US20060266212A1

US20060266212A1 - Rotating actuator

Info

Publication number: US20060266212A1
Application number: US10/543,374
Authority: US
Inventors: Andre Paunet
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2003-01-27
Filing date: 2004-01-26
Publication date: 2006-11-30
Also published as: EP1588059A1; DE602004005159D1; WO2004076866A1; FR2850434A1; ATE356295T1; EP1588059B1

Abstract

A rotating actuator includes a body and a shaft jointly defining at least one operating volume consisting of a an annular cavity compartmented by at least two partitions extending between two end surfaces of the cavity, one of the radial partitions being respectively borne by the shaft and the other by the body, and both partitions being provided on the opposite free edge thereof with a sealing element. The sealing element is extended in the direction of each end surface of the annular cavity up to each end surface, whereupon it extends into the connection area of the end surface and the body or, respectively, shaft. The sealing element is fitted is in the form of a continuous linear joint provided in kilometer length and can be cut up as it develops along one edge surface to another according to a loop-shaped trajectory.

Description

This invention relates to a rotary actuator, preferably a hydraulic actuator.
It relates more particularly to a rotary actuator of the type composed of a body and a shaft delineating between one another at least one working volume, each working volume being composed of an annular cavity compartmented by means of at least two partitions extending between two surfaces, the so-called end surfaces of said cavity, one of these radial partitions supported respectively by the shaft, the other by the body of the actuator, these radial partitions, by their free opposite edge provided with packing, coming into airtight, sliding support contact, one against the inside wall of the body, the other against the outside wall of the shaft in such a way as to form at least two chambers of variable volume that are capable of being pressurized alternately by intake of a fluid to generate relative rotational displacement of the body and the shaft.
Such an actuator is described more particularly in patents FR-A-2,618,189 and DE-1,750,352. By virtue of their design, such vane-type rotary actuators generally exhibit relatively rapid wear over time due to the presence of leaks at the level of the seals or packing that equip the section of each partition or vane. This wear is due to rubbing and possible deformations of the components of the actuator. It leads to the necessity of changing the packing relatively frequently.
When the seal is a preformed seal and is bonded at several locations, as shown in particular in FIGS. 3 and 4 of German Patent DE-1750,352, any seal wear requires an identical seal to be kept in inventory for changing it. Moreover, due to the pre-conforming, changing a seal is a long and complex operation. In addition, the design of the seal that equips the shaft of the actuator requires initiating connection operations in sensitive zones where there is a major risk of the connection not lasting over time.
Moreover, as shown by patent FR-A-1,270,078 or GB-A-926,836, rotary actuators are known in which the packing is compressed via a fluid in the direction of the wall on which it is designed to be supported in order to increase the effectiveness of sealing. However, due to the configuration of the seal, only the seal equipping the free edge of each partition can be pressurized. It is necessary to have an additional seal that cannot be pressurized to achieve sealing in the connecting zone between the body and the shaft, at the level of the end surfaces of the body. This again results in complexity of the assembly.
One objective of this invention is thus to propose a rotary actuator of the aforementioned type whose packing design is simplified especially to facilitate installation and replacement of the packing without adversely affecting the sealing efficiency.
Another objective of this invention is to propose a rotary actuator whose packing design allows pressurization of all said packing, this packing being capable, on the one hand, of ensuring a seal between chambers with a variable volume, and, on the other hand, the sealing of said chambers to the outside.
Another objective of this invention is to propose a rotary actuator whose packing design makes it possible to limit the amount of packing necessary.
Another objective of this invention is to propose a rotary actuator whose design allows implementation of an actuator of great length in which the risks of sagging of the shaft or buckling of the partitions or vanes are reduced or even eliminated.
To do this, the object of the invention is a rotary actuator of the type composed of a body and a shaft delineating between one another at least one working volume, each working volume being composed of an annular cavity compartmented by at least two partitions extending between two surfaces, the so-called end surfaces of said cavity, one of these radial partitions supported respectively by the shaft, the other by the body of the actuator, the radial partitions by their free opposite edge equipped with packing coming into airtight, sliding support contact, one against the inside wall of the body, the other against the outside wall of the shaft in such a way as to form at least two chambers of variable volume capable of being pressurized alternately, by intake of a fluid, to generate relative rotational displacement of the body and the shaft, characterized in that each packing that equips the free edge of a partition is lengthened in the direction of each end surface of the annular cavity just as far as said surface for extending into the connecting zone between the end surface and the body or respectively the shaft, this packing that equips the shaft or body being present in the form of a continuous linear seal that is available by the kilometer and that can be cut to length, for coming to rest in the groove of the actuator that is shaped depending on the desired arrangement of the seal, this seal developing from one end surface to the other following a looped trajectory, closing of the loop being obtained at least by the ends of the strip comprising the seal being brought into contact.
Due to the configuration of the packing in the form of a continuous linear seal extending from one end surface to the other as it passes the free edge of the partition and develops in the form of a closed loop, it results in the possibility of limiting the number of packings to two to obtain sealing between the chambers of variable volume and sealing to the outside at the same time.
Moreover, due to this configuration, a double sealing barrier is obtained, especially in the zone extending along one free edge of a partition.
It is likewise possible, due to this configuration in the form of a simple seal strip, at the level of the path followed by the packing in the groove arranged either in the body or in the shaft, to prevent folding of the seal at a right angle, folding that is recognized to be able to damage such a seal.
According to one preferred embodiment of the invention, the part of the packing turned toward a part of the actuator such as the partition, body or shaft with which it is integral, is capable of being exposed during operation of the actuator to a thrust force that tends to keep the so-called active part of the packing forced against the wall of the body or of the shaft with which it is in sliding support contact.
Due to this concept of the actuator, the packing, in particular its active surface, is kept permanently against the surface with which this packing is in sliding support contact in order to prevent any risk of leaks and to compensate for premature wear of the packing.
Again, due to this pressurization of the packing in combination with the design of the packing that simultaneously ensures sealing between the chambers and sealing of the chambers to the outside, a perfect result is obtained that limits the risks of leaks to a significant degree.
The invention will be well understood by reading the following description of embodiments with reference to the attached drawings in which:
FIG. 1 shows a partial diagrammatic view of a rotary actuator according to the invention in which the shaft of the actuator has been likewise shown only in the left part of the figure;
FIG. 2 shows a perspective, side-to-side view of the packings with which the shaft and the body of the rotary actuator that is the object of the invention respectively can be equipped;
FIG. 3 shows a perspective view of the packings that equip respectively the shaft and the body of the actuator in a position corresponding to the installed state on said components;
FIG. 4 shows a partial perspective view of packing that can equip a shaft provided with two vanes arranged diametrically opposite one another on the axis of the shaft;
FIG. 5 shows a partial diagrammatic view of another embodiment of an actuator according to the invention;
FIG. 6 shows a partial perspective view of the packings that equip at least one part of the actuator of FIG. 5 when these packings are not installed;
FIG. 7 shows a partial perspective view of part of the packing equipping the actuator of FIG. 5 when these packings are installed;
FIG. 8 shows a transverse cutaway view of the actuator of FIG. 5 and
FIG. 9 shows a detailed view of the partition supported by the body of the actuator.
As mentioned above, the rotary actuator 1, the object of the invention, is composed of a body 2 and a shaft 3 that delineate a working volume between one another. Thus, in the example shown in FIG. 1, the actuator comprises only a single working volume, while the actuator of FIG. 5 comprises two working volumes. Each working volume is composed of an annular cavity compartmented by at least two partitions 4, 5 extending between the two surfaces 19, 20, the so-called end surfaces of said cavity. One of these radial partitions 4 is supported respectively by the shaft 3; the other shown at 5 is supported by the body 2 of the actuator. Thus, in the examples shown in the figures, the body 2 is a parallelepipedic body formed by the assembly of two half-shells in such a way as to delineate, when the two half-shells are combined, a closed cylindrical cavity except for two passages at its ends allowing exit of the shaft 3 arranged longitudinally within the cavity that has thus been delineated by the body 2. The shaft 3 and the body 2 thus form an annular cavity compartmented by at least two radial partitions 4, 5 or vanes. These partitions or vanes can have a large number of shapes. In the examples shown, they are composed simply of a plate that can be formed from a single piece with the element of the actuator that bears it or can be connected to this element and fixed to the latter especially by nesting. Thus, in the examples shown, the body 2 and the shaft 3 each comprise a groove that is intended to house a partition with one of its edges coming to rest within said groove. The opposite, free edge of the partition for itself is equipped with packing 6, such as an elastically deformable seal. These partitions, by their free edge and more particularly via the packing 6 that equips such a free edge, thus come into airtight, sliding support contact, one against the inside wall 2A of the body 2, the other, namely the partition 5 supported by the body 2 of the actuator, against the outside wall 3A of the shaft 3. It should be noted that sliding support contact is defined as two surfaces in support contact being moved by relative displacement. Thus, the active surface of the packing and the surface of the body or of the shaft against which the packing is supported are activated by relative displacement that generates this sliding support contact between said components.
Although in the examples shown, except for the packing of FIG. 4 that corresponds to that of a shaft equipped with two vanes, the shaft 3 and the body 2 are equipped with a single vane, it is obvious that the shaft 3 could be equipped with several vanes without departing from the framework of the invention.
Due to the arrangement of the radial partitions 4, 5, the latter thus form at least two chambers 7, 8 with variable volume within the annular cavity by interworking with the body 2 and the shaft 3 of the actuator. These two chambers 7, 8 are capable of being pressurized alternately, by intake of fluid, to generate a relative rotational displacement of the body 2 and of the shaft 3. In the examples shown, the turning part of the actuator 1 is composed of the shaft 3, the body 2 being stationary. The reverse approach in which the turning part of the actuator 1 would have been composed of the body 2, the shaft 3 being stationary, could also have been implemented in an equivalent manner. In the examples shown, the intake of fluid used to feed the chambers 7 and 8 of variable volume of the actuator 1 is done by the shaft 3. It could have been done equivalently using the partition 5 that is integral with the body 2. Thus, the shaft 3 and/or the partition 5 integral with the body 2 of the actuator integrate(s) at least two lines 17, 18 that are used alternately as the fluid intake and discharge line of the chambers 7, 8 of the actuator to allow alternate pressurization of the chambers 7, 8.
The chambers 7, 8 thus alternately comprise a fluid intake chamber and a fluid discharge chamber. When the rotary actuator 1 includes only a single partition integral with the body 2 and a single partition integral with the shaft 3, it results in the possibility of driving the shaft 3 or the body 2 respectively over an angular range of roughly 360°. Several partitions equipping respectively the body 2 and the shaft 3 could have been provided in an equivalent manner. In this case, the movement of the component parts of the actuator 1 is limited to the interior of the aforementioned angular range. It could also have been envisaged that the shaft of the actuator comprise the body of a second, similar actuator whose shaft would be located coaxially to the shaft of the first actuator and within the latter. This assembly would allow rotation over more than 360° with single or double control. The operation of a rotary actuator 1 will not be described in more detail below because it is well-known to those skilled in this art.
In a manner characteristic of the invention, each packing 6 that equips the free edge of a partition 4, 5 is extended in the direction of each end surface 19, 20 of the annular cavity as far as said surface in order to extend into the connecting zone between the end surface 19, 20 and the body 2 or the shaft 3, respectively. This packing 6 that thus equips the shaft 3 or the body 2 is present in the form of a continuous linear seal that is not preformed and that is available in thousand meter lengths and can be cut to length, in order to come to rest in a groove of the actuator that is shaped depending on the desired arrangement of the seal. This seal thus develops from one end surface 19 to the other 20 following a loop trajectory, the closing of the loop being obtained at least by the ends of the strip comprising the seal being brought into contact. Initially this seal is preferably not preformed and can, if necessary, be shaped hot when the seal is being installed.
In this way, seals are obtained that correspond to the configurations shown especially in FIGS. 2 to 4. It should be noted that the end surfaces of the working volume can be composed either of supported flanges positioned on the shaft, as shown in FIG. 1, or by the end surfaces of the body 2, as shown by the ends of the body of FIG. 5, without departing from the framework of the invention. Regardless of the configuration adopted for these end surfaces, the packing extends just as far as these end surfaces to ensure a seal between the chambers with variable volume and the outside. Thus, the same packing is used at the same time for sealing chambers between themselves and for sealing the chamber to the outside without, however, complicating the configuration of this packing that has a form of a simple seal strip that is available in thousand meter lengths and that can be cut to length. Thus, any inventory of preformed seals becomes useless. Moreover, such a seal can be replaced extremely easily since it is enough to reposition the seal within the groove of the body or the shaft of the actuator.
In the examples shown, this packing 6, at the level of the free edge of each partition 4, 5, has the form of two axial branches, in this case parallel, extending from one end surface 19 to the other 20 so as to form a double sealing barrier.
In the examples shown, the closing of the loop formed by each packing 6 that develops from one end surface 19 to the other 20 following a looped trajectory is obtained by simple overlapping of the ends of the strip comprising the seal. The ends of the seal in this case, to facilitate their overlapping, are bevelled as shown in particular in FIGS. 2, 4 and 6 in which the closing zone has been circled. This closing zone is located at the level of the part of the packing that extends as far as the end surfaces in the connecting zone between the shaft and the body. In the examples shown, these packings 6 of the shaft 3 and the body 2 extend to the level of the end surfaces 19, 20 with respect to one another and are separated from one another by a connecting strip 21 such as a collar or washer, comprising a sliding track of each of the packings 6 and thus preventing packings 6 from rubbing against one another. Thus, in this embodiment, the end surfaces 19, 20 are composed of, for example, a supported flange of the shaft 3. The packings 6 of the body 2 and of the shaft 3 extend at the level of said surfaces into the same plane orthogonal to the shaft 3. The packing 6 of the shaft 3 is positioned on the periphery of said flange, preferably opposite the packing 6 that equips the body 2 of the actuator. It is in this configuration that the most efficient sealing is obtained. In the absence of the connecting strip composed, in this configuration case, of a collar, the packings would be led to rub against one another, then generating premature wear of the packing. To prevent such a phenomenon, a split collar is inserted between said packings. When the shaft 3 lacks the supported flanges, the end surfaces are arranged at the level of the body 2, as shown by one of the ends of the actuator of FIG. 5. In this case, as is shown in FIG. 7, the packings equipping the body 2 and the shaft 3 are routed into the connecting zone of the end surfaces between the body and the shaft to be arranged in two parallel planes, the connecting strip 21 being composed in this case of a washer 21 that is inserted between said packings for the same reasons as those mentioned above.
According to the number of vanes of the shaft 3, the packing of the shaft 3 can conform either to that shown in FIG. 2 in the left-hand view, or that shown in FIG. 4. Each time, this packing extends at least over part of the circular periphery of the flange that is intended to comprise one end surface before joining the other end surface by a linear portion following the free edge of the partition and then returning in the direction of the first end surface once this second end surface is still equipped in the direction of the free side of the partition.
In the example shown in FIG. 5, the shaft 3 of the actuator 1 is provided somewhere over its length with at least one supported flange 15 that is integral with the partition 4 that is carried by the shaft for the purpose of limiting the risks of buckling of the latter. This flange divides the body 2 into two working volumes, comprising one end surface of each working volume. The working volumes communicate with one another via openings 16 arranged in the flange 15. The presence of the supported flange 15, on the one hand, makes it possible to stiffen the shaft in the direction of length and to prevent sagging of the latter, and, on the other hand, to integrate at least one transverse edge of the partition 4 into said flange 15 in such a way as to limit the risks of buckling of this partition. Thanks to this solution, a longer actuator can be produced.
To complete the sealing of the assembly, the part of the packing 6 turned toward the part of the actuator, such as the partition 4, 5, body 2 or shaft 3 with which it is integral, can be subjected during operation of the actuator to a thrust force F that tends to keep the so-called active part of the packing 6 pushed against the wall of the body 1 or of the shaft 3 with which it is in sliding support contact. The active part of the packing 6 is that which will come into contact with a surface of the wall of the body 2 or of the shaft 3 to ensure tightness.
In the examples shown, the thrust force F is applied via pressurized fluid that is brought into contact with the packing 6. This pressurized fluid, brought into contact with the packing 6, is composed of the fluid that feeds the chambers 7, 8 of the actuator 1. Thus, the pressurized fluid that is intended to apply a thrust force F to the packing 6 feeds a chamber 9, the so-called pressure chamber of the packing 6 that is arranged between the packing 6 and the part of the partition 4, 5 or supported flange or the body 2 that acts as the seat for this packing 6. This chamber 9 extends preferably over the entire length of the packing 6.
To facilitate the application of such a support force, the packing can assume a shape corresponding to that shown in FIG. 9. In this case, the part of the packing 6 turned towards the partition 4 or 5 has one concave surface with the concavity turned toward said partition or toward the element of the actuator that bears it. The pressure chamber 9 of the seal as for itself can assume the shape of a cylindrical cavity.
In the examples shown, the pressure chamber 9 of the packing 6 is supplied with fluid via a line 10, 11A, 11B that communicates selectively with one or the other of the chambers 7, 8 of the actuator depending on the pressure that prevails within said chambers 7, 8.
Thus, the thrust force F applied via the pressurized fluid is directly a function of, or is controlled by, the pressure prevailing within said chambers. It is the chamber with the highest pressure that feeds fluid to the pressure chamber 9 of the packing 6. Thus, this results in that the thrust force F applied via the pressurized fluid is the highest possible due to the fact that it results from the fluid with the highest pressure within the actuator in the operating position of the latter. This fluid feed line from the pressure chamber 9 of the packing 6 is routed into a partition 4, 5 of the rotary actuator 1 and into the end surfaces 19, 20 of the shaft 3 or of the body 2. Thus, in the example shown, in particular in FIG. 8, each partition is provided with such a line. This line is composed of a first segment 11A, 11B that establishes communication between the chambers 7, 8 of the actuator. This first segment of the line thus extends from one surface of the partition to the other surface of said partition and comprises a line that crosses said partition. This line thus extends essentially perpendicular to the longitudinal axis of the shaft 3. This first segment 11A, 11B of the line ends in a second fluid feed segment 10 of the pressure chamber of the packing 6. This second segment 10 of fluid feed from the pressure chamber 9 is likewise perpendicular to the longitudinal axis of the shaft 3. However, it extends in the partition from the free edge to the opposite edge that is integral with the shaft or the body of the partition. The first segment 11A, 11B that establishes communication between the chambers 7, 8 of the actuator is equipped with a closing element 12 that can move depending on the pressure prevailing within the chambers 7, 8 of the actuator. This element 12 thus in turn closes the part 11A or 11B of the first segment extending between the chamber 7, 8 of the actuator under pressure and the discharge 13 of this first segment into the second segment 10. Thus, in the example shown in FIG. 8, the partition 4 that equips the shaft 3 is provided with a section 11A of the line ending in the chamber 8 and a section 11B of the line ending in the chamber 7. When the chamber 8 is an intake chamber supplied with pressurized fluid, while the chamber 7 is placed at the outlet, the portion of the line 11A is supplied with pressurized fluid. The closing element 12 that equips this section of the line is a ball valve 14 whose ball 14 can move between two end positions extending on either side from the discharge 13 of the first segment 11A, 11B into the second segment 10. Consequently, this ball tends to move in the direction of the chamber 7 and to close the section of the line 11B to prevent the fluid contained in the chamber 7 from reaching the section of the segment shown at 10 in the figure. When it is the chamber 7 that comprises the intake chamber, the chamber 8 then comprising an outlet chamber, reversed operation is observed, the ball 14 moving each time under the effect of the strongest pressure prevailing within one chamber in the direction of the other chamber to close the line of the other chamber, thus preventing any feed of the pressure chamber 9 of the packing 6 by the chamber with the weakest pressure. Thus, the packing is constantly exposed to the highest pressure prevailing within said chambers. This results in optimization of the support force applied to such packing and consequently optimization of the effectiveness of the packing.
As shown in particular in FIG. 9, the closing element 12 that can move depending on the pressure prevailing within the chambers of the actuator to close in turn the part of the first segment extending between the chamber 7, 8 of the actuator under pressure, and the discharge 13 of this first segment into the second segment 10 can be equipped with two radial elements that project through the inputs of the first segment to extend into the first or into the second chamber of the actuator. These projecting elements comprise end-of-travel stops for the actuator in the vicinity of the end positions of said radial partitions. They thus prevent premature wear of said partitions.
In the embodiments in which the shaft 3 is provided on each of its ends with a supported flange, the pressure prevailing in the chambers is applied to these flanges that themselves are contained within the body of the actuator. This results in a higher mechanical resistance of the assembly.
Due to the design adopted for each packing, the disassembly and replacement of such packing can be done extremely easily. In the case in which closing of the loop is obtained by simple overlapping of the ends of the strip comprising the seal, it is enough to pull on one of the ends and to remove all the packing from the groove, the body or the shaft in which it is seated until the seal is completely removed. Then, a new seal can be installed that will originate, for example, from a seal spool. This seal can be cut to length and thus promptly installed in the groove of the body or the shaft to allow the installation of new sealing.

Claims

1. Rotary actuator (1) of the type composed of a body (2) and a shaft (3) delineating between one another at least one working volume, each working volume being composed of an annular cavity compartmented by means of at least two partitions (4, 5) extending between two surfaces (19, 20), the so-called end surfaces of said cavity, one (4) of these radial partitions supported respectively by the shaft (3), the other (5) by the body (2) of the actuator, these radial partitions (4, 5) by their free opposite edge equipped with packing (6), coming into watertight, sliding support contact, one (4) against the inside wall (2A) of the body (2), the other (5) against the outside wall (3A) of the shaft (3), in such a way as to form at least two chambers (7, 8) of variable volume capable of being pressurized alternately by intake of fluid to generate relative rotational displacement of the body (2) and of the shaft (3), characterized in that

each packing (6) that equips the free edge of a partition (4, 5) is lengthened in the direction of each end surface (19, 20) of the annular cavity as far as said surface in order to extend into the connecting zone between the end surface (19, 20) and the body (2) or shaft (3) respectively, this packing (6) that equips the shaft (3) or body (2) being present in the form of a continuous linear seal that is available in thousand meter lengths and that can be cut to length, to come to rest on the groove of the actuator that is shaped depending on the desired arrangement of the seal, this seal developing from one end surface (19) to the other (20) following a looped trajectory, closing of the loop being obtained at least by the ends of the strip comprising the seal being brought into contact.

2. Rotary actuator (1) according to claim 1, wherein the packing (6) at the level of the free edge of each partition (4, 5) has the form of two axial branches extending from one end surface (19) to the other (20) so as to form a double sealing barrier.

3. Rotary actuator (1) according to claim 1, wherein the closing of the loop formed by each packing (6) that develops from one end surface (19) to the other (20) following a looped trajectory is obtained by simple overlapping of the ends of the strip comprising the seal.

4. Rotary actuator (1) according to claim 3, wherein the ends of the seal are bevelled to facilitate their overlapping.

5. Rotary actuator (1) according to claim 1, wherein the packings (6) of the shaft (3) and the body (2) extend to the level of the end surfaces (19, 20) opposite one another and are separated from one another by a connecting strip (21) such as a collar or washer, comprising a sliding track of each of the packings (6) and thus preventing the packings (6) from rubbing against one another.

6. Rotary actuator (1) according to claim 1, wherein the end surfaces (19, 20) are composed of a supported flange of the shaft (3), the packings (6) of the body (2) and of the shaft (3) extending at the level of said surfaces into a plane orthogonal to the shaft (3), the packing (6) of the shaft (3) being positioned on the periphery of said flange, preferably opposite the packing (6) that equips the body (2) of the actuator.

7. Rotary actuator (1) according to claim 1, wherein the shaft (3) of the actuator (1) is provided somewhere over its length with at least one supported flange (15) that is integral with the partition (4) supported by the shaft for the purpose of limiting the risks of buckling of the latter, this flange (15) dividing the body (2) into two working volumes and comprising one end surface of each working volume, said working volumes communicating between other another via openings (16) arranged in said flange (15).

8. Rotary actuator (1) according to claim 1, wherein the part of the packing (6) turned toward a part of the actuator, such as the partition (4, 5), body (2) or shaft (3) with which it is integral, is capable of being exposed during operation of the actuator to a thrust force (F) that tends to keep the so-called active part of the packing (6) pushed against the wall of the body (1) or of the shaft (3) with which it is in sliding support contact.

9. Rotary actuator (1) according to claim 8, wherein the thrust force (F) is applied via pressurized fluid that is brought into contact with the packing (6), this pressurized fluid being composed of the fluid that feeds chambers (7, 8) of the actuator (1).

10. Rotary actuator (1) according to claim 9, wherein the pressurized fluid that is intended to apply a thrust force (F) to the packing (6) feeds a chamber (9), the so-called pressure chamber of the packing (6), which is arranged between the packing (6) and the part of the partition (4, 5) that acts as the seat for said packing (6), this chamber (9) extending preferably over the entire length of the packing (6).

11. Rotary actuator (1) according to claim 10, wherein the pressure chamber (9) of the packing (6) is supplied with fluid via a line (10, 11A, 11B) that communicates selectively with one or the other of the chambers (7, 8) of the actuator depending on the pressure that is prevailing within said chambers (7, 8).

12. Rotary actuator (1) according to claim 11, wherein the fluid feed line from the pressure chamber (9) of the packing (6), arranged in a partition (4, 5), comprises a first segment (11A, 11B) that establishes communication between the chambers (7, 8) of the actuator, this first segment (11A, 11B) ending in a second fluid feed segment (10) from the pressure chamber (9) of the packing (6), the first segment (11A, 11B) being equipped with a closing element (12) that can move depending on the pressure prevailing within the chambers (7, 8) of the actuator (1) in order in turn to close the part (11A or 11B) of this first segment extending between the chamber (7, 8) of the actuator under pressure and the discharge (13) of this first segment into the second segment (10).

13. Rotary actuator (1) according to claim 12, wherein the closing element (12) is a ball valve (14) whose ball (14) can move between two end positions extending on either side from the discharge (13) of the first segment (11A, 11B) into the second segment (10).

14. Rotary actuator (1) according to claim 2, wherein the movable closing element (12) is equipped with two radial elements that project through the inlets of the first segment to extend into the first or into the second chamber of the actuator, these projecting elements comprising end-of-travel stops for the actuator in the vicinity of the end positions of said radial partitions.

15. Rotary actuator (1) according to claim 2, wherein the closing of the loop formed by each packing (6) that develops from one end surface (19) to the other (20) following a looped trajectory is obtained by simple overlapping of the ends of the strip comprising the seal.

16. Rotary actuator (1) according to claim 3, wherein the movable closing element (12) is equipped with two radial elements that project through the inlets of the first segment to extend into the first or into the second chamber of the actuator, these projecting elements comprising end-of-travel stops for the actuator in the vicinity of the end positions of said radial partitions.