft extension 75 extends into the slot and engages therein by means of a transverse pin 84 extending through the shaft and a pair of Slide blocks 85 are square in section to fit without lost motion across the slot. The outer end of each block is curved at 86 to engage the sides of recess 8 and to allow transverse angular movement of shaft extension 75 relative to shaft 1 in the plane of FIGURE 6. Pin 84 is tightly gripped in the end of shaft extension 75 but is free to move angulariy in the blocks 86.

Inoperation of the pump it will be seenV that slight inaccuracies in location of the universal joint 12 at the intersection of the rotation axes of the cylinder block and thrust plate are accommodated by the fact that shaft extension 75 can movetransversely angularly to shaft 1 in any direction by ,pivoting labout the axis of pin 84 and/ or pivoting about a transverse axis tothe axis of pin 84 by virtue ofy opposite sliding movements of blocks S in slot 83 and also by the fact that shaft extension 75 can move bodily in an axial direction of shaft 1 by similar sliding movements of the blocks 85. Relative rotational movement between shaft extension 75 and shaft 1 about their rotation axes is, however, positively prevented by the accurate engagement of blocks 85 .within slot 83 .and the engagement of p in S4 within the blocks 85 thus ensuring that there is no lost motion in the rotational drive between thrust plate and cylinder block. y

In all examples it will `be seen that the constant velocity universaljoint, of whatever specific type, is the driving interconnection between thrust plate and cylinder which transmits the drive through the angle between thrust plate and cylinder block axes thus ensuring that there is accurate phase relation .between thrust plate and cylinder block at all rotational positions. block is driven smoothly from the thrust plate without cyclic accelerations and decelerations thereby avoiding high cyclic: torques on the constant velocity universal joint. Further, provided that accurate phase alignment is v eifected between thrust plate and cylinder block during manufacture, as is intended by the structure of the Brown patent, the, connecting rods will liein planes substantially passing through the rotation axis of the cylinder block'- at every angular position during rotation thus ensuring that the connecting rods can exert no torque on the cylinder block and on the constant velocity universal joint during rotation. It is thereby ensured that the torque to be transmitted by the universal joint is substantially only that necessary to overcome frictional resistance of the cylinder block. The constant velocity universal joint is located at a position where it can have the largest possible diameter without interfering with the other working parts in particular the connecting rods, and thus may have the greatest possible torque capacity whilst at the same time only being subjected to a low torque. This ensures a very low rate of wear at the universal joint and, therefore, a trouble-free working life. The bodily movement of parts in the secondary universal joint of FIGURES 3 to 6 inclusive allows entire freedom for the small movements required, without restraint. The flexural movement of shaft extension-13 combined with the bodily axial movement of the splined connection at 67, 68 in FIGURE 2 achieves a like result.

We claim as our invention:

A hydraulic pump or motor of the class described comprising a rotary cylinder block formed with generally axially directed cylinders angularly spaced about its axis of rotation; a pistonreciprocative in each cylinder; a drive shaft rotative at a constant rate; a rotary thrust plate driven by said drive shaft, and disposed in operation with This ensures that the cylinder` itsaxis intersecting the axis of the cylinder block, as nearly as is. practicable, at an obtuse angle; vconnecting rods interconnecting the several pistons and the thrust plate, and arranged in planesradially of the cylinder blocks axis of rotation; av two-part constantfvelocity type primary universal jointV located with its center substantially coincident with the intersection of the two axes, and with its two parts lcoaxial respectively with the drive shaft and with the cylinder block; a shaft extension secured to a first part of the primary universal joint, that one of the cylinder block or the drive shaft with which said iirst part is coaxial being recessed to receive said shaft extension loosely; the shaft extension being slotted inwardly from its endthat' is distant from said rst part of the primary universal joint; a block closely received in and "slidable within said slot, and movable endwise into and from said slot; a pin anchoredA to said recessed member and directed transversely of the slot and through the block; said slotted shaft extension, block, and pin constitutingl a secondary universal joint arranged` to permit relative bodily movement between' the parts so connected in the direction transverseto their common rotative axis, and their relative bodily movement inthe direction of such axis, to compensate for slight inaccuracy in location of the center of theprimary universal joint;.the secondpart of .the pri References Cited inthe leof this patent UNITED STATES PATENTS 972,270 Smith Oct. 11, 1910 1,022,909 Whitney Apr. 9, 1912 V1,346,253 Rayfield July 13, 1920 1,931,969 Thoma Oct. 24, 1933 2,072,090 Anderson Mar. 2, 1937 2,081,477 Egersdorfer May 25, 1937 2,133,176 Parent' Oct. 1l, 1938 2,146,133 Tweedale Feb. 7, 1939 2,153,093 Mageeet al. Apr. 4, 1939 2,178,331 Armstrong Oct. 31, 1939 2,231,117 ,Greiner Feb.` 11, 1941 2,319,100 Anderson May 11, 1943 2,565,208 Dietiker Aug. 21, 1951 2,623,604 Keese Dec. 30, 1952 2,649,741v j Henrischsen Aug. 2,5, 1953 2,670,614 Wildhaber Mar. 2, 1954 2,718,758 Minshall et al. Sept. 27, 1955 2,733,665 Klopp Feb. 7, 1956 2,834,297` Postelet. al May 13, 1958 2,900,921 Brown Aug. 25, 1959 2,908,151 Wahlmark Oct. 13, 1959 2,956,845 Wahlmark Oct. 18, 1960 FOREIGN PATENTS D. 19,747 Germany May 9, 1956 1,034,980 Germany July 24, 1958

Images