System for clamping a part and method for sealing the inner casing of a low pressure rectifier of a turbomachine

The invention relates to a clamping system (1) comprising a clamping jaw (7) mounted on the shaft of a pneumatic or hydraulic cylinder (4), wherein said cylinder has a structure which drives the clamping jaw towards its clamping position when the pneumatic or hydraulic energy supply of the cylinder is interrupted, the pneumatic or hydraulic energy supply of the cylinder opposing the clamping, and where means (8) are provided for locking the cylinder when the clamping jaw is in a non-clamped position.

GENERAL TECHNICAL FIELD AND PRIOR ART

The present invention generally relates to clamping of parts.

It finds application advantageously in the field of aeronautics for the implementation of sealing operations and/or abradable material injection on inner ferrules of low-pressure guide vanes of turbine engines.

PRIOR ART

It is conventional to hold parts in precise positions on work benches using reference clamps.

In particular, clamping systems with manual adjustment are known. Such a system comprises for example a holding pad which forms a first jaw and which is coupled to a clamping screw. Said clamping screw runs through said pad and is engaged in a reference support on which it is desired to position the part during work.

Such a manual system has the disadvantage of not allowing uniform clamping from one clamp to another and requiring long setup times.

Moreover, the force exerted on the part is not repeatable and can be strongly variable from one operator to another.

In addition, clamping systems using hydraulic or pneumatic control are known.

There, clamping is accomplished by hydraulic or pneumatic compression.

This assumes however that a considerable hydraulic or pneumatic energy store is available, and to be able in particular to have safety reserves to deal with cases of possible failure in production of hydraulic or pneumatic energy.

The matter of energy and the maintenance of these systems are expensive.

The control and supervision of the clamping pressure has also proven to be complex.

Moreover, these techniques are poorly adapted to sealing operations and/or abradable material injection on inner ferrules of a low-pressure guide vane of a turbine engine.

In fact, during these operations, the guide vane must be put in rotation. Clamping by pneumatic or hydraulic energy would make it necessary to be able to accompany this rotation with winding of the hydraulic or pneumatic supply pipes, which is particularly complex to organize.

In particular, the centre of the guide vane cannot be used to allow such pipes to pass through, given that it is used for other functions in these operations.

Among these clamping system with hydraulic or pneumatic control, there are systems for which the control triggers the disengagement of the system (document EP 1 310 331 A2).

GENERAL PRESENTATION OF THE INVENTION

One aim of the invention is to resolve the problems of the prior art and to propose a system that does not have the aforementioned disadvantages.

More particularly, the invention proposes a clamping system including a clamping jaw mounted on the rod of a pneumatic or hydraulic ram, wherein said ram is a structure which, when supply to said ram of pneumatic or hydraulic energy is cut off, drives the clamping jaw toward its clamping position, supply to said ram of pneumatic or hydraulic energy opposing said clamping, characterized in that it includes means of locking the ram when the clamping jaw is in the release position.

The clamping system proposed makes it possible to hold the part clamped when the pneumatic supply is cut off. The various needs for supply, for energy storage, etc. are thereby eliminated.

Clamping is made very reliable and without risk for the operator.

In particular, clamping is made repeatable, whatever the type of clamp.

Because it is made permanent, the system requires few or no maintenance operations.

The invention also proposes a method of sealing and/or injection of abradable material on the inner ferrule of a low-pressure guide vane of a turbine engine, characterized in that it comprises the following steps:positioning, on a work bench, clamps including a clamping system of the aforementioned type,positioning the guide vane on said bench,removing the locking means of the ram located at the outer ferrule,clamping at least one clamp by cutting off its pneumatic or hydraulic supply.

It also proposes tooling for sealing and/or injection of abradable material on the inner ferrule of a low-pressure guide vane of a turbine engine, characterized in that it includes a work bench and at least one clamp including such a clamping system.

DESCRIPTION OF ONE OR MORE EMBODIMENTS OR IMPLEMENTATIONS

The guide vane R illustrated inFIG. 1comprises an inner ferrule VI, an outer ferrule VE and blades A assembled by welding to the inner ferrule VE.

These blades A are secured with the inner ferrule VI through an abradable surface AB.

The deposit of this abradable surface is accomplished during sealing and injection operations requiring clamping of the outer ferrule VE and the inner ferrule VI on a support structure of a work bench.

To this end, the inner ferrule VI and the outer ferrule VE are held at several points by means of reference clamps.

To accomplish this, it is proposed to use clamping systems with permanent clamping of the system1type illustrated inFIG. 2.

Such a clamping system is a system including one or more springs2exerting a force on the piston3of a ram4which is used to accomplish said clamping.

The hydraulic/pneumatic circuit10is provided, but only to ensure release of the clamping system1, no supply being required for clamping.

In the schematic example illustrated inFIG. 2, one or more spring(s)2is (are) compressed between the piston3and the bottom5aof the body5of the ram4. The piston3is secured to the rod6of the ram, which extends out of the body5. At its end opposite the piston3, said rod6is itself secured to a clamping jaw7.

A cam8is provided for blocking the clamping jaw7and the rod6in a high, disengaged position (release position). To this end, said cam8cooperates with a groove9which the rod6has and in which it is possible to engage said cam8when the jaw7is in the high position.

The positioning of the cam on the ram4or its disengagement is for example carried out manually.

When the cam8and the groove9are disengaged, the springs2push back the piston3of the ram4. Said piston3moves within the body5of the ram4. The jaw7, which moves with the piston3, is movable in the descending direction along arrow D to accomplish the clamping of the part to be clamped.

Release is obtained by supplying pneumatic energy from the circuit10along arrow E. A force is exerted against the piston3, which is movable in the rising direction along arrow M within said body5and compresses the springs2.

When the pneumatic/hydraulic energy is cut off, on the other hand, the springs2exert their compression force, but the jaw7remains in its high, release position if the cam8has been engaged in the groove9.

It can further be provided that the movement of the piston3and the rod6within the body5of the ram4occurs in a helical movement making it possible to have the jaw7rotate 90 degrees on itself when it moves toward the release position. Such a helical movement facilitates the disengagement of the part to be clamped.

Moreover, as shown inFIG. 3, the body5of the ram4can be associated with different means11(clamping jaws for example) which make it possible to attach the system1with precision to a given support.

FIG. 4illustrates the use of the clamping system of the system1type which was just described to accomplish the positioning of the ferrules VI and VE of a guide vane R on a work bench B.

The different reference clamps1are first of all attached precisely to the bench B using the attachment means11(FIG. 3) which they comprise, the clamps1and the bench B constituting a portion of the intervention tooling.

Then the guide vane R is installed on said bench B.

The blocking cams of the reference clamps1located at the outer ferrule VE are then removed.

These reference clamps1are then clamped to the outer ferrule VE by cutting off the pneumatic pressure in the circuit.

The ferrule VE thus being clamped, clamping of the outer ferrule VI is then carried out.

The guide vane R thus being held in position on the work bench B, the sealing operations are accomplished on inner surfaces of the inner ferrule as well as in its mortises.

Sealing is accomplished for example by depositing RTV silicone. This makes it possible to generate sealing of the path prior to injection of the abradable material itself.

The polymerization of the abradable material is then accomplished on the mortises of the inner ferrule.

The release/unlocking of the different clamps1is then ensured by putting the different clamps under hydraulic/pneumatic pressure.

When the different cams8are repositioned, the hydraulic/pneumatic pressure can again be cut off.

The reference clamps1can then be removed.

When the clamps1are not used, the cams8can be disengaged so as to limit the loading of the springs2.

It is understood that the energy thus required for accomplishing clamping is small.

Moreover, the clamping that is carried out is particularly reliable and is not dependent on the level of hydraulic/pneumatic pressure provided by the circuits.

It is repeatable, the clamping being the same no matter which clamp it is.

It is accomplished quickly and without effort by the user who carries out the clamping.

It does not require large amounts of hydraulic/pneumatic energy storage.

It requires only very little maintenance.