US3361038A

US3361038A - Hydraulic pumps and motors

Info

Publication number: US3361038A
Application number: US492433A
Authority: US
Inventors: Orloff George
Original assignee: Molins Machine Co Ltd
Current assignee: Molins Machine Co Ltd
Priority date: 1964-10-05
Filing date: 1965-10-04
Publication date: 1968-01-02
Anticipated expiration: 1985-01-02
Also published as: GB1085293A; DE1528486A1

Description

Jan. 2,1968 G. ORLOFF 3,361,033

HYDRAULIC PUMPS AND MOTORS Filed Oct. 4, 1965 2 Sheets-$heet 1 Jan. 2, 1968 G. ORLOFF HYDRAULIC PUMPS AND MOTORS 2 Sheets-Sheet 2 Filed on. 4, 1965 United States Patent 3,361,038 HYDRAULIC PUMPS AND MOTORS George Orlotr", Deptford, London, England, assignor to The Molins ()rganisation Limited, London, England, a corporation of Great Britain Filed Oct. 4, 1965, Ser. No. 492,433 Claims priority, application Great Britain, Oct. 5, 1964, 40,480/64 11 Claims. (CI. 92-58) ABSTRACT OF THE DISCLOSURE A hydraulic motor or pump is disclosed having at least one rotor containing a plurality of cylinders which are arranged in two rows. Ball pistons are used in the cylinders and operate on a cam track comprising two symmetrically disposed bevelled Working surfaces which contact the balls at a point offset from the axes of their respective cylinders.

This invention relates to hydraulic pumps and motors and the ilke, and more particularly to such pumps and motors of the type in which a plurality of balls serve as pistons, each ball being accommodated in a different one of a plurality of cylinders radially disposed in a rotor member, being surrounded by a stationary cam track on which the balls ride and from which they derive a reciprocating motion relative to their cylinders. In such motors, the balls are held by the rotor member against movement parallel to its rotational axis; each ball therefore rotates about an axis collinear with one of its own diameters, in the plane defined by the circle of contact with the rotor cylinder bore, and it is well known that difiiculties arise due to the fact that necessary lubricant is centrifuged away from said points of contact.

(For convenience, throughout the present specification we refer simply to hydraulic motors although the invention is equally applicable to hydraulic pumps, as such devices are reversible, i.e., they may be supplied with fluid under pressure and produce shaft rotation or, if the shaft of such a device is mechanically rotated, fluid made available to the device will be pumped.)

It is an object of the present invention to provide an improved hydraulic motor of the type defined above.

According to the invention, we provide a hydraulic motor of the type defined, in which the rotor member has two sets of balls, held in two spaced planes normal to the rotational axis of said rotor member, and the stationary cam track has two symmetrically-disposed bevelled working surfaces with which the balls of the two sets respectively coact.

It will be appreciated that the employment of bevelled working surfaces on the cam track results in the generation of end thrusts (i.e., thrusts parallel to the axis of rotation of the rotor member) but the symmetrical dis position of said surfaces causes such end thrusts to be equal and opposite. If the balls of the two sets are aligned, said end thrusts always balance, but in machines involving the present invention the balls are arranged in staggered relationship so that a small alternating end thrust appears. It will be appreciated that, due to the bevelling of the working surfaces of the cam track, the axis of rotation of each individual ball is inclined to the rotational axis of the rotor member, and the aforesaid alternating end thrust imparts to each ball a further angular movement about a different axis. In the result, the balls do not have fixed arcs of contact with the rotor member nor is the contact of each ball with the cam track confined to a single circumferential track on the ball; instead the points of contact of each ball with the rotor member and with the cam track move over the balls surface in patterns approximating to repeated figures-of-eight. It will be apparent that more satisfactory lubrication can be at tained than with prior arrangements; moreover the resultant lengthening of the track of the point of contact with the cam track materially lengthens the fatigue life of the balls which has been a critical factor in the performance of hydraulic motors of the type defined, due to the high stresses arising due to the instantaneous contact area between each ball and cam track being very small, approximating closely to a true point contact.

In order that the invention may be well understood, a preferred form of motor embodying the invention will now be described in some detail, reference being made to the accompanying drawings in which:

FIGURE 1 is a sectional side view of a motor embodying the invention;

FIGURES 2 and 3 are end and side views respectively of part of the motor of FIGURE 1, shown diagrammatically and on a larger scale;

FIGURE 4 is a view similar to FIGURE 1 but of another form of motor; and

FIGURE 5 is a section on line VV of FIGURE 4.

Referring first to FIGURES 1 to 3, the motor there shown has a plurality of balls 1 serving as pistons. Said balls 1 are ten in number, and are arranged in two groups or sets of five so that all the balls of each set lie in a common plane normal to the axis of an output shaft 2, the planes of the two sets being spaced. In each set the balls 1 are symmetrically disposed around the said axis but the balls of the two sets are in staggered positions so that, viewed axially of said output shaft, the ten balls 1 lie on imaginary lines radiating from the axis of the shaft at equal angular spacings, the balls lying on any two adjacent lines including one of each set.

The balls 1 are accommodated in individual radial bores 3 in a rotor member 4 connected to the output shaft 2. The member 4 is tubular and within it lies a stationary fluid distributor member or pintle 5 having ports 6 in its surface with which ports '7 in the otherwise closed radially inner ends of the bores 3 communicate whenever the angular relative positions of the members 4 and 5 so permit. The member 5 has internal fluid passages 8 connecting the ports 6 with external fluid connections 9 providing flow and return paths for hydraulic fluid.

Around the rotor member 4 is disposed a stationary annular member 10 providing on its inner face a cam track which is engaged by the balls 1. The configuration of this cam track is such as to allow reciprocation of the balls 1 in bores 3 whenever the rotor member 4 rotates. As is apparent from FIGURE 2, in the motor shown the member 10 provides a simple circular track for the balls 1 but said track is eccentric relative to the axis of shaft 2, accordingly each of the balls 1 undergoes one complete cycle of reciprocation whenever shaft 2 makes one complete revolution.

It will be understood that the relative positioning of the cam track and the ports 6 is such that during rotation of the member 4 each cylinder is in communication with the connection for supply of pressure fluid while the ball in that cylinder is passing over that part of the cam track which permits the ball to move outward in its cylinder and in communication with the fluid return connection while the ball is passing over that part of the cam track which constrains the ball to move inward.

The cam track in the present motor, while as just set out providing for reciprocation of the balls in conventional manner, has according to the invention a configunation (best seen in FIGURE 3) such that the balls 1 do not make contact with said cam track at points on the axes of their respective cylinders, but rather at points offset from such axes. The inner surface of the member It) has a recess or groove 11 with symmetrically bevelled end portions 12, the width and disposition of the groove 11 being such that the said bevelled end portions 12 provide the actual working surfaces, i.e,, are engaged by the balls 1; it will be seen that the balls of one set engage one of the portions 12, and the balls of the other set engage the other of such portions. The surfaces of portions 12 are not frusto-conical, but of concave toroidal form; this enables a larger contact area to be obtained between each ball and its associated portion 12, when the ball is subject to any given load and consequently undergoes a corresponding deformation at its instantaneous point of contact with the portion 12, thus reducing surf-ace stresses.

It will readily be understood that the bevelled form of the portions 12 of the cam track which are engaged by the balls 1 results in the generation of end thrusts (i.e., reaction forces parallel to the axis of the shaft 2). If the balls 1 of the two sets were aligned in pairs, these end thrusts would at any instant be equal and oppositely directed, due to the symmetrical arrangement of said bevelled end portions 12, but the staggered arrangement of the balls of the two sets prevents this balancing of the end thrusts and, during rotation of the member 4, an oscillatory residual end thrust is present, together with :a proportional oscillating couple. The inclination of the portions 12 and the axial spacing of the planes of the two sets of balls l are so chosen that these residual forces are small but their effect, in conjunction with the fact that the points of contact between the balls 1 and the cam track are ofiset from the axes of ,the respective cylinders as above noted, is to produce a complex motion of the balls 1. The point of contact of each ball 1 with its respective cam track portion 12 at any instant does not lie upon a circle around such ball (as is customary in conventional hydraulic motors of the relevant type) but upon a much longer track Comprising, approximately, a succession of figures-of-eight on the surface of the ball.

Thus, it will be understood that the working life of the balls is materially extended, because the complex motion of the balls reduces the frequency of stress alternation at those parts of the balls surface subject to varying stresses. Furthermore, there is a similarly complex relative motion between each ball and its cylinder which assists in maintaining proper lubrication of said balls, as contrasted with conventional arrangements where the balls in general rotate about axes parallel to the axis of shaft 2 and consequently tend to centrifuge lubricant away from those points where such axes of rotation meet the surface of the balls, at which points the balls are closest to the walls of the cylinders and most need the protection of an adequate lubricant film.

Various parts of the motor shown in FIGURE 1 have not been mentioned herein, as it is believed that their nature and purpose will be apparent to those skilled in the art without specific reference, e.g., bearings and oil seals or packings, and such parts may take any convenient form without departing from the scope of the invention.

It should also be understood that various changes may be made in the features to which specific reference has been made, e.g., the member may have on its inner surface a rib, with symmetrically bevelled edges, in substitution for the groove 11 and end portions 12 respectively.

Referring now to FIGURES 4 and 5, there is shown a two-rotor motor similar in many respects to the motor of FIGURES l to 3. The details of the individual rotors will therefore not be described in detail, but it will be noted that the references used in FIGURES 1 to 3 are applied to corresponding parts of FIGURES 4 and 5.

With a multi-rotor motor, it is desirable to arrange that each individual rotor has some degree of freedom of movement parallel to the axis of rotation, so that it may align itself symmetrically with its cam track. In the construction shown, two rotor members 4 are carried on a common pintle 5a and are provided with axially projecting dogs 20 on their adjoining faces. A coupling ring 21 lying between the two rotor members 4 receives the dogs 20 of both rotor members and thus the dogs and ring provide a driving connection such that the rotor members must move together in rotation but may assume such relative axial positions as are necessary for each individual rotor member to be symmetrically placed relative to its associated annular member 10 carrying the cam track for the balls ll of that rotor member. Similar dogs 22 and coupling ring 23 couple the right-hand (as seen in FIGURE 4) rotor member to a tubular output shaft 24.

(It should be noted that in FIGURE 4 the pintle 5a is drawn as if rotated through from its correct position, the latter being shown in FIGURE 5; also in FIG- URE 4 clamping bolts 3e are drawn in incorrect positions to show details otherwise not visible, bolts 30 being also correctly placed in FIGURE 5.)

In view of the length of pintle 5a, it is supported adjacent both its ends to provide sufficiently rigid support of the two rotor members. Near the left-hand end (as seen in FIGURE 4) said pintle is a suitably close fit in a casing or main frame 25 of the motor, while the righthand end of said pintle is received within the tubular output shaft 24 and supported there by a roller bearing 26. It will be noted that the bearing 26 is symmetrically placed relative to a pair of ball bearings 27 serving to carry the shaft 24 in the casing or frame 25.

It will be apparent that the structure shown in FIG- URES 4 and 5 permits desirably precise positioning of the individual rotor members relative to their cam tracks to be established on assembly and maintained during operation without requiring undue precision in manufacture and/or assembly of the parts. The inclusion of only two rotor members in the motor of FIGURES 4 and 5 is by way of example only, as three or more rotor members may readily be included, the pintle 5a and casing 25 being correspondingly lengthened.

As previously noted, the invention may be applied to pumps as well as to motors, the two forms of machine being in essence identical; as a practical matter, it is noted that for optimum performance the design of a pump will differ in detail from that of a motor, e.g., it will be somewhat differently timed.

What I claim as my invention and desire to secure by Letters Patent is:

1. A hydraulic machine of the class comprising pumps and motors, comprising a rotor member having a plurality of radially disposed cylinders, the said cylinders being arranged in two sets disposed in spaced planes normal to the rotational axis of said rotor member, a plurality of balls, each ball being accommodated in a different one of said cylinders and serving as a piston therein, a stationary annular member surrounding said rotor member and having a cam track located on the internal surface thereof, at least one portion of which is eccentric relative to the rotational axis of said rotor member, a groove formed within said cam track, said groove having opposite inwardly facing edges symmetrically bevelled and so disposed with respect to said sets of balls that each set of balls makes contact with one of said symmetrically bevelled edges at a point offset from the axes of their respective cylinders whereby during rotation of said rotor member said balls ride on said symmetrically bevelled edges giving said balls a complex rotational motion and a reciprocating motion simultaneously.

2. A hydraulic machine as claimed in claim 1 wherein said opposite symmetrically bevelled edges of said cam track are of concave toroidal form.

3. A hydraulic machine as claimed in claim 1 wherein said cam track is recessed in the internal surface of said annular member.

4. A hydraulic machine as claimed in claim 1, in which the balls of the two sets are arranged in staggered axial relationship.

5. A hydraulic machine as claimed in claim 1, in which the rotor member is carried on a coaxial stationary fluid distributor member.

6. A hydraulic machine of the class comprising pumps and motors comprising at least two rotor members each having a plurality of radially disposed cylinders, the cylinders of each rotor member being arranged in two sets disposed in spaced planes normal to the rotational axis of said rotor member, a plurality of balls, each ball being accommodated in a diiferent one of said cylinders and serving as a piston therein, a stationary annular member surrounding each of said rotor members and having a cam track located on the internal surface thereof, at least one portion of which is eccentric relative to the rotational axis of said rotor members, a groove formed within said cam track, said groove having opposite inwardly facing edges symmetrically bevelled and so disposed with respect to said two sets of balls that each set of balls makes contact with one of said symmetrically bevelled edges at a point offset from the axes of their respective cylinders whereby during rotation of said rotor members said balls ride on said symmetrically bevelled edges giving said balls a complex rotational motion and a reciprocating motion simultaneously.

7. A hydraulic machine as claimed in claim 6 wherein said opposite symmetrically bevelled edges of each of said cam tracks is of concave toroidal form.

8. A hydraulic machine as claimed in claim 6 wherein each of said cam tracks is recessed in the internal surface of each of said annular members.

9. A hydraulic machine as claimed in claim 6, in which the rotor members are carried on a coaxial stationary fluid distributor member supported adjacent both its ends.

10. A hydraulic machine as claimed in claim 6, including a shaft and in which the rotor members are drivingly coupled to one another and to the shaft by axially projecting dogs.

11. A hydraulic machine :as claimed in claim 10, including a coupling ring between adjacent rotor members and between the shaft and an adjacent one of said rotor members, each of said rings being arranged to be engaged by the dogs of the elements between which it lies.

References Cited UNITED STATES PATENTS 2,454,418 11/1948 Zimmerman 103-161 X 2,470,220 5/1949 Mott 103-161 2,712,794 7/1955 Humphreys 103-161 2,823,619 2/1958 May 92-58 X 3,044,412 7/ 1962 Orshansky 103-4 X 3,081,708 3/1963 Nyman et al. 103-161 3,118,388 1/1964 Eriksson 103-4 X 3,187,681 6/1965 Firth et al. 103-161 FOREIGN PATENTS 21,612 7/ 1961 Germany. 831,660 6/1938 France.

MARTIN P. SCHWADRON, Primary Examiner.

I. C. COHEN, Assistant Examiner.