Laser processing machine with at least an optical element that can be submitted to a flushing elementing medium

The invention relates to a laser processing machine with at least , disposed in the path of a laser beam optical Element, which at at least one in the path of laser beam lying surface via a feed device in the form of a Nozzle assembly substantially against flow freely with a is flushing medium acted upon, the nozzle assembly more having nozzle channels, which are to be treated at the edge of the Surface along juxtaposed open.

Precipitating of optical elements of the aforementioned type Deposits, such as particles or fibers can affect the functioning of the entire machine. Thus, the above-mentioned deposits cause enhanced absorption the laser beam through the respective optical element, which in the next zonal or overall significant Dimensions heats. As a result of this heating, unwanted Changing the optical properties of the optical element enter, thereby possibly deficiencies in the management and / or Shaping of the laser beam are due. In extreme cases, , the heating of the optical element to its thermal Destruction lead.

In the case of the prior art according to WO 97/06918 is to Protection of focusing a laser processing machine, a the annular nozzle surrounding the focusing lens is provided via which for cleaning the workpiece side lens surface can be fed with a purge gas. The purge gas is here over the entire edge of the circular lens surface concerned radially directed to the center thereof abandoned. From the center of the lens surface from the purge gas flows substantially perpendicular to the lens surface in the direction of the machined workpiece from. The EP-B-0695600 discloses a laser processing machine, in the case of those who today opposing Spülgasteilströme with the aim of producing a Spülgaswirbels on the workpiece side surface a focusing lens to be abandoned. The axis of the produced Spülgaswirbels runs in the transverse direction of said Lens surface.

Due to the existing flow conditions is in itself the WO 97/06918 previously known laser processing machine in the center of the lens surface is acted upon a Spülgasstau on. In the case of the prior art according to EP-B-0695600 is the at least approximately free flow of center generated Spülgaswirbels in the central area of ​​the front deposits the protected lens surface. Accordingly, the purge gas to both known laser processing machines in the lens center no or only limited Cleaning action unfold. The central portions of the focusing lenses , in the case of the prior art thus only protected deficient prior to the deposition of contaminants or are exempt from existing deposits. This is all the more serious as laser beams of laser processing machines often a Gaussian intensity distribution over the beam cross-section and, accordingly, just the central area of ​​the focusing lens of the laser processing machine a high intensity radiation is exposed and in radiation absorption due to lens contamination a particularly strong heating undergoes.

Generic Laser processing machines are known from JP 03 066 490 A, JP 04 305 391 A, DE 39 18 363 A and US 4,315,133 A.

According to JP 03 066490 A is the focusing of a laser arrangement three nozzle channels charged with cleaning air. The Nozzle ducts are at the edge of the focusing lens and there same side arranged. The one from the nozzle channels exiting air is applied to the one that the two other Nozzle channels that were found to air the other lens surface passed along. The two nozzle channels, the one and the same feed lens surface, are converging in the direction of flow aligned.

JP 04 305391 A relates to a laser welding machine with a Welding head, which is provided on the workpiece side with a protective glass is. On the workpiece side of the protective glass, a gaseous Flushing medium fed into the transverse direction of the laser beam propagation. This flushing medium flows straight to the protective glass along and its application site is discharged opposite.

As evidenced by DE 39 18 363 A has a laser processing head optical focusing element, on whose side of the workpiece by means a nozzle ring a Spülgaswirbel is generated. This is of directed the optical focusing element away and runs with its axis in the propagation direction of the laser beam.

A Spülgaswirbel from DE 39 18 363 A known type is also disclosed in US 4,315,133 A. Alternatively, US 4,315,133 A generation of transverse to the laser beam propagation direction extending and intersecting pressure air flows to the Workpiece side of the focusing lens of the laser processing head.

The present invention has set itself the goal of a laser processing machine to provide, in the case of which one or more in the path of a laser beam optical elements arranged effectively and are reliably protected against deposits or from already existing deposits to be cleaned.

This object is achieved according to the invention by the combination of features of claim 1. The substantially against non-flow Subjecting the surface concerned with Flushing medium, the formation of stagnation points in the produced Flow field at least largely prevented and therefore in all relevant surface areas of a flow rate of Flushing medium ensures sufficient deposition to prevent impurities or contaminants present to remove. Claim Proper nozzle channels provide example about their orientation and / or through their dimensioning an easy way to produce a special purpose shall Flow of the flushing medium to the surface to be acted upon. In this sense, in the case of the invention, the flow-through nozzle channels the nozzle assembly in the direction of flow diverging and to be acted upon in its extension in the flow direction along the Surface aligned like a fan running.

The usable se flow cross section of the invention Feeder can be either a part of the rim the surface to be acted upon, or to the entire extend to acting along surface. The for Rinse the actually used to acting surface, flushing medium flowed through flow cross section in both selected cases such that a flow against free admission the surface in question at least in the or the neuralgic areas concerned.

According to the invention is always taken that to at the acting surface of the respective optical element possible coverage sufficient and / or uniform flow velocities the flushing medium yield.

The characterizing feature of claim 2 as causes that with uniform velocities from the individual nozzle channels the nozzle assembly exiting streams of the flushing medium in their union after at the surface to be acted upon as have before a uniform flow rate and consequently no undesired turbulences occur. nozzle channels create circular cross-section, as in claim 4 is indicated, it is also advisable for production engineering Establish. Let it be to such nozzle ducts in a simple manner by Making drilling.

The provided in an advantageous development of the invention, characterizing feature of claim 5 relates to a simple constructive option for sealing the area of ​​the with flushing medium to be acted upon surface of the relevant optical element to the surrounding area. such Sealing can be offered a variety of reasons. Thus can be explained by the enclosure of the invention, for example, the penetration of impurities into the region of the Paths of the laser beam lying and to be acted upon with rinsing medium prevent surface. In addition, the said enclosure optionally an easy way for accommodating the nozzle channels of a nozzle assembly according to the invention. In their design, the enclosure according to the invention is expediently to the shape of the outline of with Flushing medium adapted to be acted upon surface.

The flushing medium is basically any fluid medium conceivable means of which without substantially affecting the Machine function, as without significantly affecting the optical Properties of the respective optical element whose clean impinging surface or against pollution can be protected. Describe the claims 6 and 7 Measures according to the invention, in the case of laser processing machines with a gas-filled beam guiding chamber of particular Advantage. The flushing medium is thereby as well as a the beam guiding chamber filling gas preferably nitrogen or compressed air used. According to claim 7, the Opportunity controlled simultaneously use the flushing medium to the desired internal pressure of the beam guiding space adjust, for example, to this end, leakage losses balance of the beam guiding chamber füllendem gas.

Primarily the invention is as an optical element with a flushing medium can be supplied with surface an output mirror on the laser resonator and / or at least one deflecting mirror and / or at least a focusing lens of the laser processing machine provided (claim 8).

The invention will by way of exemplary schematic Representations explained in more detail. Show it:<dl tsize="13"><dt>Fig. 1</dt><dd>can be acted upon with a flushing medium Focusing a laser cutting machine to a lens holder,</dd><dt>FIGS. 2 and 3</dt><dd>highly diagrammatic representations of the flow conditions according to the focusing lens Fig. 1</dd><dt>Fig. 4</dt><dd>the arrangement of FIG. 1 integrated into the Cutting head of a laser cutting machine,</dd><dt>Fig. 5</dt><dd>one acted upon by a flushing medium deflecting for the laser beam of a laser cutting machine on a mirror mount and</dd><dt>Fig. 6</dt><dd>acted on a with a flushing medium Output mirror of a laser resonator of a Laser cutting machine at a mirror mount.</dd></dl>

According to FIG. 1 is an optical element in the form of a focusing lens 1 a laser cutting machine in conventional and Way to a lens holder 2 is supported. On the one hand supports the focusing lens 1 case against an annular shoulder of 3 Lens holder 2 from; On the other hand, the focusing lens 1 is clamped by means of a threaded ring. 4

With a limited in Fig. 1 overhead curved surface 5 the focusing lens 1 a cylindrical inner space 6 to the lens holder 2. The cylindrical space 6 is part a nitrogen-filled gas beam guiding space of fragmentary shown laser cutting machine. A laser beam 7, which, starting from a laser resonator to the focusing lens 1 is led out is indicated in FIG. 1.

The axis-parallel wall of the cylindrical inner chamber 6 is formed from one end face 8 of the annular shoulder 3 and the inner wall a cylindrical nozzle ring 9. The latter encloses as the enclosure, the surface 5 of the focusing lens 1 and is located on its underside close to the annular shoulder 3 of Lens holder 2. For the tight connection of the nozzle ring 9 at the annular shoulder 3 ensure clamping screws 10, by wherein the nozzle ring 9 at its end remote from the annular shoulder 3 axial end is acted upon via a support ring 11th

Radially outside of the nozzle ring 9 is an annular channel 12 in the Lens holder 2 incorporated. The annular channel 12 runs over the entire circumference of the nozzle ring 9 and communicates with an external Source of nitrogen gas in the form of a with respect to the generated Gas pressure adjustable nitrogen gas pump 13 in connection. To seal the nozzle ring 9 against the lens mount 2 is a corresponding in a groove of the lens holder 2 inserted O-ring 14 is provided. The nitrogen gas pump 13 is connected via a machine control unit 15 with a device 16 for monitoring the internal pressure of the gas-filled beam guide chamber the laser cutting machine in conjunction.

As is particularly evident from Fig. 2, the nozzle ring 9 over a part of the edge of the surface 5 of the focusing lens 1 provided with nozzle ducts 17th This lead to the surface 5 of the focusing lens 1 toward juxtaposed and are used to Subjecting the surface 5 with flushing medium in the form of starting of the nitrogen gas pump 13, inter alia, via the annular channel 12 supplied nitrogen gas.

The nozzle channels 17 have been prepared and have drilling Accordingly, a circular cross section. They are evidenced by Fig. 1 inclined in their course to the horizontal and tangential directed to the center of the surface of the focusing lens 5 first Their cross-sectional areas are the same. According to FIGS. 2 and 3 run the nozzle channels 17 in the flow direction diverging and fan-like in its extension in the flow direction to the surface 5 of the focusing lens 1 along.

The discontinued to the surface 5 of the focusing lens 1 Nitrogen gas is in the annular channel 12 outside of the nozzle ring 9 at a pressure of about 2.0 bar. In the cylindrical Space 6 to the lens holder 2, the internal pressure prevails the gas-filled beam guiding space of the laser cutting machine, is slightly above the atmospheric pressure. As a result of Pressure difference on both sides of the wall of the nozzle ring 9 flowing the nitrogen gas from the annular channel 12 the speed of sound in the cylindrical space 6 inside the A nozzle ring. 9 Directly to the to the surface of the focusing lens 1 located towards mouths of the nozzle channels 17 erweitem the latter passing through streams of nitrogen gas first conical. As a result, and due to the visible in FIG. 1 taper of the annular shoulder 3 toward the focusing lens 1 out and because of the chosen inclination of the nozzle channels 17 to the horizontal meets nitrogen gas in the radial Direction of the cylindrical interior 6 also seen at a small distance from the wall of the cylindrical achsparallen Interior space 6 on the surface 5 of the focusing lens 1 on. Accordingly, only an extremely small edge zone of Surface 5 below the mouths of the nozzle channels 17 not be achieved with flushing medium. As a result of the divergence of the nozzle channels 17 results in the in FIGS. 2 and 3 illustrated fan-shaped profile of the surface of the focusing lens 5 1 sweeping nitrogen gas flow. is shown in Fig. 3 In this case, the superposition of the individual nozzles from the ducts 17 exiting streams recognizable. The union of these by Streams generated nitrogen gas flow moves over a large area and a relatively high speed through the Surface 5 of the focusing lens 1. Since the openings of the nozzle channels through 17 on the to of the surface 5 of the focusing lens 1 facing side of the nozzle ring 9 only a small angled Segment of the nozzle ring 9 are arranged, are said Openings of the nozzle channels 17 in the flow direction notwithstanding the cylindrical shape of the nozzle ring 9 almost on a Height. This leads to that the from the individual nozzle ducts 17 emerging nitrogen gas streams at their union have an approximately uniform rate. Unwanted Turbulence of the total flow can be avoided. Due to the unilateral abandonment of the nitrogen gas at the edge of the surface 5 of the focusing lens 1 is the nitrogen gas flow to flow freely on the surface 5 substantially.

All in all, resulting on the surface of the focusing lens 5 1 is a nitrogen gas flow, which is suitable for the surface 5 especially in the laser beam 7 exposed zone be kept free of debris or of strahlabsorbierenden to clean existing deposits.

Referring to FIG. 4, the lens holder 2 with the focusing lens 1 on a cutting head 18 of the laser cutting machine in the direction a double arrow 19 to be movable. This mobility the focusing lens 1 is used in a known manner of setting the focal position of the laser beam 7 relative to the to be processed Workpiece. The annular channel 12 on the outside of the nozzle ring 9 is a in Fig. 4 suggestively recognizable dip tube 20 to a housing 21 of the cutting head 18 to the nitrogen gas pump 13 connected. The dip tube 20 opens independently from the position of the annular channel 12 in the direction of the double arrow 19 into the annular channel 12 and thereby notwithstanding any focal position changes the connection between the Nitrogen gas pump 13 and the annular channel 12 ago.

As shown in FIG. 5 is an optical element in the form of a deflecting mirror 101 for deflecting a laser beam 107 also with Nitrogen gas as a flushing medium acted upon. According to structural features of the arrangement according to FIGS. 1 to 4 takes place at the deflecting mirror 101, the supply of flushing medium to a to be charged surface 105 from a nitrogen gas pump 113 via an annular channel 112 and nozzle channels 117 serving as an enclosure to the surface 105 Nozzle ring 109. In addition, especially regarding the orientation and the arrangement of the nozzle channels 117 and the flow conditions at the surface 105 may be on the above Comments on FIGS. 1 to 4 are directed.

Accordingly, reference is made to the foregoing are the basic description of the construction and Operation of the arrangement shown in Fig. 6. This includes as an optical element an output mirror 201, as usually of a laser resonator of a laser processing machine provided for extracting a laser beam generated 207 is. to clean or against deposits from deposits to protect is a surface 205, which for this purpose is charged with flushing medium, which from a external Nitrogen gas pump 213 originates and, inter alia, via an annular channel 212 enclosing and nozzle channels 217 on a surface 205 Nozzle ring 209 is supplied. Notwithstanding the above described by Ratios vary the nozzle channels 217, however, with respect to their cross-sectional shape.

In all cases shown example, the flushing medium used be used, for example, on the relevant Beam guiding chamber occurring leakage losses of the beam guiding chamber compensate füllendem gas. In the case of the arrangement according to FIGS. 1 to 4, the inner pressure of the beam guiding chamber monitored by the device 16th If unwanted 16 pressure drop generates the device a signal to the machine control 15. This in turn then controls the nitrogen gas pump 13 in terms of a corresponding increase the pressure of the supplied nitrogen gas. as a result the pressure increase is the beam guiding chamber of the laser cutting machine then fed to a quantity of flushing medium, which is sufficient compensate for the identified leakage losses.