EP0534879B1 - Hydraulic self locking double acting actuator - Google Patents

Abstract

Self-locking double-action hydraulic actuator, with a rod (2) and a piston (3) which is immobilised in a cylinder (4), characterised in that its piston (3) is tightly mounted in an external cylinder (4) and freed to move with respect to this cylinder (4) by an expansion of this cylinder in the region of the piston brought about by the pressure of a fluid, the piston being actuated by a driving fluid. The rod (2) of the actuator comprises, according to one variant, a hydromechanical device for actuation by pivoting (31) at its rear end. This invention is of interest to constructors and manufacturers of hydromechanical equipment. <IMAGE>

Description

The present invention relates to a self-locking double-acting hydraulic cylinder for carrying out an immobilization function by pressing pressure to self-maintain when the cylinder is no longer supplied.

In multiple industrial manufacturing applications, it is necessary to immobilize the part or the functional unit on which one intervenes for a machining operation.

Currently, in this type of application, the immobilization-clamping of the parts for maintenance during machining by a simple cylinder whose rod comes into bearing contact with the part to be immobilized. A jack of the prior art is known from FR-A-1,395,257.

For various applications, due to the general configuration, the space available and certain general constraints, it is preferable to make the cylinder work in traction. The jack is then placed rod up.

For other applications, the rod presses, after pivoting, on a part when it re-enters the body of the jack via a clamping arm, with a suitably shaped underside, mounted at the end of the rod.

The reverse pivoting during release makes it possible to free the upper space for the removal of the maintained part.

Under these conditions, the pressure must be maintained as long as immobilization is desired.

Thus, the hydraulic supply conduits and connections accompany the part and its support during machining and the various transit routes.

These permanent links on the move with the carrier plate constitute a hindrance in the operation of a production unit and moreover a source of trouble and incidents.

Furthermore, self-locking cylinders are known which consist of a cylinder and of an additional self-locking device of the sleeve type surrounding the rod outside the cylinder body over part of its length.

This sleeve, with an inner diameter smaller than that of the rod, is mounted tightly on the latter. It has a pressure chamber allowing it to expand sufficiently to release the moving rod.

In the absence of pressure, the sleeve blocks the rod by clamping.

A release pressure from a pressurized fluid frees the rod from the grip of the self-tightening sleeve. The released rod can move, allowing the cylinder to operate.

This release lasts only the time of application of the pressure.

The cylinder rod is therefore immobilized or released at will in a given position by the absence or application of pressure.

However, due to their constitution, and the presence of the outer blocking sleeve, such self-locking cylinders have an overall length that is too great, not making it possible to target numerous applications because of their exceptional bulk.

The primary object of the present invention is to provide a support and blocking force which persists when the pressure of the actuating fluid of the jack is canceled, that is to say even after the withdrawal of all the fluid supply connections and pressure.

Another object of the invention consists in being able to have an instantaneous application blocking force.

Yet another goal is to avoid the constant presence of hydraulic connections during the transit and machining of parts.

Yet another object of the invention is to allow the workpiece to be immobilized with the rod pivoting movement when the work or the movement of the workpiece requires release of the support.

A final goal is to be able to accommodate the self-locking support cylinder in a reduced space due to the integration of the functions. This integration, in effect, confers minimal bulk on the jack according to the invention.

All these aims are achieved by the self-locking double-acting cylinder according to the invention which overcomes the drawbacks of the prior art and is characterized in that the piston of the cylinder body is mounted clamped in a cylinder, said piston being immobilized in the cylinder. by default of fluid pressure and released in movement relative to this cylinder by a dilation brought by the pressure of a fluid.

According to a variant, the rod is pivotally movable in the piston, but immobilized in translation relative to the latter, said rod comprising at its rear end a hydromechanical device for pivoting actuation.

• . bridage d'une pièce sur un élément porteur avec ou sans dégagement de l'appui ;
• . fermeture de moules ;
• . fixation d'outils de presse ;
• . fonction d'immobilisation et de pincement ;
• . fonction de butée antivibratoire.

The invention non-limitingly targets the following fields of application:

• . clamping of a part on a load-bearing element with or without release of the support;
• . mold closing;
• . fixing of press tools;
• . immobilizer and pinch function;
• . anti-vibration stop function.

• . la figure 1 est une vue en coupe longitudinale du vérin autobloquant à double effet selon l'invention ;
• . la figure 2 est une vue en plan du vérin autobloquant selon l'invention ;
• . les figures 3, 4, 5, 6 et 7 sont des schémas successifs illustrant, avec représentation d'une base des temps, l'application des pressions pendant le fonctionnement du vérin autobloquant selon l'invention.
• . la figure 8 est une vue en coupe longitudinale, selon la ligne VIII-VIII de la figure 9, de la variante à pivotement du vérin autobloquant perfectionné selon l'invention ;
• . la figure 9 est une vue en plan de la variante à pivotement ;
• . la figure 10 est une vue en coupe transversale arrière, selon la ligne X-X de la figure 8, montrant le mécanisme d'actionnement en pivotement de la tige du vérin ;
• . la figure 11 est une vue schématique en coupe verticale illustrative d'un exemple d'application ;
• . les figures 12 à 19 sont les différents schémas d'une séquence de fonctionnement en regard d'une base des temps dont :
  • figures 12 à 15 : phase de bridage,
  • figures 16 à 19 : phase de débridage.

The technical characteristics and other advantages of the invention are set out in the description which follows, given by way of nonlimiting example on an embodiment with reference to the accompanying drawings in which:

• . Figure 1 is a longitudinal sectional view of the self-locking double-acting cylinder according to the invention;
• . Figure 2 is a plan view of the self-locking cylinder according to the invention;
• . Figures 3, 4, 5, 6 and 7 are successive diagrams illustrating, with representation of a time base, the application of pressures during the operation of the self-locking cylinder according to the invention.
• . Figure 8 is a longitudinal sectional view, along the line VIII-VIII of Figure 9, of the pivoting variant of the self-locking cylinder improved according to the invention;
• . Figure 9 is a plan view of the pivoting variant;
• . Figure 10 is a rear cross-sectional view, along line XX of Figure 8, showing the pivoting actuation mechanism of the cylinder rod;
• . FIG. 11 is a schematic view in vertical section illustrative of an example of application;
• . FIGS. 12 to 19 are the different diagrams of an operating sequence with regard to a time base including:
  • Figures 12 to 15: clamping phase,
  • Figures 16 to 19: unlocking phase.

The invention consists in incorporating into the cylinder of a jack a body of larger section than that of the cylinder so that it is normally locked in this cylinder when it is at rest and to unlock it under the action of a force or a means acting by reaction on this body to expand the cylinder and thus free this body so that it can move.

This body acts as a cylinder piston in a rod-piston assembly which becomes momentarily mobile in the cylinder of the cylinder.

This invention also aims to achieve a combination of means such that there is no seal (s) on the part of the piston in contact with the cylinder.

We will first describe the general constitution of the self-locking cylinder according to the invention.

The self-locking double-acting cylinder according to the invention consists of a cylinder body 1 conventionally comprising a rod 2 secured to a cylindrical movable body or element or cylindrical piston 3 moving in a cylinder 4 under the effect of the pressure d '' a working fluid.

The piston 3 has a generally cylindrical lateral surface comprising, for example in the middle position, a cylindrical projection 5 in contact with the internal wall opposite the cylinder 4 and two cylindrical sliding ends having a driving section and a lateral sliding surface moving along the inner side surface of a cylindrical housing serving as a guide.

The cylindrical ends are each connected to the projection 5 by a shoulder.

On one or the other of the driving faces is exerted a thrust in one direction or the other coming from the pressure of a working fluid present in the engine circuit of the jack.

According to the general inventive concept, the piston 3 of the cylinder secured to the rod 2 is engaged, by any appropriate means in the outer cylinder 4 of slightly smaller diameter. This cylinder serves on the one hand as a guide during its movements and on the other hand as a clamping sleeve during the blocking period.

The cylindrical projection 5 of the piston 3 of the jack is in contact over its entire length with the internal wall opposite the cylinder 4. It has on said external cylindrical projection a single groove helical 6.

The outer cylindrical projection 5 of the piston defines with the piston, the cylinder and the cylinder closing parts, on either side of this projection, two sections or end chambers 7 and 8 hydraulically connected together by the helical groove 6 intended to keep them under pressure.

As indicated, there is between the cylindrical surfaces facing the piston and the cylinder a mechanical tightening contact.

A sufficient pressure of oil applied against the internal surface of the cylinder 4 will deform it over practically its entire length due to the elasticity of the metal leading to a functional clearance between cylinder and piston.

The internal volume formed by the two end chambers and the helical groove 6 is hydraulically connected by an inlet 9 to a fluid placed under control under pressure by a suitable generator through a release circuit terminated by a purge 10. This circuit release includes the two end chambers, the helical groove 6, and the generator connected together by conduits. This release pressure makes it possible to cause the local expansion of the cylinder for the release of the piston 3.

One can consider using for the release of the movable assembly or piston 3 the same fluid as that used for the cylinder.

It is also possible to use different pressures in the cylinder engine circuit and in the cylinder release circuit.

The cylinder 4 is mounted between two mechanical end closure blocks respectively a front end flange 11 and a rear end flange 12 mechanically joined together by a plurality of connecting rods such as 13, by example four.

Each flange 11 and 12 has a coaxial cylindrical shoulder 14 and 15 on which each of the corresponding ends of the cylinder 4 fits.

The front flange 11 serves as a guide for the piston rod which passes through it at its center while the rear flange 12 is blind. It has a coaxial sliding-guiding cylindrical housing for the rear end of the piston which defines, with the rear driving section of the piston 3, a thrust chamber 16 in communication with the working fluid under pressure by an inlet / outlet orifice. 17.

The front flange 11 delimits with the front driving section of the piston 3 a traction chamber 18 in communication with the hydraulic motor circuit by an inlet / outlet orifice 19.

Sufficient sealing of the blocking-release zone is provided by suitable end seals such as 20 and 21 between the ends of the cylinder and each of the flanges.

High pressure type seals 22 and 23 line the end grooves of the piston outside the cylindrical projection 5.

A scraper seal 24 is placed in the front end flange 11 at its crossing by the rod 2.

The cylindrical movable element, namely the piston 3 and the closing flanges 11 and 12, constitute a true double-acting cylinder supplied by its hydraulic motor circuit of pressurized fluid which opens into the thrust 16 and traction 18 chambers.

The rod 2 can also have a head on which any suitable element for pushing or pulling on a part 25 can be mounted.

Classic cylinder functions according to the invention are ensured by a hydraulic motor circuit actuating the mobile assembly in thrust and in traction.

The rod can actuate, by its longitudinal movement, any device or mechanism for returning or transforming movement with a view to simple support or as a return to support support on a part.

We will now examine the different phases of the operation of the self-locking support cylinder according to the invention.

The pressurized fluid is sent into the release circuit for the release of the mobile assembly.

Shortly thereafter, the actuator is pushed in to impart a direct bearing or traction bearing force on the part to be maintained.

To do this, the thrust or traction chamber is supplied, and the pressure of the fluid actuates the rod in thrust or in traction. It moves to come into contact with the part.

Then only the support force is established at a maximum value, depending on the pressure.

Maintaining the part being assured, it suffices to immobilize the jack in its pressure position by canceling the pressure in the release circuit. The push or pull pressure on the cylinder piston can also be canceled.

We will now examine in detail the operating sequence illustrated in FIGS. 3 to 7.

• . l'entrée ou sortie A correspondant aux mouvements de sortie de la tige ;
• . l'entrée ou sortie B correspondant au rappel de la tige ;
• . l'entrée C d'application de la pression de dilatation ou de libération.

In these figures, the pressures are applied in three different places:

• . the inlet or outlet A corresponding to the outlet movements of the rod;
• . the inlet or outlet B corresponding to the return of the rod;
• . input C for application of the expansion or release pressure.

The references PA, PB, PC respectively designate the pressures at points A, B and C, that is to say the pressures corresponding to the thrust forces, of traction by retraction of the rod and to the release pressure.

The operation concerns a clamping in thrust, that is to say by direct support rod at the outlet.

• . dilatation-libération du piston par une pression de libération en C (figure 4) ;
• . poussée de la tige et application de la pression d'immobilisation-bridage en appui (figure 5) ;
• . position permanente d'immobilisation par pousssée, tige sortie (figure 6) ;
• . reprise de charge en vue du débridage pour dégagement de la pièce maintenue puis rentrée de la tige (figure 7).

The successive characteristic phases represented are as follows:

• . expansion-release of the piston by a release pressure at C (Figure 4);
• . pushing of the rod and application of the immobilization-clamping pressure in support (FIG. 5);
• . permanent position of immobilization by pushing, extended rod (Figure 6);
• . load resumption for unclamping for release of the part maintained then retraction of the rod (Figure 7).

The cylinder is in the initial position, that is to say immobilized at rest, rod retracted.

The part to be held by clamping is placed on its support. The phases leading to the clamping from the initial position proceed as follows.

The release pressure is applied at C to release the piston from its grip by the outer cylinder. Then, while maintaining the release pressure at C, the push pressure PA is applied at A until the desired clamping force is obtained.

The PC pressure is removed before the PA pressure is removed.

All fluid connections can be disconnected.

We are then in the permanent operating mode of push-back support.

This diet lasts for the time necessary to machining or any other intervention on the immobilized part by clamping.

The release is carried out as follows.

First, a push pressure PA is applied. Then, and while maintaining the pressure PA, the piston is released by applying the release pressure PC. The pushing pressure PA is suppressed while applying the pulling pressure PB and maintaining the release pressure PC. After recalling the rod, the traction pressure PB then possibly the release pressure PC are removed.

The jack is then found in the initial position corresponding to FIG. 4.

One of the advantages of the invention is to be able to easily and quickly rid the carrier assembly or the machining assembly of a part of all the fluidic connections under pressure.

Furthermore, the coupling and uncoupling being effected by quick couplings, these operations can be accomplished in a minimum duration.

One understands the notably important advantage of this invention which makes it possible to conserve the pressing force without fluid pressure.

The variant with integrated pivoting will now be described with reference to FIGS. 8 to 19.

More particularly, provision is made according to this variant, to mount on the outer end of the rod a clamping element by pulling the rod. This element is called clamping arm 26 (shown only in Figures 16 to 19).

According to the present variant, the rod 2 of the jack is free to pivot in the piston, thanks to an appropriate clearance, and is immobilized in translation by a rear shoulder 27 and by a ring. stop 28 mounted on the rod. Two high pressure seals 29 and 30 provide fluid insulation, between the thrust 16 and traction 18 chambers for one, and between the traction chamber 18 and the outside for the other.

There is provided, at one end of the jack, a pivoting actuation mechanism 31 of the rod 2, allowing the release of a part to be held 32 (shown only in FIG. 11) after pivoting of the clamping arm 26 mounted at the outer end of the cylinder rod 2 on its head.

Also according to the present variant, the pivoting actuation mechanism 31 is housed in the cavity of the rear end flange 12 forming the thrust chamber 16.

The pivoting actuation mechanism 31 consists of a hydromechanical device 33 with rack 34 and pinion 35, intended to rotate the rod 2 of the jack on itself, in one direction and in the other, over a certain deflection angular, for example a quarter turn, and manage to free the part 32 thus maintained from the grip of the jack.

More precisely, this hydromechanical device 33 consists of the end of the cylinder rod 2 shaped as an elongated pinion 35, on which the rectilinear translational element with toothing or rack 34 meshes.

We will now refer to Figure 10.

The rectilinear element or rack 34 has a generally cylindrical shape, shaped on its underside according to rectilinear toothing 36 occupying the majority of its length.

This toothing 36 is mounted in engagement with the pinion 35 formed in the end of the rod 2 of the jack.

The rack 34 has a push end 37 fitted with a dynamic seal 38 and an opposite end of stop 39 by its front edge 40.

The rectilinear element or rack 34 is arranged transversely to the rod 2 of the jack, and guided at each of its ends by a hollow piece of rack.

There is a hollow push piece 41 and a hollow stop piece 42 opposite the first, pieces of general conformation in plug, also serving as shutters of the push chamber 16.

Together with the rack 34, they constitute a veritable miniature cylinder.

Each hollow part 41 and 42 delimits an interior chamber 43 and 44, respectively of thrust and withdrawal assistance, and is screwed transversely in correspondence with its counterpart in the body of the rear flange.

Each hollow part 41 and 42 has an end groove fitted with a seal 45, 46. Furthermore, it has a shoulder 47, 48 having at its base an annular groove 49, 50, pierced along a channel of inward communication for the hollow push piece 41, in order to establish hydraulic communication with the working fluid. Each hollow part presses by its shoulder 47, 48 on the adjacent surface by means of a suitable circular flat seal 51, 52.

The hollow thrust piece 41, for example that on the left in FIG. 10, has an internal volume which delimits the thrust chamber 43 of the rack, hydraulically connected to the traction chamber 18 by an oblique rectilinear channel 53 extended by a tube longitudinal 54.

This power supply characteristic of the rack pushing chamber 43 through the jacking chamber 18 of the jack considerably simplifies the operation of the assembly as will be seen below.

The hollow abutment piece 42 comprises, at the rear, a shim of thickness 55 screwed onto its bottom, making it possible to stop the stroke of the rack 34 in one direction, and thus to limit the angular deviation of the rod 2.

The greater or lesser thickness of this wedge 55 conditions the angular deviation.

It is important to observe here again that the rod 2 rotates freely in the piston 3 under the action of the hydraulic pivoting device 31.

On the other hand, it is immobilized in translation relative to the latter by the retaining ring 28 and the rear shoulder 27.

On the outer end of the rod, the clamping arm 26 or any other part adapted to this clamping by pivoting-support is mounted.

We will now describe the different operating phases of the improved self-locking cylinder, with reference to FIGS. 12 to 19.

• . l'entrée ou sortie A correspondant aux mouvements de poussée en sortie de la tige et d'actionnement dans le sens retour de la crémaillère ;
• . l'entrée ou sortie B correspondant au rappel de la tige et d'actionnement dans le sens aller de la crémaillère ;
• . l'entrée ou sortie C correspondant à l'application de la pression de dilatation ou de libération du vérin.

In these figures, the pressures are applied in three different places:

• . the inlet or outlet A corresponding to the thrust movements at the outlet of the rod and actuation in the return direction of the rack;
• . the inlet or outlet B corresponding to the return of the rod and actuation in the forward direction of the rack;
• . the inlet or outlet C corresponding to the application of the expansion or release pressure of the jack.

The references PA, PB, PC respectively designate the pressures at points A, B and C, that is to say the pressures corresponding respectively, firstly to the thrust forces by exiting the rod and its pivoting in the return direction , then to the tensile forces by retraction of the rod and its pivoting go and finally to the release pressure.

To understand how it works general below, we will first explain that of the hydraulic pivoting device.

One of the features of the invention consists in having the withdrawal chamber 18 of the rod, connected to the pressure source by the orifice B, communicate with the hollow push-piece of the rack 34.

Thus, the pressure applied to the orifice B is communicated to the rack 34 which moves towards the shim 55, causing the rod of the jack to pivot.

Conversely, the return of the rack 34 is obtained by the pressure applied to the orifice A communicating with the withdrawal assistance chamber 44 of the rack.

Indeed, due to the conformation of this chamber, the internal volume thereof extends over the entire rear space of the rod 2 of the jack, except in the hollow thrust part 41 of the rack 34 suitably isolated by the seals 45 and 51.

This space is filled with oil which is pressurized by connecting port A to the pressure source.

The pressure prevailing in the entire thrust chamber 16 of the cylinder rod surrounding the hydraulic pivoting device 31 acts on the rack 34 and causes it to move back in the manner of a plunger, provided that the pressure in the part hollow pressure 41 is zero, that is to say that the orifice B is decompressed.

This return movement of the rack 34 instantly swivels the rod 2 of the actuator by a reverse angular deviation to return it to its initial release position, if the chamber 43 of the hollow thrust part 41 is not under pressure.

Otherwise, wait until the pressure in this thrust chamber 43 of the rack 34 is canceled.

The cylinder at rest is immobilized, rod 2 out and piston 3 blocked, constituting the initial position of the usual sequence of operation (Figure 5).

From this initial position, the clamping is carried out (Figures 12 to 15).

First of all, the rod 2 of the jack is pivoted on the angular difference desired by the supply of the hydromechanical pivoting device 31 through the orifice B. The rack 34 moves to the stop on the shim 55 (Figures 12 and 13), as described above.

The rod 2 cannot move longitudinally, because the jack is blocked.

The cylinder is then released, rod 2 out, by supplying it with C (FIG. 12).

Then comes the clamping phase, carried out by feeding B to bring the rod 2, by a pulling movement, in contact then in support by its clamping arm 26, on the part to be held 32 (Figure 14).

Then, the load is maintained by decompression at C, then it is decompressed at B. The jack is no longer supplied, and can maintain the clamping force indefinitely without hydraulic pressure.

We arrive here at the stable clamping position (Figure 15).

During unclamping (Figures 16 to 19), the load is first taken up, by supplying orifice B, blocked cylinder, which has the effect of avoiding instantaneous release of the rod when the cylinder is released. (figure 16).

Follows the release of the jack, rod 2 retracted, supplying C, B remaining supplied due to the load recovery (Figure 17).

Ports A and B are then simultaneously pressurized, while keeping port C supplied.

The rear end of the cylinder rod being subjected to the thrust pressure, because located in the thrust chamber 16, the force generated by the pressure coming from the orifice A is greater than the opposite force from the pressure coming orifice B acting in the traction chamber 18.

Under this motor effect, the rod 2 of the jack exits (Figure 18).

Then, we decompress at C to immobilize the jack, and at the same time we decompress B. Remains the pressure A which will return the rack 34 to the initial position causing the reverse pivoting of the rod 2 of the jack, according to the above explanations the operation of the hydraulic pivoting device 34 (FIG. 19).

An example of application is illustrated in Figure 11.

According to this example, the workpiece 32 rests on two uprights 56 and 57 of a support 58 and on two anti-vibration supports 59 and 60. The maintenance of this workpiece 32 is ensured by two self-locking pivoting cylinders 61 and 62 with arms clamping 63 and 64.

The part, thus immobilized, can be machined, for example by a milling tool 65.

The clamping is ensured during the entire machining phase by the two self-locking pivoting cylinders 61 and 62 hydraulically disconnected.

It is understood that beyond the means described, various obvious modifications and simple variants fall within the scope of the present invention.

Claims (14)

1. Self-locking supporting actuator providing a pressure support with automatic retention, comprising a rod (2) and a cylindrical piston (3) mounted in a clamping manner in a cylindrical housing (4) closed by a front end plate (11) and a rear end plate (12), the piston having, on its lateral surface, a cylindrical projection (5) and being mounted in mechanical clamping contact by its cylindrical projection (5) in the cylindrical housing (4) and released from the mechanical clamping in the cylindrical housing by the dilatation thereof over almost all its length which is effected by the pressure of a releasing fluid in a releasing circuit, then actuated in translation in the cylindrical housing (4) in one direction or the other by the pressure of a driving fluid acting in a driving circuit on one or other driving section of the piston characterised in that:

   . the piston has, on both sides of the cylindrical projection, a front end and a rear end of the piston delimiting, with this cylindrical projection, a front cylindrical shoulder of the piston and a rear cylindrical shoulder of the piston;

   . each front end plate (11) and rear end plate (12) comprises, on the one hand, a projecting coaxial cylindrical shoulder, (14) and (15) respectively, on each of which each of the corresponding ends of the cylindrical housing (4) is mounted, and, on the other hand, a coaxial cylindrical slide-guide accommodation, each of which delimits, with one end of the piston which is engaged in the accommodation, respectively one thrust chamber (16) for the rear end of the piston and one traction chamber (18) for the front end of the piston, the front and rear ends of the piston both being displaced by sliding along the inner lateral surface of one or other coaxial cylindrical slide-guide accommodation of one or other end plate serving to guide them;

   . the cylindrical housing (4), the shoulders of the piston and the front of each shoulder (13) and (14) of each front end plate (11) and rear end plate (12) delimit an end chamber, (7) and (8) respectively, communicating with the releasing fluid circuit;

   . one of the ends of the rod (2) of the piston supports a clamping part (26,64) which retains, by a mechanical contact resulting from the immobilisation, in traction or in thrust, of the rod (2), the piston on the surface to be retained, following the driving movement of the piston, and then its immobilisation by cancellation of the pressure in the releasing circuit.
2. Supporting actuator according to Claim 1, characterised in that the releasing circuit is independent of the driving circuit inside the active part of the actuator.
3. Supporting actuator according to Claim 1 or Claim 2, characterised in that the piston releasing fluid is the driving fluid of the actuator.
4. Supporting actuator according to any one of Claims 1 to 3, characterised in that the pressures are different in the driving circuit of the actuator and in the piston release circuit.
5. Supporting actuator according to any one of the preceding Claims, characterised in that the piston (3) supports, on its outer cylindrical surface, a helical groove (6), connecting the two dilation chambers (7) and (8) to one another in fluid communication with a generator, the whole forming the releasing circuit.
6. Supporting actuator according to Claim 5, characterised in that the cylinder is dilated with respect to the projection (5) by the releasing fluid, but also on the lateral surface of each end chamber (7) and (8) which it delimits in a circular manner.
7. Supporting actuator according to any one of the preceding Claims, characterised in that the end of the rod (2) supports on the part to be retained by thrust on the piston.
8. Supporting actuator according to any one of the preceding Claims 1 to 7, characterised in that the end of the rod (2) supports the part to be retained during the retraction thereof by a traction force.
9. Supporting actuator according to any one of the preceding Claims, characterised in that the rod (2) is movable in a pivotal manner in the inside of the piston (3) and immobilised in translation in relation thereto, said rod (2) comprising, at its rear end, a hydromechanical device (31) for pivotal actuation.
10. Actuator according to Claim 9,
    characterised in that the hydromechanical device (31) for pivotal actuation is accommodated in the thrust chamber (16).
11. Actuator according to Claim 9 or 10, characterised in that the hydromechanical device (31) for pivotal actuation is formed of an elongated pinion (35) formed in the end of the rod on which is engaged a rack (34) with rectilinear toothing (36), said rack being displaced transversely to the rod, in two hollow parts, a thrust part (41) and an abutment part (42) respectively, which serve to guide it.
12. Actuator according to Claim 11,
    characterised in that the inner chamber of the hollow thrust part (41) is connected hydraulically to the traction chamber (18) and is supplied with pressurised fluid through the traction chamber (18).
13. Actuator according to Claim 12,
    characterised in that the hollow abutment part (42) has, screwed to the base thereof, a shim (55) forming an adjustable abutment.
14. Actuator according to Claim 11,
    characterised in that the hollow parts (41) and (42) assume the shape of a stopper and are screwed transversely in the rear plate (12).

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