Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1997-12-29
2000-09-19
Gorgos, Kathryn
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204297R, C25D 1700
Patent
active
061206571
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a device for electroplating of disc elements, such as matrices for audio and video discs, said device comprising a housing for an electrolyte bath, the disc element being clampable in the housing in such a manner that the disc side to be plated can be in contact with the electrolyte bath while its other side is kept sealed from the electrolyte bath, and a means arranged to abut against the disc element to transmit electrical current thereto during the plating process.
In electroplating of matrices for audio and video discs it is of great importance that the current transmission to the matrix be as evenly distributed as possible around the periphery of the matrix to thereby achieve a plating layer, the thickness of which is as even and uniform as possible.
A previously known device for this purpose comprises a central hub from which there extend essentially radially a plurality of electrically conducting elements, such as antennae, strips of sheet metal or sheet metal in the form of circle sectors, which, at their distal ends, are resiliently in contact with one side of the matrix at its outer peripheral area. Thus, a certain number of contact points are obtained distributed around the periphery of the matrix. One problem which can occur in such a design is that current concentrations can be formed at the contact points between the electrically conducting elements and the matrix disc, as a result of microstructural uneven areas in the matrix disc, which can create bums in the disc and thus unevenness in both the disc and the layer thickness in the surface coating obtained.
JP-A-63-134 688 shows a device for producing a press matrix, with a plating carried out on a metal layer with signal information on a glass substrate. An elastic, electrically conducting central washer is placed on the electrolyte bath side and conducts current to the central portion of the metal layer without damage thereto when the center screw is tightened.
SUMMARY OF THE INVENTION
A primary purpose of the present invention is to suggest a solution which removes the above mentioned problems and which thus makes possible an even and dense current transmission to the matrix disc, regardless of any macro- or micro-unevennesses therein.
A purpose of the present invention is also to achieve a current transmission device which makes possible both an even current transmission and thus even heat distribution, and a radially and axially resilient tensioning of the disc during the plating process, thus avoiding mechanical stresses in the disc due to thermal movements.
In accordance with the present invention, the device described by way of introduction is characterized in that the current-transmitting means comprises at least one closed loop of an elongated, elastic, electrically conducting body arranged to be in contact with at least one side of the disc element at least at its outer peripheral area, said loop being placed so that it is sealingly separated from the electrolyte bath. There is thereby achieved in electroplating of disc matrices a very even, pliable and flexible clamping of the disc, thus assuring a favourable distribution of current and force on the disc. Both macro- and micro-unevennesses can be absorbed by the elastic, electrically conducting body, thereby resulting in a very even thickness of the disc-coating layer. By virtue of the fact that the electrically conducting body is also sealingly separated from the electrolyte bath, it is not itself subjected to any electroplating and therefore can be reused a great number of times.
The elastic, electrically conducting body can be made in many different ways within the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in more detail below with reference to the accompanying drawing, in which:
FIG. 1 is a cut-away sideview of an electroplating apparatus in which a current-transmitting device according to the invention is used, with a separate partial magnification (shown withi
REFERENCES:
patent: 3573176 (1971-03-01), Laznovsky
patent: 5167792 (1992-12-01), Kamitakahara et al.
patent: 5429733 (1995-07-01), Ishida
patent: 5522975 (1996-06-01), Andricacos
patent: 5785826 (1998-07-01), Greenspan
patent: 5843296 (1998-12-01), Greenspan
Gorgos Kathryn
Smith-Hicks Erica
Toolex Alpha AB
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