Electrolysis: processes – compositions used therein – and methods – Electrolytic erosion of a workpiece for shape or surface...
Reexamination Certificate
1999-10-28
2001-06-12
Valentine, Donald R. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic erosion of a workpiece for shape or surface...
C205S652000, C205S666000
Reexamination Certificate
active
06245212
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of providing a metal bearing component, chosen from the group consisting of a bearing ring, a roller element and a shaft of a dynamic pressure bearing, with a texture by electrochemical machining, wherein a current is passed across a narrow gap formed by said metal bearing component and an electrode means, electrolyte being supplied to the gap.
2. Description of the Related Art
Such a method is known in the art. In particular, WO96/20059 relates to a method of electrochemically machining a bearing ring for providing it with a pattern. According to this patent application an electrode is used having a non-conducting surface provided with a conducting pattern.
This method has the disadvantage that it is not capable of providing a surface with a high-definition pattern.
It is a goal of the present invention to provide a method capable of providing a surface with a high-definition surface pattern.
To this end the method according the present invention is characterized in that a ribbon is provided between the electrode means and the metal bearing component, said ribbon comprising a flexible, substantially non-conductive material provided with holes, wherein said ribbon is over part of its length put in direct contact with the metal bearing component, defining a contact zone, and the current is passed across the gap.
The ribbon serves as a mask, the holes exposing only those parts of the surface of the metal bearing component that are to be electrochemically machined. As the mask is not adhered to the surface, it can be easily removed and reused for treating another part of the surface of the metal bearing component. The part of the ribbon in contact with the metal bearing component
The Soviet patent publication SU-A-814635 describes a method of electroabrasive machining a metal object, such as a turbine blade. This method comprises moving an abrasive band along the surface of the object to be treated. The band is perforated, providing holes through which an electrolyte contacts the object to be treated. This publication does not relate to providing the surface with a texture.
SUMMARY OF THE INVENTION
According to a highly preferred embodiment, the method according to the invention is characterized in that said metal bearing component is rotated around its axis while the ribbon moves at the contact zone with the same speed and direction as the metal bearing component.
By rotating the bearing component, while the ribbon moves along with it without substantial slip, the total surface of the bearing ring to be treated can be electrochemically machined in a single step. It goes without saying that the ribbon may be actuated to rotate the bearing component, or the bearing component may be driven to move the ribbon, or both the bearing ring and the ribbon may be actuated.
According to a preferred embodiment a ribbon is used having at least two segments substantially free from holes, said segments being adjacent to a segment comprising holes, said holes-comprising segment having a length equal to the circumference of the bearing component to be machined or a multiple thereof.
In this way one can prevent that some parts of the metal bearing component are treated more often than other parts. A holes-comprising segment with a length of a multiple of the circumference of the bearing component is, for example, suitable if the bearing component is to be provided with a cross-hatched pattern. To produce said pattern said segment first comprises a length with parallel oblong holes followed by a length with parallel oblong holes set at an angle to the oblong holes in the first length.
According to another embodiment, a ribbon is used comprising an indicator means, and a detecting means is used to detect said indicator means giving an output signal depending on the position of the indicator means, which output signal is used to control the current passed over the gap.
This method also-offers a way to prevent some parts of the metal bearing component from being treated more often than other parts.
According to a preferred embodiment, a ribbon is used composed of a plastic having a high tensile strength.
Using such a ribbon of plastic having a high tensile strength is very useful for obtaining high-definition patterns without the risk of some parts of the metal bearing component being treated more often than other parts, in addition to which the ribbon is reusable.
According to a further preferred embodiment, a ribbon is used having holes which are narrow at the side of the bearing component and wider at the opposite side of the ribbon.
Holes having this configuration allow for higher current densities and faster removal of metal ions originating from the metal bearing component by electrolyte, speeding up electrochemical machining.
According to an advantageous embodiment, an endless belt is used as the ribbon.
Such a closed loop ribbon allows for repetitive treatment of the surface of the metal bearing component.
Finally the invention relates to an apparatus for electrochemical machining of a metal piece, in particular a bearing component, to provide it with a surface texture, comprising electrode means, means for supplying electrolyte and means for rotatably mounting of the metal piece.
This apparatus is characterized in that the apparatus includes a ribbon comprising a substantially non-conductive material for contact with the metal piece, said ribbon being over at least part of its length provided with holes, allowing electrolyte to contact the metal piece and a current to flow between the metal piece and said electrode.
Thus a simple apparatus is provided, capable of electrochemically machining a variety of metal pieces, and in particular bearing components.
REFERENCES:
patent: 3723269 (1973-03-01), Hofling
patent: 3880745 (1975-04-01), Shaw
patent: 4391684 (1983-07-01), Goddard
patent: 4944856 (1990-07-01), Catanese et al.
patent: 52-143937 (1977-11-01), None
patent: 2-145800 (1990-05-01), None
patent: A814635 (1981-03-01), None
patent: WO 96/20059 (1996-01-01), None
Derwent English language Abstract corresponding to JP 52-143937 No date available.
Patent Abstracts of Japan for Japanese Publication No. 02145800. No date available.
Girardin Hervé
Humbert Carole Michèle
Darby & Darby
SKF Engineering and Research Centre B.V.
Valentine Donald R.
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