EP1408177B1 - Apparatus for removing putty - Google Patents

Abstract

The tool has a mastic removing tip (28) with a shaft (36) and a head (38) reciprocated by a pneumatic vibration motor (32) operating at a frequency of 120Hz and enclosed in a casing (30). The head, which has a bevelled end with a preferable angle of 30 deg, is made from a polymer material with an optional filler of carbon or glass fibres. The tool is stowed in a container with spaces for cables and a compressed air connector and regulator.

Description

The present invention relates to a dispensing device, in particular for the repair of joints in aircraft tank structures.

The invention also covers the intervention container.

The tanks, especially in aircraft are directly constituted by the free volumes in the wings.

Indeed, the wings are made from a structure composed of ribs, stiffeners, with passages of the various organs but most of the structure is empty. Plates are then reported on this structure so as to achieve a closed volume, with the appropriate shapes and having the mechanical characteristics necessary for the flight.

The volume is thus mechanically closed but it is not waterproof since the plates are screwed or riveted and if the physical continuity is ensured, the joints between the plates are not sealed.

If it is desired to use these volumes thus made to form reservoirs of fluids and in particular of fuel, it is necessary to seal the joints and all the passages of fastening means such as aeronautical screws or rivets.

This seal is obtained by depositing beads of sealant on all joints and mastic pads on all through passages, including the fastening means.

This putty is deposited by means of a gun in more or less viscous form and then polymerized in situ at room temperature with a suitable hygrometry.

In case of too low temperature or to accelerate the operation, it is possible to use a thermoreactor especially marketed under the name "SUNAERO" so as to emit infrared radiation located in the absorption zone of the types of putty retained. The polymerization is thus accelerated.

This sealant deposit is necessarily made once the wing is complete. However, given the number of reinforcing elements, transverse stiffeners and other equipment, and given the dimensions of the wings, especially in thickness, it is found that there is little room for an operator to move and even less to work.

It is indeed necessary to access all the crossing points of fasteners and all joints, exhaustively and some are very difficult access.

For the removal of a cord with a pistol, if the operation is delicate, it requires only a reasonable physical effort, the difficulty resulting rather from the uncomfortable position of the operator and the necessary accuracy .

These mastics used are adapted to resist fuel and are very sophisticated because they resist significant temperature differences, have some qualities of hardness while allowing sufficient flexibility to avoid breaking during movements and vibrations suffered by them. different pieces.

The adhesion power is in all cases very important to eliminate any risk of delamination. Very rigorous procedures must be carried out knowing that the sealant adheres not on the metal but on the layers of protective coating and coating of which the different parts are coated.

The fact remains that there may be defects and that over time cracks appear and cause fuel leaks.

This problem often occurs in the most stressed areas such as the root of the wings or the right of the support structure of the propulsion means.

The operators remedy these defects during systematic maintenance visits or during specific interventions, if necessary.

During this repair step, you must first empty the wing volume concerned, degas it and locate the leak. Access to the interior volume is through a manhole in the wing which must be removed the trap according to specific procedures.

To ensure repair, the used sealant must be removed from the affected area and replaced with new sealant.

This is where there are significant problems that the present invention proposes to solve in the best possible way.

Indeed, the sealant is by composition even with a very high adhesion power, power that is strengthened over time. In addition, the hardness of the sealant increases with aging.

As has been explained, the access conditions of certain areas are delicate and to remove the mastic, this time it is necessary to spend a significant amount of energy.

Fortunately, leak detection procedures with a precise location of a leak make it possible to circumscribe the area and limit the extent of repair of the seal.

The solution currently consists of a mechanical scraping process using polycarbonate spatulas for example, which are sharpened and manipulated by the operators in order to scrape the best areas. This operation is therefore manual. Electrical appliances or that can generate sparks are prohibited because even after ventilation, the atmosphere can remain punctually explosive.

The document DE-892430 of the prior art proposes a pneumatic device comprising a chisel integral with means for vibratory reciprocating movement, said means for vibratory reciprocating movement taking the form of a body comprising a motor and a mandrel, said chisel comprising a rod of fastening adapted to said mandrel.

However, such a device is not suitable because it can cause under the effects of vibratory alternating movement scratches paint layers covering and protecting the various parts of the tank.

It should also be noted that only chips are allowed in order to retrieve them and remove them from the body of the wing unlike sawdust that could generate sanding. Residual dust or dust could then foul the kerosene filters and are therefore prohibited.

Similarly solutions have been experimented with chemical solutions. The products used must be neutral for the operator but also for the constituent materials of the wing. In addition, after using them, it is found that at best, we obtain a softening mastic that must still remove mechanically.

As for this cleaning with chemical solutions, it remains delicate because it is impossible to determine when the product stops acting, which disrupts the filling of the tanks.

Ultrasounds such as water jets require too large equipment and it must be possible to realize systems for simultaneous recovery of waste because it necessarily occurs projections. In addition, the penetration of water into structural interpositions can generate corrosion points that are difficult to detect.

Tests have been conducted with cryogenic products to make the sealants brittle in the hope of facilitating manual operation. But there are

health and safety issues with operators. The effectiveness of such a method is very limited.

Another constraint is due to the fact that the surfaces are coated, usually a protective primer that must be left on the metal. In addition to this delicate coating, it is imperative to avoid any scratching of the metal that would constitute a potential start of breakage. Since the material is generally an aluminum alloy, the scratches can be easily generated.

The area must be thoroughly cleaned to follow the remoulding procedure and obtain a good seal after removal of the new bead or block of caulk to be cured. The duration of this phase represents substantially half of the time required for the complete intervention.

These constraints, associated with the working conditions for the operators, make it necessary to find a more comfortable solution for the operators and more efficient for the operators. Such a solution has been sought by the operators for many years.

The intervention of the operators is long or the immobilization of an aircraft is extremely expensive. When repairs are carried out in masked time during maintenance, this is less problematic, albeit costly, but when it comes to a one-off intervention on an ill-equipped airport, in an emergency, far from the basics, the financial loss can occur. prove very high.

The present invention overcomes the above disadvantages and the adapted container allows rapid interventions anywhere, with a quality of intervention compatible with the needs and standards of aeronautics.

• figure 1, une vue d'une portion d'aile d'aéronef avec des joints et des moyens de fixation recouverts de mastic,
• figure 2A, une vue de détail d'une vis aéronautique, en perspective,
• figure 2B, une vue en coupe de la vis de la figure 2A,
• figure 3A, une vue du dispositif selon l'invention,
• figure 3B, une vue agrandie d'un embout,
• figure 3C, une vue de détail d'une variante d'embout, et
• figure 4, une vue d'un container d'intervention.

The present invention is now described with reference to the appended drawings which represent a preferred but non-limiting embodiment of the device of the present invention, the various figures representing:

• figure 1 a view of an aircraft wing portion with seals and fasteners covered with mastic,
• Figure 2A , a detailed view of an aeronautical screw, in perspective,
• Figure 2B , a sectional view of the screw of the Figure 2A ,
• figure 3A , a view of the device according to the invention,
• figure 3B , an enlarged view of a mouthpiece,
• figure 3C a detail view of a tip variant, and
• figure 4 , a view of an intervention container.

On the figure 1 , there is shown an aircraft wing portion with a complex zone comprising a joint with three plates 12-1, 12-2 and 12-3 forming an angle, the three cords 14-1, 14-2 and 14 -3 putty 14 meeting at the intersection.

This schematic representation also shows a series of means 16 for fixing plates, in this case aeronautical screws.

These screws, as we see on the Figures 2A and 2B pass through holes 20 which must be sealed.

Therefore, the solution consists of a putty deposit 14, in the form of a stud 14-4 covering the assembly of the screw 22 and its nut 24. Note that this stud extends beyond the nut to come to adhere on the same surface of the plate.

These deposits putty 14 perfectly marry the surfaces on which they are deposited, which makes the withdrawal all the more complicated.

It is recalled that aluminum and its alloys which are the aeronautical materials par excellence, corrode under the action of oxygen in the presence of an acid medium, water, chloride, which requires the coating of the all of the structure by a barrier primer which must necessarily be preserved during the demoulding operations.

As for scratches, they must be banned because aluminum and its alloys have a particular behavior. A scratch is indeed a beginning of rupture; the corrosion is concentrated on this precise point and develops at the right of this weak point. This concentration of corrosive action is a danger.

One of the important problems is therefore the choice of the removal tool because it is also necessary to determine a material that resists wear as much as possible not for reasons of economy but for reasons of performance because it is not necessary. possible for the operator to constantly change tools or to see the quality of this tool during work, the duration of intervention would be increased proportionally.

As for the inadvertent removal of primary, it can be remedied by laying a new coating on the degraded area but in this case, the duration of intervention is extended, which is not desirable.

The present invention relates to a device comprising means 26 for vibratory reciprocating movement and a tool 28 integral with these means.

The means 26 for vibratory reciprocating movement comprise a body 30 including a motor 32 and a mandrel 34 able to receive said tool 28.

Advantageously, the motor is of the pneumatic type and the connection is a fast connection of the type marketed under the name "STAUBLI". The vibratory frequency is around 120 Hz to give an order of idea.

The tool 28 comprises in this embodiment a rod 36 and a head 38.

The rod is intended to be mounted in the mandrel 34 while the head 38 is the member in contact with the sealant and the surface of the wing, intended to travel at the interface.

This head must be made of a material whose hardness is sufficient to cut mastic chips and to resist wear but not too much not to cause scratches under the effects of vibration reciprocating motion.

These two parameters being antinomic, it is understandable why so far such a device has not been developed because those skilled in the art is dissuaded from resorting to such means.

Numerous tests have been carried out and some particularly well adapted materials are shown. It is then necessary to check the performance of these tools, which may allow orientation on the final choice for this or that user.

Among the materials giving the best results are the so-called PEEK polyetheretherketones (polyetheretherketone), polyoxymethylenes, polyetherimides or epoxy resins.

As regards the yield, preference is given to polyetheretherketones loaded with carbon or fiberglass.

When the load is carbon, although the quantities are very limited, the aviation industry remains reluctant because carbon creates corrosion in contact with aluminum and its alloys.

The preference is rather for polyetheretherketones loaded with 30% fiberglass.

With regard to these materials, it is also necessary to analyze the shape of the working area of the head.

The simple and most used form is the bevel shape, especially with a vibratory alternating movement in the working axis.

Cutting angles of this bevel are analyzed 30 °, 45 ° and 60 °, symmetrical and asymmetrical

The symmetrical or asymmetric angle of 30 ° gives satisfaction by generating very little dust, producing good quality chips, without causing rebounds harmful to the operators under the alternative vibratory movements.

This is the representation that is made on the figure 3B .

The figure 3C shows a so-called special head as it can be realized, especially for some angles even more difficult to access. The shapes are then guided by the applications.

Practical tests have shown that the operator does not need to exert a major effort on the device, a pressure of a few bars is sufficient to hold the tool abutted on the sealant, the vibrating oscillatory movement ensuring the detachment of the device. putty or shavings.

In any case, a pneumatic pressure control valve is provided when it comes to this type of power source in order to obtain the adequate pressure at the end of the tool.

It should be noted that the pneumatic way is preferred because the risks of leakage have no consequences as could be the case with a hydraulic fluid.

In addition, that says hydraulic also says specific center while the compressed air is available in any workshop, even the least well equipped.

An electric motor is banned because of the conductive metallic environment and the potentially explosive atmosphere.

The invention also provides an intervention container 40, adapted to provide the overall delivery service.

Such a container 40 comprises at least one device according to the present invention with a reserve 42 of tools considered as consumable, adapted hoses including a hose 44 for connection to a source 46 of local compressed air when it is not provided, a housing 48 for regulating the delivered air pressure, a suction suction system 50 connected to the same source of supply of compressed air.

This container may also include personal protections such as glasses, gloves, masks and hearing protection.

Thus, during an intervention, the operator moves on the airport that received the immobilized aircraft with this container. He only needs a source of compressed air to connect his devices.

After the preparation of use of the tanks such as emptying, degassing, opening of the manhole, detection of the leak, operations that can also be conducted prior to his arrival, he just need to access through the hole corresponding to the area concerned.

He takes with him, in the wing, the complete device connected to the source of pressurized air after having adjusted the pressure, the suction hose 50 and possibly some spare tools 28.

To give an order of magnitude, the life of a tool is estimated at half an hour.

The operator actuates the control lever by applying with moderate effort the head against the pad or bead of sealant to remove, thus generating chips.

After doing part or all of the work, the suction of these chips keeps the area clean.

The working conditions for the operator are greatly improved and the speed of execution is incommensurate with a manual dying operation.

Even when the area is very difficult to access, the operator having no significant effort to provide can reach it and exert sufficient pressure on the device to achieve the desired result.

In addition, the working time is much shorter because the vibration frequency allows the operator to generate chips as with a chisel.

The head comes into contact with the primer and removes the sealant without degrading this primer due to the nature of the material, the angle of the head, the frequency and the power of the vibrations. The thickness of mastic is only slightly involved since the power of the tool makes it possible to cut the mastic into the mass if necessary, even in the case of mastic having aged. The operator therefore performs a reduced number of passes.

At the end of the removal of the putty in the area concerned, it is necessary to remake, which is not an operation concerned by the present invention but which is indicated for information.

This step consists in a simplified way to ensure cleaning of the area concerned with a solvent to have a perfectly clean surface.

The bead or mastic pads are made with a dispensing gun. This removal is followed by accelerated polymerization of this mastic by means of heating with infrared radiation.

Sealing being performed, it is possible to repeat a leak test including the helium test equipment described in the application for French Patent No. 02 07554 on behalf of the same holder before refilling the tank.

There are tools of the trade allowing to generate vibratory alternative movements but they remain relatively heavy.

It would be advisable to develop a specific tooling with a body of lightened material without this tool being too light because it nevertheless needs a certain inertia to ensure anti-recoil and efficiency at each vibration, also limiting the efforts of the operator .

In addition to the device according to the present invention, it may be useful to develop a variety of finishing brushes, including rotary brushes having fibers with characteristics similar to those of the heads. In this case, the dust generated remains very limited since it is finished and the suction means can allow simultaneous suction.

Claims (7)

1. A device for removing mastic, in particular for the repair of joints in aircraft tank structures, comprising means (26) for causing vibratory alternating movement and a tool (28) secured to the means, said means (26) for causing vibratory alternating movement comprising a body (30) including a motor (32) and a chuck (34) able to receive the tool (28) and said tool (28) comprising a shaft (36) able to be mounted in the chuck (34) and a head (38) designed to be in contact with the surface from which mastic is to be removed, characterised in that the head (38) is produced from a material chosen from amongst polyetheretherketones, polyoxymethylenes, polyetherimides or epoxy resins.
2. A device for removing mastic according to claim 1, characterised in that the motor (32) is of the pneumatic type with a vibratory frequency of 120 Hz.
3. A device for removing mastic according to claim 1 or 2, characterised in that the material for producing the head (38) is a polyetheretherketone loaded with carbon, or glass fibres.
4. A device for removing mastic according to claim 3, characterised in that the material for producing the head (38) is a polyetheretherketone loaded with 30% glass fibres.
5. A device for removing mastic according to any one of claims 1 to 4, characterised in that the head is in the form of a bevel and has an angle of 30°, 45° or 60°, preferably 30°.
6. A container (40) comprising at least one device according to any one of the preceding claims with a stock (42) of tools, suitable flexible tubing, in particular a tube (44) for connection to a source (46) of compressed air, and a housing (48) for regulating the air pressure delivered.
7. A container (40) according to claim 6, characterised in that it comprises a suction system (50) with a venturi connected to the same source supplying compressed air.

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