EP0283380B1 - Fluid vane actuator without internal sealings - Google Patents

Abstract

The invention relates to a fluid-operated rotary-vane device (actuator or pump), comprising a casing (3) traversed by a rotary shaft (1). A double vane (6, 6'), capable of rotating with the shaft, and two fixed partitions (5, 5') determine inside the casing two chambers (4a1, 2, 4b1, 2) of a complementarily variable volume. The vane is formed by a parallelepipedal bar attached to the shaft (1), which shaft is entirely cylindrical. The partitions (5, 5') are integral with a cover plate belonging to the casing. A very low level of inter-chamber leakage is maintained without an internal seal. <IMAGE>

Description

The present invention relates to a fluidic device with a rotary vane, intended to be used either as a motor (rotary actuator) or as a receiver (reciprocating pump), comprising a fixed casing traversed by a rotating shaft around its axis and carrying said pallet, while the interior space to the casing, forming an annular volume of revolution around the shaft, the section of which by a radial plane is rectangular and which is limited by two flat annular base surfaces and two coaxial cylindrical surfaces, respectively interior and exterior, is divided into two chambers of complementarily variable volume by a radial partition, fixed relative to the casing, and by said pallet, movable in rotation with the shaft. The latter is machined so as to have a thickness - along the direction of the axis of the shaft - equal, with very little play, to the distance separating the two flat annular surfaces limiting the annular space in this same direction , as well as a length and a cylindrical conformation of its end such that, after mounting the pallet on the shaft, the surface of its end is located on a cylinder of revolution coaxial with the shaft and of radius equal to one very small clearance, except that of the cylindrical surface externally limiting the annular space; the partition is machined so as to have a thickness - along the direction of the axis - equal, with very little play, to the distance separating the two annular surfaces mentioned above, as well as a cylindrical conformation of its edges radially contiguous to the shaft and the casing such that, after assembly of the constituent elements of the device, the surfaces of these edges are located on cylinders of revolution coaxial with the shaft.

Devices of this type are known, which can be used in particular as rotary actuators, in which the aforementioned pallet and partition are provided with a respective seal in order to avoid any leakage of fluid (hydraulic fluid or gas) between the rooms.

The presence of such internal seals has several drawbacks: subject to wear, they cause the performance of the device to drift over time, as well as pollution of the fluid used; moreover, they constitute bodies of special shape, of complex assembly and control and high prices.

EP-A-0065588 also discloses a rotary hydraulic motor devoid of seals, corresponding to the state of the art defined in the preamble of claim 1. This hydraulic motor, of complex structure, therefore expensive to manufacture, does not allow leakage rates to be controlled because of its configuration which is incompatible with sufficiently precise machining and the use, between chambers, of partitions imperfectly maintained in a fixed position, resulting in short vanishing lines and unstable. In fact, it is thanks to the viscosity of the oil used to operate it, which reduces or even eliminates leaks, that this engine is free of seals.

It is important to reduce as much as possible any leakage of fluid between chambers, which would necessarily affect the precision and the hydraulic stiffness of the device. The phenomenon of internal leakage must therefore be controlled in order to limit its importance and reduce its dispersion over a series of devices.

The present invention aims to improve a fluidic device of the type considered so as to allow, despite the omission of any internal seal, to maintain the leakage rate between chambers at a very low and well defined level, with a pressurized fluid both liquid and gaseous, in particular thanks to the achievement of precise clearances between the various elements of the device and to the creation of creepage paths as long as possible.

To this end, the device according to the invention is characterized in that its constituent parts are made of a single material, that the casing is composed of a one-piece bell-shaped body and a flange attached to the body, that the fixed partition is formed in one piece with the flange, the surfaces of the cylindrical edges of said partition offering radii respectively equal, with very little play, to those of the cylindrical surfaces limiting externally and internally the annular space, that the shaft has, at least in its part extending inside the casing and in the bores offered by the latter for its passage, a cylindrical lateral surface everywhere of the same diameter, and that the pallet is constituted by the end of a bar of substantially parallelepiped shape attached to the shaft, and mounted in a housing radially hollowed therein, the lateral surface of the shaft being machined cylindrical ement before mounting the pallet, so that, in the assembled device, the pallet and the partition ensure, without seals, low, predetermined and stable fluid leaks from one room to another in the space annular, which the flange comprises, coaxially surrounding the central bore for passage of the shaft, a first annular planar surface which forms one of the base surfaces of the annular space and from which the partition projects, radially limited by the surfaces of radii respectively equal to the limit radii of said first annular surface, the latter being surrounded by a second planar annular surface on which rests the body after assembly, the body and the assembled flange admitting the same axis, coinciding with the axis of the shaft, and that the first annular surface of the flange is in relief relative to its second annular surface, these two surfaces being connected by a circular cylindrical shoulder on which exactly fits the body by its bore which defines the cylindrical surface externally limiting the annular space.

In the assembled device, the pallet and the partition ensure, without seals, negligible leakage of fluid from one chamber to another of the annular space. In addition, the fact of dissociating the shaft and the pallet into two separate parts makes it possible to easily give the tree a cylindrical surface of extremely precise revolution, which is not possible when the shaft and the pallet are constituted by a unique piece. In addition, this same characteristic leads to a geometrically perfect conformation of the edge of the re-entrant angles which appear between the surface of the shaft and the two sides of the pallet perpendicular to the axis thereof, while a re-entrant angle cannot be machined on a single piece in a perfect manner. This is why it has been found that leaks located at the connection edges or discontinuities of the surfaces of the elements of a device with a rotary vane are the most difficult to control. The realization in two added parts of the shaft and the pallet, joined to the simplification of the forms of these two parts, has the effect of limiting the risks of localized leaks.

The arrangement according to which the first annular surface of the flange is in relief with respect to its second annular surface, these two surfaces being connected by a circular cylindrical shoulder on which exactly fits the body by its first bore, ensures extremely precise mutual positioning of the body and the flange. In addition, since it implies a distance, relative to the chambers, from the re-entrant angle situated at the foot of the partition, it considerably reduces the influence of possible leaks located at this location.

The fact that the shaft, at least in its part extending inside the casing and in the bores which the latter offers for its passage, offers a cylindrical lateral surface everywhere of the same diameter. contributes to the elimination of leaks or their influence between the chambers.

Furthermore, the lateral surface of the shaft as well as the surfaces of the pallet located opposite, with very little clearance, the base surfaces and the external cylindrical surface of the annular space, comprise a thin layer d '' a non-stick coating.

The shaft must be guided in the device housing by a pair of bearings capable of ensuring perfect positioning of a rotating part, such as plain bearings, bearings without radial play, hydrostatic bearings or passive or active magnetic bearings, the latter type of bearings being capable of providing both radial and axial shaft guidance.

When the device comprises, according to a known advantageous arrangement due to its symmetry, a second pallet and a second partition identical to the aforementioned pallet and partition and arranged in diametrically opposite position, each chamber thus being divided into two diametrically opposite compartments , between which is provided a respective communication channel passing through the shaft, the two pallets are, according to the invention, constituted by the ends of the aforementioned bar, which crosses the shaft right through, while the second partition is shaped and arranged in the same way as the first partition. This bar can be either secured to the shaft by means of a centering member, or left sliding through the shaft.

The pallet or each of the two pallets that the device comprises can be made of composite material. The realization of the component parts of the device in a single material allows it to operate in a wide temperature range.

Thanks to its particular structure and to the geometric forms, simplified to the extreme, given to its active surfaces, the device according to the invention can be devoid of any internal seal, the leaks between chambers being nevertheless extremely low. This results in frictionless and wear-free operation of the component parts of the device, which offers excellent linearity and remarkable precision, and benefits from a very long service life with performances of exceptional stability. This is why it is particularly well suited for use as a drive unit in high-quality position controls.

• Les figures 1 et 2 représentent schématiquement, en coupe transversale, un dispositif fluidique à palette rotative respectivement simple et double.
• La figure 3 représente le dispositif de la figure 2 adapté pour fonctionner comme dispositif de pompage.
• La figure 4 représente un dispositif selon l'invention en coupe transversale suivant la ligne IV-IV de la figure 5.
• La figure 5 représente le dispositif en coupe axiale suivant la ligne V-V de la figure 4.
• La figure 6 représente en perspective les principales pièces constitutives du dispositif des figures 4 et 5, avant assemblage.
• La figure 7 représente en perspective une partie des pièces visibles sur la figure 6, après assemblage.

Other characteristics and advantages of the invention will emerge more clearly from the description which follows, with reference to the appended drawings, of an exemplary embodiment which is not limiting.

• FIGS. 1 and 2 schematically represent, in cross section, a fluidic device with a rotary paddle, respectively simple and double.
• Figure 3 shows the device of Figure 2 adapted to function as a pumping device.
• FIG. 4 represents a device according to the invention in cross section along the line IV-IV of FIG. 5.
• FIG. 5 represents the device in axial section along the line VV of FIG. 4.
• Figure 6 shows in perspective the main component parts of the device of Figures 4 and 5, before assembly.
• Figure 7 shows in perspective a part of the parts visible in Figure 6, after assembly.

FIG. 1 shows a fluidic device with a rotary paddle of the type considered. It comprises a shaft 1 which can rotate about its axis 2 inside a coaxial cylindrical casing 3. In this casing, there appears an internal space 4, in the form of a circular ring with rectangular section, delimited by the lateral surface 1a of the shaft 1, by the surface of the internal bore 3a of the casing 3 and by two flat annular surfaces, centered on axis 2 and belonging to a pair of circular flanges not visible in the drawing. The annular space 4 is divided into two chambers 4a, 4b by a fixed partition 5 and by a movable pallet 6, the latter rotating with the shaft 1. The chambers 4a, 4b are connected to an external circuit of pressurized fluid (hydraulic or pneumatic) via orifices 7a, 7b drilled in the side wall of the casing 3. It is clear that when the fluid under pressure is applied to the chamber 4a via the orifice 7a, the orifice 7b of the chamber 4b being connected to the cover of the external circuit, the shaft 1 is rotated in the direction indicated by the arrow, the angle of rotation being limited to approximately 280 °. The device thus constitutes a rotary actuator.

In the case of FIG. 2, the tree 1 comprises a second pallet 6 ′, the two pallets 6, 6 ′ projecting from the shaft at the ends of the same diameter. Similarly, a second partition 5 ′ is provided, diametrically opposite the partition 5. Thus, each chamber 4a, 4b is broken down into two compartments, respectively 4a1, 4a2 and 4b1, 4b2, diametrically opposite, the two compartments of each chamber being connected by a respective channel 8, 9 drilled through the shaft 1. Thanks to this symmetrical arrangement, the action of the pressurized fluid on the shaft is balanced, at the cost of reducing the maximum angle of rotation by this one at around 100 °.

Either of the devices briefly described above can operate as a motor (jack), as indicated with respect to the device in FIG. 1. Being reversible, they can also be used as receivers (pumps or compressors). By way of example, FIG. 3 shows a double-acting pumping circuit using the device of FIG. 2, provided in addition with two complementary orifices 7′a, 7′b opening into the compartments 4a2, 4b1 of the chambers. Each of the orifices 7a, 7b, 7′a, 7′b is associated with a non-return valve 10, mounted in the fluid circuit shown with a direction such that, by imparting an alternating rotational movement to the shaft 1, obtains continuous suction effects at point A and discharge at point B of the circuit fluid.

The device according to the invention, which will be described with reference to Figures 4 and following, has the configuration illustrated in Figure 2, as immediately apparent from a comparison of this figure with Figure 4. It is composed of a stator comprising a casing 3 and two partitions 5, 5 ′ and a rotor comprising a shaft 1 of axis 2 and a double pallet 6, 6 ′, which defines, with the two fixed partitions 5, 5 ′, two divided chambers each in two compartments communicating through the shaft by channels 8, 9. These chambers extend in the annular space of rectangular section inside the casing 3, coaxially surrounding the axis 2 and externally limited by the bore 3a of the casing 3, internally through the lateral surface 1a of the shaft 1 and in the axial direction by two flat annular surfaces 11, 12, belonging to the casing 3 (FIG. 5).

The double pallet 6, 6 ′ is formed by a bar 13, of rectangular section and of length equal to the diameter of the bore 3a, its ends being rounded to the radius of curvature of said bore. This bar is mounted in a housing 14 produced through the shaft 1, in a diametrical direction (Figure 6), with dimensions such that it receives exactly the bar 13 (Figure 7).

As shown in Figures 5 and 6, the housing is made in two parts, which, after assembly, admit the axis 2 of the shaft 1 as axis of symmetry: a body 15 in the shape of a bell and a flange 16 which closes the space inside the body 15. The body 15 and the flange 16 each have a central bore, respectively 17 and 18, allowing the passage of the shaft 1. The body 15 has another bore, of larger diameter, which n is other than the bore 3a externally limiting the annular space inside the casing which extends around the shaft 1. Between these two bores 3a, 17 appears a plane annular shoulder 11 which forms one of the base surfaces limiting said space in the axial direction, the other annular base surface 12 appearing on the flange 16, around the bore 18. This annular surface 12 is surrounded by another planar annular surface 19, forming an assembly flange, on which applies the casing 15 by a surface an planar ring 20 which the latter comprises. The flange 19 is pierced with holes 21 arranged in a ring around the axis 2 and oriented parallel to it, these holes being intended to receive bolts 22 which are screwed into tapped holes 23 conjugated drilled in the annular surface 20 of the body 15, these bolts thus making it possible to assemble the latter and the flange 16 to form the casing 3. In addition, a pin 24 for angular positioning is provided projecting from the surface 20 of the body 25; it is housed in a corresponding hole 25 drilled in the surface 19 of the flange 16.

As shown in particular in Figure 6, the partitions 5, 5 ′ are integral with the flange 16, being formed by protuberances which rise in direction parallel to the axis 2, from the annular surface 12, their radially inner surface 27 directly extending the surface of the bore 18 of the flange. In addition, the surface 12 is raised relative to the surface 19, so that the cylindrical skirt of the body 15 surrounding the bore 3a fits around said surface 12 in relief, its bore 3a fitting closely on a circular cylindrical shoulder 26 which appears between the surfaces 12 and 19 due to their offset in the axial direction. Under these conditions, the radially outer surface 28 of the partitions 5, 5 ′ extends in direct extension of the cylindrical surface of the shoulder 26.

The main operations for manufacturing the parts making up the device described above will now be explained. All these parts, made of steel, have an axis of symmetry which, after their assembly, coincides with the general axis 2 of the device.

A bar 13 is machined in order to give it the rectangular section a × b desired for the double pallet 6, 6 ′ (a being the width, and b the thickness in the direction of the axis 2 which will be the axis of the double pallet after assembly). A blind hole 29 is drilled in the center of one of the faces of width a and the length of the bar is adjusted to a value slightly greater than the desired value, by machining its end faces along a cylindrical surface of the same axis 2 as the hole 29. A light milling 30 is carried out at the ends of the faces of width b so that, in the completed device, the compartments 4a1, 2, 4b1, 2 of the chambers offer a non-zero minimum volume when the double pallet 6, 6 ′ is in limit switch (figure 4).

The shaft 1 is produced in the form of a cylinder of revolution and there is hollowed out, by electro-erosion, the housing 14 at dimensions a × b of the bar 13 constituting the double pallet 6, 6 ′.

The bar 13 is put into place in the housing 14 of the shaft 1, the bar being centered by a screw 31 engaged in a threaded hole 32 drilled axially at one of the ends of the shaft 1, this hole opening into the housing 14 so that the non-threaded end 31a of the screw, of diameter conjugate with that of the hole 29 of the bar 13, penetrates therein (FIG. 5).

After assembly of the bar 13, its width a faces are whitened so as to give its thickness the value b with very high precision; Likewise, its cylindrical end faces are given a finishing machining so that these surfaces have the desired radius and are exactly coaxial with the lateral surface 1a of the shaft 1.

The flange 16 is then produced from a thick disc in which the central bore 18 is machined with a diameter very slightly greater than the diameter of the shaft 1, then the annular surface 19, and the central ring appears. remaining, by milling, then radial grinding using a grinding wheel of thickness equal to the width a of the bar 13, the two partitions 5, 5 ′, leaving to this crown a residual height c (figure 6) corresponding to the projecting offset that the annular surface 12 must have, from which the partitions 5, 5 ′ rise, over a height h₁ very slightly greater than the thickness b of the bar 13.

The machining of the body 15 includes the production, coaxially around the same axis which will be the axis 2 of the completed device, of the bore 17, identical to the bore 18 of the flange 16, these two bores serving as bearings to the cylindrical shaft 1, and the bore 3a, of diameter very slightly greater than the outside diameter of the crown of the flange which gave rise to the partitions 5, 5 ′ and to the raised annular surface 12, so that this bore can fit exactly around the shoulder 29 which externally limits the surface 12 and whose diameter is very slightly greater than the diameter of the cylindrical ends of the bar 13. The two bores 17, 3a are connected by the annular shoulder 11 whose width radial is equal to that of the annular surface 12 of the flange. The height h₂ of the bore 3a, between the planes of the annular surfaces 12 and 20, is very slightly greater than the thickness b of the pallet increased by the nesting depth c of said bore (Figure 5).

The surfaces of the component parts of the device which define the internal chambers are machined with very high precision so as to present dimensions with very low tolerance and an excellent surface condition. Thus the clearances between the various parts can be extremely reduced, namely by about 5 μm. However, the clearances between the pallet faces 6, 6 ′ perpendicular to the axis 2 and the annular surfaces 11, 12 are slightly larger, of the order of 10 μm, in order to avoid any contact between the pallet and the casing. even if the shaft 1 takes a very slight obliquity with respect to the axis 2 due to the minimal clearances which exist between said shaft and its bearings constituted by the bores 17 and 18. All these minute clearances, which, to be made visible , have been considerably exaggerated in Figures 4 and 5, ensure almost zero leakage of the fluid from one chamber to another of the device, while no joint is provided between pallet and casing, between partition and casing, nor between partition and tree. However, external seals are provided. An O-ring 33 seals between the body 15 and the flange 16; it is placed in an annular groove 34 hollowed out in the surface 20 of junction of the body with the flange. In addition, two O-rings 35, 36 are inserted between the shaft 1 and the casing 3, in annular grooves hollowed out respectively in the bores 17 and 18 (not shown in FIG. 6).

• ― angle de rotation de butée à butée: 100°
• ― cylindrée unitaire: 1 à 500 cm³/rad
• ― couple disponible: 0,1 N.m. rad/cm³.bar
• ― pression d'alimentation maximale: 500 bar
• ― hystérésis en charge: < 0,1%
• ― précision statique: 10⁻⁶ rad/N.m.

As an indication, a device as described above and represented by FIGS. 4 to 7 can offer the following characteristics:

• - rotation angle from stop to stop: 100 °
• - unit displacement: 1 to 500 cm³ / rad
• - available torque: 0.1 Nm rad / cm³.bar
• - maximum supply pressure: 500 bar
• - hysteresis under load: <0.1%
• - static precision: 10⁻⁶ rad / Nm

Claims (9)

1. Rotary vane fluid device for use either as a motor (rotary actuator) or as a receiver (reciprocating action pump), comprising a fixed casing (3) having a shaft (1) passing therethrough, which shaft is rotatable about its axis and carries said vane (6), while the inside space of the casing, forming an annular volume of revolution about the shaft has a section in a radial plane which is rectangular and which is delimited by two plane annular base surfaces (11, 12) and by two co-axial cylindrical surfaces (1a, 3a), respectively constituting an inner and an outer surface, is divided into two chambers (4a, 4b) of complementarily variable volume by a radial partition (5), which is fixed relative to the casing, and by the vane (6), movable in rotation with the shaft (1), device in which the vane (6) is machined in such a manner as to have a thickness (b) ― in the axial direction of the shaft ― which is equal, to within a very small clearance, to the distance (h₂ - c) between the two plane annular surfaces (11, 12) delimiting the annular space in that same direction, as well as a length and cylindrical shape of its ends which are such that, once the vane is mounted on the shaft, the surface of its end is situated on a cylinder of revolution co-axial with the shaft and having the same radius, to within a very small clearance, as that of the cylindrical surface (3a) delimiting externally the annular space, and the partition (5) is machined so as to have a thickness (h₁) ― in the direction of axis (2) ― equal, to within a very small clearance, to the distance (h₂ - c) separating said two annular surfaces (11, 12), as well as a cylindrical shape of its edges (27, 28) radially adjacent to the shaft (1) and to the casing (3) such that, after assembly of the components parts of the device, the surfaces of said edges are situated on cylinders of revolution co-axial to the shaft (1), characterized by the fact that its component parts are made of a single material, that the casing (3) is composed of a one-piece bell-shaped body (15) and of an end plate (16) applied to the body, that the fixed partition (5) is formed integrally with the end plate (16), the surfaces of the cylindrical edges (27, 28) of said partition having radiuses which are respectively equal, to within a very small clearance, to the radiuses of the inner and outer cylindrical surfaces delimiting the annular space, that the shaft (1) has, at least in the portion thereof extending inside the casing (3) and into the bores (17, 18) provided in said casing for the shaft to pass through, a cylindrical lateral surface (1a) of constant diameter, and that the vane (6) is constituted by the end of a bar (13) of substantially parallelepipedic shape assembled on the shaft (1), and mounted in a housing (14) formed in the latter, the lateral surface (1a) of the shaft (1) being cylindrically machined before the vane is mounted, so that, in the assembled device, the vane (6) and the partition (5) provide small, predetermined and stable fluid leakage between the two chambers of the annular space without the addition of sealing gaskets, that the end plate (16) comprises, co-axially surrounding the central bore (18) allowing the shaft (1) to pass therethrough, a first plane annular surface which forms one (12) of the base surfaces of the annular space and from which projects the partition (5), delimited radially by the surfaces (27, 28) of radiuses respectively equal to the limiting radiuses of said first annular surface (12), the latter being surrounded by a second plane annular surface (19), against which rests the body (15) after assembly, the assembled body and end plate sharing the same axis which coincides with the axis (2) of the shaft (1), and that the first annular surface (12) of the end plate (16) is axially offset relative to the second annular surface (19), said two annular surfaces being interconnected by a circularly cylindrical shoulder (26) over which the bore (3a) of the body (15) which defines the outer cylindrical surface delimiting the annular space, fits exactly.

2. Device according to claim 1, characterized by the fact that it comprises a second vane (6') and a second partition (5′) identical to said vane (6) and partition (5) and disposed diametrically opposite thereto, each chamber (4a, 4b) being thus split into two diametrically opposite compartments (4a1, 4a2, 4b1, 4b2), between which is provided a respective communication channel (8, 9) through the shaft, the two vanes (6, 6′) being constituted by the ends of said bar (13), which passes right through the shaft (1), while the second partition (5′) is shaped and disposed in the same manner as the first partition (5).

3. Device according to claim 2, characterized by the fact that the bar (13) is fixed to the shaft (1) by means of a centering member (31).

4. Device according to claim 2, characterized by the fact that the bar (13) is slidably mounted through the shaft (1).

5. Device according to any one of claims 1 to 4, characterized by the fact that the lateral surface (1a) of the shaft (1) as well as the surfaces of the vane (6) situated opposite, with very little play, the base surfaces (11, 12) and the external cylindrical surface (3a) of the annular space, comprise a thin layer of an anti-adhesive coating.

6. Device according to any one of claims 1 to 5, characterized by the fact that the shaft (1) is guided in the casing (3) by a pair of smooth bearings.

7. Device according to any one of claims 1 to 5, characterized by the fact that the shaft (1) is guided in the casing (3) by a pair of roller bearings having no radial play.

8. Device according to any one of claims 1 to 5, characterized by the fact that the shaft (1) is guided in the casing (3) by a pair of hydrostatic bearings.

9. Device according to any one of claims 1 to 5, characterized by the fact that the shaft (1) is guided in the casing (3) by a pair of passive or active magnetic bearings.

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