Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Forming nonmetal coating
Reexamination Certificate
2002-10-04
2004-11-09
Nicolas, Wesley A. (Department: 1742)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Forming nonmetal coating
C205S316000, C205S133000, C205S333000, C204S22400M, C204S275100
Reexamination Certificate
active
06814851
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and an apparatus for an anodic treatment on metallic parts. More particularly, the present invention relates to a method and an apparatus for anodizing a surface of the metallic parts.
2. Description of the Related Art
It is known that many metallic components or parts need a final treatment.
Such a surface treatment increases functionality and the lifetime of the part by improving any of various characteristics, such as protection, wear resistance, hardness, electrical conductivity, lubricity or cosmetic value.
One example of such a metallic component is the head of aluminum pistons used in combustion engines. (As used herein an aluminum component is a component at least partially made of aluminum, including aluminum alloys.) The piston head used in the internal combustion engine is placed close to a combustion zone. More particularly this portion of the piston is in contact with hot gases, and therefore, is subject to high-thermal stresses that may cause deformations or changes in the metallurgical structure. This negatively affects the functioning of the piston head.
To reduce this negative effect, a surface of the piston is treated by an anodic treatment in order to develop an anodic oxide coating that protects the metal from the high-thermal stresses. One such apparatus that performs the anodic treatment is disclosed in, for example, Japan Patent Publication (koukai) No. 9-217200 (incorporated herein by reference). According to that publication, as shown in
FIG. 7
, the apparatus includes a jacket
101
, a lid member
102
, a mask socket
103
, an O-ring
105
, an electrolyte bath
106
, a nozzle system
107
, a cathode
108
, and an anode
109
. The jacket
101
forms a part of a circulation circuit of electrolyte (reaction medium), and has a substantially cup shape. The jacket
101
has an opening, which is closed by the lid member
102
, at its upper end. The electrolyte bath
106
is provided in the jacket
101
. A hole in which the mask socket
103
is fitted is formed at the center of the lid member
102
. The mask socket
103
is substantially cylindrical in shape, and is provided at its lower opening portion with an inwardly projected flange portion. A piston
104
is placed in the mask socket
103
in an inverted position. Namely, the piston
104
is inserted into the mask socket
103
by the piston head.
The O-ring
105
is placed on flange portion of the mask socket
103
. The O-ring
105
contacts a surface of the piston head when the piston
104
is placed in the mask socket
103
. This seals a portion of the piston that is not to be anodized. The nozzle system
107
, through which the electrolyte is directed to the piston
104
, is placed in the electrolyte bath
106
. The cathode
108
is provided at an upper portion of the electrolyte bath
106
. The anode
109
contacts the piston
104
. The apparatus performs the anodic treatment on an end face of the component (piston).
In the anodizing process, the treatment target, i.e., the piston
104
, functions as an anode. Hydroxide ions generated by the electrical discharge generate oxygen which is used to oxidize the surface of the piston
104
, i.e., the anode, to form the oxide film on the surface of the piston
104
. At the same time, however, the interaction of the electrolyte and the cathode
108
generates hydrogen gas, which flows along the current of the electrolyte. This results in hydrogen adhering to the surface of the piston
104
. The hydrogen adhered to the piston
104
causes a serious problem that the hydrogen inhibits a stable anodizing reaction of the piston
104
.
As mentioned above this problem is especially problematic with this apparatus. Because a flow from the electrolyte bath to the surface of the piston
104
is not separated from the cathode
108
, the hydrogen gas generated from the cathode
108
rides the flow to the surface of the piston
104
. Namely, the hydrogen adhered to the surface of the piston
104
interferes with the anodizing reaction. As a result, a stable anodic oxide coating is not formed on the surface of the piston
104
. The cathode
108
is positioned relative to the piston
104
in order to reduce the loss by the electrical resistance, or improve the productivity. In such case, the closer the interval between the cathode
108
and the piston
104
, the higher the tendency that hydrogen adheres to the piston
104
.
SUMMARY OF THE INVENTION
According to an embodiment of the present invention an improved method for anodizing a component is provided. The method includes providing a container comprising a supply port, a drain port, and a supply passage connecting the supply port and the drain port, at least a portion of the supply passage including a reaction chamber in fluid connection with a surface of the component to be anodized, and supplying an electric current from an electrode positioned fluidly downstream of the component surface. The method further includes supplying a reaction medium from the supply port to the drain port through the supply passage. The reaction medium that is fluidly downstream of the component surface flows toward the drain port without recirculating to the reaction chamber.
In another embodiment, the method may further include at least one seal member separating a first surface of the component to be anodized from a second surface of the component no to be anodized.
According to another aspect of the present invention, an apparatus for anodizing a component is provided. The apparatus includes a container comprising a portion defining a receiving hole for receiving the component into the container, a supply port in the container for supplying a reaction medium, a drain port in the container for draining the reaction medium, a supply passage connecting the supply port and the drain port, at least a portion of the supply passage including a reaction chamber in fluid connection with a surface of the component to be anodized, and an electrode for supplying an electric current, the electrode being positioned fluidly downstream of the component surface. The supply passage causes the reaction medium that is fluidly downstream of the component surface to flow toward the drain port without recirculating to the reaction chamber.
The apparatus may further include a first seal member for separating a first surface of the component to be anodized from a second surface of the component not to be anodized. The apparatus may alternatively include two seal members, wherein the first seal member and a second seal member separate an annular surface portion of the component to be anodized from a remaining surface portion of the component not to be anodized. Preferably, the supply port and the drain port are formed on opposite sides of the container in a radial direction.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.
REFERENCES:
patent: 6322689 (2001-11-01), Omasa
patent: 2004/0016645 (2004-01-01), Rasmussen
patent: 9-217200 (1997-08-01), None
Ishikawa Masazumi
Sasaki Masato
Sugita Sachiko
Nicolas Wesley A.
Unisia Jecs Corporation
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