US3385226A - Hydraulic pumps or motors - Google Patents

Description

May 28, 1968 o. H. THOMA HYDRAULIC PUMPS OR MOTORS 5 Sheets-Sheet 1 lNvaw-roa M o .m H D a M 0 ATTORNEYS May 28, 1968 o. H. THOMA 3,385,226

HYDRAULIC PUMPS OR MOTORS Filed June 24, 1966 5 Sheets-Sheet 2 INVENT'QR AT TORN EY May 28, 1968 o. H. THOMA HYDRAULIC PUMPS OR MOTORS 5 Sheets-Sheet 3 Filed June 24, 1966 INVENTOR flan/.440 6. 7790/1441 %d-u 2 7W A oauevs United States Patent 3,385,226 HYDRAULIC PUMPS 0R MOTORS Oswald H. Thoma, Cheltenham, England, assignor to Unipat A.G., Glarus, Switzerland, a Swiss company Filed June 24, 1966, Ser. No. 560,258 Claims priority, application Great Britain, Jan. 22, 1966, 2,998/ 66 5 Claims. (Cl. 103-162) ABSTRACT OF THE DISCLOSURE An opposed axial piston pump or motor comprising a rotor formed with parallel cylinder bores in each of which is fitted a liner sleeve, with pairs of opposed pistons sliding in each sleeve and valve means for controlling the admission and discharge of fluid from the cylinders, the communicating passages between the cylinders and the valve means including radial drillings which intersect the inner and outer walls of the cylinder bores, the outer sections being closed by the cylinder sleeves, whereas ports in the sleeves communicate with the inner passage sections.

This invention relates to axial piston hydraulic pumps or motors and is particularly though not exclusively concerned with high torque hydraulic motors.

It has previously been proposed to provide an axial piston hydraulic motor with a number of cylinders spaced around a cylinder block, each cylinder containing a pair of opposed pistons, and each piston being connected through a ball joint to a sliding slipper which runs on one of a pair of inclined cam surfaces or swash plates at opposite ends of the machine. As compared with an axial piston motor having a single piston in each cylinder this double piston construction provides an increased fluid capacity and consequently a higher output torque when used as a motor. Such motors inherently require a comparatively large number of cylinders in order to obtain the maximum overall volumetric capacity, for the same reason for providing a higher torque.

Hitherto it has been the practice to form the rotary cylinder block as a single mass with the cylinders machined therein, spaced around the axis of rotation. It is of course necessary to provide fluid passages leading into each cylinder adjacent its mid-point from the rotary timing valve ports. The timing valve ports are required to be as close as possible to the rotary axis, in order to maintain at a minimum the area of the timing valve surfaces which are exposed to the high pressure fluid. If

the area is excessive the force generated will be very great, and there will also be a likelihood of excessive leakage. Hitherto the normal method has been to drill inclined passages from one end of the cylinder block leading outwardly from the rotary timing valve ports to the mid-points of the cylinders. This Prior method of construction resulted in a number of difficulties and disadvantages. In the first place it is difficult or awkward and somewhat expensive to drill these inclined passages accurately. It is also in practice not feasible to drill the passages radially inwards intersecting both walls of each of the cylinder bores and then to close up the outer part of each passage by a plug, since under the very high pressures occurring in such a machine a plug could not be relied on to close the passage safely. Furthermore in the prior construction the mass of material constituting the cylinder block increased the weight of the machine considerably and resulted in difliculties in heat treatment and in compensating for thermal expansion, and distortion.

It is an object of the present invention accordingly to provide an improved construction of axial piston pump 3,385,226 Patented May 28, 1968 or motor of the opposed piston type which will be simple and economical to manufacture and will avoid some or all of the disadvantages referred to above.

The invention consists broadly in an axial piston pump or motor comprising a rotary member provided with spaced cylinders parallel to the axis of rotation, each containing a pair of opposed pistons, a non-rotary cam member on each side of the rotary member, each cam mem ber having a surface inclined, or capable of being inclined, to a plane normal to the axis of rotation, and means acting between the pistons and the cam surfaces to cause reciprocation of the pistons as the rotary member rotates, or vice versa, the cylinders being formed by separate hollow cylindrical sleeves carried by the rotary member.

It will be understood that one or both cam members may be capable of angular adjustment about the rotary axis, for the purpose of altering the capacity of the pump or motor, for example in the manner described in British specification No. 989,606.

A particular advantage afforded by the invention is that the use of the separate cylinder sleeves greatly facilitates the formation of the fluid passages communicating with each of the cylinders. Thus before the sleeves are assembled in the rotary member it is possible to drill radially inwards through both walls of each cylinder, and each sleeve will be formed with a single port in the inner part of its wall to register with the inner portion of the radial drilling, the sleeve itself closing off the outer part of the drilling. A further advantage of the invention is that the mass of the rotary member is considerably reduced and since the cylinder sleeves are formed separately they can be of a material different from that of the other parts of the rotary member and can be separately machined, heat treat-ed and finished. The construction also facilitates replacement of the cylinder sleeves if damaged or worn without replacing the whole rotary member.

Thus according to a preferred feature of the invention a fluid pressure passage is .formed in the rotary member extending generally radially inwards, from each of the cylinders, and each cylinder sleeve closes off the outer portion of this radial passage but has a through port communicating with the inner portion of the radial passage.

The inner portion of the radial passage may be formed in an intermediate part sandwiched between two end parts, the three parts together constituting the rotary member.

The two end parts are preferably of hollow tubular form each having a radial flange at the end thereof adjacent the intermediate part.

In any case the pump or motor preferably includes a non-rotary timing member in engagement with the intermediate part, the timing member having fluid inlet and outlet passages arranged to communicate with appropriate ones of the radial passages, as the radial member rotates.

The timing member may be a timing plate having a substantially flat end surface perpendicular to the axis of rotation and engaging a corresponding fiat surface on the intermediate part.

Alternatively the timing member may have a cylindrical portion extending within a cylindrical recess in the intermediate part and having inlet and supply passages in its external cylindrical surface which engage with appropriate ones of the radial passages in the intermediate part as the rotary member rotates.

According to another preferred feature of the invention the timing member is supported from one end of the machine by a pair of elongated tubes constituting inlet and outlet passages.

According to another preferred feature of the invention the cylinder sleeves are supported by a radially projecting flange or flange assembly on the rotary member, the flange having substantially smaller axial dimensions than the cylinder sleeves.

The invention may be performed in various ways and two specific embodiments will now be described by way of example with reference to the accompanying drawings, in which:

FIGURE 1 is a sectional side elevation through a hydraulic motor according to the invention,

FIGURE 2 is a half cross-section on the line II-II in FIGURE 1,

FIGURE 3 is a cross-section on the line IIIIII in FIGURE 1,

FIGURE 4 is a sectional side elevation through an alternative form of hydraulic motor according to the invention, including a pintle-type valve, and

FIGURE 5 is a cross-section on the line VV in FIG- URE 4.

In the first example the invention is applied to a high torque axial piston hydraulic motor of the opposed piston type, comprising a cylindrical casing closed at one end by an end plate 11. Within the casing is mounted a rotary member supporting eleven cylinders equally spaced about the axis. At opposite ends of the casing there are provided annular cam members 12, 13 fixed in the casing each having an annular cam surface 14 inclined at an angle of approximately 15 to a plane perpendicular to the axis.

The rotary member is formed in three main parts, namely two hollow end parts 15, 16, each having a radial flange 17, 18, at its inner end, and an intermediate substantially flat circular plate-like part 19 sandwiched between the two' flanges. The two end parts 15, 16 are supported in roller thrust bearings 20, 21 from the casing of the machine and the end part 15 at the open end of the casing has internal splines 22 by which it can be connected to an output shaft of the motor (not shown).

The two flanges 17, 18 on the end parts, and the intermediate plate-like part 19, are formed with eleven aligned apertures spaced around the axis of rotation to receive eleven cylinder sleeves 23, each sleeve projecting axially a substantial distance beyond the respective flange. Each cylinder sleeve can be formed of a suitable material difierent from that of the rotary member, and can be suitably heat treated, machined and finished independently of the three component parts of the rotary member. Within each cylinder sleeve 23 are mounted a pair of opposed pistons 24, 25, the pistons being urged apart by a spring 26 and each piston having a spherical socket at its outer end to receive the spherical ball on a sliding slipper 27 engaging the respective annular cam surface The end plate 11 at the closed end of the machine is formed with four axial through-passages, one pair constituting fluid inlet passages 30, while the other pair constitute fluid outlet passages 31. Only one passage of each pair is shown in FIGURE 1. On the internal side of this end plate 11 the passages issue into cylindrical sockets or recesses 32 in which are mounted the ends of four elongated fluid pipes 33, 34, 35, 36. These pipes extend within the respective hollow end part 16 of the rotary member and at their opposite ends the pipes seat in four corresponding sockets 37 in a non-rotary timing plate 38. Two diametrically opposite pipes 34, 36 are rigidly interconnected by a welded web 39 to increase the torsional stifiness of the pipes which therefore hold the timing plate 38 against rotation. The timing plate has a substantially flat end surface 40 arranged to bear directly on a corresponding flat surface 41 of the intermediate part 19 of the rotary member. A stub or spigot 42 mounted in the timing plate 38 seats in a central recess in the intermediate part 19 to hold the two in alignment on the rotary axis. The two fluid inlet pipes 33, 34 each communicate with a kidney-shaped fluid inlet port 43 in the timing plate while the two outlet pipes 35, 36 communicate with a corresponding kidney-shaped outlet port 44.

Before the cylinder sleeves 23 are assembled in the rotary member the intermediate part 19 is formed with radial fluid passages 50 extending inwards from the cylinders, each radial passage at its inner end intersecting a corresponding axial drilling 51 at the same radial displacement as the kidney ports 43, 44 in the timing plate.

The method of forming these passages 50, 51 is rendered particularly easy by the use of the cylinder sleeves 23. The radial portion 50 of each passage is formed by simply drilling inwards from the outer periphery of the intermediate part 19 so as to penetrate the outer periphery at 52 and intersect both walls of each cylinder housing. The axial portion 51 of each passage is simply formed by drilling axially from the appropriate end face 41 of the intermediate part. Each cylinder sleeve 23 is preformed with one aperture 53 in its wall, which will be aligned with the inner radial portion 50 of the fluid passage, and when the cylinder sleeves 23 are assembled in the rotary member the sleeve itself will then blank or close off the outer radial portion 52 of the passage. Thus there is no necessity to use a plug to close this outer portion of the passage and moreover the sleeve itself, being a substan tially complete hoop around its outer periphery, will provide the maximum possible hoop strength resisting the internal fluid pressure. Each radial drilling 50 is formed with an enlargement at its outer end to accommodate a spring-pressed sealing sleeve 54, which also seats in a shallow recess in the respective cylinder sleeve and locates each cylinder against axial or rotational movement.

In the second example of the invention illustrated in FIGURES 4 and 5, the construction is substantially identical, with the exception of the timing member and the intermediate part of the rotary member. In this example a hollow cylindrical or pintle-type timing assembly is adopted in lieu of the axial face-type assembly of the previous example. The remaining parts are indicated by the same reference numerals as in FIGURES 1 to 3, and will not be described in detail.

In this case the timing member comprises a cylindrical member 60 fitting within a hollow cylindrical recess in the intermediate part 61, the timing member 60 being formed with annular fluid inlet and outlet grooves 62, 63 in its external cylindrical surface, each groove subtending an angle of somewhat less than The intermediate part 61 in this example is formed with straight radial fluid passages 64 which extend directly inwards from the cylinders 23 into radial ports which communicate respectively with the inlet and outlet grooves 62, 63 as the rotary member rotates. In order to provide pressure balancing in a transverse direction the cylindrical timing member 60 has arcuate grooves 66, 67, in its external cylindrical surface, each groove subtending an angle of less than 180 at the rotary axis. Each such groove section is connected by an internal drilling 68, 69, (see FIG- URE 5) with the respective groove 62, 63 on the oppo site side of the rotary axis.

In this second illustrated example, in order to absorb the axial end loads exerted by the fluid pressure on the timing member 60, tie rods 65 or other axial tension members are provided within each of the fluid pipes 33 and 35, the rods being connected at opposite ends to the timing member and to the stationary end wall of the motor. The two pipes 33 and 35 are rigidly interconnected by a welded web 39 to hold the timing member 60 against twisting about the main rotary axis. This construction allows slight universal movements of the timing member 60 relative to the casing, to allow self-alignment with the intermediate member 61.

I claim:

1. An axial piston pump or motor comprising a rotary member provided with double-ended spaced cylinder bores parallel to the axis of rotation, a separate hollow cylinder liner sleeve located in each cylinder bore, a pair of opposed pistons in each cylinder sleeve, a non-rotary cam member on each side of the rotary member, each cam member having a surface inclined, or capable of being inclined, to a plane normal to the axis of rotation, means acting between the pistons and the cam surfaces to cause reciprocation of the pistons as the rotary member rotates, or vice versa, a non-rotating distributing member having fluid admission and discharge passages, and a rotating valve member connected to rotate with said rotary member, and cooperating with said distributing member to control the admission and discharge of fluid to and from the individual cylinders, and including a fluid connecting passage between the interior of each cylinder sleeve and an associated port in said rotary valve member, each fluid connecting passage including a passage section which extends generally radially inwards from the periphery of said rotary member and intersects each of said cylinder bores, and in which each cylinder sleeve closes 011 the outer portion of this radial passage section but has a through port communicating with the inner portion of the radial passage section.

2. A pump or motor as claimed in claim 1, in which the rotary member comprises an intermediate part sandwiched between two end parts, and the inner portion of the radial passage section is formed in the said intermediate part which also constitutes said rotating valve member.

3. A pump or motor as claimed in claim 2, in which the two end parts are of hollow tubular form each having a radial flange at the end thereof adjacent the intermediate part, the two flanges and the intermediate part being formed with aligned apertures spaced around the axis of rotation thereof, said aligned apertures constituting the cylinder bores.

4. A pump or motor as claimed in claim 1, in which said non-rotating distributing member is a timing plate having a substantially flat end surface perpendicular to the axis of rotation and engaging a corresponding flat surface on said rotating valve member.

5. A pump or motor as claimed in claim 1, in which the axial length of each cylinder liner sleeve is appreciably greater than the corresponding axial length of each respective cylinder bore in said rotary member.

References Cited UNITED STATES PATENTS 2,273,468 2/1942 Ferris 103-161 2,428,809 10/1947 Parilla et al. 103-173 2,431,686 12/1947 Deschamps 103173 2,577,242 12/1951 Grad 103-462 2,601,830 7/1952 Berlyn et al. 103162 3,079,869 3/1963 Purcell 103162 3,200,762 8/1965 Thoma 103162 FOREIGN PATENTS 1,343,916 11/1963 France. 622,787 7/ 1961 Italy.

DONLEY I. STOCKING, Primary Examiner.

WILLIAM L. FREEH, Examiner.

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