GB1590534A - Hydraulic radial piston machine - Google Patents

Description

(54) HYDRAULIC RADIAL PISTON MACHINE (71) We, JEAN-LUC PONCHAUX, of French nationality, residing at La Cure de Petosse, 85570 L'Hermenault, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a rotary machine, and more particularly, to a radial piston machine using fluid under pressure.

There are a number of examples of this type of machine which illustrate different constructions having cylinders, connecting means between the pistons and an eccentric, and the system for distributing the fluid to the piston and cylinder.

There are certain disadvantages which have been found in present day hdraulic machines.

For instance, such machines in which the cylinders are fixed in the housing can, generally speaking, transmit only modest pressures because of the inefficient kinematic design thereof, and such machines have been subject to uneven wear as well as rapid wear of certain parts, as well as jamming of the pistons in such cylinders.

More technically evolved machines normally use oscillating cylinders. However, in such constructions, it has been noticed that due to the pressure applied on the cylinders while the machine is functioning are normally insufficiently compensated, and it has been found in such oscillation that the mechanical friction present generates heat and wear which deteriorates the output of the machine, thus compromising the lifespan of the material and also limiting the transmittable power. The result is that those solutions which have been provided which are theoretically satisfactory are really quite complex to manufacture and keep the manufacturing costs quite high, thus limiting the scope of the utility of such a machine and causing designers to simplfy the design by compromising the performance and wear life of the machine.

It is an aim of the present invention to provide a simple machine which eliminates many of the above-mentioned disadvantages.

More precisely, it is an aim of the present invention to provide a machine operating with fluid under pressure, comprising a housing, a plurality of piston and cylinder arrangements disposed radially about an eccentric, the eccentric being integral with a rotating shaft rotating relative to the housing, the cylinders being retained in the housing but being subject to an oscillating principal movement in conjunction with the rotation of the shaft, and means are provided for maintaining the pistons in contact with the outer surface of the eccentric.

The distributor system for the fluid associated with the machine can be of any known construction. It - can be cylindrical, planar, spherical, and either collective relative to the total number of cylinders, or it can individually feed each cylinder.

In accordance with the present invention, there is provided a hydraulic machine comprising a plurality of radially extending -pistons in a housing, a shaft mounting an eccentric in the housing, means connecting the pistons radially with the eccentric, each piston being mounted for sliding movement within a mobile cylinder, the cylinder having a spherical outer surface and being retained between a pair of retaining rings, the first retaining ring having a concave spherical surface matching with the spherical outer surface of the cylinder, means for providing fluid under pressure in an annular sealed zone between the cylinder and the first retaining ring, whereby the first ring functions as a hydrostatic pad for the cylinder, the second retaining ring being in the form of a valve seat which is hydrostatically balanced and thus limits the field of pressure which can be established above the cylinder, spring means urging the second ring in contact against the spherical surface of the cylinder, the cylinder thus having an oscillating movement subject to the rotation of the shaft relative to the housing, the cylinder being in hydrostatic equilibrium at all positions of its oscillation between the first and second retaining rings, the said cylinders being placed in communication successively with feed means and exhaust means.

The invention is further described below by way of example with reference to the accompanying drawings, in which: Figure 1 is an axial section taken through a typical hydraulic machine in accordance with the present invention; Figure 2 is a radial cross-section taken along the line A-A of Figure 1; Figure 3 is an axial cross-section similar to Figure 1 but showing a different embodiment thereof.

The embodiment shown in Figures 1 and 2 includes a hydraulic motor of the type having a rotating shaft and comprising a housing 1, a shaft 2 mounted for rotation on bearings 3a and 3b in the housing 1. The housing 1 is closed at one end by a cover 4 having an aperture allowing the fluted end 5 of the shaft 2 to protrude. The other axial end of the housing is closed by a cover 6 which includes an inlet port 6a and an outlet port 6b. The shaft 2 is cantilevered by the bearings 3a and 3b and includes a cylindrical eccentric portion 7. An annular ring 8, which includes a cylindrical bore, fits on the cylindrical eccentric and is concentric therewith. The outer surface of the ring has a spherical shape.

The housing 1 has a number of radially extending bores 9 at right angles to the surface of the eccentric 7 on the shaft 2. As shown in Figure 2, the present embodiment includes five such bores or cavities.

In each of the cavities 9, there is an arrangement of parts including a cylinder 10 having a spherical exterior surface and a cylindrical central bore which is adapted to receive in sliding relation a tubular piston 11. An abutment 12 in the form of a ring having a spherical concave segment forms a seat for the spherical cylinder 10. An annular ringtype valve 13 is held and abuts against the diametrically opposed area of the spherical cylinder 13 and is held by a ring-type spring 14.

The spring 14 is held against the spherical cylinder 10 by means of a removable cover 15 which closes the cavity 9 and is fixed thereto.

Each piston 11 includes a base part having a shoe 16 defined with a concave undersurface of spherical curvature matching with the convex spherical surface of the ring 8. The pius: tons are retained against the surface of the ring 8 by means of anchor members 17 which are hook-shaped and engage the flange-like foot 16 of each piston 11. The anchors 17 are resiliently held against the foot 16 by means of springs 18 fixed to the sides of the ring 8.

The fluid distributor can be of different types. In Figure 1 and 2, there is shown a central cylindrical distributor with which the ring 8 acts as a distribution ring to the piston and cylinder arrangements and is associated with a planar rotating joint in a radial plane.

This sytem includes a stepped piston 19 coaxially arranged with the shaft 2 and sitting in a similar stepped cavity provided in the cover 6 with which it can slide in an axial direction but which is prevented from rotating by means not shown.

We will now refer in more detail to the cylinder 10, piston 11, and the retaining seats 12, 13 and the spring 14.

In the present state of the art, hydraulic machines including oscillating cylinders, have different degrees of inefficiencies caused by poor static or dynamic equilibrium of the oscillating cylinder, an insufficient compensation of the pressure force, etc. The result is that the transmittable power of such machines is inherently limited if it is necessary to avoid rapid wear. One must, therefore, limit the speedof maximum rotation or limit the maximum pressure or more generally obtain a limitation of the transmittable power.

In accordance with the embodiment of the present invention as shown in Figures 1 and 2, the cylinder 10 has a spherical outer surface which fits in the concave spherical curve of the abutment 12 which provides a seat for the spherical cylinder lot0. A valve seat 13 having an interior concave spherical surface acts as a crown on the cylinder 10. The valve seat 13 could also have a conical surface which would theoretically limit the contact area of the seat with the spherical cylinder 10 to a circular line. The abutment 12 and the valve seat 13 define between them within the cavity 9, an annular chamber 32, called a decompression chamber, in which the internal wall is the outer cylindrical surface of the cylinder 10.

The abutment 12 includes, on the spherical concave part serving as a seat for the cylinder 10, an annular groove 33 along a generatrix of its periphery, a flattened portion 34 communicating the decompression chamber 32 with an annular space 35 at the base of the abutment 12, and with the interior of the housing 1 by means of the bore 36 shown in Figure 2.

The valve seat 13 is in the form of an internally stepped piston. The valve seat 13 is set internally by the cover 15, which is machined accordingly, and is mounted with tolerance in the radial cavity 9 of the housing 1. The valve seat 13 includes at least an axial bore 37 communicating the decompression chamber 32 with the chamber in which the annular spring 14 is placed above the valve seat 13.

An O-ring provides a seal between the internal projection of the cover 15 and the valve seat 13.

The annular groove 33 of the abutment 12 is fed with fluid by means of a radial bore 38 provided in the wall of the cylinder 10. This radial bore 38 communicates with the annu lar groove 33 at one end and with an annular groove 39 defined in the internal cylindrical bore of the cylinder 10.

Since the groove 39 is at a lower portion of the cylinder 10 relative to the piston 11, the fluid pressure in the groove 39 is appreciably inferior to the pressure generally in the cylinder 10. The annular groove 33 in the abutment is, therefore, fed by a fluid pressure which is lower than the internal fluid pressure in the circulation system of the machine, thereby reducing the chance of leakage. On the other hand, in the light of this lower pressure, with reference to the axial position of the groove 39 in the bore of the cylinder 10 and a value of the tolerance existing between the piston 11 and the bore of the cylinder 10 which serves as a guide for the piston, the abutment seat, in addition to its support role, acts as a damper, Accordingly, a hydrostatic seat is provided.

Furthermore, in view of the geometry of the abutment 12 on the one hand, depending on the dimensions of the annular groove 33 and the lateral support zone of the cylinder 10 with the valve seat 13 on the other hand, the cylinder 10 is essentially in a hydrostatic equilibrium between the two parts 12 and 13.

In other words, the sizing of the abutment 12 is such that its hydrostatic lift equilibrates approximately the pressure field delimited exteriorly by the valve seat 13 pressing the cylinder 10 against the abutment 12.

According to the embodiment of Figures 1 and 2, the valve seat 13 is itself hydrostatically equilibrated or slightly undercompensated.

This is defined by choosing its diameter contacting the guiding projection of the cover 15 with respect to the contact on the cylinder 10. In the case of hydrostaticequilibrium of the forces, the maintenance of the contact of the valve seat 13 on the cylinder 10 is provided by the spring 14.

In the case of an -overcompensation of the forces in the direction of application of the valve seat 13 on the cylinder 10, the spring 14 should still be -retained such that it maintains a contact between those parts when the hydraulic machine is inoperative.

According to the preceding .embodiment, therefore, the following advantages are obtained: static equilibrium of the cylinder about its center of rotation which coincides with its center of gravity. The balance of the oscillation allows the increase of the frequency of oscillation and, therefore, the velocity of rotation of the hydraulic machine without risk of excessive friction between the cylinder and piston and without risk of deterioration of the parts during movement, and that without interfering with the performances thereof at low speeds. It is, therefore, possible to utilize the hydraulic machine of the present invention as a low speed motor but high torque, or as a motor which is of moderate speeds with higher specific power.

-Hydrostatic equilibrium of the cylinder is attained between the abutment and the valve seat, and the total hydrostatic compen sation of the forces at the level of the abutment regardless of the pressure of the fluid in the internal circulation of the machine. The machine could, therefore, be worked under very high pressure, without risk of deterioration, and maintaining its high output over a longer period of time.

The damping feature of the abutment against the excessive sudden pressure such that the machine is insensitive to pulsating pressure and resistant to shock.

-Furthermore, in view of the construction of the machine, with hydrostatic compensation of the forces at all levels, the hydraulic machine of the present invention can undergo simultaneous pressures at both inlet and outlet ports. This feature permits the broadening of the field of utilization of the machine, and particularly as a motor used in the synchronization of jacks.

In such an application, at least two of these machines are connected mechanically so that they turn at the same speed or through a mechanical reduction such that they turn at a predetermined speed, and the fluid is supplied from the same source such that each machine gets a fraction of the total fluid proportional to its speed of rotation.

The result is that the two ports of each machine are essentially under the same pressure which can be the difference between the supply pressure and the exhaust being essentially the mechanical losses of the machine. The machine can also be used as a motor in a closed circuit control by a servo valve.

Actually, in the present state of the art, servo valves generally have a principal level including a slide valve of which the neutral position connects the inlet port of the valve to the inlet port communicating with the source of pressure. The result is that the motor, which is situated downstream of the valve, must support the adjustment pressure of the -circuit at both of its ports which, with con ventional machines, is not permissible. - The motor can also be arranged in a hydraulic series, and in this case, the motor which is situated upstream must be able to support the adjustment pressure of the circuit on its inlet port, and simultaneously at its outlet port must support an intermediate pressure between the high and low pressures of the circuit in relating to the mechanical energy prevailing at each of the motors in the hydraulic series.

It is quite evident that, in the case of hydraulic machines normally operating at low power or medium power, one can advantageously replace the hydrostatic abutment serving as a seat for the cylinder as previously described by a simple axial ball socket on which the surface would have been treated or provided with a coating in the area of support of the cylinder so as to reduce the coefficient of friction and to avoid jamming. In such a case, the valve seat 13 would simply act to limit the field of pressure acting on the top of the cylinder 10 and, therefore, limit the pressure of contact of the cylinder 10 on the abutment 12.

Other embodiments could, of course, be made. In one embodiment, the valve seat 13 could be made to act as a safety valve. For example, one can visualize a bore or a conduit (not illustrated) to communicate the decompression chamber 32 with the interior of the housing 1. The spring 14 would still be maintained so that an overpressure in the bore defined by the cylinder and piston would put the valve seat 13 in an unbalanced situation and push it against the spring 14 so as to allow a momentary leakage of the fluid towards the decompression chamber 32 and through to the interior of the housing, reducing therefore the super-pressure.

In the longitudinal cross-section of Figure 3, the overall arrangement of the hydraulic machine 1 can be found with the following main variation: the cylinder 10 has an outer surface made up of two semi-spheres of different radii. The centers of these two spheres would, however, coincide with the center of rotation of the part. In spite of the fact that there is an imbalance of the masses, such an embodiment would have the advantage of bringing the valve seat 13 closer to the abutment 12 so as to permit a reduction of the radial dimension of the machine.

WHAT I CLAIM IS:- 1. A hydraulic machine comprising a plurality of radially extending pistons in a housing, a shaft mounting an eccentric in the housing, means connecting the pistons radially with the eccentric, each piston being mounted for sliding movement within a mobile cylinder, the cylinder having a spherical outer surface and being retained between a pair of retaining rings, the first retaining ring having a concave spherical surface matching with the spherical outer surface of the cylinder, means for providing fluid under pressure in an annular sealed zone between the cylinder and the first retaining ring, whereby the first ring functions as a hydrostatic pad for the cylinder, the second retaining ring being in the form of a valve seat which is hydrostatically balanced and thus limits the field of pressure which can be established above the cylinder, spring means urging the second ring in contact against the spherical surface of the cylinder, the cylinder thus having an oscillating movement subject to the rotation of the shaft relative to the housing, the cylinder being in hydrostatic equilibrium at all positions of its oscillation between the first and second retaining rings, the said cylinders being placed in communication successively with feed means and exhaust means.

2. A machine as defined in claim 1, wherein the outer surface of the cylinder is generated by two semi-spheres of different radius but having coinciding centres, such that the spherical surface in contact with the first retaining ring is different from the spherical surface in contact with the valve seat which has a conical shape.

3. A machine as defined in claim 1 or 2, wherein the retaining ring has a conical shape which limits its contact with the outer surface of the cylinder to a circular line.

4. A machine according to claim 1, substantially as described herein with reference to and as shown in Figures 1 and 2 and Figure 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. such a case, the valve seat 13 would simply act to limit the field of pressure acting on the top of the cylinder 10 and, therefore, limit the pressure of contact of the cylinder 10 on the abutment 12. Other embodiments could, of course, be made. In one embodiment, the valve seat 13 could be made to act as a safety valve. For example, one can visualize a bore or a conduit (not illustrated) to communicate the decompression chamber 32 with the interior of the housing 1. The spring 14 would still be maintained so that an overpressure in the bore defined by the cylinder and piston would put the valve seat 13 in an unbalanced situation and push it against the spring 14 so as to allow a momentary leakage of the fluid towards the decompression chamber 32 and through to the interior of the housing, reducing therefore the super-pressure. In the longitudinal cross-section of Figure 3, the overall arrangement of the hydraulic machine 1 can be found with the following main variation: the cylinder 10 has an outer surface made up of two semi-spheres of different radii. The centers of these two spheres would, however, coincide with the center of rotation of the part. In spite of the fact that there is an imbalance of the masses, such an embodiment would have the advantage of bringing the valve seat 13 closer to the abutment 12 so as to permit a reduction of the radial dimension of the machine. WHAT I CLAIM IS:-

1. A hydraulic machine comprising a plurality of radially extending pistons in a housing, a shaft mounting an eccentric in the housing, means connecting the pistons radially with the eccentric, each piston being mounted for sliding movement within a mobile cylinder, the cylinder having a spherical outer surface and being retained between a pair of retaining rings, the first retaining ring having a concave spherical surface matching with the spherical outer surface of the cylinder, means for providing fluid under pressure in an annular sealed zone between the cylinder and the first retaining ring, whereby the first ring functions as a hydrostatic pad for the cylinder, the second retaining ring being in the form of a valve seat which is hydrostatically balanced and thus limits the field of pressure which can be established above the cylinder, spring means urging the second ring in contact against the spherical surface of the cylinder, the cylinder thus having an oscillating movement subject to the rotation of the shaft relative to the housing, the cylinder being in hydrostatic equilibrium at all positions of its oscillation between the first and second retaining rings, the said cylinders being placed in communication successively with feed means and exhaust means.

2. A machine as defined in claim 1, wherein the outer surface of the cylinder is generated by two semi-spheres of different radius but having coinciding centres, such that the spherical surface in contact with the first retaining ring is different from the spherical surface in contact with the valve seat which has a conical shape.

3. A machine as defined in claim 1 or 2, wherein the retaining ring has a conical shape which limits its contact with the outer surface of the cylinder to a circular line.

4. A machine according to claim 1, substantially as described herein with reference to and as shown in Figures 1 and 2 and Figure 3 of the accompanying drawings.