US3587404A

US3587404A - Hydraulic-machine arrangement with a plurality of machine units

Info

Publication number: US3587404A
Application number: US818502A
Authority: US
Inventors: Dietrich Kratzenberg
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 1968-04-24
Filing date: 1969-04-23
Publication date: 1971-06-28
Anticipated expiration: 1988-06-28
Also published as: FR2006863A1; GB1255818A

Abstract

A HYDRAULIC-MACHINE ARRANGEMENT FOR TWO OR MORE HYDRAULIC UNITS (E.G. PUMPS OR MOTORS) WHEREIN AT LEAST TWO SUCH UNITS ARE MOUNTED IN A COMMON SWINGABLE FRAME SUCH THAT THE FRAME, UPON ANGULAR DISPLACEMENT ABOUT ITS AXIS, ANGULARLY SHIFTS THE CYLINDER DRUMS OF THE AXIAL PISTON PUMP OR MOTOR FROM ITS NULL POSITION TO AN OPERATIVE POSITION, THE PIVOTAL FRAME HAS HOLLOW PIVOT PINS THROUGH WHICH FLUID COMMUNICATION WITH THE RESPECTIVE AXIAL PISTON MACHINES IS ESTABLISHED.

Description

United States Patent Inventor Dietrich Kratzenberg Hirtcnborn, Germany Appl. No. 818,502 Filed Apr. 23, 1969 Patented June 28, 1971 Priority Apr. 24, 1969 Germany P 17 03 260.9

HYDRAULIC MACHINE ARRANGEMENT WITH A PLURALITY OF MACHINE UNITS 3 Claims, 8 Drawing Figs.

US. Cl 91/505, 417/269 Int. Cl F011) 3/00, F01b 13/04 FieldofSearch 103/162,

[561 References Cited UNITED STATES PATENTS 2,931,250 4/1960 Ebert 74/68 7 2,987,006 6/1961 Bowers et a1. 103/1628 3,052,098 9/1962 Ebert 91/175 3,137,243 6/1964 Beck et a1. 103/1628 3,148,628 9/1964 Boydell 91/506 Primary Examiner-Carlton R. Croyle Assistant Examiner-Richard E. Gluck Attorney-Karl F. Ross ABSTRACT: A hydraulic-machine arrangement for two or more hydraulic units (e.g. pumps or motors) wherein at least two such units are mounted in a common swingable frame such that the frame, upon angular displacement about its axis, angularly shifts the cylinder drums of the axial piston pump or motor from its null position to an operative position; the pivotal frame has hollow pivot pins through which fluid communication with the respective axial piston machines is established.

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0 (Ross Attorney HYDRAULIC MACHINE ARRANGEMENT WITH A PLURALI'IY OF MACHINE UNITS My present invention relates to an axial-piston-machine arrangement having at least two axial-piston working units and, more particularly, to a hydraulic-pump or hydraulic-motor arrangement in which the capacity of the pump of motor units is controlled by tilting one member of each unit relative to another about a pivot axis.

In the commonly assigned U.S. Pat. No. 3,4l0,220, entitled "Axial-Piston Machines" of myself and others, the commonly assigned copending applications Ser. No. 708,039 and 744,489 of 25 Feb. 1968 and 12 July I968 (now US. Pat. No. 3,495,542 as well as the applications and patents mentioned therein, there are described axial-piston machines which function as pumps or motors and which are of variable capacity.

In such systems, a rotating member may carry a plurality of angularly spaced pistons which are reciprocated in dependence upon the position of a drive flange or a "swashplate" may be rotated to axially reciprocate the pistons in a so-called axial-piston pump in which the pistons lie parallel to the axis of a cylinder block.

The capacity of the pump is varied by adjusting the angle with which the drive flange intersects the axis of the cylinder drum, since the stroke of the individual pistons depends upon this angle. ln a variable-capacity axial-piston motor, hydraulic fluid is fed to the cylinders and reciprocates the axial pistons to drive the shaft, again via a plate upon which the pistons act and which may be inclined to the axis of the cylinder drum or block with varying degrees of tilt. The axial-piston pump and axial-piston motor are generally described as axial-piston machines and when two or more such machines are coupled together, they shall be referred to as axial-piston working units.

It has been proposed (see British Pat. specification 992,334) to couple two similar-type units together for joint operation and control. Systems in which the coupled units are both either axial-piston pumps or axial-piston motors, have the advantage that the total output may be twice that of a single unit and the efl'iciency of the hydraulic system is increased. For other arrangements, each of the pumps of the coupled system may operate an independent load via a respective hydraulic network.

It has been recognized in this connection that two relatively low-capacity units operate at greater cost efficiency than a single working unit with the same total capacity.

For the most part, prior art systems recognizing the aforementioned advantage, have provided each of the working units with a respective swingable housing, the housings of the two units being coupled together by a link bar, so that a single control unit, e.g. a fluid-operated servocontrol motor, can shift them jointly. The systems for supplying fluid to the units and carrying away the fluid output are relatively complex and inconvenient. Moreover, the use of several housings and their associated pivots etc. increases the spatial requirements of the units and their cost.

It is, therefore, the principle object of the present invention to provide a hydraulic system with two or more axial-piston working units which will have the above-described advantages and yet will have fewer parts, be of lower cost and require less space than heretofore.

This object and others which will become apparent hereinafter, according to the present invention, are attained by providing a common swingable frame or housing, preferably in the form of an elongated trough in which the cylinder drums of two or more working units are mounted side by side with their axes in a common plane, and a pair of pivots swingably mounting the frame in a surrounding housing for pivotal movement about an axis perpendicular to the axes of the unit but coplanar therewith.

The pivots which should lie close to the point at which the cylinder drums must tilt with respect to the drive flange or plate, are constituted as tubular members serving as fluid ports which communicate with the cylinder drums via passages formed in the swingable frame. Since only two pivots in axial alignment with one another are required for each frame and each frame receives a number of hydraulic working units, only two pivots are required in place of the pivot pair for each unit, and the units can be located closer together than in earlier systems.

According to another feature of this invention two such working units are provided in the swingable frame, one unit being proximal to each of the pivots and having its fluid passages connected to the tubular pivot, thereby defining independent fluid streams for the units, each of which terminates in a port formed by the pivots. Moreover, the outer housing may form a reservoir communicating via apertures in the swingable housing or frame with the other side of each of the axial-piston units, thereby greatly simplifying fluid connection to the units.

. According to still another feature of this invention, the floor or base of the trough-shaped swingable frame which is remote from the single-pivot axis thereof as noted earlier, is provided with kidney-shaped control and distribution ports, e.g. via a fluid-distribution or valve plate positioned on the base of the trough, upon which the cylindrical cylinder drums may rotate to bring the respective axial-piston cylinders into registry with the kidney-shaped inlet port and the kidney-shaped outlet port in alternating succession.

The kidney-shaped inlet and outlet ports will be low-pressure and high-pressure ports, respectively, when the hydraulic unit is operating as a pump and high-pressure and low-pressure ports respectively, when the units operate as motors. In either case, the low-pressure ports communicate through the swingable frame or housing, with the interior of the outer casing which constitutes a reservoir. The high-pressure kidneyshaped ports in the control plate or base of the swingable frame communicate via respective passages in the latter, with the ports formed by the tubular pivots.

The drive flanges of the hydraulic units are connected by gear means to a common shaft journaled in the outer housing opposite the controlled or valve plate, the axial pistons of the units bearing upon these drive flanges.

v'hCfl one of the shafts of a drive flange extends out of the housing and the drive flange of the other unit is coupled thereto by direct gearing, i.e. two gears in mesh with one another interconnect the shaft, the cylinder drums and shafts of the unit will rotate in opposite sense. When the units are to function identically, therefore, the kidney-shaped ports, with respect to their function, must be connected in mirror-symmetrical relationship, i.e. the mutually outermost ports of the two units must have the same function and the mutually innermost ports the same function. When the device is a pump, the outermost kidney-shaped ports of the control plane or base of the swingable frame will function as the high-pressure outlet while the innermost or centrally located portion will constitute intakes for drawing fluid into the cylinder drums.

According to another feature of this invention, the device is provided with rotary slide valves or distributors which'are connected to the kidney-shaped ports so that the total output of the assembly (total input when the device is a hydraulic motor) will be coupled together so that the capacity of the device is the sum of the capacities of the several units. Each of the kidney-shaped ports of each of the working units may be provided with a respective rotary slide valve so that the ports may be reversible in function. Furthermore, in this arrangement and/or in an arrangement in which further working units are provided in each swingable frame, the tubular pivots may be provided with a plurality of coaxial tubes defining respective ducts communicating with the respective hydraulic units.

Moreover, the passages of the frame may be cast in situ or may be build up by plates or the like which also serve as reinforcements for the swingable frame. Alternatively or in addition, the ducts may include telescoping or flexible tubes to accommodate the swinging motion of the frame.

According to still another feature of this invention, two or more swingable frames each having two or more hydraulic working units, are pivotally mounted in a common outer housing with their pivot axes preferably lying in a common plane and are interconnected with one or more link bars so that the tilting movement of one swingable frame will also tilt the other by the identical amount. The gear coupling of the hydraulic units is such that the units of each frame are coupled together by respective gears and possibly to the gears of the other units via an intermediary gear such that all of the units rotate in the same sense and a single output shaft is provided for all of them.

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a cross-sectional view taken along an axial plane in a double-pump arrangement according to this invention;

FIG. 2 is a cross-sectional view taken transversely to FIG. I;

FIG. 2A is a cross-sectional view taken along the line IIA-IIA of FIG. 1;

FIG. 3 is a cross-sectional view, partly in elevation, through a four-unit apparatus according to this invention, the swivelable housings being seen from behind;

FIG. 4 is an axial section through the device of FIG. 3 showing an alternative position of the swingable housing in dotdash lines;

FIG. 5 is a diagram illustrating a feature of the invention;

FIG. 6 is a diagrammatic view, partially in cross section, showing an alternative valve arrangement; and

FIG. 7 is an elevational view, partly broken away, illustrating further features of the invention.

In FIGS. 1, 2 and 2A, l have shown a double-pump arrangement which, of course, can also be used as a double-hydraulic motor as may be required. The outer housing or casing I, which is shown for convenience to be of one piece but will generally have a removable cover plate or be bolted together from two housing halves, rotatably receives the drive shaft 2 upon which a driving pinion 3 is mounted.

Pinion 3 meshes with the driven gear 4 of a stub shaft 5 also journaled in the housing for rotation about an axis parallel to the axis of shaft 2 and coplanar therewith, the rotational plane being represented at P in FIGS. 2 and 2A and running parallel to the paper in FIG. I. The shafts 2 and 5 each carry a drive or control flange 6 and 6', respectively, of a pair of hydraulic pumps which will be described in greater detail hereinafler and may be constituted as described in the commonly assigned patent or copending applications mentioned above.

Both of the pumping units are received in a pivotal or swingable frame or housing 9 which is elongated as shown in FIG. 2A and is provided at its open side (to the right in FIG. I) with a pair of laterally projecting hollow pivot pins 7 and 8 received in respective ball bearings 7' and d which, in turn, are lodged in recesses 7" and 8" of the housing 1 so as to allow the housing 9 to pivot about an axis A perpendicular to the axis of the shafts 2 and 5 and lying in the plane P in all operative positions of the frame 9.

The housing 9 is formed with a compartment 9' having a base 90 substantially coextensive with the open mouth of this housing. A pair of stationary axles l0 and 10' extend perpendicularly from the base 9a into the chamber 9' and are locked to the swingable housing by

lock washers

10d, 10d and nuts 10b, 10b.

The axles l0 and 10' serve to retain the drums cylinders of the axial piston pumps rotatable against the control or valve plate relative to which they are rotatable, as described in the patent and copending applications mentioned above. Between the heads 10c and 100' of these axes and the forward faces 11' and 12 of the rotatable cylinder blocks, I may pro vide bearing means to facilitate rotation of the drums I1 and 12 and take up the axial thrust as provided in these copending applications, while fluid-responsive means may be provided along the axles l0 and 10', via respective shoulders to draw the head 10c and the head 10c axially to the left as described.

The cylinder blocks II and I2 each have a rear face II", I2" slidably bearing against the control plate I5 which is formed with a pair of kidney-shaped

openings

15a, 15a serving as inlet ports for the hydraulic fluid to be pumped, and a pair of kidney-shaped

openings

15b, 15b constituting outlet ports of the respective pump units.

Needle bearings

10a, 10a, received in cylindrical cavities Ila 12a of the cylinder blocks 11, I2 rotatably mount the latter onto the axles I0 and 10'.

The cylinder blocks II and I2 are also formed with angularly equispaced cylinder bores 13, 13a adapted to communicate alternately with the

ports

15a, 15b, and 15a, 15b of the respective portion of the control plate 15 as each cylinder block is rotated by the shaft 2 or 5, respectively.

Respective axial pistons I3, 13a are axially shiftable in the bores I3, 13a to displace hydraulic fluid during the pressure stroke (to the left in FIG. I) and to draw hydraulic fluid into the respective cylinder on the intake stroke (to the right in FIG. I). Swivel rods I4, whose ball-shaped heads 14a are received in correspondingly shaped recesses 60 of the drive flange 6 or 6', couple the pistons I3 and 13a with these drive flanges to reciprocate the pistons.

The common pivotal frame or support for the pump units, which are mirror-symmetrical about a median plane M of the device (FIG. I), is provided with a pair of connecting lugs 16 which is linked to the rod 17 of a servocontrol piston 18 responsive to fluid pressure to swing the frame 9 about the axis A (clockwise in FIG. 2) to shift the pump arrangement out of its null position in which it is shown in the drawing.

At the opposite axial ends of the swingable frame 9, I provide respective fluid passages 19 and 19' which terminate at ports 19a and 190 along the base and register with the outlet ports 15!: and 15b of the control plate IS. The

pins

7 and 8 are, as previously noted, tubular and formed with passages 7a, 8a communicating respectively with passages I9 and I9 to deliver fluid to the high-pressure outlet ports 21 formed at the bearings 7 and 8' in the housing I. In other words, both kidney-shaped

outlet ports

15b and 15b lie symmetrically at outer regions of the housing 9 and are connected with outlet ports of the housing at the pivot axis A. The inlet ports 15a and I50 communicate via respective bores 20 and 20' in the base 9a, opening into the interior Ia of the housing I which constitutes a reservoir supplying hydraulic fluid to the pumping units. An inlet port 22 delivers the hydraulic fluid to the interior la of the housing.

When the shaft 2 is driven by a motor (e.g. an electric motor or a prime mover), the gears 3 and 4, which are fixed to the shafts 2 and 5 insure that both drive flanges 6 and 6' will be rotated in opposite senses with identical angular velocities, thereby setting the cylinder drums 11 and I2 into rotation about their axles I0 and 10' in opposite senses.

When the pivotal frame 9 is swung by the servo piston 18, which is hydraulically displaceable in its cylinder lb integral with the housing 1, the drums II and 12 are brought into positions in which the axes (e.g. the axis D shown in FIG. 2) no longer are aligned with the axis of the respective shaft and perpendicular to the respective drive flange 6 or 6', but are inclined to the latter as represented, for example, by the angle a in FIG. 2.

The drums II and I2 are thus swung out of their "null" position in which the volume of the cylinders I3 and I3a sweeping pass the input ports I5a, 15a, is equal to the volume as these cylinder bores sweep pass the

output ports

15b and 15b. Under the "null" condition, there is no change in the effective volume of the cylinders and the pistons do not shift through any stroke relative to the cylinder blocks.

In the upwardly swung position of the frame 9 (as seen in FIG. 2), the pistons are drawn in and out by the drive flange 6 or 6' as the drum is rotated to draw hydraulic fluid from the housing chamber 10 and through the passages 20 and 20' and then via the kidney-shaped

inlet ports

15a and 15a into the cylinders 13 and 130. As the drums sweep around so that their cylinders are successively aligned with the output ports, the pistons are driven inwardly to displace the fluid via the outlet ports b, 15b, the

passages

19 and 19 and the ports 21 to the load. Both outlets 21 are independent one from the other and can be connected via suitable valves to deliver corresponding quantities of fluid to a common line or to individual lines. Additional fluid is returned to the housing via fitting 22.

It will be apparent that the frame arrangement 9 always allows both pumps to be swung identically. It has been found, moreover, that it is advantageous to provide means for controlling the

servomotor

17, 18 in a feedback path, in accordance with the pressure developed by both of the pumping units. As shown in FIG. 5, the housing I has its shaft 2 driven by the electric motor 40 while the output ports 21 each deliver fluid via

lines

41 and 42 to

respective loads

43 and 44 in one position of the corresponding distributing

valve

45, 46. In another position, the

valves

45 and 46 may deliver the combined output of the two pumps to a common load 47. The valves may be provided in the frame 9 to selectively connect the ports of the units with pivot tubes together or undividedly as desired.

The hydraulic return from the loads proceeds via line 48 to the inlet fitting 22. In each of the

lines

41, 42, there is a pressure-

sensing element

49, 50, the combined output of which operates a control 51, for the

servomotor

17, 18.

In the embodiment illustrated in FIGS. 3 and 4, two

swingable flanges

109 and 209 are provided and are pivoted one above the other at axes A and A" defined by the

fittings

121, 121' and 221, 221" constituting outlets for the fluid as previously described. The housing 27 carries a bearing 270 (FIG. 4) in which the drive shaft 25 is journaled. This drive shaft can be tied to the usual electric motor by any conventional means. Within the housing 27, the drive shaft 25 carries a pinion 24 which meshes with the four gears I03, 203 and 104, 204 which are paired as described in connection with FIGS. 1 and 2 to operate the pump units of each frame. The device of FIGS. 3 and 4 thus has four pump units each having a kidneyshaped hydraulic inlet port 120, I and 220, 220 communicating via the respective control plate 115, 215 with the cylinder drums as represented at 111 and2l1 in FIG. 4. It will be understood that a second cylinder drum, corresponding to the drum 12, is provided in each of the

frames

109, 209 but is not visible in FIG. 4. A servomotor including a cylinder 27b, a piston 18, a piston rod 17 and a pair of lugs 16, pivotally connecting the piston rod 17 to the lower frame 209 serves to angularly shift the frames between the null position of the device represented in solid lines in FIG. 4 and the maximum pivot position shown in dot-dash lines, in which the pumps operate at maximum capacity. The single inlet 22 delivers hydraulic fluid to the interior 27c of the housing 27 from which rotation of the cylinder drums 111, 211, etc. draws the fluid into the cylinders 113,213 in which the axial pistons 113', 213 are axially shiftable by the

respective control flanges

106, 206 as the drums III, 211 are rotated about the

axles

110, 210.

The drive flange 106 of the upper pair of pumps (FIG. 3) have respective shafts 23 carrying the

gears

103, 104 in mesh with a common gear 24 so that both drums of each pair and all four of the cylinder drums are rotated in the same sense.

As shown in FIG. 5, all four outlets 21 can be connected via respective valves or distributing arrangements so that both outlets of each frame may be connected together to a common load, all four outlets may be tied to the common load, or each

outlet

121, 121', 221, 221' have been connected to an individual load. When the outlets are doubled to one load, the quantity of fluid displaced is double and the four-pump arrangement of FIGS. 3 and 4 act as a double-pump arrangement. Since the outlets may be tied together in any combination or used individually, this system may constitute effectively a triple or quadruple pump system.

As in the embodiment of FIGS. 1, 2 and 2a, the servomotor acts upon the housing at a location remote from its pivot axis A, A" which substantially lies in the plane of the drive flanges. In the embodiments of FIGS. 3 and 4, the lower frame 209 is connected to the upper frame 109 via a rigid link 26 and pivots 26' and 26" thereof.

It is self-understood that while the illustrated embodiment interconnects the two swingable frames for joint and equal pivotal displacement, it is possible to provide means for shifting these frames individually (i.e. a respective servomotor I6- l8, etc.) or to couple the frames with a linkage maintaining a predetermined relationship in the pivotal movements of one frame with respect to the other. When the frames are provided individually with servomotor means, I prefer to have them swing outwardly from one another as they move out of their null position, whereupon the symmetrical configuration of the housing is also required. Should it be desired to rotate the pumps in opposite senses as in the systems of FIGS. 1 and 2, the central pinion 24 can be dispensed with and the gears of the individual pumps meshed in a chain so that one of the pump shafts can be driven to operate all of the pumps. A chain arrangement of this type, however, depends upon exactitude in providing the teeth of the gears if the output of each pump is to equal that of the others. Of course, the pinion 24 can also be shifted from one side to mesh, for example, with both the

gears

103, 203. In this case, gears 103 and 104 and gears 203, 204 may interrnesh and the chain avoided while the units of each frame are driven in opposite senses.

In FIG. 6, I show diagrammatically how the

ports

60 and 61 of a control or valve plate 62 within a swingable frame are connected to respective ducts formed as

coaxial tubes

63 and 64 in a hollow pivot of the type shown at 7, 8 and 21 in FIG. I. These ducts are tied to a rotary slide valve 65 of the distributing type, each of the hydraulic units being provided with such a valve as described in connection with FIG. 5. The rotary slide valve 65 is hydraulically connected to the hydraulic motor 66 which mechanically operates a load 67 and to a reservoir 68, which can be the outer casing of the machine. Using the rotary slide valve 65, the functions of the

ports

60 and 61 can be interchanged and reverse rotation of the cylinder drum accommodated.

In FIG. 7, I show an arrangement where, unlike FIGS. 1 and 2A in which the ducts in the swinging frame 9 are cast in situ, the ducts 70 are built up by bolting

plates

71 and 72, 73 and 74 together to form the swinging frame, a pivot of which is shown at 75. Similar plates form the base of the trough of the swingable frame which receives the control of valve plate 76. Unused ducts can be closed by plugs 77, while the flexible tubes 78 with telescoping tube portions 79 can be used to connect the ducts 70 etc. with the load etc. When it is desired to avoid the use of rotating ducting arrangements.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art. all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

I claim:

I. A hydraulic installation comprising:

a housing;

a trough-shaped support received in said housing and having a generally flat bottom and a pair ofoutwardly turned pivot members at opposite ends of support defining a pivot axis parallel to said bottom, said bottom defining a pair of fluid-distribution surfaces each surrounding a respective rotation axis coplanar with said pivot axis but perpendicular thereto and spaced apart along the pivot axis, each of said surfaces having a pair of diametrically opposite arcuate ports centered on the respective rotation axis, said ports including inner ports relatively proximal to one another and outer ports relatively distal to one another, said trough-shaped support being provided with a pair of passages each connecting one of said outer ports with a respective one of said members for conducting fluid therethrough and at least one further passage communicating between said proximal ports at the interior of said housing around said trough-shaped support, said housing forming a pair of journals rotatably receiving said members while permitting fluid communication therethrough;

2. The hydraulic installation defined in claim I wherein two such supports are provided in said housing for swinging movement about respective parallel pivot axes lying in a common plane, said installations further comprising link means interconnecting said supports for joint swinging movement through identical angles.

3. The hydraulic installation defined in claim 2 wherein said gear means includes a respective driven gear fixed to each of the shafts of the cylinder barrels of each of said supports, and a common drive gear meshing with all of said driven gears.