Electric heating – Metal heating – By arc
Reexamination Certificate
1999-03-16
2001-03-13
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121680, C219S121760
Reexamination Certificate
active
06201210
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to the technical field of systems for marking the surface of articles. More specifically, the invention concerns the sector of marking of surfaces of articles, including moving articles, using laser beams.
It is the main object of the invention considerably to reduce the volume and price of the marking system.
BACKGROUND TO THE INVENTION
In the state of the art, it is known to use systems for marking moving objects, for example from Spanish patents n
o
8901979 and n
o
9602373 which describe a marking system using a laser which comprises a source of laser emission such as a CO
2
laser of which the bean impinges on an acousto-optical deflector to which various frequency values are applied by means of a constant gain radiofrequency amplifier, to produce different angles of deflection of the laser beam impinging on the deflector, marking the character, logo, text, etc. This information to be printed is introduced into a data acquisition unit which generates a digitised N×M matrix of dots corresponding to the impression to be made and is saved in a memory.
The deflected beams are applied to the surface to be marked by means of optical focusing means of which the function is to focus the deflected laser beam on to the surface to be marked.
Although this type of system operates perfectly, it has the drawback that the CO
2
laser tube has very large dimensions so it is difficult to site it in production lines.
A further drawback is that CO
2
laser tubes are very expensive.
It should also be mentioned that this type of system has the drawback that it is necessary to include an acousto-optical deflector which, apart from its cost, does not have a very high power output owing to the losses by absorption and the low efficiency of deflection, due to the fact that it loses laser power by the mere fact of passing through the crystal of the deflector and, furthermore, a proportion of the resultant power cannot be deflected owing to the intrinsic limitations of acousto-optical deflection.
On the other hand, laser diodes are known of which a basic characteristic is that, from a very small size, they are capable of generating a laser beam with a considerable power level and with very low energy consumption.
At present, there is no marking system which employs laser diodes to produce the marking according to a N×M matrix of dots, which would be a system with a smaller volume and lower costs.
DESCRIPTION OF THE INVENTION
To overcome the above-mentioned drawbacks and deficiencies, the invention has developed a new laser beam marking system using a marking system comprising, like conventional systems:
means for generating a laser beam;
optical means for focusing the laser beam on the surface to be marked;
a marking control unit for generating distinct signals which are applied to the means for generating a laser beam and to the optical focusing means to produce the marking according to a N×M matrix of dots;
a character generator included in the actual marking control unit and with the feature that it is characterised in that the means for generating the laser beam are formed by at least one laser diode for each dot N of the matrix, N being the vertical dots or raster dots or for at least one laser diode for each of the N×M dots of the marking matrix, M being the number of dots of the width of the matrix.
This arrangement avoids the use of CO
2
laser tubes which are very large in size and are expensive and, on the contrary, employs a plurality of laser sources formed by laser diodes which, on the other hand, are much more economical, have very small dimensions and have an adequate power level to produce the marking and with very low energy consumption.
Furthermore, this arrangement avoids the use of acousto-optical deflector, resulting in a much better energy yield since there are no losses by absorption since the various beams produced are not deflected as they are applied directly to the surface to be marked.
In a preferred embodiment of the invention, the means for generating the laser can be formed by an array of laser diodes with a combiner, for each dot of the matrix, so that the beams generated by each array of laser diodes impinge in phase on the combiner which adds them (greater power) and projects the resultant beam onto the optical focusing means. According to this preferred embodiment, the marking control unit can be equipped with:
means for activating at least one diode of each array of laser diodes for the duration of marking the dot allocated thereto; and/or
means for activating all the diodes of each array of laser diodes for the period of marking the dot allocated thereto; and/or
means for independently activating the individual laser diodes making up the array corresponding to a dot and/or
means for simultaneously activating the various arrays of laser diodes for the dot marking period, a vertical line of dots or a complete character being marked during this period; and/or
means for sequentially activating the various arrays of laser diodes in order to mark a vertical line of dots.
As known, each surface to be marked requires different energy to permit the volatility of said surface, so the marking unit modulates the dot energy in order to adapt itself to the energy requirements of the product to be marked by the selective activation of a plurality of or all diodes of the array and/or by modulating the dot duration, that is by keeping the number of diodes activated during the period required to permit marking, and/or by controlling the exciting current of each diode or array of diodes.
The system according to the invention can also comprise an optical system for correcting each of the beams generated, for which it uses an optical system for each laser beam in order to configure the laser beam by giving it the characteristics required to enable the focusing lens subsequently to generate a focal point with the maximum roundness and the minimum possible diameter. Each optical system basically consists of a beam magnifying telescope and also of a cylindrical lens in some cases.
In an embodiment of the invention, the focusing system consists of an array of microlenses, that is a small lens for each marking dot. This array of focusing microlenses together with the laser-generating diodes and the correcting optical system can be integrated within the marking pad.
According to the invention, the laser beams are directed from the diodes to the focusing system by optical fibre lines, one optical fibre line, for example, being used for each diode or for each array of diodes so as to eliminate conventional beam directing optical elements and thus avoid the problems and difficulties associated therewith such as the corresponding adjustment and alignment.
In a further embodiment of the invention, the focusing means are conventional and comprise a mechanical system designed for fastening the laser diodes or the outputs of the optical fibre so as to form a certain angle between said fibres or laser diodes and to enable the individual laser beams to be kept separate after focusing.
If the focusing means consist of a network of microlenses to allow variation of the marking height, they include means for vertically displacing all the laser diodes or optical fibres discretely until their position coincides with the contiguous focusing microelement. Therefore, to allow variation of the marking height, it is essential also to change the position of each focusing microlens.
On the other hand, if the optical focusing means are formed by conventional means in which the laser diode or optical fibre are disposed at an angle to one another, it is sufficient to enlarge or reduce the lighting angle of each laser diode or optical fibre end with respect to the focusing lens.
It is also possible for the focusing means to be formed by the arrangement of a small conventional lens for each laser beam, in which case the marking height is controlled by displacing all the laser diodes or optical fibres together with their corresp
Baron Jose Miguel Ibanez
Beringues I Algue Jordi
Sans I Ravellat Ramon
Darby & Darby
Heinrich Samuel M.
MACSA ID S.A.
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