Method for producing an optical product, such as a protective lens of a mobile phone

An object for this invention is a method for producing an optical product, such as a protective lens of a mobile phone, in which production process a planar disc preform is moved from a working phase to another, being carried at an area around a centre hole, in which working phases e.g. metallisation of frames, printing logos etc. is achieved into the disc preform, and in which method an orientation notch is achieved into the disc preform, by which notch the disc preform can be correctly aligned in every required work place for a procedure which takes place in the work place.

Protective lenses for mobile phones are nowadays produced by either plastic moulding or cutting from planar plastic discs protective lenses of desired form. It has been noticed that by using the production technique of CD/DVD discs in production of protective lenses both much better optical results and much better mechanical results are achieved than with present solutions. A production technique of this kind for protective lenses is described in the Finnish patent application FI-20020239. Achieving the orientation notch with an adequate accuracy has, however, required product development, which has led to this patent application and to the invention described in the patent application. It is characteristic for the method according to the invention that the orientation notch is detached from a disc preform e.g. by punching out a piece so that a notch is formed into which an orientation tongue can be orientated for the alignment of the disc preform at various work stations.

Various embodiments of the invention are described in dependent claims of the patent claim constellation, such as making one or several optical reading marks into the disc preform in connection with plastic moulding, which reading marks are readable with e.g. laser reading device, and the disc preform can be aligned around its axis of rotation by reading said reading marks, after which the orientation notch is cut out. A test device and tests have indicated that very good accuracies are achieved when orientation notch is aligned.

The invention is also directed to a device for implementing the method according to the invention, by means of which device an orientation notch is made. It is characteristic to a device according to the invention that the device is comprised of an optical reading device, such as a laser reading device, by which the location of a disc preform rotating around its axis can be noted, the disc preform can be stopped by a

rotating motor and the reading device of the device after the orientation, and by means of a punching device an orientation notch is punched into the disc preform by which notch the disc preform can be aligned at the location of next work stations for following working phases, such as metallisation, printing logos etc. The device comes to the production line of protective lenses right after moulding of a disc preform. In plasting moulding the identification marks for the laser come visible whereby the circular coordinates of the disc preform are readable and the orientation notch can be cut out from the disc preform.

The invention is described in the following with an example by citing the enclosed drawing, wherein

Figure 1 illustrates a cutting device of an orientation notch in an axonometric view and

Figure 2 illustrates a disc preform, into which an orientation notch is cut.

A device is comprised of a body 1, which has a rotating motor, which rotates a disc preform 2 around its axis of rotation. In the disc preform 2 there are three lines 5, which are readable with a laser reading device 4. When the disc preform 2 rotates and all three lines 5 pass the eye of the laser reading device 4, the disc preform is rotated into a desired position, after which the orientation notch is cut out. A punching device 8 cuts out a half moon formed piece out from the edge of the disc preform. Thus an orientation notch 9 is formed at the edge of the disc preform 2. The lines 5 at the disc preform are achieved already in connection with the plastic moulding of the disc preform and they are optically readable with a laser reading device. When a disc preform is transferred to next work places it is easy, accurate and certain to align the disc preform when the orientation tongue coming to the orientation notch can align itself into the orientation notch in only one way.