Electric heating – Metal heating – By arc
Reexamination Certificate
2000-03-10
2001-10-02
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121830
Reexamination Certificate
active
06297471
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a working head for processing a workpiece by means of a laser beam.
2. Description of Relevant Art
The need frequently occurs to carry out work, for example welding or cutting work, by means of a laser beam in the interior of relatively small workpieces. In this case, it is necessary to accurately position the focus of the laser beam relative to the inner surface of the workpiece.
SUMMARY OF THE INVENTION
It is the object of the invention to create a working head suitable for this purpose.
A working head according to the invention for processing a workpiece by means of a laser beam includes a housing with an inlet opening and an outlet opening for the laser beam; a focusing optical system for focusing the laser beam at a point outside the housing at a spacing upstream of the outlet opening; and a measuring arrangement, surrounding the outlet opening, for measuring a spacing between it and the workpiece in the propagation direction of the laser beam, the laser beam traversing the focusing optical system and the outlet opening and measuring arrangement along beam axes which are at an angle to one another.
It is also possible with the aid of such a working head to carry out work in the interior of relatively small workpieces and/or cavities, or in the interior of tubes having a relatively small inside diameter, because the extent of the working head transverse to its longitudinal axis is usually very much smaller than in the direction of its longitudinal axis. If such a working head is pushed into the interior of the workpiece, the laser beam emerging laterally from it can be used to carry out the desired work. Moreover, the measuring arrangement surrounding the outlet opening permits the spacing between it or the laser processing head, on the one hand, and the workpiece, on the other hand, to be accurately set or kept constant, as a result of which the focus of the laser beam can be positioned relative to the workpiece in a way desired, which leads to an improved work result.
According to a refinement of the invention, the angle between the said beam axes through the focusing optical system, on the one hand, and the outlet opening or measuring arrangement, on the other hand, can be 90°, with the result that the working head is suitable, in particular, for working in the interior of cylindrical or square tubes or tubes of other geometries. However, the said angle can also have other values, depending on the shape of the interior of a workpiece to be processed internally. For work inside a conical cavity, it would be possible given alignment of the processing head in the longitudinal direction of the cone to set the said angle such that the laser beam strikes perpendicularly on the internal conical surface.
In order to be able to adapt the angle between the respective beam axes to the respectively prevailing geometrical conditions in the interior of workpieces, according to an advantageous development of the invention, a part of the housing of the processing head which contains the outlet opening can be tilted and/or pivoted relative to a housing part containing the focusing optical system. As a result, the processing head can be used universally, including the case of the most varied internal geometries of workpieces.
In a refinement of the invention, a deflecting element for deflecting the laser beam is arranged in the beam path between the focusing optical system and outlet opening, the deflecting element being constructed, for example, as a plane mirror. Also possible, however, are other deflecting elements, for example concave mirrors, deflecting elements operating on the basis of a hologram, and the like, which can also be tuned to the respective optical properties of the focusing optical system.
The deflecting element can be inserted in this case into an opening of the housing from outside so that, if required, it can be taken out again relatively quickly, in order to be replaced by another, for example in the case of damage, or given the presence of other geometrical conditions.
For this purpose, the deflecting element is preferably seated on a support which can be connected to the housing, for example screwed in. In this case, the support can also be provided with cooling ribs on its outer surface in order to ensure better cooling of the deflecting element.
The working head according to the invention can be used as a measuring arrangement. A sensor electrode made from metallic material, is provided on the working head the spacing between it or the working head, on the one hand, and the workpiece, on the other hand, can be measured in a capacitive way when the workpiece consists of metal. Such a measuring technique is generally known and is not to be explained here further.
However, the measuring arrangement can also be present in the form of a coil which concentrically surrounds the outlet opening of the working head, with the result that the spacing between the measuring arrangement or the working head, on the one hand, and the workpiece, on the other hand, can then be measured in an inductive way. This measuring technique is also generally known and is not further explained here.
In a further refinement of the invention, the focusing optical system can be displaced inside the housing on and perpendicular to its axis of symmetry and/or central axis, in order to be able to undertake adjustment of the laser beam relative to the outlet opening.
Moreover, a protective lens can be arranged in the beam path in the region between the deflecting element and outlet opening, in order to protect the deflecting element, which is situated relatively close to the outlet opening, from outside against damage, for example against damage by metal splashes which are produced during processing of the workpiece by means of laser beam.
Again, a protective lens could be arranged in the beam path in the region between the deflecting element and focusing optical system, in order also to be able to protect the focusing optical system better from external influences. The two previously mentioned protective lenses are in this case respectively flowed around by protective gas which likewise emerges from the outlet opening during processing of the workpiece by means of the laser beam.
According to another, very advantageous development of the invention, the region of the housing of the working head situated between the focusing optical system and deflecting element can be constructed as a telescope, so that it is possible in the longitudinal direction of the working head to change the spacing between the deflecting element or outlet opening, on the one hand, and focusing optical system, on the other hand. It is thereby possible, if required, to displace the processing site even further into the interior of a workpiece into which the head, with its relatively wide end part, cannot be moved any more. In order in this case to take account of the change in focal length, the focusing optical system can likewise vary its focal length correspondingly as a function of the length of the telescope. The position of the focus of the laser beam relative to the outlet opening therefore also remains constant permanently, even in the case of a change in the spacing between the outlet opening and focusing optical system.
Finally, it is also possible for the region of the housing of the working head situated upstream of the focusing optical system in the beam direction to be constructed as a telescope, in order thereby to be able to vary the working region in the interior of a workpiece, if required, when the relatively large end part of the working head can no longer be moved into it.
REFERENCES:
patent: 4924063 (1990-05-01), Buchel et al.
patent: 5548098 (1996-08-01), Sugawara et al.
patent: 5624587 (1997-04-01), Otsuki et al.
patent: 6043452 (2000-03-01), Bestenlehrer
Birch & Stewart Kolasch & Birch, LLP
Heinrich Samuel M.
Precitec GmbH
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