METHOD FOR MANUFACTURING WATCH DIALS OF MURRINO GLASS AND DIALS OBTAINED WITH THIS METHOD

Abstract: The invention makes known a method for the manufacturing of glass watch dials obtained by processing "murrino" glass, said method comprising a phase for the axial drilling of the "murrina" disc, the hole resulting therefrom having such a diameter as to allow the passage of the watch-hand supporting shaft, and one or more honing phases by means of which the two surfaces of the "murrina" disc become parallel to each other, while the disc itself acquires a thickness which is compatible with the use of the disc as a watch dial, a phase for the trimming of the outer edge of the "murrina" disc and a subsequent phase for the polishing of at least one of the two visible surfaces of the "murrina". Said method allows the manufacturing of watch dials by using "murrinas", i.e. objects constituted by a pluralyty of small glass cylinders melted together and forming phantastic patterns.

Description: The invention concerns a method for manufacturing watch dials obtained by processing "murrino" glass. It is known that "murrino" glass or "murrina" is a glass product obtained by melting a plurality of small glass cylinders having a lenght of 5-6 mm and a diameter of 3-4 mm, placed next to each other, usually presenting different colours and arranged so as to form a predetermined pattern. The small cylinders, arranged so as to form a predetermined pattern are then melted in a glass-melting oven and the product resulting therefrom is called "murrina". The "murrinas" known at present are used essentially as pendants for necklaces or as medallions and they are usually round objects. The thickness which in the known technique measures 5-6 mm. is not reduced because of the danger of breaking the murrina when further reducing its thickness with the known technique applied in the processing of artistic glass. This limitation, i.e. the present impossibility of obtaining thin "murrinas" has prevented the realization of a dial for watches obtained from a "murrina", since a dial with a thickness of 5-6 mm. could not be used, if one considers that this is the thickness of a complete watch, when it is not even, thinner. The present invention proposes a method for manufacturing watch dials using "murrino" glass, whereby the above mentioned inconveniences will be overcome. More specifically, the purpose of the present invention is to propose a manufacturing method, whereby it is possible to obtain watch dials of "murrino" glass having a thickness of about 1 mm or less than 1 mm, for instance about 0,8 mm, and that without any danger of breaking the "murrino" glass, while obtaining smooth surfaces which are parallel to each other, such as not to prevent the free rotation of the watch hands and not to impede the movement of the watch work on the underside of the dial. All the above mentioned purposes and others, which will be better explained hereafter are reached by a method for the manufacturing of dials obtained by processing "murrino" glass, said type of glass consisting of a disc having a considerable thickness, it being obtained by melting of a plurality of small glass cylinders arranged one next to the other so as to form a pattern, wherein said method, in accordance with the patent claims, is characterized in that it comprises: a first phase of axial drilling of the "murrina" disc in order to obtain a hole having such a diameter as to allow the passage of the hand-supporting shaft; one or more honing phases on the two surfaces of the "murrina" disc, such as to obtain a reduction of thickness in accordance with the intended use of the disc as a watch dial and two flat surfaces which are parallel to each other; a phase for the trimming of the outer edge of the "murrina" disc, so as to obtain the desired outer perimeter; and a subsequent phase for polishing at least one of the two visible surfaces of the "murrina" disc. Advantageously according to the invention, after the "murrina" disc has been axially drilled, the most delicate phase is undertaken: it consists in honing the surfaces of the "murrina", so as to obtain two flat and smooth surfaces, which are parallel to each other, and a thin thickness which is compatible with the use of the disc as a watch dial. The honing process is performed in at least two phases by means of a machine having a honing disc and a support for the anchoring of the "murrina". The support on which the "murrina" is anchored is brought close to the rotating honing disc and, by performing a tangential alternate motion between the "murrina" and the honing disc a first honing of one "murrina" surface and a first reduction of its thickness are obtained. When the thickness of the "murrina" is about twice the final desired thickness, the "murrina" is removed from the support which holds it on the machine head and it is turned downside up, so that it can be placed in the support with the already honed surface face up and the surface to be honed turned face down toward the honing disc. The fixed connection between the "murrina" and its support is obtained by means of a special bonding agent resisting to temperatures of up to 150 to 250 degrees C. When the "murrina" needs to be detached from its support, the bonding agent is heated and the "murrina" will come off the support. Once the thickness has been thus reduced to a size which is compatible with the thickness of dials that can be used in normal wrist watches, the outer edge of the "murrina" disc will be trimmed and it can retain its round shape or acquire a square or rectangular or even any other shape. Finally at least one of the two visible surfaces will be polished Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and the specific example, while indicating a preferred embodiment of the invention, are given by way of illustration only, since various changes and modifications will become apparent to those skilled in the art from this detailed description, and from the drawings, wherein: Fig. 1 shows a magnified "murrina" before it is tranformed into a watch dial; Fig. 2 shows the "murrina" support which is a component of the honing machine; Fig. 3 shows the complete honing machine; Fig. 4 shows a machine suited to trim the outer edge of the "murrina" disc. With reference to Fig. 1 it shows the disc made of "murrino" glass, indicated as a whole with 1, presenting a pattern on its surface 2. Disc 1 has a thickness, indicated with 3, which ranges from 5 to 6 mm, this is why the disc will have to undergo a honing process, resulting in a reduction of its thickness, and a surface polishing process, so that it can be changed into a watch dial. The first phase of the production method according to the invention concerns the axial drilling of the "murrina" disc, said drilling being performed practically in the center with known tools, so as to obtain a hole 4 having such dimensions as to allow the easy passage of the watch-hand supporting shaft. Once the drilling phase has been completed, the "murrina" disc 1 will have to undergo the honing of its surfaces and, at the same time, the reduction of its thickness 3. To this purpose disc 1 will be fixed on support 5 which consists essentially of a metal disc belonging to a honing machine, represented in Fig. 3 and indicated with 10. Said support is attached to head 6 of the honing machine 10 by means of a ball-and-socket joint 7 which allows said support 5 to rest against the honing disc 8 belonging to the work surface 9 of the machine, so that, when "murrina" 1 is pushed into contact with the honing disc 8, support 5, which can swing, grants the correct parallelism of the "murrina" surface in relation to the honing disc 8. The junction between "murrina" 1 and support 5 is obtained by means of the bonding agent, indicated with 11, which is spread between the surface of the support 5 and the surface of the "murrina" which is in contact with said support. The bonding agent is of the plastic type; it hardens when exposed to the air and resists to high temperatures. It is obvious that other types of bonding agents also fulfil the same purpose, which is the bonding together of support 5 and of the glass "murrina" 1, provided that they can easily be removed in order to allow the subsequent bonding of the honed surface to permit processing of the opposite surface. After the desired thickness of the "murrina" has been obtained and also after it can safely be determined that its two faces are parallel to each other, it becomes necessary to trim the outer edge of the "murrina" DISC so as to obtain the desired dimensions of the dial. If the dial is to present a round shape, Fig. 4 shows that the glass "murrina" 1 with its thickness already reduced is placed between two tailstocks each complete with a suction cup 12, so that the edge can be worked on with a diamond tool 13, driven by a motor 14 belonging to a tool machine, which is indicated as a whole with 15, wherein the diamond tool 13 and "murrina" 1 can be reciprocally brought into contact. If the dial is to have a shape differing from the round one, the reciprocal contact between the "murrina" and the diamond tool will be controlled by a suitable template. The last phase of the method for the production of the dial made from a "murrina" is the polishing process of at least one of the two faces of the by now almost finished dial, which has already acquired its final dimensions. This polishing process has the purpose of improving its aesthetical aspect and make it suitable to be used for the inteded purpose. The "murrina" dial is polished by means of rollers with a cover made of foam polyurethane and impregnated with cerium-oxyde or an equivalent substance. The polishing process removes the opacity from the glass surface, which had previously been trated with an abrasive agent during the honing process, and yealds it a high gloss. With the now described method it is possible to manufacture dials of "murrino" glass or, to be more specific, dials made of a plurality of small glass cylinders forming a pre-determined pattern, having a thickness and a shape which are suited to be used in a watch, even a wrist watch, whereby the object obtained has a unique precious look. The method proposed by the invention may be completed with intermediate working phases in order to improve the product thus obtained, said phases will, however not exceed the scope of the invention, such as it is claimed hereafter.

Claims: A method for the production of watch dials made of "murrino" glass, said type of glass consisting essentially of a disc presenting a considerable thickness and obtained by melting a plurality of small glass cylinders placed next to each other so as to form a pattern, characterized in that it comprises: a first phase of the axial drilling of a "murrina" disc with a hole having such a diameter as to allow the passage of the watch-hand supporting shaft; one or more honing phases with the purpose of obtaining two surfaces of the disc which are parallel to each other, and a thickness of the disc which is compatible with the intended use of the disc as a dial for a watch; a phase of trimming of the outer edge of the "murrina" disc, such as to obtain the desired outer perimeter; and a subsequent phase of polishing at least one of the two visible surfaces of the "murrina" disc. A method according to claim 1, characterized in that the phase for the trimming of the outer edge of the "murrina" disc is a turning process performed with a diamond disc or tool according to a predetermined diameter. A method according to claim 1, characterized in that the phase for the trimming of the outer edge of the "murrina" disc is a turning process performed with a diamond disc or tool, said disc or tool operating following the shape of a template. A method according to claim 1, characterized in that the honing phase is performed through abrasion, obtained by dragging between an abrasive disc (8) and the "murrina" disc (1) which is pressed against the abrasive disc (8) by means of a support (5) being anchored to the honing machine (10) to which the abrasive disc (8) belongs, said abrasive disc (8) and said support (5) of the "murrina" disc (1) being enabled to move close to each other through appropriate means, while during the honing phase both the abrasive disc (8) and the "murrina" disc support (5) move with a relative, alternate, tangential motion. A method according to claim 4, characterized in that the binding between the "murrina" disc (1) and the support (5) of said "murrina" (1) disc on the honing machine (10) is obtained by the spreading of a bonding agent (11) or similar means. A method according to claim 4, characterized in that the support (5) of the "murrina" disc (1) is attached to the head (6) of the honing machine (10) by means of a of a ball-and-socket joint (7). A method according to claim 1, characterized in that the polishing phase viz. process is performed by means of polishing rollers, covered with foam polyurethane and impregnated with cerium oxide. A watch dial manufactured by a method according to any of the preceding claims.

Inventors: INZERILLO, GIUSEPPE, NORDIO, FRANCO
Applicants: INZERILLO, GIUSEPPE, NORDIO, FRANCO
Application year: 1990
Main classification: G04B19
IPC codes: G04D3, G04B19