U.S. patent application number 13/739238 was filed with the patent office on 2013-05-23 for device and a method for applying a coating on a workpiece by electrodeposition.
The applicant listed for this patent is Alain Le Cleac'h, Jean-Louis Thomas. Invention is credited to Alain Le Cleac'h, Jean-Louis Thomas.
Application Number | 20130126335 13/739238 |
Document ID | / |
Family ID | 40486531 |
Filed Date | 2013-05-23 |
United States Patent
Application |
20130126335 |
Kind Code |
A1 |
Thomas; Jean-Louis ; et
al. |
May 23, 2013 |
DEVICE AND A METHOD FOR APPLYING A COATING ON A WORKPIECE BY
ELECTRODEPOSITION
Abstract
The invention relates to a device and a method of applying a
coating on a workpiece by electrodeposition. A vessel is provided
that is suitable for filling with a bath of electrolyte,
anode-forming conductor means being placed in the vessel and
connected to a current generator, a cathode-forming workpiece
mounted on the mandrel of a lathe, and guidance and movement means
for guiding and moving the vessel relative to the lathe, the
guidance and movement means enabling the workpiece to be immersed
in full or in part in the bath of electrolyte.
Inventors: |
Thomas; Jean-Louis; (La
Chapelle Reanville, FR) ; Le Cleac'h; Alain;
(Chavigny Bailleuil, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Thomas; Jean-Louis
Le Cleac'h; Alain |
La Chapelle Reanville
Chavigny Bailleuil |
|
FR
FR |
|
|
Family ID: |
40486531 |
Appl. No.: |
13/739238 |
Filed: |
January 11, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12546246 |
Aug 24, 2009 |
8377282 |
|
|
13739238 |
|
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Current U.S.
Class: |
204/200 |
Current CPC
Class: |
C25D 21/14 20130101;
C25D 5/08 20130101; C25D 5/22 20130101; F02K 9/972 20130101; C25D
21/10 20130101; F05D 2230/31 20130101; C25D 5/48 20130101; C25D
17/02 20130101; C25D 7/04 20130101; C25D 17/06 20130101; F02K 9/64
20130101; C25D 17/12 20130101; C25D 17/00 20130101 |
Class at
Publication: |
204/200 |
International
Class: |
C25D 5/48 20060101
C25D005/48; C25D 17/02 20060101 C25D017/02; C25D 7/04 20060101
C25D007/04; C25D 17/06 20060101 C25D017/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 25, 2008 |
FR |
0855696 |
Claims
1. An electrodeposition device for performing electrodeposition on
a workpiece, the device comprising a vessel suitable for being
filled with a bath of electrolyte, anode-forming conductor means
placed in the vessel and connected to a current generator, and a
cathode-forming workpiece, wherein the device further comprises a
lathe, the workpiece being mounted on the mandrel of said lathe,
and guidance and movement means for guiding and moving the vessel
relative to the lathe between a first position enabling the
workpiece to be immersed in full or in part in the bath of
electrolyte, and a second position enabling the workpiece to be
machined.
2. An electrodeposition device according to claim 1, including a
set of beads made of the metal for deposition, the beads being
placed in the vessel and being suitable for remaining in permanent
contact with the conductor means under the effect of gravity while
electrodeposition is taking place.
3. An electrodeposition device according to claim 2, wherein the
metal beads are made of nickel.
4. An electrodeposition device for performing electrodeposition on
a workpiece according to claim 1, wherein the vessel containing the
bath of electrolyte includes forced circulation means for
circulating the bath of electrolyte inside the vessel.
5. An electrodeposition device according to claim 1, wherein the
conductor means include a portion of a shape that corresponds to
the outer longitudinal profile of the workpiece and which is placed
in the vessel so as to face the workpiece in the first
position.
6. An electrodeposition device according to claim 1, wherein the
vessel further includes accurate guidance means enabling it to be
moved vertically so as to conserve a constant distance between the
cathode-forming workpiece and the conductor means during
electrodeposition.
7. An electrodeposition device according to claim 1, wherein the
vessel presents a half-shell shape.
8. An electrodeposition device according to claim 1, wherein the
volume of the bath of electrolyte is maintained constant by means
for supplying water and/or electrolyte.
9. An electrodeposition device according to claim 1, wherein the
workpiece is axially symmetrical.
10. An electrodeposition device according to claim 1, wherein the
workpiece is a combustion chamber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application under
.sctn.1.53(b) of prior application Ser. No. 12/546,246, filed Aug.
24, 2009, entitled: A Device and a Method for Applying a Coating on
a Workpiece by Electrodeposition, the entire disclosure of which is
incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates to a device and to a method
for applying a coating on a workpiece by electrodeposition.
BACKGROUND OF THE INVENTION
[0003] The usual methods of depositing a metal coating on a
workpiece consist in immersing said workpiece in a vessel that
contains a bath of electrolyte together with electrode panels.
Those methods, also referred to as in situ electrodeposition
methods, present drawbacks in terms of duration and quality.
Because of corner effects associated with the electric field, the
deposit builds up faster at the ends of the workpiece. In order to
obtain a coating that is uniform, it is therefore necessary to
perform a plurality of deposition operations in succession, and
interrupt them with stages of machining in order to remove the
irregularities progressively. The workpiece is inserted a first
time in the vessel containing the bath of electrolyte in order to
receive a first deposit, then it is withdrawn from the vessel and
mounted on the mandrel of a lathe so as to be machined. It is then
introduced a second time in the bath of electrolyte to receive a
second deposit, and the stages of deposition and of machining are
thus repeated in alternation until a satisfactory coating is
obtained. Methods using direct current (DC) baths generally require
four to six passes, thereby giving rise to a significant loss of
time and to large costs. One known solution for improving the
uniformity of the deposit consists in using an alternating current
(AC) bath. That technique requires only a limited number of passes
and enables a deposit to be obtained that is more uniform, but it
does not avoid the need for the machining stage. In addition, it
gives rise to problems associated with geometry and with keeping
the chemistry of the bath constant.
[0004] Another major drawback of known electrodeposition methods is
the need to regenerate the bath of electrolyte regularly. In the
initial bath, the concentration of ions available for electrolysis
decreases as a result of the cathode reaction of deposition on the
workpiece. A commonly used solution for keeping the concentration
of said ions constant is referred to as "blending" the bath and
consists in periodically removing a volume fraction from the bath
and replacing it with an equivalent fraction of concentrated new
bath. That solution remains laborious. A solution that enables the
electrolytes to be regenerated continuously without external
intervention is known from French patent FR 2 821 627. That
document describes a method of electrodepositing nickel on a
workpiece, the method involving a vessel containing a conductor
material fastened to one of the end faces of the vessel and forming
an anode, with a sufficient quantity of nickel beads for
maintaining permanent contact with said material. The
cathode-forming workpiece that is to be covered in nickel is
situated under said vessel. Continuously regenerated by the nickel
beads, the electrolyte comes by gravity into contact with the
workpiece and is recovered below so as to be reintroduced into the
vessel. That method which takes place "outside" the vessel,
nevertheless does not reduce the length of time required for the
mounting/removal operations prior to each stage of deposition or of
machining, whenever a plurality of passes are needed.
OBJECTS AND SUMMARY OF THE INVENTION
[0005] The present invention thus seeks to simplify the
electrodeposition method, and to reduce its costs, by reducing the
handling needed for obtaining a product that is uniform and of good
quality, and also by reducing the duration of each pass.
[0006] More particularly, in a first aspect, the present invention
provides an electrodeposition device for performing
electrodeposition on a workpiece, the device comprising a vessel
suitable for being filled with a bath of electrolyte, anode-forming
conductor means placed in the vessel and connected to a current
generator, a cathode-forming workpiece mounted on the mandrel of a
lathe, and guidance and movement means for guiding and moving the
vessel relative to the lathe between a first position enabling the
workpiece to be immersed in full or in part in the bath of
electrolyte, and a second position enabling the workpiece to be
machined.
[0007] In an advantageous disposition, the device includes at least
a piece of metal for deposition that is suitable for remaining in
permanent contact with the conductor means during
electrodeposition. Preferably, it contains a set of metal beads
made of the metal for deposition, placed in the vessel, and kept
permanently in contact with the conductor means under the effect of
gravity. For example, the metal for deposition is nickel.
[0008] According to another advantageous disposition, the vessel
containing the bath of electrolyte includes forced circulation
means for circulating the bath of electrolyte inside the
vessel.
[0009] In particular, the conductor means may include a portion of
a shape that corresponds to the outer longitudinal profile of the
workpiece and this portion is placed in the vessel so as to face
the workpiece in the first position. In this way, the distance
between the surface of the cathode-forming workpiece and the
anode-forming conductor means is kept constant and the deposition
takes place in a manner that is more uniform.
[0010] Advantageously, the vessel further includes accurate
guidance means enabling it to be moved vertically so as to conserve
a constant distance between the cathode-forming workpiece and the
conductor means during electrodeposition, thereby enabling the
uniformity of the deposit to be further optimized.
[0011] In particular, the device of the invention may be applied to
a combustion chamber.
[0012] In a second aspect, the present invention provides an
electrodeposition method of performing electrodeposition on a
cathode-forming workpiece, the method consisting in:
[0013] a) mounting the workpiece on the mandrel of a lathe;
[0014] b) placing beneath the workpiece a vessel containing a bath
of electrolyte together with conductor means forming an anode and
placed in the vessel connected to a current generator;
[0015] c) immersing all or part of the workpiece in said bath of
electrolyte by moving the vessel into a first position;
[0016] d) causing the workpiece to be turned by the lathe so that
the entire surface of the workpiece for coating is immersed at
least once in the bath of electrolyte; and
[0017] e) moving the vessel containing the bath of electrolyte into
a second position, so as to break contact between the workpiece and
the bath of electrolyte.
[0018] In an advantageous disposition, after step e), the method
includes a step f) consisting in machining the workpiece on the
lathe. In particular, the series of steps b) to f) may be
implemented a plurality of times. It is thus possible to perform a
plurality of successive passes without removing the workpiece from
the mandrel of the lathe.
[0019] In another advantageous disposition, a set of beads made of
the metal for deposition is put into permanent contact with the
conductor means under the effect of gravity.
[0020] In order to enable the metal ions to disperse better in the
bath of electrolyte, the bath may be put into forced circulation
inside the vessel when the workpiece is immersed in full or in part
therein.
[0021] The method may also include a step consisting in introducing
water and/or electrolyte into the bath of electrolyte in order to
compensate for losses due both to evaporation and to cathodic
deposition.
[0022] Preferably, the vessel containing the bath of electrolyte is
moved vertically during step d), such that a constant distance is
conserved between the cathode-forming workpiece and the conductor
means during electrodeposition.
[0023] Such dispositions enable the duration of the
electrodeposition method to be reduced significantly. Since the
workpiece is mounted on the mandrel of a lathe and is immersed in
full or in part in a bath of electrolyte contained in a movable
vessel when located in the first position, it is possible to
perform the deposition and machining operations in succession
without any intermediate removal of the workpiece. After a first
deposition operation, the vessel is moved into the second position
so that the workpiece is no longer in contact with the bath of
electrolyte. Machining can then be performed without moving or
mounting the workpiece beforehand on a lathe. After machining, the
vessel is replaced in the first position under the workpiece and a
second deposition operation is performed. These steps are repeated
until a satisfactory coating is obtained. By avoiding the mounting
and removal stages concerning the workpiece and the lathe between
the deposition and machining operations, the method of the
invention is faster than the methods known in the prior art.
[0024] Furthermore, great accuracy is achieved because, given that
the workpiece remains mounted on the lathe throughout the duration
of the method, there is no longer any need to re-set the reference
thereof prior to each machining phase.
[0025] The particular shape of the conductor means, corresponding
substantially to the shape of the workpiece that is to be coated,
serves to avoid corner effects and to improve the uniformity of the
deposit. Better uniformity is also achieved because of the fact
that the precision guidance means maintain a constant distance
between the two electrodes, thereby avoiding variations in the
intensity of the field lines. Finally, mounting the workpiece on
the mandrel of a lathe enables the workpiece to be rotated slowly
during the electrodeposition method, such that its entire surface
can be coated in uniform manner.
[0026] In addition to the above-described advantages, it is
possible to further simplify the method by introducing a piece of
the metal for deposition into the vessel containing the bath of
electrolyte, which piece is put into permanent contact with the
conductor means connected to the current generator. In this way,
the electrolyte of the bath is continuously regenerated without
external intervention and implementation of the method is thus
facilitated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The invention can be better understood and other advantages
thereof appear better in the light of the following description
given purely by way of example and made with reference to the
accompanying drawings, in which:
[0028] FIG. 1 is a longitudinal section view of the device of the
present invention in a first embodiment;
[0029] FIG. 2 is a cross-section view on line A-A showing the FIG.
1 device; and
[0030] FIG. 3 is a longitudinal section view of the device of the
present invention in a second embodiment.
MORE DETAILED DESCRIPTION
[0031] The entire disclosure of U.S. application Ser. No.
12/546,246, filed Aug. 24, 2009, is incorporated by reference
herein.
[0032] FIG. 1 shows a first embodiment of the invention, applied to
a workpiece that is constituted by a cryogenic rocket engine
combustion chamber (referred to below as the "chamber"). This type
of chamber 1 is in the form of an annular copper ingot having
channels 1a referred to as "meridians" machined in the outer
periphery thereof for the purpose of allowing hydrogen to flow.
These channels 1a are filled with a specific wax, and the assembly
is covered in a layer of nickel having a thickness of 2 millimeters
(mm) to 3 mm. The chamber 1 is of an axially-symmetrical hourglass
shape with a length of 600 centimeters (cm) to 700 cm. It comprises
a first portion that is cylindrical with a diameter of about 50 cm
and that is extended by a tapering second portion that is
frustoconical with a maximum diameter that corresponds to the
diameter of the cylindrical first portion. The chamber 1 also has a
third portion that is frustoconical with a maximum diameter of
about 70 cm to 80 cm and that flares away from the second portion.
The description below relates to a device of the invention that
enables said layer of nickel to be deposited by
electrodeposition.
[0033] The chamber 1 is mounted centered on the mandrel 2 of a
lathe 3 by means of two supports 2a in the form of bodies of
revolution that are placed inside the chamber 1. In the vicinity of
the chamber 1 there is placed a vessel 4 containing a bath of
electrolyte 5. The vessel is associated with means for guiding it
and moving it (not shown) that make it possible, after the chamber
1 has been mounted on the lathe 3, for the vessel to be moved
reversibly under the chamber 1 so that at least a fraction of the
surface of the chamber 1 extending over the entire length of the
chamber along the axis of the mandrel 2 is immersed in the
electrolyte bath 5. In this way, rotating the mandrel 2 of the
lathe 3, and thus rotating the axially-symmetrical chamber 1
mounted on the mandrel, ensures that all of the outside surface of
the chamber becomes immersed. It is clear that under such
circumstances, a workpiece having a cross-section that is not
circular (a workpiece that is not axially symmetrical) would
require care to be taken to ensure that all of its zones for
covering do indeed become immersed during rotation.
[0034] Conductor means 6 are placed in the vessel 4. They comprise
a bottom portion 7 placed in the bottom of the vessel 4 and
supporting a top portion 8 that is of a shape that corresponds at
least approximately, but preferably accurately, to the outline of
the chamber 1 along the axis of the mandrel. This top portion 8
situated facing the chamber 1. A substantially constant distance is
thus maintained between the chamber 1 and the top portion 8 as a
result of the similarity of their profiles, thus making it possible
to avoid corner effects associated with the electric field and
thereby to ensure that deposition takes place more uniformly. On
the bottom portion 7 there are placed beads of nickel 9, at least
some of which are in permanent contact with the bottom portion 7 of
the conductor means 6 under the effect of gravity. The conductor
means 6 are connected to the positive terminal of a current
generator 10, thus forming an anode, while the combustion chamber 1
is connected to the negative terminal of the current generator,
thereby forming the cathode. Under the effect of the potential
difference exerted between the two electrodes, the nickel beads in
contact with the anode become polarized and release Ni.sup.2+
nickel ions that are suitable for picking up electrons present on
the cathode-workpiece (chamber 1), thereby creating a deposit of
solid nickel. Because of the beads of nickel, the concentration of
ions in its bath of electrolyte remains constant, and unlike known
methods, there is no need to continuously renew the electrolyte
contained in the vessel.
[0035] The distance between the anode and the cathode decreases as
the thickness of the deposit on the workpiece increases. In order
to conserve a constant distance between the electrodes and to avoid
variations in the intensity of the field lines, precision guidance
means (not shown) are preferably provided that enable the vessel to
be moved away vertically during the electrodeposition method.
[0036] A system is provided for circulating the bath of electrolyte
in the vessel. By way of example, this system may be made up of two
pipes 11 and 12, each connected to the bottom portion and to the
top portion of a different side face of the vessel, together with a
pump 13. The bath of electrolyte is thus subjected to forced
circulation between the bottom of the vessel where the beads of
nickel are located and the top of the vessel where the immersed
portion of the chamber is located. This circulation serves to stir
the electrolyte and to disperse the Ni.sup.2+ nickel ions towards
the workpiece that is to be covered.
[0037] A water tank 15 is also connected to the vessel 4 that
contains the bath of electrolyte 5. This connection may be provided
by a rigid duct, with the tank 15 then being constrained to move
vertically with the vessel 4. Alternatively, the pipe may be
flexible and the tank may remain stationary during the various
steps of the method. Such means for feeding water to the vessel 4
serve to compensate for losses due in particular to evaporation,
and to maintain a constant volume of electrolyte in the vessel
4.
[0038] FIG. 2 is a cross-section view of the device of the
invention. The vessel containing the bath of electrolyte is in the
form of a half-shell that enables it to match the generally
cylindrical and elongate shape of the chamber. Such a shape enables
the volume of electrolyte needed to be diminished. For example, the
vessel containing the bath of electrolyte may be semicylindrical in
shape.
[0039] Further, if necessary, a gasket can be located between the
mandrel 2 and the edge of the vessel 4 so as to provide sealing and
to avoid any electrolyte flowing out from the vessel via the
ends.
[0040] FIG. 3 shows a second embodiment of the present invention.
Elements that are common with the first embodiment retain their
reference numerals in the description below.
[0041] A bracket 17 is fastened to one of the end walls of the
vessel 4 (shown on the left in FIG. 3). It comprises a first
portion 18 forming the bottom of the bracket, which portion is
extended by a second portion 19 of shape similar to that of the
chamber 1, and a third portion 20 connected to one or the other or
both of the first and second portions. The bracket 17 forms an
anode connected to the positive pole of a current generator. As in
the above-described embodiment, the chamber 1 forming the cathode
is connected to the negative terminal of said generator. The nickel
beads 9 are retained in the vessel, in a housing defined by the end
wall and the fraction of the bracket 17 that comprises the portions
20 and 18. In this way, the beads 9 may be kept in permanent
contact with the first portion 18 of the bracket 17.
[0042] The method of using the device of the invention is described
below in greater detail.
[0043] Initially, the combustion chamber 1 is mounted on the
mandrel 2 of the lathe 3 with the help of the supports 2a. It is
preferably axially symmetrical and centered on the axis of the
mandrel 2. The vessel 4 is filled with the bath 5 of electrolyte
and the anode-forming conductor means 6 are put into contact with
the nickel beads 9 and connected to the positive terminal of the
current generator 10. By means of suitable guidance and movement
means, the vessel 4 is placed in the first position such that at
least a portion of the chamber 1 is immersed in the bath of
electrolyte. The workpiece is then set into slow rotation by the
lathe. The generator produces DC, thereby polarizing the nickel
beads via the conductor means 6. Electricity is then conveyed to
the cathode (chamber 1) by the Ni.sup.2+ ions which, on capturing
electrons, enable nickel to be depositing on the surface of the
chamber. Because of the particular shape of the top portion 8 of
the conductor means 6, deposition takes place more uniformly than
in prior art methods. Nevertheless, after each deposition operation
it remains necessary to machine the chamber in order to eliminate
irregularities. The vessel is thus subsequently withdrawn and
placed in the second position by its guidance and movement means,
and the workpiece is machined immediately on the lathe without
being removed therefrom. Thereafter the vessel is replaced in the
first position and a second deposit is made. As successive
deposition operations take place, the accurate guidance means move
the vessel and thus the anode in such a manner as to ensure that
the distance between the anode and the cathode remains constant at
all times.
[0044] Although the invention is described in the context of
depositing nickel on the outside face of the workpiece, the method
can be applied in the same manner to the inside surface of the
workpiece. Under such circumstances, conductor means are used that
have a portion of shape that corresponds to the longitudinal
profile of the inside surface of the workpiece, said portion being
placed inside the workpiece in the first position so as to face the
portion of the workpiece that is to be covered.
[0045] In the context of the present invention, it is also possible
to envisage an embodiment without metal beads, with a portion of
the chamber 1 being immersed in the vessel 4 that is filled with a
bath 5 of electrolyte that contains Ni.sup.2+ nickel ions and that
is provided with electrode panels. Such an embodiment is more
constricting since, unlike the embodiment described above, it
requires the electrolyte of the bath in which the chamber is
immersed to be recharged regularly so as to maintain a constant
concentration of ions.
* * * * *