EP0664162B1 - Device for treating workpieces of special shape - Google Patents

Description

The invention relates to the technical sector of processing metal parts, more particularly modification methods surfaces made in liquid phase.

• préparation de surfaces quelconques, notamment dégraissage, décapage chimique ou électrochimique, attaque chimique ou électrochimique,
• revêtements de surfaces, notamment dépôts de métaux ou d'alliages par voie chimique ou électrochimique, dépôts au trempé, dépôt par électrophorèse, imprégnations ou enduits,
• traitements de surfaces, notamment :
  • par conversion : phosphatation, sulfuration en bain de sels fondus, oxydation anodique, oxydation en bain de sels.
  • thermochimiques de diffusion de métalloïdes en bains de sels fondus : nitruration, cémentation, carbonitruration.

More particularly, the invention finds advantageous applications in the case of phosphating treatments, without thereby excluding other applications such as:

• preparation of any surfaces, in particular degreasing, chemical or electrochemical pickling, chemical or electrochemical attack,
• surface coatings, in particular deposition of metals or alloys by chemical or electrochemical means, dip deposits, electrophoresis deposition, impregnations or coatings,
• surface treatments, in particular:
  • by conversion: phosphating, sulfurization in a molten salt bath, anodic oxidation, oxidation in a salt bath.
  • thermochemical diffusion of metalloids in molten salt baths: nitriding, carburizing, carbonitriding.

Generally, we basically use three techniques to support and handle the parts during processing operations coatings or preparations of surfaces in liquid medium.

According to a first technique, the pieces are attached to specific assemblies. This technique is particularly applicable in the large parts or for small series. With this technique, it appears that the contact area between the mounting and the part is isolated from the reaction medium, so that at this level area, treatment is poorly done or even not performed at all.

These drawbacks are found in another technique, according to which, the parts to be treated are placed in the bottom of a basket, generally in wire mesh, or hung on its walls.

Finally, according to another technique, generally reserved for large series of small parts, the parts are arranged in bulk inside a rotating barrel. Rooms collide which causes scratches and defects themselves generators of chipping or pitting.

Finally, these different techniques do not allow treating satisfactorily, parts having areas of shapes complex, difficult to access in the liquid medium, such as pockets with downward opening, likely to trap gas bubbles causing lack of deposits, degreasing, imperfect rinses ... The treatment obtained is therefore not of high quality sufficient and its reproducibility is poor.

For example, in the case of parts to be treated with shapes similar to those illustrated in Figure 1, and arranged in a basket, we observes lack of treatment in areas of retention, bubbles air at the flange. This results in very random results as to the resistance and corrosion of the treated parts, thus causing significant scrap. For example, it has been observed that, in the case of a phosphating treatment, on two lots of 1000 pieces, each treated in two loads of 500 pieces, we have 50% of rejects for the first batch and 80% for the second lot.

In the case of bulk processing of this type of parts, the processing is correct but parts are submitted as shown previously, to shocks causing inadmissible scratches.

By patent EP 0399049, there is known a device for treatment of cylindrical parts, used in the electronics industry. This device consists of trays inclined relative to the vertical, mounted on a rotary horizontal axis. These trays have spikes implanted perpendicular to their surface and able to receive the cylindrical parts. When the axis rotates, the parts to be treat revolve around the tips and change orientation.

It is therefore necessary to provide training elements particular for the axes, due to the chemical characteristics, in the baths in which they are immersed.

It therefore appears that this device works with rotation continues cylindrical parts around the points, which generate friction on the periphery of each part. Furthermore, one cannot exclude that the parts to be treated can get stuck and therefore not turn on themselves. For this reason, it is necessary to tilt the trays receiving parts from an angle between 60 ° and 75 °. Considering from such an orientation of the plates, it appears that a generator of the bore of the part will not be treated, since it will be masked by the point.

The object of the invention is to remedy these disadvantages, in a simple, safe, effective and rational way.

The problem which the invention proposes to solve is to ability to apply a phosphating or other treatment process, in the case of parts of complex shapes with the objective obtain treatment of very good quality on all of the different parts areas, which must not have contact with each other during the treatment, with the objective of avoiding masking an area any part during treatment and finally to be able to have very easily the parts to be treated.

To solve such a problem, a device has been designed and developed for the treatment of specially shaped parts conforming to the features of claim 1.

To solve the problem of positioning the parts in an orderly manner, the means of centering and positioning consist of pins integral with the support grids, and whose section is shaped to cooperate with the bore of the parts to treat.

Depending on the parts to be treated, the pieces can be arranged to cooperate with the outside of the room.

The box has mesh walls and is driven positively in rotation, by means of a motor member controlled by a control center.

La figure 1 est une vue en coupe longitudinale d'un exemple de réalisation d'une pièce à traiter.

La figure 2 est une vue en coupe longitudinale à caractère schématique des grilles support équipées pour le positionnement et le centrage des pièces à traiter.

La figure 3 est une vue en plan correspondant à la figure 2.

La figure 4 est une vue en coupe longitudinale du caisson équipé des différentes grilles et immergé dans le bain de phosphatation.

La figure 5 est une vue correspondant à la figure 4, lors de la rotation des caissons.

La figure 6 est une vue en coupe transversale considérée selon la ligne 6.6 de la figure 5.

The invention is set out below in more detail using the appended drawings, in which:

Figure 1 is a longitudinal sectional view of an embodiment of a part to be treated.

Figure 2 is a schematic longitudinal sectional view of the support grids equipped for positioning and centering of the parts to be treated.

FIG. 3 is a plan view corresponding to FIG. 2.

Figure 4 is a longitudinal sectional view of the box equipped with different grids and immersed in the phosphating bath.

Figure 5 is a view corresponding to Figure 4, during the rotation of the boxes.

Figure 6 is a cross-sectional view taken along line 6.6 of Figure 5.

As shown in Figure 4, the device according to the invention essentially comprises a box (1) in which are mounted support grids (2) equipped with means (3) able to allow centering and the positioning in an orderly manner of the parts to be treated (4). The whole box (1) with the grids (2) is immersed in a bath (B).

The walls (1a) of the box (1) are perforated to allow immersion of the parts (4) positioned on the grids (2), in the bath (B). For example, all of the walls (1a) of the box (1) are screened. This box (1) can have a generally parallelepiped shape. Finally, this box (1) is shaped to be rotated by any means known and appropriate. For example, the box (1) is driven by of a motor member controlled by a central control unit.

The centering and positioning means (3) are constituted by pins integral with the support grids (2). These pawns (3) are shaped in section, to cooperate with the bore (4a) of the parts to process, while allowing limited movement of parts, relative said pawns.

As will be indicated in the following description, the centering pins (3) allow, during the rotational drive of the box (1), corresponding to the treatment to be carried out, the displacement of parts (4) to allow them to be treated throughout their entire area, avoiding any contact between said parts likely to affect quality of treatment.

The grids (2) are arranged in parallel rows, in the box (1). For this purpose, the box (1) has any type of arrangement allowing, on the one hand, the introduction and removal at will of the grids and, on the other hand, the positioning of the grids inside the box, according to determined and variable intervals (E). In this respect, the intervals (E) are determined according to the height (H) of the parts to be treated, to let remain between the upper part of the parts and the grid located immediately above, an empty space. This space allows the displacement by gravity of the parts (4), relative to their means of centering and positioning (3), at the time of rotation of the box or no.

Advantageously, the grids (2) are arranged in a plane horizontal.

The device according to the invention finds an application particularly advantageous for the treatment of shaped parts complex, such as those illustrated in Figure 1. In this example of embodiment, the part (4) is in the form of a cylindrical body hollow with, in its upper part, a circular peripheral rim (4b) internally curved constituting a flange.

The functioning of the device should be analyzed according to the invention.

The parts (4) are positioned in an orderly fashion on the support grids (2) while being centered on the pins (3). Thus equipped, different grids (2) are positioned inside the box (1) in respecting the intervals (E) to obtain the spaces (e). The whole the well-equipped box is immersed in the bath (B) (Figures 4 and 6).

When driving in rotation of the box (1), the parts (4), centered on the pins (3) beyond a certain position angular, tend to slide by gravity along the pins (3). The bases (4c) parts (4) take off from the support grid (2) receiving them, so that their upper parts (4b) come into contact with the grid located below (Figure 5).

These provisions therefore make it possible to deal with all of the different areas of the rooms (4). Furthermore, it does not matter that the upper parts (4b) come into contact with the grids, during the rotation of the box, since these parts have been subjected to treatment (B).

Compared to the state of the art and for treatment as previously indicated, of two lots of 1000 pieces, treated each in two loads of 500 pieces, the scrap rate is only between 1 and 3%.

Obviously, the device according to the invention applies for processing other types of parts such as components hydraulic tools for portable tools of the pruning type and of a form general cylindrical, of reduced diameter, and having a coaxial bore of reduced diameter. In this case, the positioning and centering of the parts under the conditions indicated above, i.e. with limited movement capacity, are effected by cooperating pins with the outside of the part, to allow filling of the bore by the bath.

These parts must resist both wear and corrosion, while maintaining a good surface finish during the maneuvers and having a low coefficient of friction.

• une nitruration en bain de sels fondus à base de cyanates et carbonates alcalins qui apporte la résistance à l'usure,
• une oxydation en bain de sels fondus à base de nitrates, carbonates et hydroxydes alcalins, qui améliore la résistance à la corrosion,
• une enduction polymérique d'un composé organique à haut poids moléculaire type cire, dilué dans un solvant, qui vient imprégner les porosités superficielles créées par les deux précédentes opérations et favorise le glissement.

An effective solution to meet these requirements is to use composite surface conditioning using three successive operations:

• nitriding in a bath of molten salts based on alkali cyanates and carbonates which provides resistance to wear,
• oxidation in the bath of molten salts based on nitrates, carbonates and alkali hydroxides, which improves resistance to corrosion,
• a polymeric coating of an organic compound of high molecular weight, wax type, diluted in a solvent, which impregnates the surface porosities created by the two preceding operations and promotes sliding.

The corrosion resistance imperative requires that the part be treated in its entirety, the presence of the smallest defect causing a corrosion pitting.

Comparative tests, on a private and experimental basis, of a treatment of batches of pieces (at the rate of 100 pieces per charge), according to the prior techniques (basket and bulk) and according to the invention, gave the following results: PROCESSING TECHNOLOGY % OF PIECES WITH CORROSION STITCHES AFTER 48 HOURS OF EXPOSURE TO SALT FOG in basket 95 loose 85 according to the invention 5

• aucun contact entre les pièces lors du traitement,
• la qualité obtenue du traitement dans toutes les zones de la pièce, y compris dans les zones de rétention,
• la simplicité de réalisation.

The advantages clearly emerge from the description, in particular it is emphasized and recalled:

• no contact between parts during processing,
• the quality obtained from the treatment in all areas of the room, including in the retention areas,
• the simplicity of realization.

Claims (7)

1. Apparatus for treating special-shaped parts (4) comprising:

   carrying gratings (2) provided with means (3) suitable for centering and positioning parts to be treated (4) in an ordered way and allowing for the limited movement of the parts and preventing them touching,

   gratings (2) are disposed in parallel horizontal ranks in a perforated container (1),

   container (1) is submerged in a treatment bath (B) and may be rotated by a prime mover,

   gratings (2) are spaced at an interval (E) such as to allow an empty space (e) above the parts to be treated to enable them to move under the influence of gravity in relation to centering means (3) during rotation of container (1).
2. Apparatus as claimed in claim 1, characterised in that the centering and positioning means consist of studs (3) built into the carrying gratings (2).
3. Apparatus as claimed in claim 2, characterised in that the cross section of studs (3) mates the bore of the parts to be treated (4).
4. Apparatus as claimed in claim 2, characterised in that studs (3) are disposed such as to cooperate with the outer periphery of the parts to be treated (4).
5. Apparatus as claimed in claim 1, characterised in that container (1) is fitted with features allowing for the free insertion and withdrawal of the gratings.
6. Apparatus as claimed in claim 1, characterised in that container (1) is provided with grid walls.
7. Apparatus as claimed in claim 1, characterised in that container (1) is rotated by a controlled prime mover.

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