US3037488A - Rotary hydraulic motor - Google Patents

Description

June 5, 1962 G. M. BARRETT 3,037,488

ROTARY HYDRAULIC MOTOR Filed Jan. 8, 1960 I 3 Sheets-sheaf 1 INVENTOR. aeowefl f. BarreZZ BY J9 7774-441 DA 4 G. M. BARRETT ROTARY HYDRAULIC MOTOR June 5, 1962 3 Sheets-Sheet 2 Filed Jan. 8, 1960 INVENTOR. 6 60796 Ba rreiz" June 5, 1962 c. M. BARRETT ROTARY HYDRAULIC MOTOR 3 Sheets-Sheet 3 Filed Jan. 8, 1960 B n m I 2 M M m m fi w I .EzaJOB R O m M Gsotzee M. BARRETT it PM 27% z W ATTORNEYS UnitedStates Patent 3,037,488 ROTARY HYDRAULIC MOTOR George M. Barrett, Galt, Ontario, Canada Filed Jan. 8, 1960, Ser. No. 1,381 7 Claims. (Cl. 121-61) This invention relates in general to new and useful improvements in hydraulic motors, and more particularly relates to a new and useful rotary hydraulic motor.

The present invention relates to rotary hydraulic motors of the type wherein the cylinders of the hydraulic motor are mounted in a rotor in radiating relation and the pistons of the individual cylinders react against a cam track to urge the rotation of the rotor. Heretofore, the obtaining of a pressure contact between the piston and the cam track has been a problem, in that it is necessary to provide for a rolling contact between a piston part and the cam track. As the result, numerous types of complicated roller assemblies have been provided. These, of course, are both expensive and subject to failure. The present invention is believed to distinguish over the prior rotary hydraulic motors. by providing pistons which are rotatable within their individual cylinders and which have rolling contact with the cam tracks so that one-piece pis-- tons may be utilized as opposed to the normal three or more piece pistons now in use.

Another object of the invention is to provide a rotary hydraulic motor wherein the lengths of the cylinders of the rotor of the motor are at least as great as the lengths of the pistons so that the pistons may be completely retracted within the cylinders, thus permitting the rotor to freely rotate within the housing of the motor without any circulation of hydraulic fluid whatsoever.

Still another object of the invention is to provide a novel hydraulic motor of the rotary type wherein the cam track is of a shape which provides for linear fluid consumption, and therefore eliminates pulsing and variations in torque regardless of the number of pistons carried by the rotor.

A further object of the invention is to provide a novel hydraulic motor which is provided with a fixed stator and port assembly, and a fixed camtrack, together with a rotor which rotates about the stator and within the cam track, the rotor being provided with any desired number of cylinders and pistons without changing the other structure of the motor.

Still another object of the invention is to provide in a rotary hydraulic motor a port arrangement of a nature wherein when the ports are opened and closed, there is approximately zero fluid flow, and the port opening is proportional to the piston speed, whereby flow velocity of the fluid at the port is substantially uniform.

A still further object of the invention is to provide a rotary hydraulic motor wherein the working fluid is applied in such a way that most of the load on the working parts of the hydraulic motor is balanced out, and fluid pressure is not applied to the structural parts of the motor.

With the above, and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims, and the several views illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 is an elevational view of a fluid motor constructed in accordance with the invention and coupled to a hydraulic system for operation, the hydraulic system being only schematically illustrated.

FIGURE 2 is an enlarged end view of the fluid motor of FIGURE 1, and shows the connections of the hydraulic lines thereto.

FIGURE 3 is an enlarged longitudinal vertical sec- 3,037,488 Patented June 5, 1962 tional view taken along the section line 3-3 of FIGURE 2 and shows the internal construction of the fluid motor.

FIGURE 4 a transverse sectional view, taken along the section line 4-4 of FIGURE 3, and shows the arrangement of the cylinders of the rotor, the ports in the stator, and the shape of the cam track.

FIGURE 5 is a transverse sectional view taken along the section line 55 of FIGURE 3, and shows the details of the stator in the vicinity of one end thereof to illustrate the connection between the return flow ports thereof.

FIGURE 6 is a transverse sectional view taken along the section line 6-6 of FIGURE 3, and shows the arrangement of the inlet ports in the stator and the manner in which they are connected together.

FIGURES 7, 7A, and 7B are schematic views illustrating the relationship of the various components of the hydraulic motor for one cylinder and piston when the piston is in its fully retracted position and show the relationship of the spacing between the cam track surface and the rotor and the relationship of the cylinder and an associated port.

FIGURES 8, 8A, 8B, 9, 9A, 9B, 10, 10A and 10B are views similar to FIGURES 7, 7A and 7B, respectively, and show the piston and cylinder in sequentially rotated positions from that of FIGURE 7.

Referring now to the drawings in detail, it will be seen that the embodiment of the invention illustrated in FIG- URES 1 through 6, inclusive, is generally referred to by the numeral 10. The hydraulic motor 10 includes a twopiece housing, generally referred to by the numeral 11. The housing 11 includes a generally cylindrical body member 12 and an end plate 13. The end plate 13 is suitably secured to the body 12 in sealed relation by means of a plurality of recessed cap screws 14. The cap screws 14 are best illustrated in FIGURES 2 and 3.

The end plate 13 carries a centrally located stator 15 which is illustrated as being formed integrally with the end plate 13, but which may be separate therefrom. The stator 15 is illustrated as having a central bore 16 therethrough which, if desired, may be omitted, or which may be used to receive a drive shaft connected to the rotor, if so desired.

The stator 15 has a generally cylindrical outer surface and a cylindrical rotor 17 is received thereover. In the simplest form of the invention, as illustrated in the drawings, the rotor 17 is journaled on the stator 15. The rotor 17 is provided with a plurality of cylinders 18, the cylinders 18 having their axes extending radially from the center of the rotor 17, and the cylinders opening through opposite surfaces of the rotor 17. A piston'19 is disposed in each of the cylinders 18. It is to be noted that in this form, of the invention, each piston 19 is in the form of a ball. The diameter of the individual piston 19 is substantially equal to the diameter of its respective cylinder 18. Furthermore, the length of each cylinder 18, that is, the thickness of the rotor 17, is equal to or slightly greater than the diameter of each piston 19. However, it is to be understood that each of the pistons 19 may be totally recessed within its respective cylinder 18 so that no portion thereof will project outwardly be-' yond the confines of the rotor 17. r

The housing body 12 has an interior surface; defining a cam track 20. The cam track 20 is illustrated as having three lobes, although the number of lobes may vary as is desired. Each of the lobes of the cam track 20 has a pair of similar thrust surfaces 21, 22, the pistons 19 reacting against one of the thrust surfaces to effect the rotation of the rotor and the other of the thrust surfaces reacting against the pistons to return the pistons to their retracted positions as the rotor 17 rotates. The direction of rotation of the rotor 17 will control which of the thrust surfaces is reacted against by the pistons and which reacts against the pistons to return them to their positions within the rotor 17. The thrust surfaces can be interchangeable in function to permit reversal of rotation.

The outer surface of the stator 15 in alignment with the cylinders 18 as they rotate about the stator 15, is provided with a plurality of ports. These ports include fluid pressure ports 23 and fluid return ports 24, the ports 23 and 24 being alternated about the circumference of the stator 15. A first longitudinal bore 25 extends partially through the stator 15 and opens through the end wall 13. The bore 25 opens into one of the ports 23 and is communicated with the others of the ports 23 by a groove 26 which extends about the circumference of the stator 15 and intersects all of the ports 23. The rotor '17 closely engaging the fixed stator 15 prevents leakage out of the recess 26 for all practical purposes.

The outer portion of the bore 25 is internally threaded, as at 27, and a fitting 28 is threaded thereinto. The fitting 28 is part of a hydraulic fluid supply line 29.

A second bore 30 extends into the stator 15 through the end wall 13 in ofrset relation to the center of the stator 15. The bore 30 intersects one of the ports 24 and opens thereinto. A recess 31 is formed in the exterior surface of the stator 15 remote from the end wall 13 and intersects all of the ports 24. Thus, hydraulic fluid may be returned through the ports 24, through the recess 31 and into the bore 30. At this time, it is pointed out that the ports 24 extend beyond the ports 23 away from the end wall :13, and the ports 23 extend beyond the ports 24 towards the end wall 13, whereby the recess 26 does not intersect any of the ports 24 and the recess 31 does not intersect any of the ports 23.

The outer portion of the bore 30 is internally threaded, as at 32, and a fitting 33 is threadedly engaged therein. The fitting 33 is part of the hydraulic fluid return line 34.

In the form of the invention illustrated, the rotor has a reduced cylindrical extension 35 which projects beyond the housing 11 and which has suitably coupled thereto a drive shaft 36. The rotor extension 35 is sealed with respect to the stator 15 by means of a suitable sealing ring 37 and with respect to the housing body 12 by means of a suitable sealing ring 38. If desired, the sealing rings 37 and 38 may be in the form of scaled bearings. This, of course, is merely a question of mechanical design.

There will, of course, be a small amount of leakage past the pistons into the space between the rotor 17 and the cam track 20. In order that the hydraulic fluid may be returned therefrom and thus not prevent the proper operation of the hydraulic motor 10, a drain bore 39 extends through the end wall 13 at the bottom of the housing 11. The bore 39 includes an outer enlarged portion 40 which is internally threaded and which receives a fitting 41 (FIGURE 1) of a drain line 42.

Referring now to FIGURE 1 in particular, it will be seen that the hydraulic system for the hydraulic motor 10 is schematically illustrated as including a reservoir 43 having disposed therein a hydraulic fluid supply. A line 44 extends from the reservoir 43 to a pump 45. The hydraulic fluid supply line 29 is connected to the outlet of the pump 45. The hydraulic fluid return line 34 and the drain line 42 are connected to the reservoir 43 for re turning hydraulic fluid thereto.

As is best illustrated in FIGURE 4, it will be seen that the ports 23 are so arranged that when the rotor 17 rotates and one of the cylinders 18 approaches a lobe of the cam track 20, the cylinder will uncover the port 23 and hydraulic fluid will be admitted to the cylinder behind its respective piston 19. The piston 19 will be urged outwardly and will engage one of the thrust surfaces 21, 22 which, for purposes of description, may be considered the thrust surface 21. The reaction of the piston 19 on the thrust surface 21 will result in a force urging the rotation of the rotor 17 about the stator 15. This rotative force will continue until such time as the piston 19 reaches the midpoint of the particular lobe, at which time, the respective port 23 will be momentarily closed by the rotor 17, and the particular cylinder 18 will have completely moved away from the port 23. Immediately thereafter, the cylinder 18 will uncover the next adjacent port 24, and as the piston 19 engages the thrust surface 22, the reaction of the thrust surface 22 on the piston 19 will urge the particular piston 19 inwardly with the piston 19 forcing the hydraulic fluid within its respective cylinder 18 inwardly and out through the return port 24. Since there is very little back pressure in the return system of the hydraulic motor 10, it will be seen that there will be very little resistance to the inward movement of the piston 19 and therefore very little loss of efficiency.

The number of lobes on the cam track 20 has been illustrated as three, and the number of cylinders and pistons has been illustrated as eight. Thus, each time the rotor 17 makes a complete revolution, there will be 24 power strokes. This provides for a relatively smooth force application.

The cam track 20 is symmetrical about the center line of the rotor, and is in the form of a modified polytrochoidal curve which permits the use of pistons of any number and of a variety of shapes. It will be readily apparent that the pistons 19, being of a ball configuration, roll against the cam track 20 and thus greatly reduce fric tion losses.

It will be seen that when a piston 19 has reached the end of its radial travel, the respective ports are then opened or closed, and the ports are opened and closed at a maximum speed. As a result of this, the flow of fluid through any port is virtually nil when it is being opened or closed. Consequently, cavitation, surging eddying and hydraulic shock are reduced to a very small amount and are almost independent of speed. The sum of the radial speed of all the pistons at any given time is equal to a constant. This results in a linear constant fluid flow through the motor.

Reference is now made to FIGURES 7, 7A, 7B through 10, 10A and 10B wherein it is clearly indicated that the rate of divergence of the cam track surface 21, for example, from the rotor 17 is the same as the rate of opening of the associated port 23, for example, such that the velocity of fluid flow through the port at a given speed of operation of hydraulic motor 10 remains constant. In accordance with the invention, in order to eliminate for all practical purposes any turbulence in flow, it is desired that the velocity of fluid flow through any port remains constant, and since the cross section of the cylinders 18 remains constant, only the movement of the piston 19 relative to the rotor 17 and the cross section of the opening of the port can vary. Therefore, it follows that in order to provide for the desired operation of the hydraulic motor 10, the rate of piston movement must be the same as the rate of port area increase, and since the rate of piston movement is controlled by the divergence of the cam thrust surface from the rotor, the rate of divergence of the cam thrust surface from the rotor must be the same as the rate of port area increases.

In FIGURES 7A, 8A, 9A and 10A, a comparison of the spacing between the outer surface of the rotor 17 and the cam surface 21, for example, is shown. In FIGURE 7A the rotor is touching the respective cam surface 21 so that the dimension A is zero. It will be seen that in FIGURES 8A, 9A and 10A the dimension A rapidly increases for a corresponding rotational movement of the rotor. In a like manner, in FIGURE 7B the cylinder 18 does not uncover any portion of the port 23. On the other hand, if the rotor rotates, the cylinder 18 progressively uncovers the port 23 and due to the fact that the cylinder in the particular form of hydraulic motor illustrated is circular, there is a rapid rate of change in the uncovered area of the port as compared to the relative circumferential movement of the cylinder with respect to the port. It will be readily apparent upon comparing FIGURES 7A and 7B through 10A and 10B that the rate of divergence of the cam surface 2.3 from the rotor 17 is the same as the rate of increase in cross section of the port open area.

It will be observed that the hydraulic fluid is applied into the interior of the hydraulic motor 10 in such a way that most of the load on the working parts of the hydraulic motor is balanced out and the fluid pressure is not applied to the structural parts of the hydraulic motor. It is also to be noted that the number of lobes on the cam track and the number of pistons is arbitrary as the hydraulic motor will operate with almost an unlimited number of combinations, provided that the number of pistons is not equal to the number of lobes.

The spacing of the ports is arranged in such a manner that the force on the pistons is translated into a turning force on the rotor. As each piston reaches its maximum radial travel, the outlet port is closed and the return port is opened. Further travel results in the piston being pushed inwardly, forcing the working fluid through the return port and returning the piston to its inner position ready for another pressure stroke. It will be seen that mechanical clearance or backlash is virtually eliminated by this construction. By reason of negligible backlash, reversing of the motor can be almost instantaneous without mechanical shock or overrun.

It will be seen that by placing the pistons in different planes of rotation, a very large number of cylinders can be employed without introducing mechanical complication thereby permitting a very much increased torque output at lower speeds. The upper limit of the speed of the motor is limited only by the volume of hydraulic fluid which can be admitted by the inlet and return passages. It will also be seen that the motor can be mounted with the so-called rotor in a fixed position and rotary motion being delivered through the rotation of the outer case or housing about the rotor. In addition, reversing can be accomplished by changing the direction of fluid flow, or by altering the phase relationship between the stator ports and the cam track.

At this time, it is also pointed out that changing the phase relation of the ports and cam track will result in altering torque and speed characteristics of the motor, and will make possible its efficient use with compressible fluid such as steam and air.

Although the motor may be operated in a manner to eliminate the braking action thereof, if a pressure difierential is maintained across the inlet and return passages, a braking effect on a rotating member driven by the motor can be accomplished.

From the foregoing, it will be seen that novel and advantageous provision has been made for carrying out the desired end. However, attention is directed to the fact that variations may be made in the example apparatus disclosed herein without departing from the spirit and scope of the invention, as defined in the appended claims.

I claim:

1. A rotary hydraulic motor comprising a housing, a centrally located stator supported by said housing, an inner wall of said housing defining a cam track, a cylindrical rotor mounted on said stator for free rotation, said cam track having a plurality of circumferential thrust surfaces, said rotor having a plurality of cylinders, a piston freely positioned within each of said cylinders for reciprocatory movement, inlet and outlet hydraulic passages in said stator and alternatingly opening through the surface of said stator in the form of ports disposed in operative relation to said thrust surfaces, said cylinders alternatingly uncovering said inlet and outlet ports as said rotor rotates with the hydraulic fluid passing through said inlet ports forcing said pistons into direct engagement with said cam track, said thrust surfaces each diverging from said rotor at the same rate as the port area increases into said cylinders whereby fluid flow velocity is substantially constant.

2. The rotary hydraulic motor of claim 1 wherein said cam track is generally of a polytrochoidal curve shape.

3. The rotary hydraulic motor of claim 1 wherein said cam track is generally of a polytrochoidal curve shape, and said cylinders are each of a circular cross section.

4. The rotary hydraulic motor of claim 1 wherein the lengths of said cylinders are at least as great as the lengths of said pistons whereby said pistons may completely retract within said rotor and said rotor may rotate without fluid flow.

5. The rotary hydraulic motor of claim 1 wherein said cam track is generally of a polytrochoidal curve shape, said cylinders are each of a circular cross section, and said pistons are in the form of balls having rolling con tact with said cam track.

6. The rotary hydraulic motor of claim 1 wherein said cam track and said stator are carried by separate parts of said housing and are releaseably connected together.

7. The rotary hydraulic motor of claim 1 wherein the relationship of said ports, said cam track and said cylinders is so related wherein each piston is at an end of its travel at the time the cylinder thereof moves to uncover and close said ports.

References Cited in the file of this patent UNITED STATES PATENTS 388,379 Strait Aug. 21, 1888 459,735 Benham Sept. 22, 1891 2,101,829 Benedek Dec. 7, 1937 2,823,619 May Feb. 18, 1958 2,882,831 Dannevig Apr. 21, 1959 FOREIGN PATENTS 275,796 Germany July 1, 1914

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