Abrading – Abrading process – Utilizing shield
Reexamination Certificate
2000-08-18
2002-07-23
Nguyen, George (Department: 3723)
Abrading
Abrading process
Utilizing shield
C451S038000, C451S078000
Reexamination Certificate
active
06422920
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method of obtaining a pattern of concave spaces or apertures in a plate or layer of a brittle-like material, in which method a jet of abrasive powder particles from a nozzle is directed onto a surface of the plate or layer, which plate or layer is provided with a mask so as to define the region of impact of the abrasive powder particles on the surface. The invention also relates to a brittle-like material provided with such a pattern of concave spaces or apertures, and to the special application of such a brittle-like material.
The method mentioned in the opening paragraph is known per se from the previously filed European patent application 0 660 360 in the name of the Applicant. In accordance with the method of powder blasting, particles collide at a high velocity with a substrate, particularly glass. After the impact, they generate local damage in the substrate which may lead to the removal of the small fragments from the surface. This process is iterated many times and may thus be considered as an erosion process. A glass plate having a thickness of 0.7 mm is thus provided with a metal mask. The metal mask is adhered to the plate by means of an adhesive layer so as to prevent local delamination during the powder blasting process. A spraying unit provided with a nozzle is directed onto the surface of the plate, while a jet of abrasive powder particles, for example, silicon carbide or aluminum oxide leaves the nozzle on the basis of the pressure or venturi principle and lands on the surface of the plate or layer so as to form concave spaces or apertures therein. The angle at which the jet of abrasive powder particles extends to the plate or layer is thus 90°. It is further known from this European patent application to use a plurality of nozzles, while the plate performs, for example, an iterative movement parallel to the X axis and the spraying unit performs a movement parallel to the Y axis, with both velocities being adapted to each other in such a way that the desired aperture or pattern of concave spaces, particularly ducts, is obtained in the plate. For obtaining a better homogeneity of the desired pattern, it is also known from this document to use a plurality of nozzles, each of which is passed across a part of the mask. A drawback of such a method is that the jet of abrasive powder particles directed perpendicularly to the surface of the plate makes a hole of a special shape in the plate or layer. The manufacture of substantially symmetrical concave spaces or apertures having flat bottoms is, however, not possible with such a method. Moreover, the reproducible construction of concave spaces or apertures having substantially straight side walls is not possible.
OBJECT OF THE INVENTION
It is therefore an object of the present invention to provide a method of obtaining a pattern of concave spaces or apertures in a plate or layer of a brittle-like material, which concave spaces or apertures are characterized by a substantially flat bottom.
Another object of the present invention is to provide a method of obtaining a pattern of concave spaces or apertures in a plate or layer of a brittle-like material, which spaces or apertures have substantially straight side walls.
Another object of the invention is to provide a method of obtaining a pattern of concave spaces or apertures in a plate or layer of a brittle-like material, which spaces or apertures are interconnected.
According to the invention, the method described in the opening paragraph is characterized in that at least two jets of abrasive powder particles are each directed at respective angles of &agr;
1
and &agr;
2
onto the surface of the plate or layer, which jets mutually extend at an angle of (180°-&agr;
1
-
2
), the shape of the concave spaces or apertures thus formed being not limited by the thickness of the brittle-like material.
The part of the phrase “at least two jets of abrasive powder particles” in the introduction and the claims should be considered as an embodiment in which the surface of the plate or layer is always powder-blasted at an angle. It is thus possible to place a nozzle at an angle &agr;
1
and to subsequently place the same nozzle at an angle &agr;
2
, which embodiment falls within the protective scope of the present invention. It is also possible to vary the angle &agr;
1
at which the nozzle extends to the surface of the plate or layer continuously or not continuously, which embodiment also falls within the protective scope of the present invention. In practice, two or more separate nozzles, each with a respective angle &agr;
1
and &agr;
2
will be used from a production-technical point of view.
The term “brittle-like material” mentioned in the introduction and the claims should be considered as a material in which concave spaces or apertures can be provided by means of powder blasting, for which notably glass, ceramic material, silicon and brittle synthetic materials are suitable basic materials.
The part of the phrase “not limited by the thickness of the brittle-like material” mentioned in the introduction and claims should be understood to mean that the method is suitable for providing apertures or concave spaces in any brittle-like material or combinations of one or more brittle-like materials in which the apertures or concave spaces formed extend partly or completely across the thickness of the material or combination of materials used. The shape of the apertures or concave spaces thus formed is not defined by a possible transition of material properties, as is the case in the Japanese patent publication 082 22129 to be described hereinafter. Consequently, a hard, brittle-like material as a stopper layer is not required.
Although it is known from the Japanese patent application published under no. 082 22129 on Aug. 30, 1996 to make a concave space in a brittle-like material while using a jet of abrasive powder particles, it is necessary for the method known from this publication that the brittle-like material essentially consists of two separate materials, namely a relatively soft brittle-like material and a hard brittle-like material. The relatively soft brittle-like material is provided with a mask which is subsequently subjected to the powder-blasting treatment so that the soft brittle-like material not shielded by the mask is removed by the powder particles. The concave spaces are thus only formed in the soft brittle-like material, while the transition from the relatively soft brittle-like material to the hard brittle-like material serves as a stopper layer. A concave space thus formed has a flat bottom which is formed by the hard brittle-like material that has not been removed by the jet of abrasive powder particles. Moreover, this Japanese patent application does not give any information about the special angle of the jet of abrasive powder particles with respect to the surface of the plate or layer in which the pattern of concave spaces or apertures is formed. Frit is used as a relatively soft brittle-like material, and glass is used as a hard brittle-like material. A drawback of this technology is that a top layer of frit should always be provided on the hard brittle-like material, which treatment has a cost-increasing effect. Moreover, the released frit must be removed.
The angles &agr;
1
and angle &agr;
2
used in the method according to the invention are preferably between 30° and 80°, particularly between 45° and 65°.
The use of such angles &agr;
1
and &agr;
2
has led to concave spaces or apertures with a substantially flat bottom. If the angles &agr;
1
, angle &agr;
2
are smaller than 30°, the erosion speed is low, which is undesirable for practical applications. If, in contrast, the angles &agr;
1
, angle &agr;
2
are larger than 80°, the ducts formed on the lower side as compared with ducts obtained by means of powder blasting at an angle of 90° will hardly widen, which is detrimental for obtaining symmetrical concave spaces or apertures having a substantially flat bottom and substantially straight side wal
Bouten Petrus Cornelis Paulus
Slikkerveer Peter Jan
Koninklijke Philips Electronics , N.V.
Nguyen George
Waxler Aaron
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