US3587400A - Triple ball motor spindle drive - Google Patents

Abstract

THE INVENTION RELATES TO A BALL MOTOR IN WHICH THERE ARE A NUMBER OF ROWS OF BALLS CONTAINED IN CYLINDERS, THE CYLINDERS AND BALLS IN ADJACENT ROWS BEING OF DIFFERENT SIZES. MEANS ARE PROVIDED TO RENDER INOPERATIVE ROWS OF CYLINDERS IN A PREDETERMINED ORDER SO AS TO PRODUCE A DESIRED TORQUE CURVE.

Description

Uite tates Paten Inventors Donald Firth;

Sinclair Upton Cunningham, East Kilbride, Glasgow, Scotland Appl. No. 782,664

Filed Dec. 10, 1968 Patented June 28, 1971 Priority Dec. 29, 1967 Great Britain sa on 9 Assignee National Research Development Corporation, 22990 En TRIPLE BALL MOTOR SPINDLE DRIVE 9 Claims, 8 Drawing Figs.

US. Cl 91/492, 91/180, 91/498, 92/72 Int. Cl F011b 1/06, FOlb 13/06 Field of Search 103/161 (A) (Cursory); 91/180, 204, (inquired), 205, (Cursory), 492; 60/53 (B) (Cursory); 92/72 [56] References Cited UNlTED STATES PATENTS 1,488,528 4/1924 Cordini 2,160,612 5/1939 Alpern. 2,163,080 6/1939 Benedek..... 2,303,685 12/1942 Eden et al.., 3,199,297 8/1965 Croswhite Primary Examiner- Paul E Maslousky Attorney-Cushman, Darby and Cushman ABSTRACT: The invention relates to a ball motor in which there are a number of rows of balls contained in cylinders, the cylinders and balls in adjacent rows being of different sizes. Means are provided to render inoperative rows of cylinders in a predetermined order so as to produce a desired torque curve.

PATENTED JUN28 sen SHEET 1 BF 5 n\ \w kwll PATENTEB JUN28 I971 SHEET '4 OF 5 PATENTEU IJUN28 1971 SHEET 5 BF 5 K u Q r TRIPLE BALL MOTOR SPINDLE DRIVE This invention relates to multicylinder piston motors. An object of the invention is to provide a multicylinder piston motor in which the torque capacity of the motor can be arranged to follow a predetermined curve.

According to the invention such a motor comprises a number of operating cylinders of different capacities and means to render one or more cylinders inoperative whereby the torque of the motor may be made to follow a predeter' mined curve.

The invention has particular, but not exclusive, application to multicylinder piston motors in which the pistons are in the form of balls. Ball motors are well known in themselves and usually comprise a plurality of rows of balls (of the same size) acting on a track or cam surface to produce relative rotation- -see for example copending British Pat. application Nos. 33412/64 and 56784/66. Such motors may be rotary or linear.

According to one aspect of the invention there is a ball motor with a plurality of rows of balls in cylinders the balls in each row being ofa different size to the balls in the other rows, means to supply operative fluid to all the ball containing cylinders and means to render inoperative one or more rows of cylinders.

Preferably, operating fluid for all the rows of cylinders and pistons is supplied through a common valve. Preferably, the means to render inoperative one or more rows is in the form of an isolating valve located between adjacent rows of cylinders. Preferably, there are at least three rows of cylinders with isolating valves located between each adjacent pair of cylinders. Preferably, the isolating valves are circular valve plates with apertures in them adapted to register with ports in the body of the motor containing the rows of cylinders.

According to another aspect of the invention in a ball motor of the kind in which a'number of balls bear against a cam track, the balls being contained in cylinders, and there being a number of rows of the cylinders, the sizes of the balls in the different rows are so chosen that by rendering inoperative rows of balls in sequence a predetermined torque curve is produced.

The number of rows of balls and the number of balls per row is dependent on the desired horsepower and torque curve of the motor, three rows of balls being shown in the following example merely as one possible configuration.

When a row of cylinders is rendered inoperative by cutting off the supply of operating fluid to it, it is necessary to provide means to drain the inoperative cylinders to prevent blockage.

This may be done by the same valves which are used to render the row of cylinders and pistons inoperative. The valve can include one or more apertures arranged, in the closed position of the valve, to connect the cylinders to a drain channel or channels so as to exhaust any fluid contained in the cylinders.

In the accompanying drawings is shown a ball motor, having three rows of balls of different sizes, embodying the invention.

In the drawings:

FIG. 1 is a longitudinal section through the ball motor;

FIG. 2 is a section on the line AA shown in FIG. 1;

FIG. 3 is a section on the line BB shown in FIG. I;

FIGS. 4 and 5 are scrap sections on the line CC showing the valve respectively in its closed and opened positions, the line CC being shown in FIG. 6;

FIG. 6 is a scrap section of part of the motor embodying one of the larger balls;

FIG. 7 is a graph showing a comparison between a constant horsepower torque curve and the torque plotted against r.p.m. for a motor not embodying the present invention and having three rows of balls of identical size so that the three rows have the same capacity; and

FIG. 8 is a similar curve showing how the torque available from a similar motor incorporating the present invention i.e., with different sizes of balls in the rows of cylinders, approaches much more closely the desired falling torque curve.

The motor shown in FIG. 1 comprises a cylindrical casing 10 within which is mounted a cylinder block 11 containing three rows of cylinders 12, 13 and .14, containing balls 12a, 13a and 14a respectively, the diameter of the cylinders 12 being less than the diameter of cylinders 13 which is in turn less than the diameter of cylinders 14. There are eight cylinders in each row. A spindle 15 is supported in the casing 10 by hydrodynamic bearings 16a and 16b. Attached to spindle I5 is an eccentric cam track 12b for the cylinders 12, a track 13b for the cylinders 13, and a track 1412 for the cylinders 14.

The track 14b can be seen more clearly in FIG. 2 from which it will be noted that this is a conventional ball motor in which fluid is supplied to the cylinders 14 in such a way that the balls I4e bear against the eccentric track 1412 so as to drive the spindle 15. The principle involved is well known and will not be described in detail.

Oil is supplied to the balls through a primary fluid flow or oil inlet passage 17 and there is a primary fluid return passage 18. The oil inlet passage 17 leads to a drilling 19 in the spindle 15 the drilling 19 being blocked at its outer end by a plug 20. The oil passes along the drilling 19 to a pintle valve 21. The valve 21 rotates with the spindle 15 and has a number of arcuate slots such as 22 round its exterior which will successively feed the eight passages 23, each of the passages 23 leading to one of the cylinders 12 via a secondary fluid supply and exhaust connecting passage 24. The pintle valve 21 is also connected to an oil return drilling 25 in turn connected through an annular groove 26 to the oil return passage 18.

Oil supplied and exhausted through the eight passages 24, will, as shown in FIG. I, reach all three rows of cylinders, but between row 12 and row 13 is a valve plate marked V2 and between row 13 and row 14 is another valve plate marked V1. These valve plates have apertures which, in the position shown in FIG. 1, allow the flow ofoil to all three rows ofcylinders. As shown in FIG. 3 each valve plate can be rotated to a closed position in which it blocks all the passages 24. The rotation of the valve plate is achieved by an arm 25 connected to the valve plate V1 and movable through an arc of 15 by an electromagnetically operated piston device 26. There will be a similar operating arm for the valve V2.

Considering for the moment the valve V1, between rows of cylinders 13 and 14, it will be seen that the supply and exhaust offluid to the rows of cylinders 14 can be cut off and the cylinders 14 isolated by movement of the valve plate V1. When this is done, the balls free wheel" and do not take part in driving the motor. The oil which would then be trapped between the balls 14a and the outer ends of the cylinders 14 is allowed to leak as illustrated in FIGS. 4, 5, and 6. FIG. 5 shows the valve VI in the open position in which a milled slot 27 in the face of the valve plate does not connect the cylinder 14 to a drilled hole 28 in the cylinder block. In the position shown in FIG. 4 where the valve is closed, exhaust oil from each of the cylinders 14 of the idle ball motor passes through the respective milled slot 27 and drilled hole 28 to a common annular drain channel 31 around the spindle IS. The drain channel 31 communicates with the ends of the cylinders remote from the passages 24, and also with the casing 10 as seen to the right of cylinder 14 in FIG. I.

The valve plate V2 is similarly provided with milled slots connecting to another drilling, not shown, and thence to channel 31.

When both valves V1 and V2 are closed both cylinders 13 and 14 are isolated from the oil supply and return passages, and only cylinders 12 and balls 12a are effective to drive the spindle 15.

In FIG. 7 is shown a falling torque curve 29 corresponding to constant horsepower. If three rows of cylinders of identical capacity were used by cutting out first one row and then a second row, the torque available would be as shown in the dotted line 30 in FIG. 7.

By using the present invention the torque is as shown in the dotted line in FIG. 8 which will be seen to be much closer to the desired torque curve.

In selecting the sizes for the various rows and the speed range over which each motor operates, the following desiderata apply:

1. The pump flow (of the pump which supplies the driving fluid) shall be the same at the maximum speed in each range. This ensures best utilization ofthe pump.

. The pressure at the beginning of each speed range will be equal to the maximum design pressure for the motor. This makes certain that the motor size for each of the speed ranges will be a minimum. These conditions, together with the equations relating to torque. pressure, speed and power, allow the motor sizes and the speed ranges to be calculated.

It is wasteful to have more capacity than is required because this results in a higher oil flow at a low pressure. In the example given, the torque capacity (or displacement) of the equal stage motor is six times the flow required for the graded ball motor at a maximum speed and the pressure is six times lower for the same power.

In general, the more stages in a motor then the more closely the torque capacity curve can follow the constant horsepower requirement. It will be appreciated that there is no limit to the number of stages that can be designeduntil the motor becomes unacceptably long. The choice of ball and lobe numbers depends on the torque speed requirements.

In the illustrated arrangement we require only one pintle or distributor valve'and this is designed to operate on a small diameter so that friction losses are small. The same number of balls and cam lobes are used in each row so that only one pin tle is necessary.

It will be apparent to those skilled in the art that while the invention described herein was described in the context of its use as a motor, ball motors of this type may as well be operated as pumps. This may be accomplished by merely driving the motor shaft, in this case spindle l5. As is common in the art, the generic term machine" may be used to refer to either a motor or a pump usage.

We claim:

l. A multicylinder piston machine comprising:

a primary fluid flow passage and a primary fluid return passage;

two rows of piston-and-cylinder assemblies, each row having a respective cam track with the same number of lobes to relate reciprocatory motion of the associated assemblies on the one hand, with motion peripherally of said cam track on the other hand;

a plurality of secondary fluid supply and exhaust passages each communicating with a respective pair of corresponding ones of said assemblies, one from each of said rows;

a pintle valve for permitting communication of both of said primary passages with said secondary passages in predetermined successive manner, said primary passages being communicated in alternating sequence with each one ofsaid secondary passages; and

an isolating valve including a common valve member disposed intermediate said two rows and operable to open and close secondary passages leading to one of said rows in unison to respectively communicate and isolate said one of said rows relative to said primary passages.

2. A machine according to claim 1 comprising:

a fluid drain channel, and wherein said isolating valve is further operable to respectively isolate and communicate said drain channel relative to said one row.

3. A machine according to claim 2 wherein said drain channel communicates with the ends of the cylinders of said one row of assemblies remote from said secondary passages.

4. A machine according to claim 1 wherein the piston of each of said assemblies is in the form ofa ball.

5. A machine according to claim 1 wherein said rows of assemblies have respectively different capacities.

6. A machine according to claim 1 wherein said rows are of each of circular form axially spaced one from the other along a common axis, with said secondary passages disposed in the form ofa cylindrical array about said axis.

7. A machine according to claim 5 comprising:

a fluid drain channel, and wherein said common valve member is disposed for rotation about said axis to intersect said secondary passages;

said member having a plurality of apertures therethrough to respectively open said secondary passages in one rotational position of said member; and

having a plurality of grooves in the face of said member nearer said one row to communicate the same with said drain channel in another rotational position of said member.

8. A machine according to claim 7 wherein said member is in the form of an annular plate provided with a plurality of radial bores communicating respective ones of said grooves with said drain channel.

9. A machine according to claim 1 comprising:

a third row of piston-and-cylinder assemblies similar to said two rows and communicated with said primary passages by said secondary passages; and

a second isolating valve including a second common valve member disposed intermediate said third row and said two rows, and operable to open and close said secondary passages in unison to respectively communicate at least one of said two rows, dependent on the operable position of the first-mentioned common valve member, and isolate said two rows relative to said primary passages.

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